Myospherulosis. Fine needle aspiration cytologic findings in 19 cases

An analysis was made of 19 cases of myospherulosis seen on fine needle aspirates of mammary and subcutaneous tissue masses. Myospherulosis, best seen with the Papanicolaou stain, appeared as 4 microns to 7 microns spherules that were homogeneously smooth or contained one or more internal dense bodies. The spherules were dispersed singly or aggregated into sac-like structures. Myospherulosis accompanied 16 benign and 3 malignant conditions. In two aspirates, myospherulosis was seen simultaneously with breast carcinoma; in another, fat necrosis with myospherulosis masked an underlying breast malignancy. In 10 of the 12 aspirates from patients with previous tissue trauma, it accompanied evidence of fat necrosis and mesenchymal repair; in 4 aspirates, no other underlying condition was apparent. These findings indicate that myospherulosis is not an uncommon finding in fine needle aspirates of fatty sites; it often accompanies fat necrosis and mesenchymal repair. The presence of myospherulosis in aspirates of clinically suspicious masses does not exclude an underlying malignancy.     

The contractile ring

Summary Techniques of individual cell selection and precise ultramicrotomy have been employed to demonstrate that the contractile ring of cleaving HeLa cells is a transitory cytoplasmic organelle of distinctive fine structure and location. The contractile ring is an uninterrupted annulus encircling the equator of dividing cells exactly where the cleavage furrow forms. It is about 10 microns wide, up to 0.2 microns in thickness, and is composed exclusively of circumferentially aligned thin filaments 40–70 Å in diameter. Contractile ring filaments appear to be associated with the overlying plasma membrane.Controlled experiments with a mold metabolite (cytochalasin B) reveals that within a few minutes the drug abolishes the ability of HeLa cells to undergo cytokinesis. Cytochalasin B seems to decompose the contractile ring. It has no other clearly identifiable effects on other cell structures, notably the mitotic apparatus. Cytochalasin B is the only drug known which selectively inhibits cytokinesis in animal cells.In conclusion, the contractile ring is the most likely organelle responsible for cytokinesis in HeLa cells. Similar organelles probably occur in all cleaving animal cells. Successful cleavage depends upon the structural and functional integrity of the contractile ring.     

Orderly formation of the double ring structures for plastid and mitochondrial division in the unicellular red alga Cyanidioschyzon merolae

The formation of the plastid-dividing ring (PD ring) and mitochondrion-dividing ring (MD ring) was studied in a highly synchronous culture of the unicellular red alga Cyanidioschyzon merolae. The timing and the order of formation of the MD and PD rings were determined by observing organelles around the onset of their division, using transmission electron microscopy. In  C. merolae, there is one chloroplast and one mitochondrion per cell, and the shape of the chloroplast changes sequentially from acorn-like, to round, to trapezoidal, to peanut-shaped, in that order, during the early stage of chloroplast division. None of the cells with acorn-shaped or round chloroplasts contained organelles with PD rings or MD rings, while all of the cells with peanut-shaped chloroplasts contained organelles with both PD rings and MD rings. In cells with peanut-shaped chloroplasts, the PD and MD rings were double ring structures, with an outer ring located on the cytoplasmic face of the outer membrane of the organelle, and an inner ring located in the matrix beneath the inner membrane. These results suggested that the double ring structures of the PD ring and the MD ring form when chloroplasts are trapezoidal in shape. Detailed three-dimensional observation of cells with trapezoidal chloroplasts revealed the following steps in the formation of the double ring structures of the PD and MD rings: (i) the inner ring of the PD ring forms first, followed by the outer ring; (ii) then the MD ring forms and becomes visible; (iii) when the double ring structures of the two rings have formed, the microbody then moves from its remote location to the plane of division of the mitochondrion and contraction of the PD and MD rings commences. These steps were also confirmed by computer-aided three-dimensional reconstruction of the images from serial thin sections. This study reveals the order of formation of the double ring structures of the PD and MD rings, and the behavior of the microbody around the onset of division of plastids and mitochondria. The results also provide the first evidence that the inner PD ring is not a tension element formed by the contractile pressure but a definite structure, independent of the outer ring. Received: 31 March 1998 / Accepted: 14 May 1998     

RNA TRANSPORT FROM NUCLEUS TO CYTOPLASM IN CHIRONOMUS SALIVARY GLANDS

The fine structure and cytochemistry of the extremely large RNA puffs, or Balbiani rings, in salivary gland nuclei of midge, Chironomus thummi, larvae have been investigated. The Balbiani rings are composed of a diffuse mass of electron-opaque 400 to 500 A granules, short threads about 180 to 220 A in diameter and associated fine chromatin fibrils. These components appear to be organized into brushlike elements which form the ring. Electron microscope cytochemistry has shown that the granules and short threads contain RNA. After ribonuclease digestion, only 50 to 100 A chromatin fibrils were apparent in the Balbiani ring, and the granules were no longer demonstrable. Deoxyribonuclease digestion had no apparent effect on these structures. Observations indicate that the granules are formed from the short threads and released into the nucleoplasm in which they are evenly distributed. At the nuclear envelope, many granules have been observed partially or completely within the nuclear pores. These granules become elongated and are shown to penetrate the center of the pore in a rodlike form, about 200 A in diameter. The Balbiani ring granules are not normally visible within the cytoplasm adjacent to the nuclear envelope, but have been rarely found in this region. It is suggested that the granules represent the product of the Balbiani ring, possibly a messenger RNA bound to protein, and that they regularly pass into the cytoplasm through a narrow central channel in the pores of the nuclear envelope.     

Effect of streptolysin O on erythrocyte membranes, liposomes, and lipid dispersions. A protein-cholesterol interaction

The effect of the bacterial cytolytic toxin, streptolysin O (SLO), on rabbit erythrocyte membranes, liposomes, and lipid dispersions was examined. SLO produced no gross alterations in the major erythrocyte membrane proteins or lipids. However, when erythrocytes were treated with SLO and examined by electron microscopy, rings and "C"-shaped structures were observed in the cell membrane. The rings had an electron-dense center, 24 nm in diameter, and the overall diameter of the structure was 38 nm. Ring formation also occurred when erythrocyte membranes were fixed with glutaraldehyde and OsO4 before the addition of toxin. In contrast, rings were not seen when erythrocytes were treated with toxin at 0 degrees C, indicating that adsorption of SLO to the membrane is not sufficient for ring formation since toxin is known to bind to erythrocytes at that temperature. The ring structures were present on lecithin-cholesterol-dicetylphosphate liposomes after SLO treatment, but there was no release of the trapped, internal markers, K2CrO4 or glucose. The crucial role of cholesterol in the formation of rings and C's was demonstrated by the fact that these structures were present in toxin-treated cholesterol dispersions, but not in lecithin-dicetylphosphate dispersions nor in the SLO preparations alone. The importance of cholesterol was also shown by the finding that no rings were present in membranes or cholesterol dispersions which had been treated with digitonin before SLO was added. Although rings do not appear to be "holes" in the membrane, a model is proposed which suggests that cholesterol molecules are sequestered during ring and C-structure formation, and that this process plays a role in SLO-induced hemolysis.     

雷公藤二萜类化合物精细立体结构研究

雷公藤二萜内酯类化合物在结构上有一定的相似性:它们均含有3个六元环、1个五元内酯环和1～3个二元氧环,并且具有多种生物活性。本文选择了7个具有代表性的雷公藤二萜内酯化合物并通过X衍射分析获得其三维结构数据,以已有的药理实验数据为基础,对其精细立体结构变化和生物活性关系进行了探讨。研究结果表明:雷公藤萜内酯类化合物中的A、B、C三个六元环是其活性骨架的几何依托;18位上的羰基和7～8位上的三元氧环是其活性的可能结合部位;而该类化合物的活性部位则集中在C环的取代位置上;D环不是该类化合物具有生物活性的必需骨架部分。     

Morphometry of nuclear rings at high electron microscopic resolution

In studying the fine structure of the nuclear chromatin, a new organelle was discovered, the nuclear ring. In its isolated form, this structure is rather like a geometric torus: a smooth, structureless ring. This paper presents the results of electron microscopic morphologic measurements on 424 isolated rings, i.e., rings found free of any fibrous connections. From the measurements of inner and outer diameters, other geometric features were also calculated. Overall, the size of the rings varied about fivefold. Inner and outer diameters were closely correlated, suggesting a rather stable thickness of the ring itself. The significance of the nuclear ring is as yet poorly understood. With its occasionally intimate connections to both chromatin fibers and to the inside of the inner nuclear envelope, its role is likely to be a crucial one. The membrane covering its opening is none other than the bilayer of the nuclear envelope. The concept of a patent opening or "pore" does not appear tenable in the face of this and related findings.     

G-11 staining in Turner's syndrome with mos 45,X/46,X,r(?)

Mos 45,X/46,X,r(?) in 4 patients with Turner's syndrome and no signs of virilization, and in one pair of monozygotic twins, one of them with clitoral hypertrophy, was studied using combined cytogenetic techniques and specially G-11 staining for the characterization of the X or Y origin of the rings. In all 6 patients the ring was G-11 positive, attesting its Y origin. Both twins were operated and bilateral streak gonads with a bilateral nodule of testicular tissue were found. Similar small rings were also studied in one patient with mos 46,XX/46,X,r(X) and in one nonvirilized Turner's syndrome patient with a larger ring; in these two cases the ring was G-11 negative. It seems that the small rings occasionally found in Turner's syndrome are more frequently from Y origin and therefore prophylactic gonadectomy should be considered.     

Intramolecular compactization of circular DNA in interaction with dansyl hydrazide trivaline leading to a formation of a new type of structure--triple rings

Compactization of supercoiled circular plasmid pBR322 caused by interaction with synthetic oligopeptide dansyl hydrazide trivaline capable of beta-structure formation was studied by electron microscopy. The results show that at rising input peptide concentration circular DNA molecules undergo intramolecular structural transition with the formation of compact ring structures. The compact ring structures are formed by the fiber having the thickness of 60 A. The analysis of morphology of intermediate structures and the contour length measurements enable us to conclude that 60 A-fiber contains three lying side-by-side and interwound double-stranded DNA segments. Thus, the compact ring structures are addressed to as triple rings. The triple ring have one special point, where the triple region ends are locked by a duplex DNA segment. The mechanisms responsible for the triple ring formation may be of importance for DNA and chromatin compactization processes in vivo.     

Estimating missing sapwood rings in three European gymnosperm species by the heartwood age rule

Precise dating of the year of felling is one intended outcome of dendrochronology. However, occasionally some or all sapwood rings might be missing, either due to deterioration or because they were carved off, or for some other reason. Consequently, while heartwood is preserved, sapwood might be fully or partially missing. In such cases, the year of felling must be estimated by adding a suitable number of sapwood rings. A heartwood age rule (HAR) has been advocated for Scots pine and adapted to European larch and Cembra pine, implying a linear relationship between sapwood ring count and the square root of heartwood ring count, largely irrespective of position in the stem. The same rule applied to all observations of a species, irrespective of silviculture, location or fertility of the growth site. Scots pine had twice or thrice as many sapwood rings as Cembra pine, which had 10% more rings than larch. The magnitude of model residuals was proportional to estimated sapwood ring count. Relative residuals were roughly normally distributed. To be applicable in Bayesian modelling in dendrochronology analyses, detailed information on model errors has been provided.     

M ring, S ring and proximal rod of the flagellar basal body of Salmonella typhimurium are composed of subunits of a single protein, FliF.

The flagellar basal body, a major part of the flagellar motor, consists of a rod and four rings. When the fliF gene of Salmonella typhimurium, which was previously shown to code for the component protein of the M ring, was cloned and overexpressed in Escherichia coli, the FliF subunits formed ring structures in the cytoplasmic membrane. Electron microscopic observation of the purified ring structures revealed that each was composed of two adjacent rings and a short appendage extending from the center of the rings. Antibodies raised against the purified FliF protein decorated both the M and S rings of the intact basal body. We conclude that the FliF protein is the subunit protein of the M ring, and of the S ring and of part of the proximal rod of the flagellar basal body.     

The dimensions and shapes of the furanose rings in nucleic acids

A survey was made of the geometry of furanose rings in beta-nucleotides and beta-nucleosides (as monomers related to nucleic acids) for which structures have been determined by X-ray crystallography. Mean values, and estimated standard deviations from them, were calculated for bond-lengths, bond-angles and conformation-angles. For parameters with values dependent on ring-puckering, separate calculations were made for each ring type. (The rings are puckered in one of three conformations: C-2- or C-3-endo or C-3-exo; C-2-exo has not been observed.) The results were used to compute standard furanose rings with C-2-endo, C-3-endo and C-3-exo conformations for use in nucleic acid molecular model-building. The survey also showed that the only other conformation-angle in nucleotides dependent on the furanose ring conformation corresponds to the relative orientation of the purine (or pyrimidine) base and the ring.     

Directed cellular self-assembly to fabricate cell-derived tissue rings for biomechanical analysis and tissue engineering

Each year, hundreds of thousands of patients undergo coronary artery bypass surgery in the United States.(1) Approximately one third of these patients do not have suitable autologous donor vessels due to disease progression or previous harvest. The aim of vascular tissue engineering is to develop a suitable alternative source for these bypass grafts. In addition, engineered vascular tissue may prove valuable as living vascular models to study cardiovascular diseases. Several promising approaches to engineering blood vessels have been explored, with many recent studies focusing on development and analysis of cell-based methods.(2-5) Herein, we present a method to rapidly self-assemble cells into 3D tissue rings that can be used in vitro to model vascular tissues. To do this, suspensions of smooth muscle cells are seeded into round-bottomed annular agarose wells. The non-adhesive properties of the agarose allow the cells to settle, aggregate and contract around a post at the center of the well to form a cohesive tissue ring.(6,7) These rings can be cultured for several days prior to harvesting for mechanical, physiological, biochemical, or histological analysis. We have shown that these cell-derived tissue rings yield at 100-500 kPa ultimate tensile strength(8) which exceeds the value reported for other tissue engineered vascular constructs cultured for similar durations (<30 kPa).(9,10) Our results demonstrate that robust cell-derived vascular tissue ring generation can be achieved within a short time period, and offers the opportunity for direct and quantitative assessment of the contributions of cells and cell-derived matrix (CDM) to vascular tissue structure and function.     

Filament ring formation in the dimorphic yeast Candida albicans

Stationary phase cultures of Candida albicans inoculated into fresh medium at 37 degrees C synchronously from buds at pH 4.5 and mycelia at pH 6.5. During bud formation, a filament ring forms just under the plasma membrane at the mother cell-bud junction at roughly the time of evagination. A filament ring also forms in mycelium-forming cells, but it appears later than in a budding cell and it is positioned along the elongating mycelium, on the average 2 microns from the mother cell-mycelium junction. Sections of filament rings in early and late budding cells and in mycelia appear similar. Each contains approximately 11 to 12 filaments equidistant from one another and closely associated with the plasma membrane. In both budding and mycelium-forming cells, the filament ring disappears when the primary septum grows inward. The close temporal and spatial association of the filament ring and the subsequent chitin-containing septum suggests a role for the filament ring in septum formation. In addition, a close temporal correlation is demonstrated between filament ring formation and the time at which cells become committed to bud formation at pH 4.5 and mycelium formation at pH 6.5. The temporal and spatial differences in filament ring formation between the two growth forms also suggest a simple model for the positioning of the filament ring.     

Dynamic apical surface rings in superficial layer cells of koi Cyprinus carpio scale epidermis

This study examined the novel ring‐shaped structures found in the apical surface of individual cells of the scale epidermis of koi Cyprinus carpio. These apical rings are highly dynamic structures with lifetimes ranging from a few to several minutes. While several ring forms were observed, the predominant ring morphology is circular or oval. Two distinct ring forms were identified and designated type I and type II. Type I rings have a well‐defined outer border that encircles the surface microridges. Type II rings are smooth‐surfaced, dinner‐plate‐like structures with membranous folds or compressed microridges in the centre. Type II rings appear less frequently than type I rings. Type I rings form spontaneously, arising from swollen or physically interrupted microridges but without initially perturbing the encircled microridges. After persisting for up to several minutes the ring closes in a centripetal movement to form a circular or irregular‐shaped structure, the terminal disc. The terminal disc eventually disappears, leaving behind a submembranous vesicle‐like structure, the terminal body. Type I rings can undergo multiple cycles of formation and closing. Recycling epidermal apical rings form through centrifugal expansion from the terminal disc followed by apparent contraction back to the disc structure, whereupon the cycle may repeat or cease. The findings demonstrate a novel skin surface structure in fishes and are discussed with respect to communication with the external aqueous environment.     

Chromosome chromatid rearrangements resulting from the mitotic crossing-over between sister-chromatids in ring chromosomes of Creptis capillaris

Summary All radiation-induced aberrations in dry seeds of Crepis capillaris are chromosome rearrangements. The main types of chromosome rearrangements in the above tests were asymmetrical and symmetrical exchanges, ring chromosomes and ring deletions. The majority of ring chromosomes is of a chromosomes type which brings about paired rings. Fig. 1 presents the mechanism of the production of the paired rings. In a number of cases the structure of rings proved to be quite unexpected. Among middle size rings single rings proved to occur in 18.8%, among microrings-1.9% cases. Somewhat fewer are presented by pairs of rings one inside the other. The large rings present complex figures made by tangled chromatids. Two rings make one due to mitotic crossing-over between sister-chromatids (Fig. 5). Double crossing-over would lead to the exchange of part of material between two independent rings or to one ring being thrust into the other due to different strand positions in two points of the exchange. Large rings is the provision of complicated exchanges.     

Fine Structure of the Female Intoshia variabili(Alexandrov & Sljusarev) (Mesozoa: Orthonectida)

The morphology and fine structure of female Intoshia variabili, new combination for Rhopalura variabiliAlexandrov & Sljusarev, 1992, were studied with transmission electron microscopy. The body surface is covered with a 3-layered cuticula, under which is a layer of ciliated + non-ciliated cells arranged in alternating rings around the body. Ciliated cells have lateral extensions that intercalate with the non-ciliated cells. The kinetosome of each cilium has two longitudinally oriented cross-striated rootlets. The outer surface of the ciliated cells is covered with small tubercles, and the cytoplasm of these cells contains granules, vacuoles, mitochondria, fibrillar structures and lamellary bodies. A band of dense fibrils passes through the upper part of each ring of cells, going from one cell junction to another, encircling the entire body. Between the layer of ciliated + non–ciliated cells and the oocytes, elongated contractile cells from 4–5 longitudinal columns and 1 ring, the latter at the level of ciliated rings 7–9. The contractile cells contain thick and thin longitudinally oriented fibrils. The oocytes contain a large nucleus, numerous mitochondria, electron–dense granules and 1–2 spherical structures. An anteriorly situated, ciliated goblet–like receptor, not described for any other orthonectids, consists of three closely apposed cells, the upper part of which contains densely packed cilia. The genital pore opens through a non–ciliated cell and is surrounded by several cells with granules.     

SPACING OF PARENCHYMA BANDS IN WOOD OF CARYA GLABRA (MILL.) SWEET,PIGNUT HICKORY,AS AN INDICATOR OF GROWTH RATE AND CLIMATIC FACTORS

Variations in the spacing of concentric, tangential bands of apotracheal axial wood parenchyma cells in the annual growth rings of Carya glabra (Mill.) Sweet constitute a record of changes in radial growth rate and of fluctuations in climatic factors. This relationship was determined from trees that were growing under moisture stress and consequently had highly consistent ring-width patterns from tree to tree. Band spacing decreased across a growth ring and was generally greater in wide than in narrow rings. Thus, the proportion of xylem cross-sectional area occupied by axial parenchyma tissue was inversely related to ring width. Average numbers of bands in each of 67 years were analyzed relative to ring widths. Years in which bands were unusually numerous relative to ring width were years of low April-May precipitation, leading to slow spring growth and closely spaced bands early in the growing season. Years in which band numbers were unusually low relative to ring width were years of high April-May precipitation, leading to rapid growth and widely spaced bands early in the season; low July precipitation in these years apparently curtailed growth before much of the typical late-season wood, with its closely spaced bands, could form. Parenchyma bands were aggregated within some rings, suggesting that a slowing of growth had been followed by a growth spurt. Evidence for a late-season spurt was that rings with aggregations were significantly wider than rings formed the same year and not having aggregations of bands. The number of vessels per unit of cross-sectional area was inversely related to ring width.     

Inhibitory effects of melatonin on vascular reactivity: possible role of vasoactive mediators

Melatonin (MEL), the principal hormone of the vertebral pineal gland, elicits several neurobiological effects. However, the effects of MEL on vascular tissues are still vague. The first goal of this study was to investigate the effect of MEL on isolated rabbit aortic rings and its role in the vascular reactivity to contractile agents, noradrenaline (NA) and phenylephrine (PHE) and relaxant agents (acetylcholine and sodium nitroprusside). In addition, the levels of nitric oxide (NO), cGMP, total calcium, lipid peroxides, superoxide dismutase (SOD) and glutathione (GSH) were also investigated in tissue homogenates of rabbit aortic rings preincubated (20 min) in MEL with and without contractile agents. Our results revealed that MEL has an endothelium-dependent vaso-relaxant effect and potentiated significantly the vaso-relaxant effect of acetylcholine. Moreover, MEL (10^?4 M) had a significant inhibitory effect on the contractile responses of aortic rings to both NA and PHE. In comparison with control tissue rings, the levels of lipid peroxides were significantly increased while the levels of GSH, and SOD activities were significantly decreased in tissue homogenates of aortic rings pre-incubated (20 min) in NA or PHE. In addition, the levels of NO and cGMP were significantly lower in tissue rings pre-treated with NA and PHE, respectively. Also, the levels of total calcium were significantly increased only in tissue rings pre-treated with NA. The levels of lipid peroxides were significantly decreased, while the levels of GSH, NO and cGMP and SOD activities were significantly increased in tissue homogenates of aortic rings incubated (20 min) in MEL (10^?4 M) in comparison to ring tissues incubated in NA or PHE alone. In aortic rings incubated in MEL+PHE, the levels of lipid peroxides were significantly lower while the levels of GSH and cGMP and SOD activities were significantly higher than their levels in ring tissues incubated in PHE. In aortic rings incubated in MEL+NA, the levels of lipid peroxides and total calcium were significantly lower while the levels of NO were significantly higher than their levels in ring tissues incubated in NA alone. We conclude that MEL has an endothelium dependent vasorelaxant effect and potentiates the endothelium dependent vasorelaxation induced by acetylcholine. MEL inhibits the contractile responses of aortic rings to NA and PHE. These effects may be, in part, due to re-balancing the pro-oxidant/antioxidants system, lowered calcium content and elevated NO and cGMP levels in vascular tissue.