PubMed Health⌕ Search

Biomedical subjects

L Bassas

Publications and source records attributed to L Bassas.

28 records · Page 2Linked to original sources
PubMed1989

In situ autoradiography and ligand-dependent tyrosine kinase activity reveal insulin receptors and insulin-like growth factor I receptors in prepancreatic chicken embryos.

We previously reported specific cross-linking of 125I-labeled insulin and 125I-labeled insulin-like growth factor I (IGF-I) to the alpha subunit of their respective receptors in chicken embryos of 20 somites and older. To achieve adequate sensitivity and localize spatially the receptors in younger embryos, we adapted an autoradiographic technique using whole-mounted chicken blastoderms. Insulin receptors and IGF-I receptors were expressed and could be localized as early as gastrulation, before the first somite is formed. Relative density was analyzed by a computer-assisted image system, revealing overall slightly higher binding of IGF-I than of insulin. Structures rich in both types of receptors were predominantly of ectodermal origin: Hensen's node in gastrulating embryos and neural folds, neural tube and optic vesicles during neurulation. The signal transduction capability of the receptors in early organogenesis was assessed by their ability to phosphorylate the exogenous substrate poly(Glu80Tyr20). Ligand-dependent tyrosine phosphorylation was demonstrable with both insulin and IGF-I in glycoprotein-enriched preparations from embryos at days 2 through 6 of embryogenesis. There was a developmentally regulated change in ligand-dependent tyrosine kinase activity, with a sharp increase from day 2 to day 4, in contrast with a small increase in the ligand binding. Binding of 125I-labeled IGF-I was, with the solubilized receptors, severalfold higher than binding of 125I-labeled insulin. However, the insulin-dependent phosphorylation was as high as the IGF-I-dependent phosphorylation at each developmental stage.

Animals↗
PubMed1989

Development of receptors for insulin and insulin-like growth factor-I in head and brain of chick embryos: autoradiographic localization.

In whole brain of chick embryos insulin receptors are highest at the end of embryonic development, while insulin-like growth factor-I (IGF-I) receptors dominate in the early stages. These studies provided evidence for developmental regulation of both types of receptors, but they did not provide information on possible differences between brain regions at each developmental stage or within one region at different embryonic ages. We have now localized the specific binding of [125I]insulin and [125I]IGF-I in sections of head and brain using autoradiography and computer-assisted densitometric analysis. Embryos have been studied from the latter part of organogenesis (days 6 and 12) through late development (day 18, i.e. 3 days before hatching), and the binding patterns have been compared with those in the adult brain. At all ages the binding of both ligands was to discrete anatomical regions. Interestingly, while in late embryos and adult brain the patterns of [125I]insulin and [125I] IGF-I binding were quite distinct, in young embryos both ligands showed very similar localization of binding. In young embryos the retina and lateral wall of the growing encephalic vesicles had the highest binding of both [125I]insulin and [125I]IGF-I. In older embryos, as in the adult brain, insulin binding was high in the paleostriatum augmentatum and molecular layer of the cerebellum, while IGF-I binding was prominent in the hippocampus and neostriatum. The mapping of receptors in a vertebrate embryo model from early prenatal development until adulthood predicts great overlap in any possible function of insulin and IGF-I in brain development, while it anticipates differential localized actions of the peptides in the mature brain.

Animals↗
PubMed1988

Developmental regulation of insulin and type I insulin-like growth factor receptors and absence of type II receptors in chicken embryo tissues.

Chicken embryos are a suitable model for studying the role of insulin, insulin-like growth factors I and II (IGF-I and IGF-II), and their receptors in embryogenesis. We show that plasma membranes from heart, liver, and limb buds, as reported earlier for brain, each have a distinct developmental profile for insulin receptors and type I IGF receptors. In heart and limb buds, IGF binding is higher than insulin binding, but in liver, insulin receptors dominate. Expression of these receptors is, therefore, developmentally regulated and tissue specific. The wide distribution of high-affinity receptors capable of mediating insulin and IGF actions in early organogenesis further supports the possible importance of this family of peptides for differentiation and growth in vertebrates. In all chicken embryo tissues studied, both IGF-I and IGF-II appeared to bind to a type I IGF receptor. We have not detected a receptor with the peptide binding and structural characteristics of the mammalian type II IGF receptor. The type II receptor was absent in embryos, liver from newly hatched chicks, and adipocytes from older chicks, which suggests that the chicken may lack this subtype of IGF receptor.

Animals↗
PubMed1987

Massive thyroxine intoxication: evaluation of plasma extraction.

Six patients were admitted after erroneous massive intake of levothyroxine (70-1200 mg over an interval of 2-12 days). All patients developed classical symptoms of thyrotoxicosis within 3 days of the first dose; five patients presented grade II-III coma and one became stuporous (days 7-10). Two patients developed left ventricular failure and three had arrhythmias (days 8-11). Total thyroid hormone levels in serum on admission ranged 935-7728 nmol/l for T4 (TT4) and 23-399 nmol/l for T3 (TT3). All patients received treatment with hydrocortisone and Propranolol. Propylthiouracil was also given in 3 cases. Extractive techniques (charcoal haemoperfusion and/or plasmapheresis) were initiated 8-14 days after the first dose of L-T4. The plasma disappearance rate (K) of TT4 with plasmapheresis was 30 times higher, on average, than under standard medical treatment (M). Also, K of TT4 under haemoperfusion was about five times higher than K under M. K changes for TT3 were higher under haemoperfusion than under plasmapheresis. Furthermore, extractive procedures shortened the average half life of TT4, (from 106.5 +/- 44.6 to 59.7 +/- 20.2 h, p less than 0.05).

Aged↗
PubMed1987

Insulin and IGF receptors are developmentally regulated in the chick embryo eye lens.

We have previously reported that insulin-like growth factor (IGF) receptors appear to predominate over insulin receptors in early stages of embryogenesis in the chick (days 2-3 whole embryo membranes). Overall, [125I]IGF I and II binding to specific receptors was maximal when the rate of brain growth is highest. In the present study we used the embryonic chick lens, a well-defined tissue composed of a single type of cell, to analyse whether changes of insulin and IGF I binding are correlated with changes in growth rate and differentiation state of the cells. We show that both insulin receptors and IGF receptors are present in the lens epithelial cells, and that each type is distinctly regulated throughout development. While there is a direct correlation between IGF-binding capability and growth rate of the cells, there is less relation to differentiation status and embryo age. Insulin receptors, by contrast, appear to be mostly related to the differentiated state of cells, decreasing sharply in fibers, irrespective of their developmental age.

Animals↗
PubMed1987

The insulin receptors of chick embryo show tissue-specific structural differences which parallel those of the insulin-like growth factor I receptors.

Since specific binding to receptors and biological effects of insulin and insulin-like growth factors (IGFs) are demonstrable soon after the neural tube closes and organogenesis begins in the chick embryo, in the present study we have analyzed the structural characteristics and specificity of the receptors for insulin and IGFs at this early stage of development. We show that membranes from newly differentiated chick embryo tissues (day 6 brain, day 6 heart, day 8 liver, day 12 skeletal muscle) as well as whole embryos postneurulation (day 2, stage of 27-30 somites) have two populations of receptors with distinct specificity: insulin and type I IGF (IGF-I) receptors. Both insulin and IGF-I alpha-subunits, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, had tissue-dependent heterogeneity in Mr (liver greater than heart = skeletal muscle greater than brain) ranging from 138 kilodaltons (kDa) to 129 kDa. Desialylation of the receptors by treatment with neuraminidase produced a significant change in the Mr of the alpha-subunits in liver and heart but not in brain or the whole day 2 embryo. In each tissue the pattern for insulin receptors and IGF-I receptors was strikingly similar. Our studies raise the possibility that postranslational modifications of the insulin and IGF-I receptors, characteristic of terminally differentiated tissues, are already present in early organogenesis. Further, structural heterogeneity of the binding subunit of these receptors among tissues appears to be widespread and not exclusive to the brain receptor. An insulin receptor with features similar to the neural type is the only one detected in embryos at the beginning of organogenesis (day 2). The functional implication of this developmental tissue-specific regulation of insulin and IGF-I receptors, is still speculative. Its possible importance is suggested by the fact that it occurs embryologically early and affects both insulin and IGF-I receptors in parallel.

Animals↗
PubMed1987

Insulin-related receptors in the early chick embryo: from tissue patterns to possible function.

Insulin and two closely related peptides, insulinlike growth factors I and II (IGF-I and IGF-II), as well as their respective receptors, overlap in structure, specificity, and function. Very little is known about the role of these peptides and their receptors in embryogenesis. We have found that chick embryo tissues express both insulin and IGF receptors at very early stages of organogenesis. Each type of receptor is regulated throughout embryogenesis in a manner that is tissue-specific. Substances with insulin immunoactivity and bioactivity are detected in chick embryos at prepancreatic stages (days 2 and 3). Embryos that grow in the presence of antiinsulin antibodies (which are known to neutralize the bioactivity of insulin but not that of the IGFs found in adult vertebrates) demonstrate retarded growth and impaired differentiation. These data support the hypothesis that insulin or insulin-related peptides are essential elements for normal development in the chick embryo.

Animals↗
PubMed1985

Ontogeny of receptors for insulin-like peptides in chick embryo tissues: early dominance of insulin-like growth factor over insulin receptors in brain.

Recently, we confirmed early data showing deleterious effects of exogenous insulin on chick embryos at 2 days of development, although insulin receptors were not clearly demonstrable until days 3-4. Now we report that insulin-like growth factor (IGF) receptors are present in whole embryos on day 2. The developmental patterns of [125I]IGF-I and [125I]IGF-II binding to brain were similar, and IGF-I showed approximately a 2-fold higher binding than IGF-II; there was a sharp increase from days 3 to 6, and a subsequent gradual fall during the second and third weeks of ontogeny. Competitive binding experiments with unlabeled analogs suggested that both labeled IGFs were binding to type I IGF receptors, and insulin interacted with them. The temperature and pH dependence were relatively higher than those for some other known IGF receptors. We have previously reported that [125I]insulin binding to brain is barely detectable on day 3 and shows a progressive rise throughout the rest of embryonic life. The pattern of IGF and insulin receptors appears to be organ specific, since nonneural tissues such as heart, liver, and limb buds showed different binding profiles in ontogeny. We conclude from these data that IGF receptors develop in chick embryo brain before insulin receptors and probably can mediate effects of IGF and insulin at early stages of embryogenesis.

Animals↗
PubMedDate not supplied

Choosing among different technical variations of Percoll centrifugation for sperm selection.

We compared the efficiency of different methodological variations of the centrifugation through discontinuous Percoll gradients (PC) to improve semen samples in the laboratory. Five different combinations of the number, volume and density of PC layers were assayed in 14 semen samples presenting various qualities. Each specimen was divided into five aliquots and processed simultaneously. The percentage of spermatozoa showing optimal movement (VAP > 30 microns s-1 and STR > 80%) after PC selection when the number of gradients was reduced to three or two (PC-3: 43.3%, PC-2: 41.3%) and when the volume of layers was diminished to 0.5 ml (mPC-3: 44.2%, and mPC-2: 48.1%), was higher than in classical columns with four gradients of 1 ml (PC-4: 26.3%). The absolute recovery of optimal sperm was better with PC-2, mPC-2 and mPC-3. In samples showing low concentration or motility of spermatozoa, mPC-2 was the most effective technique. PC-2 and mPC-2 showed a tendency to eliminate more red blood cells contaminating the samples. Straight line velocity and straightness were similarly improved by all the methods. We conclude that the technique of PC centrifugation with only two gradients is simpler and more effective for sperm selection and in cases of poor samples can be used with low-volume layers.

Cell Separation↗