The liquid crystalline nature of the cytoskeleton in epidermal cells of the chaetognath Sagitta

The chaetognaths have a multilayered epidermis, which is not covered by cuticle, except in the head region. Two kinds of cells are found in the epidermis: the filament-rich cells, adjacent to the basement membrane, and superficial cells, which are filament poor. The filament-rich cells, which are linked by gap junctions and columnar junctions, are highly developed in the collarette region, which joins the head and the trunk. As elsewhere in the epidermis these cells are covered by the filament poor cells which are linked by zonulae adhaerentes, gap junctions and septate junctions. The filaments present in the inner cells of the collarette form a twisted fibrous arrangement, which shows parallel series of nested arcs when observed in oblique section. Such systems are well known in numerous skeletal materials and correspond to polymerized analogues of certain liquid crystals. The amount of connective tissue is extremely reduced in Sagitta. One can hypothesize that filament-rich cells are abundant in regions which undergo strong deformations. This is the case in the collarette, in contact with the basement membrane of the epidermis (which in turn is in contact with a myotendinous system), in a region where ingested prey must go through the general cavity where there is high internal pressure.     

La sculpture et l'infrastructure du sporoderme de Ginkgo biloba comparées à celles des enveloppes polliniques des cyccadales

The Ginkgo biloba sporoderm, when examined with transmission and scanning electron microscopes, shows a sculpture and a texture which are very different from those observed in cycads.The ornamental units are “rugules” which are evenly disperesed over the pollen grain surface except on the germinal zones which is decorated with “verrucoïde” components mixed with a few ridges. (2) The exine is composed of a tripartite sexine, the middle zone of which is full of irregular pits, and of a thick and strongly lamellated nexine.     

Lamin dimers. Presence in the nuclear lamina of surf clam oocytes and release during nuclear envelope breakdown

The nuclear lamina of surf clam oocytes contains dimers of 67-kDa lamin which are stabilized by both noncovalent interactions and disulfide bonds. The latter can be reduced but re-form when the reducing agent is removed. The cysteine residues involved in these disulfide bonds are inaccessible to alkylating agents unless the protein is unfolded in urea. During nuclear envelope breakdown the lamin is released as a mixture of oligomers in which disulfide-stabilized dimers are associated noncovalently with lamin monomers. Concurrent with solubilization, both dimers and monomers are phosphorylated to a similar extent, indicating that the interactions which maintain these complexes are not destabilized by lamin phosphorylation. Our results suggest the existence of two types of interactions between the lamin molecules in the polymer, which react differently to phosphorylation during nuclear envelope breakdown.     

SD大鼠与巴马小型猪的皮肤组织学比较

目的研究及观察SD大鼠和巴马小型猪皮肤的正常比较组织学。方法取SD大鼠和巴马小型猪不同部位的皮肤进行石蜡切片、HE染色,光学显微镜观察。结果两种动物的皮肤组织学结构在以下方面存在着显著差异：1.SD大鼠的毛囊成簇分布,平均3～9成群,而巴马小型猪的毛囊较稀少;2.SD大鼠表皮较薄,没有透明层,基底细胞缺乏异质性,真皮与表皮连接面平坦,没有皮钉;而在巴马小型猪皮肤表皮和真皮连接区,有上下交错的表皮皮钉和真皮乳头;3.SD大鼠的真皮结构相对松散,真皮血管系统不发达,而巴马小型猪皮肤的真皮网织层和乳头层交界的地方,水平分布着很多的浅表小静脉和小动脉丛,这种血管分布的方式与人类皮肤中的血管分布极为类似;4.SD大鼠的汗腺只局限于足垫的皮肤,汗腺上皮只有一种细胞类型,腺细胞呈立方形或矮柱状,胞核圆形,导管短而弯曲,由两层上皮细胞组成。而巴马小型猪皮肤的汗腺是顶泌汗腺,分布于真皮和脂肪相接的真皮深层,分泌部为粗管,管腔大,盘曲成团。腺细胞呈立方形或扁平,胞核圆形或长梭形。腺细胞与基膜之间也有肌上皮细胞。导管较细而直,开口于毛囊上段。     

Lipid-cholesterol interactions. Monte Carlo simulations and theory.

Results of Monte Carlo calculations of order parameter profiles of lipid chains interacting with cholesterol are presented. Cholesterol concentrations in the simulations are sufficiently large that it is possible to analyze profiles for chains which are near neighbors of two or more cholesterol molecules, chains which are neighbors to a single cholesterol, and chains which are not near any cholesterol molecules. The profiles, show that cholesterol acts to significantly decrease the ability of neighboring chains to undergo trans-gauche isomeric rotations, although these chains are not all forced into all-trans conformations. The effect is significantly greater for chains which are neighbors to more than one cholesterol. The Monte Carlo results are next used as a guide to develop a theoretical model for lipid-cholesterol mixtures. The properties of this model and the phase diagram which it predicts are described. The phase diagram is then compared with experimentally determined phase diagrams. The model calculations and the computer simulations upon which they are based yield a molecular mechanism for several of the observed phases exhibited by lipid-cholesterol mixtures. The theoretical model predicts that at low temperatures the system should exhibit solid phase immiscibility.     

Fine structural organization of the rectum in the blowfly, Calliphora erythrocephala (Meig.) with special reference to connective tissue, tracheae and neurosecretory innervation in the rectal papillae

The rectal epithelium of Calliphora is made up of three quite distinct cell types: rectal, cortical and junctional cells. The thin wall of the rectal pouch is made up of rectal cells which are relatively simple and unspecialized; their general structure does not suggest any direct participation in ion transport. A function of ion and water transport can probably be ascribed to the cortical cells, which are arranged in the form of four cones which project into the rectal lumen. The cavity of each cone is filled up with tracheae, nerve and neurosecretory terminals, and connective tissue to form medulla. The medulla and cortex are separated from each other by deeply staining bridges or trabeculae to form an infundibular space. The most conspicuous feature of the cortex is the presence of an extensive intercellular sinus formed by complex infoldings of the lateral plasma-membranes. It is postulated that fluid, which is absorbed from the rectal lumen, is transported into the intercellular sinus and finally reaches the haemolymph via the infundibular space. The actual site of ion transport is probably the stacks of lateral plasma-membrane which are closely associated with mitochondria. The junctional cells, which are packed with microtubules, form a collar around the base of the papillae at the point of their insertion into the rectal wall. It is suggested that the neurosecretory terminals present in the medulla might release a hormone which controls rate of ion and water reabsorption by the papillae cells.     

Morphology and ultrastructure of the organ of Bellonci in the marine amphipod Gammarus setosus

The three-dimensional structure of the organ of Bellonci in the marine amphipod Gammarus setosus and the relationship between its sensory cells and concretion are described using light, transmission, and scanning electron microscopy, with chemical treatment for cell lysis, calcium chelation, glycogen staining, and lanthanum labelling. The organ is encapsulated and has three units called fuselli. Each is enclosed by two fusellar cells which generate and release calcium granule strands into the cores of the fusellar concretions, which are united in the center of the organ. The surface of each fusellus is traversed by spiral dendrites entering dorsally and ending ventrally. The spiral dendrites arise from sensory neurons contained in a palm-shaped ganglion in the center of the capsule, beyond which they are twisted like a rope before reaching the concretion. The spiral dendrites are linked in pairs by gap and tight junctions and each gives origin to two pairs of 9+0 sensory cilia 30 μm apart. The ciliary distal segments give rise to long tubules which are in contact with the calcium granule strands. The ciliary proximal segments are expanded by many long mitochondria which interdigitate with the branched striated ciliary rootlets. The concretion is suspended in the capsule cavity by axons originating from four neurons of a remote mechanoreceptor. The structure of the organ suggests that it is a sensory organ involved in the reception and integration of a variety of stimuli.     

The fine structure of the colleterial glands of Hyalophora cecropia (Lepidoptera)

The structure of cells in the colleterial glands of the Cecropia silkmoth was examined. Morphologically and functionally the gland is divided into two regions, a tubular one in which columnar protein-synthesizing cells are located, and an expanded region in which flattened cells with very different structure are most prominent. The fine structure of the latter cells which are presumed to secrete a phenolic glucoside, closely resembles that of cells described in the colleterial glands of orthopterans. The protein-secreting cells have many features normally associated with pancreatic acinar, and other cells of similar function. Among these are extensive rough endoplasmic reticulum, an elaborate Golgi complex, and a modest number of mitochondria. Other features which are less usual in cells of this type are an elaborate secretory apparatus consisting of a cuticular tubule inserted into a microvilli-lined cavity at the apical end of the cell, and large numbers of cytolysomes, myelin figures, and lipid droplets. A chitogenous cell with a very distinct and specific type of ultrastructure is found associated with the secretory cell. This cell type is attached to the cuticular elements of the gland, and the main features of its cytoplasm are extensive bundles of microtubules which presumably serve as supportive elements for the secretory cells.     

Synthesis of bioprocesses using physical properties data

The aim of this article is to illustrate and evaluate a synthesis procedure which has been extended to tackle bioprocesses. Physical property information is used to screen candidate units thereby reducing the size of the synthesis problem. In this way, only units which exploit large property differences between components in a stream are selected. This is important for bioprocesses because of the large number of components and wide range of unit operations which are available. The screening technique and bioprocess-unit-design methodologies have been incorporated within an implicit enumeration algorithm which was developed for chemical process synthesis and is implemented in Java programming language. An important advantage is the ability of the bioprocess synthesis software to generate a ranked list of flowsheets which may subsequently be analyzed in more detail. Two case studies are used to evaluate the bioprocess-synthesis technique. The first system involves a product which is secreted from the host organism. The second has significantly different characteristics in that the product is intracellular and forms inclusion bodies. The latter case study, in particular, is a large synthesis problem with 12 unit operations and 20 contaminant compounds. The results show that the synthesis methodology identifies a set of economically optimal flowsheets in a reasonable computational time which demonstrates its ability to deal with large synthesis problems. Using the synthesis methodology we can generate bioprocesses which are optimal in a system-wide, rather than unit-by-unit, sense.     

峨眉山常绿落叶阔叶混交林的生物多样性及植物区系初探

对峨眉山常绿落叶阔叶混交林的群落结构﹑组成﹑生物多样性及植物区系等几方面进行了研究分析。结果显示峨眉山阔叶混交林由226种维管束植物组成,其中被子植物73科137属207种, 占总种数的91.6%,是峨眉山阔叶混交林的重要组成部分;群落分层现象明显,为乔木层﹑灌木层﹑草本层和层外植物4层,其中草本层发育情况差;科分布型是以热带—亚热带﹑热带—温带为主,各占22.7%, 在属的水平上则以温带分布占绝对优势(52.9%),揭示了峨眉山阔叶混交林的区系性质是以温带为主的亚热带类型;生物多样性指数处于较低的水平,在经过人为干扰后,群落处于稳定的恢复阶段。     

虾塘底质的总耗氧量及其季节变化

虾塘底质的总耗氧量及其季节变化孙耀（中国水产科学研究院黄海水产研究所,青岛２６６０７１）Ｔｏｔａｌｏｘｙｇｅｎｃｏｎｓｕｍｐｔｉｏｎｏｆｓｅｄｉｍｅｎｔｉｎｓｈｒｉｍｐｐｏｎｄｓａｎｄｉｔｓｓｅａｓｏｎａｌｖａｒｉａｔｉｏｎ￥．ＳｕｎＹａｏ（Ｙｅｌｌ...     

Fluid lipid fraction in rod outer segment membrane.

Rod outer segment membrane is analyzed using the spin resonance label technique by means of two probes. The solubility of the first label,2,2,6,6-tetramethylpiperidin-1-oxyl, is correlated with the membrane fluidity which is measured using a stearic acid spin probe. The two values are compared to the solubility-fluidity relationship which characterizes a model system in which all lipids are in a fluid state. The analysis leads to the conclusion that only two thirds of the membrane lipids are fluid. This conclusion is reinforced by the observation that partial lipid removal leaves rigid lipids associated with the rhodopsin molecules.     

ULTRASTRUCTURAL ORGANIZATION OF OBLIQUELY STRIATED MUSCLE FIBERS IN ASCARIS LUMBRICOIDES

The somatic musculature of the nematode, Ascaris, is currently thought to consist of smooth muscle fibers, which contain intracellular supporting fibrils arranged in a regular pattern. Electron microscopic examination shows that the muscle fibers are, in fact, comparable to the striated muscles of vertebrates in that they contain interdigitating arrays of thick and thin myofilaments which form H, A, and I bands. In the A bands each thick filament is surrounded by about 10 to 12 thin filaments. The earlier confusion about the classification of this muscle probably arose from the fact that in one longitudinal plane the myofilaments are markedly staggered and, as a result, the striations in that plane of section are not transverse but oblique, forming an angle of only about 6° with the filament axis. The apparent direction of the striations changes with the plane of the section and may vary all the way from radial to longitudinal. A three-dimensional model is proposed which accounts for the appearance of this muscle in various planes. Z lines as such are absent but are replaced by smaller, less orderly, counterpart "Z bundles" to which thin filaments attach. These bundles are closely associated with fibrillar dense bodies and with deep infoldings of the plasma membrane. The invaginations of the plasma membrane together with intracellular, flattened, membranous cisternae form dyads and triads. It is suggested that these complexes, which also occur at the cell surface, may constitute strategically located, low-impedance patches through which local currents are channeled selectively.     

Studies on mitochondrial structure and function in Physarium polycephalum : I. Fine structure, cytochemistry, and H-uridine autoradiography of a central body in mitochondria

The fine structure, cytochemistry and autoradiography of the rod-shaped central body in the mitochondria of the slime mold, Physarum polycephalum, has been investigated. The central bodies are stained with Feulgen stain and, like the nucleoli, are stained metachromatically with azure B. At the ultrastructural level, they are composed of a semi-electron-dense axial region which is sensitive to treatment with DNase and an electron-dense peripheral region which surrounds the axial region and is sensitive to treatment with RNase. With electronmicroscopic autoradiography it has been shown that the central body and its peripheral region, after short exposure to ³H-uridine, incorporate ³H-uridine into a form, possibly RNA, which is insoluble in trichloroacetic acid and can be extracted with RNase though not with DNase. It is suggested that the central body is composed of an axial component which contains primarily DNA and a peripheral component which contains primarily RNA and that the RNA is synthesized in the central body.     

广西十万大山蕨类植物区系特征及垂直分布的数量研究

十万大山植物区系位于北回归线以南,蕨类植物非常丰富,现已发现５２仲、１１３属、２６４种。区系地理成分复杂多样,属可以划分１１种类型（变型）,可种可以划分为１４种类型（变型）。本区系具有明显的热带亲缘,热带分布属占８１．４２％,热带分布种占６６．７７％。亚洲热带分布及其变型占有较大的比例,表明本区系与亚洲热带植物区系特别是中南半岛区系有密切的亲缘关系。区系地理成分有明显的垂直分布规律,聚类分析的结果     

记江西一新的中华弓鳍鱼化石

本文记述了在江西弋阳石溪组发现的一中华弓鳍鱼。其形态特征虽与华北的师氏中华弓鳍鱼很相似,但又有很明显的差别,因此建立一新种——Sinamia poyangica, sp. nov.。在此基础上,对中华弓鳍鱼的形态变异和石溪组的时代作了讨论,并对师氏中华弓鳍鱼的复原图提出了修正的建议。     

Ultrastructure of Characiochloris acuminata Lee et Bold

The ultrastructure of the vegetative cell and zoospore of Characiochloris acuminata Lee et Bold (Chlorangiellaceae, Tetrasporales, Chlorophyceae) is described.

The vegetative cell is distinctive in having numerous contractile vacuoles which are randomly distributed in the cytoplasm and visible through the fissures of the parietal chloroplast. A single pyrenoid, embedded in the chloroplast, is penetrated by cytoplasmic canals which are lined by the chloroplast envelope. The vegetative cell is attached to the substrate or host by two flagellar remnants (retained from the zoospore stage), each of which is ensheathed in a gelatinous tube through the cell wall at the cell base. The basal bodies are apparently abscissed from the flagellar shaft by a unit membrane which becomes continuous with the plasma membrane.

The zoospore is biflagellate, with the flagella equal in length, smooth and longer than the cell body. The flagellar sheath is characteristically undulate and the two flagellar bases are connected by a dense interflagellar fibre. The large nucleus has a conspicuously inflated nuclear envelope and the pyrenoid is similar to that of the vegetative cell.     

Fluid lipid fraction in rod outer segment membrane

Rod outer segment membrane is analyzed using the spin label technique by means of two probes. The solubility of the first label, 2,2,6,6-tetramethylpiperidin-1-oxyl, is correlated with the membrane fluidity which is measured using a stearic acid spin probe. The two values are compared to the solubility-fluidity relationship which characterizes a model system in which all lipids are in a fluid state. The analysis leads to the conclusion that only two thirds of the membrane lipids are fluid. This conclusion is reinforced by the observation that partial lipid removal leaves rigid lipids associated with the rhodopsin molecules.     

Insights into the evolution of heliozoa (Protozoa, Sarcodina) as provided by ultrastructural studies on a new species of flagellate from the genus Pteridomonas

The fine structure of Pteridomonas danica , a new species of helioflagellate (protozoa), is described. The organism has a single apical flagellum which bears two rows of tripartite tubular hairs. There are two kinetosomes which are bound to each other and to the surface of the single nucleus by amorphous electron-dense material. The flagellum is surrounded by a wreath of fine arms, which are supported internally by triads of microtubules. The triads terminate on the nucleus. The mitochondria have tubular cristae which contain wisps of intracristal material. The dictyosomes are located in the posterior part of the cell, being clustered around the internal element of the contractile stalk. Extrusomes are present. Pteridomonas has substantial similarities with the colourless flagellate Ciliophrys and with the pedinellid algal flagellates. As Ciliophrys resembles the actinophryid heliozoa in several important respects, the evidence supports the contention that these heliozoa have a common ancestry with the heterokont algae and have evolved along a line involving the pedinellids and some colourless helioflagellates. If the perceived relationships are to be reflected in their taxonomy, then a substantial reclassification of these organisms is required.     

Die Gesellschaften der Klasse Festuco-Brometea im westlichen Teil des böhmischen Xerothermgebietes 1. Teil

The lowland part is the centre of the hollow, which is formed by the territory of Bohbmia. There and in the part of contigues hills are concentrated xeroterm species out of which xeroterm and subceroterm association are formed (Czech xeroterm territory). Part of them, rock and meadow steppes, belong to the class Festuco-Brometea. The centre of the occurance of these xeroterm associations in Bohemia is excentrically shifted, owing to Krušné hory (Erzgebirge) mountains rain shade. Only limited choice of them are concentrated in the western part, which stands in the centre of attention of the translated study. By the analysis of the Festuco-Brometea inside the investigated territory I found out only one order, Festucetalia valesiacae with two unions, Festucion valesiacae (in which subunions Festucenion valesiacae and Astragalo-Achilleenion can be distinguished) and Cirsio-Brachypodion, I present 19 associations of them. The associations are floristically characterised and their ecology and extension in Bohemia are designated. Some of them are subdividet into lower syntaxonomic units. Syntaxonomic units of the corresponding syntaxonomic range presented from Bohemia and the nearest xeroterm territories are compared with the published material. The units, which are nomenclatoricaly used are standardized. For chorological and synchorological purposes the subdivision of the Czech xeroterm territory into five fytogeographical districts was used. The North Bohemia forest-steppe district is the centre of the Festuco-Brometea class occurance. There is the centre of Cirrdo Brachypodion unions occurance. The occurance of the subunion Astragalo-Achilleenion is nearly limited to this territory too. The mein centres of the occurance of the subunion Festucenion valesiacae are the hollow parts of Czech xeroterm territory, Milezovka highlands and Vltava-Beroun district.