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Biomedical subjects

R J Davey

Publications and source records attributed to R J Davey.

At least 19 recordsLinked to original sources
PubMed2006

Simulation of phase separation in alcohol/water mixtures using two-body force field and standard molecular dynamics.

Standard molecular dynamics simulations have been carried out on pure alcohols and alcohol/water mixtures. A simple atom-atom force field consisting of Lennard-Jones potentials plus coulombic terms over atomic point charges, but without explicit polarization terms, has been specifically fitted to reproduce several experimental properties of the pure alcohols, and has been used for mixtures by developing combination rules with the TIP3P water model. Densities, enthalpies of vaporization, radial distribution functions, self-diffusion coefficients, and rotational correlation functions of the pure alcohols are well reproduced and compare favorably with those from more sophisticated force fields. Some key aspects of the phase behaviour are correctly reproduced by the molecular dynamics simulation, showing a distinct demixing process for the n-butanol/water mixture as opposed to the stability of the t-butanol/water mixtures. The results demonstrate the ability of a molecular dynamics simulation, even in its standard form and with easily accessible time ranges, but with a carefully optimized force field, to simulate and, to a certain extent, predict the properties of binary mixtures.

Journal Article↗
PubMed2005

Crystallization of a salt of a weak organic acid and base: solubility relations, supersaturation control and polymorphic behavior.

Control of crystallization processes for organic salts is of importance to the pharmaceutical industry as many active pharmaceutical materials are marketed as salts. In this study, a method for estimating the solubility product of a salt of a weak acid and weak base from measured pH-solubility data is described for the first time. This allows calculation of the supersaturation of solutions at known pH. Ethylenediammonium 3,5-dinitrobenzoate is a polymorphic organic salt. A detailed study of the effects of pH, supersaturation, and temperature of crystallization on the physical properties of this salt shows that the desired polymorph may be produced by appropriate selection of the pH and supersaturation of crystallization. Crystal morphology is also controlled by these crystallization conditions.

Acids↗
PubMed2004

Development of a new monoclonal antibody to ovine chimeric IgE and its detection of systemic and local IgE antibody responses to the intestinal nematode Trichostrongylus colubriformis.

The J558L cell line, previously transfected with the ovine Cepsilon gene, was induced to secrete a chimeric IgE protein composed of the ovine heavy chain and a mouse light chain with MW of approximately 80 and 26 kDa, respectively. After purification, the chimeric protein was used to immunise BALB-c mice and monoclonal antibodies (mAbs) were generated. The mAb 2F1, which had greatest anti-IgE activity in preliminary screens, was chosen for further characterisation and an examination of systemic and local IgE responses to the intestinal nematode, Trichostrongylus colubriformis. The chimeric IgE protein was not recognised in enzyme linked immunosorbent assay (ELISA) by mAbs raised against ovine IgG1, IgG2, IgA or IgM. However, 2F1 was highly specific to the chimeric IgE protein, and did not cross-react with ovine IgG1, IgG2 or IgA. Western blot analysis also showed that 2F1 and secretory IgA (sIgA) did not cross-react, and that 2F1 and the anti-IgA mAb identified different MW bands from colostrum (approximately 200 and 400 kDa, respectively). 2F1 bound to mucosal mast cells (MMC) isolated from the intestines of lambs infected with T. colubriformis, but cultured bone marrow-derived mast cells (BMMC) required prior incubation with the chimeric IgE protein for this binding to occur. Distinctive staining of plasma cells and putative mast cells were observed using 2F1 on immunohistological sections of mesenteric lymph node and jejunum.ELISA incorporating 2F1 was able to detect >0.4 ng chimeric protein. Total IgE in ovine colostrum and intestinal homogenates was quantified using a capture ELISA, with known amounts of chimeric protein used to produce a standard curve. Colostrum from outbred Merino ewes had 0.55-11.05 ng ml(-1) total IgE, and their lambs, at necropsy after infection with a total of 18,000 T. colubriformis infective larvae over a 9-week period, had 45-620 ng g(-1) total IgE in intestinal tissue. Compared to genetically susceptible lambs, antigen-specific levels of IgE were significantly higher in genetically resistant lambs after infection with 4500 T. colubriformis infective larvae (TcL3) per week for 9 weeks (161.4 versus 44.8 geometric mean titres; P=0.043). In western blots, distinctive bands (19-21 and 27 kDa) from T. colubriformis larval antigen were differentially recognised by IgE, as identified by 2F1, in intestinal homogenates from genetically resistant animals. These results have demonstrated the value of 2F1 for quantification of IgE responses in samples derived from ovine fluids and tissues using ELISA, western blots and immunohistology. In this respect, it recognises native ovine IgE and does not require pre-treatment of the sample with denaturing agents or ammonium sulphate.

Animals↗
PubMed2003

Solution crystallisation via a submerged liquid-liquid phase boundary: oiling out.

In many situations the process of crystallisation from solution is known to occur via metastable crystalline states (polymorphs or solvates). Here we present what we believe to be a novel example of small molecule crystallisation in which the initial separation of a solute rich liquid phase precedes the crystallisation event. We believe this occurs because a submerged liquid-liquid phase boundary is accessible within the metastable zone of the crystal nucleation process.

Journal Article↗
PubMed2000

Disorder and twinning in molecular crystals: impurity-induced effects in adipic acid.

The variation in physical properties of crystals grown in the presence of additives or impurities have previously been attributed to lattice disorder developed during crystallization. Adipic acid crystallized in the presence of a variety of stereochemically related impurities typifies such behavior with disorder manifest in variations of dissolution rates and enthalpies of solution and fusion. In this case the most extreme habit, produced by the presence of added monoalkanoic acids, is a rounded dumbbell that was suggested previously to be a twinned crystal. In this contribution such crystals are fully characterized both through their external morphology and by means of single crystal X-ray diffraction. These techniques show that these particles are not twinned but rather are disordered single crystals comprising a small number of slightly misaligned domains. The interaction between additive and substrate is modeled and new additives selected that induce the formation of true mechanical twins in adipic acid.

Adipates↗
PubMed2000

Protection of Merino lambs against Haemonchus contortus by trickle infection of neonates.

In two trials, lambs were trickle infected with 400 or 1000 infective larvae of Haemonchus contortus (HcL(3)), twice weekly for 4 weeks from the day of birth. Following anthelminthic treatment at 6 weeks (Trial 1) or 7 weeks of age (Trial 2), lambs were challenged 1 week later with a trickle infection totalling 5000 (Trial 1) or 10000 HcL(3) (Trial 2). In both cases, significant protection (P<0.05) ranging from 42 to 79% was achieved against egg and worm counts. Serum antibody responses as well as abomasal lymph node cell proliferation and production of interferon-gamma or interleukin (IL)-5 did not differ significantly between immunised and control lambs. The results are consistent with earlier findings that neonatal lambs can generate protective immunity against Trichostrongylus colubriformis, but the underlying mechanism(s) remain to be determined.

Animals↗
PubMed1999

Induction of protective immunity to Trichostrongylus colubriformis in neonatal merino lambs.

The premise that any bias of immune reactivity in neonatal lambs towards T-helper (TH)2 responses could benefit the induction of protection against gastrointestinal nematodes was investigated. In two trials, lambs were either trickle-immunised with 2000 infective larvae of Trichostrongylus colubriformis (TcL3), 3 times weekly from the day of birth for 6 weeks or inoculated with a recombinant T. colubriformis 17 kDa antigen in incomplete Freund's adjuvant (IFA). In trial 1, trickle immunised and control neonates challenged at 7 weeks of age had similar worm counts 10 days after challenge, but from 25 days, significant reductions (P<0.01) in mean faecal egg count and worm count in excess of 75% were displayed by the immunised lambs. The results of a second, similar trial, gave 85-91% reductions in parasitism in trickle immunised neonates (P<0.001) and around 50% protection in neonates vaccinated with recombinant 17 kDa antigen. Parasitism in immunised neonates in Trial 2 was significantly reduced (P<0.001) compared to that in 4-month-old animals. Antibody responses in trickle-immunised (protected) and challenge control (infected) neonates were almost exclusively of the IgG1 isotype compared to vaccinated animals which exhibited increased levels of anti-17kD IgG2. Trichostrongylus colubriformis infection, but not specific vaccination, induced interleukin-5 production by mesenteric lymph node cells. The results offer the tantalising prospect of generating protective immunity to gastrointestinal parasites prior to weaning in sheep; this was most effectively generated by viable parasites in this investigation.

Animals↗
PubMed1998

Attempts to generate immunity against Trichostrongylus colubriformis and Haemonchus contortus in young lambs by vaccination with viable parasites.

The ability of young Merino lambs to achieve protective immunity following vaccination via viable nematode infections was assessed. Lambs were infected from 1 month of age by repeated continuous low dose (trickle) administration of Trichostrongylus colubriformis or Haemonchus contortus infective larvae (L3), or by truncated infections with high doses of viable T. colubriformis L3. After 7 weeks all groups were drenched with anthelmintic and at 3 months of age they were re-infected with the homologous species. Protection was assessed by faecal egg counts at 3, 4, 5, 6 and 7 weeks after challenge, and worm count at 7 weeks after challenge. Young lambs were partially protected by 3 months of age against Trichostrongylus by trickle infection. This protection correlated with local mast cell and T-cell priming, increased numbers of local antigen-presenting cells and T-cells and increased worm-specific antibody titres in the intestine. However, there was no evidence that young lambs were capable of immunologically recognising H. contortus antigens following trickle infection, nor did trickle infection significantly protect young lambs against Haemonchus challenge.

Animals↗
PubMed1996

DR2/DQw1 inheritance and haplotype sharing in affected siblings from multiple sclerosis families.

Although the human leukocyte antigen DR2/DQw1 allele has been associated with multiple sclerosis, studies of DR2/DQw1 inheritance in multiple sclerosis multiplex families have yielded conflicting results. We examined this question in "high-incidence" families, defined as families with more than 50% of siblings affected. DR2/DQw1 allele frequencies were significantly increased, particularly in mothers and affected siblings (p < 0.0001). The transmission of DR2/DQw1 from both parents was more frequent in affected offspring (p = 0.005). While evidence for segregation of disease with a particular parental allele was lacking in most families, the frequency of haplotype sharing was higher in affected sib pairs (p < 0.01).

Alleles↗
PubMed1995

An analysis, using monoclonal antibodies, of the role of interferon-gamma in ovine immune responses.

A mAb (IFN-9) which neutralizes biologically active ovine and bovine IFN-gamma was used to deplete levels of the cytokine in vivo in sheep and examine the consequences for immune responses to adjuvanted antigen and skin reactivity to Bacillus-Calmette-Guerin (BCG). Groups of sheep were immunized with ovalbumin in the adjuvants, Quil A or dextran sulphate (MW 500,000; DXS), both of which elicit production of IFN-gamma. MAb anti-IFN-gamma or an isotype control mAb (anti-carbonic anhydrase positive particles) were inoculated i.v. during primary and/or secondary responses. Reactions monitored in efferent prefemoral lymph indicated that anti-IFN-gamma effectively depleted levels of IFN-gamma in lymph but had no effects on the magnitude and kinetics of lymphocyte and lymphoblast traffic, or total or isotypic titres of specific Ig. When incubated in vitro with ovalbumin, antigen-reactive cells from anti-IFN-gamma treated sheep did not produce IFN-gamma, suggesting an on-going modification to cytokine production. In contrast, skin reactions to purified-protein derivative in sheep immunized with BCG were reduced by < 40% by anti-IFN-gamma. The results indicate that IFN-gamma production may not be obligatory for delayed-type hypersensitivity reactions or for the adjuvant action of Quil A or DXS, and that specific mAb can alter the profile of cytokines produced by antigen-reactive cells in sheep.

Adjuvants, Immunologic↗
PubMed1995

Depletion of IFN-gamma, CD8+ or Tcr gamma delta+ cells in vivo during primary infection with an enteric parasite (Trichostrongylus colubriformis) enhances protective immunity.

In order to examine the role of CD8+ and WCI+ T cells and of IFN-gamma in the development of protective immunity against infection with the enteric nematode parasite Trichostrongylus colubriformis in sheep, mAb were administered during induction of the immune response to deplete or neutralize these components. Protection against the primary and challenge infections were assessed by faecal egg count and total worm count. Prolonged administration of mAb recognizing IFN-gamma and CD8+ resulted in significantly increased protection during the 6-week primary infection. CD8+ cells were depleted from blood but not intestinal mucosa. After injection of mAb (CC15) recognizing the surface antigen WCI, WCI+ and T cell receptor (Tcr) gamma delta+ cells were depleted from blood but not from enteric mucosa, and protection against challenge, although variable, was increased by up to 88%. It appears that CD8+ and WCI+/gamma delta+ cells and IFN-gamma all retard the potential development of naturally-acquired immunity against the parasite.

Animals↗
PubMed1994

Characteristics of white cell-reduced red cells stored in tri-(2-ethylhexyl)trimellitate plastic.

BACKGROUND: Standard blood storage containers contain extractable plasticizers that accumulate in blood during storage and are an unintended transfusion product. However, extractable plasticizers have a protective effect on the red cell membrane and improve red cell storage variables. Prestorage white cell reduction also improves selected red cell storage variables. STUDY DESIGN AND METHODS: The study evaluated whether the beneficial effect of prestorage white cell reduction would offset the negative effect of the absence of extractable plasticizer in red cells stored in AS-3 for 42 days at 4 degrees C. Filtered red cells stored in polyvinylchloride containers with the nonextracting plasticizer, tri-(2-ethylhexyl)trimellitate (TEHTM), were compared to unfiltered red cells stored in polyvinylchloride containers with the extractable plasticizer di-(2-ethylhexyl)phthalate (DEHP). RESULTS: Poststorage supernatant potassium and red cell osmotic fragility were significantly higher in white cell-reduced TEHTM units than in unfiltered DEHP units. The mean 24-hour recovery of the filtered TEHTM red cells was significantly lower than that of the unfiltered DEHP red cells (69.1 +/- 7.4% vs. 77.1 +/- 5.1%, p < 0.05, n = 8). CONCLUSION: These data demonstrate that white cell reduction before 42-day storage in TEHTM containers with currently approved preservatives does not yield an acceptable red cell component.

Adenosine Triphosphate↗
PubMed1993

Characteristics of red cells irradiated and subsequently frozen for long-term storage.

Irradiation of blood components eliminates the risk of transfusion-associated graft-versus-host disease. Freezing directed or rare red cell units that are irradiated but not transfused would facilitate inventory management and would increase the transfusion options for the involved patients. However, no studies have been performed to evaluate whether prestorage irradiation damages subsequently frozen red cells. Ten normal volunteers donated a unit of whole blood on two separate occasions. One unit was irradiated with 15 Gy (1500 rad), stored at 4 degrees C for 6 days, and then frozen and stored at -75 degrees C for 56 days. The other unit (control) was similarly stored but was not irradiated. Aliquots of the units were tested on Day 0 and Day 6 and, after deglycerolization, on Day 62. Comparison of means and changes in means showed no significant differences in red cell ATP, 2,3 DPG, or supernatant hemoglobin and glucose in control and irradiated units. The difference in the change in supernatant potassium from Day 0 to Day 6 in control and irradiated units was significant (1.5 to 28.6 mmol/L vs. 1.5 to 48.5 mmol/L: p < 0.0001). Irradiation did not cause significant differences in postdeglycerolization red cell recovery (control, 84.5% vs. irradiated, 81.2%) or in 24-hour posttransfusion autologous red cell survival (control, 91.1% vs. irradiated, 90.9%). Red cells can be irradiated, stored at 4 degrees C for 6 days, and subsequently frozen with no increase in detectable damage as compared to controls that were not irradiated.

Blood Preservation↗