Efficacy of self-management program associated with a spa therapy for knee osteoarthritis patients (GETT 2): a research protocol for a randomized trial

INTRODUCTION

Osteoarthritis is a chronic pathology that involves multidisciplinary management. Self-management for patients is an essential element, present in all international guidelines. During the time of the spa therapy, the patient is receptive to take the advantage of self-management workshops. The aim of this study is to assess the effects of 18 days spa therapy associated with a self-management intervention in patients with knee osteoarthritis in comparison with spa therapy alone on a priority objective, personalized and determined with the patient, chosen in the list of 5 objectives determined during the self-management initial assessment.

METHODS AND ANALYSIS

Two hundred fifty participants with knee osteoarthritis will participate to this multicenter, prospective, randomized, controlled study. All patients will benefit 18 days of spa therapy and patients randomized in the intervention group will participate to 6 self-management workshops. Randomization will be centralized. The allocation ratio will be 1:1. Data analysts and assessor will be blinded. The primary outcome is the effectiveness of the educational workshops associated with spa therapy in comparison with spa therapy alone on a priority objective, measured by Goal Attainment Scaling (GAS). The secondary outcomes are disability, health-related quality of life, and pain intensity.

ETHICS AND DISSEMINATION

Ethics were approved by the CPP Sud-Méditerranée II. The results will be disseminated in a peer-reviewed journal and disseminated at PRM, rheumatology, and orthopedics conferences. The results will also be disseminated to patients.

TRIAL REGISTRATION

Trial registration number NCT03550547. Registered 8 June 2018. Date and version identifier of the protocol. Version N°6 of March 12, 2018.

ACR Appropriateness Criteria® Staging and Follow-Up of Esophageal Cancer

This document provides recommendations regarding the role of imaging in the staging and follow-up of esophageal cancer. For initial clinical staging, locoregional extent and nodal disease are typically assessed with esophagogastroduodenoscopy and esophageal ultrasound. FDG-PET/CT or CT of the chest and abdomen is usually appropriate for use in initial clinical staging as they provide additional information regarding distant nodal and metastatic disease. The detection of metastatic disease is critical in the initial evaluation of patients with esophageal cancer because it will direct patients to a treatment pathway centered on palliative radiation rather than surgery. For imaging during treatment, particularly neoadjuvant chemotherapy, FDG-PET/CT is usually appropriate, because some studies have found that it can provide information regarding primary lesion response, but more importantly it can be used to detect metastases that have developed since the induction of treatment. For patients who have completed treatment, FDG-PET/CT or CT of the chest and abdomen is usually appropriate for evaluating the presence and extent of metastases in patients with no suspected or known recurrence and in those with a suspected or known recurrence. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

ACR Appropriateness Criteria® Epigastric Pain

Epigastric pain can have multiple etiologies including myocardial infarction, pancreatitis, acute aortic syndromes, gastroesophageal reflux disease, esophagitis, peptic ulcer disease, gastritis, duodenal ulcer disease, gastric cancer, and hiatal hernia. This document focuses on the scenarios in which epigastric pain is accompanied by symptoms such as heartburn, regurgitation, dysphagia, nausea, vomiting, and hematemesis, which raise suspicion for gastroesophageal reflux disease, esophagitis, peptic ulcer disease, gastritis, duodenal ulcer disease, gastric cancer, or hiatal hernia. Although endoscopy may be the test of choice for diagnosing these entities, patients may present with nonspecific or overlapping symptoms, necessitating the use of imaging prior to or instead of endoscopy. The utility of fluoroscopic imaging, CT, MRI, and FDG-PET for these indications are discussed. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Involvement of the Spinal Cord in Primary Mitochondrial Disorders: A Neuroimaging Mimicker of Inflammation and Ischemia in Children

BACKGROUND AND PURPOSE

Little is known about imaging features of spinal cord lesions in mitochondrial disorders. The aim of this research was to assess the frequency, imaging features, and pathogenic variants causing primary mitochondrial disease in children with spinal cord lesions.

MATERIALS AND METHODS

This retrospective analysis included patients seen at Children's Hospital of Philadelphia between 2000 and 2019 who had a confirmed diagnosis of a primary (genetic-based) mitochondrial disease and available MR imaging of the spine. The MR imaging included at least both sagittal and axial fast spin-echo T2-weighted images. Spine images were independently reviewed by 2 neuroradiologists. Location and imaging features of spinal cord lesions were correlated and tested using the Fisher exact test.

RESULTS

Of 119 children with primary mitochondrial disease in whom MR imaging was available, only 33 of 119 (28%) had available spine imaging for reanalysis. Nineteen of these 33 individuals (58%) had evidence of spinal cord lesions. Two main patterns of spinal cord lesions were identified: group A (12/19; 63%) had white ± gray matter involvement, and group B (7/19; 37%) had isolated gray matter involvement. Group A spinal cord lesions were similar to those seen in patients with neuromyelitis optica spectrum disorder, multiple sclerosis, anti-myelin oligodendrocyte glycoprotein-IgG antibody disease, and leukoencephalopathy with brain stem and spinal cord involvement and lactate elevation. Group B patients had spinal cord findings similar to those that occur with ischemia and viral infections. Significant associations were seen between the pattern of lesions (group A versus group B) and the location of lesions in cervical versus thoracolumbar segments, respectively (P < .01).

CONCLUSIONS

Spinal cord lesions are frequently observed in children with primary mitochondrial disease and may mimic more common causes such as demyelination and ischemia.

ACR Appropriateness Criteria® Liver Lesion-Initial Characterization

Incidental liver masses are commonly identified on imaging performed for other indications. Since the prevalence of benign focal liver lesions in adults is high, even in patients with primary malignancy, accurate characterization of incidentally detected lesions is of paramount clinical importance. This document reviews utilization of various imaging modalities for characterization of incidentally detected liver lesions, discussed in the context of several clinical scenarios. For each clinical scenario, a summary of current evidence supporting the use of a given diagnostic modality is reported. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

ACR Appropriateness Criteria® Jaundice

Jaundice is the end result of myriad causes, which makes the role of imaging in this setting particularly challenging. In the United States, the most common causes of all types of jaundice fall into four categories including hepatitis, alcoholic liver disease, blockage of the common bile duct by a gallstone or tumor, and toxic reaction to a drug or medicinal herb. Clinically, differentiating between the various potential etiologies of jaundice requires a detailed history, targeted physical examination, and pertinent laboratory studies, the results of which allow the physician to categorize the type of jaundice into mechanical or nonmechanical causes. Imaging modalities used to evaluate the jaundiced patient (all etiologies) include abdominal ultrasound (US), CT, MR cholangiopancreatography, endoscopic retrograde cholangiopancreatography and endoscopic US. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Use of Co2+:MgAl2O4 transparent ceramics in passive Q-switching of an Er:Glass laser at 1.534 µm

We present the implementation of Co²⁺:MgAl₂O₄ transparent ceramics as passive Q-switching elements in an Er:Glass laser at 1.534 µm. Linearly polarized pulsed output was obtained by Brewster angle inclination of the material Q-switching plate relative to the laser axis. Separate pulses were ∼105 ns long (FWHM), exhibiting ∼6.2 kW peak power at near TEM₀₀ quality. Several fundamental sample properties important for laser intracavity operation were measured; thermo-optic coefficient dn/dT = ( - 3.8 ± 1) × 10^-5 °C^-1, thermal lensing factor L^-1d(nL)/dT = 2.59 × 10^-5 °C^-1, linear expansion coefficient α = (3.9 ± 0.6) × 10^-5 °C^-1, polarizability thermal coefficient ϕ = (7.2 ± 2.2) × 10^-5 °C^-1, and damage threshold ∼6.5 J/cm².

The Perirolandic Sign: A Unique Imaging Finding Observed in Association with Polymerase γ-Related Disorders

Pathogenic variants in the polymerase γ gene (POLG) cause a diverse group of pathologies known as POLG-related disorders. In this report, we describe brain MR imaging findings and electroencephalogram correlates of 13 children with POLG-related disorders at diagnosis and follow-up. At diagnosis, all patients had seizures and 12 had abnormal MR imaging findings. The most common imaging findings were unilateral or bilateral perirolandic (54%) and unilateral or bilateral thalamic signal changes (77%). Association of epilepsia partialis continua with perirolandic and thalamic signal changes was present in 86% and 70% of the patients, respectively. The occipital lobe was affected in 2 patients. On follow-up, 92% of the patients had disease progression or fatal outcome. Rapid volume loss was seen in 77% of the patients. The occipital lobe (61%) and thalamus (61%) were the most affected brain regions. Perirolandic signal changes and seizures may represent a brain imaging biomarker of early-onset pediatric POLG-related disorders.

ACR Appropriateness Criteria® Pancreatic Cyst

Incidental pancreatic cysts are increasingly detected on imaging studies performed for unrelated indications and may be incompletely characterized on these studies. Adequate morphological characterization is critical due to the small risk of malignant degeneration associated with neoplastic pancreatic cysts, as well as the risk of associated pancreatic adenocarcinoma. For all pancreatic cysts, both size and morphology determine management. Specifically, imaging detection of features, such as pancreatic ductal communication and presence or absence of worrisome features or high-risk stigmata, have important management implications. The recommendations in this publication determine the appropriate initial imaging study to further evaluate a pancreatic cyst that was incidentally detected on a nondedicated imaging study. The recommendations are designed to maximize the yield of diagnostic information in order to better risk-stratify pancreatic cysts and assist in guiding future management. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

ACR Appropriateness Criteria® Chronic Liver Disease

The liver fibrosis stage is the most important clinical determinate of morbidity and mortality in patients with chronic liver diseases. With newer therapies, liver fibrosis can be stabilized and possibly reversed, thus accurate diagnosis and staging of liver fibrosis are clinically important. Ultrasound, CT, and conventional MRI can be used to establish the diagnosis of advanced fibrosis/cirrhosis but have limited utility for assessing earlier stages of fibrosis. Elastography-based ultrasound and MRI techniques are more useful for assessment of precirrhotic hepatic fibrosis. In patients with advanced fibrosis at risk for hepatocellular carcinoma (HCC), ultrasound is the surveillance modality recommended by international guidelines in nearly all circumstances. However, in patients in whom ultrasound does not assess the liver well, including those with severe steatosis or obesity, multiphase CT or MRI may have a role in surveillance for HCC. Both multiphase CT and MRI can be used for continued surveillance in patients with a history of HCC, and contrast-enhanced ultrasound may have an emerging role in this setting. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Role of ultrasound in the evaluation of first-trimester pregnancies in the acute setting

In patients presenting for an evaluation of pregnancy in the first trimester, transvaginal ultrasound is the modality of choice for establishing the presence of an intrauterine pregnancy; evaluating pregnancy viability, gestational age, and multiplicity; detecting pregnancy-related complications; and diagnosing ectopic pregnancy. In this pictorial review article, the sonographic appearance of a normal intrauterine gestation and the most common complications of pregnancy in the first trimester in the acute setting are discussed.

Prediction-based neural mechanisms for shielding the self from existential threat

The human mind has an automatic tendency to avoid awareness of its mortality. How this protective mechanism is implemented at the neuronal level is unknown. Here we test the hypothesis that prediction-based mechanisms mediate death-denial by shielding the self from existential threat. We provide evidence that self-specific predictive processes are downregulated during the perception of death-related linguistic stimuli and that this mechanism can predict fear-of-death. Using a magnetoencephalography visual mismatch paradigm, we show that the brain's automatic prediction response to deviancy is eliminated when death words and self-face representations are coupled, but remains present when coupled to other-face or to negative words. We further demonstrate a functional link between how death impacts self-image vs. Other-image, and show that it predicts fear-of-death. Finally, we confirm this effect in a behavioral active inference experiment showing that death-related words bias perceptual judgment on facial self and other morphed video clips. Together these results lay out, for the first time, a plausible neural-based mechanism of death-denial.

Comparison of psychometric properties between the Labin, a new electronic dynamometer, and the Jamar: Preliminary results in healthy subjects

Many instruments exist for measuring grip strength. The Jamar hydraulic hand dynamometer is currently the gold standard. The Labin is a prototype electronic dynamometer that can also measure maximum grip strength. The main objective was to compare the Labin dynamometer with the gold standard instrument, the Jamar, in a healthy population, and secondarily to compare discomfort during use. A single-center exploratory study was conducted. The subjects enrolled had to be aged between 20 and 60, be volunteers and give consent. The required number of subjects was 30. The subjects were positioned according to American Society of Hand Therapists recommendations. Maximum grip force was measured in kilograms using the mean of three successive trials. The first dynamometer used was chosen randomly. The handle's discomfort during use was rated on a simple verbal scale from 0 to 10. Thirty-four subjects were included. The concordance coefficient for peak torque between the Labin and Jamar dynamometers was 0.90 for the dominant hand and 0.83 for the non-dominant hand. The intraclass correlation coefficient for peak torque with the Labin was 0.81 [0.69; 0.89] for the dominant hand and 0.86 [0.76; 0.92] for the non-dominant hand. In our study, we have shown that the Labin prototype has acceptable validity and reproducibility. The Labin will need to be tested in pathological conditions next.

A walk on water: comparing the influence of Ai Chi and Tai Chi on fall risk and verbal working memory in ageing people with intellectual disabilities - a randomised controlled trial

BACKGROUND

Aquatic motor intervention has been found to be effective in reducing falls and improving verbal working memory among the general population. However, effects among older adults with intellectual disabilities (ID) have never been explored. The aim of this study was to examine the effects of aquatic motor intervention on fall risk and verbal working memory among older adults with ID.

METHODS

Forty-one older adults with mild to moderate ID (age: 50-66 years) were randomly assigned to 14 weeks of aquatic motor intervention (Ai Chi: N = 19) or identical on-land motor intervention (Tai Chi: N = 22). Fall risk, measured with the Tinetti balance assessment tool (TBAT), and verbal working memory, measured with the digit span forward test, were assessed pre-intervention, after 7 weeks of intervention and post-intervention.

RESULTS

Study results indicate positive effects of both aquatic and on-land motor intervention on TBAT fall risk score, while the aquatic motor intervention group improved TBAT fall risk score quicker as compared with the on-land motor intervention group. Moreover, the lower the pre-intervention TBAT score was, the higher the improvement. In addition, study findings support the positive effects of aquatic motor intervention on verbal working memory ability as measured with the digit span forward test.

CONCLUSIONS

Motor intervention, and particularly in an aquatic environment, can potentially reduce fall risk. Aquatic motor intervention may help to improve verbal working memory among older adults with ID.

Estimating summary statistics for electronic health record laboratory data for use in high-throughput phenotyping algorithms

We study the question of how to represent or summarize raw laboratory data taken from an electronic health record (EHR) using parametric model selection to reduce or cope with biases induced through clinical care. It has been previously demonstrated that the health care process (Hripcsak and Albers, 2012, 2013), as defined by measurement context (Hripcsak and Albers, 2013; Albers et al., 2012) and measurement patterns (Albers and Hripcsak, 2010, 2012), can influence how EHR data are distributed statistically (Kohane and Weber, 2013; Pivovarov et al., 2014). We construct an algorithm, PopKLD, which is based on information criterion model selection (Burnham and Anderson, 2002; Claeskens and Hjort, 2008), is intended to reduce and cope with health care process biases and to produce an intuitively understandable continuous summary. The PopKLD algorithm can be automated and is designed to be applicable in high-throughput settings; for example, the output of the PopKLD algorithm can be used as input for phenotyping algorithms. Moreover, we develop the PopKLD-CAT algorithm that transforms the continuous PopKLD summary into a categorical summary useful for applications that require categorical data such as topic modeling. We evaluate our methodology in two ways. First, we apply the method to laboratory data collected in two different health care contexts, primary versus intensive care. We show that the PopKLD preserves known physiologic features in the data that are lost when summarizing the data using more common laboratory data summaries such as mean and standard deviation. Second, for three disease-laboratory measurement pairs, we perform a phenotyping task: we use the PopKLD and PopKLD-CAT algorithms to define high and low values of the laboratory variable that are used for defining a disease state. We then compare the relationship between the PopKLD-CAT summary disease predictions and the same predictions using empirically estimated mean and standard deviation to a gold standard generated by clinical review of patient records. We find that the PopKLD laboratory data summary is substantially better at predicting disease state. The PopKLD or PopKLD-CAT algorithms are not meant to be used as phenotyping algorithms, but we use the phenotyping task to show what information can be gained when using a more informative laboratory data summary. In the process of evaluation our method we show that the different clinical contexts and laboratory measurements necessitate different statistical summaries. Similarly, leveraging the principle of maximum entropy we argue that while some laboratory data only have sufficient information to estimate a mean and standard deviation, other laboratory data captured in an EHR contain substantially more information than can be captured in higher-parameter models.

Intellectual developmental disorder with cardiac arrhythmia syndrome in a child with compound heterozygous GNB5 variants

Identification of a novel compound heterozygous of GNB5 in a patient with intellectual developmental disorder with cardiac arrhytmia (IDDCA), from non-consaguineous family. Three-dimensional modelling and in silico predictions suggest that GNB5 variants are causative of the phenotype, extending the number of IDDCA patients so far identified.

Multimodality Imaging of Vertebrobasilar Dolichoectasia: Clinical Presentations and Imaging Spectrum

Vertebrobasilar dolichoectasia (VBD) is characterized by ectasia, elongation, and tortuosity of the vertebrobasilar arteries, with a high degree of variability in clinical presentation. The disease origin is believed to involve degeneration of the internal elastic lamina, thinning of the media secondary to reticular fiber deficiency, and smooth muscle atrophy. The prevalence of VBD is variable, ranging from 0.05% to 18%. Most patients with VBD are asymptomatic and their VBD is detected incidentally; however, it is important to recognize that the presence of symptoms, which can lead to clinically significant morbidity and sometimes mortality, may influence clinical management. The most important clinical presentations of VBD are vascular events, such as ischemic stroke and catastrophic intracranial hemorrhage, or progressive compressive symptoms related to compression of adjacent structures, including the cranial nerves, brainstem, or third ventricle, causing hydrocephalus. The imaging diagnostic criteria for computed tomography and magnetic resonance (MR) imaging include three quantitative measures of basilar artery morphology: laterality score, height of bifurcation, and basilar artery diameter. The authors review the relevant anatomy and disease origin of VBD; pertinent imaging findings, including intraluminal thrombus and relation to the cranial nerves; and imaging pitfalls, such as the hyperintense vessel sign on MR images and artifacts related to slow flow in the dolichoectatic vessel. In addition, clinical manifestations, the role of radiology in diagnosis and management of this condition, and available management options are reviewed. (©)RSNA, 2016.

20: NASOPHARYNX MICROBIOME COMPOSITION VARIES OVER TIME IN PEDIATRIC ASTHMA

Purpose of Study

The application of next-generation sequencing (NGS) technology has shown that microbial communities in the respiratory airways (i.e., the microbiome) play a significant role in the onset, development and severity of asthma. However, little is known about their temporal dynamics (i.e., microbial succession), which poses a significant obstacle to identifying pulmotypes of disease and assessing inter-patient variation. Here, we couple NGS and 16S rRNA data to characterize the nasopharynx microbiome of children with asthma and determine its stability over time.

Methods Used

We collected nasal washes from 40 children with asthma enrolled in the AsthMaP-2 Project from two consecutive visits, six months apart. Total DNA was extracted and sequenced for the 16S-V4 rRNA gene region (∼250 bp) using the MySeq Illumina platform. Reads were analyzed in Mothur using the SILVAv119 reference database. Alpha diversity metrics and phylogenetic and count-base distance community indexes of beta diversity were compared across samples and time points. PCoA and NJ clustering analysis were used to assess community relatedness. Differences in alpha diversity and OTU abundance between sample pairs across time points were also compared.

Summary of Results

A mean of 27,479 clean 16S sequences corresponding to an average of 173 OTUs were sequenced and detected per sample, respectively. Representatives of Moraxella, Corynebacterium, Prevotella, Staphylococcus, Alloiococcus, Streptococcus, Peptoniphilus, Fusobacterium, and Haemophilus accounted for 36 to 99% of the reads across samples. These genera have been previously found in the nasopharynx of asthmatic and healthy children. A total of 61 OTUs from these genera were present in at least 50% of the samples (i.e., the nasal core microbiome). Significant differences in core microbiome composition were detected between sample pairs, but no directional trend (increase or decrease) was observed across sample pairs. Samples were randomly ordinated and did not cluster together.

Conclusions

Our analysis of nasal microbiomes in 40 asthmatic children revealed significant differences in composition within individuals over six months. Future cross-sectional microbiome studies need to be aware of short span temporal dynamics in nasal microbiota.

ZONE BEHAVIOR OF ENZYMES : ILLUSTRATED BY THE EFFECT OF DISSOCIATION CONSTANT AND DILUTION ON THE SYSTEM CHOLINESTERASE-PHYSOSTIGMINE

1. The kinetics of the reversible combination of one enzyme center with one molecule of a substrate or inhibitor is treated as a true bimolecular instead of a pseudomonomolecular reaction. The general equations describing such a reaction are presented and analyzed algebraically and graphically. 2. A new term, "specific concentration," is introduced to denote the concentration of reactants in units equal to the dissociation constant. Its use makes the kinetic equations universally applicable to all reversible systems of the given type. 3. It is shown that such a system exhibits three "zones" of behavior. Each zone is characterized and shown to exhibit significant differences in the function relating the concentrations of the components of the system at equilibrium. The zone boundaries are rigorously defined in terms of the specific enzyme concentration, for the mathematical error tolerable with a given experimental accuracy; and approximate boundaries for practical use are proposed. 4. The classical treatment of enzyme kinetics is shown to be a limiting case valid only for low specific enzyme concentrations (zone A) and to be inapplicable in a number of systems whose dissociation constants are very small or whose molar enzyme concentrations are very great, and in which, therefore, the specific enzyme concentrations are large. See Table I for a summary of zone differences. 5. In an enzyme system containing substrate or inhibitor, dilution before determination of reaction velocities is shown to be a crucial operation, entailing large changes in the fraction of enzyme in the form of a complex. The changes in fractional activity or inhibition with dilution are shown to be a function of specific enzyme concentration, the dilution factor, and the fraction of enzyme initially in the form of complex. Equations are given permitting the calculation of the state of the system at any concentration. The errors introduced into physiological work by failure to take the dilution effect into account are pointed out. 6. Experimental data are presented showing that the system composed of serum cholinesterase and physostigmine behaves as predicted by the dilution effect equations. 7. Two other conclusions of practical pharmacological importance are drawn from the theory of zone behavior: (a) The finding that a biological response is a linear function of the dose of a drug does not necessarily mean that the reaction is irreversible, but only that if reversible, the reactant with which the drug combines has a high specific concentration. (b) If a tissue enzyme has a high specific concentration, all reversible inhibitors will be equally potent in combining with it, regardless of their relative potency in dilute systems; provided only that their dissociation constants are within certain broad limits. 8. It is shown how the type of analysis here applied to bimolecular reactions can be applied in toto to systems of the type E + nX ⇋ EX_n, where n molecules of substrate or inhibitor unite with one enzyme center. The zone boundaries and the magnitude of the dilution effect change with n, but the general characteristics of the zones are the same for all values of n. 9. Since the analysis is based only on mass law assumptions, it is applicable to any system that is formally analogous to the one here treated.

THE MECHANISM OF ENZYME-INHIBITOR-SUBSTRATE REACTIONS : ILLUSTRATED BY THE CHOLINESTERASE-PHYSOSTIGMINE-ACETYLCHOLINE SYSTEM

The mechanism of enzyme-inhibitor-substrate reactions has been analyzed from a theoretical standpoint and illustrated by data from the system cholinesterase-physostigmine-acetylcholine. This treatment is by no means limited to a single system but should be generally applicable to others of similar type. Competitive enzyme-inhibitor-substrate systems show the same characteristic "zones of behavior" already demonstrated for non-competitive systems by Straus and Goldstein. These zones, three in number, determine the mathematical function which relates activity of an enzyme to concentration of an added substrate or inhibitor or both. The effects of suboptimal substrate concentration in such systems have been considered, and the errors arising from various common simplifications of the descriptive equations have been pointed out. The zone behavior phenomenon has been shown to be useful in determining the number of molecules of substrate or inhibitor combining reversibly with a single enzyme center. The kinetics of competitive inhibition, dilution effect, combination of inhibitor or substrate with enzyme, and destruction of inhibitor or substrate by enzyme have been analyzed and experimentally verified, and absolute velocity constants have been determined. Theoretical conclusions have been discussed from the standpoint of their physiological significance. Specifically, it has been shown that: 1. The inhibition of cholinesterase by physostigmine is competitive. A single molecule of physostigmine or acetylcholine combines with one center of cholinesterase—n = 1; and the mechanism n = 2 has been. excluded. Numerical values of the constants for this system are as follows: K_I = 3.11 x 10^–8k₁ (combination) = 8.3 x 10⁵k₂ (dissociation) = 0.026 K_S = 1.25 x 10^–3k₃ (combination) = 260 k₄ (dissociation) = 0.32 2. No definitive value can be assigned to E, the molar concentration of enzyme centers, but in 4.54 per cent dog serum, E < 1.8 x 10^–8 (E_I' < 0.58). The system therefore operates in (or nearly in) zone A at this concentration. 3. Competitive displacement of inhibitor by substrate and vice versa introduces considerable error in the usual 20 minute determination of the activity of an inhibited enzyme, unless properly corrected for. 4. Dissociation of the enzyme-inhibitor complex on dilution proceeds moderately slowly so that the full corrections for dilution cannot be applied unless time has been allowed for full dissociation. 5. Combination of physostigmine with cholinesterase is slow at all but large concentrations of inhibitor. 6. The destruction of physostigmine or acetylcholine by cholinesterase follows the predicted curve; k_D for the destruction of physostigmine is found to be > 0.00182; k_D for acetylcholine destruction is > 3500. There is no reason to assume inhibition of destruction by excess substrate or inhibitor. 7. The common assumption that enzymatic activity follows (or nearly follows) a monomolecular course is true only under limited conditions, which have been here defined. It is not valid, as a rule, for the enzymatic destruction of an inhibitor (e.g., physostigmine) and its application to such a case may lead to erroneous conclusions about the reaction mechanism.

Expanding CEP290 mutational spectrum in ciliopathies

Ciliopathies are an expanding group of rare conditions characterized by multiorgan involvement, that are caused by mutations in genes encoding for proteins of the primary cilium or its apparatus. Among these genes, CEP290 bears an intriguing allelic spectrum, being commonly mutated in Joubert syndrome and related disorders (JSRD), Meckel syndrome (MKS), Senior-Loken syndrome and isolated Leber congenital amaurosis (LCA). Although these conditions are recessively inherited, in a subset of patients only one CEP290 mutation could be detected. To assess whether genomic rearrangements involving the CEP290 gene could represent a possible mutational mechanism in these cases, exon dosage analysis on genomic DNA was performed in two groups of CEP290 heterozygous patients, including five JSRD/MKS cases and four LCA, respectively. In one JSRD patient, we identified a large heterozygous deletion encompassing CEP290 C-terminus that resulted in marked reduction of mRNA expression. No copy number alterations were identified in the remaining probands. The present work expands the CEP290 genotypic spectrum to include multiexon deletions. Although this mechanism does not appear to be frequent, screening for genomic rearrangements should be considered in patients in whom a single CEP290 mutated allele was identified.