Coronary-artery calcification in young adults with end-stage renal disease who are undergoing dialysis

BACKGROUND

Cardiovascular disease is common in older adults with end-stage renal disease who are undergoing regular dialysis, but little is known about the prevalence and extent of cardiovascular disease in children and young adults with end-stage renal disease.

METHODS

We used electron-beam computed tomography (CT) to screen for coronary-artery calcification in 39 young patients with end-stage renal disease who were undergoing dialysis (mean [+/-SD] age, 19+/-7 years; range, 7 to 30) and 60 normal subjects 20 to 30 years of age. In those with evidence of calcification on CT scanning, we determined its extent. The results were correlated with the patients' clinical characteristics, serum calcium and phosphorus concentrations, and other biochemical variables.

RESULTS

None of the 23 patients who were younger than 20 years of age had evidence of coronary-artery calcification, but it was present in 14 of the 16 patients who were 20 to 30 years old. Among those with calcification, the mean calcification score was 1157+/-1996, and the median score was 297. By contrast, only 3 of the 60 normal subjects had calcification. As compared with the patients without coronary-artery calcification, those with calcification were older (26+/-3 vs. 15+/-5 years, P<0.001) and had been undergoing dialysis for a longer period (14+/-5 vs. 4+/-4 years, P< 0.001). The mean serum phosphorus concentration, the mean calcium-phosphorus ion product in serum, and the daily intake of calcium were higher among the patients with coronary-artery calcification. Among 10 patients with calcification who underwent follow-up CT scanning, the calcification score nearly doubled (from 125+/-104 to 249+/-216, P=0.02) over a mean period of 20+/-3 months.

CONCLUSIONS

Coronary-artery calcification is common and progressive in young adults with end-stage renal disease who are undergoing dialysis.

Rapamycin-FKBP specifically blocks growth-dependent activation of and signaling by the 70 kd S6 protein kinases

The macrolide rapamycin blocks cell cycle progression in yeast and various animal cells by an unknown mechanism. We demonstrate that rapamycin blocks the phosphorylation and activation of the 70 kd S6 protein kinases (pp70S6K) in a variety of animal cells. The structurally related drug FK506 had no effect on pp70S6K activation but at high concentrations reversed the rapamycin-induced block, confirming the requirement for the rapamycin and FK506 receptor, FKBP. Rapamycin also interfered with signaling by these S6 kinases, blocking serum-stimulated S6 phosphorylation and delaying entry of Swiss 3T3 cells into S phase. Neither rapamycin nor FK506 blocked activation of a distinct family of S6 kinases (RSKs) or the MAP kinases. These studies identify a rapamycin-sensitive signaling pathway, argue for a ubiquitous role for FKBPs in signal transduction, indicate that FK506-FKBP-calcineurin complexes do not interfere with pp70S6K signaling, and show that in fibroblasts pp70S6K, not RSK, is the physiological S6 kinase.

Viral clearance without destruction of infected cells during acute HBV infection

Viral clearance during hepatitis B virus (HBV) infection has been thought to reflect the destruction of infected hepatocytes by CD8(+) T lymphocytes. However, in this study, HBV DNA was shown to largely disappear from the liver and the blood of acutely infected chimpanzees long before the peak of T cell infiltration and most of the liver disease. These results demonstrate that noncytopathic antiviral mechanisms contribute to viral clearance during acute viral hepatitis by purging HBV replicative intermediates from the cytoplasm and covalently closed circular viral DNA from the nucleus of infected cells.

Weight control and risk factor reduction in obese subjects treated for 2 years with orlistat: a randomized controlled trial

CONTEXT

Orlistat, a gastrointestinal lipase inhibitor that reduces dietary fat absorption by approximately 30%, may promote weight loss and reduce cardiovascular risk factors.

OBJECTIVE

To test the hypothesis that orlistat combined with dietary intervention is more effective than placebo plus diet for weight loss and maintenance over 2 years.

DESIGN

Randomized, double-blind, placebo-controlled study conducted from October 1992 to October 1995.

SETTING AND PARTICIPANTS

Obese adults (body mass index [weight in kilograms divided by the square of height in meters], 30-43 kg/m2) evaluated at 18 US research centers.

INTERVENTION

Subjects received placebo plus a controlled-energy diet during a 4-week lead-in. On study day 1, the diet was continued and subjects were randomized to receive placebo 3 times a day or orlistat, 120 mg 3 times a day, for 52 weeks. After 52 weeks, subjects began a weight-maintenance diet, and the placebo group (n = 133) continued to receive placebo and orlistat-treated subjects were rerandomized to receive placebo 3 times a day (n = 138), orlistat, 60 mg (n = 152) or 120 mg (n = 153) 3 times a day, for an additional 52 weeks.

MAIN OUTCOME MEASURES

Body weight change and changes in blood pressure and serum lipid, glucose, and insulin levels.

RESULTS

A total of 1187 subjects entered the protocol, and 892 were randomly assigned on day 1 to double-blind treatment. For intent-to-treat analysis, 223 placebo-treated subjects and 657 orlistat-treated subjects were evaluated. During the first year orlistat-treated subjects lost more weight (mean +/- SEM, 8.76+/-0.37 kg) than placebo-treated subjects (5.81+/-0.67 kg) (P<.001). Subjects treated with orlistat, 120 mg 3 times a day, during year 1 and year 2 regained less weight during year 2 (3.2+/-0.45 kg; 35.2% regain) than those who received orlistat, 60 mg (4.26+/-0.57 kg; 51.3% regain), or placebo (5.63+/-0.42 kg; 63.4% regain) in year 2 (P<.001). Treatment with orlistat, 120 mg 3 times a day, was associated with improvements in fasting low-density lipoprotein cholesterol and insulin levels.

CONCLUSIONS

Two-year treatment with orlistat plus diet significantly promotes weight loss, lessens weight regain, and improves some obesity-related disease risk factors.

PDGF- and insulin-dependent pp70S6k activation mediated by phosphatidylinositol-3-OH kinase

Platelet-derived growth factor receptor (PDGF-R) phosphorylation at tyrosines 740/751 and insulin receptor phosphorylation of insulin receptor substrate-1 effects the recruitment and activation of phosphatidylinositol-3-OH kinase (PI(3)K). Changes in PI(3)K activity correlate with cell growth but its downstream signal transducers are unknown. Activation of the 70/85K S6 kinases (pp70S6k) by serine phosphorylation results in 40S ribosomal protein S6 phosphorylation and is important for G1 cell-cycle transition in a variety of cells. Although receptor tyrosine kinases activate the microtubule-associated protein kinase cascade through SH2-/SH3-adaptor proteins, Sos and c-Ras, it is unclear how tyrosine kinases are coupled to the pp70S6k phosphorylation cascade. Here we report that PI(3)K mediates PDGF or insulin receptor signalling to pp70S6k. PI(3)K-mediated activation of pp70S6k is independent of conventional protein kinase C isoforms. Additionally, rapamycin blocks pp70S6k activation by all mitogens, without inhibiting PI(3)K, and acts downstream in this signalling system.

Sequence-dependent correction of random coil NMR chemical shifts

Random coil chemical shifts are commonly used to detect secondary structure elements in proteins in chemical shift index calculations. While this technique is very reliable for folded proteins, application to unfolded proteins reveals significant deviations from measured random coil shifts for certain nuclei. While some of these deviations can be ascribed to residual structure in the unfolded protein, others are clearly caused by local sequence effects. In particular, the amide nitrogen, amide proton, and carbonyl carbon chemical shifts are highly sensitive to the local amino acid sequence. We present a detailed, quantitative analysis of the effect of the 20 naturally occurring amino acids on the random coil shifts of (15)N(H), (1)H(N), and (13)CO resonances of neighboring residues, utilizing complete resonance assignments for a set of five-residue peptides Ac-G-G-X-G-G-NH(2). The work includes a validation of the concepts used to derive sequence-dependent correction factors for random coil chemical shifts, and a comprehensive tabulation of sequence-dependent correction factors that can be applied for amino acids up to two residues from a given position. This new set of correction factors will have important applications to folded proteins as well as to short, unstructured peptides and unfolded proteins.

Rapamycin selectively inhibits interleukin-2 activation of p70 S6 kinase

The macrolide rapamycin induces cell cycle G1 arrest in yeast and in mammalian cells, which suggests that an evolutionarily conserved, rapamycin-sensitive pathway may regulate entry into S phase. In mammals, rapamycin inhibits interleukin-2 receptor-induced S phase entry and subsequent T-cell proliferation, resulting in immunosuppression. Here we show that interleukin-2 selectively stimulates the phosphorylation and activation of p70 S6 kinase but not the erk-encoded MAP kinases and rsk-encoded S6 kinases. Rapamycin completely and rapidly inhibits interleukin-2-induced phosphorylation and activation of p70 S6 kinase at concentrations comparable to those blocking S phase entry of T cells (0.05-0.2 nM). The structurally related macrolide FK506 competitively antagonizes the actions of rapamycin, indicating that these effects are mediated by FKBP, which binds the transition-state mimic structure common to both rapamycin and FK506 (refs 4, 6, 9-11). The selective blockade of the p70 S6 kinase activation cascade by the rapamycin-FKBP complex implicates this signalling pathway in the regulation of T cell entry into S phase.

STAT3 serine phosphorylation by ERK-dependent and -independent pathways negatively modulates its tyrosine phosphorylation

Recent studies have indicated that serine phosphorylation regulates the activities of STAT1 and STAT3. However, the kinase(s) responsible and the role of serine phosphorylation in STAT function remain unresolved. In the present studies, we examined the growth factor-dependent serine phosphorylation of STAT1 and STAT3. We provide in vitro and in vivo evidence that the ERK family of mitogen-activated protein (MAP) kinases, but not JNK or p38, specifically phosphorylate STAT3 at serine 727 in response to growth factors. Evidence for additional mitogen-regulated serine phosphorylation is also provided. STAT1 is a relatively poor substrate for all MAP kinases tested both in vitro and in vivo. STAT3 serine phosphorylation, not its tyrosine phosphorylation, results in retarded mobility of the STAT3 protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Importantly, serine 727 phosphorylation negatively modulates STAT3 tyrosine phosphorylation, which is required for dimer formation, nuclear translocation, and the DNA binding activity of this transcriptional regulator. Interestingly, the cytokine interleukin-6 also stimulates STAT3 serine phosphorylation, but in contrast to growth factors, this occurs by an ERK-independent process.

Role of orlistat in the treatment of obese patients with type 2 diabetes. A 1-year randomized double-blind study

OBJECTIVE

Obesity is an important risk factor for type 2 diabetes. Weight loss in patients with type 2 diabetes is associated with improved glycemic control and reduced cardiovascular disease risk factors, but weight loss is notably difficult to achieve and sustain with caloric restriction and exercise. The purpose of this study was to assess the impact of treatment with orlistat, a pancreatic lipase inhibitor, on weight loss, glycemic control, and serum lipid levels in obese patients with type 2 diabetes on sulfonylurea medications.

RESEARCH DESIGN AND METHODS

In a multicenter 57-week randomized double-blind placebo-controlled study, 120 mg orlistat or placebo was administered orally three times a day with a mildly hypocaloric diet to 391 obese men and women with type 2 diabetes who were aged > 18 years, had a BMI of 28-40 kg/m2, and were clinically stable on oral sulfonylureas. Changes in body weight, glycemic control, lipid levels, and drug tolerability were measured.

RESULTS

After 1 year of treatment, the orlistat group lost 6.2 +/- 0.45% (mean +/- SEM) of initial body weight vs. 4.3 +/- 0.49% in the placebo group (P < 0.001). Twice as many patients receiving orlistat (49 vs. 23%) lost > or = 5% of initial body weight (P < 0.001). Orlistat treatment plus diet compared with placebo plus diet was associated with significant improvement in glycemic control, as reflected in decreases in HbA1c (P < 0.001) and fasting plasma glucose (P < 0.001) and in dosage reductions of oral sulfonylurea medication (P < 0.01). Orlistat therapy also resulted in significantly greater improvements than placebo in several lipid parameters, namely, greater reductions in total cholesterol, (P < 0.001), LDL cholesterol (P < 0.001), triglycerides (P < 0.05), apolipoprotein B (P < 0.001), and the LDL-to-HDL cholesterol ratio (P < 0.001). Mild to moderate and transient gastrointestinal events were reported with orlistat therapy, although their association with study withdrawal was low. Fat-soluble vitamin levels generally remained within the reference range, and vitamin supplementation was required in only a few patients.

CONCLUSIONS

Orlistat is an effective treatment modality in obese patients with type 2 diabetes with respect to clinically meaningful weight loss and maintenance of weight loss, improved glycemic control, and improved lipid profile.

Akt/PKB promotes cancer cell invasion via increased motility and metalloproteinase production

The Akt/protein kinase B (PKB) serine/threonine kinase is well known as an important mediator of many cell survival signaling pathways. Here, we demonstrate for the first time a major role of Akt/PKB in the cell invasion properties of the highly metastatic cell line HT1080. Using confocal microscopic analyses of live samples, we found Akt/PKB to be localized in the leading edge membrane area of migrating HT1080 cells. This localization was dependent on phosphoinositide 3-kinase and required the lipid binding ability of the phosphoinositide binding pleckstrin homology domain of Akt/PKB. We examined the possible function of Akt/PKB in HT1080 invasion. Surprisingly, Akt/PKB potently promoted HT1080 invasion, by increasing cell motility and matrix metalloproteinase-9 (MMP-9) production, in a manner highly dependent on its kinase activity and membrane-translocating ability. The increase in MMP-9 production was mediated by activation of nuclear factor-kappaB transcriptional activity by Akt/PKB. However, Akt/PKB did not affect the cell-cell or cell-matrix adhesion properties of HT1080. Our findings thus establish Akt/PKB as a major factor in the invasive abilities of cancer cells.

Effects of wearing N95 and surgical facemasks on heart rate, thermal stress and subjective sensations

Aim: The study was aimed at investigating the effects of wearing N95 and surgical facemasks with and without nano-functional treatments on thermophysiological responses and the subjective perception of discomfort. Method: Five healthy male and five healthy female participants performed intermittent exercise on a treadmill while wearing the protective facemasks in a climate chamber controlled at an air temperature of 25°C and a relative humidity of 70%. Four types of facemasks, including N95 (3M 8210) and surgical facemasks, which were treated with nano-functional materials, were used in the study. Results: (1) The subjects had significantly lower average heart rates when wearing nano-treated and untreated surgical facemasks than when wearing nano-treated and untreated N95 facemasks. (2) The outer surface temperature of both surgical facemasks was significantly higher than that of both N95 facemasks. On the other hand, the microclimate and skin temperatures inside the facemask were significantly lower than those in both N95 facemasks. (3) Both surgical facemasks had significantly higher absolute humidity outside the surface than both N95 facemasks. The absolute humidity inside the surgical facemask was significantly lower than that inside both N95 facemasks. (4) Both surgical facemasks were rated significantly lower for perception of humidity, heat, breath resistance and overall discomfort than both N95 facemasks. The ratings for other sensations, including feeling unfit, tight, itchy, fatigued, odorous and salty, that were obtained while the subjects were wearing the surgical facemasks were significantly lower than when the subjects were wearing the N95 facemasks. (5) Subjective preference for the nano-treated surgical facemasks was the highest. There was significant differences in preference between the nano-treated and untreated surgical facemasks and between the surgical and N95 facemasks. Discussion: We discuss how N95 and surgical facemasks induce significantly different temperature and humidity in the microclimates of the facemasks, which have profound influences on heart rate and thermal stress and subjective perception of discomfort.

IL-8 activates endothelial cell CXCR1 and CXCR2 through Rho and Rac signaling pathways

Stimulation of microvascular endothelial cells with interleukin (IL)-8 leads to cytoskeletal reorganization, which is mediated by combined activation of the CXCR1 and the CXCR2. In the early phase actin stress fibers appear, followed by cortical actin accumulation and cell retraction leading to gap formation between cells. The early response (between 1 and 5 min) is inhibited by an antibody that blocks the CXCR1. The later phase (from about 5 to 60 min), which is associated with cell retraction, is prevented by anti-CXCR2 antibody. Furthermore, anti-CXCR2, but not anti-CXCR1, antibody blocked IL-8-mediated haptotaxis of endothelial cells on collagen. The later phase of the IL-8-mediated actin response is inhibited by pertussis toxin, indicating that the CXCR2 couples to Gi. In contrast, the early phase is blocked by C3 botulinum toxin, which inactivates Rho, and by Y-27632, which inhibits Rho kinase, but not by pertussis toxin. Furthermore, the early CXCR1-mediated formation of stress fibers was prevented by dominant negative Rho. Dominant negative Rac on the other hand initially translocated to actin-rich filopodia after stimulation with IL-8 and later prevented cell retraction by blocking the CXCR2-mediated cytoskeletal response. These results indicate that IL-8 activates both the CXCR1 and the CXCR2 on microvascular endothelial cells, using different signal transduction cascades. The retraction of endothelial cells due to activation of the CXCR2 may contribute to the increased vascular permeability observed in acute inflammation and during the angiogenic response.

A comparison of surgeons' posture during laparoscopic and open surgical procedures

BACKGROUND

There is increasing recognition of surgeons' physical fatigue in the new ergonomic environment of laparoscopic surgery. The purpose of this study was to determine what the differences are in the movement of the surgeon's axial skeleton between laparoscopic and open operations.

METHODS

Surgeons' body positions were recorded on videotape during four laparoscopic (LAP) and six open (OP) operations. The percent of time the head and back were in a normal, bent, or twisted position as well as the number of changes in head and back position were tabulated using a computer program. A separate laboratory study was performed on four surgeons "walking" a 0.5-inch polyethylene tubing forward and backward using laparoscopic and open techniques. The movements of the surgeons' head, trunk, and pelvis were measured using a three-camera kinematic system (Kin). The center of pressure was recorded using a floor-mounted forceplate (Fp).

RESULTS

In the operating room surgeons' head and back positions were more often straight in laparoscopic procedures and more often bent in open operations. The number of changes in back position per minute were significantly decreased when the laparoscopic-only part of surgery was analyzed. In the laboratory the subjects' head position was significantly (p = 0.02) more upright and the anteroposterior (AP) and rotational range of motion of the head was significantly reduced during laparoscopy. Subjects' CP was more anterior and there was a significant reduction in the AP range of motion of the CP during laparoscopy.

CONCLUSIONS

Our study suggests that surgeons exhibit decreased mobility of the head and back and less anteroposterior weight shifting during laparoscopic manipulations despite a more upright posture. This more restricted posture during laparoscopic surgery may induce fatigue by limiting the natural changes in body posture that occur during open surgery.

Effect of black and green tea polyphenols on c-jun phosphorylation and H(2)O(2) production in transformed and non-transformed human bronchial cell lines: possible mechanisms of cell growth inhibition and apoptosis induction

The biological activities of theaflavin (TF), theaflavin gallate (TFG) and theaflavin digallate (TFdiG) from black tea and (-)-epigallocatechin 3-gallate (EGCG) and (-)-epigallocatechin (EGC) from green tea were investigated using SV40-immortalized (33BES) and Ha-ras gene transformed (21BES) human bronchial epithelial cell lines. Growth inhibition and cell viability were measured by trypan blue dye exclusion assay following 24 h treatment with the tea polyphenols. TFdiG, EGC and EGCG displayed comparable inhibitory effects on the growth of 21BES cells, with estimated IC(50) values of 22-24 microM. TFG exhibited a lower inhibitory activity (IC(50) 37 microM) and TF was even less effective (IC(50) 47 microM) in this cell line. A similar effect was also observed in 33BES cells. These results suggest that the gallate structure of theaflavins is important for growth inhibition. Exposure of 21BES cells to 25 microM TFdiG, EGC and EGCG for 24 h led to induction of cell apoptosis/death as determined by the Annexin V apoptosis assay. With TFdiG treatment cell death occurred early, and quickly peaked at 8-12 h. Morphological observations showed that TFdiG-treated cells appeared irregular in shape, with cytoplasmic granules, suggesting a cytotoxic effect. On the other hand, EGC and EGCG showed a lag phase before a rapid increase in apoptosis between 16 and 24 h, without any marked morphological changes, which was similar to that induced by H(2)O(2). TFdiG, EGC and EGCG induced similar amounts of H(2)O(2) formation in 21BES cells. Exogenously added catalase significantly prevented EGC- and EGCG-induced cell apoptosis, but did not prevent TFdiG-induced cell death, suggesting that H(2)O(2) is involved in the apoptosis induced by EGCG and EGC, but not in TFdiG-induced cell death. EGCG and TFdiG were shown to decrease c-jun protein phosphorylation in 21BES cells. Such inhibition is expected to result in lowered AP-1 activity, which may contribute to the growth inhibitory activity of tea polyphenols.

NMR structural and dynamic characterization of the acid-unfolded state of apomyoglobin provides insights into the early events in protein folding

Apomyoglobin forms a denatured state under low-salt conditions at pH 2.3. The conformational propensities and polypeptide backbone dynamics of this state have been characterized by NMR. Nearly complete backbone and some side chain resonance assignments have been obtained, using a triple-resonance assignment strategy tailored to low protein concentration (0.2 mM) and poor chemical shift dispersion. An estimate of the population and location of residual secondary structure has been made by examining deviations of (13)C(alpha), (13)CO, and (1)H(alpha) chemical shifts from random coil values, scalar (3)J(HN,H)(alpha) coupling constants and (1)H-(1)H NOEs. Chemical shifts constitute a highly reliable indicator of secondary structural preferences, provided the appropriate random coil chemical shift references are used, but in the case of acid-unfolded apomyoglobin, (3)J(HN,H)(alpha) coupling constants are poor diagnostics of secondary structure formation. Substantial populations of helical structure, in dynamic equilibrium with unfolded states, are formed in regions corresponding to the A and H helices of the folded protein. In addition, the deviation of the chemical shifts from random coil values indicates the presence of helical structure encompassing the D helix and extending into the first turn of the E helix. The polypeptide backbone dynamics of acid-unfolded apomyoglobin have been investigated using reduced spectral density function analysis of (15)N relaxation data. The spectral density J(omega(N)) is particularly sensitive to variations in backbone fluctuations on the picosecond to nanosecond time scale. The central region of the polypeptide spanning the C-terminal half of the E helix, the EF turn, and the F helix behaves as a free-flight random coil chain, but there is evidence from J(omega(N)) of restricted motions on the picosecond to nanosecond time scale in the A and H helix regions where there is a propensity to populate helical secondary structure in the acid-unfolded state. Backbone fluctuations are also restricted in parts of the B and G helices due to formation of local hydrophobic clusters. Regions of restricted backbone flexibility are generally associated with large buried surface area. A significant increase in J(0) is observed for the NH resonances of some residues located in the A and G helices of the folded protein and is associated with fluctuations on a microsecond to millisecond time scale that probably arise from transient contacts between these distant regions of the polypeptide chain. Our results indicate that the equilibrium unfolded state of apomyoglobin formed at pH 2.3 is an excellent model for the events that are expected to occur in the earliest stages of protein folding, providing insights into the regions of the polypeptide that spontaneously undergo local hydrophobic collapse and sample nativelike secondary structure.

Optimal operational factors for nitrite accumulation in batch reactors

The environmental factors that affected the accumulation of nitrite in nitrifying reactors were investigated using a mixed culture. A batch reactor with 50 mg-N/l of ammonia was used. The pH, temperature and dissolved oxygen concentration were varied. The concentration of unionized free ammonia also changed with the oxidation of ammonia and the variation of pH and temperature. The accumulation of nitrite was affected sensitively by pH and temperature. A higher nitrite concentration was observed at pH 8-9 or temperature around 30 degrees C. The dissolved oxygen also affected, giving the highest nitrite accumulation at around 1.5 mg/l. These were the favored conditions for nitrite production. The free ammonia concentration influenced the nitrite accumulation also, by inhibiting nitrite oxidation. The inhibition became apparent at a concentration of approximately 4 mg/l or above, but insignificant at below 1 mg/l. Thus, simultaneously high free ammonia concentration and maximum specific ammonia-oxidation rate (above 15 x 10(-3) mg-N/mg-VSS x h) were needed for a significant nitrite accumulation. When the two conditions were met, then the highest accumulation was observed when the ratio of the maximum specific oxidation rate of ammonia to the maximum specific oxidation rate of nitrite (ka/kn) was highest. Under the optimal operating conditions of pH 8, 30 degrees C and 1.5 mg/l of dissolved oxygen, as much as 77% of the removed ammonia accumulated in nitrite.

Retrospective population-based analysis of the dose-response (fecal fat excretion) relationship of orlistat in normal and obese volunteers

Orlistat, an inhibitor of gastrointestinal lipases, limits the absorption of ingested fat and could become a potential treatment for obesity. This analysis was performed to elucidate the relationship between orlistat dose and intensity of inhibition of dietary fat absorption (assessed by measuring fecal fat excretion). In 11 phase I double-blind, placebo-controlled, parallel-group randomized studies, a total of 171 subjects received oral daily doses that ranged from 30 to 1200 mg orlistat or matching placebo three times a day for 9 to 10 days. The results of the daily mean fecal fat excretion percentage (relative to ingested fat) were correlated to the orlistat daily dose. A simple maximum-effect model that included a basal value was used to fit the dose-response relationship for all evaluable subjects. The mean maximum percentage of ingested fat excreted in the feces was approximately 32% during orlistat administration compared with 5% during placebo administration. The orlistat daily dose that produced 50% of the maximum effect was 98 mg/day. The model-fitting suggests the existence of a steep portion of the dose-response curve up to approximately 400 mg/day, with a subsequent tendency to plateau at higher doses. Such an analysis was instrumental in identifying appropriate doses to be used in therapeutic trials for weight loss in obese patients.

Thrombspondin acts via integrin-associated protein to activate the platelet integrin alphaIIbbeta3

Integrin-associated protein (IAP or CD47) is a receptor for the cell/platelet-binding domain (CBD) of thrombospondin-1 (TS1), the most abundant protein of platelet alpha granules. Although it associates with alphaIIbbeta3, IAP has no known function in platelets. TS1, the CBD, and an IAP agonist peptide (4N1K) from the CBD of TS1 activate the platelet integrin alphaIIbbeta3, resulting in platelet spreading on immobilized fibrinogen, stimulation of platelet aggregation, and enhanced tyrosine phosphorylation of focal adhesion kinase. Furthermore, 4N1K peptide selectively stimulates the phosphorylation of LYN and SYK and their association with FAK. The phosphorylation of SYK is blocked by pertussis toxin, implicating a Gi-like heterotrimeric G protein. IAP solublized from membranes of unstimulated platelets binds specifically to an affinity column of 4N1K peptide. Both alphaIIb and beta3 integrin subunits and c-Src bind along with IAP. This complex of proteins is also detected with immunoprecipitation. Activation of platelets with the agonist peptide 4N1K results in the association of FAK with the IAP-alphaIIbbeta3 complex. Thus an important function of TS1 in platelets is that of a secreted costimulator of alphaIIbbeta3 whose unique properties result in its localization to the platelet surface and the fibrin clot.

Complete genome sequence of the genetically tractable hydrogenotrophic methanogen Methanococcus maripaludis

The genome sequence of the genetically tractable, mesophilic, hydrogenotrophic methanogen Methanococcus maripaludis contains 1,722 protein-coding genes in a single circular chromosome of 1,661,137 bp. Of the protein-coding genes (open reading frames [ORFs]), 44% were assigned a function, 48% were conserved but had unknown or uncertain functions, and 7.5% (129 ORFs) were unique to M. maripaludis. Of the unique ORFs, 27 were confirmed to encode proteins by the mass spectrometric identification of unique peptides. Genes for most known functions and pathways were identified. For example, a full complement of hydrogenases and methanogenesis enzymes was identified, including eight selenocysteine-containing proteins, with each being paralogous to a cysteine-containing counterpart. At least 59 proteins were predicted to contain iron-sulfur centers, including ferredoxins, polyferredoxins, and subunits of enzymes with various redox functions. Unusual features included the absence of a Cdc6 homolog, implying a variation in replication initiation, and the presence of a bacterial-like RNase HI as well as an RNase HII typical of the Archaea. The presence of alanine dehydrogenase and alanine racemase, which are uniquely present among the Archaea, explained the ability of the organism to use L- and D-alanine as nitrogen sources. Features that contrasted with the related organism Methanocaldococcus jannaschii included the absence of inteins, even though close homologs of most intein-containing proteins were encoded. Although two-thirds of the ORFs had their highest Blastp hits in Methanocaldococcus jannaschii, lateral gene transfer or gene loss has apparently resulted in genes, which are often clustered, with top Blastp hits in more distantly related groups.

Processable conducting graphene/chitosan hydrogels for tissue engineering

Electrically conductive, mechanically improved graphene/chitosan/lactic acid composites were synthesised and could be easily processed into multi-layer scaffolds using additive fabrication techniques.

Cyclic AMP inhibits Akt activity by blocking the membrane localization of PDK1

Akt is a protein serine/threonine kinase that plays an important role in the mitogenic responses of cells to variable stimuli. Akt contains a pleckstrin homology (PH) domain and is activated by phosphorylation at threonine 308 and serine 473. Binding of 3'-OH phosphorylated phosphoinositides to the PH domain results in the translocation of Akt to the plasma membrane where it is activated by upstream kinases such as (phosphoinositide-dependent kinase-1 (PDK1). Over-expression of constitutively active forms of Akt promotes cell proliferation and survival, and also stimulates p70 S6 kinase (p70S6K). In many cells, an increase in levels of intracellular cyclic AMP (cAMP) diminishes cell growth and promotes differentiation, and in certain conditions cAMP is even antagonistic to the effect of growth factors. Here, we show that cAMP has inhibitory effects on the phosphatidylinositol 3-kinase/PDK/Akt signaling pathway. cAMP potently inhibits phosphorylation at threonine 308 and serine 473 of Akt, which is required for the protein kinase activities of Akt. cAMP also negatively regulates PDK1 by inhibiting its translocation to the plasma membrane, despite not affecting its protein kinase activities. Furthermore, when we co-expressed myristoylated Akt and PDK1 mutants which constitutively co-localize in the plasma membrane, Akt activity was no longer sensitive to raised intracellular cAMP concentrations. Finally, cAMP was also found to inhibit the lipid kinase activity of PI3K and to decrease the levels of phosphatidylinositol 3,4,5-triphosphate in vivo, which are required for the membrane localization of PDK1. Collectively, these data strongly support the theory that the cAMP-dependent signaling pathway inhibits Akt activity by blocking the coupling between Akt and its upstream regulators, PDK, in the plasma membrane.

Activation of pp70/85 S6 kinases in interleukin-2-responsive lymphoid cells is mediated by phosphatidylinositol 3-kinase and inhibited by cyclic AMP

Activation of phosphatidylinositol 3-kinase (PI3K) and activation of the 70/85-kDa S6 protein kinases (alpha II and alpha I isoforms, referred to collectively as pp70S6k) have been independently linked to the regulation of cell proliferation. We demonstrate that these kinases lie on the same signalling pathway and that PI3K mediates the activation of pp70 by the cytokine interleukin-2 (IL-2). We also show that the activation of pp70S6k can be blocked at different points along the signalling pathway by using specific inhibitors of T-cell proliferation. Inhibition of PI3K activity with structurally unrelated but highly specific PI3K inhibitors (wortmannin or LY294002) results in inhibition of IL-2-dependent but not phorbol ester (conventional protein kinase C [cPKC])-dependent pp70S6k activation. The T-cell immunosuppressant rapamycin potently antagonizes IL-2-(PI3K)- and phorbol ester (cPKC)-mediated activation of pp70S6k. Thus, wortmannin and rapamycin antagonize IL-2-mediated activation of pp70S6k at distinct points along the PI3K-regulated signalling pathway, or rapamycin antagonizes another pathway required for pp70S6k activity. Agents that raise the concentration of intracellular cyclic AMP (cAMP) and activate cAMP-dependent protein kinase (PKA) also inhibit IL-2-dependent activation of pp70S6k. In this case, inhibition appears to occur at least two points in this signalling path. Like rapamycin, PKA appears to act downstream of cPKC-mediated pp70S6k activation, and like wortmannin, PKA antagonizes IL-2-dependent activation of PI3K. The results with rapamycin and wortmannin are of added interest since the yeast and mammalian rapamycin targets resemble PI3K in the catalytic domain.

Incidence of acquired CNS demyelinating syndromes in a multiethnic cohort of children

OBJECTIVE

To determine whether the incidence and clinical features of pediatric multiple sclerosis (MS) and other forms of pediatric acquired demyelinating syndromes (ADS) vary by race/ethnicity in a population-based cohort.

METHODS

We used a combination of electronic database searches followed by complete medical records review to identify all children diagnosed with MS and ADS in the multiethnic membership of Kaiser Permanente Southern California from January 1, 2004, to December 31, 2009. Incidence rates were standardized to the US census by age and gender.

RESULTS

We identified 81 incident cases of ADS from 4.87 million person-years of observation in children 0-18 years of age. The incidence rate of pediatric MS was 0.51 per 100,000 person-years (95% confidence interval [CI] 0.33-0.75) and incidence of other forms of ADS including optic neuritis, transverse myelitis, other forms of clinically isolated syndrome (CIS), and acute disseminated encephalomyelitis (ADEM) was 1.56 (95% CI 1.23-1.95) for an overall incidence of ADS of 1.66 per 100,000 person-years (95% CI 1.32-2.06). Incidence of ADS was higher in black (4.4 per 100,000 person-years, 95% CI 2.5-7.2, p < 0.001) and Asian/Pacific Islander (2.8, 95% CI 1.2-5.2, p = 0.02) than white (1.03, 95% CI 0.6-1.7) and Hispanic (1.5, 95% CI 1.1-2.1, per 100,000 person-years) children. Black children were also significantly more likely to have MS than white children (p = 0.001). Children who presented with ADEM were significantly younger than children with other types of ADS clinical presentations (mean age 5.6, range 0.7-17.6 years vs 14.6, range 2.7-18.5, respectively).

CONCLUSIONS

The incidence of pediatric acquired demyelinating syndromes is 1.66 per 100,000 person-years in a population-based cohort of Southern Californian children. The incidence of ADS and MS is higher in black children compared with white and Hispanic children.

The thrombospondin receptor integrin-associated protein (CD47) functionally couples to heterotrimeric Gi

Integrin-associated protein (IAP; CD47) is a thrombospondin receptor that forms a signaling complex with beta3 integrins resulting in enhanced alphavbeta3-dependent cell spreading and chemotaxis and, in platelets, alphaIIbbeta3-dependent spreading and aggregation. These actions of CD47 are all specifically abrogated by pertussis toxin treatment of cells. Here we report that CD47, its beta3 integrin partner, and Gi proteins form a stable, detergent-soluble complex that can be recovered by immunoprecipitation and affinity chromatography. Gialpha is released from this complex by treatment with GTP or AlF4. GTP and AlF4 also reduce the binding of CD47 to its agonist peptide (4N1K) derived from thrombospondin, indicating a direct association of CD47 with Gi. 4N1K peptide causes a rapid decrease in intraplatelet cyclic AMP levels, a Gi-dependent event necessary for aggregation. Finally, 4N1K stimulates the binding of GTPgamma35S to membranes from cells expressing IAP and alphavbeta3. This functional coupling of CD47 to heterotrimeric G proteins provides a mechanistic explanation for the biological effects of CD47 in a wide variety of systems.

Chromatin structure and gene expression

It is now well understood that chromatin structure is perturbed in the neighborhood of expressed genes. This is most obvious in the neighborhood of promoters and enhancers, where hypersensitivity to nucleases marks sites that no longer carry canonical nucleosomes, and to which transcription factors bind. To study the relationship between transcription factor binding and the generation of these hypersensitive regions, we mutated individual cis-acting regulatory elements within the enhancer that lies between the chicken beta- and epsilon-globin genes. Constructions carrying the mutant enhancer were introduced by stable transformation into an avian erythroid cell line. We observed that weakening the enhancer resulted in creation of two classes of site: those still completely accessible to nuclease attack and those that were completely blocked. This all-or-none behavior suggests a mechanism by which chromatin structure can act to sharpen the response of developmental systems to changing concentrations of regulatory factors. Another problem raised by chromatin structure concerns the establishment of boundaries between active and inactive chromatin domains. We have identified a DNA element at the 5' end of the chicken beta-globin locus, near such a boundary, that has the properties of an insulator; in test constructions, it blocks the action of an enhancer on a promoter when it is placed between them. We describe the properties and partial dissection of this sequence. A third problem is posed by the continued presence of nucleosomes on transcribed genes, which might prevent the passage of RNA polymerase. We show, however, that a prokaryotic polymerase can transcribe through a histone octamer on a simple chromatin template. The analysis of this process reveals that an octamer is capable of transferring from a position in front of the polymerase to one behind, without ever losing its attachment to the DNA.