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Biomedical subjects

A Nieto

Publications and source records attributed to A Nieto.

At least 271 records · Page 15Linked to original sources
PubMed1983

Projections of the amygdala in rats during development.

Unilateral electrolytic lesions of the amygdaloid nucleus were made in rats during development to study the timing of sequential connectivity. The patterns of neural degeneration were detected by the Fink-Heimer technique and light microscopy. The main projections were to the accumbens, caudate, septal area, habenula, hypothalamus, cingulum, thalamus, and mesencephalon. In all cases degenerated fibers were progressively more apparent with increasing age. A clear and consistent pattern of degeneration was first observed at 30 days postnatally. Because the amygdala is widely connected with numerous limbostriatal and other CNS structures, the data presented favor the possibility that the amygdaloid complex can be a crucial region for the triggering of patterns of endocrine and autonomic, as well as somatic responses.

Amygdala↗
PubMed1982

Uteroglobin-like antigens in species of Lagomorpha.

1. Uteroglobin-like antigens were found in the lung and uterus of the hare (Lepus) and the pika (Ochotona). These antigens presented an immunoreactivity indistinguishable from that of rabbit uteroglobin, as determined by radioimmunoassay. 2. The molecular weight and the subunit composition of these antigens were similar to those of rabbit uteroglobin as analyzed by SDS gel-electrophoresis. 3. Similar amounts of uteroglobin-like immunoreactivity were found in the respective lungs and uteri of hare and rabbit whereas the concentration of immunoreactivity in the pika organs was several-fold lower.

Animals↗
PubMed1981

Glucocorticoid and developmental regulation of uteroglobin synthesis in rabbit lung.

The synthesis of uteroglobin in rabbit lung was studied after the administration of glucocorticoids to intact adult animals as well as during the late stages of rabbit development. The synthesis of uteroglobin was compared with levels of translatable uteroglobin mRNA in the lung. Uteroglobin synthesis was determined both by incorporation of [25S]methionine into the protein by lung explants incubated in vitro and by radioimmunoassay measurements of uteroglobin concentration in lung. Lung poly(A)-containing mRNA, isolated by oligo(dT)--cellulose chromatography, was translated in cell-free systems and the activity of uteroglobin mRNA was determined after immunoprecipitation. Dexamethasone administration increased about 2-fold the synthesis of lung uteroglobin compared with the controls. The effect of cortisol was more moderate. Both glucocorticoids did not affect the degradation rate of lung uteroglobin, but produced increases in the translatable levels of uteroglobin mRNA parallel to those observed for uteroglobin synthesis. During the late stages of rabbit development, both the synthesis of lung uteroglobin and the translatable levels of its mRNA increase in parallel about 12-fold in a biphasic fashion. A first increase occurred between 2 days before and 2 days after birth. Starting at 5 days of age, there was a second increase in both parameters, which at 12 days of age reached values close to those observed in adult rabbits. Our results suggest that the rate of lung uteroglobin synthesis could be mainly determined by the translatable levels of its mRNA.

Aging↗
PubMed1981

Comparative measurement by radioimmunoassay of the brain microtubule-associated protein MAP2.

The presence of the microtubule-associated protein (MAP2) in the brain of several species has been investigated by SDS-gel electrophoresis and by radioimmunoassay. This assay had a sensitivity of approx. 10 ng and it was capable of measuring the protein either in purified microtubules or in crude brain extracts. As determined with this radioimmunoassay, MAP2 accounted for about 10% of the porcine brain microtubule protein and 1% of the protein from a brain extract. Taking porcine MAP2 as a reference, we have detected polypeptides with the same electrophoretic mobility in brain microtubules from cow, sheep, rat and chicken. Nevertheless, the MAP2 from these species showed a variable degree of immunoreactivity. Bovine MAP2 appeared closely related to the porcine protein whereas the rat antigen showed low cross-reaction and chicken MAP2 appeared immunologically unrelated to porcine MAP2. Our results suggest a higher variability of the MAP2 sequences as compared to that reported by other authors for the brain microtubule protein, tubulin.

Animals↗
PubMed1980

Activation of phospholipid methyltransferase by glucagon in rat hepatocytes.

Glucagon produces a time- and dose-dependent activation of phospholipid methyltransferase activity in isolated rat hepatocytes. Half-maximal effect is caused by a dose of glucagon of 1 x 10(-10) M. This activation is due to an increase of the Vmax value of the enzyme, without affecting the Km value for S-adenosylmethionine. Exogenous cyclic AMP added to isolated rat hepatocytes mimics the effect of glucagon, and the activation of phospholipid methyltransferase by a nonsaturating concentration of glucagon is spontaneously reversible within 40 min of incubation.

Animals↗
PubMed1980

Control in vivo of rat liver phosphofructokinase by glucagon and nutritional changes.

Glucagon (250 microgram/kg body wt.) intravenously injected into normal fed rats produces within 5 min a marked inactivation of liver phosphofructokinase, only observed when the enzyme activity is measured at subsaturating concentrations of fructose 6-phosphate. Since half-maximal inactivation is observed at a dose of glucagon of 0.32 microgram/body wt., a dose within the range of the physiological concentrations of the hormone, the inactivation of phosphofructokinase can occur in vivo in response to physiological changes in the concentration of glucagon. In gluconeogenic conditions (starved rats or high-protein-diet-fed rats), there is a marked inactivation of liver phosphofructokinase at subsaturating concentrations of fructose 6-phosphate similar to that found in normal fed rats after glucagon treatment. In these gluconeogenic conditions a 50% decrease in the Vmax. of the enzyme is also observed. No significant changes in phosphofructokinase activity either at subsaturating concentrations of fructose 6-phosphate or in the Vmax. of the enzyme are observed when rats are fed on a high-carbohydrate diet. In the last dietary condition, glucagon treatment produces similar effects to that described in the normal fed rats. Similar results have been obtained in the above condtions for pyruvate kinase L activity when measured at subsaturating concentrations of phosphoenolpyruvate.

Animals↗
PubMed1980

Synthesis and secretion of uteroglobin in rabbit endometrial explants cultured in vitro.

Explants from rabbit endometrium incorporate [35S] methionine into uteroglobin and other proteins in an essentially linear fashion for at least 8 h. Newly synthesized uteroglobin was characterized by gel chromatography, sodium dodecyl sulphate gel electrophoresis and immunological techniques. Labelled uteroglobin accumulates in the tissue explants during the first 3 h and then reaches a plateau level. Secretion of uteroglobin into the medium is detected after a 1-h lag period and proceeds linearly thereafter. Explants from animals treated with estradiol alone or estradiol plus progesterone (pseudopregnancy) synthesized respectively 2--3-fold and 10--20-fold more uteroglobin than explants from control animals. The rate of degradation of uteroglobin in the in vitro system was not affected by the hormonal treatment of the animals. There is a good correlation between the uteroglobin content in the uterine fluid and the rate of synthesis of uteroglobin in endometrial explants, suggesting that the in vitro system faithfully reflects the in vivo hormonal effects on uteroglobin synthesis.

Animals↗
PubMed1980

Projections of the caudate nucleus in the cat.

Circumscribed lesions of the caudate nucleus were made in four cats and two kittens. A third kitten was lesioned in the Middle Forebrain Bundle (MFB). Cats were sacrificed 8 days after the lesion and perfused intraventricularly with 10 per cent Formalin. Kittens were sacrificed 3 days after the lesion. Coronal frozen sections of the brains were made and studied under the light microscope with the Fink and Heimer staining method. Degeneration was observed in the contralateral caudate nucleus, in the homo and contralateral putamen, in the globus pallidum and in the accumbens. The substantia nigra was intensely involved as well as the red nucleus and the mesencephalic reticular formation. Patches of degeneration were also found in the superior colliculus and in the thalamus. As a preliminary conclusion we think that the projection of the caudate reaches all those structures by the middle forebrain bundle. The degeneration of the contralateral areas could be explained through a path of the anterior commissure.

Animals↗
PubMed1979

Projections to the neostriatum from the cat precruciate cortex. Anatomy and physiology.

The projections to the striatum from two cytoarchitectonically and functionally distinct subdivisions of the cat precruciate motor cortex were studied using anatomical and electrophysiological techniques. Our results indicate that the medial precruciate cortex (stimulation of which leads to movements of the axial and proximal musculature) has a widespread projection to the lateral half of the caudate nucleus. The lateral precruciate cortex (stimulation of which leads to movements of the distal musculature) has a localized projection within the caudate nucleus adjacent to the internal capsule. Both medial and lateral precruciate areas project to the putamen. These results are discussed in relation to recent studies suggesting that the basal ganglia are involved in the enabling and sequencing of movements.

Afferent Pathways↗
PubMed1979

Inactivation of phosphofructokinase by glucagon in rat hepatocytes.

Kinetic evidence of a time- and dose-dependent inactivation of phosphofructokinase by glucagon in isolated rat hepatocytes is reported. This inactivation, which persists after gel filtration of a cell-free extract on Sephadex G-25 and after 400-fold purification of the enzyme on agarose-ATP, is observed when the enzyme activity is measured at subsaturating concentrations of fructose 6-phosphate, while there is no change in Vmax. Phosphofructokinase inactivation by glucagon parallels the known inactivation of pyruvate kinase L and activation of glycogen phosphorylase alpha. Exogenous cyclic AMP mimics the effect of this hormone. Half-maximal effect for both phosphofructokinase and pyruvate kinase L is caused by a similar dose of glucagon (1 x 10(-10) M). The inactivation of phosphofructokinase by nonsaturating concentration of glucagon is reversed spontaneously within 40 min of incubation and this reversion is accelerated by insulin.

Animals↗
PubMed1978

Amino acid sequence of progesterone-induced rabbit uteroglobin.

Uteroglobin, a steroid-binding protein of the uterine secretion of the rabbit which is induced by progesterone, comprises two identical polypeptide chains of 70 amino acid residues linked by two disulfide bonds. The primary structure has been determined by using both automated and manual methods of Edman degradation. Overlapping peptides were isolated from tryptic, and CNBr digests. The sequence is not homologous to any known protein except for a small acidic region (residues 22-29) resembling a sequence found in somatotropin. The C-terminal half is relatively basic. Implications for the secondary structure are discussed.

Amino Acid Sequence↗
PubMed1978

Comparative anatomy of the caudate nucleus in different mammals.

Volumetric comparisons of the caudate nucleus of different mammals including rat, rabbit, cat, zebra, deer, antelope, bull, horse, dolphin (Stenella graffmani) and human are presented. A linear regression coefficient is obtained with its corresponding correlation coefficient. The results indicate that there is not a close correlation between the size of the caudate nucleus and the brain weight of the different animals studied when the caudate of the horse is included. When it is omitted there is a close correspondence. The caudate nucleus of the horse is extremely large in relation to its brain weight. The possible meaning of this fact is discussed. Measurement of different brain structures is of interest, both from the purely descriptive aspect and because it can suggest phylogenetic relations as well as explanation of functional differences in different animal species (1, 2).

Animals↗
PubMed1976

Translation of the mRNA for rabbit uteroglobin in cell-free systems. Evidence for a precursor protein.

Uteroglobin, an hormonally induced protein composed of two similar subunits, represents around 50% of the proteins synthesized and secreted into the uterine lumen of rabbits treated sequentially with estradiol and progesterone. The endometrium of these animals was used as a source for the isolation of the mRNA for uteroglobin. Poly(A)-rich RNA, extracted from purified polysomes with phenol chloroform and isolated on oligo(dT)-cellulose columns, contains one fourth of the total protein coding activity of the endometrium. Between 20--25% of the polypeptides synthesized by this RNA in cell-free systems derived from Krebs II ascites cells or wheat germs react with a monospecific antiserum prepared in guinea pigs against uteroglobin. The material bound to the antibody was identified as a precursor of uteroglobin according to the following criteria. 1. The product synthesized in vitro can be displaced from the complex with the specific immunoglobulin by purified uteroglobin. 2. Analysis of the immunoprecipitate on polyacrylamide gels containing urea and dodecylsulfate demonstrate the existence of a single labelled polypeptide with an apparent molecular weight larger than the uteroglobin subunits. 3. The tryptic digest of this polypeptide, labelled in vitro with [3H]lysine, shares seven peptides with mature uteroglobin labelled with the same amino acid in perfused uteri, and exhibits and additional peptide not present in uteroglobin. 4. Injection of the same mRNA preparation into Xenopus oocytes results in the production of uteroglobin. The endometrium of intact animals treated with estradiol alone also contains the same mRNA bound to polysomes but in a smaller proportion, indicating that the progesterone-induced synthesis of uteroglobin is accompanied by an accumulation of the specific mRNA in the polysomes.

Animals↗
PubMed1976

Possible phylogenetical significance of the corpus callosum with special reference to the dolphin brain (Stenella graffmani).

The surface area of the corpus callosum was measured in several animals as compared to the brain weight. A general consideration of the importance of this structure on the phylogenetic scale, with special reference to the corpus callosum of the dolphin, Stenella graffmani, is given. Some theoretical considerations about the significance of this structure upon some specialized features are mentioned.

Anatomy, Comparative↗
PubMed1975

Calcitonin biosynthesis: evidence for a precursor.

Calcitonin biosynthesis has been studied in chicken ultimobranchial glands incubated in vitro in the presence of radioactive amino acids. The results obtained suggest the existence of a biosynthetic precursor of higher molecular weight or procalcitonin. This precursor has been identified by pulse-chase experiments, molecular weight determinations, biological activity measurements and analysis of tryptic peptides. Its molecular weight is about 13000 (calcitonin, about 3500) as determined by polyacrylamide gel electrophoresis. Procalcitonin is present in small amounts in chicken ultimobranchial glands and it is biologically active in rats.

Animals↗