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

To investigate the role of cilia in mating interactions of Tetrahymena thermophila, ciliary membrane-rich fractions were isolated from two wild-type strains, a non-discharge mucocyst mutant which possesses mating behavior similar to wild-type, and a mating mutant which is able to costimulate cells of complementary mating type but cannot enter into pair formation. In each case, proteins from the ciliary membrane-rich fractions of starved, mating-competent ("initiated") cells were compared with those from non-starved, mating-incompetent ("non-initiated") cells, by gel electrophoresis and lectin blotting. In stained gels, a 43 kDa polypeptide was reduced or absent in initiated cells but present in non-initiated cells, in all strains. In silver-stained gels, a 25 kDa polypeptide was present in all strains, both initiated and non-initiated. In blots probed with Con A-peroxidase, a 25 kDa glycoprotein was present in ciliary membrane fractions from non-initiated cells and absent in membranes of initiated cells of the two wild-type strains and the mucocyst mutant, but is present in initiated and non-initiated cells of the mating mutant (several hypotheses are presented to explain these findings). In addition, ciliary proteins of the mating mutant included at least two unique Con A-binding polypeptides. Our results support the idea that development of mating competence during starvation involves an extensive remodeling of ciliary membranes, and identify a 25 kDa glycoconjugate as having a potential role in control of pair formation during mating.
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PMID:Ciliary polypeptides and glycoconjugates of wild-type and mutant Tetrahymena thermophila: starved versus nonstarved. 139 38

Effect of Erythropoietin (Ep) on the interaction of Concanavalin A (Con A) with rat erythrocytes was studied using 125I-labelled Con A. Binding of Con A to erythrocytes was dependent on time and cell concentration. Starvation caused an elevation of the lectin binding capacity of red cells which again came down towards the normal level on Ep administration to starved rats. Binding of Con A to erythrocytes decreased linearly with increasing concentration of Ep. Specificity of binding was confirmed by inhibition studies with alpha-methyl-D-mannopyranoside (Me Man) Cells from the starved rats compared to those from normal and Ep treated animals were less prone to inhibition by this sugar analog. Positive cooperative binding of Con A to rat erythrocyte was observed at low concentration of Con A but was absent at higher lectin concentrations. Starvation caused an increase in the number of binding sites per cell which returned to normal level after Ep treatment. Under identical conditions, binding affinities were not much changed in these cells. Cells from the starved animals were more susceptible to agglutination compared to those from normal and Ep-treated rats. Microviscosity and cholesterol/phospholipid ratio of red cell membrane decreased in the starved animals which retraced its way back towards the normal level after Ep treatment.
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PMID:Effect of erythropoietin on the interaction of concanavalin A with rat erythrocytes. 192 16

The total cellular mass of the small intestine is well controlled and can adapt, with hypo- or hyperplasia, to a wide variety of stimuli. Luminal nutrients, hormonal factors and pancreatic and biliary secretions have all been implicated in the regulation of intestinal mucosal growth. The polyamines (putrescine, spermidine and spermine) and the key enzyme controlling their synthesis (ornithine decarboxylase. ODC) are critical for many cell growth processes and appear to play important roles in intestinal growth. During intestinal adaptation in response to jejunectomy, lactation. pancreatic-biliary diversion, starvation-refeeding and feeding with kidney bean lectin, intestinal contents of ODC and polyamines are increased, paralleling increases in mucosal proliferative indices and DNA synthesis. With administration of the specific inhibitor of ODC (difluoromethylornithine, DFMO) the increase in ODC and polyamines is inhibited and intestinal growth is suppressed. In addition, the oral administration of exogenous polyamines results in precocious maturation of the neonatal rat intestine. These results suggest that the polyamines are important for intestinal growth.
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PMID:Polyamines in intestinal growth. 208 16

Binding of a monoclonal antibody, mAb293, to cell-surface glycoproteins of Polysphondylium pallidum is known to be blocked by L-fucose, and Fab of this antibody has been shown to inhibit intercellular adhesion of aggregation-competent cells. Mutants with delayed expression of the carbohydrate epitope, ep293, recognized by the antibody, have been shown to be retarded and altered in cell aggregation. The present study shows that ep293 is a modification of carbohydrate structure that is subject to regulation not only in mutant but also in wild-type cells; ep293 is expressed at an early stage of exponential growth in wild-type and only after 12 h of starvation in mutant PN6002. Proteins are already glycosylated before the epitope is expressed. The developmental regulation of pallidin, a lectin known to be an unglycosylated protein, was investigated in parallel with ep293 using a monoclonal antibody. Pallidin was expressed at about the same time as the carbohydrate epitope in cells of the wild-type as well as the mutant. These results indicate a regulatory signal to which various events are coupled. Induction of ep293 and expression of pallidin are two of these events, and mutants such as PN6002 are altered in the timing of the signal.
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PMID:Mutants of Polysphondylium pallidum showing delayed modifications of glycoproteins are altered in a regulatory signal for development. 244 7

The activity of lectins in different species of tsetse was compared in vivo by the time taken to remove all trypanosomes from the midgut following an infective feed and in vitro by agglutination tests. Teneral male Glossina pallidipes Austen, G. austeni Newstead and G. p. palpalis R-D. removed 50% of all Trypanosoma brucei rhodesiense Stephens & Fantham infections within 60 h. A 'refractory' line of G. m. morsitans Westwood took 170 h to kill 50% infections while a 'susceptible' line of the same species failed to kill 50%. Agglutination tests with midgut homogenates showed differences between fly stocks which accorded with differences in rate of trypanosome killing in vivo. Flies fed before an infective feed were able to remove trypanosomes from their midguts more quickly than flies infected as tenerals. Increasing the period of starvation before infection increased the susceptibility to trypanosome infection of non-teneral flies. Teneral flies showed little agglutinating activity in vitro, suggesting that lectin is produced in response to the bloodmeal. Feeding flies before infection also abolished the differences in rate of trypanosome killing found between teneral 'susceptible' and 'refractory' G. m. morsitans, suggesting that maternally inherited susceptibility to trypanosome infection is a phenomenon limited to teneral flies. Electron micrographs of midguts of G. m. morsitans suggest that procyclic trypanosomes are killed by cell lysis, presumably the result of membrane damage caused by lectin action.
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PMID:Rate of trypanosome killing by lectins in midguts of different species and strains of Glossina. 251 50

Lectins purified by affinity chromatography on immobilized asialofetuin from extracts of mouse K-1735P melanoma cells appeared as two polypeptides [L-14.5 (Mr 14,500) and L-34 (Mr 34,000)] in one-dimensional polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. However, in two-dimensional electrophoresis (isoelectric focusing followed by sodium dodecyl sulfate:polyacrylamide gel electrophoresis) the L-14.5 polypeptide was resolved into three acidic forms of pI 4.6, 4.9, and 5.8, whereas the L-34 was resolved into two polypeptides of pI 4.9 and 5.3. Antibodies directed against galactoside-binding lectins from rat and bovine lungs, mouse 3T3 fibroblasts, and mouse UV-2237 fibrosarcoma cells reacted with the K-1735P lectins in immunoblots, and normal mouse lung extracts were found to contain cross-reactive proteins that comigrated with the two melanoma lectins. Indirect immunofluorescence staining using the above antibodies demonstrated that both L-14.5 and L-34 were expressed on the surface of viable K-1735P cells. Treatment of these cells with 1 microM beta-all-trans-retinoic acid or 1 mM N6,O2'-dibutyryl cyclic AMP for 5 days induced morphological differentiation, inhibition of anchorage-dependent and anchorage-independent growths, and a selective decrease in the L-34 lectin level. Growth inhibition by starvation for serum factors, which did not induce differentiation, had no effect on the level of L-34. These results demonstrate that the melanoma lectins are immunologically related to normal cell lectins and that the two polypeptide species are expressed on the cell surface. Further, they demonstrate that the L-34 lectin level can be modulated by agents that suppress the transformed phenotype by enhancing differentiation.
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PMID:Biochemical and immunological characterization of K-1735P melanoma galactoside-binding lectins and their modulation by differentiation inducers. 253 46

The synthesis of the lectin, discoidin I, by vegetative cells of Dictyostelium discoideum (strain NC4) was monitored using immunoblot analysis and indirect immunofluorescence. Suspension cultures were used, so that the D. discoideum cell density and the concentration of bacteria could be controlled. Discoidin-I production was found to be a function of the relative densities of D. discoideum cells and food bacteria. Synthesis was initiated in exponentially growing D. discoideum cells approximately three generations before depletion of the food supply. In the growth medium of cells producing discoidin I, a soluble activity was detected that caused low-density cells to begin discoidin-I synthesis. This activity was not dialyzable and was destroyed by heat. A similar activity was produced by AX3 cells during axenic growth. Density-dependent induction of other 'early developmental' proteins was also detected in wild-type cells. These findings suggest that the expression of several 'early developmental' genes is regulated by a mechanism that measures cell density relative to food supply, not by starvation per se.
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PMID:Density-dependent induction of discoidin-I synthesis in exponentially growing cells of Dictyostelium discoideum. 362 52

Extreme intra-assay variations and/or contradictory results frequently encountered in lectin binding studies on Tetrahymena cultures prompted us to investigate the environmental factors affecting the physical or chemical properties of the cell membrane for influence on the lectin-binding capacity thereof. It was found that changes in ambient temperature, osmolarity and illumination, as well as temporary starvation, modified the lectin-binding capacity of Tetrahymena to an appreciable degree. It follows that the comparability of the experimental results presupposes the standardization of the above environmental parameters in Tetrahymena cultures used for lectin-binding studies.
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PMID:Influence of environmental (culturing) conditions on the lectin-binding capacity of Tetrahymena. 623 78

Tetrahymena pyriformis GL cells showed partly intracytoplasmic, partly intramembraneous accumulation of lectin-like proteins in conditions of starvation, as demonstrated cytochemically by reaction with antibodies to pea, lens, bean, Datura, and snail lectin. The lectins binding to simple sugars tended to accumulate in the membrane, whereas those capable of interacting with hexosamines in the cytoplasm. While the fluorescence pattern of lectin localization was generally homogeneous in normally nourished cells, it assumed a variegated appearance in starved cells, owing to patching of the membrane, and spot-like accumulation of lectins in the cytoplasm, presumably within membranes of endocytosed vesicles. Snail lectin was an exception, since its distribution remained homogeneous also in conditions of starvation.
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PMID:Lectins in the unicellular Tetrahymena. II. Impact of nutrition and sugar treatment on anti-lectin binding. 642 Oct 65

Dictyostelium discoideum MC2 is a temperature-sensitive motility mutant of AX3. Mutant cells are incapable of growth, phagocytosis, and migration under restrictive conditions (Kayman et al., J. Cell Biol. 92:705-711, 1982). We show here that at the restrictive temperature MC2 cells grown axenically or on bacteria synthesized excessive quantities of the lectin discoidin I. By two-dimensional gel electrophoresis and peptide mapping, the proteins overproduced by MC2 cells were indistinguishable from discoidin I synthesized at lower levels in AX3 cells. At least two of the three species of discoidin I were overproduced. This protein family constituted 9% of the total protein in cells that were incubated overnight at 27 degrees C in axenic medium. Although MC2 cells are defective in nutrient uptake under restrictive conditions, the overproduction of discoidin I did not appear to be part of a pleiotropic response to starvation. We propose that transcription of the coordinately regulated discoidin I genes is altered in mutant cells. This alteration may be related to the motility defects manifested by MC2.
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PMID:Overproduction of discoidin I by a temperature-sensitive motility mutant of Dictyostelium discoideum. 673 29


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