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991.
When chromosomes start to assemble in mitotic prophase, duplicated chromatids are not discernible within each chromosome.
As condensation proceeds, they gradually show up, culminating in two rod-shaped structures apposed along their entire length
within a metaphase chromosome. This process, known as sister chromatid resolution, is thought to be a prerequisite for rapid
and synchronous separation of sister chromatids in anaphase. From a mechanistic point of view, the resolution process can
be dissected into three distinct steps: (1) release of cohesin from chromosome arms; (2) formation of chromatid axes mediated
by condensins; and (3) untanglement of inter-sister catenation catalyzed by topoisomerase II (topo II). In this review article,
we summarize recent progress in our understanding the molecular mechanisms of sister chromatid resolution with a major focus
on its first step, cohesin release. An emerging idea is that this seemingly simple step is regulated by an intricate network
of positive and negative factors, including cohesin-binding proteins and mitotic kinases. Interestingly, some key factors
responsible for cohesin release in early mitosis also play important roles in controlling cohesin functions during interphase.
Finally, we discuss how the step of cohesin release might mechanistically be coordinated with the actions of condensins and
topo II. 相似文献
992.
The effects of cadmium exposure on the protein secretory functions of cultured neonatal rat hepatocytes were analyzed by both two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and electron microscopy. [35S]Methionine-labelled protein secretion was significantly depressed by cadmium exposure in a dose-dependent manner (1, 10 and 100 microM). Protein secretory patterns resolved by 2D-PAGE and analyzed by autoradiography showed that besides albumin and transferrin, three polypeptide spots decreased their radiolabelling intensities, whereas four spots appeared due to cadmium exposure. Ultrastructural alterations in cultured neonatal rat hepatocytes induced by cadmium exposure were characterized by condensation of the nuclear chromatin, appearance of intra-nuclear inclusions, decrease in number of microvilli, increase in number of intra-mitochondrial granules and transformation of rough endoplasmic reticulum to cytoplasmic vesicles in a dose-dependent manner. Both biochemical and ultrastructural findings indicate that cadmium adversely affects the protein secretory functions of cultured neonatal rat hepatocytes. 相似文献
993.
994.
Controls on the Carbon Balance of Tropical Peatlands 总被引:4,自引:0,他引:4
The carbon balance of tropical peatlands was investigated using measurements of gaseous fluxes of carbon dioxide (CO2) and methane (CH4) at several land-use types, including nondrained forest (NDF), drained forest (DF), drained regenerating forest (DRF) after
clear cutting and agricultural land (AL) in Central Kalimantan, Indonesia. Soil greenhouse gas fluxes depended on land-use,
water level (WL), microtopography, temperature and vegetation physiology, among which WL was the strongest driver. All sites
were CH4 sources on an annual basis and the emissions were higher in sites providing fresh litter deposition and water logged conditions.
Soil CO2 flux increased exponentially with soil temperature (T
s) even within an amplitude of 4–5°C. In the NDF soil CO2 flux sharply decreased when WLs rose above −0.2 and 0.1 m for hollows and hummocks, respectively. The sharp decrease suggests
that the contribution of surface soil respiration (RS) to total soil CO2 flux is large. In the DF soil CO2 flux increased as WL decreased below −0.7 m probably because the fast aerobic decomposition continued in lower peat. Such
an increase in CO2 flux at low WLs was also found at the stand level of the DF. Soil CO2 flux showed diurnal variation with a peak in the daytime, which would be caused by the circadian rhythm of root respiration.
Among the land-use types, annual soil CO2 flux was the largest in the DRF and the smallest in the AL. Overall, the global warming potential (GWP) of CO2 emissions in these land-use types was much larger than that of CH4 fluxes. 相似文献
995.
Regulation of BSF-2/IL-6 production by human mononuclear cells. Macrophage-dependent synthesis of BSF-2/IL-6 by T cells 总被引:20,自引:0,他引:20
Y Horii A Muraguchi S Suematsu T Matsuda K Yoshizaki T Hirano T Kishimoto 《Journal of immunology (Baltimore, Md. : 1950)》1988,141(5):1529-1535
Regulation of BSF-2/IL-6 production in peripheral mononuclear cells (MNC) was studied. BSF-2 mRNA expression in mitogen-stimulated MNC showed a biphasic response, the first peak around 4 h and the second peak around 48 h. This was caused by different kinetics of BSF-2 mRNA expression in distinct subpopulations of MNC; M phi expressed BSF-2 mRNA at 5 h in the absence of any stimulation, and mitogen-stimulated T cells and B cells expressed BSF-2 mRNA 48 h after stimulation. Immunohistochemical staining of the cells with anti-BSF-2 antibody demonstrated that macrophages, T cells and B cells could produce BSF-2. T cells in peripheral MNC produced BSF-2 in the presence of M phi. The requirement of macrophage for BSF-2 production in T cells could be replaced by TPA but not by IL-1 or BSF-2. 相似文献
996.
Kana Yamada Kyoko Yokomaku Risa Haruki Kazuaki Taguchi Saori Nagao Toru Maruyama Masaki Otagiri Teruyuki Komatsu 《PloS one》2016,11(2)
A hemoglobin wrapped covalently by three human serum albumins, a Hb-HSA3 cluster, is an artificial O2-carrier with the potential to function as a red blood cell substitute. This paper describes the synthesis and O2-binding properties of new hemoglobin‒albumin clusters (i) bearing four HSA units at the periphery (Hb-HSA4, large-size variant) and (ii) containing an intramolecularly crosslinked Hb in the center (XLHb-HSA3, high O2-affinity variant). Dynamic light scattering measurements revealed that the Hb-HSA4 diameter is greater than that of either Hb-HSA3 or XLHb-HSA3. The XLHb-HSA3 showed moderately high O2-affinity compared to the others because of the chemical linkage between the Cys-93(β) residues in Hb. Furthermore, the blood circulation behavior of 125I-labeled clusters was investigated by assay of blood retention and tissue distribution after intravenous administration into anesthetized rats. The XLHb-HSA3 was metabolized faster than Hb-HSA3 and Hb-HSA4. Results suggest that the molecular structure of the protein cluster is a factor that can influence in vivo circulation behavior. 相似文献
997.
Shigeki Mitaku Sayoko Ishido Yoshimi Hirano Hiroyasu Itoh Ryoichi Kataoka Nobuhiko Sait 《Biophysical chemistry》1991,40(3):217-222
The interaction which stabilizes the intermediate state of the protein folding and/or unfolding is important for understanding the structure formation mechanism of proteins. The partitioning of a hydrophobic fluorescence probe, pyrene, into the core of a ‘molten globule’ structure of bovine carbonic anhydrase B was measured, revealing a partition coefficient of about 104. The result leads to the conclusion that the compact structure of the molten-globule state is formed by the hydrophobic interaction, as detergent micelles are formed by the same interaction. 相似文献
998.
During the in vitro development of cytotoxic lymphocytes (CL), suppressor cells also develop. Spleen cells or lymph node cells harvested from mixed lymphocyte cultures (MLC) on day 2 (day-2 MLC) and added to a fresh MLC suppressed the development of CL. This suppressive effect was sensitive to treatment with anti-theta and C. The suppressive effect of day-2 MLC was not due to cytotoxic effects nor to altered kinetics of the development of both suppressor cells and CL. Although CL develop from hydrocortisone-treated spleen cells, day-2 MLC of hydrocortisone-treated spleen cells did not suppress the development of CL. These studies suggest that suppressor cells and CL are derived from different T cell subpopulations. 相似文献
999.
1000.