Non-invasive evaluation of blood oxygen saturation and hematocrit from T1 and T2 relaxation times: In-vitro validation in fetal blood

PURPOSE

We propose an analytical method for calculating blood hematocrit (Hct) and oxygen saturation (sO₂ ) from measurements of its T₁ and T₂ relaxation times.

THEORY

Through algebraic substitution, established two-compartment relationships describing R1=T1-1 and R2=T2-1 as a function of hematocrit and oxygen saturation were rearranged to solve for Hct and sO₂ in terms of R₁ and R₂ . Resulting solutions for Hct and sO₂ are the roots of cubic polynomials.

METHODS

Feasibility of the method was established by comparison of Hct and sO₂ estimates obtained from relaxometry measurements (at 1.5 Tesla) in cord blood specimens to ground-truth values obtained by blood gas analysis. Monte Carlo simulations were also conducted to assess the effect of T₁ , T₂ measurement uncertainty on precision of Hct and sO₂ estimates.

RESULTS

Good agreement was observed between estimated and ground-truth blood properties (bias = 0.01; 95% limits of agreement = ±0.13 for Hct and sO₂ ). Considering the combined effects of biological variability and random measurement noise, we estimate a typical uncertainty of ±0.1 for Hct, sO₂ estimates.

CONCLUSION

Results demonstrate accurate quantification of Hct and sO₂ from T₁ and T₂ . This method is applicable to noninvasive fetal vessel oximetry-an application where existing oximetry devices are unusable or require risky blood-sampling procedures. Magn Reson Med 78:2352-2359, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

Ehmt2/G9a controls placental vascular maturation by activating the Notch pathway

Defective fetoplacental vascular maturation causes intrauterine growth restriction (IUGR). A transcriptional switch initiates placental maturation where blood vessels elongate. However, cellular mechanisms and regulatory pathways involved are unknown. We show that the histone methyltransferase Ehmt2, also known as G9a, activates the Notch pathway to promote placental vascular maturation. Placental vasculature from embryos with G9a-deficient endothelial progenitor cells failed to expand due to decreased endothelial cell proliferation and increased trophoblast proliferation. Moreover, G9a deficiency altered the transcriptional switch initiating placental maturation and caused downregulation of Notch pathway effectors including Rbpj. Importantly, Notch pathway activation in G9a-deficient endothelial progenitors extended embryonic life and rescued placental vascular expansion. Thus, G9a activates the Notch pathway to balance endothelial cell and trophoblast proliferation and coordinates the transcriptional switch controlling placental vascular maturation. Accordingly, G9A and RBPJ were downregulated in human placentae from IUGR-affected pregnancies, suggesting that G9a is an important regulator in placental diseases caused by defective vascular maturation.

MINC 2.0: A Flexible Format for Multi-Modal Images

It is often useful that an imaging data format can afford rich metadata, be flexible, scale to very large file sizes, support multi-modal data, and have strong inbuilt mechanisms for data provenance. Beginning in 1992, MINC was developed as a system for flexible, self-documenting representation of neuroscientific imaging data with arbitrary orientation and dimensionality. The MINC system incorporates three broad components: a file format specification, a programming library, and a growing set of tools. In the early 2000's the MINC developers created MINC 2.0, which added support for 64-bit file sizes, internal compression, and a number of other modern features. Because of its extensible design, it has been easy to incorporate details of provenance in the header metadata, including an explicit processing history, unique identifiers, and vendor-specific scanner settings. This makes MINC ideal for use in large scale imaging studies and databases. It also makes it easy to adapt to new scanning sequences and modalities.

Quantification of Gestational Changes in the Uteroplacental Vascular Tree Reveals Vessel Specific Hemodynamic Roles During Pregnancy in Mice

The purpose of this study was to establish the time course and hemodynamic significance of de novo formed and enlarged uteroplacental arteries during pregnancy. Using x-ray microcomputed tomography (n = 4–7 placentas from 2–4 dams/gestational group), uteroplacental arterial vascular dimensions were measured at individual implantation sites. Dimensions and topology were used to compute total and vessel-specific resistances and cross-sectional areas. Diameter enlargement of the uterine artery (+55% by Embryonic Day 5.5 [E5.5]) and preplacental radial arteries (+30% by E8.5) was significant only in early gestation. Formation of spiral arteries (E9.5–E11.5), maternal canals, and canal branches (E11.5–E13.5) during midgestation was followed by enlargement of these vessels such that, from E9.5 to E17.5 (near term), spiral artery resistance dropped 9-fold, and canal resistance became negligible. A 12-fold increase in terminal vessel cross-sectional area was nearly sufficient to offset known increases in flow so that blood velocity entering the exchange region was predicted to increase by only 2-fold. The calculated 47% decrease in total resistance downstream of the uterine artery, determined from vascular geometry, was in accord with prior uterine blood flow data in vivo and was due to enlarging spiral artery diameters. Interestingly, radial artery resistance was unchanged after E9.5 so that radial arteries accounted for 91% of resistance and pressure drop in the uteroplacental arterial network by E17.5. These findings led us to propose functional roles for the three morphologically defined vessel types: radial arteries to reduce pressure, spiral artery enlargement to increase flow with gestation, and maternal canal elaboration and enlargement to maintain low exit velocities into the exchange region.

Relaxation properties of human umbilical cord blood at 1.5 Tesla

PURPOSE

To characterize the MRI relaxation properties of human umbilical cord blood at 1.5 Tesla.

METHODS

Relaxometry measurements were performed on cord blood specimens (N = 88, derived from six caesarean deliveries) spanning a broad range of hematocrits (Hct = 0.19-0.76) and oxygen saturations (sO₂ = 4-100%), to characterize the dependence of T₁ and T₂ on these blood properties. Adult blood data (N = 31 specimens, derived from two volunteers) were similarly studied to validate our experimental methods by comparison with existing literature. Using biophysical models previously developed for adult blood, new model parameters were estimated, which relate Hct and sO₂ to the observed cord blood relaxation times.

RESULTS

Fitted biophysical models explained more than 90% of the variation in T₁ and T₂ . In general, T₂ relaxation times of cord blood were longer (by up to 35%) than those of adult blood, whereas T₁ relaxation times were slightly shorter (by up to 10%).

CONCLUSIONS

The models and fitted parameters presented here can be used for calibration of future MRI investigations of fetal and neonatal blood physiology. This study is an important step in facilitating accurate, noninvasive assessments of fetal blood oxygen content, a valuable diagnostic parameter in the identification and treatment of fetal hypoxia. Magn Reson Med 77:1678-1690, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Altered resting-state functional connectivity in cognitively preserved pediatric-onset MS patients and relationship to structural damage and cognitive performance

OBJECTIVE

To evaluate resting-state functional connectivity (FC) and relationship to brain volumes and cognition in a sample of cognitively preserved pediatric-onset multiple sclerosis (MS) patients.

METHODS

Sixteen cognitively intact pediatric-onset MS patients and 15 healthy age- and sex-matched controls underwent cognitive testing and 3T anatomical and functional MRI. Resting-state FC patterns were examined using region-of-interest-based timeseries correlations.

RESULTS

Compared to controls, pediatric-onset MS patients demonstrated higher FC of the precuneus, particularly with the anterior cingulate cortex (z=4.21, p<.001), frontal medial cortex (z=3.48, p<.001), and cerebellum (z=3.72, p<.001). Greater T2 lesion volume and lower normalized thalamic volume were associated with reduced FC of the thalamus, especially for FC with the right superior occipital region (t=-2.87, p=.0123 and t=2.27, p=.04 respectively). FC of the left frontal medial cortex was negatively correlated with composite cognitive z-score in the pediatric-onset MS group (p<.05).

CONCLUSIONS

Greater resting-state FC between posterior and anterior brain regions is present in pediatric-onset MS. With greater disease-related structural pathology, there is a disruption of thalamo-cortical FC. In the absence of actual cognitive impairment, heightened FC of the frontal medial cortex was associated with lower cognitive performance, suggesting that greater functional resources are recruited during resting-state in patients with reduced cognitive efficiency.

Diffusion tensor magnetic resonance imaging in very early onset pediatric multiple sclerosis

Objectives:

Active myelination during childhood may influence the impact of multiple sclerosis (MS) on brain structural integrity. We studied normal-appearing white matter (NAWM) in children with MS onset before age 12 years using diffusion tensor (DT) magnetic resonance imaging (MRI).

Methods:

DT MRI scans were obtained from 22 MS children with their first attack before age 12 years, and 31 healthy controls from two referral centers. Using probabilistic tractography, brain tissue integrity within interhemispheric, intrahemispheric, and projection tracts was compared between patients and site-matched controls. The impact of disease and age at MRI on tract NAWM fractional anisotropy (FA) and mean diffusivity (MD) values was evaluated using linear models.

Results:

Compared to controls, pediatric MS patients had reduced FA and increased MD of the bilateral superior longitudinal fasciculus and corpus callosum (CC), without center-by-group interaction. CC NAWM average FA was correlated with brain T2 lesion volume. In controls, the majority of the tracts analyzed showed a significant increase of FA and decrease of MD with age. Such a linear correlation was lost in patients.

Conclusions:

In very young pediatric MS patients, DT MRI abnormalities affect brain WM tracts differentially, and are only partially correlated with focal WM lesions. Impaired maturation of WM tracts with age may be an additional factor contributing to these findings.

Artery-on-a-chip platform for automated, multimodal assessment of cerebral blood vessel structure and function

We present a compact microfluidic platform for the automated, multimodal assessment of intact small blood vessels. Mouse olfactory artery segments were reversibly loaded onto a microfluidic device and kept under physiological (i.e., close to in vivo) environmental conditions. For immunohistochemical endpoint protein analysis, automated on chip fixation and staining of the artery eliminated the need for any subsequent tissue sectioning or processing outside the chip. In a first case study, we demonstrate the blood vessel abluminal structure based on the positions of smooth muscle cell nuclei, actin filaments and voltage gated calcium channels. In a second case study we incubated smooth muscle cells (SMCs) with a calcium-sensitive dye to simultaneously assess time-dependent, agonist-induced calcium and diameter changes of pressurized resistance arteries. We expect the presented microfluidic platform to promote routine on-chip staining and quantitative fluorescence imaging of intact blood vessels from different vascular beds, tissue engineered vascular constructs and vascularized microtissues. The at least tenfold reduction in required aliquot volumes for functional assessment and staining was achieved by on-board fluid manipulation of the syringe-pump free platform and may promote its applications for screening of newly synthesized compounds.

Reduced fetal cerebral oxygen consumption is associated with smaller brain size in fetuses with congenital heart disease

BACKGROUND

Fetal hypoxia has been implicated in the abnormal brain development seen in newborns with congenital heart disease (CHD). New magnetic resonance imaging technology now offers the potential to investigate the relationship between fetal hemodynamics and brain dysmaturation.

METHODS AND RESULTS

We measured fetal brain size, oxygen saturation, and blood flow in the major vessels of the fetal circulation in 30 late-gestation fetuses with CHD and 30 normal controls using phase-contrast magnetic resonance imaging and T2 mapping. Fetal hemodynamic parameters were calculated from a combination of magnetic resonance imaging flow and oximetry data and fetal hemoglobin concentrations estimated from population averages. In fetuses with CHD, reductions in umbilical vein oxygen content (P<0.001) and failure of the normal streaming of oxygenated blood from the placenta to the ascending aorta were associated with a mean reduction in ascending aortic saturation of 10% (P<0.001), whereas cerebral blood flow and cerebral oxygen extraction were no different from those in controls. This accounted for the mean 15% reduction in cerebral oxygen delivery (P=0.08) and 32% reduction cerebral Vo2 in CHD fetuses (P<0.001), which were associated with a 13% reduction in fetal brain volume (P<0.001). Fetal brain size correlated with ascending aortic oxygen saturation and cerebral Vo2 (r=0.37, P=0.004).

CONCLUSIONS

This study supports a direct link between reduced cerebral oxygenation and impaired brain growth in fetuses with CHD and raises the possibility that in utero brain development could be improved with maternal oxygen therapy.

Cerebral maturation in the early preterm period-A magnetization transfer and diffusion tensor imaging study using voxel-based analysis

The magnetization transfer ratio (MTR) and diffusion tensor imaging (DTI) correlates of early brain development were examined in cohort of 18 very preterm neonates (27-31 gestational weeks) presenting with normal radiological findings scanned within 2weeks after birth (28-32 gestational weeks). A combination of non-linear image registration, tissue segmentation, and voxel-wise regression was used to map the age dependent changes in MTR and DTI-derived parameters in 3D across the brain based on the cross-sectional in vivo preterm data. The regression coefficient maps obtained differed between brain regions and between the different quantitative MRI indices. Significant linear increases as well as decreases in MTR and DTI-derived parameters were observed throughout the preterm brain. In particular, the lamination pattern in the cerebral wall was evident on parametric and regression coefficient maps. The frontal white matter area (subplate and intermediate zone) demonstrated a linear decrease in MTR. While the intermediate zone showed an unexpected decrease in fractional anisotropy (FA) with age, with this decrease (and the increase in mean diffusivity (MD)) driven primarily by an increase in radial diffusivity (RD) values, the subplate showed no change in FA (and an increase in MD). The latter was the result of a concomitant similar increase in axial diffusivity (AD) and RD values. Interpreting the in vivo results in terms of available histological data, we present a biophysical model that describes the relation between various microstructural changes measured by complementary quantitative methods available on clinical scanners and a range of maturational processes in brain tissue.

Venular degeneration leads to vascular dysfunction in a transgenic model of Alzheimer's disease

Most patients with Alzheimer's disease exhibit accumulation of amyloid-β peptide on leptomeningeal and cortical arterioles, or cerebral amyloid angiopathy, which is associated with impaired vascular reactivity and accelerated cognitive decline. Despite widespread recognition of the significance of vascular dysfunction in Alzheimer's disease aetiology and progression, much uncertainty still surrounds the mechanism underlying Alzheimer's disease vascular injury. Studies to date have focused on amyloid-β-induced damage to capillaries and plaque-associated arterioles, without examining effects across the entire vascular bed. In the present study, we investigated the structural and functional impairment of the feeding arteriolar versus draining venular vessels in a transgenic murine Alzheimer's disease model, with a particular focus on the mural cell populations that dictate these vessels' contractility. Although amyloid-β deposition was restricted to arterioles, we found that vascular impairment extended to the venules, which showed significant depletion of their mural cell coverage by the mid-stage of Alzheimer's disease pathophysiology. These structural abnormalities were accompanied by an abolishment of the normal vascular network flow response to hypercapnia: this functional impairment was so severe as to result in hypercapnia-induced flow decreases in the arterioles. Further pharmacological depletion of mural cells using SU6668, a platelet-derived growth factor receptor-β antagonist, resulted in profound structural abnormalities of the cortical microvasculature, including vessel coiling and short-range looping, increased tortuosity of the venules but not of the arterioles, increased amyloid-β deposition on the arterioles, and further alterations of the microvascular network cerebral blood flow response to hypercapnia. Together, this work shows hitherto unrecognized structural alterations in penetrating venules, demonstrates their functional significance and sheds light on the complexity of the relationship between vascular network structure and function in Alzheimer's disease.

Site-specific increases in utero- and fetoplacental arterial vascular resistance in eNOS-deficient mice due to impaired arterial enlargement

The sites of elevated vascular resistance that impede placental perfusion in pathological pregnancies are unknown. In the current study, we identified these sites in a knockout mouse model (eNOS(-/-)) with reduced uterine (-55%) and umbilical (-29%) artery blood flows caused by endothelial nitric oxide synthase deficiency. Uteroplacental and fetoplacental arterial vascular trees of pregnant mice near term were imaged using x-ray microcomputed tomography (n = 5-10 placentas from 3-5 dams/group). The resulting three-dimensional images were analyzed to assess vessel geometry and vascular resistance. In control and eNOS(-/-) trees, ∼90% of total uteroplacental vascular resistance was located in the radial arteries. Changes in eNOS(-/-) vessel geometry, including 30% reductions in uterine, radial, and spiral artery diameters, were calculated to increase arterial resistance downstream of the uterine artery by 2.3-fold, predicting a 57% decrease in uterine blood flow. Despite large reductions in eNOS(-/-) spiral arteries (-55% by volume) and maternal canals (-67% by volume), these vessels were relatively minor contributors to resistance. In the eNOS(-/-) fetoplacental tree, the number of arterioles (50-75 μm diameter) increased by 26%. Nevertheless, calculated resistance rose by 19%, predominantly because arteries near the periphery of the tree selectively exhibited a 7%-9% diameter reduction. We conclude that previously observed decreases in uterine and umbilical blood flows in eNOS(-/-) pregnancies are associated with markedly divergent structural changes in the uteroplacental versus fetoplacental circulations. Results showed the radial arteries were critical determinants of uteroplacental resistance in mice and therefore warrant greater attention in future studies in pathological human pregnancies.

Onset of multiple sclerosis before adulthood leads to failure of age-expected brain growth

OBJECTIVE

To determine the impact of pediatric-onset multiple sclerosis (MS) on age-expected brain growth.

METHODS

Whole brain and regional volumes of 36 patients with relapsing-remitting MS onset prior to 18 years of age were segmented in 185 longitudinal MRI scans (2-11 scans per participant, 3-month to 2-year scan intervals). MRI scans of 25 age- and sex-matched healthy normal controls (NC) were also acquired at baseline and 2 years later on the same scanner as the MS group. A total of 874 scans from 339 participants from the NIH-funded MRI study of normal brain development acquired at 2-year intervals were used as an age-expected healthy growth reference. All data were analyzed with an automatic image processing pipeline to estimate the volume of brain and brain substructures. Mixed-effect models were built using age, sex, and group as fixed effects.

RESULTS

Significant group and age interactions were found with the adjusted models fitting brain volumes and normalized thalamus volumes (p < 10(-4)). These findings indicate a failure of age-normative brain growth for the MS group, and an even greater failure of thalamic growth. In patients with MS, T2 lesion volume correlated with a greater reduction in age-expected thalamic volume. To exclude any scanner-related influence on our data, we confirmed no significant interaction of group in the adjusted models between the NC and NIH MRI Study of Normal Brain Development groups.

CONCLUSIONS

Our results provide evidence that the onset of MS during childhood and adolescence limits age-expected primary brain growth and leads to subsequent brain atrophy, implicating an early onset of the neurodegenerative aspect of MS.

Assessment of flow distribution in the mouse fetal circulation at late gestation by high-frequency Doppler ultrasound

This study used high-frequency ultrasound to evaluate the flow distribution in the mouse fetal circulation at late gestation. We studied 12 fetuses (embryonic day 17.5) from 12 pregnant CD1 mice with 40 MHz ultrasound to assess the flow in 11 vessels based on Doppler measurements of blood velocity and M-mode measurements of diameter. Specifically, the intrahepatic umbilical vein (UVIH), ductus venosus (DV), foramen ovale (FO), ascending aorta (AA), main pulmonary artery (MPA), ductus arteriosus (DA), descending thoracic aorta (DTA), common carotid artery (CCA), inferior vena cava (IVC), and right and left superior vena cavae (RSVC, LSVC) were examined, and anatomically confirmed by micro-CT. The mouse fetal circulatory system was found to be similar to that of the humans in terms of the major circuit and three shunts, but characterized by bilateral superior vena cavae and a single umbilical artery. The combined cardiac output (CCO) was 1.22 ± 0.05 ml/min, with the left ventricle (flow in AA) contributing 47.8 ± 2.3% and the right ventricle (flow in MPA) 52.2 ± 2.3%. Relative to the CCO, the flow percentages were 13.6 ± 1.0% for the UVIH, 10.4 ± 1.1% for the DV, 35.6 ± 2.4% for the DA, 41.9 ± 2.6% for the DTA, 3.8 ± 0.3% for the CCA, 29.5 ± 2.2% for the IVC, 12.7 ± 1.0% for the RSVC, and 9.9 ± 0.9% for the LSVC. The calculated flow percentage was 16.6 ± 3.4% for the pulmonary circulation and 31.2 ± 5.3% for the FO. In conclusion, the flow in mouse fetal circulation can be comprehensively evaluated with ultrasound. The baseline data of the flow distribution in normal mouse fetus serve as the reference range for future studies.

Differential HIF and NOS responses to acute anemia: defining organ-specific hemoglobin thresholds for tissue hypoxia

Tissue hypoxia likely contributes to anemia-induced organ injury and mortality. Severe anemia activates hypoxia-inducible factor (HIF) signaling by hypoxic- and neuronal nitric oxide (NO) synthase- (nNOS) dependent mechanisms. However, organ-specific hemoglobin (Hb) thresholds for increased HIF expression have not been defined. To assess organ-specific Hb thresholds for tissue hypoxia, HIF-α (oxygen-dependent degradation domain, ODD) luciferase mice were hemodiluted to mild, moderate, or severe anemia corresponding to Hb levels of 90, 70, and 50 g/l, respectively. HIF luciferase reporter activity, HIF protein, and HIF-dependent RNA levels were assessed. In the brain, HIF-1α was paradoxically decreased at mild anemia, returned to baseline at moderate anemia, and then increased at severe anemia. Brain HIF-2α remained unchanged at all Hb levels. Both kidney HIF-1α and HIF-2α increased earlier (Hb ∼70–90 g/l) in response to anemia. Liver also exhibited an early HIF-α response. Carotid blood flow was increased early (Hb ∼70, g/l), but renal blood flow remained relatively constant, only increased at Hb of 50 g/l. Anemia increased nNOS (brain and kidney) and endothelia NOS (eNOS) (kidney) levels. Whereas anemia-induced increases in brain HIFα were nNOS-dependent, our current data demonstrate that increased renal HIFα was nNOS independent. HIF-dependent RNA levels increased linearly (∼10-fold) in the brain. However, renal HIF-RNA responses (MCT4, EPO) increased exponentially (∼100-fold). Plasma EPO levels increased near Hb threshold of 90 g/l, suggesting that the EPO response is sensitive. Collectively, these observations suggest that each organ expresses a different threshold for cellular HIF/NOS hypoxia responses. This knowledge may help define the mechanism(s) by which the brain and kidney maintain oxygen homeostasis during anemia.

Assessment of flow distribution in the mouse fetal circulation at late gestation by high-frequency Doppler ultrasound

This study used high-frequency ultrasound to evaluate the flow distribution in the mouse fetal circulation at late gestation. We studied 12 fetuses (embryonic day 17.5) from 12 pregnant CD1 mice with 40 MHz ultrasound to assess the flow in 11 vessels based on Doppler measurements of blood velocity and M-mode measurements of diameter. Specifically, the intrahepatic umbilical vein (UVIH), ductus venosus (DV), foramen ovale (FO), ascending aorta (AA), main pulmonary artery (MPA), ductus arteriosus (DA), descending thoracic aorta (DTA), common carotid artery (CCA), inferior vena cava (IVC), and right and left superior vena cavae (RSVC, LSVC) were examined, and anatomically confirmed by micro-CT. The mouse fetal circulatory system was found to be similar to that of the humans in terms of the major circuit and three shunts, but characterized by bilateral superior vena cavae and a single umbilical artery. The combined cardiac output (CCO) was 1.22 ± 0.05 ml/min, with the left ventricle (flow in AA) contributing 47.8 ± 2.3% and the right ventricle (flow in MPA) 52.2 ± 2.3%. Relative to the CCO, the flow percentages were 13.6 ± 1.0% for the UVIH, 10.4 ± 1.1% for the DV, 35.6 ± 2.4% for the DA, 41.9 ± 2.6% for the DTA, 3.8 ± 0.3% for the CCA, 29.5 ± 2.2% for the IVC, 12.7 ± 1.0% for the RSVC, and 9.9 ± 0.9% for the LSVC. The calculated flow percentage was 16.6 ± 3.4% for the pulmonary circulation and 31.2 ± 5.3% for the FO. In conclusion, the flow in mouse fetal circulation can be comprehensively evaluated with ultrasound. The baseline data of the flow distribution in normal mouse fetus serve as the reference range for future studies.

Automatic anatomical labeling of the complete cerebral vasculature in mouse models

Study of cerebral vascular structure broadens our understanding of underlying variations, such as pathologies that can lead to cerebrovascular disorders. The development of high resolution 3D imaging modalities has provided us with the raw material to study the blood vessels in small animals such as mice. However, the high complexity and 3D nature of the cerebral vasculature make comparison and analysis of the vessels difficult, time-consuming and laborious. Here we present a framework for automated segmentation and recognition of the cerebral vessels in high resolution 3D images that addresses this need. The vasculature is segmented by following vessel center lines starting from automatically generated seeds and the vascular structure is represented as a graph. Each vessel segment is represented as an edge in the graph and has local features such as length, diameter, and direction, and relational features representing the connectivity of the vessel segments. Using these features, each edge in the graph is automatically labeled with its anatomical name using a stochastic relaxation algorithm. We have validated our method on micro-CT images of C57Bl/6J mice. A leave-one-out test performed on the labeled data set demonstrated the recognition rate for all vessels including major named vessels and their minor branches to be >75%. This automatic segmentation and recognition methods facilitate the comparison of blood vessels in large populations of subjects and allow us to study cerebrovascular variations.

PPARγ agonists improve survival and neurocognitive outcomes in experimental cerebral malaria and induce neuroprotective pathways in human malaria

Cerebral malaria (CM) is associated with a high mortality rate, and long-term neurocognitive impairment in approximately one third of survivors. Adjunctive therapies that modify the pathophysiological processes involved in CM may improve outcome over anti-malarial therapy alone. PPARγ agonists have been reported to have immunomodulatory effects in a variety of disease models. Here we report that adjunctive therapy with PPARγ agonists improved survival and long-term neurocognitive outcomes in the Plasmodium berghei ANKA experimental model of CM. Compared to anti-malarial therapy alone, PPARγ adjunctive therapy administered to mice at the onset of CM signs, was associated with reduced endothelial activation, and enhanced expression of the anti-oxidant enzymes SOD-1 and catalase and the neurotrophic factors brain derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the brains of infected mice. Two months following infection, mice that were treated with anti-malarials alone demonstrated cognitive dysfunction, while mice that received PPARγ adjunctive therapy were completely protected from neurocognitive impairment and from PbA-infection induced brain atrophy. In humans with P. falciparum malaria, PPARγ therapy was associated with reduced endothelial activation and with induction of neuroprotective pathways, such as BDNF. These findings provide insight into mechanisms conferring improved survival and preventing neurocognitive injury in CM, and support the evaluation of PPARγ agonists in human CM.

Cerebral malaria (CM) is a severe complication of Plasmodium falciparum infection that is associated with long-term neurocognitive impairment in about a third of survivors even when optimal anti-malarial therapy is used. Since both the parasite and the host immune response to infection play a role in the development of CM, adjunctive therapies that modulate the host response, given in conjunction with anti-parasitic therapy, may improve survival and prevent neurocognitive injury. Here we examine the effects of PPARγ agonists on neurocongitive injury using a mouse model of CM. We demonstrate that PPARγ agonists, when administered with anti-malarials, protected mice from developing brain atrophy and neurocognitive impairment. This was associated with induction of anti-oxidant and neuroprotective pathways in the brains of infected mice. We also observed the same neuroprotective pathways induced in patients with falciparum malaria that received PPARγ adjunctive therapy. Our findings suggest that PPARγ agonists may be valuable in the treatment and prevention of CM-induced neurocognitive injury, and support the testing of PPARγ agonists in patients with CM.

Quantitative determination of regional lesion volume and distribution in children and adults with relapsing-remitting multiple sclerosis

Introduction

Onset of MS occurs during childhood in about 5% of cases. It is unclear whether very young age at MS onset, when the nervous system is still myelinating, affects MS lesion accrual or regional distribution.

Objective

To compare the frequency, volume and distribution of T2 and T1 lesions in children and adults with relapsing-remitting multiple sclerosis (RRMS).

Methods

Lesions were segmented on T2- and T1-weighted MRI images from 29 children and 29 adults with RRMS, matched for disease duration.

Results

All subjects exhibited T2-weighted brain lesions. Children had higher whole-brain T2-weighted-lesion-volume (T2LV) compared to adults (mean (SD) in cm³: 12.76(2.7) vs. 10.03(3.4), p<0.0013). The supratentorial-T2LV was similar in children and adults (8.45(1.7) vs. 7.94(1.7), mean (SD), p = 0.2582), but adults were more likely to have supratentorial lesions (96.5% vs. 68.9%, p<0.012). Children were more likely to have infratentorial-T2-weighted lesions (75.9% vs. 43.4%, p<0.03), specifically in the brainstem (62.1% vs. 26.7%, p<0.019) and the pons (48.3% vs. 17.24%, p<0.024), had higher infratentorial-T2-weighted-lesion counts (4.1(5.6) vs. 1.45(2.3), p<0.021), a greater infratentorial-T2LV (4.31(2.7) vs. 2.08(2.4), p<0.0013), and a greater infratentorial-T1-weighted-lesion-volume (T1LV) (3.7(2.5) vs. 1.08(1.9), p<0.0007). Whole-brain-T1LV was higher in children (9.3(2.5) vs. 6.43(2.1), p>0.001). Adult MS patients had higher supratentorial-T1LV (5.5(0.92) vs. 6.41(2.1), mean (SD), p<0.034), whereas children were more likely to have infratentorial-T1-weighted lesions (58.6% vs. 23.3%, p<0.015).

Discussion

Onset of MS during childhood is associated with a higher volume of brain lesions in the first few years of disease relative to adults. Children with MS are more likely than adults to have T2 and T1 lesions in the infratentorial white matter, raising the possibility of preferential immune targeting of more mature myelin. Children with MS have a lower supratentorial T1 lesion burden, possibly reflecting more effective remyelination and repair in brain regions that are still engaged in active primary myelination.