Search PubMed⌕ Search

Biomedical subjects

H Cohen

Publications and source records attributed to H Cohen.

At least 271 records · Page 15Linked to original sources
PubMed1995

Reactions of low valent transition metal complexes with hydrogen peroxide. Are they "Fenton-like" or not? 4. The case of Fe(II)L, L = edta; hedta and tcma.

The question whether hydroxyl free radicals are formed in the reactions of divalent iron complexes Fe(II)L; L = edta; hedta; tcma (tcma = 1-acetato-1,4,7-triazacyclononane) with hydrogen peroxide in neutral and slightly acidic solutions was studied by using the beta elimination reaction as an assay for the formation of hydroxyl free radicals, OH. The results show that at pH < 5.5 the iron(II)peroxide intermediate complex decomposes rapidly to yield free hydroxyl radicals for L = edta and hedta. This is in contrast to the mechanism of the corresponding Fe(II)nta peroxide complex, which probably decomposes to form Fe(IV)nta which then reacts with organic substrates to yield aliphatic free radicals. Thus, the non-participating ligand L has an appreciable effect on the mechanism of reaction of the metal center with hydrogen peroxide. Blank experiments using ionizing radiation as the source of .CH2CR(CH3)OH, R = H or CH3 radicals indicate that when L = tcma intermediates of the type LFeIII-CH2CR(CH3)OHaq are formed, but their major mode of decomposition is not the beta elimination reaction. Thus, the present assay for the formation of hydroxyl free radicals by the Fenton Reaction does not fit the latter system.

Chelating Agents↗
PubMed1995

Vestibular rehabilitation with graded occupations.

These three case reports are examples of the use of graded, purposeful activities in remediating the symptoms of vestibular disorders. Therapists can design individualized treatment plans for each patient by incorporating activities of interest to the patient. The treatment activities must include the particular head movements and positions that elicit vertigo during assessment. Additionally, activities must be interesting to the individual patient. Use of interesting activities may sustain the patient's interest and motivation for the treatment program and enable the patient to relate the learning process to real life experience. The principle that graded, repetitive head movement exercise is efficacious in reducing vertigo and disequilibrium in patients with vestibular disorders is now well accepted among physicians and therapists who treat these patients. The principle of adding meaning or purpose to otherwise rote exercise is well accepted among occupational therapists and is supported by evidence from the empirical literature (Heck, 1988; Kircher, 1984; Yoder, Nelson, & Smith, 1989). This concept of adding purpose to repetitive exercise may now be extended to the treatment of patients with peripheral vestibular disorders.

Activities of Daily Living↗
PubMed1995

Differential mortality in New York City (1988-1992). Part One: excess mortality among non-Hispanic blacks.

To determine the distribution of mortality for non-Hispanic blacks and non-Hispanic whites in New York City, death certificates issued in New York City during 1988 through 1992, and the relevant 1990 US census data for New York City, have been examined. Age-adjusted death rates for blacks and whites by gender and cause of death were computed based on the US population in 1940. Also, standard mortality ratios and excess mortality were calculated using the New York City mortality rate as reference. The results showed that New York City blacks had higher age-adjusted death rates than whites regardless of cause, including stroke, AIDS, homicide, and diabetes. The rate for New York City blacks was also higher than the US total for both genders. Using New York City mortality rates as a reference, more than 80% of excess deaths in blacks occurred before age 65. Injury/poisoning was the leading cause of excess death (20.1%) in black males, while in black females, cardiovascular disease was the largest single cause of excess deaths (24.8%). The higher death rates, especially premature death, of blacks in New York City are related to conditions such as violence, substance abuse, and AIDS, for which prevention rather than medical care is the more likely solution, as well as to cardiovascular diseases, where both prevention through behavioral change, and health and medical care, can influence outcome.

Black or African American↗
PubMed1995

Differential mortality in New York City (1988-1992). Part Two: excess mortality in the south Bronx.

To display the extent of variations in mortality according to geographic regions in New York City, we have compared mortality in New York City as a whole with that of the South Bronx. Mortality records for 1988 to 1992 and 1990 US census data for New York City were linked. The 471,000 residents of the South Bronx were younger, less educated, and more likely to lack health insurance than other New Yorkers. Using age- and gender-stratified populations and mortality in New York City as standards, age-adjusted death rates and excess mortality in the South Bronx were determined. All-cause mortality in the South Bronx was 26% higher than the city as a whole. Mortality for AIDS, injury and poisoning, drug and alcohol abuse, and cardiovascular diseases were 50% to 100% higher in the South Bronx than in New York City; years of potential life lost before age 65 in the South Bronx were 41.6% and 44.2% higher for men and women, respectively, than in New York City; AIDS accounted for the largest single share of excess premature deaths (21.8%). In summary, inequalities in health status, reflected by higher mortality rates in the South Bronx, are consistent with, and perhaps caused by, lower socioeconomic status and deficient medical care among residents of this inner-city community.

Cause of Death↗
PubMed1995

Measures of blood pressure and myocardial infarction in treated hypertensive patients.

OBJECTIVE: To identify entry characteristics associated with subsequent myocardial infarction in treated hypertensive patients. DESIGN: Nested case-control study and cohort study. SETTING AND PATIENTS: The 5730 participants (mean age 53 years; 61% male and 45% Caucasian) were selected from a worksite-based, union-sponsored, systematic hypertension control program from 1973 to 1992. METHODS: In the case-control study myocardial infarction cases were matched by age, sex, year of entry to the program, years of follow-up and previous treatment status (treated or untreated) with non-event subjects. Baseline clinical and biochemical characteristics were analyzed with regard to the outcome of myocardial infarction, using univariate and multivariate analyses, respectively, in case-control and cohort studies. RESULTS: During 5.43 years of follow-up the incidence of myocardial infarction was 6.75/1000 person-years. Univariate analysis indicated that myocardial infarction cases had higher cholesterol level and were more likely to have a previous history of diabetes than controls. The initial systolic blood pressure and pulse pressure of cases were significantly higher than in controls. Logistic regression models indicated that initial pulse pressure, either as a continuous or as a categorical variable, was the only measure of blood pressure independently associated with myocardial infarction after adjustment for other risk factors. Analysis of the experience of the total 5730 as well as 2445 previously untreated patients with a cohort study generated identical results. CONCLUSION: A large pulse pressure difference appears to be the most powerful measure available of initial blood pressure to identify, in advance, those hypertensive patients at greatest risk for a subsequent myocardial infarction.

Blood Glucose↗
PubMed1995

[Prenatal diagnosis of a case of Fryns' syndrome].

Fryns' syndrome was reported for the first time in 1979 in children who died neonatally of prematurity and respiratory distress. This lethal, autosomal recessive syndrome is characterized by a diaphragmatic defect, pulmonary hypoplasia, a "coarse" face and distal limb abnormalities. This report presents a prenatal ultrasonographic diagnosis at 20 weeks' gestation of a case of Fryns' syndrome and defines the frequency of each of its abnormalities from the 38 cases listed in the literature.

Abnormalities, Multiple↗
PubMed1995

Defining disablement in otolaryngology.

Taxonomies developed by the World Health Organization and the National Institutes of Health define different levels of chronic health conditions. This paper explains these classification systems, using examples relevant to otolaryngologists. This taxonomy may provide a useful framework for thinking about the stages of patient evaluation and treatment planning. It may also facilitate consideration of findings in the literature on clinical research.

Disability Evaluation↗
PubMed1995

Nitric oxide and prostacyclin modulate the alterations in cardiac action potential duration mediated by platelets during ischaemia.

OBJECTIVE: To investigate the effects of alterations of nitric oxide (NO) and prostacyclin (PGI2) availability on platelet-mediated electrophysiological effects during myocardial ischaemia. METHODS: Transmembrane action potentials and electrograms were recorded from isolated, Langendorff-perfused guinea-pig hearts during normal perfusion, global myocardial ischaemia and reperfusion during infusion of washed human platelets. Experiments were performed in the presence of 100 microM NG-nitro-L-arginine methyl ester (L-NAME), 30 microM L-arginine, 10 microM haemoglobin, 100 microM sodium nitroprusside and 2.3 nM iloprost, or using hearts obtained from DL-lysine monoacetylsalicylate (Aspisol, 50 mg.kg-1 i.p.)-treated animals. RESULTS: Perfusion with L-NAME and haemoglobin increased perfusion pressure by 33% (P = 0.0017) and 23% (P = 0.0026) while sodium nitroprusside and iloprost reduced it (17%, P = 0.0004, and 24%, P = 0.0006). In the absence of platelets, these compounds had no effect on arrhythmogenesis, but in the presence of platelets L-NAME reduced the onset time of ventricular tachycardia during ischaemia from 19.4 (s.e.m. 2.0) min to 12.9 (2.1) min, P = 0.04 and accentuated the ischaemia-induced reduction of action potential duration at 95% repolarization (APD95): 95(6) vs. 115(5) ms, P < 0.05 at 25 min. Sodium nitroprusside in the presence of platelets attenuated the ischaemia-induced reduction in APD95, while iloprost in the presence of platelets was antiarrhythmic (ventricular fibrillation 25 vs. 75%, P = 0.04) and attenuated the reduction in APD95 during ischaemia 115(4) vs. 94(4) ms, P < 0.05 at 20 min. Infusion of platelets into hearts obtained from DL-lysine-monoacetylsalicylate-treated guinea-pigs accentuated the ischaemia-induced reduction in APD95 (94(4) vs. 119(7) ms, P < 0.05 at 20 min) and this was reversed by sodium nitroprusside (117(7) ms, P < 0.05 at 20 min). L-NAME and haemoglobin had no effect on the aggregatory responses of the platelets to 5 microM ADP and 4 micrograms.ml-1 collagen, while sodium nitroprusside and iloprost ablated the responses to ADP and reduced the responses to collagen (maximum height of the aggregatory response reduced by 75 and 84%, respectively, both P = 0.03.) CONCLUSIONS: Inhibition of NO and PGI2 synthesis exacerbates the reduction in cardiac action potential duration associated with platelet activation during ischaemia, while provision of exogenous NO and PGI2 attenuates the reduction in cardiac action potential duration. Provision of exogenous NO and PGI2 (as iloprost) was associated with inhibition of platelet reactivity.

Action Potentials↗
PubMed1994

Pathology with clinical correlations of primary central nervous system non-Hodgkin's lymphoma. The Massachusetts General Hospital experience 1958-1989.

BACKGROUND: Primary central nervous system non-Hodgkin's lymphoma (NHL-CNS) is an enigmatic disease of uncertain origin. At the Massachusetts General Hospital, 104 patients with NHL-CNS were seen from 1958 through 1989. An impression of changes in the frequency of diagnosis, character of the tumors, and therapy for this disease prompted this study of the pathologic features, clinical data, and natural history of this tumor in these 104 patients. METHODS: Histologic slides (neurosurgical specimens and autopsy tissues) were available for 99 patients. The tumors were classified by the Working Formulation classification. Immunostaining data and all clinical data were retrieved from the relevant offices and hospital charts. RESULTS: Primary central nervous system non-Hodgkin's lymphoma tripled in frequency (5.66 cases per year in 1978-89 versus 1.75 cases per year in 1958-77) and now represents 6.6% of all primary brain neoplasms (versus 3.3% before 1978; chi 2 = 17.52, P < 0.01). For the 99 tumors histologically classified, 89% were high grade. Intermediate grade lymphomas, once the second most common subtype, have disappeared since 1983. All tumors had diffuse architecture; 77% (including all 11 patients with acquired immune deficiency syndrome) were large cell subtypes. Two cases were intravascular lymphoma. With one exception, all of the 41 tumors evaluated were B-cell types; 32 of 40 had monotypic surface immunoglobulin. There was 1 T-cell lymphoma. Of 64 tumor recurrences, 29 were at the initially defined site; 12 were in the leptomeninges, 29 were in other sites in the neuraxis, and 8 were in systemic sites. Systemic metastases have not occurred since 1984. Median survival for the 68 patients who survived after diagnostic surgery and for whom follow-up information could be obtained was 19 months; 9 months for those with high grade tumors and 30.5 months for those with intermediate grade tumors. This difference was not significant (P = 0.13). A separate set of seven patients had focal tumorlike lymphoid infiltrates composed of benign-appearing lymphocytes, which were associated with good long term survival. The differential histologic diagnosis of NHL-CNS was occasionally difficult, and the spectrum of this differential was broader than generally stated. CONCLUSIONS: Primary central nervous system non-Hodgkin's lymphoma has increased in frequency even in nonimunocompromised patient populations. This increase has been accompanied by the disappearance of intermediate grade histologic types, suggesting a fundamental shift in the biology of the neoplasms. The introduction of chemotherapeutic regimens appears to have altered the natural history such that systemic metastases outside the central nervous system no longer occur, and there are now some long term survivors of this formerly uniformly fatal disease.

Brain Neoplasms↗
PubMed1994

Phospholipase A2 inhibitors regulate the proliferation of normal uterine cells.

The effects of inhibitors of phospholipase A2, cyclooxygenase, lipoxygenase and cytochrome P450 activity on the proliferation of normal rat uterine stromal cells (UIII) were studied. At non-cytotoxic doses, inhibitors of cyclooxygenase, lipoxygenase and cytochrome P450 activity had no effect; UIII cells did not lose their ability to synthesize and secrete arachidonic acid metabolites, mainly prostaglandin I2 and prostaglandin E2, after successive passages. Inhibition of prostaglandin production did not affect their proliferation. In contrast, phospholipase A2 inhibitors significantly reduced UIII cell proliferation in a reversible and dose-dependent manner. Aristolochic acid was the most potent inhibitor with an IC50 of 0.3 mumol/l on day 7 of culture. Moreover, low doses of arachidonic acid stimulated UIII cell proliferation. Thus the proliferation of normal uterine stromal cells appears to be independent of arachidonic acid oxygenated metabolites, contrary to what is observed in tumor cells, but requires an intact phospholipase A2 pathway.

Animals↗
PubMed1994

Comparison of first-trimester transvaginal amniocentesis with chorionic villus sampling and mid-trimester amniocentesis.

Between August 1989 and December 1991, 356 patients underwent first-trimester transvaginal amniocentesis (10-12 weeks). The same number of patients referred in the same period for mid-trimester amniocentesis (14-21 weeks) was matched also for maternal age and indication. A third group consisted of the first 356 cases in which chorionic villus sampling (CVS) was attempted. The overall success rate was 99.7 and 100 per cent for early and mid-trimester amniocentesis, respectively, and 97.2 per cent for CVS. The mean harvesting time was 12.8, 11, and 7.9 days, respectively. The percentage of patients rescheduled was 3.4 per cent in first-trimester amniocentesis, 1.7 per cent in mid-trimester amniocentesis, and 6.2 per cent in the CVS group. The early (less than 2 weeks) pregnancy loss was 1.7 and 0.6 per cent in early and mid-trimester amniocentesis, respectively, and 1.7 per cent in CVS. The total pregnancy loss was 3.2, 0.9, and 2.9 per cent, respectively. The rate of preterm birth was 6.0, 5.2 and 6.9 per cent, respectively. The results indicate that CVS has the shortest procedure-result interval, but the highest rescheduling rate. First-trimester amniocentesis has a higher procedure and laboratory success rate but, until otherwise proved, mid-trimester amniocentesis is the most efficient and safest procedure.

Abortion, Spontaneous↗
PubMed1994

Discrimination of facial identity and facial affect by temporal and frontal lobectomy patients.

The purpose of this study was to determine the extent to which lobectomy affects ability to discriminate facial identity or facial expression. Fifteen right temporal, 15 left temporal, 5 right frontal, and 4 left frontal lobectomy patients, pair-matched for age, sex, and education to normal control subjects, participated in this study. Tasks included a Facial Identity Matching Task and a Facial Affect Matching task. The lobectomized patients as a whole were significantly impaired on both tasks (22% decrement in performance). The patients made twice as many errors resulting from perseveration of response-set of the first condition (identity or emotion matching) into the second condition. The site of lobectomy did not influence general performance on any one task or selective performance on any subset of affective categories. It was concluded that all four brain regions play a significant and equal role in face processing, and that circuits more specifically dedicated to visual face processing, which are responsible for hemispheric dominance affects and affect/identity dissociations, are probably located more posteriorly in the brain. Finally, it was concluded that perseveration of acquired habit may, under specific conditions, characterize temporal lobe dysfunction just as much as frontal lobe dysfunction.

Adult↗
PubMed1994

Life after birth: the influence of steroid hormones on cerebral structure and function is not fixed prenatally.

Bryden, McManus, and Bulman-Fleming conclude that available empirical evidence does not support the Geschwind-Behan-Galaburda model of cerebral lateralization. One of the central assumptions of the model is that fetal testosterone plays a determinant role in the development of anomalous specialization and is associated with various behavioral, cognitive, and immunological disorders. The influence of testosterone, however, is not limited to the perinatal period. We show that hormonal effects constitute lifelong influences on aspects of brain architecture and function. These influences represent a little-known and discussed--but extremely relevant--dimension of our understanding of the biological bases of behavior.

Animals↗
PubMed1994

Prostaglandin E2 production by uterine stromal cell line UIII: regulation by estradiol and evidence of an ethanol action.

We have recently established a uterine stromal cell line (UIII). The purpose of the present study was to determine whether these cells have retained the ability to produce and release prostaglandins after several passages and whether this production was regulated. UIII cells, grown in basal conditions, released a very low amount (40.6 +/- 2.9 pg/24h/10(6) cells) of prostaglandin E2 (PGE2) though cellular content was more elevated (192 +/- 23 pg/10(6) cells). Ethanol increased the cellular content but decreased the release of PGE2, whereas estradiol 17 beta (E2) increased it in a dose-dependent manner, but had no effect on the cellular content. The PGE2 release by cells grown in medium containing 10 microM arachidonate (AA) reached 1.39 +/- 0.05 ng/24h/10(6) cells, and was further increased to 2.1 +/- 0.1 ng/24 h/10(6) cells by the addition of ethanol. Under the latter condition, E2 was ineffective. This study also showed that UIII cells expressed an immunoreactive pancreatic type 14 kD PLA2. A substantial increased 14 kD PLA2 expression was observed in ethanol-treated cells, suggesting that ethanol-effect on prostaglandin production might be partly mediated by PLA2 increase. Medium supplementation with arachidonate also resulted in a significant increase of intracellular 14 kD PLA2 expression. The present results showed that uterine stromal UIII cells have retained the enzymatic machinery to produce PGE2. Moreover these data demonstrate that ethanol and E2 affect differently uterine PGE2 production.

Animals↗
PubMed1994

Free radicals induced peptide damage in the presence of transition metal ions: a plausible pathway for biological deleterious processes.

When aqueous N2O-saturated solutions containing glycine-N-tert-butylamide (L) and Cr2+ (aq) or Cu+ (aq) are irradiated, transients with metal-carbon sigma-bonds are formed with rate constants of (4.4 +/- 0.5) x 10(7) and (5.2 +/- 0.3) x 10(9) M-1 s-1, respectively. In the chromium(II) system, after a fast process (k = 43 +/- 4 s-1), possibly chelation, the transient decomposes very slowly (k = 0.003 +/- 0.001 h-1) via a beta-elimination process to yield 2-methylpropene and glycinamide, i.e., a cleavage of the peptide bond takes place. However, in the copper(I) system the heterolytic cleavage of the sigma-bond and the reaction of the transient complex with L-Cu2+ compete efficiently with the beta-elimination process. The latter reaction leads to some modification of the amide. We suggest that the formation and decomposition of transients with metal-carbon sigma-bonds may describe an additional pathway for peptide damage induced by aliphatic free radical precursors (e.g., OH., H2O2) in the presence of transition metal ions.

Chromium↗