Longitudinal assessment of tissue properties and cardiac diffusion metrics of the ex vivo porcine heart at 7 T: Impact of continuous tissue fixation using formalin

In this study we aimed to assess the effects of continuous formalin fixation on diffusion and relaxation metrics of the ex vivo porcine heart at 7 T. Magnetic resonance imaging was performed on eight piglet hearts using a 7 T whole body system. Hearts were measured fresh within 3 hours of cardiac arrest followed by immersion in 10% neutral buffered formalin. T₂^* and T₂ were assessed using a gradient multi‐echo and multi‐echo spin echo sequence, respectively. A spin echo and a custom stimulated echo sequence were employed to assess diffusion time‐dependent changes in metrics of cardiac diffusion tensor imaging. SNR was determined for b = 0 images. Scans were performed for 5 mm thick apical, midcavity and basal slices (in‐plane resolution: 1 mm) and repeated 7, 15, 50, 100 and 200 days postfixation. Eigenvalues of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) decreased significantly (P < 0.05) following fixation. Relative to fresh hearts, FA values 7 and 200 days postfixation were 90% and 80%, while respective relative ADC values at those fixation stages were 78% and 92%. Statistical helix and sheetlet angle distributions as well as respective mean and median values showed no systematic influence of continuous formalin fixation. Similar to changes in the ADC, values for T₂, T₂^* and SNR dropped initially postfixation. Respective relative values compared with fresh hearts at day 7 were 64%, 79% and 68%, whereas continuous fixation restored T₂, T₂^* and SNR leading to relative values of 74%, 100%, and 81% at day 200, respectively. Relaxation parameters and diffusion metrics are significantly altered by continuous formalin fixation. The preservation of microstructure metrics following prolonged fixation is a key finding that may enable future studies of ventricular remodeling in cardiac pathologies.     

Diffusion Tensor Imaging of Heterotopia: Changes of Fractional Anisotropy during Radial Migration of Neurons

Purpose

Diffusion tensor imaging provides better understanding of pathophysiology of congenital anomalies, involving central nervous system. This study was aimed to specify the pathogenetic mechanism of heterotopia, proved by diffusion tensor imaging, and establish new findings of heterotopia on fractional anisotropy maps.

Materials and Methods

Diffusion-weighted imaging data from 11 patients (M : F = 7 : 4, aged from 1 to 22 years, mean = 12.3 years) who visited the epilepsy clinic and received a routine seizure protocol MRI exam were retrospectively analyzed. Fractional anisotropy (FA) maps were generated from diffusion tensor imaging of 11 patients with heterotopia. Regions of interests (ROI) were placed in cerebral cortex, heterotopic gray matter and deep gray matter, including putamen. ANOVA analysis was performed for comparison of different gray matter tissues.

Results

Heterotopic gray matter showed signal intensities similar to normal gray matter on T1 and T2 weighted MRI. The measured FA of heterotopic gray matter was higher than that of cortical gray matter (0.236 ± 0.011 vs. 0.169 ± 0.015, p < 0.01, one way ANOVA), and slightly lower than that of deep gray matter (0.236 ± 0.011 vs. 0.259 ± 0.016, p < 0.01).

Conclusion

Increased FA of heterotopic gray matter suggests arrested neuron during radial migration and provides better understanding of neurodevelopment.     

Value of Formalin Fixation for the Prolonged Preservation of Rodent Myocardial Microanatomical Organization: Evidence by MR Diffusion Tensor Imaging

Previous ex vivo diffusion tensor imaging (DTI) studies on formalin‐fixed myocardial tissue assumed that, after some initial changes in the first 48 hr since the start of fixation, DTI parameters remain stable over time. Prolonged preservation of cardiac tissue in formalin prior to imaging has been seen many times in the DTI literature as it is considered orderly. Our objective is to define the effects of the prolonged cardiac tissue exposure to formalin on tissue microanatomical organization, as this is assessed by DTI parameters. DTI experiments were conducted on eight excised rodent hearts that were fixed by immersion in formalin. The samples were randomly divided into two equinumerous groups corresponding to shorter (～2 weeks) and more prolonged (～6–8 weeks) durations of tissue exposure to formalin prior to imaging. We found that when the duration of cardiac tissue exposure to formalin before imaging increased, water diffusion became less restricted, helix angle (HA) histograms flattened out and exhibited heavier tails (even though the classic HA transmural variation was preserved), and a significant loss of inter‐voxel primary diffusion orientation integrity was introduced. The prolonged preservation of cardiac tissue in formalin profoundly affected its microstructural organization, as this was assessed by DTI parameters. The accurate interpretation of diffusivity profiles necessitates awareness of the pitfalls of prolonged cardiac tissue exposure duration to formalin. The acquired knowledge works to the advantage of a proper experimental design of DTI studies of fixed hearts. Anat Rec, 299:878–887, 2016. © 2016 Wiley Periodicals, Inc.     

The relationship between sagittal curvature and extensor muscle volume in the lumbar spine

A previous modelling study predicted that the forces applied by the extensor muscles to stabilise the lumbar spine would be greater in spines that have a larger sagittal curvature (lordosis). Because the force-generating capacity of a muscle is related to its size, it was hypothesised that the size of the extensor muscles in a subject would be related to the size of their lumbar lordosis. Magnetic resonance imaging (MRI) data were obtained, together with age, height, body mass and back pain status, from 42 female subjects. The volume of the extensor muscles (multifidus and erector spinae) caudal to the mid-lumbar level was estimated from cross-sectional area measurements in axial T1-weighted MRIs spanning the lumbar spine. Lower lumbar curvature was determined from sagittal T1-weighted images. A stepwise linear regression model was used to determine the best predictors of muscle volume. The mean lower lumbar extensor muscle volume was 281 cm³ (SD = 49 cm³). The mean lower lumbar curvature was 30 ° (SD = 7 °). Five subjects reported current back pain and were excluded from the regression analysis. Nearly half the variation in muscle volume was accounted for by the variables age (standardised coefficient, B = −3.2, P = 0.03) and lower lumbar curvature (B = 0.47, P = 0.002). The results support the hypothesis that extensor muscle volume in the lower lumbar spine is related to the magnitude of the sagittal curvature; this has implications for assessing muscle size as an indicator of muscle strength.     

Effect of hepatocyte growth factor and angiotensin II on rat cardiomyocyte hypertrophy

Angiotensin II (Ang II) plays an important role in cardiomyocyte hypertrophy. The combined effect of hepatocyte growth factor (HGF) and Ang II on cardiomyocytes is unknown. The present study was designed to determine the effect of HGF on cardiomyocyte hypertrophy and to explore the combined effect of HGF and Ang II on cardiomyocyte hypertrophy. Primary cardiomyocytes were isolated from neonatal rat hearts and cultured in vitro. Cells were treated with Ang II (1 µM) alone, HGF (10 ng/mL) alone, and Ang II (1 µM) plus HGF (10 ng/mL) for 24, 48, and 72 h. The amount of [³H]-leucine incorporation was then measured to evaluate protein synthesis. The mRNA levels of β-myosin heavy chain and atrial natriuretic factor were determined by real-time PCR to evaluate the presence of fetal phenotypes of gene expression. The cell size of cardiomyocytes was also studied. Ang II (1 µM) increased cardiomyocyte hypertrophy. Similar to Ang II, treatment with 1 µM HGF promoted cardiomyocyte hypertrophy. Moreover, the combination of 1 µM Ang II and 10 ng/mL HGF clearly induced a combined pro-hypertrophy effect on cardiomyocytes. The present study demonstrates for the first time a novel, combined effect of HGF and Ang II in promoting cardiomyocyte hypertrophy.     

Two-step anomalous diffusion tensor imaging

We extend the formalism of anomalous diffusion imaging to include directional anisotropy of fitted parameters. The resulting technique is termed anomalous diffusion tensor imaging (aDTI), and allows the directional properties of the distributed diffusion coefficient (α) and the anomalous diffusion exponent, (γ) to be analysed using the same analytical techniques as regular diffusion tensor imaging (DTI). Together, these parameters quantify the rate of diffusion (α) and the complexity of the diffusion environment (γ). We generated tensor images for the anomalous exponent tensor (Γ) and distributed diffusivity tensor (A) from in vivo human brain data and present images of eigenvalues, eigenvectors, Trace/3 (Tr), fractional anisotropy (FA) and tensor shape measures. In white matter, A is found to have a median Tr = 0.56 × 10^{? 3}mm²s^{? 1}, FA = 0.58 and Γ Tr = 0.69, FA = 0.13. We observed that white matter shows a similar anisotropic geometry for the distributed diffusion tensor as for the regular diffusion tensor, whereas the anomalous exponent tensor exhibits a different shape characteristic which may be informative of tissue microstructure. Copyright © 2011 John Wiley & Sons, Ltd.     

The pattern of the coronary arterial orifices in hearts with congenital malformations of the outflow tracts: a marker of rotation of the outflow tract during cardiac development?

Outflow tract defects, including cardiac neural crest defects (so-called conotruncal defects) and transposition of the great arteries, are due to an abnormal rotation of the outflow tract during cardiac development. Coronary orifices are often abnormal in outflow tract defects, particularly in common arterial trunk (CAT). A recent study indicates that abnormal coronary artery pattern in a mouse model with common arterial outlet (Tbx1−/− mouse mutant) could be due to a reduced and malpositioned subpulmonary coronary-refractory myocardial domain. The aim of our study was to demonstrate the relation between coronary orifices pattern in outflow tract defects in human and the abnormal embryonic rotation of the outflow tract. We analyzed 101 heart specimens with outflow tract defects: 46 CAT, 15 tetralogy of Fallot (TOF), 29 TOF with pulmonary atresia (TOF-PA), 11 double-outlet right ventricle with subaortic ventricular septal defect (DORV) and 17 controls. The position of left and right coronary orifices (LCO, RCO) was measured in degrees on the aortic/truncal circumference. The anterior angle between LCO and RCO (α) was calculated. The LCO was more posterior in TOF (31 °), TOF-PA (47 °), DORV (44 °), CAT (63 °), compared with controls (0 °, P < 0.05), and more posterior in CAT than in other outflow tract defects (P < 0.05). The RCO was more anterior in TOF (242 °), TOF-PA (245 °) and DORV (271 °) than in controls (213 °, P < 0.05), but not in CAT (195 °). The α angle was similar in TOF, TOF-PA, DORV and controls (149 °, 162 °, 133 °, 147 °), but significantly larger in CAT (229 °, P < 0.0001). In all outflow tract defects but CAT, the displacement of LCO (anterior) and RCO (posterior), while the α angle remains constant, might be due to incomplete rotation of the myocardium at the base of the outflow tract, leading to an abnormally positioned subpulmonary coronary-refractory myocardial domain. The larger α angle in CAT could reflect its dual identity, aortic and pulmonary.     

Murine MicroRNA‐214 regulates intracellular adhesion molecule (ICAM1) gene expression in genital Chlamydia muridarum infection

The hallmark of chlamydial infection is the development of upper genital pathology in the form of hydrosalpinx and oviduct and/or tubal dilatation. Although molecular events leading to genital tissue presentation and cellular architectural remodelling are unclear, early-stage host immune responses are believed to contribute to these long-term sequelae. Recently, we reported the contribution of selected infection-associated microRNAs (miRs) in the generation of host immunity at early-stage infection (day 6 after intravaginal Chlamydia muridarum challenge in C57BL/6 mice). In this report, we describe the contribution of an infection-associated microRNA, i.e. miR-214, to host immunity. Chlamydia muridarum infection in the C57BL/6 mouse genital tract significantly down-regulated miR-214 while up-regulating intracellular adhesion molecule 1 (ICAM1) gene expression. These in vivo observations were confirmed by establishing direct regulation of ICAM-1 by miR-214 in ex vivo genital cell cultures in the presence of miR-214 mimic and inhibitor. Because, ICAM-1 contributes to recruitment of neutrophils following infection, we also demonstrated that alteration of ICAM1 by miR-214 in interleukin-17A-deficient (IL-17A^−/−) mice correlated with reduction of neutrophils infiltrating genital tissue at day 6 after challenge. Additionally, these early-stage events resulted in significantly decreased genital pathology in IL-17A^−/− mice compared with C57BL/6 mice. This report provides evidence for early-stage regulation of ICAM1 by microRNAs, resulting in reduction of genital pathology associated with chlamydial infection.     

Medial gastrocnemius muscle growth during adolescence is mediated by increased fascicle diameter rather than by longitudinal fascicle growth

Using a cross-sectional design, the purpose of this study was to determine how pennate gastrocnemius medialis (GM) muscle geometry changes as a function of adolescent age. Sixteen healthy adolescent males (aged 10–19 years) participated in this study. GM muscle geometry was measured within the mid-longitudinal plane obtained from a 3D voxel-array composed of transverse ultrasound images. Images were taken at footplate angles corresponding to standardised externally applied footplate moments (between 4 Nm plantar flexion and 6 Nm dorsal flexion). Muscle activity was recorded using surface electromyography (EMG), expressed as a percentage of maximal voluntary contraction (%MVC). To minimise the effects of muscle excitation, EMG inclusion criteria were set at < 10% of MVC. In practice, however, normalised EMG levels were much lower. For adolescent subjects with increasing ages, GM muscle (belly) length increased due to an increase in the length component of the physiological cross-sectional area measured within the mid-longitudinal plane. No difference was found between fascicles at different ages, but the aponeurosis length and pennation angle increased by 0.5 cm year⁻¹ and 0.5 ° per year, respectively. Footplate angles corresponding to externally applied 0 and 4 Nm plantarflexion moments were not associated with different adolescent ages. In contrast, footplate angles corresponding to externally applied 4 and 6 Nm dorsal flexion moments decreased by 10 ° between 10 and 19 years. In conclusion, we found that in adolescents'' pennate GM muscles, longitudinal muscle growth is mediated predominantly by increased muscle fascicle diameter.     

A complementary diffusion tensor imaging (DTI)-histological study in a model of Huntington's disease

In vivo diffusion tensor imaging (DTI) was performed on the quinolinic acid (QUIN) rat model of Huntington's disease, together with behavioral assessment of motor deficits and histopathological characterization. DTI and histology revealed the presence of a cortical lesion in 53% of the QUIN animals (QUIN^+ctx). Histologically, QUIN^+ctx were distinguished from QUIN^−ctx animals by increased astroglial reaction within a subregion of the caudate putamen and loss of white matter in the external capsula. Although both techniques are complementary, the quantitative character of DTI makes it possible to pick up subtle differences in tissue microstructure that are not identified with histology. DTI demonstrated differential changes of fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD) in the internal and external capsula, and within a subregion of the caudate putamen. It was suggested that FA increased due to a selective loss of the subcortical connections targeted by degenerative processes at the early stage of the disease, which might turn the striatum into a seemingly more organized structure. When tissue degeneration becomes more severe, FA decreased while AD, RD and MD increased.     

Diffusion Tensor Imaging of Ex Vivo Cervical Spinal Cord Specimens: The Immediate and Long‐Term Effects of Fixation on Diffusivity

Diffusion tensor imaging (DTI) is an emerging noninvasive method for evaluating tissue microstructure, but is highly susceptible to in vivo motion artifact. Ex vivo experiments on fixed tissues are needed to improve DTI techniques, which require fixed tissue specimens. Several efforts have been made to study the effect of fixation on both human and mouse tissue, with varying results. Four human cervical cords and three segments of pig cervical spinal cord specimens were imaged both before and after tissue fixation using 3D multishot diffusion weighted imaging (ms‐DWEPI). Fixation caused a significant decrease in the longitudinal diffusivity whereas the relative anisotropy (RA) and radial diffusivity remained unaffected. Additionally, once adequately preserved, the diffusivity parameters of fixed tissue remain constant over time. Fixation has important effects on the diffusivity of tissue specimens. These findings have important implications for the determination of tissue microstructure and function using DTI technologies. Anat Rec, 2009. © 2008 Wiley‐Liss, Inc.     

Diffusion tensor imaging of the human calf muscle: distinct changes in fractional anisotropy and mean diffusion due to passive muscle shortening and stretching

The influence of passive shortening and stretching of the calf muscles on diffusion characteristics was investigated. The diffusion tensor was measured in transverse slices through the lower leg of eight healthy volunteers (29 ± 7 years) on a 3 T whole‐body MR unit in three different positions of the foot (40° plantarflexion, neutral ankle position (0°), and ?10° dorsiflexion in the ankle). Maps of the mean diffusivity, the three eigenvalues of the tensor and fractional anisotropy (FA) were calculated. Results revealed a distinct dependence of the mean diffusivity and FA on the foot position and the related shortening and stretching of the muscle groups. The tibialis anterior muscle showed a significant increase of 19% in FA with increasing dorsiflexion, while the FA of the antagonists significantly decreased (～20%). Regarding the mean diffusivity of the diffusion tensor, the muscle groups showed an opposed response to muscle elongation and shortening. Regarding the eigenvalues of the diffusion tensor, λ₂ and λ₃ showed significant changes in relation to muscle length. In contrast, no change in λ₁ could be found. This work reveals significant changes in diffusional characteristics induced by passive muscle shortening and stretching. Copyright © 2009 John Wiley & Sons, Ltd.     

The role of Ca2+/calmodulin-dependent protein kinase II and calcineurin in TNF-α-induced myocardial hypertrophy

We investigated whether Ca²⁺/calmodulin-dependent kinase II (CaMKII) and calcineurin (CaN) are involved in myocardial hypertrophy induced by tumor necrosis factor α (TNF-α). The cardiomyocytes of neonatal Wistar rats (1-2 days old) were cultured and stimulated by TNF-α (100 µg/L), and Ca²⁺ signal transduction was blocked by several antagonists, including BAPTA (4 µM), KN-93 (0.2 µM) and cyclosporin A (CsA, 0.2 µM). Protein content, protein synthesis, cardiomyocyte volumes, [Ca²⁺]_i transients, CaMKIIδ_B and CaN were evaluated by the Lowry method, [³H]-leucine incorporation, a computerized image analysis system, a Till imaging system, and Western blot analysis, respectively. TNF-α induced a significant increase in protein content in a dose-dependent manner from 10 µg/L (53.56 µg protein/well) to 100 µg/L (72.18 µg protein/well), and in a time-dependent manner from 12 h (37.42 µg protein/well) to 72 h (42.81 µg protein/well). TNF-α (100 µg/L) significantly increased the amplitude of spontaneous [Ca²⁺]_i transients, the total protein content, cell size, and [³H]-leucine incorporation in cultured cardiomyocytes, which was abolished by 4 µM BAPTA, an intracellular Ca²⁺ chelator. The increases in protein content, cell size and [³H]-leucine incorporation were abolished by 0.2 µM KN-93 or 0.2 µM CsA. TNF-α increased the expression of CaMKIIδ_B by 35.21% and that of CaN by 22.22% compared to control. These effects were abolished by 4 µM BAPTA, which itself had no effect. These results suggest that TNF-α induces increases in [Ca²⁺]_i, CaMKIIδ_B and CaN and promotes cardiac hypertrophy. Therefore, we hypothesize that the Ca²⁺/CaMKII- and CaN-dependent signaling pathways are involved in myocardial hypertrophy induced by TNF-α.     

Ex vivo diffusion tensor MRI reflects microscopic structural remodeling associated with aging and disease progression in normal and cardiomyopathic Syrian hamsters

Dilated cardiomyopathy (DCM) is a major cause of mortality and morbidity in cardiac patients. Aging is often an ignored etiology of pathological conditions. Quantification of DCM and aging associated cardiac structural remodeling is important in guiding and evaluating therapeutic interventions. Diffusion tensor magnetic resonance imaging (DTMRI) has recently been used for nondestructive characterization of three‐dimensional myofiber structure. In this study, we explored the potential of DTMRI in delineating microscopic structural remodeling in aging and DCM hearts. Six month (n = 10) and nine month old (n = 11) DCM (TO‐2) hamsters and their age‐matched controls (F1β) were characterized. Both aging and DCM hearts showed increased diffusivity and decreased diffusion anisotropy. DTMRI images of DCM hearts also revealed a subgroup of imaging pixels characterized by decreased radial diffusivity and increased FA. The location of these pixels showed qualitative agreement with regions of calcium deposition determined by X‐ray CT imaging. Histological analysis confirmed expanded extracellular space in aging and DCM hearts as well as substantial calcium deposition in DCM hearts. These results suggest that DTMRI may provide a noninvasive technique to delineate structural remodeling associated with aging and DCM progression at the tissue and cellular level without the use of an exogenous contrast agent. Copyright © 2009 John Wiley & Sons, Ltd.     

Measurement and modeling of diffusion time dependence of apparent diffusion coefficient and fractional anisotropy in prostate tissue ex vivo

The purpose of this study was to measure and model the diffusion time dependence of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) derived from conventional prostate diffusion‐weighted imaging methods as used in recommended multiparametric MRI protocols. Diffusion tensor imaging (DTI) was performed at 9.4 T with three radical prostatectomy specimens, with diffusion times in the range 10–120 ms and b‐values 0–3000 s/mm². ADC and FA were calculated from DTI measurements at b‐values of 800 and 1600 s/mm². Independently, a two‐component model (restricted isotropic plus Gaussian anisotropic) was used to synthesize DTI data, from which ADC and FA were predicted and compared with the measured values. Measured ADC and FA exhibited a diffusion time dependence, which was closely predicted by the two‐component model. ADC decreased by about 0.10–0.15 μm²/ms as diffusion time increased from 10 to 120 ms. FA increased with diffusion time at b‐values of 800 and 1600 s/mm² but was predicted to be independent of diffusion time at b = 3000 s/mm². Both ADC and FA exhibited diffusion time dependence that could be modeled as two unmixed water pools — one having isotropic restricted dynamics, and the other unrestricted anisotropic dynamics. These results highlight the importance of considering and reporting diffusion times in conventional ADC and FA calculations and protocol recommendations, and inform the development of improved diffusion methods for prostate cancer imaging.     

Relevance of Foxp3+ regulatory T cells for early and late phases of murine sepsis

The role of Foxp3⁺ regulatory T (Treg) cells in the course of the early hyper-inflammatory and subsequent hypo-inflammatory phases of sepsis is ambiguous. Whereas Nrp1 expression has been reported to discriminate natural Treg cells from induced Treg cells, the Treg cell stability depends on the methylation status of foxp3-TSDR. To specifically evaluate the role of Foxp3⁺ Treg cells in the early and late phases of sepsis, we induced sepsis by caecal ligation and puncture and subsequent Pseudomonas aeruginosa lung infection in a DEREG (DEpletion of REGulatory T cells) mouse model. We found an increase of Foxp3⁺ Treg cells to all CD4⁺ T cells during murine sepsis. Using a new methylation-sensitive quantitative RT-PCR method and deep amplicon sequencing, we demonstrated that natural (Nrp1⁺ Foxp3⁺) Treg cells and most induced (Nrp1⁻ Foxp3⁺) Treg cells are stable and exhibit unmethylated foxp3-TSDR, and that both Treg populations are functionally suppressive in healthy and septic mice. DEREG mice depleted of Foxp3⁺ Treg cells exhibit higher disease scores, mortality rates and interleukin-6 expression levels than do non-depleted DEREG mice in early-phase sepsis, a finding indicating that Foxp3⁺ Treg cells limit the hyper-inflammatory response and accelerate recovery. Treg cell depletion before secondary infection with P. aeruginosa 1 week after caecal ligation and puncture does not influence cytokine levels or the course of secondary infection. However, a moderate Treg cell recurrence, which we observed in DEREG mice during secondary infection, may interfere with these results. In summary, Treg cells contribute to a positive outcome after early-phase sepsis, but the data do not support a significant role of Treg cells in immune paralysis during late-phase sepsis.     

Full diffusion characterization implicates regionally disparate neuropathology in Mild Cognitive Impairment

Diffusion tensor imaging (DTI) is used to detect tissue pathology. In Alzheimer’s disease (AD) research, DTI has been used to elucidate differences in disease stages and to track progression over time and clinical severity. Many of these studies have identified the fornix as particularly vulnerable in the early stages of pathology associated with memory decline in prodromal AD. Emerging research suggests principal tensor components, axial (DA) and radial (DR) diffusivity, are more sensitive to underlying tissue pathology than are mean diffusivity (MD) and fractional anisotropy (FA). Given the established regionally specific tissue decline in MCI, we examined components of the full diffusion tensor (MD, FA, DR, and DA) for sensitivity to regional pathology associated with specific memory deficits in 18 individuals with MCI. We investigated multiple regions of interest, including fornix, temporal stem, and control regions for association with severity of impairment on multiple memory measures, including a type of neuropsychological task shown to be particularly sensitive to early memory decline in MCI. Better paired associate learning was selectively associated with lower DA (β = ?0.663, p = 0.003), but not with DR, MD, or FA of the temporal stems. Conversely, better paired associate learning was associated with lower DR (β = ?0.523, p = 0.026), higher FA (β = 0.498, p = 0.036), and lower MD (β = ?0.513, p = 0.030), but not DA in the fornix. No association was found for control regions, or for control cognitive measures. These findings suggest disparate pathology of temporal stems and fornix white matter in association with early memory impairment in MCI. Further, they highlight the methodological importance of evaluating the full tensor, rather than only summative metrics in research using DTI.     

Increased frequency and suppressive activity of CD127low/− regulatory T cells in the peripheral circulation of patients with head and neck squamous cell carcinoma are associated with advanced stage and nodal involvement

The presence of regulatory T (Treg) cells is thought to be an important mechanism by which head and neck squamous cell carcinoma (HNSCC) successfully evades the immune system. Using multicolour flow cytometry, the frequency and functional capacity of two CD4⁺ CD127^low/− Treg cell populations, separated on the basis of different levels of CD25 expression (CD25^inter and CD25^high), from the peripheral circulation of newly presenting HNSCC patients were assessed with regard to clinicopathological features and healthy controls. The frequency of circulating Treg cells was similar between HNSCC patients and healthy controls, and for patients with HNSCC developing from different subsites (laryngeal compared with oropharyngeal). However, patients with advanced stage tumours and those with nodal involvement had significantly elevated levels of CD4⁺ CD25^high CD127^low/− Treg cells compared with patients who had early stage tumours (P = 0·03) and those without nodal involvement (P = 0·03), respectively. CD4⁺ CD25^high CD127^low/− Treg cells from the entire HNSCC patient cohort and from patients whose tumours had metastasized to the lymph nodes were also shown to suppress the proliferation of effector T cells significantly more, compared with those from healthy controls (P = 0·04) or patients with no nodal involvement (P = 0·04). Additionally, CD4⁺ CD25^inter CD127^low/− Treg cells consistently induced greater suppressive activity than CD4⁺ CD25^high CD127^low/− Treg cells on the proliferation of the effector T-cell populations (CD4⁺ CD25⁻ CD127^−/+ and CD4⁺ CD25⁺ CD127⁺). Peripheral Treg cells, identified by the CD127^low/− phenotype, have been shown to be influenced by a patient''s tumour stage and/or nodal status in HNSCC; suggesting a role in tumour progression that could be manipulated by future immunotherapy.     

Effect of trimetazidine treatment on the transient outward potassium current of the left ventricular myocytes of rats with streptozotocin-induced type 1 diabetes mellitus

Cardiovascular complications are a leading cause of mortality in patients with diabetes mellitus (DM). The present study was designed to investigate the effects of trimetazidine (TMZ), an anti-angina drug, on transient outward potassium current (I_to) remodeling in ventricular myocytes and the plasma contents of free fatty acid (FFA) and glucose in DM. Sprague-Dawley rats, 8 weeks old and weighing 200-250 g, were randomly divided into three groups of 20 animals each. The control group was injected with vehicle (1 mM citrate buffer), the DM group was injected with 65 mg/kg streptozotocin (STZ) for induction of type 1 DM, and the DM+TMZ group was injected with the same dose of STZ followed by a 4-week treatment with TMZ (60 mg·kg⁻¹·day⁻¹). All animals were then euthanized and their hearts excised and subjected to electrophysiological measurements or gene expression analyses. TMZ exposure significantly reversed the increased plasma FFA level in diabetic rats, but failed to change the plasma glucose level. The amplitude of I_to was significantly decreased in left ventricular myocytes from diabetic rats relative to control animals (6.25 ± 1.45 vs 20.72 ± 2.93 pA/pF at +40 mV). The DM-associated I_to reduction was attenuated by TMZ. Moreover, TMZ treatment reversed the increased expression of the channel-forming alpha subunit Kv1.4 and the decreased expression of Kv4.2 and Kv4.3 in diabetic rat hearts. These data demonstrate that TMZ can normalize, or partially normalize, the increased plasma FFA content, the reduced I_to of ventricular myocytes, and the altered expression Kv1.4, Kv4.2, and Kv4.3 in type 1 DM.     

Fiber type characterization in skeletal muscle by diffusion tensor imaging

Fiber type distribution within a skeletal muscle, i.e. the quantification of the relative amount of type 1 (slow‐twitching) and type 2 (fast‐twitching) muscle fibers, is of great interest for the monitoring of the effects of training or the treatment of muscle diseases. The purpose of this study was to determine the feasibility of diffusion tensor imaging (DTI) as a tool for noninvasive fiber type quantification in human skeletal muscle. The right calves of 12 healthy volunteers were examined using DTI at 1.5 T. Standard DTI parameters, including fractional anisotropy (FA), and mean, radial and parallel diffusivity (MD, RD and PD, respectively), were determined in the soleus muscle. Fiber type proportion and mean fiber diameter within the soleus muscle were quantified from tissue specimens obtained via a fine needle biopsy. Linear regression analysis tested for associations between DTI and biopsy results. FA values were correlated significantly with fiber type proportion, such that higher FA values indicated a higher proportion of type 1 fibers (R² = 0.5, p = 0.01). This was based on lower diffusivity perpendicular to the main axis of the fiber in subjects with a higher type 1 fiber proportion (RD: R² = 0.52, p = 0.008). MD was also correlated with the proportion of type 1 fibers (R² = 0.37, p = 0.037), whereas PD showed no significant correlation. DTI is a promising method for the noninvasive estimation of fiber type proportion in skeletal muscle. This technique may be used to monitor training effects or may be further developed as a biomarker in certain muscle diseases. Copyright © 2013 John Wiley & Sons, Ltd.