Germination ecology of coastal plants in relation to salt environment

Responses of seed germination to salinity were examined using 37 species collected from salt marshes, cliffs, and fore (unstable) and hind (stable) sand dunes along Japanese coasts. For comparison, seed germination of nine inland species was also examined. The soil salinities in salt marshes ranged from 150 to 300 mmol/L NaCl, whereas those in fore and hind dunes ranged from 0 to 150 mmol/L NaCl, with a few exceptions. Cliff soils showed relatively high salinities up to 300 mmol/L NaCl. Ciff and foredune soils that encountered a typhoon and storm showed high salinities >300 mmol/L NaCl. Salt tolerance in seed germination of coastal plants was ordered by comparing the responses of percentage and rate of germination to salinity conditions up to 200 mmol/L NaCl, being in the order of salt marsh>cliff>foredune≅hind dune≅inland. Thse results indicate that salt tolerance in seed germination of coastal plants is closely related to the salinity conditions of their habitats. Germination experiments under favorable conditions showed that a high percentage of the seeds of salt marsh species germinate rapidly, those of diff species germinate slowly and those of foredune species exhibit a low percentage and low rate of germination. It seems that these germination characteristics contribute to the success of germination at the ‘safe site’ and the subsequent survivorship of emerged plants in their natural habitats.     

Capacity of neural crest cells from various axial levels to participate in thymic development

Summary In order to assess the capacity of neural crest from different sources to participate in thymic development, neural crest from selected axial levels was transplanted unilaterally from quail donors to the region in chick hosts from which neural crest cells normaly migrate to interact with the primordial thymus. The greatest representation of donor cells was observed after isotopic transplantation and when donor tissue was taken from the hyoid and mesencephalic regions of the neural crest. The capacity for transplants to contribute cells decreased both anteriorly and posteriorly, so that neural crest close to the usual origin of mesenchyme-producing cells contributed a larger number of donor cells around the developing thymus than neural crest from anterior and posterior regions. Cells from the transplant were inserted as an addition to the host chick cells. Thus, a special relationship and capacity for interaction in thymic development is expressed by neural crest at usual levels over a limited span of axial regions, but to some extent by all regions. This study has established that the capacity for neural crest cells from different axial levels to interact with developing organs is not uniform, but may vary, depending upon the nature of the interaction with a particular organ.This study was supported by Grant No. 2332, The Council for Tobacco Research, USA, Inc.     

Behavior of Chloroplast Nucleus during Chloroplast Development and Degeneration in Chlamydomonas reinhardii

Changes in morphology of chloroplast nuclei (cp-nuclei), totalcp-DNA content, number of cp-nuclei, oxygen-evolution activityand chlorophyll (a and b) content were examined during the degenerationand development of chloroplasts, using Chlamydomonas reinhardiicells which had been incubated on solid medium for various periods. Under 4'-6-diamidino-2-phenylindole (DAPI) epifluorescence microscopy,each cell that had been incubated for 7 days had one cell nucleus,one cup-shaped chloroplast and about 10 small, dispersed cp-nucleiin the chloroplast. One day after incubation of these cellson fresh medium, the cell volume and cp-nuclei increased insize 2-3 fold, but rapidly decreased in size after cell division.After about 7 days of incubation, cells ceased to divide andcp-nuclei began to associate with each other. At about 20 daysthey formed a ring-shaped structure surrounding the pyrenoid,followed by condensation into one cp-nuclear particle near thepyrenoid. When 41-day-old cells, having only one cp-nucleus,were reinoculated on fresh solid medium, the cp-nucleus increasedin size 2–3 fold, divided into several cp-nuclear particlesand then dispersed into the chloroplast, forming a bead-likestructure, before cell division. From microscopic fluorometry,a 4-fold increase in total cp-DNA content per chloroplast, withoutan increase in the number of cp-nuclear particles per chloroplast,occurred one day after the start of the experiment and one dayafter reinoculation of 41-day-old cells onto fresh medium. Theprocess of condensation of dispersed cp-nuclear particles intoone cp-nucleus during degeneration of the chloroplast was notaccompanied by any change in total cp-DNA content per chloroplast.A large peak of oxygen-evolution (0.6–0.9 pmoles/cell/hour)was seen one day after inoculation and reinoculation of thecells. The chlorophyll content (a+b) was high (1.2–2.2pg/cell) during the first week of incubation, after which itgradually decreased. (Received December 18, 1985; Accepted April 2, 1986)     

Flagellar movement of human spermatozoa

Flagellar movement of human spermatozoa held by their heads with a micropipette was recorded by means of a video-strobe system. Spermatozoa were studied in normal Hanks' solution, Hanks' solution with increased viscosity, cervical mucus, and hyaluronic acid. When flagellar movement in normal Hanks' solution was observed from the direction parallel to the beating plane, segments of the flagellum in focus did not lie on a straight line but on two diverging dashed lines. The distance between the two dashed lines was about 20% of the bend amplitude in the major beating plane. These observations indicate that flagellar beating of human spermatozoa in normal Hanks' solution is not planar. In contrast, segments of the flagellum in focus lay on a straight line when the spermatozoa were observed in Hanks' solution with increased viscosity, cervical mucus, or hyaluronic acid. In normal Hanks' solution, free swimming spermatozoa rotated constantly around their longitudinal axes with a frequency similar to the beat frequency, whereas little or no rotation of spermatozoa occurred in Hanks' solution with increased viscosity, in cervical mucus, or in hyaluronic acid. We conclude that human spermatozoa in normal Hanks' solution beat with a conical helical waveform having an elliptical cross section, the semiaxes of which have a ratio of 0.2. The three-dimensional geometry of the flagellar movement is responsible for the rotation of the sperm around their longitudinal axes.     

Effects of the calcium channel blocker diltiazem on the excitability of mouse oocytes

Effects of the organic Ca antagonist diltiazem on Ca channels were studied in ovulated and unfertilized oocytes of the mouse by using intracellular recording techniques. The resting potential was not affected by diltiazem. The threshold level of the Ca action potential shifted slightly toward positive voltages with diltiazem concentration, but the shift was not statistically significant. The overshoot and maximum rate of rise of the Ca action potential were inhibited by the drug in a dose-dependent manner, but higher amounts of diltiazem were necessary to cause similar blocking effects on Ca channels in mouse oocytes than in other differentiated cells. Increases of external concentration of Ca²⁺ antagonized the degree of diltiazem inhibition. However, the sequence of block of Ca²⁺, Sr²⁺, and Ba²⁺ currents was different for diltiazem vs Cd²⁺. It is suggested that diltiazem inhibition can not be explained by simple competitive scheme, ie, antagonism between diltiazem and permeant cations does not occur at the same binding site associated with the Ca channel in mouse oocytes.     

Differential haemin-mediated restoration of cytochrome P-450 N-demethylases after inactivation by allylisopropylacetamide.

Administration of allylisopropylacetamide (AIA) to phenobarbital-pretreated rats results in the destruction of several phenobarbital-inducible cytochrome P-450 isoenzymes and a correspondingly marked loss of benzphetamine N-demethylase and ethylmorphine N-demethylase activities. Accordingly, the ion-exchange h.p.l.c. or DEAE-cellulose-chromatographic profile of solubilized microsomal preparations from such rats revealed a marked decrease in the cytochrome P-450 content of several eluted fractions compared with that of microsomes from corresponding non-AIA-treated controls. Incubation of liver homogenates from such rats with haemin restores not only cytochrome P-450 content from 35 to 62% of original values, but also benzphetamine N-demethylase and ethylmorphine N-demethylase activities, from 23 to 67%, and from 12 to 36% of original values respectively. Moreover, the chromatographic profiles of microsomes prepared from such homogenates indicated increases of cytochrome P-450 content only in some fractions. Reconstitution of mixed-function oxidase activity of cytochrome P-450 by addition of NADPH: cytochrome P-450 reductase to these fractions indicated that incubation with haemin restored benzphetamine N-demethylase activity predominantly, but ethylmorphine N-demethylase activity only minimally. After injection of [14C]AIA, a significant amount of radiolabel was found covalently bound to protein in chromatographic fraction III, and this binding was unaffected by incubation with haemin. Furthermore, the extent of this binding is apparently equimolar to the amount of cytochrome P-450 refractory to haemin reconstitution in that particular fraction. Whether such refractoriness reflects structural inactivation of the apo-cytochrome remains to be determined. Nevertheless, the evidence presented very strongly argues for AIA-mediated inactivation of multiple phenobarbital-induced isoenzymes, only a few of which are structurally and functionally reparable by haemin.     

Interaction of nitrogenase with nucleotide analogs of ATP and ADP and the effect of metal ions on ADP inhibition

The interaction of a large number of ATP and ADP analogs with nitrogenase from Azotobacter vinelandii, Klebsiella pneumoniae, and Clostridium pasteurianum has been examined. Only 1,N6-etheno-ATP and 2'-deoxy-ATP served as substrates for acetylene reduction. Other triphosphates including GTP, ITP, 8-Br-ATP, alpha,beta-methylene ATP, beta,gamma-methylene ATP, 6-chloropurine riboside triphosphate, and AMP-PNP were inert, showing less than 50% inhibition at levels up to two- to fivefold greater than ATP. Xanthosine triphosphate behaved simply as a chelator of magnesium, activating the enzyme at low levels but strongly inhibiting at high levels. When nucleotide diphosphates were tested as inhibitors with enzyme from A. vinelandii, GDP, dGDP, and 6-chloropurine riboside diphosphate were ineffective, XDP was three- to fivefold less effective, and dADP and 1,N6-etheno-ADP were about equally as effective as ADP. With enzyme from C. pasteurianum, dADP was twofold less effective than ADP, XDP was fivefold less effective, and IDP and 1,N6-etheno-ADP appeared to be ineffective. Results with enzyme from K. pneumoniae were very similar to those obtained with A. vinelandii. Different metal ions were tested in the presence of both ATP and ADP to determine whether preferential binding to one nucleotide or the other might alter the ADP/ATP ratio needed for 50% inhibition of activity. Magnesium and manganese gave the same ratio, while with Fe and Co, slightly less ADP was required for equivalent inhibition. Nickel appeared to reduce the sensitivity of A. vinelandii nitrogenase to ADP inhibition while increasing that of C. pasteurianum, but both effects were less than twofold. Calcium, strontium, and aluminum ions were inert with enzymes from these organisms. Cd and Zn were also ineffective with K. pneumoniae. Two isomers of ATP beta S were prepared by enzymatic synthesis from ADP beta S. The A form was a more potent inhibitor of A. vinelandii nitrogenase.     

Effects of Net and Local Charges on the Interaction between Chemically-Modified Horse Heart Cytochrome c and P700 in Photosystem 1-Enriched Subchloroplast Particles

Effects of salt and pH on the re-reduction of P700 by chemically-modifiedhorse heart cytochrome c after a flash illumination were examinedin Triton-treated P700- enriched subchloroplast particles (TSF-1particles). At low salt concentrations net charges on the membrane surfaceand native, guanidinated or succinylated cytochrome c were majorfactors that determined the reaction rates, as in the reactionbetween plastocyanin and P700 [Tamura et al. (1981) Plant &Cell Physiol. 22: 603]. The reaction rates also depended onreactant-specific factors, particularly the localized distributionof charges on macromolecules and their interaction over shortdistances, as well as on long-range Coulombic interaction. Theeffect of this type became clearer at high salt concentrations. (Received October 7, 1982; Accepted December 20, 1982)     

Genetics of insect hemolymph α-mannosidase in the silkworm,Bombyx mori

The genetics of hemolymph alpha-mannosidase was investigated in the silkworm, Bombyx mori. By selecting individuals showing either high or low enzyme activities, homozygotes were separated, with activities varying about five-fold. No differences in the activities of beta-galactosidase and beta-N-acetylglucosaminidase were observed. Thus, it seems that high- and low-enzyme silkworms (High and Low Lines) share the same genetic background except for the gene concerning the activity of alpha-mannosidase. The synthesis of the enzyme is controlled by an autosomal allele. Furthermore, expression of the gene varies from tissue to tissue, and there is no correlation between enzyme activity and growth rate. The difference in activity between High and Low lines is due to the amount of active enzyme, not to an endogeneous activator or inhibitor. There was no isozymic difference in alpha-mannosidase.