A viral histone-like protein exploits antagonism between linker histones and HMGB proteins to obstruct the cell cycle

1. Download : Download high-res image (218KB)
2. Download : Download full-size image

     

Association Between Moringness‐Eveningness Preference and Mental/Physical Premenstrual Symptoms in Japanese Females 12 to 31 Years of Age

This study investigates the relationship between circadian typology, i.e., morningness‐eveningness (M‐E) preference, and the occurrence and severity of premenstrual mental and physical symptoms among 154 young Japanese female university students (range, 18 to 31 yrs; mean±S.D., 20.69±3.69 yrs) and 417 junior high school students (range, 12 to 15 yrs; mean±S.D., 14.29±0.67 yrs) living in an urban or suburban area of Kochi prefecture. Female university students experienced melancholy mood more frequently than did males, and the female university students who frequently became melancholy were more evening‐typed than those who did not experience melancholy. Female university students who experienced frequent fluctuations in mood and/or menstrual pain were more evening‐typed than those who were not so affected. M‐E preference of junior high school students was not correlated with stability of mood or frequency of menstrual pain. In urban areas, however junior high school students who had very stable menstrual cycles were significantly more morning‐typed than those whose menstrual cycles were not stable. In suburban areas, the bedtimes of female junior high students who had stable menstrual cycles were significantly earlier than those whose menstrual cycle duration was not stable. A physiological relationship between the circadian system, M‐E, and attributes of the menstrual cycle seems to be present in adolescent female Japanese junior high school students.     

Cell division and DNA topisomerase I activity in root meristems of pea seedlings during water stress

ABSTRACT

Low water potential, generated by PEG addition to the liquid medium of hydroponically grown pea seedlings, induces a fall in moisture content in the roots, followed by the arrest of elongation. This water stress reduces the mitotic index of root meristems during the treatment and induces the appearance of a peak of mitosis at 12 hours from the beginning of recovery. This peak suggests that during water stress the cell cycle is blocked in G2 or late S phase. In a first attempt to understand the biochemical events leading to cell cycle arrest, we tested the in vitro activity of DNA topoisomerase I extracted from stressed or control root meristems. The activity of this enzyme in extracts from stressed seedlings was lower than in controls, whereas it was higher in extracts from seedlings which had recovered from water stress for a few hours. The highest specific activity was observed with seedlings at 24 hours from the start of recovery. The fact that during stress treatments and recovery there was no variation in the synthesis of a 45 kDa protein, indicated as DNA topoisomerase I, suggested that the activity of this enzyme could be posttranslationally regulated. The hypothesis that variations in the concentration of unknown endogenous regulators of the activity of this enzyme may take place during water loss or uptake in the cytosol of meristematic cells is discussed.     

In-vitro circadian rhythm of murine bone marrow progenitor production

Hematopoietic processes display 24h rhythms both in rodents and in human beings. We hypothesized these rhythms to be in part generated by a circadian oscillator within the bone marrow. The ability of murine bone marrow granulo-monocytic (GM) precursors to form colonies following colony-stimulating factor (rm GM-CSF) exposure was investigated in liquid culture samples obtained every 3 h for a span of up to 198 h. The CFU-GM count varied rhythmically over the first 4 d of culture, with a reproducible maximum in the early morning hours, similar to that observed in vivo. These experiments provide the first evidence that bone marrow progenitors sustain in vitro circadian rhythmicity, and they demonstrate the presence of a circadian time-keeping system within these cells. The results support the potential usefulness of bone marrow cultures for investigating chronopharmacologic effects of anticancer drugs and cytokines on this target system.     

Skp1-Cul1-F-box Ubiquitin Ligase (SCFβTrCP)-mediated Destruction of the Ubiquitin-specific Protease USP37 during G2-phase Promotes Mitotic Entry

Ubiquitin-mediated proteolysis is a key regulatory process in cell cycle progression. The Skp1-Cul1-F-box (SCF) and anaphase-promoting complex (APC) ubiquitin ligases target numerous components of the cell cycle machinery for destruction. Throughout the cell cycle, these ligases cooperate to maintain precise levels of key regulatory proteins, and indirectly, each other. Recently, we have identified the deubiquitinase USP37 as a regulator of the cell cycle. USP37 expression is cell cycle-regulated, being expressed in late G₁ and ubiquitinated by APC^Cdh1 in early G₁. Here we report that in addition to destruction at G₁, a major fraction of USP37 is degraded at the G₂/M transition, prior to APC substrates and similar to SCF^βTrCP substrates. Consistent with this hypothesis, USP37 interacts with components of the SCF in a βTrCP-dependent manner. Interaction with βTrCP and subsequent degradation is phosphorylation-dependent and is mediated by the Polo-like kinase (Plk1). USP37 is stabilized in G₂ by depletion of βTrCP as well as chemical or genetic manipulation of Plk1. Similarly, mutation of the phospho-sites abolishes βTrCP binding and renders USP37 resistant to Plk1 activity. Expression of this mutant hinders the G₂/M transition. Our data demonstrate that tight regulation of USP37 levels is required for proper cell cycle progression.     

Annual changes in brain concentration of arginine vasotocin and isotocin correspond with phases of reproductive cycle in round goby,Neogobius melanostomus

Reproductive cycle of seasonally breeding fish is synchronized with changes of photoperiod and temperature in environment. We hypothesize that arginine vasotocin (AVT) and isotocin (IT) are involved in timing and synchronization of seasonal reproductive activity in the round goby (Neogobius melanostomus). To verify this hypothesis, we examined the annual profiles of brain AVT and IT in round goby males and females in relation to their reproductive cycle. Wild round gobies were exposed to annual environmental changes in their natural habitats from where they were sampled monthly over a year. AVT and IT were measured using HPLC with fluorescence detection preceded by solid-phase extraction. This study shows seasonal variations in brain AVT and IT levels. Profiles of changes were similar in males and females: the peak of AVT was observed before spawning in March-April, whereas that of IT during spawning in May–June. Furthermore, the lowest AVT level was noted out of breeding season from November to January, while the level of IT decreased immediately at the end of the spawning. The results show that high AVT levels correlate with pre-spawning period whereas the highest IT levels correspond to spawning. A significant decline in AVT and IT in non-spawning season coincided with the quiescent phase of gametogenesis in both sexes.     

Topoisomerase 1 activity during mitotic transcription favors the transition from mitosis to G1

1. Download : Download high-res image (200KB)
2. Download : Download full-size image

     

Effects of 2‐Chloro‐2′‐Deoxyadenosine on the Cell Cycle in the Human Leukemia EHEB Cell Line

To explain why 2‐chloro‐2′‐deoxyadenosine (CdA) is unable to block DNA synthesis and cell cycle progression, and paradoxically enhances progression from G1 into S phase in the CdA‐resistant leukemia EHEB cell line, we studied its metabolism and effects on proteins regulating the transition from G1 to S phase. A low deoxycytidine kinase activity and CdATP accumulation, and a lack of p21 induction despite p53 phosphorylation and accumulation may account for the inability of CdA to block the cell cycle. An alternative pathway involving pRb phosphorylation seems implicated in the CdA‐induced increase in G1 to S phase progression.     

The Blue Water Footprint of Primary Copper Production in Northern Chile

Water consumption related to the life cycle of metals is seldom reported, even though mines are often situated in very dry regions. In this study we quantified the life cycle consumption of groundwater and fresh surface water (blue water footprint [WF_blue]) for the extraction and production of high‐grade copper refined from both a copper sulfide ore and a copper oxide ore in the Atacama Desert of northern Chile. Where possible, we used company‐specific data. The processes for extracting copper from the two types of ore are quite different from each other, and the WF_blue of the sulfide ore refining process is 2.4 times higher than that of the oxide ore refining process (i.e., 96 cubic meters per metric ton [tonne] of copper versus 40 cubic meters per tonne of copper). Most of the water consumption (59% of WF_blue) in the sulfide ore process occurred at the concentrator plant, via seepage, accumulation, and also by evaporation. In the oxide ore process, the main user of water is the heap‐leaching process, with 45% of WF_blue. The crushing and agglomeration operations, electrowinning cells, and solution pools are also significant contributors to the total consumption of water in the oxide ore process. Most of the water consumed in the oxide ore process was lost to evaporation. The WF_blue of the oxide ore process can be reduced by preventing water evaporation and using more sophisticated devices during irrigation of the leaching heaps. The WF_blue of the sulfide ore refining process can be reduced by improving water recovery (i.e., reducing seepage, accumulation, and evaporation) from the tailings dam at the concentrator plant. Using seawater in the production of copper is also a promising option to reduce the WF_blue by up to 62%.     

The Life Cycle of Eimeria dispersa Tyzzer, 1929 in Turkeys

SYNOPSIS. The life cycle of a turkey strain of Eimeria dispersa Tyzzer was studied in Beltsville Small White turkeys. There were 4 asexual generations. Mature schizonts of the first generation were present 30 h postinoculation (PI); those of the 2nd, 3rd, and 4th generations were present 48, 72, and 96 h PI, respectively. Average size of schizonts and number and size of merozoites for each generation were as follows: first , 14.3 × 13.0 μm with 19.2 merozoites, each 4.5 × 1.2 μm; second , 8.0 × 7.2 μm with 13.5 merozoites, each 4.5 × 1.1 μm; third , 8.9 × 8.9 μm with 15.1 merozoites, each 5.6 × 2.1 μm; fourth , 11.6 × 10.5 μm with 6.7 merozoites, each 8.2 × 2.0 μm. Sporozoites and developmental stages of the first generation were in close association with an epithelial cell nucleus and located between the brush border and the "row" of epithelial cell nuclei; developmental stages of the other 3 generations were not associated with a nucleus and were located just under the brush border. Early macrogametes and microgametocytes were present 96 h PI. Development was confined to the epithelial cells of the villus and extended from the tip of the villus to ∼ 1/2 the distance down the sides in all areas of the intestine except the cecum. The prepatent period was between 114 and 120 h. Percentage of sporulation was 15, 57, and 90, at 24, 36, and 48 h, respectively. Sporulated oocysts averaged 24.5 × 20.2 μm.