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D H Lloyd

Publications and source records attributed to D H Lloyd.

At least 73 records · Page 4Linked to original sources
PubMed1992

Predicted alpha-helical regions of the prion protein when synthesized as peptides form amyloid.

By comparing the amino acid sequences of 11 mammalian and 1 avian prion proteins (PrP), structural analyses predicted four alpha-helical regions. Peptides corresponding to these regions of Syrian hamster PrP were synthesized, and, contrary to predictions, three of the four spontaneously formed amyloids as shown by electron microscopy and Congo red staining. By IR spectroscopy, these amyloid peptides exhibited secondary structures composed largely of beta-sheets. The first of the predicted helices is the 14-amino acid peptide corresponding to residues 109-122; this peptide and the overlapping 15-residue sequence 113-127 both form amyloid. The most highly amyloidogenic peptide is AGAAAAGA, which corresponds to Syrian hamster PrP residues 113-120 and is conserved across all species for which the PrP sequence has been determined. Two other predicted alpha-helices corresponding to residues 178-191 and 202-218 form amyloids and exhibit considerable beta-sheet structure when synthesized as peptides. These findings suggest the possibility that the conversion of the cellular isoform of PrP to the scrapie isoform of PrP involves the transition of one or more putative PrP alpha-helices into beta-sheets and that prion diseases are disorders of protein conformation.

Amino Acid Sequence↗
PubMed1992

Double blind, placebo-controlled, crossover study of evening primrose oil in the treatment of canine atopy.

Thirty-five dogs with non-seasonal atopic dermatitis were used in a double-blind, placebo-controlled crossover study of the effects of evening primrose (Oenothera biennis) oil. There was a significant treatment effect (P less than 0.05) on erythema. An analysis of the changes in plasma phospholipid levels of essential fatty acids revealed a significant (P less than 0.05) rise in linoleic acid concentration above that in the placebo group. Arachidonic acid levels in the treated group increased significantly (P less than 0.005) in the first phase and also in the second phase (P less than 0.05). In the second phase the levels of arachidonic acid in the active and placebo groups differed significantly (P less than 0.05) and there was a significant treatment effect (P less than 0.05).

Animals↗
PubMed1992

Occurrence of Staphylococcus intermedius on the hair and skin of normal dogs.

Aerobic bacterial populations were studied on the distal hair coat and at the skin surface of the shoulder, rump and abdomen of 10 healthy dogs. Coagulase negative staphylococci (CNS) were more frequently isolated from the hair than the skin at the shoulder and rump. There was no difference in the isolation rate of coagulase positive staphylococci (CPS) (Staphylococcus intermedius) between the hair and skin. Total skin counts were greatest on the abdomen whereas CNS counts from the hair were least at this site. There were no differences between CPS counts at the three sites on either hair or skin. The populations on the relatively unfavourable microenvironment of the distal hair may represent contamination rather than colonisation. The low populations of CPS at the skin surface also indicate contamination or transient colonisation rather than true resident status.

Abdomen↗
PubMed1991

Cytotoxic activity of Staphylococcus hyicus.

Culture supernatants from a number of Staphylococcus hyicus strains caused toxic effects to both murine fibroblast and porcine keratinocyte cells in culture. The extent of cytotoxicity was shown to differ between strains and may provide an indication of strain virulence. Purification of cytotoxic activity produced by S. hyicus (strain P119) using preparative isoelectric-focussing demonstrated it to be cytolytic, haemolytic and non-proteolytic. The cytotoxin demonstrates certain properties in common with the delta haemolysin of Staphylococcus aureus.

Animals↗
PubMed1991

The effect of malnutrition on vaccination against Dermatophilus congolensis infection in ruminants.

Vaccination against Dermatophilus congolensis was carried out in groups of lambs raised on optimal or energy deficient diets. The groups differed significantly in weight, body condition score and plasma total protein and albumin. All animals were then challenged with D. congolensis in a dose response infection model. The vaccine was effective in the well nourished animals, reducing the number of affected lambs in the vaccinated group and the severity of the lesions and increasing the minimum dose required to cause infection. In contrast, all of the vaccinated energy-deficient lambs developed lesions. There was some evidence of vaccine effect in these animals but this was not as marked as that seen in the well nourished lambs. The malnourished lambs, vaccinated and non-vaccinated, took longer to heal than the well nourished groups. Resistance to challenge was not associated with serum antibodies or skin test reactivity to D. congolensis antigens.

Actinomycetales↗
PubMed1990

The effect of energy malnutrition in ruminants on experimental infection with Dermatophilus congolensis.

The ability of malnourished and optimally fed animals to resist infection with D. congolensis was assessed by the dose-response to experimental inoculation. The severity of infection, as measured by scoring the lesions, was the same in both groups of lambs. However marked differences were seen between the two groups in the appearance of scabs and in the time taken for them to resolve. The malnourished animals had more persistent, chronic lesions compared with the more obvious, acute type lesions seen on the skin of the healthy controls. These results were probably related to the reduced rates of wool growth and lanolin production found in the malnourished lambs, which may reflect a reduction in the rate of cellular turnover in the skin of these animals.

3-Hydroxybutyric Acid↗
PubMed1990

The effect of recent vaccination on the dose-response to experimental Dermatophilus congolensis infection in rabbits.

Dermatophilus congolensis infection of rabbits was used to investigate the effects of active immunity on epidermal challenge following vaccination. Rabbits (three groups of four) were vaccinated intradermally with live whole-cell preparations of D. congolensis strains SS18C and FD11 (groups SSVAC and FDVAC respectively); a third group (UNVAC) remained as unvaccinated controls. Two weeks after vaccination, separate 1.5-cm2 clipped and ether-swabbed skin sites were inoculated with a 10-fold dilution range (10(7) to 10(1) zoospores per cm2 of skin) of SS18C or FD11. Lesion scores at each site were calculated from the sum of individual scores (0 to 4+) for erythema, oedema and scab formation multiplied by the percentage of the inoculated area affected. A clear dose-response relationship between the size of inoculum and the severity of lesions was seen for both D. congolensis stains in the control group (UNVAC). In the SSVAC and FDVAC groups the lesions were less severe and developed more quickly. The number of zoospores required to cause infection in the vaccinated animals was up to 10,000-fold higher for homologous inoculated sites and 100-fold for heterologous sites. Serological analysis was carried out with an ELISA system. Vaccination and challenge resulted in increases in specific antibody against D. congolensis antigens. Cross-reacting antibody to the heterologous strain of D. congolensis used was demonstrated in both vaccinated groups but did not correlate with equal protection to homologous or heterologous challenge. The dose-response relationship demonstrated by this model enabled semi-quantitative analysis of the effects of vaccination on D. congolensis infective dose and severity of infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomycetales↗
PubMed1989

Studies on antagonism between porcine skin bacteria.

Strains of Staphylococcus warneri, Staph. epidermidis and Aerococcus viridans isolated from porcine skin were shown to produce substances that inhibited the growth of Staph. hyicus. Studies of interactions between the inhibitor-producing bacteria and Staph. hyicus on cellulose acetate membranes demonstrated a significant reduction (P less than 0.001) of the Staph. hyicus population at various stages of its growth cycle, depending on the inhibitor used. Inhibitor production profiles in batch culture showed a change in production with culture growth. Trypsin and an extracellular substance from Staph. hyicus had similar effects in reducing inhibitor production. Staphylococcus hyicus was shown to produce varying amounts of a proteolytic enzyme during growth in batch culture. Such in vitro models of bacterial interaction enable potential mechanisms of disease control using inhibitor-producing organisms to be investigated and provide a basis for studies in vivo.

Animals↗
PubMed1989

Actions of bovine skin washings and sera on the motile zoospores of Dermatophilus congolensis.

Concentrated skin washings, even from vaccinated animals, failed to inhibit the motility of the infective zoospores of Dermatophilus congolensis, or to prevent them from germinating or infecting cattle; their constituent immunoglobulins did not attach to the flagella although IgA and IgG2 did bind to the cell bodies. It is concluded that the specific antibodies at the skin surface of ruminants are unlikely to have a role in zoospore immobilisation. Post vaccination sera rapidly immobilised and clumped the zoospores by means of a coat around the flagella, in which immunoglobulins, particularly IgM, were detected. IgM and IgG1 also attached to the cell bodies of the zoospores.

Actinomycetales↗
PubMed1988

Synthesis and serotonin receptor affinities of a series of enantiomers of alpha-methyltryptamines: evidence for the binding conformation of tryptamines at serotonin 5-HT1B receptors.

A procedure for the preparation of optically pure alpha-methyltryptamines (AMTs) from substituted indoles was developed. The key step in the sequence was the reductive amination of substituted indole-2-propanones with the commercially available pure enantiomers of alpha-methylbenzylamine, followed by the chromatographic separation of the resulting pair of diastereomeric amines by preparative centrifugal (Chromatotron) chromatography. Catalytic N-debenzylation then afforded the pure AMT enantiomers. Optical purity was established by chiral HPLC analysis of the 2-naphthoylamide derivatives. An improved procedure for the preparation of indole-2-propanones was also developed. To probe structure-activity relationships of serotonin receptors, affinities of the alpha-methyltryptamine enantiomers were then measured at the 5-HT2 antagonist receptor subtype, with displacement of [3H]ketanserin, and were estimated at the 5-HT1B receptor, with displacement of [3H]serotonin, respectively, in rat frontal cortex homogenates. Enantioselectivity at the receptor subtypes varied, depending on aromatic substituents. For a 5-hydroxy or 5-methoxy, the S enantiomer had higher affinity or was equipotent to the R enantiomer. This selectivity at [3H]serotonin binding sites was reversed for 4-oxygenated alpha-methyltryptamines, where a 4-hydroxy or 4-methoxy did not enhance affinity over the unsubstituted compounds. These results can be explained, for the [3H]serotonin displacement data, if the binding conformation is one where the ethylamine side chain is trans and lying in a plane perpendicular to the indole ring plane.

Animals↗
PubMed1988

Plasmids in Staphylococcus hyicus.

Fifty-one strains of Staphylococcus hyicus and six of Staph. chromogenes were collected from porcine and bovine sources in England and Belgium. Antibiotic resistance and plasmid profiles were established. Plasmids associated with resistance to tetracycline, erythromycin and streptomycin were identified in many strains; these plasmids were about the same size as those mediating similar resistances in Staph. aureus of human origin. Many small cryptic plasmids were also seen.

Animals↗
PubMed1988

Use of a monoclonal antibody in the diagnosis of infection by Dermatophilus congolensis.

A monoclonal antibody (McAb) to Dermatophilus congolensis was produced from murine hybridoma cultures and purified by affinity chromatography. Species specificity was demonstrated using indirect immunofluorescent staining; the McAb was shown to react with 10 D congolensis isolates but not with 10 Nocardia species isolates, a Rhodococcus and a Streptomyces species isolate. The McAb was used to demonstrate D congolensis in clinical material from confirmed bovine and ovine cases and presumptive equine cases of dermatophilosis by indirect immunofluorescent staining.

Actinomycetales↗
PubMed1987

Sequential production of specific antibodies in serum and at the skin surface of cattle following intradermal vaccination with Dermatophilus congolensis.

Studies of the temporal changes in specific antibody titres to D. congolensis in serum and washings from inoculated and uninoculated skin indicate that production of IgG1 and IgG2 antibody at the skin surface is a transudative process related to serum antibody concentration. Transport of IgM is likely to be based on a similar mechanism but that of IgA appears to depend on a local secretory process.

Actinomycetales↗
PubMed1987

The effect of washing on the thickness of the stratum corneum in normal and atopic individuals.

The thickness of, and number of cell layers in, the stratum corneum and the living epidermis were determined on frozen sections of washed and unwashed skin from normal and atopic individuals of both sexes. The stratum corneum of atopic patients was thinner and had fewer layers of dead cells and intercellular lipid than normal, although the living epidermis was thicker. Regular washing with soap and water had no appreciable effect on the dimensions of the living epidermis of either group but caused a reduction in the number of cell layers and the amount of sudanophilic material in the stratum corneum of both. In atopic patients little surface lipid remained, suggesting that washing with soap and water may be detrimental to the barrier function of the stratum corneum in such patients.

Administration, Topical↗