Nm In Cross Section Research Articles

Ultrastructural characterization of the locomotory cytoskeletal system of the spermatozoid inGinkgo biloba

The development of the locomotory cytoskeletal system of sperm is carefully coordinated with the development of the sperm inGinkgo biloba. Here we report further ultrastructural characterization of the locomotory cytoskeletal system in the developing spermatid and mature spermatozoid, particularly with respect to the initiation and early development of the flagellar apparatus. A multilayered structure (MLS) assembles from an electron-dense matrix that self-organizes after blepharoplast breakup and then further elongates. At the tail of the assembling MLS, the spline microtubules connect to an anterior beak of the nuclear envelope. Nuclear-pore complexes are found on the nuclear envelope close to this beak. The mitochondria which elongate and line up one behind the other are tightly associated with the MLS. The MLS ofG. biloba is composed of an upper layer of parallel spline microtubules and a lower layer consisting of a fibrous lamellar strip composed of paralled fibers about 9 nm in diameter. Higher-magnification images show that the fully assembled fibers of the lamellar strip consist of subunits which suggest that protofilaments are involved in the assembly processes. A unique cytoskeletal system of the spermatozoid inG. biloba is given by the anterior bundle of microtubules. This bundle, in which microtubules are arranged parallel to each other, forms between the plasmalemma and the MLS and is about 214–392 nm in cross section. These microtubules expand spirally along the MLS band. Other details of cellular fine structure of the mature spermatozoid are described.

Scanning Force Microscopy of the Fine Structure of Cartilage Irradiated with a CO2 Laser

Alterations of the cartilage matrix structure under non-destructive laser irradiation have been investigated by scanning force microscopy. Porcine nasal septum cartilage was irradiated with a CO2 laser with a power density of 50 W/cm(2) under two different time regimes: for 3 s and for 30 s. Short-time irradiation had little effect on the structure of the cartilage matrix. In comparison with non-irradiated cartilage, small channels of 100-400 nm in cross-section appeared. This observation gives evidence that the underlying mechanism of laser-induced stress relaxation of cartilage is based on short-time depolymerisation and subsequent re-formation of proteoglycan units. The 30 s laser treatment results in melting and denaturation of the matrix. For the first time, small crystals, 100-800 nm, were found on cut sections of the laser treated cartilage. The crystals mainly consist of resolvable sodium carbonate. Thus, they cannot be responsible for the formation of a stable cartilage configuration after laser treatment.

The Ultrastructure and Computer-enhanced Digital Image Analysis of Plasmodesmata at the Kranz Mesophyll-Bundle Sheath Interface of Themeda triandra var. imberbis (Retz) A. Camus in Conventionally-fixed Blades

The ultrastructure of the plasmodesmata at the Kranz mesophyll-bundle sheath (KMS-BS) interface in Themeda triandra, and the substructures within the plasmodesmata were investigated, using conventionally fixed leaf-blade material, enhanced by the addition of 0·1% tannic acid to the primary fixative.Examination of high-resolution electronmicrographs, and computer-enhanced digital images suggests that these plasmodesmata are complex structures, comprised of helically-arranged particulate material. The electron-dense particles are between 2·5 and 3·0 nm in diameter. These particles are specifically associated with the inner face of the inner plasmalemma membrane leaflet, and the outer region of the desmotubule wall. The electron-dense particles are presumably proteinaceous and embedded in a lipid matrix. In the constricted median portion of the KMS-BS plasmodesmata, the space between the desmotubule and the inner plasmalemma membrane leaflet and areas surrounding the proteinaceous particles thereof (the cytoplasmic sleeve) is about 3 nm in cross-section, and constitutes what we believe to be the space through which intercellular transport takes place.

Acidity and sorbate shape selectivity of H-ZSM-22, H-ZSM-48, and H-ZSM-50 zeolites

ZSM-22, ZSM-48, and ZSM-50 zeolites have unidimensional channels, formed by 10-membered rings, having pore dimensions 0.45 {times} 0.55 nm, 0.53 {times} 0.56 nm, and 0.41 {times} 0.58 nm, respectively. These zeolites belong to the class of medium-pore zeolites. The pores of ZSM-48 are near circular, whereas those of the other two zeolites are elliptical. The channels of ZSM-22 and -48 zeolites are linear and have uniform cross sections. However, the zeolite ZSM-50 has side pockets (0.58 {times} 0.68 nm in cross section and 0.81 nm deep) to the channels (4). Since these zeolites differ from each other in their channel structure, it is interesting to know the shape selectivity of these zeolites in sorption for sorbates/reactants of different critical sizes and configurations and also their acid-strength distribution. The present investigation was undertaken for obtaining information on the above. Sorbates used were: m-xylene, o-xylene, 1,2,4-TMB, isopropylbenzene, 2,2-DMB, 2,3-DMB, and isooctane.

Case for the Panel:Microtubules in Plasma Cells

Dear Sir: While studying a routine kidney biopsy, we encountered these very interesting bundles of microtubules in the endoplasmic reticulum of several interstitial plasma cells. The biopsy was from a 63-year-old male who presented with hematuria. Histologically, the glomeruli showed the features of chronic glomerulonephritis and numerous plasma cells were noted in the interstitium (Fig. 1). Several normal (Fig. 2) and atypical plasma cells with well-developed centrosomes (Fig. 3) were seen at electron microscopic level. Occasional plasma cells exhibited early microtubule formation (Fig. 41, while most showed cytoplasm filled with dilated rough endoplasmic reticulum containing profiles of both longitudinally and cross-sectioned microtubular bundles (Fig. 5). A high-power view of these structures (Fig. 6) clearly demonstrates their crystalline arrangement, Groups of 10-24 microtubules, measuring 12-1 5 nm in cross-section, were counted in single bundles. Fine bridges are discernable between the microtubules on crosssection, but not on longitudinal section (Fig. 7). Straight or rodlike microtubules have been reported in the endoplasmic reticulum of cells in various lesions.' Could these microtubules represent a distorted form of e I a b o r a t i o n of i rn m u n og I o b u I i n s ? We would very much appreciate the panel's opinion.

Cellulose biosynthesis in Acetobacter xylinum: visualization of the site of synthesis and direct measurement of the in vivo process.

In vivo synthesis of cellulose by Acetobacter xylinum was monitored by darkfield light microscopy. Cellulose is synthesized in the form of a ribbon projecting from the pole of the bacterial rod. The ribbon elongates at a rate of 2 mum min-1. The ribbon consists of approximately 46 microfibrils which average 1.6 X 5.8 nm in cross section. The observed microfibrillar elongation rate corresponds to 470 amol of glucose/cell per hr assimilated into cellulose. Electron microscopy of the process using negative staining, sectioning, and freeze-etching indicated the presence of approximately 50 individual synthetic sites organized in a row along the longitudinal axis of the bacterial rod and in close association with the outer envelope. The process of cellulose synthesis in Acetobacter is compared with that in eukaryotic plant cells.

Effect of Guanethidine on the Ultrastructure of the Small, Granule‐containing Cells in Cultures of Rat Sympathetic Ganglia1

Abstract:Sympathetic chain ganglia of newborn rats were cultured in Rose chambers with and without guanethidine. After one week, the cultures were examined by light microscopy for formaldehyde‐induced catecholamine fluorescence and by electron microscopy after fixation in 5% glutaraldehyde and 1% osmium tetroxide. Guanethidine sulphate (2 mg/l) caused an increase in the number of the small, intensely fluorescent (SIF) cells in the ganglion explants. Electron microscopic examination of guanethidine‐containing cultures revealed an increased number of small, granule‐containing (SGC) cells, which corresponded in size and shape to the SIF cells. Round vesicles (about 100 nm in diameter) and elongated vesicles (about 80 nm in cross section and about 200 nm in length) containing an electron‐dense core were observed in the cytoplasm of the SGC cells both in control and guanethidine‐containing cultures. The granular vesicles were most frequent in the periphery of the cytoplasm. In ganglia cultured with guanethidine, most SGC cells observed contained a greatly reduced number of granular vesicles as compared to SGC cells of the control cultures.

Effect of hydrocortisone on the ultrastructure of the small, intensely fluorescent, granule-containing cells in cultures of sympathetic ganglia of newborn rats.

Sympathetic chain ganglia of newborn rats were cultured in Rose chambers with or without hydrocortisone. After one week, the cultures were examined by light microscopy for formaldehyde-induced catecholamine fluorescence and by electron microscopy after fixation in 5% glutaraldehyde solution and thereafter in 1% osmium tetroxide. Hydrocortisone (10 mg/l) caused a great increase in the number of the small, intensely fluorescent (SIF) cells in the ganglion explants, and the fluorescence intensity of these cells was also increased. The SIF cells corresponded to small, granule-containing (SGC) cells in the electronmicros copic preparations, and in addition to an increase in their number there was also an increase in the size and number of granular vesicles in the presence of hydrocortisone. In control cultures the granular vesicles were round (about 100 nm in diameter) or elongated (40–150 nm in cross section and 150–250 nm in length); both types of vesicles contained electron dense cores. In hydrocortisone-containing cultures round granular vesicles up to 200 nm in diameter were also observed; the cores of these vesicles were of variable electron density. It is concluded that in tissue culture, hydrocortisone causes an increased formation of catecholamine-containing granular vesicles in SIF-SGC cells and their precursors and an increase in the number of these cells.

Some aspects of cleavage in Pomatoceros triqueter eggs

The first cleavage division of Pomatoceros triqueter eggs is described. Time-lapse microcinematographic and electron microscopic studies revealed that, prior to division, the plasma membrane was folded into pleats. These were not present after division. This fact pointed to an unfolding of the plasma membrane which enabled it to cover the increased surface area resulting from cleavage. It is suggested that the pre-cleavage folds are derived from the membranes of the cortical granules, which continue releasing their contents into the perivitelline region following fertilization and first division. Filamentous material in the form of a band was present subjacent to the plasma membrane in the region of the furrow. The individual filaments of this band measure 5 to 7 nm in cross section, the dimensions being similar to those described for other kinds of dividing cells.