Heterologously expressed Staphylococcus aureus fibronectin-binding proteins are sufficient for invasion of host cells

Staphylococcus aureus invasion of mammalian cells, including epithelial, endothelial, and fibroblastic cells, critically depends on fibronectin bridging between S. aureus fibronectin-binding proteins (FnBPs) and the host fibronectin receptor integrin alpha(5)beta(1) (B. Sinha et al., Cell. Microbiol. 1:101-117, 1999). However, it is unknown whether this mechanism is sufficient for S. aureus invasion. To address this question, various S. aureus adhesins (FnBPA, FnBPB, and clumping factor [ClfA]) were expressed in Staphylococcus carnosus and Lactococcus lactis subsp. cremoris. Both noninvasive gram-positive microorganisms are genetically distinct from S. aureus, lack any known S. aureus surface protein, and do not bind fibronectin. Transformants of S. carnosus and L. lactis harboring plasmids coding for various S. aureus surface proteins (FnBPA, FnBPB, and ClfA) functionally expressed adhesins (as determined by bacterial clumping in plasma, specific latex agglutination, Western ligand blotting, and binding to immobilized and soluble fibronectin). FnBPA or FnBPB but not of ClfA conferred invasiveness to S. carnosus and L. lactis. Invasion of 293 cells by transformants was comparable to that of strongly invasive S. aureus strain Cowan 1. Binding of soluble and immobilized fibronectin paralleled invasiveness, demonstrating that the amount of accessible surface FnBPs is rate limiting. Thus, S. aureus FnBPs confer invasiveness to noninvasive, apathogenic gram-positive cocci. Furthermore, FnBP-coated polystyrene beads were internalized by 293 cells, demonstrating that FnBPs are sufficient for invasion of host cells without the need for (S. aureus-specific) coreceptors.     

Solute-free water excretion and electrolyte-free water excretion are better terms than solute-free water clearance and electrolyte-free water clearance

International Urology and Nephrology -     

Interstitial F(2)-isoprostane 8-iso-PGF(2α) as a biomarker of oxidative stress after severe human traumatic brain injury

Oxidative stress is a major contributor to the secondary injury process after experimental traumatic brain injury (TBI). The importance of oxidative stress in the pathobiology of human TBI is largely unknown. The F(2)-isoprostane 8-iso-prostaglandin F(2α) (8-iso-PGF(2α)), synthesized in vivo through non-enzymatic free radical catalyzed peroxidation of arachidonic acid, is a widely used biomarker of oxidative stress in multiple disease states, including TBI and cerebral ischemia/reperfusion. Our hypothesis is that harvesting of biomarkers directly in the injured brain by cerebral microdialysis (MD) is advantageous because of its high spatial and temporal resolution compared to blood or cerebrospinal fluid sampling. The aim of this study was to test the feasibility of measuring 8-iso-PGF(2α) in MD, ventricular cerebrospinal fluid (vCSF), and plasma samples collected from patients with severe TBI, and to compare the MD signals with MD-glycerol, implicated as a biomarker of oxidative stress, as well as MD-glutamate, a biomarker of excitotoxicity. Six patients (4 men, 2 women) were included in the study, three of whom had a focal/mixed TBI, and three a diffuse axonal injury (DAI). Following the bedside analysis of routine MD biomarkers (glucose, lactate:pyruvate ratio, glycerol, and glutamate), two 12-h MD samples per day were used to analyze 8-iso-PGF(2α) from 24?h up to 8 days post-injury. The interstitial levels of 8-iso-PGF(2α) were markedly higher than the levels obtained from plasma and vCSF (p<0.05), supporting our hypothesis. The MD-8-iso-PGF(2α) levels correlated strongly (p<0.05) with MD-glycerol and MD-glutamate, which are widely used biomarkers of membrane phospholipid degradation/oxidative stress and excitotoxicity, respectively. This study demonstrates the feasibility of analyzing 8-iso-PGF(2α) in MD samples from the human brain. Our results support a close relationship between oxidative stress and excitotoxicity following human TBI. MD-8-iso-PGF(2α) in combination with MD-glycerol may be useful biomarkers of oxidative stress in the neurointensive care setting.     

Toward noninvasive monitoring of ongoing electrical activity of human uterus and fetal heart and brain

Objective

To evaluate whether a full-coverage fetal-maternal scanner can noninvasively monitor ongoing electrophysiological activity of maternal and fetal organs.

A big-world network in ASD: dynamical connectivity analysis reflects a deficit in long-range connections and an excess of short-range connections

Over the last years, increasing evidence has fuelled the hypothesis that Autism Spectrum Disorder (ASD) is a condition of altered brain functional connectivity. The great majority of these empirical studies relies on functional magnetic resonance imaging (fMRI) which has a relatively poor temporal resolution. Only a handful of studies has examined networks emerging from dynamic coherence at the millisecond resolution and there are no investigations of coherence at the lowest frequencies in the power spectrum—which has recently been shown to reflect long-range cortico-cortical connections. Here we used electroencephalography (EEG) to assess dynamic brain connectivity in ASD focusing in the low-frequency (delta) range. We found that connectivity patterns were distinct in ASD and control populations and reflected a double dissociation: ASD subjects lacked long-range connections, with a most prominent deficit in fronto-occipital connections. Conversely, individuals with ASD showed increased short-range connections in lateral-frontal electrodes. This effect between categories showed a consistent parametric dependency: as ASD severity increased, short-range coherence was more pronounced and long-range coherence decreased. Theoretical arguments have been proposed arguing that distinct patterns of connectivity may result in networks with different efficiency in transmission of information. We show that the networks in ASD subjects have less Clustering coefficient, greater Characteristic Path Length than controls - indicating that the topology of the network departs from small-world behaviour - and greater modularity. Together these results show that delta-band coherence reveal qualitative and quantitative aspects associated with ASD pathology.     

High blood pressure, other risk factors and longevity: the insurance viewpoint

The 1960–1962 National Health Survey indicates that about 15 per cent of the population suffers from definite hypertension (systolic pressure 160 mm Hg or higher, or diastolic pressure 95 mm Hg or higher) and that a like proportion has borderline hypertension (systolic pressure 140 to 159 mm Hg or diastolic pressure 90 to 94 mm Hg). The frequency of hypertension rises with advancing age and is greater for men than for women up to about age 50 years, but at the older ages the reverse is true.Follow-up studies of insured persons carried out over nearly 50 years have established that untreated blood pressures in excess of 140/90 mm Hg are associated with significant extra mortality over a period of years; for instance, in men under 40 with casual pressures of 150/100 mm Hg mortality was approximately 325 per cent that of standard insured risks, whereas corresponding men aged 40 and over showed a mortality of about 225 per cent. Such excess mortality increases with rise in blood pressure and is greater in the presence of other impairments or complications. On the other hand, the blood pressures optimal for longevity are those below 110 mm Hg systolic and 70 mm Hg diastolic.At ages under 55, cholesterol levels of 260 mg and higher are somewhat more common than systolic pressures of 150 mm Hg and higher (or diastolic pressures of 90 mm Hg and higher), but the reverse is true for men at ages 55 to 64 years.The Framingham and other studies show that hypertension is by and large the most important risk factor in coronary heart disease. Elevated serum cholesterol levels as a risk factor in coronary heart disease is strong at the younger ages only. Insofar as death rates from all causes are concerned, systolic pressures in excess of 150 mm Hg have a distinctly more adverse effect on mortality than does serum cholesterol of 265 mg and higher, especially at ages 45 to 64 years. This is because hypertension affects not only death rates from coronary heart disease but also those from hypertensive heart disease, cerebral vascular disease and renal complications, whereas the major effect of elevated serum cholesterol is on mortality from coronary heart disease.Inasmuch as blood pressure levels among people with slight or moderate hypertension remain relatively stable for considerable periods of time in a high proportion of cases, one of the major challenges to the clinician is to identify those hypertensive subjects in whom the underlying pathologic process is most acutely progressive.     

Absence of significant bacteremia during urinary catheter manipulation in patients with chronic indwelling catheters

The objective of this study was to quantify the microorganisms present in blood at urinary catheter removal and at reinsertion in patients with chronic indwelling urinary catheters. This was a prospective study during a 4-month period at a university-affiliated geriatric medical center. Our subjects were 33 patients with chronic indwelling urinary catheters and positive urinary cultures; the urinary catheter was usually changed once a month. A peripheral vein line was used for blood withdrawal and urinary cultures and quantitative blood cultures (Isolator) were performed during and shortly after urinary catheter removal and insertion. All patients had significant bacteriuria (greater than 10(5) cfu/mL) with an average of 2.3 microorganisms. Among the 46 sequential quantitative blood cultures performed, only two patients had bacteremia from the urinary source and at a very low concentration; one patient had 0.13 cfu/mL Str. faecalis in blood 5 minutes after removal of the urinary catheter, and the other 0.1 cfu/mL Proteus mirabilis 5 minutes after reinsertion of a new urinary catheter. None of the patients had any subjective or objective clinical problem during the 36 hours after the urinary manipulation. Clinical symptoms and bacteremia are rare events, and prophylactic antibiotics do not appear necessary during urinary catheter removal and reinsertion in elderly institutionalized patients. Further studies are necessary to identify risk factors in the rare instances of patients with bacteremia.     

Guinea pig ozone-induced airway hyperreactivity is associated with increased N-acetyl-β-D-glucosaminidase activity in bronchoalveolar lavage fluid

High level ozone exposure is known to cause acute, neutrophil-independent airway hyperreactivity in the guinea pig. The precise biochemical mechanisms involved remain unclear. Because of its potential pathophysiologic importance, we examined whether a lysosomal hydrolase, N-acetyl-β-D-glucosaminidase (NAGA) was released from the airways in vivo and from bronchoalveolar cells, specifically macrophages. Muscarinic reactivity was determined by measuring specific airway resistance (sRaw) in response to increasing doses of aerosolized acetylcholine in guinea pigs that were either exposed to air or to ozone (3.0 ppm, 2 h). The ozone-exposed animals showed substantial muscarinic hyperreactivity 30 min after exposure. In addition, both total and percent released NAGA in bronchoalveolar lavage fluid obtained immediately after reactivity testing were significantly greater in the ozone-exposed group. It was also found that substantially more NAGA was released from mixed bronchoalveolar lavage cells in response to 20 µM A23187. Moreover, bronchoalveolar macrophages of ozone-exposed animals secreted more NAGA upon stimulation in vitro by either 20 µM A23187 or 200 µg/ml opsonized zymosan. We conclude that ozone-induced airway hyperreactivity in guinea pigs is associated with the presence of increased NAGA activity in bronchoalveolar fluid. Our data suggest that bronchoalveolar macrophages may, at least in part, be responsible for release of this enzyme into the airways after ozone exposure.     

Load sharing and graft forces in anterior cruciate ligament reconstructions with the Ligament Augmentation Device

Buckle transducers were used to directly measure load sharing and overall force in three segment (semitendinosus, gracilis, Ligament Augmentation Device) and two segment (patellar tendon, LAD) composite ACL grafts during the application of anteriorly directed loads to a series of five fresh knee specimens with a pneumatic load apparatus. The total graft forces generated in the two segment and three segment composite reconstructions during this immediate postoperative state were highly variable when compared to the normal ACL in each specimen, and were irreproducible among the five specimens. Load sharing among the graft components occurred and was also variable in both reconstructions, with this variation being greater in the three segment graft. The LAD carried an average of 45% of the total graft force in the three segment graft and 28% in the two segment graft. Further work is required to clarify the source of the variability in the total graft force and load sharing observed in this study.