Voltage readout from a piezoelectric intracochlear acoustic transducer implanted in a living guinea pig.

The ability to measure the voltage readout from a sensor implanted inside the living cochlea enables continuous monitoring of intracochlear acoustic pressure locally, which could improve cochlear implants. We developed a piezoelectric intracochlear acoustic transducer (PIAT) designed to sense the acoustic pressure while fully implanted inside a living guinea pig cochlea. The PIAT, fabricated using micro-electro-mechanical systems (MEMS) techniques, consisted of an array of four piezoelectric cantilevers with varying lengths to enhance sensitivity across a wide frequency bandwidth. Prior to implantation, benchtop tests were conducted to characterize the device performance in air and in water. When implanted in the cochlea of an anesthetized guinea pig, the in vivo voltage response from the PIAT was measured in response to 80-95 dB sound pressure level 1-14 kHz sinusoidal acoustic excitation at the entrance of the guinea pig's ear canal. All sensed signals were above the noise floor and unaffected by crosstalk from the cochlear microphonic or external electrical interference. These results demonstrate that external acoustic stimulus can be sensed via the piezoelectric voltage response of the implanted MEMS transducer inside the living cochlea, providing key steps towards developing intracochlear acoustic sensors to replace external or subcutaneous microphones for auditory prosthetics.

Imunolocalização de receptores de leptina no ovário de preás (Galea spixii Wagler, 1831) / Immunolocalization of leptin receptor of Spix's Yellow-toothed Cavy (Galea spixii Wagler, 1831) ovary

A leptina, uma citocina produzida pelas células adiposas, é alvo da comunidade científica por acreditarem que ela apresente impacto sobre a reprodução dos animais promovendo a puberdade, foliculogênese e oogênese, ciclo estral e auxiliando na fecundação. A compreensão dos mecanismos que controlam a atividade reprodutiva de preás (Galea spixii) possui papel relevante para a preservação da espécie. Desta forma, o presente trabalho propôs analisar a imunolocalização dos receptores de leptina (Ob-R) no ovário de preás. Coletaram-se os ovários de 20 fêmeas adultas, não prenhes e saudáveis. As amostras foram fixadas em paraformaldeído a 4% em tampão fosfato, incluídas em parafina e seccionadas para a realização de imunohistoquímica (IHC). As secções foram fotomicrografadas e avaliadas quanto à intensidade da reação. Observou-se forte imunorreação no oócito e nas células da teca, moderada nas células do estroma ovariano e nas células luteínicas grandes e fracamente coradas nas células da granulosa, endoteliais, perivasculares e células luteínicas pequenas. Quando comparado a expressão de receptores ao longo do desenvolvimento folicular foi observado que o oócito e as células da teca se mantiveram com expressão na mesma intensidade. Entretanto, as células da granulosa apresentaram forte marcação nos estádios pré-antrais enquanto que nos folículos antrais apresentou fraca intensidade. Concluímos que em ovários de Galea spixii existe a presença de Ob-R nas principais estruturas do ovário sugerindo que este hormônio desempenhe papel fundamental na reprodução desta espécie.

Leptin, a cytokine produced by adipose cells, is the target of the scientific community for believing that it has an impact on the reproduction of the animals promoting puberty, folliculogenesis and oogenesis, estrous cycle and aiding in fertilization. The understanding of the mechanisms controlling the reproductive activity of Spix's Yellow-toothed Cavy (Galea spixii) plays a relevant role in the preservation of the species. Thus, the present study proposed to analyze the immunolocalization of leptin receptors (Ob-R) in the ovary of cavies. Ovaries from 20 adult, non-pregnant, healthy females were collected. The samples were fixed in 4% phosphate buffered paraformaldehyde, embedded in paraffin and sectioned for immunohistochemistry. The sections were photomicrographs and intensity of the reaction was measured. Strong immunoreaction was observed in oocyte and theca cells, moderate in ovarian stromal cells and large luteal cells and weak stained in granulosa, endothelial, perivascular and small luteal cells. When compared to receptor expression along follicular development it was observed that the oocyte and the theca cells remained with expression at the same intensity. However, the granulosa cells presented strong stained in the preantral stages, whereas in the antral follicles it presented low intensity. We conclude that in the ovaries of Galea spixii there is the presence of Ob-R in the main structures of the ovary sugesting that this hormone plays a fundamental role in the reproduction of this species.

Accuracy of real-time shear wave elastography in the assessment of normal liver tissue in the guinea pig (cavia porcellus).

Shear wave elastography is a novel technique enabling real-time measurement of the elasticity of liver tissue. The color map is superimposed on the classic ultrasound image of the assessed tissue, which enables a precise evaluation of the stiffness of the liver tissue. The aim of the study was to assess the stiffness of normal liver tissue in the guinea pig using shear wave elastography. The study was carried out on 36 guinea pigs using the SuperSonic Imagine Aixplorer scanner, and a 1 to 6 MH convex SC6-1 transducer. An ultrasound guided Try-Cut liver core needle biopsy was carried out in all the studied animals and the collected samples were examined to exclude pathological lesions. The mean liver tissue stiffness ranged from 0.89 to 5.40 kPa. We found that shear wave elastography is an easy, non-invasive technique that can be used to assess the stiffness of liver tissue. The obtained results can be used in future studies to assess the types and changes of liver tissue in the course of various types of liver disease.

Culture, characterization and differentiation of neural precursors from the central nervous system of guinea pigs (Cavia porcellus Linnaeus, 1758) / Cultura, caracterização e diferenciação de precursores neurais do sistema nervoso central de porquinho-da-índia (Cavia porcellus Linnaeus, 1758)

Potentially neurogenic areas were initially identified by incorporation of bromodeoxyuridine (BrdU) in cells underlying the subventricular zone (SVZ) of the lateral ventricles wall, hippocampus and olfactory bulbs of newborn guinea pigs. Neural precursors from the SVZ were cultured in suspension, generating neurospheres (NSFs), which, upon dissociation were able to generate new NSFs. Upon culture in the absence of growth factors, cells dissociated from NSFs displayed evidence for neural differentiation, giving rise to cells from neural lineage. Flow cytometry analysis for of NSFs-derived cells after differentiation revealed approximately 13.3% nestin positive, 5.5% Beta-III-tubulin positive, 9% GFAP positive and 7.8% mGalC positive. Functional assays by measurement of calcium influx upon gamma butiric amino acid (GABA) and glutamate stimuli, revealed stimulation in differentiated cells, an indicator of neuronal differentiation. The ability of guinea pig SVZ cells to originate functional neurons in vitro is promising for research and towards a future use of neural stem cells in the therapy of neurological disorders.(AU)

Áreas potencialmente neurogênicas foram identificadas por incorporação de bromodeoxiuridina (BrdU) na zona subventricular (SVZ) dos ventrículos laterais, hipocampo e bulbos olfatórios de cobaias neonatos. Precursores neurais provenientes da SVZ foram cultivados em suspensão, resultando na geração de neuroesferas (NSFs), que quando dissociadas foram capazes de proliferar e gerar novas NSFs. Quando cultivadas na ausência de fatores de crescimento, as células provenientes de NSFs dissociadas apresentaram evidências de diferenciação neuronal, dando origem a células da linhagem neural. Citometria de fluxo em células das NSFs após a diferenciação revelou aproximadamente 13,3% positivas para nestina, 5,5% positivas para Beta-III-tubulina, 9% positivas para GFAP e 7,8% positivas para mGalC. Testes de funcionalidade pela mensuração de influxo de cálcio após estímulo com ácido gama amino butírico (GABA) e glutamato revelaram a estimulação de células diferenciadas, um indicador de função neuronal. A capacidade de células da SVZ de fetos de cobaias originarem células neurais funcionais in vitro é promissora para a pesquisa e eventual uso terapêutico de células tronco em disordens do sistema nervoso.(AU)

Characterization of the estrous cycle in Galea spixii(Wagler, 1831) / Caracterização do ciclo estral de Galea spixii (Wagler, 1831)

The Galea spixii inhabits semiarid vegetation of Caatinga in the Brazilian Northeast. They are bred in captivity for the development of researches on the biology of reproduction. Therefore, the aim of this study is characterize the estrous cycle of G. spixii, in order to provide information to a better knowledge of captive breeding of the species. The estrous cycle was monitored by vaginal exfoliative cytology in 12 adult females. After the detection of two complete cycles in each animal, the same were euthanized. Then, histological study of the vaginal epithelium, with three females in each phase of the estrous cycle was performed; five were paired with males for performing the control group for estrous cycle phases, and three other were used to monitor the formation and rupture of vaginal closure membrane. By vaginal exfoliative cytology, predominance of superficial cells in estrus, large intermediate cells in proestrus, intermediate and parabasal cells, with neutrophils, in diestrus and metestrus respectively was found. Estrus was detected by the presence of spermatozoa in the control group. By histology, greater proliferation of the vaginal epithelium in proestrus was observed. We conclude that the estrous cycle of G. spixii lasts 15.8 ± 1.4 days and that the vaginal closure membrane develops until complete occlusion of the vaginal ostium, breaking after few days. Future studies may reveal the importance of this fact for the reproductive success of this animal...

Os Galea spixii habitam a vegetação semiárida da Caatinga, no Nordeste brasileiro. Eles são criados em cativeiro para realização de pesquisas relacionadas a biologia da reprodução. Sendo assim, o objetivo deste trabalho foi caracterizar o ciclo estral de G. spixii para obtenção de informações que melhorem o conhecimento do manejo reprodutivo da espécie em cativeiro. O ciclo estral foi monitorado por citologia esfoliativa vaginal em doze fêmeas adultas. Após a detecção de dois ciclos completos em cada animal, os mesmos foram eutanasiados. Em seguida foi realizado estudo histológico do epitélio vaginal com três fêmeas em cada fase do ciclo estral; cinco foram pareadas com machos para realização do grupo controle e outras três fêmeas foram utilizadas para monitorar a formação e ruptura da membrana de oclusão vaginal. Através de citologia esfoliativa vaginal, constatou-se predomínio de células superficiais em estro, células intermediárias grandes em proestro, células intermediárias pequenas e células parabasais com presença de neutrófilos em diestro e metaestro, respectivamente. O estro foi detectado pela presença de espermatozoides no grupo controle. Através de histologia, observou-se uma maior proliferação no epitélio vaginal no proestro. Concluiu-se que o ciclo estral de G. spixii dura em média 15.8 ± 1.4 dias e a membrana de oclusão vaginal se desenvolve até completa oclusão do óstio vaginal externo, rompendo-se em poucos dias. Futuros estudos podem revelar a importância deste último fato para o sucesso reprodutivo deste animal...

ADAM15 participates in fertilization through a physical interaction with acrogranin.

Mammalian fertilization is completed by direct interaction between sperm and egg. This process is primarily mediated by both adhesion and membrane-fusion proteins found on the gamete surface. ADAM1, 2, and 3 are members of the ADAMs protein family, and have been involved in sperm-egg binding. In this study, we demonstrate the proteolytic processing of ADAM15 during epididymal maturation of guinea pig spermatozoa to produce a mature form a size of 45 kDa. We find that the size of the mature ADAM15, 45 kDa, in cauda epididymal spermatozoa indicates that the pro-domain and metalloprotease domain are absent. In addition, using indirect immunofluorescence, ADAM15 was found throughout the acrosome, at the equatorial region and along the flagellum of guinea pig spermatozoa. After acrosome reaction, ADAM15 is lost from the acrosomal region and retained in the equatorial region and flagellum. In this study, we also report the first evidence of a complex between ADAM15 and acrogranin. By immunoprecipitation, we detected a protein band of 65 kDa which co-immunoprecipated together ADAM15. Analysis of the N-terminal sequence of this 65 kDa protein has revealed its identity as acrogranin. In addition, using cell-surface labeling, ADAM15 was found to be present on the cell surface. Assays of heterologous fertilization showed that the antibody against acrogranin inhibited the sperm-egg adhesion. Interestingly, ADAM15 and acrogranin were also found associated in two breast cancer cell lines. In conclusion, our results demonstrated that ADAM15 and acrogranin are present on and associated with the surface of guinea pig spermatozoa; besides both proteins may play a role during sperm-egg binding.

Progesterone receptor expression declines in the guinea pig uterus during functional progesterone withdrawal and in response to prostaglandins.

Progesterone withdrawal is essential for parturition, but the mechanism of this pivotal hormonal change is unclear in women and other mammals that give birth without a pre-labor drop in maternal progesterone levels. One possibility suggested by uterine tissue analyses and cell culture models is that progesterone receptor levels change at term decreasing the progesterone responsiveness of the myometrium, which causes progesterone withdrawal at the functional level and results in estrogen dominance enhancing uterine contractility. In this investigation we have explored whether receptor mediated functional progesterone withdrawal occurs during late pregnancy and labor in vivo. We have also determined whether prostaglandins that induce labor cause functional progesterone withdrawal by altering myometrial progesterone receptor expression. Pregnant guinea pigs were used, since this animal loses progesterone responsiveness at term and gives birth in the presence of high maternal progesterone level similarly to primates. We found that progesterone receptor mRNA and protein A and B expression decreased in the guinea pig uterus during the last third of gestation and in labor. Prostaglandin administration reduced while prostaglandin synthesis inhibitor treatment increased progesterone receptor A protein abundance. Estrogen receptor-1 protein levels remained unchanged during late gestation, in labor and after prostaglandin or prostaglandin synthesis inhibitor administration. Steroid receptor levels were higher in the non-pregnant than in the pregnant uterine horns. We conclude that the decreasing expression of both progesterone receptors A and B is a physiological mechanism of functional progesterone withdrawal in the guinea pig during late pregnancy and in labor. Further, prostaglandins administered exogenously or produced endogenously stimulate labor in part by suppressing uterine progesterone receptor A expression, which may cause functional progesterone withdrawal, promote estrogen dominance and foster myometrial contractions.

Effects of changes in vertical occlusal dimension on heart rate fluctuations in guinea pigs.

BACKGROUND: We have previously reported that the decrease of the vertical occlusal dimension (VOD) led to heart failure and abnormalities in creatine phosphokinase (CPK) in guinea pigs. In the present study, we investigated the autonomic activity and the origin of the abnormality in CPK under different occlusal conditions. MATERIALS AND METHODS: Guinea pigs were separated into the following five groups: untreated control, reduced VOD, slit, restored VOD and increased VOD groups and compared for their electrocardiogram and heart rate fluctuations for two weeks using Fluclet, computer software. RESULTS: The control group revealed no changes in heart rate fluctuations or posture. The reduced VOD group exhibited a two-phase wave of heart rate fluctuations, with the first peak 0-2 days after teeth grinding, and the second peak starting from 4 days after teeth grinding until sudden death (usually 12th day), accompanied by head drop. The slit and the restored VOD groups exhibited only the first peak. The increased VOD group, with approximately 3 mm-thick acrylic pellets bonded to the posterior teeth, showed no heart rate fluctuations. Body weight loss was most prominent in the reduced VOD group, and became much milder in the order of increased VOD, restored and slit groups. The reduced VOD group exhibited transient elevation of skeletal muscle type of CPK isozyme activity within two days after treatment. CONCLUSION: The present study suggests that the first peak of heart rate fluctuations is caused by pulpal stimulation, and the second peak by excessive contraction (excessive excitation of the motor output system and the autonomic nervous system) of the masticatory muscles. On the other hand, increased VOD did not influence either the motor or the autonomic nervous system.

Diseases of geriatric Guinea pigs and chinchillas.

Guinea pigs and chinchillas, which have become increasingly popular pets, are today more commonly presented as adult and geriatric animals. Problems of older guinea pigs and chinchillas include those related to diet and management, infections whose symptoms are more common in older animals, and neoplasia.

Estereología renal en el cobayo (Cavia porcellus) / Renal stereology in the guinea pig (Cavia porcellus)

El cobayo (Cavia porcellus) es un roedor perteneciente al Orden Rodentia y a la Familia Caviidae, utilizado como animal de laboratorio y de consumo humano. Los parámetros cuantitativos del riñón entregan importante información de su morfofunción dada su labor en la homeostasis del organismo. El objetivo de este estudio fue describir el riñón de cobayo (Cavia porcellus), analizando las características estereológicas para futuros estudios experimentales. Se utilizaron 5 cobayos machos, obtenidos del Bioterio de la Universidad de La Frontera, Temuco, Chile. El riñón de cobayo pesó 3,2 g, aproximadamente. El riñón posee 140.298 glomérulos en total, Nv de 458 mm³, Vv de 7,89% y Sv de 3,58 mm²/ mm³. El volumen glomerular del riñón fue de 1,73 x 10(4)mm³ y el diámetro glomerular de 90 jm. Factores como especie, edad, peso corporal, peso y volumen renal, son importantes a considerar, ya que diferencian los resultados en investigaciones morfofuncionales.

The guinea pig, (Cavia porcellus) is a rodent pertaining to the Rodentia group and the Caviidae family, used as a laboratory animal and for human consumption. Quantitative parameters of the kidney provides important information of its morphofunction, given its labor in the organism's homeostasis. The aim or this study was to describe the kidney of the guinea pig (Cavia porcellus), analyzing the stereological characteristics for future experimental studies. Five male guinea pigs (Cavia porcellus) obtained from the Biotery of the Universidad de la Frontera, Temuco, Chile, were used. The kidney of the guinea pig weighed approximately 3.2g. The kidney has 140,298 total glomerulus, Nv of 458 mm³, Vv of 7.89% and Svof 3.58mm²/mm³. The glomerular volume of the kidney was of 1.73 x 10(4)mm³ and a glomerular diameter of 90 urn. Factors such as species, age, body weight and renal volume, are important to consider, as they differentiate the results in the morphofunctional investigations.

Regional changes in the spatio-temporal pattern of progesterone receptor (PR) expression in the guinea-pig genital tract as parturition approaches.

Normal parturition in guinea-pig involves changes in responsiveness of the genital tract to estrogen and progesterone. To better characterize endocrine control of guinea-pig parturition, protein and mRNA expression of estrogen receptor-alpha (ERalpha) and progesterone receptor (PR) were quantitatively evaluated in lower (LUS) and upper (UUS) uterine segments, cervix (C) and pubic symphyseal ligament (PSL) at three stages of pregnancy (established based on interpubic distance, 0mm: non-relaxed group, 4-6mm: 5 days before parturition, 11-14 mm: 1-2 days prepartum) and immediately after parturition. Towards parturition, no changes in PR mRNA levels were recorded in the UUS, whereas the LUS displayed a gradual increase. PR transcripts exhibited decreased levels during parturition in C and PSL. Levels of PR mRNA were increased in the LUS compared with that of the UUS only at parturition. Regarding protein expression during parturition, PR levels decreased in the UUS whereas in the LUS increased. In C and PSL, PR protein expression decreased 1-2 days prepartum and remained low during parturition. None of the regions studied showed changes in mRNA or protein expression of ERalpha. Therefore, functional regionalization of the guinea-pig genital tract is associated with changes in the spatio-temporal pattern of PR expression as parturition approaches.

Protease-activated receptor-2 activation exaggerates TRPV1-mediated cough in guinea pigs.

A lowered threshold to the cough response frequently accompanies chronic airway inflammatory conditions. However, the mechanism(s) that from chronic inflammation results in a lowered cough threshold is poorly understood. Irritant agents, including capsaicin, resiniferatoxin, and citric acid, elicit cough in humans and in experimental animals through the activation of the transient receptor potential vanilloid 1 (TRPV1). Protease-activated receptor-2 (PAR2) activation plays a role in inflammation and sensitizes TRPV1 in cultured sensory neurons by a PKC-dependent pathway. Here, we have investigated whether PAR2 activation exaggerates TRPV1-dependent cough in guinea pigs and whether protein kinases are involved in the PAR2-induced cough modulation. Aerosolized PAR2 agonists (PAR2-activating peptide and trypsin) did not produce any cough per se. However, they potentiated citric acid- and resiniferatoxin-induced cough, an effect that was completely prevented by the TRPV1 receptor antagonist capsazepine. In contrast, cough induced by hypertonic saline, a stimulus that provokes cough in a TRPV1-independent manner, was not modified by aerosolized PAR2 agonists. The PKC inhibitor GF-109203X, the PKA inhibitor H-89, and the cyclooxygenase inhibitor indomethacin did not affect cough induced by TRPV1 agonists, but abated the exaggeration of this response produced by PAR2 agonists. In conclusion, PAR2 stimulation exaggerates TRPV1-dependent cough by activation of diverse mechanism(s), including PKC, PKA, and prostanoid release. PAR2 activation, by sensitizing TRPV1 in primary sensory neurons, may play a role in the exaggerated cough observed in certain airways inflammatory diseases such as asthma and chronic obstructive pulmonary disease.

Social stimuli cause changes of plasma oxytocin and behavior in guinea pigs

The neuropeptide oxytocin (OXT) is a key factor in the initiation and regulation of sociosexual behavior. The present study analyzes the effects of cohabitation and social challenge on plasma OXT concentration rates in guinea pig pairs in relation to male sociosexual behavior. The cohabitation phase lasted 3 days. On day 4, the pair was socially challenged by introducing an unfamiliar male. Displayed male sexual behavior varied significantly during cohabitation, with peaks on day 1. Sociopositive behavior, i.e., side-by-side contact, was increased on days 3 and 4. Cohabitation per se led to elevated plasma OXT concentrations only in males. In contrast, both sexes reacted with increased plasma OXT concentrations to the social challenge (day 4). At that time, male OXT was significantly correlated with sexual behavior and female OXT with sociosexual behavior received from the partner. Additionally, pairs were synchronized in their OXT release during days 3 and 4. We conclude that cohabitation causes sexually dimorphic plasma OXT concentration patterns in guinea pigs. Secondly, the conformity of OXT release in both sexes may represent an endocrine marker for long-term cohabitation, which is reflected behaviorally by increased spatial proximity.

The effects of superior ovarian nerve sectioning on ovulation in the guinea pig.

The effects on spontaneous ovulation associated with the unilateral or bilateral sectioning of the superior ovarian nerves (SON) were analyzed in guinea pigs at different time intervals of the estrous cycle. Day 1 of the estrous cycle was defined as the day when the animal presents complete loss of the vaginal membrane (open vagina). Subsequent phases of the cycle were determined by counting the days after Day 1. All animals were autopsied on the fifth day of the estrous cycle after surgery. Sectioning the right, left, or both SONs on day 5 (early luteal phase) resulted in a significant increase in the number of fresh corpora lutea. Ovulation increased significantly when the left SON (L-SON) was sectioned during late follicular phase (day 1) and medium luteal phase (day 8). When surgery was performed on days 1 or 8, neither sectioning the right SON (R-SON) nor sectioning the SON bilaterally had an apparent effect on ovulation rates. Similarly, ovulation rates were not affected when unilateral (right or left) or bilateral sectioning of the SON was performed during late luteal phase two (day 12). Unilateral or bilateral sectioning of the SON performed during the early luteal phase (day 5) was associated with a significant decrease in uterine weight. A comparable effect was observed when the L-SON was sectioned during late follicular phase (day 1), or medium luteal phase (day 8). No effects on uterine weight were observed when unilateral or bilateral sectioning of the SON was performed during late luteal phase. Our results suggest that in the guinea pig the SON modulates ovulation, and that the degree of modulation varies along the estrous cycle. The strongest influence of the SONs on ovulation occurs during early luteal phase, and decrease thereafter, being absent by late luteal phase. In addition, sectioning the left or the right SON caused different responses by the ovaries of adult guinea pigs. This paper discusses the mechanisms by which ovulation increased when the SON was surgically cut.

Reproductive medicine of rabbits and rodents.

The small animal practitioner is likely to be called upon to help nontraditional pets such as rabbits, rodents, and ferrets. The more information veterinarians have regarding normal anatomy, physiology, reproduction, medicine, anesthesia, and surgery of these unusual pets, the more likely they will be able to help their owners. This article presents an overview of routine and emergency reproductive concerns that the small animal practitioner may face when presented with nontraditional mammalian patients.

Effects of sympathetic denervation on follicular distribution, oestradiol and progesterone serum levels in prepubertal hemi-ovariectomized female guinea pig.

Hemi-gonadectomy performed in prepubertal female guinea pigs is followed by a compensatory ovarian hypertrophy (COH) and compensatory ovulation (CO). Sympathetic denervation diminished the COH (left ovary: 28 +/- 1.6% versus 46 +/- 4% (control), P < 0.05; and right ovary: 21.3 +/- 3.2% versus 34.2 +/- 3.7% (control), P < 0.01) and does not modify the CO. The mean follicular diameter increased only in the right ovary of hemi-gonadectomized animals. This increase is greater in the hemi-gonadectomized-denervated groups. The mean follicular diameter measured in the right and left ovaries showed an opposite response in hemi-ovariectomized and hemi-ovariectomized-denervated animals: the diameter increased in the right ovary without modifications in the left. Present results add further support to the participation of ovarian innervation on the mechanisms, which regulate follicular development.

Does nitric oxide act as a cellular messenger in muscarinic endometrial secretion in the guinea-pig?

Uterine secretory cells receive a sympathetic cholinergic secremotor innervation. Nitric oxide (NO) has been suggested to be a second messenger of neurogenic modulated glandular secretion of the seminal vesicle. Thus a similar pattern for nervous induced carbohydrate secretion of the endometrium was assumed. The nitric oxide synthase (NOS) activity was estimated via formation of L-citrulline from L-arginine and histochemically with the nicotinamide-adenine dinucleotide phosphate diaphorase (NADPH-d) nitro blue technique. The carbohydrate secretion from everted uterine horns placed in organ baths was estimated. A calcium dependent formation of citrulline was found in the uterine horn suggesting an NOS activity. Strong NADPH staining cells were found in the glandular ducts of the endometrium and in the epithelial linings of the oviduct. Carbachol induced carbohydrate secretion of the endometrium while N-nitro L-arginin (L-NNA) and N-nitro L-arginin methyl ester (L-NAME) inhibited the carbachol induced secretion. The isomer D-NAME had no effect on carbachol induced secretion. When L-arginine was administered together with L-NNA no inhibitory effect on carbachol induced secretion was seen. L-arginine only had no effect on carbohydrate secretion. The NO donor glyceryl tritrate increased carbohydrate secretion but no synergistic effect was seen in combination with carbachol. The results suggest that glandular NO production is a prerequisite for muscarinic carbohydrate secretion of the endometrium.

Different types of oestrous cycle in two closely related South American rodents (Cavia aperea and Galea musteloides) with different social and mating systems.

A comparative approach was used to investigate two closely related South American rodent species: the wild cavy (Cavia aperea) and the yellow-toothed cavy (Galea musteloides). These species of wild guinea-pig inhabit different habitats and show divergent social and mating systems. Cavia have a polygynous mating system, whereas in Galea promiscuous mating occurs. These observations correspond to functional variations in sperm characteristics, which might be interpreted as adaptations to different reproductive patterns in the females of both species. Twenty-two female C. aperea and G. musteloides (11 of each species) were investigated to elucidate differences in the characteristics of the oestrous cycles. The experimental design consisted of three stages, in which the degree of contact between the sexes was successively changed. During these stages, the reproductive cycle of the females was monitored by examining the condition of the vaginal closure membrane, analysing vaginal smears and determining serum concentrations of oestrogens and progesterone. The results revealed different types of oestrous cycle in the two species. Female C. aperea showed periodical cycles with spontaneously occurring oestrous periods, ovulation and corpus luteum activity. In contrast, in female G. musteloides, oestrus was exclusively induced by the presence of a male. However, after the induction of oestrus, ovulation and corpus luteum activity occurred spontaneously without stimuli from copulation. To date this type of oestrous cycle has not been described for any other mammalian species. Thus, these data indicate that differences in the reproductive patterns of the females may have shaped the evolution of different sperm characteristics in the males.

Protein kinase C isoform-dependent modulation of ATP-sensitive K+ channels during reoxygenation in guinea-pig ventricular myocytes.

ATP-sensitive K+ (KATP) channels activated by glucose-free anoxia close immediately upon reoxygenation in single guinea-pig ventricular myocytes, while KATP channels open persistently during reperfusion in coronary-perfused guinea-pig ventricular myocardium. To investigate the reasons behind this discrepancy, we investigated whether protein kinase C (PKC) modulates the opening of KATP channels during anoxia-reoxygenation and ischaemia-reperfusion. Exposure of guinea-pig ventricular cells to glucose-free anoxia shortened the action potential duration at 90% repolarisation (APD90) and evoked the glibenclamide-sensitive robust outward current (IK,ATP). Subsequent reoxygenation caused an immediate prolongation of APD90 and a decrease in IK,ATP within approximately 20 s. When the novel (Ca2+-independent) PKC was activated by applying 1,2-dioctanoyl-sn-glycerol (1,2DOG, 20 M) with EGTA (20 mM) in the pipette, the APD90 restored gradually after reoxygenation and the extent of recovery was appoximately 80% of the pre-anoxic value. Moreover, IK,ATP decreased slowly and remained opened for up to approximately 4 min after reoxygenation. These results suggest persistent opening of KATP channels during reoxygenation. The persistent activation of KATP channels was augmented when both novel and conventional (Ca2+-dependent) isoforms of PKC were activated by applying 1,2DOG without EGTA in the pipette. In coronary-perfused right ventricular myocardium, APD90 remained shortened for up to approximately 30 min of reperfusion. The gradual restoration of APD90 after ischaemia-reperfusion was facilitated by the KATP channel blocker glibenclamide and by the potent PKC inhibitor chelerythrine. Our results provide the first evidence that PKC activation contributes to the persistent opening of KATP channels during reoxygenation and reperfusion. We also conclude that both novel and conventional PKC isoforms co-operatively modulate the opening of KATP channels during the early phase of reoxygenation.

Nitric oxide/cyclic GMP pathway attenuates ATP-evoked intracellular calcium increase in supporting cells of the guinea pig cochlea.

We demonstrate here that nitric oxide (NO) attenuates ATP-evoked calcium transients in Deiters' and Hensen's cells, "supporting" (nonsensory) cells of the guinea pig cochlea, by means of activation of soluble guanylyl cyclase and protein kinase G. The enzymatic activities associated with the nitric oxide/cGMP/protein kinase G pathway had previously been demonstrated to be present in Deiters' and Hensen's cells. We now isolate these cells and measure changes in intracellular free calcium by using the calcium indicator fluo-3. In Deiters' cells, calcium increased rapidly in response to the application of ATP. The increase was attenuated when the pathway was stimulated by NO donors (diethylamine NONOate or sodium nitroprusside) or the cyclic GMP analog, 8-bromo-cyclic GMP. When the activation of the pathway was blocked by the additional presence of inhibitors of soluble guanylyl cyclase (LY83583) or protein kinase G (Rp-8-bromo-cyclic GMP or KT5823), the response to ATP was restored. The reactions also occurred in calcium-free media. Hensen's cells responded similarly. These results provide evidence that intracellular calcium is regulated by the NO/cGMP/protein kinase G pathway in the inner ear.