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Showing papers by "University of Leicester published in 1981"


Journal ArticleDOI
01 Oct 1981-Nature
TL;DR: In this article, the authors used extended X-ray absorption fine structure to study local order in silicate glasses around sodium and silicon atoms, and demonstrated that modifying cations like sodium have well-defined short range order that is complementary rather than incidental to the glass forming silicate network.
Abstract: Extended X-ray absorption fine structure is used to study local order in silicate glasses around sodium and silicon atoms. It is demonstrated that modifying cations like sodium have well-defined short range order that is complementary rather than incidental to the glass forming silicate network.

398 citations



Journal ArticleDOI
TL;DR: Venous invasion is shown to be related to local invasiveness of rectal carcinoma, and suggested modes of venous spread and interaction with host tissues are proposed, with implications for general attitudes to the spread of cancer and metastasis.
Abstract: Histopathological material from operation specimens of rectal adenocarcinoma was reviewed and invasion of veins identified in 51.9% of 703 cases. The extent of venous invasion, thickness of the walls of invaded veins and various other histological features were examined in detail. By follow-up studies recurrence rates, incidence of distant metastases and corrected 5-year survival rates were obtained; correlation with the histopathological results showed that invasion of extramural and thick-walled veins is associated with a poor prognosis independent of the degree of differentiation of the adenocarcinoma. Prognosis is not significantly related to the presence of necrosis of intravenous tumour and a clearly defined stroma in the intravenous growth all appear to exert a protective influence on patient survival. Whereas permeation of capillaries in vein walls, the presence of loose clumps of tumour cells in veins and direct contact between tumour cells and venous blood appear to adversely affect survival. Venous invasion is shown to be related to local invasiveness of rectal carcinoma. Suggested modes of venous spread and interaction with host tissues are proposed, with implications for general attitudes to the spread of cancer and metastasis.

209 citations


Journal ArticleDOI
TL;DR: In this article, the geochemistry of Lewisian amphibolite-facies gneisses from northwest Scotland is described with particular reference to the rare earth elements (REE) and compared with the geochemical properties of the Lewisian granulite-fa-susceptible granulites.

200 citations


Journal ArticleDOI
01 Oct 1981
TL;DR: In this paper, the problem of finding the electron reflection and transmission coefficients of a crystal slab is formally solved, and the formal solution may be used in a practical computation of the diffracted beam intensities.
Abstract: Elastic Reflection High Energy Electron Diffraction (RHEED) by solid surfaces is studied theoretically. First, the problem of finding the electron reflection and transmission coefficients of a crystal slab is formally solved. Following this, it is shown how the formal solution may be used in a practical computation of the diffracted beam intensities. These two results are applied to a study of high energy (20 keV) electron diffraction by the Ag(001) surface. Rocking curves are computed to illustrate the dependence of the reflection coefficients on the glancing angle of the incident beam, the incident beam azimuth being in the [110] direction. The curves are shown to have several features in common with a typical set of LEED I - V plots: primary Bragg peaks, secondary Bragg peaks and resonance peaks are all present. The dependence of the reflection coefficients on the deviation of the incident beam azimuth from the [110] direction is also described. Additional computations are made to illustrate the sensitivity of the RHEED pattern to the details of the surface structure: the relative heights of the peaks in the rocking curves are shown to be quite sensitive to the spacing of the topmost atomic layers.

188 citations


Journal ArticleDOI
TL;DR: In the early Proterozoic, the first large cratons were stabilized and, locally, thickened and differentiated as mentioned in this paper. But this was an era of little continental growth, falling average sea level, and intracontinental deformation, and marginal accretionary terrians had begun to develop with an average Phanerozoic growth rate of 1.64 Pg/a, and blueschists and ophiolites sensu stricto witness the advent of the extant plate tectonic regime.
Abstract: Declining radiogenic heat production since the Archaean has resulted in a secular evolution from a regime of numerous fast-moving small thin torsionally weak plates to the present regime of larger thicker torsionally stronger plates moving at an average rate of less than one-sixth of the Archaean rate; this has been accompanied by episodic changes in geological effects. By 2500 Ma B.P., about 85% of the present crustal mass had grown by the addition and amalgamation of mafic and calc-alkaline rocks in oceanic arcs at an average rate of 11.17 Pg/a. During the early Proterozoic, the first large cratons were stabilized and, locally, thickened and differentiated; the Proterozoic was an era of little continental growth, falling average sea level, and intracontinental deformation. By 700 Ma B.P . cratons had become much more stable, marginal accretionary terrians had begun to develop with an average Phanerozoic growth rate of 1.64 Pg/a, and blueschists and ophiolites sensu stricto witness the advent of the extant plate tectonic regime.

176 citations


Journal ArticleDOI
TL;DR: Although both proteins are involved in the ATP-dependent supercoiling of relaxed plasmid DNA, only the gyrB protein is required for catalyzing the cleavage of ATP, which is competitively inhibited by novobiocin and related coumarin antibiotics.
Abstract: Novobiocin-Sepharose was prepared by coupling of novobiocin to Epoxy-activated Sepharose 6B and used as an affinity adsorbent. Four novobiocin-binding proteins were isolated from crude extracts of Escherichia coli with molecular weights of 105, 92, 85 and 40 kdal. The two larger proteins were identified as the A subunit (gyrA protein) and the B subunit (gyrB protein) of DNA gyrase topoisomerase II). By this method the two gyrase components can be easily separated and purified in high yield. Although both proteins are involved in the ATP-dependent supercoiling of relaxed plasmid DNA, only the gyrB protein is required for catalyzing the cleavage of ATP. The gyrB protein ATPase activity is competitively inhibited by novobiocin and related coumarin antibiotics. ATP hydrolysis is unaffected by the addition of either gyrA protein or DNA but stimulated in the presence of both.

171 citations


Journal ArticleDOI
TL;DR: Natural mixtures of bacterial ubiquinones (coenzyme Q) were separated according to the length of the polyisoprenyl side-chain using reverse-phase thin-layer chromatography and high performance liquid chromatography to afford a rapid and sensitive means of ubiquinone characterization.
Abstract: Natural mixtures of bacterial ubiquinones (coenzyme Q) were separated according to the length of the polyisoprenyl side-chain using reverse-phase thin-layer chromatography and high performance liquid chromatography. The chromatographic systems described afford a rapid and sensitive means of ubiquinone characterization.

157 citations


Journal ArticleDOI
TL;DR: The experiments provide direct evidence for the long-suspected role of the yolk sac in mediating embryonic nutrition in the period of development prior to the establishment of a functional chorioallantoic placenta.
Abstract: Conceptuses from 9·5-day pregnant rats have been cultured for 48 h in heat-inactivated homologous serum. Embryonic development was normal. The protein contents of embryos and visceral yolk sacs after different periods of culture were recorded. When 125-labelled polyvinylpyrrolidone or [3H]dextran were added to the culture serum, radioactivity was accumulated by the yolk sac, but only background levels were detected in the embryo itself. The amount of radioactivity found in the yolk sac varied with the length of the interval before harvesting during which 125 I-labelled PVP or [3H]dextran was present. When formaldehyde-denatured 125 I-labelled bovine serum albumin was added to the culture serum, little radioactivity accumulated in the yolk sac and only background levels were found in the embryo. Trichloroacetic acid-soluble radioactivity steadily appeared in the culture serum, however. When conceptuses were cultured in glucose- and vitamin-supplemented dialysed serum from rats injected 2 h previously with [3H]leucine, radioactivity was found in both embryos and yolk sacs. The amount of radioactivity in these tissues increased with duration of exposure to 3H-labelled serum proteins. After short exposures little of the yolk sac and embryonic radioactivity was acid-insoluble, but this proportion increased with duration of exposure. These results are interpreted as follows. Intact macromolecules cannot enter the cells of the embryo itself, but are captured by pinocytosis into the cells of the visceral yolk-sac endoderm. Indigestible macromolecules such as 125 I-labelled polyvinylpyrrolidone and [3H]- dextran accumulate within the yolk-sac lysosomes, but proteins are digested there by the lysosomal enzymes. The radiolabelled digestion product of 125 I-labelled bovine albumin is [125 I]iodotyrosine, which cells cannot utilize and so is excreted into the culture serum. The labelled digestion product of the 3H-labelled rat serum proteins is [3H]leucine, which is used for protein synthesis in both embryo and yolk sac. The experiments provide direct evidence for the long-suspected role of the yolk sac in mediating embryonic nutrition in the period of development prior to the establishment of a functional chorioallantoic placenta.

143 citations


Journal ArticleDOI
TL;DR: In this article, the authors show that even with partial melting mechanisms at least two different mantle sources, with different major and trace element compositons, are required to explain the compositional differences between the major dyke types.
Abstract: The petrogenesis of bronzite-picrite, olivine-gabbro, norite and quartz-tholeiite dykes, which make up the 2.39 b.y. Scourie dyke swarm cutting the Archaean Lewisian gneisses of N.W. Scotland, is interpreted on the basis of their major and trace element geochemistry. Most of the dykes bear primary amphibole and/or phlogopite and, with one exception, are all hypersthene- or quartz-normative. Apart from one tholeiite dyke which shows relative light rare-earth element depletion, all the dykes show enrichment in light rare-earths and large-ion lithophile elements. They do not however show an equivalent enrichment in other incompatible high field strength ions such as Nb and Ta, and in this respect resemble island arc and calc-alkaline basalts. The different dyke types have distinctive rare-earth patterns and other trace element ratios which are maintained over a range of major element compositions. Petrogenetic modelling of the major and trace element compositions of the various dykes demonstrates that very few can be related by fractional crystallisation. Indeed, even with partial melting mechanisms at least two different mantle sources, with different major and trace element compositons, are required to explain the compositional differences between the major dyke types. The high degrees of mantle melting implied for the generation of the magnesium-rich bronzite-picrites suggests that their rare earth and other trace element patterns closely reflect those of their mantle source. Similar arguments, though less well constrained, can be advanced for the other dyke types. The results suggest that the sub-continental mantle source feeding the dykes was heterogeneous with respect to both major and trace elements, and that their mantle sources must have been enriched in lithophile elements. Enrichment at the time the Lewisian gneisses were generated (i.e. 2.92 b.y. ago) would be compatible with the initial 87Sr/86Sr ratios of the dykes and the inferred Rb/Sr ratios of their mantle sources. The sub-continental mantle sources have thus retained the geochemical signature of the crustgenerating processes some 500 m.y. earlier.

137 citations


Journal ArticleDOI
TL;DR: In this article, the effects that certain plasticisers have on the properties of aqueous based HPMC films of a type used for film coating tablets, and investigate whether or not the inclusion of these additives is in fact beneficial in all cases.
Abstract: The aim of this work is to examine the effects that certain plasticisers have on the properties of aqueous based hydroxypropylmethylcellulose (HPMC) films of a type used for film coating tablets, and to investigate whether or not the inclusion of these additives is in fact beneficial in all cases.The film former HPMC is being used increasingly as a coating for pharmaceutical tablets because of its suitable properties, not least of which is the ability to coat using a fully aqueous system. This greatly improves the method and safety of application.

Journal ArticleDOI
TL;DR: There is good evidence to suggest that the initial rapid stem extension in natural shade was probably due to the reduced red: far-red ratio; there is also good evidence that the latter is a phytochrome-controlled phenomenon.
Abstract: In nature, fluence rate and the red: far-red ratio are reduced in shadelight beneath vegetation; both show similar exponential decays with increasing canopy density. An assessment of the degree to which each of these factors controls development in natural shade was made by comparing Chenopodium album plants grown under vegetational shade with those grown under the controlled environment light treatments of low fluence rate, and combined low fluence rate and low red:far-red ratio. The observations of stem extension and specific leaf area from vegetational shade were entirely consistent with the effects of the controlled environment light treatments. The increase of specific leaf area in natural shade was probably due to the low fluence rate; the initial rapid stem extension in natural shade was probably due to the reduced red: far-red ratio. There is good evidence to suggest that the latter is a phytochrome-controlled phenomenon.

Journal ArticleDOI
TL;DR: The results from two long observations with the Einstein Observatory Imaging Proportional Counter (IPC) of an approximately 1 x 1 deg field centered near the galactic nucleus are presented in this article.
Abstract: The results from two long observations with the Einstein Observatory Imaging Proportional Counter (IPC) of an approximately 1 x 1 deg field centered near the galactic nucleus are presented. The X-ray images reveal a complex of weak sources within 20 arcmin of the galactic nucleus (Sgr A West) together with a region of apparently diffuse emission about 25 x 15 arcmin in extent. Three of the sources are tentatively identified: two with nearby galactic objects, and a third positionally coincident with Sgr A West itself (within the arcmin-accuracy available with the IPC). The nature of this source and the implications of both the high source density and presence of diffuse emission in the galactic center region are discussed.


Journal ArticleDOI
24 Dec 1981-Nature
TL;DR: It is shown here that nifedipine abolishes the smooth muscle action potential and the initial twitch response (I) without reducing the excitatory junction potential (e.j.p.), suggesting a fundamentally different basis of the two responses and illustrating the pharmacological value of nifingipine.
Abstract: The mechanical response of the vas deferens to single pulses or short trains of stimuli can be resolved into two distinct phases, an initial twitch response (I) attributed to the release of an unknown transmitter and a slower better maintained secondary contraction (II)1,2, attributed to noradrenaline release Recently, it has been shown that the calcium antagonist nifedipine3 eliminates the initial twitch response leaving the secondary component intact4,5 and we have now examined the electrical responses underlying these mechanical events We show here that nifedipine abolishes the smooth muscle action potential and the initial twitch response (I) without reducing the excitatory junction potential (ejp), suggesting a fundamentally different basis of the two responses and illustrating the pharmacological value of nifedipine

Journal ArticleDOI
TL;DR: In this article, the nature of back-arc extension in the East Scotia Sea is re-examined with the use of an enlarged geophysical data set, and it is shown that the present spreading episode started about 8 Ma ago, that spreading is asymmetric, and that the total rate increased from 50 to 70 m m /a about 1.5 Ma ago.
Abstract: The nature of back-arc extension in the East Scotia Sea is re-examined with the use of an enlarged geophysical data set. Well developed oceanic magnetic lineations confirm that the present spreading episode started about 8 Ma ago, that spreading is asymmetric, and that the total rate increased from 50 to 70 m m /a about 1.5 Ma ago. Most of the currently active South Sandwich volcanic island arc lies upon ocean floor only 6-8 M a old and generated at the current spreading ridge. Subsequent extension has not modified the curvature of the arc. East-west magnetic lineations of Miocene age in the Central Scotia Sea and contemporaneous low-K arc tholeiites dredged from the eastern South Scotia Ridge (Discovery Bank) indicate a regime of coupled subduction and back-arc extension preceding that occurring now. A speculative model involving a series of collisions of parts of this earlier Discovery trench with ridge crest sections of the South American-Antarctic plate boundary explains the transformation of this earlier regime into the present, self-contained Sandwich plate regime. The considerable small-scale variability observed in the back-arc region may be seen as an inevitable consequence of the action of the ridge-trench collision mechanism. The entire Scotia Sea could have formed by a similar kind of back-arc extensional modification of the South American-Antarctic plate boundary.

Journal ArticleDOI
26 Mar 1981
TL;DR: The secular variation in the geochemistry of the arc volcanics may be related to the progressive development of a lithophile element enriched mantle source beneath the arc, which contributes to the basalts produced during the early stages of arc rifting and back-arc spreading.
Abstract: The results of recent geochemical investigations of several island arc -- marginal basin systems in the Scotia Sea area and in the western Pacific are outlined. Marginal basins in different stages of evolution are represented, from those in the initial stages of formation to those with an extensive and multiple history of back-arc spreading. Some are completely intraoceanic, others have developed at continental margins. Basalts erupted at back-arc spreading centres seem to be as geochemically varied as those from normal mid-ocean ridges, and record evidence for similar processes of partial melting, fractional crystallization and magma mixing in their genesis. They appear to have been derived from mantle sources with incompatible trace element characteristics ranging from 'depleted' to 'enriched', but with the 'enriched' mantle sources being sampled during the earlier stages of back-arc spreading. Submarine back-arc basalts are more vesicular than their normal ocean ridge equivalents, and their corresponding glasses have higher water contents. This, together with other geochemical features such as the higher ratios of lithophile to high field strength elements in some back-arc basalts, suggests that a component from the subducted slab may be involved in their petrogenesis. The chemistry of the corresponding arc volcanics is described in relation to the subduction and extensional history of marginal basin development. In intraoceanic arcs the early stages of arc magmatism are dominated by the eruption of large volumes of island arc tholeiites and subsidiary high-Mg andesites. In the Mariana region, after the initial volcanic arc is split and separated by back-arc spreading, the later frontal arc volcanics have calc-alkaline characteristics. Basalts erupted during the early stages of back-arc spreading more commonly have arc-like geochemical features when the marginal basin has developed through splitting of a calc-alkaline volcanic arc. The secular variation in the geochemistry of the arc volcanics may be related to the progressive development of a lithophile element enriched mantle source beneath the arc. This source contributes to the basalts produced during the early stages of arc rifting and back-arc spreading. Ophiolite complexes which represent marginal basin floor may well carry these arc-like geochemical features.

Journal ArticleDOI
10 Jul 1981-Science
TL;DR: Calcium currents in skeletal muscle fibers of an insect, Carausius morosus, inactivate under depolarization because the current is carried across the membrane by calcium ions, rather than strontium or bariumions.
Abstract: Calcium currents in skeletal muscle fibers of an insect, Carausius morosus, inactivate under depolarization. This inactivation depends on the current being carried across the membrane by calcium ions, rather than strontium or bariumions.

Journal ArticleDOI
TL;DR: The entire ϵγγδβ-globin gene cluster in the gorilla and the yellow baboon is indistinguishable from that of man, and restriction site differences between these species are consistent with a surprisingly low overall rate of intergenic DNA sequence divergence.

Journal ArticleDOI
TL;DR: The problems and strategies of coping with terminal cancer patients on an acute surgical ward and the problems of junior nurses who are primarily responsible for the care of these dying patients are examined.
Abstract: The problems and strategies of coping with terminal cancer patients on an acute surgical ward form the focus of this paper. The effects of ward structure, organization, and communication are examined and particular attention is given to the problems of junior nurses who are primarily responsible for the care of these dying patients.


Journal ArticleDOI
TL;DR: The Archaean Karnataka craton of southern India contains Eastern and Western crustal blocks (separated by a major thurst) in which Sargur Schists occur as lenses within tonalitic Peninsular Gneisses as mentioned in this paper.
Abstract: The Archaean Karnataka craton of southern India contains Eastern and Western crustal blocks (separated by a major thurst) in which Sargur Schists occur as lenses within tonalitic Peninsular Gneisses. The Schist complex comprises pelites, quartzitic psammites, carbonates and calc-silicates, iron formations, and basic rocks, and thus provides many mineral assemblages ideal for the calculation of PT conditions. With their gneisses the Sargur rocks are unconformably overlain by the Dharwar greenstone belts, and are generally thought to be older than 3,000 my.

Journal ArticleDOI
TL;DR: Analyses using the Pattern Coefficient and Gower's Coefficient differed mainly in the relationships shown by a few of the metabolically active species, but it showed an unexpectedly close relationship between P. solanacearum and P. cepacia.
Abstract: Data published by R. Y. Stanier, N. J. Palleroni, M. Doudoroff and their colleagues on Pseudomonas have been analysed by numerical taxonomy. Records on 401 strains were used, representing 155 characters, mostly utilization of substrates as carbon-energy sources. Twenty-nine phenons were recognized, which included 394 strains: the remaining 7 remained unclustered. The results were in very good accord with the conclusions of these authors. Almost all phenons were well separated with very little overlap. Many of them corresponded to distinct species, and others corresponded to recognized biotypes. Some small groups may represent unnamed new species.

Journal ArticleDOI
10 Sep 1981-Nature
TL;DR: Experiments are reported which demonstrate that Ca inactivation may be produced directly by intracellular injection of Ca and which support the idea that Ca conductance is reduced by an increase in [Ca]i.
Abstract: Inward calcium currents are present in many excitable tissues and are involved in several cellular processes. Depending on the tissue these may include action potential generation, transmitter release and control of membrane K permeability1,2. Membrane Ca conductance is activated by depolarization in a manner essentially similar to that described for Na conductance2,3. However, it has recently been suggested that Ca channel inactivation may differ from Na inactivation in being dependent not on membrane potential directly, but on Ca entry4–7. Such a mechanism has been proposed on the basis of the observed voltage and current dependence of Ca inactivation and could be caused either by some action of Ca ions as they pass through the channel or by an effect of increased intracellular calcium concentration [Ca]i. I report here experiments which demonstrate that Ca inactivation may be produced directly by intracellular injection of Ca and which support the idea that Ca conductance is reduced by an increase in [Ca]i.

Book ChapterDOI
TL;DR: The Medium Energy Instrument on EXOSAT has been made sufficiently versatile to provide a significant advance over previous large area proportional counters when used for individual source studies of timing and spectra.
Abstract: The Medium Energy Instrument on EXOSAT, although conceived as the main instrument for occultations, has been made sufficiently versatile to provide a significant advance over previous large area proportional counters when used for individual source studies of timing and spectra. The energy range is 1.2 to 50 keV, with ΔE/E of 0.2 at 6 keV, sufficient to detect iron lines. The effective area of ~1800 cm 2 and narrow field of view (¾o x ¾o) make it suitable for the detailed study of sources down to the 0.3 mCrab confusion limit. The unique facility provided by EXOSAT, allowing uninterrupted observations of X-ray sources for periods of up to 80 hours, backed up by a high capacity data link and on-board processing, enables timing studies to be performed over the range from milliseconds to days. Sophisticated background discrimination techniques giving a rejection efficiency of ~ 99% will control the background count rate to a suitably low value in the environment of the 200,000 km orbit.

Journal ArticleDOI
TL;DR: Host reactions in and around the walls of invaded veins increase the survival rate; inflammatory damage to the vein walls and endarteritis obliterans are particularly important in this respect.
Abstract: Histologic evidence of venous invasion was demonstrated in 52 percent of 703 cases of rectal carcinoma. Quantitation of venous invasion and follow-up study showed that invasion of extramural veins was associated with a low 5 year survival rate (33 percent), whereas invasion limited to intramural veins was not. Spread into thick-walled extramural veins carries a very poor prognosis (15 of 91 patients survived 5 years). The corrected 5 year survival rate for stage C patients with invasion of thick-walled extramural veins was only 8 percent. Host reactions in and around the walls of invaded veins increase the survival rate; inflammatory damage to the vein walls and endarteritis obliterans are particularly important in this respect.


Journal ArticleDOI
TL;DR: Two physically and genetically distinct forms of succinic-semialdehyde dehydrogenase have been identified in Escherichia coli B and apparently the gene for this enzyme functions independently from the genes encoding the other enzymes of p-hydroxyphenyl-acetate degradation.
Abstract: Two physically and genetically distinct forms of succinic-semialdehyde dehydrogenase have been identified in Escherichia coli B. The two enzymes could be separated by filtration on Sephadex G-150 and their apparent molecular weights were 200 000 and 97 000. The larger enzyme, which is specific for NADP, is induced by growth on gamma-aminobutyrate. Its induction is highly coordinated with that of gamma-aminobutyrate:2-oxoglutarate transaminase, the enzyme which initiates degradation of gamma-aminobutyrate. The smaller enzyme, which is induced by growth on p-hydroxyphenylacetate, has been purified to 98% homogeneity by affinity chromatography in conjunction with conventional methods. Under standard assay conditions this enzyme acts preferentially with NAD but reduces NADP at 15% of the rate observed for NAD, primarily because of a difference in Km. Apparent Km values for succinic semialdehyde and NAD are 13.3 +/- 1.3 microM and 33.7 +/- 1.4 microM, respectively. The subunit molecular weight was estimated to be 55 000, indicating that the native enzyme is dimeric. The NAD-dependent succinic-semialdehyde dehydrogenase is also induced by exposure of cells to exogenous succinic semialdehyde, a treatment which has no effect on the amount of other enzymes of p-hydroxyphenylacetate or gamma-aminobutyrate metabolism. Apparently the gene for this enzyme functions independently from the genes encoding the other enzymes of p-hydroxyphenyl-acetate degradation. As a consequence of its induction mechanism, this NAD-dependent dehydrogenase is also present in extracts of E. coli B grown with gamma-aminobutyrate as sole nitrogen source, in addition to the NADP-specific enzyme involved in gamma-aminobutyrate metabolism. Presumably the NAD-dependent enzyme is gratuitously induced by succinic semialdehyde formed by transamination of gamma-aminobutyrate.

Journal ArticleDOI
TL;DR: It is concluded that stimulation by micrococcin of factor-dependent GTP hydrolysis results from the binding of the drug to its normal target site which involves 23-S RNA and protein L11.
Abstract: The antibiotic, micrococcin, binds to complexes, formed between bacterial 23-S ribosomal RNA and ribosomal protein L11 and, in doing so, inhibits the binding of thiostrepton. In assay systems simulating partial reactions of protein synthesis, micrococcin inhibits a number of processes believed to involve the ribosomal A site while stimulating GTP hydrolysis dependent upon ribosomes and elongation factor EF-G. The latter effect is not observed upon ribosomes lacking a protein homologous with protein L11. Nor is it apparent upon those containing 23-S RNA previously subjected to the action of a specific methylase known to render ribosomes resistant to thiostrepton. It is concluded that stimulation by micrococcin of factor-dependent GTP hydrolysis results from the binding of the drug to its normal target site which involves 23-S RNA and protein L11.

Journal ArticleDOI
TL;DR: In this article, the development of existing constitutive equations is described for high temperature creep deformation and rupture under proportional loading, and the validity of these equations has been assessed for non-proportional loading of copper and aluminium alloy test specimens.
Abstract: The development of existing constitutive equations is described for high temperature creep deformation and rupture under proportional loading. The validity of these equations has been assessed for non-proportional loading of copper and aluminium alloy test specimens. It is shown that these equations adequately describe the rupture and deformation behaviour of the aluminium alloy. The rupture behaviour of copper is closely described by the theory for proportional loading but the deformation behaviour is only approximately described by the same constitutive equations.