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Biomedical subjects

L A Davis

Publications and source records attributed to L A Davis.

At least 19 recordsLinked to original sources
PubMed2006

Postmortem diagnosis of preclinical and clinical scrapie in sheep by the detection of disease-associated PrP in their rectal mucosa.

Samples of tissue from the central nervous system (cns), the lymphoreticular system (lrs) and the rectal mucosa of a large number of scrapie-exposed sheep, with and without signs of clinical disease, were examined immunohistochemically for evidence of disease-associated prion protein (PrP(d)). The rectal mucosa has received almost no attention so far in scrapie diagnosis, despite its abundant rectoanal mucosa-associated lymphoid tissue, and its accessibility. The scrapie-confirmed cases included 244 with clinical disease, of which 237 (97.1 per cent) were positive in the rectal mucosa, and 121 apparently healthy sheep, of which 104 (86 per cent) were positive in the rectal mucosa. PrP(d) was detected in 86.4 to 91.5 per cent of the other lrs tissues of the healthy sheep examined and in 77.7 per cent of their cns tissues. The stage of infection, therefore, affected the probability of a positive result in the rectal mucosa, whereas the breed, PrP genotype, age and sex had little or no independent effect. Accumulations of PrP(d) were observed in the rectal mucosa and other lrs tissues of vrq/arr sheep with preclinical and clinical scrapie, albeit with a lower frequency and magnitude than in sheep of other PrP genotypes. Western immunoblotting analyses of samples of rectal mucosa gave the characteristic PrP glycoprofile, with a sensitivity similar to that of immunohistochemistry.

Animals↗
PubMed2002

Chronic opiate exposure in the male rat adversely affects fertility.

We examined whether morphine administration to adult male rats adversely affected pregnancy outcome after mating with drug-naive females and at what point in the complex series of steps leading to viable offspring it exerted its actions. The results indicate that chronic paternal morphine exposure markedly influenced fertility measures in a number of important ways. There was a pronounced increase in pseudopregnancies in females mated with males treated chronically with morphine (40%) when compared to controls (<6%), indicating that vaginal penetration occurred, but successful impregnation failed; only 33% of matings between drug-naive females and morphine-treated males resulted in pregnancies, as compared to 74.5% in controls. In addition, there were fewer implantation sites in gravid females mated with morphine-treated males than in controls. Taken together, these observations suggest that morphine-exposed male rats were apparently able to copulate, but there was a failure in successful impregnation of the females. These findings suggest a primary defect in either the quality of male sexual behavior or a complete failure of the fertilization or conception processes in females mated with morphine-exposed males. This potentially important effect of paternal morphine administration on conception and/or preimplementation loss of embryos has not been previously noted and deserves more systematic study.

Analgesics, Opioid↗
PubMed2001

Evaluation of a rapid western immunoblotting procedure for the diagnosis of bovine spongiform encephalopathy (BSE) in the UK.

Bovine brain tissue samples from 625 UK cattle, clinically suspected as bovine spongiform encephalopathy (BSE) cases, were used in a blind analysis to assess a rapid Western immunoblotting technique (Prionics Check; Prionics AG, Zurich), which detects bovine disease-specific protease-resistant prion protein (PrP(Sc)). By means of statutory histopathological examination, 599 of the 625 cattle were confirmed as BSE cases by the demonstration of spongiform encephalopathy, the remaining 26 being classified as negative. Duplicate samples from the same animals were also examined by electron microscopy for the presence of abnormal brain fibrils (scrapie-associated fibrils; SAFs). The Prionics technique showed a high sensitivity, particularly when compared with the fibril detection test; the detection rates were 99.3% and 92.0% respectively, with histopathology being used as the "gold standard". The false negative results by the Prionics test were possibly related to the sampling procedure. Analysis of 50 BSE-positive samples revealed similar glycoprofiles, the majority of PrP(Sc)isoforms being di-glycosylated protein. The Prionics test also detected PrP(Sc)in the four brain samples from the 26 histopathologically negative animals, apparently reducing the specificity of the test to 84.6%; however, confirmatory positive results in these samples were obtained by demonstrating SAF or by immunohistochemical examination, or both. It was concluded that the Prionics test detected PrP(Sc)in a small percentage (0.64%) of clinically suspected BSE cases showing no spongiform change. Since January 2000, the Prionics Western blot test has been introduced as one of the statutory tests for the diagnosis of clinically suspected BSE and scrapie cases in the UK.

Animals↗
PubMed2000

Nutritional status of patients with cystic fibrosis with meconium ileus: a comparison with patients without meconium ileus and diagnosed early through neonatal screening.

OBJECTIVE: This study was pursued as an extension of a randomized clinical investigation of neonatal screening for cystic fibrosis (CF). The objective was to determine if CF patients with meconium ileus (MI) were more likely to be malnourished compared with those without MI who were diagnosed during early infancy through neonatal screening. METHODOLOGY: Nutritional status was evaluated from early infancy to 13 years of age based on anthropometric, biochemical, and dietary assessments. RESULTS: MI patients (n = 32) were smaller at birth (3117 g compared with 3413 g) and were shorter (22nd percentile compared with 48th percentile) and thinner (24th percentile compared with 49th percentile) compared with non-MI early diagnosed patients (n = 50) up to 13 years of age. Poor growth was particularly evident in 26 MI patients who required surgery for MI (height and weight at the 20th percentile), whereas those treated without surgery (n = 6) showed better height (45th percentile) and weight (37th percentile). Abnormal essential fatty acid profiles were significantly more prevalent in MI compared with non-MI early-diagnosed patients before 3 years of age. Daily intakes of calorie (130% compared with 111% recommended dietary allowances) and protein (339% compared with 279% recommended dietary allowances) were higher but the percentage of fat (37% compared with 38%) and linoleic acid (4.5% compared with 4.7%) in the diet were similar between the two groups. CONCLUSIONS: These results demonstrated a clear association of MI with malnutrition in CF. The observed poor growth among our MI patients was not because of poor dietary intakes, but was related to surgical treatment for MI and poor essential fatty acid status. These findings present new challenges regarding the optimal medical treatment and nutritional intervention for CF patients with MI.

Case-Control Studies↗
PubMed1999

The reproducibility of scrapie-associated fibril and PrPSc detection methods after long-term cold storage of natural ovine scrapie-affected brain tissue.

A pool of grey matter (medulla/brain stem, cerebellum and frontal cerebral cortex) was prepared from the brains of 16 sheep with scrapie, diagnosed clinically and by the demonstration of spongiform encephalopathy. Aliquots from the pool of tissue were finely chopped or homogenized and stored at +4 degrees C or -70 degrees C, after undergoing one of several specific pre-treatments (storage with or without protease inhibitors or, alternatively, with or without the cryoprotectant, dimethyl sulphoxide). At intervals over a period of 2 years, the stored extracts were examined by electron microscopy for the presence of scrapie-associated fibrils (SAFs) and by Western immunoblotting for the disease-specific abnormal protein PrPSc. Throughout the 2-year period, SAFs and PrPSc were detected in the majority of all stored tissue extracts under all combinations of tissue preparation and pre-treatment. The combined detection rates for SAFs and PrPSc were 91% at +4 degrees C and 94% at -70 degrees C. There was no significant difference between the results obtained by the two detection methods and no specific combination of preparation method and pre-treatment was superior to any other. Storage of the samples at -70 degrees C appeared to give better results than storage at +4 degrees C, particularly with regard to fibril detection. For logistical reasons and ease of processing, and to avoid the effects of autolysis on recognizable brain regions, long-term storage at -70 degrees C, without any pre-treatment, would appear to be the method of choice.

Animals↗
PubMed1998

Precollege enrichment programs intended to increase the representation of minorities in medicine.

The authors reviewed the literature published from 1966 to 1996 to identify enrichment programs for underrepresented minority precollege students sponsored by medical schools and affiliated programs, finding 19 articles describing 27 programs. The authors categorized the reported programs according to the components they contained. Most programs contained more than one component type. Twenty-four programs had an academic enhancement component. Two thirds had a motivational component to encourage students to consider medical and other health careers. Two programs set up mentoring relationship between students and health professionals. There were four research apprenticeships and three academic partnerships between medical schools and local school districts. Twelve of the 27 programs were evaluated in the literature. Eight evaluations focused on identifying the numbers of students who continued their education into college and professional schools. Five programs reported participant satisfaction or identified other short-term outcomes such as gains on standardized tests. While the percentage of participants completing college and entering health care careers is impressive, the authors do not believe that the educational success of participants can be attributed to involvement in these programs. The authors recommend ways to improve the quality and interpretability of enrichment program evaluations. Evaluators should adopt common terminology for activities and outcomes. Participants' economic and educational disadvantages should be described. Programs' theoretical underpinnings should be identified and related to evaluation. Measures should include immediate effects as well as long-term outcomes. Where possible, data from comparison groups should be reported to support conclusions. Adequate funding needs to be available to design and complete reasonable evaluations.

Education, Medical↗
PubMed1998

Enrichment programs for undergraduate college students intended to increase the representation of minorities in medicine.

The authors reviewed the literature published from 1966 to 1996 to identify enrichment programs for underrepresented minority college students sponsored by medical schools and affiliated programs, finding 20 such programs. The programs reported in the literature underestimate the number and variety of programs known to exist by about two thirds. The authors categorized the reported programs according to the types of components they contained. Most programs contained more than one component type. Eighteen of the programs had an academic enrichment component. Thirteen programs included components focused on preparation for the admission process. Mentoring activities were a component of only four of the programs. Eighteen of the 20 programs were evaluated in the literature. The largest focus of evaluation activities was the success of program participants entering medical school. While the medical school matriculation rate was quite high, these results were difficult to interpret as the studies did not use control groups. The evaluations could not demonstrate, therefore, that the programs were responsible for increased admission of minorities to medical schools. Relatively few studies measured the immediate effects of the programs' efforts. Further, there was even less evidence of which program components in particular were effective. A more public and energetic discussion of these programs in the medical education literature is essential. In a political and social environment that calls for accountability, programs must be able to clearly and truthfully declare what they have accomplished. Without this type of public discussion, enrichment programs for underrepresented minorities may continue to appear to be worthwhile endeavors, but lacking solid support and foundation and vulnerable to losing funding.

Counseling↗
PubMed1997

Comparison of detergent and protease enzyme combinations for the detection of scrapie-associated fibrils from the central nervous system of sheep naturally affected with scrapie.

Standardized samples of tissue from the central nervous system of four sheep naturally affected with scrapie and from four healthy control sheep were subjected to a centrifugal extraction technique used to obtain scrapie-associated fibrils; the latter were then demonstrated by negative-contrast transmission electron microscopy. This regime was used to evaluate the fibril yield obtained from the 25 possible combinations of five different detergents and five different proteolytic enzymes. N-lauroylsarcosine detergent was found to be the most efficient detergent for all five enzymes, followed by sulphabetaine 3-14. Sodium dodecyl sulphate detergent was successful only in combination with a subtilisin Carlsberg enzyme. Octylglucoside and nonidet P40 detergents did not produce fibrils with any of the enzymes. Proteinase K was the least efficient of the five enzymes when used in combination with N-lauroylsarcosine; subtilisin Carlsberg, clostripain, pronase and trypsin enzymes all gave higher fibril yields. A combination of N-lauroylsarcosine detergent and subtilisin Carlsberg proteolytic enzyme gave the highest fibril yield.

Animals↗
PubMed1997

Nucleus 22 cochlear implantation results in postmeningitic deafness.

Cochlear implant surgery was performed on 13 patients with postmeningitic deafness (seven adults, six children). Two adults and two children (30.8%) had severe labyrinthitis ossificans requiring radical "drill-out." Five of 13 (38.5%) had some bone growth requiring partial drill-out, and four of 13 (30.8%) had normal insertion with no drill-out. Hearing results for patients with no bone growth were similar to nonmeningitic patients; three of four (75%) had open-set speech recognition. Performance of patients with total drill-out was poor; "auditory only" performance was limited to detection and pattern perception of speech, and no patients had open-set speech recognition. Results for patients with partial drill-out were similar to results in patients with no bone growth. Labyrinthitis ossificans not only presents surgical challenges to cochlear implantation but may also adversely affect hearing outcome.

Adolescent↗
PubMed1996

Factors predicting employment 1 year after traumatic spine fracture.

STUDY DESIGN: This prospective cohort study evaluates the employment status of 489 persons after traumatic spine fracture. OBJECTIVES: To determine the rate, type, and predictors of employment 1 year after traumatic spine fracture. SUMMARY OF BACKGROUND DATA: The limited existing literature regarding employment after spine fracture reports variable return-to-work rates, tends to be retrospective, and generally evaluates a limited number of predictor factors at a time. METHODS: Four hundred eighty-nine persons ranging in age from 15 to 64 years who had experienced a spine fracture were assessed by a single examiner at hospital discharge and 1 year postinjury. Employment status and type. discharge neural and functional status, pain level, demographics, injury level and severity, and early treatment details were evaluated. RESULTS: At 1 year postinjury, 54% of subjects were working. A higher percentage of the employed were working part time and for fewer weeks per year than preinjury. A higher percentage were working at unskilled clerical, sales, or service jobs than preinjury. The significant positive (+) and negative (-) predictors of employment were (from strongest to weakest); worked in year previous to injury (+); employed at time of injury (+); Worker's compensation Board coverage (-); spinal fracture surgery (+); high-level spine fracture (-); pain (-); Functional Independence Measure score (+); and days of stay in intensive care unit and spinal unit (-). CONCLUSIONS: For the first year after spinal fracture, unemployment is common. Those who do return to work are more likely to modify the amount and type of work they do and to have been employed preinjury.

Adolescent↗
PubMed1996

Preference for and performance with damped and undamped hearing aids by listeners with sensorineural hearing loss.

This study investigated the relationship between acoustic damping of hearing aid responses and listeners' speech discrimination and judgments of preference and sound quality. Eighteen subjects with essentially equivalent hearing impairments participated. Subjects' speech discrimination was evaluated for a male talker in quiet and in noise and for a female talker in the same conditions with hearing aids with 0 dB, -5 dB, and -10 dB of damping. Subjects also compared the damping levels using eight bipolar adjective pairs and provided judgments of overall preference. Measurements of the hearing aid responses were made in a 2-cm3 coupler and in the subjects' ears using probe microphone techniques. Smoothness of the responses was quantified using the Index of Response Irregularity (IRI) and the Frequency Response Smoothness Quantification Index (FReSQI). Subjects preferred the two damped hearing aid responses to the undamped. They also had better speech discrimination with damped hearing aid responses. The bipolar adjectives were of limited use in comparing hearing aids. A few questions about hearing aid sound quality and preference appear adequate for evaluating listeners' choice of hearing aids. Smoothness of the hearing aid responses in the test box was higher for the damped hearing aids than for the undamped. However, for real ear responses measured using a probe microphone, smoothness did not change as a function of damping level.

Acoustics↗
PubMed1996

Healthy People 2000 Goal 1.12: primary care physicians and exercise counseling.

The Healthy People 2000 Goal 1.12 was designed to increase to 50% the number of primary care physicians who regularly counsel their patients concerning the appropriate frequency, duration, type and intensity of exercise. To assess the overall progress in relation to this goal, a survey of 212 physicians was conducted in an eight county region of northern Mississippi. Fifty-nine physicians completed and returned the survey. The findings indicate that 90% of the physicians perceive exercise to be important and that they are discussing exercise with approximately 50% of their patients aged 40 and older. However, the average length of the counseling segment is two minutes or less. It is therefore probable that the appropriate frequency, duration, type and intensity of exercise may not be adequately discussed during physician-based exercise counseling.

Adult↗
PubMed1994

Acceptance of moderate drinking by alcohol treatment services in the United States.

This study was designed to survey the acceptance of moderate drinking as an outcome goal by alcohol treatment services in the United States. Of a sample of 330 randomly selected services, there were 312 potential respondents of whom 196 (63%) returned surveys that were usable. Three-quarters of respondents reported that nonabstinence was not an acceptable outcome goal for patients in their program; however, 17% of these respondents endorsed the statement that nonabstinence was acceptable for patients in other alcohol programs or for their own patients after discharge. Of the remaining one-quarter of respondents who found moderate drinking acceptable for their patients, 80% worked in outpatient programs and 70% reported moderate drinking as appropriate for only 1-25% of their clientele. Respondents endorsing moderate drinking rated the following factors as important when selecting outcome goals: severity of physiological dependence, drinking history, psychological dependence, previous treatment, criminal behavior and liver function test results.

Adolescent↗
PubMed1993

Pulmonary embolism: early recognition and management in the postanesthesia care unit.

Based on the content of this article, the reader should be able to (1) list patients who are at risk to develop pulmonary embolism; (2) identify measures to prevent pulmonary embolism; (3) list the signs and symptoms of pulmonary embolism; (4) identify diagnostic tests and pertinent findings for pulmonary embolism; (5) identify nursing priorities for a patient with pulmonary embolus; and (6) identify medical and surgical interventions to treat the patient with a pulmonary embolus.

Humans↗
PubMed1993

Electrical systems for improving locomotion after incomplete spinal cord injury: an assessment.

Simple systems for electrical stimulation (1-4 channels) with either surface, percutaneous, or implanted electrodes during locomotion were assessed in 10 subjects who had chronic, incomplete spinal cord injury (SCI). On average, the speed of locomotion was increased by 4 m/min independently of the subject's speed of locomotion without stimulation (0-50 m/min) while oxygen consumption was reduced somewhat. These simple systems can provide practical help, particularly for incomplete SCI subjects who can stand but are lacking or have very limited ability to walk. Further improvement in locomotion requires stabilization and reduction in the duration of the stance phase of locomotion.

Adult↗