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Biomedical subjects

D Fleisher

Publications and source records attributed to D Fleisher.

50 records · Page 3Linked to original sources
PubMed1986

A model for predicting performance on the NBME Part I examination.

Multiple regression analyses were employed to determine the relationships between achievement variables as predictors of the performance on Part I of the National Board of Medical Examiners examinations (NBME-I) of 366 medical students. The students' examination score averages in first- and second-year basic science courses were sequentially added to a composite Medical College Admission Test (MCAT) score to investigate the increases in prediction accuracy. Four prediction equations were cross validated on two subsequent medical school classes. While the multiple correlation between the predicted NBME-I score and the actual score significantly increased as first- and second-year course examination scores were added to the equations, the overall accuracy in predicting passing or failing did not substantially increase. The most useful equation employed a combination of the MCAT score and the first semester anatomy course examination score. The NBME-I predictions were given by letter to the 1984 and 1985 students approximately a year before they were to take the NBME-I examination so that students at risk of failure could undertake remedial study.

College Admission Test↗
PubMed1984

Physicochemical model for dose-dependent drug absorption.

A two-tank perfect-mixing tank model was used to stimulate GI absorption. The effect of drug parameters (pK alpha, solubility, and intrinsic wall permeability) and system parameters (pH profile, volume of intestinal contents, and intestinal flow rate) on drug absorption were studied by numerical data stimulation. When the dose did not exceed the solubility of the drug in the intestinal lumen, the fraction absorbed depended on the transit rate relative to the absorption rate and the pK alpha relative to the pH profile, but was independent of drug dose. Saturation of one or both tanks led to dose-dependent absorption. The model was used to simulate absorption of chlorothiazide. Good agreement between simulated and experimental data led to the conclusion that the physical characteristics of chlorothiazide, rather than a saturable transport mechanism at the intestinal wall, may be responsible for the dose-dependent absorption observed for this drug. The model was also used to simulate hydrochlorothiazide absorption. By applying the same system parameters used for chlorothiazide, the model simulation correctly predicted the dose proportionality of hydrochlorothiazide absorption. The lack of dose dependency in this case may be attributed to the higher solubility and pK alpha of hydrochlorothiazide compared with chlorothiazide.

Chemical Phenomena↗
PubMed1982

Management of the appendix in young patients with Crohn's disease.

Sixty-six young patients (average age, 17.2 years) underwent intestinal operations for Crohn's disease during a 14-year period at the UCLA Hospital. Nine had undergone previous appendectomy for suspected appendicitis, and in seven subsequent enteric fistulae and/or obstruction involving the cecum developed. None of the appendices were acutely inflamed. During the same period, a total of 125 children with Crohn's disease underwent medical or surgical care, and in none did acute appendicitis develop. Of the 66 patients under 22 years old who required intestinal resection, 60 had removal of the cecum. In a child with ileal Crohn's disease, rarely should a normal appendix be removed because of the high likelihood of complications and the low incidence of subsequent appendicitis.

Adolescent↗
PubMed1982

Intestinal absorption of amino acid derivatives: importance of the free alpha-amino group.

The intestinal absorption of L-lysine-p-nitroanilide, L-alanine-p-nitroanilide, and glycine-p-nitroanilide was studied in the presence of competitive inhibitors in a perfused rat intestine. It ws observed that L-lysine-p-nitroanilide absorption was inhibited by L-lysine methyl ester and L-arginine-beta-naphthylamide but not by N alpha-acetyl-L-lysine methyl esters. L-Alanine-p-nitroanilide absorption was inhibited by L-alinine methyl ester but not by beta-alanine methyl ester. It was further observed that N alpha-benzoyl-L-arginine-p-nitroanilide and N alpha-succinyl-L-phenylalanine-p-nitroanilide were poorly absorbed. It was concluded that the peptidase in the brush border region that serves as the hydrolysis site requires a free alpha-amino group (an aminopeptidase), and that passive absorption of these compounds occurs only to a small extent.

Amino Acids↗
PubMed1977

Diarrhea, red diapers, and child abuse: clinical alertness needed for recognition; clinical skill needed for success in management.

Three children were chronically given phenolphthalein in the form of laxatives by emotionally disturbed mothers. All children had repeated hospitalizations and extensive diagnostic testing because of recurrent intractable unexplained diarrhea. One child died. Pink-red urine and stool were passed at some time during their illnesses. The presence of phenolphthalein was tested for by application of dilute acid of dilute alkali to the diapers causing respectively disappearance of deepening of the pink-red color. Cases went undiagnosed for prolonged intervals because mothers seemed exemplary. Evidence of their psychiatric illnesses was found once the possibility was considered. Phenolphthalein poisoning should be tested for in any case of intractable diarrhea when objective evidence of intestinal mucosal damage cannot be found. The condition represents a heretofore unrecognized variant of child abuse of battering.

Cathartics↗
PubMedDate not supplied

Phenytoin interaction with enteral feedings administered through nasogastric tubes.

Inadequate drug plasma levels have been associated with the administration of phenytoin with enteral feedings through nasogastric (NG) tubes. It is demonstrated in this study that loss of phenytoin to tubing is a function of pH. Nonionized phenytoin is irreversibly bound to NG tubing from solution at the pH of enteral nutrient solutions while this is not the case for anionic phenytoin in unbuffered water or saline. In experiments pulsing phenytoin through glass vs NG tubing perfused with buffer at varying pH, reversible loss to tubing was observed at high pH while irreversible loss was observed at low pH. In addition, the irreversible loss of phenytoin was greater in NG tubing than glass particularly at low pH. It is suggested that in those cases where tubing is placed into the duodenum, inadequate gastrointestinal residence time for dissolution of phenytoin solid and suspension dosage forms coupled with irreversible drug loss from solution to NG tubing will result in decreased phenytoin absorption and subsequently lower drug plasma levels.

Animals↗