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Biomedical subjects

L Stein

Publications and source records attributed to L Stein.

At least 127 records · Page 7Linked to original sources

Pitfalls in bedside diagnosis of severe acute mitral regurgitation. Clinical and hemodynamic features.

We describe five patients with severe acute mitral regurgitation in whom delay in diagnosis contributed to their fatal outcome. Either a soft systolic murmur was not heard or was misinterpreted, or hemodynamic confirmation by bedside right heart catheterization was unduly delayed. Pitfalls in recognition of hemodynamic patterns further postponed diagnosis and therapy. The diagnosis should be suspected when, in the proper setting, significant hemodynamic deterioration occurs, and is confirmed by bedside balloon flotation catheterization. Large V waves, characteristic of acute mitral regurgitation, may be overlooked unless one pays attention to the pulmonary artery systolic pressure tracing, which often has a triangular shape and may be double peaked; the V wave occurs later causing the second peak. Careful balloon inflation will demonstrate the large V waves. Timing with simultaneous ECG recordings allow this differentiation. Pulmonary hypertension with normal pulmonary vascular resistance is typical.

Acute Disease↗

Behavioral neurochemistry of benzodiazepines.

The therapeutic effects of benzodiazepines in psychoneurosis may depend in part on their ability to disinhibit a patient's anxiety-suppressed, gratification-seeking behavior. Benzodiazepines may disinhibit behavior by reducing the activity of serotonin (and possibly acetylcholine) neurons in the brain's "punishment" system. Reduction of serotonin transmission may be due to a facilitation of gamma-aminobutyric acid(GABA)-mediated presynaptic inhibition at the serotonin nerve terminal.

Animals↗

Single-dose pharmacokinetics of macrocrystalline nitrofurantoin formulations.

The pharmacokinetics of macrocrystalline formulations of nitrofurantoin (50 mg and 150 mg) were studied after single dose administration in 10 healthy male volunteers, using a cross-over study design. The total estimation of the pharmacokinetic data was calculated simultaneously from all of the single values, using a direct search procedure based on an open two-compartment-model (with additional 2 first-order input steps for one of the 150 mg formulations). Analysis showed that the relevant pharmacokinetic parameters for the formulations studied were in comparable ranges; however, the terminal elimination half-lives, 1.2 h and 1.7 h, were 3 to 4 times longer in comparison to those currently reported in the literature. The marked discrepancy in these findings is discussed and a review of the current data on the elimination kinetics of nitrofurantoin is recommended.

Adult↗

[Multiple-dose pharmacokinetics of paracetamol and salicylamide in man after combined rectal application (author's transl)].

The pharmacokinetic behaviour of paracetamol (300 mg) and salicylamide (200 mg) in the course of combined repetitive (three times tau = 4 h) administration of suppositories was investigated in 10 healthy, male volunteers. The estimation of the pharmacokinetic constants was performed by a simultaneous curve fitting from all single values with a direct search procedure, based on an open two-compartment model and the multiple-dose equation. Both drugs showed a pharmacokinetic behaviour which was conformable to the literature data for single dose and mono substance applications. The dynamics of the absorption kinetics was decreased, as is generally seen after the application of suppositories. In spite of this both substances reached a steady state after the 3rd application. A calculation of collapse coefficients showed for paracetamol as well as for salicylamide a pharmacokinetic distribution behaviour deviating from an open one-compartment model. Due to the good conformity of the parameters, which causes the synchronism of the time-concentration curves after multiple dose application, paracetamol and salicylamide are suited combination partners as seen from a pharmacokinetic point of view.

Acetaminophen↗

Approximate steady-state properties of lattices of interacting three-state enzyme molecules: a novel phase transition.

Previous work on the cooperative behavior of lattices of interacting two-state enzyme molecules at steady state is extended here to interacting three-state enzyme molecules with a one-way cycle. The Bragg-Williams (mean field) approximation is used. A phase-transition example with a bifurcation point is discussed. Compared to conventional phase transitions (with a van der Waals loop), several new and complicated features appear. A second paper on this subject will contain a number of other examples of three-state systems.

Enzymes↗

Brain endorphins: possible role in reward and memory formation.

A role for enkephalin in the mediation of behavioral reinforcement is supported by several lines of evidence: i) central injections of enkephalin serve as reinforcement for self-administration behavior, ii) electrical stimulation of many enkephalin-rich regions serves as reinforcement for self-stimulation behavior, which is blocked by moderate doses of naloxone, and iii) long-term retention of a passive avoidance response is facilitated by immediate post-learning injections of methionine-enkephalin and morphine.

Animals↗

Postoperative biopsy of the common bile duct via the T-tube tract.

We describe our experience with the first reported cases of postoperative common bile duct forceps biopsy via a postoperative T-tube tract. Bronchial forceps biopsies were performed on two patients with fixed postoperative filling defects in the common bile duct. Because of possible complications, caution is recommended in employing this technique. Common bile duct diagnostic brushing and stricture dilatation, as well as choledochoscopy, are envisaged as further diagnostic and therapeutic tools for the radiologist.

Aged↗

Pharmacology of lorazepam.

Lorazepam reduced conflict behavior in rats and monkeys, inhibited pentylenetetrazol- and electroshock-induced convulsions, suppressed footshock-induced fighting behavior, and prevented morphine-induced stimulation in mice at lower doses than other benzodiazepines tested. This behavioral profile suggests that lorazepam will be an active anti-anxiety agent in man at low doses.

Aggression↗

Possible role of dopamine-beta-hydroxylase in the regulation of norepinephrine biosynthesis in rat brain.

In Experiment 1, the dose-response effects of three dopamine-beta-hydroxylase (DBH) inhibitors (diethyldithiocarbamate, FLA-63 and U-14, 624) on the endogenous levels of norepinephrine and dopamine in pons-medulla of rat brain were determined. In Experiment 2, the effect of low doses of diethylithiocarbamate (2.5 to 120 mg/kg) on the level of norepinephrine-3H produced from dopamine-H3 was determined. The data obtained by extrapolation of the curves in both experiments provided an estimation of the in vivo level of DBH activity and suggested that it was not present in excess. Finally, in Experiment 3, the three DBH inhibitors reduced self-stimulation (a behavior dependent upon catecholamines) in a dose-related manner and intraventricular injections of 1-norepinephrine reinstated normal rates of self-stimulation. The results from the three experiments are consistent with the idea that DBH is involved in the regulation of norepinephrine biosynthesis. The relationship of this finding to our earlier report of a deficit of DBH in post-mortem brains of schizophrenics is discussed.

Animals↗

The psychiatrist's management of patients with undiagnosed brain neoplasm.

Of 679 patients with brain neoplasms admitted to either a medical school center or a community hospital during a nine-year period, 24 had been examined by a psychiatrist before definitive diagnosis of brain neoplasm. These 24 cases were studied to evaluate the role of the psychiatrist in the management of the patients before the neoplasm was diagnosed. Such cases pose many subtle problems for psychiatrists. However, ten of the 24 patients either were sent for definitive tests by the psychiatrist with the tentative diagnosis of brain neoplasm or were triaged to other consultants to pursue that diagnosis.

Adult↗

Benzodiazepines: behavioral and neurochemical mechanisms.

The therapeutic effects of benzodiazepines in psychoneurosis may depend in part on their ability to release or disinhibit a patient's anxiety-suppressed gratification-seeking behavior. Benzodiazepines may disinhibit behavior by reducing the activity of serotonin (and possibly acetylcholine) neurons in the brain's "punishment" system. Reduction of serotonin transmission may be due to a facilitation of gamma-aminobutyric acid (GABA)-mediated presynaptic inhibition at the serotonin nerve terminal.

Acetylcholine↗