Ectopic expression of human and feline CD9 in a human B cell line confers beta 1 integrin-dependent motility on fibronectin and laminin substrates and enhanced tyrosine phosphorylation

Few molecules have been shown to confer cell motility. Although the motility-arresting properties of anti-CD9 monoclonal antibody (mAb) suggest the transmembrane 4 superfamily (TM4SF) member CD9 can induce a motorgenic signal, gene transfection studies have failed to confirm this hypothesis. We report here that ectopic expression of human CD9 (CD9h) and feline CD9 (CD9f) in the CD9-negative, poorly motile, human B cell line Raji dramatically enhances migration across fibronectin- and laminin-coated polycarbonate filters. Migration of Raji/CD9h and Raji/CD9f on either substrate was inhibited by the anti-CD9 mAb 50H.19 and by the anti-beta 1 integrin mAb AP-138. Migration of Raji/CD9h on laminin was potently inhibited by the anti-VLA-6 integrin mAb GoH3 and by the anti-VLA-4 integrin mAb 44H6, whereas migration of Raji/CD9h on fibronectin was inhibited only by mAb 44H6. Since CD9h-transfected Raji cells adhered to fibronectin as effectively as mock transfectants, expression of CD9 enhanced motility, but not adhesion. CD9-enhanced migration was inhibited by the protein tyrosine kinase inhibitor herbimycin A suggesting that tyrosine phosphorylation played a role in the generation of a motorgenic signal. Raji/CD9h transfectants adherent to fibronectin expressed 6-fold higher levels of phosphotyrosine than Raji. Raji/CD9f transfectants also phosphorylated proteins on tyrosine more effectively than Raji including a protein of 110 kDa which was phosphorylated on the motility-inducing substrates laminin and fibronectin, but not on bovine serum albumin. Our results support a role for CD9 in the amplification of a motorgenic signal in B cells involving beta 1 integrins and the activation of protein tyrosine kinases.

Quantitative mass spectrometry-based proteomics reveals the dynamic range of primary mouse astrocyte protein secretion

Growing appreciation for astrocytes as active participants in nervous system development, neurovascular metabolic coupling, and neurological disease progression has stimulated recent investigation into specific astrocyte-secreted proteins that may mediate these functions. The current work utilized SILAC-generated isotope reference proteomes to quantify relative protein abundances between the astrocyte proteome and secretome. Multidimensional GeLC-MS/MS analysis of astrocyte conditioned media and cell lysates resulted in the relative quantification of 516 proteins, 92 of which were greater than 1.5-fold enriched in astrocyte-conditioned media (ACM). Eighty of the ACM-enriched proteins had N-terminal signal peptides, comprising well-known classically secreted proteins, such as apolipoprotein E and SPARC, and several cathepsins that localize to endosomal/lysosomal compartments. The remaining twelve ACM-enriched proteins, such as vimentin, ferritins, and histones, lacked N-terminal signal peptides. Also, 47 proteins contained predicted N-terminal signal peptides but were not enriched in ACM (<1.5-fold), 25 of which were localized to ER, Golgi, or mitochondria membrane-bound compartments. Overall, by combining quantitative proteomics with subcellular localization prediction, an informative description of protein distribution can be obtained, providing insights into protein secretion.

Specific phosphorylation at serine-283 of alpha tropomyosin from frog skeletal and rabbit skeletal and cardiac muscle

Tropomyosin, extracted from the leg muscle of frogs that had been injected with [32P]orthophosphate, was fractionated into two components, alpha and beta, on a CM-cellulose column. Radioactivity was associated only with the alpha component. A single phosphorylation site was located at serine-283 (pentultimate at the COOH-terminal end) of the frog alpha tropomyosin. The same phosphorylated peptide was recovered in low yields from both rabbit skeletal alpha and cardiac tropomyosin. The presence of covalently bound phosphate in alpha tropomyosin and its absence in the beta component of rabbit skeletal muscle was suggested by 31P NMR spectroscopy. The amino acid sequences around the phosphorylation sites of frog and rabbit tropomyosin are identical. Because this sequence is not similar to any other known phosphorylation site in proteins, this indicates the existence of either specific kinase or phosphatase that can distinguish between alpha and beta tropomyosins. In a model proposed for the head-to-tail overlap of alpha tropomyosin molecules, one O-phosphoserine-283 residue could form a salt linkage with lysine-6 on one side of the overlap region and another with lysine-12 on the other side. This would predict a difference in the stability of polymers of phosphorylated and nonphosphorylated alphaalpha and alphabeta dimers of tropomyosin.

Bone mineral density in postmenopausal Chinese patients with systemic lupus erythematosus

The objective was to study the bone mineral density (BMD) and its clinical determinants in a cohort of postmenopausal patients with systemic lupus erythematosus (SLE). All postmenopausal SLE patients receiving long term glucocorticoids were identified from our medical clinics. Lumbar and femoral BMDs were measured by dual X-ray absorptiometry. Clinical determinants of BMD were studied by simple and multiple linear regression. Variables evaluated were: age, body mass index, parity, duration of menopause, smoking and alcohol drinking, duration of SLE and steroid treatment, cumulative prednisone dose, clinical and serological profile, disease activity, damage index and the use of medications. In total, 34 patients were studied. The mean age was 52.9+/-4.9 years and the median duration of SLE was 75.5 months. The mean duration of menopause was 5.2+/-3.9 years and the daily maintenance dose of prednisone was 4.0+/-2.5 mg/day. At the lumbar spine, 33% of the patients were osteopenic and 48% were osteoporotic. Two patients had thoracic and lumbar vertebral compression fractures. At the nondominant femoral neck, 74% of patients were osteopenic but only 3% was osteoporotic. In a multivariate model, the current or past use of hydroxychloroquine (HCQ) was associated with a higher spinal BMD. The presence of anti-Sm and the absence of anti-Ro were associated with a higher femoral BMD. It was concluded that osteoporosis, especially at the spine, is a common and serious problem in postmenopausal Chinese SLE patients receiving long term glucocorticoid therapy. Active intervention should be considered. The protective role of HCQ has to be confirmed with further studies.

Small nuclear RNAs from Saccharomyces cerevisiae: unexpected diversity in abundance, size, and molecular complexity

Previous work showed that the simple eukaryote Saccharomyces cerevisiae contains a group of RNAs with the general structural properties predicted for small nuclear RNAs (snRNAs), including possession of the characteristic trimethylguanosine 5'-terminal cap. It was also demonstrated that, unlike their metazoan counterparts, the yeast snRNAs are present in low abundance (200-500 molecules per haploid cell). We have now used antibody directed against the 5' cap to investigate the total set size of snRNAs in this organism. We present evidence that the number of distinct yeast snRNAs is on the order of several dozen, that the length of the capped RNAs can exceed 1000 nucleotides, and that the relative abundance of a subset of these RNAs is 1/5th to 1/20th that of the class of snRNAs described previously. These findings suggest that the six highly abundant species of snRNAs (U1-U6) typically reported in metazoans may represent a serious underestimation of the total diversity of snRNAs in eukaryotes.

The carboxy-terminal tail of the homeo domain protein alpha 2 is required for function with a second homeo domain protein

The homeo domain protein alpha 2 from Saccharomyces cerevisiae has two roles in the a/alpha cell: With MCM1, alpha 2 turns off transcription of a-specific genes; with a1 (a second homeo domain protein), alpha 2 represses transcription of haploid-specific genes. From the carboxy-terminal side of the alpha 2 homeo domain extends an unstructured 22-amino-acid residue tail. In this paper we show that the carboxy-terminal tail of alpha 2 is required for formation of a stable a1/alpha 2-operator complex and is thus required for a1/alpha 2-mediated repression of transcription. In contrast, the tail is dispensable for alpha 2/MCM1-mediated repression. These results indicate that a short, unstructured tail mediates the interaction between two homeo domain proteins.

Renal damage in systemic lupus erythematosus: a comparative analysis of different age groups

Renal damage in systemic lupus erythematosus: a comparative analysis of different age groups A Mak, CC Mok, WP Chu, CH To, SN Wong and TC Au Please note that the following pdf is a corrected version of the article which appears in the printed version of Lupus 16/1. An Erratum will also appear in print in Lupus; 16(2). The corrected line can be found in the abstract. It was changed from: Patients were categorized into childhood (age ≥6 years), adult (between 16 and 50 years) or late onset (≥50 years) SLE. To: Patients were categorized into childhood (age 16 years), adult (between 16 and 50 years) or late onset (50 years) SLE.The objective of this study was to compare the frequency and severity of renal damage in systemic lupus erythematosus (SLE) with regard to the age of disease onset. Among 287 patients with new onset SLE diagnosed between 1991 and 2003 in our hospital, we identified those who fulfilled the American College of Rheumatology (ACR) criteria for renal involvement. Patients were categorized into childhood (age <6 years), adult (between 16 and 50 years) or late onset (≥50 years) SLE. Clinical presentation of renal disease and cumulative renal damage as assessed by the renal domain of the Systemic Lupus International Collaborating Clinics/ACR damage index (SDI) were compared. A linear regression model was constructed to study the effect of age on renal damage. One-hundred and forty-nine patients were studied (134 women and 15 men), including 28 childhood, 107 adult and 14 late onset SLE patients. The mean age of SLE onset was 29.7 ± 14 years. The prevalence of renal disease was 53% in childhood onset, 50% in adult onset and 58% in late onset SLE patients (P = 0.66). At renal disease presentation, late onset SLE patients had significantly lower creatinine clearance and were more likely to be hypertensive. Histological classes of nephritis and initial treatment response, however, did not differ significantly among the patients. After a mean observation of 80.3 months, 32 (21%) patients developed renal damage (renal SDI ≥ 1). Late onset SLE patients had accrued more renal damage than the others. In a multiple regression model, age was not a significant determinant of renal damage after adjustment for baseline renal parameters, duration of renal disease, use of cyclophosphamide and initial treatment response. We concluded that the prevalence of renal disease was similar among SLE patients of different ages of onset. Late onset SLE patients had accrued more renal damage but age did not correlate with renal damage after adjustment for various clinical parameters.

G2/M arrest caused by actin disruption is a manifestation of the cell size checkpoint in fission yeast

In budding yeast, actin disruption prevents nuclear division. This has been explained as activation of a morphogenesis checkpoint monitoring the integrity of the actin cytoskeleton. The checkpoint operates through inhibitory tyrosine phosphorylation of Cdc28, the budding yeast Cdc2 homolog. Wild-type Schizosaccharomyces pombe cells also arrest before mitosis after actin depolymerization. Oversized cells, however, enter mitosis uninhibited. We carried out a careful analysis of the kinetics of mitotic initiation after actin disruption in undersized and oversized cells. We show that an inability to reach the mitotic size threshold explains the arrest in smaller cells. Among the regulators that control the level of the inhibitory Cdc2-Tyr15 phosphorylation, the Cdc25 protein tyrosine phosphatase is required to link cell size monitoring to mitotic control. This represents a novel function of the Cdc25 phosphatase. Furthermore, we demonstrate that this cell size-monitoring system fulfills the formal criteria of a cell cycle checkpoint.

Serum tumour necrosis factor-alpha is associated with poor health-related quality of life and depressive symptoms in patients with systemic lupus erythematosus

OBJECTIVES

While patients with systemic lupus erythematosus (SLE) have poorer health-related quality of life (HRQoL) and are more depressed than healthy people, the impact of proinflammatory cytokines, particularly tumour necrosis factor-alpha (TNFα), on these unfavourable psychosocial parameters is unclear. We aim to explore potential relationships between lupus-related proinflammatory cytokines, HRQoL and depressive symptoms in patients with SLE.

METHODS

Patients with SLE and age-matched healthy subjects were assessed for HRQoL and depressive and anxiety symptoms by the Short Form Health Survey-36 (SF-36) and Hospital Anxiety and Depression Scale (HADS) respectively. Using multiplex immunoassay, a panel of serum proinflammatory cytokines including TNFα, interleukin (IL)-1β, IL-6, IL-17, IL-23 and IL-33 were determined and compared between both groups. Independent associations between SF-36, serum proinflammatory cytokine levels and HADS scores were studied by regression models.

RESULTS

In total, 54 patients and 54 healthy controls were studied. Lupus patients had significantly poorer HRQoL (p < 0.001) and were significantly more depressed (p = 0.006) and anxious (p = 0.022) than their healthy counterparts. Amongst the proinflammatory cytokines studied, serum TNFα was significantly higher in lupus patients (p < 0.001). After multivariate adjustment, higher serum TNFα (β = -0.224, p = 0.047) remained significantly associated with lower SF-36, along with smoking (β = -0.253, p = 0.014) and more severe depressive symptoms (β = -0.433, p = 0.002). In healthy subjects, serum TNFα was associated with depressive symptoms but not with SF-36.

CONCLUSIONS

Higher serum TNFα level is independently associated with poorer HRQoL and more severe depressive symptoms in SLE patients. These associations suggest a potential impact of inflammatory response on depressive symptoms and the quality of life in patients with SLE.

Impact of donor arm skin disinfection on the bacterial contamination rate of platelet concentrates

BACKGROUND AND OBJECTIVES

Despite improved methods for detecting bacterial contamination of blood products, bacterial sepsis remains a significant risk in blood transfusion. This study was undertaken to investigate whether adopting a different skin disinfection protocol could reduce the rate of bacterial contamination of platelet concentrates.

MATERIALS AND METHODS

Two skin disinfection protocols were consecutively used in the routine blood collection setting during two 10-month periods: 0.5% cetrimide/0.05% chlorhexidine solution followed by 70% isopropyl alcohol (first 10-month time-period); and 10% povidone-iodine followed by 70% isopropyl alcohol (second 10-month time-period). The rates of bacterial contamination of platelet concentrates were monitored by using a surveillance programme described previously.

RESULTS

The overall bacterial contamination rate in the first time-period was 0.072%. After introduction of the povidone-iodine and isopropyl alcohol protocol, the bacterial contamination rate decreased to 0.042% (relative risk reduction: -0.42; 95% confidence interval, -0.12 to -0.61, P= 0.009). There were no differences in the types of micro-organisms identified (P = 0.7).

CONCLUSIONS

Skin disinfection by povidone-iodine and isopropyl alcohol is more effective than that by cetrimide/chorhexidine and isopropyl alcohol in reducing venepuncture-associated contamination of platelet concentrates by skin flora. Our data indicate that the disinfection protocol should be used on a routine basis and such implementation should translate into a significant improvement in blood safety to patients receiving platelet transfusion.

Outcome of protein-losing gastroenteropathy in systemic lupus erythematosus treated with prednisolone and azathioprine

OBJECTIVES

To report the efficacy of prednisolone and azathioprine (AZA) in the treatment of systemic lupus erythematosus (SLE)-related protein-losing gastroenteropathy (PLGE).

METHODS

Between 1995 and 2002, 16 consecutive patients with SLE-related PLGE were treated with a regimen consisting of high-dose prednisolone (0.8-1 mg/kg/day for 6 weeks, then tapered to < or =10 mg/day) and AZA (2 mg/kg/day). Protein leakage from the gastrointestinal tract was confirmed by 99mTc-labelled human serum albumin scintigraphy and significant urinary loss of protein was excluded. Clinical response at 6 months of therapy was assessed and patients were followed for relapse of PLGE.

RESULTS

Clinical characteristics of our patients at the time of PLGE were: age 36.2 +/- 8.7 (s.d.) yr; female:male ratio 15 : 1; mean SLE duration 29.6 +/- 65 months. Twelve patients had PLGE as the initial presentation of SLE. Fifteen (94%) patients had concomitant activity in other organs. All patients presented with oedema and eight patients (50%) had non-bloody diarrhoea. The mean serum albumin level was 22.8 +/- 5.7 g/dl. Protein leakage was at the small bowel in 11 (69%) patients and the large bowel in 5 (31%) patients. At 6 months of therapy, 14 (88%) patients had complete clinical response, 1 (6%) patient responded partially and 1 patient (6%) was treatment-refractory. Patients who responded were maintained on low-dose prednisolone (7.8 +/- 6.1 mg/day) and AZA (56.3 +/- 37 mg/day). Over a mean follow-up of 57.5 months, 1 (6%) patient had relapse of PLGE which responded to augmentation of prednisolone dosage. No patients developed alternative gastrointestinal diagnoses. Corticosteroid-induced psychosis, AZA-induced pancytopenia and herpes zoster occurred in three patients.

CONCLUSION

PLGE is an uncommon manifestation of SLE. Treatment with a combination of prednisolone and AZA is effective and well tolerated.

Neuropsychiatric lupus and reversible posterior leucoencephalopathy syndrome: a challenging clinical dilemma

Reversible posterior leucoencephalopathy syndrome (RPLS) has been increasingly recognized and reported in the literature. While the condition has been well described in patients with acute hypertension, pre-eclampsia, eclampsia, post-transplantation and chemotherapy, RPLS has been increasingly identified in patients with autoimmune diseases such as systemic lupus erythematosus (SLE). Though experience in the diagnosis and management of RPLS in patients with SLE is likely accumulating, few have systematically worked out the strategy to distinguish RPLS from neuropsychiatric SLE (NPSLE) and lupus-related complications of the central nervous system (CNS). Prompt recognition of, and differentiation between, these conditions is essential since their clinical presentations substantially overlap and yet their management strategy and subsequent outcomes can be entirely different. Indeed, inappropriate treatment such as augmentation of immunosuppression may be detrimental to patients with RPLS. A high index of suspicion of RPLS, prompt magnetic resonance imaging of the brain, including diffusion imaging, exclusion of CNS infection and metabolic derangement, a comprehensive medication review accompanied by timely and aggressive control of blood pressure and seizure are keys to successful management of RPLS. Such treatment strategy ensures a very high chance of total neurological recovery in lupus patients with RPLS.

Calcium-independent contraction and sensitization of airway smooth muscle by p21-activated protein kinase

In Triton-skinned phasic ileal smooth muscle, constitutively active recombinant p21-activated kinase (PAK3) has been shown to induce Ca(2+)-independent contraction, which is accompanied by phosphorylation of caldesmon and desmin (Van Eyk JE, Arrell DK, Foster DB, Strauss JD, Heinonen TY, Furmaniak-Kazmierczak E, Cote GP, and Mak AS. J Biol Chem 273: 23433-23439, 1998). In the present study, we investigated whether PAK has a broad impact on smooth muscle in general by testing the hypothesis that PAK induces Ca(2+)-independent contractions and/or Ca(2+) sensitization in tonic airway smooth muscle and that the process is mediated via phosphorylation of caldesmon. In the absence of Ca(2+) (pCa > 9), constitutively active glutathione-S-transferase-murine PAK3 (GST-mPAK3) caused force generation of Triton-skinned canine tracheal smooth muscle (TSM) fibers to approximately 40% of the maximal force generated by Ca(2+) at pCa 4.4. In addition, GST-mPAK3 enhanced Ca(2+) sensitivity of contraction by increasing force generation by 80% at intermediate Ca(2+) concentrations (pCa 6.2), whereas it had no effect at pCa 4.4. Catalytically inactive GST-mPAK3(K297R) had no effect on force production. Using antibody against one of the PAK-phosphorylated sites (Ser(657)) on caldesmon, we showed that a basal level of phosphorylation of caldesmon occurs at this site in skinned TSM and that PAK-induced contraction was accompanied by a significant increase in the level of phosphorylation. Western blot analyses show that PAK1 is the predominant PAK isoform expressed in murine, rat, canine, and porcine TSM. We conclude that PAK causes Ca(2+)-independent contractions and produces Ca(2+) sensitization of skinned phasic and tonic smooth muscle, which involves an incremental increase in caldesmon phosphorylation.

Dual sensor for Cd(II) and Ca(II): selective nanoliter-scale sensing of metal ions

The first selective, dual sensor for Ca(2+) and Cd(2+) capable of detection at 100 pM concentrations was designed and synthesized. The experimental observations made for the MC-cation complexes and the selectivity of compounds 1 and 2 with Ca(2+) and Cd(2+) ions were further explored using density functional theory. A first step toward a nanoliter-scale dip sensor for the dual sensing of Ca(2+) and Cd(2+) was demonstrated using microstructured optical fiber as the sensing platform which is important for ion sensing in confined spaces such as the medium surrounding cell clusters. In addition, this system displays picomolar sensitivity for these ions, with an added ability to reproducibly turn ion-binding on/off.

Mycophenolate mofetil for refractory haemolytic anemia in systemic lupus erythematosus

Mycophenolate mofetil (MMF) has been increasingly used in patients with systemic lupus erythematosus (SLE). While most information concentrates on lupus nephritis, its efficacy in nonrenal manifestations of SLE has not been systematically studied. We describe the successful use of MMF in a patient with SLE-related hemolytic anemia that was refractory to cyclophosphamide, pulse methylprednisolone, intravenous immunoglobulin and cyclosporine. The mechanisms of action of MMF are briefly reviewed.

Active disease is independently associated with more severe anxiety rather than depressive symptoms in patients with systemic lupus erythematosus

Objective

The inter-correlation between and co-existence of depression and anxiety may engender inconsistency in addressing the relationship between the severity of depression and disease activity of systemic lupus erythematosus (SLE). We aimed at identifying whether lupus disease activity is independently associated with depression and anxiety in lupus patients.

Methods

Adult lupus patients were assessed for the severity of depressive and anxiety symptoms and lupus disease activity by using the Hospital Anxiety and Depression Scale (HADS) and the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), respectively. Age- and gender-matched healthy controls (HCs) were recruited for comparison. Prevalence and severity of depressive and anxiety symptoms were compared between lupus patients and HCs. Independent relationships between the severity of anxiety (HADS-Anxiety) and depressive (HADS-Depression) symptoms, and SLEDAI were studied with regression models.

Results

In total, 110 lupus patients and 110 HCs were studied. Lupus patients had significantly higher HADS scores than HCs (10.82 ± 6.5 vs 7.34 ± 4.9, p < 0.001). Significantly more lupus patients had anxiety (40.9 vs 21.8%, p = 0.002) and depressive symptoms (15.5 vs 6.4%, p = 0.025) than HCs. Multiple linear regression analyses revealed that SLEDAI (β = 0.160, p = 0.016), calcineurin inhibitor non-use (β = –1.929, p = 0.041) and past cyclophosphamide non-use (β = –1.603, p = 0.039) independently predicted HADS-Anxiety amongst lupus patients even after adjusting for HADS-Depression. Conversely, SLEDAI (β = 0.014, p = 0.834) lost its significant univariate correlation with HADS-Depression after controlling for HADS-Anxiety and other covariates.

Conclusion

Anxiety is more common in lupus patients than in HCs, and its severity is independently associated with more active SLE regardless of the presence or absence of concomitant depression.

Early head CT in post-cardiac arrest patients: A helpful tool or contributor to self-fulfilling prophecy?

OBJECTIVE

Neuroprognostication guidelines suggest that early head computed tomography (HCT) might be useful in the evaluation of cardiac arrest (CA) patients following return of spontaneous circulation. We aimed to determine the impact of early HCT, performed within the first 6 h following CA, on decision-making following resuscitation.

METHODS

We identified a cohort of initially unconscious post-CA patients at a tertiary care academic medical center from 2012 to 2017. Variables pertaining to demographics, CA details, post-CA care, including neuroimaging and neurophysiologic testing, were abstracted retrospectively from the electronic medical records. Changes in management resulting from HCT findings were recorded. Blinded board-certified neurointensivists adjudicated HCT findings related to hypoxic-ischemic brain injury (HIBI) burden. The gray-white matter ratio (GWR) was also calculated.

RESULTS

Of 302 patients, 182 (60.2%) underwent HCT within six hours of CA (early HCT group). Approximately 1 in 4 early HCTs were abnormal (most commonly HIBI changes; 78.7%, n = 37), which resulted in a change in management in nearly half of cases (46.8%, n = 22). The most common changes in management were de-escalation in care [including transition to do not resuscitate status), withholding targeted temperature management, and withdrawal of life sustaining therapy (WLST)]. In cases with radiographic HIBI, mean [standard deviation] GWR was lower (1.20 [0.10] vs 1.30 [0.09], P < 0.001) and progression to brain death was higher (44.4% vs 2.9%; P < 0.001). The inter-rater reliability (IRR) of early HCT to determine presence of HIBI between radiology and three neurointensivists had a wide range (κ 0.13-0.66).

CONCLUSION

Early HCT identified abnormalities in 25% of cases and frequently influenced therapeutic decisions. Neuroimaging interpretation discrepancies between radiology and neurointensivists are common and agreement on severity of HIBI on early HCT is poor (k 0.11).

The effect of shear fatigue on bovine articular cartilage

The objective of this study was to investigate the effects of mechanical fatigue in the form of cyclic shear strain on articular cartilage. Three millimeter diameter full-thickness plugs were cored from the lateral aspect of bovine tibial plateaus. Sinusoidal shear strains of +/- 5, +/- 10, and +/- 15% were applied to the specimens at 100 Hz for 3 h (a total of 108 x 10(4) cycles). The mechanical shear properties of the tissue (loss and storage moduli) were determined as a function of the number of applied strain cycles. A rapid, irreversible decrease of approximately 35% of initial modulus was found to occur in both loss and storage modulus during application of the first 90,000 cycles. Further decay in the moduli was found to occur from 90 x 10(3) to 108 x 10(4) cycles, but was of considerably smaller magnitude than the initial decrease. The moduli remained relatively constant beyond application of 108 x 10(4) cycles. No consistent change in proteoglycan content was found to be associated with the fatigue process when comparing tested specimens with fresh, untested tissue, and with experimental controls. In addition, no structural defects in the mechanically altered tissue were revealed by scanning electron microscopy.

Nature of halogen bonding involving π-systems, nitroxide radicals and carbenes: a highlight of the importance of charge transfer

The recently developed adiabatic absolutely localized molecular orbital energy decomposition analysis (ALMO-EDA) has proven to be useful in determining the effects of different energy components on the geometries of complexes bound by intermolecular interactions. The authors have applied it to systems such as the water dimer, water-ion complexes, metallocenes and lone-pair type halogen-bonded (XB) dimers. In this study, we have extended the second-generation ALMO-EDA method to 40 different XB complexes by benchmarking against its classical counterpart and symmetry-adapted perturbation theory (SAPT). In addition, we have examined the nature of halogen bonding involving less studied XB acceptors, namely π-systems, radicals and carbenes, using the adiabatic ALMO-EDA analyses, particularly to shed light on how each energy component affects the geometries of the XB complexes. Our results show that the second-generation ALMO-EDA predicts a higher electrostatic energy contribution in all XB complexes compared to SAPT and classical ALMO-EDA schemes. On the other hand, when comparing across different XB acceptors, all three partition schemes produced the same qualitative finding. The adiabatic ALMO-EDA analyses indicate that while the inclusion of a charge transfer contribution is important in achieving accurate XB bond lengths and interaction energies, as well as recovering the binding site specificity of XB involving benzene and naphthalene acceptors, it is sufficient to obtain the linearity of the XB complexes in the frozen approximation.

Noncontact evaluation of articular cartilage degeneration using a novel ultrasound water jet indentation system

We previously reported a noncontact ultrasound water jet indentation system for measuring and mapping tissue mechanical properties. The key idea was to utilize a water jet as an indenter as well as the coupling medium for high-frequency ultrasound. In this paper, the system was employed to assess articular cartilage degeneration, using stiffness ratio as an indicator of the mechanical properties of samples. Both the mechanical and acoustical properties of intact and degenerated bovine patellar articular cartilage (n = 8) were obtained in situ. It was found that the stiffness ratio was reduced by 44 +/- 17% after the articular cartilage was treated by 0.25% trypsin at 37 degrees C for 4 h while no significant difference in thickness was observed between the intact and degenerated samples. A significant decrease of 36 +/- 20% in the peak-to-peak amplitude of ultrasound echoes reflected from the cartilage surface was also found for the cartilage samples treated by trypsin. The results also showed that the stiffness obtained with the new method highly correlated with that measured using a standard mechanical testing protocol. A good reproducibility of the measurements was demonstrated. The present results showed that the ultrasound water jet indentation system may provide a potential tool for the non-destructive evaluation of articular cartilage degeneration by simultaneously obtaining mechanical properties, acoustical properties, and thickness data.