Plant virus infection development as affected by heavy metal stress

The work was focused on the investigation of possible dependencies between the development of viral infection in plants and the presence of high heavy metal concentrations in soil. Field experiments have been conducted in order to study the development of systemic tobacco mosaic virus (TMV) infection in Lycopersicon esculentum L. cv. Miliana plants under effect of separate salts of heavy metals Cu, Zn and Pb deposited in soil. As it is shown, simultaneous effect of viral infection and heavy metals in tenfold maximum permissible concentration leads to decrease of total chlorophyll content in experiment plants mainly due to the degradation of chlorophyll a. The reduction of chlorophyll concentration under the combined influence of both stress factors was more serious comparing to the separate effect of every single factor. Plants' treatment with toxic concentrations of lead and zinc leaded to slight delay in the development of systemic TMV infection together with more than twofold increase of virus content in plants that may be an evidence of synergism between these heavy metal's and virus' effects. Contrary, copper although decreased total chlorophyll content but showed protective properties and significantly reduced amount of virus in plants.     

High-Speed Recording of Vacuum Arc Discharge Images in the Optical Range

Plasma Physics Reports - Switching of a short vacuum gap with an auxiliary discharge over the surface of a dielectric has been studied via high-speed recording of images of discharge plasma...     

Ultrastructure and identification of giant muscular cells in certain proboscis worms of the family Polymorphidae

The results of ultrastructure study of the giant muscular cells located at the base of proboscis receptacle are given. Peculiarities of cell ultrastructure suggest the presence of the "nuclear secretion" in these cells. By their location and morphological features they are identical to the retinacular cells formerly described by some authors.     

Subsurface Musculature of Spiny-Headed Worms (Acanthocephala) and Its Role in Formation of Intercellular Matrix

Published and original data on the organization and ultrastructure of the subsurface (cutaneous) musculature, basal plate, and intercellular matrix of acanthocephalans (spiny-headed worms) were analyzed and reviewed. Similar to flatworms, the basal plate and the intercellular matrix of acanthocephalans proved to be derived from the cutaneous musculature. Specific structure of acanthocephalan cutaneous muscles (the lacunar system, nuclear secretion, specific block arrangement of myofilaments, etc.) allows us to consider it as a special kind of smooth muscle tissue.     

Extramedullary hematopoiesis in a case of benign mixed mammary tumor in a female dog: cytological and histopathological assessment

Backgroud  

Extramedullary hematopoiesis (EMH) is defined as the presence of hematopoietic stem cells such as erythroid and myeloid lineage plus megakaryocytes in extramedullary sites like liver, spleen and lymph nodes and is usually associated with either bone marrow or hematological disorders. Mammary EMH is a rare condition either in human and veterinary medicine and can be associated with benign mixed mammary tumors, similarly to that described in this case.     

Experimental evidence of the defense role of the exocyst in the metacestode of <Emphasis Type="Italic">Microsomacanthus lari</Emphasis> Belogurov et Kulikov,in Spasskaja, 1966 (Cestoda: Hymenolepididae)

The interaction of intermediate host (Eogammarus tiuschovi) cells with the cysticercoid of Microsomacanthus lari of the cyclocercus type was examined for the case of damage of the noncellular exocyst surrounding it. Massive penetration of the host cells, supposedly haemocytes characterized by intensive secretion, into the exocyst was observed even during the first several minutes of the experiment. Large accumulations of the product of secretion (fibrous material) were concentrated in the distal areas of the endocyst glycocalix and the microvillar layer of the cysticercoid tail appendage. The results provide evidence for the defensive role of the exocyst of M. lari in the cellular response of an intermediate host organism to invasion.     

Effects of mechanical stretching of embryonic tissues on axial structure formation in <Emphasis Type="Italic">Xenopus laevis</Emphasis>

Effect of mechanical stretch on the differentiation of axial anlages and Chordin gene expression was studied in sandwich explants prepared from embryonic tissues of Xenopus laevis at the early gastrula stage in two variants: with dissected or intact dorso-medial region. In the first case, convergent cell movements were suppressed and properly organized axial organs (notochord and somites) were almost completely absent. However, they developed if the explants of such type were artificially stretched in the ventro-dorsal direction. In this case, axial organs elongated in the line of stretching, that is in the direction vertical to their normal orientation. Segmented mesoderm was always in contact with the chord anlage. In situ hybridization revealed that the area of Chordin gene expression was also extended in the direction of stretching. PCR showed that Chordin gene expression in stretched explants with disrupted dorso-medial region was statistically at the same level as in the explants with intact dorso-medial region. At the same time, the corresponding gene expression in unstretched explants with disrupted dorso-medial region was statistically higher. The obtained data indicate that mechanical stretch and associated cell movements are a necessary and sufficient condition for the formation of proper histological structure of axial organs and regulation of Chordin gene expression.     

Study of hydrodynamic instabilities of a Z-pinch during a high-current explosion of a thin wire

Results are presented from laboratory and numerical experiments on the influence of the core and associated hydrodynamic instabilities on the high-current implosion of a plasma of exploding metal wires. The experimental investigation of the discharge structure was carried out using the multiframe X-ray backlighting technique with high temporal and spatial resolution (<1 ns and 1 μm, respectively); X-pinches were used as small-sized radiation sources. The implosion of a dense Z-pinch was modeled by the free-point method with the use of a two-dimensional radiative MHD code. The onset of instabilities at the corona-core boundary was modeled by the NUTCY Eulerian code. The results show that hydrodynamic processes in the core are primarily responsible for the formation of small bright regions observed in X-rays. After the reflection of a shock wave from the axis, the rapid onset of hydrodynamic instabilities can occur at the corona-core boundary. __________ Translated from Fizika Plazmy, Vol. 26, No. 9, 2000, pp. 797–810. Original Russian Text Copyright ? 2000 by Gus’kov, Ivanenkov, Mingaleev, Nikishin, Pikuz, Rozanov, Stepniewski, Tishkin, Hammer, Shelkovenko.