Elevated Expression of the Human Parainfluenza Virus Type 1 F Gene Downregulates HN Expression

AbstractInteractions involved in the expression of parainfluenza glycoproteins were examined by expressing cDNA clones of theHNandFgenes from human parainfluenza virus type-1 (hPIV1) or Sendai virus (SV) in recombinant Semliki Forest virus (recSFV) or vaccinia-T7 expression vectors. We found that expression of a cloned F protein gene of hPIV1 resulted in downregulation of the HN proteins of hPIV1 or SV. Compared to the amount of HN expressed in the absence of F, coexpression of HN and F led to about 70% reduction in HN. This reduction of HN was observed in both total cell lysates and in protein localized on the cell surface. In contrast to hPIV1 F, SV F did not suppress the expression of HN. Northern blot analysis indicated that similar levels of HN mRNA accumulated in the absence or presence of hPIV1 F. The reduction of HN protein expression by hPIV1 F was detectable after as little as a 10-min labeling period, suggesting that downregulation occurred at the level of translation or at an early stage of protein folding. In hPIV1-infected cells, the amount of F protein synthesized was only about 15% of that of HN, whereas SV F is expressed at high levels. When the level of F in hPIV1-infected cells was artificially increased by recSFV, HN expression was suppressed. The reduction of F protein production in hPIV1-infected cells was regulated at the level of transcription. Characterization of mRNAs produced in hPIV1-infected cells showed that only 20% of the hPIV1 F mRNAs were monocistronic transcripts; 80% were bicistronic M-F readthrough mRNAs. Because proteins are suggested to be synthesized from only the first cistron of bicistronic mRNA in paramyxovirus (T. C. Wong and A. Hirano (1987)J. Virol.61, 584–589), production of F protein is likely suppressed by transcriptional regulation in hPIV1-infected cells. These results suggest that F is capable of downregulating the synthesis of HN, but that this is normally prevented in hPIV1-infected cells by suppression of F protein synthesis by transcriptional regulation

Subaqueous basaltic magmatic explosions trigger phreatomagmatism: a case study from Askja, Iceland

Sequences of basaltic pillow lavas that transition upwards with systematic gradation from pillow fragment breccias to fluidal bomb-bearing breccia to bomb-bearing lapilli tuffs are common at Askja volcano, Iceland. Based on the detailed textural investigation of three of these sequences, we argue that they record temporally continuous transition from effusive to explosive products that were erupted from and deposited at or near a single subaqueous vent. The recognition of such sequences is important as they provide evidence for controls on the onset of explosive activity in subaqueous environments. Such investigations are complicated by the interplay of magmatic gas expansion, phreatomagmatic and mechanical granulation fragmentation mechanisms in the subaqueous eruptive environment. All of the sequences studied at Askja have textural, componentry and sedimentological characteristics suggestive of a close genetic and spatial relationship between the pillow lavas and all of the overlying glassy clastic deposits. The identification of magma fragmentation signatures in pyroclasts was accomplished through detailed textural studies of pyroclasts within the full range of grain sizes of a given deposit i.e. bomb/blocks, lapilli and fine ash. These textural characteristics were compared and evaluated as discriminators of fragmentation in pyroclastic deposits. The presence of angular vitric clasts within the breccia and lapilli tuff displaying fragile glassy projections indicates little or no postdepositional textural modification. A shift in vesicle and clast textures between the pillow lavas and the large concentration of fluidal bombs in the breccia indicate that the phreatomagmatic explosions were initially triggered by magmatic vesiculation. The initial magmatic gas expansion may have been triggered by depressurization caused by the drainage of the ice-confined lake surrounding Askja. The Fuel Coolant Interactions (FCI) of the more efficient phreatomagmatic explosion was enabled by the increase in the surface area to volume ratio of the fluidal bombs in the water, producing a premix of magma and water. The onset and increasing influence of phreatomagmatic fragmentation is preserved in the presence of very fine blocky ash particles and diminished presence of larger particles such as fluidal bombs. The textural, sedimentological and environmental characteristics of these deposits suggest that phreatomagmatic explosions can be triggered by initial magmatic gas expansion, but that it is likely one of many mechanisms for triggering such explosions

On Spanish Dvandva and its restrictions

As noted by Bauer, real dvandva compounds –that is, coordinative compounds that properly express the aggregation of two different entities, not the intersection of properties in one entity– are extremely rare in English or Spanish. This article explores the empirical domain of dvandva compounding in Spanish, and notes that they are productive when not used as heads within their phrases. We propose that the explanation for this is that Spanish can only productively build dvandva compounds using flat structures without internal hierarchy. This causes the compound to look externally for a head noun that defines the interpretation of the relation established between the two members of the dvandva. The proposal also explains why proper names is preferred in dvandva compounding, given that they do not denote properties