Biomedical subjects

B P Boyer

Publications and source records attributed to B P Boyer.

9 recordsLinked to original sources

PubMed1996

Colonization by Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia in adult periodontitis patients as detected by the antibody-based Evalusite Test.

Studies were performed to evaluate the detection of disease-associated bacterial colonization in adult periodontitis patients by the antibody-based Evalusite TestTM (Eastman Kodak Company). The association of test results with disease was assessed by collecting 104 duplicate subgingival plaque samples from 26 patients. Samples were tested for Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia using both microbiological culture and the immunoassay test. The sensitivity and specificity of the 2 methods was calculated using %s of positive results in deep periodontal pockets and negative results in shallow subgingival sites. A cutoff >10(4) cultivable counts yielded the greatest discrimination between health and disease on a cross-sectional basis and established this threshold as clinically relevant for the detection of disease-associated levels of bacterial colonization by these three microorganisms. The clinical detection limit of the immunoassay test was observed to coincide with this threshold of >10(4) cultivable counts. Microbiological testing of the 4 deepest pockets using the immunoassay test was determined to be sufficient to yield a 90% confidence of detecting positive patients in a study with 59 adult subjects. The immunoassay test method was also demonstrated to be effective at detecting bacterial colonization in sets of paper point samples that were pooled for analysis. An overall agreement of 94% (288 of 306) was observed when comparing test results for duplicate sets of pooled and individual samples collected from 51 patients. These studies demonstrate that the Evalusite Test is an effective method for detecting clinically relevant colonization by the test bacteria in patients at risk for periodontal disease.

Adolescent↗

PubMed1996

Analytical performance of an immunologic-based periodontal bacterial test for simultaneous detection and differentiation of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia.

The analytical performance of a membrane-based immunoassay for the simultaneous detection and differentiation of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia (including Prevotella nigrescens) was investigated. Positive reactions were observed for 71 of 71 reference strains and recent oral isolates of A. actinomycetemcomitans, P. gingivalis, and P. intermedia. No cross-reactivity was observed with 39 other common oral and environmental species. The specificity of the test was unaffected by the presence of potential oral interferents including whole blood, white blood cells, mucin, saliva, toothpastes, and oral rinses. A proficiency test by dental professionals using a standardized set of unknown simulated samples yielded a sensitivity of 97% (116/120) and a 100% specificity (240/ 240). An additional group including dental professionals and high school students was shown to be 99% proficient (1385/1397) in distinguishing proper from improper test function when processing control samples with normal test devices and devices with simulated error conditions. Comparisons to a culture standard for 104 subgingival plaque samples collected from 26 adult periodontitis patients yielded > 98% specificity for each of the test bacteria. In addition, the detection threshold for the test was determined to be equivalent to 10(4) cultivable test bacteria when compared to the culture standard. The data indicate that this membrane immunoassay is a valid and easy-to-use method for the detection of A. actinomycetemcomitans, P. gingivalis, and P. intermedia in subgingival plaque, at levels above the detection threshold of the test.

Adult↗

PubMed1986

Ficoll and dextran enhance adhesion of Sendai virus to liposomes containing receptor (ganglioside GD1a).

Previous work has shown that high-speed centrifugation (300,000 g) of Sendai virus and liposomes in 40% (w/v) sucrose layered under a discontinuous sucrose gradient removes Sendai virus bound to liposomes containing the ganglioside GD1a, a Sendai virus receptor. Centrifugation also removes virus bound to liposomes containing other negatively charged lipids. This work shows that centrifugation of virus through a discontinuous ficoll gradient does not remove virus bound to liposomes containing GD1a but does remove virus from liposomes containing various other negatively charged lipids including the ganglioside GM1, which is not a Sendai virus receptor. The amount of virus that adheres to liposomes increases with increasing content of GD1a in the liposomes. The adhesion of virus to receptor-containing liposomes during centrifugation through a ficoll gradient results from the presence of ficoll and increases with increasing ficoll concentration. Virus also adheres to receptor-containing liposomes during centrifugation in the presence of dextran. These data indicate that caution should be used in interpreting associations demonstrated by centrifugation through dextran and ficoll gradients. They also indicate that binding of virus by ganglioside receptors can be modulated by carbohydrate polymers, which are thought not to have any specific interaction with either viruses or gangliosides.

Animals↗

PubMed1986

Time and temperature dependence of influenza virus membrane fusion at neutral pH.

The time course and temperature requirements for fusion of influenza virus membranes with liposomes at pH 7.5 were found to be consistent with the requirements for cell entry. At 37 degrees C, fusion was most rapid during the first 5 min and then continued more slowly up to at least 1 h. The amount of fusion increased semilogarithmically with increasing temperature up to 50 degrees C.

Hemagglutinin Glycoproteins, Influenza Virus↗

PubMed1985

Fusion of influenza virus membranes with liposomes at pH 7.5.

Influenza virus X-31 (H3N2) membranes fuse with liposomes containing ganglioside GD1a at pH 7.5. Fusion was demonstrated by electron microscopy and also can be measured by counting the labeled virus proteins incorporated into liposomes after bound virus has been removed. Liposomes composed of lipids that have no net charge behave as reported by other investigators and do not fuse with influenza X-31 membranes at neutral pH, but they do fuse at low pH. Therefore, the liposomal composition is a factor in whether liposomes fuse with influenza virus membranes at neutral pH, probably by determining whether binding occurs. The liposomal composition necessary for fusion at neutral pH needs to be individualized for each influenza subtype. To establish that a virus requires low pH for membrane fusion, it is first necessary to establish that fusion does not occur at neutral pH under conditions where adequate binding occurs.

Animals↗

PubMed1984

Effect of lipid composition upon fusion of liposomes with Sendai virus membranes.

How the lipid composition of liposomes determines their ability to fuse with Sendai virus membranes was tested. Liposomes were made of compositions designed to test postulated mechanisms of membrane fusion that require specific lipids. Fusion does not require the presence of lipids that can form micelles such as gangliosides or lipids that can undergo lamellar to hexagonal phase transitions such as phosphatidylethanolamine (PE), nor is a phosphatidylinositol (PI) to phosphatidic acid (PA) conversion required, since fusion occurs with liposomes containing phosphatidylcholine (PC) and any one of many different negatively charged lipids such as gangliosides, phosphatidylserine (PS), phosphatidylglycerol, dicetyl phosphate, PI, or PA. A negatively charged lipid is required since fusion does not occur with neutral liposomes containing PC and a neutral lipid such as globoside, sphingomyelin, or PE. Fusion of Sendai virus membranes with liposomes that contain PC and PS does not require Ca2+, so an anhydrous complex with Ca2+ or a Ca2+-induced lateral phase separation is not required although the possibility remains that viral binding causes a lateral phase separation. Sendai virus membranes can fuse with liposomes containing only PS, so a packing defect between domains of two different lipids is not required. The concentration of PS required for fusion to occur is approximately 10-fold higher than that required for ganglioside GD1a, which has been shown to act as a Sendai virus receptor. When cholesterol is added as a third lipid to liposomes containing PC and GD1a, the amount of fusion decreases if the GD1a concentration is low.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗

PubMed1982

Sendai virus membrane fusion: time course and effect of temperature, pH, calcium, and receptor concentration.

The conditions that optimize Sendai virus membrane fusion with liposomes have been studied. No fusion occurs in the absence of ganglioside receptors. Maximum fusion occurs when the molar ratio of ganglioside GD1a to phospholipid is 0.02 or greater. The amount of fusion at 37 degrees C increases with time up to at least 6.5 h. The rate of fusion increases from the lowest temperature tested, 10 degrees C, to 40 degrees C. Above 43 degrees C the amount of fusion decreases because of thermal inactivation of the viral proteins. There is a broad pH maximum between pH 7.5 and pH 9.0. At both ends of the pH range the amount of fusion increases and exceeds that found in the physiologic pH range. Neither ethylenediaminetetraacetic acid nor Ca2+ changes the amount of membrane fusion. The optimal conditions for membrane fusion of Sendai virus membranes with liposomes are the same as the optimal conditions for fusion with host cells and with red blood cells. Since the liposomes contain no proteins, the optimal conditions for Sendai virus membrane fusion must be determined by the viral proteins and be mostly independent of the nature or presence of the host proteins.

Animals↗

PubMed1981

Initiation of fusion and disassembly of Sendai virus membranes into liposomes.

Sendai virus penetration into liposomes consists of two steps which are fusion of the viral and liposomal membranes and viral disassembly. Penetration can occur in less than one minute. The virus first causes a liposome to envelop it and then fuses with the leading edge of the developing vacuole. Viral disassembly does not follow immediately but requires release of virus-receptor binding and probably also requires changes in the association between viral proteins.

Liposomes↗

PubMedDate not supplied

Turnaround time.

Advances in instrumentation have enabled laboratories to deliver results much more quickly. But as equipment has advanced so have expectations on turnaround time (TAT), driving up costs in the process. Laboratories must balance the needs of their clients against the need to cover their costs. In this issue, we asked our respondents: How do you address the issue of turnaround time?

Costs and Cost Analysis↗