Biomedical subjects

P Gomes

Publications and source records attributed to P Gomes.

At least 37 records · Page 2Linked to original sources

PubMed1999

L-DOPA transport properties in an immortalised cell line of rat capillary cerebral endothelial cells, RBE 4.

The present study aimed to determine the kinetics of L-3, 4-dihydroxyphenylalanine (L-DOPA) uptake in an immortalised cell line of rat capillary cerebral endothelial cells (clones RBE 4 and RBE 4B), to define the type of inhibition produced by L-5-hydroxytryptophan (L-5-HTP), 2-aminobicyclo(2,2,1)-heptane-2-carboxylic acid (BHC) and N-(methylamino)-isobutyric acid (MeAlB) and its sodium dependence. Non-linear analysis of the saturation curves for L-DOPA and L-5-HTP revealed in RBE 4 cells Km values (in microM) of 72 and 102 and in RBE 4B cells Km values (in microM) of 60 and 118, respectively. IC50 values for L-5-HTP (RBE 4, 1026 microM; RBE 4B, 831 microM) obtained in the presence of a nearly saturating (250 microM) concentration of L-DOPA were almost 5-fold those obtained when non-saturating (25 microM) concentrations of L-DOPA were used. IC50 values for BHC obtained in the presence of a nearly saturating (250 microM) concentration of L-DOPA were also 6- to 5-fold those obtained when non-saturating (25 microM) concentrations of L-DOPA were used. MeAlB (up to 2.5 mM) was found not to interfere with the uptake of L-DOPA. In RBE 4 cells, Vmax values for L-DOPA uptake were identical in the absence and the presence of 150 microM L-5-HTP or 150 microM BHC, but Km values (microM) were significantly greater (P<0.05) when L-DOPA uptake was studied in the presence of L-5-HTP or BHC. Similar findings were observed when RBE 4B cells were used. Uptake of (250 microM) L-DOPA in the absence of sodium in the incubation medium was similar to that observed in the presence of increasing concentrations of sodium (20 to 140 mM). It is concluded that RBE 4 and RBE 4B cells are endowed with the L-type amino acid transporter through which L-DOPA and L-5-HTP can be taken up, and suggested that this immortalised cell line of rat capillary cerebral endothelium might constitute an interesting in vitro model for the study of BBB mechanisms, namely those concerning solute and nutrient transfer across the brain capillary endothelium.

Animals↗

PubMed1999

Interaction between L-DOPA and 3-O-methyl-L-DOPA for transport in immortalised rat capillary cerebral endothelial cells.

The present study aimed to determine the kinetics of L-3,4-dihydroxyphenylalanine (L-DOPA) uptake in an immortalised cell line of rat capillary cerebral endothelial cells (clones RBE 4 and RBE 4B), to define the type of interaction with 3-O-methyl-L-DOPA (3-OM-L-DOPA), sensitivity to 2-aminobicyclo(2,2,1)-heptane-2-carboxylic acid (BHC), N-(methylamino)-isobutyric acid (MeAIB) and sodium. Non-linear analysis of the saturation curves for L-DOPA and 3-OM-L-DOPA revealed in RBE 4 cells Km values (in microM) of 72 (53, 91) and 40 (25, 57) and in RBE 4B cells Km values (in microM) of 60 (46, 74) and 44 (13, 75), respectively. IC50 values for 3-OM-L-DOPA (RBE 4, 642 [542, 759] microM; RBE 4B, 482 [475, 489] microM) obtained in the presence of a nearly saturating (250 microM) concentration of L-DOPA were greater than the corresponding Ki values (RBE 4, 143 [121, 170] microM; RBE 4B, 93 [92, 95] microM) obtained in the presence of a nearly saturating (250 microM) concentration of 3-OM-L-DOPA; this is compatible with a competitive type of interaction between L-DOPA and 3-OM-L-DOPA. Uptake of both L-DOPA and 3-OM-L-DOPA in RBE 4 and RBE 4B cells was sensitive to BHC with similar IC50 values. MeAIB (up to 2.5 mM) was found not to interfere with the uptake of both L-DOPA and 3-OM-L-DOPA. Uptake of (250 microM) L-DOPA and 3-OM-L-DOPA in the absence of sodium in the incubation medium was similar to that observed in the presence of increasing concentrations of sodium (20-140 mM). Homogenates of both cell lines were endowed with considerable COMT activity. Incubation of RBE 4 and RBE 4B cells with L-DOPA (25 microM) in the presence of a methyl donor (S-adenosyl-L-methionine) resulted in the formation of 3-OM-L-DOPA; this was abolished by 1 microM tolcapone. The fractional outflow of intracellular L-DOPA through the luminal and abluminal cell side was not affected by the presence of intracellular 3-OM-L-DOPA. The fractional outflow of exogenous 3-OM-L-DOPA applied from the luminal cell border was similar to that observed for 3-OM-L-DOPA with origin in L-DOPA. It is concluded that RBE 4 and RBE 4B cells are endowed with the L-type amino acid transporter through which L-DOPA and 3-OM-L-DOPA can be taken up, and 3-OM-L-DOPA behaves as a competitive inhibitor for the uptake of L-DOPA. This, however, only occurs for luminal cell inward movement but not for abluminal cell outward movement of the substrates.

Amino Acids↗

PubMed1999

Surface plasmon resonance screening of synthetic peptides mimicking the immunodominant region of C-S8c1 foot-and-mouth disease virus.

The main antigenic site (site A) of foot-and-mouth disease virus (FMDV, strain C-S8c1) may be adequately reproduced by a 15-peptide with the amino acid sequence H-YTASARGDLAHLTTT-NH(2) (A15), corresponding to the residues 136-150 of the viral protein VP1. The effect of amino acid substitutions within A15 on its antigenicity towards monoclonal antibodies (MAb) raised against antigenic site A, has been studied by means of BIAcore technology, based on surface plasmon resonance (SPR). Although these antigenicities have previously been determined from enzyme-linked immunosorbent assays (ELISA), the SPR-based technique is superior in that it allows a fast and straightforward screening of antigens while simultaneously providing kinetic data of the antigen-antibody interaction. With a view to screening fairly large libraries of individual peptides, we have inverted the typical SPR experiment by immobilizing the MAb on the sensor surface and using peptides as soluble analytes. We report the validation of this approach through the screening of 44 site A peptides, with results generally in good agreement with the relative antigenicities previously determined by competition ELISA.

Amino Acid Sequence↗

PubMed1999

Quantitation of human immunodeficiency virus type 2 DNA in peripheral blood mononuclear cells by using a quantitative-competitive PCR assay.

A new quantitative-competitive PCR-based human immunodeficiency virus type 2 (HIV-2) proviral DNA assay (QC-PCR) was developed and used to determine the proviral load in HIV-2-infected individuals. Proviral load varied considerably, with means of 1,831 copies per 10(6) peripheral blood mononuclear cells for asymptomatic subjects (n = 19) and 2,587 for AIDS patients (n = 2). HIV-2 viral and proviral loads also varied significantly over time in asymptomatic patients. These data suggest that a high level of virus replication occurs throughout the asymptomatic phase of HIV-2 infection.

Adolescent↗

PubMed1998

L-3,4-dihydroxyphenylalanine and L-5-hydroxytryptophan share the same transporter in Opossum kidney cells.

Opossum kidney (OK) cells, which have the ability to synthesise dopamine and 5-HT, have been used as an in vitro model for the study of renal actions of dopamine and 5-hydroxytryptamine (5-HT). The present study reports on the uptake of their immediate precursors L-3,4-dihydroxyphenylalanine (L-DOPA) and L-5-hydroxytryptophan (L-5-HTP). IC50 values for L-5-HTP (1569 microM) obtained in the presence of a nearly saturating (250 microM) concentration of L-DOPA were 6-fold those obtained when using non-saturating (0.25 and 25 microM) concentrations of L-DOPA (251 and 266). Vmax values (in nmol mg protein-1 6 min-1) for L-DOPA uptake are identical in the absence (13.6) and the presence of 250 microM L-5-HTP (13.3), but K(m) values (microM) are significantly greater (P < 0.05) when L-DOPA uptake was studied in the presence of L-5-HTP (90 vs 1.79). IC50 values for L-DOPA (679 microM) obtained in the presence of a near saturating (250 microM) concentration of L-5-HTP were almost 3-fold those obtained when non-saturating (0.25 and 25 microM) concentrations of L-5-HTP were used (254 and 220). Vmax values (in nmol mg protein-1 6 min-1) for L-5-HTP uptake are identical in the absence (11.2) and the presence of 250 microM L-DOPA (11.7), but K(m) values (microM) are significantly greater (P < 0.05) when L-5-HTP uptake was studied in the presence of L-DOPA (103 vs 220). It is concluded that L-DOPA and L-5-HTP share the same transporter(s) and each compound exerts a competitive type of inhibition upon the other.

5-Hydroxytryptophan↗

PubMed1997

Competitive and non-competitive inhibition of L-3, 4-dihydroxyphenylalanine uptake in Opossum kidney cells.

The present study aimed to determine the kinetics of L-3,4-dihydroxyphenylalanine (L-DOPA) uptake in Opossum kidney (OK) cells and to define the type of inhibition produced by L-5-hydroxytryptophan (L-5-HTP), cyanine 863 and 3,3'-diethyloxacarbocyanine (3,3'-DOC). Non-linear analysis of the saturation curves revealed for L-DOPA a Km (in microM) of 129 (114, 145) and a Vmax (in nmol/mg protein per 6 min) of 30.0 +/- 0.4 IC50 values for L-5-HTP (1454 microM) obtained in the presence of a nearly saturating (250 microM) concentration of L-DOPA were almost 4-fold those obtained when non-saturating (25 microM) concentrations of L-DOPA were used (330). IC50 values for cyanine 863 and 3,3'-DOC (638 and 353 microM) obtained in the presence of a nearly saturating (250 microM) concentration of L-DOPA were similar to those obtained when non-saturating (25 microM) concentrations of L-DOPA were used (654 and 339 microM). Vmax values (in nmol/mg protein per 6 min) for L-DOPA uptake were identical in the absence (36.4 +/- 0.7) and the presence of L-5-HTP (39.2 +/- 1.3), but Km values (microM) were significantly greater (P < 0.05) when L-DOPA uptake was studied in the presence of L-5-HTP (121 (100, 142) versus 318 (237, 399)). In contrast, the effect of cyanine 863 and 3,3'-DOC was to cause a significant reduction in Vmax values without significant changes in Km values. It is concluded that L-5-HTP exerts a competitive type of inhibition of L-DOPA uptake in cultured OK cells, whereas both cyanine 863, an organic cation transport inhibitor and 3,3'-DOC behave as non-competitive inhibitors.

Animals↗

PubMed1997

Opossum kidney cells take up L-DOPA through an organic cation potential-dependent and proton-independent transporter.

The present work was aimed at studying the kinetics and nature of the L-DOPA transporter in opossum kidney (OK) cells. Saturation experiments were performed in OK cells incubated for 6 min with increasing concentrations of L-DOPA (10 to 2500 microM); non-linear analysis of the saturation curve revealed for L-DOPA a K(m) of 129 microM (114, 145) and Vmax of 30.0 +/- 0.4 nmol mg protein-1 6 min-1. The uptake of L-DOPA (250 microM) was inhibited in a concentration-dependent manner by cyanine 863, an organic cation inhibitor, with a Ki value of 638 (430, 947) microM; the organic anion inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS), was devoid of effect upon the uptake of L-DOPA. The uptake of L-DOPA (250 microM) was significantly (P < 0.02) decreased (25% reduction) when cells were incubated in the presence of 137 mM K+ plus 5 mM Na+, when compared with the control condition (137 mM Na+ plus 5 mM K+); substitution of NaCl by choline chloride (137 mM) did not affect L-DOPA uptake. Similarly, inwardly or outwardly directed proton gradients of 0.5 pH units (7.9, 7.4, 6.9, 6.4 and 5.9) were found not to change L-DOPA uptake. In conclusion, the L-DOPA uptake system in OK cells has the characteristics of an organic cation potential-dependent and proton-independent transporter.

Animals↗

PubMed1996

Inhibitory effects of activin on the growth and morpholgenesis of primary and transformed mammary epithelial cells.

Activin is a member of the transforming growth factor beta superfamily, which is known to have activities involved in regulating differentiation and development. By using reverse transcription-PCR analysis on immunoaffinity-purified human breast cells, we have found that activin beta a and activin type II receptor are expressed by myoepithelial cells, whereas no expression was detected in other breast cell types. In examining 15 breast cell lines, we have found only four (HBL-100, MCF10-A, PMC-42, and BT 20) to be positive for activin beta a mRNA, whereas all expressed the activin type II receptor. Furthermore, we have found activin A to be a potent growth inhibitor of MCF- 7 cells (at 2 ng/ml), where it causes an arrest in G(1). Activin A does not appear to have an effect on the cell cycle of primary myoepithelial or luminal cells. However, we demonstrate that activin is an inhibitor of tubule formation by human mammary organoids in vitro. These are the first observations of activin and activin receptor in the normal human breast and in human breast cell lines and suggest a role for activin in mammary cell growth and morphogenesis.

Activins↗

PubMed1995

Cytogenetic findings in 31 papillary thyroid carcinomas.

Chromosome studies performed on 31 papillary thyroid carcinomas (PTCs) revealed clonal numerical and structural abnormalities in 12 tumors. The numerical clonal aberrations found were trisomy 2, trisomy 7, and loss of the Y chromosome. A nonrandom telomeric association, tas(15;16)(p13;p13), was observed in one carcinoma. Structural alterations with a breakpoint at 10q11.2 were detected in two tumors. Other chromosomes involved in rearrangements were chromosomes 1, 2, 3, 5, 7, 9, 11, 12, and 14. The observation of clonal changes of chromosome 2 [i(2)(q10) and trisomy 2] in two tumors, which were both histologically classified as tall-cell PTC variants, suggests that gain of 2q may be important in the development of this morphological variant.

Adolescent↗

PubMed1993

Cytogenetic findings in eleven gastric carcinomas.

We describe the results of the cytogenetic study of 10 primary adenocarcinomas of the stomach and one lymph node metastasis of a gastric adenocarcinoma after direct harvesting or short-term in vitro culture. All cases showed a variable number of numerical and/or structural clonal cytogenetic aberrations. Polysomy of chromosomes 2 and 20 were the most common numerical abnormalities. Rearrangements of chromosomes 1, 3, 7, and 13 were each observed in more than half the cases. Chromosomes 3 and 13 were the chromosomes more often exhibiting structural cytogenetic aberrations. In five tumors, rearrangements of chromosome 6 resulting in partial deletion of 6q were noted (common deleted region 6q21-22-->qter). The recurrent markers observed in our series were an i(8q) and an i(17q) in three and two cases, respectively. Double minutes (dmin) or homogeneously staining regions (hsr) were evident in three tumors. Contrary to the recent claim that structural abnormalities affecting 11p13-p15 were specifically involved in gastric cancer, we detected rearrangements of this region in only two cases.

Adenocarcinoma↗

PubMed1993

Cytogenetic findings in 18 follicular thyroid adenomas.

Cytogenetic study of 18 follicular thyroid adenomas showed clonal chromosome changes in 12 tumors. These results suggest the existence of at least three cytogenetically distinct subgroups: a hyperploid group characterized by the presence of a cluster of numerical changes including +5, +7, and +12 as the most frequent anomalies and, less frequently, +4, +9, +14, +16, and +17; a pseudo- or near-diploid group characterized by simple karyotypic aberrations; and a cytogenetically normal group.

Adenoma↗

PubMed1993

Thyroid nodular hyperplasia: chromosomal studies in 14 cases.

Cytogenetic study of 14 thyroid nodular hyperplasias revealed a hyperdiploid karyotype in two cases (14%) and a normal chromosomal complement in the remaining cases. Some of the numerical alterations found were identical to the ones considered characteristic of a subset of thyroid adenomas (+5, +7, +9, +12, +14, and +16). Our findings suggest that the cytogenetic events involved in the pathogenesis of thyroid hyperplastic lesions and benign tumors may be closely related, which supports the hypothesis of a biologic "continuum" between these two types of lesions.

Adult↗

PubMed1992

Loss of Y chromosome in gastric carcinoma. Fact or artifact?

Loss of chromosome Y has been reported in gastric cancer cells together with other chromosomal abnormalities. We noted loss of chromosome Y and near-diploid karyotypes in five cases of gastric adenocarcinoma, but DNA flow cytometry performed on fresh tumor tissue showed aneuploid peaks in four of them. Our findings suggest that loss of the Y chromosome in gastric cancer probably reflects the karyotype of a subpopulation of stromal cells and not a neoplasia-related chromosomal aberration.

Adult↗

PubMed1991

Ovine psittacosis and sarcoidosis in a pregnant woman.

A woman in the first trimester of pregnancy presented with pneumonia and hilar lymphadenopathy after exposure to lambing ewes. She subsequently aborted. Infection with Chlamydia psittaci of ovine origin was confirmed. Pregnant women are susceptible to this infection, which may cause life threatening disease. The patient also had features of sarcoidosis, and the two conditions ran a similar time course. There is a possibility that ovine psittacosis caused an illness indistinguishable from sarcoidosis.

Abortion, Spontaneous↗

PubMed1989

The effects of acute exercise on pulsatile LH release in high-mileage male runners.

Evidence suggests that acute exercise and endurance training has a suppressive effect on the hypothalamic-pituitary-gonadal (HPG) axis in men and women. To determine if training and acute exercise influence the neuroendocrine regulation of the HPG axis in men we examined pulsatile LH release in six male endurance runners with a training volume of at least 80 km per week, and compared this with values in six age-matched sedentary controls. Blood samples were obtained through an indwelling i.v. cannula from the subjects at 15-min intervals for 6 h following 24 h without significant physical activity and again in the runners, following 60 min of running at a speed equivalent to 5% below the anaerobic threshold. Mean LH pulse frequency and amplitude, as well as areas under the LH pulses and total LH curve, were calculated but only the mean post-exercise area under the total LH curve area was significantly lower than basal values (P less than 0.05) following exercise compared with the resting values in runners. Other measures of LH release did not change with acute exercise. Basal and pre-exercise testosterone levels were also measured and found to be at the lower end of normal men. The mean pre-exercise serum testosterone levels were significantly higher than basal levels. Mean testosterone levels, mean pulse amplitude, and mean area under the LH curve were significantly lower in resting runners than in the controls. The data suggest that exercise induces a general lowering of LH levels but does not inhibit LH pulsatile release. An anticipatory increase in serum testosterone occurred before exercise.

Exercise↗

PubMed1989

Ankle and wrist weights: their effect on physiologic responses during treadmill running.

This study examined the effects of ankle and wrist weights on acute physiologic responses during treadmill running. Eight physically active young men completed eight running tests at their predetermined "most comfortable" speeds with zero, 1.6, 3.2, and 4.8 kg of additional weight equally distributed on the ankles or wrists. Energy expenditure and heart rate increased as a linear function of the additional weight placed at both anatomic locations. The magnitudes of these responses were significantly higher with the weights at the ankles than at the wrists, and were independent of the strength and endurance of the pertinent muscle groups involved in overcoming the additional weight. Blood lactate concentrations tended to increase during the loaded runs. However, the values were not significantly different from those observed during control (zero load) runs. Perceived exertion increased significantly over the control value when the heaviest weights were placed at the ankles and wrists. Since ankle and wrist weights increase training intensity and energy expenditure during treadmill running, they may result in greater increases in cardiovascular fitness and greater weight loss than would be realized by training without their use.

Adult↗

PubMed1988

Incidence of retroviruses in some Brazilian groups.

The prevalence of human T lymphotropic virus type I (HTLV-I) and human immunodeficiency virus (HIV) antibodies was evaluated in Brazil among 116 aboriginal Indians living in a pre-Amazonian region, and in 44 patients with haematological malignant disorders being treated in Rio de Janeiro. Screening for the presence of antibodies to HIV was performed routinely for 17,224 blood donors at the National Cancer Institute, Rio de Janeiro, from January 1986 to May 1987. The results demonstrated that HIV infection was not endemic among Brazilian Indians, as none of them had antibodies to HIV, in contrast with the population of Rio de Janeiro, which showed a high prevalence (0.34%) of positivity among normal individuals. In a small group of patients with haematological disease only one with acute lymphoblastic leukaemia proved to be HIV-positive, the infection having been acquired through previous blood transfusion. None of the serum samples reacted with HTLV-I, including those of 17 non-Hodgkin's lymphoma patients. HTLV-I infection does not seem to be endemic in this country, but further large scale studies are necessary, especially in patients with haematological disorders, homosexual individuals and drug users.

Adolescent↗

PubMed1988

[Blood levels of dehydroepiandrosterone sulfate (DHEA-S) and the risk of breast cancer].

In North American women at low or high risk of developing breast cancer, as assessed by an epidemiologic questionnaire, the plasma concentration of dehydroepiandrosterone sulfate shows a statistically significant circannual variation. In adolescents, in all seasons, circulating dehydroepiandrosterone sulfate is a classifier of the risk of developing breast cancer, a relatively low concentration of this hormone being associated with an increased risk.

Adolescent↗