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I Ramírez

Publications and source records attributed to I Ramírez.

At least 19 recordsLinked to original sources
PubMed2000

Secretion of hepatic lipase by perfused liver and isolated hepatocytes.

Hepatic lipase is found in liver and in adrenal glands and ovaries. Because in adult rats, neither adrenals nor ovaries synthesize this enzyme, it is assumed that the liver is the origin of their hepatic lipase. Our aim was to study the secretion of hepatic lipase by the liver. We observed that plasma of both fed and fasted rats contained hepatic lipase activity. This activity was significantly correlated with that in the liver. Isolated livers, perfused with heparin-free medium, secreted fully active hepatic lipase to the perfusate. The addition of heparin resulted in a rapid and larger release of hepatic lipase to the perfusate. In isolated hepatocytes, heparin did not affect the secretion of hepatic lipase mass, although it increased the stability of the enzyme activity. To study the degradation of hepatic lipase by hepatocytes, protein synthesis was blocked with cycloheximide, and both secreted and intracellular hepatic lipases were analyzed by Western blotting. We observed that the amount of hepatic lipase secreted equaled the decrease of intracellular mass. The total mass of the enzyme (inside and outside the cells) remained constant, at least for 90 min. In the next experiment, 0.7 nM 125I-hepatic lipase was added to hepatocyte suspensions, and the appearance of trichloracetic acid-soluble products was analyzed. Only 12% of the radioactivity added was associated with the cells after 90 min of incubation, and less than 2% of the hepatic lipase added was degraded. Although the association was decreased in the presence of heparin, the amount of 125I-hepatic lipase degraded was not affected. Taking all these results into account, we propose a model for the continuous secretion of hepatic lipase by the liver.

Animals↗
PubMed2000

Effect of fasting on hepatic lipase activity in the liver of developing rats.

The effect of fasting on hepatic lipase was studied during postnatal development in the rat. It was found that fasting produced a significant decrease in hepatic lipase only in neonatal (1-day-old) and adult (60-day-old) rats. We studied the effect of fasting on the distribution of hepatic lipase between extracellular (heparin-releasable) and intracellular (liver-retained or residual) compartments in perfused livers, and on the secretion of hepatic lipase by isolated hepatocytes. Fasting had similar effects in neonates and adults: it decreased both the heparin-releasing and the residual activities in perfused livers, and also decreased the rate of hepatic lipase secretion by isolated hepatocytes. Finally, the effect of fasting on hepatic lipase mRNA relative abundance in developing rat livers was determined. No difference was observed among the groups studied. It is concluded that the mechanisms involved in the effect of fasting on hepatic lipase appear to be similar in neonates and adult animals and may involve the post-translational processing of the enzyme.

Aging↗
PubMed2000

Epidermal growth factor secreted from submandibular salivary glands interferes with the lipolytic effect of adrenaline in mice.

We had described that epidermal growth factor (EGF) interfered with the lipolytic effect of catecholamines in isolated adipocytes. Since catecholamines stimulate the release of EGF from submandibular salivary glands to blood plasma in male mice, we studied whether EGF affected also the lipolytic response to adrenaline in whole animals. We studied the effect of adrenaline in sialoadenectomized and sham-operated mice receiving or not a high dose of EGF following adrenaline injection. There was no difference in plasma EGF concentration between sham-operated and sialoadenectomized animals receiving saline. After adrenaline administration plasma EGF increased by 20-fold in sham-operated but did not increase in sialoadenectomized mice. Indeed, the increase was much higher (more than 100-fold) in mice receiving exogenous EGF. The effect of adrenaline on plasma concentration of both glycerol and nonesterified fatty acids was higher as lower was plasma EGF concentration. Isolated adipocytes obtained from sham-operated or sialoadenectomized mice had identical lipolytic response to adrenaline. The lipolytic response of adipocytes to isoproterenol was decreased by addition of EGF. To study whether the interference with the in vivo lipolytic effect of adrenaline had further metabolic consequences, we measured plasma beta-hydroxybutyrate concentration in plasma. There was no difference in the response to adrenaline between sham-operated and sialoadenectomized mice in spite of the difference in plasma nonsterified fatty acid concentration. Studies in isolated hepatocytes indicated that ketogenesis run at near maximal rate in this range of substrate concentration. These results suggest that EGF in the physiological range decreases the lipolytic effect of adrenaline but does not compromise further metabolic events like the enhancement of ketogenesis.

3-Hydroxybutyric Acid↗
PubMed2000

Immobilization stress induces c-Fos accumulation in liver.

Acute stress-induced injury in tissues has been revealed by both biochemical markers in plasma and microscopy. However, little is known of the mechanisms by which tissue integrity is restored. Recently, induction of early response genes such as c-fos has been reported in the heart and stomach of immobilized animals. Herein, we show that immobilization stress in mice increased plasma alanine aminotransferase activity, a marker of liver damage. c-Fos protein accumulation in liver was induced by stress after 20 minutes of immobilization and persisted for 3 hours. Immobilization also induced the release of epidermal growth factor (EGF) from submandibular salivary glands and a transient increase in EGF concentration in plasma. Although EGF administration induced a 2.5-fold increase in c-Fos mass in the liver of anesthetized mice, sialoadenectomy (which abolished the effect of immobilization on plasma EGF) did not affect the stress-induced rise in plasma alanine aminotransferase activity or liver c-Fos accumulation. Therefore, we conclude that immobilization stress induces c-Fos accumulation in liver and that this effect is not triggered by the increase in plasma EGF concentration.

Alanine Transaminase↗
PubMed1999

Mammary type I deiodinase is dependent on the suckling stimulus: differential role of norepinephrine and prolactin.

Mammary deiodinase type I (M-D1) is present only during lactation and exhibits a clear direct correlation with lactation intensity (size of litters). The present work shows that M-D1 is suckling dependent and that intervals between suckling periods no longer than 12 h are essential to maintain this activity. Moreover, we find that with only 15 min of resuckling in 12-h nonsuckled mothers, the 50% decrease in both M-D1 messenger RNA and enzymatic activity could be restored to control values. This restorative effect by suckling may involve pre- and posttranscriptional mechanisms in which norepinephrine and PRL play important roles. Norepinephrine elicits a potent stimulatory effect on M-D1 messenger RNA and enzyme activities, whereas PRL only increases M-D 1 activity and may modulate the enzyme response to norepinephrine. Oxytocin and GH had no effect. These data suggest that the adrenergic nervous system and PRL could directly participate in mammary energetic expenditure, regulating the local T3 supply.

Animals↗
PubMed1998

[Transmyocardial revascularization with laser].

Patients with severe angina pectoris, refractory to medical treatment, in which conventional revascularization (PTCA or bypass surgery) is not possible because they present advanced coronary artery disease with a poor distal bed, account for an important clinical problem due to an increasing incidence, combined with poor quality of life, an elevated risk of severe complications, repeated hospital admissions and high mortality rate. Laser transmyocardial revascularization provides a new therapeutic alternative for these patients. Although up to now there are only a few published series, with a small number of patients, the results obtained in the two ongoing multicentric studies in Europe and the United States (including more than 500 patients at present) are quite promising. It is a simple surgical procedure, but its associated mortality is not to be dismissed (in the beginning 12% and currently 5%), because patients are in an advanced evolutionary stage. In Spain this procedure has been available since April 1996 and the results have been encouraging. In our small series we have noted a significant symptomatic improvement and better quality of life.

Aged↗
PubMed1998

[Lactation performance in rural women with low bioavailability of nutrients from the regular diet].

Metabolizable energy (ME) and apparent nitrogen, fat and energy bioavailability from the habitual diet were measured in a group of lactating women from a Mexican rural community. Food intake was estimated in 40 women, age 24 +/- 3 y 3-5 m postpartum, body weight 48.7 +/- 5.4 kg and height 148 +/- 5 cm. Habitual diet was predominantly from vegetable sources based on maize (tortillas), beans, tomato, onion and chili. The daily intake was: 2224 +/- 336 kcal energy, 47.8 +/- 7.0 g protein, 44.7 +/- 11.3 fat and 408 +/- 70 g carbohydrates. Ten women were studied in balance conditions and consuming a controlled diet similar to their habitual diet. ME and apparent energy, nitrogen and fat availability were measured by metabolic balance. Milk output was measured by the test-weighing infant method and milk samples representative of 24-h were obtained for chemical analysis. Apparent digestibility of energy was 87 +/- 1.4%, from nitrogen 68.4 +/- 3.1% and 65.8 +/- 3.7 from fat. Measured ME was 1940 kcal/day. Metabolizable energy from the habitual diet by the marginally nourished lactating group was lower than the energy recommended allowance during lactation. Macronutrient's availability from the habitual diet was similar to that found in population with intake of predominantly vegetable diets and high dietary fiber content.

Adult↗
PubMed1997

Phosphorylation of nuclear proteins directs binding to salicylic acid-responsive elements.

The cis-located DNA sequence as-1 (Activation Sequence-1) from CaMV 35S promoter has been previously identified as an element that can confer inducibility by salicylic acid (SA) with immediate early kinetics. This sequence specifically binds to ASF-1 (Activation Sequence Factor-1), previously characterized in tobacco nuclear extracts. To assess whether modulation of ASF-1 binding activity can explain the activation of the as-1 sequence observed in vivo, we performed electrophoretic mobility shift assays using nuclear extracts from SA-treated and water-treated tobacco plants. Our results indicate that treatment of plants with SA increases ASF-1 binding to as-1 and to ocs, an as-1-like element from the Agrobacterium octopine synthase gene. In contrast, SA treatment has no effect on the binding of GT-1 factor to its target light-inducible box II element. Furthermore, treatment of nuclear extracts from SA-treated plants with alkaline phosphatase decreases ASF-1 binding to the as-1 element. This can be reversed by pretreatment with 10 mM NaF. Accordingly, pretreatment of nuclear extracts from control water-treated plants with ATP produces an increase in ASF-1 binding activity similar to that observed with SA. This effect of ATP is reversed by treatment with alkaline phosphatase and prevented by quercetin, a casein kinase II inhibitor. These results support the hypothesis that a nuclear protein kinase is involved in the immediate early events of transcriptional activation triggered by SA.

Arabidopsis Proteins↗
PubMed1997

Interaction between adrenaline and epidermal growth factor in the control of liver glycogenolysis in mouse.

Epidermal growth factor (EGF) stimulates glycogenolysis in mouse liver, but the effect requires concentrations that are only achieved in plasma upon adrenergic stimulation of EGF release from submandibular salivary glands. Thus, we studied the interaction between adrenaline and EGF in liver glycogen metabolism, both in whole animals and in isolated hepatocytes. Adrenaline administered to anesthetized mice stimulated both the endocrine secretion of EGF from submandibular salivary glands and the degradation of glycogen in the liver. In sialoadenalectomized mice, adrenaline administration did not increase plasma EGF concentration. In these animals, the glycogenolytic response to adrenaline was enhanced. The sensitivity of hepatocytes to adrenaline was similar in cells from sialoadenalectomized and sham-operated mice. EGF, added to isolated hepatocytes, reduced the glycogenolytic effect of adrenaline (the maximal effect but not the ED50). Adrenaline stimulated glycogen degradation through both an alpha1-adrenergic mediated Ca2+ increase and a beta-adrenergic-mediated cAMP increase. EGF did not interfere with the rise of cytosolic Ca2+ but decreased the cAMP signal. EGF did not decrease the glycogenolytic effect of phenylephrine or VP (which increased cytosolic Ca2+ but not cAMP), but EGF decreased both the glycogenolytic effect and the cAMP signal generated by glucagon or forskolin. EGF did not interfere with the glycogenolytic effect of CPT-cAMP or bt2-cAMP. The effect of EGF on cAMP was blocked by 3-isobutyl-1-methylxanthine. These results demonstrate that the effect of EGF on the glycogenolytic action of adrenaline involves interference with the generation of the cAMP signal. We suggest that EGF induces such an effect through the activation of a phosphodiesterase.

Animals↗
PubMed1996

Epidermal growth factor administration decreases liver glycogen and causes mild hyperglycaemia in mice.

Several laboratories report different effects of epidermal growth factor (EGF) on glycogen metabolism in hepatocytes. The discrepancies may be attributed to differences in the experimental conditions. It is therefore important to establish the actual effect of EGF in vivo. Because large physiological variations of EGF concentration in plasma occur in mice, we used this species to address this question. In freshly isolated mouse hepatocytes, EGF increased glycogen degradation in a dose-dependent manner. The maximal effect (36% increase over basal glycogenolysis) was smaller than maximal effects of classical glycogenolytic hormones like adrenaline or glucagon (more than 150% increase over basal). This is in keeping with the smaller effect of EGF on phosphorylase a activity. In contrast with these hormones, EGF did not inhibit glycolysis. Thus these effects of EGF in mouse hepatocytes are similar to those recently described by us in rat hepatocytes [Quintana, Grau, Moreno, Soler, Ramirez and Soley (1995) Biochem J 308, 889-894]. When administered to whole animals, EGF increased phosphorylase a activity, decreased the glycogen content in the liver and caused mild hyperglycaemia. Taking together the results obtained for isolated cells and for whole animals, we suggest that the glucosyl residues released from glycogen are used mostly by the liver rather than released to the circulation. This would be different from the action of the classical glycogenolytic hormones, adrenaline and glucagon.

Animals↗
PubMed1996

Comparison of 2 centrifugation procedures in the formalin-ethyl acetate stool concentration technique for the detection of Cryptosporidium oocysts.

A comparison between the standard formalin-ethyl acetate (FEA) stool concentration procedure (centrifugation at 400 g for 2 min) and a modification proposed to increase the recovery of Cryptosporidium oocysts (500 g for 10 min) was performed on 73 formalin-preserved stool specimens known to be positive for Cryptosporidium. False-negative results were obtained with both methods, but the increase in centrifugation time and force resulted in the detection of a higher number of oocysts and positive samples. The modified procedure had a sensitivity significantly higher than the standard method (99% compared to 86%, P = 0.0045).

Acetates↗
PubMed1996

The antilipolytic effects of insulin and epidermal growth factor in rat adipocytes are mediated by different mechanisms.

Epidermal growth factor (EGF) and insulin induced similar effects in isolated rat adipocytes. To determine whether EGF and insulin produced similar effects through the same mechanisms, we focused on lipolysis. Insulin inhibited the lipolysis stimulated by isoproterenol, glucagon (either alone or in combination with adenosine deaminase), adenosine deaminase itself, or forskolin. In contrast, EGF did not inhibit the lipolysis stimulated by forskolin or by hormones when the cells were also incubated with adenosine deaminase. The effect of insulin, but not that of EGF, on isoproterenol-stimulated lipolysis disappeared when adipocytes were incubated with 1 microM wortmannin. These results indicate that EGF and insulin affected lipolysis through different mechanisms. We observed that EGF, but not insulin, increased cytosolic Ca2+. The effect of EGF, but not that of insulin, disappeared when the cells were incubated in a Ca2+-free medium. We suggest that EGF, but not insulin, mediate its antilipolytic effect through a Ca2+-dependent mechanism which, however, do not involve Ca2+-activated protein kinase C isoforms. This is based on the following: 1) phorbol 12-myristate 13-acetate affected lipolysis in an opposite way to that of EGF; and 2) the protein kinase C inhibitor bisindolylmaleimide GF 109203X did not affect the antilipolytic action of EGF. Our results indicate that the antilipolytic effect of EGF resembles more that of vasopressin than that of insulin.

Adipocytes↗
PubMed1995

Doppler-derived gradients in normally functioning Monostrut Björk-Shiley prostheses.

In summary, reference values of Doppler gradients obtained in a large number of patients with normal-functioning mitral and aortic Monostrut Björk-Shiley prostheses are reported. It is shown that the value of the transprosthetic gradient increases with decreasing valve size in patients with aortic prostheses. No individual significant variations of the transprothetic Doppler gradient during a 3-year follow-up were observed.

Aged↗
PubMed1995

The early stimulation of glycolysis by epidermal growth factor in isolated rat hepatocytes is secondary to the glycogenolytic effect.

We have studied the relationship between the effect of epidermal growth factor (EGF) on glycogen metabolism and its effect on glycolysis, in rat hepatocyte suspensions. Although 10 nM glucagon or 10 microM adrenaline increased glycogen degradation by more than 120%, 10 nM EGF increased glycogenolysis by less than 20% in hepatocytes incubated in glucose-free medium. Both glucagon and adrenaline increased phosphorylase a activity by more than 130%; EGF increased this activity by about 30%. Under basal conditions, 65% of the glucosyl residues were released as free glucose and about 30% ended up as C3 molecules (lactate and pyruvate). Both glucagon and adrenaline decreased the proportion of glucosyl units that rendered glycolysis end-products (to 2% for glucagon and 6% for adrenaline) and increased the proportion that ended up as free glucose (to 94% and 88% of the glucosyl residues for glucagon and adrenaline respectively). EGF increased the production of both free glucose and lactate+pyruvate, but the proportion of glucosyl residues that ended up as free glucose or glycolysis end-products was unchanged. In glycogen-depleted hepatocytes incubated in the presence of 25 mM glucose, EGF affected neither glycogen deposition nor glycolysis. EGF increased cytosolic free Ca2+, and neomycin decreased both the Ca2+ signal and the glycogenolytic effect. In conclusion, our results indicate that the effect of EGF on glycolysis is secondary to the Ca(2+)-mediated stimulation of glycogenolysis in rat hepatocyte suspensions.

Animals↗
PubMed1995

Role of heterotrimeric G-proteins in epidermal growth factor signalling.

Since in 1986 it was reported that a pertussis toxin-sensitive substrate was involved in the Ca2+ signal induced by epidermal growth factor (EGF) in rat hepatocytes, much evidence accumulated to implicate heterotrimeric G-proteins in EGF action. EGF can also induce a cyclic AMP signal, but while the generation of a Ca2+ signal appears to be quite general in EGF action, the increase in cyclic AMP occurs only in few cell types. In non-transformed cell types these effects appear to involve G-proteins. EGF not only induces cell proliferation but also interacts with hormones in the short-term control of cell function in quiescent cells. Most of the known interactions are on cyclic AMP mediated hormone effects, and in many cases, the interaction between EGF and hormones involves G-proteins. Here we review the evidence accumulated in recent years that implicate G-proteins in EGF action. An understanding of the mechanisms involved may reveal new mechanisms of G-protein regulation and will contribute to our knowledge of EGF function and signal transduction.

Animals↗
PubMed1995

Protein requirements of marginally nourished lactating women.

Few experimental data regarding protein requirements of lactating women are available. This study was designed to determine the protein requirement of seven healthy lactating women from a poor Mexican community who were 2-6 mo postpartum and had a mean body mass index of 21.8 +/- 2 kg/m2. Nitrogen balances were performed at intakes of 0.8, 1.0, and 1.2 g.kg body wt-1.d-1 of a mixed protein diet (70% derived from vegetable sources). A balance at 1.2 g.kg body wt-1.d-1 of a high-quality mixed protein (80% from animal sources) was the reference. The experimental diets were designed to resemble the habitual diet in terms of energy and macronutrients. The balance responses to nitrogen intake were -35.5 +/- 12.6, -10.5 +/- 14.8, and 7.8 +/- 19.2 mg N.kg body wt-1.d-1, respectively. Equilibrium balance was attained at 178.9 +/- 25.8 mg N (1.1 g protein.kg body wt-1.d-1), close to current recommended dietary allowances, albeit the dietary protein was mostly from vegetable sources.

Adolescent↗