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Biomedical subjects

I Davidson

Publications and source records attributed to I Davidson.

At least 145 records · Page 8Linked to original sources
PubMed1975

The lead content of teeth. Evidence establishing new minimal levels of exposure in a living preindustrialized human population.

Teeth were collected from populations differing in their degree of industrialization and from prehistoric populations. Lead analysis of dentine revealed that in contemporary teeth the lead level was related to the degree of industrialization and that in prehistoric teeth very low concentrations of lead were present. Because tooth lead reflects the body burden of lead, this result suggested that the prehistoric populations and modern nonindustrial populations were exposed to environments low in lead. Teeth from a contemporary population of nonindustrialized Indians of the Lacandon forest in Mexico contain lead in concentrations comparable with those of the prehistoric populations. Comparison of the Indian teeth with teeth from a modern industrial population reveals a 45-fold difference in median tooth lead level. This finding lends support to the hypothesis that high levels of urban lead pollution result in elevated body burdens of lead.

Adult↗
PubMed1971

International reference preparation of anti-Mycoplasma gallisepticum serum.

The WHO Expert Committee on Biological Standardization requested the Central Veterinary Laboratory, Weybridge, England, to arrange a collaborative assay of material they had prepared to determine its suitability to serve as an international reference preparation of anti-Mycoplasma gallisepticum serum. Fourteen laboratories in eight countries performed comparative assays of the proposed reference preparation together with 3 immune sera from fowls. On the basis of the results obtained, the Committee established the preparation as the International Reference Preparation of Anti-Mycoplasma gallisepticum Serum and defined the International Unit as the activity contained in 0.0556 mg of the International Reference Preparation.

Agglutination Tests↗
PubMed1969

The Second International Standard for anti-Brucella abortus serum.

In 1965, the WHO Expert Committee on Biological Standardization (1966) noted that stocks of the International Standard for Anti-Brucella abortus Serum were almost exhausted and requested the Central Veterinary Laboratory, Weybridge, England, to examine a quantity of serum offered by that laboratory for its suitability to serve as a replacement, and to arrange a collaborative assay. After being distributed into ampoules and freeze-dried, the serum was assayed against the International Standard by 17 laboratories in 12 countries. On the basis of the results obtained, the serum has been established as the Second International Standard for Anti-Brucella abortus Serum and the International Unit has been defined as the activity contained in 0.09552 mg of the Second International Standard.

Agglutination Tests↗
PubMed1968

International reference preparation of anti-Newcastle-disease serum.

The Central Veterinary Laboratory, Weybridge, England, was requested by the WHO Expert Committee on Biological Standardization to obtain suitable material for an international reference preparation of anti-Newcastle-disease serum for standardizing the haemagglutination-inhibition test for Newcastle disease and to arrange a collaborative assay. Ten laboratories in 10 countries assayed a batch of immune chicken serum against 2 test preparations. On the basis of the results obtained, the material has been established as the International Reference Preparation of Anti-Newcastle-Disease Serum and the International Unit of Anti-Newcastle-Disease Serum has been defined as the activity contained in 0.1734 mg of the International Reference Preparation of Anti-Newcastle-Disease Serum.

Animals↗
PubMed1968

International reference Preparation of Newcastle Diseaase Vaccine (Live).

The Central Veterinary Laboratory, Weybridge, England, was requested by the WHO Expert Committee on Biological Standardization to arrange a collaborative assay to test a freeze-dried preparation of live Newcastle disease vaccine (Hitchner B1 strain) for its suitability to serve as an international reference preparation. Nine laboratories in 8 countries assayed the vaccine against a number of test preparations of different vaccine strains. On the basis of the results obtained, the material has been established as the International Reference Preparation of Newcastle Disease Vaccine (Live) and is considered suitable for standardizing the titration of the Hitchner B1 strain and related strains of virus.

Immunoassay↗
PubMed1968

International standard for anti-canine-hepatitis serum.

The Central Veterinary Laboratory, Weybridge, England, was requested by the WHO Expert Committee on Biological Standardization to obtain suitable material for an international standard for anti-canine-hepatitis serum and to arrange a collaborative assay. Eight laboratories in 7 countries assayed a batch of anti-canine-hepatitis serum against 3 test preparations. On the basis of the results obtained, the material has been established as the International Standard for Anti-Canine-Hepatitis Serum and the International Unit of Anti-Canine-Hepatitis Serum has been defined as the activity contained in 0.0796 mg of the International Standard.

Animals↗
PubMed1968

International standard for anti-canine-distemper serum.

The Central Veterinary Laboratory, Weybridge, England, was requested by the WHO Expert Committee on Biological Standardization to obtain suitable material for an international standard for anti-canine-distemper serum and to arrange a collaborative assay. Seven laboratories in 6 countries assayed a batch of anti-canine-distemper serum against 3 test preparations. On the basis of the results obtained, the material has been established as the International Standard for Anti-Canine-Distemper Serum and the International Unit of Anti-Canine-Distemper Serum has been defined as the activity contained in 0.0897 mg of the International Standard.

Animals↗
PubMed1966

The international reference preparation of tylosin.

The Central Veterinary Laboratory, Weybridge, England, was requested by the WHO Expert Committee on Biological Standardization to obtain suitable material for an international reference preparation of tylosin and to arrange a collaborative assay. A batch of 150 g of highly purified tylosin was assayed by ten laboratories in nine countries against the tylosin standard of a commercial manufacturer. On the basis of the results obtained, the material has been established as the International Reference Preparation of Tylosin and the International Unit for Tylosin has been defined as the activity contained in 0.001 mg of the International Reference Preparation of Tylosin.

Anti-Bacterial Agents↗
PubMed1966

The international reference preparation of hygromycin B.

The Central Veterinary Laboratory, Weybridge, England, was requested by the WHO Expert Committee on Biological Standardization to obtain suitable material for an international reference preparation of hygromycin B and to arrange a collaborative assay. A batch of 150 g of a highly purified hygromycin B was assayed in eleven laboratories in nine countries against the hygromycin B standard of a commercial manufacturer. On the basis of the results obtained, the material has been established as the International Reference Preparation of Hygromycin B and the International Unit for Hygromycin B has been defined as the activity contained in 0.0008928 mg of the International Reference Preparation of Hygromycin B.

Anti-Bacterial Agents↗
PubMed1965

Laboratory toxicity test of field trial typhoid vaccines.

It is important for the control of vaccines to develop methods for testing their toxicity in the laboratory. Two typhoid vaccines that had given different rates of reactions among vaccinated persons in extensive field trials provided a unique opportunity for exploring the validity of the laboratory assessment of their toxicity. An elaborate design of a toxicity test based on weight changes in intraperitoneally vaccinated mice is described in this paper. The results of the laboratory test reflected the experience gained in field studies.

Animals↗
PubMedDate not supplied

Cell-type specific protein binding to the enhancer of simian virus 40 in nuclear extracts.

Enhancers are cis-acting activators of transcription from homologous or heterologous promoter elements of viral and cellular genes (see refs 1-6 for reviews). The activity of the simian virus 40 (SV40) (refs 7-9) and immunoglobulin heavy-chain gene (IgH) (refs 10, 11) enhancers has been reproduced to some extent in vitro and appears to be mediated by trans-acting factors both in vitro and in vivo. The SV40 enhancer consists of multiple sequence motifs in two domains, A and B (Fig. 1, see ref. 14): domain B contains GT-I and -II and two TC motifs, of which only TC-II is important for enhancer activity in HeLa cells; and domain A contains the P and the two Sph motifs, the repetition of which generates the sequence 5'-ATGCAAAG-3', similar to the 'octameric' sequence of the IgH enhancer, (Fig. 4i; refs 14, 16), where it is important for enhancing activity. Each SV40 enhancer motif is a binding site for a protein or proteins present in HeLa cell nuclear extracts. Unlike the SV40 enhancer, which is active in HeLa and lymphoid B cells, the IgH enhancer is preferentially active in B cells, suggesting that not all the trans-acting factors necessary for its activity are present in HeLa cells. However, the IgH enhancer can compete with the SV40 enhancer in vitro in HeLa or lymphoid cell extracts and in vivo in B cells. Here we show that both human HeLa and BJA-B lymphoid B-cell nuclear extracts contain proteins that bind to specific, sometimes overlapping, motifs of the SV40 enhancer. Some binding is cell-specific, suggesting that it is not the same set of sequence motifs and proteins that is responsible for the enhancer activity in the two cell types. This is confirmed by our results obtained in vivo with mutated SV40 enhancers.

B-Lymphocytes↗
PubMedDate not supplied

Persistence of chicken herpesvirus and retroviral chimeric molecules upon in vivo passage.

Mareks disease virus (MDV), a herpesvirus, and avian leucosis virus subgroup J (ALV-J), a retrovirus, were used for experimental coinfection of chickens. Chimeric molecules having sequences of both viruses were detected by the hotspot-combined polymerase chain reaction (HS-cPCR) system. The detection of chimeric molecules provided evidence for avian retroviral inserts in the herpesvirus genome. The persistence of chimeric molecules on in vivo passage served to indicate the infectivity of the recombinant virus. The evaluation of formation and persistence of the chimeric molecules was performed in two trials involving three in vivo passages. The chimeric molecules were identified according to the primer sets, their product length, and pattern. The persistence of chimeric molecules on in vivo passages served as an indication of their ability to replicate in and infect chickens. In the first experimental passage, MDV and ALV-J prototype strains, MD11 and HC-1, were intraperitoneally (i.p.) injected into 1-day-old chicks. The second trial included two passages. Passage II chicks were injected i.p. and passage III chickens were in contact with the chickens of passage II. For passage II, enriched white blood cells from blood samples of chickens from the first trial that had chimeric molecules were injected i.p. into 1-day-old chicks. For passage III, uninfected chicks were included together with the infected chicks. Synthesis evidence for the various species of chimeric molecules was assessed in the tissues of birds of the second trial. DNA was extracted from blood and feathers and analyzed by the hotspot-combined PCR and by pulsed field gel electrophoresis. To overcome the limits of detection, three amplification assays followed by hybridization of the products to specific viral probes were conducted. A variety of chimeric molecules were detected in low concentrations. Five species of chimeric molecules were characterized in blood, tumors, and feathers. Chimeric molecules were detected in 18 of 36 dually infected birds from the first trial and in 14 of 21 dually infected birds from the second trial. The findings show that, in four out of seven groups of the second trial, the chimeric molecule species persisted on passage.

Animals↗
PubMedDate not supplied

Chicken infectious anemia virus infection in Israeli commercial flocks: virus amplification, clinical signs, performance, and antibody status.

The impact of chicken infectious anemia virus (CIAV) infection on commercial chicken flocks in Israel was examined by analyzing flocks with or without typical CIAV signs, signs of other diseases, or apparently healthy flocks. In 23 flocks (broilers and layers) of ages up to 8 wk, typical signs of CIAV infection (stunting, gangrenous dermatitis, and secondary bacterial infections) were recorded. When permitted by flock owners, in several cases among these 23 flocks the morbidity, mortality, and performance parameters were recorded; the presence of CIAV was detected by polymerase chain reaction (PCR); and the antibody status of parents and broilers was measured. In addition, total mortality, number of birds sold, total kilograms of meat sold, density (kg/m2), mean age at slaughter, daily growth rate in grams, total kilogram of food consumed, food conversion rate, and the European Index were calculated. We also surveyed flocks affected by other diseases, such as tumors, respiratory diseases, or coccidiosis, and flocks with no apparent clinical signs. The latter flocks were negative by CIAV-PCR, indicating that typical CIAV clinical signs are associated with one-step PCR-CIAV amplification. However, a small amount of CIAV might still be present in these flocks, acting to induce the subclinical effects of CIAV infection. These data indicate a link between the presence of virus sequences and typical CIAV signs and strengthen the concept that CIAV infection has a negative economic impact on the chicken industry.

Animals↗
PubMedDate not supplied

MEQ and V-IL8: cellular genes in disguise?

One of the hallmarks of oncogenic viruses is their ability to subvert the growth regulation and evade immune response of the host. There are a number of tricks devised by various virus families. Oncogenic herpesviruses often accomplish this by encoding homologs of cellular genes involved in these functions. These viral homologs sometimes are hyperactive forms of their cellular counterparts, which function to overtake the cellular pathways, other times serve as decoys to mask the cellular functions. Marek's disease virus (MDV) carries at least two genes in that category. We have previously described Meq protein (MEQ gene product), a transcriptional factor with homology to proto-oncogenes Jun and Fos in the bZIP domain. Meq dimerizes with Jun or Fos and the Meq/Jun heterodimer is able to transactivate promoters with AP-1 site. We show here that Meq and Jun colocalize in living cells, adding to the physiological significance of the dimer formation. In addition, we present data to show that Meq and Jun can functionally complement each other in cis and in trans, using transformation and transactivation assays. Finally we describe the discovery of an IL8 chemokine homolog, designated as v-IL8 (viral IL8) in the MDV genome and discuss its possible function in MDV infection.

Amino Acid Sequence↗
PubMedDate not supplied

Effect of native chicken interferon on MDV replication.

Marek's disease virus (MDV) is an oncogenic alphaherpesvirus. Its specific phosphorylated protein, pp38 has been implicated in MDV oncogenesis. In order to check whether the known anti-viral or anti-proliferative actions of interferon (IFN) are of importance in Marek's disease (MD), chicken embryo fibroblasts (CEFs) were infected with attenuated serotype-1 MDV strain CVI988, or with herpesvirus of turkeys (HVT). Different concentrations of native chicken IFN were added to the cell cultures, prior to their infection. After incubation, MDV plaques were counted. Analysis by flow cytometry for pp38 expression was performed by using three monoclonal antibodies (MAbs) and for HVT by using an anti-glycoprotein B (gB) MAb. Increasing IFN quantities caused a reduction in a stepwise manner of plaque numbers as well as a suppression of pp38 and gB expression in the CVI988- and HVT-infected cells, respectively.

Animals↗