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K H Richter

Publications and source records attributed to K H Richter.

At least 19 recordsLinked to original sources
PubMed1996

Expression of growth arrest-specific (Gas) genes in murine keratinocytes: Gas2 is specifically regulated.

In order to elucidate a possible role of growth arrest-specific (gas) genes in the regulation of tissue proliferation, we analyzed their expression in keratinocytes isolated from murine back skin. On the mRNA level gas1, gas5, and gas6 were found to be significantly expressed whereas there was a relatively low expression of gas2, gas3, and gas4. Using keratinocytes fractionated according to their density resulted in subpopulations of cells: differentiating suprabasal cells in fractions I and II; proliferative basal cells in fractions IIIa, III and IV. We found gas2 protein to be expressed more strongly in the proliferative cells than in the differentiating cells. Stimulation of hyperproliferation by 12-O-tetradecanoylphorbol-13-acetate (TPA) resulted in a transient increase of gas2 protein content concomitantly with the time of maximal cell renewal. In this respect the murine keratinocyte cell line MSCP5 resembled freshly isolated keratinocytes. There was a higher expression of gas2 protein during exponential growth than during growth arrest, induced either by serum starvation or by TGFbeta treatment. Since, in contrast to the results reported for 3T3 cells, growth arrest within these cells was not accompanied by an elevation of gas2 protein, we suggest a cell-specific regulation of its expression.

Animals↗
PubMed1996

Protein-tyrosine phosphatases expressed in mouse epidermal keratinocytes.

The importance of growth factors acting via receptor-type protein-tyrosine kinases in the continuous renewal of the epidermis from the keratinocyte stem cell population has been well established. Protein-tyrosine phosphatases (PTPases), which dephosphorylate phosphotyrosine-containing proteins, may therefore be expected to play an equally important role in the control of epidermal growth and differentiation. In this study, we have made an inventory of the various PTPases that are expressed during mouse keratinocyte proliferation and maturation. A panel of 13 different PTPases probes was obtained by combining a set of PTPase cDNAs previously cloned from mouse brain and a set of PTPase probes obtained from a normalized keratinocyte PTPase cDNA library. This PTPase cDNA panel, spanning probes for receptor-type as well as cytoplasmic-type family members, was used to monitor RNA expression levels in keratinocyte fractions isolated from murine epidermis and in keratinocyte cell cultures. No overt changes were observed in PTPase mRNA levels in all strata of mouse epidermis, but comparison of cultured cells with freshly isolated keratinocytes revealed several conspicuous differences. In the cultured Balb/MK cell line, absence of PTP delta expression and upregulation of PTP kappa and, to a lesser extent, PTP gamma mRNA ratios were observed compared to the freshly isolated cells. These results provide a basis for further research on the impact of PTPase activity on epidermal growth control.

Amino Acid Sequence↗
PubMed1995

Cloning and characterization of murine p16INK4a and p15INK4b genes.

Progression through the G1 phase of the cell cycle is regulated in part by the D-type cyclin-dependent kinases, cdk4 and cdk6. Genes encoding two specific inhibitors of these kinases, human p16(INK4a/MTS1) and p15(INK4b/MTS2), map to a region of common cytogenetic abnormalities on chromosome 9p21. The murine cognates of these genes were isolated and identified as mouse p16INK4a and p15INK4b based on their homology to their human counterparts and their selective transcriptional induction by SV40T-antigen and TGF-beta, respectively. Both genes map to position C3-C6 on mouse chromosome 4, in a region syntenic with human chromosome 9p. Amplification of polyadenylated mRNA by polymerase chain reactions revealed no expression of mouse p16INK4a in many normal tissues, whereas p15INK4b was expressed ubiquitously. Like human p16INK4a, mouse p16INK4a binds specifically to cdk4 and cdk6 in vitro and inhibits the phosphorylation of the retinoblastoma protein, pRb, by each of these cyclin D-dependent kinases. In mouse MEL erythroleukemia cells, p16INK4a associates preferentially with cdk6 under conditions where cdk4 and cdk6 are coexpressed at equivalent levels. Expression vectors encoding human or mouse p16INK4a caused G1 phase arrest in NIH3T3 fibroblasts, and cyclin D1- and cdk4-dependent pRb kinase activities were inhibited in the p16INK4a-arrested cells.

3T3 Cells↗
PubMed1991

Down-regulation of cdc2 in senescent human and hamster cells.

Senescent cells fail to respond to serum-induced signals for DNA synthesis. Because a central role for the p34cdc2 protein kinase is postulated in control of the cell cycle, we examined the status of this kinase in senescent cells and other growth-arrested cells. In growing human and Syrian hamster fibroblasts, three 35S-labeled proteins of 34-36 kDa were immunoprecipitated with p34cdc2 antiserum. Only the two slower migrating forms were phosphorylated as determined by 32P labelling. In senescent cells, which failed to incorporate [3H]thymidine, no p34cdc2 protein was synthesized and very little or no cdc2 mRNA was observed. When maintained for 48 h in 0.5% serum, young cells also retained only marginal cdc2 expression. After stimulation of low serum-arrested cells by addition of 10% serum, a time-dependent increase of cdc2 mRNA was observed, whereas serum stimulation of senescent cells did not increase cdc2 mRNA. In contrast to senescent and low serum-arrested cells, cdc2 mRNA was expressed at normal levels in cells partially growth arrested by isoleucine deficiency in G1, by aphidicolin at G1-S, by etoposide in G2, or by Colcemid in the M phase of the cell cycle, indicating that cdc2 down-regulation does not always occur upon growth arrest. Following transfection of a plasmid containing the human CDC2 gene into hamster cells, expression of human cdc2 failed to overcome the block to DNA synthesis in senescent cells. Although p34cdc2 was synthesized in the transfected cells, the multiple phosphorylated forms of the proteins were not observed. Taken together, these data support the concept that a chain of events leads to senescence. While p34cdc2 kinase may be one of the critical elements, other cell cycle controls are also involved.

Animals↗
PubMed1990

Epidermal G1-chalone and transforming growth factor-beta are two different endogenous inhibitors of epidermal cell proliferation.

Epidermal G1-chalone and transforming growth factor-beta (TGF beta), two endogenous inhibitors of epidermal cell proliferation, were compared with regard to several effects on epidermis in vivo and in vitro. Both factors inhibited DNA labeling in a rat tongue epithelial cell line, with similar kinetics and half-maximal effects at approximately 1 pg/ml (enriched chalone) and 1 ng/ml (TGF beta). For primary neonatal mouse keratinocytes, TGF beta was found to be a rather strong inhibitor of cell proliferation, whereas chalone showed only a weak effect on cells grown in medium containing 1.2 mM Ca2+ and no effect at all in the presence of 0.06 mM Ca2+. Vice versa, upon i.p. injection, only chalone was able to inhibit mouse epidermal DNA synthesis in vivo, whereas TGF beta had no effect at all. A moderate increase of transglutaminase activity in neonatal primary mouse keratinocytes was induced by both factors at concentrations of about 300 pg TGF beta/ml and 10 pg chalone fraction/ml. Chalone did not compete with [125I]TGF beta for specific binding sites on primary murine keratinocytes. A polyclonal "chalone antiserum" did not interact with TGF beta, and a neutralizing TGF beta antibody that inhibited the effect of TGF beta on cell proliferation could not block the inhibitory effect of chalone on RTE2 cells. In contrast to TGF beta, epidermal G1-chalone did not induce proliferation of NIH-3T3 cells. These results indicate that epidermal G1-chalone and TGF beta are two different inhibitors of epidermal cell proliferation.

Animals↗
PubMed1989

Cell cycle specificity and reversibility of the inhibitory effect of epidermal G1-chalone on DNA synthesis in partially synchronized RTE-2 keratinocytes in vitro.

The specific action of a pig skin fraction enriched in epidermal G1-chalone, a tissue-specific inhibitor of epidermal DNA synthesis, was investigated by means of flow cytofluorometry. The results indicate that G1-chalone inhibits progression of partially synchronized rat tongue epithelial cells (line RTE-2) through the cell cycle at a point 2 h prior to the beginning of the S-phase. Approximately 8 h after chalone addition, the cells can overcome the inhibition and begin to enter the S-phase. The duration of this delay is concentration-independent, but the fraction of cells affected is proportional to the chalone concentration. The progression of cells which already have entered S-phase is not affected. In contrast to the G1-chalone preparation, aphidicolin, a potent inhibitor of DNA polymerase alpha, clearly shows S-phase-specific inhibition. These results indicate that the epidermal G1-chalone inhibits epidermal cell proliferation in a fully reversible manner by a highly specific effect on cell cycle traverse.

Animals↗
PubMed1989

[Inhalation exposure to welding fumes of arc welders in processing Cr-Ni steel in large chemical industry].

For clearing up the inhalative load by welding fumes and gases of arc welders in industrial workshops mainly working on Cr-Ni-steels the following welding processes were studied: tungsten inert-gas (TIG), electrode-by-hand (EH), metal inert-gas (MIG), and plasma cutting (plasma). From the total load by welding fumes follows the rank TIG less than EH less than plasma less than MIG. Observing the maximum allowable concentration (MACD) for the total welding fume, no MACD for Cr and Ni was found exceeded. Regarding the welding gases ozone and CO no limit values were exceeded. From the results conclusions were made.

Air Pollutants, Occupational↗
PubMed1988

The epidermal G1-chalone: an endogenous tissue-specific inhibitor of epidermal cell proliferation.

An apparently macromolecular factor is isolated from aqueous skin extracts which inhibits DNA synthesis in vivo and in vitro with high efficacy (ID50 in vivo 0.2 pmol/g, in vitro 0.2 pM) and in a highly specific manner showing a point of attack in the late G1-phase of the cell cycle (epidermal G1-chalone). Preliminary characterization indicates an unusual highly amphipathic structure consisting of amino acids and carbohydrate. Despite its apparent molecular weight of approximately 10 kD the chalone is stable against denaturing agents and most enzymes, including proteases. An inverse correlation between chalone responsiveness of mouse epidermis in vivo and the development of hyperplasia due to injury indicates an important role of the factor in the regulation of tissue homeostasis. According to its physicochemical and biological properties the epidermal G1-chalone appears not to be related to other endogenous inhibitors of epidermal cell proliferation such as the pentapeptide pyroGlu-Glu-Asp-Ser-GlyOH and transforming growth factor beta (TGF beta).

Animals↗
PubMed1984

A system for the study of epidermal G1-chalone in cell culture. The rat tongue epithelial cell line RTE2.

A pig-skin preparation enriched in epidermal G1-chalone when administered to cells of the rat tongue epithelial line RTE2 at concentrations of 3-300 micrograms/ml (dry mass) caused a 60% reduction in cell number. Three other cell lines showed essentially no growth inhibition during chalone treatment. The kinetics of chalone inhibition were similar to those observed in mouse epidermis in vivo. Five hours after the addition of chalone preparation in fresh medium a decrease in the rate of DNA synthesis was observed. Maximum inhibition at 12 h was followed by a subsequent increase in DNA synthesis, reaching control values again after 30 h. The inhibitory effect was dose-dependent up to 3 micrograms/ml. At higher concentrations the degree of inhibition remained constant at about 50% of the control up to 300 micrograms/ml. Removal of added chalone by changing the medium at the time of maximum inhibition gave rise to a complete recovery within 9 h. These results indicate a cell-line specific, non-toxic and reversible inhibitory effect of the chalone preparation which resembles that observed in the living animal. The RTE2 cell line may thus be considered to provide a highly sensitive experimental system suitable for more detailed studies on the mechanism of action of epidermal G1-chalone.

Animals↗
PubMed1978

[Local reaction and neutralization test in smallpox vaccination after previous inoculation with MVA. Stickl's graduated vaccination (author's transl)].

Of 200 first inoculations and 8 revaccinations, the sera were examined for content of neutralizing vaccine antibodies 3 weeks after the MVA graduated inoculation. In spite of imponderables which affect the failure rate in the "clinical trial", a positive result was obtained on first vaccination in 85%. In vaccinated children with a negative neutralization test a distinct booster effect was obtained with a "main vaccination" after about six months. The same effect was seen with revaccinations. For the time being inadequately controlled cerebral convulsive diseases, severe endogenous eczema, neurodermatitis, acute allergies, malignancies, immunosuppressive therapy, cortisole and intensive antirheumatic therapy and acute and purulent diseases must be considered as contraindications.

Adult↗
PubMed1978

[Investigation of the fibroblast chalone (author's transl)].

By ultrafiltration of a cytoplasm preparation from diploid human fibroblasts (Flow 2000) we obtained a fraction which inhibited the proliferation of the same cells. We succeeded in demonstrating fibroblast chalone, because the activity was endogenous, reversible and affected murine fibroblasts, but not human cervical carcinoma cells (HeLa S3) or neuronal tumor cells of rats (B104). The chalone activity was found in the range of molecular weights between 10 000 and 100 000. The active part was of peptide nature, for proteolytic treatment destroyed the chalone activity.

Cell Division↗