Reconstitution of a porcine submaxillary gland beta-D-galactoside alpha 2----3 sialyltransferase into liposomes

Form A of the beta-D-galactoside alpha 2----3 sialyltransferase from porcine submaxillary glands was incorporated into liposomes. Incorporation was achieved by gel filtration of the enzyme in the presence of octylglucoside-phospholipid micelles. As detergent was removed during gel filtration, liposomes (average diameter, 370 A) with bound enzyme were formed and emerged unretarded from the column. The recovery of enzyme activity in the liposomes was about 40% of the initial activity starting with as little as 9 micrograms of transferase. Chromatography on Sepharose CL6B and sucrose density gradient centrifugation confirmed the association of enzyme with liposomes. In contrast to Form A, Form B of the sialyltransferase, which lacks the proposed lipid-binding domain of Form A, cannot be incorporated into liposomes. Form A of the transferase was also incorporated into liposomes composed of phosphatidylcholine, cholesterol, and a mixture of phospholipids from the membranes of the Golgi apparatus from porcine submaxillary glands. Although the transferase was distributed about equally on the internal and external surface of the phosphatidylcholine liposomes, most of the transferase was on the external surface in liposomes containing cholesterol (72%) or in liposomes containing Golgi apparatus phospholipids (88%). The enzyme bound to phosphatidylcholine liposomes was shown by kinetic analysis to have the same activity as that found in the presence of activity-stimulating detergents such as Triton X-100. Enzyme incorporated into cholesterol-containing liposomes had the same activity. In contrast, enzyme bound to liposomes formed from the Golgi apparatus mixed phospholipids had a lower activity, but one similar to that of the transferase in Golgi apparatus membranes. These studies suggest that the composition of a biological membrane may well influence the orientation of the transferase in the membrane as well as modulate its enzymic activity.     

Sepsis progression and outcome: a dynamical model

Background  

Sepsis (bloodstream infection) is the leading cause of death in non-surgical intensive care units. It is diagnosed in 750,000 US patients per annum, and has high mortality. Current understanding of sepsis is predominately observational and correlational, with only a partial and incomplete understanding of the physiological dynamics underlying the syndrome. There exists a need for dynamical models of sepsis progression, based upon basic physiologic principles, which could eventually guide hourly treatment decisions.     

Ecological dynamics of emerging bat virus spillover

Viruses that originate in bats may be the most notorious emerging zoonoses that spill over from wildlife into domestic animals and humans. Understanding how these infections filter through ecological systems to cause disease in humans is of profound importance to public health. Transmission of viruses from bats to humans requires a hierarchy of enabling conditions that connect the distribution of reservoir hosts, viral infection within these hosts, and exposure and susceptibility of recipient hosts. For many emerging bat viruses, spillover also requires viral shedding from bats, and survival of the virus in the environment. Focusing on Hendra virus, but also addressing Nipah virus, Ebola virus, Marburg virus and coronaviruses, we delineate this cross-species spillover dynamic from the within-host processes that drive virus excretion to land-use changes that increase interaction among species. We describe how land-use changes may affect co-occurrence and contact between bats and recipient hosts. Two hypotheses may explain temporal and spatial pulses of virus shedding in bat populations: episodic shedding from persistently infected bats or transient epidemics that occur as virus is transmitted among bat populations. Management of livestock also may affect the probability of exposure and disease. Interventions to decrease the probability of virus spillover can be implemented at multiple levels from targeting the reservoir host to managing recipient host exposure and susceptibility.     

Dissecting the telomere region of barley chromosome 5HL using rice genomic sequences as references: new markers for tracking a complex region in breeding

The terminal region of barley chromosome 5HL controls malt extract, diastatic power, free amino acid nitrogen, alpha-amylase activity, seed dormancy and pre-harvest sprouting. Comparative analysis of the barley and rice maps has established that the terminal region of barley chromosome 5HL is syntenic to rice chromosome 3L near the telomere end. The rice BAC (Bacterial Artificial Chromosome) sequences covering the region of chromosome 3L were used to search barley expressed sequenced tags database. Thirty-three genes were amplified by PCR (polymerase chain reaction) with the primers designed from barley ESTs (expressed sequence tag). Comparison of the sequences of the PCR generated DNA fragments revealed polymorphisms including single nucleotide polymorphism (SNP), insertions or deletions between the barley varieties. Seven new PCR based molecular markers were developed and mapped within 10 cM in three doubled haploid barley populations (Stirling × Harrington, Baudin × AC Metcalfe and Chebec × Harrington). The mapped genes maintain the micro-syntenic relationship between barley and rice. These gene specific markers provide simple and efficient tools for germplasm characterization and marker-assisted selection for barley malting quality, and ultimately lead to isolation and identification of the major gene(s) controlling multiple quality traits on barley chromosome 5HL.     

The theory of the left ventricular aneurysm

A spherical model for the human left ventricle with two different types of aneurysms, circular and rectangular-square, is proposed and meaningful relations are derived between the parameters of the aneurysms and ventricle. Such ventricular parameters as stroke volume, end-diastolic volume, and end-systolic volume are given normal human values to compute values for end-systolic radius and percentage shortening of muscle for various sized circular and rectangular-square aneurysms.     

A novel approach for multi-domain and multi-gene family identification provides insights into evolutionary dynamics of disease resistance genes in core eudicot plants

Background

Recent advances in DNA sequencing techniques resulted in more than forty sequenced plant genomes representing a diverse set of taxa of agricultural, energy, medicinal and ecological importance. However, gene family curation is often only inferred from DNA sequence homology and lacks insights into evolutionary processes contributing to gene family dynamics. In a comparative genomics framework, we integrated multiple lines of evidence provided by gene synteny, sequence homology and protein-based Hidden Markov Modelling to extract homologous super-clusters composed of multi-domain resistance (R)-proteins of the NB-LRR type (for NUCLEOTIDE BINDING/LEUCINE-RICH REPEATS), that are involved in plant innate immunity.

Results

To assess the diversity of R-proteins within and between species, we screened twelve eudicot plant genomes including six major crops and found a total of 2,363 NB-LRR genes. Our curated R-proteins set shows a 50% average for tandem duplicates and a 22% fraction of gene copies retained from ancient polyploidy events (ohnologs). We provide evidence for strong positive selection and show significant differences in molecular evolution rates (Ka/Ks-ratio) among tandem- (mean = 1.59), ohnolog (mean = 1.36) and singleton (mean = 1.22) R-gene duplicates. To foster the process of gene-edited plant breeding, we report species-specific presence/absence of all 140 NB-LRR genes present in the model plant Arabidopsis and describe four distinct clusters of NB-LRR “gatekeeper” loci sharing syntenic orthologs across all analyzed genomes.

Conclusion

By curating a near-complete set of multi-domain R-protein clusters in an eudicot-wide scale, our analysis offers significant insight into evolutionary dynamics underlying diversification of the plant innate immune system. Furthermore, our methods provide a blueprint for future efforts to identify and more rapidly clone functional NB-LRR genes from any plant species.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-966) contains supplementary material, which is available to authorized users.