The NICHD Fetal 3D Study: A Pregnancy Cohort Study of Fetal Body Composition and Volumes.

There's a paucity of robust normal fractional limb and organ volume standards from a large and diverse ethnic population. The Fetal 3D Study was designed to develop research and clinical applications for fetal soft tissue and organ volume assessment. The NICHD Fetal Growth Studies (2009-2013) collected 2D and 3D fetal volumes. In the Fetal 3D Study (2015-2019), sonographers performed longitudinal 2D and 3D measurements for specific fetal anatomical structures in research ultrasounds of singletons and dichorionic twins. The primary aim was to establish standards for fetal body composition and organ volumes, overall and by maternal race/ethnicity, and determine whether these standards vary for twins versus singletons. We describe the study design, methods, and details about reviewer training. Basic characteristics of this cohort, with their corresponding distributions of fetal 3D measurements by anatomical structure, are summarized. This investigation is responsive to critical data gaps in understanding serial changes in fetal subcutaneous fat, lean body mass, and organ volume in association with pregnancy complications. In the future, this cohort can answer critical questions regarding the potential influence of maternal characteristics, lifestyle factors, nutrition, and biomarker and chemical data on longitudinal measures of fetal subcutaneous fat, lean body mass, and organ volumes.

Impact of Pelvic Rest Recommendations on Follow-Up and Resolution of Placenta Previa and Low-Lying Placenta.

OBJECTIVE: To determine the rate of resolution of placenta previa and low-lying placenta (LLP) and the effect of pelvic rest recommendations on the timing of follow-up imaging. METHODS: Retrospective review of pregnancies with previa/LLP detected on mid-trimester exam at our ultrasound unit from 2019 to 2021. LLP was defined as the lower edge of placenta located within 2 cm of the internal cervical os. Previa was defined as any portion of the placenta touching with the internal os. Demographics, placental location, activity restrictions, and delivery outcomes were analyzed. Timing of follow-up imaging was stratified by individuals advised and not advised pelvic rest. RESULTS: Exactly 144 patients had previa and 266 had LLP on the mid-trimester exam with complete records. Previa resolution happened in 51.4% (74/144) of cases. Exactly 62% (46/74) of previa resolutions occurred by the 28-week ultrasound. Exactly 45% (65/144) of previa patients were advised pelvic rest. Most pelvic rest and non-pelvic rest patients had a 28-week scan. Even when clearance occurred, most patients in both groups had a repeat ultrasound at 32 weeks. Exactly 75% of LLP resolved by the 28-week scan, and the remainder by delivery. Exactly 12% (32/259) of LLP patients were advised pelvic rest. CONCLUSION: Most societies recommend follow-up imaging at 32 weeks; however, our results suggest this may be done sooner and closer to 28 weeks. Pelvic rest did not affect timing of repeat imaging or delivery.

Cardiac Size, Shape, and Ventricular Contractility in Fetuses at Sea Level With an Estimated Weight Less-than 10th Centile.

OBJECTIVES: To investigate cardiac size, shape, and ventricular contractility in fetuses with estimated fetal weight (EFW) <10th centile at sea level (Houston). METHODS: A prospective ultrasound study examined 37 fetuses with EFW <10th centile at sea level. High-frequency cine clips were used to evaluate the 4-chamber view including end-diastolic measurements and global sphericity index. The size, shape, and contractility of both ventricles were analyzed with speckle tracking methods. Z scores were calculated using the mean ± standard deviation (SD) derived from normal controls. Measurements were abnormal if their Z score values were <-1.65 or >+1.65. The proportion of small fetuses with abnormal parameters was compared to normal reference ranges. Results were compared to a similar published study of small fetuses at higher altitude in Denver. RESULTS: About one-third of Houston fetuses with EFW <10th centile had enlarged globular shaped 4-chamber hearts with increased right ventricle (RV) area, RV basal-apical length, RV base width, and left ventricle (LV) basal-apical length measurements. Bilateral ventricular hypertrophy was often present. An increased proportion of Houston fetuses had increased ventricular contractility. However, decreased ventricular contractility was more prevalent for higher altitude fetuses. CONCLUSIONS: Third trimester fetuses at sea level, with an EFW <10th centile, were often associated with enlarged and globular-shaped hearts. They had increased global and longitudinal ventricular contractility as compared to controls. Higher altitude fetuses also had enlarged globular-shaped hearts but with a greater proportion of cases having decreased ventricular contractility as compared to the sea level cohort.

Fetal Weight Estimation Using Automated Fractional Limb Volume With 2-Dimensional Size Parameters in Diabetic Pregnancies.

OBJECTIVES: To examine the effect of adding automated fetal fractional limb volume (FLV) with conventional 2-dimensional (2D) fetal weight estimation procedures in a cohort of diabetic pregnancies. METHODS: A pilot study of diabetic pregnancies measured standard fetal biometry within 7 days of delivery. Fractional arm volume (AVol) and fractional thigh volume (TVol) soft tissue parameters were measured with a commercially available automated software utility (5D Limb Vol; Samsung Medison Co, Ltd, Seoul, Korea). Three conventional weight prediction models that included only 2D size parameters were compared to FLV models that included AVol or TVol. Estimated and actual birth weight (BW) were assessed for the mean percent difference ± standard deviation of the percent differences. Systematic errors were evaluated by the Student t test, and random errors were compared by the Pitman test for correlated variances. The proportion of neonates with estimated fetal weight within 10% of BW was compared between groups by the McNemar test. RESULTS: Ninety gravid women were enrolled with pregestational (26.7%) or gestational (73.3%) diabetes. All prediction models were accurate, with the exception of small underestimations by the model of Schild et al (-3.8%; Ultrasound Obstet Gynecol 2004; 23:30-35). Random errors for the AVol (6.2%) and TVol (6.9%) models were significantly more precise than the other 3 prediction models: Hadlock et al (7.8%; Am J Obstet Gynecol 1985; 151:333-337), INTERGROWTH-21st (8.0%; Ultrasound Obstet Gynecol 2017; 49:478-486), and Schild et al (8.6%; P < .01). The greatest proportion of cases with BW ±10% was also classified by the AVol (91.1%) and TVol (91.1%) models, followed by Hadlock (83.3%), INTERGROWTH-21st (78.9%), and Schild (76.7%) predictions. CONCLUSIONS: The addition of automated FLV measurements to conventional 2D biometry was associated with improved weight predictions in this cohort of diabetic pregnancies.

Prenatal Ultrasound Measurement of Fetal Stomach Size Is Predictive of Postnatal Development of GERD in Isolated Cleft Lip and/or Palate.

OBJECTIVE: To determine whether prenatal ultrasound measurement of fetal stomach size, as a surrogate marker of fetal swallowing, is predictive of postnatal development of gastroesophageal reflux disease (GERD) in cases of isolated cleft lip and/or palate (CL/P). DESIGN: This is a retrospective case-control study. The outcome of interest is postnatal diagnosis of GERD in isolated CL/P. The exposure of interest is prenatal stomach size measurement by ultrasound. SETTING: The study population was selected from an academic, tertiary care center between 2003 and 2011. PATIENTS/PARTICIPANTS: Cases were neonates undergoing CL/P repair during the study period. Cases with other known structural or chromosomal abnormalities were excluded. Controls were contemporary, nondiabetic neonates that matched gestational age (within one week) to cases. Each case measurement was matched ∼1:2 with control measurement. INTERVENTIONS: None. MAIN OUTCOME MEASURE: The primary outcome was difference in mean prenatal ultrasound measurement of fetal stomach size between cases and controls. We hypothesized that patients with postnatal development of GERD would have smaller mean fetal stomach size. RESULTS: There were 32 cases including 19 patients with unilateral cleft lip and palate, 8 with unilateral cleft lip, and 4 with bilateral cleft lip and palate. Cases were noted to have smaller mean anterior-posterior and transverse fetal stomach measurements as compared to controls. This was statistically significant from 16 to 21 weeks, 25 to 27 weeks, and 28 to 36 weeks (P < .01 for all). CONCLUSIONS: Prenatal ultrasound measurement of fetal stomach size as a surrogate marker of fetal swallowing is predictive of postnatal development of GERD in isolated CL/P.

Fetal Weight Estimation Using Automated Fractional Limb Volume With 2-Dimensional Size Parameters: A Multicenter Study.

OBJECTIVES: To develop new fetal weight prediction models using automated fractional limb volume (FLV). METHODS: A prospective multicenter study measured fetal biometry within 4 to 7 days of delivery. Three-dimensional data acquisition included the automated FLV that was based on 50% of the humerus diaphysis (fractional arm volume [AVol]) or 50% of the femur diaphysis (fractional thigh volume [TVol]) length. A regression analysis provided population sample-specific coefficients to develop 4 weight estimation models. Estimated and actual birth weights (BWs) were compared for the mean percent difference ± standard deviation of the percent differences. Systematic errors were analyzed by the Student t test, and random errors were compared by the Pitman test. RESULTS: A total of 328 pregnancies were scanned before delivery (BW range, 825-5470 g). Only 71.3% to 72.6% of weight estimations were within 10% of actual BW using original published models by Hadlock et al (Am J Obstet Gynecol 1985; 151:333-337) and INTERGROWTH-21st (Ultrasound Obstet Gynecol 2017; 49:478-486). All predictions were accurate by using sample-specific model coefficients to minimize bias in making these comparisons (Hadlock, 0.4% ± 8.7%; INTERGROWTH-21st, 0.5% ± 10.0%; AVol, 0.3% ± 7.4%; and TVol, 0.3% ± 8.0%). Both AVol- and TVol-based models improved the percentage of correctly classified BW ±10% in 83.2% and 83.9% of cases, respectively, compared to the INTERGROWTH-21st model (73.8%; P < .01). For BW of less than 2500 g, all models slightly overestimated BW (+2.0% to +3.1%). For BW of greater than 4000 g, AVol (-2.4% ± 6.5%) and TVol (-2.3% ± 6.9%) models) had weight predictions with small systematic errors that were not different from zero (P > .05). For these larger fetuses, both AVol and TVol models correctly classified BW (±10%) in 83.3% and 87.5% of cases compared to the others (Hadlock, 79.2%; INTERGROWTH-21st, 70.8%) although these differences did not reach statistical significance. CONCLUSIONS: In this cohort, the inclusion of automated FLV measurements with conventional 2-dimensional biometry was generally associated with improved weight predictions.

Characterization of Placental Microvasculature Using Superb Microvascular Imaging.

Superb Microvascular Imaging (SMI; Canon Medical Systems, Tustin, CA) uses clutter suppression to extract flow signals at rapid frame rates, which provides high-resolution vessel-branching details without the need for contrast agents. The potential diagnostic benefits of SMI, as described in other areas of medicine, requires further exploration during pregnancy. In this pictorial essay, we demonstrate the complementary use of SMI compared to conventional Doppler ultrasound and how it may improve our ability to characterize placental microvascular patterns without the need for ultrasound contrast agents.

Impact of changes in maternal body composition on birth weight and neonatal fat mass in dichorionic twin pregnancies.

Background: Although the impact of gestational weight gain (GWG) on birth weight in twin pregnancies has been demonstrated, the specific components of GWG have not been delineated for twin gestations. Fetal body composition has been shown to be modifiable in singleton gestations based on nutritional intervention strategies and may prove to have similar modifications in twin gestations. Objective: We aimed to determine the relation of maternal body composition changes to birth weight, birth length, and neonatal fat mass (FM) in dichorionic-diamniotic twin pregnancies. Design: This is a prospective study of 20 women with twin gestations. Comparisons were made between body composition variables during each trimester and for the entire pregnancy and compared with the outcomes of birth weight, neonatal fat percentage, and birth length. Results: GWG within or above compared with below the IOM recommendations was associated with higher birth weights (P = 0.03, P = 0.04, respectively), but also with higher postpartum weight retention (P = 0.001). Total maternal protein gain over the pregnancy was positively associated with birth weight (P = 0.03). Changes in maternal fat-free mass (FFM), total body water (TBW), and FM from the first to the third trimester were not associated with either birth weight or neonatal FM percentage. However, maternal FM change from the second to the third trimester was significantly correlated to neonatal FM percentage (P = 0.02). Third trimester GWG and total protein gain were positively correlated with neonatal birth length (P = 0.02 and 0.03, respectively). Maternal FFM over all 3 trimesters showed a positive relation with neonatal birth length (P = 0.01). Conclusions: Significant increases in maternal protein are associated with greater birth weight and neonatal birth length. Protein accretion, in contrast to TBW and FM gains, may be the most critical component of maternal GWG in dichorionic twin gestations.

Estimated energy requirements increase across pregnancy in healthy women with dichorionic twins.

Background: Estimated energy requirement (EER) has not been defined for twin pregnancy. This study was designed to determine the EER of healthy women with dichorionic-diamniotic (DCDA) twin pregnancies. Objectives: We aimed to estimate energy deposition from changes in maternal body protein and fat; to measure resting energy expenditure (REE), physical activity level (PAL), and total energy expenditure (TEE) throughout pregnancy and postpartum; and to define the EER based on the sum of TEE and energy deposition for twin gestation. Design: This is a prospective study of 20 women with DCDA twin gestations. Maternal EER, energy deposition, REE, TEE, and PAL were obtained during the first, second, and third trimesters of pregnancy and immediately postpartum. A mixed-effects linear regression model for repeated measures with random intercept was used to test for the effects of BMI groups and time. Results: Gains in total body protein (mean ± SD: 2.1 ± 0.7 kg) and fat mass (5.9 ± 2.8 kg) resulted in total energy deposition of 67,042 ± 25,586 kcal between 0 and 30-32 weeks of gestation. REE increased 26% from 1392 ± 162 to 1752 ± 172 kcal/d across the 3 trimesters, whereas TEE increased 17% from 2141 ± 283 to 2515 ± 337 kcal/d. Physical activity decreased steadily throughout pregnancy. Reductions in physical activity did not compensate for the rise in REE and energy deposition, thus requiring an increase in dietary energy intake as pregnancy progressed. EER increased 29% from 2257 ± 325 kcal/d in the first trimester to 2941 ± 407 kcal/d in the second trimester, and stayed consistent at 2906 ± 350 kcal/d in the third trimester. Conclusion: Increased energy intake, on average ∼700 kcal/d in the second and third trimesters when compared with the first trimester, is required to support gestational weight gain and the rise in energy expenditure of DCDA twin pregnancies.

Significance and Outcomes of Fetal Growth Restriction Below the 5th Percentile Compared to the 5th to 10th Percentiles on Midgestation Growth Ultrasonography.

OBJECTIVE: To determine whether there are differences in neonatal and pregnancy outcomes in pregnancies complicated by severe fetal growth restriction, defined as estimated fetal weight below the 5th percentile, compared with estimated fetal weight in the 5th to 10th percentiles at midgestation. METHODS: We conducted a retrospective review of singleton nonanomalous gestations with estimated fetal weight at or below the 10th percentile (Hadlock et al. Radiology 1991; 181:129-133) at 18 to 24 weeks' gestation. The cohort was divided into fetuses with estimated fetal weight below the 5th percentile and estimated fetal weight in the 5th to 10th percentiles. Antenatal and neonatal outcomes were compared across the groups. RESULTS: Of the 254 growth-restricted fetuses, 91 had estimated fetal weight below the 5th percentile, and 163 were in the 5th to 10th percentiles. Fetuses below the 5th percentile were 2.82 times more likely to be born small for gestational age compared to fetuses at the 5th to 10th percentiles (P = .001). Fetuses with estimated fetal weight below the 5th percentile had higher rates of hypertensive disorders of pregnancy (relative risk [RR], 1.79; P = .04), abnormal umbilical artery Doppler waveforms (RR, 6.27; P = .01), labor induction (RR, 1.45; P = .002), neonatal intensive care unit admission (RR, 1.73; P = .02), and Apgar scores of less than 7 at 1 minute (RR, 2.05; P = .04). CONCLUSIONS: Severely growth-restricted fetuses with an estimated fetal weight below the 5th percentile at 18 to 24 weeks are born smaller and have worse antepartum and neonatal outcomes than those with an estimated fetal weight in the 5th to 10th percentiles. These findings suggest that severely growth-restricted fetuses at midgestation should be treated and counseled differently than those in the 5th to 10th percentiles.

Prospective evaluation of the safety and feasibility of a pelvic floor dilator during active labor.

INTRODUCTION AND HYPOTHESIS: The objective was to assess the safety and feasibility of using a pelvic floor dilator during active labor to prevent injuries to the levator ani muscle (LAM) and perineum. METHODS: In a prospective pilot study, a pelvic floor dilator using soft pads was introduced into the vaginal canal to gradually expand the vagina, in 30 nulliparous women and in 10 controls. The primary outcomes were adverse events related to the device. Secondary outcomes were perineal lacerations after delivery, sonographically defined levator ani injury, hiatal area dimensions, and anal sphincter disruption, all at 12-20 weeks postpartum, and maximum pelvic floor dilation, time to achieve maximum dilation, and device retention rate. RESULTS: From October 2014 through November 2016, a total of 494 women were screened, and 61 consented to the study. Thirty women used the device and 27 returned for follow-up. No maternal or neonatal injuries were related to use of the dilator. The average maximum dilation of the vaginal canal was 7.4 cm (SD 0.7, range 5.5-8.0). Dilation time averaged 27 min (SD 13, range 5-60). Device insertion adjustment was needed in 13 out of 30 cases (43%). Similar rates of 3th-4th degree perineal lacerations were seen in both groups. Levator ani avulsion was diagnosed in 2 out of 27 (7%) in the device group and in 1 out of 9 (11%) in the control group (p = 0.2). The rate of partial injury in the device group was 2 out of 27 (7%) vs 2 out of 9 (22%) in the comparison group (p = 0.2). CONCLUSION: The use of the pelvic floor dilator during active labor is feasible. No safety issues were identified.

Circadian clock cryptochrome proteins regulate autoimmunity.

The circadian system regulates numerous physiological processes including immune responses. Here, we show that mice deficient of the circadian clock genes Cry1 and Cry2 [Cry double knockout (DKO)] develop an autoimmune phenotype including high serum IgG concentrations, serum antinuclear antibodies, and precipitation of IgG, IgM, and complement 3 in glomeruli and massive infiltration of leukocytes into the lungs and kidneys. Flow cytometry of lymphoid organs revealed decreased pre-B cell numbers and a higher percentage of mature recirculating B cells in the bone marrow, as well as increased numbers of B2 B cells in the peritoneal cavity of Cry DKO mice. The B cell receptor (BCR) proximal signaling pathway plays a critical role in autoimmunity regulation. Activation of Cry DKO splenic B cells elicited markedly enhanced tyrosine phosphorylation of cellular proteins compared with cells from control mice, suggesting that overactivation of the BCR-signaling pathway may contribute to the autoimmunity phenotype in the Cry DKO mice. In addition, the expression of C1q, the deficiency of which contributes to the pathogenesis of systemic lupus erythematosus, was significantly down-regulated in Cry DKO B cells. Our results suggest that B cell development, the BCR-signaling pathway, and C1q expression are regulated by circadian clock CRY proteins and that their dysregulation through loss of CRY contributes to autoimmunity.

Talin Plays a Critical Role in the Maintenance of the Regulatory T Cell Pool.

Talin, a cytoskeletal protein essential in mediating integrin activation, has been previously shown to be involved in the regulation of T cell proliferation and function. In this study, we describe a role for talin in maintaining the homeostasis and survival of the regulatory T (Treg) cell pool. T cell-specific deletion of talin in Tln1fl/flCd4Cre mice resulted in spontaneous lymphocyte activation, primarily due to numerical and functional deficiencies of Treg cells in the periphery. Peripheral talin-deficient Treg cells were unable to maintain high expression of IL-2Rα, resulting in impaired IL-2 signaling and ultimately leading to increased apoptosis through downregulation of prosurvival proteins Bcl-2 and Mcl-1. The requirement for talin in maintaining high IL-2Rα expression by Treg cells was due, in part, to integrin LFA-1-mediated interactions between Treg cells and dendritic cells. Collectively, our data suggest a critical role for talin in Treg cell-mediated maintenance of immune homeostasis.

Automated Fractional Limb Volume Measurements Improve the Precision of Birth Weight Predictions in Late Third-Trimester Fetuses.

OBJECTIVES: Fetal soft tissue can be assessed by using fractional limb volume as a proxy for in utero nutritional status. We investigated automated fractional limb volume for rapid estimate fetal weight assessment. METHODS: Pregnant women were prospectively scanned for 2- and 3-dimensional fetal biometric measurements within 4 days of delivery. Performance of birth weight prediction models was compared: (1) Hadlock (Am J Obstet Gynecol 1985; 151:333-337; biparietal diameter, abdominal circumference, and femur diaphysis length); and (2) Lee (Ultrasound Obstet Gynecol 2009; 34:556-565; biparietal diameter, abdominal circumference, and automated fractional limb volume). Percent differences were calculated: [(estimated birth weight - actual birth weight) ÷ (actual birth weight] × 100. Systematic errors (accuracy) were summarized as signed mean percent differences. Random errors (precision) were calculated as ± 1 SD of percent differences. RESULTS: Fifty neonates were delivered at 39.4 weeks' gestation. The Hadlock model generated the most accurate birth weight (0.31%) with a mean random error of ±7.9%. Despite systematic underestimations, the most precise results occurred with fractional arm volume (-9.1% ± 5.1%) and fractional thigh (-5.2% ± 5.2%) models. The size and distribution of these prediction errors were improved after correction for systematic errors. CONCLUSIONS: Automated fractional limb volume measurements can improve the precision of weight predictions in third-trimester fetuses. Correction factors may be necessary to adjust underestimated systematic errors when using automated fractional limb volume with prediction models that are based on manual tracing of fetal limb soft tissue borders.

Are First Trimester Nuchal Septations Independent Risk Factors for Chromosomal Anomalies?

OBJECTIVES: There is conflicting information regarding the role of nuchal septations during first-trimester genetic screening. This study was designed to determine whether nuchal septations are risk factors for chromosomal anomalies, independent of increased nuchal translucency (NT), in the first trimester of pregnancy. METHODS: This retrospective cohort study included all women who underwent first-trimester genetic screening between November 2011 and December 2014. The 95th percentile for the NT measurement was calculated for each gestational week. A multivariable logistic regression analysis was performed to determine whether the visualization of nuchal septations was an independent risk factor for chromosomal analysis while controlling for confounding variables. P < .05 was considered significant. RESULTS: Chromosomal abnormalities were present in 1.0% of the population (33 of 3275). The prevalence of chromosomal abnormalities was significantly higher among fetuses with nuchal septations compared to fetuses with normal NT without septations (P < .001) and those with NT above the 95th percentile without septations (P < .001). The sonographic evidence of septations was associated with high risk of chromosomal abnormalities (odds ratio, 40.0; 95% confidence interval, 9.1-174.0) after controlling for NT measurements and other confounding variables. CONCLUSIONS: Visualization of nuchal septations during first-trimester genetic screening is a powerful risk factor for chromosomal anomalies, independent of increased NT.

A Novel Semiautomated Fractional Limb Volume Tool for Rapid and Reproducible Fetal Soft Tissue Assessment.

The purpose of this study was to document the reproducibility and efficiency of a semiautomated image analysis tool that rapidly provides fetal fractional limb volume measurements. Fifty pregnant women underwent 3-dimensional sonographic examinations for fractional arm and thigh volumes at a mean menstrual age of 31.3 weeks. Manual and semiautomated fractional limb volume measurements were calculated, with the semiautomated measurements calculated by novel software (5D Limb Vol; Samsung Medison, Seoul, Korea). The software applies an image transformation method based on the major axis length, minor axis length, and limb center coordinates. A transformed image is used to perform a global optimization technique for determination of an optimal limb soft tissue boundary. Bland-Altman analysis defined bias with 95% limits of agreement (LOA) between methods, and timing differences between manual versus automated methods were compared by a paired t test. Bland-Altman analysis indicated an acceptable bias with 95% LOA between the manual and semiautomated methods: mean arm volume ± SD, 1.7% ± 4.6% (95% LOA, -7.3% to 10.7%); and mean thigh volume, 0.0% ± 3.8% (95% LOA, -7.5% to 7.5%). The computer-assisted software completed measurements about 5 times faster compared to manual tracings. In conclusion, semiautomated fractional limb volume measurements are significantly faster to calculate when compared to a manual procedure. These results are reproducible and are likely to reduce operator dependency. The addition of computer-assisted fractional limb volume to standard biometry may improve the precision of estimated fetal weight by adding a soft tissue component to the weight estimation process.

Vitamin C Transporters, Recycling and the Bystander Effect in the Nervous System: SVCT2 versus Gluts.

Vitamin C is an essential micronutrient in the human diet; its deficiency leads to a number of symptoms and ultimately death. After entry into cells within the central nervous system (CNS) through sodium vitamin C transporters (SVCTs) and facilitative glucose transporters (GLUTs), vitamin C functions as a neuromodulator, enzymatic cofactor, and reactive oxygen species (ROS) scavenger; it also stimulates differentiation. In this review, we will compare the molecular and structural aspects of vitamin C and glucose transporters and their expression in endothelial or choroid plexus cells, which form part of the blood-brain barrier and blood-cerebrospinal fluid (CSF) barrier, respectively. Additionally, we will describe SVCT and GLUT expression in different cells of the brain as well as SVCT2 distribution in tanycytes and astrocytes of the hypothalamic region. Finally, we will describe vitamin C recycling in the brain, which is mediated by a metabolic interaction between astrocytes and neurons, and the role of the "bystander effect" in the recycling mechanism of vitamin C in both normal and pathological conditions.

Glucose transporter 1 and monocarboxylate transporters 1, 2, and 4 localization within the glial cells of shark blood-brain-barriers.

Although previous studies showed that glucose is used to support the metabolic activity of the cartilaginous fish brain, the distribution and expression levels of glucose transporter (GLUT) isoforms remained undetermined. Optic/ultrastructural immunohistochemistry approaches were used to determine the expression of GLUT1 in the glial blood-brain barrier (gBBB). GLUT1 was observed solely in glial cells; it was primarily located in end-feet processes of the gBBB. Western blot analysis showed a protein with a molecular mass of 50 kDa, and partial sequencing confirmed GLUT1 identity. Similar approaches were used to demonstrate increased GLUT1 polarization to both apical and basolateral membranes in choroid plexus epithelial cells. To explore monocarboxylate transporter (MCT) involvement in shark brain metabolism, the expression of MCTs was analyzed. MCT1, 2 and 4 were expressed in endothelial cells; however, only MCT1 and MCT4 were present in glial cells. In neurons, MCT2 was localized at the cell membrane whereas MCT1 was detected within mitochondria. Previous studies demonstrated that hypoxia modified GLUT and MCT expression in mammalian brain cells, which was mediated by the transcription factor, hypoxia inducible factor-1. Similarly, we observed that hypoxia modified MCT1 cellular distribution and MCT4 expression in shark telencephalic area and brain stem, confirming the role of these transporters in hypoxia adaptation. Finally, using three-dimensional ultrastructural microscopy, the interaction between glial end-feet and leaky blood vessels of shark brain was assessed in the present study. These data suggested that the brains of shark may take up glucose from blood using a different mechanism than that used by mammalian brains, which may induce astrocyte-neuron lactate shuttling and metabolic coupling as observed in mammalian brain. Our data suggested that the structural conditions and expression patterns of GLUT1, MCT1, MCT2 and MCT4 in shark brain may establish the molecular foundation of metabolic coupling between glia and neurons.