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Biomedical subjects

H M Cheng

Publications and source records attributed to H M Cheng.

At least 55 records · Page 3Linked to original sources
PubMed1996

Peritoneal catheter-related complications: a comparison between hemodialysis and intermittent peritoneal dialysis in the break-in period.

We prospectively monitored the clinical outcome of 89 curled, double-cuff peritoneal catheters (PC) implanted by surgeons over one year. Thirty-six cases (40%) were supported with hemodialysis (HD) (group A) and 53 cases (60%) were supported with weekly intermittent peritoneal dialysis (IPD) (small exchange volume with a cycler) (group B) for four weeks before commencing continuous ambulatory peritoneal dialysis (CAPD). PC-related complications between the two groups were compared. Ten cases failed to complete the six-month observation period (8 died, 1 received kidney transplant, and 1 defaulted follow-up),Total experience accumulated was 494 patient-months (195 patient-months in group A, 299 patient-months in group B). The incidence of pericatheter leakage (group A vs group B) was significantly higher in group B (0% vs 13%, p < 0.05). There were no significant differences in the incidence of other PC-related complications, removal of PC, and mortality rate in the two groups. The incidence of pericatheter leakage was significantly higher in diabetic patients (71% vs 22%, p < 0.05), and group B patients with leakage had a higher incidence of external cuff erosion 57% vs 7%, p < 0.005) and delay in CAPD training (71% vs 7%, p < 0.005). We conclude that both HD and IPD are equally safe renal replacement therapies in the break-in period, while patients supported with IPD had a higher incidence of pericatheter leakage, which was associated with other catheter-related morbidities including external cuff erosion and delay in CAPD training.

Adult↗
PubMed1996

Normal anatomy and lesions of the lacrimal sac and duct: evaluated by dacryocystography, computed tomography, and MR imaging.

Diseases of the lacrimal system are optimally evaluated by dacryocystography, CT, MR imaging, and nuclear scintigraphy. Dacryocystography is selected to define the lumen of the lacrimal drainage system in inflammatory disease (dacryocystitis), dacryoceles, dacryoliths, and developmental abnormalities. Dacryocystography provides supplemental information in benign and malignant tumors, principally to differentiate an intrinsic lesion from an extrinsic lesion. CT is indicated for delineation of palpable mass lesions such as cysts, benign and malignant tumors, and diseases, especially in the paranasal sinuses, affecting the lacrimal apparatus secondarily. MR imaging has limited application but is useful to differentiate fluid from solid masses within the sac and to define tumor extension from the sac into the duct and anatomic regions outside the sac and duct. MR imaging with gadolinium enhancement should be used in suspected tumors and to separate a cyst from a solid mass. Radiologic methods fail to identify the histopathology of benign and malignant tumors. Nuclear scintigraphy is helpful in patients with epiphora with no demonstrable anatomic abnormality on dacryocystography.

Diagnosis, Differential↗
PubMed1995

Linear epitopes of the replication-activator protein of Epstein-Barr virus recognised by specific serum IgG in nasopharyngeal carcinoma.

The linear antigenic epitopes of the Epstein-Barr virus replication activator protein (ZEBRA), recognised by specific serum IgG in nasopharyngeal carcinoma (NPC), were determined. This was achieved by synthesizing the entire amino acid sequence of ZEBRA as a set of 29, 22-residue peptides with an overlap of 14 amino acids. The ZEBRA peptides were tested in enzyme-linked immunosorbent assay (ELISA) for IgG binding in sera from 37 selected NPC patients who had IgG antibodies to the native ZEBRA protein. The most immunogenic epitope was peptide 1 at the amino-terminal end with 36 of the sera reactive against it. Further analysis of peptide 1, using the multipin peptide-scanning technique, defined a 10-amino-acid sequence FTPDPYQVPF, which was strongly bound by IgG. Two other regions of ZEBRA were also identified as immunodominant IgG epitopes, namely peptide 11 (amino acids 82-103) and peptide 19/20 (amino acids 146-175) with 8-13 of the NPC sera reactive against the peptides. The number of peptides reactive with individual NPC serum varies from 1 to 6 or more and there is some correlation between a greater number of peptide (at least 4) bound and a higher (at least 1:40) titre of serum IgA to viral capsid antigen. The immunodominant ZEBRA peptide 1 could be utilised in IgG ELISA for the detection of NPC.

Amino Acid Sequence↗
PubMed1995

Manipulating rat lens glucose metabolism with exogenous substrates.

Diabetic lens glucose metabolism in vivo can be altered by a number of exogenous substrates. We have chosen two, one a glucose epimer (mannose) and the other a glycolytic intermediate (pyruvate), to demonstrate the possibility of this approach. D(+)-Mannose is a D(+)-glucose epimer but in lenses incubated in 35.5 mM mannose, no mannitol (the sorbitol equivalent) was detected, while both lactate production and 31P profile appeared normal. Mannose therefore is a good glucose substitute causing no polyol formation. Mannose metabolism in the rat lens in vivo was then examined. Diabetic rats fed mannose-enriched diet over a period of 14 days showed retardation of changes in 31P metabolites, specifically the levels of phosphorylcholine and glycerophosphorylcholine, suggesting a protective effect. Rat lenses incubated in 35.5 mM glucose in the presence of 5 mM pyruvate (pyr) showed 50% lower sorbitol than without pyr. With 5 mM pyr in the drinking water, i.e. pretreatment in vivo during a 3-day diabetes induction period, the diabetic rat lens accumulated acetate and alanine when incubated in the presence of pyr. The decrease in sorbitol was most likely due to a lower glucose flux rather than an increased polyol dehydrogenase activity. Increasing glucose concentration from 5.5 to 35.5 mM or provision of exogenous pyr both caused an intermediate increase in O2 consumption in the normal lens; a maximal activity was reached with both 35.5 mM glucose and 5 mM pyruvate in the incubating medium. In the diabetic lens, O2 consumption could reach the intermediate but not the maximal level. Dietary pyr pre-treatment also prevented normal and diabetic lenses from maximal pyr-stimulated O2 consumption. The NMR and O2 consumption data together indicated activation of alanine dehydrogenase and saturation of Krebs cycle. It appears that dietary supplement of mannose can preserve 31P membrane metabolites in the diabetic lens. Mannose can be used in conjunction with hypoglycemic therapy for the management of diabetic cataract. In addition, pyruvate may be effective in enhancing lens energy metabolism and lower sorbitol production.

Animals↗
PubMed1995

The disease associations of the antibody response against the Epstein-Barr virus transactivator protein ZEBRA can be separated into different epitopes.

The BamHI-Z-encoded Epstein-Barr virus (EBV) replication activator (ZEBRA) is a key mediator of the switch from latency to productive cycle in EBV virus. Antibodies against ZEBRA are a marker of EBV reactivation and are regularly found among patients with infectious mononucleosis (IM) or nasopharyngeal carcinoma (NPC), but are only rarely found among healthy EBV-seropositive donors. In order to define the serologically reactive epitopes in the ZEBRA protein, we synthesized a set of overlapping peptides and tested them for reactivity with serum samples from EBV-seronegative persons, patients with NPC, IM, chronic fatigue syndrome, lymphoma or from healthy donors. Three major EBV-specific epitopes were found. These epitopes were further defined and optimized using substitution or truncation analogues of the peptides. Reactivity with epitope number 22 was found in 63% of NPC patients' sera, with < 2% of healthy donors' sera being positive. Serological reactivity with epitope number 19 was associated with IM (57% positive, 5% healthy donors positive). Serum antibodies against epitope 1 were found among healthy donors, but were significantly elevated among patients with NPC, IM or lymphomas. In conclusion, different serologically reactive epitopes in the ZEBRA protein associate with different EBV-associated diseases.

Antibodies, Viral↗
PubMed1995

A simple and effective video keratometric system.

We tested a personal computer-based video keratometric system used to analyze projected placido disk rings. The system consists of a Maloney surgical keratometer that projects the rings and a video camera attached to an operating microscope. Images of the rings were transmitted to a video image processing board and analyzed on a personal computer using an analysis program we developed. System precision was evaluated in 18 eyes. The values were compared with those obtained using a commercial photokeratometer (control). In all eyes, the principal meridian values differed from the controls by < 0.04 mm. In 15 eyes (83%), the measurements were within 0.03 mm of the controls. The corneal astigmatism values and cylindrical axes were within 0.12 diopters in 17 eyes (94%) and within 5 degrees in all cases, respectively. Our system, which can analyze placido disc rings projected from other systems, is sufficiently precise to measure the corneal radius of curvature and astigmatism.

Calibration↗
PubMed1995

Changes in lens organophosphate metabolites in response to endotoxin-induced uveitis.

Uveitis was induced in rats by endotoxin administration. The temporal correlation between ocular inflammatory reaction and lens metabolic change was examined. The levels of lens phosphate compounds, adenosine triphosphate (ATP), choline phosphate (CP), and inorganic phosphate (Pi), were measured using 31P-nuclear magnetic resonance (NMR) spectroscopy. Anterior chamber inflammation reaction appeared 12 h after administration, peaked at 24 h, and disappeared by 72 h. Concurrent with the active inflammation, lens Pi increased significantly 22 +/- 17% (p < 0.05) and 23 +/- 15% (p < 0.05), 12 and 24 h after administration, respectively, and returned to normal while the inflammation abated. No significant changes were observed in CP and ATP levels in the lens during the course of inflammation. The time course of the inflammation appeared closely related to the change in Pi level, which may be part of the protective mechanism of the lens against inflammation.

Adenosine Triphosphate↗
PubMed1994

Serum IgA cross-reactivity between glycine-alanine repeat sequence of EBNA-1 and keratin or collagen in nasopharyngeal carcinoma.

Inhibition studies were carried out to study possible cross-reactivity between a peptide fragment of the Epstein-Barr virus nuclear antigen, EBNA-1, and keratin/collagen. The 20-amino acid peptide (pAG), derived from a glycine-alanine repeat region of EBNA-1, uniquely makes up about one-third of the viral protein and is a dominant IgA antigenic epitope in patients with nasopharyngeal carcinoma (NPC). A small percentage of normal human sera (NHS) also binds pAG and this reactivity is examined in this study. Ten percent (2/20) and 13.4% (2/15) of IgA-pAG-positive NPC sera and NHS, respectively, were significantly inhibited by keratin in a competitive ELISA system. Conversely, 31.6% (6/19) and 30.8% (4/13) of IgA-keratin-positive NPC sera and NHS, respectively, were significantly inhibited by pAG. This indicated minimum cross-reactivity between IgA serum antibodies to EBNA-1 and keratin. Using collagen as inhibitor, none of 18 and only 2/13 IgA-pAG-positive NPC sera and NHS, respectively, were inhibited. In the collagen ELISA system, only 2/19 (10.5%) and 4/25 (16%) of IgA-collagen-positive NPC sera and NHS, respectively, were inhibited with pAG. Therefore, cross-reactivity with collagen was also low. IgA-pAG-positive NHS may therefore not be a false positive phenomenon, but whether it may represent an early serological profile related to NPC carcinogenesis remains to be determined.

Alanine↗
PubMed1994

A high incidence of serum IgG antibodies to the Epstein-Barr virus replication activator protein in nasopharyngeal carcinoma.

The BamHI Z EBV replication activator (ZEBRA) protein is involved in the switch from latency to productive cycle of Epstein-Barr virus. A recombinant ZEBRA protein was synthesized and assessed in enzyme-linked immunosorbent assay (ELISA) for serum IgG response in nasopharyngeal carcinoma (NPC) patients. In 100 NPC serum samples that were positive for IgA to the EBV viral capsid antigen (VCA), 75% had IgG anti-ZEBRA antibodies. In contrast, only 3/83 (3.6%) serum samples from healthy donors and 2/50 (4%) from other cancers were positive for IgG to ZEBRA. Interestingly, in a selected group of 100 NPC sera negative for IgA to VCA, 25% contained IgG anti-ZEBRA antibodies. This suggests that the ELISA for IgG anti-ZEBRA may also identify earlier cases of NPC not detected by the conventional immunofluorescence test for IgA to VCA.

Antibodies, Viral↗