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Biomedical subjects

D W Smith

Publications and source records attributed to D W Smith.

At least 109 records · Page 6Linked to original sources
PubMed1997

Circulatory disease mortality in the very elderly.

I describe circulatory disease mortality in age groups 85 years and over, as available from Vital Statistics of the United States. Mortality rates from all circulatory disease combined, from ischemic heart disease, and from cerebrovascular diseases increase faster with age than the mortality rate from all causes combined. The kinds of circulatory diseases causing death change with age. Although men and black people have higher mortality rates from circulatory diseases than women and white people through early old age, the gaps narrow with age, and there are sex and racial crossovers in later old age. Age groups 85 years and over have had smaller decreases in mortality rates from circulatory diseases since 1960 than middle-aged and younger elderly age groups.

Adult↗
PubMed1997

Effects of electrode configuration on psychophysical strength-duration functions for single biphasic electrical stimuli in cats.

The interface between electrode and neural target tissue is thought to influence certain characteristics of neural and behavioral responses to electrical stimulation of the auditory system. At present, the biophysical properties of this interface are not well understood. Here the effects of biphasic phase duration and electrode configuration on psychophysical threshold in response to electrical stimulation in cats are described. Five cats were trained to respond to acoustic stimuli using food as a reward in an operant reinforcement paradigm. After training, the animals were unilaterally deafened and implanted with a multicontact intracochlear electrode array. Thresholds for single presentations of biphasic current pulses were measured as a function of phase duration and electrode arrangement. Statistical analyses of the data indicated that strength-duration function slopes between 200 and 1600 microseconds/phase were significantly different for the different electrode configurations and, overall, were unrelated to the absolute level of the strength-duration function (i.e., were independent of absolute threshold). For all subjects, the slope of this function for intermediate pulse durations was dependent on electrode configuration and most shallow for radial-bipolar configurations (-3.4 dB/doubling), was steepest for monopolar arrangements (-5.9 dB/doubling), and was intermediate for longitudinal-bipolar pairings. (-4.4 dB/doubling). Slopes for both shorter and longer phase duration stimuli were not significantly different. The underlying mechanisms for these effects may include, or be a combination of altered electrical field patterns, integrated activity across multiple fibers, and stochastic behavior of individual auditory neurons to electrical stimulation.

Animals↗
PubMed1996

Cancer mortality at very old ages.

BACKGROUND: Mortality rates of all malignant neoplastic diseases combined and of most individual kinds of cancer increase with age through most of the human life span. What happens to cancer mortality rates near the end of the life span has not been described previously. People age 85 years and older are commonly considered as a single category; however information is available for cancer mortality of patients older than 85 years in 4 age groups, each covering 5-year spans. METHODS: Age-stratified mortality rates of all of the patients with malignant neoplasms combined and of cancers of several sites in 5-year age groups from 50 to more than 100 were calculated from United States vital statistics and Census data from 1990. RESULTS: Mortality rates of all of the patients with malignant neoplastic diseases combined and of cancers of most individual sites peak between ages of 80 and 100 years, and decline after ages older than those. Although mortality rates generally increase with age, the relative frequency of cancer deaths declines with age from nearly 40% of all deaths between ages of 50 and 69 years, to 4% of all deaths in patients older than age 100 years. CONCLUSIONS: People who survive to ages approaching 100 years are relatively resistant to the causes of death, including cancer, of the majority of people who die at younger ages. The basis of this resistance to cancer may be attributable to several recognized genetically controlled steps in the pathogenesis of cancer.

Age Factors↗
PubMed1996

Mosquito-borne viruses and epidemic polyarthritis.

The two most common mosquito-borne viruses associated with epidemic polyarthritis and polyarticular disease are Ross River and Barmah Forest viruses, accounting for about 90% and 10%, respectively, of serologically confirmed cases. Occasional cases of polyarticular disease in Australia have been associated with infection by other mosquito-borne arboviruses, but the role of these viruses in human disease remains to be confirmed.

Alphavirus↗
PubMed1996

Clinical surveillance for early stage breast cancer: an analysis of claims data.

This study estimates the costs of clinical follow-up for women with early stage breast cancer and evaluates the effects of patient and provider characteristics on follow-up intensity. Claims data were cumulated from 1/1/89 through 4/30/93 for a comprehensive set of follow-up tests (office visits, radiologic, and laboratory) ordered for 222 women diagnosed at a university hospital between 1/1/89 and 12/31/91. Aggregated measures of the volume and costs of follow-up over 6 month intervals were expressed in terms of Medicare's 1993 relative value units (RVUs) and their 1993 cost equivalents. Excluding the first 6 months, women received on average, 11.7 RVUs of follow-up in the first year (equivalent to a cost of $362), and 9.5 RVUs in the second year ($297). In the first year, chest x-rays, clinical chemistry tests, automated hemograms, and bone scans, accounted for 36% of the cost of follow-up, while computerized tomographic scans and magnetic resonance imaging studies accounted for 30%. Multiple regression analysis of the first year data showed that women who received radiation and/or were followed by oncology, were more likely to receive intensive follow-up. Age, race, socioeconomic status, insurance, stage, and treatment did not impact follow-up. Costs of follow-up for breast cancer are substantial, though much lower than suggested by others. Additionally, wide variations in practice are largely unexplained by patient and/or provider characteristics. In light of recent evidence questioning the benefit of intensive surveillance, this study supports the need for an accepted set of follow-up guidelines for breast cancer.

Breast Neoplasms↗
PubMed1996

Compensation seeking status and psychometric assessment of combat veterans seeking treatment for PTSD.

Examined differences between compensation seeking (CS) veterans and noncompensation seeking (NCS) veterans on the Minnesota Multiphasic Personality Inventory-2 (MMPI-2) and other psychological measures in 142 combat veterans evaluated for posttraumatic stress disorder (PTSD) at an outpatient Veterans Affairs (VA) hospital PTSD clinic. Patients were grouped on the basis of their compensation seeking status, with 69% classified as CS for PTSD. The CS veterans achieved significantly more pathological scores across a wide range of psychological inventories and MMPI-2 validity indices, although they did not differ in frequency of PTSD diagnoses from NCS veterans. Implications of these findings are discussed, and clinicians are advised to be aware of the compensation seeking status of combat-veterans being evaluated for PTSD.

Adult↗
PubMed1996

Nerve growth factor withdrawal induces the apoptotic death of developing septal cholinergic neurons in vitro: protection by cyclic AMP analogue and high potassium.

Nerve growth factor regulates the developmental programmed cell death of certain neurons in the peripheral nervous system. The functions of nerve growth factor in the central nervous system are less well characterized. Nerve growth factor withdrawal results in the protein synthesis-dependent death of a large percentage of developing septal cholinergic neurons in sandwich tissue culture. In this study double labelling techniques were used to demonstrate that septal cholinergic neurons subjected to nerve growth factor withdrawal exhibit condensed chromatin and fragmented nuclei, and are labelled intensely for fragmented DNA. These degenerative changes are characteristic of apoptotic cell death. Half of the cholinergic neurons were committed to die and could no longer be rescued by nerve growth factor reapplication following approximately 16.5 h of nerve growth factor deprivation, whereas half of the cholinergic neurons could no longer be rescued by cycloheximide addition after only 9 h of nerve growth factor deprivation, suggesting that nerve growth factor and cycloheximide effect rescue by distinct mechanisms. Addition of a cyclic AMP analogue or depolarization with high K+, but not the general nuclease inhibitor aurintricarboxylic acid, prevented the death of cultured septal cholinergic neurons subjected to nerve growth factor withdrawal. Furthermore, these agents are capable of rescuing cholinergic neurons subjected to a period of nerve growth factor withdrawal after which addition of cycloheximide is no longer protective. Thus, nerve growth factor, cyclic AMP and high K+ can effect rescue after inhibition of translation ceases to be protective. These findings suggest that under defined conditions in vitro, withdrawal of nerve growth factor from septal cholinergic neurons during a critical period of development results in the apoptotic death of these CNS neurons, which can be prevented at the post-translational level by nerve growth factor, cyclic AMP and high K+.

Animals↗
PubMed1996

Viral meningitis due to echovirus types 6 and 9: epidemiological data from Western Australia.

During the autumn of 1992, Western Australia experienced a large viral meningitis outbreak of dual aetiology. Of the 161 cases, 64% were children under 15 years of age, with the highest notification rate being in children less than 5 years of age. Echovirus 9 caused 41% of cases and occurred mainly in the metropolitan areas of Western Australia whereas echovirus 6, which caused 37% of cases, was more widespread. An enterovirus was cultured from 70% of CSF specimens, 88% of faecal specimens and 68% of upper respiratory tract specimens. High CSF white cell counts and neutrophil predominance were common. Seven cases had normal CSF white cell counts even though an enterovirus was isolated from the CSF. Therefore, the CSF findings were of restricted value in excluding viral meningitis, and did not reliably distinguish between bacterial and viral meningitis.

Adolescent↗
PubMed1996

Effect of cortisporin otic suspension on cochlear function and efferent activity in the guinea pig.

To predict cochlear receptor cell insult from therapeutic aminoglycoside antibiotics, we sought to determine whether the presence of subtoxic concentrations of Cortisporin otic suspension in the cochlea can be detected by measuring changes in efferent suppression of compound action potentials recorded from the round window. Olivocochlear efferent suppression in an earlier study was reversibly inhibited by injections of gentamicin in guinea pigs. Using that same technique, we found that 2.0 microliter of Cortisporin otic suspension (neomycin, polymyxin B, hydrocortisone) placed on the round window of guinea pigs in varying concentrations causes a rapid, permanent alteration in thresholds. Solutions of Cortisporin otic suspension diluted to a concentration of 1:20 yield a reversible loss of efferent suppression without measurable changes in compound action potential. These data suggest that the presence of Cortisporin otic suspension can be detected functionally in the cochlea at very low concentrations prior to the development of a threshold shift.

Action Potentials↗
PubMed1996

Pro-innovation bias: the case of the Giant Texas SmokeScream.

A common approach to promoting improvements in school health instruction involves development and dissemination of new curricula and teaching materials. Ironically, potential effects of innovative materials on student outcomes and actual teacher instructional practices rarely are considered important in decisions concerning use of new material. This study examined the impact of a new curricular innovation, the Giant Texas SmokeScream (GTSS), on 512 middle grade students' knowledge, perceptions, and behavioral intent about smoking. The data provided a basis for discussion of what Rogers labeled "pro-innovation bias." Data indicated the program had no effect on students. The GTSS program itself, although popular with schools, was questioned as being atheoretical in its approach to health education and ineffective in its outcomes. These data illustrate the need for programs to be based on sound theory and evaluated rigorously prior to general adoption. Additionally, program evaluations focused solely on student effects are insufficient in their assessment of adoption and implementation practices.

Adolescent↗
PubMed1996

Infantile onset of hereditary ascending spastic paralysis with bulbar involvement.

Primary lateral sclerosis and hereditary spastic paraparesis are both rare neurodegenerative disorders characterized by progressive weakness and spasticity of the lower limbs, with involvement of the corticospinal tracts and sparing of anterior horn cells. We describe a consanguineous family in which three sons developed progressive paralysis of the lower extremities in infancy with subsequent involvement of the upper extremities and bulbar muscles but cognitive sparing. This family presents the nosologic difficulty of distinguishing between hereditary spastic paraparesis and primary lateral sclerosis. We suggest that the diagnosis in this family is hereditary primary lateral sclerosis. This is the first instance of familial occurrence of primary lateral sclerosis.

Adolescent↗
PubMed1996

Racial differences on psychological measures in combat veterans seeking treatment for PTSD.

In this article, we examined racial differences in psychometric data on 4 commonly used self-report inventories administered to a group of 206 combat veterans evaluated at a Veterans Affairs Medical Center outpatient posttraumatic stress disorder (PTSD) treatment program. Patients completed the Beck Depression Inventory, Mississippi Scale for Combat-Related PTSD, Dissociative Experiences Scale (DES), and Minnesota Multiphasic Personality Inventory-2 (MMPI-2). Black veterans showed greater elevations than White veterans on the DES, and the F-K index and Scales 6 and 8 of the MMPI-2. In addition, normative data are presented for the entire sample on each measure. Results suggest that, consistent with studies using the original MMPI, these patients endorse severe levels of psychopathology across a broad range of symptoms, including depression and disturbed thinking. Implications for clinical practice and future research are addressed.

Adult↗
PubMed1995

Sulphated compounds attenuate beta-amyloid toxicity by inhibiting its association with cells.

Agents that interfere with the toxic effects of beta-amyloid protein may be therapeutically useful against Alzheimer's disease. We reported recently that several sulphated glycosaminoglycans and sulphonated dyes attenuate the toxic effects of beta-amyloid fragments beta 25-35 and beta 1-40 in two clonal cell lines. We now demonstrate that this protective effect is due to interference with beta-amyloid cell association rather than effects on beta-amyloid structure. Using an enzyme-linked immunoabsorbance assay to detect cell-associated beta 1-40, we found in a range of compounds a strong correlation between inhibition of HeLa cell association of beta 1-40 and attenuation of cellular toxicity as measured by inhibition of 3-[4,5-dimethylthia-zol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) reduction. In contrast, effects on peptide structure, as measured by Congo red binding, were generally inconsistent with the attenuating effects of the compounds on cellular toxicity. These results suggest that by binding beta-amyloid these agents prevent its interaction with cells.

Amyloid beta-Peptides↗
PubMed1995

Consensus phylogeny of Dictyostelium.

The evolutionary relationship of Dictyostelium discoideum to the yeasts, fungi, plants, and animals is considered on the basis of physiological, morphological and molecular characteristics. Previous analyses of five proteins indicated that Dictyostelium diverged after the yeasts but before the metazoan radiation. However, analyses of the small ribosomal subunit RNA indicated divergence prior to the yeasts. We have extended the molecular phylogenetic analyses to six more proteins and find consistent evidence for a more recent common ancestor with metazoans than yeast. A consensus phylogeny generated from these new results by both distance matrix and parsimony analyses establishes Dictyostelum's place in evolution between the yeasts Saccharomyces cerevisiae and Schizzosaccharomyces pombe and the worm Caenorhabditis elegans.

Animals↗
PubMed1995

Hypovolaemic and osmotic stimuli induce distinct patterns of c-Fos expression in the rat subfornical organ.

Investigation of the effects of osmotic and hypovolaemic stimuli on the pattern of subfornical organ (SFO) c-fos expression yielded three distinct distributions of activated neurons. Hypertonic saline induced c-fos expression in peripheral SFO only. PEG/water induced c-fos in the central core of SFO and PEG/saline induced c-fos in both the central and peripheral regions. Isotonic saline failed to induce SFO c-fos expression. These results are consistent with the notion of functional segregation within the SFO.

Animals↗