Detection of Hepatoid Glands and Distinctive Features of the Hepatoid Acinus

In the 1920s–1930s, skin glands of a new type, hepatoid glands, were described in 13 mammal species (Rodentia, Canidae, and Bovidae). The hepatoid glands resemble sebaceous glands in their morphology, bur radically differ from them in specific structure of the acinus and another type of secretion. Later, these data either could not be confirmed or were considered insignificant and the hepatoid glands were described as modified sebaceous glands, glands with uncertain function, or modifications of epidermis. Based on the studies of various hepatoid glands in 22 species of Carniviora and Artiodactyla, the authors described in detail the characteristic features of the hepatoid acinus, which allow a precise discrimination of hepatoid and sebaceous glands. Extracellular secretory canaliculi have been described in the hepatoid glands, as well as the richness of hepatoid glands in protein, distribution of hydrophobic lipids in certain hepatoid glands, and formation of excretory ducts and cysts. The hepatoid glands are a source of great amounts of protein secreted in the merocrine way; the secretory substance of some of these glands has a strong odor.     

Contradictions in Modern Data on the Structure and Function of Dog Hepatoid Circumanal Glands1

Since the 1950s, an erroneous viewpoint has gained a foothold in the special and reference literature that dog hepatoid circumanal glands have an abortive nature, lack efferent ducts, and show no signs of secretory activity. Nevertheless, most modern researchers indicate that these glands are actively functioning structures differentiated to exercise some function according to their histological pattern; however, no one has managed to define this function. The latest international publication (Atoji et al., 1998) considers dog circumanal hepatoid glands as a circumanal body similar to epidermis rather than glands. We discuss strong and weak points of the data on dog hepatoid circumanal glands published in 1950s–1990s in comparison with those obtained in our purposeful long-term investigation of various hepatoid glands. We strongly disagree with the viewpoint of Atoji et al. (1998); hepatoid circumanal glands of dog and other canids should be considered as odor glands, their abundant protein secretion covers the skin surface in the circumanal region, it is preserved on fecal marks, and its smell is perceived during mutual nosing of the anal region.     

Comparative Morphological Analysis of Different Hepatoid Glands: Histological Variants and the Morphofunctional Unit

Three groups can be recognized among hepatoid glands: glands synthesizing protein alone, glands synthesizing protein and hydrophobic lipids and/or melanin, and intermediate glands. Histological variants (seven in total) can be recognized within each group. Different possible combinations of hepatoid glands with other derivatives of hair follicles are considered. The first definition of the morphofunctional unit of hepatoid glands is proposed.__________Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 4, 2005, pp. 428–434.Original Russian Text Copyright © 2005 by Shabadash, Zelikina.     

Once More about Hepatoid Circumanal Glands of Dogs; History of Their Discovery and Causes of Revision of Their Structure and Function

In the skin surrounding the anus in dogs and other Canidae, there is a glandular sheet consisting of strongly developed hepatoid glands, as well as single apocrine glands and a certain number of sebaceous glands, which are much smaller and occur less frequently than the hepatoid glands. All three circumanal glands have excretory ducts connecting with the hair bags (hair funnels). The hepatoid glands of some Canidae and Bovidae were extensively studied in the 1920s–1930s, but from the beginning of the 1950s until the present, as a result of the often repeated mistake passing from one book to another, old information about the hepatoid glands was fully lost, while the new information does not answer the question about the function of this complex and well developed structure. We were successful in repeating the data of the discoverers of the hepatoid glands and proved that these glands are exocrine and that their cells excrete protein to intercellular channels and then to ducts and hair funnels. According to the published data, the odor of the secretory substance of the circumanal hepatoid glands is essential for communication in wolves and dogs.     

Evolutionary origins of the mammary gland

Because the mammary gland has no known homologue among the extant reptiles, attempts to reconstruct its evolution must focus on evidence from living mammals. Of the numerous structures that have been hypothesized to have given rise to the mammary gland, only three remain as plausible progenitors: sebaceous glands, eccrine glands and apocrine glands. Ancestral mammary glands are usually assumed to have produced a copious watery secretion like that of human eccrine sweat glands. However, in terms of anatomy, physiology, development and topographical distribution, mammary glands are more similar to apocrine and sebaceous glands than to typical eccrine glands. Nevertheless, each of the three populations of cutaneous glands exhibit specializations unlikely to be primitive for the mammary gland. The mammary gland either predated full differentiation of mammalian cutaneous glands or, more probably, evolved as a neomorphic mosaic that combined the properties of apocrine and sebaceous glands. Consequently, ancestral, prototypic lacteal glands may have had the capacity to synthesize and secrete small amounts of organic substances, as do sebaceous and apocrine glands of living mammals.     

Cultures of human tracheal gland cells of mucous or serous phenotype

There are two main epithelial cell types in the secretory tubules of mammalian glands: serous and mucous. The former is believed to secrete predominantly water and antimicrobials, the latter mucins. Primary cultures of human airway gland epithelium have been available for almost 20 yr, but they are poorly differentiated and lack clear features of either serous or mucous cells. In this study, by varying growth supports and media, we have produced cultures from human airway glands that in terms of their ultrastructure and secretory products resemble either mucous or serous cells. Of four types of porous-bottomed insert tested, polycarbonate filters (Transwells) most strongly promoted the mucous phenotype. Coupled with the addition of epidermal growth factor (EGF), this growth support produced “mucous” cells that contained the large electron-lucent granules characteristic of native mucous cells, but lacked the small electron-dense granules characteristic of serous cells. Furthermore, they showed high levels of mucin secretion and low levels of release of lactoferrin and lysozyme (markers of native serous cells). By contrast, growth on polyethylene terephthalate filters (Cyclopore) in medium lacking EGF produced “serous” cells in which small electron-dense granules replaced the electron-lucent ones, and the cells had high levels of lactoferrin and lysozyme but low levels of mucins. Measurements of transepithelial resistance and short-circuit current showed that both “serous” and “mucous” cell cultures possessed tight junctions, had become polarized, and were actively secreting Cl.     

The Tail Gland of Canids

The tail gland of canids is a hepatoid glandular organ surrounded and penetrated by powerful hair erector muscles squeezing out its lipoprotein secretion onto the skin surface. The gland is most developed in solitary species (Arctic, red, and corsac foxes) where it is represented by powerful glandular layer with large secretion containers—cisterns. It is less developed in the jackal; there are cisterns but glandular lobes do not merge into a layer. In the raccoon dog, wolf, and domestic dog the gland is composed of small lobes without cisterns. Hepatoid glands of the tail gland are represented by two histological variants distinguished by the presence or absence of hydrophobic lipids in the secretory cells. The excretory ducts are formed by lipid transformation of the cellular bands.     

Expression and function of heregulin-α and its receptors in the mouse mammary gland

Heregulin-α (HRGα) is a cytokine secreted by the mammary mesenchyme, adjacent to lobuloalveolar structures. To understand the role of HRGα and its receptors in mammary glands, and the underlying mechanisms, we performed this study to determine the expression and localization of HRGα and its receptors ErbB2 and ErbB3. We also determined the role of HRGα in the development of mammary glands, β-casein expression and secretion, Rab3A protein expression and the phosphorylation of HRGα signaling molecules using confocal laser scanning microscopy, tissue culture, capillary electrophoresis, Western blotting and enzyme-linked immunosorbent assays. We found that a peak was on pregnancy day 15. Changes of ErbB2 and ErbB3 expression were positively and linearly correlated with HRGα, indicating that HRGα positively regulates ErbB2 and ErbB3 expression. During pregnancy, HRGα enhanced the phosphorylation of STAT5, p42/p44, p38, PKC and Rab3A protein expression, stimulated the proliferation and differentiation of the ductal epithelial cells of mammary glands, and increased and maintained the expression and secretion of β-casein. During lactation, HRGα enhanced the phosphorylation of STAT5 and p38, inhibited the phosphorylation of PKC and Rab3A protein expression, maintained the morphology of the mammary glands and increased the secretion of lactoprotein to reduce the expression of β-casein in mammary epithelial cells. During involution, HRGα induced the phosphorylation of STAT3 and Rab3A protein expression, and inhibited the phosphorylation of PKC to stimulate the degeneration of mammary epithelial cells. It also inhibited the secretion of β-casein, resulting in increased levels of β-casein in mammary epithelial cells.     

Two body fluids containing bovine estrous pheromone(s)

Bovine females produce an estrous pheromone(s). Because onlyother cattle are reliable detectors of the pheromone(s), weevaluated various body fluids (cervico-vaginal mucus, serumand vulval skin gland secretion) with a bull behavioral assayin the absence of a female. It specified 15 behaviors involvingattraction to the body fluids, detection of the stimulus, andsubseqeunt sexual preparation responses. These behaviors werestereotypical and occurred in a specific sequence. We discoveredthat serum (10–15 ml) taken at estrus was behaviorallypositive, as well as vulval skin glands secretion (<1 mlon a swab, dissolved in 5 ml distilled water). We postulatethat vulval skin glands may be a specialized site for the productionor concentration of the pheromone or that the blood transportsthe pheromone(s) either from vulval skin glands or another source.     

The origins of lactation and the evolution of milk: a review with new hypotheses

Lactation is central to mammalian reproduction, and an understanding of the origins of lactation is necessary to comprehend the early evolution of the Class Mammalia. In modern mammals, lactation is a staggeringly complex phenomenon involving morphological, physiological, biochemical, ecological, and behavioural adaptations. Because such a complex web of adaptations could not have arisen de novo, lactation must have begun as a much simpler process. Hypotheses regarding the original adaptive value of proto-lacteal secretions invoke thermoregulatory, antibiotic, behavioural or nutritive functions. In this review, we evaluate each of these hypotheses and attempt to reconstruct the origins of lactation in the light of current concepts of the biology of early mammals and their ancestors, the origin of mammary glands, the evolution of extravitelline nutrient provision, and the physiology and biochemistry of milk synthesis and secretion. Drawing upon empirical evidence and theoretical considerations, we present a gradualistic scenario involving the following steps. First, incubation of eggs was aided by development of a vascularized abdominal incubation patch. Secondly, anti-microbial secretions from cutaneous glands of the incubation patch enhanced survival of eggs or offspring. At this stage, these secretions could have supplemented vitelline nutrients (in much the same way as oviductal secretions do in monotremes), perhaps facultatively. Subsequently, hypertrophy and specialization of cutaneous glands accompanied the controlled production of a copious, nutritious secretion, which eventually evolved into a primary source of energy for development and growth of the offspring. We outline important events in the evolution of milk, and suggest studies likely to provide indirect tests of the evolutionary hypotheses discussed.     

Granular cutaneous glands in the frog Physalaemus biligonigerus (Anura, Leptodactylidae): comparison between ordinary serous and 'inguinal' glands

Beside the ordinary granular (or serous) glands, the skin of the leptodactylid frog Physalaemus biligonigerus possesses peculiar clusters of large granular units, the 'inguinal' glands, located in the dorsolateral areas of the pelvic girdle. Both gland types store their specific products within the syncytial cytoplasm of the secretory unit. These secretory materials consist of spheroidal or ellipsoidal bodies (granules) with a repeating substructure. The subcellular features of the immature products of the ordinary serous and inguinal glands are identical. However, these products undergo divergent maturative processes, leading to fluidation on the one hand and condensation on the other. Secretory release into the small gland lumen was observed in both cases, involving merocrine mechanisms. On the basis of the analysis of cutaneous serous gland polymorphism in anurans, the inguinal units in P. biligonigerus do not appear to be an independent line. Rather, these large units belong to the ordinary serous type and represent a gland population specialized in the storage of remarkable amounts of product used in chemical defence of the skin.     

The histological and histochemical characteristics of the hepatoid circumanal glands in the dog: the features of similarity and difference with the skin glands of other types

Three types of skin glands, the derivatives of the outer root sheath of the hair follicle, have been compared, which are represented by hepatoid, sebaceous and apocrine sweat glands. There are three characteristic properties inherent to hepatoid glands, existence of a network of intercellular secretory tubules, lysis of some secretory cells during the duct formation which is not the fatty transformation and cyst formation.     

Chicken B-cell marker chB6 (Bu-1) is a highly glycosylated protein of unique structure

 The chB6 molecule is expressed on chicken B cells throughout most of their development, as well as on some non-lymphoid cells. It has long been used as an allotypic marker in important studies of B-cell development, though its function is unknown. We isolated a chB6 cDNA by expression cloning and sequenced two further alleles following polymerase chain reaction amplification. The results show that chB6 is a typical type I transmembrane protein, highly glycosylated in the extracellular region and carrying a large intracellular region. It has no recognizable similarity to known mammalian molecules and thus represents a unique B-cell marker. Its presence in chickens may be related to differences in the properties of B-cell development between chickens and mammalian species. The sequences of the different alleles of this gene revealed a higher level of polymorphism than expected. A restriction fragment length polymorphism linked to the CHB6 gene has been used to determine its location on the linkage map of the chicken genome, which will allow the definitive evaluation of reported associations with disease resistance. Received: 21 February 1996 / Revised: 26 March 1996     

Integrin expression in developing human salivary glands

The development and complete differentiation of salivary glands is a complex process that involves a large number of co-ordinated events. Little is known about the molecular basis for salivary gland development. However, we have reported previously that integrins appear to play a role. Integrins are heterodimeric transmembrane receptors consisting of one α and one β subunit that play a pivotal role in the interaction of cells with the extracellular matrix. Such interactions regulate the organisation of cells of tissues and organs during development as well as cell proliferation and differentiation. Using immunohistochemistry and Western and Northern blot analysis, we mapped the localisation and expression of integrins β1, β3 and β4 in human salivary glands obtained from foetuses ranging from weeks 4–24 of gestation and compared it with adult salivary glands. Integrin β1 first appeared during the canalisation stage and during the differentiation stage. A message first appeared at week 6 of development. The expression of β4 integrin protein and message was observed only in the late stage of differentiation. Integrin β3 was not detected in the developing glands; however, integrins β1, β3 and β4 were all expressed in adult salivary gland tissues. The data suggest that integrins, particularly β1, have a role to play in salivary gland development and differentiation.     

Microstructure of skin derivatives as a reflection of phylogenesis of vertebrates

The possibility of using separate signs of microstructure of skin derivatives to understand phylogenesis processes at various hierarchical levels on the example of elasmoid scale of bony fish, feathers of Paleognathae birds, hepatoid glands, and mammal hair was demonstrated and discussed. It was shown that (1) the presence of toothed sclerite growths on the surface of the elasmoid scale of bony fish provided with a central canal can serve as a proof of the evolutional relation of placoid and elasmoid scales; (2) particularities of the microstructure of feathers of Paleognathae birds accord with the branching of their phylogenetic tree; (3) the development of hepatoid glands suggests a phylogenetic relatedness of ancestor forms of cavicorns, Canidae, and Felidae; (4) the subtle construction of horse hair shows the succession of the ancient E. lenensis and northern aborigine breeds of the domestic horse, the direction of the historical process of horse domestication and adaptation of these animals to environmental conditions; (5) similarities in the microstructure of hair of the giant and red panda and bears indicate their evolutional links with Ursidae rather than raccoons.     

Organization of unusual idiosomal glands in a water mite, <Emphasis Type="Italic">Teutonia cometes</Emphasis> (Teutoniidae)

The unusual idiosomal glands of a water mite Teutonia cometes (Koch 1837) were examined by means of transmission and scanning electron microscopy as well as on semi-thin sections. One pair of these glands is situated ventrally in the body cavity of the idiosoma. They run posteriorly from the terminal opening (distal end) on epimeres IV and gradually dilate to their proximal blind end. The terminal opening of each gland is armed with the two fine hair-like mechanoreceptive sensilla (‘pre-anal external’ setae). The proximal part of the glands is formed of columnar secretory epithelium with a voluminous central lumen containing a large single ‘globule’ of electron-dense secretory material. The secretory gland cells contain large nuclei and intensively developed rough endoplasmic reticulum. Secretory granules of Golgi origin are scattered throughout the cell volume in small groups and are discharged from the cells into the lumen between the scarce apical microvilli. The distal part of the glands is formed of another cell type that is not secretory. These cells are composed of narrow strips of the cytoplasm leaving the large intracellular vacuoles. A short excretory cuticular duct formed by special excretory duct cells connects the glands with the external medium. At the base of the terminal opening a cuticular funnel strengthens the gland termination. At the apex of this funnel a valve prevents back-flow of the extruded secretion. These glands, as other dermal glands of water mites, are thought to play a protective role and react to external stimuli with the help of the hair-like sensilla.     

Using cell engineering and omic tools for the improvement of cell culture processes

Significant strides have been made in mammalian cell based biopharmaceutical process and cell line development over the past years. With several established mammalian host cell lines and expression systems, optimization of selection systems to reduce development times and improvement of glycosylation patterns are only some of the advances being made to improve cell culture processes. In this article, the advances pertaining to cell line development and cell engineering strategies are discussed. An overview of the cell engineering strategies to enhance cellular characteristics by genetic manipulation are illustrated, focusing on the use of genomics and proteomics tools and their application in such endeavors. Included in this review are some of the early studies using the ‘omic’ technique to understand cellular mechanisms of product synthesis and secretion, apoptosis, cell proliferation and the influence of the physicochemical environment. The article highlights the significance of integrating genomics and proteomics data with the vast amounts of bioprocess data for improved analysis of the biological pathways involved. Further improvements of the techniques and methodologies used are needed but ultimately, the new cell engineering strategies should provide great insight into the regulatory networks within the cell in a bioprocess environment and how to manipulate them to increase overall productivity.     

Cutaneous eccrine glands of the foot pads of the small Madagascan tenrec (<Emphasis Type="Italic">Echinops telfairi,</Emphasis> Insectivora,Tenrecidae): skin glands in a primitive mammal

In order to find correlations between skin gland morphology and specific ethological features, the cutaneous glands of the foot pads of the primitive mammal the Madagascan tenrec, Echinops telfairi, were studied by histological and various histochemical methods as well as by electron microscopy. In the foot pads specific eccrine skin glands occurred consisting of coiled ducts and tubular secretory portions, the lumina of which were considerably wider than in primate sweat glands. The secretory tubules were composed of branched myoepithelial cells and glandular cells. The latter contained abundant mitochondria, large amounts of glycogen particles and few secretory granules as well as individual heterolysosomes and myelin bodies. The lateral cell membrane was marked by extensive interdigitations. The apical membranes of all glandular cells contained proteoglycans with sulfated and carboxylated groups containing N-acetyl-glucosamine, N-acetyl-galactosamine, galactose and mannose. The expression pattern of cytokeratins of the glandular epithelium was variable and showed similarities to that of the human eccrine glands. Tubulin, vinculin and actin were expressed in the glandular epithelium. The secretory cells showed positive reactions with antibodies against antimicrobial peptides and IgA. A positive reaction was observed with antibodies against the androgen receptor. The PCNA and TUNEL reactions indicated that the tubular skin glands of Echinops are made up of a slowly renewing tissue. We conclude that the glands fulfill several functions: production of a fluid-rich secretory product, which may prevent slipping of the foot pads on the substrate during running or climbing, secretion of antimicrobial peptides and proteins, and playing a role in thermoregulation.We thank the Fendt Foundation for financial support     

Distribution of S-100 protein and its subunits in bovine exocrine glands

 The distribution of S-100 protein and its α- and β-subunits in bovine exocrine glands was studied by indirect immunohistochemistry. The entire spectrum of salivary glands, glands of the respiratory tract, intestinal glands, male and female genital glands, and skin glands was examined. S-100 and its β-subunit were identified in most serous secretory cells of mixed salivary glands, although secretory acini in some serous glands remained unreactive for these antigens. Mucous cells were constantly negative; mucoid cells were positive in the lacrimal and Harderian gland. The α-subunit of S-100 protein was identified in serous cells but the staining reaction was faint. Subunits of S-100 showed a characteristic distribution along the excretory duct systems of compound glands: S-100 and the β-subunit were present in intercalated duct epithelium, while striated duct epithelium stained for S100-α. Therefore, it is suggested that S100-α is related to resorption and secretion in striated ducts, while S100-β may govern acinar exocytosis and probably regulates proliferation and differentiation of glandular cells. Differing staining intensities for S-100 and its subunits in secretory cells of exocrine glands most probably indicate functional differences with regard to secretory activity and the cell cycle. Accepted: 11 February 1997