Therapeutic effect of melatonin in experimental uveitis.

Uveitis is a common ophthalmic disorder that can be induced in hamsters by a single intravitreal injection of bacterial lipopolysaccharide (LPS). To examine the therapeutic effects of melatonin on uveitis, a pellet of melatonin was implanted subcutaneously 2 hours before the intravitreal injection of either vehicle or LPS. Both 24 hours and 8 days after the injection, inflammatory responses were evaluated in terms of i) the integrity of the blood-ocular barrier, ii) clinical signs, iii) histopathological studies, and iv) retinal function. Melatonin reduced the leakage of proteins and cells in the anterior segment of LPS-injected eyes, decreased clinical signs such as dilation of the iris and conjunctival vessels, and flare in the anterior chamber, and protected the ultrastructure of the blood-ocular barrier. A remarkable disorganization of rod outer segment membranous disks was observed in animals injected with LPS, whereas no morphological changes in photoreceptor outer segments were observed in animals treated with melatonin. Furthermore, melatonin prevented a decrease in LPS-induced electroretinographic activity. In addition, melatonin significantly abrogated the LPS-induced increase in retinal nitric-oxide synthase activity, tumor necrosis factor-alpha, and nuclear factor kappaB p50 and p65 subunit levels. These results indicate that melatonin prevents the clinical, biochemical, histological, ultrastructural, and functional consequences of experimental uveitis, likely through a nuclear factor kappaB-dependent mechanism, and support the use of melatonin as a new therapeutic strategy for the treatment of uveitis.

Anatomy, histology, histochemistry and fine structure of the Harderian gland in the South American armadillo Chaetophractus villosus (Xenarthra, Mammalia).

The anatomical, histological, histochemical and ultrastructural characteristics of the Harderian gland of the armadillo Chaetophractus villosus were described. The gland is the largest structure in the bony orbit. It is situated in the anteroventral region of the orbit. Obvious structural differences are not observed between males and females. The gland is compound-branched tubulo-alveolar, being characterized by a single layer of columnar cells surrounded by myoepithelial cells. It possesses a single excretory duct opened into the inner canthus. All glandular cells show yellow-green autofluorescence and additionally some glandular lumen may contain dense autofluorescent solid accretions. There are two peculiar and outstanding cytoplasmic features. One is represented by the smooth endoplasmic reticulum (SER), forming a closely woven meshwork. The other one is represented by "membranous bodies" apparently derived from the SER, RER and cytoskeleton with a "Star of David" configuration situated in the supranuclear region. Three types of vesicles are detected in the cytoplasm. Histochemical staining methods reveal lipids, proteins, neutral and acidic containing glycoconjugates in secretory vesicles. The mechanism of secretion appears either merocrine or apocrine. The epithelium of the intra- and inter-lobular excretory ducts suggests secretory activity. Tubulo-acinar glands similar to those seen in the lacrimal gland and nictitans glands are found related to the intralobular and main excretory ducts. The capillary network is characterized by fenestrated endothelium. The stroma possesses unmyelinated axons and plasma cells. The normal secretion of the secretory endpieces, particularly lipids, proteins and glycoconjugates, is complemented by mucous and serous secretions released by ductal cells and glands associated to the ducts.

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.

New and peculiar cytoplasmic membranous bodies in the acinar cells of the harderian gland of the armadillo Chaetophractus villosus

A new and peculiar morphological feature in acinar cells of the Harderian gland of the South American armadillo Chaetophractus villosus (Mammalia, Dasipodidae) is reported. The gland of adult males and females was studied at macroscopic, microscopic and electron microscopic levels. The gland is the largest structure in the bony orbit. It is located in its medial (nasal) and basal side. It shows a tubuloalveolar structure characterized by large alveoli with a single layer of columnar or cuboidal cells. Myoepithelial cells are located between the secretory ones and the basement membrane. The peculiar morphological feature consists of large intracellular membranous bodies located in the supranuclear cytoplasmic region. They are seen in every acinar cell of males and females. Their size is prominent being almost as large as the nucleus. Only one body is observed in each cell. The structure of the bodies displays an outstanding geometrical pattern which differs completely from other membranous structures described in other species.

New and peculiar cytoplasmic membranous bodies in the acinar cells of the harderian gland of the armadillo Chaetophractus villosus

A new and peculiar morphological feature in acinar cells of the Harderian gland of the South American armadillo Chaetophractus villosus (Mammalia, Dasipodidae) is reported. The gland of adult males and females was studied at macroscopic, microscopic and electron microscopic levels. The gland is the largest structure in the bony orbit. It is located in its medial (nasal) and basal side. It shows a tubuloalveolar structure characterized by large alveoli with a single layer of columnar or cuboidal cells. Myoepithelial cells are located between the secretory ones and the basement membrane. The peculiar morphological feature consists of large intracellular membranous bodies located in the supranuclear cytoplasmic region. They are seen in every acinar cell of males and females. Their size is prominent being almost as large as the nucleus. Only one body is observed in each cell. The structure of the bodies displays an outstanding geometrical pattern which differs completely from other membranous structures described in other species.(AU)