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Biomedical subjects

R M Lucas

Publications and source records attributed to R M Lucas.

10 recordsLinked to original sources
PubMed1994

National and regional distributions of airborne radon concentrations in U.S. homes.

The National Residential Radon Survey was conducted during 1989 and 1990 to provide data on the frequency distribution of annual average radon concentrations in U.S. residences nationwide, in U.S. Environmental Protection Agency defined Regions, and in subgroups of the housing stock. The National Residential Radon Survey also provided housing and demographic data and a preliminary assessment of the relationship of housing and geographical characteristics to residential radon concentrations. This paper focuses solely on the national and regional estimates of annual average radon concentrations. A stratified, three-stage sampling procedure was used to select housing units for the survey. Data were collected through personal interviews with residents and placement of alpha track detectors in each level of the residences for 12 mo. The survey found an arithmetic annual average radon concentration in U.S. homes of 46.3 +/- 4.4 Bq m-3 (1.25 +/- 0.12 pCi L-1). About 6.0 +/- 1.4% of homes (5.8 million) had radon levels greater than the U.S. Environmental Protection Agency's action level for mitigation of 148 Bq m-3 (4 pCi L-1). Concentrations varied significantly across Environmental Protection Agency Regions. A lognormal distribution was found to closely approximate the major distributions of radon concentrations.

Air Pollutants, Radioactive↗
PubMed1991

A performance evaluation study of three types of alpha-track detector radon monitors.

Three models of alpha-track detector (ATD) Rn monitors were exposed in Environmental Protection Agency (EPA) Rn chambers to obtain estimates of precision and bias for the National Residential Radon Survey (NRRS). Exposures in this study ranged from 37 to 740 Bq y m-3 (1 to 20 pCi y L-1), plus blanks. These exposures correspond to the range expected in most U.S. residences. All detectors were purchased through a Rn mitigation firm to assure that the vendors did not give special attention to the ATDs used in this study. Ten ATDs of each model were studied at 12 exposures. The mean and standard deviation of the reported values for each model were calculated and compared with the continuously monitored chamber concentrations to determine the bias and precision at each exposure. Results of this analysis were discussed with the vendors, who took corrective actions. Changes in track counting procedures and calibrations improved detector performance. Readings of one detector were adjusted based on a regression of the monitored values on the reported values.

Alpha Particles↗
PubMed1989

Mucoepidermoid tumor: a case report involving the operculum of an erupting permanent second molar.

The mucoepidermoid tumor (carcinoma) accounts for approximately 6% to 8% of all salivary gland tumors. Although rare in children, it is the most common "malignant" salivary gland tumor, having been reported in major and minor (intraoral) salivary gland sites as well as in the maxilla and the mandible. In children, as in adults, it most often occurs in the parotid gland, but a significant percentage is found in the palate and retromolar pad area. Presently, there is no unanimity of opinion about whether to consider all mucoepidermoid tumors malignant or what the most appropriate treatment regimen is. The following is a case report of a mucoepidermoid tumor presumably arising from the reduced enamel epithelium in soft tissue overlying an erupting mandibular second molar in an 11-year-old boy. Theoretical origins of intraoral soft tissue mucoepidermoid tumors are discussed, as well as treatment philosophy. The importance of submitting, for microscopic diagnosis, all tissue removed during surgical procedure is illustrated in this case report.

Carcinoma↗
PubMed1989

The Initial Blood Storage Experiment--the spaceflight hardware program.

The Initial Blood Storage Experiment (IBSE) was conceived to investigate the effects of microgravity on the formed elements of human blood. The experiment flew on the January 1986, 61-C mission of the Space Shuttle Columbia. The experiment hardware was designed to provide a closely controlled temperature and air flow environment for all blood samples. During the mission, two IBSE modules were on board the orbiter and an identical set of hardware and blood samples were maintained on Earth as a control. This paper describes the development and performance of the IBSE hardware which was converted from a conceptual design to an on-orbit, man-rated, mid-deck locker experiment in 17 months.

Blood Platelets↗
PubMed1985

Nifedipine-induced gingival hyperplasia. A histochemical and ultrastructural study.

Gingival hyperplasia induced by nifedipine (Procardia), a calcium channel-blocking agent used as an anti-anginal drug, was studied. In recent months, the role of nifedipine in the etiology of gingival hyperplasia has attracted interest. The purpose of this study was to determine the causal relationship and compare nifedipine to other drug-induced (phenytoin) and nondrug-induced gingival hyperplasias. Histochemical studies revealed increased numbers of fibroblasts containing strongly sulfated mucopolysaccharides in the nifedipine- and phenytoin- (Dilantin) induced gingival hyperplasias as compared to the nondrug-induced cases. Numerous secretory granules were also noted in the fibroblast cytoplasm in the nifedipine-treated case studied by electron microscopy. These results imply that there is an increase in acid mucopolysaccharide production in the nifedipine- and phenytoin-induced gingival hyperplasias. The potential significance and comparisons of the drugs' effects at the cellular level are discussed.

Acid Phosphatase↗
PubMed1985

Intracellular localization of bacterial lipopolysaccharide using the avidin biotin complex method at the electron microscopic level.

The intracellular localization in 3T6 fibroblasts of Escherichia coli lipopolysaccharide (LPS) using the rapid avidin-biotin-immunoperoxidase technique at the electron microscopic level was studied. The role of bacterial endotoxin in the etiology of periodontal disease has been well documented previously. The purpose of the present study was to localize LPS within the cell, thereby determining which organelles concentrate the material and relate this to the cytologic pathophysiology. An increased concentration of LPS was found in the cell nuclei and, specifically, in association with nuclear chromatin and nucleoli. The concentration of LPS in the nucleus was directly related to the time of incubation, with some product appearing in that site within 2 minutes. There was no specific localization of endotoxin in mitochondria, lysosomes, Golgi, endoplasmic reticulum or ribosomes. These results imply that bacterial endotoxin may have a direct effect on nuclear components of fibroblasts. The relationship of these results to the etiologic mechanisms of periodontal disease is discussed.

Avidin↗
PubMed1979

Histochemical study of strain L fibroblasts exposed to endotoxin. The effect on cellular organelles.

Endotoxin was found to be nonselective in its cytotoxicity of cellular organelles. All organelles studied displayed some degree of alteration which became more severe as the concentration of endotoxin was increased. The data suggest that the metabolism of the cell may be compromised at concentrations of endotoxin which do not affect cell viability. The problem involved in attempting to determine the actual concentration of endotoxin at the interface between the culture medium and the cell monolayer, in vitro, and the corresponding situation, in vivo, are also discussed.

Acid Phosphatase↗
PubMedDate not supplied

Pneumatic firearm injuries: trivial trauma or perilous pitfalls?

This report describes an injury due to a pneumatic firearm. Though powder firearm injuries are generally considered serious, pneumatic weapon injuries are often viewed as minor or insignificant trauma. Children and adolescents primarily wield these weapons contributing to their "harmless" aura. However, dramatic increases in muzzle and impact velocities have transformed the newer generation of pneumatic firearms into formidable weapons. Consequently, the literature is replete with increasing incidences of serious injury due to pneumatic weapons.

Child↗