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Biomedical subjects

B Chin

Publications and source records attributed to B Chin.

54 records · Page 3Linked to original sources
PubMed1980

Automated platelet counters: a comparative evaluation of latest instrumentation.

An extensive evaluation of performance characteristics and accuracy of clinical results for two automated multiparameter whole-blood cell counters (the Coulter Counter Model S-Plus and the Ortho ELT-8) and two single-parameter semiautomated platelet counters (the J. T. Baker MK-4/HC and the Clay-Adams Ultra-Flo 100) is described. Results of comparative assays performed on more than 1,200 clinical specimens are analyzed. These results are compared with manual determinations where appropriate. Particular attention is accorded to the accuracy of platelet counts, especially at abnormal levels below 70 X 10(3)/cu mm, where falsely elevated platelet counts may lead to serious clinical consequences. Both multiparameter instruments yielded accurate results, with the exception of low values reported by the ELT-8 for mean corpuscular volumes above 100 cu micrometer. Results for platelet counts were accurate for most specimens on all four instruments; the ELT-8 was the most reliable (P < 0.01), especially for the critically low counts. Although no instrument is infallible in determining platelet counts at all levels, the authors conclude that addition of platelet-counting capability represents a significant advancement over existing instrumentation.

Evaluation Studies as Topic↗
PubMed1980

Effect of phenolic antioxidants on the mutagenicity of aflatoxin B1.

The Ames assay employing Salmonella typhimurium TA100 and TA98 was used to investigate potential interactions between aflatoxin B1 (AFB1) and the phenolic antioxidants butylated hydroxytoluene, butylated hydroxyanisole, and propyl gallate. AFB1 doses were within the linear response range, and the antioxidants were used at levels of 0 to 50 micrograms per plate. All three antioxidants were nonmutagenic in either bacterial tester strain, with or without the hepatic S-9 enzyme preparation; toxic effects were observed at doses higher than 20 micrograms per plate. Butylated hydroxytoluene and butylated hydroxyanisole substantially increased AFB1-induced mutagenesis in the two tester strains with microsomal activation. The addition of 5 to 20 micrograms of butylated hydroxytoluene or hydroxyanisole to 5 to 20 ng of AFB1 per plate caused more than a twofold increase in the number of His+ revertants. Addition of propyl gallate resulted in only a moderate increase in the number of revertants. Whereas several anticarcinogenic and antimutagenic effects by phenolic antioxidants have been reported, particularly in studies with polycyclic aromatic hydrocarbons, the enhancement of mutagenic potency of AFB1 by these compounds suggests a specificity with respect to the chemical nature of AFB1.

Aflatoxins↗
PubMed1977

Individual renal clearances determined at renal vein catheterization.

Renal para-aminohippurate (PAH) clearances were predicted in 16 kidneys of eight hypertensive patients with renal artery stenosis, pyelonephritis, or obstructive nephropathy, without individual ureteral catheterization. Predictions of left or right kidney clearance (CL or CR) were based on roentgenographic renal frontal areas (A), on total PAH clearances (CT), and on individual PAH extractions (E) measured at renal vein catheterization according to the formula (formula: see text). When these patients underwent ureteral catheterization for diagnostic reasons, individual PAH clearances were measured and ranged from 22 to 286 cm3/min. After correction for differences in total PAH clearance on the two occasions, predicted and individually measured values corresponded closely along a line of identity. The 95% confidence limit (+/- 2 SEM) for predictions of individual PAH clearance was approximately +/- 38 cm3/min and for percet of total PAH clearance distributed to left or right kidney, +/- 6%. Individual renal PAH clearances can therefore be predicted at renal vein catheterization with acceptable error. Thus, the substantially invasive procedure of ureteral catheterization is not required to ascertain left and right kidney PAH clearance in patients already at risk from renal disease.

Adolescent↗
PubMed1975

Molecular mechanisms of accommodation in Escherichia coli to toxic levels of Cd2+.

Cells of Escherichia coli strain B develop large intracellular vacuoles and exhibit an abnormally long lag phase when inoculated into a defined medium to glucose and salts containing 3 times 10-6 M Cd2+. Early in this lag, about 95% of the cells fail to form colonies when plated on nutrient broth-NaCl-agar. Prior to the initiation of proliferation, the morphology of these cells becomes normal. They regain viability in the absence of deoxyribonucleic acid replication. The rate and extent of growth are normal once proliferation begins. This reversible phenomenon of accommodation to a growth-inhibiting concentration of Cd2+ does not appear to result from a selection of mutant cells. Cells which are proliferating in the presence of Cd2+ accumulate the ion to a very high concentration. In membranes and 31% in the cytoplasm. In unaccommodated cells, the figures are 2%, 75%, and 23%, respectively. The activity of alkaline phosphatase, a zinc-metalloenzyme which is inhibited by cadmum and is located between cell wall and membrane, is not abnormally low in accommodated cells, suggesting that the cadmim is compartmentalized in these cells. Molecular sieve chromatography of cell extracts shows that the Cd2+ is associated with two classes of macromolecules. It appears that accommodation of E. coli to the presence of Cd2+ involves exclusion of the ion from the cell and reversal of damage caused by prior exposure to the ion.

Adaptation, Biological↗
PubMed1968

Adenosine triphosphate and synchronous mitosis in Physarum polycephalum.

Synchronous mitoses occur in Physarum polycephalum in the absence of cell division. Nucleoside and nucleotide profiles were prepared from synchronously growing P. polycephalum at intervals throughout the growth cycle. Comparison of these profiles demonstrates that the pool of adenosine triphosphate decreases from a high level at prophase to a minimum through mitosis and increases again in the postmitotic period. These events appear to coincide with changes in the pools of adenosine diphosphate and adenosine but not with that of adenosine monophosphate. This observed decrease in the pool of adenosine triphosphate during mitosis was confirmed by direct enzymatic assay. These results presumably reflect the energy demands of the cell during mitosis.

Adenine Nucleotides↗
PubMedDate not supplied

Gene rearrangement in cells with natural killer activity and expression of the beta-chain of the T-cell antigen receptor.

The mammalian host defence system can be divided broadly into adaptive and non-adaptive immunity. Adaptive immunity is acquired and is mediated by B and T lymphocytes. Non-adaptive immunity is mediated in part by a small subclass of heterogeneous peripheral blood mononuclear cells. This population, termed null cells, consists of haematopoietic precursors and cells mediating natural killer (NK) activity and antibody-dependent cellular cytotoxicity (ADCC). NK cells are a class of non-adherent, non-phagocytic, rapidly cytotoxic lymphocytes which can efficiently lyse a wide variety of tumour cells, virally infected cells and immature cell types of normal origin. Despite the broad range of targets, only a limited number of specificities are thought to be involved in target-cell recognition. Morphologically, NK cells are large granular lymphocytes, but they have been shown to exhibit cell-surface markers characteristic of both T cells and monocytes, raising doubt over their lineage. The recent cloning of the beta-chain of the T-cell antigen receptor has now allowed us to investigate whether some NK cells are T-cell-related. We have examined rearrangement and expression of the beta-chain of the T-cell receptor in cloned murine NK cell lines and fresh murine NK cell populations, and our results support the hypothesis that a subpopulation of NK cells is related to T cells and provide basis for examining whether some NK activity is mediated by a small number of T-cell receptors.

Animals↗
PubMedDate not supplied

A new model for computerized clinical electron beam dosimetry.

Clinical electron beams consist of primary electrons, primary bremsstrahlung generated in the regular photon and electron collimator system determining the composite beam, and some short-range contaminant photon and electron scatter arising from the lower parts of the standard or regular electron applicator. Any beam-shaping insert placed inside the applicator causes some extra ("contaminant") bremsstrahlung and electron scatter. The new dose calculation model is based on separate treatment of these components. For the calculation of the primary electron dose we use experimentally determined electron scatter functions and differential electron scatter functions. The primary bremsstrahlung is treated as an unflattened but otherwise regular x-ray beam. The contaminant components arising from the rim area of the regular electron collimator and from beam-shaping inserts are considered separately. The behavior of the in-air ionization profiles is described using the concepts of effective electron source position and effective electron source diameter. The model has been tested for several electron energies.

Computer Simulation↗