Showing papers by "University of Aberdeen published in 1981"

The Complete Amino-Acid Sequence of Hen Ovalbumin

Abstract: The complete amino acid sequence of hen ovalbumin, comprising 385 residues, has been determined. The sequence was deduced from the 17 cyanogen bromide fragments and from peptides derived by digestion with a number of proteolytic enzymes. The molecular weight of the polypeptide chain of ovalbumin is 42699. Ovalbumin has four sites of postsynthetic modification; in addition to the acetylated N terminus, the carbohydrate moiety is located at Asn-292, and the two phosphorylated serines are at residues 68 and 344. The 'signal sequence' of ovalbumin is between residues 234 and 252. The heptapeptide released during the conversion of ovalbumin to plakalbumin by subtilisin digestion corresponds to residues 346-352. The hen ovalbumin polymorphism characterised by an Asn leads to Asp replacement results from a mutation at residue 311. The amino acid sequence of ovalbumin deduced from these amino acid sequence studies is in complete agreement with the sequence of mRNA determined by McReynolds et al. [Nature (Lond.) 273, 723-728 (1978)].

CHARACTERIZATION OF THE k-SUBTYPE OF THE OPIATE RECEPTOR IN THE GUINEA-PIG BRAIN

Abstract: 1. In homogenates of guinea-pig brain, the characteristics of the binding of [3H]-ethylketazocine, an agonist for the putative kappa-receptor, were determined by estimation of the affinity and capacity of binding, by competitive inhibition for the binding site by unlabelled ligands and by selective protection of the binding site from alkylation by phenoxybenzamine. 2. At 25 degrees C the maximum number of binding sites for [3H]-ethylketazocine was about 14 pmol/g fresh brain, of which about 50% were high affinity sites. 3. In competition experiments, the high affinity binding of [3H]-ethylketazocine to the kappa-binding site was readily displaced by several kappa-agonists but not by the selective mu-ligand, D-Ala2, MePhe4, Gly-ol5-enkephalin or the selective delta ligand, D-Ala2, D-Leu5-enkephalin. In contrast, the kappa-agonists tested so far exhibit a high degree of cross-reactivity with the mu-binding site but somewhat less with the sigma-binding site. Similar specificities were observed in protection experiments. 4. The approximate proportions of the three subtypes of opiate receptor in the guinea-pig brain are 25% mu-binding sites, 45% delta-binding sites and 30% kappa-binding sites. 5. The endogenous opioids, Met-enkephalin, Leu-enkephalin and porcine beta-endorphin have only a low affinity for the kappa-binding site.

Iron Triangles, Woolly Corporatism and Elastic Nets: Images of the Policy Process*

Abstract: This paper examines three distinct images of the policy process. Iron triangles emphasize stable relations among a limited number of participants in a relatively closed policy area. Issue networks are fragmented, open and extraordinarily complex and are ill-structured for resolving conflicts and reaching authoritative decisions. The neo-corporatist literature posits a mechanistic interpretation of society: hierarchy, discipline, command and stability, though organized through sectors. These three images can be contrasted with an image of cabinet government which stresses the integrative capacities of central government. The United States can be seen to have moved to some degree from a pattern more closely captured by the iron triangle image to a looser, more complex one resembling features of the issue network image. In Britain, it is possible to detect some movement towards the complexity of the issue network approach. Despite some superficial plausibility, the corporatist image does not apply to Britain, which is best described by drawing on elements of the iron triangle and cabinet government images and some of the complexity of the issue network image. Finally, limits to the fragmentation implied by the issue network image are noted.

Energy flow in the Ythan Estuary, Aberdeenshire, Scotland

Abstract: A steady-state energy flow model has been constructed for the Ythan estuary. Nutrient and particulate organic carbon flux has been described in relation to freshwater drainage and tidal action. No rates of retention however, could be provided. Organic C to organic N ratios of detritus vary from 1:14 to 1:200 in the water column, whilst this ratio is 1:8 in the sediments of the mudflats. Primary production by benthic macrophytes, benthic algae and phytoplankton amounts to 631 g C m −2 year −1 whilst the production for zooplankton is 0·8 g C m −2 year −1 , for meiofauna 19·5 g C m −2 year −1 and for macrofauna 48·8 g C m −2 year −1 . The efficiency of energy transfer between the invertebrate macrofauna and vertebrate predators approximates to 54·2% which is higher than that recorded hitherto in various aquatic ecosystems.

The sex ratio in ectoparasitic insects

Abstract: 1 The sex ratio in 379 collections, each consisting of more than 100 individuals, of 250 different species of ectoparasite belonging to seven orders of insects is recorded The data are gathered from a broad survey of published literature 2 In general, ectoparasitic insects emerge as adults in equal numbers of each sex, although there are certain exceptions 3 The sex ratio in natural populations may alter with numerous factors, but in general it is unbalanced, females usually predominating Out of 359 collections from the host's body or home, the sex ratio of 30% showed no significant departure from unity, 63% contained significantly more females, and 7% significantly more males 4 These imbalances could be due to sampling methods but this is rare Generally they are due to one sex, usually the male, being shorter lived than the other This may be because males are often more active and smaller than females, and thus more likely to be separated from the host's body or home, succumb to host predation, or be killed by adverse climatic or nutritional conditions

Some aspects of the reproductive biology of perch Perca fluviatilis L. A histological description of the reproductive cycle

Abstract: Histological changes in the perch ovary during development are described and related to changes in gonad weight and to a macroscopic scale of maturity stages after Kesteven (1960). A single organ formed by the fusion of two primordial ovaries, a central internal oviduct, and an extremely thick chorion surrounding oocytes are characteristic features of the perch ovary. Resting oocytes can be differentiated from developing oocytes which are larger and possess a granulosa layer which permits formation of the chorion and yolk acquisition. In the maturing ovary, oocyte diameter increases rapidly and the chorion, which possesses four layers, the tunica propria, two middle zones forming a fine network, and the zona radiata, also expands. The spent ovary is disorganized with follicles and tunica wall contracted, and a number of residual oocytes may be apparent. There was no evidence of pre-ovulatory degeneration although autolysis of a small number of residual oocytes was observed. The gonadosomatic index was highest for males in September and at a maximum in females immediately prior to spawning. After spawning the index fell rapidly with lowest values recorded in June and July. Variations in the gonadosomatic index are related to developmental stages in females.

An improved general harmonic force field for ethylene

Abstract: The recent availability of certain critical experimental data, both from this and other laboratories, for isotopic species of the ethylene molecule, has enabled the previously published GHFF to be redetermined with much greater precision. Several significant changes in the force constants occur, bringing the empirical values into better overall agreement with ab initio values. Calculated data using the new force field are considered to be sufficiently reliable to be used with confidence in spectroscopic and structural applications and are listed.

The Development of Agriculture in the ‘Ager Cosanus’ during the Roman Republic: Problems of Evidence and Interpretation*

Abstract: It is a well-established view that in the century following the Hannibalic War the Italian countryside saw the expropriation of its free peasantry and the introduction of slave-staffed villas. This assumption of fact underlies much modern historical research. As one recent study put it: ‘When we compare Roman with American slavery, the growth of slavery in Roman Italy seems surprising. In the eighteenth century, slavery was used as a means of recruiting labour to cultivate newly discovered lands for which there was no adequate local labour force…. In Roman Italy…slaves were recruited to cultivate land which was already being cultivated by citizen peasants. We have to explain not only the import of slaves but the extrusion of citizens'. The usual answer has been that land was the largest single available investment for the wealth which the upper classes had derived from imperialism and was also the most socially acceptable investment. But despite postulation of a largely economic motive, the approach taken by historians has been mainly social and political. The explanation, however, and the type of approach involved owe much of their plausibility and hence popularity to what is also their greatest weakness, namely somewhat circular argumentation. The evidence on which the phenomenon and its explanation have been constructed is above all that of the literary sources, and the context in which this information is given is almost invariably political—the obvious and major instance is the Gracchan reforms. It should hardly surprise us, then, that this view of Republican agrarian history provides a neat socio-economic explanation for the political upheavals of the later Republic for which we again take our main evidence from the very same sources. Such validation is only apparent. Perhaps it speaks for the internal consistency of these literary sources; certainly it illustrates our pathetic imprisonment within the ‘facts’ and ‘interpretations’—one could say tout court the bias—of these sources. There is little to be gained from further introspective critique of this type of evidence.

The idea of the gentleman in the Victorian novel

Abstract: First published in 1981, this book represents the first comprehensive examination of Victorian society’s preoccupation with the ‘notion of the gentleman’ and how this was reflected in the literature of the time. Starting with Addison and Lord Chesterfield, the author explores the influence of the gentlemanly ideal on the evolution of the English middle classes, and reveals its central part in the novels of Thackeray, Dickens and Trollope. Combining social and cultural analysis with literary criticism, this book provides new readings of Vanity Fair and Great Expectations, a fresh approach to Trollope, and a detailed account of the various streams that fed into the idea of the gentleman.

Carrageenan: a review of its effects on the immune system.

Abstract: Carrageenans (kappa, lambda and iota) are sulphated polysaccharides isolated from marine algae that can markedly suppress immune responses both in vivo and in vitro. Impairment of complement activity and humoral responses to T-dependent antigens, depression of cell-mediated immunity, prolongation of graft survival and potentiation of tumour growth by carrageenans have been reported. The mechanism responsible for carrageenan-induced immune suppression is believed to be its selective cytopathic effect on macrophages. This property of carrageenan has led to its adoption as a tool for analysing the role of these cells in the induction and expression of immune reactivity. Systemic administration of carrageenan may, however, induce disseminated intravascular coagulation and inflict damage on both the liver and kidney. This is an important consideration in the interpretation of the effects of carrageenan in vivo and precludes its use as a clinical immune suppressant.

Structure and activity of phosphoglycerate mutase.

Abstract: The structure of yeast phosphoglycerate mutase determined by X-ray crystallographic and amino acid sequence studies has been interpreted in terms of the chemical, kinetic and mechanistic observations made on this enzyme. There are two histidine residues at the active site, with imidazole groups almost parallel to each other and approximately 0.4 nm apart, positioned close to the 2 and 3 positions of the substrate. The simplest interpretation of the available information suggests that a ping-pong type mechanism operates in which at least one of these histidine residues participates in the phosphoryl transfer reaction. The flexible C-terminal region also plays an important role in the enzymic reaction.

Unexpected antagonism in the rat vas deferens by benzomorphans which are agonists in other pharmacological tests

Abstract: The benzomorphans, ethylketazocine, bremazocine and MR 2034 are pure agonists in the guinea-pig ileum and mouse vas deferens but are competitive antagonists without agonist activity in the rat vas deferens.

Surface phosphatase activity of Sitka spruce mycorrhizas from a serpentine site

Abstract: The p -nitrophenyl phosphatase activity of mycorrhizal roots of Sitka spruce from a phosphorus deficient site was inversely proportional to the concentrations of 0.5 n acetic acid-extractable phosphorus in the decaying organic matter from which the roots were removed. This is interpreted as the derepression of phosphatase synthesis under conditions of inorganic P deficiency and is discussed in relation to the possible roles of mycorrhizal surface phosphatase activity.

The oxygen tolerance of sulfate-reducing bacteria isolated from North Sea waters

Abstract: Five strains of sulfate-reducing bacteria, previously isolated from North Sea waters and identified asDesulfovibrio vulgaris, were investigated for their abilities to survive in aerobic natural seawater. Viable organisms of all strains were recoverable after exposure to oxygen for more than 72 h. The level of the protective enzymes superoxide dismutase and catalase detectable in these strains and the low rates at which oxygen was reduced probably account at least in part for their considerable abilities to survive in aerobic environments. The autoxidizable nature of cytochromec 3 and KCN-inhibitable cytochromec oxidase activity present in these bacteria are postulated to act as possible oxygen-scavenging mechanisms analogous to the activity of NADH oxidase present in certain other strict anaerobes.

Word age-of-acquisition, reading latencies and auditory recognition

Abstract: This paper reports two experiments concerning the effects of word age-of-acquisition on word naming speed and auditory recognition of words presented at a low volume. The first experiment found significant facilitating effects of word age-of-acquisition in word naming even when word length, frequency and familiarity were taken into account. The second experiment found no evidence of age-of-acquisition effects in auditory word recognition. The results are interpreted as supporting the view that the age-of-acquisition variable mainly affects word production and has little effect on word recognition processes.

Word age-of-acquisition effects: a review

Abstract: This paper reviews research concerned with word age-of-acquisition (AOA) effects in adult word recognition and production. Methodological issues, including the use of multiple regression techniques, are considered first. The pattern of substantive results is presented and is interpreted as indicating that AOA effects are most marked in word production as against word recognition. Possible theoretical interpretations are discussed and future research possibilities are outlined.

Association of atomic oxygen and airglow excitation mechanisms

Abstract: An outline is presented of a method of calculating relative rates of association of oxygen atoms by energy transfer into the different bound states of molecular oxygen. The method takes account of the detailed form of the potential energy curves for the different states. Results are presented for seven bound states of O 2 at temperatures between 100 and 600 K and are compared with laboratory and airglow data. The 5 Π g state, not known experimentally, accounts for over 70% of the total association below 200 K. At higher temperatures it is redissociated, and the variation in its effective association rate is primarily responsible for the variation of the total rate of oxygen association with temperature. The 5 Π g state is probably involved in the production at night of the a 1 Δ g and b 1 Σ g + states of O 2 , and in the production of O( 1 S) in the airglow. It may also be produced by electron impact on O 2 , and contribute to O( 1 S) production in aurorae.