Studies on the Alkylation of Choline Acetyltransferase by Choline Mustard Aziridinium Ion

Although a potent irreversible inhibitor of high-affinity choline transport in rat brain synaptosomes, choline mustard aziridinium ion (ChM Az) appeared to be a relatively weak inhibitor of choline acetyltransferase (ChAT) in rat brain homogenates, and evidence for irreversible binding of this compound to the enzyme had not been established. Accordingly, the irreversible inactivation of partially purified rat brain ChAT by ChM Az was studied. This compound is a rather weak inhibitor of the enzyme, with 50% inhibition of ChAT activity achieved following 30 min incubation at 37 degrees C with 0.6 mM ChM Az. This result indicates that although ChM Az has affinity for many nucleophiles there was little diluting effect of the inhibitor in the crude brain homogenate which could be attributed to such reactions (50% inhibition caused by 1.8 mM ChM Az following 10 min incubation). Although the initial binding of ChM Az to ChAT may be of a competitive nature, irreversible bond formation resulted. The time-dependent alkylation reaction conformed to pseudo-first-order kinetics with an observed forward rate constant (kobs) of 0.173 min-1; the half-time (t 1/2) for irreversible binding was about 4 min. The irreversible inactivation of ChAT by ChM Az would appear to be slower than the alkylation of high-affinity choline carriers in synaptosomes by this compound, and the relatively weak inhibitory action of ChM Az against either partially purified ChAT or ChAT activity in crude rat brain homogenates is in striking contrast to previous evidence that ChAT in intact synaptosomes was inhibited irreversibly by lower concentrations of the inhibitor.     

The prevention of seed-borne diseases of flax III. The dusting, short wet and fixation methods of seed disinfection in relation to storage of the seed

Flax seed containing up to 10% of moisture was disinfected with a proprietary dry fungicide containing tetramethylthiuram disulphide (Nomersan) at the rate of 12 oz./cwt. of seed, and stored for periods of up to 18 months, without its germination being impaired.
Experiments were made with samples of seed the moisture content of which, before treatment, varied within the range of 5-8-13-2% and which were kept in a commercial store after disinfection. Treatments were carried out with an 8% solution of a soluble organo-mercurial (Ceresan U. 564) at the rates of 0-67 and 0-9 gal./cwt. applied by the short wet method, and with an organo-mercurial powder (Ceresan UT. 1875 A) at the rate of 12 oz./cwt. applied by the fixation method using 0-9 gal. of separated milk per cwt. The results obtained show that treatment by either method has the effect of lowering the percentage of viable seeds during subsequent storage and that the higher the moisture content of the seed before treatment the earlier this effect becomes apparent. It is suggested that seed to be treated by the short wet method on a commercial scale should be dried to contain about 5% of moisture, that not more than 0-67 gal./cwt. of liquid be applied and that the seed should not be stored for longer than 3 months after treatment. Following upon these suggestions, 10-ton lots of seed were treated commercially by the short wet method using a Kontramix machine and no ill effects on the crop were observed.     

Structure-activity relationship of a series of non peptidic RGD integrin antagonists targeting α5β1: part 1

Potent antagonists of the integrin α(5)β(1), which are RGD mimetics built from tyrosine are described. This letter describes the optimization of in vitro potency obtained by variation of two parts of the molecule, the basic group and the linker between the basic group and the phenyl central core.     

Isolation and Identification of Pythiaceous Fungi from Irrigation Water and their Pathogenicity to Antirrhinum, Tomato and Chamaecyparis lawsoniana

Pythiaceous fungi were isolated from irrigation water using a variety of natural and artificial baits. Isolates were also obtained by plating water samples directly on the surface of selective agar media. The selective medium of Ocana and Tsaq (1966) PlOVP, was modified by substituting rifampicin and ampicillin (10 and 500 μg cm^?3 respectively) for vancomycin to suppress bacterial growth from water samples. The pythiaceous fungi were identified as Pythiitm dissotocitm, P. middletonii, P. mamillatum, P. rostratum, Pythium“group 1”, “group 2” and “group 3” and Phytophtbom gona-podyides. All isolates of P. gonapodyides were the A1 strain and produced oospores when paired with an A2 isolate of P. drechsleri. Isolates were tested for their pathogenicity to Antirrhinum, tomato and Chatmaecyparis lawsoniana cv. Ellwoodii. Pythium middletonii and Pythium“group 1” caused severe pre-emergence damping-off of Antirrhinum seedlings, P. mamillatuni, P. rostratum and Pythium“group 3” were less pathogenic to the same host while P. dissotocum, Pythium“group 2” and Phytophthora gonapodyides were non-pathogenic. Only isolates of Pythium“group 1” were pathogenic to tomato seedlings. None of the fungi was pathogenic to rooted cuttings of Chamaecyparis lawsoniana cv. Ellwoodii.     

Evidence for single gene resistance in apple to brownheaded leafroller, Ctenopseustis obliquana, and implications for resistance to other New Zealand leafrollers

The survival and development rate of Ctenopseustis obliquana (Walker) (Lepidoptera: Tortricidae) larvae, and weight of pupae were measured on detached mature leaves of two apple (Malus domestica Borkh.) progenies derived from the resistant (R) parent ‘Prima’ crossed with the susceptible (S) cultivars ‘Liberty’ (n = 44) and ‘Red Delicious’ (n = 35). The R:S ratio in both these modified backcross families did not differ significantly from the 1:1 expected in the case of monogenic resistance, carried in a heterozygous condition in the resistant parent. The survival to pupation on the individual seedlings was either zero/very low (R) or high (S). With all resistant seedlings being heterozygous, this indicates that the resistance allele shows complete dominance over the susceptible allele. We have named this putative gene Cob1. The expression of the resistance was found to be influenced by both the colony of C. obliquana used and the time of the season when resistance was assessed. In a separate experiment with another tortricid, there was no survival of Planotortrix octoDugdale larvae on the apple cultivar ‘Prima’ and high survival on the cultivars ‘Liberty’ and ‘Red Delicious’. The similarity of the responses of the two leafroller species to these cultivars, and other published evidence concerning Planotortrix excessana (Walker) and Ctenopseustis herana(Felder and Rogerhofer), suggest that the resistance discovered to C. obliquana may be effective against all four endemic tortricid species. The implications of these findings for apple breeding and leafroller control in New Zealand are discussed.     

Screening for resistance in apple cultivars to lightbrown apple moth, Epiphyas postvittana, and greenheaded leafroller, Planotortrix octo, and its relationship to field damage

The mature leaves of 38 apple (Malus domestica Borkh.) (Rosaceae) cultivars were screened for resistance to laboratory colonies of Epiphyas postvittana (Walker) and Planotortrix octo Dugdale (Lepidoptera: Tortricidae) by measuring larval survival and development rate, and pupal weight, in no‐choice laboratory bioassays in early summer. There were few cultivar effects on larval mortality but Nevis 1, A40R04T119, and ‘Sir Prize’ reduced survival of E. postvittana. Effects on development time and weight were correlated, and were integrated into a single measure of resistance R_c. R_c varied greatly between cultivars for both leafroller species, and identified 15 and 11 cultivars with partial resistance to E. postvittana and P. octo, respectively. A further experiment with three of the cultivars in midsummer, using the laboratory colonies in comparison with new colonies (from field collected larvae), produced similar results for E. postvittana, but there was no survival of new colony P. octo larvae on two cultivars. These results for P. octo are consistent with other recent research showing extreme cultivar resistance and critical colony and seasonal influences. A series of 4‐year field trials with the 38 cultivars showed poor correlation between laboratory and field resistance for the dominant leafroller species in the field, E. postvittana. The combined data, however, identified ‘Red Dougherty’, ‘Sir Prize’, and A40R04T119 as potentially useful in breeding for resistance to this species. The implications of these findings for integrated pest management (IPM) programmes and for the breeding of leafroller‐resistant apple cultivars are discussed.     

Development of Orius vicinus (Ribaut) (Heteroptera: Anthocoridae) on Different Prey

The survival, development and adult size of Orius vicinus were studied on five prey species, the mites Aculus schlechtendali, Panonychus ulmi and Tetranychus urticae, and larvae of the insects Dasineura mali and Thrips obscuratus. Survival was high (74-100%) and O. vicinus was able to complete development on all prey species in an average of 22-26 days at 20 C. The most rapid development occurred on T. obscuratus, T. urticae and P. ulmi. Adult size was estimated from the length of the fifth instar cast skin, which averaged 2.18 to 2.48 mm on different prey. The largest bugs were obtained from feeding on T. obscuratus or D. mali. O. vicinus, which were fed A. schlechtendali, were the slowest to develop and produced the smallest adults. The results are discussed in relation to prey availability and observed predation in the field, and are compared with previous feeding studies.