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21.
α1 -Adrenergic Receptor-Mediated Downregulation of Angiotensin II Receptors in Neuronal Cultures 总被引:1,自引:0,他引:1
Previous evidence has suggested that brain catecholamine levels are important in the regulation of central angiotensin II receptors. In the present study, the effects of norepinephrine and 3,4-dihydroxyphenylethylamine (dopamine) on angiotensin II receptor regulation in neuronal cultures from rat hypothalamus and brainstem have been examined. Both catecholamines elicit significant decreases in [125I]angiotensin II-specific binding to neuronal cultures prepared from normotensive rats, effects that are dose dependent and that are maximal within 4-8 h of preincubation. Saturation and Scatchard analyses revealed that the norepinephrine-induced decrease in the binding is due to a decrease in the number of angiotensin II receptors in neuronal cultures, with little effect on the receptor affinity. Norepinephrine has no significant actions on [125I]angiotensin II binding in cultures prepared from spontaneously hypertensive rats. The downregulation of angiotensin II receptors by norepinephrine or dopamine is blocked by alpha 1-adrenergic and not by other adrenergic antagonists, a result suggesting that this effect is initiated at the cell surface involving alpha 1-adrenergic receptors. This is further supported by our data indicating a parallel downregulation of specific alpha 1-adrenergic receptors elicited by norepinephrine. In summary, these results show that norepinephrine and dopamine are able to alter the regulation of neuronal angiotensin II receptors by acting at alpha 1-adrenergic receptors, which is a novel finding. 相似文献
22.
Plant Molecular Biology - The α-Amy1 and α-Amy2 genes of wheat produce distinct subsets of α-amylase isozymes which show different patterns of expression in wheat aleurone cells and... 相似文献
23.
Dr. Sasha Malamed Jean A. Gibney Kathryn E. Loesser Colin G. Scanes 《Cell and tissue research》1985,239(1):87-91
Summary The ultrastructure of the somatotrophs of the caudal pituitary of the domestic fowl was studied quantitatively. Two age groups of male chickens were compared: 4–6 weeks and 24–30 weeks post-hatching. With age, somatotrophs decreased from about 40% to about 30% of the pituitary cell population. Their volume density decreased similarly. Mean volume of a somatotroph was the same in young and adult animals. Because the granule volume density of the somatotrophs was unchanged, but the somatotroph volume density of the gland declined, the granule volume density of the caudal pituitary gland dropped in parallel with that of the somatotrophs. Thus the volume of the gland comprised of somatotroph granules fell about 32%: from 6.57% to 4.45%. This lowered pool of stored hormone may be linked to the lowered circulating levels of growth hormone found in older animals by other investigators.The granule volume density of the somatotrophs was unchanged but the numerical density approximately doubled; thus the mean granule size decreased by 47% with age. The relationship of the size reduction of the granules to the lowered plasma growth hormone levels is not understood at present.Supported in part by Hatch and State funds from the New Jersey State Agricultural Experimental Station and NSF grants PCM 8,0227,27 and PCM 8,302197. 相似文献
24.
Anil K. Sinha V. Ann Linscombe B. Bhaskar Gollapudi George C. Jersey Colin N. Park 《Cell biology and toxicology》1985,1(4):333-342
Sister chromatid exchanges (SCE) were analyzed in peripheral blood lymphocytes from a select group of 71 healthy men, 56 nonsmokers and 15 cigarette smokers. In addition to estimating baseline SCE, data were examined to seek relationships of SCE frequencies to age and smoking. The baseline value of 7.53 SCE per cell from the 56 nonsmokers was within the range (5.60 to 9.10 SCE/cell) reported for other human populations. No relationship was found between the mean SCE frequency per cell and age. However, a significant increase in the SCE mean value was observed in smokers as compared to nonsmokers. The results of this study are compared with those of other reports on SCE effects of age and smoking.Abbreviations BUdR
5-bromo,2-deoxyuridine
- SCE
sister chromatid exchange 相似文献
25.
The protoplasting and transformation techniques described by Chang and Cohen [5] have been modified by the inclusion of mutanolysin and these techniques have been used to prepare protoplasts of a number ofBacillus spp. Cells of some, however, remained resistant to cell wall hydrolysis by both mutanolysin and lysozyme. Protoplasts were prepared from sixBacillus species, including a strain ofB. subtilis, and transformed with the plasmid pUB110. Transformation with the shuttle vector pHV33 was, however, less successful and antibiotic-resistant protoplasts, although detected, either failed to regenerate their osmotic stability or rapidly lost their antibiotic resistance. 相似文献
26.
The excretory systems of terrestrial prosobranch snails of the family Cyclophoridae, collected in Jamaica, Costa Rica and South Africa, have been examined physiologically and as regards their gross and fine structure. The process of urine formation commences in the heart, where fluid is filtered across the wall of the ventricle. Filtration through the auricular wall is believed to be negligible. The kidney, which contains three types of cell, modifies the composition of the filtrate. One type of resorptive cell, characterized by basal infoldings associated with mitochondria, takes up salts. Another type, with basal subcellular spaces, may be responsible for taking up water. The third type of cell is secretory, producing concretions of uric acid and phospholipid which are liberated into the kidney lumen when the cell degenerates.
The rate and mechanism of urine production have been investigated using injections of inulin. The filtration rate at 25°C is 0.5 μl/g/min, and in 100% R.H. the average rate of urine production is 0–39 μl/g/min.
An accessory excretory organ has been developed from the hypobranchial gland of aquatic forms. It is composed of groups of subepithelial tubular glands opening into the mantle cavity by one or a series of pores, and secreting purines, phospholipids and mucus. There is evidence that this organ becomes progressively more complex in forms occupying drier habitats.
The systems of excretion and osmoregulation in the Cyclophoridae are considered to be very similar to those in their aquatic relatives, the Viviparidae and Ampullariidae. Certainly the cyclophorids are not as well adapted to a terrestrial life as are the Pulmonata, and in many respects they may be considered "aquatic" snails living on land. 相似文献
The rate and mechanism of urine production have been investigated using injections of inulin. The filtration rate at 25°C is 0.5 μl/g/min, and in 100% R.H. the average rate of urine production is 0–39 μl/g/min.
An accessory excretory organ has been developed from the hypobranchial gland of aquatic forms. It is composed of groups of subepithelial tubular glands opening into the mantle cavity by one or a series of pores, and secreting purines, phospholipids and mucus. There is evidence that this organ becomes progressively more complex in forms occupying drier habitats.
The systems of excretion and osmoregulation in the Cyclophoridae are considered to be very similar to those in their aquatic relatives, the Viviparidae and Ampullariidae. Certainly the cyclophorids are not as well adapted to a terrestrial life as are the Pulmonata, and in many respects they may be considered "aquatic" snails living on land. 相似文献
27.
Fate of corticotrophins in an isolated adrenal-cell bioassay and decrease of peptide breakdown by cell purification 总被引:5,自引:3,他引:2 下载免费PDF全文
Hugh P. J. Bennett Gillian Bullock P. J. Lowry Colin McMartin Judith Peters 《The Biochemical journal》1974,138(2):185-194
1. The fate of corticotrophins in a trypsin-dispersed rat adrenal-cell assay system was investigated with a view to establishing whether differences in the rate of inactivation might contribute to potency differences observed between analogues. 2. Corticotrophin-(1-24)-tetracosapeptide and to a lesser extent synthetic 1-39 corticotrophins were found to be inactivated during incubation with cell suspension. 3. Peptide fragments were isolated by using [[(3)H(2)]Tyr(23)]corticotrophin-(1-24)- tetracosapeptide as a marker. The fragments indicate a peptidase with a predominantly tryptic specificity. 4. The peptidase is present in the extracellular fluid and is released from cells when they are damaged. 5. Cells were fractionated on an albumin gradient. Cells from the zona fasciculata and the zona intermedia or reticularis were present in fractions which produced fluorogenic steroids in response to corticotrophin. 6. Purification of the cells by centrifugation through albumin decreased degradation by peptidases, so that if the assay is carried out with a dilute suspension of purified cells peptide breakdown should not affect the observed potencies of adrenocorticotrophin analogues. 7. No binding of [[(3)H(2)]Tyr(23)]corticotrophin-(1-24)- tetracosapeptide to cells could be detected at low concentrations of the peptide. This indicated that less than 120 receptors/cell are occupied during stimulation by a dose that would elicit approx. 80% of the maximal response. 相似文献
28.
Stereospecific hydroxylation of 3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-trans-and 3-C-cis-(methoxycarbonylmethylene)-α-D-ribo-hexofuranose (2 and 3, respectively), with potassium permanganate in pyridine afforded 3-C-[S- and R-hydroxy-(methoxycarbonyl)methyl]-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose, (6 and 7, respectively), in a combined yield, after chromatography, of 43%. Selective formation of monomethanesulfonates (9a and 10a) and p-toluenesulfonates (9b and 10b), followed by treatment with sodium azide and reduction of the azide, afforded the methyl 2-D-(and 2-L-)(3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofuranos-3-yl)-glycinates (12a and 13a, respectively). Basic hydrolysis of the latter compounds yielded 2-D- and 2-L-(3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofuranos-3-yl)glycine (12b and 13b, respectively). The structures of the glycosyl amino acids were correlated with that of L-alanine by circular dichroism. 相似文献
29.
Colin Ogilvie 《BMJ (Clinical research ed.)》1966,1(5489):735-736
30.
A method for the determination of desferrioxamine-available iron in tissue fractions is described which involves incubation with desferrioxamine, extraction of desferrioxamine and its iron-bound form, ferrioxamine, and quantitation of these two forms of the drug by reversed-phase hplc analysis. Chelatable iron levels in the 1-10µMolar region could be accurately and reproducibly measured using this technique.
The desferrioxamine-available iron levels in both the cortex and medulla of rabbit kidneys were significantly elevated (up to 2-fold) after the organs had been subjected to 2 hours warm ischaemia or 24 hours cold storage at 0°C In hypertonic citrate solution. There was no change in the total iron content of the tissues under these circumstances and thus a redistribution of intracellular iron to more available pools had presumably taken place as a result of ischaemia. This redistribution of iron may be an important factor in the initiation of peroxidative damage to cell membranes upon reperfusion of the organ with oxygen. 相似文献
The desferrioxamine-available iron levels in both the cortex and medulla of rabbit kidneys were significantly elevated (up to 2-fold) after the organs had been subjected to 2 hours warm ischaemia or 24 hours cold storage at 0°C In hypertonic citrate solution. There was no change in the total iron content of the tissues under these circumstances and thus a redistribution of intracellular iron to more available pools had presumably taken place as a result of ischaemia. This redistribution of iron may be an important factor in the initiation of peroxidative damage to cell membranes upon reperfusion of the organ with oxygen. 相似文献