Leaf micromorphology inAgathis and its taxonomic implications

This study surveys the micromorphological surface structure of the leaves of the conifer genusAgathis (Araucariaceae) from throughout the range of the genus (Malaysia to New Zealand and Fiji) as seen with the scanning electron microscope. These data confirm that the vegetative parts ofAgathis are taxonomically highly conservative, but suggest the Melanesian and New Zealand elements to be distinctive from those of the rest of the genus, and from one another. Conclusions are compared with those that have been derived from studies based on other characters.     

Investigations on the Physical Structure and the Mechanism of Drug Release from an Enteric Matrix Microspheres with a Near-Zero-Order Release Kinetics Using SEM and Quantitative FTIR

The objectives of this study were to evaluate the physical structure and the release mechanisms of theophylline microspheres made of Eudragit S 100 polymer as an enteric polymer, combined with a nonerodible polymer, Eudragit RL 100. In the preparation process, polymer combinations (1:1) were dissolved in an organic solvent mixture composed of acetone and methanol at a specific ratio containing a theoretical drug loading of approximately 15%. Two microsphere formulations (LS1 and LS2) were prepared at two different total polymer concentrations (10% in LS1 and 12.7% in LS2). Dissolution studies were carried out using US Pharmacopeia Dissolution Apparatus II in an acidic medium for 8 h and in an acidic medium (2 h) followed by a slightly basic-buffered medium for 10 h. Both LS1 and LS2 microsphere formulations produced particles that were spherical in shape and had very narrow size distributions with one size fraction comprising 70–80% of the yield. Scanning electron microscopy and quantitative Fourier transform infrared were used for microsphere physical structure evaluation. Except for the absence of drug crystals, photomicrographs of both LS microspheres after dissolution in pH 1.2 and 7.2 buffer solutions were similar to those before dissolution. Dissolution results indicated the ability of LS microspheres to minimize drug release during the acid stage. However, in the slightly basic medium that followed the acidic stage, the drug release was sustained and controlled in its kinetics and data fitted to Peppas equation indicated a case II transport suggesting that the drug release is mainly through swelling/erosion mechanism.     

Species of the genus Quercus in Italy: Characterization by means of leaf surface observation

Abstract

We propose a study of the main species belonging to the genus Quercus in Italy, characterized and identified by means of leaf surface observation, with special attention devoted to waxes, trichomes and stomata. Comparing our results with the classification proposed by SCHWARZ (1984), we find that species belonging to Schwarz's subgenus Quercus are recognizable because their waxes are structured in vertical scales; the two other subgenera (Sclerophyllodrys and Cerris) present smooth wax structures, their distinctive feature being the shape of the stomatal rima, which is roundish in Sclerophyllodrys and elliptical in Cerris. The study characterizes Quercus pubescens Willd. and Quercus petraea Liebl. by analyzing some morphometric traits; but the authors feel that further research is needed on these critical taxonomic entities. Lastly, the study examines forms of was degeneration correlated to the phenomenon known as oak decline.     

Characteristics of Pustula tragopogonis (syn. Albugo tragopogonis) Newly Occurring on Cultivated Sunflower in Germany

In temperate climates, Pustula tragopogonis is rarely found on cultivated sunflower. In Europe, it was so far of little economic impact on other Asteraceae, except for some regions in the Mediterranean. In 2003, P. tragopogonis was found for the first time in sunflower fields in southern Germany. The pathogen has a widespread occurrence there, especially in the region around Stuttgart, BW. Fatty acid profiling, ultrastructural investigation and ITS sequencing revealed a high similarity to an 2002 isolate from southern Africa and an 2005 isolate from Australia, but revealed significant differences to P. tragopogonis s.l. on Cirsium arvense, a common weed, growing on or in the vicinity of sunflower fields in Germany. P. tragopogonis from this host can therefore be excluded from being the source of the reported infection.     

感染环形泰勒焦虫(Theileria annulata)的牛外周血白细胞的形态观察

用光镜及扫描电镜观察了体外高代培养的含牛焦虫颗粒的牛外周血白细胞的形态及在细胞周期中细胞表面的特征性变化。这种经多年传代的含虫的牛外周血白细胞恢复了分裂和繁殖的能力,目前已成为较稳定的细胞系。细胞表面具多种伪足突起,如叶状、丝状及绒毛状。细胞周期中备期细胞表面的主要特征是:S期:细胞平扁,边缘具薄的时状伪足及丝状伪足;G_2期:细胞中部隆起,表面具少量绒毛状伪足;G_1期:绒毛状结构少或无,而出现丝状及小的叶状伪足,细胞仍保持球形;M期:细胞球形,表面密被以绒毛。作者根据扫描电镜的观察认为光镜下所观察的两类细胞,实际上是反映了一种细胞处于不同发育阶段时的特征。     

Attachment may be a basis for specialization in oak aphids

ABSTRACT.

• 1 The potential role of tarsal attachment in host selection was studied in the specialist aphids Tuberculoides annulatus Hartig and Myzocallis schreiberi Hille Ris Lambers and Stroyan.
• 2 M.schreiberi could walk freely on its host, Quercus ilex and on Q.robur, whereas T.annulatus could walk freely on its host, Q.robur but had difficulty on Q. ilex.
• 3 Attachment to the rough-textured leaves of Q.robur was achieved by means of the pretarsal claws, and to the smooth upper surface of individual trichomes on the lower surface of Q.ilex using flexible pretarsal empodia.
• 4 Both behavioural and allometric differences can account for the inability of T.annulatus to grip onto Q.ilex.
• 5 The role of attachment by phytophagous insects in host plant resistance and selection is discussed.

     

Scanning Electron Microscopy of Xiphinema,Longidorus, and Californidorus Stylet Morphology

Stylet ultrastructure of five Xiphinema, four Longidorus, and three Californidorus species was compared by scanning electron microscopy. Morphological differences were seen in the odontophores and odontostyle bases between the genera and some of the species. All Xiphinema studied had well-developed odontophore flanges; the Longidorus species lacked flanges, except for weakly developed ones in L. diadecturus; and none of the Californidorus had flanges. Three sinuses were present in the odontophores of all species. The sinuses varied in length depending upon species. In Xiphinema and Californidorus the odontostyle bases had distinct overlapping collars, but in Longidorus the collars were absent except for L. diadecturus. The odontostyle-odontophore junction from a lateral view appeared as a slanted transverse line in all the species, but in a dorsal view of Xiphinema and Californidorus it was V-shaped. Dorsal longitudinal seams of the odontostyle and odontophore were observed in all the species. The dorsally located odontostyle aperture was ca. 1 μm from the anterior end in all species, except in one Longidorus sp. it was ca. 4 μm from the end.     

A Rapid Method for Microbial Sample Preparation for the Scanning Electron Microscope

A synthetic aromatic polymer has been used for preparing replicas of different microorganisms. This method of preparing highly concentrated (9.6 k) microbiological samples for scanning electron microscopy was compared with a standard method. The micrographs of the replicated samples are satisfactory. This method is rapid, cost effective and produces good results, especially in the case of spore-forming mycelial microorganisms.     

Seed morphology in some European aconites (Aconitum,Ranunculaceae)

The seed coat morphology, investigated in taxa representative of the main European groups ofAconitum, are in good agreement with the current taxonomy of the genus. The seed coat microcharacteristics (warty epidermal cells) are very constant. There is a trend for the reduction of longitudinal wings on the edges concomitant with the development of ridges and transverse wings on the faces. Another morphological progression leads from smooth to rugulose and eventually to transverse wing-bearing seed faces. A working hypothesis suggests an ecological adaptative significance to these changes.     

Ependyma and ependymal protrusions of the lateral ventricles of the rabbit brain

Summary The ependymal lining of the lateral ventricles of the rabbit brain was studied by means of scanning (SEM) and transmission electron microscopy (TEM). There exist cells devoid of cilia in the anterior horn over the region of the caudate nucleus, in the inferior horn over the hippocampus and on the opposite side over cortical regions. On the surface of some of these ependymal cells, accumulations of cytoplasmic folds and globules can be found. They bulge at different height over the ependymal cells. Clots of these cell particles are tied off from the cell, coming to lie as globules either on or between the cilia of the ependyma. TEM reveals that these tissue protrusions are cell debris consisting of different sized vesicles, cell organelles, tubuli and filaments. They originate from the ependymal layer but may reach down to subependymal cells. Multivesicular protrusions into the ventricular lumen are also observed. Possible causes of these protrusions are discussed; they are likely to be related to the age of the animals.On the ependyma of the caudate nucleus cilia, microvilli, microblebs and supraependymal neuronal cell processes are distributed unevenly over the surface. Within regions where cilia predominate there are cells which are tightly covered with microvilli. A certain direction of the course of the supraependymal neuronal fibers could not be found.The author is pleased to acknowledge useful discussions with Prof. Dr. med. E. van der Zypen. This study was partly supported by the Stanley Thomas Johnson Foundation