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Biomedical subjects

K H Chan

Publications and source records attributed to K H Chan.

At least 253 records · Page 14Linked to original sources
PubMed1986

beta 2-Microglobulin and systemic lupus erythematosus.

Serum beta 2-microglobulin (beta 2-M) was measured in 115 patients with systemic lupus erythematosus (SLE) on 192 occasions. Raised beta 2-M was found in 16.4% of patients with only extrarenal manifestations of SLE, in 29.2% of patients with renal manifestation but an endogenous creatinine clearance greater than 80 ml/min/1.73 m2 and in 65.7% of patients with decreased creatinine clearance. beta 2-M was higher in SLE than non-SLE glomerulonephritides matched for creatinine clearance. Using an arbitrary scoring system, renal, extrarenal and serological activity correlated with beta 2-M. Changes in clinical activity on repeat studies were reflected by changes in beta 2-M. Serum beta 2-M can serve as a monitor of disease activity in SLE.

Adolescent↗
PubMed1986

Potentiation of mitogenic response by extracts of the swiftlet's (Collocalia) nest.

The edible bird's nest extract from Collocalia spp. was found to contain a glycoprotein which could potentiate mitogenic response of human peripheral blood monocytes to stimulation with Concanavalin A or Phytohemagglutinin A. The potentiating effect of the extract was most marked at suboptimal mitogenic concentrations of these lectins, decreasing the 50% optimal concentration of Con A and PHA by 6- and 2.5- folds respectively. The potentiating effect was exerted early during the first 10 hours following stimulation with Con A. This potentiation activity was not dialysable, but it was stable to limited digestion with trypsin, alkaline pH and extraction with ether.

Animals↗
PubMed1985

A shared antigenic determinant between human B lymphocytes and carcinomas (BLCa).

We have raised a murine IgM monoclonal antibody (MA6) against immunoprecipitate obtained by reacting the serum of an NPC patient with extract of the Burkitt lymphoma cell line, Raji. It reacts against an antigen (BLCa) which is broadly represented on human B lymphoid tissues and cell lines but is different from the functional B-cell markers such as surface immunoglobulins, Ia products, Fc and complement receptors. BLCa was found to occur on lymphoid cell lines representing all stages of B-cell differentiation. These included the pre-B and null-cell lines, Nalm 6 and Reh, the EBV-transformed lymphoid cell lines and the myeloma cell line. MA6 was reactive against all the Burkitt lymphoma cell lines, whether or not these harbored the EBV genomes, with the exception of P3HR-I. The antibody was found to be selectively reactive against a proportion of peripheral blood B lymphocytes and to stain the B-cell-rich primary follicles and mantle zones of secondary follicles in the lymph node. However, MA6 was not reactive against cell lines of T-lymphocyte, myeloid, monocyte fibroblast or epithelial origin. It did, nevertheless selectively stain tumor cells from a variety of carcinoma tissues originating from different anatomical sites, including the nasopharynx.

B-Lymphocytes↗
PubMed1985

Evidence that respiratory tract is major reservoir for Epstein-Barr virus.

Exfoliated cells harvested from bronchial washings of 53 patients with suspected bronchogenic carcinoma were tested by means of DNA dot hybridisation using the cloned large internal repeat (IR) sequence of Epstein-Barr virus (EBV) genome as a probe. 25 of these patients gave positive results. Since the patients had diseases that were not related to the virus, this finding suggests that the lower respiratory tract is a major reservoir for EBV. Attempts at cellular localisation of the virus revealed only an occasional cell which harboured the viral genome or expressed viral capsid antigens. These cells could not account for the quantity of the viral DNA detected in bronchial washings. Moreover, patients had similar profiles of serum EBV antibodies whether they were positive or negative for EBV DNA by dot hybridisation. These findings are compatible with a state of viral latency in which cells harbour a low copy number of the viral genome. Viral expression rarely occurs in these cells, which seem to elicit a minimum host immune response. If it is assumed that each latently infected cell harbours a maximum of approximately 30 EBV genomes (which is the lower limit of detection by the in-situ hybridisation method used in this study), the findings suggest that a considerable proportion of the exfoliative cells from the lower respiratory tract, of the order of 0.1-16%, harbour latent EBV.

Adult↗
PubMed1985

Moiré patterns: an accurate technique for determination of the locus of the centres of rotation.

This study describes an accurate technique for the determination of the centre of rotation of small angles. The moiré fringe method localizes the centre of rotation by defining two primary fringes, each of which is found by the intersection of three lines. The primary fringes intersect at the centre of rotation at 90 degrees to each other, the angle least likely to produce an error in measurement. By utilizing joints with known centres of rotation, we have found that the method is extremely accurate and reproducible to within 2 mm of the real centre for angular changes as small as 3 degrees. This technique is useful in evaluating whether a joint is a simple hinge, i.e. rotating about a single axis of rotation or whether the joint moves about a changing axis of rotation referred to as a locus or centrode.

Arthrography↗
PubMed1985

Centrode patterns and segmental instability in degenerative disc disease.

Moiré fringes were used to determine centrode patterns in cadaveric spines with degenerative disc disease. The normal centrodes were compared with those with minor, mild, moderate, and severe degenerative disc disease. The most complex loci noted were those discs that showed minimal radiographic evidence of degeneration, that is, the minor and mild groups. The loci lengthened significantly (P less than 0.001) when compared with normal controls. The position of the centrode shifted downward into the body of L5 in the moderate group.

Adult↗
PubMed1985

Lactate dehydrogenase-deficient mutants of serotype g Streptococcus mutans.

Three LDH-deficient mutants of a serotype g strain of Streptococcus mutans were produced essentially as described by Hillman (1978): They were produced using ethylmethane sulfonate, and isolated using triphenyltetrazolium-glucose agar. Similar attempts to obtain mutants from a serotype c strain were unsuccessful. The g mutant did not revert during 12 weeks of daily transfer in broth, and, when grown in glucose-containing broth, they reached pH values of 4.9 to 5.0, compared with 4.4 for the parent strain. The efficiency of conversion of glucose to cell mass (Yg) was at least as great with the mutants as with the parent strain. The LDH activities of the mutants were less than 1% of that of the parent strain. Like Hillman's (1978) mutants, ethanol, acetic acid, and acetoin were the major products resulting from the metabolism of glucose. Although at pH 7.0 the mutants grew more slowly than did the parent, at pH 5 and pH 6 one of the mutants grew as rapidly as did the parent. The stability, serotype, and ability of these mutants to grow at low pH suggest their potential usefulness for replacement therapy.

Culture Media↗
PubMed1985

Serotype c Streptococcus mutans mutatable to lactate dehydrogenase deficiency.

Three lactate-dehydrogenase-deficient mutants of serotype c S. mutans were made by using, as parents, two serotype c strains that produced unusually large amounts of ethanol, acetic acid, and acetoin, and very little lactic acid, when grown in broth containing a limiting amount of glucose. The mutants, obtained with N-methyl-N'-nitro-N-nitrosoguanidine, were stable during 12 weeks of daily subculture in broth. Crude cell-free extracts of the mutants had less than 1% of the LDH-specific activity of their parent strains. The serotype c mutants resembled serotype g mutants in having molar growth yields at least as high as those of their parents. However, in contrast to the g mutants, the c mutants produced cell crops (cell mass per ml medium) that were as high as those of their parent strains.

Acetates↗
PubMed1984

Detection of interaural time differences for clicks and tone pips: effects of interaural signal disparity.

The ability to detect small interaural time differences (delta t) was determined in 4 subjects using clicks or long tone pips of various interaural signal disparities which are expressed as the extent of interaural spectral overlaps. The interaural signal disparity was varied by changing (a) the interaural pulse duration difference (delta d) for clicks, or (b) the interaural carrier frequency difference (delta f) for tone pips. In either case, the sensitivity to delta t was maximal under diotic presentations and declined with delta d or delta f. The overall sensitivity to delta t was remarkably higher for clicks than for long tone pips. The results indicate that both (a) the extent of binaural spectral overlaps and (b) the structure of acoustic stimuli are important in detecting small interaural time differences of binaural sounds.

Acoustic Stimulation↗
PubMed1984

Acute haemodynamic and myocardial metabolic effects of intravenous urapidil in severe heart failure.

The acute haemodynamic and myocardial metabolic effects of intravenous urapidil were evaluated in 12 patients with severe congestive heart failure due to coronary heart disease. Urapidil was given intravenously (0.5 mg kg-1 min-1 as a bolus) followed by infusion at a rate of 4 micrograms kg-1 min-1 for 120 min. Following urapidil administration, cardiac index increased by 29%, mean pulmonary artery wedge pressure fell by 35% and systemic vascular resistance by 33%. The fall in mean arterial pressure was moderate. No significant alterations in coronary sinus blood flow, myocardial oxygen consumption and myocardial lactate extraction occurred. No untoward effect was observed. This study shows that intravenous urapidil produces beneficial haemodynamic effects without a deleterious effect on myocardial metabolism in patients with heart failure due to coronary heart disease.

Aged↗