Adult Female Guinea Pigs Research Articles

Morphotopographic characteristics of the extrinsic innervation of the heart in guinea pigs (Cavia porcellus)

BackgroundNo reports have been made on the entire extrinsic innervation of the heart in small laboratory animals. Therefore, this study examined the detailed morphotopographic features of the extrinsic cardiac autonomic nervous system (ECANS) with its adjacent structures (1) to record the general morpho-topography and variations of the ECANS in guinea pigs, (2) to compare it with previous reports on common laboratory rodents (rats, mice, and Syrian hamsters), rabbits, domesticated animals (cats, dogs, sheep, goats, oxen, pigs, and horses), primates, and humans, and (3) to infer the macroscopic evolutionary changes they presented. MethodsThe sympathetic ganglia, vagi, and emitting cardiac nerves/branches in the cervical and thoracic regions were dissected in 24 sides of 12 formalin-fixed, arterially injected adult male and female guinea pigs under a stereomicroscope. ResultsThe ECANS in guinea pigs presented following general morphologic characteristics: (1) constant existence of the cranial cervical ganglion (CG) and placing caudal to the cranial base over the ventrolateral aspect of the longus capitis muscle, dorsomedial to the common carotid artery and communicating to the first two cervical spinal nerves, (2) the lack of the vago-sympathetic trunk, (3) the existence of the middle cervical ganglion (MG) and lying on the lateral aspect of the longus colli muscle (LC) at the level of the seventh cervical vertebra, (4) constant existence of the cervicothoracic ganglion (CT) composing generally from the caudal cervical ganglion and 1–3 thoracic ganglia and placing ventral to the first and second intercostal spaces over the lateral aspect of the LC and communicating to the eight cervical and first three thoracic spinal nerves in addition to the vertebral nerve, (5) constant existence of the limbs of the ansa subclavia (AS) joining the CT to MG, (6) the existence of individual thoracic ganglia from the 4th to the 12th and joining by single interganglionic branches (IGBs), and communicating to corresponding thoracic nerve, (7) the intimate relation between the caudal part of the thoracic sympathetic chain and the quadratus lumborum muscle, (8) the main cardiac nerves (CNs) emerging from the CT, (9) the lack of CNs springing generally from the CG, ST, AS, MG, or individual thoracic ganglia or their IGBs, and (10) the existence of the cardiac branches (CBs) emerging from the vagi and recurrent laryngeal nerves. The ECANS morphology in guinea pigs also shows sex and laterality differences. ConclusionsThe general anatomical arrangement of the sympathetic components of the ECANS in guinea pigs extremely displaced features common to rats and Syrian hamsters regardless of the existence of MG and the close relation between the thoracic sympathetic chain and the quadratus lumborum muscle. However, the position and organization of the CT, along with its rami communicantes to spinal nerves in guinea pigs quite resembled those seen in rats. The general macroscopic arrangement of the sympathetic components of the ECANS in guinea pigs resembled that seen in rabbits regardless of the organization and location of the CT. The general morphology of the sympathetic components of the ECANS demonstrated markedly morphological variations and similarities among common laboratory rodents, rabbits, domesticated animals (DNs), primates, and humans. The main variations consisted of the position of the CG and its rami communicantes with the spinal nerves, the relation between the vagi and sympathetic trunks in the neck, the existence of the MG, the location and arrangement of the CT, the origins and incidences of the cardiac nerves, and the main sympathetic contributors. The general macroscopic architecture of the parasympathetic components of the ECANS in guinea pigs quite resembled that seen in domesticated animals, primates, and humans. Evolutionary comparative morphologic characteristics of the ECANS are discussed in detail and evolutionary differences and similarities of the ECANS have been found from common laboratory rodents, rabbits, domesticated animals, and primates to humans.

Time-of-day dependent changes in guinea pig bladder afferent mechano-sensitivity

The voiding of urine has a clear circadian rhythm with increased voiding during active phases and decreased voiding during inactive phases. Bladder spinal afferents play a key role in the regulation of bladder storage and voiding, but it is unknown whether they exhibit themselves a potential circadian rhythm. Therefore, this study aimed to determine the mechano- and chemo- sensitivity of three major bladder afferent classes at two opposite day-night time points. Adult female guinea pigs underwent conscious voiding monitoring and bladder ex vivo single unit extracellular afferent recordings at 0300 h and 1500 h to determine day-night modulation of bladder afferent activity. All guinea pigs voided a higher amount of urine at 1500 h compared to 0300 h. This was due to an increased number of voids at 1500 h. The mechano-sensitivity of low- and high-threshold stretch-sensitive muscular-mucosal bladder afferents to mucosal stroking and stretch was significantly higher at 1500 h compared to 0300 h. Low-threshold stretch-insensitive mucosal afferent sensitivity to stroking was significantly higher at 1500 h compared to 0300 h. Further, the chemosensitivity of mucosal afferents to N-Oleoyl Dopamine (endogenous TRPV1 agonist) was also significantly increased at 1500 h compared to 0300 h. This data indicates that bladder afferents exhibit a significant time-of-day dependent variation in mechano-sensitivity which may influence urine voiding patterns. Further studies across a 24 h period are warranted to reveal potential circadian rhythm modulation of bladder afferent activity.

EFFECTS OF NATURAL ULTRAVIOLET RADIATION ON 25-HYDROXYVITAMIN D3 CONCENTRATIONS IN FEMALE GUINEA PIGS (CAVIA PORCELLUS)

Vertebrates have 2 methods of acquiring vitamin D: through the diet and/or secondary to exposure to ultraviolet B (UVB) radiation. Although some species (e.g., dogs) can only acquire vitamin D through their diet, many others also utilize UVB radiation to generate vitamin D. Prior to their extirpation, guinea pigs were naturally exposed to varying levels of sunlight (UVB) in their native habitat; however, in captivity we do not routinely recommend UVB radiation for these animals. Recently, it has been shown that captive guinea pigs can synthesize 25-hydroxyvitamin D (25-OHD3) after exposure to UVB lightbulbs. However, it is not known how natural sunlight impacts 25-OHD3 concentrations in this species. The purpose of this study was to determine whether 25-OHD3 concentrations in female guinea pigs exposed to natural sunlight would increase as a result of UVB exposure. Eight adult female guinea pigs were used for this study. The animals were held indoors during winter months and then placed outside in the spring when temperatures were appropriate. Blood samples were collected before the animals were placed outdoors (baseline) and 30 days after being exposed to natural sunlight. There was a significant difference in 25-OHD3 concentrations over time (P = 0.006) and values collected after the guinea pigs were housed outdoors were 1.8 times higher than baseline. This study confirmed that female guinea pigs can increase 25-OHD3 concentrations after exposure to natural sunlight. This suggests that these animals have conserved this pathway despite domestication, and supplementation should be considered to optimize captive guinea pig habitats.

Effect of Adipose-Derived Stem Cells on Induced Photoaging in the Skin of Adult Guinea Pig: Histological and Immunohistochemical Study

Introduction: The term photoaging describes the sun damaging effects on skin mainly due to chronic ultraviolet (UV) light exposure. The unsatisfactory results of the available anti-aging strategies raise the demand for alternative forms of treatments. Adipose-derived stem cells (ASCs) are available in abundant quantities, harvested by a minimally invasive procedure, safely transplanted and differentiated along multiple cell lineages. Subsequently, used in treatment of many diseases.Aim: To assess the potential ability of ASCs to ameliorate skin changes induced by chronic exposure to artificial light source similar to the sun rays in its UVA and UVB spectrum in adult female guinea pigs.Material and Methods: Adipose-derived stem cells were isolated from subcutaneous white adipose tissue of adult human donors undergoing elective liposuction surgery. Twenty adult female guinea pigs were used and were randomly divided into two groups each was subdivided into two subgroups five animals, each. Subgroup IA served as the control group. Subgroup IB was intradermally injected with phosphate buffered saline solution. Subgroup IIA served as the photoaging model. Subgroup IIB served as the photoaging model intradermaly injected with ASCs. Isolated stem cells were cultured and characterized. Skin specimens were prepared and examined using different histological and immunohistochemical techniques. Morphometric and statistical studies were also performed.Results: Subgroup IIA showed various UV damaging effects in the skin epidermis and dermis, while ASCs injection in subgroup IIB resulted in partial restoration of the skin structure.Conclusion: Intradermal injection of ASCs partially ameliorated the photo-damaging effects. Further studies are needed before ASCs clinical application.

Transplantation and survival of mouse inner ear progenitor/stem cells in the organ of Corti after cochleostomy of hearing-impaired guinea pigs: preliminary results.

In mammals, damage to sensory receptor cells (hair cells) of the inner ear results in permanent sensorineural hearing loss. Here, we investigated whether postnatal mouse inner ear progenitor/stem cells (mIESCs) are viable after transplantation into the basal turns of neomycin-injured guinea pig cochleas. We also examined the effects of mIESC transplantation on auditory functions. Eight adult female Cavia porcellus guinea pigs (250-350g) were deafened by intratympanic neomycin delivery. After 7 days, the animals were randomly divided in two groups. The study group (n=4) received transplantation of LacZ-positive mIESCs in culture medium into the scala tympani. The control group (n=4) received culture medium only. At 2 weeks after transplantation, functional analyses were performed by auditory brainstem response measurement, and the animals were sacrificed. The presence of mIESCs was evaluated by immunohistochemistry of sections of the cochlea from the study group. Non-parametric tests were used for statistical analysis of the data. Intratympanic neomycin delivery damaged hair cells and increased auditory thresholds prior to cell transplantation. There were no significant differences between auditory brainstem thresholds before and after transplantation in individual guinea pigs. Some mIESCs were observed in all scalae of the basal turns of the injured cochleas, and a proportion of these cells expressed the hair cell marker myosin VIIa. Some transplanted mIESCs engrafted in the cochlear basilar membrane. Our study demonstrates that transplanted cells survived and engrafted in the organ of Corti after cochleostomy.

Expression of matrix metalloproteinases and ovarian morphological changes in androgenized cyclic female guinea pigs.

This study was conducted to investigate expression of matrix metalloproteinases (MMPs) and ovarian morphological changes in androgenized cyclic female guinea pigs. Adult cyclic female guinea pigs were injected daily for 28 days with medium doses of testosterone propionate (TP; 1 mg/100g), high doses of TP (2 mg/100g), or saline (control). Serum concentrations of testosterone, estradiol (E2), and progesterone (P4) were measured. Histologic sections of ovaries were stained with hematoxylin-eosin and by immunohistochemistry. Expressions of steroidogenic acute regulatory protein, proliferating cell nuclear antigen, and MMP-2 and MMP-9 in the ovary were characterized by immunohistochemistry. After 28 days of TP injection, serum testosterone concentrations were increased dose-dependently. An appropriate dosage of TP could induce permanent anovulation in guinea pigs, making them a potential model for human polycystic ovary syndrome. MMP-2 and MMP-9 are jointly involved in the growth and atresia of ovarian follicles in cyclic guinea pigs. Increased numbers of atretic antral follicles in the ovary might be associated with the observed high expression of MMP-2 in androgenized cyclic guinea pigs.

A histological study of adrenal gland in guinea pig and hamster

In basic sciences, laboratory animals have a special role in investigations. In this study, the adrenal of three adult female guinea pigs and hamsters were studied. The left adrenal was larger than the right in two species. In hamster, it was in the cranial pole, and in guinea pig, it was in the craniomedial pole of the kidney. In guinea pig, the right and left glands were bean shape and in hamster, egg shape. This gland was covered by a capsule without muscle fibers in guinea pig and hamster. The peripheral cortex in hamster was divided into three zones and in guinea pig, four zones. Zona glomerulosa was composed of arcuate cords in guinea pig and clusters in hamster. The foamy cytoplasm of fasciculate in guinea pig was more than hamster. There was also a lot of lipofuscin in cytoplasm of reticularis in the two animals, especially in guinea pig. The medulla in guinea pig was long and in hamster was egg-shaped. In guinea pig, reticularis cells penetrated into medulla and invagination of cortex also was obvious in medulla of this species. In chromaffin reaction, the less electron-dense granules were epinephrine and the dense granules were norepinephrine cells.

Mechanisms mediating CCK-8S-induced contraction of proximal colon in guinea pigs

To investigate the effects of sulfated cholecystokinin octapeptide (CCK-8S) on the contractile activity of guinea-pig proximal colon. Proximal colonic smooth muscle (PCSM) strips were obtained from adult female guinea pigs and contractile response of PCSM strips was recorded using a polyphysiograph. PCSM cells were isolated by enzymatic digestion. Resting potential (RP), action potential (AP), large conductance potassium channel currents (I(BKCa)) and L-type calcium currents (I(Ca-L)) were recorded by patch-clamp techniques. (1) CCK-8S (10(-7) mol/L) enhanced the mean contractile amplitude of colonic circular muscle and longitudinal muscle (LM) strips by 56.53% + or - 11.92% (P = 0.038) and 65.93% + or - 12.98% (P = 0.019), respectively, as well as the mean frequency of LM by 31.69% + or - 13.58% (P = 0.023), which were significantly attenuated by pretreating strips with devazepide, nifedipine, iberiotoxin, thapsigargin (TG) and BAPTA-AM (BA) respectively; (2) CCK-8S (10(-7) mol/L) increased the AP amplitude by 38.6% + or - 3.2% (P = 0.015), decreased AP duration by 36.9% + or - 8.7% (P = 0.026), and depolarized the RP from -61.3 + or - 2.7 mV to -29.8 + or - 5.9 mV (P = 0.032); and (3) Compared with the normal control group, CCK-8S (10(-7) mol/L) enhanced the peak current of I(BKCa) by 18.7% + or - 2.1% (from 916 + or - 183 pA to 1088 + or - 226 pA; at +60 mV; P = 0.029), which was inhibited by respective pretreatment with iberiotoxin and devazepide. Additionally, CCK-8S (10(-7) mol/L) intensified the peak current of I(Ca-L) by 40% (from 60 + or - 8 pA to 84 + or - 11 pA; at +10 mV; P = 0.012), compared to the normal control group, which was apparently suppressed by respective pretreatment with nifedipine, devazepide, TG and BA. In the respective presence of heparin and staurosporine, CCK-8S did not significantly enhance I(BKCa) and I(Ca-L). The results suggest that CCK-8S promotes guinea-pig proximal colon contraction by CCK1 receptors, following activation of the inositol triphosphate-protein kinase C signal transduction pathway.

THE EFFECT OF VACCINIUM MYRTILLUS AND VACCINUM VITIS-IDAEA FRUITS EXTRACTS ON THE ANTIOXIDANT SYSTEM OF MAMALIAN ORGANISMS

SUMMARY The present paper deals with the study of some Vaccinium myrtillus and Vaccinum vitis-idaea fruits extracts effects on the antioxidant system of guinea pigs. Both extracts stimulated the antioxidant system of the cells: it doesnt not effect the normal function of the liver and stimulates the absorption of calcium and phosphorus. Especially; Vaccinum myrtil us stimulates the haemoglobine synthesis and also the iron absorption. It is a much more antioxidant as Vaccinum vitis-idaea as there were registered lower levels of malondial dehide (MDA) respectively higher concentration of reduced glutathione (GSH) in comparison with the Vaccinum vitis-idaea . In the same time lower activities of superoxid di smutase (SOD); glutathione peroxidase (G-px) and glutathione reduc tase (G-red) were registered in the treatment with Vaccinum myrtilus extract. Free radicals; respectively reactive species of t he oxigen (ROS) in physiological concentration are stimulating the development and t he cell division. A mutation at cell level can be the cause of permanent deviation of the oxid ative reactions with RSO development in excess. In very large doses; ROS lead to apoptosis. As there are quite few studies in this field; in the present work we study the antioxidant proper ties of some Vaccinium myrtillus and Vaccinum vitis-idaea fruits extracts on the antioxidant system of guine a pigs; as a possible oxidative stress barrier as both of the extracts co ntain antioxidant components as flavonoides; antocianines; etc. The experiment was carried on 36 adult female guinea pigs (divided in three groups) and maintained in good physiological conditions. Th ey were divided in three groups. Each group included 12 guinea pigs.L1- control; received tap water ad libitum during 14 days; L2 - received during 14 days 0.5 ml i.m. of the Vaccinium myrtillus extrac t; L3- received during 14 days 0.5 ml i.m. of the Vaccinium vitis-idaea extract After 14 days blood (on heparine); by cardiac punction and tissue samples were collect ed under general narcosis from L1; L2 and L3. The data are presented as means ± S.D. values. ANOVA; TTest were used. The best antioxidant properties has the Vaccinium myrtillus extract as it maintained a normal function of the liver (GPT; GOT and GGT were situated in normal values) and stimulates the absorption of calcium and phosphorus ; the haemoglobine synthesis and also the

The effect of relaxin on the female anterior cruciate ligament: Analysis of mechanical properties in an animal model

Background The peptide hormone relaxin, found in pregnant and non-pregnant females, has been shown to have collagenolytic effects on ligamentous tissue. Relaxin receptors have recently been identified on the human female anterior cruciate ligament (ACL). Relaxin may affect the load bearing properties of the female ACL and contribute to non-contact ACL injuries. Hypothesis The administration of recombinant relaxin ± estrogen will lead to a significant decrease in ACL integrity in the guinea pig model. Study design Controlled laboratory study. Methods Adult female guinea pigs were divided into three experimental groups. Group 1 ( n = 4) was administered only 20 µg/h of recombinant porcine relaxin for 3 weeks. Group 2 ( n = 4) was administered 20 µg/h of recombinant porcine relaxin and 5 µg/h of estradiol for 3 weeks. Group 3 ( n = 4) served as both a normal control before surgical transection of the ACL and a positive ACL tear control after transection. All hormones were administered using separate implanted osmotic pumps. ACL laxity was tested by implanting radio-opaque markers in the femur and tibia of each leg. After applying a standard anterior force (22 N), the distance between markers was measured radiographically at day 0 and day 21. The animals were then sacrificed and the ACL's were analyzed for load-to-failure using a material testing machine. Results Load-to-failure testing indicated that animals treated with relaxin only had significantly weaker ACL's ( µ = 40.4 N, p = 0.001) compared to controls ( µ = 64.1 N). The relaxin + estrogen group ( µ = 32.7 N) was also significantly weaker than controls ( p = 0.007). There were no statistical differences between relaxin and relaxin + estrogen groups. Both relaxin only and relaxin + estrogen groups showed an increase in anterior translation of the tibia after 3 weeks of infusion, but it did not achieve statistical significance. Conclusions Relaxin significantly alters the mechanical properties of the ACL in an animal model. Clinical relevance The effects of relaxin, possibly in conjunction with estrogen, may contribute to a comprehensive etiology for human female non-contact ACL injuries.

Social buffering of the cortisol response of adult female guinea pigs

When housed in spacious, mixed age/sex colonies, male guinea pigs form small harems of females with which attachment-like social bonds are established. A previous study indicated that the bonded male, but not an unfamiliar male from the same colony, could reduce the plasma cortisol response of a female when exposed to a novel environment. We examined the effect of several classes of social partners on the cortisol response of females maintained under standard laboratory housing conditions. Eight “artificial harems” comprised of one adult male and two adult females were formed in standard group-housing cages 2 weeks prior to the study. Behavior observed in these home cages indicated that interactions between males and females of the triads were overwhelmingly positive in nature. When exposed to a novel environment for 2 h, the presence of either the male or female cage mate reduced the subject female's plasma cortisol response, whereas the presence of an unfamiliar adult male did not. Changes in plasma cortisol levels were not predicted by the frequency of various social behaviors observed in the novel environment. These findings: (1) demonstrate that the buffering effect of male partners on the cortisol response of adult females can be observed in guinea pigs maintained in conventional laboratory housing; (2) indicate that unfamiliar adult males are ineffective at reducing cortisol responses of females under these conditions; and, (3) appear to be the first to show buffering effects by adult female guinea pigs on the cortisol responses of other adult females.

The effects of different harvesting techniques, adrenaline, and centrifuge on the survival of fat grafts

The effects of different harvesting techniques, local adrenaline infiltration, and centrifuge on fat graft survival and stability were studied. Twenty-four adult female Guinea pigs weighing 580–700 g were divided into three groups (groups A, B, and C), each with eight subjects. Fat grafts were harvested from the back of the animals. The left side was used for simple excision and the right for liposuction in harvesting the grafts; they were named subgroups 1 and 2, respectively. Group A was the control group. In group B, the grafts were incubated in 1/100,000 adrenaline solution for 15 min. In group C, they were centrifuged at 2,000 rpm for 3 min before placing them in the abdominal area of the same subjects. Again, the left side was used for placement of excised material and the right one for lipoaspirate. At the third postoperative month, all subjects were reoperated on to remove the grafts, and the extracted material was studied macroscopically and histopathologically. In the groups where liposuction was utilized for graft harvest, the graft resorption ratios and volume loss have been significantly increased. Adrenaline infiltration had no effect, either macroscopically or histopathologically. Although the centrifuge did not seem to have a significant effect macroscopically, the histopathologic study revealed its significant negative effects on grafts harvested by simple excision.

Aging impairs neurogenic contraction in guinea pig urinary bladder: role of oxidative stress and melatonin

The incidence of urinary bladder disturbances increases with age, and free radical accumulation has been proposed as a causal factor. Here we investigated the association between changes in bladder neuromuscular function and oxidative stress in aging and the possible benefits of melatonin treatment. Neuromuscular function was assessed by electrical field stimulation (EFS) of isolated guinea pig detrusor strips from adult and aged female guinea pigs. A group of adult and aged animals were treated with 2.5 mg x kg(-1) x day(-1) melatonin for 28 days. Neurotransmitter blockers were used to dissect pharmacologically the EFS-elicited contractile response. EFS induced a neurogenic and frequency-dependent contraction that was impaired by aging. This impairment is in part related to a decrease in detrusor myogenic contractility. Age also decreased the sensitivity of the contraction to pharmacological blockade of purinergic and sensitive fibers but increased the effect of blockade of nitrergic and adrenergic nerves. The density of cholinergic and nitrergic nerves remained unaltered, but aging modified afferent fibers. These changes were associated with an increased level of markers for oxidative stress. Melatonin treatment normalized oxidative levels and counteracted the aging-associated changes in bladder neuromuscular function. In conclusion, these results show that aging modifies neurogenic contraction and the functional profile of the urinary bladder plexus and simultaneously increases the oxidative damage to the organ. Melatonin reduces oxidative stress and improves the age-induced changes in bladder neuromuscular function, which could be of importance in reducing the impact of age-related bladder disorders.

Characterization of ventricular repolarization in male and female guinea pigs

Since both components of the delayed rectifier K + currents ( I Kr and I Ks) are present in guinea pig and human ventricle, the guinea pig appears as an interesting model to examine the contribution of these currents in sex-related difference of cardiac repolarization. Accordingly, we compared ventricular repolarization in adult male and female guinea pigs using electrophysiological protocols together with Western blots analysis and perfused heart preparation. Our results indicate that there was no sex-related difference in the expression levels of the different K + channels studied (ERG, KvLQT1, minK and Kir2.1), nor in the density of the K + currents ( I Kr, I Ks and I K1) encoded by these channels. Action potential durations and QTc intervals were also similar between males and females. In addition, we compared QTc intervals using Langendorff-perfused whole hearts in the presence of I Kr and/or I Ks blockers. The I Kr blocker (5 μM E-4031) prolonged QTc intervals to a similar extent in male (24 ± 2%) and female (29 ± 3%, p = 0.1) hearts. Similarly, the degree of QTc prolongation induced by 0.1 μM HMR1556 ( I Ks blocker) was similar in both sexes (males: 15 ± 2% and females 18 ± 2%; p = 0.2). In addition to their QT prolonging effects, the I Kr and I Ks blockers significantly reduced heart rate in both male and female guinea pigs. These studies clearly demonstrate that adult guinea pigs do not display sex differences in ventricular repolarization.

Chronic Hypoxia Decreases Endothelial Nitric Oxide Synthease Protein Expression in Fetal Guinea Pig Hearts

The underlying cellular mechanisms mediating hypoxia-induced adaptations in the fetus are poorly understood. We tested the hypothesis that hypoxia up-regulates endothelial nitric oxide synthase (NOS3, type III) protein expression in fetal hearts similar to that observed in adult hearts as a cardioprotective adaptation. This study investigates the effect of chronic hypoxia on NOS3 protein expression in hearts and carotid arteries of fetal guinea pigs exposed to normoxia or intrauterine hypoxia. Time-mated pregnant guinea pigs (term = 65 days) were housed in either normoxic room air (NMX) or exposed to 12% O(2) (hypoxia; HPX) for 14 or 28 days of duration. At near term ( approximately 60 days of gestation), pregnant mothers were anesthetized and fetal guinea pig hearts and carotid arteries were excised from NMX and HPX animals and frozen until ready for study. In addition, hearts were also excised from anesthetized adult nonpregnant female guinea pigs exposed to either NMX or HPX for 14 days. NOS3 protein was extracted from all tissues and quantified using Western blot analysis. Fetal heart samples were also prepared for localization of NOS3 protein using immunohistochemistry. Chronic hypoxia increased both maternal and fetal hematocrit after 28 days of duration. HPX decreased NOS3 protein levels in fetal guinea pig hearts by 29% after 28 days compared to NMX controls. In contrast, HPX increased both NOS3 protein levels in adult hearts by 62% and fetal carotid arteries by fourfold after 14 days of exposure compared to their respective NMX controls. Positive immunostaining of NOS3 protein of fetal hearts was localized in both cardiomyocytes and endothelial cells. Contrary to our hypothesis, the hypoxia-induced decrease in fetal guinea pig heart NOS3 protein contrasts to the protein levels measured in either adult hearts or fetal carotid arteries. These results suggest that the NOS protein expression is altered differently by hypoxia in fetal and adult hearts and in a peripheral fetal artery exposed to the same level of hypoxia. Thus, the functional role of NO in the fetal heart during hypoxia may differ from that of the adult.

Immunohistochemical Demonstration of Leptin in Pancreatic Islets of Non-Obese Diabetic and CD-1 mice: Co-localization in Glucagon Cells and its Attenuation at the Onset of Diabetes

Leptin is a 16 kD polypeptide hormone produced predominantly by white adipose tissue and exerts profound effects on food intake and energy balance. More recent studies have shown extra sites of leptin production in human and rodent tissues and have ascribed additional roles for the hormone, e.g., in immune and reproductive functions. A role for the hormone has also been implicated in insulin-dependent diabetes mellitus in the non-obese diabetic (NOD) mouse. However, whether leptin originates from islet cells of the mouse is not known. Here dual-label immunohistochemistry was employed to examine leptin expression in islet cells, and its distribution and cellular sources in pancreatic sections of female NOD/Ak and CD-1 mice of various ages. For comparison, leptin immunolabelling was examined in adult pancreatic sections from male NOD/Ak CD-1, Balb/c and FVB/N mice and female severe combined immunodeficient CB. 17 mice. Pancreatic tissues from adult female guinea pig, sheep and cattle and neonatal pigs were also studied. Our results show that in the day 1 NOD and CD-1 mice, leptin immunolabelling was observed in selective glucagon cells within the developing islets while at days 15 and 22, it became more intense and co-incident. This pattern of staining was maintained at days 40, 90, 150 and 250. In the female NOD mouse, leptin was absent in intra-islet immune cells. Its expression was variable in islets from male NOD and CD-1 mice. In spontaneously diabetic female NOD mice and following acceleration of diabetes with cyclophosphamide, despite the persistence of strong immunolabelling for glucagon in the re-distributed alpha cells, leptin expression was either absent, diminished or present in only a proportion of alpha cells. The reduction in leptin labelling was often associated with diabetic islets which had insulitis in association with only a small number of residual beta cells. Leptin expression was absent in guinea pig, ovine, bovine and neonatal porcine islet cells, despite the expression of intensely labelled glucagon cells. The present results demonstrate leptin co-localization in glucagon cells of the mouse islet. Its expression diminishes in the presence of inadequate insulin. Leptin produced within the mouse islet may have bi-directional influences on leptin and insulin regulation and may play local functions in islet development and metabolism.

Effects of functional peripheral sympathetic denervation induced by guanethidine on follicular development and ovulation of the adult female guinea pig

The present study investigates the effects of functional sympathetic peripheral denervation induced by guanethidine sulphate (GTD) to adult female guinea pigs in the follicular (FPh) or luteal phases (LPh) on their oestrous cyclicity and ovulation. No differences were observed in oestrous cyclicity or the average number of corpora lutea present in the ovaries between the control and denervated animals. Guanethidine sulphate administration resulted in a significant decrease in ovarian norepinephrine content, higher for the left ovary than for the right one. Serum oestrogen and progesterone concentrations, the mean of follicles, and its diameter were different, depending on the oestral cycle in which the treatment was performed. These results suggest that in adult normal female guinea pigs, ovarian innervation participates in the regulation of follicular development in an inhibitory way.

Effects of nonylphenol, 1,1-dichloro-2,2-bis( p-chlorophenyl)ethylene ( p,p′-DDE), and pentachlorophenol on the adult female guinea pig reproductive tract☆

The guinea pig exhibits cyclic and luteal similarities to the human, a feature not present in other small experimental animals such as rats, mice, or rabbits. Studies were undertaken to investigate the in vivo effects of three persistent environmental xenobiotics (nonylphenol, 1,1-dichloro-2,2-bis( p-chlorophenyl)ethylene [ p,p′-DDE], and pentachlorophenol) on the microanatomy of the adult female guinea pig reproductive system. The effects brought about by these compounds (40 mg/kg/day) were compared to those caused by the synthetic estrogen diethylstilbestrol (DES; 50 μg/kg/day). Adult female guinea pigs, intact and castrated, were treated with 14 daily subcutaneous (s.c.) doses of one of these agents. The 50% decline in the weight of the tract that occurred following castration, was prevented by administration of nonylphenol, p,p′-DDE, and DES, but not of pentachlorophenol. Nonylphenol produced weak estrogenic stimulation of the tract of intact animals and maintained a relatively normal histologic appearance in castrated animals. Focal mucinous metaplasia of the endometrium, however, was observed in both groups. Treatment of intact and castrated animals with p,p′-DDE resulted in cystic hyperplasia and mucinous metaplasia of the endometrium, hyperplasia of the cervical epithelium, estrogenic stimulation of the vagina, and dilation of the rete ovarii. Treatment of intact or castrated animals with DES resulted in effects that were qualitatively similar to those caused by p,p′-DDE. The appearance of the vaginal epithelium, however, was abnormal and the rete ovarii were less dilated. Pentachlorophenol had minimal effect on the histology of the tract of castrated or intact animals. These data support our hypothesis that some environmental toxicants can substitute for estradiol in regulating the microanatomy of the female reproductive tract. They indicate the potential of these compounds to act as endocrine disrupting agents.

Pre-synaptic NO-cGMP Pathway Modulates Vagal Control of Heart Rate in Isolated Adult Guinea Pig Atria

The role of nitric oxide (NO) in the vagal modulation of heart rate (HR) is controversial. We tested the hypothesis that NO acts via a pre-synaptic, guanylyl cyclase (GC) dependent pathway. The effects of inhibiting NO synthase (NOS) and GC were evaluated in isolated atrial/right vagal nerve preparations from adult (550–750 g) and young (150–250 g) female guinea pigs. Levels of NOS protein were quantified in right atria using Western blotting and densitometry. The non-specific NOS inhibitor N- ω -nitro- L -arginine (L -NA, 100 μM,n =5) significantly reduced the negative chronotropic response to vagal nerve stimulation (VNS) at 3 and 5 Hz in the adult guinea pig. This effect was reversed with 1 m ML -arginine. Similar results were observed with the specific neuronal NOS inhibitor vinyl-N5-(1-imino-3-butenyl)- L -ornithine (L -VNIO, 100 μM,n =7). Inhibition of GC with 1H-(1,2,4)-oxadiazolo-(4,3-a)-quinoxalin-1-one (ODQ, 10 μM,n =7) also significantly reduced the negative chronotropic response to VNS at 3 and 5 Hz in adult guinea pigs. Neither L -NA (n=6), L -VNIO (n=5) nor ODQ (n=6) changed the HR response to cumulative doses of carbamylcholine in adult guinea pig atria suggesting that the action of NO is pre-synaptic. The HR response to VNS was unaffected by L -NA (n=7) or ODQ (n=7) in young guinea pigs and Western blot analysis showed significantly lower levels of nNOS protein in right atria from young animals. These results suggest a pre-synaptic NO-cGMP pathway modulates cardiac cholinergic transmission, although this may depend on the developmental stage of the guinea pig.

Chronic 17beta-estradiol replacement increases nitric oxide-mediated vasodilation of guinea pig coronary microcirculation.

Estrogen is cardioprotective of the coronary circulation by mechanisms incompletely understood. This study determined the effect of chronic 17beta-estradiol replacement on dilator responses to acetylcholine and sodium nitroprusside of the isolated coronary microcirculation. Adult female guinea pigs were ovariectomized, and a 21-day-release pellet containing 0.0, 0.1, 0.25, 0.5, or 1.0 mg 17beta-estradiol was implanted subcutaneously. Serum estradiol concentrations ranged from 3.9 to 74.9 pg/mL, increasing with the dose of estradiol. After 19 to 20 days, the animals were euthanized, and their hearts were removed and perfused with buffer at constant flow on an isolated heart apparatus. Both perfusion pressure and contractile force were measured in prostaglandin F(2alpha)-constricted hearts. Vasodilation to the cumulative addition of the endothelium-dependent agonist acetylcholine (10(-9) to 10(-5) mol/L) and the nitric oxide (NO) donor sodium nitroprusside (10(-9) to 10(-5) mol/L) was measured before and after NO synthesis inhibition by nitro-L-arginine (LNA, 10(-4) mol/L). Baseline coronary resistance was unaltered by estradiol, although LNA increased resistance in estradiol-treated hearts more than in ovariectomized controls. Chronic 17beta-estradiol increased sensitivity (measured by -log EC(50) values) but not maximal response to acetylcholine compared with ovariectomized controls. Differences were abolished by LNA at all doses of estradiol. Sodium nitroprusside-induced dilation was unaffected by estradiol replacement. Chronic 17beta-estradiol replacement, at doses producing hormone levels within the physiological range, enhances dilator sensitivity of the coronary microcirculation through enhanced NO production by the endothelium, independent of changes in NO sensitivity of the vascular smooth muscle. Thus, estradiol enhances NO production as a protective mechanism of the coronary microcirculation.