Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The objective of this investigation was to throw light on the biological behavior and metabolic regulation of hepatic enzymes of the nonoxidative branch of the pentose phosphate pathway. The activities of transaldolase (EC 2.2.1.2) and trasketolase (EC 2.2.1.1) Were compared in biological conditions that involve modulation of gene expression such as in starvation, in differentiation, after partial hepatectomy, and in a spectrum of hepatomas of different growth rates. The enzyme activities were determined under optimal kinetic conditions by spectrophotometric methods in the 100,000 X g supernatant fluids prepared from tissue homogenates. The kinetic properties of transaldolase and transketolase were similar in normal liver and in rapidly growing hepatoma 3924A. For transaldolase, apparent Km values of 0.13 mM (normal liver) and 0.17 mM (hepatoma) were observed for erythrose 4-phosphate and of 0.30 to 0.35 mM for fructose 6-phosphate. The pH optima in liver and hepatoma were at approximately 6.9 to 7.2. For the transketolase substrates, ribose 5-phosphate and xylulose 5-phosphate, the apparent Km values were 0.3 and 0.5 mM, respectively, in both liver and hepatoma. A broad pH optimum around 7.6 was observed in both tissues. In organ distribution studies, enzyme activities were measured in liver, intestinal mucosa, thymus, kidney, spleen, brain, adipose tissue, lung, heart, and skeletal muscle. Taking the specific activity of liver as 100%, transaldolase activity was the highest in intestinal mucosa (316%) and in thymus (219%); it was the lowest in heart (53%) and in skeletal muscle (21%). Transketolase activity was highest in kidney (155%) and lowest in heart (26%) and skeletal muscle (23%). Starvation decreased transaldolase and transketolase activities in 6 days to 69 and 74%, respectively, of those of the liver of the normal, fed rat. This was in the same range as the decrease in the protein concentration (66%y. In the liver tumors, transaldolase activity was increased 1.5- to 3.4-fold over the activities observed in normal control rat liver. Transketolase activity showed no relationship to tumor proliferation rate. In the regenerating liver at 24 hr after partial hepatectomy, the activity of both pentose phosphate pathway enzymes was in the same range as that of the sham-operated controls. In differentiation at the postnatal age of 5, 12, 23, and 32 days, hepatic transaldolase activities were 33, 44, 55, and 72%, respectively, of the activities observed in the 60-day-old, adult male rat. During the same period, transketolase activ-ties were 18, 21, 26, and 55% of the activities observed in liver of adult rat. The demonstration of increased transaldolase activity in hepatomas, irrespective of the degree of tumor malignancy, differentiation, or growth rate, suggests that the reprogramming of gene expression in malignant transformation is linked with an increase in the expression of this pentose phosphate pathway enzyme...
 ...
PMID:Behavior of transaldolase (EC 2.2.1.2) and transketolase (EC 2.2.1.1) Activities in normal, neoplastic, differentiating, and regenerating liver. 1 80

The effects of dietary-induced acidosis on the growth and rates of complete regression of Sarcoma 180 in mice have been studied. The experiments here reported have demonstrated that mineral acidification of laboratory food produces a late decrease in tumor growth and significantly increases the rates of complete tumor regression. Blood acid-base studies also demonstrate the effects of these diets in altering the acid-base balance, and seemingly, this is independent of starvation and/or ketosis. The relationships of such in vivo acid-base metabolic changes to the control of tumor metabolism are briefly discussed. A therapeutic potential for this preliminary approach is considered.
 ...
PMID:Effects of systemic acidification of mice with Sarcoma 180. 4 Jun 91

In carcinoma of the esophagus, two major factors are operative, both of which are capable of suppressing the immune response, namely starvation and the presence of a malignant tumor. Twenty patients who were treated by palliative intubation for unresectable carcinoma of the esophagus were investigated. All patients were suffering from protein-calorie malnutrition and were shown to be in negative nitrogen balance. Lymphocyte counts and the nonspecific cellular and humoral immune response were evaluated before and after correction of the nutritional deficit. No attempt was made to reduce tumor bulk. The cellular immune response was compromised in all patients. The DNCB skin test was negative, absolute lymphocyte counts and T-lymphocyte numbers were significantly depressed, and the mitogenic response to phytohaemagglutinin (PHA) stimulation also significantly depressed. Immunoglobulin A levels were significantly elevated but serum complement concentrations were normal. Reversal of the negative nitrogen balance resulted in a significant increase in absolute and T-lymphocyte numbers, and a significant increase in the mitogenic response to PHA. The DNCB skin test, however, remained nonreactive. Nutritional repletion also significantly increased serum C(3), C(4) and C(3)PA concentrations. Reversal of negative nitrogen balance may reverse in vitro evidence of immunoparesis and produce an increase in complement concentrations, without therapeutic reduction in the tumor load.
 ...
PMID:Nutritional status and the nonspecific cellular and humoral immune response in esophageal carcinoma. 10 56

Large subcutaneous doses (2 mg/21 days) of estradiol valerate (EV) given over several months will induce a prolactin and growth hormone-secreting pituitary tumor in female rats. The medial basal hypothalami (MBHs) of such EV-treated animals were examined at different time intervals with light and electron microscopes to determine whether EV affects the MBH and to relate any observed effects to the process of tumorigenesis. The MBHs of extensively treated rats exhibited profound glial and neuronal changes. The filament content of astrocytes was greatly increased and large dense pleomorphic inclusions filled both astrocytic perikarya and processes. Degenerating neuronal elements have been observed in the neuropil of extensively treated animals. Dark cells identified as M cells were seen to engage in phagocytosis and were loaded with dense inclusions. Some neurons in MBH contained large quantities of lipofuscin that was different in appearance from that of normal females of the same age. The glial reaction developed gradually. At earlier stages of EV treatment there were fewer reactive glia and these contained fewer inclusions. Myelin figures often occurred in these early inclusions. Reactive glia in EV-treated rats did not appear in the preoptic area, dorsomedial nucleus or lateral hypothalamus but were found in ventromedial nucleus. Retired breeders and starvation-stressed rats resembled normal controls. These pathological changes in MBH may result from a direct effect of EV on the hypothalamus. It is possible that, in addition to its effects on the hypophysis, EV suppresses or injures hypophysiotropic cells in MBH, thus releasing pituitary chromophobes from inhibitory hypothalamic influences. This could result in hypersecretion and neoplasia.
 ...
PMID:Cytopathological effects of estradiol on the arcuate nucleus of the female rat. A possible mechanism for pituitary tumorigenesis. 17 Aug 18

We have studied the expression of simian virus 40 (SV40) specific tumor antigen (T-antigen) and viral RNA in SV40-transformed mouse 3T3 cells that are temperature-sensitive for the expression of the transformed phenotype (ts SV3T3). Although transformed by wild-type SV40, ts SV3T3 cells at 32 degrees behave like standard transformants, while at 39 degrees they became arrested in G1 after reaching saturation density or under conditions of serum starvation. ts SV3T3 cells at 32 degrees or exponentially growing at 39 degrees are uniformly T-antigen positive. However, after G1 arrest at 39 degrees the majority of the cells becomes T-antigen negative. Induction of proliferation in the resting cultures results in the reappearance of T-antigen in most of the cells, concomitant with the induction of DNA synthesis. The reason for the disappearance of T-antigen from ts SV3T3 cells arrested in G1 seems to reside in a transcriptional control operating on the integrated viral DNA, since these cells contain no appreciable amounts of SV40 specific RNA. Viral RNA can be easily detected in cells growint at 32 degrees or at 39 degrees. The results suggest that transcription of the viral genome in SV40-transformed cells is cell-cycle-dependent.
 ...
PMID:Regulation of viral transciption and tumor antigen expression in cells transformed by simian virus 40. 18 May 30

The dependence of protein synthesis on the intracellular content of aminoacylated tRNA has been studied in mouse ascites tumor cells deprived for various amino acids. A remarkable reduction in net protein synthesis has been found only after a drastic decrease in aminoacylation of tRNA. The quantitative correlation of protein synthesis with the degree of aminoacylation suggests that a moderate amino acid starvation primarily influences the rate of elongation at the codon concerned. These results are in contrast to the findings previously reported for HeLa cells. Some crucial steps during the determination of intracellular aminoacyl-tRNA have been investigated. The reliability of the method employed has been discussed on a theoretical basis.
 ...
PMID:Control of protein synthesis in mammalian cells by aminoacylation of transfer ribonucleic acid. 26 Jun 96

The intracellular concentrations of the adenine nucleotides were determined in suspension cultures of WRL-10A cells, a subline of the L-929 mouse fibroblasts, during the progression of the cells from exponential growth to high-density, nonproliferating populations. The development of the nonproliferating state was associated with a 50% reduction of the adenine nucleotide pool, whereas the energy charge remained at values above 0.90. This change was also observed in the early phase of starvation of low-density cultures and could be reproduced by selective simultaneous withdrawal of glucose and glutamine, which indicated interference with the de novo synthesis of purines. In this respect, therefore, nonproliferating populations of WRL-10A cells resemble purine-limited bacterial systems but not density-inhibited normal fibroblasts in which the size of the adenine nucleotide pool is known to remain unchanged. This difference in the physiologic state of nonproliferating normal and neoplastic cells is potentially significant for tumor chemotherapy.
 ...
PMID:Nonproliferating neoplastic cells in culture: behavior of the adenine nucleotides. 28 95

The effects of starvation on tumor and host growth were studied in growing male Fischer rats bearing methylcholanthrene-induced sarcomas. Tumor growth was evaluated by changes in weight, volume, and incorporation of tritiated methyl thymidine into tumor DNA, (dpm/microgram DNA). Host growth was followed by changes in total body weight, carcass weight, and dpm/microgram liver DNA. All periods of starvation (24 to 96 hr) caused significant decreases in host body and carcass weight and dpm/microgram liver DNA. Changes in tumor weight and tumor volume in fed and starved animals were equal. Tumor dpm/microgram DNA in starved animals increased (P less than 0.005) relative to fed controls at 48, 72, and 96 hr starvation intervals. Starvation allows continued tumor growth while host wasting occurs, and is accompanied by increased tumor dpm/microgram DNA in this system.
 ...
PMID:Nutritional manipulations and tumor growth. I. The effects of starvation. 49 46

Sixty-eight marine mammals stranded on the Oregon beaches were examined at necropsy. Gunshot was the primary cause of death in 30% of the pinnipeds examined. Bacterial infections (27%) and parasitism (27%) were also of major importance in the death and debilitation of Oregon marine mammals. Traumatic death or debilitation other than gunshot was observed in 11 animals (16%). Predation, starvation due to neonatal abandonment, viral encephalitis (presumptive diagnosis), dystocia and neoplasia were diagnosed as primary or contributory causes of stranding.
 ...
PMID:Causes of death in marine mammals stranded along the Oregon coast. 58 22

Host starvation is a common accompaniment to the presence of cancer. Diminished intake is a major contributor to this starvation and does not require that the oropharynx or gastrointestinal tract be the primary site. There is suggestive evidence that the normal adaptive mechanisms of the nontumor-bearing host to starvation that result in body protein conservation are not functioning in the tumor-bearing host. Cancer cachexia has some similarity to the metabolic disturbances of host metabolism that are seen in major injury or sepsis. The growing tumor shows little respect for normal constraints of host tissue growth. With the widespread availability of methods of total parenteral nutrition, the interrelationship of nutrition and host-tumor growth assumes greater importance.
 ...
PMID:Uncomplicated starvation versus cancer cachexia. 86 53


1 2 3 4 5 6 7 8 9 10 Next >>