On the interpretation of twisted patterns in elongating plant cell wall: Informations obtained with ultracryotomy

Summary Ultracryotomy, which gives anin situ visualization of wall subunits, was used to study the texture of elongating wall of mung bean hypocotyl (Phaseolus aureus). The criss-crossed texture of the wall was confirmed. The controversed disposition of the subunits in twisted patterns was analyzed on the basis of observations of oblique sections on which a mild extraction may be performed. Despite the twisted appearance within one sectioning plane, no curved subunits were seen running between the criss-crossed layers. The results confirmed that the appearance of arcs is an illusion due to thin sectioning of successive strata in which the orientation of subunits rotates.     

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.     

The fine structure and phosphatase cytochemistry of the Golgi complex and associated structures in the Sertoli cells of Syrian hamsters

The Golgi complex in the Sertoli cell of the Syrian hamster is well developed and consists of stacks of cisternae and associated vesicles. The inner- and outermost cisternae of the Golgi stacks are usually moderately dilated and exhibit numerous fenestrations. The middle portions of the intermediate cisternae are greatly flattened and not fenestrated, but toward the periphery these cisternae gradually become dilated and show a few fenestrations. On the inner aspect of the Golgi stacks the following structures are seen frequently: (1) one or two series of linearly arrayed circular profiles some of which are interconnected by tubules; (2) networks of anastomosing tubules with circular or oval meshes (800 to 1200 A in diameter); and/or (3) irregularly disposed tubules. The circular profiles and tubules are approximately 450 A in diameter. Acid phosphatase activity was localized in these anastomosing tubules when the tissues were incubated for more than one hour in a modified Gomori's medium (Barka and Anderson, 1963). Strong thiamine pyrophosphatase activity was demonstrated in the inner one to three cisternae of the Golgi stacks but not in the associated tubules. The system of the Golgi associated tubules is morphologically and histochemically distinct from the Golgi stacks and is probably equivalent to the Golgi-endoplasmic reticulum-lysosome system (GERL) in other cell types. The three dimensional aspects of the GERL-equivalent system are discussed.     

Observations on the fine structure of the pellicle pores ofEuglena granulata

Summary The structure or granules associated with the pellicle strips ofEuglena granulata (Klebs) Schmitz has been studied using light and electron microscopy. Two types of bodies can be distinguished in this association on the basis of their staining reactions, distribution, ultrastructure, and other characteristics. The first type, called pellicle pores, is distributed with regularity along certain pellicle strips; the pores are very uniform in size (about 300 m in diameter) and in content. They consist of an aperture and a compartment, the latter lined by the plasmalemma; in each compartment a dense, osmiophilic body and a series of tubules occur. The structure of the pellicle strips is modified at the points where the pellicle pores are present; the aperture extends to the cell surface in the groove between two pellicle strips. The second type of body, which undergoes vital staining with neutral red, is called a pellicle vacuole. These are variable in size (ca. 1 to 2 microns in diameter) and contain a variety of components including myelin figures, proliferated membranes, and sheets of electrondense material. The structure of these elements as well as their possible functional significance are discussed in some detail.