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

In order to perform studies on lipid mobilization in adult M. sexta, it is necessary to overcome the effects of starvation and handling, which both provoke an increase in hemolymph lipid concentration. When trehalose was injected into intact insects, a 35% decrease in the content of the diacylglycerol (DG)-rich hemolymph lipoprotein, low density lipophorin (LDLp) was observed within 30 min, but the level of LDLp returned to control values after 1 h. Decapitated insects exhibited 60% reduction in LDLp concentration and the levels remained low for at least 24 h. In contrast to intact insects, injection of trehalose into decapitated animals did not alter the LDLp concentration. After decapitation, the response to adipokinetic hormone (AKH) and the ability of the fat body to release DG into the hemolymph was maintained for at least 24 h. In decapitated insects, 6 pmol of AKH-stimulated measurable lipid mobilization and a near maximum response was obtained with 100 pmol of the hormone. The action of trehalose and AKH on the fat body triacylglycerol (TG)-lipase activity in decapitated animals was studied. Fat body homogenates from trehalose-treated insects exhibited a TG-lipase activity 40% lower than the control insects. Activation of fat body triacylglycerol-lipase was observed after injection of AKH, with the extent of activation ranging between 97 and 380% ten min after AKH injection. A time course study showed that the activation of the fat body triacylglycerol lipase preceded the increase in hemolymph LDLp concentration, suggesting that activation of the lipase initiates lipid mobilization. It is concluded that decapitated insects injected with trehalose is a very useful system for investigating the hormonal regulation of lipid mobilization in adult M. sexta.
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PMID:The use of decapitated insects to study lipid mobilization in adult Manduca sexta: effects of adipokinetic hormone and trehalose on fat body lipase activity. 901 27

Fasting induces pancreatic secretory lipase, possibly through an increased utilization of fatty acids and/or ketone bodies by the acinar cells. To test this hypothesis, the effects of L-aminocarnitine (ACA), an inhibitor of mitochondrial beta-oxidation and ketone body formation, on the pancreatic enzyme composition were studied in rats. The characteristics and reversibility of the hepatic steatosis produced by ACA in fasted animals were also investigated. In fasted rats, ACA decreased the plasma levels of beta-hydroxybutyrate, glucose and insulin, but increased that of glucagon. Fasting for 3 days increased the pancreatic lipase content by 80%. Administration of ACA (3, 10 or 30 mg kg(-1) daily) for 3 days to fasted rats led to dose-related decreases in pancreatic lipase content, the fasting-induced increase was prevented even by the lowest dose. Nevertheless, ACA in the fasted rats likewise decreased the pancreatic contents of protein, amylase and trypsinogen to varying degrees, suggesting a general defect of protein synthesis. The 3-day treatment with ACA during fasting led to dose-related, marked increases in hepatic weight and triglyceride content. Light and electron microscopy revealed lipid vesicles of varying sizes in the hepatocytes; the fat deposition was predominant in the periportal zones of the hepatic lobules. By means of electron microscopy, lipid vacuoles were observed in the centroacinar cells, but not in the acinar cells of the pancreas. In rats treated with 30 mg kg(-1) of ACA daily for 3 days while they were fasted, cessation of ACA treatment and refeeding with normal chow led to normalization of the pancreatic enzyme contents within 6 days, and gradual and complete disappearance of the hepatic steatosis within 24 days. Microscopy also demonstrated complete recovery in both the liver and the pancreas. The results indicate that pancreatic secretory lipase induction during the adaptive phase of starvation is dependent on an unhindered mitochondrial beta-oxidation of fatty acids and ketogenesis. The dose-related degree of hepatic triglyceride accumulation which can be produced readily by administration of ACA during short-term starvation in the rat may serve as a new, convenient experimental model for studies of fatty liver.
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PMID:Effect of L-aminocarnitine, an inhibitor of mitochondrial fatty acid oxidation, on the exocrine pancreas and liver in fasted rats. 1060 Feb 64

The vacuole/lysosome serves an essential role in allowing cellular components to be degraded and recycled under starvation conditions. Vacuolar hydrolases are key proteins in this process. In Saccharyomces cerevisiae, some resident vacuolar hydrolases are delivered by the cytoplasm to vacuole targeting (Cvt) pathway, which shares mechanistic features with autophagy. Autophagy is a degradative pathway that is used to degrade and recycle cellular components under starvation conditions. Both the Cvt pathway and autophagy employ double-membrane cytosolic vesicles to deliver cargo to the vacuole. As a result, these pathways share a common terminal step, the degradation of subvacuolar vesicles. We have identified a protein, Cvt17, which is essential for this membrane lytic event. Cvt17 is a membrane glycoprotein that contains a motif conserved in esterases and lipases. The active-site serine of this motif is required for subvacuolar vesicle lysis. This is the first characterization of a putative lipase implicated in vacuolar function in yeast.
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PMID:Degradation of lipid vesicles in the yeast vacuole requires function of Cvt17, a putative lipase. 1108 77

Selective disintegration of membrane-enclosed autophagic bodies is a feature of eukaryotic cells not studied in detail. Using a Saccharomyces cerevisiae mutant defective in autophagic-body breakdown, we identified and characterized Aut5p, a glycosylated integral membrane protein. Site-directed mutagenesis demonstrated the relevance of its putative lipase active-site motif for autophagic-body breakdown. aut5Delta cells show reduced protein turnover during starvation and are defective in maturation of proaminopeptidase I. Most recently, by means of the latter phenotype, Aut5p was independently identified as Cvt17p. In this study we additionally checked for effects on vacuolar acidification and detected mature vacuolar proteases, both of which are prerequisites for autophagic-body lysis. Furthermore, biologically active hemagglutinin-tagged Aut5p (Aut5-Ha) localizes to the endoplasmic reticulum (nuclear envelope) and is targeted to the vacuolar lumen independent of autophagy. In pep4Delta cells immunogold electron microscopy located Aut5-Ha at approximately 50-nm-diameter intravacuolar vesicles. Characteristic missorting in vps class E and fab1Delta cells, which affects the multivesicular body (MVB) pathway, suggests vacuolar targeting of Aut5-Ha similar to that of the MVB pathway. In agreement with localization of Aut5-Ha at intravacuolar vesicles in pep4Delta cells and the lack of vacuolar Aut5-Ha in wild-type cells, our pulse-chase experiments clearly indicated that Aut5-Ha degradation with 50 to 70 min of half-life is dependent on vacuolar proteinase A.
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PMID:Aut5/Cvt17p, a putative lipase essential for disintegration of autophagic bodies inside the vacuole. 1156 94

Many beetle species use proline and carbohydrates in a varying ratio to power flight. The degree of contribution of either fuel varies widely between species. In contrast, dung beetle species investigated, thus far, do not have any carbohydrate reserves and rely completely on proline to power energy-costly activities such as flight and, probably, walking and ball-rolling. While the fruit beetle, Pachnoda sinuata, uses proline and carbohydrates equally during flight, proline is solely oxidised during endothermic pre-flight warm-up, as well as during flight after prolonged starvation. Thus, proline seems to be the essential fuel for activity in beetles, even in flightless ones and in those that use proline in combination with carbohydrates; the latter can be completely substituted by proline in certain circumstances. It is apparent from the rapid decline of energy substrates in flight muscles and haemolymph after the onset of flight that mobilisation of stored fuels of the fat body is necessary for prolonged flight periods. This task is performed by AKH-type neuropeptides. In beetles, like in other insects, these peptides mobilise glycogen via activation of glycogen phosphorylase. They also stimulate proline synthesis from alanine and acetyl-CoA in the fat body. Acetyl-CoA is derived from the beta-oxidation of fatty acids and we propose that the neuropeptides activate triacylglycerol lipase.
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PMID:Beetles' choice--proline for energy output: control by AKHs. 1199 15

Successful adaptation to starvation in mammals depends heavily on the regulated mobilization of fatty acids from triacylglycerols stored in adipose tissue. Although it has long been recognized that cyclic AMP represents the critical second messenger and hormone-sensitive lipase (HSL)**Abbreviations used in this paper: ADRP, adipocyte differentiation-related protein; HSL, hormone-sensitive lipase; PKA, protein kinase A; TAG, triacylglycerol. the rate-determining enzyme for lipolysis, simple activation of the enzyme has failed to account for the robust augmentation of fatty release in response to physiological agonists. In this issue, Sztalryd et al. (2003) provide convincing support to the notion that the subcellular compartmentalization of lipase also regulates lipolysis, and, more importantly, that proteins other than HSL are localized to the lipid droplet and are indispensable for its optimal hydrolysis.
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PMID:Lipolysis: more than just a lipase. 1281 Jun 97

An antibiotic efflux gene cluster that confers resistance to chloramphenicol, trimethoprim, and ciprofloxacin has been identified in Burkholderia cenocepacia (genomovar III), an important cystic fibrosis pathogen. Five open reading frames have been identified in the cluster. There is apparently a single transcriptional unit, with llpE encoding a lipase-like protein, ceoA encoding a putative periplasmic linker protein, ceoB encoding a putative cytoplasmic membrane protein, and opcM encoding a previously described outer membrane protein. A putative LysR-type transcriptional regulatory gene, ceoR, is divergently transcribed upstream of the structural gene cluster. Experiments using radiolabeled chloramphenicol and salicylate demonstrated active efflux of both compounds in the presence of the gene cluster. Salicylate is an important siderophore produced by B. cepacia complex isolates, and both extrinsic salicylate and iron starvation appear to upregulate ceoR promoter activity, as does chloramphenicol. These results suggest that salicylate is a natural substrate for the efflux pump in B. cenocepacia and imply that the environment of low iron concentration in the cystic fibrosis lung can induce efflux-mediated resistance, even in the absence of antibiotic selective pressure.
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PMID:Salicylate induces an antibiotic efflux pump in Burkholderia cepacia complex genomovar III (B. cenocepacia). 1475 43

THE COMPOSITION OF ISOLATED NUCLEI AND CELL PREPARATIONS FROM TISSUES OF CALF, BEEF, HORSE, AND FOWL WAS STUDIED WITH RESPECT TO THE FOLLOWING COMPONENTS: 1. Liver and kidney arginase, catalase, and uricase; pancreatic lipase and amylase; cardiac muscle myoglobin; erythrocyte hemoglobin; intestinal alkaline phospharase. These are referred to as "special" components in view of their characteristically restricted distribution reflecting the differentiated nature of the tissues in question. 2. Esterase, beta-glucuronidase, alkaline and nucleotide phosphatases, adenosine deaminase, guanase, and nucleoside phosphorylase. These are enzymes of general distribution. The differences in nuclear composition noted with respect to the "special" components, together with the broad variability in nuclear activity found for enzymes of general distribution, led to the conclusion that nuclei are differentiated structures. The following distribution was observed: 1. "Special" components: Hemoglobin was found to be present in fowl and goose erythrocyte nuclei, but myoglobin was entirely absent from heart muscle nuclei; of the special enzymes listed, only catalase and arginase appeared to be concentrated in some of the nuclei. There was no significant nuclear concentration of lipase, amylase, uricase, or alkaline phosphatase. No simple relationship was found between the concentration of a special enzyme in a tissue and its activity in the corresponding nuclei. For example, arginase activity, which is high in mammalian liver and in fowl kidney, was found in liver, not kidney, nuclei. Similarly, catalase activity was demonstrated only in mammalian liver nuclei, although, in mammals, both liver and kidney are rich sources of this enzyme. 2. Enzymes of general distribution fell into three classes: (a) Those present in low concentrations, if at all, in the nuclei-alkaline phosphatase, the nucleotide phosphatases) and beta-glucuronidase. (b) Those present in nuclei in varying concentrations-esterase. (c) Those present in high proportions in most nuclei-adenosine deaminase, nucleoside phosphorylase, and guanase. The exceptionally low nuclear activity of intestinal mucosa with respect to these enzymes was discussed in relation to physiological considerations. The response of nuclei to changes in physiological state was demonstrated by experiments on starvation. The outstanding aspect of this response was a change in nuclear enzymatic activity opposing that observed in the cytoplasm. A comparison of fetal and adult mucosa cells led to the following tentative interpretation of the observed intracellular enzyme distribution: In cells tending to moribundity, as in those subjected to starvation, relative nuclear enzymatic activity falls. The occurrence of special enzymes in nuclei was considered in terms of differentiation, and the high nuclear concentration of the nucleoside-specific enzymes was interpreted in terms of general nuclear metabolic activity.
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PMID:Some enzymes of isolated nuclei. 1489 35

The impact of starvation on the digestive enzyme (protease, trypsin, lipase and amylase) activities of Stage I and IV Jasus edwardsii phyllosoma larvae was used to identify the nutrients metabolised or conserved during food deprivation, highlighting the most critical energy reserves. Protease activities increased significantly in both Stages I and IV phyllosoma, suggesting that protein catabolism provided energy during food deprivation. Lipase activity decreased significantly in starved Stages I and IV larvae indicating that lipid may be spared for fuelling later developmental moults. The use of protein, while sparing lipid, may provide immediate energy but not at the expense of long-term lipid energy stores which are known to be important during their lengthy larval phase. The preferential use of protein during short-term periods of starvation suggests that particular attention must be given to providing sufficient protein in artificial diets at all times. Amylase activity in starved Stage I larvae was lower than in fed animals, suggesting that the starved animals are not gaining sufficient carbohydrate. However, amylase activity was similar in fed and starved Stage IV larvae, possibly due to the catabolism of accumulated glycogen stores that were not sufficiently developed in Stage I animals.
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PMID:Digestive enzyme profiles reveal digestive capacity and potential energy sources in fed and starved spiny lobster (Jasus edwardsii) phyllosoma larvae. 1519 68

We recently reported that cultivation of oat (Avena sativa L.) without phosphate resulted in plasma membrane phosphoglycerolipids being replaced to a large extent by digalactosyldiacylglycerol (DGDG) (Andersson, M. X., Stridh, M. H., Larsson, K. E., Liljenberg, C., and Sandelius, A. S. (2003) FEBS Lett. 537, 128-132). We report here that DGDG is not the only non-phosphorous-containing lipid that replaces phospholipids but that also the content of glucosylceramides and sterolglycosides increased in plasma membranes as a response to phosphate starvation. In addition, phosphate deficiency induced similar changes in lipid composition in the tonoplast. The phospholipid-to-glycolipid replacement apparently did not occur to any greater extent in endoplasmic reticulum, Golgi apparatus, or mitochondrial inner membranes. In contrast to the marked effects on lipid composition, the polypeptide patterns were largely similar between root plasma membranes from well-fertilized and phosphate-limited oat, although the latter condition induced at least four polypeptides, including a chaperone of the HSP80 or HSP90 family, a phosphate transporter, and a bacterial-type phosphoesterase. The latter polypeptide reacted with an antibody raised against a phosphate deficiency-induced phospholipase C from Arabidopsis thaliana (Nakamura, Y., Awai, K., Masuda, T., Yoshioka, Y., Takamiya, K., and Ohta, H. (2005) J. Biol. Chem. 280, 7469-7476). In plasma membranes from oat, however, a phospholipase D-type activity and a phosphatidic acid phosphatase were the dominant lipase activities induced by phosphate deficiency. Our results reflect a highly developed plasticity in the lipid composition of the plasma membrane and the tonoplast. In addition, phosphate deficiency-induced alterations in plasma membrane lipid composition may involve different sets of lipid-metabolizing enzymes in different plant tissues or species, at different stages of plant development and/or at different stages of stress adjustments.
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PMID:Phosphate-limited oat. The plasma membrane and the tonoplast as major targets for phospholipid-to-glycolipid replacement and stimulation of phospholipases in the plasma membrane. 1592 62


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