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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The pyloric gland of Styela clava contains large glycogen deposits that are digested by treatment with alpha amylase and depleted by 15 days starvation. The deposits are surrounded by cytoplasmic regions containing smooth endoplasmic reticulum and mitochondria. The cells also have rough endoplasmic reticulum, Golgi cisterns, lysosomes, microvilli, cilia, and lateral infoldings of the plasma membrane. The fine structure of the pyloric cells and the position of tubules between the absorptive epithelium and general circulation suggest that the gland functions as the vertebrate liver in carbohydrate metabolism. The pyloric cells of Styela do not appear to be excretory in a "renal" sense, since there is no infolding of the basal plasmalemma and mitochondria are usually associated only with the glycogen deposits. However, a hepatic-like excretory role is consistent with current findings. In light of the phylogenic affinities of vertebrates and ascidians, it is possible that the pyloric gland is homologous to the liver.
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PMID:Glycogen deposits in the pyloric gland of the ascidian Styela clava (Urochordata). 83 94

1. Pisaster ochraceus has an annual reproductive cycle in which the gonads increase in size rapidly from October or November and reach a maximum in March to May, after which spawning occurs. In Patiria miniata the gonadal cycle is less pronounced and less regular. In the course of this study, animals spawned in July 1965, May 1966, and May 1967. 2. Histochemical techniques indicate that in both species glycogen or a glycogen-like carbohydrate occurs in the germinal epithelium and the follicle cells of the female, and in the spermatogonia and primary spermatocytes. A storage carbohydrate which is not removed by diastase or amylase is abundant in oocytes in the form of yolk granules 0.5 to 1.5 mu in diameter. 3. Neutral lipid droplets and phospholipid granules are abundant in all oocytes but the smallest. In the testes, lipid droplets are seen only after prolonged starvation. 4. In both species prolonged starvation results in failure of the gonads to achieve their normal size increase. Such gametes as are seen in starving speciments appear histochemically normal in some instances; in other cases they seem to be undergoing breakdown. 5. The histochemical results concerning nutrient reserves of the gonads are generally in agreement with the biochemical findings of earlier workers.
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PMID:Histochemical changes in gonadal nutrient reserves correlated with nutrition in the sea stars, Pisaster ochraceus and Patiria miniata. 97 64

Dexamethasone (DEX) inhibits growth and induces differentiation in rat pancreatic acinar AR42J cells. We wished to determine whether growth and differentiation are mutually exclusive in AR42J cells and whether DEX effects on growth and differentiation are mutually dependent or independent. Inhibition of DNA synthesis, assessed by [3H]thymidine incorporation, was detectable after 6 h, half-maximal after 12 h, and complete after 18-h DEX treatment, at which time incorporation was reduced to 9.0% of control. The half-maximal effective dose for inhibition of DNA synthesis was 0.5 nM, and maximal inhibition was achieved with 10 nM DEX. This dose-response was similar to that previously reported for DEX-induced parameters of differentiation. The rank order of potency for inhibition of DNA synthesis by various steroid hormones was DEX greater than corticosterone greater than aldosterone greater than progesterone. Hydroxyurea or serum starvation inhibited growth to the same extent as DEX but did not induce differentiation. Moreover, hydroxyurea or serum starvation did not block the ability of DEX to induce differentiation. Addition of either EGF or insulin significantly reversed the growth inhibitory effects of submaximal (1 nM) DEX. In cultures released from growth inhibition, 1 nM DEX increased cellular amylase content 5.9- to 6.5-fold, similar to the amylase increase in growth-inhibited cultures. Therefore, growth inhibition and differentiation are independent delayed events regulated by DEX in AR42J cells.
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PMID:Growth and differentiation of pancreatic acinar cells: independent effects of glucocorticoids on AR42J cells. 171 23

Process of amylase and chymotrypsinogen secretion by acinar cells has been studied applying morphological and biochemical approaches. Three conditions were investigated; resting (fed control), cholinergic stimulation and fasting. Morphometrical evaluations have shown that under stimulation, the volume density of zymogen granules decreases drastically while that of the Golgi apparatus increases. This may result from the enhancement in protein processing and the rapid discharge. Quantitation of amylase and chymotrypsinogen immunolabelings present over the cellular compartments has shown that there is no difference in the intensities between tissues from control and stimulated animals. These results imply that total amounts of protein processed by the Golgi apparatus are markedly enhanced primarily because of the increase in size of the organelle, the amounts of protein processed per unit surface remaining unchanged. Under starvation where reduction of secretion occurs, there is a significant decrease in the volume density of the Golgi apparatus but no variation in that of the zymogen granules. However, the morphological aspect of these was markedly altered since many of them present an electron luscent periphery which was devoid of immunolabeling for amylase and chymotrypsinogen. Quantitation of amylase and chymotrypsinogen immunolabelings has shown significant diminution for both enzymes. In both experimental conditions, the volume density of lysosomes was enhanced, however in none of these conditions evidence of crinophagy was observed. The morphometrical and immunocytochemical results were consistent with those obtained from biochemical determination of amylase and chymotrypsinogen contents in tissues. Correlations between results obtained from morphometric and immunocytochemical studies were made leading to a better understanding of the cellular secretory activity during experimental conditions.
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PMID:Morphometrical and immunocytochemical studies on rat pancreatic acinar cells under control and experimental conditions. 241 47

The effect of starvation for 3, 5, or 7 d on body weight, fat stores, pancreatic weight, and enzyme composition was studied in 300 g rats and was compared with a 3-d fast in 200 g rats. In the 300 g animals, fasting led to a gradual hypotrophy of the pancreas with a marked, continuous decrease in amylase content. Pancreatic lipase, trypsinogen, chymotrypsinogen, proelastase, and secretory trypsin inhibitor contents increased temporarily, but by d 7, they declined to about the initial values. This decline in enzyme levels coincided with the exhaustion of fat stores. The decrease in amylase content could be related to decreases in circulating insulin levels, whereas the temporary increase in lipase content may be owing to changes in plasma free fatty acid concentrations. In 200 g rats, starvation for 3 d led to exhaustion of fat stores that was accompanied by greater losses of pancreatic weight, protein, and amylase contents. In addition, the levels of trypsinogen and chymotrypsinogen decreased and lipase was unchanged. These findings indicate that during starvation, changes in pancreatic secretory enzymes are time-dependent and vary with the age, body weight, and/or adipose tissue mass of the rats.
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PMID:Time-course of changes in pancreatic size and enzyme composition in rats during starvation. 247 46

Axenic Tetrahymena pyriformis, syngen 1, mating type II cells were grown in Cox's defined medium. When washed and transferred into nonnutrient dilute salt solution or resuspended in the defined medium, the intact cells secrete acid hydrolases into the medium. Cells starving in the salt solution release in 5 hr about two-thirds of their beta-glucosidase, beta-N-acetylglucosaminidase, alpha-glucosidase, and amylase activities, about one-third of their deoxyribonuclease and phosphatase activities, smaller amounts of ribonuclease, and only a negligible fraction of their proteinase activity and protein content. During this period there is practically no change in the enzyme activities (except for a sudden increase of ribonuclease activity) and protein content of cells and medium together. Cells resuspended in the nutrient medium secrete enzymes as do the starved cells, but replace this loss, so that there is a continuous increase of the activities in the total system. According to isopycnic centrifugation experiments performed in sucrose gradients, the source of the hydrolases is a special population of lysosomes which disappear from the cells during starvation. This population equilibrates in the high density region of the gradients and contains the various acid hydrolases in about the proportion in which these enzymes appear in the medium.
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PMID:Secretion of acid hydrolases and its intracellular source in Tetrahymena pyriformis. 433 53

A quantitative picture is presented on the activities and distribution of three major digestive enzymes in the postembryonic and adult stages of Schizodactylus monstrosus. The activity of enzymes in adult insects of both sexes has also been studied under starvation stress and after the topical application of juvenile hormone analogue. Results show that amylase activity was much higher in the early stages of development while in later stages protease and lipase activity was more significant. Protease activity was highest in the adult male, while the activity of all the enzymes reached its maximum in pregnant females. Starvation stress in adult individuals led to a slight decline of enzyme activity which was insignificant statistically. Topical application of JHa in high doses caused a steady increase in the activity of all the enzymes of which the increase of protease was statistically significant. The probable reasons for the quantitative variation have been discussed.
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PMID:Quantification of protease, amylase and lipase in the gut of Schizodactylus monstrosus during the postembryonic developmental stage. Effect of starvation, stress and topical application of juvenile hormone analogue. 617 95

The nature and mechanism of the pancreatic exocrine dysfunction in diabetes mellitus were evaluated in vitro using isolated pancreatic acini prepared from streptozotocin-induced diabetic rats. The content of amylase and ribonuclease in diabetic acini was approximately 0.5 and 50% of the normal content, respectively. Further, reduced amounts of both enzymes were secreted by diabetic acini in response to both cholecystokinin (CCK) and carbamylcholine. However, when enzyme secretion was normalized relative to initial acinar contents, both normal and diabetic acini released enzymes at a comparable maximal rate. The time course of the release of these enzymes, and newly synthesized protein were similar in both acini. In normal acini, the effect of CCK was maximal at a concentration of 100 pM; higher concentrations led to submaximal enzyme release. The dose-response curve in diabetic acini was similarly shaped, but shifted three-fold towards higher concentration. The mobilization of cellular Ca(2+) in response to CCK was also shifted. In contrast to these results with CCK, the dose-response curve to carbamylcholine was unaltered by diabetes. The observed effects were confirmed to be due to insulin deficiency and not due to direct toxic effect of streptozotocin on acinar cells or malnutrition. Streptozotocin had no acute effect on acini when measured 24 h after administration, and alloxan, another beta cell toxin, induced similar changes in acinar enzyme content and secretory response. Moreover, the administration of exogenous insulin to diabetic rats returned the content of pancreatic amylase and the secretory response to CCK towards normal. Starvation for 48 h, although inducing a significant weight loss, did not mimic the effects of diabetes. The present studies demonstrate two major abnormalities in pancreatic exocrine secretion in the diabetic rat: (a) the content of certain digestive enzymes is markedly altered, leading to an altered amount of zymogen secretion, (b) the sensitivity to CCK is selectively reduced, most likely related to a defect in receptor activated transmembrane signaling.
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PMID:Effect of diabetes mellitus on the regulation of enzyme secretion by isolated rat pancreatic acini. 617 17

Pancreatic amylase, chymotrypsinogen, lipase and colipase were assayed, at intervals, in rats from day 16 of fetal life until weaning. In the fetus, amylase and chymotrypsinogen accumulated regularly, in parallel, until birth. Lipase and colipase accumulation slowed down between day 20 and birth. The ratio of colipase to lipase was extremely high (9.5) and decreased until weaning towards adult values. Enzyme contents of the pancreas were depleted after birth and remained low until day 14. Intestinal concentrations were equally low, showing that pancreatic depletion was not due to hypersecretion. Protein synthesis was very active, intermediate between that of the fetus and of the adult. It is concluded that in the early suckling phase the proteins synthesized are mainly constitutive and not enzymatic. Starvation followed by refeeding showed that secretion sensitivity to nutritional stimulation only appears at 14 days. During the suckling period amylase concentrations decreased, evidencing a degree of nutritional sensitivity to the low level of carbohydrate in the diet. The productive capacity for lipase underwent a slow maturation which was not even complete at weaning, since concentrations had not yet reached adult level despite the high fat content of milk. This was in part compensated for by the high proportion of colipase but shows that lipase was not adaptative during this phase and that pancreatic lipase can hardly account for lipid digestion before weaning.
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PMID:Development of pancreatic enzymes in fetal and suckling rats with emphasis on lipase and colipase. 618 10

Secretion of proteins by rat parotid glands in response to parasympathetic nerve stimulation was studied in vivo during pentobarbitone anaesthesia. Parasympathetic stimulation (3-10 Hz) via the auriculotemporal nerve resulted in a copious flow of saliva low in protein. In contrast, sympathetic stimulation (5 Hz) via the cervical sympathetic trunk evoked saliva low in volume but high in protein. Nevertheless, the specific concentrations of amylase and peroxidase (mg/mg protein) and the ratio of amylase to peroxidase remained constant. Sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis revealed a single, rapidly migrating protein band of unknown identity in proportionately greater amounts in parasympathetic saliva than in sympathetic saliva. Bilateral adrenalectomy led to reduced amylase and peroxidase secretion in response to parasympathetic stimulation both on a mg/ml and a mg/mg protein basis. SDS gel electrophoresis also demonstrated the decrease in specific amylase concentration following adrenalectomy. The ratio of amylase to peroxidase, however, was not significantly affected. Administration of 6-hydroxydopamine 17-72 h prior to adrenalectomy caused no further reduction in the secretion of amylase and peroxidase. Chronic sympathectomy of 2.5-4 months duration resulted in an increased protein secretion (mg/ml) by the parotid gland in response to parasympathetic stimulation. This increase was only slightly reduced by bilateral adrenalectomy. However, as observed in non-sympathectomized rats, adrenalectomy caused a significant reduction in the specific concentrations of both amylase and peroxidase, but did not affect the amylase to peroxidase ratios. We conclude that parasympathetic nerve stimulation of rat parotid glands after overnight starvation causes secretion of proteins in proportions similar to, but in significantly lower concentrations than those found in sympathetic saliva. Circulating catecholamines, however, influence the amount of amylase and peroxidase secreted by the rat parotid gland in response to parasympathetic nerve stimulation and account for most of the increased secretion of these enzymes following chronic sympathectomy.
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PMID:Influence of circulating catecholamines on protein secretion into rat parotid saliva during parasympathetic stimulation. 620 47


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