Biomedical subjects

U Stöcker

Publications and source records attributed to U Stöcker.

9 recordsLinked to original sources

PubMed1996

Ca2+/calmodulin-dependent and -independent down-regulation of c-myb mRNA levels in erythropoietin-responsive murine erythroleukemia cells. The role of calcineurin.

Down-regulation of c-myb mRNA levels by [Ca2+]i-increasing agents (A23187, thapsigargin, cyclopiazonic acid) and erythropoietin was comparatively studied in the erythropoietin-responsive murine erythroleukemia cell line, ELM-I-1. The Ca2+-induced suppression of c-myb mRNA could be inhibited by the calmodulin antagonists trifluoperazine and calmidazolium, as well as by cyclosporin A, an inhibitor of the Ca2+/calmodulin-dependent protein phosphatase 2B (calcineurin). KN-62, an inhibitor of Ca2+/calmodulin-dependent protein kinases, did not antagonize the Ca2+-mediated decrease in c-myb mRNA. In cyclosporin A-treated ELM-I-1 cells, a close correlation could be demonstrated between the antagonization of the Ca2+ effect on c-myb mRNA levels and inhibition of the calcineurin phophatase activity. On the other hand, FK506, which did not inhibit calcineurin activity in ELM-I-1 cells, failed to prevent the Ca2+-mediated decrease in c-myb mRNA. The erythropoietin-induced down-regulation of c-myb mRNA levels could be demonstrated also in the presence of EGTA and was resistant to calmodulin antagonists and cyclosporin A. In addition, no increase in [Ca2+]i was observed in ELM-I-1 cells in response to erythropoietin. Cyclosporin A inhibited the Ca2+-induced hemoglobin production, while the erythropoietin-mediated increase in hemoglobin synthesis was not affected. The results indicate that the Ca2+-induced decrease in c-myb mRNA and increase in hemoglobin synthesis is mediated by calcineurin, while these effects of erythropoietin occur independently of Ca2+ in ELM-I-1 cells. Calcineurin may be involved in the regulation of c-myb expression in erythroid precursor cells and Ca2+ signals via calcineurin may positively modulate the differentiation inducing action of erythropoietin.

Animals↗

PubMed1995

DMSO-like rapid decrease in c-myc and c-myb mRNA levels and induction of differentiation in HL-60 cells by the anthracycline antitumor antibiotic aclarubicin.

The anthracycline antitumor antibiotic aclarubicin is known to induce granulocytic differentiation in the human myeloid leukemia cell line HL-60. We investigated whether this effect is accompanied by changes in the expression of the protooncogenes c-myc and c-myb. Treatment of HL-60 cells with aclarubicin, 50 nM, caused a rapid decrease in c-myc and c-myb mRNA levels within 1 h and 2 h, respectively. In parallel, we demonstrated a strong induction of superoxide-anion production on day 8 of treatment. The kinetics of the effect of aclarubicin on c-myc and c-myb expression were comparable to those associated with the dimethylsulfoxide-induced granulocytic differentiation in this cell line, or to those observed following a chase with actinomycin D, 4 microM. Since aclarubicin partially inhibited total- and poly(A)(+)-RNA synthesis, this macromolecular synthesis inhibition may be causally related to the decrease in c-myc and c-myb mRNA levels. In contrast, the conventional anthracycline doxorubicin, which did not initiate differentiation, failed to affect c-myc or c-myb mRNA levels even in high cytotoxic concentrations, indicating that the suppression of c-myc and c-myb mRNA levels may be an early differentiation-related effect of aclarubicin. On the other hand, actinomycin D, 12.5 nM, and novobiocin, 300 microM, two other known inducers of granulocytic differentiation in HL-60 cells, did not induce an early decrease in c-myb or c-myc expression. Therefore, the immediate suppression of c-myc and c-myb mRNA levels, apparently, is not an obligatory step in chemically induced myeloid differentiation in HL-60 cells, but the common phenomenon in DMSO- and aclarubicin-induced differentiation.

Aclarubicin↗

PubMed1994

Early transient suppression of c-myb mRNA levels and induction of differentiation in Friend erythroleukemia cells by the [Ca2+]i-increasing agents cyclopiazonic acid and thapsigargin.

Cyclopiazonic acid and thapsigargin, inhibitors of the endoplasmic reticulum Ca2+ pump were shown to elevate [Ca2+]i in Friend erythroleukemia cells, line F4-6, at concentrations of 1-5 microM and 0.5-2 nM, respectively. At the same concentrations, these agents induced a strong suppression of c-myb mRNA levels within 3 h, whereas c-myc expression remained unaffected. The c-myb expression recovered and approached pretreatment levels at 9-12 h of incubation. The decrease in c-myb mRNA was prevented in Ca(2+)-free medium. Treatment of F4-6 cells with EGTA led to a transient increase in c-myb mRNA with the same kinetics as the Ca2+ pump inhibitor-induced suppression, indicating that c-myb expression is bidirectionally regulated by changes in [Ca2+]i. Studies on the differentiation status of F4-6 cells following cyclopiazonic acid or thapsigargin exposure demonstrated a marked increase in beta-globin mRNA synthesis at 60h and in hemoglobin production at 96 h. These results provide further evidence that a rise in the cytosolic Ca2+ concentration is capable, in Friend erythroleukemia cells, of inducing an early transient suppression of c-myb mRNA levels, which is followed by terminal erythroid differentiation.

Animals↗

PubMed1993

Calcium ionophore-induced transient down-regulation of c-myb mRNA levels in Friend erythroleukemia cells.

The effects of calcium ionophores A23187 and ionomycin on the c-myb and c-myc mRNA levels have been investigated in the Friend erythroleukemia cell line F4-6 using Northern blot analysis. Treatment of the cells with 0.5-4 microM A23187 or 1-4 microM ionomycin induced a concentration-dependent decrease in c-myb mRNA; this decrease was abolished by EGTA. c-myc mRNA levels were only moderately affected. After 12-24 h of calcium ionophore exposure, c-myb mRNA returned to pretreatment levels. No similar decrease in c-myb mRNA was seen with the sodium ionophore monensin (up to 16 microM). The dimethyl sulfoxide-induced suppression of c-myb and also of c-myc mRNA levels was not prevented in Ca(2+)-free medium and thus appeared Ca(2+)-independent. A23187 and ionomycin were capable of inducing beta-globin mRNA synthesis in F4-6 cells. Prolonged calcium ionophore exposure, however, strongly reduced cell viability and resulted only in a slight hemoglobin increase at lower concentrations. These results suggest that a rise in [Ca2+]i may be a signal leading to a transient decrease in c-myb mRNA and the initiation of erythroid differentiation in Friend cells. The transient suppression of c-myb mRNA levels represents a common feature of the action of dimethyl sulfoxide and calcium ionophores.

Actins↗

PubMed1990

Large-scale gel filtration chromatography for the production of a solvent/detergent-treated high-purity factor VIII concentrate.

To produce a tri(n-butyl)phosphate/sodium-cholate-treated intermediate-purity factor VIII (FVIII) concentrate with a specific activity of about 1 IU/mg, we used a simple gel filtration step with Sephadex G25 to remove the solvent/detergent reagents from the final product. By exchanging the Sephadex G25 gel for a new high-resolution gel (Sephacryl S400 HR), we obtained a high-purity FVIII concentrate, by simultaneous elimination of about 98% of the extraneous proteins and removal of the solvent/detergent reagents, without reducing the FVIII:c yield and without altering the production scheme. With different protein analysis techniques we analysed the resulting FVIII concentrate and, comparing it to the formerly produced intermediate-purity FVIII concentrate, demonstrated improved purity.

Cholic Acid↗

PubMed1989

Chemical and immunochemical characterization of polymers of aggregates in preparations of human serum albumin.

The polymer/aggregate fractions of three human serum albumin preparations (HSA) from different manufacturers were isolated by size-exclusion high-performance liquid chromatography (HPLC) and analyzed by different electrophoretic and immunochemical methods. All of these polymer/aggregate fractions contained only 30-50% albumin. The rest seemed to be mainly heat-denatured haptoglobin which did not react with an anti-haptoglobin serum, whereas the albumin part reacted with an anti-albumin serum. It could be shown that these polymers or aggregates are formed by disulfide bonds between albumin and the small amounts of denatured impurity globulins (haptoglobin, transferrin) during the pasteurization step. The higher the amount of these heat labile globulins in the final preparation before the pasteurization step, the higher was the polymer/aggregate content of the pasteurized albumin preparation.

Blood Protein Electrophoresis↗

PubMed1989

[Problems in the production of human albumin solutions].

Formation of particles in human albumin solutions during the 10 h pasteurisation is discussed in detail as well as the formation of albumin polymers during the course of manufacture. The problems of green colour and of aluminium ions occurring in albumin solutions are touched upon.

Blood Protein Electrophoresis↗

PubMed1985

[Stability of blood coagulation factors in plasma frozen 6 and 18 hours after blood collection].

In 50 plasma samples flash frozen at -40 degrees C within 6 h and in 50 samples flash frozen within 18 h after phlebotomy, both coagulation factors II, V, VII, VIII, IX and X as well as AT III, APTT and Quick were measured. Only factor VIII in 18-h plasma showed an average decrease from 0,99 IU/ml to 0,85 IU/ml, i. e. 15% compared to 6-h plasma. None of the other coagulation factors or parameters exhibited any change beyond normal ranges. Furthermore, 150 6-h and 150 18-h plasma samples were taken from routine production and after thawing were tested for factor VIII- and factor-V activity. In a long-term study following a one year's storage at -30 degrees C of 30 samples of 6-h plasma and 30 samples of 18-h plasma, a decrease was found with factor VIII from 0,97 IU/ml to 0,93 IU/ml in 6 h-plasma and from 0,90 IU/ml to 0,86 IU/ml in 18 h-plasma. Our results demonstrate that only minor differences exist in activity of coagulation factors of 6-h and 18-h plasma. Hence follows that by observing the instructions described, freezing must take place within an 18-h period after phlebotomy which thus allows 12 more hours for production without losses in activity.

Blood Coagulation Factors↗

PubMed1981

[Use of routinely performed spirometry in the general medical examination (author's transl)].

The value of routine spirometry was investigated in 631 unselected out-patients. The spirogram was abnormal in 17%, the ECG in 15% and the chest X-ray in 13% of patients. Pathological spirograms correlated mainly with mild or moderate obstructive ventilatory disturbances (80%) which were associated with clinical findings in only 74%. In the ECG, disturbances of repolarisation were more common (71%) than those of stimulation and conduction (29%) and were associated with clinical findings in 65%. In 91% of patients with pathological chest radiograms other investigations had indicated the necessity for an X-ray. Thus spirometry is, in addition to ECG and chest X-ray, a useful routine method. As disorders of the lung function are not always predictable by smoking habits, spirometry offers the possibility for early detection of symptom-free disease of the lung and respiratory tract.

Electrocardiography↗