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D Luk

Publications and source records attributed to D Luk.

25 records · Page 2Linked to original sources
PubMed1982

Genetic recombination in avian retroviruses.

The avian retroviruses--and probably other retroviruses as well--undergo a variety of recombinational events with relatively high efficiency. An understanding of the molecular basis of these events should provide insight into the important biological properties these agents exhibit when they become integrated into somatic or germ-line host cells, when they exchange genetic information among themselves, or when they transduce host cell genes. In this article we review molecular models for homologous recombination, against a background of the other types of recombination events that are typical of these viruses. It seems probable that the retroviruses will provide useful models for analysis of a variety of DNA rearrangements known to occur in eukaryotic cells.

Animals↗
PubMed1982

Purified matrix protein of vesicular stomatitis virus blocks viral transcription in vitro.

One of the major structural proteins of vesicular stomatitis virus is a small, nonglycosylated, matrix protein which associates with the nucleocapsid core during final stages of morphogenesis and budding. Biochemical and genetic studies suggested that the matrix protein regulates RNA synthesis both in vitro and in vivo. We have purified biologically active matrix protein from the virus and have directly shown that it significantly inhibits RNA synthesis in vitro mediated by the virion-associated RNA polymerase at low ionic strength (0.02 M). The inhibition was greater than 80% when the ratio of matrix protein to the major nucleocapsid protein in the transcribing complex was 2:1 (wt/wt). The inhibition was found to be at the level of RNA chain elongation and not at the initiation step. Electron microscopic studies revealed that inhibition of transcription by matrix protein was accompanied by a profound structural change of the transcribing nucleocapsid from an extended structure to a highly compact form. At higher ionic strength (0.12 M), the matrix protein failed to interact with the nucleocapsid. The matrix protein appears to be involved in condensing the nucleocapsid and blocking transcription during maturation of the virus particle.

Gene Expression Regulation↗
PubMed1977

Cortical thickness measurements and photon absorptiometry for determination of bone quantity.

Reproducibility of estimates of cortical bone quantity in the appendicular skeleton by two methods was studied in healthy individuals and patients undergoing long-term hemodialysis. Repeated measurements of cortical thickness (CT) at the midpoint of the second metacarpal were taken from single radiographs of both hands by two independent observers. Repeated measurements by the same observer were more reproducible and the degree of reproducibility was far greater in healthy subjects than in dialysis patients. Repeated measurements were made of bone mineral content (BMC) and bone width (W) of the distal radius by photon absorptiometry. Repeated BMC/W determinations were highly reproducible in both healthy subjects and dialysis patients. High correlation was found between BMC and cross-sectional cortical area and between both simple cortical thickness and cortical area/width. Thus the photon absorptiometric technique is superior for the serial monitoring of bone quantity, particularly in patients with uremic osteodystrophy, but results obtained by the two methods in group studies should be comparable.

Adult↗
PubMed1972

Large-scale production of lambda bacteriophage and purified lambda deoxyribonucleic acid.

Large amounts of a heat-inducible phage lambda mutant (lambdaCI857) may be obtained under standardized conditions. The phage is harvested by simple polyethylene glycol (C 6000) precipitation and purified by CsCl density gradient banding. Deoxyribonucleic acid (DNA) is extracted by cold phenol and purified by sucrose density gradient sedimentation to yield a homogenous population of unbroken lambda DNA molecules.

Cell Count↗