Age-related differences in muscle activity, stride frequency and heart rate response during walking in water.

This study aimed to examine whether walking in water produces age-related differences in muscle activity, stride frequency (SF), and heart rate (HR) response. Surface electromyography (EMG) was used to evaluate muscle activities in six older and six young subjects while they walked in water immersed to the level of the xiphoid process. The trials in water utilized the Flowmill which consists of a treadmill at the base of a water flume. The measurement of maximal voluntary contraction (MVC) of each muscle was made prior to the gait analysis. The %MVCs, which refer to the surface EMG measures, from the gastrocnemius of the older subjects were significantly lower than those of the young subjects, in every experimental condition (P<0.05). In contrast, the %MVCs from the rectus femoris (P<0.05) and the biceps femoris (P<0.001) of older subjects were significantly greater than those of young subjects in every experimental condition. Moreover, the SFs of older subjects were also significantly greater than those of young subjects (P<0.05), while the HR responses of older and young subjects were similar. In conclusion, the older subjects had increased hip musculature activity and decreased ankle plantar flexor activity while walking in water, compared with the young subjects.     

Alphoid satellite DNA is tightly associated with centromere antigens in human chromosomes throughout the cell cycle

In this study, we have examined a DNA element specific to the centromere domain of human chromosomes. Purified HeLa chromosomes were digested with the restriction enzyme Sau3AI and fractionated by sedimentation through a sucrose gradient. Fractions showing antigenecity to anticentromere (kinetochore) serum obtained from a scleroderma CREST patient were used to construct a DNA library. From this library we found one clone which has specifically hybridized to the centromere domain of metaphase chromosomes using a biotinylated probe DNA and FITC-conjugated avidin. The clone contained a stretch of alphoid DNA dimer. To determine precisely the relative location of the alphoid DNA stretch and the centromere antigen, a method was developed to carry out in situ hybridization of DNA and indirect immunofluorescent staining of antigen on the same cell preparation. Using this method, we have found perfect overlapping of the alphoid DNA sites with the centromere antigen sites in both metaphase chromosomes and nuclei at various stages in the cell cycle. We have also observed this exact correlation at the attachment sites of artificially extended sister chromatids. These results suggest the possibility that alphoid DNA repeats are a key component of kinetochore structure.     

Regulation of intracellular Mg2+ by superoxide in amnion cells.

Changes of intracellular free Mg2+ concentration ([Mg2+]i) in human amnion cells induced by superoxide anion were determined using a highly Mg(2+)-sensitive fluorescent dye Mg(2+)-fura2 or Mg(2+)-indol. Superoxide anion, produced by addition of xanthine oxidase to hypoxanthine, induced decrease of [Mg2+]i. The decrease was significantly inhibited by an anion channel blocker, 4,4'diisothiocyano-2,2' disulfonic acid stilbene (DIDS). Superoxide dismutase (SOD), injected into cells by cell fusion, also inhibited the change of [Mg2+]i, but catalase did not. Superoxide anion induced prompt increase of intracellular pH (pHi) as well as decrease of [Mg2+]i and subsequently activated the increase of intracellular free Ca2+ ([Ca2+]i) and the release of arachidonate. In contrast to superoxide anion, NH4Cl which induces increase of pHi in amnion cells increased [Mg2+]i. The elevation of basal level of [Mg2+]i by Mg(2+)-ionophore inhibited the change of [Ca2+]i and the release of arachidonate induced by superoxide anion. These results suggest that superoxide anion, transported through anion channels into cells, decreases [Mg2+]i directly, not due to a pH-effect and that the decrease of [Mg2+]i may regulate biological functions of the cells via increase of [Ca2+]i.     

Male emergence timing and mating success in the funnel-web spider,Agelena limbata (Araneae: Agelenidae)

Field observations on the relationship between male mating success and emergence timing in the funnel-web spider,Agelena limbata, were conducted.Agelena limbata is an annual species and adult males appear slightly earlier than adult females in July. As males deposit a copulatory plug at the female epigynum after copulation, copulation with virgin females is important to males. The number of copulations in males with virgin females, which strongly correlates with the longevity of males and the number of females that males courted, did not correlate with the emergence timing of males. Early emerged males and females were significantly larger in size than later ones, but the correlation coefficient between the emerged date and the cephalothorax width was not strong. Males that emerged earlier did not have any advantage in copulating with larger and more fecund females. Furthermore, virgin females first copulated on average 7.9 days after their final molt and the mortality rate of adult males increased after the final molt. These factors may favor the smaller degree of protandry in male emergence timing inA. limbata.     

Host plant conspicuousness and the distribution of eggs and larvae in the butterfly,Anthocharis scolymus (Lepidoptera: Pieridae)

We investigated how the distribution pattern of eggs and larval on the host plant, Turritus glabra, was influenced by the oviposition behavior of the pierid butterfly Anthocharis scolymus. Females searched for the host plants visually and they frequently approached taller host plants with sparse surrounding vegetation. After encountering host plants, oviposition behavior of females was independent of host plant characteristics such as height, density, and type of surrounding vegetation. A female laid eggs singly on a host plants. Most females appeared to lay their eggs regardless of the presense of eggs on the host plant. Consequently egg and larva tended to be abundant on conspicuous host plants as measured by height or relative isolation from other plants. However, overcrowding of eggs on an individual host decreased the survival rate of larvae.     

CENP-B binds a novel centromeric sequence in the Asian mouse Mus caroli.

Minor satellite DNA, found at Mus musculus centromeres, is not present in the genome of the Asian mouse Mus caroli. This repetitive sequence family is speculated to have a role in centromere function by providing an array of binding sites for the centromere-associated protein CENP-B. The apparent absence of CENP-B binding sites in the M. caroli genome poses a major challenge to this hypothesis. Here we describe two abundant satellite DNA sequences present at M. caroli centromeres. These satellites are organized as tandem repeat arrays, over 1 Mb in size, of either 60- or 79-bp monomers. All autosomes carry both satellites and small amounts of a sequence related to the M. musculus major satellite. The Y chromosome contains small amounts of both major satellite and the 60-bp satellite, whereas the X chromosome carries only major satellite sequences. M. caroli chromosomes segregate in M. caroli x M. musculus interspecific hybrid cell lines, indicating that the two sets of chromosomes can interact with the same mitotic spindle. Using a polyclonal CENP-B antiserum, we demonstrate that M. caroli centromeres can bind murine CENP-B in such an interspecific cell line, despite the absence of canonical 17-bp CENP-B binding sites in the M. caroli genome. Sequence analysis of the 79-bp M. caroli satellite reveals a 17-bp motif that contains all nine bases previously shown to be necessary for in vitro binding of CENP-B. This M. caroli motif binds CENP-B from HeLa cell nuclear extract in vitro, as indicated by gel mobility shift analysis. We therefore suggest that this motif also causes CENP-B to associate with M. caroli centromeres in vivo. Despite the sequence differences, M. caroli presents a third, novel mammalian centromeric sequence producing an array of binding sites for CENP-B.     

A Reduction in Age-Enhanced Gluconeogenesis Extends Lifespan

The regulation of energy metabolism, such as calorie restriction (CR), is a major determinant of cellular longevity. Although augmented gluconeogenesis is known to occur in aged yeast cells, the role of enhanced gluconeogenesis in aged cells remains undefined. Here, we show that age-enhanced gluconeogenesis is suppressed by the deletion of the tdh2 gene, which encodes glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a protein that is involved in both glycolysis and gluconeogenesis in yeast cells. The deletion of TDH2 restores the chronological lifespan of cells with deletions of both the HST3 and HST4 genes, which encode yeast sirtuins, and represses the activation of gluconeogenesis. Furthermore, the tdh2 gene deletion can extend the replicative lifespan in a CR pathway-dependent manner. These findings demonstrate that the repression of enhanced gluconeogenesis effectively extends the cellular lifespan.     

A role of lipophilic peptidoglycan-related molecules in induction of Nod1-mediated immune responses

Nod1 is an intracellular protein that is involved in recognition of bacterial molecules and whose genetic variation has been linked to several inflammatory diseases. Previous studies suggested that the recognition core of Nod1 stimulatory molecules is gamma-D-glutamyl-meso-diaminopimelic acid (iE-DAP), but the identity of the major Nod1 stimulatory molecule produced by bacteria remains unknown. Here we show that bacteria produce lipophilic molecules capable of stimulating Nod1. Analysis of synthetic compounds revealed stereoselectivity of the DAP residue and that conjugation of lipophilic acyl residues specifically enhances the Nod1 stimulatory activity of the core iE-DAP. Furthermore, we demonstrate that lipophilic molecules induce and/or enhance the secretion of innate immune mediators from primary mouse mesothelial cells and human monocytic MonoMac6 cells, and this effect is mediated through Nod1. These results provide insight into the mechanism of immune recognition via Nod1, which might be useful in the design and testing of novel immunoregulators.     

Electromyographic analysis of walking in water in healthy humans

This study was designed to describe and clarify muscle activities which occur while walking in water. Surface electromyography (EMG) was used to evaluate muscle activities in six healthy subjects (mean age, 23.3 +/- 1.4 years) while they walked on a treadmill in water (with or without a water current) immersed to the level of the xiphoid process, and while they walked on a treadmill on dry land. The trials in water utilized the Flowmill which has a treadmill at the base of a water flume. Integrated EMG analysis was conducted for the quantification of muscle activities. In order to calculate the %MVC, the measurement of maximal voluntary contraction (MVC) of each muscle was made before the gait analysis, thus facilitating a comparison of muscle activities while walking in water with those on dry land. The %MVCs obtained from each of the tested muscles while walking in water, both with and without a water current, were all found to be lower than those obtained while walking on dry land at a level of heart rate response similar to that used when walking on dry land. Furthermore, the %MVCs while walking in water with a water current tended to be greater when compared to those while walking in water without a water current. In conclusion, the present study demonstrated that muscle activities while walking in water were significantly decreased when compared to muscle activities while walking on dry land, that muscle activities while walking in water tended to be greater with a water current than without, and that the magnitude of the muscle activity in water was relatively small in healthy humans. This information is important to design water-based exercise programs that can be safely applied for rehabilitative and recreational purposes.