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Biomedical subjects

R W Smith

Publications and source records attributed to R W Smith.

At least 37 records · Page 2Linked to original sources
PubMed2001

Evaluation and use of sediment toxicity reference sites for statistical comparisons in regional assessments.

Sediment reference sites were used to establish toxicity standards against which to compare results from sites investigated in San Francisco Bay (California, USA) monitoring programs. The reference sites were selected on the basis of low concentrations of anthropogenic chemicals, distance from active contaminant sources, location in representative hydrographic areas of the Bay, and physical features characteristic of depositional areas (e.g., fine grain size and medium total organic carbon [TOC]). Five field-replicated sites in San Francisco Bay were evaluated over three seasons. Samples from each site were tested with nine toxicity test protocols and were analyzed for sediment grain size and concentrations of trace metals, trace organics, ammonia, hydrogen sulfide, and TOC. The candidate sites were found to have relatively low concentrations of measured chemicals and generally exhibited low toxicity. Toxicity data from the reference sites were then used to calculate numerical tolerance limits to be used as threshold values to determine which test sites had significantly higher toxicity than reference sites. Tolerance limits are presented for four standard test protocols, including solid-phase sediment tests with the amphipods Ampelisca abdita and Eohaustorius estuarius and sea urchin Strongylocentrotus purpuratus embryo/larval development tests in pore water and at the sediment-water interface (SWI). Tolerance limits delineating the lowest 10th percentile (0.10 quantile) of the reference site data distribution were 71% of the control response for Ampelisca, 70% for Eohaustorius, 94% for sea urchin embryos in pore water, and 87% for sea urchins embryos exposed at the SWI. The tolerance limits are discussed in terms of the critical values governing their calculation and the management implications arising from their use in determining elevated toxicity relative to reference conditions.

Algorithms↗
PubMed2000

Col2-GFP reporter marks chondrocyte lineage and chondrogenesis during mouse skeletal development.

Mice were generated in which a Col2-GFP transgene serves as a reporter for the chondrocyte lineage and for chondrogenesis in live embryos and newborn pups. Cells actively engaged in chondrogenesis were identified by confocal optical sectioning within their native environments in embryos and in thick tissue slices. Chondrocytes exhibiting GFP fluorescence were purified from rib cages by high-speed cell sorting of crude cell suspensions. Intensity of fluorescence correlated with biosynthesis of procollagen II in these cells. The use of these mice and their cells provides a novel approach for studying chondrocyte differentiation and chondrogenesis during skeletal development.

Animals↗
PubMed2000

RNA turnover and protein synthesis in fish cells.

Protein synthesis in fish has been previously correlated with RNA content. The present study investigates whether protein and RNA synthesis rates are similarly related. Protein and RNA synthesis rates were determined from 3H-phenylalanine and 3H-uridine incorporation, respectively, and expressed as % x day(-1) and half-lives, respectively. Three fibroblast cell lines were used: BF-2, RTP, CHSE 214, which are derived from the bluegill, rainbow trout and Chinook salmon, respectively. These cells contained similar RNA concentrations (approximately 175 microg RNA x mg(-1) cell protein). Therefore differences in protein synthesis rates, BF-2 (31.3 +/- 1.8)>RTP (25.1 +/- 1.7)>CHSE 214 (17.6 +/-1.1), were attributable to RNA translational efficiency. The most translationally efficient RNA (BF-2 cells), 1.8 mg protein synthesised x microg(-1) RNA x day(-1), corresponded to the lowest RNA half-life, 75.4 +/- 6.4 h. Translationally efficient RNA was also energetically efficient with BF-2 cells exploiting the least costly route of nucleotide supply (i.e. exogenous salvage) 3.5-6.0 times more than the least translationally efficient RNA (CHSE 214 cells). These data suggest that differential nucleotide supply, between intracellular synthesis and exogenous salvage, constitutes the area of pre-translational flexibility exploited to maintain RNA synthesis as a fixed energetic cost component of protein synthesis.

Animals↗
PubMed2000

Characterization of ginseng saponins using electrospray mass spectrometry and collision-induced dissociation experiments of metal-attachment ions.

Electrospray mass spectrometry (ESMS) and collision-induced dissociation (CID) methodologies have been developed for the structural characterization of ginseng saponins (ginsenosides). Ginsenosides are terpene glycosides containing a triterpene core to which one to four sugars may be attached. They are neutral molecules which readily form molecular metal-attachment ions in positive ion ESMS experiments. In the presence of ammonium hydroxide intense deprotonated ions are generated. Both positive and negative ion ESMS experiments were found to be useful for molecular mass and structure determination of ten ginsenoside standards. Negative ion experiments made possible the determination of the molecular mass of each ginsenoside standard, the mass of the triterpene core and the masses and sequences of the sugar residues. Positive ion ESMS experiments with the alkali metal cations Li+ or Na+ and the transition metal cations Co2+, Ni2+ and Zn2+ were also useful in determining molecular masses. These alkali and transition metal cations form strongly bonded attachment ions with the ginsenosides. As a result, the CID mass spectra of the metal attachment ions show a variety of (structure characteristic) fragmentations. These experiments can be used to determine the identity of the triterpene core, the types and attachment points of sugars to the core and the nature of the O-glycosidic linkages in the appended disaccharides. Combining the results from the negative and positive ion experiments provides a promising approach to the structure analysis of this class of natural products.

Mass Spectrometry↗
PubMed2000

Characterization of patients with primary peroneus longus tendinopathy: a review of twenty-two cases.

Between 1985 and 1996 we treated 22 patients with a diagnosis of PLT which was confirmed by MRI and/or surgery. This review identifies the shared clinical traits and associated pathology of our patients. Clinically, 82% of the patients had a cavo-varus hindfoot position. This finding was supported by measurements of the calcaneal pitch angle and the calcaneal-lst metatarsal angle which both showed the patients in this study to be in the 90th percentile for the general population for arch height. The combined MRI and surgical findings revealed injury to the peroneus longus at the cuboid notch in 17 of 22 cases. The subgroup of surgical findings demonstrated that all 6 complete tears occurred at the cuboid notch, while 8 of 9 (89%) of the partial tears involved the region of the lateral calcaneal process. In addition, the surgical findings showed 7 of the cases (33%) to have associated peroneus brevis tendon involvement, with an increased incidence when the longus pathology occurred at the cuboid notch. The findings predicated by MRI correlated well with the surgical findings, but there was a tendency for MRI to predict a more severe level of pathology. A grading system developed to compare the MRI and surgical findings is presented. This study facilitates making the diagnosis of PLT by drawing attention to the common characteristic of the cavo-varus foot position and the common locations of tendon injury.

Adult↗
PubMed2000

Outcomes in hallux rigidus patients treated nonoperatively: a long-term follow-up study.

The purpose of this study was to analyze radiographic outcome and patient satisfaction in non-operative care of hallux rigidus. Twenty-two patients representing 24 feet were surveyed and radiographed. Average follow-up was 14.4 years (range, 12-19 years). In 75% (18/24) of the feet, the patients would "still chose not to have surgery" if they had to make the decision again. The pain remained about the same in 22 feet, improved with time in one, and became worse in one. The most common reason given for not having surgery was that the pain was not severe enough. The most common type of self-care was a shoe with an "ample toe box." More patients benefited from a stiff sole than a soft sole, but the majority of patients did not cite the sole of the shoe as being important. There was measurable loss of cartilage space radiographically over time in 16 of 24 feet, and in eight of the 16 feet, the loss of cartilage space was dramatic. The majority of hallux rigidus patients rated their pain as staying the same over a twelve-year period, despite significant deterioration of joint space noted radiographically.

Adult↗
PubMed1999

Analysis of high-molecular-mass polycyclic aromatic hydrocarbons in environmental samples using liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

Polycyclic aromatic hydrocarbons (PAHs) with molecular masses higher than 300 u were analysed using LC-atmospheric pressure chemical ionization (APCI) MS in extracts of environmental samples from Hamilton, Canada including zebra mussels from Hamilton Harbour, air particulate and coal tar. The LC-APCI-MS profiles of three molecular mass classes of PAHs (326 u, 350 u and 374 u) were compared to identify potential sources of PAH contamination in Hamilton Harbour. The Hamilton air particulate profile was also compared with an urban air reference standard (NIST SRM 1649) from Washington, DC, USA. Profiles of all extracts were similar and suggested an environmental predominance of PAHs within the three isomeric molecular mass classes studied. However, PAHs of molecular mass 326 u and 350 u were detected in extracts of coal tar and zebra mussels from Hamilton Harbour but were not detected in Hamilton air. These results indicated that some high-molecular-mass PAHs may be characteristic of contamination by coal tar.

Air Pollutants↗
PubMed1999

Emergency physician treatment of acute stroke with recombinant tissue plasminogen activator: a retrospective analysis.

UNLABELLED: Stroke teams are advocated for the rapid treatment of patients who have acute ischemic stroke (AIS) with recombinant tissue plasminogen activator (rt-PA). An alternate model uses existing ED resources with specialist consultation as needed. OBJECTIVES: To evaluate the treatment of AIS with rt-PA in this alternate ED model. METHODS: A retrospective observational review was performed of consecutive patients with AIS treated with rt-PA at four hospitals affiliated with an emergency medicine residency. Emergency physicians (EPs) were directly responsible for the treatment of all patients according to predefined guidelines. Records were evaluated from the implementation of the guidelines through December 15, 1997. RESULTS: 37 patients with AIS received rt-PA. Mean age+/-SD was 63+/-16 years (range 22-87), with 25 (68%) male. Patients presented 67+/-29 minutes after stroke onset. After ED arrival, they were seen by the EP in 14+/-13 minutes, had CT in 46+/-22 minutes, and were treated in 97+/-35 minutes. Neurologist consultation occurred in the department for nine patients (24.3%), and by telephone for 14 (37.8%). Symptomatic intracerebral hemorrhage (ICH) occurred in four (10.8%, 95% CI = 0.8% to 20.8%). There were two deaths, neither associated with ICH. Neurologic outcome at discharge compared with presentation in survivors was normal for four patients (11.4%), improved for 16 (45.7%), unchanged for ten (28.6%), and worse for five (14.3%). CONCLUSIONS: In this analysis, EPs, with specialty consultation as required, successfully identified patients with AIS and delivered rt-PA with satisfactory outcomes. Important elements of this model include early patient identification, preestablished protocols, and rapid access to CT scanning and interpretation.

Acute Disease↗
PubMed1999

Tissue-specific changes in RNA synthesis in vivo during anoxia in crucian carp.

The overall energy budget for protein synthesis (i.e., transcription plus translation) is thought to consist of fixed and variable components, with RNA synthesis accounting for the former and protein synthesis the latter. During anoxia, the downregulation of protein synthesis (i.e., the variable component), to reduce energetic demand, is an important aspect of survival in crucian carp. The present study examines RNA synthesis during anoxia by labeling with [(3)H]uridine. A novel synthesis rate calculation is presented, which allows for the tissue-specific salvage of uridine, with synthesis rates finally expressed relative to DNA. After 48 h anoxia, the decline (29%) in brain RNA synthesis and increases in the heart and liver (132 and 871%, respectively) support known RNA functions during hypoxic/anoxic survival. This study provides evidence that, in an anoxia-tolerant species, survival mechanisms involving RNA are able to operate because tissue-specific restructuring of the RNA synthesis process enables fixed synthesis costs to be maintained; this may be as vital to survival as exploiting the variable energetic demand of protein synthesis.

Animals↗
PubMed1999

Proximal phalanx osteotomy for the surgical treatment of hallux rigidus.

This study reviewed 17 patients (24 great toes) treated by a single surgeon for hallux rigidus with a dorsal-closing wedge osteotomy of the proximal phalanx in conjunction with a moderate cheilectomy. The average age of patients was 47 years (range, 20-69 years). The minimum follow-up was 1 year (range, 1-16 years; median follow-up, 30 months), and all but five patients were studied for 2 years or more. Ninety-six percent of patients affirmed their decision to have surgery if they had to make the choice again. Subjectively, all patients improved. Preoperatively, 67% of the cases had severe pain by American Orthopaedic Foot and Ankle Society criteria. Postoperatively, 58% had no pain and 42% had mild pain. There was 100% union rate of the osteotomy. Seven of 10 women and 1 of 7 men still had some restrictions on footwear options postoperatively. Recovery time from the patients' perspective was 2 to 12 months (average, 5.6 months). Based on the results of this study, the authors suggest that the addition of a dorsal-closing wedge osteotomy of the proximal phalanx increases patient satisfaction, compared with their review of patients treated by cheilectomy alone. The procedure provides good pain relief and has few complications.

Adult↗
PubMed1998

Primase activity of human DNA polymerase alpha-primase. Divalent cations stabilize the enzyme activity of the p48 subunit.

DNA polymerase alpha-primase consists of four subunits, p180, p68, p58, and p48, and comprises two essential enzymatic functions. To study the primase activity of the complex, we expressed cDNAs encoding for the human p58 and p48 subunits either as single proteins or together using Escherichia coli expression vectors. Co-expression of both primase subunits allowed the purification of a heterodimer in high yields that revealed stable primase activity. Purified recombinant p48 subunit showed enzyme activity, whereas purified p58 did not. In contrast to the heterodimer, the primase activity of p48 was unstable. The activity of p48 could be stabilized by the addition of the divalent cations Mg2+ and Mn2+ but not Zn2+. On a poly(dC) template the primase activity was hardly influenced by the monovalent cation potassium. However, by using poly(dT) as a template the recombinant p48 activity was sensitive to salt, whereas recombinant p58-p48 and the bovine DNA polymerase alpha-primase purified from thymus were less sensitive to the addition of monovalent cations. A complex of bacterially expressed primase and baculovirus-expressed p180 and p68 was assembled in vitro and shown to support replication of simian virus 40 DNA in a cell-free system.

Animals↗
PubMed1998

Fractures and other injuries from falls after an ice storm.

This is a retrospective review of all patients seen at an urban emergency department for 9 days after an ice storm because of a fall on ice. Date of presentation, age, sex, and anatomic location and type of injury were tabulated. Risk factors for fractures were identified. A total of 327 injuries were identified in 259 patients. Back injury was most common (19.3%). Ninety-one patients sustained 93 fractures. Ankle fractures were most common (24.7%), followed by fractures of wrist (19.4%) and hip (14.0%). Ankle fractures were more common than other studies of falls after a snow storm. Fracture was significantly related to age (P = .0001). There was a trend for women to sustain fractures (P = .07). Unlike other mass casualty events, fractures and injuries peaked on the 5th and 6th day after the storm, allowing adequate time for mobilizing resources to care for the injured.

Accidental Falls↗
PubMed1998

The time-course of the generation effect.

The generation effect, in which items generated by following some rule are remembered better than stimuli that are simply read, has been studied intensely over the past two decades. To date, however, researchers have largely ignored the temporal aspects of this effect. In the present research, we used a variable onset time for the presentation of the to-be-remembered material, thus providing the ability to determine at what point during processing the generation effect originates. The results indicate that some benefit from generation attempts occurs even when subjects have only a few hundred milliseconds in which to process the stimulus, but that more of the benefit occurs later. This finding suggests that the generation effect results from continuous or multiple discrete stages of information accrual or strengthening of memory traces over time, rather than from a single discrete increment upon final generation.

Analysis of Variance↗