Antimicrobial susceptibility of pathogenic Escherichia coli isolated from pigs in Korea

The in vitro susceptibilities of 285 isolates of Escherichia coli from preweaned and postweaned pigs with diarrhea and edema disease were tested with the 15 commonly used antimicrobial drugs by an agar dilution minimal inhibitory concentration procedure according to National Committee for Clinical Laboratory Standards (NCCLS) guidelines. All E. coli isolates tested in this study belonged to enterotoxigenic E. coli, attaching and effacing E. coli, or Shiga toxin-producing E. coli. Field isolates had low MIC90 for ceftiofur (1 microg/ml). No correlation in antimicrobial resistance was found in three types of E. coli.     

Lectin histochemistry of Peyer's patches in the porcine ileum

Lectin staining pattern in Peyer's patches of porcine ileum was studied using twenty one biotinylated-labeled lectins as cell markers which were visualized with avidin-biotin-peroxidase complex method (ABC). WGA appears to be a selective marker for tingible body macrophages in the porcine germinal centers. ConA may be a positive marker for the lymphoid tissues, whereas 9 lectins (DBA, SBA, SJA, s-WGA, PNA, ECL, UEA-I, PHA-E, and PHA-L) may be negative markers for the lymphoid tissues in all areas.     

Isolation and characterization of a Sagiyama virus from domestic pigs.

In 2002, a strain of Sagiyama virus (SAGV) designated ML/Taiwan/02 was isolated from farmed pigs in Taiwan. The nsP1 and E1 gene sequences of the ML/Taiwan/02 strain shared 98.6 and 96.7% homology, respectively, with corresponding genes of a Japanese strain of SAGV. Nucleotide and amino acid sequence comparison revealed this strain of SAGV to be most closely related to Getah virus, as opposed to its current classification as a subtype of Ross River virus. To investigate the seroprevalence of SAGV infection in Taiwan, a total of 586 pig sera collected from 11 of 17 Taiwanese districts were tested for serum neutralizing antibodies (SNA) against SAGV. Results indicated that 51% of the samples had SNA titer > or = 4, and 40% had SNA titer > or = 48, indicative of repeated exposure to SAGV in the field. To study the pathogenicity of the ML/Taiwan/02 strain, this strain was experimentally inoculated into 4-week-old specific-pathogen-free pigs that were seronegative for SAGV. Viremia was detected during postinoculation days (PID) 2-4, when the SNA titer was < or = 16. By PID 7, viremia was no longer detectable, coinciding with the increase of SNA titer to > or = 48. Clinical illnesses or remarkable lesions were not observed. To the authors' knowledge, this is the first reported isolation of a strain of SAGV from pigs in the field. The virus is experimentally nonpathogenic to pigs but is moderately widespread, most likely via repeated exposure to virus-carrying mosquitoes.     

Determining the toxicity and hazard to fish of a rice insecticide

The experiments described were carried out to establish whether the effects of the insecticide, Ripcord (active ingredient cypermethrin), on fish, would limit its use in rice. Laboratory and field experiments were carried out, and the effects of cypermethrin were compared with those of a ‘standard insecticide’, carbofuran, widely used for pest control in rice, and a ‘positive control’, chlorfenvinphos, expected to be toxic to fish in rice paddies at insecticidally effective rates. Acute toxicity tests in the laboratory with the technical materials on the fish Tilapia nilotica showed cypermethrin, with a 96 h LC₅₀ value of 2 μg/l, to be some 20 times more toxic than chlorfenvinphos, with a 96 h LC₅₀ value of 39 μg/l, and some 250 times more toxic than carbofuran with a 96 h LC₅₀ of 480 μg/l. The LC₅₀ values obtained from laboratory tests with formulated products (cypermethrin EC, chlorfenvinphos granules and carbofuran granules) on T. nilotica and Cyprinus carpio were broadly in agreement with those obtained from the tests with the technical materials and confirmed C. carpio to have a similar susceptibility to that of T. nilotica. However, a field experiment carried out in paddy rice in Korea with commercial formulations and at commercial application rates showed that mortality of caged C. carpio was much less with cypermethrin (< 15%) than with chlorfenvinphos (97%) or carbofuran (67%). A second field experiment in Spain where cypermethrin was applied by air resulted in no mortality of caged C. carpio held in the paddy. It is concluded that the limited toxic effects of cypermethrin on fish in the field, when compared with those of chlorfenvinphos and carbofuran, make it acceptable for use in rice. The effects of cypermethrin were limited in comparison with those of chlorfenvinphos and carbofuran because only very low application rates of cypermethrin are needed to give pest control. The penetration of the liquid cypermethrin formulations into the water was also lower than that of the granular insecticides and, finally, cypermethrin was more rapidly lost from water. Together, these factors are sufficient to explain the minimal toxic effects of cypermethrin in the field when compared with chlorfenvinphos and carbofuran, despite its considerably higher acute toxicity determined in laboratory tests.     

Comparative studies on the distribution of glutamate transporters in the retinae of the Mongolian gerbil and the rat

Glutamate is the major excitatory amino acid transmitter in vertebrate retinae. Glutamate transporters therefore play an important role in the precise control of glutamate concentration in the synaptic cleft by regulating extracellular glutamate concentration. In the present study, we performed an analysis of the expressions of three glutamate transporters in gerbil retina using immunohistochemistry. In the gerbil retina, excitatory amino acid carrier 1 and glutamate transporter 1 immunoreactivity was predominant in the ganglion cells but not amacrine or bipolar cells. Glutamate/aspartate transporter (GLAST) immunoreactivity was observed in the radial gliocytes of which the dense network of fine processes was localized in the inner and outer plexiform layers. GLAST immunoreactivity was also detected in astrocytes in the nerve fibre layer. These results demonstrate that three glutamate transporters show specific distributions in the gerbil retina and suggest that the glutamate re-uptake system in the gerbil retina may be different from that of the rat.     

Dose response studies of acute feline immunodeficiency virus PPR strain infection in cats

The effects of virus dose on host response were evaluated for the PPR strain of feline immunodeficiency virus (FIV-PPR). Specific pathogen-free cats were inoculated intravenously with 50, 250 or 1250 TCID(50) of FIV-PPR. Two weeks after inoculation, virus was detected in 10(6) peripheral blood mononuclear cells (PBMCs) of all infected animals, and the CD4(+):CD8(+) T lymphocyte ratios fell from greater than 2 to approximately 1 in all infected animals within the first 8 weeks after infection. Provirus detected in all groups using PCR and 10(3) PBMC was biphasic. Nine of 15 animals were positive between weeks 2 and 4 p.i. and 14 of 15 were positive by week 8 p.i. Transient lymphadenopathy was detected in most cats receiving 1250 TCID(50) and the 250 TCID(50) of virus, whereas no lymphadenopathy was detected in the 50 TCID(50) group or the five uninfected cats. Animals that had received the largest dose seroconverted earliest (on average at week 4.0) and those receiving the least seroconverted last (on average at week 5.6). Neither neutropenia nor lymphopenia were detected. FIV-specific CTL responses of memory effector cells could be detected in animals receiving all three doses but was highly variable among individual animals. Neurological manifestations determined after 15 weeks p.i. were observed in most infected cats, including two of the three that had received 50 TCID(50) of virus. However, the observed neurologic abnormalities were markedly less severe in the animals receiving the least amount of virus. Therefore, lymphadenopathy and neurologic signs of illness were less severe and seroconversion was slower in the animals that received the lowest dose compared with those receiving the 250 and 1250 TCID(50) doses of the FIV-PPR strain.     

Comparative evaluation of antioxidant potential of alaternin (2-hydroxyemodin) and emodin

The antioxidant activities of alaternin (2-hydroxyemodin) and emodin were compared for their respective potentials to inhibit lipid peroxidation in the linoleic acid system by the thiocyanate method, to inhibit total reactive oxygen species generation in kidney homogenates using 2',7'-dichlorodihydrofluorescein diacetate, to inhibit peroxynitrite formation by the 3-morpholinosydnonimine system, which generates superoxide radical and nitrogen monooxide, and to scavenge authentic peroxynitrites. Both alaternin and emodin were found to inhibit the peroxidation of linoleic acid by the thiocyanate method in a dose-dependent manner. Whereas the former shows inhibitory activities in reactive oxygen- and nitogen-mediated reactions, the latter does not. These results indicate that alaternin is a potentially effective and versatile antioxidant and can be used to protect biological systems and functions against various oxidative stresses.