Showing papers by "University of Aberdeen published in 1995"

Chemical generation of nitric oxide in the mouth from the enterosalivary circulation of dietary nitrate.

Abstract: High concentrations of nitrite present in saliva (derived from dietary nitrate) may, upon acidification, generate nitrogen oxides in the stomach in sufficient amounts to provide protection from swallowed pathogens. We now show that, in the rat, reduction of nitrate to nitrite is confined to a specialized area on the posterior surface of the tongue, which is heavily colonized by bacteria, and that nitrate reduction is absent in germ-free rats. We also show that in humans increased salivary nitrite production resulting from nitrate intake enhances oral nitric oxide production. We propose that the salivary generation of nitrite is accomplished by a symbiotic relationship involving nitrate-reducing bacteria on the tongue surface, which is designed to provide host defence against microbial pathogens in the mouth and lower gut. These results provide further evidence for beneficial effects of dietary nitrate.

Developing and implementing clinical practice guidelines.

Abstract: Correspondence to: Dr J Grimshaw, Health Services Research Unit, University of Aberdeen, Drew Kay Wing, Polwarth Building, Foresterhill, Aberdeen AB9 2ZD The Effective Health Care bulletins have concentrated on providing systematic reviews of the research evidence on clinical and cost effectiveness to help inform decision makers and clinicians in the NHS. However, providing information by itself is rarely sufficient to stimulate corresponding change in practice. Various implementation strategies can be used to promote the use of research evidence. One approach which has received growing attention and support is the development and implementation of clinical practice guidelines.' 2 These are \"systematically developed statements to assist practitioner and patient decisions about appropriate health care for specific clinical circumstances.\"3 Some previous bulletins argued for the incorporation of the evidence on effectiveness into guidelines,4 5and it has been argued that healthcare commissioners should purchase guidelines or protocols rather than simple procedures.6 This paper examines the evidence on whether practice guidelines can change the behaviour of health professionals and how best to introduce them into clinical practice. The characteristics of high quality guidelines and how purchasers might use guidelines in commissioning are also considered.

Measuring Forearm Blood Flow and Interpreting the Responses to Drugs and Mediators

Abstract: Venous occlusion plethysmography has been widely used to study forearm blood flow. The principle of the technique is straightforward: the rate of swelling of the forearm during occlusion o...

A Model of Sympatric Speciation by Sexual Selection

Abstract: Quantitative genetic models have indicated that sexual selection may lead to speciation in isolated populations or to exaggeration of differences in male traits along a cline. We argue that where female mate preference and opposing natural selection against conspicuous males have produced a stable equilibrium in male trait genotype, a reversed female mate preference may invade the population, initially assisted by reduced male mortality. The consequent linkage disequilibrium may lead to rapid sympatric speciation. Assuming a four-locus quantitative male trait and single-locus female preference rule and overlapping generations, we present a simulation model which indicates that reversal of female mate preference in a single individual can lead rapidly to full reproductive isolation in a small population. Speciation may be produced by the proposed mechanism in allopatry, parapatry or full sympatry. We suggest that differences in mating system and its genetic bases may account for some of the differences in speciation rates among lineages.

Role of sulfate‐reducing bacteria in corrosion of mild steel: A review

Abstract: The influence of sulfate‐reducing bacteria on corrosion of mild steel is reviewed, with special emphasis on the effects of biofilm structure and function, medium composition (dissolved oxygen and ferrous ion concentrations) and the physical and chemical properties of iron sulfides. A summary of different corrosion mechanisms is critically discussed, based on electrochemical and rate process analyses. A mechanism is proposed which explains the high corrosion rates observed in the field.

Antibiotic production and biocontrol activity by Bacillus subtilis CL27 and Bacillus pumilus CL45.

Abstract: Bacillus subtilis CL27 and B. pumilus CL45 showed similar activity against Botrytis cinerea in in vitro plate assays. In a seedling bioassay, however, B. subtilis CL27 had activity similar to a commercial fungicide while B. pumilus CL45 failed completely to prevent seedling damping-off caused by Bot. cinerea. Antibiotic production by the two Bacillus strains was found to depend on the growth substrate and highest antibiotic production was found on media based on homogenized cabbage tissue. Antibiotic activity was found to depend on the pH and nutrient concentration in the assay medium. Antifungal antibiotics produced by B. subtilis CL27 and B. pumilus CL45 in different fermentation media were separated by thin layer chromatography. As suspected from the activity spectrum, three antibiotics (one with activity against Alternaria brassicicola, one with activity against Botrytis cinerea and one with activity against both fungi) could be detected in the fermentation broth of CL27, but only one in the fermentation broth of CL45. The two antibiotics produced by strain CL27 with activity against A. brassicicola were identified as peptides since their bands on the TLC plates developed a green to blue/green colour after treatment with 4,4'-tetramethyldiamino-diphenylmethane (TDM) reagent. The third antibiotics produced by strain CL27 and antibiotic produced by CL45 had a similar Rf-value and appeared not to be peptides based on the reaction with TDM. However, they showed a slightly different activity spectrum when tested against a range of different fungi. Antibiotic production was clearly indicated as the mode of action of in vivo biocontrol by strain CL27 against damping off caused by Bot. cinerea of Astilbe micro-plants, because a u.v.-induced antibiotic negative mutant strain CL27b showed no activity in seedling bioassays in vivo. Also the mutant strain CL27a which produced the two peptide antibiotics but had lost the ability to produce the non-peptide antibiotic, showed greatly reduced in vivo activity.

On the need to re‐conceptualise sustainable tourism development

Abstract: Recent years have witnessed the emergence of a dominant paradigm of sustainable tourism development, one which appears to chart a responsible course, balancing the requirements of tourism development with the protection of the environment. However, this paper argues that the predominant paradigm is too tourism‐centric, parochial and, therefore, inherently flawed, and that it effectively condones planning, management and policy approaches which fail to operationalise sustainable tourism in a manner consistent with the general aims and requirements of sustainable development. In particular, it is suggested that the tourism‐centric paradigm encourages inappropriate and inconsistent consideration of the scope and geographical scale of tourism's resource base, whilst also failing to adequately account for the intersectoral context of tourism development In order to re‐engage sustainable tourism development with its parental concerns (those of sustainable development generally), an alternative, extra‐parochial ...

The effect of osmolality and carbohydrate content on the rate of gastric emptying of liquids in man.

Abstract: 1. The effect of osmolality and carbohydrate content on the rate of gastric emptying was assessed by using the double sampling gastric aspiration technique to measure the rate of gastric emptying of isoenergetic and isosmotic solutions of glucose and glucose polymer. Six healthy male subjects were each studied on four separate occasions using a test drink volume of 600 ml. 2. The half-emptying time (t1/2, mean +/- S.E.M.) for a dilute (40 g l-1) solution of glucose (LG, 230 mosmol kg-1) was 17 +/- 1 min. This was greater than that (14 +/- 1 min) for a glucose polymer solution with the same energy content (LP, 42 mosmol kg-1). A concentrated (188 g l-1) glucose polymer solution (HP, 237 mosmol kg-1) emptied faster (t1/2 = 64 +/- 8 min) than the corresponding isoenergetic glucose solution (HG, 1300 mosmol kg-1, t1/2 = 130 +/- 18 min). 3. The dilute (40 g l-1) glucose solution emptied faster than the concentrated (188 g l-1) glucose polymer solution with the same osmolality (LG, 230 mosmol kg-1; HP, 237 mosmol kg-1). 4. The two dilute solutions (40 g l-1) delivered a similar amount of carbohydrate to the small intestine, whereas the concentrated (188 g l-1) glucose polymer solution delivered a greater amount of carbohydrate at 20, 40 and 50 min than the isoenergetic glucose solution. 5. These results indicate that both osmolality and carbohydrate content influence gastric emptying of liquids in man, but the carbohydrate content appears to have greater influence than osmolality.(ABSTRACT TRUNCATED AT 250 WORDS)

Rotation of principal components: choice of normalization constraints

Abstract: Following a principal component analysis, it is fairly common practice to rotate some of the components, often using orthogonal rotation. It is a frequent misconception that orthogonal rotation will produce rotated components which are pairwise uncorrelated, and/or whose loadings are orthogonal In fact, it is not possible, using the standard definition of rotation, to preserve both these properties. Which of the two properties is preserved depends on the normalization chosen for the loadings, prior to rotation. The usual ‘default’ normalization leads to rotated components which possess neither property.

Calprotectin‐Mediated Zinc Chelation as a Biostatic Mechanism in Host Defence

Abstract: The S-100 Ca2+ binding protein, calprotectin, isolated from neutrophil lysates, has been reported to exhibit zinc reversible biostatic activity in vitro. We verified these findings with C. albicans and investigated whether the growth inhibition resulted from zinc deprivation due to chelation by calprotectin. Calprotectin concentrations of 250 μg/ml significantly inhibited the growth of C. albicans. This was reversed by supplementing culture medium with 10 μM ZnSO4. Incubation of calprotectin in culture medium for 24 h prior to inoculation significantly reduced the minimum inhibitory concentration. When this latter medium was ultrafiltered to remove the calprotectin and then inoculated with C. albicans, significant growth inhibition was still present: again it was reversed by zinc. These findings implicate zinc chelation as a novel, potentially important host defence function of an abundant neutrophil protein.

Primary cilia in normal and pathological tissues

Abstract: The medical literature in pathology contains a surprising number of anecdotal reports of primary cilia, with authors often expressing some incredulity at finding such organelles. In this update of an earlier review, I will argue that primary cilia should by now be regarded as regular cell organelles, not some form of atypical response to unusual circumstances. In all situations in which their presence is essential, they unquestionably act as sensory transducers. Detection by electron microscopy has been the most reliable means until recently, but is time-consuming and slow for any systematic investigation or experimental approach. Immunostaining with an antibody direct against detyrosinated tubulin is rapidly changing the situation, and we can now detect their presence, frequency, disposition and overall characteristics relatively quickly, allowing better statistical analysis and correlations in abnormal physiological and pathological conditions. To be useful and meaningful, comparative studies need a reliable database of information about primary cilia under 'normal' circumstances. It is hoped that such work will in itself give much further insight into the general significance of these organelles, especially combined with the more experimental approaches that can now be adopted in the study of their development and function, which looks increasingly promising with the new technological improvements.

Fabric signature of subglacial till deformation, Breidamerkurjokull, Iceland

Abstract: The foreland of Breidamerkurjokull, Iceland, is the only locality where tills known to have undergone subglacial deformation are exposed. Till on the foreland has a two-tiered structure, consisting of a dilatant upper horizon c 0.5 m thick and a compact lower till; these horizons correspond to the ductile deforming A horizon and the brittle-ductile B horizon observed below the glacier by G. S. Boulton and co-workers. The relationship between known strain history and a variety of macrofabric elements is examined for these two genetic facies of deformation till. The upper horizon exhibits variable a-axis fabrics and abundant evidence for clast re-alignment, reflecting ductile flow and rapid clast response to transient strains. In contrast, the lower horizon has consistently well organized a-axis fabrics with a narrow range of dip values, recording clast rotation into parallel with strain axes during brittle or brittle-ductile shear. The data indicate that till strain history imparts identifiable macrofabric signatures, providing important analogues to guide the interpretation of Pleistocene tills.

An experimental study of multiple grain‐size ejecta produced by collisions of saltating grains with a flat bed

Abstract: Collision data are presented from coloured high-speed films of three size fractions of sand grains saltating over a bed of the total grain population. Each fraction was colour tagged and the proportion of each size ejected by grains colliding with the surface was recorded on a number of films taken as the bed was progressively eroded. The results confirm earlier findings that V3/V1≅0.5–0.6, Vn/V1≅.08 and the rebound angle increases with decreasing grain size. Ejected grains are examined in relation to their size, the impactor size, ejection speed and angle and the number of ejecta per collision. In addition, changes in grain parameters are observed with time. For fine impactors, ejection speeds generally increase with a decrease in ejecta size, but the fine fraction does not follow this trend for the coarse and medium impactors. Ejection angles are typically between 40° and 60°, with coarse grains having shallower mean angles than fine ejecta. The number of ejections per collision increases with a decrease in particle size for each impactor size. The general tendency for coarse particles to be ejected at lower speeds and shallower angles than fine particles will lead to sorting of the grain sizes. There is poor correlation between the forward momentum loss of the saltating grams at collision and both the forward momentum of the ejected grains and the number of ejected grains. Much of the forward momentum of the saltating grains is transfered to creeping grains. The composition and geometry of the bed are considered to be important factors in the evolution of the saltation cloud.

Developing clinically valid practice guidelines

Abstract: Valid guidelines, when appropriately disseminated and implemented, can lead to changes in clinical practice and improvements in patient outcome. Guidelines are more likely to be valid if they are developed using systematic reviews, national or regional guideline development groups (including representatives of key disciplines) and explicit links between recommendations and scientific evidence. This paper discusses the practical implications of adopting this approach for guideline development and the role of peer review guidelines as another element of the process to ensure validity. Considerable resources are required to develop evidence-linked guidelines, but this investment can be recouped by relatively small changes in the process or outcome of care. Good leadership and technical support are required for the successful development of clinically valid guidelines, which is dependent upon the small-group processes of guideline development panels and the translation of evidence into recommendations. Future guideline developers need to gain expertise in these areas. Research priorities are identified.

Growth and development of male gymnasts, swimmers, soccer and tennis players: A longitudinal study

Abstract: Summary. l~lite adult athletes are known to have physical and physiological characteristics specifically suited to their sport. However, it is not clear whether the observed adult differences arise because of training or whether the sport selects the individual with the appropriate characteristics. The purpose of this prospective study was to compare and contrast the physical development of young athletes (8-19 years), and in so doing provide a possible response to this question. Development of anthropometric characteristics and sexual maturation were assessed in a group of 232 male athletes for three consecutive years. Parental heights were used to predict target heights. The subjects were a randomly selected group of young British athletes, from four sports: soccer, gymnastics, swimming and tennis. Using a linked longitudinal cohort study design (age cohorts 8, 10, 12, 14 and 16 years) it was possible to estimate a consecutive ll-year development pattern, over the 3-year testing period. The adjusted mean (ANCOVA) height, accounting for age and pubertal status, of male swimmers (161.6_+0.6cm) was found to be significantly greater (p <0.01) than gymnasts (150.7 + 0"8 cm) and soccer players (158.7 _+ 0.6 cm), and their adjusted mean body mass (51.3 +_ 0-6 kg) significantly greater (/7 < 0"01) than the other groups. When testicular volumes were compared, it was found that swimmers had significantly larger volumes than gymnasts and tennis players from 14 to 16 years of age (p <0.05). Gymnasts' growth curve of testis size was characteristic of late maturers, the swimmers' curve was characteristic of early maturers. As all the young athletes started training prior to puberty the observed late sexual maturation of gymnasts and early maturation of swimmers suggests some form of sports-specific selection. Training did not appear to have affected these young athletes' growth and development; rather their continued success in sport appeared to be related to inherited traits.

Neurovascular dysfunction in diabetic rats. Potential contribution of autoxidation and free radicals examined using transition metal chelating agents.

Abstract: Oxygen free radical activity is elevated in diabetes mellitus and has been implicated in the etiology ofvascular complications. Recent studies have shown that impaired perfusion of nerve endoneurium is a major cause of nerve fiber dysfunction in experimental diabetes. Free radical scavenger treatment prevents the development of nerve conduction abnormalities in diabetic rats. In vitro experiments suggest that autoxidation reactions of glucose, catalyzed by free transition metal ions, are a potential source of free radicals in diabetes. We investigated whether chronic treatment with deferoxamine and trientine, transition metal chelating agents which can prevent autoxidation, could correct nerve conduction and blood flow changes in streptozotocin-diabetic rats. A 20% reduction in sciatic nerve motor conduction velocity after 2 mo diabetes was 90% ameliorated by 2 wk of treatment with deferoxamine or trientine. Sciatic endoneurial nutritive blood flow was 45% reduced by diabetes, but was completely corrected by treatment. In contrast, transition metal chelation had no effect on blood flow or conduction velocity in nondiabetic rats. Thus, the data support the hypothesis that increased free radical activity by glucose autoxidation as a result of impaired transition metal handling is a major cause of early neurovascular deficits in

Wealth Accumulation and Housing Choices of Young Households: An Exploratory Investigation

Abstract: This paper describes the wealth accumulation of American youth and relates this behavior to their eventual housing choices We develop a data set that links wealth profiles of youth with constant- quality house prices and tenure choice A panel data set is compiled for youth age 20-33 for the years 1985 through 1990 We construct wealth profiles for each household over the six year period and indicate how wealth varies with labor supply, marriage, fertility, gender, education, race/ethnicity, and tenure choice We find renters' wealth accumulates rapidly in the year before and year of first homeownership The factors related to this increase are marriage, increased labor supply by married women, and gifts/inheritances Of particular interest is the finding of an inverse U-shaped relationship between the local real price of housing and middle and upper income renters' wealth and married female labor supply Also, youth in high housing cost localities tend to live in groups at a greater rate compared to those in low cost areas

Seasonal variation in coronary heart disease in Scotland.

Abstract: STUDY OBJECTIVE--Seasonality of coronary heart disease (CHD) was examined to determine whether fatal and non-fatal disease have the same annual rhythm. DESIGN--Time series analysis was carried out on retrospective data over a 10 year period and analysed by age groups ( 75 years) and gender. SETTING--Data by month were obtained for the years 1962-71. The Registrar General provided information on deaths and the Research and Intelligence Unit of the Scottish Home and Health Department on hospital admissions. SUBJECTS--In Scotland, between 1962 and 1971, 123 000 patients were admitted to hospital for CHD, of whom 29 000 died. There were a further 97 000 CHD deaths outside hospital. These two groups were also examined as one (coronary incidence) - that is, all coronary deaths and coronary admissions discharged alive. STATISTICAL ANALYSIS AND MAIN RESULTS: Where there was a single annual peak, the sine curve was analysed by cosinor analysis. When there were two peaks the analysis was by normal approximation to Poisson distribution. In younger men (under 45 years) admitted to hospital there was a dominant spring peak and an autumn trough. A bimodal pattern of spring and winter peaks was evident for hospital admissions in older male age groups: with increasing age the spring peak diminished and the winter peak increased. In contrast, female hospital admissions showed a dominant winter/summer pattern of seasonal variation. In male and female CHD deaths seasonal variation showed a dominant pattern of winter peaks and summer troughs, with the winter peak spreading into spring in the two youngest male age groups. CHD incidence in women showed a winter/summer rhythm, but in men the spring peak was dominant up to the age of 55. CONCLUSION--The male, age related spring peak in CHD hospital admissions suggests there is an androgenic risk factor for myocardial infarction operating through an unknown effector mechanism. As age advances and reproduction becomes less important, the well defined winter/summer pattern of seasonal variation of CHD is superimposed, and shows a close relationship with the environment, especially temperature, or the autumn and early winter fall in temperature.

Paroxysmal vertigo as a migraine equivalent in children: a population‐based study

Abstract: We studied the prevalence, causes and clinical features of paroxysmal vertigo (PV) in the well-defined childhood population of the City of Aberdeen. We applied a screening questionnaire to 2165 children (10% random sample of all children 5–15 years of age) attending schools in Aberdeen. Children with a history of at least three episodes of vertigo over the past year due to unknown causes were invited for clinical interview and examination. Children with PV were compared with a group of children with migraine, and with a group of asymptomatic children matched for age and sex. Forty-five children fulfilled the diagnostic criteria for PV (prevalence rate 2.6%, 95% CI 1.9–3.4). They were noted to have clinical features in common with children with migraine, including trigger and relieving factors, associated gastrointestinal and sensory symptoms, vasomotor changes, and a similar pattern of associated recurrent disorders (such as headache, abdominal pain and cyclical vomiting), atopic diseases and travel sickn...