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K Marx

Publications and source records attributed to K Marx.

16 recordsLinked to original sources
PubMed2001

Early functional apoptotic responses of thymocytes induced by Tri-n-butyltin.

BACKGROUND: Programmed cell death, also termed apoptosis, is the main focus of interest in a variety of scientific and clinical areas. For a better understanding of the mechanisms of apoptosis, from the onset of the cellular death program to the late stages of apoptosis or apoptotic necrosis, very early functional events have to be quantified because they might be involved in temporal and causal relationships between apoptosis-related key processes. METHODS: We have established a flow cytometric technique to quantify time-dependent signals simultaneously with high temporal resolution (Deltat = 1 s) in living cells. With this technique, the response of cells to apoptosis-stimulating agents can be analyzed over 15 min. For this purpose, a thermostatted sample tube holder for repeatable interruption-free injection of substances into the cell suspension was developed. Early detectable fluorescence and scatter parameters were related to intracellular free Ca2+ concentration, [Ca2+]i (Indo-1 fluorometry), membrane permeability (propidium iodide [PI] influx), and cell volume (forward scatter). RESULTS: A T-cell line (Jurkat) served as a model system. Apoptosis was induced by the biozid Tri-n-butyltin (TBT). Dependent on the TBT concentration (0.3-10 microM), the mean free [Ca2+]i increased by a factor of 1.2-6 during a short time interval of just 2 min. Especially after low TBT concentrations (< 0.5 microM), this [Ca2+]i increase was nearly transient during the observation time of 15 min. Higher TBT concentrations (0.5-10 microM), however, induced a transient increase of [Ca2+]i (Ca-TR) only in a fraction of the cells; in another subpopulation, a steady-state Ca2+ signal (Ca-SST) was observed. The analysis of the simultaneously registered PI signals of the Ca-SST cells showed a shift to increasing PI fluorescence (by a factor of about 4) with increasing Ca2+ concentrations. In Ca-TR cells, the PI fluorescence remained nearly unchanged. These apoptosis-related changes (increase in [Ca(2+)]i and membrane permeability) could be confirmed by the additional observation of a TBT concentration-dependent decrease in cell volume measured during the same early time period. CONCLUSIONS: The simultaneously analyzed parameters (i.e., [Ca2+]i, membrane permeability, and cell volume) suggested that, in our model system of Jurkat T-cells treated with TBT, an apoptotic cell fate was indicated very early (within 15 min) by the steady-state [Ca2+]i level.

Apoptosis↗
PubMed2000

8-phenyl-10,10a-dihydropyrido

Base treatment of the pyridinium bromides 11a-e gives rise to the formation of the dihydropyridoazepines 14a-e as the only monomolecular products. The reaction takes place by initial deprotonation to the ylides 12, which undergo 8pi-electrocyclization affording the seven-membered-ring systems; no products of a dipolar 6pi-cyclization were detected. On the basis of quantum mechanical calculations a rationalization of the periselectivity of the electrocyclization process is given.

Journal Article↗
PubMed1998

Chromosomal aberrations in couples undergoing intracytoplasmic sperm injection: influence on implantation and ongoing pregnancy rates.

OBJECTIVE: To determine the incidence of chromosomal aberrations in couples undergoing intracytoplasmic sperm injection (ICSI) and their influence on subsequent implantation and ongoing pregnancy rates. DESIGN: Prospective study. SETTING: Fertility center. PATIENT(S): Candidates for ICSI. INTERVENTION(S): Chromosomes were trypsin-banded in 2,280 patients. In all cases, 10 metaphases were karyotyped. Sex chromosome analysis was performed in 10 additional metaphases. When apparent chromosomal aberrations were detected, 100 metaphases were analyzed. MAIN OUTCOME MEASURE(S): Implantation and ongoing pregnancy rates in couples with a chromosomal disorder. RESULTS: A chromosomal abnormality was demonstrated in 7.2% of all couples. Among the male partners, 4.48% had aberrations. Autosomal aberrations were present in 2.96%, and numerical or structural sex chromosome abnormalities were found in 1.52%. Among the female partners, numerical or structural abnormalities were documented in 9.79%. Only 2.32% of the female partners had autosomal structural abnormalities. Numerical or structural anomalies involving sex chromosomes were found in 7.47%. Implantation rates of 9.4% and 16.3% per embryo were observed in female partners with sex chromosome mosaicism and autosomal aberrations, respectively. In male partners, the respective rates were 3.8% and 23.1%. CONCLUSION(S): The incidence of chromosomal disorders in couples seeking ICSI treatment is considerable, especially minor mosaicism (<10%) of sex chromosomes in the female partners. Preliminary data indicate a low implantation rate in couples with minor mosaicism of sex chromosomes.

Adult↗
PubMed1997

Flow cytometric analysis of micronuclei in cell cultures and human lymphocytes: advantages and disadvantages.

Flow cytometric techniques are described to quantify micronucleus (MN) induction in cell cultures and human lymphocytes. The advantages and disadvantages of these techniques are discussed. Because a suspension of nuclei and MN has to be prepared for flow cytometric measurements, care has to be taken to avoid unspecific debris that can influence the results. Using additional flow cytometric parameters, most of the unspecific particles in the suspension can, however, be gated out. Apoptotic cells and apoptotic bodies can overlap the MN during measurement, it is, therefore, proposed not to use the technique if apoptosis is induced by the respective treatment. Advantages of the automated flow cytometric techniques are that results can be obtained in short time intervals, the frequency of MN and the DNA distribution of MN can be measured simultaneously and flow sorting can be used for a further analysis of MN using other techniques.

Apoptosis↗
PubMed1997

Reduced expression of the ICE-related protease CPP32 is associated with radiation-induced cisplatin resistance in HeLa cells.

Low-dose fractionated gamma-irradiation (three cycles of 5 x 2 Gy) induced cisplatin resistance in HeLa cells. The drug resistance was modest (Rf of about 2) and stable, similar to that found previously in murine cells after irradiation. In the drug-resistant HeLa-C3 cells, flow cytometric analysis revealed a decreased number of apoptotic cells compared with the parental cells. Drug resistance was associated with considerably enhanced expression of the p53 suppressor protein in HeLa-C3 cells after cisplatin exposure but seemed not to be regulated by the bcl-2-dependent pathway. Cisplatin resistance correlated with reduced expression of ICE-related proteases (interleukin-1beta-converting enzyme). Basal levels of the 45-kDa precursor ICE protein were reduced in HeLa-C3 cells, while those of the mature 60-kDa heterotetramer were similar. The CPP32 protease, a member of the ICE family with structural homology but different substrate specificity, was expressed at a lowered level. After drug exposure, there was a slight increase of CPP32 in HeLa-C3 cells, equivalent to about 45% of the level attained in the parental cells. This is in contrast to the CPP32 levels measured after irradiation, which were similar in sensitive and in resistant cells. As the radiosensitivity is unchanged in both cell lines, these results suggest that cisplatin resistance in HeLa-C3 cells is associated with alterations of a CPP32-linked apoptotic pathway, which is affected by the damage caused by cisplatin but not by irradiation. Whether these changes are dependent on the observed p53 modifications is now being studied in resistant clones.

Antineoplastic Agents↗
PubMed1988

Spinal cord contusion in the rat: somatosensory evoked potentials as a function of graded injury.

A weight-drop technique was used to produce mild, moderate, or severe spinal cord contusive injury in rats. At 4 weeks after injury, somatosensory evoked potentials (SEPs) were recorded with silver ball electrodes placed over the somatosensory cortex of anesthetized rats to measure the response to sciatic nerve stimulation. Both SEP area and amplitude were measured and were highly correlated with each other. Both indices of the SEP correlated inversely with the height of the weight drop and directly with the degree of residual function assessed at 4 weeks after injury. Measures of residual function consisted of a motor score, inclined plane test, and a combined behavioral score based on several neurologic functions. No correlation between latency of the SEP with degrees of contusive injury was observed. The data indicate that the SEP can be used as one criterion in the assessment of the severity of a lesion in a rat model of a graded spinal cord injury.

Animals↗
PubMedDate not supplied

[The significance of professional activity for future concepts of the elderly].

Shaping one's own way of life is essentially a matter of planning, in terms of both subject matter and time span. In an experiment involving 100 men and women of pre-pension age, the authors sought to ascertain how much the personality-forming-effects of occupational work bear upon the spheres and dimensions of people's conceptions of their old-age life. The results prove that lifelong learning, the measure of responsibility and the importance attached to one's own vocational career correlate positively with the score and time span of such conceptions.

Adaptation, Psychological↗
PubMedDate not supplied

Clonal variability of radiation-induced cisplatin resistant HeLa cells.

Low-dose fractionated gamma-irradiation (3 cycles of 5x2 Gy) induces moderate cisplatin resistance in HeLa cells which is associated with alterations of the caspase-dependent apoptotic pathway (2). There is a considerable heterogeneity in cell survival among isolated resistant clones (Rf values between 1.4 to 2.4) and in the propensity of the cells to enter apoptosis. These variations are associated with altered activation of the apoptotic pathway by members of the TNF family. The membrane receptor CD95 (Apo-1/Fas), which is upregulated immediately after cisplatin exposure in parental HeLa cells, is expressed at various levels in the resistant clones. There are also changes in the formation of the inhibitor protein I kappa B, which regulates the antiapoptotic transcription factor NF kappa B. Since the response to radiation is unchanged, the results collectively suggest that changes in the activation of the caspase-dependent signalling cascade are involved in the death pathway initiated by cisplatin but not by radiation damage.

Antineoplastic Agents↗