Establishment and maintenance of nuclear position during zoospore formation in allomyces macrogynus: roles of the cytoskeleton

The involvement of the microtubule (MT) and actin microfilament (MF) cytoskeletons in establishing nuclear positions during zoosporogenesis in Allomyces macrogynus was assessed using selective cytoskeletal disrupting treatments and documented with light microscopy. These experiments were coupled with low-speed centrifugation studies to determine the degree to which cytoskeletal elements anchor nuclear position. At the onset of zoospore formation, nuclei were positioned only in cortical cytoplasmic regions of the zoosporangia (ZS). Immunofluorescence microscopy revealed that MTs primarily emanated from centrosomal regions into the surrounding cytoplasm at this stage. During delimitation of the cytoplasm into individual uninucleate zoospores, nuclei migrated from cortical regions to become distributed throughout the cytoplasm. Coincident with nuclear migrations, MTs were primarily organized at and emanated from nuclear surfaces, forming extensive perinuclear arrays. Nuclear migrations were suppressed in ZS induced to sporulate in the presence of cytochalasin D, an actin MF inhibiting compound. Disruption of MTs with nocodazole did not block nuclear migrations, although resultant nuclear spacing was irregular. Centrifugation treatments of control and drug-treated ZS demonstrated that nuclear positions were stabilized by perinuclear MT arrays. The results indicate that nuclear motility in ZS of A. macrogynus is the result of an actin-based system while perinuclear MTs arrays function to establish and fix nuclear position during zoospore formation. Copyright 1998 Academic Press.     

Short repetitive sequences in green algal mitochondrial genomes: potential roles in mitochondrial genome evolution

Current data on green algal mitochondrial genomes suggest an unexpected dichotomy within the group with respect to genome structure, organization, and sequence affiliations. The present study suggests that there is a correlation between this dichotomy on one hand and the differences in the abundance, base composition, and distribution of short repetitive sequences we observed among green algal mitochondrial genomes on the other. It is conceivable that the accumulation of GC- rich short repeated sequences in the Chlamydomonas-like but not Prototheca-like mitochondrial genomes might have triggered evolutionary events responsible for the distinct series of evolutionary changes undergone by the two green algal mitochondrial lineages. The similarity in base composition, nucleotide sequence, abundance, and mode of organization we observed between the short repetitive sequences present in Chlamydomonas-like mitochondrial genomes on one hand and fungal and vertebrate homologs on the other might extend to some of the roles that the short repetitive sequences have been shown to have in the latter. Potential involvements we propose for the short repetitive sequences in the evolution of Chlamydomonas-like mitochondrial genomes include fragmentation and scrambling of the ribosomal-RNA-coding regions, extensive gene rearrangements, coding-region deletions, surrogate origins of replication, and chromosomal linearization.      

Accomplishments of the Trustees and laboratory staff of the Biological Stain Commission, 2002–2013

During the 12 years from 2002 to 2013, the Trustees and laboratory personnel of the Biological Stain Commission (BSC) can claim many accomplishments. These accomplishments are itemized under 11 categories: continuous publication of the official journal, Biotechnic & Histochemistry; production of four special issues of Biotechnic & Histochemistry devoted to specific dyes or stains; standardization of staining and dye purity; mechanisms of staining and prediction of dye behavior; publication of books or book chapters; effects of fixation and processing on staining; cancer research; immunohistochemistry; BSC Laboratory activities; miscellaneous publications; and administrative accomplishments.     

Glyoxal fixation: how it works and why it only occasionally needs antigen retrieval

Over the past 13 years, glyoxal has become the leading alternative to formaldehyde as a histological fixative because of its low inhalation risk, faster reaction rate and selective control over crosslinking. The latter attribute is especially important, because most of the difficulties relating to use of formaldehyde-fixed specimens for immunohistochemistry stem from its aggressive crosslinking behavior. With suitable catalysts or other reaction accelerators, glyoxal forms 2-carbon adducts with nearly all end groups in proteins and carbohydrates, leaving most of them unimpaired for subsequent immunohistochemical demonstration. Only arginine is seriously impaired by the formation of imidazoles, which is the basis for the well known arginine blockade method using glyoxal. A special glyoxal-specific antigen retrieval method using high pH and high temperature effectively reverses the blockade and restores immunoreactivity. Other methods for antigen retrieval are rarely beneficial and in most cases damage the specimen. Special stains work well, except silver methods for Helicobacter pylori. Routine hematoxylin and eosin preparations exhibit clarity and cellular detail rarely seen with formaldehyde.     

Poxvirus-induced immunostimulating effects on porcine leukocytes

The prophylactic application of inactivated parapox ovis viruses (Baypamun; Bayer AG, Leverkusen, Germany) has been shown to reduce efficiently the outbreak of stress-mediated diseases in different species. However, little is known about the basic mechanism behind this observed stimulatory property. We therefore tested eight inactivated poxvirus strains belonging to three different genera (Orthopoxvirus, Avipoxvirus, and Parapoxvirus) for their capacity to activate cells of the porcine innate and specific immune systems in vitro. The results indicated that poxviruses failed to induce increased phagocytosis, oxidative burst, or natural killer cell activity in swine. In contrast, enhanced release of interleukin-2, alpha interferon, and gamma interferon, as well as strong proliferation, could be measured. Flow cytometric analyses and cell sorting experiments identified T-helper cells as the main target responding to inactivated poxviruses: the activated cells had a CD4(high) CD25(+) major histocompatibility complex type II-positive phenotype and were the major source of secreted cytokines. Together, the results demonstrated that all tested poxviruses possessed immunostimulating capacity. These in vitro poxvirus-induced effects may be responsible at least in part for the in vivo immunostimulating capacity of inactivated poxviruses.     

Glycosylation of the thrombin-like serine protease ancrod fromAgkistrodon rhodostoma venom. Oligosaccharide substitution pattern at eachN-glycosylation site

In a previous study, we determined the structures of the glycans present in ancrod, a thrombin-like serine protease from the venom of the Malayan pit viperAgkistrodon rhodostoma (Pfeifferet al. (1992)Eur J Biochem 205:961–78). In order to allocate the various carbohydrate chains to distinctN-glycosylation sites of the molecule, we have now isolated individual glycopeptides. Peptide moieties were identified after deglycosylation with peptide-N ⁴-(N-acetyl--glucosaminyl)asparagine amidase F by amino acid analysis and sequencing. Liberated oligosaccharides were assigned to the previously deduced carbohydrate structures by high performance liquid chromatography. Although only quantitative differences were observed, the results indicate that each glycosylation site of ancrod carries its characteristic oligosaccharide pattern. Furthermore, all potential sites were shown to be substituted by carbohydrates.Abbreviations HPAE-HPLC high pH anion exchange HPLC - RP-HPLC reversed phase HPLC - PNGase-F peptide-N ⁴-(N-acetyl--glucosaminyl)asparagine amidase F - PAD pulsed amperometric detection.     

Vinculin and 36 kDa protein are not tyrosine-phosphorylated in Rous sarcoma virus infected cells which have been treated with interferon

The expression of membrane-associated transformation-specific parameters was analyzed in de novo Rous sarcoma virus (strain SR-RSV-D) infected chicken embryo fibroblasts pretreated with homologous interferon. Cellular morphology, hexose transport, microfilament organization, and tyrosine-phosphate content of two primary substrates of the transformation-generating viral kinase, pp60src, were found indistinguishable from non-infected controls. These observations support the hypothesis that vinculin and possibly 36 kDa protein are involved in microfilament organization and that tyrosine-phosphorylation of these structural proteins is a prerequisite for the rearrangement of microfilaments during transformation. In de novo infection, interferon pretreatment reduces viral protein synthesis and pp60src activity as compared to non-treated, SR-RSV-D infected cells. However, the phosphotyrosine content of total cellular proteins as measured under steady state conditions is as high in interferon-pretreated as in nontreated transformed cells.     

Sensitivity of ortho- and paramyxovirus replication to human interferon α

Replication of the influenza virus strains Influenza Ao/WSN (H0N1), fowl plague (Hav1N1) and B-Lee/40 (ATCC) and the paramyxovirus, New Castle disease virus (Victoria) are highly sensitive to human interfereon type in Madin Darby bovine kidney cells. Pretreatment of cells with human interferon type resulted in protection of the cells against viral cytopathic effect. The inhibition of the orthomyxovirus strains used in this study and New Castle disease virus replication is mediated by an inhibition of viral protein synthesis. Residual WSN virus particles released from interferon treated cells showed the same structural protein pattern as virus particles isolated from control cells. Glycosylation of the viral structural components appeared to be unaffected by interferon.