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Biomedical subjects

D Lewis

Publications and source records attributed to D Lewis.

At least 217 records · Page 12Linked to original sources
PubMed1990

A clinical trial of aligning archwires.

The physical properties of a super-elastic archwire alloy (Titanol) and Nitinol were investigated by the means of a bending test. It was found that the alloy possessed super-elastic properties. A clinical trial was then carried out to compare the properties of two types of aligning archwire. Two groups of 20 patients with crowded dentitions were randomly allocated either Titanol or Nitinol, a conventional nickel-titanium alloy aligning archwire. High quality alginate impressions were taken after archwire placement in Edgewise fixed appliances and were repeated after a mean period of 35 days. The impressions were cast in dental stone and digitized using the Reflex Metrograph. The contact points of the teeth of the labial segments, together with four stable points in the rugae were recorded. This enabled the co-ordinates for the sequential study models to be superimposed upon one another, allowing tooth movement in three dimensions to be calculated. The measurement error expressed as error variance was 0.028 mm. The coefficient of reliability was 97 per cent. When tooth movement was analysed the mean movement per contact point for Titanol was 1.7 mm and for Nitinol 1.42 mm. This difference was not statistically significant (P less than 0.05, t-test). However, a clinical impression was that the super-elastic archwire proved superior to the Nitinol, because it was more readily engaged into grossly displaced teeth.

Adolescent↗
PubMed1989

Neurologic complications in children with soft tissue and osseous sarcoma.

From 1980 to 1987, 162 consecutive children with soft tissue and osseous sarcoma were reviewed to determine the frequency and types of neurologic complications seen. Neurologic complications occurred in 43 of 162 (26.5%) patients. Children with poorly differentiated sarcomas and rhabdomyosarcoma were more likely to have neurologic complications, which occurred in 39% of patients at risk. The types of complications seen included: metastatic spinal cord compression (11%); symptomatic peripheral neuropathy (10%); intracranial metastatic disease (7.5%); seizures (6%); and acute and chronic methotrexate-related neurologic dysfunction (2.5%). Spinal cord compression frequently occurred early in disease whereas brain metastases was almost always a late finding. Symptomatic peripheral neuropathy occurred primarily in children with rhabdomyosarcoma and Ewing's sarcoma. The advent of increasingly successful therapies for children with sarcoma and the frequency of severe neurologic complications indicate that a heightened level of surveillance for neurologic compromise is required.

Adolescent↗
PubMed1989

The biodistribution of radiocopper-labeled compounds.

Porphyrins form extremely stable chelates with Cu2+. Two copper radionuclides, 67Cu and 64Cu, have attractive nuclear decay properties for use in nuclear medicine applications. We have investigated the use of radiocopper-labeled porphyrins for localization in inflamed tissue and for attachment to antibodies for tumor imaging and therapy. We have examined the biodistribution of a 67Cu labeled porphyrin, [5, 10, 15, 20-tetrakis(4-carboxyphenyl) porphinato [67Cu] copper (II)], 67 CuTCPP. The 67CuTCPP was intravenously injected into the tail vein of Fischer F344 male rats. The kidneys, liver, and spleen localize the greatest amounts of 67CuTCPP. The elimination of 67CuTCPP from the body is described by a normal exponential decay curve with a biological half-life of 108 hours and an effective half-life of 32 hours. We have also examined the biodistribution of 5-(4-carboxyphenyl)-10, 15,20-tris(4-sulfophenyl) porphinato [67Cu] copper (II) anti-Thy 1.2 antibody conjugates in normal and tumor-bearing male AKR/J mice. The liver, kidney, and tumor have the highest uptake of the 67Cu labeled antibody conjugate. In all 67Cu labeled compounds studied, the blood clearance was rapid and the bone concentration of the radiolabeled species was low.

Animals↗
PubMed1989

The role of bacterial infection of the maxillary sinus in nasal polyps.

Fifty-two adult patients with nasal polyps were studied. All patients had preoperative sinus radiographs which were coded on the degree of mucosal thickening and these were compared with the results of irrigation of the maxillary sinuses. All irrigations were sent for culture and microscopy for pus cells. Pus cells and bacteria were found in only 16 of 104 wash-outs. It was concluded that the disease results in stasis of secretions and secondary maxillary sinusitis.

Bacterial Infections↗
PubMed1989

Mechanism of insulin resistance induced by sustained levels of cytosolic free calcium in rat adipocytes.

We have recently provided evidence that elevated levels of cytosolic free Ca2+ ([Ca2+]i) decreased insulin-stimulated glucose uptake in isolated rat adipocytes. To investigate the mechanism of Ca2+ action, we examined the effects of elevated levels of [Ca2+]i on insulin binding, autophosphorylation, and tyrosine kinase activity (TKA) of insulin receptors as well as basal and insulin-stimulated cellular distribution of glucose transporters. The latter was assessed by cytochalasin-B binding to plasma membrane and cytosolic fractions. Elevated concentrations of [Ca2+]i were maintained by incubating adipocytes with a depolarizing concentration of K+ (40 mM). Basal nonstimulated glucose uptake was not altered by increased levels of [Ca2+]i. Adipocytes with higher [Ca2+]i (220 +/- 15 nM) showed 30% reduction in insulin-stimulated 2-deoxyglucose uptake compared with control cells ([Ca2+]i, 140 +/- 18 nM). Moreover, adipocytes with higher levels of [Ca2+]i demonstrated an approximately 10% reduction in autophosphorylation and TKA of insulin receptors without a change in insulin binding. Both basal and insulin-stimulated distributions of glucose transporters were unaffected by sustained levels of [Ca2+]i. The effects of elevated [Ca2+]i were not mimicked by protein kinase-C activation. These observations suggest that 1) elevated or sustained levels of [Ca2+]i impair insulin-stimulated glucose uptake; and 2) Ca2+-induced impairment appears to reside at the postbinding steps of insulin action and probably interferes with the TKA of insulin receptors and the intrinsic activity of glucose transporters.

Adipose Tissue↗
PubMed1989

Perioperative care of the liver transplant patient.

1. Communication among team members on the liver transplant team is crucial; individual responsibilities must be considered while problem solving is shared as a team. 2. A major goal of the OR nurse is to maintain the patient's skin integrity; proper patient positioning and protection is essential. 3. Constant awareness of blood and blood product availability is urgent.

Humans↗
PubMed1989

Colorimetric assay for the detection of benzimidazole resistance in trichostrongyles.

A modified version of the aphid tile-test, which is used to detect insecticide resistance in single adult aphids that are resistant or susceptible to organophosphate or carbamate insecticides, was used to compare the levels of non-specific esterases in strains of the trichostrongyle nematodes Haemonchus contortus, Ostertagia circumcincta and Trichostrongylus colubriformis which were known to be resistant or susceptible to benzimidazole (BZ) anthelmintics. This colorimetric assay has shown that there is significantly more non-specific esterase in the infective-stage larvae of BZ-resistant strains than in susceptible strains and this may prove to be of use in the detection of resistance to benzimidazole anthelmintics.

Animals↗
PubMed1989

Suicide by ingestion of T-61.

T-61 is an agent used for euthanasia of animals and is primarily administered by iv injection. When so used it rapidly induces deep anesthesia and cerebral death. We report our findings in a case of ingestion of T-61 with suicidal intent. The coroner's report stated that the individual survived for 20 to 30 min and that death was due to cardio-respiratory failure. Levels of embutramide in the blood and liver are comparable to those reported in a number of animal species following the traditional routes of administration.

Adult↗
PubMed1988

Resting energy expenditure in the critically ill: estimations versus measurement.

A prospective trial was conducted in 20 surgical intensive care unit patients receiving mechanical ventilation to compare estimates of resting energy expenditure (REE) with the measured values. The 12 women and 8 men (mean age 61.7 +/- 2.8 (s.e.m.) years) underwent a full nutritional assessment before measurement of their REE by indirect calorimetry using the MGM II metabolic cart (Utah Medical). Their REE was estimated by the Harris-Benedict formula (mean 1324 +/- 53 (s.e.m.) kcal/day) as well as an empirical formula (where empirical formula = 22 x body weight in kg) (1370 +/- 68 (s.e.m.) kcal/day). Results by either estimate were not statistically different from the measured resting energy expenditure (MREE) (1382 +/- 130 (s.e.m.) kcal/day), by one-way analysis of variance. No multiplication factors were needed to relate the Harris-Benedict formula to MREE in this critically ill population and the estimate by the empirical formula was as good and simpler to perform. Although values by the Harris-Benedict formula and empirical formula correlated significantly with MREE (P less than 0.05) the correlation coefficients were low: 0.48 and 0.45 respectively. Thus, mean estimates were excellent for the group but less predictive for the individual. Multiple linear regressions did reveal that body composition and metabolic stress were of greater predictive value, since an equation relating weight (P less than 0.003), sex (P less than 0.003), white blood cell count (P less than 0.003) and 24-h urinary creatinine excretion (P less than 0.05) could predict 76 per cent of the variation (r = 0.87) in the MREE with an overall significance of P = 0.0002. Given the importance of matching energy intake to needs in many critically ill patients who are mechanically ventilated, accurate measurement of the REE is recommended now that instrumentation is equal to the task.

Adult↗
PubMed1988

Adsorption of enzymes at the solid-liquid interface. I. Trypsin on polystyrene latex.

The enzyme, trypsin, has been used to study conformational changes which occur when protein adsorption onto well-characterized, emulsifier-free, polystyrene latex surface takes place. The adsorption isotherm is of the high affinity, Langmuirian type with plateau adsorption of trypsin of 2.8 mg m-2. The enzymic activity of adsorbed trypsin to low molecular weight substrate is found to decrease as the surface coverage decreases indicating that 'spreading' or unfolding of the native protein conformation, with consequent loss of enzymic activity, occurs. On the close packed surface such 'spreading' is inhibited by steric factors. The view that protein adsorption onto hydrophobic surfaces is dominated by the entropy gain due to protein unfolding to maximize hydrophobic interactions is thus supported.

Adsorption↗
PubMed1988

Detection of benzimidazole resistance in trichostrongylid nematodes.

Benzimidazole anthelmintics (Box 1) have an important role in the control of economically-important nematode parasites of sheep and other ruminants. But effective control and management strategies using such compounds require a clear appraisal of the resistance or susceptibility of the target worms. Currently available tests for benzimidozole resistance in trichostrongylid nematodes tend to be costly, time-consuming and technically-demanding - as a result, attention is now turning to biochemical assays.

Journal Article↗