Showing papers by "University of Glasgow published in 1970"

Mutagenesis by N-methyl-N′-nitro-N-nitrosoguanidine (NTG) in Streptomyces coelicolor

Abstract: Mutagenesis was tested by the reversion of several auxotrophic mutations and by the induction of auxotrophs. Mutagenesis at alkaline pH was quantitatively related to the release of an unstable, mutagenic intermediate of NTG decomposition, presumably diazomethane. No evidence was obtained for mutagenesis by undecomposed NTG at pH 5. At very acid pH (2.5), there was weak mutagenesis, associated with high lethality, presumably by a different mechanism from that operating at alkaline pH. Effective mutagenesis in Streptomyces requires a longer and more intense treatment than in some other microbes; suitable conditions are described.

Spindle microtubules in the dividing nuclei of trypanosomes.

Abstract: Stages in nuclear division have been identified in sections of bloodstream and cultured trypanosomes examined with the electron microscope. In the sleeping sickness trypanosome Trypanosoina rhodesiense at division the nuclear envelope and nucleolus-like endosome persist and become stretched along an axis. An acentric spindle of microtubules encases the elongating endosome As division proceeds the endosomal material fragments In bloodstream forms condensed chromatin (chromosomal material) appears to be associated with the nuclear envelope during the phase of nuclear elongation but to fall away from the envelope late in the phase of nuclear constriction. In culture forms the chromatin is not so abundant The discrete chromosomes envisaged by some light microscopists in stained preparations have not been identified using the electron microscope. The spindle may contain only continuous microtubules. It is suggested that the spindle serves to push the two halves of the nucleus apart, and that the nuclear envelope of each half may act as a vehicle in separation of the daughter genomes. In culture forms of the elasmobranch parasite T. raiae , the endosome appears to disintegrate as the spindle is formed, and from then onwards it becomes difficult to distinguish endosomal material from what might be chromatin. There is no noticeable association between chromatin-like material and the nuclear envelope. Some of the spindle tubules converge on kinetochore-like plaques and the presence of chromosomal microtubules cannot be ruled out. These preliminary studies indicate that the nuclear division process of trypanosomes is not closely akin to eukaryote mitosis, though it may bear some resemblance to nuclear division in Euglena . Within the genus Trypanosoma , moreover, the nuclear division process may vary from species to species and, possibly, even from one strain to another within a species.

Infection of the feet and nails with Hendersonula toruloidea.

Abstract: In 8 individuals a fungus infection of the feet and/or toenails was diagnosed microscopically. The only isolate, Hendersonula toruloidea, was obtained from a high proportion of culture inocula and is apparently capable of causing a condition clinically and microscopically indistinguishable from a dermatophyte infection. It would seem to be significant that H. toruloidea is most prevalent in tropical climates and there is a preponderance of individuals from such areas infected with this fungus.

The genetic analysis of regulation of amidase synthesis in Aspergillus nidulans. I. Mutants able to utilize acrylamide.

Abstract: Aspergillus nidulans uses an acetamidase enzyme to grow on acetamide as a carbon or as a nitrogen source Acrylamide is a substrate for the enzyme but does not induce its synthesis Mutants capable of growing on acrylamide as a nitrogen source have been isolated Two classes of mutant have been found —amdRc mutants on linkage group II andamdTc on linkage group IIIamdRc mutants produce high constitutive acetamidase levels The enzyme is still inducible by amides, but to a lesser extent than wild type, and is still subject to repression by ammonia and by carbon metabolites derived from glucoseamdRc mutants are semi-dominant to the wild type allele in heterozygous, diploids TheamdTc mutant is not subject to carbon metabolite repression, of the acetamidase The enzyme is inducible by amides and repressible by ammonia TheamdTc mutation also results in reduced ability to grow on formamide as a nitrogen source and to lowered levels of a second amidase enzymeamdTc is semi-dominant in heterozygous diploids

Moraines at Fjallsjökull, Iceland

Abstract: During the last 70 years, Fjallsjokull has been retreating from a position clearly marked by moraine ridges 5 to 10 m high. Inside these large moraines a series of moraine ridges, 1 to 4 m high, ha...

The fine structure of the infundibulum and magnum of the oviduct of gallus domesticus

Abstract: The mucous membrane of the infundibulum and magnum of the hen's oviduct is modified for the receipt and fertilization of the yolk and the elaboration of the bulk of the solid material making up the white of the egg. The secreting surface is arranged in a series of ridges which are particularly elaborate in the neck region of the infundibulum. The surface is lined with columnar epithelial cells and there is a sub-epithelial layer of tubular glands. There are two types of epithelial cell; ciliated, with little evidence of secretory activity; and granular, with the intracellular structure of a glycoprotein secreting cell. In the infundibulum the granular cells have electron dense granules and the tubular glands arise as invaginations from the epithelium of the deep crypts between the mucosal folds. The gland cells are structurally similar to the epithelial granular cells and have a characteristically large infranuclear granular endoplasmic reticular (GER) space filled with homogeneous material of low electron density, probably representing storage of synthesized protein. In the magnum the granules of the epithelial cells are of low electron density and fill the whole of the distended granular cell in the lower magnum, compressing the neighbouring ciliated cells. Three types of tubular gland cell are described in the magnum: Type A, filled with electron dense granules; Type B, filled with large masses of homogeneous material of low electron density; and Type C, occupied by GER cisternae together with a large and prominent Golgi area. The C cells, which are found in the magnum immediately after the passage of the egg, are regarded as the recovery phase of A cells which have discharged their granules on the passage of the egg. There is evidence that the dense granules of the A cells represent ovalbumin, the commonest protein of the egg white. The fibrous glycoprotein, ovomucin, with its large carbohydrate component, is probably produced by the granular cells of the magnum epithelium. There is a partial discharge of the secretion of the cells of the mucous membrane in response to the presence of the yolk. The nature of the secretion and the origin of some other components are discussed.

An electron microscopic study of the hydrolysis products of zirconyl chloride

Abstract: The hydrolysis products of zirconyl chloride, produced by reflux of a 0.055 M solution, have been studied by high-resolution electron microscopy. Removal of samples of the solution at various stages of hydrolysis, together with examination of the solids obtained by rapid dehydration of these samples, has enabled structural units consistent in size with the tetrameric cation [Zr(OH) 2 4H 2 O] 4 8+ to be resolved in the electron microscope. These data indicated that there were species present in solution similar to those present in crystalline zirconyl chloride octahydrate. Later stages of the hydrolysis produced polymerization of these species until monoclinic ZrO 2 was obtained. A suggested mechanism relating these various structures was supported by pH measurements taken during the hydrolysis.

Electrochemistry of Insect Muscle

Abstract: Publisher Summary Insect muscles, although always striated, can be broadly classified into skeletal, cardiac and visceral muscles. The skeletal muscles originate and insert on skeletal structures (endoskeleton orexoskeleton) while the visceral muscles invest the internal organs and lack strict origins and insertions. A number of different types of insect skeletal muscle fibre have been described. These fibres differ in the number and disposition oftheir nuclei and mitochondria, in the arrangement and amount of sarcoplasmic reticulum (SR) and sarcoplasm, and in the structure of their myofibrils. Insect skeletal muscles are innervated by two main classes of motoneurone, excitatory and inhibitory. The fibres of some muscles receive endings from more than one axon—they are polyneuronally innervated. The nature of the nervous innervation is of considerable importance in terms of the electrochemistry of insect skeletal muscle fibres for it is shown that the ionic basis for electrogenesis at inhibitory synapses is strikingly different from that at excitatory synapses. Insect cardiac muscle has a micromorphology more reminiscent of insect gut muscle and muscle of the insect reproductive system than of vertebrate cardiac muscle. Information on the innervation of insect visceral and cardiac muscles and on the nervous and endocrine control of activity of these muscles is quite extensive but, as yet, rather inconclusive.

The organ-specificity of ferritin in human and horse liver and spleen.

Abstract: 1. Ferritin was isolated from human and horse spleen and liver, and apoferritin prepared therefrom. 2. The electrophoretic mobilities of the four apoferritins were determined on polyacrylamide gels and on cellulose acetate strips, and all found to be equal. 3. Homologous ferritins share reactions of identity in immunodiffusion experiments, whereas heterologous ferritins show only partial identity. 4. The subunit molecular weight of each of the apoferritins was determined by polyacrylamide-gel electrophoresis in sodium dodecyl sulphate and by chromatography on agarose columns in 6m-guanidine–HCl. A value of approx. 18500 was found in all cases. The proteins all had sedimentation coefficients of 17–18S. It thus seems that they have identical quaternary structures. 5. The amino acid compositions of the proteins revealed distinct differences both between organs and between species. This was confirmed by analysis of the tryptic peptide patterns, where it was found that about one-third of the peptides were common to the four proteins and the other two-thirds varied from protein to protein. 6. It is concluded that the apoferritins present in the liver and spleen of human and horse are both organ- and species-specific. 7. The apoferritin isolated from the liver of a patient with idiopathic haemochromatosis was identical with normal human liver apoferritin by the criteria described above.

Polychotomous quantal response by maximum indicant

Abstract: where (D is the standardized normal distribution function, and A and B are unknown parameters. The purpose of an informative experiment which subjects n units to a stimulus, the ith unit receiving strength xi, is simply the estimation of the parameters A and B, or some function of them, for example -A/B, the so-called LD50. The mechanism traditionally visualized in this confrontation between stimulus and subject is that each subject has some specific natural tolerance to the stimulus and will respond if and only if the strength of the stimulus applied exceeds this value. On the assumption that tolerance is N(,t, o2), i.e. normally distributed with mean It and variance o2, over the experimental units, the probability that a unit, chosen at random, responds to a stimulus strength x is

Phloem exudation from castor bean: Induction by massage.

Abstract: Exudation can be induced or greatly enhanced in Ricinus by massaging the stem periodically some time before tapping the sap by making an incision. Nevertheless temporary massage during exudation stops flow completely indicating that flow is prevented normally by a pressure sensitive sealing mechanism which becomes desensitised by regular massage.

Chapter VI The Isolation of Mutants

Abstract: Publisher Summary This chapter discusses the isolation of mutants. It is aimed primarily at the microbiologist, biochemist, molecular biologist, or pathologist, who, in the course of an investigation, needs to obtain mutant organisms to further some aspect of research. The remarks that follow are not intended for those engaged in studies of well-known genetically systems, nor in studies of mutagenesis itself, where much more specialized information is available than is summarized. The objective is to obtain the desired mutants by the most economical route, and to consider the precise mechanisms involved only in so far as they bear on the choice of experimental procedures. This chapter also mentions some of the kinds of mutants that have been isolated in various micro-organisms, and sometimes to make brief reference to the purposes for which they have been used.

Radiocarbon dating of mortars.

Abstract: CONFLICTING reports have been published in recent years on the reliability of radiocarbon dating of mortars. Delibrias and Labeyrie1 found accurate dating to be possible, but Stuiver and Smith2 found incorrect age assessments. The observed discrepancies were attributed to the dilution of 14C activity by ancient carbon which may have been a residue of the limestone from which the “CaO” was initially prepared. In addition a minor dilution effect might result if calcareous sands were used in the manufacture of the original aggregate. We have investigated further the validity of the dating technique, using a number of British mortars of accurately known age and origin provided by the UK Ministry of Public Building and Works, Ancient Monuments Branch. Radiocarbon analyses of these samples were performed by methane gas counting following acid hydrolysis of the samples and conversion of the product carbon dioxide to methane by catalytic hydrogenation3.

A revised classification of the ashgill series

Abstract: In addition to past errors in correlation and to lack of information, confusion over the lower boundary of the Ashgill Series has been brought about by a tradition of making the boundaries of the graptolitic zones fit a Standard Series based on an overwhelmingly shelly succession. In an attempt to resolve the difficulties, it is here proposed to regard the Pusgillian Stage of Bancroft as the lowest stage of the Ashgill Series. Two new stages, the Cautleyan and the Rawtheyan, are proposed for those sequences recently regarded as Lower and Middle Ashgill respectively, while Bancroft's term Hirnantian is revived as a stage name for the upper part of the Series.

Studies on ulcerative dermal necrosis of salmonids

Abstract: The gross pathology and histopathology of a series of 150 cases of UDN disease of salmon Safmo sulur L. from a number of Scottish rivers is described. The lesions appeared first as small grey areas on the heads of affected fish, which gradually enlarged in size, ulcerated and became infected with fungus of the Saprolegniu group. Histologically, the earliest lesion was an acantholysis of the suprabasal cells of the epidermis developing into transient bullae which rapidly sloughed to produce a raggcd irregular epiderm's. Once the base-ment membrane was breached secondary infection by fungi rapidly ensued. The histopathology, in the early stages, was consistent with possible viral infection, or anoxic atrophy but it was considered that the most similar lesion from mammalian experi-ence, was that of the Pemphigus group of dermatoses.

The release of renin into the renal circulation of the anaesthetized dog.

Abstract: 1. In anaesthetized dogs the rate at which renin was released into the circulation of the right and left kidneys was estimated from renal blood flow, haematocrit, and the V-A renin concentration difference across the kidney. Renin was also measured in samples of renal lymph collected at the same time. 2. The effect on renin release of reducing blood flow in one kidney was studied. For all observations (control and experimental), renal venous plasma renin concentration (RVR) was directly related to arterial plasma renin concentration and to renin release; RVR was inversely related to renal plasma flow. 3. The concentration of renin in renal lymph was considerably higher than that in renal venous plasma taken at the same time. Arterial plasma renin concentration was directly related to the sum of the rates at which renin was released from the two kidneys. 4. Clamping the renal artery of one kidney for 1 hr led to a marked reduction of renal blood flow, to a marked increase in RVR and to a variable change in renin release. Removal of the clamp was followed by increased renin release and by reversal of a previously positive V-A renin difference in the control kidney. 5. On several other occasions negative V-A renin differences were observed. That is, more renin appeared to enter the kidney in arterial blood than left in the renal vein.