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

Radioiron uptake by erythrocytes, metabolic rate, erythropoietin formation during hypoxia and erythroid responsiveness to exogenous erythropoietin were determined in both starved and water deprived rats. The feed intake showed a marked and progressive reduction during water deprivation. The metabolic rates of rats deprived of either food of water declined progressively showing a 40% reduction 5d after water deprivation or starvation began. At this time, the 24 h red blood cells 59Fe incorporation was 85% lower in both starved and dehydrated rats than in normal rats. Plasma erythropoietin levels in response to hypoxia were approximately 50% decreased in both starved and dehydrated rats. Both polycythaemic starved and polycythaemic water deprived rats injected with human urinary erythropoietin showed a 75% decrease in 59Fe incorporation into erythrocytes when compared to control rats. It is suggested that depression of erythropoiesis during water deprivation in the rat depends on a reduced sensitivity to erythropoietin, possibly associated with decreased production of the hormone. Since water deprived rats drastically reduce feed intake it is suggested that secondary starvation is the principal cause of the decreased erythropoiesis induced in the rat by water deprivation.
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PMID:Mechanism of the decreased erythropoiesis in the water deprived rat. 46 63

Fasting in normal or erythropoietin treated mice results in parallel decrease of erythropoietic activity in spleen and bone marrow. In testosterone-treated animals, starvation only decreases the splenic fraction while the bone marrow erythropoiesis shows a marked increase above normal values.
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PMID:Effects of testosterone on splenic and bone marrow erythropoiesis of fasted mice. 69 5

Erythropoietic responses of fed and starved species of teleosts, viz., Clarias batrachus and Heteropneustes fossilis, to human urinary erythropoietin and thyroxine have been examined. The effects of these hormones on energy reserves have also been evaluated. Twenty-four C. batrachus were divided into two groups: half were fed regularly; the remaining fish were starved 20 days. On the 21st day each group was further divided into three subgroups of four each and received either saline, thyroxine (8 micrograms), or erythropoietin (6 IU) over 4 consecutive days. The experimental protocol was identical for H. fossilis; however, for H. fossilis two identical studies were conducted approximately 1 year apart. A decline in the rate of erythropoiesis and a stimulatory response to human urinary erythropoietin followed starvation in both species of teleosts. In addition, erythropoietin had a pronounced effect on hepatic glycogenesis of fed H. fossilis and stimulated erythropoiesis in the fed teleosts of both species. Prolonged starvation drastically depleted hepatic glycogen in C. batrachus. In contrast, it had no effect on hepatic glycogen in H. fossilis and on muscle glycogen and protein in both species. In general, while both species could respond to erythropoietin and withstand prolonged starvation, H. fossilis alone exhibited remarkable tolerance to fasting.
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PMID:Influence of human urinary erythropoietin and L-thyroxine on blood morphology and energy reserves in two tropical species of fed and starved teleosts. 258 68

The established relationship between erythropoietic activity and body growth rate in the polycythemic growing rat could be the result of either an erythropoietin (EPO)-dependent or an EPO-independent operating mechanism. The present study was thus undertaken to elucidate the nature of the aforementioned mechanism by assessing the ratio between plasma immunoreactive EPO (iEPO) concentration and erythropoietic activity in young hypertransfused rats for different body growth rates. Red blood cell (RBC)-59Fe uptake was about 75% in 21-day-old rats; it rapidly decreased with time when the animals were placed on a protein-free diet, approaching a level of about 1% by the 10th day of protein starvation. Over the same period plasma iEPO decreased from 55 mU/ml to 7 mU/ml. Body growth rate was 0. Following this "protein depletion period" the rats received diets containing different amounts of casein ("protein repletion period") added isocalorically to the protein-free diet to elicit a rise in body growth rate. Statistically significant relationships (p less than 0.001) were found between dietary casein concentration and body growth rate (r = 0.991), dietary casein concentration and RBC-59Fe uptake (r = 0.991), dietary casein concentration and plasma iEPO level (r = 0.992), body growth rate and RBC-59Fe (r = 0.986), and body growth rate and plasma iEPO level (r = 0.994) in hypertransfused polycythemic rats during the protein repletion period. These findings suggest that the correlation between erythropoietic activity and growth rate in the growing rat is the result of an erythropoietin-dependent operating mechanism, which appears to be independent of the ratio tissue oxygen supply/tissue oxygen demand.
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PMID:Correlation between erythropoietic activity and body growth rate in hypertransfused polycythemic growing rats as the result of an erythropoietin-dependent operating mechanism. 291 44

Starved animals having low levels of erythropoietin in blood showed increased MDA, fluorescent pigments, and met-Hb values whereas the hemoglobin concentration decreased significantly on starvation. In vivo and in vitro studies with Ep reversed the effects of starvation and brought these values close to normal. The activities of the enzymes (SOD, catalase, GSH-PX, GR G6PD, and 6PGD) which protect the RBC membrane directly or indirectly from peroxidative threat, decreased on starvation and restored to normal levels after Ep treatment.
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PMID:Effect of erythropoietin on membrane lipid peroxidation, superoxide dismutase, catalase, and glutathione peroxidase of rat RBC. 321 32

Liver delta-aminolevulinic acid synthetase activity was measured in mice living under abnormal atmospheric pressure conditions for 15 h. In the group living under low atmospheric pressure (51 kPa) the enzymic activity, either basal or induced by starvation and/or allylisopropylacetamide, was significantly (p less than 0.001) lower than that of the control group. In the group living under high atmospheric pressure (153 kPa) the enzymic activity was significantly (p less than 0.001) higher than the one of the controls. Our results might possibly be explained by changes in the cellular redox state, the heme oxygenase activity or the serum erythropoietin levels.
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PMID:Effect of abnormal atmospheric pressure conditions upon mouse liver delta-aminolevulinic acid synthetase activity. 408 57

The erythropoietic response of snakes was examined after injecting human urinary erythropoietin (Ep), testosterone propionate (TP), and L-thyroxine (T4), separately and in combinations, into starved ophids. The effect of starvation was reflected by a decrease in the number of erythrocytes, a fall in hemoglobin concentration, and a decline in hematocrit. Statistically significant elevation of erythrocyte number, hemoglobin concentration, and hematocrit was observed at 24 hr following the administration of Ep + T4, and Ep + TP + T4 into starved ophids. The erythrocyte number was also increased by T4 treatment at 24 hr. Furthermore, while T4 and Ep individually increased the red blood cell number at 168 hr, T4, TP + T4, and Ep + TP + T4 elevated the hemoglobin concentration and Ep + T4 and Ep + TP + T4 increased the hematocrit value. It is suggested that the influence of any one of the hormones utilized in the present study on blood morphology of fasted snakes depends to a greater extent on the presence or absence of the other hormone(s).
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PMID:Erythropoietin, testosterone, and thyroxine in the erythropoietic response of the snake, Xenochrophis piscator. 671 57

With erythroid differentiation, committed progenitor cells acquire the ability to respond to erythropoietin (Epo). Epo interacts with target cells through the Epo receptor (Epo-R), whose expression is tightly regulated in a lineage-specific fashion. Epo-R expression is presumed to be progressively activated or repressed as cells progress along the erythroid or the myeloid pathway, respectively. Little is known of the mechanisms that underlie the erythroid-specific expression of the Epo-R gene. GATA-1, the major known transcription factor involved in Epo-R gene regulation, is not erythroid-specific. We have studied the regulation of the expression of the Epo-R gene in two related human Epo-responsive cell lines, UT-7 and UT-7 Epo. These lines express Epo-R at high levels because of amplification of the endogenous gene, which is apparently not rearranged. Treatment for 6 to 24 hours with the tumor promoter, phorbol myristate acetate (PMA), or 24 hours of growth factor starvation (Epo or granulocyte/macrophage colony-stimulating factor [GM-CSF]) decreased or increased the levels of Epo-R mRNA, respectively. In the case of growth factor starvation, the increase (approximately equal to threefold) in the level of Epo-R mRNA correlated directly with an increase in the rate of Epo-R gene transcription as measured by run-off assay. Both increases were observed as early as 3 hours after the growth factor was withdrawn and were reversible; levels of mRNA and transcription rates returned to baseline 3 hours after the cells were reexposed to growth factors. The changes in Epo-R expression after growth factor starvation were coordinated with changes in the level of expression of GATA-1 that were detected both at the mRNA and at the gene transcription level under these conditions (suggesting that GATA-1 was responsible for this upregulation). During PMA treatment, after a transient increase in Epo-R mRNA at 1 hour, a progressive decline in the level of Epo-R mRNA was observed; the level of Epo-R mRNA decreased by 50%, and fell below the level of detection by 6 and 24 hours, respectively. This decrement was explained in part by a fourfold reduction in the rate of gene transcription as well as a reduction (measured as levels of Epo-R mRNA in the presence of actinomycin D) in mRNA stability. The changes in transcription rate occurred in the absence of changes in the level of GATA-1 binding activity.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Transcriptional and posttranscriptional regulation of the expression of the erythropoietin receptor gene in human erythropoietin-responsive cell lines. 826 Jul 13

The present study was performed to determine the stage of the erythropoietic pathway which is affected by starvation or protein deprivation and whose manifestation is a depressed response to exogenous erythropoietin (EPO). The response to recombinant human EPO was measured in post-hypoxic polycythemic mice by determination of 59Fe uptake into red cells, spleen and femur and/or erythroid colony forming units (CFU-E) and erythroid precursor cell concentrations in femoral marrow. Experimental mice were either starved or fed one of seven different diets whose protein (casein) content ranged from 0 to 20%. All diets were isocaloric. The response of mice maintained on the standard diet (Purina Lab chow) was taken as the normal one. Starvation during the 48-hour period immediately before EPO injection had no effect on the response to the hormone. Starvation, and protein deprivation to a lesser extent, during the 48-hour period following EPO, on the other hand, significantly reduced the response. There was a progressive increase in the response as the casein content of the diet was increased. A normal response was observed when dietary casein concentration was 10%. These findings indicate that nutritional deprivation or dietary protein alterations during the period immediately following EPO injection in polycythemic mice can have detrimental effects on the erythroid response in a model in which nutritional deprivation was relatively short and acute. They also indicate that the subnormal response is not due to a decreased size of the erythroid progenitor pool available for differentiation but to deficient rates of differentiation of erythropoietic units.
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PMID:Impaired response of polycythemic mice to erythropoietin induced by protein starvation imposed after hormone administration. 840 Dec 52

We have investigated the expression of transferrin receptor (TfR) iron regulatory protein-1 (IRP-1) and iron regulatory protein-2 (IRP-2) in liquid suspension culture of purified hematopoietic progenitor cells (HPCs) induced by a growth factor stimulus to proliferation and unilineage differentiation/maturation through the erythroid, granulocytic, monocytic and megakaryocytic lineages. In initial HPC differentiation, TfR expression is induced in both erythroid and granulopoietic cultures. In late HPC differentiation (i.e. starting from day 5 of culture) and then differentiated precursor maturation, the TfR gene is highly expressed in the erythroid lineage, whereas it is sharply downmodulated in the granulopoietic, monocytopoietic and megakaryocytic series. The elevated TfR expression in erythroid cells is: (a) mediated through a high rate of TfR gene transcription; (b) modulated by intracellular iron levels; (c) mediated by TfR mRNA stabilization through the iron regulatory protein (IRP), in that IRP-1 activity is high in erythroid lineage as compared to the levels observed in other hemopoietic lineages; and (d) dependent on exogenous erythropoietin (Epo) (this is indicated by the marked TfR and IRP-1/IRP-2 downmodulation after Epo starvation). Interestingly, analysis of IRP-1 and IRP-2 expression during hemopoietic differentiation showed that: (a) IRP-1 expression was maintained during all steps of erythroid differentiation, while it was lost in the other hemopoietic lineages; (b) IRP-2 expression was observed during all stages of hemopoietic differentiation in all four lineages. However, IRP-1 and IRP-2 expression and activity are induced when monocytes, which express only low levels of IRP-1 and IRP-2, are induced to maturation to macrophages. These studies indicate that: (a) in normal erythropoiesis, the hyperexpression of TfR, starting from early erythroid HPC differentiation, is Epo-dependent and mediated via transcriptional and post-transcriptional mechanisms; (b) in the granulopoietic, monocytopoietic and megakaryocytic pathways, the TfR is first induced and then downmodulated (the latter phenomenon is mediated via transcriptional suppression of the TfR gene and IRP inactivation).
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PMID:Mechanisms of differential transferrin receptor expression in normal hematopoiesis. 1108 86


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