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Biomedical subjects

J W Lam

Publications and source records attributed to J W Lam.

8 recordsLinked to original sources
PubMed2001

Expanding the scope of chemical vapor generation for noble and transition metals.

A modified Bergener parallel path nebulizer was used for the generation of volatile metal species of Pt, Co, Ag, Cu, Rh, Pd, Au, Ni, Ir, Ti and Mn through reaction with tetrahydroborate (III). Several physicochemical factors were identified which impact on their yield which, at present, is estimated to range from 0.02-2% absolute.

Journal Article↗
PubMed2001

Rapid fabrication of three-dimensional porous films with biomimetic patterns by natural evaporation of amphiphilic polyacetylene solutions under ambient conditions.

A simple process for fast fabrication of thin films with biomimetic morphological structures from a group of linear homopolymers is developed. Natural evaporation of tetrahydrofuran, chloroform, and hexane-dichloromethane solutions of poly(phenylacetylene)s that contain amino acid and ethylene glycol moieties under ambient conditions instantly produces three-dimensional porous films with structural patterns reminiscent of honeycombs and radiolarian shells. Morphological analysis by optical and electronic microscopy suggests that vesicles of the amphiphilic polymers serve as building blocks in the self-organization to the biomimetic structures.

Acetylene↗
PubMed1982

Fatty acid synthesis in isolated spermatocytes and spermatids of mouse testis.

In vitro incorporation of [1-14C] acetate into fatty acids and lipid classes of spermatocytes, round spermatids and condensing spermatids enriched by Staput 1 X g sedimentation was measured by thin layer and gas radiochromatography. All three cell fractions showed the full range of de novo synthetase, elongation and desaturase activities necessary for biosynthesis of fatty acids characteristic of mouse testis, but synthesis of fatty acids of greater than 16 carbons declined with progressive stages of differentiation. The magnitudes and patterns of distribution of fatty acid synthesis in the germinal cells were similar to those of whole testis incubated in vitro or injected in vivo with [14C]acetate. On the other hand, complex lipid synthesis was much more variable and incorporation into triacyglycerol was generally much lower in dispersed germinal cells than in whole testis in vitro or in vivo. Cells remained viable throughout the 15-hr incubation. Thus, isolated germinal cells are fully capable of synthesizing their constituent fatty acids, including the long-chain polyenoic acids which they accumulate, but the intratubular environment or association with Sertoli cells may be necessary for maintenance of adequate complex lipid synthesis.

Acetates↗
PubMed1980

Personalized competency-based instruction applied to medical technology education.

This paper describes the development, implementation, and evaluation of a medical microbiology course employing personalized competency-based instruction offered in the upper division of an innovative medical technology education program. Also, the effectiveness of personalized instruction is discussed in terms of career mobility for clinical practitioners, competency-based achievement, mastery of learning and student/instructor--student/proctor ratio. Its role in curriculum research and development, as well as the potential for personalized competency-based instruction to improve the quality of education for clinical laboratory personnel, is discussed.

Competency-Based Education↗
PubMed1979

Electrophoresis and diffusion in the plane of the cell membrane.

Electrophoretic and diffusional movements of concanavalin A (Con A) receptors and acetylcholine (ACh) receptors in the plane of the plasma membrane of mononucleate, spherical Xenopus myoblasts were studied by microfluorimetry and iontophoresis. We found that (a) a uniform electric field of 10 V/cm applied along the cell surface produces a partial accumulation of both types of receptors toward the cathodal pole of the cell within 30 min: (b) post-field relaxation of the culture results in the complete recovery of the uniform distribution of the Con A receptors within 10 min; and (c) in contrast to the Con A receptor in general, accumulation of ACh receptors by the electric field results in the formation of stable, localized receptor aggregates. Theoretical analyses were carried out for the distribution of charged membrane receptors at equilibrium between electrophoresis and diffusion, and for the rate of back diffusion after the removal of the field. These analyses indicated that, at 22 degrees C, the average electrophoretic mobility of the electrophoretically mobile population of the Con A receptors is about 1.9 X 10(-3) micron/s per V/cm, while their average diffusion coefficient is 5.1 X 10(-9) cm2/s.

Animals↗
PubMed1978

Lateral electrophoresis and diffusion of Concanavalin A receptors in the membrane of embryonic muscle cell.

A uniform electric field of 10 V/cm applied across the surface of embryonic toad Xenopus muscle cells results in the asymmetric accumulation of concanavalin A (Con A) receptors toward one side of the cells within 10 min, as visualized by postfield fluorescent Con A labeling. This field produces an extracellular voltage difference of 20 mV across these 20-microns wide cells. The effect is reversible in two respects: (a) Additional exposure of the cell to the same field of opposite polarity for 10 min completely reverses the asymmetric accumulation to the other side of the cell. (b) Relaxation occurs after the removal of the field and results in complete recovery of the uniform distribution in 30 min. Both the accumulation and the recovery movements are independent of cell metabolism, and appear to be electrophoretic and diffusional in nature. The threshold field required to induce a detectable accumulation by the present method is between 1.0 and 1.5 V/cm (corresponding to a voltage difference of 2-3 mV across a 20-microns wide cell). The electrophoretic mobility of the most mobile population of nonliganded Con A receptors is estimated to be about 2 x 10(-3) microns/s per V/cm, while their diffusion coefficient is in the range of 4-7 x 10(-10) cm2/s. Extensive accumulation of the Con A receptors by an electric field results in the formation of immobile aggregates. The Con A receptors appear to consist of a heterogeneous population of membrane components different in their charge properties, mobility, and capability in forming aggregates.

Animals↗