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J Prescott

Publications and source records attributed to J Prescott.

9 recordsLinked to original sources
PubMed1991

Rhodococcus equi plasmids: isolation and partial characterization.

Fifty-four strains of Rhodococcus equi from different clinical sources (mainly horses and pigs) were examined for their plasmid content by two screening methods. Plasmids were detected in 49 of 54 strains. A plasmid of approximately 80 kb was isolated from 21 of 22 isolates from horses and 20 of 28 isolates from pigs, and a 105-kb plasmid was isolated from 7 of 28 isolates from pigs. The 80-kb plasmid was significantly associated with strains of equine rather than porcine origin, and the 105-kb plasmid was significantly associated with strains of porcine origin. The type strain, ATCC 6939, consistently failed to yield a plasmid. Restriction enzyme analysis of purified plasmid DNA confirmed the relatedness of the 80-kb plasmids isolated from strains of equine and porcine origin. More differences between the restriction patterns of plasmids from strains isolated from horses and from pigs than among strains from either species were observed. Restriction enzyme analysis also showed relatedness of the 105-kb plasmid to the 80-kb plasmid. Three strains shown by others to be virulent in horses or mice possessed the 80-kb plasmid, whereas three other strains not virulent for horses or mice lacked the plasmid, although one had the 105-kb plasmid. There was a significant but not perfect association between the presence of the 80-kb plasmid and production of a diffuse 17.5-kDa thermoregulated, virulence-associated protein. Further study is needed to determine whether this plasmid is associated with virulence in R. equi.

Animals↗
PubMed1990

Specific DNA cleavage and binding by vaccinia virus DNA topoisomerase I.

Cleavage of a defined linear duplex DNA by vaccinia virus DNA topoisomerase I was found to occur nonrandomly and infrequently. Approximately 12 sites of strand scission were detected within the 5372 nucleotides of pUC19 DNA. These sites could be classified as having higher or lower affinity for topoisomerase based on the following criteria. Higher affinity sites were cleaved at low enzyme concentration, were less sensitive to competition, and were most refractory to religation promoted by salt, divalent cations, and elevated temperature. Cleavage at lower affinity sites required higher enzyme concentration and was more sensitive to competition and induced religation. Cleavage site selection correlated with a pentameric sequence motif (C/T)CCTT immediately preceding the site of strand scission. Noncovalent DNA binding by topoisomerase predominated over covalent adduct formation, as revealed by nitrocellulose filter-binding studies. The noncovalent binding affinity of vaccinia topoisomerase for particular subsegments of pUC19 DNA correlated with the strength and/or the number of DNA cleavage sites contained therein. Thus, cleavage site selection is likely to be dictated by specific noncovalent DNA-protein interactions. This was supported by the demonstration that a mutant vaccinia topoisomerase (containing a Tyr----Phe substitution at the active site) that was catalytically inert and did not form the covalent intermediate, nevertheless bound DNA with similar affinity and site selectivity as the wild-type enzyme. Noncovalent binding is therefore independent of competence in transesterification. It is construed that the vaccinia topoisomerase is considerably more stringent in its cleavage and binding specificity for duplex DNA than are the cellular type I enzymes.

Cloning, Molecular↗
PubMed1989

Coordinate increase in collagenase mRNA and enzyme levels in human fibroblasts treated with the tumor cell factor, TCSF.

Cocultures of human fibroblasts and LX-1 human lung carcinoma cells expressed 8-10 fold higher levels of collagenase mRNA than the sum of the individual cells, in parallel with similar increases in collagenase activity. Addition of the tumor cell collagenase stimulatory factor, TCSF, purified from LX-1 cells, to these fibroblasts also gave a 3-4 times increase in collagenase mRNA level. However, various fibroblast cell lines differed in their response to TCSF stimulation. Thus one cell line, GM 1391, did not respond to TCSF but responded to another potent collagenase stimulator, tetradecanoyl phorbol ester. Another cell line 5383 did not respond significantly to either agent. In each case collagenase activity and mRNA levels responded in a parallel fashion.

Cell Line↗
PubMed1988

Event-related potential indices of speech motor programming in stutterers and non-stutterers.

CNVs were recorded from stutterers and non-stutterers prior to spoken words which varied according to the number of syllables, whether the words were the same or different on each trial, and the degree of repetition within the word. The effects of these response parameters on slow potential activity recorded over the speech motor area were evident both prior to, and also during, the response, suggesting that the slow potentials were reflecting both speech pre-programming and ongoing programmed control. Differences between groups were only evident prior to the response, particularly when words were familiar and therefore likely to be entirely pre-programmed. This suggests that stutterers have difficulty in setting up the parameters of the response, rather than in ongoing programmed control.

Adult↗
PubMed1986

The effects of response parameters on CNV amplitude.

The contingent negative variation (CNV) was recorded using an inter-stimulus interval of 4 sec in the context of variations in the parameters of button press responses to be performed following S2. The response parameters manipulated were response duration, the number of fingers used, the number of discrete movements and the complexity of response sequences. The CNVs were averaged with reference to both the stimuli and the response. Variations in response parameters were apparent only in measures of response averaged CNVs. Negativity following response onset was also related to response parameters, again only for response-locked averages. These results support the contention that the CNV, like the Bereitschaftspotential (BP), is primarily related to response factors, and hence that the CNV and the BP are essentially the same phenomenon. It is suggested that the results indicate that negativity prior to, and possibly following, response onset represents the formulation of response-specific motor programs.

Adult↗