Fine structure of the spermatozoa of Chiton marginatus (mollusca: Amphineura), with special reference to nucleus maturation

The spermatozoon of Chiton marginatus is a long uniflagellate cell displaying structural features of “modified sperm.” The nucleus presents a conical shape with a long apical cylindrical extension. The chromatin is homogeneously dense. Scattered inside the condensed nucleus, a few nuclear lacunae are visible. The acrosomal complex is lacking. Some mitochondria are located in a laterofrontal structure side by side with the nucleus. The typical midpiece is absent. The cytoplasm forms a thin layer around the nucleus and the mitochondria. The proximal centriole is in a basal nuclear indent. The distal centriole serves to form the axoneme tail with the usual microtubular pattern. During nuclear maturation, the early spermatid nucleus is spherical and contains fine granular chromatin patches. The nuclear envelope shows a deposit of dense material at the base of the nucleus, forming a semicircular invagination occupied by a flocculent mass. In middle spermatid stage, the chromatin gets organized in filaments, coiled as a hank, attached over the inner surface of the basal thickening of the nuclear envelope. The nucleus starts to elongate anteroposteriorly. At the pointed apical portion of the spermatid, a group of microtubules is observed seeming to impose external pressure to the nucleus giving rise to the long apical nuclear point. The mitochondria have a basal position. Late spermatids have an elongated conical nucleus. The chromatin filaments are further condensed, and lacunae appear inside the nucleus. Some mitochondria migrate to a lateral position.     

泥螺生殖系统的组织学

泥螺为雌雄同体。生殖系统包括交媾器和生殖器本部。交媾器包括刺激器、阴茎和摄护腺;生殖器本部主要包括两性腺、缠卵腺和蛋白腺。刺激器和阴茎都具有非常发达的肌肉组织,腔壁游离面具纤毛。阴茎腔壁为单层柱状细胞;摄护腺被膜为一层薄的肌纤维,里面具有许多分泌细胞;缠卵腺被膜为单层扁平上皮,下层为环肌,腺体组织由分泌小管构成。蛋白腺主要由皮质层和导管层组成,皮质层内充满了分泌细胞,导管层由许多分泌小管构成,管壁为柱状腺细胞。     

Fine structure of the spermatozoon of Marthasterias glacialis (Linnaeus) (Echinodermata; Asteroidea), with special reference to acrosomal morphology

The sperm of Marthasterias glacialis (Linnaeus) was studied by light and electron microscopy. It is a long uniflagellated cell of the “primitive” type. The head has a spherical shape and contains a nucleus with a spheroid acrosome lying in a cup-shaped anterior fossa. The acrosome is formed by an acrosomal vesicle surrounded by the periacrosomal material. The basal specializations of the acrosomal vesicle show a clear differentiation of its constituents resembling the structure of membrane. The midpiece contains a very large annular mitochondrion which encircles two perpendicular centrioles. The distal centriole is in close association with a pericentriolar radial complex. The tail, containing a common microtubular axoneme, is projected to a variable position.     

Fine structure and functional morphology of the mouthparts of Bittacus planus and Terrobittacus implicatus (Insecta: Mecoptera: Bittacidae)

The Bittacidae are unique in Mecoptera for their adults being predaceous. However, their mouthparts have not been well documented for functional morphology to date. Here, we investigated the mouthpart morphology of the hangingflies Bittacus planus Cheng and Terrobittacus implicatus (Huang & Hua) using scanning electron microscopy. The mouthparts are of the mandibulate type and situated at the tip of an elongated rostrum. The labrum is greatly elongated, roughly twice as long as the subquadrate clypeus. The epipharynx is furnished with a row of basiconic sensilla arranged evenly as a median band extending from the apex to the base. The mandibles are slender and elongated, bearing a sharp lateral and a small mesal tooth. The maxillae are well developed, each consisting of a partially sclerotized cardo and a stipes, a hirsute galea and a lacinia, and a five-segmented maxillary palp. The sensillar pattern on the distal segment of the maxillary palp differs slightly between the two bittacid species. The labium is composed of a postmentum, a prementum, and a pair of two-segmented labial palps. The feeding mechanism of bittacids is briefly discussed in combination with the mouthpart morphology and their feeding habits.     

杧果果实的扫描电镜观察

果成熟果实呈黄色长卵形是典型的核果。其外果皮呈革质,中果皮呈肉质,内果皮呈骨质表面有纤维。内果皮包被着种子形成一个大而扁的核。种子扁形,种皮很薄,子叶呈多胚或单胚。通过对果果实结构各个层次的扫描电镜观察,为其贮藏保鲜及繁育栽培工作提供一些科学依据。     

Ultrastructure of the kidney of a South American caecilian,Typhlonectes compressicaudus (Amphibia,Gymnophiona)

Summary The ultrastructure of the distal nephron, the collecting duct and the Wolffian duct was studied in a South American caecilian, Typhlonectes compressicaudus (Amphibia, Gymnophiona) by transmission and scanning electron microscopy (TEM, SEM). The distal tubule (DT) is made up of one type of cell that has a well-developed membrane labyrinth established both by interdigitating processes and by interlocking ramifications. The processes contain large mitochondria, the ramifications do not. The tight junction is shallow and elongated by a meandering course. The connecting tubule (CNT) is composed of CNT cells proper and intercalated cells, both of which are cuboidal in shape. The CNT cells are characterized by many lateral interlocking folds. The intercalated cells have a dark cytoplasm densely filled with mitochondria. Their apical cell membrane is typically amplified by microplicae beneath which a layer of globular particles (studs) is found. The collecting duct (CD) is composed of principal cells and intercalated cells, again both cuboidal in shape. The CD epithelium is characterized by dilated intercellular spaces, which are often filled with lateral microfolds projecting from adjacent principal cells. The apical membrane is covered by a prominent glycocalyx. The intercalated cells in the CD are similar to those in the CNT. The Wolffian duct (WD) has a tall pseudostratified epithelium established by WD cells proper, intercalated cells and basal cells. The WD cells contain irregular-shaped dense granules located beneath the apical cell membrane. The intercalated cells of the WD have a dark cytoplasm with many mitochondria; their nuclei display a dense chromatin pattern.Research fellow of the Alexander von Humboldt Foundation     

胡杨、灰叶胡杨花空间分布及数量特征研究

研究了不同居群的胡杨、灰叶胡杨花空间分布及其数量特征。结果表明,无论是胡杨还是灰叶胡杨,其雄树的树高、最低花位、集花区下限、集花区上限、最高花位皆低于雌树,并且雌株与雄株的花序分布范围亦有着较大的重叠区域。在树体上,雄花序主要分布在树冠的中部,上部次之,下部最少;雌花序主要分布在树冠的上部,中部次之,下部最少。胡杨的单株花序量、花朵花药数、花药花粉量和花序花粉量均小于灰叶胡杨,而花序花朵数胡杨雄树的小于灰叶胡杨,雌树的大于灰叶胡杨。统计分析表明,不同居群胡杨的单株花序量、花序花朵数与花药花粉量是相对稳定的,而灰叶胡杨仅雄树的单株花序量是稳定的。     

Ursavus在中国的首次发现——并记禄丰古猿化石产地的其他熊类标本

本文记述的是1981年在禄丰古猿化石产地发掘中发现的熊类标本,共有二属二种和一种暂不能确定属、种的类型。其中祖熊(Ursavus)过去只见于欧洲、北美和西亚的中新世地层,在我国还是首次发现。禄丰的标本,就其大小和特征可归于Ursavus depereti;印度熊(Indarctos)过去在我国发现过两个种:中国印度熊(I.sinensis)和拉氏印度熊(I.lagrelli),禄丰的标本为前一个种;第三类型与Protursus和Ursus都有相似之处,但又有区别,鉴于材料不足,暂不订属和种。     

The digestive tract of Helicoradomenia (Solenogastres, Mollusca), aplacophoran molluscs from the hydrothermal vents of the East Pacific Rise

Abstract. Species of Helicoradomenia are constantly found at hydrothermal vent sites of the eastern and western Pacific Ocean. The digestive tract of 2 species of the genus was investigated with special focus on the ultrastructure and histochemistry of epithelia and glandular organs. The preoral cavity and foregut epithelia are composed of microvillous main cells, secretory cells producing protein-rich substances, and sensory cells with specialized cilia. The foregut bears a pair of glands with 3 types of extremely long-necked glandular cells surrounded by musculature. Each glandular cell opens directly into the radula pocket without a gland duct. The large radula apparatus consists of pairs of denticulated bars resting on a flexible radular membrane without elaboration of a subradular membrane. The midgut has a narrow, mid-dorsal tract of ciliary cells, but most of the epithelium is composed of digestive cells with a highly developed lysosomal system. The hindgut is lined by ciliated cells and free of glands. The foregut and radula seem to be highly efficient in the capture of relatively large, motile prey. Food contents within the midgut lumen and within some of the large secondary lysosomes indicate a triploblastic metazoan prey of non-cnidarian origin. The digestive tract is not adapted to microvory and there is no indication of a symbiosis with chemoautotrophic bacteria.     

Application of a microfluidic device for counting of bacteria

AIMS: To develop a miniaturized analytical system for counting of bacteria. METHODS AND RESULTS: Escherichia coli cells were used throughout the experiments. The system consists of a microfluidic chamber, a fluorescence microscope with a charge-coupled device (CCD) camera and syringe pumps. The chamber was made of a silicone rubber (30 x 30 mm and 4 mm high). The E. coli cells were flowed from a micro-nozzle fabricated in the chamber and detected with the CCD camera. The individual cells were indicated as signal peaks on a computer. The cell counts showed a good correlation compared with that of a conventional plate counting method, and results of the simultaneous detection of live and dead cells were also presented. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: The system having a small disposable nozzle has the advantages for low cost and safe medical or environmental analysis, when compared with a conventional flow cytometer. This is the first step of the development of a one-chip microbe analyzer.     

Computational simulation of internal bone remodelling around dental implants: a sensitivity analysis

This study aimed to predict the distribution of bone trabeculae, as a density change per unit time, around a dental implant based on applying a selected mathematical remodelling model. The apparent bone density change as a function of the mechanical stimulus was the base of the applied remodelling model that describes disuse and overload bone resorption. The simulation was tested in a finite element model of a screw-shaped dental implant in an idealised bone segment. The sensitivity of the simulation to different mechanical parameters was investigated; these included element edge length, boundary conditions, as well as direction and magnitude of the implant loads. The alteration in the mechanical parameters had a significant influence on density distribution and model stability, in particular at the cortical bone region. The remodelling model could succeed to achieve trabeculae-like structure around osseointegrated dental implants. The validation of this model to a real clinical case is required.     

Assessment of environmental quality by the diversity of epiphytic lichens in a semi-arid mediterranean area (Val Basento, South Italy)

The results of a bioindication study based on the diversity of epiphytic lichens in a semi-arid area of South Italy are presented. The area features the presence of an industrial zone located in a rural context. The survey was performed in 20 sampling sites. The lichen diversity values (LDV) were determined by the frequencies of all lichen species within a sampling grid placed on tree trunks. Lichens demonstrated a condition of environmental alteration extending to the industrial zone, and tending towards a recovery in the rural surroundings. The survey also showed evidence of eutrophication all over the study area.     

Morphology of the marine epiphytic diatom Cocconeis heteroidea (Bacillariophyceae)

The morphology and fine valve structure of the marine epiphytic diatom Cocconeis heteroidea Hantzsch have been investigated. The entire frustule, including the internal and external structure of the raphid valve (RV) and araphid valve (AV), and the complete cingulum, are described using light microscopy and scanning and transmission electron microscopy, using a bleaching method. The strongly sigmoid raphe terminates in elongate hooked helictoglossae internally. The hymenes, with perforations arranged in a centric array, are located near the internal openings of the areolae in the RV. The striae in the AV consist of alveoli occluded by hymenes, that have perforations arranged in a parallel array and are located near the outer surface. The complete cingulum of AV consists of three open bands without fimbriae: a valvocopula, a copula with a ligula and a pleura with a small ligula. The RV has only a valvocopula which is open type and not fimbriate.     

A cereal haemoglobin gene is expressed in seed and root tissues under anaerobic conditions

Legumes, and a very few non-legume plant species, are known to possess functioning haemoglobin genes. We describe here the characterization of a haemoglobin cDNA isolated from barley. The deduced amino acid sequence shows 71% amino acid identity with a non-legume haemoglobin gene, a further 16% of the residues being conservative replacements. The barley cDNA also hybridizes to genomic sequences in rye, maize and wheat. The demonstration of a gene from a monocotyledon with close sequence homology to the known non-legume plant haemoglobins fills a major gap in the known distribution of haemoglobin genes in the plant kingdom. The expression of the gene is induced in isolated barley aleurone layers exposed to anaerobic conditions, and the roots of flooding-stressed barley plants. The expression of the RNA under anoxic conditions is similar to that of a known anaerobic response gene, alcohol dehydrogenase. Our results suggest that the increased expression of haemoglobin RNA is an integral part of the normal anaerobic response in barley. The findings are discussed in the light of current theories of haemoglobin function and evolution.     

A Novel Capsulorhexis Technique Using Shearing Forces with Cystotome

Purpose:To demonstrate a capsulorhexis technique using predominantly shearing forces with a cystotome on a virtual reality simulator and on a human eye.Method:Our technique involves creating the initial anterior capsular tear with a cystotome to raise a flap. The flap left unfolded on the lens surface. The cystotome tip is tilted horizontally and is engaged on the flap near the leading edge of the tear. The cystotome is moved in a circular fashion to direct the vector forces. The loose flap is constantly swept towards the centre so that it does not obscure the view on the tearing edge.Results:Our technique has the advantage of reducing corneal wound distortion and subsequent anterior chamber collapse. The capsulorhexis flap is moved away from the tear leading edge allowing better visualisation of the direction of tear. This technique offers superior control of the capsulorhexis by allowing the surgeon to change the direction of the tear to achieve the desired capsulorhexis size.Conclusions:The EYESI Surgical Simulator is a realistic training platform for surgeons to practice complex capsulorhexis techniques. The shearing forces technique is a suitable alternative and in some cases a far better technique in achieving the desired capsulorhexis.     

A simplified model of scar contraction

The healing of wounds is a complex process and the contraction of the resulting scar can have a negative impact on the neighbouring skin. A finite element model of skin simulating the contraction of a scar and deformation of the surrounding skin is presented. The skin is represented by an orthotropic–viscoelastic constitutive law, which is validated against experimental data in the literature. A simplified experimental model of a contracting scar in real skin is also developed. The pattern and size of the wrinkles formed around the contracting scar in the finite element model compare favourably with those formed in the experimental model. The orthotropic nature of skin plays a significant role in the behaviour of skin around scars—the wrinkles have a preferential orientation that corresponds to a direction perpendicular to the Langer's lines in the skin. The pre-stress in skin (a property that is ignored in many skin models) is shown to be an important factor in wrinkle formation around scars. The proposed model can be used to analyse the suturing and closure of wounds of various shapes.     

Redescription of the Chengjiang arthropod Squamacula clypeata Hou and Bergström, from the Lower Cambrian, south-west China

The anatomy of the arthropod Squamacula clypeata Hou and Bergström, 1997 from the Lower Cambrian Chengjiang Lagersta¨tte is redescribed based on four newly excavated specimens. The new material was collected from localities recently discovered in the Kunming area, Yunnan Province, south-west China, and preserves remarkable details of the ventral morphology, revealed by preparation. Squamacula clypeata is dorsoventrally flattened and rounded in outline. The cephalon was covered by a wide, short shield, with a large doublure and a pair of uniramous antennae on the ventral side. The thorax consists of nine somites, each protected by a tergite and carrying at least one pair of biramous limbs. The pygidium is covered with a small rounded tergum. The endopod is segmented, equipped with short spines on the inner margin of the coxa and a claw-like structure distally, and the exopod flap-like, fringed with setae. The limbs in the pygidium are like those in the thorax in shape. Squamacula was most probably a nektobenthic predator. The spinose endopod could walk, grasp and grind. The large flap-like exopod was adapted for swimming and respiration. Its affinities lie with the Arachnomorpha, but the relationships with other known taxa remain ambiguous.     

The structure and physical properties of glucuronic acid oligomers produced by a Gluconacetobacter hansenii strain using the waste from beer fermentation broth

The aim of this work was to study the chemical structure and physical properties of water-soluble oligosaccharides (WSOS) produced by Gluconacetobacter hansenii PJK using the waste from beer fermentation broth as a basal medium. The analysis of the hydrolyzed products and the spectroscopic studies of the native WSOS showed that it is a mixture of oligomers all having a single sugar -linked glucuronic acid as building blocks with an O-acetyl and O-methyl group, in the terminal unit of the non-reducing end. The thermal studies displayed a progressive degradation of WSOS without a major weight loss throughout a range of temperatures. The melting point and pyrolysis temperature were found to be 130.16 and 275.25 °C, respectively. The optimum concentration of WSOS for a maximum emulsifying ability was found to be 0.10% (w/v). The resulting emulsions, however, did not demonstrate a noteworthy stability.