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R L Smith

Publications and source records attributed to R L Smith.

At least 217 records · Page 12Linked to original sources
PubMed1994

A dry electrode for EEG recording.

This paper describes the design, fabrication and testing of a prototype dry surface electrode for EEG signal recording. The new dry electrode has the advantages of no need for skin preparation or conductive paste, potential for reduced sensitivity to motion artifacts and an enhanced signal-to-noise ratio. The electrode's sensing element is a 3 mm stainless steel disk which has a 2000 A (200 nm) thick nitride coating deposited onto one side. The back side of the disk is attached to an impedance converting amplifier. The prototype electrode was mounted on a copper plate attached to the scalp by a Velcro strap. The performance of this prototype dry electrode was compared to commercially available wet electrodes in 3 areas of electroencephalogram (EEG) recording: (1) spontaneous EEG, (2) sensory evoked potentials, and (3) cognitive evoked potentials. In addition to the raw EEG, the power spectra of the signals from both types of electrodes were also recorded. The results suggest that the dry electrode performs comparably to conventional electrodes for all types of EEG signal analysis. This new electrode may be useful for the production of high resolution surface maps of brain activity where a large number of electrodes or prolonged recording times are required.

Electrodes↗
PubMed1994

Pathobiology of articular cartilage in trapeziometacarpal osteoarthritis. I. Regional biochemical analysis.

Biochemical analysis was performed on hyaline cartilage from four distinct quadrants in surgically harvested osteoarthritic thumb trapeziometacarpal joints and both normal and osteoarthritic cadaver specimens. Chondromalacic surfaces in the palmar contact areas of arthritic specimens were characterized by preferential loss of glycosaminoglycan, retention of collagen, and a shift in glycosaminoglycan subspecies as indicated by an increasing chondroitin sulfate/keratan sulfate ratio. In contrast, articular cartilage from the dorsal portion of arthritic joints biochemically resembled that from both the adjacent normal surfaces of the scaphoid and trapezoid facets and normal postmortem specimens. No significant difference was noted between the biochemical profiles of osteoarthritic surgical specimens and arthritic cadaver specimens. Such selective glycosaminoglycan depletion localized to the contact areas of the joint suggests an interdependent relationship between mechanical factors and biochemical matrix degradation in production of the cartilage lesion of trapeziometacarpal osteoarthritis.

Cadaver↗
PubMed1994

Pathobiology of articular cartilage in trapeziometacarpal osteoarthritis. II. Surface ultrastructure by scanning electron microscopy.

Regional variation in the surface ultrastructure of hyaline cartilage in the osteoarthritic trapeziometacarpal joint was studied by means of scanning electron microscopy. Articular surface degeneration on intact osteochondral specimens was analyzed and correlated with known patterns of gross, histologic, and biochemical disease. The earliest changes were observed in the tangential surface lamina and occurred in areas of chondromalacia in the palmar contact area of the joint. Progressive disruption of this superficial fibrillar layer of the articular cartilage was followed by disorganization of the underlying chondrocytes and matrix. In palmar regions with more advanced chondromalacia and loss of eosinophilic staining, free cellular elements and craters 20-30 microns in diameter, resembling empty chondrocyte lacunae, appeared in conjunction with the absence of any tangential surface meshwork. Eburnated areas demonstrated no fibrillar or cellular elements. Disruption of the protective surface lamina of trapeziometacarpal articular cartilage occurs in a geographic pattern corresponding to joint contact areas and regions of selective biochemical decomposition of proteoglycan matrix. These observations support an interdependent relationship between mechanically induced abrasive surface wear and biochemical matrix degradation in the production of the cartilage lesion of trapeziometacarpal osteoarthritis.

Adult↗
PubMed1994

Synthesis and biological activity of ras farnesyl protein transferase inhibitors. Tetrapeptide analogs with amino methyl and carbon linkages.

Replacement of the central amino methylene linkage of C[psi CH2NH]A[psi CH2NH]AX tetrapeptide inhibitors with carbon tethers led to compounds with potency in the nanomolar range. Some of the more potent olefinic compounds inhibit Ras processing in intact v-ras transformed NIH 3T3 cells with IC50 values in the 0.1 to 1 microM range, and inhibit selectively the anchorage-independent growth of H-ras transformed Rat1 cells at 10 microM.

3T3 Cells↗
PubMed1994

Use of intracavernous injection of prostaglandin E1 for neuropathic erectile dysfunction.

The administration and suitability of intracavernous PGE-1 in men with neuropathic erectile dysfunction is reported herein. Twenty-seven men with neuropathic erectile dysfunction (SCI, 14; multiple sclerosis, 7; discogenic disease, 6) were evaluated and treated with intracavernous PGE-1. An average of 3.2 office sessions were required to learn adequate self-injection technique and determine optimal dosage requirement. Initial dosage for SCI men was 2.5 micrograms and increased in 2.5 micrograms increments to a mean maintenance dose of 6.2 micrograms. Quarterly monitoring up to 28 months demonstrated satisfactory erectile rigidity and duration of erection in all patients electing to pursue home administration of PGE-1. During this interval, over 40% of patients dropped out of the treatment program. No priapism or changes in serum chemistries, CBC, or platelets were observed during this period. Corporal fibrosis although not palpable, was detected subclinically by penile ultrasound in two men. This study confirms the safety and efficacy of self-administered intracavernous PGE-1 for neuropathic impotence. However, because of a significant rate of voluntary cessation, patients should be counseled regarding the full range of therapeutic alternatives to intracavernous therapy.

Adult↗
PubMed1994

Thermal hyperalgesia accelerates and MK-801 prevents the development of tachyphylaxis to rat sciatic nerve blockade.

BACKGROUND: Tachyphylaxis to local anesthetics has been shown to be promoted by longer interanalgesic intervals between injections. We hypothesized that thermal hyperalgesia also would accelerate the development of tachyphylaxis. The n-methyl-D-aspartate antagonist ((+)-5 methyl-10,11-dihydro-5H-dibenzo (a,d) cyclohepten-5,10-imine, or dizocilpine) (MK-801) has been shown to prevent thermal hyperalgesia. We therefore also hypothesized that MK-801 would prevent tachyphylaxis. METHODS: Catheters were surgically implanted in rats along the sciatic nerve. After recovery and conditioning to the testing paradigm, they received repeated injections of lidocaine or 2-chloroprocaine followed by motor block testing with or without hot-plate testing at 48, 52, or 56 degrees C. In other experiments, MK-801 or saline was administered by intraperitoneal injection before sciatic nerve local anesthetic injection and sensory and motor testing. RESULTS: Rats receiving repeated lidocaine or 2-chloroprocaine injections, when repeatedly subjected to hot-plate testing at 56 degrees C, developed thermal hyperalgesia and tachyphylaxis to motor and sensory blockade. Rats receiving either no hot-plate exposure or hot-plate exposure at 48 degrees C developed no tachyphylaxis or hyperalgesia. Rats tested at 52 degrees C developed milder hyperalgesia and developed tachyphylaxis more slowly than did rats tested at 56 degrees C. Control experiments excluded artifacts due to circadian rhythm, injection volume, and learning. Rats pretreated with MK-801 showed no tachyphylaxis over a series of three injections. CONCLUSIONS: Thermal hyperalgesia accelerates the development of tachyphylaxis to rat sciatic nerve blockade, and MK-801 prevents tachyphylaxis in this model. n-Methyl-D-aspartate receptor antagonists may have future clinical utility in increasing the duration of effectiveness of prolonged local anesthetic administration.

Animals↗
PubMed1994

Use of Monte Carlo simulation for human exposure assessment at a superfund site.

This work presents a comparison of probabilistic and deterministic health risk estimates based on data from an industrial site in the northeastern United States. The risk assessment considered exposures to volatile solvents by drinking water ingestion and showering. Probability densities used as inputs included concentrations, contact rates, and exposure frequencies; dose-response inputs were single values. Deterministic risk estimates were calculated by "reasonable maximum exposure" (RME) approach recommended by the EPA Superfund program. The RME noncarcinogenic risk fell between the 90th and the 95th percentile of the probability density; the RME cancer risk fell between the 95th percentile and the maximum. These results suggest that in this case (1) EPA's deterministic RME risk was reasonably protective, (2) results of probabilistic and deterministic calculations were consistent, and (3) commercially available software Monte Carlo software effectively provided multiple risk estimates recommended by recent EPA guidance.

Adult↗
PubMed1994

Use of molecular techniques to evaluate the survival of a microorganism injected into an aquifer.

A PCR primer set and an internal probe that are specific for Pseudomonas sp. strain B13, a 3-chlorobenzoate-metabolizing strain, were developed. Using this primer set and probe, we were able to detect Pseudomonas sp. strain B13 DNA sequences in DNA extracted from aquifer samples 14.5 months after Pseudomonas sp. strain B13 had been injected into a sand and gravel aquifer. This primer set and probe were also used to analyze isolates from 3-chlorobenzoate enrichments of the aquifer samples by Southern blot analysis. Hybridization of Southern blots with the Pseudomonas sp. strain B13-specific probe and a catabolic probe in conjunction with restriction fragment length polymorphism (RFLP) analysis of ribosome genes was used to determine that viable Pseudomonas sp. strain B13 persisted in this environment. We isolated a new 3-chlorobenzoate-degrading strain from one of these enrichment cultures. The B13-specific probe does not hybridize to DNA from this isolate. The new strain could be the result of gene exchange between Pseudomonas sp. strain B13 and an indigenous bacterium. This speculation is based on an RFLP pattern of ribosome genes that differs from that of Pseudomonas sp. strain B13, the fact that identically sized restriction fragments hybridized to the catabolic gene probe, and the absence of any enrichable 3-chlorobenzoate-degrading strains in the aquifer prior to inoculation.

Base Sequence↗
PubMed1994

Autotrophic, hydrogen-oxidizing, denitrifying bacteria in groundwater, potential agents for bioremediation of nitrate contamination.

Addition of hydrogen or formate significantly enhanced the rate of consumption of nitrate in slurried core samples obtained from an active zone of denitrification in a nitrate-contaminated sand and gravel aquifer (Cape Cod, Mass.). Hydrogen uptake by the core material was immediate and rapid, with an apparent K(m) of 0.45 to 0.60 muM and a V(max) of 18.7 nmol cm h at 30 degrees C. Nine strains of hydrogen-oxidizing denitrifying bacteria were subsequently isolated from the aquifer. Eight of the strains grew autotrophically on hydrogen with either oxygen or nitrate as the electron acceptor. One strain grew mixotrophically. All of the isolates were capable of heterotrophic growth, but none were similar to Paracoccus denitrificans, a well-characterized hydrogen-oxidizing denitrifier. The kinetics for hydrogen uptake during denitrification were determined for each isolate with substrate depletion progress curves; the K(m)s ranged from 0.30 to 3.32 muM, with V(max)s of 1.85 to 13.29 fmol cell h. Because these organisms appear to be common constituents of the in situ population of the aquifer, produce innocuous end products, and could be manipulated to sequentially consume oxygen and then nitrate when both were present, these results suggest that these organisms may have significant potential for in situ bioremediation of nitrate contamination in groundwater.

Journal Article↗
PubMed1994

The fibronectin adhesin of Candida albicans.

Candida albicans possesses on its cell surface an adhesin which binds the whole viable fungus to subendothelial extracellular matrix and matrix proteins. The adhesin is composed of 75 to 80% carbohydrate and approximately 20 to 25% protein by weight. High-performance liquid chromatography of material eluted from a fibronectin-agarose affinity column demonstrates the presence of three peaks, all of which on sodium dodecyl sulfate-polyacrylamide gel electrophoresis show the presence of one protein of approximately 60 kDa. Molecular weight sizing column chromatography, however, demonstrates that the adhesin elutes with an apparent molecular mass of 42 kDa. The N terminus of the 60-kDa glycoprotein is blocked to Edman degradation. The fibronectin adhesin of C. albicans is a glycoprotein that may be present and functional as an aggregate or multimer of a 60-kDa protein.

Adhesiveness↗
PubMed1994

Membrane topology of Escherichia coli diacylglycerol kinase.

The topology of Escherichia coli diacylglycerol kinase (DAGK) within the cytoplasmic membrane was elucidated by a combined approach involving both multiple aligned sequence analysis and fusion protein experiments. Hydropathy plots of the five prokaryotic DAGK sequences available were uniform in their prediction of three transmembrane segments. The hydropathy predictions were experimentally tested genetically by fusing C-terminal deletion derivatives of DAGK to beta-lactamase and beta-galactosidase. Following expression, the enzymatic activities of the chimeric proteins were measured and used to determine the cellular location of the fusion junction. These studies confirmed the hydropathy predictions for DAGK with respect to the number and approximate sequence locations of the transmembrane segments. Further analysis of the aligned DAGK sequences detected probable alpha-helical N-terminal capping motifs and two amphipathic alpha-helices within the enzyme. The combined fusion and sequence data indicate that DAGK is a polytopic integral membrane protein with three transmembrane segments with the N terminus of the protein in the cytoplasm, the C terminus in the periplasmic space, and two amphipathic helices near the cytoplasmic surface.

Amino Acid Sequence↗
PubMed1994

Factors affecting the yield of acid-fast sputum smears in patients with HIV and tuberculosis.

OBJECTIVE: To evaluate the sensitivity of acid-fast sputum smears in the diagnosis of pulmonary Mycobacterium tuberculosis (MTB). DESIGN: Retrospective chart and radiographic film review. SETTING: Department of Veterans Affairs Medical Center in New York City. PATIENTS: All patients with positive sputum cultures for MTB during 1989 to 1991, including 100 with HIV, and 76 without HIV infection. PARAMETERS: The likelihood of a positive acid-fast sputum smear, related to chest radiograph findings, CD4 cell counts, drug sensitivity, and the presence of disseminated disease. RESULTS: Overall, 60 percent of patients with HIV had positive acid-fast smears, compared with 57 percent of non-HIV-infected patients. A relative absence of cavitary infiltrates did not substantially reduce the frequency of acid-fast smears in patients with and without HIV. Patients with HIV and CD4 count < 50, 50 to 200, and > 200 had positive acid-fast smear rates of 58 percent, 60 percent, and 56 percent, respectively; HIV-infected patients with drug-resistant organisms had 65 percent positive smears. Smear positivity was 96 percent in patients with HIV infection and disseminated MTB, CONCLUSIONS: Positive acid-fast sputum smears in culture-proven MTB occur with similar frequency in patients with and without HIV. The absence of cavitary disease did not significantly reduce the frequency of positive acid-fast smears. For patients with HIV, the likelihood of a positive smear was also independent of CD4 cell counts and drug resistance. Patients with HIV and disseminated MTB had positive sputum smears in nearly all cases.

AIDS-Related Opportunistic Infections↗
PubMed1994

Therapists' ability to identify safe maximum lifting in low back pain patients during functional capacity evaluation.

Functional capacity evaluation (FCE) of an injured worker's ability to lift weight guides the determination of whether he or she is capable of handling the physical demands of a job. The purpose of this study was to examine the interrater and intrarater reliability in determining the safe maximum floor-to-waist lift for patients with low back pain during FCE testing. Twenty-one patients with low back pain were evaluated. Patients were videotaped lifting weight in progressive increments using a kinesiophysical approach. Five experienced physical therapists viewed the videotape and judged the lifts for body mechanics safety. Safety reliability was high, indicating that therapists can accurately judge safe lifting methods during FCE. As lifting loads increased, body mechanics deteriorated, indicating the patient was approaching or had reached a biomechanical end point. Clinical information is needed, in addition to visual observations, to accurately determine when maximum lift capacity is reached.

Adult↗
PubMed1994

Fate of dimethylamine in rat and mouse.

1. [U-14C]-dimethylamine hydrochloride was administered by gavage (20 mumol/kg body weight) to adult male Wistar rat and CD1 strain mouse. 2. In both species, urine was the main route of excretion with the majority of radiolabel (91%) being voided during the first day. Additional small amounts of radioactivity were detected in the 24-72 h urine (2%), in faeces (2%) and amidst exhaled air (1%), with minor amounts remaining within the carcass (1%) after 3 days. 3. Metabolism was limited to demethylation, with the majority of the compound (89% dose; 96% urinary radioactivity) being excreted unchanged.

Animals↗
PubMed1994

Fate of dimethylamine in man.

1. The fate of [14C]-dimethylamine was investigated following oral administration to four male volunteers. 2. The major route of excretion was urine, with 94% of the administered radioactivity being voided over 3 days (87% during the first 24 h). Small amounts (1-3%) of radioactivity were found in the faeces and expired air. 3. Metabolism was limited with only 5% being demethylated to methylamine. The remainder of the dose was excreted unchanged. 4. Pharmacokinetic studies indicated rapid (t1/2ab = 8 min) and extensive absorption (bioavailability = 82%) from the gastrointestinal tract followed by widespread distribution and a fairly prompt excretion (t1/2el = 6-7 h) with a plasma clearance of 190 ml/min.

Administration, Oral↗