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Biomedical subjects

F J Moreno

Publications and source records attributed to F J Moreno.

At least 55 records · Page 3Linked to original sources
PubMed1987

Glycerogenic pathway in the rat mammary gland.

The conversions of the isotope from [1-14C]acetate, [1-14C]glucose and [6-14C]glucose to CO2 and fatty acids in acini isolated from the mammary gland at the peak of lactation were studied. The incorporation of [9,10-3H]oleate into triacylglycerol synthesis as single substrate or in combination with substrates that potentially may supply trioses-phosphate was also determined. The rate of fatty acid synthesis paralleled the activity of the hexose monophosphate shunt and the data obtained reveal that little carbon from triose stage enters the phosphohexose pool via reversal of glycolytic pathway. The results are interpreted in terms of the NADPH producing systems and phosphoenolpyruvate carboxykinase activities as well as the possible implications in lipogenic and glyceroneogenic pathways.

Acetates↗
PubMed1986

Nutritional and hormonal regulation of malic enzyme synthesis in rat mammary gland.

Cytosolic malic enzyme was purified from rat mammary gland by L-malate affinity chromatography. The pure enzyme obtained was used to produce a specific antiserum in a rabbit. Relative synthesis of malic enzyme in the mammary gland of mid-lactating rats was 0.097%, measured by labelling the enzyme in isolated acini. When food was removed, malic enzyme synthesis decreased to 35% and 20% of the control value at 4 and 6 h respectively. Incorporation of [3H]leucine into soluble proteins was constant during the first 6 h of starvation. When lactating rats (maintained with their pups) were starved for 24 h and then re-fed, the relative rate of enzyme synthesis increased 2.5-, 4-, and 4.5-fold at 3 h, 6 h and 18 h respectively after initiation of re-feeding. The relative rate of malic enzyme synthesis was about 50% of normal at 15 h after weaning, whereas the rate of synthesis of soluble proteins did not change. Administration of bromocriptine or adrenalectomy of lactating rats decreased the relative rate of synthesis of malic enzyme by 40% or 30% respectively; these effects were counteracted by hormone supplementation. Hormone therapy also caused an increase in the rate of incorporation of [3H]leucine into soluble proteins and in malic enzyme activity.

Adrenalectomy↗
PubMed1985

Effect of prolactin and glucocorticoids on P-enolpyruvate carboxykinase activity in liver and mammary gland from diabetic and lactating rats.

The administration of 2 bromo-alpha-ergocryptine, to reduce serum prolactin decreased the activity of cytosolic P-enolpyruvate carboxykinase (GTP) (EC 4.1.1.32) about 50% in both liver and mammary gland of lactating animals. Adrenalectomy had similar effects to those of bromo-alpha-ergocryptine. In contrast, there was a 50% increase in enzyme activity in the mammary gland of diabetic, lactating rats and a 10-fold increase in liver as compared with normal rats. P-enolpyruvate carboxykinase activity in mammary gland as liver is coordinately regulated by prolactin, glucocorticoids and insulin.

Adrenal Glands↗
PubMed1985

Influence of starvation/refeeding transition on lipogenesis and NADPH producing systems in adipose tissue, mammary gland and liver at mid-lactation.

Glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and malic enzyme are enzymes involved in NADPH synthesis. Their specific activities and glucose utilization by isolated cell systems have been measured in adipose tissue and mammary gland from mid-lactating rats during starvation/refeeding transition. Starvation for 24 h produced a 75-90% decrease in the specific activities of these NADPH producing systems in mammary gland. Acinis isolated from the gland of starved rats had a lower production of CO2, fatty acids and triacylglycerols from (1-14C)glucose and (6-14C)-glucose than did gland from control rats. The activities of these enzymes in adipose tissue were very low and did not undergo any measurable alteration with starvation. The ability of adipocytes from well fed lactating rats to synthesize fatty acids from (1-14C)glucose was completely blocked. However, starvation is accompanied by a marked decrease in glucose incorporation into triacylglycerols. All the variations observed "in vivo" and "in vitro" in mammary gland returned almost to normal values by refeeding the starved lactating rats.

Adipose Tissue↗
PubMed1985

Permeability and changes in carbohydrate moiety in rat endometrial epithelium during oestrus as revealed by ruthenium red.

We have used four different methods of ruthenium red (RuR) staining (RuR-Lumen, RuR-Glu, Glu/CB-RuR and RuR-OsO4) in order to study the permeability of the uterine epithelial cells of the rat during oestrus. The best results were obtained with the application of RuR-OsO4, and this test was used for the statistical analysis. In addition, the dialyzed iron and diamine test (HID) techniques corroborated the nature of the acid glycoconjugate part of luminal surface of the uterine epithelium stained by the RuR. By means of the Thiéry technique we detected the presence of neutral glycoconjugates. These results, together with statistical analysis, lead us to suggest a) that the uterine epithelial cells present a greater permeability to RuR during early oestrus (Stage II) than during the later part (Stage III) and b) that sulphate group-bearing glycoconjugates decrease in the course of the oestrus, whereas the neutral glycoconjugates remain constant.

Animals↗
PubMed1985

Silver staining of the nucleolar organizer regions (NORs) on Lowicryl and cryo-ultrathin sections.

Nucleolar organizer region (NOR) silver staining was applied to sections of fixed material. A positive reaction on cryo-ultrathin sections was found as well as on semithin and ultrathin Lowicryl sections. Repeatable staining that was easy to control was obtained by a one-step procedure after aldehyde-Carnoy fixation. Fixation of the material by formaldehyde and glutaraldehyde alone in cacodylate buffer also maintained reaction selectivity when ammonium chloride was used after fixation. Enzymatic digestion by pronase, RNase A, DNase I, or micrococcal nuclease was applied to ultrathin Lowicryl sections. Pronase digestion removed the silver-stained proteins, whereas digestion by the nucleases did not. A routine procedure is proposed for easy NOR silver staining of sections that preserves a good tissue ultrastructure and is also compatible with cytochemical and immunological investigations.

Acrylic Resins↗
PubMed1984

Fatty acyl-CoAs as feedback regulators of hexose monophosphate shunt in rat adipocytes.

The high basal glucose utilization through hexose monophosphate shunt found in our experimental conditions were almost completely inhibited by oleate, octanoate and caproate. However, the inhibition of glucose oxidation due to butyrate was about 50% whereas ketone bodies and acetate did not inhibit. The rate of triacylglycerol formation was not significantly modified with the above organic acids except oleate that presented a 5-fold increase on labeling incorporation into lipids. Oleate inhibition of glucose oxidation was completely prevented by the NADPH oxidant menadione. There was no inhibition by octanoate, caproate, butyrate or ketone bodies of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase or malic enzyme in adipose tissue homogenates. In contrast, specifically glucose-6-phosphate dehydrogenase was inhibited by oleoyl-CoA. The oleoyl-CoA inhibition was prevented by enzyme preincubation with low NADP concentration. The data lend further support for the hypothesis that fatty acids and NADP fulfill an important role in the modulation of the hexose monophosphate shunt activity.

Acyl Coenzyme A↗
PubMed1984

Forskolin inhibition of glucose metabolism in rat adipocytes independent of adenosine 3',5'-monophosphate accumulation and lipolysis.

Addition of forskolin (1 microM) to rat adipocytes incubated with insulin and 0.2 mM glucose inhibited glucose metabolism in the absence of any significant stimulation of either cAMP accumulation or lipolysis. The action of forskolin was in contrast to that of isoproterenol, since forskolin inhibited [1-14C]glucose conversion to total lipid, whereas isoproterenol had the opposite effect. Elevation of the medium glucose concentration to 10 mM reversed the inhibitory effects of forskolin on glucose metabolism. The ability of forskolin to inhibit glucose metabolism was observed whether glucose was labeled in the 1 or the 6 position. The results of the present study suggest that forskolin affects glucose metabolism independently of adenylate cyclase activation.

Adipose Tissue↗
PubMed1983

Effects of pertussis toxin treatment on the metabolism of rat adipocytes.

The protein toxin present in Bordetella pertussis vaccine blocks the inhibition of adenylate cyclase by prostaglandins and adenosine which may be secondary to ADP-ribosylation of an inhibitory guanine nucleotide-binding protein. The stimulatory effects of alpha 1-catecholamine agonists on 32P uptake into phosphatidic acid and phosphatidylinositol in isolated rat adipocytes were virtually abolished by pertussis toxin treatment. In contrast, the stimulatory effects of insulin were increased in adipocytes after pertussis toxin treatment. Pertussis toxin treatment did not alter insulin stimulation of glucose oxidation and actually increased glucose conversion to lipid. Basal lipolysis was elevated in adipocytes by pertussis toxin treatment but not basal cyclic AMP. However, the increases in cyclic AMP and lipolysis due to low concentrations of catecholamines and forskolin were markedly potentiated by pertussis toxin treatment. The inhibitory effects of adenosine on cyclic AMP stimulation due to catecholamines were abolished by pertussis toxin. These data indicate that pertussis toxin selectively interferes with inhibition of cyclic AMP accumulation in rat adipocytes by adenosine, potentiates the increases in cyclic AMP due to catecholamines, increases the stimulatory effects of insulin on adipocyte metabolism, and interferes with alpha 1-catecholamine stimulation of phosphatidylinositol turnover.

Adenylate Cyclase Toxin↗
PubMed1983

Coordination of glucose metabolism and NADPH formation in the adipose tissue and mammary gland during the lactation-weaning transition.

The capacity of fat cells from 48-hour weaned mid-lactating rats to synthesize fatty acids from (1-14C)-glucose and (6-14C)-glucose was markedly increased compared to adipocytes isolated from mid-lactating rats kept with their pups. Pentose shunt activity and glycolytic flux were also markedly increased in fat cells from weaned mid-lactating rats. Isolated fat cells from mid-lactating weaned rats, incubated with oleate and substrates that potentially may supply triosephosphate, showed a significantly stimulated triglyceride synthesis as measured by (1-14C)-oleate incorporation into the acyl moiety. The specific activities of malic enzyme, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were measured in adipose tissue and mammary gland extracts during pregnancy, lactation and weaning. These enzyme activities in the mammary gland increased in parallel from the beginning of pregnancy to the end of lactation. After weaning there was a sharp decrease in enzyme activities to levels similar to those found in mammary glands from virgin rats. In contrast, the activities of the lipogenic enzymes in adipose tissue were very low during lactation but increased rapidly after weaning.

Adipose Tissue↗
PubMed1983

Presence of cytosolic phosphoenolpyruvate carboxykinase activity in rat mammary gland.

The cytosolic P-enolpyruvate carboxykinase activity was measured in mammary gland and liver of animals at all stages of the reproductive cycle. The specific activity of this enzyme was almost absent in the mammary gland of virgin rats. Different pattern of P-enolpyruvate carboxykinase activity was obtained in liver and mammary gland during lactation cycle. The specific activity of the enzyme increased more than 40-fold in mammary gland and 2-fold in liver during the transition from mid-pregnancy to mid-lactation. Weaning of mid-lactating rats for 48 h resulted in an abrupt change in the enzyme activity in mammary gland while there was a small change in liver. In all the experiments performed, the activity of P-enolpyruvate correlates inversely with the plasma insulin levels described for the lactogenic process.

Animals↗
PubMed1982

Roles of cAMP and free fatty acids on the activity of the hexose monophosphate shunt.

Basal glucose utilization by isolated rat adipocytes have been found to be increased ten times in the presence of certain preparations of albumin. In these conditions the effects of several adrenergic agonists and related compounds on glucose oxidation, lipolysis and triacylglycerol synthesis in isolated fat cells have been studied. Oxidation of D(1(-14)C) glucose in rat adipocytes was almost completely inhibited by norepinephrine and isoproterenol when added to incubated fat cells. Agents able to modify intracellular AMP cyclic levels by different mechanisms display a similar ability to imitate the effect of lipolytic agents. The inhibition of glucose oxidation due to norepinephrine and isoproterenol is partially reverted by propanolol. Under the same conditions in which norepinephrine and isoproterenol markedly reduced glucose conversion to 14CO2, they stimulated lipolysis and triacylglycerol synthesis and in this case propanolol also reverted those actions. However, in these experimental conditions, norepinephrine and isoproterenol did not raise cAMP levels 10 min after hormone addition. It is concluded from these data that glucose oxidation through hexose monophosphate shunt, activation of lipolysis and triacylglycerol synthesis in isolated rat fat cells by lipolytic agents occurs by a mechanism(s) that depend(s) on intracellular free fatty acids levels.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1982

[Effect of hydrogen peroxide on lipolysis and glucose metabolism in isolated rat adipocytes].

Rat fat cells show a high ability to eliminate H2O2, exogenously added or produced by the glucose/glucose oxidase system. The disappearance of H2O2 is a function of both time and the number of cells in the incubation medium. H2O2, like insulin, has been found to be antilipolytic even in the absence of glucose in the medium. Treatment of fat cells with ditio-(bis)-nitrobenzoic acid abolished this antilipolytic ability. H2O2 stimulated the hexose monophosphate shunt, and fatty acids and glicerides glycerol synthesis in rat fat cells. Flux through the hexose monophosphate shunt would then be a result of the demand for NADPH, for the fatty acids synthesis. These findings indicate that peroxidase can mimic the actions of insulin on glucose utilization and lipolysis.

Adipose Tissue↗
PubMed1980

Prematurity in the rat. I. Fuels and gluconeogenic enzymes.

Changes in liver glycogen, plasma glucose, lactate, alanine and glycerol concentrations during the first 2 h after delivery by cesarean section in term and preterm rats were studied. Liver glycogenolysis initiated in both groups just after delivery, the rates of glycogenolysis being about 50 mumol/h/g wet weight. Glycogen breakdown came along with very low plasma glucose concentrations suggesting that glycogenolysis could be promoted by neonatal hypoglycemia. Plasma alanine concentrations decreased in both groups at similar rates suggesting that alanine utilization was enhanced during the first 2 h of extrauterine life. The plasma glycerol concentration increased in preterm rats but no changes were observed in term rats. The plasma lactate concentration progressively decreased during the first 2 h in term rats. However, preterm rats showed no changes in plasma lactate concentrations during the first hour, then decreased during the second hour at similar rates to those observed in term rats. These results suggest that preterm rats showed a transient resistence to lactate utilization at delivery which was overcome during the first hour of extrauterine life.

Alanine↗
PubMed1980

Prematurity in the rat. II. Effect of hypothermia.

The time-courses of liver glycogen, plasma glucose, lactate, alanine and glycerol concentrations in term and preterm rats undergoing hypothermia (30 degrees C) during the first 2 h after delivery have been studied. Hypothermia prevented liver glycogenolysis and the neonatal decrease of plasma glucose concentration in term and preterm rats during the first 2 h after delivery. Hypothermia decreased plasma glucose, lactate and alanine utilization but increased plasma glycerol concentration. These results suggest that hypothermia blunts the utilization of the main metabolic substrates but increases brown adipose tissue lipolysis for thermogenesis.

Adipose Tissue, Brown↗
PubMed1979

Effects of bilirubin on fat cell metabolism and lipolysis.

Bilirubin (0.45 mM) inhibited lipolysis and stimulated [1-14C]glucose oxidation by rat fat cells in the presence of an equimolar concentration of bovine serum albumin. Bilirubin was an insulinlike agent with respect to inhibition of lipolysis and stimulation of glucose oxidation. There was a marked inhibition of adenylate cyclase activity of fat cell ghosts by 0.001--0.1 mM bilirubin in the absence of albumin, which was largely reversed by the addition of albumin. Although both bilirubin and free fatty acids bind to albumin, the primary binding sites appear to be separate. The effects of bilirubin at a molar ratio to albumin of 2 or less were not influenced by free fatty acid-to-albumin ratios up to 3. Triglyceride lipase activity of partially purified rat fat cell homogenates was inhibited by bilirubin in the presence of an equimolar concentration of bovine albumin. These data indicate that the antilipolytic action of bilirubin is probably due to direct inhibition of triglyceride lipase through a mechanism that does not involve competition with free fatty acids for binding to albumin.

Adenylyl Cyclase Inhibitors↗