Molecular cloning and characterization of a C-type lectin in yellow catfish Tachysurus fulvidraco.

This study represents the first report of a C-type lectin (ctl) in yellow catfish Tachysurus fulvidraco. The complete sequence of ctl complementary (c)DNA consisted of 685 nucleotides. The open reading frame potentially encoded a protein of 177 amino acids with a calculated molecular mass of c.y 20.204 kDa. The deduced amino-acid sequence contained a signal peptide and a single carbohydrate recognition domain with four cysteine residues and GlnProAsp (QPD) and TrpAsnAsp (WND) motifs. Ctl showed the highest identity (56.0%) to the predicted lactose binding lectin from channel catfish Ictalurus punctatus. Quantitative real-time (qrt)-PCR analysis showed that ctl messenger (m)RNA was constitutively expressed in all examined tissues in normal fish, with high expression in trunk kidney and head kidney, which was increased following Aeromonas hydrophila challenge in a duration-dependent manner. Purified recombinant Ctl (rCtl) from Escherichia coli BL21 was able to bind and agglutinate Gram-positive and Gram-negative bacteria in a calcium-dependent manner. These results suggested that Ctl might be a C-type lectin of T. fulvidraco involved in innate immune responses as receptors (PRR).

Advanced phosphorus removal for secondary effluent using a natural treatment system.

Mechanisms for low concentrations phosphorus removal in secondary effluent were studied, and a process was developed using limestone filters (LF), submerged macrophyte oxidation ponds (SMOPs) and a subsurface vertical flow wetland (SVFW). Pilot scale experimental models were applied in series to investigate the advanced purification of total phosphorus (TP) in secondary effluent at the Chengjiang sewage treatment plant. With a total hydraulic residence time (HRT) of 82.52 h, the average effluent TP dropped to 0.17 mg L(-1), meeting the standard for Class III surface waters. The major functions of the LF were adsorption and forced precipitation, with a particulate phosphorus (PP) removal of 82.93% and a total dissolved phosphorus (TDP) removal of 41.07%. Oxygen-releasing submerged macrophytes in the SMOPs resulted in maximum dissolved oxygen (DO) and pH values of 11.55 mg L(-1) and 8.10, respectively. This regime provided suitable conditions for chemical precipitation of TDP, which was reduced by a further 39.29%. In the SVFW, TDP was further reduced, and the TP removal in the final effluent reached 85.08%.

Membrane mechanism mediates progesterone stimulatory effect on LHRH release from superfused rat hypothalami in vitro.

To determine whether the plasma membrane is a primary site for progesterone (P4) action on the neural LHRH apparatus of hypothalamic tissues derived from ovariectomized, estradiol-primed (OVX + E2) immature rats, immobilized P4 was infused directly to these tissues using a superfusion technique. Two kinds of immobilized P4 with bovine serum albumin (BSA) conjugated at positions 3 or 11, or 11-deoxycorticosterone (DOC) immobilized at position 21 of the steroid molecule, respectively, were tested for structural specificity. Among the three immobilized steroids, only P4 with BSA conjugated at position 3 (P4-3-BSA) was effective in stimulating LHRH release in vitro. P4-3-BSA at 0.5 micrograms/ml, approximately 1.7 X 10(-7) M of P4, increased LHRH levels in the superfusates to about 2.5-fold those of pretreatment levels. In addition, no conversion of P4-3-BSA to free progesterone was detected. This observation demonstrated that the plasma membrane is a primary site for the stimulating effect of P4 on LHRH release from hypothalamic tissue in vitro.