EMBRIOGENESIS OF NEURONAL ELENENTS (GLIOBLASTS AND GABAA RECEPTORS) IN THE HUMAN BRAIN NEUROIMMUNE SYSTEM UNDER PRENATAL ALCOHOL EXPOSURE

Exposure to alcohol causes imbalances in neuroimmune function and impaired brain development. Alcohol activates the innate immune signaling pathways in the brain. Neuroimmune molecules expressed and secreted by glial cells of the brain (microglia, oligodendroglia) alter the function of neurons and further stimulate the development of alcoholic behavior. Various signaling pathways and brain cells are involved in the transmission of neuroimmune signals. Glial cells are the main sources of immune mediators in the brain, which respond to and release immune signals in the central nervous system. The aim of this study was to study neuronal elements: morphometric parameters of glioblasts, synaptic structures and properties of synaptosomal GABAA-benzodiazepine receptors of the neuroimmune system in the embryogenesis of the human brain under perinatal exposure to alcohol. Changes in glioblasts in the brain tissue of human embryos and fetuses were revealed under conditions of chronic prenatal alcoholization with an increase in gestational age compared with control subgroups: a significant increase in the average number of glioblasts, the length of the perimeters of presynaptic terminal structures, postsynaptic density, presynaptic terminal regions were significantly less (p < 0.01) in the study group than in the control comparison group. Exposure to ethanol leads to a decrease in the affinity of GABAA-benzodiazepine receptors, which affects neuronal plasticity associated with the development and differentiation of progenitor cells (glioblasts and neuroblasts) during embryogenesis of the human brain and leads to suppression of GABAergic function in the brain. This causes a disruption in the interconnection of embryonic cells in the brain, leads to excessive apoptosis due to the activation of glial cells of the nervous tissue, disruption of neuroimmune function in the developing brain, changes in neuronal circuits, as well as a change in the balance of excitatory and inhibitory effects, which affects the functional activity in the central nervous system. Glial activation is a compensatory reaction caused by neuroplastic changes aimed at adapting the developing brain of the embryo and fetus under conditions of neurotoxicity and hypoxia under the influence of prenatal alcoholization of the maternal organism and the effect of ethanol on the fetus. The dynamics of changes in glial elements and receptor activity in the nervous tissue of human embryos and fetuses under conditions of prenatal exposure to alcohol indicates a more pronounced effect of alcohol on the earliest stages of human embryo development, which is of great practical importance in planning pregnancy and the inadmissibility of alcoholization of the mother in order to avoid negative consequences in offspring.

Development of the cartilaginous connecting apparatuses in the fetal sphenoid, with a focus on the alar process

The human fetal sphenoid is reported to have a cartilaginous connecting apparatus known as the alar process (AP), which connects the ala temporalis (AT) (angle of the greater wing of the sphenoid) to the basisphenoid (anlage of the sphenoid body). However, how the AP develops in humans is unclear. In addition, although the AP is a common structure of the mammalian chondrocranium, little is known about whether it is really a fundamental feature in mammals. This study examined the histological sections of 20 human embryos and fetuses from 6 to 14 weeks of development, of 20 mouse embryos from embryonic days 12–18, and of 4 rats embryos form embryonic days 17 and 20. In addition, we reconsidered the definition of the AP by comparing humans and rats with mice. In humans, the AP was continuous with the basisphenoid but was separated from the AT by a thick perichondrium. Then, the AP–AT connection had a key-and-keyhole structure. Unlike a joint, no cavitation developed in this connection. In mice, there was no boundary between the AT and the basisphenoid, indicating the absence of the AP in the mouse chondrocranium. In rats, the AP was, however, separated from the AT by a thick perichondrium. Therefore, the AP can be defined as follows: the AP is temporally separated from the AT by a thick perichondrium or a key-and-keyhole structure during the fetal period. This is the first study that confirms the absence of the alar process in the mice skull, and its presence in other mammals skull should be further investigated.

Development of sacral vertebrae in human embryos and fetuses

The aim of the study is to define the features of organogenesis and histogenesis of sacral vertebrae in human embryos, which predetermine the anatomical structure of the sacrum in postnatal ontogenesis. Material and methods. The authors studied human embryo serial sections at 17–23 stages from the Carnegie virtual embryological collection, total preparations and serial sections of the lumbosacral region of the fetal spine at 8–20 weeks of gestation without visible developmental anomalies. Histological sections were stained with hematoxylin and eosin; total preparations were stained with alizarin red and alcian blue. In addition, the study included 19 adult sacra from the anatomical collection of the Belarusian State Medical University. Results. It was found that consolidation of the anlages of the upper sacral vertebrae starts at the early stages of embryogenesis by the fusion of their costal-transverse processes. During the first half of intrauterine development, the arch and articular processes of the adjacent vertebrae remain separate from each other. In contrast to other segments of the spinal column, five primary centers of ossification are formed in the anlages of the upper sacral vertebrae

Early development of human ganglionic eminences assessed in vitro by using 7.04 Tesla micro-MRI – a pilot study

Background and aims. Ganglionic eminences are temporary structures which appear during the 5th week post-fertilization on the floor of telencephalic vesicles and disappear until the 35th week of gestation. The aim of this descriptive study of morphological research is to depict the ganglionic eminences within the embryonic and early fetal brains by using micro-MRI. Methods. Six human embryos and fetuses ranging from 21 mm crown-rump length CRL (9 gestational week GW) to 85 mm CRL (14 GW) were examined in vitro by micro-MRI. The investigation was performed with a Bruker BioSpec 70/16USR scanner (Bruker BioSpin MRI GmbH, Ettlingen, Germany) operating at 7.04 Tesla. Results. We describe the morphological characteristics of the ganglionic eminences at different gestational ages. The acquisition parameters were modified for each subject in order to obtain an increased spatial resolution. The remarkable spatial resolution of 27 µm/voxel allows visualization of millimetric structures of the developing brain on high quality micro-MR images. Conclusion. In our study we give the description of the ganglionic eminences within the embryonic and early fetal brains by using micro-MRI, which have not been previously documented in literature. Micro-MRI provides accurate images, which are comparable with the histological slices.