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Biomedical subjects

J Stevens

Publications and source records attributed to J Stevens.

At least 199 records · Page 11Linked to original sources
PubMed1994

Retinol binding proteinuria and phosphaturia: markers of paracetamol-induced nephrotoxicity.

The occurrence of hypophosphataemia in paracetamol overdose suggests that nephrotoxicity is common, impaired renal tubular reabsorption of phosphate indicating renal damage. To investigate the potential nephrotoxicity of paracetamol, we studied 148 consecutive patients with paracetamol overdose. Serial clinical and biochemical measurements were made, and a fasting overnight urine collection was obtained for creatinine (Cr), phosphate and retinol-binding protein (RBP) determination. Renal threshold phosphate concentration (TmPO4/GFR) was determined from urinary parameters by an established nomogram. The degree of hypophosphataemia correlated with the severity of overdose, and with TmPO4/GFR. The median RBP/Cr ratio was higher in those patients exhibiting biochemical hepatotoxicity compared with those without hepatotoxicity, in whom median RBP/Cr was not significantly higher than controls. Within the group of patients showing biochemical hepatotoxicity, there was a correlation between log RBP/Cr and TmPO4/GFR. RBP/Cr ratio is a less sensitive marker of renal tubular toxicity than phosphaturia in these patients, and may indicate a different mechanism of toxicity.

Acetaminophen↗
PubMed1994

An inhibitor of neurite outgrowth produced by astrocytes.

We have produced a number of astrocytic cell lines, some of which promote abundant neurite outgrowth, some of which are poor promoters of neurite outgrowth. The critical difference between these lines lies in the extracellular matrix, cell lines that are good promoters of axon growth producing a matrix that promotes axon growth, cell lines that are poor promoters of axon growth producing a non-permissive matrix. We were unable to find any consistent correlations between promotion of axon growth and production of proteases, protease inhibitors, N-cadherin, growth cone collapsing activity, and several extracellular matrix molecules. In the present study we have compared the least permissive of our cell lines, Neu7, with the most permissive, A7. Medium conditioned by the cell lines has the same properties as the matrix, since dorsal root ganglia (DRGs) grown in conditioned medium from the Neu7 line grow axons poorly, while DRGs grown in medium conditioned by A7 or primary astrocytes grow many long axons. Since matrix produced by all the cell lines contains large amounts of laminin, we looked to see whether the cells were producing laminin-blocking activity. Medium from the Neu7 line blocked laminin, while that from the A7 and primary astrocytes did not. However, when the conditioned media were heat-treated to remove neurite-promoting activity, they all had laminin-blocking activity: the blocking activity is heat stable. The neurite-promoting properties of the conditioned media therefore probably reflect a balance between promoting molecules and blockers.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Attitudes toward body size and dieting: differences between elderly black and white women.

Eating restraint and body size perceptions of 404 White and African-American women 66 to 105 years of age (mean age = 73 years) were assessed by questionnaire. Compared with overweight White women, overweight Black women were 0.6 times as likely to feel guilty after overeating, 0.4 times as likely to diet, 2.5 times as likely to be satisfied with their weight, and 2.7 times as likely to consider themselves attractive. Among those who were not overweight, Black women were half as likely as White women to consider themselves overweight. Compared with Black women, White women perceived themselves to be larger and reported a lower ideal body weight.

Black or African American↗
PubMed1994

Assessment of cartilage volume in the femorotibial joint with magnetic resonance imaging and 3D computer reconstruction.

OBJECTIVE: Our goal was the development of an accurate and objective technique to depict and quantitate articular cartilage using magnetic resonance imaging (MRI) and 3D data processing. METHODS: A method of 3D image analysis has been developed that provides a noninvasive technique of measuring cartilage volume from standard diagnostic MR images. RESULTS: Using a computer workstation, cartilage from Fast Field Echo (FFE) MR images was reconstructed into 3 dimensions (3D). The accuracy and reproducibility of both thickness and volume measurements obtained from the existing computer software was tested using calibration test objects. We describe the sources of error we encountered when attempting to quantitate cartilage using the existing computer software, the methods developed to reduce these errors, and a preliminary cartilage volume study using healthy human volunteers. CONCLUSION: We have identified errors involved in attempting cartilage volume estimations using the existing 3D computer software and have developed a data processing technique that minimizes these errors. With these objective data processing techniques we have improved the reproducibility of the technique to +/- 10-15% error. This modified technique provides a promising new method for viewing and quantifying cartilage volume from standard diagnostic MR images.

Animals↗
PubMed1994

Talking shop.

Explore the source record for details and available documents.

Delivery of Health Care↗
PubMed1994

Osmotic blood-brain barrier disruption: CT and radionuclide imaging.

PURPOSE: To compare CT and radionuclide imaging of osmotic blood-brain barrier disruption. To develop a quantitative method for imaging osmotic blood-brain barrier disruption and to see if iopamidol could be safely given intravenously in conjunction with blood-brain barrier disruption. METHODS: Forty-five blood-brain barrier disruption procedures were imaged with CT and radionuclide scans. The scans were evaluated with visual and quantitative scales. Patients were observed for adverse effects after blood-brain barrier disruption. RESULTS: There was a 4% rate of seizures in this study. There was good agreement between visual CT and radionuclide grading systems. Quantitative methods to grade disruption did not add useful information to visual interpretations. CONCLUSIONS: Nonionic iodine-based contrast medium has a lower incidence of seizures when injected intravenously in conjunction with osmotic blood-brain barrier disruption than ionic contrast material. Contrast-enhanced CT is the preferred method to image disruption because it has better spatial resolution than radionuclide techniques.

Adolescent↗
PubMed1993

Analysis of 2- and 3-series prostanoids by post-HPLC ELISA.

Measurement of cyclooxygenase products of both arachidonic acid and eicosapentaenoic acid is of broad interest due to the wide and diverse biological activities of these compounds. We developed a technique combining (i) solid-phase extraction, (ii) reversed-phase HPLC separation using a high-capacity column, and (iii) post-HPLC enzyme-linked immunosorbant assay (ELISAs) employing monoclonal antibodies for quantification of all main 2- and 3-series prostanoids within one run. Thermal and chemical stress on these labile agents was reduced by use of ionic pair reagent and high buffer strength for processing at neutral pH, alpha-tocopherole as antioxidant, and freeze-drying evaporation during critical steps of the analytical procedure. With these techniques, mixtures of 2- and 3-series prostanoids (thromboxane (Tx)B2/3, 6-keto-prostaglandin (PG)F1 alpha/2 alpha, PGF2 alpha/3 alpha, PGF2/3) were recovered from Krebs-Henseleit buffer with linear characteristics for each compound in the range between 50 and 500 pg/ml. Percentages of overall recovery ranged between 45 and 90% for the different prostanoids with satisfying reproducibility. Application of the technique to a perfused rabbit lung and human platelets challenged with free eicosapentaenoic acid demonstrated marked generation of TxB3; quantities of this trienoic prostanoid as assessed by HPLC/ELISA were well correlated to those obtained by GC/MS. Thus, convenient quantification of 2- and 3-series prostanoids in media of biological interest is achieved by combined chromatographic and immunological techniques.

Animals↗
PubMed1993

Orgaran (Org 10172) or heparin for preventing venous thrombosis after elective surgery for malignant disease? A double-blind, randomised, multicentre comparison. ANZ-Organon Investigators' Group.

This double-blind, randomised, multicentre trial in 513 patients having elective surgery for intra-abdominal or intrathoracic malignancy compared the efficacy and safety of venous thrombosis (VT) prophylaxis using 750 anti-factor Xa units of Orgaran (a mixture of low molecular weight heparinoids) given subcutaneously (sc) twice-daily with that of twice-daily injections of 5,000 units standard heparin. The main study endpoints were the development of postoperative VT detected by 125I-fibrinogen leg scanning, and the onset of clinically significant venous thromboembolism or bleeding. "Intent to treat" analysis showed a statistically non-significant trend towards less VT during Orgaran prophylaxis (10.4%) than after heparin (14.9%) and there was no difference in bleeding complications between the two study groups. Results remained similar if only patients who completed the intended course of therapy ("compliant patients") were analysed. Other trials have shown that Orgaran prevents VT after hip surgery and stroke. We now show it is also safe and effective in patients having major surgery for cancer.

Aged↗
PubMed1993

Size-dependent separation of proteins denatured in SDS by capillary electrophoresis using a replaceable sieving matrix.

The determination of molecular weights by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) is one of the most powerful electrophoretic techniques for protein characterization. A separation media has been developed which allows this type of analysis to be performed in the capillary format. A replaceable polymeric solution rather than a polymerized gel was used as the sieving matrix. This solution allowed for the separation of proteins denatured in SDS in a size-dependent manner as demonstrated by the linear correlation between the proteins' relative migration and the concentration of the sieving matrix (Ferguson plot). The logarithm of the molecular weight of protein standards correlated linearly with the relative mobility of the denatured proteins over the molecular weight range of 14,000 to 205,000. The calculated resolution at half-peak height was such that proteins that differed by as little as 4% in molecular weight would be resolved. Finally, the integrated peak areas at 215 nm were linearly proportional to the mass of the protein injected.

Animals↗
PubMed1993

The effect of a class IV hurricane on emergency department operations.

The objective of this study was to determine the impact on emergency department (ED) operations of Hurricane Hugo, a class IV hurricane that struck Charleston, South Carolina, on September 21, 1989. The study design was a retrospective record-based descriptive study and mail survey of the ED of a 300-bed regional medical center directly in the path of the storm. During the 3 weeks after the storm, ED patient volume increased 19% over that of the 3 weeks before the storm. Increased visit volumes were evident for at least 3 months. Compared with a similar period of the previous year, there was an increase in the proportion of patients seen for lacerations of all types, puncture wounds, stings, and falls. Sixty-two percent of physician offices were still closed 7 days after the storm. The direct effects of a class IV hurricane on ED operations included major alterations in the volume and types of patient visits. Because of the evacuation of approximately 40% of the coastal population and storm damage hindering travel, the increase in visit volume was less in magnitude but of longer duration has been reported in class III hurricanes.

Data Collection↗
PubMed1993

Body mass index and fat patterning as correlates of lipids and hypertension in an elderly, biracial population.

BACKGROUND: Associations between anthropometric measurements of fat patterning and risk factors for cardiovascular disease have been demonstrated in several populations composed predominantly of White, young or middle-aged adults. Fat pattern changes with aging and older adults tend to have a more central or abdominal fat distribution. Few investigators have focused on relationships of fat patterning with plasma lipids or blood pressure in older adults or in Blacks. METHODS: Body mass index (BMI), fat patterning, plasma lipids, and blood pressure were examined in participants of the Charleston Heart Study. Subjects included 216 White men, 95 Black men, 320 White women, and 155 Black women with a mean age of 72.7 years (range 61-106). RESULTS: In each of the four race and gender groups, BMI was inversely correlated with HDL cholesterol and positively correlated with hypertension. BMI tended to be positively associated with total cholesterol, although the relationships were not statistically significant. After controlling for the effects of BMI, age, smoking, and alcohol intake (using regression analysis), waist to hip ratio was associated with cholesterol levels in the White men and women and the Black men. In similar models, waist circumference in Black women was inversely associated with HDL. There were no significant relationships between waist to hip ratio and hypertension in any of the groups after controlling for BMI. CONCLUSION: In an elderly cohort, waist to hip ratio was associated with plasma lipids, but not with hypertension, when the effects of BMI were held constant.

Adipose Tissue↗
PubMed1993

High-resolution MRI in the investigation of recurrent pain after lumbar discectomy.

We used gadolinium-enhanced fat-suppressed MRI to investigate 67 patients with persistent pain after lumbar discectomy. Twenty-five patients had reoperations for lesions diagnosed in this way. Eleven were for recurrent disc prolapse at the same level and sciatica was relieved by all but one. Five operations were for prolapse at an adjacent level and all were successful. The diagnosis of sepsis was less precise, but extension of tissue enhancement into the operated disc space was found to be significant. Only three patients had evidence of arachnoiditis which suggests that this condition has been too often diagnosed as a cause of persisting low back pain.

Adolescent↗