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Biomedical subjects

R N Andersen

Publications and source records attributed to R N Andersen.

At least 37 records · Page 2Linked to original sources
PubMed1991

Alpha-fetoprotein and acetylcholinesterase are not predictive of fetal junctional epidermolysis bullosa, Herlitz variant.

Junctional epidermolysis bullosa, Herlitz variant (junctional EB-Herlitz) is a lethal autosomal recessive skin disorder currently amenable to prenatal diagnosis only by direct analysis of fetal skin. However, elevated levels of alpha-fetoprotein, as well as the presence of acetylcholinesterase in amniotic fluid, have been associated with other severe fetal genodermatoses. Fetal skin samplings were performed in ten pregnancies at risk for fetal junctional EB-Herlitz, with three fetuses affected on the basis of electron microscopic detection of blisters within the lamina lucida and abnormal hemidesmosomes. In neither affected nor unaffected pregnancies were maternal serum or amniotic fluid alpha-fetoprotein levels elevated. Moreover, alpha-fetoprotein levels in both maternal serum and amniotic fluid were not statistically different comparing affected and unaffected fetuses. Acetylcholinesterase was not present in the amniotic fluid samples of the three affected pregnancies. Unlike other severe fetal genodermatoses, neither alpha-fetoprotein nor acetylcholinesterase was predictive of junctional EB-Herlitz.

Acetylcholinesterase↗
PubMed1991

Does unexplained second-trimester (15 to 20 weeks' gestation) maternal serum alpha-fetoprotein elevation presage adverse perinatal outcome? Pitfalls and preliminary studies with late second- and third-trimester maternal serum alpha-fetoprotein.

Several reports have suggested that persons with an unexplained maternal serum alpha-fetoprotein elevation at 15 to 20 weeks' gestation are at an increased risk for a variety of other pregnancy complications (e.g., preeclampsia) and adverse perinatal outcomes (e.g., fetal death, low-birth-weight infants). However, ascertainment biases could explain some of these reported findings, and predictive value of unexplained elevated maternal serum alpha-fetoprotein levels in the prediction of pregnancy complications seems limited. If elevated second-trimester levels were truly predictive of pregnancy complications, we reason that third-trimester levels could prove even more useful. We thus studied late second-trimester and early third-trimester (24 to 36 weeks' gestation) maternal serum alpha-fetoprotein levels with the same enzyme immunoassay we use to evaluate routine second-trimester (15 to 20 weeks' gestation) levels. Values rose up to 32 weeks and fell slightly thereafter. Variance was greater than at 15 to 20 weeks but not so great as to preclude clinical usefulness in the third trimester. Of 279 women with a normal (0.4 to 2.49 multiples of the median) maternal serum alpha-fetoprotein value at 15 to 20 weeks' gestation, 270 (96.8%) showed levels in the same range later in gestation; however, none of six singleton pregnancies with unexplained maternal serum alpha-fetoprotein levels greater than 2.50 multiples of the median at 15 to 20 weeks' gestation showed maternal serum alpha-fetoprotein levels in this range at 24 to 36 weeks' gestation. The relationship between second- and third-trimester maternal serum alpha-fetoprotein levels in abnormal pregnancies remains to be elucidated in a large sample. Thus we are conducting not only cohort but also cross-sectional studies. Preliminary findings suggest that women with preterm premature rupture of membranes or with premature labor show elevated late second-trimester and early third-trimester maternal serum alpha-fetoprotein levels; however, larger sample sizes are necessary.

Female↗
PubMed1991

Inhibition of intergeneric coaggregation among oral bacteria by cetylpyridinium chloride, chlorhexidine digluconate and octenidine dihydrochloride.

The potential inhibitory effect of chlorhexidine digluconate on the intergeneric coaggregation of 11 pairs of Gram-positive organisms was compared to its ability to inhibit coaggregations of 14 pairs comprised of both a Gram-positive and a Gram-negative cell type. Dramatic differences in the inhibitory effectiveness of the antimicrobial compound on the two kinds of coaggregation pairs were found. Gram-positive pairs were not inhibited at a concentration of 0.25%, whereas the coaggregations involving a Gram-negative partner were usually completely blocked at concentrations as low as 0.01%. Similar effects to chlorhexidine digluconate were found with octenidine dihydrochloride and cetylpyridinium chloride, while sodium dodecylsulfate was inhibitory only at 10- to 50-fold higher concentrations. These results suggest that chlorhexidine digluconate, octenidine dihydrochloride, and cetylpyridinium chloride may be effective inhibitors of later microbial colonizers of dental plaque but may not disturb a normal healthy indigenous flora.

Actinomyces↗
PubMed1990

Fetomaternal transfusion depends on amount of chorionic villi aspirated but not on method of chorionic villus sampling.

Transcervical and transabdominal chorionic villus sampling are believed, on the basis of indirect evidence, to result in fetomaternal transfusion. We sought to measure this phenomenon by devising a simple method that would allow us to identify variables that influence fetomaternal transfusion. We investigated patients undergoing transcervical-chorionic villus sampling (n = 15) and transabdominal-chorionic villus sampling (n = 15), restricting the sample to subjects who required only a single catheter passage or needle insertion to obtain villi. Maternal serum alpha-fetoprotein was measured before and after the procedure along with alpha-fetoprotein concentration of the transport medium into which the villi had been aspirated. We first confirmed that the change in maternal serum alpha-fetoprotein levels after chorionic villus sampling, an indirect measure of fetomaternal transfusion, was indeed correlated with the alpha-fetoprotein concentration of transport medium into which the villi were aspirated (p = 0.0350). Fetomaternal transfusion next proved to be correlated with the amount of villi obtained (p = 0.0279). However, when adjusted for the amount of villi obtained, no significant difference was observed between transcervical and transabdominal-chorionic villus sampling with respect to the change in maternal serum alpha-fetoprotein levels after chorionic villus sampling (p = 0.8512). These data suggest that the magnitude of fetomaternal transfusion depends on the amount of villi obtained but not on the chorionic villus sampling method used.

Adult↗
PubMed1990

Differential modulation of ACTH-stimulated cortisol and androstenedione secretion by insulin.

Results of previous clinical studies suggested counter regulatory actions between insulin and DHEA(S). The present studies were performed using primary monolayer cultures of bovine fasciculata-reticularis cells to test the hypothesis that insulin directly affects adrenal androgen secretion. Although having no independent effect, insulin exhibited complex time- and concentration-specific actions on ACTH-stimulated secretion of both C21 (cortisol) and C19 (androstenedione) corticosteroids. In the presence of low concentrations (0.05-0.1 nM) of ACTH, cortisol secretion during a 2 h incubation was about 2-fold greater in the presence than in the absence of insulin (0.01-100 ng/ml). In the presence of a maximal concentration (10 nM) of ACTH, on the other hand, cortisol secretion was not affected by insulin at concentrations less than or equal to 0.1 ng/ml, but was decreased at higher insulin concentrations. ACTH-stimulated androstenedione secretion was not significantly affected by insulin during a short-term (2 h) incubation. During a prolonged (24 h) incubation, insulin produced a concentration-dependent inhibition of ACTH-stimulated cortisol secretion. At an insulin concentration of 100 ng/ml, ACTH (10 nM)-stimulated cortisol secretion declined to a level only 30% of that produced by ACTH alone. In contrast, insulin exhibited biphasic effects on the secretion of androstenedione by cells maintained in the presence of ACTH for 24 h; an effect that was most dramatic in the presence of a maximal concentration of ACTH. At an insulin concentration of 0.1 ng/ml, androstenedione secretion by cells maintained in the presence of 10 nM ACTH was increased approximately 2.5-fold. At higher concentrations of insulin, ACTH-stimulated androstenedione secretion was inhibited to an extent comparable to that in cortisol secretion. The effects of insulin on ACTH-stimulated cortisol and androstenedione secretion could not be accounted for by changes in steroid degradation or a loss in 11 beta-hydroxylase activity. These results indicate that insulin interacts with ACTH to modulate the secretion of both C21 and C19 corticosteroids and that physiological concentrations (less than or equal to 1 ng/ml) of insulin may have a long-term effect to enhance selectively adrenal androgen secretion. These data are consistent with a servo mechanism between insulin and DHEA(S) in vivo and indicate that the correlations observed clinically result, at least in part, from a direct action of insulin to modulate the rate of adrenal androgen production.

Adrenal Glands↗
PubMed1990

Intrageneric coaggregation among strains of human oral bacteria: potential role in primary colonization of the tooth surface.

Of the 122 human oral bacterial strains tested from 11 genera, only streptococci and a few actinomyces exhibited coaggregation among the strains within their respective genera. Eight of the ten streptococci showed multiple intrageneric coaggregations, all of which were inhibited by galactosides. The widespread intrageneric coaggregation among the streptococci and the less extensive coaggregation among the actinomyces offers an explanation for their accretion on cleaned tooth surfaces and their dominance as primary colonizers.

Actinomyces↗
PubMed1990

Characterization of Streptococcus gordonii (S. sanguis) PK488 adhesin-mediated coaggregation with Actinomyces naeslundii PK606.

Intergeneric coaggregation of Streptococcus gordonii (S. sanguis) PK488 and Actinomyces naeslundii PK606 was studied by using coaggregation-defective (Cog-) mutants of both strains. A streptococcal protein of 38 kilodaltons was identified with anti-S. gordonii serum absorbed with Cog- cells of the streptococcus. Absorbed immunoglobulin G specifically blocked coaggregation of the streptococcus-actinomyces pair but did not affect the coaggregation of the streptococcus with other coaggregation partners. The 38-kilodalton protein was found in the supernatant of mild sonicated cell suspensions and was extracted from whole cells with sodium barbital or with 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS). An immunoreactive protein of the same size was found in sonicated cell supernatants of several other oral streptococci that also coaggregated with A. naeslundii PK606. Inhibition of S. gordonii PK488-A. naeslundii PK606 coaggregation was not observed with any of 16 different sugars tested. We propose that a functionally similar adhesin that mediates coaggregations with A. naeslundii PK606 is expressed by several species of the genus Streptococcus.

Actinomyces↗
PubMed1989

Identification of fatty acid amides in human plasma.

A family of five long-chain fatty acid carboxamides has been identified and semi-quantified in human plasma by GC-MS. One saturated and four unsaturated amides were found. Luteal phase plasma from 16 women was studied, and all five of the amides were found in ten of the subjects, but none in the other six. The structure of these endogenous amides was established by comparing their GC and MS characteristics with those of the synthetic amides prepared by ammonolysis of corresponding long-chain fatty acid acyl chlorides.

Amides↗
PubMed1989

Coaggregation of Fusobacterium nucleatum, Selenomonas flueggei, Selenomonas infelix, Selenomonas noxia, and Selenomonas sputigena with strains from 11 genera of oral bacteria.

Twenty-eight strains of Fusobacterium nucleatum and 41 Selenomonas strains, including S. sputigena (24 strains), S. flueggei (10 strains), S. infelix (5 strains), and S. noxia (2 strains), were tested for their ability to coaggregate with each other and with 49 other strains of oral bacteria representing Actinobacillus, Actinomyces, Bacteroides, Capnocytophaga, Gemella, Peptostreptococcus, Porphyromonas, Propionibacterium, Rothia, Streptococcus, and Veillonella species. Selenomonads coaggregated with fusobacteria and with Actinomyces naeslundii PK984 but not with any of the other bacteria, including other selenomonads. In contrast, fusobacteria coaggregated with members of all genera, although not with all strains of each species tested. Each fusobacterium strain appeared to have its own set of partners and coaggregation properties, unlike their partners, whose coaggregation properties in earlier surveys delineated distinct coaggregation groups. Coaggregations of fusobacteria with the 63 gram-negative strains were usually inhibited by EDTA, whereas those with the 27 gram-positive strains were usually not inhibited. Likewise, lactose-inhibitable coaggregations were common among some strains of fusobacteria and some strains from each of the genera containing gram-negative partners but were rarely observed with gram-positive partners. Heating the fusobacteria at 85 degrees C for 30 min completely prevented coaggregation with most partners, suggesting the involvement of a protein on the fusobacteria. Heat treatment of many of the gram-negative partners not only enhanced their coaggregation with the fusobacteria but also changed lactose-sensitive coaggregations to lactose-insensitive coaggregations. Although fusobacteria coaggregated with a broader variety of oral partner strains than any other group of oral bacteria tested to date, each fusobacterium exhibited coaggregation with only a certain set of partner strains, and none of the fusobacteria adhered to other strains of fusobacteria, indicating that recognition of partner cell surfaces is selective. The strains of F. nucleatum are heterogeneous and cannot be clustered into distinct coaggregation groups. Collectively, these results indicate that coaggregation between fusobacteria and many gram-negative partners is significantly different from their coaggregation with gram-positive partners. The contrasting variety of partners for fusobacteria and selenomonads supports the concept of coaggregation partner specificity that has been observed with every genus of oral bacteria so far examined.

Actinomyces↗
PubMed1989

Inhibition of coaggregation between Fusobacterium nucleatum and Porphyromonas (Bacteroides) gingivalis by lactose and related sugars.

The coaggregation of Fusobacterium nucleatum PK1594 and Porphyromonas (Bacteroides) gingivalis PK1924 was inhibited equally well by lactose, N-acetyl-D-galactosamine, and D-galactose, which caused 50% inhibition of coaggregation at 2 mM sugar concentration. Other sugars such as D-galactosamine, D-fucose (6-deoxy-D-galactose), and alpha-methyl- and beta-methyl-D-galactosides also inhibited coaggregation. Sugar specificity was apparent, since neither L-fucose, L-rhamnose, N-acetyl-D-glucosamine, nor N-acetylneuraminic acid was an inhibitor. Protease treatment of the fusobacterium completely abolished coaggregation, whereas it had no effect on the coaggregating activity of the porphyromonad. Although numerous lactose-inhibitable coaggregating pairs are known to occur among gram-positive bacteria, this report and the accompanying survey (P. E. Kolenbrander, R. N. Andersen, and L. V. H. Moore, Infect. Immun. 57:3194-3203, 1989) are the first studies demonstrating the extensive nature of this type of interaction between gram-negative human oral bacteria. The significance of galactoside-inhibitable coaggregations between these two potential periodontal pathogens is discussed.

Acetylgalactosamine↗
PubMed1989

Fimbria-associated adhesin of Bacteroides loeschei that recognizes receptors on procaryotic and eucaryotic cells.

Inhibition studies with a set of adhesin-specific monoclonal antibodies and various sugars revealed that a fimbria-associated adhesin of Bacteroides loeschei recognizes receptors on both procaryotic and eucaryotic cells. These interactions permit this bacterium to attach to both types of cells, producing coaggregates in the presence of strains of Streptococcus sanguis and hemagglutination in the presence of neuraminidase-treated human erythrocytes.

Actinomyces↗
PubMed1988

Sedative and hypnotic effects of oral administration of micronized progesterone may be mediated through its metabolites.

Progesterone and its metabolites were measured in serum extracts by radioimmunoassay and gas chromatography-mass spectrometry, respectively, after ingestion of micronized progesterone by eight postmenopausal women. One subject received 400 mg of micronized progesterone orally that induced a hypnotic state that lasted for approximately 2 hours. Blood samples were drawn periodically from all subjects for measurement of progesterone and its metabolites in serum. Levels of serum progesterone and its metabolites increased significantly from baseline values and reached a peak between 2 and 6 hours after oral progesterone administration. Significant quantities of five compounds (progesterone, 5 alpha-pregnan-3 alpha-ol-20-one, 5 beta-pregnan-3 alpha-ol-20-one, 5 beta-pregnan-3 alpha,20 beta-diol, and 5 beta-pregnan-3 alpha-ol-11,20-dione) that have been reported to possess anesthetic qualities were identified. The sedative and hypnotic effects of oral administration of progesterone may be mediated through those compounds.

Administration, Oral↗
PubMed1988

Intergeneric rosettes: sequestered surface recognition among human periodontal bacteria.

The human oral bacteria, Streptococcus sanguis and Bacteroides loescheii, when mixed in equal numbers in vitro, formed large settling coaggregates. As the relative number of each cell type was changed, coaggregates became smaller until at cell-type ratios of 10 to 1, rosettes formed. Rosettes consisting of a streptococcal cell in the center surrounded by bacteroides cells exhibited surface recognition properties of only the bacteroides, which coaggregated with many other cell types such as Actinomyces naeslundii, and formed large settling multigeneric aggregates. The ecological significance of these results derives from the following: (i) the direct demonstration that intergeneric coaggregates can protect the central cell from or prevent its access to other cells in the environment, and (ii) the potential for these effects to occur during bacterial succession of various cell types observed in progressively more severe stages of human periodontal disease.

Bacterial Adhesion↗
PubMed1988

Coaggregation properties of human oral Veillonella spp.: relationship to colonization site and oral ecology.

The primary habitats of oral veillonellae are the tongue, dental plaque, and the buccal mucosa. Isolates were obtained from each habitat and tested for coaggregation with a battery of other oral bacterial strains. All 59 tongue isolates tested for coaggregation were Veillonella atypica or Veillonella dispar. All but one of them coaggregated with strains of Streptococcus salivarius, a predominant inhabitant of the tongue surface but not subgingival dental plaque. These tongue isolates were unable to coaggregate with most normal members of the subgingival flora such as Actinomyces viscosus, Actinomyces naeslundii, Actinomyces israelii, and Streptococcus sanguis. In contrast, 24 of 29 Veillonella isolates, of which 20 were Veillonella parvula from subgingival dental plaque samples, coaggregated strongly with the three species of Actinomyces, S. sanguis, and other bacteria usually present in subgingival plaque, but they did not coaggregate with S. salivarius. The majority of isolates from the buccal mucosa (42 of 55) has coaggregation properties like those from the tongue. These results indicate that the three human oral Veillonella species are distributed on oral surfaces that are also occupied by their coaggregation partners and thus provide strong evidence that coaggregation plays a critical role in the bacterial ecology of the oral cavity.

Actinomyces↗
PubMed1988

Characterization of monoclonal antibodies to fimbria-associated adhesins of Bacteroides loescheii PK1295.

Bacteroides loescheii PK1295 fimbriae, which mediate the lactose-sensitive coaggregation with Streptococcus sanguis 34 and the lactose-insensitive coaggregation with Actinomyces israelii PK14, were injected into mice to raise adhesin-specific monoclonal antibodies (MAbs). Supernatants of hybridomas were screened for the capacity to inhibit coaggregation and agglutinate intact bacteria. Of the 10 MAbs that were isolated, 4 were specific and potent inhibitors of the coaggregation between B. loescheii and S. sanguis and two other MAbs specifically inhibited the B. loescheii-A. israelii interaction. None of the six MAbs which inhibited adherence were capable of agglutinating whole cells of B. loescheii, whereas the four remaining MAbs agglutinated whole cells but had no effect on coaggregation. Fab fragments of two MAbs, one that inhibited the coaggregation with S. sanguis and another that inhibited the interaction with A. israelii, also were shown to inhibit the respective coaggregation interactions, suggesting that each of the immunoglobulins recognized its adhesin molecule at or near the active sites. By immunoblotting or immunoprecipitation, the S. sanguis adhesin-specific MAbs reacted with a 75-kilodalton polypeptide present in fimbria-enriched preparations, whereas the A. israelii adhesin-specific MAbs recognized a 45-kilodalton polypeptide in the same preparations. By screening hybridoma supernatants directly for their capacity to block coaggregation, we isolated MAbs which were used to establish that the B. loescheii-S. sanguis and the B. loescheii-A. israelii interactions were mediated by different adhesins.

Actinomyces↗
PubMed1987

Deprivation and repletion of androgen in vivo modifies triacylglycerol synthesis by rat hepatocytes.

Given the same quantity of fatty acid, livers from male rats esterify less fatty acid and secrete less triacylglycerol in very-low-density lipoprotein than do livers from female animals. To elucidate the role of testosterone in maintenance of this male pattern, conversion of [1-14C]oleic acid into triacylglycerol was assessed in vitro by rat hepatocytes (male) following gonadectomy and replacement with testosterone. Following castration, incorporation of fatty acid into triacylglycerol was increased. In contrast, esterification of exogenous fatty acid into phospholipid, cholesteryl esters, and diacylglycerol was unchanged. Treatment with testosterone (75 micrograms/day) reduced incorporation of exogenous fatty acid into triacylglycerol. Higher doses of testosterone (200 or 100 micrograms/day) modified the effect, such that inhibition was observed only at low oleate (0.5 mM) concentrations. At higher substrate concentrations (1.0-2.0 mM) the inhibitory effect was no longer observed. Further, a similar dose-dependent effect of testosterone was observed following in vivo treatment of castrate females with testosterone. These data support the concept of a regulatory role of testosterone in hepatic triacylglycerol synthesis. These findings also demonstrate a biphasic effect of testosterone, an effect that is dependent not only upon the dose of testosterone administered, but also on the concentration of fatty acid to which the hepatocyte is exposed in vitro.

Animals↗
PubMed1987

Characterization of lectinlike surface components on Capnocytophaga ochracea ATCC 33596 that mediate coaggregation with gram-positive oral bacteria.

The interactions between Capnocytophaga ochracea ATCC 33596 and Streptococcus sanguis H1, Actinomyces naeslundii PK984, or Actinomyces israelii PK16 are dependent on specific recognitions between heat-sensitive adhesins on C. ochracea and heat-stable structures (probably carbohydrate-containing receptors) on the surfaces of these gram-positive coaggregation partners. The coaggregation of C. ochracea with each of these three organisms was inhibited by L-rhamnose and D-fucose and to a lesser extent by beta-methyl-galactoside. The reaction with S. sanguis was the most sensitive, while the coaggregation with A. israelii was the least sensitive and was only partially inhibited by each of the sugars that were considered to be effective inhibitors. A more effective inhibition of the coaggregation between C. ochracea and A. israelii was achieved by adding a combination of the 6-deoxysugars and N-acetylneuraminic acid. To further characterize the coaggregations, naturally occurring coaggregation-defective (Cog-) mutants of C. ochracea were obtained from several different selections. Three phenotypically distinct groups of mutants were were isolated. Type 1 mutants failed to coaggregate with S. sanguis only. Type 2 mutants lost ability to interact with both S. sanguis and A. naeslundii. Type 3 mutants failed to coaggregate with all three coaggregation partners. Characterization of the Cog- mutants by sugar inhibition studies made it possible to distinguish three classes of adhesin activity.

Bacterial Adhesion↗