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Biomedical subjects

D J White

Publications and source records attributed to D J White.

At least 145 records · Page 8Linked to original sources
PubMed1996

A Quanticalc clinical comparison of professional efficiency in manual supragingival calculus debridement.

The Quanticalc (QC) dental scaler permits the assessment of work effort expended by professionals in removing supragingival calculus from the teeth. The purpose of this study was to compare the efficiency of two professionals in scaling calculus under controlled clinical conditions in like populations. One-hundred and thirty-one subjects were randomly assigned to two professionals, A and B, for QC scaling of their six Volpe-Manhold Index (VMI) teeth. VMI assessments were carried out by a separate examiner prior to QC cleaning. The QC was used to record total developed force, total strokes and force/stroke used in calculus debridement. Results demonstrated significant differences in scaling efficiency between the two professionals. These results further demonstrate the potential utility of the QC and like devices in assisting in the instruction of professionals toward the development of more efficient manual scaling procedures.

Analysis of Variance↗
PubMed1996

The comparative efficacy of two commercial tartar control dentifrices in preventing calculus development and facilitating easier dental cleanings.

Tartar control dentifrices have been proven effective in reducing the build-up of supragingival calculus deposits between professional tooth cleanings. In addition to providing consumers with a cleaner dentition, these formulations can, in principle, contribute to easier professional tooth cleaning. Until recently, clinical methods for evaluating the effects of tartar control dentifrices were limited to the assessment of area coverage of calculus on the tooth surface. The development of the Quanticalc dental scaler permits the quantitative clinical measurement of force and stroke number associated with supragingival calculus debridement. In this clinical study, two commercial tartar control dentifrices, one containing 5.0% pyrophosphate as the tartar control agent and the other containing a combination of 1.3% pyrophosphate and 1.5% Gantrez copolymer, were compared for efficacy in reducing the development of supragingival calculus between prophylaxes, and in facilitating easier calculus removal in subsequent scaling. Results showed that the two commercial dentifrices were equally effective in reducing calculus extent between prophylaxes. In contrast, the 5.0% pyrophosphate dentifrice was observed to be almost twice as effective on a percentage basis as the lower dosage pyrophosphate dentifrice in facilitating easier calculus removal. The enhanced activity of the 5.0% pyrophosphate dentifrice may be postulated to be due to elevated dosage of tartar control crystallization inhibitor or to potential side effects of copolymer in the other commercial dentifrice. Importantly, these results substantiate that the clinical benefits of tartar control dentifrices are not completely described by actions in reducing calculus build-up as assessed by VMI, and that important clinical benefits and differences in efficacy may be provided by these formulations in facilitating easier dental cleaning of supragingival calculus.

Adult↗
PubMed1995

Tissue expression of human complement inhibitor, decay-accelerating factor, in transgenic pigs. A potential approach for preventing xenograft rejection.

Since complement-mediated hyperacute rejection of xenografts prevents the use of pigs as organ donors to man, the development of transgenic animals expressing species-specific complement inhibitors could provide a strategy for overcoming hyperacute rejection. The complement inhibitor, human decay-accelerating factor (hDAF), prevents the assembly of C3 and C5 convertases. In this article, the first histologic analysis of hDAF expression in pig tissues, specifically expression in endothelial cells of pigs transgenic for hDAF, is described. Twenty-seven transgenic pigs were categorized into 4 groups based on the expression patterns in endothelial, vascular smooth muscle, and squamous epithelial cells of skin biopsy specimens. Skin biopsy specimens permitted evaluation of the pigs without the need to kill them or to perform invasive procedures. Sixteen cases demonstrated endothelial cell staining. Complete necropsy evaluation, available in 14 of the 27 pigs, correlated with the skin biopsy specimen expression of hDAF. The immunoperoxidase data matched identically with the presence of the mRNA transcript in 25 of the 26 cases where RNA data were available. Also, the staining patterns of 6 transgenic pig founders and their 9 offspring (total of 9 founder-offspring pairs) correlated. Since transgenes are variably expressed in different cell types and since tissue lysates represent a melange of cell types, histologic evaluation for protein expression in tissues from transgenic animals will be critical if they are to be bred to become clinical organ donors. In addition to endothelial expression of hDAF, its expression on vascular smooth muscle cells may be important in preventing tissue damage when breaks in the endothelium occur.

Animals↗
PubMed1995

Regulation of the complement cascade by soluble complement receptor type 1. Protective effect in experimental liver ischemia and reperfusion.

The complement cascade was inactivated in a model of rat liver ischemia with the purpose of studying the role of complement in tissue injury after ischemia and reperfusion. Soluble human complement receptor type 1 (sCR1) was administered either in a single dose of 25 mg/kg or in 2 doses of 50 mg/kg i.v. over 24 hr after vascular occlusion. Sham-operated rats, nontreated rats submitted to liver ischemia, and rats pretreated with cobra venom factor and submitted to liver ischemia were used as controls. This experiment consists of the temporary interruption of arterial and portal blood flow to the left lateral and medial lobes of the liver for 45 min, followed by a 24-hr period of follow-up after reperfusion. Liver blood flow and hemoglobin saturation were recorded for 1 hr after declamping, with statistically significant differences between the experimental groups and the untreated control group, which received liver ischemia (P < 0.001). At 24 hr, galactose elimination was assayed as a liver function test; it was significantly better in the sCR1-treated rats when compared with control rats submitted to ischemia (P < 0.01). Alanine aminotransferase levels were also significantly lower in the sCR1-treated rats at 6 and 24 hr (P < 0.05). Complement activity was reduced to 25% and 12.5% of normal rats with the respective doses of sCR1. Immunoperoxidase stainings for C3 and C9 were performed on liver sections; they showed endothelial deposits of C3 and C9 in the control group subjected to ischemia. Few C3 deposits were present in the sCR1 (25 mg/kg)-treated rats, but not in the cobra venom factor or sCR1 (50 mg/kg) groups. These results confirm that complement is inactivated by sCR1 with amelioration of reperfusion injury in the rat liver.

Animals↗
PubMed1995

The control of hyperacute rejection by genetic engineering of the donor species.

Activation of endogenous complement is inhibited both in the soluble phase and at the membrane surface by a group of structurally similar proteins. A possible solution to hyperacute rejection is to produce donor animals transgenic for human complement regulators. Mouse cells expressing the human complement regulatory proteins decay accelerating factor (DAF) or membrane cofactor protein (MCP) were produced both by hybridoma technology and by transfection with the appropriate cDNAs. The expression of either or both of these products protected the mouse cell from lysis by human (though not rabbit) complement in the presence of naturally occurring human anti-mouse antibody. This effect could be abrogated by the addition of monoclonal antibody against DAF or MCP. Hyperacute rejection of discordant organ xenografts is mediated by human complement. A 6.5 kilobase minigene for DAF has been microinjected into porcine fertilised ova. Forty-five pigs transgenic for human DAF have been produced. Of these, 65% transcribe message. The amount of message produced varied substantially from animal to animal and was independent of copy number integrated. Expression of human DAF on the porcine lymphocyte surface could be detected and this was able to downregulate human complement activation. Amounts of protein expressed on different tissues varied both from pig to pig and within animals from tissue to tissue. The pigs grow and develop normally with no evidence of ill effects due to possession of the transgene.

Animals↗
PubMed1995

Striae distensae after augmentation mammoplasty.

Three cases of striae distensae of the breast after augmentation mammoplasty are presented. The patients were all in their early 20s and nulliparous. The striae developed in the first few months after surgery. A review of the literature on striae distensae is presented. To the best of our knowledge, striae distensae occurring after augmentation mammoplasty have not previously been described.

Adult↗
PubMed1995

Delayed hypertonic saline dextran administration after burn injury.

OBJECTIVE AND DESIGN: Experimental studies in our laboratory showed that hypertonic saline dextran (HSD; 7.5 NaCl in 6% dextran 70) given as a small bolus (4 mL/kg) immediately after burn injury in guinea pigs improved cardiac contractile performance and reduced the total fluids requirements. Although these data confirm the cardioprotective effects of HSD given immediately postburn, prehospital and early inhospital management of severely burned patients consists of aggressive crystalloid fluid resuscitation to correct intravascular volume deficits. The question arose as to whether delaying HSD for several hours after initiating crystalloid resuscitation would provide cardioprotection. MATERIALS AND METHODS: Third-degree scald burns comprising 45 +/- 1% of the total body surface area (burn groups, n = 40) or 0% for controls (group 1, n = 12) were produced; in groups 2 to 5, lactated Ringer's (LR) resuscitation was initiated immediately postburn according to the Parkland formula, 4 mL/kg/% burn. In group 2, (n = 12), LR was continued for 24 hours. HSD was administered as an i.v. bolus at either 1 hour (group 3, n = 10), 4 hours (group 4, n = 9), or 8 hours postburn (group 5, n = 9); immediately after HSD administration, LR was continued (1 mL/kg/% burn) until 24 hours postburn. RESULTS: Compared to sham burn controls, hearts from burned animals treated with LR alone had significant cardiac dysfunction, as indicated by a lower left ventricular pressure and +/- dP/dt. Compared with hearts from LR-treated animals, hearts from burned animals treated with HSD 1 hour (HSD-1) and 4 hours (HSD-4) after burn injury had significantly higher LVP and +/- dP/dt. Ventricular function curves calculated for HSD-1 and HSD-4 groups were comparable to those calculated for hearts from sham burns. Delaying HSD administration until 8 hours after burn provided little cardioprotection. CONCLUSIONS: Our data indicate that HSD effectively maintains cardiac function and reduces overall total fluid requirements if administered within 4 hours after burn injury.

Animals↗
PubMed1995

The role of toxic oxygen metabolites in a young model of thermal injury.

Production of oxygen-free radicals has been proposed as one pathophysiologic mechanism for postburn cardiac contractile dysfunction in adults. To examine this hypothesis in young subjects, we studied the cardiac effects of polyethylene glycol-superoxide dismutase (PEG-SOD) and PEG-catalase (PEG-CAT), each given as 20 U/g of body weight with fluid resuscitation (Parkland formula), after a third-degree burn constituting 33% of the total body surface area in young (6- to 7-day old) guinea pigs (group 3, n = 12). Fluid-treated burns without scavenger therapy (group 2, n = 15) and sham burn controls (group 1, n = 15) were included. Animals were killed 24 hours postburn, and hearts were studied in vitro (Langendorff). Compared with sham burn controls, fluid-treated burns (group 2) had significant cardiac dysfunction as indicated by a lower peak systolic left ventricular (LV) pressure (LVP: 67 +/- 2 vs. 57 +/- 4 mm Hg, p = 0.01, mean +/- SEM), maximal rate of LV pressure development (+dP/dt max: 1169 +/- 45 vs. 988 +/- 45 mm Hg/second, p = 0.01), and fall (-dP/dt max: 1109 +/- 45 vs. 919 +/- 49 mm Hg/second, p = 0.01). In addition, LV function curves calculated for group 2 were shifted downward and to the right of those calculated for sham burn controls in the direction of contractile depression, p = 0.01. PEG-SOD/PEG-CAT treatment in burns did not significantly improve LVP (60 +/- 5 mm Hg), but scavenger therapy improved +/-dP/dt max values (1112 +/- 74 and 988 +/- 98 mm Hg/second, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Extracellular neuraminidase production by a Pasteurella multocida A:3 strain associated with bovine pneumonia.

The properties of an extracellular neuraminidase produced by a Pasteurella multocida A:3 strain that was isolated in a case of bovine pneumonia were examined during growth in a defined medium. This enzyme (isolated from concentrated culture supernatants of P. multocida A:3) was active against N-acetylneuramin lactose, human alpha-1-acid glycoprotein, fetuin, colominic acid, and bovine submaxillary mucin. Enzyme elaboration was correlated with the growth of the organism in a defined medium, with maximum quantities produced in the stationary phase. The enzyme was purified by a combination of ammonium sulfate fractionation, ion exchange on DEAE-Sephacel, and gel filtration on Sephadex G-200. The purified neuraminidase possessed a specific activity of 9.36 mumol of sialic acid released per min per mg of protein against fetuin. The enzyme possessed a pH optimum of 6.0 and a Km of 0.03 mg/ml. The P. multocida A:3 neuraminidase had a molecular weight of approximately 500,000 as estimated by gel filtration. The enzyme was stable at 4 and 37 degrees C for 3 h. Approximately 75% of the neuraminidase activity was lost within 30 min at 50 degrees C. Greater than 90% of the enzyme activity was destroyed within 10 min at temperatures of > or = 65 degrees C. The P. multocida neuraminidase does not appear to be serologically related to the Pasteurella haemolytica A1 neuraminidase since antiserum prepared against the purified P. haemolytica enzyme did not neutralize the P. multocida enzyme.

Animals↗
PubMed1995

The application of in vitro models to research on demineralization and remineralization of the teeth.

Progress in in vivo and in situ experimentation has led many researchers to speculate as to the relevance and importance of in vitro testing protocols in caries research. A Medline/Biosis search for the present review revealed well over 300 citations (since 1989) documenting in vitro tests associated with caries research on mineralization and fluoride reactivity. The present survey documents these recent applications of in vitro test methods in both mechanistic and 'profile' caries research. In mechanistic studies, in vitro protocols over the past five years have made possible detailed studies of dynamics occurring in mineral loss and gain from dental tissues and the reaction dynamics associated with fluoride anticaries activity. Similarly, in profile applications, in vitro protocols make possible the inexpensive and rapid--yet sensitive--assessment of F anticaries efficacy within fluoride-active systems, and these tests represent a key component of product activity confirmation. The ability to carry out single variable experiments under highly controlled conditions remains a key advantage in in vitro experimentation, and will likely drive even further utilization, as advances continue in physical-chemical and analytical techniques for substrate analysis in these protocols. Despite their advantages in vitro testing protocols have significant limitations, most particularly related to their inability to simulate the complex biological processes involved in caries.

Animals↗