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Biomedical subjects

M T Silva

Publications and source records attributed to M T Silva.

At least 19 recordsLinked to original sources
PubMed2006

Neutrophils, apoptosis and phagocytic clearance: an innate sequence of cellular responses regulating intramacrophagic parasite infections.

In complex organisms, apoptosis is a constitutive cell death process that is involved in physiological regulation of cell numbers and that can also be induced in the course of inflammatory and immune responses. Neutrophils are among the first cells recruited during inflammation. Neutrophils constitutively die by apoptosis at inflamed sites, and are ingested by macrophages. Recent studies investigated how phagocytic clearance of senescent neutrophils influences the survival of intracellular protozoan parasites that have been phagocytosed by, or have invaded phagocytes. The results indicate that neutrophil clearance plays an unexpected role in regulation of intramacrophagic protozoan parasite infection.

Animals↗
PubMed2003

Inhibition of neuronal nitric oxide synthase increases dopamine efflux from rat striatum.

The physiological role of nitric oxide in the control of striatal dopamine release has not been fully established, therefore, the effect of neuronally produced nitric oxide (NO) on striatal dopamine (DA) efflux were investigated using in vivo microdialysis in anaesthetised and conscious rats. In the anaesthetised rat, the nitric oxide synthase inhibitors N(G)-nitro-L-arginine methylester (L-NAME) and 7-nitroindazole monosodium salt (7-NINA) produced concentration-dependent increases in DA efflux. The L-NAME (1 mM)- and 7-NINA (1 mM)-induced increase was reduced by co-administration with the NO precursor, L-arginine (L-ARG; 1 mM) by 37% and 54% respectively, and was prevented by tetrodotoxin (TTX, 1 microM). Similarly, in conscious rats, L-NAME (1 mM) and 7-NINA (1 mM) increased DA efflux to 161% and 166% of basal efflux respectively. These data suggest that neuronally produced NO inhibits striatal DA efflux through an indirect mechanism.

Animals↗
PubMed2002

Mycobacterial infection in farmed turbot Scophthalmus maximus.

Mycobacteriosis (piscine tuberculosis) has been reported to affect a wide range of freshwater and marine fish species; however, this is the first report describing mycobacterial infections in turbot Scophthalmus maximus. High numbers of granulomas were initially observed in the organs of moribund farmed turbot. Bacteriological analysis of organs with granulomas led to the isolation of Mycobacterium marinum. Further analysis, to determine the prevalence of the infection in the farm and to identify its source, showed the occurrence of a dual infection by M. marinum and M. chelonae. The presence of Nocardia sp. in some of the fish infected with mycobacteria was also detected. The presence of granulomas in internal organs of apparently healthy fish indicated a high prevalence of the disease, a conclusion that was supported by isolating mycobacteria from all fish with or without granulomas. The infection was probably responsible for the mortality observed (approximately 2% mo(-1)), as most of the recently dead fish presented high numbers of granulomas and isolation of mycobacteria was possible from all of the fish. The isolation of M. marinum from the inlet water suggested this as the most plausible source for the infection occurring in the farm.

Animals↗
PubMed2001

Electron microscopic evidence that expression of capsular polysaccharide by Photobacterium damselae subsp. piscicida is dependent on iron availability and growth phase.

The expression of capsular polysaccharide (CPS) by the fish pathogen Photobacterium damselae subsp. piscicida was analysed in the virulent strain DI 21 in relation to the growth phase and presence or absence of available iron in the culture medium. Bacterial cells were processed for electron microscopy by a procedure that improves visualisation of the capsule through stabilisation with polycationic ferritin, and electron micrographs of ultrathin sections were scanned with an acquired computerised image analyser to measure capsular area. Cells grown under iron-limited conditions always had a significantly lower amount of capsular material on their surfaces than iron-supplemented cells, even when cells from different culture phases were compared. Irrespective of the presence or absence of iron in the culture medium the amount of CPS decreased with the age of the culture, i.e., from early log phase to late log phase to stationary phase. The in vivo significance of this regulatory role of iron remains to be investigated.

Animals↗
PubMed2001

Facilitation of latent inhibition by the atypical antipsychotic risperidone.

The action of the atypical antipsychotic risperidone on latent inhibition (LI), an animal model of schizophrenia, was investigated. The parameters of the procedure were set at values insufficient to generate LI in control rats. On the first day, rats administered 0.5, 1.0, or 2.0 mg/kg ip risperidone or vehicle were preexposed (PE) to 10 tone presentations. On the second day, they were again injected with drug or vehicle and then submitted to two conditioned stimulus (CS; tone)-unconditioned stimulus (US; shock) pairings. On the third day, suppression of their drinking response under the CS was measured. Nonpreexposed (NPE) animals were submitted to the same procedure except for the tone preexposure. On the suppression test, LI was not observed in control rats as well as in animals given 0.5 mg/kg risperidone. Animals given 1.0 and 2.0 mg risperidone, however, displayed an LI effect. The facilitation of LI by risperidone gives additional support to the LI paradigm as an animal model of schizophrenia.

Animals↗
PubMed2001

A comparison of horse-race, bingo, and video poker gamblers in Brazilian gambling settings.

In the present study Brazilian gamblers from different settings were compared on sociodemographic characteristics, gambling the behavior, and use of drugs. The SOGS was administered to 171 subjects at bingo (BG), video poker (VP), and horse-racing clubs (HR) of São Paulo. BG concentrated most women, VP the youngest and single gamblers, and HR the lowest income subjects. More VP than HR or BG gamblers reported taking time off work to gamble, as well as returning another day to win back lost money. They also had a higher number of scorable responses on the SOGS. The differences observed suggest that VP gamblers bear a greater risk of developing a pathological gambling pattern. The authors suggest that measures should be taken aimed at the prevention of pathological gambling, particularly among the young population of video poker gamblers.

Adolescent↗
PubMed2000

Glycogen granules in resting and inflammatory rainbow trout phagocytes--an ultrastructural study.

The ultrastructural image of glycogen granules in the cytoplasm of rainbow trout phagocytes in sections stained by the conventional lead or uranyl-lead stains is highly dependent on fixation conditions, the granules being visible only when adequate fixation protocols are used. Morphometry of samples processed for the detection of peroxidase or esterase activities (to specifically label neutrophils and macrophages, respectively), and simultaneously stained for the specific detection of glycogen, showed that inflammatory peritoneal neutrophils were richer in glycogen granules than resting neutrophils. This increase in glycogen content occurs after the migration from the haematopoietic tissues and peripheral blood to the inflamed foci. Glycogen granules could not be found in resting peritoneal macrophages but were found in inflammatory macrophages. The macrophage granules occurred in smaller amounts than in neutrophils, and consisted of granules identical to those of neutrophils together with significantly smaller granules. No evidence for the utilization of glycogen by neutrophils phagocytosing bacteria within the peritoneal cavity was found.

Animals↗
PubMed2000

Therapeutic efficacy of liposomal rifabutin in a Mycobacterium avium model of infection.

Liposomal formulations of rifabutin were developed, and the effects of some parameters on the incorporation efficiency were studied. The antimycobacterial activity of rifabutin incorporated into liposomes prepared with phosphatidylcholine and phosphatidylserine (molar ratio, 7:3) was evaluated in a murine model of infection with a virulent Mycobacterium avium strain (strain P1581) and was compared with that of free rifabutin. The influences of the size of the liposomal rifabutin formulation, the administered doses, and the treatment schedules on the evolution of infection were studied. Two types of treatment schedules were assayed: therapeutic and prophylactic. The therapeutic treatment started 2 weeks after infection, while the prophylactic treatment began 1 day before the experimental infection with mycobacteria. Incorporation of rifabutin in liposomes resulted in a significant enhancement of activity against M. avium infection compared to that of rifabutin in the free form in both schedules. These results demonstrate that liposomal formulations of antibiotics such as rifabutin may be effective for the treatment or prophylaxis of infectious diseases.

Animals↗
PubMed2000

Neutrophils play a protective nonphagocytic role in systemic Mycobacterium tuberculosis infection of mice.

Evidence showing that neutrophils play a protective role in the host response to infection by different intracellular parasites has been published in the past few years. We assessed this issue with regard to the infection of mice with Mycobacterium tuberculosis. We found a chronic recruitment of neutrophils to the infection foci, namely, to the peritoneal cavity after intraperitoneal infection and to the spleen and liver after intravenous inoculation of the mycobacteria. However, bacilli were never found associated with the recruited neutrophils but rather were found inside macrophages. The intravenous administration of the antineutrophil monoclonal antibody RB6-8C5 during the first week of infection led to selective and severe neutropenia associated with an enhancement of bacillary growth in the target organs of the mice infected by the intravenous route. The neutropenia-associated exacerbation of infection was most important in the liver, where a bacterial load 10-fold higher than that in nonneutropenic mice was found; the exacerbation in the liver occurred both during and after the neutropenic period. Early in infection by M. tuberculosis, neutropenic mice expressed lower levels of mRNAs for gamma interferon and inducible nitric oxide synthase in the liver compared to nondepleted mice. These results point to a protective role of neutrophils in the host defense mechanisms against M. tuberculosis, which occurs early in the infection and is not associated with the phagocytic activity of neutrophils but may be of an immunomodulatory nature.

Animals↗
PubMed2000

[Neuroradiological features of the brain in subacute combined spinal cord degeneration: case report].

Deficiency of vitamin B12 may produce neuropsychiatric disturbances. In the CNS the disease affects mainly myelin sheaths, and the spongy degeneration and diffuse demyelination of the posterior and lateral columns of the spinal cord are the classical pathological changes in patients with subacute combined degeneration. Similar changes also occur in cerebral hemispheres and MRI abnormalities in brain of such patients could be expected, but have received little attention. We report a case of pernicious anemia with neurological manifestations and brain MRI abnormalities. We discuss the neuropathological aspects and we suggest that pernicious anemia is a differential diagnosis to consider in central demyelinating lesions at MRI.

Acute Disease↗
PubMed2000

[History, effects and mechanisms of action of ecstasy (3,4-methylenedioxyamphetamine): review of the literature].

This review focuses on 3,4-methylenedioxymethamphetamine, an illegal drug known as "ecstasy." Ecstasy was introduced in Brazil in 1994. Data are lacking on the epidemiology and usage pattern of the drug in Brazil. However, there is evidence that until now the use of ecstasy has been limited to middle-class or upper-middle-class youth, so that most people, including health care professionals, are unfamiliar with the drug. However, ecstasy may be becoming more popular in Brazil, following a pattern seen in North America and Europe. Possible contributing to the drug's popularity is the fact that ecstasy is sold as a pill and is thus extremely easy to use. Ecstasy has a reputation for not being physically dangerous; however, there are many reports of adverse reactions associated with the drug. In addition, it is known that not all pills sold as ecstasy actually contain methylenedioxymethamphetamine. Since there is no quality control for the pills' contents, users never know exactly what they are taking. Thus, although users may perceive the effects of the drug as mostly positive, ecstasy is potentially dangerous. Primary and secondary interventions are needed to prevent the use of ecstasy and the occurrence of adverse reactions. To be effective, these measures must take into consideration the characteristics of the user population and the usage patterns. It is also essential to prepare health professionals for emergency medical interventions in cases of intoxication and complications resulting from the use of ecstasy.

Brazil↗
PubMed2000

Pathological and nonpathological gamblers: a survey in gambling settings.

In this first study on gambling in Brazil, pathological and non-pathological gamblers were surveyed at three bingo clubs, one video poker club, and one horse-racing club in São Paulo. The South Oaks Gambling Screen and a questionnaire were administered to 171 subjects. When compared to nonpathological gamblers, a significantly higher proportion of pathological gamblers played cards, horse races, video poker, and dice in their lifetime. The two groups were similar with respect to socially acceptable games such as lotteries, bingo, sports, and the stock market. No significant differences were observed in drug consumption except for a higher lifetime consumption of tobacco among pathological gamblers. Only 4.9% of the gamblers sought help for gambling-related problems, suggesting that gambling is not generally perceived as a mental health problem by these subjects.

Adolescent↗
PubMed1999

Human erythrocytes are protected against chromate-induced peroxidation.

In previous studies performed in this laboratory it was realized that in a broad concentration range (0.5-8 mM) dichromate does not induced red blood cell (RBC) peroxidation. To investigate the reasons behind RBC protection against chromate-induced peroxidation, the effects of 8 mM dichromate on white ghost and RBC peroxidation, RBC antioxidant system and hemoglobin status, as well as RBC osmotic fragility and morphology, were studied in more detail. It was observed that the peroxidation level induced by dichromate on RBCs is practically negligible when compared with the peroxidation induced in white ghosts. Furthermore, the osmotic fragility of RBCs exposed to dichromate is not altered, but the cells undergo echinocytic transformation, probably due to chromate-induced structural RBC membrane modifications. The activities of catalase, gluthatione peroxidase, and superoxide dismutase of RBCs exposed to dichromate were similar to those observed in controls, but the gluthatione reductase and GSH levels were significantly reduced (P<0. 05). Concomitantly, GSSG and methemoglobin levels increased and NADH-methemoglobin reductase activity decreased. These results indicate that chromate does not induce RBC peroxidation, but does promote echinocytic shape transformation, oxidation of hemoglobin and GSH, and inhibition of gluthatione reductase and methemoglobin reductase. The enzymatic antioxidant defense system and hemoglobin oxidation are probably involved in the mechanism of RBC proctection against chromate-induced peroxidation, as is discussed.

Catalase↗
PubMed1999

Solitary fibrous tumor of the pleura: a cytogenetic study.

A solitary fibrous tumor of the pleura was studied. Its karyotype was 46,XY,t(6;17) (p11.2;q23),ins(9;12)(q22;q15q24.1),inv(16)(p13.1q24). The rearrangement of 12q13-15 was also described in a subset of hemangiopericytomas of soft tissue and meninges. Because both types of tumors are morphologically and immunophenotypically quite similar, and because some of them share rearrangement of 12q13-15, the possibility of their histogenetical relatedness should be considered.

Aged↗
PubMed1999

A frequency and content analysis of alcohol advertising on Brazilian television.

OBJECTIVE: Two studies were conducted with the objective of analyzing the frequency and content of alcoholic beverage advertising on Brazilian television. METHOD: Study 1 presents a frequency analysis based on 84 hours of TV monitoring in which 1,640 commercials and 243 vignettes were recorded between 8:00 PM and 11:00 PM on the two main stations. Study 2 presents a content analysis of 139 alcoholic and 51 nonalcoholic beverage commercials aired in 1992-93, as evaluated by three trained judges. RESULTS: Study 1 showed the relative frequency of alcoholic beverage commercials (4.6%) to be higher than the frequency of other products such as cigarettes, nonalcoholic beverages and medicines, and lower than that of foods and various other items. Frequency of alcoholic "vignettes" (26.6%) was higher than the frequency of all the other product categories. Frequency data were closely matched by marketing investment data for the period. In Study 2, the most frequent themes and appeals present in alcohol commercials were relaxation, national symbolism, conformity, camaraderie and humor. Human models were present in most ads. Product-related themes such as information, quality or tradition were virtually absent, as were messages to drink moderately. However, 7.2% of the alcohol commercials displayed appeals promoting abusive drinking. CONCLUSIONS: The results seem to reflect the minimal regulation of alcohol advertising in Brazil, and a joint effort by health planners, educators, legislators, alcohol industries and advertising agencies is recommended as a necessary step to reduce alcoholic beverage problems in Brazilian society.

Advertising↗
PubMed1999

Anxiogenic-like effect of acute and chronic fluoxetine on rats tested on the elevated plus-maze.

The selective serotonin reuptake inhibitor fluoxetine (FLX) is widely prescribed for depression and anxiety-related disorders. On the other hand, enhanced serotonergic transmission is known to be classically related to anxiety. In this study, the effects of acute (5.0 mg/kg) and chronic (5.0 mg/kg, 22 days) FLX were investigated in both food-deprived and non-deprived rats tested in the elevated plus-maze. Significant main effects of the three factors (drug, food condition and administration regimen) were observed, but no interaction between them. The administration of either acute or chronic FLX resulted in an anxiogenic effect, as detected by a significant reduction in the percentage of time spent in the open arms and in the percentage of open arm entries. Food deprivation yielded an anxiolytic-like profile, probably related to changes in locomotor activity. The administration regimen resulted in an anxiolytic profile in chronically treated rats, as would be expected after 22 days of regular handling. The anxiogenic action of acute FLX is consistent with both its neurochemical and clinical profile. The discrepancy between the anxiogenic profile of chronic FLX and its therapeutic uses is discussed in terms of possible differences between the type of anxiety that is measured in the plus-maze and the types of human anxiety that are alleviated by fluoxetine.

Analysis of Variance↗
PubMed1998

Neutrophil and macrophage responses to inflammation in the peritoneal cavity of rainbow trout Oncorhynchus mykiss. A light and electron microscopic cytochemical study.

The neutrophil and macrophage responses that accompany inflammation were studied in the peritoneal cavity of rainbow trout Oncorhynchus mykiss using light and electron microscopic cytochemistry. Neutrophils of inflammatory peritoneal exudates were alpha-naphthyl butyrate esterase-negative, peroxidase-positive and rich in cytoplasmic glycogen granules. Macrophages were poor in glycogen, esterase-positive and usually peroxidase-negative. Some peroxidase-positive macrophages were due to the transfer to macrophages of neutrophilic peroxidase. The ultrastructural double labelling for glycogen-peroxidase or esterase/peroxidase was most useful for precisely characterising neutrophils and macrophages in the inflamed peritoneal cavities and for correctly labelling peroxidase-positive macrophages. Intraperitoneal injection of casein, Incomplete Freund's Adjuvant (IFA) and live or formol-killed Yersinia ruckeri resulted in a rapid influx of neutrophils, peaking at 24 to 48 h post-injection and reaching values, in the case of live bacteria, 500 x those in the resting, unstimulated peritoneal cavity. Peritoneal macrophages also increased, but the response was slower (peak at 5 d) and with more modest increases in number (7.5 x). Neutrophil and mononuclear cells returned to normal values after 15 d in the case of casein and bacteria, but continued above base values 30 d after the injection of IFA. Conversely, after the injection of phosphate buffered saline, India ink or with sham-injections, very moderate neutrophil and and macrophage responses subsided in a few hours. Phagocytosis of bacteria was studied by light microscopy of preparations stained for peroxidase by a new method which allows for the simultaneous observation of intracellular bacteria and peroxidase staining. When Y. ruckeri was injected into resting peritoneal cavities, bacteria were ingested by the resident macrophages. When the bacteria were injected into cavities with high numbers of neutrophils (due to the previous injection of casein), more neutrophils than macrophages contained bacteria. Results show that the macrophages are the resident phagocytes of the peritoneal cavity of trout, while neutrophils are present in that body cavity in significant numbers only in situations of inflammation and only as long as the inflammation persists.

Animals↗