Regulation of the juvenile hormone titre in the Colorado potato beetle

Three main topics were investigated in regulation of the titre of juvenile hormone in haemolymph of the Colorado potato beetle ( Leptinotarsa decemlineata Say): enzymic breakdown of the hormone; binding and protection of the hormone by carrier proteins; the synthetic capacity of the corpora allata.Juvenile hormone was broken down by two major pathways: ester hydrolysis by esterases and hydration of the epoxide group by epoxide hydratases in tissue. In haemolymph of the beetle, juvenile hormone is solely broken down by juvenile hormone esterases. An in vitro method was developed to measure the catalytic activity of juvenile hormone esterase from haemolymph. High activities were observed in fourth-instar larvae and in beetles just before diapause. Lower activities were found in third- instar larvae and in beetles reared with long days, at diapause and after diapause. The juvenile hormone esterase was insensitive to diisopropylfluorophosphate (DFP), an inhibitor used to distinguish between carboxylesterases and esterases specific to juvenile hormone. Electrophoresis of the esterase from haemolymph showed one or more esterases specific to juvenile hormone.The short half-life of juvenile hormone measured in vivo and in vitro in the haemolymph and inhibition studies with Triton X-100 suggests that juvenile hormone esterases in haemolymph govern breakdown. Activities of juvenile hormone esterase correlate well with the juvenile hormone titre.The sharp changes in juvenile hormone esterase suggest that esterase activity is regulated. The mechanism was studied by supplying juvenile hormone and by microsurgery. Treatment of diapausing beetles with juvenile hormone itself or analogues caused an increase in activity of juvenile hormone esterase within 24 h. Ligation or removal of corpora allata suggested that this induction was an indirect effect of juvenile hormone. Transfer from short day to long day and treatment with hormone of beetles reared with short days prevented high activity of juvenile hormone esterase. Removal of corpora allata at emergence from beetles reared with short days resulted in the same. In beetles reared with short days the titre of hormone during the first days after adult emergence probably induces the rise in esterase. Esterase activity is thus most likely controlled indirectly by the hormone, via a centre in the brains (hormostate). The level of esterase activity is probably dependent on the sensitivity of this hormostate and on the titre of the juvenile hormone.In several insects juvenile hormone is transported bound to carrier proteins. In haemolymph of larval and adult Colorado potato beetles lipoproteins of high molecular weight (>100,00 daltons) were found, capable of binding juvenile hormone, its analogues, and palmitic acid. The lipoproteins were partially separated by gel permeation chromatography and electrophoresis on polyacrylamide gel. The binding characteristics of the lipoproteins indicate low affinity (K d ≈10 -5 M), low specificity and high binding capacity. The juvenile hormone complexed to lipoproteins was protected against esterases from haemolymph to some extent. Thus these carrier lipoproteins probably play little role in the regulation of the titre of juvenile hormone.In the last part of our investigations the activity of the corpora allata was measured in vitro. High activities were observed in beetles reared with long days and in beetles after emergence. In beetles reared with short days, amounts of hormone produced were intermediate until Day 6 after emergence, thereafter declining to a low value. During diapause, production remained low. The production by corpus allatum and the activity of juvenile hormone esterase were in good agreement with the titre of juvenile hormone. The corpora allata are probably the primary regulator of the hormone titre in the Colorado potato beetle.<p/

Interactive computer graphics system for structural sizing and analysis of aircraft structures

A computerized system for preliminary sizing and analysis of aircraft wing and fuselage structures was described. The system is based upon repeated application of analytical program modules, which are interactively interfaced and sequence-controlled during the iterative design process with the aid of design-oriented graphics software modules. The entire process is initiated and controlled via low-cost interactive graphics terminals driven by a remote computer in a time-sharing mode

The effect of employers\u27 attitudes on the implementation of computer aided manufacturing techniques in the furniture industry in Western Australia

In this study, the incorporation of computers in industry is compared with the industrial revolution. It is envisaged that computers in industry will bring about similar sweeping changes to the workforce as those that took place during the eighteenth century. However, it is noted that, thus far, Australian industry leaders in general remain ignorant of these changes (Eckersley 1988,p.3) and the Western Australian furniture industry is no exception. If Australian industry in general and the Western Australian furniture industry in particular, are to avoid a similar decline in economic competitiveness to that experienced by European countries {Marcum 1986,p.28 ), there must be a change of attitude toward the implementation of computer technology. In an attempt to determine and discuss some of the reasons for this attitude within the furniture industry in Western Australia, this study isolates the Western Australian furniture industry from other industries and collects information based on the beliefs of its employers. These beliefs, in turn, lead to attitudes which may affect the implementation of C.A.M. and it is these attitudes that were tested with the use of a questionnaire designed specifically for this purpose

The role of expressed emotion and social support in psychological adjustment to myocardial infarction

This longitudinal study wished to assess the power of expressed emotion components and social support in predicting levels of a variety of intra-psychic concepts associated with recovery from myocardial infarction (M.I.). Such concepts include anxiety, depression, self-esteem, self-efficacy, attitudes towards disability, locus of control and attributional style. Previous research suggested that biological predictors of heart disease development might account for only 50% of the variance in M.I. occurrence, severity, and subsequent psychological recovery. Evidence from psycho-social research suggests that only certain aspects of social support and expressed emotion are associated with adjustment. Much of this research is cross sectional in nature and relies on a few, narrowly-defined outcome variables. The present study wished to address these methodological short-comings. Data was obtained from thirty patient-spouse couples soon after M.I. occurrence (Time 1), and from twenty-seven of these couples after approximately ten weeks (Time 2). Multiple regression analyses allowed the predictive power of expressed emotion and social support with regard to psychological adjustment to be assessed at both points in time. The relevance of such psycho-social concepts in predicting adjustment was compared to physical and demographic variables. Results are discussed in the light of previous research, the concept of adjustment, the age of the study sample, and limitations of the study design