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Biomedical subjects

K Rhoads

Publications and source records attributed to K Rhoads.

17 recordsLinked to original sources
PubMed2006

Differential modulation of plasma beta-amyloid by insulin in patients with Alzheimer disease.

BACKGROUND: Hyperinsulinemia and insulin resistance are risk factors for memory impairment and Alzheimer disease (AD). Insulin regulates levels of the amyloid beta-peptide (Abeta) in vitro in neuronal cultures and in vivo in the CSF of normal older adults. OBJECTIVE: To determine whether insulin affected plasma Abeta levels and whether such effects differed for patients with AD compared with normal older adults. METHODS: Fifty-nine patients with AD and 50 healthy older adults each received infusions of saline and of insulin (1.0 mU.kg(-1).min(-1)) with accompanying dextrose to maintain euglycemia. A subset of participants (19 AD, 12 normal) received two additional conditions, in which insulin was infused at a lower (0.33 mU.kg(-1).min(-1)) and higher (1.67 mU.kg(-1).min(-1)) rate. Plasma insulin and Abeta were measured after 120 minutes of infusion. RESULTS: Adults with AD had higher plasma insulin vs normal adults at the two higher infusion rates, despite receiving comparable amounts of insulin. For normal adults, insulin reduced plasma Abeta levels at the middle (1.0 mU.kg(-1).min(-1)) dose, with attenuated effects at lower and higher doses. In contrast, for patients with AD, insulin raised plasma Abeta levels at the two higher doses (1.0 and 1.67 mU.kg(-1).min(-1)). CONCLUSIONS: These results suggest that patients with Alzheimer disease (AD) have reduced insulin clearance and insulin-provoked plasma amyloid beta-peptide (Abeta) elevation. Abnormal regulation of peripheral Abeta by insulin may contribute to AD risk.

Aged↗
PubMed2000

Choosing to encourage or discourage: perceived effectiveness of prescriptive versus proscriptive messages.

The estimated cost of repairing damage caused to recreational sites annually is in the hundreds of millions of dollars. These depreciative activities also reduce the quality of visitors' experiences in the damaged areas. Indirect methods, such as visitor education through brochures and signs, continue to be the least controversial management approaches to depreciative acts. Yet, the literature on studies examining the most effective message presentations remains sparse. A survey mailed to randomly selected National Association for Interpretation members assessed the perceived effectiveness of communications that encouraged positive conduct (prescriptive messages) versus those that discouraged negative conduct (proscriptive messages) in wildland and urban settings. Almost invariably, respondents viewed the encouragement-based prescriptive messages as more effective than the discouragement-based proscriptive messages. This finding stands in sharp contrast to an earlier study that discovered a preponderance of proscriptive versus prescriptive messages on signs in both wildland and urban recreational environments. Thus, although the great majority of interpreters see the encouragement of positive conduct as more effective, in practice, messages on signs are much more likely to discourage negative conduct. Reasons for this discrepancy are considered.

Journal Article↗
PubMed1998

Five-year follow-up for adverse outcomes in males with at least minimally positive angiograms: importance of "denial" in assessing psychosocial risk factors.

The purpose of this study was to test the role of "denial" (spouse/friend minus self-ratings on parallel versions of the same questionnaire) in diluting the predictive value of emotional distress for cardiac events (deaths, new MIs, and/or revascularizations). One hundred forty-four men with no history of prior revascularization who had at least minimally positive diagnostic coronary angiograms, and someone they selected as "someone who knows you well," completed parallel versions of the Ketterer Stress Symptom Frequency Checklist (KSSFC). They were followed up by phone an average of 59.7 months after recruitment. Length of follow-up, baseline cardiac risk factors, and a number of baseline-obtained psychosocial risk factors were tested as prospective predictors of combined events (death by any cause, new MIs, and/or revascularizations) and current anginal frequency. Only spouse/friend observed anxiety on the KSSFC predicted current anginal frequency (p = 0.001). On the self-report version of the KSSFC, patients with one or more events reported less anger (p = 0.031), depression (p = 0.008), and anxiety (p = 0.003). These results may be attributable to "denial" because there were no differences in spouse/friend ratings, and difference scores (spouse/friend minus patient) on the KSSFC scales, particularly anger, were also related to events: AIAI (p = 0.002); depression (p = 0.063); and anxiety (p = 0.010). Denial may be a major limiting factor in accurately assessing emotional distress in cardiac populations, and may help account for a number of the previous findings.

Angiography↗
PubMed1996

Emotional distress among males with "syndrome X".

The present study examined traditional risk factors and various indices of emotional distress in males with positive angiograms (N = 122), "syndrome X" males with negative or nominal results on angiogram (N = 53), and age- and socioeconomic status-matched males with no manifest history of otherosclerotic disease (N = 56). Syndrome X patients reported more depression on the Ketterer Stress Symptom Frequency Checklist (KSSFC) than positive angiographic patients. And compared with healthy controls, they were more likely to be perceived by a spouse/friend as depressed and anxious on the KSSFC, scored higher on the Framingham Type A Scale, and reported more unprovoked nocturnal awakening. Syndrome X patients generally appear to be similar to patients with positive angiograms with regard to traditional risk factor history but are more distressed than healthy controls. This becomes most evident when denial is circumvented by discussion with significant others or inquiries are "framed" appropriately.

Analysis of Variance↗
PubMed1996

Is aspirin, as used for antithrombosis, an emotion-modulating agent?

Antiplatelet substances, generally aspirin, have become widely used for secondary prevention of ischemic heart disease. Used in relatively small doses, it is generally assumed that aspirin has no psychoactive effect. The present study took advantage of a sample of 174 males undergoing coronary angiography to see if regular aspirin use as prophylactic therapy for ischemic heart disease was associated with one or more of a number of measures of emotional distress. Aspirin use was found to be associated with less depression and anxiety or worry, as reported by the patient and as perceived by a significant other. Despite a significant association of aspirin use with the presence of documented coronary artery disease, the association of aspirin use and diminished distress could not be accounted for by the previously observed high prevalence of depressed/anxious individuals among patients with negative or nominal results on angiography, or by a number of other demographic or clinical variables such as age and socioeconomic status. Although only correlational in nature, present results raise the question of whether aspirin may have a beneficial mood-modulating effect.

Affect↗
PubMed1992

Cardiovascular responses of heart transplant recipients to graded exercise testing.

A group of orthotopic heart transplant (OHT, n = 28) and heart surgery (n = 19) patients, with similar ejection fractions and left ventricular end-diastolic pressures, were exercised to symptom-limited maximum to describe differences in cardiovascular and gas exchange responses. Testing was performed at a mean of 3 and 6 mo after surgery, respectively (P less than 0.05). OHT patients have a greater resting systolic and diastolic blood pressure (P less than 0.01) and a significantly greater (P less than 0.01) heart rate (HR) at rest in the supine and standing positions and during minutes 2 through 7 of supine recovery. Peak treadmill time was significantly less (P less than 0.01) in OHT patients. No significant differences were found for systolic blood pressure (SBP) during recovery, peak HR, ventilation, relative O2 uptake (VO2), body weight, ventilatory equivalents for O2 and CO2, O2 pulse, and HR-SBP product (peak HR x peak SBP). Peak pulse pressure, heart rate reserve, total VO2, and absolute VO2 at ventilatory threshold were significantly lower (P less than 0.01) in the OHT patients. We concluded that 1) complete cardiac decentralization is evident, 2) the significantly reduced VO2 at ventilatory threshold should be considered when activities of daily living are prescribed, and 3) SBP response is more appropriate than HR for assessing recovery of the decentralized heart after maximal exercise.

Blood Pressure↗
PubMed1991

Cardiovascular responses of heart transplant patients to exercise training.

Orthotopic heart transplantation (OHT) represents an effective alternative for individuals with end-stage heart disease. The current literature reports only the responses of OHT patients to greater than or equal to 4 mo of exercise training (ET) and frequently lacks adequate controls. Most programs currently treating OHT patients usually provide 6-12 wk of ET. This study describes the effects of a 10-wk supervised ET program in 12 male OHT patients and 5 other male OHT patients who served as a comparison group. Graded exercise tests were performed before and after ET. After ET, maximal O2 consumption was significantly greater for the ET group than the comparison group (P less than 0.05) and the mean increase in peak heart rate was 18 +/- 4 and 6 +/- 4 (SE) min-1 for ET and comparison groups, respectively (P less than 0.05). Maximal ventilation was also significantly greater for the ET group at after ET, while resting heart rate and blood pressure and peak blood pressure, O2 pulse, respiratory rate, and ventilatory equivalents for O2 and CO2 were not significantly changed. We conclude that after OHT a 10-wk ET program improves maximal O2 consumption and, by improving peak heart rate, improves O2 delivery.

Adult↗
PubMed1989

Evaluation of mouth-to-mask ventilation devices.

UNLABELLED: A number of mouth-to-mask ventilation devices have become commercially available in the past several years. In this study, we compared the volumes delivered by eight of these devices to the volumes delivered by mouth-to-mouth ventilation. METHOD: Fourteen respiratory care practitioners participated in the study. Ventilation was delivered to an adult resuscitation manikin. Each subject ventilated the manikin using mouth-to-mouth technique and each of the following mouth-to-mask devices: Boehringer EVA, Hospitak, Hudson, Intertech Safe Response, Laerdal Pocket Mask, Life Design Systems (LDS), Respironics SealEasy, and Vital Signs. Evaluation periods of 1 minute were used, minute ventilation and respiratory rate were measured, and tidal volume was calculated. RESULTS: There was a significant difference between the volumes delivered by the masks (p less than 0.001). The volumes delivered by each mask were less than mouth-to-mouth volumes (p less than 0.05 in each case). The mean +/- SD mouth-to-mouth volume was 1.04 +/- 0.32 L. The mean +/- SD volumes for each of the devices was 0.54 +/- 0.34 L for the EVA, 0.77 +/- 0.21 L for the Hospitak, 0.51 +/- 0.26 L for the Hudson, 0.81 +/- 0.35 L for the Safe Response, 0.65 +/- 0.25 L for the Pocket Mask, 0.82 +/- 0.27 L for the LDS, 0.79 +/- 0.32 L for the SealEasy, and 0.76 +/- 0.21 L for the Vital Signs. CONCLUSIONS: We found considerable variability between the volumes delivered with commercially available mouth-to-mask ventilation devices. Although the volumes delivered during mouth-to-mask technique were less than those delivered with mouth-to-mouth technique, the volumes delivered by some of the mouth-to-mask devices were large enough to allow them to be substituted for mouth-to-mouth technique.

Equipment Design↗
PubMed1987

Digiscan activity: automated measurement of thigmotactic and stereotypic behavior in rats.

Visual measures of stereotypy, margin time (thigmotaxis or wall-hugging), and center time were correlated with automated measures using a revised 16 beam version of the Digiscan Animal Activity Monitor System. Rats were injected with d-amphetamine (1.25, 2.5, 5.0 and 10.0 mg/kg), scopolamine (1.25 and 2.5 mg/kg) or saline and drugs were found to increase center time and decrease margin time in a dose-dependent manner, with the maximum effect occurring with 1.25 and 2.5 mg/kg, respectively. At higher doses, an opposite effect was observed. Extremely high correlations between visual and automated recordings of both margin time and center time were found. Since thigmotaxic or wall-hugging behavior has been used as an indicator of emotionality in rats, the results of the present study suggest that these two locomotor variables may be useful additions to the Digiscan multivariate analysis of locomotor behavior. It was also found that a redefinition of stereotypic behavior improved its correlation with visual measurements compared to earlier studies.

Animals↗
PubMed1986

Lung clearance and translocation of 239Pu and 244Cm in rats following inhalation individually or as a mixed oxide.

Wistar rats were exposed via inhalation to aerosols of 239PuO2, 244Cm oxide or a mixed Pu-Cm oxide with an activity ratio of about 1:1. Activity in lung and several extrapulmonary tissues were examined up to 120 d after exposure to determine whether calcining Pu and Cm together affected lung clearance or translocation to other sites in the body for either nuclide. Initial deposition was about 1,200 Bq (32 nCi) for 239PuO2, 4,200 Bq (115 nCi) for 244Cm, and 2,400 Bq (65 nCi) total alpha for the mixed oxide. The kinetics of single nuclides were as expected, with Pu oxide confined mainly to lung at all times and cleared with a half-time of 42 d. Curium was translocated rapidly to liver, with a peak activity of about 10% of the initial alveolar deposition at 7-14 d. Skeleton activity increased gradually, amounting to 12-15% of initial deposition near the end of the study. Lung clearance of Cm was more rapid than for Pu, with about 13% of Pu and less than 5% of Cm remaining at the end of the experiment. Both Pu and Cm remained in the lung somewhat longer when administered as a mixed oxide than the respective nuclides administered singly, and virtually all activity in the body was confined to the lung. Translocation of Cm to extrapulmonary tissues was almost entirely prevented by incorporation into the PuO2 matrix. Therefore, calcining the two radionuclides together in an aerosol altered the kinetics of both following inhalation in rats, but most dramatically for 244Cm. The resulting change in radionuclide distribution for the lung and the body following such a mixed inhalation exposure would presumably alter the long-term health effects compared to those seen with the pure compounds.

Aerosols↗
PubMed1985

Lung clearance, translocation, and acute toxicity of arsenic, beryllium, cadmium, cobalt, lead, selenium, vanadium, and ytterbium oxides following deposition in rat lung.

Young adult rats were exposed via inhalation or intratracheal instillation to oxides of arsenic, beryllium, cadmium, cobalt, lead, selenium, vanadium, and ytterbium. Serial necropsies were performed to assess the metal content in organs at times up to several weeks after exposure. The lung clearance varied widely for these compounds, and the times to remove 50% of the initial burden ranged from 18 min for vanadium to 400 days for beryllium. Arsenic, cadmium, lead, selenium, and vanadium were initially soluble in lung, but a small fraction (1-20%) remained there over the long term. Extrapulmonary tissues often accumulated substantial amounts of the soluble oxides, and whole-body retention was often greater for compounds that were more soluble in lung. Arsenic, selenium, and vanadium translocated to carcass and bone. Arsenic, cadmium, lead, and selenium accumulated in the liver, and the kidney retained cadmium and lead. Beryllium, cobalt and ytterbium did not deposit at any extrapulmonary site in significant amounts. In general, the aqueous solubility of these compounds was a poor predictor for behavior in vivo because of their interaction with metabolic processes. Of the metal oxides tested for acute lethality following pulmonary deposition, cadmium was most toxic, followed by selenium, vanadium, and arsenic.

Animals↗
PubMed1983

Long-term reactivity of lung and mediastinal lymph nodes following intratracheal instillation of sandy loam soil or Mount St. Helens volcanic ash.

The effects of Ritzville sandy loam soil and Mount St. Helens volcanic ash particles on the lung and mediastinal lymph nodes of Fischer rats were studied about 400 days after intratracheal instillation. A total of 22 or 77 mg of soil or ash was given in two or seven equally divided, consecutive, weekly intervals as a suspension in 0.5 ml saline. Significantly elevated levels of lipid-phosphorus and protein were found in lung lavages of rats given ash compared to those given soil. An enhanced histological degree of granulomatous reactivity, lipoproteinosis, fibrosis, and bronchiolar hyperplasia was seen in ash-exposed rats as compared to soil-exposed rats. Mediastinal lymph nodes of ash-exposed rats were 8-18 times larger than those of soil-exposed rats due to abundant cellular microgranuloma formation and early fibrosis. Mount St. Helens volcanic ash is apparently more biologically reactive than soil particles commonly found in eastern Washington.

Air Pollutants↗
PubMed1982

Distribution of inhaled 239PuO2 in rat and hamster lung.

The distribution of inhaled 239PuO2 in rat and hamster lung was investigated up to one year postexposure in order to determine whether differences in pulmonary dose distribution could account for the apparent difference between the two species in lung tumor response. In previous life-span studies, rats developed up to 70% lung tumors at cumulative doses less than 2000 rads, whereas hamsters developed tumors in about 3% of animals at comparable or higher doses. Morphometric methods were used to quantitate the particle distribution in different lung regions of both species following exposure at levels that produced tumors in rats. The PuO2 particles were counted on autoradiograms of lung cross-sections and classified as to their location in either subpleural or internal parenchyma, lung vasculature, or major airways. Rat lung showed a greater long-term association of particles with the major airways than hamster lung. The particles also showed a greater tendency to occur in groups for rats, the difference being more pronounced in the subpleural region than in the remainder of the lung. In previous experiments, both bronchioles and subpleural fibrotic scars appeared to be the sites of origin for lung tumors. Different dose distributions within these regions may therefore affect the tumor response to inhaled 239PuO2.

Aerosols↗
PubMedDate not supplied

Snoring and the severity of coronary artery disease in men.

Previous studies have found associations between snoring, or polysomnographic documented sleep apnea, and hypertension, cerebral vascular disease, and myocardial infarction. The present study examined the relationship of coronary artery disease (CAD) and snoring. One hundred and twenty-two males with positive angiographic studies were compared with fifty-six men, matched in age and socioeconomic status, who had no known history of coronary heart, or other atherosclerotic, disease. The percentage of subjects reporting that they snore "usually" or "always/loudly" increased across the four CAD severity groupings (nonpatient controls = 19.6%, 1 vessel = 44.4%, 2 vessel = 41.9%, 3 vessel = 56.0%) with a p value of .005. Hypertension, body mass index, and pack years of smoking were found to be associated with both coronary artery disease severity and snoring. When these variables were controlled in a multiple regression analysis, the relationship of snoring and CAD severity remained significant at p = .050.

Coronary Angiography↗