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11.
Vincent A. Murphy Quentin R. Smith Stanley I. Rapoport 《Journal of neurochemistry》1988,51(6):1777-1782
Male Fischer-344 rats, 21 days old, were fed diets containing 0 (LOD), 2,200 (CONT), or 440,000 (HID) international units of vitamin D3 per kilogram for 12 weeks. [Ca] was measured in plasma, CSF, brain, and choroid plexus. In addition, 45Ca and 36Cl transfer coefficients (KCa and KCl) for uptake from blood into CSF and brain were determined. Although plasma ionized [Ca]s in LOD and HID rats were 50% and 136%, respectively, of values in CONT animals, CSF and brain [Ca]s ranged from only 85% to 110% of respective CONT values. Choroid plexus [Ca] was increased by 37% after HID diet, but was decreased only 10% after LOD. KCa values at CSF, parietal cortex, and pons-medulla were negatively correlated with plasma ionized [Ca], whereas KCl values at CSF and brain were not different between the diet groups. The findings demonstrate that central nervous system [Ca] is maintained during chronic hypo- or hypercalcemia by saturable transport of Ca at brain barrier membranes. This transport does not seem to involve modulation by 1,25-dihydroxyvitamin D3. 相似文献
12.
13.
60-Hz electric fields: detection by female rats 总被引:1,自引:0,他引:1
Female rats were trained to detect a vertical, 60-Hz electric field using the same apparatus and procedure we used previously to study behavioral detection of the field by male rats. Each rat was trained individually to press a lever in the presence of the field and not to press in its absence. Correct detections occasionally produced a food pellet. The probability of detecting the field increased as field strength increased. The threshold of detection--ie, the field strength required for detections at a probability of 0.5 after correction for errors--varied among rats between 3 and 10 kV/m. Behavioral detection by female rats was indistinguishable from that by male rats. 相似文献
14.
Embryos of the Wistar strain and its F(1) cross (Wistar females mated with Brown Norway males) of rats were transferred nonsurgically to 48 Wistar, 17 F(1) cross and 20 Wistar-Imamichi recipients. The two types of embryos were transferred together to each recipient to compare the viability of the embryos. Pregnancy rate was 78.8% (67 85 ). The survival rate of fetuses to term was 11.5% (20 174 ) and 25.1% (42 168 ) for the Wistar and F(1) embryos, respectively. Placental weight differed significantly (P<0.05) between embryo types and among recipient types while fetus weight differed (P<0.01) only among recipient types, with a significant interaction between recipient and embryo types (P<0.01). It was concluded that the F(1) embryos (Wistar x Brown Norway) were twice as viable as Wistar embryos under the conditions provided. 相似文献
15.
Effect of prolactin and glucocorticoids on P-enolpyruvate carboxykinase activity in liver and mammary gland from diabetic and lactating rats 总被引:1,自引:0,他引:1
María F. Lobato Mertxe Careche Manuel Ros Francisco J. Moreno Josefa P. García-Ruíz 《Molecular and cellular biochemistry》1985,67(1):19-23
Summary The administration of 2 bromo--ergocryptine, to reduce serum prolactin decreased the activity of cytosolic P-enolpyruvatc carboxykinase (GTP) (EC4.1.1.32) about 50% in both liver and mammary gland of lactating animals. Adrenalectomy had similar effects to those of bromo-a-ergocryptine. In contrast, there was a 50% increase in enzyme activity in the mammary gland of diabetic, lactating rats and a 10-fold increase in liver as compared with normal rats. P-enolpyruvate carboxykinase activity in mammary gland as liver is coordinately regulated by prolactin, glucocorticoids and insulin. 相似文献
16.
A conventional balance study with 48 male weanling rats was conducted to determine true absorption and endogenous fecal excretion
of manganese (Mn) in relation to dietary Mn supply, following the procedures of a previously adapted isotope dilution technique.
After 10 d on a diet with 1.5 ppm Mn, eight animals each were assigned to diets containing 1.5, 4.5, 11.2, 35, 65, or 100
ppm Mn on a dry-matter basis. Three days later, each rat was given an intramuscular54Mn injection and kept on treatment for a balance period of 16 d.
Apparent Mn absorption assessed for the final 8 d, averaged 8.6 μg/d without significant treatment effects, although Mn intake
ranged from 18.6 to 1200 μg/d, in direct relation to dietary Mn concentrations. Mean fecal excretion of endogenous Mn for
the six treatments was 0.9, 2.7, 7.4, 11.0, 16.3, and 17.7 μg/d, respectively. These values delineate the rates to which true
absorption exceeded apparent rates. True absorption, as percent of Mn intake, averaged 28.7, 15.9, 11.7, 6.1, 3.4, and 2.0,
respectively, as compared with mean values of 23.9, 10.9, 6.2, 3.4, 1.2, and 0.5 for percent apparent absorption. It was concluded
that both true absorption and endogenous fecal excretion markedly responded to Mn nutrition and that the reduction in the
efficiency of true absorption was quantitatively the most significant homeostatic response for maintaining stable Mn concentrations
in body tissues. 相似文献
17.
Ernst Kallenbach 《Cell and tissue research》1986,246(2):455-461
Summary Sections of glutaraldehyde-OsO4-fixed, plastic-embedded rat incisor enamel were left untreated, stained, decalcifed (1% formic acid in 10% sodium citrate), or decalcified-stained. The presence of apatite crystals was monitored with electron diffraction. After brief decalcification and staining, apatite crystals and matrix components were visualized in the same field. The ghost was continuous with crystal fragments, and the coat appeared as a dense line next to crystals and ghosts. Position of ghosts and crystals at the ameloblast-enamel junction (AEJ) of the secretion zone suggested that there may be a lag of no more than 1/5 min between the elaboration of ghost and crystal. A major change in enamel morphology occurs between the AEJ and the deep enamel of the secretion zone. The ghost becomes thinner, the coat more pronounced, and the crystal enlarges. There is only little change from the deep secretion to the maturation zone enamel. 相似文献
18.
Cerebral Blood Flow and Oxidative Metabolism in Conscious Fischer-344 Rats of Different Ages 总被引:1,自引:1,他引:0
Hidenori Takei Wendy R. Fredericks Edythe D. London Stanley I. Rapoport 《Journal of neurochemistry》1983,40(3):801-805
Abstract: The cerebral metabolic rates for O2 and for glucose were measured in conscious, fasted male Fischer-344 rats at the ages of 3, 12, and 24 months, and cerebral blood flow was determined with 14 C-iodoantipyrine. The metabolic rates for oxygen and glucose were obtained by multiplying blood flow by the O2 and glucose concentration differences, respectively, between blood in the femoral artery and in the superior sagittal sinus. Mean cerebral blood flow and the metabolic rates for oxygen and glucose did not differ significantly (p > 0.05) between 3 and 12 or between 12 and 24 months. Nor did the arteriovenous differences for O2 and for glucose change significantly with age. Because the superior sagittal sinus drains blood mainly from the cerebral cortex, the results indicate that average cerebral cortical oxidative metabolism, and the coupling ratios between the cerebral metabolic rate for oxygen and cerebral blood flow and between the cerebral metabolic rate for glucose and cerebral blood flow, do not change significantly with age in the Fischer-344 rat. 相似文献
19.
Regulation of Rat Pineal Hydroxyindole-O-Methyltransferase in Neonatal and Adult Rats 总被引:4,自引:4,他引:0
The relative importance of neural, and some nonneural, mechanisms in the control of pineal hydroxyindole-O-methyltransferase (HIOMT) activity during development and in the adult rat was studied. In neonatal rats, guanethidine-treatment, bilateral superior cervical ganglionectomy (SCGX), or exposure to constant light did not prevent the initial appearance of HIOMT activity, indicating that neural stimulation of the gland is not essential for the development of HIOMT activity. In adult rats, decentralization or removal of the SCG led to a slow fall in HIOMT activity, to about 30% of control activity, indicating that the enzyme is largely under neural control. Additionally, adrenalectomy or hypophysectomy had no effect on HIOMT activity, refuting the suggestion that adrenal and/or gonadal steroids are of major importance in the regulation of this enzyme. The fall in activity of the enzyme after SCGX or exposure to constant light probably does not represent a shift in the Km of the enzyme nor the selective disappearance of a distinct molecular species. Similar changes in HIOMT activity and cyclic GMP responsiveness occur in response to alterations in the length of the daily dark period, adding further evidence to our earlier speculation that there may be a functional relationship between these two. 相似文献
20.
Abstract: The relative amounts of the different enolase isozymes present in neuroblastoma cells change during differentiation. When differentiation is induced by low serum in the presence of DMSO (dimethyl sulfoxide), there is a 50% decrease in the concentration of enolase activity associated with the form αα, and an increase in the activity associated with the γ-containing isozymes (αγ plus γγ); in the absence of DMSO, there is no decrease in αα or in total enolase activity. In order to study the mechanism of the changes in αα, cells differentiated with low serum with and without DMSO were compared. Measurements of the concentration of the α antigen by microcomplement fixation and by immunotitration demonstrate that the decreased enolase activity in DMSO cells is due to a decreased concentration of the α antigen. Measurements of the relative rate of synthesis of the antigen show that the decreased concentration of the α antigen is due to a decreased rate of synthesis. Enolase in differentiated cells is sufficiently stable (t1/2 > 100 h) that a comparison of the relative rates of degradation has not been possible. The decreased synthesis of the α subunit of enolase that occurs under these conditions appears to be a useful model system for studying the de-expression of the α gene that occurs in vivo during neuronal differentiation. 相似文献