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Biomedical subjects

K Brand

Publications and source records attributed to K Brand.

At least 91 records · Page 5Linked to original sources
PubMed1988

Alterations of cellular lipids in rat thymocytes during cell cycle progression.

This study provides information on the lipid content and composition of rat thymocytes during cell cycle progression. Cultured rat thymocytes were stimulated by concanavalin A and interleukin-2 to enter the cell cycle and to proliferate. At indicated intervals during a 96 h culture, cells were analyzed for lipid content and lipid synthesis. A growth-related 3.8-fold increase in the cellular cholesterol and a 2.8-fold increase in the phospholipid content was observed after 48 h of culture. Cholesterol synthesis, measured by [14C]acetate incorporation, increased 34-fold, whereas the synthesis of the other lipids was enhanced only 15-fold. Concerning the percentage distribution of the total fatty acids, arachidonic acid showed a significant decline between 24 and 72 h of culture, being mainly caused by the release of arachidonic acid from phosphatidylcholine. Addition of actinomycin D, an inhibitor of DNA replication, prevented the decline of cellular arachidonic acid content in a dose-dependent manner. These data suggest that both the pronounced rise of the cholesterol content as well as the decline of arachidonic acid content are closely linked to cell proliferation.

Acetates↗
PubMed1988

Variants of phosphohexose isomerase in gastrointestinal and mammary carcinoma: isoelectric focusing patterns of normal and tumor tissues derived from surgical specimens of the same patient.

The occurrence of charge variants of phosphohexose isomerase was elucidated in cancerous and, for comparison, in noncancerous tissues obtained from the same organ. Surgical specimens from 35 patients with gastrointestinal and mammary carcinoma were studied by means of the isoelectric focusing (IEF) technique. Differences in the IEF pattern could be demonstrated in 90% of the patients with gastric cancer. Corresponding values for the patients with colorectal and mammary carcinoma were 50 and 73%, respectively. Almost all normal specimens proved to be monomorphic, revealing only the major basic band with a pI of 9.1. In most of the tumors, additional bands of pI 8.9 and 8.6 were found. This "typical" IEF pattern in tumor tissues was observed in 60% of gastric and 73% of mammary tumors, but in only 36% of colorectal tumors. The results obtained suggest that the IEF pattern of phosphohexose isomerase in tumor tissue might be a useful tool for tumor diagnosis.

Breast↗
PubMed1988

Cell-cycle-related metabolic and enzymatic events in proliferating rat thymocytes.

Cell-cycle progression of rat thymocytes stimulated with concanavalin A and interleukin 2 was monitored at 12-h intervals by pulse labeling aliquots of the cell culture with [3H]thymidine, by measuring cellular DNA and protein content and by counting the number of cells in the cultures. The cell cycle was completed after 96 h of culture with the S phase peaking at 48 h. Early events in thymocyte activation were enhanced phosphatidylinositol turnover and the induction of ornithine decarboxylase. Concomitant changes were observed in the rates of DNA synthesis and glycolysis accompanied by a 20-fold increase in glucose uptake 48 h after stimulation. However, the maximal increment in the glycolytic rate preceded that of DNA synthesis by 12 h. Apart from the quantitative changes which occurred during the cell-cycle progression, there was also a change from partial aerobic glucose degradation to CO2 (26%) to almost complete anaerobic conversion of glucose to lactate (85%) and less than 3% to CO2. Glycolytic enzyme levels increased fourfold to tenfold and reached their maxima 48 h after mitogenic stimulation. Maximal increments of glycolytic enzyme activities preceded or coincided with the maximal increments of the glycolytic rate. Actinomycin D (1.5 ng/ml) completely inhibited DNA and RNA synthesis but did not show any inhibitory effect either on glycolytic enzyme induction or on enhanced glycolysis. During mitosis and return of the cells to the non-proliferative state, all of the enhanced metabolic rates returned to their initial levels and the elevated enzyme activities were decreased also. The marked changes of metabolic rates and enzyme activities observed at the various phases of the cell cycle suggest that these biochemical events may also serve as suitable parameters for evaluating the response of lymphocytes towards mitogens and lymphokines.

Animals↗
PubMed1988

Phosphohexose isomerase in hypernephroma. Significance as serum tumor marker, comparison to other glycolytic enzymes and isozyme patterns in normal and tumor tissue.

In hypernephroma an overall diagnostic sensitivity of 72% and a specificity of 87% was found for the serum tumor marker phosphohexose isomerase (PHI). Both in early stage disease and in well differentiated tumors a sensitivity of about 60% was reached. In contrast the sensitivity of three other glycolytic enzymes tested was found to be less than 20%. Since the cancer induced elevation of PHI activity in the tumor was found to be comparable to those of the other test enzymes, elevated PHI serum activities cannot be attributed to overproportional PHI synthesis and unspecific cell-lysis. In 6 of 10 cases studied differences in the PHI isozyme pattern between the tumor and the normal tissue were found suggesting the occurrence of cancer associated structural alterations of PHI.

Biomarkers, Tumor↗
PubMed1988

Ischemia-induced alterations of mitochondrial structure and function in brain, liver, and heart muscle of young and senescent rats.

Young and senescent rats (3 and 28-30 months old) were subjected to complete ischemia at 37 degrees C in order to study function and structure of mitochondria isolated from liver, heart muscle, and brain. The rates of energy-coupled respiration and ATP synthesis were found to decrease progressively in relation to time of ischemia. The respiratory rates in the absence of ADP (state 4 respiration) did not increase after exposure to ischemia, suggesting that ischemia primarily affects electron transport rather than the energy coupling system. Mitochondria of heart muscle were more affected by ischemia than mitochondria of brain and liver. Liver and heart muscle mitochondria obtained from young rats were found to be slightly more sensitive to short periods of ischemia than those isolated from senescent animals.

Adenosine Triphosphate↗
PubMed1988

Comparative experimental study of the serum prostate specific antigen and prostatic acid phosphatase in serially transplantable human prostatic carcinoma lines in nude mice.

Three different human lines of prostate carcinoma were successively transplanted on Balb/c nude mice and the serum values of the prostate specific antigen (PSA) and prostatic acid phosphatase (PAP) were determined simultaneously. In a group of the tumor-bearing animals the influence of endocrine manipulation (castration, estradiol) on the serum concentration of these tumor markers was studied. As far as untreated tumor-bearing mice are concerned, the serum values of both PAP and PSA proved to be strictly dependent on the tumor volume measured. In the exponential growth phase of the grafted tumors, linear growth was linked with a correspondingly increasing PAP and PSA serum level of the test animals. A close correlation was found to exist between the two tumor markers; however, the indicator value of PSA was 20 to 50 times higher than that of PAP under the test conditions. PSA determination yielded no false-negative results, if PAP was elevated. PAP determination was false-negative in 21 per cent of cases with measurable tumors, although the serum level of PSA already showed marked elevation. In treated animals both markers were found to decrease. Arrested growth and tumor regression was associated with falling PAP and PSA serum levels or with levels within normal range. The results of this experimental study support the conclusion that prostate specific antigen represents a substantially more sensitive tumor marker than prostatic acid phosphatase.

Acid Phosphatase↗
PubMed1988

Activities of phosphohexose isomerase and other glycolytic enzymes in normal and tumor tissue of patients with neoplastic diseases: comparison with serum activities and correlation to tumor staging and grading.

Of five glycolytic enzymes tested, only the serum activity of phosphohexose isomerase (PHI) was elevated in the vast majority of 140 patients with gastrointestinal, kidney or mammary carcinomas. However, in the tumor tissues all enzymes were increased to about the same extent. Thus, the measured increase in the serum activity of PHI is not due to a specific overproduction in the malignant cells. A general rise in the glycolytic enzyme activities in the malignant tissue could be detected already in early stages without metastases and in well-differentiated tumors.

Fructose-Bisphosphate Aldolase↗
PubMed1988

Significance of serum phosphohexose isomerase in gastrointestinal cancer at different stages.

The purpose of this study was to reevaluate the significance of serum PHI in gastrointestinal cancer at histopathologically defined stages prior to primary treatment. A total of 248 patients with malignant tumors of the gastrointestinal tract and a collective of 42 patients with noncancerous diseases were studied. The results are compared with those obtained with the established markers tissue polypeptide antigen (TPA) and carcinoembryonic antigen (CEA). Phosphohexose isomerase (PHI) revealed an overall diagnostic sensitivity of 69%, combined with a specificity of 74%. The corresponding data for TPA were found to be 73 and 47% while for CEA 26 and 95% respectively were determined. Even in the early stages of colorectal and esophageal carcinoma, PHI showed a sensitivity of about 60%. A continuous rise of PHI serum levels, correlating well with the extent of the tumor disease, could be detected. In contrast to TPA and CEA, PHI assay can be carried out with a minimum of laboratory efforts, in a short time and at low costs. These findings suggest that serum PHI assay is a useful aid for screening of gastrointestinal cancer, especially esophageal and gastric carcinoma, and a reliable marker for treatment control and follow-up.

Antigens, Neoplasm↗
PubMed1987

Role of ornithine decarboxylase on glycolytic enzyme induction during thymocyte proliferation.

Resting rat thymocytes were stimulated to cell cycle entry and proliferation by the addition of concanavalin A and interleukin 2 to the culture medium. Maximal rats of DNA and RNA synthesis and of glycolysis with a 20-fold increase in glucose uptake were observed 48 h after stimulation. Glycolytic enzyme levels increased 3-8-fold, also reaching their maxima 48 h after mitogenic stimulation. Actinomycin D (1.3-1.5 ng/ml) completely inhibited DNA and RNA synthesis in 24- and 48-h cultured cells but showed no inhibitory effect on glycolytic enzyme induction or on enhanced glycolysis. These results suggest the presence of sufficient mRNAs for the synthesis of glycolytic enzymes even though transcription is abolished by actinomycin D. Ornithine decarboxylase activity increased rapidly up to 41-fold within 6 h after stimulation with concanavalin A and interleukin 2. This rapid increase could not be prevented by actinomycin D; however, ornithine decarboxylase activity of thymocytes was affected after 24- and 48-h culture periods. Inhibition of ornithine decarboxylase by 5 mM difluoromethylornithine completely abolished glycolytic enzyme induction. This inhibitory effect could be reversed by exogeneous putrescine. The results obtained indicate the importance of early ornithine decarboxylase activation and polyamine biosynthesis for the induction of glycolytic enzymes in proliferating thymocytes.

Animals↗
PubMed1987

Pathways of glutamine and glutamate metabolism in resting and proliferating rat thymocytes: comparison between free and peptide-bound glutamine.

Pathways of glutamine metabolism in resting and proliferating rat thymocytes were evaluated by in vitro incubations of freshly prepared or 60-h cultured cells for 1-2 h with [U14C]glutamine. Complete recovery of glutamine carbons utilized in products allowed quantification of the pathways of glutamine metabolism under the experimental conditions. Partial oxidation of glutamine via 2-oxoglutarate in a truncated citric acid cycle to CO2 and oxaloacetate, which then was converted to aspartate, accounted for 76 and 69%, respectively, of the glutamine metabolized beyond the stage of glutamate by resting and proliferating thymocytes. Complete oxidation to CO2 in the citric acid cycle via 2-oxoglutarate dehydrogenase and isocitrate dehydrogenase accounted for 25 and 7%, respectively. In proliferating cells a substantial amount of glutamine carbons was also recovered in pyruvate, alanine, and especially lactate. The main route of glutamine and glutamate entrance into the citric acid cycle via 2-oxoglutarate in both cells is transamination by aspartate aminotransferase rather than oxidative deamination by glutamate dehydrogenase. In the presence of glucose as second substrate, glutamine utilization and aspartate formation markedly decreased, but complete oxidation of glutamine carbons to CO2 increased to 37 and 23%, respectively, in resting and proliferating cells. The dipeptide, glycyl-L-glutamine, which is more stable than free glutamine, can substitute for glutamine in thymocyte cultures at higher concentrations.

Animals↗
PubMed1986

A putative opioid-peptide processing activity in enriched Golgi fraction from rat brain.

A Golgi enriched fraction from rat brain was prepared. The preparation has no carboxypeptidase activity and is not contaminated with cytosol, mitochondria and lysosomes as judged by marker enzyme activities for these constituents. Associated with the Golgi membranes a putative opioid peptide processing activity was demonstrated, which acts on Dynorphin 1-13, alpha- and beta-Neoendorphin. The enzyme cleaves the bond between the paired basic residues, releasing Leucine-enkephalin-Arg6. The activity has a pH-optimum around 9 and is inhibited by serine-protease inhibitors. Intracellular location and substrate specificity suggest that this endopeptidase activity may be involved in proenkephalin processing.

Amino Acid Sequence↗
PubMed1986

[Physiologic nutritional evaluation of complete infant nutrition based on a soybean formula].

The purpose of this review is to evaluate the nutritional quality of soybean-based infant diets on the basis of results published in the scientific literature. Special consideration has been given to the use of soybean protein formulas for infants with reduced intestinal digestion and absorption capacity as well as in cases of cow's milk intolerance and allergic diseases.

Amino Acids↗
PubMed1986

Metabolic alterations associated with proliferation of mitogen-activated lymphocytes and of lymphoblastoid cell lines: evaluation of glucose and glutamine metabolism.

In vitro resting, short-term mitogen stimulated, and proliferating rat thymocytes as well as established human T and B lymphoblastoid cell lines were compared in their capacity to metabolize glucose and glutamine as energy source. Furthermore, the pathways of glutamine metabolism in these cells were studied. Compared with resting thymocytes, glucose metabolism of proliferating thymocytes was 36-fold increased during the incubation; 92% of the amount of glucose utilized was converted into trioses mainly lactate, whereas resting cells metabolized only 38% to trioses. However, the latter oxidized 19% of glucose to CO2, as opposed to 1.1% by the proliferating cells. Rates of glucose uptake and degradation to products by the malignant T lymphoblastoid cell line (Jurkat) were nearly identical with those observed with proliferating rat thymocytes, whereas the benign B lymphoblastoid cell lines (DHg-B-1 and LV-B-1) showed significantly higher rates of glucose metabolism. All three transformed lymphoblastoid cell lines, however, metabolized glucose almost completely to lactate as did the proliferating rat thymocytes. Lymphocytes are able to utilize glutamine with glutamate, aspartate and ammonia being the major end-products. A complete recovery of glutamine carbon in the products was obtained with all cells. Glutamine utilization by incubated proliferating rat thymocytes was 8-fold increased as compared to the resting cells. Again the human T lymphoblastoid cell line showed the same rates of glutamine uptake and conversion into products as did the proliferating rat thymocytes, whereas both B lymphoblastoid cell lines had about 2.5-fold enhanced rates as compared to the T cell line. The results indicate that during lymphocyte proliferation caused by mitogen stimulation as well as by permanent transformation into lymphoblastoid cell lines glucose metabolism is altered not only quantitatively but also qualitatively by changing from partly aerobic to almost complete anaerobic glucose breakdown. Glutamine has been found to be a suitable energy source for lymphocytes. About 75% of the amount of glutamate derived from glutamine entered into the citric acid cycle via the aspartate aminotransferase, and the remaining 25% via the glutamate dehydrogenase reaction. The changes in metabolic rates observed in proliferating as well as in transformed or leukemic lymphocytes appear to be reliable parameters to characterize the state of lymphocyte activation or to evaluate the efficacy of lymphokines.

Animals↗
PubMed1985

Glutamine and glucose metabolism during thymocyte proliferation. Pathways of glutamine and glutamate metabolism.

Energy metabolism in proliferating cultured rat thymocytes was compared with that of freshly prepared non-proliferating resting cells. Cultured rat thymocytes enter a proliferative cycle after stimulation by concanavalin A and Lymphocult T (interleukin-2), with maximal rates of DNA synthesis at 60 h. Compared with incubated resting thymocytes, glucose metabolism by incubated proliferating thymocytes was 53-fold increased; 90% of the amount of glucose utilized was converted into lactate, whereas resting cells metabolized only 56% to lactate. However, the latter oxidized 27% of glucose to CO2, as opposed to 1.1% by the proliferating cells. Activities of hexokinase, 6-phosphofructokinase, pyruvate kinase and aldolase in proliferating thymocytes were increased 12-, 17-, 30- and 24-fold respectively, whereas the rate of pyruvate oxidation was enhanced only 3-fold. The relatively low capacity of pyruvate degradation in proliferating thymocytes might be the reason for almost complete conversion of glucose into lactate by these cells. Glutamine utilization by rat thymocytes was 8-fold increased during proliferation. The major end products of glutamine metabolism are glutamate, aspartate, CO2 and ammonia. A complete recovery of glutamine carbon and nitrogen in the products was obtained. The amount of glutamate formed by phosphate-dependent glutaminase which entered the citric acid cycle was enhanced 5-fold in the proliferating cells: 76% was converted into 2-oxoglutarate by aspartate aminotransferase, present in high activity, and the remaining 24% by glutamate dehydrogenase. With resting cells the same percentages were obtained (75 and 25). Maximal activities of glutaminase, glutamate dehydrogenase and aspartate aminotransferase were increased 3-, 12- and 6-fold respectively in proliferating cells; 32% of the glutamate metabolized in the citric acid cycle was recovered in CO2 and 61% in aspartate. In resting cells this proportion was 41% and 59% and in mitogen-stimulated cells 39% and 65% respectively. Addition of glucose (4 mM) or malate (2 mM) strongly decreased the rates of glutamine utilization and glutamate conversion into 2-oxoglutarate by proliferating thymocytes and also affected the pathways of further glutamate metabolism. Addition of 2 mM-pyruvate did not alter the rate of glutamine utilization by proliferating thymocytes, but decreased the rate of metabolism beyond the stage of glutamate significantly. Formation of acetyl-CoA in the presence of pyruvate might explain the relatively enhanced oxidation of glutamate to CO2 (56%) by proliferating thymocytes.

Animals↗
PubMed1985

Carboxypeptidase activity in synaptic vesicles isolated from striatum and cortex of calf brain.

A carboxypeptidase activity has been found in synaptic vesicles (secretory granules) isolated from the cortex and striatum of calf brain which removes amino acids from the carboxy terminus of enkephalin-containing (EC) peptides. The formed enkephalin molecules are not further degraded by this enzyme activity. The preparations were found to be free of cytoplasmic and lysosomal constituents as determined by marker enzyme activities. The vesicle preparations of both cortex and striatum showed differences in the degradation velocities of the various EC peptides depending on size and charge of the amino acid present at the carboxy terminus. The pH optimum of the release of Met-enkephalin from Met-enkephalin-Arg6 has been shown to be between pH 5 and 6. The enzyme activity is inhibited by thiol-blocking agents such as p-hydroxymercuribenzoate and copper ions, but only slightly by metal-chelating agents.

Animals↗
PubMed1985

Amino acid pattern in human aqueous humor of patients with senile cataract and primary open-angle glaucoma.

21 amino acids have been determined in aqueous humor obtained during microsurgical intraocular procedures in 30 patients with senile cataract and 27 patients with primary open-angle glaucoma. All individual amino acids showed higher levels in the glaucomas than in the cataracts: this is valid at 2p less than 0.05 for threonine, serine, asparagine, glutamine, methionine, tyrosine, phenylalanine, histidine, tryptophan, and arginine.

Aged↗
PubMed1984

Glucose and glutamine metabolism in rat thymocytes.

The metabolism of glucose and glutamine in freshly prepared resting and concanavalin A-stimulated rat thymocytes was studied. Concanavalin A addition enhanced uptake of both glucose and glutamine and led to an increase in oxidative degradation of both substrates to CO2. With variously labelled [14C]glucose, it was shown that the pathways of glucose dissimilation were equally stimulated by the mitogen. A disproportionately large percentage of the extra glucose taken up was converted into lactate, but concanavalin A also caused an increase in the oxidation of pyruvate as judged by the enhanced release of 14CO2 from [2-14C]-, [3,4-14C]- and [6-14C]-glucose. Addition of glutamine did not affect glucose metabolism. The major end products of glutamine metabolism by resting and mitogen-stimulated rat thymocytes were glutamate, aspartate, CO2 and NH3. Virtually no lactate was formed from glutamine. Concanavalin A enhanced the formation of all end products except glutamate, indicating that more glutamine was metabolized beyond the stage of glutamate in the mitogen-activated cells. Addition of glucose caused a significant decrease in the rates of glutamine utilization and conversion into aspartate and CO2 in the absence and in the presence of concanavalin A. In the presence of glucose, almost all nitrogen of the metabolized glutamine was accounted for as NH3 released via the glutaminase and/or glutamate dehydrogenase reactions. In the absence of glucose, part (18%) of the glutamine nitrogen was metabolized by the resting and to a larger extent (38%) by the mitogen-stimulated thymocytes via a transaminase or amidotransferase reaction.

Animals↗