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Biomedical subjects

W Maurer

Publications and source records attributed to W Maurer.

At least 91 records · Page 5Linked to original sources
PubMed1976

A two emulsion autoradiographic technique and the discrimination of the three different types of labelling after double labelling with 3H- and 14C-thymidine.

The first part of the paper deals with a two emulsion autoradiographic technique for double labelling experiments with 3H- and 14C-thymidine which permits a clear discrimination of the different types of labelling. In the second part the application of this technique to cell kinetic studies is discussed. Accurate discrimination between the different types of labelling, namely purely 3H-, purely 14C- and double (3H + 14C) labelling, is only possible if the activity ratio of 3H- to 14C-thymidine is sufficiently high. This condition is necessary for a reliable distinction between those grains in the first emulsion which are due to true 3H-labelling and spurious grains which are simultaneously produced in the same emulsion by 14C-beta-particles. Experiments are described to determine the required activity ratio of 3H- to 14C-thymidine.

Animals↗
PubMed1975

[Experiments and theoretical cell kinetic calculations on the problem of in vivo synchronization with vincristine in L 1210 ascites tumor cells and crypt cells of the mouse (author's transl)].

Experiments are described on synchronizing L 1210 ascites tumor cells and jejunal crypt cells of the mouse with vincristine. In both cases the percentage of mitoses increases to a peak value 4 hrs after application of vincristine and decreases during the following 8 hrs ("releasing time") to the level of the normal mitotic index. Following this first mitotic peak no futher peak of neither the mitotic nor the labeling index was observed during 48 hrs in L 1210 ascites tumor cells and during 38 hrs in crypt epithelia. Thus, in both cell types it was not possible to obtain a synchronizing effect by applying vincristine. Based on cell kinetic considerations it was examined whether peaks of the mitotic as well as the labeling index can be expected at all under the given circumstances. The results show that the theoretical course of the mitotic index coincides with the measured values. This means that no peak of the mitotic index can be expected from the theoretical point of view. In calculating the time course of the labeling index the theoretical curve proved to depend to a high degree on the variations of the cycle time which are not known in detail, especially not after application of vincristine. However, the theoretical conditions show that also in the case of the labeling index no peak can be expected. This agrees with the experimental results. The general significance of a long "releasing time" of 8 hrs or more for the lack of a synchronizing effect is discussed.

Animals↗
PubMed1975

Autoradiographic investigations of glial proliferation in the brain of adult mice. II. Cycle time and mode of proliferation of neuroglia and endothelial cells.

The cycle time of the proliferating glial cells outside the subependymal layer of the lateral ventricle as well as that of endothelial cells was studied autoradiographically in the brains of adult and untreated mice. To determine the mean cycle time two independent methods were used. A mean cycle time of about 20 hours was obtained for glial and endothelial cells from the decrease of the mean grain number/nucleus as a function of time after tritiated thymidine (3H-TdR) injection. Another group of experiments utilized the "method of labeled S phases". With this method the passage of labeled cells through successive S phases is observed. Passing through S phase following 3H-TdR injection the 3H-labeled cells are double labeled by an additional 14C-TdR injection. This method again resulted in a cycle time of 20 hours for glial and endothelial cells. From the present work and a former study (Korr et al., '73) the following cell cycle parameters were derived: Cycle time 20 hours; S phase 9.4 hours; G2 less than three hours; (G2+M) five hours; G1 five hours. The growth fraction of glial cells related to all glial cells is only 0.004. Furthermore, the present experiments show that in the case of glial cells 17% of the daughter cells after mitosis become pyknotic and are eliminated from the glial cell population. Apart from this cell loss, after mitosis about one-fourth of the daughter cells do not enter the next S phase. These cells leave the growth fraction and are replaced by a corresponding number of non-proliferating glial cells. There is a relatively extensive permanent exchange of cells between the growth fraction and non-growth fraction of glial cell.

Animals↗
PubMed1975

[Experimental and theoretical studies on the in-vivo production of a partially synchronous proliferating cell population with vincristine].

The problem of whether vincristine can be used to synchronize partially cells in vivo was investigated. After injection of 0,0045 mug vincristine/g body-weight into mice practically all L1210-ascites tumour cells entering mitosis were arrested in metaphase up to the fourth hour. However, no second peak of the mitotic index was observed within 48 hours. Calculation of the theoretical mitotic index to be expected under the present experimental conditions also shows no second peak. The reason for this lack of synchrony is the long releasing time of the arrested cells.

Animals↗
PubMed1975

Peritonitis fibroplastica incapsulata with superadded post-operative starch powder peritonitis.

Peritonitis fibroplastica incapsulata is not generally accepted as a distinct syndrome. However, characteristic pathological alterations can be identified at laparotomy and by histological examinations. The aetiology of the disease is unknown. In the case reported a second disease arose, i.e. the peritoneal reaction to corn starch powder in the course of the surgical treatment of the peritonitis fibroplastica.

Foreign-Body Reaction↗
PubMed1975

[Proliferation kinetics of bile duct epithelia in the regenerating mouse liver after CCl4-poisoning].

Autoradiographic and morphometric methods were used in studying the proliferation of interlobular bile duct epithelia of adult NMRI mice after CC14-poisoning (1 ml/kg i.p.). DNA synthesis starts on the 2nd day after CC14 administration. The time course of the 3H-thymidine labelling index is biphasic, with a first maximum at 2.5 and a second one 5 days after CC14 injection. An S-phase of 5.8 h was measured by 3H plus 14C-TdR double-labelling experiments. Proliferation is completed 10 days after CC14-poisoning, coinciding with the restitution of the liver parenchyma. Bile-duct epithelia remain diploid during the whole proliferative period, which suggests that every S-phase leads to mitotic division. The number of duct cells in portal cross sections remains constant. A quantitative model of the CC14- induced proliferation of interlobular bile duct cells is presented after calculating the total number of S-phases, the increase in cell number, and the final percentage of 3H-labelled nuclei (continuous infusion of 3H-TdR) as a function of time: With regard to 100 bile duct cells at the onset of proliferation 20 per cent S-phases occur during the first maximum and an additional 26 per cent occur during the second maximum of DNA SYNTHESIS, WHICH LEADS TO A 1.46-FOLD INCREASE IN CELL NUMBER. As derived from continuous 3H-TdR labelling (48 per cent 3H-labelled nuclei at the 6th day) and autoradiographic grain density measurements, the second wave of S-phases is due to DNA synthesis in ductular cells that have been formed during the first proliferative maximum. It is not possible to determine whether the proliferative activity observed is induced by lethal damage to bile-duct cells in the early course of CC14-poisoning, followed by compensatory growth and replacement of degenerate cells, or by nonspecific growth stimulation, inducing hyperplastic growth and elongation of terminal bile ducts.

Animals↗
PubMed1974

Stability of DNA in Purkinje cell nuclei of the mouse. An autoradiographic study.

Neurons of the mouse were labeled with [(3)H]thymidine during their prenatal period of proliferation. The (3)H 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 (3)H 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 [(3)H]beta self-absorption in the material of the sections. Injection of a high dose of [(3)H]thymidine into young adult mice did not result in (3)H 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.

Animals↗