Showing papers by "University of Leicester published in 1971"
TL;DR: In this paper, the authors investigated the effect of oxygen consumption, filtration rate and assimilation efficiency on the acclimation of Mytilus edulis L to high and low temperature under laboratory conditions.
Abstract: Mytilus edulis L is shown to acclimate to high and low temperature under laboratory conditions The warm and cold acclimation of oxygen consumption, filtration rate and assimilation efficiency are described for groups of animals maintained at three food-cell concentrations Complete acclimation (Precht's type 2) of oxygen consumption and filtration rate occur within 14 days There is no change in assimilation efficiency within the 28-day experimental period The results are integrated and discussed in the context of a simple energy budget In terms of the energy budget there exists a marked contrast between warm and cold acclimation An “index of energy balance” is proposed in order to assess the state of the energy balance When animals are fed above the maintenance requirement the energy budget remains in an equilibrium state during cold acclimation, whereas the acclimation to a warm temperature regime disrupts the balance and represents a physiological stress During warm acclimation, prior to the re-establishment of an energy equilibrium the blood sugar level increases, suggesting that the animal is required to mobilize and utilize its energy reserves
300 citations
TL;DR: Oxygen consumption by Arctica islandica was dependent on oxygen tension and Laevicardium crassum and Mytilus edulis was independent of oxygen tension above a certain critical tension, while larger individuals were less dependent onoxy tension than smaller individuals.
151 citations
TL;DR: It is shown that the activity of the first enzyme of this pathway, methylglyoxal synthase, is regulated by Pi and DHAP in a way which suggests that it may play a role in the control of glycolysis.
145 citations
TL;DR: It is suggested that E. coli effect the uptake of C4-dicarboxylic acids through a common, inducible and highly specific transport system.
Abstract: Escherichia coli inducibly form a system effecting the uptake of a number of C4-dicarboxylic acids; glucose or inhibitors of protein synthesis prevent this induction. After growth on C4-dicarboxylic acids; glucose or inhibitors of protein synthesis prevent this induction. After growth onC4-dicarboxylic acids, washed cells take up such acids rapidly and, initially, linearly with time; the Km for this process is approx. 30 μM and the Vmax is approx. 25 nmoles X min−1 mg dry wt −1, irrespective of the identity of the acid transported. C4-dicarboxylic acids other than fumarate, succinate, malate, aspartate, and maleate, are takep up poorly. Washed cells talking up 14C-labelled C4-dicasrboxylic acids incorporate isotope mainly into macromolecular cell components; no significant intracellular accumulation of C4-acids is observed. Mutants blocked in component reactions of the tricarboxylic acid cycle are also greatly impaired in their ability to take up C4-acids; mutants blocked in reaction ancillary to the cycle are not. It is suggested that E. coli effect the uptake of C4-dicarboxylic acids througha common, inducible and highly specific transport system.
126 citations
TL;DR: In this paper, it is suggested that regulation of oxygen consumption at reduced oxygen tension is based on control of the ventilation: perfusion ratio, and that at low pO2 ventilation rate and heart frequency decreased, with increased amplitude of heart beat.
121 citations
TL;DR: In this article, measurements have been made to determine the seismic structure along the eastern branch of the East African Rift System (EARSS) in order to determine its seismic structure.
Abstract: Measurements have been made to determine the seismic structure along the eastern branch of the East African Rift System.
106 citations
TL;DR: In the early years after the war, when I was a lecturer in the Department of Political Economy at Glasgow University, I became very interested in the work of the members of the so-called Scottish Historical School, which Roy Pascal had rescued from oblivion in his remarkable article of 1938 as mentioned in this paper.
Abstract: In the early years after the war, when I was a lecturer in the Department of Political Economy at Glasgow University, I became very interested in the work of the members of the so-called Scottish Historical School, which Roy Pascal had rescued from oblivion in his remarkable article of 1938.2 I was impressed in particular by John Millar, whose work was pervaded by a theory of history and society which seemed to me to be a kind of preview of the materialist conception of history upon which I had been brought up in my revolutionary youth. I was interested also, of course, in the work of the other members of the School — notably that of Adam Ferguson, William Robertson, and Adam Smith; but these three seemed to be rather shadowy, peripheral figures in the face of the gigantic presence of the great John Millar.
103 citations
TL;DR: Calcium uptake by electrically stimulated guinea‐pig aorta was inhibited by lower concentrations of indomethacin than were required by stomach muscle.
Abstract: 1. Strips of muscle from the wall of the guinea-pig stomach contracted in response to electrical field stimulation (100 ms pulses, 0·2 Hz) or to histamine (1 μg/ml), and these responses were inhibited by indomethacin (2-20 mg/100 ml).
2. Glycerol-extracted strips of stomach muscle developed tension when exposed to a mixture of ATP, CP, magnesium chloride and calcium chloride. The tension response was not altered by indomethacin (50 mg/100 ml).
3. Indomethacin failed to alter the content of ATP or of CP in strips of stomach muscle.
4. The calcium content of strips of stomach muscle increased in response to 30 min of electrical stimulation (100 ms pulses, 0·2 Hz). The uptake of calcium and the contraction of the strips were inhibited by indomethacin (2-20 mg/100 ml) to a similar extent.
5. Calcium uptake by electrically stimulated guinea-pig aorta was inhibited by lower concentrations of indomethacin than were required by stomach muscle.
101 citations
TL;DR: (14C)-uridine is incorporated into RNA at all stages of the growth cycle of batch cultures; its continuing incorporation, when the total RNA content of the cells is rapidly decreasing, indicates a high rate of turnover of the totalRNA.
98 citations
90 citations
TL;DR: H3RNA complementary to the major component of the DNA anneals to all nuclei and to all parts of the chromosomes and the nature of the centromeric heterochromatin and its role in the meiotic divisions are discussed.
Abstract: When DNA from blood or liver of Plethodon c. cinereus is centrifuged to equilibrium in cesium chloride it separates out into 2 components. The smaller or satellite component is relatively rich in G + C and is therefore heavy, and it amounts to about 2% of the total DNA. The heavy satellite does not include the ribosomal cistrons, and it is unrelated to the nucleolar organizer. When squash preparations of cells from the testis of P. c. cinereus are incubated in synthetic E3RNA complementary to the satellite DNA, the RNA anneals specifically to the centromeric heterochromatin of spermatogonia, spermatocytes, and spermatids, and to the centromeric regions of all discernible chromosomes. RNA/DNA hybrids were located by autoradiography. H3RNA complementary to the major component of the DNA anneals to all nuclei and to all parts of the chromosomes. H3RNA complementary to nucleolar DNA from Xenopus laevis anneals specifically to the chromatin associated with nucleoli in nuclei at various stages of the meiotic divisions. The nature of the centromeric heterochromatin and its role in the meiotic divisions are discussed.
TL;DR: A working hypothesis is proposed to account for the ability of the ambient oxygen concentration to control both the activity and the energy conservation efficiency of A. vinelandii respiration.
Abstract: 1
The growth and respiration of Azotobacter vinelandii, together with the composition and activity of its membrance-bound respiratory system are compared during nitrogen-fixing batch growth at high and low aeration.
2
The aeration rate determines the length of the lag period, the extent of logarithmic growth and the respiratory activity of the culture; logarithmic growth ceases when the dissolved oxygen concentration drops to approximately 32 μM. Aconsiderable increase in whole cell respiratory activity is observed on changing from low to high aeration conditions.
3
During logarithmic, non-oxygen-limited growth, oxidase activities and respiratory carrier concentrations, with the exception of cytochrome o, remain low; the concentration of cytochrome o starts to rise when the ambient oxygen concentration falls to approximately 120 μM. Phosphorylation efficiencies, particularly at site I, are very low at high ambient oxygen concentrations but increase as the oxygen concentration decreases. Site I P/2e ratio is maximal (approx. 0.5) only when the oxygen concentration becomes growth limiting.
4
At the turnover point into non-logarithmic, oxygen-limited growth, respiratory carrier concentrations increase considerably; primary dehydrogenase activities increase by 2-fold whereas the activity of the minor phosphorylating terminal pathway increases by 9–13 fold.
5
A working hypothesis is proposed to account for the ability of the ambient oxygen concentration to control both the activity and the energy conservation efficiency of A. vinelandii respiration.
TL;DR: In this article, the authors indicate the outlines of a possible new extension from the plate tectonic theory to the study of the products of partial melting associated with global movements of plates.
Abstract: THE geological sciences have been advanced enormously by the philosophy of plate tectonics and it is appropriate now to apply data from igneous petrology to further this advance. This step is logical because magmatism is chiefly the study of the products of partial melting associated with global movements of plates. More needs to be done in this field, although the recent article by Baker and Wohlenberg1 is a valuable addition. In this letter I shall indicate the outlines of a possible new extension from the plate tectonic theory.
TL;DR: Reducing the concentration of thymine in the growth medium of thy− mutants of Escherichia coli progressively increases the replication time of their chromosomes, without affecting significantly the growth rate of the cultures, down to a concentration that is strain-specific.
TL;DR: The surface ornament of the ostracode carapace is shown to be composed of structural elements extending into the thickness of the shell.
Abstract: The surface ornament of the ostracode carapace is shown to be composed of structural elements extending into the thickness of the shell. A terminology is proposed for surface features newly revealed by scanning electron microscopy.
TL;DR: In this paper, the enthalpies of mixing HE of cyclohexane+1,4-dioxan at five temperatures and of benzene+ 1,4dioxant at four temperatures have been measured.
TL;DR: In this paper, the authors compare the seismic results of the previous article with gravity measurements from the same region, to arrive at a crustal model which is different from others proposed earlier.
Abstract: This article compares the seismic results of the previous article with gravity measurements from the same region, to arrive at a crustal model which is different from others proposed earlier.
TL;DR: The authors argue that people need to have similar meanings for the same symbols, and a way of thinking about things in common before they can communicate, and their perceptions are structured by the mental categories available to us for making sense of our world.
Abstract: some remarks about communication, attitude and culture at the outset of this paper, and then to mention some research findings about mass media and attitudes, before going on to our main argument. Communication between people is possible to the extent that they share common frameworks of interpretation. They need to have similar meanings for the same symbols, and a way of thinking about things in common before they can communicate. Our perceptions are structured by the mental categories available to us for making sense of our world.
TL;DR: In the presence of 15 per cent sucrose many cells showing breakdown of organised structure were observed; they were characterised by the persistence of mitochondria and particularly of the amyloplasts and by their high content of the electron opaque material equated with lignin.
Abstract: When suspensions of sycamore cells are cultured in a synthetic medium containing 10 mg/l 2,4-D and 025 mg/l kinetin, maximum cell yield is obtained with an initial concentration of 6 per cent sucrose There is a progressive increase in dry weight per cell, decline in extractive-free weight as a percentage of cell dry weight and increase in lignin content per cell as the initial sucrose concentration is increased from 1 per cent to 15 per cent The percentage of lignin in the extractive-free cell residue is further enhanced by increasing the level of 2,4-D to 10 mg/l or by growing the cells in an auxin-free medium containing 10 mg/l kinetin
TL;DR: Three cell clones differing from one another in growth rate and growth pattern in suspension culture, in nutrient requirement, in callus and cell morphology, in cellular fine structure and in pigmentation have been isolated from a callus of Atropa belladonna var.
TL;DR: The data presented in this paper suggest that the replication velocity is a function of, but not determined directly by, the intracellular thymidine triphosphate concentration.
TL;DR: Recent studies in several laboratories have cast doubt on this view, and have suggested that fructose is initially phosphorylated to fructose-l-phosphate with concomitant conversion of phosphoenolpyruvate (PEP) to pyruvates.
TL;DR: A mutation conferring resistance to phage BF23 and the E-group colicins in Escherichia coli K12 has been mapped at a locus, designated bfe, between arg(HBCE) and thi.
Abstract: A mutation conferring resistance to phage BF23 and the E-group colicins in Escherichia coli K12 has been mapped at a locus, designated bfe, between arg(HBCE) and thi. Mutants studied with this phenotype were recessive to wild-type and comprised a single complementation group.
TL;DR: The proportion of the respiration resistant to KCN was found to change during the life of theculture, being greatest during the lag phase and least during the linear phase, and the relationship of these changes in the electron transport pathways to the changing demand of the culture for phosphorylated and other intermediates is discussed.
Abstract: Mitochondria have been isolated from sycamore cells (Acer pseudoplatanus L.) grown in suspension culture, and resemble those of other plant tissues. Malate, succinate, and NADH are oxidized with respiratory control. The respiration is partially inhibited by antimycin A and KCN, hut not by amytal and rotenone. Octylguanidine, oligomycin, and uncouplers all affect the coupled respiration. The proportion of the respiration resistant to KCN was found to change during the life of the culture, being greatest during the lag phase and least during the linear phase. The relationship of these changes in the electron transport pathways to the changing demand of the culture for phosphorylated and other intermediates is discussed.
TL;DR: Differences in nutritional requirement provide a method for selecting constitutives from non-constitutives and vice versa.
Abstract: A regulatory mutant which leads to constitutive synthesis of enzymes involved in catabolism of nucleosides is described. It is unlinked to the structural genes whose activity is affected. The gene concerned is designated nucR. The amount of thymine required for growth (colony formation) of thy
− strains is affected by the nucR mutation. The amount required by a thy
−
drm
−strain is reduced about four fold if it carries the constitutivity mutation. The amount required by a thy
−
drm
+strain is increased at least two fold. These differences in nutritional requirement provide a method for selecting constitutives from non-constitutives and vice versa.
TL;DR: In this article, the results of investigations made on four cruciform biaxial fatigue specimens, each of which had a differently designed central region This central region consisted of a red central region.
Abstract: The results are presented of investigations made on four cruciform biaxial fatigue specimens, each of which had a differently designed central region This central region consisted of a red
TL;DR: In this paper, the experimental arrangement and operation of channel plates used in cascade is described, and the effect of ion feedback, high count rate performance and gainvoltage characteristics are discussed with a view to establishing the feasibility of the use of such a device in a rocket or satellite environment.
TL;DR: In this article, it is shown that if the answer to problem I were affirmative then so would be that to problem II; therefore our counter-example for problem II implies the existence of one for problem I.
Abstract: Problem I was raised (oral communication) by Goffman some three years ago, and I found the example then. Problem II was raised at about the same time by Topsoe; Christensen has given an affirmative answer for spaces satisfying certain additional conditions.It is easy to see that if the answer to problem I were affirmative then so would be that to problem II; therefore our counter-example for problem II implies the existence of one for problem I. It is also possible that another counter-example for problem I could be found by analysing the construction of Dieudonn6 in [1], which is also concerned (implicitly) with a failure of Vitali's theorem. Nevertheless our construction may be of independent interest.