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Biomedical subjects

E Herrera

Publications and source records attributed to E Herrera.

At least 127 records · Page 7Linked to original sources
PubMed1988

Human sperm-cervical mucus interaction and the ability of spermatozoa to fuse with zona-free hamster oocytes.

Samples of semen and cervical mucus were provided by 18 couples. Cervical mucus was obtained for each day possible and stored at 4 degrees C until all the samples were collected. Flat capillary tubes were loaded with the mucous samples and spermatozoa from the husband's semen sample were allowed to migrate through the cervical mucus (3 cm column) into culture medium. The spermatozoa recovered after migration through cervical mucus were assayed in vitro with zona-free hamster oocytes. Control experiments were carried out using spermatozoa from the same semen sample but prepared by the swimming-up technique. Altogether, 557 eggs in the control group and 1236 eggs in the experimental group were analysed, and the results demonstrated that the % of sperm penetration, the mean number of sperm decondensations per penetrated egg and the mean number of spermatozoa adhering per egg all had higher values (P less than 0.05) for the control samples than for the experimental samples. We suggest that cervical mucus modifies human spermatozoa, as measured by their interaction with zona-free hamster oocytes.

Animals↗
PubMed1988

Utilization of glucose, alanine, lactate, and glycerol as lipogenic substrates by periuterine adipose tissue in situ in fed and starved rats.

A technique previously used to study placental transfer in pregnant rats, consisting of labeled tracer infusion through the left uterine artery, was employed to determine the utilization of lipogenic substrates by periuterine adipose tissue in the fed and 48-hr starved female virgin rat. After 20 min infusion with either D[U-14C]glucose, L-[U-14C]alanine, [U-14C]glycerol or L-[U-14C]lactate, the radioactivity appearing in periuterine adipose tissue 14C-labeled lipids from the left side was always higher than that appearing in tissue from the right side. Negligible radioactivity was detected in the tissue from either side when the infusion was done with non-metabolizable derivatives such as L-[1-14C]glucose or [1-14C]alpha-aminoisobutyric acid. Simultaneous infusion of L-[U-14C]alanine and an alanine transaminase inhibitor (aminooxyacetic acid) into the left uterine artery completely blocked the conversion of the alanine transaminase inhibitor (aminooxyacetic acid) into the left uterine artery completely blocked the conversion of the alanine into periuterine adipose tissue 14C-labeled lipids. The utilization of the infused substrate for fatty acids and glyceride-glycerol synthesis by the tissue was quantified by taking into account the infused radioactivity, the difference in the amount of 14C-labeled lipids appearing in periuterine adipose tissue on the left and the right sides, the arterial plasma concentration of the studied metabolite, and the uterine horn blood flow. In fed animals, the highest fatty acid synthesis was found with lactate, followed by glucose, alanine, and glycerol. This process was intensely decreased with all the substrates in 48-hr starved rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1987

Effects of chronic ethanol treatment on amino acid uptake and enzyme activities in the lactating rat mammary gland.

The effects of chronic ethanol consumption on mammary gland amino acid uptake at the 15th day of lactation in the rat have been studied. Ethanol treatment decreased the arterial levels of Ala, Asp, Gly, Pro, Lys and Met, and increased those of Gln and alpha-amino-butyrate. Chronic ethanol treatment produced a decrease in the arteriovenous differences of Asp, Thr, Arg, Met and Phe, and increased those of Ala, Gln, Gly, Pro and Tyr. The combination of the calculated values of relative extraction and the arteriovenous differences indicate that these alterations in amino acid uptake are related to changes in the transport process for Ala, Asp, Thr, Pro, Arg, Asn, Gly, Tyr, and Phe, and that the alterations in the arteriovenous differences of Gln, Lys and Met are due to the affected arterial levels of these amino acids. Measurements of enzymatic activities in the mammary gland show that these alterations in the amino acid transport process cannot be ascribed to changes in the gamma-glutamyl cycle.

Amino Acids↗
PubMed1987

Chronic and acute ethanol impair the in vivo glucose uptake by lactating rat mammary gland.

Chronic and acute ethanol treatments increased the 3-hydroxybutyrate uptake by lactating rat mammary gland as a consequence of its high afferent concentration, without changing its relative extraction. The uptake of glucose was inhibited in the ethanol treated animals due to intrinsic alterations in the mammary gland metabolism as indicated by the decreased relative extraction and unchanged afferent concentration. These results would suggest that the elevated uptake of ketone bodies in ethanol-treated rats can be responsible, at least in part, for the decrease in glucose uptake by lactating rat mammary gland, although other direct effects of ethanol may be implied.

3-Hydroxybutyric Acid↗
PubMed1987

Effects of chronic ethanol consumption on lactational performance in rat: mammary gland and milk composition and pups' growth and metabolism.

The effects of chronic ethanol consumption on lactational performance were studied in the rat on day 15 after delivery by determining mammary gland and milk composition, while growth rate and metabolic parameters were studied in pups coming from untreated mothers but being suckled by ethanol-treated mothers. Alcohol treatment increases the dry weight and lipoprotein lipase activity in the mammary gland, and decreases both absolute and relative mammary gland weight and mammary tissue protein content. The triacylglycerol concentration of milk from treated dams is increased, whereas lactose concentration is decreased in comparison to milk from controls, although the total energy content of milk from alcohol-treated dams is higher than that from controls. Ethanol treatment produces a reduction of daily milk production. Pups nursed by alcoholic mothers show a retarded growth with respect to pups nursed by untreated mothers. Furthermore, they present a reduction in the levels of circulating glucose, insulin, glycerol and free fatty acids, whereas an increase in acetoacetate and in urea levels is observed. Pups from alcoholic mothers show reduced glycogen concentration in the liver while the protein content is increased. Plasma free amino acids in pups nursed by alcoholic mothers are lower than in control pups, the differences in Ala, Glu+Gln, Gly, Pro, 4-OH-Pro, citrulline, Cys, Tyr, Phe and the combined total values being statistically significant. We may therefore draw the conclusion that chronic ethanol treatment impairs lactational performance affecting mammary gland function as shown by the decline in milk production and altered milk composition.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Drinking↗
PubMed1987

Lipid metabolism in pregnancy.

On the basis of bibliographic references and new own data, major adaptations of lipid metabolism occurring at late gestation are reviewed. Maternal hypertriglyceridemia at late gestation results from the juxtaposition of several factors: enhanced adipose tissue lipolysis facilitating the availability to the liver of substrates for triglyceride synthesis and contributing to augmented flux of very low density lipoproteins (VLDL) into the circulation; maternal hyperphagia and unmodified gut lipid absorption increasing chylomicron formation from dietary lipid; reduced lipoprotein lipase (LPL) activity in extrahepatic tissues (especially adipose tissue) which does not allow a triglyceride removal proportional to their enhanced production. It is proposed that these changes are also responsible for the altered composition of VLDL in late pregnancy. In conditions of food deprivation the use of glycerol released from adipose tissue as preferential gluconeogenic substrate, and the enhanced maternal ketogenesis warrants the availability of fuels for the fetus. Just prior to parturition the increase in mammary gland LPL activity is responsible for the reduction in circulating triglycerides and prepares the mother for lactation.

Adipose Tissue↗
PubMed1987

Maternal factors modulating nutrient transfer to fetus.

Current knowledge of the modulation of maternal-fetal transfer of metabolites is reviewed and new data on the actual placental transport of D-glucose, L-alanine and glycerol in the rat are presented. Twenty-one day pregnant rats were infused with the 14C-labelled substrates throughout the left uterine artery. Radioactivity appearing in fetuses was corrected by the specific dilution of the tracer at maternal arterial plasma and the uterine artery blood flow to estimate placental transfer. This parameter appeared to be 127 mumol X kg-1 fetal b.w. X min-1 for D-glucose, 23 for L-alanine, and 1 for glycerol--values which are much higher than those described for larger species. There is a parallelism between the magnitude of transfer to fetus and arterial concentration in mother for each studied metabolite and actually variations in their plasmatic levels affect this transport process. This is clearly seen in the case of glucose where placental transfer is reduced during fasting hypoglycemia and greatly increased in diabetes. Placental transfer of L-alanine and blood flow to the placenta were reduced in both 48-hour starved and streptozotocin-induced diabetic late pregnant rats. Results show the main role of maternal nutrient concentration as a modulator of their transfer to fetus, the deleterious effect of reductions of uterine blood flow on placental transport of amino acids as well as the small placental transfer of glycerol as compared to either glucose or alanine.

Alanine↗
PubMed1987

Lactate production and absence of gluconeogenesis from placental transferred substrates in fetuses from fed and 48-H starved rats.

Fed and 48-h starved rats were infused on day 21.5 of gestation for 20 min through the left uterine artery with [U-14C-]-D-glucose, [U-14C]-glycerol, or [U-14C]-L-alanine. The mother and fetuses from both uterine horns were processed separately for radioactivity measurements in plasma and liver. Differences in radioactivity values between fetuses from the left and the right sides are used as indexes of placental transference of the infused tracers prior to their distribution and transformation in the maternal circulation. After infusion of [U-14C]-D-glucose, [U-14C]-glycerol, or [U-14C]-L-alanine, plasma radioactivity values and specific activities corresponding to the respective infused tracer appeared much higher in fetuses from the left than the right uterine side. Plasma 14C-lactate values also were higher in the left than the right fetuses indicating that fetoplacental structures produced lactate from those placentally transferred 14C-metabolites. No difference in plasma 14C-glucose between left and right uterine horn fetuses was observed after maternal infusion with either [U-14C]-glycerol or [U-14C]-L-alanine, either in fed or 48-h starved rats. In the mother both [U-14C]-glycerol and [U-14C]-L-alanine were efficiently converted to 14C-glucose, and this process was significantly enhanced with starvation. 14C-fatty acids present in fetal liver after maternal infusions with either [U-14C]-D-glucose or [U-14C]-glycerol were decreased by starvation whereas no fatty acid synthesis from [U-14C]-L-alanine was detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine↗
PubMed1986

Body fat in pregnant rats at mid- and late-gestation.

Carcass fat content was estimated in fed 12- and 19-day pregnant rats and fed and 48 hour starved virgin females following both specific gravity determination and direct gravimetry of extracted lipids. No change in body fat accumulation was found in 12-day pregnant rats whereas in 19-day pregnant animals it increased significantly. A significant correlation was also found when the percentage of carcass fat was plotted against specific gravity considering values from all subjects. Results indicate that in spite of reported maternal anabolic changes in the rat at midgestation fat accumulation occurs later in pregnancy when the mother has the highest food intake, which makes available sufficient substrates to support both fetal growth and body lipidic deposition.

Animals↗
PubMed1986

Comparative utilization of glycerol and alanine as liver gluconeogenic substrates in the fed late pregnant rat.

The appearance of plasma [14C]glucose in the inferior cava vein after a pulse of 0.2 mmol of [U-14C]L-alanine or [U-14C]glycerol/200 g body wt given through the portal vein was studied in fed 21 day pregnant rats and virgin controls under pentobarbital anesthesia. In both groups values were much higher when [U-14C]glycerol was the administered tracer than when [U-14C]L-alanine, and they were augmented in pregnant versus virgin animals at 1 min when receiving [U-14C]glycerol and at 2 min when receiving [U-14C]L-alanine. 20 min after the tracers rats receiving [U-14C]glycerol showed much higher liver [14C]glycogen and [14C]glyceride glycerol than those receiving [U-14C]L-alanine. Radioactivity present in liver as [14C]glyceride glycerol was greater in pregnant than in virgin rats receiving [U-14C]glycerol whereas radioactivity corresponding to [14C]fatty acids was lower in the former group receiving either tracer. At 20 min after maternal treatments fetuses showed lower plasma [14C]glycerol than [14C]alanine values but plasma [14C]glucose and liver [14C]glycogen values were much greater in fetuses from mothers receiving [U-14C]glycerol than [U-14C]L-amine. Besides showing the higher gluconeogenic efficiency in pregnant than in virgin rats, results indicate that at late gestation glycerol is used as a preferential substrate for both glucose and glyceride glycerol synthesis in liver.

Alanine↗
PubMed1986

Role of the availability of substrates on hepatic and renal gluconeogenesis in the fasted late pregnant rat.

Studies were conducted to examine the role of gluconeogenetic substrate availability on glucose production in the fasted late pregnant rat. Virgin and 21-day pregnant rats were studied after 24 hours' food deprivation. Pregnant animals showed decreased circulating glucose and gluconeogenic amino acid and increased plasma glycerol concentration. Glucose formation was studied in vivo two, five, and ten minutes after the intravenous administration of two concentrations of 14C-alanine, 14C-pyruvate, or 14C-glycerol. Concentrations of 0.2 mmols of 14C-glycerol or 14C-pyruvate, but not of 14C-alanine, enhanced 14C-glucose production in pregnant rats, whereas 1 mmol of any of the three 14C-substrates always enhanced 14C-glucose production in these rats. Both 1 mmol/L and 5 mmol/L 14C-alanine increased 14C-glucose formation in 90-minute-incubated liver slices of fasted pregnant rats, in spite of decreased cytosolic activity of alanine aminotransferase. The three substrates enhanced "in vitro" renal gluconeogenesis in pregnant rats. Under all experimental conditions studied, labeled glycerol was converted more efficiently into glucose than equivalent amounts of any other substrate used, and this difference was greater in pregnant, than in virgin animals. Results indicate that, in spite of enhanced gluconeogenetic activity, maternal glucose production in the fasted state at late gestation is limited by the deficiency of certain substrates, such as amino acids. It is proposed that glycerol derived from enhanced maternal adipose tissue lipolysis constitutes a preferential gluconeogenetic substrate in comparison with others, such as alanine, that are more efficiently transferred through the placenta to the fetus.

Alanine↗
PubMed1986

Ethanol administration in the drinking fluid to pregnant rats as a model for the fetal alcohol syndrome.

Addition of ethanol (ET) to the drinking fluid of pregnant rats has been questioned as an experimental model for the fetal alcohol syndrome (FAS). This model, however, closely simulates human alcohol intake, and in this study we used a modified version of previous protocols to overcome their major defects. A group of female rats was given 10% ET in drinking fluid for one week, 15% for the second week, 20% for the third, and 25% for the fourth, at the end of which they were mated with non-treated males and given 25% ET throughout gestation. Three groups of non-ET treated sex and age-matched rats were studied in parallel: (1) normal controls receiving solid diet ad lib, (2) paired fed rats, and (3) rats fed ad lib the solid diet mixed with 50% fiber. In the ET group, food intake decreased as ET consumption augmented, the ET calories comprising over 30% of the total energy intake during pregnancy. Total energy intake was similar for ET group and normal controls, and was higher than in paired fed animals or those on 50% fiber diet. Body weight gain in ET rats was similar to those on 50% fiber diet, lower than in normal controls and higher than in paired fed animals. At the 21st day of gestation, rats on ET had plasma ethanol levels of 147 +/- 18 mg/dl and higher plasma osmolality than in the other groups studied. In ET rats, fetal body weight was lower than in either normal controls or rats on 50% fiber diet, and fetal body length was shorter than in any other group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Effects of chronic ethanol ingestion on circulating metabolites and liver composition in the lactating rat.

A model of chronic ethanol administration has been used to study the effects of chronic ethanol consumption on the general metabolism of lactating rats on day 15 after delivery. We have studied the effects of ethanol on calories, food and fluid intake, body weight, circulating parameters such as glucose, glycerol, free fatty acids (FFA), triacylglycerols (TAG), amino acids (AA), ketone bodies, insulin and ethanol levels and liver composition. Chronic ethanol consumption markedly increases the levels of circulating B-OH-butyrate (B-OB-B), glycerol and FFA, while those of acetoacetate (AcAc), glucose, insulin and TAG remain constant. With the only exception of an increase in Glu + Gln levels, plasma AA decrease in the alcohol-treated rats, the change being significant for Ala, Pro, Lys, Arg, Val, Phe and 4-OH-proline. In the liver ethanol treatment causes an increment in TAG concentration and a decrease in glycogen content. In conclusion, chronic ethanol consumption produces notable alterations in the metabolism of lactating rats, which may diminish the efficiency of lactation, influencing milk production and, therefore, the pups' development.

Alcoholism↗
PubMed1986

Glucose tolerance tests and "in vivo" response to intravenous insulin in the unanaesthesized late pregnant rat and their consequences to the fetus.

In the late pregnant rat, blood glucose levels were lower and plasma RIA-insulin levels were slightly higher than in virgin animals. Oral and intravenous glucose tolerance tests produced parallel changes in blood glucose in both groups whereas plasma RIA-insulin increased more in the pregnant animals. Blood glucose levels after either low (0.1-1 IU/kg) or high (10 IU/Kg) doses of intravenous insulin decreased more slowly and less in pregnant than in virgin rats. Fetal blood glucose levels were not affected by maternal insulin treatment. Results show that in the unanaesthesized late pregnant rat both insulin sensitivity and responsiveness decreased and it is proposed that this insulin resistance may represent a mechanism to delay disposal of ingested nutrients by maternal tissues, ensuring their availability to the fetus.

Animals↗
PubMed1985

Hepatectomy-nephrectomy effects in the pregnant rat and fetus.

Levels of circulating glucose, glycerol, and FFA concentrations were determined before and after hepatectomy-nephrectomy in 20 day pregnant rats and virgin controls. After evisceration, blood glucose levels decreased in a parallel way in both groups whereas in pregnant rats, the blood glycerol level increased less and plasma-FFA rose more than in controls. Maternal evisceration caused reduced blood glucose and enhanced glycerol levels in fetuses, whereas fetal plasma-FFA levels were unmodified. Results indicate that extrahepatic glucose utilization remained stable in the late pregnant rat. Fetal levels of circulating glycerol, but not of FFA, appeared directly dependent on maternal levels. It is proposed that under normal conditions, glycerol availability to the fetus is low, due to its preferential utilization by maternal gluconeogenic organs which reduced the amount available for possible placental transfer.

Animals↗
PubMed1985

Placental formation of lactate from transferred L-alanine and its impairment by aminooxyacetate in the late-pregnant rat.

After 20 min infusion of L-[U-14C]alanine through the left uterine artery in 21-day-pregnant rats, the radioactivity in the plasma of fetuses from the left uterine horn was much higher than in their mothers and was composed of approximately equal parts of [14C]alanine and [14C]lactate, with a minor percentage of [14C]glucose. Radioactivity in fetal plasma was much lower when the mothers were infused with alpha-amino[14C]isobutyric acid. The simultaneous infusion of aminooxyacetate decreased materno-fetal transfer of radioactivity from [14C]alanine but not from alpha-amino[14C]isobutyric acid, and this effect corresponded to a complete disappearance of the [14C]lactate in fetal plasma without affecting [14C]alanine levels or alanine concentration in the fetuses. Placenta slices in vitro metabolized L-[U-14C]alanine into [14C]lactate and 14CO2 at the rate of 7 nmol/g per min, and this process was inhibited by the presence of 1 mM aminooxyacetate in the medium. Placental uptake of alpha-amino[14C]isobutyric acid was half that of [U-14C]alanine, and aminooxyacetate did not affect this parameter with either of the labelled compounds. Results indicate that the lower transfer to the rat fetus of the 14C atoms from alpha-amino[14C]isobutyric acid as compared to that from [14C]alanine is due not only to the diminished placental carrier system of the former but also to its non-metabolyzable condition. It is proposed that the capacity of the placenta to metabolyze L-alanine to lactate and the subsequent release of lactate to the fetus constitute important factors for the fetal metabolic economy.

Acetates↗
PubMed1985

Starvation enhances lipoprotein lipase activity in the liver of the newborn rat.

To determine to what extent lipoprotein lipase activity in the liver of the newborn rat depends on milk ingestion, its changes were studied during different nutritional conditions. Newborns were placed with nurse rats with or without ligated nipples and they were killed at 0,8 or 24 h of life. Lipoprotein lipase in newborns liver was characterized by its inhibition in the presence of 1.0 M NaCl, its specific elution at 1.5 M NaCl on heparin-Sepharose 4B column and its requirement for serum in the assay mixture to manifest its activity. In fed animals lipoprotein lipase activity and triacylglycerol content in liver as well as circulating triacylglycerols and ketone bodies increased progressively after birth. When newborns were kept starved the change in enzyme activity was significantly enhanced, whereas the increase found after birth in the other parameters disappeared. Starvation produced reduction in circulating RIA-insulin levels in the newborn rats. Results show that liver lipoprotein lipase activity in the newborn rat is controlled by a mechanism which resembles that of the enzyme in the adult heart and indicate that its presence facilitates the uptake by the liver of fatty acids from circulating triacylglycerols for their oxidation rather than deposit.

Animals↗