Biomedical subjects
M Etkin
Publications and source records attributed to M Etkin.
Use of cell-free retroviral vector preparations for transduction of cells from the marrow of chronic phase and blast crisis chronic myelogenous leukemia patients and from normal individuals.
Marrow cells were exposed to the LNL6 or G1N safety-modified variants of the N2 retrovirus, which contain the G418 bacterial resistance gene neo. The frequency of acquisition of the G418 resistance phenotype following exposure to LNL6 or G1N was compared among hematopoietic progenitor cells from the marrow of patients with chronic phase chronic myelogenous leukemia (CML), blast crisis CML, or from nonleukemic individuals. Under the conditions of our experiments, the myeloid committed progenitor cells from 3 of 6 nonleukemic individuals, 9 of 18 chronic-phase CML patients, and 2 of 4 blast crisis CML patients acquired resistance to at least 1 mg/ml G418 following incubation with cell-free supernatants from the PA317 LNL6 or PA317 G1N producer cell lines. Ten of the 32 colonies growing up in 0.8 mg/ml G418 from chronic-phase marrow exposed to LNL6 were shown to contain the neo gene by polymerase chain reaction (PCR) assay of DNA. These results were consistent with estimates of the transduction frequency based on acquisition of resistance to G418 as the number of colonies growing under G418 selection was always greater at 0.8 mg/ml G418 than at higher concentrations of G418 (1.0-1.4 mg/ml). The average transduction frequency at each G418 concentration (1.0, 1.2, and 1.4 mg/ml) in cells from blast crisis CML cells ranged from 2 to 14%, as measured by acquisition of G418 resistance. Chronic-phase CML showed slightly lower average frequencies of transduction (0.6-2.8% of the colonies are G418 resistant). The average transduction frequency of cells from nonleukemic marrow was as high as that seen from the marrow of chronic-phase CML individuals.(ABSTRACT TRUNCATED AT 250 WORDS)
Molecular approaches to purging of chronic myelogenous leukemia marrow in autologous transplantation.
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Primary mesenchyme cells of the sea urchin embryo require an autonomously produced, nonfibrillar collagen for spiculogenesis.
A collagen molecule in the sea urchin embryo was characterized by analysis of a 2.7-kb cDNA clone. This clone, Spcoll, was obtained by screening a gastrula stage Strongylocentrotus purpuratus cDNA library with a 237-bp genomic clone encoding a collagen-like sequence previously isolated by Venkatesan et al. (1986). DNA sequence analysis of the cDNA clone demonstrated the nonfibrillar nature of the encoded molecule--13 interruptions of the Gly-X-Y repeat motif were found in the 85-kDa open reading frame. The mRNA of approximately 9 kb accumulated specifically in mesenchyme cells of the embryo through development to the pluteus larva. Polyclonal antibodies generated against a Spcoll-beta-galactosidase fusion protein were utilized to identify and localize the native Spcoll. This collagen molecule of approximately 210 kDa was deposited into the blastocoel by the primary mesenchyme cells. When primary mesenchyme cells were cultured in vitro, Spcoll was secreted into the media and accumulated at sites of cell-substrate interaction. Addition of anti-Spcoll antibodies to primary mesenchyme cell cultures selectively inhibited spiculogenesis, whereas other antibodies had no inhibitory effect. Since collagen is not a component of the organic matrix of spicules (Benson et al., 1986), these results suggest that the autonomous production of Spcoll by differentiating mesenchyme cells in turn influences the point in differentiation at which these cell initiate biomineralization.
Emotional loading in dyadic interviews.
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Anticipatory responding and avoidance discrimination as factors in avoidance conditioning.
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Effects of shock type and intensity on anticipatory responses.
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Cue-producing behavior in the Capuchin monkey during reversal, extinction, acquisition, and overtraining.
In a two-choice discrimination situation, a cue-producing response produced the discriminanda for 0.05 sec. The cue-producing responses beyond those normally necessary to identify the discriminanda thus provided only redundant information. Two of the four Capuchin monkeys studied showed a large increase in cue-producing responses during reversal learning and extinction, and they reversed much faster than the two whose cue-producing responses showed little increase. During acquisition of a difficult discrimination, the cue-producing responses of the first two subjects reached a high level and during overtraining gradually reduced to their initial low level. The results were related to Wyckoff's theory of observing behavior and to the notions of uncertainty, reduction, and lack of information as extensions of the concepts of reinforcement and motivation.
Discriminated bar-press avoidance maintenance and extinction in rats as a function of shock intensity.
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