Browsing by Subject "Rats -- Physiology"
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Item 1,25-dihydroxyvitamin Db3s gut receptor kinetics in Japanese quail and vitamin D metabolism in calcium-depleted rats(Texas Tech University, 1981-08) Abel de la Cruz, Luis AndresNot availableItem Characterization of taurine binding, uptake, and release in the rat hypothalamus(Texas Tech University, 1985-08) Hanretta, Allan ThomasNot availableItem Diabetes and streptozotocin-induced alterations in the rat myocardial [beta]-adrenoceptor system(Texas Tech University, 1985-08) Ramanadham, SasankaDiabetogenic agent streptozotocin (STZ) was used to induce diabetes in male Sprague-Dawley rats. A single i.v. administration of the drug resulted in marked hyperglycemia, glycosuria, polyuria, polydipsia, and hyperphagia. The diabetic state was found to be associated with alterations in cardiovascular tissue responsiveness and sensitivity. Vascular alterations Thoracic aortic strips isolated from STZ-treated animals were found to be less responsive to calcium, relative to control animals. However sensitivity to the a-agonists, norepinephrine and methoxamine, was unchanged. In contrast to aorta, tail arteries were similar in responsiveness to calcium and supersensitive to the contractile effects of the a-agonists. The supersensitivity was found to be associated with decreased tissue norepinephrine content. This indication of neuropathy suggested that both pre- and post-junctional alterations influence sensitivity of the tail artery to a-agonists in STZ-diabetic animals. Myocardial alterations Basal rate of spontaneously beating atria and maximum chronotropic responses to isoproterenol were lowered after STZ treatment. Sensitivity to the B-agonist however, was not affected. Right ventricular tissue isolated from STZ-treated animals was found to be subsensitive to the inotropic effects of isoproterenol. The subsensitivity phenomenon was found to be accompanied by decreased myocardial B-adrenoceptor density, increased basal developed force, and supersensitivity to calcium. Detailed characterization of the subsensitivity phenomenon revealed that it was independent of (a) age of the animal, (b) duration of diabetes up to six months, (c) direct cardiotoxic effects of STZ, (d) resting tension, (e) frequency of stimulation, (f) changes in heart norepinephrine content, (g) BDF, and (h) supersensitivity to calcium. Inotropic responses obtained with methoxamine, an adenylate cyclase (AC)-independent agonist; glucagon, a receptor- and AC dependent agonist; and forskolin, a direct activator of AC; provided indirect evidence for a "defect" in the ability of isoproterenol to activate AC, via B-adrenoceptor stimulation, in hearts obtained from STZ-treated animals. This defect was linked to (1) decreased B-adrenoceptor density and (2) decrease in the high affinity state population of the B-adrenoceptor. Since the high affinity state of the receptor is a necessary intermediate for AC activation and myocardial contraction, it might be proposed that the decreased population of receptors in this state after STZ treatment contributes to the development of inotropic subsensitivity to isoproterenol. It is further proposed that the down-regulation of receptor population is related to an increase in circulating epinephrine levels, which were evident in diabetic animals. It might also be proposed that myocardial inotropic subsensitivity to B-stimulation is an important factor contributing to heart failure seen among diabetic patients.Item Effect of diabetes on composition and metabolism of heart lipids(Texas Tech University, 1980-08) Paulson, Dennis JNot availableItem Effect of feeding N-2-fluorenylacetamide and graded levels of coconut oil and corn oil on young male rats(Texas Tech University, 1980-05) Chou, Tien-loNot availableItem Effect of phytate added to a casein-based diet on endogenous zinc and study of pancreatic/biliary fluid fractions in rats(Texas Tech University, 1995-05) Kwun, In-SookThe purpose of the current research was to study the effect of phytate and Ca level on the endogenously secreted zinc. Sprague-Dawley rats (48) were fed a casein-based diet with added Na phytate containing either high (1.6 %) or low (0.8 %) Ca for 4 weeks to reduce the body Zn pool. After the depletion period, 65Zn was given IP to label the endogenous pool. Feces were collected for 3 wks (2 wks of the initial collection and 1 wk after dietary crossover). The ratios of excreted radioactivity phytate/non-phytate were determined as a measure of the phytate effect on endogenous zinc. Mean fecal 65Zn radioactivity was higher in the phytate, low Ca group (4582 ± 345 cpm/d) than in nonphytate, low Ca group (3990 ±215 cpm/d) during the initial collection period as well as during the crossover collection period, phytate group (3077 ±146 cpm/d) vs. non-phytate group (2376 ± 96 cpm/d) (p<0.0001). For the high Ca diets, the fecal 65Zn was higher for the phytate than the non-phytate during the 14 day collection (p<0.0001) but was not different after dietary crossover (p>0.05). Ratios of phytate/non-phytate ranged from 0.66-1.77 for low Ca diet and 0.64-1.99 for the high Ca diet. Since ratios above 1 represent a phytate effect on complexing endogenous Zn, this study showed phytate effect at both dietary Ca levels. At the elevated dietary Ca level, the phytate effect was synergized by dietary Ca (p<0.05). At the termination of the collection period, the common bile duct was cannulated with small bore tubing and pancreatic/biliary fluid collected with protein stimulation. Pancreatic/bniary fluid was applied to a Sephadex G-75 column and eluted with 0.01 mol/L Tris buffer, pH 8.1. Subfractions (2.5 mL) were collected for analysis of protein, total Zn concentration and 65Zn radioactivity. Distribution of protein in subfractions showed a peak corresponding to the high molecular weight protein standard (>66 kDa) in the pancreatic/biliary fluid. A more remarkable small molecular weight fraction was eluted near the 6.5 kDa protein standard. This demonstrates the presence of small molecular weight compounds in pancreatic/biliary fluid associated with zinc which may serve as ligands for the secretion of endogenous Zn into the duodenum. These ligands may dissociate Zn in the duodenum thus making it vulnerable to phytate complexation. It was estimated that the zinc concentration in the pancreatic/biliary fluid for one day (311.40 |ig/ day) was about 2.9 times greater than the zinc amount of dietary zinc consumed for one day (107.89 p-g/ day). Also, the dietary phytate group showed 72% of the zinc reabsorption which was enough to replace 63% of zinc which was secreted from pancreas for the zinc homeostasis.Item Effect of tallow and corn oil on the metabolism of 2-acetylaminofluorene (ACAF) in rats(Texas Tech University, 1977-08) Castro, Carmen ElizabethNot availableItem Effects of dietary sodium chloride on the availability and utilization of proteins in laboratory animals(Texas Tech University, 1983-05) Hussain, HadidahNot availableItem Effects of molybdenum and tungsten supplementation on N-methyl-N-nitrosourea-treated female rats(Texas Tech University, 1986-08) Chao, Wei-lin VikylNot availableItem Effects of molybdenum and tungsten supplementations on growth and mineral metabolism of female rats fed AIN-76A or lab chow(Texas Tech University, 1986-05) Yan, LinNot availableItem Effects of molybdenum and tungsten supplementations on molybdenum- and copper- enzymes of female rats fed AIN-76A or lab chow(Texas Tech University, 1986-08) Pan, Yi WenNot availableItem Electrophysiological analysis of cerebellar serotonergic mechanisms in thiamine deficiency(Texas Tech University, 1983-08) Lee, Rong-shengNot availableItem Electrophysiological responses of Purkinje cells to serotonin receptor subtype analogs in the cerebellar slice(Texas Tech University, 1989-05) Darrow, Eric JonNot availableItem Estradiol regulation of uterine nucleolar RNA synthesis(Texas Tech University, 1993-08) Brantley, Kenny MAdministration of estradiol (E) to mature ovariectomized rats results in an early (4h) increase in nucleolar transcriptional activity above controls, this increase is totally due to an increased elongation rate of nascent transcripts. Salt extraction (150 mM NaCl) of isolated nucleoli eliminates the early stimulatory effect of E on nucleolar transcriptional activity. Addition of salt extracts obtained from uterine nucleoli of animals treated with E (4h) to nucleoli isolated from uteri of control animals resulted in increased transcriptional activity. The stimulation was due to an increased rate of elongation of nascent chains in uterine nucleoli. Treatment of animals with cycloheximide (eye) or actinomycin D (AD) eliminates the E induced stimulation and the stimulatory activity of salt extract from nucleoli isolated from E treated animals on control uterine nucleoli. Alkaline phosphatase treatment of nucleoli in vitro also is able to eliminate the E induced increase in transcriptional activity. Isolated uterine nucleoli and the salt extracts (E treated and control) contain active protein kinase(s), which are capable of in vitro phosphorylating a number of proteins in nucleoli isolated from control and E treated animals using ATP or GTP as substrate. In vivo E treatment results in the phosphorylation of a single protein with an apparent molecular weight of 105 kDa. Treatment of animals with AD or eye blocks the in vivo phosphorylation of a 105 kDa protein but not the in vitro phosphorylation, suggesting that the protein substrates and at least one of the endogenous nuclear kinase(s) are not the targets of the metabolic inhibitors. Decreased in vitro phosphorylation of a number of other proteins is also observed due to AD or eye treatment in vivo. In vitro treatment of nucleoli with camptothecin, a specific inhibitor of topoisomerase I, was capable of inhibiting the E induced increase in nucleolar RNA synthesis. Results showed that topoisomerase was necessary but not sufficient for the E induced increase in nucleolar RNA synthesis. Leupeptin, an inhibitor of the processing of nucleolin, a 105 kDa phosphoprotein, was also capable of inhibiting E induced increase in nucleolar RNA synthesis. These results point to a role of phosphorylation of the 105 kDa protein in the early E induced stimulation of nucleolar RNA transcriptional activity. Nucleolin is a possible candidate for the 105 kDa protein that is phosphorylated in vivoItem Estradiol stimulation of glucose transport in rat uterus(Texas Tech University, 1985-08) Meier, Daniel AlanA study of the mechanism of the estradiol-mediated increase in glucose transport in the uteri of ovariectomized rats was undertaken. An essential first step in this study was the characterization of the glucose transport process using plasma membrane vesicles. Uterine plasma membrane preparations were obtained by centrifugation on discontinuous sucrose gradients. The specific activity of the plasma membrane marker 5'-nucleotidase was increased 10-fold while the specific activity of an endoplasmic reticulum marker glucose-6-phosphatase was increased 3-fold. D-Glucose transport into plasma membrane vesicles was inhibited by sulfhydryl reagents, phloretin, and cytochalasin B. Uptake was prevented by high osmotic pressures. The Km of glucose transport was 12.2 +_ 1.1 mM. Transport was unaffected by sodium and was energy independent. 2-Deoxyglucose transport was determined in uteri of rats grouped by stages of the reproductive cycle, i.e., diestrus 1, diestrus 2, proestrus and estrus. The rate of 2-deoxyglucose transport was highest in proestrus and lowest in diestrus 1. The increase in glucose transport in ovariectomized rats was half-maximal at approximately 5 ng estradiol/rat and reached the maximal 2 to 3-fold response after 2 hours whether measured in whole tissue or in uterine plasma membrane vesicles. Estrone and estriol treatment resulted in a similiar 2-fold increase in glucose transport while progesterone and dihydrotestosterone had no effect. Injection of protein synthesis inhibitors cycloheximide and emetine resulted in an increase in the basal glucose transport rate while having no effect on the estradiolstimulated increase in glucose transport. Treatment with the transcriptional inhibitor actinomycin D resulted in a slight increase in glucose transport with no effect on the estradiol-stimulated increase in glucose transport. Antiestrogen treatment (nafoxidine and tamoxifen) resulted in a 85-90 % decrease in the total estradiol binding sites in the cytosol but did not effect the estradiol stimulated increase in 2-deoxyglucose transport in uterine tissue. Insulin injection (0.2 mg/rat) resulted in a 40 % increase in 2-deoxyglucose transport in 24 h-starved rats in contrast to the 200 % increase seen with estradiol treatment. Insulin and estradiol treatment together were not additive in regard to the increase in 2-deoxyglucose transport in tissue. Estradiol treatment did not change binding of [1251 ] insulin to uterine plasma membranes. Estradiol treatment resulted in a 3-fold increase in the Vmax with no apparent change in the Km for 2-deoxyglucose transport. Also, estradiol treatment did not result in an increase in the amount of glucose transporters in uterine plasma membranes as measured by antibodies raised against the glucose transporter protein from human erythrocytes. In summary, estradiol stimulates the rate of glucose transport in rat uterus by increasing the rate by which the transporter protein moves glucose across the plasma membrane .Item Excitatory amino acids in the cerebellum(Texas Tech University, 1993-08) Netzeband, Jeffrey GlenIn recent years, it has been shown diat the class of excitatory amino acid transmitters is very important for neurotransmission throughout the nervous system. Glutamate and aspartate are the most common endogenous transmitters of this class, but it is now known that they exert their actions through a multitude of receptor subtypes. Furthermore, modifications of excitatory amino acid transmission are believed to underlie many forms of sensory and motor learning in the brain, whereas perturbations of these systems underlie many neuropathologies. Since the cerebellum is involved with motor coordination and the cerebellar Purkinje cell forms a crucial link in the formation of motor learning, a thorough understanding of excitatory amino acid neurotransmission would be desirable. Extracellular recording techniques were coupled with microiontophoretic application of drugs to test the effectiveness of several endogenously and exogenously occurring excitatory amino acids in exciting cerebellar Purkinje cells in the anesthetized rat. Also, further characterization of N-methyl-D-aspartate (NMDA)-mediated responses was done as some studies have suggested that Purkinje cells do not have NMDA receptors. Results from these studies indicate that agents from all classes of excitatory amino acids are enable of exciting Purkinje cells and that NMDA-induced excitations are mediated through the classically defined NMDA receptor. Additionally, serotonin was shown to depress responses elicited by some but not all of the excitatory amino acids. These results suggest that all classes of excitatory amino acids are important for neurotransmission within the cerebellum and that serotonin may selectively modulate some of these pathways, thus affecting motor learning and coordination.Item Glucose, insulin and lipase activity of rats fed chromium from beef and soy(Texas Tech University, 1983-08) Keim, Kathryn Sarah HochsprungNot availableItem Hormonal effects on Sertoli cell junctions(Texas Tech University, 1982-12) Wilkinson, Terry LNot availableItem Influence of dietary cholesterol, cholic acid, isethionic acid and methionine on cholesterol and bile acid metabolism in the rat(Texas Tech University, 1977-05) Medina, Evangeline VariasNot availableItem Influence of phytates on chromium nutrition of the rat(Texas Tech University, 1981-05) Gates, Gail EstherObjectives of this research were to produce a chromium (Cr) deficiency in rats in our laboratory as assessed by glucose removal rate and to determine if phytate would exacerbate the chromium deficiency state. Weanling male Sprague-Dawley rats were randomly assigned to one of 5 dietary groups: negative control without added chromium or phytate, low sodium phytate with 0.8% phytate, high sodium phytate with 2.8% phytate for 3 weeks then 1.4% phytate, calcium phytate with 1.8% phytate, or 5 parts per thousand chromium (chromic chloride) added to the diet. Intravenous glucose tolerance tests were performed during weeks 5, 7, and 9, and non-fasting plasma glucose values were determined during the final week of the study. Results showed that plasma glucose removal rates indicative of impaired glucose tolerance were produced. The rats fed calcium phytate seemed to exhibit the lowest glucose removal rate (1.9%/min) despite the high dietary chromium content (737 ppb). However, there were no significant differences (p<0.05) between groups in week 9. The group fed excessive chromium did not maintain a normal removal rate throughout the study. Negative controls showed the highest mean non-fasting plasma glucose level of 166+7.20 mg/dl. It was significantly higher (p<0.05) than the values of the excessive chromium group (144+5.02 mg/dl) and the high sodium phytate group (138+2.50 mg/dl). Thus, it appears that a chromium deficiency was produced in our laboratory as assessed by plasma glucose removal rate and that phytates may make chromium unavailable for Zabsorption.