Influence of application methods on the degradation of permethrin in laboratory,soil aerobic metabolism studies

The effects of application rate, volume, solvent and soil moisture content on the kinetics of mineralization and degradation, of [¹⁴C] permethrin have been studied in a sandy loam soil under standard laboratory conditions. During the incubation period, up to 32 days, the temperature and moisture level of the soil were controlled. Apart from the effects of application rate, which have been widely reported, application volume had the most significant effect on mineralization rate and T_1/2. [¹⁴C]Permethrin, at a level of a 1 mg kg^?1 in the soil, applied in 100 μl of methanol, resulted in the evolution of 14% of the applied radiochemical as [¹⁴C] carbon dioxide over 30 days. The same level applied in 1000 μl mineralized at a faster rate, with 30% [¹⁴C]carbon dioxide evolved over 30 days. The test chemical applied to soil in methanol mineralized at a significantly faster rate than a similar concentration applied in ethanol. There was no significant difference when comparing applications made using acetonitrile with those using methanol or ethanol. The addition of formulation ingredients resulted in little or no variation in mineralisation rate compared to an equivalent application volume of methanol/water.     

Oral administration of β-alanine modifies carnosine concentrations in the muscles and brains of chickens

Carnosine, and its derivative anserine, are known to function as anti‐oxidants and putative neurotransmitters. They are especially rich in the breast muscle (Musculus pectoralis superficialis, MPS) of chickens. To clarify whether the concentrations of carnosine and anserine are altered by dietary management, the effect of oral administration of their constituent, β‐alanine (β‐Ala), was determined in the MPS and brains of chickens. Birds were orally administered β‐Ala (22 mmol/kg) twice a day for five consecutive days (from 2 to 6 days old). In the MPS, carnosine was increased by β‐Ala, whereas anserine and taurine were decreased. The concentrations of other free amino acids in the MPS were also modified by β‐Ala. In the brain, the oral administration of β‐Ala increased anserine and carnosine and decreased taurine, but caused no changes to other free amino acid concentrations. These results suggest that orally administered β‐Ala increases carnosine concentrations in both the MPS and brains of chickens. However, the effects of β‐Ala on other concentrations differ depending on the tissues.     

In vitro antimicrobial inhibition profiles of Mycoplasma bovis isolates recovered from various regions of the United States from 2002 to 2003.

Antimicrobial therapy continues to be important in reducing losses due to pneumonic forms of Mycoplasma bovis disease in beef and dairy calves. Although M. bovis diseases have been documented as frequent and economically important in the United States, there are no published reports on the antimicrobial activity of approved compounds against US strains. In this study, the authors report on the activity of 9 different antimicrobials against 223 recently recovered isolates of M. bovis. These isolates represent accessions from 5 geographic regions of the United States and were grouped by 4 tissues of origin (milk, respiratory, joint, or ear and eye). A broth microdilution test was used to determine minimum inhibitory concentration (MIC) values by reading redox changes detected in broth with alamarBlue (resazurin) indicator. For each antimicrobial, the median, MIC50, MIC90, mode, and range were calculated, and the values used for comparisons. In the absence of accepted breakpoint values, published MIC cutoff values for animal mycoplasmas as well as Clinical Laboratory Standards Institute interpretive criteria were used as a reference to define in vitro activity. The MIC values from active antimicrobials were found to distribute independently of region of origin of the isolates or of tissue of origin. Enrofloxacin, florfenicol, and spectinomycin were found to be active compounds in vitro. Oxytetracycline and chlortetracycline were active against more than half of the isolates. Very few isolates were inhibited by tilmicosin and none by erythromycin, ampicillin, or ceftiofur. The antimicrobial profiles determined for these US strains were remarkably similar to those reported for European isolates. However, unlike in Europe, there appears to be no diversity of profiles when US isolates are grouped by region or tissue of origin.     

Occurrence of Piscirickettsiosis-like syndrome in tilapia in the continental United States.

From 2001 to 2003, tilapia (Oreochromis sp.) farms in Florida, California, and South Carolina experienced epizootics of a systemic disease causing mortality. The fish exhibited lethargy, occasional exophthalmia, and skin petechia. The gills were often necrotic, with a patchy white and red appearance. Grossly, the spleen and kidneys were granular with whitish irregular nodules throughout. Granulomatous infiltrates were observed in kidney, spleen, testes, and ovary tissues, but not in the liver. The granulomas contained pleomorphic coccoid bacteria, measuring 0.57 +/- 0.1 x 0.8 +/- 0.2 microm, that were Giemsa-positive, acid-fast-negative, and Gram-negative. The bacteria had a double cell wall, variable electron-dense and -lucent areas, and were present in the cytoplasm and within phagolysosomes. The syndrome was associated with cold stress and poor water conditions. These findings are consistent with an infectious process caused by a Piscirickettsia-like bacterium described previously in tilapia in Taiwan and Hawaii. This report involves the first identified cases of a piscirickettsiosis-like syndrome affecting tilapia in the continental United States.     

Vitamin D status of wild Ricord's iguanas (Cyclura ricordii) and captive and wild rhinoceros iguanas (Cyclura cornuta cornuta) in the Dominican Republic.

Calcidiol (25-hydroxyvitamin D) values are reported for 22 wild Ricord's iguanas (Cyclura ricordii) and seven wild rhinoceros iguanas (Cyclura cornuta cornuta). Calcitriol (1,25-hydroxyvitamin D) values are reported for 12 wild Ricord's iguanas and seven wild rhinoceros iguanas. These animals were captured as part of a larger health assessment study being conducted on Ricord's iguanas in Isla Cabritos National Park, Dominican Republic. A total of 13 captive rhinoceros iguanas held outdoors at Parque Zoológico Nacional were also sampled for comparison. Mean concentrations of 25-hydroxyvitamin D were 554 nmol/L (222 ng/ml) with a range of 250-1,118 nmol/L (100-448 ng/ml) for wild Ricord's iguanas, 332 nmol/L (133 ng/ml) with a range of 260-369 nmol/L (104-148 ng/ml) for wild rhinoceros iguanas, and 317 nmol/L (127 ng/ml) with a range of 220-519 nmol/L (88-208 ng/ml) for captive rhinoceros iguanas. On the basis of these results, serum concentrations of at least 325 nmol/L (130 ng/ml) for 25-hydroxyvitamin D should be considered normal for healthy Ricord's and rhinoceros iguanas.     

Mycobacteriosis in a black-tailed deer (Odocoileus hemionus columbianus) caused by Mycobacterium kansasii.

An eviscerated hunter-harvested female black-tailed deer (Odocoileus hemionus columbianus) was submitted to the Washington Department of Fish and Wildlife. The deer was emaciated, devoid of adipose tissue, and the parietal surface of the thoracic cavity contained multiple granulomas. Acid-fast bacteria were detected histologically from the granulomas and were isolated and identified as Mycobacterium kansasii, a nontuberculous mycobacterium sporadically reported to cause tuberculosis-like disease in a variety of vertebrates. This was the first report of symptomatic disease caused by M. kansasii in free-ranging deer. This case indicates that atypical mycobacteria can cause tuberculosis-like disease in free-ranging deer and illustrates the importance of identifying causative agents of tuberculosis-like disease in wildlife.     

Induced Disease Resistance in Plants by Chemicals

Plants can be induced locally and systemically to become more resistant to diseases through various biotic or abiotic stresses. The biological inducers include necrotizing pathogens, non- pathogens or root colonizing bacteria. Through at network of signal pathways they induce resistance spectra and marker proteins that are characteristic for the different plant species and activation systems. The best characterized signal pathway for systemically induced resistance is SAR (systemic acquired resistance) that is activated by localized infections with necrotizing pathogens. It is characterized by protection against a broad range of pathogens, by a set of induced proteins and by its dependence on salicylic acid (SA) Various chemicals have been discovered that seem to act at various points in these defense activating networks and mimic all or parts of the biological activation of resistance. Of these, only few have reached commercialization. The best- studied resistance activator is acibenzolar-5-methyl (BION). At low rates it activates resistance in many crops against a broad spectrum of diseases, including fungi, bacteria and viruses. In monocots, activated resistance by BION typically is very long lasting, while the lasting effect is less pronounced in dicots. BION is translocated systemically in plants and can take the place of SA in the natural SAR signal pathway, inducing the same spectrum of resistance and the same set of molecular markers. Probenazole (ORYZEMATE) is used mainly on rice against rice blast and bacterial leaf blight. Its mode of action is not well understood partly because biological systems of systemically induced resistance are not well defined in rice. Treated plants clearly respond faster and in a resistant manner to infections by the two pathogens. Other compounds like beta-aminobutyric acid as wdl as extracts from plants and microorganisms have also been described as resistance inducers. For most of these, neither the mode of action nor reliable pre-challenge markers are known and still other pathways for resistance activation are suspected. Resistance inducing chemicals that are able to induce broad disease resistance offer an additional option for the farmer to complement genetic disease resistance and the use of fungicides. If integrated properly in plant health management programs, they can prolong the useful life of both the resistance genes and the fungicides presently used.     

Reinvestigating adjuvants for the wild oat herbicide,flamprop-M-isopropyl. II: Field performance

A field trials programme was conducted in which the performance of a new emulsifiable concentrate formulation (ECI) of flamprop-M-isopropyl containing the adjuvant, ‘Dobanol’ 25-7, in a ratio of 2:1 (by weight) with the AI, was compared with the current commercial formulation of ‘Commando’, in combination with its recommended adjuvant, ‘Swirl’, for the control of wild oat (Avena fatua L.) in wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). A further treatment, in which the ‘Dobanol’ 25-7: AI ratio was increased to 4:1 by the spray tank addition of the former, was also included. The mean results from six trials (five wheat, one barley) showed that the addition of ‘Swirl’ to ‘Commando’ was beneficial, increasing wild oat floret control from a mean value of 80% to 92% at current recommended rates (flamprop-M-isopropyl, 600 g ha^?1; ‘Swirl’, 2.5 litre ha^?1). However, combinations of flamprop-M-isopropyl and ‘Dobanol’ 25-7 gave superior levels of control even at lower AI application rates. For example, a mean level of 96% control of Avena spp. was obtained at 300 g AI ha^?1 with 1200 g ha^?1 ‘Dobanol’ 25–7; with even better control at higher rates of application of both components. This improvement in performance was accompanied by a higher risk of crop phytotoxicity than observed with the ‘Commando’/‘Swirl’ mixtures. Symptoms initially were scorch and subsequently growth depression, particularly of tillers. None of the mean values in the six ‘efficacy’ trials reached commercially unacceptable levels, but in a further six ‘crop effects’ trials (three wheat, three barley), in which double rates were applied, the levels of phytotoxicity did become unacceptable and subsequently reduced grain yields. In contrast, two barley ‘crop effects’ trials gave yields higher than the control plots, possibly through the effects of reducing stem length and lodging thereby enabling more efficient harvesting. Nevertheless, there were rates of application of flamprop-M-isopropyl in the range 300–400 g ha^?1 with ratios of ‘Dobanol’ 25-7 in the range 2:1 to 4:1 that would achieve high levels of control of Avena spp. without undue risk of crop phytotoxicity and further trials are planned to support this new adjuvant system.     

Electrophysiological identification of site-insensitive mechanisms in knockdown-resistant strains (kdr,super-kdr) of the housefly larva (Musca domestica)

The effects of pyrethroids were studied upon isolated segmental nerves and neuromuscular junctions in both susceptible (Cooper) and knockdown-resistant (kdr; super-kdr) strains of housefly larvae (Musca domestica L.). Isolated segmental nerves contained neither cell bodies nor synaptic contacts; thus, any effects of pyrethroids were attributed solely to their actions upon voltage-dependent Na⁺ channels. Threshold concentrations of the type II pyrethroid, deltamethrin, required to elevate the spontaneous firing rate of these nerves were determined. Both resistant strains were about ten times less sensitive to deltamethrin than the susceptible strain, but insensitivity of super-kdr nerves was no greater than in the less resistant kdr strain. At neuromuscular junctions, the minimum concentrations of pyrethroids needed to trigger massive increases in the frequency of miniature excitatory postsynaptic potentials (mEPSPs) were determined for deltamethrin and the type I pyrethroid, fenfluthrin. With fenfluthrin there was no detectable difference between the junctions of kdr and super-kdr strains, which were both about ten-fold less sensitive than Cooper junctions. With deltamethrin, kdr junctions were about 30 times less sensitive than those of Cooper; super-kdr junctions were dramatically insensitive to deltamethrin, being some 10000- and 300-fold less sensitive than those of Cooper and kdr respectively. Thus, in the synaptic assay, super-kdr conferred an extension in resistance over kdr only against the type II pyrethroid, it being ineffective against fenfluthrin. We suggest that kdr resistance comprises at least two site-insensitive areas within the nervous system. One involves insensitivity of the Na⁺ channel and has similar efficacy in both kdr and super-kdr strains against type I and II pyrethroids; the other is associated with the presynaptic terminal and is particularly effective in super-kdr resistance against type II pyrethroids. The latter could be associated with Ca²⁺-activated phosphorylation of proteins involved with neurotransmitter release. Such phosphorylation reactions are known to be perturbed by pyrethroids, especially by type II compounds.     

Failure of viral protein 3 of infectious bursal disease virus produced in prokaryotic and eukaryotic expression systems to protect chickens against the disease

In recent years, infectious bursal disease virus (IBDV) has become a serious economic problem as a result of the emergence of new and very virulent strains. Most of the antibodies produced against IBDV are for the structural proteins viral protein (VP) 2 (VP2) and VP3. The purpose of this study was to test the potential of recombinant VP3 to induce protective antibodies. The gene for VP3 was isolated from a virulent strain of the virus and cloned into prokaryotic (Escherichia coli) and eukaryotic (baculovirus) expression systems. The protein expressed by both systems was of the expected size (32 kD) and was detected by anti-IBDV antibodies. Following partial purification, the polypeptides were injected into intact birds and induced the production of high levels of anti-IBDV antibodies, as detected by immunoblot and enzyme-linked immunosorbent assay tests. These antibodies did not prevent changes in the bursa and mortality when birds were challenged with a virulent IBDV strain after vaccination with the recombinant VP3. The results show that VP3 polypeptide cannot be used as a subunit vaccine against IBDV and raise questions concerning the nature of the neutralizing epitope on this structural protein.