Rice two-pore K+ channels are expressed in different types of vacuoles

Potassium (K+) is a major nutrient for plant growth and development. Vacuolar K+ ion channels of the two-pore K+ (TPK) family play an important role in maintaining K+ homeostasis. Several TPK channels were previously shown to be expressed in the lytic vacuole (LV) tonoplast. Plants also contain smaller protein storage vacuoles (PSVs) that contain membrane transporters. However, the mechanisms that define how membrane proteins reach different vacuolar destinations are largely unknown. The Oryza sativa genome encodes two TPK isoforms (TPKa and TPKb) that have very similar sequences and are ubiquitously expressed. The electrophysiological properties of both TPKs were comparable, showing inward rectification and voltage independence. In spite of high levels of similarity in sequence and transport properties, the cellular localization of TPKa and TPKb channels was different, with TPKa localization predominantly at the large LV and TPKb primarily in smaller PSV-type compartments. Trafficking of TPKa was sensitive to brefeldin A, while that of TPKb was not. The use of TPKa:TPKb chimeras showed that C-terminal domains are crucial for the differential targeting of TPKa and TPKb. Site-directed mutagenesis of C-terminal residues that were different between TPKa and TPKb identified three amino acids that are important in determining ultimate vacuolar destination.     

Developing seeds of Arabidopsis store different minerals in two types of vacuoles and in the endoplasmic reticulum

Mineral-accumulating compartments in developing seeds of Arabidopsis were studied using high-pressure-frozen/freeze-substituted samples. Developing seeds store minerals in three locations: in the protein storage vacuoles of the embryo, and transiently in the endoplasmic reticulum (ER) and vacuolar compartments of the chalazal endosperm. Energy dispersive x-ray spectroscopy and enzyme treatments suggest that the minerals are stored as phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate) salts in all three compartments, although they differ in cation composition. Whereas embryo globoids contain Mg, K, and Ca as cations, the chalazal ER deposits show high levels of Mn, and the chalazal vacuolar deposits show high levels of Zn. The appearance of the first Zn-phytate crystals coincides with the formation of network-like extensions of the chalazal vacuoles. The core of these networks consists of a branched network of tubular ER membranes, which are separated from the delineating tonoplast membranes by a layer of cytosolic material. Degradation of the networks starts with the loss of the cytosol and is followed by the retraction of the ER, generating a network of collapsed tonoplast membranes that are resorbed. Studies of fertilized fis2 seeds, which hyperaccumulate Zn-phytate crystals in the chalazal vacuolar compartments, suggest that only the intact network is active in mineral sequestration. Mineral determination analysis and structural observations showed that Zn and Mn are mobilized from the endosperm to the embryo at different developmental stages. Thus, Zn appears to be removed from the endosperm at the late globular stage, and Mn stores appear to be removed at the late bent-cotyledon stage of embryo development. The disappearance of the Mn-phytate from the endosperm coincides with the accumulation of two major Mn binding proteins in the embryo, the 33-kD protein from the oxygen-evolving complex of photosystem II and the Mn superoxide dismutase. The possible functions of transient heavy metal storage in the chalazal endosperm are discussed. A model showing how phytic acid, a potentially cytotoxic molecule, is transported from its site of synthesis, the ER, to the different mineral storage sites is presented.     

Origin and formation of different types of vacuoles induced by the multiplication of the alphavirus Sindbis virus in various cell systems

Spherule-containing vacuoles and nucleocapsid-bearing vacuoles (cytopathic vacuoles types 1 and 2 respectively of Grimley et al. 1968) induced by Alphavirus Sindbis were studied in brains from newborn mice, chicken embryo fibroblasts, and two lines of tumoral glial cells from muridae. Endoplasmic reticulum (ER) elements and finely granular electron-dense material also seen in contact with nucleocapsids seemed to be involved in the formation of the classical single-membrane spherule-containing vacuoles. A second type of spherule-containing vacuoles were characterized by their double membrane and an amorphous electron-dense content and were probably derived from mitochondria. Nucleocapsid-bearing vacuoles were formed from modified ER elements and seemed to be linked to excessive synthesis of viral material. Such ER alterations were not observed in RG6 cells. In these cells, there were only spherule-containing vacuoles, while nucleocapsids were seen associated with the cytoplasmic membrane only.     

An X-ray microanalysis survey of the concentration of elements in the cytoplasm of different mammalian cell types

Electron probe energy dispersive X-ray microanalysis was performed on freeze-dried tissue sections. The dry weight concentration of elements (mmole/kg dry weight) was measured in the cytoplasm of several cell types from adult mice and rats. This comparative investigation showed: (1) That the energy dispersive X-ray spectrum of element concentration from the cytoplasm of a specific cell type allows one to distinguish this specific cell type from other cell types with considerable accuracy. (2) That there is a relationship between the concentration of the various elements and the ultrastructural features of the cytoplasmic regions being analyzed. For example, areas rich in ribosomes are also rich in P, K and Mg. (3) These data support the idea that K is directly involved in the control of protein synthesis. The catalog of element concentrations in the cytoplasm of 13 cell types from both mice and rats should be of value to others who seek to answer various questions about these cell types.     

Tonoplast stability and survival of isolated vacuoles in different buffers

The mechanism of sucrose transport into vacuoles isolated from leaf tissue has been studied only in barley (Hordeum vulgare) mesophyll cells. In this tissue, sucrose transport was reported to be a facilitated diffusion. We have observed a facilitated diffusion of sucrose into vacuoles isolated from this tissue. However, no pH dependence was observed. Evidence is presented indicating that the pH dependence of sucrose uptake into vacuoles may be an artifact, reflecting tonoplast instability and survival of isolated vacuoles in different buffers. Apparently vacuoles do not withstand exposure to some commonly used buffers.     

Unique response of Cyanophyceae to copper

A study was made of the tolerance to Cu of 11 strains of Cyanophyceae and 7 strains of eukaryotes. These had all been tested within 6 months after isolation for their photosynthetic activity when exposed to Cu (Takamuraet al., 1989) and had repeatedly been subcultured in the medium without Cu for 2 years. Photosynthetic measurements were made in two ways: precultured in medium without Cu or precultured (for one subculture) in medium containing Cu (645 g 1^–1). The results were compared with those obtained within 6 months of isolation. The tolerance of the eukaryotes did not change significantly in any case, but most strains of Cyanophyceae lost their tolerance to Cu within a few subcultures in medium without Cu; however tolerance recovered following one subculture in medium containing an intermediate level of Cu. This rapid adaptation cannot be explained by a constitutive mutation.     

On the validity of the genusDactylococcopsis (Cyanophyceae)

Summary The genusDactylococcopsis Hansg. 1888 (Cyanophyceae) is based on the typeD. rupestris, which was later identified as a green algae. Most of the many species described later were also placed to other groups of algae. Several authors even doubted about the existence of the genus. As, however, some species of Cyanophyceae correspond to the original generic diagnosis, the name Dactylococcopsis Hansg. ex R. et F.Chod. 1925 has been proposed as a nomen conservandum, and a new type (D. smithii R. et F.Chod.) has been defined. Further speciesD. linearis Geitl. 1935 and D.Planctonica Teil. 1942 has been unambiguously described till now.     

Immunoelectron microscopic evidence for different compartments in the secretory vacuoles of the rat seminal vesicles

Summary Immunoelectron microscopy of the rat seminal vesicle was performed using specific antibodies to secretory proteins. Proteins were precipitated from rat seminal vesicle secretion and were separated by SDS—polyacrylamide gel electrophoresis. Among the great number of bands the two most prominent bands were selected and designated SVS II and IV. Their apparent molecular weights were 48 kDa and 16.5 kDa respectively. The bands were excised from the gels and used for antibody production in rabbits. The respective antisera were used for immunohistochemical studies both at the light and electron microscopic levels in the rat seminal vesicle and the different prostatic lobes in infantile, adult and castrated animals. A positive immunoreaction was observed in seminal vesicle and lateral prostatic epithelium of the intact adult rat, while it was lacking in prepubertal and castrated animals. The subcellular distribution of both proteins was clearly different: SVS II was exclusively confined to the electron dense core of the secretory vacuoles, while SVS IV was detected only in the clear halo surrounding the central granule. It is suggested that the spatial arrangement of both proteins in the seminal vesicle secretion vacuole reflects a particular functional significance of each of these proteins. These proteins may serve as a tool in the study of regulation of androgendependent protein synthesis.     

Three different types of organization of the vir regulon in group A streptococci

Summary The DNA of group A streptococci (GAS) encodes several important virulence factors such as the antiphagocytic M protein, the Ig-Fc-binding M-related proteins (FcrA-like and EnnX-like) and the complement factor-inactivating C5a peptidase. The corresponding genes emm, fcrA, ennX, and scpA, respectively, were assumed to be located close together in the GAS genome. Additionally, emm and scpA have been found to be under the positive, coordinate control of the virR locus, which led to the designation vir regulon for the corresponding genomic segment. In order to map the vir regulons of many GAS serotypes and to analyse any correlation between the organization of vir regulons and circumscribed heterogeneities within the emm, virR, and scpA genes, an approach using several distinct sets of polymerase chain reaction (PCR) experiments was chosen. By examination of the genomic DNA of 42 GAS isolates from 36 different M serotypes three patterns of vir regulon topography were found. The first, designated large vir regulon (LVR), consists of virR -fcrA(-like) emm - ennX(-like) - scpA. The second, designated small vir regulon (SVR), contains virR - emm- scpA, and the last, designated unusual vir regulon (UVR), resembles SVR but contains additional heterogeneous sequences between emm and scpA. The patterns correlate with heterogeneities at the 3 ends of the virR and scpA genes, with the M classification system and the occurrence of specific non-coding intervening sequences within the vir regulons. The potential impact of these patterns on models to account for generation of vir regulons is discussed.     

Competition between toxic and nontoxic Microcystis (Cyanophyceae) under different light and temperature conditions

正Dear Editor,In aquatic environments,cyanobacteria usually proliferate faster than other phytoplankton assemblages during warm seasons,particularly in eutrophic waters(Ma et al.,2015).Microcystis,a common cyanobacterial genus that potentially produces microcystins(MCs)and nontoxic strains,dominates in eutrophic freshwater bodies,and its biomass increases quickly during the warm period;these changes result in increased water turbidity and changes in light quality and quantity in the water column(Li and Li,2012).Additionally,     

A(beta) generation in autophagic vacuoles

Alzheimer's disease (AD) is the most common form of dementia among older people. It is characterized by the extracellular accumulation of beta-amyloid (Abeta) deposits called senile or neuritic plaques. Abeta is generated by the proteolytic cleavage of Abeta precursor protein (APP) by beta and gamma-secretases localized in the secretory and endocytic compartments. In this issue, Yu et al. (on p. 87) report a novel mechanism for the generation of Abeta peptides, which takes place in autophagic vacuoles (AVs) that accumulate in AD brains.     

A common mechanism for the mechanosensitive regulation of apoptosis in different cell types and for different mechanical stimuli

In all kinds of tissue cells are influenced by mechanical forces. In vivo fibroblasts are exposed to mechanical tension and endothelial cells are subjected directly to hemodynamic flow. It has been shown that disturbance of the mechanical stimulus leads to apoptosis by induction of an autocrine loop with thrombospondin-1 as ligand and an integrin/integrin associated protein (CD47) complex as receptor. In the present study the nature of the mechanical stimulus has been exchanged for these two cell types. If fibroblasts are subjected to laminar flow apoptosis decreases about 20-fold whereas turbulence leads to an significant increase compared with the static conditions. If endothelial cells grown on thin silicone membranes are exposed to permanent and pulsatile uniaxial strain, the cells are completely devoid of apoptosis. The thrombospondin-1 secretion as well as the expression of CD47 occurs exclusively under mechanical relaxation respectively turbulence. So different types of cells seem to share a common sense deciding whether a mechanical stimulus induces or suppresses apoptosis and use a common molecular machinery for the regulation of the process.     

A comparative study of the membrane structure in different types of muscle fibers in the frog

The muscle membrane of slow and fast fibers in cruralis and iliofibularis muscles and of intermediate fibers in submaxillaris muscle of the frog is studied in freeze-fracture replicas. A comparison of membrane folds, number, size and distribution of caveolae and of intramembrane particles (IMP) is given. In slow muscle fibers, the membrane folds are systematically present at the level of the I zone with a transversal continuity, whereas in fast and intermediate types the membrane folds are small and are randomly distributed. In slow muscle the caveolae are more numerous at the I zone than in the part corresponding to the center of the sarcomere. In fast muscle, small groups of caveolae form linear patterns, and in intermediate fibers the distribution is random. The number of caveolae in slow muscle fibers is two times more than in fast and intermediate fibers. The mean area of caveolae opening is largest in fast and smallest in slow muscle fibers. The number of IMP is significantly different in the three types of fibers, being highest in slow and lowest in intermediate fibers. The different pattern of folds in slow fibers may correspond to the different contractile properties of this fiber type. The presence of double the number of caveolae in slow fibers correlated to the less elaborate T system in this fiber type shows the possibility that slow fibers may be the result of an arrest during development for the performance of a different function. The difference in IMP density in the three muscle fiber types may be interpreted as the difference in their electrical properties.     

A study on the different types of spermatogonia in buffalo (Bubalus bubalis).

As a first step to understanding spermatogenesis in the buffalo bull the cytological details of different types of spermatogonia were determined in adult buffalo bulls. Morphological changes in the nuclear details were used as a basis for classifying the different types of spermatogonia. The type A spermatogonia had a spherical to ovoid nucleus with finely granulated chromatin, homogeneously dispersed in the nucleoplasm and having one to two nucleoli adhering to the nuclear membrane. The type A0 spermatogonia were characterized by nuclei containing moderately stained, finely granulated chromatin and a nucleolus attached to the nuclear envelope. The A1 type spermatogonia, on the other hand, have pale stained, finely granulated chromatin with the nucleolus adhering to the nuclear membrane. The nuclei of A2 type spermatogonia resembled those of type A1, but contained coarse granular chromatin dispersed in the pale nucleoplasm. The intermediate type of spermatogonia acquired a central position of the nucleolus, but the chromatin remained coarsely granulated and non-clumped. Three classes of type B (B1-B3) spermatogonia were determined on the degree of clumping of the chromatin and the central position of the nucleolus. The type B1 cells were characterized by nuclei containing a few flakes of lightly stained chromatin and a centrally located nucleolus. The type B2 cells showed comparatively more clumping of chromatin than type B1 spermatogonia, which was dispersed at random in the pale nucleoplasm and along the nuclear envelope. The type B3 spermatogonia demonstrated chromophilic chromatin dispersed in the slightly grey nucleoplasm and adhering along the nuclear membrane. Since there seems to be a succession of events following differentiation of type A1 spermatogonia till the last type B cell differentiates into resting primary spermatocytes, may intermediate stages between the presently described classes of type A (A0-A2) and type B (B1-B3) could also be located in sections of the seminiferous tubules.     

A surface roughness comparison of cartilage in different types of synovial joints

The naturally occurring structure of articular cartilage has proven to be an effective means for the facilitation of motion and load support in equine and other animal joints. For this reason, cartilage has been extensively studied for many years. Although the roughness of cartilage has been determined from atomic force microscopy (AFM) and other methods in multiple studies, a comparison of roughness to joint function has not be completed. It is hypothesized that various joint types with different motions and regimes of lubrication have altered demands on the articular surface that may affect cartilage surface properties. Micro- and nanoscale stylus profilometry was performed on the carpal cartilage harvested from 16 equine forelimbs. Eighty cartilage surface samples taken from three different functioning joint types (radiocarpal, midcarpal, and carpometacarpal) were measured by a Veeco Dektak 150 Stylus Surface Profilometer. The average surface roughness measurements were statistically different for each joint. This indicates that the structure of cartilage is adapted to, or worn by, its operating environment. Knowledge of cartilage micro- and nanoscale roughness will assist the future development and design of treatments for intra- articular substances or surfaces to preserve joint integrity and reduce limitations or loss of joint performance.     

Stream vegetation in different landscape types

A methodology is proposed for assessing the ecological value of streams in the catchment of the Moravská Dyje River. It is concluded that by using a wide range of parameters that a more objective assessment is achieved than if only one were used. The landscape of the catchment studied contains excessive amounts of nutrients and, in comparison to its natural state, has become too uniform.