Age, sex, and grip strength determine architectural bone parameters assessed by peripheral quantitative computed tomography (pQCT) at the human radius

The purpose of this study was to estimate the relation of some noninvasively derived mechanical characteristics of radial bone including architectural parameters for bone strength to grip strength and muscle cross-section. Sixty-three males between 21 and 78yr of age and 101 females between 18 and 80yr of age were measured at the nondominant forearm using peripheral quantitative computed tomography (pQCT). We assessed the integral bone mineral density (BMD(I)) and content (BMC(I)) by pQCT at the distal and at the mid-shaft radius. Integral bone area (Area(I)), cortical thickness (C-th), and a newly proposed index for bone strength; the stress-strain index (SSI) were also calculated. The dynamometrically measured maximum grip strength was taken as a mechanical loading parameter and muscle cross-section as a substitute for it. Sex, grip strength, BMC(I) and BMD(I) (distal radius) were identified in a multiple regression analysis to significantly predict bone strength as expressed by SSI, after adjusting for all other independent variables, including age and sex (p<0.0001). Grip strength was closest related to age, sex, BMD(I) and SSI(p) of the distal radius. The cross-sectional area of muscle was not significantly determining the grip strength within the analysis model. In conclusion, our results suggested that architectural parameters at the distal radius were better related to grip strength than to cross-sectional muscle area in both males and females. Maximum muscle strength as estimated by grip strength might be a stronger determinant of mechanical characteristics of bones as compared with cross-sectional muscle area.     

Xoom is maternally stored and functions as a transmembrane protein for gastrulation movement in Xenopus embryos

Xoom has been identified as a novel gene that plays an important role in gastrulation of Xenopus laevis embryo. Although Xoom is actively transcribed during oogenesis, distribution and function of its translation product have not yet been clarified. In the present study, the polyclonal antibody raised against Xoom was generated to investigate a behavior of Xoom protein. Anti-Xoom antibodies revealed that there are two forms of Xoom protein in Xenopus embryos: (i) a 45 kDa soluble cytoplasmic form; and (ii) a 44 kDa membrane-associated form. Two forms of Xoom protein were ubiquitously detected from unfertilized egg to tadpole stage, with a qualitative peak during blastula and gastrula stages. Immunohistochemical examination showed that Xoom protein is maternally stored in the animal subcortical layer and divided into presumptive ectodermal cells during cleavage stages. Enzymatic digestion of membrane protein and immunologic detection of Xoom showed that Xoom exists as a membrane-associated protein. To examine a function of Xoom protein, anti-Xoom antibodies were injected into blastocoele of stage 7 blastula embryo. Anti-Xoom antibodies caused gastrulation defect in a dose- dependent manner. These results suggest that maternally prepared Xoom protein is involved in gastrulation movement on ectodermal cells.     

Molting of Gnathostoma doloresi (Nematoda: Gnathostomatoidea) in the definitive host

Premolt, molting, and postmolt worms of Gnathostoma doloresi (Nematoda: Gnathostomatoidea) recovered from the stomach wall of naturally infected wild boars Sus scrofa leucomystax in Miyazaki, Japan, were examined morphologically. The only molt observed was that from the advanced third-stage to the adult stage. It is strongly suggested that the gnathostomes molt only once in the definitive host.     

Dioctophymatid nematode larva found from human skin with creeping eruption

A female dioctophymatid nematode larva, presumably belonging to the genus Dioctophyme, was found in a dermal granuloma accompanied by creeping eruption in the left inner thigh of a 26-yr-old Chinese woman who had stayed in Japan for 4 yr. Morphology of the sectioned worm is described in detail. This is the fourth case of dermal infection with dioctophymatid larva in humans.     

Model dependence of the phylogenetic inference: relationship among carnivores, Perissodactyls and cetartiodactyls as inferred from mitochondrial genome sequences

Some previous analysis of mitochondrial proteins strongly support the Carnivora/Perissodactyla grouping excluding Cetartiodactyla (Artiodactyla + Cetacea) as an outgroup, but the support of the hypothesis remains equivocal from the analysis of several nuclear-encoded proteins. In order to evaluate the strength of the support by mitochondrial proteins, phylogenetic relationship among Carnivora, Perissodactyla, and Cetartiodactyla was estimated with the ML method by using the updated data set of the 12 mitochondrial proteins with several alternative models. The analyses demonstrate that the phylogenetic inference depends on the model used in the ML analysis; i.e., whether the site-heterogeneity is taken into account and whether the rate parameters are estimated for each individual proteins or for the concatenated sequences. Although the analysis of concatenated sequences strongly supports the Carnivora/Perissodactyla grouping, the total evaluation of the separate analyses of individual proteins, which approximates the data better than the concatenated analysis, gives only ambiguous results, and therefore it is concluded that more data are needed to resolve this trichotomy.     

Cloning and expression of the N,N-dimethylformamidase gene from Alcaligenes sp. strain KUFA-1

N,N-Dimethylformamidase (DMFase) from Alcaligenes sp. strain KUFA-1, a bacterium that can grow on N,N-dimethylformamide (DMF) as the sole carbon and nitrogen source, catalyzes the first step of the DMF degradation. The DMFase gene dmfA1A2 was cloned in Escherichia coli, and its nucleotides were sequenced. The deduced amino acid sequence of the enzyme consisted of two alpha- and two beta-subunits with 132 and 762 amino acids, respectively, and had little similarity to sequences in protein databases, including various amidases. The protein may be a new kind of amidase. DMFase activity was detected in E. coli cells transformed with an expression plasmid of the cloned DMFase gene. The properties of recombinant DMFase purified from E. coli were identical to those of Alcaligenes DMFase.     

Structural basis for the resistance of Tay-Sachs ganglioside GM2 to enzymatic degradation

To understand the reason why, in the absence of GM2 activator protein, the GalNAc and the NeuAc in GM2 (GalNAcbeta1-->4(NeuAcalpha2-->3)Galbeta1-->4Glcbet a1-1'Cer) are refractory to beta-hexosaminidase A and sialidase, respectively, we have recently synthesized a linkage analogue of GM2 named 6'GM2 (GalNAcbeta1-->6(NeuAcalpha2-->3)Galbeta1-->4Glcbet a1-1'Cer). While GM2 has GalNAcbeta1-->4Gal linkage, 6'-GM2 has GalNAcbeta1-->6Gal linkage (Ishida, H., Ito, Y., Tanahashi, E., Li, Y.-T., Kiso, M., and Hasegawa, A. (1997) Carbohydr. Res. 302, 223-227). We have studied the enzymatic susceptibilities of GM2 and 6'GM2, as well as that of the oligosaccharides derived from GM2, asialo-GM2 (GalNAcbeta1-->4Galbeta1--> 4Glcbeta1-1'Cer) and 6'GM2. In addition, the conformational properties of both GM2 and 6'GM2 were analyzed using NMR spectroscopy and molecular mechanics computation. In sharp contrast to GM2, the GalNAc and the Neu5Ac of 6'GM2 were readily hydrolyzed by beta-hexosaminidase A and sialidase, respectively, without GM2 activator. Among the oligosaccharides derived from GM2, asialo-GM2, and 6'GM2, only the oligosaccharide from GM2 was resistant to beta-hexosaminidase A. Conformational analyses revealed that while GM2 has a compact and rigid oligosaccharide head group, 6'GM2 has an open spatial arrangement of the sugar units, with the GalNAc and the Neu5Ac freely accessible to external interactions. These results strongly indicate that the resistance of GM2 to enzymatic hydrolysis is because of the specific rigid conformation of the GM2 oligosaccharide.     

Targeted inactivation of the gene psaK encoding a subunit of photosystem I from the cyanobacterium Synechocystis sp. PCC 6803

Mutant strains of the unicellular cyanobacterium Synechocystissp. PCC 6803, in which the psaK gene was insertionally inactivatedby targeted mutagenesis, were constructed. The gene is one ofthe two potential PsaK-coding genes which have been found asa result of the genome project with this cyanobacterium. Oneof the mutants was characterized in detail. A monocistronic,480-nucleotide mRNA of psaK was absent in total RNA from themutant cells. Inactivation of psaK had little effect on theaccumulation of polypeptides in the isolated PSI complexes exceptfor a polypeptide with an apparent molecular mass of 4.6 kDawhich was absent in the mutant. The amino-terminal amino acidsequence of the 4.6-kDa polypeptide confirmed that it was thetranslation product of psaK and further revealed a presequenceof PsaK. Characteristics of photoautotrophic growth at differenttemperatures, the amount of chlorophyll per cell, photosyntheticelectron transport rates with various electron acceptors, thekinetics of charge recombination between P700⁺ and reduced F_A/F_B,and the molar ratio of chlorophyll to P700, of the mutant werenot significantly different from those of the wild type. Furthermore,the trimer to monomer ratio of the PSI complexes isolated fromthe mutant was similar to that isolated from the wild type. (Received July 27, 1998; Accepted October 13, 1998)     

Ala99ser mutation in RIα Regulatory Subunit of protein kinase A causes reduced kinase activation by cAMP and arrest of hormone-dependent breast cancer cell growth

Expression of the RI regulatory subunit of protein kinase A type I is increased in human cancer cell lines, in primary tumors, in cells after transformation, and in cells upon stimulation of growth. Ala99 (the pseudophosphorylation site) of human RI was replaced with Ser (RI-p) for the structure-function analysis of RI. MCF-7 hormone- dependent breast cancer cells were transfected with an expression vector for the wild-type RI or mutant RI-p. Overexpression of RI-P resulted in suppression of protein kinase A type II, the isozyme of type I kinase, production of kinase exhibiting reduced cAMP activation, and inhibition of cell growth showing an increase in G0/G1 phase of the cell cycle and apoptosis. The wild-type RI overexpression had no effect on protein kinase A isozyme distribution or cell growth. Overexpression of protein kinase A type II regulatory subunit, RII, suppressed RI and protein kinase A type I and inhibited cell growth. These results show that the growth of hormone-dependent breast cancer cells is dependent on the functional protein kinase A type I.