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

Starved cells of Candida utilis accumulated Zn2+ by two different processes. The first was a rapid, energy- and temperature-independent system that probably represented binding to the cell surface. The cells also possessed an energy-, pH-, and temperature-dependent system that was capable of accumulating much greater quantities of the cation than the binding process. The energy-dependent system was inhibited by KCN, Na2HAsO4, m-chlorophenyl carbonylcyanide hydrazone, N-ethylmaleimide, EDTA and diethylenetriaminepenta-acetic acid. The system was specific inasmuch as Ca2+, Cr3+, Mn2+, Co2+ or Cu2+ did not compete with, inhibit, or enhance the process, Zn2+ uptake was inhibited by Cd2+. The system exhibited saturation kinetics with a half-saturation value of 1.3 muM and a maximum rate of 0.21 (nmol Zn2+) min(-1) (mg dry wt(-1)) at 30 degrees C. Zn2+ uptake required intact membranes since only the binding process was observed in the presence of nystatin, toluene, or sodium dodecyl sulphate. Cells did not exchange recently accumulated toluene, or sodium dodecyl sulphate. Cells did not exchange recently accumulated 65Zn following the addition of a large excess of non-radioactive Zn2+. Similarly, cells pre-loaded with 65Zn did not lose the cation during starvation, and efflux did not occur when glucose and exogenous Zn2+ were supplied after the starvation period. Efflux was only observed after the addition of toluene or nystatin, or when cells were heated to 100 degrees C. Cells fed a large quantity of Zn2+ contained a protein fraction resembling animal cell metallothionein. In batch culture, cells of C. utilis accumulated Zn2+ only during the lag phase and the latter half of the exponential-growth phase.
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PMID:Accumulation and storage of Zn2+ by Candida utilis. 0 25

Structural heterogeneity has been demonstrated for growth hormone (GH) receptors from a number of species, and both high and low affinity art receptors have been characterised by ligand binding studies. In the present study, we have transfected Chinese hamster ovary (CHO-K1) cells with a cDNA clone encoding a full-length transmembrane ovine (o) GH receptor, under the regulatory control of the human metallothionein IIA promoter. A stably transfected cell line was established (GHR9.5) which expresses on the cell surface a single class of receptor which binds 220,000 [125I]oGH molecules at high affinity (Kd = 0.30 nM) which is comparable to the affinity established for endogenous oGH receptors in postnatal sheep liver microsomes (Kd = 0.27 nM, Freemark et al. (1987) Endocrinology 120, 1865-1872). The expressed receptor also binds ovine placental lactogen (oPL, 205,000 binding sites per cell) with high affinity (Kd = 0.76 nM). The presence of two species of oGH receptor was detected in GHR9.5 cells using affinity cross-linking analysis (M(r) 148,000 and M(r) 73,000) and given that the oGH receptor cDNA codes for a non-glycosylated receptor of M(r) 69,914, it is likely that these cross-linked species correspond to homodimeric and monomeric forms of the oGH receptor, each binding to a single molecule of GH. Parallel cross-linking studies with sheep liver microsomes also demonstrated two oGH receptor species (M(r) 133,000 and M(r) 58,000), the difference in relative molecular weights between the transfected and endogenous receptors presumably resulting from tissue-specific post-translational modifications. In the presence of oGH, the GHR9.5 cells respond by increasing total cellular protein synthesis by 27% relative to non-GH-exposed GHR9.5 cells, indicating the functionality of the expressed receptor. We also demonstrate unequivocally that oPL, through a specific interaction with the transfected oGH receptor, is able to mediate a similar cellular response (38% protein synthesis induction). Responsiveness to oGH and oPL in the GHR9.5 cells is dependent on serum starvation prior to oGH exposure and occurs only with prolonged exposure (greater than 2 h) to oGH. This cellular stimulation occurs independently of c-fos transcription which has previously been shown to be one of the earliest events associated with GH action in tissues expressing endogenous GH receptors (Doglio et al. (1989) Proc. Natl. Acad. Sci. USA 86, 1148-1152; Slootweg et al. (1990) J. Mol. Endocrinol. 4, 265-274).
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PMID:Functional expression of an ovine growth hormone receptor in transfected Chinese hamster ovary cells. 151 79

Simultaneous treatment of rats with ethanol (EtOH) and methylmercury (MeHg) increases the frequency of lesions in the rat kidney. Therefore, it was of interest to us to study the effects of simultaneous treatment of rats with MeHg and EtOH on kidney metallothionein (MT) and mercury residues levels in kidneys of rats maintained on 70% of ad libitum diet. Treatment with MeHg alone induced kidney MT the most (twice) compared to its pair-fed control. Simultaneous treatment with MeHg and EtOH also induced kidney MT but to a lesser degree than treatment with MeHg alone (by about 30%). Ethanol by itself caused a slight increase in kidney MT although starvation resulting from pair-feeding with mercury-treated animals may have contributed to this observation. Simultaneous treatment with MeHg and 2 g/kg EtOH caused a significant reduction in inorganic mercury levels in the kidney (P less than 0.05) compared to treatment with MeHg alone or in combination with 1 g/kg EtOH. Corresponding with the decrease in kidney inorganic mercury levels was a significant increase in urine inorganic mercury levels in this group compared to treatment with 1 g/kg ethanol + MeHg.
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PMID:Combined effects of methylmercury and ethanol on renal metallothionein and mercury residues in rats fed restricted amounts of a liquid diet. 200 70

Wild-type Neurospora crassa, strain Singapore, was transformed with a N. crassa metallothionein promoter/protyrosinase fusion gene. Transformants produced tyrosinase during vegetative growth, as determined by Western analyses and activity assays. This is in sharp contrast to wild-type strains, where this enzyme is only expressed in situations of starvation or sexual differentiation. Complete integration of a 400 bp metallothionein promoter-fragment leads to constitutive expression of protyrosinase, whereas a 3.6 kb promoter-fragment conferred copper inducibility on the reporter gene in four transformants. A transformant with high constitutive tyrosinase levels was able to produce melanin on complete medium agar plates supplemented with 1 mg/ml L-tyrosine.
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PMID:Expression of tyrosinase in vegetative cultures of Neurospora crassa transformed with a metallothionein promoter/protyrosinase fusion gene. 214 80

Stress and starvation increased liver metallothionein (MT) and decreased liver glutathione (GSH) levels. Serum cysteine plus cystine levels were increased by stress. The exogenous administration of GSH, while not modifying hepatic GSH content, increased liver MT levels in basal and starved rats but not in stressed rats. Liver and serum cysteine levels were increased by GSH administration, a process partially reverted by the irreversible inhibitor of gamma-glutamyl transpeptidase, alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid. Mouse and rat liver MT levels were also increased by buthionine sulfoximine, an inhibitor of GSH synthesis, indicating that GSH is not a necessary precursor of MT. In addition, the hepatic MT content was increased by the administration of cysteine in a dose-response manner. These results suggest that hepatic MT synthesis is elevated by increased cysteine pools, and that MT, GSH and cysteine levels are somehow inter-related. MT, besides GSH, may be contemplated as a putative intracellular reservoir of cysteine in the liver of adult rats.
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PMID:On the metallothionein, glutathione and cysteine relationship in rat liver. 224 42

To date, stress has been reported to induce metallothionein (MT) synthesis in the liver only. In the present experiment, the effects of food and water deprivation alone or of immobilization stress plus food and water deprivation on liver, brain, and heart MT have been studied in adult male rats. Liver and brain MT levels were increased by immobilization stress as soon as 6 h after the onset of stress. Eighteen hours of immobilization, which is accompanied by food and water deprivation, further increased liver and brain MT levels and significantly increased heart MT content. A specific effect of immobilization was evident in all three tissues, because the effect of food and water deprivation alone was significantly lower than that of immobilization plus starvation. Changes in MT apparently were not related to changes in cytosolic Zn.
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PMID:Liver, brain, and heart metallothionein induction by stress. 237 May 51

The present experiment was designed to examine the influence of pregnancy on basal and stress levels of serum and liver metallothionein (MT). Eighteen-day pregnant rats showed higher serum MT levels and lower liver MT levels than nulliparous rats, suggesting that a great MT mobilization from the liver into the serum was present in the former rats. Serum MT levels were not changed by either restraint or starvation. It is unlikely that the lower liver MT levels showed by pregnant rats were due to competition by progesterone for glucocorticoid receptors, as previously suggested, since the corticosterone/progesterone ratio was unchanged in pregnant rats. Liver MT response to food and water deprivation with or without restraint was somewhat different in nulliparous and pregnant rats. Thus, food and water deprivation for 24 h caused higher liver MT induction in pregnant than in nulliparous rats. When food and water deprivation was accompanied by restraint stress a further increase in liver MT was observed in nulliparous but not in pregnant rats. This suggests that food and water deprivation may be a more severe stress in pregnant rats because of the additional demands of the growing fetuses. Fetal liver MT was increased by restraint stress but not by food and water deprivation. The role of Zn influx into the liver is discussed.
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PMID:Differences between pregnant and nulliparous rats in basal and stress levels of metallothionein. 337 Feb 60

The effects of starvation and refeeding of 2-wk-old turkey poults on serum and tissue levels of zinc, copper and iron were investigated. Serum concentrations of zinc and copper declined during 4 d of starvation. Refeeding for 24 h following a period of starvation restored serum copper to levels similar to those in the fed controls but failed to elevate zinc levels. Liver concentrations and total quantities of zinc, copper and iron increased throughout starvation. Refeeding the starved poults reduced hepatic metal concentrations but caused a further increase in total metal content. This was apparently related to the large increase in liver mass, and the effect was most pronounced in poults starved 1 d prior to refeeding. Starvation also caused an increased zinc concentration and content and a reduced copper content in the pancreas, duodenal mucosa and kidney. Iron content of the pancreas and kidney increased during starvation, but that of the duodenal mucosa declined. Starvation evoked a progressive increase in the cytosolic zinc concentration from liver, pancreas, duodenal mucosa and kidney. A major part of this increase was accounted for as zinc bound to metallothionein (MT). Refeeding rapidly reduced cytosolic and MT-bound zinc in each of these tissues. It was concluded that starvation and refeeding had major effects on tissue trace metal status. A function is proposed for MT during starvation as a mechanism for the conservation of body zinc stores. Zinc, released as a consequence of tissue catabolism, is repartitioned into a soluble storage site (MT), which can be rapidly mobilized to meet the demands of new tissue synthesis once anabolic metabolism resumes.
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PMID:Effects of starvation and refeeding on tissue zinc, copper and iron in turkey poults. 357 61

Parenchymal and non-parenchymal cells were isolated from the livers of control, starved, Zn2+-injected and Cd2+-injected rats. Parenchymal cells were prepared by differential centrifugation after perfusion of the liver with collagenase. Non-parenchymal cells were separated from parenchymal cells by unit-gravity sedimentation and differential centrifugation. Yields of 2 x 10(8) non-parenchymal cells with greater than 95% viability and less than 0.2% contamination with parenchymal cells were obtained without exposing cells to Pronase. Metallothioneins-I and -II were identified in parenchymal cells and non-parenchymal cells from Zn2+-treated rats. The metallothionein contents of parenchymal cells, non-parenchymal cells and intact liver were quantified by a competitive 203Hg-binding assay. Administration of heavy-metal salts significantly increased the metallothionein content of both cell populations, although the concentration of the protein was approx. 2.5-fold greater in parenchymal cells than in non-parenchymal cells. Overnight starvation increased the metallothionein content of parenchymal cells without altering that of non-parenchymal cells. The potential significance of this differential response by different liver cell types with regard to the influence of Zn2+ on stress-mediated alterations in hepatic metabolism is discussed.
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PMID:Identification of metallothionein in parenchymal and non-parenchymal liver cells of the adult rat. 711 46

A novel rice genomic sequence encoding coding segments homologous to other metallothionein-like genes was isolated from Oryza sativa genomic library. This sequence, hereby designated as rgMT (rice genomic metallothionein-like gene), consists of two exons and one intron. From the coding sequence, it is predicted that rgMT encodes one protein of 74 amino acids. Differential expression of rgMT in rice plants was observed as mature transcripts were more abundant in roots than in leaves and sheaths. Under different stress conditions, such as excess heavy metals and heat shock, expression of rgMT was significantly elevated. This was especially noticeable with 250 microM CuCl2 for 16 h, 40 degrees C heat for 2 h and 0.06% DMSO for 1 h. Under sucrose starvation, rgMT transcripts also increased with time up to 72 h. During recovery from sucrose starvation, the transcripts declined slightly within 12 h of recovery. rgMT transcripts were also seen to have increased expression in senescent leaves. These results support the notion that rgMT is a stress-inducible gene in rice heretofore unreported.
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PMID:A novel stress-inducible metallothionein-like gene from rice. 763 10


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