Formation of Catechol Oxidase in Seed Coats of Pisum elatius during Seed Maturation

The catechol oxidase present in the seed coat of Pisum elatiusat various stages of seed maturation was partially characterized.The pH dependence and response to inhibitors and stimulatorsof the enzyme was determined. Inhibitors of protein synthesisand enzyme activity were introduced into the developing seedsvia the pod. During the early stages of seed maturation, theincreased enzyme activity was probably due to de novo synthesiswhile the increase in the later stages of maturation can bestbe accounted for on the basis of activation of pre-existingenzyme, perhaps due to conformational changes in the enzyme.The evidence for this view is discussed.     

Psychoactive substance use among medical students in a Nigerian university

The study was aimed at determining the prevalence, pattern and factors associated with psychoactive substance use among medical students in the University of Ilorin, Nigeria. All consenting medical students were requested to compile a 22-item modified, pilot-tested semi- structured self-report questionnaire based on the World Health Organization''s guidelines for student substance use survey. It was found that the most currently used substances were mild stimulants (33.3%), alcohol (13.6%), sedatives (7.3%) and tobacco (3.2%). Except for tobacco, the use of these substances seemed to be only instrumental. Substance use was directly associated with male gender, living alone, self-reported study difficulty, being a clinical student, and being aged 25 years or more. There was an inverse relationship of substance use with religiosity and good mental health.     

Defensive larval secretions of leaf beetles attract a specialist predator Parasyrphus nigritarsis

1. Noxious larval secretions of leaf beetles, which repel generalist predators, do not deter specialist syrphid fly predators (genus Parasyrphus ). These flies cause considerable mortality to the beetles, but little is known about their foraging behaviour.
2. Larvae of Parasyrphus nigritarsis were attracted to the volatile larval secretions produced by two prey species Phratora vitellinae and Linaeidea aenea. Parasyrphus nigritarsis feeds on both beetles in nature. Phratora vitellinae feeds on willows and utilizes host plant compounds for secretion production, while the alder-feeding L. aenea produces an autogenous secretion.
3. Fly larvae were strongly attracted to pieces of filter paper treated with larval secretion of the beetles. They attempted to feed on them for up to 7 min, and were equally attracted to the secretions of Ph. vitellinae and L. aenea . Fly larvae were also attracted to pure salicyl aldehyde, the main component of the secretion of Ph. vitellinae .
4. Fly larvae searched extensively for prey on leaves that had been damaged by beetle larvae. They also followed trails made with solutions containing faecal matter of prey larvae. They showed no differential preference for Ph. vitellinae or L. aenea , but always rejected larvae of the non-prey leaf beetle Agelastica alni .
5. Beetle secretions thus play an important, but unexpected, role in the feeding behaviour of P. nigritarsis . This predator uses the beetle secretion to locate its prey. The implications of these results for three trophic level interactions are discussed.