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Biomedical subjects

D C Smith

Publications and source records attributed to D C Smith.

At least 163 records · Page 9Linked to original sources
PubMed1992

An affinity purified ovine antivenom for the treatment of Vipera berus envenoming.

A novel antivenom for treating patients with Vipera berus bite has been developed. Sheep are immunised monthly with relatively small amounts of Vipera berus (common adder) venom and the resultant antisera pooled. The immunoglobulin fraction is precipitated with sodium sulphate then cleaved with papain to produce Fab fragments. Finally, those Fab fragments that are directed specifically against components in the venom are purified by affinity chromatography on columns comprising V. berus venom coupled to cyanogen bromide activated Sepharose 4B. The resultant product is some three times more effective than the non-purified Fab in protecting mice against the lethal venom effects.

Animals↗
PubMed1992

Passive blood/contrast agent exchange in angiographic catheters and its effects on platelets.

A static column of contrast agent or saline in an angiographic catheter will passively exchange with blood during angiography. The authors investigated the time course of this exchange in 5.5- and 7-F polyethylene catheters inclined at various angles. Passive blood exchange occurred 2 cm into the catheters within 7-15 seconds at most catheter tip angles, except for those catheters oriented so that their tips were nearly horizontal. In a separate series of experiments, the effect of contrast agent on platelet function and blood clotting was analyzed. The agent was sufficiently diluted in blood so as to simulate an angiographic procedure. The studies were performed in 60 cylindrical polyethylene containers with both unheparinized and heparinized blood. Use of an ionic contrast agent, more than a nonionic agent, lengthened the time for platelet aggregation (mean increases for ionic vs nonionic agents were 46.4 and 37.1 seconds, for unheparinized and heparinized blood, respectively), platelet adhesion to polyethylene surfaces (mean increases, 46.0 and 64.2 seconds), and platelet-stimulated coagulation (mean increases, 38.5 and 43.9 seconds). Conventional, intermittent flushing with saline or filling the catheter with contrast agent may be insufficient to prevent blood from rapidly back-filling the catheter tips. Contrast agents (ionic more than nonionic) distributed in the patient's blood volume inhibit platelet coating of catheter lumens and/or blood clotting under such circumstances.

Angiography↗
PubMed1992

Effects of angiographic needle size and subsequent catheter insertion on arterial walls. An in vitro experiment in human cadavers.

RATIONALE AND OBJECTIVES: It is widely believed that down-sizing catheters, and possibly needles, will decrease damage to the entry vessel in the performance of angiography. The purposes of this in vitro experiment are to determine if smaller needles produce less arterial wall damage than larger needles and to assess the influence of subsequent catheter insertion. METHODS: Each iliac artery pair from 35 fresh human cadavers was punctured three times with an 18-g needle and three times with a 21-g needle, for a total of 210 punctures. In two of each set of three, a 5- or 7-F dilator was passed. One hundred ninety-eight puncture tracts were usable and examined microscopically. They were graded on a scale of 1 to 3 in each of four categories: size of tract, margin irregularity, approximation of edges, and shape of tract. RESULTS: Chi-square analysis of the grading scores showed a significant shift of cases into lower damage grades when the smaller gauge needle was used for initial punctures (P < .0005). The subsequent insertion of a dilator, however, imposed further damage, such that the initial differences due to needle gauge were obliterated (P > .2). CONCLUSION: These data indicate that a 21-g needle produces less arterial wall damage than an 18-g needle, but that any safety conferred by the smaller needle is eliminated by the subsequent insertion of a 5- or 7-F catheter.

Adolescent↗
PubMed1992

Substance P modulates autonomic nerve activity in canine hearts.

We examined the hypothesis that substance P (SP) acts as an "afferent neuromodulator" in the heart regulating the response of the cardiac autonomic nerves to reflexes originating in the heart. We employed the acute, isovolumic canine heart preparation in which the amplitude of the chamber pressure accurately reflects changes in contractility. The heart was decentralized except for one-half of the right vagus, which was left intact to permit afferent communication with the central nervous system, while the remaining one-half was tightly ligated so that the distal part could be used for efferent stimulation. SP was injected in doses of 2-10 micrograms ic. There were no significant inotropic responses to 2 and 5 micrograms SP, whereas 10 micrograms produced positive inotropy of 5-15%. When vagal tone was elevated with sustained vagal stimulation, the same doses of SP increased contractility by 12-28%. Similarly, during right stellate ganglion stimulation (SS), SP decreased contractility 8-22%. After the intact half of the right vagus was sectioned, SP modulation of vagal responses was unaffected, while modulation of atrial, but not ventricular, responses to SS was significantly attenuated. When tested on a series of cardiac-denervated dogs, SP had no effect on cardiac inotropy at any dose. However, when contractility was increased with isoproterenol infusion, SP caused a small decrease in ventricular contractility. These results suggest that SP acts as a modulator of cardiac autonomic neural tone. It is possible that the neuropeptide is released from intramyocardial afferent collateral fibers and inhibits the elevation in vagal or sympathetic nerve activity initiated by activation of cardiac primary afferent nerves.

Animals↗
PubMed1992

Examination by X-ray photoelectron spectroscopy of the adsorption of chlorhexidine on hydroxyapatite.

X-ray photoelectron spectroscopy (XPS) was used for determination of the effects of chlorhexidine (CHX) solutions (0.2% and 1% solutions of the digluconate salt) on the elemental composition of hydroxyapatite surfaces. So that the nature of the adsorbed species after they were washed with water could be identified, comparisons were made with reference spectra for CHX obtained from a CHX digluconate film and CHX dichloride powder. The XPS results clearly indicated the retention of CHX moieties, which could be ascertained from the spectra by the presence of N and Cl, features unique to CHX. The spectral envelopes were virtually identical to those obtained from the reference spectra. High-resolution C 1s spectra also gave support for the retention of CHX; however, the spectra differed from those of the CHX digluconate film in that no feature attributable to the C-OH of the gluconate anion was present, consistent with the view that the CHX cation remains behind to form an electrostatic bond with the phosphate groups of the hydroxyapatite. The N:Cl ratio for the washed samples was found to be higher than that for the reference samples and may be indicative of partial decomposition of the CHX. Decomposition was also seen to be induced by x-ray exposure. While the high-resolution spectra presented here do not directly address the controversy on the mechanism for the anti-plaque efficacy of CHX, they do provide the necessary basis for the application of XPS to future in vitro studies on the retention of CHX to dental surfaces.

Adsorption↗
PubMed1992

Hypercalcemia and neuroendocrine carcinoma of the prostate: a report of three cases and a review of the literature.

PURPOSE: Hypercalcemia is a rare complication of prostate cancer, and no definite association with any histologic subtype of prostatic malignancy has been documented. We have recently seen three patients who developed hypercalcemia in the setting of prostate cancer. All had neuroendocrine carcinoma of the prostate (NCPs), which prompted an exploration of the potential association of hypercalcemia with NCP. DESIGN: An extensive review of literature published in the English-language was conducted to identify cases of hypercalcemia associated with prostate cancer and well-documented cases of NCP. RESULTS: We found 17 reported cases of hypercalcemia clearly associated with prostate cancer and a total of 61 cases of well-documented NCP. Including our cases, 11 of the 20 reported cases of hypercalcemia associated with prostate carcinoma were in patients with neuroendocrine carcinomas. CONCLUSION: Hypercalcemia in the setting of prostate cancer should prompt a search for unusual histologies.

Adenocarcinoma↗
PubMed1991

Dental implant materials. I. Some effects of preparative procedures on surface topography.

The effect of different treatments for preparing implant materials was examined by scanning electron microscopy and by contact angle measurements. The materials examined were Ti6A14V alloy, Co-Cr-Mo alloy, A12O3, and synthetic hydroxyapatite. Samples were prepared with solid or porous surfaces of these materials. These were detergent-cleaned and then either autoclaved (steam sterilization), radiation-sterilized, nitric acid-etched, or plasma-cleaned. The results of wettability studies indicated marked changes in surface energy corresponding to the different preparation methods, and differences in surface morphology were also observed. These differences could have significant consequences on in vivo implant behaviour as mediated by tissue-implant interactions.

Alloys↗
PubMed1991

Dental implant materials. II. Preparative procedures and surface spectroscopic studies.

The tissue response to an implant may involve both physical and chemical factors. There is little reliable information on the effects of these parameters and the associated ionic release on the cell-material interaction because the majority of studies have not fully characterized the implant material. In this work surface spectroscopy using ISS, ESCA, and SIMS was carried out on Ti6A14V, Co-Cr-Mo, A12O3, and hydroxyapatite dental implant materials that had been subjected to six commonly used preparative procedures. The results showed that each procedure generated an individualistic composition for the outermost surface of each material. These differences could be significant in cellular and tissue response. Improved understanding of these factors requires defined and reproducible surfaces.

Alloys↗
PubMed1991

Release of metal ions from dental implant materials in vivo: determination of Al, Co, Cr, Mo, Ni, V, and Ti in organ tissue.

Little is known of the release of trace elements in vivo from dental implant materials. Conflicting data have been reported in the literature as to the levels of trace elements released and their potential consequences, mainly because of sampling and analytical methodological errors. In this study methods for average concentration levels of Al, Cr, Co, Mo, Ni, Ti, and V in organs were developed using rabbit tissue from an in vivo implantation study. At least 50% of the brain, liver, lung, kidney, and spleen were taken minimizing contamination. The tissue was homogenized by cryogenic milling at LN2 temperature and then freeze-dried. Samples were digested in nitric acid and hydrogen peroxide using microwave energy. Standard reference materials were utilized for quality control. One liver sample was analyzed 10 times to assess the method precision. Absorbance values in blanks, standards, and test samples were measured using a Varian GTA 95 graphite furnace and 875 spectrophotometer. Very satisfactory method precision and quality control were recorded. Low or very low levels of the trace elements were found in the various organs.

Alloys↗
PubMed1991

Neutralization of kinin-releasing enzymes from viperid venoms by antivenom IgG fragments.

The activities of kinin-releasing enzymes in the venoms of Vipera xanthina xanthina, V. lebetina obtusa, V. aspis aspis, V. lebtina schweizeri, V. ammodytes ammodytes and V. berus berus were determined using a specific radioimmunoassay for kinin. The kinin-releasing activities of all the viperid venoms measured in vitro were neutralized, to varying extents, by two commercially available monospecific antivenoms in the form of F(ab')2 (Zagreb) and Fab (TAb) immunoglobin fragments, indicating a high degree of cross-neutralization of those enzymes.

Animals↗
PubMed1991

Neutralization of kinin-releasing enzymes of crotalid venoms by monospecific and polyspecific antivenoms.

The amounts of kinin-releasing enzymes in the venoms of Crotalus atrox, Crotalus adamanteus, Crotalus scutulatus scutulatus and Agkistrodon piscivorus piscivorus were measured by determining the amounts of kinin released from a sheep kininogen substrate by means of a specific radioimmunoassay. Four monospecific and two commercial polyspecific antivenom IgG samples were tested for their ability to reduce the kinin-releasing activities of the four crotalid venoms measured in vitro. All of the antivenom IgG samples were able to neutralize venom kininogenase activity to varying extents. On of the commercial polyspecific antivenoms was of equal or higher potency than the corresponding monospecific antivenoms for three of the venoms tested, indicating a high degree of cross-neutralization. F(ab')2 and especially Fab fragments of that polyspecific antivenom IgG were also effective in reducing the kinin-releasing activities of the four crotalid venoms.

Animals↗
PubMed1991

Scanning electron microscopy observations on the penetration and structure of resin tags in bleached and unbleached bovine enamel.

The purpose of this study was to determine the effect of hydrogen peroxide on the ability of composite resin to penetrate bovine enamel etched with phosphoric acid. In a previous investigation, the flattened enamel surfaces of extracted bovine incisors were immersed in either saline (control) or 35% hydrogen peroxide (experimental) for 5 or 30 min before or after acid etching with 37% phosphoric acid gel for 60 s. A standard-sized light-cured resin cylinder was then bonded to the enamel surface. The specimens were stored in a water bath at 37 degrees C for 1 day or 7 days, after which the enamel-resin bond was tensile tested to failure. Sixteen of the failed specimens (eight control and eight experimental) were randomly selected for the present scanning electron microscopic study to evaluate the appearance of the resin tags at the resin-enamel interface. In the control specimens, the tags were well defined and contiguous with resin which was uniformly adherent to the enamel surface. In the experimental specimens, large areas of the enamel surface were free of resin. When tags were present, they were fragmented, poorly defined, and penetrated to a lesser depth than in the saline controls. The changes observed suggest that there may be interaction between resin and residual peroxide at or near the enamel surface.

Acid Etching, Dental↗
PubMed1991

Guide wire traversal test: retrospective study of results with fibrinolytic therapy.

The validity of the guide wire traversal test as a predictor of the outcome of selective fibrinolytic infusion therapy was investigated. A retrospective analysis of 51 consecutive urokinase infusions at the authors' institution revealed that the initial attempt at guide wire traversal of clotted vessels was successful in 36 patients and unsuccessful in 15. In those 15 patients in whom the initial guide wire traversal was unsuccessful, urokinase was infused proximal to the occlusion for 2-8 hours. In 10 of these 15 vessels, either guide wire traversal (n = 7) or complete lysis with only proximal infusion (n = 3) was then achieved. Final results for this group of 15 patients were similar to those found in the group of 36 patients in whom initial attempts at guide wire traversal were successful (chi 2 contingency analysis, P greater than .8). There were no statistically significant differences between these two groups with regard to ages of the grafts, duration of vessel occlusion prior to treatment, infusion times, or patient gender composition. These data indicate that failure to traverse a clotted vessel with a guide wire does not preclude successful urokinase fibrinolytic therapy in a substantial percentage of patients.

Aged↗