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Biomedical subjects

D A Smith

Publications and source records attributed to D A Smith.

At least 217 records · Page 12Linked to original sources
PubMed1991

A portable bladder scanner.

Nurse practitioners are the primary care providers in a variety of health care settings. Often the NP is the first health care provider to suspect a problem based on history, observations, diagnosis, and patient comfort. In making a diagnosis, the NP must be cognizant of all available diagnostic techniques and procedures. A simple and easy method for ultrasonic bladder scanning has developed over the past several years. NPs can utilize this technique in their clinical practices.

Humans↗
PubMed1990

The theory of sliding filament models for muscle contraction. III. Dynamics of the five-state model.

The five-state model derived in the last paper is shown to provide a unified description of most dynamical behaviour of striated muscle, with a set of rate constants in accord with in-vitro values. It predicts several observed phenomena beyond the scope of older models. Rapid binding of M.ADP.Pi to actin generates a high-frequency tail in the Nyquist plot for AC stiffness, which is only weakly dependent on contraction velocity. Known effects of changes in Ca2+ level are predicted if Ca2+ activates only the phosphate-release step, e.g. in the relaxed-state there is substantial stiffness at high frequencies and weak stiffness at low frequencies. Under partial activation the tension drops with increasing extension speed, and Nyquist plots suggest that the reverse phosphate step should be unaffected by Ca2+. Lowering the phosphate level increases tension and also the first two loop amplitudes of the Nyquist plot. The model also yields an improved tension-velocity characteristic, acceptable length-step response, and simulates Brenner & Eisenberg's "stop and stretch" experiment which is shown to be closely related to isometric activation. Oscillatory length response to small tension steps is shown to be a general feature of any model whose AC stiffness can be fitted by a three-term Kawai formula. The model must be enlarged to include the rigor-state, and to describe the effects of variations in ATP and ADP levels correctly.

Adenosine Diphosphate↗
PubMed1990

The theory of sliding filament models for muscle contraction. II. Biochemically-based models of the contraction cycle.

A seven-state sliding filament model is proposed which differs from the model of Eisenberg & Greene. It is based on a simplified version of the in-vitro contraction cycle of Stein et al., and also has some desirable dynamical features of the empirical three-state model of Nishiyama & Murase. Appropriate x-dependences for all reaction rates are derived from the transition-state theory. The seventh-state is assumed to be a high-tension intermediate of A.M.ATP, from which direct but x-dependent dissociation can occur. If the final A.M.ATP state has a sufficiently lower tension than that of A.M.ADP.Pi, then the dominant escape path from the intermediate state is shown to be direct dissociation of the actin-myosin bond. This leads to an approximate five-state model for active and relaxed muscle in which A.M and the final A.M.ATP state are omitted.

Actins↗
PubMed1990

Induction and purification of kievitone hydratase from Fusarium solani f. sp. phaseoli.

Fusarium solani f. sp. phaseoli is capable of detoxifying the major isoflavonoid phytoalexins produced by its host plant Phaseolus vulgaris. One of the enzymic activities involved is kievitone hydratase (KHase), a secreted glycoprotein which catalyses the conversion of kievitone to the less fungitoxic derivative, kievitone hydrate. Even under conditions of substrate induction, the enzyme is expressed at levels that are too low for satisfactory purification. Therefore, several other isoflavonoids were tested as inducers in culture. Among the phytoalexins produced by the host plant, phaseollinisoflavan was the best inducer, elevating the level of secreted enzyme eight-fold. Treatment with biochanin A, a product of chickpea, resulted in a 16-fold increase of secreted activity. The maximum rate of induction was observed 9-24 hr after addition of biochanin A, during which time several metabolites of the inducer were also present. KHase was purified from filtrates of biochanin A-induced cultures. Denaturing gel electrophoresis indicated that two species of Mr 47,000 and 49,000 copurified with the activity. N-Terminal sequence analysis indicated that the two species possessed related, or identical, polypeptide moieties. Comparison with the size of the non-denatured enzyme, previously determined to be ca 100,000, indicates that its native state is a dimer.

Amino Acid Sequence↗
PubMed1990

Longitudinal prediction of marital discord from premarital expressions of affect.

Theoretical and empirical analyses suggest that affective features of dyadic communication bear importantly on relationship satisfaction. A circumplex model that originated in research on the structure of affect was first replicated using data from premarital problem-solving discussions. Negativity, Positivity, and Disengagement emerged as the three primary factors. Multiple regression analyses, controlling for premarital relationship satisfaction, showed affective Disengagement at premarriage to be negatively associated with marital satisfaction at 18 (n = 84) and 30 (n = 72) months after marriage. Negativity of premarital affective expression correlated negatively with premarital satisfaction (n = 88) but not with postmarital satisfaction. Two variables formed by combining affect factors contributed to the prediction of 30-month marital satisfaction. Elements associated with current marital satisfaction appear to differ from those associated with later marital satisfaction.

Adult↗
PubMed1990

Effect of 6-cyano-2,3-dihydroxy-7-nitro-quinoxaline (CNQX) on dorsal root-, NMDA-, kainate- and quisqualate-mediated depolarization of rat motoneurones in vitro.

1. Mature in vitro rat spinal cord preparations have been used to compare the depressant effects of 6-cyano-2,3-dihydroxy-7-nitroquinoxalinedione (CNQX) and kynurenate on transmission from low threshold myelinated primary afferents in dorsal roots. EC50 values +/- s.e.mean (number of preparations in parentheses) for depression of the monosynaptic ventral root reflex were respectively 1.0 +/- 0.3 microM (5) and 135 +/- 15 microM (3) for CNQX and kynurenate. Transmission through superior cervical ganglia was not significantly affected by concentrations of CNQX up to 100 microM or kynurenate up to 5 mM. 2. Immature in vitro rat spinal cord preparations were used to measure dose-ratios for antagonism of depolarizations induced by N-methyl-D-aspartate (NMDA), kainate or quisqualate by 4, 10 and 25 microM CNQX. In the presence of 0.75 mM Mg2+ pA2 values +/- s.e.mean were respectively 4.62 +/- 0.05 (16), 5.79 +/- 0.01 (4) and 5.59 +/- 0.05 (16) for each agonist. These values were not significantly altered in the absence of added Mg2+. The mean pA2 values for kainate were significantly higher than those for quisqualate (P less than 0.01). 3. Antagonism of NMDA-induced depolarizations was evident at 10 and 25 but not 4 microM CNQX. The antagonism of NMDA was reversed by D-serine (100 and 200 microM). 4. A similarity between the relative potencies of both CNQX and kynurenate for depression of synaptic transmission and antagonism of amino acid-induced depolarizations indicates that monosynaptic transmission from myelinated primary afferents to motoneurones is mediated by kainate and/or quisqualate sub-types of non-NMDA receptors.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1990

sti35, a stress-responsive gene in Fusarium spp.

A stress-induced mRNA was identified in the phytopathogenic fungus Fusarium oxysporum f. sp. cucumerinum. Treatment of the fungus with ethanol resulted in the induction of a major mRNA species encoding a protein of approximate Mr 37,000. A full-length cDNA clone of the induced message was obtained. RNA blot analysis indicated that the mRNA was induced by various other stresses, including treatment with copper(II) chloride and heat (37 degrees C). However, it was not greatly induced by treatment with phaseollinisoflavan, an antifungal isoflavonoid produced by Phaseolus vulgaris (French bean). In contrast, phaseollinisoflavan induced the homologous mRNA in the related bean pathogen Fusarium solani f. sp. phaseoli. A genomic clone of the F. solani f. sp. phaseoli gene was obtained, and both this and the cDNA clone from F. oxysporum f. sp. cucumerinum were sequenced. The latter indicated an open reading frame of 320 codons encoding a 34,556-dalton polypeptide. The corresponding reading frame in F. solani f. sp. phaseoli was 324 codons, 89% identical to the F. oxysporum f. sp. cucumerium sequence, and was interrupted by a short intron. The gene was designated sti35 (stress-inducible mRNA). Although computer homology searches were negative, the cloned gene was observed to cross-hybridize to DNAs of other filamentous fungi, Saccharomyces cerevisiae, and soybean. Thus, sti35 appears to be a common gene among a variety of eucaryotes.

Amino Acid Sequence↗
PubMed1990

Effect of a beta-blocker on altered body position: induced ocular hypertension.

The intraocular pressures (IOP) were measured in both eyes of 25 healthy volunteers in various body positions. One eye was pretreated with levobunolol 0.5% or placebo applied in a masked, randomised fashion, while the other served as control. IOP changes in response to levobunolol and to changes in position were significant (p less than 0.0001). However, pressure rises relative to position were not significantly different in eyes treated with drug vs placebo. Levobunolol did not alter relative changes in IOP from changes in body position. However, the overall lowering effect may offer some protection to patients with glaucoma.

Adolescent↗
PubMed1990

Convergence in world urbanization? A quantitative assessment.

"Cross-national data are used to explore the question of whether world urban patterns and processes are converging or diverging. We compare tabular data on overall percent urban, urban primacy, overurbanization, and urban bias across world-system strata and global regions. The evidence suggests continuing differences and little evidence for convergence. To determine whether world-system effects have causal efficacy, we conclude with a regression analysis. These results provide strong evidence for a world-system explanation of continuing differences in overall level of urbanization and urban primacy, and a developmentalist approach seems to explain persisting divergence in levels of urban bias."

Demography↗
PubMed1990

Quantitative gamma-ray computed tomography of the radius in normal subjects and osteoporotic patients.

A new design of gamma-ray computed tomography (CT) scanner was used to measure bone density in 516 normal adults and in 116 female patients with osteoporotic fractures. Trabecular bone density (TBD) was measured for a core of the ultradistal radius; cortical bone mass per unit length (MLS) and mass per unit volume (MVS) were computed for the radius shaft. TBD, MLS and MVS peaked at the age of about 40 in females and fell by 32%, 15% and 24%, respectively, by the age of 65. In males, TBD decreased from the third decade and MLS and MVS peaked in the fourth decade. The corresponding falls by 65 years were 20%, 6% and 7%. In patients with Colles' fracture TBD and MLS were reduced by 13% and 10%, respectively, relative to age matched normal female subjects. For patients with vertebral crush fracture the reductions relative to age matched normal females were 36%, 17% and 16% for TBD, MLS and MVS. In fracture patients the deficit in TBD was significantly greater than that for cortical bone but TBD was no better at discriminating normal and osteoporotic individuals because of its larger normal range. We conclude that gamma-ray CT may best be used for monitoring changes in bone rather than as a diagnostic screening tool.

Adult↗
PubMed1990

Design of toxicokinetic studies.

1. Toxicokinetics is defined as pharmacokinetic studies in animals during actual toxicity studies or under conditions mimicking them (species, duration, dose level, etc.). 2. Toxicology studies require toxicokinetics to check whether systemic exposure reflects administered dose. In particular, it is important to know whether the absence of toxicity at a given dose is due to the innocuousness of the compound or to its poor bioavailability. 3. Pivotal toxicology studies may require different toxicokinetic support than that of early studies, as more is learned of the compound and its metabolites. Considerations need to be placed on such factors as the choice of biological matrix for drug assay, the relevance of metabolites, and which dose levels require the most pharmacokinetic investigation.

Animals↗
PubMed1990

The psychoacoustics of profound hearing impairment.

A group of profoundly hearing-impaired adults is being studied in order to determine their residual auditory capabilities. Most tests use acoustic contrasts that have relevance for the perception of speech, so that the results obtained may be used to guide the development of appropriate hearing aids. All the listeners are postlingually deafened, with losses greater than 95 dB HL at and above 500 Hz, and least loss at low frequencies. Trends in detection thresholds, discomfort levels, dynamic ranges, intensity discrimination (both static and dynamic), frequency selectivity, spectral shape discrimination, gap detection, tone/noise discrimination, frequency discrimination and phase sensitivity are reported and discussed. Generally speaking, temporal resolving power seems to be more resistant to degradation than mechanisms of frequency selectivity. Furthermore, at least some of the differences in performance between normal and profoundly-impaired listeners may be attributable to the loss of frequency selectivity. Implications are drawn for hearing aid fitting and design, and comparisons made to the electro-auditory abilities of users of single-channel cochlear implants.

Adult↗
PubMed1990

OBRA--its effect on the mentally ill in South Dakota nursing homes.

Mental illness is quite prevalent in the nursing home population. The Omnibus Budget Reconciliation Act of 1987 (OBRA), as it relates to nursing homes, has many facets including preadmission screening, periodic assessment, formalized patient rights, and gives reviewers a broader list of sanctions for offending facilities. OBRA does away with the designation of skilled and intermediate levels of care. It provides for evaluation of special needs of the mentally retarded and developmentally disabled and expects relocation of residents in need of specialized treatments. Similarly, it requires evaluation of the mentally ill in nursing homes for appropriateness of placement and discourages admission of potential nursing home residents with mental illness. This last aspect of OBRA and its potential effect of the long term care system, the mental health system, and the budget of the state of South Dakota are the subject of this paper.

Aged↗