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Biomedical subjects

B Davis

Publications and source records attributed to B Davis.

At least 109 records · Page 6Linked to original sources
PubMed1997

A computer-interfaced vertometer system for contact lenses.

BACKGROUND: The conventional vertometer (lensometer) is difficult to use for accurate measurement of contact lenses whose back vertex power (BVP) varies across the optic zone. BVPs of multifocal rigid and soft contact lenses have previously been measured using a conventional vertometer incorporating the Scheiner principle, which makes use of two light paths equidistant from the center of the lens. METHODS: We have developed a computer-based vertometer system based on the Scheiner principle which can be used to produce a profile of BVPs across rigid and soft contact lenses. A computer interface to the vertometer allows rapid acquisition of readings and software-based ray tracing derives in-air dioptric power readings across the optic zone at specific ray heights. RESULTS: Results are presented for soft and rigid, and spherical and aspheric surface contact lenses. CONCLUSIONS: The system improves the measurement resolution of a standard vertometer and shows an acceptable level of precision and accuracy for most applications.

Contact Lenses↗
PubMed1997

Differences between chest pain observation service patients and admitted "rule-out myocardial infarction" patients.

OBJECTIVE: To compare and contrast the patient characteristics of ED patients at low risk for acute cardiac ischemia who were assigned to a chest pain observation service vs those admitted to a monitored inpatient bed for "rule-out acute myocardial infarction" (R/O MI). METHODS: This was a retrospective, cross-sectional comparison of adult patients considered at relatively low risk for cardiac ischemia and who were evaluated in 1 of 2 settings: a short-term observation service and an inpatient monitored bed. All patients had an ED final diagnosis of "chest pain," "R/O MI," or "unstable angina" during the 7-month study period. Demographic features and presenting clinical features were examined as a function of site of patient evaluation. RESULTS: Of 531 study patients, 265 (50%) were assigned to the observation service. Younger age (OR = 1.75, 95% CI 1.26, 2.44, for each decrement of 20 years), the complaint of "chest pain" (OR = 2.35, 95% CI 1.34, 4.12), and the absence of prior known coronary artery disease (OR = 1.64, 95% CI 1.13, 2.38) were the principal independent factors associated with assignment to a chest pain observation service bed. CONCLUSIONS: Patients evaluated in a chest pain observation service appear to have different clinical characteristics than other individuals admitted to a monitored inpatient bed for "R/O MI." Investigators should address differences in clinical characteristics when making outcome comparisons between these 2 patient groups.

Adult↗
PubMed1997

Prospective study of equine colic incidence and mortality.

A prospective study of one year was conducted on 31 horse farms to obtain population based estimates of incidence, morbidity and mortality rates of equine colic. Farms with greater than 20 horses were enrolled by randomly selecting horse owners from 2 adjacent counties of Virginia and Maryland. Descriptive information for 1427 horses was collected at the initiation of the study and updated at 3 month intervals. Time on the farm during the study was tabulated for each horse. When colic was reported by the owner, investigators visited the farm to obtain information about the colic. The crude incidence density rate of colic was 10.6 colic cases/100 horse-years, based on 104 cases/358,991 horse-days. The median farm specific incidence density rate was 7 cases/100 horse-years, and the range for individual farms varied from 0 to 30 colic cases/100 horse-years. A specific diagnosis was not made for 84 (81%) of colic episodes. Seventy colic episodes (67%) were treated by a veterinarian. Drugs were used in 83 (80%) colic episodes, and 78 (75%) of colic cases were mild, requiring no treatment or resolving after only one treatment. Four horses required colic surgery. Fourteen (13%) horses had more than one episode of colic during the year. Mortality from all causes of death was 2.5 deaths/100 horse-years, mortality rate for colic was 0.7 deaths/100 horse-years. Proportional mortality rate of colic, 28%, was higher than for any other cause of death. Horses less than age 2 years or greater than age 10 years had lower incidence than horses age 2-10 years. No difference in colic risk between genders was identified. Arabian horses had the lowest and Thoroughbreds the highest breed specific incidence rates. Horses used for eventing, or in training had a statistically significant higher incidence rate of colic compared to mature horses with no use (pets, retired, on pasture with no stated purpose). Horses used for lessons or with no use had the lowest incidence rates.

Age Factors↗
PubMed1997

Prospective study of equine colic risk factors.

A 1 year prospective study was conducted on 31 horse farms to identify risk factors for equine colic. Farms were randomly selected from a list from 2 adjacent counties of Virginia and Maryland, USA. The association between colic and farm or individual horse risk factors related to management, housing, pasture, use, nutrition, health and events was first examined by univariate statistical analysis. Individually significant (P < = 0.25 for farm factors, P < = 0.10 for horse factors) variables were used in a stepwise multivariable forward logistic regression to select explanatory factors (P < = 0.05). Analysis was conducted at 2 levels: farm and individual horse with farm specified as a random effects variable. No farm-level variables were significant. Significant horse-level variables included: age, odds ratio (OR) = 2.8 for horses age 2-10 years compared to < 2 years; history of previous colic, OR = 3.6 relative to no colic; changes in concentrate feeding during the year (1 per year, OR = 3.6, more than 1, OR = 2.2) relative to no changes; more than 1 change in hay feeding during the year, OR = 2.1 relative to no changes; feeding high levels of concentrate (> 2.5 kg/day dry matter, OR = 4.8, > 5 kg/day dry matter, OR = 6.3) relative to feeding no concentrate; and vaccination with monocytic ehrlichiosis vaccine during the study, OR = 2.0 relative to no vaccination. Feeding a whole grain with or without other concentrate components reduced risk, OR = 0.4, relative to feeding no whole grain. Results of the study suggest that diet and changes in diet are important risks for colic in a population of horses on farms.

Analysis of Variance↗
PubMed1997

Effect of practice guidelines on therapeutic bed use.

Therapeutic beds, though clinically beneficial, can prove to be costly if their use is not directed. In this research utilization project, the use of therapeutic beds in five patient care units and one intensive care unit in a 300-bed acute care hospital were evaluated before and after the implementation of practice guidelines. Usage time and cost for each patient were measured and compared over the same four-month period in 1994 and 1995. Our findings indicated there were no significant differences between the two groups with regard to the time patients spent on therapeutic beds and the total cost of these beds. The mean time on the bed and the mean cost per patient were, however, lower for the practice guideline group. It was concluded that even without demonstrating significant differences, practice guidelines are a useful tool in providing a standard for nursing practice when caring for patients in the acute care setting.

Beds↗
PubMed1996

Determination of benzidine, N-acetylbenzidine, and N,N'-diacetylbenzidine in human urine by capillary gas chromatography/negative ion chemical ionization mass spectrometry.

We report an isotope dilution mass spectrometry method using capillary gas chromatography/negative ion chemical ionization to quantitate urine concentrations of benzidine (BZ) and of its acetylated metabolites N-acetylbenzidine (ABZ) and N,N'-diacetylbenzidine (DABZ). Urine samples were purified by solid-phase extraction columns, reduced with LiAlH4/THF, and derivatized with pentafluoropropionic anhydride. The derivatives were measured by selected ion monitoring relative to deuterium-labeled internal standards. A detection limit as low as 0.5, 0.8, and 1.5 ppt for BZ, ABZ, and DABZ, respectively, can easily be achieved. Urinary concentrations of ABZ substantially exceed those of either BZ or of DABZ in workers exposed to BZ or BZ-based dyes. This method has been successfully used to measure BZ, ABZ, and DABZ in 1.0-ml urine samples collected from workers involved in manufacturing BZ and BZ-based dyes. The method should be applicable to the measurement of other aromatic amines and their acetylated metabolites.

Benzidines↗
PubMed1996

Hematopoietic transcriptional regulation by the myeloid zinc finger gene, MZF-1.

Transcriptional regulators control much of hematopoiesis. One such transcriptional regulator is the myeloid zinc finger gene MZF-1. MZF-1 has been localized to the telomere of chromosome 19q, where a large number of related zinc finger genes reside. It has been found to be essential in granulopoiesis. It is a bi-functional transcriptional regulator, repressing transcription in non-hematopoietic cells, and activating transcription in cells of hematopoietic origins. Its consensus DNA binding site has been isolated, and sites in several promoters of myeloid-specific genes, such as CD34, lactoferrin, and myeloperoxidase, have been defined. In co-transfection experiments MZF-1 has been found to regulate transcription from the CD34 promoter.

Base Sequence↗
PubMed1996

The association among gastric mucosal pH, endotoxemia, and low systemic vascular resistance after cardiopulmonary bypass.

OBJECTIVE: Previously, it was found that a number of patients suffer a "low systemic vascular resistance syndrome" after cardiopulmonary bypass, and this was hypothesized to be secondary to endotoxemia, resulting from intestinal ischemia during bypass. DESIGN: Prospective cohort. SETTING: University teaching hospital. PARTICIPANTS: Thirty-two patients undergoing cardiac surgery. INTERVENTIONS: A number of variables relating to adequacy of tissue perfusion were measured at seven time periods perioperatively: cardiac output, systemic vascular resistance, oxygen delivery and consumption, oxygen extraction ratio, gastric mucosal pH, serum lactate, and endotoxin levels. MEASUREMENTS AND MAIN RESULTS: Investigators could not find any association between systemic vascular resistance and mucosal pH or endotoxin levels after bypass. There were significant changes in oxygen flux and extraction ratio (p < 0.001) as well as serum lactate (p < 0.001). There was no significant change in endotoxin levels or mucosal pH. The systemic vascular resistance at 6 hours postbypass could be predicted from the vascular resistance reading at 1 hour postbypass by a regression equation. A significant correlation between systemic vascular resistance and mixed venous oxygen was found at 4 and 6 hours postbypass (p < 0.01) as well as with oxygen extraction (p < 0.01). There was a negative correlation between mucosal pH and serum lactate, particularly at 6 hours postbypass (p < 0.01). There was no correlation between mucosal pH and endotoxin levels, oxygen flux, or cardiac output. CONCLUSIONS: The investigators therefore could not find any evidence that intestinal ischemia during bypass, as measured by gastric mucosal pH, predisposes to endotoxemia, or low systemic vascular resistance after cardiac surgery.

Adult↗
PubMed1996

Towards the complete structural characterization of a protein folding pathway: the structures of the denatured, transition and native states for the association/folding of two complementary fragments of cleaved chymotrypsin inhibitor 2. Direct evidence for a nucleation-condensation mechanism.

BACKGROUND: Single-module proteins, such as chymotrypsin inhibitor 2 (CI2), fold as a single cooperative unit. To solve its folding pathway, we must characterize, under conditions that favour folding, its denatured state, its transition state, and its final folded structure. To obtain a "denatured state' that can readily be thus characterized, we have used a trick of cleaving CI2 into two complementary fragments that associate and fold in a similar way to intact protein. RESULTS: Fragment CI2(1-40)-which contains the sequence of the single alpha-helix, spanning residues 12-24-and CI2(41-64), and mutants thereof, were analyzed by NMR spectroscopy, the transition state for association/folding was characterized by the protein engineering method, and the structure of the complex was solved by NMR and X-ray crystallography. Both isolated fragments are largely disordered. The transition state for association/folding is structured around a nucleus of a nearly fully formed alpha-helix, as is the transition state for the folding of intact CI2, from residues Ser12 to Leu21, Ala16, a residue from the helix whose sidechain is buried in the hydrophobic core, makes interactions with Leu49 and Ile57 in the other fragment. Ala16 makes its full interaction energy in the transition state for the association/folding reaction, just as found during the folding of the intact protein. CONCLUSIONS: The specific contacts in the transition state from a nucleus that extends from one fragment to the next, but the nucleus is only "flickeringly' present in the denatured state. This is direct evidence for the nucleation-condensation mechanism in which the nucleus is only weakly formed in the ground state and develops in the transition state. The low conformational preferences in the denatured state are not enough to induce significant local secondary structure, but are reinforced by tertiary interactions during the rapid condensation around the nucleus.

Amino Acid Sequence↗
PubMed1996

A novel hypothalamic peptide, pituitary adenylate cyclase-activating peptide, regulates the function of rat granulosa cells in vitro.

Pituitary adenylate cyclase-activating peptide (PACAP) is a novel peptide that was isolated from ovine hypothalamic tissue on the basis of its ability to stimulate cAMP accumulation in cultured rat pituitary cells. Recently we demonstrated that PACAP can stimulate cAMP accumulation and secretory function in cultured rat Sertoli cells. Since ovarian granulosa cells share many properties with Sertoli cells, we have examined the effect of PACAP (consisting of 38 or 27 amino acid residues) on cultured granulosa cell function. Granulosa cells were obtained from the ovaries of 25-day-old rats implanted with a silastic capsule containing diethylstilbestrol 5 days prior to culture. PACAP 38 (0.1 microM-0.01 pM), both alone and in the presence of the phosphodiesterase inhibitor, methylisobutylxanthine, stimulated cAMP accumulation 4-8-fold with an ED50 of approximately 100 pM. Maximal PACAP 38 or PACAP 27 stimulation of granulosa cell cAMP was significantly greater than that produced by a maximally effective concentration of FSH. Because PACAP 38 and 27 have 68% sequence homology with vasoactive intestinal peptide (VIP), and since VIP stimulates granulosa cell cAMP accumulation and estradiol and progesterone secretion, we examined the possibility that PACAP could be acting via the VIP receptor. VIP stimulated cAMP only at concentrations of 10 nM or greater, whereas the PACAP stimulation was evident at 10 pM. Moreover, only one of three potent VIP antagonists inhibited VIP stimulation of cAMP accumulation, and only at 1 microM or greater. This VIP antagonist did not inhibit PACAP 38 action at 2000-fold excess concentration. Interestingly PACAP 38 was more effective than PACAP 27 with regard to steroid secretion and the ability to induce LH responsiveness. PACAP and VIP stimulation of granulosa cell cAMP accumulation or estradiol or progesterone secretion was not additive. Thus, these data support the hypothesis that granulosa cells have specific PACAP 38 receptors and that VIP acts via these receptors. In addition, PACAPs 38 and 27 are more potent stimulators of cAMP accumulation in luteinized granulosa cells than LH. These results both pre- and postovulation, along with previous data indicating that the PACAPs are found in the ovaries, suggest a role for PACAP in the regulation of ovarian function.

1-Methyl-3-isobutylxanthine↗
PubMed1996

Illness experiences and health recovery behaviors of patients in southern Appalachia.

The purpose of this exploratory study was to gain a better understanding of the influences of Appalachian culture and rural living on illness experiences and health recovery behaviors. The study sample consisted of 257 randomly selected adult patients admitted to medical-surgical units in eight hospitals in West Virginia. Patients completed interviews in the hospital and by phone and in their homes 1 month after hospital discharge. In addition, 203 nurses and 79 physicians completed a values survey and decisional control questions. The triangulation of quantitative and qualitative data suggested that culture, age, gender, and rural residence affected responses to illness and recovery. Traditional values and roles persisted in this population and influenced health behaviors. The findings of this study support the need for culturally sensitive care and for innovative education programs to reduce health risks.

Adaptation, Psychological↗
PubMed1996

Restructuring dermatology education at Cleveland medical centers affiliated with Case Western Reserve University.

We describe our response to the changing needs for dermatologic education and training at Cleveland medical centers affiliated with Case Western Reserve University School of Medicine (CWRU) located in Cleveland, Ohio. Our departmental plan for change is a multifaceted approach that alters the number of dermatology residents we train and also the way we interact with and educate our generalist colleagues. Like many other dermatologists, we have both idealistic and practical reasons for increasing our involvement in interdisciplinary education. One of our primary objectives is maximizing quality of care for dermatologic patients in our community. Traditionally, the majority of skin care in the United States has been provided by nondermatologists, and with the growth of managed care, this proportion is increasing. This has motivated us to increase our medical student teaching activities and to support the American Academy of Dermatology in its current efforts to develop a dermatology core curriculum for students. We should also be involved in the education of generalist physicians, since prior studies have suggested that their knowledge of dermatology needs improvement. Our goals should be both to improve the direct patient care skills of primary care physicians and to teach clinically appropriate referral thresholds. The American Academy of Dermatology has recently issued guidelines for the referral of dermatology patients in managed care settings to help ensure that our specialty has input into this process. In addition, teaching gatekeeper physicians to use appropriate referral criteria is important to many dermatologists in capitated managed care systems who often prefer limited as opposed to unrestricted access to their services.

Curriculum↗