All-atom empirical potential for molecular modeling and dynamics studies of proteins

New protein parameters are reported for the all-atom empirical energy function in the CHARMM program. The parameter evaluation was based on a self-consistent approach designed to achieve a balance between the internal (bonding) and interaction (nonbonding) terms of the force field and among the solvent-solvent, solvent-solute, and solute-solute interactions. Optimization of the internal parameters used experimental gas-phase geometries, vibrational spectra, and torsional energy surfaces supplemented with ab initio results. The peptide backbone bonding parameters were optimized with respect to data for N-methylacetamide and the alanine dipeptide. The interaction parameters, particularly the atomic charges, were determined by fitting ab initio interaction energies and geometries of complexes between water and model compounds that represented the backbone and the various side chains. In addition, dipole moments, experimental heats and free energies of vaporization, solvation and sublimation, molecular volumes, and crystal pressures and structures were used in the optimization. The resulting protein parameters were tested by applying them to noncyclic tripeptide crystals, cyclic peptide crystals, and the proteins crambin, bovine pancreatic trypsin inhibitor, and carbonmonoxy myoglobin in vacuo and in crystals. A detailed analysis of the relationship between the alanine dipeptide potential energy surface and calculated protein φ, χ angles was made and used in optimizing the peptide group torsional parameters. The results demonstrate that use of ab initio structural and energetic data by themselves are not sufficient to obtain an adequate backbone representation for peptides and proteins in solution and in crystals. Extensive comparisons between molecular dynamics simulations and experimental data for polypeptides and proteins were performed for both structural and dynamic properties. Energy minimization and dynamics simulations for crystals demonstrate that the latter are needed to obtain meaningful comparisons with experimental crystal structures. The presented parameters, in combination with the previously published CHARMM all-atom parameters for nucleic acids and lipids, provide a consistent set for condensed-phase simulations of a wide variety of molecules of biological interest.

Biochemical basis of lipofuscin, ceroid, and age pigment-like fluorophores

Serious studies of the formation mechanisms of age-related pigments and their possible cellular influence have been hampered for a long time by discrepancies and controversies over the definition, fluorescence emission, origin, and composition of these pigments. This review discusses several critical controversies in this field and lay special emphasis on the cellular and biochemical reactions related to the formation mechanisms of lipofuscin, ceroid, advanced glycation end-products (AGEs), and age pigment like fluorophores (APFs). Various amino compounds and their reaction with secondary aldehydic products of oxygen free radical-induced oxidation, particularly lipid peroxidation, are important sources of the fluorophores of ceroid/lipofuscin, which progressively accumulate as a result of phagocytosis and autophagocytosis of modified biomaterials within secondary lysosomes of postmitotic and other cells. Lipofuscin is the classical age pigment of postmitotic cells, while ceroid accumulates due to pathologic and experimental processes. There are good reasons to consider both ceroid and lipofuscin as materials of the same principal origin. The age-related intracellular fluorophores of retinal pigment epithelium (RPE) seems to represent a special class of lipofuscin, which partly contains derivatives of retinoids and carotenoids. Saccharide-originated fluorophores, principally AGEs formed during glycation/Maillard reactions, may be mainly responsible for the extracellular fluorescence of long-lived proteins, such as collagen, elastin, and lens crystalline. Although lipofuscin, ceroid, AGEs, and APFs can be produced from different types of biological materials due to different side reactions of essential biology, the crosslinking of carbonyl-amino compounds is recognized as a common process during their formation.

Molecular dynamics simulation of unsaturated lipid bilayers at low hydration: parameterization and comparison with diffraction studies

A potential energy function for unsaturated hydrocarbons is proposed and is shown to agree well with experiment, using molecular dynamics simulations of a water/octene interface and a dioleoyl phosphatidylcholine (DOPC) bilayer. The simulation results verify most of the assumptions used in interpreting the DOPC experiments, but suggest a few that should be reconsidered. Comparisons with recent results of a simulation of a dipalmitoyl phosphatidylcholine (DPPC) lipid bilayer show that disorder is comparable, even though the temperature, hydration level, and surface area/lipid for DOPC are lower. These observations highlight the dramatic effects of unsaturation on bilayer structure.

TLR engagement prevents transplantation tolerance

In many experimental models, heart, pancreas and kidney allografts are accepted long-term following costimulation-targeting therapies, whereas skin, lung and intestine resist the induction of tolerance under the same regimens. We noted that a common feature of the resistant organs is their constant exposure to commensal microbes and hypothesized that these microorganisms may stimulate Toll-like receptors (TLRs), promote alloresponses and prevent tolerance induction. This hypothesis prompts the predictions that TLR engagement at the time of transplantation should avert tolerance to heart allografts in animals treated with costimulation-targeting therapies, whereas inhibition of TLR signaling should promote tolerance to skin allografts under the same conditions. Indeed, engagement of a single TLR was sufficient to prevent anti-CD154-mediated long-term cardiac allograft acceptance and correlated with abolished intragraft recruitment of CD4+/FoxP3+ regulatory T cells and the development of linked-suppression. Conversely, a lack of donor and recipient MyD88-dependent signaling led to successful skin allograft acceptance in anti-CD154-treated animals. Thus, the status of TLR signaling contributes to the resistance versus susceptibility of organs to transplantation tolerance.

Hypoglycaemic symptoms, treatment satisfaction, adherence and their associations with glycaemic goal in patients with type 2 diabetes mellitus: findings from the Real-Life Effectiveness and Care Patterns of Diabetes Management (RECAP-DM) Study

AIMS

This study was undertaken to evaluate (i) factors associated with patient-reported hypoglycaemia; (ii) association of patient-reported hypoglycaemic symptoms with treatment satisfaction and barriers to adherence and (iii) association between treatment satisfaction, adherence and glycaemic control among patients with type 2 diabetes who added a sulphonylurea or a thiazolidinedione to ongoing metformin.

METHODS

This observational, cross-sectional, multicentre study was conducted in seven countries (Finland, France, Germany, Norway, Poland, Spain and UK) from June 2006 to February 2007. Patients with type 2 diabetes who added a sulphonylurea or a thiazolidinedione to ongoing metformin therapy on a date (index date) from January 2001 through January 2006 and who had at least one haemoglobin A1C (HbA1C) measurement in the 12-month period before the visit date were eligible. Questionnaires were used to ascertain patients' reports of hypoglycaemic symptoms, treatment satisfaction, and treatment adherence. The Treatment Satisfaction Questionnaire for Medication was used to measure patients' treatment satisfaction. An adherence and barriers questionnaire was used to measure patients' adherence to treatment. Glycaemic control was based on documented HbA1C measurements within the prior 12 months.

RESULTS

The mean +/- s.d. age was 62.9 +/- 10.6 years, and the mean +/- s.d. duration of diabetes was 7.8 +/- 5.1 years. HbA1C in this population of patients who had failed metformin monotherapy and were treated with oral antihyperglycaemic agents was below the International Diabetes Federation goal of 6.5% in only 477 (27.9%) patients. Approximately 38% of patients reported hypoglycaemic symptoms during the past year. Hypoglycaemia was significantly more likely in patients with a history of macrovascular complications of diabetes (OR = 1.346; 95% CI = 1.050-1.725) and with no regular physical activity (OR = 1.295; 95% CI = 1.037-1.618). Patients reporting hypoglycaemia had significantly lower treatment satisfaction scores (71.6 +/- 17.6 vs. 76.3 +/- 16.8; p < 0.0001 for global satisfaction). Compared with their counterparts reporting no hypoglycaemic symptoms, patients with such symptoms were also significantly more likely to report barriers to adherence, including being unsure about instructions (37.0 vs. 30.5%; p = 0.0057). Patients at HbA1C goal had significantly higher treatment satisfaction and adherence compared with those who were not.

CONCLUSIONS

Patients' reports of hypoglycaemic symptoms are common in European outpatients with type 2 diabetes and are associated with significantly lower treatment satisfaction and with barriers to adherence. In addition, being at HbA1C goal is associated with treatment satisfaction and adherence.

Structure and function of S-adenosylhomocysteine hydrolase

In mammals, S-adenosylhomocysteine hydrolase (AdoHcyase) is the only known enzyme to catalyze the breakdown of S-adenosylhomocysteine (AdoHcy) to homocysteine and adenosine. AdoHcy is the product of all adenosylmethionine (AdoMet)-dependent biological transmethylations. These reactions have a wide range of products, and are common in all facets of biometabolism. As a product inhibitor, elevated levels of AdoHcy suppress AdoMet-dependent transmethylations. Thus, AdoHcyase is a regulator of biological transmethylation in general. The three-dimensional structure of AdoHcyase complexed with reduced nicotinamide adenine dinucleotide phosphate (NADH) and the inhibitor (1'R, 2'S, 3'R)-9-(2',3'-dihyroxycyclopenten-1-yl)adenine (DHCeA) was solved by a combination of the crystallographic direct methods program, SnB, to determine the selenium atom substructure and by treating the multiwavelength anomalous diffraction data as a special case of multiple isomorphous replacement. The enzyme architecture resembles that observed for NAD-dependent dehydrogenases, with the catalytic domain and the cofactor-binding domain each containing a modified Rossmann fold. The two domains form a deep active site cleft containing the cofactor and bound inhibitor molecule. A comparison of the inhibitor complex of the human enzyme and the structure of the rat enzyme, solved without inhibitor, suggests that a 17 degrees rigid body movement of the catalytic domain occurs upon inhibitor/substrate binding.

Differential immune responses to alpha-gal epitopes on xenografts and allografts: implications for accommodation in xenotransplantation

Xenograft recipients produce large amounts of high-affinity anti-Gal IgG in response to Galalpha1-3Galbeta1- 4GlcNAc-R (alpha-gal) epitopes on the graft. In contrast, ABO-mismatched allograft recipients undergo "accommodation," a state of very weak immune response to ABO antigens. These differences in anti-carbohydrate immune response were studied in alpha1,3galactosyltransferase knock-out mice. Pig kidney membranes administered to these mice elicited extensive production of anti-Gal IgG, whereas allogeneic kidney membranes expressing alpha-gal epitopes elicited only a weak anti-Gal IgM response. Anti-Gal IgG response to xenograft membranes depended on helper T cell activation and was inhibited by anti-CD40L antibody. These T cells were activated by xenopeptides and not by alpha-gal epitopes. Moreover, allogeneic cell membranes manipulated to express xenoproteins also induced anti-Gal IgG response. Xenoglycoproteins with alpha-gal epitopes are processed by anti-Gal B cells. Xenopeptides presented by these cells activate a large repertoire of helper T cells required for the differentiation of anti-Gal B cells into cells secreting anti-Gal IgG. Alloglycoproteins with alpha- gal epitopes have very few immunogenic peptides and fail to activate helper T cells. Similarly, ineffective helper T-cell activation prevents a strong immune response to blood group antigens in ABO-mismatched allograft recipients, thus enabling the development of accommodation.

Effect of inappropriate initial empiric antibiotic therapy on outcome of patients with community-acquired intra-abdominal infections requiring surgery

To assess the significance of initial empiric parenteral antibiotic therapy in patients requiring surgery for community-acquired secondary peritonitis, 425 patients hospitalized between January 1999 and September 2001 in 20 clinics across Germany were followed for a total of 6,521 patient days. Perforated appendix (38%), colon (27%), or gastroduodenum (22%) were the most common sites of infection. Escherichia coli was the most common pathogen. A total of 54 (13%) patients received inappropriate initial parenteral therapy not covering all bacteria isolated, or not covering both aerobes and anaerobes in the absence of culture results. Clinical success, predefined as the infection resolving with initial or step-down therapy after primary surgery, was achieved in 322 patients (75.7%; 95% confidence interval (CI), 70.6-81.2). Patients were more likely to have clinical success if initial antibiotic therapy was appropriate (78.6%; 95% CI, 73.6-83.9) rather than inappropriate (53.4%; 95% CI, 41.1-69.3). Patients having clinical success were estimated to stay 13.9 days in hospital (95% CI, 13.1-14.7), while those who had clinical failure stayed 19.8 days (95% CI, 17.3-22.3). In conclusion, appropriateness of initial parenteral antibiotic therapy was a predictor of clinical success, which in turn was associated with length of stay.

Oxidative modification of a carboxyl-terminal vicinal methionine in calmodulin by hydrogen peroxide inhibits calmodulin-dependent activation of the plasma membrane Ca-ATPase

In order to investigate the possibility that calmodulin (CaM) may be a principal target of reactive oxygen species (ROS) produced under conditions of oxidative stress, we have examined wheat germ CaM for the presence of highly reactive sites that correlate with the loss of function. Using reversed-phase HPLC and FAB mass spectrometry after proteolytic digestion, we have identified the sites of modification by hydrogen peroxide. We find that one of the vicinal methionines (i.e., Met146 or Met147) near the C-terminus of CaM is selectively oxidized. The ability of CaM to bind and to activate the plasma membrane (PM)-Ca-ATPase from erythrocytes was measured. There is a 30-fold decrease in the calcium affinity of oxidatively modified CaM. While there is a little change in the binding constant between the carboxyl-terminal domain of calcium-saturated CaM and a peptide homologous to the autoinhibitory sequence of the PM-Ca-ATPase, we find that there is a 9-fold reduction in the affinity of the amino-terminal domain of CaM with respect to the ability to bind target peptides. The extent of oxidative modification to one of the vicinal methionines near the carboxyl-terminal domain correlates with the loss of CaM-dependent activation of the PM-Ca-ATPase. The presence of oxidatively modified CaM prevents native CaM from activating the PM-Ca-ATPase, indicating that the oxidatively modified CaM binds to the autoinhibitory sequence on the Ca-ATPase in an altered nonproductive conformation. We suggest that the functional sensitivity of CaM to the oxidation of one of the C-terminal vicinal methionines permits CAM to serve a regulatory role in modulating cellular metabolism under conditions of oxidative stress. The predominant oxidation of a methionine near the carboxyl terminal of CaM is rationalized in terms of the enhanced solvent accessibility of these vicinal methionines.

Decreased plasma membrane calcium transport activity in aging brain

We have assessed the functional properties of both calmodulin (CaM) and the plasma membrane Ca(2+)-ATPase in brains of young, middle aged, and old Fisher 344 rats. Under optimal conditions of saturating Ca2+ and ATP, the CaM-activated Ca(2+)-ATPase activity was decreased with increasing age, particularly when CaM isolated from the brains of aged rats was used to stimulate the enzyme. In the case of CaM, structural modifications within the primary sequence of the protein from aged brains were identified. We found that during normal biological aging approximately 6 methionine residues were modified to their corresonding sulfoxide per CaM, and no other amino acids were modified. Some aspects of the age-related decline in the effectiveness of CaM as an activator of Ca(2+)-ATPase could be simulated using a range of reactive oxygen species (including hydrogen peroxide and oxoperoxynitrite) and, in the latter case, the extent of oxidative modification of specific methionine residues was directly related to their surface accessibility. The pattern of oxidative modification of the methionines in the aged CaM was less straightforward, though both in vitro oxidation of CaM and aging within the brain markedly decreased the functional properties of this important Ca(2+)-regulating protein.

Hypoglycaemia in patients with type 2 diabetes treated with a combination of metformin and sulphonylurea therapy in France

CONTEXT

Hypoglycaemia from antihyperglycaemic drugs may have a significant impact on patients' health-related quality of life. Combination use of metformin and a sulphonylurea has become increasingly common; yet, the impact of hypoglycaemia on quality of life in these patients is not well documented.

OBJECTIVE

To examine patient-reported experience of hypoglycaemia, worry about hypoglycaemic symptoms and the impact of hypoglycaemia on patients' quality of life associated with use of sulphonylurea co-administered with metformin.

DESIGN

This was an observational, cross-sectional, multi-centre study.

SETTING

A total of 98 primary care centres in France during October to December 2005.

PATIENTS

A total of 400 patients with type 2 diabetes, who were > or = 35 years old and who had been treated with metformin and a sulphonylurea for at least 6 months, completed questionnaires during their usual primary care office visit.

MAIN OUTCOME MEASURES

Frequency and severity of hypoglycaemic symptoms in the past 6 months, the Worry subscale of the Hypoglycaemic Fear Survey-II (HFS-II) and the EuroQol-5 Dimensions (EQ-5D) questionnaire.

RESULTS

A total of 136 (34%) patients reported experiencing hypoglycaemia, of whom 78 (58%) experienced mild, 40 (30%) experienced moderate and 16 (12%) experienced severe or very severe symptoms. Mean score on the HFS-II Worry scale was higher for patients who reported having hypoglycaemia than for those who did not (19.0 vs. 10.2; p < 0.0001) and increased with severity of hypoglycaemic symptoms. In linear regression analyses, more severe symptoms of hypoglycaemia were significantly associated with higher scores on the HFS-II Worry scale (p = 0.0162) among patients with hypoglycaemic symptoms. Summary scores on the EQ-5D were lower for patients who reported hypoglycaemia than for those who did not (p = 0.0001) and, in multivariate analysis, the experience of hypoglycaemia was negatively associated with the EQ-5D summary score (p < 0.0001).

CONCLUSION

The occurrence and severity of hypoglycaemic symptoms were associated with increased patient worry about hypoglycaemia and lower health-related quality of life among type 2 diabetic patients being treated with both metformin and a sulphonylurea.

miR-27a regulates endothelial differentiation of breast cancer stem like cells

Recent studies suggested that cancer stem cells (CSCs) are capable of differentiating into endothelial cells and tumor endothelium may be derived from CSCs. But the mechanism remains unclear. We showed that vascular endothelial growth factor (VEGF) induced the expression of endothelial markers in breast cancer stem like cells (BCSLCs). In addition, the VEGF-treated BCSLCs formed capillary structure in matrigel and released vWF upon histamine treatment. The miR-27a expression was significantly increased in VEGF-treated BCSLCs. Antagonizing miR-27a by miR-27a anti-sense oligos (ASOs) in VEGF-treated BCSLCs led to decreased endothelial markers and function, while increasing miR-27a in BCSLCs resulted in enhanced endothelial properties. VEGF enhanced the transcription of miR-27a by increasing RUNX1 binding to miR-27a promoter. Increased miR-27a paralleled the reduced expression of ZBTB10, a known miR-27a target. Both expression of miR-27a and knockdown of ZBTB10 in BCSLCs promoted in vivo angiogenesis and tumor metastasis. Further, we demonstrated that VEGF-treated BCSLCs secreted more endogenous VEGF compared with undifferentiated BCSLCs. Thus, miR-27a promotes angiogenesis by mediating endothelial differentiation of BCSLCs and it may be a new target for anti-angiogenesis cancer therapy.

miR-34a functions as a tumor suppressor modulating EGFR in glioblastoma multiforme

Chromosome 1p36.23 is frequently deleted in glioblastoma multiforme (GBM). miR-34a localizes in this region. Our experiments found that miR-34a was often deleted and epidermal growth factor receptor (EGFR) was frequently amplified in genomic DNA of 55 GBMs using single-nucleotide polymorphism DNA microarray. Notably, we found that the mean survival time was significantly shortened for patients whose GBMs had both EGFR amplification and miR-34a deletion. Expression of miR-34a was significantly lower in GBM samples compared with normal brain tissue. Forced expression of miR-34a in GBM cells decreased their ability to migrate and profoundly decreased their levels of cyclin-A1, -B1, -D1, and -D3, as well as cyclin-dependent kinase and increased expression of cyclin kinase inhibitor proteins (p21, p27). Also, human GBM cells (U251) stable overexpressing mir-34a formed smaller tumors when growing as xenografts in immunodeficient mice compared with wild-type U251 GBM cells. Furthermore, the protein expression of EGFR decreased in the cells with forced overexpression of miR-34a. Additional studies showed that mir-34a targeted Yin Yang-1 (YY1) and YY1 is a transcription factor that can stimulate the expression of EGFR. Thus, our data suggest that miR-34a acts as a tumor suppressor by inhibiting growth of GBM cells in vitro and in vivo associated with moderating the expression of cell-cycle proteins and EGFR. Moreover, we discovered for the first time that both deletion of miR-34a and amplification of EGFR were associated with significantly decreased overall survival of GBM patients.

Liver ischemia contributes to early islet failure following intraportal transplantation: benefits of liver ischemic-preconditioning

Early graft failure following intraportal islet transplantation (IPIT) represents a major obstacle for successful islet transplantation. Here, we examined the role of islet emboli in the induction of early graft failure and utilized a strategy of ischemic-preconditioning (IP) to prevent early islet destruction in a model of syngeneic IPIT in STZ-induced diabetic mice. Numerous focal areas of liver necrosis associated with the islet emboli were observed within 24 h post-IPIT. Pro-inflammatory cytokines, IL-1beta and IL-6, were significantly increased 3 h after IPIT, while TNF-alpha was elevated for up to 5 days post-IPIT. Caspase-3 and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling positive cells were observed in the transplanted islets trapped in areas of necrotic liver at 3 h and 1 day post-IPIT. Hyperglycemia was corrected immediately following IPIT of 200 islets, but recurrence of hyperglycemia was observed within 14 days associated with a poor response to glucose challenge. IP, a procedure of pre-exposure of the liver to transient ischemia and reperfusion, protected the liver from embolism-induced ischemic injury and prevented early islet graft failure. These data suggest that islet embolism in the portal vein is a major cause of functional loss following IPIT that can be prevented by liver IP.

Cost-effectiveness of screening for asymptomatic carotid stenosis

PURPOSE

The benefit of carotid endarterectomy for patients who are asymptomatic with > 60% carotid stenosis has been established by the Asymptomatic Carotid Atherosclerosis Study (ACAS). Which screening strategy is most appropriate is still unclear. This study assessed the cost-effectiveness of ultrasound screening for asymptomatic carotid stenosis.

METHODS

Cost-effectiveness analysis was performed with a Markov model and with data from ACAS and other studies.

RESULTS

For 60-year-old patients with a 5% prevalence of 60% to 99% asymptomatic stenosis, duplex ultrasound screening increased average quality-adjusted life years (QALY; 11.485 vs 11.473) and lifetime cost of care ($5500 vs $5012) under base-case assumptions. The incremental cost per QALY gained (cost-effectiveness ratio) was $39,495. Screening was cost-effective with the following conditions: disease prevalence was 4.5% or more, the specificity of the screening test (ultrasound) was 91% or more, the stroke rate of patients who were medically treated was 3.3% or more, the relative risk reduction of surgery was 37% or more, the stroke rate associated with surgery was 160% or less than that of the North American Symptomatic Carotid Endarterectomy Trial or ACAS perioperative complication rates, and the cost of ultrasound screening was $300 or less. A one-time screening, compared with a screening every 5 years, had more QALY (11.485 vs 11.482) and lower cost ($5500 vs $5790). Screening without arteriography, compared with screening with arteriographic verification, provided few additional QALYs (11.486 vs 11.485) at additional cost ($6896 vs $5500). The cost-effectiveness ratio was sensitive to assumptions about the stroke rate of patients who were asymptomatic and other variables.

CONCLUSIONS

Screening for asymptomatic carotid stenosis can be cost-effective when both screening and carotid endarterectomy are performed in centers of excellence.

Progressive decline in the ability of calmodulin isolated from aged brain to activate the plasma membrane Ca-ATPase

To identify possible relationships between the loss of calcium homeostasis in brain associated with aging and alterations in the function of key calcium regulatory proteins, we have purified calmodulin (CaM) from the brains of Fischer 344 rats of different ages and have assessed age-related alterations in (i) the secondary and tertiary structure of CaM and (ii) the ability of CaM to activate one of its target proteins, the plasma membrane (PM) Ca-ATPase. There is a progressive, age-dependent reduction in the ability of CaM to activate the PM-Ca-ATPase, which correlates with the oxidative modification of multiple methionines to their corresponding methionine sulfoxides. No other detectable age-related posttranslational modifications occur in the primary sequence of CaM, suggesting that the reduced ability of CaM to activate the PM-Ca-ATPase is the result of methionine oxidation. Corresponding age-related changes in the secondary and tertiary structure of CaM occur, resulting in alterations in the relative mobility of CaM on polyacrylamide gels, differences in the intrinsic fluorescence intensity and solvent accessibility of Tyr99 and Tyr138, and a reduction in the average alpha-helical content of CaM at 20 degreesC. Shifts in the calcium- and CaM-dependent activation of the PM-Ca-ATPase are observed for CaM isolated from senescent brain, which respectively requires larger concentrations of either calcium or CaM to activate the PM-Ca-ATPase. The observation that the oxidative modification of CaM during normal biological aging results in a reduced calcium sensitivity of the PM-Ca-ATPase, a lower affinity between CaM and the PM-Ca-ATPase, and the reduction in the maximal velocity of the PM-Ca-ATPase is consistent with earlier results that indicate the calcium handling capacity of a range of tissues including brain, heart, and erythrocytes isolated from aged animals declines, resulting in both longer calcium transients and elevated basal levels of intracellular calcium. Thus, the oxidative modification of selected methionines in CaM may explain aspects of the loss of calcium homeostasis associated with the aging process.

Distribution of clinically relevant antibiotic resistance genes in Lake Tai, China

Lake Tai is China's third largest freshwater lake and an important water resource for agriculture, industrial sectors, and as drinking water for several large cities. In this study, the occurrence of five antibiotic resistance genes (sul1, bla_TEM, bla_NDM-1, bla_CTX-M-32, mcr-1) was investigated in water and sediment samples collected from Lake Tai. Antibiotic resistances are currently increasing, posing a significant threat to public health. The sulfonamide resistance gene sul1 was highly abundant in all analyzed water and sediment samples. In addition, the two β-lactamase genes bla_TEMand bla_NDM-1 - encoding clinically relevant antibiotic resistances - were detected in 67.1 and 7.3% of the water samples and in 70.7 and 15.4% of the sediment samples. The third β-lactamase gene, bla_CTX-M-32, was only detected in water samples (13.4%), while the colistin resistance gene mcr-1 was not detected in any of the samples. No significant variations between different sampling sites or time points could be observed. The investigation of drinking water treatment at Lake Tai, using lake water as influent, showed a significant reduction of the antibiotic resistance genes through the treatment process. Microbial source tracking showed only low fecal contamination by humans, ruminants, and pigs, indicating the relevance of other sources such as fish farms. Overall, our results provide important insights into the occurrence and abundance of antibiotic resistance genes in the Lake Tai water system and their elimination via drinking water treatment.

Dlk1 in normal and abnormal hematopoiesis

Dlk1 (Pref-1) is a transmembrane and secreted protein, which is a member of the epidermal growth factor-like family, homologous to Notch/Delta/Serrate. We have found by real-time RT-PCR that Dlk1 mRNA levels were high in CD34(+) cells in 10 of 12 MDS samples compared with CD34(+) cells from 11 normals. Also, Dlk1 mRNA was elevated in mononuclear, low density bone marrow cells from 11/38 MDS patients, 5/11 AML M6 and 2/4 AML M7 samples. Furthermore, 5/6 erythroleukemia and 2/2 megakaryocytic leukemia cell lines highly expressed Dlk1 mRNA. Levels of Dlk1 mRNA markedly increased during megakaryocytic differentiation of both CMK megakaryoblasts as well as normal CD34(+) hematopoietic stem cells. High serum levels of Dlk1 occurred in RA (4/10) and essential thrombocythemia (2/10) patients. Functional studies showed that forced expression of Dlk1 enhanced proliferation of K562 cells growing in 1% fetal bovine serum. Analysis of hematopoiesis of Dlk1 knockout mice suggested that Dlk1 contributed to granulocyte, megakaryocyte and B-cell clonogenic growth and was needed for generation of splenic B-cells. In summary, Dlk1 is overexpressed in selected samples of MDS (especially RA and RAEB) and AML (particularly M6, M7), and it appears to be associated with normal development of megakaryocytes and B cells.

DLK1: increased expression in gliomas and associated with oncogenic activities

DLK1 (delta-like) is a transmembrane and secreted protein in the epidermal growth factor-like homeotic family. Although expressed widely during embryonic development, only a few tissues retain the expression in adults. Neuroendocrine tumors often highly express this protein; therefore, we hypothesized that brain tumors might also express it. This study found that the expression of DLK1 in gliomas was higher than that in normal brain (P < 0.05). After stable transfection of a DLK1 cDNA expression vector into GBM cell lines, their proliferation was increased. Furthermore, they lost contact inhibition, had enhanced anchorage-independent growth in soft agar, and had significantly greater capacity to migrate. Western blot studies showed that expression of cyclin D1, CDK2, and E2F4 were increased, and Rb levels were decreased in these cells. DLK1 was found on the cell surface and secreted in the medium from the transfected GBM cells. DLK1-enriched condition medium stimulated the growth of glioblastoma multiforme cell lines and explants. DLK1 antibody blocked cell growth stimulated by DLK1. In summary, these results suggest that DLK1 may play a role in the formation or progression of gliomas.

Glutamyl hydrolase. pharmacological role and enzymatic characterization

gamma-Glutamyl hydrolase (GH, EC 3.4.19.9) is a lysosomal and secreted glycoprotein that hydrolyzes the gamma-glutamyl tail of antifolate and folate polyglutamates. Tumor cells that have high levels of GH are inherently resistant to classical antifolates, and further resistance can be acquired by elevations in GH following exposure to this class of antitumor agents. The highest level of expression in normal tissues occurs in the liver and kidney in humans. When panels of tumors are compared with normal tissues, GH expression is elevated in cancerous hepatic and breast tissue. A second poly-gamma-glutamate hydrolyzing enzyme, glutamate carboxypeptidase II, is a transmembrane protein whose active site is on the outside of the cell, occurring in the prostate gland, small intestine, brain, kidney, and tumor neovasculature. It is a high-affinity (nanomolar), low-turnover, zinc co-catalytic enzyme. In contrast, GH is a low-affinity (micromolar), high-turnover enzyme that has a cysteine at the active site. Data are presented suggesting that Cys110 is the nucleophile that attacks the gamma-amide linkage and causes hydrolysis. GH is being evaluated as an intracellular target for inhibition in order to enhance the therapeutic activity of antifolates and fluorouracil.

The sensitivity of carboxyl-terminal methionines in calmodulin isoforms to oxidation by H(2)O(2) modulates the ability to activate the plasma membrane Ca-ATPase

The oxidative modification of methionines within the primary sequence of calmodulin (CaM) results in an inability to activate the PM-Ca-ATPase fully, and may contribute to alterations in calcium homeostasis under conditions of oxidative stress. To identify differences in the sensitivities of CaM isoforms to oxidative modification, we have compared the function and patterns of oxidative modification resulting from the exposure of CaM isolated from bovine testes and wheat germ to H(2)O(2). In comparison to CaM isolated from wheat germ, vertebrate CaM is functionally resistant to oxidant-induced loss of function. The decreased functional sensitivity of vertebrate CaM correlates with a 75 +/- 3% reduction in the rate of oxidative modification of a methionine near the carboxyl terminus (i.e., Met(144) or Met(145)). The extent of oxidative modification to other methionines in these CaM isoforms is similar. These results suggest that the sensitivity of Met(144) or Met(145) to oxidation modulates the ability of CaM to activate the PM-Ca-ATPase. Consistent with this interpretation, a CaM mutant in which glutamines were substituted for Met(144) and Met(145) fully activates the PM-Ca-ATPase irrespective of the oxidative modification of the other seven methionines to their corresponding methionine sulfoxides. The extent of oxidative modification to individual methionines in vertebrate CaM by H(2)O(2) correlates with the time-averaged surface accessibility of individual sulfurs calculated from molecular dynamics simulations. Thus, the sensitivity of individual methionines to oxidative modification is directly related to the solvent accessibility. These results indicate that sequence differences between vertebrate and plant CaM alter the sensitivity of methionines near the carboxyl terminus to oxidative modification because of alterations in their solvent accessibility. We suggest that these sequence differences between CaM isoforms have a regulatory role in modulating the functional sensitivity of CaM to conditions of oxidative stress.

Glycaemic control among patients with type 2 diabetes mellitus in seven European countries: findings from the Real-Life Effectiveness and Care Patterns of Diabetes Management (RECAP-DM) study

OBJECTIVE

This study was undertaken to assess glycaemic control as well as changes in glycaemic control over time in patients with type 2 diabetes mellitus (T2DM) who added a sulphonylurea (SU) or thiazolidinedione (TZD) to their metformin monotherapy in typical treatment settings within seven European countries.

METHODS

An observational, cross-sectional multicentre study with retrospective medical chart review was conducted in Finland, France, Germany, Norway, Poland, Spain and UK. T2DM patients who added a SU or a TZD to metformin monotherapy between January 2001 and January 2006 (i.e. index date) and who had > or = 1 haemoglobin A1C (HbA1C) measurement within 12 months before the visit date, which occurred from June 2006 to February 2007, were included in the study. Demographic and clinical data were collected from medical records. The main study outcome measure was the proportion of patients with adequate glycaemic control (defined according to the International Diabetes Federation as HbA1C < 6.5%) using the most recent HbA1C measurement before the visit date. In addition, patients were grouped based upon the interval from the index date to the most recent HbA1C measurement to evaluate goal attainment and treatment changes over time.

FINDINGS

In this European cohort of 2023 T2DM patients on metformin and either an SU or a TZD (mean age = 60.4 years), 25.5% of patients had adequate glycaemic control. The average HbA1C level was 7.2% after a mean of 2.6 years of treatment with combination oral antihyperglycaemic agent (AHA) therapy. Among the patients (n = 227) with most recent HbA1C measurement within 1 year after first adding an SU or a TZD, 27% had adequate glycaemic control (HbA1C < 6.5%), with a mean (s.d.) HbA1C of 7.1% (1.0); 1.3% of these patients were using some type of insulin therapy. Among the patients (n = 176) with most recent HbA1C measurement occurring > or = 5 years after adding an SU or a TZD, 20% had adequate glycaemic control, with a mean (s.d.) HbA1C of 7.4% (1.17), and 29.6% of these patients were using insulin. Overall, patients with (vs. without) adequate glycaemic control had significantly (p < 0.05) lower HbA1C levels (7.6 vs. 8.2%) at the time of adding an SU or a TZD to ongoing metformin monotherapy, were less likely to report a history of macrovascular complications (20 vs. 26%) and were more often engaged in physical activity three to five times a week (29 vs. 23%).

CONCLUSIONS

Approximately one quarter of European out-patients with T2DM had adequate glycaemic control after a mean of 2.6 years following initiation of combination AHA therapy. Overall glycaemic control modestly declined over time, even though more patients were being treated with insulin. These findings highlight the progressive nature of the disease and need for more effective disease management/therapeutic alternatives.

Cost-effectiveness of MR angiography in cases of limb-threatening peripheral vascular disease

PURPOSE

To evaluate the cost-effectiveness of magnetic resonance (MR) angiography in the preoperative planning of treatment in patients with limb-threatening peripheral vascular disease (PVD).

MATERIALS AND METHODS

A decision model was developed to study the effects of MR angiography on the outcome and cost of treatment. The authors calculated the incremental cost per quality-adjusted life-years gained (ie, cost-effectiveness ratio) when conventional angiography was replaced or supplemented with MR angiography. Previously reported data regarding the accuracies of MR and conventional angiography were used in the analysis.

RESULTS

The cost-effectiveness ratio of MR angiography ranged from negative (cost-reducing) values to $78,000. For the base case in which the sensitivity and specificity of MR angiography for the evaluation of inflow vessels were 92% and 88% and those of conventional angiography were 97% and 97%, respectively, the cost-effectiveness ratio was $25,895.

CONCLUSION

MR angiography may be a cost-effective alternative to conventional angiography in patients with limb-threatening PVD if its accuracy for the inflow evaluation reaches certain thresholds. Further prospective investigation is warranted.