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M Masata

Publications and source records attributed to M Masata.

10 recordsLinked to original sources
PubMed2006

NORs and their transcription competence during the cell cycle.

In human cells ribosomal genes are organized as clusters, NORs, situated on the short arms of acrocentric chromosomes. It was found that essential components of the RNA polymerase I transcription machinery, including UBF, can be detected on some NORs, termed "competent" NORs, during mitosis. The competent NORs are believed to be transcriptionally active during interphase. However, since individual NORs were not observed in the cell nucleus, their interphase status remains unclear. To address this problem, we detected the competent NORs by two commonly used methods, UBF immunofluorescence and silver staining, and combined them with FISH for visualization of rDNA and/or specific chromosomes. We found that the numbers of competent NORs on specific chromosomes were largely conserved in the subsequent cell cycles, with certain NOR-bearing homologues displaying a very stable pattern of competence. Importantly, those and only those NORs that were loaded with UBF incorporated bromo-uridine in metaphase after stimulation with roscovitine and in telophase, suggesting that competent and only competent NORs contain ribosomal genes transcriptionally active during interphase. Applying premature chromosome condensation with calyculin A, we visualized individual NORs in interphase cells, and found the same pattern of competence as observed in the mitotic chromosomes.

Cell Cycle↗
PubMed2005

Dynamics of replication foci in early S phase as visualized by cross-correlation function.

To monitor gradual changes in the replication foci distribution during early S phase, different segments of newly synthesized DNA were visualized by immunocytochemical mapping of two consecutively incorporated deoxythymidine analogs in pulse-chase-pulse experiments in HeLa cells. The resulting dual-labeled fluorescence images were evaluated using cross-correlation function (CCF) analysis. General changes of CCF shape due to image deterioration caused by blur, noise, and lateral sampling (pixel size) were also discussed. Using CCF analysis of model images simulating either random initiation of new replication foci, or the firing of new foci in close proximity to completed ones, we were able to ascribe the changes in the early S replication foci distribution to the latter mechanism. In contrast to the data published previously, we monitored the dynamics of all replication foci for up to 3 h. In addition, we showed that the replication foci dynamics is well described by random walk model, so that the average de-localization of individual foci is proportional to square root of the applied chase.

DNA↗
PubMed2003

[Management of uterine myomas in women of fertile age].

OBJECTIVE: Review of current knowledge about uterine fibroids management in young women. Analysis of possible diagnostic and therapeutic algorithms regarding fertility preserving. DESIGN: Review article. SETTING: Department of Obstetrics and Gynecology, 1st Faculty of Medicine and the General Faculty Hospital, Charles University, Prague. METHODS: Analysis of the facts in literature (texts in medical journals, monographies, textbooks, internet database Medline and Ovid) and authors' clinical experience. CONCLUSIONS: Alternatives of treatment of infertility in women with uterine fibroids have significantly enlarged in past 10 years. However none of the indicated methods is perfect. Expectation does not exclude the risk of growth of fibroids and abortion. The effect of pharmacological therapy is only temporary. Myomectomy is associated with the risk of surgical complications, fibroids' recurrence and uterine rupture in subsequent gestation. Although uterine artery embolisation (on an average) halves the fibroids volume, the long-term effect of the method on female fertility is still unknown. Nevertheless it seems convenient to advise the active approach to all women planning pregnancy and having significant (submucous or intramural) fibroid even before spontaneous or assisted conception. Most recent studies indicate significant improvement of reproduction outcomes after myomectomy, especially in young women with the absence of other factors of infertility. Only the results of randomized, controlled trials (that are still awaited) will inform us about comparison of the effects and risks of myomectomy and uterine artery embolization in management of infertility.

Adult↗
PubMed2001

Non-isotopic mapping of ribosomal RNA synthesis and processing in the nucleolus.

The precise location of ribosomal RNA (rRNA) synthesis within the nucleolus is the subject of recent controversy; some investigators have detected nascent RNA in the dense fibrillar components (DFCs) while others have localized transcription to the fibrillar centers (FCs). We endeavored to resolve this controversy by applying a new technique for non-isotopic labeling of RNA and examined the synthesis and movement of non-isotopically labeled rRNA within the nucleolus. We found that rRNA is synthesized only in a restricted area of DFCs, also involving the boundary region with FCs. We traced a movement of RNA from transcription sites through DFCs to granular components. Our results indicate functional compartmentalization of DFCs with respect to the synthesis and processing of precursor rRNA. In situ mapping of the 5' leader sequence of the 5' external transcribed spacer together with transcription labeling indicated that transcription and the first steps in processing of precursor rRNA are spatially separated. Surprisingly, the results also pointed to a partially extended conformation of newly synthesized precursor rRNA transcripts.

Animals↗
PubMed2001

The supply of exogenous deoxyribonucleotides accelerates the speed of the replication fork in early S-phase.

Earlier studies have established that the average speed of a replication fork is two to three times slower in early S-phase than in late S-phase and that the intracellular 2'-deoxyribonucleoside 5'-triphosphate pools grow during S-phase. In this study, the effect of the exogenous 2'-deoxyribonucleoside 5'-triphosphate (dNTP) supply on the average replication speed in a synchronised population of human HeLa cells was tested. The speed of replication fork movement was measured on extended DNA fibers labelled with 2'-deoxythymidine analogues 5-chloro-2'-deoxyuridine and 5-iodo-2'-deoxyuridine. We show that the introduction of exogenous dNTPs accelerates the replication process at the beginning of DNA synthesis only. In late S-phase, the administration of additional dNTPs has no effect on the speed of replication forks. The availability of 2'-deoxynucleotides seems to be a rate-limiting factor for DNA replication during early S-phase.

DNA Replication↗
PubMed1997

[Does maximum short-term electric stimulation cause contraction of the pelvic floor muscles?].

Electric stimulation is successfully used in the treatment of the stress and urgent type of incontinence. Electric stimulation of the muscles of the pelvic floor causes reflex contraction of the striated peri- and paraurethral muscles and is associated with concurrent reflex inhibition of the detrusor muscle. The therapeutic results depends greatly on the total or at least partially preserved innervation of the muscles of the pelvic floor by the pudendal nerve. One of the possible stimuli of the pelvic floor muscles is maximal electric stimulation (MES) and the objective of our study was to evaluate the effect of MES on the muscles of the pelvic floor or to detect possible changes by US and urodynamic examination. The study comprised women with the stress type of incontinence (GSI). The group was formed by 40 women with GSI, 20 were subjected to US examination and urodynamic examination (n = 20). The group of subjects subjected to urodynamic examination was extended to 40 (n = 40). For electrostimulation a Conmax apparatus was used. The applied frequency was 20 Hz, the amplitude from 0 to 90 mA (grades 0.6), pulse duration 0.75 ms. During the cystometric examination the authors recorded a significant increase of the maximal urethral closure pressure (MUCP), prolongation of the functional (FUL) and anatomical length (AUL) of the urethra during MES. During US examination the authors recorded a significant diminution of the gamma angle, a reduction of the mobility of the UV junction and prolongation of the anatomical length of the urethra during MES. From the investigation ensues that the pelvic floor muscles are contracted during MES and those changes contribute to an increase of the muscular tonus and contracting capacity of the muscles of the pelvic floor and thus cause among other things elevation of the neck of the urinary bladder. The elevation contributes to the normalization of the intraabdominal transmission of pressure to the proximal urethra and thus to treatment of the stress type of urinary incontinence.

Electric Stimulation Therapy↗
PubMed1997

[Ultrasound imaging of the urethral sphincter].

The integrity and functional capacity of the urethral sphincter is one of the important prerequisites of urinary incontinence in women. Urodynamic investigations revealed repeatedly that the maximum closure pressure in the median portion of the urethra corresponds to the maximal thickness of the external urethral sphinctor (rhabdosphincter urethrae). This striated muscle is adapted to maintain a relatively steady tonus which assists the closure mechanism of the urethra [4]. In the submitted study the authors focused attention on the ultrasonic visualization of the internal urethral sphincter in order to assess the relationship between the size of this sphincter and the stress type of incontinence (genuine stress incontinence-GSI). The investigation comprised thirty women with confirmed GSI and a control group of thirty asymptomatic volunteers. During perineal ultrasonic examination of women in a supine position by means of an ACUSON 128 XP 10 apparatus using a convex probe with a frequency of 5 MHz the authors recorded statistically significant differences in the areas and maximal thickness of the urethral sphincter in women with stress incontinence and symptom-free women. From the results ensues that the size of this muscle is much smaller in women suffering from GSI.

Adult↗
PubMed1996

[Changes in the position of the urethra and bladder neck during pregnancy and after delivery].

It is estimated that some 30-50% women suffer occasionally from urinary incontinence. At the end of pregnancy these complaints are more marked. In the author's group of 44 women 55% suffered from stress incontinence. The psychosocial impact of impaired function of the lower urinary pathways in women on different spheres of the patient's life is so serious that it calls for a qualified approach of a specialist. The increased mobility of the UV junction in incontinent women has been described by several authors [6, 12, 13]. It was also proved in the author's investigation closely before delivery and 3-5 days after delivery. Six weeks after delivery no differences were found in the mobility of the UV junction in continent and incontinent women. If the difference of the gamma angle (formed by the axis of the symphysis and the connecting line between the UV junction and the lower margin of the symphysis) during contraction of the muscles of the pelvic floor and Valsalva's manoeuvre (intraabdominal pressure raised by 30 cm H2O) is more than 30 degrees during the 40th week of gestation or 3-5 days after delivery (when this mobility is even greater), then the woman is liable to develop the stress type of incontinence and the authors recommend to use Kolpexin after the puerperium for exercise and strengthening of the muscles of the pelvic floor. Changes in the length of line p and angle beta are not statistically significant and cannot assess the disposition for development of urinary incontinence.

Adult↗
PubMed1994

[Antibiotic prophylaxis in cesarean section].

Childbirth by Caesarean section is associated with 7-10x more complications than spontaneous childbirth [28] whereby the second place is held by infection. One of the possible ways how to prevent these infectious complications is antibiotic prophylaxis. Views on the latter still differ as regards selection of the antibiotic, its effectiveness, onset of administration, dosage, period of administration etc. Prophylaxis should meet the following demands; it should be aimed, of short-term character, bactericide and non-toxic-these demands are met by cephalosporins of the second generation [11]. The objective of the present work was to evaluate the contribution of the prophylactic administration of antibiotics, i.e. a cephalosporin of the second generation-Zinacef (Cefuroxime). The group was formed by 23 women to whom a dose of Zinacef was administered after childbirth by Caesarean section and subsequently twice after 8-hour intervals (1.5-0.75-0.75 i.m.). The control group (23 women) did not have this prophylaxis. In both groups the authors compared the indication of s.c., time of loss of amniotic fluid before s.c., results of cultivations from the cervix, vagina, amniotic fluid, lochiae and sutures. The authors evaluated the postoperative course where they were interested in infectious complications, the temperature curve, period of hospitalization, the necessity to administer another antibiotic or to proceed with the antibiotic therapy after the prophylactic dose. The results are clearly in favour of the prophylactic administration of antibiotics to the risk group of patients delivering by Caesarean section.

Adult↗