The differentiation of glial cells and glia limitans in organ cultures of chick spinal cord

Summary Differentiation of glial cells and the glia limitans in organ cultures of chick spinal cord explanted at early neural tube stages, alone or with adjacent tissues, was studied by electron microscopy. Oligodendrocytes and astrocytes comparable to those seen in the chicken in vivo were observed, mainly in areas of good neuronal differentiation. A glia limitans with basal lamina, comparable to that in vivo, was found when spinal cord was bordered by normally adjacent tissues. When it was surrounded by vitelline membrane only, a characteristic limiting layer of glial processes, but no basal lamina, was seen. Contact with a filter membrane (Millipore) elicited excessive differentiation of glial filaments and modified cell fine structure; no glia limitans was formed. Supported by Grant 5 RO 1 NB 0637 from the United States Public Health Service.     

Beitrag zur Kenntnis der Sinnesorgane von Symphylen (Myriapoda)

Zusammenfassung Am Präanalsegment von Scutigerella befindet sich ein Paar Trichobothrien, das komplizierter gebaut ist als entsprechende Sinnesorgane anderer Arthropoden. Die distalen Fortsätze von sechzehn Sinneszellen stehen mit der Gelenkmembran des nach allen Seiten beweglichen Sinneshaares in Verbindung. Aus ihrer Anordnung kann geschlossen werden, daß Scutigerella mit Hilfe des Trichobothriums mindestens acht verschiedene Richtungen unterscheiden kann. Der adäquate Reiz für die Trichobothrien dürften Luftbewegungen sein.

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Sense organs of symphyla (Myriapoda)I. Ultrastructure of the trichobothrium of Scutigerella immaculata newport

Summary One pair of trichobothria is situated on the lateral portions of the preanal segment of Scutigerella. They are rather complicated compared to similar organs of other Arthroods. The distal portions of 16 sense cells are connected to the elastic membrane of the sense hair which can be turned in every direction. From the arrangement of the distal parts of the sense cells it may be concluded that Scutigerella can distinguish at least eight different directions. Probably movements of the air are the adequate stimulus for the trichobothrium.

Für technische Mitarbeit danke ich Frl. M. Genehr und Fr. G. Schröer, für die Anfertigung der Zeichnung Fr. C. St. Friedemann.     

节肢动物的信息素研究

随着化学生态学(chemical ecology)和行为生态学(behavioral ecology)的蓬勃发展,近年来信息素(pheromone)研究进展较快,发表的论文与日俱增,但研究的进度很不平衡——脊椎动物以哺乳类研究较多,而无脊椎动物则以昆虫类研究较多。后者是可以理解的,一因昆虫的种类多、数量大,易于取材;二因昆虫具有重大经济意义,特别是有害昆虫的防治(利用性信息素作为诱捕剂),对农业丰收与森林保护关系极大。值得注意的是,近年来甲壳动物的信息素研究也日益受到重视,论文也日益增多。但和昆虫比较起来,它仍处于萌芽状态。作者深信,随着虾、蟹类养殖业和捕捞业的蓬勃发展,这类高等甲壳动物的     

青蛙松果体神经节细胞对吲■胺的电反应

作者在明或暗适应青蛙(Rana esculenta)的松果体上,应用微量离子电泳施药方法,就5-甲氧基色胺(5-MT)、褪黑激素(MEL)与γ-氨基丁酸(GABA)对电生理上已鉴别的无色感神经节细胞自发放电的影响进行了对比研究。用5-MT检测了48个神经元,用MEL和GABA分别检测了50个神经元。GABA对其中80％的神经元有显著抑制作用,其余无反应。在用吲哚胺检测的神经元中,MEL只对36％的神经元有抑制作用,5-MT除对56％的神经元产生抑制作用外,还对6％的细胞活性有增强作用。根据5-MT和MEL在青蛙松果体内的作用特点看,吲哚胺化合物可能是一种神经调节物质,而不是神经递质。     

Genetic characterization of a double-flowered tobacco plant obtained in a transformation experiment

Summary A leaf-disk transformation experiment was performed with tobacco (Nicotiana tabacum L.) using a binary vector and a strain of Agrobacterium tumefaciens that carried a wild-type Ti-plasmid, pTiBo542. Although the majority of kanamycin-resistant, transgenic plants was morphologically normal, one of the plants was double-flowered and had a slightly wavy stem and leaves whose edges were bent slightly upwards. The abnormal morphology was controlled by a single, dominant Mendelian gene. Young plants that carried this gene were distinguishable from normal plants at the stage of cotyledons. The homozygotes, with respect to this gene, were more seriously deformed than the heterozygotes. DNA segments derived from the binary vector and from the T_L-and T_R-DNA of pTiBo542 were detected in the double-flowered plant, but the T-DNA genes involved in biosynthesis of phytohormones were absent from the plant. The abnormal morphology, the resistance to kanamycin, and the segments of foreign DNA were genetically linked, and the linkage was very tight, at least between the abnormal morphology and the resistance to kanamycin; the meiotic recombination frequency was less than 0.02%, if recombination occurred at all.     

Two-compartment model for rabbit skin organ culture

Summary A new method was developed for rabbit skin organ culture. In a two-compartment model, skin discs were cultured on a Millicell-HA insert unit with a microporous membrane which allows transport of culture medium via the dermis into the epidermis, whereas the epidermal side remains free of direct contact with culture medium. In this relatively simple two-compartment organ culture model, rabbit skin could be cultured for 7 d in RPMI 1640 medium supplemented with fetal bovine serum, or for 2 d in RPMI 1640 medium supplemented with cofactors. The histomorphology and ultrastructure of 7-d cultured rabbit skin discs was essentially similar to that of freshly isolated rabbit skin. Keratinocytes in the stratum basale continued to divide during organ culture. The terminal differentiation of the epidermis continued in vitro as was found by the presence of keratohyalin granules, the intact stratum corneum, and keratin expression. Furthermore, glucose consumption continued until culture Day 7, but thereafter it declined rapidly. Concomitantly, degenerative changes were found. At the end of the 7-d culture period the distance between single dermal collagen fibrils had increased as compared to noncultured skin. This model of skin organ cultures can be used to study biological processes, dermal toxicity, and penetration and metabolism of xenobiotics in intact skin. Furthermore, within certain limits, processes responsible for repair and regeneration of damaged skin can also be studied in this model because the rabbit skin can be cultured for 7 d. The present study was financially supported by grants of Duphar B. V. (Weesp, Netherlands), the European Community, and the Dutch animal welfare organizations Samenwerkingsverband van de Nederlandse Vereniging tot Bescherming van Dieren en de Nederlandse Bond tot Bestrijding van de Vivisectie, Anti-Vivisectie Stichting en Stichting Schoonheid Zonder Wreedheid.     

CORRELATED EVOLUTION OF SELF-FERTILIZATION AND INBREEDING DEPRESSION: AN EXPERIMENTAL STUDY OF NINE POPULATIONS OF AMSINCKIA (BORAGINACEAE)

The relation between inbreeding depression and rate of self-fertilization was studied in nine natural populations of the annual genus Amsinckia. The study included two clades (phylogenetic lineages) in which small-flowered, homostylous populations or species are believed to have evolved from large-flowered, heterostylous, self-compatible ones. In one lineage the small-flowered species is tetraploid with disomic inheritance. Rates of self-fertilization were 25% to 55% in the four large-flowered, heterostylous populations; 72% in a large-flowered but homostylous population; and greater than 99.5% in the four small-flowered, homostylous populations, which produce seed autonomously. When present, inbreeding depression occurred in the fertility but not the survival components of fitness. Using a cumulative fitness measure incorporating both survival and fertility (flower number), we found inbreeding depression to be lower in the four very highly self-fertilizing populations than in the five intermediate ones. The Spearman rank correlation between inbreeding depression and selfing rate for the nine populations was –0.50, but was not statistically significant (P = 0.12). Inbreeding depression was greater in the two tetraploid populations than in the very highly self-fertilizing, diploid ones. Phenotypic stability of progeny from self-fertilization tended to be higher in populations with lower inbreeding depression. We conclude that levels of self-fertilization and inbreeding depression in Amsinckia are determined more by other factors than by each other. Estimates of mutation rates and dominance coefficients of deleterious alleles, obtained from a companion study of the four highly self-fertilizing populations, suggest that a strong relationship may not be expected. We discuss the relationship of the present results to current theory of the coevolution of self-fertilization and inbreeding depression.     

Intraspecific larval competition in two solitary parasitoids, Apoanagyrus (Epidinocarsis) lopezi and Leptomastix dactylopii

Analysis of total aromatic amino acid (free and bound) in some cucumber accessions selected previously for resistance to western flower thrips, Frankliniella occidentalis (Pergande) [Thysanoptera: Thripidae], indicated that low concentrations of these essential nutrients, relative to total leaf protein, were correlated with a reduction in damage by the insect. Further analysis of samples of four important horticultural crops (lettuce, tomato, pepper and cucumber) with unknown levels of resistance to thrips showed a significant genotypic variation in the concentrations of total aromatic amino acids relative to the total leaf protein. Accessions from each crop with low or high concentrations of aromatic amino acids in proteins were exposed to thrips larvae. Regression analysis showed a highly significant positive correlation between aromatic amino acid concentration in leaf protein and thrips damage, regardless of crop species. It is concluded that higher concentrations of aromatic amino acids in plant proteins are important for successful thrips development. These results provide plant breeders with a promising tool for indirect selection without using undesirable insect bioassays.     

Floral symmetry and nectar guides: ontogenetic constraints from floral development, colour pattern rules and functional significance

The accord between symmetries of flower shape (external contours) and nectar guides (internal contours) was examined using the bulbous flora of South Africa, and in the general floras of Britain, Alpine Colorado, Canadian Arctic and Israel. It was found that radially symmetrical flowers have radially symmetrical nectar guides whereas bilaterally symmetrical flowers have bilaterally symmetrical nectar guides. It is suggested that the complementarity between the external and the internal contours of the flower increases the probability that, and efficiency with which, a bee moves into the flower's centre and towards the sporophylls and access to floral rewards, regardless of the flower's form and the bee's previous experience. Patterns of coloration of tepals against background and nectar guides against tepals also accord with behavioural and sensory characteristics of pollinators. It is suggested that the complementarity of contours is probably constrained by floral development, but patterns of coloration of tepals against background and nectar guides against tepals is constrained by pollinators' sensory physiology.     

Allonia decandra: Floral remains of the tribeHamamelideae (Hamamelidaceae) from Campanian strata of southeastern USA

A single flower, detached anthers with in situ pollen grains, and isolated seeds from Campanian strata (Upper Cretaceous) of Georgia, southeastern USA, document the presence of plants assignable toHamamelidaceae in the Upper Cretaceous. The fossil flower is actinomorphic, pentacyclic and pentamerous. Irregular sepals are preserved as lobes of the floral cup, and petals are narrow, with parallel margins. The androecium has two whorls of functional stamens. Anthers are tetrasporangiate, dehisce through two valves, and have strongly elongate connective protrusions which converge over the center of the flower. The organizational and architectural features of the fossil document its affinity within subtribeLoropetalinae (Hamamelideae, Hamamelidoideae). Cladistic phylogenetic analyses using parsimony were conducted to explore the relationships between the fossil flower and extant genera of the tribeHamamelideae. The strict consensus of the four most parsimonious trees showsHamamelideae andLoropetalinae as well-supported monophyletic taxa. The fossil flower is clearly included within theLoropetalinae, and is placed as sister taxon to the southeastern Asian genusMaingaya. The occurrence of fossils assignable toLoropetalinae during the Campanian documents the existence ofHamamelidaceae with a level of floral organization and character evolution equivalent to that of extant genera, early in the evolutionary history of the family.