Chemical, bacteriological and sensory examination of split, dried, smoked bream on the market in Zambia

A critical examination of the market quality of split, dried and smoked bream (Tilapia spp.) was chemically, bacteriologically and organoleptically conducted for the period of August 1968 to January 1969. The aim of this survey was to obtain basic information for the development of national quality standards for the commodity. Relationships of cooked meat score to pH, fish size, appearance and smell score, and water content wcre significantly correlated and responsive. Therefore, these parameters were proposed to be used as indices for the quality standards of the products.

Increasing the genetic uniformity of bighead carp [Aristichthys nobilis (Richardson)] by means of spontaneous diploidization of gynogenetically activated eggs

Three groups of gynogenetic diploid bighead carp were successfully obtained by means of artificial gynogenesis. The activation rates of gynogenesis varied from 75.9% to 98.8%, and the frequency of spontaneous diploidization was around 0.4%. Over 2000 normally gynogenetic diploid fry were obtained in three gynogenetic groups. The haploid karyotype consisted of nine metacentric, 12 submetacentric, three subtelocentric chromosomes and 45 arms. The chromosome number was 48 from gynogenetic diploid. The results showed that the genetic material of offspring was maternal. The aneuploid hybrid embryos of bighead carp and Xingguo red common carp with chromosome numbers ranging from 28 to 73 did not survive post hatch, likely the result of incompatibility between the nucleus and the cytoplasm of two parents. Sixty RAPD primers from three groups were used for total DNA amplification of gynogenetic offspring, maternal and 'paternal' fish. A total of 451 bands were amplified from three kinds of samples above. From maternal bighead carp, 256 bands were amplified; however, there were 251 shared bands between maternal and gynogenetic bighead carp. From artificial gynogenetic offspring, two 'paternal' DNA segments without an expression function were found. An UPGMA tree showed that gynogenetic offspring were closely clustered and the genetic identity among them was very high (0.956).

Oxidative damage in unfertilized eggs of Chinese rare minnow (Gobiocypris rarus) exposed to nonylphenol

In the present study, female Chinese rare minnows (Gobiocypris rarus) were used as in vivo models and exposed to nonylphenol (NP) at concentrations of 1 to 200 mu g/L for 21 d under semistatic conditions. Molecular biomarkers of oxidative stress were measured in unfertilized eggs and included reactive oxygen species (ROS), lipid peroxidation products (thiobarbituric acid-reactive substances [TBARS] and protein carbonyl), superoxide dismutase activity, and glutathione. Cathepsin D activity as an indicator of egg viability also was assayed. Nonylphenol induced ROS formation in unfertilized eggs in all exposed groups compared to the controls. The levels of protein carbonyl and TBARS in unfertilized eggs were significantly increased (p < 0.05) at 10 to 200 and 100 to 200 mu g/L, respectively. Good positive correlations were shown between ROS induction and levels of TBARS and protein carbonyl in eggs (R = 0.918, p < 0.05 and R = 0.784, p < 0.05, respectively). Superoxide dismutase activity in eggs was significantly inhibited (p < 0.05) in the 50 to 200 mu g/L exposure groups. Glutathione levels in eggs were significantly depleted (p < 0.05) at 100 to 200 mu g/L concentrations. In addition, ROS induction resulted in oxidative damage to lipid and protein in chorions. Significant reductions (p < 0.05) of the protein and lipid contents in chorions were both found in the 50 to 200 mu g/L exposure groups. A previous study found that NP exposure could lead to chorion thinning in zebra fish. Thus, the reductions in protein and lipid contents in chorion could be the reason for chorion thinning by NP exposure. Meanwhile, cathepsin D activity was significantly inhibited (p < 0.05) in all exposure groups. The results demonstrated that NP-induced oxidative stress could damage the chorion of unfertilized eggs and lead to a decline in gamete quality in female Chinese rare minnow.

Identification of differentially expressed genes from the cross-subfamily cloned embryos derived from zebrafish nuclei and rare minnow enucleated eggs

Cross-species nuclear transfer (NT) has been used to retain the genetic viability of a species near extinction. However, unlike intra-species NT, most embryos produced by cross-species NT were unable to develop to later stages due to incompatible nucleocytoplasmic interactions between the donor nuclei and the recipient cytoplasm from different species. To study the early nucleocytoplasmic interaction in cross-species NT, two laboratory fish species (zebrafish and rare minnow) from different subfamilies were used to generate cross-subfamily NT embryos in the present study. Suppression subtractive hybridization (SSH) was performed to screen out differentially expressed genes from the forward and reverse subtractive cDNA libraries. After dot blot and real-time PCR analysis, 80 of 500 randomly selective sequences were proven to be differentially expressed in the cloned embryos. Among them, 45 sequences shared high homology with 28 zebrafish known genes, and 35 sequences were corresponding to 22 novel expressed sequence tags (ESTs). Based on functional clustering and literature mining analysis, up-and down-regulated genes in the cross-subfamily cloned embryos were mostly relevant to transcription and translation initiation, cell cycle regulation, protein binding, etc. To our knowledge, this is the first report on the determination of genes involved in the early development of cross-species NT embryos of fish. (C) 2007 Elsevier Inc. All rights reserved.

Cytoplasmic impact on cross-genus cloned fish derived from transgenic common carp (Cyprinus carpio) nuclei and goldfish (Carassius auratus) enucleated eggs

In previous studies of nuclear transplantation, most cloned animals were obtained by intraspecies nuclear transfer and are phenotypically identical to their nuclear donors; furthermore, there was no further report on successful fish cloning since the report of cloned zebrafish. Here we report the production of seven cross-genus cloned fish by transferring nuclei from transgenic common carp into enucleated eggs of goldfish. Nuclear genomes of the cloned fish were exclusively derived from the nuclear donor species, common carp, whereas the mitochondrial DNA from the donor carp gradually disappeared during the development of nuclear transfer (NT) embryos. The somite development process and somite number of nuclear transplants were consistent with the recipient species, goldfish, rather than the nuclear donor species, common carp. This resulted in a long-lasting effect on the vertebral numbers of the cloned fish, which belonged to the range of goldfish. These demonstrate that fish egg cytoplasm not only can support the development driven by transplanted nuclei from a distantly related species at the genus scale but also can modulate development of the nuclear transplants.

Effect of temperature and photoperiod on hatching of eggs of Tokunagayusurika akamusi (Tokunaga) (Diptera : Chironomidae)

The hatching time of eggs of Tokunagayusurika akamusi (Tokunaga) decreased significantly when temperature was increased from 5degreesC to 25degreesC; eggs fail to hatch at 30degreesC. The percentage of T akamusi eggs that developed into normal larva also was negatively correlated with temperature. The hatching time decreased with lengthened photoperiod.

Dried field populations of Nostoc flagelliforme (Cyanophyceae) require exogenous nutrients for their photosynthetic recovery

The effects of nutrients on the photosynthetic recovery of Nostoc flagelliforme during re-hydration were investigated in order to see if their addition was necessary. Net photosynthesis was negligible in distilled water without nutrient-enrichment. Addition of K+ resulted in significant enhancement of net photosynthesis, whereas other nutrients (Fe3+, Mg2+, Na+, NO3-, PO43-, Cl-) and trace-metals (A(5)) showed little effect. The recovered net photosynthetic activity increased with the increased K+, and reached the maximum at concentrations above 230 mu M. Desiccation and re-hydration did not affect the dependence of photosynthetic recovery on K+. It was concluded that dried field populations of N. flagelliforme require exogenous addition of potassium for photosynthetic recovery and that growth may be potassium-limited in nature.

Effects of hydrostatic pressure on microtubule organization and cell cycle in gynogenetically activated eggs of olive flounder (Paralichthys olivaceus)

Indirect immunofluorescence staining was used to detect cytological changes of isolated blastodisks during mitosis of flounder haploid eggs treated with hydrostatic pressure. Changes in microtubule structure and expected cleavage suppression were observed from blastodisk formation to the third cell cycle, with obvious differences between treated and control eggs. In most eggs, microtubules were disassembled and the nucleation capacity of the centrosome was temporarily inhibited after pressure treatment. Within 15-20 min after treatment, the nucleation capacity of the centrosome began to gradually recover, with slow regeneration of microtubules; approximately 25 min after treatment, the nucleation capacity of the centrosome recovered completely, regenerated distinct bipolar spindles, and the first mitosis ensued. During the second cell cycle, approximately 61% of the embryos were at the two-cell stage, with a monopolar spindle in each blastomere; that treatment was effective was based on second cleavage blockage. Approximately 15% of the eggs still remained at the one-cell stage and had a monopolar spindle (treatment was effective, according to the general model of first cleavage blockage). However, treatment was ineffective in approximately 15% of the embryos (bipolar spindle in each blastomeres) and in another 8% (bipolar spindle in one of the two blastomeres and a monopolar spindle in the other; both mechanisms operating in different parts of the embryo). This is the first report elucidating mitotic gynogenetic diploid induction by hydrostatic pressure in marine fishes and provides a cytological basis for developing an efficient method of inducing mitotic gynogenesis in olive flounder. (C) 2007 Elsevier Inc. All rights reserved.