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Biomedical subjects

U Wick

Publications and source records attributed to U Wick.

17 recordsLinked to original sources
PubMed2005

FISH studies on the telomeric regions of the T-cell acute lymphoblastic leukemia cell line CCRF-CEM.

So far, the problem of an influence of translocations on the telomeres of the involved chromosomes has not been addressed yet in human cells. Therefore, the telomeres of a karyotypically rather well characterized T-cell acute lymphoblastic leukemia (T-ALL) cell line (CCRF-CEM) with several marker chromosomes were examined using peptide nucleic acid (PNA) telomere FISH probes to compare the telomere length of these markers with that of the chromosome arms of their origin. In addition, chromosome libraries, centromeric probes, and subtelomeric DNA probes were used to further define the marker chromosomes. Two markers could be newly defined and a concise karyotype of the cell line could be obtained by these detailed examinations: 42-47,X,-X,del(5) (q35?),t(5;15)(q14;q13.2),t(8;9)(p11;p24),del(9)(:p13-->qter)/inv(9)(pter-->p12::q21-->p12::q21-->qter),+13,+20,+der(22)(p+ [HSR?])[cp]. The relative telomere length of all chromosomes showed considerable interchromosomal, intercellular, and inter-passage variation. However, it could be shown, that in four different passages of the examined cell line the observed differences between relative telomere lengths of the markers and the chromosomes of their origin, with two exceptions (short arms of del/inv9 and der22), were not significant. On the other hand, because of its mentioned variability, telomere length alone is not sufficient to reliably define the derivation of markers.

Cell Line, Tumor↗
PubMed2005

Studies on the action of mitomycin C and bleomycin on telomere lengths of human lymphocyte chromosomes.

In order to address the problem of the action of cytostatics on chromosome ends, telomere length was measured in human lymphocyte cultures exposed to mitomycin C (MMC) and bleomycin (BLM). Telomere-specific PNA probes were used for the quantitative estimation of the relative telomere length of each individual chromosome by fluorescence in situ hybridization. A high inter-cellular and inter-individual variability of relative telomere lengths was found throughout all experiments. Different responses could be observed with respect to the action of the examined mutagens: The total average fluorescence intensity of labeled telomere repeats was decreased under the action of MMC in two of the experiments, while two revealed no significant alteration. BLM caused no significant change of total average telomeric signal intensity in four, a clear decrease in one of the six experiments, and an increase in another. Although all chromosome ends contributed to the observed trends, single telomeres were affected in a very distinct way. The highest concentration of MMC (1 microg/ml) induced significant shortening of telomeres of the chromosome arms; 2q, 3p, 5q, 7p, 10q, 11p, 13q, 17p, 18p&q, and 21q in two independent experiments. In one BLM experiment with 8 microg/ml, the most distinct decrease (p< or =0.005) of telomeric fluorescence was found at the ends of chromosome arms; 1q, 6p, 17p, 20p&q, and 22q. The increase of telomeric signal intensity affected the telomeres of some individual chromosome arms more than others, e.g. 4q, 6p, 7p, 8p, 13p, and 18q. Although the telomere length of the individual chromosome arms varied widely, clear trends could be observed with respect to the rank which was occupied by telomeric length of the various chromosome arms. The telomeres of the 1p, 3p, 4q, 5p, 12q, and 13q chromosome arms throughout all experiments were among the longest; and those of 13p, 15p, 21p, and 22p were among the shortest telomeres of the karyotype. From these data, it can be concluded that MMC affects the telomeric repeat area of chromosomes more than BLM, which mostly had no significant effect on telomere length in the performed experiments.

Adult↗
PubMed2005

The order of PNA-FISH-detected chromosomal telomere lengths in human T-cells is rather stable, even under the influence of strong mutagens.

The nucleo-protein structure of an intact telomere protects each chromosome from being recognized as a break and subsequently being degraded. The DNA component of this structure, the telomeric repeats, undergo attrition with every cell division, as well as in response to endogenous events, like oxidative stress. Exposure to exogenous damage promotes this process and leads to growth arrest, apoptosis and eventually to malignant transformation. It was thought that the shortest chromosome ends in humans are the most susceptible ones to become dysfunctional telomeres, and have therefore an important role in cell death and cancer. Here, we show that a stable hierarchy exists in the form of a telomere length profile of the whole human karyotype. This rank order is conserved between different human cell types and individuals, is maintained throughout a lifetime, and seems to be genetically determined. As a particular feature, this telomere length profile differs only marginally when normal human cell cultures and malignant transformed cells are compared. The profile is moreover stable when these different human cells are exposed to mutagens such as bleomycin or mitomycin C. From these findings, the question arises if also the stably long telomeres have a basic biological function.

Bleomycin↗
PubMed2005

Are telomeres a specific target for mutagenic attack by cytostatics in neoplastic cells?

Damage to telomeres induced by cytostatic therapy theoretically could generate telomere shortening and, subsequently, induce an additional genomic instability in neoplastic cells. Model experiments were carried out to examine this hypothesis. Cells of the T-ALL derived cell line CCRF-CEM were exposed to various different concentrations of Bleomycin (BLM) or Mitomycin C (MMC) for various times. Telomere lengths of metaphase chromosomes of the exposed cells were compared with those without this exposure (controls). In addition, telomerase activity was determined with a TRAP assay under the given conditions using the BLM experiments as a model. Although slight changes of total telomere length could be found in single experiments, the differences between exposed and non-exposed cells were not significant. Also, a considerable telomerase activity was shown which, however, did not substantially differ between exposed and non-exposed cells. From these data it may be concluded that, at least in the examined cell line, telomeres are not a preferential target for this kind of mutagenic attack.

Bleomycin↗
PubMed1995

Restriction fragment length polymorphisms at the apoprotein genes AI, CIII and B-100 and in the 5' flanking region of the insulin gene as possible markers of coronary heart disease.

Several sequence variations were examined for being endogenous "risk markers" in the development of CHD. The "markers" in this study included: the PstI-SstI RFLPs in the apo AI-CIII gene cluster, the EcoRI-MspI RFLPs in the apo B100 gene and the SstI RFLP in the 5' flanking region of the insulin gene. The study population comprised 700 individuals of German origin. A strong association of these "markers" to the disease phenotype predicts their loss in healthy individuals with ages above that of the prevalent incidence of CHD. In contrast, these "markers" should accumulate in diseased persons. A significant age-dependent selection was observed for the EcoRI RFLP in the apo B100 gene. This was the case when the allele and genotype frequencies of healthy old individuals were compared with those of newborns. In contrast, no RFLP showed significant differences in allele and genotype distributions between patients defined by coronary angiography and controls. In the group of patients, but not controls, several RFLP genotypes were found to be associated with significantly higher serum levels of cholesterol and triglycerides. This was true in the case of serum cholesterol comparing the genotypes S1S2 with those of S1S1 (p = 0.05) observed for the SstI polymorphic site in the 3' noncoding region of the apo CIII gene. Significantly higher levels of triglycerides were found within the heterozygous patients P1P2 (p = 0.045) and S1S2 (p = 0.02) than in the homozygotes P1P1 and S1S1 for the PstI-SstI RFLPs at the apo AI-CIII gene cluster.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

An 87 bp deletion in exon 5 of the LDL receptor gene in a mother and her son with familial hypercholesterolemia.

DNA analysis of the low density lipoprotein receptor (LDLR) gene was performed in two persons with familial hypercholesterolemia (FH). Southern blot experiments indicated the heterozygous loss of an EcoRI site in exon 5 of the LDLR gene. Upon amplification and sequencing of exon 5 in both probands, an 87-bp deletion in a heterozygous state could be evaluated. This is a novel mutation, most probably leading to the formation of a nonfunctional LDLR. Analysis of the deletion breakpoints revealed the presence of a six-base-pair consensus sequence 5'TGA/GA/GG/TA/C3', which is characteristic of small deletions in different genetic defects.

Adult↗
PubMed1993

Direct versus indirect molecular diagnosis of fragile X mental retardation in 40 German families at risk.

In order to test whether the direct molecular diagnostic approach for fragile X mental retardation (Martin-Bell syndrome, MBS) really makes diagnosis of this disease more precise, we evaluated the results of direct diagnosis in 40 German families at risk together with the results of an earlier study with closely linked flanking markers in the same families. Of 84 men analysed, 43 showed clinical signs. In 39 of these affected men the disease could be confirmed by direct diagnosis. Compared to cytogenetic data, one man was false negative and two were false positive. Two men, whose status could not be determined by means of RFLP data, proved to be normal transmitting males (NTMs). However, the possibility of being an NTM had to be rejected in one case on RFLP data. Fragile X syndrome could be confirmed in 10 of the 13 women with clinical signs. Compared to cytogenetic data there were three cases of false negative results and one of false positive. All 36 obligate carrier women were detected by the direct approach. In addition, 22 women were newly identified as normal transmitting females (NTFs), among them one woman who could not be identified by cytogenetic means or by analysis with closely linked markers. These findings are discussed in view of the relative reliability of the three diagnostic approaches to MBS. Special attention is drawn to the significance of false negative and false positive results in direct diagnosis.

Base Sequence↗
PubMed1990

[Analysis of alpha 1-antitrypsin deficiency using DNA methods].

Deficiency of alpha 1-antitrypsin can be diagnosed by DNA methods that are quick and also give reproducible results. Direct DNA analysis of the M, S, and Z alleles of the alpha 1-antitrypsin gene is possible when two molecular biology techniques are combined: a part of the gene is enzymatically replicated according to the pattern of the human DNA that is to be investigated. On hybridization with the various allele-specific pieces of synthetic DNA the copies that have come about in this way give a signal corresponding to the genotype. Only a small amount of material (0.5 microgram DNA) is needed for the investigation. This method is thus suitable for prenatal diagnosis when this is requested by members of a family known to be affected. A total of 53 samples were typed and investigations were carried out in six families.

Alleles↗
PubMed1979

Oscillations of cyclic nucleotide concentrations in relation to the excitability of Dictyostelium cells.

Aggregating cells of Dictyostelium discoideum are able to release cyclic AMP periodically. The oscillations of cAMP generation are associated with changes in adenylate cyclase activity. Cyclic AMP receptors on the cell surface are functionally coupled to the oscillating system as evidenced by phase shifts that are induced by small pulses of extracellular cAMP. An important element of the oscillating system is the signal processing from surface receptors to the adenylate cyclase. This pathway exhibits adaptation resulting in the suppression of responses to constant, elevated concentrations of cAMP. The signal input for adenylate cyclase activation is, therefore, a change in the extracellular cAMP concentration with time. Oscillations in the absence of detectable changes of intra- or extracellular cAMP concentrations suggest the possibility that there is a metabolic network in D. discoideum cells that undergoes oscillations without coupling to adenylate cyclase. Cyclic GMP concentrations oscillate with a slight phase difference in advance of that of cAMP, suggesting that the two nucleotide cyclases might not be activated by the same mechanism. Elevation of extracellular calcium exerts an inhibitory effect on the accumulation of cAMP and on the second of the two cGMP peaks.

Adenylyl Cyclases↗
PubMed1978

Cyclic-AMP stimulated calcium influx into aggregating cells of Dictyostelium discoideum.

Within about 10 seconds after stimulation of Dictyostelium discoideum cells with cyclic AMP an increased rate of 45Ca influx was observed. Part of the cellular calcium reappeared in the extra-cellular medium between 1 and 3 minutes after stimulation. No effect of 5'AMP on calcium distribution was found. The transient calcium influx is discussed in connection with chemotaxis and other cyclic-AMP induced responses.

Calcium↗
PubMed1975

Cell communication by periodic cyclic-AMP pulses.

At the surface of aggregating cells of the slime mould, Dictyostelium discoideum, two different sites interacting with extracellular cAMP are detectable: binding sites and cycl-nucleotide phosphodiesterase. Both sites are developmentally regulated. An adequate stimulus for the chemoreceptor system in D. discoideum is the change of cAMP concentration in time, rather than concentration per se: long-term binding of cAMP causes only short-term response. The system is, consequently, adapted to the recognition of pulses rather than to steady-state concentrations of cAMP. The ce,lls are, nevertheless, able to sense stationary spatial gradients and to respond to them by chemotactic orientation. The possibility is discussed that they do so by transforming spatial concentration changes into temporal ones, using extending pseudopods as sensors. The cAMP recognition system is part of a molecular network involved in the generation of spatio-temporal patterns of cellular activities. This system controls the periodic formation of chemotactic signals and their propagation from cell to cell. The phosphodiesterase limits the duration of the cAMP pulses and thus sharply separates the periods of signalling; the binding sites at the cell surface are supposed to be the chemoreceptors. The control of cellular activities via cAMP receptors can be studied with biochemical techniques with cell suspensions in which spatial inhomogeneities are suppressed by intense stirring, whereas the temporal aspect of the spatiotemporal pattern is preserved. Under these conditions it can be shown that the extracellular cAMP concentration changes periodically, and that the phase of the cellular oscillator can be shifted by external pulses of cAMP. It can also be shown that small cAMP pulses induce a high output of cAMP, which demonstrates signal amplification, a function necessary for a cellular relay system.

3',5'-Cyclic-AMP Phosphodiesterases↗