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De Stefano N, Matthews PM, Fu L, Narayanan S, Stanley J, Francis GS, Antel JP, Arnold DL. Axonal damage correlates with disability in patients with relapsing-remitting multiple sclerosis. Results of a longitudinal magnetic resonance spectroscopy study. Brain 1998; 121 ( Pt 8):1469-77. [PMID: 9712009 DOI: 10.1093/brain/121.8.1469] [Citation(s) in RCA: 369] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
It has been difficult to establish a strong correlation between total brain T2-weighted lesion volume on MRI and clinical disability in multiple sclerosis, in part because of the lack of pathological specificity of T2-weighted MRI signal changes. Proton magnetic resonance spectroscopy studies have shown that measurements of the resonance intensity of N-acetylaspartate (which is localized exclusively in neurons and neuronal processes in the mature brain) can provide a specific index of axonal damage or dysfunction. Here we report a 30-month longitudinal study of 29 patients with multiple sclerosis who had either a relapsing or a secondary progressive clinical course. Conventional brain MRI and single-voxel proton magnetic resonance spectroscopy examinations were obtained at intervals of 6-8 months with concurrent clinical evaluation. At the onset of the study, the brain N-acetylaspartate:creatine resonance intensity ratio was abnormally low for the whole group of patients (control mean = 2.93 +/- 0.2, patient mean = 2.56 +/- 0.4, P < 0.005). There were no significant differences between the relapsing and secondary progressive subgroups. Over the follow-up period, there was a trend towards a decrease (8%) in the brain N-acetylaspartate:creatine ratio for the 11 relapsing patients and a significant (P < 0.001) correlation between changes in the brain N-acetylaspartate:creatine ratio and expanded disability scale scores for the patients in this group. This correlation was even more evident for the patients who had clinically relevant relapses during the 30 months of follow-up (seven of 11 patients). Increases in T2-weighted lesion volumes (35% in 30 months for the group as a whole, P < 0.0001, without differences between the subgroups) did not correlate with disability either in the group of patients as a whole or in the different subgroups. We conclude that indices of axonal damage or loss such as brain N-acetylaspartate may provide a specific measure of pathological changes relevant to disability. Total T2-weighted lesion volumes, although more sensitive to changes with time than brain N-acetylaspartate, may be less relevant to understanding the progression of disability.
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De Stefano N, Narayanan S, Francis GS, Arnaoutelis R, Tartaglia MC, Antel JP, Matthews PM, Arnold DL. Evidence of axonal damage in the early stages of multiple sclerosis and its relevance to disability. ARCHIVES OF NEUROLOGY 2001; 58:65-70. [PMID: 11176938 DOI: 10.1001/archneur.58.1.65] [Citation(s) in RCA: 304] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
OBJECTIVE To assess axonal damage and its contribution to disability at different stages of multiple sclerosis (MS). BACKGROUND Recent in vivo imaging and in situ pathologic studies have demonstrated that substantial axonal damage accompanies the inflammatory lesions of MS. However, the relation of axonal damage to the duration of MS and its contribution to disability at different stages of the disease remain poorly defined. DESIGN We performed proton magnetic resonance spectroscopic imaging in 88 patients with a wide range of clinical disability and disease duration to measure N-acetylaspartate (NAA, an index of axonal integrity) relative to creatine (Cr) in a large central brain volume that included mostly normal-appearing white matter on magnetic resonance imaging. RESULTS We observed that the NAA/Cr values were abnormally low in the early stages of MS, even before significant disability (measured using the Expanded Disability Status Scale [EDSS]) was evident clinically, and declined more rapidly with respect to EDSS at lower than at higher EDSS scores (P<.001). The correlation of NAA/Cr values with EDSS score was significantly (P<.03) stronger in patients with mild disability (EDSS score <5, Spearman rank order correlation = -0.54, P<.001) than in patients with more severe disability (EDSS score >/=5, Spearman rank order correlation = -0.1, P<.9). When similar analyses were performed in patients with MS grouped for duration of disease, the subgroup with early disease duration (<5 years) also showed central brain NAA/Cr resonance intensity ratios significantly lower than healthy controls (P<.001). CONCLUSION Cerebral axonal damage begins and contributes to disability from the earliest stages of the disease.
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Lee S, Potamianos A, Narayanan S. Acoustics of children's speech: developmental changes of temporal and spectral parameters. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 1999; 105:1455-68. [PMID: 10089598 DOI: 10.1121/1.426686] [Citation(s) in RCA: 287] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Changes in magnitude and variability of duration, fundamental frequency, formant frequencies, and spectral envelope of children's speech are investigated as a function of age and gender using data obtained from 436 children, ages 5 to 17 years, and 56 adults. The results confirm that the reduction in magnitude and within-subject variability of both temporal and spectral acoustic parameters with age is a major trend associated with speech development in normal children. Between ages 9 and 12, both magnitude and variability of segmental durations decrease significantly and rapidly, converging to adult levels around age 12. Within-subject fundamental frequency and formant-frequency variability, however, may reach adult range about 2 or 3 years later. Differentiation of male and female fundamental frequency and formant frequency patterns begins at around age 11, becoming fully established around age 15. During that time period, changes in vowel formant frequencies of male speakers is approximately linear with age, while such a linear trend is less obvious for female speakers. These results support the hypothesis of uniform axial growth of the vocal tract for male speakers. The study also shows evidence for an apparent overshoot in acoustic parameter values, somewhere between ages 13 and 15, before converging to the canonical levels for adults. For instance, teenagers around age 14 differ from adults in that, on average, they show shorter segmental durations and exhibit less within-subject variability in durations, fundamental frequency, and spectral envelope measures.
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Comparative Study |
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Fu L, Matthews PM, De Stefano N, Worsley KJ, Narayanan S, Francis GS, Antel JP, Wolfson C, Arnold DL. Imaging axonal damage of normal-appearing white matter in multiple sclerosis. Brain 1998; 121 ( Pt 1):103-13. [PMID: 9549491 DOI: 10.1093/brain/121.1.103] [Citation(s) in RCA: 276] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The current study was designed to determine the relative distribution of decreases of N-acetylasparate (NAA), a marker of axonal damage, between lesions and normal-appearing white matter of patients with established multiple sclerosis and to test for associations between changes in the ratio of NAA to creatine/phosphocreatine (NAA:Cr) in those compartments and changes in disability. Data were collected from a 30-month longitudinal study of 28 patients with either a relapsing course with partial remissons and no progression between attacks (relapsing/remitting) (11 patients) or a course of progressively increasing disability, following a period of relapsing/remitting disease (secondary progressive) (17 patients). Proton magnetic resonance spectroscopic imaging (MRSI) and conventional MRI examinations were performed at 6-8-month intervals with concurrent clinical assessments of disability. General linear models were used to test associations between MRSI, MRI, lesion volume and clinical data. Analysis confirmed that the NAA:Cr ratio is lower in lesions than in the normal-appearing white matter (-15.3% in relapsing/remitting multiple sclerosis and -8.8% in secondary progressive multiple sclerosis). The lower NAA:Cr ratio per unit lesion volume previously observed for secondary progressive relative to relapsing/remitting patients was found to result from a lower ratio (8.2%, P < 0.01) in the normal-appearing white matter rather than from any differences within lesions. The importance of changes in the normal-appearing white matter was emphasized further with the observation that the NAA:Cr ratio in the normal-appearing white matter accounted for most of the observed 15.6% (P < 0.001) decrease in the NAA:Cr ratio in the brains of relapsing/remitting patients over the period of study. The decrease in the NAA:Cr ratio in normal-appearing white matter correlated strongly (P < 0.001) with changes in disability in the relapsing/remitting subgroup. These results add to data suggesting that axonal damage or loss may be responsible for functional impairments in multiple sclerosis. The accumulation of secondary axonal damage in the normal-appearing white matter may be of particular significance for understanding chronic disability in this disease.
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Abstract
Abstract
Measurement of creatinine has many applications. We review the determination of urinary creatinine as a valid index of completeness of 24-h urine collection, the clinical utility of the determination of creatinine clearance ratios, and measurement of the ratio of the clearance of specific analytes, such as amylase, to the ratio of clearance of creatinine. The chemistry and variables that affect the Jaffé reaction are reviewed, and attempts at improvement of specificity are discussed. We also review and assess techniques other than the Jaffé reaction for measurement of creatinine.
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250 |
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Reddy H, Narayanan S, Arnoutelis R, Jenkinson M, Antel J, Matthews PM, Arnold DL. Evidence for adaptive functional changes in the cerebral cortex with axonal injury from multiple sclerosis. Brain 2000; 123 ( Pt 11):2314-20. [PMID: 11050031 DOI: 10.1093/brain/123.11.2314] [Citation(s) in RCA: 194] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Axonal injury occurs even in the earliest stages of multiple sclerosis. Magnetic resonance spectroscopic imaging (MRSI) measurements of brain N:-acetylaspartate (NAA), a marker of axonal integrity, show that this axonal injury can occur even in the absence of clinically evident functional impairments. To test whether cortical adaptive responses contribute to the maintenance of normal motor function in patients with multiple sclerosis, we performed MRSI and functional MRI (fMRI) examinations of nine multiple sclerosis patients who had unimpaired hand function. We found that activation of the ipsilateral sensorimotor cortex with simple hand movements was increased by a mean of fivefold relative to normal controls (n = 8) and that the extent of this increase was strongly correlated (sigma = -0.93, P = 0.001) with decreases in brain NAA. These results suggest that compensatory cortical adaptive responses may help to account for the limited relationship between conventional MRI measures of lesion burden and clinical measures of disability, and that therapies directed towards promoting cortical reorganization in response to brain injury could enhance recovery from relapses of multiple sclerosis.
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Duthie SJ, Narayanan S, Blum S, Pirie L, Brand GM. Folate deficiency in vitro induces uracil misincorporation and DNA hypomethylation and inhibits DNA excision repair in immortalized normal human colon epithelial cells. Nutr Cancer 2001; 37:245-51. [PMID: 11142099 DOI: 10.1207/s15327914nc372_18] [Citation(s) in RCA: 153] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Epidemiological studies have indicated that folic acid protects against a variety of cancers, particularly cancer of the colorectum. Folate is essential for efficient DNA synthesis and repair. Moreover, folate can affect cellular S-adenosylmethionine levels, which regulate DNA methylation and control gene expression. We have investigated the mechanisms through which folate affects DNA stability in immortalized normal human colonocytes (HCEC). DNA strand breakage, uracil misincorporation, and DNA repair, in response to oxidative and alkylation damage, were determined in folate-sufficient and folate-deficient colonocytes by single cell gel electrophoresis. In addition, methyl incorporation into genomic DNA was measured using the bacterial enzyme Sss1 methylase. Cultured human colonocyte DNA contained endogenous strand breaks and uracil. Folate deficiency significantly increased strand breakage and uracil misincorporation in these cells. This negative effect on DNA stability was concentration dependent at levels usually found in human plasma (1-10 ng/ml). DNA methylation was decreased in HCEC grown in the absence of folate. Conversely, hypomethylation was not concentration dependent. Folate deficiency impaired the ability of HCEC to repair oxidative and alkylation damage. These results demonstrate that folic acid modulates DNA repair, DNA strand breakage, and uracil misincorporation in immortalized human colonocytes and that folate deficiency substantially decreases DNA stability in these cells.
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Reddy H, Narayanan S, Woolrich M, Mitsumori T, Lapierre Y, Arnold DL, Matthews PM. Functional brain reorganization for hand movement in patients with multiple sclerosis: defining distinct effects of injury and disability. Brain 2002; 125:2646-57. [PMID: 12429592 DOI: 10.1093/brain/awf283] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Previous work has demonstrated potentially adaptive cortical plasticity that increases with brain injury in patients with multiple sclerosis. However, animal studies showing use-dependent changes in motor cortex organization suggest that functional changes also may occur in response to disability. We therefore wished to test whether brain injury and disability lead to distinguishable patterns of activation with hand movement in patients with multiple sclerosis. By employing a passive as well as an active movement task, we also wished to test whether these changes were independent of voluntary recruitment and thus more likely to reflect true functional reorganization. Fourteen patients [Extended Disability Status Score (EDSS) 0-7.5] with relapsing-remitting multiple sclerosis were selected on the basis of pathology load and hand functional impairment for three study groups: group 1, low diffuse central brain injury (DCBI) as assessed from relative N-acetylaspartate concentration (a marker of axonal integrity) and normal hand function (n = 6); group 2, greater DCBI and normal hand function (n = 4); and group 3, greater DCBI and impaired hand function (n = 4). Functional MRI (fMRI) was used to map brain activation with a four-finger and both one-finger passive and active flexion-extension movement tasks for the three groups. Considering all the patients, we found increased activity in ipsilateral premotor and ipsilateral motor cortex (IMC) and in the ipsilateral inferior parietal lobule with increasing global disability (as assessed from the EDSS score). These changes appear to define true functional reorganization, as fMRI activations in IMC (r = 0.87, P < 0.001) and in the contralateral motor cortex (r = 0.67, P < 0.007) were highly correlated between active and passive single finger movements. We attempted to disambiguate any distinct effects of disability and brain injury by direct contrasts between patients differing predominantly in one or the other. To make these contrasts as powerful as possible, we used impairment of finger tapping as a measure of disability specific to the hand tested. A direct contrast of patients matched for DCBI, but differing in hand disability (group 3 - group 2) showed greater bilateral primary and secondary somatosensory cortex activation with greater disability alone. A contrast matched for hand disability, but differing in DCBI (group 2 - group 1) showed a different pattern of changes with relative ipsilateral premotor cortex and bilateral supplementary motor area activity. We conclude that the pattern of brain activity with finger movements changes both with increasing DCBI and with hand disability in patients with multiple sclerosis, and that these changes are distinct. Those related directly to disability may reflect responses to altered patterns of use. As injury- and disability-related activation changes are found even with passive finger movements, they may reflect true brain reorganization.
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Comparative Study |
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Narayanan S, Fu L, Pioro E, De Stefano N, Collins DL, Francis GS, Antel JP, Matthews PM, Arnold DL. Imaging of axonal damage in multiple sclerosis: spatial distribution of magnetic resonance imaging lesions. Ann Neurol 1997; 41:385-91. [PMID: 9066360 DOI: 10.1002/ana.410410314] [Citation(s) in RCA: 143] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We performed magnetic resonance imaging and magnetic resonance spectroscopic imaging on 28 patients with multiple sclerosis stratified for disability and clinical course (relapsing with at least partial remissions or secondary progressive disease). Lesions were segmented on the conventional proton density and T2-weighted magnetic resonance images, and lesion distribution images were generated for, each patient. The conventional magnetic resonance and spectroscopic images were transformed into a standard brain-based stereotaxic coordinate space, allowing comparison of images from different patients on a voxel-by-voxel basis. The spatial distribution of lesions in the transformed magnetic resonance images did not differ significantly between the relapsing and the progressive disease groups. We then generated from the individual data sets, group lesion probability distribution images for the relapsing and the progressive disease groups. The spatial distribution of metabolites was characterized with respect to lesion distribution using the magnetic resonance spectroscopic images transformed into stereotaxic space and averaged. The neuronal marker N-acetylaspartate was diffusely lower in the multiple sclerosis patients than in normal control subjects. Comparison of the averaged metabolite and T2-weighted lesion probability images confirmed loss of N-acetylaspartate in regions of both high and low lesion probability. This suggests that diffuse axonal volume loss or dysfunction extends beyond the inflammatory lesions of multiple sclerosis, perhaps due to microscopic disease or wallerian degeneration along projection pathways of axons traversing the lesions.
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Clinical Trial |
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143 |
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Reddy H, Narayanan S, Matthews PM, Hoge RD, Pike GB, Duquette P, Antel J, Arnold DL. Relating axonal injury to functional recovery in MS. Neurology 2000; 54:236-9. [PMID: 10636158 DOI: 10.1212/wnl.54.1.236] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
A patient was followed after the new onset of hemiparesis from relapse of MS with serial MR spectroscopy and functional MRI. The association of clinical improvement with recovery of N-acetylaspartate, a marker of neuronal integrity, and progressive reduction of abnormally large functional MRI cortical activation with movement demonstrates that dynamic reorganization of the motor cortex accompanies remission of MS.
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Case Reports |
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De Stefano N, Narayanan S, Matthews PM, Francis GS, Antel JP, Arnold DL. In vivo evidence for axonal dysfunction remote from focal cerebral demyelination of the type seen in multiple sclerosis. Brain 1999; 122 ( Pt 10):1933-9. [PMID: 10506094 DOI: 10.1093/brain/122.10.1933] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
To test for axonal damage or dysfunction in white matter tracts remote from acute demyelinating lesions, we used brain proton magnetic resonance spectroscopic imaging to measure changes in N-acetyl aspartate (NAA), an index of neuronal integrity, in the white matter of the normal-appearing hemisphere of three patients with large, solitary brain demyelinating lesions of the type seen early in multiple sclerosis. During the acute phase of their disease, all patients showed normal ratios of NAA to creatine (Cr) resonance intensity throughout the hemisphere contralateral to the lesion. However, on examination 1 month later, all of the patients showed abnormally low NAA/Cr resonance intensity ratios (reduction of NAA/Cr by 22-35%) in voxels of the contralateral hemisphere which were homologous to the demyelinating lesion. Other voxels in the normal-appearing hemisphere showed normal NAA relative resonance intensities. The decrease in NAA/Cr in voxels of the normal-appearing hemispheres resolved in all patients after 6 months, with a time course similar to that observed for NAA from voxels within the lesions. We conclude that effects of damage or dysfunction to axons traversing inflammatory lesions can be transmitted over long distances in the normal-appearing white matter. Such remote, secondary effects may be an expression of dysfunction of axons in projection pathways or of the reorganization of functional pathways seen in brains recovering from an acute injury.
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Comparative Study |
26 |
135 |
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Koga T, Jiang N, Gin P, Endoh MK, Narayanan S, Lurio LB, Sinha SK. Impact of an irreversibly adsorbed layer on local viscosity of nanoconfined polymer melts. PHYSICAL REVIEW LETTERS 2011; 107:225901. [PMID: 22182035 DOI: 10.1103/physrevlett.107.225901] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Indexed: 05/26/2023]
Abstract
We report the origin of the effect of nanoscale confinement on the local viscosity of entangled polystyrene (PS) films at temperatures far above the glass transition temperature. By using marker x-ray photon correlation spectroscopy with gold nanoparticles embedded in the PS films prepared on solid substrates, we have determined the local viscosity as a function of the distance from the polymer-substrate interface. The results show the impact of a very thin adsorbed layer (~7 nm in thickness) even without specific interactions of the polymer with the substrate, overcoming the effect of a surface mobile layer at the air-polymer interface and thereby resulting in a significant increase in the local viscosity as approaching the substrate interface.
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Narayanan S, De Stefano N, Francis GS, Arnaoutelis R, Caramanos Z, Collins DL, Pelletier D, Antel JP, Arnold DL. Axonal metabolic recovery in multiple sclerosis patients treated with interferon beta-1b. J Neurol 2001; 248:979-86. [PMID: 11757963 DOI: 10.1007/s004150170052] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Patients with multiple sclerosis (MS) can benefit from treatment with interferon beta-1b. However, the mechanisms of action of this drug are incompletely understood and effects of interferon beta-lb on axonal injury are not known. A measure of axonal injury can be obtained in vivo using magnetic resonance spectroscopy to quantify the resonance intensity of the neuronal marker, N-acetylaspartate (NAA). In a small pilot study, we performed combined magnetic resonance imaging and magnetic resonance spectroscopic imaging on 10 patients with relapsing-remitting MS before and 1 year after starting treatment with subcutaneous interferon beta-lb. Resonance intensities of NAA relative to creatine (Cr) were measured in a large, central brain volume. These measurements were compared with those made in a group of 6 untreated patients selected to have a similar range of scores on the Expanded Disability Status Scale and mean NAA/Cr at baseline. NAA/Cr in the treated group [2.74 (0.16), mean (SD)] showed an increase of 5.5% 12 months after the start of therapy [2.89 (0.24),p = 0.05], while NAA/Cr in the untreated group decreased, but not significantly [2.76 (0.1) at baseline, 2.65 (0.14) at 12 months,p > 0.1]. NAA/Cr had become significantly higher in the treated group at 12 months than in the untreated group (p = 0.03). Our data suggest that, in addition to losing axons, patients with chronic multiple sclerosis suffer from chronic, sublethal axonal injury that is at least partially reversible with interferon beta-lb therapy.
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Clinical Trial |
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133 |
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Matthews PM, De Stefano N, Narayanan S, Francis GS, Wolinsky JS, Antel JP, Arnold DL. Putting magnetic resonance spectroscopy studies in context: axonal damage and disability in multiple sclerosis. Semin Neurol 1998; 18:327-36. [PMID: 9817537 DOI: 10.1055/s-2008-1040884] [Citation(s) in RCA: 130] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Recent magnetic resonance imaging (MRI) and magnetic resonance spectroscopic (MRS) techniques have focused the attention of the multiple sclerosis (MS) research community on reanalysis of classic pathological approaches that have suggested significant axonal injury in this demyelinating disease. There now is abundant evidence from animal work that substantial "innocent bystander" damage to axons can occur with central nervous system (CNS) inflammation. Given the close interactions between axons and glia, it is no surprise that glial damage leads to secondary axonal changes. MRI, MRS, and MRS imaging studies have emphasized that axonal loss or damage in MS can be both substantial and early. The dynamic observations that are allowed by these noninvasive measures of pathology have demonstrated direct correlations between these axonal changes and disability, making a compelling case for increased emphasis on finding treatments of MS that may limit damage to CNS axons or salvage injured axons.
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Review |
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Pike GB, De Stefano N, Narayanan S, Worsley KJ, Pelletier D, Francis GS, Antel JP, Arnold DL. Multiple sclerosis: magnetization transfer MR imaging of white matter before lesion appearance on T2-weighted images. Radiology 2000; 215:824-30. [PMID: 10831705 DOI: 10.1148/radiology.215.3.r00jn02824] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To determine the evolution of magnetization transfer (MT) in white matter regions before and after plaque development in patients with multiple sclerosis (MS). MATERIALS AND METHODS In a 5-year longitudinal evaluation, 30 patients with MS underwent conventional magnetic resonance (MR) imaging, MT MR imaging, and clinical assessment. Cross-sectional data in 12 healthy subjects were also collected. Semiautomated lesion classification with use of T2-weighted MR images was used to measure the time course of the MT ratio (calculated with MR data acquired without and with MT saturation) in every voxel and to help analyze the relationship with the status of lesions depicted on T2-weighted images. RESULTS There was a significant (P <.001) temporal decline in lesion MT ratio after lesion appearance on T2-weighted images. A significant (P <. 001) progressive decline in MT ratio was also present in voxels that later became lesions, prior to initial detection on T2-weighted images. Even 1(1/2) years prior to lesion appearance, the MT ratio (33.3%) in regions destined to become such lesions was significantly (P <.001) lower than that in both white matter in healthy subjects (41.3%) and other normal-appearing white matter in patients with MS (38.1%). CONCLUSION The MT ratio reveals progressive focal abnormalities in MS that antedate by up to 2 years the appearance of lesions on T2-weighted MR images.
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Comparative Study |
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Matthews PM, Pioro E, Narayanan S, De Stefano N, Fu L, Francis G, Antel J, Wolfson C, Arnold DL. Assessment of lesion pathology in multiple sclerosis using quantitative MRI morphometry and magnetic resonance spectroscopy. Brain 1996; 119 ( Pt 3):715-22. [PMID: 8673485 DOI: 10.1093/brain/119.3.715] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Quantitative measurement of MRI-defined brain lesions can provide an index of the extent and activity of disease in multiple sclerosis patients. However, the relationships between these indices and clinical features are not well-understood. Heterogeneity of the pathological changes underlying MRI lesions may be an important factor determining the correlation between MRI lesion volumes and clinical measures. Recent studies have suggested that with magnetic resonance spectroscopy (MRS), it may be possible to define chemical changes that better reflect the pathological changes in multiple sclerosis. Here we report results of combined quantitative brain T2-weighted MRI lesion volume and proton MRS examinations that demonstrate heterogeneity of the chemical pathology underlying brain lesions in patients selected on the basis of similar clinical disability but differing with respect to the presence or absence of clinical relapses. We examined 29 patients with disease characterized by either clear relapses with at least partial remissions (RR) or secondary, chronic progression after an earlier history of a more relapsing and remitting course (SP). Total hemispheric lesion volume was greater (P < 0.04) in the RR (32.5 +/- 20.9 cm3) than in the SP (16.2 +/- 9.0 cm3) patients, despite the longer duration of disease in the latter group. Central brain N-acetyl aspartate: creatine (NAA:Cr) ratios were reduced relative to normal controls (4.0 +/- 0.3, n = 19) by similar amounts in the two patients groups (RR, 3.1 +/- 0.5; SP, 3.2 +/- 0.4; P < 0.0001). The ratio lesion volume:(NAA:Cr) was greater for the RR group (11.7 +/- 9.3 cm3) than for the SP group (5.4 +/- 3.3 cm3, P < 0.05), implying a greater average degree of axonal loss per unit lesion volume defined by MRI for subjects in the SP group or, alternatively, a greater proportion of lesions without axonal damage or loss in the RR group. Our results emphasize a limitation of using T2-weighted MRI lesion volume alone and suggest that combined analysis of MR-based chemical and imaging data might allow improved non-invasive assessment of lesion pathology in order to better understand its relationship to clinical features of multiple sclerosis.
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Tartaglia MC, Narayanan S, De Stefano N, Arnaoutelis R, Antel SB, Francis SJ, Santos AC, Lapierre Y, Arnold DL. Choline is increased in pre-lesional normal appearing white matter in multiple sclerosis. J Neurol 2002; 249:1382-90. [PMID: 12382153 DOI: 10.1007/s00415-002-0846-6] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE Our aim was to determine if the resonance intensity of choline-containing compounds (Cho) measured using proton magnetic resonance spectroscopy (MRS) was increased in pre-lesional normal appearing white matter (NAWM) in patients with multiple sclerosis (MS) relative to NAWM that remained stable in subsequent scans. BACKGROUND The Cho peak in MR spectra is associated with membrane phospholipids and increases in acute MS plaques, possibly even before the appearance of MRI-visible MS lesions. METHODS Three combined proton MRI and MRS imaging examinations of the corpus callosum and adjacent periventricular white matter were performed on 12 MS patients at intervals of 6 months. Proton density (PD) images were visually matched across 3 time points and the lesion volume in each voxel of the volume of interest was determined. The voxels were subdivided into four groups based on the presence or absence of lesion at baseline and change or no change in lesion volume on the subsequent scan. RESULTS We found a significantly higher baseline Cho/Creatine (Cr) ratio in NAWM voxels that displayed MRI visible lesions 6 months later than NAWM voxels that remained unchanged (1.57 +/- 0.30 and 1.37 +/- 0.33, respectively, p < 0.001). The 12-month interval data revealed similar pre-lesional elevated Cho/Cr, (1.51 +/- 0.29 versus 1.39 +/- 0.32, p = 0.009). Voxels that contained lesion at baseline and increased in lesion volume at 6 months also showed a significantly higher Cho/Cr ratio than those whose lesion volume did not change (1.60 +/- 0.32 and 1.49 +/- 0.36, respectively, p = 0.043). CONCLUSIONS The results of this study are consistent with focal pre-lesional myelin membrane pathology in the NAWM at least 12 months before lesions become visible on conventional MRI. This could reflect altered myelin chemistry or the presence of inflammation as seen in experimental allergic encephalomyelitis.
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Till C, Ghassemi R, Aubert-Broche B, Kerbrat A, Collins DL, Narayanan S, Arnold DL, Desrocher M, Sled JG, Banwell BL. MRI correlates of cognitive impairment in childhood-onset multiple sclerosis. Neuropsychology 2011; 25:319-32. [PMID: 21534686 DOI: 10.1037/a0022051] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
OBJECTIVE Brain MRI measures were correlated with neuropsychological function in 35 pediatric-onset multiple sclerosis (MS) patients and 33 age- and sex-matched healthy controls. METHOD Mean age of MS patients was 16.3 ± 2.3 years with average disease duration of 4.3 ± 3.1 years. Cortical gray matter, thalamic, and global brain volumes were calculated for all participants using a scaling factor computed using normalization of atrophy method to normalize total and regional brain volumes for head size. T1- and T2-weighted lesion volumes were calculated for MS patients. RESULTS Cognitive impairment (CI) was identified in 29% of the MS cohort. Cognitive deficits predominantly involved attention and processing speed, expressive language, and visuomotor integration. Relative to controls, the MS group showed significantly lower thalamic volume (p < .001), total brain volume (p < .008), and gray matter volume (p < .015). Corpus callosum area and thalamic volume differentiated patients identified as having CI from those without CI (p < .05). Regression models controlling for disease duration and age indicated that thalamic volume accounted for significant incremental variance in predicting global IQ, processing speed, and expressive vocabulary (ΔR2 ranging from .43 to .60) and was the most robust MRI predictor of cognition relative to other MRI metrics. CONCLUSIONS The robust association between cognitive function and reduced size of thalamus and global brain volume in pediatric-onset MS patients implicate neurodegenerative processes early in the disease course, and suggest that plasticity of an immature central nervous system is not sufficient to protect patients from the deleterious consequences of MS on cognitive neural networks. (PsycINFO Database Record (c) 2011 APA, all rights reserved).
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Research Support, Non-U.S. Gov't |
14 |
107 |
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Chen JT, Narayanan S, Collins DL, Smith SM, Matthews PM, Arnold DL. Relating neocortical pathology to disability progression in multiple sclerosis using MRI. Neuroimage 2005; 23:1168-75. [PMID: 15528116 DOI: 10.1016/j.neuroimage.2004.07.046] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2004] [Revised: 07/08/2004] [Accepted: 07/12/2004] [Indexed: 10/26/2022] Open
Abstract
Cortical grey matter (cGM) develops a substantial burden of pathology in multiple sclerosis (MS). Previous cross-sectional studies have suggested a relationship between measures of cortical atrophy and disability. Our objective was to develop a method for automatically measuring the apparent cGM thickness as well as the integrity of the interface between cGM and subcortical white matter (GM/WM) both globally and regionally on T(1)-weighted MRI, and use this method in a longitudinal investigation of how these measures differed between patients with stable MS and patients with progressing disability. Measurements were made over the whole brain and for anatomically specified cortical regions, both cross-sectionally at baseline and longitudinally on two MRI scans performed on average 1 year apart. We found a higher average rate of apparent loss of cGM thickness across the whole brain in the group that progressed over the interscan interval compared to the group that remained stable (progressing = -3.13 +/- 2.88%/year, stable = 0.06 +/- 2.31%/year, P = 0.002). This difference was detected with regional measures in parietal and precentral cortex. In contrast, change in the GM/WM interface integrity did not show detectable regional differences, although the group of MS patients whose disability progressed showed a significant decrease in GM/WM interface integrity compared to the stable group (P = 0.003). Regional measures of apparent loss of cGM thickness enhance sensitivity to cortical pathological changes. A measure of integrity offers a new index of disease-associated cortical changes at the GM/WM interface. The results suggest that progression of disability in MS is associated with the progression of MRI-detectable cortical pathology.
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Journal Article |
20 |
104 |
20
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Abstract
The preanalytic phase is an important component of total laboratory quality. A wide range of variables that affect the result for a patient from whom a specimen of blood or body fluid has been collected, including the procedure for collection, handling, and processing before analysis, constitute the preanalytic phase. Physiologic variables, such as lifestyle, age, and sex, and conditions such as pregnancy and menstruation, are some of the preanalytic phase factors. Endogenous variables such as drugs or circulating antibodies might interact with a specific method to yield spurious analytic results. The preanalytic phase variables affect a wide range of laboratory disciplines.
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Review |
25 |
96 |
21
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Mani C, Selvakumar N, Narayanan S, Narayanan PR. Mutations in the rpoB gene of multidrug-resistant Mycobacterium tuberculosis clinical isolates from India. J Clin Microbiol 2001; 39:2987-90. [PMID: 11474030 PMCID: PMC88277 DOI: 10.1128/jcm.39.8.2987-2990.2001] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mutations in the 81-bp rifampin resistance-determining region (RRDR) of the rpoB gene were analyzed by DNA sequencing of 50 Mycobacterium tuberculosis clinical isolates (44 resistant and 6 sensitive) from various parts of India. Fifty-three mutations of 18 different kinds, 17 point mutations and one deletion, were observed in 43 of 44 resistant isolates. Three novel mutations and three new alleles within the RRDR, along with two novel mutations outside the RRDR, are reported in this study.
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research-article |
24 |
94 |
22
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Trojan DA, Arnold D, Collet JP, Shapiro S, Bar-Or A, Robinson A, Le Cruguel JP, Ducruet T, Narayanan S, Arcelin K, Wong AN, Tartaglia MC, Lapierre Y, Caramanos Z, Da Costa D. Fatigue in multiple sclerosis: association with disease-related, behavioural and psychosocial factors. Mult Scler 2007; 13:985-95. [PMID: 17468448 DOI: 10.1177/1352458507077175] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We determined biopsychosocial correlates of general, physical, and mental fatigue in MS patients, by evaluating the additional contribution of potentially modifiable factors after accounting for non-modifiable disease-related factors. Fifty-three ambulatory MS patients, along with 28 normal controls were recruited for a cross-sectional study. Subjects completed the Multidimensional Fatigue Inventory (MFI) and Fatigue Severity Scale. Potential correlates evaluated were: disease-related factors (disease duration and type, immunomodulating treatment, muscle strength, pain, forced vital capacity (FVC), respiratory muscle strength, body mass index, disability, fibromyalgia), behavioural factors (physical activity, sleep quality) and psychosocial factors (depression, stress, self-efficacy). Multivariate models were calculated for MFI General, Physical, and Mental Fatigue. Age-adjusted multivariate models with non-modifiable factors included the following predictors (P < or = 0.10) of 1) MFI General and Mental Fatigue: none; and 2) MFI Physical Fatigue: FVC and disability. The following potentially modifiable predictors (P < or = 0.10) made an additional contribution to the models 1) MFI General Fatigue: sleep quality, self-efficacy, pain; 2) MFI Physical Fatigue: self-efficacy, physical activity; and 3) MFI Mental Fatigue: stress, self-efficacy. Fatigue in MS is multidimensional. Correlates of general and physical fatigue are disease-related, behavioural and psychosocial factors. Correlates of mental fatigue are psychosocial factors. Potentially modifiable factors account for a considerable portion of fatigue.
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Research Support, Non-U.S. Gov't |
18 |
91 |
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Clay PG, Nag S, Graham CM, Narayanan S. Meta-Analysis of Studies Comparing Single and Multi-Tablet Fixed Dose Combination HIV Treatment Regimens. Medicine (Baltimore) 2015; 94:e1677. [PMID: 26496277 PMCID: PMC4620781 DOI: 10.1097/md.0000000000001677] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Revised: 08/21/2015] [Accepted: 09/02/2015] [Indexed: 01/08/2023] Open
Abstract
Availability of a single source review of once-daily fixed-dose single tablet regimen (STR) and multiple tablet fixed-dose regimen (MTR) would optimally inform healthcare providers and policy makers involved in the management of population with human immunodeficiency virus (HIV).We conducted a meta-analysis of published literature to compare patient adherence, clinical, and cost outcomes of STR to MTR.Published literature in English between 2005 and 2014 was searched using Embase, PubMed (Medline in-process), and ClinicalTrials.Gov databases. Two-level screening was undertaken by 2 independent researchers to finalize articles for evidence synthesis. Adherence, efficacy, safety, tolerability, healthcare resource use (HRU), and costs were assessed comparing STR to MTR. A random-effects meta-analysis was performed and heterogeneity examined using meta-regression.Thirty-five articles were identified for qualitative evidence synthesis, of which 9 had quantifiable data for meta-analysis (4 randomized controlled trials and 5 observational studies). Patients on STR were significantly more adherent when compared to patients on MTR of any frequency (odds ratio [OR]: 2.37 [95% CI: 1.68, 3.35], P < 0.001; 4 studies), twice-daily MTR (OR: 2.53 [95% CI: 1.13, 5.66], P = 0.02; 2 studies), and once-daily MTR (OR: 1.81 [95% CI: 1.15, 2.84], P = 0.01; 2 studies). The relative risk (RR) for viral load suppression at 48 weeks was higher (RR: 1.09 [95% CI: 1.04, 1.15], P = .0003; 3 studies) while RR of grade 3 to 4 laboratory abnormalities was lower among patients on STR (RR: 0.68 [95% CI: 0.49, 0.94], P = 0.02; 2 studies). Changes in CD4 count at 48 weeks, any severe adverse events (SAEs), grade 3 to 4 AEs, mortality, and tolerability were found comparable between STR and MTR. Several studies reported significant reduction in HRU and costs among STR group versus MTR.Study depicted comparable tolerability, safety (All-SAE and Grade 3-4 AE), and mortality and fewer Grade 3 to 4 lab abnormalities and better viral load suppression and adherence among patients on FDC-containing STR versus MTR; literature depicted favorable HRU and costs for STRs.These findings may help decision makers especially in resource-poor settings to plan for optimal HIV disease management when the choice of both STRs and MTRs are available.
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Comparative Study |
10 |
86 |
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Sled JG, Levesque I, Santos AC, Francis SJ, Narayanan S, Brass SD, Arnold DL, Pike GB. Regional variations in normal brain shown by quantitative magnetization transfer imaging. Magn Reson Med 2004; 51:299-303. [PMID: 14755655 DOI: 10.1002/mrm.10701] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A quantitative magnetization transfer imaging (qMTI) study, based on a two-pool model of magnetization transfer, was performed on seven normal subjects to determine, on a regional basis, normal values for the pool sizes, exchange, and relaxation parameters that characterize the MT phenomenon. Regions were identified on high-resolution anatomical scans using a combination of manual and automatic methods. Only voxels identified as pure tissue at the resolution of the quantitative scans were considered for analysis. While no left/right differences were observed, significant differences were found among white-matter regions and gray-matter regions. These regional differences were compared with existing cytoarchitectural data. In addition, the pattern and magnitude of the regional differences observed in white matter was found to be different from that reported previously for an alternative putative MRI measure of myelination, the 10-50-ms T2 component described as myelin water.
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Journal Article |
21 |
79 |
25
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Djanaguiraman M, Narayanan S, Erdayani E, Prasad PVV. Effects of high temperature stress during anthesis and grain filling periods on photosynthesis, lipids and grain yield in wheat. BMC PLANT BIOLOGY 2020; 20:268. [PMID: 32517754 PMCID: PMC7285450 DOI: 10.1186/s12870-020-02479-0] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 06/01/2020] [Indexed: 05/03/2023]
Abstract
BACKGROUND Short episodes of high temperature (HT) stress during reproductive stages of development cause significant yield losses in wheat (Triticum aestivum L.). Two independent experiments were conducted to quantify the effects of HT during anthesis and grain filling periods on photosynthesis, leaf lipidome, and yield traits in wheat. In experiment I, wheat genotype Seri82 was exposed to optimum temperature (OT; 22/14 °C; day/night) or HT (32/22 °C) for 14 d during anthesis stage. In experiment II, the plants were exposed to OT or HT for 14 d during the grain filling stage. During the HT stress, chlorophyll index, thylakoid membrane damage, stomatal conductance, photosynthetic rate and leaf lipid composition were measured. At maturity, grain yield and its components were quantified. RESULTS HT stress during anthesis or grain filling stage decreased photosynthetic rate (17 and 25%, respectively) and grain yield plant- 1 (29 and 44%, respectively), and increased thylakoid membrane damage (61 and 68%, respectively) compared to their respective control (OT). HT stress during anthesis or grain filling stage increased the molar percentage of less unsaturated lipid species [36:5- monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)]. However, at grain filling stage, HT stress decreased the molar percentage of more unsaturated lipid species (36:6- MGDG and DGDG). There was a significant positive relationship between photosynthetic rate and grain yield plant- 1, and a negative relationship between thylakoid membrane damage and photosynthetic rate. CONCLUSIONS The study suggests that maintaining thylakoid membrane stability, and seed-set per cent and individual grain weight under HT stress can improve the photosynthetic rate and grain yield, respectively.
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research-article |
5 |
77 |