Ionoregulatory and endocrine responses to disturbed salt and water balance in Mozambique tilapia exposed to confinement and handling stress

This study assessed the endocrine and ionoregulatory responses by tilapia (Oreochromis mossambicus) to disturbances of hydromineral balance during confinement and handling. In fresh water (FW), confinement and handling for 0.5, 1, 2 and 6 h produced elevations in plasma cortisol and glucose; a reduction in plasma osmolality was observed at 6 h. Elevations in plasma prolactins (PRL₁₇₇ and PRL₁₈₈) accompanied this fall in osmolality while no effect upon growth hormone (GH) was evident; an increase in insulin-like growth-factor I (IGF-I) occurred at 0.5 h. In seawater (SW), confinement and handling increased plasma osmolality and glucose between 0.5 and 6 h; no effect on plasma cortisol was seen due to variable control levels. Concurrently, both PRLs were reduced in stressed fish with only transient changes in the GH/IGF-I axis. Next, the branchial expression of Na⁺/K⁺/2Cl^? cotransporter (NKCC) and Na⁺/Cl^? cotransporter (NCC) was characterized following confinement and handling for 6 h. In SW, NKCC mRNA levels increased in stressed fish concurrently with elevated plasma osmolality and diminished gill Na⁺, K⁺-ATPase activity; NCC was unchanged in stressed fish irrespective of salinity. Taken together, PRL and NKCC participate in restoring osmotic balance during acute stress while the GH/IGF-I axis displays only modest responses.     

Coxiella burnetii stimulates production of RANTES and MCP-1 by mononuclear cells: modulation by adhesion to endothelial cells and its implication in Q fever

Q fever is an infectious disease caused by Coxiella burnetii, which may become chronic when cytokine network and cell-mediated immune responses are altered. Chemokines, such as Regulated upon Activation, Normal T cell Expressed and Secreted (RANTES, CCL5) and Monocyte Chemoattractant Protein-1 (MCP-1, CCL2), are specialized in the trafficing of peripheral blood mononuclear cells (PBMC), and are associated with T cell polarization that is essential for intracellular survival of C. burnetii. The present study investigated whether or not the infection status (no infection and acute or chronic infection with C. burnetii) of donors, affected the production of the two chemokines by PBMC with or without stimulation with virulent and avirulent C. burnetii. Our findings indicate that in vitro exposure to virulent or avirulent C. burnetii stimulated the production of RANTES and MCP-1 in PBMC obtained from healthy adults. The co-cultivation of endothelial cells and human PBMC resulted in an increased production of MCP-1 and the up-regulation of RANTES, which were contact-dependent. Unstimulated PBMC from patients with acute or chronic Q fever overproduced MCP-1. Interestingly, the addition of C. burnetii resulted in an increased production of RANTES and MCP-1 by PBMC obtained from patients with chronic Q fever, and the co-cultivation of PBMC with endothelial cells amplified increased production of chemokines. Circulating levels of RANTES and MCP-1 were also increased in chronic Q fever. We suggest that the overproduction of RANTES and MCP-1 secondary to the contact of PBMC with endothelium may perpetuate exaggerated inflammatory responses leading to inappropriate PBMC trafficking and to the pathogenesis of Q fever.     

Transplantation of both kidneys from one donor rat

We have developed a technique for harvesting and transplanting two kidneys from one donor rat. Our method involves end-to-end anastomosis of the renal artery and the renal vein. Because of the short distance between the caudal vena cava and the right kidney, renal transplantation is not feasible on the right side of the recipient. The right donor kidney was therefore transplanted to the left side. Graft morphology was assessed on paraffin sections. We observed no differences between conventionally transplanted kidneys (n = 116) and right kidneys transplanted according to the method described (n = 40). In conclusion, our technique is simple, saves time and reduces the number of donor rats.     

Genetic evidence that expression of NahG modifies defence pathways independent of salicylic acid biosynthesis in the Arabidopsis-Pseudomonas syringae pv. tomato interaction

The salicylic acid (SA)-induction deficient (sid) mutants of Arabidopsis, eds5 and sid2 accumulate normal amounts of camalexin after inoculation with Pseudomonas syringae pv. tomato (Pst), while transgenic NahG plants expressing an SA hydroxylase that degrades SA have reduced levels of camalexin and exhibit a higher susceptibility to different pathogens compared to the sid mutants. SID2 encodes an isochorismate synthase necessary for the synthesis of SA. NahG was shown to act epistatically to the sid mutant phenotype regarding accumulation of camalexin after inoculation with Pst in eds5NahG and sid2NahG plants. The effect of the pad4 mutation on the sid mutant phenotype was furthermore tested in eds5pad4 and sid2pad4 double mutants, and it was demonstrated that PAD4 acts epistatically to EDS5 and SID2 regarding the production of camalexin after inoculation with Pst. NahG plants and pad4 mutants were also found to produce less ethylene (ET) after infection with Pst in comparison to the wild type (WT) and sid mutants. Both PAD4 and NahG acted epistatically to SID regarding the Pst-dependent production of ET that was found to be necessary for the accumulation of camalexin. Early production of jasmonic acid (JA) 12 h after inoculation with Pst/avrRpt2 was absent in all plants expressing NahG compared to the other mutants tested here. These genetic studies unravel pleiotropic changes in defence signalling of NahG plants that are unlikely to result from their low SA content. This adds unexpected difficulties in the interpretation of earlier findings based solely on NahG plants.     

Effects of fasting on growth hormone/insulin-like growth factor I axis in the tilapia,Oreochromis mossambicus

Effects of fasting on the growth hormone (GH)-insulin-like growth factor I (IGF-I) axis were examined in the tilapia (Oreochromis mossambicus) acclimated to fresh water. Fasting for 2 weeks resulted in significant reductions in body weight, specific growth rate and hepatosomatic index in both males and females. Significant reductions in specific growth rates were observed after 1 and 2 weeks in both sexes, although the decrease in body weight was not significant in the female. A significant reduction was also seen in the condition factor of females after 2 weeks. No change was seen in the gonadosomatic index in either sex. Two weeks of fasting also produced a significant reduction in plasma IGF-I but not in plasma GH, prolactin (PRL(188)) or cortisol. Significant reductions in the hepatic IGF-I mRNA were seen in both sexes. On the other hand, a significant increase was observed in cortisol receptor mRNA in the female liver. Plasma IGF-I levels were correlated significantly with specific growth rate, condition factor and hepatosomatic index, indicating that plasma IGF-I is a good indicator of growth in the tilapia. No change was seen in plasma glucose or osmolality after 2 weeks of fasting. During fasting, tilapia appears to convert metabolic energy from growth to basal metabolism including maintenance of ion and water balance.     

Terminal phase males stimulate ovarian function and inhibit sex change in the protogynous wrasse Thalassoma duperrey

Under experimental conditions, the probability of sex change in the protogynous wrasse Thalassoma duperrey is determined largely by an individual's relative size within a social group. Natural populations, however, contain two distinct male phenotypes that may also play a role in regulating sex change. To investigate potential effects of male phenotype, the ability to change sex, ovarian histology and serum estradiol-17 beta levels were examined in females maintained under controlled social settings. Large females housed with smaller or larger terminal phase males had significantly larger gonadosomatic indices than females housed singly, with other females or with smaller initial phase males. Similarly, ovaries of females housed with terminal phase males showed no histological evidence of sex change, whereas large females from other social groupings were in advanced stages of sex change. These results demonstrate terminal phase males inhibit sex change regardless of their size relative to the female. Furthermore, gonadosomatic indices, ovarian histology, and serum estradiol-17 beta levels of females housed with terminal phase males indicate normal ovarian function whereas ovaries of other treatment groups appear quiescent or are undergoing sex change. Consequently, terminal phase males may be required for normal ovarian development which may, in turn, inhibit sex change in T. duperrey.     

Nutritional Requirements of Microbacterium thermosphactum

Microbacterium thermosphactum requires cysteine, α-lipoate, nicotinate, pantothenate, p-aminobenzoate, biotin, and thiamin for aerobic growth in glucose-mineral salts medium. Glucose cannot be replaced by Casamino Acids or acids of the tricarboxylic acid cycle as sole carbon and energy sources. The organism can also grow anaerobically in the minimal synthetic medium.     

Characterization of presenilin-amyloid precursor interaction using bacterial expression and two-hybrid systems for human membrane proteins

An Escherichia coli system was used to produce the human membrane proteins presenilin 1 and amyloid precursor protein and to analyse their interaction. Our data indicate that the main binding site for amyloid precursor protein is located in the N-terminal three-transmembrane segments of presenilin and not in the proposed active site containing the two conserved aspartate residues. The data also suggest the presence of an additional segment of sufficient hydrophobicity at the C-terminus of PS1 to act potentially as a transmembrane segment. The implications of these findings for the function of gamma-secretase are discussed.