A collapsible opening-closing net for zooplankton sampling through ice

The English umbrella net is a new-design vertical closing netdeveloped to sample zooplankton populations in under-ice environments.Operating on the principle of an umbrella, this wide-mouth netfits through a hole drilled in sea ice and expands below theice to sample the water column. A messenger-activated releasecloses the net for a discrete sample and collapses the frameso that it can be retrieved back through the hole in the ice.Nets of this design were used for extensive sampling on Fletcher'sIce Island (T-3) in the Arctic Ocean.     

Risk assessment of Hass avocado and Mexican Lauraceae for attack by redbay ambrosia beetle (Coleoptera: Curculionidae: Scolytinae)

1. The redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), vectors the mycopathogen that causes laurel wilt, a lethal vascular disease of trees in the Lauraceae. Since being detected in Georgia, USA in 2002, this invasive pest has become established in 11 additional states.
2. With continued spread, X. glabratus will likely enter Mexico. In advance of this event, this study was initiated to assess the risk posed to eight native laurels and Hass avocados, the predominant cultivar grown in Mexico.
3. Wood bolts from each species were used in (a) field tests to determine the relative attraction of female X. glabratus, (b) laboratory bioassays to evaluate boring preferences, and (c) GC–MS analyses to identify host kairomones. For comparison, tests included control bolt treatments consisting of silkbay (an attractive U.S. laurel) and Simmonds avocado (a Florida cultivar susceptible to laurel wilt).
4. Hass avocado and two native laurels (Persea schiedeana and Ocotea heribertoi vel aff.) were highly attractive to females and elicited strong boring responses. These species were high in sesquiterpene hydrocarbons, including α-copaene and α-cubebene.
5. Results of this study suggest that X. glabratus could become a serious agricultural and forest pest upon incursion into Mexico, with severe economic and ecological impacts.

     

Regulation of the cellular DNA double-strand break response.

DNA double-strand breaks occur frequently in cycling cells, and are also induced by exogenous sources, including ionizing radiation. Cells have developed integrated double-strand break response pathways to cope with these lesions, including pathways that initiate DNA repair (either via homologous recombination or nonhomologous end joining), the cell-cycle checkpoints (G1-S, intra-S phase, and G2-M) that provide time for repair, and apoptosis. However, before any of these pathways can be activated, the damage must first be recognized. In this review, we will discuss how the response of mammalian cells to DNA double-strand breaks is regulated, beginning with the activation of ATM, the pinnacle kinase of the double-strand break signalling cascade.     

The mycelial cell wall of Penicillium charlesii G. Smith NRRL 1887

Mycelial cell wall preparations of Penicillium charlesii G. Smith have been shown to have a total neutral carbohydrate content of 69%. Glucosamine which comprises 12% of the wall is present principally as chitin. Lipids comprise 37.5% of the wall while polypeptides comprise 19.5%. No galactofuranose units are present in the wall of this organism which is known to produce an extracellular β-1,5-galactofuranose containing polymer.     

Amino acids and quaternary nitrogen compounds in the germinating wheat grain

The tissues of the quiescent wheat grain contained free amino acids and quaternary nitrogen compounds. During germination the amino acid levels increased several fold. In the aleurone tissue and starchy endosperm glutamine was the predominant amino acid. Asparagine was predominant in the seedling tissues. Choline and glycine betaine were the principal quaternary nitrogen compounds present. The aleurone tissue and the embryo/seedling contained large quantities of glycine betaine. The increase in free amino acid levels in the aleurone tissue during the first 2 days of germination occurred independently of the embryo. After the second day, the further increase in levels was dependent upon the presence of the embryo and of gibberellic acid (GA). Estimation of the individual amino acids and quaternary nitrogen compounds released from incubating aleurone layers into aqueous media revealed a selective release of some compounds and retention of others. The process was regulated by GA. Possible mechanisms for the release of amino acid and its control by GA are discussed.     

Prebiotic photosynthetic reactions

Historically, numerous attempts have been made to mimic — by means of inorganic model reactions — the photosynthetic fixation of CO₂ by green plants. The literature in this field is strewn with claims and counter-claims. Two factors have led us to reexamine this subject: firstly; doubts concerning the highly reducing model for the atmosphere of the primitive Earth and secondly; recent results which demonstrate that photoreductive fixation is feasable on a suitable catalytic surface, for both CO₂ and N₂. The latter observation is of particular interest due to the well-known susceptability of NH₃ to photolytic destruction. Our review of the literature leads us to suggest that similar processes would have been plausible for the primitive Earth and could have been prebiotic precursors to an early development of CO₂-fixing autotrophs.     

Left ventricular diastolic filling and systolic function of young and older trained and untrained men.

Aging is associated with impaired early diastolic filling; however, the effect of endurance training on resting diastolic function in older subjects is unclear. Heart rate and ventricular loading conditions affect mitral inflow velocities measured by Doppler echocardiography; therefore, tissue Doppler imaging of mitral annular velocity, which is relatively preload independent, was combined with mitral inflow velocity and maximal oxygen consumption (V(o2 max)) in young (20-35 yr) and older (60-80 yr) trained and untrained men to determine whether endurance training is associated with an attenuation of age-associated changes in diastolic filling. As expected, V(o2 max) was higher in trained men (P < 0.01) and lower in older men (P < 0.01). Peak early mitral inflow velocity (E) and early-to-late mitral inflow velocity ratios were lower in older vs. young men (P < 0.01); however, there was no training effect (P > 0.05). Peak early mitral annular velocity (E') was higher and peak late mitral annular velocity (A') was lower in young vs. older men (P < 0.01). A significant interaction effect was found for A', E'/A', and peak systolic mitral annular velocity (S'). Training was associated with lower A' in young and higher A' in older men. S' was greater in trained vs. untrained older men (P < 0.05), but it was similar in trained and untrained young men. These findings suggest that early diastolic filling is not affected by training in older men, and the effect of training on A' and S' is different in young and older men.