In situ studies on physiological and biochemical responses of four fishes with different trophic levels to toxic cyanobacterial blooms in a large Chinese lake

Physiological and biochemical responses of four fishes with different trophic levels to toxic cyanobacterial blooms were studied in a large net cage in Meiliang Bay, a hypereutrophic region of Lake Taihu. We sampled four fishes: the phytoplanktivorous Hypophthalmichthys molitrix and Aristichthys nobilis, the omnivorous Carassius auratus, and the carnivorous Culter ilishaeformis. Alterations of the antioxidant (GSH) and the major antioxidant enzymes (CAT, SOD, GPx, GST) in livers were monitored monthly, and the ultrastructures of livers were compared between the bloom and post-bloom periods. During the cyanobacterial blooms, the phytoplanktivorous fishes displayed only slight ultrastructural changes in liver, while the carnivorous fish presented the most serious injury as swollen endomembrane system and morphologically altered nuclei in hepatocytes. Biochemically, the phytoplanktivorous fishes possessed higher basal GSH concentrations and better correlations between the major antioxidant enzymes in liver, which might be responsible for their powerful resistance to MCs. This article provided physiological and toxicological evidences for the possible succession of fish communities following occurrence of toxic cyanobacterial blooms and also for the applicability of using phytoplanktivorous fish to counteract toxic cyanobacterial blooms in natural waters. (C) 2007 Elsevier Ltd. All rights reserved.

Identification of genome organization in the unusual allotetraploid form of Carassius auratus gibelio

The unusual allotetraploid form with unequal contribution of chromosome sets was discovered from the gynogenetic offspring of Carassius auratus gibelio stimulated by red common carp sperm. In this study, genomic in situ hybridization (GISH) and fluorescent in situ hybridization (FISH) with 45S rDNA probe are used. The GISH results lead to the identification of species-specific chromosomes, which permits to demonstrate the origin and genome organization in the allotetraploid form. Moreover, chromosome localization of 45S rDNA and co-localizations of 45S rDNA and Cyprinus carpio genomic DNA further confirm that one extra 45S rDNA positive chromosome in the allotetraploid form originates from the paternal haploid genome of C carpio, and other 5 45S rDNA-containing chromosomes are from the maternal genome of Carassius auratus gibelio. And, the correlation between 45 rDNA and the nucleolar organizer regions (NORs) is confirmed by silver nitrate staining. The data provide direct experiment evidence that the allotetraploid actually contains three chromosome sets of Carassius auratus gibelio and one chromosome set of C carpio, and will be a useful genetic material for both basic research and breeding practice. (c) 2006 Elsevier B.V. All rights reserved.

In situ studies on the bioaccumulation of microcystins in the phytoplanktivorous silver carp (Hypophthalmichthys molitrix) stocked in Lake Taihu with dense toxic Microcystis blooms

The phytoplanktivorous silver carp is an important biomanipulation fish to control cyanobacterial blooms and is also a food fish with the greatest production in China. The accumulation of the hepatotoxic microcystins (MCs) determined by LC-MS in various organs of silver carp was studied monthly in Lake Taihu dominated by toxic Microcystis aeruginosa. Average recoveries of spiked fish samples were 78% for MC-RR and 81% for MC-LR. The highest content of MCs was found in the intestine (97.48 mu g g(-1) DW), followed by liver (6.84 mu g g(-1) DW), kidney (4.8 8 mu g g(-1) DW) and blood (1.54 mu g g(-1) DW), and the annual mean MC content was in the order of intestine > liver > kidney > blood > muscle > spleen > gallbladder > gill. Silver carp could effectively ingest toxic Microcystis cells (up to 84.4% of total phytoplankton in gut contents), but showed fast growth (from 141 g to 1759 g in I year in mean weight). Silver carp accumulated less microcystins in liver than other animals in the same site or other fish from different water bodies at similar level of toxin ingestion. There was possible inhibition of the transportation of the most toxic MC-LR across the gutwall. Muscle of silver carp in Lake Taihu should not be consumed during period of dense Microcystis blooms while viscera were risky for consumption in more months. (c) 2006 Elsevier B.V. All rights reserved.

Methylmercury, total mercury and total selenium in four common freshwater fish species from Ya-Er Lake, China

Snakehead fish (Ophiocephalus argus cantor), silver carp (Hypophthalmichthys molitrtix), crucian carp (Carassius carassius), and common carp (Cyprinus carpio) are four common freshwater fish species in China. In this study, the level of methylmercury (MeHg), total mercury (T-Hg), and total selenium (T-Se) in muscle samples of these four fish species from Ya-Er Lake, China, were analyzed using atomic fluorescence spectrometry coupled with high-performance liquid chromatography, and inductively coupled plasma mass spectrometry. The concentrations of MeHg in all the fish species were significantly correlated with those of T-Hg. Higher T-Hg and MeHg concentrations had accumulated in the snakehead fish, which is a strongly predatory fish, than in the other three species. The concentration ratios of MeHg and T-Hg in the muscles of these four fish species were almost equal. Conversely, there was negative correlation between the concentrations of T-Hg and T-Se, which implies that there is a competition between these two elements with respect to bioaccumulation. It is noteworthy that of all the muscle samples tested, the level of T-Hg exceeded the maximum allowable limit in fish [0.4 mg kg(-1) (w/w) recommended by the World Health Organization] in 38.46% of those of the silver carp, 18.18% of those of the crucian carp, and 100% of those of snakehead fish. These results show that the consumption of contaminated fish is a potential threat to human health and that necessary preventive measures to safeguard public health should be emphasized.

An in situ estimate of food consumption by icefish in Lake Chaohu, China

The icefish (Neosalanx taihuensis) of Lake Chaohu, China, foraged almost exclusively on crustacean zooplankton in both spring and summer. The icefish showed diurnal feeding periodicity, with peak feeding in the morning. No food was observed in icefish guts collected at night. Our results indicate that that the icefish was a particulate feeder and light intensity greatly affected its foraging on zooplankton. Daily consumption of zooplankton by icefish varied significantly both diurnally and among seasons, which ranged from 0.22 to 2.23 g (wet weight) per 100 g wet fish weight at temperatures between 16.3 degrees C (spring) and 28.8 degrees C (summer).

Chromosomal in situ hybridization of Cyprinus carpio genomic DNA repetitive sequence CR1

Common carp Cyprinus carpio genomic DNA repetitive sequence CR1 has been DIG-labeled and hybridized in situ against chromosomes of red common carp (Cyprinus carpio L. Xingguo red var.). It is found that the repetitive sequence CR1 is mainly localized at the centromeric regions of chromosomes of the red common carp, The application of the chromosomal in situ hybridization technique on fish and the relationship between CR1 repetitive sequence distribution and its function have been discussed.

Preparation and luminescence properties of in situ formed lanthanide complexes covalently grafted to a silica network

Lanthanide-doped sol-gel-derived materials are an attractive type of luminescent materials that can be processed at ambient temperatures. However, the solubility of the lanthanide complexes in the matrix is a problem and it is difficult to obtain a uniform distribution of the complexes. Fortunately, these problems can be solved by covalently linking the lanthanide complex to the sol-gel-derived matrix. In this study, luminescent Eu3+ and Tb3+ bipyridine complexes were immobilized on sol-gel-derived silica. FT-IR, DTA-TG and luminescence spectra, as well as luminescence decay analysis, were used to characterize the obtained hybrid materials. The organic groups from the bipyridine-Si moiety were mostly destroyed between 220 and 600 degreesC. The luminescence properties of lanthanide bipyridine complexes anchored to the backbone of the silica network and the corresponding pure complexes were comparatively investigated, which indicates that the lanthanide bipyridine complex was formed during the hydrolysis and co-condensation of TEOS and modified bipyridine. Excitation at the ligand absorption wavelength (336 nm for the hybrid materials and 350 nm for the pure complexes) resulted in strong emission of the lanthanide ions: Eu3+ D-5(0)-F-7(J) (J = 0, 1, 2, 3, 4) and Tb3+ D-5(4)-F-7(J) (J = 6, 5, 4, 3) emission lines due to efficient energy transfer from the ligands to the lanthanide ions.

In situ synthesis of terbium-benzoic acid complex in sol-gel derived silica by a two-step sol-gel method

Terbium complexes with benzoic acid and its derivatives o-hydroxybenzoic acid and p-hydroxybenzoic acid were in situ synthesized in sol-gel derived silica matrix via a two-step sol-gel process. The formation process of the complex was characterized by fluorescence spectra, absorption spectra and IR spectra. The gels that contain in situ synthesized complexes exhibit the characteristic emission bands of terbium ion. The fluorescence lifetimes of Tb3+ in the silica gels are longer than those in the pure complexes and in the solutions that contain the corresponding complexes. (C) 2000 Elsevier Science Ltd. All rights reserved.

Preparation and luminescence properties of terbium-Sal complex in-situ synthesized in silica matrix by a two-step sol-gel process

In-situ synthesis of terbium complex with salicylic acid (Sal) in silica matrix was made by a two-step sol-gel process. The terbium complex with salicylic acid was formed in sol-gel derived silica gel, and confirmed by the luminescence excitation spectra and infrared(IR) spectra. As compared to the pure terbium complex powder, the silica gel containing terbium complex exhibits its characteristic emission and presents a longer fluorescence lifetime than that for the pure complex. The luminescence properties of the complex containing;silica gel were investigated and compared with that of both terbium doped the silica gel and thp pure complex powder. The reasons leading to the above results were also discussed.

Luminescence characteristics of europium and terbium complexes with 1,10-phenanthroline in-situ synthesized in a silica matrix by a two-step sol-gel process

In-situ synthesis of europium and terbium complexes with 1,10-phenanthroline (phen) in silica matrix by a two-step sol-gel process has been proposed. The formation of europium and terbium complexes with phen in sol-gel derived silica gel were confirmed by the luminescence excitation spectra. The silica gels that contain in-situ synthesized europium and terbium complex exhibit the characteristic emission bands of the rare earth ions. Furthermore. the rare earth ions present longer fluorescence lifetimes than the comparable pure complex powder and the complexes dissolved in ethanol solutions. The luminescence properties of the silica gels codoped with europium (or terbium) and phen were also investigated with respect to the gels doped with europium (or terbium). (C) 1999 Elsevier Science B.V. All rights reserved.

Microstructure and wear resistance of in situ TiCp composite coating by laser cladding

A new in situ method was realized by one step laser cladding to produce Ni-base alloy composite coating reinforced by in situ reacted and gradiently distributed TiCp particles. The submicron TiCp particles were formed and uniformly distributed because of the in situ reaction and trapping effect under the rapid solidification condition. And, TiCp particles were of gradient distribution on a macro scale and their volume fraction increased from 1.86% at the layer/substrate interface to a maximum 38.4% at the surface of the layer. Furthermore, the in situ generated TiCp/gamma-Ni interfaces were free from deleterious surface reactions. Additionally, the clad coating also revealed a high microhardness of gradient variation with the layer depth and the superior abrasive wear resistance.

Laser Melted TiC Reinforced Nickel Aluminide Matrix in situ Composites

Titanium carbide reinforced nickel aluminide matrix in situ composites were produced using a newly patented laser melting furnace. Microstructure of the laser melted TiC/(Ni3Al–NiAl) in situ composites was characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Results showed that the constituent phases in the laser melted in situ composites are TiC, Ni3Al and NiAl. Volume fraction of TiC and NiAl increase with increasing content of titanium and carbon. The growth morphology of the reinforcing TiC carbide has typically faceted features, indicating that the lateral growth mechanism is still predominant growth mode under rapid.

Adlayer Structures of DL-Homocysteine and L-Homocysteine Thiolactone on Au(111) Surface: an in situ STM Study

The adsorption Of DL-homocysteine (Hcy) and L-homocysteine thiolactone (HTL) on Au(1 1 1) electrode was investigated in 0.1 M HClO4 by cyclic voltammetry and in situ scanning tunneling microscopy (STM). Hcy and HTL molecules formed highly ordered adlayers on Au(1 1 1) surface. High-resolution STM images revealed the orientation and packing arrangement in the ordered adlayers. Hcy molecules formed (2root3 x 3root3)R30degrees adlayer structure and H-bonds between carboxyl groups were assumed to be responsible for the origin of tail-to-tail or head-to-head molecular arrangement, while HTL molecules formed (4 x 6) adlayer structure, and two different orientations and appearances in the ordered adlayer were found. Structural models were proposed for the two adlayers.

In situ formation by laser cladding of a TiC composite coating with a gradient distribution

An in situ method was developed to produce an Ni alloy composite coating reinforced by in situ reacted TiC particles with a gradient distribution, using one-step laser cladding with a pre-placed powder mixture on a 5CrMnMo steel substrate. Dispersed and ultra-fine TIC particles were formed in situ in the coating. Most. of the TiC particles, with a marked gradient distribution, were uniformly distributed within interdendritic regions because of the trapping effect of the advancing solid-liquid interface. In addition, the TiC-gamma-Ni interfaces generated in situ were found to be free from any deleterious surface reaction. Finally, the microhardness also showed a gradient variation, with the highest value of 1250 Hv0.2 and the wear properties of the coating were significantly enhanced.