Uptake of nitrobenzylthioinosine and purine beta-L-nucleosides by intracellular Toxoplasma gondii

Intracellular Toxoplasma gondii grown in human foreskin fibroblast cells transported nitrobenzylthioinosine [NBMPR; 6-[(4-nitrobenzyl)mercapto]-9-beta-D-ribofuranosylpurine], an inhibitor of nucleoside transport in mammalian cells, as well as the nonphysiological beta-L-enantiomers of purine nucleosides, beta-L-adenosine, beta-L-deoxyadenosine, and beta-L-guanosine. The beta-L-pyrimidine nucleosides, beta-L-uridine, beta-L-cytidine, and beta-L-thymidine, were not transported. The uptake of NBMPR and the nonphysiological purine nucleoside beta-L-enantiomers by the intracellular parasites also implies that Toxoplasma-infected cells can transport these nucleosides. In sharp contrast, under the same conditions, uninfected fibroblast cells did not transport NBMPR or any of the unnatural beta-L-nucleosides. beta-D-Adenosine and dipyridamole, another inhibitor of nucleoside transport, inhibited the uptake of NBMPR and beta-L-stereoisomers of the purine nucleosides by intracellular Toxoplasma and Toxoplasma-infected cells. Furthermore, infection with a Toxoplasma mutant deficient in parasite adenosine/purine nucleoside transport reduced or abolished the uptake of beta-D-adenosine, NBMPR, and purine beta-L-nucleosides. Hence, the presence of the Toxoplasma adenosine/purine nucleoside transporters is apparently essential for the uptake of NBMPR and purine beta-L-nucleosides by intracellular Toxoplasma and Toxoplasma-infected cells. These results also demonstrate that, in contrast to the mammalian nucleoside transporters, the Toxoplasma adenosine/purine nucleoside transporter(s) lacks stereospecificity and substrate specificity in the transport of purine nucleosides. In addition, infection with T. gondii confers the properties of the parasite's purine nucleoside transport on the parasitized host cells and enables the infected cells to transport purine nucleosides that were not transported by uninfected cells. These unique characteristics of purine nucleoside transport in T. gondii may aid in the identification of new promising antitoxoplasmic drugs.     

Reliability,Surgeon Preferences,and Eye-Tracking Assessment of the Stress Examination of the Ankle Syndesmosis

The diagnosis and stabilization of ankle syndesmotic injuries after acute injury remains an area of controversy in the foot and ankle surgical literature, seemingly without universal consensus. The primary objective of this investigation was to determine the frequency of agreement and reliability of the stress examination of the ankle syndesmosis. Secondary objectives were to determine surgeon preferences and protocols with respect to the ankle syndesmosis and to use gaze recognition software to perform an eye-tracking assessment during performance of stress examinations. Twelve foot and ankle surgeons, 12 residents, and 12 students were shown 5 intraoperative fluoroscopic still images and videos of the stress examination of the ankle syndesmosis. They were asked to evaluate the result as being “positive” or “negative” for syndesmotic stability. The overall reliability of the interpretation of the stress examination of the ankle syndesmosis was a kappa of 0.123 (surgeons 0.087; residents 0.019; students 0.237), indicating “slight” agreement. Survey results indicated wide variability in the perioperative preferences and protocols of surgeons dealing with the evaluation and treatment of the ankle syndesmosis. Eye-tracking results also demonstrated variability in the anatomic structures of interest focused on during performance of this testing. The results of this investigation provide evidence of reliability well below what would be expected of a gold standard test during stress examination of the ankle syndesmosis. These results indicate that future scientific endeavors are required to standardize the performance and interpretation of this testing.     

干细胞移植治疗时间窗与临床疗效的荟萃分析

目的:探讨寻找干细胞移植治疗急性心肌梗死的最佳移植治疗时间,指导临床应用,提高临床疗效。方法:应用计算机检索medline2000-01/2006-05文章,检索词为:"stem cell transplantation and/or acute myocardialinfarction(AMI)and/or chronic heart failure or ischemic cardiomyopathy",限定文章语言种类为English;同时计算机检索中国期刊全文数据库,相同时间的文章,检索词:"干细胞移植治疗,干细胞移植与急性心肌梗死,干细胞移植治疗与心力衰竭或慢性缺血性心肌病",限定文章语言种类为中文。共检索到300余篇与主题有关的文献,其中12篇有价值的文章见参考文献。移植时间取平均值,并按射血分数值和P值进行列表、作图。对干细胞移植时间与射血分数值之间的关系进行分析。结果:在急性心肌梗死后2～5d和9d以后进行干细胞移植治疗疗效较24h内及6～8d为好。结论:干细胞移植治疗急性心肌梗死的移植时间与临床疗效之间可能存在一定的相关性。经冠脉注入干细胞比经静脉或经心内膜下注入可以更好地改善左室功能,但还需要进一步的临床资料证实。     

Expression of apoptosis-inducing factor (AIF) in the aged rat brain

The mitochondrial flavoprotein apoptosis-inducing factor (AIF) promotes cell death upon nuclear translocation or by impinging on mitochondrial respiratory complex-I activity. Because decreased complex-I activity is associated with brain aging, we investigated the expression and distribution of AIF in frontal cortex, hippocampus and striatum of aged Long-Evans rat brains. We found that AIF was: (i) more abundantly expressed in striatum than in the other two brain regions, (ii) enriched in deep layers of frontal cortex and in the pyramidal cell layer of hippocampus, and (iii) overall mainly localized to mitochondria, but significantly more translocated to the nucleus in the deep layers of frontal cortex. Altogether, our data point to a difference in regionl AIF expression patterns, and provide evidence for the involvement of AIF in the cell death of a subpopulation of cortical neurons in aged animals.     

A comparative histological analysis of human pulp following direct pulp capping with Propolis, mineral trioxide aggregate and Dycal

Background:  Permanent teeth pulp exposures have traditionally been treated with calcium hydroxide pulp capping. The aim of this study was to investigate the response of human pulp tissue which were mechanically exposed to a new material, Propolis and compare it with two existing and commonly used pulp capping agents (mineral trioxide aggregate and Dycal).
Methods:  Thirty-six intact human premolars were mechanically exposed. Teeth were divided into six groups of 6 teeth each and were capped with Propolis, mineral trioxide aggregate and Dycal. Final restoration was done with posterior composite resin using light cured glass ionomer cement as a liner. The teeth were then extracted on the 15th or the 45th day and processed for histological evaluation.
Results:  Differences in inflammatory response and dentine bridge formation of the exposed pulp to the three different materials were statistically calculated using chi-square test and were found to be non-significant. There was more pulp inflammation in teeth treated with Dycal than with Propolis and MTA on the 15th as well as on the 45th day. Propolis and MTA showed bridge formation in more teeth, and the bridges were in closer proximity to pulp capping material than teeth treated with Dycal on the 45th day.
Conclusions:  The response of pulps to Propolis as a pulp capping agent was comparable to MTA and Dycal.     

Experience with Vacuum-assisted closure of sternal wound infections following cardiac surgery and evaluation of chronic complications associated with its use

OBJECTIVES: We report our experience in use of Vacuum-assisted closure therapy (VAC) in the treatment of poststernotomy wound infection with emphasis on recurrent wound-related problems after use of VAC and their treatment. METHODS: Between July 2000 and June 2003, 2706 patients underwent various cardiac procedures via median sternotomy. Forty-nine patients with postoperative sternal wound infection (1.9%) were managed with VAC. Wounds were classified as either superficial sternal wound infection (28 patients) or deep sternal wound infection (21 patients). In the superficial sternal wound infection group, 23 patients had VAC as definitive treatment (GroupA), while five patients (Group B) had VAC followed by surgical closure. Similarly, in the deep sternal wound infection group, 12 patients had VAC as definitive treatment (Group C), while nine patients had VAC followed by surgical closure (Group D). Patients were discharged after satisfactory wound closure. Upon discharge patients were followed up at interval of three to six months. Recurrent sternal problems when identified were investigated and additional surgical procedures were carried out when necessary. RESULTS: There were nine deaths, all due to unrelated causes except in one patient who died of right ventricular rupture (Group C). Nine patients in Group A had recurrent wound problems of which six had VAC system for > 21 days. Three patients underwent extensive debridement due to sternal osteomyelitis. All eight patients in Group B presented with chronic wound-related problems and underwent multiple debridements. Four patients had laparoscopic omental flaps. In contrast 14 patients (Group B and D) who were treated with shorter duration of VAC followed by either a flap or direct surgical closure, did not present with recurrent problems. CONCLUSION: VAC therapy is a safe and reliable option in the treatment of sternal wound infection. However, prolonged use of VAC system as a replacement for surgical closure of sternal wound appears to be associated with recurrent problems of the sternal wound. Strategy of use of VAC for a short duration followed by early surgical closure appears favorable.     

Synthesis, biological evaluation and molecular modeling studies of N6-benzyladenosine analogues as potential anti-toxoplasma agents

Toxoplasma gondii is an opportunistic pathogen responsible for toxoplasmosis. T. gondii is a purine auxotroph incapable of de novo purine biosynthesis and depends on salvage pathways for its purine requirements. Adenosine kinase (EC.2.7.1.20) is the major enzyme in the salvage of purines in these parasites. 6-Benzylthioinosine and analogues were established as "subversive substrates" for the T. gondii, but not for the human adenosine kinase. Therefore, these compounds act as selective anti-toxoplasma agents. In the present study, a series of N(6)-benzyladenosine analogues were synthesized from 6-chloropurine riboside with substituted benzylamines via solution phase parallel synthesis. These N(6)-benzyladenosine analogues were evaluated for their binding affinity to purified T. gondii adenosine kinase. Furthermore, the anti-toxoplasma efficacy and host toxicity of these compounds were tested in cell culture. Certain substituents on the aromatic ring improved binding affinity to T. gondii adenosine kinase when compared to the unsubstituted N(6)-benzyladenosine. Similarly, varying the type and position of the substituents on the aromatic ring led to different degrees of potency and selectivity as anti-toxoplasma agents. Among the synthesized analogues, N(6)-(2,4-dimethoxybenzyl)adenosine exhibited the most favorable anti-toxoplasma activity without host toxicity. The binding mode of the synthesized N(6)-benzyladenosine analogues were characterized to illustrate the role of additional hydrophobic effect and van der Waals interaction within an active site of T. gondii adenosine kinase by induced fit molecular modeling.