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Biomedical subjects

S Walker

Publications and source records attributed to S Walker.

At least 325 records · Page 18Linked to original sources
PubMed1988

Determinants of low serum concentrations of salicylates in patients with Kawasaki disease.

The mechanisms leading to the previously reported difficulties in achieving therapeutic serum concentrations of salicylates in Kawasaki disease were studied in eight children, once during the acute (febrile) phase and again during the nonfebrile (subacute) phase of the disease. Salicylate bioavailability was impaired during the acute phase of the disease (47.7% +/- 6.6%), and increased significantly thereafter to 75.1% +/- 9.3%. During the febrile phase there was a significant correlation between salicylate bioavailability and steady-state serum concentrations. Salicylate renal clearance was significantly higher during the febrile phase (14.45 +/- 2.5 mL/kg.h), compared with the nonfebrile phase (7 +/- 1.6 mL/kg.h, P less than 0.05). The change in salicylate clearance could be explained by decreased protein binding in the acute phase (82.5% +/- 1.9%) with substantially more free salicylates caused by significantly lower serum albumin concentrations. Changes in urine metabolites during the acute and subacute phases were consistent with the changes in dose administered (100 mg/kg in the acute phase vs 10 mg/kg in the subacute phase). The pattern of metabolites excreted in the urine of children with Kawasaki disease receiving 100 mg/kg was similar to that in children with juvenile rheumatoid arthritis receiving the same dose.

Arthritis, Juvenile↗
PubMed1988

Coping strategies in rheumatoid arthritis.

Our purpose was to investigate the importance of the coping process for patients with rheumatoid arthritis (RA). Eighty-four patients with classic or definite RA were examined. The relationship between coping strategies and psychological status, functional status, pain, and disease activity was analyzed. Coping was measured by an adapted version of the Ways of Coping Scale, and measures of psychological status, life stress, functional status, pain, and disease activity were also obtained. Canonical correlation revealed a significant relationship between the coping process and psychological status. Coping also was significantly related to functional status, but not to pain or disease activity. Patients who coped by restructuring life goals were found to have better psychological adjustment and functional status than patients who hoped for unrealistic solutions or engaged in self-blame.

Activities of Daily Living↗
PubMed1988

Pain in rheumatoid arthritis: relationship to demographic, medical, and psychological factors.

Our purpose was to investigate the relationship among demographic, medical, and psychological factors and self-reported pain in 135 patients with classic or definite rheumatoid arthritis (RA). Patients were examined using the systemic index, articular index, McGill Pain Questionnaire, Symptom Checklist-90-R, and a pain visual analogue scale. Multiple regression analyses found no significant relationships between pain and the medical variables. However, age, income, and selected psychological variables were significantly correlated with pain reports. The greatest pain management challenge occurred in patients who were middle-aged, living on limited incomes, and experiencing major stresses in everyday life. These high risk pain patients were also worry-prone and felt isolated and lacking in social support. Attention to these related psychosocial problems is recommended as an important pain management strategy in RA.

Arthritis, Rheumatoid↗
PubMed1987

Safety and efficacy of inferior vena caval occlusion to rapidly alter ventricular loading conditions in idiopathic dilated cardiomyopathy.

To investigate the safety and efficacy of inferior vena caval (IVC) balloon occlusion for preload alteration in humans, 13 patients with dilated cardiomyopathy were studied before and during repeated (total of 78) IVC occlusions. Left and right ventricular (LV and RV) micromanometer pressures were simultaneously measured and M-mode and 2-D echocardiograms were recorded at end expiration. Complications were limited to abdominal discomfort in 2 patients. With IVC occlusion, RV collapse fluoroscopically shifted the heart toward midline and ventricular septal motion was frequently disordered. Significant (p = 0.001) changes occurred in RV and LV systolic peak pressures (from 19 +/- 6 to 12 +/- 5 mm Hg and from 129 +/- 34 to 109 +/- 25 mm Hg, respectively). LV and RV end-diastolic pressures also decreased significantly (from 18 +/- 7 to 6 +/- 6 mm Hg and from 5 +/- 3 to 2 +/- 2 mm Hg, respectively) (both p less than or equal to 0.0055). Similarly, LV end-diastolic diameter decreased 13% (from 61 +/- 11 to 53 +/- 12 mm, p = 0.0002). Mean heart rate did not change significantly (from 76 +/- 19 to 78 +/- 21 beats/min). Thus, IVC balloon occlusion provides a safe method of repeatedly altering loading conditions in humans. This approach allows for acquisition of important information regarding cardiac chamber dynamics while minimizing the effects of reflex mechanisms and avoiding use of pharmacologic agents.

Adult↗
PubMed1987

HPLC measurement of penticainide and desalkylpenticainide in biological fluids.

A simple HPLC method has been developed to measure the antiarrhythmic agent penticainide and its N-desalkyl metabolite in biological fluids. Solvent extraction of a small (200 microL) sample volume with direct analysis of the extract is used to measure the plasma and urinary concentrations of these compounds attained during chronic therapy, although a larger sample volume (1.0 mL) and prior concentration of the extract are required for single oral dose work. In each case chromatographic analysis is performed using a microparticulate (5 microns) silica column and methanolic ammonium perchlorate (10 mM, pH 6.7) as eluent with UV detection (260 nm). No endogenous sources of interference have been encountered and potential interference from other drugs is minimal.

Anti-Arrhythmia Agents↗
PubMed1987

Refractoriness of neurons mediating intracranial self-stimulation in the anterior basal forebrain.

The post-stimulation excitability of neurons mediating electrical self-stimulation of the anterior basal forebrain was evaluated psychophysically in the rat. Rats with electrodes in the nucleus accumbens, caudate nucleus, lateral preoptic area, diagonal band, or anterior medial forebrain bundle pressed a lever to earn 0.5-s trains of conditioning (C) and test (T) pulse pairs. The C-T interval was systematically varied and the effectiveness of the T-pulse was estimated by measuring the frequency of pulse pairs required to sustain criterion responding. All sites tested demonstrated similar recovery; T-pulse effectiveness, normalized against the effect of the C-pulse, was lowest at delays of 0.4-0.8 ms and it rose monotonically until 5 ms when it achieved an effectiveness plateau of one. Increasing the current of the T-pulse by 50 or 60% failed to hasten recovery, suggesting that the recovery profiles primarily reflect the activation of neurons very soon after emergence from absolute refractoriness. Compared to lateral hypothalamic and ventral tegmental self-stimulation, the neurons that support self-stimulation in the ventral basal forebrain recover more slowly; recovery here is only about half done by the time lateral hypothalamic placements demonstrate complete recovery.

Animals↗
PubMed1987

Ionized calcium levels during liver transplantation.

Plasma ionized calcium and total calcium concentrations were measured during 26 liver transplant operations. The level of ionized calcium decreased during the early part of the operation, reaching its lowest point during the anhepatic period, but rose again after revascularization of the new liver. Calcium chloride was given with the aim of reversing these decreases, which were associated with the use of blood products preserved in citrate-phosphate-dextrose anti-coagulant-containing adenine (CPD-A). Ionic hypocalcaemia is a result of intra-operative citrate loading in the presence of poor or absent (during the anhepatic phase) liver function; aggressive correction of low ionized calcium levels, especially during the early stages of the operation, is required to prevent this effect.

Adult↗
PubMed1986

Interaction of monoclonal antibodies directed against bromodeoxyuridine with pyrimidine bases, nucleosides, and DNA.

Although antibodies directed against bromodeoxyuridine (BrdU) are being used in both clinical and basic research laboratories as tools to study and monitor DNA synthesis, little is known about the epitopes with which they react. Four monoclonal antibodies directed against BrdU were produced and were characterized to learn more about the epitopes on BrdU which are important for antibody recognition, to identify compounds other than BrdU which react with the antibodies and which might interfere with immunologic assays for BrdU, and to characterize the reaction of these antibodies with BrdU-containing DNA. By radioimmunoassays, the antibodies generally reacted well with 5-iododeoxyuridine, 5-fluorodeoxyuridine, and 5-nitrouracil. However, none of the antibodies reacted well with uridine--indicating that a substituent on uridine C5 was essential for antibody reactivity--or with 5-bromo- or iodo-cytosine, indicating that the region around pyrimidine C4 is important for antibody recognition. Although the antibodies reacted with 5-halogen-substituted uracil bases, the antibodies reacted much better with the corresponding halogenated nucleosides, indicating that the sugar moiety was important for recognition. The presence of a triphosphate group on C'5 of BrdU (i.e., BrdUTP) did not detectably alter antibody recognition. Three of the antibodies reacted only with purified DNA containing BrdU, whereas one antibody, which exhibited a weak interaction with thymidine, also reacted with BrdU-free DNA. S1 nuclease treatment of purified DNA suggested that all four monoclonal antibodies reacted exclusively with single-stranded regions of BrdU-containing DNA. Comparison of detecting DNA synthesis by [3H]TdR incorporation followed by autoradiography with that by BrdU incorporation followed by indirect immunofluorescence indicated that the latter technique was both an accurate and a sensitive measure of DNA synthesis.

Animals↗
PubMed1986

Herpes without vesicles: limited, recurrent genital lesions in an immunodebilitated host.

We have reported a case of herpes genitalis in a man with acquired immunodeficiency syndrome (AIDS), who was receiving chemotherapy for Hodgkin's disease. The herpes infection was recurrent but limited, without vesicles or the progressive lesions usually seen in AIDS. Studies excluded known causes, and the unusual character of the infection long obscured and delayed diagnosis. Even atypical, culture-negative penile ulcers in immunodebilitated patients may be herpetic. Retrospective study of our patient's penile biopsy specimen using immunoperoxidase reaction was positive for herpesvirus. The existence of effective treatment mandates vigorous pursuit of the diagnosis.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Recurrent neural tube defects, risk factors and vitamins.

Data from our trial of periconceptional vitamin supplementation for the prevention of neural tube defects have been analysed to assess the influence of various factors on recurrence rates of neural tube defect. Our data suggest that the risk of recurrence of neural tube defect is influenced by the number of previous neural tube defects, area of residence, immediately prior miscarriage, and interpregnancy interval. None of these factors, however, contributed any significant differential risk between supplemented and unsupplemented mothers. Hence we conclude that the highly significant difference in recurrence rates of neural tube defect between supplemented and unsupplemented mothers was due to vitamin supplementation.

Abortion, Spontaneous↗
PubMed1986

Colonic absorption of sulfated and nonsulfated bile acids in rat.

Absorption of sulfated and nonsulfated chenodeoxycholic and glycochenodeoxycholic acid was studied in the colon and the data were compared with the absorption rates in the ileum. Absorption of nonsulfated chenodeoxycholic acid in the colon was in the same range of magnitude as in the ileum. Glycochenodeoxycholic acid absorption in the colon was lower than in the terminal ileum. Sulfated bile acids were not absorbed in the colon. In the ileum, absorption of sulfated bile acids was significantly (p less than 0.01) lower than the absorption of nonsulfated bile acids. Little absorption of sulfated bile acids in the ileum and lack of absorption in the colon both contribute to the rapid turnover and excretion of bile acid sulfates.

Animals↗
PubMed1986

Stability and availability of cyclosporine stored in plastic syringes.

The stability and availability of cyclosporine from the oral dosage form when stored in plastic syringes were examined. Solutions of cyclosporine were stored in plastic syringes for 28 days at 25 degrees C. Half of the solutions remained in room light, and samples were obtained at 3, 6, and 12 hours and 1, 2, 3, 4, 5, 6, 7, 14, 21, and 28 days. The remaining samples were protected from light, and samples were obtained at 1, 3, 5, 7, 14, 21, and 28 days. Samples stored in plastic were compared with control solutions stored in the original amber bottle. All samples were analyzed for unchanged cyclosporine by high-pressure liquid chromatography. Cyclosporine was stable and completely available from the oral dosage form when stored in plastic syringes for up to 28 days. There was no difference in the stability of cyclosporine between the solutions exposed to room light and those protected from light. Solutions of the oral dosage form of cyclosporine may be stored in plastic syringes without protection from light for up to 28 days.

Chromatography, High Pressure Liquid↗