Modulation of the host cell proteome by the intracellular apicomplexan parasite Toxoplasma gondii.

To investigate how intracellular parasites manipulate their host cell environment at the molecular level, we undertook a quantitative proteomic study of cells following infection with the apicomplexan parasite Toxoplasma gondii. Using conventional two-dimensional electrophoresis, difference gel electrophoresis (DIGE), and mass spectrometry, we identified host proteins that were consistently modulated in expression following infection. We detected modification of protein expression in key metabolic pathways, including glycolysis, lipid and sterol metabolism, mitosis, apoptosis, and structural-protein expression, suggestive of global reprogramming of cell metabolism by the parasite. Many of the differentially expressed proteins had not been previously implicated in the response to the parasite, while others provide important corroborative protein evidence for previously proposed hypotheses of pathogen-cell interactions. Significantly, over one-third of all modulated proteins were mitochondrial, and this was further investigated by DIGE analysis of a mitochondrion-enriched preparation from infected cells. Comparison of our proteomic data with previous transcriptional studies suggested that a complex relationship exits between transcription and protein expression that may be partly explained by posttranslational modifications of proteins and revealed the importance of investigating protein changes when interpreting transcriptional data. To investigate this further, we used phosphatase treatment and DIGE to demonstrate changes in the phosphorylation states of several key proteins following infection. Overall, our findings indicate that the host cell proteome responds in a dramatic way to T. gondii invasion, in terms of both protein expression changes and protein modifications, and reveal a complex and intimate molecular relationship between host and parasite.

Ultrasonically enhanced vancomycin activity against Staphylococcus epidermidis biofilms in vivo.

Infection of implanted medical devices by Gram-positive organisms such as Staphylococcus ssp. is a serious concern in the biomaterial community. In this research the application of low frequency ultrasound to enhance the activity of vancomycin against implanted Staphylococcus epidermidis biofilms was examined. Polyethylene disks covered with a biofilm of S. epidermidis were implanted subcutaneously in rabbits on both sides of their spine. The rabbits received systemic vancomycin for the duration of the experiment. Following 24 h of recovery, one disk was insonated for 24 or 48 h while the other was a control. Disks were removed and viable bacteria counted. At 24 h of insonation, there was no difference in viable counts between control and insonated biofilms, while at 48 h of insonation there were statistically fewer viable bacteria in the insonated biofilm. The S. epidermidis biofilms responded favorably to combinations of ultrasound and vancomycin, but longer treatment times are required for this Gram-positive organism than was observed previously for a Gram-negative species.

Mechanisms underlying the manipulation of host apoptotic pathways by Toxoplasma gondii.

The establishment of a productive infection by an obligate intracellular pathogen is dependent on subversion of cellular defences. Apoptosis, or programmed cell death, is a property of metazoan cells that plays a critical role in inhibiting the proliferation of invasive organisms and viruses thereby protecting uninfected cells and limiting damage to the host organism. Not surprisingly, manipulation of the machinery of apoptosis plays a critical role in the pathogenesis of several intracellular pathogens. Toxoplasma gondii, arguably one of the most successful protozoan pathogens, has evolved several strategies to inhibit both the initiation and propagation of the apoptotic cascade. Recent work from several groups indicates an exquisite level of sophistication in the mechanisms to inhibit apoptosis along its diverse pathways. Much of this ability appears to centre around the manipulation of host transcription, specifically of genes involved in the pro-survival/anti-apoptotic response effectively manipulating the infected cell into a highly anti-apoptotic state. The implications of these observations extend beyond Toxoplasma biology to the broader area of microbial pathogenesis and cell signalling in mammalian cells.

Estabilidade da carne bovina em atmosfera estabilizada após maturaçäo em embalagem a vácuo / Aged beef stability in modified atmosphere packages

Cortes em bifes de alcatra e contrafilé foram acondicionados a vácuo e maturados durante 20 dias a 0ºC. Posteriormente, foram retirados da embalagem e acondicionados em atmosfera modificada ( composiçäo gasosa inicial de 68 por cento de oxigênio, 15 por cento de nitrogênio, 17 por cento de gás carbônico e 66 por cento de oxigênio, 17 por cento de nitrogênio, 18 por cento de gás carbônico, respectivamente ). Para fins comparativos, prepararam-se amostras dos mesmos cortes em ar atmosférico. Periodicamente, o produto estocado a 1 ñ 1ºC foi avaliado quanto à qualidade microbiológica, sensorial, perda de líquido e pH. Também se avaliou a composiçäo gasosa do espaço-livre das embalagens com atmosfera modificada. A atmosfera modificada, no sistema em teste, teve pouco efeito sobre o crescimento de aeróbios psicrotrófilos, provavelmente porque os cortes apresentaram altas contagens iniciais de bactérias lácticas, devido a prévia estocagem a vácuo. Durante a estocagem, a perda de líquido exsudado e a variaçäo de pH foram semelhantes nos dois sistemas de acondicionamento, para ambos os cortes. A vida útil dos bifes de alcatra estocados em ar e atmosfera modificada foi de 5 e 6 dias, respectivamente. Os fatores limitantes da aceitabilidade foram a cor da carne ( ar e atmosfera modificada ), a descoloraçäo ( ar ) e a uniformidade da cor ( atmosfera modificada ). A vida útil dos bifes de contrafilé foi aumentada de 4 dias em ar para 7 dias em atmosfera modificada, sendo que os fatores limitantes da vida útil foram os mesmos citados para a alcatra, acrescidos da cor da gordura do produto mantido em ar