RESUMEN
Light and transmission electron microscopy were used to investigate the life cycle and ultrastructure of an undescribed isolate of Pasteuria that parasitizes the soybean cyst nematode, Heterodera glycines. Studies also were conducted to determine the host specificity of Pasteuria. The endospores that attached to the cuticle of second-stage juveniles (J2) of H. glycines in soil did not germinate until the encumbered nematodes invaded soybean roots. Thereafter, the bacterium developed and completed its life cycle only in females. The stages of endosporogenesis were typical of Pasteuria spp. The mature endospore, like that of P. nishizawae, the only other Pasteuria known to infect H. glycines, produces an epicortical layer that completely surrounds the cortex, an outer spore coat that tapers progressively from the top to the base of the central body, and a double basal adhesion layer. However, subtle differences exist between the Pasteuria from North America and P. nishizawae with regard to size of the central body, nature and function of the mesosomes observed in the earlier stages of endosporogenesis, and appearance of the fibers lining the basal adhesion layer and the exosporium of the mature endospore. Endospores of the North American Pasteuria attached to J2 of H. schachtii, H. trifolii, and H. lespedezae but not to Meloidogyne arenaria race 1, Tylenchorhynchus nudus, and Labronema sp. Results from this study indicate that the North American Pasteuria is more similar to P. nishizawae than to any other known member of the genus. Additional evidence from comparative analysis of 16S rDNA sequences is needed to clarify whether these two Pasteuria belong to the same species.
RESUMEN
ABSTRACT Barley yellow dwarf virus strain PAV (BYDV-PAV) RNA and the 17-kDa protein were localized in BYDV-PAV-infected oat cells using in situ hybridization and in situ immunolocalization assays, respectively. The in situ hybridization assay showed labeling of filamentous material in the nucleus, cytoplasm, and virus-induced vesicles with both sense and antisense nucleic acid probes, suggesting that the filamentous material found in BYDV-PAV-infected cells contains viral RNA. BYDV-PAV negative-strand RNA was detected before virus particles were observed, which indicates that RNA replication is initiated before synthesis of viral coat protein in the cytoplasm. The 17-kDa protein was associated with filamentous material in the cytoplasm, nucleus, and virus-induced vesicles. The labeling densities observed using antibodies against the 17-kDa protein were similar in the nucleus and cytoplasm. No labeling of the 17-kDa protein was observed in plasmodesmata, but filaments in the nuclear pores occasionally were labeled. Since BYDV-PAV RNA and 17-kDa protein colocalized within infected cells, it is possible that single-stranded viral RNA is always associated with the 17-kDa protein in vivo. The 17-kDa protein may be required for viral nucleic acid filaments to traverse the nuclear membrane or other membrane systems.
RESUMEN
The present study investigated the effect of phospholipid transfer protein (PLTP) on transformation of discoidal HDL (d-HDL) to vesicular structures by using primarily KBr density gradient centrifugation, non-denaturing gradient gel electrophoresis, and electron microscopy. The incubation of reconstituted d-HDL preparations containing apo-AI with PLTP resulted in the formation of vesicular structures differing in hydrated densities and sizes. The extents of transformation were dependent upon PLTP concentrations and incubation times. Substantial transformations occurred, even with plasma concentrations of PLTP, within 4 h of incubation at 37 degrees C. After 8 h of incubation, almost 80% of d-HDL was converted to vesicular structures with a hydrated density of 1.07 g ml-1. The d-HDL-vesicle transformation appeared to be triggered by the PLTP-mediated displacement of apo-AI. This apo-AI displacement might have led to the fusion of transiently produced apo-AI deficient particles, producing thermodynamically stable vesicular structures. The cross-linking of apo-AI in d-HDL almost completely prevented d-HDL-vesicle transformation. The addition of free apo-AI to the PLTP/d-HDL incubation mixtures also greatly reduced the transformation. The conversion of smaller vesicles of density 1.07 g ml-1 to larger vesicles of density 1.05 g ml-1 also seemed to have been affected by PLTP-mediated apo-AI displacement. We described the possible implications of the transformation of d-HDL into vesicular structures in lipid and lipoprotein transport processes under physiological and pathological conditions.
Asunto(s)
Proteínas Portadoras/metabolismo , Lipoproteínas HDL/química , Proteínas de la Membrana/metabolismo , Proteínas de Transferencia de Fosfolípidos , Apolipoproteína A-I/metabolismo , Centrifugación por Gradiente de Densidad , Reactivos de Enlaces Cruzados/metabolismo , Electroforesis en Gel de Poliacrilamida , Humanos , Lipoproteínas HDL/metabolismo , Lipoproteínas HDL/ultraestructura , Microscopía Electrónica , Tamaño de la Partícula , Proteolípidos/química , Proteolípidos/ultraestructura , Succinimidas/metabolismoRESUMEN
Epiphyses of the femura from 8-week-old broiler chicks were examined for morphology using scanning electron microscopy and for elemental composition using energy dispersive x-ray microanalysis. Birds between the ages of 4 and 8 weeks were subjected to either 25 or 35 C environments and given tap or carbonated drinking water. The morphological appearance of the epiphyses was affected by the kind of drinking water but not the thermal environment. Elemental constituents, however, were affected by both environmental temperature and drinking water.