Wholemount imaging reveals abnormalities of the aqueous outflow pathway and corneal vascularity in Foxc1 and Bmp4 heterozygous mice.

Mutations in the FOXC1/Foxc1 gene in humans and mice and Bmp4 in mice are associated with congenital anterior segment dysgenesis (ASD) and the development of the aqueous outflow structures throughout the limbus. The aim of this study was to advance our understanding of anterior segment abnormalities in mouse models of ASD using a 3-D imaging approach. Holistic imaging information combined with quantitative measurements were carried out on PECAM-1 stained individual components of the aqueous outflow vessels and corneal vasculature of Foxc1(+/-) on the C57BL/6Jx129 and ICR backgrounds, Bmp4(+/-) ICR mice, and wildtype mice from each background. In both wildtype and heterozygotes, singular, bifurcated and plexus forms of Schlemm's canal were noted. Of note, missing portions of the canal were seen in the heterozygous groups but not in wildtype animals. In general, we found the number of collector channels to be reduced in both heterozygotes. Lastly, we found a significant increase in the complexity of the corneal arcades and their penetration into the cornea in heterozygotes as compared with wild types. In conclusion, our 3-D imaging studies have revealed a more complex arrangement of both the aqueous vessels and corneal arcades in Foxc1(+/-) and Bmp4(+/-) heterozygotes, and further advance our understanding of how such abnormalities could impact on IOP and the aetiology of glaucoma.

The three-dimensional organisation of the post-trabecular aqueous outflow pathway and limbal vasculature in the mouse.

The mouse eye has been used as a model for studies on the microanatomy of the outflow pathways but most of what is known comes from histological sections. These studies have focused mainly on the morphological features of the trabecular meshwork, Schlemm's canal and aqueous channels that link to the superficial episcleral vasculature. However, the anatomical architecture of the aqueous outflow vessels and their relationship to each other and to the general vascular circulation is not well understood. The aim of this study was to provide a detailed description of the microarchitecture of the aqueous outflow vessels and their relationship to the superficial limbal/episcleral vasculature throughout the entire limbus. The aqueous outflow vessels and blood and lymphatic vessels were imaged in PECAM-1 and LYVE-1 immunostained whole anterior segments of adult mice and three-dimensional (3-D) reconstructions of the optical sections were generated to reveal the aqueous, blood and lymphatic architecture. The arterial supply, venous drainage, organisation of perilimbal vasculature, collector channels/aqueous veins and the morphology of Schlemm's canal were revealed in their entirety and the relationships between these structures is described. Schlemm's canal was PECAM-1 positive but there was no affinity for the lymphatic marker LYVE-1. We show that Schlemm's canal is a continuous circular structure and more often seen as a single, broad, varicose vessel with short regions appearing as a plexus. Aqueous veins link Schlemm's canal to the superficial vasculature and there were no direct links seen between the canal and the lymphatic vessels.

The distribution of mucous secreting cells in the gastrointestinal tracts of three small rodents from Saudi Arabia: Acomys dimidiatus, Meriones rex and Meriones libycus.

The proportion of mucin phenotypes (which form the protective biofilm of the gastrointestinal tract) differs between intestinal regions. This study examines the distribution of mucin secreting cells in the gastrointestinal tracts of the Eastern spiny mouse (Acomys dimidiatus), King jird (Meriones rex) and Libyan jird (Meriones libycus), which inhabit the dry and hot deserts of Saudi Arabia. Intestinal tract samples were processed to wax and tissue sections stained with Alcian Blue-Periodic Acid Schiff (AB-PAS) and High Iron Diamine-Alcian Blue (HID-AB) in order to determine different mucin phenotypes by quantitative analysis. Mixed mucin secreting cells (combined neutral and acid) was the predominant mucin secreting cell type observed throughout the gastrointestinal tract in all species. Acid mucin secreting goblet cells were mainly located in the colon. A. dimidiatus presented with significantly more total sialo than sulfomucin secreting cells while the opposite was true for both Meriones species. The distribution of mucin secreting cells is therefore similar to previously reported results for small mammals not living under arid conditions.

Comparative gastrointestinal morphology of three small mammalian insectivores: Acomys spinosissimus (Rodentia), Crocidura cyanea (Eulipotyphla), and Amblysomus hottentotus (Afrosoricida).

The gastrointestinal morphology was investigated in three mammalian insectivorous species, namely Acomys spinosissimus, Crocidura cyanea, and Amblysomus hottentotus. The aim of the study was to provide a comprehensive morphological comparison between the different species and to explore whether anatomical gastrointestinal adaptations are associated with the insectivorous diet of these species. The shape, proportional length, and proportional surface areas of the different gastrointestinal regions were recorded and compared in the three insectivores. Hematoxylin and Eosin (H&E) and Alcian Blue/Periodic Acid Schiff (AB/PAS) were used for morphological assessment. In all three species, the stomach was simple and uncompartmentalized. The internal aspect of the stomach in A. spinosissimus was hemi-glandular, containing stratified squamous epithelium in the fundus, with glandular epithelium in the body and pyloric region. However, C. cyanea and A. hottentotus had wholly glandular stomachs. Paneth cells were not observed in the intestinal tracts of C. cyanea and A. hottentotus. Acomys spinosissimus was the only species studied that had a cecum. The proximal colonic region of A. spinosissimus had V-shaped mucosal folds. Histologically, C. cyanea had villi throughout the entire gastrointestinal tract (GIT), whereas for A. hottentotus villi were not present in the most distal gastrointestinal regions. In both C. cyanea and A. hottentotus, longitudinal mucosal folds were present in the distal part of the colon. The GITs of C. cyanea and A. hottentotus showed little morphological differentiation namely, a simple, glandular stomach and the lack of a cecum.

A comparative histochemical study of the distribution of mucins in the gastrointestinal tracts of three insectivorous mammals.

The distribution of mucous secreting goblet cells was examined in the gastrointestinal tracts of three insectivores namely: Acomys spinosissimus (Southern African spiny mouse), Crocidura cyanea (Reddish gray musk shrew) and Amblysomus hottentotus (Hottentot golden mole) in order to improve our understanding of the quality and composition of the protective intestinal biofilm. Intestinal tracts were fixed and processed to wax for histology. Serial transverse sections were stained using alcian blue-periodic acid Schiff, alcian blue-aldehyde fuchsin and alcian blue-high iron diamine techniques. Photomicrographs of the stained sections were analyzed by quantifying the number of goblet cells containing mucins per mm(2) in the surface epithelial or crypt areas. Neutral mucins predominated in the gastric epithelium of all three insectivores, while sialomucins were absent in the stomach of C. cyanea. In all three species, goblet cells producing a mixture of neutral and acid mucins were most abundant throughout the intestinal tract as were cells secreting a mixture of sulfomucins and sialomucins. However, differences between the insectivore species were observed in the qualitative expression and distribution of mucins throughout the intestinal tract. Similarities between the insectivores of this study and other distantly related species suggest that mixed mucin goblet cells are essential for the formation of the biofilm, irrespective of their diet or taxonomy.

The comparative anatomy of the abdominal gastrointestinal tract of six species of African mole-rats (Rodentia, Bathyergidae).

The gastrointestinal tracts (GITs) of six species of African mole-rats (Bathyergidae) were compared. The aim was to provide a comprehensive anatomical comparison between the different species. The relative shape, length, and surface areas were taken into account to determine whether the GITs are phylogenetically constrained or exhibit anatomical adaptations in response to diets. In all six species the stomach was simple and glandular. With the exception of Heterocephalus glaber, the caecum was coiled in a flat spiral, the ascending colon was arranged in a loop of varying lengths, and a mucosal colonic papillary-lined groove was present in the ascending colon in all species. By contrast, the caecum in H. glaber was uncoiled, the ascending colon was not looped, and the groove was not papillated. A caeco-appendix was observed only in Bathyergus suillus and Georychus capensis. Hierarchical multivariate cluster analysis on the presence/absence of nine anatomical structures associated with the GIT of mole-rats revealed that H. glaber was anatomically the least similar of the six species (77.6% similarity) with respect to the nine GIT variables included. All Cryptomys species were the same (100% similarity), and two species B. suillus and G. capensis grouped together and were more similar to the Cryptomys genus (95% similarity) than they were to H. glaber. These findings support previous phylogenetic classifications. The voluminous caeco-colon in B. suillus may be explained by its ingestion of grasses in addition to below-ground storage organs of plants. We conclude that phylogeny and diet affect the GIT anatomy of the African mole rats studied here.

Homologous substitution of ACE C-domain regions with N-domain sequences: effect on processing, shedding, and catalytic properties.

Angiotensin-converting enzyme (ACE) exists as two isoforms: somatic ACE (sACE), comprised of two homologous N and C domains, and testis ACE (tACE), comprised of the C domain only. The N and C domains are both active, but show differences in substrate and inhibitor specificity. While both isoforms are shed from the cell surface via a sheddase-mediated cleavage, tACE is shed much more efficiently than sACE. To delineate the regions of tACE that are important in catalytic activity, intracellular processing, and regulated ectodomain shedding, regions of the tACE sequence were replaced with the corresponding N-domain sequence. The resultant chimeras C1-163Ndom-ACE, C417-579Ndom-ACE, and C583-623Ndom-ACE were processed to the cell surface of transfected Chinese hamster ovary (CHO) cells, and were cleaved at the identical site as that of tACE. They also showed acquisition of N-domain-like catalytic properties. Homology modelling of the chimeric proteins revealed structural changes in regions required for tACE-specific catalytic activity. In contrast, C164-416Ndom-ACE and C191-214Ndom-ACE demonstrated defective intracellular processing and were neither enzymatically active nor shed. Therefore, critical elements within region D164-V416 and more specifically I191-T214 are required for the processing, cell-surface targeting, and enzyme activity of tACE, and cannot be substituted for by the homologous N-domain sequence.