Characterization of white matter alterations using diffusion kurtosis imaging in patients with amyotrophic lateral sclerosis

BACKGROUND

To evaluate the degeneration of the corticospinal tract (CST) and corpus callosum (CC) in patients with motor neuron disease and upper motor neuron (UMN) dysfunction using diffusion kurtosis imaging (DKI).

METHODS

Twenty-seven patients and 33 healthy controls underwent magnetic resonance imaging along with clinical and neuropsychological testing. Tractography of diffusion tensor images was performed to extract tracts of the bilateral CST and CC. Group mean differences both across the entire averaged tract and along each tract were assessed, including correlations between diffusion metrics and clinical measures. Tract-based spatial statistics (TBSS) was performed to evaluate the spatial distribution of whole-brain microstructural abnormalities in patients.

RESULTS

In comparison to controls, patients had significantly higher mean and radial diffusivity and lower fractional anisotropy (FA), kurtosis anisotropy, mean kurtosis (MK), and radial kurtosis (RK) in the CST and CC (p < .017). Along-the-tract analysis revealed changes concentrated in the posterior limb of the internal capsule, corona radiata, and primary motor cortex (false-discovery rate p < .05). FA of the left CST correlated with disease progression rate, whereas MK of the bilateral CST correlated with UMN burden (p < .01). TBSS results corroborated along-tract analysis findings and additionally revealed reduced RK and MK in the fornix, where diffusion tensor imaging (DTI) changes were absent.

CONCLUSION

DKI abnormalities in the CST and CC are present in patients with UMN dysfunction, potentially revealing complementary information to DTI regarding the pathology and microstructural alterations occurring in such patients. DKI shows promise as a potential in vivo biomarker for cerebral degeneration in amyotrophic lateral sclerosis.

Motor cortex functional connectivity is associated with underlying neurochemistry in ALS

OBJECTIVE

To identify structural and neurochemical properties that underlie functional connectivity impairments of the primary motor cortex (PMC) and how these relate to clinical findings in amyotrophic lateral sclerosis (ALS).

METHODS

52 patients with ALS and 52 healthy controls, matched for age and sex, were enrolled from 5 centres across Canada for the Canadian ALS Neuroimaging Consortium study. Resting-state functional MRI, diffusion tensor imaging and magnetic resonance spectroscopy data were acquired. Functional connectivity maps, diffusion metrics and neurometabolite ratios were obtained from the analyses of the acquired multimodal data. A clinical assessment of foot tapping (frequency) was performed to examine upper motor neuron function in all participants.

RESULTS

Compared with healthy controls, the primary motor cortex in ALS showed reduced functional connectivity with sensory (T=5.21), frontal (T=3.70), temporal (T=3.80), putaminal (T=4.03) and adjacent motor (T=4.60) regions. In the primary motor cortex, N-acetyl aspartate (NAA, a neuronal marker) ratios and diffusion metrics (mean, axial and radial diffusivity, fractional anisotropy (FA)) were altered. Within the ALS cohort, foot tapping frequency correlated with NAA (r=0.347) and white matter FA (r=0.537). NAA levels showed associations with disturbed functional connectivity of the motor cortex.

CONCLUSION

In vivo neurochemistry may represent an effective imaging marker of impaired motor cortex functional connectivity in ALS.

A Case Study of Psychogenic Non-Epileptic Seizures in a patient with Dependent Personality Disorder

Introduction

Psychogenic Nonepileptic Seizures (PNES) refer to the dissociative condition which resembles seizures but does not involve epileptic synchronous cortical activity (Huff, 2021). 20% of people visiting epilepsy clinics have PNES (Huff, 2021). Depression, anxiety, and personality disorders predispose towards PNES (Ekanayake, 2018).

Objectives

To present a case of PNES in a patient with dependent personality disorder (DPD) and to discuss the sociocultural aspects.

Methods

A case study.

Results

A 23-years old, married female presented with 20 days history of episodes of ‘falling down, rolling on ground, and involuntary movements of her head.’ The episodes typically lasted from 20-25 minutes. During the episodes, patient closed her eyes but remained conscious and expressed her distress with gestures, and tearfulness was also observed. Her condition improved when she was offered water. The clinical picture of these episodes evolved with time. Her EEG and serum prolactin levels following the episodes were normal. Accordingly, a diagnosis of PNES was made. No acute stressor was present. The patient also fulfilled the criteria of Dependent Personality Disorder (DPD) (American Psychiatric Association, 2013). During communication with the patient, it appeared that the patient and her attendants perceived the train of questioning as investigational rather than therapeutic. Efforts were made towards a more empathetic understanding of their point of view, and the tailoring of long-term management in accordance with their sociocultural context.

Conclusions

The socio-cultural context is important in the management of PNES and a sensitive, and collaborative approach is recommended. Assessment of personality should be considered in patients presenting with PNES.

Disclosure

No significant relationships.

Distinct patterns of progressive gray and white matter degeneration in amyotrophic lateral sclerosis

Progressive cerebral degeneration in amyotrophic lateral sclerosis (ALS) remains poorly understood. Here, three-dimensional (3D) texture analysis was used to study longitudinal gray and white matter cerebral degeneration in ALS from routine T1-weighted magnetic resonance imaging (MRI). Participants were included from the Canadian ALS Neuroimaging Consortium (CALSNIC) who underwent up to three clinical assessments and MRI at four-month intervals, up to 8 months after baseline (T₀ ). Three-dimensional maps of the texture feature autocorrelation were computed from T1-weighted images. One hundred and nineteen controls and 137 ALS patients were included, with 81 controls and 84 ALS patients returning for at least one follow-up. At baseline, texture changes in ALS patients were detected in the motor cortex, corticospinal tract, insular cortex, and bilateral frontal and temporal white matter compared to controls. Longitudinal comparison of texture maps between T₀ and T_max (last follow-up visit) within ALS patients showed progressive texture alterations in the temporal white matter, insula, and internal capsule. Additionally, when compared to controls, ALS patients had greater texture changes in the frontal and temporal structures at T_max than at T₀ . In subgroup analysis, slow progressing ALS patients had greater progressive texture change in the internal capsule than the fast progressing patients. Contrastingly, fast progressing patients had greater progressive texture changes in the precentral gyrus. These findings suggest that the characteristic longitudinal gray matter pathology in ALS is the progressive involvement of frontotemporal regions rather than a worsening pathology within the motor cortex, and that phenotypic variability is associated with distinct progressive spatial pathology.

Progressive Neurochemical Abnormalities in Cognitive and Motor Subgroups of Amyotrophic Lateral Sclerosis: A Prospective Multicenter Study

OBJECTIVE

To evaluate progressive cerebral degeneration in amyotrophic lateral sclerosis (ALS) by assessing alterations in N-acetylaspartate (NAA) ratios in the motor and prefrontal cortex within clinical subgroups of ALS.

METHODS

Seventy-six patients with ALS and 59 healthy controls were enrolled in a prospective, longitudinal, multicenter study in the Canadian ALS Neuroimaging Consortium. Participants underwent serial clinical evaluations and magnetic resonance spectroscopy at baseline and 4 and 8 months using a harmonized protocol across 5 centers. NAA ratios were quantified in the motor cortex and prefrontal cortex. Patients were stratified into subgroups based on disease progression rate, upper motor neuron (UMN) signs, and cognitive status. Linear mixed models were used for baseline and longitudinal comparisons of NAA metabolite ratios.

RESULTS

Patients with ALS had reduced NAA ratios in the motor cortex at baseline (p < 0.001). Ratios were lower in those with more rapid disease progression and greater UMN signs (p < 0.05). A longitudinal decline in NAA ratios was observed in the motor cortex in the rapidly progressing (p < 0.01) and high UMN burden (p < 0.01) cohorts. The severity of UMN signs did not change significantly over time. NAA ratios were reduced in the prefrontal cortex only in cognitively impaired patients (p < 0.05); prefrontal cortex metabolites did not change over time.

CONCLUSIONS

Progressive degeneration of the motor cortex in ALS is associated with more aggressive clinical presentations. These findings provide biological evidence of variable spatial and temporal cerebral degeneration linked to the disease heterogeneity of ALS. The use of standardized imaging protocols may have a role in clinical trials for patient selection or subgrouping.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that MRS NAA metabolite ratios of the motor cortex are associated with more rapid disease progression and greater UMN signs in patients with ALS.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov Identifier: NCT02405182.

Magnetic resonance imaging analysis of human skull diploic venous anatomy

Background:

The skull diploic venous space (DVS) represents a potential route for cerebrospinal fluid (CSF) diversion and absorption in the treatment of hydrocephalus. The goal of this study was to carry out a detailed characterization of the drainage pattern of the DVS of the skull using high-resolution MRI, especially the diploic veins draining to the lacunae laterales (LLs) since the LLs constitute an important channel for the CSF to access the superior sagittal sinus and subsequently the systemic circulation. The objective was to identify those skull regions optimally suited for an intraosseous CSF diversion system.

Methods:

High-resolution, T1-weighted MRI scans from 20 adult and 16 pediatric subjects were selected for analysis. Skulls were divided into four regions, that is, frontal, parietal, temporal, and occipital. On each scan, a trained observer counted all diploic veins in every skull region. Each diploic vein was also followed to determine its final drainage pathway (i.e., dural venous sinus, dural vein, LL, or indeterminate).

Results:

In the adult age group, the frontal and occipital skull regions showed the highest number of diploic veins. However, the highest number of draining diploic veins connecting to the lacunae lateralis was found in the frontal and parietal skull region, just anterior and just posterior to the coronal suture. In the pediatric age group, the parietal skull region, just posterior to the coronal suture, showed the highest overall number of diploic veins and also the highest number of draining diploic veins connecting to the LL.

Conclusion:

This study suggested that diploic venous density across the skull varies with age, with more parietal diploic veins in the pediatric age range, and more occipital and frontal diploic veins in adults. If the DVS is ultimately used for CSF diversion, our anatomical data point to optimal sites for the insertion of specially designed intraosseous infusion devices for the treatment of hydrocephalus. Likely the optimal sites for CSF diversion would be the parietal region just posterior to the coronal suture in children, and in adults, frontal and/or parietal just anterior or just posterior to the coronal suture.

MRI Texture Analysis Reveals Brain Abnormalities in Medically Refractory Trigeminal Neuralgia

Background: Several neuroimaging studies report structural alterations of the trigeminal nerve in trigeminal neuralgia (TN). Less attention has been paid to structural brain changes occurring in TN, even though such changes can influence the development and response to treatment of other headache and chronic pain conditions. The purpose of this study was to apply a novel neuroimaging technique-texture analysis-to identify structural brain differences between classical TN patients and healthy subjects. Methods: We prospectively recruited 14 medically refractory classical TN patients and 20 healthy subjects. 3-Tesla T1-weighted brain MRI scans were acquired in all participants. Three texture features (autocorrelation, contrast, energy) were calculated within four a priori brain regions of interest (anterior cingulate, insula, thalamus, brainstem). Voxel-wise analysis was used to identify clusters of texture difference between TN patients and healthy subjects within regions of interest (p < 0.001, cluster size >20 voxels). Median raw texture values within clusters were also compared between groups, and further used to differentiate TN patients from healthy subjects (receiver-operator characteristic curve analysis). Median raw texture values were correlated with pain severity (visual analog scale, 1-100) and illness duration. Results: Several clusters of texture difference were observed between TN patients and healthy subjects: right-sided TN patients showed reduced autocorrelation in the left brainstem, increased contrast in the left brainstem and right anterior insula, and reduced energy in right and left anterior cingulate, right midbrain, and left brainstem. Within-cluster median raw texture values also differed between TN patients and healthy subjects: TN patients could be segregated from healthy subjects using brainstem autocorrelation (p = 0.0040, AUC = 0.84, sensitivity = 89%, specificity = 70%), anterior insula contrast (p = 0.0002, AUC = 0.92, sensitivity = 78%, specificity = 100%), and anterior cingulate energy (p = 0.0004, AUC = 0.92, sensitivity = 78%, specificity = 100%). Additionally, anterior insula contrast and duration of TN were inversely correlated (p = 0.030, Spearman r = -0.73). Conclusions: Texture analysis reveals distinct brain abnormalities in TN, which relate to clinical features such as duration of illness. These findings further implicate structural brain changes in the development and maintenance of TN.

A prospective harmonized multicenter DTI study of cerebral white matter degeneration in ALS

OBJECTIVE

To evaluate progressive white matter (WM) degeneration in amyotrophic lateral sclerosis (ALS).

METHODS

Sixty-six patients with ALS and 43 healthy controls were enrolled in a prospective, longitudinal, multicenter study in the Canadian ALS Neuroimaging Consortium (CALSNIC). Participants underwent a harmonized neuroimaging protocol across 4 centers that included diffusion tensor imaging (DTI) for assessment of WM integrity. Three visits were accompanied by clinical assessments of disability (ALS Functional Rating Scale-Revised [ALSFRS-R]) and upper motor neuron (UMN) function. Voxel-wise whole-brain and quantitative tract-wise DTI assessments were done at baseline and longitudinally. Correction for site variance incorporated data from healthy controls and from healthy volunteers who underwent the DTI protocol at each center.

RESULTS

Patients with ALS had a mean progressive decline in fractional anisotropy (FA) of the corticospinal tract (CST) and frontal lobes. Tract-wise analysis revealed reduced FA in the CST, corticopontine/corticorubral tract, and corticostriatal tract. CST FA correlated with UMN function, and frontal lobe FA correlated with the ALSFRS-R score. A progressive decline in CST FA correlated with a decline in the ALSFRS-R score and worsening UMN signs. Patients with fast vs slow progression had a greater reduction in FA of the CST and upper frontal lobe.

CONCLUSIONS

Progressive WM degeneration in ALS is most prominent in the CST and frontal lobes and, to a lesser degree, in the corticopontine/corticorubral tracts and corticostriatal pathways. With the use of a harmonized imaging protocol and incorporation of analytic methods to address site-related variances, this study is an important milestone toward developing DTI biomarkers for cerebral degeneration in ALS.

CLINICALTRIALSGOV IDENTIFIER

NCT02405182.

The effects of body mass index on outcomes for patients undergoing surgical aortic valve replacement

Background

Most of the studies of obesity and postoperative outcome have looked predominantly at coronary artery bypass grafting with fewer focused on valvular disease. The purpose of this study was to compare the outcomes of patients undergoing aortic valve replacement stratified by body mass index (BMI, kg/m^2).

Methods

The Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease registry captured 4780 aortic valve replacements in Alberta, Canada from January 2004 to December 2018. All recipients were stratified by BMI into five groups (BMI: < 20, 20–24.9, 25–29.9, 30–34.9, and > = 35). Log-rank test and Cox regression were used to examine the crude and adjusted survival differences.

Results

Intra-operative clamp time and pump time were similar among the five groups. Significant statistical differences between groups existed for the incidence of isolated AVR, AVR and CABG, hemorrhage, septic infection, and deep sternal infection (p < 0.05). While there was no significant statistical difference in the mortality rate across the BMI groups, the underweight AVR patients (BMI < 20) were associated with increased hazard ratio (1.519; 95% confidence interval: 1.028–2.245) with regards to all-cause mortality at the longest follow-up compared with normal weight patients.

Conclusion

Overweight and obese patients should be considered as readily for AVR as normal BMI patients.

Quantifying changes on susceptibility weighted images in amyotrophic lateral sclerosis using MRI texture analysis

Objective: Susceptibility-weighted imaging (SWI) has been used to identify neurodegeneration in amyotrophic lateral sclerosis (ALS) through qualitative gross visual comparison of signal intensity. The aim of this study was to quantitatively identify cerebral degeneration in ALS on SWI using texture analysis. Methods: SW images were acquired from 17 ALS patients (58.4 ± 10.3 years, 13M/4F, ALSFRS-R 41.2 ± 4.1) and 18 healthy controls (56.3 ± 17.6 years, 9M/9F) at 4.7 tesla. Textures were computed within the precentral gyrus and basal ganglia and compared between patients and controls using ANCOVA with age and gender as covariates. Texture features were correlated with clinical measures in patients. Texture features found to be significantly different between patients and controls in the precentral gyrus were then used in a whole-brain 3D texture analysis. Results: The texture feature autocorrelation was significantly higher in ALS patients compared to healthy controls in the precentral gyrus and basal ganglia (p < 0.05). Autocorrelation correlated significantly with clinical measures such as disease progression rate and finger tapping speed (p < 0.05). Whole brain 3D texture analysis using autocorrelation revealed differences between ALS patients and controls within the precentral gyrus on SWI images (p < 0.001). Conclusion: Texture analysis on SWI can quantitatively identify cerebral differences between ALS patients and controls.

Alzheimer's disease: 3-Dimensional MRI texture for prediction of conversion from mild cognitive impairment

INTRODUCTION

Currently, there are no tools that can accurately predict which patients with mild cognitive impairment (MCI) will progress to Alzheimer's disease (AD). Texture analysis uses image processing and statistical methods to identify patterns in voxel intensities that cannot be appreciated by visual inspection. Our main objective was to determine whether MRI texture could be used to predict conversion of MCI to AD.

METHODS

A method of 3-dimensional, whole-brain texture analysis was used to compute texture features from T1-weighted MR images. To assess predictive value, texture changes were compared between MCI converters and nonconverters over a 3-year observation period. A predictive model using texture and clinical factors was used to predict conversion of patients with MCI to AD. This model was then tested on ten randomly selected test groups from the data set.

RESULTS

Texture features were found to be significantly different between normal controls (n = 225), patients with MCI (n = 382), and patients with AD (n = 183). A subset of the patients with MCI were used to compare between MCI converters (n = 98) and nonconverters (n = 106). A composite model including texture features, APOE-ε4 genotype, Mini-Mental Status Examination score, sex, and hippocampal occupancy resulted in an area under curve of 0.905. Application of the composite model to ten randomly selected test groups (nonconverters = 26, converters = 24) predicted MCI conversion with a mean accuracy of 76.2%.

DISCUSSION

Early texture changes are detected in patients with MCI who eventually progress to AD dementia. Therefore, whole-brain 3D texture analysis has the potential to predict progression of patients with MCI to AD.

Corticospinal tract degeneration in ALS unmasked in T1-weighted images using texture analysis

The purpose of this study was to investigate whether textures computed from T1-weighted (T1W) images of the corticospinal tract (CST) in amyotrophic lateral sclerosis (ALS) are associated with degenerative changes evaluated by diffusion tensor imaging (DTI). Nineteen patients with ALS and 14 controls were prospectively recruited and underwent T1W and diffusion-weighted magnetic resonance imaging. Three-dimensional texture maps were computed from T1W images and correlated with the DTI metrics within the CST. Significantly correlated textures were selected and compared within the CST for group differences between patients and controls using voxel-wise analysis. Textures were correlated with the patients' clinical upper motor neuron (UMN) signs and their diagnostic accuracy was evaluated. Voxel-wise analysis of textures and their diagnostic performance were then assessed in an independent cohort with 26 patients and 13 controls. Results showed that textures autocorrelation, energy, and inverse difference normalized significantly correlated with DTI metrics (p < .05) and these textures were selected for further analyses. The textures demonstrated significant voxel-wise differences between patients and controls in the centrum semiovale and the posterior limb of the internal capsule bilaterally (p < .05). Autocorrelation and energy significantly correlated with UMN burden in patients (p < .05) and classified patients and controls with 97% accuracy (100% sensitivity, 92.9% specificity). In the independent cohort, the selected textures demonstrated similar regional differences between patients and controls and classified participants with 94.9% accuracy. These results provide evidence that T1-based textures are associated with degenerative changes in the CST.

Scientific overview on CSCI-CITAC Annual General Meeting and 2017 Young Investigators' Forum

The 2017 Annual General Meeting of the Canadian Society of Clinician Investigators (CSCI) and Clinician Investigator Trainee Association of Canada/Association des Cliniciens-Chercheurs en Formation du Canada (CITAC/ACCFC) was a national Annual General Meeting (AGM) held in Toronto, Ontario November 20-22, 2017, in conjunction with the University of Toronto Clinician Investigator Program Research Day. The theme for this year's meeting was "Roll up your sleeves-How to manage your physician scientist career", emphasizing lectures and workshops that were designed to provide tools for being proactive and successful in career planning. The keynote speakers were Dr. Rod McInnes (McGill University and Canadian Institutes of Health Research Acting President), who was the Distinguished Scientist Award recipient, Dr. David Goltzman (McGill University), who was the 2017 Henry Friesen Award recipient, Dr. Gillian Hawker (University of Toronto), Dr. Mike Sapieha (Université de Montréal), who was the 2017 Joe Doupe Award recipient, and Dr. Alex MacKenzie (Children's Hospital of Eastern Ontario Research Institute, University of Ottawa). The workshops, focusing on career development for clinician scientists, were hosted by Dr. Lisa Robinson, Dr. Nicola Jones, Kevin Vuong, Fran Brunelle, Dr. Jason Berman and Dr. Alan Underhill. Further to this, the Young Investigators' Forum encompasses presentations from scientist-clinician trainees from across the country. All scientific abstracts are summarized in this review. There were over 100 abstracts showcased at this year's meeting during the highlighted poster sessions, with six outstanding abstracts selected for oral presentations during the President's Forum.

Evaluating the cerebral correlates of survival in amyotrophic lateral sclerosis

Objective

To evaluate cerebral degenerative changes in ALS and their correlates with survival using 3D texture analysis.

Methods

A total of 157 participants were included in this analysis from four neuroimaging studies. Voxel-wise texture analysis on T1-weighted brain magnetic resonance images (MRIs) was conducted between patients and controls. Patients were divided into long- and short-survivors using the median survival of the cohort. Neuroanatomical differences between the two survival groups were also investigated.

Results

Whole-brain analysis revealed significant changes in image texture (FDR P < 0.05) bilaterally in the motor cortex, corticospinal tract (CST), insula, basal ganglia, hippocampus, and frontal regions including subcortical white matter. The texture of the CST correlated (P < 0.05) with finger- and foot-tapping rate, measures of upper motor neuron function. Patients with a survival below the media of 19.5 months demonstrated texture change (FDR P < 0.05) in the motor cortex, CST, basal ganglia, and the hippocampus, a distribution which corresponds to stage 4 of the distribution TDP-43 pathology in ALS. Patients with longer survival exhibited texture changes restricted to motor regions, including the motor cortex and the CST.

Interpretation

Widespread gray and white matter pathology is evident in ALS, as revealed by texture analysis of conventional T1-weighted MRI. Length of survival in patients with ALS is associated with the spatial extent of cerebral degeneration.

Training the next generation of Canadian Clinician-Scientists: charting a path to success

Clinician-scientists are physicians with training in both clinical medicine and research that enables them to occupy a unique niche as specialists in basic and translational biomedical research. While there is widespread acknowledgement of the importance of clinician-scientists in today’s landscape of evidence-based medical practice, training of clinician-scientists in Canada has been on the decline, with fewer opportunities to obtain funding. With the increasing length of training and lower financial compensation, fewer medical graduates are choosing to pursue such a career. MD-PhD programs, in which trainees receive both medical and research training, have the potential to be an important tool in training the next generation of clinician-scientists; however, MD-PhD trainees in Canada face barriers that include an increase in medical school tuition and a decrease in the amount of financial support. We examined the available data on MD-PhD training in Canada and identified a lack of oversight, a lack of funding and poor mentorship as barriers experienced by MD-PhD trainees. Specific recommendations are provided to begin the process of addressing these challenges, starting with the establishment of an overseeing national body that would track long-term outcome data for MD-PhD trainees. This national body could then function to implement best practices from individual programs across the country and to provide further mentorship and support for early-career physician-scientists. MD-PhD programs have the potential to address Canada’s growing shortage of clinician-scientists, and strengthening MD-PhD programs will help to effect positive change.

White matter structural network abnormalities underlie executive dysfunction in amyotrophic lateral sclerosis

Research in amyotrophic lateral sclerosis (ALS) suggests that executive dysfunction, a prevalent cognitive feature of the disease, is associated with abnormal structural connectivity and white matter integrity. In this exploratory study, we investigated the white matter constructs of executive dysfunction, and attempted to detect structural abnormalities specific to cognitively impaired ALS patients. Eighteen ALS patients and 22 age and education matched healthy controls underwent magnetic resonance imaging on a 4.7 Tesla scanner and completed neuropsychometric testing. ALS patients were categorized into ALS cognitively impaired (ALSci, n = 9) and ALS cognitively competent (ALScc, n = 5) groups. Tract-based spatial statistics and connectomics were used to compare white matter integrity and structural connectivity of ALSci and ALScc patients. Executive function performance was correlated with white matter FA and network metrics within the ALS group. Executive function performance in the ALS group correlated with global and local network properties, as well as FA, in regions throughout the brain, with a high predilection for the frontal lobe. ALSci patients displayed altered local connectivity and structural integrity in these same frontal regions that correlated with executive dysfunction. Our results suggest that executive dysfunction in ALS is related to frontal network disconnectivity, which potentially mediates domain-specific, or generalized cognitive impairment, depending on the degree of global network disruption. Furthermore, reported co-localization of decreased network connectivity and diminished white matter integrity suggests white matter pathology underlies this topological disruption. We conclude that executive dysfunction in ALSci is associated with frontal and global network disconnectivity, underlined by diminished white matter integrity. Hum Brain Mapp 38:1249-1268, 2017. © 2016 Wiley Periodicals, Inc.

Diabetes risk assessment among squatter settlements in Pakistan: A cross-sectional study

INTRODUCTION

Diabetes mellitus (DM) has evolved as a major public health concern worldwide, as its prevalence is increasing exponentially. Pakistan now ranks seventh among the countries with the highest burden of DM. It is expected to become one of the major causes of morbidity within the next 25 years. Therefore, finding an effective way to identify individuals at risk of developing diabetes is a necessity. The Finnish Diabetes Risk Score (FINDRISC) has proved to be an effective noninvasive screening tool for identifying individuals at risk for developing diabetes. The objective of this study was to determine the frequency of individuals who are at risk for developing DM and their risk of developing DM over the next 10 years using the FINDRISC tool.

METHODS

A cross-sectional survey was conducted on 241 adults. The data were collected using the FINDRISC questionnaire followed by calculation of a summated score and analysis to determine the association between the risk factors under study and the risk of developing diabetes.

RESULTS

Out of 241 study participants, 137 (56.8%) were men and 104 (43.1%) were women. Our study showed that 129 (53.5%) participants had low risk, 68 (28.2%) had slightly elevated risk, 27 (11.2%) had moderate risk and 17 (7%) had high risk of developing DM.

CONCLUSION

The general population should be educated about the importance of healthy lifestyle, with special emphases on maintaining an ideal body mass index and a low-risk waist circumference, along with daily fruit and vegetable intake and physical activity of at least 30 min/day.

Febrile neutropenia in paediatric peripheral blood stem cell transplantation, in -vitro sensitivity data and clinical response to empirical antibiotic therapy

OBJECTIVE

To find the in-vitro sensitivity data and clinical response in order to determine the changes required in empiric antibiotic therapy for management of febrile neutropenia in paediatric patients undergoing peripheral blood stem cell transplantation.

DESIGN

A descriptive study.

PLACE AND DURATION OF STUDY

Paediatric bone marrow transplant unit at Bismillah Taqee Institute of Health Sciences and Blood Disease Center from September 1999 to May 2004.

PATIENTS AND METHODS

All patients were treated according to institutional protocol for febrile neutropenia. Empirical antibiotics include Ceftriaxone and Amikacin. In non-responders, changes made included Imipenem and Amikacin, Piperacillin Tazobactum/Tiecoplanin or Vancomycin/Cloxacilin/Ceftazidime. In non-responders, amphotaracin was added until recovery.

RESULTS

Out of 52 patients, 5 did not develop any fever; in the remaining 47 patients there were 57 episodes of febrile neutropenia. The mean days of febrile episodes were 4.71 (range 3-8). Fever of unknown origin (FUO) occurred in 31 (54.3%) episodes. Microbiologically documented infection (MDI) occurred in 17 (29.8%) episodes of fever. Clinically documented infection (CDI) occurred in 9 (15.7%) episodes. Gram-negative organisms were isolated in 10 while gram-positive organisms in 7. Klebseilla, S. aureus were the most common isolates. Empirical therapy was effective in 12 of the 33 (36%) episodes. Out of 28, 26 (92%) responded to Imipenem/Amikacin as second line therapy while those who received any other second line combination, only 11 out of 22 (50%) showed response. Systemic Amphotericin was used in 4 patients, 2 responded. Infection related mortality rate was 4%.

CONCLUSION

Gram-negative infections predominated, Imipenem/ Amikacin found to be most effective therapy while a low mortality rate is recorded in our setting suggesting good infection control.

Role of Ca2+, Mg2+ and K+ ions in determining apoptosis and extent of suppression afforded by bcl-2 during hybridoma cell culture

We have addressed the possibility that Ca2+, Mg2+ and K+ ions play a central role in governing the morphological and biochemical changes attributed to apoptotic cell death. By removing Ca2+, Mg2+ or K+ ions from the cell culture medium we were able to assess the contribution of each ion to hybridoma cell growth and viability. The differences were explained in terms of a possible reduction in their respective intracellular levels. From several lines of evidence, the deprivation of K+ ions was the most detrimental to cellular growth and viability and induced significant levels of early apoptotic cells. Another effect of this deprivation was to weaken the plasma membranes without causing membrane breakdown; exposure to high agitation rates confirmed fragility of the cell membranes. Removal of Mg2+ caused a reduction in the levels of early apoptotic cells and predisposed cells to high levels of primary necrotic death. The lower levels of apoptotic cells failed to demonstrate the classic nuclear morphology associated with apoptosis, while retaining other apoptotic features. These results highlighted the importance of utilizing several assays for the determination of apoptosis. The absence of Ca2+ appeared to be the mildest insult, but its deprivation did accelerate a significant decline in culture by increasing apoptotic death. Hybridoma cells overexpressing the apoptotic suppressor gene bcl-2 were protected from the predominantly necrosis inducing effects of Mg2+ ion deprivation and apoptosis inducing effects of Ca2+ ion deprivation. However, apoptosis was not as effectively suppressed in bcl-2 cells responding to incubation in K+ free medium. The inclusion of bcl-2 activity in the mechanisms of Ca2+ Mg2+ or K+ deprivation induced cell death emphasizes a close relationship between ionic dissipation and the apoptotic process.

Role of vitamins in determining apoptosis and extent of suppression by bcl-2 during hybridoma cell culture

The identification of cell culture media components that may instigate apoptosis in cell lines used for the production of commercial antibodies and recombinant proteins, is crucial to aid the development of improved media for reduced cell death and to understand the role of nutrient components in cell survival and maintenance. Here we determine the impact of depriving all or individual B-group media vitamins either, D-CaPantothenate (DCaP), choline chloride (CC), riboflavin (Rb), i-inositol, nicotinamide (NAM), pyridoxal hydrochloride (PyrHCl), folic acid (FA), or thiamine hydrochloride (ThHCl) on hybridoma cell growth and viability using fluorescence microscopy techniques. Cultivation in media deprived of all these vitamins prevented cell proliferation from reaching maximum capacity while increasing cell death rate, predominantly via apoptosis. Deletion of either DCaP, CC, or Rb showed that these components were most likely responsible for the development of apoptosis. Exclusion of either i-inositol, NAM or PyrHCl failed to inhibit cell growth and viability, while marginal improvements in viability were noted by ThHCl deprivation and more so by FA exclusion. Over-expression of the anti-apoptotic gene bcl-2 suppressed cell death initiated by all or single vitamin (either DCaP, CC or Rb) deprivation. The involvement of bcl-2 activity, established a close association between small vitamin molecules particularly DCaP, CC or Rb and the biochemical activation of apoptosis.

Important considerations in the development of public health advisories for arsenic and arsenic-containing compounds in drinking water

Drinking water contamination by arsenic remains a major public health problem. Acute and chronic arsenic exposure via drinking water has been reported in many countries of the world; especially in Argentina, Bangladesh, India, Mexico, Thailand, and Taiwan, where a large proportion of drinking water (ground water) is contaminated with a high concentration of arsenic. Research has also pointed out significantly higher standardized mortality ratios and cumulative mortality rates for cancers of the bladder, kidney, skin, liver, and colon in many areas of arsenic pollution. General health effects that are associated with arsenic exposure include cardiovascular and peripheral vascular disease, developmental anomalies, neurologic and neurobehavioral disorders, diabetes, hearing loss, portal fibrosis of the liver, lung fibrosis, hematologic disorders (anemia, leukopenia, and eosinophilia), and carcinoma. Although, the clinical manifestations of arsenic poisoning appear similar, the toxicity of arsenic compounds depends largely u[on the chemical species and the form of arsenic involved. On the basis of its high degree of toxicity to humans, and the non-threshold dose-response assumption, a zero level exposure is recommended for arsenic, even though this level is practically non-attainable. In this review, we provide and discuss important information on the physical and chemical properties, production and use, fate and transport, toxicokinetics, systemic and carcinogenic health effects, regulatory and health guidelines, analytical methods, and treatment technologies that are applied to arsenic pollution. Such information is critical in assisting the federal, state and local officials who are responsible for protecting public health in dealing with the problem of drinking water contamination by arsenic and arsenic-containing compounds.

Use of intracellular pH and annexin-V flow cytometric assays to monitor apoptosis and its suppression by bcl-2 over-expression in hybridoma cell culture

Accurate identification and quantitation of apoptosis is essential for developing efficient strategies for optimisation of culture viability and productivity in cell lines of industrial significance. We have examined the possibility of using carboxy-seminaphthorhodafluor-1-acetoxymethylester (carboxy SNARF-1-AM), a pH sensitive fluoroprobe and FITC-labelled annexin V (AV), a probe specific to phosphatidylserine exposed on the surface of apoptotic cells, to monitor apoptosis and to determine the relationship between intracellular pH (pHi), apoptosis and cell cycle in hybridoma cells. Temporal changes in the distribution of proliferative capacity (S phase), metabolic activity (pHi), and cell death population dynamics were effectively and reliably determined using flow cytometry. Intracellular acidification was shown to precede the occurrence of apoptosis during batch culture and after treatment with campothecin, staurosporine and under adverse bioreactor conditions such as glutamine deprivation and oxygen deficiency. These results showed that the decrease in pHi can be used as an indicator of cellular deterioration and cell death. AV in combination with propidium iodide permitted the identification of viable, transient apoptotic and necrotic cells in heterogeneous cultures of control (PEF) cells. Hybridoma cells over-expressing bcl-2 were protected from intracellular acidification and phosphatidylserine exposure, which was associated with the suppression of apoptosis in these cells. A decrease in pHi was apparent even before the accumulation of the normally acidic G1 phase and the development of a sub-G1 region, characteristic of apoptotic cell behaviour. The pHi assay can therefore be used as a tool to predict future cell culture performance. reserved.

Transgenic mice expressing the human high-affinity immunoglobulin (Ig) E receptor alpha chain respond to human IgE in mast cell degranulation and in allergic reactions

The high-affinity receptor for immunoglobulin (Ig) E (Fc epsilon RI) on mast cells and basophils plays a key role in IgE-mediated allergies. Fc epsilon RI is composed of one alpha, one beta, and two gamma chains, which are all required for cell surface expression of Fc epsilon RI, but only the alpha chain is involved in the binding to IgE. Fc epsilon RI-IgE interaction is highly species specific, and rodent Fc epsilon RI does not bind human IgE. To obtain a "humanized" animal model that responds to human IgE in allergic reactions, transgenic mice expressing the human Fc epsilon RI alpha chain were generated. The human Fc epsilon RI alpha chain gene with a 1.3-kb promoter region as a transgene was found to be sufficient for mast cell-specific transcription. Cell surface expression of the human Fc epsilon RI alpha chain was indicated by the specific binding of human IgE to mast cells from transgenic mice in flow cytometric analyses. Expression of the transgenic Fc epsilon RI on bone marrow-derived mast cells was 4.7 x 10(4)/cell, and the human IgE-binding affinity was Kd = 6.4 nM in receptor-binding studies using 125I-IgE. The transgenic human Fc epsilon RI alpha chain was complexed with the mouse beta and gamma chains in immunoprecipitation studies. Cross-linking of the transgenic Fc epsilon RI with human IgE and antigens led to mast cell activation as indicated by enhanced tyrosine phosphorylation of the Fc epsilon RI beta and gamma chains and other cellular proteins. Mast cell degranulation in transgenic mice could be triggered by human IgE and antigens, as demonstrated by beta-hexosaminidase release in vitro and passive cutaneous anaphylaxis in vivo. The results demonstrate that the human Fc epsilon RI alpha chain alone not only confers the specificity in human IgE binding, but also can reconstitute a functional receptor by coupling with the mouse beta and gamma chains to trigger mast cell activation and degranulation in a whole animal system. These transgenic mice "humanized" in IgE-mediated allergies may be valuable for development of therapeutic agents that target the binding of IgE to its receptor.

A leukocyte lipid up-regulates the avidity of lymphocyte function-associated antigen-1

An acidic lipid termed leukocyte adhesion lipid (LAL) was isolated from PMA stimulated lymphoid and myeloid cell lines HL60, Jurkat, K562 and U937 but not from unstimulated cells or PMA treated Cos7 cells. LAL treated peripheral blood leukocytes (PBL) adhered strongly to IL-1 beta activated human umbilical vein endothelial cells (HUVEC), and the interaction could be inhibited by antibodies to intercellular adhesion molecule (ICAM-1) or lymphocyte function-associated antigen-1 (LFA-1). Leukocytes treated with LAL maintained the high avidity state of LFA-1 for at least 1 hr whereas the avidity of LFA-1 in PMA treated cells declined after 30 min. LAL was stable to heat (100 degrees C, 10 min), alkaline phosphatase and proteinase K treatments. Chemical analysis suggested that LAL contained unsaturated lipids. Our findings provide evidence for the involvement of lipids in LFA-1 activation.

Characterization of the gene for the human high affinity IgE receptor (Fc epsilon RI) alpha-chain

The Fc epsilon RI couples the mast cell-surface binding of IgE and Ag to a complex series of intracellular events culminating in cell activation and degranulation. The alpha-chain of Fc epsilon RI constitutes the Ig-binding subunit of this heterotetrameric receptor, and is itself a member of the Ig gene superfamily. We have isolated a human genomic DNA clone containing the entire Fc epsilon RI alpha gene, and completely sequenced a region from 1257 bp 5' of the transcription start site, to 513 bp 3' of the last exon of the gene. As with the previously characterized rat and mouse genes, human Fc epsilon RI alpha consists of five exons and four introns, and spans 5889 bp of genomic DNA. The splice donor and acceptor sites deduced by comparison with the cDNA sequence corresponded exactly to the locations found in analogous rodent genes. By mapping the 5' end of Fc epsilon RI alpha transcripts we found three major transcription initiation sites 24, 27, and 29 bp upstream of the ATG translation initiation codon. As well, several longer minor transcripts were seen, with a maximum of 60 nt of 5'-untranslated sequence. About 650 bp of DNA upstream of the ATG translation initiation codon were compared among human, rat, and mouse Fc epsilon RI alpha sequences in search of common motifs that might mediate conserved regulatory interactions with DNA binding proteins. A 172-bp region of the human Fc epsilon RI alpha 5'-flanking sequence was highly conserved in both rodent species. Further studies will be required to determine whether these or other sequences are involved in Fc epsilon RI alpha gene regulation.

Characterization of the gene for the human high affinity IgE receptor (Fc epsilon RI) alpha-chain

The Fc epsilon RI couples the mast cell-surface binding of IgE and Ag to a complex series of intracellular events culminating in cell activation and degranulation. The alpha-chain of Fc epsilon RI constitutes the Ig-binding subunit of this heterotetrameric receptor, and is itself a member of the Ig gene superfamily. We have isolated a human genomic DNA clone containing the entire Fc epsilon RI alpha gene, and completely sequenced a region from 1257 bp 5' of the transcription start site, to 513 bp 3' of the last exon of the gene. As with the previously characterized rat and mouse genes, human Fc epsilon RI alpha consists of five exons and four introns, and spans 5889 bp of genomic DNA. The splice donor and acceptor sites deduced by comparison with the cDNA sequence corresponded exactly to the locations found in analogous rodent genes. By mapping the 5' end of Fc epsilon RI alpha transcripts we found three major transcription initiation sites 24, 27, and 29 bp upstream of the ATG translation initiation codon. As well, several longer minor transcripts were seen, with a maximum of 60 nt of 5'-untranslated sequence. About 650 bp of DNA upstream of the ATG translation initiation codon were compared among human, rat, and mouse Fc epsilon RI alpha sequences in search of common motifs that might mediate conserved regulatory interactions with DNA binding proteins. A 172-bp region of the human Fc epsilon RI alpha 5'-flanking sequence was highly conserved in both rodent species. Further studies will be required to determine whether these or other sequences are involved in Fc epsilon RI alpha gene regulation.

Differential regulation of human progesterone receptor A and B form-mediated trans-activation by phosphorylation

Hormone-dependent phosphorylation of progesterone receptors (PRs) plays a functional role in their transcriptional activity. However, hormone-independent phosphorylation has also been shown to modulate the chicken PR-mediated trans-activation in the presence of phosphorylating agents. The present study was designed to investigate the effects of protein kinase A- and protein kinase C-mediated signal transduction pathways on the regulation of the activity of the two forms of human PR (hPRA and hPRB). Similar to chicken PR, hPR was activated by 8-bromo-cAMP (8-Br-cAMP) in the absence of ligand, whereas 8-Br-cAMP synergized with the progestin agonist R5020 to amplify hPRA- and hPRB-mediated reporter activity. Interestingly, the effect of 8-Br-cAMP was much more pronounced on hPRA-induced trans-activation than on hPRB. This differential regulation by 8-Br-cAMP could also be mimicked by okadaic acid. Both mouse mammary tumor virus-thymidine kinase-chloramphenicol acetyl transferase and progesterone response element-thymidine kinase-chloramphenicol acetyl transferase showed a similar response to 8-Br-cAMP in the presence of R5020. Protein kinase C, on the other hand, did not discriminate between hPRA- and hPRB-mediated trans-activation. Unlike 8-Br-cAMP, phorbol 12-myristate 13-acetate did not cause marked ligand-independent trans-activation through either of the two receptor forms. RU486, an antagonist of progestin, preferentially blocked R5020-induced trans-activation compared to R5020 + 8-Br-cAMP synergism. As expected, H-89, a specific inhibitor of protein kinase A was more effective in inhibiting ligand-independent activity. Western analysis of transfected receptors suggested that 8-Br-cAMP and 8-Br-cAMP + R5020 but not R5020 alone down-regulated the level of hPRB in COS-1 cells. Only marginal modulation of hPRA levels was observed with R5020 treatment in the presence and absence of 8-Br-cAMP. These data suggest that R5020 and 8-Br-cAMP mediate PR-dependent transactivation through distinct pathways, and that phosphorylation can differentially regulate the activity of hPRA and hPRB forms, an observation which may be important for selective target gene activation in vivo by progestins.

Spermine dialdehyde, a novel ex vivo purging agent for both allogenic and autologous bone marrow transplantations

The use of ex vivo purging agents has shown to be beneficial for both allogeneic and autologous bone marrow transplantations. We have shown previously that spermine dialdehyde (SDA), an oxidized product of spermine, when used in phosphate-buffered saline (PBS) preferentially inhibits T-cell proliferation while sparing myeloid cells. Lethally irradiated mice were rescued by reconstitution with SDA-treated allogeneic marrow and showed no sign of graft-vs-host disease (GVHD). In this paper, we show by HPLC analysis that SDA degraded rapidly in PBS but remained intact in saline. Administered in saline, SDA was more inhibitory on leukemic cell lines than normal myeloid or T-cells. Lethally irradiated mice receiving a syngeneic bone marrow leukemic cell mixture treated ex vivo with SDA in saline did not manifest leukemia. Thus, the preferential inhibitory effect of SDA and its degraded products in different buffers suggest that SDA could act as a novel purging agent for both allogeneic and autologous bone marrow transplantations.

Purification, characterization, and structural elucidation of the active moiety of the previously called "suppressor activating factor (SAF)"

Upon extensive purification of the serum-free supernatant produced by a mutant T cell line (6T-CEM), an immunosuppressive activity was found to reside in an oxidized product of spermine, spermine dialdehyde (SDA). The activity was purified to homogeneity from a serum-free supernatant by using gel filtration chromatography and reverse-phase C18 HPLC. Fast Atom Bombardment (FAB) mass spectral analysis revealed its MW to be 202 and Electron Impact (EI) analysis of the acetylated material identified the purified molecule to be spermine. In the presence of human or rodent plasma, spermine exhibited no immunosuppressive activity up to 2 mg/ml. However, when assayed in the presence of FCS, which contains polyamine oxidase (PAO), spermine is oxidized to its corresponding dialdehyde which is active at 0.1 microM/ml. We have previously described a high molecular weight suppressor activating factor (SAF) found in the serum-containing supernatant of the 6T-CEM cell line. Our preliminary biological data suggest that SDA is probably responsible for the immunosuppressive activities previously observed for the SAF. The strong affinity of SDA for proteins and thiocompounds may account for the apparent high MW previously reported for SAF.

Mechanism of action of a suppressor-activating factor (SAF) produced by a human T cell line

We previously described a potent suppressor-activating factor (SAF) produced constitutively by a 6-thioguanine-resistant mutant of the human T cell line CEM. In the present study, we investigated the mechanism of action of SAF. After a brief (4- to 18-hr) exposure to SAF at 37 degrees C, T lymphocytes (either unseparated, or purified OKT4+ and OKT8+ subpopulations), but not B lymphocytes, suppressed allogeneic and syngeneic T cells in co-culture experiments, apparently via the release of a suppressor activity. The total T cell-released suppressor activity (TRSA) accumulated after 3 days culture post-treatment was about 100- to 500-fold higher than the original suppressor activity (SAF) added to trigger the release. Arresting protein or DNA synthesis, or even killing the cells did not affect the release of TRSA by T lymphocytes, but lowering the incubation temperature to 4 degrees C reduced it drastically. Pre-treatment of T lymphocytes with the metabolic inhibitor, sodium azide, or the adenylate cyclase stimulator, prostaglandin E2, or the addition of exogenous dibutyryl cAMP, all suppressed the release of TRSA. The presence of monoclonal antibody OKT3, but not OKT4 or OKT8, enhanced the release of TRSA. The presence of OKT11 blocked the release of SAF. The functional characteristics of TRSA appeared to be identical to those of SAF. However, unlike SAF, interaction of T lymphocytes with TRSA triggered only marginal enhancement of suppressor activity. In addition, the kinetics of the suppression mediated by SAF showed a much larger increment as a function of time than that mediated by TRSA. Taken together, the data suggest that SAF might represent an activated form of SAF, and that the continuous activation of SAF by lymphocytes in culture may account for its high potency in suppressing T cell proliferation in vitro.

Mechanism of action of a suppressor-activating factor (SAF) produced by a human T cell line

We previously described a potent suppressor-activating factor (SAF) produced constitutively by a 6-thioguanine-resistant mutant of the human T cell line CEM. In the present study, we investigated the mechanism of action of SAF. After a brief (4- to 18-hr) exposure to SAF at 37 degrees C, T lymphocytes (either unseparated, or purified OKT4+ and OKT8+ subpopulations), but not B lymphocytes, suppressed allogeneic and syngeneic T cells in co-culture experiments, apparently via the release of a suppressor activity. The total T cell-released suppressor activity (TRSA) accumulated after 3 days culture post-treatment was about 100- to 500-fold higher than the original suppressor activity (SAF) added to trigger the release. Arresting protein or DNA synthesis, or even killing the cells did not affect the release of TRSA by T lymphocytes, but lowering the incubation temperature to 4 degrees C reduced it drastically. Pre-treatment of T lymphocytes with the metabolic inhibitor, sodium azide, or the adenylate cyclase stimulator, prostaglandin E2, or the addition of exogenous dibutyryl cAMP, all suppressed the release of TRSA. The presence of monoclonal antibody OKT3, but not OKT4 or OKT8, enhanced the release of TRSA. The presence of OKT11 blocked the release of SAF. The functional characteristics of TRSA appeared to be identical to those of SAF. However, unlike SAF, interaction of T lymphocytes with TRSA triggered only marginal enhancement of suppressor activity. In addition, the kinetics of the suppression mediated by SAF showed a much larger increment as a function of time than that mediated by TRSA. Taken together, the data suggest that SAF might represent an activated form of SAF, and that the continuous activation of SAF by lymphocytes in culture may account for its high potency in suppressing T cell proliferation in vitro.

A mutant human T-cell line producing immunosuppressive factor(s)

6T-CEM-20, a subclone of a 6-thioguanine-resistant mutant derived from the human-T-cell line CEM, secreted into the medium, a high titered immunosuppressive factor specific for T cells. The cell-free supernatant was very potent in suppressing, via a noncytotoxic mechanism, mitogen-activated T-cell proliferation, cytotoxic T-cell functions, and pokeweed mitogen (PWM)-stimulated plaque-forming cells (PFC). Lower dilutions of the supernatant (10(-1)-10(-2] abrogated T-cell functions within 24 hr whereas higher dilutions (10(-3)-10(-7] required a culture period of up to 4 days with lymphocytes to arrest T-cell activities. The suppressive activity was most pronounced when the factor was added in the early part of the culture period. The factor was sensitive to heat treatment and both low and high pH (most stable at physiological pH). Preliminary purification with column chromatography indicates that the active moiety was contained in the high-molecular-weight fraction (MW greater than 200,000). Data from coculture experiments suggested that T lymphocytes, which were exposed for 5-12 hr to the active supernatant or the partially purified material, suppressed allogeneic T-cell proliferation in a dose-related manner. This suppressor factor which we called suppressor-activating factor (SAF) might have activated a suppressor population or induced the production of a suppressor factor which in turn mediated the observed suppression. Both the molecular structure and the detailed mechanism of action are under investigation.

The complete amino acid sequence of the rabbit P2 protein

P2 protein is a small basic protein (Mr = 14,820) found in peripheral nerve myelin and spinal cord myelin. There is now overwhelming evidence that P2 protein is the crucial antigen involved in the induction of experimental allergic neuritis, an autoimmune disease of the peripheral nervous system. The complete amino acid sequence of rabbit P2 protein was derived by sequence analysis of cyanogen bromide peptides and peptides obtained by proteolysis using Staphylococcus aureus V8 enzyme, trypsin, or clostripain. There are 131 amino acids and an excess of the basic amino acids lysine and arginine; histidine is absent. There are 3 highly hydrophobic regions in the P2 molecule. Probability analysis of the sequence predicts a high degree of beta structure, essentially in agreement with CD data.

Allergic neuritis: phospholipid requirement for the disease-inducing conformation of the P2 protein

The P2 protein, a small, highly ordered basic protein of peripheral nerve myelin, is a potent inducer of allergic neuritis in rats when complexed with phospholipids such as phosphatidylserine. Isolated P2 protein administered without lipid is a poor neuritogen, and if first oxidized with performic acid, aminoethylated in 8 M urea or heat denatured, it loses nearly all activity. When the aminoethylated or oxidized forms are combined with phosphatidylserine, however, they recover essentially full neuritogenic activity. Complexing with lipid also greatly enhances the activity of the heart denatured form. Spleen cells sensitized to the aminoethylated and heated forms of P2 protein show a pronounced mitogenic response to either of these forms as well as to the P2 protein itself, but only when sensitization is initiated with the lipid complex. These data indicate that the lipid complex reverses the distortion acquired by chemical treatment or denaturation and converts the P2 molecule into a conformation approximating that of the native P2 protein in myelin. These studies imply that the neuritogenic domain, while highly sensitive to denaturing conditions, requires interaction with phospholipids in order to attain the most favourable conformation for inducing a cell-mediated response that leads to disease.

Allergic neuritis: a neuritogenic peptide from the P2 protein that induces disease in rats

Peptide CN1, a large 93 residue peptide, derived from residues 21-113 of the bovine and rabbit P2 protein of sciatic nerve myelin, induces severe allergic neuritis in Lewis rats. When complexed with phosphatidylserine and tested at 50 microgram dosage in Freund's complete adjuvant, it induces severe clinical and histologic signs (cellular infiltration and demyelination of the sciatic nerve) in most animals. It is as potent in disease induction as the P2 protein on a weight basis. In contrast, when not complexed with phosphatidylserine, Peptide CN1 induced only mild clinical signs and histologic lesions in 3 of 10 rats. CNBr peptides CN2 and CN3, derived from the carboxyl and amino terminal ends, respectively, were not active. Spleen and lymph node cells from rats sensitized to Peptide CN1 responded to both P2 and Peptide CN1 in culture in the mitogenic assay. These data show that the major neuritogenic domain for the rat resides in the CN1 region.

Allergic neuritis: a neuritogenic peptide from the P2 protein that induces disease in rats

Peptide CN1, a large 93 residue peptide, derived from residues 21-113 of the bovine and rabbit P2 protein of sciatic nerve myelin, induces severe allergic neuritis in Lewis rats. When complexed with phosphatidylserine and tested at 50 microgram dosage in Freund's complete adjuvant, it induces severe clinical and histologic signs (cellular infiltration and demyelination of the sciatic nerve) in most animals. It is as potent in disease induction as the P2 protein on a weight basis. In contrast, when not complexed with phosphatidylserine, Peptide CN1 induced only mild clinical signs and histologic lesions in 3 of 10 rats. CNBr peptides CN2 and CN3, derived from the carboxyl and amino terminal ends, respectively, were not active. Spleen and lymph node cells from rats sensitized to Peptide CN1 responded to both P2 and Peptide CN1 in culture in the mitogenic assay. These data show that the major neuritogenic domain for the rat resides in the CN1 region.

The PO glycoprotein of peripheral nerve myelin

The PO glycoprotein, the major protein of peripheral nerve myelin, is a hydrophobic glycoprotein which can be isolated in soluble and insoluble forms from rabbit sciatic nerve myelin following extensive defatting and mid acidic extraction. The PO glycoprotein was localized exclusively in peripheral nervous system (PNS) myelin of sciatic nerve and rootlets by the immunofluorescent technique using goat anti-PO serum which showed a single precipitin band in double diffusion and did not cross-react with the myelin basic protein or P2 protein. Central nervous system (CNS) myelin from brain and spinal cord was negative by the immunofluorescent procedure. The major glycoprotein bands in PNS myelin, in addition to the PO glycoprotein at 28K, exist at 23K and 19K, as shown by gel electrophoresis in dodecyl sulfate. These glycoproteins, isolated by gel filtration in 2% dodecyl sulfate, show identity to the PO glycoprotein in their monosaccharide profile and overlapping tryptic peptides on peptide mapping. We conclude that both the 23K and 19K glycoproteins are derived from the PO glycoprotein by in situ proteolysis; the 23K glycoprotein has the identical amino terminal sequence. The 19K glycoprotein, beginning with amino-terminal methionine, is identical with the TPO glycoprotein, shown previously to originate from tryptic hydrolysis of the PO glycoprotein in isolated myelin. A tryptic glycopeptide containing 27 amino acids was isolated from the PO glycoprotein and sequenced. It contained a relatively high proportion of aspartic acid (four residues) and glutamic acid (two residues), thus exhibiting a high negative charge. We conclude that the total carbohydrate of the PO, 23K, and 19K glycoproteins does indeed exist as a single nonasaccharide moiety linked through N-acetylglucosamine to Asp-14 of the glycopeptide in a N-glycosidic linkage. These results further support the role of the PO glycoprotein as a typical amphipathic membrane protein.

The PO protein. The major glycoprotein of peripheral nerve myelin

A glycoprotein, referred to as PO protein, was isolated from rabbit sciatic nerve myelin by gel filtration on Agarose 0.5 m in dodecyl sulfate. The purified myelin was first defatted and extracted at pH 2. The water-soluble proteins such as myelin basic protein and P2 protein were extracted leaving a glycoprotein-rich residue, from which the PO protein was isolated. The purified protein showed a single band on gel electrophoresis in dodecyl sulfate when stained with Coomassie Blue of periodic acid-Schiff reagent. The carbohydrate, comprising 6.3% by weight, appears to exist as a nonasaccharide unit having 3 mannose, 3 N-acetylglucosamine, 1 sialic acid, 1 galactose and 1 fucose residue. The polypeptide moiety has a high content of non-polar amino acids. A single amino acid, isoleucine, was found at the NH2-terminal end by dansyl and Edman procedures. The PO protein is the major protein of peripheral nerve myelin.

Biosynthesis of bacterial glycogen. Characterization of the subunit structure of Escherichia coli B glucose-1-phosphate adenylyltransferase (EC 2.7.7.27)

ADP-glucose pyrophosphorylase has been isolated in homogeneous form from an Escherichia coli B mutant, AC70R1, derepressed in the synthesis of glycogen synthetic enzymes. The enzyme has been found to be identical with the wild type enzyme with respect to kinetic properties, molecular weight, and immunological reactivity. The AC70R1 enzyme is composed of four identical subunits of molecular weight of approximately 50,000. This is based on the findings that: (a) gel electrophoresis under denaturing conditions shows only one component; (b) tryptic mapping shows only enough peptides to account for a single polypeptide subunit; (c) digestion with carboxypeptidase B releases stoichiometric amounts of arginine; and (d) NH2-terminal sequencing shows a single sequence for the first 27 residues.