RESUMEN
1. Fasting of ad libitum- or maintenance-fed steers for 4 to 9 days did not alter basal lipolytic rates in vitro. 2. Epinephrine stimulation of adipose tissue of fasted steers resulted in greater (P less than 0.05) lipolysis than in tissue from fed steers. 3. Prostaglandin E2 (PGE2) did not alter epinephrine-stimulated lipolysis in ad libitum- or maintenance-fed cattle. 4. Indomethacin did not influence basal lipolysis, even in the presence of PGE2. 5. Insulin neither affected basal lipolysis nor inhibited dibutyl cAMP-stimulated lipolysis.
Asunto(s)
Tejido Adiposo/metabolismo , Dinoprostona/farmacología , Epinefrina/farmacología , Indometacina/farmacología , Lipólisis/fisiología , Adenilil Ciclasas/metabolismo , Tejido Adiposo/efectos de los fármacos , Animales , Bucladesina/metabolismo , Bovinos , Ayuno/fisiología , Técnicas In Vitro , Insulina/farmacología , Lipólisis/efectos de los fármacos , MasculinoRESUMEN
Effects of exogenous prostaglandin E2 (PGE2) on rates of lipolysis in sections of subcutaneous adipose tissue biopsied from fed and fasted Holstein steers were determined. The interaction of PGE2 with several exogenous effectors of lipolysis and of the adenylate cyclase-cAMP system also was measured. Epinephrine increased basal (nonstimulated) lipolysis approximately one-fold. Prostaglandin E2 had no effect on either basal or epinephrine-stimulated lipolysis. Dibutyryl cAMP increased rate of lipolysis .4-fold, whereas theophylline increased lipolysis more than one-fold. Theophylline had an additive effect on epinephrine-stimulated lipolysis. Dibutyryl cAMP increased theophylline-stimulated lipolysis but not epinephrine-stimulated lipolysis. Prostaglandin E2 had no effect on epinephrine-, dibutyryl cAMP- or theophylline-stimulated lipolysis. Fasting decreased basal lipolysis by 40%. Furthermore, lipolysis in tissue incubated with PGE2, epinephrine or PGE2 plus epinephrine decreased from 30 to 50% upon fasting. As also shown with tissue from fed steers, PGE2 did not alter basal or epinephrine-stimulated lipolysis in tissue from fasted steers. Influences of exogenous effectors on lipolysis in adipose tissue from fed and fasted steers indicate that PGE2 does not control the adenylate cyclase-cAMP system that regulates lipolysis in bovine adipose tissue.
Asunto(s)
Tejido Adiposo/metabolismo , Lipólisis/efectos de los fármacos , Prostaglandinas E/farmacología , Tejido Adiposo/efectos de los fármacos , Animales , Bucladesina/farmacología , Bovinos , Dinoprostona , Epinefrina/farmacología , Masculino , Orquiectomía , Teofilina/farmacologíaRESUMEN
Forty crossbred steers of similar birth date and fed the same growing-finishing diet were used to study adipocyte changes in six fat depots during growth from 11 to 19 mo of age. Steers were slaughtered at 2-mo intervals. Adipose tissue samples were obtained from kidney, mesenteric and brisket fat and subcutaneous, intermuscular and intramuscular fat from the 10th to 12th rib section. The osmium tetroxide fixation technique was used for determination of cell size and number. Except for three brisket fat samples, distributions of adipocyte diameters from six different fat depots were monophasic during the age range considered in this study. At 17 mo of age, the mean adipocyte diameter, in decreasing order, was: kidney fat greater than mesenteric greater than subcutaneous greater than intermuscular greater than intramuscular greater than brisket fat. Fat deposition during growth to 19 mo of age occurred mainly by hypertrophy of adipocytes. An apparent cell hyperplasia occurred in the intramuscular fat depot from 11 to 15 mo and in the brisket fat depot after 15 mo of age. Based on cellularity characteristics, evidence exists to classify intramuscular and brisket fat depots as late-developing ones. Cell number/gram of intramuscular adipose tissue was a better predictor of marbling score than was fat cell diameter.
Asunto(s)
Tejido Adiposo/citología , Bovinos/crecimiento & desarrollo , Animales , Composición Corporal , Bovinos/anatomía & histología , Recuento de Células/veterinaria , Lípidos/análisis , Masculino , Músculos/análisisRESUMEN
Acid phosphatase activity biochemically in the primary tumor of 20 patients with prostatic carcinoma, was studied in an attempt to understand the basis for a correlation or lack of correlation between serum and/or bone marrow acid phosphatase levels and the presence and/or clinical behavior of prostatic carcinoma. The enzyme activity was similarly measured in 19 patients with benign prostatic hyperplasia as controls. On the average, enzyme activities were lower (P less than 0.002) in the tissues from patients with carcinoma. There was no correlation of enzyme activity in tumor with the age of the patient, stage of disease, degree of differentiation of the tumor, or serum acid phosphatase activity.
Asunto(s)
Fosfatasa Ácida/análisis , Carcinoma/enzimología , Hiperplasia Prostática/enzimología , Neoplasias de la Próstata/enzimología , Fosfatasa Ácida/sangre , Factores de Edad , Anciano , Humanos , Masculino , Persona de Mediana Edad , Neoplasias de la Próstata/patologíaRESUMEN
We studied arginase activity in human prostatic tissue in 15 patients with benign hyperplasia and 27 patients with prostatic carcinoma. Arginase specific activity is greater (p less than 0.0001) in prostatic carcinomas than in hyperplastic prostates. Arginase specific activity is correlated inversely (p less than 0.0001) with the histological grade of the tumor.
Asunto(s)
Arginasa/metabolismo , Hiperplasia Prostática/enzimología , Neoplasias de la Próstata/enzimología , Anciano , Humanos , Concentración de Iones de Hidrógeno , Masculino , Persona de Mediana Edad , Pronóstico , Próstata/enzimología , Neoplasias de la Próstata/patologíaRESUMEN
Many previous studies have shown that a proportion of patients with carcinoma of the prostate have increased activity of the creatine kinase (E.C. 2.7.3.2) isoenzyme designated BB in sera from their peripheral blood. We have analyzed tissues from prostatic hyperplasia of 22 patients and from prostatic carcinoma of 23 additional patients. Prostatic carcinomas contain less (p less than 0.001) creatine kinase activity (units/g) than do prostates with benign prostatic hyperplasia. The facts that (a) histochemical studies that we performed confirmed the observation reported previously by others that creatine kinase activity is found primarily in the epithelial elements of hyperplastic prostates and prostatic carcinomas, (b) the carcinomas that we examined had, on the average, a somewhat larger epithelial component than the hyperplastic prostates that we examined, and (c) prostate cancer was found to contain less creatine kinase activity than hyperplastic prostates suggest that the epithelial cells in prostate cancers contain less creatine kinase activity per cell than do those from hyperplastic prostates. The BB form of creatine kinase accounts for 98% of the activity in prostatic carcinoma and in prostates without cancer. Creatine kinase has been discussed as a possible marker for prostatic carcinoma, and we had hoped that it might be useful for the assay of tumor burden. Our data suggest that, if creatine kinase is to be useful in the monitoring of tumor burden, it will be useful only in the contexts of particular patients studied longitudinally since the creatine kinase activity varies enormously among different prostatic carcinomas.
Asunto(s)
Creatina Quinasa/metabolismo , Hiperplasia Prostática/enzimología , Neoplasias de la Próstata/enzimología , Anciano , Creatina Quinasa/aislamiento & purificación , Humanos , Isoenzimas , Cinética , Masculino , Persona de Mediana EdadRESUMEN
Hexosaminidase activity in prostatic tissue has been compared in 15 patients with benign prostatic hyperplasia and 15 patients with prostatic carcinoma. The ratio of enzymatic activity for the two substrates tested (p-nitrophenyl-2-acetamido-2-deoxy-beta-D-glucopyranoside and p-nitrophenyl-2-acetamido-2-deoxy-beta-D-galactopyranoside) was not significantly different in the two groups of patients. The proportion of hexosaminidase represented by the B isozyme was not significantly different for the two groups of patients. Prostatic tissue hexosaminidase was greater (p = 0.0141) in carcinomatous prostates than in hyperplastic prostates.
Asunto(s)
Acetilglucosaminidasa/metabolismo , Hexosaminidasas/metabolismo , Próstata/enzimología , Hiperplasia Prostática/enzimología , Neoplasias de la Próstata/enzimología , Anciano , Humanos , Isoenzimas/metabolismo , Cinética , Masculino , Persona de Mediana Edad , Especificidad por SustratoRESUMEN
Samples of subcutaneous, intermuscular and mesenteric adipose tissues from beef steers were fixed with osmium tetroxide, and freed adipocytes were counted with an automatic particle counter to determine whether a lognormal distribution function would describe adipocyte size distributions more accurately than a normal distribution function. Modes and medians of size distributions generally were larger than means for adipocyte size distributions modeled with a lognormal distribution function. Normalized third and fourth moments of predicted lognormal distributions often were close to 0 and 3, respectively, which are expected values for a normally distributed population. Considerable variation was observed in the skewness of adipocyte size distributions. Both normal and lognormal models for adipocyte size distribution yielded similar means. The lognormal model yielded a greater standard deviation than the normal model for adipocyte size distributions. Smaller chi-square values were found for size distributions modeled with a lognormal than with a normal distribution function. Results suggest that a lognormal distribution function more accurately models the size distributions of bovine adipocytes.
Asunto(s)
Tejido Adiposo/citología , Bovinos/anatomía & histología , Animales , Recuento de Células , MasculinoRESUMEN
Rates of fatty acid synthesis from lactate and acetate and activities of selected lipogenic and NADPH-generating enzymes were determined in subcutaneous, intermuscular and intramuscular adipose tissues of cattle that were 11-19 months of age. Fatty acid synthesis from lactate and acetate increased from 11 to 13 months of age in subcutaneous and intermuscular adipose tissues; synthesis from lactate increased until 17 months of age. In intramuscular adipose tissue, synthesis from lactate also increased until 17 months of age while that from acetate continually increased. Activities of NADPH-generating enzymes increased in all three fat depots from 11 to 13 months of age, and little change occurred thereafter. Acetyl-CoA carboxylase activity was constant over entire growth period in all depots. Activity of ATP-citrate lyase increased from 11 to 13 months of age in subcutaneous and intermuscular adipose tissues, but did not increase until 19 months of age in intramuscular adipose tissue. In all cases, activities of ATP-citrate lyase were sufficient to support synthesis from lactate; therefore, lactate conversion to fatty acids in bovine adipose tissues seems to use the citrate cleavage pathway for generation of cytosolic acetyl-CoA.
Asunto(s)
Tejido Adiposo/metabolismo , Bovinos/metabolismo , Ácidos Grasos/biosíntesis , Lactatos/metabolismo , ATP Citrato (pro-S)-Liasa/metabolismo , Acetatos/metabolismo , Envejecimiento , Animales , Glucosafosfato Deshidrogenasa/metabolismo , Isocitrato Deshidrogenasa/metabolismo , Ácido Láctico , Fosfogluconato Deshidrogenasa/metabolismoRESUMEN
Contributing factors in the regulation of triglyceride deposition in and fatty acid release from bovine adipose tissue were investigated. Six Holstein steers were fasted for 9 days and then refed for 41 days. Blood samples from the jugular vein and adipose tissue samples from backfat biopsies were taken during fasting and refeeding periods. Concentrations of plasma free fatty aids, glycerol and cholesterol and activity of lipoprotein lipase in adipose tissue from fasted and refed steers were measured. Plasma free fatty acid concentration increased almost eightfold during fasting. After 4 days of refeeding, free fatty acids in plasma had returned to basal concentration. Fasting had no effect on plasma cholesterol concentration; during refeeding, concentration decreased slightly and then returned to the basal concentration. Lipoprotein lipase activity decreased to 37% of the basal concentration during fasting and increased to 100% above prefasting values during refeeding. Significant changes in plasma free fatty acid and glycerol concentrations and in activity of lipoprotein lipase in adipose tissue during fasting and refeeding suggest that fatty acid mobilization and triglyceride uptake by adipose tissue of cattle adapt to great changes in energy intake. Correlations of measured blood metabolites in fasted and refed steers demonstrate that changes in rates of lipolysis and of triglyceride uptake by adipose tissue vary in a reciprocal manner.
Asunto(s)
Tejido Adiposo/enzimología , Bovinos/sangre , Ayuno , Animales , Bovinos/metabolismo , Colesterol/sangre , Ácidos Grasos no Esterificados/sangre , Glicerol/sangre , Lipoproteína Lipasa/metabolismo , MasculinoRESUMEN
In vitro experiments were conducted to determine the rates of lactate, acetate, and glucose conversions to glycerol, CO2, and fatty acids by subcutaneous adipose tissue of cattle. To study the pathway for lactate utilization as a carbon source for lipogenesis, the effect of each of four substates (lactate, acetate, pyruvate, and glucose) on the rate of conversion of the other three was determined. The rates of lactate conversion to fatty acids and to glycerol were greater than those for acetate and glucose. Acetate, however, was oxidized to CO2 at greater rates than either lactate or glucose. Acetate was used for fatty acid synthesis at greater rates than pyruvate was less than that from lactate but greater than that from glucose. Acetate additions to the incubation media decreased the synthetic rates from lactate, pyruvate, and glucose. Pyruvate decreased rates of fatty acid synthesis from glucose but slightly (not statistically significant) stimulated synthesis from lactate and acetate. Lactate decreased glucose and pyruvate utilization but had no effect upon that of acetate. Our results clearly demonstrated that lactate can be used for fatty acid synthesis as well as for glycerogenesis by bovine adipose tissue.