Observations on the structure of pullulan

An extracellular α-glucan, pullulan, elaborated by a strain of Pullularia pullulans, contains 0.6% of a maltotetraose subunit, as well as the already known major component, maltotriose. The majority, at least, of the maltotetraose is contained within the polymeric chains and is linked, through its terminal glucose units, by α-1→6— bonds.     

Observations on the structure of bacilysin.

1. Elementary analysis and other properties of a highly purified preparation of bacilysin indicated that a possible molecular formula for the substance is C(12)H(18)N(2)O(5). The results of electrometric titration were consistent with the hypothesis that the substance was a peptide containing one free alpha-amino group and one free carboxyl group. 2. Hydrolysis of bacilysin with 6n-hydrochloric acid at 105 degrees yielded l-alanine and l-tyrosine, but the ultraviolet spectrum of the substance showed that no tyrosine residue was present in the molecule and a nuclear-magnetic-resonance spectrum indicated that olefinic and aromatic protons were absent. The dinitrophenyl (DNP) derivative of bacilysin yielded DNP-alanine on acid hydrolysis. 3. Bacilysin was hydrolysed by leucine aminopeptidase (EC 3.4.1.1) and by Pronase to give alanine and an uncharacterized amino acid. Its infrared spectrum was consistent with the presence of a peptide grouping in the molecule. 4. The optical rotatory dispersion of bacilysin and its reaction with thiosemicarbazide indicated that the substance contained an aldehyde or ketone group. Its behaviour on catalytic reduction and its reaction with sodium thiosulphate and with certain thiols suggested that an epoxide group was present. 5. A possible type of structure for bacilysin is considered in the light of its known properties.     

商陆科植物的子房结构观察

商陆科植物几种雌蕊类型的发育和结构进行了观察,结果表明,商陆科植物的心皮发生后,首先形成一个开放的心皮,开口在心皮的腹侧,开口的封闭都是由心皮边缘的：表皮细胞及表皮下的几层细胞的分裂和生长完成。单心皮雌蕊在子房封闭后不留任何痕迹,而多心皮雌蕊的心皮封闭后留下明显的封闭线。封闭线由栅栏组织状组织构成。栅栏组织状组织一直延伸到珠柄,在珠柄基部形成毛刷状结构。离生心皮的隔在子房的生长过程中生长很少,心皮的大部分是分离的;合生心皮的隔在心皮的生长过程中与心皮同步生长,心皮始终是合生的。成熟子房的结构基本相同,子房壁为薄壁细胞,除表皮以外其他细胞均无太：大区别。在子房外侧壁中均匀地分布有3～5个维管束,隔中有一个维管束。胚珠生于子房的基部腹侧。     

Observations on structure and differentiation in plasmodesmata

Summary The fine structure of plasmodesmata in a number of plant tissues has been examined following fixation in glutaraldehyde. The structure of plasmodesmata is not constant. Variations occur between species, tissues and between different cellular situations in a single tissue. The nature of these variations is described and related to current theories of the formation and function of plasmodesmata. Evidence is presented that the young cell wall after division contains a large number of plasmodesmata, probably functionally and structurally identical, and that the development process involves characteristic modifications both to the distribution of plasmodesmata within the wall, and to the structure of individual plasmodesmata. The probable importance of the endoplasmic reticulum is stressed in relation to the formation and functioning of plasmodesmata.     

Observations on the vacuolar structure of the human syncytiotrophoblast

Summary The literature on the vacuolar structure of the human syncytiotrophoblast is briefly reviewed. Personal observations based on light and electron microscopic investigations are described and illustrated. The nature of the different kinds of syncytial vacuolation is discussed. In particular dilated vacuoles, which may be very large indeed, receive special attention; situated adjacent to the syncytial nuclei they have been called juxtanuclear vacuoles. They are directly continuous with the perinuclear spaces, and often receive tubular communications from the endoplasmic reticular system. The possible functional role of the syncytial vacuolar system is discussed in the light of the authors' findings and the related literature.Dedicated to Professor Dr. Kurt Goerttler on the occasion of his seventieth birthday.     

Observations on the structure of mechanically stretched chromatin fibrils

During the spreading of human chromosomes prepared from cultured human lymphocytes, the peripheral fibers attaching the chromosome to the support film are mechanically stretched. The stretching reveals structural elements of the fibers; some of these features have been described earlier, for extracted chromatin. The molecule of DNA is bared through stretching and binds labeled actinomycin D in consequence. One of the prominent features of stretched fibers is the irregularity of resulting structures. This paper further demonstrates the excellent resolution obtainable by electron impact evaporation of tungsten.     

Observations on the fine structure of a methane-oxidizing bacterium

Structural details of membranes, intracellular organelles, and the cell wall of a methane-utilizing bacterium identified as aMethylomonas sp. were studied by electron microscopy. The cell wall structure is similar to that found in other gram-negative bacteria. The cytoplasmic membrane shows invaginations, presumably forming the internal membrane bundles. Two types of polar organelles were encountered. In older cells myelin-like structures were observed. Under certain cultural conditions bleb-formation and possibly accumulation of reserve materials occurred. We wish to thank Mrs. M. H. Bakker-van der Velden, Mrs. W. H. Batenburgvan der Vegte and Miss J. C. de Bruyn for making the electron microscopical preparations and photographs. Thanks are due to Mr R. S. M. Revell of the Philips E. M. Application Laboratory, Eindhoven, for the photographs with the goniometer attachment.