His1 and His2 are distantly related, spindle-shaped haloviruses belonging to the novel virus group, Salterprovirus

Spindle-shaped viruses are a dominant morphotype in hypersaline waters but their molecular characteristics and their relationship to other archaeal viruses have not been determined. Here, we describe the isolation, characteristics and genome sequence of His2, a spindle-shaped halovirus, and compare it to the previously reported halovirus His1. Their particle dimensions, host-ranges and buoyant densities were found to be similar but they differed in their stabilities to raised temperature, low salinity and chloroform. The genomes of both viruses were linear dsDNA, of similar size (His1, 14,464 bp; His2, 16,067 bp) and mol% G+C (approximately 40%), with long, inverted terminal repeat sequences. The genomic termini of both viruses are likely to possess bound proteins. They shared little nucleotide similarity and, except for their putative DNA polymerase ORFs, no significant similarity at the predicted protein level. A few of the 35 predicted ORFs of both viruses showed significant matches to sequences in GenBank, and these were always to proteins of haloarchaea. Their DNA polymerases showed 42% aa identity, and belonged to the type B group of replicases that use protein-priming. Purified His2 particles were composed of four main proteins (62, 36, 28 and 21 kDa) and the gene for the major capsid protein was identified. Hypothetical proteins similar to His2 VP1 are present in four haloarchaeal genomes but are not part of complete prophages. This, and other evidence, suggests a high frequency of recombination between haloviruses and their hosts. His1 and His2 are unlike fuselloviruses and have been placed in a new virus group, Salterprovirus.     

Islets of Langerhans from prohormone convertase‐2 knockout mice show α‐cell hyperplasia and tumorigenesis with elevated α‐cell neogenesis

Antagonism of the effects of glucagon as an adjunct therapy with other glucose‐lowering drugs in the chronic treatment of diabetes has been suggested to aggressively control blood glucose levels. Antagonism of glucagon effects, by targeting glucagon secretion or disabling the glucagon receptor, is associated with α‐cell hyperplasia. We evaluated the influence of total glucagon withdrawal on islets of Langerhans using prohormone convertase‐2 knockout mice (PC2‐ko), in which α‐cell hyperplasia is present from a young age and persists throughout life, in order to understand whether or not sustained glucagon deficit would lead to islet tumorigenesis. PC2‐ko and wild‐type (WT) mice were maintained drug‐free, and cohorts of these groups sampled at 3, 12 and 18 months for plasma biochemical and morphological (histological, immunohistochemical, electron microscopical and image analytical) assessments. WT mice showed no islet tumours up to termination of the study, but PC2‐ko animals displayed marked changes in islet morphology from α‐cell hypertrophy/hyperplasia/atypical hyperplasia, to adenomas and carcinomas, these latter being first encountered at 6–8 months. Islet hyperplasias and tumours primarily consisted of α‐cells associated to varying degrees with other islet endocrine cell types. In addition to substantial increases in islet neoplasia, increased α‐cell neogenesis associated primarily with pancreatic duct(ule)s was present. We conclude that absolute blockade of the glucagon signal results in tumorigenesis and that the PC2‐ko mouse represents a valuable model for investigation of islet tumours and pancreatic ductal neogenesis.     

Quantitative diffusion weighted imaging for differentiation of benign and malignant breast lesions: The influence of the choice of b‐values

Purpose:

To evaluate the influence of the choice of different combinations of b‐values on the ADC and on the diagnostic performance of quantitative diffusion weighted imaging (DWI) in breast lesions.

Materials and Methods:

Seventy‐three patients (90 lesions) underwent 3 Tesla (T) breast MRI including a DWI‐scan using b‐values 0, 150, 499, and 1500 s/mm² and histological analysis. Five combinations of b‐values were used to calculate the ADC, each with different sensitivities to perfusion and diffusion effects. The median ADC of benign lesions, noninvasive carcinomas and invasive carcinomas and the diagnostic performance of the five methods were compared.

Results:

Eighty‐eight lesions were analyzed (37 benign, 13 noninvasive carcinomas, 38 invasive carcinomas). The median ADC was highest in benign lesions, intermediate in noninvasive carcinomas and lowest in invasive carcinomas for all methods. Calculating the ADC with the lowest 2 b‐values yielded the highest ADC for all lesions types; the highest 2 b‐values yielded the lowest ADC. The area under the receiver operating characteristic curve was approximately equal for all methods.

Conclusion:

The ADC of breast lesions varied substantially with the choice of different b‐values, indicating that absolute ADC threshold values to differentiate benign and malignant lesions should be interpreted with caution. However, the diagnostic performance of quantitative DWI was not affected by the choice of different b‐values. J. Magn. Reson. Imaging 2010;31:1100–1105. © 2010 Wiley‐Liss, Inc.     

Optimization of Salmonella enterica serovar typhi DeltaaroC DeltassaV derivatives as vehicles for delivering heterologous antigens by chromosomal integration and in vivo inducible promoters

Novel candidate live oral vaccines based on a Salmonella enterica serovar Typhi ZH9 (Ty2 DeltaaroC DeltassaV) derivative that directed the expression of either the B subunit of Escherichia coli heat-labile toxin or hepatitis B virus core antigen from the bacterial chromosome using the in vivo inducible ssaG promoter were constructed. The levels of attenuation of the two S. enterica serovar Typhi ZH9 derivatives were similar to that of the parent as assessed by measuring the replication of bacteria within human macrophage-like U937 cells. The expression of heterologous antigen in the respective S. enterica serovar Typhi ZH9 derivatives was up-regulated significantly within U937 cells compared to similar S. enterica serovar Typhi ZH9 derivative bacteria grown in modified Luria-Bertani broth supplemented with aromatic amino acids. Immunization of mice with these S. enterica serovar Typhi ZH9 derivatives stimulated potent antigen-specific serum immunoglobulin G responses to the heterologous antigens.