Showing papers by "University of Hertfordshire published in 1971"

Diagnosis of Resistance to Organophosphorus Insecticides in Myzus persicae (Sulz.)

Abstract: THE chemical control of the green peach aphid Myzus persicae (Sulz.), which damages many crops both directly and by transmitting numerous virus diseases, is seriously jeopardized by the world wide occurrence of resistance to organophosphorus insecticides. In the United Kingdom resistance previously confined to glasshouse crops now occurs in the field. Nothing is known about the nature of the resistance mechanism(s) in these insects and little about the patterns of resistance. We wish to report (1) large differences in the activity of ali-esterases of susceptible and resistant aphids which can be used to determine resistance even in single aphids, (2) large differences in some properties of these enzymes between susceptible and resistant aphids and house flies, and (3) a marked decrease or increase in resistance when the aphids are treated with insecticides in the presence of ‘Sesamex’ (2-(3,4-methylene-dioxyphenyl)3,6,9-trioxaundecane). This is evidence that multi-function oxidases are involved in resistance to organophosphorus insecticides in aphids.

Minimization Algorithms Making Use of Non-quadratic Properties of the Objective Function

Abstract: This paper proposes modifications to the matrix updating formulae used in the FletcherPowell (1963), Broyden (1970) and Fletcher (1970) methods for function minimization, and discusses some properties of these modified formulae. A function minimization algorithm incorporating the new expressions has been programmed and the results of tests with some well-known functions are reported.

The Characterization of Starch and Its Components. Part 3. The Technique of Semi‐Micro, Differential, Potentiometric, Iodine Titration, and the Factors Affecting It

Abstract: An improved apparatus for the semi-micro, differential, potentiometric titration of starch and its components with iodine is described. The necessary experimental manipulations are given in detail. The factors affecting the measurement — the amount of dimethylsulphoxide present, the buffer concentration, the method of dissolving the starch, the defatting procedure used on the starch, and the temperature of measurement — are critically examined. The new technique results in values of iodine binding capacity for starches which are 5- 15% higher than previous measurements. The significance of this finding is discussed.

Oxidative metabolism of pyrethrins in mammals.

Abstract: THE natural pyrethrins present in pyrethrum flowers (Chrysanthemum cinerariaefolium) have attracted attention for more than a century because they are powerful insecticides yet have very low toxicity to mammals1,2. Concern about the persistence of some insecticides in mammals and in the environment has stimulated a consideration of the degradability of widely used compounds, both old and new. The two principal insecticidal constituents of pyrethrum, pyrethrins I and II (Fig. 1), do not persist in the environment because they are unstable when exposed to light and air3. There is some information about the metabolism of pyrethrin I and related compounds in houseflies4,5, but little is known of the fate of pyrethrum constituents in mammals6,7 even though man is often exposed to pyrethrins from household aerosols and other sources. We therefore examined the degradation of pyrethrin I and of pyrethrin II in rats fed separately with large amounts of pure tritium-labelled pyrethrins I and II, prepared with high specific activities by a new procedure involving a direct exchange reaction on (+)-pyrethrolone8. The metabolites were isolated in milligram quantities from urine; nuclear magnetic resonance (NMR) and mass spectrometry (MS) showed that each of the principal metabolites retains the cyclopropane ester linkage and is formed by modification of both the acid and alcohol moieties. The oxidation of the acid side chain is similar in type to that encountered previously in other systems4,5, but the establishment of attack on the alcohol part is new and involves the unsaturated side chain as detailed below.

Heavy Metals and the Fertilization of Rainbow Trout Eggs

Abstract: THE effects of poisons on the development and survival of fertilized fish eggs have often been described but little information is available on the effects of such substances on either the gametes or fertilization. Mann, for example, has reported1 that a dodecylbenzenesulphonate detergent caused a 26% loss of mobility of trout spermatozoa at a concentration of 5 mg l.−1, and the anaesthetic drug tricaine methanesulphonate was found2 not to affect fertilization provided that the concentration did not exceed 50 mg l.−1. The effects of heavy metals on these life stages and processes do not, however, seem to be known, even though these poisons are common pollutants of river waters in industrial areas. We report here results of preliminary tests made at this laboratory into the effects of copper and nickel on the fertilization of eggs of the rainbow trout, Salmo gairdneri Richardson.

Selecting tests in diagnostic keys with unknown responses.

Abstract: HERE we outline a method for constructing diagnostic keys from test results, some of which are unknown. The method is then modified to reduce the number of different tests used. Elsewhere1 we discuss an application to yeasts, in which the primary purpose is not so much the construction of a key, but to find how few out of a set of tests is required to identify all the yeasts.

Damaged Starch Determination in Wheat Flours in Relation to Dough Water Absorption

Abstract: Four methods (three enzymatic and one non-enzymatic) for damaged starch determination have been applied to 51 flours of known moisture and protein contents and known water absorption. The three enzyme methods for damaged starch give results in substantial agreement and in conjunction with the other parameters predict dough water absorption by multiple regression equations more closely than does a colorimetric method.

Stimuli Eliciting Mating Behaviour of Bumblebee (Bomb Us Pratoruml.) Males

Abstract: 1. Males were attracted to queens presented near a visiting place, but usually ignored those offered elsewhere along a flight route. 2. A black object the size of a queen successfully elicited inspection and attempts to mate; the orange and yellow bands on a queen's body and her movements seemed not to do so. 3. The odour of a queen is important in inducing males to alight on her. Odour differences probably account for the greater attractiveness of young than old queens.

The influence of turbulent flow on the sensory assessment of viscosity in the mouth.

Abstract: Low viscosity Newtonian fluids exhibit turbulence in a cone-plate viscometer at high rates of shear which are comparable to those operating in the mouth during sensory assessment of the viscosity of the same fluids Saliva reduces this effect to some small extent, possibly due to its content of mucin and other proteinaceous substances The net result is that these fluids appear to have a higher viscosity in the mouth than when they are examined in a viscometer at low rates of shear Higher viscosity non-Newtonian food materials such as Carnation milk and ice cream do not exhibit turbulent flow, and the only effect exerted by saliva is a reduction in the viscosity at all rates of shear

A case of Prader-Willi syndrome in a girl with a small extra chromosome.

Abstract: A characteristic case of Prader‐Willi syndrome is reported in a girl who showed, additionally, the presence of a small extra chromosome, possibly a fragment of a D or G group chromosome. Available members of the proposita's family were found to be phenotypically and cytologically normal. The case is compared with those previously reported.

Dermatoglyphic patterns and clinical diagnosis by discriminant function.

Abstract: Clinical diagnosis, based upon dermatoglyphic characters, can only be made in terms of probability because no dermatoglyphic sign is pathognomonic. The same peculiarities occur both in normal and abnormal samples but with different frequencies. In order to improve discrimination between each abnormal type and the normal, constituent characters can be combined ; even so, results indicate that there is considerable overlapping of normal and abnormal distributions. Nevertheless, an account of the construction of discriminants for distinguishing some well-known clinical types, dermatoglyphically, may be of interest. Three sources of information were available : patterns on fingers, palms and soles. All loops and certain triradii were recorded ; their identification did not involve measurement and their presence or absence is not dependent on age. For each clinical group the differences in frequency between normals and abnormals could be used as weighting factors for discriminant purposes, and this was done for a number of conditions with respect to each of the three pattern sources. Having established a weighting system for an abnormal condition, this can be used to test any given case in order to see how far the peculiarities present resemble those found in the specified condition. The resemblance can be measured against the difference between normal and abnormal on each specific discriminant and the answer can be given in terms of probability of belonging to the specified type. Discriminants for mongols have been worked out for palmar dermatoglyphics by Ford Walker (1957) and for a combination of anatomical traits by Beckman, Gustavsson & Norring (1965). In the present paper differences between normals and trisomies D, E and G and 4-5 shorter arm, or Bp, deletion, respectively, were established by combining data from the previous observations so as to construct four sets of discriminant weightings.

Investigation of central cholinergic mechanisms in the conscious mouse

Abstract: 1. An investigation of central cholinoceptors in the mouse has been made by injecting cholinomimetic drugs into the cerebral ventricles and seeing how their effects were modified by prior administration of atropine-like substances and other drugs.2. Carbachol or oxotremorine injected in small doses intracerebroventricularly into conscious mice caused hypothermia, gross tremor and a variety of parasympathomimetic effects including lachrymation and salivation. Acetylcholine injected in this way was active only in much larger doses.3. Methacholine and pilocarpine also caused a variety of parasympathomimetic effects after intracerebroventricular injection but virtually no hypothermia or tremor.4. Nicotine injected intracerebroventricularly caused mild hypothermia, fine tremor but no parasympathomimetic effects.5. Atropine-like drugs, tricyclic antidepressants and amphetamine antagonized the hypothermia induced by intracerebroventricular carbachol or oxotremorine.6. The sites of action of the atropine-like drugs are in the brain; those of the tricyclic antidepressants and amphetamine are in the periphery probably on heat generating beta-adrenoceptor mechanisms.7. It is concluded that the atropine sensitive cholinoceptors in the brain vary in their sensitivities to cholinomimetic drugs, other than acetylcholine, and may exist in isoreceptor forms.8. Peripheral atropine sensitive cholinoceptors may also exist in isoreceptor forms.

Mechanical drive transmission systems

Abstract: A mechanical drive transmission, especially for rack and pinion vehicle steering gear, having the drive transmitting components supported in a non-metallic molded housing which is rigid enough to maintain good bearing support of the components, resilient enough to provide good shock absorbing characteristics, and strong enough to withstand the same magnitude of shocks and loads as heretofore used metallic housings. The non-metallic housings of this invention are preferably formed by injection molding to accurate dimensions and need not be machined or threaded to properly support the drive transmitting components. Preferred materials for the housing are nylons, acrylonitrile-butadienestyrenes, polyacetals, and polypropylenes which may be reinforced with glass fibers.

Studies on Starches of High Amylose-Content. Part 14. The Fractionation of Amylomaize Starch by Aqueous Leaching†

Abstract: Amylomaize starch is known to contain an anomalous material which does not conform to the classical definitions of either amylose or amylopectin. A detailed study of this polysaccharide has not yet been carried out, principally because of the difficulty of obtaining it in sufficient quantity. This paper presents a rapid and simple method by which the isolation may be achieved.

Truck Tire Groove Cracking Theory and Practice

Abstract: The work described has aimed at clarifying the mechanism of groove cracking in tires. Basic studies of the fracture mechanics of rubber have shown that the rate of growth of a crack is independent of sample shape and type of deformation when it is expressed in terms of the available elastic energy. An empirical method is described which enables the energy to be estimated for a tire groove from measurement of the amount by which a crack opens under stress. The method also enables the strain to be determined and can, in principle, be applied to any stressed article. Using this approach and the crack growth characteristics of the tread rubber, the rate of growth of groove cracks in a tire can be predicted. Satisfactory quantitative agreement is found between observed and predicted behavior suggesting that the mechanism has been correctly identified. The work indicates relevant design factors and material properties and enables an appropriate laboratory test for groove cracking resistance to be defined.

Effects Due to Groups of Buildings

Abstract: For the past 5-10 years architects have realized the need for information on the aerodynamics of the environment around groups of buildings. The high wind speeds in precincts around tall or exposed buildings have surprised their designers who have sought remedies, and the publicity about windy environments around existing buildings has led to requests for advice about developments on the drawing board. In the absence of a general theory for the prediction of air flow patterns and wind speeds around groups of buildings, the problem has been studied in wind tunnels. The paper describes typical town centre developments in which a problem of wind environment has arisen, and gives a brief account of the investigation of specific cases. The broad conclusions from some twenty case studies made by the Building Research Station in response to inquiries from industry are summarized. In seeking to generalize, a series of investigations of the air flow around small groups of idealized model buildings has been conducted, and some comparisons between model and full-scale measurements have been made. This has led to a design method for use in planning the layout of small groups of buildings, which draws on the data from model tests and also meteorological information and comfort criteria. This work is outlined, and future research needs are also discussed.

Seed production of agropyron repens (l.) beauv. in arable crops in england and wales in 1969

Abstract: Summary. Spikes oi Agropyron repens (L.) Beauv. were collected from field crops (mostly spring barley and winter wheat) in England and Wales near the time of crop harvest. Seeds per spike were counted and their germination tested in soil in the glasshouse. About 95% of the samples contained viable seeds; about one third of the samples had fewer than 5 viable seeds/spike, a third between 6 and 15 and a third more than 15. The average number of viable seeds/spike for all samples was 13. Spikes from spring barley (152 samples) had an average of 11 and a maximum of 51 viable seeds and those from winter wheat (42 samples), 20 and 48 respectively. Samples collected within 3 weeks after mid-July had fewer viable seeds/spike than those collected later. Samples containing morphologically-different spikes had more viable seeds/spike than apparently uniform samples, and spikes from dense field populations more seeds than those from sparse populations.

Effects of light intensity, photoperiod and nitrogen on the growth of seedlings of agropyron repens (l.) beauv. and agrostis gigantea roth

Abstract: Summary. Seeding of Agropyron repens (L.) Beauv. und Agrostis gigantea Roth were grown in two photoperiods and with amounts of nitrogen. On two occasions plants transferred between photoperiods. The early growth of the seedlings was increased most by increasing the light intensity, but later nitrogen had the greatest effect. In short photoperiods, plants of both species were decumbent and had many more shoots than in long photoperiods. At the end of the experiment, plants of both species responded more to nitrogen in bright than in dim light, and the dry weight of Agropyron was increased more than that of Agrostis by increased photoperiod and nitrogen. Agropyron initiated rhizomes sooner than Agrostis; it had fewer rhizomes but they were longer and thicker and weighed more. Brighter light, longer photoperiod and nitrogen all increased rhizome weight. Photoperiod did this mainly by producing more rhizomes, light by increasing thickness or density, and nitrogen by both. The effects of photoperiod and nitrogen on the rhizome dry weight of Agropyron, but not of Agrostis, were additive. Transferring plants from short to long photoperiods or from long to short, respectively increased or decreased total growth, but had an opposite effect on the rhizomes.

Observations on changes in the female reproductive system of the wheat bulb fly Leptohylemyia coarctata (Fall.)

Abstract: In Leptohylemyia coarctata (Fall.) the germarium cuts off oocytes which develop through the stages 00 and 0 and I-V, recognised in other Cyclorraphous flies, in 4–5 weeks. All eggs of one batch of the gonadotrophic cycle ripen at the same time. After oviposition, the split intima, the remains of the follicular epithelium, and the nurse cells slowly contract to form the follicular relic. Flies swept from winter wheat during June and July and caught in water traps in July and August showed all stages of egg development. In 1970, 24·7% of the females swept from the crop had completed the first, 4–7% the second and 0–4% the third gonadotrophic cycle. All the eggs were not laid at the same time. During later gonadotrophic cycles, some ovarioles were non-functional. Flies laid one or two batches of eggs, rarely three. In 1970, many flies were attacked and killed by E. muscae . Only one out of 115 newly emerged female wheat bulb flies presented with foods usually found in the crop or citrated blood contained mature eggs after 24–27 days in small cages. Those fed only on 0·1 M glucose survived but did not deposit yolk in the ovum; those provided only with yeast paste died. Honey dew from cereal aphids was the main source of sugar. Water in droplet form and space to move seem necessary for the maturation of the eggs.

Effect of β-adrenoceptive blocking agents on the response to bronchoconstrictor drugs in the guinea-pig air overflow preparation

Abstract: Summary 1 Propranolol augmented the bronchoconstrictor response to methacholine or histamine, recorded by air overflow in the anaesthetized, vagotomized guinea-pig 2 After adrenalectomy, propranolol was still active, though less so than before 3 In the pithed guinea-pig, there was no augmentation of the effect of bronchoconstrictors on air overflow The action of propranolol could thus be due to the β-adrenoceptor blockade of compensatory sympathetic bronchodilator activity, as concluded by McCulloch, Proctor & Rand (1967) 4 Electrical stimulation of the thoracic region of the spinal cord of the pithed guinea-pig reduced the effect of bronchoconstrictors on air overflow This reduction could be blocked by propranolol; practolol was much less effective