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At least 1,765 records · Page 98Linked to original sources
PubMed1964

THE RELATIONS BETWEEN DNA, RNA, AND PROTEIN IN NORMAL EMBRYONIC CELL NUCLEI AND SPONTANEOUS TUMOUR CELL NUCLEI.

Interferometric and photometric measurements have been made successively on individual cell nuclei derived from normal embryonic tissues and spontaneous tumour tissues of the mouse grown in vivo. From the measurements, the relations between nucleic acid and dry mass content have been studied in the two types of nuclei and the results shown to be consistent with differences in cell metabolism previously reported to exist in vitro. In the nuclei of normal embryonic cells, the syntheses of DNA, nuclear RNA, and protein appear to be closely associated, whereas in the tumour cell nuclei an appreciable fraction of the chromatin RNA and protein synthesis is dissociated from the replication of DNA.

Animals↗
PubMed1964

OFF-PEAK ABSORPTION MEASUREMENTS IN FEULGEN CYTOPHOTOMETRY.

The use of off-peak measurements in Feulgen cytophotometry is reported, using intact diploid (x) and tetraploid (y) nuclei of the human anterior pituitary gland as the experimental model studied. Results indicate that the ratio y/x is similar at the 14 wavelengths examined over the range 450 mmicro to 650 mmicro. The value of this ratio was 1.95, falling slightly under the theoretical ratio of 2.0. It was concluded that off-peak absorption measurements are of value in Feulgen cytophotometry. A discussion of the possible justification of off-peak absorption measurements was presented for the case in which the Beer-Lambert relationship was experimentally determined to be followed at a peak wavelength, for all concentrations under discussion, and the curves preceding and/or following the peaks were straight lines coming from a common point. If the curve best fitting the data is a straight line, it follows that the rate of change of absorbance with respect to a linear wavelength scale is constant. This means that for a given increase, or decrease, in wavelength, the same change in absorbance is obtained. From this it follows that absorbance readings at any wavelength in such a region will be equally valid to those taken at the peak. While the finding of such a linear relationship at several concentrations does not guarantee that it will occur at all other concentrations, it is suggestive. The closer the spectra approximate straight lines, the more valid does the use of off-peak measurements become.

Cell Nucleus↗
PubMed1965

MICROSCOPIC DETERMINATION OF BONE PHOSPHORUS BY QUANTITATIVE AUTORADIOGRAPHY OF NEUTRON-ACTIVATED SECTIONS.

Longitudinal sections of human cortical bone were submitted to thermal neutrons. gamma-ray spectra were recorded repeatedly during 15 days following irradiation. They showed that Na(24) is predominant as early as 3 hours after activation and that all the gamma-emitters have decayed on the 15th day. When the gamma-rays have disappeared, beta-rays are still produced by the sections. It was proved by the absorption curve in aluminium that all these beta-rays are issued from the P(32) induced in the sections by activation of P(31). Therefore autoradiograms registered 15 days after activation reveal the distribution of P(32) in the sections. gamma-ray spectra and beta-ray absorption curves of neutron activated sections of ivory demonstrated a mineral composition similar to that of bone. Autoradiograms of ivory sections activated for various times were used to establish the relation between the optical density of the autoradiograms and the radioactivity in P(32). When the bone autoradiograms are compared with the ivory standards of known radioactivity, the optical densities of single osteons (Haversian systems), can be related to their phosphorus contents. Autoradiograms and microradiograms of the same sections were examined side by side. The least calcified osteons, that contain 80 per cent of the calcium of the fully calcified osteons, also contain about 80 per cent of the phosphorus of the fully mineralized osteons. It is concluded that the Ca:P ratio remains constant while mineralization of bone tissue is being completed.

Activation Analysis↗
PubMed1959

The nature, significance, and evaluation of the Schwarzschild-Villiger (SV) effect in photometric procedures.

The Schwarzschild-Villiger effect has been experimentally demonstrated with the optical system used in this laboratory. Using a photographic mosaic specimen as a model, it has been shown that the conclusions of Naora are substantiated and that the SV effect, in large or small magnitude, is always present in optical systems. The theoretical transmission error arising from the presence of the SV effect has been derived for various optical conditions of measurement. The results have been experimentally confirmed. The SV contribution of the substage optics of microspectrophotometers has also been considered. A simple method of evaluating a flare function f(A) is advanced which provides a measure of the SV error present in a system. It is demonstrated that measurements of specimens of optical density less than unity can be made with less than 1 per cent error, when using illuminating beam diameter/specimen diameter ratios of unity and uncoated optical surfaces. For denser specimens it is shown that care must be taken to reduce the illuminating beam/specimen diameter ratio to a value dictated by the magnitude of a flare function f(A), evaluated for a particular optical system, in order to avoid excessive transmission error. It is emphasized that observed densities (transmissions) are not necessarily true densities (transmissions) because of the possibility of SV error. The ambiguity associated with an estimation of stray-light error by means of an opaque object has also been demonstrated. The errors illustrated are not necessarily restricted to microspectrophotometry but may possibly be found in such fields as spectral analysis, the interpretation of x-ray diffraction patterns, the determination of ionizing particle tracks and particle densities in photographic emulsions, and in many other types of photometric analysis.

Coloring Agents↗
PubMed1964

STUDIES RELATING TO THE SERUM RESISTANCE OF CERTAIN GRAM-NEGATIVE BACTERIA.

Paracolobactrum ballerup, an organism considered completely insusceptible to the bactericidal action of the antibody-complement system, became extremely sensitive to immune serum and even to normal serum, in conjunction with complement, when cultivated at temperatures above 37 degrees C. This conversion to serum sensitivity was associated with the loss of the organism's Vi antigen and its tendency to assume a rough state. It did not result in a genetic change in the organism, however, since reincubation of serum-sensitive P. ballerup at 37 degrees C resulted in a restoration of its resistance. The loss of serum resistance as a result of cultivation temperatures above 37 degrees C may be of significance as an example of the enhancement of host defense mechanisms induced by fever. Special conditions of testing indicated that P. ballerup cultured at 37 degrees C and S. paratyphosa C, organisms considered insusceptible to serum bactericidal action, were not entirely refractory to serum. These conditions included simply a relatively low ratio of the number of test organisms to serum volume and an extended incubation period of the organisms with serum bactericidal substances, or even without these substances, prior to the initiation of bactericidal action. It is likely, therefore, that an absolute distinction between serum-sensitive and serum-resistant Gram-negative organisms does not exist, but rather that there is a very broad distribution of serum sensitivity among these organisms.

Animals↗
PubMed1964

FURTHER OBSERVATIONS ON THE RELEVANCE OF SEROLOGIC RECAPITULATIONS OF HUMAN INFECTION WITH INFLUENZA VIRUSES.

By use of a photometric method which objectively distinguishes between homologous and heterologous antibody reactions, the age distribution of specifically reacting swine and Asian antibodies present in sera of persons not recently exposed to either virus was established. The findings support the thesis that the unique distribution by age of swine and Asian antibodies recognizes two past periods of prevalence of swine and Asian-like viruses, respectively. The findings apparently refute the conclusion that the existence of age-specific Asian and swine antibody patterns is primarily attributable to the undirected or passive accumulation of experience with Asian or swine antigens present as minor antigenic components in most strains of influenza A.

Animals↗