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Biomedical subjects

B A White

Publications and source records attributed to B A White.

At least 19 recordsLinked to original sources
PubMed2003

Differential protein phosphorylation-dephosphorylation in response to carbon source in Ruminococcus flavefaciens FD-1.

AIMS: The aims of this study were to study the effect of cellobiose or cellulose as a carbon source on the differential protein phosphorylation-dephosphorylation of cytoplasmic and membrane-associated proteins from Ruminococcus flavefaciens FD-1. METHODS AND RESULTS: SDS-PAGE analysis was used to compare in vitro labelled proteins (32P-ATP) isolated from R. flavefaciens FD-1 grown on either cellobiose or cellulose as the carbon source. Distinctly different protein phosphorylation patterns were detected depending on carbon source and cell fraction. Analysis of the nature of the phosphorylated proteins indicates that phosphorylated proteins from cellobiose grown cultures are phosphorylated on serine residues, whereas phosphorylated proteins from cellulose grown cultures are phosphorylated on threonine residues. CONCLUSIONS: The results of this comparative analysis show a shift from serine phosphorylation of proteins to a threonine phosphorylation when R. flavefaciens FD-1 cells are grown on cellulose as opposed to cellobiose. There appears to be a role for these phosphorylation events in sensing the carbon source for growth and regulating co-ordinated metabolism in R. flavefaciens FD-1. SIGNIFICANCE AND IMPACT OF THE STUDY: We have demonstrated that there is a protein phosphorylation system in R. flavefaciens FD-1 that may be the primary sensing system for carbon source by R. flavefaciens FD-1 and the further regulation of gene expression related to cellulose degradation.

Autoradiography↗
PubMed2003

Expression pattern and role of a 60-kilodalton progesterone binding protein in regulating granulosa cell apoptosis: involvement of the mitogen-activated protein kinase cascade.

Progesterone (P4) inhibits both granulosa cells and spontaneously immortalized granulosa cells (SIGCs) from undergoing apoptosis. P4 does so through a plasma membrane-initiated event. It appears that P4's membrane-initiated actions are mediated by a 60-kDa P4 binding protein (P4BP), which is detected by an antibody directed against the ligand binding domain of the nuclear P4 receptor (i.e., C-262). Immunohistochemical analysis revealed that a C-262-detectable protein was first observed in the periphery of a few granulosa cells within early antral-stage follicles. In nonatretic antral follicles, this protein was detected at the periphery of virtually all granulosa cells. In contrast, granulosa cells of atretic follicles lost the distinct peripheral localization of this C-262-detectable protein. This reduction in the membrane localization was also observed by Western blot analysis. To assess the temporal changes in this 60-kDa P4BP during apoptosis, studies were conducted using SIGCs. That this 60-kDa protein is important in mediating P4's action was confirmed by the observation that C-262 but not IgG attenuated P4's antiapoptotic action. Interestingly, the membrane localization of this 60-kDa P4BP was maintained but the ability of P4 to prevent apoptosis was lost within 20 min of initiating the apoptotic cascade. In addition, Erk-1 and -2 phosphorylation (i.e., activity) increased within 20 min of P4 withdrawal. Further, P4 suppressed the increase in the Erk-1 phosphorylation if administered within 5 but not 20 min of initiating the apoptotic cascade. Moreover, the mitogen-activated protein kinase kinase (MEK) inhibitor, PD98059, reduced the percentage of SIGCs undergoing apoptosis in the absence of P4. Because MEK phosphorylates Erk, these observations suggests that 1) the increase in Erk-1 activity is an important part of the apoptotic cascade, 2) P4 promotes granulosa cell viability by modulating the activity of Erk-1, and 3) P4 becomes "uncoupled" from its antiapoptotic signal transduction mechanism within 20 min of initiating apoptosis, even though the membrane localization of the 60-kDa P4BP is maintained.

Animals↗
PubMed2002

Membrane-initiated events account for progesterone's ability to regulate intracellular free calcium levels and inhibit rat granulosa cell mitosis.

It has been proposed that the antimitogenic action of progesterone (P(4)) is mediated through a membrane receptor that has GABA(A) receptor-like characteristics. To test this hypothesis, studies were designed to compare the antimitogenic effects of P(4) with its gamma amino butyric acid(A) (GABA(A)) receptor-activating metabolite, 5alpha-pregnane-3alpha-21-diol-20-one (5alpha3alpha). These studies revealed that P(4) was more effective than 5alpha3alpha in blocking mitogen-dependent mitosis of both small granulosa cells (GCs) and spontaneously immortalized granulosa cells (SIGCs). Ligand binding studies illustrated that P(4) bound to SIGCs with an apparent dissociation constant (K(d)) of 0.32 +/- 0.09 microM, whereas 5alpha3alpha bound with an apparent K(d) of 40 +/- 19 microM. Further, the GABA(A) antagonist, bicuculline, did not attenuate P(4)'s antimitotic action in SIGCs. Finally, reverse transcriptase-polymerase chain reaction (RT-PCR) studies demonstrated that none of the 6 known alpha chains of the GABA(A) receptors to which bicuculline binds were detected in SIGCs. Taken together, these studies suggest that P(4) does not mediate its action via a GABA(A)-like receptor. Additional studies revealed that P(4) regulated intracellular free calcium levels ([Ca(2+)](i)) as part of its antimitotic action. Specifically, P(4) maintained a basal [Ca(2+)](i) level that was slightly lower than normal. Increasing extracellular calcium not only increased basal [Ca(2+)](i) but also attenuated P(4)'s antimitogenic effect. P(4)'s actions appeared to be initiated at the membrane, since horseradish peroxidase conjugated-P(4) (HP-P(4)), which is cell impermeable, was as effective in blocking mitosis as P(4). Progesterone receptor (PR) mRNA was not detected in SIGCs by RT-PCR analysis, which is consistent with the findings in GCs. However, a 60-kDa protein was detected within crude membrane fractions of both GCs and SIGCs using an antibody directed against the ligand binding domain of the PR (C-262). This antibody was also used in immunocytochemical studies to detect a protein that was associated with the plasma membrane of SIGCs. It is proposed that this 60-kDa protein mediates P(4)'s membrane-initiated actions.

Animals↗
PubMed2002

Development, validation, and application of PCR primers for detection of tetracycline efflux genes of gram-negative bacteria.

Phylogenetic analysis of tetracycline resistance genes, which confer resistance due to the efflux of tetracycline from the cell catalyzed by drug:H(+) antiport and share a common structure with 12 transmembrane segments (12-TMS), suggested the monophyletic origin of these genes. With a high degree of confidence, this tet subcluster unifies 11 genes encoding tet efflux pumps and includes tet(A), tet(B), tet(C), tet(D), tet(E), tet(G), tet(H), tet(J), tet(Y), tet(Z), and tet(30). Phylogeny-aided alignments were used to design a set of PCR primers for detection, retrieval, and sequence analysis of the corresponding gene fragments from a variety of bacterial and environmental sources. After rigorous validation with the characterized control tet templates, this primer set was used to determine the genotype of the corresponding tetracycline resistance genes in total DNA of swine feed and feces and in the lagoons and groundwater underlying two large swine production facilities known to be impacted by waste seepage. The compounded tet fingerprint of animal feed was found to be tetCDEHZ, while the corresponding fingerprint of total intestinal microbiota was tetBCGHYZ. Interestingly, the tet fingerprints in geographically distant waste lagoons were identical (tetBCEHYZ) and were similar to the fecal fingerprint at the third location mentioned above. Despite the sporadic detection of chlortetracycline in waste lagoons, no auxiliary diversity of tet genes in comparison with the fecal diversity could be detected, suggesting that the tet pool is generated mainly in the gut of tetracycline-fed animals, with a negligible contribution from selection imposed by tetracycline that is released into the environment. The tet efflux genes were found to be percolating into the underlying groundwater and could be detected as far as 250 m downstream from the lagoons. With yet another family of tet genes, this study confirmed our earlier findings that the antibiotic resistance gene pool generated in animal production systems may be mobile and persistent in the environment with the potential to enter the food chain.

Animal Feed↗
PubMed2001

The dentogingival epithelial surface area revisited.

Recent studies implicating periodontitis as a cause of systemic diseases have reported that the surface area of periodontal pockets exposed to bacterial biofilm ranges from 50 cm2 to 200 cm2. Since the root surface area of the typical human dentition (excluding 3rd molars) is 75 cm2, these estimates appear too large. The goal of this study was to relate linear periodontal probing measurements to the dentogingival surface area (DGES). The DGES comprises both the sulcular and junctional epithelium, present in health, as well as any intervening pocket epithelium present in periodontitis. Formulas to estimate the DGES from clinical measures were derived from a meta-analysis of root surface areas, published values of root length, and a study that related the percent remaining root surface area to the percent remaining root length. These formulas were applied to a survey of the adult US population, the Veterans Affairs (VA) Dental Longitudinal Study, and a population of individuals visiting a periodontist. Individuals without periodontitis had a typical DGES of 5 cm2. Among individuals with periodontitis, the mean DGES in the three samples ranged from 8 cm2 (ranging from 1 cm2 to 29 cm2) to 20 cm2 (ranging from 2 cm2 to 44 cm2). It was concluded that the mean DGES among individuals with periodontitis ranges from 8 cm2 to 20 cm2, considerably smaller than the range of 50 cm2 to 200 cm2 currently assumed.

Adult↗
PubMed2001

State of the evidence base for medically necessary oral health care.

OBJECTIVE: The purpose of this article was to highlight the recent call for an evidence-based approach to public policy decision making with respect to funding dental services and the need this creates for enhanced clinical research activities. STUDY DESIGN: Systematic reviews on topics of importance to oral health care practitioners are being conducted and published by various national and international groups. Recent activities to assess evidence to support medically necessary dental services were reviewed. RESULTS: An Institute of Medicine Committee on Medicare Coverage Extensions found little published scientific evidence that directly assessed the effectiveness of dental services in preventing or managing systemic health outcomes for patients with head and neck cancer, lymphoma, leukemia, organ transplantation, and heart valve repair or replacement. CONCLUSIONS: The scientific community must strive to meet the challenge of conducting well-designed randomized, controlled trials that test the impact of dental treatment interventions on systemic health to meet the growing need for evidence to support or refute widely accepted dental treatment protocols for medically complex patients.

Clinical Protocols↗
PubMed2001

Ten-year survival rates of teeth adjacent to treated and untreated posterior bounded edentulous spaces.

STATEMENT OF PROBLEM: Failure to replace a single missing posterior tooth may lead to a variety of dental problems, which may ultimately result in tooth loss. However, little is known about the fate of the adjacent teeth if a missing posterior tooth is not replaced. PURPOSE: This retrospective study evaluated the survival of teeth adjacent to treated and untreated posterior bounded edentulous spaces. MATERIAL AND METHODS: Data were obtained from electronic treatment records from the Kaiser Permanente Dental Care Program, Portland, Ore. A final sample of 317 patients who met the study inclusion criteria was identified. Each bounded edentulous space was placed in 1 of 3 treatment categories: untreated, restored with a fixed partial denture, or restored with a removable partial denture. Subsequent treatment and the status of the teeth adjacent to the bounded edentulous space were followed through December 1999. Ten-year Kaplan-Meier survival estimates were generated for each treatment group, and differences in survival were evaluated with the log-rank chi-square test (alpha=.05). RESULTS: There was a significant difference in survival among the 3 treatment categories (P=.005). Spaces restored with a fixed partial denture had longer 10-year survival estimates (92%) than those that remained untreated (81%). Spaces restored with a removable partial denture had the poorest 10-year survival rate (56%). CONCLUSION: Under the conditions and selection bias associated with this retrospective study, the survival of teeth adjacent to a single posterior edentulous space was negatively associated with removable partial denture placement compared with no treatment or the use of a fixed partial denture.

Adolescent↗
PubMed2001

Characterization of a putative membrane receptor for progesterone in rat granulosa cells.

Progesterone (P(4)) inhibits granulosa cell apoptosis in a steroid-specific, dose-dependent manner, but these cells do not express the classic nuclear P(4) receptor. It has been proposed that P(4) mediates its action through a 60-kDa protein that functions as a membrane receptor. The present studies were designed to determine the P(4) binding characteristics of this protein. Western blot analysis using an antibody that recognizes the P(4) binding site of the nuclear P(4) receptor (C-262) confirmed that the 60-kDa protein was localized to the plasma membrane of both granulosa cells and spontaneously immortalized granulosa cells (SIGCs). To determine whether this protein binds P(4), proteins were immunoprecipitated with the C-262 antibody, electrophoresed, transferred to nitrocellulose, and probed with a horseradish peroxidase-labeled P(4) in the presence or absence of nonlabeled P(4). This study demonstrated that the 60-kDa protein specifically binds P(4). Scatchard plot analysis revealed that (3)H-P(4) binds to a single site (i.e., single protein), which is relatively abundant (200 pmol/mg) with a K(d) of 360 nM. (3)H-P(4) binding was not reduced by dexamethasone, mifepristone (RU 486), or onapristone (ZK98299). Further studies with SIGCs showed that P(4) inhibited apoptosis and mitogen-activated protein kinase kinase (MEK) activity, and maintained calcium homeostasis. These studies taken together support the concept that the 60-kDa P(4) binding protein functions as a low-affinity, high-capacity membrane receptor for P(4).

Animals↗
PubMed2001

Characterization of two novel saccharolytic, anaerobic thermophiles, Thermoanaerobacterium polysaccharolyticum sp. nov. and Thermoanaerobacterium zeae sp. nov., and emendation of the genus Thermoanaerobacterium.

Two anaerobic, thermophilic, Gram-positive, non-spore forming bacteria with an array of polysaccharide-degrading enzymes were isolated from the leachate of a waste pile from a canning factory in Hoopeston, East Central Illinois, USA. The results of 16S rDNA sequence homology indicated that their closest relatives belong to the saccharolytic, thermophilic and anaerobic genera of Thermoanaerobacterium and Thermoanaerobacter. Although, the evolutionary distances between these bacteria and their closest relatives are greater than 11%, there is no defining phenotypic characteristic for the creation of a new genus. It is proposed that these bacteria should be placed in the genus Thermoanaerobacterium, which requires emendment of the genus description with regard to the reduction of thiosulfate to sulfur, because neither isolate is capable of this reduction. Thermoanaerobacterium polysaccharolyticum reduces thiosulfate to sulfide, whereas Thermoanaerobacterium zeae is unable to reduce thiosulfate. The cells of both isolates are rod-shaped and exist as single cells or sometimes in pairs. Cells are motile by means of flagella. Growth occurs between 45 and 72 degrees C, with optimum temperature of 65-68 degrees C at pH 6.8. The pH range for growth is from 4 to 8 at a temperature of 65 degrees C. Both organisms ferment glucose, arabinose, maltose, mannose, rhamnose, sucrose, trehalose, xylose, cellobiose, raffinose, melibiose and melezitose. The major end products of fermentation with glucose are ethanol and CO2, with lesser amounts of acetate, formate, lactate and hydrogen. The DNA G+C contents of Thermoanaerobacterium polysaccharolyticum sp. nov. and Thermoanaerobacterium zeae sp. nov. are 46 and 42 mol%, respectively. The type strains are KMTHCJT (= ATCC BAA-17T = DSM 13641T) and mel2T (= ATCC BAA-16T = DSM 13642T), respectively.

Bacteria, Anaerobic↗
PubMed2001

Clinical factors related to noncompletion of root canal therapy.

OBJECTIVES: This study identified clinical factors related to noncompletion of root canal therapy (RCT) among patients in a dental health maintenance organization (HMO) based in Portland, OR. METHODS: A secondary analysis of a case-control study was conducted using data from 303 individuals enrolled continuously in the HMO from January 1, 1987, through December 31, 1994, who received endodontic access on a permanent nonwisdom tooth in 1987 or 1988. Person- and tooth-level characteristics were evaluated to compare patients whose accessed tooth was obturated by December 31, 1994, with patients whose accessed tooth was not obturated by that date. Written and electronic records were reviewed to ascertain study variables, and multivariate logistic regression models were developed to describe differences between the two groups. RESULTS: Incomplete RCT was more common among patients who were symptomatic prior to access and had more missing first molars at access. It also was more common among teeth that were decayed, had more pockets > or = 5 mm, and had fewer decayed or filled surfaces at access. CONCLUSIONS: Because patients with greater evidence of past and current oral disease were less likely to have completed RCT, they may require additional counseling about the importance of carrying through with prescribed treatment.

Adult↗
PubMed2001

Movement of teeth adjacent to posterior bounded edentulous spaces.

Bounded edentulous spaces (BES)-a missing posterior tooth with intact adjacent teeth-are thought to lead to arch collapse resulting from the movement of adjacent teeth. To determine the rate of change in distance between teeth adjacent to a BES, we examined three successive measurable radiographs of 116 untreated posterior BES cases. The distance between the teeth (DBT) adjacent to the space was measured, and change in DBT (delta DBT) between pre-extraction and follow-up radiographs was calculated. We used linear spline regression to construct models for tooth movement and to identify factors associated with delta DBT. The mean delta DBT was < 1 mm during the first year post-extraction, and the DBT continued to decrease at a successively slower rate each following year. Overall and for each tooth type, the greatest rates of decrease in DBT were seen in the zero to two-year period. In a multivariable model, time since extraction and tooth type were significantly associated with delta DBT. These findings suggest that movement of teeth adjacent to a posterior BES after the first two years is usually gradual and minor within the time frame of this study.

Adult↗
PubMed2001

Extending Medicare coverage to medically necessary dental care.

BACKGROUND: Periodically, Congress considers expanding Medicare coverage to include some currently excluded health care services. In 1999 and 2000, an Institute of Medicine committee studied the issues related to coverage for certain services, including "medically necessary dental services." METHODS: The committee conducted a literature search for dental care studies in five areas: head and neck cancer, leukemia, lymphoma, organ transplantation, and heart valve repair or replacement. The committee examined evidence to support Medicare coverage for dental services related to these conditions and estimated the cost to Medicare of such coverage. RESULTS: Evidence supported Medicare coverage for preventive dental care before jaw radiation therapy for head or neck cancer and coverage for treatment to prevent or eliminate acute oral infections for patients with leukemia before chemotherapy. Insufficient evidence supported dental coverage for patients with lymphoma or organ transplants and for patients who had undergone heart valve repair or replacement. CONCLUSIONS: The committee suggested that Congress update statutory language to permit Medicare coverage of effective dental services needed in conjunction with surgery, chemotherapy, radiation therapy or pharmacological treatment for life-threatening medical conditions. PRACTICE IMPLICATIONS: Dental care is important for members of all age groups. More direct, research-based evidence on the efficacy of medically necessary dental care is needed both to guide treatment and to support Medicare payment policy.

Cost-Benefit Analysis↗
PubMed2001

Health care utilization and cost among health maintenance organization members with temporomandibular disorders.

AIMS: Little has been reported on the use of health care services and consequent costs among persons with temporomandibular disorders (TMD). This project compared the use and cost of medical and dental care services for TMD patients and matched comparison subjects. METHODS: Patients were continuously enrolled members of Kaiser Permanente Northwest Division who had at least 1 TMD Clinic visit or TMD-related procedure between January 1990 and December 1995 (n = 8,801). An equal number of comparison subjects were identified electronically and matched on 14 variables, including age and gender. Utilization and cost estimates were determined and compared for selected medical and dental services. RESULTS: For both groups, the mean age was about 40.5 years, and approximately 80% were female. The TMD subjects used significantly more services than did comparison subjects and had mean costs that were 1.6 times higher for all services. Outpatient visits accounted for about 40% of the difference in mean costs. About 10% of TMD subjects and comparison subjects accounted for about 40% and 47% of the costs in each group, respectively. Female TMD subjects and comparison subjects had higher costs than their male counterparts, and male TMD subjects had higher costs than female comparison subjects. CONCLUSION: Patients with TMD used more of all types of services and had higher costs. A small proportion of the subjects accounted for a large proportion of the costs. Gender was an important factor in utilization and cost. Utilization and cost differences were consistent over a wide range of service categories and could not be explained by TMD alone.

Adult↗
PubMed2001

Clinical decision-making for dental caries management.

Scientific information on diagnosis, prevention, and management of dental caries and associated indicators of risk continues to increase rapidly. Patients vary in clinically important ways, however, and uncertainty affects our understanding of risk; diagnostic and prognostic information; efficacy and effectiveness of many preventive, diagnostic, and treatment alternatives; and outcomes associated with clinical strategies. Consequently, challenges abound for clinicians to identify, evaluate, and incorporate new information, patient preferences, and uncertainties into clinical practice. Clinical decision-making--an analytical approach that makes explicit use of information to quantify probabilities and outcomes to analyze decisions under conditions of uncertainty--can provide a framework to analyze the impact of uncertainty of clinical information. Diagnostic, effectiveness, and outcome information is quantified and combined in an explicit way to serve as a tool for clinicians, not as a replacement for clinical judgment or experience. Such an approach has the potential to improve clinical practice and help dentists do their jobs better by structuring the decision problem and assessing probabilities and utilities. Clinical decision-making also helps dentists communicate with each other by identifying clinical controversies, thereby characterizing how and why disagreements may arise and what additional data may be needed to address a clinical question.

Decision Making↗
PubMed2000

Identification of adult populations at high risk for dental caries using a computerized database and patient records: a pilot project.

OBJECTIVES: The purpose of this study is to test the usefulness of dental insurance claims history, supplemented with radiographic caries diagnoses, as a means of identifying caries-active and caries-inactive working adults, as determined by bacterial levels. Computerized identification of at-risk groups may facilitate subject selection for clinical trials designed to test caries-preventive strategies. METHODS: Two groups of subjects were initially selected from an insurance database based upon their dental service utilization during a one-year period: a "low restorative" group of individuals defined as persons who had received no restorative treatment, and a "high restorative" group comprised of individuals who had received at least three multisurfaced restorations. A chart review confirmed a diagnosis of caries in the high restorative group and an absence of caries in the low restorative group. Subjects were then approached for saliva collection. The low and high restorative groups were compared for salivary mutans streptococci and lactobacilli levels, stimulated flow rate, and buffer capacity (n = 48). RESULTS: The high and low restorative groups differed in mutans streptococci levels, but not on other measures. CONCLUSIONS: A group of subjects who had recently received multisurfaced restorations that were placed for reasons of caries had significantly higher levels of mutans streptococci and potential for continued caries activity when compared to a group of subjects who had received no restorations and were caries free.

Adult↗