Fermín Sánchez-Medina

Acid-soluble nucleotides of human milk at different stages of lactation

The acid-soluble ribonucleotides of human milk were measured by enzymic and ion-exchange chromatographic procedures at different stages of lactation. Human colostrum and milk contained CMP, AMP, GMP, UMP, GDP-mannose, UDP-N-acetyl-glucosamine, UDP-N-acetyl-galactosamine, UDP-glucose, UDP-galactose, UDP and other minor nucleotides. Cytidine and adenosine derivatives were present in relatively higher amounts than in milk from ruminant species. The nucleotide concentration decreased with advancing lactation. Human milk at 3 months of lactation contained about 10 mumol/100 ml nucleotides, which represented about 75% of the amount of nucleotides present in human colostrum. Human milk did not contain orotic acid. The UDP-glucose/UDP-galactose ratio was constant during lactation and was similar to that of milks from ruminant species.

Evolution of gluconeogenic enzyme activities during starvation in liver and kidney of the rainbow trout (Salmo gairdneri)

1. There was a general increase in the activities of enzymes involved in gluconeogenesis in liver and kidney of rainbow trout, Salmo gairdneri, during the second month of starvation. 2. The need of gluconeogenesis during the first month of the starvation period was probably minimal because of the utilization of liver glycogen as a source of blood glucose. 3. The decline of fat was more pronounced than that of protein total content in absolute values, suggesting that lipid reserved were the main sources of energy during starvation.

Effect of stress on liver and muscle glycogen phosphorylase in rainbow trout (salmo gairdneri)

Abstract 1. 1. In rainbow trout ( Salmo gairdneri ), liver and muscle glycogen concentrations decreased in response to severe physical disturbance, liver glycogen recovered 30 min after the treatment, probably due to an increase in gluconeogenesis. 2. 2. The activity of glycogen phosphorylase in muscle and liver was increased during disturbance, the former being affected by AMP, the latter not. 3. 3. Lactate and glucose concentrations in blood increased in the early stages of the treatment. Lactate was probably converted into glucose to be used as the source of energy during the disturbance.

Changes in the Protein Fractions of Human Milk during Lactation

The changes in the absolute and relative contents of alpha- and kappa-caseins, lactoferrin, alpha-lactalbumin, serum albumin and lysozyme in human milk have been studied through the period of lactation. Protein fractions of 209 samples were analyzed by a discontinuous polyacrylamide gel electrophoresis method. beta- and kappa-caseins decreased from colostrum to mature milk although their relative percentages remained constant. They accounted for 12-15 and 9-13% of the total protein in human milk, respectively. Lactoferrin decreased in absolute and relative amounts with advancing lactation. This protein represented 32-19% of the human milk proteins. alpha-Lactalbumin slightly decreased from colostrum to transitional milk but there was an increase in mature milk by 16-30 days. The percentages of this protein in colostrum and mature milk were approximately 23 and 30%, respectively. Serum albumin also decreased with advancing lactation, but the differences between transitional and mature milk were not statistically significant. Lysozyme increased from colostrum to mature milk both in relative and absolute amounts. Colostrum contained about 262 micrograms/ml, and mature milk 1,246 micrograms/ml, representing 1.5 and 12.1% of total milk proteins.

Hormonal effects on the liver glucose metabolism in rainbow trout (Salmo gairdneri).

1. Glucagon, adrenaline and dibutyril cyclic AMP increased the release of glucose to the medium during incubation of liver slices from rainbow trout (Salmo gairdneri) while insulin had no effect. 2. Glycogen content decreased only slightly after cyclic AMP addition and even increased in the presence of glucagon and adrenaline. Consequently, the release of glucose was due mainly to gluconeogenesis. 3. This is corroborated by the reduction of glucose liberation in presence of alpha-cyanocinnamate, an inhibitor of gluconeogenesis.

STIMULATION OF RAT KIDNEY GLUCONEOGENIC ABILITY BY INHIBITION OF LIVER GLUCONEOGENESIS

1. Introduction It is generally recognized that the liver is the major gluconeogenic tissue concerned with the regulation of glycemia because of the relative organ size as compared to that of the kidney cortex. In fact, glucose formed by the kidneys should provide only a small fraction of the blood glucose under normal physiological conditions, considering the renal removal of lactate, the main gluconeogenic precursor [1] . However, Owen et al. have reported that renal glucose production after prolonged fasting in obese patients approached that of the liver, which is decreased in these conditions [2]. On the other hand, Niederland et al. showed that kidneys of partially hepatectomized rats synthetized more glucose both in vitro and in vivo than the sham-operated animals [3] and Jones et al. reported a significant increase in net renal glucose production in fasted anesthetized dogs in which liver gluconeogenesis was inhibited by ethanol administration [4]. In previous work from this laboratory it has been reported that a stimulation of rat kidney phosphoenol- pyruvate carboxykinase activity in experimental liver disease induced by galactosamine when hepatic gluconeogenesis was severely impaired. In these conditions, the rise in renal phosphoenolpyruvate carboxykinase activity was accompanied by a slight but significant increase in renal gluconeogenic ability [5] . Taking these findings altogether it could be assumed that kidneys play an important role in glucose homeostasis when liver functional capacity diminishes. In this context we have undertaken the

Involvement of gluconeogenesis in the hyperglycemia induced by glucagon, adrenaline and cyclic AMP in rainbow trout (Salmo gairdneri)

Abstract 1. 1. The injection of adrenaline or dibutyril cyclic AMP to rainbow trout, Salmo gairdneri was followed by an increase in blood glucose and lactate. 2. 2. The injection of glucagon was followed by hyperglycemia without increase in blood lactate. 3. 3. None of these treatments produced significant alterations in liver glycogen. 4. 4. The simultaneous injection of dibutyril cyclic AMP and α-cyano-hydroxy-cinnamate resulted in a substantially smaller increase in blood glucose concentration than the injection of dibutyril cyclic AMP alone. 5. 5. These results show that hyperglycemia was due to gluconeogenesis under these circumstances, confirming the key role of this process in the trout.

Plasma Polyunsaturated Fatty Acids in Liver Cirrhosis With or Without Chronic Hepatic Encephalopathy: A Preliminary Study

Fatty acid levels (from C14:0 to C22:6n3) in plasma lipid fractions were prospectively studied in 11 cirrhotic patients with chronic hepatic encephalopathy and compared with those in 23 cirrhotic patients without chronic hepatic encephalopathy with similar age, sex distribution, and liver and nutritional status, and in 11 age- and sex-matched, healthy subjects. Plasma lipid fractions were separated by thin-layer chromatography and fatty acids were identified by capillary column gas-liquid chromatography. Total n6 polyunsaturated fatty acid plasma levels were lower in cirrhotic patients--with and without chronic hepatic encephalopathy--than in control subjects. In addition, arachidonic acid levels, both in total lipids and fractions, were lower in patients with than in those without chronic encephalopathy. On the other hand, a selective decrease of plasma docosahexaenoic acid (a major component of neuronal membranes) was observed in those patients with chronic encephalopathy as compared with both control and cirrhotic subjects without chronic encephalopathy. These findings may be due to various mechanisms. Differences in long-chain polyunsaturated fatty acid content in fish- and meat-restricted diets partly may account for these findings. However, it could be speculated that polyunsaturated fatty acid biosynthesis may be reduced further in patients with chronic hepatic encephalopathy because of either a decrease in portal essential fatty acid extraction in the postabsorptive phase due to portal-systemic shunting or to the effect of protein-restricted diets. Furthermore, the finding of low plasma docosahexaenoic acid in these patients raises the possibility that this deficiency might be an additional pathogenic factor in chronic hepatic encephalopathy.

The mechanism of the increase in renal ammoniagenesis in the rat with acute metabolic acidosis

Chronic metabolic acidosis causes several biochemical changes in the rat kidney: perhaps the most prominent of these is the increase in ammonia production from glutamine and the increase in activity of phosphate-dependent glutaminase [ 11. The changes with acute acidosis are less clear and although there is an early increase in total renal production of ammonia [2] no enzymatic change has been described to explain this. Since changes in pH and bicarbonate alone could not be the stimulus for this renal metabolic adaptation, we looked for and demonstrated the presence of a factor in the plasma of acutely acidotic rats which stimulated glutamine uptake and ammoniagenesis by renal slices from normal rats [3]. We now describe a possible mechanism for this ammoniagenie response to acute acidosis in the rat. Our studies have focussed on the kidney since although the liver, brain and intestine metabolise glutamine, none of these organs show any enzymatic adaptation in response to metabolic acidosis.

Metabolic changes induced by urethane-anesthesia in rats

1. Fasting hyperglycemia was observed in urethane-anesthetized rats. No significant changes had been observed in fed animals. The effect is dose-dependent, being ineffective doses lesser than 1.4 g/kg of body weight. 2. Urethane originates a rise in glycemia during the first 10 min of anesthesia followed by control values at 30 min, and a latter hyperglycemic phase for more than 60 min that remain at 2 hr. 3. The negative correlationship between plasma glucose, lactate and amino acid levels suggest that gluconeogenesis may be the main responsibility of the observed hyperglycemia during the first phase, but it is possible that during the second phase a decrease in the consumption of glucose may take place as a consequence of the competitive effects of ketone bodies increased during the first 30 min of anesthesia. 4. We postulate that the mechanism of the hyperglycemic response to urethane is a sympathetic response with release of catecholamines both in the liver and in the adrenal gland which enhances gluconeogenesis and lipolysis.