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Biomedical subjects

J Medina

Publications and source records attributed to J Medina.

At least 73 records · Page 4Linked to original sources
PubMed1999

The Arabidopsis CBF gene family is composed of three genes encoding AP2 domain-containing proteins whose expression Is regulated by low temperature but not by abscisic acid or dehydration.

We have identified two genes from Arabidopsis that show high similarity with CBF1, a gene encoding an AP2 domain-containing transcriptional activator that binds to the low-temperature-responsive element CCGAC and induces the expression of some cold-regulated genes, increasing plant freezing tolerance. These two genes, which we have named CBF2 and CBF3, also encode proteins containing AP2 DNA-binding motifs. Furthermore, like CBF1, CBF2 and CBF3 proteins also include putative nuclear-localization signals and potential acidic activation domains. The CBF2 and CBF3 genes are linked to CBF1, constituting a cluster on the bottom arm of chromosome IV. The high level of similarity among the three CBF genes, their tandem organization, and the fact that they have the same transcriptional orientation all suggest a common origin. CBF1, CBF2, and CBF3 show identical expression patterns, being induced very rapidly by low-temperature treatment. However, in contrast to most of the cold-induced plant genes characterized, they are not responsive to abscisic acid or dehydration. Taken together, all of these data suggest that CBF2 and CBF3 may function as transcriptional activators, controlling the level of low-temperature gene expression and promoting freezing tolerance through an abscisic acid-independent pathway.

Abscisic Acid↗
PubMed1998

Similarity and the development of rules.

Similarity-based and rule-based accounts of cognition are often portrayed as opposing accounts. In this paper we suggest that in learning and development, the process of comparison can act as a bridge between similarity-based and rule-based processing. We suggest that comparison involves a process of structural alignment and mapping between two representations. This kind of structure-sensitive comparison process--which may be triggered either by experiential or symbolic juxtapositions--has a twofold significance for cognitive development. First, as a learning mechanism, comparison facilitates the grasp of structural commonalities and the abstraction of rules; and, second, as a mechanism for the application and extension of previously acquired knowledge, comparison processes facilitate the application of abstract knowledge to new instances.

Adult↗
PubMed1998

[The value of cardiac troponin I as diagnostic test in the study of chest pain].

BACKGROUND AND OBJECTIVES: Cardiac troponin I is a highly sensitive and specific myocardial injury marker. We have analyzed the use of cardiac troponin I values in the diagnosis of coronary artery disease, in previously healthy patients who developed chest pain with inconclusive analytical and ECG diagnostic findings. PATIENTS, MATERIAL AND METHODS: A one year cross-sectional consecutive study was conducted, in a total of 37 patients with no previously known heart disease who were admitted to the coronary unit for suspected anginal chest pain with normal cardiac enzymes and ECG. Abnormal cardiac troponin I levels at admission were defined as > or = 0.4 ng/ml, and were compared with coronary angiography or exercise test results and related to the duration of pain and the time from the appearance of symptoms to blood extraction. RESULTS: Thirty-three of the 37 initially included patients were studied. Coronary artery disease was diagnosed in 22, 15 of whom had increased troponin I values, yielding a sensitivity of 68% (48%-84%) and a specificity of 82% (53%-97%). In the subgroup of patients with pain lasting > 30 min, sensitivity reached 85% (59%-97%) and specificity 83% (42%-99%). There were no significant differences between subgroups with different time delays from appearance of symptoms to blood extraction. CONCLUSIONS: Cardiac troponin I is very useful for the studying ischemic chest pain without a definitive diagnostic ECG nor biochemical data, resulting in a high sensitivity and specificity for myocardial ischemic injury detection. Its diagnostic value increases in cases of prolonged pain episodes.

Adult↗
PubMed1998

14-3-3 proteins are part of an abscisic acid-VIVIPAROUS1 (VP1) response complex in the Em promoter and interact with VP1 and EmBP1.

Protein-DNA complexes were formed when nuclear extracts from embryogenic rice suspension cultures or maize embryos were incubated with an abscisic acid-VIVIPAROUS1 (VP1) response element (Em1a) from the Em promoter. Monoclonal antibodies generated to GF14, a 14-3-3 protein from plants, resulted in gel retardation of the Em1a-protein complexes. Antibodies generated to the C and N termini of GF14 detected protein isoforms in rice nuclear and cytoplasmic extracts, but no differences in distribution of the GF14 isoforms were recognized between the nucleus and cytoplasm or when abscisic acid-treated and untreated tissues were compared. When recombinant GF14 fusion proteins from rice were added to nuclear extracts, novel complexes were formed that required the dimerization domain of GF14. Chemical cross-linking showed that GF-14 interacted with the basic leucine zipper factor EmBP1, which binds specifically to Em1a, and with VP1, which transactivates Em through Em1a. GF14 proteins from rice were shown to interact with VP1 in yeast through the dimerization domain of GF14. Our results indicated that GF14 interacts with both site-specific DNA binding proteins (i.e., EmBP1) and tissue-specific regulatory factors (i.e., VP1) and may provide a structural link between VP1 and the Em1a transcriptional complex.

14-3-3 Proteins↗
PubMed1998

[Antitumor gene therapy using suicide genes].

Tumor cells transduced with retrovirus carrying the herpes simplex-1 virus thymidine kinase (HSV-tk) are capable of transforming the antiviral drug ganciclovir (GVC) into a metabolic form only toxic to dividing cells. The efficiency of this suicide gene therapy is increased by a "bystander" effect resulting not only in the death of the recipient cell, but also in the death of non modified surrounding cells. Even though the mechanism of this "bystander" effect remains to be elucidated, strong evidence suggest that the immune system plays a main role to achieve complete tumor eradication. In the present study we evaluate the efficiency of this suicide system on three different tumor models: one human melanoma, one murine melanoma, and a rat glioblastoma. Tumors were established by injection of tumor cells s.c. in nude and C57Bl/6 mice, respectively, and stereotactically into the brain of Sprague Dawley rats. Animals in the treated group were co-injected with packaging cells producing recombinant retrovirus carrying the HSV-tk gene, and followed by i.p. administration of GVC. In short term studies, we observed inhibition of tumor growth for all the tumor models evaluated (p < 0.01). In long term studies, using the C6 rat glioma line, 50% of the animals survived longer than 75 days (p < 0.0001), and were able to reject a contralateral challenges with C6 parental cells. Histological and immunohistochemical analysis showed the presence at an inflammatory infiltrate composed by T lymphocytes, macrophages and polymorphonuclear cells. These data demonstrate that suicide genes might represent an attractive form of cancer gene therapy in the treatment of brain tumors and their intracerebral dissemination.

Animals↗
PubMed1997

Cyclosporine A-induced contraction of isolated rat aortic smooth muscle cells.

The mechanisms by which the immunosuppressive drug cyclosporine A (CsA) induces hypertension and nephrotoxicity are still not fully understood. Although smooth muscle cell (SMC) contraction is probably the mechanism of vasoconstriction, the direct contractive effect of CsA on SMCs has not yet been demonstrated. Thus, it was the purpose of this study to evaluate the direct effects of CsA in cultured SMCs through interactive image analysis. In aortic SMCs, CsA at the concentrations of 0.01, 0.1 and 1 microM, caused a concentration-dependent decrease of the planar cross-sectional area (PCSA) after 30 min and 60 min of treatment. The PCSA decreases were statistically significantly different from control at all concentrations. No cytotoxicity was observed under these conditions. Ten minutes preincubation of SMCs with a monoclonal antibody against endothelin-1 (ET-1) significantly prevented the CsA effects at 1 microM. When the same antibody was heat inactivated or an unspecific antibody (anti-desmin immunoglobulin G) was applied, the CsA-induced contractions were not affected. These data suggest that CsA can cause a direct contractive effect on vascular SMCs. This effect is partly mediated by ET-1.

Animals↗
PubMed1995

Acute otitis media in childhood: a study of 20,532 cases.

We present a study of acute otitis media among 20,532 Spanish children during a 6-month period from January through June 1991. The study was done by distributing a questionnaire to all Spanish pediatricians. Of the patients 51.7% were girls and 48.3% boys; 68.7% of all children were younger than 5 years. The most frequent symptoms were otalgia or irritability, 92.7%; fever, 63.5%; otorrhea, 24.9%; vomiting, 21.4%; and another concomitant upper respiratory tract infection, 65.5%. Otitis was bilateral in 45.6% of the cases. The most frequently used antibiotic was cefixime (38%), followed by amoxicillin-clavulanate (22.2%), amoxicillin (15.3%), 2nd-generation cephalosporins (13.5%) and macrolides (8.8%). In 11.8% of the patients, a change in the initial antibiotic therapy was required due to adverse effects. Resolution of symptoms occurred in 77.8% of the patients.

Acute Disease↗
PubMed1995

Effects of prenatal diazepam on two-way avoidance behavior, swimming navigation and brain levels of benzodiazepine-like molecules in male Roman high- and low-avoidance rats.

Utilizing psychogenetically selected Roman high- and low-avoidance rats (RHA/Verh and RLA/Verh), the present experiments investigated the effects of prenatally administered vehicle and diazepam (1 and 3 mg/kg per day, SC) on the behavior and neurochemistry of adult, male offspring. Active, two-way avoidance behavior was analyzed in 96 rats, at 6 months of age, and swimming navigation in 68 others, at 11 months. Three weeks after testing, selected brain areas from the latter animals were immunoassayed for benzodiazepine (BZD)-like molecules. The 3 mg/kg dose of diazepam both decreased freezing behavior in the shuttle box and reduced the hippocampal content of BZD-like molecules in the RLA/Verh male rats. Swimming navigation (spatial learning), at which the RLA/Verh rats were more adept, was not specifically affected by prenatal diazepam in either rat line. The possibility exists that an increased hippocampal release of BZD-like substances may be necessary to alter shuttle box behavior in RLA/Verh rats.

Animals↗
PubMed1995

Effects of somatostatin on cultured human mesangial cells.

The present experiments were devoted to analyzing the hypothesis that somatostatin (SS) could modulate glomerular filtration rate by interacting with mesangial cells. Studies were performed in cultured human mesangial cells, passages 3-5. Radioligand experiments demonstrated the presence in the cells of two kinds of receptors, with high (dissociation constant 14 pM. Number of sites: 426 fmol/mg) and low (dissociation constant 56 pM. Number of sites: 20, 111 fmol/mg) affinity. SS prevented in a dose-dependent manner the reduction in planar cell surface area induced by 100 nM Angiotensin II (AII). This effect was not inhibited by the blockade of the vasorelaxing prostaglandins (indomethacin, 10 microM), nitric oxide (L-N-methyl-arginine, 0.2 mM), adenylate cyclase (2,5'-dideoxyadenosine, 0.1 mM), or guanylate cyclase (Methylene blue, 30 microM; LY-83583, 10 microM), but it was potentiated by zaprinast, an inhibitor of the cyclic GMP (cGMP)-specific phosphodiesterase. SS also blocked the increase in myosin light chain phosphorylation induced by AII. SS increased cGMP synthesis by cultured human mesangial cells, an effect that seemed to be dependent on the stimulation of a particulate guanylate cyclase. Preincubation of the cells with pertussis toxin (0.5 microgram/ml) inhibited the effect of SS on the AII-dependent changes in planar cell surface area, as well as the SS-dependent cGMP stimulation. In summary, these results demonstrate the ability of SS to relax cultured human mesangial cells, thus supporting a role for this peptide in the regulation of the glomerular filtration rate. The SS-dependent mesangial cell relaxation may be due to changes in the intracellular concentrations of cGMP, as a consequence of the activation of a particulate guanylate cyclase.

Angiotensin II↗
PubMed1995

[Hereditary spherocytosis: clinical characteristics and treatment with splenectomy].

PURPOSE: To analyse the clinico-biological characteristics at diagnosis, the clinical course, and the response to splenectomy of a series of patients with hereditary spherocytosis (HS). PATIENTS AND METHODS: The clinical records of 61 patients diagnosed of HS along 30 years were reviewed. The diagnosis was based upon the existence of family history, physical findings, blood cell examination, reticulocyte count, peripheral blood spherocytes, red-cell osmotic fragility, auto-haemolysis, serum haptoglobin, LDH, non-conjugated bilirubin and direct anti-human globulin test. Data regarding the time of diagnosis and clinical course were taken into account in every case. Within the sub-group of 29 patients undergoing splenectomy, the changes in haemoglobin rates and reticulocyte and platelet counts after surgery were evaluated. RESULTS: Of the 61 patients, 35 were men and 26 women; the median age at diagnosis was 13 years (range: 0-64 years). Family history was positive in only 40% of the cases. The mean haemoglobin rate was 112 g/L (range: 46-151 g/L), over 60% of the patients having anaemia. The mean reticulocyte count was 282 x 10(9)/L (range: 31-583 x 10(9)/L), this being above 100 x 10(9)/L in 91% of the cases. Red-cell osmotic fragility with fresh blood was increased in 86% of the cases, and in 97% after blood incubation. Serum haptoglobins were decreased, whereas LDH was increased in 58% of the patients and non-conjugated bilirubin in 72%. Splenomegaly appeared in the clinical course in 87% of the patients; cholelithiasis was present in 31.5% of them. Haemoiytic crises were seen in 45% of patients, aplastic phases in 7%, and transfusion was needed by 16% of the patients to variable extents. Splenectomy was performed in 50% of the instances before 14 years of age (range: 4-64 years), and it increased haemoglobin rates in 40 g/L, anaemia being corrected in all cases; the mean reticulocyte count returned to normal, but thrombocytosis developed after surgery, it being present in 82% of the cases 2-3 months later. CONCLUSIONS: (1) Wide clinical variability is seen in HS, from severe forms requiring frequent transfusion to asymptomatic cases. (2) Highly frequent findings in HS are reticulocytosis and splenomegaly; relatively frequent were anaemia, haemolytic crisis and cholelithiasis, in this order. (3) Anaemia was always corrected after splenectomy, which also rose the haemoglobin rate even in the cases without anaemia, and returned the reticulocyte count to normal values.

Adolescent↗
PubMed1994

Sexual differences in the effect of the GABAergic system on LH secretion and in the hypothalamic ontogenesis of GABAA receptors in prepubertal rats.

The administration of aminooxyacetic acid (AOAA), which increases hypothalamic GABA concentrations, induced a significant increase in LH levels in female rats of 12, 16 and 18 days of age. This stimulatory effect of AOAA on serum LH levels was not observed at 21 and 25 days of age whereas a significant decrease in the LH concentrations by AOAA was found at 30 days of age. The neonatal androgenization of female rats abolished the effects of AOAA and no effects of AOAA were found in male rats at the different ages studied. The muscimol binding sites in medial basal and preoptic anterior hypothalamic areas showed a significant different sexual ontogenic pattern. Males rats castrated at birth showed a very similar ontogenic pattern of [3H]muscimol binding sites to female rats and significantly different to male control rats. It is concluded that there are sexual differences in the effect of GABAergic system on LHRH-LH secretion and in the development of hypothalamic GABAA receptors during sexual maturation. These differences are probably connected with the neonatal exposure to androgens that would induced changes in the composition and probably in the properties of GABAA receptor that in turn modified its effects on LHRH neurons.

Aging↗
PubMed1994

Recovery of central noradrenergic neurons one year after the administration of the neurotoxin DSP4.

The long-term effects of the systemic administration of DSP4 (N-(2-chloroethyl)N-ethyl-2-bromobenzylamine hydrochloride), a selective noradrenergic neurotoxin, on the endogenous levels of monoamines and their metabolites and on alpha- and beta-adrenoceptors in selected brain regions of the rat were examined. After 7 days, DSP4 caused a marked reduction (about 80%) of endogenous noradrenaline levels in locus coeruleus-innervated regions. At 90, 240 and 300 days after DSP4 injection, a partial and gradual recovery (50%, 41% and 25% of control values, respectively) of the noradrenaline cortical levels was evident. One year after DSP4 administration, brain regional noradrenaline stores were almost completely recovered. No changes in 5-hydroxytryptamine levels were observed in the three time intervals, but a mild decrease in cortical and hippocampal 5-hydroxyindolacetic acid levels was found 7 days after DSP4 injection. Following the profound noradrenaline depletion seen at 7 days, the cerebral cortical density of alpha 1-, alpha 2- and beta-adrenoceptors was significantly increased. Assessment of adrenergic receptors in cerebral cortex at 365 days after DSP4 injection, indicated that alpha 1- and alpha 2-adrenoceptor densities did not differ from control values; however, the density of beta-adrenoceptors remained increased. No changes were observed in the affinities of the three types of adrenoceptors studied. These results indicate that after a selective noradrenergic denervation induced by DSP4, there is a slow and gradual recovery of noradrenaline stores and of alpha 1- and alpha 2-adrenoceptor populations, suggesting a possible regrowth and/or collateral sprouting of noradrenergic terminals.

Animals↗
PubMed1994

[Lyme disease in the province of Soria: clinico-epidemiologic study].

BACKGROUND: To determine the prevalence of the Borrelia burgdorferi infection in the Soria Province, and the detection of the human disease cases. METHODS: By an indirect immunofluorescence technique, we had studied total antibodies (IgG, IgM and IgA) against B. burgdorferi (B 31 strain) in the sera of 298 people (150 men y 148 women) of the Soria Province. The results were considered positive when the titers were same or upper to 1/256. All positive sera were tested for specific IgM antibodies by same method; IgM results were considered positive when the titers were upper to 1/16. RESULTS: 13.1% of the people had positive results (39 sera): 14 for women (9.5%) and 25 for men (16.7%). We detected 14 sera with positive IgM. We demonstrated titers same or upper to 1/256 in all age group, with a major prevalence in the age group between 41 and 50 years (22.6%). In all areas of the Province we detected positive results and in many of this areas the positivity was upper to 30% of the studied sera. 12 persons with positive IgM or high titers of total antibodies presented signs or symptoms of disease in relation with B. burgdorferi infection; 6 persons had alterations of the liver function do not explicable by other etiology. CONCLUSIONS: The B. burgdorferi infection present a high prevalence in this Province and a wide geographic distribution, with high endemic areas. We demonstrated patients with symptomatology compatible with Lyme borreliosis, and we wish to emphasize the frequency of alterations of the liver function in this group of people.

Adolescent↗
PubMed1993

Differential cholinergic and non-cholinergic actions of acetylcholinesterase in the substantia nigra revealed by fasciculin-induced inhibition.

The effects of the peptide fasciculin (FAS), a potent inhibitor of acetylcholinesterase (AChE) have been examined, following unilateral microinfusion, on tissue levels of monoamines in the rat substantia nigra and concomitant circling behaviour. Although FAS inhibited 87% of total AChE, the levels of dopamine and its metabolites remained unchanged. Furthermore, the treatment induced modest contraversive rotation which was markedly enhanced in the presence of a systemic challenge with apomorphine. This behavioural effect of FAS was partially reversed by systemically administered atropine. Any possible interaction of FAS with nigral dopamine systems was further investigated by testing the peptide in animals that five days earlier had undergone a 6-hydroxydopamine (6-OHDA) lesion of the SN such that dopamine and AChE were significantly but not completely reduced. In a majority of these animals, FAS treatment caused a reversal of the lesion induced ipsiversive rotation, ie restored contraversive rotation. It is concluded that in the SN, FAS can have biochemical and behavioural actions independent of local dopamine systems and linked to cholinergic transmission. In addition, treatment with FAS in the substantia nigra also reveals the possible existence of at least two distinct pools of AChE with, respectively, non-cholinergic and cholinergic actions.

3,4-Dihydroxyphenylacetic Acid↗