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J Cohen

Publications and source records attributed to J Cohen.

At least 595 records · Page 33Linked to original sources
PubMed1995

Pattern of ecological shifts in the diversification of Hawaiian Drosophila inferred from a molecular phylogeny.

BACKGROUND: The endemic Hawaiian drosophilids, a unique group that are remarkable for their diversity and rapid proliferation, provide a model for analysis of the process of insular speciation. Founder events and accompanying random drift, together with shifts in sexual selection, appear to explain the dramatic divergence in male morphology and mating behaviour among these flies, but these forces do not account for their spectacular ecological diversification into a wide array of breeding niches. Although recognized as contributing to the success of this group, the precise role of adaptive shifts has not been well defined. RESULTS: To delineate the pattern of ecological diversification in the evolution of Hawaiian Drosophila, we generated a molecular phylogeny, using nucleotide sequences from the yolk protein gene Yp1, of 42 endemic Hawaiian and 5 continental species. By mapping ecological characters onto this phylogeny, we demonstrate that monophagy is the primitive condition, and that decaying leaves were the initial substrate for oviposition and larval development. Shifts to decaying stems, bark and tree fluxes followed in more derived species. By plotting female reproductive strategies, as reflected in ovarian developmental type, on the molecular tree, we also demonstrate a phylogenetic trend toward increasing fecundity. We find some statistical support for correlations between ecological shifts and shifts in female reproductive strategies. CONCLUSIONS: Because of the short branches at the base of the phylogram, which lead to ecologically diverse lineages, we conclude that much of the adaptive radiation into alternate breeding substrates occurred rapidly, early in the group's evolution in Hawaii. Furthermore, we conclude that this ecological divergence and the correlated changes in ovarian patterns that adapt species to their ecological habitats were contributing factors in the major phyletic branching within the Hawaiian drosophilid fauna.

Adaptation, Physiological↗
PubMed1995

Differences in the shedding of soluble TNF receptors between endotoxin-sensitive and endotoxin-resistant mice in response to lipopolysaccharide or live bacterial challenge.

TNF-alpha plays a pivotal role in the pathogenesis of septic shock. It exerts its effects by binding two cell surface receptors, designated TNF-R I and II, also referred to as the p55 and p75 receptors, respectively. TNF-Rs are transmembrane proteins, which on cleavage of their extracellular domains, result in the release of soluble fragments (sTNF-R). sTNF-R levels increase markedly during infection, and may serve to modulate TNF-alpha bioactivity. The mechanisms regulating this process are uncertain. To investigate this, we measured sTNF-R release in endotoxin-sensitive C3H/HeN and endotoxin-resistant C3H/HeJ mice given LPS or live Gram-negative bacteria. In C3H/HeN mice, there was a rapid early response during the first 4 h, and a second peak at 8 h, particularly noticeable in the case of the p75 receptor. Prior administration of neutralizing Abs to TNF-alpha or IFN-gamma had no effect on receptor shedding. Surprisingly, C3H/HeJ mice also responded to both bacterial challenge and to LPS by shedding sTNF-R; the magnitude and duration of the early response was not substantially different from C3H/HeN mice, although the second peak was absent. Peritoneal macrophages from C3H/HeN mice responded promptly (5 h) when stimulated with LPS in vitro, and by 22 h levels had increased five- to 10-fold. In contrast, cells from C3H/HeJ mice demonstrated only a very modest response at 22 h following maximal stimulation. The data suggest that there may be at least two separately regulated pathways that control sTNF-R shedding in these mice.

Animals↗
PubMed1995

The culture of credit.

Scientific ideals call for collaboration and sharing. But in today's competitive scientific enterprise, a tremendous premium is placed on individual credit, setting the stage for conflict.

Animals↗
PubMed1995

[The use of amphotericin B in a general hospital].

BACKGROUND: Amphotericin B (AmB) remains the standard treatment for most systemic mycosis. In addition to the ordinary deoxycholate formulation (AmB-DC), liposomal AmB (AmB-LP) is available in the United Kingdom. The aim of this study was to determine the patterns of usage of AmB in the present situation. METHODS: A 3 month prospective audit (August-October 1992) and a 3 year retrospective analysis of usage and expenditure in a United Kingdom University Hospital were carried out. RESULTS: A total of 42 courses and 564 days of treatment with AmB were analysed during the prospective audit. The total cost of AmB was 38,000 pounds (roughly 7,600,000 pesetas). AmB-LP accounted for 92% of the expenditure on AmB and 72% of the total expenditure on antifungals during the survey period. In 60% of the courses AmB was given as an empiric treatment. Only 65% of the days of treatment with AmB-LP were used according to the institution guidelines. The estimated cost of the days of treatment with AmB-LP that did not follow the institution guidelines was 9,500 pounds (roughly 1,800,000 pesetas). The retrospective analysis revealed a striking increase in the expenditure on AmB since the release of AmB-LP. There was an steady growth in the usage of both AmB-DC and AmB-LP over the 3 year period analysed. CONCLUSIONS: AmB is being increasingly used, mainly as an empiric treatment. The release of AmB-LP has had a great impact on the AmB budget. The current prescriptions habits of AmB-LP could be improved. To ensure an appropriate usage a direct control of AmB-LP might be advisable.

Amphotericin B↗
PubMed1995

Implications of small reductions in diastolic blood pressure for primary prevention.

OBJECTIVES: To estimate the impact of small reductions in the population distribution of diastolic blood pressure (DBP), such as those potentially achievable by population-wide lifestyle modification, on incidence of coronary heart disease (CHD) and stroke. DESIGN: Published data from the Framingham Heart Study, a longitudinal cohort study, and from the National Health and Nutrition Examination Survey II, a national population survey, were used to examine the impact of a population-wide strategy aimed at reducing DBP by an average of 2 mm Hg in a population including normotensive subjects. SETTING/PARTICIPANTS: White men and women aged 35 to 64 years in the United States. MAIN OUTCOME MEASURES: Incidence of CHD and stroke, including transient ischemic attacks (TIAs). RESULTS: Data from overviews of observational studies and randomized trials suggest that a 2-mm Hg reduction in DBP would result in a 17% decrease in the prevalence of hypertension as well as a 6% reduction in the risk of CHD and a 15% reduction in risk of stroke and TIAs. From an application of these results to US white men and women aged 35 to 64 years, it is estimated that a successful population intervention alone could reduce CHD incidence more than could medical treatment for all those with a DBP of 95 mm Hg or higher. It could prevent 84% of the number prevented by medical treatment for all those with a DBP of 90 mm Hg or higher. For stroke (including TIAs), a population-wide 2-mm Hg reduction could prevent 93% of events prevented by medical treatment for those with a DBP of 95 mm Hg or higher and 69% of events for treatment for those with a DBP of 90 mm Hg or higher. A combination strategy of both a population reduction in DBP and targeted medical intervention is most effective and could double or triple the impact of medical treatment alone. Adding a population-based intervention to existing levels of hypertension treatment could prevent an estimated additional 67,000 CHD events (6%) and 34,000 stroke and TIA events (13%) annually among all those aged 35 to 64 years in the United States. CONCLUSIONS: A small reduction of 2 mm Hg in DBP in the mean of the population distribution, in addition to medical treatment, could have a great public health impact on the number of CHD and stroke events prevented. Whether such DBP reductions can be achieved in the population through lifestyle interventions, in particular through sodium reduction, depends on the results of ongoing primary prevention trials as well as the cooperation of the food industry, government agencies, and health education professionals.

Adult↗