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1.
J Small Anim Pract ; 65(1): 47-55, 2024 01.
Artículo en Inglés | MEDLINE | ID: mdl-37800196

RESUMEN

OBJECTIVES: To describe the clinical presentation, treatment and outcomes of cats diagnosed with thymic epithelial tumours and to determine prognostic factors for survival and recurrence. MATERIALS AND METHODS: Clinical records of cats diagnosed with a thymic epithelial tumour between 1999 and 2021 at three referral institutions were retrospectively reviewed. RESULTS: Sixty-four cats were included. Paraneoplastic syndromes were present in nine cats and metastatic disease was seen in two cats, one at diagnosis and one at the time of recurrence. Median tumour diameter was 6 cm (range, 2 to 15) and a cystic appearance was described on imaging in 25 cats. Surgical excision was attempted in 54 cats with a perioperative mortality rate of 11%. Median survival time for cats surviving to hospital discharge was 897 days (range, 21 to 3322). The 1-, 2- and 5-year survival rates for surgically treated thymic epithelial tumour were 86%, 70% and 66%, respectively. Survival was longer for cats with Masaoka-Koga stage I and II tumours compared to stages III and IV (1366 days versus 454 days; P=0.002). Masaoka-Koga stage was the only significant prognostic factor detected on multi-variable analysis, with stage III and IV tumours associated with increased risk of death (hazard ratio: 5.67, 95% confidence interval: 1.29 to 24.91, P=.021). Tumour recurrence occurred in 11 cats at a median of 564 days (range, 93 to 1095); no significant prognostic factors for recurrence were identified. CLINICAL SIGNIFICANCE: Cats with thymic epithelial tumours had a good long-term prognosis following surgery. Tumour recurrence can occur late in the disease course and ongoing monitoring should therefore be considered. Masaoka-Koga stage may influence survival time and could be used to predict outcome.


Asunto(s)
Enfermedades de los Gatos , Neoplasias Glandulares y Epiteliales , Gatos , Animales , Pronóstico , Recurrencia Local de Neoplasia/veterinaria , Estudios Retrospectivos , Neoplasias Glandulares y Epiteliales/cirugía , Neoplasias Glandulares y Epiteliales/veterinaria , Estadificación de Neoplasias , Enfermedades de los Gatos/cirugía
2.
Resuscitation ; 195: 110087, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-38097108

RESUMEN

Standardized reporting of data is crucial for out-of-hospital cardiac arrest (OHCA) research. While the implementation of first responder systems dispatching volunteers to OHCA is encouraged, there is currently no uniform reporting standard for describing these systems. A steering committee established a literature search to identify experts in smartphone alerting systems. These international experts were invited to a conference held in Hinterzarten, Germany, with 40 researchers from 13 countries in attendance. Prior to the conference, participants submitted proposals for parameters to be included in the reporting standard. The conference comprised five workshops covering different aspects of smartphone alerting systems. Proposed parameters were discussed, clarified, and consensus was achieved using the Nominal Group Technique. Participants voted in a modified Delphi approach on including each category as a core or supplementary element in the reporting standard. Results were presented, and a writing group developed definitions for all categories and items, which were sent to participants for revision and final voting using LimeSurvey web-based software. The resulting reporting standard consists of 68 core items and 21 supplementary items grouped into five topics (first responder system, first responder network, technology/algorithm/strategies, reporting data, and automated external defibrillators (AED)). This proposed reporting standard generated by an expert opinion group fills the gap in describing first responder systems. Its adoption in future research will facilitate comparison of systems and research outcomes, enhancing the transfer of scientific findings to clinical practice.


Asunto(s)
Reanimación Cardiopulmonar , Socorristas , Paro Cardíaco Extrahospitalario , Humanos , Teléfono Inteligente , Reanimación Cardiopulmonar/métodos , Desfibriladores , Paro Cardíaco Extrahospitalario/terapia
4.
Tech Coloproctol ; 24(10): 1063-1070, 2020 10.
Artículo en Inglés | MEDLINE | ID: mdl-32594270

RESUMEN

BACKGROUND: Technical factors affect oncologic outcomes in rectal cancer surgery. The anatomy of the bony pelvis can affect technical aspects of surgery, but is seldom considered preoperatively. We performed a morphometric analysis of the bony pelvis in patients having rectal cancer resection to assess its effect on surgical specimen quality. METHODS: We performed a retrospective analysis of a prospectively maintained database of patients who had resection for rectal cancer from January 2014 to December 2017. Preoperative magnetic resonance imaging (MRI) and computed tomography (CT) images were accessed and measurements of sacrococcygeal distance, sacrococcygeal recess depth/area, sacrococcygeal angulation, anteroposterior pelvic inlet/outlet, pubic height and interspinous distance were made. Outcome measures included anatomical variation, operating time and mesorectal specimen grade. In patients having extra-levator abdominoperineal excision (eLAPE) with coccygectomy, the completeness of coccygeal resection was assessed by postoperative CT scan. Data were analysed using binomial and multinomial logistic regression and linear regression. RESULTS: One hundred and twenty-two consecutive rectal cancer resections were performed (39 open, 42 laparoscopic, 12 laparoscopic-converted and 29 robotic). The median age was 72 years (range: 29-88 years). The male:female ratio was 83:39. Eighty-one patients had anterior resection, 8 had low Hartmann's resection and 32 had APE. Of those who had APE, 21 had eLAPE (all with coccygectomy). Females had a larger pelvic inlet (female: 124.9 mm, male: 114.9 mm), interspinous diameter(female:112.8 mm, male:97.6 mm), sacrococcygeal depth (female:42.6 mm, 39.35 mm) and sacrococcygeal area recess than males (female: 3697 mm2, male: 3481.5 mm2). Males had a greater pubic height (female: 51.8 mm, male: 54.05 mm) and greater sacrococcygeal distance (female: 116.7 mm, male: 123.65 mm) than females. In patients having anterior resection, tumour distance from the anal verge (p = 0.004), sacrococcygeal distance (p = 0.006) and sacrococcygeal curvature (p = 0.002) were associated with specimen quality. In patients who had eLAPE, median preoperative coccygeal length was 41 mm (IQR: 35.1-45.5). The median length of coccygeal resection was 9 mm (IQR: 1-17.45 mm). The median length of coccyx remaining postoperatively was 33 mm (IQR: 21.35-39 mm). CONCLUSIONS: Sacrococcygeal curvature and distance as well as tumour distance from the anal margin were associated with specimen quality in anterior resection. Coccygectomy was not performed as completely as surgeons thought. Surgeons should include sacrococcygeal bony anatomy in rectal cancer surgical planning to potentially improve outcomes in both anterior resection and eLAPE approaches.


Asunto(s)
Laparoscopía , Proctectomía , Neoplasias del Recto , Anciano , Canal Anal , Femenino , Humanos , Masculino , Neoplasias del Recto/diagnóstico por imagen , Neoplasias del Recto/cirugía , Recto/diagnóstico por imagen , Recto/cirugía , Estudios Retrospectivos , Resultado del Tratamiento
5.
Water Sci Technol ; 75(5-6): 1169-1176, 2017 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-28272045

RESUMEN

Urban runoff is known to transport a significant pollutant load consisting of e.g. heavy metals, salts and hydrocarbons. Interactions between solid and dissolved compounds, proper understanding of particle size distribution, dissolved pollutant fractions and seasonal variations is crucial for the selection and development of appropriate road runoff treatment devices. Road runoff at an arterial road in Augsburg, Germany, has been studied for 3.5 years. A strong seasonal variation was observed, with increased heavy metal concentrations with doubled and tripled median concentrations for heavy metals during the cold season. Correlation analysis showed that de-icing salt is not the only factor responsible for increased pollutant concentrations in winter. During the cold period, the fraction of dissolved metals was lower compared to the warm season. In road dust, the highest metal concentrations were measured for fine particles. Metals in road runoff were found to show a significant correlation to fine particles SS63 (<63 µm). Therefore, it is debatable whether treatment devices only implementing sedimentation processes provide sufficient removal rates.


Asunto(s)
Tamaño de la Partícula , Material Particulado/análisis , Estaciones del Año , Transportes , Contaminantes Químicos del Agua/análisis , Cloruros/análisis , Conductividad Eléctrica , Alemania , Metales Pesados/análisis
6.
Dalton Trans ; 46(4): 1172-1178, 2017 Jan 24.
Artículo en Inglés | MEDLINE | ID: mdl-28054070

RESUMEN

The synthesis of molybdenum oxo-amidinate complexes MoO2(R2AMD)2 [AMD = N,N'-di-R-acetamidinate; R = Cy (2; cyclohexyl) and iPr (3)], and their characterization by 1H, 13C NMR, X-ray diffraction, and thermogravimetric analysis is reported. Quartz-crystal microbalance and X-ray photoelectron spectroscopic studies confirm that 3 is an improved ALD precursor versus the R = t-butyl derivative for MoO3 film growth. Complex 3 is accessible in higher yields (80%+), is easier to handle without mass loss, and in conjunction with O3 as the second ALD reagent, yields nitride-free MoO3 films.

7.
J Appl Microbiol ; 103(5): 1453-60, 2007 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-17953556

RESUMEN

AIM: To analyse the growth of Bacillus anthracis during simulations of the UK anthrax vaccine manufacturing process. METHODS AND RESULTS: Simulated vaccine production runs were performed using the toxigenic, acapsulate Sterne 34F(2) strain of B. anthracis in semi-defined medium. After rising during the logarithmic growth phase, the pH of the culture starts to fall at about 18 h from pH 8.7 to reach <7.6 at 26 h, coincident with consumption of glucose and optimal production of protective antigen (PA; 7.89 g ml(-1), SD 1.0) and lethal factor (LF; 1.85 g ml(-1), SD 0.29). No increased breakdown of toxin antigens was seen over the 26-32 h period. When glucose was exhausted, amino acids (principally serine) were utilized as an alternative carbon source. Sporulation was not observed during the 32 h. CONCLUSIONS: PA and LF, the principal constituents in the UK anthrax vaccine, undergo little degradation during vaccine fermentation. The vaccine manufacturing process is robust and reproducible. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first detailed analysis of the manufacturing process used for the UK acellular anthrax vaccine; insight gained into the process will support continued and safe vaccine manufacture.


Asunto(s)
Vacunas contra el Carbunco/biosíntesis , Bacillus anthracis/crecimiento & desarrollo , Reactores Biológicos , Antígenos Bacterianos/biosíntesis , Bacillus anthracis/inmunología , Toxinas Bacterianas/biosíntesis , Medios de Cultivo , Ensayo de Inmunoadsorción Enzimática , Fermentación , Concentración de Iones de Hidrógeno
8.
Antimicrob Agents Chemother ; 50(6): 2042-9, 2006 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-16723564

RESUMEN

The effects of a variety of oxazolidinones, with different antibacterial potencies, including linezolid, on mitochondrial protein synthesis were determined in intact mitochondria isolated from rat heart and liver and rabbit heart and bone marrow. The results demonstrate that a general feature of the oxazolidinone class of antibiotics is the inhibition of mammalian mitochondrial protein synthesis. Inhibition was similar in mitochondria from all tissues studied. Further, oxazolidinones that were very potent as antibiotics were uniformly potent in inhibiting mitochondrial protein synthesis. These results were compared to the inhibitory profiles of other antibiotics that function by inhibiting bacterial protein synthesis. Of these, chloramphenicol and tetracycline were significant inhibitors of mammalian mitochondrial protein synthesis while the macrolides, lincosamides, and aminoglycosides were not. Development of future antibiotics from the oxazolidinone class will have to evaluate potential mitochondrial toxicity.


Asunto(s)
Antibacterianos/farmacología , Mitocondrias Cardíacas/efectos de los fármacos , Mitocondrias Cardíacas/metabolismo , Mitocondrias Hepáticas/efectos de los fármacos , Mitocondrias Hepáticas/metabolismo , Oxazoles/farmacología , Inhibidores de la Síntesis de la Proteína , Animales , Células de la Médula Ósea/citología , Cloranfenicol/farmacología , Relación Dosis-Respuesta a Droga , Técnicas In Vitro , Pruebas de Sensibilidad Microbiana , Mitocondrias/efectos de los fármacos , Mitocondrias/metabolismo , Estructura Molecular , Conejos , Ratas , Relación Estructura-Actividad , Tetraciclina/farmacología
9.
JPEN J Parenter Enteral Nutr ; 29(4): 221-8, 2005.
Artículo en Inglés | MEDLINE | ID: mdl-15961676

RESUMEN

BACKGROUND: To determine the consequences of severe undernutrition and refeeding on whole-body metabolism and protein synthesis. METHODS: Respiratory quotient (RQ), resting energy expenditure (REE), and whole-body protein synthesis (WBPS) were assessed in undernourished patients, with anorexia nervosa (n = 8) or with coexistent disease (n = 17). Results were compared with 17 healthy controls. Six anorexic patients and 13 disease patients consented to study after nutrition support. RESULTS: Mean body mass index was 12.46 +/- 0.53 kg/m2 in the anorexia patients and 13.81 +/- 0.40 kg/m2 in the disease patients (controls 23.71 +/- 0.72 kg/m2; p < .001). Compared with controls, RQ was similar in anorexia patients (0.85 +/- 0.05 vs 0.90 +/- 0.05) but lower in the disease patients (0.76 +/- 0.03 vs 0.90 +/- 0.05; p = .02). REE was lower in the patients (anorexia 1058 +/- 134.0 kcal/d, disease 1189 +/- 101.4 kcal/d vs 1828 +/- 89.76 kcal/d; p < .001); however, expressed as kcal/kg/d, it was higher (anorexia 32.17 +/- 4.25, disease 31.30 +/- 2.14 vs 25.07 +/- 1.00; p < .05). WBPS was lower in the patients (anorexia 140.9 +/- 10.54 g/d, disease 119.8 +/- 8.57 g/d vs 305.0 +/- 21.64 g/d; p < .001); however, when expressed as g/kg/d, the anorexia patients were similar to controls, whereas the disease patients were lower (3.11 +/- 0.24 vs 4.27 +/- 0.32; p < .05). Refeeding increased RQ in the disease patients (0.84 +/- 0.03 vs 0.76 +/- 0.03; p < .05), and normalized REE (anorexia 27.65 +/- 3.05 kcal/kg/d, disease 28.90 +/- 1.85 kcal/kg/d). WBPS increased in the disease patients (173.6 +/- 16.38 g/d vs 116.5 +/- 10.15 g/d; p < .01). CONCLUSIONS: Undernutrition is associated with increased REE (kcal/kg/d). Reduction in RQ and protein synthesis (g/kg/d) was evident in those patients with coexistent disease. Refeeding resulted in normalization of RQ, REE (kcal/kg/d), and protein synthesis (g/kg/d).


Asunto(s)
Anorexia Nerviosa/metabolismo , Metabolismo Energético/fisiología , Desnutrición/metabolismo , Desnutrición/terapia , Apoyo Nutricional/métodos , Proteínas/metabolismo , Análisis de Varianza , Anorexia Nerviosa/complicaciones , Metabolismo Basal , Índice de Masa Corporal , Dióxido de Carbono/metabolismo , Estudios de Casos y Controles , Enfermedad Crónica , Humanos , Cinética , Desnutrición/etiología , Consumo de Oxígeno/efectos de los fármacos , Consumo de Oxígeno/fisiología , Biosíntesis de Proteínas , Índice de Severidad de la Enfermedad
10.
Inflamm Bowel Dis ; 10(5): 618-25, 2004 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-15472524

RESUMEN

INTRODUCTION: Impaired pancreatic function has been reported in Crohn's disease, the cause of which is uncertain. This study investigated the effect of malnutrition, and subsequent re-feeding, on digestive function and protein synthesis in Crohn's disease patients. METHODS: Gastric acid and pancreatic secretion studies were performed on malnourished Crohn's patients before, and after a period of intensive nutritional support. Whole body, as well as pancreatic enzyme protein synthesis was investigated by [14C]leucine isotope incorporation studies. Results were evaluated in comparison to normal healthy volunteers. RESULTS: The mean body mass index (BMI) of the Crohn's patients was 14.14 kg/m2. The Crohn's patients had reduction in the secretion of gastric acid (7.36 versus 25.53 mEq/h; P < 0.01), and the pancreatic enzymes, amylase (759.6 versus 2305 U/h; P < 0.01), lipase (33.01 versus 118.6 U/h; P < 0.01) and trypsin (97.43 versus 341.4 U/h; P < 0.01). Resting energy expenditure (REE), expressed in relation to body mass, was greater in the malnourished Crohn's disease patients (38.25 versus 25.36 kcal/kg/d; P = 0.01). Total body protein synthesis was reduced (2.82 versus 4.39 g protein/kg/d; P < 0.05), with significant impairment in the synthesis of pancreatic enzymes, and reduction of zymogen stores. Following re-feeding, the BMI of the Crohn's patients improved to 16.80 +/- 0.66 kg/m2. Pancreatic enzyme synthesis improved, with significant increase in pancreatic enzyme stores and secretion, to levels similar to control values. Gastric acid secretion also improved, although still lower than the control value. CONCLUSION: Malnutrition may play a significant role in the impairment of gastric acid and pancreatic secretion in Crohn's disease patients.


Asunto(s)
Amilasas/metabolismo , Enfermedad de Crohn/fisiopatología , Ácido Gástrico/metabolismo , Lipasa/metabolismo , Desnutrición/etiología , Tripsina/metabolismo , Adulto , Índice de Masa Corporal , Estudios de Casos y Controles , Enfermedad de Crohn/complicaciones , Metabolismo Energético , Femenino , Humanos , Masculino , Apoyo Nutricional , Páncreas/fisiología
11.
Dev Biol (Basel) ; 111: 321-6, 2002.
Artículo en Inglés | MEDLINE | ID: mdl-12678256

RESUMEN

The characterisation and evaluation of the UK licensed human anthrax vaccine depends on several in vivo tests that determine its safety and potency. Assays for the determination of functionally active and/or immunoreactive toxin components and S-layer proteins have been developed and applied to the characterisation of anthrax vaccine. These technologies may support production of consistent and effective vaccines, and may ultimately reduce the requirements for in vivo testing.


Asunto(s)
Vacunas contra el Carbunco , Antígenos Bacterianos/metabolismo , Toxinas Bacterianas/análisis , Adenilil Ciclasas/metabolismo , Animales , Antígenos Bacterianos/química , Antígenos Bacterianos/inmunología , Bacillus anthracis/química , Bacillus anthracis/inmunología , Bacillus anthracis/metabolismo , Toxinas Bacterianas/inmunología , Endopeptidasas/metabolismo , Ensayo de Inmunoadsorción Enzimática , Humanos , Técnicas In Vitro , MAP Quinasa Quinasa 1 , Macrófagos/inmunología , Macrófagos/metabolismo , Ratones , Quinasas de Proteína Quinasa Activadas por Mitógenos/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo
13.
Chem Rev ; 101(4): 953-96, 2001 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-11709862

RESUMEN

The goal of the "Opportunities for Catalysis Research in Carbon Management" workshop was to review within the context of greenhouse gas/carbon issues the current state of knowledge, barriers to further scientific and technological progress, and basic scientific research needs in the areas of H2 generation and utilization, light hydrocarbon activation and utilization, carbon dioxide activation, utilization, and sequestration, emerging techniques and research directions in relevant catalysis research, and in catalysis for more efficient transportation engines. Several overarching themes emerge from this review. First and foremost, there is a pressing need to better understand in detail the catalytic mechanisms involved in almost every process area mentioned above. This includes the structures, energetics, lifetimes, and reactivities of the species thought to be important in the key catalytic cycles. As much of this type of information as is possible to acquire would also greatly aid in better understanding perplexing, incomplete/inefficient catalytic cycles and in inventing new, efficient ones. The most productive way to attack such problems must include long-term, in-depth fundamental studies of both commercial and model processes, by conventional research techniques and, importantly, by applying various promising new physicochemical and computational approaches which would allow incisive, in situ elucidation of reaction pathways. There is also a consensus that more exploratory experiments, especially high-risk, unconventional catalytic and model studies, should be undertaken. Such an effort will likely require specialized equipment, instrumentation, and computational facilities. The most expeditious and cost-effective means to carry out this research would be by close coupling of academic, industrial, and national laboratory catalysis efforts worldwide. Completely new research approaches should be vigorously explored, ranging from novel compositions, fabrication techniques, reactors, and reaction conditions for heterogeneous catalysts, to novel ligands and ligation geometries (e.g., biomimetic), reaction media, and activation methods for homogeneous ones. The interplay between these two areas involving various hybrid and single-site supported catalyst systems should also be productive. Finally, new combinatorial and semicombinatorial means to rapidly create and screen catalyst systems are now available. As a complement to the approaches noted above, these techniques promise to greatly accelerate catalyst discovery, evaluation, and understanding. They should be incorporated in the vigorous international research effort needed in this field.

15.
Drug Metab Dispos ; 29(12): 1614-28, 2001 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-11717181

RESUMEN

Rofecoxib is a potent and highly selective cyclooxygenase-2 inhibitor used for the treatment of osteoarthritis and pain. Following administration of [4-(14)C]rofecoxib to intact rats, the plasma C(max) (at approximately 1 h) was followed by a secondary C(max) (at approximately 10 h), which was not observed in bile duct-cannulated rats. Following administration of [4-(14)C]5-hydroxyrofecoxib to intact or bile duct-cannulated rats, radiolabeled rofecoxib was detected in plasma, and once again a secondary C(max) for rofecoxib was observed (at approximately 10 h), which occurred only in the intact animals. These results indicate that reversible metabolism of rofecoxib to 5-hydroxyrofecoxib occurs in the rat and that the process is dependent upon an uninterrupted bile flow. Studies on the contents of the gastrointestinal tract of rats showed that conversion of 5-hydroxyrofecoxib to parent compound occurs largely in the lower intestine. Treatment of rats with [5-(18)O]5-hydroxyrofecoxib, followed by liquid chromatography-tandem mass spectrometry analyses of plasma samples, confirmed that 5-hydroxyrofecoxib undergoes metabolism to the parent drug, yielding [1-(18)O]rofecoxib, [2-(18)O]rofecoxib, and unlabeled rofecoxib. Similarly, treatment with [1,2-(18)O(2)]rofecoxib afforded the same three isotopic variants of rofecoxib. These findings are consistent with a metabolic sequence involving 5-hydroxylation of rofecoxib, biliary elimination of the corresponding glucuronide, and deconjugation of the glucuronide in the lower gastrointestinal tract. Reduction of the 5-hydroxyrofecoxib thus liberated yields a hydroxyacid that cyclizes spontaneously to regenerate rofecoxib, which is reabsorbed and enters the systemic circulation. This sequence represents a novel form of enterohepatic recycling and reflects the susceptibility of 5-hydroxyrofecoxib, as well as rofecoxib itself, to reversible 2-furanone ring opening under in vivo conditions.


Asunto(s)
Inhibidores de la Ciclooxigenasa/farmacocinética , Lactonas/metabolismo , Lactonas/farmacocinética , Animales , Bilis/metabolismo , Biotransformación , Radioisótopos de Carbono , Cromatografía Líquida de Alta Presión , Furanos/metabolismo , Absorción Intestinal , Marcaje Isotópico , Espectroscopía de Resonancia Magnética , Masculino , Isótopos de Oxígeno , Ratas , Ratas Sprague-Dawley , Sulfonas , Distribución Tisular
16.
J Am Chem Soc ; 123(42): 10221-38, 2001 Oct 24.
Artículo en Inglés | MEDLINE | ID: mdl-11603972

RESUMEN

Organolanthanide complexes of the general type Cp'(2)LnE(TMS)(2) (Cp' = eta(5)-Me(5)C(5); Ln = La, Sm, Y, Lu; E = CH, N; TMS = SiMe(3)) serve as effective precatalysts for the rapid intramolecular hydrophosphination/cyclization of the phosphinoalkenes and phosphinoalkynes RHP(CH(2))(n)()CH=CH(2) (R = Ph, H; n = 3, 4) and H(2)P(CH(2))(n)C triple bond C-Ph (n = 3, 4) to afford the corresponding heterocycles and respectively. Kinetic and mechanistic data for these processes exhibit parallels to, as well as distinct differences from, organolanthanide-mediated intramolecular hydroamination/cyclizations. The turnover-limiting step of the present catalytic cycle is insertion of the carbon-carbon unsaturation into the Ln-P bond, followed by rapid protonolysis of the resulting Ln-C linkage. The rate law is first-order in [catalyst] and zero-order in [substrate] over approximately one half-life, with inhibition by heterocyclic product intruding at higher conversions. The catalyst resting state is likely a lanthanocene phosphine-phosphido complex, and dimeric [Cp'(2)YP(H)Ph](2) was isolated and cystallographically characterized. Lanthanide identity and ancillary ligand structure effects on rate and selectivity vary with substrate unsaturation: larger metal ions and more open ligand systems lead to higher turnover frequencies for phosphinoalkynes, and intermediate-sized metal ions with Cp'(2) ligands lead to maximum turnover frequencies for phosphinoalkenes. Diastereoselectivity patterns also vary with substrate, lanthanide ion, and ancillary ligands. Similarities and differences in hydrophosphination vis-à-vis analogous organolanthanide-mediated hydroamination are enumerated.

17.
Org Lett ; 3(20): 3091-4, 2001 Oct 04.
Artículo en Inglés | MEDLINE | ID: mdl-11574002

RESUMEN

[reaction: see text] This contribution reports the organolanthanide-catalyzed intramolecular hydroamination/cyclization of amines tethered to 1,2-disubstituted alkenes to afford the corresponding mono- and disubstituted pyrrolidines and piperidines by using coordinatively unsaturated complexes of the type (eta(5)-Me(5)C(5))(2)LnCH(TMS)(2) (Ln = La, Sm), [Me(2)Si(eta(5)-Me(4)C(5))(2)]NdCH(TMS)(2), [Et(2)Si(eta(5)-Me(4)C(5))(eta(5)-C(5)H(4))]NdCH(TMS)(2), and [Me(2)Si(eta(5)-Me(4)C(5))((t)()BuN)]LnE(TMS)(2) (Ln = Sm, Y, Yb, Lu; E = N, CH) as precatalysts. [Me(2)Si(eta(5)-Me(4)C(5))((t)BuN)]LnE(TMS)(2) mediates intramolecular hydroamination/cyclization of sterically demanding amino-olefins to afford disubstituted pyrrolidines in high diastereoselectivity (trans/cis = 16/1) and in good to excellent yield.


Asunto(s)
Alquenos/química , Aminas/química , Elementos de la Serie de los Lantanoides/química , Piperidinas/síntesis química , Pirrolidinas/síntesis química , Conformación Molecular , Compuestos Organometálicos/química
18.
J Am Chem Soc ; 123(30): 7287-91, 2001 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-11472155

RESUMEN

We investigate here the relationship between molecular architecture and two-photon absorption (TPA) processes in a class of alkyl-substituted 4-quinopyran chromophores. We find that TPA cross sections diverge as the one-photon gap energy nears one-half of the two-photon gap. The molecular strategy proposed here to tune these two-excitation gaps for maximizing TPA cross sections is to twist the molecule about the bond connecting the chromophore donor and acceptor phenylene fragments. Extremely large TPA cross sections, determined by the absorption bandwidth, can then be realized (imaginary part of the third-order polarizability approximately 2.6 x 10(5) x 10(-36) esu) for fundamental photon energies near 1.0 eV, when the torsional angle approaches 104 degrees. The required torsional angle is achieved by introduction of sterically encumbered 2,2',2' ',2' " tertiary alkyl substituents.

19.
Proc Natl Acad Sci U S A ; 98(13): 7113-6, 2001 Jun 19.
Artículo en Inglés | MEDLINE | ID: mdl-11416196

RESUMEN

Materials with high electrical conductivity and optical transparency are needed for future flat panel display, solar energy, and other opto-electronic technologies. In(x)Cd(1-x)O films having a simple cubic microstructure have been grown on amorphous glass substrates by a straightforward chemical vapor deposition process. The x = 0.05 film conductivity of 17,000 S/cm, carrier mobility of 70 cm2/Vs, and visible region optical transparency window considerably exceed the corresponding parameters for commercial indium-tin oxide. Ab initio electronic structure calculations reveal small conduction electron effective masses, a dramatic shift of the CdO band gap with doping, and a conduction band hybridization gap caused by extensive Cd 5s + In 5s mixing.

20.
Nutrition ; 17(3): 230-5, 2001 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-11312065

RESUMEN

Severe undernutrition has been associated with reduced secretions of gastric acid and pancreatic enzymes. This may be the result of an impaired gut mucosal response to food and primary gastric parietal and pancreatic acinar cell secretory dysfunction as a consequence of the poor nutritional state. To investigate the relative contributions of these factors, severely undernourished patients underwent enteral-meal-stimulated (ES; n = 7) or intravenous hormone (pentagastrin and cholecystokinin-8)-stimulated (HS; n = 12) gastric acid and pancreatic enzyme secretion before and after a period of nutritional support. Results were evaluated in comparison with normal healthy control subjects (ES = 7, HS = 10). In the control subjects, enteral-meal and cholecystokinin-8 stimulation resulted in similar outputs of the pancreatic enzymes amylase (2213 versus 2305 U/h), lipase (84.93 versus 118.6 U/h), and trypsin (498.9 versus 341.4 U/h), whereas acid output was significantly lower in the ES group (10.90 versus 25.53 mEq/h; P < 0.01). Compared with controls, malnourished groups had significantly reduced secretions of amylase (ES = 870.1 U/h, HS = 686.5 U/h; P < 0.02), lipase (ES = 30.68 U/h, HS = 25.96 U/h; P < 0.02), and trypsin (ES = 175.6 U/h, HS = 109.3 U/h; P < 0.01). The response to enteral-meal or CCK-8 stimulation was comparable. Gastric acid was similarly reduced in the undernourished patients (ES = 4.39 mEq/h, HS = 5.04 mEq/h; P < 0.01). After refeeding, secretion of amylase (ES = 2351 U/h, HS = 2228 U/h) and lipase (ES = 58.83 U/h, HS = 84.91 U/h) improved to levels not significantly different from controls, whereas trypsin (ES = 226.4 U/h, HS = 213.1 U/h; P < 0.03) and acid secretion (ES = 3.52 mEq/h, HS = 11.85 mEq/h; P < 0.01) remained significantly impaired. Severe undernutrition was associated with primary gastric parietal and pancreatic acinar cell dysfunction, which, at least in the case of pancreatic enzymes, appeared to be the determining factor controlling secretion in these patients.


Asunto(s)
Ácido Gástrico/metabolismo , Trastornos Nutricionales/fisiopatología , Apoyo Nutricional , Páncreas/metabolismo , Adulto , Estudios de Casos y Controles , Nutrición Enteral , Humanos , Absorción Intestinal , Mucosa Intestinal/fisiopatología , Páncreas/enzimología , Pentagastrina/administración & dosificación , Sincalida/administración & dosificación
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