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Biomedical subjects

A Cohen

Publications and source records attributed to A Cohen.

At least 595 records · Page 33Linked to original sources
PubMed1989

Age-related bone loss in lumbar vertebrae of CW-1 female mice: a histomorphometric study.

Age-related changes in vertebral cortical and trabecular bone were quantitated in female CW-1 mice. Histomorphometric measurements involved the use of two different systems of image analysis: Olympus Cue 2 and Zeiss Morphomat 10. The peak of bone mass, both cortical and trabecular, was found in mice aged 13.5 months. Thereafter, there was a progressive decline in the area occupied by bone tissue and this became highly significant in elderly female and male mice. A loss of about 60% of bone tissue was encountered in both the trabecular and cortical bone, as determined by automated image analysis system. Hence, aging CW-1 mice reveal structural features consistent with vertebral osteopenia. Despite the fact that to date we lack the precise etiology for the above-mentioned phenomenon, it is suggested that the laboratory mouse might serve as an appropriate experimental model for investigations related to age-related bone loss.

Aging↗
PubMed1989

Limitations of cough in maintaining blood flow during asystole: assessment by two-dimensional and Doppler echocardiography.

It has been previously demonstrated that patients can maintain consciousness by vigorously coughing during episodes of prolonged ventricular asystole or ventricular fibrillation. Using two-dimensional Doppler echocardiography and arterial blood pressure recordings, we evaluated the changes that occur during coughing in nine patients who were dependent on pacemakers and in whom periods of asystole could be induced. During asystole in each patient the mitral valve stayed partially open and the left ventricular area comprised 87% and 90% (apical four-chamber view, short-axis view, respectively) of the area during diastole of paced rhythm. Peak arterial pressure during coughing and asystole was 80% of peak systolic pressure of paced rhythm (P = 0.001). Left ventricular area during coughing was 110% (both apical four-chamber view and short-axis views) of the area during asystole when patients were not coughing. Both the mitral and aortic valves showed no appreciable motion during coughing. During coughing the mean flow velocity across the mitral valve was 0.06 +/- 0.03 m/sec and the flow velocity integral was 0.03 +/- 0.02 cm. Thus coughing during asystole produced minimal flow despite a rise in brachial arterial pressure.

Aged↗
PubMed1989

Serum IgG and IgA antibodies to Chlamydia in ectopic pregnancies.

The possible association of Chlamydia trachomatis with ectopic pregnancies was evaluated in a case-control study, comprising 35 women with ectopic pregnancy and 294 apparently healthy women who served as controls. Chlamydia-specific IgG and IgA antibodies were determined by single serovar (L2) inclusion immunoperoxidase assay (IPA). Socio-demographic characteristics, gynecological history and contraceptive methods were also evaluated. An inverse relationship was found between the educational levels and the prevalence of IgG and IgA antibodies to chlamydia. The prevalence rate of elevated IPA IgG (titer greater than or equal to 128) and IPA IgA (titer greater than or equal to 16) specific to chlamydia was significantly higher in women with ectopic pregnancy versus controls (32% vs 8%, respectively, for IgG: odds ratio = 4.9; and 26% vs 4% for IgA: odds ratio = 7.5). Chlamydia trachomatis was not isolated in cell cultures in 10 specimens available from fallopian tubes of women with ectopic pregnancy. Only 9% of the women recall having pelvic inflammatory disease (PID) indicating that most of the infections were asymptomatic. Women who did not use IUD had a higher proportion of chlamydia-specific IgG and IgA seropositives, though not statistically significant, as compared to IUD users. This study further supports the hypothesis that subclinical infection of the tube with C. trachomatis may underlie ectopic pregnancies.

Adolescent↗
PubMed1989

Deleterious synergistic effects of ascorbate and copper on the development of Plasmodium falciparum: an in vitro study in normal and in G6PD-deficient erythrocytes.

The effects of ascorbate and copper on the development of Plasmodium falciparum were studied in two modes: pretreatment of uninfected erythrocytes followed by infection by P. falciparum and treatment of parasitized erythrocytes. Pretreatment of G6PD(+) cells with ascorbate caused a slight enhancement in parasite development, while in G6PD(-) cells a suppressive effect on the plasmodia was demonstrated. Copper alone interfered with parasite growth in both cell types. The combination of copper and ascorbate arrested parasite maturation, an effect which was more pronounced in G6PD(-) cells. Synergism between copper and ascorbate was better demonstrated following the treatment of infected erythrocytes: while ascorbate alone supported parasite development and copper alone had only a marginal suppressive effect, the combination of copper and ascorbate yielded a marked inhibition of parasite growth. Ascorbate proved destructive to the parasites in the presence of adventitious copper, or on the second day of the parasite life cycle. In these cases it acted as a pro-oxidant, while in other systems, in particular in the presence of a chelator, ascorbate acted as an antioxidant and promoted parasite growth. The understanding of the role of transition metals and free radicals in parasite development and injury could shed light on novel approaches to fight malaria.

Animals↗
PubMed1989

Liver transplantation for metabolic disorders.

Liver transplantation for metabolic disorders continues to be an expanding field, both in the range of indications and patient numbers. In most large series it accounts for approximately 7% of all adult transplants and 29% of all childhood transplants. As the results of medical therapy are improved so too are the results of liver transplantation, and hence more patients are being considered for the latter therapy. The benefits of this treatment are not only the prolongation of and improvement in the quality of life for the patient, it has also given insight into the basic metabolic defects of many disorders.

Humans↗
PubMed1989

Illusory conjunctions inside and outside the focus of attention.

This article addresses 2 questions that arise from the finding that visual scenes are first parsed into visual features: (a) the accumulation of location information about objects during their recognition and (b) the mechanism for the binding of the visual features. The first 2 experiments demonstrated that when 2 colored letters were presented outside the initial focus of attention, illusory conjunctions between the color of one letter and the shape of the other were formed only if the letters were less than 1 degree apart. Separation greater than 2 degrees resulted in fewer conjunction errors than expected by chance. Experiments 3 and 4 showed that inside the spread of attention, illusory conjunctions between the 2 letters can occur regardless of the distance between them. In addition, these experiments demonstrated that the span of attention can expand or shrink like a spotlight. The results suggest that features inside the focus of attention are integrated by an expandable focal attention mechanism that conjoins all features that appear inside its focus. Visual features outside the focus of attention may be registered with coarse location information prior to their integration. Alternatively, a quick and imprecise shift of attention to the periphery may lead to illusory conjunctions among adjacent stimuli.

Adult↗
PubMed1989

Foodborne botulism: an international outbreak.

We report an outbreak of fishborne botulism caused by type E Clostridium botulinum. The eight cases, six in Israel and two in New York City, resulted from the consumption of ribbetz or kapchunka, a freshwater whitefish soaked in brine and air-dried, that was processed commercially in New York. Half the cases were males; the age range was 9 to 77 years. Five of the victims were hospitalized; the oldest died, and two others required ventilatory assistance. Laboratory confirmation of botulism was obtained in three cases. Prolonged lack of refrigeration during transatlantic flight and packaging contributing to an anaerobic environment were felt to be contributing environmental factors in the Israeli cases. Rapid communication and full cooperation between Israeli and US health authorities limited the extent of the outbreak. Despite adequate understanding of how foodborne botulism may be avoided, outbreaks still occur, particularly among people consuming certain high-risk or ethnic foods.

Adolescent↗
PubMed1989

Memory of food intake in the distant past.

Long term recalls of dietary intake are frequently used in case-control studies, but their validity and reliability have not been established. In this study, 91 middle-aged adults (median age, 50 years) who were participants in the Longitudinal Study of Child Health and Development at the Harvard School of Public Health in Boston, Massachusetts, starting in the early 1930s, were asked in 1984-1985 to report present food intake and to recall food intakes at ages 5-7 years. 18 years, and 30 years using food frequency questionnaires. Their recalled intakes were validated by comparison with historical records of intake collected during the earlier time periods. Recall of food intake in the distant past was a better predictor of historical intake than was current diet. However, correlations between recalled and historical consumption for individual foods and food groups were generally low, rarely exceeding 0.3. Current intakes exerted a powerful influence on accuracy of recall. The consideration of participant characteristics did not prove to be consistently useful in explaining variations in food item and food group-related recall. The authors conclude that recall of food intake in the distant past may be a sufficiently valid estimate of past intake to justify its collection.

Boston↗
PubMed1989

Dichotomy of the glial cell response to axonal injury and regeneration.

Neurons in the mammalian central nervous system (CNS) have a poor capacity for regenerating their axons after injury. In contrast, neurons in the CNS of lower vertebrates and in the peripheral nervous system (PNS) of mammals are endowed with a high posttraumatic capacity to regenerate. The differences in regenerative capacity have been attributed to the different compositions of the respective cellular environments and to different responses to injury the nonneuronal cells display, which range from supportive and permissive to nonsupportive and hostile for regeneration. The same cell type may support or inhibit regeneration, depending on its state of maturity or differentiation. Astrocytes and oligodendrocytes are examples of cells in which such a dichotomy is manifested. In developing and in spontaneously regenerating nerves, these cells support (astrocytes) and permit (oligodendrocytes) growth. However, in nonregenerating adult mammalian nerves, astrocytes form the nonsupportive scar tissue; and the mature oligodendrocytes inhibit axonal growth. Maturation of these cells may be regulated differently during development than after injury. Among the putative regulators are factors derived from astrocytes, resident microglia; or cytokines produced by macrophages. During development, regulation leads to a temporal separation between axonal growth and maturation of the cellular environment, which might not occur spontaneously after injury in a nonregenerating CNS without intervention at the appropriate time. Data suggest that temporal intervention aimed at the glial cells might enhance the poor regenerative capacity of the mammalian CNS. Possible regulation of the nonneuronal cell response to injury via involvement of protooncogenes is proposed.

Animals↗
PubMed1989

Optic nerve regeneration in adult fish and apolipoprotein A-I.

Fish optic nerves, unlike mammalian optic nerves, are endowed with a high capacity to regenerate. Injury to fish optic nerves causes pronounced changes in the composition of pulse-labeled substances derived from the surrounding non-neuronal cells. The most prominent of these injury-induced changes is in a 28-kilodalton (kDa) polypeptide whose level increases after injury, as revealed by one-dimensional gel electrophoresis and autoradiography. The present study identified as apolipoprotein A-I (apo-A-I) a polypeptide of 28 kDa in media conditioned by regenerating fish optic nerves. The level of this polypeptide increased after injury by approximately 35%. Apo-A-I was isolated by gel-permeation chromatography from delipidated high-density lipoproteins (HDL) that had been obtained from carp plasma by sequential ultracentrifugation. Further identification of the purified protein as apo-A-I was based on its molecular mass (28 kDa) as determined by gel electrophoresis, amino acid composition, and microheterogeneity studies. The isolated protein was further analyzed by immunoblots of two-dimensional gels and was found to contain six isoforms. Western blot analysis using antibodies directed against the isolated plasma protein showed that the 28-kDa polypeptide in the preparation of soluble substances derived from the fish optic nerves (conditioned media, CM) cross-reacted immunologically with the isolated fish plasma apo-A-I. Immunoblots of two-dimensional gels revealed the presence of three apo-A-I isoforms in the CM of regenerating fish optic nerves (pIs: 6.49, 6.64, and 6.73). At least some of the apo-A-I found in the CM is derived from the nerve, as was shown by pulse labeling with [35S]methionine, followed by immunoprecipitation. The apo-A-I immunoactive polypeptides in the CM of the fish optic nerve were found in high molecular-weight, putative HDL-like particles. Immunocytochemical staining revealed that apo-A-I immunoreactive sites were present in the fish optic nerves. Higher labeling was found in injured nerves (between the site of injury and the brain) than in non-injured nerves. The accumulation of apo-A-I in nerves that are capable of regenerating may be similar to that of apo-E in sciatic nerves of mammals (a regenerative system); in contrast, although its synthesis is increased, apo-A-I does not accumulate in avian optic nerves nor does apo-E in rat optic nerves (two nonregenerative systems).

Animals↗
PubMed1989

Advances in catheter ablation use of unipolar electrograms.

Ventricular tachycardia in man can be eliminated by relatively small lesions in the reentrant circuit. This report includes a review of available energy sources, and methods for localizing arrhythmias. Methods to assure contact and prevent perforation using low frequency electrograms are presented including the new finding of reverse ST deflection with contact. Experience with laser energy in dogs showed discrete homogenous lesions. When compared with DC shock the animals showed far less arrhythmia and the lack of far field effect greatly reduced echo abnormalities in the post shock period. Studies with radiofrequency show ability to produce localized lesions similar to the laser but with a more flexible catheter. Localization requires a correlation of techniques including pacemapping, activation maps and pacing during tachycardia. Early activation (less than -60 ms) at times 180-320 ms, with comparable pace to QRS during tachycardia with no change in morphology best localized the slow zone of the reentrant circuit. The low frequency unipolar electrogram from the tip and immediately proximal electrode revealed contact with ST deviation. The distal deviation was always greater than the proximal RV free wall and posterior basal produced depression rather than elevation of the electrogram. While the mechanism of ST reversal with contact is not understood and may relate to the type of indifferent reference used (Wilson central terminal), the ST depression reveals the same information about contact that elevation does in most areas of the heart studied in our patients.

Animals↗
PubMed1989

Suppression of recA deficiency in plasmid recombination by bacteriophage lambda beta protein in RecBCD- ExoI- Escherichia coli cells.

Plasmid recombination, like other homologous recombination in Escherichia coli, requires RecA protein in most conditions. We have found that the plasmid recombination defect in a recA mutant can be efficiently suppressed by the beta protein of bacteriophage lambda. beta protein is required for homologous recombination of lambda chromosomes during lytic phage growth in a recA host and is known to have a strand-annealing activity resembling that of RecA protein. The bioluminescence recombination assay was used for genetic analysis of beta-protein-mediated plasmid recombination. Efficient suppression of the recA mutation by beta protein required the absence of the E. coli nucleases exonuclease I and RecBCD nuclease. These nucleases inhibit a RecA-mediated plasmid recombination pathway that is more efficient than the pathway functioning in wild-type cells. Like RecA-mediated plasmid recombination in RecBCD- ExoI- cells, beta-protein-mediated plasmid recombination depended on concurrent DNA replication and on the activity of the recQ gene. However, unlike RecA-mediated plasmid recombination, beta-protein-mediated recombination in RecBCD- ExoI- cells was independent of recF and recJ activities. We propose that inactivation of exonuclease I and RecBCD nuclease stabilizes a recombination intermediate that is involved in RecA- and beta-protein-catalyzed homologous pairing reactions. We suggest that the intermediate may be linear plasmid DNA with a protruding 3' end, since these nucleases are known to interfere with the synthesis of such linear forms. The different recF and recJ requirements for beta-protein-dependent and RecA-dependent recombinations imply that the mechanisms of formation or processing of the putative intermediate differ in the two cases.

Bacterial Proteins↗
PubMed1989

The antigastrolesive activity of rioprostil, a 16-methyl prostaglandin-E1 analogue in healthy volunteers.

The antigastrolesive activity of rioprostil, an orally effective synthetic 16-methyl analogue of prostaglandin-E1, with potent antisecretory and antigastrolesive properties in animals, is evaluated in a series of studies involving 166 healthy male volunteers. Three double-blind, randomized, parallel, placebo-controlled studies are conducted independently at three study centres. In two studies the protective effect of rioprostil against endoscopically-demonstrated mucosal changes caused by concurrent administration of aspirin is examined. The third study evaluates the inhibitory effect of rioprostil on faecal blood loss produced by co-administration of aspirin. Oral doses of rioprostil give significant dose-dependent protection against aspirin-induced mucosal changes. The total mucosal scores at day 3 and day 11 are significantly lower in each of the rioprostil + aspirin groups compared with the aspirin treated group. The total mucosal scores generally decrease with increasing rioprostil dose. Daily faecal blood loss is significantly lower in each of the groups of subjects treated with rioprostil + aspirin, compared with those treated with aspirin + placebo. This study shows that rioprostil provides significant protection against mucosal damage caused by high doses of concomitantly administered aspirin.

Adult↗
PubMed1989

Evaluation of the UNOS point system for kidney recipient selection.

1. The ultimate distribution of 479 consecutive cadaver donor kidneys in the Los Angeles area was examined to determine whether the distribution had been equitable. Half of the kidneys had been allocated by the UNOS point system (or slight modifications thereof) and half by the transplant centers according to their own criteria. 2. With respect to waiting time, the pool of 1,000 was composed of 14% patients who had waited more than 2 years. The UNOS point system forced the transplantation of more patients (27%) who had waited longer than 2 years than the nonpoint system (11%). 3. Although the waiting pool was composed of 28% waiting for retransplantation, the UNOS point system resulted in transplantation of 16% and the nonpoint system, 8%. 4. In the waiting pool, 16% of the patients had cytotoxic antibodies reactive to more than 80% of the panel, whereas 11% of the transplants by the UNOS point system were transplanted into highly sensitized patients and only 2% of the patients transplanted by the nonpoint system were highly sensitized. 5. In Los Angeles, where 11% of the population is Black, 10% of the kidneys transplanted were into Black patients. Since 18% of the waiting pool of patients were Black, some shortfall was noted. However, this can be attributed to the fact that only 7% of the donors were Black. The importance of increasing donation from the Black community is emphasized. 6. Because of the limited pool size of 1,000 patients only a small number of 0 B,DR transplants were achieved.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation Studies as Topic↗
PubMed1989

[Nyctohemeral changes in arterial pressure in hospitalized subjects].

Systolic and diastolic arterial blood pressures (SBP, DBP) were measured in 181 consecutive patients (pts) by non-invasive method (oscillometric recorder SpaceLabs 90202). Hospitalised pts (N = 54) and ambulatory pts (N = 127) did not differ significantly in 24 hrs mean SBP, diurnal SBP, DBP nor heart rate (HR): respectively 132.9 vs 136.1 137.6 vs 138.2 86.2 vs 84.4 mmHg 79.6 vs 77.1 bpm. The circadian variation of HR was identical in the 2 groups. During night (0-6 hr AM) pressures decreased significantly less in hospitalised pts than in outpatients: respectively SBP - 6.4 vs - 17.9 p. cent DBP - 5.7 vs - 17 p. cent SBP day/SBP night ratio 1.06 vs 1.17 (p less than 0.001). This "equalization" was observed since the first day of hospitalisation, even if pts were not restricted to bed (pts in intensive care unit were excluded). It did not depend on age, sex, mean SBP nor antihypertensive treatments. Heart work, as evaluated by HR.SBP product, did not differ significantly during the day in the 2 groups. In hospitalised pts it decreased twice less and remains at a significantly higher level than in outpatients: respectively - 166 vs - 300 906 vs 792 cmHg/min (p less than 0.001). The standard deviation of SBP was significantly correlated with the SBP day/SBP night ratio (r = 0.64 p less than 0.001). The chronology of the circadian variations of HR and SBP are identical, but their amplitude differed in hospitalised pts suggesting that the regulatory mechanisms of HR and SBP are different.

Adult↗
PubMed1989

[Aortic and mitral endocarditis caused by Haemophilus paraphrophilus with abscess of the aortic ring and cerebral embolism].

We report the first case of aortic and mitral Haemophilus paraphrophilus endocarditis complicated by abscess of the aortic annulus in a 30-year old man with post-rheumatic mitral regurgitation. We recall the peculiar clinical features and course of this bacterial endocarditis of uncommon origin. We insist, in particular, on the occurrence of cerebral embolism and on the two-dimensional echocardiographic diagnosis of an aortic annulus abscess confirmed at surgery. Cure was obtained by aortic and mitral valve replacement and by the prolonged antibiotic therapy made necessary by the presence of cerebral lesions. After 3 months, there were no neurological sequelae, but doppler-echocardiography showed a persistent washed out pouch the reports of which with the surrounding structures were determined by transoesophageal echocardiography: moderate aortic regurgitation was detected at that level.

Abscess↗
PubMed1989

[Evaluation by Doppler echocardiography of systolic and diastolic functions of the left ventricle of the athlete's heart].

A doppler-echocardiographuc study of left ventricular hypertrophy and systolic functions was performed in 99 professional cyclists and 26 age, body surface and blood pressure-matched controls. The following T-mode echocardiographic parameters were determined: wall thickness and cavitary diameter, left ventricular mass (LVM), fibre shortening fraction (FSF) and ejection fraction (EF). The following doppler parameters were measured at the annulus (a) and tip (p) of the mitral valve leaflets: protodiastolic velocity peak (E), velocity peak during atrial systole (A) and A/E ratio. Compared with controls, the cyclists showed a significant increase of LVM (305 +/- 53 vs 174 +/- 41 g, p less than 0.0001) and of the h/R ratio of mean wall thickness (h) to cavitary radius (R) (0.40 +/- 0.04 vs 0.35 +/- 0.06, p less than 0.001). There was no significant difference between the two groups as regards FSF, EF and protodiastolic filling peak (E). In contrast, subjects in the cyclist group showed a significant increase of Ap (0.39 +/- 0.07 vs 0.47 +/- 0.09, p less than 0.001), Aa (0.36 +/- 0.07 vs 0.41 +/- 0.08, p less than 0.01) and A/Ep (0.54 +/- 0.12 vs 0.62 vs 0.62 +/- 0.11, p less than 0.0001). It is concluded that professional cyclists have an increase in size of their left ventricle and that repercussions of this enlargement on ventricular filling only appear during the atrial systole and are related to a slower heart rate.

Adult↗