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Biomedical subjects

P R Cook

Publications and source records attributed to P R Cook.

142 records · Page 8Linked to original sources
PubMed1977

The superhelical density of nuclear DNA from human cells.

Structures resembling nuclei may be released by gently lysing human cells in solutions containing non-ionic detergents and high concentrations of salt. These structures, which we call nucleoids, sediment in sucrose gradients containing the intercalating agent, actinomycin D, in the manner characteristic of superhelical DNA. We have determined the concentration of actinomycin that minimises the rate of sedimentation of nucleoids. At this concentration, we have determined the amount of drug bound per base pair of DNA by means of a double-labelling procedure. Assuming that each molecule of actinomycin bound to nucleoid DNA unwinds the double helix by 26 degrees, we calculate that there is one supercoil every 90-180 base pairs in nucleoid DNA. These values lie within the range found for the circular DNA molecules of plasmids and viruses.

Binding Sites↗
PubMed1976

Conformational constraints in nuclear DNA.

We have investigated DNA superstructure in a wide range of nuclei of higher cells by gently lysing cells to release structures that resemble nuclei but are depleted of nuclear proteins. The sedimentation properties of these structures, which we call nucleoids, have been examined in sucrose gradients containing the intercalating agent, ethidium. The sedimentation rate of nucleoids derived from the growing cells of mammals, birds, amphibians and insects varies in the manner characteristic of circular and superhelical molecules of DNA. These characteristic changes in sedimentation rate are abolished by irradiating the nucleoids with low doses of gamma-rays, a procedure known to introduce single-strand scissions into DNA. We have also investigated by similar means DNA superstructure in nucleoids derived from a variety of different chick cells. Nucleoids derived from adult hen erythrocytes differ from the other nucleoids studied in that their sedimentation rate does not vary in the manner characteristic of supercoiled DNA.

Animals↗
PubMed1976

Characterization of nuclear structures containing superhelical DNA.

Structures resembling nuclei but depleted of protein may be released by gently lysing cells in solutions containing non-ionic detergents and high concentrations of salt. These nucleoids sediment in gradients containing intercalating agents in a manner characteristic of DNA that is intact, supercoiled and circular. The concentration of salt present during isolation of human nucleoids affects their protein content. When made in I-95 M NaCl they lack histones and most of the proteins characteristic of chromatin; in 1-0 M NaCl they contain variable amounts of histones. The effects of various treatments on nucleoid integrity were investigated.

Acridines↗
PubMed1975

Linkage of the loci for glucose-6-phosphate dehydrogenase and for inosinic acid pyrophosphorylase to the X chromosome of the field-vole Microtus agrestis.

It has been proposed that there are strong selective pressures which have acted during the evolution of mammals to conserve the linkage of genes on the X chromosome. If so, loci that are known to be X-linked in one mammalian species should be X-linked in others. The loci for glucose-6-phosphate dehydrogenase (E.C. 1.1.1.49) and for inosinic acid pyrophosphorylase (E.C. 2.4.2.8) are known to be X-linked in a variety of mammals. The linkage of these loci to the X chromosome of the field-vole, Microtus agrestis, is indicated by the pattern of segregation of these loci in hybrid cells derived by fusion of mouse cells with vole lymphocytes.

Aminopterin↗
PubMed1975

Supercoils in human DNA.

The three-dimensional structure of a double-stranded DNA molecule may be described by distinguishing the helical turns of the DNA duplex from any superhelical turns that might be superimposed upon the duplex turns. There are characteristic changes in the hydrodynamic properties of superhelical DNA molecules when they interact with intercalating agents. The hydrodynamic properties of nuclear structures released by gently lysing human cells are changed by intercalating agents in this characteristic manner. The characteristic changes are abolished by irradiating the cells with gamma-rays but may be restored by incubating the cells at 37 degrees C after irradiation. These results are interpreted as showing that human DNA is supercoiled. A model for the structure of the chromosome is suggested.

Binding Sites↗
PubMed1971

Mitotic separation of two human X-linked genes in man--mouse somatic cell hybrids.

SIX INTERSPECIFIC SOMATIC HYBRID CELL LINES WERE DERIVED FROM A MOUSE LINE DEFICIENT IN HYPOXANTHINE: guanine phosphoribosyltransferase (HGPRT) and human diploid cells with normal enzyme activity. Human HGPRT was present in all six hybrids and the clones derived from them. However, in two of the six, and in some clones from another two, human glucose-6-phosphate dehydrogenase (G6PD) was absent. Since the structural loci for both these enzymes are X-linked in man, these findings suggest that these two loci have separated quite frequently through chromosome breakage and that they must be rather far apart on the X chromosome.

Animals↗
PubMedDate not supplied

Summer program for pre-matriculating nursing students.

The National League for Nursing reported in 1984 that while Black nursing students represent 15.89% of admissions to baccalaureate programs in the southern region of the United States, they represent only 8.17% of the graduating nursing students. The average percentage of enrolled Black nursing students at the Medical College of Georgia School of Nursing for 1981-85 was only 7.68%. In view of the need for minority nursing students, it is necessary to increase the number of minorities enrolled and to improve retention rates of these students. A Nursing Student Educational Enrichment Program (S.E.E.P.), a summer pre-matriculating curriculum, was developed for minority nursing students which utilized a variety of campus-wide services and was based in the School of Nursing. The S.E.E.P. nursing students attended classes with all campus S.E.E.P. students who were enrolled in other health profession classes, and also completed two courses specific for nursing students: Decision-Making and Therapeutic Communication. This article examines the development and implementation of the nursing courses, with a focus on the curriculum design, program evaluation, and program specifics.

Black or African American↗