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C Muller

Publications and source records attributed to C Muller.

At least 91 records · Page 5Linked to original sources
PubMed1995

P-glycoprotein stability is affected by serum deprivation and high cell density in multidrug-resistant cells.

The control of P-glycoprotein (Pgp) expression in multidrug-resistant cells (MDR) is complex and may be regulated at different levels. We have investigated Pgp stability in four different human and hamster MDR cell lines. Using a pulse-chase procedure we show that Pgp half-life is between 14 and 17 h in all these cell lines when they are growing exponentially. However, in the presence of a low level of serum, Pgp half-life is increased four to sixfold. A similar effect is observed when the cell cultures are maintained in high cell density. The increased Pgp stability appears to be differently regulated as serum deprivation results in a general enhanced degradation of total cytoplasmic and membrane proteins. Moreover, the observed serum effect suggests the involvement of growth factors in the control of Pgp stability. These findings suggest that protein stability may be an important factor in the regulation of Pgp expression.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Elevated levels of serum carbohydrate deficient transferrin are not specific for alcohol abuse in patients with liver disease.

BACKGROUND: Serum carbohydrate deficient transferrin is a marker of chronic alcohol consumption; it increases above normal in healthy individuals after a daily alcohol intake of more than 60 g/d for more than 2 weeks. The influence of liver disease itself on carbohydrate deficient transferrin levels has not been sufficiently established. METHODS: We investigated serum levels of carbohydrate deficient transferrin in 196 consecutive patients admitted to our Gastroenterology and Hepatology Unit and correlated this parameter with the patients' statements about alcohol intake during the previous 2 weeks and with other markers of chronic alcohol consumption. RESULTS: In our patient population, carbohydrate deficient transferrin had the best overall performance with respect to sensitivity (88%), specificity (82%), and negative predictive value (98%), as compared to other markers, although specificity was much lower than previously reported in patients without liver disease. In the group of patients with liver disease, sensitivity and specificity were 90% and 73%, respectively, and in patients without liver disease, 80% and 88%. The negative predictive value was excellent (96% for patients with liver disease and 99% for patients without liver disease). CONCLUSIONS: Thus, in a patient with a negative interview for chronic alcohol abuse and normal carbohydrate deficient transferrin level, alcohol is unlikely to be the cause of liver disease, and further investigations to establish the etiology of liver disease are warranted. An increased carbohydrate deficient transferrin level, however, cannot be regarded as reliable evidence for chronic alcohol abuse in patients with liver disease.

Adolescent↗
PubMed1995

Measurement of epidermal moisture content by magnetic resonance imaging: assessment of a hydration cream.

The moisture content of the epidermis was measured by magnetic resonance imaging (MRI), using transverse relaxation time. The spatial resolution was 86 microns, allowing a quantitative, accurate and localized determination of variations in epidermal hydration. The wrists of 15 volunteers were studied before and after application of a hydration cream. Results showed an increase of 15% of epidermal T2 after application of the cream. Moisture content curves varied according to different degrees of skin dryness. This study demonstrates that MRI is a useful tool in evaluation of epidermal hydration.

Administration, Cutaneous↗
PubMed1995

Massive isotretinoin intoxication.

We report a case of acute intoxication due to a massive overdose of isotretinoin. A 29-year-old male patient ingested 900 mg of isotretinoin corresponding to 12.5 mg (kg/day) or 30 times the prescribed dosage and 1 day later the patient experienced mild headache. Forty-eight hours later, cheilitis, diffuse cutaneous xerosis and desquamation of the forehead and of the external auditory meatus occurred; cutaneous xerosis and cheilitis resolved spontaneously, We determined the serum level of isotretinoin and of 4-oxo-isotretinoin, its natural metabolite in sera taken 4, 5, 6 and 11 days following ingestion. The side-effects were mild and represented only exacerbations of some common isotretinoin side-effects. To date, three other cases of isotretinoin overdosage have been reported. There was a low toxicity of isotretinoin overdose.

Adult↗
PubMed1995

Lack of correlation between expression and function of P-glycoprotein in acute myeloid leukemia cell lines.

In a panel of acute myeloblastic leukemia (AML) cell lines, representative of distinct differentiation stages, we investigated the possible correlation between drug-resistance and both expression and function of the multidrug resistance (MDR)-related P-glycoprotein (P-gp). The AML cell lines were KG1a, KG1, TF1, HEL, ML1, and two non drug-selected P-gp positive subclones originating from HL-60 (HL-60JD) and U937 (U937AQ). All these cells overexpressed the mdr1 gene (analyzed by RT-PCR) and displayed variable levels of P-gp expression. Flow cytometric semi-quantitative evaluation of P-gp with two P-gp specific monoclonal antibodies (MRK16 and UIC2) showed the following P-gp expression hierarchy: TF1 < KG1a < HEL < KG1 < HL-60JD < ML1 < U937AQ; the latter expressing 13 times more P-gp than TF1. When P-gp function was assessed by Rhodamine 123 (Rh123) efflux kinetics, we found that only KG1a and KG1 cells, which have an early (immature) CD34+ CD33- CD38- phenotype, and to a lesser extent TF1, with an intermediate (CD34+ CD33+ CD38+) phenotype, displayed significant P-gp activity which could be inhibited by both verapamil and SDZ PSC 833. In contrast, the other more mature CD33+ CD34- AML cell lines presented no Rh123 efflux capacity although they expressed higher P-gp levels. Daunorubicin (DNR) accumulation studies showed that inhibitors of P-gp increased DNR accumulation only in the immature AML cells whereas they had no impact on the mature AML cell lines. MTT drug cytotoxicity assay confirmed that the immature AML cells were 10-15-fold more resistant to DNR than the mature AML cells. Although P-gp inhibitors were able to increase the cytotoxicity of DNR in AML cells which displayed functional P-gp, they could not increase DNR cytotoxicity to levels comparable to that of the CD34- CD33+ cells, suggesting that DNR resistance of immature AML cells may not solely be related to P-gp. With drug-selection, AML subclones displayed higher levels of P-gp expression and higher extruding capacities, and therefore chemoresistance, and this independently of their initial differentiation phenotype. Finally, this study provides evidence for a lack of correlation between expression and function of P-gp in AML cells; this relationship being dependent upon leukemic cell differentiation in unselected myeloid leukemic cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Evidence for transcriptional control of human mdr1 gene expression by verapamil in multidrug-resistant leukemic cells.

We investigated the mechanism of verapamil (VRP) effects on mdr1 gene expression in two leukemic multidrug-resistant (MDR) cell lines, K562/ADR and CEM VLB100. Exposure to VRP for 24 hr resulted in a decrease in mdr1 mRNA levels that was dose related at concentrations between 15 and 50 microM. The maximal decrease of mdr1 mRNA levels was found to be 6-fold in the K562/ADR cells and 3-fold in the CEM VLB100 cells. The effect of VRP on mdr1 mRNA levels was, however, biphasic. At 100 microM VRP, which strongly inhibited cell proliferation, a 2-fold increase of mdr1 mRNA levels was observed in the K562/ADR cells. To determine whether the decrease of mRNA levels resulted from post-transcriptional mechanisms, mRNA stability was studied after blocking of transcription with actinomycin D in VRP-treated cells and in control cells. This study revealed that mdr1 mRNA was stable in both cell lines and no increase in mdr1 mRNA degradation was observed in the 30 microM VRP-treated cells versus control cells (half-lives of 23 hr versus 14 hr for the K562/ADR cells and 15.5 hr versus 10.0 hr for the CEM VLB100 cells). The suggestion of a transcriptional mechanism was confirmed by nuclear run-on assays. A 4-fold decrease in the mdr1 gene transcription rate was observed in the 30 microM VRP-treated CEM VLB100 cells. The decreased transcription rate could be due to the decrease in mdr1 proximal promoter activity observed in CEM VLB100 cells transiently transfected with the mdr1 promoter fused to the chloramphenicol acetyltransferase gene. Indeed, after exposure to 30 microM VRP, chloramphenicol acetyltransferase activity was decreased by 2-fold. This study reports for the first time a down-regulation of mdr1 gene transcription by a pharmacological agent. These results provide further identification of the regulatory mechanisms involved in the overexpression of mdr1 in MDR cells and may help in the development of new strategies for MDR reversal.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Effect of the protein kinase C inhibitor staurosporine on chemosensitivity to daunorubicin of normal and leukemic fresh myeloid cells.

The effect of the protein kinase C (PKC) inhibitor staurosporine (ST) on the chemosensitivity of normal (colony-forming unit granulocyte-macrophage [CFU-GM]) and leukemic (acute myeloid leukemia-CFU [AML-CFU]) myeloid progenitors to daunorubicin (DNR) was evaluated. Primary colony inhibition assays allowed us to characterize two distinct groups of AML, a DNR-resistant group (patients no. 1 through 6), which displayed significantly lower DNR sensitivity than normal CFU-GM (D50 = 11.3 +/- 1.4 ng/mL v 1.8 +/- 0.5 ng/mL, after 7 days of exposure, respectively; P < 0.01) and a DNR-sensitive group (patients no. 7 through 12) with D50 = 2.7 +/- 0.4 ng/mL. This classification remained unaltered when assessed by secondary colony inhibition assay (evaluating the self-renewal fraction of AML-CFU) or by viability assay (evaluating the ultimately differentiated blast cell population), suggesting that the DNR sensitivity profile in maintained throughout AML-CFU differentiation. DNR resistance of the differentiated blast cell population was not correlated with the level of P-glycoprotein (P-gp) expression but rather with the ability to extrude rhodamine 123 (Rh123). ST used at subtoxic concentrations induced a twofold to threefold enhancement of DNR cytotoxicity, increased Rh123 accumulation, and decreased Rh123 efflux kinetics in resistant AML cells. These effects were observed for ST concentrations much lower than those required to displace the P-gp-binding probe azidoprazosin, suggesting that ST might act through its PKC inhibitory effect and not through P-gp binding. Finally, this study provides evidence that DNR resistance in AML cells is, at least in part, related to the multidrug-resistance (MDR) phenotype. Because P-gp function can be downregulated by ST, it seems likely that the MDR pheno-type can be functionally regulated by cellular signalization in AML cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Verapamil decreases P-glycoprotein expression in multidrug-resistant human leukemic cell lines.

We studied the effect of verapamil on Pgp expression (Pgp) in MDR human leukemia cell lines, K562/ADR and CEM VLB100. In the K562/ADR cell line, addition of verapamil to the culture medium (15 microM concentration) resulted in a 3-fold decrease in Pgp expression after 72 hr exposure. The effect of verapamil was reversible, and Pgp expression reached the level of untreated controls 24 hr after discontinuation of verapamil. Similar results were obtained with the human vinblastine-resistant cell line, CEM VLB100. On the contrary, no effect on Pgp expression was observed when the cells were treated with nifedipine or diltiazem (2 other calcium-channel blockers), even at doses that inhibited cell proliferation. The level of Pgp mRNA in the presence of verapamil was measured by Northern blot and was also decreased 2-fold (with the maximum reached within 24 hr), suggesting a transcriptional or post-transcriptional mechanism for verapamil. We further established that the effect of verapamil on Pgp expression led to an increase in DNR and VLB accumulation and cytotoxicity. These results suggest that verapamil acts specifically on Pgp expression in these drug-selected leukemic cells. The identification of a potentially novel mechanism of action may provide new insights as to how chemosensitization may be more effectively applied in vivo.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Optimization of immunohistochemical detection of P-glycoprotein in chronic lymphoid disorders.

To optimize the immunohistochemical detection of the multidrug resistance (MDR)-associated P-glycoprotein (P-gp) in chronic lymphoid disorders, the authors compared the sensitivity of three different monoclonal antibodies (MoAb) directed against P-gp (C219, JSB-1, and MRK 16) by using the APAAP technique on four tissue preparations obtained from lymphoid tumors: Cryostat sections, ModAMEX processed sections, frozen cytospin preparations, and fresh cytospin preparations. Tumor samples were obtained from patients with previously treated chronic lymphocytic leukemia (6 cases) or non-Hodgkin's malignant lymphoma (4 cases). Lymph nodes (n = 9), spleen (n = 3), and blood (n = 5) were analyzed. JSB-1 MoAb detected P-gp in 4 of 12 cases (33.3%) on either frozen sections or ModAMEX processed sections, and in 6 of 17 cases (35.3%) on frozen cytospin preparations. The sensitivity of JSB-1 was significantly improved when fresh cytospin preparations were used with an incidence of P-gp positive samples as high as 70.6% (P < .05). C219 MoAb was unreactive with lymphoid cells whatever the technique used, whereas this antibody stained stromal cells. MRK 16 MoAb was equally reactive to JSB-1 on fresh cytospin preparations, but unreactive when the other preparations were used. The specificity of JSB1 MoAb was confirmed by both Western blot analysis and Rhodamine 123 efflux assay. The authors used JSB-1 MoAb on fresh cytospin smears prepared from 28 CLL patients. Overall incidence of P-gp positive cases was 39.2%. Univariate analysis showed that P-gp expression was correlated with prior therapy, refractoriness to treatment, Rai stratification, and time of tissue storage after diagnosis. The authors recommend the use of JSB-1 on fresh cytospin preparations for the immunocytochemical detection of P-gp in chronic lymphoid disorders.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

bcl-2 proto-oncogene and Epstein-Barr virus latent membrane protein-1 expression in AIDS-related lymphoma.

The expression of bcl-2 protein and Epstein-Barr virus (EBV) latent membrane protein 1 (LMP-1) was investigated in 18 cases of lymphoma occurring in the acquired immunodeficiency syndrome (AIDS). EBV small RNAs were detectable in tumour cells in all cases by in situ hybridization with EBER oligonucleotides. LMP-1 expression was detected in 61% of the cases, and 55% were positive for bcl-2. Dual expression of LMP-1 and bcl-2 was found in 8/18 (44%) cases, while five cases (28%) expressed either LMP-1 or bcl-2 and five expressed neither. Thus, there was an inconsistent relationship between the presence of EBV and the expression of bcl-2. One LMP-1 negative case was found to express bcl-2 in reactive lymphocytes but not in lymphoma cells. No clinical features were found to correlate statistically with LMP-1 or bcl-2 expression in the tumour cells. However, CD4 counts at diagnosis were significantly lower in bcl-2 positive cases (P < 0.05). The respective roles of EBV LMP-1 and the expression of bcl-2 in lymphogenesis in AIDS patients remains complex and is not yet fully understood.

Adult↗
PubMed1994

Effects of feeding practices on milk fat concentration for dairy cows.

Thirty-seven dairy farms, using high producing (7500 kg/yr per cow on average) Montbéliarde cows that were fed hay-based rations, were included in a detailed survey involving the structure of the farm and the herd, the quality of forage, the feeding practices in winter and summer, and genetic characteristics of the cows (breeding values and herd effects). These data were used to analyze variation in milk fat concentration among farms, particularly variation linked to environmental factors, as assessed by the herd effect. When farms were ranked according to herd effect of fat concentration, farms with the highest herd effects fed concentrate to cows in rolled form, distributed forage before or with the concentrate, and provided hay in the trough in summer. The effects of such practices on digestive phenomena in the rumen are discussed. This study supported the use of herd effects to identify factors related to variation in dairy cow performance.

Animal Feed↗
PubMed1994

[Pharmacological control of P-glycoprotein expression].

Calcium channel inhibitors, such as verapamil, have been identified as having the ability to modulate the multidrug-resistant (MDR) phenotype due to overexpression of P-glycoprotein (Pgp). We have studied the effect of verapamil on Pgp expression levels in a cell line originating from acute myeloblastic leukemia and resistant to adriamycin, K562/ADR. In this line, the addition of 15 microM verapamil in the culture medium gives a 3-fold decrease of Pgp expression after 72 hours of treatment. Similar results have been obtained for two other MDR cell lines, which suggest that this phenomenon is not specific of a single model. The level of mdr1 mRNAs is decreased in the presence of verapamil (with a maximum effect obtained at the 24th hour), which suggests that the mechanism of action of verapamil is transcriptional and/or post-transcriptional. We have also studied the effect of verapamil on the level of expression of mdr1 mRNAs in non-drug selected cells such as the HEL line (human acute myeloblastic leukemia) and the parental K562 line, which present a very low level of expression of Pgp, detectable only by PCR. In these lines, verapamil treatment has no effect on the level of expression of mdr1 mRNAs. The effect of verapamil is therefore restricted to drug-selected lines presenting high levels of Pgp expression. The impact of the negative regulation of Pgp expression on the MDR phenotype has been studied in the K562/ADR line. When the cells are treated for 72 h by verapamil, there is a decrease of resistance and an increase of intracellular accumulation of anticancer agents such as daunorubicin or vinblastine. Negative regulation of Pgp expression appears therefore as a possible strategy for MDR phenotype reversal. The effect of verapamil, whose molecular mechanism of action is being studied, could constitute a basis for this strategy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

[The clinic as profit center and management with reference figures].

Financial responsibility is one of the important aspects of hospital management. At the hospital of Uster a trial with a profit center concept was started in October 1991. This concept included development of management tools such as reference figures to check costs, returns and performance. Thus it was possible to obtain an equilibrium between personnel costs and performance within 6 months. In the first half of 1993 the budgeted performance figures for 1993 have so far been reached. Although a complete implementation of a profit center concept in a public hospital does not seem possible, a profit center-like structure helps to obtain financial control and enables the hospital management to readily adapt to changing conditions.

Budgets↗
PubMed1994

Antisense inhibition of myeloperoxidase increases the sensitivity of the HL-60 cell line to vincristine.

Myeloperoxidase (MPO), a heme-peroxidase found in the HL-60 myeloblastic cell line, is involved in vincristine (VCR) metabolism and the inactivation of this drug. We have examined whether decreased MPO activity correlated with increased sensitivity to VCR toxicity in myeloid leukemia cells. We have used MPO antisense RNA to reduce 60% of the MPO activity in the HL-60 cells. The MPO-deficient HL-60 cell line, C15, was significantly more sensitive to VCR than the parental MPO-positive cell line. Both cell lines were negative for P170-glycoprotein expression. Conversely, an MPO-positive C15 subclone was more resistant to VCR than the MPO-deficient C15 cell line. No significant differences in cytotoxic effects were observed between MPO-positive and MPO-deficient cells, following treatment with either daunorubicin or actinomycin D, two multidrug resistance-related drugs. These results strongly support an important role for MPO in VCR resistance in HL-60 cells. Antisense manipulation of the MPO content of myeloid cells could be of potential interest in leukemia treatment.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

[1-year follow-up of laparoscopic cholecystectomy in an unselected patient sample. Objective findings and subjective status].

We report on the 1-year follow-up after laparoscopic cholecystectomy in a consecutive series of 116 unselected patients. So far no such follow-up data have been published. The follow-up rate was 94%. All patients have been personally assessed on the base of a standardized follow-up form either at the hospital (58%) or by the general practitioner (42%). Using an adapted modified Visick classification we have found an excellent or good result in 96% of the patients. Although there were some minor dyspeptic complaints and a few abnormal laboratory findings no patient had a suspicion of residual or recurrent gall stones. There has been no reoperation. In conclusion laparoscopic cholecystectomy yields very satisfactory short-term results 1 year after operation even in an unselected population of patients.

Adult↗
PubMed1994

[Is the intravenous cholangiogram of value in the preoperative period?].

The need for a routine preoperative intravenous cholangiogram (IVC) has been controversially discussed. We decided to assess if preoperative criteria such as history, clinical examination or laboratory findings could be used for selective indication for preoperative IVC. In a series of 146 patients with a preoperative IVC before undergoing laparoscopic cholecystectomy, history, clinical findings and laboratory results (bilirubin, transaminases, alkaline phosphatase, amylase) have been correlated with the radiological findings. ERCP was taken as the standard to assess the value of IVC. A normal IVC was quite reliable in excluding any pathology of the bile ducts or common bile duct stones. Thus specificity reached 96% and the negative predictive value was 97%. On the other hand a pathological IVC proved not to be a valid predictor of true pathological alterations. Sensitivity was only 60% and the positive predictive value just 55%. Over all accuracy was quite satisfactory (94%). We could not find a correlation between history, clinical or laboratory findings and the final result as assessed by ERCP. Therefore we could not find any useful parameters to define a selective policy for indication of preoperative IVC. On the other hand the IVC still proved useful to exclude relevant pathological findings. At the time being there is no strong argument for abandoning routine preoperative IVC.

Cholangiography↗