Transit times through the cycle phases of jejunal crypt cells of the mouse

Mean transit times as well as variances of the transit times through the individual phases of the cell cycle have been determined for the crypt epithelial cells of the jejunum of the mouse. To achieve this the fraction of labelled mitoses (FLM) technique has been modified by double labelling with [3H] and [14C]thymidine. Mice were given a first injection of [3H]thymidine, and 2 hr later a second injection of [14C]thymidine. This produces a narrow subpopulation of purely 3H-labelled cells at the beginning of G2-phase and a corresponding subpopulation of purely 14C-labelled cells at the beginning of the S-phase. When these two subpopulations progress through the cell cycle, one obtains FLM waves of purely 3H- and purely 14C-labelled mitoses. These waves have considerably better resolution than the conventional FLM-curves. From the temporal positions of the observed maxima the mean transit times of the cells through the individual phases of the cycle can be determined. Moreover one obtains from the width of the individual waves the variances of the transit times through the individual phases. It has been found, that the variances of the transit times through successive phases are additive. This indicates that the transit times of cells through successive phases are independently distributed. This statistical independence is an implicit assumption in most of the models applied to the analysis of FLM curves, however there had previously been no experimental support of this assumption. A further result is, that the variance of the transit time through any phase of the cycle is proportional to the mean transit time. This implies that the progress of the crypt epithelial cells is subject to an equal degree of randomness in the various phases of the cycle

STABILITY OF DNA IN PURKINJE CELL NUCLEI OF THE MOUSE : An Autoradiographic Study

Neurons of the mouse were labeled with [3H]thymidine during their prenatal period of proliferation. The 3H activity of the Purkinje cell nuclei was then studied autoradiographically 8, 25, 55, and 90 days after birth. The measured grain number per nucleus decreased by about 14% between the 8th and 25th postnatal days and then remained constant up to 90 days. There was no significant decrease of the 3H activity of the Purkinje cell nuclei after correction of the measured grain number per nucleus for increasing nuclear volume of the growing Purkinje cells and for the influence of [3H]β self-absorption in the material of the sections. Injection of a high dose of [3H]thymidine into young adult mice did not result in 3H labeling of either Purkinje or other neurons in other brain regions. The results agree with the concept of metabolic stability of nuclear DNA. "Metabolic" DNA could not be observed in these experiments

In vivo cell synchrony in the L1210 mouse leukaemia studied with 5-fluorouracil or 5-fluorouracil followed by cold thymidine infusion.

[3H]-TdR and [3]-udR labelling indices and mitotic indices were followed in tumour-bearing mice after application of either 5-fluorouracil (FU) alone or of FU followed by cold TdR infusion. With FU alone, accumulation of cells at the beginning of S was found, but there was no indication of a synchronous passage of the accumulated cells further round the cycle. When FU injection was followed by cold TdR infusion, a synchronous passage of the accumulated cells through the cycle was observed. However, there was a large variation in the response of individual mice to this treatment

Enhancement of the ferromagnetic order of graphite after sulphuric acid treatment

We have studied the changes in the ferromagnetic behavior of graphite powder and graphite flakes after treatment with diluted sulphuric acid. We show that this kind of acid treatment enhances substantially the ferromagnetic magnetization of virgin graphite micrometer size powder as well as in graphite flakes. The anisotropic magnetoresistance (AMR) amplitude at 300 K measured in a micrometer size thin graphite flake after acid treatment reaches values comparable to polycrystalline cobalt.Comment: 3.2 pages, 4 figure

Relation of endocrine gland weight to body weight in growing and mature female dairy goats

Digitized 2007 AES.Includes bibliographical references (page 22)

Bond Formation in Electrosorbates

The electrosorption valency y is defined and its meaning is thoroughly discussed. Exiptl. dent. of y is demonstrated for systems Au/Bi3+ and Pt/Cu2+. It is found that for homonuclear ions in aq. solns. the ratio y/z, where z stands for Nernst valency, is successfully correlated with the electro.negativity difference I XM - Xs I of the electrode metal M and the sorbate S. For small electronegativity differences, y/z •is close to unity indicating large covalency. Bond formation in electrosorbates in non-aq. solvents and at single crystal plames of various orientations are briefly discussed

Atom lithography with two-dimensional optical masks

With a two-dimensional (2D) optical mask, nanoscale patterns are created for the first time in an atom lithography process using metastable helium atoms. The internal energy of the atoms is used to locally damage a hydrofobic resist layer, which is removed in a wet etching process. Experiments have been performed with several polarizations for the optical mask, resulting in different intensity patterns, and corresponding nanoscale structures. The results for a linear polarized light field show an array of holes with a diameter of 260 nm, in agreement with a computed pattern. With a circularly polarized light field a line pattern is observed with a spacing of 766 nm. Simulations taking into account many possible experimental imperfections can not explain this pattern.Comment: 5 pages, 4 figure

Grazing Endophyte Infested Tall Fescue and Changes in Bovine Blood Components and Gain

Tall fescue (Festuca arundinacea) is utilized on more than 15 million ha of pasture in the eastern USA and over 80% of the plants in this area are infested with the endophyte Neotyphodium coenophialum. Tall fescue toxicosis results from consumption of the infested (E+) grass host and is an important problem that causes considerable economic loss to producers. However, the agronomic attributes of tall fescue make it an attractive forage because of its ability to withstand cool temperatures, drought, poor soil conditions and intensive defoliation. There is need to understand mechanisms of animal physiology that are affected by the alkaloids produced by the endophyte/grass association. Blood serum samples were collected from steers (Bos taurus) grazing either E+ or endophyte free (E-) tall fescue in spring and summer during three consecutive years and were related to animal performance. Consistent and significant changes associated with E+ tall fescue were noted for daily gain, prolactin, albumin/globulin ratio, alanine aminotransferase, cholesterol, creatinine, globulin, total bilirubin, total serum protein, copper, red blood cells, mean corpuscular volume, mean corpuscular hemoglobin, and eosinophils. Thus, repeatable changes that occur in serum biochemical and blood cellular values of cattle grazing E+ tall fescue were identified and will aid in understanding the pathogenesis of the toxicosis