[The occurrence of hemodynamic effective elements in the intestinal blood vessel system]. / Uber das Vorkommen hämodynamisch wirksamer Elemente im intestinalen Blutgefässsystem.

Arterioles, precapillary sphincters, capillary endothelium, and pericytes probably regulate the blood flow in the intestinal microvascular bed similar to other regions of the body because of their equipment with contractile filaments. Only throttle veins with their arrangement of pools and their characteristics probably exert influence on the hemodynamic qualities of the blood flow in the intestinal mucosa.

[The functional morphology of the large intestinal mucosa of the ox (Bos primigenius f. taurus), sheep (Ovis ammon f. aries) and goat (Capra aegagrus f. hircus)]. / Zur funktionellen Morphologie der Dickdarm-Mukosa von Rind (Bos primigenius f. taurus), Schaf (Ovis ammon f. aries) und Ziege (Capra aegagrus f. hircus).

The mucous membrane of the large intestine of the ox, sheep and goat was studied using light and electron microscopy. The surface epithelium possesses the well-known complement of organelles with a conspicuous number of mitochondria as a source of energy for absorptive activities. Occasionally, brush cells are found in the epithelium; the functional significance of this type of cell is still under discussion. In the present material, electron-lucid spheroids (diameter: 45 x 35 nm), which tend to fuse, appear in the supranuclearly located osmiophilic granules. The structure and appearance of the epithelium cells in the crypts of these species correspond to previous descriptions in other mammals. In the epithelial cells of the deep glandular region, dense accumulations of mainly rounded granules (diameter up to 400 nm) are found apically in the cytoplasm. Their functional significance is still under discussion. Acid phosphatase activity, as a marker enzyme for lysosomes, points to degenerative processes in connection with the physiological death of enterocytes. In contrast, the negative alkaline phosphatase reaction indicates that, according to our findings, the epithelial transport of substances in the large intestine of ruminants--in principle contrary to the situation in the small intestinal enterocytes--occurs without the aid of this enzyme. The demonstrated ATPase activity on the other hand, is related to a primary active ion transport linked with membrane exchange of non-electrolytes in connection with transepithelial events of absorption and secretion in the large intestine.

[Morphogenesis of the submucosal gland of cattle (Bos primigenius f. taurus)]. / Uber die Morphogenese der Glandulae submucosae des Rindes (Bos primigenius f. taurus).

In the 10th week of gestation the development of duodenal glands in the bovine intestinum starts by circumscript epithelial proliferation. Their secretory channels are in contact with the crypts. Already in the early fetal stage ultrastructurally there are an inconspicuous equipment with organelles in the apical cytoplasm and single globular granules, which demonstrate the differentiation of epithelial cells into duodenal glandular cells. Until the mid-point of the pregnancy the granular endoplasmic reticulum strongly develops as a condition for the impressive increase in the formation of the prosecretory granules. Finally, in the second half of the pregnancy, granules varying in structure and electronic density, but mostly showing an intensively osmiophilic and fine granular material, are the predominant cytoplasmic structures. Like in goblet cells capsulated vacuoles seem to play a role in the formation of the secretory granules. Recent, extensive studies concerning our results have been discussed.

[Further contribution on glycogen in fetal intestinal epithelium]. / Ein weiterer Beitrag zum Glykogen im fetalen Darmepithel.

In the first half of pregnancy the well-known occurrence of glycogen incorporation in the supra- and infranuclear cytoplasm of the villous enterocytes was verified. This enormous glycan store is evidently of very little functional importance. It seems to be an expression of a disordered glycogenolysis. These masses of glycogen are incorporated into impressive glycogenosomes, which are the predominante cytoplasmic inclusions for a short period of time. According to the present results it is not certain whether lysosomal glycogenolysis happens. There is no morphological or functional evidence for a utilization og glycogen.

[Further contribution on the fine structure of fetal goblet cells. Investigations on the small intestine of cattle]. / Ein weiterer Beitrag über die Feinstruktur der fetalen Becherzelle. Untersuchungen am Dünndarm des Rindes.

Early in the fetal development, i.e. at the time both of the growth of intestinal villi and crypts and the epithelial cell differentiation the goblet cells also appear. The maturation of goblet cells progresses during their migration from the base of the villi respectively of the crypts to the villous top. As in the bovine large intestine there are vesicles and capsulated vacuoles, which contain vesicles, as single elements or as conglomerates in the immature goblet cells of the small intestine. These images deliver a scenario of the mechanism of secretory granule production and probably play a role in the formation of mucus.

[Functional morphology of the large intestinal mucosa of horses (Equus przewalskii f. caballus) with special regard to the epithelium]. / Uber die funktionelle Morphologie der Dickdarm-Mukosa vom Pferd (Equus przewalskii f. caballus) unter besonderer Berücksichtigung ihres Epithels.

The mucous membrane of the caecum and colon ascendens of adult horses was first studied using light and transmission electron microscopy. In the surface epithelium there was an inconspicuous constellation of organelles, otherwise there was a lot of mitochondria as a source of energy for absorptive performances. Moreover, enlarged intercellular spaces exist as an indication of an increased uptake of water and electrolytes. In the basal region of Lieberkühn's crypts there were single enteroendocrine cells and numerous granules in the apical epithelial cytoplasm. The functional meaning of these granules is contrarily discussed in the literature. There was no epithelial activity of alkaline phosphatase. Against that a small positive reaction of adenosine triphosphatase was observed at the lateral plasmalemata of the epithelial cells. The sense of these findings with regard to the transport of substances in the equine large intestine is discussed.

[Early fetal development of the small intestine mucosa in cattle (Bos primigenius taurus)]. / Uber die frühfetale Entwicklung der Dünndarm-Mukosa des Rindes (Bos primigenius taurus).

The development of the bovine small intestine was examined in 24 embryos and fetuses by light microscopic, scanning and transmission electron microscopic methods. Special reference was paid to the genesis of the epithelium and particularly of the villi intestinales. The primitive intestine consists of one layer of epithelial cells surrounded by mesenchym and tunica serosa. The fetal intestine (up to the 24th week of gestation) shows all the morphologic structures of the adult. In small intestine the development of cryptae and villi intestinales starts before the 7th week of gestation and progresses with a proximo-distal gradient. Epithelial proliferation that gives rise to primary epithelial villi makes epithelium become temporarily stratified. Finger-like secondary villi develop by proliferation of the mesenchym. In addition to this process mucosal folds occur in duodenum giving rise to villi by segmentation. At the same time the differentiation of epithelium starts. The fetal small intestine, like many other fetal tissues displays masses of glycogen.

[Prenatal development of the lamina epithelialis in the phase of vacuolization of villous epithelial cells. Investigations on the intestines of cattle (Bos primigenius taurus L., 1758)]. / Uber die pränatale Entwicklung der Lamina epithelialis in der Phase der Vakuolisierung villärer Epithelzellen. Untersuchungen am Darm des Rindes (Bos primigenius taurus L., 1758).

The development of the bovine small intestine was examined in 39 embryos and fetuses by light microscopic and transmission electron microscopic methods. Special reference was paid to the histogenesis of the ephithelium. In contrast to the duodenum the epithelium of jejunum and ileum undergoes a degeneration by vacuolation of its villous epithelial cells. The demonstration of the acid phosphatase activity of these vacuoles shows their lysosomal character. This degenerative process of the small intestinal epithelium is also known in large intestine where it leads to the destruction of the intestinal villi. Both seem to be part of a 'principle of construction of the intestine of the vertebrates' (Wille, 1984).

[Intramural vascular system of the large intestine of mammals. A study of the literature]. / Uber das intramurale Blutgefässsystem des Dickdarms der Säuger--Eine Literatur-Studie.

From a morphological point of view, too, the summarizing synopsis of the intramural vascular system of the large intestine of mammals shows, that the functional aspect is prominent. As in other studied species the exclusively on the epithelial side existing 'fenestrated endothelium' of the pericryptal and subepithelial capillaries is doubtless the most important structural mark of the large intestinal function, too. Moreover, the direction of the mucosal capillary blood flow informs, that at first the release of the essential substances for the glandular secretion will take place, before epithelial transports concerning the resorption occur. As for the hemodynamic regulatory structures in the wall of the blood-vessels there are obviously differences in their existence depending on the species, respectively they are completely absent such as in the ruminants. Finally, it should be mentioned, that arterio-venous anastomoses could not be detected.

[Intramural blood vessels of the large intestine of the horse (Equus przewalskii f. caballus)]. / Uber die intramuralen Blutgefässe des Enddarms vom Pferd (Equus przewalskii f. caballus).

The vascular system of the large intestine of 12 horses was examined by means of vascular corrosion casts, histology and transmission electron microscopy providing the following results. The Aa. et Vv. breves et longae leave the mesenteric vessels, respectively the subserously on the teniae lying cecal vessels to reach the tela subserosa at the mesenteric margin. The short vessels enter the deeper layers of the wall instantly, whereas the Aa. et Vv. longae move towards the submucosa by penetrating the muscular layers after a variable subserous course. The tela submucosa contains an arterial and a venous vascular plexus. In broader areas of the submucosa a three-dimensional vascular network can be found. This consists of a deep and a superficial vascular plexus, which are closely interconnected. The deep plexus is applied to the inner circular muscles, whereas the superficial plexus is adjacent to the muscularis mucosae. The (deep) arterial plexus receives its afflux from the Aa. breves et longae and supplies parts of the circular muscle layer with recurrent muscle branches. The vascularisation of the mucosa also originates from the submucosal (superficial) plexus. In the basal tunica mucosa, the ascending arteries form a transversal network from which arterioles branch into periglandular capillaries around each Lieberkühn crypt. Close to the lumen, a polygonal subepithelial capillary system is formed. The capillaries turn into postcapillary venules immediately below the epithelium of the mucosal surface. Veins move vertically through the submucosa to enter the submucosal plexus after few inflowing side branches. Branches of the subserous-submucosal connections form an intermuscular plexus between the circular and longitudinal muscular layer. This plexus supplies the capillaries of the tunica muscularis. The subepithelial capillaries are predominantly lined with a fenestrated endothelium, whereas the capillaries of the pericryptal mucosa mainly show a continuous endothelial lining. The latter contain multiple vesicles, which may fuse in order to form transcytoplasmic channels. Sphincter-like muscle bundles at the transition points from capillaries to venules may provide hemodynamic regulatory structures in the submucosa of the horse. Veins with circumferential cushions of smooth muscle fibres, so-called 'throttle veins', are also found.

[Vascular system in the large intestine of the dog (Canis lupus f. familiaris)]. / Das Blutgefässsystem des Enddarms vom Hund (Canis lupus f. familiaris)

The vascular system of the large intestine of 10 dogs was examined by means of vascular corrosion casts, histology and transmission-electron microscopy. The tela submucosa contains an arterial and a venous vascular plexus. In broader areas of the submucosa, a deep and a superficial vascular plexus, which are interconnected, can be found. The plexus are orientated parallel to the layers of the intestinal wall. On the one hand, these vessels naturally provide self-sufficiency and drainage of the submucosa, and, moreover, direct branches to the stratum circulare of the muscular layer. On the other hand, the submucosal vascular plexus is the 'distributional network' for the functional plexus of the tunica mucosa. The arteries, which ascend to the tunica mucosa, supply a flat arterial network underneath the intestinal glands. Bundles of only a few arteriolae originate from this in order to supply the pericryptal capillaries. In the vicinity of the cryptal orifices, these turn into a network of subepithelial capillaries, which is post-connected to the periglandular capillary plexus. From this 'terminal circulatory pathway', the blood is drained off by veins that enter the submucosal plexus. It is characteristic that the postcapillary venules often begin as part of the capillary network. As in other species, the subepithelial capillaries are pre-dominantly lined with a 'fenestrated endothelium', whereas the capillaries of the pericryptal areas show a continuous endothelium. The latter contains multiple vesicles that may fuse in order to form transcytoplasmic channels as a morphological equivalent for transcappillar-epithelial and vice versa occurring transport of substances.

[The blood vessel system of the large intestine of swine (Sus scrofa f. domestica)]. / Das Blutgefässsystem des Enddarms vom Schwein (Sus scrofa f. domestica).

The circulatory system of the large intestine of 27 pigs was examined by means of corrosion anatomy (vascular casts), histology and electron microscopy. The results were as follows: The Aa. et Vv. breves et longae leave the mesenteric vessels and reach the wall of the intestine at the mesenteric margin. The short vessels enter the deeper layers of the wall, whereas the Aa. et Vv. longae, by taking a variable subserous course, reach the submucosa after penetrating the muscular layers. The tela submucosa contains an arterial and a venous vascular plexus. Where the submucosa is larger, there is a three-dimensional vascular network, a deep and superficial vascular plexus that are closely interconnected. The deep plexus is applied to the inner circular muscles, whereas the superficial plexus is adjacent to the muscularis mucosae. The deep arterial plexus receives its afflux from the Aa. breves et longae and provides part of the circular muscle layers with recurrent muscle branches. The vascularization of the mucosa is derived from the (superficial) submucosal plexus. The arteries that ascend the tunica mucosa ramify, in the form of a brush, into some arterioles. In the basal part of the mucosa, they turn into a periglandular capillary system, i.e. a network around each Lieberkühn crypt. Close to the lumen, a polygonal subepithelial capillary system is formed. Below the epithelium of the mucosal surface, the capillaries turn into postcapillary venules. These are running vertically through the submucosa, with few inflowing side branches, and finally enter the submucosal plexus An intermuscular plexus is formed by anastomoses between the circular and the longitudinal muscular layers from the branches of the subserous-submucosal connections. This intermuscular plexus provides the capillaries for the tunica muscularis. The subepithelial capillaries are, above all, furnished with a so-called fenestrated endothelium, whereas the capillaries of the pericryptal mucosa mainly show a continuous endothelium. The latter contains multiple vesicles that can fuse to form transcytoplasmic channels. In the wall of the large intestine of the pig, there are no sure indications as to the existence of either arterio-venous anastomoses or haemodynamic regulatory structures.

[Intramural blood vessel system of the large intestine of domestic ruminants]. / Uber das intramurale Blutgefässsystem des Dickdarms der Hauswiederkäuer.

The vascular system of the large intestine of 15 cattle, 10 sheep and 5 goats has been examined by means of corrosion vascular casts, histology and electron microscopy. The results are as follows: The course and ramification of the intestinal vessels are identical in the caecum, colon and rectum. Furthermore, as expected, amongst the species studied no substantial differences in the vascular architecture of the large intestinal wall could be determined. The extramural vessels reach the wall of the intestine at the mesenteric margin. Their branches build arterial or venous networks in the tela subserosa, which then divide into branches in the direction of the antimesenteric region. The connections between the blood vessels of the tela subserosa and the tela submucosa as well as the branches to the muscular layers emerge from these networks. In the tela submucosa an arterial and venous system can be found. The obvious vascular arrangement in the submucosa is arranged not only parallel to the stratum circulare of the tunica muscularis but also along the prevailing direction of the lamina muscularis mucosae. From this arrangement both a deep and a superficial submucosal vascular plexus can be denominated. The recurrent branches for the circular muscle layer as well as the afferent and efferent vessels of the mucosa originate from submucosal arteries and veins. The arterioles of the tunica mucosa branch at the level of the basal crypts into a periglandular capillary system running close to the lumen into a subepithelial capillary system. Here the capillaries drain into venules which advance to the region of the intestinal glands and consequently drain into collecting veins in the submucosa. Capillaries of the subepithelial lamina propria mucosae are furnished with continuous or fenestrated endothelial linings as the morphological equivalent of the secretory or resorption processes, respectively. In the walls of the large intestine of the bovine, sheep and goat there are neither arterio-venous anastomoses nor hemodynamic regulatory structures such as sphincters or so-called throttle veins at the points of transition from capillaries to venules. These results are in accord with the findings in the small intestine of domestic ruminants (Hummel 1980).

[Lysosomal structures in the intestinal epithelium of mammals during their pre- and postnatal development. A micromorphometric-functional synopsis]. / Uber lysosomale Strukturen im Darmepithel des Säugers während seiner prä- und postnatalen Entwicklung. Eine mikromorphologisch-funktionelle Synopse.

The first lysosomes appear in the stratified embryonic intestinal epithelium during its transition into the simple columnar form. This occurs concurrently with the initial villogenesis. Lysosomes situated basally in the epithelium are presumably the precursor of the first giant lysosomes in the lower small intestine of rodents. Immediately after establishment of the simple configuration a special form of secondary lysosomes can be observed, i.e. glycogenosomes, in the ephemerally existing huge glycogen containing areas. During subsequent fetal intestinal development one observes two events in the epithelial cells, which are the same in principle but differ in one essential point, while they exhibit partially impressive structures. On the one hand there are autophagic degenerative lysosomal processes in the villous epithelium until birth, that lead to a surface without villi in the large intestine, where they occur particularly frequently. On the other hand giant lysosomes originate perinatally in the lower small intestine as well as in the caecum and colon ascendens, in which protein molecules, which were transported by a system of inframicrovillar membranes, are lysosomally degraded, which can be defined as a heterophagic event.

[Endocrine cells in the epithelium of the fetal large intestine of cattle (Bos primigenius taurus) from the cytomorphological aspect]. / Uber endokrine Zellen im fetalen Dickdarmepithel des Rindes (Bos primigenius taurus) unter zytomorphologischem Aspekt).

In the epithelium of the fetal bovine large intestine there are endocrine cells, predominantly at the base of the crypts. According to morphological characteristics, EC-cells and L-cells can be readily distinguished.

[The cytomorphology of goblet cells of the fetal intestine. Studies of the large intestine of cattle (Bos primigenius taurus)]. / Uber die Zytomorphologie der Becherzelle des fetalen Darmes. Untersuchungen am Dickdarm des Rindes (Bos primigenius taurus).

In the region of the base of the intestinal crypts undifferentiated goblet cells display a configuration and constellation of organelles and membrane structures that are indicative of their importance for function. These images at this stage of development deliver a scenario of the mechanism of secretory granule production: aggregates of protein vesicles from the "transitional elements" (PALADE) of the granular endoplasmic reticulum are, so to speak, rolled up on the trans side of the Golgi apparatus by inversion of peripheral membrane segments of the innermost Golgi lamellae, thereby forming corpuscles. The origin of the capsulated vacuoles, which contain vesicles as single elements or as conglomerates, is well established. Their capsule consists of a trilaminar external and external and internal membrane; between them lies condensed material of the Golgi apparatus. In the opinion of the present author, the development of the ensheathed vacuoles represents a basic, more general mechanism. In contrast, the further steps of synthesis, for the formation of secretory granules, are more heterogeneous. Condensation of the vesicles and the inner capsular membrane results in the formation of a prosecretory granule, which in the basic element in the process of secretory granule production. The prosecretory granules develop singly or by fusion with other granules to give primary secretory granules. The complexity of this mechanism of secretory granule formation, however, becomes evident when considering the apposition of capsulated vacuoles and prosecretory--primary--secondary secretory granules, of prosecretory and primary secretory granules as well as prosecretory granules and secondary secretory granules. Generally, primary granules show a tendency to become secondary secretory granules or to fuse with them. During maturation of the goblet cells the secretory granules fuse to form larger mucous bodies in the theca by fusion of the laminae of the membranes; a final product, there is a homogeneous mucous mass devoid of membranes.

[The embryonic development of the intestinal mucosa with special reference to its epithelium]. / Uber die Embryonalentwicklung der Darmschleimhaut unter besonderer Berücksichtigung ihres Epithels.

Electron microscopic examinations were made of different parts of the bovine intestine (n = 13) up to the 10th week of embryonic development. During the 'phase of undifferentiated epithelium' the embryonic intestinal epithelium can be classified as stratified and is perhaps a pool of cells. Microvilli of the apical plasmalemma appear at first in neighboring and opposing cells in the centre of the epithelium. They already show microfilaments as well as a glycocalix. The supranuclear cytoplasm shows many granules, vesicles and arciform structures which may be used in the process of microvilli formation. The importance of infranuclear basal granules in the peripheral epithelial cells is still unknown; perhaps they are merely phylogenetic remnants of a principle of development common to all vertebrate intestines. Single cilia which are formed in the periluminal cytoplasm presumably suppress mitotic activities of the epithelial cells and induce their ensuing differentiation. Epithelial proliferation is the initial event of villigenesis, giving rise to epithelial primary villi. Immediately following is the formation of secondary villi during proliferation of the mesenchyme.

[Glycogen in the fetal intestinal epithelium]. / Uber das Glykogen im fetalen Darmepithel.

In the phase of differentiated epithelium the well-known phenomenon of glycogen incorporation in the supra- and infranuclear cytoplasm of the villous enterocytes was verified. Contrary to the role of glycan in the production of pentoses for the biosynthesis of nucleic acid in embryonic cells (Sasse 1968), which display a high rate of metabolism and proliferation, this enormous glycogen store is evidently of very little functional significance. It seems to be an expression of a disordered glycogenolysis. These masses of glycogen are incorporated into impressive glycogenosomes, which are the predominate cytoplasmic inclusion for a short period of time. According to the present results it is not certain whether lysosomal glycogenolysis takes place. There is no morphological or functional evidence for a reutilization of glycogen.