Search PubMed⌕ Search

Biomedical subjects

D A Baker

Publications and source records attributed to D A Baker.

At least 73 records · Page 4Linked to original sources
PubMed1993

Transcripts of the multidrug resistance genes in chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum.

Homologues of the mammalian multidrug resistance gene have been identified in isolates and clones of Plasmodium falciparum and designated pfmdr1 and pfmdr2. Mutations in pfmdr1 have been associated with chloroquine resistance but confirmation could not be obtained in a genetic cross. We have examined the copy number and expression of pfmdr1 and pfmdr2 in chloroquine-sensitive and -resistant P. falciparum and have found no relationship between the copy number of either gene and chloroquine resistance. However, a marked correlation was seen between levels of mRNA transcribed for each gene and chloroquine resistance. Two transcripts of pfmdr1 were detected, and in the asexual blood cycle an 8 kb transcript appeared first, followed by the appearance of a 7 kb species.

Animals↗
PubMed1993

Development of a piezopolymer pressure sensor for a portable fetal heart rate monitor.

A piezopolymer pressure sensor has been developed for service in a portable fetal heart rate monitor, which will permit an expectant mother to perform the fetal nonstress test, a standard predelivery test, in her home. Several sensors are mounted in an array on a belt worn by the mother. The sensor design conforms to the distinctive features of the fetal heart tone, namely, the acoustic signature, frequency spectrum, signal amplitude, and localization. The components of a sensor serve to fulfill five functions: signal detection, acceleration cancellation, acoustical isolation, electrical shielding, and electrical isolation of the mother. A theoretical analysis of the sensor response yields a numerical value for the sensor sensitivity, which is compared to experiment in an in vitro sensor calibration. Finally, an in vivo test on patients within the last six weeks of term reveals that nonstress test recordings from the acoustic monitor compare well with those obtained from conventional ultrasound.

Biosensing Techniques↗
PubMed1992

Bombesin-induced hypothermia: a dose-response and receptor antagonist study.

Bombesin infusion into the preoptic area (POA) has previously been shown to induce hypothermia in rats that are food deprived or made hypoglycemic with insulin. The present study evaluated the potency and receptor specificity of this response. Bombesin was microinfused into the POA of food-deprived rats (n = 7) and insulin-pretreated rats (n = 7) at doses of 0, 5, 12, 25, and 50 ng/0.5 microliters. Changes in core body temperature (rectal) were assessed at 1 h. Hypothermia was observed under both conditions with doses as low as 5 ng (3.1 pM) as compared to vehicle (0 ng). In a separate study, infusion of the reduced peptide bond analog (Psi13,14 Leu14)bombesin (2.5 micrograms) prior to bombesin injection (25 ng) was found to prevent the hypothermic response observed in the bombesin control condition. These data suggest that bombesin is a potent hypothermic agent that interacts with gastrin-releasing peptide receptors localized within the POA region to impact thermoregulation.

Animals↗
PubMed1992

Herpes simplex virus infections.

This review discusses current reports on herpes simplex virus infections as they relate to the use of laboratory testing, infections in the neonate, herpes simplex virus association with human immunodeficiency virus infection, and updating the current therapy and management of genital herpes. Findings over the past year are important in the clinical management of patients with genital herpes. All health care workers who manage patients with genital herpes need to know the limitations of serologic testing. Current information suggests that serologic commercial testing that is most commonly available cannot discriminate between infections caused by herpes simplex virus type 1 and type 2. Laboratory methods still rely on culturing herpes simplex virus in living cells in vitro. However, the availability of monoclonal antibodies allows for rapid assays for the confirmation of cultured herpes simplex virus. In addition, assays have been developed and tested, suggesting that perhaps antigen-detection systems may be available that could replace culturing the virus in living cells. New information on neonatal herpes points out the predictors of morbidity and mortality in newborns who contract herpes within the first few weeks of life. Information concerning asymptomatic shedding in labor will provide the clinician with a better understanding of this disease entity in the pregnant woman. Several studies have confirmed that herpes simplex virus infection is a risk factor for developing human immunodeficiency virus infection. A new study clearly shows that treatment using daily acyclovir therapy over a prolonged period of time can control and may modify herpesvirus infection.

Acyclovir↗
PubMed1991

Computationally two-dimensional finite-difference model for hollow-fibre blood-gas exchange devices.

The goal of this research is to develop a predictive model with good absolute accuracy for blood-gas exchange devices. The proposed model, unlike existing models, is able to predict gas transfer to blood flowing outside oxygenating fibres without experimental data. The proposed model uses a finite-difference numerical technique to solve computationally two-dimensional gas exchange problems such as gas transfer to blood outside hollow fibres. The model is compared to bovine and human experimental data from the small test cells with microporous polypropylene fibres. The test cell flow rates range from 1 m litre min-1 to 5 m litre min-1 for a 72-fibre device. Shear-augmented oxygen diffusion appears to be present, although good accuracy is obtained with a nonaugmented diffusion model, particularly at lower flows. The maximum deviation of oxygen saturation predicted by a shear-augmented bovine blood model from the experimental regression line was 1.7 per cent.

Animals↗
PubMed1991

Pleural effusion in aneuploidy.

Three consecutive cases of isolated pleural effusion in aneuploid fetuses are reported. The presence of pleural effusion in trisomy 13 had not been described in the literature previously. Early development of pleural effusion is usually associated with fetal hydrops and carries a poor prognosis. Late development of pleural effusion can be treated in utero. A karyotype should be performed in all cases of pleural effusion prior to in utero pleuroamniotic shunting.

Adult↗
PubMed1991

Characterization of murine polyclonal antisera and monoclonal antibodies generated against intact and denatured human papillomavirus type 1 virions.

Human papillomavirus type 1 (HPV1) virions, both as intact virion particles (IVP) and as detergent-denatured virions (DDV), were used to prepare polyclonal antisera and monoclonal antibodies (MAbs) in BALB/c mice. Anti-IVP antiserum contained type-specific HPV1 L2-reactive antibodies and no detectable HPV1 L1-reactive antibodies. Anti-IVP MAbs recognized a linear epitope between L2 amino acids 102 and 108 (PIDVVDP). Anti-DDV antiserum contained type-specific HPV1 L1-reactive and HPV1 L2-reactive antibodies. An anti-DDV MAb recognized a linear epitope between L1 amino acids 127 and 133 (AENPTNY). HPV1a L1- and L2-encoded polypeptides expressed in Saccharomyces cerevisiae and by in vitro translation were equivalent in size to the major and minor virion capsid proteins, respectively.

Amino Acid Sequence↗
PubMed1990

Multicenter clinical evaluation of the Du Pont Herpchek HSV ELISA, a new rapid diagnostic test for the direct detection of herpes simplex virus.

A new 4h rapid enzyme-immunoassay for direct detection of herpes simplex virus (HSV) antigen (Du Pont Herpchek) was evaluated with 743 clinical samples collected at obstetrics and gynecology (OB/GYN), sexually transmitted diseases (STD), and ophthalmology clinics. The sensitivity and specificity of Herpchek was 98.0% and 98.4% respectively compared to virus isolation in cell culture. Confirmatory blocking ELISA tests, clinical history and follow up indicate that the true specificity of the test is 100%.

Adult↗
PubMed1990

Growth and toxigenesis of C. botulinum type E in fishes packaged under modified atmospheres.

Modified atmosphere packaging of fresh fish is used to market high quality products in some European countries. The potential risk of C. botulinum growth in these extended shelf-life foods is still a concern; especially since toxigenesis may precede organoleptic spoilage. This paper will present toxigenic data from rockfish, salmon and sole muscle tissues which were inoculated with a pool of non-proteolytic C. botulinum type E at seven levels (10(-2)-10(4) spores/sample), and stored under vacuum and 100% CO2, at incubation temperatures between 30 and 4 degrees C, for up to 60 days. Factorial experimental design allowed predictive formulae to be developed able to describe the lag time prior to C. botulinum toxigenesis and the probability of one spore to initiate toxigenesis based upon the storage conditions. Accurate characterization of the microbial ecology of C. botulinum in modified atmosphere-packaged fish, will support safe exploitation of these packaging systems in the market place, and identify critical control points for potential product or process abuses.

Animals↗
PubMed1990

Amniotic fluid index: an appropriate predictor of perinatal outcome.

Qualitative amniotic fluid volume determination is a routine part of the fetal biophysical profile score. Quantitative amniotic fluid volume measurement, however, is not a factor in the determination of the standard biophysical profile score. This study is a retrospective analysis of antepartum assessment of amniotic fluid volumes and their relationship to neonatal outcomes. The amniotic fluid index was calculated for all patients examined and perinatal outcome was studied for all patients assessed. Patients with reduced or increased amniotic fluid volume had a significant increase in meconium-stained amniotic fluid, Apgar scores less than 7 at 1 and 5 minutes, major congenital anomalies, admission to the neonatal intensive care unit, and were more likely to require delivery by cesarean section for fetal distress. This study suggests that a quantitative ultrasound measurement of amniotic fluid volume represents an effective discriminatory test to be used in pregnancy evaluation.

Amniotic Fluid↗
PubMed1990

Regulatory agency concerns in the manufacturing and testing of monoclonal antibodies for therapeutic use.

Monoclonal antibody-based therapeutic products are subject to the same regulatory review procedures and submissions requirements as more traditional pharmaceutical agents. In addition, the FDA often asks for specific information on the unique aspects of the manufacture, characterization, and testing of these products. Agency concern begins with the origin of the hybridoma cell line and continues through preclinical safety testing and clinical trials. Specific regulatory issues are often decided on a case-by-case basis with the FDA reviewers. Implementing an effective strategy for identifying and addressing these issues and concerns is a critical part of the development process.

Animals↗
PubMed1990

Topical podofilox for the treatment of condylomata acuminata in women.

The purpose of this study was to determine the efficacy and safety of 0.5% podofilox solution (Condylox) for the treatment of genital warts in women. Thirty-seven women with anogenital warts applied the solution to the surface of these warts twice daily for 3 days, followed by 4 drug-free days. A minimum of two and a maximum of four treatment cycles were given. The subjects were evaluated weekly for the first 4 weeks and again at 6 and 10 weeks. At the end of 10 weeks, the mean number of warts per patient was reduced from 6.27 to 1.1, and half of the patients were completely cleared of warts. Only eight of 37 subjects (21.6%) developed new warts during the study period. Approximately 15% of patients reported "severe" local reactions to the treatment after the first treatment cycle, but this was reduced to only 5% by the last treatment cycle. During the same period, the patients reporting no side effects increased from 44 to 86%. The only woman who discontinued the study did so because of dizziness and epigastric discomfort, probably unrelated to drug use. Thus, 0.5% podofilox solution appears to be an effective treatment for condylomata acuminata, with acceptable side effects that are local and temporary.

Administration, Topical↗
PubMed1989

Effect of low-dose oral contraceptives on natural killer cell activity.

Several reports indicate an association between oral contraceptives and increased infection rates. One mechanism that could explain this increased infection rate is a decrease in immune function. A study comparing T cell subsets showed no differences in numbers between oral contraceptive users and controls. In this study, natural killer cell activity was compared in women before and 3 and 6 months after oral contraceptive use. There was a statistically significant decrease in NK cell activity after three months. There was no further decrease by six months and the differences were no longer significant due to greater variability. No infections were reported during the study period. Thus, the observed reduction in NK activity was either physiologically insignificant or the previously reported increase in infections may be the result of non-immunological factors.

Adolescent↗