23 results on '"Schulte MD"'
Search Results
2. Second-line therapy with nivolumab plus ipilimumab for older patients with oesophageal squamous cell cancer (RAMONA): a multicentre, open-label phase 2 trial
- Author
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Matthias P Ebert, ProfMD, Nadja M Meindl-Beinker, PhD, Tobias Gutting, MD, Martin Maenz, PhD, Johannes Betge, MD, Nadine Schulte, MD, Tianzuo Zhan, MD, Philip Weidner, MD, Elke Burgermeister, PhD, Ralf Hofheinz, ProfMD, Arndt Vogel, ProfMD, Stefan Angermeier, MD, Claus Bolling, MD, Maike de Wit, ProfMD, Ralf Jakobs, ProfMD, Meinolf Karthaus, ProfMD, Gertraud Stocker, MD, Peter Thuss-Patience, MD, Tobias Leidig, PhD, Timo Gaiser, ProfMD, Jakob N Kather, ProfMD, and Nicolai Haertel, MD
- Subjects
Geriatrics ,RC952-954.6 ,Medicine - Abstract
Summary: Background: The overall survival of patients with advanced and refractory oesophageal squamous cell carcinoma, mostly aged 65 years and older, is poor. Treatment with PD-1 antibodies showed improved progression-free survival and overall survival. We assessed the safety and efficacy of combined nivolumab and ipilimumab therapy in this population. Methods: This multicentre, open-label, phase 2 trial done in 32 sites in Germany included patients aged 65 years and older with oesophageal squamous cell carcinoma and disease progression or recurrence following first-line therapy. Patients were treated with nivolumab (240 mg fixed dose once every 2 weeks, intravenously) in the safety run-in phase and continued with nivolumab and ipilimumab (nivolumab 240 mg fixed dose once every 2 weeks and ipilimumab 1 mg/kg once every 6 weeks, intravenously). The primary endpoint was overall survival, which was compared with a historical cohort receiving standard chemotherapy in the intention-to-treat population. This study is registered with ClinicalTrials.gov, NCT03416244. Findings: Between March 2, 2018, and Aug 20, 2020, we screened 75 patients with advanced oesophageal squamous cell carcinoma. We enrolled 66 patients (50 [76%] men and 16 [24%] women; median age 70·5 years [IQR 67·0–76·0]), 44 (67%) of whom received combined nivolumab and ipilimumab therapy and 22 (33%) received nivolumab alone. Median overall survival time at the prespecified data cutoff was 7·2 months (95% CI 5·7–12·4) and significantly higher than in a historical cohort receiving standard chemotherapy (p=0·0063). The most common treatment-related adverse events were fatigue (12 [29%] of 42), nausea (11 [26%]), and diarrhoea (ten [24%]). Grade 3–5 treatment-related adverse events occurred in 13 (20%) of 66 patients. Treatment-related death occurred in one patient with bronchiolitis obliterans while on nivolumab and ipilimumab treatment. Interpretation: Patients aged at least 65 years, with advanced oesophageal squamous cell carcinoma might benefit from combined nivolumab and ipilimumab therapy in second-line treatment. Funding: Bristol Myers Squibb.
- Published
- 2022
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3. Elective shoulder surgery during the coronavirus disease 2019 pandemic in Germany: the patients' perspective
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Benjamin Bockmann, MD, Arne Johannes Venjakob, MD, Malte Holschen, MD, Wolfgang Nebelung, MD, and Tobias Ludger Schulte, MD
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COVID-19 ,Elective procedures ,Shoulder arthroscopy ,Digitalization ,Local healthcare restrictions ,Hospital types ,Orthopedic surgery ,RD701-811 ,Diseases of the musculoskeletal system ,RC925-935 - Abstract
Background: The coronavirus disease 2019 (COVID-19) pandemic has impeded the treatment of elective shoulder patients all over the world. Owing to the constraints in personnel and operation theater capacities, many patients who should undergo planned surgeries could not receive medical care. In our study, we examined the status quo of elective shoulder arthroscopy during the pandemic in Germany. Methods: Using a nonprofit database, 40 shoulder units that performed the most arthroscopic rotator cuff repairs in Germany in 2018 were identified. Following a standardized protocol, the web pages of these units were screened, and their strategy for elective procedures during the COVID-19 pandemic was analyzed. Special emphasis was put on the use of new digital technologies. Results: At the time of the study, no unit had stopped scheduling appointments for elective shoulder patients because of the pandemic. Almost all units (97.5%) offered explicit information about COVID-19 and their strategies toward it. The possibilities of visiting patients in shoulder units varied owing to local restrictions. Two units (5%) offered digital consultations. Conclusion: At the time of the study, elective shoulder procedures could be planned and carried out at the largest centers in Germany. Local restrictions had a great influence on the organization of the procedure and hospital stay during the COVID-19 pandemic. Digital consultations were not available in every unit.
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- 2021
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4. Massive Chylous Ascites After Living Donor Nephrectomy Successfully Treated With Lymphatic Embolization
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Anthony Hiffa MD, Kelly Schulte MD, Muhammad Saeed MD, and Imran Gani MD
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Medicine (General) ,R5-920 ,Pathology ,RB1-214 - Abstract
Chylous ascites may result from a variety of pathological conditions, most of them from nontraumatic causes, such as congenital defects of the lymphatic system, infections, liver cirrhosis, and malignancy. Rarely, chylous ascites occurs as an iatrogenic complication after left-sided laparoscopic donor nephrectomy (LDN). Injury to the cisterna chyli and its main lymphatic tributaries around the para-aortic region intraoperatively can cause the lymphatic fluid to accumulate. There is currently no standardized treatment for chylous ascites as there have only been 54 cases documented to date. Most patients can be managed with conservative therapy. Recommended guidelines include high-protein and low-fat diet with medium-chain triglycerides. Paracentesis is often used as a diagnostic and therapeutic first-line measure with total parenteral nutrition (TPN), bowel rest, and somatostatin analogue as adjunct therapies. We present a case of massive chylous ascites refractory to conservative therapy. The patient had progressive abdominal distention and unintentional weight gain 2 weeks postoperatively warranting multiple paracenteses of >7 L of chylous fluid. Ultimately, the patient was successfully treated with lymphatic embolization using N-butyl cyanoacrylate glue.
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- 2022
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5. Severe recalcitrant otic lichen planus treated with mycophenolate mofetil
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Lisa N. Guo, BS, Jennifer J. Shin, MD, SM, Stephanie Schulte, MD, and Joseph F. Merola, MD, MMSc
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lichen planus ,mycophenolate mofetil ,otitis externa ,otitis media ,Dermatology ,RL1-803 - Published
- 2021
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6. Caring for Your Adopted Child : An Essential Guide for Parents
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Elaine E. Schulte, MD, MPH, FAAP, Robin Michaelson, Elaine E. Schulte, MD, MPH, FAAP, and Robin Michaelson
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- Adopted children, Adoption, Adoptive parents, Parenting
- Abstract
With knowledge and compassion, Caring for Your Adopted Child offers the wisdom that adoptive parents need to provide the best possible care for their children. Whether a child joins a family through domestic adoption, international adoption, or foster care, he or she may have needs that require additional consideration. The coauthors, both adoptive parents, weave professional and personal experiences with essential information on: • Partnering with a pediatrician before adoption • Helping a child transition into a family • Understanding health issues and conditions that are more prevalent in children who are adopted • Supporting a child's emotional health and attachment • And promoting positive adoption conversation as a child matures This comprehensive resource offers trusted parenting advice from a leading adoption medicine expert and the American Academy of Pediatrics, focusing on the physical and emotional well-being of adopted children.
- Published
- 2019
7. Neoadjuvant Chemotherapy in High-Grade Myxoid Liposarcomas: Looking Forward to What Is Next.
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Schulte B, Mach N, and Olivier T
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- Humans, Chemotherapy, Adjuvant, Neoplasm Grading, Antineoplastic Combined Chemotherapy Protocols therapeutic use, Neoadjuvant Therapy, Liposarcoma, Myxoid pathology, Liposarcoma, Myxoid drug therapy
- Published
- 2024
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8. Early postmortem beef muscle proteome and metabolome variations due to supranutritional zinc and ractopamine hydrochloride supplementation.
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Schulte MD, Hochmuth KG, Steadham EM, Lonergan SM, Hansen SL, and Huff-Lonergan E
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- Animals, Cattle, Male, Diet veterinary, Red Meat analysis, Meat analysis, Phenethylamines pharmacology, Proteome drug effects, Proteome metabolism, Muscle, Skeletal metabolism, Muscle, Skeletal drug effects, Dietary Supplements, Animal Feed analysis, Metabolome drug effects, Zinc metabolism
- Abstract
It was hypothesized that the longissimus thoracis (LT) muscle proteome, phosphoproteome, and metabolome could explain postmortem metabolism and tenderness differences in muscle from cattle supplemented zinc (Zn) and/or ractopamine hydrochloride (RH). High percentage Angus steers (N = 20) were fed in a 2 × 2 factorial assigned to Zn and RH treatments: control (CON; n = 10; analyzed 36 mg Zn/kg dry matter [DM]) or supranutritional Zn supplementation (SUPZN; n = 10; control diet + 60 mg Zn/kg DM [from ZnSO4] + 60 mg Zn/kg DM [from Zn-amino acid complex]) for the entire 89-d trial. During the 28 d before harvest, steers were blocked by body weight within Zn treatments to RH treatments of 0 (NO; n = 10) or 300 mg (RAC; n = 10) per steer per day. Steers were harvested at the Iowa State Meat Laboratory, where pH decline (1, 3, 6, and 24 h postmortem) was measured. At 24 h postmortem, LT muscle sections were removed from carcasses, and steaks were analyzed for Warner-Bratzler shear force (WBSF) values at 1, 3, 7, and 14 d postmortem. Muscle samples were taken at 1 h, 1, 3, 7, and 14 d postmortem for the following analysis: troponin-T degradation (1, 3, 7, and 14 d postmortem), myosin heavy chain analysis (1 h postmortem), sarcoplasmic proteome analysis through tandem mass tagging analysis (1 h and 1 d postmortem), metabolome analysis (1 h and 1 d postmortem), and phosphoproteome analysis (1 h postmortem). SUPZN-NO tended to have a lower (P = 0.06) pH at 6 h postmortem and a lower WBSF value (P = 0.06) at 1 d postmortem. CON-RAC had a higher (P = 0.04) pH at 6 h postmortem and WBSF value (P < 0.01) at 1 d postmortem. A lower pH at 6 h postmortem and lower WBSF value at 1 d postmortem in the SUPZN-NO treatment was accompanied by more sorbitol and fructose at 1 d postmortem, and less myosin regulatory light chain 2 at 1 h postmortem, and less adenosine monophosphate deaminase 1 (AMPD1) at 1 d postmortem than all other treatments. A higher pH at 6 h postmortem and higher WBSF value at 1 d postmortem in CON-RAC and SUPZN-RAC was accompanied by more soluble structural proteins (troponin-T and myosin-7) at 1 h postmortem than CON-NO. At 1 h postmortem, CON-RAC had more glyceraldehyde-3-phosphate dehydrogenase than CON-NO or SUPZN-RAC. Differences in energy metabolism enzymes, metabolites, and structural proteins may affect ATP production, rigor development, and lactate buildup which may explain the differences in postmortem metabolism and tenderness development at 1 d postmortem., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science.)
- Published
- 2024
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9. Matrix metalloproteinase- 9 may contribute to collagen structure modification during postmortem aging of beef.
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Koulicoff LA, Heilman T, Vitanza L, Welter A, Jeneske H, O'Quinn TG, Hansen S, Huff-Lonergan E, Schulte MD, and Chao MD
- Subjects
- Cattle, Animals, Muscles, Aging, Dietary Supplements, Matrix Metalloproteinase 9, Collagen
- Abstract
Matrix metalloproteinases (MMPs) are responsible for the turnover of intramuscular connective tissue in live animals. We hypothesize that MMPs may play a role in postmortem aging of beef muscles for the degradation of connective tissues. Four different experiments were performed to: 1) characterize MMP activity during postmortem aging of beef; 2) determine if the native beef MMP can contribute to connective tissue degradation in a simulated standard industry postmortem aging condition; 3) explore approaches to improve the native beef MMP activity and 4) characterize MMP activity in beef from cattle supplemented with supranutritional level of Zn. In experiment 1, MMP was active throughout the entire aging periods (3, 21, 42 and 63 d) for beef muscles Longissimus lumborum, Gluteus medius and Gastrocnemius, and the unknown MMP responsible for the collagen degradation was identified as MMP-9 by Western Blot. In experiment 2 and 3, MMP-9 activity was noticeable in the gels after 42 d of storage in the cooler. Moreover, the addition of ZnCl
2 in the model system significantly increased MMP-9 activity when compared to the control (P < 0.01). In experiment 4, Longissimus thoracis from animals supplemented with a supranutritional Zn level had increased Zn availability and MMP-9 activity than those from animals fed with a control diet (P < 0.05). Further research is needed better understand MMP-9 mechanism during postmortem aging of meat. With a better understanding of MMP-9 in the aging process, the beef industry can provide better connective tissue management strategies for lower-quality beef cuts., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest associated with this research., (Copyright © 2023 Elsevier Ltd. All rights reserved.)- Published
- 2023
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10. Early postmortem muscle proteome and metabolome of beef longissimus thoracis muscle classified by pH at 6 hours postmortem.
- Author
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Schulte MD, Hochmuth KG, Steadham EM, Lonergan SM, Hansen SL, and Huff-Lonergan EJ
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- Animals, Cattle, Desmin metabolism, Postmortem Changes, Proteome metabolism, Muscle, Skeletal metabolism, Proteomics, Muscles metabolism, Paraspinal Muscles, Metabolome, Hydrogen-Ion Concentration, Meat analysis, Calpain
- Abstract
The objective was to identify metabolome and proteome differences at 1 h and 1 d postmortem between longissimus thoracis (LT) muscle classified based on 6 h pH values. Twenty beef LT rib sections were sorted based on 6 h postmortem pH values into low (LpH; pH < 5.55; n = 9) and high (HpH; pH > 5.84; n = 8) pH classifications. Warner-Bratzler shear force (WBSF), desmin degradation, and calpain-1 autolysis were measured. Two-dimensional difference in gel electrophoresis (3-10, 4-7, and 6-9 pH range) and Tandem mass tagging (TMT) protein analyses were employed to determine how the sarcoplasmic protein profile varied across pH classification. Non-targeted metabolomic analyses were conducted on extracts prepared at 1 h and 1 d postmortem. The LpH classification had a lower WBSF value at 1 d postmortem, which was explained by greater calpain-1 autolysis and desmin degradation at 1 d postmortem. Proteome and metabolome analysis revealed a phenotype that promotes more rapid energy metabolism in the LpH group. Proteome and metabolome analyses identified energy production, apoptotic, calcium homeostasis, and proteasome systems influencing pH classifications that could explain the observed pH, proteolysis, and beef tenderness differences. SIGNIFICANCE: This study is the first to identify proteomic and metabolomic variations early (1 h and 1 day) postmortem that are linked to differences in early (6 h) postmortem pH values and to tenderness differences at 1 day postmortem. This study integrates postmortem biochemical features (protein degradation, proteome, and metabolome variations) to postmortem pH decline and eating quality of beef steaks. Potential biomarkers of more rapid postmortem metabolism linked to earlier tenderization in beef are suggested. Identification of these biochemical features will assist in predicting the eating quality of beef products., (Copyright © 2022 Elsevier B.V. All rights reserved.)
- Published
- 2023
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11. Setting the geological scene for the origin of life and continuing open questions about its emergence.
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Westall F, Brack A, Fairén AG, and Schulte MD
- Abstract
The origin of life is one of the most fundamental questions of humanity. It has been and is still being addressed by a wide range of researchers from different fields, with different approaches and ideas as to how it came about. What is still incomplete is constrained information about the environment and the conditions reigning on the Hadean Earth, particularly on the inorganic ingredients available, and the stability and longevity of the various environments suggested as locations for the emergence of life, as well as on the kinetics and rates of the prebiotic steps leading to life. This contribution reviews our current understanding of the geological scene in which life originated on Earth, zooming in specifically on details regarding the environments and timescales available for prebiotic reactions, with the aim of providing experimenters with more specific constraints. Having set the scene, we evoke the still open questions about the origin of life: did life start organically or in mineralogical form? If organically, what was the origin of the organic constituents of life? What came first, metabolism or replication? What was the time-scale for the emergence of life? We conclude that the way forward for prebiotic chemistry is an approach merging geology and chemistry, i.e., far-from-equilibrium, wet-dry cycling (either subaerial exposure or dehydration through chelation to mineral surfaces) of organic reactions occurring repeatedly and iteratively at mineral surfaces under hydrothermal-like conditions., Competing Interests: Conflict of interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
- Published
- 2023
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12. Characterizing membrane phospholipid hydrolysis of pork loins throughout three aging periods.
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Chao MD, Donaldson EA, Wu W, Welter AA, O'Quinn TG, Hsu WW, Schulte MD, and Lonergan SM
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- Animals, Hydrolysis, Membranes chemistry, Spectrometry, Mass, Electrospray Ionization, Sus scrofa, Food Handling methods, Phospholipids chemistry, Pork Meat analysis
- Abstract
Three chops from 20 pork carcasses were aged for 1, 8, and 21 days. Electrospray ionization-tandem mass spectrometry was used to comprehensively analyze profiles of phospholipids from each sample (n = 60). Total phospholipid quantity decreased 4-folds (P < .01) from 1 to 21 days of aging in pork loins. Phosphatidylinositol (PI) and phosphatidylserine (PS) increased by 30% and 73%, respectively, from 1 to 21 days of aging in pork loins (P < .01). This increase was mainly due to relative percentage increase from PI 38:4 (18:0-20:4) and PS 36:2 (18:0-18:2; P < .01). The results also showed that the relative percentage of lysophosphatidylcholine increased by 35% after short term aging (8d), and phosphatidic acid increased by 10-folds after extended aging (21d; P < .01). These results documented that phospholipids undergo enzymatic hydrolysis during aging, but also indicated that lipid species containing 18:2 or 20:4 within PI and PS were slightly more resistant to enzymatic hydrolysis compared with the other phospholipids., Competing Interests: Declaration of Competing Interest None., (Copyright © 2020 Elsevier Ltd. All rights reserved.)
- Published
- 2020
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13. The Ladder of Life Detection.
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Neveu M, Hays LE, Voytek MA, New MH, and Schulte MD
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- Fossils, Mars, Models, Theoretical, Exobiology, Origin of Life
- Abstract
We describe the history and features of the Ladder of Life Detection, a tool intended to guide the design of investigations to detect microbial life within the practical constraints of robotic space missions. To build the Ladder, we have drawn from lessons learned from previous attempts at detecting life and derived criteria for a measurement (or suite of measurements) to constitute convincing evidence for indigenous life. We summarize features of life as we know it, how specific they are to life, and how they can be measured, and sort these features in a general sense based on their likelihood of indicating life. Because indigenous life is the hypothesis of last resort in interpreting life-detection measurements, we propose a small but expandable set of decision rules determining whether the abiotic hypothesis is disproved. In light of these rules, we evaluate past and upcoming attempts at life detection. The Ladder of Life Detection is not intended to endorse specific biosignatures or instruments for life-detection measurements, and is by no means a definitive, final product. It is intended as a starting point to stimulate discussion, debate, and further research on the characteristics of life, what constitutes a biosignature, and the means to measure them.
- Published
- 2018
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14. The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments.
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Goesmann F, Brinckerhoff WB, Raulin F, Goetz W, Danell RM, Getty SA, Siljeström S, Mißbach H, Steininger H, Arevalo RD Jr, Buch A, Freissinet C, Grubisic A, Meierhenrich UJ, Pinnick VT, Stalport F, Szopa C, Vago JL, Lindner R, Schulte MD, Brucato JR, Glavin DP, Grand N, Li X, and van Amerom FHW
- Abstract
The Mars Organic Molecule Analyzer (MOMA) instrument onboard the ESA/Roscosmos ExoMars rover (to launch in July, 2020) will analyze volatile and refractory organic compounds in martian surface and subsurface sediments. In this study, we describe the design, current status of development, and analytical capabilities of the instrument. Data acquired on preliminary MOMA flight-like hardware and experimental setups are also presented, illustrating their contribution to the overall science return of the mission. Key Words: Mars-Mass spectrometry-Life detection-Planetary instrumentation. Astrobiology 17, 655-685., Competing Interests: No competing financial interests exist.
- Published
- 2017
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15. Psychological interventions for adults with bipolar disorder: systematic review and meta-analysis.
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Oud M, Mayo-Wilson E, Braidwood R, Schulte P, Jones SH, Morriss R, Kupka R, Cuijpers P, and Kendall T
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- Counseling, Family psychology, Humans, Randomized Controlled Trials as Topic, Recurrence, Treatment Outcome, Bipolar Disorder therapy, Cognitive Behavioral Therapy methods, Depression therapy, Family Therapy methods, Mental Health standards
- Abstract
Background: Psychological interventions may be beneficial in bipolar disorder., Aims: To evaluate the efficacy of psychological interventions for adults with bipolar disorder., Method: A systematic review of randomised controlled trials was conducted. Outcomes were meta-analysed using RevMan and confidence assessed using the GRADE method., Results: We included 55 trials with 6010 participants. Moderate-quality evidence associated individual psychological interventions with reduced relapses at post-treatment (risk ratio (RR) = 0.66, 95% CI 0.48-0.92) and follow-up (RR = 0.74, 95% CI 0.63-0.87), and collaborative care with a reduction in hospital admissions (RR = 0.68, 95% CI 0.49-0.94). Low-quality evidence associated group interventions with fewer depression relapses at post-treatment and follow-up, and family psychoeducation with reduced symptoms of depression and mania., Conclusions: There is evidence that psychological interventions are effective for people with bipolar disorder. Much of the evidence was of low or very low quality thereby limiting our conclusions. Further research should identify the most effective (and cost-effective) interventions for each phase of this disorder., (© The Royal College of Psychiatrists 2016.)
- Published
- 2016
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16. Organic sulfur metabolisms in hydrothermal environments.
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Rogers KL and Schulte MD
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- Energy Metabolism, Pacific Ocean, Thermodynamics, Hydrothermal Vents microbiology, Organic Chemicals metabolism, Seawater microbiology, Sulfur Compounds metabolism
- Abstract
Sulfur is central to the metabolisms of many organisms that inhabit extreme environments. While biotic and abiotic cycling of organic sulfur compounds has been well documented in low-temperature anaerobic environments, cycling of organic sulfur in hydrothermal environments has received less attention. Recently published thermodynamic data have been used to estimate aqueous alkyl thiol and sulfide activities in deep-sea hydrothermal systems. Here we use geochemical mixing models to predict fluid compositions that result from mixing end-member hydrothermal fluid from the East Pacific Rise with bottom seawater. These fluid compositions are combined with estimates of methanethiol and dimethylsulfide activities to evaluate energy yields for potential organic sulfur-based metabolisms under hydrothermal conditions. Aerobic respiration has the highest energy yields (over -240 kJ/mol e⁻) at lower temperature; however, oxygen is unlikely to persist at high temperatures, restricting aerobic respiration to mesophilic communities. Nitrite reduction to N₂ has the highest energy yields at higher temperatures (greater than ∼40 °C). Nitrate and nitrite reduction to ammonium also yield significant energy (up to -70 kJ/mol e⁻). Much lower, but still feasible energy yields are calculated for sulfate reduction, disproportionation, and reduction with H₂. Organic compound family and the activity of methanethiol and dimethylsulfide were less important than metabolic strategy in determining overall energy yields. All metabolic strategies considered were exergonic within some portion of the mixing regime suggesting that organic sulfur-based metabolisms may be prevalent within deep-sea hydrothermal vent microbial communities., (© 2012 Blackwell Publishing Ltd.)
- Published
- 2012
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17. Volumes of aqueous alcohols, ethers, and ketones to T = 523 K and p = 28 MPa.
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Schulte MD, Shock EL, Obsil M, and Majer V
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- 2-Propanol chemistry, Acetone chemistry, Atmospheric Pressure, Benzyl Alcohol chemistry, Cyclohexanols chemistry, Ether chemistry, Ethyl Ethers chemistry, Glycols chemistry, Hexanones chemistry, Pentanes, Temperature, Alcohols chemistry, Ethers chemistry, Ketones chemistry, Solutions chemistry, Thermodynamics
- Abstract
Densities of dilute aqueous solutions of isopropanol, 1,5-pentanediol, cyclohexanol, benzyl alcohol, diethyl ether, 1,2-dimethoxyethane, acetone, and 2,5-hexanedione were measured by means of a vibrating-tube flow densimeter at temperatures near T = (302, 373, 423, 473, and 521) K at a pressure of p = 28 MPa. At the lowest and highest temperatures, measurements were also made close to the saturation vapour pressure of water to investigate the effect of pressure on the volumes of solutes. Apparent molar volumes were calculated for each solute and extrapolated to give partial molar volumes at infinite dilution. The variation of the volume with temperature, pressure, and structure of solute is discussed qualitatively, and group contributions are determined at the temperatures of measurements and p = 28 MPa. Several equations proposed in the literature for correlating the partial molar volumes at infinite dilution as a function of state parameters are tested. Parameters of one selected equation are tabulated allowing calculation of the partial molar volumes at infinite dilution at temperatures and pressures up to T = 573 K and p = 40 MPa. respectively.
- Published
- 1999
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18. Geochemical constraints on chemolithoautotrophic reactions in hydrothermal systems.
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Shock EL, McCollom T, and Schulte MD
- Subjects
- Archaea, Hydrogen chemistry, Hydrogen-Ion Concentration, Minerals chemistry, Origin of Life, Oxidation-Reduction, Water Microbiology, Evolution, Chemical, Hot Temperature, Hydrogen Sulfide chemistry, Seawater chemistry, Sulfur chemistry, Thermodynamics
- Abstract
Thermodynamic calculations provide the means to quantify the chemical disequilibrium inherent in the mixing of reduced hydrothermal fluids with seawater. The chemical energy available for metabolic processes in these environments can be evaluated by taking into account the pressure and temperature dependence of the apparent standard Gibbs free energies of reactions in the S-H2-H2O system together with geochemical constraints on pH, activities of aqueous sulfur species and fugacities of H2 and/or O2. Using present-day mixing of hydrothermal fluids and seawater as a starting point, it is shown that each mole of H2S entering seawater from hydrothermal fluids represents about 200,000 calories of chemical energy for metabolic systems able to catalyze H2S oxidation. Extrapolating to the early Earth, which was likely to have had an atmosphere more reduced than at present, shows that this chemical energy may have been a factor of two or so less. Nevertheless, mixing of hydrothermal fluids with seawater would have been an abundant source of chemical energy, and an inevitable consequence of the presence of an ocean on an initially hot Earth. The amount of energy available was more than enough for organic synthesis from CO2 or CO, and/or polymer formation, indicating that the vicinity of hydrothermal systems at the sea floor was an ideal location for the emergence of the first chemolithoautotrophic metabolic systems.
- Published
- 1995
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19. Reply to the comment by S.L. Miller and J.L. Bada on "Summary and implications of reported amino acid concentrations in the Murchison meteorite"
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Shock EL and Schulte MD
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- Glycine analysis, Glycine chemistry, Hot Temperature, Hydrolysis, Selection Bias, Solubility, Water, Amino Acids analysis, Amino Acids chemistry, Chemistry Techniques, Analytical methods, Exobiology methods, Meteoroids
- Published
- 1993
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20. Aldehydes in hydrothermal solution: standard partial molal thermodynamic properties and relative stabilities at high temperatures and pressures.
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Schulte MD and Shock EL
- Subjects
- Aldehydes analysis, Atmospheric Pressure, Carboxylic Acids chemistry, Earth, Planet, Evolution, Chemical, Evolution, Planetary, Geologic Sediments analysis, Geologic Sediments chemistry, Hydrocarbons chemistry, Mexico, Seawater chemistry, Aldehydes chemistry, Computer Simulation, Hot Temperature, Models, Chemical, Thermodynamics
- Abstract
Aldehydes are common in a variety of geologic environments and are derived from a number of sources, both natural and anthropogenic. Experimental data for aqueous aldehydes were taken from the literature and used, along with parameters for the revised Helgeson-Kirkham-Flowers (HKF) equations of state, to estimate standard partial molal thermodynamic data for aqueous straight-chain alkyl aldehydes at high temperatures and pressures. Examples of calculations involving aldehydes in geological environments are given, and the stability of aldehydes relative to carboxylic acids is evaluated. These calculations indicate that aldehydes may be intermediates in the formation of carboxylic acids from hydrocarbons in sedimentary basin brines and hydrothermal systems like they are in the atmosphere. The data and parameters summarized here allow evaluation of the role of aldehydes in the formation of prebiotic precursors, such as amino acids and hydroxy acids on the early Earth and in carbonaceous chondrite parent bodies.
- Published
- 1993
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21. Extraterrestrial synthesis: reply.
- Author
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Shock EL and Schulte MD
- Subjects
- Cocaine chemical synthesis, Glycine chemistry, Water, Amino Acids chemical synthesis, Meteoroids, Thermodynamics
- Published
- 1991
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22. Summary and implications of reported amino acid concentrations in the Murchison meteorite
- Author
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Shock EL and Schulte MD
- Subjects
- Chemistry Techniques, Analytical statistics & numerical data, Exobiology statistics & numerical data, Glycine analysis, Glycine chemistry, Hot Temperature, Hydrolysis, Reproducibility of Results, Selection Bias, Solubility, Water, Amino Acids analysis, Amino Acids chemistry, Chemistry Techniques, Analytical methods, Exobiology methods, Meteoroids
- Abstract
A study of literature reports of the concentrations of amino acids in extracts from the Murchison meteorite shows that many of the concentration ratios are constant. There are two possible interpretations of these ratios. One is that they are controlled by the pathways through which the amino acids formed, from which it follows that the amino acids are distributed in the same proportions throughout the meteorite. The other interpretation is that the ratios result from the analytical procedures used to extract the amino acids from the meteorite. These methods rely heavily on high-temperature (100 degrees C) aqueous extraction and subsequent high-temperature acid hydrolysis. A correlation was observed in the present study between the relative concentrations of several amino acids in the meteorite extracts and their relative aqueous solubilities at 100 degrees C (alanine, valine, leucine, isoleucine, norleucine, aspartic acid, glutamic acid and glycine). The extract solutions are dilute, and far from the saturation limits, but these correlations suggest that the sampling procedure affects directly the reported concentrations for these amino acids. Ratios of the concentration of serine to those of glycine are also constant but cannot be accounted for solely by relative solubilities, and, as suggested elsewhere, serine as well as phenylalanine and methionine may be terrestrial contaminants. Data for beta-alanine, alpha-aminobutyric acid, proline, sarcosine, alloisoleucine, beta-aminoisobutyric acid, beta-aminobutyric acid, and threonine also show constant abundances relative to glycine, but lack of solubility data at extraction conditions prohibits evaluating the extent of possible sampling bias for these amino acids. If the extraction process does not bias the results, and all extractable amino acids are removed from meteorite samples, then the properties of amino acids which control both their solubilities and their concentrations in the meteorite need to be established. The possibility of sampling bias needs to be tested experimentally before concluding that extraction is complete, and that the constant relative abundances indicate that the relative concentrations of amino acids are homogeneous in the meteorite.
- Published
- 1990
- Full Text
- View/download PDF
23. Amino-acid synthesis in carbonaceous meteorites by aqueous alteration of polycyclic aromatic hydrocarbons
- Author
-
Shock EL and Schulte MD
- Subjects
- Ammonia chemistry, Carbon Dioxide chemistry, Oxygen chemistry, Oxygen Isotopes, Thermodynamics, Amino Acids chemical synthesis, Extraterrestrial Environment, Fluorenes chemistry, Meteoroids, Polycyclic Aromatic Hydrocarbons chemistry, Pyrenes chemistry
- Abstract
It has been suggested that amino acids and other organic compounds found in carbonaceous meteorites formed by aqueous alteration in the meteorite parent bodies. Observations of carbonaceous material in interstellar grains and interplanetary dust particles indicate that condensed organic compounds may have been present in meteorite parent bodies at the time of aqueous alteration. One group of compounds thought to be representative of this carbonaceous material is the polycyclic aromatic hydrocarbons (PAHs). Recently it was proposed that PAHs condense on SiC grains in the molecular envelopes of carbon-rich red-giant stars, which would allow for their subsequent incorporation into meteorite parent bodies during accretion. This incorporation mechanism is supported by the identification of SiC grains in carbonaceous chondrites. The possibility therefore exists that PAHs, and/or other condensed organic compounds, represent the starting material for aqueous alteration which leads to the formation of amino acids and other water-soluble organic compounds. Here we present calculations of the distribution of aqueous organic compounds in metastable equilibrium with representative PAHs as functions of the fugacities of O2, CO2 and NH3. The results reported here for pyrene and fluoranthene, two PAHs with different structures but the same stoichiometry, differ greatly but indicate that the formation of amino and carboxylic acids is energetically favourable at probable parent-body alteration conditions. The actual reaction mechanisms involved could be revealed by consideration of isotope data for PAHs, amino acids, other organic compounds and carbonates in carbonaceous chondrites.
- Published
- 1990
- Full Text
- View/download PDF
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