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Biomedical subjects

R L White

Publications and source records attributed to R L White.

At least 91 records · Page 5Linked to original sources
PubMed1994

Propagation of mouse and human T cells with defined antigen specificity and function.

Difficulties maintaining fully functional CD4+ T cells in culture have historically limited the study of their role in tumour rejection as well as other clinical applications. As the therapeutic value of current antitumour CD8+ T cell adoptive therapy becomes better defined, a strong impetus exists to determine optimal conditions for culturing antitumour CD4+ T cells. Our goal is to promote broadly polyclonal, antigen-specific CD4+ T cell responses of either Th1 or Th2 character for use in antitumour therapy or allograft facilitation, respectively. Similar obstacles exist in murine and human cultures: (1) during even brief periods of culture CD4+ T cells develop high 'background' reactivity to class II-positive antigen-presenting cells; (2) maintenance of antigen specificity as evidenced by cytokine secretion and short-term proliferation assays is insufficient to ensure bulk numerical expansion; (3) Th1-type CD4+ T cells often lose their potential for antigen-specific secretion of interleukin 2 on re-stimulation (though remain inducible by 12-O-tetradecanoylphorbol 13-acetate/ionomycin); (4) during prolonged culture selection pressure favours CD4+ subpopulations that recognize artifactual antigens such as culture medium proteins; (5) even with optimal culture conditions, cultured CD4+ T cells may function differently in vivo to uncultured CD4+ T cells. We have devised various strategies to surmount these obstacles by use of selected cytokines, antigen-presenting cells and timely culture manoeuvres.

Animals↗
PubMed1994

Drug degradation during HPLC analysis of aztreonam: effect on pharmacokinetic parameter estimation.

OBJECTIVE: To assess the impact of degradation of aztreonam, a beta-lactam antibiotic, during HPLC analysis on pharmacokinetic parameter estimates. METHODS: The baseline (B) serum concentration-time data from a published pharmacokinetic study of aztreonam were degraded using first-order equations and a degradation rate constant (0.014 h-1) determined from a preliminary degradation study. Samples were mathematically degraded for autosampler run times of 8-13 h (D1) to approximate a normal work day and for autosampler run times of 16-17 h (D2) and compared with B data. It was assumed that B data were nondegraded and that changes in chromatography were the result of degradation of azetreonam and not to any changes in chromatographic conditions. A two-compartment model was used to fit the data and pharmacokinetic parameters were calculated using standard equations. Statistical significance between all pharmacokinetic parameters for B and D1 and B and D2 was determined using the paired, two-tailed Student's t-test. RESULTS: Increased variability was noted for all pharmacokinetic parameters for D1 and D2 compared with B. Statistically significant differences were found for clearance (B < D1, p = 0.0095 and B < D2, p = 0.0194), steady-state volume of distribution (B < D2, p = 0.0392), and area under the serum concentration-time curve (B > D1, p = 0.0497). CONCLUSIONS: Aztreonam degradation resulted in increased variability in pharmacokinetic parameter estimates. Investigators should be cognizant of this and preliminary studies should be performed to characterize degradation for the length of the expected autosampler run.

Aztreonam↗
PubMed1994

Renal dysfunction associated with the administration of high-dose interleukin-2 in 199 consecutive patients with metastatic melanoma or renal carcinoma.

PURPOSE: To describe the incidence and management of renal dysfunction associated with the use of high-dose interleukin-2 (IL-2) (as is currently approved) in the treatment of cancer patients. PATIENTS AND METHODS: One hundred ninety-nine consecutive patients with metastatic renal carcinoma or melanoma were treated with intravenous bolus infusions of IL-2 alone (720,000 IU/kg) every 8 hours. RESULTS: Patients received 310 courses (589 cycles) of therapy and most experienced oliguria, hypotension, and weight gain; 13% of cycles were discontinued due to increased serum creatinine levels. Creatinine values (mean pretherapy, 1.2 mg/dL) increased during therapy and peaked (mean, 2.7 mg/dL) approximately 1 day after discontinuation of the second cycle of IL-2. Off therapy, toxicities reversed promptly and creatinine values returned to baseline. Higher peak creatinine values occurred in patients with renal carcinoma (v melanoma), older patients, males (v females), and those who had undergone prior nephrectomy. These same patient subsets received fewer doses of IL-2, but clinical responses were not associated with creatinine values or number of IL-2 doses administered. Urinalyses showed the appearance of protein, bilirubin, RBCs, WBCs, and granular casts during therapy, which cleared completely on follow-up evaluation. CONCLUSION: High-dose IL-2 can be safely administered to cancer patients. The associated renal dysfunction is transient and without evidence of intrinsic long-term renal damage. Practical guidelines for patient management have been identified.

Adolescent↗
PubMed1993

NADH fluorescence of isolated ventricular myocytes: effects of pacing, myoglobin, and oxygen supply.

Endogenous fluorescence was used to measure the extent of reduction of mitochondrial NAD in individual, isolated rat cardiac myocytes. NAD reduction was determined from emitted fluorescence at 415 and 470 nm during brief epi-illumination at 365 nm. NAD reduction of resting myocytes, superfused with medium equilibrated with 95% O2/5% CO2, was 27 +/- 3% (SE) (n = 78), comparable to that in beating whole heart. Increasing intracellular Ca2+ did not significantly change NAD reduction. NAD reduction decreased reversibly to 11 +/- 1% (n = 78) in contracting myocytes electrically paced at 5 Hz for 10 min. Oxygen uptake was stimulated fivefold. There was minimal change in sarcoplasmic pH measured by fluorescence of carboxy-seminaphthorhodafluor-1. However, NAD reduction increased reversibly in response to electrically paced contractions when: (a) myoglobin was inactivated with sodium nitrite (37 +/- 7%; n = 48); or (b) cells were more densely layered and gassed with 20% O2/5% CO2 (48 +/- 3%; n = 30). We conclude that (a) the ratio NADH/NAD is decreased in well-oxygenated cells with increased work; (b) steady-state NAD reduction is increased with increased work when oxygen delivery is limited; and (c) functional myoglobin ensures an oxygen supply to the mitochondria of working cells.

Animals↗
PubMed1993

A somatic cell hybrid map of human chromosome 13.

We have constructed a chromosome 13 somatic cell hybrid map using seven cell lines: PGMEA6, a hybrid containing the entire chromosome 13, and six hybrids containing various deletions of chromosome 13 (BARF7, PPF22, KBF11, KSF39, CF25, and CF27). We have mapped 80 markers that define 10 regions of chromosome 13 with respect to 10 breakpoints in the mapping panel; these regions range in size from 4 to 24 Mb, with an average size of 8 Mb. The 80 markers sublocalized on our mapping panel include 10 Alu-PCR clones, 6 of which were converted to sequence-tagged sites; 40 (CA)n repeat-containing clones, 27 of which are microsatellite PCR markers; 8 (AAAG)n repeat-containing PCR markers, 1 two-allele PCR marker, 4 genes or expressed sequences, and 17 anonymous DNA probes. This low-resolution physical map can be used as a backbone map for more refined physical mapping using radiation hybrids or yeast artificial chromosomes.

Animals↗
PubMed1993

The identification of 5-hydroxy-L-norvaline in cultures of pyridoxine auxotrophs of Escherichia coli B.

Gc-ms and hplc have been employed to identify 5-hydroxy-L-norvaline (L-2-amino-5-hydroxypentanoic acid) in the culture fluids of pyridoxine-starved cultures of two pyridoxine auxotrophs of Escherichia coli B. The production of 5-hydroxynorvaline is shown to be secondary to pyridoxine starvation of the cultures, and the quantities of 5-hydroxynorvaline are similar to those of the common protein amino acids present in these cultures. This is the first time that 5-hydroxynorvaline has been identified as a product of bacterial metabolism.

Amino Acids↗
PubMed1993

Impact of different statistical methodologies on the evaluation of the in-vitro MICs for Bacteroides fragilis of selected cephalosporins and cephamycins.

The purpose of this study was to assess the effect of different MIC statistics on the in-vitro evaluation of cefoxitin, cefotetan, ceftizoxime, cefotaxime, desacetylcefotaxime, and cefotaxime:desacetylcefotaxime (1:1 ratio) against clinical isolates of Bacteroides fragilis from the Medical University of South Carolina. MICs were determined by the agar dilution method following NCCLS guidelines. Statistical analyses included arithmetic and geometric means, median, mode, MIC50, MIC90, and range. Differences between antimicrobial agents were determined using parametric and nonparametric methods. Consistent with previous in-vitro studies on anaerobes with these agents, a wide range in the MICs was observed. The arithmetic mean MIC was lowest for cefotetan, but the geometric mean MIC was lowest for ceftizoxime. Using the MIC90, cefotetan was at least a two-fold dilution more active than the other agents. After natural logarithmic transformation of the MIC data, analysis of variance with the Scheffé post-hoc test demonstrated that the MICs of ceftizoxime were significantly lower than those of cefoxitin (P < 0.001), cefotetan (P < 0.05), cefotaxime (P < 0.05), and desacetylcefotaxime (P < 0.001). Median and mode MICs were lowest for ceftizoxime and cefotaxime:desacetylcefotaxime. Using published breakpoints, cumulative percent susceptibility was similar for all agents studied. In this analysis of the antimicrobial susceptibility of B. fragilis in our institution, the in-vitro activity of the cephalosporins and cephamycins tested appeared to be very similar when all statistical data were evaluated. Since apparent in-vitro activity may be influenced by the statistic evaluated, we suggest that all MIC data be reported to allow for a more complete analysis of microbiological potency.

Analysis of Variance↗
PubMed1993

Nutrient effects on growth and the production of 5-hydroxy-4-oxonorvaline by Streptomyces akiyoshiensis.

5-Hydroxy-4-oxonorvaline (HON) was produced optimally by Streptomyces akiyoshiensis in media containing starch and casein supplemented with high concentrations of phosphate and magnesium sulfate; cultures grown at initial pH values between 6.3 and 6.6 yielded HON titres of 13-14 mM. Physiological analysis of HON production provided evidence that the excess inorganic constituents in this medium played an important role in optimizing production. In simple defined media buffered at pH 5.5-6.0 and inoculated with either a spore suspension or washed vegetative mycelium, formation of HON was less than one-third the amount produced in the starch-casein-salts medium. Production was markedly affected by the carbon and nitrogen sources used; media containing starch and potassium nitrate or aspartate supported the highest yields of HON. In starch-nitrate media, production was suppressed by excess nitrogen source, and the HON titre decreased 3-fold as the phosphate content was increased from 0.5 to 5 mM; growth was not appreciably altered. The results suggest that the high level of HON production in the complex starch-casein-salts medium is associated with sequestration of metabolic ammonium and reduced availability of phosphate through formation of the poorly soluble magnesium ammonium phosphate.

Aminolevulinic Acid↗
PubMed1993

Image recovery from data acquired with a charge-coupled-device camera.

A model for data acquired with the use of a charge-coupled-device camera is given and is then used for developing a new iterative method for restoring intensities of objects observed with such a camera. The model includes the effects of point spread, photoconversion noise, readout noise, nonuniform flat-field response, nonuniform spectral response, and extraneous charge carriers resulting from bias, dark current, and both internal and external background radiation. An iterative algorithm is identified that produces a sequence of estimates converging toward a constrained maximum-likelihood estimate of the intensity distribution of an imaged object. An example is given for restoring images from data acquired with the use of the Hubble Space Telescope.

Algorithms↗
PubMed1993

Intraoperative transesophageal echocardiography.

Intraoperative echocardiography in patients undergoing cardiac surgery was first described in 1972. Interest in intraoperative echocardiography has grown in recent years due to the extensive information provided by 2-dimensional (2-D) and color-flow Doppler imaging via the transesophageal approach. The value of this technique also has been verified in large clinical studies involving patients undergoing cardiac surgery. Intraoperative transesophageal echocardiography (TEE) is very useful in preoperative formulation of surgical plans and in immediate post-operative assessment of surgical results in patients undergoing valve surgery.

Echocardiography↗
PubMed1992

The CEPH consortium linkage map of human chromosome 15q.

The CEPH consortium map of chromosome 15q is presented. The map contains 41 loci defined by genotypes generated from CEPH family DNAs with 45 different probe and restriction enzyme combinations contributed by 10 laboratories. A total of 29 loci have been placed on the map with likelihood support of at least 1000:1. The map extends from 15q13 to 15q25-qter. Multipoint linkage analyses provided estimates that the male, female, and sex-averaged maps extend for 127, 190, and 158 cM, respectively. The largest interval is 21 cM and is between D15S37 and D15S74. The on-average locus spacing is 5.6 cM and the mean genetic distance between the 21 uniquely placed loci is 8 cM.

Chromosome Mapping↗
PubMed1992

Growth morphology of Streptomyces akiyoshiensis in submerged culture: influence of pH, inoculum, and nutrients.

Most media in which the growth of shaken submerged cultures of Streptomyces akiyoshiensis was examined did not support the formation of well-dispersed mycelial suspensions. Investigation of the culture conditions promoting dispersed growth showed the pH of the culture medium to be of critical importance; an initial value of 5.5 minimized aggregation of the mycelium while supporting adequate biomass production. In cultures started at this pH, spore inocula gave better mycelial dispersal than did vegetative inocula; with spore inocula, growth morphology was also less affected by inoculum size. The composition of the nutrient solution influenced the extent of mycelial dispersal; slow growth was often associated with clumping but no clear correlation was observed between pellet formation and the ability of carbon or nitrogen sources to support rapid growth. Increasing the phosphate concentration from 0.5 to 15 mM caused a modest decrease in mycelial aggregation. Conditions promoting a well-dispersed mycelium suitable for studying the physiological control of secondary metabolism also supported the formation of 5-hydroxy-4-oxonorvaline by S. akiyoshiensis.

Aminolevulinic Acid↗
PubMed1992

Effects of a videotape feedback package on the peer interactions of children with serious behavioral and emotional challenges.

Peer interactions are among the greatest challenges experienced by children who have severe emotional and behavioral problems. This study evaluated an intervention package designed to increase the ratio of these children's desirable to undesirable interactions. The package included three principal components: (a) observation of videotapes following regularly scheduled peer activity sessions; (b) self-evaluation of the children's peer interactions observed on the videotapes; and (c) delayed feedback and reinforcement for desirable peer interactions. Five students from two elementary schools participated. Multiple baseline designs and one reversal were used to evaluate the effects of the intervention package. The results showed that the intervention produced lower levels of undesirable peer interactions and higher ratios of desirable to undesirable interactions for all participants. The results are discussed in regard to their conceptual and applied implications and in terms of specific directions for future research.

Affective Symptoms↗
PubMed1992

Ex vivo protein binding of clindamycin in sera with normal and elevated alpha 1-acid glycoprotein concentrations.

Clindamycin is a lincosamide antibiotic that binds primarily to alpha 1-acid glycoprotein (AAG), an acute-phase serum protein. Many studies have shown that AAG concentrations increase in response to stress, including infection, myocardial infarction, and trauma. The objectives of this study were to determine the serum protein binding of various clindamycin concentrations in sera with normal and elevated AAG concentrations. Serum was obtained from 4 healthy volunteers and 12 patients with pathophysiologic conditions known to elevate serum AAG concentrations. Timing for collection was determined from the literature, corresponding with the expected peak concentration for each disease state. Samples were assayed for AAG by radial immunodiffusion and were spiked with clindamycin to achieve total concentrations of 10 micrograms/ml (n = 18), 4 micrograms/ml (n = 10), and 2 micrograms/ml (n = 7). Protein binding was determined by ultrafiltration and subsequent high-performance liquid or gas chromatography. Protein binding was dependent on the serum concentrations of both AAG and clindamycin. When AAG concentrations increased from 101-150 mg/dl to 201 mg/dl or greater, mean protein binding increased from 81.2% to 92.4% (p = 0.1265) and from 61.3% to 88.6% (p less than 0.05) at clindamycin concentrations of 2 and 4 micrograms/ml, respectively. With AAG concentrations between 101 and 150 mg/dl, mean protein binding increased from 62.4% at 10 micrograms/ml to 81.2% at 2 micrograms/ml (p = 0.1514). Since AAG concentrations may increase in certain patients, the concentration of free (pharmacologically active) drug may fall below the minimum inhibitory concentration for several pathogens earlier in a dosing interval.

Chromatography, Gas↗
PubMed1992

Pharmacoeconomic evaluation of treatment of penetrating abdominal trauma.

The hospital, pharmacy, and antibiotic costs for patients with penetrating abdominal trauma were compared with reimbursement received; these costs were also analyzed to assess the potential impact of a total prospective pricing system (PPS). During a four-year period, 46 patients admitted solely for penetrating abdominal trauma were retrospectively evaluated: their discharge summaries indicated that, for 9 patients, reimbursement was based on diagnosis-related groups (DRGs) under the PPS; 9 patients had private insurance; and 28 were classified as "self-paying/no insurance." All costs, corrected for inflation, were reported in 1989 dollars. Antibiotics represented 22.5%, 1.7%, and 0.5% of pharmacy, hospital, and DRG reimbursement, respectively; pharmacy costs were 8.5% of hospital costs and 2.3% of DRG reimbursement. For all 46 patients, a net loss of $295 per patient was incurred. Four patients accounted for 43% of the hospital costs. If the hospital had been reimbursed for all of these patients by prospective pricing and DRGs, it would have had a median profit of $9730 in 42 of 46 patients. Costs exceeded DRG reimbursement in the remaining four patients by a median of $8210. Antibiotic costs and pharmacy costs represent a small portion of hospital costs and DRG reimbursement for patients with penetrating abdominal trauma; thus, cost containment efforts in these patients should be directed at other ancillary services and length of stay.

Abdominal Injuries↗
PubMed1991

The CEPH consortium linkage map of human chromosome 1.

This paper describes the Centre d'Etude du Polymorphisme Humain (CEPH) consortium linkage map of human chromosome 1. The map contains 101 loci defined by genotypes generated from CEPH family DNAs with 146 different contributions from 11 laboratories. A total of 58 loci are uniquely placed on the map with likelihood support of at least 1000:1. The map extends from loci in the terminal bands of both chromosome arms (locus D1Z2 in 1p36.3 and D1S68 in 1q44) and is anchored at the centromere by the D1Z5 alpha-satellite polymorphism. With the exception of a single locus, the remaining loci are arrayed on the fixed map in short intervals and their possible locations are indicated. Multipoint linkage analyses provided estimates that the male, female, and sex-averaged maps extend for 308, 478, and 390 cM, respectively. The sex-averaged map contains only four intervals greater than 15 cM, and the mean genetic distance between the 58 uniquely placed loci is 6.7 cM.

Chromosome Mapping↗