Histone variant macroH2A contains two distinct macrochromatin domains capable of directing macroH2A to the inactive X chromosome

Chromatin on the inactive X chromosome (Xi) of female mammals is enriched for the histone variant macroH2A that can be detected at interphase as a distinct nuclear structure referred to as a macro chromatin body (MCB). Green fluorescent protein-tagged and Myc epitope-tagged macroH2A readily form an MCB in the nuclei of transfected female, but not male, cells. Using targeted disruptions, we have identified two macrochromatin domains within macroH2A that are independently capable of MCB formation and association with the Xi. Complete removal of the non-histone C-terminal tail does not reduce the efficiency of association of the variant histone domain of macroH2A with the Xi, indicating that the histone portion alone can target the Xi. The non-histone domain by itself is incapable of MCB formation. However, when directed to the nucleosome by fusion to core histone H2A or H2B, the non-histone tail forms an MCB that appears identical to that of the endogenous protein. Mutagenesis of the non-histone portion of macroH2A localized the region required for MCB formation and targeting to the Xi to an ~190 amino acid region.     

SUMMER DIVING BEHAVIOR OF MALE WALRUSES IN BRISTOL BAY, ALASKA

Pacific walruses ( Odobenus rosmarus divergens ) make trips from ice or land haul-out sites to forage for benthic prey. We describe dive and trip characteristics from time-depth-recorder data collected over a one-month period during summer from four male Pacific walruses in Bristol Bay, Alaska. Dives were classified into four types. Shallow (4 m), short (2.7 min), square-shaped dives accounted for 11% of trip time, and many were probably associated with traveling. Shallow (2 m) and very short (0.5 min) dives composed only 1% of trip time. Deep (41 m), long (7.2 min), square-shaped dives accounted for 46% of trip time and were undoubtedly associated with benthic foraging. V-shaped dives ranged widely in depth, were of moderate duration (4.7 min), and composed 3% of trip time. These dives may have been associated with navigation or exploration of the seafloor for potential prey habitat. Surface intervals between dives were similar among dive types, and generally lasted 1–2 min. Total foraging time was strongly correlated with trip duration and there was no apparent diel pattern of diving in any dive type among animals. We found no correlation between dive duration and postdive surface interval within dive types, suggesting that diving occurred within aerobic dive limits. Trip duration varied considerably within and among walruses (0.3–9.4 d), and there was evidence that some of the very short trips were unrelated to foraging. Overall, walruses were in the water for 76.6% of the time, of which 60.3% was spent diving.     

Studies on the energy metabolism of opossum Didelphis virginiana erythrocytes--II. Comparative aspects of 2-deoxy-D-glucose catabolism in opossum and human red cells in vitro

1. G-6-P, F-6-P, F-1, 6-P, DHAP and GA-3-P in opossum erythrocytes were found at levels above those reported in human red cells. 2. About 1% of the radioactivity provided as [1-14C] DOG to red cells of both species was recovered as 14CO2 in 1 hr. 3. Unlike [1-14C] DOG, radiochromatography of extracts of cells incubated DOG revealed two diffusible radiolabelled compounds in the supernatant of cell suspensions. 4. The catabolism of DOG was quantitatively and qualitatively similar in opossum and human erythrocytes under the conditions of this study.     

The botany,uses and production ofWasabia japonica (Miq.) (Cruciferae) Matsum

Wasabi (Wasabia japonica) is a unique native plant and a traditional condiment crop of Japan. It is used in traditional Japanese raw fish and noodle dishes and in several modern foods for its hot taste and tangy flavor. Japanese farmers grow the crop in wet upland orchard soils for leaves, petioles and small enlarged stems, and in flooded gravel and sand fields along streams or near springs to produce whole plants and large succulent green enlarged stems. Recent studies in Japan have demonstrated numerous enzymatic and biocidal properties of the plant. This review of Japanese and other literature details the history, uses, botany, cultivars, ecological requirements, production techniques, insect pests and diseases of wasabi.     

Primary Succession on a Hawaiian Dryland Chronosequence

We used measurements from airborne imaging spectroscopy and LiDAR to quantify the biophysical structure and composition of vegetation on a dryland substrate age gradient in Hawaii. Both vertical stature and species composition changed during primary succession, and reveal a progressive increase in vertical stature on younger substrates followed by a collapse on Pleistocene-aged flows. Tall-stature Metrosideros polymorpha woodlands dominated on the youngest substrates (hundreds of years), and were replaced by the tall-stature endemic tree species Myoporum sandwicense and Sophora chrysophylla on intermediate-aged flows (thousands of years). The oldest substrates (tens of thousands of years) were dominated by the short-stature native shrub Dodonaea viscosa and endemic grass Eragrostis atropioides. We excavated 18 macroscopic charcoal fragments from Pleistocene-aged substrates. Mean radiocarbon age was 2,002 years and ranged from < 200 to 7,730. Genus identities from four fragments indicate that Osteomeles spp. or M. polymorpha once occupied the Pleistocene-aged substrates, but neither of these species is found there today. These findings indicate the existence of fires before humans are known to have occupied the Hawaiian archipelago, and demonstrate that a collapse in vertical stature is prevalent on the oldest substrates. This work contributes to our understanding of prehistoric fires in shaping the trajectory of primary succession in Hawaiian drylands.     

Macrosatellite epigenetics: the two faces of DXZ4 and D4Z4

Almost half of the human genome consists of repetitive DNA. Understanding what role these elements have in setting up chromatin states that underlie gene and chromosome function in complex genomes is paramount. The function of some types of repetitive DNA is obvious by virtue of their location, such as the alphoid arrays that define active centromeres. However, there are many other types of repetitive DNA whose evolutionary origins and current roles in genome biology remain unknown. One type of repetitive DNA that falls into this class is the macrosatellites. The relevance of these sequences to disease is clearly demonstrated by the 4q macrosatellite (D4Z4), whereupon contraction in the size of the array is associated with the onset of facioscapulohumeral muscular dystrophy. Here, I describe recent findings relating to the chromatin organization of D4Z4 and that of the X-linked macrosatellite DXZ4, highlighting the fact that these enigmatic sequences share more than a similar name.     

An analysis of the interaction of a platinum complex and radiation with CHO cells using the molecular theory of cell survival.

A mathematical analysis is developed from the concepts of the molecular theory of cell survival to explain the cytotoxic action of a platinum complex on CHO cells and its synergistic interaction with radiation. In the analysis, it is assumed that both inter- and intra-strand cross-links induced by the Pt complex in the DNA contribute to cell killing and that the synergistic effect arises from the interaction between an intra-strand cross-link and a radiation-induced single-strand break on complementary strands of the DNA. The analysis is shown to be compatible with experimental results. Further, a mechanistic model is developed in an attempt to explain in more detail the processes which appear to be involved in the expression of the cytological damage.