Showing papers by "University of Leicester published in 1972"

Creep rupture under multi-axial states of stress

Abstract: R esults are presented of metallographic examinations of specimens which have been creep tested at high temperatures and under different conditions of steady applied stress. The interaction between the growth of micro-fissures or voids and the mode of final rupture is discussed. The applied-stress versus rupture-life characteristics of a number of commercial alloys are presented together with simple expressions which are shown to describe approximately the stress-sensitive nature of their rupture behaviour.

“Good” and “Bad” Phenograms

Abstract: Sackin, M. J. (Medical Research Council Microbial Systemnatics Unit, Leicester Univ., Leicester, England) 1972. "Good" and "Bad" phenograms. Syst. Zool. 21:225-226.This paper presents a measure for characterizing a phenogram and measuring its usefulness. Rohlf and Fisher (1968) have illustrated differing types of phenogram which arise from clustering random data by different methods, but they state that "no quantitative indices have been developed previously which completely describe the form and shape of a phenogram." This note is an attempt to meet the challenge offered by Rohlf and Fisher, with the introduction of the b vector (b stands for "branching"), which is a very simple measure and summarizes several useful properties of a phenogram. Intuitively the phenogram in Figure 1 looks better than the one in Figure 2. The first one is symmetrical and the second is highly skew (as these terms are used by Rohlf and Fisher, 1968). The numbers along the tips of the phenograms are the elements of b and are simply the number of branchings passed when travelling from the base to the tip. Thus, for figure 1, b-

Inducible phosphoenolpyruvate-dependent hexose phosphotransferase activities in Escherichia coli

Abstract: 1. A method is described for measuring the rate of phosphoenolpyruvate-dependent phosphotransferase activity for a variety of hexoses in toluene-treated suspensions of Escherichia coli. 2. The specific activities of the phosphotransferases that catalyse the phosphorylation of hexoses are greatly affected by the carbon source for growth. 3. In all strains of E. coli tested, fructose phosphotransferase activity is induced by growth on fructose. 4. Strains of E. coli differ greatly in the rate at which they phosphorylate glucose, but all strains possess at least a low glucose phosphotransferase activity under any tested condition of growth. Glucose phosphotransferase activity is further induced by growth on glucose; this does not occur in a mutant that lacks the ability to take up methyl α-d-[14C]glucopyranoside and hence grows poorly on glucose. 5. When growing on fructose, two strains of E. coli synthesize the inducible glucose phosphotransferase system gratuitously, and to specific activities higher than observed during growth on glucose. A phosphotransferase catalysing the phosphorylation of mannose is similarly induced.

Origin and structure of embryoids arising from epidermal cells of the stem of Ranunculus sceleratus L.

Abstract: Embryoids are initiated from single highly cytoplasmic cells of the stem epidermis of plantlets of Ranunculus sceleratus L. derived from callus cultures. The embryoids show embryological development of the Crucifer type except that the suspensor is reduced or suppressed. The cells of the young embryoids have a large central nucleus surrounded by small vacuoles, a cytoplasm rich in free ribosomes or ribosomes in small polysomes, prominent amyloplastids and abundant spherosomes. These cells also frequently contain multivesicular and myelin bodies. The spherosomes are observed in various stages of development; they are typically arranged in a layer below the cell wall, the space between the spherosomes and the wall being rich in spherical vesicles and microtubules. As embryoid development proceeds the plastids show internal differentiation; globular centres and, surrounding them, electron-transparent droplets are associated with the origin of the thylakoid membranes. The walls of the embryogenic cells are initially rich in plasmodesmata but as the embryoid develops cytoplasmic continuity with the embedding tissue is severed and the embryoid is clearly delineated. The embryology and fine structure of the embryoid cells is compared with that of zygotic embryos of Capsella and Ranunculus .

The purification and properties of Escherichia coli methylglyoxal synthase.

Abstract: 1. Methylglyoxal synthase was purified over 1500-fold from glycerol-grown Escherichia coli K 12 strain CA 244. The purified enzyme was inactivated by heat or proteolysis, had a molecular weight of approx. 67000, a pH optimum of 7.5 and was specific for dihydroxyacetone phosphate with Km 0.47mm. 2. The possibility that a Schiff-base intermediate was involved in the reaction mechanism was investigated but not confirmed. 3. The purified enzyme lost activity, especially at low temperature, but could be stabilized by Pi. Two binding sites for Pi may be present on the enzyme. Of other compounds tested only the substrate, dihydroxyacetone phosphate, and bovine serum albumin showed any significant stabilizing effect. 4. Phosphoenolpyruvate, 3-phosphoglycerate, PPi and Pi were potent inhibitors of the enzyme. Kinetic experiments showed that PPi was apparently a simple competitive inhibitor, but inhibition by the other compounds was more complex. In the presence of Pi the enzyme behaved co-operatively, with at least three binding sites for dihydroxyacetone phosphate. 5. It is proposed that methylglyoxal synthase and glyceraldehyde 3-phosphate dehydrogenase play important roles in the catabolism of the triose phosphates in E. coli. Channelling of dihydroxyacetone phosphate via methylglyoxal would not be linked to ATP formation and could be involved in the uncoupling of catabolism and anabolism.

Delayed recovery from a sedative: correlation of the plasma levels of diazepam with clinical effects after oral and intravenous administration

Abstract: SUMMARY Plasma levels of diazepam were obtained in student volunteers after both oral and intravenous administration. Correlation with clinical effects showed that after oral administration, the onset of drowsiness and relaxation after 10–15 minutes was asso—ciated with a rapid absorption of the drug. When diazepam was administered intravenously, a pronounced clinical effect was observed for one hour after injection. This was followed by recovery at 2 hours, but subsequently the subjects reported recurrence of clinical symptoms at about 6 hours. This reappearance of drug action was shown to coincide with the remobilisation of diazepam in the subjea, supplemented by the slow build up of the metabolite Ro 5–2180 (desmethyldiazepam). It was not associated solely with the levels of Ro 5–2180. From these results it appears that patient recovery is not complete for several hours.

"Lymphomatoid" pityriasis lichenoides: a variant with histological features simulating a lymphoma. A clinical and histopathological study of 15 cases with details of long term follow up.

Abstract: Summary.— The clinical and histopathological features of 15 cases with “lymphomatoid” pityriasis lichenoides are described. The eruption was characterized by the continuous formation of papules which involuted spontaneously to leave scars. The papules closely resembled those found in typical pityriasis lichenoides acuta or chronica, but in some cases larger ulceronecrotic lesions also occurred. The disease had often persisted for many years without evidence of systemic involvement. In 1 male, however, the outcome was fatal after an interval of 16 years. The spectrum of histopathological findings varied considerably from a benign-looking infiltrate, usually in the smaller papules, to those which suggested a highly malignant infiltrate because of the presence of numerous large atypical cells. Preliminary histochemical investigations suggest that the large cells are derived from histiocytes and are distinct from leukaemic blast cells or Hodgkin's giant cells.

The nucleolus and its genes in amphibian oogenesis.

Abstract: Summary 1. Amphibian oocyte nucleoli may be solid and round, or they may take the form of beaded rings. Transformation of the nucleoli from the solid form to the ring form and back again may be a regular feature of oogenesis. The variation in circumference of freshly isolated unstretched ring nucleoli is continuous over a range of about fivefold. The longest rings may measure several hundred micra. All oocyte nucleoli have two structural zones, core and cortex. The core consists of finely fibrous material and is analogous to the ‘pars amorpha’ of earlier authors. The cortex has a granular fine structure and is analogous to the ‘nucleolonema’. The beads of ring nucleoli have both core and cortex components. Some solid nucleoli are multicored. 2. When all nucleoli are single cored, the number of nucleoli in an oocyte nucleus remains constant throughout the lampbrush phase of oogenesis. When nucleoli are multicored, the number of nucleoli may vary, but the number of nucleolar cores remains constant. 3. Oocyte nucleoli of between 6 and 12μ diameter have dry masses of between 50 and 200 μμg. 610% of the nucleolar dry mass is attributable to RNA. 4. Each nucleolus has a small DNA component. This component is in the form of a long circular duplex. In solid nucleoli it meanders through the substance of the nucleolar core. It forms the axis of a ring nucleolus and the structural integrity of the ring is maintained by the DNA component. 5. Both round and ring types of nucleoli from some salamanders and frogs have a membrane component attached to them. This takes the form of a membranous tube or a chain of vesicles ending near to or within a depression in the surface of the nucleolar core. Nothing is known at present of the function of the nucleolar membrane. 6. Nucleoli are sites of synthesis of ribosomal RNA. The DNA of the nucleolar core has the base sequence needed for transcription of ribosomal RNA. RNA is transcribed, complexed with protein and eventually distributed between 50S and 30S ribonucleoprotein particles. The 30S particle does not accumulate in the nucleolus. The 50S particle matures in the nucleolus and probably constitutes a substantial portion of the nucleolar cortex. 7. During the pachytene stage in ovaries of young amphibia 20–30 μμg. of extra-chromosomal nucleolar DNA are synthesized. In early diplotene this DNA disperses into thousands of tiny granules which become distributed over the inner surface of the nuclear envelope. A nucleolus then grows in association with each granule. 8. Isolation and purification of nucleolar DNA from pachytene oocytes, and from germinal vesicles, has shown that it contains the sequences for 18 and 28S ribosomal RNA, and it represents the products of an amplification of the genes for ribosomal RNA. 9. In Xenopus the gene complex which is amplified consists of about 450 tandem repeats of a region of double stranded DNA which includes sequences complementary to 28 S and 18 S ribosomal RNA alternating with a spacer sequence. The density of the ribosomal DNA, including the spacer DNA, in somatic cells of X. laevis is 1.7236 g. cm-3, and that of the oocyte amplified rDNA is 1.729. Both DNAs are 67% G + C. The somatic rDNA has 4.5% 5-methyl-deoxycytidylic acid which accounts for its lower density. The spacer sequences are uniform within a species, but differ from one species to another. 10. In oocytes, rDNA is amplified by using one or both of the chromosomal nucleolar organizers as a primary template. Amplification starts in oogonia and proceeds slowly until the pachytene stage. Rapid synthesis of DNA takes place in pachytene and early diplotene stages over a period of about 20 days. It seems likely that DNA synthesis proceeds in a cascade pattern such that each new replica itself serves as a template for further replication. Evidence for synthesis of a primary RNA template upon which the amplified rDNA is made is equivocal. 11. Whatever the size of the nucleolar organizer in an amphibian, and however many ribosomal cistrons it may incorporate, the amplification system in the oocyte is scaled accordingly, so that only a certain number of additional ribosomal cistrons and associated spacer are synthesized. Each of the eight germinal vesicles in an Ascuphus oocyte amplifies its rDNA to only one-eighth of the extent seen in the single oocyte nuclei from other anurans. Mononucleolate Xenopus, whose oocytes have only half the usual complement of chromosomal ribosomal DNA, nevertheless amplify to the level found in the normal wild-type individuals. Triploid Ambystoma, with hexaploid oocytes, appear to amplify their rDNA to three times the extent seen in their diploid relatives. It is clear that the level of gene amplification is related to the number of chromosomal organizers in the oocyte nucleus. It also seems that the level of amplification may be related to the volume of the oocyte nucleus. 12. The lampbrush chromosomes of at least some amphibia carry attached oocyte nucleoli at sites whose positions correspond to those of the somatic nucleolar organizers. The lampbrush nucleolar organizer in the axolotl is often marked by round or ring-like objects attached to the chromosome. 13. These lampbrush nucleolar organizers may carry solid or ring-like nucleoli. The attached nucleoli are thought to be permanently located there. They are not sequentially grown and detached from the chromosome. Attached ring or loop-like nucleoli may form ‘double bridges’, indicating that at least in some cases they are an integral part of the chromosome axis. In Plethodon the lampbrush nucleolar organizer consists of a long stretch of non-chromomeric axis that may appear single or double. There are ring or solid nucleoli attached at intervals along this axis. It is possible that these attached rings are products of amplification of the nucleolar organizer and that they became re-attached to the chromosomal organizer by a process analogous to recombination during or soon after the main phase of amplification.

Some effects of stress in the adult on the larval development of Mytilus edulis.

Abstract: ONCE triggered by temperature and food stimuli, vitellogenesis in bivalve molluscs proceeds to completion in spite of suboptimal environmental conditions1,2. Following maturation, however, disintegration of gametes occurs unless further stimuli are received to initiate their release from the animal (spawning), which poses the question, how are the larvae that develop from gametes produced in sub-optimal conditions affected by the stress experienced by the adult?

The structure of Liquid Water

Abstract: Professor Symons describes the outcome of work at Leicester on water structure.

Enzyme synthesis in myxamoebae of the cellular slime mould Dictyostelium discoideum during growth in axenic culture.

Abstract: 1. The specific activities of β-N-acetylglucosaminidase, acid phosphatase, α-mannosidase, β-glucosidase, UDP-glucose pyrophosphorylase and alkaline phosphatase have been determined in myxamoebae of the cellular slime mould Dictyostelium discoideum Ax-2 grown on different media and in different phases of the growth cycle. 2. Variations in enzymic composition occur with changes in growth medium and phase of the growth cycle. 3. The intracellular location of the enzymes studied has been determined. 4. Two enzymes, β-N-acetylglucosaminidase and α-mannosidase, are not only synthesized preferentially as the myxamoebae enter the stationary phase of growth but they are also excreted. The excretion process appears to be specific, because other enzymes that occur in the same intracellular fraction are not excreted.

Images of the village community: a study in Anglo-Indian Ideology

Abstract: To a degree exceptional even in that age of historical recovery and sociological discovery, awareness of the village community was a creation of the later nineteenth century. With due allowance for the contribution of the German historical school, it was—within the English-speaking world—an Anglo-Indian creation. In England, save for a handful of ‘survivals’, the village community was a purely historical phenomenon, studied by historians; but in India it was an omnipresent reality, utilized by revenue officials in assessing and collecting the land revenue. From the efforts of these groups—historians and revenue officials—to comprehend substantially similar institutions two intellectual traditions derived. Originating in complete independence of one another, both traditions converged in the third quarter of the nineteenth century for a brief, intense, period of cross-fertilization—only to separate as totally again. What made their convergence possible was the rising popularity of evolution and ‘comparative method’—which insisted on the essential identity of the defunct English village community and the living Indian village, separate in space and time, but co-existent in the same phase of social evolution. Then disillusion with unilinear evolutionary schemes and the exhaustion of comparative method—its apparent inability to produce any fresh discovery—drove them apart.

Properties of the Invertases of Cultured Sycamore Cells and Changes in Their Activity during Culture Growth

Abstract: When cultured sycamore cells are homogenised in a phosphate-citrate buffer at pH 7.0 and the homogenate centrifuged two fractions are obtained both of which show the presence of an acid (opt. pH 4.0–4.5) and a neutral (opt. pH 7.0–7.4) invertase. The activity of the insoluble pellet appears to be located in its cell wall fragments. The acid and neutral invertases of the soluble fraction can be separated by fractional precipitation with (NH4SO4. The activities of these enzymes are low in stationary phase cells but they increase following subculture to reach peaks of activity towards the end of the period of most active cell growth and division and then decline again as the cells begin to enter stationary phase. The activities of both enzymes are higher in the cell wall than in the soluble fraction and the acid invertase reaches higher levels of activity than the neutral enzyme in both fractions. When cells are subcultured there occurs within a few hours an increase in the acid invertase and a decline in the neutral invertase activity in the cell wall fraction and a decline in the acid invertase of the soluble fraction prior to the large net increases in the activities of both enzymes in both locations which occurs as the cells embark upon cell division. The pattern of changes in the invertase activities through the growth cycle of batch propagated cultures is similar whether the cells are grown in sucrose, or glucose, or sucrose plus glucose; the highest levels of activities were recorded in the glucose-grown cells. The total yield of invertase activities and the distribution of activities between the soluble and cell wall fractions of the homogenates are affected by the pH of the extraction medium (within the range pH 4.0–8.0). It has not proved possible to completely remove the invertases from the cell wall fraction; upwards of 50 % of the acid invertase was recovered from this fraction by treatment with Triton-X followed by urea, but these treatments inactivated a high proportion of the neutral enzyme. These findings are compared with other studies on the activity and intra-cellular distribution of plant invertases and the possible roles of these enzymes discussed.

On the creep rupture of structures

Abstract: A study is made of the failure times of structures made of materials which suffer creep deformation and which crack according to the Kachanov law in which strain and damage rates are given in terms of the existing stress and state of damage. For certain types of structures, it is shown that lower bound estimates of the failure time can be made by considering the variation of a certain global parameter.

IMPERIALISM AND THE PROFESSIONS: Notes on the Development of Professional Occupations in Britain's Colonies and the New States.*

Abstract: The sociology of the professions, as a specialist field, today stands almost alone in ignoring the third world. Despite the weight of fashion, textbooks and readers on the subject obstinately exclude the by now obligatory chapter or section on development. While in some circumstances such spirited rearguard inaction might evince sneaking admiration, an exclusion of the problems of underdevelopment is difficult to understand. This lacuna in the literature is particularly surprising as those social scientists who are concerned with the fate of the third world continually point to the significance of professional occupations for economic and social development. In fact, a maj or theme of the sociology of professions as it relates to changes in the distribution of power in industrialized societies, finds a direct parallel in the literature concerned with 'elites' and emergent stratification systems in the underdeveloped countries of Africa and Asia. The parallel exists to the extent that in both contexts the professions have been regarded as a positive force for social and economic betterment. The professions in the industrialised world have been seen as moderating the excesses of economic individualism by providing an occupational basis for corporate identity while, at the same time, tempering the impersonalising effects of bureaucratic organisation by upholding the values associated with individual responsibility: armed only with the authority of expertise they have humanised the formal hierarchies of the great public and private corporations. In short, the professions have provided many social theorists with a basis for optimism about the possibility of a democratic and prosperous future.! This rosy view of the professions as democratic and humanising

The Fine Structure of the Embryogenic Callus of Ranunculus Sceleratus L

Abstract: Sections of callus of Ranunculus sceleratus reveal its organization into cellular aggregates, the superficial cells of which are highly cytoplasmic and the inner cells of which are larger, have less-dense cytoplasm and are more highly vacuolated. Expansion and ultimate death of some of the internal cells leads to cell separation and break up of the aggregates. Many of the superficial cells are involved in the initiation of embryoids in the callus and they correspond in structure with the embryogenic cells of the seedling stem epidermis. The embryoids are retarded in their development in presence of 2,4-dichlorophenoxyacetic acid (2,4-D) and embryoid development becomes more rapid and more prolific when cultures are transferred to a medium without 2,4-D. The similarity between the embryogenic cells of the callus cultures and those of the seedling stem epidermis extends to cell size, nuclear size, degree of vacuolation, abundance of ribosomes and mitochondria, presence of amyloplasts and prominence of spherosomes. The various forms of spherosome are described and their possible function discussed. Amyloplasts differentiating into chloroplasts are observed in the more advanced embryoids. There is evidence that embryoids can arise from single cells but it is uncertain whether all are of single-cell origin. The embryogenic cells are in protoplasmic continuity with surrounding cells when they embark upon embryogenesis. Some of the superficial cells, also clearly undergoing active division, are of rather different structure; characteristically their nuclei show a high degree of chromatin condensation and their cytoplasm contains bundles of fibrous material. It is suggested that these cells do not function directly in embryogenesis. The internal cells of the aggregates have a low density of ribosomes and very few ER profiles or normal mitochondria. Extremely elongated mitochondrial structures following the outline of the nucleus are observed in these cells. An unidentified structure is frequently observed in cells in which cytoplasmic disorganization appears to be occurring.

Some extremal properties and energy theorems for inelastic materials and their relationship to the deformation theory of plasticity

Abstract: Fora certain class of time-independent inelastic materials it may be shown that the final state of stress following a class of stress histories may be related to the resultant strain through relationships which are identical to those of an elastic material. This result, together with extremal properties of the defined elastic material, allows a more meaningful definition of a deformation theory of plasticity than has previously been available. The theory is developed in general terms and then specialized to a class of elastic-plastic constitutive relationships.

Effect of hormonal state on cell number and functional maturation of the brain.

Abstract: IT is known that thyroid administration interferes with postnatal cell formation1 and affects the functional maturation of the brain2,3. Glucocorticoids also inhibit cell division in the brain4–6, but the ultimate behavioural consequences of treatment during infancy with thyroid and with adrenocortical hormones seem to be different2,7. In attempting to understand these differences a study was made of the effects of cortisol on postnatal cell formation in the rat brain. Further details are given elsewhere8.

Effect of metronidazole on hydrogen production by Clostridium acetobutylicum

Abstract: 1. When metronidazole (1-β-hydroxyethyl-2-methyl-5-nitroimidazole) was added at 50 μg/ml to a liquid (35°C) culture of Clostridium acetobutylicum (0.5 mg dry wt of organisms/ml), it inhibited growth for only 2 h; thereafter, growth resumed at a slower and arithmetic rate. Consumption of glucose and excretion of acetate plus butyrate continued, though at diminished rates, during the period of bacteriostasis, and the ATP content of the organisms did not decline. 2. Metronidazole inhibited production of H2 by a culture of Cl. acetobutylicum, yet it only temporarily halted formation of H2 from pyruvate by cell extracts, and had no deleterious effect on the simultaneous production of acetyl phosphate and CO2. After a relatively short time no residual metronidazole was detectable in this cell-free system and H2 production resumed at its former rate. 3. The drug did not inhibit the hydrogenases of either Cl. acetobutylicum or Cl. pasteurianum, but having an E′0 at pH 7 of approx. -0.23 V (on the hydrogen scale), it acted as a preferential acceptor of electrons from reduced ferredoxin (or reduced viologen dyes). Reduction of metronidazole was a 6 electron process compatible with complete reduction of its 5-nitro group. Yet, although the expected decrease in absorbance at 320 nm was observed, the 5-amino derivative did not accumulate (probably due to its intrinsic lability). 4. Since many aryl nitro compounds are similarly able to accept electrons from reduced ferredoxin, it seems that additional reasons might have to be sought to explain the unique effectiveness of metronidazole as an antimicrobial agent.

The anti-inflammatory effect of catecholamines in the peritoneal cavity and hind paw of the mouse

Abstract: 1. Carrageenin or 5-hydroxytryptamine-induced oedema of the mouse hind paw was antagonized by catecholamines acting on both alpha- and beta-adrenoceptors.2. Increased permeability of the mouse peritoneum induced by the local injection of acetic acid or pro-inflammatory mediators was antagonized by catecholamines acting predominantly on beta-adrenoceptors.3. The anti-inflammatory effect of catecholamines was due neither to hyperglycaemia nor to the release of adrenal cortical hormones.

Effect of growth conditions on development of the cellular slime mould, Dictyostelium discoideum.

Abstract: The effect of growth in the presence and absence of 86 mM glucose on fruiting-body number and size, fruiting-body proportions and morphogenesis in the slime mould Dictyostelium discoideum , strain Ax-2, has been investigated. Cells grown in the absence of glucose (n.s. cells) formed 2·1 times more fruiting bodies than glucose-grown cells allowed to differentiate under the same conditions and at the same cell density. Glucose fruiting bodies were 2·6 times larger than n.s. fruiting bodies. During aggregation, n.s. aggregation streams generally broke up into numerous secondary aggregation centres. Glucose streams generally did not break up but moved into the initial aggregation centre. Each secondary centre formed one small grex, whereas initial centres fragmented into several grexes which were larger than those formed from secondary centres. The preponderance of secondary centres in n.s. aggregation and of initial centres in glucose aggregation accounts for the difference in size and number of fruiting bodies. We speculate about the mechanism giving rise to the morphogenetic difference. The spore: stalk ratio was 3·95:1 in glucose fruiting bodies and 2·70:1 in n.s. fruiting bodies. This difference is not related to the difference in fruiting-body size because proportions are size invariant for both fruiting-body types. Some difference in the physiological mechanism which determines proportions is suspected.

Remanent Magnetization in Meteorites

Abstract: ALTHOUGH the existence of natural remanent magnetization in meteorites has been taken as evidence for a primaeval magnetic field in the original bodies—presumably of asteroidal dimensions—from which meteorites formed1, it seems surprising that an asteroidal core (∼ 100 km diameter as an upper limit) can sustain convective motions efficient enough to produce the magnetic field, ∼ 10−1 to 1 G, required by the NRM measurements2. Moreover, recent data suggest that iron meteorites are not necessarily fragments of a much larger core, as had been supposed, but formed as small bodies embedded in a silicate matrix3. As there is no other obvious internal mechanism for generating NRM, could an external mechanism be responsible? During the early history of the solar system, the magnetic field of the Sun may have been much more intense than it is at present, possibly ∼ 100 G (ref. 4), and the rotation of the Sun may have been much more rapid. A recent estimate for solar spin damping by the solar wind gives an e-folding time ∼2.2×109 yr (ref, 5). There are two mechanisms by which NRM could have been created in meteorites under these conditions.

The effects of indomethacin on calcium, sodium, potassium and magnesium fluxes in various tissues of the guinea-pig.

Abstract: 1. Isolated tissues of the guinea-pig were bathed with Krebs solution at 37° C and subjected to 100 ms pulses of electrical stimulation for 30 min at a frequency of 0·1 or 1·0 Hz. The tissues were then dried, ashed, and the ash analysed for calcium, sodium, potassium and magnesium. 2. Gastric smooth muscle, cardiac and skeletal muscles and brain all showed a gain of sodium and calcium and a loss of potassium in response to electrical stimulation, but there was no significant change in the magnesium content of any of these tissues. 3. Indomethacin (0·5 mM) reduced the calcium content of unstimulated gastric smooth muscle and reduced the gain of calcium and sodium in response to electrical stimulation, but slightly increased the net loss of potassium in response to electrical stimulation. 4. Gastric smooth muscle which had gained calcium as a result of electrical stimulation, gradually lost it again when stimulation ceased. Indomethacin (0·5 mM) hastened the net loss of calcium from previously stimulated muscle. 5. Indomethacin (0·5 mM) failed to alter the calcium, sodium, potassium and magnesium contents of unstimulated cardiac muscle, skeletal muscle and brain. In these tissues indomethacin (0·5 mM) also failed to prevent the changes in the content of these minerals which occurred in response to electrical stimulation.