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Biomedical subjects

S Mitchell

Publications and source records attributed to S Mitchell.

At least 145 records · Page 8Linked to original sources
PubMed1991

Factors affecting light scatter in contact lens wearers.

We measured forward light scatter at 3.5, 10, and 28 degrees using a portable stray light meter. Subjects included 66 normal subjects (age range 19 to 79 years), 17 established hydrophilic contact lens wearers, and 15 rigid gas permeable (RGP) contact lens wearers. Contact lens deposits were measured using a modified Rudko procedure and a Leitz/Wild Makroscope M240. Corneal health was assessed using slitlamp biomicroscopy. Results showed a significant increase in light scatter with age, particularly after the age of 40 years. Stray light scores were significantly lower in pigmented non-Caucasian subjects, particularly at larger angles. The stray light scores were significantly greater in contact lens wearers than in age-matched normals, but were not found to correlate with the amount of lens deposits. Scores from hydrophilic lens wearers after removal of their lenses were significantly higher than results from RGP wearers after removal of their lenses and from age-matched normals. This suggests the presence of subclinical corneal edema in some of these subjects.

Adult↗
PubMed1991

Computed tomographic evaluation of gallstone calcification for biliary lithotripsy.

As the Food and Drug Administration trials for biliary lithotripsy in the United States near completion, future criteria for patient eligibility remain to be defined. Gallstone calcification greater than 3-mm partial rim on plain film (KUB) or oral cholecystogram (OCG) has excluded patients thus far, since early results of gallstone clearance (lithotripsy plus chemodissolution) were suboptimal with calcified stones. To evaluate the usefulness of these criteria for gallstone fragmentation, computed tomographic (CT) scans were performed on 20 patients immediately prior to lithotripsy to evaluate gallstone density and 24 hours after lithotripsy to observe the CT appearance of fragmentation. The adequacy of fragmentation was determined by pre- and post-lithotripsy sonography. This report constitutes the results of these investigations.

Calcinosis↗
PubMed1990

Evidence for interconnections between the two segments of the globus pallidus in primates: a PHA-L anterograde tracing study.

Small injections of the lectin Phaseolus vulgaris-leucoagglutinin (PHA-L) in the external segment of the pallidum (GPe) in the squirrel monkey (Saimiri sciureus) and in the rhesus monkey (Macaca mulatta) led to anterograde labeling of fibers in the internal segment of the pallidum (GPi). These fibers formed numerous large varicosities reminiscent of terminal boutons, which closely surrounded GPi cell bodies and primary dendrites. Conversely, PHA-L injections in the GPi of squirrel monkeys produced anterograde fiber labeling in the GPe. However, in contrast to fibers in GPi, those in GPe did not make prominent pericellular contacts. Instead, they displayed a rather linear course, had long intervaricose segments, and appeared to contact several GPe neurons along their course by close appositions on cell bodies and primary dendrites. These results suggest the existence of a reciprocal connection between the two pallidal segments, which may play a crucial role in the functional organization of the basal ganglia in primates.

Animals↗
PubMed1990

5HT2 receptor changes in rat cortex and platelets following chronic ritanserin and clorgyline administration.

Chronic administration of clorgyline or ritanserin to adult rats for 28 days followed by a 3 day drug-free period results in a significant decrease in 5HT2 receptor number (Bmax) in rat frontal cortex from 315.23 +/- 10.72 fmol/mg protein to 249.63 +/- 13.99 fmol/mg protein and 222.55 +/- 17.17 fmol/mg protein, respectively. On rat blood platelets, ritanserin significantly increases recept number from 26.18 +/- 3.83 fmol/mg protein to 50.94 +/- 7.96 fmol bound/mg protein, whereas clorgyline has no significant effect (21.32 +/- 4.78 fmol/mg protein). Following both drug regimens, the affinity (Kd) of the respective ligands for the receptor is not significantly different from controls: the mean Kd value of the three groups for [3H]ketanserin is 1.57 +/- 0.05 nM in cortex and 0.83 +/- 0.25 nM for [125I]iodolysergic acid diethylamide (LSD) on platelets. Clorgyline increases serotonin (5HT) and noradrenaline (NA) levels in cerebellum, and decreases 5-hydroxyindole acetic acid (5HIAA) and homovanillic acid (HVA): ritanserin does not change the levels of the amines or their metabolites. The data shows that platelet and brain changes are not comparable after ritanserin administration. The receptor binding data demonstrates that curve fitting to two data points provides information which is comparable to and as statistically robust as that obtained from eight point saturation curves. Thus, if pilot studies show that the data follows a rectangular hyperbola, two point assays (optimal at 0.1 Kd and 3 Kd) can be used to obtain estimates of Bmax and Kd.

Animals↗
PubMed1990

A cumulative review of studies on travellers, their experience of illness and the implications of these findings.

A cumulative review of illness experienced by 13,816 travellers returning to Scotland since 1977, shows an overall attack rate of 36%. Alimentary complaints predominated; 18% of travellers had these alone and a further 10% had other symptoms as well as their gastro-intestinal disorder. Higher attack rates were noted in those taking package holidays. Inexperience of travel, smoking, more southerly travel and younger age (particularly those between 20- and 29-years-old) were other contributing factors. A similar pattern emerged from a I year study of hospital in-patients with travel related admissions. Serological studies of 470 travellers showed that 20% had incomplete immunity to poliomyelitis; 25% of those tested (312 travellers) had serological evidence of typhoid immunisation, I.9% (of 760 travellers) had antibodies to Legionella pneumophila, 64% (5II travellers tested) had antibodies to hepatitis A, 87% (288 tested) had adequate levels of tetanus antitoxin but only 40% of the 225 travellers tested had adequate levels of diphtheria antitoxin. Amongst a subgroup of 645 travellers the travel agent was the most frequently consulted source of pre-travel health advice. This carries particular significance for the dissemination of relevant advice in view of the inadequacies found from study of the health information in travel brochures. These findings, viewed against the perspective of the continuing growth in international travel, means that travellers, the medical profession, the travel trade, health educators, global health agencies and health authorities in those countries accepting and encouraging tourists, will be required to recognise the health implications of further tourism development if this problem of illness associated with travel is to be brought under control.

Adolescent↗
PubMed1990

Long-term survival after chemotherapy with cisplatinum, adriamycin and cyclophosphamide for carcinoma of the ovary.

Forty six patients with FIGO Stage II, III, and IV ovarian cancer received treatment with cisplatinum, adriamycin and cyclophosphamide. After a minimum follow-up time of 60 months 13 patients remain free of recurrence. The overall 5-year survival is 39% and the median survival is 39 months. The 5-year survival for Stages II, III, and IV is 64%, 40% and 0% respectively. The 5-year actuarial survival for those who had less than 2 cm residual disease (including those with complete debulking) is 72%, while for those who had greater than 2 cm residual disease (including those who had biopsy only) is 15%. None of the patients have developed any second neoplasm.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1990

Cosmetic results of early breast carcinoma treated with wide local excision, external beam radiotherapy and iridium-192 boost.

Cosmetic results of 80 patients with axillary lymph node negative or unknown T1 and T2 carcinoma of the breast who were treated with wide local excision, external beam radiotherapy and iridium-192 boost, were evaluated by the patient and the radiotherapist at 18-36 months. Their overall cosmetic results were assessed as good, very good or excellent by 80% of the patients. The radiotherapist's assessment was similar but in general the patients score was more favourable. After a follow-up of 24-72 months recurrence was found in only one patient at 40 months. This approach offers good cosmesis with low local recurrence rates in early breast carcinoma patients with negative axillary lymph nodes.

Adult↗
PubMed1989

Computerized electrocardiographic interpretation: an analysis of clinical utility in 5110 electrocardiograms.

This study describes the initial experience with a computerized electrocardiographic interpretation system in a teaching hospital. The sensitivity and specificity of the 13,375 diagnostic statements that were used to describe the first 5110 electrocardiograms were analysed to determine the predictive accuracy of computerized electrocardiographic interpretation. Reviewing cardiologists inserted 1320 statements, deleted 1792 statements and modified 484 computerized statements. The over-all sensitivity and specificity (and standard error [SE]) of computerized diagnosis was 90.1% +/- 0.3% and 89.6% +/- 0.2%, respectively, with an over-all positive predictive accuracy (+/- SE) of 87.1% +/- 0.3% and a negative predictive accuracy (+/- SE) of 92.2% +/- 0.2%. Sensitivity and specificity were lowest for the category of ST-T wave changes (83.1% +/- 0.8% and 84.1% +/- 0.7%, respectively) and were highest for the category of sinus rhythm (96.6% +/- 0.3% and 97.0% +/- 0.6%, respectively). The positive predictive accuracy of computerized diagnosis was lowest for the category of hypertrophies (74.2% +/- 1.0%) and was highest for the category of sinus rhythm (99.5% +/- 0.1%), while for the category of myocardial infarctions it was 87.6% +/- 0.8%. The negative predictive accuracy ranged from 96.7% +/- 0.3% for the category of hypertrophies to 81.8% +/- 1.3% for the category of sinus rhythm. We conclude that the computerized analysis of electrocardiograms has a satisfactory predictive accuracy when used in an environment with a high prevalence of abnormalities. Electrocardiograms that are classified as normal by computerized analysis may not require checking; however, all electrocardiograms with abnormalities should be interpreted by a competent electrocardiographer.

Cardiology↗
PubMed1989

Ibotenate-induced total septal lesions reduce resistance to extinction but spare the partial reinforcement extinction effect in the rat.

Rats were given sham operations, vehicle injections, or injections of the axon-sparing excitotoxin ibotenic acid into the septum. In Experiment 1, behavioural testing commenced 16 days after the operation; in Experiment 2 behavioural testing commenced following testing on another task, 31 days after the operation. The rats were trained to run in an alley for food reward given on every trial (Continuous Reinforcement, CR) or on a random fifty percent of trials (Partial Reinforcement, PR) and then the running response was extinguished. All the experimental groups showed the normal partial reinforcement extinction effect (PREE) in that PR-trained animals were significantly more resistant to extinction than CR-trained animals. However the rats with ibotenic acid lesions also showed a significant decrease in resistance to extinction regardless of training condition. The same pattern of results was seen at each of the two post-operative testing times. The results were thus readily replicable, and entirely unlike previous reports of the behavioural effects on this task of conventional septal lesions of equivalent size. In Experiment 3, neurochemical analysis of the hippocampus in rats with ibotenic acid-induced lesions demonstrated that choline acetyl-transferase levels were reduced to the same extent as in rats with comparable conventional lesions.

Animals↗
PubMed1989

Interventional uroradiology.

Major interventional uroradiologic techniques including percutaneous nephrostomy, vascular augmentation and reduction procedures, percutaneous cyst aspiration, chronic peritoneal dialysis catheter manipulation and urethroplasty are reviewed. A brief history of the development and techniques for performing these procedures are included. The results of clinical series are assessed and their role in patient management is addressed. The development of these procedures has had a significant impact on patient care by providing effective nonoperative therapy.

Angioplasty, Balloon↗
PubMed1989

Changes in energy expenditure and work during response acquisition in rats.

The principle of least effort predicts that behavior will tend to maximum efficiency. To test this prediction, changes in the energy expended (VO2) and work performed per reinforcement were monitored continuously as rats learned to press a beam with a criterion force for liquid food rewards. All 12 subjects exhibited significant decreases in energy expended per reinforcement over the 16 days of observation. Of these, 10 subjects also decreased the work performed per reinforcement. Analyses of motor performance were undertaken to determine how motor programs for changing efficiency were generated. The 10 animals showing decreased work reinforcement also exhibited significant decreases in the variability of temporal and kinetic response features and in mean response magnitude (time integral of force or work per response) as a function of practice. Adjustments in work output were primarily accomplished by modifying temporal response features (response duration and, initially, interresponse time). The kinetic features (response recruitment and peak force) remained relatively constant for these animals. The remaining 2 subjects differed in that response recruitment increased after Day 9, resulting in progressively larger amounts of work being performed to earn each reinforcement, and the interval between successive reinforcements decreased.

Animals↗
PubMed1988

A proposed mechanism for chlorpromazine jaundice--defective hepatic sulphoxidation combined with rapid hydroxylation.

On the basis of previous experimental studies we postulated that individuals who were phenotypically good hydroxylators but poor sulphoxidisers would be susceptible to chlorpromazine jaundice. Sulphoxidation capacity was assessed in 12 subjects with a history of chlorpromazine jaundice, using S-carboxymethyl-L-cysteine as an in vivo probe. Following an oral dose of 750 mg, unchanged compound and sulphoxide metabolites were measured in urine. All 12 subjects (100%) were shown to be poor sulphoxidisers compared to 22% of normal controls (P less than 0.001) and 23.8% of liver disease controls (P less than 0.001). No subjects with a history of chlorpromazine jaundice had an impaired hydroxylation capacity as assessed by recovery of 4-hydroxydebrisoquine in urine following oral debrisoquine. The results support the hypothesis and demonstrate an inherent metabolic basis of susceptibility to chlorpromazine jaundice.

Adult↗
PubMed1988

The effects of two therapeutic communities on illicit drug users between 6 months and 1 year after treatment.

Thirty former residents of two different therapeutic communities for illicit drug users were interviewed between 6 months and 1 year after terminating treatment to determine how successfully they had been in adjusting to society. Two findings of this research concerned the amount of time the former residents spent in their therapeutic communities: Time in treatment was associated with fewer arrests once they graduated from these programs and was also associated with less drug use.

Adult↗
PubMed1988

Cadaveric renal transplantation at the University of Pittsburgh: a two and one-half-year experience with the point system.

From January 1, 1986 to July 30, 1988, 530 consecutive cadaver kidney transplantations were performed with patient selection by a point system that took into account time awaiting an organ, donor-recipient matching, degree of presensitization, and some less important factors. The effect of the system was to diminish judgmental factors in case selection which in the past, had probably operated to the disadvantage of "undesirable" potential recipients, including older ones. Primary 1-year graft survival (74%) and graft survival after retransplantation (71%) were lower than in the earlier time. However, the results with triple-drug therapy using CsA, AZA and P demonstrated 88% 1-year graft survival for primary graft recipients and 74% in highly sensitized patients, with comparable patient mortality. These latter observations provide some assurance that the concepts of equitable access and efficient utilization of a scarce resource are not mutually exclusive.

Actuarial Analysis↗