Frictional properties of Hartley guinea pig knees with and without proteolytic disruption of the articular surfaces

OBJECTIVE: To apply a pendulum technique to detect changes in the coefficient of friction of the articular cartilage of the intact guinea pig tibiofemoral joint after proteolytic disruption. DESIGN: Twenty-two hind limbs were obtained from 11 3-month old Hartley guinea pigs. Twenty knees were block-randomized to one of two treatment groups receiving injections of: (1) alpha-chymotrypsin (to disrupt the superficial layer of the articular surface) or (2) saline (sham; to control for the effects of the intra-articular injection). The legs were mounted in a pendulum where the knee served as the fulcrum. The decay in pendulum amplitude as a function of oscillation number was first recorded and the coefficient of friction of the joint was determined from these data before injection. Ten microliters of either isotonic saline or 1 Unit/microL alpha-chymotrypsin was then injected into the intra-articular joint space and incubated for 2h. The pendulum test was repeated. Changes in the coefficient of friction between the sham and alpha-chymotrypsin joints were compared. One additional pair of knees was used for histological study of the effects of the injections. RESULTS: Treatment with alpha-chymotrypsin significantly increased the coefficient of friction of the guinea pig knee by 74% while sham treatment decreased it by 8%. Histological sections using Gomori trichrome stain verified that the lamina splendens was damaged following treatment with alpha-chymotrypsin and not following saline treatment. CONCLUSIONS: Treatment with alpha-chymotrypsin induces mild cartilage surface damage and increases the coefficient of friction in the Hartley guinea pig knee.     

CB2: a cannabinoid receptor with an identity crisis

CB₂ was first considered to be the ‘peripheral cannabinoid receptor’. This title was bestowed based on its abundant expression in the immune system and presumed absence from the central nervous system. However, multiple recent reports question the absence of CB₂ from the central nervous system. For example, it is now well accepted that CB₂ is expressed in brain microglia during neuroinflammation. However, the extent of CB₂ expression in neurons has remained controversial. There have been studies claiming either extreme-its complete absence to its widespread expression-as well as everything in between. This review will discuss the reported tissue distribution of CB₂ with a focus on CB₂ in neurons, particularly those in the central nervous system as well as the implications of that presence. As CB₂ is an attractive therapeutic target for pain management and immune system modulation without overt psychoactivity, defining the extent of its presence in neurons will have a significant impact on drug discovery. Our recommendation is to encourage cautious interpretation of data that have been presented for and against CB₂''s presence in neurons and to encourage continued rigorous study.This article is part of a themed issue on Cannabinoids. To view the editorial for this themed issue visit http://dx.doi.org/10.1111/j.1476-5381.2010.00831.x     

Virulence Genes and Genotypic Associations in Nasal Carriage,Community-Associated Methicillin-Susceptible and Methicillin-Resistant USA400 Staphylococcus aureus Isolates

It is not well understood why strains of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), a major cause of skin and soft tissue infections, became successful so quickly, overtaking the place of methicillin-sensitive S. aureus (MSSA) in many communities. To evaluate the genetic basis of differences in their virulence traits, 293 S. aureus isolates consisting of three cohorts, genotypically defined clinical CA-MRSA (n = 77), clinical MSSA (n = 103), and nasal carriage MSSA (n = 113), collected over a 19-year period in two Midwestern states in the United States, were (i) extensively genotyped and (ii) screened for 40 known virulence genes which included those for enterotoxins, leukocidins, hemolysins, and surface proteins and several newly identified putative toxin genes from the USA400 lineage of CA-MRSA. Genotypically, nasal carriage and clinical MSSA isolates were much more diverse than was the CA-MRSA group, which was found to be of USA400 lineage only. Virulence gene profiles of the three groups showed that CA-MRSA strains harbored significantly higher percentages (≥95%; P value, <0.05) of the sea, sec, sec4, seg2, seh, sek, sel, sel2, ear, ssl1, lpl10, lukSF-PV, lukD, lukE, and clfA genes than did the carriage and the clinical MSSA group (range, 0% to 58%). Genes of the enterotoxin gene cluster, seg, sei, sem, sen, and seo, were present in the clinical and carriage isolates but not in the CA-MRSA group. These results suggest that the presence of additional virulence factors in USA400 CA-MRSA strains compared to the nasal carriage and clinical MSSA strains probably contributed to their enhanced virulence.Staphylococcus aureus both is a benign commensal and common pathogen in humans and is responsible for a variety of infections, ranging from superficial skin and soft tissue infections to bacteremia, endocarditis, and osteomyelitis (33). Based on its susceptibility to beta-lactams, S. aureus is commonly described as methicillin-susceptible S. aureus (MSSA) or methicillin-resistant S. aureus (MRSA) (15). Infections due to health care-associated MRSA (HA-MRSA) have been a problem since the 1970s; however, starting in the 1990s, new strains of MRSA, referred to as community-associated MRSA (CA-MRSA), appeared in community dwellers and were genetically different from HA-MRSA strains (7). Until recently, individuals who presented with infections due to CA-MRSA typically have had none of the established risk factors associated with HA-MRSA, such as recent hospitalization, surgery, dialysis, long-term care residence, or indwelling medical devices. Lately however, CA-MRSA strains have been reported from both the community and the health care settings (25, 45). Genotyping tools such as pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and spa typing have helped in distinguishing the genotypes of CA-MRSA strains from those of other S. aureus strains (2, 14, 26). In PFGE, SmaI-restricted S. aureus genomes are compared to determine their genetic relatedness and also compared against the reference USA genotypes (USA100, USA200, etc., up to USA1200) as described by the Centers for Disease Control and Prevention (CDC) (34, 53). Of these, CA-MRSA isolates mostly belong to USA300 and USA400 clones and in some cases USA1000 and USA1100 clones as well. HA-MRSA isolates generally belong to USA100, USA200, and USA500 (34, 35). One of the two major clones of CA-MRSA, USA400, recognized in the early 1990s and initially referred to as the MW2 clone, was the predominant CA-MRSA clone that initially circulated in the midwestern United States in the 1990s (8, 17, 40, 52). The second and more recent CA-MRSA clone, USA300, was first recognized in 2000 and has since spread throughout the world (54). More than a thousand MLST allelic profiles for S. aureus have been identified so far, of which CA-MRSA strains are primarily represented by sequence type 1 (ST1) (USA400) and ST8 (encompasses USA300 and USA500). Of the several thousand spa types in the Ridom database (http://spaserver.ridom.de/), the most predominant CA-MRSA spa types are t008 and t128.CA-MRSA strains, besides their distinct PFGE, ST, and spa profiles, almost ubiquitously possess the Panton-Valentine leukocidin (PVL or lukSF-PV) genes, in contrast to only 1% to 5% of S. aureus strains overall having these genes (33, 50, 57). The PVL toxin has been implicated in many skin and soft tissue infections and lethal necrotizing pneumonia, but the exact role of PVL during S. aureus infections remains controversial (10, 28, 31, 58). The genome sequence of the CA-MRSA strain MW2 of the USA400 lineage showed the presence of several additional putative toxin genes (e.g., ear, sec4, sel2, seg2, ssl1 [set16], and lpl10) compared with other S. aureus strains that had been sequenced (1). Some of these toxin genes share homology with classic staphylococcal enterotoxin genes that encode pyrogenic exotoxins (49) typically produced during the post-exponential phase of growth, and the genes encoding these exotoxins are most often carried on plasmids, bacteriophages, or pathogenicity islands. The classic staphylococcal enterotoxin genes (sea, seb, sec, sed, see, seg, seh, sei, sej, sek, sel, sem, sen, and seo) are commonly found in strains of S. aureus (12, 23, 39, 42, 43, 46, 62). Pyrogenic exotoxin genes are common in S. aureus, and as many as 73% of S. aureus isolates carry at least one of the genes encoding a classic pyrogenic exotoxin; however, the distribution among various clonal types differs (3). Strains of USA400 CA-MRSA typically have been shown to possess the sea, sec, seh, and sek enterotoxin genes, whereas HA-MRSA strains usually carry the sed, seg, sei, sej, sem, sen, and seo enterotoxin genes (40). Currently, the distribution of the newly identified putative toxin genes (seg2, sel2, sec4, ssl1, and lpl10) (1) from the MW2 strain has not been reported from among CA-MRSA strains in general or from clinical and nasal carriage MSSA strains. Since CA-MRSA isolates are able to cause disease in humans without predisposing risk factors and have spread rapidly in communities, these strains may possess a greater number of toxin genes than do the other strains of S. aureus.The aim of this study was to compare the genotypes of clinical CA-MRSA USA400, clinical MSSA, and colonizing nasal carriage MSSA isolates and determine the frequency and distribution of the classic enterotoxin genes as well as the new putative toxin genes in them. Our results showed that MSSA strains were much more diverse in their genotypes than were CA-MRSA USA400 strains. In addition, CA-MRSA USA400 strains possessed a distinct array of toxin genes compared to MSSA strains. These data may provide insight into the success of CA-MRSA USA400 and its ability to cause severe disease in previously healthy people.     

Refinement of the locus for hereditary congenital facial palsy on chromosome 3q21 in two unrelated families and screening of positional candidate genes

Hereditary congenital facial palsy (HCFP) is an autosomal-dominant disorder consisting of paresis or paralysis of the VIIth (facial) cranial nerve. Genetic heterogeneity for this disorder has been suggested based on linkage analysis in two large Dutch families. Two loci have been identified, one on chromosome 3q21.2-q22.1 (HCFP1) and another on chromosome 10q21.3-q22.1 (HCFP2). Here, we report linkage analysis in a large Pakistani family with dominant congenital facial palsy. A region cosegregating with the disorder was identified on the long arm of chromosome 3, which overlaps with the previously identified HCFP1 locus on chromosome 3q21-q22, thus confirming the involvement of this locus in HCFP. The critical region could be reduced from 5.7 to 3.0 cM between the markers D3S3607 and GDB ID:11524500. In addition, mutation analysis on seven candidate genes: KLF15, FLJ40083, PODXL2, TMCC1, PLEXIN-A1, PLEXIN-D1, and GATA-2, was performed. All genes are located within the critical interval of the Dutch HCFP1 family. The genes PODXL2, PLEXIN-D1, GATA-2, and TMCC1 are also located within the smaller critical interval of the Pakistani HCFP family. Based on the results obtained, all seven genes could be excluded as causative genes in HCFP.     

Recalibration of risk prediction models in a large multicenter cohort of admissions to adult, general critical care units in the United Kingdom

OBJECTIVE: To assess the performance of published risk prediction models in common use in adult critical care in the United Kingdom and to recalibrate these models in a large representative database of critical care admissions. DESIGN: Prospective cohort study. SETTING: A total of 163 adult general critical care units in England, Wales, and Northern Ireland, during the period of December 1995 to August 2003. PATIENTS: A total of 231,930 admissions, of which 141,106 met inclusion criteria and had sufficient data recorded for all risk prediction models. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The published versions of the Acute Physiology and Chronic Health Evaluation (APACHE) II, APACHE II UK, APACHE III, Simplified Acute Physiology Score (SAPS) II, and Mortality Probability Models (MPM) II were evaluated for discrimination and calibration by means of a combination of appropriate statistical measures recommended by an expert steering committee. All models showed good discrimination (the c index varied from 0.803 to 0.832) but imperfect calibration. Recalibration of the models, which was performed by both the Cox method and re-estimating coefficients, led to improved discrimination and calibration, although all models still showed significant departures from perfect calibration. CONCLUSIONS: Risk prediction models developed in another country require validation and recalibration before being used to provide risk-adjusted outcomes within a new country setting. Periodic reassessment is beneficial to ensure calibration is maintained.     

A multifunctional cytoprotective agent that reduces neurodegeneration after ischemia

Cellular and molecular pathways underlying ischemic neurotoxicity are multifaceted and complex. Although many potentially neuroprotective agents have been investigated, the simplicity of their protective mechanisms has often resulted in insufficient clinical utility. We describe a previously uncharacterized class of potent neuroprotective compounds, represented by PAN-811, that effectively block both ischemic and hypoxic neurotoxicity. PAN-811 disrupts neurotoxic pathways by at least two modes of action. It causes a reduction of intracellular-free calcium as well as free radical scavenging resulting in a significant decrease in necrotic and apoptotic cell death. In a rat model of ischemic stroke, administration of PAN-811 i.c.v. 1 h after middle cerebral artery occlusion resulted in a 59% reduction in the volume of infarction. Human trials of PAN-811 for an unrelated indication have established a favorable safety and pharmacodynamic profile within the dose range required for neuroprotection warranting its clinical trial as a neuroprotective drug.     

Study protocol: Home-based physical rehabilitation for survivors of a critical illness [ACTRN12605000166673]

Introduction  

Numerous primary studies and several review papers have highlighted delayed physical and psychological recovery for survivors of critical illness, often beyond 6 months after discharge. This randomized controlled trial with blinded assessment aims to test the effects of an 8-week, home-based, individually tailored physical rehabilitation programme on physical and psychological recovery for survivors of a critical illness after discharge from hospital.