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Biomedical subjects

L Cohen

Publications and source records attributed to L Cohen.

At least 379 records · Page 21Linked to original sources
PubMed1987

Clinical clues to magnesium deficiency.

Two cases of congestive heart failure with coexistent magnesium and potassium depletion are described. The prolonged QTc intervals and ventricular premature beats of the first patient and the idionodal tachycardia of the second patient disappeared only after magnesium repletion, which normalized both extra- and intracellular potassium and magnesium levels. The third patient had a case of urosepsis while on total parenteral nutrition. He developed diarrhea, hypocalcemia, hypokalemia, hypomagnesemia, weakness, muscular fasciculations and athetoid movements. The neurological manifestations were relieved and the biochemical abnormalities normalized only after magnesium repletion.

Aged↗
PubMed1987

Evidence that uncharged verapamil inhibits myocardial contractility.

The object of this study was to determine the molecular species of verapamil (Vp) which is responsible for the negative inotropic activity of the drug. Toward this end, we developed a model system which allowed us to determine the concentrations of protonated and neutral Vp and four congeners in solution and bound to an amphiphilic interface. We then determined the effect of Vp and these congeners on twitch tension in sheep trabecular muscle and correlated species abundance with biologic activity. The cumulative log dose-response curves of Vp, acyano-Vp and nor-Vp were sigmoidal. The concentrations of drug which were required to inhibit twitch tension by 50% (IC50) were 1000 +/- 240, 3350 +/- 620 and 7140 +/- 950 nM, respectively (mean +/- S.D.; P less than .01). Quaternary-Vp, an amphiphilic, nonionizable protonated derivative, produced some nonspecific inhibition which never reached 50%. Tetrahydroxy-Vp, a hydrophilic ionizable derivative, was inactive. Concentrations of the membrane-bound, neutral form of Vp, acyano-Vp and nor-Vp were comparable at their IC50 values (86 +/- 19, 104 +/- 19 and 121 +/- 16 nM, respectively; mean +/- S.D.; P, N.S.). In contrast, the concentrations of the membrane-bound, protonated form were significantly different and accounted for the "apparent" difference in the IC50 values. Based on these data, we conclude that: 1) ionizability and amphiphilicity are required for the negative inotropic effects of verapamil, acyano-Vp and nor-Vp; 2) twitch tension correlates best with the concentration of the membrane-bound neutral form of each drug; and 3) the potency differences between Vp, acyano-Vp and nor-Vp, as reflected by their IC50 values, are apparent, not real.

Animals↗
PubMed1986

Ionization and surface properties of verapamil and several verapamil analogues.

We have investigated the ionization and surface properties of verapamil (5-[(3,4-dimethoxyphenethyl)methylamino]-2-(3, 4-dimethoxyphenyl)-2-isopropylvaleronitrile, 1) and several verapamil analogues since these properties appear to be involved in the biologic activities of these compounds. Our results show that verapamil and its analogues are surface-active and bind to amphiphilic surfaces. The affinity toward, as well as the capacity of, an amphiphilic surface for verapamil and its ionizable analogues is pH dependent, with the surface having both higher affinity and capacity for the neutral form of the molecules. Thus, verapamil exists as protonated and neutral forms, both of which are free in solution and adsorbed to the interface, and the ionization of verapamil at an interface changes with respect to its ionization in solution. From analyses of the pH dependency of surface binding and of solution and interfacial ionizations, we determined the values of the four equilibrium constants. These equilibrium constants permit correlative studies between the pH-dependent abundance of each species and biologic activity. We discuss preliminary studies which indicate that the negative inotropic effect of verapamil is mediated by the membrane-bound neutral form of the drug.

Absorption↗
PubMed1986

Fast neutron therapy for malignant astrocytomas. A review.

The treatment of supratentorial malignant gliomas has continued to be a major problem for neurosurgeons and oncologists. Post-operative conventional radiotherapy is known to prolong survival and to enhance the quality of life. Local persistence of tumor kills the majority of patients. Fast neutron irradiation is being utilized to treat malignant gliomas based on its reputed radiobiological advantages for treatment of large tumors and the encouraging preliminary reports showing tumor eradication in post-radiation biopsy and autopsy specimens. This paper reviews the results of fast neutron irradiation alone and in combination with photons and hypoxic cell sensitizers. Survival comparisons do not show any superiority for neutrons compared to conventional radiation. However, post-neutron radiation tissue samples have shown less aggressive and minimal residual tumor in many instances. At the same time radiation necrosis has emerged as a significant problem. In summary, even though neutron irradiation can eradicate malignant gliomas a therapeutic window has yet to be identified.

Astrocytoma↗
PubMed1986

Neurologic outcome in premature infants with transient asymptomatic hyperammonemia.

We studied the short-term and long-term effects of transient asymptomatic neonatal hyperammonemia on neurologic function in 21 preterm infants with normal ammonium levels and 25 with hyperammonemia (range 40 to 72 mumol/L) during the first weeks of life. The hyperammonemic infants were prospectively randomized to treatment with orally administered arginine free base 1 to 2 mmol/kg/day for 2 months (n = 13) or to a no-treatment control group (n = 12). Cortical function was assessed by auditory response and habituation during the first month of life. An auditory response was shown by 64% of the hyperammonemic infants and 43% of the normoammonemic infants (P not significant). Plasma ammonium levels at the time of examination bore no consistent relationship to whether an infant responded to an auditory stimulus. Number of trials to reach auditory habituation was also not different, and plasma ammonium level did not correlate with the presence or absence of habituation. IQ testing at 6, 12, 18, and 30 months showed no significant differences between groups. Early plasma ammonium levels did not have an effect on 30-month IQ scores. These findings suggest that transient asymptomatic hyperammonemia in premature infants is not associated with short-term or long-term neurologic deficits through 30 months of age. This study does not support the need for treatment of transient asymptomatic hyperammonemia in the premature infant.

Acoustic Stimulation↗
PubMed1986

Calculation of clinical r.b.e. values for neutrons.

A method is described for calculating r.b.e. values for normal tissues at risk in clinical neutron beam therapy. This is based on the assumption that with high l.e.t. radiations the slope of the cell survival curve is steeper, mainly in the initial or low-dose region. This effect is quantified by using two coefficients, one (epsilon) to produce a proportionate increase in the initial slope, and a second (eta) determining the change in the terminal slope (D0) of the survival curve. Analysis of published experimental data shows epsilon to be a variable quantity, different for different tissues; epsilon is larger when the survival curve has a large shoulder or slope ratio (rho). By contrast, eta is relatively constant (for a given beam) and less dependent on the tissue or end-point studied. For low doses, the r.b.e. approaches epsilon, which can be calculated given eta (characteristic of the beam) and rho (characteristic of the relevant tissue) [epsilon = eta + rho(eta - 1)]. This provides a useful approximation to the clinical r.b.e. for specific tissues relative to conventionally fractionated low-l.e.t. photons.

Cell Survival↗
PubMed1986

High density lipoprotein cholesterol: prognosis after myocardial infarction. The Israeli Ischemic Heart Disease Study.

In people without overt clinical coronary heart disease (CHD), reduced levels of high density lipoprotein cholesterol (HDLC) are a known predictor of a first myocardial infarction (MI), and of death from CHD. Less is known about the role of HDLC in the prognosis of patients with coronary heart disease. In 130 men with electrocardiographic evidence of myocardial infarction examined in the Israeli Ischemic Heart Disease Study in 1963, the relationship of HDLC to prognosis was examined. Approximately 60% (77 men) died between 1963 and 1978. Analysis of mortality by HDLC quartiles revealed the highest rate, 74%, in the bottom HDLC quartile (less than 30 mg/dl). Quartile analysis was also performed for HDLC as a per cent of total cholesterol (PHDL), known as a better predictor of CHD incidence. Mortality was as high as 81% in the bottom quartile (PHDL less than 13%), with a relative mortality risk of 1.71 for subjects in the bottom quartile compared to those in the top quartile (PHDL greater than or equal to 19%). Initial mean PHDL in patients surviving 15 years was significantly higher than in those dying during that time (17.8% versus 16.2%, p less than 0.05). Multivariate analysis, using the Cox proportional hazards model, indicated an association close to conventional statistical significance between HDLC and long-term mortality (p = 0.069). The results are comparable with those reported by the Coronary Drug Project Study. Further investigations of larger cohorts of CHD survivors are needed before firm conclusions about the role of HDLC and the potential for the use of HDLC affecting drugs or lifestyle changes can be drawn.

Adult↗
PubMed1986

Gastrointestinal endoscopy in octagenarians.

Seventy-five patients, 80-90 years old, each having approximately three associated diseases, underwent a total of 104 gastrointestinal endoscopies. Of these, 73 were upper (29 emergencies) and 31 lower endoscopies (21 were rigid sigmoidoscopies). There were two very mild short-lived complications; vomiting and bleeding. We found 16 gastric ulcers, 16 duodenal or pyloric ulcers, and 11 cases of esophagitis. Bleeding duodenal (8) or gastric (4) ulcers and polyps or malignant tumors (7) were seen less often. In 34 of 68 lesions the endoscopic and x-ray findings were the same. In the other 34 there were 10 endoscopic failures to identify colonic diverticula, hiatus hernia, and gastroesophageal reflux that were seen radiologically. In 24 patients, diagnoses were not made radiologically, but were recognized at endoscopy. The safety and accuracy of endoscopy in the old and sick does not differ from that in younger patients.

Aged↗
PubMed1986

Dental hygienists in nontraditional settings: practice and patient characteristics.

The dental hygienist's role in the treatment of special populations in nontraditional settings is an important one. Little is known about the hygienist's practice characteristics in these settings, nor about the patients receiving care. To gain needed information, a representative sample of the entire population of licensed hygienists in the United States was screened (n = 38,380). This screening identified 1,205 hygienists practicing in nontraditional settings. These hygienists were sent comprehensive questionnaires examining practice and patient characteristics. Completed questionnaires were returned by 1,016 (84.3%) hygienists. This report describes reported hygiene practice characteristics; hygienist interactions with patients and providers; and patient characteristics, including age, medical/emotional/social conditions, and dental treatment needs. Major findings of respondents' reports reveal that: approximately 90 percent of patients were in need of dental/dental hygiene services with approximately one in four requiring only dental hygiene services; the dental hygienists perceived a high level of acceptance of their role by patients and providers; the majority of patients treated were categorized as generally medically healthy (65.7%); and the clinical practice of dental hygiene in nontraditional settings mirrors that of private practice.

Adolescent↗
PubMed1986

Strains of Streptococcus mutans and Streptococcus sobrinus attach to different pellicle receptors.

We compared the levels of adsorption of Streptococcus mutans JBP and Streptococcus sobrinus 6715 to experimental pellicles formed from unsupplemented and glucosyltransferase (GTF)-supplemented saliva. Pellicles formed on hydroxyapatite beads from GTF or from saliva-GTF mixtures possessed detectable GTF activity. Low levels of GTF activity were also detected in clarified whole human saliva, but not in samples of submandibular saliva. The adsorptive behavior of S. mutans JBP to pellicles formed from saliva or saliva-GTF mixtures was strikingly different from that of S. sobrinus 6715. S. mutans JBP adsorbed in higher numbers to pellicles formed from whole or submandibular saliva than to buffer-treated hydroxyapatite under the assay conditions used, in which blocking with albumin was used. In contrast, S. sobrinus 6715 attached in lower numbers and did not show enhanced adsorption to pellicles prepared from saliva. Pellicles prepared from the high-molecular-weight mucin fraction of submandibular saliva effectively promoted adsorption of S. mutans JBP, but none of the saliva fractions tested enhanced the attachment of S. sobrinus 6715 above the levels of buffer controls. Exposure of pellicles which contained GTF to sucrose to permit in situ synthesis of glucan markedly enhanced attachment of S. sobrinus 6715 but not attachment of S. mutans JBP. Also, the presence of sucrose throughout the adsorption period did not enhance attachment of S. mutans JBP. Both organisms possessed cell-associated GTF, and GTF preparations derived from S. sobrinus 6715 and Streptococcus sanguis FC-1 behaved like GTF derived from S. mutans JBP. S. sobrinus 6715 attached in high numbers to dextran-treated hydroxyapatite, whereas S. mutans JBP did not. These observations suggest that S. mutans JBP cells possess an adhesin which binds to salivary components in the pellicles. In contrast, S. sobrinus 6715 cells appear to possess an adhesin which binds to glucan in the pellicles. Four additional strains of S. mutans and four additional strains of S. sobrinus behaved qualitatively like strains JBP and 6715, respectively, and thus the differences observed appear to be representative of these species. Collectively, our data indicate that S. mutans and S. sobrinus attach to different receptors in experimental pellicles.

Adhesiveness↗