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Biomedical subjects

C E Becker

Publications and source records attributed to C E Becker.

At least 19 recordsLinked to original sources
PubMed1996

Treatment of pneumothorax in the patient with AIDS.

With the diagnosis of the adult immunodeficiency syndrome (AIDS), a patient's risk of sustaining a nontraumatic pneumothorax increases to 450 times that of the general population. The approach to pneumothorax that occurs in the patient with AIDS differs from the strategy that is used for spontaneous pneumothorax in immunocompetent young adults. The modifications in treatment are predicated on understanding the etiology of spontaneous lung collapse in the patient with AIDS.

AIDS-Related Opportunistic Infections↗
PubMed1995

Retention of styrene following controlled exposure to constant and fluctuating air concentrations.

An experiment was designed to determine whether the respiratory retention of styrene vapor, as estimated from measurements of end-exhaled air, was the same during periods of both constant and fluctuating exposure. Six human subjects were exposed to styrene inside a experimental chamber. A computer-controlled system was used to generate time-varying air concentrations of styrene over 4-5h in both multistep sequences of constant exposure (four subjects exposed to 15-99 ppm of styrene in 100-min steps) and fluctuating patterns representative of occupational exposures (two subjects exposed to mean concentrations of styrene of 50 ppm). In the latter case, lognormally distributed exposures, which fit one of two first-order autoregressive models, were generated at intervals of 2.5 min. It was found that the concentration of styrene in end-exhaled air was reduced by about half if the subject inhaled one to three breaths of clean air prior to sampling. This suggests that significant amounts of styrene were desorbed from the lining of the lungs during the initial exhalation. The retention of styrene vapor during constant exposures was 0.935 and was independent of the level. During each of the two sets of fluctuating exposure the retention of styrene was also constant and was independent of both the variance and autocorrelation coefficient. However, the retention of styrene during the fluctuating exposure (estimates ranged from 0.957 to 0.973) was significantly higher than that observed during the constant exposures.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Plantar fibromatosis: a review of primary and recurrent surgical treatment.

Plantar fibromatosis can be quite disabling to the patient, as well as a technical challenge to the surgeon. Patients who undergo previous local excisions and in whom aggressive recurrences develop are difficult to manage successfully. We present a consecutive series of five primary procedures on patients with painful plantar fibroma and seven revision operations on patients with recurrent plantar fibroma. The average follow-up was 47 months (range, 22-66 months) in the primary group and 40 months (range, 21-78 months) in the revision group. The overall results were satisfactory in four of the five primary operations, with only one recurrence. In the revision group, five of seven results were satisfactory with no recurrences. The major complication that led to unsatisfactory results was the development of a postoperative neuroma. In this article, we outline our present surgical techniques of wide primary excision and a staged revision procedure with delayed split-thickness skin graft closure. These techniques can be used successfully to manage this disabling, progressive disease.

Adult↗
PubMed1994

Factors influencing bone lead concentration in a suburban community assessed by noninvasive K x-ray fluorescence.

OBJECTIVE: To determine the influence of demographic, exposure and medical factors on the bone lead concentration of subjects with background (nonindustrial) environmental lead exposure. DESIGN: Survey. SETTING: Suburban residential community. PARTICIPANTS: A total of 101 subjects (49 males, 52 females; aged 11 to 78 years) were recruited from 49 of 123 households geographically located in a suburban residential neighborhood unexposed to any major source of industrial lead emissions. MAIN OUTCOME MEASUREMENTS: Cortical bone lead concentrations in the midshaft of the tibia were noninvasively measured by in vivo K x-ray fluorescence. Blood lead concentrations were measured by anodic stripping voltammetry. An administered questionnaire assessed potential sources of lead exposure and medical conditions affecting bone metabolism. RESULTS: After the exclusion of one outlier, log-transformed bone lead concentration was highly correlated with age (r = .71; P < or = .0001). Bone lead concentration showed no significant change up to age 20 years, increased with the same slope in men and women between ages 20 and 55 years, and then increased at a faster rate in men older than 55 years. In addition to the variables age and sex, the best fitting multiple regression model for bone lead concentration (R2 = .66; P < or = .0001) revealed a positive correlation with total pack-years of cigarette smoking and a negative correlation with a history of having nursed an infant for longer than 2 weeks. Blood lead concentrations of the subjects were low (geometric mean, 0.24 mumol/L [4.9 micrograms/dL]) and after log transformation were weakly correlated with log-transformed bone lead concentration (r = .23; P = .02). CONCLUSIONS: The age- and sex-related increases in bone lead concentration found by K x-ray fluorescence concur with published postmortem studies of bone lead concentration and are consistent with the kinetics of bone turnover and secular trends in lead exposure. These data help to establish a reference range for assessing the lead burden of other populations with environmental or occupational lead exposure.

Adolescent↗
PubMed1994

Variability in the disposition of chlorzoxazone.

Chlorzoxazone is 6-hydroxylated by cytochrome P450 2E1 (CYP 2E1), which bioactivates many toxic and carcinogenic molecules. Seventeen volunteers of varying age, ethnicity, and gender received a 250 mg tablet of chlorzoxazone and their blood and urine were sampled frequently for 8 h. V/F = 42 +/- 21 L and CL/F = 412 +/- 120 mL min-1. Comparison of these values with a study by other investigators using a suspension dosage form suggested that relative Ftablet approximately 0.7. The fraction excreted in the urine as 6-hydroxychlorzoxazone (fe,6-OH) was 0.39 +/- 0.20 and that portion of the total CL accounted for by CYP 2E1-mediated metabolism (CL6-OH) was 163 +/- 95 mL min-1. Thus, while V/F and CL/F varied by factors of less than five, fe,6-OH varied 16-fold and CL6-OH varied 28-fold. These results suggested that there was considerable inter-individual variability in the metabolism of chlorzoxazone to 6-hydroxychlorzoxazone. This variability will significantly affect the construction of physiologically based pharmacokinetic models that use the 6-hydroxylation of chlorzoxazone as a marker for an individual's CYP 2E1 phenotype.

Administration, Oral↗
PubMed1994

Formate in serum and urine after controlled methanol exposure at the threshold limit value.

Methanol will be present as a new air pollutant when methanol-powered vehicles are introduced in the United States. Little is known about the effect of low-dose methanol exposure. It is controversial whether or not formate, the main metabolite responsible for methanol's acute toxicity, is a sensitive biological marker of toxicity or exposure. We studied the effect of a 4-hr exposure at rest to 200 ppm of methanol vapors on endogenous serum formate and on urinary formic acid excretion. A randomized, double-blind study of human exposure to a constant concentration of methanol was performed in a whole-body exposure chamber. Twenty-six healthy volunteers, each serving as his or her own control, participated in sham and methanol exposures. Urine (at 0, 4, 8 hr) and serum specimens (15 time points over 8 hr) collected before, during, and after the exposure were measured for formate. We found no significant differences in serum formate concentration between exposure and control conditions either at any time point or for area under the curve. Mean concentrations at the end of the exposure were: exposed 14.28 +/- 8.90 mg/l and control 12.68 +/- 6.43 mg/l. A slight, but nonsignificant (p = 0.08), increase in urine formate excretion rate was found at 4 hr (exposed 2.17 +/- 1.69 mg/4 hr and control 1.67 +/- 1.02 mg/4 hr). Age, sex, folic acid level, and smoking were not significant covariates. At 200 ppm, methanol exposure does not contribute substantially to endogenous formate quantities. Serum and urine formate determinations are not sensitive biological markers of methanol exposure at the threshold limit value.

Absorption↗
PubMed1993

Evaluating the clarity of research reports written for research subjects.

It is not simple to report research results to the people who participated in the research as subjects of study. Few evaluations have examined subjects' understanding of written research findings. In two recent studies of solvent exposure, subjects received brief summaries of the research. Before they were sent, the summaries were evaluated by research, health, and communication specialists as well as by representatives of the target audience. For one of the studies, interviews were conducted with subjects before and after they received the reports. Although the subjects said they understood the summary, their answers to questions about its content indicated otherwise. The results suggest that researchers not rely on subjects' self-assessments of their understanding but instead design methods to test subjects' knowledge directly. Those tests would be most valuable if applied in formative evaluations, when the opportunity exists to improve the research summaries.

Evaluation Studies as Topic↗
PubMed1993

Hydroxocobalamin as a cyanide antidote: safety, efficacy and pharmacokinetics in heavily smoking normal volunteers.

The safety, efficacy and pharmacokinetic parameters of 5 g of hydroxocobalamin given intravenously, alone or in combination with 12.5 g of sodium thiosulfate, were evaluated in healthy adult men who were heavy smokers. Sodium thiosulfate caused nausea, vomiting, and localized burning, muscle cramping, or twitching at the infusion site. Hydroxocobalamin was associated with a transient reddish discoloration of the skin, mucous membranes, and urine, and when administered alone produced mean elevations of 13.6% in systolic and 25.9% in diastolic blood pressure, with a concomitant 16.3% decrease in heart rate. No other clinically significant adverse effects were noted. Hydroxocobalamin alone decreased whole blood cyanide levels by 59% and increased urinary cyanide excretion. Pharmacokinetic parameters of hydroxocobalamin were best defined in the group who received both antidotes: t1/2 (alpha), 0.52 h; t1/2 (beta), 2.83 h; Vd (beta), 0.24 L/kg; and mean peak serum concentration 753 mcg/mL (560 mumol/L) at 0-50 minutes after completion of infusion. Hydroxocobalamin is safe when administered in a 5 gram intravenous dose, and effectively decreases the low whole blood cyanide levels found in heavy smokers.

Adult↗
PubMed1993

Patterns of chronic granulomatous disease.

We report the clinical course of an adult patient with chronic granulomatous disease, an inherited disorder of neutrophil function that is generally limited to the pediatric population. The biochemical and functional disorders of the neutrophil in chronic granulomatous disease are examined. The mode of inheritance and expression of this disease is profiled to aid the clinician who must consider this diagnosis in the adult patient with recurrent infections.

Adult↗
PubMed1992

Challenges of worker notification in neurotoxic studies of the central nervous system.

Researchers who study the central nervous system (CNS) face special challenges in notifying study participants about the research results. There are human research guidelines regarding the communication of information to subjects at the outset of a CNS research study. Yet there are few guidelines on how to communicate to the subject the research findings and the interpretation of individual results at the study's conclusion. The research subjects may desire detailed information, unequivocal conclusions, understandable interpretations, and clear suggestions about what to do next. Fulfilling these needs, however, is not a simple task for the researcher because outcomes are predicated on statistical uncertainty and the research tests may not be appropriate for individual assessment. We describe methods we have used to communicate with research subjects in two CNS neurotoxic field studies. We suggest that further research examine this important notification process.

Central Nervous System Diseases↗
PubMed1992

Cushing's syndrome associated with lung tumors.

The production of corticotropin or corticotropin-releasing factor by non-pituitary, non-adrenal tumors may rarely be associated with an overt clinical expression of hypercortisolism. Recent studies have emphasized the importance of careful thoracic evaluation when such ectopic hormone secretion is suspected.

ACTH Syndrome, Ectopic↗
PubMed1992

The validity of study group assignments based on occupational histories obtained from questionnaires.

This study examined the validity of self-reported work histories for use in epidemiological studies of toxic exposures. Two uses that were examined were the assignment of subjects to exposure groups and the estimation of exposure duration. Questionnaire responses and data extracted from employment files were compared for 161 retired automobile workers. The questionnaire method assigned subjects to two extreme groups with 99% accuracy but rejected 30% of the subjects because of ambiguous data. Self-reports of exposure duration correlated moderately with the file estimates (r = .63, P = .01). The discrepancy between subjects' estimates and actual exposure duration correlated with subjects' job mobility. The findings indicate that the validity of self-report data declines with the precision required of the data, but that self-reports may have sufficient validity for studies that use extreme-group designs.

Algorithms↗
PubMed1992

The P300 event-related potential. The effects of sleep deprivation.

We monitored 15 healthy young adults during 18 hours of sleep deprivation. Subjects were repeatedly tested on measures of the P300 (P3) event-related potential, reaction time, body temperature, and a subjective rating of fatigue. Statistically significant decreases in P3 amplitude (P < or = .01) and increases in P3 latency (P < or = .0001) were found during sleep deprivation. These changes correlated with body temperature and fatigue and were not due to circadian variation. Reaction time did not show a significant change over time. We conclude that the P3 potential is a more sensitive cognitive measure of sleep deprivation than reaction time, a measure commonly used in previous studies. We provide a review of the literature on the P3 and recommend the use of the P3 as a marker to examine sleep deprivation in health professionals.

Adult↗
PubMed1992

Sleep deprivation and house staff performance. Update 1984-1991.

All English language studies since 1984 of sleep deprivation and house staff performance are reviewed. Manual and computer surveys identified 14 such studies. Our goal is to examine whether the current literature supports the hypothesis that sleep deprivation significantly impairs house staff performance. Our review finds that the current data remain inconclusive. The causes for this uncertainty include different methodologies in assessing performance, the arbitrary definitions of sleep deprived and rested states, and lack of separation of the effects of acute and chronic sleep deprivation. Our review notes striking difference in reported effects of sleep deprivation depending on medical specialty. Surgical studies most frequently show little effect of sleep deprivation. All studies since 1990 support the hypothesis that sleep deprivation significantly impairs performance. Most studies support the impairment of physician mood with increasing sleep deprivation.

Clinical Competence↗
PubMed1991

Neurotoxic effects of methylene chloride: are they long lasting in humans?

The neurotoxicity of methylene chloride (MC) is of special interest because of its acute effects on the central nervous system (CNS) and its metabolic conversion to carbon monoxide. A cohort study of retired airline mechanics was conducted to examine the hypothesis that long term exposure to MC results in lasting effects on the CNS. Retirees were studied to eliminate effects of current occupational exposures. The total retiree population (n = 1758) was surveyed to identify mechanics who met specific occupational, demographic, and medical criteria. A group of eligible retirees having long term exposure to MC and another group with low probability of exposure to solvents were given a comprehensive battery of physiological and psychological tests. The exposure groups were similar for all potential confounders that were measured. No statistically significant differences between groups were detected on outcome measures, although subtle differences in attention and memory were identified. Thus no firm evidence was found to support the hypothesis of lasting CNS effects in retired mechanics with long term exposure to MC.

Aged↗
PubMed1990

Micronucleated erythrocytes as an index of cytogenetic damage in humans: demographic and dietary factors associated with micronucleated erythrocytes in splenectomized subjects.

Erythrocytes containing micronuclei serve as an indicator of genotoxic exposure in splenectomized individuals. Micronucleated erythrocytes, derived from cytogenetically damaged RBC precursors, are not selectively removed from peripheral blood in individuals who lack splenic function. The relationship between micronucleated cell frequencies and demographic, environmental, and dietary factors was examined in 44 subjects with previous splenectomy due to trauma. Their micronucleated cell counts fit a log-normal distribution, with geometric means of 3.3 micronucleus-containing cells/1000 reticulocytes and 2.7/1000 normochromatic erythrocytes. A multiple regression analysis showed that drinking five cups of coffee or tea/day (relative to none) was associated with an approximately 2-fold higher frequency of micronucleated cells. Weaker statistical associations were also noted with micronucleus frequency and the consumption of calcium supplements (associated with a higher frequency) and vitamins A, C, or E (lower frequency). An apparent trend of higher micronucleus counts with age was attenuated when other factors were considered in the regression. Cigarette smoking and decaffeinated coffee consumption were among the factors not associated with elevated micronucleated cell frequencies. Because the occurrence of micronuclei in reticulocytes reflects cytotoxic exposures within the past 3-8 days, it may be possible to test directly the relationship of these factors to micronucleus formation through intervention studies.

Chromosome Aberrations↗
PubMed1990

Influence of race, tobacco use, and caffeine use on the relation between blood pressure and blood lead concentration.

A number of studies have suggested a small to moderate positive relation between blood pressure and blood lead concentration in males (2-4 mmHg/In(microgram/dl]. However, this 1986 study of San Francisco bus drivers suggests larger relations in black males (n = 132) for both systolic pressure (7.5 mmHg/In(microgram/dl] and diastolic pressure (4.7 mmHg/In(microgram/dl] at very low blood lead concentrations (2-21 micrograms/dl). This increase appears to result from negative confounding, particularly after taking into account tobacco use. Relations are even larger in blacks who infrequently use caffeine (16.7 and 10.4 mmHg/In(microgram/dl) for systolic and diastolic pressure, respectively). In contrast, a negative relation between systolic pressure and blood lead concentration (-5.7 mmHg/In(microgram/dl] is suggested in nonblack males (n = 117). These findings indicate that race, lead accumulation, and physiologic effects related to caffeine use (e.g., catecholamine effects) may interact to produce marked differences in effect on blood pressure.

Black or African American↗