Tyrosine hydroxylase- and nitric oxide synthase-immunoreactive nerve fibers in mitral valve of young adult and aged Fischer 344 rats

Using confocal fluorescence microscopy we studied, in whole mounts of heart mitral valves of young adult and aged Fischer 344 rats, the distribution of nerves containing the catecholamine marker tyrosine hydroxylase (TH) or the synthetic enzyme marker for nitric oxide, nitric oxide synthase (NOS). TH-IR was localized in two separate nerve plexuses which do not intermingle. The 'major' plexus arose from the annulus region, traversed the basal zone of the valve, and ramified in the intermediate zone to form a dense network of fine fibers. The 'minor' plexus was restricted to the distal zone and originated from bundles that ascended the chordae tendineae to enter the valve cusp. A concentric zone located between the major and minor plexuses was devoid of TH-IR nerve fibers. Both plexuses demonstrated (i) nerves that contained numerous varicosities along the length of each fiber, (ii) many terminal axons and (iii) different shaped terminal axon endings. With age, the density of TH-IR innervation in the mitral valve was markedly reduced; and nerve fibers of the minor plexus were limited to the chordae tendinae, without extending into the valve cusp itself. NOS-IR fibers in the mitral valve formed a loose network that extended from the annulus to more than halfway down the cusp. The varicose beads of the terminal NOS-IR axons appeared to become progressively smaller and less intensely fluorescent until they disappeared at the terminal endings, which showed no specializations. No NOS-IR fibers were observed in the distal zone of the valve leaflet or in the chordae. In the aged mitral valve, the density of NOS-IR nerves was decreased, as compared with NOS-IR innervation in the young adult valve. The existence of TH and NOS as well as other signal molecule markers in heart valve nerves and the disparate patterns of their distribution and localization provide evidence supporting the theory that heart valve nerves form a complex reflexogenic control system in the mitral heart valve. In summary, two distinct neural architectures are described for TH-IR and NOS-IR valve nerves, respectively. The former are believed to be axons dedicated to sympathetic motor functions. The NOS-IR valve nerves may have sensory and/or postganglionic parasympathetic motor functions. An implication of these findings is that different, but perhaps related, valve functions may be mediated by separate, dedicated circuits.     

Muscle adaptations to hindlimb suspension in mature and old Fischer 344 rats

We examined skeletal and cardiac muscle responses of mature (8 mo) and old (23 mo) male Fischer 344 rats to 14 days of hindlimb suspension. Hexokinase (HK) and citrate synthase (CS) activities and GLUT-4 glucose transporter protein level, which are coregulated in many instances of altered neuromuscular activity, were analyzed in soleus (Sol), plantaris (PI), tibialis anterior (TA), extensor digitorum longus (EDL), and left ventricle. Protein content was significantly (P < 0.05) lower in all four hindlimb muscles after suspension compared with controls in both mature (21-44%) and old (17-43%) rats. Old rats exhibited significantly lower CS activities than mature rats for the Sol, Pl, and TA. HK activities were significantly lower in the old rats for the Pl (19%) and TA (33%), and GLUT-4 levels were lower in the old rats for the TA (38%) and EDL (24%) compared with the mature rats. Old age was also associated with a decrease in CS activity (12%) and an increase in HK activity (14%) in cardiac muscle. CS activities were lower in the Sol (20%) and EDL (18%) muscles from mature suspended rats and in the Sol (25%), Pl (27%), and EDL (25%) muscles from old suspended rats compared with corresponding controls. However, suspension was associated with significantly higher HK activities for all four hindlimb muscles examined, in both old (16-57%) and mature (10-43%) rats, and higher GLUT-4 concentrations in the TA muscles of the old rats (68%) but not the mature rats. These results indicate that old age is associated with decreased CS and HK activities and GLUT-4 protein concentration for several rat hindlimb muscles, and these variables are not coregulated during suspension. Finally, old rat skeletal muscle appears to respond to suspension to a similar or greater degree than mature rat muscle responds.     

Sodium appetite after transection of the chorda tympani nerve in Wistar and Fischer 344 rats.

Acute sodium depletion in rats leads to dramatic increases in intake of hypertonic NaCl solutions, a behavior known as sodium appetite. The importance of signals conveyed by the chorda tympani (ChT) nerve to the expression of sodium appetite is unclear. The effects of bilateral ChT transection were examined on the short- and long-term response to sodium depletion in Wistar and Fischer 344 (F344) rat strains, because Wistar rats normally display a NaCl preference in the absence of need whereas F344 rats avoid NaCl. In both strains, sodium appetite after ChT transection and treatment with the diuretic furosemide was delayed and blunted or eliminated. The results suggest that signals conveyed by the ChT nerve are important in the expression of a sodium appetite. Effects on F344 rats are particularly interesting because ChT transection surgery appears to have opposite effects on NaCl intake depending on whether F344 rats are sodium replete or deplete. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of voluntary exercise on maximal oxygen uptake in young female Fischer 344 rats

The effect of voluntary exercise on maximal oxygen uptake (VO2 max) was studied in young female Fischer 344 rats. After 10 weeks of wheel-running training, the absolute VO2 max and VO2 max relative to body mass increased without a decline in body mass. The running speed eliciting VO2 max, heart and soleus muscle mass, and succinate dehydrogenase (SDH) activity in the soleus muscle also increased. These results suggest that voluntary exercise is an effective means of increasing the aerobic exercise capacity of young female Fischer 344 rats.     

Distribution and excretion of radiolabelled tert-butylhydroquinone in Fischer 344 rats

Uniformly 14C-ring-labelled tert-butylhydroquinone (TBHQ) was diluted with non-radioactive TBHQ and administered orally (for excretion studies) to Fischer 344 rats. An average of 72.9% and 10.6% of the administered radioactivity was recovered in the urine and faeces, respectively, of male rats, and 77.3% and 8.2% in the urine and faeces, respectively, of female rats in 4 days. No significant sex-related differences were found in either excretion, tissue distribution or urinary metabolites of TBHQ-derived radiolabel. For distribution studies, intraperitoneal doses were administered to female rats, and tissue levels of radiolabel were determined at various times after dosing. The parent compound quickly disappeared from tissue in vivo. The highest concentrations of radiolabel were found in the liver and kidneys. The urinary metabolites consisted of conjugated TBHQ and unidentified polar substance(s).     

Development of the enhanced neural response to NaCl in Fischer 344 rats

Duplications of the esophagus or stomach alone are infrequent, and complete foregut duplication has only rarely been described. Most combined esophagogastric duplications present within the first year of life, and if communication with the normal alimentary tract does occur, it does so only either above or below the diaphragm. This report illustrates a case of continuous duplication of the esophagus and stomach with communication to the normal alimentary tract at both proximal and distal ends. Operative management and a review of the literature and embryology are described.     

Muscle regeneration in young and old rats: effects of motor nerve transection with and without marcaine treatment

We tested the hypothesis that after skeletal muscle regeneration in old compared with young rats damage to the motor nerve rather than damage to muscle fibers determines the magnitude of the deficits in muscle mass and maximum force (Po). The mass and Po of extensor digitorum longus (EDL) muscles of young (4 months) and old (24 months) male rats were compared two months following (i) Marcaine treatment plus simultaneous motor nerve transection, (ii) motor nerve transection alone, and (iii) Marcaine treatment alone (from data compiled previously). In both the nerve transection-only and Marcaine with nerve transection groups the recovery of mass and Po was significantly greater in young than in old rats. This is in contrast to our previous data showing that in the absence of nerve damage Marcaine-treated muscle in old rats regenerates as well as that in young rats. Our hypothesis was supported, and we conclude that impaired axonal regeneration, re-establishment of nerve-muscle contact, or both, is the critical component in the impaired regeneration of muscle grafts in old as compared with young rats.     

Effect of dehydroepiandrosterone on mitogen-induced lymphocyte proliferation and cytokine production in young and old F344 rats

The steroid hormone intermediate, dehydroepiandrosterone (DHEA), has been proposed as a therapeutic agent for the treatment of immunosenescence in mouse model. In the present study, the in vitro effect of DHEA on mitogen-induced lymphocyte proliferation and cytokine production was evaluated in a rat model. Spleen lymphocytes were isolated from young (4-6 months) and old (24-26 months) F344 rats and were incubated with DHEA for 30 min. The induction of lymphocyte proliferation, interleukin-2 (IL-2), and interferon-gamma (IFN-gamma) production by concanavalin A (Con A) was measured in a culture medium supplemented with either fetal calf serum (FCS) or with serum-free medium (Nutridoma-SR, N-SR). The induction of lymphocyte proliferation and IL-2 production by Con A decreased significantly with age, whereas induction of IFN-gamma increased with age. Treatment of lymphocytes with DHEA did not significantly alter Con A-induced proliferation or the production of IL-2 or IFN-gamma by spleen lymphocytes isolated from either young or old rats. These data indicate that in vitro DHEA treatment appears to have no immunomodulatory effect on the age-related changes in mitogen-induced proliferation or cytokine production in rat lymphocytes.     

Time- and dose-dependent development of potassium bromate-induced tumors in male Fischer 344 rats

Potassium bromate (KBrO3) is a rodent carcinogen and a nephro- and neurotoxicant in humans. KBrO3 is used in cosmetics and food products and is a by-product of water disinfection by ozonization. KBrO3 is carcinogenic in the rat kidney, thyroid, and mesothelium and is a renal carcinogen in the male mouse. The present study was designed to investigate the relationship of time and dose to bromate-induced tumors in male Fischer 344 (F344) rats and to provide some insight into the development of these tumors. KBrO3 was dissolved in drinking water at nominal concentrations of 0, 0.02, 0.1, 0.2, and 0.4 g/L and administered to male F344 rats as the sole water source for 12, 26, 52, 78, or 100 wk. Renal cell tumors were present after 52 wk of treatment only in the high-dose group. Mesotheliomas developed after 52 wk of treatment on the tunica vaginalis. Mesotheliomas were present at sites other than the testicle after 78 wk of treatment, indicating that their origin was the testicular tunic. Thyroid follicular tumors were present as early as 26 wk in 1 rat each from the 0.1- and 0.2-g/L groups. The present study can be used as a basis for the determination of dose-time relationships of tumor development for a better understanding of KBrO3-induced cancer.     

Differential effects of pharmacological doses of melatonin on malondialdehyde and glutathione levels in young and old rats

BACKGROUND: The free radical theory of aging suggests the oxygen-derived species as the causative agents and free radical scavengers as the defense systems in aging process. The exact role of the free radical scavenging effects of melatonin in aging remains to be clarified. OBJECTIVE: In this experimental study, we investigated the age-related changes of malondialdehyde (MDA), a lipid peroxidation product, and glutathione (GSH) and the effects of exogenous melatonin. METHODS: Plasma, liver, and lung MDA and GSH levels of 9- and 28-month-old rats were measured. RESULTS: Plasma, lung, and liver MDA levels of old rats were significantly higher than those of the young ones (p = 0.024, p = 0.005, and p = 0.0007, respectively). However, while the lung GSH levels were found to be significantly decreased in the control group of old rats as compared with young ones (p = 0.005), the liver GSH levels were unchanged. Plasma MDA levels were found to be significantly lower in the melatonin group of old rats as compared with the control group (p = 0.020) but lung and liver MDA levels were not significantly different. There were no significant differences in the levels of measured parameters between both groups of young rats. CONCLUSION: Our results suggest that increased levels of lipid peroxidation products may have a role in aging, and exogenous melatonin may delay the aging process of tissues by means of its free radical scavenging effects.     

The effect of time after treatment, treatment schedule and animal age on the frequency of 6-thioguanine-resistant T-lymphocytes induced in Fischer 344 rats by N-ethyl-N-nitrosourea

The persistence of 6-thioguanine-resistant (TGr) T-lymphocytes was investigated in Fischer 344 rats treated with N-ethyl-N-nitrosourea (ENU) using two schedules. Male rats, aged 3 months, were given i.p. injections containing a total of 0, 50 or 100 mg ENU/kg either as a single treatment (single-dose group) or divided among 10 weekly treatments (split-dose group). At 1, 3, 5, 10, 20, 30 and 50 weeks after the single-dose treatment, and 10, 20, 30 and 50 weeks after beginning the split-dose regimen, animals were assayed for the frequency of TGr spleen lymphocytes. ENU produced significant dose- and time-dependent responses in the single- and the split-dose treatment groups. Although a few of the 50 mg/kg split-dose treatments were significantly higher than the comparative single-dose groups, the number of TGr lymphocytes produced by the two dosing regimens were generally similar. The frequency of TGr cells for control animals increased with the age of the animals. The mode of ENU administration did not greatly influence the percent cloning efficiency (%CE) of the non-selection cultures, although the %CE declined in animals over 10 months of age. To investigate the relationship between the frequency of TGr cells and the age of the animals at the time of ENU administration, additional rats aged 17 months were treated with a single dose of ENU and at 1, 5 and 10 weeks following exposure, the frequencies of TGr cells were determined from the isolated lymphocytes. No difference in mutagen sensitivity between rats treated at 3 months of age and those treated at 17 months of age was detected at the time points evaluated. The data demonstrate the persistence of ENU-induced TGr T-lymphocytes in the rat and suggest that the dose and possibly the treatment schedule, but not the age of the animal at the time of treatment, affect the response.     

Glucose transporter content and enzymes of metabolism in nerve-repair grafted muscle of aging Fischer 344 rats

Aging and grafting are associated with decreased ability of muscle to sustain power, likely reflecting diminished fuel availability. To assess mechanisms that may contribute to availability of glucose, we studied GLUT-1 and GLUT-4 protein as well as mRNA contents and enzymes of glucose metabolism in grafted and control medial gastrocnemius (MG) muscles of 6-, 12-, and 24-mo-old male Fischer 344 rats. There was no effect of age or grafting on MG GLUT-4 content. There was both an age- and graft-associated increase in GLUT-1 content (P = 0.0044 and 0.0063, respectively). There was no effect of aging or grafting on hexokinase and phosphofructokinase activity or on protein and glycogen content. Muscle mass and citrate synthase activity were significantly diminished with grafting. Citrate synthase activity was significantly greater in the 12-mo-old compared with the 6- and 24-mo-old animals. Grafting in combination with aging had no impact on any of the parameters measured. We conclude that diminished glucose transporter expression cannot explain the decreased ability of aged muscle to sustain power. In addition, we conclude that the diminished ability of the grafted MG muscle to sustain power may be explained, in part, by a decrease in energy available from oxidative metabolism.     

Immunohistochemical studies on sympathetic and non-sympathetic nerve fibers and neuronal cell bodies in the pineal gland of cotton rats, Sigmodon hispidus

This study evaluated the performance of sapphire and fused silica hemispherical tips under the same exposure conditions. Lesions produced in the chicken breast and a blood field were sectioned for light and transmission polarizing microscopy. Lesion size and thermal damage area were recorded as a function of the tips accumulated exposure. The tips transmission was measured after every 1,000 J of exposure. Fused silica tips lasted for approximately 5,000 J and experienced significant surface and transmission deterioration. The sapphire hemispherical tips lasted for > 12,000 J with no surface and transmission deterioration. Lesions produced with the fused silica tips generally increased in depth with use, and depths of 6 mm were common. Lesions produced by the sapphire tips were subsurface spherical areas of coagulation with the tissue surface relatively intact. This difference in resulting lesions may be attributed to the higher thermal conductivity of sapphire.     

Effect of testosterone propionate treatment on thyrotropin secretion of young and old rats in vitro

The aim of this study was to evaluate the influence of androgens on TSH secretion during aging in Dutch rats. Male young (2 months) and old (16-21 months) rats were castrated (Cx) or sham-operated (C) and received testosterone propionate (TP--4 mg/Kg B.W., i.m., 7 days) or vehicle. Female adult (3 months) and old (12 and 17 months) intact rats received TP or corn oil in the same dose. The rats were decapitated, trunk blood was collected and anterior pituitaries were dissected out for in vitro incubation. In Cx young male rats, only TSH pituitary content showed lower levels than in their controls. Cx TP-treated rats showed higher serum TSH and in vitro basal and TRH-induced TSH secretion, but TP only partially reversed the decrease in pituitary TSH promoted by castration. The old male rats showed lower basal in vitro TSH secretion and pituitary TSH content. In Cx old male rats, serum and basal in vitro TSH concentrations were higher than those of old controls and TP treatment further increased basal in vitro TSH secretion, as well as, stimulated TRH-induced TSH secretion. Interestingly, TP had no effect on intact young or old male rats. However, in intact old female rats, TP stimulated in vitro TSH secretion but, as observed in the intact male, TP had no effect on adult female rats. These results suggest a stimulatory role of testosterone on TSH secretion of young and old male rats. Thereafter, it seems that the testes of old rats secrete some testicular factor that inhibits TSH secretion. However, in male rats with normal testosterone levels TP treatment did not increase further TSH secretion, but in old female rats it had a stimulatory effect.     

Uptake and release of catecholamines in sympathetic nerve fibres in the spleen of the cod, Gadus morhua

The problems of lung function testing methods in epidemiological studies were assessed in a study population of 853 men aged 40-70. The Helium-rebreathing-method, the X-ray densitometry, the oxygen-method were evaluated for the estimation of the residual volume in epidemiological conditions. The Pneumotest was proved for measurement of unequal ventilation. The necessity of reference values for these methods is discussed.     

Oncogenicity testing of 2-ethylhexanol in Fischer 344 rats and B6C3F1 mice

An increasing number of studies, both experimental and epidemiologic, have provided evidence that filtering glaucoma surgery may be less effective than initially described. Of a number of risk factors for failure, duration and number of antiglaucoma drugs prior to surgery seem to play a critical role and highly accumulated antiglaucoma topical treatments significantly reduce success rates. Histopathological studies have confirmed that topically applied drugs may exert toxic effects to the corneoconjunctival surface, and induce chronic infraclinical inflammation, as shown by the presence of immune and inflammatory infiltrates in multitreated eyes. The origin of topical inflammation has not yet been clearly determined, but a common component of ophthalmic drugs, the benzalkonium chloride used as preservative in almost all antiglaucoma preparations, has shown strong evidence of toxicity. A number of questions remain to be investigated, but suppression of preservatives from chronically applied drugs should be a critical issue in the near future.     

Protective effects of glutathione on bromodichloromethane in vivo toxicity and in vitro macromolecular binding in Fischer 344 rats

Bromodichloromethane (BDCM), a carcinogenic water disinfection by-product, has been shown to be metabolized to intermediates that covalently bind to lipids and proteins, and this binding has been associated with trihalomethane-induced renal and hepatic toxicity. In this study, the effects of glutathione (GSH) on in vivo BDCM toxicity and in vitro BDCM macromolecular binding were evaluated. The in vivo toxicity of BDCM in animals pretreated with buthionine sulfoximine (BSO, a glutathione synthesis inhibitor) and in untreated male Fischer 344 rats was investigated. In another experiment, covalent binding to protein and lipid was quantified after [14C]BDCM was incubated with hepatic microsomal and S9 fractions and renal microsomes from F344 rats, under aerobic and anaerobic conditions, with and without added GSH. After oral dosing with BDCM, the BSO-pretreated animals had greatly increased levels of serum indicators of hepatotoxicity and serum and urinary indicators of nephrotoxicity compared to those in animals dosed solely with BDCM. Histopathological examination revealed that hepatic necrosis was more severe than renal necrosis in the BSO-treated rats. When GSH was added to an aerobic incubation, protein binding was decreased in hepatic microsomal and S9 fractions by 92 and 83%, respectively. GSH also decreased lipid binding by 55% in hepatic microsomal incubations carried out under anaerobic conditions. Addition of GSH decreased renal microsomal protein (aerobic) and lipid binding (anaerobic) by 20 and 43%, respectively. These data indicate that GSH is an important protective factor in the toxicity associated with BDCM.     

Function of galanin in the anterior pituitary of estrogen-treated Fischer 344 rats: autocrine and paracrine regulation of prolactin secretion

Estrogen is a robust stimulator of galanin synthesis and secretion in the anterior pituitary. Galanin is colocalized in lactotrophs in the estrogen-treated anterior pituitary, and its roles in lactotroph function are still being elucidated. In the present studies, we quantified the phenotypes of estrogen-treated Fischer 344 rat anterior pituitary cells expressing the galanin gene by dual in situ hybridization. The total population of galanin-positive pituitary cells increased from undetectable levels to 16% of all cells after 2 weeks of estrogen treatment. More than 90% of the galanin-positive cells coexpressed PRL messenger RNA, and one-third of the lactotrophs expressed galanin messenger RNA. We hypothesized that galanin in the anterior pituitary may contribute to the heterogeneous secretion of PRL, and that one of the functions of galanin is to regulate PRL secretion in an autocrine/paracrine manner. To test this hypothesis, we performed the reverse hemolytic plaque assay combined with in situ hybridization to measure PRL secretion and galanin gene expression within the same individual cells. PRL secretion from galanin-positive lactotrophs was significantly greater than that from galanin-negative lactotrophs. Moreover, treatment with galanin antiserum significantly attenuated PRL secretion from galanin-positive cells, and treatment with galanin significantly enhanced PRL secretion from galanin-negative lactotrophs. In conclusion, these data provide direct evidence that galanin derived from the estrogen-treated anterior pituitary stimulates PRL secretion in both autocrine and paracrine manners.     

Changes in natural killer cell activity and prostaglandin E2 levels during the progression of diethylnitrosamine-induced hepatocarcinogenesis in Fischer 344 rats

The sequential changes of natural killer cell (NK) activity and prostaglandin E2 (PGE2) during hepatocarcinogenesis induced by diethylnitrosamine (DEN) in male Fischer 344 rats were investigated. DEN at a concentration of 40 ppm was administered in drinking water for 10 weeks. At weeks 5, 10, 20 and 30, rats were autopsied and the development of glutathione S-transferase placental form positive foci (GST-P+ foci) at weeks 5 and 10 and hepatocellular tumors at weeks 20 and 30 were examined. The labeling index of bromodeoxyuridine (BrdU) an indicator of DNA synthesis, was also sequentially checked. GST-P+ foci were found to increase with age. Hepatocellular nodules increased until week 20, but by week 30 when the incidence of hepatocellular carcinoma was 100%, the incidence of nodules had decreased. BrdU positive cells also increased with age, and by week 30 when the incidence of hepatocellular carcinoma was 100%, the number of BrdU-positive cells had decreased. NK cell activity increased until week 10, but at week 20, was less than in the untreated control group. The level of PGE2 increased until week 5, but at week 10, levels were not significantly different from those seen in the untreated control group. On the basis of these results, we concluded that NK activity is closely related to the progression of hepatocarcinogenesis, but PGE2 levels show no significant change.