Biomedical subjects

A Fernandez

Publications and source records attributed to A Fernandez.

At least 19 recordsLinked to original sources

PubMed1992

Cardiac manifestations of cocaine abuse: a cross-sectional study of asymptomatic men with a history of long-term abuse of "crack" cocaine.

OBJECTIVES: The objective of this study was to evaluate the prevalence of cardiac abnormalities in young, asymptomatic long-term "crack" cocaine abusers. BACKGROUND: Although the cardiac complications of cocaine abuse have received widespread attention, the prevalence of cardiac abnormalities in asymptomatic long-term cocaine abusers is unknown. METHODS: History, physical examination, electrocardiogram (ECG) and echocardiogram were performed in 52 consecutive long-term cocaine abusers admitted to a drug rehabilitation program. Findings were compared with those in 14 age-matched normal volunteers and 14 age-matched normotensive patients admitted to a psychiatric service who had a pattern of smoking and alcohol consumption similar to that of the study patients. RESULTS: The ECG findings were abnormal in 29% of cocaine abusers, and included nonspecific ST-T wave changes in 15%, abnormal ST segment elevation in 10%, old inferior infarction in 2%, old anteroseptal infarction in 2% and abnormal precordial R wave progression in 10%. When compared with normal volunteers and control patients, cocaine abusers had increased left ventricular posterior wall thickness (1.12 vs. 0.76 and 0.85 cm, respectively, p < 0.0001), increased septal thickness (1.13 vs. 0.76 and 0.86 cm, p < 0.001) and higher left ventricular mass index (142 vs. 84 and 94 g/m2, p < 0.0001). Left ventricular diastolic filling variables did not differ significantly among the three groups. Diastolic filling variables were similar in cocaine abusers with and without left ventricular hypertrophy, and the prevalence of left ventricular hypertrophy did not differ significantly between those who used no alcohol or < 35 ml/week of alcohol and those who consumed > or = 500 ml/week of alcohol. Left ventricular segmental wall motion abnormalities were present in 11 subjects (21%) and the ejection fraction was decreased (< 0.45) in 2 (4%). CONCLUSIONS: Electrocardiographic and echocardiographic abnormalities are common in long-term cocaine abusers. Despite the frequent occurrence of left ventricular hypertrophy, Doppler-derived diastolic filling pattern was not altered. Concomitant alcohol use did not affect the prevalence of these abnormalities.

Age Factors↗

PubMed1992

Striatal neuropeptide levels in Parkinson's disease patients.

Substance P (SP), Met-enkephalin (Met-enk) and cholecystokinin-8-S (CCK-8-S) were measured by a combined HPLC/RIA method in the caudate nucleus and anterior putamen from controls and from Parkinson's disease (PD) patients. SP levels were reduced in caudate in PD, but unchanged in putamen. No differences in Met-enk content were found in parkinsonians compared to controls. However, a significant correlation between DA and Met-enk levels in caudate nucleus from PD was observed. The concentration of CCK-8-S was unaltered in caudate nucleus or putamen in PD. The decrease in caudate nucleus SP levels might be related to the decrease in nigral SP levels in PD, while the reduction in Met-enk levels appears to be a feature of a subgroup of parkinsonian patients.

Aged↗

PubMed1992

Nitric oxide from endothelium and smooth muscle modulates responses to sympathetic nerve stimulation: implications for endotoxin shock.

The influence of nitric oxide (NO) on vascular responses to transmural stimulation (TNS) of noradrenergic nerves was studied in isolated rings of rat iliac arteries. TNS produced frequency-dependent contractions in all vessels. The NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) significantly enhanced TNS responses in intact vessels, but not in those in which the endothelium had been removed. However, in endothelium-denuded rings incubated for 8 hours, L-NMMA increased the contractions induced by nerve stimulation, an effect which was prevented by treatment with dexamethasone or cycloheximide, and enhanced by incubation with lipopolysaccharide and gamma-interferon. Addition of L-arginine reversed the effect of L-NMMA in intact rings; however, it significantly decreased below control values TNS-induced contractions in vessels without endothelium. The results indicate that a) the arterial response to noradrenergic nerve stimulation is modulated by NO originating either in endothelial cells or in smooth muscle cells after induction of NO synthase activity, and b) once NO synthase is induced, the limiting step in NO production is the availability of the substrate L-arginine. An overproduction of vascular NO in the presence of endotoxin or other inflammatory stimuli may prevent the vascular response to sympathetic stimuli and contribute to the vasodilation observed in inflammation or endotoxic shock.

Acetylcholine↗

PubMed1992

A new monoclonal antibody for detection of EGF-receptors in western blots and paraffin-embedded tissue sections.

The prognostic significance of the epidermal growth factor receptor status (EGF-R-status) for certain human tumors requires the development of antibodies useful for clinical application. We used purified receptor preparations to generate monoclonal antibodies immunoreactive with the EGF-R purified from placenta membranes and A431 tumors. Four of the hybridomas contained antibodies (R2, R3, R5, and R9) which recognized both antigens. Antibody R3 was shown to display the following properties: it binds with a KD value of about 10(-9)-10(-10) M to the receptor, a half maximal inhibition of EGF-binding is achieved at 5 x 10(-8) M, and in Western blots of cell membranes R3 specifically detects the EGF-R at 0.1 micrograms/ml. R3 inhibits EGF-dependent clonogenic growth of NRK cells and completely blocks EGF stimulated autophosphorylation of the receptor. Moreover, R3 also detects EGF-R in paraffin-embedded tissue sections taken from human salivary gland, term placenta, and adult skin and mammary carcinomas. Thus, R3 can be used in retrospective diagnostic clinical studies and might help to develop new immunotherapeutic intervention.

Animals↗

PubMed1992

Autonomic neuropathy and immunological abnormalities in Chagas' disease.

Chagas' disease (American Trypanosomiasis) is caused by infection with the haemoflagellate parasite Trypanosoma cruzi, which is transmitted from animals to man by the Reduviidae bug. The human disease is characterized by two phases. In the first (acute phase) parasitaemia is high and general symptoms variable. The next, which is lifelong (chronic phase), is characterized by inflammatory lesions in cardiac and skeletal muscle, gastrointestinal, the autonomic nervous system. Parasites are difficult to detect in blood and affected tissues. Lesions within the autonomic nervous system, lead to development of cardiomyopathy, megaoesophagus and megacolon. The discrepancy between the profusion of inflammatory lesions and the absence of parasites suggests the development of autoimmunity probably of a cell-mediated type. Several autoimmune abnormalities have been noted during Trypanosoma cruzi infection. These include suppression of the specific response to autoantibodies directed against antigens located in the endocardium and in nerves, and development of cell-mediated immunity against host antigens (cytotoxic T- and delayed type hypersensitivity T-cells). These autoimmune disorders are thought to be responsible for much of the pathological damage in chronic Chagas' disease.

Animals↗

PubMed1992

Localization of African swine fever viral antigen, swine IgM, IgG and C1q in lung and liver tissues of experimentally infected pigs.

An immunohistological study was carried out on lungs and livers of pigs experimentally infected with two different African swine fever virus (ASFV) isolates. ASFV antigen, swine immunoglobulins (IgM and IgG) and (Clq) complement were demonstrated in both organs at different stages of infection. The ASFV antigen was mainly found in mononuclear phagocytic system (MPS) cells. Immunoglobulins and complement were observed in plasma, infected and non-infected phagocytic cells and cell debris. These findings suggest the presence, in acute infection, of immune complexes which may be involved in immunopathogenic mechanisms.

African Swine Fever↗

PubMed1992

Protein phosphatase type 1 in mammalian cell mitosis: chromosomal localization and involvement in mitotic exit.

We have examined the role of protein phosphatase type 1 (PP-1) in mammalian cell mitosis. Immunofluorescence using anti-PP-1 antibodies revealed that PP-1, which is mainly localized in the cytoplasm of G1 and S phase cells, accumulates in the nucleus during G2 phase and intensely colocalizes with individual chromosomes at mitosis. This increase in nuclear PP-1 in G2/M cells was confirmed by immunoblotting on subcellular fractions. Microinjection of neutralizing anti-PP-1 antibodies before division blocked cells at metaphase, whereas injection of PP-1 in one pole of an anaphase B cell accelerated cytokinesis and the reflattening of the injected cell. These results reveal a specific cell cycle-dependent redistribution of PP-1 and its involvement in reversing p34cdc2-induced effects after mid-mitosis in mammalian cells.

Animals↗

PubMed1992

cdc25 is a nuclear protein expressed constitutively throughout the cell cycle in nontransformed mammalian cells.

A family of proteins homologous to the cdc25 gene product of the fission yeast bear specific protein tyrosine phosphatase activity involved in the activation of the p34cdc2-cyclin B kinase. Using affinity-purified antibodies raised against a synthetic peptide corresponding to the catalytic site of the cdc25 phosphatase, we show that cdc25 protein is constitutively expressed throughout the cell cycle of nontransformed mammalian fibroblasts and does not undergo major changes in protein level. By indirect immunofluorescence, cdc25 protein is found essentially localized in the nucleus throughout interphase and during early prophase. Just before the complete nuclear envelope breakdown at the prophase-prometaphase boundary, cdc25 proteins are redistributed throughout the cytoplasm. During metaphase and anaphase, cdc25 staining remains distributed throughout the cell and excludes the condensed chromosomes. The nuclear locale reappears during telophase. In light of the recent data describing the cytoplasmic localization of cyclin B protein (Pines, J., and T. Hunter. 1991. J. Cell Biol. 115:1-17), the data presented here suggest that separation in two distinct cellular compartments of the cdc25 phosphatase and its substrate p34cdc2-cyclin B may be of importance in the regulation of the cdc2 kinase activity.

Amino Acid Sequence↗

PubMed1992

Serum response factor p67SRF is expressed and required during myogenic differentiation of both mouse C2 and rat L6 muscle cell lines.

The 67-kD serum response factor (p67SRF) is a ubiquitous nuclear transcription factor that acts by direct binding to a consensus DNA sequence, the serum response element (SRE), present in the promoter region of numerous genes. Although p67SRF was initially implicated in the activation of mitogen-stimulated genes, the identification of a sequence similar to SRE, the CArG box motif, competent to interact with SRE binding factors in many muscle-specific genes, has led to speculation that, in addition to its function in cell proliferation, p67SRF may play a role in muscle differentiation. Indirect immunofluorescence using affinity-purified antibodies specifically directed against p67SRF reveals that this factor is constitutively expressed and localized in the nucleus of two skeletal muscle cell lines: rat L6 and mouse C2 myogenic cells during myogenic differentiation. This result was further confirmed through immunoblotting and Northern blot analysis. Furthermore, specific inhibition of p67SRF in vivo through microinjection of purified p67SRF antibodies prevented the myoblast-myotube transition and the expression of muscle-specific genes such as the protein troponin T. We further showed that anti-p67SRF injection also inhibited the expression of the myogenic factor myogenin, implying an early requirement for p67SRF in muscle differentiation. These results demonstrate that p67SRF is involved in the process of skeletal muscle differentiation. The potential action of p67SRF via CArG sequences is discussed.

Animals↗

PubMed1992

Immunocytochemical study of the ultimobranchial tubule in Wistar rats.

A systematic immunohistochemical study of the ultimobranchial tubule (UBT) has been carried out in 45 Wistar rats of different ages (0, 5, 10, 15, 20, 25, 30, 60 and 120 days). The existence of calcitonin immunoreactive cells in the UBT wall has been demonstrated in a 5-days old rat. In addition, immunohistochemical studies for thyroglobulin revealed positive staining in follicular cells connected to the UBT and, occasionally, in isolated cells lying within solid clusters from the UBT. These last results together with the continued and repeated existence of numerous mitosis and PAS (+) microfollicles, apparently rising from the UBT, support the hypothesis that the ultimobranchial body (UBB) may contribute partially to the formation of a part of the follicular component.

Animals↗

PubMed1992

Distribution of ASFV antigens in pig tissues experimentally infected with two different Spanish virus isolates.

Lymph nodes, spleen, liver, lung and kidney obtained from pigs experimentally infected with two African Swine Fever Virus (ASFV) isolates of differing virulence were fixed by perfusion with glutaraldehyde and embedded in paraffin. An immunoperoxidase technique using a polyclonal anti-ASFV serum was performed on tissue sections in order to detect ASFV antigen. The distribution of ASFV antigen in such infected organs is shown and the differences between both infections compared and discussed. Monocytes, macrophages, hepatocytes, endothelial cells, neutrophils and epithelial cells were found to contain ASFV antigens.

African Swine Fever↗

PubMed1992

Distribution of bovine virus diarrhoea viral antigens in the central nervous system of cattle with various congenital manifestations.

Distribution of bovine viral diarrhoea virus (BVDV) antigens in the central nervous system (CNS) of 26 cattle persistently BVDV infected, 11 cattle with mucosal disease (MD), and 32 calves with congenital brain malformations was studied using monoclonal antibodies against BVDV epitopes. In persistently infected cattle and in cattle with MD, a widespread infection of neurons was present. Predilection sites for BVDV antigens were the cerebral cortex and the hippocampus. In calves with congenital encephalopathies, viral antigen-containing neurons could only be detected in the CNS of four animals. From the topographical distribution of BVDV antigens in these four postnatal cases with end-stage lesions, no conclusions could be drawn concerning the pathogenesis of BVDV-induced encephalopathies.

Animals↗

PubMed1992

Determination of heavy metals in human liver.

The levels of Cr (2.49 +/- 0.89 ppm), Mn (5.08 +/- 1.60 ppm), Ni (1.81 +/- 0.95 ppm) and Pb (4.43 +/- 3.12 ppm) were measured in dessicated liver from 44 cases of sudden traumatic death considered as representative of the general population in our area, after ruling out the presence of any underlying disease. Atomic absorption spectrophotometry and electrothermal atomization was carried out after hot, acid digestion, of the dessicated samples. After cancelling the influence of age and cause of death, a significant, positive correlation between Cr/Mn (P = 0.0009; R = 0.493) and Cr/Ni (P = 0.0245; R = 0.347) levels was found.

Adult↗

PubMed1992

Low turnover bone disease is the more common form of bone disease in CAPD patients.

CAPD is considered a risk factor for low turnover bone disease. This was previously attributed to aluminum accumulation. We evaluated by biochemical and histomorphometric parameters (including double tetracycline labelling), 26 patients maintained on CAPD for 12-14 months. Three (11.5%) showed mild hyperparathyroidism, 5 (19.2%) osteitis fibrosa, 3 (11.5%) mixed forms, 4 (15%) osteomalacia and 11 (42.3%) adynamic bone disease. Only one patient with diabetes mellitus showed an aluminum stained bone surface > 10%. Intact PTH serum levels were lower in LTBD (133.2 +/- 128 vs 468.2 +/- 451 pg/ml; p < 0.05). We also evaluated prospectively 11 patients who underwent a bone biopsy at start of dialysis and after 12 months of CAPD treatment. Bone biopsies pre CAPD demonstrated normal-high bone turnover disease in 8/11 (72.7%) and low turnover bone disease in 3/11 (27%). In the follow-up biopsies, 2 patients showed osteitis fibrosa and other two mild forms. Low turnover bone disease was found in 7 patients (3 osteomalacia and 4 adynamic bone disease). We conclude that the predominant bone lesion in our CAPD patients is low turnover bone disease, predominantly adynamic forms, and aluminum does not seem to play a role on its genesis. Low intact PTH serum levels may be a predictor of low turnover bone disease.

Bone and Bones↗

PubMed1992

Peritoneal dialysis efficiency in CAPD patients in treatment with rHuEPO.

Possible modifications in peritoneal behaviour that can be caused by erythropoietin (EPO) treatment and/or correction of anemia in the ultrafiltration and peritoneal diffusion were studied in 24 CAPD patients. The evolution of the patients on the medium run was also studied. The dialysate to plasma ratio, the peritoneal clearance and the mass transfer coefficient of urea and creatinine and the ultrafiltration volume were studied, baseline, after reaching the hemoglobin target, and after eight months of treatment. The group of patients developed a decrease in the dialysate to plasma ratio and in the peritoneal clearance of creatinine. After evaluating the effects of the hemoglobin and the hematocrit, we found a decrease in the dialysate to plasma ratio of urea and creatinine, and in the peritoneal clearance of creatinine. A decrease was also found in the mass transfer coefficients of urea and creatinine. An increase in the ultrafiltration was also found in the patients with hemoglobin levels higher or equal to 11 g/dl. Those changes are reversible after turning the hemoglobin levels back to levels lower than 11 g/dl.

Adult↗

PubMed1992

Role of fos-AP-1 binding sequence (FAP) in the induction of c-fos expression by purified C-kinase and in c-fos down-regulation following serum induction.

Microinjection of purified calcium phospholipid-dependent protein kinase (C-kinase) resulted in the rapid and transient induction of c-fos in quiescent rat embryo fibroblats. This C-kinase-induced expression of c-fos was prevented by in vivo competition using co-injection of oligonucleotides corresponding to the sequence of either the serum response element (SRE) or the fos AP-1 binding sequence (FAP) adjacent to SRE. This indicates that both these sequences must be involved in the binding/activation of protein factors required for the induction of c-fos by C-kinase. In contrast, the induction of c-fos by serum or by casein kinase II microinjection, which is also inhibited by injection of SRE oligonucleotides, is only delayed and then markedly prolonged by injecting TRE/FAP sequence, demonstrating that the FAP site plays a prominent role in vivo in the down-regulation of the endogenous c-fos gene expression.

Animals↗

PubMed1992

Resistance of Ha-ras oncogene-induced progressor tumor variants to tumor necrosis factor and interferon-gamma.

To elucidate the mechanisms by which tumor cells escape the immune defenses of the normal host, we have isolated progressor tumor variants from a regressor tumor cell line by transfection with an activated Ha-ras oncogene. We previously found that the progressor phenotype of Ha-ras-induced variants was not due to loss of tumor-specific or major histocompatibility complex antigens. In this study, we investigated whether there is any correlation between in vivo tumor growth and in vitro sensitivity of regressor and progressor tumor cells to tumor necrosis factor (TNF). The regressor UV-2240 tumor cells, which do not grow in normal syngeneic mice, were sensitive to killing by TNF, whereas the Ha-ras oncogene-induced progressor tumor variants of UV-2240, which produce tumors in normal syngeneic hosts, were resistant to killing by TNF. Interferon-gamma (IFN-gamma) enhanced TNF-induced cytotoxicity of the regressor tumor cells, but it had no effect on Ha-ras-induced progressor tumor variants. The resistance of the Ha-ras-induced progressor variants to TNF and IFN-gamma could be attributed to a decrease in the number of TNF receptors on their cell surface. However, there was no correlation between TNF and IFN-gamma sensitivity of tumor cells and sensitivity to killing by activated macrophages, NK or NC cells. These results indicate that in some murine tumor cells, there may be a relationship between in vivo tumor growth and in vitro resistance to cytolysis by TNF and IFN-gamma. Although the response of the Ha-ras-induced progressor variants to TNF and IFN-gamma produced endogenously in immunocompetent mice is unknown, one can infer that some tumors escape the immune defenses of the normal host by becoming resistant to certain cytokines produced by the immune system.

Animals↗

PubMed1991

Cyclin A is required for the onset of DNA replication in mammalian fibroblasts.

Cyclin A protein is synthesized and localized into the nucleus at the onset of S phase in nontransformed mammalian fibroblasts. Inhibition of cyclin A synthesis or activity through microinjection of plasmids encoding antisense cyclin A cDNA or affinity-purified anti-cyclin A antibodies during G1 phase was shown to abolish the nuclear staining for cyclin A in plasmid-injected cells, and both procedures led to inhibition of DNA synthesis. No similar effect was observed with injection of other antisense vectors including antisense cyclin B, and reinjection of purified human cyclin A protein into cyclin A antisense-injected cells effectively relieved this inhibition of DNA synthesis. Taken together, these data suggest that cyclin A plays a major role in the control of DNA replication in mammalian cells.

Animals↗