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Biomedical subjects

R Wheeler

Publications and source records attributed to R Wheeler.

81 records · Page 5Linked to original sources
PubMedDate not supplied

Comparison of NIOSH 5040 method versus Aethalometer to monitor diesel particulate in school buses and at work sites.

This study, undertaken initially to understand apparent differences between two recent reports of diesel particulate matter (DPM) inside school buses, involved side-by-side comparisons of two different methods for measuring ambient and occupational exposures to DPM. The NIOSH 5040 method yields time-weighted-average measurements of elemental carbon (EC) and organic carbon (OC), whereas the Aethalometer yields near-real time measures of carbonaceous particles (black carbon or BC) by optical absorption. The two methods were compared on three school buses and in three different work sites. Three side-by-side sampling configurations were used (open-faced filter with and without two different cyclones) in triplicate along with two or three Aethalometers. BC readings were correlated with results from open-faced cassettes, but there were statistically significant differences between the results of side-by-side Aethalometers. In addition, Aethalometer airflow rates were inaccurate, the instruments were sensitive to vibration, optical calibration could not be performed, and historically derived conversion factors to relate EC and BC were not appropriate. The Aethalometer could prove useful for monitoring of industrial work sites, but only after a method for external calibration and improvements in pump design and vibration isolation are developed.

Carbon↗
PubMedDate not supplied

Modeling the effects of light, carbon dioxide, and temperature on the growth of potato.

This study examined the effects of light, temperature and carbon dioxide on the growth of potato (Solanum tuberosum L.) in a controlled environment in order to ascertain the best growing conditions for potato in life support systems in space. 'Norland' and 'Russet Burbank' were grown in 6-L pots of peat-vermiculite for 56 d in growth chambers at the University of Wisconsin Biotron. Environmental factor levels included continuous light (24-h photoperiod) at 250, 400, and 550 micromoles m-2 s-1 PPF; constant temperature at 16, 20, and 24 degrees C; and CO2 at approximately 400, 1000, and 1600 microliters L-1. Separate effects analysis and ridge analysis provided a means to examine the effects of individual environmental factors and to determine combinations of factors that are expected to give the best increases in yields over the central design point. The response surface of Norland indicated that tuber yields were highest with moderately low temperature (18.7 degrees C), low CO2 (400 microliters L-1) and high light (550 micromoles m-2 s-1 PPF). These conditions also favored shorter stem growth. Russet Burbank tuber yields were highest at moderately low temperature (17.5 degrees C), high CO2 (1600 microliters L-1) and medium analyses will be used to project the most efficient conditions for growth of potatoes in closed ecological life support systems (CELSS) in space colonies.

Carbon Dioxide↗
PubMedDate not supplied

Part-time doctors: reduced working hours for primary care physicians.

Women are entering the professional workforce in increasing numbers, and male professionals are more likely than ever to be involved in dual-career families. For primary care physicians the traditional 50-70-hour work week increasingly creates conflict between professional and other personal goals. Many believe that unless physicians work these long hours they will be unable to successfully provide personal, high-quality continuing care to their patients. Long-term career development for physicians who choose nontraditional arrangements has also presented problems. The authors review the literature on part-time work for physicians, then discuss their experiences as part-time family physicians at an academic health center. Various specific strategies are recommended for physicians and institutions considering part-time employment.

Adult↗
PubMedDate not supplied

Doctors having families: the effect of pregnancy and childbearing on relationships with patients.

Family physicians care for patients in all stages of the life-cycle, while at the same time proceeding themselves through the course of adult development. The purpose of this study was to examine, from the doctor's point of view, changes in the doctor-patient relationship resulting from the physician's pregnancy and child-bearing. Five faculty family physicians participated via individual interviews and group discussion. Two women without children, the clinical psychologist interviewer, and other faculty family physicians joined in the review of the interviews and the group discussion. Comprehensibility, reciprocity, mutuality, identification, credibility, availability for long-term relationships, nurturing, and support emerged as themes in the evolution of relationships with patients. The process of examining the effect of childbearing on our relationships with patients unexpectedly revealed how the dual expectation of career and motherhood causes colleagues without children to feel inadequate. On the other hand, the study itself had the positive effect of facilitating the resolution of long-standing tensions among group members. We conclude that becoming mothers, a significant life change, had a transforming effect on our clinical work with patients and that studying this effect as a group fostered growth in the relationships among the participants.

Adult↗
PubMedDate not supplied

Gram negative bone and joint infection: sixty patients treated with amikacin.

Sixty patients with bone and joint infections secondary to gram negative infection were evaluated in relation to treatment with amikacin. Forty-seven of these patients had osteomyelitis, and 13 had joint infections, including 3 prosthetic replacements. The patients' average was 35 years and there was no predilection for any particular skeletal location. Only 6 patients had no associated predisposing medical problems. Of these problems fracture, diabetes and narcotic abuse were most common. Thirty patients had Psuedomonas infection, and 15 others had multiple pathogens including Pseudomonas. Aminoglycoside antibiotics had been previously used in 25. Amikacin was given for an average of 22 days with a mean dose of 13.4 mg/kg. Bone and synovial fluid levels of amikacin were in therapeutic range. At least 48 patients had concurrent local wound treatment in addition to parenteral administration of amikacin. In 47 patients enough information was available to determine the efficacy of treatment. Twenty-seven (57%) of these patients were considered cured, both clinically and for bacteriologic response; and additional 9 (19%) were considered partially cured. Amikacin is effective against susceptible pathogens in bone and joint infections and is a reasonable choice when aminoglycoside antibiotic is indicated.

Adolescent↗
PubMedDate not supplied

Totally implanted drug delivery system for hepatic arterial chemotherapy.

A totally implanted drug delivery system for hepatic arterial chemotherapy was evaluated in 13 patients with metastatic (11 colon and one carcinoid) or primary (one hepatoma) cancer of the liver. During laparotomy, a Silastic catheter was positioned in the hepatic artery for infusion to the entire liver arterial vasculature as ascertained by low-flow radionuclide angiography with 99Tc-macroaggregated albumin. The catheter was connected to a subcutaneously implanted model 400 Infusaid pump (Metal Bellows Corp, Sharon, MA). Each pump had a 50-ml volume and a set rate (3--6 ml/day) and required refill every 8--16 days. A side port bypassed the pumping mechanism and allowed direct catheter injection for nuclide angiography, for bolus drug administration, or for clearing of a blocked catheter. Pump refills and side port injections were performed by percutaneous injection. The 13 patients in this ongoing study received a median of 6 months (range, 4.5--17) of continuous hepatic arterial infusion. The pump performed reliably with stable (+/- 10%) flow rates and only one malfunction in 2800 cumulative days of use. Flow distribution determined by low-flow radionuclide angiography did not change in 12 patients. Patient acceptance was excellent, with the ability to participate fully in normal daily activities. Eleven patients showed partial hepatic tumor regressions documented by physical examination and nuclide liver scans. All patients were treated with 5-fluorodeoxyuridine. Two patients failed 5-fluorodeoxyuridine therapy and subsequently responded briefly to dichloromethotrexate. This implanted system should facilitate future investigation of regional chemotherapy using these and other agents.

Adult↗
PubMedDate not supplied

Implanted system for intraventricular drug infusion in central nervous system tumors.

We have developed a totally implanted drug delivery system capable of maintaining constant cerebrospinal fluid (CSF) drug levels through continuous intraventricular infusion in outpatients. This system was used to infuse methotrexate (MTX) intraventricularly in seven patients with incurable CNS malignancies. One patient with meningeal diffuse histiocytic lymphoma, five patients with grade III--IV astrocytomas, and one patient with melanoma metastatic to the brain were treated with this system for 4--40+ weeks. The system consists of an Infusaid pump (Metal Bellows Corp, Sharon, MA), implanted subcutaneously in the infraclavicular fossa, which delivers a drug-containing solution at a set rate (3--5 mg/day) through a subcutaneous silastic catheter to a Rickham ventriculostomy reservoir and into a lateral ventricle. System placement and maintenance were readily tolerated. Constant MTX infusion at rates of 0.5--10 mg/day generated corresponding constant CSF drug levels in the range of 2--30 microM. Simultaneous serum MTX levels were undetectable (less than 0.01 microM), indicative of a 200- to 3000-fold selective regional concentration advantage for this approach. CNS toxic effects included transient meningism and fever (four patients), transverse myelitis (one), and the development of a diffuse hypodensity of the white matter on computerized tomographic scan which was not associated with any neurologic deficit (two). The usual systemic toxic effects (myelosuppression and mucositis) of MTX were not seen. The patient with meningeal lymphoma has had a complete remission of meningeal disease continuing past 10 months. Computerized tomography showed that three of the five high-grade astrocytomas had 25% size reductions in tumors lasting 2--6 months. This system may provide a means for improved treatment of meningeal tumor although its role in the treatment of intraparenchymal brain tumors is less clear. Of greater consequence, however, is the demonstrated ability of this system to maintain a controlled CSF drug level which should prove useful in many areas of therapeutic research.

Adult↗
PubMedDate not supplied

Growth patterns for infants weighing less than 801 grams at birth to 3 years of age.

Anthropometric measurements of infants weighing < 801 gm were monitored to evaluate growth patterns from birth to 36 months chronologic age, using both standard growth percentiles and Z score descriptors. Mean gestational age was 25.8 weeks, and birth weight was 708.4 gm. The infants had growth delay at hospital discharge with some catch-up growth occurring in the first year. Discrete changes in body growth using the Z score as a descriptor showed movement from a negative SD at 12 months toward the reference mean of zero at 36 months. However, mean length remained < 5th percentile, and mean weight was at approximately the 10th percentile for chronologic age. At 36 months 45% of infants had a head circumference smaller than the 5th percentile for chronologic age. Birth weight < 701 gm was a significant predictor of smaller occipital-frontal circumference at 3 years (p = 0.03). Interruption of intrauterine growth after extremely premature birth appears to have long-term effects on growth outcome much like prenatal growth retardation.

Anthropometry↗