Showing papers by "University of Oxford published in 1970"

Seasonal changes in oak leaf tannins and nutrients as a cause of spring feeding by winter moth caterpillars

Abstract: Concentration in the spring of feeding by caterpillars of the winter moth, Operophtera brumata L., and other species of Lepidoptera on oak trees in England is believed to be related to seasonal changes in the texture and chemical composition of the leaves. Increasing leaf toughness is a proximate, though probably not ultimate, factor preventing late larval feeding by the winter moth, the commonest spring species on oak. Early feeding coincides with maximum leaf protein content and mimum leaf sugar content, with suggests that availability of nitrogen, rather than of carbohydrate, may be a limiting factor for spring—feeding larvae. The content of oak leaf tannins, which inhibit the growth of winter moth larvae, increases during the summer and may render leaves less suitable for insect growth by further reducing the availability of nitrogen and perhaps also by influencing leaf palatability. Oak trees are extensively damaged by insect attack, and it is likely that leaf tannins have a defensive function against insects as well as against other herbivores and against pathogens.

The influence of nitrogen oxides on the atmospheric ozone content

Abstract: The probable importance of NO and NO2 in controlling the ozone concentrations and production rates in the stratosphere is pointed out. Observations on and determinations of nitric acid concentrations in the stratosphere by Murcray et al. (1968) and Rhine et al. (1969) support the high NO and NO2 concentrations indicated by Bates/Hays (1967). Some processes which may lead to production of nitric acid are discussed. The importance of O (1S), possibly produced in the ozone photolysis below 2340 A, on the ozone photochemistry is mentioned.

Amnesic syndrome: consolidation or retrieval?

Abstract: Amnesic patients can remember verbal material if they are tested with a method of partial information. The present experiments show that such retention depends more on the method of retrieval than on the method of acquisition. It is suggested here that long-term memory can be demonstrated in the patients if methods are used that eliminate incorrect and interfering responses.

Relativistic calculation of atomic structures.

Abstract: The current state of the art in relativistic calculation of atomic structures is surveyed. The theory is modelled on the practice in non-relativistic calculations, using many-particle wave functions built from Dirac central field spinors. The Hamiltonian includes quantum electrodynamic effects in the form of the Breit approximation for the interaction energy of two electrons. Within the limits for which this is valid, it is possible to construct matrices for one- and two-particle operators and hence to perform atomic structure calculations which automatically include the major relativistic effects. The theory can be greatly simplified by using Racah's tensor operators. Major applications have utilized the Hartree or Hartree-Fock methods, and the relevant equations are formulated in detail. Numerical Hartree-Fock solutions for the average of the ground configuration have now been obtained for most elements with atomic number less than 103, and some solutions have also been obtained for ions. The s...

The effect of amiodarone, a new anti‐anginal drug, on cardiac muscle

Abstract: 1. Amiodarone (2-butyl, 3-(4-diethylaminoethoxy, 3,5-diiodo, benzoyl) benzofuran hydrochloride), an anti-anginal drug which causes coronary dilatation and depresses myocardial oxygen consumption, was found to protect anaesthetized guinea-pigs against ouabain-induced ventricular fibrillation. 2. A 5% (73·4 mM) solution of amiodarone had no local anaesthetic action on guinea-pig skin. 3. Amiodarone, 20 mg/kg (29·4 μmol/kg) given daily for 6 weeks intraperitoneally, had no effect on the resting potential or action potential height, and only a small effect on the maximum rate of depolarization, of isolated rabbit atrial or ventricular muscle fibres as shown by intracellular recording. It caused a considerable prolongation of the action potential in both tissues. 4. Simultaneous administration of thyroxine (5 μg; 6·26 nmol), given daily for 3 weeks intraperitoneally, prevented the prolongation by amiodarone of the duration of the action potential. 5. Treatment of rabbits with 20 mg/kg of amiodarone daily intraperitoneally for 6 weeks had no effect on the weight of the thyroid gland, but was associated with a reduction in body growth rate. 6. Treatment of rabbits with 10 mg/kg (60·3 μmol/kg) of potassium iodide (equal in its iodine content to that of 20 mg/kg of amiodarone), given daily for 6 weeks intraperitoneally, had no effect on body growth rate or the duration of cardiac action potentials. 7. It was concluded that amiodarone had effects on cardiac action potentials similar to those which occur after thyroidectomy.

The Fit of the Southern Continents

Abstract: A computer fit of the 500-fathom contour of most of the southern continents is supported by geological and geophysical data.

Technique for Identifying Y Chromosomes in Human Interphase Nuclei

Abstract: CASPERSSON et al.1,2 have reported the staining of mitotic chromosomes in various organisms using fluorescent acridine derivatives. According to Zech3, the distal portion of the human Y chromosome fluoresces brightly when stained with quinacrine mustard. Vosa4 has observed similar fluorescence using quinacrine dihydro-chloride, which is more easily obtainable. We therefore investigated the possibility of positively identifying male nuclei in interphase by virtue of this staining property of the Y chromosome.

Molecular Photoelectron Spectroscopy

Abstract: The principal features of helium 584 angstrom photoelectron spectra of molecular vapours are outlined. Factors affecting the number of bands observed and their relation to the number of occupied electronic energy levels are discussed. The effect of the molecular translational velocity on the fundamental line widths attainable is considered and is shown to be significant though generally small compared with the much more common line broadening arising from ionic decomposition. Sharp lines are often to be associated with the presence of classical lone pairs but exceptions are noted. Structural effects in the lone pair ionization of chloro- and bromo-compounds are indicated. Some evidence is given for a correlation between the change in vibrational frequency produced upon ionization and the difference between adiabatic and vertical ionization energies. The use of such a correlation in the analysis of vibrational fine structure is exemplified by considering the examples of methylfluoride, 1,1-difluoroethylene, sulphur hexafluoride, ketene and pyrazine. A comparison between the p.e. spectra of butadiene, acrolein and glyoxal is used to indicate the utility of the method in creating energy level diagrams for related series of compounds.

A third class of anti-arrhythmic action: Effects on atrial and ventricular intracellular potentials, and other pharmacological actions on cardiac muscle, of MJ 1999 and AH 3474

Abstract: Summary 1 Both MJ 1999 and AH 3474 protected guinea-pigs anaesthetized with urethane against ouabain-induced ventricular fibrillation. 2 MJ 1999 had 1/90, and AH 3474 1/30, of the activity of procaine in reducing the height of the action potential of frog sciatic nerve. 3 MJ 1999 and AH 3474 reduced the rate of rise of intracellularly recorded action potentials at concentrations in excess of 160 × 10−6m (50 mg/l.). It was concluded that direct depression of depolarization could have contributed little to the protection against ouabain-induced fibrillation. 4 MJ 1999, but not AH 3474, greatly prolonged the duration of the action potential in acute experiments on isolated atrial and ventricular muscle, and prolonged the Q-Tc interval of the electrocardiogram in anaesthetized guinea-pigs. It is suggested that this effect contributes to anti-arrhythmic activity. 5 At concentrations up to 80 × 10−6m AH 3474 had positive chronotropic and inotropic effects on isolated rabbit atrial muscle, but at higher concentrations these were superseded by negative effects. MJ 1999 was depressant at all concentrations studied, the threshold concentrations being 19 × 10−6m for chronotropic, and 162 × 10−6m for inotropic effects.

The temperature and strain-rate dependence of the shear strength of mild steel

Abstract: An account is given of experiments in which the shear flow stress of mild steel was measured at temperatures from 195 to 713°K and strain rates from 10−3 to 4 × 104 sec−1 The experimental results obtained at room temperatures are compared with those of earlier tension tests The rate sensitivity of the flow stress, (∂τ/∂ In γ) T , is found to be a decreasing function of temperature, except at the highest strain rates; at these rates a large increase in the rate sensitivity is observed, the flow stress at constant temperature varying approximately linearly with strain rate The data are interpreted in terms of thermal activation rate theory and the theory of the damping of dislocation motion by phonon viscosity

The natural control of a population of Tawny owls (Strix aluco)

Abstract: A long-term study was made (1947-59) of the numbers and breeding success of the Tawny owl (Strix aluco L.) in a woodland habitat near Oxford. Parallel studies were made of the numbers and distribution of the owl's two main prey species, the Wood mouse (Apodemus sylvaticus (L.)) and the Bank vole (Clethrionomys glareolus (Schr.)). The life-cycles of all these three interrelated species were worked out and special attention was paid to the habit of strict territoriality of the owl (on the evidence of vocalizations and of the recovery, from the regurgitated pellets of the owl, of marking rings placed on the rodents) and to the sequence of losses which occurred during the breeding of the owl. The owls' vocal defence of their territories enabled an accurate census to be made of the adult population each spring and the fact that the fledged young remained for a long time in their parents' territories made it possible to count the number of young produced each year. Investigation of the breeding habits of the owls showed that the number of fledged young produced fell far short of what was possible: some pairs of owls refrained from breeding at all, others laid eggs but failed to hatch them, yet others hatched young but failed to rear them to fledging. By and large this degree of reproductive “failure” was associated with the numbers and availability of rodent prey. At an exceptionally low density of prey no owls even attempted to breed; as densities increased, correspondingly greater numbers of fledged young were produced up to a ceiling where no more young were produced however much higher the level of abundance of the rodents rose. In spite of these wide variations in the numbers of prey and in the numbers of fledged young produced, the population of adult owls remained notably stable, increasing from a low level of 17 pairs in 1947, owing to the emergency mortality of an exceptionally hard winter, to about 30 pairs in 1955, after which the population remained stationary until the end of the study in 1959. It is clear that this stability is maintained by those young which fail to find a territory either starving or moving outside the study area, which in most cases amounts to the same thing. Thus regulation of the population studied was due to territorial intolerance acting to produce subsequent mortality, though it is not certain that this applies over a larger area.

Mechanism of eosinophilia. II. Role of the lymphocyte.

Abstract: A possible role for the lymphocyte in the mechanism of eosinopoiesis has been examined. Procedures known to deplete or inactivate the pool of recirculating lymphocytes such as neonatal thymectomy, administration of antilymphocyte serum, and prolonged thoracic duct drainage, either singly or in combination, resulted in a highly significant reduction in the eosinophil response to trichinosis. Irradiated animals exposed to parasitic challenge did not develop eosinophilia unless reconstituted with lymphocytes as well as bone marrow cells. When "memory" cells were used instead of normal lymphocytes, a "secondary" type of eosinophil response was observed. Transfer of a primary eosinophilia was achieved adoptively with a population of living large lymphocytes from thoracic duct lymph and peripheral blood, but not with blood plasma or cell-free lymph. The potency of the active lymphocytes was not impaired by enclosing them in cell-tight diffusion chambers, indicating that they exerted an effect on bone marrow by agency of a diffusible factor. The demonstration of a role for lymphocytes in induction of the eosinophil response to this kind of stimulus supports the conclusion that eosinophilia belongs in the category of immunologic phenomena.

Free and protein-bound glutathione in normal and cataractous human lenses.

Abstract: Protein-bound glutathione was identified and measured in normal and cataractous human lenses. In a major group of cataracto us lenses the bound glutathione concentration was higher than normal. Study of normal lenses showed that their glutathione content is age-dependent, decreasing steadily from about 3.5mumol/g of lens at age 20 years to about 1.8mumol/g of lens at age 65 years. Cataract brings further decreases.

Effects of foveal prestriate and inferotemporal lesions on visual discrimination by rhesus monkeys.

Abstract: Ablation of inferotemporal cortex in monkeys impairs visual discrimination learning, and inferotemporal cortex receives visual information from striate cortex by way of the circumstriate belt. Yet most previous studies have failed to find any discrimination impairment after partial ablations of the circumstriate belt.

Topography of the retina and striate cortex and its relationship to visual acuity in rhesus monkeys and squirrel monkeys.

Abstract: Density of cones and ganglion cells was studied in horizontal sections of retina in the rhesus monkey (Macaca, mulatta) and the squirrel monkey (Saimiri sciureus). The lower angular density of cones in the fovea of Saimiri correlates with its visual acuity, which is poorer than that of Macaca (0.74 and 0.65 min of arc respectively). Cone density falls more steeply with angular eccentricity from the fovea in Saimiri, in accordance with its relatively poorer peripheral acuity. Comparable results were obtained with retinal ganglion cells, but the comparisons at the fovea itself are more difficult because of the lateral displacement of these elements in the foveal region. The cortical magnification of the visual field (that is, the number of mm of cortex per degree of visual field) is lower for both the foveal and parafoveal representations at the striate cortex in Saimiri. This was correlated with its poorer foveal and parafoveal acuity. It was shown that with increasing eccentricity from the fovea, the fall in the magnification of the visual field at the striate cortex is approximately proportional to the decrease in ganglion cell density at the retina. The results of this study, in which acuity and topography of the visual system are compared in two species of monkey, are consistent with the view that both retinal topography, and the cortical magnification of the visual field, are closely related to visual acuity.

On the Mechanism of Desensitization at Cholinergic Receptors

Abstract: Evidence is presented that desensitization to cholinergic agonists in chick and leech muscle is a process involving receptor inactivation. Various possible mechanisms that could account for slow inactivation of receptors by agonists were analyzed mathematically, and expressions were obtained for the rate and extent of desensitization expected under various conditions. With the majority of agonists tested there appeared to be the same relationship between the response and the amount of desensitization produced. Certain agonists, however, were relatively more effective in causing desensitization. The kinetics of development of and recovery from desensitization were studied in chick and frog muscle. Reactivation of desensitized receptors occurred exponentially. In chick muscle the rate constant for recovery was the same (0.3 min-1) regardless of what agonist had been used to produce the desensitization. In chick muscle, tubocurarine decreased pari passu the response and the desensitization produced by carbachol or suxamethonium. Tubocurarine increased the desensitization produced by the partial agonist n-decyltrimethylammonium. These results are compatible with the cyclic model for desensitization suggested by Katz and Thesleff [J. Physiol. (London) 138, 63 (1957)], with the additional factor that certain drugs may have a preferential affinity for desensitized, compared with normal, receptors. The process of receptor activation may be very closely related to the transition from normal to desensitized receptors brought about by agonist drugs.

Equilibrium relations between the cytoplasmic adenine nucleotide system and nicotinamide–adenine nucleotide system in rat liver

Abstract: 1. The ratio [ATP]/[ADP][Pi], as measured by direct determination of the three components in rat liver, was found in various nutritional states to have approximately the same value as the ratio [ATP]/[ADP][Pi] calculated from the concentrations of lactate, pyruvate, glyceraldehyde phosphate and 3-phosphoglycerate on the assumption that lactate dehydrogenase, glyceraldehyde phosphate dehydrogenase and 3-phosphoglycerate kinase are at near-equilibrium in the liver. This implies that the redox state of the NAD couple in the cytoplasm is linked to, and partially controlled by, the phosphorylation state of the adenine nucleotides. 2. The combined equilibrium constant of the glyceraldehyde 3-phosphate dehydrogenase and 3-phosphoglycerate kinase reactions at 38°C and I0.25, was found to be 5.9×10−6. 3. The fall of the [NAD+]/[NADH] ratio in starvation and other situations is taken to be the consequence of a primary fall of the [ATP]/[ADP][HPO42−] ratio.

Ethylene, the Natural Regulator of Leaf Abscission

Abstract: Natural leaf fall is triggered by increased ethylene production in senescing cells close to abscission zones.

The Communication of Inferior and Superior Attitudes by Verbal and Non‐verbal Signals*

Abstract: Ratings were made by 120 subjects of 18 video-tapes in which verbal and non-verbal cues for Inferior, Equal and Superior were varied and combined in a 3 times 3 design. The typed messages (verbal alone) were rated by further subjects, as were video-tapes of a performer reading numbers (non-verbal alone); the two sets of cues alone had identical effects on ratings. In combination, both kinds of cue had a reduced effect, but it was found that non-verbal cues now had 4.3 times the effect of verbal cues on shifts of ratings, and accounted for 10.3 times as most variance; verbal cues were only able to act as multipliers of consistent nonverbal cues. There was little evidence of double-bind effects. Analysis of individual differences showed that females were relatively more responsive to non-verbal compared with verbal cues, and that more neurotic subjects found the combination of Superior (non-verbal) with Inferior (verbal) unpleasant, and responded more to verbal cues for Inferior-Superior.

Dislocations and stacking faults

Abstract: The properties of linear defects in crystals (dislocation lines) and of planar defects (stacking faults) are important in almost every branch of solid state physics. This article is intended to give a comprehensive introduction to dislocation theory for the physicist who is not a specialist in crystal plasticity. It begins with a survey of the established theory relating to the geometrical and topological properties of dislocations, the elastic theory of dislocations in a continuum, the atomistic or core properties of dislocations, and the dynamics of moving dislocations. General methods for finding the elastic field of an arbitrary dislocation loop are outlined, and the results of some recent calculations using anisotropic elasticity are summarized. These include the prediction, partially confirmed by experiment, that dislocations in certain ranges of orientation may have negative line tension. The current importance of atomistic calculations of core structure and related problems is emphasized, and the methods available for these calculations are discussed. More detailed descriptions of dislocation and stacking fault configurations are given for some of the common crystal structures, and recent work on complex defects resulting from vacancy aggregation in close-packed structures is included. The experimental and theoretical evidence for the recent conclusion that screw dislocations in body-centred cubic metals have an asymmetric core is also reviewed. The rather controversial theory of thermally activated dislocation motion is described in a separate section, and examples are given of the application of this theory to various models of the obstacles encountered by moving dislocations. The final section is concerned with the theory of dislocations in grain boundaries and interphase boundaries, and includes the concept of the surface dislocation tensor.

Effects of ischaemia on content of metabolites in rat liver and kidney in vivo.

Abstract: 1. The time-course of changes in content of intermediates of glycolysis in rat liver and kidney cortex after severance of blood supply was investigated. 2. The decline in content of ATP was more rapid in kidney (1.7–0.5μmol/g in 30s) than in liver (2.7–1.6μmol/g in 60s). In both tissues AMP and Pi accumulated. 3. Net formation of lactate was 1.7μmol/g during the second minute of ischaemia in liver from well-fed rats, 1.1μmol/g in liver from 48h-starved rats, and about 1.0μmol/g during the first 30s of ischaemia in kidney. Net formation of α-glycerophosphate was rapid, especially in liver. 4. In kidney the concentration of β-hydroxybutyrate rose, but that of α-oxoglutarate and acetoacetate decreased. 5. In both organs the concentrations of fructose diphosphate and triose phosphates increased during ischaemia and those of other phosphorylated C3 intermediates decreased. 6. The concentration of the hexose 6-phosphates rose rapidly during the first minute of ischaemia in liver, but decreased during renal ischaemia. 7. In kidney the content of glutamine fell after 2min of ischaemia, and that of ammonia and glutamate rose. 8. The redox states of the cytoplasmic and mitochondrial NAD couple in kidney cortex were similar to those in liver. 9. The regulatory role of glycogen phosphorylase, pyruvate kinase and phosphofructokinase is discussed in relation to the observed changes in the concentrations of the glycolytic intermediates.

The physiological role of liver alcohol dehydrogenase.

Abstract: 1. Yeast alcohol dehydrogenase was used to determine ethanol in the portal and hepatic veins and in the contents of the alimentary canal of rats given a diet free from ethanol. Measurable amounts of a substance behaving like ethanol were found. Its rate of interaction with yeast alcohol dehydrogenase and its volatility indicate that the substance measured was in fact ethanol. 2. The mean alcohol concentration in the portal blood of normal rats was 0.045mm. In the hepatic vein, inferior vena cava and aorta it was about 15 times lower. 3. The contents of all sections of the alimentary canal contained measurable amounts of ethanol. The highest values (average 3.7mm) were found in the stomach. 4. Infusion of pyrazole (an inhibitor of alcohol dehydrogenase) raised the alcohol concentration in the portal vein 10-fold and almost removed the difference between portal and hepatic venous blood. 5. Addition of antibiotics to the food diminished the ethanol concentration of the portal blood to less than one-quarter and that of the stomach contents to less than one-fortieth. 6. The concentration of alcohol in the alimentary canal and in the portal blood of germ-free rats was much decreased, to less than one-tenth in the alimentary canal and to one-third in the portal blood, but detectable quantities remained. These are likely to arise from acetaldehyde formed by the normal pathways of degradation of threonine, deoxyribose phosphate and β-alanine. 7. The results indicate that significant amounts of alcohol are normally formed in the gastro-intestinal tract. The alcohol is absorbed into the circulation and almost quantitatively removed by the liver. Thus the function, or a major function, of liver alcohol dehydrogenase is the detoxication of ethanol normally present. 8. The alcohol concentration in the stomach of alloxan-diabetic rats was increased about 8-fold. 9. The activity of liver alcohol dehydrogenase is generally lower in carnivores than in herbivores and omnivores, but there is no strict parallelism between the capacity of liver alcohol dehydrogenase and dietary habit. 10. The activity of alcohol dehydrogenase of gastric mucosa was much decreased in two out of the three germ-free rats tested. This is taken to indicate that the enzyme, like gastric urease, may be of microbial origin. 11. When the body was flooded with ethanol by the addition of 10% ethanol to the drinking water the alcohol concentration in the portal vein rose to 15mm and only a few percent of the incoming ethanol was cleared by the liver.

Discharge patterns of coxal levator and depressor motoneurones of the cockroach, periplaneta americana

Abstract: 1. Observation of movements of the metathoracic legs of the cockroach before and after section of peripheral nerves allowed identification of muscles involved in flexion and extension of the femur. 2. Extracellular recordings from the nerves to these coxal muscles show that during rhythmic leg movements bursts of activity in a number of levator motor axons were strongly reciprocal and generally non-overlapping with those of a slow depressor motor axon. 3. These reciprocal patterns persisted after removal of all sensory input from the legs. 4. The durations of levator bursts were relatively constant compared to those of the depressor, corresponding to the behavioural observations on leg protraction time. The pattern was asymmetric: levator bursts could be generated without depressor activity, but never the reverse. 5. No evidence was found for inhibitory collateral pathways between antagonist motoneurones. 6. It is proposed that levator motoneurones are driven by a group of bursting interneurones which simultaneously inhibit the ongoing depressor activity.

Preliminary Experiments on the Chemistry and Pharmacology of Cannabis

Abstract: There are at least six pharmacologically effective components of cannabis. Their effects on mice include a lowering of body temperature, catalepsy, analgesia and an extension of barbiturate sleeping time, with doses from 25 to 200 mg/kg.

Mechanism of eosinophilia i. factors affecting the eosinophil response of rats to trichinella spiralis

Abstract: The phenomenon of eosinophilia was studied in rats using inoculation with Trichinella larvae as the experimental stimulus. Comparisons were made between the eosinophil response accompanying active infestation via the gastrointestinal tract and that resulting from parenteral inoculation of larvae or their products. A vigorous eosinophilia could be provoked by a single intravenous injection of intact parasites. In this circumstance the larvae lodged in the lungs causing an acute inflammatory reaction which led to their disintegration within 24 hr. Intraaortic injection also produced a significant response, whereas inoculation of the same number of parasites by the intramuscular, intraperitoneal, or subcutaneous routes did not cause eosinophilia. Eosinophilia likewise failed to develop if parasites were homogenized before intravenous injection, so that they were not arrested in the lungs. Antibody levels, as measured by a hemagglutination technique, using whole larval extract as antigen, did not correlate closely with the eosinophil response. The findings are interpreted as suggesting that increased eosinophil production is induced under some circumstances as a consequence of interaction between intact parasites and certain host cells in blood and tissue. No evidence was found for the existence of a specific constituent of the parasite capable of stimulating eosinophil production. Attention is directed to features of eosinophilia which fit with the concept that this phenomenon belongs in the category of immunologic reactions.