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Biomedical subjects

Y L Chan

Publications and source records attributed to Y L Chan.

At least 217 records · Page 12Linked to original sources
PubMed1979

Plasmapheresis in glomerulonephritis.

Plasmapheresis together with immunosuppressive drug therapy has been used in the treatment of 17 patients with glomerulonephritis [Goodpasture's syndrome (4), systemic lupus erythematosus (4), mesangiocapillary glomerulonephritis (2), glomerulonephritis associated with cirrhosis (2), nonspecific mesangial proliferative glomerulonephritis (3), Henoch-Schoenlein purpura glomerulonephritis (1) and glomerulonephritis associated with infective endocarditis (1)]. Use of the Haemonetics Model 30 blood cell separator, exchanging two liters of plasma with 5% albumin in Hartmann's solution has provided a safe, effective but relatively expensive procedure, capable of producing a marked reduction of fibrinogen, complement components, anti-glomerular basement membrane antibody and immune complex concentrations. Removal of one or more of these factors is felt to be at least partly responsible for the improvement in renal function and clinical well-being demonstrated in patients with Goodpasture's syndrome, systemic lupus erythematosus and other forms of glomerulonephritis associated with the presence of circulating immune complexes.

Adolescent↗
PubMed1978

Degradation of phenylalanine:pyruvate transaminase after glucagon treatment.

Using a single-isotope and immune precipitation technique the half-life (t 1/2) of hepatic phenylalanine:pyruvate transaminase (aminotransferase, EC 2.6.1.--, Number not yet assigned) from glucagon-treated rats was determined to be 2.8 days, similar to that of the control rats (t 1/2 = 3.3 days). The half-life of rat liver total soluble proteins also remained unchanged after glucagon treatment (t 1/2 = 2.7 days in glucagon-treated rats; t 1/2 = 2.8 days in normal). Thus, glucagon has no effect on the degradation of phenylalanine:pyruvate transaminase. Furthermore, the degradation rates are similar for both the holoenzyme and the apoenzyme of phenylalanine:pyruvate transaminase.

Animals↗
PubMed1978

GLC determination of caffeine in plasma using alkali flame detection.

A rapid, specific, and sensitive GLC assay for caffeine in plasma was developed utilizing alkali flame-ionization detection. The procedure involves the addition of mepivacaine as an internal standard, alkalinization of the sample, and extraction with chloroform. Peak height ratio measurements produced linear standard curves in the 0.25-10.0-microgram/ml range. Absolute sensitivity from a 1.0-ml plasma sample was 0.1 microgram/ml. The relative standard deviation of a 2.0-microgram/ml pooled plasma standard run repeatedly over several months was 5.2%. The method is applicable to time-concentration studies in human and animal plasma following typical oral doses of caffeine.

Animals↗
PubMed1977

Paraquat poisoning is not necessarily fatal.

This paper describes a case of deliberate ingestion of paraquat successfully managed with gastric lavage, forced diuresis, haemodialysis, gastrointestinal purgation and the adminstration of specific adsorbents.

Adult↗
PubMed1977

Effect of parathyroid hormone and cyclic adenosine 3',5'-monophosphate on isotonic fluid reabsorption: polarity of proximal tubular cells.

Isotomic fluid reabsorption (JV) of rat renal proximal tubules was examined by the shrinking droplet method in combination with simulatneous perfusion of blood capillaries. Sensitivity of JV measurement was improved by using each punctured tubule for control measurements: 1) Parathyroid hormoen (PTH) on the contraluminal cell side reduced JV in a dose-response behavior. The maximal inhibition was achieved at a PTH concentration of 10(-5) M, the half maximal inhibition at a concentration of 3 X 10(-9) M. PTH on the luminal cell side had a small inhibitory effect. 2) Cyclic AMP inhibited JV preferentially when applied to the luminal cell side. On the luminal cell side, both cyclic AMP and dibutyryl cyclic AMP inhibited JV in a similar dose-dependent behavior. Concentrations of both nucleotides as low as 10(-10) M had a definite inhibitory effect. Tested at a high concentration, N6-butyryl cyclic AMP was almost as effective as cyclic AMP. Deoxy cyclic AMP, 5' AMP, cyclic guanosine monophosphate (cyclic GMP), dibutyryl cyclic GMP had no effect. ATP inhibited JV to a very small extent. 3) The reduction of JV after administration of PTH and dibutyryl cyclic AMP was not additive. The similar inhibitory effect of PTH at the contraluminal cell face and of cyclic AMP at the luminal cell face suggests the following sequence of events in the mediation of the action of PTH: 1) activation of adenylate cyclase by PTH in the contraluminal cell membrane, and 2) action of the generated cyclic AMP on the luminal cell membrane. The interaction of cyclic AMP and the luminal cell membrane is initiated at the luminal cell surface.

Absorption↗
PubMed1977

IgA nephropathy: a syndrome of uniform morphology, diverse clinical features and uncertain prognosis.

Isolated glomerulonephritis with mesangial IgA deposits was the most common single finding encountered in a large biopsy series in an Australian community and was found in 50 patients, 18% of those presenting for the investigation of primary glomerular disease. A uniform histopathological picture of mesangial enlargement, with or without focal and segmental features was present. A tendency to progression was suggested by the frequent presence of glomerulosclerosis, interstitial scarring and vascular hyalinization. Because of the uniform histological immunofluorescence and ultrastructural appearances, the term IgA nephropathy has been used for this condition. The clinical picture, however, was heterogenous. Presenting symptoms included macroscopic hematuria (34%), proteinuria (32%) acute nephritis (10%), nephrotic syndrome (6%), malignant hypertension (8%), acute renal failure (6%) and chronic renal failure (4%). There was a striking correlation of increased blood pressure and decreased renal function with increasing age. While the period of follow-up was too short to assess individual patient data, a gradual and progressive decrease in renal function over several decades is suspected in patients with this condition.

Adolescent↗
PubMed1976

Cellular mechanisms of renal tubular transport of I-dopa and its derivatives in the rat: microperfusion studies.

Proximal tubular transport of L-3,4-dihydroxyphenylalanine (L-dopa) and its derivatives were studied in the rat kidney by microperfusion and capillary perfusion techniques in situ. With the use of microperfusion techniques alone, it was found that L-dopa, L-3-methoxy-4-hydroxyphenylalanine, L-tyrosine and L-phenylalanine rapidly disappeared from the perfusate. The rates of reabsorption were calculated to be 2.05 X 10(-12), 2.13 X 10(-12), 6.35 X 10(-12) and 7.14 X 10(-12) mol/cm/sec, respectively. In contrast, L-alpha-methyldopa and dopamine were only slightly reabsorbed. The permeability coefficients were calculated to be 0.35 X 10(-4) and 0.21 x 10(-4) and 0.21 x 10(-4) cm/sec, respectively. The rate of reabsorption of L-dopa was greatly reduced in the presence of L-phenylalanine in the perfusate, but was not affected by D-dopa. With the stop-flow microperfusion technique with simultaneous capillary perfusion, the zero net flux transtubular concentration difference (deltaC) of labeled dopa was measured. When the initial concentration of 2 mM labeled L-dopa was perfused, the luminal concentration fell to a plateau level of 1.5 mM after a contact time of 20 seconds; i.e., deltaC was 0.5 mM. The net flux was much less than the efflux, suggesting the presence of a secretory or passive back flux of L-dopa. The deltaC of L-dopa was not influenced by the decarboxylase inhibitor, MK-486, and monoamine oxidase inhibitor, pheniprazine, but was significantly reduced by NaCN. Thus the reabsorption of L-dopa in the proximal convoluted tubule is an active process with great structural specificity.

Absorption↗
PubMedDate not supplied

The primary structure of rat ribosomal proteins P0, P1, and P2 and a proposal for a uniform nomenclature for mammalian and yeast ribosomal proteins.

The covalent structures of rat ribosomal proteins P0, P1, and P2 were deduced from the sequences of nucleotides in recombinant cDNAs. P0 contains 316 amino acids and has a molecular weight of 34,178; P1 has 114 residues and a molecular weight of 11,490: and P2 has 115 amino acids and a molecular weight of 11,684. The rat P-proteins have a near identical (16 of 17 residues) sequence of amino acids at their carboxyl termini and are related to analogous proteins in other eukaryotic species. A proposal is made for a uniform nomenclature for rat and yeast ribosomal proteins.

Amino Acid Sequence↗
PubMedDate not supplied

On the conformation of the alpha sarcin stem-loop of 28S rRNA.

A synthetic RNA that is a substrate for the cytotoxin alpha sarcin has been examined by NMR. The molecule in question includes the entire sequence of the so-called alpha sarcin loop from rat 28S rRNA (U4316-C4332), and it is cleaved at the residue that corresponds to G4325, the site of alpha sarcin cleavage in 28S rRNA. The data show that the terminal stem designed into the molecule's sequence exists, as expected, and that its loop has a definite structure, which is stable to at least 40 degrees C under ionic conditions compatible with its cleavage by alpha sarcin.

Animals↗
PubMedDate not supplied

Diagnosing paediatric mediastinal lipoblastoma using ultrasound-guided percutaneous needle biopsy: review and report.

Lipoblastoma is a rare tumor of embryonal fat occurring predominantly in the first three years of life. This benign tumor has potentials to local invasion and rapid growth. We reported a rare case of mediastinal lipoblastoma. The computed tomography (CT) and ultrasound (US) features, and the roles of percutaneous transthoracic US-guided needle biopsy, are discussed.

Biopsy, Needle↗
PubMedDate not supplied

Ultrasonographic hip morphometry in infants.

Ultrasonographic study of 463 normal children (926 hips) from birth to 6 months of age with equal sex distribution was performed. Hip morphometry, including Graf's alpha and beta angles. Morin's head coverage percentage, and head size were measured. Using the same technique, a group of 52 babies was measured longitudinally from birth to 6 months of age, with three measurements taken for each hip for a total of 312 measurements. Results showed that the boys had a consistently higher alpha angle, a lower beta angle, better head coverage, and larger head size through the 6 months. Differences between the right and left hips were only noted in the beta angle. The containment of the hip was found to increase rapidly in the first 4 months. Comparing data from the longitudinal versus the cross-sectional group, no statistically significant differences were detectable in all the parameters measured. Intraobserver variations were found to be best with alpha angle measurements, with a standard deviation of 3.22 degrees.

Age Distribution↗