Skin Gland Secretions Research Articles

Silicon gels with sustainable self-replenishment: Fluid drag reduction through viscosity dependency

Slippery liquid infused surfaces (SLISs) provide excellent dynamic lubrication properties by storing the lubricant internally to form a homogeneous liquid layer to insulate external ambient fluids. However, the kinetic instability caused by lubricant depletion gradually degrades the surface slippery performance. Herein, inspired by skin gland secretion system, silicon gels with sustainable self-replenishment were prepared using polydimethylsiloxane (PDMS) and commercially available dimethyl silicone oils. By carefully tuning the kinematic viscosity and content of infused oil, the surfaces of corresponding silicon gels demonstrated significant syneresis behavior, and the lubricating oils released from the surface were still detected after continuous wiping for more than 120 days. More importantly, when the ratio of working fluid to infused oil was 6.8, the maximum drag reduction of silicon gel in Couette flow could reach up to about 16%, while the surfaces remained long-lasting water repellency under the continuous shear action of encapsulated water. Self-replenishable silicon gels exhibiting strong kinetic stability were expected to provide valuable design insights for robust slippery interfaces.

Naturally occurring variability in larval period length is associated with intraspecific differences in late tadpoles of a South American true toad

AbstractThe larval period in anurans is highly plastic. Even though larval period length and larval size have been the most studied characteristics showing intraspecific variability, other features such as morphology, behavior, food preferences and physiology have also been described as plastic. Metamorphic changes are triggered by thyroid and interrenal hormones, and environmental signals modulate the onset of metamorphosis via the hypothalamic–pituitary–interrenal axis. The South American bufonid toad Rhinella arenarum from nearby Buenos Aires City has a larval period of 30–120 days under the same environmental conditions. The goal of this study was to evaluate life‐history traits in tadpoles from different localities and potential morphological differences among tadpoles with different larval period length. For this purpose, we reared under natural conditions tadpoles from two different localities nearby Buenos Aires City and in three different years measured their size at the end of metamorphosis and recorded their larval period length. The external appearance, histo‐morphology and morphometry of the skin and kidney/interrenal complex were studied in metamorphs with short and long larval periods (SLP and LLP, respectively). We observed a larval period lasting 30–120 days in tadpoles from different localities or years. SLP metamorphs were smaller, darker, had less protruding eyes without eyelids, a thinner epidermis and fewer skin glands than LLP metamorphs. The secretion of skin glands from SLP tadpoles had acidic glycoconjugates. Kidney size was similar between LLP and SLP metamorphs, but the former had an adult‐like histomorphology. Interrenal gland in LLP early and late climax tadpoles had cells with a high nucleus/cell diameter ratio, a sign of highly active steroidogenic cells. Overall, these results show that intraspecific variability in size, skin and interrenal gland development is associated with differences in larval period length. Distinct skin gland number and secretion, along with distinct interrenal histology at late climax, could have physiological consequences in the post‐metamorphic life.

Functional Protein Composition in Femoral Glands of Sand Lizards (Lacerta agilis).

Proteins are ubiquitous macromolecules that display a vast repertoire of chemical and enzymatic functions, making them suitable candidates for chemosignals, used in intraspecific communication. Proteins are present in the skin gland secretions of vertebrates but their identity, and especially, their functions, remain largely unknown. Many lizard species possess femoral glands, i.e., epidermal organs primarily involved in the production and secretion of chemosignals, playing a pivotal role in mate choice and intrasexual communication. The lipophilic fraction of femoral glands has been well studied in lizards. In contrast, proteins have been the focus of only a handful of investigations. Here, we identify and describe inter-individual expression patterns and the functionality of proteins present in femoral glands of male sand lizards (Lacerta agilis) by applying mass spectrometry-based proteomics. Our results show that the total number of proteins varied substantially among individuals. None of the identified femoral gland proteins could be directly linked to chemical communication in lizards, although this result hinges on protein annotation in databases in which squamate semiochemicals are poorly represented. In contrast to our expectations, the proteins consistently expressed across individuals were related to the immune system, antioxidant activity and lipid metabolism as their main functions, showing that proteins in reptilian epidermal glands may have other functions besides chemical communication. Interestingly, we found expression of the Major Histocompatibility Complex (MHC) among the multiple and diverse biological processes enriched in FGs, tentatively supporting a previous hypothesis that MHC was coopted for semiochemical function in sand lizards, specifically in mate recognition. Our study shows that mass spectrometry-based proteomics are a powerful tool for characterizing and deciphering the role of proteins secreted by skin glands in non-model vertebrates.

An insight into the skin glands, dermal scales and secretions of the caecilian amphibian Ichthyophis beddomei.

The caecilian amphibians are richly endowed with cutaneous glands, which produce secretory materials that facilitate survival in the hostile subterranean environment. Although India has a fairly abundant distribution of caecilians, there are only very few studies on their skin and secretion. In this background, the skin of Ichthyophis beddomei from the Western Ghats of Kerala, India, was subjected to light and electron microscopic analyses. There are two types of dermal glands, mucous and granular. The mucous gland has a lumen, which is packed with a mucous. The mucous-producing cells are located around the lumen. In the granular gland, a lumen is absent; the bloated secretory cells, filling the gland, are densely packed with granules of different sizes which are elegantly revealed in TEM. There is a lining of myo-epithelial cells in the peripheral regions of the glands. Small flat disk-like dermal scales, dense with squamulae, are embedded in pockets in the dermis, distributed among the cutaneous glands. 1-4 scales of various sizes are present in each scale pocket. Scanning electron microscopic observation of the skin surface revealed numerous glandular openings. The skin gland secretions, exuded through the pores, contain fatty acids, alcohols, steroid, hydrocarbons, terpene, aldehyde and a few unknown compounds.

Marinobufagenin extraction from Rhinella marina toad glands: Alternative approaches for a systematized strategy.

Marinobufagenin is a bufadienolide compound detected mainly in skin and parotoid gland secretions of Rhinella marina (L.) toad. Bufadienolides regulate the Na+ /K+ -ATPase pump by inhibiting the cardiotonic steroid dependent-site and act as cardiac inotropes with vasoconstrictive properties. Marinobufagenin and other bufadienolides, such as telocinobufagin and bufalin, are thought to be found endogenously in mammals in salt-sensitive hypertensive states such as essential hypertension, congestive heart-failure, and preeclampsia. The role of marinobufagenin as antimicrobial agent and its cytotoxic potential have also been recognized. The particular interest around marinobufagenin prompts us to consider the Rhinella marina toad venom as a possible source for molecules with pharmacological and/or diagnostic potential. In this article, two different approaches of extraction and purification of marinobufagenin from Rhinella marina (L.) venom are studied: (i) Preparative thin-layer chromatography combined to mass spectrometry and/or ultraviolet detection and (ii) solid-phase extraction coupled with fractionation on high-performance liquid chromatography. Different chromatographic conditions are tested for each approach. The solid-phase extraction combined with high-performance liquid chromatography fractionation approach was preferred as it offered a greater yield, was less time-consuming and allowed us to selectively isolate marinobufagenin. Both protocols aim to provide efficient and convenient methods for toad venom extraction, based on an easily automatable and systematized strategy.

Mass spectrometry-directed structure elucidation and total synthesis of ultra-long chain (O-acyl)-ω-hydroxy fatty acids

The (O-acyl)-ω-hydroxy FAs (OAHFAs) comprise an unusual lipid subclass present in the skin, vernix caseosa, and meibomian gland secretions. Although they are structurally related to the general class of FA esters of hydroxy FAs (FAHFAs), the ultra-long chain (30-34 carbons) and the putative ω-substitution of the backbone hydroxy FA suggest that OAHFAs have unique biochemistry. Complete structural elucidation of OAHFAs has been challenging because of their low abundance within complex lipid matrices. Furthermore, because these compounds occur as a mixture of closely related isomers, insufficient spectroscopic data have been obtained to guide structure confirmation by total synthesis. Here, we describe the full molecular structure of ultra-long chain OAHFAs extracted from human meibum by exploiting the gas-phase purification of lipids through multi-stage MS and novel multidimensional ion activation methods. The analysis elucidated sites of unsaturation, the stereochemical configuration of carbon-carbon double bonds, and ester linkage regiochemistry. Such isomer-resolved MS guided the first total synthesis of an ultra-long chain OAHFA, which, in turn, confirmed the structure of the most abundant OAHFA found in human meibum, OAHFA 50:2. The availability of a synthetic OAHFA opens new territory for future investigations into the unique biophysical and biochemical properties of these lipids.

Skin glands of an aquatic salamander vary in size and distribution and release antimicrobial secretions effective against chytrid fungal pathogens.

Amphibian skin is unique among vertebrate classes, containing a large number of multicellular exocrine glands that vary among species and have diverse functions. The secretions of skin glands contain a rich array of bioactive compounds including antimicrobial peptides (AMPs). Such compounds are important for amphibian innate immune responses and may protect some species from chytridiomycosis, a lethal skin disease caused by the fungal pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal). While the bioactivity of skin secretions against Bd has been assessed for many amphibian taxa, similar studies are lacking for Bsal, a chytrid fungus that is especially pathogenic for salamanders. We studied the skin glands and their potential functions in an aquatic salamander, the three-toed amphiuma (Amphiuma tridactylum). Skin secretions of captive adult salamanders were analyzed by RP-HPLC and tested against the growth of Bd and Bsal using in vitro assays. We found that compounds within collected skin secretions were similar between male and female salamanders and inhibited the growth of Bd and Bsal. Thus, skin secretions that protect against Bd may also provide protection against Bsal. Histological examination of the skin glands of preserved salamanders revealed the presence of enlarged granular glands concentrated within caudal body regions. A site of potential gland specialization was identified at the tail base and may indicate specialized granular glands related to courtship and communication.

Identification of Bufadienolides from the Boreal Toad, Anaxyrus boreas, Active Against a Fungal Pathogen.

Amphibian granular glands provide a wide range of compounds on the skin that defend against pathogens and predators. We identified three bufadienolides-the steroid-like compounds arenobufagin, gamabufotalin, and telocinobufagin-from the boreal toad, Anaxyrus boreas, through liquid chromatography mass spectrometry (LC/MS). Compounds were detected both after inducing skin gland secretions and in constitutive mucosal rinses from toads. We described the antimicrobial properties of each bufadienolide against Batrachochytrium dendrobatidis (Bd), an amphibian fungal pathogen linked with boreal toad population declines. All three bufadienolides were found to inhibit Bd growth at similar levels. The maximum Bd inhibition produced by arenobufagin, gamabufotalin, and telocinobufagin were approximately 50%, in contrast to the complete Bd inhibition shown by antimicrobial skin peptides produced by some amphibian species. In addition, skin mucus samples significantly reduced Bd viability, and bufadienolides were detected in 15 of 62 samples. Bufadienolides also appeared to enhance growth of the anti-Bd bacterium Janthinobacterium lividum, and thus may be involved in regulation of the skin microbiome. Here, we localized skin bacteria within the mucus layer and granular glands of toads with fluorescent in situ hybridization. Overall, our results suggest that bufadienolides can function in antifungal defense on amphibian skin and their production is a potentially convergent trait similar to antimicrobial peptide defenses found on the skin of other species. Further studies investigating bufadienolide expression across toad populations, their regulation, and interactions with other components of the skin mucosome will contribute to understanding the complexities of amphibian immune defense.

Biological activities of skin and parotoid gland secretions of bufonid toads (Bufo bufo, Bufo verrucosissimus and Bufotes variabilis) from Turkey.

Toad glandular secretions and skin extractions contain numerous natural agents which may provide unique resources for novel drug development. Especially the skin-parotoid gland secretions of toads from genus Bufo contain as many as 86 different types of active compounds, each with the potential of becoming a potent drug. In the present study, crude skin-parotoid gland secretions from Bufo bufo, Bufo verrucosissimus and Bufotes variabilis from Turkey were screened against various cancer cells together with normal cells using MTT assay. Furthermore, the antimicrobial properties of skin secretions were tested on selected bacterial and fungal species for assessing the possible medical applications. Antimicrobial activity of skin secretions was studied by determining minimal inhibitory concentration (MIC) in broth dilution method. Hemolytic activity of each skin-secretion was also estimated for evaluating pharmaceutical potential. Both skin-parotoid gland secretions showed high cytotoxic effect on all cancerous and non-cancerous cell lines with IC50 values varying between <0.1μg/ml and 6.02μg/ml. MIC results of antimicrobial activity tests were found to be between 3.9μg/ml and 250μg/ml. No hemolytic activities on rabbit red blood cells at concentrations between 0.5μg/ml and 50μg/ml were observed. In conclusion, skin-parotoid secretions of bufonid toads might be remarkable candidates for anti-cancer and antimicrobial agents without hemolytic activities.

Hybrid advantage in skin peptide immune defenses of water frogs (Pelophylax esculentus) at risk from emerging pathogens

Heterogeneity in immune defense effectors can benefit hosts encountering a variety of parasites and pathogens. Antimicrobial peptides (AMPs) are a diverse set of immune defense effectors in many amphibians, and are secreted from dermal granular glands to protect the skin from infection. Over 50 different skin peptides have been reported from the European water frog hybridogenic complex (Pelophylax esculentus complex), consisting of the hybrid P. esculentus, and the parent species Pelophylax lessonae and Pelophylax ridibundus. In central Europe the hybrid is sympatric with only P. lessonae, while in other areas all three species can co-occur. Amphibian immune defenses are likely under selective pressure from emerging pathogens such as the chytrid fungus Batrachochytrium dendrobatidis (Bd). To assess if hybridization affects immune defenses against Bd, we compared skin peptides of the three species in terms of (i) quantity, (ii) activity against Bd, (iii) repertoire, and (iv) stability. Hybrids secreted AMPs at higher quantities and with greater fungicidal activity compared to cohabiting P. lessonae. Compared to P. ridibundus, AMPs from hybrids were of similar quantity but slightly greater antifungal activity. Mass spectrometric analyses (MALDI-TOF) revealed that of all three species P. esculentus has the greatest peptide diversity, a repertoire inclusive of peptides occurring in either one or the other parent species. Measurements of degradation dynamics indicate that peptides remain relatively stable on the skin of all species for over an hour after induction of skin gland secretions. Our data demonstrate that the hybrid has more effective peptide defenses against Bd and a richer peptide repertoire than either parent species. Hybrid advantage in environments hosting virulent pathogens may contribute to disassortative mating preferences, and we suggest that AMP diversity may be analogous to major histocompatibility complex (MHC) heterozygosity by benefiting hosts encountering multiple parasites.

An unusual kynurenine‐containing opioid tetrapeptide from the skin gland secretion of the Australian red tree frog Litoria rubella. Sequence determination by electrospray mass spectrometry

The Kyn-containing peptide FP-Kyn-L(NH(2)) is an unusual minor component of the skin peptide profile of the Australian red tree frog Litoria rubella collected from an area within a 20 kilometre radius of Alice Springs in central Australia. The structure was determined by electrospray mass spectrometry and synthesis. The major component of the skin secretion is the analogous tryptophyllin peptide FPWL(NH(2)). Both peptides show opioid activity at 10(-7) M, and are likely to act via the μ opioid receptor.

Chemocommunication among domestic cats, mediated by the olfactory and vomeronasal senses. I. Chemocommunication.

Chemocommunication functions are known in many social mammals, such as gerbils, hamsters, and deer. But also mammals known as at least partly solitary do communicate by chemical signals. The existence and use of pheromones in domestic cats was the subject of this study. It turned out that male and female cats spent much time in exploring their own and foreigners' urine and skin gland secretion rubbed off on several objects. Male receivers performed sniffing and flehmen more frequently than females on the same urine, whereas female cats paid more attention to skin gland secretion. Both urine and cheek gland secretion of the female donor appeared to contain pheromones which inform the tomcat about her hormonal phase.

Composition of indolealkylamines of Bufo rubescens cutaneous secretions compared to six other Brazilian bufonids with phylogenetic implications

The composition of indolealkylamines of Bufo rubescens cutaneous secretions was compared to those from six other Brazilian bufonids. Skin, parotoid and tibial gland secretions were obtained for analysis by thin-layer chromatography. A triple-quadrupole mass spectrometer was used to confirm the indolealkylamines standards (serotonin, 5-HT; bufotenin, BTN; dehydrobufotenin, DHB and bufotenidin, BTD). We observed clear variation in the composition of indolealkylamines of the cutaneous secretions studied and also between those found in the skin and parotoid gland secretions of the same species. We discuss the utility of indolealkylamines to the phylogeny of this group of toads.

Odorant source used in Eurasian beaver territory marking.

Mammals use urine, feces, or the secretion of specialized skin glands to mark their territories. These sources can carry different information and, thus, have different functions. Presently it is not known if beavers (Castor spp.) deposit castoreum (primarily a mixture of secondary metabolites from urine) from the castor sacs and secretion from the anal glands (AGS) together or alone when scent marking their territories. We hypothesized that castoreum would be the main scent signal used in the defense of beaver territories during winter and predicted that castoreum would be deposited more often than AGS. A total of 96 scent marks on snow were collected from January 1 to March 31, 1997-1999 in the Bø River, Telemark County, Norway. In order to obtain control material, we chemically analyzed AGS and castoreum from 60 dead beavers collected during January-May 1997-1999. We compared the compounds found in the dead beavers with compounds found in the scent marks on snow. Samples were analyzed by using gas chromatography-mass spectrometry (GC-MS). All 96 scent marks contained compounds from castoreum, whereas compounds from AGS were found in only four scent marks. This suggests that beavers do not specifically deposit AGS on scent mounds as they do with castoreum and that the AGS compounds we found probably were remnants of AGS from the feet or fur following pelt lubrication or coprophagy behavior. We conclude that castoreum is the main scent signal used in the defense of beaver territories during winter.

Host Defence Antibacterial Peptides from Skin Secretions of Australian Amphibians. The Relationship Between Structure and Activity

Abstract: Peptides have been isolated and characterised from the secretions of skin glands of twenty five species of Australian amphibian. Many peptides are host defence agents, showing, for example, neuropeptide and/or antibacterial activity. This review describes the relationship between activity and structure of the antibacterial peptides, particularly the caerin and uperin groups of peptide from the genera Litoria and Uperoleia.

Sex-Specific Regulation of Marking Behavior by Sex Hormones and Conspecifics Scent in Tree Shrews (Tupaia belangeri)

HOLST, D. v. AND F. EICHMANN.Sex-specific regulation of marking behavior by sex hormones and conspecifics scent in tree shrews (Tupaia belangeri).PHYSIOL BEHAV 63(2) 157–164, 1998.—In tree shrews (Tupaia belangeri), both males and females mark their surroundings with urine and skin gland secretions. In this study we examined in standard tests the modulation of marking behavior of male and female tree shrews by hormones and chemical signals of conspecifics. Males mark more frequently than females in the absence of conspecific scent. Female scent elicits only low marking responses in both sexes. Male scent stimulates marking of both sexes, with a much higher response in females. Increasing amounts of male scent result in a corresponding increase in marking by females. In contrast, male marking is maximally stimulated by low scent concentrations of male conspecifics, whereas higher scent concentrations inhibit male marking. Gonadectomy diminishes male marking activities under all scent conditions, whereas in females only the response to male scent is reduced. In unscented cages, the low marking activities of castrated males and intact females are stimulated by treatment with testosterone or estradiol. In the presence of male scent, however, only testosterone, but not estradiol, stimulates marking of castrated males. Marking of intact males or females is not increased by either hormone. As this study shows, external (scent of conspecifics) and internal factors (sex hormone levels) interact to regulate tree shrews’ marking behavior in a sex-specific manner. These results are discussed with respect to the sex-specific contexts and functions of tree shrews’ marking behavior.

Chemoreception in Crocodilians: Anatomy, Natural History, and Empirical Results

Anatomical and behavioral aspects of chemoreception in crocodilians are reviewed. Extant crocodilians possess valvular nostrils regulated by smooth muscles; paired nasal cavities, each with three conchae; and flaps closing the rear of the buccopharyngeal passage to channel inspired air through the nasopharyngeal duct. Olfaction is enhanced by gular pumping, whereby the floor of the pharynx is alternately lowered and raised to pulse air through the nasal cavity. Taste buds occur on the tongue, palate, and pharyngeal walls. Crocodilians in nature or in semi-natural enclosures locate distant carrion or concealed meat, implying chemoattraction to food. The American alligator exhibits underwater head-waving and mouth-opening in response to aqueous and chloroform extracts of meat. Alligators increase gular pumping in response to the scents of various meats, indicating that they detect food chemicals by olfaction. Paired gular and paracloacal glands on the integument of crocodilians are thought to produce pheromones. Juvenile crocodilians exhibit heightened gular pumping in response to airborne skin gland secretions. Observations of adults suggest that gular and paracloacal glands produce chemical signals used in mating and/or nesting activities, but behavioral responses to skin gland exudates are too poorly documented to ascribe pheromonal properties.

A chemistry of mammalian pheromones

Many mammalian social odors do not elicit an observable specific response in the recipient and therefore strictly cannot be considered to be pheromones. The pheromones now known in mammals are mostly transferred by contact and detected by accessory olfaction, which further indicates that pheromones in mammals should not be considered to be even a subclass of social odors. Aphrodisin, a female hamster pheromone that elicits sexual behavior in male hamsters, is a member of the lipocalycin family of 20 kDa extracellular proteins, and it is most closely related to rat odorant binding protein. Homologous proteins occur in the urine and scent glands of mice, rats and possibly voles, where they may serve as pheromone binding proteins. A 20 kDa protein, pheromaxein, binds the known pheromones androstenol and related steroids in boar saliva, and uncharacterized small proteins have been found in monkey and human skin gland secretions. Thus it appears that proteins may generally be associated with mammalian pheromones.

Gular and paracloacal gland secretions of crocodilians: A comparative analysis by thin-layer chromatography

The gular and the paracloacal gland secretions of 21 crocodilian species, including representatives of all extant genera— Alligator, Caiman, Crocodylus, Gavialis, Melanosuchus, Osteolaemus, Paleosuchus, and Tomistoma—were analysed by thin-layer chromatography. Secretions from one adult male and one adult female were examined separately for most species. Gular and paracloacal gland chromatograms display bands consistent with sterols, free fatty acids, triglycerides, steryl esters, and other compound classes. Comparisons of gular and paracloacal chromatograms of each species suggest qualitative and/or quantitative differences in the compounds produced in each gland type. Our results provide tentative evidence for taxonomic variation in crocodilian skin gland secretions. Comparisons of gular and paracloacal gland chemicals of extant species allow inferences to be made on the chemicals produced by these organs in ancestral crocodilians.

Call and skin glands secretion induced by stimulation of midbrain in urodele ( Andrias davidianus)

Stimulation of the midbrain induced calls, gaping, tail lashing, locomotion and secretion of skin glands in the cryptobranchidae, Andrias davidianus, which is a rare precious animal in China. These responses can be considered as a complex of action related to escape. Most of the sites where calls and secretion of skin glands could be induced were found in the outside of central nucleus of the torus semicularis. This is the first description of this cluster of functions in the midbrain of Andrias davidianus.