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Biomedical subjects

M Edgerton

Publications and source records attributed to M Edgerton.

15 recordsLinked to original sources
PubMed1998

Candidacidal activity of salivary histatins. Identification of a histatin 5-binding protein on Candida albicans.

Candida albicans is the predominant species of yeast isolated from patients with oral candidiasis, which is frequently a symptom of human immunodeficiency virus infection and is a criterion for staging and progression of AIDS. Salivary histatins (Hsts) are potent in vitro antifungal agents and have great promise as therapeutic agents in humans with oral candidiasis. The molecular mechanisms by which Hsts kill yeast cells are not known. We report here, that unlike other antimicrobial proteins, Hsts do not display lytic activities to lipid membranes, measured by release and dequenching of the fluorescent dye calcein. Analysis of the magnitude and time course of Hst-induced calcein release from C. albicans cells further showed that loss of cell integrity was a secondary effect following cell death, rather than the result of primary disruption of the yeast cell membrane. 125I-Hst 5 binding studies indicated that C. albicans expressed a class of saturable binding sites (KD = 1 microM), numbering 8.6 x 10(5) sites/cell. Both Hst 3 and Hst 4 competed for these binding sites with similar affinities, which is consistent with the micromolar concentration of Hsts required for candidacidal activity. Specific 125I-Hst 5 binding was not detected to C. albicans spheroplasts, which were 14-fold less susceptible to Hst 5 killing, compared with intact cells in candidacidal assays. In overlay experiments, 125I-Hst 5 bound to a 67-kDa protein detected in C. albicans whole cell lysates and crude membrane fractions, but not in the yeast cell wall fraction. Consistent with the overlay data, cross-linking of 125I-Hst 5 to C. albicans resulted in the appearance of a specific 73-kDa 125I-Hst 5-containing complex that was not detected in the cell wall. 125I-Hst 5-binding protein of similar size was also observed in susceptible S. cerevisiae strain TI#20. This is the first description of Hst 5 binding sites on C. albicans which mediate cell killing and identification of a 67-kDa yeast Hst 5-binding protein. The binding characteristics of Hst 5 are in agreement with the observed potency of its biological effect and provide crucial information to the use of Hst 5 as a therapeutic agent. The presence of a specific C. albicans Hst 5-binding protein provides further insight into the potential mechanism of yeast killing and suggests a basis for differential activity between yeast killing and the nontoxic nature of Hsts to humans.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Delineation of an active fragment and poly(L-proline) II conformation for candidacidal activity of bactenecin 5.

Bactenecin 5 and its fragments [BN22 (1-22), BN16 (7-22), and BC24 (20-43)] were synthesized by solid-phase methods. Their antifungal activities on Candida albicans have been studied and compared with those of the native bactenecin 5. The conformational preferences of these peptides in aqueous and nonaqueous solutions and in lipid vesicles were examined by circular dichroism. The highly active N-terminal fragment (BN16) was examined in aqueous solution using 500 MHz two-dimensional NMR. Bactenecin 5 and its fragments are potent candidacidal agents against C. albicans. The N-terminal fragments (BN22 and BN16) of bactenecin 5 are relatively more active than the C-terminal fragment BC24, especially at lower concentrations. The N-terminal region (7-22) which retains the activity of the whole molecule appears to be the functional domain for candidacidal activity. The CD spectra of bactenecin 5 and its fragments are reminiscent of the CD spectrum of poly(L-proline) type II structure in aqueous and nonaqueous solutions and also in lipid vesicles. The temperature dependence of NH chemical shifts and 1H/2H exchange effect on amide resonances suggest the absence of intramolecularly hydrogen-bonded NH groups. The coupling constant (JNH-CalphaH) values, conformational restriction offered by the Pro residues (phi = -60 degrees +/- 15 degrees), the set of medium- and short-range nuclear Overhauser effects observed for the active N-terminal fragment (BN16), and the restrained structure calculation using DIANA suggest that poly(L-proline) type II conformers of the peptide molecules could be significantly populated in aqueous solution. The ability of bactenecin peptides to induce disruption of lipid vesicles correlates well with their activity. Our results suggest that poly(L-proline) type II structure may, indeed, be the biologically active conformation for candidacidal activity of bactenecin peptides.

Amino Acid Sequence↗
PubMed1995

Co-expression of the neurokinin NK2 receptor and G-protein components in the fission yeast Schizosaccharomyces pombe.

The fission yeast Schizosaccharomyces pombe has proven useful for studying molecular interactions between a range of signal transduction components. We now report the first co-expression of a mammalian seven-transmembrane receptor and G-protein components in S. pombe. We selected the human neurokinin NK2 receptor together with its G-protein-signalling partner Gq for this study. Yeast membrane fractions showed high levels of NK2 receptor-binding activity (1159 +/- 534 (n = 3) fmol/mg protein) although initial experiments with intact cells revealed an absence of receptors at the cell surface. Using a construct comprising the NK2 coding sequence fused with the signal sequence from an endogenous phosphatase (phoI), we detected approximately 400 NK2 receptors/cell in unbroken yeast. Successful co-expression of the NK2 receptor with the G-protein subunits G alpha q, beta 1 or beta 2 and gamma 3 failed to modulate agonist binding, suggesting the absence of functional interaction between these components. As an alternative test of G alpha q function, we next expressed its downstream effector target phospholipase C-beta 1 (PLC beta 1) in S. pombe. Although PLC beta 1 undergoes powerful in vitro activation by G alpha q derived from baculovirus-infected Sf9 cells and mammalian cells, G alpha q expressed in S. pombe is totally ineffective. Similar results were also achieved with the G-protein subunit G alpha 16. Together, these data suggest that seven-transmembrane receptors can be expressed in S. pombe at high levels and directed to the cell surface although their interaction with co-expressed G-proteins in undetectable. Production of inactive G alpha-chains in S. pombe may account for these observations.

Amino Acid Sequence↗
PubMed1995

Functional domain and poly-L-proline II conformation for candidacidal activity of bactenecin 5.

The functional domain for candidacidal activity of bactenecin 5 has been determined by synthesizing bactenecin 5 and its fragments [1-22 (BN22), 7-22 (BN16) and 20-43 (BC24)]. The N-terminal sequence BN16 retained the candidacidal potency of the parent molecule and this region appears to be the candidacidal domain. The circular dichroism spectra of these peptides indicate the presence of largely poly-L-proline II conformations in aqueous solutions and in lipid vesicles. The coupling constant (JNH-C alpha H) values, and a set of medium- and short-range nuclear Overhauser effects observed for the N-terminal peptide (BN16) in the two-dimensional nuclear magnetic resonance suggest that poly-L-proline II helix could be the biologically active conformation.

Amino Acid Sequence↗
PubMed1995

Surface-modified poly(methyl methacrylate) enhances adsorption and retains anticandidal activities of salivary histatin 5.

Denture-induced stomatitis is a common intraoral disease which is associated with high levels of Candida albicans adhesion to a denture surface. The aim of this study was to produce a surface-modified denture resin, which is usually manufactured from poly(methyl methacrylate) (PMMA), carrying an immobilized anticandidal protein. PMMA was modified by surface polymerization of methyl methacrylic acid to enhance adsorption of a potent candidacidal salivary protein, histatin 5. The modified PMMA showed higher surface adsorption and desorption of histatin 5 than the unmodified material. Because histatin 5 destabilizes C. albicans cell membranes and allows efflux of intracellular molecules, candidacidal activity was monitored by dye release from fungal cells. Adsorbed histatin 5 did not release dye from the yeast cells; however, dye was detected as histatin was desorbed from the surface. In an adhesion assay, modified PMMA decreased human submandibular-sublingual saliva (HSMSL) mediated adherence of yeast cells to the polymer. Precoating histatin 5 onto unmodified PMMA also abolished HSMSL-mediated adhesion. These experiments show that dental acrylic may be surface modified and loaded with histatin 5 as a means of controlled release of histatin 5 to an affected area. This surface modification may additionally reduce adhesion of C. albicans cells to the saliva-coated material.

Adsorption↗
PubMed1993

Biocompatibility: its future in prosthodontic research.

The future of prosthodontic research will involve replacing lost tissues by using scientific methods that evaluate biomaterials and treatment designs based on desired biologic outcomes. The present concept of a biocompatible material is one that elicits an appropriate host response in a specific application. To design optimal biomaterials, three interactive components should be considered: the chemical nature of the surface, the mediating pellicle layer, and microbial and host response. Surface chemistry determines which molecules are selectively absorbed onto a surface from oral fluids. The pellicle-coated surface should be designed to elicit a more desirable host response. Pellicle composition can be altered by chemically changing the surface, precoating surfaces with biological molecules, or using synthetic materials designed to mimic natural tissues. Several surface-sensitive techniques are available to assess these modifications, including vibrational spectroscopy, electron microscopy for chemical analysis, and bioanalytical methods. To develop more biocompatible materials, a further understanding of pellicle formation as a function of surface composition, microbial adhesion to biomaterials, and cellular reaction to implant biomaterials is necessary. This knowledge will facilitate development of new biologically based rationales for treatment modalities in restorative dentistry.

Biocompatible Materials↗
PubMed1993

Human submandibular-sublingual saliva promotes adhesion of Candida albicans to polymethylmethacrylate.

The purpose of this study was to identify components of saliva that interact with Candida albicans in solution and that may modulate adhesion to dental acrylic (polymethylmethacrylate [PMMA]) surfaces. Saliva-derived pellicles extracted from C. albicans blastoconidia and hyphal-form cells mixed with fresh human submandibular-sublingual saliva (HSMSL) contained predominantly high- and low-molecular-weight mucins (MG1 and MG2, respectively). In contrast, few components from fresh human parotid saliva were adsorbed to yeast cells. Coating PMMA beads with HSMSL significantly enhanced (10-fold) adhesion of both growth forms of C. albicans compared with human parotid saliva (2-fold), suggesting a role for mucins in adhesion. HSMSL-enhanced adhesion was completely abolished by preadsorbing HSMSL with either blastoconidia or hyphal-form cells prior to coating PMMA. However, coating PMMA with purified salivary mucins or the addition of mucin to preadsorbed saliva did not enhance or restore adhesion to levels found with fresh HSMSL. Adhesion assays employing guanidine-treated fresh HSMSL showed a complete lack of Candida binding, suggesting that subjecting HSMSL to dissociating conditions may alter a property of salivary mucins crucial for C. albicans adhesion. Protease and glycosidase treatment of yeast cells significantly reduced adhesion to HSMSL-coated PMMA. In addition, preincubation of C. albicans with mannose and galactose inhibited adhesion to HSMSL-coated PMMA. These results suggest that mucins may play a role in C. albicans adhesion to saliva-coated PMMA and that a glycoprotein on the yeast surface may be involved in these events.

Adsorption↗
PubMed1992

Characterization of acquired denture pellicle from healthy and stomatitis patients.

Little information is available about the acquired pellicle layer that is formed on denture surfaces or its role in regulating microbial colonization of the prosthetic surface. Because denture-induced stomatitis is associated with increased numbers of Candida albicans and other microorganisms on the denture surface, the acquired denture pellicle (ADP) may play a role in modulating this colonization. This study examined and compared ADP from healthy patients and patients with stomatitis by chemical and immunochemical methods. The ADP was found to be composed of a selectively adsorbed layer containing salivary amylase, high molecular weight mucin (MG1), lysozyme, albumin, and sIgA. Salivary cystatins, proline-rich proteins, and low molecular weight mucin (MG2) were not detected. ADP amino acid composition was distinct from any of the ductal salivas, but had many similarities with enamel pellicle. Immunoblots of ADP from patients with stomatitis identified additional serum components, degradation products, and C. albicans cell components that were not detected in ADP from healthy patients. Quantification of these molecules in ADP could lead to a diagnostic test for oral mucosal disease underlying a denture base. Identification of specific molecules in denture pellicle that promote adhesion of C. albicans may elucidate a mechanism of fungal cell colonization on the denture surface. Future studies that chemically modify the denture acrylic resin surface to immobilize antimicrobial proteins may be a means of decreasing pathogenic plaque development.

Adhesiveness↗
PubMed1991

Location of abnormalities in panoramic radiographs of edentulous patients.

A series of 308 panoramic radiographs of edentulous patients was examined for the presence of pathoses to determine whether any predictive basis could be found for occurrence of abnormalities by sex, age, or location. Radiolucencies, radiopacities, and retained roots and teeth were recorded by size and by anterior or posterior location in edentulous jaws. Radiopacities were the most frequently found abnormality (18% of subjects), followed by retained roots (8%), radiolucencies (3%), and retained teeth (3%). No significant correlation was found by chi-square test between type or location of abnormality and sex of the patient. There was, however, a significant relationship between location and type of abnormality. Radiopaque and radiolucent lesions were more frequently found in the mandible, and unerupted teeth and retained roots were more frequently seen in the posterior maxilla. Selective radiographs to detect retained roots and unerupted teeth in the posterior maxilla may be most productive in terms of prosthodontic treatment outcome. Otherwise, this study finds no basis for selection of intraoral sites for specific intraoral radiographs of asymptomatic edentulous patients.

Aged↗
PubMed1990

Salivary histatin 5: dependence of sequence, chain length, and helical conformation for candidacidal activity.

Histatin 5 (Asp1-Ser-His-Ala4-Lys-Arg-His-His8-Gly-Tyr-Lys-Arg12-Lys-Ph e-His-Glu16-Lys-His - His-Ser20-His-Arg-Gly-Tyr24), one of the basic histidine-rich peptides present in human parotid saliva and several of its fragments, 1-16 (N16), 9-24 (C16), 11-24 (C14), 13-24 (C12), 15-24 (C10), and 7-16 (M10), were synthesized by solid-phase procedures. Native histatin 5 from human parotid saliva was also purified. Their antifungal activities on two strains of Candida albicans have been studied and their conformational preferences both in aqueous and non-aqueous solutions examined by circular dichroism. The synthetic histatin 5, C16, and C14 peptides were highly active and inhibited the growth of C. albicans. The candidacidal activity data of synthetic histatin 5 were comparable to the values of the native histatin 5 isolated from parotid saliva and those reported previously, although the assay system used and the strains examined were different. The C16 fragment was as active as the whole peptide itself, whereas the N16 fragment was far less active than C14, suggesting that the sequence at the C-terminal is important for its fungicidal activity. An increase in the chain length of the C-terminal sequence from 12 to 16 residues increased the candidacidal activity, thereby indicating that a peptide chain length of at least 12 residues is necessary to elicit optimum biological activity. The CD spectra of these linear peptides showed that they are structurally more flexible, and they adopt different conformations depending on the solvent environment. CD studies provided evidence that histatin 5 and the longer fragments, C16, N16, and C14 preferred alpha-helical conformations in non-aqueous solvents such as trifluoroethanol and methanol, while in water and pH 7.4 phosphate buffers, they favored random coil structures. The shorter sequences seemed to adopt either turn structures or unordered structures both in aqueous and non-aqueous solutions. It appears that the sequence at the C-terminal of histatin 5 with a minimum chain length of 14 residues and alpha-helical conformation are the important structural requirements for appreciable candidacidal activity.

Amino Acid Sequence↗
PubMed1987

Maternal prenatal, infancy and concurrent predictors of maternal reports of child psychopathology.

RESEARCH on parent perceptions of infant temperament and child maladjustment has evolved from an initial interpretation of parent reports as objective, veridical descriptions of the child to an interpretation of parent reports as social perceptions that reflect both objective qualities of children and personality characteristics of parents (Bates 1983). Evidence that parents' descriptions reflect generalized behavior of their children is provided by modest correlations between parent and teacher reports of child behavior (Becker and Krug 1964; Glidewell et al. 1959; Rutter et al. 1970). Although limited agreement of parents and teachers in descriptions of child behavior might be interpreted as evidence of situational specificity of behavior (Mischel 1968), an alternative interpretation is that characteristics of parents influence their perceptions of child behavior. This longitudinal study tests hypotheses that maternal characteristics during pregnancy and infancy, prior to the development of stable child characteristics, predict mothers' reports of child psychopathology during the kindergarten year.

Child↗
PubMedDate not supplied

Evaluation of the clinical predictability of hydroxyapatite-coated endosseous dental implants: a review of the literature.

Although the use of hydroxyapatite-coated (HA-coated) endosseous implants in the treatment of dental patients has been established, their clinical predictability remains controversial. This study is an analysis of the clinical predictability and indications for use of HA-coated endosseous implants. This study also discusses the biochemical composition of commercial HA coatings in relation to in vivo predictability, potential concerns, and potential advantages of HA coatings. Clinical studies suggest that HA-coated implants have short-term survival rates (ranging from 6 months to 6 years) that are comparable to short-term survival rates of titanium implants. In addition, clinical data suggest that HA-coated implants may be valuable treatment modalities when placing implants (1) in type IV bone, (2) in fresh extraction sites, (3) in grafted maxillary and/or nasal sinuses, or (4) when using shorter implants (less than or equal to 10 mm). However, long-term controlled studies are required to validate these observations.

Alveolar Bone Loss↗
PubMedDate not supplied

Experimental salivary pellicles formed on titanium surfaces mediate adhesion of streptococci.

The goal of this study was to characterize salivary components of titanium pellicles and to determine how experimental pellicles affect adhesion of several strains of streptococci to titanium surfaces. Titanium experimental pellicles were formed by incubation of fresh human parotid or human submandibular-sublingual saliva on pure titanium beads. Pellicle was recovered from the beads using sodium dodecyl sulfate buffer and was subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting to identify adsorbed salivary components. Streptococcus anginosus, S. oralis, and S. salivarius recovered from in vivo titanium plaque and five reference strains of streptococci were used in adhesion assays to titanium beads with and without experimental salivary pellicles. The experimental pellicle formed on titanium was found to be composed of selected proteins from human parotid and human submandibular-sublingual saliva. Salivary alpha-amylase and proline-rich proteins were found in all experimental pellicles, while sIgA, high-molecular weight mucin, and proline-rich glycoproteins were detected in one of the experimental pellicles examined. Adhesion of fresh isolates and reference stains of S. anginosus, S. oralis, and S. salivarius to saliva-coated titanium was reduced compared to that of titanium without saliva coating. However, adhesion of laboratory strains of S. gordonii and S. sanguis was found to be significantly greater to experimental pellicles of human submandibular-sublingual saliva than was the adhesion of the fresh isolates, suggesting that streptococci-colonizing implant surfaces may be inherently less adhesive than other bacterial strains. This study found that salivary pellicles are selectively formed on titanium and mediate in vitro adhesion of streptococci.

Adsorption↗