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Goss AM, Gower B, Soleymani T, Stewart M, Pendergrass M, Lockhart M, Krantz O, Dowla S, Bush N, Garr Barry V, Fontaine KR. Effects of weight loss during a very low carbohydrate diet on specific adipose tissue depots and insulin sensitivity in older adults with obesity: a randomized clinical trial. Nutr Metab (Lond) 2020; 17:64. [PMID: 32817749 PMCID: PMC7425171 DOI: 10.1186/s12986-020-00481-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 07/22/2020] [Indexed: 11/10/2022] Open
Abstract
Background Insulin resistance and accumulation of visceral adipose tissue (VAT) and intermuscular adipose tissue (IMAT) place aging adults with obesity at high risk of cardio-metabolic disease. A very low carbohydrate diet (VLCD) may be a means of promoting fat loss from the visceral cavity and skeletal muscle, without compromising lean mass, and improve insulin sensitivity in aging adults with obesity. Objective To determine if a VLCD promotes a greater loss of fat (total, visceral and intermuscular), preserves lean mass, and improves insulin sensitivity compared to a standard CHO-based/low-fat diet (LFD) in older adults with obesity. Design Thirty-four men and women aged 60–75 years with obesity (body mass index [BMI] 30-40 kg/m2) were randomized to a diet prescription of either a VLCD (< 10:25:> 65% energy from CHO:protein:fat) or LFD diet (55:25:20) for 8 weeks. Body composition by dual-energy X-ray absorptiometry (DXA), fat distribution by magnetic resonance imaging (MRI), insulin sensitivity by euglycemic hyperinsulinemic clamp, and lipids by a fasting blood draw were assessed at baseline and after the intervention. Results Participants lost an average of 9.7 and 2.0% in total fat following the VLCD and LFD, respectively (p < 0.01). The VLCD group experienced ~ 3-fold greater loss in VAT compared to the LFD group (− 22.8% vs − 1.0%, p < 0.001) and a greater decrease in thigh-IMAT (− 24.4% vs − 1.0%, p < 0.01). The VLCD group also had significantly greater thigh skeletal muscle (SM) at 8 weeks following adjustment for change in total fat mass. Finally, the VLCD had greater increases in insulin sensitivity and HDL-C and decreases in fasting insulin and triglycerides compared to the LFD group. Conclusions Weight loss resulting from consumption of a diet lower in CHO and higher in fat may be beneficial for older adults with obesity by depleting adipose tissue depots most strongly implicated in poor metabolic and functional outcomes and by improving insulin sensitivity and the lipid profile. Trial registration NCT02760641. Registered 03 May 2016 - Retrospectively registered.
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Affiliation(s)
- Amy M Goss
- Department of Nutrition Sciences, University of Alabama at Birmingham, 640 Webb Building, 1675 University Blvd, Birmingham, AL 35294-3360 USA
| | - Barbara Gower
- Department of Nutrition Sciences, University of Alabama at Birmingham, 640 Webb Building, 1675 University Blvd, Birmingham, AL 35294-3360 USA
| | - Taraneh Soleymani
- Department of Nutrition Sciences, University of Alabama at Birmingham, 640 Webb Building, 1675 University Blvd, Birmingham, AL 35294-3360 USA
| | - Mariah Stewart
- Department of Nutrition Sciences, University of Alabama at Birmingham, 640 Webb Building, 1675 University Blvd, Birmingham, AL 35294-3360 USA
| | - May Pendergrass
- Department of Nutrition Sciences, University of Alabama at Birmingham, 640 Webb Building, 1675 University Blvd, Birmingham, AL 35294-3360 USA
| | - Mark Lockhart
- Department of Medicine, Division of Radiology, University of Alabama at Birmingham, Birmingham, AL 35294 USA
| | - Olivia Krantz
- Department of Health Behavior, University of Alabama at Birmingham, Birmingham, AL 35294 USA
| | - Shima Dowla
- Department of Health Behavior, University of Alabama at Birmingham, Birmingham, AL 35294 USA
| | - Nikki Bush
- Department of Nutrition Sciences, University of Alabama at Birmingham, 640 Webb Building, 1675 University Blvd, Birmingham, AL 35294-3360 USA
| | - Valene Garr Barry
- Department of Nutrition Sciences, University of Alabama at Birmingham, 640 Webb Building, 1675 University Blvd, Birmingham, AL 35294-3360 USA
| | - Kevin R Fontaine
- Department of Health Behavior, University of Alabama at Birmingham, Birmingham, AL 35294 USA
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Goss AM, Dowla S, Pendergrass M, Ashraf A, Bolding M, Morrison S, Amerson A, Soleymani T, Gower B. Effects of a carbohydrate-restricted diet on hepatic lipid content in adolescents with non-alcoholic fatty liver disease: A pilot, randomized trial. Pediatr Obes 2020; 15:e12630. [PMID: 32128995 DOI: 10.1111/ijpo.12630] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 02/11/2020] [Indexed: 01/24/2023]
Abstract
BACKGROUND Non-alcoholic fatty liver disease (NAFLD) has emerged as the most common form of liver disease among adolescents in industrialized countries. While lifestyle intervention remains the hallmark treatment for NAFLD, the most effective dietary strategy to reverse NAFLD in children is unknown. OBJECTIVE The objective of this study was to determine the effects of a moderately CHO-restricted diet (CRD) vs fat-restricted diet (FRD) in adolescents with NAFLD on reduction in liver fat and insulin resistance. METHODS Thirty-two children/adolescents (age 9-17) with obesity and NAFLD were randomized to a CRD (<25:25:>50% energy from CHO:protein:fat) or FRD (55:25:20) for 8 weeks. Caloric intakes were calculated to be weight maintaining. Change in hepatic lipid content was measured via magnetic resonance imaging, body composition via dual energy X ray absorptiometry and insulin resistance via a fasting blood sample. RESULTS Change in hepatic lipid did not differ with diet, but declined significantly (-6.0 ± 4.7%, P < .001 only within the CRD group. We found significantly greater decreases in insulin resistance (HOMA-IR, <.05), abdominal fat mass (P < .01) and body fat mass (P < .01) in response to the CRD vs FRD. CONCLUSION These findings suggest that consumption of a moderately CHO-restricted diet may result in decreased hepatic lipid as well as improvements in body composition and insulin resistance in adolescents with NAFLD even in the absence of intentional caloric restriction. Larger studies are needed to determine whether a CHO-restricted diet induces change in hepatic lipid independent of change in body fat.
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Affiliation(s)
- Amy M Goss
- Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Shima Dowla
- School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - May Pendergrass
- Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Ambika Ashraf
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Mark Bolding
- Department of Radiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Shannon Morrison
- School of Nursing, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Alesha Amerson
- Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Taraneh Soleymani
- Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Barbara Gower
- Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USA
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Brown AW, Altman DG, Baranowski T, Bland JM, Dawson JA, Dhurandhar NV, Dowla S, Fontaine KR, Gelman A, Heymsfield SB, Jayawardene W, Keith SW, Kyle TK, Loken E, Oakes JM, Stevens J, Thomas DM, Allison DB. Childhood obesity intervention studies: A narrative review and guide for investigators, authors, editors, reviewers, journalists, and readers to guard against exaggerated effectiveness claims. Obes Rev 2019; 20:1523-1541. [PMID: 31426126 PMCID: PMC7436851 DOI: 10.1111/obr.12923] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Revised: 07/13/2019] [Accepted: 07/14/2019] [Indexed: 12/16/2022]
Abstract
Being able to draw accurate conclusions from childhood obesity trials is important to make advances in reversing the obesity epidemic. However, obesity research sometimes is not conducted or reported to appropriate scientific standards. To constructively draw attention to this issue, we present 10 errors that are commonly committed, illustrate each error with examples from the childhood obesity literature, and follow with suggestions on how to avoid these errors. These errors are as follows: using self-reported outcomes and teaching to the test; foregoing control groups and risking regression to the mean creating differences over time; changing the goal posts; ignoring clustering in studies that randomize groups of children; following the forking paths, subsetting, p-hacking, and data dredging; basing conclusions on tests for significant differences from baseline; equating "no statistically significant difference" with "equally effective"; ignoring intervention study results in favor of observational analyses; using one-sided testing for statistical significance; and stating that effects are clinically significant even though they are not statistically significant. We hope that compiling these errors in one article will serve as the beginning of a checklist to support fidelity in conducting, analyzing, and reporting childhood obesity research.
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Affiliation(s)
- Andrew W Brown
- Department of Applied Health Science, Indiana University School of Public Health-Bloomington, Bloomington, Indiana
| | - Douglas G Altman
- Centre for Statistics in Medicine, Nuffield Department of Orthopaedics, Rheumatology, and Musculoskeletal Sciences, University of Oxford, Oxford, UK
| | - Tom Baranowski
- Department of Pediatrics, Baylor College of Medicine, USDA/ARS Children's Nutrition Research Center, Houston, Texas
| | - J Martin Bland
- Department of Health Sciences, University of York, York, UK
| | - John A Dawson
- Department of Nutritional Sciences, Texas Tech University, Lubbock, Texas
| | | | - Shima Dowla
- School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Kevin R Fontaine
- Department of Health Behavior, School of Public Health, University of Alabama at Birmingham, Birmingham, Alabama
| | - Andrew Gelman
- Department of Statistics and Department of Political Science, Columbia University, New York, New York
| | - Steven B Heymsfield
- Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, Louisiana
| | - Wasantha Jayawardene
- Department of Applied Health Science, Indiana University School of Public Health-Bloomington, Bloomington, Indiana
| | - Scott W Keith
- Department of Pharmacology and Experimental Therapeutics, Division of Biostatistics, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania
| | | | - Eric Loken
- Neag School of Education, University of Connecticut, Storrs, Connecticut
| | - J Michael Oakes
- Department of Epidemiology, School of Public Health, University of Minnesota, Minneapolis, Minnesota
| | - June Stevens
- Departments of Nutrition and Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina
| | - Diana M Thomas
- Department of Mathematical Sciences, United States Military Academy, West Point, New York
| | - David B Allison
- Department of Epidemiology and Biostatistics, Indiana University School of Public Health-Bloomington, Bloomington, Indiana
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Pelham JH, Hanks L, Aslibekyan S, Dowla S, Ashraf AP. Higher hemoglobin A1C and atherogenic lipoprotein profiles in children and adolescents with type 2 diabetes mellitus. J Clin Transl Endocrinol 2018; 15:30-34. [PMID: 30547005 PMCID: PMC6282872 DOI: 10.1016/j.jcte.2018.11.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 11/29/2018] [Accepted: 11/29/2018] [Indexed: 12/22/2022]
Abstract
Aim Significant knowledge gaps exist regarding lipoprotein profiles in children with type 2 diabetes mellitus (T2DM). The primary objective was to analyze the type and nature of lipoprotein abnormalities present in children with T2DM and to identify determinants of adverse lipoprotein profiles. The secondary objective was to assess associations with elevated glycated hemoglobin (HbA1C), i.e., <8% vs. ≥8.0% and pediatric dyslipidemias in the setting of T2DM. Methods This retrospective chart review included children with T2DM who had undergone lipoprotein analysis and were not on lipid lowering medications (n = 93). Results The participants (mean age 15.2 ± 2.7y) were 71% female and 78% African American (AA). Adjusted for age, sex, and race, BMI z-score was positively associated with LDL-pattern B (pro-atherogenic profile with small dense LDL particles) (P = 0.01), and negatively associated with total HDL-C (P = 0.0003). HbA1C was robustly positively associated with the LDL-C, apoB and LDL pattern B (all P < 0.001). Patients with an HbA1C >8% had significantly higher total cholesterol (191.4 vs. 158.1 mg/dL, P = 0.0004), LDL-C (117.77 vs. 92.3 mg/dL, P = 0.002), apoB (99.5 vs. 80.9 mg/dL, P = 0.002), non-HDL-C (141.5 vs. 112.5, P = 0.002), and frequency of LDL pattern B (57% vs. 20%, P = 0.0008). Conclusion HbA1C and BMI were associated with adverse lipoprotein profiles, and may represent two major modifiable cardiovascular risk factors in the pediatric T2DM population. Patients with an HbA1C higher than 8.0% had significantly worse atherogenic lipid profile, i.e., higher LDL-C, non-HDL-C, apoB and LDL pattern B, suggesting adequate glycemia may improve adverse lipoprotein profiles.
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Affiliation(s)
- James Heath Pelham
- Univerisity of Alabama School of Medicine, University of Alabama at Birmingham, 1720 2nd Ave South, Birmingham, AL 35294-0113, United States
| | - Lynae Hanks
- Department of Pediatrics/Division of Pediatric Endocrinology and Metabolism, Children's of Alabama, University of Alabama at Birmingham, CPPII M30, 1601 4th Ave S, Birmingham, AL 35233, United States
| | - Stella Aslibekyan
- Department of Epidemiology, UAB School of Public Health, Birmingham, AL, United States
| | - Shima Dowla
- Univerisity of Alabama School of Medicine, University of Alabama at Birmingham, 1720 2nd Ave South, Birmingham, AL 35294-0113, United States
| | - Ambika P Ashraf
- Department of Pediatrics/Division of Pediatric Endocrinology and Metabolism, Children's of Alabama, University of Alabama at Birmingham, CPPII M30, 1601 4th Ave S, Birmingham, AL 35233, United States
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Dowla S, Pendergrass M, Bolding M, Gower B, Fontaine K, Ashraf A, Soleymani T, Morrison S, Goss A. Effectiveness of a carbohydrate restricted diet to treat non-alcoholic fatty liver disease in adolescents with obesity: Trial design and methodology. Contemp Clin Trials 2018; 68:95-101. [PMID: 29601997 DOI: 10.1016/j.cct.2018.03.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 03/20/2018] [Accepted: 03/22/2018] [Indexed: 01/22/2023]
Abstract
BACKGROUND Non-alcoholic fatty liver disease (NAFLD) is the most common liver disorder among children in the developed world and can progress to cirrhosis, hepatocellular carcinoma, and liver failure. No evidence-based dietary guidelines exist on the most effective diet prescription to treat NAFLD. OBJECTIVE To compare the effect of a carbohydrate (CHO)-restricted diet vs fat-restricted diet, the current standard of care, on changes in hepatic fat infiltration, body composition, and metabolic health over an 8-week period among overweight and obese children diagnosed with NAFLD. METHODS In this two-arm, parallel design randomized controlled trial (RCT), 40 participants aged 9 to 18 years were randomized to a CHO restricted diet (<25:>50:25% daily calories from CHO: fat: protein) or control, fat restricted diet (55,20:25% daily calories from CHO: fat: protein). This family-based diet intervention included: (1) a 2-week supply of groceries to feed a four-person household specific to the assigned diet; and (2) extensive education on diet implementation through biweekly, diet-specific group and individualized counseling sessions with participants and one parent or guardian led by a registered dietitian (RD). The primary outcome measure of this study was hepatic lipid, measured using magnetic resonance spectroscopy (MRS). Secondary outcomes included liver transaminases; markers of inflammation (hsCRP, IL-6, TNF-α); body composition; visceral adipose tissue; and insulin resistance. All testing was conducted at baseline and week 8; hepatic transaminases were also measured at weeks 2 and 4. This RCT is registered with ClinicalTrials.gov (ID: NCT02787668).
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Affiliation(s)
- Shima Dowla
- Department of Health Behavior, University of Alabama at Birmingham, Birmingham, AL, United States; School of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - May Pendergrass
- Department of Nutrition, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Mark Bolding
- Division of Advanced Medical Imaging Research, Department of Radiology, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Barbara Gower
- Department of Nutrition, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Kevin Fontaine
- Department of Health Behavior, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Ambika Ashraf
- Division of Pediatric Endocrinology, Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Taraneh Soleymani
- Department of Nutrition, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Shannon Morrison
- School of Nursing, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Amy Goss
- Department of Nutrition, University of Alabama at Birmingham, Birmingham, AL, United States.
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Bakari M, Wamsele J, MacKenzie T, Maro I, Kimario J, Ali S, Dowla S, Hendricks K, Lukmanji Z, Neke NM, Waddell R, Matee M, Pallangyo K, von Reyn CF. Nutritional status of HIV-infected women with tuberculosis in Dar es Salaam, Tanzania. Public Health Action 2013; 3:224-9. [PMID: 26393034 DOI: 10.5588/pha.13.0028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 08/14/2013] [Indexed: 11/10/2022] Open
Abstract
SETTING Tuberculosis (TB) treatment clinics in Dar es Salaam, Tanzania. OBJECTIVE To quantify anthropometrics and intake of en-ergy and protein among human immunodeficiency virus (HIV) positive women with TB. DESIGN HIV-positive women with newly diagnosed TB were assessed on their anthropometric characteristics and dietary intake. Energy and protein intake were determined using Tanzania food composition tables and compared with standard recommendations. Patients were re-evaluated after 4-6 months of anti-tuberculosis treatment. RESULTS Among 43 women, the baseline median CD4 count was 209 cells/µl (range 8-721); 19 (44%) had a CD4 count of <200; 20 (47%) were on antiretroviral therapy. Body mass index was <18.5 kg/m(2) in 25 (58%); the median food insecurity score was 6. The median level of kcal/day was 1693 (range 1290-2633) compared to an estimated need of 2658; the median deficit was 875 kcal (range -65-1278). The median level of protein/day was 42 g (range 27-67) compared to 77 g estimated need; the median protein deficit was 35 g (range 10-50). The median weight gain among 29 patients after 4-6 months was 6 kg. CONCLUSION HIV-positive women with TB have substantial 24-h deficits in energy and protein intake, report significant food insecurity and gain minimal weight on anti-tuberculosis treatment. Enhanced dietary education together with daily supplementation of 1000 kcal with 40 g protein may be required.
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Affiliation(s)
- M Bakari
- Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - J Wamsele
- Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - T MacKenzie
- Geisel School of Medicine at Dartmouth and Dartmouth-Hitchcock Medical Center, Hanover, New Hampshire, USA
| | - I Maro
- Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - J Kimario
- Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - S Ali
- Geisel School of Medicine at Dartmouth and Dartmouth-Hitchcock Medical Center, Hanover, New Hampshire, USA
| | - S Dowla
- Geisel School of Medicine at Dartmouth and Dartmouth-Hitchcock Medical Center, Hanover, New Hampshire, USA
| | - K Hendricks
- Geisel School of Medicine at Dartmouth and Dartmouth-Hitchcock Medical Center, Hanover, New Hampshire, USA
| | - Z Lukmanji
- Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - N M Neke
- Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - R Waddell
- Geisel School of Medicine at Dartmouth and Dartmouth-Hitchcock Medical Center, Hanover, New Hampshire, USA
| | - M Matee
- Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - K Pallangyo
- Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - C F von Reyn
- Geisel School of Medicine at Dartmouth and Dartmouth-Hitchcock Medical Center, Hanover, New Hampshire, USA
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Abstract
OBJECTIVES Different indices of axonal excitability are now being measured in human subjects, both normal volunteers undergoing some test manoeuvre and patients with a variety of peripheral nerve disorders. The reproducibility of these indices has not previously been established, and was determined for cutaneous afferents in the median nerve of 12 healthy subjects, using threshold tracking techniques. METHODS Refractoriness and supernormality were determined as the change in stimulus current required to produce a predetermined target potential when conditioned by a supramaximal stimulus at appropriate conditioning-test intervals. Strength-duration time constant was calculated from the threshold currents using unconditioned test stimuli of 0.1 ms and 1.0 ms. The effects of changes in membrane potential on these indices was assessed by applying subthreshold DC currents (from 50% depolarizing to 50% hyperpolarizing), using the reciprocal of threshold (i.e., 'excitability') as an indicator of membrane potential. The intraindividual reproducibility was determined by repeating the study on each subject up to 10 times. RESULTS Refractoriness and supernormality were variable between subjects (mean +/- SD of 31.5 +/- 9.5% and 13.2 +/- 3.8%, respectively) and within subjects (coefficient of variation 0.2104 and 0.21849, respectively). TauSD showed even greater interindividual variability (499.2 +/- 115 micros) and intraindividual variability (coefficient of variation 0.2339). The slopes of relationships between each of the indices and axonal 'excitability' suggest that refractoriness is extremely sensitive to changes in excitability (0.9767 +/- 0.1907), tauSD less so (0.3766 +/- 0.1322), supernormality least (0.2223 +/- 0.1268). CONCLUSIONS Under controlled conditions, refractoriness is the most sensitive and least variable of the indices of axonal excitability. However, small decreases in temperature greatly increase refractoriness but have little effect on tauSD. Given that 3 indices reflect different biophysical mechanisms, nodal and internodal, greater insight into the functional state of peripheral nerve axons will come when there are coherent changes in all 3 indices.
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Affiliation(s)
- I Mogyoros
- Department of Neurology, Prince of Wales Hospital and Prince of Wales Medical Research Institute, University of New South Wales, Randwick, Australia.
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Mogyoros I, Lin C, Dowla S, Grosskreutz J, Burke D. Strength-duration properties and their voltage dependence at different sites along the median nerve. Clin Neurophysiol 1999; 110:1618-24. [PMID: 10479029 DOI: 10.1016/s1388-2457(99)00087-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
OBJECTIVES There is some evidence that the ease with which ectopic activity can be induced varies systematically along the course of a nerve and is greater at more proximal sites. Recent studies have implicated a non-inactivating threshold conductance, possibly due to persistent Na+ channels, in ectopic activity associated with ischaemia and hyperventilation. This conductance is largely responsible for the voltage dependence of strength-duration time constant (tauSD), and changes in it can explain the time constant changes that occur during hyperventilation and ischaemia. METHODS To determine whether the strength-duration properties of motor axons of the median nerve vary along the course of the nerve, tauSD and rheobase were calculated at wrist, elbow and axilla in 15 healthy subjects, and the relationship of these properties to threshold was assessed using DC polarizing current to change axonal excitability. RESULTS tauSD was similar at the 3 stimulating sites but increased less at the axilla with depolarizing current. CONCLUSIONS These data indicate that the greater tendency for ectopic activity to arise from proximal segments of motor axons cannot be explained by differences in the conductances that contribute to tauSD and underlie its dependence on axonal excitability. The findings provide further support for the view that the precise relationship of the stimulating electrodes to the nerve has little effect on tauSD, at least when it is measured in the forearm.
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Affiliation(s)
- I Mogyoros
- Department of Neurology, Prince of Wales Hospital, Prince of Wales Medical Research Institute, Randwick, N.S.W., Australia.
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Dowla S. Saliva: its anti-infectious properties. Odontostomatol Trop 1982; 5:31-4. [PMID: 6953396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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