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C M MACLEOD

Publications and source records attributed to C M MACLEOD.

At least 19 recordsLinked to original sources
PubMed1963

INTRASPECIES AND INTERSPECIES TRANSFORMATION REACTIONS IN PNEUMOCOCCUS AND STREPTOCOCCUS.

The efficiency of transformation of pneumococcus and a strain of viridans streptococcus (strain D) to streptomycin resistance is influenced by the species in which the mutation to resistance occurred, as well as by the species in which the mutated gene has been replicated. Pneumococcus and streptococcus strain D transform in higher frequency with DNA that has been replicated in bacteria of the same species than with DNA from the heterologous species. However, the difference between the frequencies of interspecific and intraspecific transformation is much greater with pneumococcus as receptor than with streptococcus. In addition pneumococcus transforms in higher frequency with wholly homologous (pneumococcal) DNA than with DNA from pneumococci that have replicated the streptococcal Sm(r) gene. Pneumococcus is transformed in lower frequency by wholly heterologous (streptococcal) DNA than by DNA from streptococci that have replicated the pneumococcal Sm(r) gene. Streptococcus behaves similarly in that wholly homologous (streptococcal) DNA transforms it more efficiently than when the transforming fragment contains a pneumococcal moiety. Streptococcus is transformed in the same or lower frequency by wholly heterologous (pneumococcal) DNA than by DNA from pneumococci that have replicated the streptococcal Sm(r) gene. When erythromycin resistance was used as genetic marker instead of streptomycin resistance, similar results were found.

DNA↗
PubMed1962

Alkaline phosphatase content and the effects of prednisolone on mammalian cells in culture.

The alkaline phosphatase content of different tissue culture cell lines has been shown to vary from no detectable activity to high enzyme concentration. Within the epithelial lines studied alkaline phosphatase is either constitutive or inducible. Two epithelial cell strains in which alkaline phosphatase was "absent" could be induced to develop significant amounts of the enzyme when grown in the presence of Delta(1)-hydrocortisone. Phosphate did not repress enzyme induction by prednisolone. Under conditions of deadaptation the induced enzyme was diluted by cell multiplication. The mouse fibroblastic L line and several human fibroblastic lines did not contain alkaline phosphatase when grown under the conditions described nor could they be induced to produce the enzyme when cultivated in medium with prednisolone. Delta(1)-Hydrocortisone has other characteristic effects on established mammalian cell cultures which vary among cell lines. Human epithelial lines show reduction in cell multiplication with increase in mitotic index. The cytoplasm is increased and cell volume is nearly doubled. Mouse fibroblasts show a similar reduction in cell multiplication with a decrease in mitotic index. There is no increase in cell cytoplasm. Human fibroblast strains show no inhibition of multiplication or alteration in total cell protein when grown in medium containing prednisolone. Antisera prepared against "negative" prednisolone-inducible human cell lines and against a positive human line inhibited alkaline phosphatase activity to an equal degree.

Alkaline Phosphatase↗
PubMed1959

Determination of type in capsulated transformants on pneumococcus by the genome of non-capsulated donor and recipient strains.

Capsulated transformants producing type II polysaccharide have been obtained by reactions between a number of R mutants of type II pneumococcus. All the IIR strains except II-R36 yielded extracts which transformed 2 VIIIR strains to VIIIS. Two of the IIR strains were transformed to VIIIS by an extract of 1 VIIIR strain. The most striking result was the production of both IIS and VIIIS transformants by the action of extracts of both VIIIR strains applied to cells of II-RB. This suggests that the determination of capsular type in pneumococcus does not depend on single allelomorphic genes; it seems more likely that a number of genes may be required to determine type specificity, and that some genes may be common to different types, possibly in connection with common biochemical pathways for some stages of polysaccharide synthesis. This is further indicated by the finding that extracts of capsulated strains of each of the types I, II, III, VII, VIII, XIV, and XVIII are capable of giving IIS transformants with 1 or more of the IIR strains in addition to the expected donor-type transformants. Strain II-R36 was transformed by extracts of all S types except type VII, but the only transformants found were of the donor type. It appears that II-R36 may have multiple genetic deficiencies for type II capsulation, possibly in the form of a deletion. This may be the case also with IIIS strains since only IIIS transformants were found when IIIS extract was applied to any of the IIR strains.

Polysaccharides↗