Biomedical subjects

C Cox

Publications and source records attributed to C Cox.

At least 397 records · Page 22Linked to original sources

PubMed1988

Comparison of frequency distributions in flow cytometry.

A number of methods have previously been considered for the statistical comparison of flow cytometric frequency distributions. For two distributions, the foremost of these is the Kolmogorov-Smirnov (K-S) test, which has been criticized as "too sensitive." We discuss some alternative methods based on the Poisson distribution. The assumption of Poisson variation within channels allows the use of channel-by-channel confidence intervals and chi-square tests. These are simple and more appropriate for discrete data than the K-S test. Graphical displays of these and other techniques are presented. We also attempt to set the problem in an appropriate context. We argue that any statistical procedure must rest on a reasonable understanding of the nature of the variability in the system. This understanding takes the form of an appropriate probability model, which may be approximate but must provide a reasonably accurate description of the data. Incomplete understanding of the data can lead to inappropriate analysis. We discuss the assumptions that underlie our techniques and consider extensions to more complex situations.

Flow Cytometry↗

PubMed1988

Correction of cellular autofluorescence in flow cytometry by mathematical modeling of cellular fluorescence.

A method for the correction of background fluorescence in flow cytometry with special relevance to the quantitation of low levels of cellular surface membrane antigens is presented. The method is based on the mathematical modeling of cellular fluorescence distributions of background fluorescence (autofluorescence control or irrelevant antibody control) and total fluorescence (positively stained cells). Algorithms based on two models and utilizing only the routinely available background and total fluorescence histograms are developed and implemented in computer programs. These allow estimation of the fluorescence histogram corresponding exclusively to immunofluorescence staining of the cell surface antigen of interest. Thus, the correction of background fluorescence is effected solely with software processing of routinely available data; no additional hardware or parameter determinations are necessary. Two models were chosen to be physically plausible and to represent extremes in correlation between background and probe fluorescence. Extremes were chosen to assess the solution dependence on model and to provide bounds to the actual solution when no information on correlation is available. Results are presented for both computer simulations and for an actual assay of the CR1 complement receptor on human erythrocytes to test and illustrate the technique. Alternatively, data can be tested assuming a particular model to explore the relationship, if any, between specific and nonspecific fluorescence.

Algorithms↗

PubMed1988

Predicting survival in infants with persistent pulmonary hypertension of the newborn.

Since persistent pulmonary hypertension of the newborn (PPHN) often occurs as a life-threatening illness, it would be advantageous to identify the highest-risk infants within the first 24 hours of life so that transfer to centers with extracorporeal membrane oxygenation (ECMO) or high-frequency ventilation can be facilitated. Fifty-three infants with PPHN were evaluated retrospectively. A multivariate discriminant analysis of risk factors determined that lowest pH, critical PaCO2, highest inspiratory pressure (PI), maximum ventilator rate, and 5-minute Apgar score were significantly different between the 35 survivors (66%) and the 18 infants (34%) who had died when examined within the first 24 hours of life. A clinical scoring system was designed based on these five criteria, which predicted outcome accurately in 93% of infants. A logistic regression analysis was performed as a check on these results and found that lowest pH, critical PaCO2, and PI predicted outcome with great accuracy. These results suggest that the use of these scoring systems within the first 24 hours of age may help predict outcome in infants with PPHN.

Apgar Score↗

PubMed1988

Multinomial regression models based on continuation ratios.

This paper concerns continuation ratio models for multinomial responses. These are conditional probabilities used in logit models to define the dependence of the multinomial proportions on explanatory variables and unknown parameters. A distinctive feature of these models is that if one models the various continuation ratios separately, then resulting estimates and test statistics are asymptotically independent. This allows the partitioning of likelihood ratio statistics and the search for effects in specific categories of an ordinal response variable. Models that use the same parameters for different continuation ratios are suitable for estimating more global differences. The fitting of these models to actual data is illustrated, including an example from a pharmaceutical study. The results show that different models are suitable for modelling complementary sorts of differences between multinomial response distributions.

Adult↗

PubMed1988

Lack of effect of continuous wave ultrasound exposure on in vivo Chinese hamster cheek pouch epithelial mitotic index.

Chinese hamster cheek pouches were everted and the epithelia exposed in vivo for 1 min to continuous wave 1.07 MHz ultrasound at intensities ranging from 0.5 to 10.0 W cm-2. Since the mitotic index of the hamster epithelium exhibited a circadian rhythm, the times of sonication and tissue sampling were arranged to allow for detection of a division delay as evidenced by a change in mitotic index in cells insonated in the early S or late S/early G2 phases of the cell cycle. There was no demonstrated effect of the ultrasound exposures on mitotic index.

Animals↗

PubMed1988

Increased sister chromatid exchanges in Chinese hamster ovary cells exposed to high intensity pulsed ultrasound.

This study comprised two repeat experiments in which Chinese hamster ovary (CHO) cells were exposed to nominal peak intensity Im = 2500 W/cm2, 2.5 MHz, pulsed ultrasound. Cells contained in a 0.53 cm diameter chamber in 0.48 cm thick Plexiglas were exposed to 10 microseconds pulses at 200 Hz prf in 9 sites for 3 min per site for a total duration of 27 min. The -3 dB focal beamwidth was 0.115 cm at an axial distance of 4.8 cm. Analysis of the pooled data from each series of experiments showed a statistically significant increase in the mean frequency of sister chromatid exchanges (SCE) in exposed compared to control cells. The results show a high degree of variability in the controls and insonated samples, which suggests that large numbers of insonations may be required in studies with SCE to reduce the high probability of missing an effect. The results of this series of experiments provide the first confirmation of an increase in SCEs following exposure to pulsed ultrasound.

Animals↗

PubMed1988

Vitamin supplement use, by demographic characteristics.

Detailed data on vitamin supplement use are presented for nine specific vitamins and minerals by a wide range of demographic and behavioral characteristics. Previously recorded but uncoded data from the first National Health and Nutrition Examination Survey (1971-1974) have been coded and analyzed, providing the only detailed vitamin use data in a representative sample large enough to examine joint distributions and multivariate analyses of numerous characteristics. Significantly fewer black persons than white persons consume vitamins regularly, and the difference is especially pronounced for specific vitamins: fourfold for vitamin E, sixfold for vitamin A, and 10-fold for vitamin C. Significant differences were also seen for age, sex, geographic region, education, poverty, type of alcoholic beverage consumed, and Quetelet index. Data are presented indicating that supplement use has not increased notably between the time of the survey and 1983, and thus the supplement use data are considered to be reasonably representative of current patterns of supplementation practice in the United States.

Adult↗

PubMed1988

Relation of EEG alpha background to parietal lobe function in Alzheimer's disease as measured by positron emission tomography and psychometry.

Fourteen patients with Alzheimer's disease were evaluated by psychometric testing, fluorodeoxyglucose positron emission tomography (PET), and EEG. They were divided into two groups according to the EEG findings. Group A (seven patients) had normal alpha backgrounds and group B (seven patients) had decreased alpha backgrounds. Group A had significantly higher WAIS Performance IQ scores (p = 0.005) than group B. Group A also had higher Weschler Memory Scale scores (p = 0.047) and parietal glucose metabolic rates (p = 0.038) than group B, but these differences are not statistically significant given the multiple comparisons made between the two groups. Relative intactness of parietal lobe function, as measured by psychometric testing and PET, appears to correlate with preservation of EEG alpha background. The EEG may be useful in assessing regional cortical involvement or the clinical stage in Alzheimer's disease.

Aged↗

PubMed1988

Surfactant replacement therapy at birth: final analysis of a clinical trial and comparisons with similar trials.

A randomized trial of surfactant replacement therapy at birth was conducted at the University of Rochester between June 1983 and November 1985. Thirty-four premature infants, 25 to 29 weeks' gestational age, received a preventilatory dose of a calf lung surfactant extract in saline prepared at the University of Rochester. A control group of 31 infants received a preventilatory dose of saline alone. The major finding of this trial is that a single preventilatory dose of calf lung surfactant extract reduces the severity of the respiratory distress syndrome during the first 24 hours of life. The beneficial effects, however, are not sustained in many infants and diminish after 24 hours of life. The survival rate was 71% in both the control and surfactant-treated groups. There was a lower incidence of pneumothorax in the surfactant-treated group. There were no differences in the incidence of bronchopulmonary dysplasia, patent ductus arteriosus, and intraventricular hemorrhage. No adverse effects of surfactant replacement therapy were identified. Results of this study suggest that multiple postventilatory doses of surfactant will be required for optimal therapy.

Clinical Trials as Topic↗

PubMed1988

Weak low frequency electromagnetic fields and chick embryogenesis: failure to reproduce positive findings.

Fertilised chicken eggs were incubated for 48 hours while exposed to pulsed trains of magnetic fields having a duration of 0-5 ms, a rise time of 42 microsecond, and a pulse repetition rate of 100 at a magnetic field flux density of 1 microT. Some eggs were exposed to 1,552 rad X-rays as a positive control. After exposure the embryos were scored blind for a variety of morphological features. X-irradiated eggs displayed highly significant and repeatable anatomical alterations. There were no differences between magnetic field-exposed, sham-exposed and control eggs.

Animals↗

PubMed1988

Home births.

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Delivery, Obstetric↗

PubMed1988

Estimation of mercury burdens in rats by chelation with dimercaptopropane sulfonate.

The chelation of mercury by 2,3-dimercaptopropane-1-sulfonate (DMPS) and its usefulness in the estimation of mercury burdens was investigated by exposing male, Sprague-Dawley rats to 203HgCl2 (0.1-2 mg of Hg per kg i.p.) or 203Hg vapor (0.5-2.0 mg of Hg per m3). DMPS (0.2-2.0 mmol/kg) was injected i.p. at times ranging from 1 to 38 days after exposure to the mercurial. Urine and feces were collected for 24 hr before and after DMPS treatment. Whole body mercury levels, tissue levels and excretion of mercury were measured by radioactivity counting. After DMPS treatment there was a significant decrease of whole body mercury levels and an increase in urinary excretion. The increase in urinary excretion was directly proportional to the whole body burden of mercury at the time of dosing with DMPS in animals dosed with HgCl2 and exposed to mercury vapor. Furthermore, the increase in urinary excretion induced by DMPS was almost equal to the amount of mercury lost from the kidneys.

Animals↗

PubMed1988

Cost busters fair: increasing staff awareness of cost effective practice.

Losses in excess of $1,000,000 from uncharged supplies, which were inadequately documented in the medical record, prompted the formation of a multidepartmental task force to attack the problem. A project, the Co$t Busters Fair, was planned and developed to target nurses, physicians, nursing assistants, and medical attendants. Goals of the fair were to increase awareness of factors affecting cost and to clarify misconceptions about charting practices.

Anniversaries and Special Events↗

PubMed1987

Are national hospital data adequate for coding injury severity?

The purpose of this study was to determine whether accurate severity scores, using the abbreviated injury scale (AIS), could be produced from hospital discharge data held on the National Health Statistics Centre (NHSC) computer files. The data from two New Zealand trauma studies, in which AIS scores had been assigned to patient injuries, were linked to the patient data on NHSC computer files and AIS scores assigned for those injuries that were present. Sixty-five percent of the injuries for which a link was made were scorable and of these, there was 54% agreement between the AIS scores generated from NHSC data and the scores from the trauma studies. Percent agreement varied with body area, whether the injury was from a single or multiple injury victim, and with the severity of injury. Recommendations include a revision of data collection and NHSC data coding to incorporate AIS scores, and to educate medical personnel regarding AIS in order that they collect appropriate information so that AIS may be coded on the patient's discharge form.

Data Collection↗

PubMed1987

Fetal methylmercury poisoning. Relationship between concentration in single strands of maternal hair and child effects.

Pregnant women consumed bread that was prepared from methylmercury-treated wheat. Single strands of maternal head hair were analyzed by x-ray fluorescence spectrometry. The index of fetal exposure was the maximum hair mercury concentration during gestation. Effects were measured by the frequency of psychomotor retardation, seizures, and neurological signs in the children. A dose-response relationship was demonstrated for fetal effects of methylmercury. Analysis of single hair strands provides a better index of acute or subacute fetal exposure than analysis of bundles of hair; the duration and degree of exposure are more accurately defined. A sex difference in response is discussed.

Developmental Disabilities↗

PubMed1987

Effects of 60-Hz electric fields on cellular elongation and radial expansion growth in cucurbit roots.

Serial longitudinal and transverse sections were prepared from roots of Cucumis sativus and Cucurbita maxima that had been exposed/sham-exposed to 60-Hz electric fields for 0-2 days. Field exposures were selected to produce a 10-20% or a 70-80% growth inhibition in whole roots of both species. Cortical cell length and diameter were measured using a microscope and eyepiece micrometer; measurements were conducted "blind." In both species, inhibition of cellular elongation was associated with exposure to electric fields (EF). Cellular radial expansion was apparently unaffected by exposure to electric fields. The diameters of radially unexpanded or fully expanded C. sativus cortical cells were about 25-30% smaller than those of comparable cells in C. maxima roots. Previous studies of the relationship between rates of root growth and applied EF strength showed that the response thresholds of C. sativus and C. maxima differed by a similar relative amount. These results are consistent with the postulate that EF-induced effects in roots are elicited by induced transmembrane potentials.

Analysis of Variance↗

PubMed1987

Improved model for specimen classification based on single-cell classifiers.

We consider probabilistic models for specimen classification procedures based on systems which classify individual cells as normal or abnormal. The models which we consider generalize those discussed previously by Castleman and White (Anal. Quant. Cytol. 2:117-122, 1980; Cytometry 2:155-158, 1981) and by Timmers and Gelsema (Cytometry 6:22-25, 1985). In particular, they include the biologically plausible possibility that the specimen contains cells which are intermediate between the extremes of normal and abnormal. We find that if these additional cells occur differentially in normal and abnormal specimens, then specimen classification can become substantially more efficient when the cell classifier has different error rates for these cells.

Cervix Uteri↗

PubMed1987

The clearance of manganese chloride in the primate.

Two macaque monkeys inhaled trace amounts of 54MnCl2 for 30 min. Subsequently the chest, head, and fecal radioactivity were monitored for over a year. The chest data curve required a sum of three exponential terms, with half-times ranging from 0.2 to 187 days, to attain a satisfactory fit. Head levels peaked 40 days after acute inhalation exposure and remained elevated for over a year. The excretion of manganese through the feces was best described by a sum of two exponentials. One had a half-time of less than 1 day and the second had a half-time of 50 to 60 days. A third macaque received a 6-week continuous exposure to 54Mn through a subcutaneous osmotic pump. With this route, manganese clearance from the head occurred at a faster rate than after acute inhalation exposure. Fecal elimination following continuous subcutaneous exposure resembled that following acute inhalation. Kinetic analyses suggested that the long half-times of manganese in the head following inhalation reflected both slow disappearance from the head and replenishment from other depots.

Animals↗