Complex Membrane Structures Research Articles

Fine structure of methane and other hydrocarbon-utilizing bacteria.

SUMMARY Methane-utilizing bacteria were examined by electron microscopy and found to possess complex membranous structures within the cytoplasm. Two types of membrane organization were recognized. One type consisted of pairs of membranes which either extended throughout the organism or were arranged at the periphery where they ran parallel to the cytoplasmic membrane. The other type consisted of vesicular discs of membrane organized into bundles which were distributed throughout the organism. Bacteria utilizing C2 to C4 gaseous n-alkanes and C11 to C18 liquid n-alkane mixture did not possess such extensive membranous structures. The former contained membranous bodies of the mesosome type, whilst the latter possessed only a cytoplasmic membrane. These structural differences add to the growing list of properties separating CH4-utilizing bacteria from those utilizing C2 and higher n-alkanes.

Inclusion bodies and tubular structures in Chenopodium amaranticolor plants infected with strawberry latent ringspot virus.

SUMMARY The first change observed in cells of leaves systemically infected with strawberry latent ringspot virus was the formation of inclusion bodies near the nucleus. The inclusions were largely composed of endoplasmic reticulum, complex membranous structures and ribosomes. Three days later their outer parts contained unbranched, double-walled, slightly flexuous tubules about 50 nm. wide and up to at least 2·5 μm long. Each tubule, or occasionally two or three tubules, was enclosed in a membranous sheath 80 to 120 nm. in diameter, joined to the endoplasmic reticulum. The tubules contained a single row of up to 100 or more darkly stained virus-like particles. Some tubules ended within the inclusion and some at plasmodesmata, in which virus-like particles occurred. The central, predominantly membranous, regions of the inclusions contained masses of faintly stained, apparently hollow structures resembling empty shells of virus coat protein.

The fine structure of the sense organs of the cephalopod mollusc Nautilus.

The structure of the rhinophore, digital tentacles, post-ocular tentacles and the eye of Nautilus macromphalus are described. The rhinophore is composed of mucous cells, ciliated cells, and flask-shaped ciliated cells. The latter are probably olfactory receptors. The digital tentacles are composed of mucous cells and pigmented cells. Motor-end-plates found in the muscle layer below the epithelium of the digital tentacles are similar to those described in other cephalopods. The post-ocular tentacle contains receptor cells that bear macrocilia. These may be mechanoreceptors. The retina is composed of retinula cells and supporting cells. A complex rhabdom is formed at the distal ends of the retinula cells. The supporting cells send processes up between these rhabdoms. Both types of cells contain pigment granules but the retinula cell has a complex membranous structure in its perikaryon. No synapses were found at the bases of the retinula cells. At the side of the retina are mucous cells that are presumed to produce the jelly-like substance that fills the inside of the eye in life. The likely function of the eye is discussed and it is suggested that it is capable of simple discriminations. It is suggested that the sense organs are probably comparatively unchanged from those of fossil nautiloids.

ELECTRON MICROSCOPE STUDY OF MYCOBACTERIUM LEPRAE AND ITS ENVIRONMENT IN A VESICULAR LEPROUS LESION

Imaeda, Tamotsu (Instituto Venezolano de Investigaciones Cientificas, Caracas, Venezuela) and Jacinto Convit. Electron microscope study of Mycobacterium leprae and its environment in a vesicular leprous lesion. J. Bacteriol. 83:43-52. 1962.-Biopsied specimens of a borderline leprosy lesion were observed with the electron microscope. In this lesion, the majority of Mycobacterium leprae were laden with cytoplasmic components. The bacilli were separated from the cytoplasm of host cells by an enclosing membrane, thus differing from the environment of well-developed lepra cells in lepromatous lesions. The cell wall is composed of a moderately dense layer. A diffuse layer is discernible outside the cell wall, separated from it by a low density space. It is suggested that the cell wall is further coated by a low density layer, although the nature of the outermost diffuse layer has not yet been determined. The plasma membrane consists of a double layer, i.e., dense inner and outer layers separated by a low density space. The outer layer is closely adjacent to the cell wall. In the region where the outer layer of the plasma membrane enters the cytoplasm and is transformed into a complex membranous structure, the inner layer encloses this membranous configuration. Together they form the intracytoplasmic membrane system. In the bacterial cytoplasm, moderately dense, presumably polyphosphate bodies are apparent. As neither these bodies nor the intracytoplasmic membrane system are visible in the degenerating bacilli, it seems probable that these two components represent indicators of the state of bacillary activity.

The normal fine structure of opossum testicular interstitial cells.

The interstitial tissue of the opossum testis includes interstitial or Leydig cells, macrophages, and small cells which morphologically resemble mesenchymal cells. The latter are thought to give rise to mature interstitial cells. The most prominent feature of the interstitial cell cytoplasm is an exceedingly abundant agranular endoplasmic reticulum. This reticulum is generally in the form of a meshwork of interconnected tubules about 300 to 450 A in diameter, but occasionally it assumes the form of flattened, fenestrated cisternae resembling those of pancreatic acinar cells, except for the lack of ribonucleoprotein particles on the surface of the membranes. The interstitial cells vary considerably in their cytoplasmic density. The majority are quite light, but some appear extremely dense, and in addition usually have a more irregular cell surface, with numerous small pseudopodia. These differences may well reflect variations in physiological state. Cytoplasmic structures previously interpreted as "crystalloids" consist of long bundles of minute parallel tubules, each about 180 A in diameter, which seem to be local differentiations of the endoplasmic reticulum. The mitochondria are rod-shaped, and contain a moderately complex internal membrane structure, and also occasional large inclusions that are spherical and homogeneous. The prominent juxtanuclear Golgi complex contains closely packed flattened sacs and small vesicles. The results of the present study, coupled with biochemical evidence from other laboratories, make it seem highly probable that the agranular endoplasmic reticulum is involved in the synthesis of the steroid hormones produced by the interstitial cell. This finding therefore constitutes one of the first functions of the agranular reticulum for which there is good morphological and biochemical evidence.