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Biomedical subjects

E Chan

Publications and source records attributed to E Chan.

158 records · Page 9Linked to original sources
PubMed1976

The role of disulphide bonds in Heinz body attachment to membranes.

The mechanism of binding of oxidant-induced Heinz bodies to red cell membrane was studied. Heinz bodies induced by acetylphenylhydrazine in intact cells or in the presence of membrane remained attached to membrane when separated by a sucrose gradient. Incubation with sulphydryl reagents failed to free intact Heinz bodies from or prevent attachment to membranes, although the amount of haem was reduced. Thus disulphide bonds do not appear to be a major mechanism of attachment of Heinz bodies to red cell membrane.

Binding Sites↗
PubMed1976

Amphotropic host range of naturally occuring wild mouse leukemia viruses.

Seven murine leukemia virus field isolates (uncloned) from wild mice (Musmusculus) of four widely separated areas in southern California show an unusually wide in vitro host range. They replicate well in human, feline, canine, guinea pig, rabbit, rat, and mouse cells, whereas bovine, hamster, and avian cells are resistant. Since this host range includes that of both mouse tropic (ecotropic) and xenotropic murine leukemia viruses, they are designated as "amphotropic". No purely xenotropic virus component is detectable in these field isolates. They may represent the "wild" or ancestral viruses from which the ecotropic and xenotrophic murine leukemia virus strains of laboratory mice have been derived.

Animals↗
PubMed1976

Hepatic carbamyl phosphate synthetase and ornithine transcarbamylase in mouse influenze A and influenze B infection.

In mice infected with mouse-adapted influenza A/PR/8/34, hepatic carbamyl phosphate synthetase (CPS) activity was reduced to 88%, and ornithine transcarbamylase (OTC) was reduced to 83% of control values. In mice infected with mouse-adapted B/Lee/40, CPS activity was 98% was 94% of control values. These limited reductions in enzyme activity were attributed to a nonspecific debilitating effect of acute influenzal pneumonia. These findings suggest that the pronounced reduction of CPS and OTC activities reported in Reye's syndrome in man are not a general manifestation of the severity of influenza infection.

Adult↗
PubMedDate not supplied

The solution conformational features of two highly homologous antigenic peptides of foot-and-mouth disease virus serotype A, variant A and USA, correlate with their serological properties.

The solution structure of a peptide corresponding to the VP1 region 141-160 of foot-and-mouth disease virus (FMDV) serotype A variant USA has been studied by NMR and computer calculations and compared with the results from a study on a highly homologous peptide deriving from serotype A, variant A. The two peptides differ in their serological behavior and contain the immunodominant epitope of the virus which partly overlaps with its receptor binding region. Distance constraints, derived both from 2D and 3D homonuclear NMR and 2D-heteronuclear NMR experiments, were combined with DG calculations to yield 50 structures. After refinement through EM and restrained molecular dynamics simulations the selected structures shared several general features. In particular the 151-158 region was a helix in all cases while a large loop similar to that found in peptide A but comprising less residues and stabilized by an H-bond between the side chains of D147 and S150 was found in the majority of structures. A further loop, common to all structures, was identified around the RGD sequence (145-147). This was different from that found in the corresponding region of peptide A as were the conformations of the individual residues within the RGDX sequence. The different structural features shown by the two peptides were rationalized in terms of the S148 (peptide A) to F148 (peptide USA) mutation. The second mutation, that at position 153 (L in A, P in USA) did not appear to affect the structure of the peptide significantly although the different dimensions of the loop in the central region and the type of H-bond stabilizing it could be potentially ascribed to this second mutation. All criteria used pointed to different structural features for the two peptides consistent with their serological behaviour.

Amino Acid Sequence↗
PubMedDate not supplied

The effect of pentoxifylline on current perception thresholds in patients with diabetic sensory neuropathy.

Diabetic peripheral neuropathy is a common, painful, and disabling condition that is known to occur by two mechanisms: hyperglycemia and arterial blood flow occlusion. Pentoxifylline (Trental) functions by improving erythrocyte flexibility in blood vessels, which could increase the delivery of oxygen to occluded nerve vessels. This 1-year clinical trial was aimed at ascertaining the effects of pentoxifylline on diabetic sensory neuropathy. Fifty patients with type I or II diabetes were evaluated in a randomized, double-blind, parallel group and placebo-controlled study. Pentoxifylline effectiveness was evaluated by measuring glycated hemoglobin, blood pressure and current perception threshold (CPT). The CPT results showed no statistically significant effect of pentoxifylline on mean nerve sensory perception thresholds in ankle and toe at 5, 250 and 2000 Hz. There were no significant changes in glycated hemoglobin or in systolic and diastolic blood pressure during the trial. Thus, glycated hemoglobin and blood pressure did not explain the lack of pentoxifylline effect on diabetic neuropathy. In conclusion, pentoxifylline appears not to add benefits to the clinical treatment of diabetic sensory neuropathy of the lower extremity.

Adult↗
PubMedDate not supplied

Low mortality among patients with spinal cord injury and bacteremia.

We reviewed 103 episodes of bacteremia in 93 patients with spinal cord injury who had bacteremia during initial hospitalization (39 patients) or readmission (54 patients) during 1978-1988. Eighteen episodes (18%) were due to polymicrobial infections. Urinary tract infections (47%), infected pressure areas (19%), and pneumonia (9%) were the most frequent primary infections and sources of the bacteremia. The bacteria most frequently associated with urinary tract infections were enterococci (26%), Escherichia coli (26%), Pseudomonas species (20%), and Klebsiella pneumoniae (12%). Bacteria most frequently isolated from patients with infected pressure areas were anaerobes and Staphylococcus aureus. Bacteremia was the cause of death for 8 patients (9%). The urinary tract was identified only once as the source of gram-negative bacteremia in an immunocompetent patient who died. The reason for the low mortality in patients with spinal cord injury is unclear.

Adolescent↗
PubMedDate not supplied

Comparison of four latex kits for detection of E. coli O157.

OBJECTIVE: To compare four Escherichia coli O157 test kits for detection of E. coli O157:H7 isolated from clinical specimens. DESIGN: One hundred two Escherichia coli O157:H7 isolates obtained from stored specimens and 99 non-sorbitol fermenting enterobacteriaceae isolates from current clinical specimens were tested against four latex kits: Wellcolex, RIM, Prolex, and Oxoid. Each isolate was tested against all four kits on the same day. SETTING: Provincial Laboratory of Saskatchewan, Canada. PATIENTS: Patients from Saskatchewan with diarrhea submitted stool specimens through their family physicians to the Provincial Laboratory for detection of enteric pathogens including E. coli O157:H7. RESULTS: The sensitivity and specificity of each test kit were: Wellcolex 100%, 99%; RIM 100%, 99%; Prolex 99%, 100%; Oxoid 100%, 100%. The Prolex kit failed to detect one E. coli O157:H7 isolate. CONCLUSION: All kits tested were able to identify E. coli O157 isolated from stool specimens. Further study with Prolex is needed to assess the significance of the one missed E. coli O157 isolate.

Bacteriological Techniques↗
PubMedDate not supplied

Administration of insulin by continuous ambulatory peritoneal dialysis.

Many patients with diabetic nephropathy undergoing continuous ambulatory peritoneal dialysis (CAPD) use their peritoneal access to administer insulin. Compared with the subcutaneous route, intraperitoneal (IP) insulin may display more consistent absorption, produce more physiologic insulin concentrations, and be more convenient to administer. However, there are no well-controlled trials that have demonstrated a clinically significant difference in glycemic control between IP and subcutaneous administration. For patients who choose to begin IP insulin at the time CAPD is initiated, the starting dose is 2-3 times the previous subcutaneous dose. For patients previously stabilized on CAPD, the conversion factor may be less. Doses are divided equally between bags. Some authors recommend adding more insulin to bags with a higher concentration of dextrose. In addition, the dose should be decreased when added to a bag used for an overnight dwell. Exchanges performed during the day may be timed to start 30 minutes before a meal. Unless clinical trials demonstrate a difference in efficacy between subcutaneous and peritoneal insulin administration, the route will remain a matter of patient preference.

Absorption↗
PubMedDate not supplied

Anemia severity and missed dialysis treatments in erythropoietin-treated hemodialysis patients.

Neither the sociodemographic correlates nor the biochemical/clinical consequences of missed dialysis treatments have been well defined. During a 10 week period, the authors enumerated missed dialysis treatments among 430 patients randomly selected from a pool of 1,395 hemodialysis patients. A forward logistic regression model was used to determine whether a relationship existed between missed dialysis treatments and the following independent variables: age, gender, race, renal diagnosis, length of time on maintenance hemodialysis, co-morbidity index, modified Karnofsky score, employment status, household residents, and laboratory indices. Forty-three (10%) of 430 patients missed a total of 96 treatments. Despite equivalent treatment with erythropoietin, patients who missed dialysis treatment(s) had a lower mean hematocrit (27 +/- 4.3%) at the end of the study than those patients who underwent all treatments (29 +/- 4.5%) (p = 0.0287). Mean serum albumin and creatinine levels were equivalent in compliant and noncompliant patients. Recent starts (p = 0.0048), and younger patients (p = 0.0424) were most likely to miss dialysis treatment(s). One of the major consequences of missed dialysis treatment(s) is exacerbation of anemia, and younger patients and freshly started patients are more likely to miss scheduled dialysis treatments than their respective counterparts.

Adult↗
PubMedDate not supplied

Complications of thyroid surgery.

The current study reports complications from thyroidectomy in 253 consecutive patients from 1988 to 1992. There were 10 temporary cases of hypoparathyroidism. After total thyroidectomy, one of 34 patients (3.2%) developed permanent hypoparathyroidism. Complications of recurrent laryngeal nerve (RLN) injury or hypoparathyroidism were no more common following completion thyroidectomy than total thyroidectomy. Unplanned RLN injury was seen in 13 patients of which 7 were permanent (2.1% of 334 nerves at risk). All 13 patients with RLN injury experienced a reduction in speech "loudness", but only 3 reported "hoarseness". The RLN may be injured without serious vocal disability. Eleven of 171 right RLN's at risk were injured as compared to 2 of 163 left RLN's. The volume of thyroid tissue resected was positively associated with RLN injury (p < 0.05) and not hypoparathyroidism. These findings are discussed. Hypoparathyroidism, not "symptomatic" RLN injury, is the most problematic complication impacting on the decision whether or not to perform total or completion thyroidectomy.

Female↗