Biochanin A improves fibre fermentation by cellulolytic bacteria

Aims

The objective was to determine the effect of the isoflavone biochanin A (BCA) on rumen cellulolytic bacteria and consequent fermentative activity.

Methods and Results

When bovine microbial rumen cell suspensions (n = 3) were incubated (24 h, 39°C) with ground hay, cellulolytic bacteria proliferated, short‐chain fatty acids were produced and pH declined. BCA (30 μg ml^?1) had no effect on the number of cellulolytic bacteria or pH, but increased acetate, propionate and total SCFA production. Addition of BCA improved total digestibility when cell suspensions (n = 3) were incubated (48 h, 39°C) with ground hay, Avicel, or filter paper. Fibrobacter succinogenes S85, Ruminococcus flavefaciens 8 and Ruminococcus albus 8 were directly inhibited by BCA. Synergistic antimicrobial activity was observed with BCA and heat killed cultures of cellulolytic bacteria, but the effects were species dependent.

Conclusions

These results indicate that BCA improves fibre degradation by influencing cellulolytic bacteria competition and guild composition.

Significance and Impact of the Study

BCA could serve as a feed additive to improve cellulosis when cattle are consuming high‐fibre diets. Future research is needed to evaluate the effect of BCA on fibre degradation and utilization in vivo.     

Down-regulation of IRAK-4 is a component of LPS- and CpG DNA-induced tolerance in macrophages

Macrophages are important mediators of the immune response to infection by virtue of, amongst other things, their ability to secrete cytokines (e.g. TNF) that trigger inflammation. However, excessive systemic release of inflammatory cytokines can cause septic shock and ultimately death. Tolerance is an adaptive mechanism that prevents macrophage activation and inflammatory cytokine production. The activation of macrophages by pathogens is largely mediated by Toll-like receptors (TLRs). IRAK-4 and IRAK-1 are proximal protein kinases in TLR signalling pathways; IRAK-1 is activated via its phosphorylation by IRAK-4. The rapid degradation of IRAK-1 following its TLR-induced activation has been proposed to represent a major mechanism for tolerance. Here, we established that IRAK-1 degradation is insufficient to cause tolerance; in the absence of IRAK-1, IRAK-4 likely activates downstream signalling proteins (e.g. NF-kappaB) via IRAK-2. Significantly, tolerance coincided with IRAK-4 down-regulation, which occurred at the protein level via proteolytic degradation as well as at the mRNA level. Gene silencing experiments confirmed the importance of IRAK-4 for the regulation of TNF expression. The different kinetics of IRAK-4 and IRAK-1 down-regulation may result in both quantitative and qualitative differences in TLR signalling and potentially allow macrophages to temporally modify their inflammatory responses. Furthermore, differences in the kinetics and extent of IRAK-4 down-regulation by TLR ligands may provide a mechanism whereby macrophages can tailor their inflammatory response according to the location and/or type of pathogen detected.     

H‐Cadherin expression reduces invasion of malignant melanoma

Melanocytic behavior, survival, and proliferation are regulated through a complex system of cell–cell adhesion molecules. Pathologic changes leading to development of malignant melanoma, upset the delicate homeostatic balance between melanocytes and keratinocytes and can lead to altered expression of cell–cell adhesion and cell–cell communication molecules. Malignant transformation of melanocytes frequently coincides with loss of E‐cadherin expression. We now show loss of another member of the superfamily of classical cadherins, H‐cadherin (CDH13), which may be involved in the development of malignant melanoma. The provided data show that H‐cadherin expression is lost in nearly 80% of the analyzed melanoma cell lines. Knockdown of H‐cadherin using siRNA increases invasive capacity in melanocytes. Functional assays show that the re‐expression of H‐cadherin decreases migration and invasion capacity, as well as anchorage‐independent growth in comparison to control melanoma cells. Furthermore, melanoma cells, which re‐express H‐cadherin via stable transfection show a reduction in rate of tumor growth in a nu/nu mouse tumor model in comparison to the parental control transfected cell lines. Our study presents for the first time the down‐regulation of H‐cadherin in malignant melanomas and its possible functional relevance in maintenance healthy skin architecture.     

Early virus-associated bystander events affect the fitness of the CD8 T cell response to persistent virus infection

Chronic Ag exposure during persistent viral infection erodes virus-specific CD8 T cell numbers and effector function, with a concomitant loss of pathogen control. Less clear are the respective contributions of Ag-specific and Ag-nonspecific (bystander) events on the quantity, quality, and maintenance of antiviral CD8 T cells responding to persistent virus infection. In this study, we show that low-dose inoculation with mouse polyomavirus (PyV) elicits a delayed, but numerically equivalent, antiviral CD8 T cell response compared with high-dose inoculation. Low-dose infection generated virus-specific CD8 T cells endowed with multicytokine functionality and a superior per cell capacity to produce IFN-gamma. PyV-specific CD8 T cells primed by low-dose inoculation also expressed higher levels of IL-7Ralpha and bcl-2 and possessed enhanced Ag-independent survival. Importantly, the quantity and quality of the antiviral CD8 T cell response elicited by dendritic cell-mediated immunization were mitigated by infection with a mutant PyV lacking the dominant CD8 T cell viral epitope. These findings suggest that the fitness of the CD8 T cell response to persistent virus infection is programmed in large part by early virus-associated Ag-nonspecific factors, and imply that limiting bystander inflammation at the time of inoculation, independent of Ag load, may optimize adaptive immunity to persistent viral infection.     

Structure of Ddn, the deazaflavin-dependent nitroreductase from Mycobacterium tuberculosis involved in bioreductive activation of PA-824

Tuberculosis continues to be a global health threat, making bicyclic nitroimidazoles an important new class of therapeutics. A deazaflavin-dependent nitroreductase (Ddn) from Mycobacterium tuberculosis catalyzes the reduction of nitroimidazoles such as PA-824, resulting in intracellular release of lethal reactive nitrogen species. The N-terminal 30 residues of Ddn are functionally important but are flexible or access multiple conformations, preventing structural characterization of the full-length, enzymatically active enzyme. Several structures were determined of a truncated, inactive Ddn protein core with and without bound F(420) deazaflavin coenzyme as well as of a catalytically competent homolog from Nocardia farcinica. Mutagenesis studies based on these structures identified residues important for binding of F(420) and PA-824. The proposed orientation of the tail of PA-824 toward the N terminus of Ddn is consistent with current structure-activity relationship data.     

Molecular mapping of soybean rust resistance in soybean accession PI 561356 and SNP haplotype analysis of the Rpp1 region in diverse germplasm

Soybean rust (SBR), caused by Phakopsora pachyrhizi Sydow, is one of the most economically important and destructive diseases of soybean [Glycine max (L.) Merr.] and the discovery of novel SBR resistance genes is needed because of virulence diversity in the pathogen. The objectives of this research were to map SBR resistance in plant introduction (PI) 561356 and to identify single nucleotide polymorphism (SNP) haplotypes within the region on soybean chromosome 18 where the SBR resistance gene Rpp1 maps. One-hundred F(2:3) lines derived from a cross between PI 561356 and the susceptible experimental line LD02-4485 were genotyped with genetic markers and phenotyped for resistance to P. pachyrhizi isolate ZM01-1. The segregation ratio of reddish brown versus tan lesion type in the population supported that resistance was controlled by a single dominant gene. The gene was mapped to a 1-cM region on soybean chromosome 18 corresponding to the same interval as Rpp1. A haplotype analysis of diverse germplasm across a 213-kb interval that included Rpp1 revealed 21 distinct haplotypes of which 4 were present among 5 SBR resistance sources that have a resistance gene in the Rpp1 region. Four major North American soybean ancestors belong to the same SNP haplotype as PI 561356 and seven belong to the same haplotype as PI 594538A, the Rpp1-b source. There were no North American soybean ancestors belonging to the SNP haplotypes found in PI 200492, the source of Rpp1, or PI 587886 and PI 587880A, additional sources with SBR resistance mapping to the Rpp1 region.     

Can shooting be an effective management tool for foxes? Preliminary insights from a management programme

Historically, shooting has been a popular method for controlling foxes in Australia, but past research has shown it to be an ineffective method for significantly reducing fox population numbers. These past studies investigated shooting when conducted in isolated, one‐off programmes. In more recent years large, coordinated group fox management programmes has become popular in both agricultural and conservation areas. These landscape scale programmes give more chance of long‐term respite from predation damage by slowing down the immigration rates of foxes into the culled area. Studies have been conducted investigating the effectiveness of large‐scale group fox management programmes that primarily used 1080 baiting as the method of control to protect vulnerable livestock and small animal. This study investigated the potential of a large‐scale group programme that used shooting as the main form of control to reduce the impact of fox predation.     

The rhabditid nematode Phasmarhabditis hermaphrodita as a potential biological control agent for slugs

A nematode, Phasmarhabditis hermaphrodita, known to be associated with slugs but not previously thought to be parasitic, was shown to be a parasite capable of killing the pest slug Deroceras reticulatum. The parasite infects slugs in the area beneath the mantle surrounding the shell, causing a disease with characteristic symptoms, particularly swelling of the mantle. Infection leads to death of the slug, usually between seven and 21 days afterwards. The nematode then spreads and multiplies in the cadaver. In an experiment where individual D. reticulatum were exposed to different numbers of P. hermaphrodita, a significant positive relationship was found between nematode dose and slug mortality. In two experiments on host range, the nematode was found to infect and kill all pest slug species tested: Deroceras caruanae, Arion distinctus, Arion silvaticus, Arion intermedius, Arion ater, Tandonia sowerbyi and T. budapestensis, in addition to D. reticulatum.