Characterization of the protective response against a homologous challenge infection with Strongyloides venezuelensis in rats

The protective response in rats against a homologous challenge infection with Strongyloides venezuelensis was characterized. In an initial infection with 1000 filariform larvae and migrating larvae (L(3)) of S. venezuelensis, the population of L(3) in the lungs on day 3 postinfection (PI), and that of adult worms in the small intestine on day 7 PI, were 180.8+/-14.5 and 336.8+/-70.7, respectively. The latter were gradually expelled towards day 42 PI. After the initial infection, the rats developed strong immunity against a homologous challenge infection as manifested by a marked reduction in worm populations, stunted body length and width, damage to reproductive organs, impaired egg production and rapid expulsion of the worms by day 14 after challenge. Expulsion of the worms was preceded by a significantly elevated (P<0.05) peripheral blood eosinophil (PBE) count, both in the initial (200.0+/-26.5 x 10(3)ml) and the challenge infection (400.9+/-165.4 x 10(3)ml). These findings suggest that rats acquire strong homologous immunity following initial exposure to S. venezuelensis. It is suggested that PBEs are involved in worm expulsion. A major target of these effector mechanisms is the reproductive system of S. venezuelensis.     

Evaluation of the Sprague-Dawley rat as a model for vertical transmission of Brucella abortus

Vertical transmission of Brucella abortus in Sprague-Dawley (SD) rats was verified with microbiologic, serologic, and polymerase chain reaction (PCR) methods. The 38 initially Brucella-free SD rats, weighing 200 to 250 g, were injected subcutaneously with 50 microL of a suspension containing 1 x 10(9) colony-forming units (cfu) of B. abortus biotype 1 Korean isolate. The rats were allowed to mate with uninfected SD rats. The isolate was detected by culture and by AMOS (abortus, melitensis, ovis, suis) PCR in testis tissue of infected male rats and splenic tissue of infected female rats. By 7 d after inoculation, the results of both the rose bengal test (RBT) and the plate agglutination test (PAT) were positive for antibody against B. abortus; the reciprocal antibody titre ranged from 200 to 400 in the 1-mo-old offspring and 800 in their dams. The infected rats directly transmitted Brucella to their breeding partners and offspring. Fetuses of infected dams were found to be infected at 20 d of gestation. These data are discussed in relation to a model for epizootic and zoonotic cases possibly involving wild animals. Additional rigorous experiments are warranted to explore the value of this model in developing measures to prevent congenital brucellosis.     

Biological activities of conjugated linoleic acid (CLA) and effects of CLA on animal products

Conjugated linoleic acid (CLA) is a collective term for a group of positional (c8, c10; c9, c11; c10, c12, and c11, c13) and geometric (cis,cis; cis,trans; trans,cis; and trans,trans) isomers of octadecadienoic acid (linoleic acid) with conjugated double bond system. Dietary CLA increased the ratio of saturated fatty acid (SFA) and decreased unsaturated fatty acid (USFA) in the egg yolk and CLA sources for fat improved the color stability possibly by inhibition of lipid oxidation and oxymyoglobin oxidation in beef patties. Also dietary CLA reduced purge loss in pork loin, it could be due not only to high intramuscular fat content but also to stability of cell membrane lipids assumed by the observed delay in lipid oxidation for CLA. Cholesterol content in egg yolk was significantly decreased by a supply of dietary CLA for 5 weeks feeding. Dietary CLA and storage of CLA eggs increased the firmness of hard-cooked egg yolk and the texture of yolks from hard-cooked CLA eggs was rubbery and elastic and yolk were more difficult to break using an Instron. The eggs produced by hens fed CLA were hard and were characterized by a reddish yolk when cooled to 4 °C for 10 weeks. Several studies have determined the antioxidant property of CLA. The oxidative reactions could influence CLA concentrations by either causing the formation of linoleic acid radicals, which in turn could be converted to CLA by hydrogen donors, or causing the oxidative destruction of the conjugated double-bond system of CLA.     

Diversity and detection of Korean Erwinia pyrifoliae strains as determined by plasmid profiling, phylogenetic analysis and PCR

Twenty-five strains of Erwinia pyrifoliae were investigated for their plasmid profiles and genetic relatedness. Four types of plasmid profile were observed for the first time, suggesting intraspecific plasmid profile diversity in E. pyrifoliae . Moreover, BOX-PCR and phylogenetic analysis based on the 16S-23S intergenic transcribed spacer (ITS) region showed genetic variations among E. pyrifoliae strains, although all strains were clustered in one group and separated from E. amylovora . On the other hand, ERIC-PCR and phylogenetic analysis based on partial groEL gene sequences revealed close genetic relatedness among the strains. Amplification with EpSPF and EpSPR primers of a fragment of approximately 0·65 kb from the genomic DNA of all E. pyrifoliae strains, but not from E. amylovora strains, suggested that this primer set is useful for identification of this pathogen.     

Molecular serotyping and antimicrobial resistance profiles of Actinobacillus pleuropneumoniae isolated from pigs in South Korea

Background: Actinobacillus pleuropneumoniae (APP) causes porcine pleuropneumonia (PP).

Objective: Serotypes and antimicrobial resistance patterns in APP isolates from pigs in Korea were examined.

Methods: Sixty-five APP isolates were genetically serotyped using standard and multiplex PCR (polymerase chain reaction). Antimicrobial susceptibilities were tested using the standardized disk-agar method. PCR was used to detect β-lactam, gentamicin and tetracycline-resistance genes. The random amplified polymorphic DNA (RAPD) patterns were determined by PCR.

Results: Korean pigs predominantly carried APP serotypes 1 and 5. Among 65 isolates, one isolate was sensitive to all 12 antimicrobials tested in this study. Sixty-two isolates was resistant to tetracycline and 53 isolates carried one or five genes including tet(B), tet(A), tet(H), tet(M)/tet(O), tet(C), tet(G) and/or tet(L)-1 markers. Among 64 strains, 9% and 26.6% were resistance to 10 and three or more antimicrobials, respectively. Thirteen different antimicrobial resistance patterns were observed and RAPD analysis revealed a separation of the isolates into two clusters: cluster II (6 strains resistant to 10 antimicrobials) and cluster I (the other 59 strains).

Conclusion: Results show that APP serotypes 1 and 5 are the most common in Korea, and multi-drug resistant strains are prevalent. RAPD analysis demonstrated that six isolates resistant to 10 antimicrobials belonged to the same cluster.     

Large-scale screening of rice accessions to evaluate resistance to bakanae disease

Bakanae disease is an important fungal disease in the world. No rice (Oryza sativa L.) varieties have been found to be completely resistant to this disease. To facilitate accurate, uniform and simultaneous screening of many rice accessions, we developed an inoculation method for microconidia of Fusarium fujikuroi using a tissue embedding cassette and seedling tray. Standards for evaluating the inoculated rice seedlings as healthy or unhealthy were also established. The method was fast and reproducible for accurately evaluating resistance to bakanae disease in rice.     

Lidocaine hydrochloride—sodium bicarbonate as an anesthetic for soft-shelled turtle Pelodiscus sinensis

ABSTRACT:   Attempts were made to understand how the different sizes (mean body weight of 4.1 ± 0.8 g for small and 182.6 ± 23.7 g for large) of the soft-shelled turtle Pelodiscus sinensis are affected by different temperature (25°C or 30°C), and different concentrations (700, 1000 and 1300 p.p.m.) of anesthetic lidocaine hydrochloride–sodium bicarbonate. The soft-shelled turtles were fed to satiation once daily. Three-way anova design (size × temperature × concentration of lidocaine hydrochloride) with duplicate was used. Twenty each of large and small soft-shelled turtles were distributed into six 30-L tanks. Exposure time of the soft-shelled turtle was affected by all factors (temperature, concentration and size). Exposure time of the soft-shelled turtle for anesthetizing decreased with increase in temperature and in concentration of lidocaine hydrochloride, and decrease in size. Recovery time for the soft-shelled turtle was also affected by all factors. Recovery time of the soft-shelled turtle increased with increase in temperature, concentration of lidocaine hydrochloride, and size. According to these results, lidocaine hydrochloride (1000 p.p.m.)–sodium bicarbonate seemed an effective anesthetic for sedating and handling the soft-shelled turtle. However, when an anesthetic is recommended for wide use, especially on commercially important edible organisms, the time organism takes to metabolize and excrete anesthetic chemicals from its body to a safe level must be given to allow fitness for human consumption.     

Automatic submerging and surfacing performances of model submersible fish cage system operated by air control

An automatic, submersible fish cage system using air control was developed and a set of model experiments were conducted to examine the automatic submerging characteristics of the cage. The components of the fish cage consist of a rigid frame assembly with 6 variable ballast tanks and 6 fixed ballast tanks. The variable ballast tanks were used to change the buoyancy characteristics of the system by air control so that the fish cage can either be placed at the surface or submerged. The cage is free to move vertically within a water column by adjusting the weight and the buoyancy with an air control system. The model of this system, with dimensions of 2.20 m in diameter and length and 1.04 m in net cage depth, was constructed to be 1/10 the size of the full-scale system. In the model experiments, the submerging and surfacing characteristics of the cage were regulated with measurements from a water-pressure gauge and a gyroscope incorporated into the automatic control system. Model tests were performed in a still water tank and a large wave tank to develop the algorithm required to control the cage system and to verify the ability of the automatic submersion mechanism to function. The control system was designed so that when the variable ballast tanks were flooded with water, the model descended. To raise the system, compressed air is injected into the tanks by opening the main evacuation valve on the manifold. After the required amount of compressed air is supplied, the main evacuation valves can be shut and as a result, the fish cage becomes buoyant. Measured performance results in a still water tank are then compared with calculations from a previously developed numerical technique. The submerging and surfacing characteristics of the fish cage were relatively similar to the measurements obtained with the physical model experiments using air control. The cage was submerged to a target depth when incidence wave heights were higher than the critical wave height and raised when little wave actions were detected in a wave tank. On the other hand, the cage was placed at the surface when incidence wave heights were the same as the critical wave height or lower.