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Biomedical subjects

R B Stewart

Publications and source records attributed to R B Stewart.

At least 73 records · Page 4Linked to original sources
PubMed1991

Chromatographic purification and characterization of antigens A and D from Mycobacterium paratuberculosis and their use in enzyme-linked immunosorbent assays for diagnosis of paratuberculosis in sheep.

The protein antigens A and D were purified from culture filtrates and sonic extracts of laboratory strains of Mycobacterium paratuberculosis by salt precipitation and chromatography. The characterization of antigen A is shown here, and both antigens were evaluated along with lipoarabinomannan antigen in indirect enzyme-linked immunosorbent assays (ELISA) for the serodiagnosis of ovine paratuberculosis. After anion-exchange (DEAE-5PW) and hydrophobic (phenyl-5PW) chromatography using high-performance liquid chromatography, antigen A showed a prominant band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) at 31 kDa with small amounts of low-molecular-mass proteins but with no evidence of antigen D. A single precipitin arc was evident with purified antigen A in crossed immunoelectrophoresis. The determination of the N-terminal amino acid sequence showed a high degree of homology between the 31-kDa component of antigen A and antigens of the BCG85 complex of Mycobacterium bovis BCG, a total of 24 of 26 residues being identical to those of BCG85C. A prominant SDS-PAGE band at 400 kDa and a single crossed-immunoelectrophoresis arc was also evident for antigen D after gel filtration (Sephacryl S-200), anion-exchange (DEAE-Sephacel), and concanavalin A-Sepharose affinity chromatography. By ELISA, purified antigen A detected antibody in the sera of 18 of 22 paratuberculosis-infected sheep (82% sensitivity), whereas the purified antigen D detected antibody in all 22 infected animals (100% sensitivity). Combined ELISA results showed increased specificity with some loss in sensitivity.

Amino Acid Sequence↗
PubMed1991

Correlates of cognitive dysfunction in an ambulatory elderly population.

Mini-Mental State Examination (MMSE) scores were studied in an ambulatory elderly population to identify correlates with self-reported signs, symptoms, diseases, drugs and laboratory values. A total of 1,264 subjects were studied including 844 women and 420 men. In this study, 5.0% of men and 5.3% of women scored less than 24 on the MMSE. A linear-regression model revealed eleven factors of significance in predicting scores on the MMSE. The most important predictors were age (p less than 0.0001), self-reported memory loss (p less than 0.0001), complaints of swollen feet or ankles (p less than 0.0010), the total number of diseases reported (0.0006) and the serum lactate dehydrogenase concentration (p less than 0.0098). Results suggest that cognitive function in the elderly is not related to the general level of health or consistently affected by specific disease states.

Aged↗
PubMed1991

Correlates of Beck Depression Inventory scores in an ambulatory elderly population: symptoms, diseases, laboratory values, and medications.

BACKGROUND: Depression is one of the most important psychiatric disorders of older people. Between 1% and 5% of elderly persons who live in the community have major depression. Depressed elderly people are thought to be more likely to complain of symptoms such as headache, constipation, and pain than of disordered mood. The purpose of this study was to determine whether certain symptoms, diseases, or drugs used by older people correlate with scores on the Beck Depression Inventory. METHODS: Beck Depression Inventory scores were obtained in an ambulatory elderly population to identify correlates with self-reported signs, symptoms, diseases, drugs, and laboratory values. A total of 1048 participants were studied, including 712 women and 336 men. RESULTS: In this study, 13.7% of the men and 20.7% of the women had scores suggesting possible depression. A linear regression model revealed eight factors of significance in predicting scores on the Beck Depression Inventory. The most important predictors were the total number of symptoms reported by the patient (P less than .0001), and subjective complaints of memory loss (P less than .0003) and of pain in the abdomen (P less than .0004). CONCLUSIONS: Clinically, the results of this study suggest that depression is underdiagnosed in older patients and that multiple somatic symptoms are the best indicator of depression in this population.

Abdominal Pain↗
PubMed1990

Prehospital use of nifedipine for severe hypertension.

The prehospital management of severe hypertension is limited by a paucity of pharmacologic agents suitable for field use. This prospective study was designed to test the safety and efficacy of intraoral nifedipine therapy in 50 patients with severe hypertension being transported by an urban emergency medical service system. Ten milligrams of nifedipine were administered. Serial blood pressure determinations were obtained at 3, 5, 10, and 15 minutes and patients were observed for possible side effects. A marked effect on systolic blood pressure (SP), diastolic blood pressure (DP), and mean arterial pressure (MAP) was evident and was statistically significant in all three categories by 3 minutes. MAP decreased from 169 to 129 mm Hg (delta MAP of 40 mm Hg) at 15 minutes with parallel changes in the SP (55 mm Hg) and delta DP (32 mm Hg). These changes were highly significant (P less than .01) when compared with those of 50 historical controls. No evidence of severe adverse effects were noted. Nifedipine appears to be a promising agent for the prehospital treatment of severe hypertension, but its proper role is not yet defined.

Administration, Oral↗
PubMed1990

Sources of meaning through the lifespan.

185 men and women representing five developmental ages ranging from younger to older adulthood (17 to 96 yr) completed several measures to assess the amount and origins of most meaningful events in a person's life. As assessed by a modification of the Purpose-in-Life Test, the amount of purpose did not vary per se with age or sex. Similarly, the sources of meaning did not alter across time or sex. Themes of involvement emerged as the salient sources of meaning and included love, work, births of children, independent pursuits, accidents, illnesses, deaths, separations, or divorces, and to a lesser extent major purchases. The common sources and their timing are discussed within the context of a lifespan developmental model.

Adult↗
PubMed1990

A new 1.9-mu wavelength laser for neurosurgery.

The 1.9-mu wavelength component of a 1.9/1.06-mu two-wavelength laser with near-continuous wave properties was tested for its potential use in neurosurgery. The 1.9-mu wavelength has tissue-ablative capabilities, while the 1.06-mu wavelength (Nd:YAG) is suitable for achieving hemostasis. The advantages of the 1.9-mu wavelength over the CO2 laser include its ability to transmit through silica fiberoptic delivery systems and its deeper penetration in water (approximately 100 mu, a depth 10 times greater than for the CO2 laser), which is compatible with irrigation during ablation. To test the effectiveness of the laser, bilateral craniotomies were performed in anesthetized rats immobilized in a stereotactic frame. Under an operating microscope, lesions were made on the cortex by delivering the 1.9-mu laser beam through a 400-mu fiber at an average power of 1 W over a range of fluences. Subjective intraoperative observations were notable for minimal bleeding, absence of charring when the tissue was irrigated with a thin stream of saline, and uniform lesion formation. For comparison, lesions were generated with a commercially available continuous-wave CO2 laser at equivalent power and fluences. Histological specimens were divided into three groups based on the study after laser application: acute (30 minutes), subacute (48 hours), and chronic (14 days). The extent of thermal injury for the 1.9-mu laser in the acute lesions was quantitatively and histologically similar to that generated by the CO2 laser. Regions of injury extended approximately from the apex of the lesion, and crater depths generated by both lasers were similar (250 to 750 mu) in the range of fluences investigated (1.25 to 10 kJ/sq cm). Subacute and chronic histological specimens demonstrated inflammatory and repair responses that correlated with the acute injury regions in both the 1.9-mu and CO2 laser-treated specimens. This study demonstrates a neurosurgical potential for a new two-wavelength laser that ablates tissue effectively with limited thermal injury. The 1.9-mu laser is comparable to the widely used CO2 laser but offers several unique advantages, including the ability for delivery through a fiberoptic system and to irrigate tissue during use.

Animals↗
PubMed1990

Mutants of rabies viruses in skunks: immune response and pathogenicity.

In studies to develop an oral rabies vaccine for wildlife, the immune response to and pathogenicity of two types of mutants of rabies viruses were examined. Forty-five small plaque mutants were selected from cultures of ERA rabies virus treated with 8-azaguanine or 5-fluorouracil and tested for pathogenicity in mice. Two of these mutants AZA 1 and AZA 2 (low pathogenicity in mice) were given to skunks by oral (bait), intestinal (endoscope) and intramuscular routes. Additionally, challenge virus standard (CVS) rabies virus and mutants of this and ERA rabies virus (CVS 3766 and 3713, and ERA 3629) that were resistant to neutralization by specific antiglycoprotein monoclonal antibodies (and apathogenic in mice) were tested by various routes in skunks. Skunks given AZA 1 and AZA 2 were challenged at three months postinoculation with street rabies virus. After oral administration, there were very low rates of seroconversion with AZA 1 and AZA 2 and on challenge only 2/7 given AZA 1 and 1/8 given AZA 2 survived. None of the skunks given the other mutants orally seroconverted. AZA 2 produced a high rate of seroconversion (8/8) by the intestinal route and all challenged skunks in this group survived (7/7). All skunks vaccinated intramuscularly with AZA 1 (4/4) or AZA 2 (4/4) developed high levels of rabies neutralizing antibodies and survived challenge. The mutant CVS 3766, while apathogenic when given intracerebrally to adult mice, was consistently pathogenic by this route (and intranasally) in skunks. These results demonstrate that skunks are highly resistant to oral immunization by live rabies virus vaccines and that pathogenicity (by intracerebral route) of the mutant CVS 3766 is markedly different in mice and skunks.

Animals↗
PubMed1989

Conditioned place aversion mediated by self-administered ethanol in the rat: a consideration of blood ethanol levels.

A previous experiment has shown that rats will avoid environmental cues that have been associated with a history of ethanol self-administration. One possible explanation for this conditioned place aversion may be related to the temporal parameters of that experiment. During the initial segment of each 90-min conditioning/drinking trial (when most of the drinking occurred) the blood ethanol levels (BELs) were low and may well have produced positive effects at that time. However, as the drug continued to be absorbed and BELs increased during the remainder of the 90-min trial, the final (and conditioned) drug effects may have been aversive. In the present experiment the trial length was shortened to a 15-min period so that only low BELs would be temporally paired with the conditioning environment. A conditioned preference for that environment was predicted. Twelve rats were trained to self-administer ethanol in one environment and had water available in a different environment. Eight control animals had only water in both environments. BELs were measured and found to be low (16.8 to 57.6 mg%) and rising during the conditioning trials. However, when given a choice between the two environments, the rats avoided the environment in which they formerly consumed ethanol. No change in preference was noted for the control animals. This result was in accordance with previous findings but did not support the hypothesis that low, excitatory BELs would mediate a conditioned place preference in the rat.

Alcohol Drinking↗
PubMed1989

Systemic angiotensin II acts at the subfornical organ to suppress voluntary alcohol consumption.

The subfornical organ plays a role in a number of the effects of blood-borne angiotensin II (ANG II) including the increase in water drinking and blood pressure and the release of vasopressin from the pituitary. Recently it has been shown that systemically administered ANG II also reduces voluntary alcohol intake. The present study assessed the role of the SFO in alcohol consumption by examining the effects of SFO lesions on voluntary alcohol intake and on the suppression of voluntary alcohol intake by ANG II. Whereas the lesion did not alter alcohol consumption per se, it did significantly attenuate the ability of ANG II to reduce alcohol intake. This effect was not due to a lesion-induced change in the pharmacokinetics of alcohol and was observed only in those animals whose lesions produced a functional deficit, i.e., abolishing the increase in water drinking produced by ANG II. These results indicate that the SFO mediates the effect of systemically administered ANG II on alcohol intake but does not otherwise affect the regulation of alcohol consumption.

Alcohol Drinking↗
PubMed1989

The beta adrenergic agonist isoproterenol suppress voluntary alcohol intake in rats.

The effects of isoproterenol on alcohol consumption were examined to investigate whether beta adrenergic stimulation can reduce voluntary alcohol intake. Two and one-half, 5 and 10 micrograms/kg isoproterenol administered subcutaneously (SC) just prior to alcohol availability produced a dose-dependent reduction in alcohol intake and elevation in water intake. Blood alcohol levels measured subsequent to a SC injection of 5 micrograms/kg isoproterenol or vehicle followed by an intraperitoneal injection of 2.5 g/kg alcohol showed that the adrenergic agonist did not alter the distribution or metabolism of alcohol. Since beta adrenergic agonists such as isoproterenol are potent releasers of renin, these findings support previous work showing that different kinds of interventions which share the common property of elevating activity in the renin-angiotensin system (beta adrenergic stimulation in the present case) consistently result in the reduction of voluntary alcohol intake.

Alcohol Drinking↗
PubMed1989

Medication compliance in the elderly.

Patient compliance with physician's medication instructions has been a growing concern for nearly two decades. Elderly patients are thought to have more difficulty following prescription instructions because they generally have more medications prescribed, often suffer from cognitive decline, and frequently have physical limitations such as failing eyesight and hearing. Exhibiting a genuine concern to patients for the importance of drug therapy and adherence to directions is the first step to improve compliance. Providing adequate verbal and written medication instruction, and implementing routine assessment of medication compliance should greatly improve response to drug therapy and decrease adverse effects.

Aged↗
PubMed1989

Incidence of hypertension in an ambulatory elderly population.

Investigations of the natural history of blood pressure have generally evaluated mean systolic and diastolic pressure changes. While information, this information is not directly applicable to clinical practice settings, in which patients are usually classified as normotensive or hypertensive. We measured the actual incidence of hypertension, using two different definitions, in an ambulatory elderly population of 2,584 individuals over an 8-year period. Using the less stringent blood pressure definition (systolic blood pressure greater than 140 mmHg and diastolic blood pressure greater than or equal to 90 mmHg), 884 (34.2%) participants were normotensive and 1,700 (65.8%) were hypertensive at an initial screening. The average annual incidence of hypertension over the subsequent eight years was 13.2%, and life tables demonstrated a gradual risk of developing hypertension. The development of hypertension was not associated with gender or age; while older age groups had a greater chance of developing hypertension than younger, the difference did not reach statistical significance.

Age Factors↗
PubMed1989

Resting heart rates in an ambulatory elderly population: an evaluation of age, sex, symptoms, and medication.

In a cross-sectional analysis of 2,301 ambulatory elderly subjects, the mean resting heart rate for women (66.2/min) was significantly higher than for men (63.6/min), p less than 0.0001, and heart rate was positively correlated with age for both men and women. Resting heart rate was positively correlated with the number of drugs used (p less than 0.05), number of symptoms reported (p less than 0.05), systolic (p less than 0.01), and diastolic (p less than 0.0001) blood pressure. Of 975 participants who were followed longitudinally over an 8-year period there was a significant decrease in resting heart rate of approximately 2.75/min, p less than 0.0001.

Aged↗
PubMed1989

Nutritional supplements in the ambulatory elderly population: patterns of use and requirements.

Older persons are thought to be the most frequent consumers of vitamin and mineral supplements. In this review, the use of nutritional supplements by the elderly was found to be common but was not greatly different from other age groups. Elderly persons living in Dunedin, Florida, reported nutritional supplement use less frequently than a random sample of registered nurses. Neither the Food and Nutrition Board of the National Academy of Sciences/National Research Council nor the World Health Organization has recognized the need for increasing the vitamin and mineral allowances for healthy elderly adults above those recommended for healthy young adults. It is important to recognize, however, that the elderly are at greater risk of developing nutritional deficiencies as a result of acute and chronic diseases, drug use, and social isolation, and they require careful monitoring.

Aged↗