Expanded thermal niche for a diving vertebrate: A leatherback turtle diving into near-freezing water

The global distribution of extant reptiles is more limited than that of mammals or birds, with low reptilian species diversity at high latitudes. Central to this limited geographical distribution is the ectothermic nature of reptiles, which means that they generally become torpid at cold temperatures. However, here we report the first detailed telemetry from a leatherback turtle (Dermochelys coriacea) diving in cold water at high latitude. An individual equipped with a satellite tag that relayed temperature-depth profiles dived continuously for many weeks into sub-surface waters as cold as 0.4 °C. Global warming will likely increase the foraging range of leatherback turtles further into temperate and boreal waters.     

Diet changes in the carbon and nitrogen content of the copepod Metridia lucens

Diel changes in the near-surface (0–50 m) abundance, prosomelength, and carbon and nitrogen content of the copepod Metridialucens were measured in Deep Cove, Doubtful Sound, New Zealand(45°27'S, 167°9'E) between 3 and 6 September 1996. Metridialucens showed maximal abundance a night, suggesting a patternof normal diel vertical migration (DVM). The change in abundancesuggested that the descent of the population occurred –1h prior to dawn and the ascent –1 h after dusk. However,a proportion of the population remained near the surface duringthe day. Although there was no diel pattern in the prosome lengthof M.lucens collected near the surface, there was a marked dielcycle in the measured carbon and nitrogen contents, with maximalvalues being measured towards the end of the night prior tothe downward migration. We suggest that this diet cycle in themeasured elemental content was caused by DVM occurring morestrongly in those animals which had a better body condition,i.e. a higher elemental content per unit length.     

Selective inhibition of Escherichia coli recBC activities by plasmid-encoded GamS function of phage lambda

The gam locus of bacteriophage lambda encompasses two coding sequences with the same reading frame and translational stop, one corresponding to an Mr 11646 polypeptide (gamS gene), the other to an Mr 16349 polypeptide (gamL gene). A DNA segment encoding gamS but not gamL was placed under lambda pR promoter control (regulated by the cIts857-coded repressor) on a multicopy plasmid, and an insertion mutation (gamS201) was constructed. Expression of gamS+, but not gamS201, inhibited Escherichia coli RecBC nuclease in vivo; the criteria were inhibition of chromosomal DNA degradation after UV irradiation and plating of T4 gene 2- phages. The recB+ C+ bacteria expressing gamS+ were completely or partially similar to recC- mutants with respect to certain phenotypes: defective plating of phages P1 and P2, ability to plate (in a recA- background) lambda red- gam- phages, reduced resistance to UV irradiation, defective SOS induction, decreased colony-forming ability.     

Arabidopsis thaliana,a versatile model system for study of eukaryotic genome-maintenance functions

The genome of the model plant Arabidopsis thaliana encodes many orthologs of human genome-maintenance proteins, and in several important cases plant DNA repair and mutation-antagonism functions resemble their mammalian counterparts more closely than do those of established microbial models. These orthologs, in conjunction with the powerful tools now available for work with Arabidopsis and the practical advantages of its small size and rapid life cycle, now make it an attractive model system for study of eukaryotic DNA repair and mutagenesis. Already, null mutations that inactivate proteins involved in repair of DNA double-strand breaks or in DNA translesion synthesis and are lethal in mice have proved to be tolerated by plants. This review compares in some detail the genome-maintenance activities encoded by plants, mammals and microbes, and describes important Arabidopsis tools and life cycle characteristics. It concludes with selected examples that illustrate Arabidopsis advantages and/or reveal new insights into genome-maintenance functions of general interest.     

Vegetative axillary bud dormancy induced by shade and defoliation signals in the grasses

Vegetative axillary bud dormancy and outgrowth is regulated by several hormonal and environmental signals. In perennials, the dormancy induced by hormonal and environmental signals has been categorized as eco-, endo- or para-dormancy. Over the past several decades para-dormancy has primarily been investigated in eudicot annuals. Recently, we initiated a study using the monoculm phyB mutant (phyB-1) and the freely branching near isogenic wild type (WT) sorghum (Sorghum bicolor) to identify molecular mechanisms and signaling pathways regulating dormancy and outgrowth of axillary buds in the grasses. In a paper published in the January 2010 issue of Plant Cell and Environment, we reported the role of branching genes in the inhibition of bud outgrowth by phyB, shade and defoliation signals. Here we present a model that depicts the molecular mechanisms and pathways regulating axillary bud dormancy induced by shade and defoliation signals in the grasses.Key words: axillary bud, dormancy, shade, phytochrome, defoliation, shoot branching, teosinte branched1, MAX2, cell cycle, sorghumThe dormancy and outgrowth of axillary buds is regulated by several plant hormones such as auxin, cytokinins, abscisic acid and strigolactones, and by environmental factors such as light quality, quantity and duration as well as water, temperature and nutrient status.^1–3 Since the fate of an axillary bud is regulated by such diverse hormonal and environmental signals and their interactions, the type of dormancy induced varies. In perennials, three types of bud dormancy have been identified.^4,5 Dormancy mediated by factors within the bud is known as endo-dormancy; while dormancy induced by factors within the plant but outside the bud is called paradormancy or correlative inhibition; the best known example being apical dominance. Dormancy induced due to unfavorable environmental conditions is known as eco-dormancy. Although there is an indepth knowledge about para-dormancy in annuals,⁶ few studies have been conducted on eco-dormancy. Similarly, studies of endo-dormancy have largely been restricted to low-temperature mediated growth-cessation of axillary buds of perennial plants.^7,8 To understand the regulation of dormancy and outgrowth of axillary buds in monocots, we initiated a study on the molecular mechanisms inhibiting bud outgrowth by shade and defoliation signals in sorghum. Our results published in the January 2010 issue of Plant, Cell & Environment indicate that different types of dormancy may be induced in axillary buds of annual grasses by various signals and there may be overlapping and independent molecular mechanisms mediating induction of axillary bud dormancy.     

The Drosophila tctex-1 light chain is dispensable for essential cytoplasmic dynein functions but is required during spermatid differentiation

Variations in subunit composition and modification have been proposed to regulate the multiple functions of cytoplasmic dynein. Here, we examine the role of the Drosophila ortholog of tctex-1, the 14-kDa dynein light chain. We show that the 14-kDa light chain is a bona fide component of Drosophila cytoplasmic dynein and use P element excision to generate flies that completely lack this dynein subunit. Remarkably, the null mutant is viable and the only observed defect is complete male sterility. During spermatid differentiation, the 14-kDa light chain is required for the localization of a nuclear "cap" of cytoplasmic dynein and for proper attachment between the sperm nucleus and flagellar basal body. Our results provide evidence that the function of the 14-kDa light chain in Drosophila is distinct from other dynein subunits and is not required for any essential functions in early development or in the adult organism.     

Changes in odor quality discrimination following recovery from olfactory nerve transection

Following recovery from olfactory nerve transection, animals regain their ability to discriminate between odors. Odor discrimination is restored after new neurons establish connections with the olfactory bulb. However, it is not known if the new connections alter odor quality perception. To address this question, 20 adult hamsters were first trained to discriminate between cinnamon and strawberry odors. After reaching criterion (> or = 90% correct response), half of the animals received a bilateral nerve transection (BTX) and half a surgical sham procedure. Animals were not tested again until day 40, a point in recovery when connections are re-established with the bulb. When BTX animals were tested without food reinforcement, they could not perform the odor discrimination task. Sham animals, however, could discriminate, demonstrating that the behavioral response had not been extinguished during the 40 day period. When reinforcement was resumed, BTX animals were able to discriminate between cinnamon and strawberry after four test sessions. In addition, their ability to discriminate between these two familiar odors was no different than that of BTX and sham animals tested with two novel odors, baby powder and coffee. These findings suggest that, after recovery from nerve transection, there are alterations in sensory perception and that restoration of odor quality discrimination requires that the animal must again learn to associate individual odor sensations with a behavioral response.      

Digital image analysis of AgNORs in cervical smears of women with premalignant and malignant lesions of the uterine cervix

We performed a hospital-based, unmatched case-control study to investigate the association between progressive stages of cervical neoplasia and digital analysis of cell proliferation by silver stained nucleolus organizer region associated proteins (AgNORs). We measured cell proliferation levels in the cervical epithelial cells of 10 women with low grade squamous intraepithelial lesions (LG-SIL), eight with high grade squamous intraepithelial lesions (HG-SIL), 11 with cervical cancer (CC) and eight with no cervical lesions (controls) using the AgNORs technique. Cell proliferation was measured by digital image analysis (DIA). DIA revealed increased total areas of AgNORs in HG-SIL and CC compared to LG-SIL and control patients. AgNORs with a kidney or cluster shape exhibited greater areas than those with a spherical or long shape. We propose a cut-off of 118 pixels to differentiate benign (control and LG-SIL) from malignant (HG-SIL and CC) lesions. DIA of AgNORs is a simple and inexpensive method for studying proliferation. The increased total area of AgNORs in malignant lesions provides information regarding cell behavior and may be related to cervical carcinogenesis; however, further validation studies are required to establish its usefulness in cytological analysis.