Extensive changes in cytokeratin expression patterns in pathologically affected human gingiva

The stratified squamous epithelium of the oral gingiva and the hard palate is characterized by a tissue architecture and a cytoskeletal composition similar to, although not identical with, that of the epidermis and fundamentally different from that of the adjacent non-masticatory oral mucosa. Using immunocytochemistry with antibodies specific for individual cytokeratins, in situ hybridization and Northern blots of RNA with riboprobes specific for individual cytokeratin mRNAs, and gel electrophoresis of cytoskeletal proteins of microdissected biopsy tissue samples, we show changes in the pattern of expression of cytokeratins and their corresponding mRNAs in pathologically altered oral gingiva. Besides a frequently, although not consistently, observed increase in the number of cells producing cytokeratins 4 and 13 (which are normally found as abundant components in the sulcular epithelium and the alveolar mucosa but not in the oral gingiva) and a reduction in the number of cells producing cytokeratins 1, 10 and 11, the most extensive change was noted for cytokeratin 19, a frequent cytokeratin in diverse one-layered and complex epithelia. While in normal oral gingiva cytokeratin 19 is restricted to certain, sparsely scattered cells of --or near--the basal cell layer, probably neuroendocrine (Merkel) cells, in altered tissue of inflamed samples it can appear in larger regions of the basal cell layer(s) and, in apparently more advanced stages, also in a variable number of suprabasal cells. Specifically, our in situ hybridization experiments show that this altered suprabasal cytokeratin 19 expression is more extended at the mRNA than at the protein level, indicating that cytokeratin 19 mRNA synthesis may be a relatively early event during the alteration. These changes in cytokeratin expression under an external pathological influence are discussed in relation to other factors known to contribute to the expression of certain cytokeratins and with respect to changes occurring during dysplasia and malignant transformation of oral epithelia.     

An abundant and ubiquitous homo-oligomeric ring-shaped ATPase particle related to the putative vesicle fusion proteins Sec18p and NSF.

We have discovered a ring-shaped particle of 12.5 nm diameter, 14.5S and apparent molecular weight of approximately 570,000 that displays 6-fold radial symmetry and is composed of a single kind of an acidic (pI approximately 5.5) polypeptide of Mr 97,000 (p97). Using antibodies to this protein we have detected its occurrence in a wide range of cells and tissues of diverse species from frog to man, including highly specialized cells such as mammalian erythrocytes and spermatozoa. In Xenopus laevis oocytes, the particle is found in both isolated nuclei and in manually enucleated ooplasms, which corresponds to immunofluorescence staining dispersed over both nucleoplasm and cytoplasm. The particle has a N-ethylmaleimide (NEM)-inhibitable Mg2(+)-ATPase activity, and its amino acid sequence, as deduced from cDNA clones, displays considerable homology to the mammalian NEM-sensitive fusion protein (NSF) and yeast Sec18p believed to be essential for vesicle fusion in secretory processes, indicating that these three proteins belong to the same multigene family.     

Cyclophilin A is required for the replication of group M human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus SIV(CPZ)GAB but not group O HIV-1 or other primate immunodeficiency viruses.

The human immunodeficiency virus type 1 (HIV-1) Gag polyprotein binds to cyclophilin A and incorporates this cellular peptidyl prolyl-isomerase into virions. Disruption of cyclophilin A incorporation, either by gag mutations or by cyclosporine A, inhibits virion infectivity, indicating that cyclophilin A plays an essential role in the HIV-1 life cycle. Using assays for packaging of cyclophilin A into virions and for viral replication sensitivity to cyclosporine A, as well as information gleaned from the alignment of Gag residues encoded by representative viral isolates, we demonstrate that of the five lineages of primate immunodeficiency viruses, only HIV-1 requires cyclophilin A for replication. Cloned viral isolates from clades A, B, and D of HIV-1 group M, as well as a phylogenetically related isolate from chimpanzee, all require cyclophilin A for replication. In contrast, the replication of two outlier (group O) HIV-1 isolates is unaffected by concentrations of cyclosporine A which disrupt cyclophilin A incorporation into virions, indicating that these viruses are capable of replicating independently of cyclophilin A. These studies identify the first phenotypic difference between HIV-1 group M and group O and are consistent with phylogenetic studies suggesting that the two HIV-1 groups were introduced into human populations via separate zoonotic transmission events.     

Specificity and sequence requirements for interactions between various retroviral Gag proteins.

We previously established a genetic assay for retroviral Gag polyprotein multimerization (J. Luban, K. B. Alin, K. L. Bossolt, T. Humaran, and S. P. Goff, J. Virol. 66:5157-5160, 1992). Here we use this assay to demonstrate homomeric interactions between Gag polyproteins encoded by six different retroviruses. Of the Gag polyproteins tested, only those encoded by closely related retroviruses formed heteromultimers. To determine the primary sequence requirements for human immunodeficiency virus type 1 Gag polyprotein multimerization, we studied the effects on multimerization of deletion and linker insertion mutations. Sequences necessary for this process were located between the C-terminal one-third of the capsid domain and the C terminus of the nucleocapsid domain.     

Conditioning of Parsley (Petroselinum crispum L.) Suspension Cells Increases Elicitor-Induced Incorporation of Cell Wall Phenolics

The elicitor-induced incorporation of phenylpropanoid derivatives into the cell wall and the secretion of soluble coumarin derivatives (phytoalexins) by parsley (Petroselinum crispum L.) suspension cultures can be potentiated by pretreatment of the cultures with 2,6-dichloroisonicotinic acid or derivatives of salicylic acid. To investigate this phenomenon further, the cell walls and an extracellular soluble polymer were isolated from control cells or cells treated with an elicitor from Phytophthora megasperma f. sp. glycinea. After alkaline hydrolysis, both fractions from elicited cells showed a greatly increased content of 4-coumaric, ferulic, and 4-hydroxybenzoic acid, as well as 4-hydroxybenzaldehyde and vanillin. Two minor peaks were identified as tyrosol and methoxytyrosol. The pretreatment effect is most pronounced at a low elicitor concentration. Its specificity was elaborated for coumarin secretion. When the parsley suspension cultures were preincubated for 1 d with 2,6-dichloroisonicotinic, 4- or 5-chlorosalicylic, or 3,5- dichlorosalicylic acid, the cells exhibited a greatly increased elicitor response. Pretreatment with isonicotinic, salicylic, acetylsalicylic, or 2,6-dihydroxybenzoic acid was less efficient in enhancing the response, and some other isomers were inactive. This increase in elicitor response was also observed for the above-mentioned monomeric phenolics, which were liberated from cell walls upon alkaline hydrolysis and for "lignin-like" cell wall polymers determined by the thioglycolic acid method. It was shown for 5-chlorosalicylic acid that conditioning most likely improves the signal transduction leading to the activation of genes encoding phenylalanine ammonia lyase and 4-coumarate: coenzyme A ligase. The conditioning thus sensitizes the parsley suspension cells to respond to lower elicitor concentrations. If a similar mechanism were to apply to whole plants treated with 2,6-dichloroisonicotinic acid, a known inducer of systemic acquired resistance, one can hypothesize that fungal pathogens might be recognized more readily and effectively.     

Vertically stratified frugivore community composition and interaction frequency in a liana fruiting across forest strata

Vertical stratification is a key feature of tropical forests and structures plant–frugivore interactions. However, it is unclear whether vertical differences in plant-frugivore interactions are due to differences among strata in plant community composition or inherent preferences of frugivores for specific strata. To test this, we observed fruit removal of a diverse frugivore community on the liana Marcgravia longifolia in a Peruvian rain forest. Unlike most other plants, Marcgravia longifolia produces fruits across forest strata. This enabled us to study effects of vertical stratification on fruit removal without confounding effects of plant species and stratum. We found a high number of visits of a few frugivore species in the understorey and a low number of visits of many different frugivores in the canopy and midstorey. Whereas partial and opportunistic frugivores foraged across strata with differing frequencies, obligate frugivores were only found eating fruits in the higher strata. Avian frugivores foraging in the canopy were mainly large species with pointed wings, whereas under- and midstorey avian foragers were smaller with rounded wings. Our findings suggest a continuous shift in the frugivore community composition along the vertical gradient, from a few generalized frugivores in the understorey to a diverse set of specialized frugivores in the canopy. This shift in the frugivore community leads to correlated, reciprocal changes from specialized to generalized plant-frugivore interactions. Thus, we conclude that vertical niche differentiation between species in tropical forests persists even when food resources are available across strata. This highlights its role for promoting biodiversity and ecosystem functioning.     

The challenge of estimating kelp production in a turbid marine environment

Coastal kelp forests produce substantial marine carbon due to high annual net primary production (NPP) rates, but upscaling of NPP estimates over time and space remains difficult. We investigated the impact of variable underwater photosynthetically active radiation (PAR) and photosynthetic parameters on photosynthetic oxygen production of Laminaria hyperborea, the dominant NE-Atlantic kelp species, throughout summer 2014. Collection depth of kelp had no effect on chlorophyll a content, pointing to a high photoacclimation potential of L. hyperborea towards incident light. However, chlorophyll a and photosynthesis versus irradiance parameters differed significantly along the blade gradient when normalized to fresh mass, potentially introducing large uncertainties in NPP upscaling to whole thalli. Therefore, we recommend a normalization to kelp tissue area, which is stable over the blade gradient. Continuous PAR measurements revealed a highly variable underwater light climate at our study site (Helgoland, North Sea) in summer 2014, reflected by PAR attenuation coefficients (K_d) between 0.28 and 0.87 m⁻¹. Our data highlight the importance of continuous underwater light measurements or representative average values using a weighted K_d to account for large PAR variability in NPP calculations. Strong winds in August increased turbidity, resulting in a negative carbon balance at depths >3–4 m over several weeks, considerably impacting kelp productivity. Estimated daily summer NPP over all four depths was 1.48 ± 0.97 g C · m⁻² seafloor · d⁻¹ for the Helgolandic kelp forest, which is in the range of other kelp forests along European coastlines.