Studies on germination of chrysanthemum pollen II. Occurrence of a germinationpromoting substance

The in vitro germination of chrysanthemum pollen is promotedby adding floral organs, excepting anther, to a basal mediumconsisting of sucrose and boric acid. Some other plant organs,such as young fruit of tomato and onion bulb, are also effective.In Chrysanthemum morifolium, the percentage of pollen germinationin the presence of such plant tissues is two to three timesas high as in the control (10 %). In Ch. leucanthemum, it ishigher than 50 %, in contrast to the control in which no germinationis noted. This promotion of germination may be due to a substance extractablefrom the tissues with water, ether or methanol. The promoting substance is not identical with several knowngrowth regulators or with the Ca ion. (Received November 21, 1967; )     

Quantitation and Visualization of Ultraviolet‐Induced DNA Damage Using Specific Antibodies: Application to Pigment Cell Biology

The major types of DNA damage induced by sunlight in the skin are DNA photoproducts, such as cyclobutane pyrimidine dimers (CPDs), (6‐4)photoproducts (6‐4PPs) and Dewar isomers of 6‐4PPs. A sensitive method for quantitating and visualizing each type of DNA photoproduct induced by biologically relevant doses of ultraviolet (UV) or sunlight is essential to characterize DNA photoproducts and their biological effects. We have established monoclonal antibodies specific for CPDs, 6‐4PPs or Dewar isomers. Those antibodies allow one to quantitate photoproducts in DNA purified from cultured cells or from the skin epidermis using an enzyme‐linked immunosorbent assay. One can also use those specific antibodies with in situ laser cytometry to visualize and measure DNA photoproducts in cultured cells or in the skin, using indirect immunofluorescence and a laser‐scanning confocal microscope. This latter method allows us to reconstruct three‐dimensional images of nuclei containing DNA photoproducts and to simultaneously examine DNA photoproducts and histology in multilayered epidermis. Using those techniques, one can determine the induction and repair of these three distinct types of DNA photoproducts in cultured cells and in the skin exposed to sublethal or suberythematous doses of UV or solar simulated radiation. As examples of the utility of these techniques and antibodies, we describe the DNA repair kinetics following irradiation of human cell nuclei and the photoprotective effect of melanin against DNA photoproducts in cultured pigmented cells and in human epidermis.     

RECONSTRUCTION OF AN APPARATUS OF NEOSTRACHANOGNATHUS TAHOENSIS FROM ORITATE,JAPAN AND SPECIES OF NEOSTRACHANOGNATHUS FROM OMAN

Abstract: The apparatus of an Early Triassic conodont Neostrachanognathus tahoensis Koike, 1998 from Oritate, Kumamoto Prefecture, Japan, and a species of Neostrachanognathus from Oman were reconstructed. On the basis of five natural assemblages from the Oritate area, the three‐dimensional apparatus model of N. tahoensis is interpreted as bilaterally symmetrical and composed of 14 elements consisting of pairs of P₁, P₂, P₃, S₁, S₂, S₃, and S₄ elements. The P₁ and P₂ elements are coniform elements, the P₃ elements are digyrate forms, and the S elements are bipennate ramiforms. The S elements are arranged rostrally in the apparatus and the pairs of the P₁, P₂, and P₃ elements are subvertically arranged caudally and ventrally to the S array. One of the natural assemblages was formed by rostrocaudal collapse of the apparatus on the sea floor, whereas the other assemblages indicate that conodont animals came to rest nearly parallel with the substrate prior to burial. A collection of isolated elements from Jabal Safra, Oman, includes a second species of Neostrachanognathus with a comparable apparatus.     

A new anhydrobiotic midge from Malawi,Polypedilum pembai sp.n. (Diptera: Chironomidae), closely related to the desiccation tolerant midge,Polypedilum vanderplanki Hinton

The sleeping chironomid (Polypedilum vanderplanki Hinton) lives on temporary rock pools in the semi‐arid tropical regions of Africa. Its larvae are able to survive the dry season in a completely desiccated ametabolic state known as anhydrobiosis. So far, P. vanderplanki was the only species among all insects showing demonstrated anhydrobiotic ability. Here, we show that a new related species originating from Malawi, Polypedilum pembai sp.n. , is also anhydrobiotic and that its desiccation tolerance mechanism is probably similar to what is observed in P. vanderplanki. The new species, P. pembai sp.n. , is described with special attention to the common and different morphological features, compared with P. vanderplanki. Phylogenetic analysis showed that both species are closely related, suggesting that anhydrobiosis evolved only once in their common ancestor about 49 Ma somewhere in Africa, before the divergence of two species, one in the sub‐Saharan area and another in southeastern Africa.     

Comparison of the response to phosphorus deficiency in two lupin species,Lupinus albus and L. angustifolius,with contrasting root morphology

White lupin (Lupinus albus) produces cluster roots, an adaptation to low soil phosphorus (P). Cluster roots exude large levels of P‐solubilizing compounds such as citrate and malate. In contrast, narrow leaf lupin (L. angustifolius) is closely related to L. albus, but does not produce cluster roots. To examine the different strategies for P acquisition, we compared the growth, biomass allocation, respiratory properties and construction cost between L. albus and L. angustifolius under P‐deficient conditions. Both Lupinus species were grown in hydroponic culture with 1 or 100 μM P. Under the P‐deficient regime, L. albus produced cluster roots with little change in biomass allocation, while L. angustifolius significantly increased biomass allocation to roots. The rate of cyanide‐resistant SHAM (salicylhydroxamic acid)‐sensitive respiration was high in cluster roots and very low in roots of L. angustifolius. These results suggest a low alternative oxidase (AOX) activity in L. angustifolius roots, and thus, ATP would be produced efficiently in L. angustifolius roots. The construction cost was highest in cluster roots and lowest in L. angustifolius roots. This study shows that under P deficiency, L. albus produces high‐cost cluster roots to increase the P availability, while L. angustifolius produces large quantities of low‐cost roots to enhance P uptake.     

Initiation of Sperm Motility Induced by Cyclic AMP in Hamster and Boar

When the plasma membrane of hamster and boar spermatozoa was extraced by treatment with Triton X-100 and the demembranated spermatozoa were transferred to a reactivating medium containing only ATP, axonemes were initially immotile, and then gradually became motile. Under these experimental conditions, the cAMP content in the reactivating medium increased soon. This suggests that cAMP is synthesized from ATP by adenylate cyclase involved in incompletely removed or solubilized residual sperm membrane and that the autosynthesized cAMP causes the delay in motility initiation. This delayed initiation of motility did not occur when phosphodiesterase was added to the reactivating medium and the phosphodiesterase-dependent quiescent sperm became motile instantaneously at any time when excess cAMP was supplemented. Furthermore, demembranated sperm which were diluted in the reactivating medium containing ATP and cAMP, immediately became motile. cAMP levels in the cell increased during the initiation of sperm motility in both species. These results suggest that cAMP is the real factor indispensable for the initiation of sperm motility at ejaculation in mammals.     

Studies on Unequal Cleavage in Sea Urchins II. Surface Differentiation and the Direction of Nuclear Migration

Cortical features of the meso- and macromeres differ from those of the micromeres in sea urchins. At the end of the 8-cell stage, the four animal cells have a continuous row of vesicles lining the free surface of the cell by transmission electron microscopy (TEM) and the nuclei and the resulting mitotic apparatuses (MA) remain at the cell centers and eventually divide equally into eight mesomeres. In the four vegetal cells, narrow gaps can be seen in the vesicular rows near the vegetal pole. The resting nuclei migrate to these gaps and on forming the spindles, they point directly to the gaps. The result is formation of vesicle-free micromeres and vesicle-covered macromeres by unequal divisions.     

FURTHER OBSERVATIONS ON THE CLUSTERS OF GRANULAR MATERIAL AROUND THE CENTRIOLE IN THE SEA URCHIN EGG: CHANGES IN DISTRIBUTION DURING MITOSIS*

Changes in the distribution of pericentriolar material, which was called “clusters of granular material”, in a previous paper were observed during mitosis of the sea urchin egg by electron microscopy using thick sections. At prophase, small clusters in an early stage of formation were observed near the nucleus. At prometaphase, the clusters appeared to aggregate loosely at the poles of the spindle. They formed large masses at metaphase, while at late anaphase they became reduced in size and formed an array at right angles to the spindle axis. Some clusters still remained near the karyomeres at telophase and then became closely associated with the daughter nucleus. The clusters were closely associated with the astral microtubules and spindle microtubules at prophase and prometaphase, respectively. The granular material is suggested to be a nucleating site of microtubule assembly during mitosis.     

Scanning Electron microscopic Study on the Early Development of Silkworm Eggs (Bombyx mori L.)

Morphological changes of the surface of eggs of the silkworm Bombyx mori L. were studied during early developmental stages by scanning electron microscopy. The egg surface was covered with numerous microvilli at least until 4 h after oviposition. At 6 h the microvilli were replaced by ruffle-like microprojections. This suggests that developmental changes of the surface structure may occur without direct influence of cleavage nuclei. Immediately before blastoderm cell formation, microvilli reappeared in the presumptive groove area. The ruffles seen on the apical portion of newly-formed blastoderm cells gradually became flattened, while microvilli developed on the lateral side of the cells. The mode of blastoderm cell formation is different from the typical one seen in most species of insects.     

Studies on germination of chrysanthemum pollen I. Effect of sugars on germination

1. 1. The percentage of chrysanthemum pollen stained with Nitroblue tetrazolium ranged from 60 to 90 %, indicating the presenceof active succinate dehydrogenase in the pollen.
2. 2. Exogenousapplication of oligosaccharides such as sucrose,lactose andraffinose at concentration of 20 to 35 % favoredgerminationof chrysanthemum pollen. However, the germinationrate was notelevated higher than 10 % in most of the chrysanthemumcultivars.
3. 3. Sugar content of chrysanthemum pollen was less than 10%of the fresh weight. The sugar was composed of glucose, fructoseand sucrose, the amount of sucrose being about four times asmuch as that of glucose or fructose.
4. 4. The ß-fructofuranosidaseactivity of chrysanthemumpollen was very high. These and relevantresults suggest thatthe poor germination of chrysanthemum pollenis due neitherto abortion nor to the deficiency of specialsugars in the pollen.

(Received November 14, 1967; )