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Biomedical subjects

J E Davis

Publications and source records attributed to J E Davis.

At least 19 recordsLinked to original sources
PubMed1992

Male sterilization.

This review of recent information and advances in the area of male sterilization deals with recent epidemiologic studies that discuss potential ill effects hypothesized to be a result of vasectomy, including carcinoma of the prostate and carcinoma of the testicle. Rebuttals to these hypotheses are presented. Recent advances in techniques of vasectomy including the "no-scalpel" vasectomy technique and open-ended vasectomy are presented, including the rationale for their use. A good deal of attention is given to postvasectomy follow-up, particularly the use of the technique of measuring numbers of ejaculations following vasectomy rather than the period of time afterward to determine when a man is sterile. The final two sections deal with complications of vasectomy and the most recent percentages on reversing vasectomy with particular reference to return of sperm to the ejaculate and pregnancy rates.

Aftercare↗
PubMed1991

Modulation of Na-H antiporter activity in human lymphoblasts by altered membrane cholesterol.

The effects of changes in membrane cholesterol on Na-H antiporter activity in culture human lymphoblasts are described. Lymphoblast cholesterol alteration was achieved with liposomes of phosphatidylcholine (cholesterol depletion) or phosphatidylcholine plus cholesterol (cholesterol enrichment). Lymphoblast intracellular pH (pHi) was examined by fluorimetry using cells loaded with the pH-sensitive dye 2',7'-bis(2-carboxyethyl)5(6)-carboxyfluorescein, and the Na-dependent proton efflux rate at a pHi of 6.0 was taken as the maximum velocity of the Na-H antiporter. Lymphoblast membrane cholesterol depletion activated the Na-H antiporter, and enrichment of membrane cholesterol caused inhibition of the antiporter activity. This study demonstrates that in situ modification of membrane cholesterol can modulate the activity of the Na-H antiporter.

Carrier Proteins↗
PubMed1991

Development and operation of the Wisconsin Research Network.

In 1987, the Wisconsin Academy of Family Physicians developed the Wisconsin Research Network (WReN) to support practice-based primary care research throughout Wisconsin. WReN has three objectives: to support the research efforts of individual physicians in community practices, to facilitate collaborative research among practicing physicians, and to provide academically based investigators with access to community practice sites. Due to a policy of actively encouraging membership, WReN has grown to 460 members during its 4-year history. Five WReN-supported papers have been published, and 22 state and national level presentations of WReN-supported research results have been made. Competitive grants totaling more than $2 million have been awarded to university-based investigators for studies using the resources of WReN. This paper describes the development, organization, and success of WReN as well as the challenges which must be addressed.

Family Practice↗
PubMed1991

Changes in body fluid compartments during a 28-day bed rest.

The extravascular fluid responses to real or simulated space-flight are not well-documented. In this study serial isotope measurements were used to obtain measurements of the body fluid responses of 10 22-29-year-old men during 28 d of simulated microgravity (bed rest). The subjects were maintained on a controlled metabolic diet for 7 d before the study, during 14 d of ambulatory control, 28 d of horizontal bed rest, and 14 d of ambulant recovery. Fluid compartments were measured on control days 1 and 9, bed rest days 2, 14, and 28, and recovery days 7 and 14. By day 2 of bed rest, plasma volume (PV) and extra-cellular volume (ECV) decreased significantly by an average 209 and 533 ml, respectively. Red cell volume (RCV) and total body water (TBW) decreased more slowly, with average losses of 128 and 1,316 ml, respectively, after 28 d of bed rest. Early in the bed rest, TBW loss was mostly from the ECV. Thereafter, the TBW deficit was derived from the intracellular compartment, which decreased an average of 838 ml after 28 d. These results suggest losses from all fluid compartments during bed rest, with no evidence of restoration of ECV after 1-2 weeks.

Adult↗
PubMed1990

Lack of detectable endocytosis of B lymphocyte MHC class II antigens using an antibody-independent technique.

MHC class II complexes may intercept ingested foreign Ag as the nascent class II molecules exit the cell or as mature complexes recycle between the outer membrane and an internal compartment. To examine endocytosis of HLA-DR, we radiolabeled B lymphoblastoid cells, warmed the cells to allow internalization of membrane proteins, and then subjected viable cells to neuraminidase (NANAse)3 digestion. DR complexes were precipitated and analyzed by two-dimensional PAGE for shifts in isoelectric point signifying sensitivity to or protection from NANAse treatment. DR molecules were completely sensitive to the enzyme with or without specific antibody in the medium during the 37 degrees C incubation, suggesting that no detectable endocytosis had occurred. Control transferrin receptors, which readily internalize, showed marked protection. Assay sensitivity was measured by proportionate mixing of mock and NANAse-treated lysates; precipitated sialylated molecules were detectable at the 10% level. Monensin treatment to block recycling also failed to reveal any internally accumulated. NANAse-protected DR molecules. Measurements of turnover for surface-labeled DR complexes revealed a t 1/2 of approximately 36 h. We conclude that no large endocytically-derived pool of HLA-DR molecules exists within cells and suggest that the majority of mature DR molecules do not actively undergo internalization but reside at the cell surface after synthesis/transport for significantly long periods of time.

Animals↗
PubMed1990

Alcohol use among college students: responses to raising the purchase age.

On December 1, 1985, New York State raised its alcohol purchase age from 19 to 21. We used a quasi-experimental research design to explore the changes in alcohol use behaviors and attitudes of undergraduates at a large central New York university before and after this legislation was enacted. The overwhelming majority of this undergraduate population is under 21 years old and is thus affected by the new legislation. A comparison of data from the two survey times revealed that 90% of the undergraduates sampled continued to drink at least occasionally. Our analysis of drinking quantity showed a slight moderation in alcohol consumption overall, with the greatest changes occurring for the heaviest drinkers--men and members of Greek organizations. Even with apparent moderation in student drinking, reported negative consequences such as physical injuries were more common. A change in drinking location to less-controlled environments, such as private rooms and unmonitored parties, is offered as one possible explanation.

Adult↗
PubMed1990

Intracellular transport and peptide binding properties of HLA class II glycoproteins.

Protein antigens internalized by an antigen presenting cell are degraded into peptides, a subset of which binds to the class II glycoproteins encoded by the major histocompatibility complex to form epitopes recognized by specific T cells. Current evidence suggests that the immunogenic peptides are generated in an endosomal, acidic compartment containing internalized antigen, proteinases, and exocytic class II molecules. These exocytic class II glycoproteins are associated during transport from the endoplasmic reticulum to the endosomal compartment with an additional glycoprotein, the invariant chain. Proteolytic degradation of the invariant chain in the endosomal compartment dissociates it from the class II glycoproteins, which only then acquire the capacity to bind peptides. After peptide binding occurs, the class II-peptide complexes are transported to the antigen-presenting cell surface for recognition by T cells.

Biological Transport, Active↗
PubMed1989

A method to increase recovery of fentanyl from urine.

Fentanyl, a highly lipophilic drug (pk(a) 7.7), is a common drug of abuse. The current standard techniques to detect fentanyl in urine have low recovery rates and poor sensitivity. We report a modified solvent extraction technique that can recover between 63 and 86% of the drug with a detection limit of 0.2 ng/10 ml of urine. In addition, we report the duration of urinary fentanyl excretion in 11 adolescent patients administered either low (less than 10 mg/kg) or high (20-40 mg/kg) doses of fentanyl as part of anesthesia. The mean duration of urinary fentanyl excretion was similar in the two groups, with duration ranging from 1 to 5 days, and urine fentanyl concentration ranging from 0.1 ng to 10.3 ng/10 ml of urine.

Adolescent↗
PubMed1989

Effects of cholestatic hepatic disease and chronic renal failure on alfentanil pharmacokinetics in children.

The role of the liver and the kidney in alfentanil metabolism has not been defined. The effects of cholestatic hepatic disease and chronic renal failure on the pharmacokinetics of alfentanil were evaluated in 9 children undergoing liver transplantation and 10 children undergoing kidney transplantation. These findings were compared with data from 10 children with normal hepatic and renal function undergoing other surgical procedures. There was no statistical difference among the 3 groups with respect to apparent volume of distribution, half-life, or clearance. In a subgroup of 3 patients undergoing liver transplantation alfentanil kinetics were determined both before and after the allograft was incorporated into the recipient's circulation. Though both volume of distribution and elimination half-life increased in the posttransplantation period, only the decrease in clearance was statistically significant. Thus, it appears that alfentanil may be a useful anesthetic agent in pediatric patients with cholestatic hepatic disease or chronic renal failure. The dose of alfentanil in these patients need not be altered except in the period immediately after liver transplantation.

Adolescent↗