Fetal Research Articles

MORPHOMETRIC PARAMETERS OF THE HUMAN FETUS PONS 17-18 WEEKS OF INTRAUTERINE DEVELOPMENT

Relevance. Currently, increased interest is observed in the early stages of postnatal ontogenesis in research of age-related changes in the systems of the human body.
 Aim: To define the macrometric parameters of the pons of human fetuses of 17-18 weeks of fetal development, the sizes and area of the cranial nerve nuclei contained in pons, as well as the size and area of the nerve cells that form these nuclei.
 Materials and methods: We performed an anatomical and histological examination of 10 human fetuses at the stage of 17-18 weeks of intrauterine development.
 Results: The boundaries of the nucleus of the abductor nerve are unclear, the neurons of the nucleus are spherical or rounded in shape. The vestibular nucleus of the vestibulocochlear nerve has an indeterminate shape, the boundaries of the nucleus are not clear, neurons with different areas of the nucleus are noted, from large to small. The motor nucleus of the facial nerve has an elongated shape, with not clear outer edges, the nerve cells are dome-shaped. The principal nucleus of the trigeminal nerve has a rounded shape.
 Conclusions: We established that at 17-18 weeks of intrauterine development of human fetuses, the nucleus of the abductor nerve, the motor nucleus of the facial nerve, the principal nucleus of the trigeminal nerve, and the vestibular nucleus of the vestibulocochlear nerve were visualized. Nucleus of the abductor nerve has the largest area, the smallest -has the vestibular nucleus of the vestibulocochlear nerve. The largest area of neurons of the vestibular nucleus was established in comparison with the area of the nucleus of the facial, trigeminal and abductor nerves. The diameter and area of the nuclei of the cells of the abductor nerve, the motor nucleus of the facial nerve, and the principal nucleus of the trigeminal nerve have almost the same size, while the area of the neurons of the vestibulocochlear nerve is different, there is a group of neurons with a large area, and there is a group with a much smaller area of neurons.

Gelişmekte olan insan fetüslerinin ve yetişkinlerin derisinde EZH2 ekspresyonu: karşılaştırmalı bir çalışma

Purpose: In animals, the appropriate levels of Enhancer of zeste homolog 2 (EZH2), a well-established epigenetic regulator, are essential for the embryonic development of skin and appendages. We aimed to explore the EZH2 expression patterns in the skin of human fetuses and compare them with adults.
 Materials and Methods: We performed EZH2 immunohistochemical staining in skin samples from the scalp region of 67 fetuses and from the farthest surgical margin of the lip wedge resection, where no lesions were found, of 23 adults. EZH2 scores were evaluated according to the literature. 
 Results: Epidermal (r = − 0.528), dermal (rs = − 0.509), and hair follicle (r = − 0.576) EZH2 scores were inversely correlated with gestational age. Epidermal and hair follicle EZH2 scores were significantly higher in adults compared to fetuses. There were significant and positive correlations between epidermal, dermal, and hair follicle EZH2 scores among fetuses and adults.
 Conclusion: Lower levels of EZH2 may be necessary for final cutaneous differentiation and maturation before birth. Our findings may have a therapeutic impact on cutaneous disorders with differentiation defects, chronic wounds, and alopecias.

Deciphering Oligodendrocyte Lineages in the Human Fetal Central Nervous System Using Single-Cell RNA Sequencing.

Oligodendrocytes form myelin sheaths and wrap axons of neurons to facilitate various crucial neurological functions. Oligodendrocyte progenitor cells (OPCs) persist in the embryonic, postnatal, and adult central nervous system (CNS). OPCs and mature oligodendrocytes are involved in a variety of biological processes such as memory, learning, and diseases. How oligodendrocytes are specified in different regions in the CNS, in particular in humans, remains obscure. We here explored oligodendrocyte development in three CNS regions, subpallium, brainstem, and spinal cord, in human fetuses from gestational week 8 (GW8) to GW12 using single-cell RNA sequencing. We detected multiple lineages of OPCs and illustrated distinct developmental trajectories of oligodendrocyte differentiation in three CNS regions. We also identified major genes, particularly transcription factors, which maintain status of OPC proliferation and promote generation of mature oligodendrocytes. Moreover, we discovered new marker genes that might be crucial for oligodendrocyte specification in humans, and detected common and distinct genes expressed in oligodendrocyte lineages in three CNS regions. Our study has demonstrated molecular heterogeneity of oligodendrocyte lineages in different CNS regions and provided references for further investigation of roles of important genes in oligodendrocyte development in humans.

SOME OPTIONS OF FETAL TOPOGRAPHY OF THE LONG BRANCHES OF THE CROSS PLEXUS

In the conditions of wartime, the frequency of damage to the nerves of the lower extremity increased sharply. Open injuries make up the vast majority of peripheral nerve injuries. Understanding variations in the topography and the condition of the surrounding soft tissue structures allows for a detailed assessment of the condition of the peripheral nerves of the lower limb, to diagnose the exact site of damage, the type of neuropathy, and to choose treatment and rehabilitation tactics. The purpose of the study will be to establish variants of the fetal topography of the long branches of the sacral plexus. The material for the study of topographical and anatomical features of the long branches of the sacral plexus was 26 human fetuses of 5-7 months. The sciatic nerve is the largest nerve in humans, originating from the ventral division of spinal nerves L4 to S3 and containing fi bers from both the posterior and anterior lumbosacral plexuses. The sciatic nerve runs along the entire back surface of the lower limb up to the foot. The sciatic nerve innervates a signifi cant part of the skin and muscles of the thigh, lower leg, and foot. It was established that the long branches of the sacral plexus can be subjected to compression or damage in diff erent parts of its anatomical course. Among the variants of the anatomical variability of the long branches of the sacral plexus, the topography of the sciatic nerve is the most common. In the three studied fetuses of 180.0 mm, 215.0 mm, 255 mm TKD, a high branching variant of the sciatic nerve was detected, and the features of the long branches of the sacral plexus in the specifi ed fetuses were unilateral. In this case, when assessing clinical symptoms, practicing doctors should take into account options for bilateral asymmetry. Prospects for further research. Deepening the study of the variant anatomy of the long branches of the sacral plexus in human fetuses of diff erent ages.

Morphological variability of the fibularis brevis tendon in human fetuses

IntroductionThe morphological variability of the fibularis brevis tendon in adults is well known. However, studies on its classification in the human fetus do not exist. The aim of this study was to provide the first comprehensive classification of the fibularis brevis tendon based on its insertion in human fetuses. The second aim of the study is to evaluate the prevalence of fibularis digiti quinti. Material and MethodsForty-three spontaneously aborted human fetuses were studied (21 male, 22 female, 86 lower limbs). All were from a Central European population), aged 18–38 weeks of gestation at the time of death. ResultsThree main types of fibularis brevis tendon were distinguished. The most common was Type I (77%), characterized by a single distal attachment. The tendon was attached to the tuberosity at the base of the fifth metatarsal, on the lateral side. The second most common was Type II (19%) - a bifurcated distal attachment. The main tendon was attached to the tuberosity at the base of the fifth metatarsal on the lateral side. Based on the attachment site of the accessory tendon, four subtypes were determined: Type IIA - the accessory tendon attached to the dorsal surface of the base of the fifth metatarsal. At the side of attachment, the fibularis brevis tendon was connected with a portion of the fibularis tertius tendon. Type IIB - the accessory tendon attached to the proximal part of the shaft of the fifth metatarsal. Type IIC - the accessory tendon was attached to the fascia covering the fourth interosseous space. Type IID - the accessory tendon was fused with fibularis longus tendon. Type III is the rarest (4%) - triple branched distal attachment. The main tendon was attached to the tuberosity at the base of the fifth metatarsal. The first accessory tendon was attached to the proximal part of the shaft of the fifth metatarsal, and the second accessory tendon was attached to the fascia covering the fourth interosseous space. The fibularis digiti quinti was present in 24 feet (28%) of the 86 lower limbs dissected. ConclusionThe fibularis brevis is characterized by high morphological variability. The proposed classification consists of three main Types (I-III), with Type II divided into subtypes (A-D). The fibularis digiti quinti is not closely related to the type of fibularis brevis tendon.

Hormonal Determinants of Growth and Weight Gain in the Human Fetus and Preterm Infant.

The factors controlling linear growth and weight gain in the human fetus and newborn infant are poorly understood. We review here the changes in linear growth, weight gain, lean body mass, and fat mass during mid- and late gestation and the early postnatal period in the context of changes in the secretion and action of maternal, placental, fetal, and neonatal hormones, growth factors, and adipocytokines. We assess the effects of hormonal determinants on placental nutrient delivery and the impact of preterm delivery on hormone expression and postnatal growth and metabolic function. We then discuss the effects of various maternal disorders and nutritional and pharmacologic interventions on fetal and perinatal hormone and growth factor production, growth, and fat deposition and consider important unresolved questions in the field.

A marginal branch of the left hepatic artery running along the umbilical vein and supplying the anterior surface of the liver left lobe: a report of 5 cases in 12 Japanese human fetuses.

In human fetuses, the left hepatic artery (LHA) issues the marginal artery that runs along the umbilical vein and, sometimes, reaches the umbilicus. The further observation demonstrated that, in 5 of 12 Japanese midterm fetuses (crown-rump length mm: 46, 50, 54, 59, 102), the marginal artery issued not only a thin umbilical branch but also a liver parenchymal branch that took a posterosuperior recurrent course in a peritoneal fold and supplied the anterior surface of the liver left lobe (segment III). However, in 22 Spanish fetuses of which gestational ages corresponded to the Japanese ones, we did not find the parenchymal branch. Therefore, between human populations, there seemed to be a considerable difference in the incidence as to whether or not the marginal artery issues the liver parenchymal branch. The parenchymal branch might be degenerated at the later stages due to friction between the liver free surface and growing diaphragm.

АНАТОМИЧЕСКАЯ ХАРАКТЕРИСТИКА ЗУБНЫХ АЛЬВЕОЛ НИЖНЕЙ ЧЕЛЮСТИ ПЛОДА В ПРОМЕЖУТОЧНОМ ПЛОДНОМ ПЕРИОДЕ ОНТОГЕНЕЗА ЧЕЛОВЕКА

Fundamental research on human fetal anatomy today has serious applied significance for the 
 implementation of the principles of prediction and prevention of congenital pathology. The aim is to give an 
 anatomical characteristic of the dental alveoli of the mandible of the fetus in the intermediate fetal period of 
 human ontogenesis. Materials and methods. 110 lower jaws of human fetuses of the second trimester of 
 different sex were studied using ultrasound scanning and morphological techniques. Results. In the body of 
 69
 the mandible, dental alveoli can be visualized using morphological techniques throughout the intermediate 
 fetal period of ontogenesis and by ultrasound scanning from week 19 of intrauterine development in an amount 
 of 8-10. The average sizes of the dental alveoli are 2.2±0.6 mm for medial incisors, 2.3±0.7 mm for lateral 
 incisors, 2.4± 0.7 mm for canines, and 3.3±1.0 mm for molars. Dental alveoli of the lower jaw in fetuses from 
 14 to 28 weeks of fetal development grow with a growth intensity range of 57.8-83.3%. The incisors and 
 canines change heterochronously from 14 to 23 weeks of gestation with a growth rate of IR=51-52.6%, from 
 24 to 27 weeks of pregnancy with a growth rate of 34%-34.5%. The dental alveoli of molars are characterized 
 by uniform growth. Conclusion. The anatomical features of the structure of dental alveoli have been estab lished, which can be used as additional markers for the detection of congenital pathology of the fetus during a 
 screening study of pregnant women. Keywords: dental alveolus, mandible, fetus, intermediate fetal period, 
 ultrasound scanning method, morphological techniques

Pregnancy-related maternal physiological adaptations and fetal chemical exposure

Prenatal life represents a susceptible window of development during which chemical exposures can permanently alter fetal development, leading to an increased likelihood of disease later in life. Therefore, it is essential to assess exposure in the fetus. However, direct assessment in human fetuses is challenging, so most research measures maternal exposure. Pregnancy induces a range of significant physiological changes in women that may affect chemical metabolism and responses. Moreover, placental function, fetal sex, and pregnancy complications may further modify these exposures. The purpose of this narrative review is to give an overview of major pregnancy-related physiological changes, including placental function and impacts of pregnancy complications, to summarize existing studies assessing chemical exposure in human fetal organs, and to discuss possible interactions between physiological changes and exposures. Our review reveals major knowledge gaps in factors affecting fetal chemical exposure, highlighting the need to develop more sophisticated tools for chemical health risk assessment in fetuses.

Anatomical Variations of the Musculocutaneous Nerve in the Human Fetus

Knowing the motor branches and variations of the musculocutaneous nerve to the muscles along its course will facilitate the treatment of flexor spasticity and supracondylar fractures of the humerus in order to minimize nerve lesion. In fetal cadavers, the purpose of our study was to determine the number and course of the formation variations and motor branches of the musculocutaneous nerve. The significance of studying fetal nerve variations is due to injury to the brachial plexus roots during birth. Our study was conducted using the anatomical dissection technique on 102 upper limbs from 51 fetuses ages ranged from 17 to 40weeks. Throughout its course, the variations and motor branches of the musculocutaneous nerve were analyzed. In 13.7% of cases, the musculocutaneous nerve did not pierce the coracobrachialis. The musculocutaneous nerve gave the muscles 1-3 motor branches. Additionally, motor branches terminated with 1-7 fringes. The biceps brachii motor branches of the musculocutaneous nerve were typed. Accordingly, 15.6% were type 1A, 3.9% were type 1B, 35.4% were type 1C, and 19.6% were type 1D. It was determined that 23.5% of the extremities were type 2 and that 1.9% were type 3. The distance between the musculocutaneous nerve's motor branches and the acromion was proportional to the arm's length. There were no statistically significant differences between the sides and genders for any measurement. Our study's findings will aid in the diagnosis and treatment of pediatrics, orthopedics, surgical sciences, and radiology conditions. It reduces the risk of iatrogenic injury and postoperative complications. We also believe that our research will serve as a resource for anatomists and other scientists.

Immunohistochemical Localization of Endothelin- 1 and Endothelin A Receptor in Human Primary Tooth Enamel Organ.

Enamel organ (EO) is an ectodermal derived structure, which is involved in the different aspects of tooth development. Tooth development shares the same regulatory molecules and genes expressed in other developing organs. Endothelin- 1 (ET-1) and Endothelin A receptor (ETAR), (ET-1/ETAR) axis, are involved in differentiation of embryonic stem cells and organ development. The present study aimed to investigate the ET-1 and ETAR expression profiles during the development of human primary tooth EO with the relatively large sample size. In this experimental study, 33 human fetuses aged from 13 to 23 weeks (3 samples from each fetal age) were collected. The sampleswere divided into three age groups (<16 weeks, <19 weeks, ≥19 weeks) and cut for hematoxylin and eosin (H&E) and immunohistochemistry (IHC) staining. A two-way ANOVA test was conducted to examine the expression levels of ET-1 and ETAR in different layers of human primary tooth EO. The statistical significance was assumed at p ≤ 0.05. There were statistically significant differences between the expression levels of ET-1/ETAR axis in the four-layered human primary tooth EO in different fetal ages (13-23 weeks). Besides, there were significant differences between the expression levels of ET-1/ETAR axis in all layers of human primary enamel organ and types of teeth. Due to the profile of expression of ET-1/ETAR axis, it can be concluded that this axis contributes to the differentiation of all human primary EO layers and secretion of enamel. ET-1/ETAR axis is one of the signaling molecules, which may have crucial roles in tooth development.

Biomonitoring equivalents for perfluorooctanoic acid (PFOA) for the interpretation of biomonitoring data

BackgroundPerfluorooctanoic acid (PFOA) is detected in the blood of virtually all biomonitoring study participants. Assessing health risks associated with blood PFOA levels is challenging because exposure guidance values (EGVs) are typically expressed in terms of external dose. Biomonitoring equivalents (BEs) consistent with EGVs could facilitate health-based interpretations. ObjectiveTo i) derive BEs for serum/plasma PFOA corresponding to non-cancer EGVs of the U.S. Environmental Protection Agency (U.S. EPA), the Agency for Toxic Substances and Disease Registry (ATSDR) and Health Canada, and ii) compare with PFOA concentrations from national biomonitoring surveys. MethodsStarting from EGV points of departure, we employed pharmacokinetic data/models and uncertainty factors. Points of departure in pregnant rodents (U.S. EPA 2016, ATSDR) were converted into fetus and pup serum concentrations using an animal gestation/lactation pharmacokinetic model, and equivalent human fetus and child concentrations were converted into BEs in maternal serum using a human gestation/lactation model. The point of departure in adult rodents (Health Canada) was converted into a BE using experimental data. For epidemiology-based EGVs (U.S. EPA 2023, draft), BEs were directly based on epidemiological data or derived using a human gestation/lactation pharmacokinetic model. BEs were compared with Canadian/U.S. biomonitoring data. ResultsNon-cancer BEs (ng/mL) were 684 (Health Canada, 2018) or ranged from 15 to 29 (U.S. EPA, 2016), 6–10 (ATSDR, 2021) and 0.2–0.8 (U.S. EPA, 2023, draft). Ninety-fifth percentiles of serum levels from the 2018–2019 Canadian Health Measures Survey (CHMS) and the 2017–2018 National Health and Nutrition Examination Survey (NHANES) were slightly below the BE for ATSDR, and geometric means were above the non-cancer BEs for the U.S. EPA (2023, draft). ConclusionNon-cancer BEs spanned three orders of magnitude. The lowest BEs were for EGVs based on developmental endpoints in epidemiological studies. Concentrations in Canadian/U.S. national surveys were higher than or close to BEs for the most recent non-cancer EGVs.

Distribution of macrophages in the developing cochlea of the common marmoset, a primate model animal.

Macrophages are essential immune cells in the cochlea that contribute to inflammation, tissue repair, and homeostasis. They also play an important role in local cochlear immunity. The developmental immigration and maturation of macrophages in the cochlea have been investigated and are considered essential for normal hearing acquisition. Most of our current knowledge regarding cochlear development is based on rodent models because of the ethical challenges of using human fetal samples for research. However, inter-species differences between rodents and humans have been reported. In this study, we used a primate animal model to investigate the distributions of macrophages in the developing cochlea. The common marmoset (Callithrix jacchus), a small monkey species that inhabits the New World, was used as the model. We investigated the distribution of macrophages in the developing cochlea of the common marmoset by performing immunohistochemical analyses of cochlear tissue from common marmoset embryos at different development stages. We revealed detailed distribution changes in the macrophages of a primate animal model cochlea. This observation indicates that most of the changes in the general distribution of macrophages were well preserved between rodents and this primate. The distribution changes observed in the common marmoset were also compatible with observations in the human fetus; although, observations in the human fetus are limited. Our observations in this study also revealed several differences between common marmosets and rodents. The time course of immunological development and maturations established in this study will aid in the study of the primate-specific developmental biology of the inner ear. These observations may eventually lead to new therapeutic strategies for hearing loss in humans. In addition, understanding the immunological steady-state of the cochlea may help in the study of age- and genetic-induced hearing loss and in the design of regenerative therapies.

Umbilical cord gas analysis: clinical implications of a comprehensive, contemporary determination of normal ranges

Umbilical cord gases are often used to assess the impact of labor and delivery on the fetus. However, no large series exists that reflects contemporary obstetrical practice or that analyzed blood gas ranges by route of delivery. Baseline, prelabor acid-base status in the human fetus is also poorly defined, rendering the assessment of blood gas changes during labor difficult. This study aimed to define normal umbilical cord gas and lactate values, stratified by mode of delivery, in a large contemporary series in which universal umbilical cord gas evaluation was dictated by protocol. This was a retrospective cohort study. We analyzed the umbilical cord gas and lactate data of an unselected population of infants born between March 2012 and April 2022 at a large teaching hospital. These values were then analyzed by mode of delivery and, for cesarean deliveries, by indication for cesarean delivery and type of anesthesia. Umbilical cord gas values from infants delivered by elective cesarean delivey under general anesthesia without labor were considered representative of baseline, prelabor values. Data were available for 45,475 infants. The median arterial pH values and interquartile ranges for vaginal births, elective cesarean deliveries without labor, and cesarean deliveries performed for fetal heart rate concerns were 7.27 (0.09), 7.27 (0.06), and 7.25 (0.09), respectively. Arterial lactate values for these same 3 groups were 4.1 (2.5), 2.5 (1.2), and 4.0 (2.8) mmoles/L, respectively. Because of the very large sample size, most comparisons yielded differences that were statistically significant, but clinically irrelevant. Of all the infants, 14% had an arterial pH <7.20; a pH value of 7.1 represents 2 standard deviations from the mean. This large, population-based study of umbilical cord gas and lactate levels in an unselected population, stratified by delivery mode, represents a previously unavailable benchmark for the evaluation of umbilical cord gases. Arterial umbilical cord pH values for infants delivered by elective caesarean delivery without labor (median pH 7.28) reflect a lower prelabor fetal pH baseline than previously assumed. This finding, coupled with our determination that a 2 standard deviation below normal pH limit of 7.1, instead of the historic arbitrary pH of 7.2 threshold, helps to explain the poor positive predictive value of electronic fetal heart rate monitoring, a test designed to detect arterial pH levels that have fallen from an assumed baseline near pH 7.4 to an assumed potentially injurious pH level of <7.2. Uncomplicated labor, even when prolonged, does not generally lead to a clinically significant cumulative hypoxic stress to the human fetus. These findings, along with our determination that there is no difference in the acid-base status among infants delivered by cesarean delivery for fetal heart rate concerns, help to explain the failure of current approaches in labor and delivery management to reduce the rates of neonatal hypoxic-ischemic encephalopathy and cerebral palsy, conditions that almost always reflect developmental events rather than the effects of labor on the fetus.

The growth and developmental of the myodural bridge and its associated structures in the human fetus

Myodural bridge (MDB) is a dense connective tissue between suboccipital muscle and dura mater. However, there are few reports on the development and maturation of the human MDB. This study aims to explore the developmental relationship between suboccipital muscle and MDB. 30 head and neck specimens from human fetuses (F) ranging from the 12th to 41st week (W) were made into histological sections. The F12W sections showed evidence that the dura mater dominated by fibroblasts, attached to the posterior atlanto-axial membrane (PAAM) which completely sealed the atlanto-axial space. In the F13W stage, myofibrils of the suboccipital muscle fibers increased significantly in number. At the F14W stage, a gap was observed at the caudal end of the PAAM. Numerous myodural bridge-like structures were observed blending into the dura mater through the gap. At the F19W stage, muscle cells mature. Starting at the F21W stage, the MDB were observed as fibroblasts that cross the atlanto-axial interspace and attach to the dura mater. Therefore, the traction generated by the suboccipital muscles seems to promote the maturity of MDB. This study will provide new morphological knowledge to support future research on the function of the human MDB and regulating the development mechanism of MDB.

Nanog, Stat-3, and Sox-5 involvement in human fetal temporomandibular joint late development

Background and aimThe temporomandibular joint (TMJ) is a synovial joint that allows the complex movements essential for life. It connects the jawbone to the skull, working as a sliding hinge. Moreover, pluripotent stem cells are a source of precursors and tissue-specific cells in developing organisms, however, their biodistribution in developing fetal tissues is weakly studied. The aim of our study was analyse immunohistochemical expression of Nanog, Oct-4, Sox-2 and Stat-3 and Sox-5, in TMJ tissue samples from human fetuses aged between the 12th and 20th weeks of intrauterine life. Materials and methodsWe fixed and processed TMJ tissue samples from human fetuses, histological sections and immunohistochemical procedures were carried out. ResultsTMJ histological studies examination did not reveal any difference in the tissue organization between the samples in the studied periods. Immunohistochemical analysis demonstrated that Oct-4 and Sox-2 lack their expression in TMJ. In contrast, Nanog was expressed in nucleous of proliferative layer of mandibular condyle, Stat-3 was expressed in nuclear cells of articular disc, Stat-3 and Sox-5 showed positive nuclear and cytoplasmic immunostaining in codrocyte layers and in ossification areas. ConclusionsNanog acts in maintanence of pluripotency, Stat-3 in articular disc acts as a transcriptional factor. Stat-3 and Sox-2 act in chondrocyte and osteoblast diferentiation. Distribution of the cells, which express Nanog, Stat-3, and Sox-5 in TMJ tissue during fetal development, can help further understand its physiology, pathology, and repairing capacities.

Morphogenesis of the pulmonary vein and left atrial appendage in human embryos and early fetuses.

The left atrium wall has several origins, including the body, appendage, septum, atrial-ventricular canal, posterior wall, and venous component. Here, we describe the morphogenesis of left atrium based on high-resolution imaging (phase-contrast X-ray computed tomography and magnetic resonance imaging). Twenty-three human embryos and 19 fetuses were selected for this study. Three-dimensional cardiac images were reconstructed, and the pulmonary veins and left atrium, including the left atrial appendage, were evaluated morphologically and quantitatively. The positions of the pericardial reflections were used as landmarks for the border of the pericardial cavity. The common pulmonary vein was observed in three specimens at Carnegie stages 17-18. The pericardium was detected at the four pulmonary veins (left superior, left inferior, right superior, and right inferior pulmonary veins) at one specimen at Carnegie stage 18 and all larger specimens, except the four samples. Our results suggest that the position of the pericardial reflections was determined at two pulmonary veins (right and left pulmonary vein) and four pulmonary veins almost simultaneously when the dorsal mesocardial connection between the embryo and heart regressed. The magnetic resonance images and reconstructed heart cavity images confirmed that the left atrium folds were present at the junction between the body and venous component. Three-dimensional reconstruction showed that the four pulmonary veins entered the dorsal left atrium tangentially from the lateral to the medial direction. More specifically, the right pulmonary veins entered at a greater angle than the left pulmonary veins. The distance between the superior and inferior pulmonary veins was shorter than that between the left and right pulmonary veins. Three-dimensional reconstruction showed that the venous component increased proportionally with growth. No noticeable differences in discrimination between the right and left parts of the venous component emerged, while the junction between the venous component and body gradually became inconspicuous but was still recognizable by the end of the observed early fetal period. The left superior pulmonary vein had the smallest cross-sectional area and most flattened shape, whereas the other three were similar in area and shape. The left atrial appendage had a large volume in the center and extended to the periphery as a lobe-like structure. The left atrial appendage orifice increased in the area and tended to become flatter with growth. The whole left atrium volume^(1/3) increased almost proportionally with growth, parallel to the whole heart volume. This study provided a three-dimensional and quantitative description of the developmental process of the left atrium, comprising the venous component and left atrial appendage formation, from the late embryonic to the early fetal stages.

The dynamic expression of SOX17 in germ cells from human female foetus and adult ovaries after specification.

SOX17 has been identified as a critical factor in specification of human primordial germ cells, but whether SOX17 regulates development of germ cells after sex differentiation is poorly understood. We collected specimens of gonadal ridge from an embryo (n=1), and ovaries of foetuses (n=23) and adults (n=3). Germ cells were labelled with SOX17, VASA (classic germ cells marker), phosphohistone H3 (PHH3, mitosis marker) and synaptonemal complex protein 3 (SCP3, meiosis marker). SOX17 was detected in both cytoplasm and nucleus of oogonia and oocytes of primordial and primary follicles from 15 to 28 gestational weeks (GW). However, it was exclusively expressed in cytoplasm of oogonia at 7 GW, and in nucleus of oocytes in secondary follicles. Co-expression rates of SOX17 in VASA+ germ cells ranged from 81.29% to 97.81% in foetuses. Co-staining rates of SOX17 and PHH3 or SCP3 were 0%-34% and 0%-57%, respectively. Interestingly, we distinguished a subpopulation of SOX17+VASA- germ cells in fetal ovaries. These cells clustered in the cortex and could be co-stained with the mitosis marker PHH3 but not the meiosis marker SCP3. The dynamic expression of SOX17 was detected in human female germ cells. We discovered a population of SOX17+ VASA- germ cells clustering at the cortex of ovaries. We could not find a relationship between mitosis or meiosis and SOX17 or VASA staining in germ cells. Our findings provide insight into the potential role of SOX17 involving germ cells maturation after specification, although the mechanism is unclear and needs further investigation.

Biometrics of the suspensory ligament of the thyroid and its correlation with the morphometry of the thyroid gland in cadavers of human fetuses

Introduction: Berry’s ligament (BL) is a known anatomical structure, which connects the thyroid gland to the tracheal wall, but its biometry has so far been little explored. Objective: In the present study, we sought to perform the BL biometry, correlating it with the morphometry of the thyroid gland. Material and method: Without the aid of optical instruments, the BL of 24 thyroid glands of human fetuses were dissected. With the gland in an anatomical position, the biometric data of the BL and the gland were taken. The data were treated statistically to establish the correlation between the length and height of the BL with the biometric data of the thyroid gland. Result: Significant correlations were found at the 5% level for the width of the thyroid gland and the weight of the gland, as well as for the length of the left lobe and the width of the right and left thyroid lobes, all in relation to the length of the LB and also the length in relation to the width of the gland and the isthmus of the thyroid gland. There was no significant correlation between the BL height and the morphometric findings of the right and left lobes and the isthmus of the thyroid gland. Conclusion: Knowledge of the anatomy of the BL is essential to prevent, in particular, injuries to the RLN, during thyroidectomy or parathyroidectomy.

Kyoto Collection in The Anatomical Record.

Human embryology began at the end of the 19th century and has developed using valuable human embryo specimens; the Carnegie and Blechshmidt Collections are famous examples. Although established after these two collections, the Kyoto Collection of Human Embryos and Fetuses has become the largest collection worldwide, and its major asset is 1044 serial tissue sections comprising 547 normal and 497 abnormal cases. Morphological changes have been the focus of analysis owing to the absence of fresh embryos in the Kyoto Collection. Furthermore, analysis methods have undergone significant changes. For example, morphometrics has been used to quantitatively analyze shape changes, although it may result in the loss of information on shape changes, which can hinder the visualization of analysis results. However, geometric morphometrics has been recently introduced to the fetal and embryonic stages to circumvent this problem. With the development of DNA analysis kits, several hundred DNA base pairs have been extracted from the Kyoto Collection of studies conducted from the 2000s to the 2010s through genetic analysis. Future technological advances are eagerly awaited.