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Biomedical subjects

M Adrian

Publications and source records attributed to M Adrian.

At least 19 recordsLinked to original sources
PubMed2001

The formation of empty shells upon pressure induced decapsidation of turnip yellow mosaic virus.

The stability of turnip yellow mosaic virus (TYMV) was investigated under pressure, using solution neutron small angle scattering. Dissociation products were characterized by analytical ultracentrifugation and electron microscopy. At pH 6.0, TYMV remained unaffected by pressure, up to 260 Megapascals (MPa), the highest pressure reached in these experiments. At pH 8.0, TYMV remained unaffected by pressure up to 160 MPa, but decapsidated irreversibly above 200 MPa, giving rise to more and more empty shells upon increasing pressure. The organization of these empty shells was similar to that of the capsid of native virions, apart from the presence of a hole corresponding to the loss of a group of 5-8 coat protein subunits, through which the RNA may have escaped. At variance with other small isometric viruses, the capsid of TYMV never dissociated under pressure into subunits or small aggregates of subunits. This exceptional behavior of TYMV is probably due to the importance of van der Waals contacts and hydrogen bonds in the stability of its capsid.

Capsid↗
PubMed2001

Transmission electron microscopical studies on some haemolymph proteins from the marine polychaete Nereis virens.

The hexagonal bilayer haemoglobin molecule from Nereis virens has been investigated in a comparative study using several different negative stain electron microscopical specimen preparations (i.e. by conventional adsorption to continuous carbon support films, by the negative staining-carbon film technique and by negative staining across the holes of holey carbon support films with air-drying and rapid freezing/cryo-negative staining). The benefits and limitations of these different approaches are indicated, with the overall conclusion that negative staining with ammonium molybdate across holes creates the best possibilities for molecular imaging, and also has the potential for the creation of two-dimensional (2D) crystals/arrays at the fluid-air interface. Of the different negative staining procedures presented, cryo-negative staining reveals the greatest details of N. virens haemoglobin. This is exemplified by the direct visualisation of the central linker-assembly within the haemoglobin molecule, a structural feature less clearly defined by the other negative staining techniques. A discoidal lipoprotein molecule (diameter 30-60nm; thickness ca 8nm) has been detected in N. virens, which represents the first documented account of an annelid haemolymph lipoprotein. The biological implications of this lipoprotein for lipid transport remain to be established. The presence of a low concentration of ferritin molecules in N. virens haemolymph is also shown, assisted by the formation of small 2D ferritin arrays in negatively stained specimens prepared across holes.

Animals↗
PubMed2000

Self-assembly of beta-amyloid 42 is retarded by small molecular ligands at the stage of structural intermediates.

Assemblyof the amyloid-beta peptide (Abeta) into fibrils and its deposition in distinct brain areas is considered responsible for the pathogenesis of Alzheimer's disease (AD). Thus, inhibition of fibril assembly is a potential strategy for therapeutic intervention. Electron cryomicroscopy was used to monitor the initial, native assembly structure of Abeta42. In addition to the known fibrillar intermediates, a nonfibrillar, polymeric sheet-like structure was identified. A temporary sequence of supramolecular structures was revealed with (i) polymeric Abeta42 sheets during the onset of assembly, inversely related to the appearance of (ii) fibril intermediates, which again are time-dependently replaced by (iii) mature fibrils. A cell-based primary screening assay was used to identify compounds that decrease Abeta42-induced toxicity. Hit compounds were further assayed for binding to Abeta42, radical scavenger activity, and their influence on the assembly structure of Abeta42. One compound, Ro 90-7501, was found to efficiently retard mature fibril formation, while extended polymeric Abeta42 sheets and fibrillar intermediates are accumulated. Ro 90-7501 may serve as a prototypic inhibitor for Abeta42 fibril formation and as a tool for studying the molecular mechanism of fibril assembly.

Amyloid beta-Peptides↗
PubMed2000

Stilbene content of mature Vitis vinifera berries in response to UV-C elicitation.

A method using HPLC analysis has been used to compare the level of resveratrol and its derivatives, piceid, pterostilbene and epsilon-viniferin, in grapevine berries of three Vitis vinifera varieties. The concentration of these compounds has been evaluated in healthy and Botrytis cinerea infected grape clusters, both in natural vineyard conditions and in response to UV elicitation.

Chromatography, High Pressure Liquid↗
PubMed1999

Changes in the phytoalexin content of various Vitis spp. in response to ultraviolet C elicitation.

The phytoalexin production potential of three American Vitis species and that of three cultivars of Vitis vinifera were evaluated in response to UV-C irradiation. Time course changes in resveratrol, piceid, epsilon-viniferin, and pterostilbene contents were studied within 3 days after a short UV-C irradiation. Results show that the two major stilbenes accumulated as a response to UV-C elicitation are resveratrol and epsilon-viniferin, a resveratrol dehydrodimer, the concentration of both compounds usually reaching quantities >100 microgram/g of fresh weight. In contrast, piceid and pterostilbene were constantly produced in low quantities. Owing to the results obtained, the role of stilbene phytoalexins in the resistance of grapevines to diseases is discussed.

Plant Extracts↗
PubMed1999

Unexpected property of trehalose as observed by cryo-electron microscopy.

Trehalose is an agent useful in maintaining the integrity of many biological systems submitted to various stresses. It is also presumed to improve specimen preparation for electron microscopy and to reduce beam damage. Here we study the effect of trehalose on the preparation and observation by cryo-electron microscopy of thin vitrified films of biological suspensions. We observe that trehalose, as compared to sucrose, can indeed reduce electron beam damage to biological particles, as determined from the dose necessary for the onset of bubbling. Surprisingly, we also find that the contrast of biological particles is higher in a vitrified solution of trehalose than in one of sucrose. This effect can be explained if the water evaporation during the specimen preparation is less in the presence of trehalose than with sucrose, but we do not yet understand the underlying reasons since the evaporation properties of both sugars are similar at a macroscopic level. We conclude that trehalose is truly a remarkable substance and that more investigation is needed in order to fully understand its properties, and that the addition of ca. 3-5% trehalose to biological suspensions is a simple and useful method to reduce commonly arising drying artefacts and water evaporation in the thin film vitrification method.

Journal Article↗
PubMed1999

Polymorphism of turnip yellow mosaic virus empty shells and evidence for conformational changes occurring after release of the viral RNA. A differential scanning calorimetric study.

Turnip yellow mosaic virus (TYMV) is a small isometric plant virus which decapsidates by releasing its RNA through a hole in the capsid, leaving behind an empty shell [R. E. F. Matthews and J. Witz, (1985) Virology 144, 318-327]. Similar empty shells (artificial top component, ATC) can be obtained by submitting the virions to various treatments in vitro. We have used differential scanning calorimetry, analytical sedimentation, and electron microscopy to investigate the thermodenaturation of natural empty shells (NTC, natural top component) present in purified virus suspensions, and of several types of ATCs. ATCs divided in two major classes. Those obtained by alkaline titration, by the action of urea or butanol behaved as NTC: their thermograms contained only one peak corresponding to the irreversible dissociation of the shells and the denaturation of the coat protein. The temperature of this unique transition varied significantly with pH, from 71 degrees C at pH 4.5 to 84 degrees C at pH 8.5. The thermograms of ATCs obtained by freezing and thawing, or by the action of high pressure, contained two peaks: shells dissociated first into smaller protein aggregates at 57 degrees C (at pH 5.0) to 61 degrees C (at pH 8.5), which denatured at the temperature of the unique transition of NTC. Shells obtained by heating virions to 55 degrees C at pH 7.6, changed conformation after the release of the viral RNA, as upon continuous heating to 95 degrees C, their thermograms were similar to those of the shells obtained by freezing and thawing, whereas after purification they behaved like NTC. Structural implications of these observations are discussed.

Calorimetry, Differential Scanning↗
PubMed1998

Cholesterol-Streptolysin O Interaction: An EM Study of Wild-Type and Mutant Streptolysin O.

We present transmission electron microscopical data from negatively stained specimens of cholesterol following interaction with the thiol-activated bacterial toxin streptolysin O (SLO) (wild-type and a number of cysteine substitution mutants), with and without chemical modification of the cysteine residues. Two experimental systems were used, one with an aqueous suspension of cholesterol microcrystals and the other with immobilized thin planar cholesterol crystals attached to a carbon film. In both systems the wild-type SLO and two cytolytically active mutants, Cys 530 --> Ala (C530A) and Ser 101 --> Cys (S101C), readily generated the characteristic SLO arc- and ring-like oligomers on the surface of cholesterol microcrystals and immobilized planar cholesterol crystals. An underlying array of bound toxin can sometimes be detected. In the presence of high concentrations of SLO monomer, extensive sheet-like networks of linked oligomers extend from the microcrystals. The SLO mutant Thr250 --> Cys (T250C), which also possesses a relatively high cytolytic activity, has been found to create ring-like toxin oligomers somewhat more slowly than wild-type SLO, but the linear monomolecular layer array of cholesterol-bound toxin is more readily detected. With mutant Asn402 --> Cys (N402C), which has approximately 10% cytolytic activity compared to wild-type SLO, the formation of ring-like oligomers is markedly reduced, with incomplete arcs and the parallel arrays predominating. Chemical modification of the functional cysteine groups of SLO mutants T250C and N402C completely inhibits the formation of toxin oligomers, but does not prevent the ability of these mutants to bind to cholesterol as a linear array. Such chemical modification is also known to abolish hemolysis/cytolysis. For both mutant T250C and N402C the parallel array of bound SLO adopts an orientation that appears to be determined by the underlying lattice of the crystalline cholesterol. The cholesterol-binding of biotinylated SLO mutant N402C was confirmed by labeling in suspension with 5-nm streptavidin-conjugated colloidal gold particles. Removal of the maltose-binding protein from the SLO fusion products increases the order of the monolayer array of biotinylated SLO bound to cholesterol crystals. Overall, our data support the concept that there is sterospecific binding of the SLO monomer to crystalline cholesterol bilayers, prior to oligomer formation. With the mutants tested, cysteine modification does not prevent binding to cholesterol, but subsequent release and oligomer formation are blocked. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Is community-based treatment an add-on or a substitution for hospital treatment of alcoholism? Some evidence from Canada.

OBJECTIVES: This study determined whether the development of community treatment of alcohol problems acted as an add-on or a substitution for the utilization of inpatient hospital services in Ontario. METHODS: Complex modelling and graphic analyses using econometric multiple regression techniques were performed on data for the 48 counties of Ontario (Canada) for the period 1972 to 1988, combining both cross-sectional and time series analysis. RESULTS: After controlling for differences in alcohol consumption, in health care characteristics such as the supply of physicians or hospital occupancy rates, and in socioeconomic characteristics of the population, when community treatment became available, hospital utilization for the treatment of alcohol problems decreased and community services were substituting for hospital treatment. In addition, nonresidential services had an overall greater importance in producing this effect (elasticities at the mean of -0.11 to -0.14 depending on the region) than community-based residential treatment. The effect was larger in the southern than in the northern counties of Ontario. Testing of the modelling techniques showed statistically significant and satisfactory modelling of the forces at work. CONCLUSIONS: Where community-based treatment was available, it was used in preference to inpatient hospital treatment; however, there may be a slightly more complex relationship present in the southern urban counties (which contain the larger metropolitan areas) than in the northern and southern rural counties..

Adolescent↗
PubMed1997

Transmission electron microscopy and scanning force microscopy of poly r(A-U) and poly r(A-U)-ethidium bromide.

Transmission electron microscopy and scanning force microscopy of negative-stained, carbon-coated replica and mica-adsorbed preparations of 200 microM poly r(A-U) and 50 microM ethidium bromide/200 microM poly r(A-U) have been employed to evaluate ethidium-induced changes in poly r(A-U) topology. Poly r(A-U) alone exhibits elongated conformations 85-115 nm in length that possess a number of hairpin loops as well as single-stranded domains. While the double-stranded domains are found predominately at the base of the hairpin loops (diameter = 5-30 nm), other rod-like (presumably double-stranded) regions ranging from 25-80 nm in length are present in other portions of the poly r(A-U). In contrast with the poly r(A-U) alone, the EB/poly r(A-U) combination appears as a heterogeneous population of condensed structures whose lengths and widths vary from 12-88 nm and 15-45 nm, respectively. These conformational changes are due to a number of factors, including the displacement of ordered water surrounding the poly r(A-U) and charge shielding of the phosphate groups of the poly r(A-U) upon the binding of the ethidium.

Adenine↗
PubMed1996

Does allowing the sale of wine in Quebec grocery stores increase consumption?

OBJECTIVE: To determine if allowing wine sales in corner grocery stores, beginning in 1978 for domestic Quebec wines and then in 1983 for imported wines, in addition to sales in government monopoly stores, led to an increase in alcohol consumption. METHOD: Aggregate retail sales data for the period 1953 to 1990 were analyzed using econometric regression techniques. Time series (unit root) analysis and structural modeling were used to take into account the effect of price, income and other social, economic and demographic factors in order to determine the effect of factors underlying consumption behavior in both the long and short term. RESULTS: In the post-intervention period, wine consumption continued along the rising trend established in the pre-intervention period, with an apparent shift in favor of domestic wine consumption. The increase in wine consumption was highest in the period immediately following privatization, but the increase eventually dampened down within a few years. There was no fundamental change in the responsiveness of wine consumption to price. CONCLUSION: Our findings suggest that the level of wine consumption can be controlled through price changes when alcohol availability increases through increased sales outlets.

Adolescent↗
PubMed1995

Temporal coupling between external auditory information and the phases of walking.

The purpose of this study was to investigate the effects of an imposed external auditory constraint upon the temporal organization of walking. Ten subjects were videotaped walking normally (N) and with instructions to couple naturally, at mid-swing, or at toe-off to a metronome beat. Based upon an analysis of variance and post hoc Scheffé tests most temporal variables were not significantly different among conditions. The duration of swing phase was significantly different between natural coupling and toe-off. The deviation from the metronome beat was significantly different between the natural coupling and both mid-swing and toe-off. Subjects generally were not successful in achieving coupling during the latter conditions. Thigh and shank phase portraits were used to describe the system's organization to the external constraint.

Acoustic Stimulation↗
PubMed1995

Substance use as a measure of social integration for women of different ethnocultural groups into mainstream culture in a pluralist society: the example of Canada.

Analysis of Canadian data from the 1989 National Alcohol and Drugs Survey was used to identify profiles of alcohol and other drug-using behaviors among Canadian women of different ethnic or cultural groups. The profile considered 110 different substance use variables including alcohol or drug type used, quantity, frequency, drinking or drug-taking circumstances, beverage preference, reasons for drinking or not drinking, and opinions regarding appropriate drinking or drug-taking behavior of Canadian women who described themselves as belonging to the "Canadian," French, English, German/Dutch, Irish, Scottish, Ukrainian/Polish, Italian/Portuguese, and "Other" (Chinese, Jewish, and "Other") ethnic or cultural groups. Alcohol, tobacco, and drug use behavior was found to differ by ethnocultural group. Further, each ethnocultural group was found to differ from the national average. The amount of difference between the national average and each ethnocultural group was related to the period of arrival and the length of time that an ethnocultural group has been present in Canada. The degree of similarity or difference between each ethnocultural group and the mainstream national average for alcohol, tobacco, and drug use and drug-use behavior may be used to measure the degree of social integration of each ethnocultural group and the degree of acculturation of women of specific ethnocultural groups into mainstream Canadian society.

Acculturation↗
PubMed1994

Structure of intracellular mature vaccinia virus observed by cryoelectron microscopy.

Intracellular mature vaccinia virus, also called intracellular naked virus, and its core envelope have been observed in their native, unfixed, unstained, hydrated states by cryoelectron microscopy of vitrified samples. The virion appears as a smooth rounded rectangle of ca. 350 by 270 nm. The core seems homogeneous and is surrounded by a 30-nm-thick surface domain delimited by membranes. We show that surface tubules and most likely also the characteristic dumbbell-shaped core with the lateral bodies which are generally observed in negatively stained or conventionally embedded samples are preparation artifacts.

Cryoultramicrotomy↗
PubMed1994

Community-based facilities may be replacing hospitals for the treatment of alcoholism: the evidence from Ontario.

We examined hospital utilization and use of community facilities for the treatment of alcohol problems in Ontario using Statistics Canada, Hospital Medical Records Institute records, and other administrative records. Between 1974 and 1986 there was a large drop in utilization of hospital services for treatment of alcohol problems. Rates of alcohol inpatient cases in general hospitals dropped by 47% and in mental hospitals by 33%. At the same time, there was an increase in overall availability of hospital beds and bed-days of care for all medical conditions, and no change in the total number of hospital discharges (1.3 million) and occupancy rates (80-85%). Also at the same time, the number of community-based programs for the treatment of alcohol problems increased, as did the number of persons or cases treated by them. This was associated with a drop of inpatient cases treated for alcohol problems in 38 out of 48 counties in Ontario (P < .0005). Multiple regression techniques were used to take into account the effect of the slight decline in overall alcohol consumption in this period. We found that after controlling for changes in alcohol consumption, the addition of one community-based alcohol treatment program was associated with a reduction in the number of cases treated on a hospital inpatient basis for alcohol-related problems, with a short-run drop of 27.1 hospital cases within 1 year of a community facility's availability and a long-run reduction of 52.2 cases. (P < .005).

Adult↗
PubMed1993

Atomic force microscopy of DNA in aqueous solutions.

DNA on mica can be imaged in the atomic force microscope (AFM) in water or in some buffers if the sample has first been dehydrated thoroughly with propanol or by baking in vacuum and if the sample is imaged with a tip that has been deposited in the scanning electron microscope (SEM). Without adequate dehydration or with an unmodified tip, the DNA is scraped off the substrate by AFM-imaging in aqueous solutions. The measured heights and widths of DNA are larger in aqueous solutions than in propanol. The measured lengths of DNA molecules are the same in propanol and in aqueous solutions and correspond to the base spacing for B-DNA, the hydrated form of DNA; when the DNA is again imaged in propanol after buffer, however, it shortens to the length expected for dehydrated A-DNA. Other results include the imaging of E. coli RNA polymerase bound to DNA in a propanol-water mixture and the observation that washing samples in the AFM is an effective way of disaggregating salt-DNA complexes. The ability to image DNA in aqueous solutions has potential applications for observing processes involving DNA in the AFM.

1-Propanol↗
PubMed1993

Organization of turnip yellow mosaic virus investigated by neutron small angle scattering at 80 K: an intermediate state preceding decapsidation of the virion?

The organization of turnip yellow mosaic virus has been investigated by neutron small angle scattering at 300 K and 80 K in buffers containing various amounts of D2O. We confirm that in native virions, no substantial part of the RNA is located at a radius larger than ca. 100-110 A, i.e., that there is very little interpretation of the RNA into the capsid. At 80 K, scattering curves do not depend much upon contrast, from 40% D2O to 100% D2O buffers, but are strongly affected by interparticle interference. We could, however, show that it is not the case for the subsidiary intensity maximum at q approximately 0.06 A-1. From the position of this maximum, we conclude that upon freezing, the radius of the capsid expands by c.a. 3.5% and the RNA penetrates deeply into the protein shell. Biological implications of this conformational change immediately preceding decapsidation are discussed.

Capsid↗