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

Two criteria are suggested for assessing the relevance of biochemical events occurring early in sporulation. The first is thymidine starvation, a condition known to inhibit sporulation. This also inhibits the production of metalloprotease, serine protease, and ribonuclease; alpha-amylase production, however, is unaffected. The second is the effect of a regulator mutation which increases the production of the proteases. In the mutant, ribonuclease is produced in correspondingly large quantities whereas alpha-amylase production is unaffected. We conclude that, whereas the serine protease is part of the main sequence of events leading to formation of the spore, the metalloprotease is a side effect, i.e., connected with the main sequence but not part of it. Ribonuclease could, on present evidence, be either in the main sequence or a side effect associated with it. Amylase, however, seems to be separately regulated and neither directly nor indirectly connected with the sporulation sequence.
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PMID:Criteria for categorizing early biochemical events occurring during sporulation of Bacillus subtilis. 80 78

Four alpha-amylase-encoding cDNA (alpha Amy-C) clones were isolated from a cDNA library derived from poly(A)+RNA of gibberellic acid (GA3)-treated rice aleurone layers. Nucleotide sequence analysis indicates that the four cDNAs were derived from different alpha Amy genes. Expression of the individual alpha Amy gene in germinating seeds and cultured suspension cells of rice was studied using gene-specific probes. In germinating seeds, expression of the alpha Amy genes is positively regulated by GA3 in a temporally coordinated but quantitatively distinct manner. In cultured suspension cells, in contrast, expression of the alpha Amy genes is negatively and differentially regulated by sugars present in the medium. In addition, one strong and one weak carbohydrate-starvation-responsive alpha Amy genes have been identified. Interactions between the promoter region (HS501) of a rice alpha Amy gene and GA3-inducible DNA binding proteins in rice aleurone cells were also studied. A DNA mobility-shift assay showed that the aleurone proteins interact with two specific DNA fragments within HS501. One fragment is located between nt -131 to -170 and contains two imperfect directly repeated pyrimidine elements and a putative GA3-response element. The other fragment is located between nt -92 to -130 that contains a putative enhancer sequence. The interactions between aleurone proteins and these two fragments are sequence-specific and GA-responsive.
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PMID:Regulation of alpha-amylase-encoding gene expression in germinating seeds and cultured cells of rice. 133 78

We present evidence to show that the alpha-amylase gene family in rice is under two different modes of regulation: 1) hormonal regulation in germinating seeds, and 2) metabolic repression in cultured cells by available carbohydrate nutrients. Expression of alpha-amylase genes in deembryoed rice seeds is known to be induced by exogenous gibberellic acid. On the other hand, expression of alpha-amylase genes in suspension-cultured cells is induced by the deprivation of carbohydrate nutrient. A lag period of 2-4 h is required for the induction of alpha-amylase mRNA in sucrose-depleted medium. The induction of alpha-amylase expression is extraordinarily high and levels of alpha-amylase mRNA can be increased 8-20-folds after 24 h of sucrose starvation. The synthesis and secretion of alpha-amylase is also dependent upon the level of carbon source. The derepression or repression of alpha-amylase synthesis can be readily reversed by the deprivation or replenishment of sucrose in the medium, respectively. Glucose and fructose exert a repression on the alpha-amylase synthesis similar to that of sucrose. A hypothesis that explains the induction of alpha-amylase synthesis by carbohydrate starvation is proposed. Our data have suggested a hitherto undiscovered, potentially important control mechanism of carbohydrate metabolism in higher plants.
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PMID:Metabolic derepression of alpha-amylase gene expression in suspension-cultured cells of rice. 193 56

Previous studies have shown that reduction of mastication has marked effects on the structure and biochemistry of the rat parotid gland. Acute starvation results in the formation in the acinar cells of large autophagic vacuoles which contain lysosomal hydrolases and within which secretory granules appear to undergo degradation. In this study we used electron microscopic immunocytochemistry and antibodies to two secretory proteins, alpha-amylase and B1-immunoreactive protein, to determine whether secretory proteins are present in autophagic vacuoles of parotid acinar cells of starved rats. Small vacuoles were observed after 24-h starvation; they increased in size and number up to 72-h starvation. Both secretory proteins were present in the secretory granules and in the dense content of the autophagic vacuoles, as shown by immunogold labelling. The lighter matrix of the vacuoles was unlabelled. These findings confirm that secretory granules may fuse with lysosomal structures, where their content of secretory proteins is presumably degraded. Thus, the rat parotid appears to be similar to other secretory cells in which cellular levels of stored secretory proteins may be regulated by the process of crinophagy.
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PMID:Ultrastructural immunocytochemical localization of secretory proteins in autophagic vacuoles of parotid acinar cells of starved rats. 314 90

Regulation of alpha-amylase gene expression in Aspergillus awamori was studied by analyzing the enzyme activity levels, rate of protein synthesis, and alpha-amylase-specific mRNA levels under various conditions of growth. alpha-Amylase synthesis was sensitive to catabolite repression as glucose repressed its synthesis by about fourfold. The stimulation of alpha-amylase synthesis in the presence of its substrate starch was shown to be due to derepression rather than induction as the enzyme was synthesized at similar rates in both starch and starvation media. Repression and derepression of enzyme synthesis was found to be mediated at the translational level. The cellular levels of alpha-amylase-specific mRNA as measured by an in vitro translation assay system, were almost identical under all conditions of enzyme synthesis. Relative in vivo and in vitro alpha-amylase mRNA template activities suggest that alpha-amylase mRNA is translated much more efficiently during the derepression than under the conditions of repressed synthesis.
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PMID:Translational control of alpha-amylase gene expression in Aspergillus awamori. 349 55

The influence of a short-term ischemia of the pancreas for the pathogenesis of a hemorrhagic necrotising pancreatitis was investigated in 28 mongrel dogs. Ischemia of the pancreas in 20 minute intervals repeated three times did not leave any macroscopic, histologic or electron microscopic changes and no alterations of the level of the alpha-amylase, the lipase, and the glucose in the serum. An ischemia of 20 minutes' duration by starvation of the celiac artery and the superior mesenteric artery produces a hemorrhagic necrotising pancreatitis under the precondition of a following pancreatic edema by ligature of the pancreatic duct and secretomotoring with secretin and pancreozymin. The necrosis starts histologically in the perilobular adipose and affects the parenchyma later. Whether the lipase is the starting enzyme for the acute pancreatitis or only conditions the early adipose necrosis should be discussed after these findings. Already a fugitive pancreatic edema produces a hemorrhagic necrotising pancreatitis after previous ischemic damage.
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PMID:[Animal experiment studies on the role of ischemia in the pathogenesis of acute pancreatitis]. 633 88

Upon fractionation of a post mitochondrial supernatant from rat liver, phosphorylase kinase activity was largely recovered in the cytosol and the smooth endoplasmic reticulum (SER) fraction. The presence of phosphorylase kinase in SER vesicles was not due to an interaction of the enzyme with glycogen particles, since previous elimination of SER glycogen either by 48 h animal starvation or by treatment of the membrane fraction with alpha-amylase did not significantly alter phosphorylase kinase activity content. Washing of the initial pellet of SER fraction (crude SER) by dilution and recentrifugation, released in the supernatant an amount of phosphorylase kinase activity, which is dependent on: i) the degree of dilution, ii) the number of washes, iii) the ionic strength of the washing solution and iii) the presence or absence of Ca2+. Crude SER-associated phosphorylase kinase was marginally affected by increased concentrations of antibody against rabbit skeletal muscle holoenzyme which nevertheless drastically inhibited cytosolic enzyme activity, while it showed a higher resistance to partial proteolysis and a different Western blotting profile with anti-phosphorylase kinase when compared with the soluble kinase. A small but significant fraction of SER phosphorylase kinase was strongly associated with the microsomal fraction being partly extractable only in presence of detergents. This membrane-bound enzyme form exhibited an alkaline pH optimum, in contrast to the neutral pH optima of both soluble and weakly associated phosphorylase kinase.
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PMID:The association of phosphorylase kinase with membranes of rat liver smooth endoplasmic reticulum. 871 29

Expression of alpha-amylase genes in cultured rice suspension cells is induced by sucrose starvation. To study the mechanism of sugar metabolite regulation on the expression of individual alpha-amylase genes, DNA fragments specific to each of eight rice alpha-amylase genes were synthesized and used as gene-specific probes. Comparison of the relative abundance of mRNA revealed that expression of the eight alpha-amylase genes in rice cells was differentially regulated by sucrose starvation. Accumulation of all the alpha-amylase mRNAs increased in response to sucrose starvation; however, levels of the alphaAmy3 and alphaAmy8 mRNAs were distinctly higher and constituted 90% of total alpha-amylase mRNAs. RNA gel blot and nuclear run-on transcription analyses demonstrated a positive correlation between the increased transcription rates and the elevated steady-state levels of alpha-amylase mRNAs induced by sucrose starvation. The half-lives of alphaAmy3, alphaAmy7, and alphaAmy8 were prolonged by sucrose-starvation; however, the stability of the three mRNAs seems controlled by different mechanisms. The translation inhibitors cycloheximide and anisomycin preferentially blocked the sucrose-suppressed expression of alphaAmy3 but not that of alphaAmy7 and alphaAmy8. These inhibitors also enhanced the sucrose starvation-induced accumulation of alphaAmy3 mRNA but not that of alphaAmy7 or alphaAmy8 mRNAs. Cycloheximide did not significantly alter the transcription rates of alpha-amylase genes, suggesting that labile proteins may selectively stabilize the alphaAmy7 and alphaAmy8 mRNAs but destabilize the alphaAmy3 mRNA.
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PMID:Carbohydrate starvation stimulates differential expression of rice alpha-amylase genes that is modulated through complicated transcriptional and posttranscriptional processes. 890 Jan 87

Expression of alpha-amylase genes during seedling development plays a key role in production of sugar from the starch stored in the cereal seed. Rice alpha-amylase Amy3D promoter/GUS constructs in transgenic rice cell lines were studied to identify cis elements in the promoter of this metabolite-regulated gene. Three sequences having the greatest effects on Amy3D gene expression included the amylase element (TATCCAT), the CGACG element, and a G box-related element (CTACGTGGCCA). These promoter cis elements are needed for high-level expression of Amy3D under conditions of sugar starvation. The involvement of G box cis-elements in environmental stress responses suggest a link between the nutrient stress and the environmental stress responses of the plant.
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PMID:Three cis-elements required for rice alpha-amylase Amy3D expression during sugar starvation. 948 74

Expression of alpha-amylase genes in both rice suspension cells and germinating embryos is repressed by sugars and the mechanism involves transcriptional regulation. The promoter of a rice alpha-amylase gene alphaAmy3 was analyzed by both loss- and gain-of-function studies and the major sugar response sequence (SRS) was located between 186 and 82 base pairs upstream of the transcription start site. The SRS conferred sugar responsiveness to a minimal promoter in an orientation-independent manner. It also converted a sugar-insensitive rice actin gene promoter into a sugar-sensitive promoter in a dose-dependent manner. Linker-scan mutation studies identified three essential motifs: the GC box, the G box, and the TATCCA element, within the SRS. Sequences containing either the GC box plus G box or the TATCCA element each mediated sugar response, however, they acted synergistically to give a high level glucose starvation-induced expression. Nuclear proteins from rice suspension cells binding to the TATCCA element in a sequence-specific and sugar-dependent manner were identified. The TATCCA element is also an important component of the gibberellin response complex of the alpha-amylase genes in germinating cereal grains, suggesting that the regulation of alpha-amylase gene expression by sugar and hormone signals may share common regulatory machinery.
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PMID:Sugar response sequence in the promoter of a rice alpha-amylase gene serves as a transcriptional enhancer. 955 59


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