PubMed Health⌕ Search

Biomedical subjects

D P Kessler

Publications and source records attributed to D P Kessler.

7 recordsLinked to original sources
PubMed1998

Extracting medical knowledge for a coded problem list vocabulary from the UMLS Knowledge Sources.

INTRODUCTION: The Unified Medical Language System (UMLS) Knowledge Sources embody a rich source of medical knowledge. We sought to extract a portion of this knowledge by incorporating information about relationships between UMLS concepts into an existing problem list vocabulary. METHODS: We matched terms from the coded problem list of The Medical Record (TMR), a computer-based patient record system, with those found in the UMLS Metathesaurus. Those UMLS concepts that participate in 'parent' relationships with the matched TMR concepts were translated back into TMR codes and the relationship information was retained for integration into the coded problem list of TMR. RESULTS: Of the coded problems currently in use in TMR, 67% (1627/2436) could be matched by normalized string matches to the UMLS Knowledge Sources. Of these matched TMR concepts, 91% (1488/1627) participated in at least one UMLS-identified parent relationship but only 28% of the matched concepts (454/1627) participated in parent relationships that already matched to a TMR code. As a result, although 67% of TMR codes were matched to UMLS concepts, only 19% of our original problem list (454/2436) could be augmented by relationship information contained in UMLS without improving the rate of matches or adding additional UMLS concepts as coded problems in TMR. CONCLUSION: This study illustrates the rapid decline in overall rates of matching that result from a multiplicative effect of successive matches of terms to concepts, concepts to relationships and concepts back to entry terms. This effect will hamper any effort to extract relationship knowledge from the UMLS for incorporation into an entry vocabulary that is not already one of the source vocabularies of the UMLS Metathesaurus.

Humans↗
PubMed1982

A reciprocating, single-needle hemodialyzer with bidirectional flow of sorbent suspension.

Previous theoretical analysis has indicated that adequate mass transfer is possible in a dialyzer with reciprocating membrane motion provided that the dialysate concentration of uremic substances is kept low. Earlier models have utilized a collection of sorbents (charcoal, urease, and a cation exchanger) constrained next to the dialyzer membranes. We have designed a new dialyzer with a sorbent suspension having free access from a reservoir to the spaces between membrane packages. At a treatment rate of 150 ml/min/m2, the in vitro creatinine clearance is 75 ml/min/m2, which agrees within experimental accuracy with the theoretical prediction. The creatinine clearance, flow resistance, and compliance of the dialyzer are constant during four to six hours of testing. In vivo tests have been performed during urea and creatinine infusion in a normal dog and in a dog with 3/4 nephrectomy. The in vivo creatinine clearance agrees within 10% with the in vitro clearance. Sodium, potassium, calcium, and bicarbonate fluxes are acceptable for patients in renal failure. The new design allows a higher capacity for urea and creatinine, since larger amounts of sorbent may be used.

Absorption↗
PubMed1976

Kinetic analysis of penicillin degradation in acidic media.

Degradation of penicillin in acidic media (pH 2.7) was monitored by high-pressure liquid chromatography and UV spectroscopy. The effects of temperature, buffer concentration, and ionic strength were examined. A degradation pathway is proposed, and the apparent first-order rate constant and energy of activation were calculated for each reaction. One or more degradation products containing a sulfhydryl group, a functional group often suggested as having a major role in eliciting allergic responses to penicillin therapy, were present throughout the degradation scheme.

Acids↗
PubMed1974

Genetic analysis of the leucine region in Escherichia coli B-r: gene-enzyme assignments.

Genetic mapping by transduction and conjugation using F(-) and F' strains carrying either point mutations in the l-arabinose or leucine regions or ara-leu fusion-deletion mutations has resulted in a detailed genetic map of the arabinose-leucine region of Escherichia coli B/r. These studies have identified four genes in the leucine region having the same order as found in Salmonella typhimurium: ara... leuDCBA.

Acyltransferases↗
PubMed1969

Cold-sensitive mutations in Salmonella typhimurium which affect ribosome synthesis.

A number of mutations (45) expressed as cold-sensitive conditional lethal pheno-types were screened by transduction for their linkage to the streptomycin-resistance locus; 7 showed such linkage. Of these, two were studied in greater detail. The sedimentation profiles of ribosomes from cultures grown at low temperature differed from wild type and from one another. Both mutants lost ribonucleic acid control at low temperature. It is suggested that a high proportion of mutants expressing a cold-sensitive phenotype harbor mutations in genes affecting ribosome synthesis or regulation.

Bacterial Proteins↗
PubMed1969

Arabinose-leucine deletion mutants of Escherichia coli B-r.

The control of ara gene expression was studied in mutants of Escherichia coli B/r containing deletions which fused the l-arabinose gene complex with the leucine operon (the normal gene order being araDABIOC...leuDCBAO). Complementation experiments with stable merodiploids showed that expression of ara genes cis to araC-leu deletions was controlled by the trans-acting product of the araC gene. Expression of ara genes cis to araB-leu deletions was under leucine control. These studies confirm the existence of a region between genes araC and araB essential for normal activator controlled expression of the ara structural genes. One deletion was characterized as an araO-leu deletion. Its effect on ara gene expression was unique in that ara genes were susceptible to potential regulation by both l-arabinose and leucine. These experiments suggest that two different species of messenger ribonucleic acid (mRNA) may be produced for the ara-leu region as a result of this deletion. One, under l-arabinose-activator control, is initiated in the l-arabinose region; the other, under leucine control, is initiated in the leucine region. The latter indicates that araI can be transcribed. Whether araI is transcribed in the former instance (mRNA made under activator control) remains to be established.

Arabinose↗