Invalidity for Pseudomonas aeruginosa of an accepted model of bacterial permeability to beta-lactam antibiotics.

The accepted model for the penetration of beta-lactam antibiotics into gram-negative bacteria is that proposed by Zimmermann and Rosselet (Antimicrob. Agents Chemother. 12:368-372, 1977). The model assumes (i) that diffusion of the antibiotic molecules across the outer membrane obeys Fick's law and can be characterized by a permeability constant for any given combination of organism and drug, (ii) that drug hydrolysis within the periplasm obeys Michaelis-Menten kinetics, and (iii) that a steady state is rapidly attained between drug uptake and hydrolysis. The model has allowed accurate prediction of antibiotic MICs for Escherichia coli strains from a knowledge of their beta-lactamase production and permeability characteristics. It has been suggested that the model is inappropriate for Pseudomonas aeruginosa, but attempts to confirm this have been bedevilled by experimental difficulties in estimating permeability coefficients for this species. In the present study, we tested a prediction of the model that the overall resistance of P. aeruginosa transconjugants containing a plasmid-encoded beta-lactamase should continue to depend partly on permeability. Transconjugants with PSE-4 beta-lactamase were constructed in host strains with widely different levels of intrinsic, presumably impermeability-determined resistance. Contrary to the prediction of the model, all the transconjugants developed identical overall levels of resistance to substrate beta-lactams, such as azlocillin and cefoperazone, irrespective of the initial levels of intrinsic resistance of the recipient strains. We conclude that the model is inappropriate for P. aeruginosa, and possible explanations for the organism's behavior are discussed.     

Depressive symptoms and muscular fitness contribute independently to the ability to perform daily life activities in people with bipolar disorder

Background: Compared with healthy controls, people with bipolar disorder experience muscle weakness. The extent to which muscle weakness influences the performance of daily life activities such as walking in people with bipolar disorder requiring hospitalization is unclear. Aims: The primary aim of the current study was to explore whether depressive symptoms and muscular fitness independently contribute to the walking capacity in people with bipolar disorder. A secondary aim was to identify variables that could explain the variability in muscular fitness. Methods: Forty-two inpatients with bipolar disorder performed a standing broad jump test (SBJ), a measure of muscular performance, and the six minute walk test (6MWT) in addition to the International Physical Activity Questionnaire (IPAQ), the Depressive Symptomatology Self Report (QIDS) and a full-fasting metabolic screening. Results: The correlation between the 6MWT (595.0?±?127.3m) and SBJ (126.2?±?48.6m) was high (r?=?0.72, p?Conclusions: Depressive symptoms and muscular fitness contribute independently to daily life functioning in people with bipolar disorder. Thus, muscular rehabilitation strategies might offer a strategy for improving performance of daily life activities in this group.     

Intact protein analysis in the biopharmaceutical field

In recent years, a growing number of biopharmaceutical proteins have been produced and are already available, or will be soon available, in the market. These molecules are more complex to analyze than conventional low molecular weight drugs, and thus need powerful analytical approaches for the entire development and delivery process. This review summarizes the analytical techniques available for intact protein determination and the main development steps in which they are applicable. A strong emphasis has been put on separation techniques, liquid chromatography and electrophoretic techniques, but mass spectrometry and spectroscopic approaches are also mentioned. Overall, we highlight how several analytical strategies are necessary to obtain global information.     

Reconstruction of juxta-articular huge defects of distal femur with vascularized fibular bone graft and Ilizarov's distraction osteogenesis

BACKGROUND: We evaluate the effect of reconstructing huge defects (mean, 15.8 cm) of the distal femur with Ilizarov's distraction osteogenesis and free twin-barreled vascularized fibular bone graft (TVFG). METHODS: We retrospectively reviewed a consecutive series of five patients who had cases of distal femoral fractures with huge defects and infection that were treated by the Ilizarov's distraction osteogenesis. After radical debridement, two of the five cases had free TVFG and monolocal distraction osteogenesis, and another two cases had multilocal distraction osteogenesis with knee fusion because of loss of the joint congruity. The other case with floating knee injury had bilocal distraction osteogenesis and a preserved knee joint. The mean defect of distal femur was 15.8 cm (range, 14-18 cm) in length. RESULTS: The mean length of distraction osteogenesis by Ilizarov's apparatus was 8.2 cm. The mean length of TVFG was 8 cm. The average duration from application of Ilizarov's apparatus to achievement of bony union was 10.2 months (range, 8-13 months). At the end of the follow-up, ranges of motion of three knees were 0 to 45 degrees, 0 to 60 degrees, and 0 to 90 degrees. Two cases had knee arthrodesis with bony fusion because of loss of the joint congruity. There were no leg length discrepancies in all five patients. In addition, three patients had pin tract infections and one case had a 10 degree varus deformity of the femur. CONCLUSIONS: Juxta-articular huge defect (>10 cm) of distal femur remains a challenge to orthopedic surgeons. Ilizarov's technique provides the capability to maintain stability, eradicate infection, restore leg length, and to perform adjuvant reconstructive procedure easily. In this study, we found that combining Ilizarov's distraction osteogenesis with TVFG results in improved patient outcome for patients with injuries such as supracondylar or intercondylar infected fractures or nonunion of distal femur with huge bone defect.     

TIMPs and cardiac remodeling: ‘Embracing the MMP-independent-side of the family’

Unraveling the biological role of tissue inhibitors of metalloproteinases (TIMPs) during cardiac remodeling and the progression of heart failure has proven to be an enormous challenge. Remodeling of the cardiac extracellular matrix (ECM), regulated by matrix metalloproteinases (MMPs) and their endogenous inhibitors, TIMPs, is a well-established paradigm in cardiac health and disease. Originally, TIMPs were thought to function exclusively as endogenous inhibitors of MMP activity, thereby fine-tuning MMP-mediated ECM degradation and numerous related processes. However, during the last two decades, the concept of MMP-independent TIMP-mediated receptor signaling and regulation of cell fate has emerged. Although our current knowledge is still limited, in this review, we highlight some of the novel data, illustrating the MMP-independent biological properties of the four TIMP family members. Moreover, we discuss how these cell-specific insights may contribute to the process of cardiac remodeling, disease and failure. Finally, we identify where additional research is needed that will codetermine the possible future of TIMPs as therapeutic targets.     

Enhanced expression of the P2X4 receptor in Duchenne muscular dystrophy correlates with macrophage invasion

Following molecular and immunohistochemical analysis of the purinergic P2X4 receptor subunit in dystrophin-deficient muscle we have identified a distinct subpopulation of P2X4-positive cells infiltrating the dystrophic fibres. These cells were absent from normal muscle and rarely present in the dystrophic muscle taken before and after the onset of degeneration. We have identified these P2X4-positive cells as macrophages, demonstrating for the first time that human and mouse tissue macrophages express P2X4 in addition to P2X7 receptor subunits both in vitro and in situ. Moreover, we have demonstrated that the increase in the P2X4 expression is yet another feature of an inflammatory response identified in DNA arrays of dystrophic muscle. Immunohistochemical analysis failed to localise discernible expression of P2X4 protein in adult skeletal or cardiac muscle fibres, whilst myoblasts in culture expressed low levels of this subunit, as detected by RT-PCR and Western blotting. In light of the involvement of macrophages in the dystrophic process, the function of P2X receptors and their role in the Duchenne pathology as well as their potential role in therapeutic applications are discussed.