Showing papers by "Cardiff University published in 1969"

The proteolytic action of arvin on human fibrinogen.

Abstract: 1. Human fibrinogen was subjected to proteolysis by enzyme preparations (clinical Arvin and IRC-50 Arvin) from the venom of Agkistrodon rhodostoma. 2. IRC-50 Arvin releases three peptides from fibrinogen, and these were identified as fibrinopeptides AP, AY and A. 3. The less purified ;clinical' Arvin releases, in addition to fibrinopeptides AP, AY and A, small amounts of two heptapeptides derived from fibrinopeptides AP and A, probably because it contains another enzyme as well as Arvin. 4. No fibrinopeptide B is released by either Arvin preparation. 5. Thus, although Arvin is known to differ from ;reptilase' from Bothrops jararaca in that it does not activate the enzyme that cross-links fibrin (fibrin-stabilizing factor), it is identical with reptilase with respect to the peptides that it liberates from fibrinogen.

The effect of Eh on regulatory processes in facultative anaerobes

Abstract: On increasing aeration rate in chemostat cultures of E. coli the redox potential (Eh) of the culture changes from −l50 mv to +250 mv. During this period only a slight increase in measured dissolved oxygen concentration is observed. It is suggested that Eh be used as a control variable for aeration in the oxygen limited growth condition, whilst dissolved oxygen concentration be used as control variable in the presence of excess oxygen. Change in cytochrome b1, three tricarboxylic acid cycle enzymes and hydrogenase can be related to culture Eh. These changes are discussed.

The effect of abscisic acid on stem elongation and correlative inhibition

Abstract: Summary The mature length of the second internode (which was undergoing rapid vacuolation at the time of treatment with ABA) was not appreciably affected by doses of ABA below 20 μg per plant although the rate of elongation was depressed for the first 2 days after treatment, the depression being as much as 50% in tall varieties. Doses of ABA in excess of 20 μg not only depressed elongation rate immediately, but resulted in shorter internode length at maturity. Etiolated seedlings showed a stimulation of elongation rate and mature length in the dwarf ‘Meteor’, hut no statistically significant differences in the tall variety ‘The Pilot’ with doses below 20 μg ABA. Higher doses of ABA caused immediate cessation of elongation in vacuolating internodes, but only postponed the onset of vacuolation in younger internodes. Lighted plants also showed this postponement of the onset of vacuolation in the younger internodes at higher doses; in both lighted and etiolated seedlings the normal growth rate was resumed after a delay of between 3 and 7 days. Decapitation reduced elongation rate during the subsequent 48 hours either with or without ABA. In the absence of ABA there was a subsequent recovery in growth rate of the dwarf variety so that the final length of the second internode was the same for both intact and decapitated plants. But decapitation of the tall variety produced a marked reduction in mature length of the second internode, as it did in all ABA treated plants both dwarf and tall, intact and decapitated. The only significant interaction between decapitation and ABA on elongation rate occurred in the tall variety: during the first 24 hours all doses of ABA produced approximately the same big reduction in elongation rate in intact plants but had no statistically significant effect on decapitated plants; during the second day only the higher doses of ABA reduced the elongation rate of intact plants while all three levels produced the same big reduction in elongation rate of the decapitated plants. In the dwarf variety there was no significant interaction between the decapitation and ABA effects. Lateral bud outgrowth in decapitated plants was inhibited by ABA, and 100 μg per plant achieved inhibition comparable to that produced by the apex in intact plants. Hence ABA may possibly be the inhibitory substance demonstrated to be responsible for the phenomena of correlative inhibition.

Theoretical effects of exponential band tails on the properties of the injection laser

Abstract: Calculations have been made of various GaAs injection laser properties, assuming the high doping levels present in these devices to be responsible for the formation of band tails with density of states varying as exp ( −E E 0 ) . Simple analytical expressions are obtained for carrier concentrations and emission rates, which are not possible for other forms of the band tail density of states. These expressions facilitate the solution of the laser kinetic equations and thus exact relations are derived for threshold currents, lasing frequencies, I–V characteristics, and light power outputs, both above and below threshold, within the scope of the initial approximation.

The metabolism of potassium dodecyl [35S]-sulphate in the rat

Abstract: The metabolic fate of potassium dodecyl [35S]sulphate was studied in rats Intraperitoneal and oral administration of the ester into free-ranging animals were followed by the excretion of the bulk of the radioactivity in the urine within 12hr, approximately 17% being eliminated as inorganic [35S]sulphate Similar results were obtained in experiments in which potassium dodecyl [35S]sulphate was injected intravenously into anaesthetized rats with bile-duct and ureter cannulae Analysis of urinary radioactivity revealed the presence of a new ester sulphate (metabolite A) This metabolite was isolated, purified and subsequently identified as the sulphate ester of 4-hydroxybutyric acid by paper, thin-layer and gas chromatography, by paper electrophoresis and by comparison of its properties with those of authentic butyric acid 4-sulphate The identity of the metabolite was confirmed by isotope-dilution experiments When either purified metabolite A or authentic potassium butyric acid 4[35S]-sulphate was administered to free-ranging rats the bulk of the radioactivity was eliminated unchanged in the urine within 12hr, approx 20% of the dose appearing as inorganic [35S]sulphate Whole-body radioautography and isolated-liver-perfusion experiments implicated the liver as the major site of metabolism of potassium dodecyl [35S]sulphate It is suggested that butyric acid 4-sulphate probably arises by ω-oxidation of dodecyl sulphate to a fatty acid-like compound, which is then degraded by β-oxidation

Studies on the pelvis in British Muridae and Cricetidae (Rodentia)

Abstract: The morphology and its variation of the bony pelvis in British species of Muridae and Cricetidae have been studied. The investigation began with the application of a mensural method for demonstrating sexual dimorphism and it is shown that for all species except those of Rattus the male os coxa can be distinguished from the female over a wide range of ages. During the study it became obvious that there are ranges of morphological variation in os coxae both inter- and intraspecific. There are constant interpecific differences which allow identification of os coxae of these rodents at least to genus and in many cases to species. Detailed descriptions of the morphology of the os coxa of each species are given together with an identification key. Intraspecific variation is mainly sex-dependent and comprises sexual dimorphism, male pubertal changes and female parturition changes. The changes in the male are from epicene, through pubertal, to post-pubertal phase, with the first of these resembling the agonadal, female, form and the last with a posterior border thickened and tuberculate in relation to the hypertrophied penis and its associated glands and musculature. These phases are not equally obvious in all species, but the pelvis in all except Rattus and Mus shows some evidence of the sexual development of the animal. In females the form of the pelvis may be modified during successive pregnancies to allow a wider pelvic outlet for parturition. Resorption and remoulding of the female pelvis allows the recognition of non-parous, uniparous and multiparous animals in all Cricetid species, in Micromys and, more doubtfully, in Mus, but not in Apodemus and Rattus. Non-sex-dependent intraspecific variation, comprising differences in rugosity related to muscularity is also described. The observations are discussed in relation to earlier experimental work, to the need for basic research on small mammal reproduction and population structure, and to the use of the pelvis in the analysis of osteological assemblages, such as occur in owl pellets.

The Physiology of Encystment of Hartmannella castellanii

Abstract: SYNOPSIS. Some aspects of the physiology of encystment of the soil amoeba Hartmannella castellanii in a replacement encystment medium consisting of 5 × 10-2 M MgCl2 have been investigated. It is suggested that measurement of the cellulose produced during encystment in the synthesis of the cyst wall is a more reliable measure of the process than other methods tried. The degree of encystment was dependent on the physiologic state of the amoebae and the composition of the growth medium, but the initial pH of the encystment medium (C. 4.0-8.5) had little effect on the process. The requirement for Mg during encystment was probably not due to its deficiency during growth. Encystment was inhibited to varying extents by inhibitors of protein synthesis, tetracycline and chloramphenicol and also by arsenate, arsenite and iodoacetate; sodium fluoride, malonate and 2, 4-dinitrophenol were without marked effect. Addition of glucose and α-ketoglutarate to the replacement medium led to improvement in the encystment response. The presence of glutamate and histidine during encystment led to cell death. Other carbon and nitrogen sources had no effect. During encystment there was an increase in the metabolic activity of the amoebae, as measured by their oxygen consumption. This was accompanied by a decrease of about 40% in cellular dry weight and protein content. Of the other chemical components, there were marked initial increases in the levels of total carbohydrates and pentose which were followed by their depletion during cellulose synthesis. Encystment was completed after about 64 hr when the synthesis of cellulose was complete and the oxygen uptake of the amoebae fell to an immeasurable level.

Electronic air filter means

Abstract: AN ELECTRONIC AIR FILTER MEANS INCLUDING DUCT MOUNTED AIR FILTER STRUCTURES AND WALL MOUNTED AIR FILTER STRUCTURES, EACH ADAPTED TO RECEIVE AIR FLOW THROUGH A PRE-FILTER ASSEMBLY, A PLURALITY OF IONIZER ASSEMBLIES, PARTICLE COLLECTOR MEANS, AFTER-FILTER AGGLOMERATOR ASSEMBLY, AND UTILIZING CONTROL MEANS TO PROVIDE POWER FOR THE PROPER CHARGING OF FOREING PARTICLES WITHIN THE AIR FOR REMOVING THE SAME ON PASSAGE THERETHROUGH. MORE PARTICULARLY, DISCLOSED IS AN AIR FILTERING MEANS HAVING MODULAR ELECTROSTATIC PRECIPITATOR MEANS OPERABLE TO SEPARATE FOREING PARTICLES FROM A GIVEN AIR FLOW THERETHROUGH, THE PRECIPITATOR MEANS HAVING IONIZER UNITS AND PARTICLE COLLECTOR UNITS READILY REMOVABLE FOR SERVICE AND MAINTENANCE WITH A MINIMUM AMOUNT OF TIME AND EFFORT REQUIRED.

Studies on the host-parasite interface of strigeoid trematodes. IV. The ultrastructure of the lappets of Apatemon gracilis minor Yamaguti, 1933.

Abstract: The ultrastructure of the lappets of Apatemon gracilis minor Yamaguti, 1933, has been described The tegument covering the lappets is characterized by the presence of long seta-like structures and unicellular gland cells which exhibit a holocrine type of secretion The setae contain extensions of the tegument cytoplasm and are supported by a bundle of fibrils The unicellular gland cells are pear-shaped with the tapering neck supported by a ring of 50–60 microtubules The secretion consists of relatively large, membrane bounded bodies containing a fine granular material The lappets are regarded as representing a specialized host–parasite interface in which adaptation exists for attachment to the host tissue and the discharge of secretion from the parasite at this region The concept of the specialized host–parasite interface is discussed and extended to include Apatemon gracilis minor The author wishes to acknowledge the research grant provided by the SRC for the purchase of a vacuum coating unit and an AEI EM 6 electron microscope The progress of this study was greatly facilitated by the excellent assistance of Mr T Davies and Miss C Green The stereoscan micrograph (P1 1, fig 2) is published by permission of the Cambridge Instrument Company

Encystment in Amoebae

Abstract: Publisher Summary This chapter focuses on encystment of amoebae. Many of the eucaryotic protista appear to be capable of encystment. In some cases, the formation of a cyst is related to the processes of sexual or asexual reproduction, but it is generally considered to be a response to environmental conditions that are suboptimum for growth of the organism. Encystment usually involves a drastic reorganization of the subcellular structure of the vegetative cell in which cilia, flagella, vacuoles, and other inclusions disappear. Much of our knowledge of encystment is based on data, which are included in reports of a general nature. Encystment can also be considered as an example of cellular differentiation. Many of the earlier investigations of encystment were carried out in mixed cultures, which ranged from the completely agnotobiotic to monoxenic cultures in which the protozoan was grown with a known microbial associate, usually a bacterium. The first ten hours of encystment in non-nutrient replacement media is marked, in H . castellanii, by an increase in the rate of oxygen uptake of the amoebae. After this initial increase, the rate of oxygen consumption decreases gradually to an immeasurable value by the time cyst formation is complete. The amoebae also show changes in the utilization of exogenous substrates during the first ten hours of encystment.

A path integral approach to disordered systems

Abstract: The exact expression for the average propagator of a completely disordered system is evaluated by using a method of expansion in terms of cumulants defined over the Feynman measure. The expansions are evaluated for a one-dimensional model of delta function potentials and for a three-dimensional screened Coulomb potential to give the asymptotic form of the density of states for | E | →∞. Using a functional Taylor expansion it is shown that the average propagator may be expanded to give approximate non-linear integral equations for either the average propagator or average Green function. Using the cumulant formulation it is shown that an effective quantum potential may be defined in terms of which the propagator may be calculated.

Inhibitor of factor viii in mild haemophilia

Abstract: Summary. Two patients with mild haemophilia developed inhibitors of Factor VIII during replacement therapy to cover major surgery. The inhibitors inactivated not only transfused antihaemophilic factor but also the patient's own Factor VIII and temporarily converted them to severe haemophiliacs. The activity of the inhibitors rapidly declined, possibly as a result of steroid therapy, and both patients eventually regained their previously mild haemophilic state.

Extravascular protein in the renal medulla

Abstract: The permeability to protein of the vessels of the renal medulla in the rat was studied by intravenous injection of Evans' Blue or fluorescent-labelled serum, followed by perfusion of the whole vascular system with saline. The vessels of the inner medulla and the vasa recta of the vascular bundles of the outer medulla were found to be rapidly and freely permeable to protein. Electron microscopy, after the injection of ferritin, Thorotrast or colloidal gold, showed the vessels probably concerned in the protein leak to be ascending vasa recta and the capillaries of the medulla. The findings support suggestions that extravascular albumen is important in the process of concentration of the urine.

A simple replication technique for the study of biological tissues by electron microscopy.

Abstract: Extensive use has been made of the ' ultra-thin sectioning' technique for the study of biological tissues by electron microscopy, and a new understanding of the relationship between structure and function has developed from these studies. However, these techniques have been of little value in the study of hard body or pathogenic particle localization within tissues. The thinner the tissue section, the more liable it is to disintegrate and tear when hard particles, embedded in the tissue, are caught on the cutting edge of the ultramicrotome knife. Although the diamond knife has been useful in the study of such particles, the possible deposition of the particle by the knife in a false position, and the disintegration of fine crystals embedded within the tissue makes the sectioning technique unreliable for investigations of this type. The technique described in this communication provides a relatively simple means for studying such particles by use of a replicative procedure. Many specimen types can be studied by this method including fresh or fixed tissue and paraffin-embedded sections (Pooley & Henderson, 1966a, b). It can be used for the identification of foreign bodies within biological tissue such as lung or tumour tissue, and for the localization of the material within the tissue. Furthermore, the examination of the surfaces of biological material, such as blood cells, muscle and bone, is possible with this technique. Such preparations are of value when used in association with the scanning electron microscope, which is concerned primarily with the details of the surface structure. Tissue to be examined is embedded in sheets of cellulose acetate. Fresh unfixed material can be embedded directly whereas tissue which is softer or wet is dehydrated in vacuo to provide increased rigidity. Paraffin from routinely fixed histological specimens is removed by immersion in xylene, before dehydrating in ethanol and embedding on cellulose acetate. The sheets of cellulose acetate, at least 0.5 mm thick, are cut into 25 x 25 mm squares which are then mounted (Fig. la) on a microscope slide for ease of handling. The surface of the cellulose acetate is softened with acetone and the tissue is embedded either by merely allowing it to settle, or as is occasionally required, by the application of some direct pressure (Fig. Ib). Care is necessary to prevent complete immersion of the surface to be replicated. Histological sections mounted on a slide, are impressed on to the softened surface of the cellulose acetate and left to harden (Fig. lc). Scalpel trimming of the embedded

The Dependence of Cd Diffusion and Electrical Conductivity in CdS on Cd Partial Pressure and Temperature

Abstract: The diffusion coefficient of Cd in undoped single crystal CdS has been measured at 850 °C as a function of Cd pressure, pCd, by a radiotracer method. The electrical conductivity of similar CdS samples has also been measured as a function of pCd in the temperature range 660 to 950 °C. It is concluded that the defects V″Cd and Cd are responsible for Cd diffusion at 850 °C and that a satisfactory account of the results can be given in terms of Cd interstitials and vacancies plus a residual shallow foreign donor. A model for the defect structure in CdS at 850 °C is presented in terms of Cd vacancies and interstitials. Der Diffusionskoeffizient von Cd wurde bei 850 °C als Funktion des Cd-Drucks, pCd, in undotierten CdS-Kristallen mit einer Radiotracermethode untersucht. Die elektrische Leitfahigkeit ahnlicher CdS-Proben in Abhangigkeit von pCd wurde ebenfalls im Temperaturbereich 660 bis 950 °C gemessen. Es wird geschlossen, das die V″Cd und Cd-Defekte fur die Cd-Diffusion bei 850 °C verantwortlich sind, und das eine befriedigende Deutung der Ergebnisse mit der Annahme von Cd auf Zwischengitterplatzen und Cd-Leerstellen und einem restlichen flachen Fremddonator gegeben werden kann. Ein Modell der Defektstruktur in CdS bei 850 °C wird mit Cd-Leerstellen und Cd-Zwischengitterplatzen angegeben.

Correlation problems of metamorphosed Pre-Cambrian rocks in Wales and S.E. Ireland

Abstract: The lithological and structural characteristics of the metamorphosed Pre-Cambrian rocks of Wales and Leinster are reviewed, and the Dutch Gin Schists are not accepted as a stratigraphical unit. The Bray Series, Cullenstown Group, Ballycogly Group and Bedded Succession of North Wales are regarded as parts of a single Monian System which accumulated in a Caledonoid trough and was involved in a late Pre-Cambrian orogeny. The latter also affected the pre-Monian basement, parts of which (possibly unrelated to one another) are seen in the gneisses of Co. Wexford (Rosslare Complex), Lleyn and Anglesey.