Effects of sprint training on contractility and [Ca(2+)](i) transients in adult rat myocytes.

The effects of 6-8 wk of high-intensity sprint training (HIST) on rat myocyte contractility and intracellular Ca(2+) concentration ([Ca(2+)](i)) transients were investigated. Compared with sedentary (Sed) myocytes, HIST induced a modest (5%) but significant (P < 0.0005) increase in cell length with no changes in cell width. In addition, the percentage of myosin heavy chain alpha-isoenzyme increased significantly (P < 0.02) from 0.566 +/- 0.077% in Sed rats to 0.871 +/- 0.006% in HIST rats. At all three (0.6, 1.8, and 5 mM) extracellular Ca(2+) concentrations ([Ca(2+)](o)) examined, maximal shortening amplitudes and maximal shortening velocities were significantly (P < 0.0001) lower and half-times of relaxation were significantly (P < 0.005) longer in HIST myocytes. HIST myocytes had significantly (P < 0.0001) higher diastolic [Ca(2+)](i) levels. Compared with Sed myocytes, systolic [Ca(2+)](i) levels in HIST myocytes were higher at 0.6 mM [Ca(2+)](o), similar at 1.8 mM [Ca(2+)](o), and lower at 5 mM [Ca(2+)](o). The amplitudes of [Ca(2+)](i) transients were significantly (P < 0.0001) lower in HIST myocytes. Half-times of [Ca(2+)](i) transient decline, an estimate of sarcoplasmic reticulum (SR) Ca(2+) uptake activity, were not different between Sed and HIST myocytes. Compared with Sed hearts, Western blots demonstrated a significant (P < 0.03) threefold decrease in Na(+)/Ca(2+) exchanger, but SR Ca(2+)-ATPase and calsequestrin protein levels were unchanged in HIST hearts. We conclude that HIST effected diminished myocyte contractile function and [Ca(2+)](i) transient amplitudes under the conditions studied. We speculate that downregulation of Na(+)/Ca(2+) exchanger may partly account for the decreased contractility in HIST myocytes.     

Functional variation among frugivorous birds: implications for rainforest seed dispersal in a fragmented subtropical landscape

Seed dispersal plays a critical role in rainforest regeneration patterns, hence loss of avian seed dispersers in fragmented landscapes may disrupt forest regeneration dynamics. To predict whether or not a plant will be dispersed in fragmented forests, it is necessary to have information about frugivorous bird distribution and dietary composition. However, specific dietary information for frugivorous birds is often limited. In such cases, information on the seed-crushing behaviour, gape width and relative dietary dominance by fruit may be used to describe functional groups of bird species with respect to their potential to disperse similar seeds. We used this information to assess differences in the seed dispersal potential of frugivorous bird assemblages in a fragmented rainforest landscape of southeast Queensland, Australia. The relative abundance of frugivorous birds was surveyed in extensive, remnant and regrowth rainforest sites (16 replicates of each). Large-gaped birds with mixed diets and medium-gaped birds with fruit-dominated diets were usually less abundant in remnants and regrowth than in continuous forest. Small-gaped birds with mixed diets and birds with fruit as a minor dietary component were most abundant in regrowth. We recorded a similar number of seed-crushing birds and large-gaped birds with fruit-dominated diets across site types. Bird species that may have the greatest potential to disperse a large volume and wide variety of plants, including large-seeded plants, tended to be less abundant outside of extensive forests, although one species, the figbird Sphecotheres viridis, was much more abundant in these areas. The results suggest that the dispersal of certain plant taxa would be limited in this fragmented landscape, although the potential for the dispersal of large-seeded plants may remain, despite the loss of several large-gaped disperser species.     

A recent insertion of an alu element on the Y chromosome is a useful marker for human population studies

A member of the Alu family of repeated DNA elements has been identified on the long arm of the human Y chromosome, Yq11. This element, referred to as the Y Alu polymorphic (YAP) element, is present at a specific site on the Y chromosome in some humans and is absent in others. Phylogenetic comparisons with other Alu sequences reveal that the YAP element is a member of the polymorphic subfamily-3 (PSF-3), a previously undefined subfamily of Alu elements. The evolutionary relationships of PSF-3 to other Alu subfamilies support the hypothesis that recently inserted elements result from multiple source genes. The frequency of the YAP element is described in 340 individuals from 14 populations, and the data are combined with those from other populations. There is both significant heterogeneity among populations and a clear pattern in the frequencies of the insertion: sub-Saharan Africans have the highest frequencies, followed by northern Africans, Europeans, Oceanians, and Asians. An interesting exception is the relatively high frequency of the YAP element in Japanese. The greatest genetic distance is observed between the African and non-African populations. The YAP is especially useful for studying human population history from the perspective of male lineages.      

Neurotherapeutic Effects of Bee Venom in a Rotenone-Induced Mouse Model of Parkinson’s Disease

Neurophysiology - Parkinson’s disease (PD) is a widespread progressive neurodegenerative disease; its main neuropathological hallmark is massive loss of dopaminergic neurons. Most PD studies...     

NMR structure of the full-length linear dimer of stem-loop-1 RNA in the HIV-1 dimer initiation site

The packaging signal of HIV-1 RNA contains a stem-loop structure, SL1, which serves as the dimerization initiation site for two identical copies of the genome and is important for packaging of the RNA genome into the budding virion and for overall infectivity. SL1 spontaneously dimerizes via a palindromic hexanucleotide sequence in its apical loop, forming a metastable kissing dimer form. Incubation with nucleocapsid protein causes this form to refold to a thermodynamically stable mature linear dimer. Here, we present an NMR structure of the latter form of the full-length SL1 sequence of the Lai HIV-1 isolate. The structure was refined using nuclear Overhauser effect and residual dipolar coupling data. The structure presents a symmetric homodimer of two RNA strands of 35 nucleotides each; it includes five stems separated by four internal loops. The central palindromic stem is surrounded by two symmetric adenine-rich 1-2 internal loops, A-bulges. All three adenines in each A-bulge are stacked inside the helix, consistent with the solution structures of shorter SL1 constructs determined previously. The outer 4-base pair stems and, proximal to them, purine-rich 1-3 internal loops, or G-bulges, are the least stable parts of the molecule. The G-bulges display high conformational variability in the refined ensemble of structures, despite the availability of many structural restraints for this region. Nevertheless, most conformations share a similar structural motif: a guanine and an adenine from opposite strands form a GA mismatch stacked on the top of the neighboring stem. The two remaining guanines are exposed, one in the minor groove and another in the major groove side of the helix, consistent with secondary structure probing data for SL1. These guanines may be recognized by the nucleocapsid protein, which binds tightly to the G-bulge in vitro.     

PKCzeta is required for microtubule-based motility of vesicles containing the ntcp transporter

Intracellular trafficking regulates the abundance and therefore activity of transporters present at the plasma membrane. The transporter, Na+-taurocholate co-transporting polypeptide (ntcp), is increased at the plasma membrane upon treatment of cells with cAMP, for which microtubules (MTs) are required and the PI3K pathway and PKCzeta have been implicated. However, trafficking of ntcp on MTs has not been demonstrated directly and the regulation and intracellular localization of ntcp is not well understood. Here, we utilize in vitro and whole-cell immunofluorescence microscopy assays to demonstrate that ntcp is present on intracellular vesicles that bind MTs and move bidirectionally, using kinesin-1 and dynein. These vesicles co-localize with markers for recycling endosomes and early but not late endosomes. They frequently undergo fission, providing a mechanism for the exclusion of ntcp from late endosomes. PI(3,4,5)P3 activates PKCzeta and enhances motility of the ntcp vesicles and overcomes the partial inhibition produced by a PI3-kinase inhibitor. Specific inhibition of PKCzeta blocks the motility of ntcp-containing vesicles but has no effect on late vesicles as shown both in vitro and in living cells transfected with ntcp-GFP. These data indicate that PKCzeta is required specifically for the intracellular movement of vesicles that contain the ntcp transporter.     

Photoperiod sensing of the circadian clock is controlled by EARLY FLOWERING 3 and GIGANTEA

ELF3 and GI are two important components of the Arabidopsis circadian clock. They are not only essential for the oscillator function but are also pivotal in mediating light inputs to the oscillator. Lack of either results in a defective oscillator causing severely compromised output pathways, such as photoperiodic flowering and hypocotyl elongation. Although single loss of function mutants of ELF3 and GI have been well studied, their genetic interaction remains unclear. We generated an elf3 gi double mutant to study their genetic relationship in clock‐controlled growth and phase transition phenotypes. We found that ELF3 and GI repress growth differentially during the night and the day, respectively. Circadian clock assays revealed that ELF3 and GI are essential that enable the oscillator to synchronize the endogenous cellular mechanisms to external environmental signals. In their absence, the circadian oscillator fails to synchronize to the light–dark cycles even under diurnal conditions. Consequently, clock‐mediated photoperiod‐responsive growth and development are completely lost in plants lacking both genes, suggesting that ELF3 and GI together convey photoperiod sensing to the central oscillator. Since ELF3 and GI are conserved across flowering plants and represent important breeding and domestication targets, our data highlight the possibility of developing photoperiod‐insensitive crops by adjusting the allelic combination of these two key genes.