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D J White

Publications and source records attributed to D J White.

At least 91 records · Page 5Linked to original sources
PubMed1997

Hyperacute lung rejection in a pig-to-human transplant model: the role of anti-pig antibody and complement.

BACKGROUND: The physiology of hyperacute rejection of pig lung by human blood and the role of antispecies antibody and complement in this phenomenon have not previously been characterized. METHODS: Human blood was perfused through an ex vivo pig heart-lung preparation. In the treatment groups, blood was either unmodified or modified to deplete alternative pathway complement (heat treatment), anti-pig antibody, or both. Control experiments were performed with unmodified and heat-treated pig blood. Physiologic parameters, organ survival, and immunohistology were the primary outcome measures assessed. RESULTS: Pig lung was consistently damaged by human blood within 45 min (median 20 min), as evidenced by elevated pulmonary vascular resistance and parenchymal injury. Immunohistologic studies of perfused lungs showed prominent deposition of IgM and classical pathway component, C4, and weaker deposition of alternative pathway component, properdin. Heat treatment did not impede the rise in pulmonary vascular resistance or significantly prolong survival. Depletion of anti-pig antibody prolonged survival (median 90 min) and attenuated the rise in pulmonary vascular resistance. Antibody absorption, combined with heat treatment of plasma, prevented the elevation in pulmonary vascular resistance and yielded median graft survival (210 min) similar to pig blood perfusion (approximately 240 min). CONCLUSIONS: These results show that elevated pulmonary vascular resistance and pulmonary parenchymal injury are mediated at least in part by antispecies antibody and heat-sensitive pathways. They are consistent with the hypothesis that complement activation contributes significantly to acute lung damage in the pig-to-human species combination.

Animals↗
PubMed1997

Morphology of hDAF (CD55) transgenic pig kidneys following ex-vivo hemoperfusion with human blood.

Discordant xenotransplantation of pig kidneys into man may be possible in the future using transgenic organs which regulate complement activity. It was the aim of this experimental study to characterize morphologic alterations of organs transgenic for human decay accelerating factor (hDAF/CD55) perfused with human blood since no data on function of these organs after exposure to human blood are available. An ex-vivo system was developed that allows computer driven pressure-controlled perfusion of kidneys including a separate cartridge oxygenator circuit. Following cold ischemia time of 1-4 hr, 8 kidneys from heterozygote transgenic animals (TG) and 9 control kidneys (C) were perfused with 500 ml freshly drawn heparinized human blood at physiological conditions. A histologic grading system from 0 to +4 was used to describe the histologic findings. Using a mouse antihuman DAF moAB, hDAF was stained on all TG kidneys both on glomerular capillary (4+) and vascular endothelium (2+), but there was no detectable hDAF-expression on controls. No difference in xenoantibody deposition on vascular endothelium was seen between both groups. There was comparable staining for complement fraction C4 in both groups, but significant reduction of C3 and C9 staining on glomerular and vascular endothelium in TG. P-selectin was expressed on a higher level in C (+4) compared with TG (+2). Neutrophil extravasation [NP-57 elastase] was higher in C (80.2 vs. 32.2 C vs. TG [values as n/high power field]). Tubular epithelial cell swelling and mild necrosis was paralleled by glomerular hemorrhage and platelet microthrombus formation in both groups as seen in transmission electron microscopy. The observed results allow the conclusion that hDAF expression on transgenic pig kidneys was sufficient to inhibit complement activation beyond C3 during xenoperfusion with human blood despite xenoantibody deposition.

Animals↗
PubMed1997

Coating of human decay accelerating factor (hDAF) onto medical devices to improve biocompatibility.

In passing blood through an artificial circulatory system, the blood is exposed to surfaces that result in activation of the complement system. The consequences of the activation of complement can be extremely serious for the patient ranging from mild discomfort to respiratory distress and even anaphylaxis. An entirely novel approach was to express recombinant GPI anchored human decay accelerating factor (hDAF) using the baculovirus system and then coat the recombinant protein onto the surfaces of these materials to reduce complement activation. Expression of hDAF in Sf9 cells was shown by ELISA, FACS analysis, and Western blot. Functional activity was tested by CH50 assay. For the coating experiments a small scale model of a cardiovascular bypass circuit constructed from COBE tubing was used. hDAF was either coated onto the circuit using adsorption or covalently linked via the photoreactive crosslinker, p-azidobenzoyl hydrazide. After coating, heparinised human blood was pumped around the circuit and samples were collected into EDTA collection tubes at different time points. Complement activation was measured using a Quidel C3a-des-arg EIA. The photolinked circuits gave a reduction in C3a production of 20-50%, compared to 10-20% seen with an absorbed hDAF circuit. Furthermore, the inhibition of complement was seen over the whole time scale of the photolinked circuit, 60-90 min, whilst in the adsorbed circuit inhibition was not seen to a significant degree after 60 min. The time scale of a standard cardiac bypass is 45-90 min, therefore, the photolinked circuit results are encouraging, as significant inhibition of complement activation is seen within this time frame.

Adsorption↗
PubMed1997

Analysis of transgene integration sites in transgenic pigs by fluorescence in situ hybridization.

The production of pigs transgenic for human decay accelerating factor (hDAF) as potential donors for clinical organ xenotransplantation was reported several years ago. For this purpose it is required that high levels of hDAF are expressed at relevant sites in transplantable organs. Currently, homozygous lines have been produced as well as lines from crosses between heterozygous animals from different founder lines, termed 'jigsaw' pigs. The purpose of the 'jigsaw' crosses is to combine the desirable hDAF protein expression patterns found in different founder lines. Initial selection of the 'jigsaw' pigs is based on the inheritance of the hDAF integration sites from both lines. Litters with potential homozygous transgenics and 'jigsaw' transgenics were analysed by fluorescence in situ hybridization (FISH) and slot blot analysis. Results show that both slot blot analysis and FISH are suitable to distinguish between pigs that are heterozygous and homozygous fir hDAF. However, FISH has the advantage of producing results more rapidly. For the identification of 'jigsaw' pigs FISH analysis was required since slot blot analysis lacked the required accuracy. On basis of these results, FISH analysis was made part of the routine screening programme for hDAF transgenic pigs.

Animals↗
PubMed1997

Xenogeneic transplantation.

Hyperacute rejection, the previously insurmountable obstacle to pig-to-human xenografts, has been overcome. There is reason to hope that concerted research will overcome the remaining obstacles. Pigs will be produced expressing other regulators of complement activation molecules in addition to decay accelerating factor. Modification of antigenic structure of cells could also be achieved. There is now some hope that large scale clinical xenotransplantation could become a reality.

Animals↗
PubMed1997

Dental calculus: recent insights into occurrence, formation, prevention, removal and oral health effects of supragingival and subgingival deposits.

Dental calculus, both supra- and subgingival occurs in the majority of adults worldwide. Dental calculus is calcified dental plaque, composed primarily of calcium phosphate mineral salts deposited between and within remnants of formerly viable microorganisms. A viable dental plaque covers mineralized calculus deposits. Levels of calculus and location of formation are population specific and are affected by oral hygiene habits, access to professional care, diet, age, ethnic origin, time since last dental cleaning, systemic disease and the use of prescription medications. In populations that practice regular oral hygiene and with access to regular professional care, supragingival dental calculus formation is restricted to tooth surfaces adjacent to the salivary ducts. Levels of supragingival calculus in these populations is minor and the calculus has little if any impact on oral-health. Subgingival calculus formation in these populations occurs coincident with periodontal disease (although the calculus itself appears to have little impact on attachment loss), the latter being correlated with dental plaque. In populations that do not practice regular hygiene and that do not have access to professional care, supragingival calculus occurs throughout the dentition and the extent of calculus formation can be extreme. In these populations, supragingival calculus is associated with the promotion of gingival recession. Subgingival calculus, in "low hygiene" populations, is extensive and is directly correlated with enhanced periodontal attachment loss. Despite extensive research, a complete understanding of the etiologic significance of subgingival calculus to periodontal disease remains elusive, due to inability to clearly differentiate effects of calculus versus "plaque on calculus". As a result, we are not entirely sure whether subgingival calculus is the cause or result of periodontal inflammation. Research suggests that subgingival calculus, at a minimum, may expand the radius of plaque induced periodontal injury. Removal of subgingival plaque and calculus remains the cornerstone of periodontal therapy. Calculus formation is the result of petrification of dental plaque biofilm, with mineral ions provided by bathing saliva or crevicular fluids. Supragingival calculus formation can be controlled by chemical mineralization inhibitors, applied in toothpastes or mouthrinses. These agents act to delay plaque calcification, keeping deposits in an amorphous non-hardened state to facilitate removal with regular hygiene. Clinical efficacy for these agents is typically assessed as the reduction in tartar area coverage on the teeth between dental cleaning. Research shows that topically applied mineralization inhibitors can also influence adhesion and hardness of calculus deposits on the tooth surface, facilitating removal. Future research in calculus may include the development of improved supragingival tartar control formulations, the development of treatments for the prevention of subgingival calculus formation, the development of improved methods for root detoxification and debridement and the development and application of sensitive diagnostic methods to assess subgingival debridement efficacy.

Adult↗
PubMed1997

Podophyllin 0.5% or 2.0% v podophyllotoxin 0.5% for the self treatment of penile warts: a double blind randomised study.

OBJECTIVE: To compare the effectiveness and cost of self treatment of penile warts with a commercial preparation of podophyllotoxin 0.5% (PDX 0.5%) with podophyllin 0.5% and podophyllin 2.0% sourced from Podophyllum emodii. DESIGN: A prospective double blind randomised study. SUBJECTS: 315 patients with penile warts attending two departments of genitourinary medicine. MAIN OUTCOME MEASURES: Absence of warts, cessation of treatment due to severe side effects at 5 weeks. RESULTS: Of the 315 patients, 244 conformed to the protocol. Analysis was on an intention to treat basis. At 5 weeks no significant differences were found in the extent of healing of warts or in side effects for the three treatment groups. The costs of drug treatment (excluding staff time) are at least pounds 10.00 less for podophyllin than podophyllotoxin. A fourfold variation in the active constituents of the podophyllin preparations did not produce appreciably different clinical responses. In a subanalysis no evidence of deterioration in effectiveness of podophyllin over time was demonstrated. CONCLUSIONS: Penile warts in selected cases can be safely treated with 0.5-2.0% podophyllin self applied by the patient at a fraction of the cost of commercially available podophyllotoxin. The shelf life of the podophyllin extracts is at least 3 months. These findings may be especially relevant in countries where resources for health care are limited.

Condylomata Acuminata↗
PubMed1997

Women with recurrent vaginal candidosis have normal peripheral blood B and T lymphocyte subset levels.

OBJECTIVE: To compare the B and T lymphocyte subset levels of otherwise healthy women suffering from frequently recurrent vaginal candidosis with a healthy control group. SUBJECTS: 26 unselected otherwise healthy women of reproductive age with at least four attacks of vaginal candidosis in the past year and more than three vaginal isolates of a moderate or heavy growth of Candida albicans. Controls were 26 patients or clinical and laboratory staff (asymptomatic for genital infection) matched for time of day and age within 5 years. Only three patients accepted an HIV test. All proved HIV negative. No controls were tested. MAIN OUTCOME MEASURES: T lymphocyte subsets (CD4 and 8) and B lymphocytes (CD 19) as estimated from the total lymphocyte count and flow cytometry. RESULTS: No statistically significant difference between patients and controls. CONCLUSION: No significant difference was found between patients and controls in levels of lymphocyte subsets.

Adult↗
PubMed1997

Expression of human decay accelerating factor may protect pig lung from hyperacute rejection by human blood.

BACKGROUND: Hyperacute rejection currently prevents clinical application of discordant lung xenografts. Pigs transgenic for human regulators of complement activation offer one promising potential solution to this problem. METHODS: Using fresh human blood in an ex vivo lung perfusion model, we studied eight different strains of pigs transgenic for human decay accelerating factor. Survival (by blood flow and gas transfer criteria) were correlated with immunohistologic evidence of pulmonary human decay accelerating factor expression and complement activation. RESULTS: With human blood perfusion, blood flow through the unmodified pig lung rapidly falls and is not restored by continuous infusion or high-dose bolus of prostacyclin. Airway pressure also rises rapidly and is followed promptly by loss of gas transfer. Four of the transgenic pig strains showed no difference from this pattern. Immunohistochemistry for human decay accelerating factor revealed low or no pulmonary expression in these lungs. In contrast, two of five transgenic pig lungs that had significant decay accelerating factor expression demonstrated recovery of pulmonary blood flow within 1 hour, and rejection was delayed, from less than 20 minutes in controls to about 1 hour. Complement activation, particularly the alternative pathway, was inhibited in lungs with high levels of endothelial decay accelerating factor expression. CONCLUSIONS: Lungs from some strains of pig transgenic for human decay accelerating factor demonstrate incomplete physiologic and histologic protection from hyperacute rejection. Although complement-independent pathogenic mechanisms may present a formidable obstacle, pig lungs transgenic for human complement regulatory proteins may facilitate discordant lung transplantation in human beings.

Animals↗
PubMed1997

A comparison of stabilized stannous fluoride dentifrice and triclosan/copolymer dentifrice for efficacy in the reduction of gingivitis and gingival bleeding: six-month clinical results.

This parallel-group, double-blind, placebo-controlled clinical trial directly compared the efficacy of two antimicrobial dentifrice formulations for the control of plaque, gingivitis and gingival bleeding during six months of use following a pre-test randomization period. Test antimicrobial dentifrices for the study included: a stabilized stannous fluoride formulation (Crest Plus Gum Care-currently marketed in U.S.) comprised of 0.454% SnF2 in a stabilized silica abrasive base; and a formulation containing triclosan (Colgate Total, currently marketed outside the U.S. in numerous countries) comprised of 0.30% triclosan. 2.0% Gantrez co-polymer and 0.243% NaF in a silica abrasive base. The control dentifrice was a conventional fluoride dentifrice comprised of 0.243% NaF in a silica abrasive base. Clinical evaluations included Turesky et al. plaque, Löe-Silness gingivitis and gingival bleeding, and Meckel stain. The stabilized stannous fluoride dentifrice exhibited significant efficacy in the reduction of both gingivitis (20.5%) and gingival bleeding (33.4%) after six months relative to the placebo control (p < 0.05). In direct comparison, the stabilized stannous fluoride dentifrice reduced gingivitis and gingival bleeding significantly relative to the triclosan/copolymer dentifrice (p < 0.05). These results establish: 1) the superior clinical efficacy of a stabilized stannous fluoride dentifrice relative to a triclosan/copolymer dentifrice in the chemotherapeutic control of gingivitis and gingival bleeding; 2) the important contribution of clinical test design/sensitivity in assessing the therapeutic efficacy of antimicrobial agents; and 3) the value of head-to-head comparative studies in establishing the therapeutic relevance of clinical effects of formulations for the reduction of gingivitis.

Adult↗
PubMed1997

The comparative efficacy of stabilized stannous fluoride dentifrice, peroxide/baking soda dentifrice and essential oil mouthrinse for the prevention of gingivitis.

This double-blind parallel-design clinical study compared the efficacy of a stabilized stannous fluoride dentifrice (Crest Plus Gum Care), baking soda and peroxide (NaF) dentifrice (Mentadent), and essential oil mouthrinse (Listerine) to a conventional NaF dentifrice (Crest) for the control of plaque, gingivitis and gingival bleeding over six months. Following an initial baseline examination and stratification, subjects received a complete oral prophylaxis and were distributed assigned test products. Following three and six months, subjects re-visited the clinic for examinations. Evaluations at baseline and at 3 and 6 months included soft tissue status. Löe-Silness gingivitis/gingival bleeding, Silness-Löe plaque and dental stain. Results subsequent to six months of product use were as follows: At six months, the stabilized stannous fluoride dentifrice was observed to produce statistically significant 17.5% reductions in gingivitis and 27.5% reductions in gingival bleeding relative to the NaF dentifrice. The combination of sodium fluoride dentifrice and essential oil mouthrinse produced statistically significant reductions of 7.4% in gingivitis and 10.8% in plaque as compared with the NaF dentifrice. The stabilized stannous fluoride dentifrice produced statistically significant reductions in both gingivitis (10.8%) and gingival bleeding (23.0%) relative to the combination of sodium fluoride dentifrice and essential oil mouthrinse. The baking soda and peroxide (NaF) dentifrice did not provide reductions in gingivitis, plaque or gingival bleeding as compared with the conventional NaF dentifrice. The stabilized stannous fluoride dentifrice provided statistically significant reductions in gingivitis as compared with the baking soda and peroxide dentifrice following six months of use, and both the essential oil mouthrinse and stabilized stannous fluoride dentifrice provided statistically significant reductions in gingivitis as compared with the baking soda and peroxide dentifrice following three months of use. These results support: 1) the efficacy of stabilized stannous fluoride dentifrice and the combination of sodium fluoride dentifrice and essential oil mouthrinse for the prevention of gingivitis; 2) the superior activity of stabilized stannous fluoride dentifrice as compared with a combination of sodium fluoride dentifrice and essential oil mouthrinse for the control of gingivitis and gingival bleeding; and 3) the lack of efficacy for baking soda and peroxide dentifrice for the control of plaque, gingivitis and gingival bleeding as compared with conventional fluoridated dentifrice.

Adult↗
PubMed1997

A comparison of intraoral antimicrobial effects of stabilized stannous fluoride dentifrice, baking soda/peroxide dentifrice, conventional NaF dentifrice and essential oil mouthrinse.

The intraoral antimicrobial activity of four commercial oral products-conventional NaF dentifrice (Crest), baking soda/peroxide/NaF dentifrice (Mentadent), essential oil mouthrinse (Listerine) and SnF2 dentifrice (Crest Plus Gum Care)-have been compared in three test regimens. Formulations were compared for their ability to suppress the regrowth and apical extension of dental plaque following toothbrushing during thirty hours of non-brushing where products were used as oral rinses (30-hour plaque regrowth model). Formulations were also compared for their ability to suppress the colony-forming units (cfu) of facultative anaerobic bacteria sampled from buccal gingival surfaces following use (Gingival Surface Microbial Index-GSMI model). Lastly, formulations were compared for effects in suppressing the glycolytic metabolic activity and regrowth activity of in vivo-treated dental plaques sampled at various periods following topical use and incubated under controlled ex vivo conditions (Plaque Glycolysis and Regrowth-PGRM model). In thirty-hour plaque regrowth testing, the rank ordered antimicrobial efficacy of formulations followed SnF2 > essential oils > NaF = water = baking soda/peroxide. In GSMI testing, all formulations were shown to suppress the cfu of facultative anaerobic bacteria relative to baseline, although SnF2 treatment was observed to reduce bacterial levels to a significantly greater degree than NaF dentifrice or baking soda/peroxide dentifrice up to two hours following brushing. In PGRM testing, the SnF2 dentifrice provided significant inhibition of bacterial metabolism and regrowth following topical application when compared with the NaF dentifrice as control. The baking soda/peroxide dentifrice provided no reduction in either bacterial metabolism or regrowth in PGRM. Previous studies had demonstrated modest effects for essential oil rinse in reducing PGRM plaque regrowth, with no effects for this treatment on plaque metabolism. Overall, these results demonstrate that SnF2 dentifrice provides substantial intraoral antimicrobial effects. The essential oil mouthrinse also exhibits significant intraoral antimicrobial effects, albeit apparently less than SnF2 dentifrice. The baking soda/peroxide dentifrice did not produce any antimicrobial effects following in vivo use compared with conventional dentifrice. These results provide mechanistic rationale for the chemotherapeutic efficacy of SnF2 and essential oil formulations in reducing gingivitis, while providing no support for the expectation of clinical efficacy for formulations containing baking soda and peroxide.

Adult↗
PubMed1997

The comparative clinical efficacy of pyrophosphate/triclosan, copolymer/triclosan and zinc citrate/triclosan dentifrices for the reduction of supragingival calculus formation.

Three triclosan-containing "multi-benefit" dentifrices were compared for clinical efficacy in reducing supragingival calculus formation following a dental prophylaxis. A total of 544 subjects completed a double-blind parallel-group clinical study using the Volpe-Manhold Index (VMI) to record severity and occurrence of supragingival calculus. The study design included a pre-test period where the calculus formation rate was measured in subjects brushing with a placebo dentifrice. Following a prophylaxis, subjects were stratified for age, gender and VMI scores and assigned to one of four treatments: 1) a dentifrice containing 5.0% soluble pyrophosphate/0.145% fluoride as NaF/silica abrasive/0.28% triclosan (hereafter PPi/TCS-comparable to Crest Complete dentifrice, Procter & Gamble, UK); 2) a commercial dentifrice containing 2.0% Gantrez acid copolymer/ 0.145% fluoride as NaF/silica abrasive/0.30% triclosan (hereafter Gan/TCS-Colgate Total dentifrice, Colgate-Palmolive Company, UK); 3) a commercial dentifrice containing 0.5% zinc citrate trihydrate/0.15% fluoride as sodium monofluorophosphate/silica abrasive/0.20% triclosan (hereafter Zn/TCS-Mentadent P dentifrice, Unilever, UK); and 4) a control dentifrice comprised of 0.145% fluoride as NaF/silica abrasive (hereafter Control). Subjects were instructed to use their assigned dentifrice at least twice per day and to brush as they do normally. Supragingival calculus formation was assesed at two and four months using site-specific and whole-mouth VMI indices for both calculus severity and occurrence. Following four months of use, the PPi/TCS dentifrice provided statistically significant reductions in calculus severity (22-23%) and occurrence (15%) as compared with the Control dentifrice. The Zn/TCS dentifrice also provided significant reductions in calculus severity (17-19%) and occurrence (12-13%) as compared with the Control. The Gan/TCS produced no statistically significant reductions in calculus formation (occurrence or severity) compared with the Control. The PPi/TCS dentifrice provided statistically significant reductions in calculus severity (15-21%) and occurrence (12-16%) as compared with the Gan/TCS dentifrice. These results support the clinical effectiveness of PPi/TCS and Zn/TCS dentifrices for the reduction of supragingival dental calculus formation following a dental prophylaxis.

Adolescent↗
PubMed1997

Transgenic human decay accelerating factor makes normal pigs function as a concordant species.

BACKGROUND: Increasing interest has focused on xenotransplantation as a potential solution to the organ shortage. To overcome hyperacute rejection, pigs have been produced that are transgenic for human decay accelerating factor (DAF). For the evaluation of the effects of human DAF, an ex vivo working heart model was used. METHODS: We compared hemodynamic performance of four transgenic pig hearts (group A) with that of four Landrace pig hearts (group B) and eight rhesus monkey hearts (group C). For perfusion fresh blood had been taken from healthy volunteers. From the coronary sinus effluent, samples were taken for the determination of 6-keto prostaglandin F1 alpha, prostaglandin E2, creatine phosphokinase, and lactate dehydrogenase, respectively. Hemodynamic parameters were measured continuously for 150 minutes after the start. After 15 minutes of reperfusion, the Langendorff-mode was switched to the working heart model. After hearts failed to pump against the afterload column, experiments were terminated, and tissue sections were taken for electron microscopy. RESULTS: Groups A and C showed superior cardiac performance as measured by stroke work index (SWI) that exceeded group B by 2.5 to 3 times (p < 0.05). In all three groups the SWI slowly decreased during perfusion. In group B, SWI decreased to a minimum as early as 90 minutes after the start. In all groups, 6-keto prostaglandin F1 alpha and prostaglandin E2 as indicators of endothelial cell activation increased. In group B, however, the levels exceeded those of groups A and C by six and nine times, respectively (p < 0.05). As markers of myocardial damage, creatine phosphokinase and lactate dehydrogenase increased in all groups. But again levels in group B exceeded those of groups A and C by four to five times (p < 0.05). Electron microscopy revealed single cell necrosis in group B, whereas groups A and C showed interstitial edema only. CONCLUSIONS: Our experiments indicate a crucial role of DAF in preventing rejection in discordant species combinations. Transgenic human DAF seems to inhibit successfully complement-mediated damage to the endothelial cell, thus preventing endothelial activation and consequently myocardial damage. Transgenic human DAF makes a discordant species (pig) function as a concordant species, that is, hyperacute rejection does not occur.

6-Ketoprostaglandin F1 alpha↗