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Biomedical subjects

A M Da Silva

Publications and source records attributed to A M Da Silva.

16 recordsLinked to original sources
PubMed2001

Using chemical and physical parameters to define the quality of Pardo River water (Botucatu-SP-Brazil).

This paper aims to study the ecological system of the Pardo River, at the source and lower-order passages, which are in the Botucatu area, São Paulo State, Brazil. This study was carried out to determine water quality with some chemical-physical indicators, coliforms, and chemical species of samples taken monthly, 1995/02-1996/01, from eight sampling stations sited along the Pardo River. The results in the river monitoring are discussed based on annual averages, analysis of variance, and compared to Tukey's Studentized Range--HSD, and principal component analysis (PCA) was applied to normalize data to assess association between variables. We can conclude that the variables used are very efficient for identifying and that the dry season shows the worst water quality. These were caused by organic matter, nutrients (originate) from anthropogenic sources (spatial sources) and mainly municipal wastewater, affecting the quality and hydrochemistry of the river water, which have been differentiated and assigned to polluting sources. Meanwhile, the degree of degradation of the Pardo River is low (sewage treatment carried out by the city of Pardinho is efficient), leaving the water of the river suitable for use by the population of Botucatu, after conventional treatment (Conama, Resolução No. 20, CONAMA, Brazilia DF, 09-23, 1986--the water of the Pardo river is classified as level 03).

Brazil↗
PubMed2001

Dissipation of triadimefon on the solid/gas interface.

The dissipation of triadimefon, as pure solid and in the Bayleton 5 commercial formulation, was studied under controlled and natural conditions. Volatilization and photodegradation were shown to be the main dissipation processes. The volatilization results can be described by an empirical model assuming exponential decay of the volatilization rate. The filler of the commercial formulation is determinant for the volatilization but has little effect on the photodegradation rates. The main photoproducts were identified and a reaction mechanism proposed.

Environmental Pollutants↗
PubMed1999

Medical technology assessment photic stimulation--standardization of screening methods.

RATIONALE: In many EEG laboratories in Europe, intermittent photic stimulation (IPS) is not performed routinely, and consequently, great variation exists in the type of photo stimulator used, the methodology employed, and the interpretation of the EEG curves, thus leading to different outcomes. METHODOLOGY: It was decided to hold a consensus meeting with experts in the field of photic stimulation from various European countries. This meeting was held at the Stichting Epilepsie Instellingen Nederland, Heemstede, the Netherlands. The consensus reached was presented and discussed at the 9th European Congress of Clinical Neurophysiology in Ljubjana in June 1998. RESULTS: Patients should be positioned at a distance of 30 cm from the photic stimulator (nasion to lamp) with dim surrounding lights, just enough to see the patient. Flashes should be delivered in separate trains of 10 s for each frequency, with intervals of 7 s minimum. First stimulation occurs with eyes open followed after 5 s by eye closure, while starting at 1 Hz progressing to 20 Hz, unless generalised epileptiform discharges are evoked at a lower frequency. Then, frequencies should start at 60 Hz decreasing to 25 Hz. The following frequencies should be used: 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 60, 50, 40, 30 and 25 Hz. The total duration is a maximum of 6 min (patients without a reaction to IPS). In interpreting the evoked responses, a clear distinction should be made between epileptiform responses confined to the occipital area (OSW), starting occipitally and spreading to frontal regions (OGSW), or generalised from the start (GSW). Other responses include generalised spikes (OR). CONCLUSION: This standard is safe, relatively quick, simple and reliable. Comparison of data within patients and between patients of various laboratories will also be possible. This will improve the quality of the care of the individual patient and make collaborative research possible.

Electroencephalography↗
PubMed1994

Calcium uptake and gp80 messenger RNA destabilization follows cAMP receptor down regulation in Dictyostelium discoideum.

The mechanism by which high concentrations of cAMP selectively destabilize the gp80 mRNA in Dictyostelium discoideum was investigated. This treatment which leads to down-regulation of the cAMP receptor was also found to cause an increase in calcium uptake. Given this observation, we sought a role for calcium as a second messenger in the degradation of the gp80 mRNA. Changes in the mRNA levels were examined after treating cells with compounds known to alter their intracellular Ca2+ concentrations. This included the use of A23187, Ca2+, 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate HC1 (TMB-8), LiCl and 8-p-chlorophenylthioadenosine 3',5'-cyclic monophosphate (ClPhS-Ado-3':5'-P). The sum of the data suggest that it is the cAMP-induced influx of Ca2+ across the plasma membrane, as apposed to a cAMP-mediated release of Ca2+ from intracellular stores, that initiates gp80 mRNA degradation. Treatment of cells with Concanavalin A (ConA) to induce cAMP receptor down-regulation, also causes a reduction in gp80 mRNA levels and an increase in calcium uptake.

Animals↗
PubMed1989

A comparative study of anti-Trypanosoma cruzi serum obtained in acute and chronic phase of infection in mice.

The IgG antibody content, specificity, lytic activity, clearance capacity and protective ability of mouse anti-Trypanosoma cruzi serum was determined during the course of infection. The IgG antibody content increased during the course of infection, reaching its highest level in the serum collected in the chronic phase of the infection. The T. cruzi antigens recognized by antibodies using the protein transfer technique also increased with time of infection. Antibodies present in day 22 post-infection (p.i.) serum were already able to recognize all the antigens detected by antibodies present in serum from the chronic phase. The lytic and clearance ability were not detected on day 7 p.i., but appeared on day 14 p.i. and reached their highest level on day 45 p.i. The protective ability was present in serum of the chronic phase, but was absent from the acute serum. The IgG antibody content of the acute serum was four times less than that of the chronic serum. When the IgG antibody concentration of the acute serum was equalized to that of the chronic serum, the acute serum was as able to protect the infected animals as the chronic serum. It is suggested that the disagreement between the protective ability of anti-T. cruzi antisera collected in the acute or in the chronic phase of the infection is due to a quantitative rather than a qualitative difference.

Acute Disease↗
PubMed1988

Central nervous system site of action for the hypotensive effect of clonidine in the cat.

The purpose of our study was to determine whether clonidine exerts its centrally mediated hypotensive action at three sites that influence arterial pressure located in the medulla, specifically associated with the intermediate area of the ventrolateral medulla. The "intermediate area" lies approximately 1.5 mm caudal to the border of the trapezoid body (caudal border) and 4 mm lateral to the midline. One of the sites that influence arterial pressure lies in the nucleus reticularis rostroventrolateralis. The second site lies in close proximity to the rostral part of the nucleus reticularis lateralis (rLRN) and also near the A1 area. The third site lies in the most rostral area and medial to the nucleus reticularis rostroventrolateralis, that is in the nucleus paragigantocellularis lateralis. Unilateral microinjections of 0.22 and 0.43 nmol of clonidine into the rLRN produced dose-dependent decreases in arterial pressure. The 0.43 nmol dose of clonidine had no effect when unilaterally or bilaterally microinjected into either the nucleus reticularis rostroventrolateralis or into the nucleus paragigantocellularis lateralis. Microinjection of the alpha-2 adrenoceptor antagonist, idazoxan (16.6 nmol), unilaterally into rLRN had no effect per se, but prevented the hypotensive effect of a subsequent microinjection of clonidine. Similarly, bilateral microinjection of idazoxan into rLRN counteracted the hypotensive effect of i.v. administered clonidine. These data indicate that clonidine acts at alpha-2 adrenoceptors in the rLRN to produce hypotension.

Adrenergic alpha-Antagonists↗
PubMed1985

Comparative cardiorespiratory effects produced by taurine and glycine applied to the ventral surface of the medulla.

The purpose of our study was to determine whether taurine, like other naturally occurring central nervous system amino acid neurotransmitters (e.g., gamma-aminobutyric acid and glycine), act at the ventral surface of the medulla to influence cardiorespiratory activity. This was accomplished by monitoring cardiorespiratory activity. This was accomplished by monitoring cardiorespiratory activity in chloralose-anesthetized cats and then applying several doses of taurine locally to the ventral medullary surface chemosensitive areas. We found that 2 and 4 mumol of taurine applied to the intermediate area of the ventral surface produced cardiorespiratory depression, whereas taurine, in a similar dose range, produced only respiratory depression when applied to the rostral area. In contrast, taurine applied to the caudal area had no cardiorespiratory effects. Similar experiments with glycine revealed that this inhibitory amino acid elicited a similar pattern of cardiorespiratory depression as taurine. Furthermore, strychnine, an antagonist of glycine, counteracted the cardiorespiratory depressant effects of both taurine and glycine effectively. Pretreatment with strychnine prevented most of the cardiorespiratory depressant effects of taurine and glycine. 6-Aminomethyl-3-methyl-4H-1, 2,4-benzothiadiazine-1,1-dixoide, a putative antagonist of taurine, had antagonistic effects similar to those of strychnine in both treatment and pretreatment studies. 6-Aminomethyl-3-methyl-4H-1,2,4-benzothiadiazine-1,1-dioxide, per se, increased tidal volume when applied to the intermediate area; strychnine had no effect. These results indicate that taurine acts at the chemosensitive areas on the ventral surface of the medulla to produce cardiorespiratory depression, and these effects are due to an interaction of taurine with receptors similar to, but probably not identical with, glycine receptors.

Animals↗
PubMed1983

Activation of central nervous system cholecystokinin receptors stimulates respiration in the cat.

Cholecystokinin-octapeptide (CCK-OP) was injected into the lateral brain ventricle of chloralose-anesthetized cats while monitoring pulmonary ventilation, mean blood pressure (BP) and heart rate (HR). Initial values for respiratory minute volume, BP and HR were 436 +/- 32 ml/min, 126 +/- 8 mm Hg and 204 +/- 9 beats/min, respectively. CCK-OP in doses of 8.8 x 10(-13) to 8.8 x 10(-10) M (i.e., 1 to 1000 ng) increased respiratory minute volume by +56 +/- 18 ml/min to +370 +/- 73 ml/min, respectively. This response was due to an increase in tidal volume (P less than .05) with no effect on respiratory rate. Most of these doses increased BP and HR (P less than .05). These responses were mimicked when CCK-OP was administered into and restricted to the lateral and 3rd ventricles, whereas no significant responses occurred with administration into the 4th ventricle. The highest dose of CCK-OP, when given i.v., produced no significant effects. Central nervous system injections (lateral ventricle) of CCK-OP in deafferented animals also produced respiratory and cardiovascular stimulation, but higher doses were required. Central nervous system injections of comparable doses of desulfated CCK-OP or pentagastrin had no effect on respiratory minute volume, BP or HR. Proglumide (0.8 and 8.0 mg), a specific CCK receptor antagonist, prevented both respiratory and cardiovascular effects induced by CCK-OP. These doses of proglumide exerted no antagonism of CO2-induced respiratory stimulation. These data suggest that a specific receptor reacting with CCK-OP may be important for the control of respiration.

Animals↗
PubMed1982

Foreign body aspiration.

The problem of aspiration of a foreign body is discussed: the range of clinical problems is presented and the pathogenesis explained. The role of bronchoscopy as a diagnostic and therapeutic procedure is pointed out and the need for a highly skilled team of surgeons and anaesthetists highlighted.

Age Factors↗
PubMed1982

Respiratory depression produced by glycine injected into the cisterna magna of cats.

Glycine (0.8-64.8 mumol) was administered into the cisterna magna of alpha-chloralose anesthetized cats to determine its effect on ventilation. Glycine caused a dose-related decrease in respiratory minute volume with the highest dose resulting in a decrease from 454 +/- 35 to 159 +/- 44 ml/min (p less than 0.05). This decrease was due primarily to a reduction in tidal volume which decreased from 31 +/- 2 to 12 +/- 2 ml (p less than 0.05). The two largest doses tested (21.6 and 64.8 mumol) also produced a decrease in respiratory rate from 14 +/- 1 to 11 +/- 1 and from 15 +/- 1 to 12 +/- 1 breaths/min (p less than 0.05), respectively. Apnea occurred in 2 of 7 animals given 64.8 mumol of glycine. No consistent dose-related changes in inspiratory and expiratory durations were observed. Intravenous administration of glycine (64.8 mumol) did not affect respiratory activity. These results indicate that glycine causes respiratory depression by an action in the central nervous system.

Animals↗
PubMed1981

[Visualization of oxitalan fibers in normal human skin by the alkaline tetrazolium test].

The "elastic system" of the connective tissue includes the oxytalan, the elaunin and the elastic fibers. The oxytalan fibers are formed by the microfibrillar component of the elastic fibers (elastic microfibrils). In the human skin the oxytalan fibers are found in the papillary dermis perpendicularly oriented to the dermo-epidermal junction. It was previously demonstrated by biochemical analysis that sulfur amino acids are present in the elastic microfibrils. Based on these data we could visualize the oxytalan fibers in the human dermis using the nitroblue tetrazolium (NBT) technique.

Amino Acids↗
PubMed1980

The immediate effect on lung function of smoking filtered and nonfiltered cigarettes.

We measured and compared the effect of smoking a filtered and a nonfiltered cigarette on instantaneous maximal expiratory flow rates (Vmax50 and Vmax25) and airway resistance (Raw). We found a significant increase in Raw after both cigarettes, and a small decrease in Vmax50 after smoking the nonfiltered cigarette. The change in Vmax50 after smoking the filtered cigarette was not significant. We suggest, on the basis of these data, that filtered cigarette smoke reduces some of the constituents that cause bronchoconstriction in the large and central airways.

Adolescent↗
PubMed1975

The effect of prostaglandin F2beta on expiratory flow rates.

Prostaglandin F2beta (PGF2beta), a stereoisomer of F2alpha was administered by ultrasonic nebulization to eight patients with bronchial asthma and four normal subjects in increasing doses up to 200 mug maximum dose. Maximum expiratory flow (MEF) and forced vital capacity (FVC) were analyzed at 5, 15, 30, 60 and 120 minutes after administration of aerosol. All expiratory flow rates were reduced after 5 minutes. Some increase in terminal flow rates was observed after 60 minutes. We conclude that PGF2beta in not an effective bronchodilator at this dose level.

Asthma↗