Alanine aminotransferase activity in mammary tissue, muscle and liver of dam rat during lactation and weaning.

Transamination reaction is the first step in the catabolism of most of the L-amino acids. Alanine is an important molecule in the inter-organ nitrogen transport, conveying them from muscle to the liver. Amino groups from this amino acid are generally first transferred to alpha-ketoglutarate in the cytosol of liver cells to form glutamate and leaving behind the corresponding alpha-keto acid analog. Measurements of the alanine aminotransferase (EC2.6.1.2.) activity were compared in liver, mammary gland and skeletal muscle in virgin, lactating and weaning dam rats. In this study liver was the principal tissue involved in alanine transamination, while muscle showed a reduction in the enzyme activity during lactation. Results indicate an increase in alanine amino-transferase activity in the mammary gland during lactation and weaning when compared with virgin rats. This suggests that mammary gland during lactation is an important extra-hepatic tissue involved in the metabolism of alanine and probably shunted into the pathways for amino group metabolism in terms of nitrogen economy.

Characterization of a fluorometric method for lipoprotein lipase.

A fluorometric assay for determining lipoprotein lipase (LPL) activity is described. Dibutyrilfluorescine (DBF) was used as substrate for the enzyme and the fluoresceine liberated by enzymatic hydrolysis of the substrate was measured. Extracts of acetone powder from adipose tissue as an enzyme source showed characteristics of lipoprotein lipase activity, i.e., inhibition by NaCl and optimum activity in alkaline pH. There was close agreement in LPL activity when the same sample was measured simultaneously using either dibutyrilfluorescine or tri[9,10(3)H]oleylglycerol as substrate. The extent of inhibition of lipoprotein lipase by NaCl was similar with both methods. The fluorometric method detected changes in LPL activity in heart and adipose tissue related to the nutritional status of the animal with the same specificity and sensitivity than did the radioactive method. The fluorometric method is as sensitive, less expensive and less time consuming than the radioactive method.

Changes in cathepsin D activity of maternal tissues during lactation and weaning in rats.

BACKGROUND: A loss of proteins from maternal tissues during lactation has been demonstrated. Protein loss could be explained by intracellular proteolysis. METHODS: Cathepsin D activity was studied in the liver, muscle and mammary gland of lactating and weaned rat dams. Lactation was studied at maximal milk production (L-14) and at the final stage of lactation (L-21). RESULTS: Basal activity (virgin rats) was three times higher in liver and mammary gland than in muscle. At both stages, L-14 and L-21, cathepsin D activity increased in liver (50%) as well as in the gland (164%), but no change was observed in muscle, when compared with controls. Twenty-four hours after litter separation, enzyme activity in the liver decreased to basal levels, while in the mammary gland cathepsin D activity showed a significant decrease but remained higher than control levels. CONCLUSION: Our results show that liver exhibits adaptive changes in the catabolism of proteins in response to the increased demands imposed by lactation on the maternal organism, and when the stimuli disappear activity returns to basal levels. The high activity in mammary gland indicates fast turnover of structures and biomolecules as an answer to the high synthetic activity in this tissue. Activity remained higher in the weaning rats, as a result of the regression process which the mammary gland is undergoing.

[Bovine and rat albumin used as a biodegradable matrix for the slow release of insulin]. / Albúmina bovina y de rata usada como una matriz biodegradable para la liberación lenta de insulina.

The daily treatment of insulin-dependent diabetes includes one or several insulin injections per day. About 50 years ago non-hormonal molecules were added to insulin in order to enhance its half life. In this report albumin microspheres, serving as a matrix for crystalline insulin, were used for delivery of insulin. They were implanted in a group of rats with alloxan-induced diabetes. Body weight, plasma glucose and insulin were measured at periodic intervals. The stability, bacterial purity and pyrogenicity of the microspheres were tested. Five days after the microspheres were implanted the mean concentrations of glucose (32.9 vs 5.7 nMol/L) and insulin (2.9 vs 20.2 microU/mL) and the body weight (217 vs 250 g) returned to values comparable to those in the non-diabetic state. They remained stable for 15 days; afterwards, glucose increased and the latter two decreased: all became abnormal 20 days after implantation. When the microspheres were implanted on three occasions in the same animal at 15 days intervals, glucose and insulin concentrations and body weight remained within the limits observed in 100 non-diabetic rats, and no antibodies against albumin or insulin were detected.

[Plasma clearance of ethanol and its excretion in the milk of rural women who consume pulque]. / Depuración plasmática de etanol y su excreción en la leche de mujeres rurales que consumen pulque.

Women from rural areas of the central plateau of Mexico drink during pregnancy and lactation a mild alcoholic beverage called pulque as a galactogogue. Ethanol present in milk could have a harmful effect on growth and development of breast-fed children. The purpose of this study was to quantify the ethanol consumed as pulque by eleven lactating rural women as well as its clearance rate in blood and milk. Mothers were separated in two groups depending upon the ethanol ingested in a single dose of pulque 0.21 +/- 0.08 g/kg of body weight (group A) and 0.44 +/- 0.11 g/kg (group B). Maximal concentration of ethanol was reached in milk at 60 minutes and almost equaled that in plasma. Both groups showed a similar clearance pattern regardless of the volume of pulque ingested. Clearance rates between groups were different: ethanol concentration in milk at 60 min were 8.4 +/- 3.0 mg/dL for group A and 26.2 +/- 7.0 mg/dL for group B. Two hours later ethanol levels were 3.6 +/- 3.4 mg/dL and 23.3 +/- 9.4 mg/dL respectively. Clearance rates were slower in mothers showing the highest concentration of ethanol in milk. The present data demonstrate that there is no differential elimination of ethanol in maternal blood and milk following ingestion of a moderate amount of pulque during lactation. The amount of ethanol received by infants through milk is relatively low and therefore it is unlikely to have harmful effects on them. Pulque consumption adds about 350 kcal/day to the customary dietary intake of these lactating women.

PIP: This work assessed the quantity of ethanol consumed in pulque, a mildly alcoholic beverage from the maguey cactus, and its clearance rate in the blood and milk of 11 rural women in the state of Mexico. 27% of women in the rural and semirural areas of central Mexico drink pulque with their meals. Pulque is believed to stimulate milk production in lactating women. The 11 women lived in the community of San Mateo Capulhuac. All exclusively breast fed their infants, who ranged in age from 3-12 months. On the study day the women breakfasted on tortillas, beans, soup and tea, accompanied by their usual quantity of pulque. During the study, samples of milk and blood were taken from the women at 60, 90, and 120 minutes after 1st ingestion of pulque. The volume of pulque consumed was measured and a sample was saved to determine the ethanol content. Mature pulque showed little variation in ethanol concentration or in total carbohydrates, independently of temperature or duration of storage. The average concentration of ethanol in pulque produced in San Mateo Capulhuac was 3.08 + or - 1.09 g/dL, with a minimum of 1.35 and a maximum of 4.70. The 11 mothers were divided into 2 groups depending on whether the maximum concentration of ethanol quantified in their blood and milk was less than 20 mg/dL (group A) or greater than 20 (group B). The mothers in group A had younger infants, lower body weights, and smaller volumes of pulque ingested on average than the mothers in group B. The average dose of ethanol ingested with pulque was .21 + or - .08 g/kg body weight for group A and .44 + or - .22 g/kg of body weight for group B. concentrations of ethanol in the blood were similar to those in milk for both groups at 60, 90, and 120 minutes. The maximum ethanol concentration occurred 60 minutes after ingestion. Maximum concentrations of ethanol in milk were 8.4 + or - 3.0 mg/dL for group A and 26.2 + or - 7.0 mg/dL for group B, slightly lower than the maximal plasma concentrations in each group. Ethanol levels in blood and milk of group A declined rapidly, with 63% of the ethanol disappearing from the blood and 52% from the milk at 120 minutes. At 120 minutes the ethanol concentration had declined by only 5.5% in the blood and 11% in the milk of group B. Pulque contributes about 350 kcal per day to these women, who have daily caloric intakes averaging 2100 kcal. The relatively small amount of ethanol taken in by infants through milk is unlikely to have harmful effects.

Human semen ribonuclease. Location, properties and inhibition by sodium dodecyl sulfate, zinc sulfate and EDTA.

Optimal conditions were established for RNase activity measurement. The enzyme was measured in human seminal plasma as well as in spermatozoa. Results suggest that sperm enzyme may come from seminal plasma contamination and that RNase may be used as a marker enzyme for seminal plasma contamination. Sodium dodecylsulfate, a reagent utilized to produce the solubilization of the spermatozoa, produced a very strong inhibition of the RNase at low concentrations (530 muM). Zinc sulfate and EDTA also produced inhibition of the RNase activity. Such inhibition may be very useful in future studies of RNA metabolism in human spermatozoa.

Electrophoretic patterns of total, nuclear, and flagellar proteins from ejaculated human spermatozoa.

By means of selective solubilization methods and slab gel electrophoresis, reproducible patterns of 19, 37, and 56 protein bands were found to be associated with nuclear, "flagellar," and total human spermatozoa, respectively. Forty protein bands were found between the molecular weight of 12,400 to 160,000 daltons. Twelve bands were associated with values lower than 12,400 daltons. The nuclear major bands were located in a low molecular weight zone, while "flagellar" ones were located in a high molecular weight zone. None of these bands represents degradation products since a) in the solubilized samples neither acrosin, chymotrypsin, nor trypsin activities were present, b) in the presence of two protease inhibitors the same electrophoretic patterns were observed, and c) labelled globins added during sample manipulation were quantitatively recovered without degradation.

Effects of ethanol consumption during pregnancy and lactation on the outcome and postnatal growth of the offspring.

Although information about the pregnancy outcome of alcoholic mothers is relatively abundant, no information is available about the effects of ethanol consumption on the infant's postnatal growth. This investigation aims to describe the physical growth of 32 infants born to mothers accustomed to drinking pulque, a mild alcoholic beverage, on a daily basis during pregnancy and lactation and to quantitate the ethanol disposed through the milk, as well as to identify cases of newborns with fetal alcohol syndrome. No full-blown cases of the syndrome were found: birth weight was similar to their non-drinking counterpart, but the relative risk of newborns to drinking mothers to have a low birth weight was 3.39. Ethanol found in milk accounted for 40 mg/day available to the infant. The postnatal growth of infants of ethanol drinkers was similar to that of controls. Further studies on their mental development are required in order to understand the extent of the effects of such a habit.

PIP: The physical growth of 32 infants born to mothers accustomed to drinking pulque, a mild alcoholic beverage, on a daily basis during pregnancy and lactation was studied. 110 clinically healthy mothers aged 15-44 years with parity from 2 to 4 were recruited during the last trimester of gestation from among the pregnant women of San Mateo Capulhuac, a village of 4000 inhabitants, where the prevalence of natural lactation is 95% up to 6 months postpartum. All were exclusively breast feeding their infants. The final sample included 94 nonsmoking mothers; of these, 32 drank 1-2 liters of pulque per day during pregnancy. A group of 62 nondrinking mothers of similar age, parity, and height for age ratio served as controls. 6 mothers received, .12-.31 gm/kg Blood and milk samples were taken at intervals up to 189 minutes after pulque had been consumed. Weight for age, weight for height, and height for age were calculated based on reference data published by the US National Center for Health Statistics (NCHS). The group of pulque-drinking mothers had an average age of 29.0 + 5.9 years, height of 151.0 + 5.0 cm while nondrinking mothers were 25.5 + 6.0 years and 149.0 + 5.2 cm, respectively. The estimated ethanol ingestion per day varied from 3.3 to 58 gm/day. No full-blown cases of the fetal alcohol syndrome were found: birth weight was similar to their nondrinking counterparts but the relative risk of newborns to drinking mothers to have a low birth weight was 3.39. Ethanol found in milk accounted for 40 mg/day available to the infant. Compared with the NCHS reference both groups had significantly lower mean length and weight from 3 months of age (p .001). This was reflected by a low percentage of infants with adequate weight and length/age ratios (47 and 58%, respectively). More than 90% ad an adequate weight/length ratio.

Lipid content and lipoprotein lipase activity in skeletal muscle of lactating and weaned rats.

The aim of the investigation was to study the changes in lipid content and lipoprotein lipase (LPL) activity of skeletal muscle of lactating and weaned rats, in order to gain insight on the role of skeletal muscle in the metabolism of triacylglycerols not used by the mammary gland after weaning. Sprague-Dawley rats fed ad libitum were killed 0, 8, 12, and 24 h after litter separation on the 14th day of lactation. Electron microscopy, as well as determinations of the total fat and phospholipid content were performed on muscles of the right hind limb. Lipoprotein lipase activity was determined in extracts of acetone powder of skeletal muscle, mammary gland, and adipose tissue using dibutyryl fluorescine as substrate. Fat droplets were identified in the muscle interfiber spaces of weaning rats. Muscle total fat and phospholipids were higher in weaned than in lactating rats. After litter separation, lipoprotein lipase activity increased significantly in muscle and in adipose tissue (fourfold), while activity in the mammary gland decreased. The increased muscle lipoprotein lipase activity in the weaned rats seems to be associated with the higher content of fat and with the presence of fat droplets.

A high dietary lipid intake during pregnancy and lactation enhances mammary gland lipid uptake and lipoprotein lipase activity in rats.

Rats fed a diet with high fat concentration produce larger amounts of milk with a higher lipid concentration than rats fed a lower fat diet. This investigation was designed to study the relationship between dietary fat intake, mammary gland lipid uptake and lipogenesis in rat dams fed, during pregnancy and lactation, one of two purified diets, with equal energy density, containing 2.5 (LL) or 20 g fat/100 g diet (HL). Milk lipid concentration and fatty acid composition were determined at d 14 of lactation. Mammary gland lipogenesis, lipoprotein lipase (LPL) activity and the uptake of [1-(14)C]triolein by the mammary gland and its transfer to the pups was measured. The intestinal absorption of oral (14)C-lipid, (14)CO(2) production and the amount of (14)C-lipid transferred to the pups (milk clot + pups carcass) were significantly higher in the HL group than in the LL group (P < 0.05). Mammary gland lipogenesis was 75% lower and LPL activity was 30% higher in the HL group (P < 0.05). Medium-chain fatty acids (C6-C14) excretion was 46% lower and that of long-chain fatty acids was 142% (P < 0.001) higher in the HL group than in the LL group. The higher milk lipid excretion in the rats fed a high-fat diet resulted from a larger uptake of dietary lipid by the mammary gland, indicated by a larger transfer of (14)C-lipid to the pups and by a higher LPL activity in the mammary gland.

Changes in the composition of mammary tissue, liver and muscle of rat dams during lactation and after weaning.

This investigation was conducted to evaluate the changes in the total content of protein and RNA in liver and muscles of rat dams before and after acute separation from their litters. Groups of 8-12 rats fed ad libitum were killed on the 12th (group L12) and 20th d (group L20) of lactation and on the 1st (group W1) and 7th d (group W7) after weaning. Nonpregnant, nonlactating rats paired for age served as controls. Dry matter, protein, DNA and RNA levels of the mammary gland, liver and muscles of the right hindlimb were determined. Wet weight and total organ or tissue protein, DNA and RNA were higher in mammary glands of L12 and L20 than in age-matched controls. These values were lower in groups W1 and W7 than in the lactating groups. No changes were noted in the total liver protein or DNA content, but total liver RNA was greater in groups L12 and L20 than in controls or group W1. Total muscle dry matter, DNA and RNA were significantly lower in groups L12 and L20 than in groups W1 and W7. Muscle protein content increased progressively from the 12th to 20th d of lactation to a peak in group W1, and it decreased to values found in age-matched controls in group W7. Although the muscle protein mass of the hindlimb during peak lactation (group L12) was only 63% of that in nonlactating control rats, within 1 d of weaning it was significantly higher than in nonlactating rats. Similar changes in RNA suggest that these changes in protein content are related to an adaptative mechanism designed to handle the surplus of plasma amino acids not used by the mammary gland after weaning.