Acyl-CoA-binding protein in the armadillo Harderian gland: its primary structure and possible role in lipid secretion

The organ of vision morphology of the southern two-toed sloth (Choloepus didactylus Linnaeus, 1758; Pilosa, Choloepodidae)

The Choloepus didactylus is a species belonging to the Choloepodidae family of the Folivora suborder. This study concerns the anatomical, morphometrical, histological and histochemical examination of the eye tunics, eyelids and orbital glands in the three adult Choloepus didactylus coming from the Wroclaw Zoological Garden. The cornea consists of four layers since Bowman's membrane was absent. The presence of palisades of Vogt formed from 14/15 to 20/21 layers of epithelial cells was demonstrated. Macroscopically, the tapetum lucidum was not identified, while degenerative choroidal tapetum lucidum cellulosum was found microscopically. The ciliary muscle was found with our histological approach. The pupil was round in shape (post-mortem). The presence of tarsal glands has not been demonstrated in both eyelids. The conjunctiva-associated lymphoid tissue (CALT) has been shown in the upper and lower eyelids. The superficial gland of the third eyelid produced a seromucous secretion. The third eyelid was shaped like a curved arch and composed of hyaline cartilage. The deep gland of the third eyelid was big and multilobar acinar simple with serous character. The lacrimal gland produced mucous secretion. The results of our research indicate that the features of the eye anatomy in the southern two-toed sloth (C. didactylus) are also typical of the Folivora suborder and have common features and differences with Vermilingua.

Structure of armadillo ACBP: a new member of the acyl-CoA-binding protein family

The X-ray structure of the tetragonal form of apo acyl-CoA-binding protein (ACBP) from the Harderian gland of the South American armadillo Chaetophractus villosus has been solved. ACBP is a carrier for activated long-chain fatty acids and has been associated with many aspects of lipid metabolism. Its secondary structure is highly similar to that of the corresponding form of bovine ACBP and exhibits the unique flattened alpha-helical bundle (up-down-down-up) motif reported for animal, yeast and insect ACBPs. Conformational differences are located in loops and turns, although these structural differences do not suffice to account for features that could be related to the unusual biochemistry and lipid metabolism of the Harderian gland.

Catabolism of the octadecaneuropeptide ODN by prolyl endopeptidase: identification of an unusual cleavage site

The octadecaneuropeptide ODN (QATVGDVNTDRPGLLDLK), a biologically active fragment of diazepam-binding inhibitor, exerts a number of behavioral and neurophysiological activities. The presence of a proline residue in the sequence of ODN led us to investigate the role of proline endopeptidase (PEP) in the catabolism of this neuropeptide. The effect of PEP on the breakdown of ODN and related analogs was studied by combining RP-HPLC analysis and MALDI-TOF MS characterization. Incubation of ODN with PEP generated two products, i.e. ODN3-18 and ODN5-18 which resulted from cleavage of the Ala-Thr and Val-Gly peptide bonds. S 17092, a specific PEP inhibitor, significantly reduced the PEP-induced cleavages of ODN. Similarly, [Ala2]OP showed S 17092-sensitive post-alanine cleavage, while [pGlu1]ODN and OP (ODN11-18) were not catabolized by the enzyme. For all these peptides, cleavage of the Pro-Gly peptide bond by PEP was never observed, even after prolonged incubation times. In contrast, PEP hydrolyzed human urotensin II at the canonical post-proline site. Collectively, these data suggest that the Ala2 residue is the preferential cleavage site of ODN and that the Pro-Gly bond of ODN is not hydrolyzed by PEP. In addition, this study reveals for the first time that the endoproteolytic activity of PEP can specifically take place after a valine moiety.

Optical characterization of armadillo acyl-CoA binding protein

Acyl-CoA binding protein (ACBP) and fatty acid binding protein (FABP) are intracellular transporters of activated and free fatty acids, respectively. Unlike other tissues with active lipid metabolism, armadillo Harderian gland contains much more ACBP than FABP. To characterize armadillo ACBP structure and binding properties, we produced it in Escherichia coli and carried out detailed fluorescence and circular dichroism spectroscopy studies. The K(D) for palmitoyl-CoA, measured directly by fluorescence and rotatory power, was 34+/-12 and 75+/-39 nM, respectively. The structure of armadillo ACBP appears to be very similar to that of bovine and rat liver ACBPs.

Histology, histochemistry and fine structure of the lacrimal and nictitans gland in the South American armadillo Chaetophractus villosus (Xenarthra, Mammalia)

The anatomical, histological, histochemical and ultrastructural characteristics of the lacrimal gland (LG) and nictitans gland (NG) of the armadillo Chaetophractus villosus were described. The histochemical and histological features of both glands in male and female adult animals were compared. The tissues were processed with conventional techniques for light and transmission electron microscopy. Fixed specimens were submitted to a battery of tests for glycans, glycosaminglycans, glycoconjugates, proteins, and lipids. The LG of the armadillo may be considered within the set of glandulae lacrimales superior in which primates, carnivores, perisodactyls and artiodactyls are included. The localization of the NG was similar to that of other mammals. Lacrimal and NG were histologically and histochemically identical. The secretory endpieces consisted of three cell types: (1) Mucous cells (MC) with different types of mucous secretory granules with neutral and sialic acid-containing glycoconjugates (GCs). (2)Seromucous cells (SMC) showing a variety of moderately electron dense secretory granules with flocculent material with carboxylated acidic, neutral, and sialic acid-containing GCs. Intercellular canaliculi with junctional complexes and basolateral intercellular spaces were frequent. (3) Serous cells (SC) with electron dense secretory granules. Histochemically, they showed the strongest reaction for proteins and neutral, weakly acid and carboxylated acidic GCs. The epithelium of the intra- and inter-lobular excretory ducts showed secretory activity, junctional complexes, and wide basolateral intercellular spaces with lateral folds. The endpieces and ducts were surrounded by myoepithelial cells. The stroma was characterized by fenestrated endothelium, unmyelinated axons, and abundant plasma cells. MC, SMC, and the duct system were richly innervated by hypolemmal nerve terminals.

Magnetic resonance imaging of the rat Harderian gland

The intra-orbital lacrimal gland (Harderian gland, or HG) of the female rat was studied by magnetic resonance imaging (MRI) to evaluate whether MRI can be used to visualize the gland in vivo and localized-1H-spectroscopy detect its lipid content. The results were correlated with post-mortem anatomical sections, and with light and electron microscopy. On MRI, HG presented as a mass located between the ocular bulb and the orbit. In strongly T2W sequences the secretory structures had a reduced signal while intraparenchymal connective tissue was visible. T2-quantitative maps values of HG (60.12 +/- 8.15 ms, mean +/- SD) were different from other tissues (i.e. muscular tissue, T2 = 44.79 +/- 3.43 ms and olfactory bulb, T2 = 79.26 +/- 4.25 ms). In contrast-enhanced-MRI, HG had a signal-intensity-drop of 0.074 +/- 0.072 (mean +/- SD), after injection of AMI-25, significantly different from the muscle (0.17 +/- 0.10). Localized MRI spectra gave a large part of the signal originating from fat protons, but with a significant percentage from water protons. At light and electron microscopy the lipid deposition appeared to be composed of low-density material filling a large part of the cytoplasm, and the porphyrin aggregates were easily recognizable. The data demonstrate that an in vivo study of the HG was feasible and that high-field MRI allowed analysis of the gross anatomy detecting the lipid content of the gland.