Allometry of hepatic weight growth in human staged fetuses

The growth of the hepatic weight was correlated to fetal parameters of maturity (gestational age, crown-rump length and weight) in 70 human fetuses ranging from 14 to 39 weeks post-conception using the allometric method. The growth of the hepatic weight presents moderate positive allometry relative to age and C-R length, and isometry relative to fetal weight. The coefficiens of correlation are very high (p less than 0.001, Table 1). This study presents growth curves of the hepatic weight useful in medical branches such as anatomy, forensic medicine, fetopathology, medical imagery, onstetrics and pediatrics.     

Cardiac growth in staged human fetuses: an allometric approach

The human cardiac growth was studied on 30 staged fetuses (gestational age ranged from 10 to 38 weeks post conception, WPC). The hearts were quantitatively evaluated considering their weight and the following linear parameters: the pulmonary (da.p.) and aortic (dA) internal diameters, the right (VR) and left (VL) ventricular wall thickness, the ventricular width (dV), and the length "sulcus terminalis-apex cordis" (Lst-apex). The data were correlated with the gestational age by using the allometric method (Y = bX alpha). The equations and the growth curves are presented. In the fetal life, we observe that the body weight is 134 times larger than the heart weight, the Lst-apex is 1.07 times larger than the dV, the da.p. is 1.50 times larger than the dA, and the VL is 1.19 times larger than the VR.     

Development of the cardiac blood vessels in staged human embryos

Serial paraffin sections (mostly stained with hematoxylin and eosin) of 52 human embryos at stages ranging from 13 to 20 (approximate ovulation age of 5-8 weeks) were examined. The first sign of definitive blood vessels was found to be localized in the apical incisure of the heart of an embryo at stage 14. Blood vessels of this kind closely resembled 'blood islands' in appearance, being composed of primitive erythroblasts surrounded by an outer layer of endothelium. At stage 16, a funnel-like invagination of the endothelium was recognized in the posterior wall of the sinus venosus. This structure was considered to represent one of the cardiac veins (probably the middle cardiac vein). A faint endothelial sprout of the left coronary artery was detected at stage 18, while the right one was observed later, at stage 19. Finally, at stage 20, both of the coronary arteries invariably existed with a covering of mesenchymal cells.     

Early ontogeny of the central benzodiazepine receptor in human embryos and fetuses

The early ontogeny of the central benzodiazepine receptor (BZR) was investigated in human embryos and fetuses between 7 and 26 weeks of gestation. Brain tissue was gained from terminated pregnancies or spontaneous abortions. Binding studies, which were performed with 3H-flunitrazepam (FNZ), revealed that specific benzodiazepine binding is already detectable at an embryonal age of 7 weeks post conceptionem. Binding at this early stage can be displaced potently by clonazepam and the inverse agonist beta-CCE. Additionally, 3H-FNZ binding is enhanced by GABA. Thus, benzodiazepine binding is of the central type. Receptor density increases steeply in whole brain between weeks 8 and 11 of gestation. In frontal cortex receptor density increases gradually between weeks 12 and 26 of gestation. No specific fetal disease entity (including trisomy 21) was consistently associated with exceptionally high or low Bmax-values.     

Regulation of intestinal peptidases by nutrients in human fetuses and children

Nutrient interactions during intestinal digestion has been established in animals. The present study investigated the effect of different nutrients on intestinal dipeptidase, tripeptidase, carboxypeptidase (EC 3.4.12.-) and aminopeptidase N (ApN) (EC 3.4.11.2) activities in human fetuses and children. The effect of nutrients on isolated porcine kidney ApN was also studied. Sucrose, lactose and tributyrin had no effect on di-, tri-, and carboxypeptidase activities of mucosal homogenates, but tributyrin significantly (20-50%) inhibited both fetal and postnatal ApN activity in the small intestine and colon. The pH-independent inhibition of ApN is specific for tributyrin and to the product of its hydrolysis, butyric acid. Glycerol, triolein, and natural oils did not affect ApN activity. The inhibition of ApN by tributyrin was dose and time dependent and occurred in enterocyte brush border membranes as well as in the purified enzyme from porcine kidney. The kinetics of the purified ApN showed that the tributyrin effect is primarily competitive and associated mainly with an increase in K(m). These observations demonstrate the possibility of intestinal and kidney ApN regulation by lipids and products of their hydrolysis. We speculate that nutrient interactions arose quite early in the evolution and represent a mechanism for the regulation of food digestion.     

Development of the notochord in normal and malformed human embryos and fetuses.

In view of its possible involvement in early embryogenesis and teratogenesis, the developmental characteristics of the human notochord were studied by light and electron microscopy and immunohistochemistry on 20 human conceptuses (5th-22nd week). At the earliest embryonic stages examined, the notochord is closely related to both the pharyngeal endoderm and the neuroectoderm of the posterior (tail) end of the neural tube. In both regions the interspace is bridged by slender cytoplasmic processes, lined with basal lamina and filled with amorphous extracellular material containing collagen types III and IV and laminin. The notochordal cells express cytokeratin brightly and vimentin weakly. As embryonic age progresses, the notochord gradually separates from the epithelia, becomes the axis of developing spinal column and undergoes progressive cell degeneration and rearrangement within the vertebral bodies. This is associated with extensive production of extracellular material and the first appearance of fibronectin. Intracellularly, the expression of vimentin gradually increases, while that of cytokeratin slightly weakens. Changes in the notochord parallel other developmental events in axial organs. In anencephalic fetuses the course of the notochord is irregular and partly interrupted with segments outside the basichondrocranium in specimens with craniorachischisis.     

Development of the innervation pattern in the upper limb of staged human embryos

The upper limb nerves of 8 human embryos (Carnegie stages 13-21) were studied by reconstruction. In stage 13, upper limb nerves (C5-T1) extended from the spinal cord. In stage 14, these nerves united to form the nascent brachial plexus. In stages 16 and 17, the median nerve, the radial nerve and the ulnar nerve entered into the hand plate. In stages 20 and 21, the upper limb nerves were observed in an orientation and arrangement similar to those in the adult.     

Types of neural cells in the spinal ganglia of human embryos and early fetuses

Spinal ganglial of human embryos and fetuses ranging in C.-R. length from 15 to 74 mm and in age from 6 1/2 to 11 postovulatory weeks were studied by light and electron microscopy. A sequence of events in differentiation and maturation enabled five types of cells to be distinguished: 1. apolar, undifferentiated neuroblasts are the main cells at 6 1/2 to 7 1/2 weeks; 2. early bipolar neuroblasts (strictly speaking, types 2 to 5 are immature neurons) predominate at the end of the embryonic period proper (8 postovulatory weeks); 3. intermediate bipolar neuroblasts are characteristic of the early fetal period; 4. late bipolar neuroblasts, in which two proceses arise separately from one pole of the cell, appear at about 10 postovulatory weeks; 5. unipolar neuroblasts are found within another week and, by that time, cells of types 1 and 2 are no longer present.     

The origin of the ectodermal ring in staged human embryos of the first 5 weeks

Seven embryos of stages 10-16 (3-5 weeks) were studied for their external form by means of graphic reconstructions. This is the first systematic report on the general surface anatomy of the early human embryo. The brain has been described and illustrated in a previous publication, and the present article is concerned particularly with an important although neglected feature: the ectodermal ring, described by Schmitt [Morph. Arb., Jena 8: 236-303, 1898] and named by Blechschmidt [Funktionsentwicklung. I. Mechanische Gegenwirkungen. Musterschmidt, G?ttingen 1948]. Late in stage 10, three longitudinal bands can be seen on the surface: somitic, intermediate, and lateral plate. The intermediate band, which partly overlies nephrogenic tissue, is the site of the future ectodermal ring, which begins as an inverted U at stage 11 and is completed caudally in stage 12. The ectodermal ring, which may well be an important example of epithelial-mesenchymal interaction, comprises six parts: (a) rostral part, containing the situs neuroporicus, and olfactory and lens discs; (b) pharyngeal part, the covering of the pharyngeal arches; (c) occipital and cervicothoracic parts, related at first to the four occipital somites and later to the cervicothoracic junction; (d) membral part, represented by a preliminary ectodermal thickening, followed within 2 days by the apical ectodermal ridge; (e) intermembral part, related at first to the underlying coelom, and mesonephric duct and ridge; (f) caudal part, containing the cloacal membrane and a temporary 'caudal ectodermal ridge'. It is stressed that the incorrectly named 'Milchstreifen' is merely the intermembral part, in which the mammary crest ('Milchlinie' or 'Milchleiste') appears 1 week later.     

Adaptive characteristics of growth of human embryos and fetuses during the intrauterine life]

Under observations was the dynamics of growth of human embryos and fetuses in embryogenesis which is directly dependent on the month of the intrauterine life. Coefficients of correlation and regression were calculated and with their help the average growth of the general length of fetuses in each month of prenancy was determined. The enlargement of the fetus length was found to be more intensive in the embryonic and prefetal periods.     

Scanning electron microscopy of developing papillae on the tongue of human embryos and fetuses

The appearance and differentiation of papillae on dorsal andlateral surfaces of human embryonic and fetal tongues, at variousdevelopmental ages, were studied by scanning electron microscopy.Formaldehyde and phosphate buffer fixation provided satisfactorypreservation. At 8–9 weeks, the anterior two-thirds ofthe tongue showed no obvious signs of papillae. In contrast,just anterior to the sulcus terminalis rounded elevations wereseen, suggesting initial signs of circumvallate papillae. At10–13 weeks, the distribution and shape of elevationson the anterior two-thirds of the tongue indicated the beginningof fungiform papillae. Openings located on the dorsal surfaceof many of these fungiforms contained an amorphous central structureprojecting out of the papilla. First signs of foliate papillaewere seen at 10 weeks. At 15–18 weeks, fungiform and filiformpapillae were recognized, although sometimes their borders wereobscured by scaling epithelial cells. At 23–26 weeks,all papillae exhibited their adult form. ^*Presented, in part, at the VIth International Symposium onOlfaction and Taste, Gif-sur-Yvette, Paris, France, 15–17thJuly, 1977.     

Immunohistochemical localization of entactin and laminin in mouse embryos and fetuses

The temporal appearance and the anatomic distribution of entactin in the developing mouse embryo was studied by light and electron microscopic immunohistochemistry and compared with the appearance and the distribution of laminin. Immunohistochemically detectable entactin first appeared in the hatched blastocysts, in contrast to laminin which became apparent as early as the 8-cell stage of development. However, beginning with the appearance of entactin in the hatched blastocyst, antibodies to these two basement membrane glycoproteins co-localized in all extraembryonic matrices. These findings indicate that the synthesis of entactin and laminin is asynchronous in the early stages of mouse embryonic development but becomes synchronized in the postimplantational stages of development.     

Neural stem and progenitor cells of human embryos and fetuses as a basis of biomedical new technologies

Isolation and cultivation of stem and progenitor cells of human embryos and fetuses at the age of 7-12 weeks of gestation have been described. The embryonic cells of human brain formed neurospheres with heterogenous composition. Cell differentiation took place not only in the presence of serum or as a result of attachment of neurosphere to a sublayer, but also in floating neurospheres in the presence of mitogens. In most neurospheres, the nestin-immunopositive cells were located near the surface while the cells stained for beta-tubulin III and glial fibrillar acid protein, as compact groups inside the neurospheres.