PubMed Health⌕ Search

Biomedical subjects

A Ferreira

Publications and source records attributed to A Ferreira.

At least 19 recordsLinked to original sources
PubMed1992

The major Thiobacillus ferrooxidans outer membrane protein forms low conductance ion channels in planar lipid bilayers.

A protein isolated and purified from the outer membrane of the acidophilic, chemolithotrophic bacterium, Thiobacillus ferrooxidans with an oligomeric molecular weight of 90,000 Da (p90) was incorporated into phosphatidylethanolamine planar lipid bilayers. The protein formed slightly anionic channels in KCl solutions, with a conductance of 25 pS in 100 mM KCl. The current-voltage relationship was linear between +/- 60 mV, and the conductance was a saturating function of the salt concentration. These channels fluctuated from a single open to closed state at low potentials, but present flickering activity at higher potentials.

Bacterial Outer Membrane Proteins↗
PubMed1992

Expression of the class III beta-tubulin isotype in developing neurons in culture.

The expression of the class III beta-tubulin isotype was studied in cultured brain neurons by means of a monoclonal antibody (TuJ1). The results obtained indicate that during early axonal outgrowth most of the class III beta-tubulin is not incorporated into microtubules, a phenomenon which is also observed under conditions which alter the rate and extent of the neurite outgrowth response. On the other hand, a dramatic increase in its incorporation into microtubules is observed after the neurons have differentiated their neurites as axons and dendrites. In addition, the appearance of colchicine-resistant microtubules containing this isotype, a phenomenon which occurs late in neurite development, is highly coincident with the appearance of stable microtubules containing high molecular weight microtubule-associated proteins (MAPs). This pattern is different from that of the accumulation and incorporation of other beta-tubulin isotypes into microtubules. Taken collectively, our results indicate that differences exist in the in vivo utilization of tubulin isotypes in developing brain neurons and suggest that the class III beta-tubulin isotype is not a primary factor involved in the regulation of microtubule assembly during early neurite outgrowth, but that it may be important for maintaining further neurite elongation and/or determining some unique binding property of MAPs to specific microtubule subsets.

Animals↗
PubMed1992

Preliminary characterization of anticomplementary components of hydatid cyst fluid.

Sheep hydatid cyst fluid (SHCF) was fractionated on Sephacryl HR S-200 and the anticomplementary activity (alpha-C activity) determined in the fractions obtained; 67% of total alpha-C activity of SHCF was recovered in the void volume fraction (SHCF-I) which contained 61% of SHCF carbohydrates. The bulk of the activity of SHCF-I was eluted by FPLC chromatofocusing on Mono P HR at pH 5.9. After heating at 100 degrees C for 15 min, SHCF and SHCF-I conserved 74 and 54%, respectively of their alpha-C activity. In addition, 37 and 11% of SHCF and SHCF-I alpha-C activity, respectively bound to Protein A. Components not bound to Protein A (SHCFPA and SHCF-IPA) were fractionated on Con A-Sepharose; 71 and 65%, respectively of their total alpha-C activity was retained by this lectin indicating the presence of alpha-D mannoside and alpha-D glucoside residues in the active molecules. Our results suggest that SHCF could contain two classes of alpha-C components: immune complexes and thermoresistant molecules with high carbohydrate content.

Animals↗
PubMed1992

Diazepam facilitates acceptance of alien lambs by postparturient ewes.

The aim of this study was to determine the effect of diazepam on the behavior of parturient ewes towards alien lambs. There is evidence that benzodiazepines cause behavioral changes during the lactation period in rats. In two independent experiments, it was found that the ewes acceptance of alien lambs significantly increased following a single injection of the benzodiazepine, diazepam, given either 1 or 12 h after parturition. In a third experiment, in which the alien lamb was not permitted to suckle during a period of 2 h after the injection, the diazepam treatment did not provoke significant differences in maternal behavior of the ewes, although in the ewes treated with diazepam, suckling clearly tended to increase. At the dose employed (20 mg), administered 1 h after birth, diazepam caused no signs of sedation as assessed in an open-field test carried out 3 h after parturition. This doesn't eliminate the possibility of diazepam having a sedative effect in the period of 2 h immediately after its administration and before the test and, in this way, facilitating suckling which could be responsible for the maternal behavior observed after this period. As diazepam gives rise to an enhanced GABAergic activity in the brain, these observations suggest that a GABAergic mechanism could also play a role in the process whereby ewes form a selective bond with their own offspring.

Aggression↗
PubMed1992

Suppression of kinesin expression in cultured hippocampal neurons using antisense oligonucleotides.

Kinesin, a microtubule-based force-generating molecule, is thought to translocate organelles along microtubules. To examine the function of kinesin in neurons, we sought to suppress kinesin heavy chain (KHC) expression in cultured hippocampal neurons using antisense oligonucleotides and study the phenotype of these KHC "null" cells. Two different antisense oligonucleotides complementary to the KHC sequence reduced the protein levels of the heavy chain by greater than 95% within 24 h after application and produced identical phenotypes. After inhibition of KHC expression for 24 or 48 h, neurons extended an array of neurites often with one neurite longer than the others; however, the length of all these neurites was significantly reduced. Inhibition of KHC expression also altered the distribution of GAP-43 and synapsin I, two proteins thought to be transported in association with membranous organelles. These proteins, which are normally localized at the tips of growing neurites, were confined to the cell body in antisense-treated cells. Treatment of the cells with the corresponding sense oligonucleotides affected neither the distribution of GAP-43 and synapsin I, nor the length of neurites. A full recovery of neurite length occurred after removal of the antisense oligonucleotides from the medium. These data indicate that KHC plays a role in the anterograde translocation of vesicles containing GAP-43 and synapsin I. A deficiency in vesicle delivery may also explain the inhibition of neurite outgrowth. Despite the inhibition of KHC and the failure of GAP-43 and synapsin I to move out of the cell body, hippocampal neurons can extend processes and acquire as asymmetric morphology.

Animals↗
PubMed1992

[New indications for gamma globulins].

Intravenous immunoglobulin (IV Ig) has been shown its therapeutic value in primary immunodeficiency diseases associated with a profound impairement of IgG-mediated antibody production. In recent years its range of indications has been extended to some secondary immunodeficiency disorders such as chronic lymphocytic leukemia and children with symptomatic HIV infection IV Ig is also of value in cytomegalovirus infection in transplant recipients. The use of IV Ig in some immunoregulatory disorders, namely immune thrombocytopenic purpura and Kawasaki syndrome has also been proved. Preliminary studies suggests a benefit in myasthenia gravis, Guillain-Barré syndrome, polymyositis, chronic demyelinating diseases and steroid dependent asthma. Little is known about the mechanism of action of IV Ig in these immunoregulatory disorders. In sum, IV Ig has a few proved indications and many potential ones. Carefully controlled clinical trials are needed to determine the effectiveness of IV Ig in these conditions.

Autoimmune Diseases↗
PubMed1991

Cardiac myocytes and dendritic cells harbor human immunodeficiency virus in infected patients with and without cardiac dysfunction: detection by multiplex, nested, polymerase chain reaction in individually microdissected cells from right ventricular endomyocardial biopsy tissue.

Two hundred fifteen patients infected with human immunodeficiency virus (HIV) participated in a prospective longitudinal study of HIV-related heart disease. Evaluation included signal-averaged electrocardiography and echocardiography. Fifteen patients underwent endomyocardial biopsy, 5 had cardiovascular symptoms and 10 did not. Cardiac myocytes or dendritic cells were prepared by individual cell microdissection to sort them from other cell types such as interstitial cells or circulating blood elements. HIV proviral sequences were amplified in samples of 15 to 20 cells of each type by multiplex, nested, polymerase chain reaction and hybridized to 32P-labeled probes specific for regions within the gag and pol genes of HIV-1. The results showed the presence of HIV sequences in myocytes of 2 of 5 patients with cardiac symptoms and in 6 of 10 without. Thus, symptomatic HIV cardiomyopathy did not appear to be a direct consequence of the virus on myocardial cells. In dendritic cells, HIV sequences were detected in 5 of 5 patients with cardiac symptoms and in 8 of 10 with apparently normal ventricular function. Furthermore, dendritic cells were somewhat more numerous in the myocardium of symptomatic than asymptomatic patients. Our studies are the first to directly detect the HIV genome in purified cardiac myocytes from patients with and without cardiac dysfunction. Our findings do not support a direct role of the virus in myocardial dysfunction. However, the results do suggest that the interstitial dendritic cells may be involved in some manner in the development of cardiac dysfunction observed in HIV-infected patients.

Adult↗
PubMed1991

Octadecyl silica: a solid phase for protein purification by immunoadsorption.

Immunoaffinity chromatography involves binding of an antigen or antibody to a solid matrix, usually agarose, frequently using the cyanogen bromide method. These methods are laborious, rather expensive, and their use has been mostly restricted to immunopurifications on the microscale. We propose here the use of octadecyl silica (SiCl8) beads, a matrix for HPLC, as an alternative solid phase for protein immunopurification and immunoadsorption. Antibodies or antigens are strongly bound to SiCl8 by a simple incubation; radiolabeled antibodies can only be eluted from SiCl8 by detergent-containing solutions. After the remaining free binding sites have been saturated with bovine serum albumin, SiCl8 is incubated with the antigen- or antibody-containing crude preparations and is then poured into a minicolumn. The nonspecifically bound proteins are removed by washing; specific proteins are eluted by disruption of the antigen-antibody complexes with a low pH buffer. With this methodology, we have obtained high purity preparations of proteins in single steps, even when these proteins are present in trace amounts (picograms) in a complex mixture such as human serum. Similarly, specific antibodies against an intracellular parasite (Trypanosoma cruzi) were completely absorbed from human serum with SiCl8 coated with parasite antigens.

Animals↗
PubMed1991

Binding and production of insulin-like growth factor-I in rat mammary gland.

1. Mammary tissue from pregnant rat presents low and high affinity IGF-I functional receptors. 2. Mammary explants from pregnant and lactating rats secrete IGF-I and its production was related to the developmental stage of the gland. 3. An inverse relationship between IGF-I production and tissue binding capacity was observed.

Animals↗
PubMed1991

Purification and primary structure of glucagon from ostrich pancreas splenic lobes.

Glucagon is a highly conserved polypeptide hormone which appears to play a more important role in regulation of glycaemia in birds than insulin. Ostrich glucagon was isolated and purified from ostrich pancreas splenic lobes using an adapted acid ethanol extraction procedure, gel filtration, ion exchanges, and HPLC steps. The purified glucagon fraction appeared to contain small quantities of a more acidic contaminant (polyacrylamide gel isoelectric focussing, PAGE) but appeared homogeneous on SDS-PAGE. Amino acid analysis and sequence analysis showed identity with the duck hormone. Identity with the duck hormone was confirmed by liquid phase as well as gas phase sequencing. The ostrich glucagon preparation seemed to have a higher Km than the porcine homologue in stimulating glycerol release from isolated chicken adipocytes.

Adipose Tissue↗
PubMed1991

Immunological follow-up in children born to HIV-1 infected mothers.

From November 1985 to January 1990 we examined 156 children born to 154 HIV-1 seropositive mothers every 3 months. Eighty-seven infants were over 18 months by January 1990. Six of them met the CDC criteria of HIV-1 infection or died from AIDS; a transmission rate of 7%. Six of the children aged less than 18 months also met the CDC criteria of HIV-1 infection. These 12 infected children were compared with the 81 presumably unifected children. The perinatal findings were similar in both groups. Most of the HIV-1 infected babies showed early abnormalities in humoral and cellular immunity, hypergammaglobulinemia, low percentage of CD4 circulating lymphocytes and increased spontaneous in vitro immunoglobulin production. These changes were persistent in the HIV-1 infected children, but sporadic in those uninfected. Immunological abnormalities were frequently found before clinical symptoms appeared. We conclude that repeated immunological abnormalities in babies born to HIV-1 seropositive mothers are suggestive of HIV-1 infection.

AIDS Serodiagnosis↗
PubMed1991

Autoantibodies in patients with IgA and IgG2 deficiencies.

Patients with primary immunodeficiencies have a high incidence of autoantibodies, mainly of no clinical significance. It has recently been suggested that patients with a combined IgA-IgG2 deficiency have more autoantibodies than those patients with isolated deficiencies. We have studied 42 patients with selective IgA deficiency, nine with isolated IgG2 deficiency and 13 with combined IgA-IgG2 deficiency, and have found that the combined IgA-IgG2 deficiency has no influence on autoantibody prevalence, except for anti-IgA antibodies. The presence of chronic respiratory infections (a clinical feature commonly associated with both selective IgA and IgG2 deficiencies) is unrelated to the prevalence of autoantibodies. The most frequent autoantibodies found are anti-IgA and anti-cardiolipin. Most of the autoantibodies have been found to be devoid of actual clinical significance. Only three patients had overt autoimmune disease.

Adolescent↗
PubMed1991

[Sickle cell anemia: cerebral angiography changes].

Two cases of sickle cell disease with neurological complications are described. Cerebral angiograms were performed and a characteristic moyamoya-like angiographic pattern was demonstrated. This pattern results from a compensatory vascularization which may follow occlusion of the arteries at the base of the brain in several diseases. The risks of angiography and appropriate precautions are emphasized.

Anemia, Sickle Cell↗
PubMed1991

An immunogenetically defined and immunodominant Trypanosoma cruzi antigen.

Two strains of mice, A. SW (H-2s) and A.CA (H-2f), were immunized with live trypomastigotes or epimastigotes of the Tulahuen strain of Trypanosoma cruzi or with their sonicates. By immunowestern blotting, sera from A.SW mice, but not from A.CA, recognized, in an immunodominant fashion, a 45 kDal polypeptide (Tc45) present in both epimastigotes and trypomastigotes. Since A.SW and A.CA strains are congenic for the major histocompatibility H-2 complex, recognition of Tc45 seems to be controlled by this genetic region or by gene(s) located in its immediate vicinity. Subcellular fractionation revealed that Tc45 is mainly present at the cytoplasmic compartment.

Animals↗
PubMed1991

Estrogen-enhanced neurite growth: evidence for a selective induction of Tau and stable microtubules.

Estrogen stimulates the neurite outgrowth response of medial basal hypothalamic neurons maintained in culture. We show here that one effect of estrogen is to promote an increase in tau, but not in tubulin, microtubule-associated protein 1a (MAP-1a), or MAP-2 protein levels. This response precedes and accompanies an increase in stable microtubules and in neurite length. Taken collectively, our data suggest that estrogen-enhanced neurite growth is mediated by a selective induction of microtubule-stabilizing factors, namely, the tau proteins.

Animals↗
PubMed1991

Soluble class I histocompatibility antigens (s-HLA) and beta 2-microglobulin at delivery.

In this work we have quantified soluble class I histocompatibility antigens (s-HLA) and beta 2-microglobulin (beta 2 m) in sera of HIV+ or HIV- mothers at delivery and in cord blood sera of their newborn children. The results obtained for beta 2 m show that cord blood sera of newborn children have higher concentrations than their mothers, implying that most of the beta 2 m in the newborn is self-produced as described previously. s-HLA serum concentrations in the newborn children are significantly lower than in their mothers or in age-matched controls. Moreover, HIV+ mothers have significantly higher serum concentrations than HIV- mothers or an age-matched control group. These results suggest that s-HLA does not cross the placental barrier.

Female↗
PubMed1990

Coexpression of lactosyl and gangliotetraosyl gangliosides in rat cerebellar radial glial cells in culture.

The expression of gangliosides of the lactosylceramide (LC) and of the gangliotetraosylceramide (GTC) series on the surface of cells from rat embryonic cerebellar tissue was investigated by double-color indirect immunofluorescence. GD3 was assumed to be representative of LC and was detected using a specific monoclonal antibody. GM1 was assumed to be representative of GTC and was detected using the binding of cholera toxin followed by the binding of cholera toxin antibodies. The expression of polysialosylated GTC (polysialosyl-GTC) was detected using the cholera toxin-cholera toxin antibody experimental approach after conversion of polysialosyl-GTC to GM1 by treatment of the cells with neuraminidase. To distinguish the major neural cell types present in the cultures the expression of the following cell type-specific markers was investigated: neuron-specific enolase and microtubule-associated protein-2 (MAP-2) as probes for neuronal cells and the intermediate filament protein glial fibrillar acidic protein (GFAP) as a probe for astroglial cells. More than 80% of cells dissociated from cerebellar tissue of 15-day-old rat embryos (E15) are positive for the expression of GD3 and about 50% for the expression of GM1 and polysialosyl-GTC, but most are negative for the expression of neuron-specific enolase, MAP-2, and GFAP. After culturing for 4 days (E15 + 4) most cells that show characteristics of neuronal cells are positive for the expression of polysialosyl-GTC and "inactivate" the expression of GD3. Most cells with characteristics of radial and stellate glial cells are also positive for the expression of polysialosyl-GTC, but unlike neuron-like cells, they do not "inactivate" the expression of GD3.

Animals↗