Three-Day Dietary Manipulation in Multiple Sclerosis: Exercise and Fatigue Outcomes

Background

In persons with multiple sclerosis (MS), the effect of nutrition on exercise performance and fatigue remains unknown. The objective was to determine whether a 3-day diet high in triglycerides (FAT) compared with a 3-day diet high in carbohydrates (CARB) would improve fatigue and exercise performance in persons with MS.

Methods

A randomized controlled crossover design was incorporated to study FAT versus CARB on submaximal cycling endurance (60% of peak oxygen consumption), substrate utilization, and fatigue in 12 persons with mild-to-moderate MS (Expanded Disability Status Scale score, 2.0-5.0) and 12 age- and sex-matched controls.

Results

There were no differences in cycling time between diets in either group (P = .29). The MS group had no changes in fatigue between diets (P = .64); the control group demonstrated increased total mental fatigue after FAT (P = .05). The control group increased carbohydrate oxidation by 24% at rest and 13% during exercise after CARB. Similarly, the control group significantly increased fat oxidation after FAT by 22% at rest and 68% during exercise (P = .01). These changes were not seen in the MS group. Compared with controls, persons with MS oxidized approximately 50% less fat during exercise after FAT (P = .05).

Conclusions

Neither CARB nor FAT altered submaximal exercise performance or baseline fatigue in the MS group. The results suggest that persons with MS are unable to adapt to dietary changes and oxidize fatty acids as efficiently as controls.

Computed tomography findings of metabolic syndrome in patients with acute colonic diverticulitis

INTRODUCTION

Many factors associated with colonic diverticulitis are also part of the clinical definition of the metabolic syndrome. Computed tomography (CT) is commonly performed in symptomatic patients, such as those with suspected or known acute diverticulitis, and could add additional value for the health of these patients by identifying and reporting CT biomarkers of metabolic syndrome, if present and detectable. The purpose of this study was to identify CT biomarkers of metabolic syndrome in patients with acute colonic diverticulitis.

METHODS

We retrospectively reviewed 243 patients (mean-60 yrs, M:F:126:117) diagnosed with colonic diverticulitis on CT between March 2015 and March 2017 for hepatic steatosis, vascular calcifications, abdominal diameters and fat volumes. Criteria of metabolic syndrome were obtained from medical records. Differences in imaging biomarkers were compared using chi-square comparisons stratified by metabolic syndrome, abdominal diameter and fat volume.

RESULTS

Of 243 patients, 33% demonstrated hepatic steatosis and 71% atherosclerotic vascular calcifications on CT. 28% met criteria for metabolic syndrome. Patients with metabolic syndrome had higher occurrence of hepatic steatosis, sagittal diameter ≥ 35 cm, visceral fat > 5000 cm³ and subcutaneous fat > 8300 cm³ (P < 0.05), but not vascular calcifications (P > 0.05).

CONCLUSIONS

CT biomarkers of metabolic syndrome are commonly encountered in patients with acute diverticulitis. Recognizing and reporting these findings can guide towards further evaluation for metabolic syndrome.

Impact of Nutritional Intake on Function in People with Mild-to-Moderate Multiple Sclerosis

Background

We sought to assess the associations between nutrition and ambulation, daily activity, quality of life (QOL), and fatigue in individuals with mild-to-moderate disability with multiple sclerosis (MS).

Methods

This cross-sectional pilot study included 20 ambulatory adult volunteers with MS (14 women and 6 men; mean ± SD age, 57.9 ± 10.2 years; mean ± SD Expanded Disability Status Scale score = 4.1 ± 1.8). Primary outcome variables included dietary assessment and the 6-Minute Walk Test (6MWT). Secondary measures included the Timed 25-Foot Walk test, Timed Up and Go test, daily activity, and three self-report questionnaires: the 12-item Multiple Sclerosis Walking Scale, the 36-item Short Form Health Survey (SF-36), and the Modified Fatigue Impact Scale.

Results

Significant correlations were seen between the percentage of diet comprising fats and the 6MWT (r = 0.51, P = .02) and the physical functioning component of the SF-36 (r = 0.47, P = .03). The percentage of carbohydrates was significantly correlated with the 6MWT (r = -0.43, P = .05), daily activity (r = -0.59, P = .005), and the physical functioning component of the SF-36 (r = -0.47, P = .03). Cholesterol, folate, iron, and magnesium were significantly positively correlated with the physical functioning component of the SF-36 and the 6MWT.

Conclusions

These findings indicate better ambulation, daily function, and QOL with increased fat intake, decreased carbohydrate intake, and increased intake of the micronutrients cholesterol, folate, iron, and magnesium in people with mild-to-moderate MS. This pilot study highlights the potential impact of diet on function and QOL in MS.

Validity and Reliability of Four Clinical Gait Measures in Patients with Multiple Sclerosis

BACKGROUND

The gold standards for assessing ambulation are the Expanded Disability Status Scale (EDSS) and the Timed 25-Foot Walk (T25FW) test. In relation with these measures, we assessed the reliability and validity of four clinical gait measures: the Timed Up and Go (TUG) test, the Dynamic Gait Index (DGI), the 2-Minute Walk Test (2MWT), and the 6-Minute Walk Test (6MWT). Patient self-report of gait was also assessed using the 12-item Multiple Sclerosis Walking Scale (MSWS-12).

METHODS

Individuals 20 years or older with a diagnosis of multiple sclerosis (MS) and an EDSS score of 2.0 to 6.5 completed the MSWS-12, T25FW test, TUG test, DGI, 2MWT, and 6MWT. All the tests were repeated 2 weeks later at the same time of day to establish their reliability and concurrent validity. Predictive validity was established using the EDSS.

RESULTS

Forty-two patients with MS were included. All measures showed high test-retest reliability. The TUG test, 2MWT, and 6MWT were significantly correlated with the T25FW test (Spearman ρ = -0.902, -0.919, and -0.905, respectively). The EDSS was also significantly correlated with all the walking tests. The MSWS-12 demonstrated the highest correlation to the EDSS (ρ = 0.788).

CONCLUSIONS

The TUG test, the DGI, the 2MWT, and the 6MWT exhibited strong psychometric properties and were found to be significant predictors of the EDSS score. Use of these tests to prospectively monitor the effects of medical and rehabilitation treatment should be considered in the comprehensive care of patients with MS.

HDAC1,2 inhibition and doxorubicin impair Mre11-dependent DNA repair and DISC to override BCR-ABL1-driven DSB repair in Philadelphia chromosome-positive B-cell precursor acute lymphoblastic leukemia

Philadelphia chromosome-positive (Ph+) B-cell precursor acute lymphoblastic leukemia (ALL) expressing BCR-ABL1 oncoprotein is a major subclass of ALL with poor prognosis. BCR-ABL1-expressing leukemic cells are highly dependent on double-strand break (DSB) repair signals for their survival. Here we report that a first-in-class HDAC1,2 selective inhibitor and doxorubicin (a hyper-CVAD chemotherapy regimen component) impair DSB repair networks in Ph+ B-cell precursor ALL cells using common as well as distinct mechanisms. The HDAC1,2 inhibitor but not doxorubicin alters nucleosomal occupancy to impact chromatin structure, as revealed by MNase-Seq. Quantitative mass spectrometry of the chromatin proteome along with functional assays showed that the HDAC1,2 inhibitor and doxorubicin either alone or in combination impair the central hub of DNA repair, the Mre11–Rad51–DNA ligase 1 axis, involved in BCR-ABL1-specific DSB repair signaling in Ph+ B-cell precursor ALL cells. HDAC1,2 inhibitor and doxorubicin interfere with DISC (DNA damage-induced transcriptional silencing in cis)) or transcriptional silencing program in cis around DSB sites via chromatin remodeler-dependent and -independent mechanisms, respectively, to further impair DSB repair. HDAC1,2 inhibitor either alone or when combined with doxorubicin decreases leukemia burden in vivo in refractory Ph+ B-cell precursor ALL patient-derived xenograft mouse models. Overall, our novel mechanistic and preclinical studies together demonstrate that HDAC1,2 selective inhibition can overcome DSB repair ‘addiction’ and provide an effective therapeutic option for Ph+ B-cell precursor ALL.

A Framework of Care in Multiple Sclerosis, Part 2: Symptomatic Care and Beyond

The Consortium of Multiple Sclerosis Centers (CMSC) convened a Framework Taskforce composed of a multidisciplinary group of clinicians and researchers to examine and evaluate the current models of care in multiple sclerosis (MS). The methodology of this project included analysis of a needs assessment survey and an extensive literature review. The outcome of this work is a two-part continuing education series of articles. Part 1, published previously, covered the updated disease phenotypes of MS along with recommendations for the use of disease-modifying therapies. Part 2, presented herein, reviews the variety of symptoms and potential complications of MS. Mobility impairment, spasticity, pain, fatigue, bladder/bowel/sexual dysfunction, cognitive dysfunction, and neuropsychiatric issues are examined, and both pharmacologic and nonpharmacologic interventions are described. Because bladder and bowel symptoms substantially affect health-related quality of life, detailed information about elimination dysfunction is provided. In addition, a detailed discussion about mental health and cognitive dysfunction in people with MS is presented. Part 2 concludes with a focus on the role of rehabilitation in MS. The goal of this work is to facilitate the highest levels of independence or interdependence, function, and quality of life for people with MS.

CME/CNE Article: A Framework of Care in Multiple Sclerosis, Part 1: Updated Disease Classification and Disease-Modifying Therapy Use in Specific Circumstances

Activity Available Online: To access the article, post-test, and evaluation online, go to http://www.cmscscholar.org.

TARGET AUDIENCE

The target audience for this activity is physicians, physician assistants, nursing professionals, and other health-care providers involved in the management of patients with multiple sclerosis (MS).

LEARNING OBJECTIVES

Apply new information about MS to a comprehensive individualized treatment plan for patients with MSIntegrate the team approach into long-term planning in order to optimize rehabilitation care of patients with MSAccreditation Statement: This activity has been planned and implemented in accordance with the accreditation requirements and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint providership of the Consortium of Multiple Sclerosis Centers (CMSC), Nurse Practitioner Alternatives (NPA), and Delaware Media Group. The CMSC is accredited by the ACCME to provide continuing medical education for physicians. The CMSC designates this journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity. Nurse Practitioner Alternatives (NPA) is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's Commission on Accreditation. NPA designates this enduring material for 1.0 Continuing Nursing Education credit. Laurie Scudder, DNP, NP, has served as Nurse Planner for this activity. She has disclosed no relevant financial relationships. Disclosures: Francois Bethoux, MD, Editor in Chief of the International Journal of MS Care (IJMSC), has served as Physician Planner for this activity. He has received royalties from Springer Publishing and has received intellectual property rights from Biogen. Laurie Scudder, DNP, NP, has served as Nurse Planner for this activity. She has disclosed no relevant financial relationships. Scott D. Newsome, DO, MSCS (author), has served on scientific advisory boards for Biogen, Genentech, Novartis, and Genzyme, and has performed contracted research (institution received funds) for Biogen, Genentech, and Novartis. Philip J. Aliotta, MD, MSHA, CHCQM, FACS (author), has served on speakers' bureaus for Astellas Pharma, Actavis, Augmenix, and Allergan and has performed contracted research for Allergan. Jacquelyn Bainbridge, PharmD (author), has disclosed no relevant financial relationships. Susan E. Bennett, PT, DPT, EdD, NCS, MSCS (author), has served on speakers' bureaus for Acorda Therapeutics, Biogen, and Medtronic; has received consulting fees from and performed contracted research for Acorda Therapeutics; and is chair of the Clinical Events Committee at Innovative Technologies. Gary Cutter, PhD (author), has participated on Data and Safety Monitoring Committees for AMO Pharma, Apotek, Gilead Pharmaceuticals, Horizon Pharmaceuticals, Modigenetech/Prolor, Merck, Merck/Pfizer, Opko Biologics, Neuren, Sanofi-Aventis, Reata Pharmaceuticals, Receptos/Celgene, Teva Pharmaceuticals, NHLBI (Protocol Review Committee), and NICHD (OPRU Oversight Committee); has received consulting fees from and/or served on speakers' bureaus and scientific advisory boards for Cerespir, Genzyme, Genentech, Innate Therapeutics, Janssen Pharmaceuticals, Klein-Buendel Incorporated, MedImmune, Medday, Nivalis, Novartis, Opexa Therapeutics, Roche, Savara, Somahlution, Teva Pharmaceuticals, Transparency Life Sciences, and TG Therapeutics; and is President of Pythagoras, Inc., a private consulting company located in Birmingham, AL. Kaylan Fenton, CRNP, APNP, MSCN (author), has disclosed no relevant financial relationships. Fred Lublin, MD (author), has received consulting fees/fees for non-CME/CE activities from Bayer HealthCare Pharmaceuticals, Biogen, EMD Serono, Novartis, Teva Neuroscience, Actelion, Sanofi/Genzyme, Acorda, Questcor/Mallinckrodt, Roche/Genentech, MedImmune, Osmotica, Xenoport, Receptos/Celgene, Forward Pharma, Akros, TG Therapeutics, AbbVie, Toyama, Amgen, Medday, Atara Biotherapeutics, Polypharma, Pfizer, Johnson & Johnson, Revalesio, Coronado Bioscience, and Bristol-Myers Squibb; has served on speakers' bureaus for Genentech/Roche and Genzyme/Sanofi; has performed contracted research for Acorda, Biogen, Novartis, Teva Neuroscience, Genzyme, Xenoport, and Receptos; is the co-chief editor of Multiple Sclerosis and Related Disorders; and has an ownership interest in Cognition Pharmaceuticals. Dorothy Northrop, MSW, ACSW (author), has disclosed no relevant financial relationships. David Rintell, EdD (author), has received consulting fees from Novartis and has served as a patient education speaker for Teva Neuroscience. He started as a salaried employee of Sanofi Genzyme in November 2015. Dr. Rintell's work on this project was completed before he became a salaried employee of Sanofi Genzyme.Bryan D. Walker, MHS, PA-C (author), has served on scientific advisory boards for EMD Serono and Sanofi Genzyme and owns stock in Biogen. Megan Weigel, DNP, ARNP-C, MSCN (author), has received consulting fees from Mallinckrodt, Genzyme, and Genentech, and has served on speakers' bureaus for Bayer Corp, Acorda Therapeutics, Teva Neuroscience, Biogen, Mallinckrodt, Genzyme, Novartis, and Pfizer. Kathleen Zackowski, PhD, OTR, MSCS (author), has performed contracted research for Acorda Therapeutics. David E. Jones, MD (author), has received consulting fees from Biogen and Novartis, and has performed contracted research for Biogen. One anonymous peer reviewer for the IJMSC has performed contracted research (institution received funds) for Novartis, Chugai, and Biogen. Another reviewer has received consulting fees and served on speakers' bureaus for Biogen, Sanofi Genzyme, Genentech, EMD Serono, and Novartis. The third reviewer has disclosed no relevant financial relationships. Lori Saslow, MS (medical writer), has disclosed no relevant financial relationships. The staff at the IJMSC, CMSC, NPA, and Delaware Media Group who are in a position to influence content have disclosed no relevant financial relationships. Note: Disclosures listed for authors are those applicable at the time of their work on this project and within 12 months previously. Financial relationships for some authors may have changed in the interval between the time of their work on this project and publication of the article. Funding/Support: Funding for the Framework of Care consensus conference was provided by the Consortium of Multiple Sclerosis Centers, Mallinckrodt Pharmaceuticals, and Mylan Pharmaceuticals. Method of Participation: Release Date: December 1, 2016 Valid for Credit Through: December 1, 2017 In order to receive CME/CNE credit, participants must: Review the CME/CNE information, including learning objectives and author disclosures.Study the educational content.Complete the post-test and evaluation, which are available at http://www.cmscscholar.org. Statements of Credit are awarded upon successful completion of the post-test with a passing score of >70% and the evaluation. There is no fee to participate in this activity. Disclosure of Unlabeled Use: This CME/CNE activity may contain discussion of published and/or investigational uses of agents that are not approved by the FDA. CMSC, NPA, and Delaware Media Group do not recommend the use of any agent outside of the labeled indications. The opinions expressed in the educational activity are those of the faculty and do not necessarily represent the views of CMSC, NPA, or Delaware Media Group. Disclaimer: Participants have an implied responsibility to use the newly acquired information to enhance patient outcomes and their own professional development. The information presented in this activity is not meant to serve as a guideline for patient management. Any medications, diagnostic procedures, or treatments discussed in this publication should not be used by clinicians or other health-care professionals without first evaluating their patients' conditions, considering possible contraindications or risks, reviewing any applicable manufacturer's product information, and comparing any therapeutic approach with the recommendations of other authorities.

Best Practices for Intrathecal Baclofen Therapy: Screening Test

INTRODUCTION

Intrathecal baclofen (ITB) screening assesses response to a test dose of ITB on spasticity and function and identifies adverse reactions.

METHOD

An expert panel consulted on best practices after conducting an extensive literature search and conducting an online survey.

RESULTS

A successful trial may confirm predetermined goals, which may include improved mobility/positioning, decreased time/improved independence for activities, less home exercise, better wheelchair tolerance, decreased caregiver time, improved sleep, and reduced pain, or may modify goals and expectations. Individuals should not be tested in the presence of active medical issues (e.g., MS exacerbations, active urinary tract infection, nonhealing wounds). Oral antispasmodics can be weaned before trial if a goal is to eliminate them. The standard baclofen test dose is a 50-mcg bolus, 25 mcg in very small children or patients who rely on spasticity for mobility. Patients unresponsive to the standard dose may require 75 mcg or 100 mcg; 24 hours should elapse between bolus doses. Cardiopulmonary parameters should be checked frequently during the first two hours postinjection, and spasticity measures assessed at least twice within four hours. Observation continues until the patient is stable and recovers from hypertonia. Adverse events include spinal headaches, nausea/vomiting, urinary retention, hypotension, seizures, drowsiness/sedation, respiratory depression, and coma. Before implantation, team members must discuss starting dose, drug concentration, delivery mode, pump size and location, and catheter tip placement. Patients/caregivers should understand the commitment necessary for ITB therapy.

CONCLUSIONS

Screening helps identify appropriate candidates for ITB.

Selecting Rehabilitation Outcome Measures for People with Multiple Sclerosis

Despite the well-known benefits of using standardized outcome measures (OMs) in clinical practice, a variety of barriers interfere with their use. In particular, rehabilitation therapists lack sufficient knowledge in selecting appropriate OMs. The challenge is compounded when working with people with multiple sclerosis (MS) owing to heterogeneity of the patient population and symptom variability in individual patients. To help overcome these barriers, the American Physical Therapy Association appointed the Multiple Sclerosis Outcome Measures Task Force to review and make evidence-based recommendations for OM use in clinical practice, education, and research specific to people with MS. Sixty-three OMs were reviewed based on their clinical utility, psychometric properties, and a consensus evaluation of the appropriateness of use for people with MS. We sought to illustrate use of the recommendations for two cases. The first case involves a 43-year-old man with new-onset problems after an exacerbation. The second case pertains to an outpatient clinic interested in assessing the effectiveness of their MS rehabilitation program. For each case, clinicians identified areas that were important to assess and various factors deemed important for OM selection. Criteria were established and used to assist in OM selection. In both cases, the described processes narrowed the selection of OMs and assisted with choosing the most appropriate ones. The recommendations, in addition to the processes described in these two cases, can be used by clinicians in any setting working with patients with MS across the disability spectrum.

3-Epi-25 hydroxyvitamin D in pregnancy

OBJECTIVE

The physiological importance of the C3 epimers of vitamin D (3-epi-25OHD2/3) is uncertain and there have been limited studies determining the levels of these epimers in human populations. The aims of the current study were (1) to determine 3-epi-25OHD2/3 levels throughout non-diabetic and T1DM pregnancy, (2) to examine the relationships between 25OHD and 3-epi-25OHD, (3) to assess the impact of maternal BMI on 3-epi-25OHD and examine associations with markers of glycaemic control.

METHODOLOGY

An observational study of 52 pregnant controls without diabetes and 65 pregnant women with T1DM in a university teaching hospital. 25OHD and 3-epi-25OHD were measured by liquid chromatography tandem mass spectrometry.

RESULTS

3-Epi-25OHD was found in 90.2% of control (median 0.9nmol/L; range 0.1-5.9nmol/L), and in 94.5% of T1DM, women (median 1.4nmol/L; range 0.1-10.5nmol/L). In both control and T1DM groups, maternal and cord 3-epi-25OHD correlated significantly with 25OHD. Seasonal variation in maternal 3-epi-25OHD levels was evident in both groups; Summer levels were significantly higher than all other seasons in the control group (p<0.001) and significantly higher than Spring (p=0.003) and Winter (p<0.001) in the T1DM group. In T1DM women HbA1c was significantly negatively correlated with 3-epi-25OHD at trimesters 1 and 2 (p=0.049; p=0.001) and with cord 3-epi-25OHD (p=0.012). Maternal BMI >30kg/m(2) had a significant negative impact on 3-epi-25OHD.

CONCLUSION

Maternal 3-epi-25OHD exhibits seasonal variation and, in common with cord 3-epi-25OHD, correlates with 25OHD throughout both non-diabetic and T1D pregnancy. In T1DM women 3-epi-25OHD is associated with a key marker of glycaemic control.

Intrathecal baclofen in multiple sclerosis: Too little, too late?

The majority of patients with multiple sclerosis (MS) have symptoms of spasticity that increasingly impair function as the disease progresses. With appropriate treatment, however, quality of life can be improved. Oral antispasticity medications are useful in managing mild spasticity but are frequently ineffective in controlling moderate to severe spasticity, because patients often cannot tolerate the adverse effects of increasing doses. Intrathecal baclofen (ITB) therapy can be an effective alternative to oral medications in patients who have a suboptimal response to oral medications or who cannot tolerate dose escalation or multidrug oral regimens. ITB therapy may be underutilized in the MS population because clinicians (a) are more focused on disease-modifying therapies rather than symptom control, (b) underestimate the impact of spasticity on quality of life, and (c) have concerns about the cost and safety of ITB therapy. Delivery of ITB therapy requires expertly trained staff and proper facilities for pump management. This article summarizes the findings and recommendations of an expert panel on the use of ITB therapy in the MS population and the role of the physician and comprehensive care team in patient selection, screening, and management.

Imaging dislocations in gallium nitride across broad areas using atomic force microscopy

We have employed an atomic force microscope with a high sampling rate to image GaN samples grown using an epitaxial layer overgrowth technique and treated with silane and ammonia to enlarge the surface pits associated with threading dislocations (TDs). This allows TDs to be identified in high pixel density images tens of microns in size providing detailed information about the spatial distribution of the TDs. An automated software tool has been developed, which identifies the coordinates of the TDs in the image. Additionally, we have imaged the same sample using Kelvin probe force microscopy, again at high pixel density, providing data about the local changes in surface potential associated with hundreds of dislocations.

Effective Rehabilitation Methods in Patients with Multiple Sclerosis

The role of rehabilitation in managing symptoms of multiple sclerosis (MS) and promoting functional recovery has grown exponentially over the past 12 years. Evidence now supports strength and aerobic training for individuals with mild or moderate disease. An emerging body of evidence suggests that exercise may play a role in the production of brain-derived neurotrophic factor in individuals with MS, and the combination of pharmacological management and rehabilitation may produce better outcomes than one therapeutic intervention alone. Rehabilitation and exercise should be a major focus in the comprehensive management of MS.

Reliability of the Dynamic Gait Index in individuals with multiple sclerosis

OBJECTIVES

To determine if the Dynamic Gait Index (DGI) is a reliable tool for assessing balance in people with multiple sclerosis (MS) and to determine the validity of the DGI by using the 6.1-m timed walk.

DESIGN

Instrument reliability test: physical therapists viewed a videotape of 10 subjects with MS performing the DGI and scored their gait by using DGI criteria. Two weeks after the first session, therapists' viewed the videotape again and scored subjects' gait to establish interrater reliability.

SETTING

Hospital-based outpatient rehabilitation clinic.

PARTICIPANTS

Eleven physical therapists and 10 people with MS.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Total DGI scores and each of the 8 DGI items were compared between and within raters (physical therapists). Time to walk 6.1m was compared with the total DGI score to examine concurrent validity.

RESULTS

Interrater reliability for total DGI scores was .983, with each of the 8 items ranging from .910 to .976 (intraclass correlation coefficient, P<.05). Intrarater reliability for total DGI scores ranged between .760 and .986 (Pearson bivariate analysis, P<.05). An inverse relationship of -.801 (Pearson bivariate analysis, P<.01) existed between the total DGI scores and the 6.1-m walk.

CONCLUSIONS

The DGI is a reliable functional assessment tool that correlated inversely with timed walk, showing its concurrent validity.

What Constitutes Advanced Assessment?

As programs to prepare advanced practice nurses for primary care have flourished during the past decade, faculty aspire to teach a health assessment course that is more than a review of undergraduate work. Therefore, course faculty constructed a list of advanced assessment competencies. The purpose of this descriptive study was to validate the competencies clinical preceptors' rated as important via a mailed survey. Overall, the competencies received high mean ratings. The item receiving the highest mean score was "detects and interprets abnormalities in rate and rhythm" from the heart body system. Items within the gynecological and breast systems received the highest ratings. This study suggests a need to help advanced practice nursing students master all advanced assessment competencies on the survey.

Active range of motion utilized in the cervical spine to perform daily functional tasks

This was a descriptive study to examine active range of motion required in the cervical spine during functional tasks of daily living. The objective of this study was to determine the mean active range of motion of the cervical spine required to perform 13 daily functional tasks. Previous research has examined the absolute ranges of cervical motion for women and men 20-60 years of age; however, no previous study has determined the amount and type of motion that is required for routine activities of daily living. Twenty-eight college-aged students (n = 28) served as healthy subjects and performed three trials of 13 daily tasks of functional activity. The subject's starting position and end range of motion for flexion-extension, rotation, and side bending of each task were observed and recorded using the cervical range of motion device. The three trials were averaged, and ranges of motion across the 28 subjects were reported. Of the 13 daily functional tasks performed, tying shoes (flexion-extension 66.7 degrees), backing up a car (rotation 67.6 degrees), washing hair in the shower (flexion-extension 42.9 degrees), and crossing the street (rotation head left 31.7 degrees and rotation head right 54.3 degrees) required the greatest full active range of motion of the cervical spine. Flexion-extension and rotation of the cervical spine are important to enable functional activity. Four of the 13 daily tasks performed required 30-50% of active range of motion. Side bending was seen to be coupled with rotation in completion of tasks. This article provides a baseline of normal motion of the neck required for activities of daily living and can be used in the assessment of disease states and disability.

Uracil-initiated base excision DNA repair synthesis fidelity in human colon adenocarcinoma LoVo and Escherichia coli cell extracts

The error frequency of uracil-initiated base excision repair (BER) DNA synthesis in human and Escherichia coli cell-free extracts was determined by an M13mp2 lacZ alpha DNA-based reversion assay. Heteroduplex M13mp2 DNA was constructed that contained a site-specific uracil target located opposite the first nucleotide position of opal codon 14 in the lacZ alpha gene. Human glioblastoma U251 and colon adenocarcinoma LoVo whole-cell extracts repaired the uracil residue to produce form I DNA that was resistant to subsequent in vitro cleavage by E. coli uracil-DNA glycosylase (Ung) and endonuclease IV, indicating that complete uracil-initiated BER repair had occurred. Characterization of the BER reactions revealed that (1) the majority of uracil-DNA repair was initiated by a uracil-DNA glycosylase-sensitive to Ugi (uracil-DNA glycosylase inhibitor protein), (2) the addition of aphidicolin did not significantly inhibit BER DNA synthesis, and (3) the BER patch size ranged from 1 to 8 nucleotides. The misincorporation frequency of BER DNA synthesis at the target site was 5.2 x 10(-4) in U251 extracts and 5.4 x 10(-4) in LoVo extracts. The most frequent base substitution errors in the U251 and LoVo mutational spectrum were T to G > T to A >> T to C. Uracil-initiated BER DNA synthesis in extracts of E. coli BH156 (ung) BH157 (dug), and BH158 (ung, dug) was also examined. Efficient BER occurred in extracts of the BH157 strain with a misincorporation frequency of 5.6 x 10(-4). A reduced, but detectable level of BER was observed in extracts of E. coli BH156 cells; however, the mutation frequency of BER DNA synthesis was elevated 6.4-fold.

Fidelity of uracil-initiated base excision DNA repair in DNA polymerase beta-proficient and -deficient mouse embryonic fibroblast cell extracts

Uracil-initiated base excision DNA repair was conducted using homozygous mouse embryonic fibroblast DNA polymerase beta (+/+) and (-/-) cells to determine the error frequency and mutational specificity associated with the completed repair process. Form I DNA substrates were constructed with site-specific uracil residues at U.A, U.G, and U.T targets contained within the lacZalpha gene of M13mp2 DNA. Efficient repair was observed in both DNA polymerase beta (+/+) and (-/-) cell-free extracts. Repair was largely dependent on uracil-DNA glycosylase activity because addition of the PBS-2 uracil-DNA glycosylase inhibitor (Ugi) protein reduced ( approximately 88%) the initial rate of repair in both types of cell-free extracts. In each case, the DNA repair patch size was primarily distributed between 1 and 8 nucleotides in length with 1 nucleotide repair patch constituting approximately 20% of the repair events. Addition of p21 peptide or protein to DNA polymerase beta (+/+) cell-free extracts increased the frequency of short-patch (1 nucleotide) repair by approximately 2-fold. The base substitution reversion frequency associated with uracil-DNA repair of M13mp2op14 (U.T) DNA was determined to be 5.7-7.2 x 10(-4) when using DNA polymerase beta (+/+) and (-/-) cell-free extracts. In these two cases, the error frequency was very similar, but the mutational spectrum was noticeably different. The presence or absence of Ugi did not dramatically influence either the error rate or mutational specificity. In contrast, the combination of Ugi and p21 protein promoted an increase in the mutation frequency associated with repair of M13mp2 (U.G) DNA. Examination of the mutational spectra generated by a forward mutation assay revealed that errors in DNA repair synthesis occurred predominantly at the position of the U.G target and frequently involved a 1-base deletion or incorporation of dTMP.

Who should be screened for asymptomatic carotid artery stenosis? Experience from the Western New York Stroke Screening Program

OBJECTIVE

Identification of significant asymptomatic carotid artery stenosis (ACAS) is important because of the stroke-risk reduction observed with carotid endarterectomy. The authors developed and validated a simple scoring system based on routinely available information to identify persons at high risk for ACAS using data collected during a community health screening program at various sites in western New York. A total of 1331 unselected volunteers without previous stroke, transient ischemic attack, or carotid artery surgery were evaluated by personal interview and duplex ultrasound. The main outcome measure was carotid artery stenosis > 60% by duplex ultrasound. In the derivation set (n = 887), 4 variables were significantly associated with ACAS > 60%: age > 65 years (odds ratio [OR] = 4.1, 95% confidence interval [CI] = 2.6-6.7), current smoking (OR = 2.0, 95% CI = 1.2-3.5), coronary artery disease (OR = 2.4, 95% CI = 1.5-3.9), and hypercholesterolemia (OR = 1.9, 95% CI = 1.2-2.9). Three risk groups (low, intermediate, and high) were defined on the basis of total risk score assigned on the basis of the strength of association. The scheme effectively stratified the validation set (n = 444); the likelihood ratio and posttest probability for ACAS in the high-risk group were 3.0 and 35%, respectively, and in the intermediate and low-risk groups were 1.4 and 20% and 0.4 and 7%, respectively. Routinely available information can be used to identify persons in the community at high risk for ACAS. Doppler ultrasound screening in this subgroup may prove to be cost-effective and have an effect on stroke-free survival.

Inactivation of DNA mismatch repair by increased expression of yeast MLH1

Inactivation of DNA mismatch repair by mutation or by transcriptional silencing of the MLH1 gene results in genome instability and cancer predisposition. We recently found (P. V. Shcherbakova and T. A. Kunkel, Mol. Cell. Biol. 19:3177-3183, 1999) that an elevated spontaneous mutation rate can also result from increased expression of yeast MLH1. Here we investigate the mechanism of this mutator effect. Hybridization of poly(A)(+) mRNA to DNA microarrays containing 96.4% of yeast open reading frames revealed that MLH1 overexpression did not induce changes in expression of other genes involved in DNA replication or repair. MLH1 overexpression strongly enhanced spontaneous mutagenesis in yeast strains with defects in the 3'-->5' exonuclease activity of replicative DNA polymerases delta and epsilon but did not enhance the mutation rate in strains with deletions of MSH2, MLH1, or PMS1. This suggests that overexpression of MLH1 inactivates mismatch repair of replication errors. Overexpression of the PMS1 gene alone caused a moderate increase in the mutation rate and strongly suppressed the mutator effect caused by MLH1 overexpression. The mutator effect was also reduced by a missense mutation in the MLH1 gene that disrupted Mlh1p-Pms1p interaction. Analytical ultracentrifugation experiments showed that purified Mlh1p forms a homodimer in solution, albeit with a K(d) of 3.14 microM, 36-fold higher than that for Mlh1p-Pms1p heterodimerization. These observations suggest that the mismatch repair defect in cells overexpressing MLH1 results from an imbalance in the levels of Mlh1p and Pms1p and that this imbalance might lead to formation of nonfunctional mismatch repair complexes containing Mlh1p homodimers.

Fidelity of uracil-initiated base excision DNA repair in Escherichia coli cell extracts

The error frequency and mutational specificity associated with Escherichia coli uracil-initiated base excision repair were measured using an M13mp2 lacZalpha DNA-based reversion assay. Repair was detected in cell-free extracts utilizing a form I DNA substrate containing a site-specific uracil residue. The rate and extent of complete uracil-DNA repair were measured using uracil-DNA glycosylase (Ung)- or double-strand uracil-DNA glycosylase (Dug)-proficient and -deficient isogenic E. coli cells. In reactions utilizing E. coli NR8051 (ung(+) dug(+)), approximately 80% of the uracil-DNA was repaired, whereas about 20% repair was observed using NR8052 (ung(-) dug(+)) cells. The Ung-deficient reaction was insensitive to inhibition by the PBS2 uracil-DNA glycosylase inhibitor protein, implying the involvement of Dug activity. Under both conditions, repaired form I DNA accumulated in conjunction with limited DNA synthesis associated with a repair patch size of 1-20 nucleotides. Reactions conducted with E. coli BH156 (ung(-) dug(+)), BH157 (ung(+) dug(-)), and BH158 (ung(-) dug(-)) cells provided direct evidence for the involvement of Dug in uracil-DNA repair. The rate of repair was 5-fold greater in the Ung-proficient than in the Ung-deficient reactions, while repair was not detected in reactions deficient in both Ung and Dug. The base substitution reversion frequency associated with uracil-DNA repair was determined to be approximately 5.5 x 10(-)(4) with transversion mutations dominating the mutational spectrum. In the presence of Dug, inactivation of Ung resulted in up to a 7.3-fold increase in mutation frequency without a dramatic change in mutational specificity.

WRN helicase expression in Werner syndrome cell lines

Mutations in the chromosome 8p WRN gene cause Werner syndrome (WRN), a human autosomal recessive disease that mimics premature aging and is associated with genetic instability and an increased risk of cancer. All of the WRN mutations identified in WRN patients are predicted to truncate the WRN protein with loss of a C-terminal nuclear localization signal. However, many of these truncated proteins would retain WRN helicase and/or nuclease functional domains. We have used a combination of immune blot and immune precipitation assays to quantify WRN protein and its associated 3'-->5' helicase activity in genetically characterized WRN patient cell lines. None of the cell lines from patients harboring four different WRN mutations contained detectable WRN protein or immune-precipitable WRN helicase activity. Cell lines from WRN heterozygous individuals contained reduced amounts of both WRN protein and helicase activity. Quantitative immune blot analyses indicate that both lymphoblastoid cell lines and fibroblasts contain approximately 6 x 10(4)WRN molecules/cell. Our results indicate that most WRN mutations result in functionally equivalent null alleles, that WRN heterozygote effects may result from haploinsufficiency and that successful modeling of WRN pathogenesis in the mouse or in other model systems will require the use of WRN mutations that eliminate WRN protein expression.

Mutation of an active site residue in Escherichia coli uracil-DNA glycosylase: effect on DNA binding, uracil inhibition and catalysis

The role of the conserved histidine-187 located in the leucine intercalation loop of Escherichia coli uracil-DNA glycosylase (Ung) was investigated. Using site-directed mutagenesis, an Ung H187D mutant protein was created, overproduced, purified to apparent homogeneity, and characterized in comparison to wild-type Ung. The properties of Ung H187D differed from Ung with respect to specific activity, substrate specificity, DNA binding, pH optimum, and inhibition by uracil analogues. Ung H187D exhibited a 55000-fold lower specific activity and a shift in pH optimum from pH 8.0 to 7.0. Under reaction conditions optimal for wild-type Ung (pH 8.0), the substrate preference of Ung H187D on defined single- and double-stranded oligonucleotides (25-mers) containing a site-specific uracil target was U/G-25-mer > U-25-mer > U/A-25-mer. However, Ung H187D processed these same DNA substrates at comparable rates at pH 7.0 and the activity was stimulated approximately 3-fold relative to the U-25-mer substrate. Ung H187D was less susceptible than Ung to inhibition by uracil, 6-amino uracil, and 5-fluorouracil. Using UV-catalyzed protein/DNA cross-linking to measure DNA binding affinity, the efficiency of Ung H187D binding to thymine-, uracil-, and apyrimidinic-site-containing DNA was (dT20) = (dT19-U) >/= (dT19-AP). Comparative analysis of the biochemical properties and the X-ray crystallographic structures of Ung and Ung H187D [Putnam, C. D., Shroyer, M. J. N., Lundquist, A. J., Mol, C. D., Arvai, A. S., Mosbaugh, D. W., and Tainer, J. A. (1999) J. Mol. Biol. 287, 331-346] provided insight regarding the role of His-187 in the catalytic mechanism of glycosylic bond cleavage. A novel mechanism is proposed wherein the developing negative charge on the uracil ring and concomitant polarization of the N1-C1' bond is sustained by resonance effects and hydrogen bonding involving the imidazole side chain of His-187.

Highly mutagenic bypass synthesis by T7 RNA polymerase of site-specific benzo[a]pyrene diol epoxide-adducted template DNA

We have previously developed an in vitro system that allows quantitative evaluation of the fidelity of transcription during synthesis on a natural template in the presence of all four nucleotides. Here, we have employed this system using a TAA ochre codon reversion assay to examine the fidelity of transcription by T7 RNA polymerase past an adenine residue adducted at the N6-position with (-)-anti-trans- or (+)-anti-trans-benzo[a]pyrene diol epoxide (BPDE). T7 RNAP was capable of transcribing past either BPDE isomer to generate full-length run-off transcripts. The extent of bypass was found to be 32% for the (-)-anti-trans-isomer and 18% for the (+)-anti-trans-isomer. Transcription past both adducts was highly mutagenic. The reversion frequency of bypass synthesis of the (-)-anti-trans-isomer was elevated 11,000-fold and that of the (+)-anti-trans-isomer 6000-fold, relative to the reversion frequency of transcription on unadducted template. Adenine was misinserted preferentially, followed by guanine, opposite the adenine adducted with either BPDE isomer. Although base substitution errors were by far the most frequent mutation on the adducted template, three- and six-base deletions were also observed. These results suggest that transcriptional errors, particularly with regard to damage bypass, may contribute to the mutational burden of the cell.

Site-directed mutagenesis and characterization of uracil-DNA glycosylase inhibitor protein. Role of specific carboxylic amino acids in complex formation with Escherichia coli uracil-DNA glycosylase

Bacteriophage PBS2 uracil-DNA glycosylase inhibitor (Ugi) protein inactivates uracil-DNA glycosylase (Ung) by acting as a DNA mimic to bind Ung in an irreversible complex. Seven mutant Ugi proteins (E20I, E27A, E28L, E30L, E31L, D61G, and E78V) were created to assess the role of various negatively charged residues in the binding mechanism. Each mutant Ugi protein was purified and characterized with respect to inhibitor activity and Ung binding properties relative to the wild type Ugi. Analysis of the Ugi protein solution structures by nuclear magnetic resonance indicated that the mutant Ugi proteins were folded into the same general conformation as wild type Ugi. All seven of the Ugi proteins were capable of forming a Ung.Ugi complex but varied considerably in their individual ability to inhibit Ung activity. Like the wild type Ugi, five of the mutants formed an irreversible complex with Ung; however, the binding of Ugi E20I and E28L to Ung was shown to be reversible. The tertiary structure of [13C,15N]Ugi in complex with Ung was determined by solution state multi-dimensional nuclear magnetic resonance and compared with the unbound Ugi structure. Structural and functional analysis of these proteins have elucidated the two-step mechanism involved in Ung.Ugi association and irreversible complex formation.

Mismatch repair in extracts of Werner syndrome cell lines

Werner syndrome (WS) is an autosomal recessive disease, the phenotype of which is a caricature of premature aging. WS cells and cell lines display several types of genetic instability, and WS patients have an increased risk of developing cancer. The WS locus (WRN) encodes a protein that shows significant sequence homology to the RecQ family of DNA helicases. Because a DNA helicase may function in DNA mismatch repair, we examined extracts of WS cell lines for mismatch repair activity. Extracts from four different WS lymphoblastoid cell lines containing different WRN mutations and from three within-pedigree control cell lines were all proficient in mismatch repair. In marked contrast, extracts from three independent WS fibroblastoid cell lines were deficient in repair of base-base and insertion/deletion mismatches. Extracts of one of these lines restored activity to extracts of mismatch repair-deficient tumor cells with defined mutations in hMSH2, hMSH3, hMSH6, hMLH1, or hPMS2. This suggests that the WRN mutation in this fibroblast line is not a dominant negative inhibitor of mismatch repair activity and that the repair defect does not reside in these five known mismatch repair genes. Defective mismatch repair in fibroblastoid but not lymphoblastoid cells is consistent with the possibility that WRN protein could have a cell type- and/or tissue-specific role in mismatch repair. Alternatively, a mutation in WRN could predispose cells to mutations in other genes required for mismatch repair activity, at least one of which could be an unknown gene.

Performance of female college students and sexual abuse survivors on the Brief Symptom Inventory

The relation between childhood molestation and current adjustment, as measured by the Brief Symptom Inventory (BSI), was examined among women college students. Results suggest that the normative data available for the BSI are inappropriate for interpreting the performance of women college students and, particularly, students who have survived sexual abuse.

Tertiary structure of uracil-DNA glycosylase inhibitor protein

The Bacillus subtilis bacteriophage PBS2 uracil-DNA glycosylase inhibitor (Ugi) is an acidic protein of 84 amino acids that inactivates uracil-DNA glycosylase from diverse organisms. The secondary structure of Ugi consists of five anti-parallel beta-strands and two alpha-helices (Balasubramanian, S., Beger, R.D., Bennett, S.E., Mosbaugh, D.W., and Bolton, P.H. (1995) J. Biol. Chem. 270, 296-303). The tertiary structure of Ugi has been determined by solution state multidimensional nuclear magnetic resonance. The Ugi structure contains an area of highly negative electrostatic potential produced by the close proximity of a number of acidic residues. The unfavorable interactions between these acidic residues are apparently accommodated by the stability of the beta-strands. This negatively charged region is likely to play an important role in the binding of Ugi to uracil-DNA glycosylase.

Processivity of Escherichia coli and rat liver mitochondrial uracil-DNA glycosylase is affected by NaCl concentration

Escherichia coli uracil-DNA glycosylase was shown to catalyze the hydrolysis of a site-specific uracil residue from a defined single-stranded oligonucleotide (25-mer). With duplex 25-mer, the rate of uracil removal from double-stranded DNA containing a U.G mispair was approximately 2-fold greater than a U.A base pair. The mechanism by which E. coli and rat liver mitochondrial uracil-DNA glycosylase located sequential uracil residues within double-stranded DNA was investigated. Two concatemeric polynucleotide substrates were constructed by ligation of homologous 5'-end 32P-labeled 25-mer double-stranded oligonucleotides that contained either a site-specific U.G or U.A target site at intervals of 25 nucleotides along one strand of the DNA. Reaction of uracil-DNA glycosylase with these concatemeric DNAs, followed by alkaline hydrolysis of the resultant AP-sites, would produce predominantly [32P]25-mer products, if a processive mechanism was used to locate successive uracil residues, or oligomeric multiples of [32P]25-mer, if a distributive mode was exhibited. Both the bacterial and the mitochondrial enzymes were found to act processively on U.A- and U.G-containing DNA in the absence of NaCl, based on the initial rate of 25-mer produced relative to the total amount of uracil excised. Approximately 50% of the total uracil excised resulted in the release of 25-mer product. The addition of NaCl (> or = 50 mM) caused reduced processivity on both U.A- and U.G-containing DNA substrates. The mode of action of uracil-DNA glycosylase was very similar to that observed for the EcoRI endonuclease cleavage of restriction sites contained in the same DNA substrate which was used as a positive control.

Secondary structure of uracil-DNA glycosylase inhibitor protein

The Bacillus subtilis bacteriophage PBS2 uracil-DNA glycosylase inhibitor (Ugi) is an acidic protein of 84 amino acids that inactivates uracil-DNA glycosylase from diverse organisms (Wang, Z., and Mosbaugh, D. W. (1989) J. Biol. Chem. 264, 1163-1171). The secondary structure of Ugi has been determined by solution state multidimensional nuclear magnetic resonance. The protein adopts a single well defined structure consisting of five anti-parallel beta-strands and two alpha-helices. Six loop or turn regions were identified that contain approximately one half of the acidic amino acid residues and connect the beta-strands sequentially to one another. The secondary structure suggests which regions of Ugi may be involved in interactions with uracil-DNA glycosylase.

Human immune response to Pseudomonas aeruginosa mucoid exopolysaccharide (alginate) vaccine

Chronic lung infection with mucoid Pseudomonas aeruginosa is the major pathologic feature of cystic fibrosis. Previous studies suggested that a failure to produce opsonic antibody to the mucoid exopolysaccharide (MEP; also called alginate) capsule is associated with the maintenance of chronic bacterial infection. Provision of MEP-specific opsonic antibodies has therapeutic potential. To evaluate the ability of MEP to elicit opsonic antibodies, humans were immunized with two lots of MEP vaccine that differed principally in molecular size. Lot 2 had a larger average MEP polymer size. Both vaccines were well tolerated, but lot 1 was poorly immunogenic, inducing long-lived opsonic antibodies in only 2 of 28 vaccinates given doses of 10 to 150 micrograms. In contrast, at the optimal dose of 100 micrograms, lot 2 elicited long-lived opsonic antibodies in 80 to 90% of the vaccinates. The antibodies elicited by both lots enhanced deposition of C3 onto mucoid P. aeruginosa cells and mediated opsonic killing of heterologous mucoid strains expressing distinct MEP antigens. These results indicate that the polymers of MEP with the largest molecular sizes safely elicit opsonic antibodies in a sufficiently large proportion of vaccinates to permit studies of active and passive immunization of cystic fibrosis patients against infection with mucoid P. aeruginosa.

UV-catalyzed cross-linking of Escherichia coli uracil-DNA glycosylase to DNA. Identification of amino acid residues in the single-stranded DNA binding site

Photochemical cross-linking of Escherichia coli uracil-DNA glycosylase (Ung) to oligonucleotide dT20 was performed to identify amino acid residues that reside in or near the DNA-binding site. UV-catalyzed cross-linking reactions produced a covalent Ung x dT20 complex which was resolved from uncross-linked enzyme by SDS-polyacrylamide gel electrophoresis. Cross-link formation required native Ung and was inhibited by increasing concentrations of NaCl in a manner characteristics of NaCl inhibition of Ung catalytic activity. The Ung x dT20 complex was purified to apparent homogeneity, and mass spectrometry revealed that Ung was cross-linked to dT20 in 1:1 stoichiometry as a 31,477 dalton complex. Purified Ung x dT20 lacked detectable uracil-DNA glycosylase activity and failed to bind single-stranded DNA. Recently, we demonstrated that the bacteriophage PBS2 uracil-DNA glycosylase inhibitor (Ugi) binds Ung and prevents further interaction with DNA (Bennett, S. E., Schimerlik, M. I., and Mosbaugh, D. W. (1993) J. Biol. Chem. 268, 26879-26885). Addition of the Ugi protein to the cross-linking reaction blocked formation of the Ung x dT20 cross-link. Conversely, the Ung x dT20 cross-link was refractory to Ugi binding. Upon trypsin digestion of Ung x dT20, four distinct products were identified as peptide x dT20 cross-links. A combination of amino acid sequence and mass spectrometric analysis revealed that four tryptic peptides (T6, T18, T19, and T18/19) were adducted to dT20. These observations suggest that dT20 is cross-linked to the Ung DNA-binding site.

Regulation of intracellular creatine in erythrocytes and myoblasts: influence of uraemia and inhibition of Na,K-ATPase

The regulation of intracellular creatine concentration in mammalian cells is poorly understood, but is thought to depend upon active sodium-linked uptake of creatine from extracellular fluid. In normal human erythrocytes, creatine influx into washed cells was inhibited by 40 per cent in the absence of extracellular sodium. In washed cells from uraemic patients, sodium-independent creatine influx was normal, whereas the sodium-dependent component of creatine influx was 3.3 times higher than normal, possibly reflecting the reduced mean age of uraemic erythrocytes. In spite of this, the intracellular creatine concentration was no higher than normal in uraemic erythrocytes, implying that some factor in uraemic plasma in vivo inhibits sodium-dependent creatine influx. Both in normal and uraemic erythrocytes, the creatine concentration was 10 times that in plasma, and the concentration in the cells showed no detectable dependence on that in plasma, suggesting that the intracellular creatine concentration is controlled by an active saturable process. Active sodium-dependent accumulation of creatine was also demonstrated in L6 rat myoblasts and was inhibited when transport was measured in the presence of 10(-4) M ouabain or digoxin, implying that uptake was driven by the transmembrane sodium gradient. However, when creatine influx was measured immediately after ouabain or digoxin had been washed away, it was higher than in control cells, suggesting that Na,K-ATPase and/or sodium-linked creatine transport are up-regulated when treated with inhibitors of Na,K-ATPase.

Kinetics of the uracil-DNA glycosylase/inhibitor protein association. Ung interaction with Ugi, nucleic acids, and uracil compounds

The bacteriophage PBS2 uracil-DNA glycosylase inhibitor (Ugi) inactivates Escherichia coli uracil-DNA glycosylase (Ung) by forming an Ung.Ugi protein complex with 1:1 stoichiometry. Stability of the Ung.Ugi complex was demonstrated by the inability of free Ugi to exchange with Ugi bound in preformed complex. Ung was reacted with fluorescein 5-isothiocyanate to produce fluorescent-Ung (F-Ung), which retained full uracil-DNA glycosylase activity and susceptibility to Ugi inactivation. Addition of Ugi to F-Ung under steady-state conditions resulted in saturable (15%) fluorescence quenching at a F-Ung.Ugi ratio of 1:1.4. Dissociation constants determined for the F-Ung interaction with M13 DNA, uracil-containing DNA, and poly(U) equaled 600, 220, and 190 microM, respectively. While F-Ung associated with nucleic acid polymers was able to bind Ugi efficiently, F-Ung bound in the F-Ung.Ugi complex could no longer effectively bind nucleic acid. Stopped-flow kinetic analysis suggested the F-Ung/Ugi association was described by a two-step mechanism. The first step entailed a rapid pre-equilibrium distinguished by the dissociation constant Kd = 1.3 microM. The second step led irreversibly to the formation of the final complex and was characterized by the rate constant k = 195 s-1. We infer Ugi inactivates Ung through the formation of an exceptionally stable protein-protein complex.

Effects of dietary phosphorus and protein in dogs with chronic renal failure

Four diets were formulated to contain: 16% protein and 0.4% phosphorus--diet 1; 16% protein and 1.4% phosphorus--diet 2; 32% protein and 0.4% phosphorus--diet 3; and 32% protein and 1.4% phosphorus--diet 4. Forty-eight dogs were fed diet 1 for 3 months after surgical reduction of renal mass, then were allotted to 4 groups of 12 dogs each, with equal mean values for glomerular filtration rate (GFR). Dog of groups 1-4 were fed diets 1-4, respectively, for 24 months. Data collected from the dogs during and at termination of the study were analyzed statistically for effects of dietary protein, phosphorus (P), time, and interactions between these factors. During the 24 months of study, 24 dogs developed uremia and were euthanatized for necropsy. Necropsy also was performed on the remaining 24 dogs after they were euthanatized at the end of the study. Dog survival was significantly enhanced by 0.4% P diets (vs 1.4% P diets), but survival was not significantly influenced by amount of dietary protein. The 0.4% P diets (vs 1.4% P diets) significantly increased the period that GFR remained stable before it decreased, but dietary protein did not have significant effect. Significant blood biochemical changes attributed to P, protein, and time were identified during the study. Terminally, plasma parathyroid hormone concentration was significantly increased from prediet values in all groups of dogs. Urine protein excretion was not significantly affected by dietary amount of either protein or P, when measured by either timed urine collection or urine protein-to-creatinine ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of the Escherichia coli uracil-DNA glycosylase.inhibitor protein complex

The Bacillus subtilis bacteriophage PBS2 uracil-DNA glycosylase inhibitor (Ugi) protein was characterized and shown to form a stable complex with Escherichia coli uracil-DNA glycosylase (Ung). As determined by mass spectrometry, the Ugi protein had a molecular weight of 9,474. We confirmed this value by sedimentation equilibrium centrifugation and determined that Ugi exists as a monomeric protein in solution. Amino acid analysis performed on both Ugi and Ung proteins was in excellent agreement with the amino acid composition predicted from the respective nucleotide sequence of each gene. The Ung.Ugi complex was resolved from its constitutive components by nondenaturing polyacrylamide gel electrophoresis and shown to possess a 1:1 stoichiometry. Analytical ultracentrifugation studies revealed that the Ung.Ugi complex had a molecular weight of 35,400, consistent with the complex containing one molecule each of Ung and Ugi. The acidic isoelectric points of the protein species were 6.6 (Ung) and 4.2 (Ugi), whereas the Ung.Ugi complex had an isoelectric point of 4.9. Dissociation of the Ung.Ugi complex by SDS-polyacrylamide gel electrophoresis revealed no apparent alteration in the molecular weight of either polypeptide subsequent to binding. Furthermore, when the Ung.Ugi complex was treated with urea and resolved by urea-polyacrylamide gel electrophoresis, both uracil-DNA glycosylase and inhibitor activities were recovered from the dissociated complex. Thus, the complex seems to be reversible. In addition, we demonstrated that the Ugi interaction with Ung prevents enzyme binding to DNA and dissociates uracil-DNA glycosylase from a preformed DNA complex.

Renal prostaglandins, effective renal plasma flow and glomerular filtration rate in healthy elderly subjects

This study tests the hypothesis that the age-associated reduction in glomerular filtration rate (GFR) and the presence of glomerulosclerosis renders effective renal plasma flow (ERPF) prostaglandin dependent. Ten healthy elderly volunteers were studied in a single-blind placebo-controlled manner using indomethacin to suppress the renal prostaglandins. There was no significant difference in ERPF or GFR following indomethacin when compared with placebo. These results suggest that blocking renal prostaglandins does not significantly alter ERPF or GFR in healthy elderly people.