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Biomedical subjects

D Wilson

Publications and source records attributed to D Wilson.

At least 181 records · Page 10Linked to original sources
PubMed1998

Should we be frightened of bracken? A review of the evidence.

OBJECTIVE: To assess the risk to human health of the plant bracken (Pteridium sp). DESIGN: An evaluation of studies of human and animal populations exposed to bracken, together with a review of expert reports and advice to the public. MAIN RESULTS: Bracken induced disease has been demonstrated in animals in both laboratory and field studies. Depending on the species, diseases in animals associated with the plant have included; cancers of the alimentary and urogenital tract, lung and breast; haematuria; retinal degeneration; and, thiamine deficiency. Potential exposure of human populations is through: food either directly (people in some parts of the world eat bracken as a traditional dish) or indirectly by consuming animals fed on bracken; milk; water; inhalation and ingestion of spores; and insect vectors. Four studies of human populations (two analytical and two observational) failed to assess adequately confounding factors and other sources of bias, so that conclusions about a risk to human health from bracken cannot firmly be drawn. Establishing exposure is also extremely difficult in populations (such as the United Kingdom) where direct consumption of bracken is rare. CONCLUSION: Bracken is a common plant worldwide. It is toxic to many animal species and to several organ systems. There is no tumour (or other disease) that is pathognomic of exposure in animals, though cancers of the alimentary and urogenital tract seem to be the most commonly associated. It is not possible to extrapolate from animal models to humans. Studies of human populations, do not establish a clear risk of bracken to human health, largely because of methodological problems. Testing the evidence against traditional criteria of causality only fulfils the criterion of biological plausibility. Despite this, current public information implies a serious risk to human health from bracken, and increasing media coverage of the subject is likely to lead to greater public concern. Further epidemiological studies are required.

Animals↗
PubMed1998

Responses to stress and novelty in adult rats born vaginally, by cesarean section or by cesarean section with acute anoxia.

The aim of this study was to test the hypothesis that alterations in birth conditions, specifically vaginal birth vs. birth by Cesarean section (C-section) vs. birth by C-section with an added period of acute global anoxia, produces long-term differences in behavioral responses to stress or novelty in the rat at adulthood. In comparison to animals born by rapid C-section alone, animals born by C-section with 10 or 15 min of added anoxia were significantly more immobile during forced swim stress administered for 6 trials over several weeks. In a step-down passive avoidance task, there were no group differences in acquisition or retention of the avoidance response. However, when initially placed in the passive avoidance apparatus before delivery of shock, animals born by C-section with 15 min of anoxia required significantly more pretrials to step down from the wooden platform, than did vaginally born or C-sectioned animals. No group differences were observed on measures of exploratory behavior in an elevated plus-maze or of approach behavior either to food or to a novel object in an open field. These findings suggest that birth conditions which include a degree of perinatal hypoxia can contribute to variability in selective responses to stress and novelty in the adult rat.

Acute Disease↗
PubMed1998

Ultrasound image texture analysis for characterizing intramuscular fat content of live beef cattle.

The primary factors in determining beef quality grades are the amount and distribution of intramuscular fat percentage (IMFAT). Texture analysis was applied to ultrasound B-mode images from ribeye muscle of live beef cattle to predict its IMFAT. We used wavelet transform (WT) for multiresolutional texture analysis and second-order statistics using a gray-level co-occurrence matrix (GLCM) technique. Sets of WT- and GLCM-based texture features were calculated from ultrasonic images from 207 animals and linear regression methods were used for IMFAT prediction. WT-based features included energy ratios, central moments of wavelet-decomposed subimages and wavelet edge density. The regression model using WT features provided a root mean square error (RMSE) of 1.44 for prediction of IMFAT using validation images, while that of GLCM features provided an RMSE of 1.90. The prediction models using the WT features showed potential for objective quality evaluation in the live animals.

Adipose Tissue↗
PubMed1998

Outcome after surgery for perianal fistula: predictive value of MR imaging.

OBJECTIVE: The purpose of this study was to determine if MR findings are predictive of long-term outcome in a cohort of patients whose initial surgery was performed without access to the findings of MR imaging. SUBJECTS AND METHODS: Forty patients with surgically proven perianal fistulas underwent preoperative dynamic contrast-enhanced MR imaging. The MR and surgical findings were independently recorded on an identical anatomic form. Three patients were subsequently lost to follow-up. The outcome for the remaining 37 patients was determined from surgical review, case notes, and questionnaires. Minimum follow-up period was 14 months (range, 14-39 months). Outcome was determined by one observer who was unaware of the initial MR grading and had not been present during surgery. Outcome was considered unsatisfactory if further surgery was required. RESULTS: MR imaging was better than surgical exploration in predicting outcome (for MR imaging: positive predictive value, 73%; negative predictive value, 87%; sensitivity, 89%; and specificity, 68%; for surgical exploration: positive predictive value, 57%; negative predictive value, 64%; sensitivity, 73%; and specificity, 47%). MR classification of fistulas was significantly associated with outcome (p = .0004), and surgical classification was not significantly associated with outcome (p = .22, chi-square test). Also MR grades differed significantly for patients with satisfactory and unsatisfactory outcomes (p < .001, Mann-Whitney U test). CONCLUSION: MR imaging is valuable in the management of patients with perianal fistulas. MR imaging accurately reveals surgical anatomy and can be used to make better predictions regarding patient outcome than surgical findings.

Adult↗
PubMed1997

Discovery of CGS 27023A, a non-peptidic, potent, and orally active stromelysin inhibitor that blocks cartilage degradation in rabbits.

Structure-activity relationships of a lead hydroxamic acid inhibitor of recombinant human stromelysin were systematically defined by taking advantage of a concise synthesis that allowed diverse functionality to be explored at each position in a template. An ex vivo rat model and an in vivo rabbit model of stromelysin-induced cartilage degradation were used to further optimize these analogs for oral activity and duration of action. The culmination of these modifications resulted in CGS 27023A, a potent, orally active stromelysin inhibitor that blocks the erosion of cartilage matrix.

Administration, Oral↗
PubMed1997

Developmental toxicity study in rats and rabbits administered an emulsion containing medium chain triglycerides as an alternative caloric source.

Triglyceride-containing lipid emulsions have been designed as caloric sources that can be administered intravenously to patients that cannot meet their nutritional needs by conventional parenteral therapies. In their study, we evaluate the developmental toxicity of a 20% lipid emulsion that contains a 3:1 ratio of medium chain triglyceride (MCT) to one long chain containing lipid emulsion (LCT). This emulsion was administered by intravenous infusion to rats and rabbits at dosages of 1 and 4.28 g lipid/kg body weight (g lipid/kg) at dose volumes of 5 and 21.4 mL/kg, respectively, once daily during organogenesis to assess the potential developmental toxicity of the test article. The control group received 0.9% saline at a dose volume of 21.4 mL/kg. Animals were observed for clinical signs of toxicity and adverse effects on body weights and feed consumption. On Day 20 (rats) or Day 29 (rabbits), females were necropsied and examined for maternal and embryo/fetal toxicity. Fetuses were removed, weighed, and examined for external, soft tissue, and skeletal abnormalities. Dosages of 4.28 g lipid/kg resulted in lower feed consumption for rats and rabbits, an expected finding based on the high-caloric nature of the test article. Potentially test article-related gross necropsy findings, including enlarged lymph nodes and spleen, small thymus, and enlarged renal pelvis, for rats given 4.28 g lipid/kg were present at a low incidence. There were no adverse effects on fetal parameters for rats even in the presence of some maternal toxicity. However, embryo and fetal toxicity (i.e., resorptions) and skeletal abnormalities were present for rabbits given 4.28 g lipid/kg. Under the conditions of this study, the no-observable-effect level for developmental toxicity was greater than or equal to 4.28 g lipid/kg for rats and greater than or equal to 1 g lipid/kg but less than 4.28 g lipid/kg for rabbits.

Abnormalities, Drug-Induced↗
PubMed1997

Effect of hemorrhagic hypotension on cortical oxygen pressure and striatal extracellular dopamine in cat brain.

This study investigated the relationships between blood pressure, cortical oxygen pressure, and extracellular striatal dopamine in the brain of adult cats during hemorrhagic hypotension and retransfusion. Oxygen pressure in the blood of the cortex was measured by the oxygen dependent quenching of phosphorescence and extracellular dopamine, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) by in vivo microdialysis. Following a 2 h stabilization period after implantation of the microdialysis probe in the striatum, the mean arterial blood pressure (MAP) was decreased in a stepwise manner from 132 +/- 2 Torr (control) to 90 Torr, 70 Torr and 50 Torr, holding the pressure at each level for 15 min. The whole blood was then retransfused and measurements were continued for 90 min. As the MAP was lowered there was a decrease in arterial pH, from a control value of 7.37 +/- 0.05 to 7.26 +/- 0.06. The PaCO2 decreased during bleeding from 32.3 +/- 4.8 Torr to 19.6 +/- 3.6 Torr and returned to 30.9 +/- 3.9 Torr after retransfusion. The PaO2 was 125.9 +/- 15 Torr during control conditions and did not significantly change during bleeding. Cortical oxygen pressure decreased with decrease in MAP, from 50 +/- 2 Torr (control) to 42 +/- 1 Torr, 31 +/- 2 Torr and 22 +/- 2 Torr, respectively. A statistically significant increase in striatal extracellular dopamine, to 2,580 +/- 714% of control was observed when MAP decreased to below 70 Torr and cortical oxygen pressure decreased to below 31 Torr. When the MAP reached 50 Torr, the concentration of extracellular dopamine increased to 18,359 +/- 2,764% of the control value. A statistically significant decrease in DOPAC and HVA were observed during the last step of bleeding. The data show that decreases in systemic blood pressure result in decrease in oxygen pressure in the microvasculature of the cortex, suggesting vascular dilation is not sufficient to result in a full compensation for the decreased MAP. The decrease in cortical oxygen pressure to below 32 Torr is accompanied by a marked increase in extracellular dopamine in the striatum, indicating that even such mild hypoxia can induce significant disturbance in brain metabolism.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1997

Ocular abnormalities in thin basement membrane disease.

AIM/BACKGROUND: Alport syndrome is an X linked disease that results in renal failure, deafness, and ocular abnormalities including a dot and fleck retinopathy and anterior lenticonus. The ultrastructural appearance of the glomerular basement membrane in thin basement membrane disease (TBMD) resembles that seen in some patients with Alport syndrome, and in some cases this disease is inherited too. The aim of this study was to determine whether patients with TBMD have any ocular abnormalities. METHODS: The eyes of 17 unrelated individuals with TBMD were studied by slit-lamp, including biomicroscopic fundus examination with a 78 D lens, by direct ophthalmoscopy, and by fundal photographs. The findings were compared with those in patients with IgA glomerulonephritis or Alport syndrome, and in normals. RESULTS: No patient with TBMD had a dot and fleck retinopathy or anterior lenticonus. A corneal dystrophy (n = 2) or pigmentation (n = 1), and retinal pigment epithelial clumping and maculopathy (n = 1) were noted. Corneal, lens, and retinal dots were found in five (29%), three (18%), and 16 (94%) patients, respectively, but these were also demonstrated in individuals with other renal diseases and in normal individuals. CONCLUSIONS: The dot and fleck retinopathy and anterior lenticonus typical of Alport syndrome do not occur in TBMD. The protein abnormality and genetic defect in TBMD are not known, but the lack of ocular lesions suggests that the abnormal protein in this disease is more sparsely distributed or less important in the basement membranes of the eye than of the kidney. Alternatively, the protein may be less affected by the mutations responsible for TBMD.

Adolescent↗
PubMed1997

Joint position sense and rehabilitation in the anterior cruciate ligament deficient knee.

BACKGROUND: Impaired joint position sense (JPS) has been shown in anterior cruciate ligament (ACL) deficient and osteoarthritic knees. The relation between JPS and function is uncertain. The aim of this study was to determine further if ACL deficient knees show abnormal JPS and the effect of exercise therapy on JPS, and also to assess the relation between JPS, functional stability, and strength. METHODS: Fifty patients (46 men and four women, mean age 26.3 years) with unilateral ACL deficient knees were assessed on admission and after rehabilitation (5 hours a day for four weeks). JPS was assessed by reproduction of passive positioning using a visual analogue incorporating a goniometer. Knee stability was analysed by self report questionnaire (score 0-280) and functional activity test (single leg hop and figure of eight run). Isokinetic dynamometry was performed to evaluate quadriceps and hamstring peak torque strength. Controls were either age and sex matched individuals or the contralateral knee. Statistical analysis was by Wilcoxon signed rank test and Spearman rank order correlation coefficient. RESULTS: JPS was impaired in ACL deficient knees. The mean (SD) errors in reproducing angles were 9.4 (3.1) degrees and 7.1 (2.3) degrees for the ACL deficient knee and control knee respectively (P < 0.0005). There was no improvement in JPS after rehabilitation (9.4 (3.1) degrees and 8.5 (3.2) degrees before and after rehabilitation respectively, P = 0.14). There was improvement as ascertained from the questionnaire (on admission 202 (32.1), after rehabilitation 243 (25.4), P < 0.0001) and functional activity testing (hop: on admission 148.7 (37.3) cm, after rehabilitation 169.8 (31.1) cm, P < 0.0005; figure of eight: on admission 48.4 (16.6) seconds, after rehabilitation 41.6 (3.4) seconds, P < 0.0001). Quadriceps strength improved (peak torque on admission 198.5 (58.9) Nm, after rehabilitation 210.5 (54.2) Nm, P < 0.05), but not hamstring strength (peak torque on admission 130.6 (28.1) Nm, after rehabilitation 135.5 (27.7) Nm, P = 0.24). JPS did not correlate with the functional activity tests (hop and figure of eight run), the responses to the questionnaire, or strength. There was no correlation between the responses to the questionnaire and functional activity tests or muscle strength. CONCLUSIONS: JPS was impaired in ACL deficient knees. Although knee stability improved with exercise therapy, there was no improvement in JPS. The role of JPS in the stability of ACL deficient knees remains unclear.

Adult↗
PubMed1997

Meniscal flounce MR imaging.

PURPOSE: To determine the prevalence of a meniscal flounce, the magnetic resonance (MR) imaging characteristics, and whether the flounce is associated with a meniscal tear. MATERIALS AND METHODS: Knee MR images obtained in 3,159 examinations over 2 years were prospectively evaluated. Ten adult patients (six with true flounces, four with flouncelike folds associated with meniscal tears) with an S-shaped fold in the free edge of a meniscus on sagittal images were included. Five underwent arthroscopic surgery. RESULTS: The prevalence of a flounce was 0.2% (six of 3,159 examinations). Five occurred in the medial meniscus (MM) and one occurred in the lateral meniscus (LM). All appeared truncated in the coronal plane. Four meniscal tears also demonstrated flouncelike folds. Three were confirmed with surgery and one was confirmed with clinical findings. Of the 3,159 MR examinations, 1,151 demonstrated an MM tear, 832 an LM tear, 542 MM degeneration, and 270 LM degeneration. CONCLUSION: A meniscal flounce is a fold that occurs in the absence of a tear, and presence of it does not increase the prevalence of a tear. Because tears may result in a flouncelike fold, a flounce should be considered a normal variant only in the absence of other indications of a meniscal tear.

Adolescent↗