Showing papers by "University of Birmingham published in 1984"

An assessment of the relative roles of crust and mantle in magma genesis: an elemental approach

Abstract: The elemental compositions of terrestrial igneous rocks are reviewed with special emphasis on those elements that partition strongly into the liquids in mafic and ultramafic systems. Published data are supplemented by 79 new major- and trace-element analyses. The magmatism of ocean basins is considered in terms of a model that has the following main features: (i) density layering in the sub-lithospheric upper mantle, so that the more fertile source of ocean-island basalts (o.i.b.) underlies the less fertile source of mid-ocean ridge basalts (m.o.r.b.); (ii) the genesis of all mantle-derived magmas restricted to very small degrees of partial fusion; (iii) genesis of m.o.r.b. source mantle as residuum from the loss of a melt fraction (forming o.i.b. magmas and lithospheric veins) from o.i.b.-source mantle; (iv) subduction of o.i.b;- veined lithosphere, with a thin veneer of m.o.r.b. and sediments, to the 670 km seismic discontinuity, followed by re-heating of these components and their buoyant upwelling into the o.i.b.-source reservoir; (v) very little chemical communication across the 670 km discontinuity. All continental anorogenic magmatism (distant from subduction zones in space and time) seems to be related ultimately to the o.i.b.-source mantle reservoir, which therefore must extend beneath the lithospheric roots of continents. The minor sodic-alkalic magmatism of continents is effectively identical in composition to o.i.b. Some continental flood basalts are similar but the majority contain minor contamination (rarely more than 15%) from fusible sialic rocks. Although substantial amounts of sediments appear to be subducted, only a small proportion of them seems to re-appear in the products of island-arc and Cordilleran magmatism. Much larger sediment fractions enter the sparse ultrapotassic magmatism that occurs far behind some subcontinental subduction zones and also characteristically follows the subduction related magmatism of collisional orogenies. The remaining subducted sediments finally pass into the o.i.b.-mantle source reservoir. It is well established that, during and immediately after collisional orogeny, the fusion of sialic crust contributes substantially (or even occasionally exclusively) to batholithic magmatism. Nevertheless, the elemental variation in such magmas implies that the role of fractional crystallization in their genesis has tended to be underestimated in recent years. Mantle-derived mafic to ultramafic magmas appear to be directly or indirectly (as heat sources) involved at deep crustal levels in the parentage of most batholithic intermediate and acid magams. These mantle-derived liquids are subduction-related before continental collisions and then change to o.i.b., several million years after subduction ceases. Enhanced subduction of terrigenous sediments during the final stages of ocean closure leads to the large subducted sialic fractions which re-emerge in the ultrapotassic mafic magmas that characteristically appear immediately after a continental collision.

The effect of age on variability in gait.

Abstract: The intercycle variability in gait of two temporal parameters (stride time and double-support time) and the step-to-step variability of two spatial parameters (step length and stride width) were assessed in 64 healthy adults, 32 aged 21 to 47 and 32 aged 66 to 84. For all parameters the median values of the coefficient of variation did not differ significantly between the two groups. They were below 6% for step length and stride time but much higher for stride width and double-support time (between 17 and 27%). These differences in variability are discussed in relation to the control systems involved. Step length and stride time are thought to be determined predominantly by the gait-patterning mechanism, whereas stride width and double-support time may be determined predominantly by balance-control mechanisms. The results suggest that, in both age groups, the gait-patterning mechanisms are more consistent in their operation than are the balance-control mechanisms and that increased variability in gait should not be regarded as a normal concomitant of old age.

The Other Transition: From the Ancient World to Feudalism*

Abstract: Much Analysis of the Congeries of Changes that is Generally known as the "end of the ancient world in the west" — or some similar name — has been harmed by considerable lack of clarity as to what is actually meant by the phrase. The concept of the end of antiquity of course means different things to different sorts of historians, but many speak of it as if these different things all coexisted equally, intermingled in some giant classical bran-tub. Graeco-Roman paganism, secular Latin literature, temples, the emperor, the senate, slavery, togas. Feudalism was already present in the Roman empire as a subsidiary economic system long before the Germans came, and indeed in so far as the German invaders had such things as a landed aristocracy, these largely resulted from Roman influence. In the west, Europe was faced with the degradations, but also the possibilities, of feudalism.

Stepwise enzymatic dephosphorylation of inositol 1,4,5-trisphosphate to inositol in liver

Abstract: Many receptors for hormones, neurotransmitters and other signals cause hydrolysis of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) and effect a rise in cytosolic Ca2+ concentration1–7. The inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) liberated during PtdIns(4,5)P2 breakdown seems to serve as a second messenger that activates the release of Ca2+ from a nonmitochondrial intracellular compartment7–12. As expected if it is an important intracellular messenger, Ins(1,4,5)P3 is relatively rapidly degraded, both within stimulated cells13,14 and when added to homogenates of blowfly salivary gland15 or to permeabilized, but not intact, hepatocytes10. Here we report that the dephosphorylation reactions responsible for the conversion of Ins(1,4,5)P3 to free inositol in rat liver are catalysed by two or more enzymes, and that these reactions are distributed between the plasma membrane and cytosol. The Ins(1,4,5)P3 5-phosphatase and inositol 1-phosphate (Ins(1)P) phosphatase of liver appear similar to enzymes described previously in erythrocytes16 and brain17.

Cause of death in rheumatoid arthritis

Abstract: A series of 489 consecutive patients with definite or classical rheumatoid arthritis was followed for a mean of 11.2 years. Cohort-analysis of the series showed a three-fold increase in mortality overall in comparison with age- and sex-specific rates in the general population. In patients first seen in hospital early in the course of the disease (less than 5 years from onset), the excess of deaths from circulatory, respiratory and musculoskeletal disorders was highly significant. Malignant disease and digestive system disorders accounted for a small excess of borderline significance. Patients who were referred later (greater than 5 years from onset) experienced, in addition, a highly significant excess of deaths from infections and disorders of the digestive and genito-urinary system but not from malignant neoplasms.

Coli surface antigens 1 and 3 of colonization factor antigen II-positive enterotoxigenic Escherichia coli: morphology, purification, and immune responses in humans.

Abstract: Enterotoxigenic Escherichia coli (ETEC) of serotype O6:H16, biotype A, bearing colonization factor antigen II (CFA/II) possesses two distinct coli surface antigens, CS1 and CS3, whereas CFA/II-positive ETEC of serotype O8:H9 manifests only CS3. CS1 has been shown to be fimbrial in nature, but heretofore the morphology of CS3 has not been described. Accordingly, by immune electron microscopy we investigated the morphological characteristics of CS3 on bacterial cells and after purification. CS3 was found to consist of thin (2-nm), flexible, wiry, "fibrillar" fimbriae, visible both on bacteria (O6:H16, biotype A, and O8:H9 strains) and in the pure state. In contrast, CS1 exists as wider (6-nm), rigid fimbriae on the surface of O6:H16, biotype A, strains. By the use of antisera to CS1 and CS3 in immune electron microscopy, immunodiffusion in gel, and immunoblotting techniques, CS1 and CS3 were found to be immunologically as well as morphologically distinct. Six of nine volunteers who developed diarrhea after challenge with an O139:H28 ETEC strain bearing CS1 and CS3 had significant serological rises to purified CS1 and CS3 antigens, suggesting that both antigens are elaborated in vivo, play a role in pathogenesis, and stimulate an immune response.

Lipid peroxidation in rheumatoid arthritis: thiobarbituric acid-reactive material and catalytic iron salts in synovial fluid from rheumatoid patients.

Abstract: 1. Thiobarbituric acid (TBA)-reactive material is present in serum and knee joint synovial fluid from rheumatoid patients, consistent with lipid peroxidation occurring in vivo. 2. The amount of TBA-reactive material in synovial fluid correlates with the concentration of iron salts present as determined by the bleomycin method, presumably because iron is an important catalyst of radical reactions in vivo. 3. There appear to be significant correlations between the contents of TBA-reactive material and bleomycindetectable iron in synovial fluid and the activity of rheumatoid arthritis as assessed with a clinical index of local inflammation and with various laboratory parameters.

Rapid accumulation of inositol phosphates in isolated rat superior cervical sympathetic ganglia exposed to V1-vasopressin and muscarinic cholinergic stimuli.

Abstract: An accumulation of 3H-labelled inositol phosphates is observed when prelabelled rat superior cervical sympathetic ganglia are exposed to [8-arginine]vasopressin or to muscarinic cholinergic stimuli. The response to vasopressin is much greater than the response to cholinergic stimuli. The response to vasopressin is blocked by a V1-vasopressin antagonist, and oxytocin is a much less potent agonist than vasopressin. Vasopressin causes no increase in the cyclic AMP content of ganglia. These ganglia therefore appear to have functional V1-vasopressin receptors that are capable of activating inositol lipid breakdown, but no V2-receptors coupled to adenylate cyclase. The first [3H]inositol-labelled products to accumulate in stimulated ganglia are inositol trisphosphate and inositol bisphosphate, suggesting that the initiating reaction in stimulated inositol lipid metabolism is a phosphodiesterase-catalysed hydrolysis of phosphatidylinositol 4,5-bisphosphate (and possibly also phosphatidylinositol 4-phosphate). This response to exogenous vasopressin occurs in ganglia incubated in media of reduced Ca2+ concentration. The physiological functions of the V1-vasopressin receptors of these ganglia remain unknown.

The effect of long-term vasodilatation on capillary growth and performance in rabbit heart and skeletal muscle

Abstract: The long-term effect of adenosine and of a new xanthine derivative, l-(5-oxohexyl)-3-methyl- 7-propylxanthine (HWA 285) on capillary density was studied in rabbits. Doses of both agents were established in acute experiments such that they would produce a prolonged increase in coronary and skeletal muscle blood flows without significantly affecting blood pressure or cardiac output. These doses were then chronically administered (3 to 5 weeks) by continuous intravenous infusion from portable infusion pumps carried by the rabbits. Control animals were infused with saline. Long-term administration of adenosine and HWA 285 was well tolerated by the animals. In the acute experiments, adenosine (42 μmol·h−1 iv) reduced the heart rate and produced an increase in coronary blood flow (studied using 15μm radioactive microspheres) and conductance of 38% and 65% respectively, with increases in skeletal muscle of 65% and 92%. Blood pressure, cardiac output and cardiac minute work were not affected. HWA 285 (57 μmol·h−1) slightly but significantly increased blood pressure, but did not affect heart rate, cardiac output or minute work. Coronary and skeletal muscle blood flow were increased by 41% and 72%, with conductance increases of 33% and 62% respectively. The number of all capillaries present was studied in the heart and skeletal muscle using histochemical staining for alkaline phosphatase. Myocardial capillary density (capillaries per mm2, means±SE) was 3092±97 in the adenosine infused group and 2870+153 in the HWA 285 infused group compared with 2426±93 in the controls, ie an increase of 27% (p<0.001) and 18% (p<0.02) respectively. Capillary/fibre ratio in extensor digitorum longus (EDL) muscle was increased from 1.13±0.09 in saline infused control rabbits to 1.42±0.04 (p<0.01) with adenosine and 1.38±0.05 (p<0.01) with HWA 285. Resting cardiac minute and stroke work, and maximal cardiac minute work and stroke work under the effect of noradrenaline were not significantly affected by long-term infusion of either drug. Peak isometric tension and fatiguability in the extensor digitorum longus (EDL) muscles of the vasodilator-infused animals showed no significant difference from control values. Long-term administration of adenosine and the xanthine derivative, in doses which produce marked increases in coronary and muscle blood flow, thus produces an increase in capillarity in both heart and skeletal muscle without any effect on their performance.

Attachment coefficients for the reactions of electrons with CCl4, CCl3F, CCl2F2, CHCl3, Cl2 and SF6 determined between 200 and 600 K using the FALP technique

Abstract: The rate coefficients, beta , for the attachment reactions of electrons with CCl4, CCl3F, CCl2F2, CHCl3, Cl2 and SF6 have been measured under truly thermal conditions over the approximate temperature range 200-600K using a flowing-afterglow/Langmuir probe apparatus. The beta values obtained at 300K are 3.9*10-7, 2.6*10-7, 3.2*10-9, 4.4*10-9, 2.0*10-9 and 3.1*10-7 cm3 s-1 respectively. From the variation with temperature of beta for the CCl2F2, CHCl3 and Cl2 dissociative attachment reactions, activation energies, Ea, of 0.15, 0.12 and 0.05 eV respectively were derived. The beta for CCl4, CCl3F and SF6 are close to their theoretical limiting values within the temperature range investigated. While Cl- was the only product ion observed for the reactions involving chlorine-containing molecules, both SF6- and SF5- were observed for the SF6 reaction. The data obtained are compared with previous data and the separate influences of electron temperature and gas temperature are noted.

Theoretical and methodological difficulties in Bandura's self-efficacy theory

Abstract: Perceived self-efficacy was introduced by Bandura (1977) as “an integrative theoretical framework to explain and predict psychological changes achieved by different modes of treatment” (p. 191). Subsequent empirical studies appear to support the contention that self-efficacy ratings on specific behavioral tasks are accurate predictors of subsequent behavioral performance on those tasks. In this paper we examine the conceptual basis of self-efficacy theory. In particular, the distinction between outcome and efficacy expectations is analyzed in relation to fear and avoidant behavior. We conclude that self-efficacy theory is conceptually problematic and, in particular, that the central concept of efficacy expectations is not unambiguously differentiated from outcome expectations, despite Bandura's (1978) claim to the contrary. Similarly, we suggest that what is actually being assessed in the empirical studies is unclear. We conclude that the empirical findings are less impressive when the circumscribed nature of the behavioral tasks is recognized. Finally, we suggest that resolutions of both the conceptual and methodological difficulties are necessary before Bandura's (1978) claim, that self-efficacy is a unifying construct, can be properly evaluated.

A vasopressin-like peptide in the mammalian sympathetic nervous system

Abstract: Vasopressin was among the first mammalian hormonal peptides to be identified and to have its structure determined. Its only undisputed physiological role is as a circulating neurohypophyseal antidiuretic hormone. Other notable effects of vasopressin on peripheral tissues include contraction of vascular smooth muscle, leading to elevation of blood pressure, and activation of glycogenolysis in liver. It has long been clear that vascular smooth muscle and hepatocytes are relatively insensitive to the low concentrations of vasopressin normally present in the circulation, and the physiological significance of their responses has therefore been in doubt. We now report that a new bioactive and immunoreactive vasopressin-like peptide (VLP) is widely distributed in the sympathetic nervous system of mammals, both in the principal noradrenergic neurones of ganglia and in nerve fibres innervating peripheral tissues. In addition to other peptides described in the mammalian sympathetic nervous system, VLP must be considered as a possible mediator of the non-adrenergic responses to sympathetic activation. Moreover, many of the effects previously attributed to circulating vasopressin may be neurally evoked.

The effect of microstructure and environment on fatigue crack closure of 7475 aluminum alloy

Abstract: The effects of slip character and grain size on the intrinsic material and extrinsic closure contributions to fatigue crack growth resistance have been studied for a 7475 aluminum alloy. The alloy was tested in the underaged and overaged conditions with grain sizes of 18 μm and 80 μm. The fracture surface exhibited increased irregularity and planar facet formation with increased grain size, underaging, and tests in vacuum. These changes were accompanied by an increased resistance to fatigue crack growth. In air the 18 μm grain size overaged material exhibited relatively poor resistance to fatigue crack growth compared with other microstructural variants, and this was associated with a lower stress intensity for closure. All materials exhibited a marked improvement in fatigue crack growth resistance when tested in vacuum, with the most significant difference being ˜1000× at a ΔK of 10 MPa m1/2 for the 80 μm grain size underaged alloy. This improvement could not be accounted for by either an increase in closure or increased crack deflection and is most likely due to increased slip reversibility in the vacuum environment. The intrinsic resistance of the alloy to fatigue crack growth was microstructurally dependent in vacuum, with large grains and planar slip providing the better fatigue performance.

Successful transplantation across major histocompatibility barrier of deoxyguanosine-treated embryonic thymus expressing class II antigens

Abstract: Foreign tissues grafted into healthy recipients are usually rejected by the hosts' immune system largely by means of major histocompatibility complex (MHC) products expressed on donor cells1. During ontogeny, developing T lymphocytes acquire tolerance to self-MHC antigens and the thymus has been considered as the most likely site for the abrogation of self-reactive clones2. We demonstrate here that embryonic thymus lobes, when organ cultured in the presence of deoxyguanosine, which is toxic to proliferating embryonic thymic lymphocytes but does not affect the epithelial framework, when transplanted to the kidney capsule of normal healthy histoincompatible mice, are not rejected despite their continued expression of both class I and class II donor MHC products3 but do not induce tolerance. This suggests that immunogenicity is not solely a function of MHC antigen expression but is also influenced by the type of cell upon which the antigens are expressed and, if the thymus is involved in the induction of tolerance to self-MHC products, this is a function of a component other than the epithelium, perhaps thymic dendritic cells.

The glomerular tip lesion: a previously undescribed type of segmental glomerular abnormality.

Abstract: We describe a distinctive and previously undescribed abnormality of the kidney. It consists of a combination of changes in the glomerulus and in the proximal convoluted tubule. The glomerular abnormality consists of a well-localized collection of intracapillary foam cells and marked vacuolation of the adjacent glomerular epithelial cells. The abnormality is always situated in the same position in the glomerular tuft namely adjacent to the origin of the proximal convoluted tubule, with adhesion to Bowman's capsule. The rest of the tuft appears normal by light microscopy but shows foot-process fusion by electron microscopy. The abnormality of the proximal convoluted tubular cells invariably affects the first part of the tubule adjacent to the glomerulus but in some cases involves the tubules more extensively in the cortex. Study of a series of 100 2-micron serial sections from one case indicated that probably every glomerulus had a lesion at the origin of the tubule. A study of 185 renal biopsies nearly all with segmental lesions revealed biopsies from 20 patients with this distinctive abnormality. There were 14 males, age 20-57, median 44 years, and six females age 19-65, median 22 years, all presenting with proteinuria, nearly all with the nephrotic syndrome. All except four were treated with steroids and in all those treated the proteinuria improved. Only one patient not treated with steroids had progressive renal impairment. Four patients died, none from renal failure. This lesion, the glomerular tip lesion, as we have called it, seems to be a well-defined and specific pathological entity. It has some similarities to minimal change nephropathy but there are clear and important differences. Previously it may have been included in series of cases of 'focal glomerulosclerosis' but that term is imprecise and is generally taken to have an unfavourable clinical course. For these reasons it is inappropriate to use 'focal glomerulosclerosis' as a name for the glomerular tip lesion.

A positive feedback loop between spinal cord nociceptive pathways and antinociceptive areas of the cat's brain stem.

Abstract: Electrophysiological evidence has been obtained suggesting the presence of reciprocal excitation between descending pathways from the nucleus raphe magnus (NRM) and adjacent reticular formation (Ret.F) and spinal cord neurones projecting to these brain stem areas. In decerebrate and decerebellate cats, 40 spinal cord neurones were recorded whose recording sites were in or close to lamina VIII of the lumbar spinal cord. All 40 neurones recorded in the lumbar cord were postsynaptically excited by electrical stimulation of the NRM, the Ret.F. or most commonly, of both. The excitation was mediated by fast-conducting fibres and lasted for over 100 msec after a single shock. The shortest latency responses were obtained following stimulation of the contralateral Ret.F. These neurones had complex peripheral inputs subjected to descending controls. All the neurones could be excited by deep pressure of the ipsilateral and/or contralateral hind limbs. Peripheral inhibitory inputs were also observed. Eighteen out of the 40 neurones had axons that projected to NRM and the adjacent Ret.F. Conduction velocities ranged between 31.6 and 91 m/sec. In addition, 11 other axons were recorded in the white matter of the cervical cord from neurones projecting to NRM and Ret.F. Conduction velocities of this group of axons ranged between 13 and 70 m/sec. The majority of the axons projecting to NRM and Ret.F. were found to join pathways in the ventro-lateral quadrant of the spinal cord either ipsi- or contralaterally to their Ret.F. destination. Recordings were also made from 12 neurones whose recording sites were located in the NRM and Ret.F. Their responses to electrical stimulation of sites within lamina VIII of the lumbar spinal cord were studied. Only excitatory responses could be evoked by such stimulation. These results are discussed in relation to the mechanisms of activation of central antinociceptive systems.

Unity in diversity

Abstract: Biochemical Adaptation. By Peter W. Hochachka and George N. Somero. Princeton University Press: 1984. Pp.537. Hbk $60, £60; pbk $19.50, £15.

Morphology and cross-linkage of stereocilia in the guinea-pig labyrinth examined without the use of osmium as a fixative.

Abstract: Hair cells of the guinea-pig cochlea and vestibular system were prepared for electron-microscopic examination by fixing in glutaraldehyde without the use of osmium. An extensive array of cross-links was seen between the apical ends of the stereocilia, by both scanning and transmission electron microscopy. Some cross-links ran laterally between stereocilia of the same row. Others ran laterally between the stereocilia of the different rows, holding the tips of the shorter stereocilia in towards the longer stereocilia of the next row. In addition, each tip on the shorter stereocilia gave rise to a single, upwards pointing link, which ran upwards to join the adjacent taller stereocilium of the next row. We suggest that distortion of this link might be involved in the mechanics or even the membrane biophysics of sensory transduction. With this method of preservation, all the apical surface membranes of the hair cells appeared rough, and contained dense granules. The roughness was greatest in the parts of the stereocilia to which the cross-links were attached. The mitochondrial and synaptic membranes of the hair cells appeared normal.