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Biomedical subjects

I Davidson

Publications and source records attributed to I Davidson.

At least 127 records · Page 7Linked to original sources
PubMed1985

All six GC-motifs of the SV40 early upstream element contribute to promoter activity in vivo and in vitro.

Recombinants in which the six GC-motifs (I-VI) present in the upstream element of the SV40 early promoter region have been point mutated either individually or in pairs were used to determine the possible contribution of each GC-motif to the function of the overlapping early-early and late-early SV40 promoters. GC-motif I, and to a lesser extent, GC-motifs II and III, are critical for initiation at the early-early start sites. GC-motifs IV-VI play a subsidiary role. Mutations in GC-motifs I and II do not decrease the activity of the late-early promoter, whereas mutations in the GC-motifs III-VI have a moderate effect on it. The in vivo phenotype of the GC-motif mutants can be almost fully reproduced in vitro using a nuclear extract. DNase I protection footprinting experiments using wild-type or mutated templates and nuclear extracts indicate that each GC-motif behaves principally as an independent protein-binding site, presumably for transcription factor Sp1. The effect of changing the position of the 21-bp repeat region on initiation from the early-early and late-early start sites indicates that there is little flexibility in the position in which this upstream element can efficiently activate initiation of transcription from these start sites.

Base Sequence↗
PubMed1985

Expression of an immediate early polypeptide and activation of a viral origin of DNA replication in cells containing a fragment of herpes simplex virus DNA.

A thymidine kinase cotransformation procedure has been used to introduce the sequences encoding the herpes simplex virus type 1 (HSV-1) immediate early protein, Vmw175, into permissive cells either in the presence or the absence of the adjacent origin of viral DNA replication. Cells transformed by either origin-plus or origin-minus DNA were capable of expressing functional Vmw175 as indicated by their ability to complement the growth at the nonpermissive temperature of an HSV-1 mutant, ts K, containing a temperature-sensitive lesion in the Vmw175 gene. A proportion of the virus yield from cells transformed with the origin-plus, but not the origin-minus, plasmid exhibited a ts+ phenotype. The generation of ts+ virus correlated with an amplification of input plasmid DNA sequences which occurred following superinfection, suggesting that recombination between the ts mutant and the amplified viral DNA sequences had taken place. Encapsidation of the amplified DNA sequences was also detected, suggesting that in addition to a functional origin of replication and Vmw175 gene the transformed cells also retain the viral DNA packaging signals.

Capsid↗
PubMed1984

Ecology of leishmaniasis in the south of France. 20. Dispersal of Phlebotomus ariasi Tonnoir, 1921 as a factor in the spread of visceral leishmaniasis in the Cévennes.

The dispersal of Phlebotomus ariasi was studied in mark-release-recapture experiments in the summer of 1980 in a valley on the north-eastern slopes of the Oiselette range in the Cévennes mountains, in the commune of Roquedur, Gard, 50 km north of Montpellier, France. More than 5,000 specimens of P. ariasi were marked with fluorescent powders and released in 9 batches at 3 different places. Seven batches were engorged females and two were unengorged females and males. From 1-29 days after release, 497 marked sandflies (approximately 9%) were recaptured by active searches with UV lamps or in 58 CDC light traps set up in groups of 4 or 5 at 12 recapture stations. Females released engorged generally remained within 250 m of the release point for the first eight days while the bloodmeal was being digested after which there was a tendency to disperse to distances greater than 350 m presumably in a search for oviposition sites or another bloodmeal. The furthest distance to which a female released engorged was shown to move was 925 m; it was caught 12 days after release. Some of the females released unfed quickly moved away from release points, sometimes to distances of 1,000 m or more. One of these was caught 68.5 hrs after release at a station 2,200 m from the release point. Male sandflies tended to stay near the point of release and were not recaptured at distances greater than 600 m. There was no evidence that the movement of the sandflies was assisted by wind. Observations on the dispersal of female sandflies confirm that leishmaniasis can be more widely spread than generally assumed by the movements of the vector.

Animals↗
PubMed1982

Somatic cell hybridization between bovine leukemia virus-infected lymphocytes and murine plasma cell tumors: cell fusion studies with bovine cells.

Hybridization of peripheral blood lymphocytes from bovine leukemia virus-infected cows with murine myeloma cells resulted in the generation of hybrid cells secreting immunoglobulins composed of various combinations of heavy and light chains of both bovine and murine Ig origin. Some hybrid cells derived from the light-chain producer, but non-secretor murine myeloma NSI cell line, secreted IgM molecules composed of bovine mu-chain linked to bovine and/or murine light chains. Other hybridomas secreted mouse and bovine light-chain dimers and/or monomers, or failed to secrete any Ig polypeptide chain whatsoever. Immunoglobulins secreted by hybridomas obtained upon hybridization of bovine cells with the IgG-secreting murine myeloma P2X63 cell line, contained bovine mu-chain in one of the seven hybridomas obtained, and bovine light chain in two of them. All the cell lines secreted murine light- and gamma-chains.

Animals↗
PubMed1982

Membrane IgM of bovine lymphocytes.

The membrane immunoglobulins of peripheral blood lymphocytes (PBL) obtained from four bovine-leukemia-virus infected calves and from a normal cow were isolated and characterized. They were found to consist of an IgM exhibiting a mu-chain of an apparent molecular weight (AMW) of 95,000 daltons, which is 10,000 daltons more than found for the mu-chain of serum IgM. It thus seems that this is a property of membrane-bound IgM of bovine origin.

Animals↗
PubMed1982

Hepatitis B among Indochinese refugees in Great Britain.

Six hundred and thirty-two blood samples from 879 consecutive admissions to one resettlement camp for Indochinese refugees in Great Britain were screened for markers of hepatitis B (HB) virus infection. The overall prevalence of HB surface antigen (HBsAg) was 15%, being 16% in those aged 40 years or less, and falling to 8% in those older than 40 (P less than 0.05). No significant difference in prevalence was found between males and females. HBe antigen was detected in 56% of those with HBsAg and was demonstrable in 55-76% of those under 30 years of age. HBe antibody was found in 21% of HBsAg-positive refugees. In those under 40 years old, HB core (HBc) antibody was commoner in males (P less than 0.01). HBc antibody prevalence increased significantly with age in females (P less than 0.01) but not in males. There was no definite evidence that vertical transmission of hepatitis B was present in the group studied.

Adolescent↗
PubMed1980

Peripheral neural representation of spatial dimensions of a textured surface moving across the monkey's finger pad.

1. The responses of single cutaneous mechanoreceptive fibres evoked by a geometrically patterned surface sweeping across the skin were examined. The surfaces used were each a fine diamond-shaped array of "dots' in relief against a flat background. The fibres examined were rapidly adapting, slowly adapting and Pacinian fibres innervating the monkey's finger pad skin. 2. Each fibre's response to the two-dimensioned surface was assessed using a procedure in which the surface was swept across the fibre's receptive field many times, the position of the surface relative to the underlying receptive field being precisely known at any instant in time. Between each successive sweep the stimulus surface was shifted lateral to the direction of movement by a small increment. The response pattern generated by this scanning procedure specified the extent to which a single response of the fibre was dependent on the spatial and temporal dimensions of the stimulus. 3. The invariant spatial features of the moving surface were represented only in the responses of populations of fibres; responses of the constituent fibres always confounded the information relayed about the surface pattern and its rate of movement across the skin. 4. Factors determining the representation of the spatial and temporal characteristics of the moving surface in the responding mechanoreceptive fibre population were examined. These included the response characteristics of the constituent fibres, the innervation density, and the total number of fibres engaged by the moving surface.

Action Potentials↗
PubMed1979

Bronchodilatation and the site of airway resistance in severe chronic bronchitis.

Twenty-one patients with severe chronic bronchitis and emphysema (FEV1 less than 1 1) inhaled 80 microgram of the atropine-like agent ipratropium or placebo in a double-blind study and three hours later inhaled 200 microgram salbutamol. After 80 microgram ipratropium, mean FEV1 was significantly greater than after 200 microgram salbutamol (P less than 0.025), but the difference was only 40 ml and the clinical significance of this difference is unproved. There was no correlation between the patient's response to ipratropium and the response to salbutamol. When salbutamol was administered three hours after ipratropium, the FEV1 rose to higher levels than after either agent alone (P less than 0.01). Studies breathing 80% helium/20% oxygen suggest that ipratropium dilates both large and small airways. There was no correlation between the response to helium/oxygen and the response to either bronchodilator. The results suggest that in severe chronic bronchitis and emphysema ipratropium is at least as effective as salbutamol, and that such patients should have reversibility studies with salbutamol alone, ipratropium alone, and after both agents together. The combination of ipratropium and salbutamol may be clinically useful.

Aged↗
PubMed1978

The International Reference Preparations of Clostridium welchii (C. perfringens) beta and epsilon toxoids.

The Central Veterinary Laboratory, Weybridge, England was requested by the WHO Expert Committee on Biological Standardization to obtain suitable materials for international standards for Clostridium welchii (C. perfringens) beta and epsilon toxoids and to arrange collaborative assays. Preparations were obtained and dispensed as freeze-dried toxoids in ampoules. The toxoids were assayed by nine laboratories in eight countries. On the basis of the results obtained, the materials have been established as the International Reference Preparations of Clostridium welchii (C. perfringens) Beta and Epsilon Toxoids.

Animals↗
PubMed1978

International standard for anti-Brucella abortus serum: comparison of the complement-fixing activity of the first and second international standards and the EEC standard.

Although the three standards have similar agglutinating activities, it was found that the first International Standard had about half the complement-fixing activity of the second International Standard and the EEC standard. The complement-fixing activities of the latter two standards were similar. On the basis of these results, showing that the agglutination and complement-fixation tests measure different biological activities in anti-Brucella abortus sera, the WHO Expert Committee on Biological Standardization in 1976 assigned separate unitages of agglutinating and complement-fixing activity to the second International Standard for Anti-Brucella abortus Serum.

Agglutination Tests↗
PubMed1976

An international survey of clostridial sera and vaccines.

The papers present the results of a survey of the usage, assay and specification of veterinary clostridial sera and vaccines in 23 countries. Thirteen of the countries use up to 8 different antisera. All the countries use vaccines, which are prepared from 13 species and types of clostridia. Vaccines containing up to 8 such components are commonly employed. Criteria for the design and interpretation of assays are discussed and evidence for efficacy summarized.

Animals↗