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Biomedical subjects

A Felipe

Publications and source records attributed to A Felipe.

87 records · Page 5Linked to original sources
PubMed1990

Circadian changes in glycogen content in rat interscapular brown adipose tissue: effect of cold exposure and food deprivation.

The effects of food deprivation and cold exposure on brown adipose tissue (BAT) glycogen and lipid levels during the circadian cycle were studied. BAT glycogen levels in control animals followed a definite circadian cycle, showing an increase during the light period. In cold-exposed animals the pattern was different, with minimal values at the beginning of the dark period. Food deprivation caused a decrease in BAT glycogen concentration only after 48-hours. In contrast to the control animals, where BAT and liver showed a different glycogen pattern, in the cold exposed group the observed changes were similar. During cold exposure, lipid stores in BAT were decreased. The results obtained in this work highlight with the important role of glycogen and lipid stores in BAT thermogenesis.

Adipose Tissue, Brown↗
PubMed1990

Pharmaco-toxicological effects of acetaminophen in rodents. Battery of tests to screen potential analgesic acetaminophen derivatives.

The pharmacological effects of acute oral administration of acetaminophen have been extensively evaluated in rodents. Using this drug as reference compound we have also standardized several pharmaco-toxociological tests in order to select new analgesic-antipyretic acetaminophen derivatives. According to the results obtained in this work, the following battery of assays is proposed to screen these compounds: a) pharmacological: antipyretic activity against Brewer's yeast-induced pyresis in rats; analgesic activity against chemical-induced writhings in mice and paw pressure test in rats; b) toxicological: oral acute toxicity in mice with and without phenobarbital pretreatment; determination of SGOT and SGPT activities as well as total bilirubin in mice. The usefulness of this procedure in the evaluation of drug effects is also considered.

Acetaminophen↗
PubMed1989

Na+-dependent alanine transport in plasma membrane vesicles from late-pregnant rat livers.

Liver plasma membrane vesicles retaining Na+-dependent L-alanine transport were purified from either virgin or 21-d pregnant rats. Kinetic analysis of L-alanine uptake data revealed that vesicles from pregnant rats show a slight increase in Vmax without significantly affecting Km. Plasma membrane marker recoveries were used to calculate alanine utilization indexes. These data showed that the overall liver capacity to take up alanine was increased 2-fold in late pregnant rats. When considering utilization indexes in the physiologic range of L-alanine concentrations in blood (0.1-2 mM), we found a highly significant enhancement of the liver capacity to take up this amino acid. It is concluded that, at late pregnancy, when amino acid requirements by the fetus are high, amino acid disposal by the maternal liver is not limited by a low transport capacity; thus, other mechanisms should be contributing to the nitrogen sparing at late pregnancy.

Alanine↗
PubMed1988

Glutamine as a major nitrogen carrier to the liver in suckling rat pups.

We measured the amino acid concentrations in the afferent and efferent vessels of the liver in anaesthetized fed adult rats and in fed suckling rat pups. A much higher content of glutamine in the portal vein and the aorta than in hepatic veins suggests that this amino acid is actively taken up by the liver of fed suckling rat pups, conversely to what is found in adult rats. In an attempt to characterize further the mechanism(s) contributing to this enhanced glutamine uptake, we monitored the time course of 1 mM-glutamine transport into plasma-membrane vesicles purified from the livers of either adult or suckling rats. The concentrative Na+-dependent uptake of glutamine was lower in those vesicles obtained from pups than in those obtained from adult rats. Glutaminase and glutamine synthetase activities in livers from both experimental groups were also measured. Glutaminase and glutamine synthetase activities in suckling rats were about 3-fold higher and 2-fold lower respectively than those in adult rats. It is concluded that glutamine is a main nitrogen carrier to the liver in fed suckling rats. A high availability of this amino acid and an enzyme imbalance between glutamine-synthesizing and -degrading activities may account for the net uptake found in vivo.

Amino Acids↗
PubMed1988

Carrier-mediated uptake of L-(+)-lactate in plasma membrane vesicles from rat liver.

Plasma membrane vesicles from rat liver transported L-lactate into the inner vesicular space. Kinetic analysis of L-lactate uptake gave a Km value of approx. 2.9 mM. Selective inhibition was found in a similar pattern to that described for the hepatic lactate carrier. L-Lactate transport was enhanced when a pH gradient was created across the plasma membrane. Vesicles obtained from fasted rats showed a higher uptake of L-lactate than those from fed rats, when incubated with physiological concentrations of L-lactate.

Alanine↗
PubMed1988

Effects of maternal hypocaloric diet feeding on neonatal rat brown adipose tissue.

Hypocaloric diet (control diet diluted 1:1 with cellulose) feeding during pregnancy caused a reduction in the body weight of rat pups at birth whereas the main parameters of brown adipose tissue composition and thermogenic activity were unaffected. When prenatally underfed rat pups were nursed by untreated dams eating control diet during lactation, early (day 4 of life) and late (day 13 of life) neonatal body weight was rehabilitated and brown adipose tissue remained essentially unchanged. When prenatally underfed rat pups were nursed by dams that were fed with the hypocaloric diet during lactation, neonatal body weight continued lower at the two mentioned days of life and the overall thermogenic capacity of brown fat (GDP binding/g body weight) was substantially depressed. The reduction of the brown fat thermogenic capacity in these pups is mainly due to a hypotrophy of the mitochondrial component of the tissue as indicated by the lowered cytochrome oxidase activity. Results indicate that mild maternal underfeeding during lactation may depress brown adipose tissue thermogenic function in neonates whereas similar hypocaloric intakes during pregnancy did not alter brown fat thermogenic capacity.

Adipose Tissue, Brown↗
PubMed1988

Effect of luminance on photopic visual acuity in the presence of laser speckle.

Visual acuity in coherent and incoherent light has been determined by using square-wave gratings of 100% contrast. Luminance was varied from 3 to 400 cd/m2. Coherent illumination resulted in a 40% loss of visual acuity. This is probably due to the masking effect of coherent spatial noise (speckle). However, the most interesting finding is the change in shape of the photopic visual-acuity-luminance function. With coherent illumination, the function is vertically displaced and of a different gradient. An increase in luminance produces a decrease in visual acuity. This indicates that the masking effect of the speckle is dependent on luminance. Two observers were used, and similar results were obtained by both.

Adult↗
PubMed1988

Visual reaction-time versus action-time.

The reaction-time for movement was found to be around 150 ms and was compared with the time required to take action while two moving lines are on a collision course. Subjects were trained to either avoid or maximize collision. They did so accurately. The action-time was about one-third the reaction-time.

Humans↗
PubMed1988

Sequential visual reaction times.

The reaction-time to a series of successive digits was measured on two subjects. After practice, it was found that whilst the reaction time to the onset of the series was constant at 150 ms, the response time to additional digits became less and less to asymptote to a level of about 50 ms. The time course of this 'chorus-line' phenomenon was studied in greater temporal detail by varying the interval in steps of 20 ms. The effect was greatest at 200 ms. Thereafter, it declined and for long intervals reached the value of a standard reaction time. On a third inexperienced subject, the learning period was established; this was about 300-400 presentations. The implications of these findings are discussed against the background of everyday visual motor behaviour.

Adult↗
PubMed1987

Reduced noradrenaline turnover in brown adipose tissue of lactating rats.

Brown adipose tissue properties as well as noradrenaline turnover in the tissue were determined in 15-day lactating rats and virgin controls. Brown adipose tissue thermogenic activity was reduced in lactating rats as shown by a decrease in weight, cytochrome oxidase activity and mitochondrial GDP-binding. The noradrenaline turnover rate was lower in brown adipose tissue from lactating rats. It is suggested that diminished sympathetic activity in brown adipose tissue may be a major cause of the reduced tissue thermogenic activity during lactation.

Adipose Tissue, Brown↗
PubMed1986

Sequential changes in brown adipose tissue composition, cytochrome oxidase activity and GDP binding throughout pregnancy and lactation in the rat.

The sequential appearance of changes in interscapular brown adipose tissue composition, cytochrome oxidase activity and GDP binding was studied throughout pregnancy and lactation in the rat. Brown adipose tissue was hypertrophied during pregnancy because of progressive lipid accumulation, whereas its mitochondrial component and GDP binding to brown fat mitochondria were unchanged. In early lactation (day 5) there was a decrease in the overall GDP binding to brown fat only because of the lower mitochondrial protein content. In late stages of lactation (days 10 and 15), the amount of tissue and its mitochondrial protein content were minimal and the GDP binding per mitochondrial protein decreased substantially. Scatchard analysis in day-15-lactating rats indicated a large decrease in GDP binding sites without any changes in affinity. It is concluded that the diminished thermogenic activity of brown fat in lactation is attained through changes at different structural levels of the tissue occurring in a characteristic sequential trend; first a reduction in its mitochondrial component, and only later, at mid-lactation, a decrease in the specific mitochondrial proton conductance pathway activity.

Adipose Tissue, Brown↗
PubMed1986

Brown adipose tissue activity in hypocaloric-diet fed lactating rats.

Hypocaloric diet feeding reduced the mitochondrial protein content and whole tissue GDP-binding in interscapular brown adipose tissue from both virgin and lactating rats. A reduction in brown fat lipoprotein lipase activity was also detected in underfed virgin and lactating animals. These results indicate that lactation in the rat, even though it produces a reduction in brown fat activity, does not impair the capacity of the tissue to respond to a diminished caloric intake by lowering its activity further.

Adipose Tissue, Brown↗
PubMedDate not supplied

[The radiotherapy control of cervical adenopathies in undifferentiated epithelial tumors of the head and neck. The prognostic factors].

A total of 90 patients with undifferentiated carcinomas tumors the head and neck with clinical neck nodes who received intended radical irradiation, were studied by means of a multivariant analysis of 9 variables which defined cervical lymph node disease in oder to determine the prognostic factors for the control of the above mentioned adenopathy. The factors were as follows: lymph node response post-irradiation (p = 0.0000), condition of the primary (controlled-non controlled) (p = 0.0208).

Carcinoma↗