Short Communication

Anaerobic metabolism and oxygen carrying-capacity of white shrimp (Penaeus vannamei) exposed to short term (three days) and long term (two weeks) moderate hypoxia (2-2.6 mg/L) was investigated. Glucose and lactate levels in hemolymph increased under both hypoxic conditions, indicating an activation of anaerobic pathways during the two-weeks exposure period. In muscle, no differences of glucose and lactate levels were observed between the control group and the exposed groups. In animals exposed to hypoxia for two weeks, hemocyanin and copper in hemolymph were higher than in animals under normoxic conditions or exposed for three days. These results indicate that an increase in oxygen carrying-capacity in shrimp is evident only after a sustained condition of hypoxia. Copper levels in the hepatopancreas decreased in both hypoxic conditions, suggesting a mobilization of copper stores for hemocyanin synthesis. These results indicate that penaeid shrimp can tolerate moderate hypoxic conditions by physiological adaptations, such as anaerobic metabolism and increased oxygen carrying-capacity. These adaptations require an adequate dietary supply of proteins and copper for hemocyanin synthesis and of carbohydrates for anaerobic metabolism.     

Length‐weight relationship for sea catfishes (Siluriformes: Ariidae) from the southeastern Gulf of California with new records on maximum length

The parameters of length‐weight relationship (LWR) are presented for seven species of catfish from the southeastern Gulf of California. Samples were obtained every three months, in Bahia de Matanchen (using bottom trawl nets consistent of 72 hauls, with mesh sizes of 3.2 cm in the wings and 2.54 cm in the cod‐end) from February to November, 2016 and in the San Blas estuarine system (using gill nets consistent of 32 hauls, with mesh sizes of 5 cm) from August, 2015 to May, 2016 respectively. The allometric coefficient (b) of LWR varied from 2.797 for the Cominate Sea Catfish (Occidentarius platypogon (Günther, 1864)) to 3.373 for the Tete Sea Catfish (Ariopsis gilberti (Jordan & Williams, 1895)). Four species reached new records on maximum total length (Tete Sea Catfish, A. gilberti; Widehead Sea Catfish, A. guatemalensis (Günther, 1864); Conguito Sea Catfish, Cathorops liropus (Bristol, 1897); and Curator Sea Catfish, C. raredonae Marceniuk, Betancur‐R, & Acero, 2009). For six of these species this accounts for the first report on estimations of LWR parameters.     

Ly1+ PRO-B lymphocyte clones. Phenotype, growth requirements and differentiation in vitro and in vivo.

Several clones obtained from the bone marrow of a BALB/c mouse were found to contain the heavy and light chain Ig genes in the germline configuration, to express Ly1 and to carry the B cell lineage markers B-220, Lyb8 and BP-1; these clones are Pgp-1+, LFA-1+, J11d+, Mac-1+ and Thy1-, Lyt2-, L3T4-, GM1.2- and Ia-. Three clones analyzed in detail (Lyd9, LyH7 and Lyb9) have receptors for interleukin (IL) 2 and IL3 as assessed with the 7D4 and CC11 monoclonal antibodies respectively. They grow in rIL3 but not in rIL2 or rIL1; both rIL4 and rIL5 also promote their proliferation, albeit to a much lesser extent than rIL3. None of the interleukins tested alone or in various combinations promoted the clones to differentiate in vitro along the B cell pathway. Treatment with 5-Azacytidine (5-Aza) induced cell surface Ia expression but not rearrangement or expression of Ig genes. However, 5-Aza-treated Lyd9, LyH7 and Lyb9 cells co-cultured with X-ray irradiated accessory cells and LPS gave rise to Ly1+, IgM+ B lymphocytes (range 14-51%) including mu + kappa + (78-93%), and mu + lambda + (9-25%) B lymphocytes. In vivo, the Lyd9, LyH7 and Lyb9 clones gave rise to IgM+ B lymphocytes (8.5-17%) including mu + kappa +, and mu + lambda +, but not to Lyt2+ or L3T4+ T lymphocytes after 4-6 weeks of transfer into Scid mice. Our results indicate that Ly1+ IgM+ cells comprise a subpopulation of B lymphocytes that is derived from IL3-responsive Ly1+ PRO-B lymphocytes.     

Nitrogen regulation of glutamine synthetase in Neurospora crassa.

A higher activity of glutamine synthetase (EC 6.3.1.2) was found in Neurospora crassa when NH4+ was limiting as nitrogen source than when glutamate was limiting. When glutamate, glutamine or NH4+ were in excess, a lower activity was found. Immunological titration and sucrose gradient sedimentation of the enzyme established that under all these conditions enzyme activity corresponded to enzyme concentration and that the octamer was the predominant oligomeric form. When N. crassa was shifted from nitrogen-limiting substrates to excess product as nitrogen source, the concentration of glutamine synthetase was adjusted with kinetics that closely followed dilution by growth. When grown on limiting amounts of glutamate, a lower oligomer was present in addition to the octameric form of the enzyme. When the culture was shifted to excess NH4+, glutamine accululated at a high rate; nevertheless, there was only a slow decrease in enzyme activity and no modification of the oligomeric pattern.     

Expression of adipogenesis markers in a murine stromal cell line treated with 15-deoxy Delta(12,14)-prostaglandin J2, interleukin-11, 9-cis retinoic acid and vitamin K2.

Recent studies have demonstrated that bone marrow stromal cells can undergo adipogenesis or osteoblastogenesis in vivo, and in vitro, and that peroxisome proliferator-activated receptor gamma (PPAR gamma) plays a central role in the control of adipocyte differentiation. In the present study, we treated a murine stromal cell line (TMS-14) with a cocktail of dexamethasone, insulin and glucose (DIG cocktail), which caused the cells to convert to fat-laden cells with adipocyte-like morphology. We also exposed TMS-14 cells to DIG cocktail followed by 15-deoxy Delta(12,14)-prostaglandin J2 (15d-PGJ2), a ligand of PPAR gamma, interleukin- 11 (IL-11), 9-cis retinoic acid (9-cis RA) and vitamin K2. 15d-PGJ2 enhanced DIG cocktail-induced adipogenesis, whereas IL-11, 9-cis RA and vitamin K2 each inhibited adipogenesis induced by DIG cocktail. The gene expressions of four adipogenesis markers, PPAR gamma 2, adipocyte P2 (aP2), adipocyte determination and differentiation factor 1 (ADD1), and fatty acid synthase (FAS) were enhanced by DIG cocktail and these expressions were more enhanced by 15d-PGJ2, in contrast they were attenuated by 9-cis RA. IL-11 also attenuated the adipogenesis markers except ADD1. Western blotting showed that 15d-PGJ2 enhanced the levels of PPAR gamma, C/EBP alpha and RXR alpha proteins, while IL-11 and 9-cis RA decreased the level of PPAR gamma protein, but not C/EBP alpha protein and vitamin K2 decreased the level of C/EBP alpha protein. We also tested the effect of 15d-PGJ2 on osteoblastogenesis, using TMS-12 cells, another stromal cell clone from the same mouse, which differentiate into osteoblasts spontaneously. 15d-PGJ2 did not affect osteoblastogenesis, as detected by von Kossa staining and Cbfa-1 gene expression. These data indicate that 15d-PGJ2 enhances the expression of both PPAR gamma and C/EBP alpha and as a result it stimulates adipogenesis in murine bone marrow cells.     

Stark effect measurements on monomers and trimers of reconstituted light-harvesting complex II of plants

The electric-field induced absorption changes (Stark effect) of reconstituted light-harvesting complex II (LHCII) in different oligomerisation states-monomers and trimers-with different xanthophyll content have been probed at 77 K. The Stark spectra of the reconstituted control samples, containing the xanthophylls lutein and neoxanthin, are very similar to previously reported spectra of native LHCII. Reconstituted LHCII, containing lutein but no neoxanthin, shows a similar electrooptical response in the Chl a region, but the Stark signal of Chl b around 650 nm amounts to at most approximately 25% of that of the control samples. We conclude that neoxanthin strongly modifies the electronic states of the nearby Chl b molecules causing a large electrooptical response at 650 nm stemming from one or more Chls b in the control samples. Ambiguities about the assignment of several bands in the Soret region [Biochim. Biophys. Acta 1605 (2003) 83] are resolved and the striking difference in electric field response between the two lutein molecules is confirmed. The Stark effect in the carotenoid spectral region in both control and neoxanthin-deficient samples is almost identical, showing that the neoxanthin Stark signal is small and much less intense than the lutein Stark signal.     

Larvicide and oviposition deterrent effects of fruit and leaf extracts from Melia azedarach L. on Aedes aegypti (L.) (Diptera: Culicidae)

Aedes aegypti (L.) (Diptera: Culicidae), the main urban vector of dengue, has developed resistance to various insecticides, making its control increasingly difficult. We explored the effects of Argentine Melia azedarach L. (Meliaceae) fruit and senescent leaf extracts on Ae. aegypti larval development and survival, by rearing cohorts of first instar mosquitoes in water with different extract concentrations. We also analysed oviposition deterrent activity in choice tests with extract-treated ovitraps. The leaf extract showed a strong larvicide activity, with all larvae dying before pupation, and significantly delayed development time. It strongly inhibited oviposition by Ae. aegypti females. The fruit extract showed much weaker effects. This first report of highly effective larvicidal, growth regulating and oviposition deterrent activity of a senescent leaf extract of M. azedarach against Ae. aegypti, suggests that such extract could represent a promising tool in the management of this mosquito pest.     

Solution structure and NMR characterization of the binding to methylated histone tails of the plant homeodomain finger of the tumour suppressor ING4

Plant homeodomain (PHD) fingers are frequently present in proteins involved in chromatin remodelling, and some of them bind to histones. The family of proteins inhibitors of growth (ING) contains a PHD finger that bind to histone-3 trimethylated at lysine 4, and those of ING1 and ING2 also act as nuclear phosphoinositide receptors. We have determined the structure of ING4 PHD, and characterised its binding to phosphoinositides and histone methylated tails. In contrast to ING2, ING4 is not a phosphoinositide receptor and binds with similar affinity to the different methylation states of histone-3 at lysine 4.     

General mutagenesis of F plasmid TraI reveals its role in conjugative regulation

Bacteria commonly exchange genetic information by the horizontal transfer of conjugative plasmids. In gram-negative conjugation, a relaxase enzyme is absolutely required to prepare plasmid DNA for transit into the recipient via a type IV secretion system. Here we report a mutagenesis of the F plasmid relaxase gene traI using in-frame, 31-codon insertions. Phenotypic analysis of our mutant library revealed that several mutant proteins are functional in conjugation, highlighting regions of TraI that can tolerate insertions of a moderate size. We also demonstrate that wild-type TraI, when overexpressed, plays a dominant-negative regulatory role in conjugation, repressing plasmid transfer frequencies approximately 100-fold. Mutant TraI proteins with insertions in a region of approximately 400 residues between the consensus relaxase and helicase sequences did not cause conjugative repression. These unrestrictive TraI variants have normal relaxase activity in vivo, and several have wild-type conjugative functions when expressed at normal levels. We postulate that TraI negatively regulates conjugation by interacting with and sequestering some component of the conjugative apparatus. Our data indicate that the domain responsible for conjugative repression resides in the central region of TraI between the protein's catalytic domains.