Cardiovascular disease in the JCR:LA-cp rat

The intimate association between the Golgi complex and the microtubule cytoskeleton plays an important role in Golgi structure and function. Recent evidence indicates that the dynamic flow of material from the ER to the Golgi is crucial to maintaining the integrity of the Golgi complex and its characteristic location within the cell, and it is now clear that this flow is dependent on the ongoing activity of microtubule motor proteins. This review focuses primarily on recent microinjection and expression studies which have explored the role of individual microtubule motor proteins in controlling Golgi dynamics. The collective evidence shows that one or more isoforms of cytoplasmic dynein, together with its cofactor the dynactin complex, are required to maintain a juxtanuclear Golgi complex in fibroblasts. Although questions remain about how dynein and dynactin are linked to the Golgi, there is evidence that the Golgi-spectrin lattice is involved. Kinesin and kinesin-like proteins appear to play a smaller role in Golgi dynamics, though this may be very cell-type specific. Moreover, new evidence about the role of kinesin family members continues to emerge. Thanks in part to recent advances in our understanding of these molecular motors, our current view of the Golgi complex is of an organelle in flux, undergoing constant renewal. Future research will be aimed at elucidating how and to what extent these motor proteins function as regulators of Golgi function.     

Vasculopathy and insulin resistance in the JCR:LA-cp rat

The fluorescent dye FM1-43 labels nerve terminals in an activity-dependent fashion and has been found increasingly useful in exploring the exo- and endocytosis of synaptic vesicles and other cells by fluorescence methods. The dye distributes between the aqueous phase and the lipid membrane but the physical-chemical parameters characterizing the adsorption/partition equilibrium have not yet been determined. Fluorescence spectroscopy alone is not sufficient for a detailed elucidation of the adsorption mechanism since the method can be applied only in a rather narrow low-concentration window. In addition to fluorescence spectroscopy, we have therefore employed high sensitivity isothermal titration calorimetry (ITC) and deuterium magnetic resonance (2H-NMR). ITC allows the measurement of the adsorption isotherm up to 100 microM dye concentration whereas 2H-NMR provides information on the location of the dye with respect to the plane of the membrane. Dye adsorption/partition isotherms were measured for neutral and negatively-charged phospholipid vesicles. A non-linear dependence between the extent of adsorption and the free dye concentration was observed. Though the adsorption was mainly driven by the insertion of the non-polar part of the dye into the hydrophobic membrane interior, the adsorption equilibrium was further modulated by an electrostatic attraction/repulsion interaction of the cationic dye (z=+2) with the membrane surface. The Gouy-Chapman theory was employed to separate electrostatic and hydrophobic effects. After correcting for electrostatic effects, the dye-membrane interaction could be described by a simple partition equilibrium (Xb=Kcdye) with a partition constant of 103-104 M-1, a partition enthalpy of DeltaH=-2.0 kcal/mol and a free energy of binding of DeltaG=-7.8 kcal/mol. The insertion of FM1-43 into lipid membranes at room temperature is thus an entropy-driven reaction following the classical hydrophobic effect. Deuterium nuclear magnetic resonance provided insight into the structural changes of the lipid bilayer induced by the insertion of FM1-43. The dye disturbed the packing of the fatty acyl chains and decreased the fatty acyl chain order. FM1-43 also induced a conformational change in the phosphocholine headgroup. The -P-N+ dipole was parallel to the membrane surface in the absence of dye and was rotated with its positive end towards the water phase upon dye insertion. The extent of rotation was, however, much smaller than that induced by other cationic molecules of similar charge, suggesting an alignment of FM1-43 such that the POPC phosphate group is sandwiched by the two quaternary FM1-43 ammonium groups. In such an arrangement the two cationic charges counteract each other in a rotation of the -P-N+ dipole.     

Cardioprotective and hypolipidemic effects of nisoldipine in the JCR:LA-cp rat

The JCR:LA-cp rat exhibits the obesity/insulin resistance/hypertriglyceridemia syndrome in an extreme form. These normotensive rats spontaneously develop advanced atherosclerosis and ischemic myocardial lesions. The calcium channel antagonist, nisoldipine, was administered to obese rats of the JCR:LA-cp strain in drinking water at a dose of 1 mg/kg from age 6 weeks. Nisoldipine-treated rats showed no change in food consumption or body weight compared with control animals. Plasma glucose and insulin levels also were unchanged in the nisoldipine-treated rats. Insulin-mediated total glucose turnover, an index of insulin sensitivity as measured by euglycemic insulin clamp, was similarly not improved. Serum triglyceride levels in obese male rats were markedly reduced (57%; p < 0.001, at age 12 weeks), whereas obese female rats showed no significant change in triglyceride levels and an increase in esterified cholesterol in response to nisoldipine treatment. The impaired endothelium-dependent (nitric oxide-mediated) vascular relaxation of the male cp/cp rats was not improved by nisoldipine treatment. The severity of atherosclerotic raised lesions in the aortic arch of male cp/cp rats was significantly reduced (p < 0.01) by nisoldipine treatment, and this was accompanied by a major reduction in the incidence of ischemic myocardial lesions (85%; p < 0.01). Thus nisoldipine treatment ameliorates atherosclerotic damage and myocardial injury even in the presence of gross obesity, hyperinsulinemia, and significant hyperlipidemia. This effect appears to involve protection of the vascular wall from atherogenesis and probably antivasocontractile effects at the smooth muscle level as well.     

Cardioprotective effect of probucol in the atherosclerosis-prone JCR:LA-cp rat

The second epidermal growth factor (EGF)-like domain of human coagulation factor VII is a potent inhibitor of the FVIIa/tissue factor complex, the predominant initiator of coagulation in vivo. This domain has now for the first time been cloned and expressed in Escherichia coli as an affinity fusion protein. The fusion protein was secreted into the periplasm of E. coli and purified by affinity chromatography. The purified protein consisted of a fusion protein with the expected molecular weight, and in addition, a significant fraction of oligomers cross-linked by intermolecular disulfide bonds. Despite the presence of oligomers, the purified protein was a potent inhibitor of the extrinsic blood coagulation pathway with an IC50 value of about 20 microM. The biological activity was retained after liberation of the EGF domain by proteolytic cleavage.     

Age- and sex-related differences in left- and right-hemisphere processing by learning disabled children.

Age and sex differences in left- and right-hemisphere processing were assessed with 2 dichotic listening tasks in a sample of 48 control and 48 learning-disabled (LD) children ranging in age from 6 yrs 9 mo to 12 yrs 4 mo. Children were presented with consonant–vowel syllables (CVs) and simple square-wave and complex square-wave tones. Neither age nor sex differences in response accuracy or lateralized processing of CV stimuli were evident for control children. Borderline significance was obtained for tonal stimuli. In contrast, CV stimuli elicited a bilateral response in younger LD children, and tonal stimuli elicited a bilateral response in all LD children. Furthermore, control children were oppositely lateralized for verbal and nonverbal stimuli, whereas LD Ss exhibited a general processing bias to the same hemisphere. These data support the theory that LD children may lack the necessary functional specialization required for lateralized processing of such stimuli. In addition, these data do not fully support the developmental invariance hypothesis and may even suggest a putative right-hemisphere or bilateral processing deficiency in LD children. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age- and strain-related differences in dehydrogenase activity and glycogen levels in CBA and C57 mouse cochleas

In the C57 mouse strain, loss of sensory hair cells (HCs) begins during early adulthood, starting in the base of the cochlea and progressing toward the apex as aging continues. In contrast, the CBA mouse strain exhibits no significant cochlear histopathology until relatively late in life. These strain and age differences may be related to differences in cochlear energy metabolism. To examine this possibility, we used dehydrogenase and glycogen histochemistry to evaluate the metabolic capacities of HCs and stria vascularis (SV) in cochleas of C57 and CBA mice. Reaction product density was quantified and compared as a function of strain (1.5-month-old C57 mice vs. CBA mice) and age (CBA mice, 1.5, 18 and 36 months). Young C57 mice had significantly less HC dehydrogenase activity than CBA mice of any age, lower HC glycogen levels than 18-month-old CBA mice and lower SV glycogen levels than 18- or 36-month-old CBA animals. Within the CBA strain, HC dehydrogenase activity decreased significantly between 1.5 and 18 months of age, while glycogen levels in both HCs and SV increased over the same time period. Between 18 and 36 months, HC dehydrogenase activity and SV glycogen levels remained stable. The results show that there are significant age-related changes in energy metabolism in the inner ear of CBA mice that are correlated with age-related hearing loss. Genetically determined deficits in cochlear metabolic capacity in C57 mice could be linked to the early onset of hearing loss in this strain.     

Effect of morphine and stadol on lipid content in liver of rat

The effects of repeated accumulative increasing doses (5, 10, 20 and 40 mg/kg body weight) of morphine and stadol on lipid content have been studied in liver of rat. The results obtained indicate that significant increases were recorded in hepatic triglycerides (TG) content after 1 and 12 hrs of morphine treatment while non-significant increases were recorded after stadol administration. After 36 hrs of treatment with either of the two drugs, the liver TG content was decreased which may indicate that drug tolerance might have developed. The phospholipids content showed increases especially after 12 hrs of morphine or stadol administration. The results obtained suggest enhanced phospholipid synthesis under the action of both drugs. Highly significant increases occurred in cholesterol content after 1, 12 and 24 hrs of treatment of both drugs. This might reflect the occurrence of decreased catabolism and turnover of cholesterol during the experiment. Total lipids content of liver showed marked and highly significant increases after 12 hrs of morphine and after 12 and 24 hrs of stadol administration respectively. The data obtained suggest that morphine and stadol may be hepatotoxic to rats.     

Sex differences in the relationship between activity and weight loss in the rat.

Access to a running wheel combined with restricted feeding produced body weight loss at an equivalent rate in male and female litter-mate rats (Experiment 1). Thus, despite weighing less and running more, females were not more vulnerable to this procedure. When factors influencing weight loss were varied, no sex difference was found in adaptation to a new feeding schedule or in the effect of single versus group housing (Experiment 2). The apparent critical difference was that body weight loss increased running in males but not in females (Experiment 3). In all rats, rapid recovery of body weight occurred when food access was no longer restricted (Experiment 1), suggesting that "activity-based anorexia" is a misnomer for weight loss by rats in a running wheel. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spontaneous activity of otolith-related vestibular nuclear neurons in the decerebrate rat

The discharge properties of lateral and descending vestibular neurons responsive to constant velocity off-vertical axis rotations (OVAR) in the clockwise (CW) and counterclockwise (CCW) directions, were studied at the stationary and earth-horizontal position of decerebrate adult rats. From the coefficient of variation (CV), the spontaneous activities of OVAR-responsive neurons were classified into regular and irregular patterns. Of the neurons (n = 36) that showed symmetric and stable bidirectional response sensitivity (delta defined as CW gain over CCW gain) to OVAR (10 degrees tilt), some exhibited progressive phase shift with velocity (1.75-15 degrees/s) while others exhibited stable response phase. Most neurons of the former group (93% or 12/13) showed regular discharge pattern while only 22% (n = 5/23) of the latter group showed such a pattern. Though the phase-stable neurons showed a significantly higher average CV than the phase-shifted neurons, there was no significant difference between the mean spontaneous firing rates of these neurons. The neurons (n = 17) that showed asymmetric and variable delta to OVAR velocity can also be grouped-those that exhibited a greater gain with rotations directed towards the side of recording (I neurons) showed irregular discharge pattern while those that exhibited a greater gain with rotations directed towards the side contralateral to recording (C neurons) showed regular discharge pattern. The I and C neurons also exhibited significant difference in mean firing rates. The relationship between the response characteristics of the OVAR-responsive neurons and their spontaneous activity at the stationary and earth-horizontal position is discussed.     

Sex differences in the activity of gamma-aminobutyric acidergic neurons in the rat hypothalamus

The rate of GABA turnover was determined in nine microdissected brain regions in adult male and female rats. In the medial preoptic nucleus (central aspect) and ventromedial nucleus (ventrolateral aspect) of the hypothalamus, areas involved in the regulation of gonadotropin secretion and sex behavior, GABAergic neuronal activity was about 2-fold greater in males than females. These results demonstrate a striking sexual dimorphism in the activity of specific populations of hypothalamic GABAergic neurons.     

Calcium modulates the influence of length changes on the myofibrillar adenosine triphosphatase activity in rat skinned cardiac trabeculae

The relationship between adenosine triphosphate (ATP) turnover and muscle performance was investigated in skinned cardiac trabeculae of the rat at different [Ca2+] and two different sarcomere lengths (1.8 microns and 2.2 microns) at 20 degrees C. ATP turnover was measured photometrically by enzymatic coupling of the regeneration of ATP to the oxidation of reduced nicotinamide adenine dinucleotide. The trabeculae were studied under isometric conditions and when the length was altered repetitively at a frequency of 23 Hz, with a square wave, by 5% of the initial length. The isometric ATPase activity amounted to 0.48 mM/s. Isometric ATP turnover and force were proportional at different [Ca2+]. During length changes at maximal activation (pCa 4.27) and 2.2 microns sarcomere length, ATPase activity increased to up to 162% whereas at low [Ca2+], ATPase activity decreased with respect to the isometric value at that pCa. At pCa 5.5, ATPase activity was reduced to 33%. These results indicate that during the length changes the apparent cross-bridge detachment rate is increased and the apparent attachment rate is decreased. The findings suggest that the Fenn effect, i.e. the increase in energy turnover above the isometric value during shortening, is present in cardiac trabeculae at high levels of activation, but is absent or reversed at lower levels of activity.     

Single-unit activity of cerebellar nuclear cells in the awake genetically dystonic rat

We have established a cell culture system that reproduces morphogenic processes in the developing mammary gland. EpH4 mouse mammary epithelial cells cultured in matrigel form branched tubules in the presence of hepatocyte growth factor/scatter factor (HGF/SF), the ligand of the c-met tyrosine kinase receptor. In contrast, alveolar structures are formed in the presence of neuregulin, a ligand of c-erbB tyrosine kinase receptors. These distinct morphogenic responses can also be observed with selected human mammary carcinoma tissue in explant culture. HGF/SF-induced branching was abrogated by the PI3 kinase inhibitors wortmannin and LY294002. In contrast, neuregulin- induced alveolar morphogenesis was inhibited by the MAPK kinase inhibitor PD98059. The c-met-mediated response could also be evoked by transfection of a c-met specific substrate, Gab1, which can activate the PI3 kinase pathway. An activated hybrid receptor that contained the intracellular domain of c-erbB2 receptor suffices to induce alveolar morphogenesis, and was observed in the presence of tyrosine residues Y1028, Y1144, Y1201, and Y1226/27 in the substrate-binding domain of c-erbB2. Our data demonstrate that c-met and c-erbB2 signaling elicit distinct morphogenic programs in mammary epithelial cells: formation of branched tubules relies on a pathway involving PI3 kinase, whereas alveolar morphogenesis requires MAPK kinase.     

Methamphetamine causes lipid peroxidation and an increase in superoxide dismutase activity in the rat striatum

The administration of methamphetamine to experimental animals results in damage to nigrostriatal dopaminergic neurons. In the present study, we demonstrated that both the acute repeated and the chronic administration of methamphetamine causes an increase in thiobarbituric acid reactive substances, which are indicators of lipid peroxidation, and superoxide dismutase activity in the rat striatum. The results of present study strengthen the notion that reactive oxygen species may play an important role in the methamphetamine-induced neurotoxicity.     

Changes in hepatic fatty acid degradation and blood lipid and ketone body content during development of the rat

The following have been measured during the development of the laboratory rat: the rate of oxidation of palmitoylcarnitine, decanoylcarnitine, and 14C-palmitate by liver mitochondria; the concentrations of ketone bodies in the blood; the plasma concentrations of non-esterified fatty acids, glycerol, and triglyceride. In each case, a rise after birth and a fall at weaning were observed. These changes can be correlated with the dietary changes which occur at these times. However, during the suckling period, when a constant high fat content diet is consumed, further marked changes in the parameters measured were observed which cannot be related to nutritional factors.     

NADPH-diaphorase-positive ganglion cells of the rat adrenal gland: age- and sex-related changes in their number, size, and distribution

The rat adrenal gland contains ganglion cells able to synthesize nitric oxide (NO). This messenger molecule controls and modulates adrenal secretory activity and blood flow. The present study analyzed the number, size, and distribution of NO-producing adrenal neurons in adulthood and during postnatal development by means of beta-nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry. This method reliably visualizes the enzyme responsible for NO generation. The reactive neurons per adrenal gland were 350-400 in both male and female adult rats. The positive nerve cell bodies were mostly located in the medulla, few being detected within the cortex and the subcapsular region. Dual labeling with anti-microtubule-associated protein 2 antibody, specific for neuronal elements, confirmed this distribution. Anti-microtubule-associated protein 1b antibody identified a subset of NADPH-d-positive neurons, displaying different degrees of maturation according to their position within the adrenal gland. At birth, there were about 220 NADPH-d-labeled neurons per adrenal gland in both sexes. As confirmed by dual immunocytochemical labeling, their great majority was evenly distributed between the cortex and the subcapsular region, the medulla being practically devoid of stained neurons. After birth, the number of adrenal NADPH-d-positive ganglion cells displayed a strong postnatal increase and reached the adult-like distribution after 1-2 months. During the period of increase, there was a transient difference in the numbers of these cells in the two sexes. Thus we present here evidence of plasticity in the number, size, and distribution of NADPH-d-positive adrenal neurons between birth and adulthood; in addition, we describe transient sex-related differences in their number and distribution during the 2nd postnatal week, which are possibly related to the epigenetic action of gonadal hormones during this period.     

Gender differences in myocardial blood flow dynamics: lipid profile and hemodynamic effects

OBJECTIVES: The purpose of the study was to compare myocardial blood flow (MBF) in hyperlipidemic postmenopausal women and age-matched hyperlipidemic men, and to analyze the relationship between cholesterol subfractions and myocardial blood flow in men and women. BACKGROUND: Women are protected from coronary artery disease (CAD) events until well after menopause, in part due to gender-specific differences in lipid profiles. METHODS: To examine the effect of these influences on coronary microcirculation, MBF was quantitated with N-13 ammonia/PET (positron emission tomography) at rest and during adenosine hyperemia in 15 women and 15 men, all nondiabetic, who were matched for age and total cholesterol levels (53+/-4 vs. 50+/-8 years, p = NS, 6.44+/-1.1 vs. 6.31+/-0.85 mmol/liter, or 249+/-41 vs. 244+/-33 mg/dl, p = NS). RESULTS: Women had significantly higher high density lipoprotein (HDL) and lower triglyceride (Tg) levels than did men, and they showed significantly higher resting MBF and stress MBF levels. Significant correlations were found between resting and hyperemic MBF and HDL and Tg levels (r = 0.44, p < 0.02 for stress MBF vs. HDL; r = 0.48, p < 0.007 for stress MBF vs. Tg). Gender was the strongest predictor of hyperemic MBF in multivariate analysis. Women responded to adenosine hyperemia with a significantly higher heart rate than did men, and hemodynamic factors correlated significantly with blood flow both at rest and during stress. CONCLUSIONS: These data suggest that the favorable lipid profile seen in women may be associated with preserved maximal blood flow in the myocardium.     

Effects of hypothyroidism and undernutrition on DNA content and thymidine kinase activity during cerebellar development in the rat

Passage route into stomach compartments of liquid feeds containing a marker was studied by feeding a liquid supplement and molasses from a lick-wheel feeder and by infusing the liquid supplement into the reticulorumen 30 min prior to sampling contents of the reticulorumen and abomasum and 4 h prior to sampling blood for plasma glucose. Recovery from reticulorumen and concentration of marker in abomasal ingesta gave no evidence of rumen bypass, this supported by a gross correlation of .92 between rumen ammonia nitrogen and nonprotein nitrogen intake from liquid feeds. Plasma glucose values were not different. Preinfusion and postinfusion plasma glucose values were similar for abomasal infusion of about 454 g of molasses, 20% crude protein liquid supplement, and for the basal diet. Values were lower for abomasal infusion of the 35% crude protein liquid supplement (Pro-Lix) than for the 20% crude protein liquid supplement. When complete rations containing 11.5, 13.0, and 14.5% crude protein were supplemented with either molasses or a 20% crude protein liquid supplement fed from lick-wheel feeders, intake averaged .53 and .34 kg per animal daily for the respective liquid feeds. There was no effect on milk yield, solids-corrected milk, milk fat content, protein content, solids-not-fat percent, or body weight change. There was an interaction of protein level and liquid feeds in which plasma glucose was increased by liquid feeds in higher but not in lower protein diets.     

8-hydroxyguanine levels in nuclear DNA and its repair activity in rat organs associated with age

8-Hydroxyguanine (8-OH-Gua) is one of the most abundant types of oxidative DNA damage. The levels of 8-OH-Gua, and its repair activity, were quantified in 3-week-, 5-month-, and 30-month-old male Sprague-Dawley rat organs such as liver, kidney, spleen, lung, small intestine, and brain. The levels of 8-OH-Gua were significantly higher in the 5-month-old rat kidney and brain and 30-month-old rat spleen when compared to that of the 3-week-old rats. However, no significant differences were found in the organs between 5- and 30-month-old rats that were due to the aging process. The repair activity levels of kidney, spleen, and lung were higher than those of liver, small intestine, and brain. This pattern was consistent for the three age stages.     

Renoprotective differences between perindopril and enalapril in the diabetic hypertensive rat do not reflect glomerular angiotensin-converting enzyme activity

1. The various angiotensin-converting enzyme inhibitors have structural differences which affect their affinities for the catalytic sites on converting enzyme. We postulated that such differences might result in differences in renoprotective efficacy. We investigated this in the diabetic spontaneous hypertensive rat. We also investigated whether these differences might reflect variations in glomerular or plasma angiotensin-converting enzyme activity. 2. One week after induction of diabetes, rats were started on antihypertensive therapy: enalapril, 10 mg.day-1.kg-1, or perindopril, 4 mg.day-1.kg-1, in the drinking water. After 3 months, the rats were killed, blood samples were taken and tissues were harvested. Angiotensin-converting enzyme activity in isolated glomeruli and plasma was measured by fluorimetric assay. Glomerular protein content was also determined. 3. Urinary protein excretion was significantly lower in perindopril-treated rats than in either controls (P < 0.0005) or enalapril-treated rats (P < 0.05). Glomerular protein content was also lower in perindopril-treated rats (P < 0.05 versus enalapril; P < 0.005 versus control). There was no difference in glomerular angiotensin-converting enzyme activity between the two inhibitors although both were lower than control values (enalapril P < 0.025; perindopril P < 0.025). Plasma angiotensin-converting enzyme activity was significantly lower in the perindopril group than in either control (P < 0.005) or the enalapril group (P < 0.01). 4. We conclude that in the spontaneous hypertensive rat with streptozotocin-induced diabetes, perindopril is more effective than enalapril in reducing proteinuria and glomerular protein accumulation. This difference does not result from differences in glomerular-converting enzyme activity.