拉萨高原居民肺容量的测定

对年龄、身高和体重相同的拉萨男性世居藏族39人和男性移居汉族43人的肺容量进行了测定。结果显示:藏族组的肺活量(VC)、肺总容量、胸围均大于汉族组,残气量有大于汉族组之趋势(P=0.06)。胸围的大小与VC呈正相关。5岁前和18岁后移居高原者之肺容量无差别。结果提示,拉萨世居藏族具有较大的肺容量,这对提高肺弥散功能和维持运动时的血氧饱和度有重要意义。     

The vacuolar H+-ATPase of Saccharomyces cerevisiae is required for efficient copper detoxification, mitochondrial function, and iron metabolism

Mutations in the GEF2 gene of the yeast Saccharomyces cerevisiae have pleiotropic effects. The gef2 mutants display a petite phenotype. These cells grow slowly on several different carbon sources utilized exclusively or primarily by respiration. This phenotype is suppressed by adding large amounts of iron to the growth medium. A defect in mitochondrial function may be the cause of the petite phenotype: the rate of oxygen consumption by intact gef2 cells and by mitochondrial fractions isolated from gef2 mutants was reduced 60%–75% relative to wild type. Cytochrome levels were unaffected in gef2 mutants, indicating that heme accumulation is not significantly altered in these strains. The gef2 mutants were also more sensitive than wild type to growth inhibition by several divalent cations including Cu. We found that the cup5 mutation, causing Cu sensitivity, is allelic to gef2 mutations. The GEF2 gene was isolated, sequenced, and found to be identical to VMA3, the gene encoding the vacuolar H ⁺-ATPase proteolipid subunit. These genetic and biochemical analyses demonstrate that the vacuolar H ⁺-ATPase plays a previously unknown role in Cu detoxification, mitochondrial function, and iron metabolism.     

Sequence Analyses and Phylogenetic Characterization of the ZIP Family of Metal Ion Transport Proteins

Several novel but similar heavy metal ion transporters, Zrt1, Zrt2, Zip1-4 and Irt1, have recently been characterized. Zrt1, Zrt2 and Zip1-4 are probably zinc transporters in Saccharomyces cerevisiae and Arabidopsis thaliana whereas Irt1 appears to play a role in iron uptake in A. thaliana. The family of proteins including these functionally characterized transporters has been designated the Zrt- and Irt-related protein (ZIP) family. In this report, ZIP family proteins in the current databases were identified and multiply aligned, and a phylogenetic tree for the family was constructed. A family specific signature sequence was derived, and the available sequences were analyzed for residues of potential functional significance. A fully conserved intramembranous histidyl residue, present within a putative amphipathic, α-helical, transmembrane spanning segment, was identified which may serve as a part of an intrachannel heavy metal ion binding site. The occurrence of a proposed extramembranal metal binding motif (H X H X H) was examined in order to evaluate its potential functional significance for various members of the family. The computational analyses reported in this topical review should serve as a guide to future researchers interested in the structure-function relationships of ZIP family proteins. Received: 31 March 1997/Revised: 14 May 1998     

A change in twist of actin provides the force for the extension of the acrosomal process in limulus sperm: the false-discharge reaction

One of the most spectacular motions is the generation of the acrosomal process in the limulus sperm. On contact with the egg, the sperm generates a 60-mum-long process that literally drills its way through the jelly surrounding the egg. This irresversible reaction takes only a few seconds. We suggested earlier that this motion is driven by a change in twist of the actin filaments comprising the acrosomal process. In this paper we analyze the so-called false discharge, a reversible reaction, in which the acrosomal filament bundle extends laterally from the base of the sperm and not anteriorly from the apex. Unlike the true discharge, which is straight, the false discharge is helical. Before extension, the filament bundle is coiled about the base of the sperm. In the coil, the bundle is not smoothly bent but consists of arms (straight segments) and elbows (corners) so that the coil looks like a 14-sided polygon. The extension of the false discharge works as follows: starting at the base of the bundle, the filaments change their twist which concomitantly changes the orientations of the elbows relative to each other; that is, in the coil, the elbows all like in a common plane, but after the change in twist, the plane of each elbow is rotated to be perpendicular to that of its neighbors. This change transforms the bundle from a compact coil into an extended left- handed helix. Because the basal end of the bundle is unconstrained, the extension is lateral. The true discharge works the same way but starts at the apical end of the bundle. The apical end, however, is constrained by its passage through the nuclear canal, which directs the extention anteriorly. Unlike the false discharge, during the true discharge the elbows are melted out, making the reaction irreversible. This study shows that rapid movement can be regenerated by actin without myosin and gives us insight into the molecular mechanism.     

Stomatal frequency of Betula pubescens and Pinus sylvestris shows no proportional relationship with atmospheric CO2 concentration

We investigated the relationship between stomatal frequency and a range of atmospheric CO₂ concentrations ([CO₂]_atm) in Betula pubescens and Pinus sylvestris , two important boreal trees in Scandinavia. If strong relationships exist, they can be used to reconstruct past [CO₂]_atm from stomatal frequency of fossil Betula and Pinus leaves. Responses of epidermal characters (stomatal density (SD), epidermal cell density (ED), stomatal index (SI)) to different CO₂ concentrations were investigated utilising (1) the lower partial pressure of CO₂ at increasing altitudes for B. pubescens , and in herbarium specimens of B. pubescens and P. sylvestris collected during the post-industrial rise of [CO₂]_atm from c. 280 ppmv to c. 360 ppmv in 1997 and (2) concentrations (560 ppmv) and temperatures (3° summer) above present day in the CLIMEX greenhouse experiment. All the results show no clear relationship between SD or SI and [CO₂] _atm for either B. pubescens or P. sylvestris. Most likely there are stronger genetically and environmentally induced factors that affect the development of the leaves. Problems with collecting representative samples from herbarium specimens are discussed. Since the effects of changes in [CO₂]_atm cannot be statistically modelled, B. pubescens and P. sylvestris are not suitable for reconstructing past atmospheric CO₂ concentrations from fossil leaves using stomatal density or stomatal index     

Molecular Cloning, Chromosomal Localization, and Cell Cycle-Dependent Subcellular Distribution of the A-Kinase Anchoring Protein, AKAP95

The cyclic AMP-dependent protein kinase (PKA) type II is directed to different subcellular loci through interaction of the RII subunits with A-kinase anchoring proteins (AKAPs). A full-length human clone encoding AKAP95 was identified and sequenced, and revealed a 692-amino acid open reading frame that was 89% homologous to the rat AKAP95 (V. M. Coghlan, L. K. Langeberg, A. Fernandez, N. J. Lamb, and J. D. Scott (1994)J. Biol. Chem.269, 7658–7665). The gene encoding AKAP95 was mapped to human chromosome 19p13.1-q12 using somatic cell hybrids and PCR. A fragment covering amino acids 414–692 of human AKAP95 was expressed inEscherichia coliand shown to bind RIIα. Competition with a peptide covering the RII-binding domain of AKAP Ht31 abolished RIIα binding to AKAP95. Immunofluorescence studies in quiescent human Hs-68 fibroblasts showed a nuclear localization of AKAP95, whereas RIIα was excluded from the nucleus. In contrast, during mitosis AKAP95 staining was markedly changed and appeared to be excluded from the condensed chromatin and localized outside the metaphase plate. Furthermore, the subcellular localizations of AKAP95 and RIIα overlapped in metaphase but started to segregate in anaphase and were again separated as AKAP95 reentered the nucleus in telophase. Finally, RIIα was coimmunoprecipitated with AKAP95 from HeLa cells arrested in mitosis, but not from interphase HeLa cells, demonstrating a physical association between these two molecules during mitosis. The results show a distinct redistribution of AKAP95 during mitosis, suggesting that the interaction between AKAP95 and RIIα may be cell cycle-dependent.     

Effects of 17β-estradiol on the distribution and activity of some oxydative enzymes of uterine and cervical epithelium in neonatal mice

Summary The following enzymes were studied histochemically in uterine and cervical epithelium from neonatal mice treated with 17-estradiol for the first four days after birth: NADH-, NADPH-, succinate-, -glycerophosphate-, lactate-, glucose-6-phosphate-, and 17-OH-steroid dehydrogenases.It was demonstrated that estradiol administration had a marked influence on distribution and activity of several of the enzymes compared with the control animals. In cervix there was an increase of activity for most of the enzymes, especially in the apical parts of the epithelium cells. The uterine epithelium was also estradiol sensitive as regards most enzymes, and in the case of glucose-6-phosphate dehydrogenase there was a dramatic enhancement of reaction in the uterus of the experimental animals. The differences obtained between cervical and uterine epithelium are described.17-OH-steroid dehydrogenase could not be detected histochemically in the present material.Supported by the Norwegian Research Council for Science and the Humanities.     

A histochemical study of the oxidation of 17β-estradiol in human term placenta at different incubation conditions

Summary The present study deals with the histochemical demonstration of 17-estradiol dehydrogenase in human term placenta using the polyvinyl alcohol method to reduce diffusion artefacts. Incubations took place with both NAD⁺ and NADP⁺ as coenzymes and at different pH values of the incubation medium. The NAD⁺ linked enzyme reaction showed a greater activity than the NADP⁺ linked, both in the trophoblast as well as in connective tissue. There were differences in staining intensity at the different pH values, and strongest reaction was observed using glycine-NaOH buffer pH 10 in the incubation medium. Owing to a non-enzymatically reduction of nitro blue tetrazolium by reduced NAD⁺, the demonstration of 17-estradiol dehydrogenase is independent of diaphorase at this high pH. The findings are discussed in relation to data about nothing dehydrogenase and biochemically determined pH optima for the enzymatic reactions dealt with in this work.The following Abbreviations are used in this Article NAD⁺ -nicotinamide adenine dinucleotide - NADP⁺ nicotinamide adenine dinucleotide phosphate - NBT nitro blue tetrazolium - PVA polyvinyl alcohol - tris tris (hydroxymethyl)-aminomethane - 17-OH-SDH 17-OH-steroid-dehydrogenase Supported by The Norwegian Research Council for Science and the Humanities. Skilful assistance of Mrs. E. Alvestad, Mrs. Aa. Flatnes and Mrs. F. Sørensen is greatfully acknowledged.     

Novel insertion mutation in Caenorhabditis elegans.

The mutation e1662 is an allele of the Caenorhabditis elegans unc-54 gene induced with the difunctional alkylating agent 1,2,7,8-diepoxyoctane. unc-54 encodes the major myosin heavy chain isozyme of body wall muscle cells. Filter-transfer hybridization and DNA sequence analysis show that e1662 is an insertion of 288 base pairs of DNA within unc-54. The inserted DNA is identical to a 288-base pair region of unc-54 located ca. 600 base pairs from the insertion site. Thus, e1662 is a displaced duplication. A 14-base pair sequence located at one end of the duplicated segment is found adjacent to the site of insertion. These homologous sequences are juxtaposed head-to-tail by the insertion event. e1662 thus contains a tandem direct repeat extending across one of its junctions.     

The Gene Structures of Spontaneous Mutations Affecting a CAENORHABDITIS ELEGANS Myosin Heavy Chain Gene

We have isolated spontaneous mutations affecting the unc-54 major myosin heavy chain gene of Caenorhabditis elegans (variety Bristol). Spontaneous unc-54 mutants occur in C. elegans populations at a frequency of approximately 3 X 10(-7). We have studied the gene structure of 65 independent unc-54 mutations using filter-transfer hybridization techniques. Most unc-54 mutations (50 of 65) exhibit no abnormalities detected with these techniques; these mutations are small lesions affecting less than 100 base pairs. Approximately 17% of the mutations (11 of 65) are simple deletions, ranging in size from less than 100 base pairs to greater than 17 kilobases. One isolate contains two separate deletions, each of which affects unc-54. Two mutants contain tandem genetic duplications that include a portion of unc-54 and extend 8-10 kilobases beyond the 5' terminus of the mRNA. Conspicuously absent from our collection of spontaneous unc-54 mutations are any resulting from insertion of transposable genetic elements. Such mutants, if they occur, must arise at a frequency of less than 5 X 10(-9).