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.

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.

Imaging of DNA by scanning force microscopy

The scanning probe microscopies applied to the sequencing of DNA is a challenging goal attempted by several groups. But one limitant parameter has been the sample preparation of DNA molecules. Here we report how to hold DNA molecules fixed on mica substrate and we show the three-dimensional configuration of double-stranded DNA obtained with our scanning force microscope. We can image DNA under negative supercoiling, a feature of general importance controlling the activities of DNA. We compared the electron micrographs of a carbon replica of the same DNA specimen with scanning force images which demonstrates well the feasibility and accuracy of our scanning probe measurements.

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.

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.

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.

Estimating the effect of native Indian population on county alcohol consumption: the example of Ontario

Multiple regression analysis of cross-sectional 1985-1986 Ontario county data indicated that the presence of Native Indians on reserves is a significant factor in explaining differences in county alcohol consumption levels. Consumption in counties with reserves was higher than in those without reserves by roughly 1.48 liters of absolute alcohol per adult; consumption increased as the Native reserve population increased (p less than 0.05). When income, employment, household crowding, type of industrial activity, northern isolation, and tourism were included, we could account for over 60% of the variation in alcohol consumption between Ontario counties (p less than 0.01). Every extra $1,000 in income per tax return was associated with a 0.297-liter reduction in absolute alcohol consumption. Efforts to reduce alcohol consumption in the Native population would have their greatest impact when associated with improved economic conditions.

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.

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%.

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.

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.

Benzodiazepine use and abuse in Canada

Benzodiazepines are frequently prescribed, yet the extent of their use in Canada has not been described. Such data would be valuable in assessing patient exposure to benzodiazepines and would provide a context to estimate the risk-benefit ratio of these drugs. Analysis of benzodiazepine sales in 1978-87 in Canada, expressed as the defined daily dose (DDD) per 1000 inhabitants per day, showed that the use of these drugs was stable during the first half of the decade, at 33 DDD/1000 inhabitants per day, then steadily increased from 1983 to 1987, reaching 48 DDD/1000 inhabitants per day in 1987. The total use of slowly eliminated benzodiazepines declined, whereas the overall use of rapidly eliminated benzodiazepines increased linearly. In 1978-83 Canada had the second-lowest total benzodiazepine use among several Western countries. The patterns of use and abuse of rapidly eliminated benzodiazepines in 1978-84 showed a close correlation. Our findings indicate that data on drug use can be monitored and linked to clinical data, providing a mechanism for monitoring the relation between use and related illness.

Effect of heel lifts on ground reaction force patterns in subjects with structural leg-length discrepancies

The purpose of this study was to determine the effect of heel lifts on ground reaction force patterns in subjects with structural leg-length discrepancies (LLDs). Eighteen subjects with LLDs ranging from 4.8 to 22.2 mm participated in this study. Subject age range was from 20 to 63 years. A force platform was used to obtain ground reaction force data for four conditions. Data were collected prior to fitting of the heel lift and after a three-week break-in period. Data were analyzed by use of a two-factor within-subject analysis of variance for repeated measures. Before heel-lift fitting, maximum lateral force was greater in the short leg than in the long leg. After heel-lift fitting, maximum vertical force was greater within both legs, and maximum medical force was greater in the long leg than in the short leg. The results suggest that although heel lifts are used to achieve pelvic levelness, the use of heel lifts also resulted in increased ground reaction forces, which may cause increased joint stresses within the lower extremities.

Effects of foot orthoses on center-of-pressure patterns in women

The purpose of this study was to determine the effects of foot orthoses on the pattern of center of pressure in women with forefoot deformities during walking. Nine subjects with a forefoot varus and nine subjects with a forefoot valgus walked across a force platform three times for each of the following five treatment conditions: 1) barefoot, 2) shoes only, 3) rigid orthoses with shoes, 4) semi-rigid orthoses with shoes, and 5) soft orthoses with shoes. Force data were analyzed to determine the area under the center-of-pressure curve. A significant omnibus F ratio was obtained for treatments (p less than .001) and the deformity X treatments interaction (p less than .05) using a two-factor, mixed analysis of variance for repeated measures. Tukey's post hoc comparisons for the Varus Group resulted in significant differences (p less than .05) between the following treatment conditions: 1) barefoot and shoes only, 2) barefoot and rigid orthoses with shoes, 3) barefoot and semi-rigid orthoses with shoes, and 4) barefoot and soft orthoses with shoes. Tukey's post hoc comparisons for the Valgus Group resulted in significant differences (p less than .05) between the following treatment conditions: 1) barefoot and rigid orthoses with shoes, 2) barefoot and semi-rigid orthoses with shoes, and 3) barefoot and soft orthoses with shoes. The shoes-only treatment condition, in comparison with the barefoot condition, significantly reduced the center-of-pressure area for the Varus Group only.(ABSTRACT TRUNCATED AT 250 WORDS)

Length and shape variants of the bacteriophage T4 head: mutations in the scaffolding core genes 68 and 22

The shape and size of the bacteriophage T4 head are dependent on genes that determine the scaffolding core and the shell of the prohead. Mutants of the shell proteins affect mainly the head length. Two recently identified genes (genes 67 and 68) and one already known gene (gene 22), whose products are scaffold constituents, have been investigated. Different types of mutants were shown to strongly influence the proportion of aberrantly shaped particles. By model building, these shape variants could be represented as polyhedral bodies derived from icosahedra, through outgrowths along different polyhedral axes. The normal, prolate particle is obtained by elongation along a fivefold axis. The mutations of the three core genes (genes 67, 68, and 22) affect the width mainly by lateral outgrowths of the prolate particle, although small and large isometric particles are also found. Many of the aberrant particles are multitailed, suggesting a correlation between tail attachment sites and shape.

Cryo-electron microscopy of vitrified specimens

Cryo-electron microscopy of vitrified specimens was just emerging as a practical method when Richard Henderson proposed that we should teach an EMBO course on the new technique. The request seemed to come too early because at that moment the method looked more like a laboratory game than a useful tool. However, during the months which ellapsed before the start of the course, several of the major difficulties associated with electron microscopy of vitrified specimens found surprisingly elegant solutions or simply became non-existent. The course could therefore take place under favourable circumstances in the summer of 1983. It was repeated the following years and cryo-electron microscopy spread rapidly. Since that time, water, which was once the arch enemy of all electronmicroscopists, became what it always was in nature – an integral part of biological matter and a beautiful substance.

Envelope structure of Semliki Forest virus reconstructed from cryo-electron micrographs

The basic principles of the architecture of many viral protein shells have been successfully established from electron microscopy and X-ray data, but enveloped viruses have been more difficult to study because they resist crystallization and are easily deformed when prepared for electron microscopy. To avoid the limitations of conventional techniques when applied to enveloped viruses, we have used a cryo-electron microscopy method in which unfixed and unstained viruses are observed in an unsupported thin layer of vitrified suspension. Because of electron beam damage, the many different views required for high-resolution three-dimensional reconstruction cannot be obtained from a tilt series of the same particle. The images of many differently oriented viruses are combined using a novel reconstruction method, 'reconstruction by optimized series expansion' (ROSE). The structure of the envelope of Semliki Forest virus has been reconstructed to 3.5-nm resolution. The T = 4 geometry of the surface lattice, the shape of the trimeric spikes and their arrangement on the lipid bilayer are visualized.

Cryo-electron microscopy of vitrified SV40 minichromosomes: the liquid drop model

The structure of SV40 minichromosomes has been studied by cryo-electron microscopy of vitrified thin layers of solution. In high-salt buffer (130 mM NaCl), freshly prepared minichromosomes are condensed into globules 30 nm or more in diameter. On the micrograph, they appear to be formed by the close packing of 10 nm granules which give rise to a 10 nm reflection in the optical diffractogram. The globules can adopt many different conformations. At high concentration, they fuse into a homogeneous 'sea' of closely packed 10 nm granules. In low-salt buffer (less than 10 mM NaCl), the globules open, first into 10 nm filaments, and then into nucleosome-strings. The 'liquid drop' model is proposed to explain the condensed structure of the minichromosome in high-salt buffer: nucleosomes stack specifically on top of one another, thus forming the 10 nm filaments. 10 nm filaments in turn, tend to aggregate laterally. Optimizing both these interactions results in the condensation of 10 nm filaments or portions thereof into a structure similar to that of a liquid. Some implications of this model for the structure of cellular chromatin are discussed.

pH-dependent membrane fusion is promoted by various colicins

The ability of colicin A, a bacteriocin produced by some Enterobacteriaceae, to fuse phospholipid vesicles at acidic pH, was demonstrated by electron microscopy and resonance energy transfer. The fusion depends on protein concentration and on the nature of the phospholipids. Vesicles, prepared from Escherichia coli phospholipids, fused one or more rounds at pH 4.5 upon addition of stoichiometric amounts of colicin A. Fusion was not only induced by pore-forming colicins (E1, K) but also by colicins that contain nuclease activities (E2, E3). By recombinant DNA technology it is shown that the first glycine-rich 70 NH2-terminal amino acids and, most probably, the extreme COOH-terminal end of colicin A are involved in the fusion activity of the protein. The physiological relevance of this property of colicins is discussed.

Cryo-electron microscopy of vitrified insect flight muscle

Frozen hydrated sections of vitrified unstained insect flight muscle in the rigor and relaxed states were studied by cryo-electron microscopy. High resolution images with good contrast were obtained. As judged from direct images and from the comparison of optical diffractograms with X-ray diffraction patterns obtained from glycerinated muscle fibres, the vitrified specimen is well preserved. Preparation artifacts encountered in conventional plastic sections are avoided. The preservation of the relaxed structure also seems better than in freeze-etched replicas as the 14.5 nm repeat of crossbridges on thick filaments is easily visible.

Glycolysis and glucose oxidation in the rat heart under nonrecirculating perfusion conditions

Isolated rat hearts were perfused according to Langendorff and as a working heart preparation with glucose as the only exogenous substrate under nonrecirculating conditions to avoid accumulation of heart metabolites and, thereby, changes in the composition of the perfusion medium. In the absence of insulin or at low work, oxidation of endogenous substrates as glycogen is of importance for myocardial energy metabolism. Accordingly, about 1/3 of the glucose oxidized by the heart was derived from myocardial glycogen. Lipolysis of endogenous triglycerides and oxidation of the fatty acids produced were, however, low in normal rat hearts. By contrast, in the presence of insulin or at high work load endogenous substrates play a minor role for energy provision. About 80% of the total oxygen consumption could be attributed to the oxidation of exogenous glucose. Furthermore, insulin exerted its major effect in accelerating glucose uptake and glycolysis, but had little influence on PDH-activity. Insulin increased lipolysis in control hearts, however, changes in the endogenous triglycerides were less than valves calculated from the rate of lipolysis. Thus, glycerol release can be taken as a measure for lipolysis, but not as a measure for fatty acid oxidation, since the produced fatty acids were partly reesterified to glycerides. On the basis of the metabolic data obtained, the oxygen and energy balance was calculated. We conclude that a sufficient energy provision is only warranted if the rat heart is perfused either in the presence of insulin or at higher--more physiological--work load.

Cryo-electron microscopy of viruses

Thin vitrified layers of unfixed, unstained and unsupported virus suspensions can be prepared for observation by cryo-electron microscopy in easily controlled conditions. The viral particles appear free from the kind of damage caused by dehydration, freezing or adsorption to a support that is encountered in preparing biological samples for conventional electron microscopy. Cryo-electron microscopy of vitrified specimens offers possibilities for high resolution observations that compare favourably with any other electron microscopical method.

Effect of phenformin on the metabolism of glucose, pyruvate and acetate in guinea-pig heart

In the isolated perfused heart of the guinea-pig, phenformin could be shown to have a characteristic effect on cardiac performance and metabolism. In the working heart, phenformin (1 mmol1/1) decreased dp/dt and increased the end diatolic pressure; this reduced heart performance could not be explained by changes in the content of energy-rich compounds. Furthermore, phenformin increased lactate production in hearts perfused with glucose as substrate and inhibited the utilisation of pyruvate, but not of acetate. The activity of the purified pyruvate dehydrogenase complex was not influenced by phenformin, but the active form of the pyruvate dehydrogenase complex (PDHa) was diminished. This effect may be explained by an inhibition of the pyruvate dehydrogenase phosphatase. An inhibition of pyruvate dehydrogenase and, coincidently, of oxygen consumption might contribute to the development of lactic acidoses and, particularly, might be deleterious for the heart.

[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.

[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.

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.

[Cutaneous lesions with papillomatous structure associated with viruses in the green lizard (Lacerta viridis Laur.)]

Numerous papillomata affecting the skin of the dorsal part of the body occur in a population of Lacerta viridis reared in the laboratory. Electron microscopic study of three of these growths revealed the presence of viral particles belonging, from the morphological aspect, to the groups of the viruses of Herpes, Reo and Papova.

[A biochemical and cytological explanation of cochlear otospongiosis]

Carrying on their study about the enzymatic activity of the otospongiotic micro-foci and the hydrolytic activity of the perilymph, the authors present their work concerning the value of trypsin and alpha-1-anti-trypsin in the perilymph of otospongiotic patients operated on by stapedectomy. They describe the method used and give the obtained results which permit to believe that the values of trypsin, and a contrario of anti-trypsin, appear to constitute an index of the severity of the progression. Moreover, the authors have investigated the eventual toxic action of various trypsin concentrations on the hair cells of the Corti organ in the guinea-pig. This study has been carried through successfully by means of the electron microscopic scanning method which allows to obtain an "electron cochleogramme in situ". They explain the method and come to the conclusion that the intensity and extension of the Corti hair cells alterations in a cochlea receiving a perfusion with trypsin solutions, are tightly related to the trypsin concentration. However, they do not pretend so far that these results reflect exactly the anatomo-pathologic reality during the slow progression of otospongiosis towards cochlear deterioration. These two series of experimentation appear to confirm their enzymatic concept of otospongiosis: the long, slow and extremely capricious progression of the disease is the duplicate of its cytologic progression, the contact between hydroltic enzymes and Corti cells having the same capricious character. These findings perfectly corroborate the previus ones they made in this field, as well as the correlations they have established between hydrolytic activity of the perilymph and audiometric progression. Consequently, they believe that the mechanism of the otospongiotic disease is provoked by the rupture of the balance trypsin/anti-trypsin in the otospongiotic micro-foci and thus in the inner ear fluids.

[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.

[Ultrastructural characteristics of several constituants of limb buds in the embryos of the slowworm (Anguis fragilis L.) and the green lizard (Lacerta viridis Laur.)]

Ultrastructural characteristics of the cells of the apical crest, of the mesoblast and of the ventral processes of somites, in the anlage of the anterior limb buds of embryos of the slow-worm (Anguis fragilis) and of the green lizard (Lacerta viridis) are described at early stages of the development. Differences between the two species studied are brought to light.