Background-Obstructive sleep apnoea (OSA) impairs vigilance and may lead to an increased rate of driving accidents. In uncontrolled studies accident rates and simulated steering performance improve following treatment with nasal continuous positive airway pressure (NCPAP). This study seeks to confirm the improvement in steering performance in a randomised controlled trial using subtherapeutic NCPAP as a control treatment. Conclusions-Therapeutic NCPAP improves steering performance and reaction time to target stimuli in patients with OSA, lending further support to the hypothesis that OSA impairs driving, increases driving accident rates, and that these improve following treatment with NCPAP. (Thorax 2000;55:224-231) Methods-Fifty

Apoptosis causes characteristic morphological changes in cells, including membrane blebbing, cell detachment from the extracellular matrix, and loss of cell-cell contacts. We investigated the changes in focal adhesion proteins during etoposide-induced apoptosis in Rat-1 cells and found that during apoptosis, p130cas (Crk-associated substrate [Cas]) is cleaved by caspase-3. Sequence analysis showed that Cas contains 10 DXXD consensus sites preferred by caspase-3. We identified two of these sites (DVPD 416 G and DSPD 748 G) in vitro, and point mutations substituting the Asp of DVPD 416 G and DSPD 748 G with Glu blocked caspase-3-mediated cleavage. Cleavage at DVPD 416 G generated a 74-kDa fragment, which was in turn cleaved at DSPD 748 G, yielding 47-and 31-kDa fragments. Immunofluorescence microscopy revealed well-developed focal adhesion sites in control cells that dramatically declined in number in etoposide-treated cells. Cas cleavage correlated temporally with the onset of apoptosis and coincided with the loss of p125FAK (focal adhesion kinase [FAK]) from focal adhesion sites and the attenuation of Cas-paxillin interactions. Considering that Cas associates with FAK, paxillin, and other molecules involved in the integrin signaling pathway, these results suggest that caspase-mediated cleavage of Cas contributes to the disassembly of focal adhesion complexes and interrupts survival signals from the extracellular matrix. INTRODUCTIONApoptotic cell death is a fundamental biological process crucial for proper organism development and for maintenance of tissue homeostasis (Raff, 1992). Apoptosis causes characteristic morphological changes that include membrane blebbing, decreased adhesion and intercellular contacts, chromatin condensation, nuclear fragmentation, and the packing of the nuclear fragments into membrane-enclosed apoptotic bodies (Wyllie et al., 1980;Darzynkiewicz et al., 1994). Caspases are a family of highly conserved aspartate-specific cysteine-proteases related to mammalian interleukin-1␤-converting enzyme, which are involved in the final execution phase of apoptosis (Nicholson, 1996;Nicholson and Thornberry, 1997). The substrates for caspases are now known to include a growing number of molecules involved in cytoskeletal regulation and signaling, including ␣-fodrin, gelsolin, growth arrest-specific gene (Gas 2), MEKK-1, and PKC (Brancolini et al., 1995;Emoto et al., 1995;Martin et al., 1995;Ghayur et al., 1996;Cardone et al., 1997;Kothakota et al., 1997;Janicke et al., 1998). Recent studies have shown that attachment to the extracellular matrix (ECM) actively regulates cell survival, and that cells undergoing apoptosis lose their connections to neighboring cells and to the ECM. For example, epithelial and endothelial cells undergo apoptosis ("anoikis") when displaced from the ECM (Frisch and Francis, 1994;Re et al., 1994), whereas cell adhesion to ECM suppresses apoptosis in mammary epithelial cells (Frisch and Francis, 1994;Boudreau et al., 1995;Aharoni et al., 1996).Cell attachment to the ECM i...

Patients with obstructive sleep apnoea (OSA) are reported to have an increased risk of road traffic accidents. This study examines the nature of the impairment during simulated steering in patients with OSA, compared to normal subjects following either sleep deprivation or alcohol ingestion. Twenty-six patients with OSA and 12 normal subjects, either deprived of one night's sleep or following alcohol ingestion [mean (SD) alcohol blood level 71.6 mg dl(-1) (19.6)], performed a simulated steering task for a total of 90 min. Performance was measured using the tendency to wander (SD), deterioration across the task, number of 'off-road' events and the reaction time to peripheral events. Control data for OSA, sleep deprivation and alcohol were obtained following treatment with nasal continuous positive airway pressure (nCPAP), after a normal night of sleep, and following no alcohol, respectively. Patients with untreated OSA, and sleep-deprived or alcohol-intoxicated normal subjects performed significantly less well, compared to their respective controls (P<0.01 for all tests), with untreated OSA lying between that of alcohol intoxication and sleep deprivation. Alcohol impaired steering error equally throughout the whole drive, whilst sleep deprivation caused progressive deterioration through the drive, but not initially. Untreated OSA was more like sleep deprivation than alcohol, although there was a wide spread of data. This suggests that the driving impairment in patients with OSA is more compatible with sleep deprivation or fragmentation as the cause, rather than abnormal cognitive or motor skills.

Burkholderia pseudomallei and Burkholderia mallei, classified as category B priority pathogens, are significant human and animal pathogens that are highly infectious and broad-spectrum antibiotic resistant. Currently, the pathogenicity mechanisms utilized by Burkholderia are not fully understood, and correct diagnosis of B. pseudomallei and B. mallei infection remains a challenge due to limited detection methods. Here, we provide a comprehensive analysis of a set of 13 novel Burkholderia collagen-like proteins (Bucl) that were identified among B. pseudomallei and B. mallei select agents. We infer that several Bucl proteins participate in pathogenesis based on their noncollagenous domains that are associated with the components of a type III secretion apparatus and membrane transport systems. Homology modeling of the outer membrane efflux domain of Bucl8 points to a role in multi-drug resistance. We determined that bucl genes are widespread in B. pseudomallei and B. mallei; Fischer’s exact test and Cramer’s V2 values indicate that the majority of bucl genes are highly associated with these pathogenic species versus nonpathogenic B. thailandensis. We designed a bucl-based quantitative PCR assay which was able to detect B. pseudomallei infection in a mouse with a detection limit of 50 CFU. Finally, chromosomal mapping and phylogenetic analysis of bucl loci revealed considerable genomic plasticity and adaptation of Burkholderia spp. to host and environmental niches. In this study, we identified a large set of phylogenetically unrelated bucl genes commonly found in Burkholderia select agents, encoding predicted pathogenicity factors, detection targets, and vaccine candidates.

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Keratinized epidermis constitutes a powerful barrier of the mucosa and skin, effectively preventing bacterial invasion, unless it is wounded and no longer protective. Wound healing involves deposition of distinct extracellular matrix (ECM) proteins enriched in cellular fibronectin (cFn) isoforms containing extra domain A (EDA). The streptococcal collagen-like protein 1 (Scl1) is a surface adhesin of group A (GAS), which contains an N-terminal variable (V) domain and a C-terminally located collagen-like domain. During wound infection, Scl1 selectively binds EDA/cFn isoforms and laminin, as well as low-density lipoprotein (LDL), through its V domain. The trimeric V domain has a six-helical bundle fold composed of three pairs of anti-parallel α-helices interconnected by hypervariable loops, but the roles of these structures in EDA/cFn binding are unclear. Here, using recombinant Scl (rScl) constructs to investigate structure-function determinants of the Scl1-EDA/cFn interaction, we found that full-length rScl1, containing both the globular V and the collagen domains, is necessary for EDA/cFn binding. We established that the surface-exposed loops, interconnecting conserved α-helices, guide recognition and binding of Scl1-V to EDA and binding to laminin and LDL. Moreover, electrostatic surface potential models of the Scl1-V domains pointed to a conserved, negatively charged pocket, surrounded by positively charged and neutral regions, as a determining factor for the binding. In light of these findings, we propose an updated model of EDA/cFn recognition by the Scl1 adhesin from GAS, representing a significant step in understanding the Scl1-ECM interactions within the wound microenvironment that underlie GAS pathogenesis.

The streptococcal collagen-like proteins 1 and 2 (Scl1 and Scl2) are major surface adhesins that are ubiquitous among group A Streptococcus (GAS). Invasive M3-type strains, however, have evolved two unique conserved features in the scl1 locus: (i) an IS1548 element insertion in the scl1 promoter region and (ii) a nonsense mutation within the scl1 coding sequence. The scl1 transcript is drastically reduced in M3-type GAS, contrasting with a high transcription level of scl1 allele in invasive M1-type GAS. This leads to a lack of Scl1 expression in M3 strains. In contrast, while scl2 transcription and Scl2 production are elevated in M3 strains, M1 GAS lack Scl2 surface expression. M3-type strains were shown to have reduced biofilm formation on inanimate surfaces coated with cellular fibronectin and laminin, and in human skin equivalents. Repair of the nonsense mutation and restoration of Scl1 expression on M3-GAS cells, restores biofilm formation on cellular fibronectin and laminin coatings. Inactivation of scl1 in biofilm-capable M28 and M41 strains results in larger skin lesions in a mouse model, indicating that lack of Scl1 adhesin promotes bacterial spread over localized infection. These studies suggest the uniquely evolved scl1 locus in the M3-type strains, which prevents surface expression of the major Scl1 adhesin, contributed to the emergence of the invasive M3-type strains. Furthermore these studies provide insight into the molecular mechanisms mediating colonization, biofilm formation, and pathogenesis of group A streptococci.

Summary The human‐adapted pathogen group A Streptococcus (GAS) utilizes wounds as portals of entry into host tissue, wherein surface adhesins interact with the extracellular matrix, enabling bacterial colonization. The streptococcal collagen‐like protein 1 (Scl1) is a major adhesin of GAS that selectively binds to two fibronectin type III (FnIII) repeats within cellular fibronectin, specifically the alternatively spliced extra domains A and B, and the FnIII repeats within tenascin‐C. Binding to FnIII repeats was mediated through conserved structural determinants present within the Scl1 globular domain and facilitated GAS adherence and biofilm formation. Isoforms of cellular fibronectin that contain extra domains A and B, as well as tenascin‐C, are present for several days in the wound extracellular matrix. Scl1‐FnIII binding is therefore an example of GAS adaptation to the host's wound environment. Similarly, cellular fibronectin isoforms and tenascin‐C are present in the tumor microenvironment. Consistent with this, FnIII repeats mediate GAS attachment to and enhancement of biofilm formation on matrices deposited by cancer‐associated fibroblasts and osteosarcoma cells. These data collectively support the premise for utilization of the Scl1‐FnIII interaction as a novel method of anti‐neoplastic targeting in the tumor microenvironment.