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Biomedical subjects

L Green

Publications and source records attributed to L Green.

At least 307 records · Page 17Linked to original sources
PubMed1973

Comparison of three culture media for isolation of Mycobacterium tuberculosis: a 6-year study.

Among 2,648 specimens positive on culture for Mycobacterium tuberculosis over a 6-year period, 82% grew on Lowenstein-Jensen medium (LJ), 79% on American Trudeau Society (ATS), and 56% on Middlebrook 7H10 (7H10). When these commercial culture media were compared in regard to the number of acid-fast bacilli seen on the original smears, LJ cultures were found to have the highest isolation rates for each smear category, and 7H10 had the lowest rates. Comparing the media from the aspect of number of mycobacterial colonies produced, LJ and ATS had the highest average colony counts, followed by 7H10. These findings were relatively constant over the 6-year period. One possible reason for the low positive rate of 7H10 was the lack of CO(2) enrichment.

Bacteriological Techniques↗
PubMed1972

Commitment, choice and self-control.

When offered a choice (Choice Y) between a small immediate reward (2-sec exposure to grain) and a large reward (4-sec exposure to grain) delayed by 4 sec, pigeons invariably preferred the small, immediate reward. However, when offered a choice (Choice X) between a delay of T seconds followed by Choice Y and a delay of T seconds followed by restriction to the large delayed reward only, the pigeon's choice depended on T. When T was small, the pigeons chose the alternative leading to Choice Y (and then chose the small, immediate reward). When T was large, the pigeons chose the alternative leading to the large delayed reward only. The reversal of preference as T increases is predicted by several recent models for choice between various amounts and delays of reward. The preference for the large delayed alternative with long durations of T parallels everyday instances of advance commitment to a given course of action. Such commitment may be seen as a prototype for self-control.

Journal Article↗
PubMed1971

Establishment and maintenance of repression by bacteriophage lambda: the role of the cI, cII, and c3 proteins.

To define the events necessary for the establishment and maintenance of repression in a lambda-infected cell, we have studied the requirements for efficient synthesis of the cI protein ("lambda-repressor"). Three classes of lambda mutants defective in the establishment of repression are also defective in the appearance of cI protein activity at the normal time. Two of these mutational classes (cII(-) and cIII(-)) probably result from inactivation of lambda-specified proteins, but the third class (cy(-)) may involve a structural defect. We conclude that at least three regulatory elements are likely to be required for the normal turn-on of cI protein synthesis in an infected nonlysogenic cell: cII and cIII proteins and an "active" y-region of lambda DNA. From these and other results, the complete role of cII and cIII proteins in the establishment of repression may involve a bifunctional regulatory activity: positive regulation of the cI gene and negative regulation of late genes. A possible molecular model for cII and cIII action is discussed. Since the cII and cIII genes are repressed by the cI protein under conditions of stable lysogeny, a separate mechanism is required for the maintenance of cI protein synthesis. After infection of a lysogen by cII(-) phage, the rate of increase of cI protein activity is substantially greater than after infection of a nonlysogen. From these and other results, the cI protein may also have a bifunctional regulatory activity: positive regulation of the cI gene and negative regulation of early lytic genes.

Autoradiography↗
PubMed1970

Growth of Venezuelan equine encephalomyelitis virus in human diploid cell strain WI-38.

We demonstrated that Venezuelan equine encephalomyelitis (VEE) virus replicated in and adapted rapidly to human diploid cell strain WI-38. Peak titers of approximately 10(9.8) mouse intracerebral 50% lethal doses were obtained at low passage levels in Eagles basal medium supplemented with calf serum. VEE virus replicated poorly in serum-free medium. Propagation of VEE virus was accompanied by the production of hemagglutinin and cytopathogenic effects.

Antibodies↗
PubMed1970

Gamma-irradiated Venezuelan equine encephalitis vaccines.

The efficacy of Formalin-inactivated Venezuelan equine encephalitis (VEE) vaccine has been reported to be low for man. Although a live VEE vaccine has been shown to be highly effective for the protection of laboratory workers, local and systemic reactions have occurred in approximately 20% of inoculated individuals. Therefore, studies were initiated in an attempt to produce an inactivated vaccine of high potency with low toxicity. Inactivated VEE vaccines were prepared by exposing virus suspensions to 8 x 10(6) or 10 x 10(6) r of gamma radiation. Irradiated VEE vaccines prepared from virus suspensions produced in Maitland-type chick embryo (MTCE) cell cultures and in monolayer cultures of human diploid strain WI-38 cells were highly immunogenic for mice and guinea pigs. Guinea pigs vaccinated with a series of three inoculations of vaccine (MTCE) survived challenge with at least 10(8.4) mouse intracerebral 50% lethal doses of VEE virus. Irradiated vaccines induced high levels of serum-neutralizing and hemagglutinin-inhibiting antibodies in guinea pigs and rabbits. These findings suggest that ionizing radiation may be effective in the preparation of an inactivated VEE vaccine.

Animals↗
PubMed1970

Clinical laboratory personnel: is there a shortage in California?

In a study of vacancy rates for laboratory personnel in California to determine if there is in fact a serious or critical shortage of qualified individuals in this group of allied health professionals, it was found that while the answer is still elusive, it would appear that although the shortage may be somewhat greater than normal it is not critical in most areas of the state. For most areas, the situation seems to have improved from 1966 to 1968. There are a few geographical areas, predominantly rural, where shortages of licensed personnel are critical. Vacancy rates also are higher in hospital laboratories. Recruitment difficulties in these situations may be related to insufficient incentives, including but not necessarily limited to salaries. Training in California laboratories may facilitate recruitment in specific instances, and may assume greater importance in the future as working conditions for health professionals continue to improve in other states. And finally, the use of laboratory assistants, aides, and clerks can materially assist the laboratory work, thereby freeing the licensed professional staff to accept responsibilities commensurate with the increasing sophistication of laboratory knowledge and practice.

California↗