MXene Clay (Ti2C)-Containing In Situ Polymerized Hollow Core-Shell Binder for Silicon-Based Anodes in Lithium-Ion Batteries

Silicon, an attractive anode material, suffers fast capacity fading due to the electrical isolation from massive volumetric expansion upon cycling. However, it holds a high theoretical capacity and low operation voltage in its practical application. In this study, a new water-based binder, MXene clay/hollow core-shell acrylate composite, was synthesized through an in situ emulsion polymerization technique to alleviate the fast capacity fading of the silicon anode efficiently. The efficient introduction of conductive MXene clay and the hollow core-shell structure, favorable to electron and ion transport in silicon-based electrodes, gives a novel conceptual design of the binder material. Such a strategy could alleviate electrical isolation after cycling and promises better electrochemical performance of the high-capacity anodes. The effect of the MXene introduction and hollow core-shell on the binder performance is thoroughly investigated using various characterization tools by comparison with no MXene-containing, core-shell acrylate, and commercial styrene-butadiene latex binders. Consequently, the silicon-based electrode containing the MXene clay/hollow core-shell acrylate binder exhibits a high capacity retention of 1351 mAh g-1 at 0.5C after 100 cycles and good rate capability of over 1100 mAh g-1 at 5C.

Post-acute cognitive and mental health outcomes amongst COVID-19 survivors: early findings and a call for further investigation

Click here to view the Original Article by R. Méndez et al

Minimizing two-dimensional Ti3C2Tx MXene nanosheet loading in carbon-free silicon anodes

Silicon anodes are promising for high energy batteries because of their excellent theoretical gravimetric capacity (3579 mA h g-1). However, silicon's large volume expansion and poor conductivity hinder its practical application; thus, binders and conductive additives are added, effectively diluting the active silicon material. To address this issue, reports of 2D MXene nanosheets have emerged as additives for silicon anodes, but many of these reports use high MXene compositions of 22-66 wt%, still presenting the issue of diluting the active silicon material. Herein, this report examines the question of what minimal amount of MXene nanosheets is required to act as an effective additive while maximizing total silicon anode capacity. A minimal amount of only 4 wt% MXenes (with 16 wt% sodium alginate and no carbon added) yielded silicon anodes with a capacity of 900 mA h gSi-1 or 720 mA h gtotal-1 at the 200th cycle at 0.5 C-rate. Further, this approach yielded the highest specific energy on a total electrode mass basis (3100 W h kgtotal-1) as comapared to other silicon-MXene constructs (∼115-2000 Wh kgtotal-1) at a corresponding specific power. The stable electrode performance even with a minimal MXene content is attributed to several factors: (1) highly uniform silicon electrodes due to the dispersibility of MXenes in water, (2) the high MXene aspect ratio that enables improved electrical connections, and (3) hydrogen bonding among MXenes, sodium alginate, and silicon particles. All together, a much higher silicon loading (80 wt%) is attained with a lower MXene loading, which then maximizes the capacity of the entire electrode.

Sulfonation of alginate grafted with polyacrylamide as a potential binder for high-capacity Si/C anodes

A systematic approach for how to find an appropriate polymer binder for high-capacity LIB anodes is presented in this study. As an example, a newly-developed SAlg-g-PAAm binder, alginate functionalized with sulfo groups and subsequently grafted with polyacrylamide, is used for the Si/C electrode. Various characteristics of the binder polymer itself, two basic characteristics of the electrode with respect to the binder, and the effect of the binder on cell performance are subsequently investigated. In all respects, the SAlg-g-PAAm polymer is a very promising binder for high-capacity anodes. The sulfo groups in the binder improve the ionic conductivities in both the binder and the electrode, leading to reduced charge transfer resistance. In addition, the sulfonation of the alginate grafted with polyacrylamide significantly enhances the mechanical and adhesion properties of the binder and consequently decreases the volume change generated during cycles. These advantages of the SAlg-g-PAAm binder ultimately lead to a considerable enhancement in the electrochemical performance of the high-capacity Si/C electrodes.

A systematic approach for how to find an appropriate polymer binder for high-capacity LIB anodes is presented in this study.

Recommendations for the Nomenclature of Cognitive Change Associated with Anaesthesia and Surgery-20181

Cognitive change affecting patients after anaesthesia and surgery has been recognised for more than 100 yr. Research into cognitive change after anaesthesia and surgery accelerated in the 1980s when multiple studies utilised detailed neuropsychological testing for assessment of cognitive change after cardiac surgery. This body of work consistently documented decline in cognitive function in elderly patients after anaesthesia and surgery, and cognitive changes have been identified up to 7.5 yr afterwards. Importantly, other studies have identified that the incidence of cognitive change is similar after non-cardiac surgery. Other than the inclusion of non-surgical control groups to calculate postoperative cognitive dysfunction, research into these cognitive changes in the perioperative period has been undertaken in isolation from cognitive studies in the general population. The aim of this work is to develop similar terminology to that used in cognitive classifications of the general population for use in investigations of cognitive changes after anaesthesia and surgery. A multispecialty working group followed a modified Delphi procedure with no prespecified number of rounds comprised of three face-to-face meetings followed by online editing of draft versions.Two major classification guidelines [Diagnostic and Statistical Manual for Mental Disorders, fifth edition (DSM-5) and National Institute for Aging and the Alzheimer Association (NIA-AA)] are used outside of anaesthesia and surgery, and may be useful for inclusion of biomarkers in research. For clinical purposes, it is recommended to use the DSM-5 nomenclature. The working group recommends that 'perioperative neurocognitive disorders' be used as an overarching term for cognitive impairment identified in the preoperative or postoperative period. This includes cognitive decline diagnosed before operation (described as neurocognitive disorder); any form of acute event (postoperative delirium) and cognitive decline diagnosed up to 30 days after the procedure (delayed neurocognitive recovery) and up to 12 months (postoperative neurocognitive disorder).

Recommendations for the Nomenclature of Cognitive Change Associated With Anaesthesia and Surgery-2018

Cognitive change affecting patients after anaesthesia and surgery has been recognised for more than 100 yr. Research into cognitive change after anaesthesia and surgery accelerated in the 1980s when multiple studies utilised detailed neuropsychological testing for assessment of cognitive change after cardiac surgery. This body of work consistently documented decline in cognitive function in elderly patients after anaesthesia and surgery, and cognitive changes have been identified up to 7.5 yr afterwards. Importantly, other studies have identified that the incidence of cognitive change is similar after non-cardiac surgery. Other than the inclusion of non-surgical control groups to calculate postoperative cognitive dysfunction, research into these cognitive changes in the perioperative period has been undertaken in isolation from cognitive studies in the general population. The aim of this work is to develop similar terminology to that used in cognitive classifications of the general population for use in investigations of cognitive changes after anaesthesia and surgery. A multispecialty working group followed a modified Delphi procedure with no prespecified number of rounds comprised of three face-to-face meetings followed by online editing of draft versions.Two major classification guidelines [Diagnostic and Statistical Manual for Mental Disorders, fifth edition (DSM-5) and National Institute for Aging and the Alzheimer Association (NIA-AA)] are used outside of anaesthesia and surgery, and may be useful for inclusion of biomarkers in research. For clinical purposes, it is recommended to use the DSM-5 nomenclature. The working group recommends that 'perioperative neurocognitive disorders' be used as an overarching term for cognitive impairment identified in the preoperative or postoperative period. This includes cognitive decline diagnosed before operation (described as neurocognitive disorder); any form of acute event (postoperative delirium) and cognitive decline diagnosed up to 30 days after the procedure (delayed neurocognitive recovery) and up to 12 months (postoperative neurocognitive disorder).

Recommendations for the nomenclature of cognitive change associated with anaesthesia and surgery-2018

Cognitive change affecting patients after anaesthesia and surgery has been recognised for more than 100 yr. Research into cognitive change after anaesthesia and surgery accelerated in the 1980s when multiple studies utilised detailed neuropsychological testing for assessment of cognitive change after cardiac surgery. This body of work consistently documented decline in cognitive function in elderly patients after anaesthesia and surgery, and cognitive changes have been identified up to 7.5 yr afterwards. Importantly, other studies have identified that the incidence of cognitive change is similar after non-cardiac surgery. Other than the inclusion of non-surgical control groups to calculate postoperative cognitive dysfunction, research into these cognitive changes in the perioperative period has been undertaken in isolation from cognitive studies in the general population. The aim of this work is to develop similar terminology to that used in cognitive classifications of the general population for use in investigations of cognitive changes after anaesthesia and surgery. A multispecialty working group followed a modified Delphi procedure with no prespecified number of rounds comprised of three face-to-face meetings followed by online editing of draft versions. Two major classification guidelines [Diagnostic and Statistical Manual for Mental Disorders, fifth edition (DSM-5) and National Institute for Aging and the Alzheimer Association (NIA-AA)] are used outside of anaesthesia and surgery, and may be useful for inclusion of biomarkers in research. For clinical purposes, it is recommended to use the DSM-5 nomenclature. The working group recommends that 'perioperative neurocognitive disorders' be used as an overarching term for cognitive impairment identified in the preoperative or postoperative period. This includes cognitive decline diagnosed before operation (described as neurocognitive disorder); any form of acute event (postoperative delirium) and cognitive decline diagnosed up to 30 days after the procedure (delayed neurocognitive recovery) and up to 12 months (postoperative neurocognitive disorder).

Broad-scale impacts of salmon farms on temperate macroalgal assemblages on rocky reefs

Intensive fish culture in open sea pens delivers large amounts of nutrients to coastal environments. Relative to particulate waste impacts, the ecological impacts of dissolved wastes are poorly known despite their potential to substantially affect nutrient-assimilating components of surrounding ecosystems. Broad-scale enrichment effects of salmonid farms on Tasmanian reef communities were assessed by comparing macroalgal cover at four fixed distances from active fish farm leases across 44 sites. Macroalgal assemblages differed significantly between sites immediately adjacent (100m) to fish farms and reference sites at 5km distance, while sites at 400m and 1km exhibited intermediate characteristics. Epiphyte cover varied consistently with fish farm impacts in both sheltered and exposed locations. The green algae Chaetomorpha spp. predominated near fish farms at swell-exposed sites, whereas filamentous green algae showed elevated densities near sheltered farms. Cover of canopy-forming perennial algae appeared unaffected by fish farm impacts.

A combination of excimer laser treatment and topical tacrolimus is more effective in treating vitiligo than either therapy alone for the initial 6 months, but not thereafter

BACKGROUND

There are insufficient data on the long-term outcome of a combination therapy that comprises phototherapy and topical administration of tacrolimus.

AIM

To evaluate the clinical efficacy according to the duration of treatment and in vitro results of a combination therapy involving topical tacrolimus and an excimer laser in the treatment of vitiligo.

METHODS

In total, 276 patients with nonsegmental vitiligo were treated with an excimer laser twice weekly, or with tacrolimus ointment twice daily, or both. The melanin contents and levels of melanogenic enzymes were measured in cultured human melanocytes treated with tacrolimus and/or excimer laser.

RESULTS

After adjusting for potential confounders, the combination of tacrolimus plus excimer laser was significantly more effective than either tacrolimus or excimer laser alone (P < 0.001 and P < 0.01, respectively) for the first 6 months. However, this superiority was not observed after the initial 6 months of treatment. In vitro, the combination of tacrolimus plus excimer laser led to a higher level of melanogenesis than with either treatment alone.

CONCLUSIONS

A combination treatment with topical tacrolimus and an excimer laser may be useful as an induction therapy for up to 6 months, but continuation of this therapy for > 6 months might not provide a better final outcome than monotherapy.

A double core–shell modification of bulk TiO2 microspheres into porous N-doped-graphene carbon nanoflakes/N-doped TiO2 microspheres for lithium-ion battery anodes

Nitrogen (N) doping and double core–shell modification of TiO₂ for lithium battery application.

In situ synthesis and cell performance of a Si/C core-shell/ball-milled graphite composite for lithium ion batteries

A high-capacity silicon-carbon core-shell (Si/C) supported by ball-milled graphite (BMG) was synthesized in situ using a hydrosilylation reaction and tested as an anode material for lithium ion batteries (LIBs) in the investigation of the effects of dual buffer layers of carbon shell and BMG. The Si/C/BMG sample effectively absorbed high volumetric expansion/contraction generated during charge/discharge process due to the assistance of dual elastic buffers of carbon shell and BMG. As a result, after 50 charge/discharge cycles, the Si/C/BMG electrodes still had a very high capacity of 1615 mAh/g, whereas raw Si, Si/C, and a mechanical mixture of Si/C and BMG were less than 500 mAh/g. The results of various electrochemical characterization techniques revealed that the dual buffer layers were favorable in decreasing electron and ion transfer resistance. It was also shown from ex situ TEM results that the carbon layers behaved as anti-amorphization layers decreasing the amorphization rate of crystalline Si during the alloying/dealloying of Li with Si.

Performance enhancement of polymer electrolyte membrane fuel cells by dual-layered membrane electrode assembly structures with carbon nanotubes

The effect of dual-layered membrane electrode assemblies (d-MEAs) on the performance of a polymer electrolyte membrane fuel cell (PEMFC) was investigated using the following characterization techniques: single cell performance test, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). It has been shown that the PEMFC with d-MEAs has better cell performance than that with typical mono-layered MEAs (m-MEAs). In particular, the d-MEA whose inner layer is composed of multi-walled carbon nanotubes (MWCNTs) showed the best fuel cell performance. This is due to the fact that the d-MEAs with MWCNTs have the highest electrochemical surface area and the lowest activation polarization, as observed from the CV and EIS test.

SnO2 nanoparticles distributed on multi-walled carbon nanotubes and ball-milled graphite as anode materials of lithium ion batteries

SnO2 nanoparticles were supported on ball-milled graphite (BMG) or carbon nanotubes (CNTs) using a chemical reduction method with ethylene glycol, and the electrochemical properties of the nanocomposites were evaluated as anode active materials of lithium-ion batteries. The BMG and CNTs contributed to an increase in both the capacity enhancement and cyclic stability compared to that of commercial graphite. In particular, the mixture electrode of SnO2/BMG:SnO2/CNT = 3:1 (in weight ratio) showed higher performance in the reversible capacity and cyclic stability than did the SnO2/BMG and SnO2/CNT electrodes. This might be resulted from the network formation for excellent electronic path by CNT distributed on SnO2/BMG composites.

Preparation of nano-sized graphite-supported CuO and Cu-Sn as active materials in lithium ion batteries

Nano-sized Cu-Sn and Cu oxide particles supported on ball-milled graphite were synthesized, and their electrochemical characteristics for use as anode active materials in lithium-ion batteries were investigated. The samples were also characterized via FE-SEM, XRD, and TGA. Most of the Cu oxides on BMG were monoclinic CuO crystals, whereas the Cu-Sn particles were composed of hexagonal Cu3Sn and tetragonal SnO2 crystals. These particles may contribute to an increase in the reversible capacity of lithium ion batteries.

Reassembled graphene-platelets encapsulated silicon nanoparticles for Li-ion battery anodes

Among lithium alloy metals, silicon is an attractive candidate to replace commercial graphite anode because silicon possesses about ten times higher theoretical energy density than graphite. However, electrically nonconducting silicon undergoes a large volume changes during lithiation/delithiation reactions, which causes fast loss of storage capacity upon cycling due to electrode pulverization. To alleviate these problems, electrodes comprising Si nanoparticles (20 nm) and graphene platelets, denoted as SiGP-1 (Si = 35.5 wt%) and SiGP-2 (Si = 57.6 wt%), have been prepared with low cost materials and using easily scalable solution-dispersion methods. X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) analyses indicated that Si nanoparticles were highly dispersed and encapsulated between graphene sheets that stacked into platelets in which portions of graphite phases were reconstituted. From the galvanostatic cycling test, SiGP-1 exhibited a reversible lithiation capacity of approximately 802 mAh/g with excellent capacity retention up to 30 cycles at 100 mA/g. Further cycling with a step-increase of current density (100-1,000 mA/g) up to 120 cycles revealed that it has an appreciable power capability as well, showing 520 mAh/g at 1,000 mA/g with capacity loss of 0.2-0.3% per cycle. The improved electrochemical performance is attributed to the robust electrical integrity provided by flexible graphene sheets that encapsulated dispersed Si nanopraticles and stacked into platelets with portions of reconstituted graphite phases in their structure.

The utility of in-phase/opposed-phase imaging in differentiating malignancy from acute benign compression fractures of the spine

BACKGROUND AND PURPOSE

Benign and malignant fractures of the spine may have similar signal intensity characteristics on conventional MR imaging sequences. This study assesses whether in-phase/opposed-phase imaging of the spine can differentiate these 2 entities.

METHODS

Twenty-five consecutive patients who were evaluated for suspected malignancy (lymphoma [4 patients], breast cancer [3], multiple myeloma [2], melanoma [2], prostate [2], and renal cell carcinoma [1]) or for trauma to the thoracic or lumbar spine were entered into this study. An 18-month clinical follow-up was performed. Patients underwent standard MR imaging with an additional sagittal in-phase (repetition time [TR], 90-185; echo time [TE], 2.4 or 6.5; flip angle, 90 degrees ) and opposed-phase gradient recalled-echo sequence (TR, 90-185, TE, 4.6-4.7, flip angle, 90 degrees ). Areas that were of abnormal signal intensity on the T1 and T2 sequences were identified on the in-phase/opposed-phase sequences. An elliptical region of interest measurement of the signal intensity was made on the abnormal region on the in-phase as well as on the opposed-phase images. A computation of the signal intensity ratio (SIR) in the abnormal marrow on the opposed-phase to signal intensity measured on the in-phase images was made.

RESULTS

Twenty-one patients had 49 vertebral lesions, consisting of 20 malignant and 29 benign fractures. There was a significant difference (P < .001, Student t test) in the mean SIR for the benign lesions (mean, 0.58; SD, 0.02) compared with the malignant lesions (mean, 0.98; SD, 0.095). If a SIR of 0.80 as a cutoff is chosen, with >0.8 defined as malignant and <0.8 defined as a benign result, in-phase/opposed-phase imaging correctly identified 19 of 20 malignant lesions and 26 of 29 benign lesions (sensitivity, 0.95; specificity, 0.89).

CONCLUSION

There is significant difference in signal intensity between benign compression fractures and malignancy on in-phase/opposed-phase MR imaging.

Relationship between circulating cytokine levels and thyroid function following bone marrow transplantation

The relation between thyroid hormone changes and cytokines in bone marrow transplantation (BMT) patients has not been studied. This prospective study was designed to determine the relation between thyroid hormones and cytokine levels after BMT and their effects on the mortality. We studied 80 patients undergoing allogeneic BMT. Serum thyroid hormone parameters and cytokine levels were measured before and serially during 6 months after BMT. Serum T(3) decreased to a nadir 3 weeks post-BMT and serum T(4) was lowest at 3 months post-BMT. Serum thyroid stimulating hormone (TSH) sharply decreased to a nadir at 1 week and recovered. Serum interleukin-6 increased for 2 weeks after BMT and declined thereafter. Serum tumor necrosis factor-alpha increased for 3 weeks after BMT and declined thereafter. After 3 weeks post-BMT, both cytokine levels were negatively correlated with serum T(3) and T(4) levels. A total of 29 patients died before 1 year post-BMT and 51 patients survived longer than 1 year. Those patients who died before 1 year post-BMT had significantly lower levels of T(4) at 3 weeks, 3 and 6 months than surviving patients. In conclusion, increased levels of serum IL-6 and TNF-alpha were negatively correlated with thyroid hormone concentrations in BMT recipients suggesting the role of these cytokines in euthyroid sick syndrome.

The role of cytokines in the changes in bone turnover following bone marrow transplantation

Osteoporosis is a common disease among patients undergoing transplantation and a loss of bone mass is usually detected after bone marrow transplantation (BMT), particularly during the immediate post-BMT period. Post-BMT bone loss is primarily related to gonadal dysfunction and immunosuppression. Cytokines, especially interleukin 6, play an important role in the pathogenesis of postmenopausal osteoporosis. However, the pathogenetic role of cytokines in post-BMT bone loss is unknown and data on the changes of cytokines in accordance with bone turnover markers are scarce. The aim of this study was to assess the relationship between bone turnover markers and cytokines, which are regularly sampled at peripheral blood and bone marrow before and after allogeneic BMT. This prospective study included two analyses. The first was a study of 46 BMT recipients (M/F 28/18), examining the relationship between bone turnover markers and serum cytokines that were measured before and at 1 week, 2 weeks, 3 weeks, 4 weeks and 3 months after BMT. Serum intact parathyroid hormone was measured before BMT and at 3 weeks after BMT and its relation to other cytokines and bone turnover markers was evaluated. The second analysis was a study of 14 (M/F 9/5) of 46 patients in whom bone marrow plasma cytokines [interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-alpha)] were measured at 3 weeks after BMT. The relationship between bone marrow plasma cytokines and bone turnover markers was studied because bone marrow is the microenvironment where the real changes in bone turnover occur. Serum type I collagen carboxyterminal telopeptide (ICTP), a bone resorption marker, increased progressively until 4 weeks (peak) after BMT and then decreased thereafter. Serum osteocalcin, a bone formation marker, decreased progressively until 3 weeks after BMT and then increased thereafter. Serum IL-6 increased until 2 weeks after BMT and declined thereafter. Serum TNF-alpha increased until 3 weeks after BMT and declined thereafter. There was a significant positive correlation between serum ICTP and bone marrow IL-6 levels at 3 weeks after BMT, when a marked change in bone metabolism occurs following BMT. However, a correlation between bone turnover markers and bone marrow TNF-alpha or peripheral blood cytokines was not found. At 3 months after BMT, there was a significant negative correlation between the mean daily steroid dose and the serum osteocalcin level (r = -0.43, p < 0.05). The correlation between the Mean daily steroid dose and serum ICTP was also significant (r = 0.41, p < 0.05). Our data suggest that the progressive increase in bone resorption during the immediate post-BMT period is related to both steroid dose and the increase in bone marrow IL-6, which is a potent stimulator of bone resorption in vivo.

C-terminal heparin-binding domain of fibronectin regulates integrin-mediated cell spreading but not the activation of mitogen-activated protein kinase

Fibronectin (FN) stimulates multiple signalling events including mitogen-activated protein kinase (MAPK) activation. During cell spreading, both the cell-binding domain and the C-terminal heparin-binding domain (HepII) of FN co-operatively regulate cytoskeleton organization. However, in comparison with the large number of studies on the functions of cell-binding domain, there is little information about the role of HepII. We therefore investigated the effect of HepII on integrin-mediated cell spreading and adhesion on FN and MAPK activation. In contrast with cells on FN substrates, rat embryo fibroblasts on FN120, which lacks HepII, were less spread, had weaker adhesion to FN and failed to form focal adhesions and actin stress fibres. Phosphotyrosine was present in the focal contacts of rat embryo fibroblasts on FN within 30 min but was absent from cells on FN120. Overall, tyrosine phosphorylation was much less in cell lysates from cells on FN120, with decreased phosphorylation of focal adhesion kinase ('pp125FAK') on tyrosine-397, implying additional regulation of tyrosine phosphorylation by HepII. Nevertheless, adhesion-mediated MAPK activity was similar in cells on FN and on FN120. Furthermore, cells spread on FN and on FN120 substrates showed similar MAPK activation in response to treatment with epidermal growth factor and with platelet-derived growth factor. Consistently, overexpression of syndecan-4, which binds to HepII, enhanced cell spreading and adhesion on FN but did not affect integrin-mediated MAPK activation. We therefore conclude that both HepII and syndecan-4 regulate integrin-mediated cell spreading but not MAPK activation.

Solution structure of the dimeric cytoplasmic domain of syndecan-4

The syndecans, transmembrane proteoglycans which are involved in the organization of cytoskeleton and/or actin microfilaments, have important roles as cell surface receptors during cell-cell and/or cell-matrix interactions. Since previous studies indicate that the function of the syndecan-4 cytoplasmic domain is dependent on its oligomeric status, the conformation of the syndecan-4 cytoplasmic domain itself is important in the understanding of its biological roles. Gel filtration results show that the syndecan-4 cytoplasmic domain (4L) itself forms a dimer stabilized by ionic interactions between peptides at physiological pH. Commensurately, the NMR structures demonstrate that syndecan-4L is a compact intertwined dimer with a symmetric clamp shape in the central variable V region with a root-mean-square deviation between backbone atom coordinates of 0.95 A for residues Leu(186)-Ala(195). The molecular surface of the 4L dimer is highly positively charged. In addition, no intersubunit NOEs in membrane proximal amino acid resides (C1 region) have been observed, demonstrating that the C1 region is mostly unstructured in the syndecan-4L dimer. Interestingly, two parallel strands of 4L form a cavity in the center of the dimeric twist similar to our previously reported 4V structure. The overall topology of the central variable region within the 4L structure is very similar to that of 4V complexed with the phosphatidylinositol 4,5-bisphosphate; however, the intersubunit interaction mode is affected by the presence of C1 and C2 regions. Therefore, we propose that although the 4V region in the full cytoplasmic domain has a tendency for strong peptide--peptide interaction, it may not be enough to overcome the repulsion of the C1 regions of syndecan-4L.

Rat embryo fibroblasts require both the cell-binding and the heparin-binding domains of fibronectin for survival

Fibronectin (FN) is known to transduce signal(s) to rescue cells from detachment-induced apoptosis (anoikis) through an integrin-mediated survival pathway. However, the functions of individual FN domains have not been studied in detail. In the present study we investigated whether the interaction of the cell-binding domain of FN with integrin is sufficient to rescue rat embryo fibroblasts (REFs) from detachment-induced apoptosis. REFs attached and spread normally after plating on substrates coated with either intact FN or a FN fragment, FN120, that contains the cell-binding domain but lacks the C-terminal heparin-binding domain, HepII. REFs on FN maintained a well-spread fibroblastic shape and even proliferated in serum-free medium at 20 h after plating. In contrast, previously well-spread REFs on FN120 started losing fibroblastic shape with time and detached from FN120-coated plates after approx. 8 h. Nuclear condensation indicated apototic cell death. This was due to the decreased activity/stability of focal adhesion kinase (pp125FAK) in the absence of HepII domain. A peptide in the HepII domain [peptide V, WQPPRARI (single-letter amino acid codes)], which has previously been implicated in cytoskeletal organization, rescued apoptotic changes. Consistently, pp125FAK phosphorylation was increased, and both cleavage of pp125FAK and activation of caspase 3 on FN120 were partly blocked by peptide V. Thus the interaction of the cell-binding domain with integrin has a major role in cell survival but is itself not sufficient for cell survival. One or more additional survival signals come from the HepII domain to regulate pp125FAK activity/stability.

Changes in autoimmune thyroid disease following allogeneic bone marrow transplantation

Autoimmune diseases can be transmitted and eliminated by bone marrow transplantation (BMT). There have been several cases of autoimmune thyroid disease (AITD) occurring after BMT, but AITD remission has been rarely reported. We present four cases in which the remission or transfer of AITD occurred after an allogeneic BMT. Two patients with severe aplastic anemia (SAA) showed evidence of remission of Hashimoto's thyroiditis which they had before allogeneic BMT. One patient with SAA, which developed during treatment with propylthiouracil for Graves' disease, underwent allogeneic BMT and showed evidence of Graves' disease remission following BMT. In one patient, new AITD occurred after an allogeneic BMT from an HLA-matched sibling who already had AITD. These cases support the evidence that the immune system is newly reconstituted after BMT, and severe autoimmune disease can be an indication for BMT. To fully understand the real changes in autoimmune status after BMT, long-term prospective studies are necessary.

Responsiveness of the state of O-linked N-acetylglucosamine modification of nuclear pore protein p62 to the extracellular glucose concentration

O-linked N-acetylglucosamine (O-GlcNAc) modification has been described in many proteins, including nuclear pore glycoproteins. In the present study we investigated the effect of extracellular glucose on the level of modification of nuclear pore protein p62 by O-GlcNAc. We found that exposure of cells to a high concentration of glucose caused an increased level of modification of p62 with O-GlcNAc, whereas the modification of other proteins did not change detectably. The increased O-GlcNAc modification of p62 in response to glucose required the metabolism of glucose to glucosamine. The exposure of the cells to glucosamine itself also caused increased O-GlcNAc modification, whereas mannosamine and galactosamine did not. Furthermore, changes in glucose concentrations within the physiological range induced the O-GlcNAc modification in p62 in rat aortic smooth-muscle cells, indicating that this modification of p62 might occur in an intact animal. These results imply that the ambient glucose concentration has an impact on the level of O-GlcNAc modification of proteins such as p62, and that functional changes in some of these proteins might ensue.

Regulation of early events in integrin signaling by protein tyrosine phosphatase SHP-2

The nontransmembrane protein tyrosine phosphatase SHP-2 plays a critical role in growth factor and cytokine signaling pathways. Previous studies revealed that a fraction of SHP-2 moves to focal contacts upon integrin engagement and that SHP-2 binds to SHP substrate 1 (SHPS-1)/SIRP-1alpha, a transmembrane glycoprotein with adhesion molecule characteristics (Y. Fujioka et al., Mol. Cell. Biol. 16:6887-6899, 1996; M. Tsuda et al., J. Biol. Chem. 273:13223-13229). Therefore, we asked whether SHP2-SHPS-1 complexes participate in integrin signaling. SHPS-1 tyrosyl phosphorylation increased upon plating of murine fibroblasts onto specific extracellular matrices. Both in vitro and in vivo studies indicate that SHPS-1 tyrosyl phosphorylation is catalyzed by Src family protein tyrosine kinases (PTKs). Overexpression of SHPS-1 in 293 cells potentiated integrin-induced mitogen-activated protein kinase (MAPK) activation, and potentiation required functional SHP-2. To further explore the role of SHP-2 in integrin signaling, we analyzed the responses of SHP-2 exon 3(-/-) and wild-type cell lines to being plated on fibronectin. Integrin-induced activation of Src family PTKs, tyrosyl phosphorylation of several focal adhesion proteins, MAPK activation, and the ability to spread on fibronectin were defective in SHP-2 mutant fibroblasts but were restored upon SHP-2 expression. Our data suggest a positive-feedback model in which, upon integrin engagement, basal levels of c-Src activity catalyze the tyrosyl phosphorylation of SHPS-1, thereby recruiting SHP-2 to the plasma membrane, where, perhaps by further activating Src PTKs, SHP-2 transduces positive signals for downstream events such as MAPK activation and cell shape changes.

Syndecan proteoglycans and cell adhesion

It is now becoming clear that a family of transmembrane proteoglycans, the syndecans, have important roles in cell adhesion. They participate through binding of matrix ligand to their glycosaminoglycan chains, clustering, and the induction of signaling cascades to modify the internal microfilament organization. Syndecans can modulate the type of adhesive responses induced by other matrix ligand-receptor interactions, such as those involving the integrins, and so contribute to the control of cell morphology, adhesion and migration.

Solution structure of a syndecan-4 cytoplasmic domain and its interaction with phosphatidylinositol 4,5-bisphosphate

Syndecan-4, a transmembrane heparan sulfate proteoglycan, is a coreceptor with integrins in cell adhesion. It has been suggested to form a ternary signaling complex with protein kinase Calpha and phosphatidylinositol 4,5-bisphosphate (PIP2). Syndecans each have a unique, central, and variable (V) region in their cytoplasmic domains, and that of syndecan-4 is critical to its interaction with protein kinase C and PIP2. Two oligopeptides corresponding to the variable region (4V) and whole domain (4L) of syndecan-4 cytoplasmic domain were synthesized for nuclear magnetic resonance (NMR) studies. Data from NMR and circular dichroism indicate that the cytoplasmic domain undergoes a conformational transition and forms a symmetric dimer in the presence of phospholipid activator PIP2. The solution conformations of both free and PIP2-complexed 4V have been determined by two-dimensional NMR spectroscopy and dynamical simulated annealing calculations. The 4V peptide in the presence of PIP2 formed a compact dimer with two twisted strands packed parallel to each other and the exposed surface of the dimer consisted of highly charged and polar residues. The overall three-dimensional structure in solution exhibits a twisted clamp shape having a cavity in the center of dimeric interface. In addition, it has been observed that the syndecan-4V strongly interacts not only with fatty acyl groups but also the anionic head group of PIP2. These findings reveal that PIP2 promotes oligomerization of syndecan-4 cytoplasmic domain for transmembrane signaling and cell-matrix adhesion.

Syndecan-4 proteoglycan cytoplasmic domain and phosphatidylinositol 4,5-bisphosphate coordinately regulate protein kinase C activity

Phosphatidylinositol 4,5-bisphosphate (PIP2) is involved in the organization of the actin cytoskeleton by regulating actin-associated proteins. The transmembrane heparan sulfate proteoglycan syndecan-4 also plays a critical role in protein kinase C (PKC) signaling in the formation of focal adhesions and actin stress fibers. The cytoplasmic domain of syndecan-4 core protein directly interacts with and potentiates PKCalpha activity, and it can directly interact with the phos- phoinositide PIP2. We, therefore, investigated whether the interaction of inositol phosphates and inositol phospholipids with syndecan-4 could regulate PKC activity. Data from in vitro kinase assays using purified PKCalpha beta gamma show that in the absence of phosphatidylserine and diolein, PIP2 increased the extent of autophosphorylation of PKCalpha beta gamma and partially activated it to phosphorylate both histone III-S and an epidermal growth factor receptor peptide. This activity was dose-dependent, and its calcium dependence varied with PKC isotype/source. Addition of the cytoplasmic syndecan-4 peptide, but not equivalent syndecan-1 or syndecan-2 peptides, potentiated the partial activation of PKCalpha beta gamma by PIP2, resulting in activity greater than that observed with phosphatidylserine, diolein, and calcium. This study indicates that syndecan-4 cytoplasmic domain may bind both PIP2 and PKCalpha, localize them to forming focal adhesions, and potentiate PKCalpha activity there.

Serine phosphorylation of syndecan-2 proteoglycan cytoplasmic domain

Protein kinase C (PKC) is involved in cell-matrix and cell-cell adhesion, and the cytoplasmic domain of syndecan-2 contains two serines (residues 197 and 198) which lie in a consensus sequence for phosphorylation by PKC. Other serine and threonine residues are present but not in a consensus sequence. We investigated phosphorylation of syndecan-2 cytoplasmic domain by PKC, using purified GST-syndecan-2 fusion proteins and synthetic peptides corresponding to regions of the cytoplasmic domain. A synthetic peptide encompassing the entire cytoplasmic domain of syndecan-2 was phosphorylated by PKC with high affinity. Peptide mapping and substitution studies showed that both serines were phosphoacceptors, but each had slightly different affinity, with that of serine-197 being higher than serine-198. The efficiency of phosphorylation was concentration-dependent. At low concentrations, the cytoplasmic domain peptides were monomeric, with 2 mol/mol serine phosphorylation. At higher concentrations, however, the peptides formed dimers, with only 0.5 mol/mol phosphorylation. Concentration-dependent dimerization was not altered by phosphorylation. Phosphorylation is, therefore, dependent on the conformation of syndecan-2 cytoplasmic domain, but does not affect its oligomeric status.

Multimerization of the cytoplasmic domain of syndecan-4 is required for its ability to activate protein kinase C

The transmembrane proteoglycan syndecan-4, which is a coreceptor with integrins in cytoskeleton-matrix interactions, appears to be multimerized in vivo. Both purified and recombinant core proteins form sodium dodecyl sulfate-resistant oligomers, and we now report that a synthetic peptide corresponding to the central region of syndecan-4 cytoplasmic domain (4V) also oligomerizes. The degree of oligomerization correlates with the previously reported ability to bind protein kinase C (PKC) and regulate its activity. Only multimeric recombinant syndecan-4 core protein, but not the monomeric protein, potentiated the activity of PKCalpha, and only oligomeric syndecan-4 cytoplasmic peptides were active. Changes in peptide sequence caused parallel loss of stable oligomeric status and ability to regulate a mixture of PKCalphabetagamma activity. A synthetic peptide encompassing the whole cytoplasmic domain of syndecan-4 (4L) containing a membrane-proximal basic sequence did not form higher order oligomers and could not regulate the activity of PKCalphabetagamma unless induced to aggregate by phosphatidylinositol 4,5-bisphosphate. Oligomerization and PKC regulatory activity of the 4V peptide were both increased by addition of N-terminal cysteine and reduced by phosphorylation of the cysteine thiol group. Concentration of syndecan-4 at sites of focal adhesion formation may enhance multimerization and both localize PKC and potentiate its activity to induce stable complex formation.

Syndecan-4 proteoglycan regulates the distribution and activity of protein kinase C

During cell-matrix adhesion, both tyrosine and serine/threonine kinases are activated. Integrin ligation correlates with tyrosine phosphorylation, whereas the later stages of spreading and focal adhesion and stress fiber formation in primary fibroblasts requires interactions of cell surface proteoglycan with heparin-binding moieties. This correlates with protein kinase C (PKC) activation, and PKCalpha can become localized to focal adhesions in normal, but not transformed, cells. PKC activation has been thought to be downstream of initial receptor-ligand interactions. We now show, however, that syndecan-4 transmembrane heparan sulfate proteoglycan and PKC co-immunoprecipitate and co-patch in vivo. The core protein of syndecan-4 can directly bind the catalytic domain of PKCalpha and potentiate its activation by phospholipid mediators. It can also directly activate PKCalpha in the absence of other mediators. This activity resides in the sequence LGKKPIYKK in the center of the short cytoplasmic domain, and other syndecans lack this sequence and PKC regulatory properties. Syndecan-4 is a focal adhesion component, and this interaction may both localize PKC and amplify its activity at sites of forming adhesions. This represents the first report of direct transmembrane signaling through cell surface proteoglycans.

Plasma and urinary concentrations of methamphetamine after oral administration of famprofazone to man

1. To obtain further evidence for the metabolic formation of methamphetamine from famprofazone in man, concentrations of methamphetamine in plasma, as well as in urine, were measured by g.l.c. In addition, intact famprofazone and famprofazone N-oxide were analysed in the urine. 2. Methamphetamine appeared in plasma 1 h after a single 100 mg dose of the drug to two male subjects, and the concentration maintained between 24 and 44 ng/ml over 2-12 h, declining to 10 ng/ml and an undetectable level respectively after 24 h. 3. Total urinary excretion of methamphetamine over 72 h was 1.9 mg for a 25 mg dose and 2.2 mg for a 50 mg dose. After a 100 mg dose, 4.6 mg of methamphetamine was excreted over 36 h. Neither intact famprofazone nor famprofazone N-oxide were detected when the urine samples after the 100 mg dose were examined. 4. The results provide further evidence that methamphetamine is a bona fide human metabolite of famprofazone and suggest that at least 20% dose may be broken down via the pathways leading to the formation of methamphetamine. This could have significant clinical implications as the result of pharmacological activity of this metabolite.