Fiber specific changes in sphingolipid metabolism in skeletal muscles of hyperthyroid rats.

Thyroid hormones (T3, T4) are well known modulators of different cellular signals including the sphingomyelin pathway. However, studies regarding downstream effects of T3 on sphingolipid metabolism in skeletal muscle are scarce. In the present work we sought to investigate the effects of hyperthyroidism on the activity of the key enzymes of ceramide metabolism as well as the content of fundamental sphingolipids. Based on fiber/metabolic differences, we chose three different skeletal muscles, with diverse fiber compositions: soleus (slow-twitch oxidative), red (fast-twitch oxidative-glycolytic) and white (fast-twitch glycolytic) section of gastrocnemius. We demonstrated that T3 induced accumulation of sphinganine, ceramide, sphingosine, as well as sphingomyelin, mostly in soleus and in red, but not white section of gastrocnemius. Concomitantly, the activity of serine palmitoyltransferase and acid/neutral ceramidase was increased in more oxidative muscles. In conclusion, hyperthyroidism induced fiber specific changes in the content of sphingolipids that were relatively more related to de novo synthesis of ceramide rather than to its generation via hydrolysis of sphingomyelin.

Recurrent bilateral serous cystadenomas in a premenarchal girl: a case report and literature review.

BACKGROUND: Ovarian serous cystadenomas are rare in children. No case of recurrence after surgical resection in a premenarchal girl has been published. CASE: An 8-year-old presented with abdominal pain and ultrasound showed bilateral ovarian cystic masses with normal clinical and laboratory exam. Cystectomies were performed revealing serous cystadenomas. Ten months later, her pain returned and ultrasound showed new cysts. Persistence of cysts and symptoms required repeat surgery with the same pathology. SUMMARY AND CONCLUSION: Premenarchal girls with ovarian cystic masses require surgical intervention in cases of persistent symptoms, uncertain diagnosis, or concern for ovarian torsion. With reassuring imaging and tumor markers, conservation of the ovary can be achieved with cystectomy alone. Ultrasound follow-up is recommended after surgical resection until bimanual exam can be performed.

[Telomerase in diseases of the digestive system]. / Telomeraza w chorobach przewodu pokarmowego.

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.

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.

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.

Nonrandom arrangement of bovine satellite I DNA within the interphase nucleus of Madin-Darby bovine kidney cells.

The distribution of bovine satellite DNA was examined in Madin-Darby bovine kidney cells for each hour of interphase. Cells were grown on coverslips and probed using biotinylated cloned fragments of bovine satellite I DNA. Hybridization was detected using a streptavidin-alkaline phosphatase conjugate. Cells were projected onto a grid of fixed dimensions and the distribution of hybridization signal was recorded. A chi 2 analysis of fit compared this distribution of signals to a random distribution generated from the poisson distribution. Nuclear localization of bovine satellite I DNA was found to be nonrandom throughout interphase except at the G1/S border and S = 6 h. Moreover, distinct patterns of hybridization were also observed at specific times during interphase.

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.