PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “DESOXYRIBONUCLEIC ACID”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed1953

Transformation of type specificity of meningococci; change in heritable type induced by type-specific extracts containing desoxyribonucleic acid.

Heritable type-specific traits have been induced in meningococcus populations by exposure to desoxyribonucleic acid (DNA)-containing extracts derived from meningococcus cells of the type desired. The DNA has been shown to be an essential component of the transforming extract. As in the H. influenzae system, the reaction between the susceptible cell and the DNA responsible for the heritable change requires less than 15 minutes. Only a minute proportion of the total cells exposed to the DNA extracts for a short time are susceptible to the change; but in the growth and reproduction of bacteria susceptible cells appear with fairly predictable frequency. Type I specific traits have been induced in populations of RIIa and SIIa cells. Type IIa specificity has been induced in RIIa cells.

DNA↗
PubMed1949

Quantitative cytochemical determination of desoxyribonucleic acid with the Feulgen nucleal reaction.

The possibility of using the Feulgen nucleal reaction for a quantitative cytochemical estimation of desoxyribonucleic acid (DNA) was investigated. The intensity of the reaction in nuclei was determined by absorption measurements with the microscope. The accuracy of such measurements was tested by comparison with measurements on the same material with a Beckman spectrophotometer. The values obtained with the microscope agreed within a few per cent with those obtained with the Beckman spectrophotometer. Furthermore, the errors introduced by uneven distribution of absorbing material, by variations in the numerical aperture of the system, and by variation in the area used on the phototube were investigated empirically. The following variables were studied with regard to their effect on the intensity of the Feulgen reaction: type of fixation, time of hydrolysis after acetic acid-alcohol and formalin fixation, time of staining in leucobasic fuchsin, method of preparation of leucobasic fuchsin. The intensity of the Feulgen reaction in liver and erythrocyte nuclei of various vertebrates, fixed in acetic acid-alcohol, was then compared with the DNA content of these nuclei as determined by chemical analysis on a known number of nuclei. The intensity of the reaction was found to be proportional to the DNA content of the nuclei, if nuclei of similar structure and DNA concentration were compared. In nuclei of different structure and DNA concentration (i.e. liver and erythrocyte nuclei), fixed in acetic acid-alcohol, the intensity of the Feulgen reaction was, however, not proportional to the DNA content. This difficulty was overcome by isolating nuclei in sucrose and by fixing them in formalin. Uniform distribution of DNA and therefore uniform coloring after the Feulgen reaction were thus obtained. In such nuclei with uniform distribution of absorbing material the Feulgen reaction was found to be proportional to the DNA content of nuclei, even if they differed greatly in their DNA concentration. The Feulgen nucleal reaction is not quantitative in an absolute sense. For absolute determinations nuclei of known DNA content must be treated together with the unknown material to serve as standard. From these data it therefore appears possible to determine cytochemically relative amounts of DNA in cellular structures by measuring their absorption after treatment with the Feulgen nucleal reaction.

Animals↗
PubMed1980

[Effects of inhibin on the in vitro synthesis of desoxyribonucleic acid in the rat testis].

Three preparations of inhibin extracted from ram rete testis fluid (RTF) and from human seminal plasma (HSP) reduce tritiated thymidine incorporation into testicular desoxyribonucleic acids (DNA) in vitro. Effect of low molecular inhibin from RTF is dose-dependent. Castrated ram serum does not modify testicular DNA synthesis in vitro. Besides their suppressive action on follicle stimulating hormone (FSH) secretion in vivo and in vitro, these inhibin preparation display a direct inhibiting effect on testicular DNA synthesis and, thus, on mitotic activity. Identity between inhibin and testicular chalones are discussed.

Animals↗
PubMed1955

A microphotometric study of the syntheses of desoxyribonucleic acid and nuclear histone.

1. The fast green stain of Alfert and Geschwind for nuclear basic protein is shown to obey the Beer-Lambert laws when used on purified histone. Interference from acid substances other than nucleic acids as a possible source of error is indicated. 2. Use of this technique after a modified Feulgen stain enables determination of relative amounts of desoxyribonucleic acid and histone in the same individual cells. 3. DNA and histone are shown to have the same distribution in formalin-fixed nuclei. 4. The syntheses of DNA and histone proceed simultaneously resulting in the doubling of both these substances prior to cell division. 5. The standard error for histone values is greater than that for DNA; however, the source of this variability is not known.

Cell Nucleus↗
PubMed1951

Determination of inherited traits of H. influenzae by desoxyribonucleic acid fractions isolated from type-specific cells.

Change of non-typable (R) strains of H. influenzae into the specific type of origin or new types (S) has been effected in vitro in a predictable fashion within a single 24 hour growth period, by a desoxyribonucleic acid-containing fraction isolated from type-specific cells of the type desired. Only a small proportion of the population of R cells are susceptible to the change induced in inherited characteristics by the desoxyribonucleic acid fraction. The data suggest that the number of susceptible cells present in any given population size varies with the specific type of origin of the R cells; a lesser degree of variation in different independent cultures of the same strain and population size has been demonstrated. The results suggest that the R H. influenzae cells which are susceptible to transformation arise as the result of mutation. It has been demonstrated that the reaction necessary for transformation takes place virtually immediately if susceptible cells are present. Furthermore it has been shown that the change which enables an R cell to form a colony of type-specific organisms has been completed within 15 minutes in an environment which does not permit cell multiplication.

DNA↗