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Biomedical subjects

M Francis

Publications and source records attributed to M Francis.

At least 73 records · Page 4Linked to original sources
PubMed1987

A note on the assessment of exposure using one-sided tolerance limits.

Conceptual problems with OSHA's use of an absolute standard have led to alternative methods of assessing exposures to toxic materials in the workplace. One of these methods employs a one-sided tolerance limit. This statistical approach is explored from three points of view--identifiability, sampling strategies and statistical power. In general, assessing risk in the work environment with tolerance limits is found to give inadequate answers in several important respects.

Humans↗
PubMed1987

Antiarrhythmic efficacy and hemodynamic effects of cibenzoline in patients with nonsustained ventricular tachycardia and left ventricular dysfunction.

This was a prospective single-blind, placebo-controlled study of cibenzoline in 21 patients with five or more runs of nonsustained ventricular tachycardia (VT) and left ventricular dysfunction (mean left ventricular ejection fraction 36 +/- 24%). Ambulatory electrocardiographic monitoring revealed a baseline of 616 +/- 431 runs of VT/day on placebo. Of the 18 patients tolerating the drug, 14 (77%) patients initially had a 75% or greater reduction in VT (177 +/- 164 runs of VT/day, p less than .05). A repeat ambulatory electrocardiogram documented long-term suppression of VT in 13 of 14 patients at 1 month (2.1 +/- 1.3 runs VT/day, p less than .01), in 10 of 14 patients at 3 months (2.5 +/- 1.9 runs VT/day, p less than .01), and in nine of 14 patients at 6 months (1.5 +/- 0.8 runs VT/day, p less than .01). Aggravation of arrhythmia or drug failure was seen in four of 18 (22%) patients (new onset of sudden cardiac death, two patients; sustained VT, two patients). Hemodynamic measurements were obtained with the use of right heart catheterization in patients at rest and exercising during the placebo phase and after 60 hr of oral cibenzoline. Group hemodynamic variables, both measured and derived, showed no detrimental effect of cibenzoline. However, in three of 21 patients (mean ejection fraction 21%), cibenzoline was discontinued due to severe depression of left ventricular function. Caution is recommended in the use of cibenzoline in patients with left ventricular ejection fractions of less than 25%.

Aged↗
PubMed1986

The influence of averaging time on the distribution of exposures.

Personal exposures to toxic airborne agents in the work environment often are approximately log-normally distributed. While the arithmetic mean of these distributions is independent of the averaging time of the measurement in a stationary environment, this is not the case for the variance. In general, the variance decreases with increasing averaging time, but the rate of decrease depends upon the autocorrelation structure of the exposure time series. If the autocorrelation structure can be determined, a knowledge of the parameters of the distribution of exposures at one averaging time allows the estimation of those for any other averaging time. Regardless of the autocorrelation situation, these results suggest that current ACGIH guidelines for assessing short-term exposures need examination and may require modification.

Air Pollutants, Occupational↗
PubMed1982

Nucleotide sequence of a spinach chloroplast proline tRNA.

The nucleotide sequence of a spinach chloroplast proline tRNA (sp. chl. tRNApro) has been determined. This tRNA shows more overall homology to phage T4 proline tRNA (61% homology) than to eukaryotic proline tRNAs (53% homology) or mitochondrial proline tRNAs (36-49% homology). Sp. chl. tRNApro, like all other chloroplast tRNAs sequenced, contains a methylated GG sequence in the dihyrouridine loop and lacks unusual structural features which have been found in many mitochondrial tRNAs.

Base Sequence↗
PubMed1982

Partial purification and characterization of a membrane-associated steroid-binding protein from Pseudomonas testosteroni.

A steroid-binding protein obtained from the supernatant of the final wash from the preparation of membrane vesicles was purified severalfold to near homogeneity. The protein binds C18 and C19 steroids but has the highest affinity for androstenedione (Kd = 1.6 x 10(-10) M). The molecular weight is 51,000 - 58,000. Binding activity is slightly inhibited by Cu2+, Ca2+, and Mg2+ and completely inhibited by Zn2+. The protein has no detectable steroid degradative activity. Analysis of androstenedione binding revealed negative cooperativity of binding for this ligand and may indicate a regulatory function for this protein. It is postulated that this protein binds the steroid after testosterone is converted to androstenedione.

Androgen-Binding Protein↗
PubMed1981

Membrane-associated steroid-binding proteins of Pseudomonas testosteroni.

Previous studies have established the presence of periplasmic steroid-binding proteins in induced Pseudomonas testosteroni. This study reports the presence of two additional steroid-binding proteins which can be released from the cytoplasmic membrane during preparation of membrane vesicles. These two proteins differ from each other and from the periplasmic protein in some of their characteristics and steroid specificity, and appear to be distinct from the two membrane-bound steroid dehydrogenases, 3 beta and 17 beta-hydroxysteroid dehydrogenase and 1-ene-dehydrogenase.

17-Hydroxysteroid Dehydrogenases↗
PubMed1979

Age-associated changes in T-B cell cooperation demonstrated by the allogeneic effect.

The allogeneic effect results in an increase in the number of antibody-producing cells (PFC) when the allogeneically stimulated lymphoid cells and the antibody-producing cells are from young individuals. This increase depends on the interaction of allogeneically stimulated T-cells and precursor plasma cells (B-cells). Age-associated deficiencies in these two cell populations were studied in these experiments by use of allogeneically stimulated T-cells from old donors or responding B-cells from old recipients. These experiments showed that lymphocytes from 20-month-old mice were capable of inducing an increase in PFC in young recipients. However, the allogeneic effect was ineffectual in 12-month-old mice. These data suggest that the T-helper function is equally capable in mice 4 to 20 months old, but that the B-cell is not as effectively recruited. The possible causes for limited B-cell recruitment are discussed.

Age Factors↗
PubMedDate not supplied

A comparison of the cardiovascular responses to carotid injections of ionic and nonionic contrast media.

Selective injection of contrast media into the canine common carotid artery results in alterations in carotid flow, heart rate, and systemic arterial pressure. In this study the responses to injections of the nonionic agents metrizamide and iopamidol were compared to the responses to the ionic agents meglumine iothalamate, meglumine sodium diatrizoate, mannitol, and saline solution. Heart rate and pressure responses were smallest for metrizamide, greater for iopamidol, and greater still for the hypertonic ionic agents: responses were roughly correlated to agent osmolality. Carotid flow increased with all agents and was roughly proportional to the agent's osmolality. The exception was metrizamide which despite its lowest osmolality, produced a large increase in flow which was maintained much longer than for other agents. The total response to the nonionic agents was judged less severe than to the ionic agents; however, the responses to all agents were transient and not life threatening.

Animals↗