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Biomedical subjects

F Legros

Publications and source records attributed to F Legros.

At least 37 records · Page 2Linked to original sources
PubMed1994

[Anopheles of Senegal. An annotated and illustrated list].

Twenty species of Anopheles are presently known from Senegal. An. gambiae, An. arabiensis, An. pharoensis, An. rufipes and An. ziemanni have an extensive distribution. Probably because of climatic change, An. funestus is no more found in some areas and An. paludis tend to disappear. An. melas is located in coastal areas. The other species, namely An. coustani, An. brohieri, An. brunnipes, An. domicola, An. flavicosta, An. freetownensis, An. hancocki, An. maculipalpis, An. nili, An. pretoriensis, An. squamosus and An. wellcomei, are mainly found in southern Senegal. Only An. gambiae, An. arabiensis and An. funestus are of epidemiological significance as vectors of malaria and bancroftian filariasis. Twelve arboviruses have been isolated from eight Anopheles species. Each Anopheles species is illustrated and an identification key is given.

Animals↗
PubMed1993

Malaria morbidity among children exposed to low seasonal transmission in Dakar, Senegal and its implications for malaria control in tropical Africa.

To measure morbidity due to malaria and to study its relationship with transmission and parasitemia in children living in an area of low malaria endemicity, a cohort study of 343 schoolchildren was undertaken during a one-year period in Dakar, Senegal. From parallel investigations on transmission and the frequency of malaria as a cause for outpatient visits, three different seasons were chosen for close monitoring of different clinical parasitologic, and sero-immunologic parameters. The daily incidence rates of malaria parasitemia and primary attacks were at a maximum level during the high transmission season (0.00198 and 0.00185 new cases/person/day, respectively) and decreased considerably during the season of low transmission. For each given period, the values of these two rates were close to each other, suggesting that each new infection was followed by a clinical attack. During the period of maximum transmission, clinical malaria prevalence was 1.36% and malaria was responsible for 36% of school absences due to medical reasons. At the end of the period of minimum transmission, clinical malaria prevalence was 0.15% and malaria was responsible for 3% of school absences due to medical reasons. In contrast, parasite prevalence hardly varied with the season (minimum 3.6%, maximum 7.5%). In a one-year period, the total number of new malarial infections was estimated between 173 and 230. Because of the existence of a vector density gradient in the area concerned, the annual malaria incidence varied considerably according to the children's place of residence.(ABSTRACT TRUNCATED AT 250 WORDS)

Absenteeism↗
PubMed1992

Vector density gradients and the epidemiology of urban malaria in Dakar, Senegal.

The dispersion of anopheline mosquitoes from their breeding places and its impact on malaria epidemiology has been investigated in Dakar, Senegal, where malaria is hypoendemic and almost exclusively transmitted by Anopheles arabiensis. Pyrethrum spray collections were carried out along a 910-meter area starting from a district bordering on a permanent marsh and continuing into the center of the city. According to the distance from the marsh, vector density (the number of An. arabiensis per 100 rooms) at 0-160, 160-285, 285-410, 410-535, 535-660, 660-785, and 785-910 meters was 84, 40, 5, 2, 2, 0.4, and 0, respectively, during the dry season, and 414, 229, 110, 84, 99, 69, and 21, respectively, during the rainy season. The proportion of 8-11-year-old children with negative immunofluorescent antibody test results for Plasmodium falciparum was 17%, 28%, 44%, 54%, 50%, 63%, and 73%, respectively, in these different sections. Malaria prevalence in the community was maximum in the area bordering on the marsh where it ranged from 1% to 15% (average 6%) according to age and season of the year. These findings show the epidemiologic importance of vector density gradients in Dakar. The implications for malaria control in urban areas are discussed.

Adolescent↗
PubMed1992

Susceptibility of Plasmodium falciparum strains to mefloquine in an urban area in Senegal.

A total of 47 nonimmune febrile patients from Pikine, Senegal, with greater than 1,000 Plasmodium falciparum asexual forms per microliter whole blood were given 12.5 mg per kg body weight of mefloquine in a single oral dose and were followed up daily until day 7 and also on day 14 of the study. Seven of the patients who vomited, four who had 4-aminoquinolines in their blood, and five dropouts were excluded. Fever and parasitaemia were suppressed within four days until day fourteen in 29 of the 31 remaining patients, including 10 with P. falciparum strains that had a low sensitivity to mefloquine. Two failures were due to poor absorption of mefloquine. The presence of P. falciparum strains with low in vitro susceptibility to mefloquine did not affect, within 14 days, the clinical and parasitological efficacy of a single oral dose mefloquine regimen in patients who had received no previous antimalarial treatment and who did not have partial immune protection.

Adolescent↗
PubMed1991

Tick-borne borreliosis in west Africa.

Reported cases of tick-borne relapsing fever due to the spirochaete Borrelia crocidurae are rare in West Africa, and few epidemiological data are available. To see how common relapsing fever is in Senegal thick blood smears from cases of fever of unknown origin and from randomly selected clinic outpatients from a rural dispensary were examined for Borrelia. The prevalence of Borrelia infections in small mammals was also assessed. Borrelia was seen in smears of 12 (0.9%) of 1340 children. All children who tested positive had complained of acute fever. Prevalence was 0% (0/496), 0.5% (2/417), 1.6% (5/308), and 4.2% (5/119) at ages 0-1, 2-4, 5-9, and 10-14, respectively. 26 other instances of borreliosis were seen in patients from different regions of Senegal. Blood samples from 7 of these patients were inoculated intraperitoneally into white mice; serious infection developed in all mice. Borrelia was seen in thick smears from 65 of 461 wild rodents or insectivores. Six rodents species were infected. From a sample of 93 rodents, 33.3% were infected, as judged by intraperitoneal inoculation of white mice, compared with 14.1% by direct smear examination. The findings suggest that borreliosis has a wide distribution and a high incidence in Senegal. This disease may be a major cause of morbidity in rural areas throughout much of West Africa.

Acute Disease↗
PubMed1989

Local anti-P32 humoral response in tuberculous meningitis.

We report five cases of severe pulmonary tuberculosis admitted to hospital with a suspicion of meningeal involvement. The diagnosis of tuberculous meningitis was confirmed by standard bacteriological techniques in two of the five patients. Specific IgG class antibodies directed against the recently purified BCG antigen P32 were detected by a dot immunoblotting technique in the serum and in the cerebrospinal fluid of each patient; however, a higher anti-P32 immunoglobulins/total immunoglobulins ratio was observed in the cerebrospinal fluid of patients with tuberculous meningitis than in their serum while the reverse situation was observed in the other patients.

Adult↗
PubMed1989

An automated micromethod for detection of lytic antimycobacterial antibodies by immune lysis of liposomes sensitized to tuberculin.

Calcein was concentrated inside multilamellar liposomes (MLV) by encapsulation through an osmotic gradient in order to increase its quenching. Immune lysis of these MLV sensitized to PPD by direct encapsulation or by exposure to preformed vesicles was studied in the presence of rabbit anti-BCG serum and of a non-immune rabbit serum as a source of complement, successively added in the wells of a microplate to a final volume of 0.1 ml. A 40 to 50% release of encapsulated calcein was observed after 5 min using a Titertek Fluoroskan II. Preformed liposomes exposed to PPD were more sensitive to anti-BCG serum than liposomes formed in PPD. Trials with human sera revealed a significantly higher level of specific lytic immunoglobulins in tuberculous patients than in non-tuberculous subjects. Key words: Liposome immune lysis assay; lytic antimycobacterial antibodies; tuberculosis, human; test automation.

Antibodies, Bacterial↗
PubMed1989

[The effect of 2 chloroquine-based drug strategies (prevention and therapy of febrile cases] on malaria transmission].

A 3 years study was decided in 12 villages of the South-West Burkina Faso to compare the chemoprophylaxis and the chemotherapy of febrile cases as potential malaria control strategies. During the first year pretreatment data were collected. During the two following years a programme carried out (I) prophylaxis (10 mg chloroquine/kg body weight) was given weekly to all children under 14 years old in 5 villages, and (II) therapy (10 mg chloroquine/kg body weight) was given in a single dose to all febrile cases in 7 other villages. Chloroquine tablets were distributed by health workers belonging to the community. Both prophylaxis and therapy reduced the gametocyte rate in children (2-9 years) respectively of 63% and 45%. The analysis of the evolution after the first year of the sporozoite rate of anopheline was made difficult by concomitant natural variations of mosquitoes longevity and by mosquitoes displacements. Significant variations of sporozoite rate can be explained by natural variations of mosquitoes longevity. But data from the rice field villages support evidence that reduction of the pool of parasite infective for vectors induced the decrease of Anopheles gambiae s. l. sporozoite rate. Therefore our results reflect a trend more than a strict reduction of malaria transmission.

Adolescent↗
PubMed1988

A multidot immunobinding assay for the serodiagnosis of tuberculosis. Comparison with an enzyme-linked immunosorbent assay.

A simple dot immunobinding (dot blot) assay procedure has been developed for the detection of antibodies directed against a soluble mycobacterial antigen preparation. This technique was compared with the widely used ELISA, in a study of samples from tuberculous patients. Dot blots were read on a densitometer. The correlation between both assays was excellent (r = 0.91; P less than 0.001); 90% of sera from tuberculous patients were detected using both techniques and a serial two-fold dilution method. Assessments of the end-points of titration curves by reflectometry and simple visual interpretation gave similar results. The dot blot assay is easier to perform and appears to be a practical alternative to ELISA for the detection of anti-mycobacterial antibodies in tuberculous patients.

Adult↗
PubMed1988

Detection of lytic antimycobacterial antibodies by immune lysis of liposomes sensitized to tuberculin.

Two procedures were used in order to incorporate purified protein derivative tuberculin (PPD) from M. tuberculosis, strain H37Rv, into calcein-containing liposomes: formation of multilamellar vesicles (MLV) in a PPD solution or exposure of preformed MLV to this solution. Immune lysis of these PPD-sensitized MLV was studied in the presence of a hyperimmune anti-M. tuberculosis sheep serum using a specific pathogen-free rabbit serum as a source of complement. A 50% release of encapsulated calcein was observed spectrofluorometrically after 30 min and remained unchanged up to 2 h. The release of calcein in the absence of complement or of anti-H37Rv serum or by liposomes which did not contain PPD never exceeded 1-2%. Liposomes formed in PPD solution were more sensitive to anti-H37Rv serum than preformed liposomes exposed to PPD. Trials with human sera from ten tuberculous patients revealed the presence of specific lytic immunoglobulins. In the presence of sera from skin test negative, non-tuberculous subjects, calcein release was significantly lower. This opens the way to a new method for the study of the humoral immunity in tuberculosis.

Animals↗
PubMed1988

The humoral immune response after BCG vaccination in humans: consequences for the serodiagnosis of tuberculosis.

The IgM and IgG response to BCG vaccination was investigated in 75 adults, tuberculin negative before vaccination, using an enzyme-linked immunosorbent assay with purified protein derivative (PPD) as antigen. The mean optical density (OD) increased significantly (p less than 0.001) in both immunoglobulin classes. Increase in at least one class was significant in 89% of the subjects. The observed increase in anti-PPD IgG was rather small but comparable to that seen in 17 newly diagnosed tuberculosis patients with negative direct smear [mean OD (SD): 0.59 (0.38) in vaccinated and 0.70 (0.48) in patients] but significantly lower (p less than 0.001) than that seen in 31 newly diagnosed patients with positive direct smear [mean OD (SD): 1.07 (0.67)]. With 55% of sera above the upper normal limit, smear positive patients differentiated (p less than 0.001) from vaccinated subjects (20% of positive sera) whilst smear negative patients (29% of positive sera) did not. We conclude that BCG vaccination induces a definite but small increase in anti-PPD serum IgM and IgG, which is likely to interfere when interpreting serological tests for the diagnosis of tuberculosis, especially in those patients who would most benefit from an early and fast diagnosis.

Adult↗
PubMed1983

Changes in characteristics of rat adrenal glomerulosa cells under acute and chronic treatment with ACTH.

Groups of Long Evans rats were treated with 15 IU ACTH/day for 1-9 days and sacrificed at different intervals during and after treatment. Aldosterone and corticosterone plasma levels were increased above control values for the entire duration of treatment and were decreased to control values as early as 3 days posttreatment. The uptake of [125I]angiotensin II [( 125I]AII) by adrenocortical glomerulosa cell suspensions was diminished by 71% at day 9 of treatment and this [125I]AII-uptake capacity slowly returned to control values after cessation of treatment (66.0% of control at day +19). The association constants at equilibrium (Ka) for AII receptors were similar in both treated (0.19 X 10(9) M -1 at day 9) and control (0.12 X 10(9) M -1) rats, whereas the number of AII-binding sites was lowered in the glomerulosa cells of treated (Nmax = 6 fmol/50 000 cells) compared with control (29 fmol) animals. In vitro cell suspensions from treated rats had, compared with controls, a lowered basal aldosterone and an increased corticosterone output. Addition of ACTH (10(-8) M) to these cell suspensions showed no effect on the aldosterone or corticosterone output, whereas a significant stimulation was observed for cells obtained from control animals. Studies on rats treated 9 days and sacrificed 19 days after cessation of treatment demonstrated that the basal aldosterone and coriticosterone output from zona glomerulosa cells suspensions was comparable with that of control rats; the steroid output of these cells could be further stimulated in vitro by addition of ACTH.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex↗
PubMed1983

Dynamic 131I-labelled insulin distribution in rabbits as seen by in-vivo scintigraphic studies.

The kinetics of 131I-labelled insulin distribution in heart, liver, kidneys and urinary bladder of rabbits were studied in vivo by gamma-camera techniques combined with plasma measurements (glucose concentrations and chromatographic separation of insulin and its degradation products). The distribution space of radioiodinated insulin differed from the vascular bed delineated by radioiodinated serum albumin. During a 20-min gamma-camera recording, radioactive degradation products only appeared in the plasma after 10-12 min. Previous administration of a 10 000-fold excess of unlabelled insulin and 5 ml glucose (20%) did not modify the evolution of 131I-labelled insulin cardiac invasion and the subsequent linear decrease of radioactivity. Conversely, wash-out of radioactivity from the liver and kidney was accelerated after preadministration of this excess of unlabelled hormone, binding in these organs accounting for this acceleration. Urinary bladder filling was imaged later than cardiac, hepatic or renal labelling and was only accelerated by polyuria induced by glucose injection, independent of preadministration of unlabelled hormone.

Animals↗
PubMed1982

Comparison and evaluation of different methods for alpha-MSH labelling.

We have studied the behaviour of 125I-labelled alpha-MSH under different experimental conditions. Until now, the chloramine T method had been used by most investigators with variable results. We have tested three other labelling techniques based on 125I mild oxidation: (1) an enzymatic method with lactoperoxidase, (2) a sparingly soluble chloramine method (T.D.G.U.) and (3) modified chloramine T procedure, 'the iodine volatilization method'. Labelled hormone obtained after each kind of iodination was assayed for immunoreactivity. In addition, time course degradation was measured by classical RIA incubation procedures. Charcoal-dextran was used to separate bound and free antigen. We have found chloramine T-iodinated alpha-MSH to be significantly more damaged than preparations obtained by other methods and to be less stable when stored at -18 degrees C. No differences were found between the differently labelled 125I-labelled alpha-MSH fresh preparations in binding to surface receptors of human melanoma cell lines in culture.

Animals↗