A study of pyrolysis of polymethylsiloxanes by Fourier transform infrared.

This paper is dedicated to a comparative study of pyrolysis of decamethylcyclopentasiloxane and hexamethyldisiloxane, widely used as precursors for CVD of silicon dioxide films. The pyrolysis process was carried out in a hot-wall horizontal tube reactor made from quartz within the temperature range 25-1000 degrees C. FTIR spectroscopy has been used for the analysis of gaseous reaction products in the exhaust line of the reactor. It has been found that transformation of DMPSO was initiated by the open ring in the precursor molecules with its further transformation to linear biradicals followed by the chain's growth due to radical reactions. HMDSO transformation is connected with separation of silanon, silyl and methyl radicals with following multi-type interactions of siloxane radicals and formation of non-rigorously organized three-dimensional molecules.

Chemical vapour deposition of nitrogen-doped titanium dioxide thin films.

Nitrogen-doped titanium dioxide is often considered as a promising nanomaterial for photocatalytic applications. Here we report the first results of a study of APCVD of N-doped TiO2 thin films prepared with the use of ammonia as a source of nitrogen and titanium tetraisopropoxide (TTIP) as a source of Ti and O atoms. The obtained films were analyzed with X-ray diffraction, infrared spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, UV-Vis spectroscopy, and ellipsometry. It was found that the film growth rate in the TTIP-NH3-Ar reaction system varied insignificantly with substrate temperature in the range of 450,..., 750 degrees C and did not exceed 4.4 nm/min. Yellow and orange layers with nitrogen content of about 7.6% were formed at the deposition temperature higher than 600 degrees C. The results of the structure analysis of the deposited films showed that addition of ammonia led to stabilization of the amorphous phase in the films. The effect of ammonia on optical and photocatalytic properties was also considered.

[Preliminary results of a multicenter randomized study on the treatment of acute promyelocytic leukemias]. / Predvaritel'nye rezul'taty mnogotsentrovogo randomizirovannogo issledovaniia po lecheniiu ostrykh promielotsitarnykh leikozov.

AIM: To study efficacy of maintenance therapy of patients with acute promyelocytic leukemia (APL) in the APL treatment Russian multicenter trial. MATERIAL AND METHODS: The trial was made with participation of 18 hematological departments of clinics in Russia. A total of 68 APL patients entered the trial. The maintenance therapy consisted of 5-day courses of cytostatic drugs which alternated or did not alternate with 5-day courses of ATRA. Cytogenetic tests were made in 31 patients, t(15;17) was detected in 26 of them. Molecular examination conducted in 28 patients discovered chimeric transcript PML/RARa in 26 of them. Of 20 patients examined in Hematological Research Center, 7 (35%) had a bcr 1/2 variant of the transcript PML/RARa, 13 (65%)--bcr 3 variant. RESULTS: 65 patients were eligible for assessment. A complete remission was achieved in 90% cases. No resistance was observed. In follow-up within 30 months the recurrence rate was similar on both treatments. The results of the induction therapy and survival in patients with different variants of the transcripts were also similar. Overall 2.5 year survival for all the patients was 77%, recurrence-free--80%. The survival analysis in patients with leukocytosis higher and lower 10 x 10(9)/l found no statistical differences by the survival. Patients with hyperleukocytosis had higher early lethality than patients with leukocytes under 10 x 10(9)/l (25% vs 5.3%, p = 0.03). CONCLUSION: The APL 06.01 protocol showed high efficacy of the relevant maintenance which provides a complete molecular remission in the majority of patients with probable recurrence-free 2.5 year survival 80%.

[Prevention of neuroleukemia by intrathecal administration of cytosar and methotrexate in acute lymphoblastic leukemia in adults]. / Profilaktika neiroleikemii intratekal'nymi vvedeniiami tsitozara i metotreksata pri ostrom limfoblastnom leikoze u vzroslykh.

AIM: To find out whether efficacy of neuroleukemia (NL) prevention by intrathecal administration of cytosar and methotrexate in remission induction phase in adult patients with acute lymphoblastic leukemia (ALL) depends on the risk factors. MATERIALS AND METHODS: The study covered 68 ALL patients. The diagnosis was made by cytological, histological and cytochemical tests of the peripheral blood and bone marrow. Immunophenotyping was performed in 48 patients. The treatment followed the German protocol 04.89 in modification of the Hematological Research Center of the Russian Academy of Medical Sciences. Prevention of NL consisted in intrathecal administration of cytosar (30 mg), methotrexate (15 mg) and dexamethasone (4 mg) once a week for 6 weeks beginning on induction day 1, further in consolidation, reinduction and once in 3 months in maintenance. Radiation of the brain was not conducted. Treatment of leuroleukemia consisted of intrathecal administration of the above drugs twice a week up to normalization of the liquor with subsequent their administration 5 times and craniospinal radiation in a dose 36 Gy. Further intrathecal administrations were made according to the protocol. RESULTS: Correlation was not found between age of the patients and frequency of neuroleukemia onset, between neuroleukemia incidence and peripheral blood leukocytosis at diagnosis. Results of NL prevention with cytosar and methotrexate given intrathecally in induction of remission (14.6% of neurorecurrences) are comparable with the results of NL prevention by radiation of the brain with intrathecal administration of methotrexate obtained in the German cooperative trial. CONCLUSION: NL prevention in ALL adult patients by intrathecal cytosar and methotrexate in remission induction is effective.

Telomere shortening, telomerase expression, and chromosome instability in rat hepatic epithelial stem-like cells.

Telomeres, which are specialized structures consisting of T2AG3 repeats and proteins at the ends of chromosomes, may be essential for genomic stability. To test whether telomere length maintenance preserves genomic stability in rats (Rattus rattus and Fischer 344), we assayed telomerase activity and telomere length in the rat hepatic epithelial stem-like cell line WB-F344 during aging in vitro and in tumor-derived lines. Telomerase activity in the parental WB-F344 line was repressed at low and intermediate passage levels in vitro and reexpressed at high passages. Southern blot hybridization and quantitative fluorescence in situ hybridization analyses demonstrated that telomeres were significantly eroded at intermediate passage levels, when telomerase was repressed, and at high passage levels, when telomerase was expressed. Fluorescence in situ hybridization analysis also revealed interstitial telomeric sequences in rat chromosomes. Tumor-derived WB-F344 cell lines that express telomerase had variably shortened telomeres. Cytogenetic analyses performed on WB-F344 cells at low, intermediate, and high passages demonstrated that chromosome instability was most severe in the intermediate passage cells. These data suggest that telomere shortening during aging of rat hepatic epithelial stem-like WB-F344 cells in vitro and during selection of tumorigenic lines in vivo may destabilize chromosomes. Expression of telomerase in high passage cells appeared to partially stabilize chromosomes.

[The empirical antibiotic therapy of patients with acute leukemias: the results of a multicenter study]. / Empiricheskaia antibioticheskaia terapiia u bol'nykh ostrymy leikozami: itogi mnogotsentrovogo issledovaniia.

AIM: To evaluate efficacy of ampicilline/sulbactame and fluconasole in the regimen of empirical antibiotic therapy in patients with acute leukemia. MATERIALS AND METHODS: The trial covered 14 hematological departments of Russia and 1 of Ukraine. Acute myeloid leukemia patients were included. 92 cases of fever in 56 patients with analysis of efficacy in 66 cases were considered. At the first stage of empirical antibiotic therapy, cefoperason (4 g/day) and gentamycin (240 mg/day) were administered. If no response was reached, ampicilline/sulbactam (7.5 g/day) was added. This was the second stage. If no response occurred for 5 days the three drugs were joined by fluconasol (400 mg followed by 200 mg). RESULTS: Fever of unclear genesis was cured in 82% (28 of 34), clinical infection--in 80% (20 of 25), microbiologically confirmed infection--in 4 of 7 cases. A complete response to the empirical antibiotic therapy was registered in 52 of 66 cases (79%). 7(10.5%) patients died of infectious complications. 7(10.5%) received other antibiotics.

Chromosomal instability is correlated with telomere erosion and inactivation of G2 checkpoint function in human fibroblasts expressing human papillomavirus type 16 E6 oncoprotein.

Cell cycle checkpoints and tumor suppressor gene functions appear to be required for the maintenance of a stable genome in proliferating cells. In this study chromosomal destabilization was monitored in relation to telomere structure, lifespan control and G2 checkpoint function. Replicative senescence was inactivated in secondary cultures of human skin fibroblasts by expressing the human papillomavirus type 16 (HPV-16) E6 oncoprotein to inactivate p53. Chromosome aberrations were enumerated during in vitro aging of isogenic control (F5neo) and HPV-16E6-expressing (F5E6) fibroblasts. We found that structural and numerical aberrations in chromosomes were significantly increased in F5E6 cells during aging in vitro and fluorescence in situ hybridization (FISH) analysis using chromosome-specific probes demonstrated the occurrence of rearrangements involving chromosome 4 and 6 in genetically unstable F5E6 cells. Flow cytometry and karyotypic analyses revealed increased polyploidy and aneuploidy in F5E6 cells only at passages > 16, although these cells displayed defective mitotic spindle checkpoint function associated with inactivation of p53 at passages 5 and 16. G2 checkpoint function was confirmed to be gradually but progressively inactivated during in vitro aging of E6-expressing cells. Aging of F5neo fibroblasts was documented during in vitro passaging by induction of a senescence-associated marker, pH 6.0 lysosomal beta-galactosidase. F5E6 cells displayed extension of in vitro lifespan and did not induce beta-galactosidase at high passage. Erosion of telomeres during in vitro aging of telomerase-negative F5neo cells was demonstrated by Southern hybridization and by quantitative FISH analysis on an individual cell level. Telomeric signals diminished continuously as F5neo cells aged in vitro being reduced by 80% near the time of replicative senescence. Telomeric signals detected by FISH also decreased continuously during aging of telomerase-negative F5E6 cells, but telomeres appeared to be stabilized at passage 34 when telomerase was expressed. Chromosomal instability in E6-expressing cells was correlated (P < 0.05) with both loss of telomeric signals and inactivation of G2 checkpoint function. The results suggest that chromosomal stability depends upon a complex interaction among the systems of telomere length maintenance and cell cycle checkpoints.

Construction of chicken x human microcell hybrids for human gene targeting.

Human chromosomes 1, 2, 3, and 11 were tagged with pSV2 neo and transferred via microcell fusion from mouse A9 human monochromosomal hybrids to a chicken pre-B cell line, DT40, proficient for homologous recombination. Hybrids containing two copies of human chromosome 11 were transfected with targeting vectors containing a mammalian selectable gene with either the D11S16 or HRAS genomic sequences corresponding to two different chromosome 11 loci. Analysis of stable transfectants showed a high frequency (approximately 80%) of targeted integration of these constructs into each of the homologous loci of human chromosome 11 in DT40 hybrids. The results suggest that any human genomic sequences on human chromosomes transferred into DT40 cells could be targeted at high frequency, thereby allowing for subsequent modification of human genes and chromosomes.

XYY syndrome in children with acute lymphoblastic leukemia.

Certain constitutional chromosomal abnormalities increase the risk of malignancy and/or decrease treatment tolerance. We identified two patients with the XYY syndrome among a total of 444 male children with acute lymphoblastic leukemia who had complete cytogenetics studies. In both cases, the leukemic cell karyotype suggested a constitutional XYY abnormality that was confirmed in studies of lymphocytes obtained during remission. The incidence rate in our series is higher than that of the XYY syndrome in the general population (0.0045 vs. 0.001), but not significantly so. This finding and a literature review failed to confirm an increased frequency of the XYY syndrome among children with acute lymphoblastic leukemia. Both of our patients remain in remission 24 and 28 months, respectively, postdiagnosis. Their tolerance of intensive treatment, including high-dose methotrexate, suggests that the untoward treatment toxicity seen in patients with chromosomal abnormalities such as trisomy 21 does not extend to the XYY syndrome.

A subtle deletion of 12p by routine cytogenetics is found to be a translocation to 21q by fluorescence in situ hybridization: t(12;21)(p13;q22).

A 4-year-old boy with acute lymphoblastic leukemia (ALL) whose leukemic cells contained at diagnosis a del(6q) had a different clone at relapse, characterized by an abnormal short arm of chromosome 12 (12p). Fluorescence in situ hybridization (FISH) analysis using a cosmid probe from the 12p12-13 region indicated a translocation of the 12p to another unknown chromosome of "G-group" size. Further analysis by dual chromosome painting confirmed the presence of a translocation, identified as t(12;21)(p13;q22). Previously reported cases showed this translocation at diagnosis of ALL, whereas this is the first case showing the specific t(12;21)(p13;q22) at relapse. This case study illustrates the value of FISH in resolving subtle recurrent chromosomal rearrangements that escape detection by routine cytogenetic analysis. Subsequent molecular evaluation of the patient's leukemic cells with the t(12;21) demonstrated a TEL/AML1 fusion protein.

Heterogeneity of hyperdiploid (51-67) childhood acute lymphoblastic leukemia.

We studied the fully banded chromosomes of 182 children with hyperdiploid (51-67) acute lymphoblastic leukemia (ALL) to better delineate the heterogeneity of this disease subtype. Forty-six percent of the cases had numerical changes exclusively, while the remainder had structural as well as numerical changes. Chromosome 21 was added most often (97% of cases), followed by chromosomes 6 (86%), X (81%), 14 (80%), 4 (76%), 18 (68%), 17 (68%), 10 (56%), 8 (34%) and 5 (26%). Chromosomal translocations, including the t(1;19)(q23;p13) and t(9;22)(q34;q11), were detected in only 20% of the cases, as compared with 50% in ALL in general. The most common structural alterations were duplication of the 1q arm and isochromosome of 17q, present in 25 (14%) and nine (5%) cases, respectively. The presence of absence of structural abnormalities in these cases did not influence event-free survival, as assessed in 168 patients enrolled in three successive protocols for children with newly diagnosed ALL. By contrast, patients with 51-55 chromosomes per leukemic cell (n=105) appeared to fare worse than the 56-67 subgroup (n=63) (5-year probability of event-free survival = 72 +/- 5% (s.e.) vs 86 +/- 5%; P=0.04 by the stratified log-rank test). The poorer prognosis of the 51-55 subgroup was partly due to the higher frequency of isochromosome of 17q; 6/7 patients with the isochromosome in this group have had an adverse event. Other unfavorable features within the hyperdiploid (51-55) ALL subgroup include a low prevalence of trisomies of chromosomes 4 and 10 and a higher proportion of patients with leukocyte counts greater than 50 X 10(9)/l when compared to hyperdiploid (56-67). Thus, ALL defined by 51-55 chromosomes appears to be a clinicobiologic entity quite distinct from cases with higher modal numbers.

Childhood acute lymphoblastic leukemia with equivocal chromosome markers of the t(1;19) translocation.

The t(1;19)(q23;p13) or its derivative encodes an E2A-PBXI fusion transcript and protein that has been shown to have important prognostic and therapeutic implications in patients with acute lymphoblastic leukemia (ALL). We describe two childhood cases in which a der(22)t(1;22)(q21-23;p13) cytogenetically mimicked a der(19)t(1;19)(q23;p13). In one case, which was phenotyped as early pre-B ALL with hyperdiploidy but lacked evidence of an E2A-PBX1 gene fusion by molecular study, the poor banding quality of chromosomes led to misinterpretation of the cytogenetic findings; a correct diagnosis was established only after analysis by the fluorescence in situ hybridization (FISH) method. The second case, which was classified as pseudodiploid pre-B ALL, had both a derivative 19 and a derivative 22 but lacked sufficient cells for evaluation of E2A-PBX1 gene fusion. This case was included in order to compare the der(19)t(1;19) and the der(22)t(1;22) and to pinpoint the difficulty in distinguishing these markers. FISH analysis can resolve diagnostic uncertainty in cases of ALL with equivocal chromosome 19 markers.