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R M Barbosa

Publications and source records attributed to R M Barbosa.

14 recordsLinked to original sources
PubMed2000

[First report of Aedes albopictus in areas of Mata Atlantica, Recife, PE, Brazil].

This is the first report of the presence of Aedes albopictus in the native rain forest, near the urban area of Recife (State of Pernambuco, Brazil). Adult female mosquitoes were collected using human bait. Mosquitoes in aquatic stages were looked for in treeholes, bamboos, bromeliads and old tires. The existence of Ae. albopictus in the metropolitan area of Recife poses a potential risk for the interaction of this mosquito species with the urban human population.

Aedes↗
PubMed1998

Control of pulsatile 5-HT/insulin secretion from single mouse pancreatic islets by intracellular calcium dynamics.

1. Glucose-induced insulin release from single islets of Langerhans is pulsatile. We have investigated the correlation between changes in cytosolic free calcium concentration ([Ca2+]i) and oscillatory insulin secretion from single mouse islets, in particular examining the basis for differences in secretory responses to intermediate and high glucose concentrations. Insulin release was monitored in real time through the amperometric detection of the surrogate insulin marker 5-hydroxytryptamine (5-HT) via carbon fibre microelectrodes. The [Ca2+]i was simultaneously recorded by whole-islet fura-2 microfluorometry. 2. In 82 % of the experiments, exposure to 11 mM glucose evoked regular high-frequency (average, 3.4 min-1) synchronous oscillations in amperometric current and [Ca2+]i. In the remaining experiments (18 %), 11 mM glucose induced an oscillatory pattern consisting of high-frequency [Ca2+]i oscillations that were superimposed on low-frequency (average, 0.32 min-1) [Ca2+]i waves. Intermittent high-frequency [Ca2+]i oscillations gave rise to a similar pattern of pulsatile 5-HT release. 3. Raising the glucose concentration from 11 to 20 mM increased the duration of the steady-state [Ca2+]i oscillations without increasing their amplitude. In contrast, both the duration and amplitude of the associated 5-HT transients were increased by glucose stimulation. The amount of 5-HT released per secretion cycle was linearly related to the duration of the underlying [Ca2+]i oscillations in both 11 and 20 mM glucose. The slopes of the straight lines were identical, indicating that there is no significant difference between the ability of calcium oscillations to elicit 5-HT/insulin release in 11 and 20 mM glucose. 4. In situ 5-HT microamperometry has the potential to resolve the high-frequency oscillatory component of the second phase of glucose-induced insulin secretion. This component appears to reflect primarily the duration of the underlying [Ca2+]i oscillations, suggesting that glucose metabolism and/or access to glucose metabolites is not rate limiting to fast pulsatile insulin release.

Animals↗
PubMed1996

Real time electrochemical detection of 5-HT/insulin secretion from single pancreatic islets: effect of glucose and K+ depolarization.

We report a highly sensitive electrochemical approach suitable for the real time measurement of insulin release from single islets of Langerhans, the functional endocrine units in the pancreas. The method is based on the detection of the insulin surrogate 5-hydroxytryptamine (5-HT) by carbon fibre microelectrodes implanted in the islets. Based on the combination of this novel approach with the simultaneous microfluorometric recording of cytosolic free Ca2+ concentration ([Ca2+]i), we demonstrate that glucose-stimulated islets secrete 5-HT/insulin in a pulsatile fashion under physiological conditions, and that this activity is encoded by synchronous [Ca2+]i oscillations. The sensitivity to detect variations in minute amounts of secreted materials is partially conferred by the fact that the tracer is released into a relatively confined space (the intraislet interstitial space).

Animals↗
PubMed1996

Electrochemical studies of zinc in zinc-insulin solution.

The electrochemical determination of zinc arising from zinc-insulin complexes was investigated and it was demonstrated that zinc in zinc-insulin solution can be measured in the presence of dissolved oxygen by square-wave anodic stripping voltammetry (SWASV) at mercury thin-film electrodes on glassy carbon disc minielectrode and cylindrical carbon fibre microelectrode substrates. Reoxidation signals arise from complexed zinc at low insulin concentrations (< 100 nmol l-1) and from labile zinc at higher concentrations; the latter can be quantified through linear calibration curves. Batch injection analysis with SWASV was successfully tested for the determination of zinc in zinc-insulin solutions in small sample volumes. Since intracellularly stored insulin exists in the form of a zinc-insulin complex, these techniques are very promising for the indirect study of insulin release from pancreatic beta-cells.

Amino Acid Sequence↗
PubMed1995

Cell-specific purinergic receptors coupled to Ca2+ entry and Ca2+ release from internal stores in adrenal chromaffin cells. Differential sensitivity to UTP and suramin.

We have assessed the relative contribution of Ca2+ entry and Ca2+ release from internal stores to the [Ca2+]i transients evoked by purinergic receptor activation in bovine adrenal chromaffin cells. The [Ca2+]i was recorded from single cells using ratiometric fura-2 microfluorometry. Two discrete groups of ATP-sensitive cells could be distinguished on the basis of their relative capacity to respond to ATP in the virtual absence of extracellular Ca2+. One group of cells (group I) failed to respond to ATP in the absence of Ca2+, was completely insensitive to UTP, and displayed suramin-blockable [Ca2+]i transients when challenged with ATP in the presence of external Ca2+. ATP activated a prominent and rapidly inactivating Mn2+ influx pathway in group I cells, as assessed by monitoring Mn2+ quenching of fura-2 fluorescence. In contrast, a second group of ATP-sensitive cells (group II) exhibited pronounced [Ca2+]i rises when challenged with ATP and UTP in the absence of Ca2+ and was completely insensitive to suramin. ATP and UTP activated a delayed and less prominent Mn2+ influx pathway in group II cells. Contrary to the nicotinic receptor agonist DMPP, which evoked a preferential release of epinephrine, ATP evoked a preferential release of norepinephrine, and UTP had no effect on secretion. Suramin nearly suppressed ATP-evoked norepinephrine release. We conclude that chromaffin cells contain two distinct and cell-specific purinoceptor subtypes. Although some cells express a P2U-type purinoceptor coupled to Ca2+ release from internal stores and to the associated slow Ca2+ refilling mechanism, other cells express a suramin-sensitive and UTP-insensitive purinoceptor exclusively coupled to Ca2+ influx, probably an ATP-gated channel. It is suggested that the ATP-gated channel is preferentially localized to norepinephrine-secreting chromaffin cells and supports specifically hormone output from these cells. Thus, the biochemical pathways involved in the exocytotic release of the two major stress-related hormones appear to be regulated by distinct signaling systems.

Adenosine Triphosphate↗
PubMed1995

Action of immobilized xanthine oxidase on purines.

Xanthine oxidase was covalently immobilized on polyacrylamide gel beads, polyamide-11 and dacron. Hypoxanthine (15 ml of 200 microM), prepared in 0.1 M phosphate buffer, pH 8.0, was circulated through a column containing 1.0 g derivatized enzyme at a flow rate of 1.0 ml/min at 28 degrees C. Specific activities of 0.660, 0.072 and 0.016 Units/mg of protein were demonstrable for the polyacrylamide gel beads, dacron and polyamide-11 derivatives, respectively. The action of these water insoluble enzyme derivatives on 6-mercaptopurine (15 ml of 660 microM) was also investigated, under the same experimental conditions, showing specific activities of 0.063 Units/mg, 0.574 muUnits/mg and 0.118 muUnits/mg, respectively. The 6-mercaptopurine oxidative pathway catalyzed by immobilized xanthine oxidase on dacron stopped at the intermediate compound, 6-mercapto-8-hydroxypurine, so that no 6-thiouric acid was produced, whereas the immobilized preparations using polyacrylamide gel beads and polyamide-11 behaved like the soluble enzyme, namely, 6-thiouric acid was the final product. The behavior of dacron-xanthine oxidase compound was similar to that previously described for the derivatives obtained with carboxymethylcellulose and chitosan. The hypoxanthine oxidative pathway catalyzed by xanthine oxidase immobilized on these three supports was similar to the soluble enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Enzymes, Immobilized↗
PubMed1993

Differential modulation of pancreatic beta-cell bursting by intracellular pH in the presence and absence of a K-ATP channel blocker.

The study of the influence of intracellular pH (pHi) changes on the mechanism underlying pancreatic beta-cell bursting has been hampered by concomitant effects on the activity of background ATP-dependent K+ (K-ATP) channels. beta-cells were made to burst in the absence of active K-ATP channels by raising external Ca2+ in the presence of 11 mM glucose and tolbutamide. An alkalinizing pHi shift (exposure to 20 mM NH4Cl) increased the burst active phase duration. Conversely, an acidifying shift (NH4Cl withdrawal) suppressed the electrical activity. This is the mirror image of the effects recorded in the absence of tolbutamide. Glibenclamide and quinine suppressed the alkalinization-evoked hyperpolarization. This study emphasizes the differential sensitivity of different beta-cell ion channels to pHi and the prevalent role of K-ATP channels as electrical transducers of cytoplasmic pH changes under regular physiological conditions.

Adenosine Triphosphate↗
PubMed1993

Bursting electrical activity in pancreatic beta-cells: evidence that the channel underlying the burst is sensitive to Ca2+ influx through L-type Ca2+ channels.

In glucose-stimulated pancreatic beta-cells, the membrane potential alternates between a hyperpolarized silent phase and a depolarized phase with Ca2+ action potentials. The molecular and ionic mechanisms underlying these bursts of electrical activity remain unknown. We have observed that 10.2-12.8 mM Ca2+, 1 microM Bay K 8644 and 2 mM tetraethylammonium (TEA) trigger bursts of electrical activity and oscillations of intracellular free Ca2+ concentration ([Ca2+]i) in the presence of 100 microM tolbutamide. The [Ca2+]i was monitored from single islets of Langerhans using fura-2 microfluorescence techniques. Both the high-Ca(2+)- and Bay-K-8644-evoked [Ca2+]i oscillations overshot the [Ca2+]i recorded in tolbutamide. Nifedipine (10-20 microM) caused an immediate membrane hyperpolarization, which was followed by a slow depolarization to a level close to the burst active phase potential. The latter depolarization was accompanied by suppression of spiking activity. Exposure to high Ca2+ in the presence of nifedipine caused a steady depolarization of approximately 8 mV. Ionomycin (10 microM) caused membrane hyperpolarization in the presence of 7.7 mM Ca2+, which was not abolished by nifedipine. Charybdotoxin (CTX, 40-80 nM), TEA (2 mM) and quinine (200 microM) did not suppress the high-Ca(2+)-evoked bursts. It is concluded that: (1) the channel underlying the burst is sensitive to [Ca2+]i rises mediated by Ca2+ influx through L-type Ca2+ channels, (2) both the ATP-dependent K+ channel and the CTX- and TEA-sensitive Ca(2+)-dependent K+ channel are highly unlikely to provide the pacemaker current underlying the burst.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1992

High external Ca2+ levels trigger membrane potential oscillations in mouse pancreatic beta-cells during blockade of K(ATP) channels.

Glucose depolarizes the pancreatic beta-cell and induces membrane potential oscillations, but the nature of the underlying oscillatory conductance remains unknown. We have now investigated the effects of the Ca2+ ionophore ionomycin and high external Ca2+ concentration ([Ca2+]o) on glucose-induced electrical activity and whole islet intracellular free Ca2+ concentration ([Ca2+]i), under conditions where the K(ATP) channel was blocked (100 microM tolbutamide or 4 microM glibenclamide). Raising [Ca2+]o to 10.2 or 12.8 mM, but not to 5.1 or 7.7 mM, turned continuous electrical activity into bursting activity. High [Ca2+]o (12.8 mM) regenerated a pattern of fast [Ca2+]i oscillations overshooting the levels recorded in tolbutamide. Ionomycin (10 microM) raised the [Ca2+]i and synergized with 5.1 mM Ca2+ to hyperpolarize the beta-cell membrane. The data indicate that a [Ca2+]i-sensitive and sulphonylurea-insensitive oscillatory conductance underlies the beta-cell bursting activity.

Adenosine Triphosphate↗
PubMedDate not supplied

[Detection of capsular polysaccharide antigen of Cryptococcus neoformans in patients with AIDS and neurocryptococcosis in São Paulo, Brazil].

Capsular polysaccharide antigen (AgPC) of Cryptococcus neoformans was detected by latex agglutination technique (LA) in cerebrospinal fluid and serum of patients with AIDS during their first central nervous system manifestation of the disease. Direct mycological examination and culture were used as controls. Sensitivity was 100% by LA allowing an early specific treatment of cryptococcosis. Initial titres of AgPC in such patients can be > 1000000 and it appears that when such titres are present in the serum they are related to mortality during treatment. Surviving patients showed positivity of the direct mycological examination and AgPC of C. neoformans in cerebrospinal fluid and sera even after treatment and clinical recovery.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

The Brazilian experience with Cytotec.

Cytotec, the commercial name for misoprostol, which is a synthetic analogue of prostaglandin E1, was approved for use in Brazil in 1986 to treat gastric and duodenal ulcers. The drug can and has also been used to induce abortion, which has created controversy in a country in which induced abortion is illegal. A study of the drug was undertaken in 1992 that included analyses of the drug's sales profile, of information published by the media, and of its use from women's and gynecologists' points of view, the latter examined using qualitative methodologies. The analysis of Cytotec's sales volume showed quick growth from its introduction until the first half of 1991, when its use was restricted by the Ministry of Health. For women, Cytotec's main advantages have been that it is relatively inexpensive, convenient to use, and can be used in private. Data obtained from gynecologists show that Cytotec's addition to the obstetric therapeutic arsenal was welcome and also confirmed the drug's influence in reducing the complications of illegal abortions shown in other studies.

Abortion, Illegal↗
PubMedDate not supplied

Sexuality and reproductive health care in São Paulo, Brazil.

Gender inequalities influence the quality of reproductive health care in many ways. The lack of gender sensitivity in the provision of activities related to illness prevention and health care, as well as women's difficulties in controlling their own sexuality, are fundamental aspects of this problem. Two recent studies carried out in São Paulo, Brazil, examined factors associated with the use of methods to control fertility and to prevent STDs/AIDS. Both studies identified a strong resistance to extending the use of barrier methods among the female population, even though doing so is particularly important to help contain the spread of HIV/AIDS among women in this country. Findings include that gender-sensitive strategies must be developed to stimulate the process of behavior change. These strategies should be combined with holistic approaches to women's health care, so that prenatal and gynecological care, family planning, cervical cancer screening, and STDs/AIDS prevention are included within the same program.

Adolescent↗