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Biomedical subjects

A González

Publications and source records attributed to A González.

At least 19 recordsLinked to original sources
PubMed1992

Epidermal growth factor receptor in synaptic fractions of the rat central nervous system.

Functional relationships between epidermal growth factor (EGF) and neural tissues have of late attracted increasing interest. However, in spite of reported EGF effects on neurons, the expression of the EGF receptor (EGF-R) has not yet been unambiguously demonstrated in these cells. This 170-kDa protein bears an intracellular tyrosine kinase domain in which activity is ligand-dependent. We give definitive evidence here for its presence in neonatal and adult rat neurons showing also, for the first time, its binding and functional tyrosine kinase activities in the synaptic region. Immunohistochemistry using a polyclonal antibody prepared against the receptor purified from rat liver showed positive staining localized exclusively to neurons without regionalization to any particular brain zone. Binding studies made in Percoll-obtained synaptosomes revealed specific high affinity 125I-EGF binding sites (Kd, 1.42 x 10(-10) +/- 0.58 M) accounting for 17% of total binding and a great majority of low affinity (Kd, 2.55 x 10(-9) +/- 0.35 M) binding sites. Higher binding capacity was found in synaptosomal fractions obtained from newborn rats. The identity of the synaptosomal EGF binding activity with the 170-kDA EGF-R protein was demonstrated by cross-linking experiments. Furthermore, EGF-Affi-Prep affinity chromatography adsorbs a 170-kDa protein with EGF-R immunoreactivity from whole homogenates of adult rat brain. Phosphorylation assays made in freeze-thawed or intact synaptosomes showed EGF-induced tyrosine phosphorylation in the range of 170-, 126-150-, 124-, 113-, 98-, and 70-kDa proteins including the EGF-R. Thus, the EGF-R/EGF regulatory system could have a role in synaptic function that remains to be explored.

Animals↗
PubMed1992

Comparative analysis of the vasotocinergic and mesotocinergic cells and fibers in the brain of two amphibians, the anuran Rana ridibunda and the urodele Pleurodeles waltlii.

To obtain more insight into the vasotocinergic and mesotocinergic systems of amphibians and the evolution of these neuropeptidergic systems in vertebrates in general, the distribution of vasotocin (AVT) and mesotocin (MST) was studied immunohistochemically in the brains of the anuran Rana ridibunda and the urodele Pleurodeles waltlii. In Rana, AVT-immunoreactive cell bodies are located in the nucleus accumbens, the dorsal striatum, the lateral and medial part of the amygdala, an area adjacent to the anterior commissure, the magnocellular preoptic nucleus, the hypothalamus, the mesencephalic tegmentum, and in an area adjacent to the solitary tract. In Pleurodeles, AVT-immunoreactive somata are confined to the medial amygdala, the preoptic area, and an area lateral to the presumed locus coeruleus. In both species, the distribution of MST-immunoreactive cell bodies is more restricted: in the frog, MST-immunoreactive somata are present in the medial amygdala and the preoptic area, whereas, in the urodele, cell bodies are found only in the preoptic area. Both in Rana and Pleurodeles, AVT- and MST-immunoreactive fibers are distributed throughout the brain and spinal cord. A major difference is that in Rana the number of MST-immunoreactive fibers is evidently higher than that of AVT-immunoreactive fibers, whereas the opposite is found in Pleurodeles. This holds, in particular, for the forebrain and the brainstem. The presence of several extrahypothalamic AVT-immunoreactive cell groups and the existence of well-developed extrahypothalamic networks of AVT- and MST-immunoreactive fibers are features that amphibians share with amniotes. However, this study has revealed that major differences exist not only between species of different classes of vertebrates, but also within a single class. In order to determine whether features of these neuropeptidergic systems are primitive or derived, a broad selection of species of each class of vertebrates is needed.

Animals↗
PubMed1992

Novel genetic markers of rheumatoid arthritis in Chilean patients, by DR serotyping and restriction fragment length polymorphism analysis.

OBJECTIVE: The analysis of genetic markers of rheumatoid arthritis (RA) in a population in which the DR4 serotype is not strongly associated with the disease. METHODS: Chilean RA patients (56 seropositive and 22 seronegative) and 141 controls were studied by serotyping. Southern blot analysis of Bam HI restriction fragment length polymorphism (RFLP) was done in genomic DNA from 46 patients with seropositive RA, 17 patients with seronegative RA, and 45 controls, using a complementary DNA probe specific for DRB1 genes. RESULTS: The prevalence of the HLA-DR9 haplotype was strikingly higher in seropositive RA patients (21%) than in controls (3%) (Pcorr less than 0.0008, by Fisher's exact test; relative risk [RR] = 9.34). The prevalence of DR4 and DR1 haplotypes, although slightly increased, did not achieve a significant preponderance. The simultaneous presence of two Bam HI fragments (3.6 kb and 4.5 kb) was found with higher prevalence in seropositive patients (83%; RR = 9; Pcorr less than 0.00002) than in controls (36%), and seemed higher in seronegative RA patients as well (71%; RR = 4). Furthermore, its prevalence remained increased in comparisons of DR4 positive controls (36%) with DR4 positive seropositive patients (100%; RR = 67; Pcorr less than 0.0002) and DR4 positive seronegative patients (100%; RR = 36; Pcorr less than 0.006), even after excluding the DR9 positive individuals. A tendency toward higher association with DR1 seropositive RA patients (67%; RR = 12), a group with no DR4 or DR9 positive individuals, than in DR1 positive controls (14%), was also observed. CONCLUSION: The HLA-DR9 haplotype was definitively consolidated as a very strong genetic marker exclusively for seropositive RA in Chilean patients, as suggested by our previous observations. RFLP analysis showed that the simultaneous presence of 3.6-kb and 4.5-kb Bam HI fragments constituted a better RA marker than did any of the heretofore studied haplotypes. These fragments together would be linked to RA independently of the DR1, DR4, and DR9 haplotypes. The overall evidence indicates that Chilean seropositive RA patients display a genetic background that is different from that underlying RA susceptibility in other populations and suggests the existence of common, as well as distinct, genetic elements predisposing to seronegative and seropositive RA.

Adult↗
PubMed1992

Interferon-alpha in acute posttransfusion hepatitis C: a randomized, controlled trial.

To assess the efficacy of interferon-alpha in acute hepatitis C, 28 patients with acute posttransfusion hepatitis were randomized to receive 3 million units of recombinant interferon-alpha three times weekly for 12 wk or no treatment. Biochemical, histological and serological parameters were monitored during 1 yr of follow-up. Serum ALT levels were normal at the end of therapy in 73% of treated patients and only in 38% of control patients (p = 0.06); these differences disappeared at 6 and 12 mo of follow-up. Anti-hepatitis C virus seroconversion occurred later and at a lower rate in the group of patients who received interferon-alpha. Treated patients had a trend toward less severe hepatic lesions with lower histological activity as compared with the control group, but no statistical differences were observed. No severe side effects of interferon-alpha were detected during the study. In summary, a 3-mo course of interferon-alpha in acute hepatitis C is safe and might have some effect in diminishing disease activity only during the treatment period; however, and probably because of a small sample size, no benefit of interferon-alpha in the long-term outcome of this disease was demonstrated.

Adolescent↗
PubMed1992

Diagnosis of subacute ventricular wall rupture after acute myocardial infarction: sensitivity and specificity of clinical, hemodynamic and echocardiographic criteria.

When ventricular free wall rupture after acute myocardial infarction is not followed by sudden death, it is referred to as subacute ventricular rupture. The sensitivity and specificity of clinical, hemodynamic and echocardiographic diagnostic variables obtained at bedside are unknown and were therefore prospectively studied in 1,247 consecutive patients with acute myocardial infarction including 33 patients with subacute ventricular rupture diagnosed at operation (group A) and 1,214 patients without ventricular rupture (at operation, postmortem study or at discharge) (group B). The incidence of syncope, recurrent chest pain, hypotension, electromechanical dissociation, cardiac tamponade, pericardial effusion, high acoustic intrapericardial echoes, right atrial and right ventricular wall compression identified in two-dimensional echocardiograms and hemopericardium demonstrated during pericardiocentesis was higher in group A than in group B (p less than 0.00001). The presence of cardiac tamponade, pericardial effusion greater than 5 mm, high density intrapericardial echoes or right atrial or right ventricular wall compression had a high diagnostic sensitivity (greater than or equal to 70%) and specificity (greater than 90%). The number of false positive diagnoses was always high for each diagnostic variable alone (greater than 20%), but the combination of clinical (hypotension), hemodynamic (cardiac tamponade) and echocardiographic variables allowed a sensitivity of greater than or equal to 65% with a small number of false positive diagnoses (less than 10%) and provided useful information for therapeutic decisions. The diagnosis of subacute ventricular rupture requires a surgical decision. Twenty-five (76%) of the 33 patients with subacute ventricular rupture survived the surgical procedure and 16 (48.5%) are long-term survivors. Thus, subacute ventricular wall rupture is a relatively frequent complication after acute myocardial infarction that can be accurately diagnosed and successfully treated.

Cardiac Catheterization↗
PubMed1992

Effect of myotonia induced by anthracene-9-carboxylic acid on mitochondrial calcium, plasma creatinine-phosphokinase and aldolase activity in the rat.

The frequent association of myotonia with dystrophy and the knowledge that calcium is increased in injured skeletal muscle cells suggest a possible relationship between cell calcium and myotonic alterations. This investigation has been performed to study the role of calcium in experimental myotonia induced by anthracene-9-carboxylic acid (9-AC) in rats treated with several regimens of food and exercise. Thirty-two rats were divided into 4 groups of 8 rats each, one control and 3 experimental groups. The treatments included caffeine plus exercise (group 2), and a calcium-rich diet (group 3); these procedures were designed to increase intracellular calcium; another group was treated with 9-AC as a myotonia-inducer (group 4). The treatment for all groups lasted 60 days. No significant differences in plasma sodium, potassium, chloride and calcium between control and experimental groups were observed. Whole muscle calcium in wet tissue samples did no change with any treatment. On the contrary, mitochondrial calcium showed a significantly higher concentration in group 3 and 4. CPK and aldolase activities in groups 1, 2 and 3 were similar; but in group 4 these enzyme activities were significantly higher (p less than 0.05). The electrical and mechanical responses were not altered in any rat with any experimental treatment. Our data suggest that myotonia is a predisposing factor for an altered mitochondrial calcium homeostasis in this model; in addition, the enzyme activities of CPK and aldolase were increased in the rats of group 4 implicating that myotonia is a crucial factor in the development of enzymatic abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Apoptosis in human thymocytes after treatment with glucocorticoids.

Treatment of unfractionated human thymocytes in culture with the synthetic glucocorticoid dexamethasone induced cell death, as measured by trypan blue exclusion, after several hours of incubation. In purified subsets of human cortical and medullary thymocytes dexamethasone caused cell lysis with similar kinetics in both populations; 50% of thymocytes were killed after 20-24 h of incubation with the steroid. The mechanism of dexamethasone-induced cell death seems to correspond to apoptosis since degradation of DNA into oligonucleosome-sized fragments could be observed in the cultures treated with the steroid. A certain degree of DNA fragmentation and cell death could also be observed in control cultures of thymocytes. In contrast, peripheral T lymphocytes were resistant to the cytolytic effect of glucocorticoid hormone. The killing of human thymocytes by dexamethasone was inhibited by cycloheximide, suggesting that this cell death program requires a fully operating protein synthesis machinery and perhaps the induction of new proteins.

Cell Death↗
PubMed1992

Intrafamilial outbreak of Mediterranean spotted fever.

The existence of intrafamilial outbreaks of spotted-fever group rickettsioses has seldom been reported, and their true incidence is not known. We here report the occurrence of Mediterranean spotted fever (MSF) in three members of a family: a boy, his grandmother and his grandfather. The infection resolved uneventfully in the boy, and followed a more protracted course in the two older patients, who suffered complications including drowsiness, clotting defects and acute renal failure. This finding highlights the importance of conditioning factors such as age and associated illnesses in the prognosis of infection due to Rickettsia conorii, and suggests that strict surveillance of individuals at risk of infection is necessary for prompt recognition of the onset of the illness and initiation of antibiotic treatment without delay.

Aged↗
PubMed1992

Cloning of a yeast gene coding for the glutamate synthase small subunit (GUS2) by complementation of Saccharomyces cerevisiae and Escherichia coli glutamate auxotrophs.

A Saccharomyces cerevisiae glutamate auxotroph, lacking NADP-glutamate dehydrogenase (NADP-GDH) and glutamate synthase (GOGAT) activities, was complemented with a yeast genomic library. Clones were obtained which still lacked NADP-GDH but showed GOGAT activity. Northern analysis revealed that the DNA fragment present in the complementing plasmids coded for a 1.5kb mRNA. Since the only GOGAT enzyme so far purified from S. cerevisiae is made up of a small and a large subunit, the size of the mRNA suggested that the cloned DNA fragment could code for the GOGAT small subunit. Plasmids were purified and used to transform Escherichia coli glutamate auxotrophs. Transformants were only recovered when the recipient strain was an E. coli GDH-less mutant lacking the small GOGAT subunit. These data show that we have cloned the structural gene coding for the yeast small subunit (GUS2). Evidence is also presented indicating that the GOGAT enzyme which is synthesized in the E. coli transformants is a hybrid comprising the large E. coli subunit and the small S. cerevisiae subunit.

Blotting, Northern↗
PubMed1992

Cytoarchitecture and ultrastructural characteristics of the area octavolateralis of the urodele amphibian Pleurodeles waltlii.

The cytoarchitecture of the area octavolateralis (AOL) in Pleurodeles waltlii is studied by means of normal stained material. In addition, the main ultrastructural features of the cells in the AOL are described. In the AOL, three columns, one upon the other (dorsal, intermediate and ventral), are present. Each one includes a medially located cell group and lateral neuropil. While rostrally the three are well represented, the dorsal subdivision do not reach the same caudal extent where the intermediate column forms a small lobe. The ultrastructure of the neurons in the AOL reveals similarities with other cell types in the amphibian brain. A comparative analysis of the ultrastructure of vestibular cells with other vertebrates is also discussed.

Animals↗
PubMed1992

[Serological diagnosis of pulmonary tuberculosis using ELISA and the A60 antigen].

BACKGROUND: Study of the utility of a serologic technic in the clinic diagnostic of the pulmonary tuberculosis. METHODS: An indirect enzyme-linked immunosorbent assay (ELISA) for detecting serum antibodies (IgG) against the antigen A60 has been applied to 170 tuberculosis patients (151 adults and 19 children) and 35 healthy children not protected with BCG. RESULTS: The ELISA results obtained with tuberculosis patients were: 84.8% positive IgG in adults and 21.1% in children. The percentage of serologically positive cases in healthy children against the antigen A60 was 11.5%. All the results were statistically significant (p less than 0.01). CONCLUSIONS: This test can be successfully applied as a support technique in the diagnosis of pulmonary tuberculosis in adults, it will be necessary to know the endemic situation in each community analysed.

Adult↗
PubMed1992

Differential effect of tumour necrosis factor on human thymocyte subpopulations.

We have studied the effect of tumour necrosis factor (TNF) on purified human thymocyte subpopulations. For this purpose human thymocytes were purified by negative selection with three rounds of several antibodies plus complement. TNF was able to co-stimulate in a dose-response manner the proliferation of single positive (SP) CD3+ CD4+ or CD3+ CD8+ thymocytes in the presence of optimal doses of interleukin-2 (IL-2), phytohaemagglutinin (PHA), anti-CD3 antibodies or phorbol esters. However, CD1+ CD3low CD4+ CD8+ cortical thymocytes did not proliferate significantly in response to any stimulus alone or in combination. The TNF proliferative effect on SP thymocytes was blocked by an anti-IL-2R alpha antibody. In addition, TNF enhanced the expression of the IL-2R alpha but not IL-2R beta on the cell surface of CD1- CD3+ SP thymocytes over the levels induced by the other primary stimuli, inducing as a consequence, an increase in the number of high affinity IL-2R. Furthermore, TNF was able to increase IL-2R alpha mRNA levels on SP thymocytes. On the other hand, TNF was mitogenic in the absence of any other stimulus for CD1- CD3- CD4- CD8- prethymocytes, as was IL-2, and this proliferation was not blocked by anti-IL-2R alpha antibodies. Furthermore, the proliferation of this subset in response to IL-2 and TNF was additive. TNF was able to increase directly the cell surface expression of both chains, IL-2R beta and IL-2R alpha, and the IL-2R alpha messenger RNA (mRNA) levels of CD1- CD3- CD4- CD8- prethymocytes. In summary, our results suggest that TNF may have an important role as a co-stimulatory signal in some human thymocyte subpopulations by inducing the expression of IL-2R.

Antigens, CD↗
PubMed1992

[Concepts about AIDS among the adult population of Managua].

Nicaragua has the lowest prevalence of AIDS in Central America. In other countries where AIDS is more prevalent, the first epidemic of asymptomatic infections with human immunodeficiency virus (HIV) and the second of clinical cases of AIDS have been followed by a third epidemic of fear and discrimination. In December 1989 a study was conducted to investigate knowledge and attitudes about AIDS in a sample of 287 adults in Managua. Most of the interviewees had heard of the disease from newspapers and television, and more than 90% understood how HIV was principally transmitted. However, between one-third and one-half the interviewees believed that HIV could be transmitted by causal contact such as kissing (53%) or by mosquito bites (49%). In addition, the majority considered that isolation of HIV-infected persons and control of immigration into the country would be effective measures for preventing the spread of the disease. These results are similar to findings from studies carried out in other countries of Latin America where the HIV and AIDS epidemics started much earlier. This would suggest that the so-called "third epidemic" of discrimination and fear is affecting Nicaragua in advance of the other two.

Acquired Immunodeficiency Syndrome↗