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Biomedical subjects

G Ramírez

Publications and source records attributed to G Ramírez.

At least 55 records · Page 3Linked to original sources
PubMed1995

HIV/AIDS in Costa Rica: epidemiological and sociological features, 1993.

Acquired immunodeficiency syndrome (AIDS) was first detected in Costa Rica in 1983. For four years most known cases were in hemophiliac men. Thereafter, AIDS in homosexual and bisexual men predominated. By December 31 of 1993, 563 persons had been diagnosed with the syndrome, 71% of them homosexual and bisexual men, 10% heterosexual men and women, 6% hemophiliacs, 2% intravenous drug abusers (IVDA's), 2% women and men who had blood transfusions, 1.4% infants born to HIV-infected mothers and 7% unknown. The epidemics in homosexual/bisexual men and in heterosexual women and men are rising; cases in infants and in persons who received blood or coagulation factors, are stagnant. The steady increase in AIDS among women is linked to exposure to bisexual partners. The moderate nature of the national epidemic reflects, in part, the low incidence of IVDA, the universal screening of blood donors for antibodies to the human immunodeficiency virus (HIV) since 1985, and the prompt banning of unsafe coagulation factors. The projection of AIDS for the year 2000 is 2,304 cases (606 accumulated incidence per million inhabitants). A national educational campaign, radio and television programs and other preventive actions, apparently did not influence the rate of receptive anal intercourse without condom (about 80%) during 9 years of the epidemic. Persons with HIV/AIDS often are deprived of social and medical benefits or are subjected to harassment and exploitation by the health sector. More efficient prevention must target children, adolescents and adults in reproductive age, to promote safer lifestyles, through education and counseling effected through primary health care.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Immune response to porins isolated from Salmonella typhi in different mouse strains.

Outer membrane proteins (OMPs) are able to induce protection against the challenge with S. typhi in a murine model. Both humoral and cellular immunity are involved in the protective mechanisms. In order to determine whether the responsiveness to S. typhi porins is genetically controlled in mice, different strains were immunized i.p. with 30 micrograms of OMPs isolated from S. typhi 9,12,Vi:d at days 0 and 7. On day 21, spleen cells were recovered and the lymphoproliferative response to porins was assessed. The highest responses were found in mice with H-2k and H-2a haplotypes (C3H/HeJ and A/J), intermediate responses were found in mice with H-2b haplotype (C57Bl/6) and the lowest responses in H-2d mice (Balb/c). These results demonstrate that the responsiveness to S. typhi porins is in part controlled by the major histocompatibility complex class II molecules and will help to further study the mechanisms of the immune response to these proteins.

Animals↗
PubMed1994

Differential effects of guanine nucleotides on kainic acid binding and on adenylate cyclase activity in chick optic tectum.

In G protein-coupled receptors, neurotransmitter-induced binding of GTP to G proteins triggers the activation of effector systems while simultaneously decreasing the affinity of the transmitter for its specific binding site within the receptor-G protein complex. In the present study we show that, in the chick optic tectum, guanine nucleotides inhibit the binding of the glutamate analog, kainate, and activate adenylate cyclase by different mechanisms and acting on different sites. GMP-PNP, a non-hydrolyzable analog of GTP, binds tightly to G proteins so that the binding is stable even after exhaustive washing. By use of this property, we have prepared membrane samples in which G protein GTP-binding sites are pre-saturated with GMP-PNP. Experiments carried out with these membranes show that GMP-PNP, GDP-S and GMP inhibit the binding of [3H]kainate by interacting with site(s) unrelated to G proteins, whereas GMP-PNP activates adenylate cyclase activity by binding to G proteins.

Adenylyl Cyclases↗
PubMed1994

A meta-analysis of randomized trials of prenatal smoking cessation interventions.

OBJECTIVE: Our purpose was to assess the effect of prenatal smoking interventions on rates of smoking cessation and low birth weight. STUDY DESIGN: We used a meta-analysis model to compare and summarize smoking cessation and low birth weight outcomes with the risk ratio used as a common metric. We located 11 randomized, controlled trials with objective validation of smoking status; four of these studies also measured rates of low birth weight. RESULTS: Risk ratios for smoking cessation ranged from 0.9 to 7.1. The combined risk ratio for the homogeneous group of 10 studies was 1.50 (95% confidence interval 1.22 to 1.86) after the outlier study with a risk ratio of 7.1 was excluded. This was a 50% increase in smoking cessation. Low birth weight risk ratios of 0.6 for two studies that achieved a 50% increase in cessation suggested that the incidence of low birth weight was decreased. CONCLUSION: Prenatal smoking cessation interventions increase rates of smoking cessation during pregnancy, and there is evidence that they reduce the incidence of low birth weight.

Female↗
PubMed1991

Chondroitinases release acetylcholinesterase from chick skeletal muscle.

Bacterial chondroitinases (both ABC and AC types) release asymmetric and globular forms of AChE from chick skeletal muscle samples. Heparinases, however, including heparitinase I, fail to do so under different incubation conditions. These results do not support the direct implication of the heparin/heparan sulfate family of GAGs in the interaction of the different AChE molecular forms with the muscle ECM. GAGs of the chondroitin/dermatan sulfate group could however be involved, either directly or indirectly, in the attachment of the AChE collagen-like tail to the muscle basal lamina.

Acetylcholinesterase↗
PubMed1991

Solubilization of asymmetric acetylcholinesterase by polyanions.

A number of polyanions, including polysulfates (sulfated glycosaminoglycans (GAGs), dextran and pentosan sulfates, and polyvinylsulfate), polyphosphates (tetrapolyphosphate, polyadenylate) and polycarboxylates (polyaspartate, polyglutamate) solubilize asymmetric acetylcholinesterase (AChE) from chick muscle at low ionic strength, and partially or totally displace AChE tailed forms bound to heparin-agarose columns. The previously reported solubilization of asymmetric AChE by heparin, or the proven affinity of the tailed enzyme forms for this GAG, cannot therefore be taken as direct proof of the involvement of heparin-like heparan sulfate proteoglycans in the anchorage of the collagenous tail of the enzyme to the basal lamina in skeletal muscle.

Acetylcholinesterase↗
PubMed1991

Two types of asymmetric acetylcholinesterase in chick hindlimb muscle: developmental profiles, in vivo and in cell culture, and recovery after inactivation.

1. We have analyzed the behavior of two types of asymmetric molecular forms (A forms) of acetylcholinesterase (AChE) during development of chick hindlimb muscle, in vivo and in cell culture, and upon irreversible inactivation of peroneal muscle AChE with diisopropylfluorophosphate (DFP) in vivo. 2. In agreement with previous developmental studies on chick muscle, globular forms of AChE (G forms) are predominant in chick hindlimb at early embryonic ages, being gradually replaced by A forms as hatching (and, therefore, onset of locomotion) approaches. Of the two A-form types, AI appears and accumulates significantly earlier than AII, so that A/G and II/I ratios higher than 1 are attained only at about hatching time. 3. Cultures prepared from 11-day chick embryo hindlimb myoblasts express both types of A forms, with a combined activity of 27% of total AChE after 12 days in culture. AI forms appear again earlier and are much more abundant than type II asymmetric species through the life span of cultures. 4. All AChE activity in the peroneal muscle is irreversibly inactivated by injection of DFP in vivo. The recovery of A forms follows the same sequence described for normal development, with a delayed and slower recovery of AII forms as compared with AI. 5. Several hypotheses involving tail polypeptides or tissue target molecules, or posttranslational interconversion, are proposed to help explain the earlier appearance and accumulation of AI forms in chick muscle.

Acetylcholinesterase↗
PubMed1991

Effects of guanine nucleotides on kainic acid binding and on adenylate cyclase in chick optic tectum and cerebellum.

Adenylate cyclase activity and binding of neurotransmitters to some receptors can be modulated simultaneously by guanine nucleotides. Furthermore it has been shown, in different neurotransmitter systems, that the ability of GTP to inhibit agonist binding is related to the capacity of the transmitter to modulate adenylate cyclase activity. In the present report we show that in chick optic tectum and cerebellum the effects of guanine nucleotides on kainic acid binding and on adenylate cyclase activity can be dissociated. In lysed membrane preparations, GTP, GDP, and GMP, or their analogs, displace binding of kainic acid with the same efficiency, whereas only GTP stimulates adenylate cyclase. In vesicle preparations, all three nucleotides inhibit binding of kainic acid without modifying adenylate cyclase activity. The present results suggest that, if adenylate cyclase is indeed coupled to this particular type of excitatory amino acid receptor, the coupling mechanism would be probably different from those operating in other neurotransmitter systems and also that the displacement of kainic acid by GDP and GMP (and even perhaps by GTP) is not likely to depend on the interaction between the receptor and a Gs-protein-mediated effector system.

Adenylyl Cyclases↗
PubMed1991

Polymyositis complicating D-penicillamine treatment.

Although there is good evidence that D-penicillamine can induce polymyositis, the exact pathogenic mechanism remains unclear. We report two patients with psoriatic arthritis and primary biliary cirrhosis respectively, who developed polymyositis while receiving D-penicillamine treatment for their primary diseases. Whether D-penicillamine treatment was the sole cause of polymyositis or acted as a trigger for the development of a secondary autoimmune disease is discussed.

Adult↗
PubMed1991

Antiendothelial cell antibodies in patients with the antiphospholipid syndrome.

Antiendothelial cell antibodies (AECA) have been detected in 20 out of 30 patients (67%) with thrombosis associated with antiphospholipid antibodies. Seven patients had systemic lupus erythematosus and 13 had the "primary" antiphospholipid syndrome. Seven patients had both IgG and IgM AECA, 9 had IgG AECA only, and 4 had only IgM AECA. None of 30 control patients with thrombotic events not related to antiphospholipid antibodies had a positive titre of AECA (P less than 0.001). No correlation between AECA, antinuclear antibodies, anti-dsDNA antibodies, anti-neutrophil cytoplasm antibodies, precipitating antibodies to soluble nuclear and cytoplasmic antigens or complement components was found. The possible role of these AECA in the pathogenesis of thrombotic events is discussed.

Adult↗
PubMed1990

Asymmetric acetylcholinesterase is absent from chick retina, but present in choroid, ciliary muscles and iris.

Freshly dissected chick neural retina and pigmented epithelium do not apparently contain asymmetric molecular forms (A-forms) of acetylcholinesterase (AChE). The neighboring choroid, and the ciliary muscles and iris, are however rich in type II A-forms (high salt/EDTA-extractable). Most if not all the asymmetric AChE activity detected in chick 'whole retina' preparations could then be explained in terms of contamination by non-retinal eye tissues.

Acetylcholinesterase↗
PubMed1990

Ontogeny of binding sites for [3H] kainic acid in chick and rat cerebellar membranes: a comparative study.

We have analyzed the developmental properties of kainate receptors in cerebellar membranes prepared from chick and rat, two vertebrate species with contrasting patterns of functional maturation. Single populations of binding sites have been characterized in the avian and rodent membranes with apparent dissociation constants (Kd) in the 210-280 nM and 40-55 nM ranges, respectively; the number of binding sites (Bmax) increases with age in both species, reaching a maximum of 187 pmol/mg in the case of 10-day chicks vs. 1.28 pmol/mg in 75-day rats. The ontogenetic profiles of kainate receptors in chick and rat cerebella are in consonance with the patent differences in motor development at birth.

Aging↗
PubMed1990

Isolation of a galactose-binding lectin from the venom of the snake Bothrops godmani (Godmann's pit viper).

A galactose-binding lectin, isolated from the venom of B. godmani by affinity chromatography, is an acidic protein (pI 4.9) with a subunit mol. wt of about 14,000, occurring mostly as a disulfide-linked dimer of 28,000. A small proportion of lectin appears as a monomer and as a tetramer. The lectin agglutinates erythrocytes from mice, rabbit, cow and human (all ABO types, either Rh positive or negative), but does not agglutinate horse, sheep, goat and snake (Oxybelis aeneus, Colubridae) erythrocytes. The agglutinating activity is inhibited by 1 mM EDTA. The lectin is devoid of lethal, hemorrhagic, myotoxic, proteolytic and phospholipase A2 activities. It is not mitogenic for human peripheral blood mononuclear cells. The only effect observed was a moderate induction of edema in the footpad of mice, with a minimal edema-forming dose of 22 micrograms. This effect developed rapidly, and was significantly inhibited by i.p. administration of cyproheptadine, a histamine and serotonin antagonist, before injection of the lectin. Despite the edema-forming activity observed, the low concentration of lectin in crude venom, together with its relatively low potency, suggest that this lectin is not a key component in the development of edema following envenomations by B. godmani.

Animals↗
PubMed1990

Adult-onset polymyositis-dermatomyositis: description of 25 patients with emphasis on treatment.

A retrospective study of 25 patients with polymyositis-dermatomyositis (PM-DM) is analyzed with special attention to the effects of therapy and follow-up. All patients (100%) complained of muscle weakness and 68% of these demonstrated typical skin changes of DM. All patients, except 2, received corticosteroids at the onset of the disease, 23 were treated with azathioprine, 7 received cyclophosphamide, 4 methotrexate, and 1 had total body irradiation. Among the patients adequately treated with azathioprine, 75% had a good response, but 5 patients did not improve. Cyclophosphamide was used subsequently in 2, with a satisfactory response in 1. Another patient had a striking response to oral methotrexate, and total body irradiation helped to improve another patient. Although high dose corticosteroids were the preferred starting medication for the treatment of PM-DM, it is important to detect those patients who do not respond adequately and/or develop side effects. In these circumstances, the prompt use of immunosuppressive agents appears justified.

Adult↗