Monika Kressin

Light and electron microscopic investigation of the lectin-binding pattern in the oxyntic gland region of bovine abomasum

For the first time the expression of glycoconjugate residues in the oxyntic gland region of bovine abomasum has been investigated by means of lectin histochemistry. For light microscopic investigations, a battery of ten lectins, Con A, PSA, UEA I, WGA, LEA, SNA, RCA120, MPA, DBA and SBA was used. For electron microscopic examinations, WGA and RCA120 were utilized. The staining pattern of the lectins in all exocrine cell types of the oxyntic gland region is described. Compared to the results of monogastric species our study reveals some similarities, but just as many differences in the composition of glycoconjugate residues in bovine exocrine cell types. Typical for surface mucous cells is the amount of L-fucose, N-acetyl glucosamine residues and Galbeta1, 4GlcNAc sequences in the secretory granules. SNA could serve as a marker for surface mucous cells, because this lectin exclusively stains the plasma membrane and the secretory granules of surface mucous cells and the extracellular mucus. L-fucose and N-acetyl glucosamine are typical for the secretory granules of mucous neck cells. In addition, the secretory granules show the highest amount of N-acetyl galactosamine residues of all exocrine cells, so that DBA and SBA are recommended as marker lectins for mucous neck cells. Most lectins strongly stain the intracellular membrane system of oxyntic cells. The cocktail of glycoconjugates in the vicinity of the HCI production site provide protection against chemical injury. In chief cells only the apical plasma membrane is more or less labeled with all lectins apart from SNA. Specific marker lectins for oxyntic cells or chief cells of the bovine have not been characterized.

Re-visiting the Protamine-2 locus: deletion, but not haploinsufficiency, renders male mice infertile

Protamines are arginine-rich DNA-binding proteins that replace histones in elongating spermatids. This leads to hypercondensation of chromatin and ensures physiological sperm morphology, thereby protecting DNA integrity. In mice and humans, two protamines, protamine-1 (Prm1) and protamine-2 (Prm2) are expressed in a species-specific ratio. In humans, alterations of this PRM1/PRM2 ratio is associated with subfertility. By applying CRISPR/Cas9 mediated gene-editing in oocytes, we established Prm2-deficient mice. Surprisingly, heterozygous males remained fertile with sperm displaying normal head morphology and motility. In Prm2-deficient sperm, however, DNA-hypercondensation and acrosome formation was severely impaired. Further, the sperm displayed severe membrane defects resulting in immotility. Thus, lack of Prm2 leads not only to impaired histone to protamine exchange and disturbed DNA-hypercondensation, but also to severe membrane defects resulting in immotility. Interestingly, previous attempts using a regular gene-targeting approach failed to establish Prm2-deficient mice. This was due to the fact that already chimeric animals generated with Prm2+/− ES cells were sterile. However, the Prm2-deficient mouse lines established here clearly demonstrate that mice tolerate loss of one Prm2 allele. As such they present an ideal model for further studies on protamine function and chromatin organization in murine sperm.

Das Blutgefäßsystem des Darmes von Gallus domesticus

Summary The vascular system of the chicken intestine was investigated by corrosion cast, light and electron microscopic methods. In the intestinal villi the “Fontainentyp” is present with a single arteriole rising to the apex and draining into subepithelial capillaries. Occasionally ramifications of the arteriole occur in the upper third of the villi. Another variation is splitting of the arteriole into a capillary net at the base of the villi in the caeca between the regions with and without villi. At the tip, at the margins and at the base of the villi the capillaries fuse into venules, which proceed to the inside and empty into veins. At the base above the propria they form a superficial net with connecting veins arising to an inferior venous plexus below the region of crypts. The submucosal collecting veins descend from short vascular truncs, which originate from the inferior plexus and cross the muscularis mucosae. Elements of a vasoregulatory system like arterio-venous marginal loops, submucosal arterio-venous anastomoses, sphincter-arteries, precapillary sphincters and sphincterveins well know in the literatur are not found in the intestine of the domestic chicken. Therefore arterioles, capillaries and muscle bundles concentric around the veins in the villi seem to take over this function.

Cell behavior of human mesenchymal stromal cells in response to silica/collagen based xerogels and calcium deficient culture conditions

Herein, we aim to elucidate osteogenic effects of two silica-based xerogels with different degrees of bioactivity on human bone-derived mesenchymal stromal cells by means of scanning electron microscopy, quantitative PCR enhanced osteogenic effects and the formation of an extracellular matrix which could be ascribed to the sample with lower bioactivity. Given the high levels of bioactivity, the cells revealed remarkable sensitivity to extremely low calcium levels of the media. Therefore, additional experiments were performed to elucidate cell behavior under calcium deficient conditions. The results refer to capacity of the bone-derived stromal cells to overcome calcium deficiency even though proliferation, migration and osteogenic differentiation capabilities were diminished. One reason for the differences of the cellular response (on tissue culture plates versus xerogels) to calcium deficiency seems to be the positive effect of silica. The silica could be detected intracellularly as shown by time of flight-secondary ion mass spectrometry after cultivation of primary cells for 21 days on the surfaces of the xerogels. Thus, the present findings refer to different osteogenic differentiation potentials of the xerogels according to the different degrees of bioactivity, and to the role of silica as a stimulator of osteogenesis. Finally, the observed pattern of connexin-based hemichannel gating supports the assumption that connexin 43 is a key factor for calcium-mediated osteogenesis in bone-derived mesenchymal stromal cells.

Development of the Glandular Epithelium of the Bovine Parotid Gland during Ontogenesis

The development of the parotid gland was examined in 36 bovine embryos and foetuses with a crown‐rump‐length (CRL) from 28 up to 1000 mm by light, transmission electron microscopical and actin‐immunohistochemical methods.

Der Rumpfdarm des Burunduk (Eutamias sibiricus, Laxm. 1769): Makroskopische und lichtmikroskopische Untersuchungen*

The canalis alimentarius of the Burunduk (Eutamias sibiricus), a rodent belonging to the family Sciuridae, were examined macroscopically (12 animals) and light microscopically (three animals).

Oxyntic cell differentiation during physiological cell renewal in abomasal mucosa of adult cattle.

The origin and differentiation of the oxyntic cell lineage during physiological cell renewal was investigated by light and electron microscopy in the abomasal mucosa of adult cattle. The morphologically heterogeneous oxyntic cell population exhibits various developmental subtypes depending on the position within the oxyntic unit. Pre-oxyntic cells of the isthmus and neck represent the immature precursors. Though heterogeneous with respect to the degree of canalicular and tubulovesicular membrane development, they all contain secretory granules resembling those of either isthmus cells, immature surface mucous cells, neck cells or young chief cells. A secretory granule-free stem cell is not present in the bovine. Downward to the gland base genesis of canalicular as well as tubulovesicular membranes is gradually completed; thus pre-oxyntic cells give rise to mature oxyntic cells. Older degenerative oxyntic cells, primarily located within the gland bottom, are characterized by progressive involution of canalicular and tubulovesicular membranes. Towards the pit, differentiation of pre-oxyntic cells is associated with atypical and incomplete development of canaliculi and tubulovesicles. In consequence, these superficial oxyntic cells have a reduced secretory capacity from a morphological point of view.

Die Differenzierung der Oberflächenzellinie im Labmagen adulter Rinder * The Differentiation of the Surface Mucous‐cell Line in the Abomasum of the Adult Cow

The differentiation of the surface mucous‐cell lineage during physiological cell renewal was investigated using light and electron microscopy in the abomasal mucosa of adult cattle. The surface mucous cells constitute a morphologically and functionally heterogeneous population, whose members correspond to different developmental stages, arranged in a distoproximal gradient from the depth of the pit towards the free luminal surface. The cell lineage comprises immature pre‐pit cells near the proliferative isthmus, mature pit cells within the foveola, and older interfoveolar cells lining the free surface. Ultrastructurally, differentiation can be traced towards a predominantly mucus‐producing cell type and finally towards a surface‐protective cell variant, which degenerates in situ and is extruded into the lumen without affecting epithelial integrity.

Actin in Stratified Squamous Keratinized Epithelium

Actin filament distribution patterns were revealed in a stratified squamous keratinized epithelium using phalloidin‐fluorescent and immunogold labeling techniques applied on bovine luminal pilar as a model tissue. In non‐keratinized cell types, actin concentrates on the microfilament‐rich cellular cortex as well as on cytoplasmic processes and protrusions. In cornified cells labeling is distributed diffusely over the amorphous cytoplasm. A constant feature in all cell types is plasmalem‐mal labeling. Desmosomes exhibit deposition on their plasmalemmal leaflets, the dense central stratum and plaques. Desmosomal as well as cytoplasmic keratinfilament bundles also label for actin, the latter often in a cross‐banded manner. These cellular distribution patterns of actin filaments are discussed with respect to the singificance of the microfilaments in the process of cell shape determination, stratification, and cell adhesion.

Proliferation in the gastric epithelium of bovine abomasum during foetal development as revealed by Ki-67 immunocytochemistry.

For the first time, proliferative cells in the abomasal mucosa of 30 bovine foetuses with a crown–rump length of 34 to 1000 mm (approximately 45–250 days of gestation) were detected using the antibody MIB‐1 against the (human) nuclear‐associated protein Ki‐67. At the beginning of mucosal development, the epithelium is stratified and MIB‐1 positive cells are scattered all over the epithelium. With the formation of gastric pit/gland invaginations, the proliferative cells are mostly confined to the basal half or third of the gastric pit/gland unit, both in the regio glandulae propriae and in the regio glandulae pyloricae. From the 27th week in the regio glandulae propriae and the 30th week in the pyloric gland region, respectively, the proliferative cells move upwards and are situated in the bottom of the pit and the upper part of the gland, whereas the base of the gland is free of labelling.