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Biomedical subjects

A Polson

Publications and source records attributed to A Polson.

At least 55 records · Page 3Linked to original sources
PubMed1983

Midgut and viral associated proteases of Heliothis armigera.

The role played by the gut juice of insects in the infective process of insect viruses was examined. Analysis of larval gut extract of Heliothis armigera by SDS-PAGE revealed protease activity associated with components of molecular weights 48,000 and 94,000. Proteases were found to be associated with occlusion bodies and virions of both nuclear polyhedrosis virus (NPV) and cytoplasmic polyhedrosis virus (CPV) infecting H. armigera. CPV occlusion bodies were dissolved by gut juice extract at pH 8.0, trypsin and chymotrypsin at pH 8.0, and carbonate-chloride solution at pH 10.5. Trypsin treatment was selective for occlusion bodies of CPV at pH 8.0, whereas solutions more alkaline than pH 10.0 without added enzymes were adequate to digest NPV occlusion bodies. This property was used to identify and separate the two types of viruses from a mixed infection. Gut extract proteases have characteristics similar to those of trypsin.

Animals↗
PubMed1982

Initial healing of periodontal pockets after a single episode of root planing monitored by controlled probing forces.

THE PURPOSE OF the present study was to evaluate, using controlled probing forces, the response of periodontal pockets to a single episode of root planing. The clinical characteristics of 128 pockets (3-7 mm depth) distributed in ten subjects, were monitored immediately before and 1, 2, 3, and 4 weeks after a single episode of subgingival root planing. The clinical parameters measured were: pocket depth and bleeding after probing with 15 gm, 25 gm, 50 gm of controlled probing force and manual probing, gingival margin location, loss of attachment, gingival and plaque indices. Oral hygiene instruction and supragingival prophylaxis were given at each time point. An average aggregated score for each subject for each parameter was calculated at each time point. A repeated measure all-within analysis of variance was done, and the Tukey multiple range test was used to assess the significance of differences among and between the means. Plaque and gingival indices decreased significantly after 1 week. Significant pocket depth reduction (initial) occurred 1 week after root planing, and reduced further (secondary) at 3 weeks. Initial pocket reduction was associated with significant gingival recession, whereas secondary pocket reduction was associated with significant gain of clinical attachment. Bleeding upon probing was virtually absent after 3 weeks. All probing changes were detected more consistently using controlled insertion pressures. It was concluded that substantial reduction in pocket depth occurs within 3 weeks after a single episode of root planing owing to initial gingival recession and secondary gain in clinical attachment.

Adult↗
PubMed1982

Maintenance of healed periodontal pockets after a single episode of root planing.

The present study evaluated the clinical stability of healed periodontal pockets over a 3 month time period to determine whether this time interval is appropriate for periodontal maintenance therapy. The clinical characteristics of 128 pockets (3-7 mm depth) distributed in 10 patients, were monitored immediately before and 4, 8 and 16 weeks after a single episode of subgingival root planing. The clinical parameters measured were: pocket depth and bleeding after probing with 15, 25 and 50 gm and manual probing, gingival margin location, clinical attachment level, and gingival and plaque indices. Oral hygiene instruction and supragingival cleaning were given at each time point. An average aggregated score for each subject and for each parameter was calculated at each time point. A repeated measure all within analysis of variance was done, and the Tukey multiple range test was used to assess the significance of differences among and between the means. The significant decreases in plaque, gingival and bleeding indices, and pocket depth as well as the significant gingival recession and gain of clinical attachment which were present at the 4 week point were maintained at 8 and 16 weeks after root planing. It was concluded that the favorable clinical changes which occur in periodontal pockets within 1 month after a single episode of subgingival root planing combined with improved oral hygiene can be maintained for an additional 3 month time period.

Dental Plaque↗
PubMed1982

Determination of the number of Fab1 pieces which react with high molecular weight antigens.

The sedimenting-droplet technique was used for the determination of the masses of immune Fab1 pieces which may bind to antigenic sites on three haemocyanins. Similar experiments were conducted on three viruses which belong to the Tobamo group. It was calculated that 384 homologous Fab1 pieces could bind to a molecule of the haemocyanin of Burnupena cincta and 950 homologous Fab1 pieces to a virion of tobacco mosaic virus. By taking special precautions the number of undegraded antibody molecules which can bind to a Tobacco mosaic virus particle may be determined with the same technique.

Animals↗
PubMed1981

Electro-extraction of viruses from infected plant tissue.

An apparatus is described which was used for rapid extraction of viruses from frozen and thawed infected plant tissues. The novel principle is the establishment of a potential gradient of 15 to 20 volts/cm at approximately 90 degrees across the leaves of the infected plant while the leaves are surrounded by buffer of low molarity and of the appropriate hydrogen ion concentration. To keep the leaves in the correct orientation they were placed as single layers between coarse rigid plastic gauze. The method, termed electro-extraction, was used as the initial step in the purification of turnip yellow mosaic, tobacco mosaic and maize streak viruses. An electron micrograph of the purified maize streak virus is presented.

Freezing↗
PubMed1981

Associations between crestal lamina dura and periodontal status.

The purpose of the present study was to investigate associations between radiographic crestal lamina dura and the clinical periodontal status of the corresponding interdental area. The population consisted of 90 individuals (53 females and 37 males), ages 21 to 45 years (mean 31 years), who underwent a comprehensive periodontal examination. Buccal and lingual to the contact point at each interdental area four different clinical criteria were scored as being present or absent: (i) visual inflammation, (ii) bleeding after probing with 25 gm force, (iii) pocket depth greater than 3 mm after probing with 50 gm force, (iv) loss of connective tissue attachment. Bite-wing and full-mouth periapical radiographs were taken and processed using standardized techniques. Each interdental crestal area on the radiographs was examined and scored for presence or absence of an intact lamina dura. Statistical analyses were undertaken using correlated means to compare the presence or absence of lamina dura with the individual and simultaneous clinical criteria. No significant differences were obtained between any of the comparisons and, in addition, there was no correlation between lamina dura images on periapical and bite-wing radiographs. The results indicated that crestal lamina dura on radiographs did not appear to be related to the presence or absence of clinical inflammation, bleeding upon probing, periodontal pockets or loss of attachment.

Adult↗
PubMed1980

Isolation of viral IgY antibodies from yolks of immunized hens.

Antibodies were isolated from the yolks of hens that were immunized with a variety of plant viruses by the use of polyethylene glycol (PEG). A concentration of 3.5% of the polymer caused the lipids and vitellin to separate, and the IgY was then precipitated with 12% PEG. The titre of the isolated antibody appears to remain at a high level after cessation of the course of immunization. Antibodies derived from the yolks of hens appear to have titres similar to those found in serum of rabbits immunized simultaneously. The observation made by several authors that a high salt concentration enhances fowl serum antibody precipitin titres could not be corroborated with 'yolk' antibodies directed against several plant viruses.

Animals↗
PubMed1980

Antibodies to proteins from yolk of immunized hens.

Immunoglobulins IgY, extracted from yolks of hens immunized against several proteins and natural mixtures of proteins were examined by the Ouchterloney gel diffusion and Laurell immuno-electrophoresis techniques. The molecular weights of the proteins ranged from 8 x 10(6) to less than 2 x 10(4). The hens produced IgY antibodies readily when injected with the high molecular antigens > 150 000 but did not react as well to antigens of relatively low molecular weight < 30 000. Optimal precipitin reactions were obtained with low molecular antigens when the agarose gel contained 1.5 M NaCl. Salt concentration (0.15-1.5 M NaCl) has no effect on the precipitin reaction in gels on the systems of high molecular antigens and their IgY antibodies apart from a displacement of the precipitin line. From the relative positions of the precipitin lines to the wells containing the reactants it would appear that the IgY formed dimers when the concentration of NaCl is 1.6 M and remain as monomers in gels containing 0.15 M NaCl. An explanation of the salt effect is offered.

Amoeba↗
PubMed1979

An insert for the reorienting gradient rotor for virus extraction from infected plants.

A device made of nylon and which is inserted in the bowl of the reorienting gradient rotor is described. This insert acts as a container for holding infected plant tissues for the purpose of separating virus by centrifugal force from intact and fresh plants, from frozen and thawed plants and from plant tissue disintegrated by mechanical means. The extracted fluid represents 80 to 90% of that present in the untreated plant tissue. Electron micrographs taken of concentrates of the viruses prepared by the centrifugation extraction procedure indicate that extraneous materials are reduced to a low level.

Centrifugation, Density Gradient↗
PubMed1978

Electrophoresis in gels suspended in hydrophobic solvents.

Protein components in mixtures may be separated by zone electrophoresis in columns of gel suspended in hydrophobic solvents. The method is useful for the location of specific antibodies in IgG electrophoretic spectra.

Electrophoresis, Agar Gel↗
PubMed1978

Preparative immunoabsorption electrophoresis.

A method for separating a component from a mixture of antigens is described. The component which may be a virus or subfraction of a virus, is isolated by driving the mixture by electrophoresis through a gel containing precipitating antibodies directed against the unwanted components. The method is illustrated by the isolation of hepatitis B antigen from whole serum and by the separation of wild cucumber mosaic virus from a strain of tobacco mosaic virus.

Absorption↗
PubMed1977

A theory for the displacement of proteins and viruses with polyethylene glycol.

The displacement action of polyethylene glycol of different molecular weights may be linked to the ability of the polymers to form coiled particles in solution. From conclusions drawn from their sedimentating properties in centrifugal fields the polyethylene glycols of low molecular weights, as expected, are less randomly coiled than those of higher molecular weight. It is suggested that protein molecules have the ability to diffuse into the coils of the polyethylene glycol from which they are excluded when the random coiling increases with increasing polymer concentration. From considerations based on the interaction of the polymer filament with the displaced particle the distribution of the substance between the coils and the intermolecular spaces may be predicted semi-quantitatively.

Chemical Phenomena↗
PubMed1977

Isolation of viruses by electro-extraction of infected plants.

The isolation of viruses from infected plant material by a process termed electro-extraction appeared to be a convenient and simple method of obtaining viruses in a fair state of purity. The method has the advantage over the conventional methods of virus purification that the infected plant tissue is not disintegrated and that organic solvents such as chloroform and butanol are avoided. The procedure used was demonstrated on the extraction of tobacco mosaic virus (TMV) from infected tobacco and turnip yellow mosaic virus (TYMV) from chinese cabbage plants. To obtain the virus it was found advisable to freeze and thaw the plants prior to extraction.

Electrophoresis↗
PubMed1976

Formaldehyde treated gelatin as a gel exclusion agent.

A high molecular weight fraction of gelatin precipitated from a solution of Difco gelatin with polyethylene glycol has several favourable properties in gel exclusion chromatography. To manufacture the gel exclusion agent, the gelatin was dissolved in hot water, allowed to set in the cold and rendered insoluble by reaction with formaldehyde. When finely disrupted and used as bed material in columns this gel is capable of separating protein components from mixtures of proteins of widely different molecular weights. Favourable properties include elasticity at relatively low concentration, its availability and its inexpensive nature.

Animals↗