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Biomedical subjects

D A Davies

Publications and source records attributed to D A Davies.

At least 19 recordsLinked to original sources
PubMed1989

Practical uses of ultrasound in early pregnancy in cattle.

Using a 'real-time' ultrasound scanner with a 3.5 MHz rectal transducer, a herd of 80 Friesian cows were scanned at weekly intervals during early pregnancy to assess the accuracy of pregnancy diagnosis, and the accuracy of twin detection. The growing fetuses were also measured to determine the relationship between crown-rump length and age. The accuracy of detection of pregnancy was inversely proportional to the age of the cow (r -0.967), the accuracy of detection of twinning was 100 per cent and there was strong correlation between fetal crown-rump length and age (r 0.98).

Animals↗
PubMed1986

Specific transfer factor protects mice against lethal challenge with herpes simplex virus.

Bovine transfer factor (TFd) specific to herpes simplex virus (HSV)1 or to HSV2 was prepared by immunizing calves with the corresponding virus. The TFd preparations were then injected into Swiss mice in an attempt to protect them against a subsequent lethal challenge with HSV1 or HSV2 virus. It was thus shown that injection of anti-HSV TFd protects the mice against the corresponding HSV virus, whereas the injection of a nonspecific TFd (anti-CMV) fails to protect against a challenge with HSV1. Furthermore, a dose-response effect was observed, since potent TFd preparations were ineffective when they were used at one-fifth of the original concentration. It seems, therefore, that animal models may be used to assay the potency of TFd preparations specific for herpes viruses.

Animals↗
PubMed1979

The influence of carbohydrases on the growth of fungal pathogens in vitro and in vivo.

Mixtures of mycolytic enzymes from various sources release protoplasts from living fungal tissue under suitable conditions. Such enzyme mixtures obtained from Coprinus comatus (mycolase I), Physarum polycephalum (mycolase II) and Lycoperdon pyriforme (mycolase III) are of low toxicity in mammals when given parenterally and are able to cure experimental systemic fungal infections in mice when administered alone or in conjunction with normally ineffective levels of conventional antimycotic drugs such as amphotericin B. The effect is believed to be due to enzymic degradation of the fungal cell wall either killing the fungus directly or enhancing activity of existing antifungal agents by increasing access to the cell interior.

Amphotericin B↗
PubMed1979

[Active enhancement using B-lymphocytes].

B-lymphocytes given 7 days prior to auxiliary heterotopic heart transplantation significantly delay transplant rejection. T-lymphocytes or purified erythrocytes have no effect at all on the subsequent heart graft. The beneficial effect of blood transfusions could be due to the transfusion of B-lymphocytes, which create a state of active enhancement in the transplant recipient.

Animals↗
PubMed1978

Cross-reactivity with mouse antigens in the ferritin immunogenetic (IR-gene) system.

Structural similarity between antigens and self molecules could be responsible for low antibody responses in different immunogenetic (IR-gene) systems. B10.M and B10.D2 strains are high responders, whilst A. Thy-1-1 mice are low responders, following primary immunization with ferritin in saline. Cross-reactivity between mouse-self antigens and ferritin was tested by antigen excess and radioimmunoassay techniques, using cells obtained from normal, unimmunized high- and low-responder mice, to compete for specific antibody. Low-responder A.Thy-1-1 mouse cells consistently displaced more anti-ferritin antibodies than did high-responder B10.M and B10.D2 mouse cells at varying antibody and cell concentrations and these differences were statistically significant (P less than 0.001). It is suggested that the responder status of different strains of mice, following primary immunization with ferritin in saline, could be explained by the degree of cross-activity between self determinants and antigen, such that low responders cross-react to a greater degree with the test antigen than do high-responder mice. A similar mechanism of cross-reactivity could operate in the pathogenesis of HLA-linked diseases.

Animals↗
PubMed1977

Genetic control of the immune response to ferritin in F1 hybrid mice.

The immune response to the antigen horse spleen ferritin, has been investigated in ten inbred parental strains and seven different F1 hybrid strains of mice, using an antigen excess technique. The degree of dominance in an F1 hybrid system can be estimated by using the Fisher dominance index. The responses in F1 hybrid animals, obtained from crosses of high and low responder parents, varied from dominant to recessive but the overall mean dominance index for the ferritin immunogenetic system was found to be -0.0467 +/- 0.0083 (mean +/- s.e.), a value close to zero, which suggests a codominant mode of inheritance of IR-genes to ferritin and this is consistent with most published data in other F1 IR-gene systems.

Animals↗
PubMed1976

The effects of erythrocyte-absorbed H-2 alloantisera on mixed lymphocyte culture reactions.

One-way mixed lymphocyte culture reactions were inhibited by the addition of H-2 alloantisera directed against the stimulator cell type. The sera retained their original inhibitory activity after the removal from them of conventional H-2K antibodies by exhaustive absorption with erythrocytes. The absorbed antisera had specificity for Ia but not H-2 antigens thereby indicating that the inhibitory activity of the sera is a function of antibodies against I region products. H-2 and Ia alloantisera directed against the responder cell type did not specifically inhibit culture reactions: they either had no effect or they apparently increased stimulation. This increase appeared to be immunologically specific, at least in part, and to require some heat-labile normal serum component for its elicitation. It is concluded that treatment of responder cells inactivates or destroys some normally inactive or inhibitory subpopulation such that the remaining cells respond better to allogeneic stimulation. Both the anti-stimulator and the anti-responder effects were seen with either whole serum or crude immunoglobulin preparations when one of these was added to the culture or used for pretreating cells before establishing the culture.

Animals↗
PubMed1976

The detection of Ia antibodies in polyspecific H-2 alloantisera absorbed with erythrocytes.

H-2 alloantisera contain Ia antibodies whose detection is obscured by the presence of serodominant K,D specificities. A method is described whereby Ia antisera can be prepared by absorbing conventional H-2 sera with donor-strain erythrocytes. The analysis of such absorbed antisera has led to the identification of the new specificity Ia.16, and the redefinition of the specificities H-2.34 and H-2.46 as complex Ia specificities which map in the I-A region of the H-2 complex. A number of other so-called H-2 specificities also appear to have Ia-like properties.

Animals↗
PubMed1976

Genetic control of the immune response to ferritin in mice.

The immune response to the antigen horse spleen ferritin was tested in sixteen inbred strains of mice. Using a fixed antigen percentage bound isotope technique, it was found that the quantity of antibody produced was related to the genetic status of the responding animal. A continuous distribution of responses was obtained, which were found to be linked to H-2 loci and the 2 non-H-2 loci 'Tla' and 'Theta' and these responses are detectable following primary immunization. It is suggested that the continuous distribution of quantitative antibody responses to ferritin, is compatible either with a large number of IR-genes or with a cross tolerance hypothesis requiring no IR-genes at all.

Analysis of Variance↗
PubMed1975

The dominant role of Ia antibodies in the passive enhancement of H-2 incompatible skin grafts.

The ability of H-2 antisera and their constituent K and Ia antibodies to enhance the survival of skin allografts was investigated. Ia sera were prepared from H-2 alloantisera by exhaustive absorption with donor-strain RBC and the absorbed K antibodies were also recovered by acid elution of the RBC. The removal of conventional K/D antibody in no way diminished the activity of enhancing sera over wide dose ranges in two different incompatibility systems. The recovered K/D antibodies in the doses used had at best a trivial enhancing effect. The dominant role of Ia antibodies in enhancement was confirmed by showing significant prolongation of graft survival in third-party systems where the sera covered only some of the Ia antigens in incompatibilities involving K,D and Ia differences and in homologous systems using Ia sera fractionated into their constituent mono-specificities. It is concluded that enhancement is a function of antibodies directed against Ia antigens (I region products) and that antibody against conventional histocompatibility antigens such as H-2.K, D, and by homology HL-A and Ag-B has only a minor role in passive enhancement.

Absorption↗