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Biomedical subjects

D C Smith

Publications and source records attributed to D C Smith.

At least 199 records · Page 11Linked to original sources
PubMed1990

Mammographic and histologic correlations of microcalcifications.

The majority of microcalcifications found on mammograms are associated with benign disease; however, some types accompany malignant disease. By correlating histologic with mammographic findings, the radiologist may gain an understanding of the morphologic characteristics and distribution of microcalcifications. We present radiologic and histologic images from a series of cases of nonpalpable, clustered microcalcifications. Such microcalcifications can be divided into two basic histologic groups: lobular and ductal. Although rounded, similarly shaped lobular calcifications can be differentiated mammographically from ductal calcifications with their irregular margins and varying size and shape, both types can be associated with benign and malignant processes. Biopsy is usually needed to confirm the diagnosis when clustered microcalcifications are found at mammography.

Breast↗
PubMed1990

Thrombin generation in nonclottable mixtures of blood and nonionic contrast agents.

The four newly introduced contrast agents--iopamidol, iohexol, ioversol, and ioxaglate--are of much lower osmolality than conventional agents, and claims have been made that they are substantially safer. A chromogenic assay for thrombin was applied to 1:1 (50%), 2:1 (67%), and 4:1 (80%) contrast agent-whole blood mixtures, each containing enough contrast agent to render them unclottable. Thrombin generation occurred in the nonionic-whole blood mixtures and increased with time. No thrombin could be detected in any ioxaglate-whole blood mixtures. The authors conclude that this difference presents a novel hazard in that iopamidol, iohexol, and ioversol permit thrombin generation to occur while inhibiting the fibrin polymerization step of blood coagulation, thus posing a significant, albeit theoretical, threat to patient well-being.

Adult↗
PubMed1990

Bleeding marginal ulcers: angiographic evaluation.

The authors reviewed angiograms of patients who had previously undergone gastrojejunostomy and who were suffering from gastrointestinal bleeding. In five patients the site of bleeding was a surgically or endoscopically proved marginal ulcer. Only two of these ulcers were supplied by jejunal branches of the superior mesenteric artery; three of the five were supplied by gastric branches of the celiac artery. Thus, in angiography of patients with bleeding from marginal ulcers, the celiac, as well as the superior mesenteric, artery may need to be investigated.

Aged↗
PubMed1990

Preliminary surface analysis of etched, bleached, and normal bovine enamel.

X-ray photoelectron spectroscopic (XPS) and secondary ion-mass spectroscopic (SIMS) analyses were performed on unground un-pumiced, unground pumiced, and ground labial enamel surfaces of young bovine incisors exposed to four different treatments: (1) immersion in 35% H2O2 for 60 min; (2) immersion in 37% H3PO4 for 60 s; (3) immersion in 35% H2O2 for 60 min, in distilled water for two min, and in 37% H3PO4 for 60 s; (4) immersion in 37% H3PO4 for 60 s, in distilled water for two min, and in 35% H2O2 for 60 min. Untreated unground un-pumiced, unground pumiced, and ground enamel surfaces, as well as synthetic hydroxyapatite surfaces, served as controls for intra-tooth evaluations of the effects of different treatments. The analyses indicated that exposure to 35% H2O2 alone, besides increasing the nitrogen content, produced no other significant change in the elemental composition of any of the enamel surfaces investigated. Exposure to 37% H3PO4, however, produced a marked decrease in calcium (Ca) and phosphorus (P) concentrations and an increase in carbon (C) and nitrogen (N) concentrations in unground un-pumiced specimens only, and a decrease in C concentration in ground specimens. These results suggest that the reported decrease in the adhesive bond strength of resin to 35% H2O2-treated enamel is not caused by a change in the elemental composition of treated enamel surfaces. They also suggest that an organic-rich layer, unaffected by acid-etching, may be present on the unground un-pumiced surface of young bovine incisors. This layer can be removed by thorough pumicing or by grinding. An awareness of its presence is important when young bovine teeth are used in a model system for evaluation of resin adhesiveness.

Acid Etching, Dental↗
PubMed1990

Motivational readiness and the participation of children with learning and behavior problems in psychoeducational decision making.

Efficacy of a brief cognitive-affective intervention to enhance motivational readiness for participating in a psychoeducational decision-making conference was explored. Although outcomes specific to the preconference intervention were not found, findings of relevance to the hypothesized positive relationship between motivational readiness and actual participation in decision making are reported. The positive and negative findings are discussed in terms of implications for enhancing motivational readiness and for understanding the limited impact of skill training to improve participation and decision making.

Adolescent↗
PubMed1990

Composition and characteristics of glass ionomer cements.

Glass ionomer cement materials are currently available for restoration, cavity lining and basing, luting, and preventive applications. The in vitro performance is a function of composition, manipulation, and placement. In general, the cements may be characterized as strong, stiff, hard materials that are adhesive to calcified tissue, have low toxicity, and are potentially anticariogenic through fluoride leaching.

Chemical Phenomena↗
PubMed1989

Enhanced acetylcholine release from denervated atria: intrinsic neural supersensitivity.

Atrial tissue from denervated dog hearts was incubated with [3H]choline. When compared with controls, nicotine released more acetylcholine (ACh) from denervated atria at 10(-5) and 2 x 10(-5) M, but not at 5 x 10(-5) M. In parallel contractility studies using tissue from these same atria, the negative inotropic response to nicotine was enhanced at 5 x 10(-6) and 10(-5) M, but not at 2 x 10(-5) or 5 x 10(-5) M nicotine. These results indicate that denervation (i.e. decentralization) supersensitivity of the intrinsic cardiac nerves of canine hearts is characterized by enhanced release of ACh.

Acetylcholine↗
PubMed1989

The Pocket Speech Aid.

A rapid-access but limited vocabulary communication aid for the non-vocal and speech impaired is useful in some well defined situations. The design and construction of such a device is described. Three distinct situations have been identified where an aid is essential and an initial evaluation has shown the Pocket Speech Aid to be very successful.

Biomedical Engineering↗
PubMed1989

Physical properties of calcium hydroxide and glass-ionomer base and lining materials.

Compressive, diametral tensile and flexural strengths, moduli of elasticity, pH, and acid solubility values were compared for six calcium hydroxide cements, seven glass-ionomer cements, and one calcium aluminate cement. Results indicated that the glass-ionomer materials were generally stronger than the calcium hydroxide liners. Prisma VLC Dycal showed the lowest value for modulus of elasticity and the least acid solubility. The glass-ionomer materials were initially acidic, reaching a final pH between 5.4 and 7.3, whereas the calcium hydroxide and calcium aluminate cements were strongly alkaline at all time intervals.

Calcium Hydroxide↗
PubMed1989

Antimalarials. 16. Synthesis of 2-substituted analogues of 8-[(4-amino-1-methylbutyl)amino]-6-methoxy-4-methyl-5-[3- (trifluoromethyl)phenoxy]quinoline as candidate antimalarials.

A series of 2-substituted analogues of the exceptional drug 8-[(4-amino-1-methylbutyl)amino]-6-methoxy-4-methyl-5-[3- (trifluoromethyl)phenoxy]quinoline (I) were prepared and evaluated for both suppressive and prophylactic antimalarial activity. The preparation of analogues of compound I was of interest due to the high level of both blood and tissue schizonticidal activity demonstrated by this compound. One analogue, 8a, was found to be both more active and less toxic than the parent compound I. In addition, three analogues of example 8a were prepared. Although two of the three analogues showed significant antimalarial activity, both were inferior to compound 8a.

Aminoquinolines↗
PubMed1989

Oxygen desaturation following sedation for regional analgesia.

Moderate to severe arterial oxygen desaturation (SaO2 75-88%) occurred in three of four patients who were given sedation during regional conduction block without the administration of oxygen. No desaturation occurred in six patients given oxygen 2 litre min-1 via a nasal catheter during similar procedures. It is concluded that patients undergoing regional conduction block with concurrent sedation should receive additional oxygen routinely unless a pulse oximeter is available for monitoring.

Aged↗
PubMed1989

Sedation during spinal anaesthesia: a case for the routine administration of oxygen.

We have studied the effect of sedation with midazolam on arterial oxygen saturation during spinal anaesthesia in two groups of patients: one group received supplementary oxygen, the other group breathed room air. A significant reduction in oxygen saturation was observed in patients not receiving supplementary oxygen; six of 15 patients in this group developed hypoxaemia or severe hypoxaemia which was corrected immediately by administration of oxygen. There were no episodes of hypoxaemia in any patient in the group receiving supplementary oxygen. It is concluded that oxygen should be administered routinely to patients receiving sedatives during spinal anaesthesia.

Aged↗
PubMed1989

Pulse oximetry in the recovery room.

Haemoglobin oxygen saturation (SO2) was measured percutaneously with a pulse oximeter, in a group of 150 healthy ambulant volunteers to determine the range of normal values. The measuring site was not arterialised in advance. SO2 was below 94% in 13.3% of cases, while in no case was it below 90%. SO2 was then measured in 350 patients in the recovery room after a variety of surgical and anaesthetic procedures. Only 1.1% of patients who received additional oxygen following general anaesthesia exhibited an SO2 below 90%, compared to 16.7% of similar cases who did not receive additional oxygen. Administration of additional oxygen raised the SO2 above 90% in all the latter cases. In only 55.3% of those who did not receive additional oxygen was the SO2 above 94%, compared to 86.7% of normal volunteers and 73.9% of patients who received additional oxygen. This study reiterates the need to administer supplemental oxygen to all patients in the recovery room, unless facilities are available to measure SO2. A lower alarm limit of 90% is appropriate for the peri-operative period when using the Criticare Systems 501 oximeter.

Adolescent↗
PubMed1989

Adhesion of a glass ionomer cement to bleached and unbleached bovine dentin.

Cylinders of Fuji Type II glass ionomer restorative cement were bonded to the superficial dentin layer of young bovine incisor teeth that had previously been subjected to 4 different treatments: 1) teeth immersed in 35% hydrogen peroxide for 60 min and etched with 37% phosphoric acid gel for 60 s; 2) teeth immersed in saline for 60 min and etched with 37% phosphoric acid for 60 s; 3) teeth etched with 37% phosphoric acid for 60 s and immersed in 35% hydrogen peroxide for 60 min; or 4) teeth etched with 37% phosphoric acid for 60 s and immersed in saline for 60 min. Specimens were stored in water at 37 degrees for 1 and 7 days, prior to tension and shear testing. A total of 128 teeth were tested: 8 teeth in each group for each day and for each test. Statistical analysis of the results indicated that there was a highly significant reduction in bond strength of the cement when dentin was exposed to hydrogen peroxide as compared with saline. SEM examination of randomly selected fractured test specimens indicated that bond failure was cohesive in nature, suggesting that the hydrogen peroxide treatment adversely affected the setting process of the glass ionomer cement.

Adhesiveness↗
PubMed1989

Differing mechanisms of clotting inhibition by ionic and nonionic contrast agents.

The anticoagulant potency of ioxaglate has been shown to be approximately twice that of iopamidol and iohexol. Those findings were obtained with use of the thrombin time as a test and platelet-poor plasma as a thrombin substrate. The authors confirmed these findings with use of a whole-blood version of the same test. However, the thrombin time measures only the final stages of the clotting process. A measure of the entire intrinsic pathway would more nearly simulate the situation in the angiographic suite. When measured with such an assay, the anticoagulant potency of ioxaglate was equivalent to that of diatrizoate and was approximately four times that of iopamidol and iohexol. Because of this difference in potency, it seemed likely that the ionic agents were inhibiting the clotting cascade at a late stage as well as at an earlier stage. To investigate this possibility, whole blood-contrast agent mixtures were activated, incubated for several minutes, and then diluted with either citrated or heparinized whole blood. There was rapid clot formation when the unclotted iopamidol and iohexol mixtures were diluted with citrated whole blood but not when they were diluted with heparinized whole blood. The ionic mixtures did not clot in the presence of either anticoagulant. Thus, in unclottable mixtures nonionic agents still permitted the generation of procoagulants. These procoagulants are theoretically capable of causing clotting on reinjection.

Anticoagulants↗
PubMed1989

Medial brachial fascial compartment syndrome: anatomic basis of neuropathy after transaxillary arteriography.

The authors reviewed their experience with 320 transaxillary arteriograms, as well as the English-language literature on neuropathy complicating transaxillary arteriography. Three of their patients had median and ulnar motor and sensory nerve injury, and six others had only sensory involvement. The occurrence or severity of nerve injury did not correlate well with the size or presence of an observable axillary or arm hematoma. Dissection of the axillae and arms of 25 human cadavers revealed a tough medial brachial fascial compartment (MBFC) outside a thin axillary sheath. The median and ulnar nerves were within the MBFC at an arterial puncture site just lateral to the anterior axillary fold. The radial and musculocutaneous nerves exited the MBFC more proximally. The different levels at which the major nerves of the brachial plexus exit the MBFC explain the anatomic distribution of the nerve injuries associated with compression by a hematoma after transaxillary arteriography.

Adult↗