Taenia hydatigena—V. Surface structure of the adult worm and evaginated scolex

Scanning electron microscopy (SEM) of the surface of the adult tapeworm and the freshly evaginated scolex from the cysticercus indicated that in Taenia hydatigena there was a variety of microthrix form. This variety was found between different areas on the same specimen and between the adult and freshly evaginated scolex. In the latter there was a noticeable absence of pointed spikes from most areas. Artifacts attributable to techniques of preparation are also discussed.     

不同温度下黄曲霉菌菌丝超微形态的比较研究

为探究黄曲霉菌的毒素合成是否影响菌丝超微形态,本研究结合扫描和透射电镜技术比较观察产毒(28℃和30℃)和不产毒(37℃和40℃)温度下培养的不同发育阶段的黄曲霉菌菌丝形态和超微结构.扫描电镜结果显示:28℃下,在24h和44h菌丝体表面有丝状粘性分泌物附着,48-72h之间菌丝体逐渐出现皱缩、塌陷和扭曲现象,而37℃...     

An electron microscope study of the tegument of Hunterella nodulosa Mackiewicz and McCrae, 1962 (cestoidea: Caryophyllidea)

Ultrastructural observations using transmission and scanning electron microscopy reveal the tegument to be basically similar to that of other cestodes. The syncytial distal cytoplasm is devoid of organelles except for rod-shaped bodies, believed to be secretory vesicles, and lamellated bodies which probably contribute the raw material for new microtriches. There is evidence that these vesicles originate from the Golgi found in the sub-cuticular cells.Three types of microtriches are described: typical ones with well-developed spines, ones with short filaments instead of spines, and ones with no spines. Microtriches with spines are found only on the anterior part of the worm and may serve to anchor the worm. Microtriches on the posterior have no spines and are believed to be primarily involved in the absorption of nutrients. Between these two regions there is a transitional zone where all three types of microtriches can be found. In general the microtriches are quite uniformly distributed throughout the surface of the worm. The presence of cestodarian-like microtriches raises interesting evolutionary questions.Histochemical tests localized acid and alkaline phosphatase activity on various parts of the tegument, as well as on host intestine, while acian blue tests showed that acid mucopolysaccharide levels correspond with the concentration of the tegument vesicles.     

A scanning electron microscopic investigation of the outer surfaces of Gorgoderina attenuata

The external surface of Gorgoderina attenuata is characterized by ridges that encircle the worm at regular intervals. On the ridges are protuberances that give a beaded appearance to the tegumental surface. Ridges running perpendicular to the encircling bands are apparent close to both suckers. The raised protuberances of the tegumental areas may serve to increase the absorptive surface. A pit-like cavity was observed on the dorsal surface of the oral sucker. In addition numerous raised structures which appear to be of two types were present on the surface of the oral sucker. One type resembles a depression with a small knob barely visible in the center and the second type consists of button-like patches of tissue. From their structure and location these are tentatively identified as sensory organs.     

二个不同发育阶段茶银尺蠖雌蛾性腺超微结构的比较研究

本文利用扫描电镜和透射电镜分别对不同发育阶段的茶银尺蠖Scopula subpunctaria Herrich-Schaeffer雌蛾性信息素腺体进行了观察和研究,对探索信息素的合成途径提供科学依据。结果表明,雌蛾性信息素腺体位于第8、9/10腹节的节间膜上,由其表皮下方的单层上皮细胞组成,并几乎覆盖整个节间膜形成一个近乎完整的环状。成熟雌蛾(3日龄)性腺的超微结构照片显示性腺细胞具有发达的微绒毛、质膜内褶、大量的脂滴、细胞间的运输孔道以及细胞桥粒等结构组织。而在未成熟雌蛾(羽化5h内)性腺细胞内,这些结构均明显缺失或发育不完整。     

Ultrastructure of plant chromosomes by high-resolution scanning electron microscopy

A technique is described for using standard squash preparations of mitotic and meiotic chromosomes for both light microscopy and subsequent high-resolution scanning electron microscopy for investigation of the same specimen. Depending on the microscope and conditions of preparation, a resolution of a few nanometers is routinely possible. Tilting of the specimen provides a three-dimensional insight into chromosomal structures. Combination of material-dependent signals of backscattered electrons with the secondary electron image allows an unambiguous localization of surface markers.     

Periodic Acid-Methenamine Silver Stain for Mycobacteria in Tissue Sections

The electron microscope has proven very effective for visualization of various morphological features of bacteria. Cationized ferritin (CF) is a stain commonly used to increase the electron microscopic resolution of bacterial cells, thereby enabling detailed analysis of their morphological and structural features. CF has been useful for microscopic examination of the bacterial capsule, cell wall, S-layer, and various unique morphological structures. In addition, as a cation, CF binds only to negatively charged molecules. Thus, CF has been used to identify sites of anionic charge on the bacterial cell surface, which has led to insights concerning the formation and turnover of bacterial peptidoglycan and the S-layer proteins. As a cation, however, CF may also interact with certain cellular components, causing erroneous interpretation of microscopic results. This review provides a discussion of both the strengths and weaknesses of CF when used as a stain for electron microscopy.     

Nectary structure and nectar secretion in Maxillaria coccinea (Jacq.) L.O. Williams ex Hodge (Orchidaceae)

BACKGROUND AND AIMS: It had previously been assumed that Maxillaria spp. produce no nectar. However, nectar has recently been observed in Maxillaria coccinea (Jacq.) L.O. Williams ex Hodge amongst other species. Furthermore, it is speculated that M. coccinea may be pollinated by hummingbirds. The aim of this paper is to investigate these claims further. METHODS: Light microscopy, histochemistry, scanning and transmission electron microscopy. KEY RESULTS: This is the first detailed account of nectar secretion in Maxillaria Ruiz & Pav. A 'faucet and sink' arrangement occurs in M. coccinea. Here, the nectary is represented by a small protuberance upon the ventral surface of the column and nectar collects in a semi-saccate reservoir formed by the fusion of the labellum and the base of the column-foot. The nectary comprises a single-layered epidermis and three or four layers of small subepidermal cells. Beneath these occur several layers of larger parenchyma cells. Epidermal cells lack ectodesmata and have a thin, permeable, reticulate cuticle with associated swellings that coincide with the middle lamella between adjoining epidermal cells. Nectar is thought to pass both along the apoplast and symplast and eventually through the stretched and distended cuticle. The secretory cells are collenchymatous, nucleated and have numerous pits with plasmodesmata, mitochondria, rough ER and plastids with many plastoglobuli but few lamellae. Subsecretory cells have fewer plastids than secretory cells. Nectary cells also contain large intravacuolar protein bodies. The floral morphology of M. coccinea is considered in relation to ornithophily and its nectary compared with a similar protuberance found in the entomophilous species M. parviflora (Poepp. & Endl.) Garay. CONCLUSIONS: Flowers of M. coccinea produce copious amounts of nectar and, despite the absence of field data, their morphology and the exact configuration of their parts argue strongly in favour of ornithophily.     

Morphological alterations of Pseudomonas aeruginosa and Escherichia coli by nocardicin A

Abstract Pseudomonas aeruginosa and Escherichia coli were exposed to nocardicin A, and were subsequently observed with transmission and scanning electron microscopes. Although the nocardicin A-induced morphological alterations such as bulges and spheroplast formations were observed both in P. aeruginosa and E. coli , their positions on the cell surface were different in the two species.     

综述与专论：体电子显微学前沿

电子显微成像技术的快速发展使得对完整细胞、组织乃至整个机体进行高分辨三维结构解析研究成为可能,这些可进行大尺度生物样品三维结构研究的电子显微成像技术统称为体电子显微学技术（volume electron microscopy,vEM）。近年来,vEM在研究尺度、分辨率、吞吐量和易用性等方面发展迅速,在整个生命科学领域的应用呈爆炸式增长,该技术因此被《自然》（Nature）评为2023年最值得关注的七项前沿技术之一。然而,vEM相关技术的发展和应用在国内起步较晚,亟待进一步推广。本综述涵盖了vEM的发展历程、技术分类、样品制备、数据收集、图像处理等全方位的内容,便于生命科学、医学等领域研究人员去了解、学习、应用和进一步发展该技术。     

Ootaxonomy and eggshell ultrastructure of Phlebotomus sandflies

The eggshell structure of four sandfly species: Phlebotomus perniciosus Newstead, P.perfiliewi Parrot, P.papatasi Scopoli and P.duboscqi Neveu-Lemaire, was examined by scanning and transmission electron microscopy (SEM and TEM). At the TEM level, the eggshell appears to have a homogeneous vitelline envelope and a thick chorion. At SEM level, the eggshell of all species is characterized by the outer chorion forming a series of fifteen to twenty longitudinal sinuous ridges, cross-linked in places to form a pattern of polygons, each line of the chorion consisting of columns arranged in a palisade. The aeropyle region of the egg is described for the first time in phlebotomine sandflies. Specific characters of the eggshell topography are described for distinguishing between these and other species of Phlebotomus.     

Structure and development of stellate trichomes in Andradea ftoribunda Fr. Allem. (Nyctaginaceae)

LOURO, R. P., MIGUENS, F. C. & MACHADO, R. D., 1992. Structure and development of stellate trichomes in Andradea ftoribunda Fr. Allem. (Nyctaginaceae). Trichomes occur on both faces of young leaves. They are peltate-stellate on the abaxial face, and comprise a stalk and radiating cells with a rudimentary central apex. On the adaxial face the trichomes arc stellate with a large apex comprising one to three cells. In both cases the stalk is formed by three to six cells of which the most distal may contain a tannoid substance. In the adult leaf only the abaxial surface exhibits stellate trichomes, with two to three celled stalks. The central region of radial cells is depressed. On the adaxial side the hairs are shed during maturation of the leaf.     

Adhesion by Paired Pectoral and Pelvic Fins in a Mountain-Stream Catfish, Pseudocheneis sulcatus (Sisoridae)

We describe the adhesive nature of the pectoral and pelvic fins in the catfish Pseudocheneis sulcatus, as examined by scanning electron microscopy. The outer rays of these fins are modified into structures that bear prominent transverse ridges and grooves. The outer epidermal cells of the ridges are thrown into elongated spines. Mucous pores (openings of mucous glands) are frequently present (100m apart) in the epidermis of the ridges and show entangled mucus droplets. In the pectoral fins, they are present towards the contour areas of the outer rays, but they are absent in the pelvic fins. In the latter, mucous pores are present near the base of the ridges (distal to the inner rays). Spines as well as mucous pores are absent in the cells that line the groove between two adjacent ridges. We suggest that in this species adhesion is effected by suction pressure generated by the musculature attached to the grooves and ridges, and that mucus and the spines aid in this process.