Effect of methabenzthiazuron on growth and nitrogenase activity in Vicia faba

The effects of the herbicide methabenzthiazuron (175 and 220 g ha^-1) on vegetative and reproductive growth, nodulation and nitrogenase activity of Vicia faba were studied in the field under Mediterranean conditions. Nitrogenase activity of excised nodules was estimated using the acetylene reduction assay four times during the developmental period. Leaf area index, dry weight and nitrogen content of the different parts of the plants were measured. Methabenzthiazuron-treated plants showed an increase in nodulation, nitrogenase activity and vegetative growth at early pod fill. Methabenzthiazuron also caused an increase in leaf N content and fruits. These were transient effects found during early and mid pot fill. Nevertheless, plants treated with these sublethal doses of herbicide improved seed production and nitrogen content of seeds at harvest time. The stimulatory effect of methabenzthiazuron on N₂ fixation and vegetative growth seems not be related with the transient stimulatory effect on photosynthetic capacity, also caused by the herbicide, since the stimulatory effect on N₂ fixation was apparent during pod fill, when photosynthetic capacity declined and was not modified by methabenzthiazuron.     

Use of hydrogen cyanamide for apple and plum thinning

Effects of various concentrations of Dormex (a.i. 49% hydrogen cyanamide) on fruit thinning of Rome Beauty apple (Malus domestica Borkh.), Friar and Simka plums (Prunus salicina Lindley) were studied. A full bloom application of Dormex at all tested concentrations decreased Rome Beauty apple fruit set and yield, and increased fruit weight. Dormex at 0.25% (v/v) resulted in adequate apple thinning, indicated by production of an optimum fruit weight (320 g). Prebloom and full bloom applications of Dormex at greater than 0.75% reduced plum fruit set and yield in Friar. Full bloom application of Dormex at 0.50% showed a satisfactory fruit set, yield, and fruit weight in Friar plum. Prebloom Dormex application had no significant effect on `Simka' plum fruit set or yield, but full bloom application decreased fruit set and yield.     

Use of a Plasmid DNA Probe To Monitor Populations of Bacillus pumilus Inoculant Strains in Hay

We are evaluating naturally occurring isolates of Bacillus pumilus for use as microbial hay preservatives. Seven isolates of B. pumilus from hay contained a 42-kb cryptic plasmid (pMGD296). We wished to determine whether pMGD296 could be used as a molecular marker to follow populations of these isolates in hay over time. Southern blots and colony blots of 69 isolates of B. pumilus and other Bacillus spp. were probed with ³²P-labeled pMGD296. Twenty-nine probe-positive isolates were identified; of these, 28 contained a plasmid with a restriction profile identical to that of pMGD296. One isolate from untreated hay contained a 40-kb plasmid (pMGD150) that was homologous to pMGD296 but had a different restriction fragment pattern. Regions of homology between the two plasmids were identified by Southern blotting, and a 1.9-kb HindIII-PstI fragment of pMGD296 lacking strong homology to pMGD150 was cloned in pUC18. The cloned fragment hybridized only with isolates containing pMGD296 and was used to estimate populations of these isolates in treated and untreated hay.     

Flavin-containing monooxygenase: a major detoxifying enzyme for the pyrrolizidine alkaloid senecionine in guinea pig tissues

Evidence based on optimal pH, thermal stability, and enzyme inhibition data suggests that the NADPH-dependent microsomal N-oxidation of the pyrrolizidine alkaloid senecionine is carried out largely by flavin-containing monooxygenase in guinea pig liver, lung, and kidney. In contrast, the hepatic microsomal conversion of senecionine to the pyrrole metabolite (+/-)-6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (DHP) is catalyzed largely by cytochrome P450. However, the rate of senecionine N-oxide formation (detoxication) far exceeded the rate of DHP formation (activation) in guinea pig liver microsomes over a range of pHs (pH 6.8 to 9.8). In guinea pig lung and kidney microsomes, N-oxide was the major metabolite formed from senecionine with little or no production of DHP. The high rate of detoxication coupled with the low level of activation of senecionine in liver, lung, and kidney may help explain the apparent resistance of the guinea pig to intoxication by senecionine and other pyrrolizidine alkaloids.     

Comparison of rainbow trout and mammalian cytochrome P450 enzymes: evidence for structural similarity between trout P450 LMC5 and human P450IIIA4

Studies were undertaken to determine the immunochemical relationship between constitutive trout cytochrome P450s and mammalian cytochrome P450IIIA enzymes. Polyclonal antibodies (IgG) generated against trout P450 LMC5 reacted strongly with P450IIIA1 in dexamethasone-induced rat liver microsomes and with P450IIIA4 in human liver microsomes in immunoblots. In contrast, rabbit anti-P450 LMC1 IgG did not recognize these proteins in rat and human liver microsomes. Reciprocal immunoblots using anti-rat P450IIIA1 showed that this antibody does not recognize trout P450 LMC1 or LMC5. However, anti-human P450IIIA4 IgG was found to cross react strongly with P450 LMC1 and LMC5. Progesterone 6 beta-hydroxylase activity of trout liver microsomes, a reaction catalyzed by P450 LMC5, was markedly inhibited by anti-P450IIIA4 and by gestodene, a mechanism-based inactivator of P450IIIA4. These results provide evidence for a close structural similarity between trout P450 LMC5 and human P450IIIA4.     

A study on melanogenesis and catecholamine biosynthesis during Bufo bufo development

Tyrosinase and L-DOPA decarboxylase activities have been investigated during Bufo bufo development since catecholamines and melanin are formed from common substrates in homologous cells. Catecholamines first appear at stage 13 (neural plate), but tyrosinase, at a very low level, and L-DOPA decarboxylase are present throughout all of prior development. Hence, L-DOPA decarboxylase activity is not likely to be correlated with the control of catecholamine synthesis, although at stage 17 it is mainly localized in the nonneural part of the embryo. The distribution of young melanosomes and L-DOPA decarboxylase suggest a separation between melanogenesis and catecholamine synthesis.     

Growth and characterization of human skin epithelial cell cultures

Summary In 129 of 140 attempts, human skin cells were successfully cultured on the dermal collagen bed of sterile, dead pigskin. Diploid epithelial cells grew selectively on the collagen bed; fibroblasts grew on the glass surfaces of the culture dishes. The cultures could be subdivided physically up to six times at a 1:2 split ratio, but at least 24 to 48 cell generations were produced over the months the cells could be carried. Much of the cell multiplication resulted in maturation into distinct basal, squamous, granular, and keratinized cell layers. The cultured cells were considered epithelial because of their shape, possession of intercellular bridges, desmosomes and tonofibrils, and because they formed maturating epithelium in vitro and upon transplantation back to the original human donor. As the cells grew they digested the pigskin collagen, thus producing clear zones that could be used to monitor and quantitate cell growth. Multiplication of epithelial cells, rather than migration, was indicated by mitotic figures in colchicine-treated cultures and by DNA synthesis. Expert technical assistance was provided by Nancy Allen (cell culture); William Towler (electron microscopy); James Malone, Nona Scaife, and Joy M. Nicolet (cytogenetics); R. Thomas Campbell and Dorothy Sarver (photography); and V. L. Angerstein, Susan Ekker, and Arnater Yarbrough (histology). This work was supported by The United Fund Cancer Society of Summit County, the Greater Cleveland Associated Foundation (grant no. 3G3490X1), the National Institute of General Medical Services (grant no. 1 R01 GM 21929-01), and the Charles E. Merrill Trust.     

The isolation and identification of the female sex pheromones of the red bollworm moth, Diparopsis castanea

The female sex pheromones of the red bollworm moth, Diparopsis castanea, were isolated by solvent extraction of the terminal abdominal segments of the female moth followed by purification of the solvent extract by liquid-solid and gas chromatography. The pheromones were identified by gas chromatographic analysis, micro-ozonolysis, infra-red and mass spectroscopy, and comparison with synthetic material. The major pheromone was 9,11-dodecadien-1-yl acetate (80 : 20 trans : cis). Minor components identified were trans 9-dodecen-1-yl acetate, 11-dodecen-1-yl acetate, and dodecan-1-yl acetate.     

Proteins toxic to arthropods in the venom of elapid snakes.

It has been found that the lethal action of elapid snake venoms to arthropods (fly larvae and isopods) is due to proteic factors differing from the toxins which are strongly and specifically active on mammals.This conclusion was based on the following: (1) Lack of any correlation between the toxic activity on larvae, isopods, and mice of ten elapid snake venoms. (2) Absence of any toxicity to arthropods in pure toxins isolated and purified from several elapid snake venoms according to their lethality. (3) Electrophoretical separation of the venom of the snake Naja mossambica mossambica (= N. nigricollis mossambica) resulted in fractions active either to arthropods and/or to mice. (4) Separation of the above venom by gel filtration on Sephadex G-50 enabled the isolation of fractions highly toxic to arthropods. (5) The above fractions demonstrated a high phospholipase activity corresponding to about 80 per cent of the total activity of the whole venom. The link between phospholipase and toxicity to arthropods will serve as a target for further investigation.It appears that the phenomenon of diversity in toxic activities of different proteins to different groups of organism, as previously demonstrated in scorpion venoms, is equally shared by elapid snake venoms.