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Biomedical subjects

D L Harris

Publications and source records attributed to D L Harris.

At least 73 records · Page 4Linked to original sources
PubMed1991

The current and future need for minority medical faculty.

Little progress has been made in increasing the number of minority faculty members at US medical schools. From 1975 through 1989, underrepresented minority medical faculty increased only 0.3%--from 2.7% to 3.0%. In the field of medicine in general, only 3% of physicians are African-American and 3% are Hispanic, while the African-American and Hispanic populations are approximately 12% and 7%, respectively, of the total US population. A number of factors have caused the persistent underrepresentation of minority health professions trainees: inadequate or inappropriate career counseling, admissions policies, relatively high attrition rates after matriculation, substantial costs of education, and lack of appropriate mentors and role models. Helping minority students overcome these obstacles requires providing them with appropriate information, preparation, motivation, and opportunities at all stages of the educational process. Attention must focus on recruiting minority students into the scientific, academic professions if an increase is to occur in numbers of underrepresented minorities in all specialties of medicine. The Health Resources and Services Administration and private foundations have committed to providing funds to educational institutions to help encourage minority students to pursue academic careers. Leadership at these institutions must also commit to increasing the numbers of underrepresented minority faculty and senior administrators.

Ethnicity↗
PubMed1991

AIDS awareness among rural Utah physicians.

Studies of physicians' attitudes and knowledge of the acquired immunodeficiency syndrome (AIDS) and the clinical precautions they take against exposure to the human immunodeficiency virus (HIV) have focused on urban physicians. To determine rural physicians' knowledge and attitudes about AIDS, a questionnaire was mailed to 321 physicians practicing in rural Utah. Of the 169 physicians who completed questionnaires, 96% thought that their community or area of service had only a minor or no problem with AIDS; 89%, however, thought that their chance of seeing a patient who was HIV-positive was fair to moderate. Of the 169 respondents, 3% were not sure whether they would even treat a patient who had AIDS, 67% said they would, and 30% said they would not. Although all physicians are at risk of seeing a patient who has had exposure to HIV and other blood-borne diseases such as hepatitis B, only 55% of the respondents felt a need to take clinical precautions to prevent their exposure to the virus. Our study shows the need for all rural Utah physicians to reevaluate their risk of exposure to HIV, to increase precautionary measures for their own protection, to consider the ethical responsibility of treating AIDS patients, and to take a more active role in teaching their patients how to protect themselves from exposure to the virus.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Photophysics of tryptophan in bacteriophage T4 lysozymes.

Bacteriophage T4 lysozyme contains three tryptophan residues in distinct environments. Lysozymes with one or two of these residues replaced by tyrosine are used to characterize the photophysics of tryptophan in these individual sites. The fluorescence spectra, average lifetimes, and quantum yields of these three single-tryptophan variants are understandable in terms of the neighboring residues. The emission spectra and radiative lifetimes are found to be the same for all three species while the quantum yield and decay kinetics are quite distinct. The variation of the average nonradiative rate constant is correlated with neighboring quenching groups. Quenching by I- correlates with exposure of the tryptophan residue based on the crystal structure. Complex behavior is observed for the time dependence of the fluorescence decay in all three cases, including that of the immobile tryptophan-138 residue. The complexity of the fluorescence decay is ascribed to heterogeneity in the nonradiative rate constant among microstates. Energy transfer between tryptophan residues is inferred to occur from comparison of the quantum yields of the two-tryptophan and single-tryptophan proteins and is discussed in terms of the Förster mechanism.

Muramidase↗
PubMed1990

Outcome of pregnancies experienced during residency.

To investigate potential adverse effects of residency training on pregnancy outcome, a cohort study was conducted among 45 university-affiliated residency programs. Outcomes of the first pregnancy experienced during residency were compared between 92 female residents and 144 spouses of male residents. Despite long hours, sleep deprivation, and an increase in perceived stress, the female residents were as likely to give birth to a live, full-term newborn as the spouses of male residents. For white cohort members, an increased risk of premature labor without delivery was identified (RR = 12.3, 95% confidence interval 2.4-61.6). No significant differences were found in prematurity, spontaneous and therapeutic abortions, or presence of congenital abnormalities in the infants. Method of delivery and use of anesthetics and of other medications were similar in both groups. Pregnancy outcomes between the two groups were similar; however, the increased risk for premature labor among female residents is a cause for concern and should be further investigated.

Adult↗
PubMed1989

Synthetic site-directed ligands.

Complexes of nucleotides, peptides and aromatic hapten-like compounds with immunoglobulin fragments were studied by X-ray analysis. After tri- or hexanucleotides of deoxythymidylate were diffused into triclinic crystals of a Fab (BV04-01) with specificity for single-stranded DNA, extensive changes were detected throughout the structure of the protein. The Fab co-crystallized with a tri- or pentanucleotide in a different space group (monoclinic), an observation sometimes correlated with alterations in the structure of the 'native' protein. Structural analyses of the co-crystals are in progress for direct comparisons with the unliganded Fab. In crystals of a human (Mcg) Bence-Jones dimer, synthetic opioid peptides, chemotactic peptides or dinitrophenyl (DNP) derivatives could be diffused into a large conical binding cavity. The conformations of both the ligand and the protein were usually altered during the binding process. At the base of the cavity tyrosine residues could be displaced like trap-doors to permit entry of some opioid peptides and DNP compounds into a deep binding pocket. In co-crystals of the dimer and bis(DNP)lysine, two ligand molecules were bound in tandem, one in the main cavity and the second in the deep pocket. One ligand adopted an extended conformation, with the epsilon-DNP ring near the floor of the main cavity and the alpha-DNP group in solvent outside the binding site. There were no significant conformational changes in the protein. In contrast, the second ligand was very compact, with DNP rings immersed in the deep pocket, and the binding site was expanded to accommodate the oversized ligand. Peptides designed to be specific for the main cavity were incrementally constructed from minimal binding units by M. Geysen, G. Trippick, S. Rodda and their colleagues. A pentapeptide optimized for binding by this method was diffused into a crystal of the dimer and found by Fourier difference analysis to lodge exclusively in the main cavity as predicted. Binding regions in the BV04-01 Fab and the Mcg dimer were markedly different in size and shape. The Fab had a groove-type site, in which a layer of sidechains acted like a false floor over regions analogous to the cavity and deep pocket of the Bence-Jones dimer.

Antibodies, Monoclonal↗
PubMed1989

One-stage repair of hypospadias using split preputial flaps (Harris). The first 100 patients treated.

An analysis is presented of the outcome in the first 100 patients treated by a new technique for the repair of hypospadias and congenital short urethra associated with chordee. Further reconstructive surgery was required in 24 patients. The effect of the position of the meatus, the length of the reconstructed urethra and the method of urinary drainage are analysed. Minor complications are described. A significantly higher complication rate was associated with a perurethral than with a suprapubic catheter; 5 of the 38 patients in whom a suprapubic catheter was used developed complications requiring reconstructive surgery. Possible causes of the complications are discussed and the results compared with those of other methods. It was concluded that this is a satisfactory method of repair for hypospadias associated with chordee.

Adult↗
PubMed1989

Adapting best linear unbiased prediction (BLUP) for timely genetic evaluation: I. Progeny traits in a single contemporary group for each sex.

The first step of a procedure to partially circumvent the voluminous calculations with extremely large matrices for the usual algorithms for a BLUP (best linear unbiased prediction) approach is presented. This procedure, specific for a hierarchical portion of a model relevant to many animal breeding populations, is pertinent especially for polytocous species such as swine and poultry. For these, the occurrence of full-sib families makes the inclusion of dam effects in the model more necessary than in dairy or beef cattle models, where dam effects often are omitted. The formulas are derived for the hierarchical model for sires, dams within sires, individuals within full-sib family, and records within individuals, showing a relatively simple structure for such predictors. These formulas provide the basis for an alternative computing algorithm for obtaining evaluations having the statistical properties of best linear unbiased prediction. Formulas also are developed to approximate the prediction error variances for such models. Following this, the methodology for combining separate BLUP predictors, both error-independent and correlated, is developed.

Algorithms↗
PubMed1989

Adapting best linear unbiased prediction (BLUP) for timely genetic evaluation: II. Progeny traits in multiple contemporary groups within a herd.

The second step of a procedure to partially circumvent the voluminous calculations for some BLUP (Best Linear Unbiased Prediction) computing algorithms for genetic evaluation is presented. In addition, the procedure allows timely evaluations of each contemporary group. This procedure is pertinent especially for polytocous species such as swine and poultry, for which the occurrence of full-sib families makes the inclusion of dam effects in the model necessary and tests are completed throughout the year. Formulas are developed for a model including sires, dams, individuals within full-sib families and records within individuals. This model has a fundamentally hierarchical structure but includes some cross-classification. The formulas for predictors combine information across contemporary groups within a herd and incorporate relationships between sires and(or) dams in that herd. Formulas to approximate prediction error variances also are developed.

Algorithms↗
PubMed1989

Computer modeling of sheep reproduction: I. An algorithm for quantifying anestrous cycles in ewes.

An algorithm that mathematically describes annual estrous activity in ewes is given. The function fitted as the ordinate is similar to a normal distribution function related to date as the abscissa. The data used were collected from literature on different breeds and from different locations of the world; all studies had been specifically conducted to study estrous activity in ewes in these locations. Parameters estimated in an iterative procedure from the algorithm were length of time during which estrous cycles occurred (SA), a measure of asymmetry (SD), day of mid-estrous (DE), highest incidence of estrus (MX) and lowest incidence of estrus (MN), day of lowest incidence of estrus (DN) and day of mid-anestrous season (DA). Incidence of estrus is defined as the proportion of ewes exhibiting an active estrus. These parameters were estimated for several breeds and locations. The data, as collected, were inadequately cross-classified to allow for unconfounded estimation. However, analyses of fitted parameters that describe the curves gave quantitative results about the influences of breed of sheep, location, latitude and altitude and indicated which parameters were associated with these factors. Breeds differed significantly for SA, DE, MX and DA. Locations differed for DE, MX and DA. Latitude was associated with differences in DE, DN and DA with altitude also associated with differences in DE and DA. There were no significant effects on SD even though breeds differed sizably in SD.

Algorithms↗
PubMed1989

Computer modeling of sheep reproduction: II. Accelerated reproduction in sheep.

A computer simulation program was written in SLAM (Simulation Language for Alternative Modeling) to simulate certain biological aspects involved in alternative systems of reproduction in sheep. Four fundamental lambing schemes, once a year, three times in 2 yr, twice a year and continuous schemes, along with modifications of these schemes, are simulated. Parameters of greatest effect in this simulation were the average spread of the estrous season (SA), the measure of asymmetry (SD) and the maximum proportion of ewes exhibiting estrus (MX). It was demonstrated that the greater the SA values (longer estrous seasons and shorter anestrous seasons), the more advantageous it was to breed frequently. The SD and MX parameters influenced to a lesser degree the lambing results obtained from these simulations. The relative merits of certain breeds and locations for out-of-season breeding were studied and evaluated for annual and seasonal fertility.

Algorithms↗
PubMed1989

Cosmetic surgery.

The psychotherapeutic nature of cosmetic surgery is emphasised by outlining the range of symptoms from which patients suffer and by explaining the sequence of psychological reactions which cause them. The principles which govern the selection of patients are defined. A brief account of each of the main cosmetic operations is given together with notes on their limitations and risks.

Abdomen↗
PubMed1988

Female residents not at increased risk for adverse pregnancy outcome.

A cohort study was conducted among 45 university-affiliated residency programs to investigate potential adverse effects of residency training on pregnancy outcome. Pregnancy outcomes between female residents and spouses of male residents were similar; however, the increased risk for premature labor among female residents is a cause for concern and should be further investigated.

Adult↗
PubMed1987

A mild method for the preparation of disulfide-linked hybrids of immunoglobulin light chains.

A method is described for the hybridization of immunoglobulin light chains (Bence-Jones proteins) from different patients. The interchain half-cystine residues in the light chains from one subject are converted into mixed disulfides with 2,2'-dithiodipyridine. In the Bence-Jones dimer from a second patient the interchain disulfide bond is reduced with dithiothreitol. A covalently linked hybrid molecule is produced by the reaction of the mixed disulfide with the reduced thiol. In favorable cases the mild treatment yields heterodimers which can be crystallized for X-ray diffraction studies. The procedure can also be employed for converting a monomer into a covalent dimer. The engineered dimer of one kappa chain (Jen) crystallizes in the same space group as an aggregate of monomers, but the unit cell is only one-third as large.

Bence Jones Protein↗
PubMed1987

House calls in Utah.

To learn the criteria Utah physicians use in making or not making house calls and their specialty, age and frequency of calls, a random sample of half of Utah's physicians in family practice, general practice and general medicine was surveyed. Of 225 respondents, 70% reported making house calls at an average rate of 2.6 per month. More family practitioners made house calls than did internists; older physicians made more house calls than their younger counterparts. An estimated 82% of the calls were for patients aged 65 years and older. The most frequently stated reasons for making house calls were that patients were homebound and to assess the family or home situation. Reasons given for not making house calls were inefficient use of time and lack of equipment or necessary facilities.

Adult↗
PubMed1987

Family medicine's place in predoctoral medical education: a survey of US medical school deans and department chairmen.

Family medicine faculty at medical schools throughout the United States have stated that their specialty should be recognized as a required part of the predoctoral medical curriculum. Other medical faculty members have expressed disagreement. Support for family medicine as an integral part of medical education can be found in several sources, among them the Flexner Report and the Report of the Panel on the General Professional Education of the Physician (GPEP). A survey of deans of US medical schools and department chairs of family medicine at the same schools highlights the divergent views of the place of family medicine in predoctoral medical education. Family medicine faculty must argue convincingly that medical education should not be limited to an information transfer process before they will succeed in having family medicine recognized as a required part of medical education throughout the country.

Curriculum↗
PubMed1986

Autoclaved liquid medium for propagation of Treponema hyodysenteriae.

Three liquid media that differ slightly in composition but not in the method of preparation were developed for the propagation of Treponema hyodysenteriae and Treponema innocens. The three media are unique in that all components are sterilized by autoclaving before use. These media supported better growth of T. hyodysenteriae than did previously used liquid media.

Animals↗