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Biomedical subjects

A Rogers

Publications and source records attributed to A Rogers.

At least 127 records · Page 7Linked to original sources
PubMed1993

Disseminated trichosporonosis in a neutropenic murine model.

Life-threatening disseminated infection with Trichosporon beigelii (trichosporonosis) is a rare mycosis most commonly seen in patients with hematologic malignancies made neutropenic by cytotoxic therapy. This infection is usually resistant to conventional antifungal therapies. Poor correlation between therapeutic outcome of trichosporonosis and in vitro susceptibility of clinical isolates of T. beigelii to antifungal agents is often reported. To obtain a better understanding of its pathogenesis, and to aid in the future study of the therapy of this disease, a murine model of trichosporonosis was developed. The in vitro growth of clinical isolates of T. beigelii was first studied. Subsequently, mice made neutropenic with cyclophosphamide were inoculated intravenously with the fungus to produce the disease model. Inoculum size which produced 100% mortality, yet allowed an apparent therapeutic window (6 x 10(6)) was determined. Tissue distribution and burden of organism during the course of infection was examined by viability and histopathologic studies. T. beigelii disseminated rapidly in this model, involving numerous organs including the heart, brain, kidneys, lungs, and liver. The heart and kidneys of the infected animals showed evidence of infection as early as 6 hours following inoculation. Further understanding of the pathogenesis of trichosporonosis in the neutropenic host was imparted by this study. This will aid in the future study of antibiotic treatment of this disease and its untreated progression.

Animals↗
PubMed1993

Luria-Delbrück fluctuation analysis: estimating the Poisson parameter in a compound Poisson distribution.

Estimating the mutation rate from a Luria-Delbrück fluctuation experiment involves estimating the Poisson parameter in a compound Poisson distribution. The efficiency with which this can be estimated depends on how well the other random factors have been characterized. The assumption that cell growth can be represented as a stochastic pure birth or Yule process is biologically unrealistic but contributes little to the bias and variance of a maximum likelihood estimator of the mutation rate.

Algorithms↗
PubMed1992

Effect of calcium and phosphate ions on hemolysis induced by Pyrularia thionin and Naja naja kaouthia cardiotoxin.

Pyrularia thionin is a strongly basic bioactive peptide of 47 amino acids isolated from nuts of Pyrularia pubera. It is hemolytic, cytotoxic and activates an endogenous phospholipase A2 in 3T3 cells. Earlier studies have shown that the cardiotoxin from Naja naja kaouthia has similar activities and binds to the same site as Pyrularia thionin. Since the peptides appear to bind to the phospholipids of cell membranes to elicit their cellular responses, the effect of modifying the electrostatic environment was studied by separately adding phosphate ion and Ca2+, and by removing Ca2+ from the membrane by treatment with EGTA. Analysis of erythrocyte hemolysis for both Pyrularia thionin and cardiotoxin shows that the reactions follow Michaelis-Menten kinetics, with the peptides serving as the substrate. The basal rate of hemolysis in physiological saline is markedly increased by the addition of phosphate in the 5-10 mM range and also by removing membrane-bound Ca2+ by incubation of the cells with 10 mM EGTA. These treatments do not change the apparent K(m) values, but increase the V(max), indicating that more binding sites are made available by these treatments. On the other hand, added Ca2+ in the 5-10 mM range competitively inhibits the reaction by inhibiting the binding of the peptide to the membrane.

Antimicrobial Cationic Peptides↗
PubMed1992

Binding properties of Pyrularia thionin and Naja naja kaouthia cardiotoxin to human and animal erythrocytes and to murine P388 cells.

Pyrularia thionin and snake venom cardiotoxin are strongly basic peptides which induce hemolysis, depolarization of muscle cells and activation of endogenous phospholipase A2. An earlier study of the hemolysis reaction indicated that the two peptides bind to and compete for the same site on human erythrocytes. A recent study examined the hemolysis induced by both peptides as the phosphate and Ca2+ content of the reaction mixture was varied. The results of the recent study (VERNON, L. P. and ROGERS, A., Toxicon 30, 701-709) agree with this companion study on the binding of 125I-labeled pyrularia thionin and cardiotoxin to erythrocytes under the same conditions. Added phosphate ion at 5 mM and removal of membrane-bound Ca2+ by treatment with 10 mM EGTA make more binding sites of the same affinity available to both peptides, which are shown to bind in a competitive fashion to the same site. Addition of 10 mM Ca2+ to the medium decreases peptide binding due to competitive binding of Ca2+ to the same site on the membrane. For human erythrocytes the number of binding sites/cell for the thionin ranged from 0.7 to 1.7 x 10(5) and for cardiotoxin from 0.82 to 1.6 x 10(5). The calculated dissociation constants (Kd) from the Scatchard plots ranged from 0.43 to 1.1 microM for the thionin and from 0.40 to 0.98 microM for the cardiotoxin. The binding sites for thionin and cardiotoxin with sheep erythrocytes were 1.7 and 2.0 x 10(4) sites/cell, respectively, and both cow and horse erythrocytes demonstrated 2.7 x 10(4) sites/cell for the thionin. Binding studies with murine P388 cells showed 7.0 and 9.5 x 10(6) sites per cell for Pyrularia thionin and cardiotoxin, respectively.

Animals↗
PubMed1992

Heterogeneity, spatial population dynamics, and the migration rate.

"In this paper, I examine some of the ways in which widely used migration indices are affected by the impacts of heterogeneity and selection, which act within a multistate perspective of spatial population dynamics that permits increments as well as decrements in the selectivity (and return) process. As a result, several commonly used indices of migration introduce a specification bias into the analysis--a bias that reflects the relative weighting accorded to component migration rates by the initial population compositions and spatial distributions." This paper was originally presented at the 1991 Annual Meeting of the Population Association of America.

Bias↗
PubMed1992

Development of the Virginia Congenital Anomalies Reporting and Education System (VaCARES): two pilot projects.

In 1986 legislation established the Virginia Congenital Anomalies Reporting and Education System (VaCARES). The system has three goals: to collect data that can be used to evaluate possible causes of congenital anomalies, to improve diagnosis and treatment, and to let parents and physicians know what resources are available to aid children born with anomalies. All children (from birth to age 2) with congenital anomalies admitted to Virginia hospitals after January 1, 1987, are being reported to VaCARES; VaCARES then contacts their families and physicians. Before the system was implemented statewide, its procedures were thoroughly tested through two pilot projects in selected hospitals. During the pilots, it was concluded that birth certificates alone are inadequate for case ascertainment. According to hospital reports, the incidence of all congenital anomalies during Pilot II was 562 out of 10,034 births (5.6%); birth certificates showed an incidence of only 83 out of 10,034 births (0.8%). During Pilot I, 3,466 (73.8%) of the diagnoses reported were perinatal conditions; the list of reportable conditions was accordingly altered, reducing perinatal conditions reported in Pilot II to 5 diagnoses (0.4%). It was estimated that there will be about 5000 to 7000 reports submitted to VaCARES each year. It was also shown that parents should be sent general rather than specific information about their child's birth defect and that quality control and close contact with reporting hospitals are essential to maintain the integrity of the registry data.

Congenital Abnormalities↗
PubMed1992

Effects of treatment on airway inflammation and thickening of basement membrane reticular collagen in asthma. A quantitative light and electron microscopic study.

We have obtained airway mucosal biopsies by fiberoptic bronchoscopy for light and electron microscopic analysis of three distinct airway levels of the left lung in three subject groups. Group A: 11 subjects with mild atopic asthma (mean age, 29 yr; %FEV1, 89 to 116%; mean PC20 histamine, 2.42 mg/ml), each biopsied twice, one prior to 4 wk of treatment with either inhaled terbutaline (250 micrograms, two puffs four times daily; n = 5) or inhaled budesonide (200 micrograms, one puff twice daily; n = 6) followed by a second biopsy to allow determination of the effects of treatment. Group B: 10 subjects with severe asthma receiving long-term (average, 3.7 yr) corticosteroid treatment were biopsied once only (mean age, 28 yr; %FEV1, 86 to 129%; mean PC20 histamine, 1.85 mg/ml). Group C: 12 normal healthy control subjects (mean age, 35 yr; %FEV1, 92 to 135%; PC20 histamine greater than 16 mg/ml) biopsied once. By light microscopy of plastic-embedded sections, Group A asthmatics had an increased cellular infiltrate when compared with either the healthy control group or the Group B asthmatics (p less than 0.05). Both asthma groups had a thickening of basement membrane reticular collagen compared with the healthy control group (p less than 0.01). Compared with the control group, there was an increase in the percentage of the total cells that were mast cells (p less than 0.01) and eosinophils (p less than 0.05) in Group A and of eosinophils (p less than 0.01) and histiocytes (p less than 0.01) in Group B. The results of cell counts by electron microscopy largely supported these findings, and, in addition, they demonstrated an increased frequency of foci of free eosinophil granules and decreased numbers of neutrophils (p less than 0.01). By light microscopy, budesonide reduced the percentage of mast cells and eosinophils (p less than 0.05). But for the percentage of lymphocytes, which increased (p less than 0.05), terbutaline was without effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

The internal migration and spatial redistribution of the foreign-born population in the United States: 1965-70 and 1975-80.

"This article examines the importance of place of birth [for] the internal migration and spatial redistribution patterns of the foreign-born population in the United States during the 1965-70 and the 1975-80 periods, relying principally on the Public Use Microdata Sample (PUMS) files for our input data. The diverse nationalities are aggregated into eight different regions of origin: Mexico, Puerto Rico, Rest of South and Central America, Europe, Asia, Africa and Oceania, Canada and the Rest of the World. First, the regional distribution of these eight groups at the 1970 and 1980 censuses are examined. Next, the spatial redistribution of the foreign-born population and its changes over time are studied...." This paper was originally presented at the 1990 Annual Meeting of the Population Association of America.

Age Factors↗
PubMed1992

Heterogeneity and selection in multistate population analysis.

If one subgroup of individuals in a population has a higher death rate than the others, then over time the surviving population will include a larger share of those with the lower death rate. As a result, the aggregate average death rate for this increasingly more robust population will decline. This conclusion, however, can be drawn only for nonrecurrent events experienced by populations that do not exchange members with one another--that is, for noninteracting populations. Studies of changes in marital status, labor force activity, residential location, and active life, for example, all should focus on patterns of recurrent events among interacting populations (that is, multistate populations). Selection arising from heterogeneity will occur, but the consequences for average measures become unpredictable a priori. This paper explores such aspects of the selection effects of heterogeneity in multistate populations and illuminates some of their consequences for commonly used rates.

Aged↗
PubMed1991

Expression of the Wilms' tumor gene WT1 in the murine urogenital system.

The Wilms' tumor gene WT1 is a recessive oncogene that encodes a putative transcription factor implicated in nephrogenesis during kidney development. In this report we analyze expression of WT1 in the murine urogenital system. WT1 is expressed in non-germ-cell components of the testis and ovaries in both young and adult mice. In situ mRNA hybridization studies demonstrate that WT1 is expressed in the granulosa and epithelial cells of ovaries, the Sertoli cells of the testis, and in the uterine wall. In addition to the 3.1-kb WT1 transcript detected by Northern blotting of RNA from kidney, uterus, and gonads, there is an approximately 2.5-kb WT1-related mRNA species in testis. The levels of WT1 mRNA in the gonads are among the highest observed, surpassing amounts detected in the embryonic kidney. During development, these levels are differentially regulated, depending on the sexual differentiation of the gonad. Expression of WT1 mRNA in the female reproductive system does not fluctuate significantly from days 4 to 40 postpartum. In contrast, WT1 mRNA levels in the tesis increase steadily after birth, reaching their highest expression levels at day 8 postpartum and decreasing slightly as the animal matures. Expression of WT1 in the gonads is detectable as early as 12.5 days postcoitum (p.c.). As an initial step toward exploring the tissue-specific expression of WT1, DNA elements upstream of WT1 were cloned and sequenced. Three putative transcription initiation sites, utilized in testis, ovaries, and uterus, were mapped by S1 nuclease protection assays. The sequences surrounding these sites have a high G + C content, and typical upstream CCAAT and TATAA boxes are not present. These studies allowed us to identify the translation initiation site for WT1 protein synthesis. We have also used an epitope-tagging protocol to demonstrate that WT1 is a nuclear protein, consistent with its role as a transcription factor. Our results demonstrate regulation of WT1 expression during development of the gonads, implicate WT1 in genitourinary development, and provide a molecular framework toward understanding genitourinary defects observed among hereditary cases of Wilms' tumor.

Amino Acid Sequence↗
PubMed1991

Applications of the Heligman/Pollard model mortality schedule.

"The United Nations working manual for MORTPAK-Lite, a software package for demographic measurement, includes among its 16 computer programs a routine (UNABR) that graduates a set of age-specific probabilities of dying...for the standard set of five-year age groups into a set of single-year probabilities of dying. The graduation is effected with an eight-parameter 'law of mortality' known as the Heligman/Pollard model mortality schedule. Model mortality schedules...are useful in mortality analysis and forecasting. Several such applications are illustrated in this article: a historical time-series analysis, a forecasting application, studies of causes of death, spatial differences and sex-specific mortality disaggregated by race." The geographical focus is on the United States, England, and Australia.

Age Factors↗
PubMed1991

A prospective trial comparing Biobrane, Duoderm and xeroform for skin graft donor sites.

Many new dressings have been introduced for use on split-thickness skin graft donor sites in an effort to reduce pain at the donor site and decrease healing time, while maintaining a low infection rate and cost. To assess these factors in two such dressings, Biobrane (temporary wound dressing) (Winthrop) and Duoderm (hydrocolloid dressing) (Convatec), we compared them with a conventional fine mesh gauze dressing, xeroform, in a prospective, randomized study of 30 donor sites in the same number of patients. Wounds were considered healed when they were 100 per cent re-epithelialized and required no further dressings. Patient self-assessment of pain was quantified on a scale of zero to ten, with ten being the most severe pain. Donor sites dressed with xeroform had a healing time of 10.5 days, which was significantly better (p less than 0.05) than Duoderm (15.3 days) or Biobrane (19.0 days), although the protocol for Duoderm use (wound visualization at seven day intervals) extended the apparent healing times in this group. Duoderm was the most comfortable dressing (0.53 grade) when compared with Biobrane (1.44) and xeroform (2.41, p less than 0.05). No infections occurred in donor sites dressed with xeroform, but two developed in patients using Biobrane. One patient with a Duoderm dressing had a donor site infection during a drug-related neutropenic reaction. Xeroform was the least expensive dressing to use ($1.16 per patient), followed by Duoderm ($54.88 per patient) and Biobrane ($102.57 per patient). The results of our study confirm the usefulness of xeroform as a donor site dressing as it promotes relatively rapid healing, is easy to use and is inexpensive. We found Duoderm to be ideal for smaller donor sites when pain could be significantly reduced with minimal increase in cost. Biobrane is too costly and the infection rate too high for it to be used routinely as a skin graft donor site dressing.

Bandages↗