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

1. The rates of oxygen consumption were measured in 6-8-day-old rabbits at 34 and 15 degrees C after varying periods of starvation and cold exposure. At the start of the experiment the rabbits had been fasted for 24 hr. Eight rabbits were studied immediately, six after 24 and six after 48 hr in a cold environment (20 degrees C), and twelve after a further 48 hr in a warm environment (34 degrees C). All the animals had a similar increase in oxygen consumption during the final hour of cold exposure (15 degrees C).2. The rabbits kept at 20 degrees C lost 83% of the fat stored in their brown adipose tissue within 24 hr and a further 11% in the next 24 hr. The fat content of white adipose tissue had fallen by 75% at 48 hr. In contrast rabbits kept unfed at 34 degrees C had lost 47% of the fat in brown adipose tissue and 44% of the fat in white adipose tissue after 48 hr.3. In six rabbits subcutaneous thermocouples demonstrated that local heat production continued in brown adipose tissue after 48 hr cold exposure.4. In the rabbits kept at 34 degrees C the final cold exposure caused a large increase in the serum free fatty acid and glycerol concentrations. Much lower concentrations were found in rabbits kept at 20 degrees C.5. The results show that the fat stored in the brown adipose tissue of young rabbits exposed to cold is preferentially used for heat production. When this store of fat is exhausted, brown adipose tissue still produces heat presumably by oxidizing fat and glucose taken from the circulation.
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PMID:Fat metabolism and heat production in young rabbits. 534 20

Two carbamyl phosphate synthetases, the first an arginine-synthetic enzyme (CPS(arg)) and the second a pyrimidine-synthetic enzyme (CPS(pyr)), are shown to be present in Neurospora. The two enzymes can be separated on the basis of size and are distinguished by several different properties. Both CPS(pyr) and CPS(arg) have substrate requirements of adenosine triphosphate, HCO(3) (-), and l-glutamine, although NH(4) (+) in high concentration will partially replace glutamine. CPS(pyr) activity can be completely inhibited by 5 x 10(-4) to 10 x 10(-4)m uridine triphosphate (UTP). CPS(pyr) is cold-labile and can be protected against cold inactivation by UTP. The synthesis of CPS(pyr) and aspartate transcarbamylase (ATC), the initial enzymatic steps of the pyrimidine pathway, are co-derepressed by pyrimidine starvation. Mutations affecting CPS(pyr) and ATC all map at the same locus, pyr-3. Three classes of mutants with respect to the two activities were found: CPS(+)ATC(-), CPS(-)ATC(+), and CPS(-)ATC(-). The distribution of these mutants on the genetic map, together with other data, indicate that the two activities are carried by a bifunctional protein.
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PMID:Pyrimidine-specific carbamyl phosphate synthetase in Neurospora crassa. 543 4

1. The concentration of blood glucose, free fatty acids and serum glycerol of the doe, new-born and young rabbits have been measured in order to evaluate the effects of age, starvation and environmental temperature on the circulating concentrations of these metabolites.2. The blood glucose, free fatty acid and glycerol concentrations were lower in the new-born than in the mother rabbit.3. Starvation for 24 hr of new-born and young rabbits in a thermal neutral environment did not alter the serum free fatty acid or glycerol concentrations. The blood glucose of unfed rabbits fell during the first 24 hr of life.4. Cold exposure (15 or 25 degrees C) for 1 hr caused a rise in the concentration of blood glucose, serum free fatty acids and glycerol.5. When the metabolic response of new-born and young rabbits to cold exposure was measured, it was found that there was a direct correlation between the serum glycerol concentration and the metabolic response. The greatest rise in the serum free fatty acids occurred in the blood of rabbits with the poorest metabolic response to cold.6. It is suggested that in the steady state during cold exposure the serum glycerol concentration may indicate the rate of triglyceride hydrolysis in brown adipose tissue.
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PMID:The effects of age and environmental temperature on the blood concentrations of glucose, free fatty acids and glycerol in new-born rabbits. 576 89

Sobek, J. M. (University of Southwestern Louisiana, Lafayette), J. F. Charba, and W. N. Foust. Endogenous metabolism of Azotobacter agilis. J. Bacteriol. 92:687-695. 1966-Ribonucleic acid, deoxyribonucleic acid, cellular carbohydrate, and the cold trichloroacetic acid and acidic alcohol fractions of the cell do not appear to function as endogenous reserves for Azotobacter agilis. The immediate endogenous reserve of cells grown on glucose, acetate, or succinate was poly-beta-hydroxybutyric acid (PHB). Viability of the cells during starvation was dependent upon the initial levels of PHB and the growth substrate. Cells with high initial PHB levels survived longer than cells with lower levels. Cells from succinate-grown cultures had lower PHB levels than cells from glucose-grown cultures, but were capable of maintaining their viability longer. Cellular protein may also serve as a secondary endogenous reserve substrate for this organism.
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PMID:Endogenous metabolism of Azotobacter agilis. 592 42

The effect of aging was evaluated on norepinephrine content of the heart (ventricles) and spleen of 3- and 24-month-old F344 and Sprague-Dawley rats utilizing a sensitive radioenzymatic assay. To assess sympathetic nervous system activity, the decline in organ norepinephrine content was compared in young and old F344 rats 6 hours after blockade of norepinephrine synthesis with alpha-methyl-p-tyrosine, a tyrosine hydroxylase inhibitor. Three conditions were studied: (a) normal, (b) brief starvation (54 hours), and (c) cold exposure (6 hours, 4 degrees C). There was no significant age-related difference in steady state organ norepinephrine concentration. Based on the response to alpha-methyl-p-tyrosine, aging did not affect the rate of heart and spleen norepinephrine synthesis and, therefore, sympathetic nervous system impulse activity during normal or cold stress conditions. Starvation, however, did not suppress sympathetic nervous system activity to the heart in old animals, as it did in the young rats.
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PMID:Influence of aging and tyrosine hydroxylase inhibition on tissue levels of norepinephrine during stress. 612 30

Phosphoenolpyruvate carboxykinase (EC 4.1.1.49) (PEPcK) activity is high in the liver, brown fat, and small intestinal mucosa of suckling rats. Starvation results in a rise in hepatic activity in newborn and older animals, but a fall in brown fat from rats younger than 14 days. At that age, activity rises in all three tissues on fasting. Both triiodothyronine (T3) and dexamethazone depress activity in gut and (as previously reported) in brown fat, but elevate it in liver. Cold exposure also has a similar effect. Both alpha-antagonist and agonist injections result in elevated hepatic activity. T3 given together with these more than doubles the effect of either drug or T3 given alone. In brown fat only antagonists decrease PEPcK activity, whereas in gut both agonists and antagonist have an inhibitory effect. It is concluded that PEPcK activity in the three tissues responds differently to the same stimuli with gut mucosa being more similar to, but not the same as, brown fat than to liver.
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PMID:Regulation of phosphoenolpyruvate carboxykinase during postnatal development in the rat. 631 62

The metabolic interactions of cold exposure, cold acclimation, and starvation on glucose tolerance and plasma insulin levels were studied in precannulated, unrestrained, and unanesthetized rats. Cold exposure (48 h at 5 degrees C) significantly reduced the insulin response to intravenous glucose injection (P less than 0.01) while improving glucose tolerance (P less than 0.01). Starvation (48 h at 25 degrees C) also reduced the insulin response (P less than 0.01) but did not significantly alter glucose tolerance. "Accelerated starvation" induced by starving rats for 48 h at 5 degrees C dramatically reduced both basal and glucose-stimulated insulin levels while even improving glucose tolerance, resulting in a 15-fold reduction in the insulinogenic index. Cold acclimation (3 wk at 5 degrees C) induced essentially the same alterations as cold exposure. Approximately reversed changes were observed when cold-acclimated rats were returned to a warm environment for 15-18 h. Results from these studies indicate that 1) cold exposure and starvation, but not cold acclimation, act synergistically in decreasing the sensitivity and/or the capacity of pancreatic islets for secreting insulin in response to glucose stimulation; 2) glucose tolerance and possibly insulin sensitivity of peripheral tissues are enhanced by cold exposure and starvation, although glucose tolerance is improved by cold exposure only, not by starvation; 3) an improved glucose tolerance with barely detectable plasma insulin levels was obtained in cold-starved rats under normal physiological conditions.
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PMID:Interactions of cold exposure and starvation on glucose tolerance and insulin response. 636 28

Plasma corticosterone levels were determined in serial samples obtained from 3 groups of rats: 1) starved, 2) cold-treated (4 degrees C), and 3) starved and cold treated (4 degrees C). Starvation resulted in an increase of plasma corticosterone on the 3rd day and the increase henceafter was linear with the number of days of treatment up to day 13 whereas upon cold exposure, the plasma corticosterone levels first increased on day 1 up to day 3, and then declined on day 9. Cold and starvation in combination led to a greater elevation of plasma corticosterone level than cold or starvation alone. It is concluded that the increase of plasma corticosterone during starvation or cold may be related to altered metabolism under such circumstances, and that the effect of cold and starvation are synergistic and may be mediated by different neural mechanisms.
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PMID:Interaction of cold and starvation in the regulation of plasma corticosterone levels in the male rat. 646 11

The present studies examine the effect of starvation together with cold or hot exposure on thyroid hormone levels in rats. At 23 degrees C starved for 5 days, serum thyroid hormone levels decreased significantly compared with fed rats, averaging 3.6 +/- 0.5 micrograms/dl of thyroxine (T4), 47 +/- 11 ng/dl of triiodothyronine (T3), 1.4 +/- 0.3 ng/dl of free T4 and 39.6 +/- 5.1 pg/ml of reverse T3, respectively. At 15 degrees C rats starved for 5 days, serum free T4 level significantly more increased than that of 23 degrees C starved rats, while serum T4 level and T3 did not increase significantly. At 30 degrees C rats whether concomitant starvation or not, serum thyroid hormone levels of both group markedly more decreased than control rats. These experiment provide additional evidence that thyroid gland and the peripheral metabolism of thyroid hormone respond to variety situations such as cold or hot exposure together with starvation or not.
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PMID:[Factors affecting the serum thyroid hormone concentration during fasting in rats--with special reference to the relation with temperature]. 662 62

Protein synthetic rates were measured in tissues of Notothenia corriceps, N. gibberifrons and Chaenocephalus aceratus in vivo at 2 degrees C by a method in which high doses of 14C-phenylalanine are used for stabilization of specific radioactivity. Rates in N. coriiceps, as per cent of tissue protein synthesized per day, were: liver 10.4, head kidney 3.5, testis 2.6, spleen 2.1, kidney 1.9, gill 1.6, heart 1.4, pectoral muscle 1.0, epaxial muscle 0.37, brain 0.42. With the exception of liver and head kidney (9.8 and 3.4, respectively) all rates in the icefish C. aceratus were significantly reduced compared to the nototheniids, consistent with the dependence of protein synthesis on oxidative metabolism. Icefish lack hemoglobin in the blood. The effects of two-week starvation were tissue-specific. Rates declined markedly in pectoral and epaxial muscle, were unchanged in liver, kidney, brain, heart and testis, and were increased in gill and head kidney. The results are discussed in relation to cold adaptation of Antarctic fishes and to the adaptation of metabolism required during non-feeding periods and for species which lack an oxygen-binding pigment in their blood.
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PMID:A comparative study of protein synthesis in nototheniids and icefish at Palmer Station, Antarctica. 664 Nov 75


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