Search PubMed⌕ Search

Biomedical subjects

D L Smith

Publications and source records attributed to D L Smith.

At least 397 records · Page 22Linked to original sources
PubMed1983

Determination of active hydrogen content by fast atom bombardment mass spectrometry following hydrogen-deuterium exchange.

Fast atom bombardment mass spectrometry following hydrogen--deuterium exchange in [hydroxy-2H3]glycerol and 2H20 has been studied as a means of establishing active hydrogen content in molecules of unknown structure. Nucleotides, carbohydrates, one peptide and complex antibiotics, in the mass region to 1500 daltons and 29 exchangeable hydrogens were examined, with a correct hydrogen count unambiguously measured in every case. The method is experimentally simple and applicable on a microgram scale, to salts and a variety of polar compounds of biological origin.

Anti-Bacterial Agents↗
PubMed1983

Remedial human factors engineering - part 1.

Some generic problems have been observed in present-generation nuclear power plant control rooms. This paper presents an initial attempt to develop remedial solutions. In Part 1, enhancement methodology is discussed in general terms. Part 2 will explore detailed panel enhancement options as applied to a specific case history.

Journal Article↗
PubMed1983

Nonselective beta-receptor stimulation and blockade and left ventricular function.

The effects of increasing doses of intravenous isoproterenol on left ventricular (LV) size and function were assessed before and after oral propranolol (80 mg). Eleven normal subjects were studied by M-mode echocardiography. The isoproterenol dose was increased until heart rate had risen by 25 to 30 b.p.m. LV end-diastolic (LVED) dimension (46.6 +/- 1.3 mm) was increased by isoproterenol (to 48.8 +/- 1.5 mm) and decreased by propranolol (to 45 +/- 1 mm). LV end-systolic dimension was decreased by isoproterenol and increased by propranolol. Isoproterenol increased LVED dimension despite the opposing effect of the tachycardia, whereas propranolol decreased LVED dimension despite its negative inotropic and chronotropic effects. These results suggest that nonselective beta-receptor stimulation or blockade can affect cardiac output through direct cardiac actions and by influencing venous return.

Adrenergic beta-Antagonists↗
PubMed1983

Purification and characterization of the unusual deoxynucleoside, alpha-N-(9-beta-D-2'-deoxyribofuranosylpurin-6-yl)glycinamide, specified by the phage Mu modification function.

Bacteriophage Mu encodes a protein that modifies approximately equal to 15% of DNA adenine residues to a new and unusual form. Modified DNA was enzymatically digested to deoxynucleosides, and the products were fractionated by HPLC. A modified adenine nucleoside, designated dA'x, was purified and its molecular structure was established by mass spectrometry. We show that dA'x is alpha-N-(9-beta-D-2'-deoxyribofuranosylpurin-6-yl)-glycinamide. The dA'x obtained from DNA was indistinguishable from the synthetic product with respect to its chromatographic behavior (HPLC and gas chromatography) and mass spectrum. Acid hydrolysis degrades dA'x to produce N6-carboxymethyladenine; this compound corresponds to the base Ax observed in earlier studies.

Chromatography, High Pressure Liquid↗
PubMed1983

Proprioception and spatial neglect after stroke.

Proprioception and neglect were studied in 287 patients surviving up to one week after the onset of their stroke. The presence of proprioceptive loss indicated a more extensive lesion and a larger proportion of these patients had impairment of intellectual function, motor power in the upper and lower limb, and postural function. Proprioceptive loss also had an adverse effect on the level of independence achieved by discharge, final placement, mortality and length of stay in hospital. In 87% of the survivors recovery of proprioception had occurred by eight weeks. Significant neglect was associated with high mortality and poor outcome for functional recovery.

Aged↗
PubMed1983

Diuretic and cardiovascular effects of indapamide in hypertensive subjects: a dose-response curve.

In a single-blind, placebo-controlled study, the effects were evaluated of increasing doses of indapamide (1.0, 2.5 and 5.0 mg/day, each dose for 4 weeks) on volume and haemodynamic status of 10 hypertensive subjects. Body weight showed a decrease of 0.5 kg at the 1 mg dose, of 1.0 kg at the 2.5 mg dose and no further decrease at 5 mg. Plasma volume did not change. Mean arterial pressure decrease in 8 subjects by about 20 mmHg; 2 patients were classified as 'non-responders'. The decrease in blood pressure was accompanied by a reduction in total peripheral resistance and no change in cardiac output. LV end-diastolic volume decreased by about 20 ml. These results suggest that indapamide not only has a diuretic effect, but also acts as a veno-arterial vasodilator.

Adult↗
PubMed1983

Evidence for a nonoxidative mechanism of human natural killer (NK) cell cytotoxicity by using mononuclear effector cells from healthy donors and from patients with chronic granulomatous disease.

In vitro natural killer (NK) activity expressed by blood mononuclear cells from patients with chronic granulomatous disease of childhood (CGD) was equivalent to that expressed by cells from normal, healthy volunteers. Because neutrophils and monocytes from these same donors exhibited extremely depressed oxidative functions, our data could be interpreted to show that a) NK cells derived from a unique and separate cellular lineage unaffected by the disease-related oxidative defect, or b) the in vitro cytolytic mechanism(s) of NK cells were not dependent on oxygen metabolites. These hypotheses were examined by using as NK effector cells large granular lymphocytes (LGL) from healthy donors whose monocytes and neutrophils had normal oxidative functions. Such functions were measured in the nitroblue tetrazolium dye reduction assay, which is a qualitative measurement of superoxide anion production; by reduction of ferric cytochrome c, a more specific and quantitative measurement of superoxide anion production; and in the luminol-enhanced chemiluminescence assay, an extremely sensitive measure of several reactive oxygen radicals, including superoxide anion, hydroxyl radical, and singlet oxygen. Whereas monocytes and neutrophils from healthy donors were readily stimulated with zymosan or phorbol myristate acetate (PMA) in each of these assays. LGL produced no detectable amounts of oxygen metabolites when co-incubated either with K562 erythroleukemia cells, PMA, E. coli endotoxin, or the calcium ionophore A23187. Thus, because NK cell activity is normal in CGD patients with major oxidative defects, and because no reactive oxygen metabolites could be detected in LGL that simultaneously exhibited potent NK activity, we conclude that in vitro NK activity by human mononuclear cells involves a lytic mechanism(s) independent of oxygen metabolites.

Cell Differentiation↗
PubMed1983

Dental casting alloys: technical and economic considerations in the USA.

In the USA, gold alloys have played a prominent role in oral health maintenance for more than 100 years. Recently, however, a marked trend toward substitution of palladium-silver and nickel-chromium based materials for the more costly gold alloys has been observed. It is estimated that 60-80 per cent of all permanent dental appliances (crowns and bridges) are now fabricated from non-gold alloys. For the most part, increased user demand for alloy products of relatively low intrinsic value has affected adversely the profitability of the larger USA casting alloy suppliers. The likelihood of a reversal of the trend occurring during the 1980s is not great. All major USA dental alloy manufacturers have found it necessary to market an ever increasing spectrum of low cost alloy products. Impetus for this production of a new generation of dental casting alloys has risen mainly from the perceived purchasing patterns of current and future customers. It is anticipated that the 'down-grading' of dental casting alloys will continue until plastics, mouldable ceramics or other inexpensive industrial materials replace metals in the fabrication of permanently cemented dental devices. Until then, it is likely that gold alloys will remain the ultimate prosthetic materials in the minds of dental academicians while technique-sensitive and unproved metallic products of low intrinsic value will continue to gain greater acceptance by practising dentists, laboratory technicians and patients.

Chemical Phenomena↗
PubMed1982

Identification of nucleosides in hydrolysates of transfer RNA by high-resolution mass spectrometry.

High-resolution mass spectrometry has been investigated as a technique for identification of modified nucleosides in unfractionated hydrolysates of transfer RNA. The method is based on recognition of predetermined sets of exact mass values which are characteristic of individual nucleoside components. Mass spectra are photographically recorded in a non-time-resolved fashion, so that differing rates of nucleoside vaporization are of no consequence. Experimental parameters of sensitivity, spectrometer resolution and rates of vaporization were studied. Under typical conditions, 1-4 micrograms of tRNA are hydrolyzed, converted to volatile trimethylsilyl derivatives, and mass spectra of the resulting mixture recorded during 3 min at resolution 20 000; 75-100% of the minor nucleosides are usually identified in a single recording. The method is complementary to conventional methods of identification which rely on chromatographic mobilities, and can in principle be generally applied to recognition of biologically or chemically modified bases in nucleic acid.

Chemical Phenomena↗
PubMed1982

Therapy impact on functional outcome in a controlled trial of stroke rehabilitation.

In a randomized controlled trial of management of acute stroke in the elderly, a higher proportion of patients were assessed as independent in self-care in a stroke unit compared with patients with similar levels of neurologic impairment treated in medical units. The use of physical therapy and occupational therapy in the stroke unit and medical units was compared. Patients in the stroke unit received less therapy over a shorter period of time; however, a higher proportion had occupational therapy beginning at a much shorter interval after admission. Early introduction of rehabilitation by therapists may be more important than the amount of duration of treatment.

Activities of Daily Living↗