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Biomedical subjects

J F Michel

Publications and source records attributed to J F Michel.

At least 19 recordsLinked to original sources
PubMed2003

[Role of patient travel in transmission of human African trypanosomiasis in a highly endemic area of the Ivory Coast].

Human African trypanosomosis (HAT) remains a major public health problem in Subsaharan Africa. The region around the town of Bonon in middle western Côte d'Ivoire is a highly endemic HAT zone. The purpose of this study was to assess the role of travelling of infected patients in transmission of HAT. The study population included a total of 96 patients in whom HAT had been diagnosed actively or passively between 1999 and 2000. Information on each patient's residence and workplaces, i.e. water site, and farm field, was used to calculate the mean distance traveled and mean number of places visited daily by each patient. Findings indicated that both parameters, i.e., distance traveled and number of places visited, were significantly higher for patients living in Bonon than those living in hamlets or homesteads. Based on analysis of patient movements the endemic zone could be divided into three subdivisions with different modes of disease transmission. This study was performed as a preliminary step for a larger investigation designed to allow specific targeting of HAT hot spots based mainly on a geographic information system.

Cote d'Ivoire↗
PubMed2002

[Tsetse fly wings, an identity card of the insect?].

The size of tsetse flies is often associated with population dynamics and vectorial capacity parameters. Adult fly size is generally estimated from measurements of wing segments. To take measure of the wing, a semi-automatic software was developed by CIRAD-EMVT and IRD. It was used in wild populations of Glossina tachinoides Westwood and G. palpalis gambiensis Vanderplank (Diptera: Glossinidae) trapped near Bobo-Dioulasso, Burkina Faso. From an numeric picture of the wing, the software calculates the length of vein segments, the ratios between these lengths, the surface of the tsetse characteristic "hatchet cell", and the greyness on the wings. The data were interesting at the level of taxonomy. In addition, they help specify physiological characteristics of the studied populations.

Algorithms↗
PubMed2001

[New tools for the study of animal trypanosomiasis in the Sudan: model-building of dangerous epidemiological passage by remote sensing geographic information systems].

Recent studies in a rangeland area of Burkina Faso showed that riparian tsetse flies (Glossina tachinoides and G. palpalis gambiensis) were found along the main rivers, but depending on their location, they had different hosts and were not infected by the same trypanosomoses. There were different epidemiological situations within a distance of a few kilometres, and local assessment of the trypanosome risk thus called for a global approach taking account of the environmental and human factors involved in the interfaces between hosts and vectors. Various types of information concerning entomology, parasitology, ecology, land occupation and animal production systems were fed into a Geographical Information System. High spatial resolution remote sensing tools and original modelling methods were used to detect the valley landscapes most favourable to tsetse flies, and describe land use by herds. The impact of trypanosomes appeared to depend largely on animal movements, watering practices and the degree of contact with riparian tsetse flies. Linking these types of information revealed the most dangerous sites in epidemiological terms, which in this case represented some 18% of the network initially surveyed.

Animals↗
PubMed2001

[Different potentials of a geographic information system for studies in epidemiology: example of animal trypanosomiasis in the Sudan region].

The epidemiology of vector-borne diseases is complex due to variability in the ecology of the different actors involved, i.e., hosts, parasites and vectors. Transmission of animal trypanosomiasis in the West African savannah region is an excellent example of this complexity. Because of the importance of place and time in determining the interface between host and vector, a broad view of the overall environment is necessary to understand the variety of situations that can be encountered in an epidemiological system. Spatial distribution is a key factor for risk evaluation. State-of-the-art geographic information systems (GIS) have provided new insight into this complex epidemiology. GIS is a powerful technology that has been used mainly in map-making. An enormous amount of knowledge can be gained simply by geographical data projection. However GIS also allows juxtaposition of different types of information, creation of new variables, testing of theories and correlations, and generation of predictive models. The purpose of this article is to exemplify the potential applications of GIS using a recent study carried out on animal trypanosomiasis in a cattle-raising area of Burkina Faso.

Animals↗
PubMed1999

Polymerase chain reaction as a diagnosis tool for detecting trypanosomes in naturally infected cattle in Burkina Faso.

African animal trypanosomoses constitute the most important vector-borne cattle diseases in sub-Saharan Africa. Generally it is considered that there is a great lack of accurate tools for the diagnosis of the disease. During a trypanosomosis survey in the agro-pastoral zone of Sideradougou, Burkina Faso, 1036 cattle were examined for trypanosomes using microscopy. The PCR was applied on a subset of 260 buffy-coat samples using primers specific for Trypanosoma congolense savannah and riverine-forest groups, T. vivax, and T. brucei. Parasitological examination and the molecular technique were compared, showing a better efficiency of the latter. In the near future, the PCR is likely to become an efficient tool to estimate the prevalence of African trypanosomoses in affected areas.

Animals↗
PubMed1995

Ex vivo studies of polymorphonuclear neutrophils from patients with early-onset periodontitis (III). CR3 and LFA-1 expression by peripheral blood and gingival crevicular polymorphonuclear neutrophils.

In this study, we assessed the LFA-1 (CD18/CD11a) and CR3 (CD18/CD11b) expression on peripheral polymorphonuclear leukocytes (PB-PMN) and crevicular fluid polymorphonuclear leukocytes (CF-PMN), by subjects with a healthy periodontium (n = 7), gingivitis (n = 8), early-onset periodontitis (n = 17) and adult periodontitis (n = 8). Using flow cytometry analysis, the %s of CD18, CD11a and CD11b positive cells and the absolute numbers of fluorescent molecules were determined. No significant difference could be found among the 4 groups, for these 2 kinds of parameters, in PB-PMN or CF-PMN. However, a great difference could be noted between the results obtained from PB-PMN and those obtained from CF-PMN. The %s of positive CF-PMN were significantly lower than those of PB-PMN for the 3 sub-units (p < 0.001). The levels of CD18 and CD11b expressed by CF-PMN were higher than those expressed by PB-PMN and the difference was significant for CD11b (p < 0.001). On the contrary, the level of CD11a expressed on CF-PMN was significantly lower than that expressed by PB-PMN (p < 0.001). Hence, our current results show that early-onset periodontitis PMN can be quite normal and this fact is not surprising insofar as, in our study, these cells were perfectly functional and all the subjects were in good health. We concluded that the analysis of the leukocyte adhesion receptors expression on PB-PMN does not appear useful for helping to establish a differential diagnosis between the different forms of periodontitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Expression of the alpha-subunit of CR4 (CD11c) by peripheral blood and crevicular fluid neutrophils.

This work determined the levels of expression of CD11c by neutrophils (PMNs) collected from subjects with various periodontal conditions. The percentages of CD11c-positive crevicular fluid PMNs were significantly lower than those of peripheral blood PMNs, but the levels of CD11c expression were similar in PB-PMNs and CF-PMNs (P<0.001). On the other hand, no significant difference could be found between the groups, either for the percentages of CD11c-positive cells or for the CD11c expression levels.

Adult↗
PubMed1995

Dental injuries among schoolchildren aged from 6 to 15, in Rennes (France).

A representative sample of 2020 schoolchildren, aged 6 to 15 years, was randomly selected from 85 state and private schools in Rennes and distributed in 10 groups, according to their age. Type and prevalence of dental injuries were determined in each group, using Ellis & Davey's classification, giving rise to a subset of 345 subjects. Simple enamel fracture was the predominant injury (59.4%), occurring most often on maxillary central incisors. Most time (77.1%), the trauma affected only one tooth. Mean prevalence of dental injuries was 13.6% from 2020 subjects. Boys showed a higher prevalence than girls (respectively 17% and 10.2%), but this difference was only significant for age-groups 12 and 13 (p < 0.001) and for the whole group of 6-15 (p < 0.001).

Adolescent↗
PubMed1994

Ex vivo studies of polymorphonuclear neutrophils from patients with early-onset forms of periodontitis. (I). Chemotactic assessment using the under agarose method.

The polymorphonuclear neutrophil (PMN) appears to be an important cell in the protection of the host from pathogenic periodontal microorganisms and, despite some reports to the contrary, it is generally assumed that early-onset forms of periodontal disease (including both juvenile and rapidly progressing periodontitis) are associated with a defect in PMN chemotactic behaviour. The purpose of the present study was to examine the peripheral PMN chemotactic behaviour, using the under agarose method, in 4 groups, namely healthy periodontium group (n = 7), gingivitis group (n = 8), early-onset periodontitis group (n = 17) and adult periodontitis group (n = 8). PMN from early-onset periodontitis patients showed normal random and chemotactic locomotory behaviour when compared with those of PMN from subjects of the other groups. No statistically significant difference could be found among the 4 studied groups, with regard to spontaneous and oriented migration.

Adult↗
PubMed1994

Ex vivo studies of polymorphonuclear neutrophils from patients with early-onset-periodontitis (II). Chemiluminescence response analysis.

Previous studies have indicated that oxygen-free radicals may cause damage to the periodontal tissues. This study compared the luminol-dependent chemiluminescence response (after stimulation with either opsonized zymosan or phorbol myristate acetate (PMA) of peripheral blood polymorphonuclear leukocytes (PMN) isolated from human subjects with a healthy periodontium (n = 7), gingivitis (n = 8), adult periodontitis (n = 8), or early-onset periodontitis (n = 17). These results were also compared with those obtained in a larger reference group which consists of 50 subjects without infection or inflammation, selected on the basis of laboratory investigations. An enhanced response was defined as being 2 standard deviations above the reference group mean; a reduced response was defined as being 2 standard deviations below this mean. Although PMN from patients with either gingivitis or periodontitis were often functionally activated (when compared to the PMN from the reference group), no significant differences could be found between the 4 groups, with regard to the chemiluminescence response means obtained in a basal state or after stimulation.

Adult↗
PubMed1990

["T" lymphocytes. Their role in periodontal disease].

The immune response is now proved to be of great importance in the control of periodontal diseases. The predominant role of T lymphocytes in the mechanisms of specific immunity is admitted and is related to the functions of effectors T cells and T-helper cells, controlling the response of macrophages and the antibody production. The relations between the evolution of the disease and the tissular T/B and T4/T8 ratio and the lymphocyte function tests are discussed.

CD4-Positive T-Lymphocytes↗
PubMed1989

Development of protection and of self-cure in lambs infected daily with Ostertagia circumcincta.

Lambs were infected daily with 1000 Ostertagia circumcincta larvae. At intervals of 4 weeks groups of lambs were each challenged with a dose of 28,000 larvae, and their worm burdens compared with those of unchallenged controls. The measure of their ability to resist a challenge infection, which would have determined their degree of "protection", was obscured by the separate phenomenon of self-cure. Evidence suggested that the different manifestations of self-cure were determined by the state of resistance of the host and followed a set chronological sequence.

Animals↗
PubMed1988

[Evaluation of the activity of leukocytes during experimental periodontitis in the monkey].

Polymorphonuclear leucocytes play an important role in the defense mechanisms and destruction of periodontal tissues. The leucocytes number and activity were compared during an induced periodontitis in 3 Cercopithecus cephus. On day 0, the 3 animals presented a localized marginal gingivitis. On 2 animals a severe marginal periodontitis was induced unilaterally: 42 days later leucocytes were sampled in the peripheral blood, in the gingival blood and in the gingival sulcus on the experimental and control sites as well as on the 2 hemijaws of the control animal. For each sample, a leucocyte count and a chemiluminescence test were done. Different results related to the disease severity were obtained with these tests for gingival blood and sulcular fluid.

Animals↗
PubMed1987

[Chemiluminescence of phagocytic cells in chronic gingivitis and adult periodontitis].

Measurement of chemiluminescence (CL) produced by phagocytic cells spontaneously or upon stimulation by phorbol myristate acetate (PMA) was performed in patients with gingivitis and adult periodontitis, and in control healthy subjects. The study was performed simultaneously on phagocytic cells obtained from peripheral blood and from gingival blood, and on crevicular leukocytes. An elevated CL production was obtained in quiescent and PMA-stimulated phagocytic cells from peripheral blood in patients with gingivitis or periodontitis compared to non-diseased controls. Chemiluminescence produced by unstimulated crevicular phagocytes was similar to that of peripheral blood phagocytes in normal subjects, but it was decreased in periodontitis. Upon PMA stimulation, the CL response of crevicular phagocytes remained low in the three groups of subjects.

Adult↗