Showing papers by "University of Aberdeen published in 1987"

Characteristics of alcohol/polyol dehydrogenases. The zinc-containing long-chain alcohol dehydrogenases.

Abstract: Sixteen characterized alcohol dehydrogenases and one sorbitol dehydrogenase have been aligned. The proteins represent two formally different enzyme activities (EC 1.1.1.1 and EC 1.1.1.14), three different types of molecule (dimeric alcohol dehydrogenase, tetrameric alcohol dehydrogenase, tetrameric sorbitol dehydrogenase), metalloproteins with different zinc contents (1 or 2 atoms per subunit), and polypeptide chains from different kingdoms and orders (mammals, higher plants, fungus, yeasts). Present comparisons utilizing all 17 forms reveal extensive variations in alcohol dehydrogenase, but with evolutionary changes that are of the same order in different branches and at different times. They emphasize the general importance of particular residues, suggesting related overall functional constraints in the molecules. The comparisons also define a few coincidences between intron positions in the genes and gap positions in the gene products. Only 22 residues are strictly conserved; half of these are Gly, and most of the remaining ones are Pro or acidic residues. No basic residue, no straight-chain hydrophobic residues, no aromatic residues, and essentially no branched-chain or polar neutral residues are invariable. Tentative consensus sequences were calculated, defining 13 additional residues likely to be typical of but not invariant among the alcohol dehydrogenases. These show a predominance of Val, charged residues, and Gly. Combined, the comparisons, which are particularly relevant to the data base for protein engineering, illustrate the requirements for functionally important binding interactions, and the extent of space restrictions in proteins with related overall conformations and functions.

Site characteristics and the distribution of tree species in mixed dipterocarp forest on tertiary sediments in central Sarawak, Malaysia

Abstract: Site data from 291 forest inventory plots in Mixed Dipterocarp Forest in central Sarawak were simplified by factor analysis. The distribution of the 33 commonest canopy tree species was related to site factor scores by 't' tests. There appears to be a degree of edaphic influence on the distribution of many species. Fairly constant soil characteristics related to the lithology of the parent material appear to be more important than ephemerally variable pro- perties such as organic matter or exchangeable cations. Magnesium appears to be particularly important, possibly because of an effect on the capacity of mycorrhizal root systems to absorb phosphorus.

Macroalgal mats and species abundance: a field experiment

Abstract: A field experiment was carried out whereby the density of macroalgae ( Enteromorpha spp.) was manipulated and the resultant changes in sediment infaunal density were monitored. Four densities of Enteromorpha spp. were used: 0,0·3, 1, and 3 kg FW m −2 , corresponding to control, low-, medium-, and high-density plots. The experiment ran from May to October 1985 and was sampled on three occasions. By July, the density of Corophium volutator was reduced at all weed levels when compared to control plots, whereas densities of Hydrobia ulvae , Macoma balthica, Nereis diversicolor , and Capitella capitata , all increased. Samples taken in October when the weed mats were buried in the sediment showed fewer differences than in July. Macoma, Nereis , and Capitella were still significantly more abundant at medium and high weed densities. Corophium showed no significant treatment effect. There was, however, a highly significant difference in population size structure for Corophium . Measurements of sediment redox potential and silt content under medium- and high-density plots revealed rapid anoxia with a significant increase in siltation.

Vegetation, Fire and Herbivore Interactions in Heathland

Abstract: Publisher Summary Studies on heathlands in N.W. Europe have provided a remarkably detailed picture of interactions between the heath vegetation, the major herbivores, and disturbance by fire. Low nutrient status and disturbances such as fire and herbivory are identified as the main factors controlling the dynamics of heath systems. The classical idea of the “Calluna cycle” should be interpreted as one of a larger set of possible pathways for heath vegetation development. Production, shoot nutrient content, and species composition are all greatly affected by the age of the dominant, Calluna vulgaris. Stand age also affects the outcome of fire. Variations in the regenerative capacity of the dominant and associated species in stands of different ages determine the post-fire vegetation response. The effects of disturbance on the vegetation vary with disturbance intensity and scale. Light-moderate grazing or fires at certain frequencies may maintain heathland communities in a relatively productive state and with Calluna as the dominant. More intense grazing or frequent fires may lead to the replacement of Calluna by graminaceous species. Phytophagous insects have similar effects but on a smaller scale. For conservation purposes, traditional management practices may require to be continued or restored, although variations may be necessary to promote biotic diversity.

The effect of dietary molybdenum and iron on copper status, puberty, fertility and oestrous cycles in cattle

Abstract: Two experiments were conducted to examine the effects of supplementation of a control diet of barley grain and barley straw containing 4 mg copper (Cu)/kg dry matter (D.M.) either with 5 mg molybdenum (Mo)/kg D.M. or with 500 or 800 mg iron (Fe)/kg D.M. on puberty, fertility and oestrous cycles of cattle. Puberty occurred normally in control, Fesupplemented and control animals on a restricted intake whereas it was delayed by 12 and 8 weeks respectively by Mo supplementation. This effect of Mo was not due to the low Cu status since this was equally low in the Fe-supplemented animals, nor was it due to the reduced growth rate since puberty occurred normally in control animals that had a similar live-weight gain. A significant reduction in the pulsatile release of luteinizing hormone was observed within 11 weeks of the Mo supplementation and before any of the other clinical signs were evident, suggesting that Mo may be affecting puberty by altering the release of luteinizing hormone either directly or indirectly.Mo supplementation significantly reduced the percentage conception rate to 12–33% compared with 57–80% in control and Fe-supplemented animals. This effect was not dependent on the rate of live-weight gain which was standardized across the different treatments at approximately 0·6 kg/day. Within 12 weeks of the replacement of dietary Fe by Mo a lower conception rate occurred; replacing dietary Mo by Fe led to a normal conception rate within 12 weeks without any accompanying changes in Cu status or in the rate of live-weight gain. The plasma Mo concentrations, however, changed significantly during these alterations in dietary supplementation. The pre-ovulatory peak height of luteinizing hormone was significantly lower in animals on the Mo-supplemented diet compared with control and Fe-supplemented animals, but the administration of LHRH did not alter the conception rate.More Mo-supplemented animals failed to ovulate following prostaglandin induced synchronization in comparison with the other treatments, and by the 84th week a significantly greater number of Mo-supplemented animals (12/18) had become anoestrous compared with the other groups (2/30). Cu repletion of these anoestrous Mo animals for a period of 20 weeks did not result in resumption of normal oestrous cycles, but ovulation and oestrus were induced by progesterone and LHRH treatment. Results in the latter part of the study indicated that Mo caused superovulation.These data show that Mo supplementation delayed the onset of puberty, decreased the conception rate and caused anovulation and anoestrus in cattle without accompanying changes in Cu status or in live-weight gain. It is suggested that these effects of Mo are associated with a decreased release of luteinizing hormone that might be due to an altered ovarian steroid secretion.

Evaluating changes in league structure: the reorganization of the Scottish Football League

Abstract: This article investigates the relationship between league structure and the demand for professional team sport using data from the Scottish Football League (SFL) 1971 to 1980. The SFL was restructured in 1975 and thus provides an excellent opportunity for the empirical analysis of the influence of league structure. The general channels by which league structure affects demand are explored. Estimates are made of the impact on individual clubs by predicting what attendances would have been in the absence of the league reorganization. Finally, the distribution of attendances across clubs is examined for evidence of the influence of league structure.

Hard-setting soils

Abstract: . Hard-setting soils are widespread in dry regions. Their properties are described and a physical explanation for hard-setting behaviour is given. The limitations on soil management and physical fertility caused by hard-setting depend on timing of rainfall or irrigation with respect to cultivations and crop development, and much research is needed to quantify reductions in crop yield imposed by these limitations.

An experimental investigation of the effects of shorebird and flatfish predation on estuarine invertebrates

Abstract: Shorebirds and flatfish were selectively excluded from areas of mudflat of the Ythan estuary in two separate experiments. Exclosures and control areas were monitored over several months for sediment and faunal characteristics and compared by 2-way ANOVA. There was no significant effect of the exclosures on sediment properties, due to the relatively large open area of the exclosure material used. Exclosures had little effect on invertebrate densities. The results are discussed in relation to prey mobility and the effects of predation estimated from energy demands of the predators. It is suggested that, over the study period, predators did not significantly affect the numbers of invertebrates in the mudflats. Over the winter period, Corophium within exclosures were significantly larger than those in control areas, probably due to size-selective predation by shorebirds.

The effect of dietary molybdenum and iron on copper status and growth in cattle.

Abstract: Summary The effects of supplementation of a barley-barley straw diet containing 4 mg copper (Cu)/kg dry matter (D.M.) either with 5 mg molybdenum (Mo)/kg D.M. or with 500 mg iron (Fe)/kg D.M. on the Cu status, growth and clinical condition of calves are described. Liver and plasma Cu concentrations declined rapidly within 12–16 weeks to levels indicating severe Cu deficiency in both the Mo- and Fe-supplemented groups. The changes in Cu status were similar for both supplements and did not differ significantly from each other. Clinical signs of Cu deficiency, as indicated by reduced growth rate and changes in hair texture and colour, were evident after 16–20 weeks only in animals on the Mosupplemented diet. The reduced growth rate was accompanied by a decreased food intake and reduced efficiency of food utilization. The Mo-supplemented animals also exhibited an altered Fe metabolism, particularly when the growth rate was affected. The results confirm earlier reports that the effects of Mo on growth and clinical condition are independent of its effect on Cu status and suggest that the altered production might be due to effects on the control of food intake, food utilization, or Fe metabolism.

Steady-state and transient growth of autotrophic nitrifying bacteria

Abstract: Growth of the autotrophic nitrifying bacteria Nitrosomonas europaea and Nitrobacter sp. was studied in continuous culture. Steady state growth kinetics of both organisms conformed with that predicted by chemostat theory, modified to account for maintenance energy requirement. Steady state data were used to calculate the maximum specific growth rate, the saturation constant for growth, the true growth yield and the maintenance coefficient. Transient growth was studied by imposing step changes in dilution rate. Step increases resulted in overshoots and oscillations in substrate concentration before establishment of a new steady state while step decreases in dilution rate were followed by monotonic changes in substrate concentration. The size of overshoots in substrate concentration following step increases in dilution rate was dependent on both the magnitude of the increase and of the dilution rate prior to the change.

Tumours acquire their vasculature by vessel incorporation, not vessel ingrowth

Abstract: This study was designed to investigate the early development of tumour circulation using a transplantable mouse mammary adenocarcinoma. Tumour cells (10(6] were injected subcutaneously into the flank and groups of treated mice were killed at 24 h intervals up to 12 days; the tumours and surrounding tissues being processed by standard histological methods. Sections of tumour were sub-divided into neoplastic tissue, vessels and connective tissue using computer-assisted morphometric techniques: the host tissue around the tumour was similarly quantified for vessels and connective tissue. With increasing tumour size, the proportion of vessels within tumours rapidly increased to reach a plateau of approximately 1.5 per cent of tumour volume, a 400 per cent increase on the vascular density of normal subcutaneous tissue. Within tumours, vascular density was always higher at the periphery than the centre. The most pronounced increase in vascular density affected the host tissue around the tumour. It is not clear why vascular development is most prominent outwith the tumour when postulated angiogenic factors, such as tumour angiogenesis factor, are presumably released within. Our results imply, however, that tumours acquire their vasculature by infiltration into, and expansion between, a network of newly formed vessels in the surrounding connective tissue.

Compositional Model for Calcium Silicate Hydrate (C-S-H) Gels, Their Solubilities, and Free Energies of Formation

Abstract: A compositional model based on available structural evidence is proposed for amorphous calcium silicate hydrogel. It is applicable to gels in the (Ca/Si),solid range 1.0 to 1.4 and is formulated to take account of dimeric silicate species in the solid. Its composition is represented by CaxH6−2xSi2O7·zCa(OH)2·nH2O where x and z are not independently obtainable; x+z, however, is evaluated from the Ca/Si ratio. The model is applied to representative solubility data; Ksp and free energies of formation for C-S-H's in this composition range are evaluated.

Estimation of premorbid intellectual status in depression

Abstract: The validity of the NART and Vocabulary subtest of the WAIS as measures of premorbid IQ in depression was assessed by comparing a group of depressed patients (n = 39) with matched controls. The Vocabulary performance of the depressed group was significantly poorer than controls but there was no significant difference in NART performance.

Activation of rainbow trout macrophages

Abstract: Rainbow trout peritoneal macrophages were stimulated in vitro using Concanavalin A (Con A) and in vivo using formalin-killed Aeromonas salmonicida in Freund's incomplete adjuvant (FIA). Whether these cells had been activated was determined by the measurements of oxygen anions (NBT reduction), H2O2 production (oxidation of phenol red), RNA synthesis (3H-uridine incorporation), acid phosphatase activity and bactericidal activity. In vitro-stimulated macrophages showed an increased NBT reduction and 3H-uridine incorporation over a range of Con A concentrations, compared with untreated control macrophages, but no detectable increases in H2O2 production or bactericidal activity were observed. On the other hand, in vivo-stimulated peritoneal cells showed increases in all the assays compared with FIA-elicited control cells, and were considered to have been activated.

Is birth weight determined genetically

Abstract: Birthweight correlations were analysed among 505 intergenerational pairs of first births to women aged 18-25 identified from a large obstetric data bank. After standardisation for fetal sex, maternal height, gestational age, and proteinuric pre-eclampsia residual correlations of between 0.1402 and 0.1725 were found, suggesting only a small genetic effect. It is concluded that genetic factors play only a small part in determining birth weight.

Molecular cloning of cDNA for human complement component C1s. The complete amino acid sequence.

Abstract: The complete amino acid sequence (673 residues plus 15 residues of leader sequence) of human complement component C1s has been determined by nucleotide sequencing of cDNA clones from a human liver library probed with synthetic oligonucleotides. Much of the sequence is supported by independent amino acid sequence information. The cDNA sequence contains an anomalous "intron-like" sequence, including a stop codon, that can be discounted because of the amino acid sequence evidence. The N-terminal chain (422 residues) of C1s, like that of C1r with which it is broadly homologous, contains five domains: domains I and III are homologous to one another and to similar regions in C1r, domain II is homologous to the epidermal growth factor sequence found in C1r and several other proteins, and domains IV and V are homologous to one another and to the 60-residue repeating sequence found in C1r, C2, factor B, C4-binding protein and some apparently unrelated proteins. The sequence of the C-terminal chain (251 residues) agrees with that already established to be the "serine protease" domain of C1s.

Geographic variation within an island: univariate and multivariate contouring of scalation, size, and shape of the lizard gallotia galloti

Abstract: Microgeographic variation of the vegetarian lizard Gallotia galloti within the island of Tenerife is described using univariate analysis, correlation, multiple group principal component analysis, canonical analysis, transects, and contours. The size varies locally in a mosaic pattern while head shape shows a WNW-ESE cline in the south. The scalation (scale and femoral pore counts) has two facets to its geographic variation, both of which are incongruent with the primary variation in the size and shape. The scalation shows categorical variation (stepped cline) between northern and southern populations and also a strong clinal relationship with altitude. The possible causes of this variation are considered and adaptation to current ecological conditions appears to be implicated for at least the altitudinal variation, although the pertinent factors are not obvious. It is apparent that vertebrate populations distributed across small islands do not necessarily offer the advantage of a discrete homogeneous unit for evolutionary studies but can offer the opportunity for studying microgeographic variation.