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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
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

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↗
PubMed1982

Effect of anthelmintic treatment on the milk yield of dairy cows in England, Scotland and Wales.

One hundred and twenty dairy herds collaborated in a trial to determine the effect on milk yield of anthelmintic treatment given at calving. Cows and heifers were divided into five groups. Three were each given a different anthelmintic: thiabendazole, fenbendazole or levamisole. One group was given a placebo and the fifth was untreated. Analysis of data from 9000 lactations showed a treatment effect just significant at the 5 per cent level, of 42 kg milk, 1.8 kg fat and 1.4 kg protein. There was no evidence that the three anthelmintics differed in their effect on yield. The effect of treatment was not greater in heifers than in cows, nor was there a difference between spring and autumn calvers. There was no indication that the effect of treatment was markedly greater in some herds than others and it was not related to periparturient faecal egg count.

Animals↗
PubMed1981

Worm burdens of dairy heifers in England and Wales.

The size and composition of abomasal worm burdens from 143 casualty and cull dairy heifers were estimated. Over 60 per cent had totals of less than 10,000, only four exceeded 100,000 and the overall mean was 16,285. Ostertagia ostertagi was almost always present and usually formed the major proportion of the total. Trichostrongylus axei was recorded in 83 heifers and was the most common species on 17 occasions. The numbers of arrested early fourth stage worms were highest in winter and declined rapidly during spring. O lyrata was only found when O ostertagi was present and always as a small percentage of the total. Similarly in the case of two of the minor species, Skrjabinagia kolchida (= Grosspiculagia podjapolskyi) was never found independently of O leptospicularis (= O crimensis). These relationships are regarded as suggestive of polymorphism.

Animals↗
PubMed1981

Further observations on the action of fenbendazole against inhibited fourth stage larvae of Ostertagia ostertagi.

Two further trials are reported on the effect of fenbendazole on inhibited Ostertagia ostertagi larvae. In the first trial fenbendazole successfully eliminated inhibited burdens of O ostertagi, while in the second trial the effect was variable. As a result of these trials and previous reports it is concluded that a single oral dose of fenbendazole cannot be relied upon to prevent winter (type 2) ostertagiasis.

Animals↗
PubMed1981

Use of anthelmintics for cattle in England and Wales during 1978.

A study of anthelmintic treatments received by 40,000 cattle during 1978 on a random sample of 240 farms in England and Wales showed that most were given against gastrointestinal nematodes for purposes of prophylaxis. Analysis of the data indicates that of an estimated pounds 15m spent on anthelmintics and their administration, most was far less effectively employed than it might have been. Errors of three kinds were common, some classes of cattle being dosed unnecessarily, animals being dosed at an unfavourable occasion or time of year, and anthelmintics being directed at parasites against which they had no action. Existing knowledge on the control of helminths is not effectively used; most dosing was done without advice from an identifiable source.

Animals↗