The effects of chronic immune stimulation on muscle growth in rainbow trout

Successful production of aquaculture species depends on efficient growth with low susceptibility to disease. Therefore, selection programs have focused on rapid growth combined with disease resistance. However, chronic immune stimulation diminishes muscle growth (a syndrome referred to as cachexia), and decreases growth efficiency in production animals, including rainbow trout. In mammals, recent results show that increased levels of pro-inflammatory cytokines, such as those seen during an immune assault, specifically target myosin and MyoD and inhibit muscle growth. This suggests that increased disease resistance in fish, a desired trait for production, may actually decrease the growth of muscle, the main aquacultural commodity. To test this possibility, a rainbow trout model of cachexia was developed and characterized. A six-week study was conducted in which rainbow trout were chronically immune stimulated by repeated injections of LPS. Growth indices were monitored, and whole body and muscle proximate analyses, real-time PCR, and Western blotting were conducted to examine the resulting cachectic phenotype. Muscle ratio was decreased in fish chronically immunostimulated, however expression levels of MyoD2 and myosin were not decreased compared to fish that were not immunostimulated, indicating that while muscle accretion was altered, the mechanism by which it occurred was somewhat different than that characterized in mammals. Microarray analysis was used to compare gene expression in fish that had been chronically immunostimulated versus those that had not to identify possible alternative mechanisms of cachexia in fish.     

Allelic and phenotypic spectrum of plasma triglycerides

The genetic underpinnings of both normal and pathological variation in plasma triglyceride (TG) concentration are relatively well understood compared to many other complex metabolic traits. For instance, genome-wide association studies (GWAS) have revealed 32 common variants that are associated with plasma TG concentrations in healthy epidemiologic populations. Furthermore, GWAS in clinically ascertained hypertriglyceridemia (HTG) patients have shown that almost all of the same TG-raising alleles from epidemiologic samples are also associated with HTG disease status, and that greater accumulation of these alleles reflects the severity of the HTG phenotype. Finally, comprehensive resequencing studies show a burden of rare variants in some of these same genes - namely in LPL, GCKR, APOB and APOA5 - in HTG patients compared to normolipidemic controls. A more complete understanding of the genes and genetic variants associated with plasma TG concentration will enrich our understanding of the molecular pathways that modulate plasma TG metabolism, which may translate into clinical benefit. This article is part of a Special Issue entitled Triglyceride Metabolism and Disease.     

The chromodomain-containing NH<Subscript>2</Subscript>-terminus of Chromator interacts with histone H1 and is required for correct targeting to chromatin

The chromodomain protein, Chromator, can be divided into two main domains, a NH₂-terminal domain (NTD) containing the chromodomain (ChD) and a COOH-terminal domain (CTD) containing a nuclear localization signal. During interphase Chromator is localized to chromosomes; however, during cell division Chromator redistributes to form a macro molecular spindle matrix complex together with other nuclear proteins that contribute to microtubule spindle dynamics and proper chromosome segregation during mitosis. It has previously been demonstrated that the CTD is sufficient for targeting Chromator to the spindle matrix. In this study, we show that the NTD domain of Chromator is required for proper localization to chromatin during interphase and that chromosome morphology defects observed in Chromator hypomorphic mutant backgrounds can be largely rescued by expression of this domain. Furthermore, we show that the ChD domain can interact with histone H1 and that this interaction is necessary for correct chromatin targeting. Nonetheless, that localization to chromatin still occurs in the absence of the ChD indicates that Chromator possesses a second mechanism for chromatin association and we provide evidence that this association is mediated by other sequences residing in the NTD. Taken together these findings suggest that Chromator's chromatin functions are largely governed by the NH₂-terminal domain whereas functions related to mitosis are mediated mainly by COOH-terminal sequences.     

The species–area relationship in centipedes (Myriapoda: Chilopoda): a comparison between Mediterranean island groups

The present study article examines the shapes of centipede species–area relationships (SARs) in the Mediterranean islands, compares the results of the linear form of the power model between archipelagos, discusses biological significance of the power model parameters with other taxa on the Aegean archipelago, and tests for a significant small‐island effect (SIE). We used 11 models to test the SARs and we compared the quality‐of‐fit of all candidate models. The power function ranked first and Z‐values was in the range 0.106–0.334. We assessed the presence of SIEs by fitting both a continuous and discontinuous breakpoint regression model. The continuous breakpoint regression functions never performed much better than the closest discontinuous model as a predictor of centipede species richness. We suggest that the relatively low Z‐values in our data partly reflect better dispersal abilities in centipedes than in other soil invertebrate taxa. Longer periods of isolation and more recent island formation may explain the somewhat lower constant c in the western Mediterranean islands compared to the Aegean islands. Higher breakpoint values in the western Mediterranean may also be a result of larger distance to the mainland and longer separation times. Despite the differences in the geological history and the idiosyncratic features of the main island groups considered, the overall results are quite similar and this could be assigned to the ability of centipedes to disperse across isolation barriers. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 146–159.     

Pigments,Parasites and Personalitiy: Towards a Unifying Role for Steroid Hormones?

A surging interest in the evolution of consistent trait correlations has inspired research on pigment patterns as a correlate of behavioural syndromes, or "animal personalities". Associations between pigmentation, physiology and health status are less investigated as potentially conserved trait clusters. In the current study, lice counts performed on farmed Atlantic salmon Salmo salar naturally infected with ectoparasitic sea lice Lepeophtheirus salmonis showed that individual fish with high incidence of black melanin-based skin spots harboured fewer female sea lice carrying egg sacs, compared to less pigmented fish. There was no significant association between pigmentation and lice at other developmental stages, suggesting that host factors associated with melanin-based pigmentation may modify ectoparasite development to a larger degree than settlement. In a subsequent laboratory experiment a strong negative correlation between skin spots and post-stress cortisol levels was revealed, with less pigmented individuals showing a more pronounced cortisol response to acute stress. The observation that lice prevalence was strongly increased on a fraction of sexually mature male salmon which occurred among the farmed fish further supports a role for steroid hormones as mediators of reduced parasite resistance. The data presented here propose steroid hormones as a proximate cause for the association between melanin-based pigmentation and parasites. Possible fundamental and applied implications are discussed.     

Immunoreactivity of gastric ECL and A-like cells in fasted and fed rats and mice.

The oxyntic mucosa of rat and mouse stomach harbors histamine-producing ECL cells and ghrelin-producing A-like cells. The ECL cells are known to be active when the circulating gastrin levels are elevated in response to food intake. The A-like cells are the main source of circulating ghrelin. In response to starvation, the circulating ghrelin is elevated as a hunger signal. The aim of the present work was to study the correlation between the immunoreactivities and cellular activities of the ECL cells and A-like cells. Rats were either fed or fasted for 48 h and mice for 24 h. Immunohistochemical examination with antiserum against chromogranin A-derived fragment pancreastatin revealed both the ECL cells and the A-like cells without a difference between fasted and fed animals. Histamine was limited to the ECL cells with no significant difference between fasted and fed animals. Histidine decarboxylase (HDC) immunoreactivity occurred predominately in the ECL cells of the fed, but not fasted, animals in which the HDC enzymatic activity in the oxyntic mucosa was higher than in fasted animals. Ghrelin immunoreactivity was increased in terms of intensity, but not cell density in fasted animals. Thus, the immunoreactivities of ECL cells and A-like cells might be affected by starvation.     

Characterization of the self-splicing products of two complex Naegleria LSU rDNA group I introns containing homing endonuclease genes.

The two group I introns Nae.L1926 and Nmo.L2563, found at two different sites in nuclear LSU rRNA genes of Naegleria amoebo-flagellates, have been characterized in vitro. Their structural organization is related to that of the mobile Physarum intron Ppo.L1925 (PpLSU3) with ORFs extending the L1-loop of a typical group IC1 ribozyme. Nae.L1926, Nmo.L2563 and Ppo.L1925 RNAs all self-splice in vitro, generating ligated exons and full-length intron circles as well as internal processed excised intron RNAs. Formation of full-length intron circles is found to be a general feature in RNA processing of ORF-containing nuclear group I introns. Both Naegleria LSU rDNA introns contain a conserved polyadenylation signal at exactly the same position in the 3' end of the ORFs close to the internal processing sites, indicating an RNA polymerase II-like expression pathway of intron proteins in vivo. The intron proteins I-NaeI and I-NmoI encoded by Nae.L1926 and Nmo.L2563, respectively, correspond to His-Cys homing endonucleases of 148 and 175 amino acids. I-NaeI contains an additional sequence motif homologous to the unusual DNA binding motif of three antiparallel beta sheets found in the I-PpoI endonuclease, the product of the Ppo.L1925 intron ORF.     

Recessive Resistance in Pisum sativum and Potyvirus Pathotype Resolved in a Gene-for-Cistron Correspondence between Host and Virus

Pea seed-borne mosaic potyvirus (PSbMV) isolates are divided into pathotypes P-1, P-2, and P-4 according to their infection profile on a panel of Pisum sativum lines. P. sativum PI 269818 is resistant to P-1 and P-2 isolates and is susceptible to P-4 isolates. Resistance to P-1 is inherited as a single recessive gene, denoted sbm-1, and the pathogenicity determinant has previously been mapped to the virus-coded protein VPg. In the cultivar Bonneville, a second recessive gene, sbm-2, confers specific resistance to P-2. By exchanging cistrons between a P-2 and a P-4 isolate, the P3-6k1 cistron was identified as the PSbMV host-specific pathogenicity determinant on Bonneville. Exchange of P3-6k1 did not affect infection on PI 269818, and infection of Bonneville was not altered by substitution of the VPg cistron, indicating that P3-6k1 and VPg are independent determinants of pathotype-specific infectivity. On PI 269818 the pathogenicity determinant of both P-1 and P-2 mapped to the N terminus of VPg. This suggests that VPg from the P-1 and P-2 isolates are functionally similar on this host and that resistance to P-1 and P-2 in PI 269818 may operate by the same mechanism. Identification of VPg-sbm-1 and P3-6k1-sbm-2 as independent pairs of genetic interactors between PSbMV and P. sativum provides a simple explanation of the three known pathotypes of PSbMV. Furthermore, analysis of beta-glucuronidase-tagged P-2 virus indicated that sbm-2 resistance affected an early step in infection, implying that the P3-6k1 region plays a critical role in potyvirus replication or cell-to-cell movement.