Prolactin levels during the periparturitional period in the biparental cotton-top tamarin (Saguinus oedipus): interactions with gender, androgen levels, and parenting

Unlike biparental bird and rodent species, mating and parenting occur simultaneously in cotton-top tamarins, Saguinus oedipus, providing a unique model for examining endocrine interactions. This study was designed to determine the relationship of prolactin to testicular androgens during parenting and mating. Specifically we examined (1) the patterns of postpartum prolactin excretion in male and female tamarins with and without infant survival; (2) the relationship between androgen and prolactin levels during the periparturitional period in male tamarins; and (3) male hormonal response to the postpartum mating that occurs simultaneously with paternal care. All females showed an elevation in prolactin during the first week postpartum and when infants died, female prolactin levels decreased significantly. Infant survival during the first 15 days did not influence male levels of prolactin, cortisol, or the testicular androgens testosterone and dihydrotestosterone (DHT). Prolactin did not show an inverse relationship with any of the androgens (testosterone, DHT) studied during the postpartum period. No significant differences in hormones were found between prepartum levels and the first, second, and third 5-day blocks postpartum for all 10 males. Males who had infant-care experience showed an increase in testosterone during the first 5 days postpartum and prolactin levels correlated with the number of previous births a male had experienced. However, the most significant changes in testosterone occurred in males whose mates ovulated during the first 15 days following birth in contrast to males whose mates ovulated later than 15 days. These results indicate that unlike females, male tamarins are not showing hormonal changes in response to infants. Urinary androgens did not show an inverse relationship to prolactin in male tamarins, but were elevated concurrent with the female's fertile period.     

Functional morphology of the gills of the shortfin mako,Isurus oxyrinchus,a lamnid shark

This study examines the functional gill morphology of the shortfin mako, Isurus oxyrinchus, to determine the extent to which its gill structure is convergent with that of tunas for specializations required to increase gas exchange and withstand the forceful branchial flow induced by ram ventilation. Mako gill structure is also compared to that of the blue shark, Prionace glauca, an epipelagic species with lower metabolic requirements and a reduced dependence on fast, continuous swimming to ventilate the gills. The gill surface area of the mako is about one‐half that of a comparably sized tuna, but more than twice that of the blue shark and other nonlamnid shark species. Mako gills are also distinguished from those of other sharks by shorter diffusion distances and a more fully developed diagonal blood‐flow pattern through the gill lamellae, which is similar to that found in tunas. Although the mako lacks the filament and lamellar fusions of tunas and other ram‐ventilating teleosts, its gill filaments are stiffened by the elasmobranch interbranchial septum, and the lamellae appear to be stabilized by one to two vascular sacs that protrude from the lamellar surface and abut sacs of adjacent lamellae. Vasoactive agents and changes in vascular pressure potentially influence sac size, consequently effecting lamellar rigidity and both the volume and speed of water through the interlamellar channels. However, vascular sacs also occur in the blue shark, and no other structural elements of the mako gill appear specialized for ram ventilation. Rather, the basic elasmobranch gill design and pattern of branchial circulation are both conserved. Despite specializations that increase mako gill area and efficacy relative to other sharks, the basic features of the elasmobranch gill design appear to have limited selection for a larger gill surface area, and this may ultimately constrain mako aerobic performance in comparison to tunas. J. Morphol. 271:937–948, 2010. © 2010 Wiley‐Liss, Inc.     

Hemolymph microbiome of Pacific oysters in response to temperature,temperature stress and infection

Microbiota provide their hosts with a range of beneficial services, including defense from external pathogens. However, host-associated microbial communities themselves can act as a source of opportunistic pathogens depending on the environment. Marine poikilotherms and their microbiota are strongly influenced by temperature, but experimental studies exploring how temperature affects the interactions between both parties are rare. To assess the effects of temperature, temperature stress and infection on diversity, composition and dynamics of the hemolymph microbiota of Pacific oysters (Crassostrea gigas), we conducted an experiment in a fully-crossed, three-factorial design, in which the temperature acclimated oysters (8 or 22 °C) were exposed to temperature stress and to experimental challenge with a virulent Vibrio sp. strain. We monitored oyster survival and repeatedly collected hemolymph of dead and alive animals to determine the microbiome composition by 16s rRNA gene amplicon pyrosequencing. We found that the microbial dynamics and composition of communities in healthy animals (including infection survivors) were significantly affected by temperature and temperature stress, but not by infection. The response was mediated by changes in the incidence and abundance of operational taxonomic units (OTUs) and accompanied by little change at higher taxonomic levels, indicating dynamic stability of the hemolymph microbiome. Dead and moribund oysters, on the contrary, displayed signs of community structure disruption, characterized by very low diversity and proliferation of few OTUs. We can therefore link short-term responses of host-associated microbial communities to abiotic and biotic factors and assess the potential feedback between microbiota dynamics and host survival during disease.     

A vectored measles virus induces hepatitis B surface antigen antibodies while protecting macaques against measles virus challenge

Hepatitis B virus (HBV) acute and chronic infections remain a major worldwide health problem. Towards developing an anti-HBV vaccine with single-dose scheme potential, we engineered infectious measles virus (MV) genomic cDNAs with a vaccine strain background and expression vector properties. Hepatitis B surface antigen (HBsAg) expression cassettes were inserted into this cDNA and three MVs expressing HBsAg at different levels generated. All vectored MVs, which secrete HBsAg as subviral particles, elicited humoral responses in MV-susceptible genetically modified mice. However, small differences in HBsAg expression elicited vastly different HBsAg antibody levels. The two vectors inducing the highest HBsAg antibody levels were inoculated into rhesus monkeys (Macaca mulatta). After challenge with a pathogenic MV strain (Davis87), control naive monkeys showed a classic measles rash and high viral loads. In contrast, all monkeys immunized with vaccine or a control nonvectored recombinant vaccine or HBsAg-expressing vectored MV remained healthy, with low or undetectable viral loads. After a single vaccine dose, only the vector expressing HBsAg at the highest levels elicited protective levels of HBsAg antibodies in two of four animals. These observations reveal an expression threshold for efficient induction of HBsAg humoral immune responses. This threshold is lower in mice than in macaques. Implications for the development of divalent vaccines based on live attenuated viruses are discussed.     

Innate versus adaptive immunity in sticklebacks: evidence for trade-offs from a selection experiment

In vertebrates, the immune system consists of two arms of different characteristics: the innate and the acquired immune response. Parasites that are only shortly exposed to the immune system are most efficiently attacked by fast, constitutive innate immune mechanisms. Here, we experimentally selected within four fish families for high innate resistance versus susceptibility of three-spined sticklebacks (Gasterosteus aculeatus) against infection with the eye-fluke (Diplostomum pseudospathacaeum), a parasite whose metacercariae are protected from the immune system within the eye lens. We predicted that in families with high susceptibility, the adaptive immune system would be upregulated when challenged with infection. In accordance, we found that MHC class IIB expression is increased by approximately 50% in those lines selected for higher parasite load (i.e. low innate response). This suggests extensive genetic correlations between innate and adaptive immune system and/or crosstalk between both lines of defense. An efficient, specific innate immune response might reduce overall activation of the immune system and potentially alleviate associated effects of immunopathology.     

ESCRT proteins and cell signalling

Subunits of the endosomal sorting complex required for transport (ESCRT) were identified as components of a molecular machinery that sorts ubiquitinated membrane proteins into the intraluminal vesicles (ILVs) of multivesicular endosomes (MVEs) for subsequent delivery to the lumen of lysosomes or related organelles. As many of the membrane proteins that undergo ESCRT-mediated sorting are signalling receptors that are ubiquitinated in response to ligand binding, ESCRT subunits have been hypothesized to play a crucial role in attenuation of cell signalling by mediating ligand-induced receptor degradation. Here we discuss this concept based on the examples from loss-of-function studies in model organisms and cell lines. The emerging picture is that ESCRTs are indeed involved in downregulation of receptor signalling pathways associated with cell survival, proliferation and polarity. In addition, the recent discovery of a positive role for the ESCRT pathway in Wnt signalling through sequestration of an inhibitory cytosolic component into MVEs illustrates that ESCRTs may also control signalling in ways that are independent of degradative receptor sorting.