Search PubMed⌕ Search

Biomedical subjects

R Rohrbach

Publications and source records attributed to R Rohrbach.

At least 55 records · Page 3Linked to original sources
PubMed1976

[Influence of calcitonin on the quantitative cytoarchitecture of juvenile rats, a morphometric study on rat hepatocytes (author's transl)].

UNLABELLED: 1. INTRODUCTION: Using ultrastructural-morphometric analysis of liver parenchymal cells, following long term calcitonin administration, the suggestion that calcitonin influences intermediate as well as calcium metabolism has been strengthened. 2. MATERIALS AND METHODS: The experiments were performed with 10 young male Wiatar rats. 5 animals received salmon calcitonin intraperitoneally every day for 6 weeks, 5 untreated animals served as controls. All animals had free access to water and Altromin-R-standard diet. The morphometric investigations were carried out by a method analogous to that of Weibel (1969). 3. RESULTS AND DISCUSSION: By comparison with controls smaller cells and nuclei were seen. Following calcitonin treatment the mitochondrial content of liver parenchymal cells was markedly reduced. On the other hand the surface of cristae was doubled. A proportional membrane and enzyme production in the sense of an adaption, or a disproportional membrane and enzyme synthesis as a misadaption is discussed as the pathogenetic mechanism. Furthermore the number as well as the volume of peroxisome, and lysosomes was reduced. Total liver calcium decreased, whereas serum calcium concentration increased slightly. This can be explained through raised renal reabsorption as a compensatory effect of parathyroid hormone.

Animals↗
PubMed1976

Effects of methylcholanthrene on epidermal growth regulators. II. Variations in the S-factor.

There is increasing evidence to support the existence of tissue-specific growth-inhibitory chemical substances which can be found in extract homogenized cells. In the epidermis, two such tissue-specific factors (which also have cell-cycle specificity) have been found. These factors act specifically on different phases of the cell cycle (epidermal G1 and G2 chalones, respectively). This paper concerns a study of the effect of 20-methylcholanthrene on the epidermal G1 chalone. The variations in epidermal G2 inhibitor after such treatment were described in a previous paper. Hairless mice received a single topical application of 0.2 ml 0.5% solution of the carcinogen. The short time effect of the carcinogen application on epidermal DNA synthesis was first studied. Other groups of carcinogen-treated mice were then killed at similar time intervals, and the treated area of skin was homogenized and extracted with water. The inhibitory effect of these extracts on normal epidermal G1 cells was assayed in normal hairless mice. The obtained inhibition was registered as an expression of G1 inhibitor concentration in the skin extracts. The first experiment confirmed that a single carcinogen application provokes a short block in epidermal DNA synthesis, followed by a high, biomodal peak of increased activity with the first and maximum peak on day 2, and a smaller peak on day 8 after treatment. The second experiment showed that the content of G1 chalone in the skins of treated animals varied inversely to the alterations in epidermal DNA synthesis, revealing almost no chalone activity on day 2, and reduced chalone activity on day 8.

Animals↗
PubMed1976

Growth parameters of the hairless mouse epidermis after bleomycin treatment: possible interaction with epidermal chalones.

Hairless mice were given two injections of 2 mg bleomycin i.p. on two successive days. By a stathmokinetic method, micro-flow fluorometry and autoradiography, many kinetic parameters were measured. Bleomycin affected cell proliferation in epidermis by depressing the number of cells in and the passage of cells through the different cell cycle phases, i.e. S, G2 and M in a biphasic manner. The time between the two minima corresponded to the mean generation time of the basal cells. Skin extracts produced from animals at different time intervals after the bleomycin injection show that bleomycin interferred only slightly with the G1-chalone, but had a more pronounced effect on the content of G2 of the skin, increasing and reducing the chalone effect in a biphasic manner. The study gives some support to the theory that the particularly good effect of bleomycin in squamous cell epithelium may be due to an interference of bleomycin with keratinization and chalone production. The protein synthesis showed only a minimal depression where the kinetic parameters were heavily depressed.

Animals↗
PubMed1976

Effects of D-penicillamine administration to rats, induction of renal changes: preliminary communication.

Oral administration of synthetic D-penicillamine to rats induces alterations of the renal mesangium, apparently without involvement of immune mechanisms. Alterations of mitochondria, especially enlargement, were seen in the proximal tubular epithelium. These results are discussed in the light of recent findings in "penicillamine" nephritis and diseased human kidneys in general.

Animals↗
PubMed1975

Mitochondriosis of the hepatocytic cytoplasm in rachitic rat liver after calcitonin-treatment (a cytophotometric and morphometric study).

A calcium-rich rachitogenic vitamin-D deficiency and additional doses of calcitonin cause serious changes in cell structure and metabolism, which can be demonstrated by cytophotometry and morphometry. The experiments were made with 9 male juvenile Wistar rats. 6 animals were kept on a vitamin-D deficient diet for 6 weeks and 3 of these animals got injections with salmon-calcitonin S.C. during the last 14 days every second day. The remaining 3 animals, fed with altromin-R standard diet were kept for control purposes only. The morphometric analysis of the liver parenchymal cells was based on the statements by Weibel and the cytophotometric examinations were made according to the Sandritter technique. As a consequence of the altered metabolic condition a great volume reduction of cells and cell nuclei is found in the animals with vitamin-D deficiency, which were treated with calcitonin. In comparison with the control animals the hepatocytes show hardly any tetraploid nuclei, which points to an inhibited polyploidization. The cytoplasm shows an oncocytic transformation with megamitochondria. As reason for this mitochondriopathy an extreme and abnormal growth as well as a mutation of the mitochondrial genom are under discussion. Furthermore the total endoplasmic reticulum (volume and membrane surface), the peroxisomes and the ribosomes are strongly reduced. Due to the serious cell injury the other organelles are also reduced in number and volume, which points to a chronic hypocalcemia.

Animals↗
PubMed1975

[The regulation of cell proliferation by chalones experimental investigations on epidermal hyperplasia (author's transl)].

The pattern of epidermal cell proliferation, following a single application of a hyperplasia inducing agent, can well be interpreted in cybernetic terms. This concept implies that the local concentration of a possible growth inhibiting signal substance should exhibit variations compatible with the changes seen in the cell kinetics of the epidermis. This signal substance has been called the epidermal chalone, first preliminary characterized by Bullough et al. (1964c). Meanwhile a considerable number of other chalone systems have been identified in different organs. From the experimental results a chalone was considered an anti-mitotic substance, which is synthesized within the same tissue on which it specifically acts. It was found not to be species-specific; it reveals a rapid and reversible inhibition by diffusion and passes throughout the tissue and into the blood. Later investigations have exhibited that the epidermal chalone probably consists of at least two separate compounds (proteins), one acting on cells in the postsynthetic, pre-mitotic G 2-phase, the other one on cells in late G 1 (Marks, 1971; Elgjo et al., 1971, 1972). The proliferative behavior of epidermal cells following an application of different irritants was the main subject of the present investigations. All experiments were performed in vivo with hairless mouse epidermis, which was treated with 20-methylcholanthrene (MCA) as carcinogen and crotonoil as cocarcinogen, both dissolved in acetone, and with repeated Scotch tape stripping. Different methods were employed in order to determine epidermal proliferation parameters such as: a. the cytophotometrically measured amount of nucleic deoxyribonucleic acid (DNA) of Feulgen-stained epidermal basal cells, b. the total DNA content of whole epidermis, c. the number of Colcemid(R) arrested metaphases (mitotic rate) in the basal cell layer, d. the incorporation of H3-thymidine into DNA of epidermal basal cells. The number of epidermal basal cells revealing an increased DNA content is significantly lowered for more than 24 hours after MCA and for 12 hours after Crotonoil administration. This effect was not observed after Scotch tape stripping. In all the treated groups this period was followed by a proliferation wave exhibiting more cells with an increased DNA-content during the first 6-10 days after irritation. Only after MCA treatment this higher cell number appeared with a lag phase of 3 to 4 days and coincided with a decrease of the total amount of epidermal DNA. All irritants produced a marked epidermal hyperplasia during the first two weeks after application.

Animals↗