Browsing by Subject "Rats"
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Item A comparison of proteins synthesized and secreted by peri-implantation embryos of rats and mice(Texas Tech University, 1992-08) Liu, Shao-tungPsychoyos (1973) has defined embryo implantation in rodents as the result of coordinated interactions between a uterus that is "receptive" and an embryo that has reached the "blastocyst stage" of development. In rats and mice, uterine "receptivity" is vaguely understood as the ability of the endometrium to undergo decidualization and formation of the maternal plancenta; it is achieved only after exposure to ovarian hormones secreted in a specific sequence (Psychoyos 1976) . The process of decidualization involves profound changes in both morphological and biocherical characteristics of the endometrial stroma including a localized increase in vascular permeability and tissue edema, increased rates of cell proliferation, differentiation of stromal cells into so-called "decidual cells," and increases in synthesis of DNA, RNA and protein (De Feo 1967 and Finn 1977). Because decidualization only occurs in areas adjacent to the blastocysts and can be observed even before their attachment to the uterus, it is believed that a soluble factor from the embryo must exist which acts as a signal to trigger the reaction. Although the nature of the soluble factor has not been determined, it has been proposed at one time or another that steroids, histamine, prostaglandins or proteins from the embryos are responsible (see Kennedy 1983; Weitlauf 1988, for reviews).Item A study of the influence of dietary protein on resistance of the albino rat to whole body irradiation at multiple sublethal doses(Texas Tech University, 1958-08) Rivers, Jerry MargaretNot availableItem Affective responses in cocaine-experienced rats reveal cue-induced drug craving and cocaine reward magnitude(2011-08) Maier, Esther Yvonne; Duvauchelle, Christine L.; Schallert, Timothy; Gonzales, Rueben A.; Gore, Andrea C.; Monfils, Marie H.The development and persistence of cocaine dependence are greatly influenced by emotional affect and cocaine associative learning. Cocaine is known to enhance nucleus accumbens (NAcc) dopamine, serve as a positive reinforcer and produce negative effects, such as anxiety that may influence cocaine intake behavior. In the first study, I investigated the effects of the anxiolytic, diazepam on NAcc dopamine levels and cocaine self-administration behavior. These are two factors associated with cocaine rewarding effects. Diazepam has no effect on NAcc dopamine, but affects cocaine self-administration. This supports the notion that decreasing the anxiogenic effects of cocaine increases the rewarding value in a dopamine independent manner. Therefore, increasing the aversive effects of cocaine might be a novel approach to fight cocaine dependence. In the second study, I studied cocaine-induced associative learning and changes in affect during cocaine conditioning and extinction. 50-kHz ultrasonic vocalizations (USVs) in rats are thought to reflect positive affect and occur upon appetitive stimuli and with cocaine delivery. First, I explored whether USVs might be elicited in anticipation of impending drug delivery. Shortly into conditioning, rats elicited USVs when placed in the cocaine-associated environment. USVs progressively increased, indicating a growing learned association between cocaine intake and cocaine-associated cues. This suggests that USVs may be a useful model for investigating cocaine craving and serve as a pharmacological target for interventions aimed to reduce cocaine craving and relapse. I then examined the effects of short-term deprivation of cocaine and cocaine cues on cocaine-conditioned USVs, which were both exaggerated after abstinence. The results may have clinical implications, in that intermittently avoiding cues or context may enhance drug cue salience and increase the probability of relapse. Motivational aspects of cocaine were assessed comparing commonly measured lever response rate and locomotion with cocaine-induced USVs during cocaine administration and extinction. In agreement with prevailing findings, lever responding for cocaine and cocaine-induced locomotor activity increased across conditioning sessions. However, the number of USVs evoked in response to cocaine infusion decreased with cocaine experience. These findings suggest growing tolerance to the rewarding properties of cocaine. These studies underscore the value of USV assessment during drug dependence studies.Item An experimental analysis of learning on the double-pattern maze(Texas Tech University, 1959-06) Harris, Charles StanleyNot availableItem Body weight loss and peptic ulcers in the albino rat(Texas Tech University, 1958-08) Moon, Harold LeonNot availableItem Cardiodynamic adaptive mechanisms of two kinds of stress in right and left ventricles of rat heart(Texas Tech University, 1982-05) George, Colleen O'Connordefinition of stress according to Selye is, ...the rate of wear and tear in the body " (42). Selye's ideas are expressed in a model of a general adaptation to the environment mediated by individual organs, particularly those of the nervous and endocrine systems. Adaptation is defined in the context of acclimatization; that is, an individual organism exhibits physiological and/or anatomical adjustments to a change in its immediate environment. Three levels of the stress syndrome are the alarm reaction, resistance, and exhaustion. Couched in different terminology, Ursin, Evind, and Seymour (49) view stress as a type of coping which is defined as advantageous changes in behavior or physiological responses to noxious or adverse stimulation. In their model, stress is viewed in the context of problem solving. Two kinds of adverse stimulation that have been studied at length are exposure to hypoxia and exercise. In both situations, the circulatory system demonstrates adaptation to the stressors. In the case of chronic adaptation to hypoxia, well described changes include increases in hematocrit, hemoglobin, RBC coimt, O2 carrying capacity and specific gravity of the blood, and total blood volume (50). Pulmonary hypertension and right ventricular hypertrophy also develop. Chronic adaptation to exercise, on the other hand, has been observed to result in an increased capillary density in skeletal and cardiac muscle, increased heart volume and weight, increased blood volume and cardiac output during maximal work, and increased stroke volume during rest, submaximal, and maximal work (5). Other increases have been observed in maximal oxygen uptake and blood lactate tolerance during maximal work. Decreases have been noted in heart rate at rest and during submaximal work. Other decreases have been found in oxygen uptake and blood lactate at given submaximal work loads.Item Developmental difference in the expression of neuronal damage following simulated hypoxia with cerebellar Purkinje cells(Texas Tech University, 1998-12) Barenberg, Paul DavidMorphological changes leading to neuronal cell death following a hypoxic insult in the brain are unclear. Cerebellar Purkinje cells (PCs) have been shown to exhibit selective vulnerability to hypoxia. In previous studies, PCs, in adult rats exposed to hypoxia, have shown a necrotic morphology, characterized by swelling of the cells, loss of membrane integrity, and lysis. In contrast, morphological changes in neonatal PCs following hypoxic injury consisted of cytoplasmic darkening and microvacuolization. This change, known previously as coagulative necrosis, has since been referred to as "dark cell degeneration" (DCD). The intent of the present study was to identify and characterize the mode of toxicity in 9-day-old and 21-day-old rat cerebellar Purkinje cells following hypoxic injury. Subsequent studies were designed to determine whether h5^oxic-induced DCD in PCs from 9-day-old rats represented an apoptotic event. Sagittal cerebellar slice preparation was used in the hypoxic model. Treated slices were submerged in Acsf and exposed to 30' of hypoxia (95% N2, 5% CO2) followed by 60' and 120' reoxygenation periods. The handling control slices were submerged in Acsf and exposed to an oxygenated environment (95% O2, 5% CO2) followed by reoxygenation periods. A Toluidine blue stain at the light microscopic level was used to characterize the morphological differences in the younger and older PCs. To identify whether DCD occurring in 9-day-old rat PCs is related to apoptosis, the following analyses were performed: DNA fragmentation using gel electrophoresis and in situ DNA labeling (TUNEL) and chromatin condensation observed with Hoechst nuclear stain. Purkinje cells stained with Toluidine blue exhibited 67%(±8) DCD and 10% (±2) necrosis in the 9-day-old rats compared to 70%(±12) necrosis and 30%(±5) DCD in the 21-day-old rats. PCs from 9-day-old rat slices displayed shrunken, rounded appearance with darkened nuclei and vacuolated cytoplasm, all morphological characteristics of apoptosis. In addition to morphological similarities to apoptosis, PCs from the 9-day-old rat showed with Hoechst staining, chromatin clumping. Using DNA gel electrophoresis, hypoxic-treated cerebellar slices exhibited DNA laddering upon the formation of oligonucleosomal-sized fragments of DNA (180-200bp) TUNEL assay which provides cellular specificity of the apoptotic activity in the cerebellar slice showed limited staining in the nucleus of the PCs of the treated slice. From the present findings, brain maturity influences the morphological phenotype of neurodegeneration of the Purkinje cells in response to a hypoxic insult. Based upon the lack of TUNEL staining in the PC nuclei, the hypoxic-induced DCD in PCs does not appear to resemble a classic type of apoptosis.Item Dietary fat and antioxidant status relating to colon carcinogenesis(Texas Tech University, 1993-05) Tsai, Shwu-yarEpidemiological evidence has linked dietary fat with colorectal cancer in humans but with mixed results. Studies using animal models have shown that high fat diets containing predominantly corn oil, beef tallow or lard induce colon tumorigenesis to a greater extent than corresponding low fat diets; however, these findings are still inconclusive. Recently, some research indicated differences according to the types of fat used and support the concept that diets high in unsaturated fatty acids have a greater tumor-promoting capability than diets high in saturated fatty acids. The mechanism was proposed that free radicals were involved in colon carcinogenesis. Therefore, a polyunsaturated fatty acid (PUFA) diet would increase antioxidant activity to prevent free radical damage. Several studies have indicated that dietary lipids influence the liver microsomal mixed function oxidase system. It has been reported that the elevation of dietary polyunsaturated fatty acid intake increases the activity of the liver microsomal enzymes responsible for carcinogen metabolism. Some studies directed the diet-related effect on the susceptibility of colonic cells to nuclear-damaging agents. However, there have been very few studies on the effects of dietary fat and nuclear aberrations due to xenobiotics challenge. The purpose of this study was to examine the effect of amount and type of dietary fat on the (1) colon mucosal antioxidant status; (2) liver microsomal demethylase activity; (3) liver microsomal and cytosolic mutagenic activation; and (4) colonic epithelial nuclear aberrations during colon carcinogenesis.Item Differential reinforcement of discrete trial inhibitory behavior in hippocampectomized rats(Texas Tech University, 1969-08) Posey, Thomas BlakeNot availableItem Effects of fetal X-irradiation on maze performances of two generations of albino rats(Texas Tech University, 1962-08) Luchsinger, Vincent PNot availableItem Effects of oxyntomodulin on intestinal adaptation in the rat(Texas Tech University, 1995-05) Zhu, ZhuochenEnteroglucagon (EG) has long been suggested to be an enterotrophic (mucosal growth) factor based on circumstantial evidence. This study evaluated the effects of/«- vivo infusions of synthetic rat oxyntomodulin (OXN, a bioactive form of EG) and glucagon on intestinal adaptation in rats. Osmotic minipumps which deliver peptides or saline intravenously for up to two weeks were implanted into rats fed with either lab chow or a carbohydrate-free diet. At sacrifice, the entire small intestine was removed, and glucose and proline uptake across the brush border was measured using the everted sleeve method. Gut morphology was also measured to assess effects on growth. Surprisingly, OXN infusion had no effect on intestinal growth, despite the putative correlation between EG and enterocyte proliferation. In contrast, infusion of OXN increased active glucose uptake by 13-48% in proximal gut, and by nearly 300% in the ileum. However, OXN showed no effect on proline uptake. On the other hand, glucagon infusion increased active glucose uptake by 100-150% in the proximal and middle part of the intestine, but only showed modest effect on the distal gut. Similarly, glucagon infusion had no effects on proline uptake or intestinal growth. These results were affected by diet since rats fed with lab chow and infused with lower dose of OXN showed no effects. This study demonstrates for the first time that OXN or glucagon increases intestinal nutrient absorption by specifically stimulating glucose uptake. These results do not support the long-standing hypothesis of OXN as a gut growth factor.Item Effects of prenatal and acute administration of nortriptyline on spontaneous activity and maze learning of neonatal rats(Texas Tech University, 1972-08) Crane, Patricia O'LearyNot availableItem Effects of prenatal malnutrition on maternal behavior of the rat and behavioral development of the offspring(Texas Tech University, 1978-05) Villescas, RamiroCrnic (1976) has pointed out that the behavioral results of miany studies involving early malnutrition have been confounded by disturbances in the maternal environment of the rat pup. Based on observations of maternal behavior reported by some investigators (Massaro et al., 1974; Seitz, 1954; Smart & Preece, 1973) it is clear that malnutrition during the lactation period results in observable changes in the maternal behavior of the rat. The major criticism of nutritional studies is that confounding variables which covary with the experimental variables are seldom controlled or even reported by the experimenter; this would include changes in (1) the amount of time the mother spends with the pups in the nest when litter size is increased (Grota & Ader, 1969) or food consumption by the mother is restricted (Simonson, Sherwin, Anilane, Yu, & Chow, 1969; Smart & Preece, 1973); (2) pup competition for milk when litter size is increased (Grota & Ader, 1979; Seitz, 1954), and (3) deficits in retrieval when the mother is restricted in the daily food consumption (Smart & Preece, 1973) or when protein content in the diet is restricted (Weiner, Fitzpatrick, Levin, Smotherman, & Levine, in press). At this point, it must be concluded that all methods for producing early malnutrition via the mother ultimately have an effect on the early maternal environment of the neonatal rat.Item Estrogen and the aging brain of male rats(2016-12) Nutsch, Victoria Lynn; Dominguez, Juan M.; Gore, Andrea C., 1964-; Hofmann, Hans; Cummings, Molly; Gonzales, RuebenGonadal steroid hormones exert an influence on many aspects of neurobiology in men, including memory, learning and sexual dysfunction. Though testosterone is the main circulating gonadal steroid hormone in males, estradiol is also important, and together these hormones play complementary roles. While the specific roles of estrogen have been studied to some extent in young adults, little is known during aging, when sexual behavior can become impaired. I used a rodent model to examine estradiol’s role in sexual behavior and gene expression in 3 regions, selected for their importance in behavioral neuroendocrine functions and high concentrations of estrogen receptors: the medial preoptic area (mPOA), medial amygdala (MeA), and bed nucleus of the stria terminalis (BnST). My studies focused first on how age and sexual experience affects expression and activation of estrogen receptor α (ERα) and androgen receptor (AR) after sexual behavior in aging intact males. Quantification of neurons expressing hormone receptors in the mPOA revealed that neither ERα nor androgen receptor (AR) showed an age-related change in expression in the mPOA. While both ERα and AR were activated after copulation, the age-related changes were specific to ERα in the central mPOA. There were only mild deficits in sexual behavior. Serum estradiol was also elevated in both aged and copulating animals, but estradiol concentrations only correlated with sexual behavior in aged animals. In a second study, I determined how hormone deprivation (castration) and replacement with estradiol caused changes to gene expression in the mPOA, BnST and MeA. Each region had unique patterns of gene expression in response to aging and estradiol treatment. The mPOA only had changes in expression as a result of hormone administration, while the BnST had primarily age-related changes. The MeA had the greatest number of affected genes, mainly interactions between estradiol treatment and aging. These studies emphasize the importance of estradiol in aging males, and the need for continued study on its role in neuroendocrine and sexual function.Item Immunoglobulin Absorption in Ileal Tissue of the Neonatal Rat(Texas Tech University, 1972-08) Jack, Jerry HNot Available.Item Interruption of olivocerebellar tract to the fastigial nucleus alters cardiorespiratory reflexes(Texas Tech University, 2001-05) Purdom, Amanda ReneeNot availableItem Ionic contributions to the oscillatory firing activity of rat cerebellar Purkinje cells(Texas Tech University, 1993-05) Chang, Whasook SeoIntrinsic rhythmic firing patterns of neurons are believed to be mediated by sequential activation of a set of membrane ionic conductances. One of the most significant properties of oscillatory neurons in general is the presence of a negative slope resistance (NSR) region in the steadystate, whole cell voltage clconp current-voltage relationship (I-V curve). Although it has been emphasized that rhythmic activity may form a basis for an intrinsic functional context of the cerebellum, ionic conductances involved in oscillatory activity in cerebellar Purkinje cells (PCs) have yet to be fully determined. The major objective of this dissertation was to investigate the contribution of various conductances such as sodium (iNa)/ calcium (Ica)/ cationic inward (Ih)/ ^^d calcium-activated potassium (iR/ca))oscillatory activity of PCs.Item Opioid receptor modulation of norepinephrine secretion in the caudal dorsomedial medulla of rats: in vivo studies(Texas Tech University, 2001-05) Russell, Amy LynnOur knowledge of how opioids mfluence brainstem neurochemistry is derived principally from in vitro studies. Before we can fiiUy understand how opioids impact cardiovascular function, it is necessary to learn more about their role in vivo. Using microdialysis, male Sprague-Dawley rats were perfused with a microdialysis probe located adjacent to the nucleus of the solitary tract (nTS), with Ringer's, or Ringer's containing beta-endorphin or the selective opioid receptor agonists, [D-Ala^ N-Me-Phe^ Gly-ol]-Enkephalm(DAMGO), U-50488H. or [DPen23]-Enkephalin (non-pCL DPDPE). Microdialysate samples were collected and analyzed for norepinephrine (NE) by high performance liquid chromatography electrochemical (HPLC-EC) detection. DAMGO, a selective muopioid agonist, inhibited potassium (K^)-induced NE release in the nTS. DPDPE, a selective deltaopioid agonist and U-50488H, a kappa-agonist, did not have any affects on K^-induced NE release in the nTS. DAMGO effects on NE secretion were not observed in the presence of the mu/delta selective-opioid receptor antagonist, naloxone. These studies illustrate the ability of selective opioid receptor agonists to influence K"^ -evoked NE release and that the inhibitory effects are mediated through mu-opioid receptors in vivo.Item Population dynamics of rodents of the Mesquite Plains-High Plains ecotone(Texas Tech University, 1968-06) Womochel, Daniel RobertNot availableItem Something to Fear: Perception of Defining Characteristics of Animals, Evaluation of Animals, and the Moderating Role of Speciesism(Texas A&M International University, 2015-06) Waters, Allison Elaine; Muñoz, MonicaSpeciesism, a form of prejudice wherein a person gives or takes value away from an organism based upon how he or she categorizes living things, is most likely a form of flexible evolutionary adaptation. However, with increasing awareness of humanity's impact on the environment and growing morality, speciesism is increasingly becoming a disadvantage. Speciesism can be reflected in actions from unethical breeding habits to outright attacks on certain animals. The purpose of this study was to examine if altering the physical appearance of animals affects the person's attitudes towards those animals. It was hypothesized that altering physical characteristics of some animals would increase attractiveness of the animals and this effect would be moderated by speciesism. Fifty-six university students were asked to rate each of a series of 20 animal images to measure their specific animal attitudes, defined as their evaluation of the appearance, predicted behavior, and threat potential of those animals. The control group (Condition 1) evaluated 9 unaltered animal images and the experimental group (Condition 2) evaluated the altered versions of those images. Speciesism was measured as a potential moderator of altering the image. Hierarchical regression showed altering the image to be a significant predictor (β = -.271, p = .043) of attitudes. Speciesism, however, was neither a significant predictor by itself (β = -.144, p = .276) nor significantly strengthened or weakened the effect of altering the images (β = -.516, p = .197).