Biomedical subjects

S R Larson

Publications and source records attributed to S R Larson.

10 recordsLinked to original sources

PubMed2001

Mode of reproduction and amplified fragment length polymorphism variation in purple needlegrass (Nassella pulchra): utilization of natural germplasm sources.

A dominant plant of the California grasslands, purple needlegrass [Nassella pulchra (Hitchc.) Barkworth] is an important revegetation species in its native range. The amplified fragment length polymorphism (AFLP) method was used to elucidate mode of reproduction and nucleotide variation among 11 natural populations and three selected natural germplasm releases of N. pulchra. A total of 12 co-dominant AFLPs, informative within eight populations, failed to reveal any heterozygous individuals, indicating very high selfing rates (S(H)=1). Estimates of nucleotide diversity within populations ranged from 0 to 0.00069 (0.00035 average), whereas the total nucleotide divergence among populations ranged from 0.00107 to 0.00382 (0.00247 average). Measures of population differentiation (GS) in terms of Shannon-Weaver diversity values and estimated nucleotide substitutions were 0.90 and 0.86, respectively. Although some of the sample populations contained a mixture of true breeding genotypes, most populations could be distinguished unambiguously. Moreover, geographical distance between the natural source populations was significantly correlated with genetic distance (r = 0.60) among the corresponding sample populations. Results indicate that inbreeding, combined with founder effects and/or selection, has contributed to the differentiation of N. pulchra populations. Foundation seed populations of the selected natural germplasm releases were genetically well defined and most similar to natural seed collected near the corresponding source populations. Thus, these commercial germplasm sources will be made practically available and useful for conservation plantings within the intended areas of utilization.

California↗

PubMed2001

Development of a STS marker assay for detecting loss of heterozygosity in rice hybrids.

The RAPD (random amplified polymorphic DNA) markers OPE15750 and OPE15300 were affected by loss of heterozygosity (LOH) in rice hybrids AMR x 'M202' and AMR x 'L202'. The markers were mapped to the same locus at or near the centromere of rice chromosome 2. The two RAPD products were cloned, sequenced, and found to have lengths of 734 bp and 297 bp, respectively. The 297-bp sequence shares a 98% homology with one end of the 734-bp sequence, accounting for the cross-hybridization previously observed between the two clones. Based on the DNA sequence of the 734-bp fragment, a pair of STS (sequence-tagged site) primers was designed and tested. Rice plants homozygous for either OPE15734 or OPE15297 all produced PCR fragments of the same length, 482 bp. However, the two PCR products were discernible by digestion with the restriction enzyme XbaI prior to gel electrophoresis. The STS product from plants homozygous for OPE15734 was cut into two fragments of 239 and 240 bp, which appeared as one single band in an agarose gel; whereas the STS product from plants homozygous for OPE15297 was not cut by XbaI and was characterized by a 482-bp band in the agarose gel. These STS primers were tested in rice hybrids and F2 progenies derived from the hybrids of AMR x 'M202' and AMR x 'L202'. Homozygosity for OPE15297 was confirmed for all F2 panicle rows derived from AMR x 'M202'. In contrast, F2 panicle rows of AMR x 'L202' exhibited two different segregation patterns (genotypes), i.e., either uniformly homozygous for the 240-bp marker (OPE15734/OPE15734) or segregating for the 482- and 240-bp markers (OPE15734/OPE15297). This STS-marker system provides a robust assay for detecting the occurrence of LOH in rice hybrid progenies.

Base Sequence↗

PubMed2000

Linkage mapping and nucleotide polymorphisms of the 6-SFT gene of cool-season grasses.

Fructan plays an important role as an alternate carbohydrate and may contribute to drought and cold-stress tolerances in various plant species. The gene coding for sucrose:fructan 6-fructosyltransferase (6-SFT; EC 2.4.1.10), an enzyme that catalyzes the formation and extension of beta-2,6-linked fructans (levans), is important to fructan synthesis in many cool-season grasses, including cereal species. In this study, we compared a conserved sequence from the 6-SFT gene in barley with comparable sequences in 20 other cool-season grasses. We detected several DNA length polymorphisms, including variations in one simple-sequence repeat (SSR) in a 6-SFT intron of the barley cultivars Steptoe and Morex. Using the 'Steptoe' x 'Morex' doubled-haploid mapping population, the 6-SFT gene was genetically mapped to the distal region in the short arm of barley chromosome 1 (7H), where it is closely linked with trait locus Rpg1. Primers designed from other conserved regions of the barley 6-SFT gene successfully amplified 351- or 354-bp sequences of this gene from diverse cool season grass species. Sequence identities of the PCR products were greater than 80% among the 21 species. Phylogeny, as determined using these DNA sequences, is similar to that obtained from rDNA ITS sequences, and congruent with our current knowledge of genome relationships.

Base Sequence↗

PubMed1998

Vanicosides C-F, new phenylpropanoid glycosides from Polygonum pensylvanicum.

The isolation of the protein kinase C inhibitors, vanicoside A (1) and vanicoside B (2), from Polygonum pensylvanicum prompted continued interest in the active principles of this plant. A new, more efficient isolation procedure has been developed to facilitate separation of homologues of vanicosides A and B from the complex extract. Several new phenylpropanoid glycosides have since been isolated. The structures of these principles were determined to be 2'-O-acetylhydropiperoside (4), 6'-O-p-coumarylhydropiperoside (5), 4'-O-acetylvanicoside A (6), and 3'-O-acetylvanicoside B (7) using negative ion FABMS, 1H NMR, and 2D NMR techniques.

Chromatography, High Pressure Liquid↗

PubMed1993

Use of a disposable carbon dioxide detector with emergency intubation in a hyperbaric chamber.

Emergency intubation in a hyperbaric chamber can be complicated by the confined space, inadequate lighting and high levels of background noise. Inadvertent esophageal intubation may be difficult to recognize in these conditions. In more controlled settings such as the operating room, the detection of end-tidal carbon dioxide is the standard procedure for verifying proper placement of the endotracheal tube. Within a hyperbaric chamber, a capnograph may not be readily available for this purpose. We present a case report describing the use of a simple disposable colorimetric carbon dioxide detector for rapid verification of endotracheal tube position following emergency intubation in a hyperbaric chamber.

Adult↗

PubMed1987

Investigation and work-up of tight building syndrome.

In recent years, incidents involving health-related complaints due to poor indoor air quality have increased dramatically. These problems have generally occurred in new or remodeled buildings. Following relocation to a new building, some employees began to experience health complaints, including upper respiratory tract irritation, headaches, fatigue, and eye irritation. A questionnaire was designed which elicited information about specific work locations, symptom experience, and timing of such symptoms. Although no causative agent(s) could be isolated, the data collected indicate that over the 5-week time period of investigation the rate and persistence of new symptoms decreased. The health complaints experienced appeared to be neither persistent nor pervasive enough to constitute an ongoing health and safety hazard at the facility. Reasons were proposed why some new and/or remodeled buildings have this type of problem while others do not.

Adult↗

PubMed1985

Mortality among members of a heavy construction equipment operators union with potential exposure to diesel exhaust emissions.

A historical prospective mortality study was conducted on a cohort of 34 156 male members of a heavy construction equipment operators union with potential exposure to diesel exhaust emissions. This cohort comprised all individuals who were members of the International Union of Operating Engineers, Locals 3 and 3A, for at least one year between 1 January 1964 and 31 December 1978. The mortality experience of the entire cohort and several subcohorts was compared with that of United States white men, adjusted for age and calendar time. The comparison statistic was the commonly used standardised mortality ratio (SMR). Historical environmental measurements did not exist, but partial work histories were available for some cohort members through the union dispatch computer tapes. An attempt was made to relate mortality experience to the union members' dispatch histories. Overall mortality for the entire cohort and several subgroups was significantly lower than expected. When cause specific mortality was examined, however, the study provided suggestive evidence for the existence of several potential health problems in this cohort. Mortality from liver cancer for the entire cohort was significantly high. Although mortality from lung cancer for the entire cohort was similar to expected, a positive trend by latency was observed for lung cancer. A significant excess of mortality from lung cancer was found among the retirees and the group for whom no dispatch histories were available. Other dispatch groups showed no evidence of lung cancer excess. In addition, the total cohort experienced significant mortality excess from emphysema and accidental deaths.

Accidents, Occupational↗

PubMed1985

Comparison of SMR, PMR, and PCMR in a cohort of union members potentially exposed to diesel exhaust emissions.

A comparison of cause specific standarised mortality ratios (SMRs) and proportionate mortality ratios (PMRs) or proportionate cancer mortality ratios (PCMRs) was made based on the mortality experience of a cohort of 34 156 members of a heavy equipment operators union. Two types of PMRs or PCMRs were used in the comparison: those based on all deaths and those based on deaths known to the union only. The comparison indicated that, for the entire cohort, both types of PMRs were poor indicators for cancer risk and produced a large number of false positives. On the other hand, PCMRs appeared to be better than PMRs for assessing the direction of site specific cancer risk, but they tended to overstate the magnitude of risk. Analysis by duration of union membership or latency indicated that PMRs or PCMRs based on deaths known to the union tended to overestimate the risk of lung cancer by disproportionately larger amounts in groups with shorter time than in groups with longer time. This differential bias had the net effect of reducing the gradient of any trend or eliminating the trend entirely. In conclusion, PMR or PCMR, based on reasonably sufficient death ascertainment, has a certain usefulness in generating hypotheses, but they are not useful or reliable in measuring the magnitude of risk or in detecting trends in dose response analysis. No conclusion should be drawn from either PMR or PCMR.

Air Pollutants, Occupational↗

PubMed1983

Feasibility of identifying high-risk occupations through tumor registries.

The primary objective of this study was to assess the feasibility of using a population-based tumor registry to identify occupational groups at high risk of developing cancer. The study group comprised 6,424 union members residing in the San Francisco/Oakland Standard Metropolitan Statistical Area (SMSA) who represent six occupations: asbestos workers, bakers, painters, plasterers, plumbers and roofers. Computer linkage of union rosters to the California Tumor Registry (CTR) file identified incident cases of cancer. The CTR's age-sex-year-specific incidence rates were used to calculate the expected number of cancer cases, and estimated standardized incidence ratios (SIRs). The results demonstrate, as expected, increased cancer incidence (SIR = 498) for trachea, bronchus, lung and pleura among asbestos workers, a group widely recognized as having high risk for respiratory cancers, and among painters (SIR = 199). Strengths and weaknesses of such an approach are discussed.

Asbestos↗

PubMedDate not supplied

High-performing physician executives.

Physician leadership extends beyond traditional clinical disciplines to hospital administration, group practice management, health policy making, management of managed care programs, and many business positions. What kind of person makes a good physician executive? What stands out as the most important motivations, attributes, and interests of high-performing physician executives? How does this compare with non-physician health care executives? Such questions have long been high on the agenda of executives in other industries. This article builds on existing formal assessments of leadership attributes of high-performing business, government, and educational executives and on closer examination of health care executives. Previous studies looked at the need for innovative, entrepreneurial, energetic, community-oriented leaders for positions throughout health care. Traits that distinguish excellence and leadership were described by Brown and McCool.* That study characterized successful leaders in terms of physical strengths (high energy, good health, and propensity for hard work), mental strengths (creativity, intuition, and innovation), and organizational strengths (mission orientation, vision, and entrepreneurial spirit). In this investigation, a subset of health care executives, including physician executives, was examined more closely. It was initially assumed that successful physician executives exhibit many of the same positive traits as do nonphysician executives. This assumption was tested with physician leaders in a range of administrative and managerial positions. We also set out to identify key differences between physician and nonphysician executives. Even with our limited exploration, it seems to us that physician executives probably do differ from nonphysician executives.

Creativity↗