Responses in muscle sympathetic activity to acute hypoxia in humans

Responses in muscle sympathetic activity (MSA) to acute hypoxia were studied in 13 healthy male subjects under hypobaric hypoxic conditions at a simulated altitude of 4,000, 5,000, and 6,000 m. Efferent postganglionic MSA was recorded directly with a tungsten microelectrode inserted percutaneously into the tibial nerve. Heart rate (HR) and respiratory rate (RR) were counted respectively from the R wave of an electrocardiogram and from the respiratory tracing recorded by the strain-gauge method. The average values of the MSA burst rate and total activity of MSA (burst rate x mean burst amplitude) at 4,000, 5,000, and 6,000 m were 36.4 +/- 2.6, 39.1 +/- 3.1, and 40.2 +/- 4.2 (SE) bursts/min and 616 +/- 138, 794 +/- 190, and 764 +/- 227 arbitrary units, respectively. These values were significantly higher than the values of 27.1 +/- 2.9 bursts/min and 446 +/- 28 at sea level. HR increased significantly at altitudes, but RR did not show significant change. Under severe hypoxic conditions beyond 5,000 m, there were large interindividual differences in the MSA responsiveness to hypoxia. The results indicate that MSA is activated under hypoxia by stimulating the chemoreceptors. However, the central controlling mechanisms that would be affected by hypoxia may also influence the MSA responsiveness under severe hypoxia.     

A soybean growth model based on compensatory growth following defoliation

On the basis of an artificial defoliation experiment, a new growth model of soybean was formulated through a modification of Rudd's (1980) model with regard to his equations for dry matter allocation. Compensatory growth for leaf damage was modelled by a single process in which the dry matter allocation changes dynamically according to the severity of leaf damage. The sums of squared differences between simulations and experimental soybean yields were much smaller in our modified model than in Rudd's original model. The modified model gave a better simulation of yield loss due to defoliation that varied in time and intensity. The relationship between various times and intensities of defoliation and yield loss was shown, which is essential for establishing the dynamic economic injury level in IPM.     

Ultrastructural localization of carbonic anhydrase activity in the rat choroid plexus epithelial cell

Summary Localization of carbonic anhydrase activity was studied electron microscopically on cells of the rat choroid plexus epithelium. For the ultracytochemical detection of these activities, Yokota's technique (1969), which is the modification of Hansson's method (1967) was employed. Numerous electron dense reaction products were observed in the microvilli of the choroidal epithelial cell. The reaction deposits were also remarkably present in the infoldings of the basal plasmalemma but to a lesser extent than in the microvilli. The localization sites were mainly on the plasma membrane, but some reaction products were also observed in the cytoplasm near the plasma membrane. Hardly any reaction product was found in the intracellular organelles except for the mitochondria in which reaction products were occasionally observed on the cristae. These activities were completely inhibited by acetazolamide. As the carbonic anhydrase activity was histochemically seen in the microvilli and the basal infoldings, it is likely that carbonic anhydrase is related to an active transport process in the secretion of cerebrospinal fluid as is Na⁺, K⁺-ATPase (Masuzawa et al. 1980).     

Peculiarities of sexual reproduction inFagus crenata forests in relation to annual production of reproductive organs

Annual production rates of reproductive organs inFagus crenata forests in the lower area of the species' range were studied using 10 litter traps in 1980–1986. The production rates of dispersed pollen were estimated by multiplying the number of fallen male inflorescences per ha per year by the mean amount of pollen per inflorescence before anthesis. Large annual fluctuations in the production rates of male and female inflorescences were recognized, whereas their annual trends were synchronized with each other. Pollen production rates were within the range 1.0–6900 (mean: 1630)×10⁹ha⁻¹ yr⁻¹, the maximum/minimum ratio attaining 7000.F. crenata was the lowest producer of pollen among seven tree species studied: the number of pollen grains equivalent to a single ovule was in the range 6.0–14×10⁴. Furthermore, the mean dry weight of a single pollen grain (3.77×10⁻⁵mg) was higher than for wind-pollinated species. Three factors seemed to cause the low seed fertility ofF. crenata. The dry-matter production rate in the best seed year reached 3252 kg ha⁻¹ yr⁻¹, of which pollen accounted for 259 kg ha⁻¹ yr⁻¹. Unproductive years with less than 10% of the maximum production occurred four times in a 7-yr period. In such years there were fewer male and female inflorescences, and more fruit dropped as a result of insect damage. Lower nut dissemination would play an important role in suppressing any increase in nut predators, and fewer flowers would be produced to avoid wastage of photosynthates in a cool-temperate climate.     

Structure of the summer under fast ice microbial community near Syowa Station,eastern Antarctica

Temporal variations in the microbial community structure of plankton, which is composed of autotrophic and heterotrophic pico-, nano- and microplankton, were investigated during the austral summer of 2005/2006 under fast ice near Syowa Station, eastern Antarctica. Autotrophic algal populations were composed almost entirely of diatoms followed by phytoflagellates such as autotrophic dinoflagellates and cryptophytes. Among the microbial community, heterotrophic biomass was dominated by heterotrophic dinoflagellates and naked ciliates and finally exceeded autotrophic biomass. Qualitative microscopic analysis revealed that heterotrophic dinoflagellates were ingesting large number of diatoms. Synchronizing fluctuation of naked ciliates with phytoflagellates suggested a predator–prey relationship between them. Our results suggest that the pelagic food webs under the extensive ice-covered areas in coastal Antarctic regions are not short but complex.     

Sequence-specific DNA recognition by basic peptides.

A chiral template with C2 symmetry has been used for modeling a dimeric interface of DNA binding protein. An oligopeptide derived from the basic region of MyoD, a recently described "helix-loop-helix" class of DNA binding protein, has been tethered to the template. Among the four models which differ in chirality and polarity with respect to the arrangement of two subunits, only one dimer model with right-handed and C-terminus to C-terminus arrangement of the peptide subunits binds DNA containing native MyoD binding sequence.     

Circadian rhythms in digestive enzymes in the small intestine of rats. I. Patterns of the rhythms in various regions of the small intestine.

The activities of the digestive enzymes, maltase [EC 3.2.1.20], sucrase [EC 3.2.1.26], trehalase [EC 3.2.1.28], Leucine aminopeptidase [EC 3.4.11.1], and alkaline phosphatase [EC 3.1.3.1] were measured in various regions of the small intestine of rats. The activities of all these enzymes were much higher in the jejunum than in the ileum, and in the distal regions of the ileum no sucrase, trehalase or alkaline phosphatase activity was detected. In the jejunum, the activities of all the enzymes tested exhibited clear circadian variations with the highest activity at 0000-0400 h and the lowest at 1200 h when the rats were fed ad libitum. In the ileum, maltase and sucrase also exhibited circadian variations, but the amplitude of the rhythm was smaller than that in the jejenum. Trehalase and alkaline phosphatase did not show any circadian variation in the ileum. Leucine aminopeptidase showed a circadian variation in the ileum with the same amplitude as in the jejunum. The phase of the circadian variations shifted about half a day when the rats were fed in the daytime, but the amplitude of the rhythm did not change.     

Amphipathic α-Helices in Apolipoproteins Are Crucial to the Formation of Infectious Hepatitis C Virus Particles

Apolipoprotein B (ApoB) and ApoE have been shown to participate in the particle formation and the tissue tropism of hepatitis C virus (HCV), but their precise roles remain uncertain. Here we show that amphipathic α-helices in the apolipoproteins participate in the HCV particle formation by using zinc finger nucleases-mediated apolipoprotein B (ApoB) and/or ApoE gene knockout Huh7 cells. Although Huh7 cells deficient in either ApoB or ApoE gene exhibited slight reduction of particles formation, knockout of both ApoB and ApoE genes in Huh7 (DKO) cells severely impaired the formation of infectious HCV particles, suggesting that ApoB and ApoE have redundant roles in the formation of infectious HCV particles. cDNA microarray analyses revealed that ApoB and ApoE are dominantly expressed in Huh7 cells, in contrast to the high level expression of all of the exchangeable apolipoproteins, including ApoA1, ApoA2, ApoC1, ApoC2 and ApoC3 in human liver tissues. The exogenous expression of not only ApoE, but also other exchangeable apolipoproteins rescued the infectious particle formation of HCV in DKO cells. In addition, expression of these apolipoproteins facilitated the formation of infectious particles of genotype 1b and 3a chimeric viruses. Furthermore, expression of amphipathic α-helices in the exchangeable apolipoproteins facilitated the particle formation in DKO cells through an interaction with viral particles. These results suggest that amphipathic α-helices in the exchangeable apolipoproteins play crucial roles in the infectious particle formation of HCV and provide clues to the understanding of life cycle of HCV and the development of novel anti-HCV therapeutics targeting for viral assembly.     

Generation of Rhesus Macaque-Tropic HIV-1 Clones That Are Resistant to Major Anti-HIV-1 Restriction Factors

Human immunodeficiency virus type 1 (HIV-1) replication in macaque cells is restricted mainly by antiviral cellular APOBEC3, TRIM5α/TRIM5CypA, and tetherin proteins. For basic and clinical HIV-1/AIDS studies, efforts to construct macaque-tropic HIV-1 (HIV-1mt) have been made by us and others. Although rhesus macaques are commonly and successfully used as infection models, no HIV-1 derivatives suitable for in vivo rhesus research are available to date. In this study, to obtain novel HIV-1mt clones that are resistant to major restriction factors, we altered Gag and Vpu of our best HIV-1mt clone described previously. First, by sequence- and structure-guided mutagenesis, three amino acid residues in Gag-capsid (CA) (M94L/R98S/G114Q) were found to be responsible for viral growth enhancement in a macaque cell line. Results of in vitro TRIM5α susceptibility testing of HIV-1mt carrying these substitutions correlated well with the increased viral replication potential in macaque peripheral blood mononuclear cells (PBMCs) with different TRIM5 alleles, suggesting that the three amino acids in HIV-1mt CA are involved in the interaction with TRIM5α. Second, we replaced the transmembrane domain of Vpu of this clone with the corresponding region of simian immunodeficiency virus SIVgsn166 Vpu. The resultant clone, MN4/LSDQgtu, was able to antagonize macaque but not human tetherin, and its Vpu effectively functioned during viral replication in a macaque cell line. Notably, MN4/LSDQgtu grew comparably to SIVmac239 and much better than any of our other HIV-1mt clones in rhesus macaque PBMCs. In sum, MN4/LSDQgtu is the first HIV-1 derivative that exhibits resistance to the major restriction factors in rhesus macaque cells.     

Rat <Emphasis Type="Italic">wct</Emphasis> mutation prevents differentiation of maturation-stage ameloblasts resulting in hypo-mineralization in incisor teeth

A recent study provided genetic and morphological evidence that rat autosomal-recessive mutation, whitish chalk-like teeth (wct), induced tooth enamel defects resembling those of human amelogenesis imperfecta (AI). The wct locus maps to a specific interval of rat chromosome 14 corresponding to human chromosome 4q21 where the ameloblastin and enamelin genes exist, although these genes are not included in the wct locus. The effect of the wct gene mutation on the enamel matrix synthesis and calcification remains to be elucidated. This study clarifies how the wct gene mutation influences the synthesis of enamel matrix and its calcification by immunocytochemistry for amelogenin, ameloblastin and enamelin, and by electron probe micro-analysis (EPMA). The immunoreactivity for enamel proteins such as amelogenin, ameloblastin, and enamelin in the ameloblasts in the homozygous teeth was the same as that in the heterozygous teeth from secretory to transitional stages, although the homozygous ameloblasts became detached from the enamel matrix in the transitional stage. The flattened ameloblasts in the maturation stage of the homozygous samples contained enamel proteins in their cytoplasm. Thus, the wct mutation was found to prevent the morphological transition of ameloblasts from secretory to maturation stages without disturbing the synthesis of enamel matrix proteins, resulting in the hypo-mineralization of incisor enamel and cyst formation between the enamel organ and matrix. This mutation also prevents the transfer of iron into the enamel.