Strains of Taenia taeniaeformis were shown to possess markedly differing infectivities for Sprague-Dawley rats and CFI mice. Strains from Scotland, Belgium and Iraq were more infective for mice than rats while this situation was reversed with a Malaysian strain. There were also differences in their ability to infect hosts of different ages within the range 3-12 weeks of age.
The development of Breinlia booliati is described in its natural host, Rattus sabanus and in an inbred strain of laboratory albino rat. The growth of the parasite is similar in both the rat hosts. The third moult occurs between six-eight days and the final moult between 24-28 days. Larvae were recovered initially from the skin and carcass. After five weeks, developing stages were seen only in the thoracic and abdominal cavities, the site of development of the adult worms. Worms became sexually mature by 11-12 weeks and there was considerable growth in length of the female worms after this stage.
1. A series of experiments were conducted to investigate the effect of endogenous opioids on blood pressure of laboratory rats during stress. 2. Rats subjected to 120 min immobilization showed a significant drop in systolic pressure which could be prevented by pretreatment injections of naloxone. 3. Adrenalectomized rats subjected to the same kind of stress showed a drop in systolic pressure equivalent to only 30% of the systolic pressure drop in the intact animals. This decrease in systolic pressure could also be prevented by pretreatment injections of naloxone. 4. It was concluded that the decrease in systolic pressure in intact rats during immobilization was mostly due to endogenous opioids released from the adrenal glands, whereas opioids of other origins such as the pituitary gland, were also important.
Although there are multiple rodent models of the metabolic syndrome, very few develop vascular complications. In contrast, the JCR:LA-cp rat develops both metabolic syndrome and early atherosclerosis in predisposed areas. However, the pathology of the normal vessel wall has not been described. We examined JCR:LA control (+/+) or cp/cp rats fed normal chow diet for 6 or 18 mo. JCR:LA-cp rats developed multiple features of advanced cystic medial necrosis including "cysts," increased collagen formation and proteoglycan deposition around cysts, apoptosis of vascular smooth muscle cells, and spotty medial calcification. These appearances began within 6 mo and were extensive by 18 mo. JCR:LA-cp rats had reduced medial cellularity, increased medial thickness, and vessel hypoxia that was most marked in the adventitia. In conclusion, the normal chow-fed JCR:LA-cp rat represents a novel rodent model of cystic medial necrosis, associated with multiple metabolic abnormalities, vascular smooth muscle cell apoptosis, and vessel hypoxia.NEW & NOTEWORTHY Triggers for cystic medial necrosis (CMN) have been difficult to study due to lack of animal models to recapitulate the pathologies seen in humans. Our study is the first description of CMN in the rat. Thus the JCR:LA-cp rat represents a useful model to investigate the underlying molecular changes leading to the development of CMN.
Male Sprague Dawley rats were fed semipurified diets containing 20% fat for 15 weeks. The dietary fats were corn oil, soybean oil, palm oil, palm olein and palm stearin. No differences in the body and organ weights of rats fed the various diets were evident. Plasma cholesterol levels of rats fed soybean oil were significantly lower than those of rats fed corn oil, palm oil, palm olein or palm stearin. Significant differences between the plasma cholesterol content of rats fed corn oil and rats fed the three palm oils were not evident. HDL cholesterol was raised in rats fed the three palm oil diets compared to the rats fed either corn oil or soybean oil. The cholesterol-phospholipid molar ratio of rat platelets was not influenced by the dietary fat type. The formation of 6-keto-PGF1 alpha was significantly enhanced in palm oil-fed rats compared to all other dietary treatments. Fatty acid compositional changes in the plasma cholesterol esters and plasma triglycerides were diet regulated with significant differences between rats fed the polyunsaturated corn and soybean oil compared to the three palm oils.
Male albino rats were chronically loaded with sodium by giving 1% NaCl solution as the sole source of drinking water. Daily fluid intake, daily urinary output and daily Na+ and K+ excretion rates were compared with control rats receiving tap water for six weeks. At the end ofsix weeks, sodium loaded animals were found to have raised plasma Na+ concentration, lowered plasma K+ concentration and lowered haematocrit value. Sodium loaded rats were also significantly more responsive to the pressor effect of submaximal doses of adrenaline, noradrenaline and angiotensin II given intravenously. It is concluded that the increase in sensitivity to adrenaline and noradrenaline may be due to changes in EGF and alterations of plasma electrolytes concentration. For angiotensin II, additionally, it may be due to low circulating endogenous angiotensin II, consequent of reduction in renin release attributed to chronic sodium loading.
The dorsal skin of 18 healthy Sprague-Dawley rats was used to investigate the reaction of connective tissue to buffered and unbuffered glutaraldehyde. Both the agents produced well-circumscribed lesions that underwent resolution within 30 days. Observation also shows that 2.0% buffered and unbuffered glutaraldehyde maintained a relatively inflammation-free status in connective tissue.
The effect of specific alpha[ or alpha2 adrenoceptor agents on the response of rat superior mesenteric-portal vein to field stimulation was investigated. In. a dose related manner, phenylephrine (alpha[ agonist) and yohimbine (alpha2 antagonists) increased while prazosin (alpha[ antagonist) and clonidine (alpha2 agonist) decreased the response of the vein to field stimulation. These effects are the same as those seen with these agents on rat and mouse vas deferens. It is suggested that, as in vas deferens, alpha1 postsynaptic and alpha2 presynaptic receptors exist in rat superior mesenteric-portal vein and that these receptors may be sufficiently sensitive in vein for their existence to be of significance in the action of these agents at clinical doses.
1. Steroid hormones have been shown to regulate the concentration of adrenergic and muscarinic receptors in many tissues. 2. The cyclic adenosine 3',5'-monophosphate (cAMP) content in rat lung tissues in response to either dexamethasone, corticosterone, deoxycorticosterone or progesterone for 7 days were measured following intraperitoneal injection of isoprenaline just before sacrificed. 3. There was a significant increase in cAMP level (P less than 0.001) in dexamethasone and corticosterone-treated rats compared to controls that received isoprenaline alone. 4. Pretreatment with deoxycorticosterone and progesterone suppressed the increase in cAMP in response to isoprenaline. 5. The effect of glucocorticoids in causing bronchodilatation in asthmatic patients is partly due to the restoration of adenyl cyclase responsiveness to beta-agonist.
The possible role of cyclic adenosine 3',5'-monophosphate (cAMP) in mediating the action of steroid hormones was investigated using the rat lung. Male rats were adrenalectomized and treated with olive oil, dexamethasone, corticosterone, deoxycorticosterone (DOC) or progesterone. At the end of 10 days, 100 micrograms isoprenaline/kg was injected intraperitoneally 5 min before the animals were killed to stimulate cAMP production. Adrenalectomy significantly decreased cAMP levels in the rat lung. Dexamethasone and corticosterone pretreatment reversed the effect of adrenalectomy whereas progesterone pretreatment but not DOC pretreatment significantly decreased lung cAMP levels. Cyclic AMP levels in normal female rats, whether pregnant or not, were not significantly different from those in male rats. We concluded that the absence of glucocorticoid, as after adrenalectomy, decreased the cAMP levels in rat lungs and that this could be reversed by either dexamethasone or corticosterone replacement. Progesterone reduced the cAMP content in rat lungs by acting as a glucocorticoid antagonist or by acting directly via progesterone receptors.
Breinlia booliati exhibited nocturnal subperiodicity in its natural host, Rattus sabanus in contrast to experimentally infected laboratory-reared albine rats which showed irregular fluctuations of microfilariae throughout the 24 hour cycle. All the infected albino rats showed a prepatent period between 11-14 weeks postinoculation. Three patterns of microfilaraemia were discerned during the course of infection 38/49 rats displayed a single peak, 4/49 displayed 2 peaks about 12-15 weeks apart and 7/49 showed a sustained high plateau-like pattern of microfilaraemia. Cortisone had no effect on microfilarial levels when administered to rats near postpatency and some at postpatency.
Gonadectomized male albino rats aged 7 weeks were given 1.5 mg/kg testosterone propionate daily and inoculated with 50 third-stage larvae of Angiostrongylus malaysiensis. The treatment significantly increased the number of larvae and adult worms recovered from the brain and pulmonary arteries, respectively, and the rats exhibited smaller thymus glands. The total numbers of leukocytes, monocytes, neutrophils, and especially eosinophils increased significantly post-infection, but the counts were higher in the untreated infected controls. Presumably, immunosuppressive effects of testosterone may at least partly be responsible for the higher loads of A. malaysiensis worms found in male rats as compared with females in the field.
Paddy (unmilled rice), milled rice and maize-bound 14C residues were prepared using 14C-succinate-labelled malathion at 10 and 152 ppm. After 3 months, the bound residues accounted for 12%, 6.5% and 17.7% of the applied dose in paddy, milled rice and maize respectively in the grains treated at 10 ppm. The corresponding values for the 152 ppm were 16.6%, 8.5% and 18.8%. Rats fed milled rice - bound 14C-residues eliminated 61% of the 14C in the faeces and 28% in the urine. The corresponding percentages for paddy and maize were 72%, 9% and 53%, 41% respectively; indicating that bound residues from milled rice and maize were moderately bioavailable. When rice-bound malathion residues (0.65 ppm in feed) were administered to rats in a 5 week feeding study, no signs of toxicity were observed. Plasma and RBC cholinesterase activities were slightly inhibited: blood urea nitrogen was significantly elevated in the test animals. Other parameters examined showed no or marginal changes.
Female Sprague-Dawley rats, 50 days of age, were treated with a single dose of 5 mg of 7,12-dimethylbenz(a)anthracene intragastrically. 3 days after carcinogen treatment, the rats were put on semisynthetic diets containing 20% by weight of corn oil (CO), soybean oil (SBO), crude palm oil (CPO), refined, bleached, deodorized palm oil (RBD PO) and metabisulfite-treated palm oil (MCPO) for 5 months. During the course of experiments, rats fed on different dietary fats had similar rate of growth. Rats fed 20% CO or SBO diet have higher tumor incidence than rats fed on palm oil (PO) diets; however differences of mean tumor latency periods among the groups were not statistically significant. At autopsy, rats fed on high CO or SBO diets had significantly more tumors than rats fed on the three PO diets. Our results showed that high PO diets did not promote chemically induced mammary tumorigenesis in female rats when compared to high CO or SBO diets. CO and SBO differ greatly from the palm oils in their contents of tocopherols, tocotrienols, and carotenes. But further experiments would be required to determine whether the observed differences in tumor incidence and tumor numbers were due to the differences in these minor components or due to the unique triglyceride structure of the palm oils. Analysis of the fatty acid profiles of plasma total lipids of tumor-bearing rats and of the tumor total lipids showed that, with the exception of arachidonic acid, the fatty acid profiles reflect the nature of the dietary fats. At autopsy, there were no differences in the plasma total cholesterol contents among rats fed on different dietary fats, but rats fed on palm oil diets had a significantly higher plasma triglyceride level than that of rats fed CO or SBO diets. As for the tumor lipids, there were no significant differences in the triglyceride, diglyceride, and phospholipid levels when the CO or SBO groups were compared to the palm oil groups.
Capillary gas chromatographic 'steroid profiling' has been utilised to separate and quantify the metabolites (derivatized as methyloximes and/or trimethylsilyl ethers) formed from pregnenolone after incubation with rat testicular microsomes. A wide range of steroid metabolites was found, indicating that both the 5-ene and 4-ene pathways of testosterone biosynthesis were operating, as well as 16 alpha-hydroxylation, 20 beta-reduction and the formation of several C19 steroids (the 16-androstenes). At the concentration used, Metyrapone markedly inhibited 16 alpha- and 17-hydroxylation and side-chain cleavage of 17-hydroxylated C21 steroids. 16-Androstene production was also markedly inhibited and the formation of other metabolites was affected to lesser extents. Oxytocin abolished the formation of all C21 and C19 metabolites of pregnenolone.
Twenty authentic steroids, derivatized as O-methyl oximes (MO), trimethylsilyl (TMS) ethers or as MO-TMS ethers have been subjected to capillary gas chromatography using two different columns. Virtually all of the steroid derivatives have been resolved, one difficult pair to separate being 5,16-androstadien-3 beta-ol and 5 alpha-androst-16-en-3 beta-ol on the non-selective phase OV-1. Where syn and anti forms of MO derivatives arose, these were also resolved under the conditions utilised. This technique of 'steroid profiling' has been applied to the separation and quantification of metabolites of pregnenolone which were formed during incubations of the microsomal and cytosolic fractions from rat testes. The majority of the metabolites were found in the microsomal incubation. These compounds included some odorous 16-androstenes as well as other C21 and C19 steroids, the formation of which was consistent with the 5-ene and 4-ene pathways of testosterone biosynthesis being operative. In addition, evidence was obtained for 16 alpha-hydroxylation of C21 steroids. Very much less metabolic activity was found in the cytosolic fraction of rat testes. Metabolic pathways have been proposed which both confirm and extend earlier work. We conclude that the rat testis can only form some of the odorous, possibly pheromonal, 16-androstenes and that these are quantitatively less important than in the porcine testis.
In Malaysia, an aqueous extract of Tinospora crispa stems is taken orally to treat diabetes mellitus. In the present study, normal and alloxan-diabetic rats were used to evaluate the hypoglycaemic properties of the extract. A hypoglycaemic effect was observed in moderately diabetic rats with concomitant improvement in insulinaemia. After a 2-week treatment with the extract (4 g/l in the drinking water), these rats also showed improvement in glucose tolerance. Moreover, acute intravenous treatment with the extract (50 mg/kg) caused an increase in plasma insulin levels. The data support the traditional belief that T. crispa extract could improve diabetic conditions by virtue of its action on the endocrine pancreas.
The effects of long-term administration of tocotrienol on hepatocarcinogenesis in rats induced by diethylnitrosamine (DEN) and 2-acetylaminofluorene (AAF) were investigated by determining the activities of gamma-glutamyl transpeptidase (GGT), alkaline phosphatase (ALP), glutathione S-transferases (GSTs), and glutathione (GSH) levels in blood and liver. Twenty-eight male 7- to 8-wk-old Rattus norwegicus rats, weighing 120-160 g, were used in this study. The rats were divided into four treatment groups: a control group on a basal diet, a group fed a basal diet supplemented with tocotrienol (30 mg/kg food), a group treated with DEN/AAF, and a group treated with DEN/AAF and fed a diet supplemented with tocotrienol (30 mg/kg food). Blood was collected monthly, and GGT, ALP, and GSH levels were determined. The rats were killed after 9 mo, and the livers were examined morphologically. Grayish white nodules (2/liver) were found in all the DEN/AAF-treated rats (n = 10), but only one of the rats treated with DEN/AAF and supplemented with tocotrienol (n = 6) had liver nodules. A significant increase in the level of blood and liver GSH, ALP, and GGT activities was observed in the DEN/AAF-treated rats. Liver GSTs were similarly increased with DEN/AAF treatment. Tocotrienol supplementation attenuated the impact of the carcinogens in the rats.