Formation of the skeletal system of white rat and golden hamster embryos during experimental hypovitaminosis B1

In pregnant females B1-hypovitaminosis was induced by injecting various doses of oxythiamine--a specific antimetabolite for B1 vitamin. The rat and hamster embryos were respectively treated on the 20th and 15th days of development after the technique suggested by Dauson-Dyban with staining the osseous anlages of the skeletons with alizarine red. The results of the investigations performed in 193 skeletons of the rat embryos and in 196 skeletons of the golden hamster embryos revealed a progressive decrease, as the dose of oxythiamine increased, in length of ossification anlages of the extremity bones. However, susceptibility to lesions in various bones of the extremity and skull skeletons was not similar under conditions of progressive oxythiamine-induced B1-hypovitaminosis and depended on time of their anlage formations.     

Embryonic development of the human duodenum

Epithelial duodenal anlage takes place at the end of the first month of the human embryogenesis in connection with appearance of the pancreatic epithelial germs. It has a form of a short arch with a spindle-like enlargement of the middle ductal part. Formation of the hepato-duodenal ligament and of the duodenal mesentery results in appearance of the given organ anlage with a three-layered wall in 5.5-6-week-old embryos. The anlage makes an arch, protruding to the right and forward with a spindle-like enlargement of the middle ductal part. It is tightly connected with the forming anlage of the pancreatic head, when the pancreatic epithelial anlages are fusing. An intensive growth of the pancreatic head is accompanied with emergence and enlargement of the superior, descending and inferior parts of the duodenum, that acquires a semicircular form in 8-8.5-week-old embryos. Its transitional stage is a curved semicircle having a form of a distended spiral coil; that reflects an uneven growth of the organ in the human embryogenesis.     

The development and structure of the optic nerve in normal embryos and fetuses of the white rat and after x-ray irradiation]

With the aim to reveal the ionising radiation effect to formation and structure of the optic nerve (ON), 55 white rat intact embryos and fetuses and 77 experimental embryos and fetuses, subjected to x-ray irradiation on the 10th-14th day of development, have been studied. The main regularities in formation of the ON have been stated under normal conditions. Certain disturbances in formation of the ON and in the internal membrane of the optic vesicle (future retina) under effect of x-rays in the dose of 2.24 Gy have been detected during the intrauterine period of development--folds, rosellas of retina, retardation in differentiation of the retina nervous layer, aberration of the ON growth with a subsequent reduction, the ON hypo- and aplasia, retardation in formation of neural sheaths, absence of intraspace between the sheaths.     

Differentiation of joints in transplants developing on chorioallantois

The wing of the chick embryos (the 17th-21st stages of development according to Hamburger--Hamilton) were transplanted on the chorioallantois of the chick embryo-recipients, incubated for 8.5-9.5 days. Differentiation of the joints was studied in serial histological sections and in translucent preparations of the skeleton stained with alcian blue. The transplants for the investigation were taken on the 1st-11th days after transplantation. In the transplants all three segments of the wing always developed. The development of the external form of the extremity, chondrogenesis and osteogenesis of the skeletal anlages were about 24 h late. Histological changes, specific for the early period of the articular interzone and cleft formation corresponded to the control embryos data, but were one day younger. In future the changes did not progress, and passed into regression, demonstrating as fusion of the articular surfaces. In the transplants blood vessels formed networks of irregular form that surrounded the articular zones. Some branches run from them into mesenchyme, situating around the joint. According to the literature data, these vessels are connected with formation of the articular cleft and in the control embryos blood vessels of the articular capsule develop from them. In the transplants they are dilated, twisted (especially in the ulnar joint area) and do not penetrate into the developing prechondral and then into the cartilage bridges of the fusing articular surfaces. Numerous blood accumulations, as well as extravasates are often seen near the deformed anlages of bones. Thus, disturbance of blood supply in the transplants and lack of innervation in them, discussed in the literature, result in fusion of the articular surfaces.     

A nutritional model of late embryonic vitamin A deficiency produces defects in organogenesis at a high penetrance and reveals new roles for the vitamin in skeletal development

Vitamin A plays an essential role in vertebrate embryogenesis. In the present study, pregnant vitamin A-deficient (VAD) rats were maintained during early pregnancy on the short half-life vitamin A metabolite, all-trans retinoic acid (atRA), in an amount sufficient to support normal development to E10.5, with a higher level of atRA (250 μg atRA/g diet) provided from embryonic day (E) 8.5-10.5 to prevent mid-gestational resorption. When limiting amounts of atRA (1.5 or 12 μg/g diet) were provided after E10.5, a highly reproducible and penetrant state of late fetal vitamin A deficiency (late VAD) was induced in the organs of developing fetuses. In addition, late VAD fetuses displayed both anteriorization of cervical regions and novel posteriorization events at the thoracic and sacral levels of the skeleton, and showed sternal and pelvic malformations not previously observed in early VAD or genetic models. The expression of several Hox genes (Hoxd3 and Hoxb4) was altered in late VAD embryos, with a reduction in Hoxd3 noted as early as 1 day after instituting deficiency. All late VAD-induced malformations were prevented by the addition of retinol starting at E10.5, whereas provision of a high level of atRA throughout pregnancy improved but could not completely rescue the development of all organ systems. This work defines a nutritional model in which vitamin A deficiency can be induced during fetal development, and reveals new functions for the vitamin in the development of the axial and appendicular skeleton.     

Development of mucous cells in taste discs of anurans

Differentiation of the lingual taste discs (TDs) was studied in tadpoles of Rana esculenta, Hyla arborea and Pelobatesfuscus by means of LM, TEM, and SEM. The process of differentiation of mucous cells (MCs) within a TD anlage was investigated subsequently from 39th to 46th Gosner's developmental stage. In R. esculenta and P. fuscus, the MCs are distinguishable in TD anlages not earlier than at the 42nd tadpole Gosner's stage. At that stage TDs anlages are covered by a single layer of ordinary epithelial cells. Starting from the stage 44, tips of TDs progressively open outside and free surfaces of MCs can be distinguished as an area with numerous microfolds. At developmental stages 45 and 46, numerous electron-dense secretory granules can be seen in the supranuclear cytoplasm of MCs. The presence of mucopolysaccharides in H. arborea and P. fuscus was observed from the 44th-45th tadpole developmental stage.     

The development of the clavicle in man

The development of the human clavicle was studied in 50 to 60 d old human embryos. Our findings are summarized as follows: The whole clavicle develops from a cartilaginous anlage. In the middle part of the clavicle, an osseus cuff develops very early by the ossification in the perichondrium. In the lumen of this cuff, a cartilaginous cork persists which is resorbed and replaced by bone and marrow later than in other bones. It is possible that cartilaginous nests may persist in the middle part of the clavicle. In both extremities of the clavicle, the normal enchondral ossification exists as it is described in other anlages. It is difficult to explicate the syndrome of the cleido-facial and cleido-cranial dysostoses only as disturbances of the endesmal ossification.     

Development of the thoracic duct in the prenatal period of human ontogeny

In 40 series of histological sections performed in human embryos and prefetuses from 4 up to 20 weeks of development, as well as in 20 corpses of fetuses and stillborns, it has been stated that the anlage of the thoracic duct appear in 6-7-week-old fetuses as lymphatic clefts surrounded with mesenchymal cells that are situated near large veins in the areas of the most active morphogenesis. Connecting with each other, the clefts form the jugular and retroperitoneal lymph sacs and a well branching network of canals. From the latter, on the 7th-8th week of development a plexus of lymph vessels appear, and later on (on the 8th-9th week)--bilaterally situating trunks of the thoracic duct. Further development of the thoracic duct is connected with the lymph nodes formation, their germs appear on the 9th-10th week along the course of the left trunk, as well as along the ductal branches and anastomoses. The formation of the lymph nodes results in reduction of some trunks and plexuses of the thoracic duct. Owing to this, its form in 14-15-week-old prefetuses resembles the one in newborns. Disturbances in the formation processes of the lymph nodes along the course of the reducing ductal areas, as well as their formation along the course of its main trunk can result in various structural variants of the thoracic duct in children and grown-up persons. Histogenesis of the thoracic duct wall and formation of the lymph nodes are not completed by birth.     

A new rapid radiological procedure for routine teratological use in bone ossification assessment: a supplement for staining methods

BACKGROUND: Presently, bone ossification is assessed by the study of single-stained fetal bones (alizarin red-S) or double-stained bones and cartilaginous structures (alcian blue followed by alizarin red-S). Both methods, especially double-staining, are labor-intensive, time-consuming, and provide qualitative information regarding skeleton ossification. Quantitative evaluation of ossification is more difficult and is usually based on determination of calcium and other minerals in the bone by means of atomic absorption spectrometry. Here we introduce a simple new method that allows quantitative determination of skeleton ossification before routine staining examination. METHODS: Fetuses delivered by laparotomy on the 16th and 21st day of gestation as well as 1-day-old rat pups were examined. The fetuses and pups were prenatally subcutaneously exposed to sodium valproate or to physiological saline. Lateral, prone, and supine digital radiograms of each fetus were taken using the Digora-Soredex digital radiography system and the Planmeca Intra intraoral X-ray machine. According to the best visualization, the data concerning vertebra were analyzed. All the fetuses were then routinely double-stained using alcian blue and alizarin red-S. RESULTS: Malformations of axial skeleton (rib, sternum, and thoracic and sacral vertebra) were found in valproate-treated groups. Unlike cartilage malformations, the bone changes were detected in similar frequency in radiological and staining methods. Differences in densities according to the degree of ossification in the vertebral arches and bodies at different levels of the vertebral column, between drug-treated and negative control groups were noted. CONCLUSIONS: The preliminary results suggest that digital radiography examination is a useful method in determining delaying of skeleton ossification not detectable by other methods. It balances qualitative and quantitative aspects of the presently used methods and is also simple, objective, fast, and relatively inexpensive.     

Pre-natal development of the adrenal gland in the mallard duck (Anas platyrhynchos)

Summary The differentiating nephrotome in the 10-day-old mallard duck embryo is able to synthesize corticosterone, aldosterone and deoxycorticosterone even though an adrenal anlage cannot be identified histologically until the 12th day of incubation. At this time, sudanophilic cells containing much smooth endoplasmic reticulum and numerous mitochondria with tubular cristae are located adjacent to the developing mesonephros. Chromaffm cells appear in this region on about the 14th day of embryogenesis. A discrete glandular structure containing measurable quantities of corticosteroids can be identified on the 15th day, and during the next 2 days the tissue becomes encapsulated. Concomitantly, the ACTH-inducible rates of corticosteroid hormone synthesis increase several fold. The corticotropic responsiveness of the developing adrenal steroidogenic tissue increases progressively during the remainder of embryogenesis.This work was supported by grants to James Cronshaw and W.N. Holmes from the University of California Committee on Research and the National Science Foundation (DIR-8820923), Washington, DC, USA     

Loss of fibula in mice overexpressing Hoxc11

This study demonstrates severe malformations of the appendicular skeleton in mice overexpressing Hoxc11. Consistent with the endogenous expression pattern, the most conspicuous defect in Hoxc11 overexpressing neonates is aplasia/hypoplasia of the fibula. This is preceded at day 15.5 of embryonic development by marked reduction of chondrocyte proliferation, lack of PTHR expressing prehypertrophic cells, and the absence of hypertrophic and calcifying chondrocytes. Combined with the lack of an overt phenotype in the majority of Hoxc11 overexpressing embryos at day 13.5, the data suggest inhibition of chondrocyte differentiation during the elongation phase of the fibula bone as a primary effect of elevated Hoxc11 expression. This interpretation is further corroborated by Hoxc11 reporter gene expression in the joint areas at embryonic day 15.5, suggesting an involvement of the periarticular perichondrium in generating the mutant phenotype.     

Origin of abnormality in a human simelian foetus as elucidated by our knowledge of vertebrate development

In this paper we attempt to explain the abnormality of a simelian foetus with reference to our present knowledge of vertebrate development. The various developmental defects seem to have a single common origin: the speeding-up of the progression of cell differentiation in the notochord anlage--which is the organization centre of the embryo--during the regression of the Hensen's node. Cell activity involved in the morphogenetic movements in the chordamesoderm probably stopped before it should have. The elongation of the notochord anlage was not completed, resulting in the defective development of the posterior part of the foetus. A number of pairs of posterior trunk somites were not induced. Consequently (1) the pelvic limb buds, whose posterior parts were missing, fused, bringing in further developmental deviations in the limb skeleton and abdominal muscles; (2) there are no vertebrae between the first sacral vertebra and the misshaped coccyx formed by the tail bud. The derivatives of the posterior endoderm (hindgut, bladder and ureters) were not induced either. The cauda equina is deficient. The absence of functional kidneys and the presence of embryonic urinary tubules in the pelvic cysts which are wrapped up by gut epithelium suggest the induction of the metanephric mesenchyme by ectopic endoderm. The speeding-up of differentiation in the notochord anlage also probably resulted in the excessive extension of its anterior region which is the organizer of brain structures. This explains the overdevelopment of the nose and of the neurocranium, and the low position of the ear. A gene mutation as well as a mechanical stress are the possible causes of the abnormal behaviour of the notochord anlage.     

Analysis of morphogenetic movements in the development of the notum anlage of Drosophila melanogaster

Summary A comparison of the morphogenetic maps of the notum anlage of Drosophila melanogaster derived from the gynandromorph data and mosaics induced by somatic crossing-over during the first instar larval stage revealed that practically no major morphogenetic movements occur in the development of the anlage between the blastoderm and first instar larval stages and the adult stage. By comparing the morphogenetic map derived from gynandromorphs and the fate map derived from data on the transplantation of fragments of the mature wing imaginal disc, it was observed that no major morphogenetic movements occur in the notum anlage between the stages of the allocation of the disc and the mature disc. The results are consistent with the observations of other authors concerning the larval development of eye-antenna, wing and leg discs.     

Disorders of vaginal development in the progeny of white rats exposed to x-ray irradiation

One hundred and twenty white rat embryos 13-22-day-old have been irradiated with x-rays (the dose 250 R) on the 12th-14th day of embryogenesis. The embryos have been divided into series of sagittal, frontal, transversal sections and stained by means of general histological methods. The irradiation performed on the days mentioned does not affect formation of the paramesonephric ducts. In all the experimental animals the caudal end of the paramesonephric duct is separated from the mesonephric duct as a solid cellular cord in which the lumen appears later. In the experimental females the disturbances developed after irradiation are manifested first of all in retardation of the main stages of the organ's formation; the retardation is observed: in fusion of the paramesonephric ducts, in resorption of the medial septum between the fused ducts, in separating the sinuous part of the vagina from the urogenital sinus, in recanalization of the vaginal epithelial cord. More severe lesions are presented as agenesia of the vaginal sinuous part and as its atresia represented by a transversal septum of the organ. The disorders in the vagina development are depended on massive primary necrobiotic radial lesions of the mesenchymal cells around the epithelial anlages of the small pelvis.     

The development of lymphoid and haemopoietic tissues in pig fetuses

This paper presents the results of the development of lymphatic and haemopoietic organs in pig fetuses of various ages. The thymus appears to be the first lymphatic organ in these fetuses as well as in other animal species so far studied. On the 77th day the thymus is fully morphologically developed. The accumulations of lymphocytes in the spleen appear on the 70th day. The development of periarteriolar formations takes place around the 84th day of gestation. Further development of lymphoid tissue in the lymph nodes, tongue (tonsilla lingualis) and intenstine is described. Lymphatic follicles were observed both in the tongue and the small intestine on the 77th day. The dynamics of haemopoietic activity in the liver and bone marrow is characterized. The germinal centers in lymphoid folicles were never observed as well as cells of the plasmatic series.     

Embryogenesis of the human pharyngeal tonsil

By means of histological, histochemical, immunological and morphometric methods 78 pharyngeal tonsils of human embryos at the age of 12-40 weeks have been investigated. The character of the organ's anlage at 12-14 weeks of development as longitudinal folds on the dorsal wall of the rhinopharynx and changes in correlation of the lymphoid and epithelial tissues are presented in the process of the tonsil embryogenesis. Occupation of the organ with lymphocytes takes place on the 16th week of development. The embryos possess already two classes of T- and B-lymphocytes and their subclasses: auto-E-RFC, EAC-RFC, IgM and IgG positive cells; their kinetics is demonstrated in the process of the organ's development. A comparison on lymphocyte quantity, participating in cell-dependent immunity of the tonsil in fetuses, children and mature persons is presented.     

Ossification of the cartilage skeleton of the extremities of human embryos

Certain sequence in appearance of ossification points has been stated in the cartilage models of the superior and inferior extremities of the human embryos at the end of the embryonal and the beginning of the fetal periods of development. The change in the size (length) of the ossification points in anlages of the long tubular bones during the successive stages of embryogenesis is of linear character and can be described by means of the equation y = ax + b, where y--age of the embryo (days), x--length of the osseous points. Coefficients a and b are calculated for estimation the age of the embryos according to the length of the osseous points in the anlages of the brachial, femoral and radial bones.     

Growth of the jugular lymph sacs and establishment of the topography of the cervical portion of the thoracic duct during early human ontogenesis

In 196 human embryos, prefetuses, fetuses and newborns, by means of a complex of morphological methods, development of the jugular lymphatic sacs and the process of settling of the thoracic duct cervical part topography have been studied. The jugular lymphatic sac anlages take place on the 6th week of the development. From the lymphatic cleft, situating in the mesenchyme near the anterior cardinal veins, multichambered cavities laid with endotheliocytes are forming,--the jugular lymphatic sacs. Connection of the initially close lymphatic sacs with the venous system takes place secondarily by the end of the embryonic period of development. In the area of the sac ostia a valve is formed, that makes morphological premises for unidirected lymph flow into the venous system. The lymph nodes developing at the place of the reducing jugular lymphatic sacs, ensure formation: from the left jugular lymphatic sac--the cervical part of the thoracic duct, from the right jugular lymphatic sac--the right lymphatic duct and the jugular and the subclavicular lymphatic trunks. Variability in the form and topography of these structures are determined both by the form and construction of the jugular lymphatic sacs and by developmental peculiarities of the lymph nodes at their place. The process of settling of the thoracic duct cervical part topography depends on age changes of its size and form, as well as on development of structures situating nearby, and by the time of birth it is not completed.     

Light- and electronmicroscopic investigations of the development of the stria vascularis in the ductus cochlearis of the guinea pig fetus

Our studies on exactly dated guinea pig fetuses show: Already in early stages of development (37th day), in the anlage of the vascular stria vesicular invaginations of the apical plasmalemma of epithelial cells are noted and regarded as a sign of an exchange of substances between epithelial cells and the endolymph. As to the direction of substance transport, the morphological finding allows no decision. From the 42nd to the 44th day of development, the subepithelial basal lamina becomes progressively indistinct. From the 45th day onward, the basal lamina is not yet demonstrable. The largest part of the chromophobe cells of the vascular stria derives from the mesenchyme. The question, whether some of the chromophobe cells are of epithelial origin, as some authors propose, will hopefully be clarified in further studies.     

The effect of gamma irradiation on the structure and enzymatic activity of the nuclear membrane of the liver in pregnant rats and their embryos]

Morphological and biochemical investigations of pregnant rats and embryo liver cell nuclei after in vivo irradiation in the doses of 1 and 2 Gr revealed their high radiosensitivity at all stages of gestation and embryonal development. At damaging effect of radiation, we managed to observe sharp accumulation of products of lipid peroxide oxidation and suppression of the activities of such enzymes as cytochrome-c-oxidase, NAD.N-cytochrome-c-reductase, ATPase and RNAase in liver nuclei of pregnant rats and embryos. The changes of such a kind are shown to intensify with the increasing of irradiation doses. The most profound inhibition of the activities of these enzymes in liver nuclei of embryos irradiated in utero was observed during the period of organogenesis (the 13th day of the development) and in fetal period of embryogenesis (the 17th day of the development), as well as at the 13th and 17th day of gestation. The morphological data also demonstrate the high level of cell nucleus sensitivity to the action of radiation during gestation and embryogenesis.