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Biomedical subjects

J Bernal

Publications and source records attributed to J Bernal.

At least 73 records · Page 4Linked to original sources
PubMed1995

Identification of the mitochondrial NADH dehydrogenase subunit 3 (ND3) as a thyroid hormone regulated gene by whole genome PCR analysis.

We previously described a modification of the whole genome PCR method which allowed us to characterize several genes whose expression is regulated by thyroid hormone in the mouse liver. Following this procedure, we now report the identification of the mitochondrial NADH dehydrogenase subunit 3 (ND3) gene as target of thyroid hormone. ND3 gene expression is regulated by thyroid hormone in rat brain and heart. Sequencing and electrophoretic mobility shift assays confirmed the presence of a thyroid hormone receptor (TR)/c-erbA specific binding site in the mitochondrial ND3 gene. Hypothyroidism decreases ND3 mRNA levels in several brain areas such as cortex and hippocampus during the early postnatal development. In line with the recent findings showing the presence of TR/c-erbA alpha and beta proteins inside the mitochondria, our results suggest the possibility of direct transcriptional regulation of mitochondrial genes by thyroid hormone.

Aging↗
PubMed1995

Induction of platelet-derived growth factor B/c-sis by the v-erbA oncogene in glial cells.

The v-erbA oncogene codes for a mutated form of the thyroid hormone receptor TR/c-erbA-alpha. Thyroid hormone (triiodothyronine, T3) regulates glial functions such as myelination and both astrocytes and oligodendrocytes have been shown to express thyroid hormone receptors (TRs). To study putative effects of v-erbA on glial precursors, we have expressed it in a glial clonal cell line established from early embryonal mouse brain. We have found that v-erbA increases cell survival in serum-free conditions. Moreover, v-erbA-expressing cells show a substantial growth in the presence of insulin or IGF-I, whereas normal and TR/c-erbA-over-expressing cells progressively degenerate. By Northern blotting, immunofluorescence, immunoprecipitation, and neutralization experiments, we show that v-erbA actions are mediated by an increase in the levels of PDGF B/c-sis mRNA and protein. We used anti-PDGF receptor and anti-phosphotyrosine antibodies to show the constitutive activation of PDGF receptors in B3.1 + v-erbA cells, and neutralizing anti-PDGF antibodies to demonstrate that v-erbA enhances the secretion of active PDGF into the culture medium. Our data indicate that v-erbA induces PDGF B/c-sis, a factor involved in the generation of gliomas, the most common central nervous system tumor in humans.

3T3 Cells↗
PubMed1995

Thyroid hormone regulates stromelysin expression, protease secretion and the morphogenetic potential of normal polarized mammary epithelial cells.

Stromelysins are a group of proteases which degrade the extracellular matrix and activate other secreted proteases. Stromelysin (ST)-1 and ST-2 genes are induced by tumor promoters, oncogenes and growth factors, and have been involved in acquisition of the malignant phenotype. We show here that the thyroid hormone (T3) increases ST-1 and ST-2 expression in a non-transformed mouse mammary epithelial cell line (EpH4) in a way that is dependent on the level of thyroid receptor/c-erbA (TR alpha-1) expression. In agreement with this, T3 increases the secreted stromelysin activity and enhances the gelatinolytic activity of type IV collagenase. We have also demonstrated that T3 affects the epithelial polarity of EpH4 cells, diminishing the transepithelial electrical resistance of monolayers cultured on permeable filters, causing an abnormal distribution of polarization markers and the disruption of the organized 3-D structures formed by these cells in type I collagen gels. These results indicate that the ligand-activated TR alpha-1 plays an important role in regulating the morphogenetic and invasive capacities of mammary epithelial cells. Because the c-erbA locus is altered in several types of carcinoma, an altered or deregulated TR alpha-1 expression may also be important for breast cancer development and metastasis.

Animals↗
PubMed1995

Frequency source analysis in patients with brain lesions.

In a previous study (Harmony et al. 1993) we observed that the volume of lesions was correlated only with delta power, while the volume and density of edema showed a significant correlation with theta and alpha power, suggesting two independent origins of activity in the delta and theta bands in patients with space-occupying lesions. Our goal in this paper is to show, through a different technique, in a narrow band spectral analysis, that brain lesions are characterized by activity in the delta domain and that edema is better correlated with activity within the theta range. Frequency source analysis based on the Maximum Likelihood (ML) test for rejection of isotropicity was applied to the EEG at rest of 36 patients with space-occupying intracranial lesions. The ML test was rejected at frequencies below 1 Hz and in the low range of the delta rhythm in 31 patients. The origin of the equivalent dipoles at these frequencies was within the volume of the lesion in 27 patients. In 15 patients out of 19 with vasogenic edema the ML test was rejected at frequencies in the theta range. The equivalent dipoles at these frequencies were all within the volume of the edema.

Astrocytoma↗
PubMed1995

EEG activation patterns during the performance of tasks involving different components of mental calculation.

In this study we demonstrate the existence of different patterns of EEG activation during the performance of 4 different tasks involving different components of mental calculation in normal subjects. The EEG was recorded in all monopolar leads of the 10/20 system using linked ear lobes as reference. Absolute and relative power were calculated in the delta (1.5-3.5 Hz), theta (3.5-7.5 Hz), alpha (7.5-12.5 Hz) and beta (12.5-19 Hz) bands. The tasks were presented randomly and the EEG segments preceding presentation of the stimulus were considered as the rest corresponding to the task requested by the stimulus. Tasks were of 4 different types, involving number comprehension, recognition of mathematical symbols, the calculation process and the spatial component. ANOVAs between the rest periods showed no differences in any band. Neither did ANOVAs between tasks. However, other variables (task minus rest), which were calculated as the differences in power between task and rest respectively, showed significant differences between tasks in the delta and beta bands in the frontal lobes. In addition, new variables were calculated as the difference between tasks, since many factors were common across several tasks. These variables correspond to the EEG change due to a specific component of mental calculation. Significant differences were obtained in delta and theta bands in right posterior areas and in the beta band in frontal areas. We concluded that the EEG differences observed during different components of mental calculation suggest the participation of different networks.

Adult↗
PubMed1995

Comparison of Z and multivariate statistical brain electromagnetic maps for the localization of brain lesions.

Conventional Z maps provide probability statements about the deviation of observed values from the norm. Galán et al. (1994) introduced Simultaneous Significance Probability Scales to detect abnormalities over the whole map, making use of the information provided by the topographic structure of dependencies. They also described multivariate brain electromagnetic (MBE) maps for compact presentation of complex spatio-temporal information. In this paper, using the distance-based localization receiver operating characteristic curves (DL-ROC curves), we compare the localization provided by computed tomography with that provided by Z and MBE maps in 61 patients with brain lesions. Maps were calculated for absolute power and relative power in delta, theta, alpha and beta bands for voltage and current source densities (CSD). In each patient, all maps were compared and the map with the highest value of the area of the DL-ROC curve was considered to be the "best map." Z maps of CSD were the "best maps" in 24 patients. In the voltage montage, we observed that multivariate maps add some information not contained in the Z maps. However, for CSD, Z maps were more accurate than multivariate maps. A very consistent finding was the observation that lesions were better detected by maps analyzing the delta band, while edema was better represented by maps in the theta range.

Brain Damage, Chronic↗
PubMed1995

Longitudinal quantitative EEG study of children with different performances on a reading-writing test.

In a previous paper, using the same test for the evaluation of reading-writing abilities, Harmony et al. (1990b) reported that children with severe difficulties had more delta in fronto-temporal regions, and this was interpreted as a sign of underlying cerebral dysfunction. Children with severe and minor difficulties in the test had more diffuse theta absolute and relative powers and less alpha relative power. As theta decreases with age, while alpha increases, these results suggested that children with minor and severe difficulties in reading had a maturational lag with respect to those with normal performance. We conducted this study in order to test this hypothesis. Two different EEG records were obtained with an interval of 2.58-3.15 years in 49 children classified in 3 groups according to their performance in a reading-writing test. Group 1: adequate performance for age and degree (control group); group 2: below level performance with minor difficulties; and group 3: below level performance, with severe difficulties. The mean age of the groups in the first study was 9 years. Absolute (AP) and relative powers (RP) in the delta, theta, alpha and beta bands were computed for each session. In general, groups 3 and 2 showed greater changes than group 1 from session to session. ANOVAs performed by session clearly demonstrate many significant differences between groups in the first study, while few significant differences in parieto-occipital regions in theta RP were observed in the second session. These results point toward a maturational spurt of children from groups 2 and 3.

Brain↗
PubMed1995

Electroencephalographic coherences discriminate between children with different pedagogical evaluation.

The relationship of reading-writing ability and EEG coherences was studied in 84 subjects from two age groups 7.0-8.9 and 9-11.2 years old. All children were divided into three groups according to their performance on a pedagogical test: ped1, normal children; ped2, children with mild problems; ped3, children with reading-writing disability. The following results were obtained: in general, children showed higher coherences in groups with poor performance in the delta, theta and beta bands. In the alpha band, higher coherence values were related to better performance. The exceptions to this general pattern were rare. Group ped2 had higher coherences in delta, theta and alpha bands than ped1 and ped3, in left temporal leads. In older children the same tendency was observed, but group differences in the theta, alpha and beta bands were few. In this age range, the significant group differences were almost all interhemispheric coherences. The discriminant analysis that classified subjects by their coherence values gave very good results, fact that demonstrates, that EEG coherence is a highly sensitive measurement indicating not only the existence of a reading-writing problem, but also the degree of its severity.

Age Factors↗
PubMed1995

Thyroid hormones and brain development.

Thyroid hormone is a major physiological regulator of mammalian brain development. Cell differentiation, migration and gene expression are altered as a consequence of thyroid hormone deficiency or excess. The physiological role of thyroid hormone can perhaps be defined so as to ensure the timed coordination of different developmental events through specific effects on the rate of cell differentiation and gene expression. All triiodothyronine (T3) receptor isoforms are expressed in the brain and their spatial and temporal patterns of expression suggest unique and complementary functions for the different isoforms. Cell biology studies suggest a role for T3 and its receptors in oligodendroglial and neuronal differentiation and the control of cell death. Some of the effects on neuronal differentiation might be due to an action of thyroid hormone on the production of neurotropins and their receptors. In recent years a number of T3-dependent genes have been identified in the rat brain, such as myelin protein-encoding genes or specific neuronal genes, and thyroid hormone-responsive elements have been demonstrated in some of these genes. The identification of the gene network regulated by thyroid hormone during brain development, the elucidation of the mechanism of regulation and the clarification of the physiological roles of the regulated genes remain major goals for future studies.

Animals↗
PubMed1994

Isolation of genomic DNA fragments corresponding to genes modulated in vivo by a transcription factor.

A new methodology for the identification of genes modulated by transcription factors in vivo is described. Mouse genomic DNA fragments bound by the thyroid hormone receptor (T3R) were selected and amplified in vitro. Subsequent hybridisation with biotinylated cDNA allowed the selection of those DNA fragments containing binding sites for T3R that corresponded to transcribed DNA. Expression analysis of the corresponding genes showed that more than 80% are indeed modulated by thyroid hormones in vivo in the liver. Together with the presence of consensus binding sites for T3R this result suggests that the selected DNA fragments may contain T3R transcriptional regulatory elements. This method, extensive to other ligand-modulated transcription factors, might be useful to all transcription factors with slight modifications.

Animals↗
PubMed1994

Characterization of the promoter region and flanking sequences of the neuron-specific gene RC3 (neurogranin).

RC3 encodes a thyroid hormone-dependent, calmodulin-binding, protein kinase C substrate (neurogranin, p17) present in the dendritic spines of discrete neuronal populations in the forebrain. Its physiological role could be related to synaptic plasticity, memory, and other processes. In the present work we have isolated and sequenced 2.4 kbp of genomic DNA upstream from the origin of transcription and determined its nucleotide sequence. The major features of the RC3 promoter are the absence of TATA and CAAT boxes and the presence of an Initiator sequence surrounding the cap site. By sequence analysis we identified several cis-acting regulatory elements, among them response elements for retinoic acid and steroid (glucocorticoids/progesterone) hormone receptors. An oligonucleotide containing the retinoic acid responsive element bound to retinoic acid receptors specifically in vitro and conferred retinoic acid regulation to a heterologous promoter after transfection in COS-7 cells. Retinoic acid and dexamethasone, respectively, increased activity of the RC3 promoter in neuroblastoma cells when a deletion construct containing the retinoic acid and the glucocorticoid responsive elements was cotransfected with retinoic acid receptor or glucocorticoid receptor expression vectors. When added together all-trans retinoic acid and dexamethasone had additive effects. Despite the fact that RC3 expression in vivo is thyroid hormone-dependent, no evidence for the presence of a thyroid hormone responsive element was found within the 2.4 kbp flanking region analyzed and thyroid hormone did not increase reporter activity after cotransfection of suitable constructs with thyroid hormone receptor expression vectors. Our results suggest that the expression of RC3 in vivo could be subject to complex physiological signals, including retinoids and steroid hormones in addition to thyroid hormones.

Amino Acid Sequence↗
PubMed1994

Expression of neurotrophins and the trk family of neurotrophin receptors in normal and hypothyroid rat brain.

Thyroid hormone deficiency has dramatic effects on rat brain maturation. The expression of genes encoding neurotrophins and the trk family of neurotrophin receptors has been evaluated in several brain regions of normal and of neonatal or adult hypothyroid rats to analyze whether they are subject to thyroid hormone action. We found that hypothyroidism decreased trk mRNA levels in its major site of expression, the striatum, on postnatal days 5 (P5; 45%) and 15 (P15; 25%) and also in adults (35%). In contrast, no differences in trkB or trkC mRNAs levels were observed in any brain region at studied ages. According to previous reports, p75LNGFR mRNA was elevated in hypothyroid cerebellum as compared to age-matched controls on P5 and P15. We have also observed a distinct pattern for neurotrophin genes. The level of NGF mRNA was 20-50% lower in the cortex, hippocampus, and cerebellum of hypothyroid rats on neonatal hypothyroid rats on P15 and also after adult-onset hypothyroidism. Treatment of neonatally-induced hypothyroid rats with a single injection of triiodothyronine led to the recovery of hippocampal but not cortex NGF mRNA levels to that of control animals. On the contrary, no differences in the relatively high expression of the two mRNAs encoding BDNF were observed in any brain area. In contrast to a recent report, we did not find a reduction in brain NT-3 mRNA levels in hypothyroid animals. If any, the effect of thyroid deficiency in the hippocampus and cortex seems to be an early upregulation of NT-3 expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

[Knowledge and attitudes about AIDS and sex behavior among school and university students of main urban cities of the country].

A national survey was conducted interviewing 4,522 students and 334 teachers. The result can be extrapolated to young people over 15 years of age and living in the large urban centers of the country. Thus the results can be extrapolated to approximately 330,000 persons. A good theoretical knowledge was detected but invalidated by erroneous beliefs, such as believing that A.I.D.S. is not contagious if relations are held within the same social group, that can be avoided by post-coital genital cleaning or by inquiring about the partner's previous sexual conduct. Forty four two per cent of the surveyed student are sexually active, and of this 32.6% of the men and 10.8% of the women have sexual relations with others outside their regular partners. The 72.9% believe that there is no possibility of A.I.D.S. contagion or that is very low. The erroneous beliefs, the high level of sexual activity the precocious initiation of sexual activity with prostitutes prostitutes and promiscuity among the surveyed, together with the generalized and false perception that there are not possibilities of contagiouness confirm that our youth is in very high risk level of contracting A.I.D.S. virus. Government politic is required to provide a global solution to this problem.

Acquired Immunodeficiency Syndrome↗
PubMed1994

c-erbA and v-erbA modulate growth and gene expression of a mouse glial precursor cell line.

The c-erbA alpha protooncogene coding for the thyroid hormone (T3) receptor (TR alpha 1) and the viral, mutated v-erbA oncogene were expressed in an immortal mouse glial cell line (B3.1) using retroviral vectors. c-erbA alpha expression led to a decrease in cell proliferation in high and low serum conditions, both in the presence and in the absence of T3. In serum-free medium, c-erbA-expressing cells (B3.1 + TR alpha 1) were completely arrested, whereas cells expressing v-erbA (B3.1 + v-erbA) showed a higher DNA synthesis rate than normal B3.1 cells. Although proliferation of all three cell types was stimulated by platelet-derived growth factor and basic fibroblast growth factor, differences were also observed in the response to these agents. B3.1 + TR alpha 1 cells were more sensitive to platelet-derived growth factor than B3.1 and B3.1 + v-erbA cells. In contrast, B3.1 cells responded to basic fibroblast growth factor better than B3.1 + TR alpha 1 or B3.1 + v-erbA cells. Insulin-like growth factor I potentiated the action of platelet-derived growth factor and basic fibroblast growth factor. Again, different responses to treatment with insulin-like growth factor I alone were observed; B3.1 + TR alpha 1 cells did not respond to it, whereas B3.1 + v-erbA cells showed a dramatic stimulation by this agent. Interestingly, in the presence of T3, the blockade in B3.1 + TR alpha 1 cell proliferation was accompanied by the down-regulation of the typical astrocytic genes, glial fibrillary acidic protein and vimentin. These hormone effects were not found in v-erbA-expressing cells. In addition, v-erbA inhibited the basal expression of the cyclic nucleotide phosphodiesterase gene, an oligodendrocytic marker.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Unliganded c-erbA/thyroid hormone receptor induces trkB expression in neuroblastoma cells.

Neurotrophins are responsible for the differentiation and survival of neurons in the developing and in the adult nervous system. They bind to specific membrane receptors with tyrosine kinase activity whose prototype is the product of the trkA proto-oncogene. TrkB, a member of this family, is the receptor for the neurotrophins brain derived growth factor (BDNF) and neurotrophins-3, -4/5. In this study, we show that stable expression of the c-erbA proto-oncogene, which encodes the alpha 1-isoform of the nuclear receptor for thyroid hormone (Tr alpha 1) induces the expression of trkB mRNA with a concomitant decrease to undetectable levels of trkA and trkC mRNAs in the mouse neuroblastoma N2a cell line. trkB induction by c-erbA is ligand independent, since addition of T3 had no effect. The induced trkB transcript encodes a functional gp145trkB protein, which is phosphorylated on tyrosine in response to BDNF. Furthermore, induction of trkB mRNA is also caused by transient expression of either TR alpha 1 or beta 1 isoforms. Our results are compatible with the idea that there are certain pathways which are under control of unliganded thyroid hormone receptor, and that one of these pathways results in regulation of trk expression.

Animals↗
PubMed1993

Retinoic acid posttranscriptionally up-regulates proteolipid protein gene expression in C6 glioma cells.

The proteolipid protein (PLP) gene codes for the major central nervous system myelin protein. We have studied the effects of different agents on the expression of the PLP gene in C6 glioma cells. Retinoic acid (RA), but not dexamethasone, estradiol, insulin, growth hormone, or vitamin D3, had a drastic effect, increasing 10-20-fold the level of PLP mRNA. Concomitantly, RA also induced the appearance of the corresponding immunoreactive protein. The increase in PLP RNA level showed a slow kinetics and was blocked by cycloheximide, suggesting a posttranscriptional regulation by RA. Nuclear run-on assays confirmed that the rate of PLP gene transcription was unchanged by RA. In contrast, we found that retinoic acid augmented PLP mRNA stability, causing a substantial increase in its half-life. RA action was independent of cell density, serum, or PDGF but was partially inhibited by bFGF. On the other hand, thyroid hormone caused a moderate increase in PLP mRNA levels in C6 cells but only when the low numbers of thyroid receptors in these cells were increased by retrovirally mediated expression of an exogenous c-erbA/TR alpha-1 gene. Our results indicate that RA specifically up-regulates PLP expression in glioma C6 cells at a posttranscriptional level by increasing PLP RNA half-life.

Animals↗