Ultrastructural pathology of leaf cells of ryegrass (Lolium multiflorum) infected with ryegrass mosaic virus.

Ryegrass mosaic virus particles and virus induced lamellar inclusions were found in mesophyll and epidermal cells of virus infected ryegrass leaves. The lamellar inclusions were occasionally found in phloem cells also. Virus particles occurred in cytoplasm, inside plasmodesmata and often in membrane bound sacs embedded in a matrix between plasmalemma and cell wall at or near plasmodesmata. Electron dense plugs protruding from plasmodesmata, finger-like cell wall outgrowths and cell wall deposits usually at plasmodesmata were also observed. Cytopathological changes in organelles in infected cells included dense deposits in the cisternae of endosplasmic reticulum and Golgi apparatus, mitochondria with electron-dense or opaque matrix, proliferating cristae and deteriorating unit membrane; and disintegrating chloroplasts.     

Ultrastructure of parenchymal leaf cells of different soybean varieties systemically infected with soybean mosaic virus

A comparative study was made of the ultrastructure of parenchyma leaf cells of different soybean varieties systemically infected with soybean mosaic virus (SMV). It has been shown that virus accumulation and formation of virus-specific cylindrical inclusions (CIs) occur in the infected cells, in addition to intracellular changes showing stimulation of lytic processes, such as activation of smooth endoplasmic reticulum and Golgi apparatus, formation of cytoplasmic vacuoles, cytosegresomes, myelin-like bodies, different disturbances in the structure of cell organelles. Many infected cells demonstrated microbodies with invagination in which cylindrical inclusions were often found showing signs of destruction. It is suggested that such microbodies possess autophagic activity towards CIs. A possible relation of the observed virus-induced ultrastructural cell changes with the degree of SMV affection of investigated varieties is discussed     

Cytopathology of soybean tissue culture cells infected with southern bean mosaic virus

Summary Virus distribution patterns and ultrastructural changes in soybean callus cells after infection with the type, or bean strain, of southern bean mosaic virus (SBMV) were observed. Calli grown in liquid Linsmaier and Skoog (LS) medium were inoculated with SBMV and incubated in fresh LS medium. Calli were sampled at 5, 10, 15, and 20 d after inoculation and examined by transmission electron microscopy. Five days after inoculation, viruslike particles (VLP) measuring 22 to 27 nm in d were observed in the cytoplasm. The particles formed loose aggregates with some tendency to associate in regular patterns. By the 10th d after infection, particles were observed in the vacuoles in similar loose arrangements. Viruslike particles were readily identified in vacuoles because of the absence of ribosomes. Crystalline aggregations of VLP were found from Day 10 to Day 20 in the cytoplasm only. Five days after inoculation particles similar to the VLP observed in the cytoplasm also were present in nuclei. Other cytopathic effects were noted, particularly several types of inclusion bodies. These observations differ considerably from reports of the type strain in intact bean plant tissues in the frequent occurrence of VLP in vacuoles and virus crystals in cytoplasm of soybean callus infected with the same strain of virus. Michigan Agricultural Experiment Station Journal Article Number 10020. We thank Dr. Karen Baker for useful suggestions.     

Short-lived infected cells support virus replication in sooty mangabeys naturally infected with simian immunodeficiency virus: implications for AIDS pathogenesis

Sooty mangabeys (SMs) naturally infected with simian immunodeficiency virus (SIV) do not develop AIDS despite high levels of virus replication. At present, the mechanisms underlying this disease resistance are poorly understood. Here we tested the hypothesis that SIV-infected SMs avoid immunodeficiency as a result of virus replication occurring in infected cells that live significantly longer than human immunodeficiency virus (HIV)-infected human cells. To this end, we treated six SIV-infected SMs with potent antiretroviral therapy (ART) and longitudinally measured the decline in plasma viremia. We applied the same mathematical models used in HIV-infected individuals and observed that SMs naturally infected with SIV also present a two-phase decay of viremia following ART, with the bulk (92 to 99%) of virus replication sustained by short-lived cells (average life span, 1.06 days), and only 1 to 8% occurring in longer-lived cells. In addition, we observed that ART had a limited impact on CD4(+) T cells and the prevailing level of T-cell activation and proliferation in SIV-infected SMs. Collectively, these results suggest that in SIV-infected SMs, similar to HIV type 1-infected humans, short-lived activated CD4(+) T cells, rather than macrophages, are the main source of virus production. These findings indicate that a short in vivo life span of infected cells is a common feature of both pathogenic and nonpathogenic primate lentivirus infections and support a model for AIDS pathogenesis whereby the direct killing of infected cells by HIV is not the main determinant of disease progression.     

Electron microscopy of cocksfoot streak virus and its differentiation from ryegrass mosaic virus in naturally infected Dactylis glomerata plants

The length and rigidity of some cocksfoot streak virus (CSV) particles were greater (1) in ammonium molybdate negative stain at pH 5 than at pH 8 and (2) when magnesium was added either directly to extracted plant sap or indirectly via increased plant uptake. Most CSV particles were flexuous and 750–760 run long in low concentrations of magnesium but many were rigid and 800–810 nm long in higher concentrations. In sodium phosphotungstate and ammonium molybdate at pH 5, frequency distributions of particle lengths from cocksfoot plants infected with both CSV and ryegrass mosaic virus (RMV) produced two modal peaks, one at less than 700 nm (RMV) and the other at more than 750 nm (CSV); in ammonium molybdate at pH 8, however, only one peak (at 725 nm) was resolved. In ultrathin sections of CSV-infected cocksfoot leaves, virus-like particles were scattered or in bundles within the cytoplasm, or aligned in aggregates near the tonoplast. Some cells contained pinwheel inclusions, often with attached or associated laminar plates and occasionally with scroll-like or circular tubes. These CSV-induced inclusions were easily distinguished from those induced by RMV, even when both types occurred in the same cell.     

ICR 小鼠自然感染小鼠肝炎病毒后抗原抗体的变化

目的：了解小鼠肝炎病毒（ MHV）污染的设施内,ICR小鼠自然感染后MHV抗原抗体存在情况。方法选择50只ICR小鼠,通过更换“脏垫料”的方式进行饲养,分别在实验第2,4,8,14,21,28,35,42,56和84天各剖杀动物5只,采集血清、盲肠内容物、粪便、肝脏以及肺脏检测抗原抗体分布情况。结果实验开始第2天,肺脏中检出小鼠肝炎病毒,检出率为20％（1/5）,第4天开始,肝脏、肺部、盲肠以及粪便中均可检出小鼠肝炎病毒;84天后,肺脏、盲肠、粪便和肝脏阳性检出率降为0。实验第8天,血清中抗体检出阳性,阳性率为100％（5/5）,直至第84天实验结束,抗体阳性率仍维持在100％（5/5）。结论血清学方法可作为日常监督主要诊断方法,而抗原检测方法只能应用于早期诊断。     

Ultrastructural changes in naturally aged Pinus pinea seeds

The decline of germination observed after storage of Pinus pinea L. seeds up to 35 years at room temperature was accompanied by an increase in their ability to leak reducing sugars, probably as a consequence of membrane alterations due to senescence. Results of studies of the cell ultrastructure of viable and non-viable seeds before and after imbibition indicate that such is the case. Noticeable changes occurred in the ultrastructure of endosperm and embryo cells with germinability loss, even in the unimbibed condition. The main alterations were spherosome coalescence, plasmalemma separation from the cell wall and chromatin aggregation.     

Primary pathological changes in cells infected with tick-borne encephalitis virus]

Synthesis and the content of RNA and protein in cells of the pig embryo kidneys infected with tick--borne encephalitis virus were studied by means of autoradiography and cytophotometry. Acceleration of synthesis and accumulation of RNA (in cellular structures) were estimated as over 125--200% of the initial level followed by a decrease in 12 hr when the virus release from the cells occurred. By the 2nd and 6--8th hr of infection (in the period of synthesis of early and late virus material), two peaks of protein contents over 123--131% were observed. The RNA and protein shifts are well correlated with the virus reproduction stages.     

Electroporation-mediated infection of tobacco leaf protoplasts with tobacco mosaic virus RNA and cucumber mosaic virus RNA

Conditions were established for the introduction of both tobacco mosaic virus (TMV) and cucumber mosaic virus (CMV) RNAs into tobacco mesophyll protoplasts by electroporation. The proportion of infected protoplasts was quantified by staining with viral coat protein-specific antibodies conjugated to fluorescein isothiocyanate. Approximately 30–40% of the protoplasts survived electroporation. Under optimal conditions, up to 75% of these were infected with TMV-RNA. Successful infection was demonstrated in 19 out of 20 experiments. Optimal infection was achieved with several direct current pulses of 90 sec at a field strength of 5 to 10 kV/cm. Changing the position of the protoplasts within the chamber between electric pulses was essential for achievement of high rates of infection. Optimal viral RNA concentration was about 10 g/ml in a solution of 0.5 M mannitol without buffer salts.