[The postnatal development of the rat harderian gland. II. Enzyme-histochemical studies]

Cell biology of the harderian gland

The harderian gland is an orbital gland of the majority of land vertebrates. It is the only orbital gland in anuran amphibians since the lacrimal gland develops later during phylogenesis in some reptilian species. Perhaps because it is not found in man, little interest was paid to this gland until about four decades ago. In recent years, however, the scientific community has shown new interest in analyzing the ontogenetic and morphofunctional aspects of the harderian gland, particularly in rodents, which are the preferred experimental model for physiologists and pathologists. One of the main characteristics of the gland is the extreme variety not only in its morphology, but also in its biochemical properties. This most likely reflects the versatility of functions related to different adaptations of the species considered. The complexity of the harderian gland is further shown in its control by many exogenous and endogenous factors, which vary from species to species. The information gained so far points to the following functions for the gland: (1) lubrication of the eye and nictitating membrane, (2) a site of immune response, particularly in birds, (3) a source of pheromones, (4) a source of saliva in some chelonians, (5) osmoregulation in some reptiles, (6) photoreception in rodents, (7) thermoregulation in some rodents, and (8) a source of growth factors.

Postnatal development of the harderian gland in the Syrian golden hamster (Mesocricetus auratus): a light and electron microscopic study

The main objective of the present investigation was to study the morphological and chronological aspects of the development of the Harderian gland in the Syrian golden hamster. Tissues were obtained from male and female hamsters at days 1,3,5,7,10,12,15,17,20,27,37,46, and 90 after birth and processed for light and transmission electron microscopy. The present observations indicate that a well-defined temporal sequence in microscopic and ultrastructural modification is recognizable in the development of the hamster Harderian gland. Four stages of development were proposed. Between days 1-5 (first stage), the gland shows characteristics of an immature structure. The glandular cells contain many free ribosomes, few and small organelles, and large irregular-shape nuclei. Between days 7-17 (second stage), there is a marked increase of organelles involved in synthesis and secretion. The gland begins the secretion of lipids and porphyrins, but no morphological differences between male and female glands are observed. Between days 20-36 (third stage), the morphological differences between the two sexes appear and progressively develop. In 45-day-old hamsters, the Harderian gland possesses the structural characteristics of adult glands, and further developmental changes are essentially quantitative in nature (fourth stage). At all stages of development, the population of secretory cells has a uniform appearance. The morphological results are discussed as well as the possible relationship of this temporal sequence with hormonal changes.

Ultrastructural study of lamellar and nucleolus-like bodies in the harderian gland during postnatal development of the hamster (Mesocricetus auratus)

Membranous structures identified as lamellar bodies (LBs) and dense intracytoplasmic bodies referred to as nucleolus-like bodies (NLBs) have been found in the hamster Harderian gland during neonatal stages. Both structures appear between 8 and 12 postnatal days, coinciding with the beginning of secretory activity. LBs in males and NLBs in both sexes gradually decrease in number with further differentiation of the glandular cells. The morphological features of these cytoplasmic structures are described, and their origin as well as their possible functional significance are discussed.

Ultrastructure of the harderian gland in male albino rats

Harderian glands of adult male albino rats were examined by light and transmission electron microscopy. The animals were divided into the following experimental groups: (1) castrated only, (2) castrated with testosterone replacement and (3) sham operated controls. Two types of secretory cells, designated as A and B, comprise the glandular epithelium and are distinguished on the basis of morphologic differences in the following cellular components: cytoplasmic secretory vacuoles, mitochondria and smooth endoplasmic reticulum (SER). Cell type A is more numerous and contains larger secretory vacuoles than cell type B which is characterized by the presence of large numbers of mitochondria and packet-like arrangement of SER profiles. The glandular secretion appears to be elaborated via merocrine mechanisms and consists primarily of lipids and a fibrogranular substance. The latter component may consist of porph,yrin compounds. Nerve endings are found in the connective tissue interstices of the gland. Direct synapses were not observed in association with either gland cells or myoepithelial cells. Castration did not produce significant alterations in the morphology of the glandular epithelium. Results of the investigation suggest that the rat Harderian gland may serve as a useful model for the study of cellular mechanisms involved in the production of human porphyrias.

[Enzymhistochemical investigations on the Harderian gland of rat and guinea pig under the influence of TSH and thyrohormones (author's transl)]

After application of TSH, trijodthyronine and thyroxine enzyme histochemical investigations were carried out on the Harderian glands of albino rats and guinea pigs. Marked changes were seen after a treatment of 9 days with TSH. Thereby in B-cells of rat appeared big vacuoles, which were clearly to be seen after oxidoreductase-reactions, but hardly to be seen after hydrolase-reactions. In guinea pigs the cells of the gland are strongly vacuolised both in controls and in treated animals. But this last group shows a great hypertrophy of the gland with widening of tubuli and acini. In both species of animals the steroid-3-beta-ol-dehydrogenase-reaction is negative. Nomenclature, specific reactions of the animals treated with hormones, function of the Harderian gland and its relevance in investigations of experimental exophthalmos are discussed.