ABSTRACT
The extent of increasing anthropogenic impacts on large marine vertebrates partly depends on the animals' movement patterns. Effective conservation requires identification of the key drivers of movement including intrinsic properties and extrinsic constraints associated with the dynamic nature of the environments the animals inhabit. However, the relative importance of intrinsic versus extrinsic factors remains elusive. We analyze a global dataset of â¼2.8 million locations from >2,600 tracked individuals across 50 marine vertebrates evolutionarily separated by millions of years and using different locomotion modes (fly, swim, walk/paddle). Strikingly, movement patterns show a remarkable convergence, being strongly conserved across species and independent of body length and mass, despite these traits ranging over 10 orders of magnitude among the species studied. This represents a fundamental difference between marine and terrestrial vertebrates not previously identified, likely linked to the reduced costs of locomotion in water. Movement patterns were primarily explained by the interaction between species-specific traits and the habitat(s) they move through, resulting in complex movement patterns when moving close to coasts compared with more predictable patterns when moving in open oceans. This distinct difference may be associated with greater complexity within coastal microhabitats, highlighting a critical role of preferred habitat in shaping marine vertebrate global movements. Efforts to develop understanding of the characteristics of vertebrate movement should consider the habitat(s) through which they move to identify how movement patterns will alter with forecasted severe ocean changes, such as reduced Arctic sea ice cover, sea level rise, and declining oxygen content.
Subject(s)
Animal Migration , Databases, Factual , Oceans and Seas , Vertebrates , Animals , EcosystemABSTRACT
Activated carbon cloths (ACCs) were used as biofilms supports in the anaerobic biotransformation of 4-nitrophenol (4NP). As received ACC material (AW) was oxidized with HNO3 (OX) and then functionalized with anthraquinone-2,6-disulfonate (AQ). The three ACCs were packed in hybrid UASB reactors and seeded with anaerobic granular sludge for biotransformation experiments. The results indicated that ACC-packed bioreactors improved the biotransformation of 4NP by twofold as compared to the control reactor without support materials. However, the biotransformation effciency of AW, OX and AQ was very similar (59%), indicating the role of ACC as biofilm support and not as redox mediator. After 4NP biotransformation several physicochemical and biological changes were observed like (1) the point of zero charge (pHPZC) shift from acidic values (AW = 5.0, OX = 3.4, AQ = 3.1) to neutral values (pHPZC = 7.6 on average), (2) increase in the concentration of acidic and basic surface functional groups over ACC materials and the amount of supported biomass on ACCs due to biofilm formation, and (3) enrichment of exoelectrogenic microorganisms belonging to the genera Geobacter over carbonyl-rich ACC surface as revealed by 16S rRNA amplicon sequencing. Overall, the results suggest that chemical modifications of ACCs changed the microbial composition of the biofilm, but the higher concentration of carbonyl groups on ACC did not affect the biotransformation of 4NP.
Subject(s)
Bioreactors , Charcoal , Biodegradation, Environmental , Biofilms , Biotransformation , Nitrophenols , RNA, Ribosomal, 16S , Sewage , Waste Disposal, FluidABSTRACT
BACKGROUND: Neuromuscular impairment makes individuals with cerebral palsy (CP) more prone to drooling. Among the treatment options, there are procedures that interfere with saliva production. It is imperative to evaluate the effect of the different modalities since the reduction in salivary flow rate/production may exacerbate the risk of dental caries. MATERIAL AND METHODS: The aim of this study was to compare the effects of different treatments for drooling on caries risk and salivary parameters in children and adolescents with CP. STUDY DESIGN: A total of 142 children and adolescents with CP, aged 6 to 18 years, were assigned to groups based on the different treatments they had received for drooling: G1-anticholinergic drugs (n = 18), G2-botulinum toxin injection (n = 16), G3-salivary glands surgery (n = 16), G4-no treatment (n = 42), and G5-non-drooling subjects (n = 50). All participants were evaluated on the Simplified Oral Hygiene Index, and for the prevalence of dental caries (decayed, missing, and filled teeth index and white spot lesions). Unstimulated whole saliva was collected, and salivary flow rate and osmolality were measured. Chi-square, ANOVA and Poisson regression were calculated. Prevalence ratios and their respective 95 % confidence intervals were obtained. The significance level was fixed at 5%. RESULTS: No differences were found in the decayed, missing, and filled teeth index (p = 0.128) and Simplified Oral Hygiene Index (p = 0.674) among the different groups. G3 presented significantly higher percentages of WSL (p < 0.001), lower values of salivary flow rate (p < 0.001), and higher values of osmolality (p < 0.001). The white spot lesion prevalence ratio was higher only for G3 (Prevalence ratio = 14.36; IC 95% = 4.64-44.40; p < 0.001). CONCLUSIONS: Children and adolescents with CP who had received surgical treatment for drooling exhibited higher number of white spot lesions because of the reduced salivary flow rate and higher salivary osmolality.
Subject(s)
Cerebral Palsy/complications , Dental Caries/epidemiology , Sialorrhea/complications , Sialorrhea/therapy , Adolescent , Botulinum Toxins/therapeutic use , Brazil , Child , Cholinergic Antagonists/therapeutic use , Cross-Sectional Studies , DMF Index , Female , Humans , Male , Oral Hygiene , Osmolar Concentration , Prevalence , Regression Analysis , Saliva , Salivary Glands/surgery , Sialorrhea/surgeryABSTRACT
BACKGROUND: Cerebral palsy (CP) is a permanent neurological disorder accompanied by secondary musculoskeletal masticatory disorder, with repercussion on chewing and deglutition functions. In these conditions, the liquids ingestion is compromised resulting in salivary osmolality alteration. The objective of this study was to compare salivary osmolality, caries experience and caries risk between normoreactive individuals and patients with CP. MATERIAL AND METHODS: The participants were 4-20 years old: 52 patients with CP treated at a reference rehabilitation centre (study group, SG), and 52 normoreactive individuals (control group, CG). Saliva was collected for five minutes using cotton rolls. Following centrifugation, salivary osmolality was determined by freezing point depression osmometry. Evaluations included caries experience (DMFT index), and caries risk based on a caries-risk assessment tool (CAT). Descriptive and inferential statistics (Chi square and Student t tests) were used to compare the groups. Receiver operating characteristic (ROC) analyses were performed and the area under the ROC curve (Az) was calculated. The level of significance was set at 5%. RESULTS: The groups were homogeneous for sex (p=0.843) and age (p=0.128). In the SG, spastic type CP was the most prevalent (80.8%), and patients showed significantly higher salivary osmolality values compared with the CG (p<0.001). No significant differences in caries experience (p=0.159) or caries risk (p=0.297) were observed. ROC curve analysis determined a salivary osmolality cutoff point of >74 for the SG and >54 for the CG in the presence of dental caries. A significant correlation was verified between salivary osmolality and the DMFT index for the SG (p≤0.05). CONCLUSIONS: Although patients with CP showed higher salivary osmolality values, higher caries experience and caries risk were not observed compared with normoreactive individuals.
Subject(s)
Dental Caries/epidemiology , Saliva/chemistry , Adolescent , Cerebral Palsy/complications , Child , Child, Preschool , Dental Caries/etiology , Female , Humans , Male , Osmolar Concentration , Risk Assessment , Young AdultABSTRACT
OBJECTIVE: The objective of this study was to determine dental caries frequency and to analyze salivary and bacterial factors associated with active and inactive systemic lupus erythematous (SLE) patients. Also, a proposal to identify dental caries by a surface, teeth, and the patient was developed. MATERIAL AND METHODS: A cross-sectional, blinded study that included 60 SLE patients divided into two groups of 30 subjects each, according to the Activity Index for Diagnosis of Systemic Lupus Erythematous (SLEDAI). The decayed, missing, and filled teeth (DMFT) index and Integrative Dental Caries Index (IDCI) were used for analyzing dental caries. The saliva variables recorded were: flow, pH, and buffer capacity. The DNA copies of Streptococcus mutans and Streptococcus sobrinus were estimated by real-time PCR. RESULTS: The caries frequency was 85% for SLE subjects (73.3% for inactive systemic lupus erythematous (ISLE) and 100% for active systemic lupus erythematous (ASLE)); DMFT for the SLE group was 12.6 ± 5.7 and the IDCI was (9.8 ± 5.9). The ASLE group showed a salivary flow of 0.65 compared with 0.97 ml/1 min from the ISLE group; all variables mentioned above showed a statistical difference (p < 0.05). The salivary pH was 4.6 (6.06 for ISLE and 3.9 for ASLE). The DNA copies of S. mutans and S. sobrinus were high; all variables mentioned above show a significant statistical difference (p < 0.05) between groups. CONCLUSION: SLE patients had high DMFT and IDCI scores that were associated with a decrease in salivary flow, pH, and buffer capacity. There were high counts of S. sobrinus and S. mutans species, and IDCI is a useful tool to provide more detail about dental caries in epidemiological studies.
Subject(s)
Dental Caries/metabolism , Dental Caries/microbiology , Lupus Erythematosus, Systemic/metabolism , Lupus Erythematosus, Systemic/microbiology , Saliva/metabolism , Adolescent , Adult , Aged , Bacterial Load , Cross-Sectional Studies , DNA, Bacterial/analysis , Female , Humans , Male , Middle Aged , Saliva/microbiology , Streptococcal Infections/microbiology , Streptococcal Infections/physiopathology , Streptococcus mutans/genetics , Streptococcus mutans/isolation & purification , Streptococcus sobrinus/genetics , Streptococcus sobrinus/isolation & purification , Young AdultABSTRACT
Vestibular rehabilitation is effective and safe in patients with instability. However, there is insufficient evidence for distinguishing between efficacies of different dosage of therapies. Therefore, the aim of the present study was to verify whether there were differences between two computerised dynamic posturography (CDP) therapies of different numbers of sessions, in order to establish the optimal strategy. We conducted a prospective, comparative study of two different dosage of CDP therapy (a 5-session group and another of 10-session group) in patients with instability due to chronic unilateral peripheral vestibular disorder. We used balanced block randomisation to include 13 patients in each group. Improvement was assessed using the Dizziness Handicap Inventory and the CDP with the sensorial organisation test (SOT) and limits of stability (LOS). We found a statistically significant improvement in both groups in composite score, visual and vestibular input (SOT); and in reaction time, distance and directional control (LOS). If we compare the groups regarding these improvements, we found that 10-session group showed a greater benefit in distance covered and directional control of LOS. Since significant improvement is obtained with only five sessions, we believe this to be the optimal number of treatment sessions for most patients with chronic unilateral peripheral vestibular disorder. Nevertheless, those patients with more reduced limits of stability, and consequently greater likelihood of falling as a result of their diminished base of support, are candidates for rehabilitation protocols with a greater number of sessions.
Subject(s)
Biofeedback, Psychology/methods , Labyrinthitis/rehabilitation , Postural Balance , Vestibular Diseases/rehabilitation , Vestibular Neuronitis/rehabilitation , Adult , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Photic Stimulation/methods , Treatment OutcomeABSTRACT
INTRODUCTION: In cardiorenal syndrome type 1 (CRS1), vascular congestion is central to the pathophysiology of heart failure and thus a key target for management. The venous evaluation by ultrasound (VExUS) system could guide decongestion effectively and thereby improve outcomes. METHODS: In this randomized clinical trial, patients with CRS1 (i.e., increase in creatinine ≥0.3 mg/dL) were randomized to guide decongestion with VExUS compared to usual clinical evaluation. The primary endpoint was to assess kidney function recovery (KFR), and the key secondary endpoint was decongestion evaluated by physical examination and changes in brain natriuretic peptide (BNP) and CA-125. Exploratory endpoints included days of hospitalization and mortality. RESULTS: From March 2022 to February 2023, a total of 140 patients were randomized 1:1 (70 in the VExUS and 70 in the control group). KFR was not statistically different between groups. However, VExUS improved more than twice the odds to achieve decongestion (odds ratio [OR]: 2.6, 95% CI: 1.9-3.0, p = 0.01) and the odds to reach a decrease of BNP >30% (OR: 2.4, 95% CI: 1.3-4.1, p = 0.01). The survival at 90 days, recongestion, and CA-125 were similar between groups. CONCLUSION: In patients with CRS1, we observed that VExUS-guided decongestion did not improve the probability of KFR but improved the odds to achieve decongestion.
Subject(s)
Cardio-Renal Syndrome , Heart Failure , Humans , Diuretics , Recovery of Function , Kidney/diagnostic imaging , Heart Failure/complications , Heart Failure/drug therapy , Heart Failure/diagnosis , Natriuretic Peptide, BrainABSTRACT
UNLABELLED: The aim of this study was to characterize the main periodontal bacterial species in Down syndrome (DS) patients with and without periodontitis. METHOD: This cross-sectional study involved 75 DS patients, 45 with and 30 without periodontitis. Informed consent, health and dental questionnaires and periodontitis diagnosis were performed PCR and LAMP assays were performed on subgingival dental plaque sample. RESULTS: Tannerella forsythia was the most frequent bacteria detected in the group with and without periodontitis (95.5 and 63.3%) followed by Treponema denticola (88.8 and 50%) and Porphyromonas gingivalis (53.3 and 25% respectively). There were statistical differences between groups (p < 0.05). Pg fimA type I was the most frequent Porphyromonas gingivalis genotype. Two different sets of primers (Aa-F/Aa-R and ltx3/ltx4) were used to detect Aggregatibacter actinomycetemcomitans and different frequencies were obtained, (68% and 14.6% respectively), they had a weak correlation (Cohen Kappa = 0.16). After sequencing of PCR products, ltx3/ltx4 showed more specificity. JP2 clone of A. actinomycetemcomitans was not detected in any sample. CONCLUSIONS: The composition of oral biofilm is fundamental for the development of periodontal disease independently of immunological alterations associated with DS. The frequency of detection of A. actinomycetemcomitans reported in the literature has a wide range, because the primers and probes applied
Subject(s)
Biofilms/classification , Dental Plaque/microbiology , Down Syndrome/microbiology , Periodontitis/microbiology , Aggregatibacter actinomycetemcomitans/classification , Aggregatibacter actinomycetemcomitans/genetics , Aggregatibacter actinomycetemcomitans/isolation & purification , Bacterial Toxins/genetics , Bacteroides/isolation & purification , Cross-Sectional Studies , DNA Primers , DNA, Bacterial/analysis , Exotoxins/genetics , Female , Fimbriae Proteins/analysis , Genotype , Humans , Male , Microbial Consortia , Periodontal Attachment Loss/classification , Periodontal Attachment Loss/microbiology , Periodontal Pocket/classification , Periodontal Pocket/microbiology , Periodontitis/classification , Periodontium/microbiology , Pili, Sex/genetics , Porphyromonas gingivalis/genetics , Porphyromonas gingivalis/isolation & purification , Tooth Loss/classification , Treponema denticola/isolation & purification , Young AdultABSTRACT
AIM: To determine if the presence of developmental enamel defects (DED) in the primary dentition is a risk indicator for the presence of DED in the permanent dentition in children with mixed dentition, as well as others factors. MATERIALS AND METHODS: A cross-sectional study was undertaken in 1296 school children ages six to 72 years. The DED [FDI; 1982] in both dentitions were identified by means of an oral exam scoring enamel opacities [classified as demarcated or diffused], and enamel hypoplasia. Sociodemographic and socioeconomic variables were collected through a questionnaire. Socioeconomic status (SES) was determined based on the occupation and maximum level of education of parents. Statistical analysis included logistic regression. RESULTS: Mean age of participants was 8.40 +/- 1.68; 51.6% were boys. DED prevalence was 7.5% in the permanent dentition and 10.0% in the primary dentition. The logistic regression model, adjusting for sociodemographic and socioeconomic variables, showed that for each primary tooth with DED, the odds of observing DED in the permanent dentition increased 7.38 times [95% CI = 1.17-1.64; p < 0.001]. CONCLUSION: An association between DED presence in both permanent and primary dentitions was observed. Further studies are necessary to fully characterise such relationship.
Subject(s)
Dental Enamel/abnormalities , Tooth, Deciduous/abnormalities , Child , Cross-Sectional Studies , Dental Enamel Hypoplasia/epidemiology , Educational Status , Epidemiologic Studies , Family Characteristics , Female , Humans , Male , Mexico/epidemiology , Occupations , Parents/education , Prevalence , Risk Factors , Social ClassABSTRACT
Numerical and computational modelling of flow and pollutant dynamics in urban drainage systems is becoming more and more integral to planning and design. The main aim of integrated flow and pollutant models is to quantify the efficiency of different measures at reducing the amount of pollutants discharged into receiving water bodies and minimise the consequent negative water quality impact. The open source toolbox CITY DRAIN developed in the Matlab/Simulink environment, which was designed for integrated modelling of urban drainage systems, is used in this work. The goal in this study was to implement and test computational routines for representing sediment and pollutant loads in order to evaluate catchment surface pollution. Tested models estimate the accumulation, erosion and transport of pollutants--aggregately--on urban surfaces and in sewers. The toolbox now includes mathematical formulations for accumulation of pollutants during dry weather period and their wash-off during rainfall events. The experimental data acquired in a previous research project carried out by the Environmental Engineering Research Centre (CIIA) at the Universidad de los Andes in Bogotá (Colombia) was used for the calibration of the models. Different numerical approaches were tested for their ability to calibrate to the sediment transport conditions. Initial results indicate, when there is more than one peak during the rainfall event duration, wash-off processes probably can be better represented using a model based on the flow instead of the rainfall intensity. Additionally, it was observed that using more detailed models (compared with an instantaneous approach) for representing pollutant accumulation do not necessarily lead to better results.
Subject(s)
Computer Simulation , Geologic Sediments , Models, Theoretical , Water Movements , Water Pollutants, Chemical , Cities , Colombia , Rivers , Sanitary Engineering , Time Factors , Uncertainty , Water Pollutants , Water Pollution/prevention & controlABSTRACT
We have carried out density-functional theory (DFT) calculations for the chromium pnictide BaCr2P2, which is structurally analogous to BaFe2As2, a parent compound for iron-pnictide superconductors. Evolutionary methods combined with DFT predict that the chromium analog has the same crystal structure as the latter. DFT also predicts Néel antiferromagnetic order on the chromium sites. Comparison with a simple electron-hopping model over a square lattice of chromium atoms suggests that it is due to residual nesting of the Fermi surfaces. We have confirmed the DFT predictions directly after the successful synthesis of polycrystalline samples of BaCr2P2. X-ray diffraction recovers the predicted crystal structure to high accuracy, while magnetic susceptibility and specific-heat measurements are consistent with a transition to an antiferromagnetically ordered state below [Formula: see text] K.
ABSTRACT
We identified 100 scientific questions that, if answered, would have the greatest impact on conservation practice and policy. Representatives from 21 international organizations, regional sections and working groups of the Society for Conservation Biology, and 12 academics, from all continents except Antarctica, compiled 2291 questions of relevance to conservation of biological diversity worldwide. The questions were gathered from 761 individuals through workshops, email requests, and discussions. Voting by email to short-list questions, followed by a 2-day workshop, was used to derive the final list of 100 questions. Most of the final questions were derived through a process of modification and combination as the workshop progressed. The questions are divided into 12 sections: ecosystem functions and services, climate change, technological change, protected areas, ecosystem management and restoration, terrestrial ecosystems, marine ecosystems, freshwater ecosystems, species management, organizational systems and processes, societal context and change, and impacts of conservation interventions. We anticipate that these questions will help identify new directions for researchers and assist funders in directing funds.
Subject(s)
Biodiversity , Climate Change , Conservation of Natural Resources/methods , Ecology/methods , Environmental Restoration and Remediation/methods , Research/trends , Organizations, Nonprofit , Social Environment , Species SpecificityABSTRACT
We discuss the emergence of a spontaneous temperature and critical current spatial modulation in current-carrying high-temperature superconducting wire. The modulation of the critical current along the wire on a scale of 3-10 mm forces a fraction of the transport current to crisscross the resistive interface between the superconducting film and normal metal stabilizer attached to it. This generates additional heat that allows such a structure to be self-sustainable. Stability and the conditions for experimental observation of this phenomenon are also discussed.
ABSTRACT
Case Report. A nine-year-old patient with a diagnosis of tuberous sclerosis (with no pathological record) that showed calcifications at the brain level. Besides, the case showed the Vogt triad (epilepsy, mental retardation, and sebaceous adenoma). The patient clinically showed a volume increase of hard consistency, without suppuration and no sessile that included the following teeth 73, 74, and 75. Cone beam computed tomography (CBCT) was obtained, and it displayed a delimited unilocular lesion. After surgical excision, the histopathological report was desmoplastic fibroma (DF). It was observed that the patient had an aggressive recurrence of DF at four months after surgery treatment. Due to these clinical findings, resective osseous surgery and curettage were carried out. It is uncommon to find these two pathologies together (DF and tuberous sclerosis). Since DF is a benign pathology but very invasive and destructive, it is necessary a constant follow-up examination due to a high recurrence frequency.
ABSTRACT
OBJECTIVE: To compare the effect of topical, intravenous, and intracuff lidocaine on reducing coughing during emergence from general anesthesia. PATIENTS AND METHODS: Patients with an ASA physical status of I or II were enrolled if they were over 18 years of age and scheduled for elective surgery lasting between 60 and 120 minutes under balanced anesthesia with orotracheal intubation. Enrolled patients were randomly assigned to one of 3 treatment groups (intravenous lidocaine, topical lidocaine, or intracuff lidocaine) or to the control group. Numerical variables were described as mean (SD) or median and interquartile range, depending on distribution. Categorical variables were described using frequencies (number) and percentages. Multiple-group comparisons were performed using analysis of variance, the Kruskal-Wallis test, or the chi2 test, as appropriate. A level of P < .05 was considered to be statistically significant. RESULTS: We enrolled 80 patients; data for 78 were entered into analysis. Thirteen patients (65%) presented coughing in the control group, 5 (263%) in the topical lidocaine group, 3 (15.8%) in the intracuff group, and 3 (16%) in the intravenous group (P < .05). CONCLUSIONS: Intravenous lidocaine and intracuff lidocaine significantly reduce the incidence of coughing during emergence from anesthesia.
Subject(s)
Anesthesia Recovery Period , Anesthesia, General , Anesthetics, Local/administration & dosage , Antitussive Agents/administration & dosage , Cough/prevention & control , Intubation, Intratracheal/adverse effects , Lidocaine/therapeutic use , Postoperative Care/methods , Postoperative Complications/prevention & control , Administration, Topical , Adult , Anesthetics, Local/pharmacology , Antitussive Agents/pharmacology , Cough/epidemiology , Cough/etiology , Double-Blind Method , Female , Humans , Incidence , Injections, Intravenous , Laryngoscopy , Larynx/drug effects , Lidocaine/administration & dosage , Lidocaine/pharmacology , Male , Middle Aged , Postoperative Complications/epidemiology , Postoperative Complications/etiology , Vocal Cords/drug effectsABSTRACT
Frontal sinus obliteration is accomplished with many materials such as fat, bone, muscle and alloplasts. Fat obliteration is very common but not devoid of morbidity. An alternative method of treatment with PRP platelet rich plasma and human bank bone or autogenous cortical shavings is presented for obliteration and craniofacial repair. A patient with severe symptomatic fronto-orbital fibrous dysplasia underwent reconstruction with PRP. After an uneventful recovery there was complete remission of the symptoms and early bone formation; 18 months after surgery the patient remains asymptomatic and free from sequels. PRP associated to an allograft or to cortical bone shavings seems to be a safe and simple treatment with the advantage of the absence of donor site surgery and morbidity.
Subject(s)
Fibrous Dysplasia of Bone/surgery , Frontal Sinus/surgery , Paranasal Sinus Diseases/surgery , Platelet Transfusion , Aged , Blood Platelets/physiology , Bone Transplantation , Cartilage/transplantation , Female , Follow-Up Studies , Frontal Bone/surgery , Humans , Orbital Diseases/surgery , Plasma , Plastic Surgery Procedures , Temporal Bone/surgery , Wound Healing/physiologyABSTRACT
We obtain the exact low-energy spectrum of two mobile holes in a t-J model for an isolated layer in an iron-pnictide superconductor. The minimum d xz and d yz orbitals per iron atom are included, with no hybridization between the two. After tuning the Hund coupling to a putative quantum critical point (QCP) that separates a commensurate spin-density wave from a hidden-order antiferromagnet at half filling, we find an s-wave hole-pair groundstate and a d-wave hole-pair excited state. Near the QCP, both alternate in sign between hole Fermi surface pockets at the Brillouin zone center and emergent electron Fermi surface pockets at momenta that correspond to commensurate spin-density waves (cSDW). The dependence of the energy splitting with increasing Hund coupling yields evidence for a true QCP in the thermodynamic limit near the putative one, at which the s-wave and d-wave Cooper pairs are degenerate. A collective s-to-d-wave oscillation of the macroscopic superconductor that couples to orthorhombic shear strain is also identified. Its resonant frequency is predicted to collapse to zero at the QCP in the limit of low hole concentration. This implies degeneracy of Cooper pairs with s, d and [Formula: see text] symmetry in the corresponding quantum critical state. We argue that the critical state describes Cooper pairs in hole-doped iron superconductors at the Lifshitz transition, where electron bands first rise above the Fermi level. We thereby predict that the s-to-d-wave collective mode observed by Raman spectroscopy in Ba1-x K x Fe2As2 at optimal doping should also be observed at higher doping near the Lifshitz transition.
ABSTRACT
The activity of matrix-bound monomers of arginase (L-arginine amidinohydrolase, EC 3.5.3.1) was not changed by incubation with p-hydroxymercuribenzoate. When the chemically modified, matrix-bound monomers were incubated with soluble subunits in the presence of Mn2+, dimers were obtained. These dimers were hybrids between modified and native monomers. The results obtained are in accord with a D2-symmetry where two dimers meet to form the tetrameric enzyme. From kinetic studies it is concluded that the structure of the active sites of arginase is not affected by the chemical modification with p-hydroxymercuribenzoate.
Subject(s)
Arginase/metabolism , Enzymes, Immobilized/metabolism , Liver/enzymology , Binding Sites/drug effects , Humans , Hydroxymercuribenzoates/pharmacology , Kinetics , Macromolecular Substances , Manganese/pharmacologyABSTRACT
The kinetic properties of argininosuccinase (L-argininosuccinate arginine-lyase, EC 4.3.2.1.) were investigated. Negative cooperativity was observed in the response of the enzyme to the substrate argininosuccinate and GTP behaved as a positive allosteric effector. These effects were observed in 60 mM potassium phosphate but not in 50 mM Tris-HCl. Structural changes in the protein molecule are suggested to explain previous observations of Michaelis-Menten kinetics for this enzyme.
Subject(s)
Argininosuccinate Lyase/metabolism , Liver/enzymology , Lyases/metabolism , Allosteric Regulation/drug effects , Argininosuccinic Acid/metabolism , Guanosine Triphosphate/pharmacology , Humans , Kinetics , Protein ConformationABSTRACT
The reaction kinetics of human liver arginase (L-arginine amidinohydrolase, EC 3.5.3.1) in terms of arginine concentration is strikingly altered by varying the pH. Lowering the pH from the optimum (9.5) toward a more physiological value (7.5) there is a transition from hyperbolic to sigmoidal kinetics. The cooperative effects are observed in the presence and absence of the product ornithine. Dimers of arginase exhibit typical Michaelis-Menten kinetics even in the presence of ornithine. Dimer-dimer interactions are suggested to explain the kinetic properties of arginase at pH 7.5.