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Biomedical subjects

M Hebert

Publications and source records attributed to M Hebert.

At least 19 recordsLinked to original sources
PubMed1992

Outbreaks of summer rotavirus linked to laboratory practices. The National Rotavirus Surveillance System.

In temperate regions rotavirus diarrhea is a disease of the cooler months of the year, but little is known about its patterns in the summer. We report on the first year of national surveillance of rotavirus, during which we actively investigated patterns of summer activity. We obtained data on rotavirus testing from 85 laboratories in 48 states, conducted a survey of their testing practices and retested for confirmation positive specimens from laboratories reporting high rates of positivity during the summer. During 1989 participating laboratories reported 4011 specimens tested for rotavirus during July and August, of which 436 (11%) were said to be positive. Most laboratories reported low rates of positivity during these months (median percent positive, 3), but five had very high rates of summer positivity (> 30%). These five laboratories were geographically separated, and neighboring laboratories showed little rotavirus activity. Positive specimens submitted by four of these centers with high rates of summer rotavirus could not be confirmed. A survey of laboratory methods found one commercial assay (TestPack) and two laboratory practices (failure to use controls and involvement of more than six technicians in the testing process) to be associated with high rates of summer positivity. Moderate rates of positivity (11 to 30%) were fond frequently in the southwest during July and August; reference testing of specimens from these laboratories confirmed positivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical Laboratory Techniques↗
PubMed1989

Thrombin-treated endothelium primes neutrophil functions: inhibition by platelet-activating factor receptor antagonists.

We have shown previously that fluid phase platelet-activating factor (PAF) can enhance or "prime" polymorphonuclear (PMN) responses to subsequent stimulation with agonists such as formyl-methionine-leucine-phenylalanine (FMLP). Since thrombin induces PAF production in endothelial cells, we tested whether this thrombin-provoked endothelial PAF primes responses of marginated PMNs. Monolayers of human umbilical vein endothelial cells were exposed to either thrombin (0.5-5.0 units/ml) or buffer for up to 5 min and then PMNs were layered on top of the endothelial cells. After a further 5 min incubation, the PMNs were stimulated with a suboptimal concentration of FMLP (10(-7) M), and their superoxide production, elastase release, adhesion to endothelium, and capacity to cause endothelial cell lysis and detachment were assessed. Thrombin pretreatment significantly enhanced each of these FMLP-stimulated neutrophil responses. The extent of this enhancement correlated with both the dose and duration of thrombin treatment of endothelial cells and also the duration of PMN incubation with thrombin-exposed endothelium. Evidence that the augmentation was due to endothelial-derived PAF was obtained as follows: (1) thrombin induced [3H]acetate incorporation into endothelial PAF (assayed in lipid extracts); (2) antithrombin III conjointly inhibited this [3H]acetate uptake and prevented the priming effect of thrombin-treated endothelium on PMN responses; and (3) the PAF receptor antagonist BN52021, when preincubated with PMNs, also effectively blocked the enhancement of PMN responses. We conclude that thrombin stimulation of endothelial cells initiates a sequence of events culminating in the production of PAF--a membrane phospholipid capable of priming marginated PMNs. We suggest that this coagulation-fostered endothelial/PMN interaction may underlie a paracrine response that may potentiate PMN-mediated endothelial injury during sepsis and other thrombin-generating disorders.

Endothelium, Vascular↗
PubMed1979

Sampling gastro-enterologists' opinions--an OMGE study.

This study describes a pilot project to sample gastroenterologists' opinions on a variety of interesting and controversial topics. At the Madrid World Congress, a sample of delegates were asked to respond to a questionnaire distributed at the meeting itself. A total of 224, representative of those attending by discipline and by geographical area, did so. The results were analysed in two days and presented to the Congress within 72 hours. Amongst the findings were several of interest. Vagotomy is now the most common operation for (elective) duodenal ulcer surgery. Three-quarters of those responding prescribe high-fibre diet for chronic diverticular disease. Over 80% routinely prescribe sulphazalazine for patients with ulcerative colitis--even in remission. The most useful mode of detection of gastro-intestinal cancer is now felt to be endoscopy, even ahead of double contrast radiology. The results should be interpreted with caution, although the survey represents findings in over 200 hospitals. The principle of an on-the-spot rapid attitude survey has been established as feasible. It is proposed to repeat the exercise on a wider scale at the next World Congress in Stockholm in 1982.

Attitude of Health Personnel↗
PubMed1979

Comparison of serum theophylline concentrations measured by high pressure liquid chromatography and quantitative enzyme-multiplied immunoassay technique.

Safe, effective theophylline therapy depends on the rapid determination of serum theophylline concentrations. Two rapid methods that require less than 0.1 ml of serum are high pressure liquid chromatography (HPLC) and quantitative enzyme-multiplied immunoassay technique (EMIT). A comparison of these two methods was carried out using 117 serum samples routinely collected from asthmatic patients in Charity Hospital of Louisiana at New Orleans. After determination by the EMIT method, specimens were analyzed by HPLC in a different laboratory. Mean serum theophylline concentrations in 100 specimens containing more than trace concentrations were 14.5 mcg/ml by the EMIT method, compared with 12.1 mcg/ml by HPLC. The paired t test showed this to be a highly significant difference (p less than 0.0005). Whichever method of determination of theophylline concentration is used, frequent validation of results by comparison with those of other laboratories seems indicated.

Asthma↗
PubMed1978

Social grouping cannot account for cerebral effects of enriched environments.

Several experiments were conducted to test whether, as suggested by Welch et al. in this journal, mere group living (social stimulation) can account for the significant differences in measures of brain anatomy and brain chemistry that develop between rodents housed in groups in enriched environments and rodents housed singly in restricted environments; the alternative hypothesis was that features of the inanimate environment can significantly affect brain measures of animals living in a social group. Groups of 12 male rats were assigned for 30 days to several types of environment: (a) large cage without stimulus objects, (b) large cage containing varied stimulus objects, (c) large cage containing a maze whose pattern of barriers was changed daily, and (d) a seminatural outdoor environment; in each experiment, littermates of rats in the social conditions were housed in isolation in small colony cages. At the end of the 30-day period, measures were taken of weights of brain regions, RNA and DNA contents of regions of cerebral cortex, and acetylcholinesterase activities of brain regions. Although the number of rats housed together was constant for conditions a--d and cage size was constant for conditions a--c, the magnitudes of the cerebral measures varied significantly as a function of the inanimate stimulus conditions. The differences from isola;ion-housed littermates was greatest in condition d and smallest in condition a. Thus, social grouping alone is inadequate to explain the cerebral effects of enriched environments and the inanimate stimulus conditions must be taken into account.

Acetylcholinesterase↗
PubMed1977

Relatively brief environmental enrichment aids recovery of learning capacity and alters brain measures after postweaning brain lesions in rats.

Enriched postlesion experience aided in overcoming effects of simultaneous bilateral cerebral lesions made at 30 days of age in one experiment with inbred Fischer rats and in a second experiment with the Berkeley S1 strain. The lesions were directed to the occipital cortex, but in most cases there was also some impairment of the hippocampus. For 60 days after operations, half of the rats lived in small individual cages and half lived in groups in large enriched-environment cages. They were then pretrained and tested on the standard 12 Hebb-Williams problems. Daily injections of methamphetamine (vs. saline) during the period of differential experience in the first experiment produced no effect on the behavioral scores. The second experiment included groups that received only 2 hr/day of enriched experience, and they benefited as much as groups that remained in the enriched environment 24 hr/day. The results of both experiments demonstrated significant beneficial effects of environment when bilateral lesions were made at a later age and when the periods of enriched experience were shorter than had previously been tested. Two additional experiments revealed significant effects of both lesions and environment on weight and RNA/DNA of brain regions.

Age Factors↗