Rhodamine 123 as a vital stain for mitochondria of plant cells

Abstract. Rhodamine 123 (Rh 123), a relatively new mitochondrial marker, little used in the study of plant cells, was tested on excized leaves of Elodea canadensis Michx. and on suspension-cultured cells of Ranunculus serbicus Vis. In both preparations, the dye accumulated rapidly and selectively in the mitochondria whose number, morphology and cell distribution could be easily observed. In the presence of Rh 123, cytoplasmic movements could also be perceived and the spatial arrangement of the mitochondria with respect to that of the auto-fluorescent chloroplasts was studied in connection with a normal or altered cytoskeletal framework. The specific uptake of Rh 123 by the organdies seemed to be potential-dependent since it was influenced by cations, ionophores and inhibitors of electron transport. Short exposures to the stain were practically non-toxic, whereas prolonged treatments (6–20 h) provoked specific alterations in structure of the mitochondria. The data reported here indicate that Rh 123 may be an excellent vital stain to study the morphology, function and dynamics of the mitochondria in living plant cells.     

Complexity and tissue specificity of the mitochondrial respiratory chain

There is a renewed interest in the structure and functioning of the mitochondrial respiratory chain with the realization that a number of genetic disorders result from defects in mitochondrial electron transfer. These so-called mitochondrial myopathies include diseases of muscle, heart, and brain. The respiratory chain can be fractionated into four large multipeptide complexes, an NADH ubiquinone reductase (complex I), succinate ubiquinone reductase (complex II), ubiquinol oxidoreductase (complex III), and cytochromec oxidase (complex IV). Mitochondrial myopathies involving each of these complexes have been described. This review summarizes compositional and structural data on the respiratory chain proteins and describes the arrangement of these complexes in the mitochondrial inner membrane. This biochemical information is provided as a framework for the diagnosis and molecular characterization of mitochondrial diseases.     

Effect of chloramphenicol and lincomycin on chloroplast DNA amplification in greening pea leaves

The light-induced increase in chloroplast DNA was not inhibited by two inhibitors of protein synthesis on 70S polysomes, chloramphenicol and lincomycin, in greening pea leaves. The changes in chloroplast DNA were observed by fluorescence microscopy and measured by hybridization to specific cloned probes. The results suggest that the light-induced increase in chloroplast DNA proceeds without de novo protein synthesis in the chloroplast, in agreement with those with mutants and cultured leaf tissue.     

Levels and Distribution of the Calcium-Modulated Proteins S100 and Calmodulin in Rat C6 Glioma Cells

To understand better the mechanisms involved in the transduction of a calcium signal into an intracellular response via multiple calcium-modulated proteins, we have examined the calcium-modulated proteins, S100 and calmodulin, and their intracellular targets in rat C6 glioma cells. Subconfluent, confluent, and postconfluent C6 cells contain predominantly, if not exclusively, the S100 beta polypeptide. The level of S100 beta in C6 cells increases approximately 20-fold from subconfluency to postconfluency whereas the level of calmodulin increases only about two-fold. The subcellular distribution of S100 beta and calmodulin in mitotic cells is similar. However, the subcellular distribution of these proteins in interphase cells is different and appears to change with cell density. Gel overlay analysis demonstrated that the S100- and calmodulin-binding protein profiles are significantly different and that some of the binding proteins appear to change in intensity with cell density. These data demonstrate that S100 beta is the predominant S100 polypeptide in C6 cells and suggest that changes in S100 beta and S100 beta-binding proteins may be involved in regulating S100-mediated intracellular processes in C6 cells. Our studies also suggest that the levels of S100 and calmodulin may be differentially regulated in C6 cells.     

Meloidogyne mayaguensis n. sp. (Meloidogynidae), a Root-knot Nematode from Puerto Rico

Meloidogyne mayaguensis n. sp. is described and illustrated from specimens obtained from galled roots of eggplant, Solanum melongena L., from Puerto Rico. The perineal pattern of females is round to ovoid with fine, widely spaced striae. It has occasional breaks of striation laterally and a circular tail tip area lacking striae. The stylet, 15.8 μm long, has reniform knobs that merge gradually with the stylet shaft. Males have a high, rectangular, smooth head region, not set off from the body contour. The labial disc is continuous with the medial lips which do not slope posteriorly. The styler, 22.9 μm long, has large rounded backward sloping knobs; the shaft is of uneven diameter. Mean body length of second-stage juveniles is 453.6 μm. The truncate head region is not annulated, and the rounded, slightly raised labial disc and the crescentic medial lips form dumbbell-shaped lip structures. The stylet, 11.6 μm long, has rounded, posteriorly sloping knobs. The slender tail, 54.4 μm long, gradually tapers to a bluntly pointed tip. Tomato, tobacco, pepper, and watermelon are good hosts; cotton and peanut are not hosts. M. mayaguensis n. sp. reproduces by mitotic parthenogenesis and has a somatic chromosome number of 2n = 44-45. The enzyme patterns are unique among Meloidogyne species.     

Tylenchulus graminis n. sp. and T. palustris n. sp. (Tylenchulidae), from Native Flora of Florida,with Notes on T. semipenetrans and T. furcus

Tylenchulus graminis n. sp. and T. palustris n. sp. are described and illustrated from broomsedge (Andropogon virginicus L.) and pop ash (Fraxinus caroliniana Mill.), respectively. T. graminis resembles T. furcus in having a distinct anus, but T. graminis second-stage juveniles (J2) do not have a bifid tail. T. semipenetrans does not have a perceptible anus. The mature female of T. graminis has a mucronate pointed terminus while T. semipenetrans has a smooth and round terminus. T. graminis males have wider stylet knobs and basal bulb and a longer tail than T. semipenetrans males. T. graminis J2 have a longer posterior body portion (without large fat globules) than T. semipenetrans J2. T. palustris resembles T. semipenetrans in having an undetectable anus but differs by the short and conoid mature female postvulval section. The male of T. palustris has larger stylet knobs and basal bulb than those of T. semipenetrans and a bluntly rounded tail terminus, which is tapered in T. semipenetrans. T. palustris differs from T. furcus and T. graminis in having an undetectable anus, by the conoid postvulval section of mature females, by the shorter and rounded tail of males, and the shorter J2 posterior body section without large fat globules. T. graminis and T. palustris are parasites of indigenous flora of Florida.     

The presence of ring formed actin filaments in plant cells

Summary Ring formed actin filaments were observed in tobacco BY-2 cells. The change of this structure during culture was followed by fluorescence microscopy.     

Intramolecular localization of epitopes within an oligomeric protein by immunoelectron microscopy and image processing

Three epitopes have been localized by immunoelectron microscopy on subunit Aa6 of the 4 x 6-meric hemocyanin of the scorpion Androctonus australis. Soluble immunocomplexes composed of monoclonal antibodies and of native hemocyanin were purified, negatively stained with uranyle acetate by the single-layer technique, and examined under the electron microscope (EM). The molecule images were digitized, aligned, and submitted to correspondence analysis according to the method of Van Heel and Frank (Ultramicroscopy 6:187-194, 1981). A high-precision localization of the attachment point of the Fab arm to the antigen was achieved through a careful analysis of the average images. This method easily allowed the discrimination of epitopes located in different domains (Mr 20 kDa) of the same subunit. Nonoverlapping epitopes located in the same structural domain of subunit Aa6 could be distinguished by the stain exclusion patterns of their Fab arms. The method is general and may be used for epitope mapping in any antigen producing definite EM views.     

Cytological aspects of in vitro androgenesis in wheat (Triticum aestivum L.) using fluorescent microscopy

Summary Two winter wheat genotypes (Diószegi 200 and Mv 15) were compared for their in vitro androgenic capacity. On average, the induction frequency of embryogenic structures was 71.7% in Diószegi 200 and only 4.3% in Mv 15. The haploid induction ability of the two genotypes differed considerably, with Diószegi 200 being much higher. The difference in the in vitro inductability of the microspores may result from genetic differences which are manifested in the survival rate of the microspores during the culture period and their adaptability to in vitro conditions. Special DNA fluorochrornes were suitable for studying the different pathways of in vitro androgenesis. Our data indicate that the repeated equal divisions of the microspore nucleus might lead to pollen embryo formation, and subsequent divisions of the vegetative portion of the pollen grain after the first asymmetric microspore mitosis can result in pollen callus formation.     

鲤鳃表面结构扫描电镜研究

鲤的鳃丝表面显示了由三边形一六边形不等的表皮细胞,呈现出各种图案式的结构。