Xiangtao Lin

Sexual dimorphism and asymmetry in human cerebellum: An MRI-based morphometric study

Structural sexual dimorphism and asymmetry in human cerebellum have been described in previous research, but results remain inconclusive or even conflicting. In this study, gender differences and hemispheric asymmetries in global and regional human cerebellum gray matter (GM) were estimated in an age-matched sample (n=112) of young Chinese adults. An optimized voxel-based morphometry (VBM) in spatial unbiased infratentorial template (SUIT) space together with an automated atlas-based volumetric approach were performed for mapping regional gray matter (GM) gender-related differences across the entire cerebellum. The two methods provided consistent findings on gender differences. The cerebellar GM volume was significantly larger in the anterior and middle posterior lobes of male group. In addition, a trend of greater GM volume in lateral posterior lobe of female group was observed. With the created symmetric cerebellar template, the asymmetric properties of cerebellar hemisphere were also assessed by VBM analysis, showing rightward asymmetry distributed in most cerebellar lobules and leftwards asymmetry distributed in the lobules around the medial posterior lobe. Gender differences in males showed higher leftward asymmetry sparsely within a few lobules and lower rightward asymmetry mainly within lobule Crus II, as compared with females. The acquired detailed morphologic knowledge of normal human cerebellum could establish a baseline for comparison with pathologic changes in the cerebellum. Moreover, our results might help to address controversies in thestudy of sexual dimorphisms and asymmetric patterns in human cerebellum.

The pineal volume: a three-dimensional volumetric study in healthy young adults using 3.0 T MR data

It is usually difficult to distinguish small pineal tumors via routine or enhanced magnetic resonance (MR) scan. The knowledge of normal pineal size is helpful to detect small pineal lesions, while very few true volumetric data of pineal glands have been reported. Therefore, we obtained the accurate reference range of normal pineal volumes in 112 individuals aged 20–30 years recruited randomly from a healthy community sample. Transverse and sagittal 3.0 T magnetic resonance data were obtained using three‐dimensional (3D) T1‐weighted FSPGR and T2‐weighted SE sequences. True pineal volumes were measured from T1‐weighted images, while estimated volumes were calculated using pineal length, width and height. All the glands were divided into three types according to the maximum inner diameter of pineal cysts. The prevalence of asymptomatic pineal cyst is 25.00%, with a slight female predominance. In the whole sample, we found no gender differences of pineal volume, but a significant gender difference of pineal volume index. A significant correlation between pineal volume and asymptomatic cyst was found. After excluding cases with big pineal cysts, there were significant correlations between pineal volume and head circumference, body height and body weight, respectively. This study suggests that asymptomatic pineal cysts may exert an important influence on pineal volume.

Spatial-temporal atlas of human fetal brain development during the early second trimester

During the second trimester, the human fetal brain undergoes numerous changes that lead to substantial variation in the neonatal in terms of its morphology and tissue types. As fetal MRI is more and more widely used for studying the human brain development during this period, a spatiotemporal atlas becomes necessary for characterizing the dynamic structural changes. In this study, 34 postmortem human fetal brains with gestational ages ranging from 15 to 22 weeks were scanned using 7.0 T MR. We used automated morphometrics, tensor-based morphometry and surface modeling techniques to analyze the data. Spatiotemporal atlases of each week and the overall atlas covering the whole period with high resolution and contrast were created. These atlases were used for the analysis of age-specific shape changes during this period, including development of the cerebral wall, lateral ventricles, Sylvian fissure, and growth direction based on local surface measurements. Our findings indicate that growth of the subplate zone is especially striking and is the main cause for the lamination pattern changes. Changes in the cortex around Sylvian fissure demonstrate that cortical growth may be one of the mechanisms for gyration. Surface deformation mapping, revealed by local shape analysis, indicates that there is global anterior-posterior growth pattern, with frontal and temporal lobes developing relatively quickly during this period. Our results are valuable for understanding the normal brain development trajectories and anatomical characteristics. These week-by-week fetal brain atlases can be used as reference in in vivo studies, and may facilitate the quantification of fetal brain development across space and time.

D-β-hydroxybutyrate inhibits the apoptosis of PC12 cells induced by 6-OHDA in relation to up-regulating the ratio of Bcl-2/Bax mRNA

D-beta-hydroxybutyrate (DbetaHB) is a predominant member of ketone bodies produced by hepatocytes and, to a lesser extent, by astrocytes. It is an alternative source of energy in the brain when glucose supply is depleted such as during starvation. It has been reported that ketone bodies could protect dopaminergic culture. However, the biological function of DbetaHB in Parkinson disease (PD) is still unclear. In the present work, we investigated the role of DbetaHB in protecting rat pheochromocytoma (PC12) cells from apoptosis induced by 6-Hydroxydopamine (6-OHDA). DbetaHB rescued PC12 cells from apoptotic death induced by 6-OHDA by MTT assay, acridine orange (AO) staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining and the activity of caspase-3. DbetaHB prevented the decrease of cell viability and the increase of caspase-3 activity induced by 6-OHDA in a dose-dependent manner in PC12 cells. AO and TUNEL staining showed that DbetaHB prevented the apoptosis of PC12 cells induced by 6-OHDA. The ratio of Bcl-2/Bax at mRNA levels, which regulates the apoptosis of PC12 cells when exposed to 6-OHDA, increased when DbetaHB was preincubated. The data showed that DbetaHB inhibited the apoptosis of PC12 cells induced by 6-OHDA in relation to up-regulating the ratio of Bcl-2/Bax mRNA.

Functional changes in the frontal cortex in Parkinson’s disease using a rat model

In recent years, investigations of the pathologic mechanism of Parkinsons disease (PD) have mainly concentrated on the basal ganglia. However, recent studies have confirmed that pathological changes in PD are accompanied by functional motor changes of the cerebral cortex. Rats were injected with 6-hydroxydopamine and ascorbic acid in the right substantia nigra. In this rat model of PD, magnetic resonance spectroscopy showed the ratio of N-acetyl-aspartic acid to creatine in a lesion in the right frontal cortex was significantly lower than the same ratio in a control group of rats. The ratio of choline to creatine in a lesion in the right frontal cortex was not significantly different between the PD-model rats and control rats. In addition, the optical densities of neurofilament protein and synaptophysin positive sites decreased significantly on the side of the brain with the injury compared with the side without the injury, and with both sides in the control rats. The density of synapses in the frontal cortex on the lesioned side was decreased compared with the unlesioned side. There were abnormal changes in the presynaptic membrane, postsynaptic membrane and synaptic vesicles, and the typical synaptic structure was no longer apparent on the lesioned side. We hypothesized loss of neurons and synapses, abnormal synaptic structure and neuron and synaptic dysfunction of the frontal cortex with a lesion in the injury side of the frontal cortex in PD-model rats. These changes might have an important role in the pathologic mechanism of PD.

Development of fetal brain of 20 weeks gestational age: Assessment with post-mortem Magnetic Resonance Imaging

BACKGROUND The 20th week gestational age (GA) is at mid-gestation and corresponds to the age at which the termination of pregnancy in several countries and the first Magnetic Resonance Imaging (MRI) can be performed, and at which the premature babies may survive. However, at present, very little is known about the exact anatomical character at this GA. OBJECTIVE To delineate the developing fetal brain of 20 weeks GA and obtain the three dimensional visualization model. MATERIALS AND METHODS 20 fetal specimens were scanned by 3.0 T and 7.0 T post-mortem MRI, and the three dimensional visualization model was obtained with Amira 4.1. RESULTS Most of the sulci or their anlage, except the postcentral sulcus and intraparietal sulcus, were present. The laminar organization, described as layers with different signal intensities, was most clearly distinguished at the parieto-occipital lobe and peripheral regions of the hippocampus. The basal nuclei could be clearly visualized, and the brain stem and cerebellum had formed their common shape. On the visualization model, the shape and relative relationship of the structures could be appropriately delineated. The ranges of normal values of the brain structures were obtained, but no sexual dimorphisms or cerebral asymmetries were found. CONCLUSIONS The developing fetal brain of 20 weeks GA can be clearly delineated on 3.0 T and 7.0 T post-mortem MRIs, and the three dimensional visualization model supplies great help in precise cognition of the immature brain. These results may have positive influences on the evaluation of the fetal brain in the uterus.

Development of the Fetal Cerebral Cortex in the Second Trimester: Assessment with 7T Postmortem MR Imaging

BACKGROUND AND PURPOSE: Few investigators have analyzed the fetal cerebral cortex with MR imaging of high magnetic strength. Our purpose was to document the sulcal development and obtain quantitative measurements of the fetal brain in the second trimester. MATERIALS AND METHODS: The brains of 69 fetal specimens, with GA 12–22 weeks, were first scanned on a 7T MR imaging scanner. Then the sequential development of the different fissures and sulci was analyzed, and quantitative measurements of the cerebral cortex were obtained. RESULTS: A new chronology of sulcal development during 12–22 weeks GA was summarized. Before 12 weeks, few sulci were present; by 16 weeks, many sulci were present. The 16th week could be considered the most intensive time point for sulcal emergence. Most sulci, except for the postcentral sulcus and intraparietal sulcus, were present by 22 weeks GA. Measurements of the fetal brains, each with different growth rates, linearly increased with GA, but no sexual dimorphisms or cerebral asymmetries were detected. CONCLUSIONS: The second trimester is the most important phase, during which most sulci are present and can be clearly shown on 7T postmortem MR imaging. It is apparent that the specific time during which neuropathologic features of sulci appear, previously thought to be well understood, should be redefined. Quantitative data provide assistance in the precise understanding of the immature brain. The present results are valuable in anatomic education, research, and assessment of normal brain development in the uterus.

Development of the human fetal cerebellum in the second trimester: a post mortem magnetic resonance imaging evaluation

The cerebellum is one of the most important structures in the posterior cranial fossa, but the characterization of its development by magnetic resonance imaging (MRI) is incomplete. We scanned 40 fetuses that had no morphological brain disorder at 14–22 weeks of gestation using 7.0 T MRI. Amira 4.1 software was used to determine morphological parameters of the fetal cerebellum, which included the cerebellar volume (CV), transverse cerebellar diameter (TCD), and the length and width of the vermis. The relationship between these measurements and gestational age (GA) was analysed. We found that the primary fissure was visible at week 14 of gestation. From week 16, the prepyramidal fissure, the secondary fissure and the dentate nucleus could be identified. The posterolateral fissure and the fourth ventricle were recognized at week 17, whereas the tentorium of the cerebellum was visible at week 20. The relationships between GA and CV, TCD, and the width and length of the vermis were described adequately by second‐order polynomial regression curves. The ratios between TCD and vermis length and between TCD and vermis width decreased with GA. These results show that 7.0 T MRI can show the trajectory of cerebellar development clearly. They increase our understanding of normal cerebellar development in the fetus, and will facilitate the diagnosis of pathological intrauterine changes in the cerebellum.

Cerebral glucose metabolism: Influence on perihematomal edema formation after intracerebral hemorrhage in cat models

Background: Most intracerebral hemorrhage (ICH) imaging studies focus on structural brain changes. Stereotactic neuroimaging techniques such as magnetic resonance imaging (MRI) and positron emission tomography/computed tomography (PET/CT) are helpful in the diagnosis of ICH, monitoring the subsequent recovery and investigating its functional mechanisms. Purpose: To explore the influence of the changes in cerebral glucose metabolism on perihematomal edema formation in an experimental cat model of ICH. Material and Methods: Forty-eight cats were divided into 1 sham operation group (6 cats) and 7 ICH model groups (42 cats)”. The ICH model groups were injected with 1.0 ml autologous nonheparinized blood into their thalami using accurate stereotactic guidance apparatus. MRI and 18F-fluorodeoxyglucose (FDG) PET/CT scans were acquired at 2, 6, 12, 24, 48, 72, and 120 h following the intervention. Pearsons correlation test was used to evaluate the association between T2-weighted signal intensity and the edema volume. Students t test and q test were used to identify the times of significant temporal changes. Results: The volume of perilesional edema did not significantly increase from 2 h to 12 h after ICH, but then increased by 229.4% at 24 h, peaked (by 273.5%), and steadily decreased by 72 h. The FDG intensity in perihematomal edema tissues was markedly reduced 2 h after ICH on PET images, reached its lowest level at 12 h, and then steadily increased at 24 h and 48 h. The changes of standard absorption value (SUV) in perihematomal edema were consistent with those of FDG intensity. Conclusion: Perihematomal glucose metabolism abnormalities have a close relationship with the formation of vasogenic edema. Furthermore, abnormal glucose metabolism may impair capillary integrity and increase blood–brain barrier permeability.

Development of fetal cerebral cortex: assessment of the folding conditions with post-mortem Magnetic Resonance Imaging

Quantitative data of fetal cortical folding and its developmental changes supply important information in the estimation of fetal age and assessment of brain maturation, so the increasing tendencies of cortical growth and its folding conditions at the beginning of the second and third trimesters with post‐mortem Magnetic Resonance Imaging (MRI) were analyzed. 131 fetal specimens of 14–40 weeks gestational age (GA) were selected and scanned with 3.0 T MR. Then the length of folded cortical margin (LFCM) and length of unfolded cortical margin (LUCM) were measured by Photoshop and ZoomMagic software. Degrees of cortical folding (DCF) were calculated by means of (LFCM − LUCM)/LFCM. Growth curves were obtained between the 3 above values and GA, and significant differences in age stages, hemispheres and genders were analyzed. The relationship between LFCM in centimeters, DCF and GA in weeks was described by two exponential growth curves [LFCM = 5.325 exp(0.079GA); DCF = 11.890 exp(0.043GA)]. The curves increased rapidly after 26 weeks GA, which could be recognized as a cut‐off point of fetal cortical and sulcal development. LUCM and GA were described by a logarithmic growth curve which slowed down after 26 weeks GA [LUCM = 30.580 Ln(GA) − 72.490]. Significant differences of the 3 values before and after 26 weeks GA (p < 0.01), but not any in hemispheres and genders were noticed. These results, which may be valuable in assessing normal brain development and can serve as a model in clinical settings, indicate that the cerebral volume first increases and is then followed by increases of the surface area.