Effect of canopy cover,seeding depth,and soil moisture on emergence of Centaurea maculosa and C. diffusa*

The effects of canopy cover, seeding depth, and soil moisture on emergence of Centaurea maculosa Lam. and C. diffusa Lam. were studied. Canopy cover had no effect on ermergence rate (seedlings/day/100 seeds) of either species. Seeds of both species emerged faster when placed on the soil surface. Emergence rate decreased as seeding depth increased. Both species required more than 55% initial soil moisture to initiate emergence, with 65–70% being optimum. Percentage emergence followed exactly the same trend as emergence rate. C. maculosa had better emergence characteristics over a wider range of conditions than C. diffusa, possibly being some of the reasons for the former having a wider geographical distribution in the United States and Canada.     

Metabolic fate of [14C]endrin in bluegill fish

Bluegill absorbed 85% of 1 ppb of endrin from water within 48 hr under static exposure conditions. The absorbed radiocarbon was eliminated linearly with a half-life of about 4 weeks. Analyses of eliminated radioactivity revealed only conjugated metabolites. 12-anti-Hydroxyendrin and 12-syn-hydroxyendrin were tentatively identified by cochromatography using thin-layer chromatography/autoradiography and gas chromatography. These metabolites were also present as conjugates in the fish organs. Seventy-three percent of the absorbed radioactivity recovered from fish extracts was in the form of unchanged endrin.     

Melanin biosynthesis in Pyricularia oryzae: Site of tricyclazole inhibition and pathogenicity of melanin-deficient mutants

Tricyclazole (5-methyl-1,2,4-triazolo[3,4-b]benzothiazole) inhibits melanin synthesis in Pyricularia oryzae at concentrations less than 0.01 μg/ml. The primary site of inhibition in the biosynthetic pathway occurs between scytalone and vermelone. Accumulation of several metabolites derived from melanin precursors along branch pathways is associated with inhibition of melanin biosynthesis. At low tricyclazole concentrations (0.01–1 μg/ml), predominant accumulation of 2-hydroxyjuglone and 3,4-dihydro-3,4,8-trihydroxy-1-(2H)-naphthalenone (3,4,8-DTN) occurs as a result of the primary block between 1,3,8-trihydroxynaphthalene and vermelone. As the concentration of tricyclazole is increased from 1 to 10 μg/ml, flaviolin accumulation is markedly enhanced, whereas that of 3,4,8-DTN and 3,4-dihydro-4,8-dihydroxy-1-(2H)-naphthalenone is depressed, indicating possible secondary sites of inhibition in the main and branch pathways. Five melanin-deficient mutants of P. oryzae that phenotypically resemble the tricyclazole-treated wild-type strain were nonpathogenic or rarely infected two rice varieties. Three of the mutants studied were genetically defective in the melanin biosynthetic pathway at the site blocked by tricyclazole in the wild type. The wild-type strain converted both scytalone and vermelone to melanin; whereas the three mutants and the tricyclazole-treated wild type converted only vermelone to melanin. The data suggest a relationship between melanin biosynthesis and pathogenicity in P. oryzae.     

Comparative inhibition of the juvenile hormone esterases from Trichoplusia ni,Tenebrio molitor, and Musca domestica

Twenty-seven compounds were screened as potential inhibitors of juvenile hormone esterases. Of these compounds O-ethyl-S-phenyl phosphoramidothiolate provided the best inhibition for the cabbage looper, Trichoplusia ni (Hubner), and the yellow mealworm, Tenebrio molitor L., while the juvenile hormone esterases of the house fly, Musca domestica L., were best inhibited by a juvenoid carbamate (1-(m-phenoxy-N-ethyl carbamate)-3,7-dimethyl-7-methoxy-2E-octene). The inhibition patterns of T. ni and T. molitor are similar, while those of M. domestica are relatively different. Further studies on the juvenile hormone and α-napthyl acetate esterases of T. ni showed that they could be differentially inhibited. Diisopropyl phosphorofluoridate and an alkyl trifluoromethyl ketone selectively inhibit the hydrolysis of α-naphthyl acetate and juvenile hormone, respectively, while O-ethyl-S-phenyl phosporamidothiolate inhibits both enzymes. The juvenile hormone esterases of T. ni also appear to be unique enzymes that are selective for juvenile-hormone-like molecules. The in vivo inhibition of T. ni juvenile hormone esterases by O-ethyl-S-phenyl phosphoramidothiolate slows the in vivo hydrolysis of juvenile hormone and results in delayed pupation and malformed larvae that resemble larval-pupal intermediates. Thus, the esterases involved in juvenile hormone metabolism appear to be important in juvenile hormone regulation.     

Physiological actions of dinoterb,a phenol derivative: 2. Effects on isolated plant mitochondria and chloroplasts

Dinoterb, a contact herbicide, affects respiration and photosynthesis of mitochondria and chloroplasts. On mitochondria, at low concentrations, it acts as an uncoupler of oxidative phosphorylation; at higher concentrations, it inhibits the electron transport chains, probably before cytochrome c. On chloroplasts, dinoterb has a stimulatory effect on oxygen uptake in the reduced dichlorophenol-indophenol→methyl viologen couple; however, it is also an inhibitor of the Hill reaction and its site of inhibition is located before plastoquinone, near photosystem II.     

Egg production in relation to the results of a long term serological survey of 73 flocks of fowl

Summary Seventy-three flocks of fowl were tested at regular intervals for the presence of precipitins to fowl adenovirus (AV) and infectious bronchitis virus (IBV), haem-agglutinating inhibiting antibodies to BC14 virus, and of agglutinins to Mycoplasma gallisepticum (M.g.) and Mycoplasma synoviae (M.s.). In all the eight flocks affected with Egg Drop Syndrome (EDS '76), egg production problems were associated with increasing numbers of BCI4 virus reactors and AV reactors. In flocks showing production problems other than EDS '76 without any apparent cause, the average percentage of AV reactors increased significantly after the rearing period; this was not true of IBV reactors. BC14 reactors were either absent or present only once, in small numbers and with low titres, during the test period. The average percentage of AV reactors did not increase after the rearing period either in normally producing flocks or in flocks with production problems for which other diseases or dietary errors plausibly accounted for these problems. All this suggests a pathogenic role of AV in production problems. One can conclude from the high percentage of reactors in all groups of flocks that sub-clinical IBV infections are common. The percentage of IBV reactors during the laying period of flocks with EDS '76 was significantly higher than that of normally producing flocks. It is therefore suggested that subclinical IBV infection could be among the factors causing stress, acting as a trigger for EDS '76. All M.g.-infected flocks showed production problems; M.s. infections could not be related to egg production disturbances.     

Nitrate poisoning in cattle

Summary In a series of experiments the effect of administering KNO(2) was studied, during parturition, on the capability of oxygen transport of maternal blood and on oxygen transfer to foetal blood. The following blood parameters were analysed, MHb percentage, pO(2), O(2)-saturation, pH, pCO(2), and (NO(2)) in maternal arterial blood (carotid art.) and venous blood (jugular vein) and in foetal arterial blood (umbilical art.) and venous blood (umbilical vein). The relative O(2)-saturation was calculated from the estimated O(2)-saturation by multiplying with the factor Hb (mmol/1) minus MHb (mmol/1), divided by Hb (mmol/1). In addition, blood pressure in the carotid artery, heart rate, and respiration rate in the dam were continuously recorded for some hours. A dosage of 9 to 12 mg of NO(2)/kg body weight intravenously or of 30 mg of NO(2)/kg body weight orally to the dam caused much higher MHb percentages and NO(2) contents in the maternal blood than in the foetal blood. In maternal blood the ratio of NO(2) content td MHb percentage was proportional to that in foetal blood. In the arterial blood, MHb percentages were almost as high as in the venous blood. After administering of nitrite, relative O(2)-saturation dropped simultaneously with the increase in methaemoglobin. Nitrite treatment caused a drop in the maternal blood pressure; heart rate and respiration rate increased. O(2)-saturation in the blood in the umbilical vein was much lower in the animals with nitrite treatment than in those without. These experimental results show clearly that the oxygen capacity of the blood decreases after nitrite treatment. In pregnant cows the oxygen supply to the foetus will be adversely affected after nitrate intake, especially by the lower oxygen transfer via the placenta, though hardly at all by methaemoglobin formation in the foetal blood. When the oxygen transfer to the foetal blood decreases too sharply, intra-uterine death and ultimately abortion may result.     

Egg transmission of egg drop syndrome 1976 virus in fowl

Summary Egg transmission of egg drop syndrome 1976 virus (BC14 virus) in fowl was demonstrated in the second and third week after experimental infection. Eggs of BC14 virus infected hens were incubated weekly after disinfection with formaline gas. After 18 days of incubation, eggs with live embryos were homogenized. This egg material was fed to adult hens, housed in isolators. Seroconversion in these birds demonstrated egg transmission. It is suggested that egg transmission occurs as a result of viremia.     

Total hemolytic complement values in normal and diseased dog populations

The optimum conditions for handling and storage of canine sera for total hemolytic complement assays were assessed. Sera from 113 normal dogs and 217 clinical admissions to the University of Pennsylvania Veterinary Hospital were assayed for total hemolytic complement levels. Normal sera had a mean value of 185 CH50 units. Sera from animals with systemic lupus erythematosus and hemorrhagic gastroenteritis, had significantly lower mean levels of complement than the normal group. Sera from dogs with generalized demodectic mange, tumors, various inflammatory diseases, hypothyroidism, seborrhea, and rheumatoid arthritis had values significantly higher than the normal population.     

Experimental infection of calves with two strains of bovine virus diarrhoea virus: certain immunological reactions

Certain immunological responses of 4-6 month old calves experimentally inoculated with either cytopathic or non-cytopathic bovine virus diarrhoea virus (BVDV) were compared with those of uninfected control calves. The tests used to demonstrate the immunological responses were the transformation of lymphocytes by PHA mitogen, the percentage of lymphocytes with surface immunoglobulin, and the antibody titres induced by an intravenous inoculation of killed Brucella abortus. There were no significant differences between the two groups of calves and therefore, the mild experimental disease produced by BVDV did not appear to affect adversely the immunological response.