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Biomedical subjects

A Campbell

Publications and source records attributed to A Campbell.

At least 271 records · Page 15Linked to original sources
PubMed1977

Interocular transfer of visual discriminations in goldfish after selective commissure lesions.

Goldfish with transections of the intertectal commissure learned but failed to transfer interocularly a simple visually cued avoidance task in a shuttle box, whereas posterior commissure lesions had no effect on this simple transfer task. However, fish with tectal commissure lesions could show normal interocular transfer of a shape discrimination, once discrimination pretraining with color cues had been carried out with each eye separately. Lesions of anterior commissure had no effect on either shape or color transfer, but fish with intended cuts of the postoptic commissures showed striking deficits of interocular transfer. As with comparable studies in the pigeon, it is concluded that postoptic, but not tectal, commissures are required for interocular transfer in the goldfish.

Animals↗
PubMed1976

Significance of constitutive integrase synthesis.

One conceivable function for constitutive integrase formation by lambda prophage is to stabilize the inserted state by catalyzing reinsertion of prophages that are accidentally excised. As this hypothesis implies a dynamic equilibrium betwen inserted and noninserted DNA, the existence of such an equilibrium is explored. By examining the frequency with which prophages appear in an initially unoccupied chromosomal site of a lysogenic bacterium in which the prophage attachment site is duplicated, the off-rate is estimated as less than 10(-2) per generation for wild-type lambda, and less than 4 x 10(-4) for N- mutants of lambda. From the rate of integrase-catalyzed haploidization of certain partial diploid strains, the rate of spontaneous integrase activity is estimated as 3 x 10(-3) per generation. From these values I conclude that constitutive integrase will not appreciably stabilize the inserted state by virtue of its known activity.

Coliphages↗
PubMed1975

The orthomolecular treatment of cancer. III. Reticulum cell sarcoma: double complete regression induced by high-dose ascorbic acid therapy.

The response of a patient with histologically proven reticulum cell sarcoma to no treatment other than large doses of ascorbic acid is described. At the time of first diagnosis, the disease was widely disseminated, and a very dramatic regression of all parameters of disease activity was induced by the continuous administration of large doses of ascorbic acid. Reduction in dosage some months later coincided with reactivation of the disease process. The reinstitution of regular high-dose ascorbic acid therapy induced a second complete remission. The case report is illustrated by serial radiographs. The significance of the therapeutic response is briefly discussed in relation to general schemes of cancer management.

Adult↗
PubMed1975

Inhibition of development in Dictyostelium discoideum by sugars.

Sugars such as glucose, maltose, and trehalose, which are metabolized by Dictyostelium discoideum and which enhance vegetative growth, inhibit the development of the slime mold at concentrations which stimulate growth maximally. They block the acquisition of aggregation competence as well as aggregation. The same sugars also inhibit the degradation of preformed glycogen ribonucleic acid, and protein, which is characteristic of development and which occurs when the amoebas are starved by incubation in dilute phosphate buffer.

Carbohydrates↗
PubMed1974

Int-constitutive mutants of bacteriophage lambda.

The constitutive production of small amounts of trpB enzyme in an Escherichia coli strain carrying lambdacI857 prophage within the trpC gene has been examined in derivatives of this strain from which portions of the prophage have been deleted. Enzyme production requires a site (p(I)) within the prophage close to the left prophage end. Selection for mutants of this lysogen that grow on low concentrations of indole yielded two types of mutations within the prophage: (a) v2-type, in which all phage genes controlled by the major leftward operator are derepressed; and (b) int-c type, in which the only phage gene derepressed is int. The int-c mutations lie in the same part of the prophage as p(I). All int-c mutants appear deficient in xis gene function, even when derepressed.

Chromosome Mapping↗
PubMed1974

A deletion mutation placing the galactokinase gene of Escherichia coli under control of the biotin promoter.

A deletion has been isolated which fuses galK and presumably galT to the promoter and operator of the bioA operon. The deletion has endpoints in bioA and galE, and leaves the operator-proximal end of bioA intact and the regulatory sites themselves functional. In bacterial strains which carry the deletion, the expression of galK is regulated by biotin, although due to the inefficiency of the bioA promoter even the fully derepressed level of galactokinase is low. Electron micrographic examination of the mutation shows that it is a simple deletion, uncomplicated by other chromosomal abnormalities.

Biotin↗
PubMed1974

DNA polymerase I-dependent mutants of coliphage lambda.

Mutagenized lysates of bacteriophage lambda were screened for mutants unable to plate on DNA polymerase I-deficient (polA(-)) hosts. The mutants obtained were all recombination deficient (red(-)). These mutants, like red(-) and gam(-) mutants previously isolated by others, grow more poorly than wild-type lambda even on polA(+) hosts (burst size 14 to 30% of wild-type lambda.) In a polA(-) host, the burst size of red(-) and gam(-) mutants is reduced an additional five- to tenfold, and lysis is delayed. Wild-type lambda grows normally in polA(-) hosts. Neither lambdaN(-)nin (which doesn't express red or gam) nor lambdabio phages (from which all or part of the red-gam region is deleted) form plaques on polA(-) hosts. Apparent revertants, able to plate on polA(-) hosts, have been selected from both lambdaN(-)nin and lambdabio. Those derived from N(-)nin seem to be N(-)nin cro(-) mutants; whereas those coming from lambda bio have a new bypass mutation (pas) that lies between genes P and Q.

Chromosome Mapping↗