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Biomedical subjects

A Richard

Publications and source records attributed to A Richard.

At least 91 records · Page 5Linked to original sources
PubMed1990

Ultrastructural and biochemical findings in brain cell cultures infected with canine distemper virus.

To study the pathomechanism of demyelination in canine distemper (CD), dog brain cell cultures were infected with virulent A75/17-CD virus (CDV) and examined ultrastructurally. Special attention was paid to the oligodendrocytes, which were specifically immunolabelled. In addition, cerebroside sulfotransferase (CST), an enzyme specific for oligodendrocyte activity was assayed during the course of the infection. Infection and maturation as well as CDV-induced changes were found in astrocytes and brain macrophages. Infection of oligodendrocytes was rarely seen, although CST activity of the culture markedly decreased and vacuolar degeneration of these cells occurred, resulting in their complete disappearance. We concluded that the degeneration of oligodendrocytes and demyelination is not due to direct virus-oligodendrocyte interaction, but due to CDV-induced events in other glial cells.

Animals↗
PubMed1990

Selective degeneration of oligodendrocytes mediated by reactive oxygen species.

The mechanism underlying demyelination in inflammatory canine distemper encephalitis is uncertain. Macrophages and their secretory products are thought to play an important effector role in this lesion. Recently, we have shown that anti-canine distemper virus antibodies, known to occur in chronic inflammatory lesions, stimulate macrophages leading to the secretion of reactive oxygen species (ROS). To investigate whether ROS could be involved in demyelination, dog glial cell cultures were exposed to xanthine/xanthine oxidase (X/XO), a system capable of generating O2-. This treatment resulted in a specific time-dependent degeneration and loss of oligodendrocytes, the myelin producing cells of the central nervous system. Initial degeneration was not associated with a decrease in viability of oligodendrocytes as judged by trypan blue and propidium iodide exclusion. Astrocytes and brain macrophages were not affected morphologically by this treatment. Further, an evaluation of the effect of several ROS scavengers, transition metal chelators and inhibitors of poly (ADP-ribose) polymerase suggests that a metal dependent formation of .OH or a similar highly oxidizing species could be responsible for the observed selective damage to oligodendrocytes.

Animals↗
PubMed1990

[Carotid sinus hypersensitivity. Medium and long-term development in patients treated by ventricular pacing].

The problem of pacing patients with carotid sinus hypersensitivity (CSH) is the choice and criteria of selection of the pacing mode. The authors studied 29 patients with CSH treated by VVI pacing over a period of 10 years. The average follow-up was 34 months (range 6 to 96 months). Three of the 27 patients (11%) who were asymptomatic at the outset continued to have symptoms. The nature of the CSH was well-defined in 25 patients; 19 of the 20 cases of cardio-inhibitory CSH and 4 of the 5 cases of mixed CSH were asymptomatic. These two poor clinical results were analysed: the patient with the cardio-inhibitory CSH (one recurrence in 84 months) had a drop of 40 mmHg in systolic blood pressure which fulfilled criteria of the cardio-inhibitory form of CSH (a drop of 30 to 50 mmHg). The second case was a complete therapeutic failure with 3 recurrent syncopal episodes. The patient had a mixed form of CSH (B.P. drop of 65 mmHg) associated with a "pace maker syndrome" (drop of 50 mmHg in systolic blood pressure at the onset of VVI pacing without any sino carotid massage). The authors conclude that the cases of CSH which, during their investigation, are best corrected by dual-chamber pacing or which are associated with a significant pacemaker effect or present retrograde ventriculo-atrial conduction, should receive dual-chamber pacemakers.

Aged↗
PubMed1989

Astrocytic infection in canine distemper virus-induced demyelination.

Acute canine distemper virus (CDV)-induced demyelinating lesions were examined with double-labelling immunocytochemistry simultaneously demonstrating CDV antigen and glial fibrillary acidid protein (GFAP) as marker for astrocytes. It was shown that 64% of all astrocytes within the demyelinating lesions were infected and that 95% of all infected cells counted in the lesions were astrocytes. These results suggest that the astrocyte is the main target for CDV and that astroglial infection may play an important role in the mechanism of demyelination.

Animals↗
PubMed1989

Evaluation of the benefit of setting up a decentralised obstetric-surgical structure in order to reduce maternal mortality and transfers in the Ivory Coast.

Our purpose is to study the way to reduce maternal mortality when introducing a structured obstetric and surgical center to a community previously without such a center. The study was done in Ivory Coast, where such a structure was set up in 1982 in a rural hospital at Divo. It has been observed that with such a structure there are no more transfers of women from Divo to the teaching hospital at Cocody, and a reduction in maternal mortality at Divo. This observation regarding the value of bringing obstetric services to communities currently without them could be a way among those available to reduce maternal mortality in a developing country such as the Ivory Coast.

Cote d'Ivoire↗
PubMed1989

[Detection of coronary restenosis using myocardial tomoscintigraphy with thallium 201. A series of 85 cases].

UNLABELLED: After a successful coronary angioplasty (less than 50 p. 100 residual stenosis and no complication), can restenosis be detected by a non-invasive method? We tested the value of stress thallium 201 myocardial scintigraphy by comparing this method with clinical angina and the conventional exercise-induced angina test. The study was prospective and involved 85 patients (74 men, 11 women; mean age 54.7 years, range 33-78 years). Sixty patients were suffering from angina, 13 had post-infarction angina and 12 had mild necrosis. Angioplasty had been performed on a single vessel (LAD in 57 cases, right in 18 cases and CX in 10 cases). After 6.4 +/- 1.8 months, all patients were re-evaluated under treatment, undergoing successively an exercise test, a stress and recovery myocardial scintigraphy and a coronary angiography. Restenosis was defined as a more than 50 p. 100 reduction of diameter on two orthogonal planes and was observed in 22 cases (26 p. 100). 19 patients were suffering from angina, 12 had restenosis, 10 were asymptomatic but had restenosis. Eighteen exercise tests were pathological; 10 corresponded to restenosis and 12 were normal in spite of restenosis. Myocardial scintigraphy was regarded as positive when, outside a necrotic territory, a lack of uptake at stress was reversible or became worse at redistribution. 27 tests were positive, 18 corresponded to restenosis, 4 were normal in spite of restenosis. The diagnostic values of the three methods were compared: (Table: see text). CONCLUSIONS: (1) stress myocardial scintigraphy has the best sensitivity and specificity; (2) if it is negative, restenosis is very unlikely; (3) coronary angiography may be performed only in case of symptoms and/or of positive stress scintigraphy.

Adult↗
PubMed1989

Decentralization of maternity care.

One of the main reasons for the high maternal mortality rates in developing countries is the need to transfer patients long distances to city hospitals when they develop complications. Local obstetric facilities would relieve this situation.

Cote d'Ivoire↗
PubMed1989

[Impact of the spraying of deltamethrin in a focus of leishmaniasis in Bolivia].

After one month of entomological observations to record pretreatment data, a sub Andean village of Yungas, Bolivia (alt. 1500 m) was sprayed at the beginning of the rainy season (January 1987). Houses were treated inside and outside with deltamethrin at 0.025 g/sq.m.; kennels, hen-houses and stacks of adobe were also sprayed in the same way. As a result of the treatment, Lutzomyia longipalpis, the local vector of visceral leishmaniasis, disappeared from houses and animal shelters for 9 and 10 months respectively. The impact of the treatment on the populations of Lu. nuneztovari and anglesi, the presumed vector of tegumentary leishmaniasis, was not obvious. As compared with pretreatment data, the rate of engorged females in houses decreased by two, and their density was also reduced. But these data are difficult to interpret due to the natural seasonal variation in density in this species. Moreover, the information from the control village did not correspond as expected. Lu. n. anglesi is a highly exophilic species in this area, a behaviour which could explain the limited impact of the treatment on this sandfly.

Aerosols↗
PubMed1989

[Epidemiology of cutaneous leishmaniasis in Bolivia. 1. Description of study zone and prevalence of the disease].

An epidemiological survey of tegumentary leishmaniasis (Leishmania (Viannia) braziliensis) was carried out in three regions of Bolivia in the Andean foothill and Amazonian forest. It was based on the record of lesions and scars on all the inhabitants of selected representative villages. In the Yungas, an area cultivated from the XVIIth century, males and females are equally infested, mostly before they were 10 years old (65%); 48% of scars were on the head. In Alto Beni and Pando, areas covered with primary rain forest, males are significantly more affected than females. The majority of scars were on the legs. The males of the three areas were equally affected. These results suggest that: --in the Yungas, contamination takes place among children in villages during the night; --in the Alto Beni and in the Pando, the infection rate is linked to the professional activities of adults, and men are more at risk than women. Only 7% of the lesions are evolving in grave forms of mucocutaneous ulcers. These forms represent the main load of the disease from the public health point of view. It has been found heavier in the Yungas (1.32%) and in the Alto Beni (1.14%) than in the Pando (0.21%). It should be noted that the first infection can give raise to several lesions. But reinfections are rare, which supports the view that the first infection is protective against the following ones.

Adolescent↗
PubMed1989

[Epidemiology of cutaneous leishmaniasis in Bolivia. 2. Transmission patterns].

In Bolivia the transmission of tegumentary leishmaniasis due to Leishmania (V.) braziliensis depends both on environmental factors and human activities. In the Yungas, transmission takes place in the houses during the night. The vector is Lutzomyia nuneztovari anglesi Le Pont & Desjeux, which enters the houses after 10 p.m. and leaves them before 6 a.m. This transmission pattern explains why men and women are equally infected, generally before 10 years old. Some more adults are infected very likely in coffee plantations or in the relict forest where the same vector species abounds and bites in daytime. In the Alto Beni, pioneers, mainly males, are infected when clearing the forest. Three Psychodopygus species have been shown to be the vectors. The risk is drastically decreasing when people establish in plantations or nearby villages because sandfly vectors do not get easily out of the forest cover. In the Pando, forest people are infected when harvesting Brazil-nuts or bleeding the rubber-trees, the two main activities in the area. It is very likely that Ps. c. carrerai is one of the vectors. Pando and Alto Beni primary rain-forests are natural primary foci of Le. braziliensis. So far the mammalian reservoirs are unknown but the circulation of the parasite has been proven by the fast contamination of receptive people entering the forest. The Yungas primary forest may be also considered as a relict focus. The cultivated area of the Yungas is an anthropic secondary focus. The vector Lu. n. anglesi became adapted to coffee plantations from which it enters the houses and transmits the parasite to man.

Adolescent↗
PubMed1989

[Macrophages in central nervous canine distemper: friends or foes?].

Brain macrophages play an important role in the CNS. We review some biological aspects of brain macrophages in vivo and in vitro. The criteria and methods used for the identification of these cells are considered. They include some morphological features such as the use of histochemical and immunocytochemical techniques for internal and surface components. In the second part of this review, we describe the role of brain macrophages in canine distemper encephalitis as proposed earlier by us. Studies in cultured dog glial cells infected with canine distemper virus (CDV) have shown that brain macrophages stimulated by anti-CDV antibodies will release reactive oxygen species as measured by chemiluminescence. This response depends on the presence of viral antigens on the surfaces of infected cells and is mediated by the interaction of antigen-bound antibodies with Fc receptors on brain macrophages. These observations support the hypotheses that brain macrophages may contribute to the damage of the white matter observed in canine distemper encephalitis.

Animals↗
PubMed1988

A CASE-SAR study of mammalian hepatic azoreduction.

A group of 36 aryl azo dyes were examined for their ability to be reduced by rat liver microsomal azoreductase. This group of azo dyes featured a variety of substituents, including sulfonic acid, phenol, nitro, amide, and methyl functionalities on phenyl, alpha-naphthyl, and beta-naphthyl rings. Reduction rates for each dye were obtained using a spectrophotometric method and anaerobic incubation conditions. These rates ranged from 0 to 7.35 nmol dye reduced/min.mg protein. The reduction rates and dye structures provided the data for a CASE-SAR (computer automated structure evaluation-structure-activity relationship) fragment analysis, and three major structure fragments associated with the ability of this group of azo dyes to be reduced were identified. The three CASE fragments correctly label 92% of the azo dye structures as active or inactive and may be useful in future predictions of the ability of azo dyes to undergo reduction by rat liver azoreductase.

Animals↗
PubMed1988

[Electrophysiological study of pro-arrhythmogenic effects of erythromycin].

Three cases of torsades de pointe induced by erythromycin have recently been reported. After observing a new case, the authors tried to demonstrate the possible mechanism of the arrhythmogenic action of this molecule. Twenty-two patients undergoing electrophysiological studies in the catheter laboratory to determine the cause of syncope were given an intravenous injection of 10 mg/Kg of erythromycin lactobionate. The drug was injected in 1 minute (bolus) in 11 patients (Group A). The other 11 patients (Group B) received the drug by slow intravenous infusion (20 minutes). Electrophysiological parameters were measured before and after erythromycin. A significant prolongation of the atrial refractory periods (+39 ms), ventricular refractory periods (+20 ms), QT (+20 ms) and QTC intervals (+42 ms) was observed in Group A. These electrophysiological effects could explain an arrhythmogenic action similar to that of antiarrhythmic drugs in Group I of Vaughan-Williams' classification. The slow intravenous infusion of erythromycin in Group B considerably reduced these undesirable secondary effects. This difference was directly related to serum concentrations of the molecule.

Adult↗