Biomedical subjects

O Viñas

Publications and source records attributed to O Viñas.

At least 55 records · Page 3Linked to original sources

PubMed1993

Effects of cold environment on mitochondrial genome expression in the rat: evidence for a tissue-specific increase in the liver, independent of changes in mitochondrial gene abundance.

The abundance of the mitochondrially encoded mRNA for subunit II of cytochrome c oxidase (COII mRNA) increases in the liver of rats exposed to environmental cold stress (4 degrees C ambient temperature). Only transient increases or no changes in COII mRNA levels were observed in brown fat and soleus muscle respectively. The time course of the liver COII mRNA increase was compared with the effects of cold stress on mitochondrial 16S ribosomal RNA expression and indicated that cold induces a rapid (few hours) increase in the liver mitochondrial mRNA levels and high levels of both messenger and ribosomal RNA mitochondrial transcripts are present after a few days of cold exposure. No changes in mitochondrial DNA abundance relative to total cellular DNA were observed in the liver of rats at any time during cold stress. It is concluded that mitochondrial genome expression is specifically increased in the liver of cold-exposed rats through different mechanisms, independent of changes in mitochondrial genome abundance.

Acclimatization↗

PubMed1993

Ontogeny of thyroid hormone receptors and c-erbA expression during brown adipose tissue development: evidence of fetal acquisition of the mature thyroid status.

We have determined the developmental changes in thyroid hormone receptor expression and thyroid hormone status in rat brown adipose tissue (BAT). The present study demonstrates that c-erbA alpha and -beta genes are expressed in the developing BAT. The 6.5-kilobase (kb) beta 1, 2.6-kb alpha 2, 5.5-kb alpha 1, and 6.6-kb alpha transcripts showed peak values on day 20 of fetal life. High affinity T3-binding sites were found in fetal BAT. Binding capacity was similar (18-day-old fetuses) or higher (20-day-old fetuses) than in postnatal or adult brown fat. In contrast, T3 receptors were scarce in fetal liver, and values in adult liver were similar to those in fetal BAT on day 20. The profiles of iodothyronine 5'-deiodinase, nuclear T3 content, and receptor occupancy also showed peak values in fetal BAT on day 20, but they were very low in fetal liver. Thus, BAT has already achieved complete maturation of its thyroid status on day 20 of gestational age. This highly tissue-specific developmental pattern is unique among other mammalian thyroid-sensitive tissues studied to date. Between days 18 and 20 of rat fetal development, there is a specific induction of the uncoupling protein gene expression, the main marker of differentiated adipocytes. The results suggest that thyroid hormones may be involved in the establishment of the differentiated phenotype of the brown fat cell in fetal life.

Adipose Tissue, Brown↗

PubMed1992

Changes in alanine and glutamine transport during rat red blood cell maturation.

Alanine and glutamine transport have been studied during red blood cell maturation in the rat. Kinetic parameters of Na(+)-dependent L-alanine transport were: Km 0.43 and 1.88 mM and Vmax 158 and 45 nmoles/ml ICW/min for reticulocytes and erythrocytes, respectively. During red cell maturation in the rat there is a loss of capacity and affinity of the system ASC for L-alanine transport. The values for Na(+)-dependent L-glutamine transport in reticulocytes were Km 0.51 mM and Vmax 157 nmoles/ml ICW/min. On the other hand, a total loss of L-glutamine transport mediated by both N and ASC systems is demonstrated in mature red cells. This seems to indicate that during rat red cell maturation the system N disappears. Furthermore, the system ASC specificity in mature cells changes, and glutamine enters the red cell by non-mediated diffusion processes.

Alanine↗

PubMed1991

Induction of interleukin 2 (IL 2) and interferon-gamma and enhancement of IL 2 receptor expression by a CD26 monoclonal antibody.

The ability of the 134-2C2 monoclonal antibody (mAb; CD26) to transmit an activation signal and to affect T cell proliferation has been studied. The 134-2C2 mAb, although not being mitogenic by itself, is able to increase the proliferation of purified T cells in the presence of exogenous interleukin 2 (IL2) or phorbol 12-myristate 13-acetate (PMA). No effect of our mAb was observed on the proliferation of T cells induced by other stimuli such as Sepharose-bound CD3 mAb, phytohemagglutinin or calcium ionophore. Since the co-stimulatory effect of 134-2C2 mAb on PMA-induced T cell proliferation was strongly inhibited by an anti-Tac antibody, its involvement on the IL2/IL2 receptor pathway was investigated. An increased IL2 secretion in T cells cultured with PMA plus 134-2C2 mAb was observed and Northern blot analysis showed that the mAb 134-2C2 acts synergistically with PMA favoring the induction of both IL2 and interferon-gamma mRNA synthesis, as well as the enhancement of IL2 receptor and transferrin receptor mRNA expression. Studies on mechanisms implicated in signal transduction showed that 134-2C2 mAb modifies neither intracellular calcium levels nor phosphoinositide breakdown. Additionally, no effect was exerted on protein kinase C translocation. These data suggest that the CD26 antigen is involved in T cell activation in an IL2/IL2 receptor-dependent pathway.

Antibodies, Monoclonal↗

PubMed1991

Increased CD5-positive B lymphocytes in type I diabetes.

CD5+ B lymphocytes have been implicated in the production of polyspecific and monospecific antibodies that bind self-antigens, and increased proportions of this B cell subset occur in patients with some autoimmune diseases. We investigated the proportion of peripheral blood CD5+ B lymphocytes in type I diabetic patients. Compared with 18 age-matched healthy subjects, 11 out of 28 (39.2%) type I diabetic patients had increased proportions of circulating CD5. B lymphocytes with no alterations in the numbers of circulating B and T lymphocytes. Although all patients with increased CD5 B lymphocytes also had serum islet cell antibodies and/or insulin autoantibodies, the occurrence of increased proportions of CD5+ B lymphocytes and serum autoantibodies was not significantly correlated. Increased proportions of CD5+ B lymphocytes was not related to the time elapsed since the clinical onset of diabetes. In addition, regardless of being increased or normal, the proportion of CD5+ B lymphocytes appeared as a relatively constant phenotype after 1 year of follow-up studies at 3-month intervals in eight patients. Although the significance of these findings remains to be established, the possibility exists that CD5+ cells play a role in the pathogenesis of type I diabetes.

Adolescent↗

PubMed1990

Ontogeny and perinatal modulation of gene expression in rat brown adipose tissue. Unaltered iodothyronine 5'-deiodinase activity is necessary for the response to environmental temperature at birth.

We have performed a sequential study on the abundance of the mRNA for uncoupling protein (UCP), subunit II of cytochrome-c oxidase (COII) and lipoprotein lipase in brown adipose tissue during the fetal and postnatal periods. Moreover, we have determined whether these parameters can be modulated by ambient temperature in the early hours after birth, and at which point in development this sensitivity first appears. UCP gene expression in the fetal and neonatal period has particular features when compared with overall mitochondriogenesis (COII mRNA expression) or with the expression of lipoprotein lipase mRNA. There is a specific induction of UCP gene expression between days 18 and 19 of pregnancy followed by a specific increase of UCP gene expression in utero and a further increase after birth. The acquisition of the physiological apparatus capable of the response to UCP and lipoprotein lipase gene expression to the environmental temperature is not achieved until the last day of fetal development. This result suggests that mechanisms of beta-adrenergic modulation of gene expression in brown fat are already established at birth. From an experiment on iopanoic acid treatment of pregnant mothers, it was concluded that iodothyronine 5'-deiodinase activity is not necessary for the expression of the mRNAs for UCP, COII and lipoprotein lipase in the fetus whereas it is necessary for the acquisition of temperature sensitivity to these parameters at birth.

Adipose Tissue, Brown↗

PubMed1990

Lipoprotein lipase mRNA expression in brown adipose tissue: translational and/or posttranslational events are involved in the modulation of enzyme activity.

Lipoprotein lipase mRNA abundance in rat brown adipose tissue increases during the first 24 h of cold exposure. Lipoprotein lipase mRNA levels do not change in brown fat throughout pregnancy and lactation, whereas enzyme activity is significantly lowered. After 5 h of acute cold or noradrenaline administration there is a 2-fold increase in lipoprotein lipase mRNA abundance, whereas lipoprotein lipase activity is stimulated to more than 6-fold the basal values. It is concluded that translational and/or posttranslational mechanisms are involved in the noradrenergic modulation of lipoprotein lipase activity in brown fat.

Acclimatization↗

PubMed1990

The epsilon-subunit of ATP synthase from bovine heart mitochondria. Complementary DNA sequence, expression in bovine tissues and evidence of homologous sequences in man and rat.

The epsilon-subunit of ATP synthase from bovine heart mitochondria is assembled into the extrinsic membrane sector, F1-ATPase. The mature protein is 50 amino acid residues in length and its function is unknown. It is a nuclear gene product that is imported into the organelle. A mixture of 64 oligonucleotides 17 bases long, designed on the basis of the known protein sequence, was synthesized and used as a hybridization probe to isolate a cognate cDNA clone from a bovine library. The DNA sequence of this clone was determined, and the protein sequence of the epsilon-subunit deduced from it agrees exactly with that determined by direct sequence analysis of the protein isolated from bovine hearts. The bovine cDNA was used as a hybridization probe to examine the expression of the epsilon-subunit in various bovine tissues. mRNAs related to the cDNA are found in all of these tissues, and no evidence was obtained of the presence of mRNAs for the epsilon-subunit with similar coding sequences and dissimilar 3' non-coding regions. By hybridization experiments with digests of DNA from cow, man and rat it has been shown that sequences related to the bovine cDNA are present in the genomes of all three species. More than one related sequence was detected in all cases, indicating the presence in all three genomes of more than one gene and/or pseudogenes.

Amino Acid Sequence↗

PubMed1990

Changes in glycine and leucine transport during red cell maturation in the rat.

Both glycine and leucine transport in rat red blood cells have been studied. The glycine uptake showed two different components, one sodium-dependent and another diffusion-like process. In contrast, leucine uptake was sodium independent. Both, Na(+)-dependent glycine and the overall leucine uptake in red blood cells showed a saturable pattern. Kinetic parameters in reticulocytes were: i) glycine: apparent Km 0.16 mM; Vmax 100.2 nmol/ml ICW/min; ii) leucine: apparent Km 2.11 mM; Vmax 3.88 mumol/ml ICW/min. The erythrocytes kinetic parameters were: i) glycine: apparent Km 0.17 mM; Vmax 9.47 nmol/ml ICW/min; leucine; apparent Km 4.77 mM; Vmax 7.42 mumol/ml ICW/min. The Kd values (sodium independent glycine uptake) were similar in both kind of cells, but the importance of this component in total glycine uptake in erythrocytes was much higher than in reticulocytes. Our results confirm that rat red blood cells have both saturable leucine and Na(+)-dependent glycine uptake, but some important changes occur during cell maturation.

Animals↗

PubMed1990

Cationic and anionic amino acid transport studies in rat red blood cells.

The transport of L-proline, L-lysine and L-glutamate in rat red blood cells has been studied. L-proline and L-lysine uptake were Na(+)-independent. When the concentration dependence was studied both showed a non-saturable uptake assimilable to a difussion-like process, with high Kd values (0.718 and 0.191 min-1 for L-proline and L-lysine respectively). Rat red blood cells showed high impermeability to L-glutamate. No sodium dependence was observed and the Kd value was low (0.067 min-1). Our results show firstly, that rat red blood cells do not have amino acid transport systems for anionic and cationic amino acids and secondly that erythrocytes show no sodium-dependent L-proline transport, and that these cells are very permeable to this amino acid.

Alanine↗

PubMed1989

Adaptative decrease in expression of the mRNA for uncoupling protein and subunit II of cytochrome c oxidase in rat brown adipose tissue during pregnancy and lactation.

Uncoupling-protein (UCP) mRNA expression is decreased to 15% of virgin control levels between days 10 and 15 of pregnancy, and remains at these low values during late pregnancy and lactation. Abrupt weaning of mid-lactating rats causes a slight but significant increase in UCP mRNA. Expression of mRNA for subunit II of cytochrome c oxidase (COII) decreased to half that of virgin control in late pregnancy and during lactation. Whereas COII mRNA expression is in step with the known modifications of brown-fat mitochondria content during the breeding cycle of the rat, UCP mRNA expression appears to be diminished much earlier than the mitochondrial proton-conductance-pathway activity. On the other hand, the reactivity of brown fat to increase expression of UCP and COII mRNAs in response to acute cold or noradrenaline treatment is not impaired during lactation.

Adipose Tissue, Brown↗

PubMed1989

ATP synthase from bovine mitochondria: complementary DNA sequence of the import precursor of a heart isoform of the alpha subunit.

The alpha-subunit of ATP synthase from mitochondria is a major component of the extrinsic membrane sector of the enzyme. It is encoded in nuclear DNA. A family of overlapping complementary DNA clones encoding its precursor has been isolated from a bovine library by using in the first instance a mixture of 128 synthetic oligonucleotides designed on the basis of the known protein sequence, and the sequence of the full-length cDNA has been determined. The deduced protein sequence shows that the alpha-subunit of ATP synthase has a presequence of 43 amino acids that is not present in the mature protein. Presumably it directs the protein into the mitochondrial matrix and is removed during the import process. The encoded protein sequence is also longer by one amino acid at its C-terminal end than the protein isolated from F1-ATPase, but this alanine residue may have been removed artifactually during release of the F1-ATPase particle from the inner mitochondrial membrane. With the exception of one uncertainty caused by an ambiguity at one position in the nucleotide sequence, the mature protein sequence encoded in the cDNA is exactly the same as the sequence determined previously by direct analysis of the protein isolated from bovine heart mitochondria [Walker et al. (1985) J. Mol. Biol. 184, 677-701]. The cDNA sequence differs in 158 nucleotides over a region of alignment of 1097 nucleotides from a partial cDNA for the alpha-subunit that has been isolated from a bovine cDNA derived from liver RNA [Breen (1988) Biochem. Biophys. Res. Commun. 152, 264-269].(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1989

Iodothyronine 5'-deiodinase activity as an early event of prenatal brown-fat differentiation in bovine development.

Iodothyronine 5'-deiodinase activity appears to be a type I enzyme in bovine brown adipose tissue, on the basis of its high Km for 3,3',5'-tri-iodothyronine ('reverse T3') (in the micromolar range) and sensitivity to propylthiouracil inhibition. This enzyme activity is already detectable in perirenal adipose tissue of bovine fetuses in the second month of gestation, reaches peak values around the seventh month of fetal life, declines before birth, becomes lower after parturition and finally undetectable in the adult cow. Iodothyronine 5'-deiodinase activity is present in the pericardic, peritoneal and intermuscular adipose depots of the neonatal calf, but it is always undetectable in the subcutaneous adipose tissue. It is concluded that iodothyronine 5'-deiodinase is a specific feature of brown fat in the bovine species that is not shared by white adipose tissue. white adipose tissue. Peak values of 5'-deiodinating activity appear as an early event in the prenatal differentiation programme of bovine brown-fat cells as they occur when uncoupling-protein-gene expression first starts.

Adipose Tissue, Brown↗

PubMed1989

Altered ultrastructure of lactating rat mammary epithelial cells induced by chronic ethanol ingestion.

The ethanol and acetaldehyde uptake by the lactating rat mammary gland as well as their effects on this gland at the ultrastructural level have been studied. The extraction of acetaldehyde was greater than that of ethanol both after chronic and acute ethanol treatment. Chronic ethanol administration resulted in a loss of the mammary cell polarization, in a reduction of the Golgi dictyosomal elements and in several abnormalities at the level of casein maturation and secretion, whereas lipid synthesis and secretion did not seem to be affected. Normal spherical casein micelles took on a filament-like structure and casein vesicles appeared fused together forming macrovesicles. All these alterations were specific of ethanol and/or acetaldehyde action and were not due to the associated malnutrition, as deduced from the lack of visible effects in the nutritional control group.

Acetaldehyde↗

PubMed1988

Iodothyronine 5'-deiodinase activity and thyroid hormone content in brown adipose tissue during the breeding cycle of the rat.

Brown adipose tissue iodothyronine 5'-deiodinase activity is significantly lower in 17-day pregnant rats compared with virgin controls and remains low during late pregnancy and lactation. It fully recovers with abrupt weaning, but only partially with spontaneous weaning. Even though this profile of changes is remarkably in step with the known pattern of modifications in brown fat thermogenesis during the breeding cycle, the lowered iodothyronine 5'-deiodinase activity appearing between days 15 and 17 of pregnancy occurs earlier than the reduction in brown adipose tissue thermogenesis. Brown fat 3,3',5-tri-iodothyronine content is also reduced in late pregnant, early and mid-lactating rats, most probably as a consequence of the lowered 5'-deiodination of thyroxine in situ. Acute insulin treatment increases brown fat iodothyronine 5'-deiodinase activity in virgin animals as well as in late-pregnant and lactating rats, despite the lowered basal enzyme activity levels in the latter groups. Thus an impaired response to insulin in brown fat does not appear to be a factor leading to the lowered iodothyronine 5'-deiodinase activity during late pregnancy and lactation.

Adipose Tissue, Brown↗

PubMed1988

Evidence for a differential physiological modulation of brown fat iodothyronine 5'-deiodinase activity in the perinatal period.

Brown adipose tissue iodothyronine 5'-deiodinase increases progressively in fetuses from the day 17 of pregnancy on, it reaches peak values on the 20th day of gestation and declines in the last days of fetal life as well as during the first day of life. Birth of premature fetuses causes a sudden drop in the enzyme activity. Postmaturity is associated to a decrease in brown fat 5'-deiodinase similar to that found after birth in fetuses born at term. In the first hours of life brown fat iodothyronine 5'-deiodinase is essentially insensitive to the cold-stimulus. Present data indicates that, differently from adult rats, brown fat iodothyronine 5'-deiodinase activity during the perinatal period is dissociated from the thermogenic activity of the tissue. It is suggested that factors different from the action of the sympathetic nervous system may play a main role in brown fat iodothyronine 5'-deiodinase activity modulation in the fetal and neonatal life.

Adipose Tissue, Brown↗

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↗