Morphology and development of rhabdovirus-like particles inCuscuta odorata (Convolvulaceae) simultaneous infected with virus and mycoplasma-like organisms

Summary Electron microscopic examination ofCuscuta odorata, used for transmission trials, revealed mycoplasma-like organisms (MLO) as well as rhabdovirus-like particles, unknown toCuscuta. The virus infection is confined to certain phloem-parenchyma cells and a 1–2 cell thick layer of parenchyma cells with thickened walls surrounding the central cylinder. Virus particles, mostly bacilliform, could be detected mainly in the nucleus but also in the cytoplasm. They reach a length of 350–400 nm and a diameter of approximately 75 nm. Virus assembly takes place exclusively in the nucleus. Virus maturation occurs in membrane bound areas within the nucleus, which have no connection with the perinuclear space. Formation of nucleocapsids is always associated with a nuclear viroplasm. Envelopment of virus particles occurs in these membrane bound areas. Budding into the perinuclear space does not occur. Virus infection leads to degeneration and finally to death of the protoplast.Abbreviations cy cytoplasm - m membrane stacks - mt mitochondria - my mycoplasma-like organisms - nc nucleocapsid - ncp nucleocapsid particles - nf nuclear filaments - np nucleoplasm - nu nucleus - nvp nuclear viroplasm - oc obliterated cells - p plastid - pc passage cells - ph phloem - ps perinuclear space - spc strand of parenchymatous cells - v virus particle - x xylem     

Occurrence of Mycoplasma-like Organisms in Parenchyma Cells of Cuscuta odorata (Ruiz et Pav.)

In shoots of the dodder Cuscuta odorata mycoplasma-like organisms (MLO) were observed to occur in nearly all mature sieve elements. Their frequency within the sieve elements varied from a few organisms to high concentrations. In addition, MLO, were found in other cell types. By identifying these cells and investigating the location in the vascular tissue three different types of cells infected with MLO could be distinguished: (1) phloem parenchyma cells, (2) parenchyma cells separating the five vascular bundles of C. odorata and (3) cells in the outer region of the vascular system next to the cells looking like an endodermis. Within the cells of the types 2 and 3, MLO occurred in large numbers and at different morphological structures., Therefore, we assume that the MLO multiply in these cells.     

An in situ Freeze-Fracture Study of Spiroplasma citri and the Corn Stunt Spiroplasma

Spiroplasma citri and the corn stunt spiroplasma in sieve cells of Catharanthus roseus were investigated using freeze -fracture electron microscopy. Only the particle studded fracture faces of the plasmalemma could be exposed and not the surfaces of both the extraplasmatic and the plasmatic leaflet. The extraplasmatic fracture face (EF) shows a lower particle density than the plasmatic fracture face (PF). On the PF particle free areas could be observed, which are helically arranged in helical filaments. We suppose that the cytoplasmic fibrils, probably involved in motility processes and in maintaining the helical shape, underly the particle free area only.     

The evaluation of sixteen carcinogens in the rat using the micronucleus test.

Sixteen carcinogens were evaluated in rats for their ability to induce micronuclei. The direct acting agent, ethyl methanesulfonate and the procarcinogens/promutagens, cyclophosphamide and 4-nitroquinoline-1-oxide, induced dose-related increases in micronucleated polychromatophilic erythrocytes. Aflatoxin B1 also significantly increased the number of micronucleated polychromatophillic erythrocytes for 2 doses although no dose-response could be detected. Dimethylnitrosamine produced variable results. The remaining 11 compounds, 2-acetylaminofluorene, 4-aminobiphenyl, benzidine, diethylnitrosamine, dimethylbenzanthracene, 1,2-dimethylhydrazine, ethionine, ethyl carbamate, hexametapol, metronidazole, and beta-naphthylamine, failed to induce significantly increased numbers of micronuclei. The large number of false negative results obtained in the present investigations using the micronucleus test suggests that in vivo cytogenetic assays utilizing bone marrow may also lack the sensitivity needed to detect clastogenic effects of procarcinogens/promutagens which require tissue specific metabolic activation.     

Über die Pleomorphie von MLO in Catharanthus roseus (Vinca rosea)

About the pleomorphism of MLO in Catharanthus roseus (Vinca rosea) MLO of the flower greening (virescence)-type of Primula in the phloem of Catharanthus roseus (Vinca rosea) were fixed in two different ways. After prefixation with OsO4 they showed a diminished pleomorphic morphology, most MLO were spherical. With the fixation of KARNOVSKY (1965) and subsequent treatments with OsO4 and uranyl acetate, however, an extremely high pleomorphism was observed. Such pleomorphic MLO in single thin sections are probably the expression of a threedimensional network-like connection. The concentration of MLO in the sieve elements seems to influence the pleomorphism only insignificantly.     

Effect of neurotensin on pancreatic function in man

The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.     

Elektronenmikroskopische Untersuchungen der „Bakteroiden“ des Regenwurms Lumbricus terrestris L.

Ohne Zusammenfassung     

Effect of Metalaxyl on the incidence and severity of Pearl millet downy mildew disease in Northern Nigeria

Pearl millet downy mildew (DM) incidence, severity and yield losses of two pearl millet varieties (local and improved) due to the disease were determined in the field. Significant differences in the disease incidence and severity were recorded in the plots sown with metalaxyl-treated seeds and those sown with non-treated seeds, indicating the efficacy of the fungicide on the fungus. Yield losses due to non-treatment of seeds with metalaxyl was 40.88 and 45.39% in a local variety and 43.00 and 18.60% in an improved variety in the 2000 and 2001 cropping seasons respectively. Significant differences between plots sown with metalaxyl-treated and those sown with non-treated seeds were obtained for other yield components such as 1000-grains weight, panicle length and weight.