Modulation of the Ca2+- or Pb2+-activated K+-selective channels in human red cells. I. Effects of propranolol

To study the effect of propranolol on the Ca2+- or Pb2+-activated K+ permeability in human erythrocytes, K+ effluxes were compared with single-channel currents. The results demonstrate that propranolol has a twofold effect: (1) it renders the channel protein more sensitive to Ca2+ or Pb2+; and (2) it simultaneously inhibits channel activity and slightly reduces single-channel conductance. The number of active channels is not affected.     

Messenger RNA sequence and expression of rat pancreatitis-associated protein, a lectin-related protein overexpressed during acute experimental pancreatitis.

Rat pancreatitis-associated protein (PAP) is an additional protein appearing in pancreatic juice after induction of prancreatic inflammation. Its messenger RNA was cloned and sequenced from pancreas. The deduced amino acid sequence revealed that PAP was synthetized as a preprotein with, in its mature form, a predicted molecular weight of 16,630. A search in protein data bases revealed a marked homology with the carbohydrate binding region of animal lectins; no hemagglutination activity could be shown for PAP, but the protein induced extensive bacterial aggregation. In healthy rats, the very low level of PAP expression in pancreas could be increased up to 4-fold by physiological stimuli such as chronic hormonal or cholinergic stimulation of pancreatic secretion and adaptation of rats to a carbohydrate-rich diet. By contrast, induction of acute experimental pancreatitis by retrograde injection of sodium taurocholate resulted in dramatic overexpression. Pancreatic concentration of PAP mRNA increased more than 300 x within 12 h whereas concentrations of mRNAs encoding major secretory proteins such as amylase decreased. PAP overexpression persisted during the 2 days of the acute phase and then returned to the control level during pancreatic recovery. PAP mRNA could not be evidenced in liver, stomach, salivary glands, brain, kidney, or testis. Its pattern of expression during severe pancreatic aggression suggests that it might be a stress protein involved in the control of bacterial proliferation.     

Characterization of the variable-number tandem repeats in vrrA from different Bacillus anthracis isolates.

PCR analysis of 198 Bacillus anthracis isolates revealed a variable region of DNA sequence differing in length among the isolates. Five polymorphisms differed by the presence of two to six copies of the 12-bp tandem repeat 5'-CAATATCAACAA-3'. This variable-number tandem repeat (VNTR) region is located within a larger sequence containing one complete open reading frame that encodes a putative 30-kDa protein. Length variation did not change the reading frame of the encoded protein and only changed the copy number of a 4-amino-acid sequence (QYQQ) from 2 to 6. The structure of the VNTR region suggests that these multiple repeats are generated by recombination or polymerase slippage. Protein structures predicted from the reverse-translated DNA sequence suggest that any structural changes in the encoded protein are confined to the region encoded by the VNTR sequence. Copy number differences in the VNTR region were used to define five different B. anthracis alleles. Characterization of 198 isolates revealed allele frequencies of 6.1, 17.7, 59.6, 5.6, and 11.1% sequentially from shorter to longer alleles. The high degree of polymorphism in the VNTR region provides a criterion for assigning isolates to five allelic categories. There is a correlation between categories and geographic distribution. Such molecular markers can be used to monitor the epidemiology of anthrax outbreaks in domestic and native herbivore populations.     

Decreased Plakophilin-1 Expression Promotes Increased Motility in Head and Neck Squamous Cell Carcinoma Cells

Desmosomes are prominent cell-cell adhesive junctions found in a variety of epithelial tissues, including the oral epithelium. The transmembrane core of the desmosome is composed of the desmosomal cadherins that interact extracellularly to mediate cell-cell adhesion. The cytoplasmic domain of desmosomal cadherins interact with plaque proteins that in turn interact with the keratin intermediate filament cytoskeleton. Plakophilin 1 is a major desmosomal plaque component that functions to recruit intermediate filaments to sites of cell-cell contact via interactions with desmoplakin. Decreased assembly of desmosomes has been reported in several epithelial cancers. We examined plakophilin-1 expression in an esophageal squamous cell carcinoma tissue microarray and found that plakophilin-1 expression inversely correlates with tumor grade. In addition, we sought to investigate the effect of plakophilin-1 expression on desmosome assembly and cell motility in oral squamous cell carcinoma cell lines. Cell lines expressing altered levels of plakophilin-1 were generated and the ability of these cells to recruit desmoplakin to sites of cell-cell contact was examined. Our results show that decreased expression of plakophilin-1 results in decreased desmosome assembly and increased cell motility and invasion. These data lead us to propose that loss of plakophilin-1 expression during head and neck squamous cell carcinoma (HNSCC) progression may contribute to an invasive phenotype.     

Unprecedented Melioidosis Cases in Northern Australia Caused by an Asian Burkholderia pseudomallei Strain Identified by Using Large-Scale Comparative Genomics

Melioidosis is a disease of humans and animals that is caused by the saprophytic bacterium Burkholderia pseudomallei. Once thought to be confined to certain locations, the known presence of B. pseudomallei is expanding as more regions of endemicity are uncovered. There is no vaccine for melioidosis, and even with antibiotic administration, the mortality rate is as high as 40% in some regions that are endemic for the infection. Despite high levels of recombination, phylogenetic reconstruction of B. pseudomallei populations using whole-genome sequencing (WGS) has revealed surprisingly robust biogeographic separation between isolates from Australia and Asia. To date, there have been no confirmed autochthonous melioidosis cases in Australia caused by an Asian isolate; likewise, no autochthonous cases in Asia have been identified as Australian in origin. Here, we used comparative genomic analysis of 455 B. pseudomallei genomes to confirm the unprecedented presence of an Asian clone, sequence type 562 (ST-562), in Darwin, northern Australia. First observed in Darwin in 2005, the incidence of melioidosis cases attributable to ST-562 infection has steadily risen, and it is now a common strain in Darwin. Intriguingly, the Australian ST-562 appears to be geographically restricted to a single locale and is genetically less diverse than other common STs from this region, indicating a recent introduction of this clone into northern Australia. Detailed genomic and epidemiological investigations of new clinical and environmental B. pseudomallei isolates in the Darwin region and ST-562 isolates from Asia will be critical for understanding the origin, distribution, and dissemination of this emerging clone in northern Australia.     

Estimating plant abundance using inflated beta distributions: Applied learnings from a lichen–caribou ecosystem

Quantifying abundance and distribution of plant species can be difficult because data are often inflated with zero values due to rarity or absence from many ecosystems. Terrestrial fruticose lichens (Cladonia and Cetraria spp.) occupy a narrow ecological niche and have been linked to the diets of declining caribou and reindeer populations (Rangifer tarandus) across their global distribution, and conditions related to their abundance and distribution are not well understood. We attempted to measure effects related to the occupancy and abundance of terrestrial fruticose lichens by sampling and simultaneously modeling two discrete conditions: absence and abundance. We sampled the proportion cover of terrestrial lichens at 438 vegetation plots, including 98 plots having zero lichens. A zero‐inflated beta regression model was employed to simultaneously estimate both the absence and the proportion cover of terrestrial fruticose lichens using fine resolution satellite imagery and light detection and ranging (LiDAR) derived covariates. The probability of lichen absence significantly increased with shallower groundwater, taller vegetation, and increased Sphagnum moss cover. Vegetation productivity, Sphagnum moss cover, and seasonal changes in photosynthetic capacity were negatively related to the abundances of terrestrial lichens. Inflated beta regression reliably estimated the abundance of terrestrial lichens (R² = .74) which was interpolated on a map at fine resolution across a caribou range to support ecological conservation and reclamation. Results demonstrate that sampling for and simultaneously estimating both occupancy and abundance offer a powerful approach to improve statistical estimation and expand ecological inference in an applied setting. Learnings are broadly applicable to studying species that are rare, occupy narrow niches, or where the response variable is a proportion value containing zero or one, which is typical of vegetation cover data.     

The genome and variation of Bacillus anthracis

The Bacillus anthracis genome reflects its close genetic ties to Bacillus cereus and Bacillus thuringiensis but has been shaped by its own unique biology and evolutionary forces. The genome is comprised of a chromosome and two large virulence plasmids, pXO1 and pXO2. The chromosome is mostly co-linear among B. anthracis strains and even with the closest near neighbor strains. An exception to this pattern has been observed in a large inversion in an attenuated strain suggesting that chromosome co-linearity is important to the natural biology of this pathogen. In general, there are few polymorphic nucleotides among B. anthracis strains reflecting the short evolutionary time since its derivation from a B. cereus-like ancestor. The exceptions to this lack of diversity are the variable number tandem repeat (VNTR) loci that exist in genic and non genic regions of the chromosome and both plasmids. Their variation is associated with high mutability that is driven by rapid insertion and deletion of the repeats within an array. A notable example is found in the vrrC locus which is homologous to known DNA translocase genes from other bacteria.