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Biomedical subjects

R B Wallace

Publications and source records attributed to R B Wallace.

At least 91 records · Page 5Linked to original sources
PubMed1995

Adenine nucleotide depletion in cryopreserved human cardiac valves: the "stunned" leaflet interstitial cell population.

Preparation protocols for human cardiac valves are intended to minimize cytotoxicity because it has been thought that viable leaflet interstitial cells may enhance homograft durability. Preimplantation factors influencing the status of these cells at the time of transplantation include ischemia, disinfection, and cryopreservation freezing programs. In these experiments, adenine nucleotide quantitation was undertaken to assess metabolic consequences of preparation; preharvest ischemia served as an independent variable to examine the relationship between time of procurement (postmortem) and high-energy phosphate status of the cryopreserved leaflets at thaw. Nucleotides were measured using high-performance liquid chromatography performed on extracts of semilunar cusps from 25 cryopreserved human valves with documented ischemic times. Results indicate total adenine nucleotides (TAN; [ATP] + [ADP] + [AMP], in nmol TAN/mg leaflet protein) are higher (P < 0.05) after < 2 h of harvest ischemia (1.16 +/- 0.36) than with ischemic times of 3-6 h (undetected), 7-12 h (0.18 +/- 0.07), and 13-20 h (0.06 +/- 0.06). Depletion of ATP was similar, with many leaflets devoid of detectable levels. Net utilization of leaflet energy stores demonstrates time dependency when assayed after completed processing. However, relatively elevated catabolites, even with brief ischemia, and infrequently identified ATP, ADP, and AMP, suggest a consumption so accelerated that the following cryopreservation it is virtually independent of procurement-associated ischemia. We conclude resumption of a functional cell population obligates significant de novo phosphoanhydride boned reformation or a repopulation of dead/dying interstitial cells from a subset surviving the apparently severe rigors of valve preparation.

Adenine Nucleotides↗
PubMed1995

Depressive symptoms in the elderly: association with total white blood cell count.

1. The white blood cell (WBC) count in those with high depressive symptoms and non-depressed participants in the Established Populations for Epidemiologic Studies of the Elderly (EPESE) were compared. 2. Of 3769 participants 10.8% had high depressive symptoms as assessed by the Centers for Epidemiologic Studies Depression (CES-D) Scale. The mean white blood cell count was higher in the high depressive symptoms group compared to the non-depressed group (6.8 +/- 0.12 x 10(9) WBC/1 and 6.5 +/- 0.03 x 10(9) WBC/1, respectively, p < 0.01). 3. Because older adults frequently have disabling chronic conditions which could both influence their leukocyte count and cause depressive symptoms, models were developed which controlled for the potential confounding. Even after adjusting for potential confounders, high depressive symptoms were still associated with higher white blood cell counts.

Adult↗
PubMed1995

Age-related hearing loss and bone mass in a population of rural women aged 60 to 85 years.

Demineralization of the cochlear capsule in conjunction with age-related bone mass loss may be one biologic factor contributing to hearing loss in the elderly. In other metabolic bone diseases, including Paget's disease of the bone and cochlear otosclerosis, demineralization of the cochlea has been associated with sensorineural hearing loss. In 1988/1989, the relation between hearing loss and bone mass of the radius and femoral neck was studied cross-sectionally in 369 women aged 60 to 85 years from three rural communities. Hearing sensitivity was measured using audiometry, and bone mineral density of the radius and femoral neck was measured using single- and dual-photon densitometry, respectively. Three variables, ascertained by interview, were associated with an increased odds for hearing loss: age, family history of hearing loss before the age of 50 years, and current use of more than two nonestrogen, nonthiazide prescription medications. After consideration of the effect of these three variables, women with femoral neck bone mass values below the mean value of 0.696 g/cm2 for this population had a 1.9 greater odds of having a hearing loss (confidence interval: 1.30, 2.50). This study demonstrated a consistent adjusted association between femoral neck bone mass and age-related hearing loss in a population of rural women aged 60 to 85 years. No consistent association was observed between radial bone mass and hearing loss.

Absorptiometry, Photon↗
PubMed1995

The role of N omega-nitro-L-arginine in modulation of pulmonary vascular tone in the maturing newborn pig.

Current therapeutic modalities for treatment of newborn pulmonary hypertensive crisis include but are not limited to the administration of nitric oxide (endothelium-derived relaxing factor). However, few data are available on the role of endogenously produced endothelium-derived relaxing factor in the modulation of pulmonary vascular tone in the neonate. In the current study, we investigated the acute effects of N omega-nitro-L-arginine (a potent competitive inhibitor of endothelium-derived relaxing factor synthase) on the pulmonary vasculature of anesthesized open-chest 48-hour-old (n = 8) and 2-week-old (n = 7) Yorkshire pigs. After baseline data were acquired, all animals received a 10 mg/kg per minute infusion of N omega-nitro-L-arginine for 10 minutes. To discern distal and proximal pulmonary arterial vessel changes, input mean and characteristic impedance were respectively determined. Pulmonary vascular resistance was also calculated (units determined in dyne.sec.cm-5 plus or minus the standard error of the mean). Results showed N omega-nitro-L-arginine infusion did not significantly alter baseline pulmonary arterial pressure (22,370 +/- 1473 dyne/cm2), pulmonary vascular resistance (5171 +/- 805 dyne.sec.cm-5), input impedance (6343 +/- 806 dyne.sec.cm-5), or characteristic impedance (2073 +/- 418 dyne.sec.cm-5) in 48-hour-old pigs. In 2-week-old pigs, infusion of N omega-nitro-L-arginine elevated pulmonary arterial pressure (18,162 +/- 1415 dyne/cm2 versus 23,838 +/- 1810 dyne/cm2, p = 0.015), pulmonary vascular resistance (810 +/- 137 dyne.sec.cm-5 versus 1519 dyne.sec.cm-5, p = 0.030), and input impedance (2302 +/- 251 dyne.sec.cm-5 versus 2900 +/- 255 dyne.sec.cm-5, p = 0.018). Characteristic impedance was not altered in 2-week-old pigs. These data indicate that N omega-nitro-L-arginine infusion resulted in pulmonary arteriolar vasoconstriction in 2-week-old pigs, but not in 48-hour-old pigs. This finding suggests that endothelium-derived relaxing factor does not modulate basal pulmonary arteriolar tone during the early newborn period, but does play a significant role in 2-week-old pigs. These data also suggest that the functional role for endothelium-derived relaxing factor is confined to the distal arteriolar pulmonary bed and does not extend to the larger proximal arterial vessels.

Animals↗
PubMed1995

Serum creatinine levels in older adults: relationship with health status and medications.

We aimed to examine the association of serum creatinine with health status and current medications in the population of older adults. We employed a cross-sectional study within an ongoing cohort of 3999 residents of three communities of the Established Populations for Epidemiologic Studies of the Elderly who had venepuncture at the 6-year follow-up when they were aged 71 years and older. Serum creatinine levels, history of diabetes and heart attack, current medications, and blood pressure were measured. Creatinine levels were higher in men than in women, and in blacks than in whites. Higher creatinine levels were observed in persons with a history of diabetes or heart attack, and in those reporting use of cimetidine and diuretic medications. Persons taking frusemide and the potassium-sparing diuretics had higher creatinine levels than those taking thiazides. This study confirms associations of higher creatinine with male sex, older age, black race, history of diabetes and cimetidine use reported from cross-sectional research in younger populations and in smaller, more selected groups of older adults. Longitudinal studies will be necessary to strengthen our understanding of the causes of changes in kidney function in the older population.

Activities of Daily Living↗
PubMed1995

Intermittent claudication and subsequent cardiovascular disease in the elderly.

BACKGROUND: This study reports the prevalence of intermittent claudication (IC) in ambulatory community-resident adults age 65 years or older, compares cardiovascular risk factors and comorbidity of persons with and without IC, and examines the independent association of IC in predicting all cause and cardiovascular mortality, myocardial infarction, stroke, and disability. METHODS: Data are from a pooled sample of 8996 older adults from the East Boston, New Haven, and Iowa sites of the Established Populations for Epidemiologic Studies of the Elderly, conducted between 1982 and 1988. RESULTS: 2.4% and 1.5% of men and women, respectively, reported IC. Persons with IC had significantly higher rates of diabetes and cardiovascular comorbidity than persons without IC, and they were more likely to smoke. Claudication predicted higher rates of mortality, myocardial infarction, stroke, and disability independent of associated cardiovascular conditions and risk factors. Among persons with a history of angina, myocardial infarction, and/or stroke, those who reported IC had a twofold greater risk of cardiovascular mortality. CONCLUSION: The study demonstrated that IC is an important predictor of mortality and cardiovascular morbidity in ambulatory older adults independent of associated coronary ischemia and cardiovascular disease risk factors. Results suggest that inclusion of a measure of IC improves the prediction of cardiovascular morbidity and mortality in older adults.

Activities of Daily Living↗
PubMed1995

Sleep complaints among elderly persons: an epidemiologic study of three communities.

The frequencies of five common sleep complaints--trouble falling asleep, waking up, awaking too early, needing to nap and not feeling rested--were assessed in over 9,000 participants aged 65 years and older in the National Institute on Aging's multicentered study entitled "Established Populations for Epidemiologic Studies of the Elderly" (EPESE). Less than 20% of the participants in each community rarely or never had any complaints, whereas over half reported at least one of these complaints as occurring most of the time. Between 23% and 34% had symptoms of insomnia, and between 7% and 15% percent rarely or never felt rested after waking up in the morning. In multivariate analyses, sleep complaints were associated with an increasing number of respiratory symptoms, physical disabilities, nonprescription medications, depressive symptoms and poorer self-perceived health. Sleep disturbances, particularly among older persons, oftentimes may be secondary to coexisting diseases. Determining the prevalence of specific sleep disorders, independent of health status, will require the development of more sophisticated and objective measures of sleep disturbances.

Age Factors↗
PubMed1995

Occult caffeine as a source of sleep problems in an older population.

OBJECTIVE: To evaluate the impact of caffeine in medication on sleep complaints in a community population of persons aged 67 or older. DESIGN: Cross-sectional analysis. SETTING: Iowa 65+ Rural Health Study. PARTICIPANTS: Those who completed their own interview, including a section on the use of medications, during the third annual in-person follow-up in 1984-1985. MEASUREMENTS MAIN OUTCOMES: trouble falling asleep or other sleep complaints. Covariates: use of caffeine-containing medication, spasmolytic, or sympathomimetic drug; number of drugs used; depressive symptoms; self-perceived health; comorbidity, hip fracture, arthritis, ulcer of stomach or intestines; and consumption of caffeinated beverages. RESULTS: The prevalence of caffeinated medication use by participants was 5.4%. Those reporting the use of any caffeine-containing medication were at an increased risk of having trouble falling asleep (Odds Ratio [OR] = 1.79, 95% confidence interval [CI] = 1.19-2.68). There was no significant risk of other reported nighttime or daytime sleep problems associated with use of caffeine-containing drugs. Even after adjusting for other factors that could interfere with initiation of sleep, such as painful disease, depressive symptoms, polypharmacy, use of specific medications known to interfere with sleep, and coffee consumption, the use of caffeine-containing medication still presented a significantly increased risk of having trouble falling asleep (OR = 1.60, CI = 1.04-2.46). Although those participants using over-the-counter analgesic medication containing caffeine had an increased risk of trouble falling asleep (OR = 1.88, CI = 1.22-2.90), there was no significant risk of trouble falling asleep for those who took similar noncaffeinated OTC analgesic drugs (OR = 1.26, CI = 0.87-1.83). CONCLUSIONS: The use of caffeine-containing medication is associated with sleep problems. Healthcare providers should be aware of potential problems associated with over-the-counter medications containing caffeine and should counsel patients about the potential of sleep problems. Older patients should be encouraged to read the label on medications and to select drugs that are caffeine-free when that is possible.

Aged↗
PubMed1995

Risk factors for motor vehicle crashes among older drivers in a rural community.

OBJECTIVE: To estimate the motor vehicle crash rate in a cohort of older drivers from a rural community and to identify health-related conditions that increase their risk for crash involvement. DESIGN: Cohort study with 5 years of crash-record surveillance. SETTING: The Iowa 65+ Rural Health Study, one of four Established Populations for Epidemiologic Studies of the Elderly (EPESE). PARTICIPANTS: A total of 1791 drivers aged 68 years and older. MAIN MEASURES: Exposure measures of physical, mental, and sensory well-being from a health interview survey; outcome measure of police-reported crashes maintained by the Iowa Department of Motor Vehicles. RESULTS: Between 1985 and 1989, 206 drivers were involved in 245 state-recorded crashes. The estimated annual crash involvement rate for these rural older drivers (28 per 1000 driving-years) was about 20% less than the national average for drivers aged 65 years and over (36 per 1,000). An increased risk for motor vehicle crashes was associated with episodes of back pain (Relative Risk = 1.4, P < .05), use of nonsteroidal anti-inflammatory drugs (RR = 1.7, P < .01), and poor performance on a free-recall memory test (RR = 1.4, P < .05). CONCLUSIONS: If these and other geriatric conditions are confirmed as risk factors for motor vehicle crashes, medical guidelines for license renewal may need updating and health professionals may need new instruments to detect older patients at high risk for unsafe driving.

Accidents, Traffic↗
PubMed1995

Cardiac operations in patients aged 70 years and over: mortality, length of stay, and hospital charge.

BACKGROUND: With emphasis today on cost containment in health care, the results and costs of cardiac operations in elderly patients are being scrutinized. METHODS: Our computerized database was used to obtain the characteristics of patients undergoing cardiac operations from January 1990 to July 1994. A study group of 628 patients aged 70 years and over was identified, and comparisons were made between them and adult patients less than 70 years of age. RESULTS: In the elderly group the 30-day mortality was 33 of 628 (5.3%), and the overall hospital mortality was 40 (6.4%). During this time the 30-day mortality for all adult patients less than 70 years old was 49 of 1787 (2.7%; p < 0.003) and the hospital mortality was 59 (3.3%; p < 0.001). The mean length of postoperative hospital stay (days +/- standard error) in all surviving patients aged 70 years and over was 11.6 +/- 0.4 days, compared with 8.5 +/- 0.2 days in patients less than 70 years old (p < 0.001). Over the time of the study the length of stay in patients less than 70 years old declined from 9.6 +/- 0.4 to 7.2 +/- 0.6 days, whereas it stayed the same for elderly patients. The 30-day mortality and length of stay increased with the risk category of the Parsonnet model. The mean hospital charge for patients aged 70 and over was 114% of that for younger patients. CONCLUSIONS: Although mortality, length of stay, and hospital charge are increased in patients 70 years of age and over, they are not excessively so. The results support the continued performance of cardiac surgical procedures in select elderly patients.

Aged↗
PubMed1995

Nonsteroidal antiinflammatory drugs and cognitive decline in the elderly.

OBJECTIVE: To better define the role of nonsteroidal antiinflammatory drugs (NSAID) in cognitive decline of the elderly. METHODS: Population based inception cohort of the rural elderly. NSAID user status was characterized as high dose, low/medium dose, or nonuser at 2 successive in-person interviews 3 years apart (F3 and F6). Respondents were from the Iowa 65+ Rural Health Study, one of the 4 cohorts of the National Institute on Aging's Established Populations for Epidemiologic Studies of the Elderly. Memory decline was assessed by a change in immediate word recall between F3 and F6. Multivariable logistic regression models were created to determine important predictors of the F3 to F6 recall memory decline in groups with poor, average, and good word recall at the F3 interview. Specific NSAID were compared to assess which drugs, if any, were associated with memory decline. RESULTS: The 2 factors most strongly associated with a significant immediate word recall decline between F3 and F6 among individuals in the average F3 word recall group were limitation in functional status [odds ratio (OR) = 2.31, 95% Confidence Interval (CI) (1.51, 3.52)] and high dose NSAID use [OR = 2.04, 95% CI (1.07, 3.89)]. No single NSAID agent was significantly more strongly associated with word recall decline than the others. However, in exploratory analyses use of high dose NSAID of the proprionic acid family neared significance for recall decline [OR = 3.17, 95% CI (0.92, 10.9). CONCLUSION: In elderly respondents with average baseline recall memory, high dose NSAID were a significant risk factor for longitudinal memory decline in this community based cohort. Although a large scale clinical trial is needed to definitely address this issue, we provide further evidence that NSAID play a role in cognitive dysfunction in the elderly.

Aged↗
PubMed1994

Pulmonary hydraulic impedance response to cromakalim (BRL 34915) in newborn pigs.

Cromakalim (BRL 34915), a novel vasodilator, is used clinically to manage systemic hypertension. Its effects on the intact newborn pulmonary circulation remain unclear. The purpose of this study was to determine the response of both the mean and pulsatile pulmonary hemodynamic parameters to intravenous infusion of BRL 34915 (0.1 mg/kg/min for 10 min) in 48-hr-old open-chest Yorkshire pigs. Animals were divided into two groups: Group I pigs had a high mean baseline pulmonary artery pressure (PAP) (> 17 mm Hg), while Group II pigs had a low to normal baseline mean PAP (< 17 mm Hg). Following instrumentation for high-fidelity recordings of PAP and flow, baseline data were acquired. Employing Fourier analysis, characteristic impedance (Zo), input mean impedance (Zm), impedance harmonic moduli (units in dyn sec cm-5), and phase angles (radians) were determined. Pulmonary vascular resistance (PVR) was calculated and aortic pressure (AP, mm Hg) was also measured. All values = mean +/- SEM. Group I animals ("high tone") underwent a decrease in PAP (17.9 +/- 1.6 mm Hg vs 13.6 +/- 1.9 mm Hg, P = 0.008) and PVR (4310 +/- 816 dyn sec cm-5 vs 3713 +/- 687 dyn sec cm-5, P = 0.04). Group II animals ("low tone") responded with an increase in PAP (11.5 +/- 0.4 mm Hg vs 16.6 +/- 1.8 mm Hg, P = 0.029). AP decreased in Group I (40 +/- 3.8 mm Hg vs 21.5 +/- 2.8 mm Hg, P = 0.008) and Group II (51.2 +/- 10.8 mm Hg vs 31.2 +/- 10.9 mm Hg, P = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Dual structural and functional phenotypes of the porcine aortic valve interstitial population: characteristics of the leaflet myofibroblast.

The cellular properties of semilunar cardiac valve leaflets may be more complex than previously assumed. In particular, the cells of the leaflet matrix which are likely critical to proper cusp function are a poorly described population to date. We hypothesized that, similar to the matrix cells of atrioventricular valves, aortic valve leaflet interstitial cells (AoLIC's) possess characteristics of both fibroblasts (matrix secretion) and smooth muscle cells (contraction). Porcine AoLIC's were structurally examined for contractile and stress fiber protein assemblies using transmission electron microscopy and immunocytochemistry. Contractile function in response to vasoactive stimuli was directly assessed using AoLIC's cultured on flame-polymerized silicone, with cell contraction identified by the appearance of wrinkles in the substratum after challenge with each agent. The structural analyses showed cellular microfilaments were often organized into various contractile arrangements including polygonal networks, and that AoLIC's are rich in smooth muscle-specific alpha-actin. Incomplete basal laminae often associated with myofibroblasts were observed. Contraction experiments indicated a responsivity of similar latency, but variable peak and duration to 10(-7) M L-epinephrine, 3.2 x 10(-7) M angiotensin II, 110 microM carbachol, 50 mM KCl, 3.2 x 10(-7) M bradykinin, 110 microM isoproterenol, and 5 x 10(-7) M endothelin I. Soluble and insoluble matrix secretion was confirmed with FITC-conjugated monoclonal antibodies to chondroitin sulfate, fibronectin, and prolyl-4-hydroxylase. These data show that the AoLIC's are best designated as myofibroblasts. The unusual features of the myofibroblast may be central to lifelong aortic leaflet durability.

Animals↗
PubMed1994

Drug data coding and analysis in epidemiologic studies.

In epidemiologic studies that collect comprehensive information on medication use, the complexity of dealing with a large number of trade and generic names may limit the utilization of these data bases. This paper shows the specific advantage of using two coding systems, one to maximize efficiency of data entry, and the other to facilitate analysis by organizing the drug ingredients into hierarchical categories. The approach used by two large surveys, one in the USA and one in Italy, is described: the Established Populations for Epidemiologic Studies of the Elderly (EPESE) and the 'Gruppo Italiano di Farmacovigilanza nell' Anziano' (GIFA). To enter the medications into a computerized database, codes matching the drug product names are needed. In the EPESE the prescription and over the counter drug products are coded with the Drug Products Information Coding System (DPICS) and the Iowa Nonprescription Drug Products Information Coding System (INDPICS), respectively. The GIFA study uses the coding system of the Italian Ministry of Health (MINSAN), with a unique numeric code for each drug product available in Italy. To simplify the analytical process the drug entry codes are converted into hierarchical coding systems with unique codes for specific drug ingredients, chemical and therapeutic categories. The EPESE and GIFA drug data are coded with the Iowa Drug Information System (IDIS) ingredient codes, and the Anatomical Therapeutic and chemical (ATC) codes, respectively. Examples are provided that show coding of diuretics in these two studies and demonstrate the analytic advantages of these systems.

Adverse Drug Reaction Reporting Systems↗
PubMed1994

A short physical performance battery assessing lower extremity function: association with self-reported disability and prediction of mortality and nursing home admission.

BACKGROUND: A short battery of physical performance tests was used to assess lower extremity function in more than 5,000 persons age 71 years and older in three communities. METHODS: Balance, gait, strength, and endurance were evaluated by examining ability to stand with the feet together in the side-by-side, semi-tandem, and tandem positions, time to walk 8 feet, and time to rise from a chair and return to the seated position 5 times. RESULTS: A wide distribution of performance was observed for each test. Each test and a summary performance scale, created by summing categorical rankings of performance on each test, were strongly associated with self-report of disability. Both self-report items and performance tests were independent predictors of short-term mortality and nursing home admission in multivariate analyses. However, evidence is presented that the performance tests provide information not available from self-report items. Of particular importance is the finding that in those at the high end of the functional spectrum, who reported almost no disability, the performance test scores distinguished a gradient of risk for mortality and nursing home admission. Additionally, within subgroups with identical self-report profiles, there were systematic differences in physical performance related to age and sex. CONCLUSION: This study provides evidence that performance measures can validly characterize older persons across a broad spectrum of lower extremity function. Performance and self-report measures may complement each other in providing useful information about functional status.

Activities of Daily Living↗