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Biomedical subjects

R B Wallace

Publications and source records attributed to R B Wallace.

At least 163 records · Page 9Linked to original sources
PubMed1991

Sleep patterns in rural elders: demographic, health, and psychobehavioral correlates.

Altered sleep patterns, including changes in bedtime, sleep latency, total sleep time, and arising time, have been reported to occur with increasing age. We examine self-reported sleep patterns in a geographically-defined population (n = 3097) of persons aged 65 years and older. Sleep patterns were characterized according to demographic variables, clinical conditions, and physical, psychological, and social functioning. Sleep latency and total hours of sleep increased with age, and older respondents went to bed earlier. The percentage of respondents who reported feeling rested in the morning decreased with age. Women went to bed later, had longer sleep latency, and fewer hours of sleep than men, and were less likely to report feeling rested than men. Sleep patterns were also related to educational attainment, self-perceived health status, physical functional status, psychotropic drug use, alcohol use, depressive symptoms, life satisfaction, and social and recreational activity level. This population study suggests that sleep problems among the elderly are sometimes associated with treatable health conditions and modifiable behavioral and environmental characteristics.

Age Factors↗
PubMed1991

Longitudinal application of cognitive function measures in a defined population of community-dwelling elders.

The nature and extent of possible age-related changes in cognitive function have primarily been examined in nonrandom samples, and have not been well described in population-based studies. We examined longitudinal changes in performance on a mental status examination and recall and recognition memory tests in a population-based (n = 1953) study of community-dwelling elders. Advanced age was associated with poorer performance on all tests and more rapid decline longitudinally on the mental status and recall and recognition memory tests. Less-educated persons performed more poorly. Lower levels of educational attainment were predictive of more rapid declines on the mental status examination and recall memory test among women. Subsequent survivorship was associated with preserved performance on the mental status and recall memory tests. These findings suggest that there are age-associated changes in cognitive function, and have implications for population-based studies of cognitive function and survey research in general.

Age Factors↗
PubMed1991

The effect of temperature and oligonucleotide primer length on the specificity and efficiency of amplification by the polymerase chain reaction.

The polymerase chain reaction (PCR) is most effectively performed using a thermostable DNA polymerase such as that isolated from Thermus aquaticus. Since temperature and oligonucleotide length are known to control the specificity of oligonucleotide hybridization, we have investigated the effect of oligonucleotide length, base composition, and the annealing temperature on the specificity and efficiency of amplification by the PCR. Generally, the specificity of PCR is controlled by the length of the oligonucleotide and/or the temperature of annealing of the primer to the template. An empirical relationship between oligonucleotide length and ability to support amplification was determined. This relationship allows for the design of specific oligonucleotide primers. A model is proposed which helps explain the observed dependence of PCR on annealing temperature and length of the primer.

Base Sequence↗
PubMed1991

Leg pain in the rural Iowa 65+ population. Prevalence, related factors, and association with functional status.

Research tabulating the existence and effects of pain and related factors in the elderly is lacking, in spite of the continued growth of the aged population. Leg pain, in particular, may interfere with activities and interpersonal interactions. This study of 3,097 rural elderly examines the prevalence of complaints of leg pain and related factors in a geographically-defined population. Findings indicate that leg pain is clearly a common experience which impacts daily activities of the elderly.

Age Factors↗
PubMed1991

Persistence of bcr-able gene expression following bone marrow transplantation for chronic myelogenous leukemia in chronic phase.

The bcr-abl RNA transcript is the molecular counterpart of the Philadelphia chromosome and is detectable by an extremely sensitive polymerase chain reaction assay in most patients with chronic myelogenous leukemia. To determine the effectiveness of ablative radiochemotherapy and bone marrow transplantation in eradicating molecular evidence of the malignant clone, we assayed for bcr-abl RNA expression in specimens from 19 patients with CML in chronic phase (CP) who have survived for at least one year post-BMT. We correlated these results with the patients' remission status based on cytogenetic analysis and BM morphology, and with evidence of mixed hematopoietic chimerism by analysis of RBC antigen and DNA restriction fragment length polymorphism patterns. Thirteen of the 19 patients had detectable bcr-abl RNA at some time following BMT. Twelve of these patients have remained in remission by morphologic and karyotypic criteria from 16.6 to 63.7 months following BMT. One of these 13 patients relapsed both by cytogenetic and clinical criteria at 28.1 months after BMT. Six of these 13 patients are still positive at the time of their most recent analysis. Only two patients have evidence for mixed chimerism of normal hematopoietic elements by either RBC antigen or DNA RFLP patterns. These results suggest that, in some patients transplanted for CML in CP, small numbers of residual leukemic cells may persist or reappear transiently without leading to clinical relapse. The definition of complete remission in CML may need to be revised in light of the enhanced ability to detect minimal residual disease by PCR technology.

Adult↗
PubMed1991

Long-term lung preservation with the PAF antagonist BN 52021.

Platelet activating factor (PAF, 1-alkyl-2(R)-acetyl-glycero-3- phosphorylcholine) is a phospholipid that is released by a variety of cells. The similarity between the pathophysiological effects of PAF and posttransplant pulmonary dysfunction led to an evaluation of a PAF antagonist as an adjunct to lung preservation. The ginkgolide B, BN 52021, was selected as the PAF antagonist to be studied because of the large data base available on this compound. BN 52021 was given to the donor and recipient (10 mg/kg i.v.) prior to harvest and transplantation and was included in 1 L of preservation solution (10 mg/kg) used for flushing the pulmonary artery and for storage. Left single-lung transplantation was performed following a 22-hr preservation period at 10 degrees C. Arterial oxygen tension (pO2), pulmonary vascular resistance (PVR), alveolar arterial oxygen difference (A-aDO2), and dynamic lung compliance (DLC) were recorded for 6 hours following ligation of the native pulmonary artery. At the end of 6 hr pO2 was 243.5 +/- 61.5 vs. 71.7 +/- 10.2 mmHg (P less than 0.02) for the controls. A-aDO2 was less in the BN 52021 groups: 431.8 +/- 58.3 vs. 606.0 +/- 9.8 mmHg in the control groups (P less than 0.001), and PVR was significantly less in the BN 52021 group: 346 +/- 70.8 vs. 663 +/- 64.3 dynes/sec/cm-5 (P less than 0.035). We conclude that PAF antagonists like BN 52021 may be useful adjuncts for lung preservation. The effects of BN 52021 are easily explained by PAF antagonist activity in ischemic and reperfusion-induced pulmonary dysfunction. However this study does not exclude that BN 52021 may have direct effects.

Animals↗
PubMed1991

Perceived purpose of prescription drugs: the Iowa 65+ Rural Health Study.

In order to assess elderly patients' knowledge of their medications, the Iowa 65+ Rural Health Study asked a rural, elderly population the purpose of their prescription drugs. Ten percent of all drug purposes reported were considered inappropriate by our criteria. There was some variability between therapeutic categories and their frequency of purpose misperception. For 40 percent of drugs whose purpose was inappropriate, the respondent reported another drug for which that purpose would have been appropriate. Respondents were as likely to state a medication's appropriate purpose whether it had been dispensed by a pharmacy or a physician. The highest percentage of drugs whose purpose was appropriately perceived was dispensed by mail-order pharmacies.

Aged↗
PubMed1991

Morbidity and disability in older persons in the years prior to death.

BACKGROUND: A large proportion of the disease and disability which affects older persons occurs in the years just prior to death. Little prospective evidence is available which quantifies the burden of morbidity and disability during these years. METHODS: In three community-based cohorts of persons age 65 and older, chronic conditions and disability were evaluated for the three years prior to death in 531 persons who had three annual assessments and then died within one year of the third assessment. Number of chronic conditions, prevalence of disability in activities of daily living (ADLs), and prevalence of disability on a modified Rosow-Breslau scale were determined for these decedents and compared to 8821 members of the cohorts known to have survived. RESULTS: Prevalence rates of disease and disability increased during the follow-up for both decedents and survivors, with decedents generally having higher rates than survivors. Disability rates prior to death, but not the number of diseases, increased with increasing age at death. The odds ratio for disability in ADLs at any of the three assessments for decedents versus survivors ranged from 3.0 to 4.2 in the three communities. In each community the odds ratio for ADL disability was higher in women decedents versus survivors than in men decedents versus survivors. CONCLUSIONS: These results have important implications for disability levels in future older populations in which death is projected to occur at increasingly higher ages.

Activities of Daily Living↗
PubMed1991

A model of lifetime osteoporosis impact.

The study goal was to use population-based data to model aspects of lifetime osteoporosis impact not previously studied, specifically: (1) to estimate person-years of fracture-related functional impairment against the trajectory of functional status in the general population; (2) jointly to consider hip, vertebral, and Colles' fractures in estimating the percent of women who will ever fracture; and (3) to estimate the lifetime number of fractures expected in a cohort of 10,000 50-year-old white postmenopausal women. The model estimates that 54% of 50-year-old women will sustain osteoporosis-related fractures during their remaining lifetimes. Beyond the functional impairment expected in similarly aged, unfractured women, osteoporosis-related fractures are estimated to cause 6.7% of women to become dependent in basic activities of daily living; 7.8% are expected to require nursing home care for an average of 7.6 years.

Cohort Studies↗
PubMed1991

Long-term results of aortic valve replacement with nonviable homografts.

Between 1965 and 1972, 250 patients (186 men and 64 women; median age, 48 years) underwent aortic valve replacement with homografts preserved with beta-propiolactone (98 patients) or irradiation (152 patients); operative mortality was 6% (15 patients). Follow-up to death, reoperation, or recent evaluation was completed in 95% of patients, and median follow-up time was 11.4 years. Thromboembolic events occurred in two patients (0.21 events/100 patients/yr). Risk of reoperation was 22% at 5 years, 62% at 10 years, 85% at 15 years, and 95% at 20 years. Factors associated with increased risk of reoperation were young age, male sex, native aortic valve insufficiency, previous aortic valve surgery, history of endocarditis, and larger homograft size. Survival at 5, 10, 15, and 20 years was 85%, 66%, 53%, and 38%, respectively. Late survival was diminished in older patients and those with native aortic valve insufficiency and coronary artery disease. Aortic valve replacement with nonviable homografts has a high risk of late tissue degeneration and need for reoperation. However, the incidence of thromboemboli is minimal, and grafts can be replaced with low risk (4.5%) so that overall patient survival is similar to that observed with other bioprosthetic or mechanical heart valves.

Actuarial Analysis↗
PubMed1991

Iron chelation therapy and lung transplantation. Effects of deferoxamine on lung preservation in canine single lung transplantation.

Reperfusion injury is a limiting factor in lung transplantation. Deferoxamine is an iron chelator that inhibits the formation of oxygen-derived free radicals. We investigated the effects of deferoxamine on posttransplantation lung function in a canine model of single lung transplantation. Twelve dogs underwent left lung transplantation after 20- to 24-hour hypothermic storage in a modified Euro-Collins solution. In six experiments donor and recipient received a 10 mg/kg dose of deferoxamine before harvest and transplantation, and 10 mg/kg was added to the preservation solution. Arterial oxygen tension, alveolar-arterial oxygen difference, pulmonary vascular resistance, and dynamic lung compliance were measured. Data were recorded for 6 hours after ligation of the native pulmonary artery. At the end of the study the mean arterial oxygen tension was 175.1 mm Hg for the deferoxamine treated group versus 71.1 mm Hg for the control group (p less than 0.001), and the alveolar-arterial oxygen difference was less in the deferoxamine-treated group: 502.3 versus 606.0 mm Hg (p less than 0.001). The mean pulmonary vascular resistance was lower throughout the study, and after 6 hours it was 455.1 dynes/sec/cm(-5) in the deferoxamine-treated group versus 663.7 dynes/sec/cm(-5) in the control group (p less than 0.035). Compliance was similar in both groups. We conclude that deferoxamine improves lung preservation and early posttransplantation function in canine single lung transplantation.

Animals↗
PubMed1991

Reduction of myocardial infarction after emergency coronary artery bypass grafting for failed coronary angioplasty with use of a normothermic reperfusion cardioplegia protocol.

Emergency coronary artery bypass grafting is necessary in 2.7% to 13.5% of patients undergoing elective percutaneous transluminal coronary angioplasty. Myocardial infarction develops in 11% to 49% of these patients, with 18% to 46% of infarcts resulting in new Q waves. Since February 1987 a revised protocol for myocardial preservation has been used in 19 patients undergoing emergency bypass grafting for failed angioplasty. Cardioplegia is induced with a normothermic blood cardioplegic solution. Multiple maintenance doses of cold (4 degrees C) blood cardioplegic solution are then delivered through the aortic root and vein grafts. Before the aortic crossclamp is removed, normothermic reperfusion cardioplegic solution is delivered through the aortic root and vein grafts. This group was compared with all patients undergoing emergency bypass grafting for failed angioplasty before February 1987. These 45 patients received cold induction of cardioplegic solution, multiple maintenance doses of cold cardioplegic solution, and no reperfusion cardioplegic solution. The prevalence of myocardial infarction in the group receiving cold cardioplegic solution was 65% versus 26% in the group receiving normothermic cardioplegic solution (p less than 0.007). Multivariate analysis identified the use of the normothermic cardioplegia protocol (p less than 0.005), nontotal occlusion of the angioplasty vessel (p less than 0.03), and presence of collateral flow to the angioplasty vessel (p less than 0.04) as being independently associated with absence of myocardial infarction.

Angioplasty, Balloon, Coronary↗
PubMed1990

Thiazide diuretic agents and the incidence of hip fracture.

Thiazide diuretic agents lower the urinary excretion of calcium. Their use has been associated with increased bone density, but their role in preventing hip fracture has not been established. We prospectively studied the effect of thiazide diuretic agents on the incidence of hip fracture among 9518 men and women 65 years of age or older residing in three communities. At base line, 24 to 30 percent of the subjects were thiazide users. In the subsequent four years, 242 subjects had hip fractures. The incidence rates of hip fracture were lower among thiazide users than nonusers in each community; the Mantel-Haenszel relative risk of hip fracture, adjusted for community and age, was 0.63 (95 percent confidence interval, 0.46 to 0.86). The protective effect of the use of thiazides was independent of sex, age, impaired mobility, body-mass index, and current and former smoking status; the multivariate adjusted relative risk of hip fracture was 0.68 (95 percent confidence interval, 0.49 to 0.94). Furthermore, the protective effect was specific to thiazide diuretic agents, since there was no association between the use of antihypertensive medications other than thiazides and the risk of hip fracture. These prospective data suggest that in older men and women the use of thiazide diuretic agents is associated with a reduction of approximately one third in the risk of hip fracture.

Age Factors↗
PubMed1990

The search for causes of idiopathic intracranial hypertension. A preliminary case-control study.

Idiopathic intracranial hypertension (pseudotumor cerebri) is a condition that occurs predominantly in obese women. It consists of elevated spinal fluid pressure, normal spinal fluid contents, papilledema, and headaches with normal imaging studies. Long lists of putative causes and associations have arisen, many consisting of individual case reports. We did a retrospective case-control study on 40 patients and 39 age- and sex-matched control subjects to examine the incidence of these associated conditions. Our results are only suggestive due to the small sample size; however, obesity and recent weight gain occurred more commonly in patients with idiopathic intracranial hypertension than in control subjects. All forms of menstrual abnormalities, incidence of pregnancy, antibiotic use, and oral contraceptive use were equal in both groups. A larger multicenter study will be needed to more completely characterize the risk factors for this condition.

Adolescent↗
PubMed1990

Genotype and phenotype: a practical approach to the immunogenetic analysis of lymphoproliferative disorders.

Determination of cell lineage and clonality in lymphoproliferative disorders (LPD) is greatly enhanced by molecular genetic analysis in conjunction with morphologic and immunologic techniques. We now report on a technique in which we used cryostat-cut, fresh-frozen sections (CCFFS) prepared from tissues in a manner that allows DNA hybridization studies to be coordinated readily with routine morphologic and immunohistologic studies. Thirty-seven cases representing a broad spectrum of reactive and malignant LPD were examined with this method. Samples of DNA were extracted from frozen sections, subjected to Southern blot hybridization, and probed for rearrangements of the immunoglobulin (Ig) heavy-chain and the kappa and lambda light-chain genes, as well as for the T-cell receptor beta-chain gene. We also evaluated the effects of (1) diagnostic category of LPD, (2) volume of the tissue sample, and (3) fibrosis, necrosis, and ice crystal artifacts in the sample on the recovery of DNA. Ice artifact and sample size had the greatest negative impacts on the quantity and condition of DNA recovered. Of 19 samples involved by B-cell LPD, the results of immunogenetic studies were consistent with the immunophenotypes in all but one case. Of the T-cell lymphomas from which sufficient DNA was available (three out of five of the T-cell cases), all showed rearrangements of the T-cell beta-chain gene. In order to reduce sample processing time, we evaluated alternate blot hybridization methods, rapid alkaline transfers, and direct hybridization of synthetic oligonucleotides in dried agarose gels, and found that they decreased the time required for hybridization studies. In summary, the use of CCFFS as the source of DNA allows study of gene rearrangements and, at the same time, preserves frozen-tissue blocks in tumor banks for further immunologic studies. The development of time-effective methods will make the routine use of molecular-genetic analysis more practical in the diagnostic hematopathology laboratory.

Culture Techniques↗
PubMed1990

The relationship of 1,25-dihydroxyvitamin D and radial bone mass.

We assessed the association between radial bone mass and vitamin D considering age, estrogen sufficiency and thiazide use in 373 women, aged 20-80 years in a geographically defined area. We measured cortical bone mass of the radius, using photon absorptiometry, and serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D, using preliminary chromatography and protein-binding assay. We found that 1,25-dihydroxyvitamin D levels were higher in premenopausal women and postmenopausal women using estrogen replacement as compared to postmenopausal women (P less than 0.02). Users of thiazide-based antihypertensive medications had significantly lower 1,25-dihydroxyvitamin D than their age-matched peers (P less than 0.02). Dietary calcium intake was negatively associated with 1,25-dihydroxyvitamin D levels. Estimates of vitamin D intake from diet or sunlight were not associated with 1,25-dihydroxyvitamin D levels; nor were levels of 1,25-dihydroxyvitamin D related to 25-hydroxyvitamin D levels. 1,25-Dihydroxyvitamin D was negatively and significantly associated with radial bone mass, contributing approximately 6% of the explained variability of bone mass measurements. Together age, body size, thiazide use and 1,25-dihydroxyvitamin D accounted for about 47% of the explained variability in radial bone mass measurement. 1,25-Dihydroxyvitamin D was not associated with bone mass in women currently using a thiazide medication.

Adult↗
PubMed1990

Retinol, supplemental vitamin A and bone status.

Studies of hypervitaminosis A in animals and anecdotal reports of accidental vitamin A poisoning in humans suggest impairment of bone remodeling and increased numbers of fractures. Because of the widespread use of high-dose vitamin A supplements which may produce subclinical hypervitaminosis associated with decreased bone mass and increased risk of fracture, we studied the relationship between current vitamin A supplement use, serum retinol levels, radial bone mass and fracture history in a geographically-defined population of 246 postmenopausal women, 55-80 years of age. More than 36% of this population used a vitamin A supplement with 8% of these consuming an amount in excess of 2000 retinol equivalents (RE)/day. Serum retinol was measured using high-pressure liquid chromatography and radial bone mass was measured using single photon absorptiometry. After controlling for age, current estrogen replacement, and current thiazide antihypertensive use, we observed no statistically significant relationship between vitamin A supplement use or serum retinol with radial bone mass or fractures.

Adult↗