Podcasts about connexin

Send us a textImagine discovering that a simple misdiagnosis dramatically shaped your early years. That's exactly what happened to Dr. Mark Campbell-Foster, our guest and Director of Audiology Sales and Marketing at Redux. Mark takes us through his journey from a childhood misinterpreted as developmental delays to the revelation of his hearing loss at Children's Hospital Boston—a turning point that fueled both personal and professional growth. He navigates the intricacies of deaf culture, explores genetic underpinnings like Connexin 26 in his family, and stresses the life-changing importance of accurate diagnoses.As Mark recounts his high school years with hearing aids and the monumental transition to cochlear implants, we hear about the hurdles of living in a predominantly hearing world. The challenges are numerous, including the emotional and social aspects of needing to self-advocate. Mark shares the poignant moment when he realized hearing aids were no longer enough, prompting a life-altering decision for a cochlear implant. His story is a compelling mix of personal resilience and family adaptation, illustrating the emotional and practical aspects of embracing new hearing experiences.Mark's professional journey is equally inspiring, showing how he brings personal experience into his work with Redux. Mark celebrates the community and technological support that have been foundational to his success, highlighting the importance of connection and innovation in the field of audiology. Join us for this episode full of insights and inspiration as we explore the intersection of personal challenges and professional triumphs in hearing health. Connect with the Hearing Matters Podcast TeamEmail: hearingmatterspodcast@gmail.com Instagram: @hearing_matters_podcast Twitter: @hearing_mattasFacebook: Hearing Matters Podcast

In this episode of the Hack podcast, Leon, Paul, and Dean engage in an insightful conversation with Furqan Alamgir, Chief Executive Officer at Connexin. Furqan shares his journey as an entrepreneur and how he grew Connexin into one of the fastest-growing technology companies in the UK. He also discusses the challenges he faced along the way and how he overcame them to achieve success. One of the key topics discussed in this episode is the importance of collaboration and connectivity in today's digital age. Furqan highlights how Connexin plays a crucial role in providing connectivity solutions to businesses, cities, and communities. He also talks about their innovative approach to smart infrastructure and its potential to transform how we live and work. They also explore people, processes, and technology as the three fundamental elements of a prosperous enterprise. Furqan highlights the significance of passion and curiosity as crucial factors for success. Tune in to hear Furqan Alamgir's story and learn more about the future of connectivity. Keep an eye out for Connexin as it continues to expand and revolutionise the technology industry.

Rohr 2004- Gap junction blockade can cause a wide QRS Vink 2004 Connexin 43 is the most important protein for connexon formation and cardiac signal transmissionCallier 2012- Bupropion does not block sodium channels, and does exhibit similar effects on the cardiac action potential as known gap junction  Burnham 2014 Bupropion has an IC50 for connexin 43 >50 uMol, larger than other drugs such as fluoextine and lamotrigineShaikh Quereshi 2014 Bupropion interferes with connexin43 production and localization in chicken cardiac myoctes at concentration >50 uMol

 This antidepressant is the #1 cause of major (life threatening) effects in overdose reported to U.S. Poison CentersIt is difficult to manage due toPotential for delays seizuresUnique cardiogenic shock in overdosePotential wide complex arrhythmia refractory to Sodium Bicarbonate Potential interference with brain death testingToxicityIt increases dopamine and norepinephrine, it also blocks the gap junction in the cardiac myocyteRohr 2004- Gap junction blockade can cause a wide QRVink 2004 Connexin 43 is the most important protein for connexon formation and cardiac signal transmissionCallier 2012- Bupropion does not block sodium channels, and does exhibit similar effects on the cardiac action potential as known gap junctionBurnham 2014 Bupropion has an IC50 for connexin 43 >50 uMol, larger than other drugs such as fluoextine and lamotrigineShaikh Quereshi 2014 Bupropion interferes with connexin43 production and localization in chicken cardiac myoctes at concentration >50 uMolEffectsSympathetic toxidromeSeizuresTL;DRYour patient can seize 8-24 hours in, usually they have neurologic symptoms and tachycardia before handTachycardia may be masked by coingestions and symptoms may be very delayedDo not discharge a patient without discussing observation time with a toxicologist or poison centerDo not dismiss tachycardia and anxiety as situational in a bupropion overdoseShepherd 2004- Seizures in primarily sustained release productsMost seizures had prodromal neuropsychiatric symptomsStarr 2009- Seizure in XL products. Tachycardia, tremor, agitation most associated with seizuresSeizure occured as late as 24 hours and 25% occurred after 8 hoursOfferman 2020- Primarily sustained/extended release productsTachycardia duration, and extent (>120) predicted seizure. (Hypotnesion and neuropsych symptoms also predict)Late seizure occurred only in those with symptoms on presentationThose who had cardiac arrest had prehospital seizure= bad signRianprakaisang 2021- ToxIC review of risk factors for seizuresQTc and HR>140 predict seizuresUnique cardiogenic shock in overdosePotential wide complex arrhythmia refractory to Sodium Bicarbonate Potential interference with brain death testingTreatment DecontaminationAggressive whole bowel irrigation or charcoal may be indicated if large ingestionSupportive careIntubation if airway compromisedBenzodiazepine for agitationBenzodiazepines and GABA-ergic AED's for status epilepticsTachycardia, tremor, and agitation are risk factor for seizuresTachycardia may be masked by alpha 2 agonist co ingestionsSeizures may occur 24 hour outSodium bicarbonate for wide QRS (it may be refractory)Inodilators and vasopressors for cardiogenic shockECMO for refractory shock or arrhythmiaAwareness that severe bupropion toxicity can mimic brain deathsend analytical confirmation of bupropion if possible to rule out confoundingEnhanced eliminationlimited options due to protein binding, not routineFocused antidoteConsider IV fat emulsion if the patient is peri arrestObservation timesTalk to a toxicolleague about observation times, decontamination, and use of invasive therapies to avoid falling into a trapNot all ingestions are made the same   

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.02.09.527850v1?rss=1 Authors: Fadjukov, J., Wienbar, S., Milicevic, N., Hakanen, S., Vihinen-Ranta, M., Ihalainen, T. O., Schwartz, G. W., Nymark, S. Abstract: Retinal pigment epithelium (RPE) at the back of the eye is a monolayer of cells with an extensive network of gap junctions that contributes to retinal health in a multitude of ways. One of those roles is the phagocytosis of photoreceptor outer segments. This renewal is under circadian regulation and peaks after light onset. Connexin 43 (Cx43) is the most predominantly expressed gap junction protein in RPE. In this study, we examine how gap junctions and specifically, Cx43 phosphorylation, contribute to phagocytosis in both human embryonic stem cell derived RPE and mouse RPE monolayers. We show that both Rac1 and CDK5 have differences in protein localization at different points in phagocytosis, and that by using their effectors, the capability of RPE for phagocytosis changes. CDK5 has not yet been reported in RPE tissue, and here we show that it likely regulates Cx43 localization and resulting electrical coupling. We find that gap junctions in RPE are temporally highly dynamic during phagocytosis and that regulation of gap junctions via phosphorylation is likely critical for maintaining eye health. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

In this episode...Dr Bahijja Raimi-Abraham speaks with Professor Anna David (Consultant in obstetrics and maternal/fetal medicine at University College London Hospital (UCLH)) her development of the world's first "Standard Maternal and Fetal Adverse Event Terminology". Additional Information Spencer, RN, Hecher, K, Norman, G, et al. Development of standard definitions and grading for Maternal and Fetal Adverse Event Terminology. Prenat Diagn. 2021 Thank you for listening! If you liked the episode, please give us a five-star rating and review. Buy a Coffee for Monday Science Episode image credit: Photo from Barrett, D. W., David, A. L., Thrasivoulou, C., Mata, A., Becker, D. L., Engels, A. C., Deprest, J. A., and Chowdhury, T. T. (2016) Connexin 43 is overexpressed in human fetal membrane defects after fetoscopic surgery. Prenat Diagn, 36: 942– 952. doi: 10.1002/pd.4917. Subscribe, follow, comment, leave a review and get in touch ! Submit your questions or send your voice note questions (up to 30 seconds) here . https://www.mondaysciencepodcast.com/ e. info@mondaysciencepodcast.com --- Send in a voice message: https://anchor.fm/mondayscience/message

In S2 episode 23, Ralph Varcoe MD and Chief Growth Officer at Connexin joins the show to talk about the impact of smart cities

In this remarkable live episode of Lets Talk Leadership: The Culture Edit, our hosts Sandra Patel Stewart and Elly Nettleton are joined by 4 pioneering leaders; Furqan Alamgir, CEO and Founder of Connexin,  Mike O'Brien, Co-chair and Founder of Opencast Software, Natasha Sayce-Zelem, Global Head of Engineering at Amazon and Paul Trotter, Deputy CTO at Atom bank and a live engaged audience. Discussing how they have cultivated an authentic, positive culture where tech teams can thrive, these four influential leaders are put on the hot seat, revealing their challenges, testing points, career development, leadership journey and core leadership principles.

In this episode...Dr Bahijja Raimi-Abraham speaks with Professor Anna David (Consultant in obstetrics and maternal/fetal medicine at University College London Hospital (UCLH)) about preterm births, fetal surgery, and fetal gene therapy. Thank you for listening! If you liked the episode, please give us a five-star rating and review. Buy a Coffee for Monday Science Episode image credit: Photo from Barrett, D. W., David, A. L., Thrasivoulou, C., Mata, A., Becker, D. L., Engels, A. C., Deprest, J. A., and Chowdhury, T. T. (2016) Connexin 43 is overexpressed in human fetal membrane defects after fetoscopic surgery. Prenat Diagn, 36: 942– 952. doi: 10.1002/pd.4917. --- Send in a voice message: https://anchor.fm/mondayscience/message

In this episode...Dr Bahijja Raimi-Abraham speaks with Professor Anna David (Consultant in obstetrics and maternal/fetal medicine at University College London Hospital (UCLH)) her development of the world's first "Standard Maternal and Fetal Adverse Event Terminology". Additional Information Spencer, RN, Hecher, K, Norman, G, et al. Development of standard definitions and grading for Maternal and Fetal Adverse Event Terminology. Prenat Diagn. 2021 Thank you for listening! If you liked the episode, please give us a five-star rating and review. Buy a Coffee for Monday Science Episode image credit: Photo from Barrett, D. W., David, A. L., Thrasivoulou, C., Mata, A., Becker, D. L., Engels, A. C., Deprest, J. A., and Chowdhury, T. T. (2016) Connexin 43 is overexpressed in human fetal membrane defects after fetoscopic surgery. Prenat Diagn, 36: 942– 952. doi: 10.1002/pd.4917. Subscribe, follow, comment, leave a review and get in touch ! Submit your questions or send your voice note questions (up to 30 seconds) here . https://www.mondaysciencepodcast.com/ e. info@mondaysciencepodcast.com --- Send in a voice message: https://anchor.fm/mondayscience/message

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.11.03.366179v1?rss=1 Authors: St Clair, J. R., Westacott, M. J., Farnsworth, N. L., Kravets, V., Schleicher, W. E., Miranda, J. G., Heintz, A., Ludin, N. W. F., Benninger, R. K. Abstract: Type2 diabetes results from failure of the {beta}-cell to compensate for insulin resistance, such as in obesity. Insulin secretion is governed by a series of metabolic and electrical events which can fail during the progression of diabetes. {beta}-cells are electrically coupled via Cx36 gap junction channels, thereby coordinating the pulsatile dynamics of electrical activity, Ca2+ and insulin release across the islet, enhancing insulin action. Pulsatile insulin release is disrupted in human type2 diabetes, although whether this disruption results from diminished gap junction coupling is unclear. Factors such as pro-inflammatory cytokines and free fatty acids disrupt gap junction coupling under invitro conditions. Here we test whether gap junction coupling and coordinated Ca2+ dynamics are disrupted in type2 diabetes, and whether recovery of gap junction coupling can recover islet function. We examine islets from healthy donors and those with type2 diabetes, as well as islets from db/db mice and islets treated with a cocktail of proinflammatory cytokines (TNF-, IL-1{beta}, IFN-{gamma}) or free fatty acids (palmitate). We modulate gap junction coupling using Cx36 over-expression or pharmacological activation via modafinil. We also develop a peptide mimetic (S293) of the c-terminal regulatory tail of Cx36 designed to compete against its phosphorylation and downregulation. Cx36 gap junction permeability and coordinated Ca2+ dynamics were disrupted in islets from human donors with type2 diabetes, as well as in islets from db/db mice or treated with proinflammatory cytokines or palmitate. Cx36 over-expression, modafinil treatment and S293 peptide all enhanced Cx36 gap junction coupling and protected against declines in coordinated Ca2+ dynamics. Cx36 over-expression and S293 peptide also reduced apoptosis induced by proinflammatory cytokines. Critically S293 peptide rescued gap junction coupling and Ca2+ dynamics in islets from both db/db mice and a sub-set of T2D donors. Thus, recovering or enhancing Cx36 gap junction coupling can improve islet function in diabetes. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.27.223651v1?rss=1 Authors: Brunal, A. A., Clark, K. C., Ma, M., Pan, Y. A. Abstract: Connexins are transmembrane proteins that form hemichannels allowing the exchange of molecules between the extracellular space and cell interior. Two hemichannels from adjacent cells dock and form a continuous gap junction pore, thereby permitting direct intercellular communication. Connexin 36 (Cx36), expressed primarily in neurons, is involved in the synchronous activity of neurons and may play a role in aberrant synchronous firing, as seen in seizures. To understand the reciprocal interactions between Cx36 and seizure-like neural activity, we examined three questions: a) does Cx36 deficiency affect seizure susceptibility, b) does seizure-like activity affect Cx36 expression patterns, and c) does acute blockade of Cx36 conductance increase seizure susceptibility. We utilize the zebrafish pentylenetetrazol (PTZ; a GABA(A) receptor antagonist) induced seizure model, taking advantage of the compact size and optical translucency of the larval zebrafish brain to assess how PTZ affects brain-wide neuronal activity and Cx36 protein expression. We exposed wild-type and genetic Cx36-deficient (cx35.5-/-) zebrafish larvae to PTZ and subsequently mapped neuronal activity across the whole brain, using phosphorylated extracellular-signal-regulated kinase (pERK) as a proxy for neuronal activity. We found that cx35.5-/- fish exhibited region-specific susceptibility and resistance to PTZ-induced hyperactivity compared to wild-type controls, suggesting that genetic Cx36 deficiency may affect seizure susceptibility in a region-specific manner. Regions that showed increased PTZ sensitivity include the dorsal telencephalon, which is implicated in human epilepsy, and the lateral hypothalamus, which has been underexplored. We also found that PTZ-induced neuronal hyperactivity resulted in a rapid reduction of Cx36 protein levels. 30 minutes and one-hour exposure to 20 mM PTZ significantly reduced the expression of Cx36. This Cx36 reduction persists after one-hour of recovery but recovered after 3-6 hours. This acute downregulation of Cx36 by PTZ is likely maladaptive, as acute pharmacological blockade of Cx36 by mefloquine results in increased susceptibility to PTZ-induced neuronal hyperactivity. Together, these results demonstrate a reciprocal relationship between Cx36 and seizure-associated neuronal hyperactivity: Cx36 deficiency contributes region-specific susceptibility to neuronal hyperactivity, while neuronal hyperactivity-induced downregulation of Cx36 may increase the risk of future epileptic events. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.27.222323v1?rss=1 Authors: Choi, B. Y., Lee, C. J., Oh, D.-Y., Jang, M. W., Lee, E. Abstract: Genes that are primarily expressed in cochlear glia-like supporting cells (GLSs) have never been clearly associated with progressive deafness. Herein, we present a novel deafness locus mapped to chromosome 3p25.1 and a new auditory neuropathy spectrum disorder (ANSD) gene TMEM43 mainly expressed in GLSs. We identify p.R372X of TMEM43 by linkage analysis and exome sequencing in two large Asian families. The knock-in (KI) mouse with p.R372X mutation recapitulates a progressive hearing loss with histological abnormalities exclusively in GLSs. Mechanistically, TMEM43 interacts with Cx26 and Cx30 gap junction channels, disrupting the passive conductance current in GLSs in a dominant-negative fashion when the p.R372X mutation is introduced. Based on the mechanistic insights, cochlear implant was performed on two patients and speech discrimination was successfully restored. Our study highlights a pathological role of cochlear GLSs by identifying a novel deafness gene and its causal relationship with ANSD. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.22.216598v1?rss=1 Authors: Mozafari, S., Deboux, C., Laterza, C., Ehrlich, M., Kuhlmann, T., Martino, G., Baron-Van Evercooren, A. Abstract: Oligodendrocytes are extensively coupled to astrocytes, a phenomenon ensuring glial homeostasis and maintenance of CNS myelin. Molecular disruption of this communication occurs in demyelinating diseases such as multiple sclerosis. Less is known about the vulnerability and reconstruction of the panglial network during adult demyelination-remyelination. Here, we took advantage of LPC-induced demyelination to investigate the expression dynamics of the oligodendrocyte specific connexin 47 (Cx47) and whether this dynamic could be modulated by grafted iPSC-neural progeny. Our data show that deconstruction of the panglial network following demyelination is larger in size than demyelination. Loss of Cx47 expression is timely rescued during remyelination and accelerated by the grafted neural precursors. Moreover, mouse and human iPS-derived oligodendrocytes express Cx47, which co-labels with astrocyte Cx43, indicating their integration into the panglial network. These data suggest that full lesion repair following transplantation occurs by panglial reconstruction in addition to remyelination. Targeting panglial elements by cell therapy or pharmacological compounds may help accelerating or stabilizing re/myelination in myelin disorders. Copy rights belong to original authors. Visit the link for more info

Eine effektive Regulation der Gewebedurchblutung erfordert eine Koordination der Reaktion einzelner Gefäßzellen bzw. verschiedener Gefäßabschnitte. Der zur Koordination erforderliche interzelluläre Signalaustausch kann zumindest teilweise über Gap Junction-Kanäle erfolgen, die als interzelluläre Verbindungen den Austausch von elektrischen und chemischen Signalstoffen zwischen benachbarten Zellen ermöglichen. Dieser Austausch kann über die Modulation der Permeabilität von Gap Junction-Kanälen reguliert werden. Aus Untersuchungen an Modellzellen (HeLA-Zellen) war bereits bekannt dass NO eine solche Modulatorwirkung ausübt, wenn die Gap Junctions nur Connexin 37 (Cx37) enthalten während kein Effekt von NO auf Gap Junctions zu beobachtet war, wenn Gap Junctions aus Cx43 oder Cx40 gebildet wurden. Da Endothelzellen normalerweise alle drei Connexine exprimieren, sollte in der vorliegenden Arbeit untersucht werden, inwieweit NO in diesen Zellen überhaupt eine nachweisbare Wirkung auf die Gap Junction Permeabilität und damit auf den Signalaustausch entfaltet. Als Modell des Signalaustauschs wurde die Ausbreitung von Calciumwellen jeweils zwischen Endothelzellen oder glatten Muskelzellen allein oder zwischen beiden Zelltypen untersucht. Nach Auslösung von interzellulären Calciumwellen als Folge einer mechanischen Stimulation von einzelnen Zellen konnte zunächst gezeigt werden, dass die interzelluläre Ausbreitung von Calcium unter den gewählten Versuchsbedingungen über Gap Junctions-erfolgte. Im Gegensatz zum Modellsystem der HeLa Zellen, in denen nur Cx37 exprimiert war, zeigte NO in den Endothelzellen (humane Nabelschnur, alle drei Connexine exprimiert) abgesehen von einer geringradigen Verzögerung keinen Hemmeffekt auf die Gap Junction-abhängige Ausbreitung von Calcium-Signalen. Wurde jedoch Cx43 durch Behandlung mit siRNA herunterreguliert, führte NO auch in den Endothelzellen zu einer Hemmung der interzellulären Calciumwellenausbreitung. Auch in intakten Endothelzellen, die mit glatten Muskelzellen kokultiviert wurden, ließ sich bei genauerer Analyse ein Hemmeffekt von NO nachweisen. Dieser war jedoch auf die Zellbereiche beschränkt, in denen Endothelzellen und glatte Muskelzellen unmittelbar benachbart waren (myoendotheliale Junctions). In diesen myoendo-thelialen Gap Junctions, fanden wir auf der Endothelseite immunhistochemisch überwiegend Cx37 exprimiert. Aufgrund dieser präferentiellen Lokalisation von Cx37 scheint daher NO eine besondere Rolle bei der Modulation des Calciumaustauschs (und potentiell auch anderer Signalmoleküle wie IP3 oder cyclische Nukleotide) zu spielen. Die Kontrolle des Calciumaustauschs könnte funktionell eine calciumabhängige glattmuskuläre Kontraktion bei Endothelstimulation verhindern und somit die endothelabhängige Dilatation verstärken. Diese bisher unbekannte NO-Wirkung auf Cx37-exprimierende Gap Junctions könnte einen weiteren Mechanismus der Gefäßtonusregulation darstellen.

Mon, 14 Nov 2011 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/13743/ https://edoc.ub.uni-muenchen.de/13743/1/Behrens_Juliane.pdf Behrens, Juliane ddc:540, ddc:500, Fakultät für Chemie und Pharmazie

Eliana Scemes im TR 3-Seminar

Background: Pluripotent embryonic stem (ES) cells that can differentiate into functional cardiomyocytes as well as vascular cells in cell culture may open the door to cardiovascular cell transplantation. However, the percentage of ES cells in embryoid bodies (EBs) which spontaneously undergo cardiovascular differentiation is low (< 10%), making strategies for their specific labeling and purification indispensable. Methods: The human connexin 40 (Cx40) promoter was isolated and cloned in the vector pEGFP. The specificity of the construct was initially assessed in Xenopus embryos injected with Cx40-EGFP plasmid DNA. Stable Cx40-EGFP ES cell clones were differentiated and fluorescent cells were enriched manually as well as via fluorescence-activated cell sorting. Characterization of these cells was performed with respect to spontaneous beating as well as via RT-PCRs and immunofluorescent stainings. Results: Cx40-EGFP reporter plasmid injection led to EGFP fluorescence specifically in the abdominal aorta of frog tadpoles. After crude manual enrichment of highly Cx40-EGFP- positive EBs, the appearance of cardiac and vascular structures was increased approximately 3-fold. Immuno fluorescent stainings showed EGFP expression exclusively in vascular-like structures simultaneously expressing von Willebrand factor and in formerly beating areas expressing alpha-actinin. Cx40-EGFP-expressing EBs revealed significantly higher numbers of beating cardiomyocytes and vascular-like structures. Semiquantitative RT-PCRs confirmed an enhanced cardiovascular differentiation as shown for the cardiac markers Nkx2.5 and MLC2v, as well as the endothelial marker vascular endothelial cadherin. Conclusions: Our work shows the feasibility of specific labeling and purification of cardiovascular progenitor cells from differentiating EBs based on the Cx40 promoter. We provide proof of principle that the deleted CD4 (Delta CD4) surface marker-based method for magnetic cell sorting developed by our group will be ideally suitable for transference to this promoter. Copyright (c) 2008 S. Karger AG, Basel.

Vaskuläre Erkrankungen sind als Ursache für Mortalität und Morbidität führend in westlichen Industrieländern. Es gibt zunehmend Hinweise darauf, dass oxLDL eine herausragende Rolle bei der Atheroskleroseinduktion bzw. -progression zukommt. Die initiale Wirkung von im Blut zirkulierendem oxLDL findet auf der Ebene der Interaktion mit dem vaskulären Endothel statt und resultiert in der endothelialen Dysfunktion. Da die Zellfunktion durch die Integrität der Endothelzellschicht bzw. deren interzelluläre Kommunikation mitbestimmt ist, wäre es denkbar, dass für die oxLDL-induzierten Veränderungen im Endothel u. a. die Beeinflussung der Zell-Zell-Kommunikation via Gap Junctions eine Rolle spielt. Bislang war jedoch wenig darüber bekannt, welchen Einfluss oxLDL auf die interzelluläre Kommunikation über Gap Junctions in Endothelzellen ausübt. Außerdem war es nicht geklärt, inwiefern diese Veränderungen in der Zell-Zell-Kommunikation die Induktion und den Schweregrad der oxLDL-induzierten Apoptose beeinflussen. Ziele der Studie waren daher i) zu analysieren, ob und über welche Mechanismen oxLDL einen Einfluss auf die interzelluläre Kommunikation über Gap Junctions in Endothelzellen ausübt, ii) zu untersuchen, welche Bedeutung der interzellulären Kommunikation über Gap Junctions bzw. einzelnen Connexinen bei der Induktion der Apoptose zukommt. Mittels der Dye-Transfer-Methode nach Farbstoffinjektion in eine einzelne Zelle konnten wir zeigen, dass oxLDL eine signifikante Steigerung der interzellulären Kommunikation über Gap Junctions in HUVEC induziert. Dieser Effekt ist dosisabhängig: er zeigte sich nur bei geringen oxLDL-Konzentrationen (15 bzw. 26 μg/ml) und wurde bei weiterer Erhöhung der Konzentration bis auf 100 μg/ml wiederum aufgehoben. Die durch oxLDL verstärkte Zell-Zell-Kommunikation wurde in Endothelzellen durch einen cAMP/PKA abhängigen Mechanismus vermittelt, wobei die cAMP-Freisetzung durch ein Cyclooxygenaseprodukt, wahrscheinlich Prostacyclin, getriggert wurde. Mittels immunhistochemischer Färbungen für Cx37 und Cx43 konnten wir nicht bestätigen, dass die oxLDL-induzierte Verstärkung der Zell-Zell-Kommunikation infolge einer Hochregulation der Connexin-Expression auftritt. Im zweiten Teil der Studie wurde der Einfluss von oxLDL auf die Apoptoseinduktion analysiert. Die Apoptose wurde mittels der Annexin V - Propidium Iodid Färbung bzw. durch Nachweis des Mitochondrienmembranpotentials durchflusszytometrisch erfasst. OxLDL verursachte einen signifikanten Anstieg der Apoptoserate in HUVEC. Zur Aufklärung der Rolle bestimmter Connexine wurden weitere Experimenten in Cx-transfizierten HeLa-Zellen durchgeführt. In diesen Zellen erhöhen einzelne Connexine die Apoptoserate in unterschiedlichem Ausmaß: Cx43 > Cx40 > Cx37. Um zu prüfen, ob die bloße Anwesenheit der Connexine dafür von Bedeutung war oder ob von Connexinen gebildete Gap Junctions dafür von Bedeutung waren, wurden weitere Experimente durchgeführt. Dafür wurden in einem neuen Versuchsansatz Zellen in Suspension (keine Zell-Zell-Kontakte) sowie adhärente Zellen im Monolayer (bestehende Zell-Zell- Kontakte) einer proapoptotischen Stimulation durch Streptonigrin unterzogen. Die Zellen in Suspension wiesen erst zu einem deutlich späteren Zeitpunkt apoptotische Veränderungen auf. Das deutet auf eine Beteiligung der Gap Junctions bei der Apoptoseinduktion hin. Diese Interpretation wurde durch Befunde einer weiteren Versuchsreihe bestätigt. Bei Inkubation von apoptotischen Cx43-positiven Zellen mit intakten Zellen wurde die Apoptoserate der Letzteren nur dann signifikant erhöht, wenn diese ebenfalls Connexin 43 exprimierten und funktionelle Gap Junctions mit den bereits apoptotischen Zellen de novo bilden konnten. Somit demonstriert diese Arbeit, dass Gap Junctions eine wichtige Rolle bei der Apoptoseinduktion spielen. In nachfolgenden Studien soll in Atherosklerose-Modellen überprüft werden, ob und inwiefern die hier beschriebenen Mechanismen auch unter den In-Vivo-Bedingungen bei den oxLDL-assoziierten Gefäß/Endothelschäden eine Rolle spielen.

The objective of this work was to examine follicular and oocyte growth in canine ovaries with light and electron microscopic techniques and to characterize canine oocytes during in vitro maturation. Ovaries of healthy bitches of different ages (4 months to 12.5 years)and breeds were used, which had undergone elective ovariohysterectomy at local veterinary clinics. The ovaries of 15 bitches were fixed in Bouin`s solution or paraformaldehyde (4%) for immunohistochemical studies and of three bitches in Karnovsky`s solution for electron microscopic evaluation. COCs and oocytes were recovered from 61 other bitches by slicing the ovaries. They were then examined before and after in vitro maturation (24 to 72 hours) in modified TCM-199 either by native evaluation or after fixation in paraformaldehyde (4%) and nuclear staining (propidium iodide/Hoechst 33342), immunofluorescence or glycohistochemistry. The evaluation of the fluorescence microscopic staining was performed by confocal laser scanning microscopy. Oocytes and COCs after 0, 24, 72 and 90 hours of in vitro maturation were also subjected to electron microscopic examination. The morphology of the canine ovary in light and electron microscopic aspects is comparable to that of other domestic animals. Primordial, primary, secondary and tertiary follicles were regularly seen. The diameter of the oocytes and of the germinal vesicle, as well as the thickness of the zona pellucida, clearly increases during oocyte development. Growing canine oocytes are characterized ultrastructurally by rapid growth in the number of cellular organelles, particularly mitochondria, smooth endoplasmatic reticulum and lipid droplets. Mitotic division starting at the primary follicle stage can be regularly observed by immunostaining with the proliferation marker Ki-67. Further immunohistochemical studies on ovaries indicate that estrogen receptors alpha and beta, as well as MMP-1, -2, -14 and TIMP-2 show a specific distribution in bitches. Canine oocytes could easily be isolated by slicing the ovaries. The number of recovered oocytes was clearly influenced by the age of the donor bitch but not by the breed, the reproductive status or the transportation time between time of surgery in the veterinary clinic and the recovery of the oocytes in the laboratory. 48% of all isolated oocytes had a dark homogenous ooplasm and multiple dense layers of cumulus cells. After in vitro maturation, morphological changes like the formation of vesicles and the loss of cumulus cells could be observed in most of the COCs. Immediately after recovery, the nuclei of all oocytes were at the germinal vesicle stage, although the chromatin showed different degrees of condensation. While first signs of the resumption of meiosis were seen after 24 hours of culture, only one oocyte in metaphase II could be seen after 72 hours. Nuclear and cytoplasmatic maturation could be detected by electron microscopy for up to 24 hours of in vitro culture, as well as signs of degeneration, which were even more prominent after longer culture periods. The immunoreaction of ZP3beta, alpha-Tubulin and Connexin 43 and the binding sites of the lectins WGA and SBA showed characteristic changes in canine oocytes and COCs before and after in vitro maturation.

In the present study, the testes of 32 bovine embryos with different crown-rump length (2.5- 90 cm CRL) and of 15 sexually mature bulls (Deutsches Fleckvieh) were investigated using light- and electron microscope as well as glycohistochemical and immunohistochemical methods. The gestation period was divided into 3 stages; early, mid, and late gestation. Developmental changes in the testicular morphogenesis were therefore analyzed in details during these phases. Generally, embryonic development of bovine testis involves the same mechanism described in other mammals. At the first stage of this study (2.5 cm CRL/43 dpc), the anlage of the testes protruded to the coelomic cavity as paired bean-shaped structures on either side of the dorsal mesentery medial to the mesonephros. It consists of primitive testicular cords, interstitium, and rete testis blastema. Proceeding with fetal age, these basic testicular structures are further differentiated. The tunica albuginea is separated into two layers: an outer fibrous layer (tunica fibrosa) with some mesenchymal cells, numerous fibroblast, and much fibrous content and an inner cellular layer with several blood vessels (tunica vasculosa). The testicular cords are surrounded by a marked basal lamina and peritubular cells and lined by two types of cells: a large number of dark polygonal cells with irregular nuclei, pre-Sertoli cells and small number of large light round cells with relatively round nuclei, the prespermatogonia. The average number of the germ cells per cross section of cord increases, particularly form 3.5 to 14 cm CRL, resulting in a germ cell maximum at the end of this stage (14 cm CRL). Although most of the germ cells are located toward the periphery of the cord, some are also found in the center. Pre-Sertoli cells form a complete layer at the periphery of the cords. Generally, these cells are irregular in shape and numerous but considerably smaller than the germ cells. Unlike prespermatogonia, mitotic figures are seen in pre-Sertoli cells during the whole embryonic life. As a consequence of the expansion in the interstitium, the seminiferous cords are progressively separated from each other. The testicular interstitium is rapidly differentiated and is composed of several islets or clusters of polygonal Leydig cells, peritubular flattened cells surrounding the testicular cords, connective tissue cells, and numerous blood vessels. In the present study, fetal Leydig cells were first recognized at 3.5 cm CRL. Thereafter, the average number of these cells is rapidly increased to attain their maximum with the end of the first gestation period (14 cm CRL). This generation of Leydig cells however dedifferentiates progressively with developmental age. A continuous system of basal lamina joins the testicular cords with rete strands from 10 cm CRL and onwards. This system establishes the first connection between these two testicular components via ill-developed uncanalized straight tubules (tubuli recti). Rete testis channels are lined by simple layer of cuboidal epithelium with round nuclei occupying most of the cytoplasm and enclosed by well-defined basal lamina. The adult bovine testis is enclosed by a connective tissue capsule, tunica albuginea, composed predominantly of collagen fibers and few elastic fibers. Most of the testicular parenchyma is made up of the convoluted seminiferous tubules (tubuli seminiferi contorti), two-ended convoluted loops, with both ends opening into the rete testis via specialized terminal segments. The seminiferous tubules of sexually mature bulls are enclosed by a distinct lamina propria and are lined by two cell populations, non-proliferating Sertoli cells and highly proliferating spermatogenic cells. The bovine lamina propria consists of basal lamina, collagen and elastic fibers, and 3-5 layers of partially overlapping myofibroblasts. Additionally, fibrocytes, collagen fibrils, and fibroblasts-like cells form the outermost border of the tubulus. Sertoli cells are easily identifiable elements of the seminiferous epithelium. Adult Sertoli cells are large irregularly shaped cells with their broad bases resting on the basal lamina while the remaining cytoplasmic processes extend upward to the tubular lumen. They are characterized by round or oval euchromatin-rich nuclei situating in the basal portion near the basal lamina of the seminiferous tubules. Adult bovine germ cells are present in four morphologically different groups, i.e., spermatogonia, spermatocytes, spermatids, and spermatozoa. The seminiferous cycle stages are identified using changes in the germ cell nuclei as well as location and shape of spermatids. According to this method, eight stages are defined in the seminiferous epithelium of bovine. The interstitial or intertubular tissue of adult bovine testis consists of Leydig cells, macrophages, scattered lymphocytes and plasma cells, and contains numerous blood and lymph vessels. Not all Leydig cells have contact to blood or lymph capillaries. The excurrent duct system of the adult bovine testis consists of terminal segment of the convoluted seminiferous tubules, straight tubules, and rete testis. The terminal segment can be further subdivided into a proximal (transitional) region, middle portion, and distal part (terminal plug). The proximal region is lined by typical Sertoli cells while the last two parts are lined by modified Sertoli cells. The tubulus rectus of adult bovine testis is composed of three morphologically different regions: a proximal cup-shaped region, a middle narrow stalk, and a distal festooned portion. The rete testis is a complicated centrally positioned meshwork of intercommunicating channels that lies within the mediastinum testis parallel to the long axis of epididymis. The simple cuboidal epithelium of straight tubules and rete testis is shown to contain some lymphocytes and macrophages. The cellular distribution of glycoconjugates within the fetal and adult bovine testis was investigated using thirteen (ConA, PSA, LCA, PNA, GSA-I, ECA, DBA, SBA, HPA, VVA, WGA, UEA-I, LTA) different fluorescein isothiocyanate (FITC) conjugated lectins. In fetal testes, detection of sugar moieties by lectins was carried out on Bouin õ s-fixed paraffin-embedded sections while in adult it was performed on both Bouin õ s-fixed paraffin-embedded and acetone-fixed frozen sections. Only five lectins (PSA, PNA, GSA-I, DBA, WGA) showed a positive reaction in the embryonic testes. PNA, GSA-I, DBA, and WGA were detected in the germ cells whereas PSA, DBA and WGA labeled the fetal Leydig cells. None of the lectins used was observed in the pre-Sertoli cells. Further on, some lectins were seen in tunica albuginea (PSA, PNA, GSA-I, WGA), basal lamina of testicular cords (PSA, WGA), interstitial blood vessels (PSA, GSA-I, WGA), mediastinum testis (PSA, PNA, WGA) and rete testis epithelium (PNA). In adult animals, spermatogonia and spermatocytes were positively stained with PSA, LCA, DBA, SBA, and VVA. All the lectins investigated except that of the fucose-binding lectin (UEA-I and LTA) were definitely detected in the acrosome of round and elongated spermatids. These results indicate a role for carbohydrates in spermiogenesis. Apical Sertoli cells processes and Leydig cells were weakly stained with PSA and LCA as well. DBA binding sites were also seen in the Leydig cells. Immunohistochemical studies were performed using the Avidin-Biotin-Peroxidase Complex (ABC) method for localization of fibroblast growth factor-1 (FGF-1), fibroblast growth factor-2 (FGF-2), S-100, laminin, alpha-smooth muscle actin (á -SMA), vascular endothelial growth factor (VEGF), connexin 43 (Cx43), CD4, CD8, CD68, angiotensin-converting enzyme (ACE), and galactosyltransferase (GalTase) in the bovine testis. The expression of FGF-1 and FGF-2 was further investigated in the adult bovine testis using in situ hybridization and PCR. Immunohistochemically, FGF-1 was seen in the Sertoli cells, Leydig cells, endothelium of the blood vessels, and epithelium of straight tubules and rete testis of fetal and adult testis. It was additionally detected in spermatogonia and spermatids of sexual mature animals. FGF-2 exhibited a striking positive reaction in fetal (from 6 to 30 cm CRL) and adult Leydig cells. Moreover, it showed marked reaction in the endothelium of blood vessels and in the epithelium of tubulus rectus and rete testis. FGF-2 was also localized in some spermatogonia, and myofibroblasts. By means of in situ hybridization, FGF-1 and FGF-2 mRNA were found in Leydig and Sertoli cells as well as in the modified Sertoli cells of the terminal segment. FGF-1 transcripts were additionally recognized in the straight tubules and rete testis epithelium. Distinct S100 immunostaining was observed in the Sertoli cells, endothelium of blood vessels and in the rete testis epithelium of fetal and adult testis. Laminin was localized to the basal lamina of seminiferous tubules, blood vessels, myofibroblasts, and rete testis. Although á -SMA was detected in smooth muscle cells of the blood vessels, no immunoreactivity was seen in the peritubular cells during the whole gestation period. The myofibroblasts surrounding the seminiferous tubules and rete testis showed intense positive reaction for á -SMA in the adult testis. VEGF was detected in the acrosomes of the elongating spermatids. Connexin 43 was localized to gap junctions between Leydig cells in the fetal and adult life as well as to the seminiferous epithelium apical to spermatogonia and basal to spermatocytes, a position correlating with Sertoli-Sertoli cell junctions. The detection of cells positive for CD4, CD8, CD68 within the adult testis interstitium clearly indicate the presence of lymphocytes and macrophages within this testicular compartment. GalTase showed striking positive reaction in the Golgi complex of Sertoli cells, Leydig cells, and some spermatocytes as well as at the cell membrane of elongating spermatids and in the simple cuboidal epithelium of rete testis. ACE positive reaction was found in the prespermatogonia (only at 6-10 cm CRL) and in fetal and adult testicular blood vessels. The functional significance of these immunocytochemically-demonstrated proteins is discussed.