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Biomedical subjects

R Keen

Publications and source records attributed to R Keen.

10 recordsLinked to original sources
PubMed1989

Effects of inhibition of fatty acid oxidation on myocardial kinetics of 11C-labeled palmitate.

The effects of glucose and lactate infusion on palmitate oxidation were compared with the effect of 2-tetradecylglycidic acid (TDGA), an irreversible inhibitor of the carnitine acyltransferase I, in normoxic canine myocardium. The initial capillary transit retention fraction of [1-11C]palmitate and its fractional distribution between oxidation and esterification in myocardium were measured by the residue detection method after intracoronary tracer injection, as well as by effluent measurements of 11CO2, the end product of palmitate oxidation. TDGA reduced the initial capillary transit retention fraction (from 56 +/- 13% to 37 +/- 6%; p less than 0.001) and oxidation of palmitate (n = 19), as also evidenced by the decrease in the fraction of tracer released as 11CO2 from 28 +/- 5% to 6 +/- 3% (p less than 0.001). Infusion of carbohydrate (glucose or lactate; n = 6) reduced 11CO2 production from 30 +/- 7% to 7 +/- 4% (p less than 0.05) but did not alter the initial capillary transit retention fraction of tracer (59 +/- 5% vs. 56 +/- 10%; NS). The latter was due to increased esterification into neutral lipids (41 +/- 11% of injected palmitate after carbohydrate infusion versus 21 +/- 12% in control conditions), as measured from multiexponential curve fittings. When carbohydrates were given after inhibition of palmitate oxidation by TDGA (n = 7), the 11C tissue clearance kinetics were strikingly similar to those observed after carbohydrate infusion alone. Thus, enhanced metabolic trapping of [1-11C]palmitate in myocardium resulted in initial capillary transit retention fractions that were not different from control conditions (41 +/- 5% vs. 48 +/- 12%; NS) despite inhibition of oxidation. The results show that the intracellular metabolism of palmitate contributes to the control of its uptake by myocardium. The findings are consistent with inhibition of palmitate oxidation by carbohydrates occurring at the same site as TDGA.

Animals↗
PubMed1989

A preliminary investigation of the pragmatic abilities of a group of language disordered children.

The communicative acts, conversational acts, and breakdown repair abilities of six language-disordered children with a syntactic age of +/- 3 years old as determined by the LARSP (Crystal, Fletcher, Garman: 1976) were investigated. Sampling of each subject involved two separate naturalistic interactions with a familiar adult and a language disordered peer. The data obtained from the transcriptions were analysed in terms of linguistic and nonlinguistic behaviours on the Communication Profile by Wollner and Geller (1982). Specific patterns of deficit and strengths were observed and these trends were related to recent literature in this area. The study emphasises that there is as much heterogeneity in the pragmatic skills as in the other communication skills of language disordered children, although this is due to some extent to the limitations of assessment in naturalistic settings. It also indicates individual areas of pragmatic deficit that require remediation.

Child, Preschool↗
PubMed1986

MRI simulator for instruction in pulse-sequence selection.

An ordinary desk-top microcomputer was programmed to simulate MR images for specified spin-echo pulse sequences. Model pixel maps of proton density and T1 and T2 relaxation times were made from published estimated values for regions of the human head, neck, and spine. Images were generated and displayed from the model maps and user-specified pulse-sequence parameters in less than 30 sec/image. Models for various pathologic conditions, including calcification, subacute hemorrhage, porencephaly, lipoma, and multiple sclerosis, were superimposed on the images of normal anatomy to create unknown cases. Simulated images can easily demonstrate the effect of pulse-sequence selection on the contrast of normal structures and pathologic conditions. Use of simulated images is an excellent technique for gaining experience in pulse-sequence selection. Low-cost microcomputers can provide adequate image detail and reasonable image display time of synthetic MR images for teaching purposes.

Computer-Assisted Instruction↗
PubMed1985

Retention and clearance of C-11 palmitic acid in ischemic and reperfused canine myocardium.

Free fatty acids are the major energy source for cardiac muscle. Oxidation of fatty acid decreases or even ceases during ischemia. Its recovery after transient ischemia remains largely unexplored. Using intracoronary carbon-11 palmitic acid as a tracer of myocardial fatty acid metabolism in an open chest dog model, retention and clearance of tracer in myocardium were evaluated at control, during ischemia and after reperfusion following a 20 minute occlusion of the left anterior descending coronary artery. Myocardial C-11 time-activity curves were analyzed with biexponential curve-fitting routines yielding fractional distribution and clearance half-times of C-11 palmitic acid in myocardial tissue. In animals with permanent occlusion and intracoronary injection of C-11 palmitic acid distal to the occlusion site, the relative size and half-time of the early clearance curve component differed markedly from control values and did not change with ongoing ischemia. Conversely, in animals with only 20 minutes of coronary occlusion, the relative size of the early C-11 clearance phase was still significantly depressed at 20 and 90 minutes of reperfusion but returned to control level at 180 minutes. Tissue C-11 clearance half-times remained significantly prolonged throughout the reperfusion period. Regional function in reperfused myocardium monitored with ultrasonic crystals recovered slowly and was still less than control after 3 hours of reperfusion. The data indicate that after transient ischemia, myocardial fatty acid metabolism fails to recover immediately. Because the metabolic recovery occurs in parallel with recovery of regional function, C-11 palmitic acid in conjunction with positron tomography may be useful for studying regional fatty acid metabolism noninvasively after an ischemic injury, and may be helpful in identifying reversible tissue injury.

Animals↗
PubMed1985

History and physical examination by oral and maxillofacial surgeons: the development of a physical assessment course.

Qualified oral surgeons may be granted hospital privileges to perform history and physical examinations on their patients as a result of a JCAH policy change, which became effective in January 1982. Oral surgeons must apply for and be granted this privilege from their affiliate hospitals and must demonstrate their qualifications. Various criteria can be used to assess qualification, including a review of the applicant's training in physical diagnosis in residency training, and participation in physical assessment continuing education programs. Review courses that feature hands-on practice are useful to oral surgeons interested in updating and refining their skills. Since the University of Illinois began offering a review course in 1981, 91 oral surgeons have completed the 2-day intensive review program. A follow-up survey of the participants indicates that the oral surgeons are applying for medical staff privileges. In a survey of 30 oral surgeons who participated in the course during 1982, 13 (43%) indicated that they had obtained the privilege to perform histories and physical examinations from their local hospitals.

Clinical Competence↗
PubMed1984

Colorimetric measurement of glycosylated protein in whole blood, red blood cells, plasma and dried blood.

A colorimetric method for the measurement of whole-blood glycosylation (WBG), glycosylated haemoglobin in red blood cells (GHb), glycosylated plasma protein (GPP) and dried-blood glycosylation (DBG) is described which is rapid, inexpensive and precise. GHb correlated well with HbA1 measured by cation-exchange chromatography and was also correlated with WBG, DBG and GPP. DBG, which showed good correlation with GHb, could be measured on several drops of blood dried on filter paper treated with glucose oxidase. Filter papers are posted to the laboratory prior to clinic visits, and by having the DBG result available more rational diabetic management is possible. For DBG, the intra- and inter-assay coefficient of variation at three levels is less than 6%. Reference values in non-diabetic children have been calculated and are compared with values obtained in 'good' clinical diabetic control and in 'fair' control. The filter-paper assay DBG method has a high degree of patient acceptance.

Blood Glucose↗