Showing papers by "University of Leicester published in 1976"
TL;DR: An analysis is presented of existing and new multi-orientation and multiprobe techniques and it is shown how they can be used to remove systematic and variable errors.
Abstract: There is an increasing demand for more accurate surface metrology instruments and for techniques which will allow complicated or large parts to be measured in situ. An analysis is presented of existing and new multi-orientation and multiprobe techniques and it is shown how they can be used to remove systematic and variable errors.
248 citations
184 citations
TL;DR: In this paper, a grid of values that approaches the smoothest surface passing through the control points is generated, and a grid can be automatically contoured automatically by standard routines, producing acceptable results.
146 citations
TL;DR: Greenstone belts as discussed by the authors are high grade complexes containing rocks that have been deformed and recrystallised at high temperatures and pressures, such as granitic gneisses derived from granitic rocks.
Abstract: Two kinds of geological terrain formed before 2,500 Myr ago. First, the greenstone belts, which are linear basins full of sediments and volcanics, possibly comparable with the marginal basins that occur behind modern island arcs. Second, and the subject of this paper, are high grade complexes containing rocks that have been deformed and recrystallised at high temperatures and pressures—granitic gneisses derived from granitic rocks are particularly common. Examples occur in north-western Scotland, Greenland, the Labrador coast, the Limpopo Belt in southern Africa, southern India, and probably the Aldan and Kola shields in the USSR. These complexes are so similar lithologically that broad generalisations about their tectonic evolution are justifiable. No major attempt has been made to see if they share any similarities with modern geological environments whose origins are better understood. We suggest that they are ancient analogues of the modern deep seated granitic batholiths located along the main arc axis of active plate margins of North and South America, for example in California and the Andes; accordingly, they are complementary to the greenstone belts in their back-arc setting.
87 citations
82 citations
TL;DR: Neither M nor Ymax ATP are constant values for E. coli, being highest under excess energy growth conditions where it may reflect energy wastage by the cell.
Abstract: 1. The energetics of Escherichia coli W growing aerobically in continuous culture have been investigated. Conditions were chosen such that growth was limited by the availability of carbon or oxygen (energy-limited cultures), or of ammonium of sulphate ions (excess energy cultures). 2. Under glycerol-limited conditions YmaxO2 (true molar growth yield with respect to oxygen) and YmaxATP (true molar growth yield with respect to ATP equivalents) were 50.9 g cells-mol O-02(-1) and 12.7 g cells-mol ATP equivalents-1 respectively; these values were not substantially altered during growth limited by oxygen, ammonium or sulphate. In contrast, M (the energy requirement for maintenance purposes) increased from approximately 2 mmol ATP equivalents-h-1-g cells-1 during energy-limited growth to 16.8 and 30.8 mmole ATP equivalents-h-1-g cells-1 when growth was limited by ammonium and sulphate ions respectively. 3. Replacement of glycerol by other limiting carbon sources caused YmaxATP to alter within the range 13.9 (glucose) to 7.1 (acetate) g cells-mol ATP equivalents-1 in the order glucose greater than galactose greather than arabinose greater than fructose greater than glycerol greater than fumarate greater than lactate greater than pyruvate greater than acetate. In each case the experimental value of YmaxATP was less than or equal to 55% of the theoretical value calculated from the known energy requirements for the biosynthesis of cell materials. 4. It is concluded from these results that neither M nor Ymax ATP are constant values for E. coli. M varies with the energy supply, being highest under excess energy growth conditions where it may reflect energy wastage by the cell. On the other hand, YmaxATP varies with the nature of the growth substrate and thus reflects the different energy requirements for the synthesis of cell material from different carbon sources.
78 citations
TL;DR: Trabeculae isolated from ferret heart and from other mammalian hearts have been mounted in a way that enables the tension generated to be measured while the composition of the bathing fluid is rapidly altered.
Abstract: 1. Trabeculae isolated from ferret heart and from other mammalian hearts have been mounted in a way that enables the tension generated to be measured while the composition of the bathing fluid is rapidly altered.
2. Application of caffeine to these trabeculae initiates a rapid transient contracture and depresses the strength of regularly evoked heart beats.
3. The strength of the contractures, the rate of tension development and the rate of spontaneous relaxation are all increased by raising the concentration of the applied caffeine.
4. The strength of the caffeine contracture is relatively unaffected by changes in the bathing Na+, K+ or Ca2+ concentrations, but is reduced by exposure to the free-base form of local anaesthetics.
5. Lowering of the temperature has complex effects on the amplitude of the caffeine contracture due to the differing temperature sensitivities of the contraction and spontaneous relaxation.
6. Following a caffeine contracture, a period of perfusion by caffeinefree solution is required before a full-sized contracture can be evoked by the re-application of caffeine. This re-priming of the caffeine contracture has a sigmoidal time course that can be fitted by a two compartment model. The rate constants of the filling of each of the compartments can be obtained analytically, and are found to be increased by raising the extracellular calcium concentration, [Ca]o, by stimulating the preparation or by raising the temperature. Reducing the [Na]o or raising the [K]o has little effect on these processes.
7. The presence of traces of caffeine in the perfusing fluid between the conditioning and test challenges with the caffeine contracture solution reduces the extent of the re-priming without much affecting its rate.
8. The behaviour of several model systems have been compared with that of the heart with the aid of an analogue computer. A four compartment closed system has been found to simulate the results presented in this paper.
9. It appears that caffeine has its effects by acting to increase the rate of release of activator calcium from one part of a non-homogeneous intracellular relaxing system present within the mammalian heart, which is likely to be the sarcoplasmic reticulum.
74 citations
TL;DR: The gas phase developed above spinach suspension cultures critically affected their growth and greening, and ethylene accumulation inhibited greening and was antagonised when the culture gas phase was enriched with carbon dioxide.
Abstract: The gas phase developed above spinach suspension cultures critically affected their growth and greening. Ethylene accumulation inhibited greening; this effect of ethylene was antagonised when the culture gas phase was enriched with carbon dioxide. Greening was enhanced by reducing the partial pressure of oxygen below the air level; this effect was observed when oxygen supply did not restrict growth.
70 citations
TL;DR: It is proposed that if trypan blue in teratogenic doses similarly inhibits pinocytosis by the yolk sac during the organogenetic period teratogenesis might result from a transient interruption in the flow of metabolites through theYolk sac to the embryo.
Abstract: Day 17.5 yolk sacs from rats injected with partially denatured 125I-labeled bovine serum albumin (I-BSA) were cultured in vitro by a raft technique. The rates of release of [125I] iodotyrosine were similar in control yolk sacs and in yolk sacs from rats preinjected with trypan blue. Day 17.5 rat yolk sacs were also cultured in medium containing I-BSA. Following pinocytic uptake the substrate was degraded intracellularly and [125I]iodotyrosine released into the medium. Trypan blue, when present in the medium in concentrations above 100 ug/ml, inhibited pinocytosis of I-BSA and so decreased the rate of [125I]iodotyrosine production. Trypan blue similarly decreased the rate of pinocytic uptake of 125I-labeled polyvitiylpyrrolidone. Pinocytic uptake of macromolecules was not decreased in yolk sacs from rats pretreated with trypan blue. The relevance of these results to the mechanism of teratogenic action of trypan blue is discussed. It is proposed that if trypan blue in teratogenic doses similarly inhibits pinocytosis by the yolk sac during the organogenetic period teratogenests might result from a transient interruption in the flow of metabolites through the yolk sac to the embryo.
70 citations
TL;DR: At low temperatures the exchange rate becomes sufficiently slow in the pH range 4 to 8 to enable us to detect resolved resonances from the individual hydroxyl protons, and the results are interpreted in terms of strong hydrogen bonding between water and glucose.
Abstract: THE solvation of sugars by water has not been extensively studied in spite of its biochemical importance. Relaxation rates for 17O in monosaccharides have been used to study solvation1,2, the revised2 estimate of the solvation number being 5±1 water molecules for D-glucose and 2.5±1 for D-ribose at 5 °C, in agreement with 6±1 and 2.5±1 (respectively) derived from dielectric relaxation amplitudes. Again, compressibility data for aqueous sugars have been used3 to derive solvation numbers for monosaccharides, with results ranging from 2.5 to 4.0 at 25 °C. One limiting factor in nuclear magnetic resonance (NMR) studies of aqueous sugars is that the rate of proton exchange is fast and no separate resonances from the hydroxyl protons appear. We now report that at low temperatures the exchange rate becomes sufficiently slow in the pH range 4 to 8 to enable us to detect resolved resonances from the individual hydroxyl protons. The results are interpreted in terms of strong hydrogen bonding between water and glucose, the effective solvation number being at least 10.
59 citations
TL;DR: It is concluded that nick-translation is a useful and altogether efficient method of labelling nucleic acids for subsequent use in experiments involving in situ hybridizations.
Abstract: A technique is described for preparation of 3H-labelled DNA by nick-translation employing deoxyribonuclease I and DNA polymerase I. The labelled DNA can be obtained in high yield with specific activities of 106 cpm/μg or more. Ribosomal DNA, isolated from ovaries of young Xenopus laevis, and whole DNA from Plethodon cinereus were labelled in this way. The rDNA was used for in situ hybridization to meiotic chromosomes from P. cinereus, P. vehiculum and P. dunni. Autoradiographs of in situ hybrids were exposed for 5 to 10 days, by which time nucleolus organizer regions on the chromosomes of all 3 species were clearly and specifically labelled. In all eases, labelling was confined to a short region near the middle of the short arm of both halves of a medium length bivalent. It is concluded that nick-translation is a useful and altogether efficient method of labelling nucleic acids for subsequent use in experiments involving in situ hybridizations.
TL;DR: Cell cultures of Nicotiana sybestris and Capsicum annuum, both without and following exposure to the mutagen, EMS, have been submitted to chilling for 21 days at —3 CC and +5 °C respectively and the cell lines derived from the surviving cells tested for their subsequent resistance to the chilling treatment.
TL;DR: In this article, the authors extracted chondrules from the Bjurbole and Chainpur chondritic meteorites by gentle crushing and hand-picking, and examined individual chond rules with apparatus incorporating two orthogonal binocular microscopes, and their three major axes measured.
TL;DR: Analysis of the pattern of synthesis of about 29 individual envelope polypeptides by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and autoradiography revealed that the great majority followed the patterns of the bulk measurements, with a discrete increase in rate of synthesis early in the cycle.
TL;DR: Analysis of plasmodial development, using time-lapse cinematography, showed that bin nucleate cells were formed as a result of nuclear division in uninucleate cells, and developed into plas modia by further nuclear divisions and cell fusions.
Abstract: Strain CL ofPhysarum polycephalum forms multinucleate plasmodia within clones of uninucleate amoebae. The plasmodia have the same nuclear DNA content as the amoebae. Analysis of plasmodial development, using time-lapse cinematography, showed that binucleate cells were formed as a result of nuclear division in uninucleate cells. Binucleate cells developed into plasmodia by further nuclear divisions and cell fusions. No fusions involving uninucleate cells were observed. A temporary increase in cell and nuclear size occurred at the time of binucleate cell formation.
TL;DR: It is shown in Experiment II that subjects' laughter, smiling, and looking are facilitated by increases in the laughter and smiling of coactors and, in Experiment III, that audiences are less effective in promoting high levels of responses.
TL;DR: The technique of affinity chromatography is described, used to achieve purification to homogeneity of CAT in high yield, to attach the free amino of chloramphenicol (CM base) or of p-amino chlorampshenicol to the free carboxyl group of substituted Sepharose [Seph-NH-(CH&-COOH] by formation of an amide bond following activation by a water soluble carbodiimide.
TL;DR: Hypocotyls of embryos from unripe and soaked ripe seeds of Phaseolus vulgaris and Acer pseudoplatanus are shown to be capable of transporting auxin, which shows the characteristics of active transport in the basipetal but not the acropetal direction.
Abstract: SUMMARY
Hypocotyls of embryos from unripe and soaked ripe seeds of Phaseolus vulgaris and Acer pseudoplatanus are shown to be capable of transporting auxin. The transport is strongly polar and shows the characteristics of active transport in the basipetal but not the acropetal direction. A procambial cylinder and a few phloem elements have been formed in these hypocotyls.
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TL;DR: In this article, the sintering behavior of magnesium aluminate spinel on both sides of the stoichiometry has been investigated and it was found that the composition close to the stochastic composition, but slightly enriched in magnesia can be sintered to translucency in a free flowing hydrogen environment.
Abstract: The sintering behaviour of magnesium aluminate spinel on both sides of the stoichiometry has been investigated. It is found that the composition close to the stoichiometric composition, but slightly enriched in magnesia can be sintered to translucency in a free flowing hydrogen environment. The grain size decreases with magnesia content; the addition of yttria, however, results in a highly bimodal grain structure. Prolonged exposure of the spinel in a high temperature sodium vapour environment forms Na2O · 5Al2O3 and some traces of Na2O · 11Al2O3 predominantely at the grain boundaries and near the surface of the specimen. Some possible sintering mechanism and factors affecting the in-line transmission are discussed.
TL;DR: By effective flushing of the cultures with CO2 -free air it is possible to demonstrate that carbon dioxide is essential to the initiation of the growth in suspension culture or on agar plates of cultured sycamore cells and attempts to replace the carbon dioxide requirement by non-toxic levels of organic or amino acids have not been successful.
Abstract: Carbon dioxide (optimum concentration c. 1.0%) is essential to the initiation of the growth in suspension culture or on agar plates of cultured sycamore cells. By effective flushing of the cultures with CO2 -free air it is possible to demonstrate this requirement with initial cell densities up to 50 × 103 cells ml-1 . This growth-promoting activity of carbon dioxide is not related to any effect it may have on the pH of the culture medium. The cells fix applied carbon dioxide into organic and amino acids but attempts to replace the carbon dioxide requirement by non-toxic levels of organic or amino acids have not been successful.
TL;DR: An isotope dilution technique has been used to analyze the synthesis of metabolically stable nucleic acids during the mitotic cycle in surface plasmodia of the slime mould Physarum polycephalum and results are discussed in relation to the pattern of replication of the genes for rRNA.
Abstract: 1
An isotope dilution technique has been used to analyze the synthesis of metabolically stable nucleic acids during the mitotic cycle in surface plasmodia of the slime mould Physarum polycephalum. Microplasmodia that had been labelled with [3H]uridine were used to prepare a surface culture, after a period of growth long enough to ensure that radioactivity was present only in tRNA, rRNA and DNA. The synthesis of rRNA or nuclear DNA during the growth of the surface plasmodium was then followed by measuring the specific activity of the nucleic acid.
2
Synthesis of rRNA during the mitotic cycle shows the following characteristics: (a) it is low during the immediate period of nuclear division, (b) synthesis is then continuous throughout interphase and (c) the rate of synthesis increases 5–6-fold between the beginning and end of interphase. These results are discussed in relation to the pattern of replication of the genes for rRNA.
3
Approximately 80 % of the nuclear DNA replicates during the first 90 min of the mitotic cycle; completion of replication, however, occupies the remainder of interphase.
TL;DR: Two types of creep testing machine, one to apply bi-axial tension to cruciform specimens and the other, torsion to disc-shaped specimens, have been constructed in the course of an investigaton of the behaviour of copper subject to multi-axisial stress systems as mentioned in this paper.
Abstract: Two types of creep testing machine, one to apply bi-axial tension to cruciform specimens and the other, torsion to disc-shaped specimens, have been constructed in the course of an investigaton of the behaviour of copper subject to multi-axial stress systems. Problems of bending in biaxial tension and buckling in torsion were encountered subsequent to construction of the machines. In the former case the deficiency was accepted and eccentric loading used to control the bending within acceptable limits. In the latter case microscopic examination was found necessary in order to define creep failure.
TL;DR: Binding studies using labelled β-adrenoceptor antagonists have demonstrated binding sites on erythrocyte ghosts and cardiac membranes that seem to satisfy fully the criteria associated with β adrenoceptors.
Abstract: IN VITRO binding of 3H-catecholamines to plasma membranes from a variety of tissues has been reported1–4. In none of these studies, however, has the binding satisfied criteria necessary for identification of true β adrenoceptors (for example, stereospecificity and high affinity for potent β-adrenoceptor antagonists). On the other hand studies using labelled β-adrenoceptor antagonists have demonstrated binding sites on erythrocyte ghosts and cardiac membranes that seem to satisfy fully the criteria associated with β adrenoceptors5–7.
TL;DR: In this article, the authors analysed 136 samples for total mercury and the results presented in Fig. 1 and in Table 1 are compared with other data, and found that the levels found are, in general, somewhat higher than in other, more limited, surveys.
Abstract: THE Mersey estuary consists of a wide, shallow upper region, separated from the sea by deeper ‘narrows’. The upper estuary (Fig. 1) is an area of continuous accretion of sediment, observed since the mid-nineteenth century with occasional short periods of depletion. The main freshwater inflows are the River Mersey itself, flowing over Howley Weir, and the Manchester Ship Canal, entering the estuary at Eastham Locks. The River Weaver flows into the Manchester Ship Canal at Weston1. The area is industrialised and heavily populated and the estuary receives both domestic sewage from surrounding towns and industrial effluent1,2. We are aware of no published data for mercury concentrations in the sediments of the estuary, and have undertaken such measurements. Samples were obtained from the places shown in Fig. 1. We analysed 136 samples for total mercury and the results presented in Fig. 1 and in Table 1 are compared with other data. The levels found are, in general, somewhat higher than in other, more limited, surveys.
TL;DR: In this article, the authors compared the performance of conventional hydrodynamic and recessed hydrostatic bearings with slot-entry bearings and showed that a much improved performance can be obtained by using non-return valves in the supply lines.
Abstract: Slot-entry bearings are compared with conventional hydrodynamic bearings and also with recessed hydrostatic bearings. Whereas recessed bearings are not ideal for hybrid operation, improvements in load capacity can be achieved by the use of non-return valves in the supply lines. However, it is shown that a much improved performance may be obtained from slot-entry bearings. Slot-entry bearings have additional advantages of manufacturing simplicity and compactness when compared with other hybrid bearings.Experimental results for recessed bearings and for slot-entry bearings justify computer solutions at moderate values of eccentricity ratio and speed parameters.