Showing papers by "University of Liverpool published in 1995"

Structure and properties of carotenoids in relation to function.

Abstract: The basic principles of structure, stereochemistry, and nomenclature of carotenoids are described and the relationships between structure and the chemical and physical properties on which all the varied biological functions and actions of carotenoids depend are discussed. The conjugated polyene chromophore determines not only the light absorption properties, and hence color, but also the photochemical properties of the molecule and consequent light-harvesting and photoprotective action. The polyene chain is also the feature mainly responsible for the chemical reactivity of carotenoids toward oxidizing agents and free radicals, and hence for any antioxidant role. In vivo, carotenoids are found in precise locations and orientations in subcellular structures, and their chemical and physical properties are strongly influenced by other molecules in their vicinity, especially proteins and membrane lipids. In turn, the carotenoids influence the properties of these subcellular structures. Structural features such as size, shape, and polarity are essential determinants of the ability of a carotenoid to fit correctly into its molecular environment to allow it to function. A role for carotenoids in modifying structure, properties, and stability of cell membranes, and thus affecting molecular processes associated with these membranes, may be an important aspect of their possible beneficial effects on human health.--Britton, G. Structure and properties of carotenoids in relation to function.

Punishment in animal societies.

Abstract: Although positive reciprocity (reciprocal altruism) has been a focus of interest in evolutionary biology, negative reciprocity (retaliatory infliction of fitness reduction) has been largely ignored. In social animals, retaliatory aggression is common, individuals often punish other group members that infringe their interests, and punishment can cause subordinates to desist from behaviour likely to reduce the fitness of dominant animals. Punishing strategies are used to establish and maintain dominance relationships, to discourage parasites and cheats, to discipline offspring or prospective sexual partners and to maintain cooperative behaviour.

Sustained high‐density turbidity currents and the deposition of thick massive sands

Abstract: The origin of massive sands in turbidite successions has commonly been attributed to the rapid dumping of sand due to flow unsteadiness in collapsing, single surge-type, high-density turbidity currents. The general applicability of this model is questioned here, and we propose that rapid deposition of massive sands also occurs due to non-uniformity in prolonged, quasi-steady high-density turbidity currents. We attempt to eliminate ambiguity in the use of the terms ‘deceleration’and ‘unsteadiness’with respect to non-uniform sediment gravity flows, and stress that, as with any particulate current, unsteadiness is not a prerequisite of sediment deposition. We propose a mechanism of gradual aggradation of sand beneath a sustained steady or quasi-steady current, and upward-migration of a depositional flow boundary that is dominated by grain hyperconcentration and hindered settling. Formation of tractional structures is prevented by the absence of a sharp rheological interface between the lowest parts of the flow and the just-formed dewatering deposit. Deposition continues as long as the downward grain flux to the depositional flow boundary is balanced by grain supply from above or from upcurrent. Massive sand deposited in this way is not, strictly, a result of ‘direct suspension sedimentation’in that it is characterized by grain interactions, hindered settling, shear and, possibly, by interlocking of grains. The thickness of the resulting massive sand bears no relation to the thickness of the parental current, and the vertical variation within the deposit may reveal little about the vertical structure of the current, even during deposition. Thin, normally graded tops or mud drapes represent the eventual waning of sustained currents.

The prediction of chronicity in patients with an acute attack of low back pain in a general practice setting

Abstract: Study Design Three hundred patients, attending their general practitioners with attacks of acute low back pain, formed the subject population for a study of fear avoidance and other variables in the prediction of chronicity Follow-up was at 2 and 12 months Objective The hypothesis of be tested was that evidence of psychological morbidity, particularly fear-avoidance behavior, would be manifest from the onset of the presenting attack in suceptible subjects Summary of Background Data While back pain is an almost universal human experience, only about 5% of sufferers seek medical advice Most of these respond to conservative treatment However, approximately 10% of those who experiment an acute attack of low back pain go on to become chronic sufferers Methods Psychosocial and physiological data (including fear-avoidance measures) were collected from a sample of 300 acute low back pain patients within 1 week of presentation and at 2 months, to try to predict 12 month outcome Results Data analysis showed that subjects who had not recovered by 2 months were those who went on to become chronic low back pain patients (73%) Using multiple regression analyses, fear-avoidance variables were the most successful in predicting outcome Using multiple regression analyses, fear-avoidance variables were the most successful in predicting outcome Using multiple discriminant function analyses, the results suggest that the outcome in terms of the future course of low back pain can be correctly classified in 66% from fear-avoidance variables alone and 88% of patients from all variables Conclusions The results suggest that, at the earliest stage of low back pain, fear of pain should be identified by clinicians and, where this is severe, pain confrontation should arguably form part of the approach to treatment

The Modified Dental Anxiety Scale: validation and United Kingdom norms.

Abstract: The Corah Dental Anxiety Scale (CDAS) has been used extensively in epidemiology and clinical research. It is brief and is claimed to have good psychometric properties. However, it does not include any reference to local anaesthetic injections, a major focus of anxiety for many. Also, the multiple choice answers for three of the four questions are not clearly in order of severity of anxiety as the CDAS intends. The answers differ among the questions thus making them difficult to compare. They include descriptions of physiological reactions and anxiety, confusing two loosely related components of the experience. The Modified Dental Anxiety Scale (MDAS) described, added a question on anxiety about oral injections. New multiple choice answers, in clear order of anxiety and the same for each question, were provided. Twenty five dental personnel all confirmed independently the order of the multiple choice answers for the MDAS. They disagreed among themselves however, about the appropriate sequence for the answers denoting intermediate anxiety in the CDAS. Therefore the CDAS, unlike the MDAS, can provide meaningful measures only of extremely high or extremely low dental anxiety. Of 1392 subjects tested, 13 per cent expressed extreme anxiety about injections on the MDAS but were only 'fairly' or less anxious about drilling. Thus, the CDAS, unlike the MDAS, must overlook subjects very afraid of injections only. Data confirm the high reliability and validity of the MDAS and provide norms for phobic and nonphobic subjects.

Clifford Algebras and the Classical Groups

Abstract: The Clifford algebras of real quadratic forms and their complexifications are studied here in detail, and those parts which are immediately relevant to theoretical physics are seen in the proper broad context. Central to the work is the classification of the conjugation and reversion anti-involutions that arise naturally in the theory. It is of interest that all the classical groups play essential roles in this classification. Other features include detailed sections on conformal groups, the eight-dimensional non-associative Cayley algebra, its automorphism group, the exceptional Lie group G2, and the triality automorphism of Spin 8. The book is designed to be suitable for the last year of an undergraduate course or the first year of a postgraduate course.

Dynamics of Weed Populations

Abstract: What are the ecological attributes of weeds that confer the ability to interfere with human activities? Roger Cousens and Martin Mortimer place weed management within an ecological context, with the focus on the manipulation of population size. The dynamics of abundance and spatial distribution are considered at both geographic and local scales. The basic processes of dispersal, reproduction and mortality are described, together with the factors that influence them. Management is shown to modify patterns of behaviour that are intrinsic to populations. Attention is given to the evolution and management of resistance to herbicides. This book provides weed science with the conceptual basis that has previously been lacking. It also gives ecologists access to the extensive database on the population ecology of weeds.

Face processing impairments after amygdalotomy

Abstract: We report an investigation of face processing impairments in D.R., a 51-year-old woman with a partial bilateral amygdalotomy. D.R. was able to recognize pre-operatively familiar faces, but she showed generalized problems of name retrieval and a more circumscribed deficit affecting the recognition of faces learnt post-operatively. In contrast to her poor memory for new faces, D.R.'s ability to match simultaneously presented photographs of unfamiliar faces was unimpaired. However, D.R. also experienced deficits in expression processing which compromised the recognition of emotion from people's faces; she was poor both at matching and at identifying photographs of emotional facial expressions. In addition, her interpretation of eye gaze direction was defective, showing a more general problem in reading social signals from the face. The presence of impairments affecting the learning of new faces and the comprehension of gaze direction and facial expressions of emotion is consistent with the hypothesis of a role for the amygdala in learning and social behaviour.

Fault overlap zones within developing normal fault systems

Abstract: Overlap zones between normal faults have been studied using a variety of 2D and 3D seismic reflection datasets. The overlaps are of two types, (i) relay zones in which displacement is transferred between the overlapping faults and (ii) non-relay overlaps in which displacement is not transferred. Overlap zones are continually formed and destroyed during the growth of a fault system. Overlap zones are formed either by interference between initially isolated faults or as a result of bifurcation of a single fault. The mode of overlap formation is reflected in the 3D geometry of the overlapping faults which may be either unconnected or linked at a branch-line or branch-point. Seismic reflection data from regions of growth faulting, and also sandbox analogue data, allow analysis of fault development through time. Reconstructions of the displacement distribution on some faults with sharp bends and associated hanging-wall splays, show that the bends originated as overlap zones which were later breached to form through-going faults. Depending on the displacements of relay-bounding faults, the effect of relay zones on hydrocarbon reservoirs may be to (a) provide structural closure, (b) form gaps in otherwise sealing faults or (c) increase reservoir connectivity.

Phonological Working Memory and Speech Production in Preschool Children

Abstract: This study investigates whether phonological working memory is associated with spoken language development in preschool children. Assessments were made of speech corpora taken from 3-year old child...

The Physiology of Fungal Nutrition

Abstract: The nutrition of a vegetative fungal colony can be viewed as a web of interconnected processes. In this volume, the author provides a mechanistic basis to the subject, focusing on the processes at the plasma membrane, the modulating effects of the fungal wall, and the fate of nutrients entering the fungus. The major emphasis is physiological, but biochemical and molecular biological information has also been drawn upon when appropriate, to reflect the power of a multifaceted approach and further encourage such study. A comprehensive review of what is known about the more commonly studied fungal species is complemented by information on other fungi, to provide an indication of the diversity of nutritional processes which exist in the fungal kingdom.

Second primary tumors in patients with head and neck squamous cell carcinoma

Abstract: Background. The concept that a patient could develop cancer twice was first put forward by Billroth. Second primary neoplasms are a particular feature of head and neck cancer. Methods. This study examines the records of 3436 patients with squamous cell carcinoma of the head and neck, of whom 274 subsequently developed a second neoplasm. Results. The actuarial second primary rate was 9.1% at 372 months, and median time to presentation for the second tumor was 36 months. Second tumors were more likely to occur in male patients younger than 60 years at the time of their index tumor, and who had laryngeal and oral cavity index tumors. Patients whose index tumor was small at diagnosis had a greater chance of developing a second tumor as did those with no cervical lymph node metastases to the neck. Radiotherapy to the index tumor was not associated with an increased risk of developing a second tumor. The commonest sites for second tumors were the head and neck (50%) and the lung (34%), and 86% were squamous cell carcinomas. The tumor-specific mortality for those who developed a second primary tumor was 20% after 15 years compared with 44% for patients who did not develop a second primary tumor. The 5-year survival for patients who developed a secondary tumor from the time of its diagnosis was 26%. Conclusions. Second primary tumors in the head and neck of patients with cancer are not uncommon. If the second tumor occurs in the head and neck region, the prognosis is reasonably good. Cancer 1995;75:1343-53.

Social networks, support cliques, and kinship

Abstract: Data on the number of adults that an individual contacts at least once a month in a set of British populations yield estimates of network sizes that correspond closely to those of the typical “sympathy group” size in humans. Men and women do not differ in their total network size, but women have more females and more kin in their networks than men do. Kin account for a significantly higher proportion of network members than would be expected by chance. The number of kin in the network increases in proportion to the size of the family; as a result, people from large families have proportionately fewer non-kin in their networks, suggesting that there is either a time constraint or a cognitive constraint on network size. A small inner clique of the network functions as a support group from whom an individual is particularly likely to seek advice or assistance in time of need. Kin do not account for a significantly higher proportion of the support clique than they do for the wider network of regular social contacts for either men or women, but each sex exhibits a strong preference for members of their own sex.

A self-rating scale for measuring neuroleptic side-effects. Validation in a group of schizophrenic patients.

Abstract: BACKGROUND A study was conducted to validate a comprehensive self-rating scale for measuring side-effects of neuroleptic drugs. METHOD The Liverpool University Neuroleptic Side Effect Rating Scale (LUNSERS), which includes 'red herring' items, was twice administered to 50 DSM-III-R schizophrenic patients, who were also interviewed using the UKU side-effect rating scale; 50 unmedicated controls also completed the LUNSERS: RESULTS The test-retest reliability of the LUNSERS was good (r = 0.811, P < 0.001) as was its concurrent validity against the UKU (r = 0.828, P < 0.001). Scores correlated with chlorpromazine equivalent doses (r = 0.310, P < 0.02). ROC analysis demonstrated that the scale discriminated between patients and non-medicated controls, who scored differently for real side-effects but not for 'red herring' items. CONCLUSIONS The LUNSERS is an efficient, reliable and valid method of assessing neuroleptic side-effects.

Chronic Obstructive Pulmonary Disease

Abstract: Chronic obstructive pulmonary disease (COPD) is a major cause of death and disability worldwide. Recognition that the burden of this disorder will continue to increase over the next 20 years despite medical intervention has stimulated new research into the underlying mechanisms, leading to a rational basis for evaluation of existing therapies, and has suggested novel treatment approaches. Tobacco exposure remains the main but not exclusive cause of COPD. Whether the lung is injured by changes in the balance of proteases and antiproteases, tissue damage by oxidative stress, or a combination of the two is still not known. The genetic basis of susceptibility to COPD is now being studied as is the role of computed tomography in the identification of structural damage in individuals with less symptomatic disease. Clinical diagnosis still relies heavily on an appropriate history confirmed by abnormal spirometry. Smoking cessation is possible in a substantial proportion of individuals with symptoms but is most effective if withdrawal is supported by pharmacological treatment. Treatment with long-acting inhaled bronchodilators and, in more severe disease, inhaled corticosteroids reduces symptoms and exacerbation frequency and improves health status. Rehabilitation can be even more effective, at least for a year after the treatment. Recent guidelines have made practical suggestions about how to optimise these treatments and when to consider addition of oxygen, surgery, and non-invasive ventilation. Regular review of this guidance is important if future management advances are to be implemented effectively.

Effects of alternative male mating strategies on characteristics of sperm production in the Atlantic salmon (Salmo salar): theoretical and empirical investigations

Abstract: Atlantic salmon ( Salmo salar ) males mature as either tiny precocious parr before seaward migration, or as older and larger anadromous males. Anadromous males dominate the spawning redds and aggressively defend females against parr intrusions. Parr gain fertilizations by sneaking in to ejaculate while anadromous males and females spawn. Such differences in mating advantage generate asymmetries in risk of sperm competition between the male strategies. Theoretical sperm competition models predict that males typically mating in disfavoured roles (here, the parr strategy) should be selected to offset this disadvantage by investing more into spermatogenesis to achieve fertilization success. First, we present a theoretical model which analyses gametic expenditure for salmon parr and anadromous male reproductive strategies. We then use the natural variance in mating pattern within this species to compare empirically how males invest in spermatogenesis. A range of reproductive traits were measured for both male strategies. Absolutely, anadromous males have larger testes and produce greater numbers of sperm than parr males. However, results show that parr invest relatively more heavily into total spermatogenesis, and have a larger gonosomatic index than anadromous males. Relative to body size, parr produced greater numbers of sperm and volumes of stripped ejaculate. There was no difference in sperm length between the two male strategies. However, more sperm were motile in parr ejaculates, and these sperm lived longer than anadromous male sperm. Our findings may explain how male parr, under elevated risks of sperm competition and occupying a disfavoured mating role (parr weigh only 0.15% of the average body mass of anadromous males) achieve disproportionately high fertilization success.