ABSTRACT
Children with relapsed/refractory (R/R) neuroblastoma (NB) and medulloblastoma (MB) have poor outcomes. We evaluated the efficacy of nifurtimox (Nfx) in a clinical trial for children with R/R NB and MB. Subjects were divided into three strata: first relapse NB, multiply R/R NB, and R/R MB. All patients received Nfx (30 mg/kg/day divided TID daily), Topotecan (0.75 mg/m2 /dose, days 1-5) and Cyclophosphamide (250 mg/m2 /dose, days 1-5) every 3 weeks. Response was assessed after every two courses using International Neuroblastoma Response Criteria and Response Evaluation Criteria in Solid Tumors (RECIST) criteria. One hundred and twelve eligible patients were enrolled with 110 evaluable for safety and 76 evaluable for response. In stratum 1, there was a 53.9% response rate (CR + PR), and a 69.3% total benefit rate (CR + PR + SD), with an average time on therapy of 165.2 days. In stratum 2, there was a 16.3% response rate, and a 72.1% total benefit rate, and an average time on study of 158.4 days. In stratum 3, there was a 20% response rate and a 65% total benefit rate, an average time on therapy of 105.0 days. The most common side effects included bone marrow suppression and reversible neurologic complications. The combination of Nfx, topotecan and cyclophosphamide was tolerated, and the objective response rate plus SD of 69.8% in these heavily pretreated populations suggests that this combination is an effective option for patients with R/R NB and MB. Although few objective responses were observed, the high percentage of stabilization of disease and prolonged response rate in patients with multiply relapsed disease shows this combination therapy warrants further testing.
Subject(s)
Cerebellar Neoplasms , Medulloblastoma , Neuroblastoma , Child , Humans , Topotecan/adverse effects , Nifurtimox/therapeutic use , Medulloblastoma/drug therapy , Neoplasm Recurrence, Local/pathology , Neuroblastoma/drug therapy , Neuroblastoma/etiology , Cyclophosphamide , Antineoplastic Combined Chemotherapy Protocols/adverse effectsABSTRACT
The use of cross-sectional imaging in the pediatric population continues to rise, particularly the use of MRI. Limiting motion artifact requires cooperative subjects who do not move during imaging, so there has been an increase in the need for pediatric sedation or anesthesia. Over the last decade, concern has increased that exposure to anesthesia might be associated with long-term cognitive deficits. In this review we report current understanding of the effects of anesthesia on the pediatric population, with special focus on long-term developmental and cognitive outcomes, and suggest how radiologists can use new technologies or imaging strategies to mitigate or minimize these potential risks.
Subject(s)
Anesthesia/adverse effects , Anesthetics/adverse effects , Diagnostic Imaging , Neurotoxicity Syndromes/etiology , Child , Humans , Magnetic Resonance ImagingABSTRACT
BACKGROUND: The primary aim of this Phase I study was to determine the maximum tolerated dose (MTD) of TPI 287 and the safety and tolerability of TPI 287 alone and in combination with temozolomide (TMZ) in pediatric patients with refractory or recurrent neuroblastoma or medulloblastoma. The secondary aims were to evaluate the pharmacokinetics of TPI 287 and the treatment responses. PROCEDURE: Eighteen patients were enrolled to a phase I dose escalation trial of weekly intravenous infusion of TPI 287 for two 28-day cycles with toxicity monitoring to determine the MTD, followed by two cycles of TPI 287 in combination with TMZ. Samples were collected to determine the pharmacokinetic parameters C(max), AUC(0-24), t(1/2), CL, and Vd on day 1 of cycles 1 (TPI 287 alone) and 3 (TPI 287 + TMZ) following TPI 287 infusion. Treatment response was evaluated by radiographic (CT or MRI) and radionuclide (MIBG) imaging for neuroblastoma. RESULTS: We determined the MTD of TPI 287 alone and in combination with temozolomide to be 125 mg/m(2). The non-dose-limiting toxicities at this dose were mainly anorexia and pain. The dose-limiting toxicities (DLTs) of two patients at 135 mg/m(2) were grade 3 hemorrhagic cystitis and grade 3 sensory neuropathy. CONCLUSIONS: Overall, TPI 287 was well tolerated by pediatric patients with refractory and relapsed neuroblastoma and medulloblastoma at a dose of 125 mg/m(2) IV on days 1, 8, and 15 of a 28 day cycle.
Subject(s)
Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Dacarbazine/analogs & derivatives , Medulloblastoma/drug therapy , Neuroblastoma/drug therapy , Taxoids/administration & dosage , Taxoids/therapeutic use , Adolescent , Adult , Child , Child, Preschool , Dacarbazine/administration & dosage , Dacarbazine/pharmacokinetics , Dacarbazine/toxicity , Female , Humans , Infusions, Intravenous , Male , Maximum Tolerated Dose , Neoplasm Recurrence, Local , Taxoids/pharmacokinetics , Taxoids/toxicity , TemozolomideABSTRACT
PURPOSE: To analyze the foveal avascular zone (FAZ) in normal eyes using optical coherence tomography angiography. METHODS: Prospective noncomparative case series. The parafoveal region of 70 eyes from 67 healthy subjects was imaged using optical coherence tomography angiography to visualize the superficial and deep capillary plexuses and correlated with standard macular volume scans using spectral domain optical coherence tomography to determine foveal morphology. RESULTS: In all 70 eyes imaged, 2 vascular plexuses could be detected within the retina: a superficial plexus within the ganglion cell layer and a deep plexus within the inner nuclear layer. A measurable FAZ was visualized in both plexuses in all imaged eyes. The FAZ area was variable in the study population with a mean of 0.266 mm² ± 0.097 mm² in the superficial plexus (range: 0.071 mm²-0.527 mm²) and a mean of 0.495 mm² ± 0.227 mm² in the deep plexus (range: 0.160 mm²-0.795 mm²). The FAZ area was significantly larger in the deep plexus (P < 0.0001) compared with superficial plexus. The FAZ area in both plexuses correlated inversely with central macular thickness and central macular volume (P < 0.0001). No significant correlation was found between superficial plexus FAZ area and age (P = 0.55) or sex (P = 0.34). In the same manner, no significant correlation was found between deep plexus FAZ area and age (P = 0.13) or sex (P = 0.13). CONCLUSION: Optical coherence tomography angiography provides a noninvasive method to visualize and measure the superficial and deep plexus FAZ in a normal population. The FAZ can vary in size and shape, with the FAZ area significantly larger in the deep compared with the superficial plexus. Both superficial and deep FAZ area correlate inversely with foveal thickness and volume.
Subject(s)
Fluorescein Angiography , Fovea Centralis/anatomy & histology , Fovea Centralis/blood supply , Retinal Vessels/anatomy & histology , Tomography, Optical Coherence , Adolescent , Adult , Aged , Child , Female , Healthy Volunteers , Humans , Male , Middle Aged , Prospective StudiesABSTRACT
Like most organizations, The Children's Hospital of Philadelphia (CHOP) generates a lot of data of varying types, from clinical to staffing and operations. However, these datasets are separated, preventing effective analytics. To improve workforce management and care delivery, CHOP's Nursing department collaborated with the Data & Analytics team to create a dashboard-based platform for analyzing workforce metrics and patient outcomes, aiding nursing leaders in decision-making. This project involved multiple phases with contributions from Nursing, Data & Analytics, CHOP's Data Trust Office, and Human Resources. Key performance indicators were identified, and a variety of data sources were aggregated to provide a comprehensive view of the nursing enterprise. The resulting platform offers automated, current, and reliable analytics on various aspects, including nursing demographics, education, survey results, staffing actuals by job group, and patient and family experience data. The platform's usability was assessed using a modified Health Information Technology Usability Evaluation Scale survey, with a 29% response rate primarily from senior directors and managers. The findings showed high usability and satisfaction, indicating the dashboard is a valuable decision-support tool. Lessons learned include the need for analytics education for nurses and mid-managers, the inclusion of critical nursing-specific metrics (and development of the data pipelines making them possible), and the integration of multidisciplinary team metrics for comprehensive nursing analytics.
Subject(s)
Leadership , Philadelphia , Humans , Decision Support Systems, Clinical , Hospitals, PediatricABSTRACT
OBJECTIVES: 1) To develop and validate laser speckle flowmetry (LSF) as a quantitative tool for individual microvessel hemodynamics in large networks. 2) To use LSF to determine if structural differences in the dorsal skinfold microcirculation (DSFWC) of C57BL/6 and BALB/c mice impart differential network hemodynamic responses to occlusion. METHODS: We compared LSF velocity measurements with known/measured velocities in vitro using capillary tube tissue phantoms and in vivo using mouse DSFWCs and cremaster muscles. Hemodynamic changes induced by feed arteriole occlusion were measured using LSF in DSFWCs implanted on C57BL/6 and BALB/c mice. RESULTS: In vitro, we found that the normalized speckle intensity (NSI) versus velocity linear relationship (R(2) ≥ 0.97) did not vary with diameter or hematocrit and can be shifted to meet an expected operating range. In vivo, DSFWC and cremaster muscle preparations (R(2) = 0.92 and 0.95, respectively) demonstrated similar linear relationships between NSI and centerline velocity. Stratification of arterioles into predicted collateral pathways revealed significant differences between C57BL/6 and BALB/c strains in response to feed arteriole occlusion. CONCLUSIONS: These data demonstrate the applicability of LSF to intravital microscopy microcirculation preparations for determining both relative and absolute hemodynamics on a network-wide scale while maintaining the resolution of individual microvessels.
Subject(s)
Laser-Doppler Flowmetry/methods , Microcirculation/physiology , Muscle, Skeletal/blood supply , Animals , Arterioles/physiology , Blood Flow Velocity/physiology , Male , Mice , Mice, Inbred BALB CABSTRACT
OBJECTIVE: The purpose of this study is to evaluate the feasibility of ultrafast 3-T MRI in the evaluation of children with acute lower abdominal pain for the detection of appendicitis. SUBJECTS AND METHODS: Forty-two pediatric patients (30 girls and 12 boys; mean age, 11.5 years; age range, 4-17 years) with acute abdominal pain were prospectively studied. Ultrafast 3-T MRI was performed with a three-plane single-shot turbo spin-echo sequence and an axial T2-weighted turbo spin-echo sequence with fat suppression. All scans were performed without sedation or oral or IV contrast agent. Scan times were less than 8 minutes 45 seconds (median, 5 minutes 40 seconds). Patients underwent CT or ultrasound or both as a comparison study to the MRI examination. The MRI, CT, and ultrasound examinations were interpreted independently by four board-certified radiologists who were blinded to patient information, study interpretations, surgical pathologic findings, and final diagnosis. RESULTS: Twelve of 42 cases of acute appendicitis were detected with 100% sensitivity, 99% specificity, 100% negative predictive value, and 98% positive predictive value, all of which were statistically significant (p < 0.01). The pooled and individual receiver operating characteristic curves for radiologists' interpretation of the diagnosis of acute appendicitis were greater than 0.95 in all cases (p < 0.01) CONCLUSION: Ultrafast 3-T MRI is a feasible alternative imaging modality for the diagnosis of acute appendicitis in children, particularly in cases where ultrasound is equivocal or nondiagnostic, as an alternative to CT. Ultrafast MRI requires no sedation and no oral or IV contrast agent and has no associated radiation exposure risks.
Subject(s)
Abdominal Pain/diagnosis , Appendicitis/diagnosis , Magnetic Resonance Imaging/methods , Adolescent , Child , Child, Preschool , Diagnosis, Differential , Feasibility Studies , Female , Humans , Male , Predictive Value of Tests , Prospective Studies , Sensitivity and Specificity , Tomography, X-Ray Computed/methods , Ultrasonography/methodsABSTRACT
The primary aim of this phase 1 study was to determine the maximum tolerated dose (MTD) and evaluate the safety of nifurtimox alone and in combination with cyclophosphamide and topotecan in multiple relapsed/refractory neuroblastoma pediatric patients. The secondary aim was to evaluate the pharmacokinetics of nifurtimox and the treatment response. To these ends, we performed a phase 1 dose escalation trial of daily oral nifurtimox with toxicity monitoring to determine the MTD, followed by 3 cycles of nifurtimox in combination with cyclophosphamide and topotecan. Samples were collected to determine the pharmacokinetic parameters maximum concentration, time at which maximum concentration is reached, and area under the curve between 0 and 8 hours. Treatment response was evaluated by radiographic and radionuclide (I-metaiodobenzylguanidine) imaging, measurement of urinary catecholamines, and clearance of bone marrow disease. We determined the MTD of nifurtimox to be 30 mg/kg/d. The non-dose-limiting toxicities were mainly nausea and neuropathy. The dose-limiting toxicities of 2 patients at 40 mg/kg/d were a grade 3 pulmonary hemorrhage and a grade 3 neuropathy (reversible). Overall, nifurtimox was well tolerated by pediatric patients at a dose of 30 mg/kg/d, and tumor responses were seen both as a single agent and in combination with chemotherapy. A Phase 2 study to determine the antitumor efficacy of nifurtimox is currently underway.
Subject(s)
Antineoplastic Combined Chemotherapy Protocols/adverse effects , Neuroblastoma/drug therapy , Nifurtimox/adverse effects , Adolescent , Antineoplastic Combined Chemotherapy Protocols/pharmacokinetics , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Child , Child, Preschool , Cyclophosphamide/adverse effects , Cyclophosphamide/pharmacokinetics , Cyclophosphamide/therapeutic use , Female , Humans , Male , Maximum Tolerated Dose , Neuroblastoma/prevention & control , Nifurtimox/pharmacokinetics , Nifurtimox/therapeutic use , Recurrence , Topotecan/adverse effects , Topotecan/pharmacokinetics , Topotecan/therapeutic use , Treatment OutcomeABSTRACT
The delta phalanx is an unusual condition occurring in the hand or the foot that can be distinguished from a secondary ossification center on radiographic evaluation based on the well-defined phalangeal epiphyses typically evident by 24-30 months of age. MR imaging of the delta phalanx offers the advantage of visualizing sites of unossified bone before the age these findings are typically visible with radiography. We describe the case of a 15-month-old boy who presented with soft-tissue fusion of the third and fourth digits of the right hand. Radiograph and MR evaluation revealed soft-tissue intra-axial syndactyly of the third and fourth digits and a delta phalanx involving the proximal phalanx of the involved fourth digit.
Subject(s)
Finger Phalanges/pathology , Magnetic Resonance Spectroscopy , Syndactyly/diagnosis , Humans , Infant , MaleABSTRACT
BACKGROUND: Exposure to air pollution is associated with cardiovascular disease, including increased morbidity and mortality rates. OBJECTIVE: The aim of this investigation was to assess the effect, in rats, of intratracheal instillation of particulate air pollution on biomarkers of leucocyte activation and vascular endothelial damage. METHODS: Air pollution particles (PM10) were instilled into rats, and blood samples were taken three days and six weeks post instillation. Plasma neutrophil elastase and Von Willebrand factor were measured by ELISA. RESULTS: Plasma neutrophil elastase increased from 175±44âng/ml at baseline to 288±26âng/ml 3 days post instillation (pâ=â0.038). vWF increased from 0.160±0.015 IU/ml at baseline to 0.224±0.015 IU/ml at 3 days post and 0.208±0.01 IU/ml at 6 weeks post (pâ=â0.006, ANOVA). sICAM-1 increased from 17.75±0.70âng/ml at baseline to 19.03±0.33âng/ml at 3 days post and 21.72±1.16âng/ml at 6 weeks post (pâ=â0.009, ANOVA). CONCLUSION: Instillation caused prolonged systemic inflammation, activation of blood leucocytes and damage to the vascular endothelium.
Subject(s)
Air Pollution/analysis , Endothelium, Vascular/physiopathology , Inflammation/etiology , Nanoparticles/metabolism , Animals , Cardiovascular Diseases , Male , Rats , Rats, Sprague-DawleyABSTRACT
There are several mimickers of choroidal melanoma. We report a patient with recent family stress who developed blurred vision to 20/50 OD and was found to have unilateral central serous chorioretinopathy and a coincidental choroidal nevus. After 1 year without resolution of the subretinal fluid, the patient was referred for our opinion. On examination, visual acuity was 20/50 in the right eye and 20/20 in the left eye. The left eye was normal. Evaluation of the right eye showed a small, pigmented submacular choroidal lesion measuring 4 mm × 3 mm. Ultrasonography documented an isoechoic mass measuring 1.71 mm in thickness. Optical coherence tomography showed subretinal fluid with shaggy photoreceptors and hyper-reflective material within the subretinal fluid, likely indicative of lipofuscin within macrophages. Autofluorescence revealed orange pigment overlying the lesion. These features were strongly suggestive of small choroidal melanoma with five risk factors for tumor growth. Treatment with Iodine-125 plaque brachytherapy was performed on the patient. The readers should keep in mind that choroidal melanoma can manifest as a tiny choroidal mass with related multimodal imaging features of subretinal fluid and orange pigment.
ABSTRACT
Hypertension, decreased glucose tolerance, adverse lipid profiles and low physical activity levels are associated with increased type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD) risk. High intensity interval training (HIIT), a low volume, reduced time, high intensity programme, may be a useful alternative to current government guidelines which specify a minimum of 150 minutes of physical activity per week. We describe a personalised programme of high intensity exercise which provides significant improvements in CVD risk markers. Healthy volunteers undertook 6 weeks of HIIT. T2DM and CVD risk predictors including glucose tolerance, VO2max, blood pressure (BP), and lipids were measured before and after HIIT. HIIT training was associated with beneficial changes in a range of predictors of blood flow and cardiovascular risk. There was a heterogeneous response to HIIT, with some subjects responding with favourable changes and others being non-responders to HIIT. In responders, HIIT was associated with a statistically significant (pâ=â0.023) increase in VO2max, from 45.4 (38.4,52.5) to 56.9 (51.2,65.7) (median (interquartile range)(ml/min/kg)). In responders HIIT resulted in a decrease in systolic BP from 127 (126,129) to 116 (106,122) (mmHg) with pâ=â0.026 and a decrease is diastolic blood pressure from 72 (69,74) to 57 (56,66) with pâ=â0.026. There was also some evidence of a beneficial change in blood lipid and glucose concentrations with HIIT. In conclusion, personalised HIIT has potential as an intervention to improve blood flow and cardiovascular health.
Subject(s)
Cardiovascular Diseases/epidemiology , Diabetes Mellitus, Type 2/epidemiology , Exercise Therapy/methods , Cardiovascular Diseases/therapy , Diabetes Mellitus, Type 2/therapy , Healthy Volunteers , Humans , Risk Factors , Treatment OutcomeABSTRACT
BACKGROUND: Neuroblastoma (NB) is the most common cancer in infancy and most frequent cause of death from extracranial solid tumors in children. Ornithine decarboxylase (ODC) expression is an independent indicator of poor prognosis in NB patients. This study investigated safety, response, pharmacokinetics, genetic and metabolic factors associated with ODC in a clinical trial of the ODC inhibitor difluoromethylornithine (DFMO) ± etoposide for patients with relapsed or refractory NB. METHODS AND FINDINGS: Twenty-one patients participated in a phase I study of daily oral DFMO alone for three weeks, followed by additional three-week cycles of DFMO plus daily oral etoposide. No dose limiting toxicities (DLTs) were identified in patients taking doses of DFMO between 500-1500 mg/m2 orally twice a day. DFMO pharmacokinetics, single nucleotide polymorphisms (SNPs) in the ODC gene and urinary levels of substrates for the tissue polyamine exporter were measured. Urinary polyamine levels varied among patients at baseline. Patients with the minor T-allele at rs2302616 of the ODC gene had higher baseline levels (p=0.02) of, and larger decreases in, total urinary polyamines during the first cycle of DFMO therapy (p=0.003) and had median progression free survival (PFS) that was over three times longer, compared to patients with the major G allele at this locus although this last result was not statistically significant (p=0.07). Six of 18 evaluable patients were progression free during the trial period with three patients continuing progression free at 663, 1559 and 1573 days after initiating treatment. Median progression-free survival was less among patients having increased urinary polyamines, especially diacetylspermine, although this result was not statistically significant (p=0.056). CONCLUSIONS: DFMO doses of 500-1500 mg/m2/day are safe and well tolerated in children with relapsed NB. Children with the minor T allele at rs2302616 of the ODC gene with relapsed or refractory NB had higher levels of urinary polyamine markers and responded better to therapy containing DFMO, compared to those with the major G allele at this locus. These findings suggest that this patient subset may display dependence on polyamines and be uniquely susceptible to therapies targeting this pathway. TRIAL REGISTRATION: Clinicaltrials.gov NCT#01059071.
Subject(s)
Eflornithine/pharmacology , Neuroblastoma/drug therapy , Ornithine Decarboxylase Inhibitors/pharmacology , Phenotype , Polyamines/metabolism , Adolescent , Child , Child, Preschool , Eflornithine/adverse effects , Eflornithine/pharmacokinetics , Eflornithine/therapeutic use , Etoposide/adverse effects , Etoposide/pharmacology , Etoposide/therapeutic use , Female , Humans , Infant , Male , Neuroblastoma/enzymology , Neuroblastoma/genetics , Neuroblastoma/urine , Ornithine Decarboxylase/metabolism , Ornithine Decarboxylase Inhibitors/adverse effects , Ornithine Decarboxylase Inhibitors/pharmacokinetics , Ornithine Decarboxylase Inhibitors/therapeutic use , Polyamines/urine , Recurrence , Safety , Treatment OutcomeABSTRACT
BACKGROUND: Exposure to particulate air pollution is associated with an increased risk of cardiovascular disease. The mechanism by which exposure increases risk is poorly understood but could involve changes in the flow properties of blood. OBJECTIVE: The aim of this investigation was to assess the effect, in rats, of intratracheal instillation of particulate air pollution on leukocyte flow properties by measurement of polymorphonucleocyte (PMN) and monocyte actin polymerisation. METHODS: Rats were exposed to particulate air pollution by intratracheal instillation of PM10. Blood was collected from test and control animals at 3 days (n=10) and 6 weeks (n=10) after dust instillation. Partial differential leukocyte counts were performed. The intracellular F-actin content of blood PMNs and monocytes was determined by staining with FITC-phalloidin and flow cytometric determination of mean florescence intensity (MFI). RESULTS: There were no significant changes in PMN MFI (p=0.369, ANOVA) or cell counts (p=0.753, ANOVA). There was a significant increase in monocyte MFI (p=0.004, ANOVA) and a decrease in monocyte cell count (p=0.003, ANOVA) in instilled rats. CONCLUSIONS: Intratracheal instillation of air pollution particles resulted in an increase in blood monocyte actin polymerisation, which may cause trapping of monocytes. This could be a mechanism by which exposure to air pollution increases the risk of cardiovascular disease.
Subject(s)
Actins/metabolism , Monocytes/cytology , Particulate Matter/chemistry , Trachea/pathology , Animals , Cardiovascular System/drug effects , Cytoskeleton/metabolism , Flow Cytometry , Hemorheology/physiology , Inflammation , Leukocytes/cytology , Male , Monocytes/drug effects , Neutrophils/cytology , Particle Size , Polymerization , Rats , Rats, Sprague-Dawley , Trachea/drug effectsABSTRACT
The rapid development of the offshore renewable energy sector has led to an increased requirement for Marine Spatial Planning (MSP) and, increasingly, this is carried out in the context of the 'ecosystem approach' (EA) to management. We demonstrate a novel method to facilitate implementation of the EA. Using a real-time interactive mapping device (touch-table) and stakeholder workshops we gathered data and facilitated negotiation of spatial trade-offs at a potential site for tidal renewable energy off the Mull of Kintyre (Scotland). Conflicts between the interests of tidal energy developers and commercial and recreational users of the area were identified, and use preferences and concerns of stakeholders were highlighted. Social, cultural and spatial issues associated with conversion of common pool to private resource were also revealed. The method identified important gaps in existing spatial data and helped to fill these through interactive user inputs. The workshops developed a degree of consensus between conflicting users on the best areas for potential development suggesting that this approach should be adopted during MSP.
Subject(s)
Ecosystem , Renewable Energy , Seawater , Water Movements , Congresses as Topic , Decision Support Techniques , Geography , ScotlandABSTRACT
We previously reported the presence of both haloalcohol and haloalkanoate dehalogenase activity in the Agrobacterium sp. strain NHG3. The versatile nature of the organism led us to further characterise the genetic basis of these dehalogenation activities. Cloning and sequencing of the haloalcohol dehalogenase and subsequent analysis suggested that it was part of a highly conserved catabolic gene cluster. Characterisation of the haloalkanoate dehalogenase enzyme revealed the presence of two stereospecific enzymes with a narrow substrate range which acted on D-2-chloropropionic and L-2-chloropropionoic acid, respectively. Cloning and sequencing indicated that the two genes were separated by 87 bp of non-coding DNA and were preceded by a putative transporter gene 66 bp upstream of the D-specific enzyme.
Subject(s)
Hydrolases/genetics , Hydrolases/metabolism , Rhizobium/enzymology , Rhizobium/genetics , Cloning, Molecular , DNA, Bacterial/genetics , Genes, Bacterial , Hydrocarbons, Chlorinated , Hydrolases/chemistry , Kinetics , Molecular Sequence Data , Molecular Weight , Propionates/chemistry , Propionates/metabolism , Rhizobium/growth & development , Stereoisomerism , Substrate SpecificityABSTRACT
Cellobiohydrolase IB is the first native enzyme from the filamentous fungus Talaromyces emersonii to be crystallized. It is a highly thermostable exo-acting enzyme. The native enzyme (MW = 56 kDa) was crystallized using the hanging-drop vapour-diffusion method with ammonium phosphate (dibasic) as a precipitant at pH 8.5. The crystal belongs to the tetragonal space group P4(1)2(1)2, with unit-cell parameters a = b = 74.43, c = 176.92 A, and diffracted to 1.77 A resolution at room temperature.
Subject(s)
Cellulose 1,4-beta-Cellobiosidase/chemistry , Talaromyces/chemistry , Binding Sites , Catalytic Domain , Crystallization/methods , Crystallography, X-Ray , Fungal Proteins/chemistry , Molecular Sequence Data , PhosphatesABSTRACT
A novel methylotroph, strain M2, capable of utilizing methanesulfonic acid (MSA) as a sole source of carbon and energy was the subject of these investigations. The initial step in the biodegradative pathway of MSA in strain M2 involved an inducible NADH-specific monooxygenase enzyme (MSAMO). Partial purification of MSAMO from cell-free extracts by ion-exchange chromatography led to the loss of MSAMO activity. Activity was restored by the mixing of three distinct protein fractions designated A, B and C. The reconstituted enzyme had a narrow substrate specificity relative to crude cell-free extracts. Addition of FAD and ferrous ions to the reconstituted enzyme complex resulted in a fivefold increase in enzyme activity, suggesting the loss of FAD and ferrous ion from the multicomponent enzyme on purification. Analysis of mutants of strain M2 defective in the metabolism of C1 compounds indicated that methanol was not an intermediate in the degradative pathway of MSA and also confirmed the involvement of a multicomponent enzyme in the degradation of MSA by methylotroph strain M2.