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SUMMARY: To establish an unprovable diagnostic indicative index reference for ultrasound examination of the fetal cerebral ventricles, based on the morphological characteristics throughout fetal nervous system development. Key ultrasonic morphological indicators of fetal ventricular development, which includes frontal horn width (FHW), occipital horn width (OHW), width of 3rd ventricle, cavity of septum pellucidum (CSP), width and length of 4th ventricle and thalamo-occipital distance (TOD) had been measured and analyzed collectively. All data of the indicators was collected on singleton pregnant woman between 16-39 weeks of gestational age (GA), between November 2017 and June 2021 at the Second Hospital of Dalian Medical University. A total of 235 pregnant women were enrolled in the cross section study; another 36 pregnant women voluntarily joined a timeline-tracking follow-up study (cohort study) under the same examining criteria. A decrease of FHW and OHW of the lateral ventricles was observed as GA increased; while dimensional values of TOD, 3rd ventricle, CSP, as well as 4th ventricle increased with GA. Most of these indicators showed an enhanced variation tendency within a certain period of GA. Moreover, values of FHW and TOD showed asymmetry of the two hemispheres within the whole GA. Our findings revealed the morphological regularity of fetal ventricular development, which would instructively enhance the relative clinical ultrasound diagnosis; moreover, TOD also showed regularly changes as GA increased, suggesting that TOD should be considered as an additional routine ultrasonic indicator for fetal ventricular development.

RESUMEN: El objetivo del estudio fue establecer un índice de referencia indicativo diagnóstico no demostrable para el examen ecográfico de los ventrículos cerebrales fetales, basado en las características morfológicas a lo largo del desarrollo del sistema nervioso fetal. Indicadores morfológicos ultrasónicos clave del desarrollo ventricular fetal, que incluyen el ancho del cuerno frontal (FHW), el ancho del cuerno occipital (OHW), el ancho del tercer ventrículo, la cavidad del septo pelúcido (CSP), el ancho y el largo del cuarto ventrículo y la distancia tálamo-occipital (TOD) fueron medidos y analizados conjuntamente. Todos los datos de los indicadores se recopilaron en mujeres embarazadas de un solo feto entre 16 y 39 semanas de edad gestacional (EG), entre noviembre de 2017 y junio de 2021 en el Segundo Hospital de la Universidad Médica de Dalian. Un total de 235 mujeres embarazadas se inscribieron en el estudio transversal; otras 36 mujeres embarazadas se unieron voluntariamente a un estudio de seguimiento de línea de tiempo (estudio de cohorte) bajo los mismos criterios de examen. Se observó una disminución de FHW y OHW de los ventrículos laterales a medida que aumentaba la GA; mientras que los valores dimensionales de TOD, tercer ventrículo, CSP y cuarto ventrículo aumentaron con GA. La mayoría de estos indicadores mostraron una tendencia de variación mejorada dentro de un cierto período de GA. Además, los valores de FHW y TOD mostraron asimetría de los dos hemisferios dentro de toda la AG. Nuestros hallazgos revelaron la regularidad morfológica del desarrollo ventricular fetal, lo que mejoraría de manera instructiva el diagnóstico clínico de ultrasonido relativo; además, TOD también mostró cambios regulares a medida que aumentaba la GA, lo que sugiere que TOD debe considerarse como un indicador ultrasónico de rutina adicional para el desarrollo ventricular fetal.

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The subventricular zone (SVZ) is a neurogenic region that continually gives rise to olfactory bulb (OB) GABAergic interneurons in mammals. The newly generated neuroblasts already express GABA while migrating to this structure along the rostral migratory stream (RMS). Here, we investigate in early postnatal rat if SVZ/RMS cells undertake the same synthetic pathway by which GABA is produced in differentiated neurons, i.e. the decarboxylation of glutamate by the glutamic acid decarboxylase (GAD), or, if an alternative pathway, the conversion of putrescine into GABA, also contributes to GABA synthesis. We show here that GAD immunoreactivity is not significantly detectable within the SVZ/RMS. However, strong immunolabeling is found within the OB. Nevertheless, low GAD enzymatic activity (as compared with OB) is detected in the SVZ/RMS. SVZ/RMS explants convert approximately 30% of all captured radiolabeled putrescine into GABA in vitro, showing that this pathway is important for GABA synthesis in the SVZ. We also show that SVZ/RMS, OB and choroid plexus explants are able to synthesize putrescine, as analyzed by ornithine decarboxylase (ODC) activity, providing neuroblasts with different sources of putrescine for GABA production. During early stages of neuroblast differentiation, in which neurotransmitter choice may still be undefined, an alternative pathway for GABA synthesis guarantees the production of GABA, necessary for neuroblast proliferation and migration in the SVZ/RMS.

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Ependymal cells appear to be totally differentiated during the first 3 weeks in the mouse brain. Early during postnatal development ependymal cells differentiate and undergo metabolic activation, which is accompanied by increased glucose uptake. We propose that ependymal cells induce an overexpression of the glucose transporter, GLUT1, during the first 2 weeks after delivery in order to maintain the early metabolic activation. During the first postnatal day, GLUT1 is strongly induced in the upper region of the third ventricle and in the ventral area of the rostral cerebral aqueduct. During the next 4 days, GLUT1 is expressed in all differentiated ependymal cells of the third ventricle and in hypothalamic tanycytes. At the end of the first week, ependymal cell differentiation and GLUT1 overexpression is concentrated in the latero-ventral area of the aqueduct. We propose that ependymal cell differentiation and GLUT1 overexpression is a synchronous process in the ventricular wall.

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The anterior subventricular zone (SVZa) is the site for postnatal neurogenesis of interneurons of the olfactory bulb (OB). Concurrently or after proliferation, neuronal precursors therein migrate within it to reach the OB, an event known as the rostral migratory stream (RMS). We used bromodeoxyuridine (BrdU) incorporation with short survival times to investigate the distribution of S-phase nuclei in the SVZa/RMS of the postnatal mouse. We observed that they were distributed along a radial, outside-in, decreasing gradient that persisted until postnatal day 10 (P10), then faded away to finally disappear by P16. After longer post-injection survival times labeled cell distribution became homogeneous. GFAP-positive glia are present at the periphery but not at the core of the SVZa. Our results represent the first evidence of a discrete spatial organization of a cell cycle phase within the SVZ, and also suggests a segregation of proliferating and migrating cells in the rostral migratory stream of the early postnatal mouse.

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Lateral cerebral ventricular volume in 36 preterm infants with or without an intraventricular hemorrhage, and with or without posthemorrhagic hydrocephalus, was measured longitudinally and compared with the ventricular index measurements of the same ventricles. A poor correlation was found (r2 = 0.67). To determine a reason for this poor relationship, we analyzed the volumes of the regions of the ventricles by a segmental volume analysis. The occipital region of the lateral cerebral ventricle enlarged at a much faster rate (1.904 +/- 0.477 ml/day) than either the anterior region (0.546 +/- 0.253 ml/day; p less than 0.01) or the middle region (-0.209 +/- 0.334 ml/day; p less than 0.01) in infants with posthemorrhagic hydrocephalus. The rate of growth of the middle region of the lateral cerebral ventricles was the same for all infants. Linear indexes, such as the ventricular index and the lateral ventricular ratio, do not allow for accurate serial estimates of ventricular size in posthemorrhagic hydrocephalus because of asymmetric growth of the lateral cerebral ventricle. We conclude that sequential volume measurements are more useful than ventricular index measurements to follow ventricular size sequentially in infants with posthemorrhagic hydrocephalus.

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