Showing papers by "University of Birmingham published in 1978"

New Studies in Philosophy, Politics, Economics and the History of Ideas

Abstract: Following on F. A. Hayek's previous work Studies in Philosophy, Politics, and Economics (1967), New Studies in Philosophy, Politics, Economics and the History of Ideas collects some of Hayek's most notable essays and lectures dealing with problems of philosophy, politics and economics, with many of the essays falling into more than one of these categories. Expanding upon the previous volume the present work also includes a fourth part collecting a series of Hayek's writings under the heading 'History of Ideas.' Of the articles contained in this volume the lectures on 'The Errors of Constructivism' (chapter 1) and 'Competition as a Discovery Procedure' (chapter 12) have been published before only in German, while the article on 'Liberalism' (chapter 9) was written in English to be published in an Italian translation in the Enciclopedia del Novicento by the Istituto della Enciclopedia Italiana at Rome.

The measurement of tolerance to edaphic factors by means of root growth

Abstract: SUMMARY The tolerance of plants to toxic metals is frequently measured by comparing rates of root growth in culture solutions with and without the addition of the metal, but many variants of the technique are available. Toxicity is often reduced by the presence of other ions, particularly calcium. Control growth rates may be measured beforehand on the same roots or in parallel on a duplicate set. With a single toxic concentration tolerance is defined as the ratio of the two growth rates; with a range of concentrations the slope of the regression of growth on concentration may be used, but there are some complications with stimulation at low concentrations. Probit analysis may be valuable. There is good evidence that tolerance differences are largely of genetical origin.

The power of the classical twin study.

Abstract: SUMMARY A method based on the non-central chi-square distribution is developed for the calculation of sample sizes required to reject, with given probability, models of variation when they are II wrong". The method is illustrated with reference to simple alternative models of variation in MZ and DZ twins reared together. Simulation of twin experiments finds the empirical power in good agreement with that predicted by the method. Tables are produced showing the sample sizes required for 95 per cent rejection at the 5 per cent level of inappropriate models of variation. For equivalent cases it is always found easier to reject an inappropriate simple genetical model of variation than an inappropriate simple environmental model. For several frequendy encountered cases, more than 600 pairs of twins would be required to reject inappropriate alternative models. The optimum proportion of MZ and DZ twins in a sample will vary with the .. true .. model Of variation but is most likely to be between two-thirds and one-half of DZ twin pairs. The possibility of detecting genetical non-additivity with the classical twin study is investigated by theoretical power calculations and simulation. In the absence of genotype-environment interactions, distributional skewness and mean-variance regression in DZ twins are found to be more powerful tests of directional dominance (or unequal gene frequencies) than the standard model fitting procedure and these tests may be worthwhile in future studies.

Model-fitting approaches to the analysis of human behaviour

Abstract: Model-fitting methods are now prominent in the analysis of human behavioural variation. Various ways of specifying models have been proposed. These are identical in their simplest form but differ in the emphasis given to more subtle sources of variation. The biometrical genetical approach allows flexibility in the specification of non-additive factors. Given additivity, the approach of path analysis may be used to specify several environmental models in the presence of assortative mating. In many cases the methods should yield identical conclusions. Several statistical methods have been proposed for parameter estimation and hypothesis testing. The most suitable rely on the method of maximum likelihood for the estimation of variance and covariance components. Any multifactorial model can be formulated in these terms. The choice of method will depend chiefly on the design of the experiment and the ease with which a data summary can be obtained without significant loss of information. Examples are given in which the causes of variation show different degrees of detectable complexity. A variety of experimental designs yield behavioural data which illustrate the contribution of additive and non-additive genetical effects, the mating system, sibling and cultural effects, the interaction of genetical effects with age and sex. The discrimination between alternative hypotheses is often difficult. The extension of the approach to the analysis of multiple measurements and discontinuous traits is considered

Comparison of amino acid sequence of troponin I from different striated muscles.

Abstract: The sequence of troponin I from fast and slow skeletal and cardiac muscle shows strong homology in the region which binds to actin and is responsible for inhibition of the actomyosin ATPase. More differences are found in the N-terminal region which binds to troponin C.

A comparison of the killer character in different yeasts and its classification.

Abstract: The interactions between 20 killer yeasts of various genera and species were examined. Ten distinct groups were recognised with respect to killer activity and 10 distinct groups with respect to resistance to killer action. Using both killing and resistance phenotypes, 13 classes of killer yeast were found. With the exception of Torulopsis glabrata NCYC 388, non-Saccharomyces strains of yeast were not killed by a member of the genus Saccharomyces. The killer character of the 3 killing groups of Saccharomyces identified could be cured by treatment with cycloheximide or incubation at elevated temperature and the effectiveness of these procedures was indicative of the category of killer yeast examined. Killer yeasts not belonging to the genus Saccharomyces could not be cured of their activity. Double-stranded ribonucleic acids were extracted only from Saccharomyces spp. and the molecular weights of the species present were a function of the killer class to which a strain belonged. By an analysis of the effects of proteolytic enzymes, temperature and pH on killer activity and by gel chromatography of crude preparations of killer factors, the toxins of different killer classes were shown to be biochemically distinct. However all toxins had certain properties in common consistent with there being a protein component essential to killer action.

LISPB — IV. Crustal structure of Northern Britain

Abstract: Summary. This paper presents those results from the 1974 Lithospheric Seismic Profile in Britain (LISPB) which relate to the compressional velocity structure of the crust and uppermost mantle beneath Northern Britain. A combination of interpretation techniques suitable for modelling laterally inhomogeneous media, including two-dimensional ray-tracing and time-term analysis, has resulted in a detailed seismic cross-section across the Caledonian orogenic belt. The main features of this section are a possible horizontal discontinuity in the Pre-Caledonian’basement, a change in the relationship between the lower crust and the uppermost mantle from north to south and a considerable thickening of the crust beneath the Caledonian fold belt. These results place considerable constraints upon tectonic models for the evolution of the Caledonides in particular in their implication of differing crustal structures north and south of the Southern Uplands and their indication of the primary significance of the Southern Uplands Fault.

Unrepaired DNA strand breaks in irradiated ataxia telangiectasia lymphocytes suggested from cytogenetic observations

Abstract: It is suggested here that the unusually high level of radiation-induced chromosome and chromatid-type aberrations in cells from patients with ataxia telangiectasia, compared with normals, is due to a significantly increased fraction of unrepaired double and single strand breaks. A hypothesis is proposed to explain how unrepaired and misrepaired DNA single or double strand breaks might be the basic lesion leading to the typical chromosome aberrations seen following X-irradiation of both normal or AT cells.

Two types of vagal preganglionic motoneurones projecting to the heart and lungs.

Abstract: 1. A study has been made of eighty-four cells in the cat's nucleus ambiguus whose axons projected to the cardiac (seventy-four) and pulmonary (ten) branches of the right vagus. Their axonal conduction velocities were all in the range of B fibres (2.8-15.5 m/sec).2. Pulmonary branch projecting neurones were usually spontaneously active (nine out of ten) and fired in phase with inspiration. Their activity showed no pulse modulation.3. Ten cardiac branch projecting neurones had properties indistinguishable from those of pulmonary branch projecting neurones. Inspiratory-firing cells projecting to either branch are believed to be bronchoconstrictor in function.4. The remaining sixty-four cells that projected to the cardiac branch had properties expected of cardioinhibitory neurones. Most (fifty-four) were silent until activated by ionophoresis of excitant amino acids. All showed an expiratory discharge when active, and of twenty-seven tested twenty-three showed a cardiac modulation of their discharge. When the aortic baroreceptors were denervated, the cardiac rhythm was always abolished reversibly by carotid occlusion.5. Ionophoretic activation of expiratory firing (presumed cardioinhibitory) cells slowed the heart (fifteen out of eighteen neurones tested). Excited inspiratory-firing cells never had this effect (eleven tested).6. Both types of neurones were found in the nucleus ambiguus, but presumed cardioinhibitory cells tended to be found more caudally and ventrally than presumed bronchoconstrictor neurones.

The baroreceptor input to cardiac vagal motoneurones

Abstract: 1. A study has been made of twenty-three cardiac vagal motoneurones (c.v.m.s) in the nucleus ambiguus of chloralose-anaesthetized cats.2. C.v.m.s were identified as described previously (McAllen & Spyer, 1978). They were either spontaneously active (five units) or induced to fire by the ionophoresis of DL-homocysteic acid (DLH). Evidence is presented that above threshold, the DLH dose is not critical for the ability to show a baroreceptor influence.3. The influence of the baroreceptors was determined by plotting pulse-triggered histograms of c.v.m. activity. If the aortic baroreceptors were denervated, the pulse synchronous activity disappeared reversibly on carotid occlusion (eight out of eight cases). In five out of fifteen cells studied, when aortic baroreceptor pathways were intact, a small degree of cardiac modulation survived carotid occlusion.4. Estimates of the central delay of the baroreceptor-vagal reflex were made by timing the c.v.m. response to both electrical stimulation of the sinus nerve and natural baroreceptor stimulation. When both methods were used on individual units, electrical stimulation invariably gave shorter values. Natural stimulation gave values that fell into two ranges (20-60 msec and 70-110 msec), suggesting the involvement of two pathways.5. Using higher currents, four c.v.m.s were induced to fire tonically during inspiration. Their activity in this phase showed a cardiac rhythm just as during expiration. Similarly, they responded to sinus nerve stimulation throughout the respiratory cycle.6. This result is discussed in relation to the observation of others that the baroreceptor-cardiac reflex is ineffective during inspiration. It is proposed that there is no need to invoke a ;gate' early in the pathway but that this phenomenon and the present observations are best explained by summation of influences at the c.v.m. cell membrane.

Rapid transbilayer diffusion of 1,2-diacylglycerol and its relevance to control of membrane curvature

Abstract: SHEETZ AND SINGER have proposed that the actions of certain amphipathic drugs in producing curvature of the membrane of human red blood cells (RBCs) could be explained by assuming that these drugs selectively entered one of the leaflets of the lipid bilayer, thus causing lateral expansion of that leaflet relative to the other1. The membrane was therefore forced to curve in order to accommodate this extra material and the direction of this curvature was predictable, leading to production of either stomatocytes or echinocytes. Membrane curvature, leading to the formation of stomatocytes or echinocytes, can also be produced by subjecting human RBCs to phospholipase C attack2–5. In this report we attempt to explain these phospholipase C-induced changes in terms of Sheetz and Singer's model, taking into account the observation that 1,2-diacylglycerol (the product of phospholipase C action), unlike phospholipids, can migrate rapidly across the membrane bilayer. Rapid transbilayer migration of 1, 2-diacylglycerol has previously been inferred from the observed increase in the rate of synthesis of phosphatidate in intact RBCs that have been exposed to phospholipase C: this phosphatidate is formed from diacylglycerol and cytosolic ATP by diacylglycerol kinase, presumably at the inner surface of the membrane2. We have now used this procedure, in which the endogenous diacylglycerol kinase of the erythrocyte is used to trap 1, 2-diacylglycerol appearing on the inner surface of the red cell membrane, to compare the time courses of phospholipase C-catalysed production of diacylglycerol and of the appearance of phosphatidate, and thus obtain an estimate of the rate of transbilayer migration of 1, 2-diacylglycerol.

Aquatic and aerial respiration in the shore crab,Carcinus maenas (L.), acclimated to 15°C

Abstract: 1. Oxygen consumption\((\dot V_{O_2 } )\) and heart rate of crabs acclimated to 15°C and exposed to water or air for 3 h were not significantly different (Fig. 1). 2. When in air crabs ventilate their branchial chambers in both the forward and reversed direction (Fig. 3). 3. Exposure to air caused a marked reduction in oxygen tension of the postbranchial haemolymph\((Pa_{O_2 } )\) and a fall in pHa associated with an increase in\(Pa_{CO_2 }\). Oxygen content\((Ca_{O_2 } )\) and the\(a - v_{O_2 }\) content difference were maintained relatively high due to the oxygen binding characteristics of the haemocyanin (Table 1 and Fig. 4). 4. The concentration of lactic acid in the haemolymph was not affected by exposure to air (Table 1). 5. Exposure to air for 3 h was associated with a small reduction in total mass caused by evaporative water loss with a concomitant increase in haemolymph sodium concentration (Table 1). 6. The gill lamellae are relatively well spaced out and derive physical support from their covering of chitin. They may, therefore, be suited structurally for respiratory gas exchange in both water and air (Fig. 5).

Respiratory and Circulatory Changes in the Lobster (Homarus Vulgaris) During Long Term Exposure to Moderate Hypoxia

Abstract: 1.Within a few hours of the lobsters being placed in the experimental chamber in normoxic water (P o2 , 130-135 mmHg), their heart rate, oxygen uptake (V o2 ) and ventilation volume (V u ) were relatively high. The scaphognathites were simultaneously active on both sides (bilateral ventilation) for 50% of the time, active on one side only (unilateral ventilation) for 32% of the time and simultaneously inactive (respiratory pause) for 18% of the time. Percentage extraction of O 2 (% Ext.) was relatively low. 48h after having been set up, heart rate, V O2 and V g had decreased significantly, % Ext. had increased and bilateral ventilation occupied 25% of the time. Heart rate was low and the beat irregular. 2.Upon subsequent exposure to hypoxia (P O2 , 50-55 mmHg), P a , O 2 , fell, there was initial hyperventilation, bilateral ventilation for 89% of the time, heart beat was more regular but V o2 did not change significantly. An initial increase in pHa caused the O 2 affinity of the Hey to rise. After 72h exposure to hypoxia V g and pHa had declined, but V g was still higher than at the end of the period of normoxia. Blood lactate, V o2 and % Ext. were not significantly different from the values recorded after 48 h in normoxic water. Upon return to normoxic water, V g and the time the animals spent ventilating both branchial chambers fell, but V o2 increased. 3.It is concluded that for settled lobsters, V o2 could be maintained during moderate hypoxia by increasing V g maintaining a regular heart beat, and at least initially by increasing the O 2 affinity of the Hey.

The seasonal incidence of mania and its relationship to climatic variables

Abstract: Monthly hospital admission rates (HA) for mania were classified by sex, type of admission (first, or re-admission) and by country (England and Wales or Scotland). Of the 8 classes thus created, all but one showed a statistically significant annual cycle with a peak in Summer and trough in Winter. There was no significant difference in phase or amplitude between male and female cycles. A linear increase in yearly re-admission rates was found during the 8 years of the English and the 11 years of the Scottish data. Current month's mean daily temperature (lag0) and last month's (lag1) mean day-length and mean daily hours of sunshine correlated better with admission rate than did the values for other months. In a multiple regression analysis temperature made the other 2 climatic variables redundant in accounting for variation in HA.