Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of starvation on the cell morphology of Dictyostelium discoideum were studied with different cytochemical techniques, and with a morphometric method by which the surface areas of the cell membrane and of the digestive system can be determined. During the first 2 h, the cell membrane becomes very wrinkled and many phagocytic cups and filopods are formed. These changes are in accord with the 40 percent increase in the cell surface area to cytoplasmic volume ratio observed, which is mainly due to a strong decrease in the cytoplasmic volume. At this time of starvation, cells are able to ingest twice as many yeast as during growth. Afterwards, while the phagocytic ability decreases, the phagocytic cups disappear, and all the cells become bristled with many thin filopods. In spite of these morphological changes, no quantitative or topological differences have been observed concerning the polysaccharide content of the plasma membrane, whether it was stained with phosphotungstic acid, silver proteinate, or ruthenium red. During this time, the digestive vacuoles imbricate one into the other. Part of the vacuoles are degraded by this process, thus leading to an atrophy of the digestive apparatus. The digestive apparatus is progressively replaced by an autophagic system. Polysaccharide stainings and morphological observations show that the cytosegresomes seem to originate from the food vacuoles which flatten and sequester portions of cytoplasm. After 5 h of starvation, the digestive system is entirely transformed into an autophagic apparatus. The cell population appears to be homogeneous with respect to these changes. Therefore, potential precursors of prestalk and prespore cells were not observed.
 ...
PMID:Changes of the cell surface and of the digestive apparatus of Dictyostelium discoideum during the staruation period triggering aggregation. 14 40

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.
 ...
PMID:Ciliary polypeptides and glycoconjugates of wild-type and mutant Tetrahymena thermophila: starved versus nonstarved. 139 38

As Tetrahymena thermophila cells differentiate from their vegetative life cycle to sexual reproduction, their polypeptide pattern undergoes a series of changes. These changes have been traced in extracellular, cellular, and subcellular compartments. The first alteration is induced by the nutritional shift-down and results in stimulation of at least one ciliary polypeptide and affects a series of polypeptides from other compartments. The second alteration is induced by mixing starved cells of complementary mating types and this stimulates the synthesis of nine ciliary polypeptides before pairs have formed and eight afterwards. At least five of these early and one of the late conjugation-related ciliary polypeptides are removed by low concentrations of EDTA, indicating that they are located on the external side of the plasma membrane. No differences were observed between polypeptides excreted during starvation and after mixing of complementary mating types. At Tris concentrations restrictive for conjugation, cilia lack the conjugation-related polypeptides. Some of these are instead found among the excreted polypeptides. Using O'Farrell gels and silver staining on isogenic cells of all possible mating types, we have been unable to correlate changes in polypeptide patterns to specific mating types.
 ...
PMID:Polypeptides during early conjugation in Tetrahymena thermophila. 395 87

After long term starvation, the crayfish, Procambarus clarki was administered protein silver, iron lactate and olive oil, and its hepatopancreas was subsequently examined by electron microscopy. The reserve cells showed changes suggesting the absorption of these materials from the acinar lumen had taken place. In contrast, the hindgut of crayfish seemed to have no absorptive ability. In crustaceans the hepatopancreas is the largest gland in the body. The chief functions of this gland are the secretion of digestive juice into the stomach and absorption of digested food. It is also where materials which are necessary for hardening of animals that have undergone ecdysis are stored. Although these roles are commonly accepted, the absorptive ability of the gland has been rarely studied. Yonge (1924) and van Weel (1955) attempted to obtain evidence for the absorptive function of hepatopancreas cells of Nephrops norvegicus and Atya spinides using iron lactate and iron saccharate, and obtained some positive results. They used the histochemical Prussian blue test to demonstrate absorbed iron. Vonk (1960) referred to the results of a few authors who had tried to show fat deposits in reserve cells of the hepatopancreas after the administration of olive oil to the animals. But because starvation did not affect the quantity of stored fat in the hepatopancreas cells, the attempt failed to reveal the absorption of fat by the hepatopancreas. In the present paper, the authors describe the results of studies on the absorption of experimentally administered materials by hepatopancreas cells of the crayfish, Procambarus clarki, using electron microscopy.
 ...
PMID:Absorption of experimentally administered materials by the hepatopancreas cells of the crayfish, Procambarus clarki. 650 62

As was shown using various reagents (Ag+, Cd2+) and solvents (ethanol, methanol), Thiobacillus ferrooxidans cells accumulate colloidal sulfur when they grow in the medium 9K containing elemental sulfur. Colloidal sulfur is accumulated in the periplasmic space, in large, bipolarly arranged spherical structures and in simple invaginates of the cytoplasmic membrane. T. ferrooxidans cells accumulate the sulfur at a highest rate during the stationary phase of growth and can use it as a source of energy under the conditions of starvation. The factors causing sulfur accumulation in T. ferrooxidans cells are discussed.
 ...
PMID:[Nature of the sulfur-containing component and its function in Thiobacillus ferrooxidans]. 664 91

The Escherichia coli DnaK homologue in Vibrio sp. strain S14 was shown to possess chaperone function for translocation during carbon starvation. This was demonstrated by using the method of co-immunoprecipitation. DnaK co-precipitated with the carbon starvation-specific periplasmic space protein Csp5 three hours after the onset of carbon starvation. Pulse-chasing of the protein with radiolabelled methionine followed by the addition of an excess of unlabelled methionine demonstrated that the Csp5 protein was translocated across the inner membrane. Only the cytoplasmic unprocessed precursor form of Csp5 co-precipitated with DnaK. The non-covalent binding between the two proteins was found to be ATP-dependent, as the addition of ATP released the interaction between DnaK and the precursor form of Csp5, as was shown on silver-stained SDS-polyacrylamide gels and by Western blot analysis. We suggest that DnaK maintains the carbon starvation-inducible protein Csp5 in a translocation-competent form in the cytoplasm.
 ...
PMID:The DnaK homologue of the marine Vibrio sp. strain S14 binds to the unprocessed form of a carbon starvation-specific periplasmic protein. 791 11

A simple one-step method employing potassium persulphate as an oxidising agent in presence of catalyst, Ag2+, for the oxidation of beta-hydroxybutyrate (beta-OHB) to acetoacetate (AcAc) has been developed and standardized. Under the condition of assay, beta-OHB (0.079-0.395 microM) was quantitatively transformed to AcAc. The reaction linearity was observed from 0.079 to 0.634 microM. Optimum conditions were: pH, 6.2; temp., 40 degrees C; persulphate saturation, 40% and catalyst, 1.82 mM. Under the experimental condition, no reversal of inhibition caused by chloride (22.96 mM) was observed at Ag+ concentrations (9.09 and 18.18 mM), while higher conc. of Ag+ (27.27 mM) caused significant reversal of inhibition (about 60%). The maximum reversal of inhibition was achieved at Ag+ (36.36 mM). The level of ketone bodies, when estimated by the present method, was greatly enhanced during starvation period and about 2- and 12-fold higher level of ketone bodies was observed (compared to control) in rats fasted for 24 and 48 hr respectively.
 ...
PMID:A simple chemical method for the oxidation of beta-hydroxybutyrate; application of the method for the estimation of ketone bodies. 850 27

A specific and sensitive homologous radioimmunoassay for eel (Anguilla anguilla L.) growth hormone (angGH) has been developed. The antiserum, raised against purified angGH and used at 1:20,000 final dilution, did not cross-react with eel prolactin or thyrotropin, carp gonadotropin II, bovine GH, or serum from hypophysectornized eel. The inhibition curves for eel pituitary extracts and serum were parallel to that of angGH standard. The ED50 value was between 1 and 2 ng/tube and the recovery of purified angGH added to the serum was about 100%. In immunocytochemical studies, the antiserum, used at 1:1000 dilution, specifically labeled the somatotrophs in the pituitaries of the glass, yellow, and silver eels. The GH contents were determined in the pituitaries of glass, yellow, and silver eels and in the serum at the yellow and silver stages. GH variations during the transformation of the yellow to silver eel were examined. The results indicated a decrease in GH production between the yellow and the silver eels, possibly related to the cessation of growth at the silver stage. In contrast to the situation in the naturally fasting silver eel, submitting yellow eels to 3 months of starvation (experimental fasting) greatly increased GH production. This suggests a variation in the regulation of GH according to the type of fasting (natural or experimental) and/or the stage of the fish (yellow or silver).
 ...
PMID:Development of a radioimmunoassay for European eel growth hormone and application to the study of silvering and experimental fasting. 880 66

Candida albicans is a dimorphic fungus that can grow either as yeast or as mycelia. The mycelial form may be required for tissue penetration and therefore may have a role in pathogenesis. The protein profiles of the cell-free S100 fraction from budding yeast cells and germ tube-forming cells (an early stage of the transition between yeast and mycelia) were evaluated using two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). Yeast growth or germ tube formation was induced in carbon-starved cells at 37 degrees C by either glucose, galactose or N-acetylglucosamine at pH 4.5 or pH 6.7. More than 400 constitutively synthesised polypeptides were identified on 2-D PAGE by silver staining. A few polypeptides which seem to reflect the release from carbon starvation were detected, but no polypeptides unique to either morphology were observed. Fractionation of S100 preparations by polyethylenimine or heparin-agarose affinity chromatography, which have been used to detect DNA-binding proteins, revealed several proteins that were synthesised on the resumption of cell growth or in response to pH difference. Heparin-agarose also bound novel polypeptides in the size range 130-200 kDa that were preferentially synthesised in germ tube-forming cells. These results suggest that any protein factors that might exert a regulatory role early in germ tube formation are of low abundance, and that a minor group of soluble proteins involved in C. albicans morphogenesis may be differentially synthesised.
 ...
PMID:Differential profiles of soluble proteins during the initiation of morphogenesis in Candida albicans. 882 49

The marine oligotrophic ultramicrobacterium Sphingomonas alaskensis RB2256 has a physiology that is distinctly different from that of typical copiotrophic marine bacteria, such as Vibrio angustum S14. This includes a high level of inherent stress resistance and the absence of starvation-induced stress resistance to hydrogen peroxide. In addition to periods of starvation in the ocean, slow, nutrient-limited growth is likely to be encountered by oligotrophic bacteria for substantial periods of time. In this study we examined the effects of growth rate on the resistance of S. alaskensis RB2256 to hydrogen peroxide under carbon or nitrogen limitation conditions in nutrient-limited chemostats. Glucose-limited cultures of S. alaskensis RB2256 at a specific growth rate of 0.02 to 0.13 h(-1) exhibited 10,000-fold-greater viability following 60 min of exposure to 25 mM hydrogen peroxide than cells growing at a rate of 0.14 h(-1) or higher. Growth rate control of stress resistance was found to be specific to carbon and energy limitation in this organism. In contrast, V. angustum S14 did not exhibit growth rate-dependent stress resistance. The dramatic switch in stress resistance that was observed under carbon and energy limitation conditions has not been described previously in bacteria and thus may be a characteristic of the oligotrophic ultramicrobacterium. Catalase activity varied marginally and did not correlate with the growth rate, indicating that hydrogen peroxide breakdown was not the primary mechanism of resistance. More than 1,000 spots were resolved on silver-stained protein gels for cultures growing at rates of 0.026, 0.076, and 0.18 h(-1). Twelve protein spots had intensities that varied by more than twofold between growth rates and hence are likely to be important for growth rate-dependent stress resistance. These studies demonstrated the crucial role that nutrient limitation plays in the physiology of S. alaskensis RB2256, especially under oxidative stress conditions.
 ...
PMID:Specific growth rate plays a critical role in hydrogen peroxide resistance of the marine oligotrophic ultramicrobacterium sphingomonas alaskensis strain RB2256. 1122 24


1 2 3 4 Next >>