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Biomedical subjects

K Kurek

Publications and source records attributed to K Kurek.

7 recordsLinked to original sources
PubMed1999

Biological effects of a bifunctional DNA cross-linker. II. Generation of micronuclei and attached micronuclear-like structures.

Madin-Darby bovine kidney (MDBK) cells were treated with the bifunctional DNA cross-linker, L-7, to examine the generation of micronuclei and other nuclear abnormalities. The preceding paper demonstrates that L-7 treatment induces the formation of triradial and quadriradial chromosomes in MDBK cells. These chromosomes are believed to result from interduplex DNA cross-links formed between G-C rich centromeric satellite DNA regions on non-sister chromatids. Treatment produces a majority of centromere-positive micronuclei. In addition, many daughter cells remain attached by chromatin bridges which are sometimes beaded with micronuclei. Up to 15% of cell nuclei become lobular and fused with numerous micronuclear-like structures attached to their membranes. These attached structures are classified as attached micronuclear-like structures (AMNLS). Fluorescence in situ hybridization (FISH) using a centromeric satellite sequence was performed on treated cells. Hybridization reveals that intercellular bridges are composed of centromeric sequences and initiate at centromeric foci in daughter cells. Furthermore, the majority of junctions between AMNLS and nuclei contain an enhancement of centromeric signal. The frequency of AMNLS appears dependent on the concentration of L-7 and the duration of treatment. Similar results were found for the generation of cross-linked chromosome products in the previous paper. We suggest that AMNLS result from the abnormal mitotic segregation of cross-linked chromosome products.

Animals↗
PubMed1999

Biological effects of a bifunctional DNA crosslinker. I. Generation of triradial and quadriradial chromosomes.

Interduplex crosslinks by a bifunctional anthramycin DNA crosslinker produced triradial and quadriradial chromosomes. The crosslinker alkylates guanine at N-2. Bovine chromosomes contain GC-rich density satellite DNAs at the centromeric heterochromatin and is the basis for the formation of triradial and quadriradial chromosomes at the centromeres. The in situ crosslinking of interphase chromosomes indicates that the distance between centromeres is 17.5 A. We conclude that the nuclear matrix associated DNA in the centromeric heterochromatin of interphase chromosomes are positioned close enough for crosslinking to occur. We propose a model for the generation of triradial and quadriradial chromosomes based upon the number of interduplex crosslinks between two chromosomes.

Animals↗
PubMed1999

[Telomerase in diseases of the digestive system].

Synthesis of dezoxyrybonucleic acid at the ends of chromosomes by telomerase is the main process leading to indefinite cell proliferation. In contrary to majority of malignant tissues the telomerase activity is not detected in the most somatic cells. Detection of telomerase may be than an alternative to widely used diagnostic markers. It is proved that detection of telomerase activity is a useful method supporting cytology. Recent data confirm the correlation between the value of enzyme activity and progress of some cancers of digestive system. Therefore telomerase could play an important role in screening programs. Actually, the methods of detecting the enzyme activity are expensive and time consuming so their application in everyday clinical practice is limited. Simple immunohistochemical and immunoenzymatic methods are tested. New therapeutic procedures become available after describing the role of telomerase in carcinogenesis. The telomerase inhibitors are supposed to play an important role in the therapy of cancer. Such therapy could be efficacious in majority of cancers in which carcinogenesis depends on telomerase activation. Telomerase inhibitors are likely to be used in connection with surgery and followed by radio- or/and chemotherapy but the potentials of antitelomerase therapy should be defined more accurately.

Gastrointestinal Neoplasms↗
PubMed1979

Evaluation of the modified API 20C system for identification of clinically important yeasts.

The modified API 20C system (Analytab Products, Inc.) containing 19 carbohydrate assimilation tests was used to identify stock cultures of clinical isolates and routine clinical isolates from the Mayo Clinic mycology laboratory. The system provided correct identifications for 96% of the 505 organisms tested. The API 20C represents a commercial system useful for the identification of yeasts from clinical specimens. Although reliable, it is not a complete system and must be used in conjunction with microscopic morphological features for definitive identification. Since the system requires 72 h for identification, it is not designed for the rapid presumptive identification of such organisms as Cryptococcus neoformans; other biochemical tests must be used for this purpose.

Diagnosis, Differential↗