The influence of storing beef aerobically or in vacuum packs on the shelf life of mince

Aims: To investigate the influence of aerobic or vacuum pack storage of beef trimmings on the microbiology, colour and odour of subsequently produced mince. Methods and Results: Trimmings stored aerobically for 7 or 10 days and in vacuum packs for 7, 10, 14 or 22 days at 0 or 5°C were minced, stored aerobically at 0 or 5°C for up to 7 days and examined daily to determine Total viable, Pseudomonas, Lactic acid bacteria, Brochothrix thermosphacta, and Enterobacteriaceae counts, colour and odour. Mincing reduced counts, particularly of Pseudomonas, B. thermosphacta and Enterobacteriaceae, probably because of the action free radicals released from muscle and bacterial cells. Storage of vacuum‐packed trimmings for 22 days resulted in improved mince colour and inhibition of the growth of Pseudomonas. Conclusions: The shelf life of mince from trimmings is directly influenced by the trimmings storage conditions, and longer‐term vacuum storage of trimmings produced improvements in mince quality. Significance and Impact of the Study: There appears to be no scientific rationale for limiting the storage of vacuum packaging beef trimmings to 15 days, prior to mince production, as stated in EU 835/2004. This study identifies advantages in storing trimmings in vacuum packs for at least 21 days prior to mincing, in terms of improved mince quality.     

HLA class I-driven evolution of human immunodeficiency virus type 1 subtype c proteome: immune escape and viral load

Human immunodeficiency virus type 1 (HIV-1) mutations that confer escape from cytotoxic T-lymphocyte (CTL) recognition can sometimes result in lower viral fitness. These mutations can then revert upon transmission to a new host in the absence of CTL-mediated immune selection pressure restricted by the HLA alleles of the prior host. To identify these potentially critical recognition points on the virus, we assessed HLA-driven viral evolution using three phylogenetic correction methods across full HIV-1 subtype C proteomes from a cohort of 261 South Africans and identified amino acids conferring either susceptibility or resistance to CTLs. A total of 558 CTL-susceptible and -resistant HLA-amino acid associations were identified and organized into 310 immunological sets (groups of individual associations related to a single HLA/epitope combination). Mutations away from seven susceptible residues, including four in Gag, were associated with lower plasma viral-RNA loads (q < 0.2 [where q is the expected false-discovery rate]) in individuals with the corresponding HLA alleles. The ratio of susceptible to resistant residues among those without the corresponding HLA alleles varied in the order Vpr > Gag > Rev > Pol > Nef > Vif > Tat > Env > Vpu (Fisher's exact test; P < or = 0.0009 for each comparison), suggesting the same ranking of fitness costs by genes associated with CTL escape. Significantly more HLA-B (chi(2); P = 3.59 x 10(-5)) and HLA-C (chi(2); P = 4.71 x 10(-6)) alleles were associated with amino acid changes than HLA-A, highlighting their importance in driving viral evolution. In conclusion, specific HIV-1 residues (enriched in Vpr, Gag, and Rev) and HLA alleles (particularly B and C) confer susceptibility to the CTL response and are likely to be important in the development of vaccines targeted to decrease the viral load.     

Involvement of stretch-activated ion channels in strain-regulated glycosaminoglycan synthesis in mesenchymal stem cell-seeded 3D scaffolds

The objective of this study was to determine if cyclic tensile strain would regulate the rate of glycosaminoglycan synthesis via stretch-activated ion channels in adult mesenchymal stem cells seeded in a collagen type I-glycosaminoglycan scaffold and treated with TGF-beta1. The application of 10% cyclic tensile loading at 1Hz for 7 days significantly increased the rate of glycosaminoglycan synthesis, as assessed using [(35)S] sulphate incorporation. This increase was attenuated in the presence of a stretch-activated ion channel inhibitor (10microM gadolinium chloride) demonstrating the involvement, in part, of these ion channels in the mechanotransduction pathway that couples cyclic tensile loading to matrix synthesis.     

Discovery of potent cholecystokinin-2 receptor antagonists: elucidation of key pharmacophore elements by X-ray crystallographic and NMR conformational analysis

A novel series of cholecystokinin-2 receptor (CCK-2R) antagonists has been identified, as exemplified by anthranilic sulfonamide 1 (pK(i)=7.6). Pharmacokinetic and stability studies indicated that this series of compounds suffered from metabolic degradation, and that both the benzothiadiazole and piperidine rings were rapidly oxidized by liver enzymes. A combination of synthesis, computational methods, (1)H NMR conformational studies, and X-ray crystallographic analyses were applied to elucidate key pharmacophore elements, and to discover analogs with improved pharmacokinetic profiles, and high receptor binding affinity and selectivity.     

Loss of insulin-like growth factor I receptor-dependent expression of p107 and cyclin A in cells that lack the extracellular matrix protein secreted protein acidic and rich in cysteine.

The extracellular matrix-associated glycoprotein secreted protein acidic and rich in cysteine (SPARC) has been implicated in the control of cell proliferation during tissue remodeling, wound healing, and malignant development. Here, we describe a novel mechanism through which SPARC influences cell cycle progression in embryonic fibroblasts derived from Sparc-nullizygous (-/-) mice. SPARC-deficient cells were indistinguishable from wild-type cells in their ability to initiate DNA synthesis after treatment with either fetal bovine serum or platelet-derived growth factor. In contrast, Sparc -/- cells responded poorly to activation of the insulin-like growth factor receptor (IGFI-R) by insulin. This defect was traced to reduced expression of the IGFI-R in Sparc -/- cells. Consistent with impaired cell cycle progression through S-phase, insulin-stimulated Sparc -/- cells also revealed reduced expression of two key regulators of S phase progression (cyclin A and thymidine kinase), whereas expression of the G1 phase progression regulators cmyc or cyclin D1 was unaffected. An examination of the status of retinoblastoma family pocket proteins in Sparc -/- cells revealed a selective and dramatic reduction in levels of the retinoblastoma-related protein p107. Exogenous platelet-derived growth factor restored expression of the IGFI-R and IGFI-R dependent DNA synthesis as well as induction of cyclin A, thymidine kinase, and p107 in insulin-stimulated Sparc -/- cells. These results suggest that SPARC-dependent matrix to cell interactions contribute to the regulation of p107 and cyclin A through IGFI-R dependent pathway(s).     

Mechano-regulation of stem cell differentiation and tissue regeneration in osteochondral defects

Cartilage defects that penetrate the subchondral bone can undergo spontaneous repair through the formation of a fibrous or cartilaginous tissue mediated primarily by mesenchymal stem cells from the bone marrow. This tissue is biomechanically inferior to normal articular cartilage, and is often observed to degrade over time. Whether or not biomechanical factors control the type and quality of the repair tissue, and its subsequent degradation, have yet to be elucidated. In this paper, we hypothesise a relationship between the mechanical environment of mesenchymal stem cells and their subsequent dispersal, proliferation, differentiation and death. The mechano-regulation stimulus is hypothesised to be a function of strain and fluid flow; these quantities are calculated using biphasic poroelastic finite element analysis. A finite element model of an osteochondral defect in the knee was created, and used to simulate the spontaneous repair process. The model predicts bone formation through both endochondral and direct intramembranous ossification in the base of the defect, cartilage formation in the centre of the defect and fibrous tissue formation superficially. Greater amounts of fibrous tissue formation are predicted as the size of the defect is increased. Large strains are predicted within the fibrous tissue at the articular surface, resulting in significant cell apoptosis. This result leads to the conclusion that repair tissue degradation is initiated in the fibrous tissue that forms at the articular surface. The success of the mechano-regulation model in predicting many of the cellular events that occur during osteochondral defect healing suggest that in the future it could be used as a tool for optimising scaffolds for tissue engineering.     

Evolution of mechanoregulation of bone growth will lead to non-optimal bone phenotypes

Mechanical forces acting on the bones during growth affect their final shape and strength. Mechanoregulation of bone growth may be recognized in embryogenesis, and also in the adaptation of the adult skeleton to changes in mechanical loading. Mechanoregulatory responses for tissues have arisen during evolution, but does evolution give rise to responses that produce optimal skeletal phenotypes? In this paper, we investigate the emergence of an optimal mechanoregulation response in a population. By combining equations describing long bone growth with a genetic algorithm to describe evolutionary change, we created a computational model to simulate the evolution of mechanoregulation in bone growth. A population of individuals is created where each individual is assigned a diploid gene set which controls the growth and remodelling of the bone. At maturity, each bone is assessed and its 'fitness' calculated; fitness is quantified as bone strength relative to bone mass. The simulation continues for many generations, and includes mutations and a varying environment. The genes present in the population are tracked and the evolution of parameters governing mechanoregulation is calculated. The results indicate that a population may converge to one bone growth algorithm but, more usually, a range of mechanoregulation algorithms for different individuals will persist after many generations. Even if the population converges to one mechanoregulation law, convergence to the 'optimum' bone was never found. Although many researchers propose that natural selection has pushed skeletal structure towards an optimum, our computational model suggests that this is unlikely to be the case.