Reduced microstructural integrity of the white matter underlying anterior cingulate cortex is associated with increased saccadic latency in schizophrenia

The anterior cingulate cortex (ACC) is a key component of a network that directs both spatial attention and saccadic eye movements, which are tightly linked. Diffusion tensor imaging (DTI) has demonstrated reduced microstructural integrity of the anterior cingulum bundle as indexed by fractional anisotropy (FA) in schizophrenia, but the functional significance of these abnormalities is unclear. Using DTI, we examined the white matter underlying anterior cingulate cortex in schizophrenia to determine whether reduced FA is associated with prolonged latencies of volitional saccades. Seventeen chronic, medicated schizophrenia outpatients and nineteen healthy controls had high-resolution DTI scans. FA maps were registered to structural scans and mapped across participants using a surface-based coordinate system. Cingulate white matter was divided into rostral and dorsal anterior regions and a posterior region. Patients showed reduced FA in cingulate white matter of the right hemisphere. Reduced FA in the white matter underlying anterior cingulate cortex, frontal eye field, and posterior parietal cortex of the right hemisphere was associated with longer saccadic latencies in schizophrenia, though given the relatively small sample size, these relations warrant replication. These findings demonstrate that in schizophrenia, increased latency of volitional saccades is associated with reduced microstructural integrity of the white matter underlying key cortical components of a right-hemisphere dominant network for visuospatial attention and ocular motor control. Moreover, they suggest that anterior cingulate white matter abnormalities contribute to slower performance of volitional saccades and to inter-individual variability of saccadic latency in chronic, medicated schizophrenia.     

An Assessment of the Incidence of Prolonged Postoperative Bleeding After Dental Extraction Among Patients on Uninterrupted Low Dose Aspirin Therapy and to Evaluate the Need to Stop Such Medication Prior to Dental Extractions

Purpose

To propose that low dose aspirin therapy need not be withdrawn for routine dental extraction procedure.

Aim

This study was designed to evaluate the post operative bleeding in patients on low dose aspirin therapy by dividing them into two groups: one with withdrawing and the other without withdrawing the regime before dental extraction.

Materials and Methods

This study included 80 patients on low dose aspirin therapy. They were divided into two groups of 40 patients each; Group I (control group) included patients on who were asked to stop the medication 5 days prior to dental extraction; Group II (test group) included patients who were asked not to stop the medication prior to dental extraction. Strict atraumatic extractions were performed by a single surgeon. Data were analyzed using the independent “t” test @ 80 % power.

Results

The mean pre-operative bleeding time in the control group was 87.75 s and the test group was 95.75 s which was statistically significant (p < 0.05). The mean pre-operative clotting time in the control group was 228.63 s and the test group was 246.25 s which was also statistically significant (p < 0.05). No patients in either group had any episode of prolonged postoperative bleeding following extraction from the surgical site and no local haemostatic measures had to be used except for one patient in Group II.

Conclusion

Authors conclude from this study that dental extraction procedures in patients on low-dose therapy can be safely carried out without stopping the antiplatelet therapy.

     

Fibrinogen Birmingham: a heterozygous dysfibrinogenemia (A alpha 16 Arg- ---His) containing heterodimeric molecules

Fibrinogen was isolated from the plasma of a 25-year-old female with a history of mild bleeding and several recent moderate to severe hemorrhagic episodes. Coagulability with thrombin approached 100% and varied directly with the time of incubation with the enzyme. High- performance liquid chromatography analysis of thrombin-induced fibrinopeptide release demonstrated retarded fibrinopeptide A (FPA) and fibrinopeptide B (FPB) release and the presence of an abnormal A peptide (FPA) amounting to 50% of the total. The same biochemical abnormalities were found in her asymptomatic father. Amino acid analysis and carboxypeptidase digestion of FPA demonstrated the substitution of His for Arg at A alpha 16. In contrast to the thrombin- and reptilase-sensitive Arg-Gly bond in the normal A alpha chain, the abnormal A alpha chain (A alpha) sequence is resistant to reptilase attack but is slowly cleaved by thrombin. To evaluate whether Birmingham A alpha and A alpha chains had been assembled nonselectively into heterodimeric (ie, 50% A alpha, A alpha) and homodimeric (ie, 25% A alpha, A alpha; 25% A alpha, A alpha) species, the clot and the clot liquor resulting from reptilase treatment of normal or Birmingham fibrinogen were separated, and each was then further incubated with thrombin to release remaining fibrinopeptides. Assuming that fibrinogen Birmingham contained heterodimeric molecules and that these and the normal molecules were completely incorporated into a reptilase clot, the expected coagulability would be 75%. In addition, subsequent thrombin treatment of the reptilase clot would release 50% of the total FPA and 75% of the total FPB present in the original sample. On the other hand, if only homodimeric fibrinogen species (50% A alpha, A alpha; 50% A alpha, A alpha) existed, the maximum reptilase coagulability would be 50%, and after thrombin treatment, 50% of the total FPB and no FPA would be recovered from the reptilase clot. We found the propositus's fibrinogen to be 68% coagulable, and we recovered 45% of the FPA and 70% of the FPB from the reptilase clot. Essentially the same coagulability and distribution of fibrinopeptides was found in the reptilase clot from her father's fibrinogen. We therefore conclude that fibrinogen Birmingham contains heterodimeric species (A alpha, A alpha) amounting to approximately 50% of the circulating fibrinogen molecules. The existence of heterodimers is consistent with a nonselective intracellular process of constituent chain assembly of dimeric plasma fibrinogen molecules.     

Antibiofilm and Membrane-Damaging Potential of Cuprous Oxide Nanoparticles against Staphylococcus aureus with Reduced Susceptibility to Vancomycin

The antimicrobial effects of copper ions and salts are well known, but the effects of cuprous oxide nanoparticles (Cu₂O-NPs) on staphylococcal biofilms have not yet been clearly revealed. The present study evaluated Cu₂O-NPs for their antibacterial and antibiofilm activities against heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) and vancomycin-intermediate S. aureus (VISA). Nanoscaled Cu₂O, generated by solution phase technology, contained Cu₂O octahedral nanoparticles. Field emission electron microscopy demonstrated particles with sizes ranging from 100 to 150 nm. Cu₂O-NPs inhibited the growth of S. aureus and showed antibiofilm activity. The MICs and minimum biofilm inhibitory concentrations ranged from 625 μg/ml to 5,000 μg/ml and from 2,500 μg/ml to 10,000 μg/ml, respectively. Exposure of S. aureus to Cu₂O-NPs caused leakage of the cellular constituents and increased uptake of ethidium bromide and propidium iodide. Exposure also caused a significant reduction in the overall vancomycin-BODIPY (dipyrromethene boron difluoride [4,4-difluoro-4-bora-3a,4a-diaza-s-indacene] fluorescent dye) binding and a decrease in the viable cell count in the presence of 7.5% sodium chloride. Cu₂O-NP toxicity assessment by hemolysis assay showed no cytotoxicity at 625 to 10,000 μg/ml concentrations. The results suggest that Cu₂O-NPs exert their action by disruption of the bacterial cell membrane and can be used as effective antistaphylococcal and antibiofilm agents in diverse medical devices.     

Structural and functional analysis of two di-domain aromatase/cyclases from type II polyketide synthases

Aromatic polyketides make up a large class of natural products with diverse bioactivity. During biosynthesis, linear poly-β-ketone intermediates are regiospecifically cyclized, yielding molecules with defined cyclization patterns that are crucial for polyketide bioactivity. The aromatase/cyclases (ARO/CYCs) are responsible for regiospecific cyclization of bacterial polyketides. The two most common cyclization patterns are C7–C12 and C9–C14 cyclizations. We have previously characterized three monodomain ARO/CYCs: ZhuI, TcmN, and WhiE. The last remaining uncharacterized class of ARO/CYCs is the di-domain ARO/CYCs, which catalyze C7–C12 cyclization and/or aromatization. Di-domain ARO/CYCs can further be separated into two subclasses: “nonreducing” ARO/CYCs, which act on nonreduced poly-β-ketones, and “reducing” ARO/CYCs, which act on cyclized C9 reduced poly-β-ketones. For years, the functional role of each domain in cyclization and aromatization for di-domain ARO/CYCs has remained a mystery. Here we present what is to our knowledge the first structural and functional analysis, along with an in-depth comparison, of the nonreducing (StfQ) and reducing (BexL) di-domain ARO/CYCs. This work completes the structural and functional characterization of mono- and di-domain ARO/CYCs in bacterial type II polyketide synthases and lays the groundwork for engineered biosynthesis of new bioactive polyketides.The biosynthesis of type II aromatic polyketide natural products has been extensively investigated because of the versatile pharmacological properties of these compounds (1–7). The type II polyketide synthase (PKS) is composed of dissociated enzymes that are used iteratively and are responsible for the elongation, cyclization, and modification of the polyketide chain (Fig. 1) (3, 4, 8, 9). The regiospecific cyclization of an acyl carrier protein (ACP)-linked linear poly-β-ketone intermediate is a key transformation catalyzed by type II PKSs. However, the enzymatic mechanism of cyclization remains poorly understood (10–14). Without such knowledge, the polyketide cyclization pattern cannot be predicted; a full understanding of this process at the molecular level is essential for future biosynthetic engineering efforts.Open in a separate windowFig. 1.Schematic diagram of ARO/CYC activity and cyclization specificity in representative type II PKSs. The monodomain ARO/CYCs TcmN (PDB ID 2RER) and WhiE (PDB ID 3TVR) act on unreduced polyketide intermediates to generate C9–C14 cyclized and aromatized products. The monodomain ARO/CYC ZhuI (PDB ID 3TFZ) and di-domain ARO/CYC StfQ act on unreduced polyketide intermediates to generate C7–C12 cyclized and aromatized products. The di-domain ARO/CYC BexL acts on C9 reduced, C7–C12 cyclized intermediates and catalyzes the aromatization of the C7–12 cyclized ring by dehydration of the C9 hydroxyl group.In 2008, we reported the crystal structure of the first aromatase/cyclase (ARO/CYC) (TcmN ARO/CYC), which is a single-domain protein (15). On the basis of the structural analysis and mutagenesis results, we proposed that monodomain ARO/CYCs contain an active site and are capable of catalyzing polyketide cyclization and aromatization. Since then, we have performed structural and biochemical studies of two other monodomain ARO/CYCs: WhiE and ZhuI (Fig. 1) (16, 17). These studies provided strong evidence supporting our hypothesis that ARO/CYC is the site of polyketide cyclization. However, many type II PKSs contain di-domain ARO/CYCs that have two seemingly identical domains (18–23). Why these enzymes require two domains (as opposed to just one) and how they conduct the cyclization/aromatization are not understood.The di-domain ARO/CYCs are found in both nonreducing and reducing PKSs (18, 24). In nonreducing systems, the di-domain ARO/CYCs regiospecifically cyclize a polyketide between C7 and C12, followed by aromatization (18). In reducing systems, a ketoreductase (KR) first regiospecifically cyclizes the linear poly-β-ketone from C12 to C7, followed by a highly specific C9-carbonyl reduction (7, 25). A di-domain ARO/CYC then catalyzes the dehydration of the C9 hydroxyl, followed by first-ring aromatization (Fig. 1) (14). Therefore, in a nonreducing system, the growing poly-β-ketone intermediate is transported directly from the ketosynthase (KS) to the ARO/CYC. In contrast, in a reducing system, the intermediate needs to be transported from KS to KR and then to ARO/CYC. Before this study, there was no knowledge of whether there is any difference between the di-domain ARO/CYCs in reducing versus nonreducing PKSs, nor any information on the role that ARO/CYCs may play in determining the product specificity of reducing and nonreducing PKSs. The key issue that has hampered the investigation of this group of enzymes is the difficulty in protein crystallization.To critically compare the reducing and nonreducing di-domain ARO/CYCs, we have chosen StfQ as a model nonreducing di-domain ARO/CYC and BexL as a model reducing di-domain ARO/CYC (Fig. 1). StfQ is a di-domain ARO/CYC from Streptomyces steffisburgensis and is part of the nonreducing PKS catalyzing the biosynthesis of steffimycin, which shows promising antitumor activities (26–28). StfQ is the enzyme responsible for the C7–C12 first-ring cyclization and aromatization of the elongated poly-β-ketone substrate. In contrast, BexL is a di-domain ARO/CYC in the reducing PKS responsible for the biosynthesis of the anticancer agent BE-7585A. The linear poly-β-ketone precursor of BE-7585A is first cyclized, then reduced at the C9 position by KR, and then aromatized by BexL (Fig. 1) (24). Both StfQ and BexL use 20-carbon poly-β-ketone substrates; therefore, the structural enzymology of these two ARO/CYCs offers a great opportunity for side-by-side comparison with insight into the catalytic mechanisms of di-domain ARO/CYCs. Here we present the first structural and biochemical characterization, to our knowledge, of two di-domain ARO/CYCs, StfQ and BexL, using X-ray crystallography, structure-based mutagenesis, in silico docking, and in vitro functional assays.     

Hemoglobin interaction with GP1bα induces platelet activation and apoptosis: a novel mechanism associated with intravascular hemolysis

Intravascular hemolysis increases the risk of hypercoagulation and thrombosis in hemolytic disorders. Our study shows a novel mechanism by which extracellular hemoglobin directly affects platelet activation. The binding of Hb to glycoprotein1bα activates platelets. Lower concentrations of Hb (0.37–3 μM) significantly increase the phosphorylation of signaling adapter proteins, such as Lyn, PI3K, AKT, and ERK, and promote platelet aggregation in vitro. Higher concentrations of Hb (3–6 μM) activate the pro-apoptotic proteins Bak, Bax, cytochrome c, caspase-9 and caspase-3, and increase platelet clot formation. Increased plasma Hb activates platelets and promotes their apoptosis, and plays a crucial role in the pathogenesis of aggregation and development of the procoagulant state in hemolytic disorders. Furthermore, we show that in patients with paroxysmal nocturnal hemoglobinuria, a chronic hemolytic disease characterized by recurrent events of intravascular thrombosis and thromboembolism, it is the elevated plasma Hb or platelet surface bound Hb that positively correlates with platelet activation.     

Soluble stem cell factor in human serum

Stem cell factor (SCF) is a recently described factor active in the early stages of hematopoiesis. It can exist in membrane-bound form and in proteolytically released soluble form. The levels and nature of SCF in human serum are described. As determined by an enzyme-linked immunosorbent assay performed for 257 samples, SCF level in serum averaged 3.3 +/- 1.1 ng/mL. The serum SCF was partially purified by immunoaffinity chromatography and analyzed by glycosidase treatments in conjunction with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. The results show that the SCF has N- linked and O-linked carbohydrate and corresponds to the soluble form, at or about 165 amino acids in length. The findings suggest functional importance for soluble SCF in humans.     

When Advocacy Obscures Accuracy Online: Digital Pandemics of Public Health Misinformation Through an Antifluoride Case Study

Objectives. In an antifluoridation case study, we explored digital pandemics and the social spread of scientifically inaccurate health information across the Web, and we considered the potential health effects.Methods. Using the social networking site Facebook and the open source applications Netvizz and Gephi, we analyzed the connectedness of antifluoride networks as a measure of social influence, the social diffusion of information based on conversations about a sample scientific publication as a measure of spread, and the engagement and sentiment about the publication as a measure of attitudes and behaviors.Results. Our study sample was significantly more connected than was the social networking site overall (P < .001). Social diffusion was evident; users were forced to navigate multiple pages or never reached the sample publication being discussed 60% and 12% of the time, respectively. Users had a 1 in 2 chance of encountering negative and nonempirical content about fluoride unrelated to the sample publication.Conclusions. Network sociology may be as influential as the information content and scientific validity of a particular health topic discussed using social media. Public health must employ social strategies for improved communication management.Approximately 74% of Internet users in the United States use social networking sites1 such as Facebook, which has 1 billion users worldwide, and YouTube, which is the second most used search engine globally.2 Much of the content shared peer-to-peer across these and other social sites is copied from, derivative of, or in response to traditional media content.3 News sites, Facebook, YouTube, and blogs are among the “most trustworthy” sources for retail information, and all have a strong influence on purchasing decisions,4 demonstrating the power of both expert and professional and amateur- and peer-created content. Additionally, 8 of 10 Internet users seek health information online.5 This collective evidence suggests that these Internet users are likely using social media sites to obtain health information.6Although social networks play a vital role in health behaviors,7–9 searching for health information online can be problematic, specifically information on childhood vaccinations and community water fluoridation (CWF, or fluoridation). Decreasing childhood vaccination rates and preventable disease outbreaks in the United States have resulted in widespread discussion across mainstream and social media sites in recent years.8–17 Yet, according to 1 study, because of deficient reporting by popular media, less than 25% of survey respondents were aware that the majority of scientific evidence supports the safety and effectiveness of vaccines.18Additionally, antifluoride activists are organizing on social media sites19 with the intention of lobbying the Environmental Protection Agency’s Office of Water, despite having proposed arguments that do not align with current scientific consensus about CWF in the United States.20–22 The Departments of Labor, Health and Human Services, and Education Appropriations Bill 2015 subcommittee draft report states, “The Committee is concerned about conflicting information in the media regarding the benefits of community fluoridation.”23 Seemingly, communication challenges contributing to suboptimal beliefs and behaviors about these leading24 public health interventions do not exist in isolation.Public health is encountering an emerging threat of “digital pandemics,” the rapid far-reaching spread of unrestricted and scientifically inaccurate health information across the Web through social networks.25 Improved communication between researchers and media reporters is indeed recommended but is only part of the solution. Public health challenges stemming from online misinformation are at the complex intersection of scientific research, mass media, and the emergence of social network activism through user-created content and consumer reception of information.We performed, to our knowledge, a first of its kind observational study designed to explore this challenge and the epidemiology of digital pandemics.     

Studies on the ultrastructure of fibrin lacking fibrinopeptide B (beta- fibrin)

Release of fibrinopeptide B from fibrinogen by copperhead venom procoagulant enzyme results in a form of fibrin (beta-fibrin) with weaker self-aggregation characteristics than the normal product (alpha beta-fibrin) produced by release of fibrinopeptides A (FPA) and B (FPB) by thrombin. We investigated the ultrastructure of these two types of fibrin as well as that of beta-fibrin prepared from fibrinogen Metz (A alpha 16 Arg----Cys), a homozygous dysfibrinogenemic mutant that does not release FPA. At 14 degrees C and physiologic solvent conditions (0.15 mol/L of NaCl, 0.015 mol/L of Tris buffer pH 7.4), the turbidity (350 nm) of rapidly polymerizing alpha beta-fibrin (thrombin 1 to 2 U/mL) plateaued in less than 6 min and formed a "coarse" matrix consisting of anastomosing fiber bundles (mean diameter 92 nm). More slowly polymerizing alpha beta-fibrin (thrombin 0.01 and 0.001 U/mL) surpassed this turbidity after greater than or equal to 60 minutes and concomitantly developed a network of thicker fiber bundles (mean diameters 118 and 186 nm, respectively). Such matrices also contained networks of highly branched, twisting, "fine" fibrils (fiber diameters 7 to 30 nm) that are usually characteristic of matrices formed at high ionic strength and pH. Slowly polymerizing beta-fibrin, like slowly polymerizing alpha beta-fibrin, displayed considerable quantities of fine matrix in addition to an underlying thick cable network (mean fiber diameter 135 nm), whereas rapidly polymerizing beta-fibrin monomer was comprised almost exclusively of wide, poorly anastomosed, striated cables (mean diameter 212 nm). Metz beta-fibrin clots were more fragile than those of normal beta-fibrin and were comprised almost entirely of a fine network. Metz fibrin could be induced, however, to form thick fiber bundles (mean diameter 76 nm) in the presence of albumin at a concentration (500 mumol/L) in the physiologic range and resembled a Metz plasma fibrin clot in that regard. The diminished capacity of Metz beta-fibrin to form thick fiber bundles may be due to impaired use or occupancy of a polymerization site exposed by FPB release. Our results indicate that twisting fibrils are an inherent structural feature of all forms of assembling fibrin, and suggest that mature beta-fibrin or alpha beta-fibrin clots develop from networks of thin fibrils that have the ability to coalesce to form thicker fiber bundles.