Biomedical subjects

S C Holt

Publications and source records attributed to S C Holt.

At least 91 records · Page 5Linked to original sources

PubMed1991

Extraction, purification, and characterization of major outer membrane proteins from Wolinella recta ATCC 33238.

The outer membrane of Wolinella recta ATCC 33238 was isolated by French pressure cell disruption and differential centrifugation. Outer membrane proteins (OMPs) were solubilized by Zwittergent 3.14 extraction and separated by DEAE-Sephacel ion-exchange chromatography. The major OMPs that were found in W. recta ATCC 33238 and in several other Wolinella spp. consisted of proteins with apparent molecular masses of 51, 45, and 43 kDa. These three conserved proteins were purified to essential homogeneity by one- and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and characterized chemically. Heating at between 75 and 100 degrees C revealed both the 43- and 51-kDa proteins to be heat modified from apparent molecular masses of 32 and 38 kDa, respectively. The 45-kDa protein was unmodified at all temperatures tested. Two-dimensional isoelectric focusing-SDS-PAGE revealed the 51-kDa protein to be composed of multiple pIs between a pH of 5.0 and greater than 8.0 while the 43- and 45-kDa proteins had a pI of approximately 6.0. N'-terminal amino acid sequence analysis of the first 30 to 40 amino acids and search of the Protein Identification Resource data base for similar proteins only revealed the 43-kDa protein to be similar to the P.69 OMP of Bordetella pertussis; however, the homology was weak (33%). Amino acid analysis revealed the 43-kDa protein to be noncharged and the 45- and 51-kDa proteins to be hydrophilic, containing between 38 to 42% polar residues but no cysteine. This study reports the purification and partial characterization of three conserved proteins in W. recta ATCC 33238.

Amino Acid Sequence↗

PubMed1991

Hemolytic activity in the periodontopathogen Porphyromonas gingivalis: kinetics of enzyme release and localization.

Porphyromonas gingivalis W50, W83, A7A1-28, and ATCC 33277 were investigated for their abilities to lyse sheep, human, and rabbit erythrocytes. All of the P. gingivalis strains studied produced an active hemolytic activity during growth, with maximum activity occurring in late-exponential-early-stationary growth phase. The enzyme was cell bound and associated with the outer membrane. Fractionation of P. gingivalis W50 localized the putative hemolysin almost exclusively in the outer membrane fraction, with significant hemolytic activity concentrated in the outer membrane vesicles. Ca2+ and Mg2+ ions significantly increased the expression of hemolytic activity. Hemolytic activity was inhibited by proteinase K, trypsin, the proteinase inhibitors Na-P-tosyl-L-lysine chloromethyl ketone and benzamidine, the metabolic inhibitor M-chlorophenyl-hydrazone, and iodoacetate. KCN and sodium azide (NaN3) only partially inhibited P. gingivalis hemolytic activity, while antiserum to whole cells of each of the P. gingivalis strains had a significant inhibitory effect on hemolytic activity. The P. gingivalis W50 hemolysin was inhibited by cysteine, dithiothreitol, and glutathione at concentrations of at least 10 mM; at low concentrations (i.e., 2 mM), dithiothreitol did not completely inhibit hemolytic activity. Heating to temperatures above 55 degrees C resulted in an almost complete inhibition of hemolytic activity. The effect of heme limitation (i.e., iron) on hemolysin production indicated that either limitation or starvation for heme resulted in significantly increased hemolysin production compared with that of P. gingivalis grown in the presence of excess heme.

Animals↗

PubMed1991

Virulence of Wolinella recta in a murine abscess model.

The virulence of Wolinella recta isolates was studied in an experimental animal model by using monoinfection of BALB/c mice. Infection with clinical isolates of W. recta 576 and W. recta 234 induced dry, flat, depressed gangrenous necrotic skin lesions, whereas W. recta ATCC 33238 failed to induce a similar lesion. Histological examination of the skin lesion 72 h postinfection revealed coagulation necrosis of the epidermis, subcutis and cutaneous truncus muscle, with marked exudation of serum proteins and neutrophils. Virulence-modulating agents such as dexamethasone, galactosamine, hydrazine sulfate, and dextran microcarrier beads were used in conjunction with W. recta infection. Dexamethasone, hydrazine sulfate, and dextran beads enhanced the infectivity and pathogenicity of W. recta for lesion formation and tissue destruction compared with what was found in untreated control mice. Galactosamine sensitization enhanced the virulence potential of W. recta to such an extent that a lethal outcome was observed. Laboratory passage of clinical isolates demonstrated a decreased virulence in high-passage strains, which correlated with the minimal virulence observed in the extensively passaged W. recta ATCC 33238. Serum immunoglobulin G (IgG) and IgM responses were detected in the serum of infected animals, and cross-reacting antibody indicated variation in the antigenic makeup of various W. recta strains. Enhanced IgG antibody responses were observed following the secondary challenge. Mice with acquired antibody response to initial infection remained susceptible to lesion formation with subsequent challenge, but the size of the lesion was significantly reduced, indicating partial protection. Serum IgG and IgM antibody levels were significantly increased by active immunization when compared with levels in mice which had recovered from infection. The immunization significantly decreased the lesion size; however, even these high levels of antibody failed to abrogate the lesion induction.

Abscess↗

PubMed1991

Chemical and biological activities of a 64-kilodalton outer sheath protein from Treponema denticola strains.

This study examined the distribution of the major outer sheath proteins (MOSP) in several Treponema denticola strains and reports the isolation of a 64-kDa protein from the outer sheath of human clinical isolate T. denticola GM-1. The outer sheath was isolated by freeze-thaw procedures, and the distribution of outer sheath proteins was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). T. denticola GM-1, MS25, SR-5, and three low-passage clinical isolates possessed an MOSP with a relative molecular mass of 60 to 64 kDa. This MOSP was absent in T. denticola ATCC 35404 (TD-4) and clinical isolate SR-4. The latter possessed an MOSP of 58 kDa. 125I labeling revealed both MOSP to be dissociated forms of higher-molecular-mass oligomeric units between 116 and 162 kDa. Two-dimensional SDS-PAGE confirmed the modifiability of these MOSP. Isoelectric focusing of the 64-kDa MOSP indicated a pI of 6.7. Immunoblots with antiserum to GM-1 whole cells revealed the 64-kDa protein to be immunogenic and not cross-reactive with the MOSP of TD-4 or SR-4, and monospecific antibody to the 64-kDa protein recognized common epitopes on the high-molecular-weight oligomeric protein. These antibodies did not react with any component of TD-4 whole cells in immunoblots or in immunogold electron microscopy. Fab fragments inhibited the adherence of T. denticola GM-1 to human gingival fibroblasts by 78% (1:1,600; 0.72 micrograms of protein per ml), while TD-4 adherence was not inhibited. Amino acid analysis revealed a slightly acidic protein, devoid of cysteine, with 36% hydrophobic residues. Cyanogen bromide fragmentation of the 64-kDa protein revealed that a 42-kDa fragment contained a T-L-D-L-A-L-D segment which was 100% homologous with an integrin alpha subunit of a human leukocyte adhesion glycoprotein p 150,95.

Amino Acid Sequence↗

PubMed1991

Roles of porphyrins and host iron transport proteins in regulation of growth of Porphyromonas gingivalis W50.

Porphyromonas gingivalis (Bacteroides gingivalis) requires iron in the form of hemin for growth and virulence in vitro, but the contributions of the porphyrin ring structure, porphyrin-associated iron, host hemin-sequestering molecules, and host iron-withholding proteins to its survival are unknown. Therefore, the effects of various porphyrins, host iron transport proteins, and inorganic iron sources on the growth of P. gingivalis W50 were examined to delineate the various types of iron molecules used for cellular metabolism. Cell envelope-associated hemin and iron stores contributed to the growth of P. gingivalis in hemin-free culture, and depletion of these endogenous reserves required eight serial transfers into hemin-free medium for total suppression of growth. Comparable growth of P. gingivalis was observed with 7.7 microM equivalents of hemin as hemoglobin (HGB), methemoglobin, myoglobin, hemin-saturated serum albumin, lactoperoxidase, cytochrome c, and catalase. Unrestricted growth was recorded in the presence of haptoglobin-HGB and hemopexin-hemin complexes, indicating that these host defense proteins do not sequester HGB and hemin from P. gingivalis. The iron chelator 2,2'-bipyridyl functionally chelated hemin-associated iron, resulting in dose-dependent inhibition of growth in hemin-restricted cultures at 1 to 25 microM 2,2'-bipyridyl concentrations. In the absence of an exogenous iron source, protoporphyrin IX did not support P. gingivalis growth. These findings suggest that the iron atom in the hemin molecule is the critical constituent for growth and that the tetrapyrrole porphyrin ring structure may represent an important vehicle for delivery of iron into the P. gingivalis cell. P. gingivalis does not have a strict requirement for porphyrins, since growth occurred with nonhemin iron sources, including high concentrations (200 muM) of ferric, ferrous, and nitrogenous inorganic iron, and P. gingivalis exhibited unrestricted growth in the presence of host transferrin, lactoferrin, and serum albumin. The diversity of iron substrates utilized by P. gingivalis and the observation that growth was not affected by the bacteriostatic effects of host iron-withholding proteins, which it may encounter in the periodontal pocket, may explain why P. gingivalis is such a formidable pathogen in the periodontal disease process.

Animals↗

PubMed1991

A flagella-less mutant of Borrelia burgdorferi. Structural, molecular, and in vitro functional characterization.

A nonmotile mutant of Borrelia burgdorferi, the etiologic agent of Lyme disease, was isolated and characterized. The mutant was compared with the wild-type predecessor as well as with a motile back-revertant of the same genetic background. The mutant lacked, by morphologic, biochemical, and immunologic criteria, the major structural protein of flagella, flagellin. This mutation was not associated with major DNA rearrangements or with failure of transcription. An apparent consequence of a loss of flagella was reduced ability to penetrate human endothelial cell layers in vitro. In another assessment of functional significance, the flagella-less mutant was equal if not superior to flagella-bearing, isogenic isolates when examined in an enzyme-linked immunosorbent assay for anti-B. burgdorferi antibodies in the sera of Lyme disease patients. These studies of a mutant, the first among pathogenic Borrelia spp. to be characterized, indicate that the flagellum and motility it confers play a role in B. burgdorferi's invasion of human tissues. A flagella-less B. burgdorferi may be useful as the basis of a more specific immunoassay and a vaccine for protection against Lyme disease.

Blotting, Western↗

PubMed1991

Factors in virulence expression and their role in periodontal disease pathogenesis.

The classic progression of the development of periodontitis with its associated formation of an inflammatory lesion is characterized by a highly reproducible microbiological progression of a Gram-positive microbiota to a highly pathogenic Gram-negative one. While this Gram-negative microbiota is estimated to consist of at least 300 different microbial species, it appears to consist of a very limited number of microbial species that are involved in the destruction of periodontal diseases. Among these "putative periodontopathic species" are members of the genera Porphyromonas, Bacteroides, Fusobacterium, Wolinella, Actinobacillus, Capnocytophaga, and Eikenella. While members of the genera Actinomyces and Streptococcus may not be directly involved in the microbial progression, these species do appear to be essential to the construction of the network of microbial species that comprise both the subgingival plaque matrix. The temporal fluctuation (emergence/disappearance) of members of this microbiota from the developing lesion appears to depend upon the physical interaction of the periodontal pocket inhabitants, as well as the utilization of the metabolic end-products of the respective species intimately involved in the disease progression. A concerted action of the end-products of prokaryotic metabolism and the destruction of host tissues through the action of a large number of excreted proteolytic enzymes from several of these periodontopathogens contribute directly to the periodontal disease process.(ABSTRACT TRUNCATED AT 250 WORDS)

Gram-Negative Bacteria↗

PubMed1991

Normal pelvic anatomy using transvaginal scanning.

The fine spatial and contrast resolution accorded by TVS provides us with the opportunity to see the uterus, ovary, and larger pelvic vessels with detail and accuracy. Other structures may also be visualized but not with the same finesse, regularity, or attention. Transvaginal color Doppler imaging and pulsed waveform analysis capabilities now provide us with the opportunity of distinguishing vascular and nonvascular structures, and gives us the ability to determine the normal and abnormal flow characteristics of pelvic viscera. Improvements in TVS technology will undoubtedly expand our future capabilities and applications.

Female↗

PubMed1990

Iron-regulated outer membrane proteins in the periodontopathic bacterium, Bacteroides gingivalis.

Hemin has been implicated in the pathogenesis of the oral pathogen, Bacteroides gingivalis. In order to elucidate the role of hemin (iron) in the growth and expression of outer membrane proteins, B. gingivalis strain W50 was grown with and without hemin to induce iron-limitation. Cells grew slower under iron stress and growth was completely inhibited in the absence of added hemin. The outer membrane protein profiles of B. gingivalis grown under iron-replete and iron-restricted conditions were studied by extrinsic radiolabelling with [125I] and polyacrylamide gel-electrophoresis. The induction of 10 surface proteins, with apparent molecular weights of 26, 29, 50, 56, 58, 60, 62, 71, 77, and 80 Kd, was observed in B. gingivalis grown under iron-restricted conditions. These proteins were repressed under iron-replete conditions. We postulate the involvement of the iron-regulated proteins in hemin uptake and virulence in B. gingivalis.

Bacterial Outer Membrane Proteins↗

PubMed1990

Actinobacillus actinomycetemcomitans mitogenicity for B cells can be attributed to lipopolysaccharide.

The purpose of this investigation was to determine the component(s) of whole Actinobacillus actinomycetemcomitans bacteria responsible for B cell mitogenic activity. Congenitally athymic "nude" rats were used as a source of B cells devoid of T lymphocyte activity. Spleen cells were cultured with, or without, whole formalin-killed A. actinomycetemcomitans bacteria or with purified LPS from A. actinomycetemcomitans. Dose-response curves to A. actinomycetemcomitans cells or to A. actinomycetemcomitans-LPS showed that responses were dose dependent. If optimal quantities of both A. actinomycetemcomitans and A. actinomycetemcomitans-LPS were added in combination, the proliferative responses were the same as if either was added alone, i.e., the responses were not additive. Polymyxin B at 2 micrograms/well completely abrogated the proliferative response of athymic rat splenocytes to 10(7) A. actinomycetemcomitans cells or to 1.25 micrograms A. actinomycetemcomitans-LPS/well. Therefore, the in vitro early proliferative response of B cells to A. actinomycetemcomitans can be attributed to the presence of LPS on A. actinomycetemcomitans cells. A considerable portion of the in situ lymphocytic gingival response to A. actinomycetemcomitans infection seen in periodontal disease patients may be a B cell mitogenic response to the LPS of this bacterium.

Actinobacillus↗

PubMed1990

Comparative studies of the outer membranes of Bacteroides gingivalis, strains ATCC 33277, W50, W83, 381.

Outer membrane fractions from Bacteroides gingivalis strains ATCC 33277, 381, W50, and W83 were isolated by French pressure cell disruption and the distribution of major and minor proteins was determined by SDS-PAGE electrophoresis after treatment with 2% Sarkosyl and 2% Triton X-100. Heat-modifiability of the outer membrane proteins (OMPs) from these B. gingivalis strains was also determined after treatment at 100 degrees C and analysis by both 1- and 2-dimensional SDS-PAGE. The distribution of the OMPs on the surface of these B. gingivalis strains was determined by 125I labelling. For the most part of the OMPs of B. gingivalis presented a complex distribution, with OMPs observed between 123 kD and 13 kD. While the distribution of the OMPs was strain specific, OMPs common to all of the strains were observed. Two percent Sarkosyl treatment of the OMs at room temperature resulted in the solubilization of approximately 60% of the OMP. The Sarkosyl-insoluble MOMPs had relative molecular weights between 110 kD and 20 kD. Many of the OMPs which were separated at room temperature were heat-modified at either 65 degrees C or 100 degrees C. Heating of the OMs at 100 degrees C resulted in the heat modification of the majority of those OMPs observed at room temperature. Sarkosyl-100 degrees C OMs displayed MOMPs at apparent molecular weights between 90 kD and 15 kD. Radioiodination of the B. gingivalis strains ATCC 33277, 381, W83 and W50 revealed between 7 and 14 MOMPs at the cell surface depending upon the strain. The complexity of the OM of these B. gingivalis strains indicated the possibility of identifying and separating those OMPs involved in a variety of biological functions, including virulence, transport, and cell interaction.

Autoradiography↗

PubMed1990

Effect of Actinobacillus actinomycetemcomitans, Wolinella recta and Bacteroides gingivalis on the viability of retinoic acid-induced and dimethyl sulfoxide-induced HL-60 cells.

We studied the interactions between viable and heat-killed, opsonized and unopsonized periodontopathic bacteria with both uninduced and induced HL-60 promyelocytic leukemia cells. The cells were induced to differentiate into granulocyte-like cells by incubation with retinoic acid (RA) or dimethyl sulfoxide (DMSO). When unopsonized, Wolinella recta ATCC 33228 significantly suppressed the net proliferation of uninduced HL-60 cells, Actinobacillus actinomycetemcomitans strain Y4 was markedly lethal to the cells, and Bacteroides gingivalis ATCC 33277 had no effect. Unopsonized and opsonized A. actinomycetemcomitans and W. recta had equally potent lethal effects on induced HL-60 cells. Unopsonized B. gingivalis was not lethal to the induced cells in the dose used (100 bacteria/HL-60 cell), but opsonized B. gingivalis was lethal, especially in the first 24 h. The killing effects of A. actinomycetemcomitans and W. recta were largely eliminated if they were heated (56 degrees C, 30 min) before being added to the induced HL-60 cells. RA-induced HL-60 cells were more sensitive to the lethal effects of A. actinomycetemcomitans and W. recta than were DMSO-induced cells. The results suggest that the HL-60 cell line may be a useful model for studying granulocyte-bacteria interactions.

Actinobacillus↗

PubMed1990

Interaction of gram-negative periodontal pathogens with retinoic acid-induced and dimethyl sulfoxide-induced HL-60 cells.

As a first step toward elucidating the reasons for differences among periodontal pathogens in their cytotoxic effects on HL-60 cells, we used transmission electron microscopy to examine morphological aspects of granulocyte-bacteria interactions. Unopsonized Actinobacillus actinomycetemcomitans strain Y4 and Bacteroides gingivalis ATCC 33277 adhered to, and were phagocytosed by, retinoic acid-induced and dimethyl sulfoxide-induced HL-60 cells. In contrast, there was only minimal interaction between Wolinella recta ATCC 33238 and these induced granulocyte-like cells. Only isolated examples of adherence of W. recta to HL-60 cells were seen. In specimens prepared for routine transmission electron microscopy, ingested W. recta were not observed. In immunogold experiments, phagocytosed W. recta were noted, but only rarely. Opsonization of A. actinomycetemcomitans, B. gingivalis and W. recta with specific antisera appeared to increase their level of interaction with the HL-60 cells. We suggest that the HL-60 cell line may be useful in elucidating structure-function relationships between human neutrophil-like cells and putative periodontopathogens.

Actinobacillus↗

PubMed1990

Effects of topical applications of meclofenamic acid and ibuprofen on bone loss, subgingival microbiota and gingival PMN response in the primate Macaca fascicularis.

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to alter periodontitis in both animals and humans. This study was initiated in the nonhuman primate (Nhp) model to determine the effect of two NSAIDs on preexisting gingivitis, the conversion of gingivitis to periodontitis, the associated subgingival microbiota, and the gingival PMN response. Eighteen cynomolgus monkeys were divided into three groups and treated on a blind basis with ibuprofen 8%, meclofenamic acid 5%, or placebo applied topically 5 days/week for 20 wk. After 4 wk of treatment, periodontitis was initiated in one quadrant by the placement of silk ligatures. Clinical parameters, bone loss by densitometric analysis of radiographs (CADIA), and cultural microbiology of subgingival plaque were monitored. In situ PMN chemotaxis was assessed by quantitating the PMNs which entered the sulcus in response to a challenge with n-formyl-methionyl-leucyl-phenylalanine (FMLP). No significant differences in the clinical parameters were noted by treatment groups. Radiographic bone loss was detected in all experimental sites in placebo animals as compared with 67% and 44% for ibuprofen and meclofenamic acid animals, respectively. Mean CADIA scores/animal showed a significant loss in bone density for placebo at 6 and 16 wk, no change for ibuprofen animals, and a significant increase in density for meclofenamic acid animals. The microbiota of all groups changed with ligation consistent with previous reports of disease initiation in the Nhp.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗

PubMed1990

Interaction of Treponema denticola TD-4, GM-1, and MS25 with human gingival fibroblasts.

The adherence of Treponema denticola GM-1, TD-4, and MS25 to human gingival fibroblasts (HGFs) was studied to serve as an introduction to investigations into the interactions of these oral bacteria with human host cells. Under both aerobic (5% CO2) and anaerobic (85% N2 plus 10% H2 plus 5% CO2) environments, the interactions with the HGFs were such that strains GM-1 and MS25 were consistently more adherent than strain TD-4. Polyclonal antibodies to GM-1 inhibited GM-1 adherence by 70%, while MS25 and TD-4 showed differing degrees of cross-reactive inhibition, indicative of common but not identical epitopes on the surface of the three T. denticola strains. Pretreatment of the three strains with trypsin did not inhibit adherence; proteinase K did, however, inhibit this interaction by 80%. Trypsin pretreatment of the HGFs resulted in increases in adherence of 50 and 86% for GM-1 and MS25, respectively, while a decrease of 41% was noted for TD-4. Exposure of the T. denticola strains to sugars and lectin pretreatment of the HGFs implicated adherence mediation by mannose and galactose residues on the HGF surface. Periodate treatment of HGFs resulted in a 50% drop in adherence for GM-1 and MS25, but did not decrease that of TD-4. Addition of fetal bovine serum inhibited adherence of the three strains to differing degrees, with TD-4 being the most susceptible. Addition of purified fibronectin (100 micrograms/ml) resulted in greater than 50% inhibition in GM-1 and MS25 adherence, while a 25% increase occurred with TD-4. While strain differences were noted in some of the parameters studied, the results indicate two possibilities for T. denticola-HGF adherence: a lectinlike adhesin(s) on the T. denticola surface with affinity for galactose and mannose on the HGF surface, and a serum host factor(s) bridging T. denticola and HGFs.

Antibodies, Bacterial↗

PubMed1990

Surface characteristics of Wolinella recta ATCC 33238 and human clinical isolates: correlation of structure with function.

Selected characteristics of the surface of Wolinella recta ATCC 33238 and three W. recta clinical isolates (CI) were studied as well as the adherence of these strains to human gingival fibroblasts (HGF). W. recta ATCC 33238 and the CI were examined by electron microscopy, electrophoresis, isoelectric focusing, and adherence to HGF. Electron microscopic examination of CI revealed the presence of a periodic paracrystalline layer external to and associated with the outer membrane. This surface layer (S layer) was not observed on ATCC 33238. Whole cells and outer envelope protein profiles of the CI revealed major bands of 159- to 138-kilodalton proteins which were barely detectable in ATCC 33238. Repeated in vitro subculturing of the CI on solid or liquid medium resulted in both the physical loss of this layer and the loss of the high-molecular-weight proteins. Low-passage-number CI demonstrated 40 to 60% less adherence to HGF than ATCC 33238. These observations suggest that short term in vitro-subcultured W. recta strains possess surface characteristics which are significantly different from those of their long-term in vitro-subcultured counterparts. These differences may have significant effects on host cell interactions.

Bacterial Adhesion↗

PubMed1990

Effects of antibiotics on synthesis and persistence of sigma E in sporulating Bacillus subtilis.

A potential regulatory link between the activation of a sporulation-specific sigma factor (sigma E) and forespore septum formation was investigated by treating Bacillus subtilis with inhibitors of protein or peptidoglycan synthesis and monitoring the consequences of these treatments on sigma E activation and septation. Western blot (immunoblot) and electron microscopic analyses revealed that both the formation of sigma E and septation were inhibited to a similar degree when either rifampin or chloramphenicol was added at different times before the second hour into sporulation but that penicillin preferentially blocked septation. We interpret these results as indicating that the syntheses of the gene products for both septation and sigma E activation occur at approximately the same time in development but that synthesis of an intact septum is unlikely to be a prerequisite for the formation of sigma E. We observed that penicillin could not only block septation but, depending on the time of its addition, could also inhibit both the activation of sigma E and the synthesis of its precursor. The basis of this effect is unknown, but it is not due to an overall disruption of protein synthesis. The incorporation of [35S] methionine by the sporulating cultures was unaffected by penicillin treatment. A time course study of the effects of rifampin and chloramphenicol treatments on sigma E levels revealed that both the synthesis of sigma E and its disappearance from sporulating cultures is inhibited by these antibiotics. This suggests that ongoing macromolecular synthesis is required for the turnover of sigma E.

Anti-Bacterial Agents↗

PubMed1990

Endovaginal US: demonstration of cardiac activity in embryos of less than 5.0 mm in crown-rump length.

The authors reviewed the endovaginal ultrasonographic (US) findings for 96 patients with embryos with crown-rump lengths of less than 5.0 mm. Of the 71 patients with adequate follow-up, initial endovaginal US demonstrated cardiac activity in 46 embryos and no cardiac activity in 25. Initial endovaginal US failed to demonstrate cardiac activity in five of 40 normal embryos, three with crown-rump lengths of less than 2.0 mm and two, between 2.0 and 3.9 mm. Endovaginal US identified cardiac activity in all 12 normal embryos with crown-rump lengths of 4.0-4.9 mm. The presence of cardiac activity was associated with a 24% risk of spontaneous abortion. In embryos between 2.0 and 4.9 mm in crown-rump length, absent cardiac activity was associated with a 91% risk of abortion. All 17 patients with vaginal bleeding and embryos demonstrating no cardiac activity subsequently aborted. The embryonic yolk sac was absent in 35% of patients who subsequently aborted. Variation outside of the 95% confidence limits of the mean for crown-rump length compared with mean gestational sac diameter and yolk sac diameter was also helpful in predicting an abnormal outcome. Nonvisualization of cardiac activity at endovaginal US in embryos less than 4.0 mm in crown-rump length may be normal and warrants follow-up US examination.

Abortion, Spontaneous↗