Search PubMed⌕ Search

Biomedical subjects

D C Smith

Publications and source records attributed to D C Smith.

At least 181 records · Page 10Linked to original sources
PubMed1991

Heparin supplementation of nonionic contrast agents.

Diatrizoate has been widely used clinically for many years and has been effective in inhibiting clot formation in catheters and syringes. The authors attempted to determine the amount of heparin required to raise the anticoagulant potency of ioversol, iohexol, or iopamidol to that of diatrizoate. The anticoagulant potency of ioxaglate was also examined. One hundred eighty glass syringes containing unmodified diatrizoate, unmodified ioxaglate, or a nonionic contrast agent mixed with incremental amounts of heparin were contaminated with venous blood from 10 healthy volunteers. The syringes were then repeatedly disturbed to simulate the frequent handling that occurs during an angiographic procedure. The weights of the clots in the syringes at 30 minutes were plotted against heparin levels and indicated that, for the average sample studied, the "diatrizoate-equivalent" heparin level for ioversol, iohexol, or iopamidol was less than 1.5 U (USP) of heparin per milliliter. An additional margin of anticoagulation is probably desirable. The 97.5 percentile of the distribution of the diatrizoate equivalents in the population was estimated to require a heparin dose of 3.5 U/mL.

Anticoagulants↗
PubMed1991

Use of angiographic needles with or without stylets: pathologic assessment of vessel walls after puncture.

There is controversy as to whether angiographic needles without stylets produce more arterial damage than those with stylets. Iliac arteries from 15 fresh human cadavers were punctured 56 times with either an 18-gauge angiographic needle with a stylet or one without a stylet (28 punctures with each needle type). These puncture sites were serially sectioned and examined microscopically. Each needle tract was evaluated for margin irregularity, shape of puncture, and approximation of edges. No statistically significant differences in arterial wall changes were found. The authors' data suggest that the choice of beveled needle use in angiography can probably be made on a basis other than concern for differences in vessel wall damage secondary to the presence or absence of a stylet.

Angiography↗
PubMed1991

Central enhancement of evoked electromyographic monitoring of neuromuscular function.

Central neural influences on neuromuscular transmission may explain the frequent failure of evoked electromyographic (EEMG) responses to return to control values during offset of neuromuscular block. This study, performed in conscious subjects, did not demonstrate any change in EEMG response of either the first dorsal interosseous muscle during onset of ulnar nerve block or the flexor hallucis brevis during onset of subarachnoid block. It is concluded that central enhancement of EEMG response via a neural mechanism does not explain the observed failure of EEMG monitoring of neuromuscular block.

Adult↗
PubMed1991

alpha-Glucuronidase and Other Hemicellulase Activities of Fibrobacter succinogenes S85 Grown on Crystalline Cellulose or Ball-Milled Barley Straw.

Fibrobacter succinogenes produces an alpha-glucuronidase which cleaves 4-O-methyl-alpha-d-glucuronic acid from birch wood 4-O-methyl-alpha-d-glucuronoxylan. Very low levels of alpha-glucuronidase activity were detected in extracellular enzyme preparations of F. succinogenes on birch wood xylan substrate. The release of 4-O-methyl-alpha-d-glucuronic acid was enhanced when the birch wood xylan substrate was predigested by either a purified Schizophyllum commune xylanase or a cloned F. succinogenes S85 xylanase. These data suggest that the alpha-glucuronidase is unable to cleave 4-O-methyl-alpha-d-glucuronic acid from intact xylan but can act on unique low-molecular-weight glucuronoxylan fragments created by the cloned F. succinogenes xylanase. The cloned xylanase presumably must account for a small proportion of the indigenous xylanase activity of F. succinogenes cultures, since this xylanase source does not support high glucuronidase activity. The alpha-glucuronidase and associated hemicellulolytic enzymes exhibited higher activities in culture fluid from cells grown on ball-milled barley straw than in that of cellulose-grown cells. The profile of xylanases separated by isoelectric focusing (zymogram) of culture filtrate from cells grown on barley straw was more complex than that of culture filtrates from cells grown on cellulose. These data demonstrate that F. succinogenes produces an alpha-glucuronidase with an exacting substrate specificity which enables extensive cleavage of glucuronic acid residues from xylan as a consequence of synergistic xylanase action.

Journal Article↗
PubMed1991

Cloning of a xylanase gene from Fibrobacter succinogenes 135 and its expression in Escherichia coli.

A genomic library consisting of 4- to 7-kb EcoRI DNA fragments from Fibrobacter succinogenes 135 was constructed using a phage vector, lambda gtWES lambda B, and Escherichia coli ED8654 as the host bacterium. Two positive plaques, designated lambda FSX101 and lambda FSX102, were identified. The inserts were 10.5 and 9.8 kb, respectively. A 2.3-kb EcoRI fragment that was subcloned from lambda FSX101 into pBR322 also showed xylanase activity. Southern blot analysis showed that the cloned EcoRI fragment containing the xylanase gene had originated from F. succinogenes 135. The cloned endo-(1,4)-beta-D-xylanase gene (pFSX02) was expressed constitutively in E. coli HB101 when grown on LB and on M9 medium containing either glucose or glycerol as the carbon source. Most of the beta-D-xylanase activity was located in the periplasmic space. Zymogram activity stains of nondenaturing polyacrylamide gels and isoelectric focusing gels showed that several xylanase isoenzymes were present in the periplasmic fraction of the E. coli clone FSX02 and they probably were due to posttranslational modification of a single gene product. Comparison of the FSX02 xylanase and the xylanase from the extracellular culture fluids of F. succinogenes 135 and S85 for their ability to degrade oat spelt xylan showed that, for equal units of beta-D-xylanase activity, hydrolysis by the cloned gene product was more complete. However, unlike the unfractionated mixture of xylanases from F. succinogenes 135 and S85, the enzyme from E. coli FSX02 was unable to release arabinose from oat spelt xylan.

Animals↗
PubMed1991

Adhesion to bovine dentin--surface characterization.

X-ray photo-electron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) were used to characterize the dentin surface, to determine the effects of different pre-conditioning procedures on the elemental composition of the dentin surface, and to investigate the interaction between dentin and a dentin bonding agent (ScotchBond) by studying the changes in the elemental composition of dentin as a result of the interaction. Scanning electron microscopy (SEM) was used to characterize sample surface morphology, which was then correlated with surface elemental composition. The results showed that: (a) the elemental composition of the smear layer was similar to that of the underlying dentin; (b) cleaning with hydrogen-peroxide did not produce any modification in the elemental composition of the dentin surface; and (c) acid-etching led to an almost complete demineralization of the dentin, leaving behind an organic-rich surface. The results suggest that bonding systems that use acid-etching as a pre-conditioning procedure should be based on agents able to interact with the organic components of dentin, since bonding agents that rely on a chelation-to-calcium reaction are unlikely to be successful. The investigation of the interaction between the bonding agent and dentin led to a postulated adhesive-bonding reaction mechanism and suggested a partially cohesive failure in the bonding agent during fracturing of a dentin-bonding-agent-bonded assembly.

Acid Etching, Dental↗
PubMed1991

Dental cements.

A wide variety of dental cements continues to be used in clinical dentistry. No new system has been developed in the last few years, but the continued development of the glass ionomer and adhesive resin cements has extended clinical techniques and led to a decline in the use of the traditional phosphate and zinc oxide-eugenol materials. The more critical manipulation of the newer materials has led to problems related to marginal leakage and to pulpal sensitivity. Strong bonding to metallic surfaces can be achieved by appropriate surface treatments, but bonding to the tooth surface is less certain. More longer-term clinical research is required before new and improved cementing systems can be developed.

Dental Bonding↗
PubMed1991

Determination of chromium, cobalt and molybdenum in synovial fluid by GFAAS.

An artificial knee joint made of a cobalt alloy (Cr 27-38%, Mo 5-7%, others 9%, Co balance) failed in an orthopaedic patient with severe tissue reaction. Samples of synovial fluid and blood were analyzed for cobalt, chromium and molybdenum concentration using graphite furnace atomic absorption spectrophotometry (GFAAS). NIST SRM 909 Human Serum containing 91.3 micrograms/L chromium was used as the Cr Standard. To obtain reliable values for cobalt and molybdenum, three different independent analytical methods were employed to analyze each sample: 1) dilution of the samples with Triton TX-100 solution, followed by GFAAS; 2) microwave decomposition of the samples, followed by GFAAS; 3) classic nitric-perchloric acid decomposition of the samples, followed by GFAAS. The two decomposition methods were used to control the accuracy of the dilution method. The results showed that the non-decomposition method gave comparable results to the decomposition techniques for analysis of synovial fluid and blood. The data revealed that the patient had elevated levels of Co, Cr and Mo in both synovial fluid and blood with the values being 2-3 orders of magnitude higher in the synovial fluid from the affected knee.

Chromium↗
PubMed1991

The establishment and validation of the mobile immunization team concept at a clinic level.

Faced with unacceptably low and declining overall immunization compliance, as well as specific flu immunization compliance, the Executive Committee of a 32-person Air National Guard clinic asked the nursing service to devise a method of correcting these deficiencies as rapidly as possible and maintaining immunization compliance at a rate of 90% or better of the total patient population of approximately 1,100 full-time and Guard personnel for whom the clinic was responsible. The concept of a mobile immunization team was devised and validated over a 2-year interval. In order to successfully develop and implement this concept, command emphasis and a high level of cooperation from both clinic personnel and the Unit Commanders involved was requested and received. The make-up of the team, risk management, the timing and place of team visits, and record keeping were among the problems addressed and resolved. The mobile immunization team concept was a success, achieving excellent overall immunization compliance and outstanding compliance with the flu immunization program over a 2-year period.

Health Promotion↗
PubMed1990

Intraventricular infusions of antibodies to amyloid-beta-protein precursor impair the acquisition of a passive avoidance response in the rat.

Intraventricular infusions of an antiserum raised against a 14 amino acid residue in the extracellular domain of amyloid-beta-protein precursor significantly decreased stepdown latency, at both 24 h and 48 h recall times, in rats trained to avoid an electroshock by remaining on a platform. The antiserum was effective when infused up to 2.5 h following training and no retention deficit was noted when it was administered at 4h or 6h after training. An antiserum generated against a 17 amino acid residue of the A4 amyloid peptide had no effect on learning. Thus the amyloid precursor protein, which is aberrantly processed in Alzheimer's disease, appears to be directly involved in memory formation.

Adult↗
PubMed1990

Entrapment of a folded-over introducer sheath in the iliofemoral artery: an unusual complication of PTCA guiding catheter exchange.

An arterial introducer sheath became folded over in the iliac artery during PTCA. This probably resulted from withdrawal of a doubled over Judkins left coronary guiding catheter through the introducer sheath. Nonsurgical, atraumatic removal was accomplished after the acute bend of the introducer sheath had been withdrawn to the site of arterial entrance.

Adult↗
PubMed1990

Effects of alternating monocular occlusion on the development of visual callosal connections.

During normal postnatal development there is a partial elimination of the callosal projections of cortical areas 17 and 18 in the cat. Visual experience early in life can modulate this process. In the present study, we investigated how restricting visual experience to alternating monocular occlusion affects the development of the callosal connections of cortical areas 17 and 18. Alternating monocular occlusion exaggerates the normally occurring partial elimination of immature callosal projection: it causes a significant reduction in the total number of neurons in the supragranular layers that send an axon through the corpus callosum and marginally increases the distribution of these neurons across areas 17 and 18. Examination of these data in the context of the effects of other types of abnormal early visual experience on the corpus callosum and on the anatomy and physiology of areas 17 and 18 indicates that the postnatal development of the corpus callosum is under the control of multiple, interacting influences which differ in the magnitude and quality of their effects. The data also support the conclusion, drawn from our results in prior studies, that normal visual stimulation is necessary for the stabilization of the normal complement of callosal projections.

Animals↗
PubMed1990

Myomectomy as a reproductive procedure.

This series of 64 myomectomies describes the indications, technique, and efficacy of the procedure; the majority of operations were performed on large multinodular uteri. Indications included enlarging pelvic mass, menorrhagia, anemia, and pregnancy wastage in women who wished to preserve reproductive capability. Although infertility was not the primary indication in any case, 32 patients were nulligravid. Only 10 patients were parous and 14 had a history of spontaneous abortion or pregnancy wastage. The average age of the patients was 35.8 years (range, 27 to 47 years). There were no major complications and no patients received blood transfusions. Follow-up revealed three patients with recurrent tumors necessitating repeat procedures. Successful pregnancies have occurred in 40% of those attempting pregnancy. It is concluded that successful myomectomy can be performed in most patients regardless of uterine size, thereby preserving reproductive potential.

Adult↗
PubMed1990

The influence of time of hydrogen peroxide exposure on the adhesion of composite resin to bleached bovine enamel.

Standard sized cylinders of a small particle light-cured resin were bonded to the flattened labial surface of young bovine incisor teeth which had been previously subjected to four different treatments: (a) immersion in 35% hydrogen peroxide and etched with 37% phosphoric acid gel for 60 s, (b) immersion in saline and etched for 60 s, (c) etched for 60 s and immersion in hydrogen peroxide, and (d) etched for 60 s and immersion in saline. Two hydrogen peroxide and saline immersion periods were used, 5 and 30 min. Specimens were stored in water at 37 degrees C for 1 and 7 days before tensile and shear testing. A total of 256 teeth were used, 8 for each treatment group, each immersion period, and each water storage period for each test. Statistical analysis of the results indicated that there was a highly significant reduction in the adhesive bond strength of the resin when the enamel was exposed to hydrogen peroxide and that the reduction was, within the limits of this study, time dependent. The bond strength was unaffected by the etching order and the period of water storage. Scanning electron microscopic examination of randomly selected fractured peroxide-treated specimens indicated that the failure occurred primarily at the bonding resin-enamel interface and that it was associated with areas of resin nonattachment and an alteration in resin quality. It is suspected that these changes were caused by the presence of residual peroxide or peroxide-related substances at or near the enamel surface.

Adhesiveness↗