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Cerebellar neurons are generated from the rhombic lip and the neuroepithelium. In this study, we analyze the histogenesis of the cerebellar neuroepithelium in terms of cellular kinetics. The experimental animals are the offspring of pregnant dams injected with 5-bromo-2ʹ-deoxyuridine (BrdU) on embryonic day 13. We infer the fraction of S-phase cells by examining a range of survival times after a single BrdU-exposure and a cumulative BrdU-labeling sequence, which allow for the derivation of cell-cycle parameters and phase durations. The current results indicate that the dose of BrdU employed (35 mg/kg) provides saturation S-phase labeling from at least 1 h after marker delivery. The duration of G2, mitotic phase, and G1 are 1.2, 0.5, and 6.9 h, respectively. The duration for the S-phase, growth fraction, and the whole cycle are obtained on the basis of two proliferative models, steady-state and exponential growth. Both models provided similar results. In conclusion, our results indicate that the steady-state and the cumulative S-phase labeling paradigms can be adopted to analyze cell cycle parameters in the cerebellar neuroepithelium. Current results can help in understanding the regulatory mechanisms of cerebellar histogenesis and the cell biological mechanisms of the proliferative cycle of the neuroepithelium. [ABSTRACT FROM AUTHOR]

During the first rapid divisions of early development in many species, the DNA:cytoplasm ratio increases until the midblastula transition (MBT) when transcription resumes and cell cycles lengthen. S phase is very rapid in early embryos, about 20–30 times faster than in differentiated cells. Using a combination of DNA fiber studies and a Xenopus laevis embryonic in vitro replication system, we show that S phase slows down shortly after the MBT owing to a genome wide decrease of replication eye density. Increasing the dNTP pool did not accelerate S phase or increase replication eye density implying that dNTPs are not rate limiting for DNA replication at the Xenopus MBT. Increasing the ratio of DNA:cytoplasm in egg extracts faithfully recapitulates changes in the spatial replication program in embryos, supporting the hypothesis that titration of soluble limiting factors could explain the observed changes in the DNA replication program at the MBT in Xenopus laevis. [ABSTRACT FROM AUTHOR]

Numerous studies exploring oncogenic Ras or manipulating physiological Ras signalling have established an irrefutable role for Ras as driver of cell cycle progression. Despite this wealth of information the precise signalling timeline and effectors engaged by Ras, particularly during G1, remain obscure as approaches for Ras inhibition are slow-acting and ill-suited for charting discrete Ras signalling episodes along the cell cycle. We have developed an approach based on the inducible recruitment of a Ras-GAP that enforces endogenous Ras inhibition within minutes. Applying this strategy to inhibit Ras stepwise in synchronous cell populations revealed that Ras signaling was required well into G1 for Cyclin D induction, pocket protein phosphorylation and S-phase entry, irrespective of whether cells emerged from quiescence or G2/M. Unexpectedly, Erk, and not PI3K/Akt or Ral was activated by Ras at mid-G1, albeit PI3K/Akt signalling was a necessary companion of Ras/Erk for sustaining cyclin-D levels and G1/S transition. Our findings chart mitogenic signaling by endogenous Ras during G1 and identify limited effector engagement restricted to Raf/MEK/Erk as a cogent distinction from oncogenic Ras signalling. [ABSTRACT FROM AUTHOR]

Comment on: Ali MM, et al. Nature Communications 2018; 9:883. [ABSTRACT FROM AUTHOR]

Lamins constitute an integral structural component of the nuclear lamina. However, their impact on the structure and stability of chromosome territories, and on the regulation of gene expression is explored to a lesser extent. By 3D-FISH, Camps and colleagues showed that lamin B1 (LMNB1) is required for proper chromosome condensation in interphase nuclei, and deficiency of LMNB1 triggers the relocation of the epigenetic mark of facultative heterochromatin, H3K27me3, toward the interior of the nucleus. Additionally, LMNB1 repression slowed cellular growth due to S-phase delays and increased genomic instability. Finally, silencing of LMNB1 resulted in enlarged nuclear speckles and in extensive changes in alternative splicing of multiple genes. Altogether, the data suggest a central role of LMNB1 for the condensation of chromosome territories, for the distribution of heterochromatin, and for the regulation of gene expression and splicing. [ABSTRACT FROM PUBLISHER]

Because of their superior mechanical properties and high corrosion resistance in aqueous environments, duplex stainless steels are the material of choice for equipment used in the off-shore gas and oil industry. However, wear in chloride containing water (i.e. corrosion wear) is considered as a major concern. During the past decade, a new low temperature plasma surface alloying technique has been developed to achieve combined improvements in hardness, wear resistance and fatigue properties of austenitic stainless steels, without impairing their corrosion behaviour due to the formation of S-phase. However, few researchers have applied this technique to duplex stainless steel (DSS) and no work has been reported for super DSS (SDSS). In this paper, SDSS 2507 has been DC plasma nitrided under a range of treatment conditions. Energy dispersive X-ray spectroscopy (EDX), Glow discharge Spectrometry (GDS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterise the microstructure of the surface treated layers. Mechanical properties were evaluated using microhardness, electrochemical corrosion, dry and corrosion wear tests. A dense super hard surface layer was produced uniformly across all the samples. The austenitic grains formed an S-phase and the original ferritic region formed ε-nitride. The surface hardness, the load bearing capacity and dry wear results, increased with increasing treatment temperature; the samples treated under lower temperatures exhibited the best corrosion and corrosion wear resistance. [ABSTRACT FROM AUTHOR]

With properties such as low hardness and poor friction and wear, austenitic stainless steel (0Cr17Ni14Mo2) has been widely used in chemical plants, food industries and mechanical engineering that are exposed to severe friction .The carburised layer is usually obtained through gas carburisating at the temperature of 450-500°C, during which, proper processing conditions are applied to investigate its structure, wear resistance and abrasion mechanism. The high carbon supersaturated solid solution strengthening layer (S-phase) was obtained from the experiment presents a uniform white layer that indicate much better corrosion resistance. It can be clearly seen that the depth of carburised layer significantly increases as temperature incrases while other conditions sustain, However, corrosion resistance of the carburised layer at the temperature of 450 and 470°C is much better than that at the temperature of 500°C. The atomic concentration of C in the surface layer reaches 6% with hardness at 1000 HV25. Wear resistance increases by 3-4 times without imparing its corrosion resistance. [ABSTRACT FROM AUTHOR]

In this article, (C, N) alloyed austenitic stainless steel coatings (SSC) (or hybrid S-phase with both carbon and nitrogen) were produced by a magnetron sputtering deposition process combined with ion implantation (CMSII). This technique involves a periodical high energy ion bombardment of the coating during its growth, which has a beneficial effect on the structure and properties of the deposited coating. The influence of the nitrogen and carbon addition to the deposition atmosphere on the structure, chemical composition, and coating morphology was investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and glow discharge optical spectrometry (GDOS) techniques. Wear tests were carried out and the results were compared with low temperature plasma nitrided austenitic stainless steel. Corrosion behavior in Ringer's solution was also evaluated. [ABSTRACT FROM AUTHOR]

Purpose: To assess the cell cycle-dependent influence of gemcitabine on ionizing radiation-induced DNA double-strand breakage (DSB) and rejoining measured by pulsed-field gel electrophoresis (PFGE). Materials and methods: WIDR cells (human colon carcinoma) were synchronized by serum starvation/stimulation providing populations with 7% (G1) or 50% S-phase cells, respectively. Following drug treatment (0.5 μg/ml for 2 hours) cells were irradiated (up to 90 Gy) or incubated for repair (up to 6 h after 40 Gy). Cell cycle changes were monitored by flow cytometry, DNA fragmentation was assessed by PFGE as fraction of electrophoretically mobile DNA. Results: Without drug treatment, irradiated S-phase cells exhibited lower PFGE signals than the G1 cells due to the well known electrophoretic immobility of replicative DNA fragments, but DSB rejoining was not different. Gemcitabine pretreatment increased the apparent initial radiation-induced DNA fragmention specifically for S-phase cells. This effect was rapidly reversed (1 h) during incubation for repair. Conclusions: The data indicate that gemcitabine causes the formation of additional radiation-induced DSB in S-phase cells or destabilizes the replicative structures that otherwise prevent DNA fragment migration during PFGE. The latter would be rapidly restituted superimposing DSB rejoining. This is discussed in relation to the recently proposed role of mismatch repair in gemcitabine radiosensitization. [ABSTRACT FROM AUTHOR]

Objectives The main purpose of this study was to investigate the feasibility of fine needle aspiration (FNA) of neck node metastases in head and neck squamous cell carcinoma (HNSCC) for evaluating changes in DNA ploidy and S-phase fraction (SPF) during cytotoxic treatment. The results of flow cytometric (FCM) and image cytometric (ICM) analyses of ploidy were compared. Secondly, the association of SPF and ploidy with the metabolic rate (MR) of 2- 18 F-fluoro-deoxy-2-D-glucose (FDG) in positron emission tomography (PET) was studied. Material and Methods Between 1993 and 1999, 47 patients with locally advanced, non-resectable HNSCC underwent FDG PET prior to (PET 1 ) and early during (PET 2 ) cytotoxic radical treatment. The MR of FDG was calculated separately in primary tumours and lymph node metastases. Immediately after both PET scans, FNA of node metastases was done in 29 patients at PET 1 and in 27 at PET 2 . DNA ploidy was evaluated using FCM and manually using ICM. The SPF was evaluated using FCM only. Results At PET 1 it was possible to evaluate the SPF using FCM in only 13/29 aspirations due to a poor cell yield or large amounts of debris. Ploidy was obtained in 23/29 aspirates using FCM and in 27/29 using ICM. A discordance in ploidy findings was apparent, with more non-diploid clones being detected by ICM than FCM. Eradication of non-diploid clones during therapy was observed in six cases using FCM, of which only one was confirmed by ICM. Neither SPF nor ploidy status showed any strong correlation with the MR of FDG. Conclusion FNA of HNSCC metastases demands a high and qualitatively good cell yield for FCM examinations. ICM is laborious but feasible and offers more accurate detection of non-diploid cell clones. Ploidy and SPF were not strongly associated with FDG metabolism. [ABSTRACT FROM AUTHOR]

In 24h studies of bone marrow (BM), circadian stage-dependent variations were demonstrated in the proliferative activity of BM cells from subsets of 35 healthy diurnally active men. On an average, the percentage of total BM cells in deoxyribonucleic acid (DNA) synthesis phase was 188% greater at midday than at midnight (circadian rhythm: p = 0.018; acrophase or peak time of 13:16h). Patients with malignant disease (n = 15) and a normal cortisol circadian rhythm showed higher fractions of BM cells in S-phase at midday. Colony-forming units—granulocyte/macrophage (CFU-GM), an indicator of myeloid progenitor cells, showed the same circadian variation as DNA S-phase (average range of change or ROC = 136%; circadian rhythm: p < 0.001; acrophase of 12:09h). Deoxyribonucleic acid S-phase and CFU-GM in BM both showed a circannual rhythm (p = 0.015 and 0.008) with an identical acrophase of August 12. The daily peak in BM glutathione content, a tripeptide involved in cellular defense against cytotoxic damage, preceded BM proliferative peaks by 4-5 h (ROC = 31-90%; circadian rhythm: p = 0.05; acrophase of 08:30h). Myeloid (ROC = 57%; circadian rhythm: p = 0.056; acrophase at 08:40h) and erythroid (ROC = 26%; circadian rhythm: p = 0.01; acrophase of 13:01h) precursor cells were positively correlated (r = 0.41; p < 0.001), indicating a circadian temporal relationship and equal influence on S-phase of total BM cells. Yield of positive selected CD34+ progenitor stem cells also showed significant circadian variation (ROC = 595%; circadian rhythm: p = 0.02; acrophase of 12:40h). Thus, the temporal synchrony in cell cycling renders BM cells more sensitive at specific times to hematopoietic growth factors and cell cycle-specific cytotoxic drugs. Moreover, proper timing of BM harvesting may improve progenitor cell yield. When using marker rhythms in the blood to allow for individualized timing of BM procedures, the times of low values in white blood corpuscles, neutrophils,... [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to evaluate the role of p53 as prognostic factor in renal cell carcinoma (RCC) and its relation to clinicopathological factors. Material and methods: The nuclear accumulation of p53 protein was determined by immunohistochemical analysis in RCC specimens from 90 patients and was correlated with clinical stage, grade, DNA ploidy, S-phase fraction and cancer-specific survival. Results: p53 overexpression was observed in 17 of 90 (19%) tumours. There was a significant correlation to stage (p = 0.016) and grade (p = 0.020) but not to DNA ploidy or S-phase. Patients with high p53 immunoreactivity had shorter cancer-specific survival (p = 0.003) than those with normal p53 protein expression. This difference was found in papillary and chromophobe tumour types (p < 0.0001) but not in conventional RCC. Conclusions: In patients with RCC, significant correlations between p53 protein expression and tumour stage, grade and survival time were observed. For patients with chromophobe and papillary tumour types, but not in conventional RCC, p53 immunoreactivity gave prognostic information, suggesting that the prognostic differences in p53 immunoreactivity might be due to disparate genetic abnormalities in the different RCC types. [ABSTRACT FROM AUTHOR]