Effect of high levels of dietary vitamin C on the blood responses of matrinxã (Brycon amazonicus)

Juvenile matrinx? (Brycon amazonicus) were fed with different dietary vitamin C (ascorbic acid or AA) concentrations for 2 months in order to evaluate its effect on the physiological condition of this species. Five treatments were tested: Reference diet-RD (350 mg AA kg(-1) and 45% crude protein commercial feed); C400, C500, C600 and C800 with supplementation of 400, 500, 600 and 800 mg AA kg(-1). Fish fed 800 mg AA kg(-1) supplemented diets presented greater weight gain and survival. Hematocrit, hemoglobin concentrations and erythrocytes showed significant increase (p<0.05) in C600 and C800 relatively to the others. Total leukocyte values were significantly higher in fish fed vitamin C supplemented diets relatively to those fed RD and leukocytes count of C600 and C800 were the highest among the treatments. Monocytes were the only cells of fish defense mechanism that presented variation, and C600 and C800 presented the lowest values (P<0.05). Glucose level was significantly different relatively to RD only in C400 and the plasmatic total protein values for fish fed vitamin C supplemented diets were higher than for fish fed the RD. Fish plasmatic ions (Na(+) and Cl(-)) were significantly lower for C500, C600 and C800 relatively to C400 and RD. The physiological profile and the growth performance of matrinx? suggest that diet supplemented with 800 mg AA kg(-1) can improve its performance and increase the survival rate.     

The karyotype of Nodipecten nodosus (Bivalvia: Pectinidae)

Earlier karyotypical work on Nodipecten nodosus embryos indicated that this species has a diploid number of 38, with six pairs respectively of metacentric and submetacentric chromosomes and seven pairs of subtelocentric chromosomes, although there were some difficulties in obtaining complete metaphases. The present work provides additional results on specific regions of the chromosomes in N. nodosus and, by meiotic studies, confirms the chromosome number with more reliability. Active nucleolar organizer regions (NOR), detected in mitotic metaphases from embryos, can be characterized in N. nodosus by a high level of heteromorphism of NOR-sites, indicating that these regions are not appropriate as chromosomal markers in this species. The procedure for detecting constitutive heterochromatin of chromosomes allowed us to observe most of the heterochromatic blocks at a pericentromeric position and some at telomeric and interstitial positions. The analysis of meiotic chromosomes from gonad tissue revealed the presence of 19 bivalents during metaphase I, all homomorphic and isopicnotic, confirming the previously described diploid chromosomal number of 38 for N. nodosus. From these results, some evolutionary aspects of the Pectinidae are briefly discussed.     

Leishmania: genus identification based on a specific sequence of the 18S ribosomal RNA sequence

The analysis of PvuII restriction patterns of Leishmania spp. and Trypanosoma spp. genomic DNA showed genus distinctive profiles. A specific PvuII site was detected in the 5' domain of 18S ribosomal DNA of Leishmania. A 20-mer oligonucleotide encompassing this PvuII region was synthesized. This sequence, when utilized as probe, on short exposures of dot tests, detected 10(3) whole promastigotes of all Leishmania species analyzed but did not hybridize with T. cruzi or human nucleic acids. Two other oligonucleotides were synthesized to be used as primers for amplification through polymerase chain reaction of the 18S ribosomal DNA region containing the PvuII site. The probes described may be useful for the detection of Leishmania spp. under clinical and epidemiological trials.     

“More than meets the eye”: phylogeographic inferences and remarkable cryptic diversity and in endemic catfish Parotocinclus (Loricariidae: Hypoptopomatinae) from neglected and impacted basins in South America

Conservation Genetics - The restricted range, taxonomic uncertainties and the apparent phylopatric behavior of Parotocinclus (dwarf plecos) make this fish group an excellent model to infer...     

Respiratory responses of the air-breathing fish Hoplosternum littorale to hypoxia and hydrogen sulfide

The present study analyzes the respiratory responses of the neotropical air-breathing fish Hoplosternum littorale to graded hypoxia and increased sulfide concentrations. The oxygen uptake (VO2), critical O2 tension (PcO2), respiratory (fR) and air-breathing (fRA) frequencies in response to graded hypoxia were determined for fish acclimated to 28 degrees C. H. littorale was able to maintain a constant VO2 down to a PcO2 of 50 mm Hg, below which fish became dependent on the environmental O2 even with significant increases in fR. The fRA was kept constant around 1 breath h(-1) above 50 mm Hg and increased significantly below 40 mm Hg, reaching maximum values (about 4.5 breaths h(-1)) at 10 mm Hg. The lethality to sulfide concentrations under normoxic and hypoxic conditions were also determined along with the fRA. For the normoxic fish the sulfide lethal limit was about 70 microM, while in the hypoxic ones this limit increased to 87 muM. The high sulfide tolerance of H. littorale may be attributed to the air-breathing capability, which is stimulated by this compound.     

Effect of medium composition on the production of tetanus toxin by Clostridium tetani

The tetanus toxin is a neurotoxin synthesized by the bacillus Clostridium tetani that, after detoxification with formaldehyde, still exhibits antigenic and immunologic properties, hence its denomination of tetanus toxoid. Such a neurotoxin is produced by cultivation of the microorganism in vegetative form on a relatively complex specific medium containing glucose and peptone. The simultaneous effects of the starting levels of glucose (G0) and N-Z Case TT (NZ0) as carbon and nitrogen sources, respectively, on the production of tetanus toxin have been investigated in this work in static cultivations by means of a five-level star-shaped experimental design and evaluated by response surface methodology (RSM) for optimization purposes. The highest final average yield of tetanus toxin (72 Lf/mL), achieved at G0= 9.7 g/L and NZ0= 43.5 g/L, was 80% higher than that obtained with standard cultivations (G0= 8.0 g/L and NZ0= 25.0 g/L).     

The liver monooxygenase system of Brazilian freshwater fish

Content of cytochromes b5 and P-450, and activities of NADPH-cytochrome c (P-450) reductase (NCR) and 7-ethoxyresorufin O-deethylase (EROD) were measured in liver microsomes prepared from two South American endemic fish, Brycon cephalus and Colossoma macropomum, from tilapia, Oreochromis niloticus, and from Swiss mice, Mus musculus, which served as a control. Strong hemoglobin binding to fish liver microsomal membranes (FLM) altered visible spectra of microsomal cytochromes. Consequently, special precautions during FLM preparation, including liver perfusion followed by repeated washing of microsomes, were required in the study of microsomal cytochromes from these fish. FLM from all fish studied here had a significantly lower content of microsomal cytochromes but a similar level of NCR and EROD activities compared to mouse liver microsomes (MLM). Strong response of the monooxygenase system in O. niloticus to water pollution was detected with both specific cytochrome P-450 content and EROD activity increasing sharply. The optical spectra of hemoglobin from B. cephalus and C. macropomum were analyzed and some differences in shape and relative extinction were observed compared to known hemoglobins.     

Cell-detaching Escherichia coli (CDEC) strains from children with diarrhea: Identification of a protein with toxigenic activity

Twenty-four strains of cell-detaching Escherichia coli (CDEC) isolated from stool specimens in different cities in Brazil were examined for virulence properties. Aerobactin production and multiple antibiotic resistance were observed in most of the isolates. In hybridization studies, the alphahly, pap, and cnf sequences, common properties of this category of E. coli, were found in a minority of isolates. Half of the CDEC isolates had enteroaggregative DNA sequences (pet, astA, aggA), six strains carried the shet1 gene, nine strains carried the daaC sequence, and one strain carried the stp gene. Thirteen strains induced fluid accumulation in the rabbit intestinal loop assay. Supernatant filtrate of one of those strains, which did not hybridize with any of the toxin probes tested, induced destructive lesions in the rabbit ileal loop and enterotoxic activity in the Ussing chamber. A 12-kDa protein purified by 60% ammonium sulfate precipitation of the supernatant filtrate demonstrated a toxigenic effect that was inhibited by the anti-12-kDa protein antiserum.     

Growth,parasitic infection and hematology in Colossoma macropomum Cuvier, 1818 fed diets containing Allium sativum

The aim of this study was to investigate the effects of a dietary Allium sativum (garlic) addition on growth, parasite infestation and blood parameters in Colossoma macropomum (tambaqui) using 12 net‐cages (1 m³). There were four treatments with three replicates each (15 fish per replicate). Tambaqui of 112.4 g mean weight were fed for 45 days with diets containing 0, 15, 30 and 45 g of fresh garlic kg^?1 feed. Garlic did not affect the tambaqui survival, growth, feed conversion, body condition, plasma glucose levels, total plasma protein levels or red blood cells. Total leukocyte and lymphocyte numbers decreased in fish fed diets containing 45 g garlic kg^?1 feed, but neutrophils decreased in fish fed diets containing 15, 30 and 45 g garlic kg^?1 diet, while the number of immature leukocytes increased in fish fed 30 g and 45 g garlic kg^?1diet. Gills in fish fed 30 and 45 g kg^?1 diet had lower infestation (52% and 63%, respectively) of Anacanthorus spathulatus (Monogenea) compared to controls. The application of garlic in diets improved the response of leukocytes and enhanced the resistance to infections by monogeneans.