Showing papers in "Anatomy and Embryology in 1975"

Loss of Dendritic Spines in Aging Cerebral Cortex

Abstract: Previous work has shown that the dendritic spines of pyramidal neurons of the cerebral cortex are sensitive to a wide variety of environmental and surgical manipulations. The present study shows that the normal aging process also affects these spines. The spines were studied with the light microscope in Golgi preparations from rats ranging in age from 3 to 29.5 months. Visible spines were counted on either 25 or 50 μ segments of the basal dendrites, apical dendrites, oblique branches, and terminal tufts of layer V pyramidal cells in area 17. A progressive loss of spines occurred at each of these loci. The smallest observed spine loss (24%) occurred on the dendrites of the terminal tuft, and the largest (40%) on the oblique branches. Age-related spine loss appears to affect all animals, and for animals of any one age the overall loss is similar. However, the cell-to-cell variability within an individual animal is pronounced, some cells with high spine densities being present at every age examined. As a general rule, there is a positive relationship between visible spine density along the apical dendrite as it traverses layer IV and the thickness of the dendrite. With advancing age, the relatively thick dendrites decrease in number so that the thinner dendrites make up an increasingly larger proportion of the total apical dendrite population. Questions that remain for the future include the genesis of the spine loss, its relation to other aging changes, and its functional significance for the neuron.

Fine structure of labelled axons in the cerebellar cortex and nuclei of rodents and primates after intraventricular infusions with tritiated serotonin.

Abstract: The cerebellar cortex and deep cerebellar nuclei in rats and rhesus monkey were studied after treatment with monoamine oxidase inhibitor and continuous intraventricular infusion with 10(-5) M serotonin-3H. Autoradiographs were prepared for light and electron microscopy. The cerebellum contained no labelled cells. Labelled unmyelinated axons arrive from the brain stem via the periventricular zones of the aqueduct and fourth ventricle. In the parafloccular cortex about 1 per cent of the mossy fibers are labelled, together with a small number of fine varicose axons in the molecular layer that run parallel to the folial axes (less than 0.1%). In the paravermal and vermal cortex there are few labelled fibers in the granular layer and a five-fold greater number of labelled axons in the molecular layer (about 0.5%). Apparently three systems of serotonin-containing axons are present in the cortex: mossy fibers, parallel fiber-like, and a diffuse system in granular and molecular layers. The fastigial (medial), interpositus, and dentate (lateral) nuclei, lateral vestibular and other vestibular nuclei all have numerous labelled axons. The dentate and interpositus nuclei receive labelled fibers which arrive through the superior cerebellar peduncle as well as from the periventricular area. Six morphologically different classes of labelled axon terminals have been differentiated. Class 1a, the mossy fiber rosettes, and class 1b, the CAT2 axons, have small, round, clear synaptic vesicles and large granular vesicles (lgv); class 2 axons have a distinctive collection of round granular vesicles; class 3 boutons have numerous tubular profiles, a few containing dense dots, packed in a dark axoplasmic matrix; class 4 axons have tiny 250 A granular vesicles, clear tubular profiles and occasional LGV; class 5 terminals have numerous LGV, both round and elongated, with clear round and tubular profiles; class 6 terminals have LGV, clear and granular synaptic vesicles and clear tubular profiles. All these axons have LGV 900 A in diameter with 500-600 A variably dense centers that do not fill the vesicle, and Gray's type 1 axodendritic or axasomatic synapses on postsynaptic locations in the cortex and nuclei. Labelled axons in the cortex end as mossy fibers upon granule cell dendrites in glomeruli (Class 1a) or upon dendrites of cortical interneurons, e.g. Golgi cells, basket and stellate cells, and not on Purkinje cells. ...

The timing and sequence of events in the development of the limbs in the human embryo

Abstract: A documented scheme of the early development of the human limbs is presented. It is based on (1) published and unpublished personal observations, and (2) reports of other workers who personally studied staged human embryos. The necessity of studying staged embryos in determining the precise sequence of developmental events is stressed.

The onset of synaptogenesis in rat temporal cortex.

Abstract: The onset of synaptogenesis was studied in the temporal cortex of rat fetuses whose age ranged between 15 and 19 days of gestation. First synapses were found at a surprisingly early stage of cortical development: on day 16. These contacts showed relatively few vesicles and very inconspicuous membrane-thickenings. They were located in the marginal layer, above as well as below the narrow band formed by the newly arrived first neuroblasts of the prospective cortical plate. The postsynaptic structures were probably dendrites of the horizontally or obliquely orientated neurons scattered throughout the marginal layer (such neurons were seen even within the cell-dense band). On day 17, the cortical plate separated the differentiated cells definitely into a superficial and a deep population. As on the following days, synapses were found above and below the cortical plate but not within it. In addition to contacts showing the same features as those described on day 16, there were already synapses with numerous vesicles and clearly asymmetric membrane thickenings. On days 18 and 19 the borders of the cortical plate became more clear-cut. The well-differentiated neurons situated above and below this plate could now be identified as Retzius-Cajal cells of the prospective molecular layer and as polymorphous cells of the layer VI b respectively. The presence of axo-somatic contacts on these neurons provided direct evidence that both cell types are targets for synapses. Desmosome-like junctions were found even in the youngest fetuses studied. Their roughly symmetric membrane thickenings were clearly more conspicuous than those of earliest synapses. Desmosome-like junctions occurred very frequently between structures which subsequently were never seen to become synaptically linked. During the entire period studied, numerous coated vesicles fused with cell membranes were noted. Such “open” vesicles were seen on neurons (sometimes in the immediate vicinity of synapses) but also on non-nervous, extracortical as well as intracortical structures. Thus there does not seem to be a specific relationship between desmosome-like junctions and coated vesicles on the one hand and synapse formation on the other.

Differentiation of the neural plate and neural tube in the young chick embryo. A study by scanning and transmission electron microscopy.

Abstract: The differentiation of the presumptive neural plate, the neural plate and the neural tube have been investigated in the chick embryo by SEM, TEM and histochemical techniques. The relationship of these tissues to neighbouring structures, including extracellular materials, has also been studied. When SEM micrographs of primitive streak stage embryos were examined in stereo, it was found that cells which had been invaginating at the time of fixation were similar in shape to fibroblasts migrating in vitro. It was concluded that SEM stereo pairs could provide evidence about the mode and direction of cell migration. Many more mid-bodies have been found associated with the developing neural tissue than with the lateral ectoderm. It was found possible to recognise mid-bodies not only by TEM but also by SEM. It is therefore proposed that SEM montages may be used for assessing which regions of a tissue have recently undergone extensive mitosis. The beads on the specialised threads seen in the early stages of development are now considered to be formed from mid-bodies. Similar, but unbeaded threads have been described which span the gap between the neural folds just prior to the dorsal closure of the neural tube and it seems probably that these threads help to close the neural tube. It is suggested that the beaded threads arise by incomplete separation of two daughter cells at mitosis, whereas the unbeaded threads form by outgrowth of cell processes.

Internal structure of cat extraocular muscle.

Abstract: Teasing preparations of cat extraocular muscles (EOM) were used to study the arrangement of muscle fibers and the distribution of the different cholinesterase-positive sites, i.e. (1) large motor endplates, (2) small motor endings of the “en grappe” type, (3) myotendinous junctions and (4) myomyous junctions. The distribution of these cholinesterase-positive structures gives clear evidence of a complex muscle architecture of cat EOM. In the global layer of cat EOM, only multiply innervated muscle fibers run the whole length of the muscle. The focally innervated muscle fibers are generally shorter; they are usually arranged in series of two to three fibers being interconnected by myomyous junctions. Moreover, muscle fiber splitting is frequently present resulting in a netlike arrangement of muscle fibers. Most of the myomyous junctions occur between focally innervated muscle fibers, but also end-to-side connections of focally to multiply innervated muscle fibers are observed; multiply innervated muscle fibers have not been found connected to each other. In this layer, large motor endplates are distributed in several bands between origin and insertion. In the orbital layer all muscle fibers run from tendon to tendon, focally as well as multiply innervated ones. Here, large motor endplates are confined to a band in the middle of the muscle, and myomyous junctions are generally absent.

In utero development and maturation of the retina of a non-primate mammal: a light and electron microscopic study of the guinea pig.

Abstract: A light and electron microscopic examination of retinogenesis in the fetal guinea pig has revealed an early development of synapses and photoreceptor cells Differentiation of the neural retina begins around day 23 of gestation By 34 days the retina reaches its maximum thickness It differentiates an inner plexiform layer in which vesicle-containing processes and primitive synapses are evident Synaptic ribbons are found in processes of this layer by 43–45 days of gestation An outer plexiform layer develops within the neuroblast layer at 40 days of gestation; from its first appearance the outer plexiform layer contains synapses complete with synaptic ribbons Receptor terminals of the α, paranuclear and β type are present well before birth Photoreceptor cells form inner segments by 40 days; the formation of outer segments is indicated by 45 days but not widespread until 49 days The retina appears mature by day 51–57 It is clear that the primate is not unique in the early differentiation of its retinal synapses relative to the time of maturation of its photoreceptor cells The potential functional capacities of precocious retinae, and the mechanisms of synapse development are discussed

The structural organization of the kidney of the desert rodent Psammomys obesus.

Abstract: The architecture of the desert rodent Psammomys obesus has been studied by means of standard histologic procedures and by single nephron injections. As other rodent kidneys (rat, mouse), the Psammomys kidney consists of two types of nephrons, 66% short looped and 34% long looped nephrons. The cortex is composed of 4 to 5 layers of glomeruli, which lie closely put together, the glomeruli often touch each other. The superficial and the midcortical glomeruli give rise to short looped neophrons, the juxtamedullary to long looped nephrons. In the strongly developed medulla the inner stripe shows the most striking pattern. It consists of two distinct compartments, that of the giant vascular bundles and that of the interbundle regions. The giant vascular bundles consist of about 8 to 14% arterial vasa recta and 39 to 47% venous vasa recta; furthermore they include the thin descending limbs of the short loops of Henle which amount to 44 to 51% of the bundle structures. The tubules of the interbundle regions surround the bundles in a regular pattern. The inner zone is almost completely surrounded by the renal pelvis; the long broad papilla protrudes into the ureter. The thin descending limbs of short looped nephrons traverse the inner stripe inside the giant vascular bundles. Leaving the bundles they turn back within the inner stripe; their ascending limbs lie in the interbundle region. Both limbs of the long loops of Henle run in the interbundle region, together with the ascending limbs of the short loops and the collecting ducts. The long loops penetrate deeply the inner zone. Many bends are found near the tip of the papilla. The renal pelvis has a very specialized form. It penetrates the inner stripe with many complexely shaped extensions, which surround the giant vascular bundles. Large parts of the bundles with their thin walled structures are thus separated from the pelvic urine only by a single layer of cuboidal epithelium. The possible functional importance of the described specializations of the Psammomys kidney (giant vascular bundles, large inner zone, special shape of the renal pelvis) for the urine concentrating and urea recyclng mechanisms is discussed.

Morphology of the epididymis of the cock (Gallus domesticus) and its effect upon the steroid sex hormone synthesis. I. Ontogenesis, morphology and distribution of the epididymis.

Abstract: The epididymis of the cock is divided into a main part and an appendix epididymidis. The main part of the epididymis is firmly connected to the testis. The sperm transporting tubes open into the ductus epididymidis along its entire length. The rete testis, as the most proximal part of the epididymis, develops from mesenchym cells. The rete testis connects the tubuli seminiferi with the ductuli efferentes proximales which develop from the Bowman's capsules of the mesonephros. The ductuli efferentes distales develop from the proximal tubules, conducting segments (loops of Henle), and the distal tubules of the mesonephros. The short ductuli conjugentes which open into the ductus epididymidis, originate from the connecting segments of the mesonephros. In the sexually mature cock the rete testis, the ductuli efferentes proximales, and the ductus epididymidis all show an enlargement in the lumen. In the ductuli efferentes proximales and in the ductus epididymidis one can observe a formation of globuli and cell protrusion which lead to a loss of the surface structure of the epithelial cells. The appendix epididymidis and the capsula fibrosa of the adrenal gland are joined by connective tissue. The appendix epididymidis consists of the blindly ending ductus aberrans (the crainal continuation of the ductus epididymidis) and the ductuli aberrantes which open into the ductus aberrans. The blind ends of the ductuli aberrantes end in the capsula fibrosa of the adrenal gland.

Morphology of the epididymis of the cock (Gallus domesticus) and its effect upon the steroid sex hormone synthesis. II. Steroid sex hormone synthesis in the tubuli epididymidis and the transformation of the ductuli aberrantes into hormone producing noduli epididymidis in the capsule of the adrenal gland of the capon.

Abstract: Distinct histochemical and ultrastructural signs of a steroid hormone synthesis are found in the sexually mature cock, particularly in the ductuli efferentes proximales of the main part of the epididymis and in the blind ends of the ductuli aberrantes of the appendix epididymidis. These signs are more distinct in the appendix epididymidis of the capon since the blind ends of the ductuli aberrantes transform into steroid sex hormone producing noduli epididymidis after they sprout out intensively and branch inside or beneath the adrenal capsule. The signs of virility were lost immediately after castration. They become more distinct again due to the hormonal activity of the noduli. Due to the morphologic agreement the noduli epididymidis of the capon are homologous to the noduli epoophori of the hen.

Hyperplasia of oligodendrocytes in quaking mice.

Abstract: The number of neuroglial cells in selected fiber tracts of 90-day-old quaking and normal mice was determined by a combination of light and electron microscopy. Oligodendrocytes of quaking mice are normal in number in the anterior commissure and corticospinal tract (in the cervical spinal cord) but are increased two- to fourfold in the optic nerve and the fasciculi cuneatus and gracilis (in the cervical spinal cord). The nuclei and perikarya are normal in size or smaller than normal. Those tracts with the greatest hyperplasia of oligodendrocytes also have the greatest conten of myelin, suggesting that cell number influences content of myelin. However, the volume of myelin per oligodendrocyte also varies, between 2 and 11% of normal, in the different tracts of the mutant. The hyperplasia of oligodendrocytes in quaking mice may arise as compensation for their decreased production of myelin and reflect a normal plasticity in the processes of myelination. If so, the mutant may be a useful system for study of the regulation of myelogenesis.

The development of the circulating blood volume of the chick embryo

Abstract: The circulating blood volume of the chick embryo was determined from the 4th up to the 18th day of hatching. In contrast to former studies, there was employed a radioisotope dilution method with albumin-bound I131. The findings are in close correspondence to those of the earlier studies. The blood volume does not display an entirely perfect curve of exponential growth, i.e., the doubling time increases steadily. The blood volume attains a peak value between the 16th and 18th day and decreases somewhat toward the end of the hatching period. There has been postulated a reduction of total red cell volume and hemoglobin caused by the involution of the extraembryonic circulatory system. The destruction of the erythrocytes seems to take place in the endodermal epithelium of the proximal yolk sac, where an accumulation of iron could be demonstrated on the 19th and 20th days.

Studies on the liver of Xenopus laevis. I. The ultrastructure of the parenchymal cell.

Abstract: The liver of Xenopus laevis was examined with electron microscopy. Its structure was found to be markedly different from that of mammals, particularly regarding the morphology of the hepatocytes to be classified as typical. It was established that the main function of such a cell is the storage of glycogen, and further that it possesses only scant organelles and other inclusions. Since this type of cell was found most frequently in the liver of untreated animals, it was designated as normal cell. The fact appears noteworthy that in the normal liver of Xenopus laevis an abundance of cell types occur which are otherwise found to be proliferated under experimental conditions, e.g. cells with pronouncedly augmented RER, enlarged Golgi complexes, increased lipid inclusions etc. This high number of divergent hepatocytes and the fact that all intermediate stages between the individual extremes are present and not to be accounted for by the position of the cell within the liver was interpreted as being the expression of a cyclic passage of the various stages of activity. It is of special interest that augmented degradation of glycogen in the liver cell takes place only during vitellogenesis. Acute and chronic hunger, as well as adaptation to cold, hardly affect the morphology of the normal cell, especially as far as the glycogen is concerned. The possible causes for this are discussed.

Direct and mediated effects of testosterone: the development of intersexes in sex reversed mosaic mice, heterozygous for testicular feminization.

Abstract: The X-linked Tfm mutation causes androgen insensitivity in the target cells of testerone. Due to random X-inactivation, XX-mice heterozygous for Tfm are mosaics in respect to androgen sensitivity. By the autosomal "sex reversal" mutation, Tfm-heterozygotes were converted to males during embryonic life so that male sex organs developed in which the mosaic was expressed. The mutual influence of both components of the mosaic is analysed. It is shown that cellular differentiation is directly induced by testosterone, while the formation of organ anlagen and proliferation are locally mediated effects.

[Intercellular junctions in the guinea pig stria vascularis as shown by freeze-etching (author's transl)].

Abstract: Mit der Gefrieratztechnik wurden Art, Vorkommen und Ausdehnung von Zonulae und Fasciae occludentes (= “tight junctions”) und Nexus (= “gap junctions”) in der Stria vascularis des Meerschweinchens untersucht. Die Zonulae occludentes der Marginalzellen, welche die Intercellularraume der Stria vascularis zum Kalium-reichen Endodolymphraum hin begrenzen, sind vom “intermediate to tight”-Typ. Fasciae occludentes nehmen weite Teile der Zelloberflachen der Basalzellen ein und bilden eine Barriere zum Ligamentum spirale laterale. “Gap junctions” verbinden alle drei Zelltypen der Stria vascularis und die Basalzellen mit Zellen des Ligamentum spirale laterale. Oft fullen die “gap junctions” an den Basalzellen Areale der “tight junctions” aus. Sie werden als das morphologische Korrelat fur die elektrotonische Ubertragung von Membranpotentialen angesehen und sind vermutlich eine wichtige Voraussetzung fur die Entstehung des endocochlearen Potentials. Auserhalb der Zellverbindungsbereiche zeigen vor allem die Zellauslaufer der Marginalzellen eine Partikeldichte, die auf eine hohe Aktivitat dieser Membranen hinweist.

A quantitative electron microscopic study of atypical structures in normal human cerebral cortex.

Abstract: Biopsy samples of the cerebral cortex from four normal human brains were examined in the electron microscope for the presence of abnormalities related to neurones and neuroglia. Atypical forms of axons, axon terminals and dendrites, many of them similar to those described in a variety of pathological and experimental material, were found to occur in small but appreciable numbers. Neuroglia exhibiting atypical inclusions occurred but were much less common. Physiologically altered neuronal perikarya were not encountered apart from one neuronal death. An area of 3.6 × 105 μ2 was scanned from each brain and atypical structures were categorised and counted. The possible implications of the presence of these structures in normal brain is discussed and the need for neuropathologists and neuroanatomists to be aware of the existence of atypical forms of neuronal processes in normal human and animal brains is emphasised.

Surface coat of the palatal shelf epithelium during palatogenesis in mouse embryos.

Abstract: The palatal shelf epithelium of NMRI-mouse embryos was examined by electron microscopy during palatogenesis (day 14+2 hrs p.c. to day 14+10 hrs p.c.). A ruthenium red positive surface coat was observed on the epithelium of the vertically projected and horizontally rotated palatal processes. The surface coat on the tips of these processes was especially thick and was observed to be shed after fusion. The localization and the quantitative changes of the ruthenium red positive material during closure of the palatal shelves suggest that the surface coat may be involved in the initial process of palatal epithelial adhesion.

Use of polarized light for quantitative determination of the adjustment of the tangential fibres in articular cartilage

Abstract: According to recent research the course of the tangential fibres is gaining increasing importance for the analysis of the first signs of pathological alterations in the articular cartilage.

The postnatal development of the ovary in the "nude" mouse.

Abstract: The postnatal development of the ovary of the heterozygous nude (nu/+) mouse with the genetic background BALB/c is very similar--if not identical-- to that of other mouse strains. As other BALB/c mice, the nu/+ females become sexually mature during the 5th week post partum (p.p.). At this age the ovaries corpora lutea at various stages of differentiation. In the ovaries of newborn and 1 week-old homozygous (nu/nu) mice, the differentiation of oocytes into primary and secondary follicles is delayed. In the third postnatal week, the ovaries of homozygous females contain more atretic follicles than those of their heterozygous littermates. This increased degeneration of follicles may account for the greater mass of secondary interstitial tissue, which is observed in the ovaries of adult nu/nu females. In nine out of the 5 to 7 week-old nu/nu mice studied, the ovaries contained no-/or only very few corpora lutea. Thus in homozygous nude females, the onset of sexual maturity is delayed. This ovarial immaturity may persist throughout life. In other animals development may become normal. In addition to the impaired postnatal development of the ovary, unspecific inflammation of the uterine wall (endo- and/or myometritis) was detected in 47% of nu/nu animals older than five weeks. No direct correlation was, however, found between the delay of sexual maturation and the inflammatory changes in the uterus as many of the animals with an endo- or myometritis possessed mature ovaries. The low fertility of the female homozygous "nude" mouse seems, therefore, to be caused not only by an impaired differentiation of the ovary but also by inflammatory processes in the uterus.

Secretory phenomena at the ependyma of the IIIrd ventricle of the embryonic rat.

Abstract: On the basis of previous observations of the third ventricle, the brains of rat embryos in the 17 to 21 gestation days were examined by light-and electron microscope as well as histochemically.

Functional structure of the glomerular filtration barrier and the proximal tubuli in the developing foetal and neonatal pig kidney.

Abstract: 1 The detailed anatomy of the structures forming the glomerular filtration barrier and the proximal tubules was studied during development of foetal and neonatal pigs 2 In the glomerular filtration barrier during ontogenetic development an increased number of fenestrae was noted in the endothelium The condensation decreased in the glomerular basement membrane and an increase in the widths of the pedicles was observed 3 The proximal tubular cells revealed a highly specialised organisation with an enlarged cell surface (microvilli) towards the lumen In the apical part of the cell a zone containing vesicles probably pinched off from the base of the microvilli was observed At the base of the cell elongated mitochondria and electron dense bodies were found 4 An increase in the number of vesicles was observed in the proximal tubular cells from piglets receiving colostrum and exhibiting proteinuria Judging from these results it seems probable that the nephrons are able to function already in the metanephros of the pig foetuses of 4 cm CR-length 5 The results imply that there was no structural evidence of an immature glomerular filtration barrier being the cause of neonatal proteinuria On the other hand an enhanced involvement of the cells of the proximal tubules was noted and this is interpreted to be due to the absorption of proteins from the primary urine after onset of colostrum ingestion by the newborn piglet

Quantitative investigations of visual brain structures in wild and domestic sheep.

Abstract: A cytoarchitectonic subdivision into visual structures and neocortical grey and white matter has been made from frontal serial sections of brains of mouflons (Ovis ammon musimon) and domestic sheep (Ovis ammon f. aries). The reduction rates determined for the volumes of the brain areas are calculated by means of intraspecific allometric methods. The overall decrease of visual brain structures in domestic sheep compared with wild sheep amounts to 25.9%, The greatest reduction is found in the striate area (30.2%), followed by the lateral geniculate body (25.4%), the optic tract (20.6%) and finally the superior colliculus (12.1%). The neocortex as a whole decreases in sheep under domestication by 26.4% in volume. The reduction rate of neocortical grey matter amounts to 24.9%, that of the white matter to 28.9%. The changes of brain size in domestic sheep may be functionally correlated to changes of the environmental conditions which are due to domestication.

A cytoarchitectonic volumetric comparison of the area gigantopyramidalis in wild and domestic sheep

Abstract: The area gigantopyramidalis has been circumscribed on frontal serial sections of brains of mouflons (Ovis ammon musimon) and domestic sheep (Ovis ammon f. aries). A brief description of the topography and lamination of the area 4 is given.

Studies on the liver of Xenopus laevis. II. The ultrastructure of the peritoneal cover and the perihepatic layer.

Abstract: The peritoneal cover and the subcapsular region of the liver of Xenopus laevis were examined with electron microscopy. In the subcapsular region a prominent perihepatic layer two to ten cells wide was found. This perihepatic layer is mainly composed of granulocytopoietic tissue. Other cell types found in the perihepatic layer were lymphocytes, pigment cells and fat storing cells. The presence of a perihepatic granulocytopoietic layer in the liver of Xenopus laevis is in contrast to current opinion that such a layer is a characteristic typical of urodeles. The phylogenetic significance of such a layer in anurans and the developmental processes of the individual cell types of the perihepatic layer are discussed. Furthermore the possible participation of the perihepatic layer in the immune response is considered.

Evolution of mesenchymal cells in fetal rat lung.

Abstract: The evolution of connective tissue cells in the developing fetal rat lung is studied under the electron microscope from the 15th until the 21st day of gestation and is compared to the evolution of epithelial cells. Three successive types of stem cells ("mesocytoblasts") are present during the first stages of lung development studied (15 to 18 days of gestation). These stem cells appear to be able to differentiate into fibroblasts or into smooth muscle cells, according to their localization along the broncho-alveolar tubule. Myoblasts are situated near the bronchial epithelium, whereas fibroblasts occur under the alveolar epithelium. Epithelo-mesenchymal interactions are assumed to play a role in this differentiation process. Synthesis of both, collagen and elastic fibers and of cytoplasmic filaments by fibroblasts as well as by myoblasts reveal the multiple potentialities of the mesenchymal stem cell and suggest a common origin. The early fibroblast in characterized by long cytoplasmic processes which contain numerous cytofilaments, and by the presence of collagen fibers in the vicinity of the cell. Later on, (20 days of gestation) the mature fibroblast of the lung mesenchyme shows areas of RER, glycogen and lipidic vacuoles in its cytoplasm. Cytofilaments are numerous within very long cytoplasmic processes and elastic and collagen fibers are very frequent beside the cytoplasmic membrane. The earliest fibroblast differentiation occurs under the epithelium of primitive respiratory bronchioles, which indicate the limit between the bronchial and the alveolar territories. Later on, differentiating fibroblasts are found throughout the whole alveolar walls. Connective tissue cells other than mesenchymal stem cells, fibroblasts or myoblasts are observed during lung development. Vacuolar cells, similar to Hofbauer cells, transiently appear on the 16th day of gestation. On the 20th and the 21st day macrophage-like cells are present in the septal space of the alveolar wall. The absence of intermediate stages of differentiation and parallel evolution of blood cells suggest that those connective tissue cells are differentiated elsewhere and have then migrated from blood into lung mesenchyme. No cell death has been observed in the developing lung.

Fixation of foetal pig liver for electron microscopy. I. The effect of various aldehydrs and of delayed fixation.

Abstract: Light and electron microscopic investigations of the ability of various fixatives to preserve foetal pig liver tissue (immersion fixed 5 min, 20 min, and 40 min after the death of the mother) gave the following results:

Absorption of the impact energy in the palmar soft tissues.

Abstract: In 30 anatomical specimens of the forearm the dynamic fracture of radius has been performed with a special hammer. In these specimens the pure kinetic energy of the fracture of the radius and the absorption of the impact energy in the palmar soft tissues has been determined.

Alkaline phosphatase in the bovine endometrium and trophoblast during the early phase of implantation.

Abstract: Alkaline phosphatase in the endometrial and chorionic epithelium from the 22nd to 24th day post insemination was investigated according to the method of Hugon and Borgers (1966a, b). In the precontact phase the reaction products of this enzyme were found light microscopically in the caruncular and intercaruncular area in the apical part of the uterine surface epithelium. Although a definite, continuing reaction line between the maternal and fetal epithelium was present in the apposition phase, there was no activity of this phospho-monoesterase ascertainable following consolidated adhesion. Independent of implantation, lead salt precipitate was observed in the apical cytoplasma in the upper third of the uterine epithelial glands. Electron microscopic investigations in the precontact phase demonstrated the localisation of the reaction products of this hydrolase as electron dense grains on the outer plasma lamella of the uterine microvilli. During apposition this reaction appeared on the microvilli of the dark uterine epithelium and the cell membrane of the trophoblast cells. In addition to the existence of alkaline phosphatase on the microvilli of the uterine glandular cells, reaction products were discernable in the kinocilia between the inner lamellar of their plasma membranes and the tubules ring, as well as between the latter and the central tubule pair. There is a possibility that this hydrolase plays a role in the transport of metabolites for the purpose of histiogenic uterine milk production.

Fine structure of the interrenal cell in the quail and the pigeon.

Abstract: The ultrastructural characteristics of the interrenal cell were investigated in the quail and the pigeon after fixation by intravascular addominal perfusion. These is no significant fine structural difference between cells belonging to subcapsular and central regions of the gland. The interrenal cell in both species possesses nuclear bodies, polymorphic mitochondria with tubulo-vesicular cristae and tubular crystalline inclusions, considerable amounts of endoplasmic reticulum, ergastoplasm, a well developed Golgi apparatus, coated vesicles, microtubules, filaments, cilia, ribosomes, a profusion of liposomes, dense bodies with varied inner structure, pinocytic invaginations of cell membrane and intercellular attachment devices. The pigoen adrenocortical cell also possesses intranuclear lipidlike inclusions and fibrous bundle (this being never recorded in adrenocortical cell), annulate lamellae, and a variety of cytosomes, probably lipofucsin in nature. The significance and cytophysiological role of various organelles and inclusions have been discussed in the light of earlier data obtained on avian adrenocortical cells.

Malformed vertebrae: a new mutant with the "wirbel-rippen syndrom" in the mouse.

Abstract: A new skeletal mutant in the house mouse, “malformed vertebrae” (Mv), is described. It is semidominant. The skeletal malformations can be traced back to disturbed somite formation.