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Biomedical subjects

M Adrian

Publications and source records attributed to M Adrian.

At least 19 recordsLinked to original sources
PubMed1992

The apical localization of transcribing RNA polymerases on supercoiled DNA prevents their rotation around the template.

The interaction of Escherichia coli RNA polymerase with supercoiled DNA was visualized by cryo-electron microscopy of vitrified samples and by classical electron microscopy methods. We observed that when E. coli RNA polymerase binds to a promoter on supercoiled DNA, this promoter becomes located at an apical loop of the interwound DNA molecule. During transcription RNA polymerase shifts the apical loop along the DNA, always remaining at the top of the moving loop. This relationship between RNA polymerase and the supercoiled template precludes circling of the RNA polymerase around the DNA and prevents the growing RNA transcript from becoming entangled with the template DNA.

Binding Sites↗
PubMed1992

Scanning force microscopy and cryo-electron microscopy of tobacco mosaic virus as a test specimen.

In this study, tobacco mosaic virus (TMV) provides a resolution criterion for specimen preparation methods as well as for imaging parameters of the scanning force microscope (SFM). We present scanning force microscopic images of the virus embedded in 0.5% buffered phosphotungstic acid solution adsorbed on a freshly cleaved mica surface, and imaged under atmospheric conditions. Individual TMV particles were clearly identified with a characteristic shape of long rods of about 300 nm long and 60-70 nm in apparent width due to the geometric parameters of the tip. The structure of the virus was compared with cryo-electron microscopic data of vitrified suspensions observed to a resolution of 1.15 nm. Uncoated TMV particles were also deposited on evaporated titanium thin films and imaged by SFM.

Cryopreservation↗
PubMed1992

In vitro decapsidation of turnip yellow mosaic virus investigated by cryo-electron microscopy: a model for the decapsidation of a small isometric virus.

The in vitro decapsidation of a small isometric plant virus, turnip yellow mosaic virus (TYMV), was investigated by cryo-electron microscopy. Cryo-electron micrographs of TYMV and empty shells show that rapidly frozen virions still contain their RNA. Images of vitrified virions resemble closely those previously obtained by negative staining. Rapidly frozen virions decapsidate upon thawing although they remain well dispersed on the grid. The escape of the RNA through a hole at the periphery of the capsid could be visualized. The results suggest a model for the in situ decapsidation of small icosahedral viruses.

Capsid↗
PubMed1991

Secreted acid phosphatase of Leishmania mexicana: a filamentous phosphoglycoprotein polymer.

In the promastigote, or insect stage, most species of the parasitic protozoan Leishmania secrete an acid phosphatase. The enzyme purified from the culture medium of Leishmania mexicana is shown to be a complex [13.3% (wt/wt) protein, 74.4% (wt/wt) carbohydrate, and 12.3% (wt/wt) phosphate] composed of a predominant phosphorylated glycoprotein with a relative molecular mass of 100 kDa and noncovalently associated high molecular mass (proteo)phosphoglycans. Electron microscopy discloses long filaments composed of a central chain of protein subunits surrounded by a diffuse glycocalix that can be decorated by monoclonal antibodies or concanavalin A. In contrast to the polymeric structure of the L. mexicana enzyme, the acid phosphatase secreted by Leishmania donovani is mono- or oligomeric but not filamentous.

Acid Phosphatase↗
PubMed1991

The three-dimensional structure of reovirus obtained by cryo-electron microscopy.

The structures of reovirus serotypes T2J (Jones), T3D (Dearing) and the T3D core particle have been determined by cryo-electron microscopy and image processing. At a resolution of 30 A the two serotypes have similar features. The core is visible within the virus structure. The outer surface of the virus particles contains 120 holes at T = 13.1 local 6-fold axes. The holes penetrate into the virus as far as the surface of the internal core shell. Protrusions extending 4 nm from the virus surface surround each hole on the outside of the virus. At the 5-fold axes on the surface of the virus flat 'penton craters' form covers over the underlying core spikes. The detailed structure of the reovirus shell is very different to that of rotavirus although both have holes at T = 13.1 axes. Little evidence was seen of reovirus fibres extending from the virus surface.

Image Processing, Computer-Assisted↗
PubMed1991

Long-term trends in male drunkenness arrests in metropolitan Toronto: effects of social-setting detoxication centers.

Drunkenness arrest rates for adult males in Toronto decreased substantially during the period 1966 to 1987. In 1971 there was a change in legislation permitting police to take public inebriates to detoxication centers. Drunkenness rates continued to decline at a rate similar to that for the previous 3 years. The next year drunkenness arrests increased but subsequently declined at a rate which was 50% greater than that which preceded the change in legislation. Since 1973 year by year changes in the rate of male drunkenness arrests have not been consistently related to rates of police admission to detoxication centers or to total admissions to detoxication centers. The results suggest that recent trends in drunkenness arrests have been influenced by the 1971 change in legislation and the increased use of detoxication centers. However, the influence of other factors must also be considered.

Alcoholism↗
PubMed1990

Structure of adenovirus fibre. I. Analysis of crystals of fibre from adenovirus serotypes 2 and 5 by electron microscopy and X-ray crystallography.

An analysis by electron microscopy in amorphous ice and X-ray diffraction of four types of three-dimensional crystals of adenovirus fibre is presented. Fibre from adenovirus type 2 (Ad2) crystallizes in two forms depending on whether it is native or cleaved near the N terminus at Tyr17. Fibre from Ad5 also crystallizes in two forms, both of which contained fibre cleaved at Tyr17. Analysis of the packing of the fibres in each of these crystals suggests that the overall length of the fibre may be considerably longer (about 350 to 370 A) than previously reported. Crystals of cleaved Ad2 fibre are of sufficient quality to be characterized by X-ray diffraction. They are of space group C2 and cell dimensions a = 134.4 A, b = 77.6 A, c = 539.4 A, beta = 92.7 degrees. These crystals are remarkable in that, despite being monoclinic, the ab plane forms a perfect hexagonal lattice. This is explained by a trigonal packing of the trimeric fibre heads in the crystal. A similar feature is found for one type of Ad5 crystal, although the hexagonal lattice is 12% smaller. The crystals of cleaved Ad2 show very strong meridional intensity at a Bragg spacing of 4.4 A and weaker diffuse intensity corresponding to layer-lines of spacing 26.4 A. This must reflect the quasiperiodicity of the structure of the fibre shaft, which is apparent in the primary sequence. The occurrence of these features combined with the new determination of the length of the fibre (see also the accompanying paper) require a reappraisal of the cross-beta model of the fibre shaft proposed by Green et al.

Adenoviridae↗
PubMed1990

Direct visualization of supercoiled DNA molecules in solution.

The shape of supercoiled DNA molecules in solution is directly visualized by cryo-electron microscopy of vitrified samples. We observe that: (i) supercoiled DNA molecules in solution adopt an interwound rather than a toroidal form, (ii) the diameter of the interwound superhelix changes from about 12 nm to 4 nm upon addition of magnesium salt to the solution and (iii) the partition of the linking deficit between twist and writhe can be quantitatively determined for individual molecules.

DNA, Superhelical↗
PubMed1990

Evaporation during preparation of unsupported thin vitrified aqueous layers for cryo-electron microscopy.

Evaporation of water cannot be fully avoided when an unsupported thin vitrified film of an aqueous suspension is prepared for cryo-electron microscopy. This results in increasing concentration of solute which could affect the observed material. We have quantitatively studied this effect by measuring the contrast of polystyrene spheres in a metrizamide solution. The drying effect is generally negligible when specimens are prepared on a hydrophilic perforated support but it is frequently important when hydrophobic films are used instead. A flow of humid air, double blotting with minimal exposure of the thin liquid film to the atmosphere, or an automatic plunger optimizing the blotting conditions are simple methods for reducing drying effects. With this third device acting on a hydrophilic supporting film, the increase of solute concentration is limited to less than 20%.

Cold Temperature↗
PubMed1990

Influence of carnitine acyltransferase inhibitors on the performance and metabolism of rat cardiac muscle.

The effects of carnitine palmitoyl transferase I inhibitors were studied in isolated perfused rat heart and in in vivo studies with normal and diabetic rats. In isolated perfused rat hearts of acutely diabetic and Zucker rats, clomoxir (sodium 2[5(4-chlorophenyl)pentyl]oxirane-2-carboxylate) inhibited the oxidation rate of endogenous fatty acids and increased the oxidation rate of glucose. Etomoxir, an analogue of clomoxir, was used in the in vivo studies with normal and chronic diabetic rats. Etomoxir (18 mg/kg) was given daily for 6 days by intraperitoneal injection. This carnitine palmitoyl transferase inhibitor significantly ameliorated the decreased heart performance in diabetic rats. The concentrations of glucose, glycerol, triacylglycerol, cholesterol, and phospholipids in serum were lower compared with untreated diabetic animals. On the other hand, the lipid and the carnitine content of heart and liver increased in the etomoxir-treated rats. Carnitine palmitoyl transferase inhibitors have clear antidiabetic effects, but before using as an oral antidiabetic drug, the long-term changes of the lipid and carnitine metabolism should be evaluated.

Acyltransferases↗
PubMed1978

[Spirochetes: coiling direction].

On electron micrographs of spirochetes, the axial fibers are alternatively visible and hidden, i.e. above then under the cytoplasmic cylinder. From this observation the sense of coiling can be inferred. Leptospires are right-handed structures. So are other spirochetes, but it is less conspicuous. The opposite, however, appears on most published photographs and on schematic drawings. The explanation would be that the preparation introduced into the electron microscope was not facing the photographic plate, but turned to the electron beam. Also the picture must not be turned over, neither in the photographic laboratory nor when used as a slide.

Leptospira↗
PubMed1978

[Absorption and oxidation rate of arginine and malate (author's transl)].

Six normal volunteers received L-Arginin and DL-Malat p.o. in order to test absorption and utilisation of these compounds. Both compounds are almost completely reabsorbed from the intestine and then metabolized. Only about 2% of the arginine applied are recovered in the urine. 15% of arginine and 45% of malate applied are metabolized within 8 hours. If absorption is unimpaired oral therapy of hyperammoniemia would require application of the malate-arginine solution for every 3 hours, if constant plasma levels are to be achieved.

Adolescent↗
PubMed1977

[Audiometry and cytological study of the external hair cells of 4 strains of mice].

The auditory apparatus of two strains of mices with normal audition is compared to that of two substrains with genetic auditory impairment. Audiometry by auditory evoked potentials at the inferior collicular level indicates complete deafness for one substrain and a 40-48 dB S.P.L. hearing loss at all frequencies for the other. Scanning and transmission electron microscopy demonstrate hair impairment of the external hair cells and degeneration of the chondriosome for the two deaf substrains.

Animals↗
PubMed1977

Electrogoniometric analysis of equine metacarpophalangeal joint lameness.

Electrogoniometry was used qualitively and quantitatively to assess the movements of the normal and pathologic metacarpophalangeal joints of selected horses. A total of 4 Thoroughbreds, 1 normal and 3 with clinical and radiographic changes in the metacarpophalangeal joints of 1 limb, were evaluated at the walk and trot. Goniograms of the affected joints were compared with those of the normal horse and the normal contralateral metacarpophangeal joint. Qualitative asymmetry was recognized on the goniograms, and the ranges of motion were quantified and related to the clinical and radiologic observations.

Animals↗
PubMed1975

[Electron microscopic study of the penetration and distribution of somitic cells in the mesoblast of the limb buds of reptiles (Anguis fragilis and Lacerta viridis)].

Based on characteristics of mitochondria and on the amount of lipid inclusions, a distinction between somitic cells and mesoblastic somatopleural cells is possible, at the early stages of the development of the limb bud in Reptiles (Anguis fragilis and Lacerta viridis). The dislocation of the ventral processes of the somites and the localisation of the somitic cells in the mesoblast of the anterior limb buds could be studied.

Allantois↗