Biomedical subjects

J R Scott

Publications and source records attributed to J R Scott.

At least 73 records · Page 4Linked to original sources

PubMed1997

Transcriptional control of genes encoding CS1 pili: negative regulation by a silencer and positive regulation by Rns.

The adherence of enterotoxigenic Escherichia coli (ETEC) to the human small intestine is an important early event in infection. Attachment is thought to be mediated by proteinaceous structures called pili. We have investigated the regulation of expression of the genes encoding CS1 pili found on human ETEC strains and find that there are at least three promoters, P1 and P2, upstream of the coo genes, and P3, downstream of the start of cooB translation. We identified a silencer of transcription which extends over several hundred bases overlapping the cooB open reading frame. This silencer is dependent on the promoter and/or upstream region for its negative effect. The DNA binding protein H-NS is a repressor of coo transcription that acts in the same region as the silencer, so it is possible that H-NS is involved in this silencing. Rns, a member of the AraC family, positively regulates transcription of the coo operon and relieves the silencing of CS1 expression.

Bacterial Adhesion↗

PubMed1997

DNA binding by the Xis protein of the conjugative transposon Tn916.

We purified the Xis protein of the conjugative transposon Tn916 and showed by nuclease protection experiments that Xis bound specifically to sites close to each end of Tn916. These specific binding sites are close to, and in the same relative orientation to, binding sites for the N-terminal domain of Tn916 integrase protein. These results suggest that Xis is involved in the formation of nucleoprotein structures at the ends of Tn916 that help to correctly align the ends so that excision can occur.

Base Sequence↗

PubMed1997

Prevention of compartment syndrome associated with dorsal lithotomy position.

There is a clear association between the dorsal lithotomy position and the development of a postoperative compartment syndrome. Compartment syndrome occurs when elevated pressure in an osteofascial compartment compromises local perfusion and often results in neurovascular damage and permanent disability. Surgeons must recognize this association and provide appropriate preventative measures, have a high index of suspicion in all patients, and be prepared to make an early diagnosis when it is encountered. We will report four cases we encountered, discuss the etiology, analyze the literature, and propose a modification on patient positioning that has minimized the incidence of compartment syndrome at our institution. A variety of intraoperative events, including hypotension, hypoxemia, leg elevation, hip and knee flexion, direct pressure, and compressive bandages may all contribute to compartmental ischemia. Ischemia is followed by reperfusion, capillary leakage from the ischemic tissue, and a further increase in tissue edema. Increased edema causes further embarrassment of perfusion and perpetuation of the cycle, ultimately resulting in neuromuscular compromise secondary to ischemia. To prevent this destructive cycle, emphasis must be placed on maintaining a high index of suspicion in all patients, minimizing leg elevation, and on the importance of early diagnosis and intervention.

Adult↗

PubMed1996

Complementation of divergent mga genes in group A Streptococcus.

The gene (mga4) encoding the positive regulatory protein, Mga4, was cloned and sequenced from an M type 4 strain (AP4) of Streptococcus pyogenes. The deduced amino acid (aa) sequence of this "divergent Mga' shows 88% identity to the prototype Mga1 in its N-terminal half, which contains all three of the predicted helix-turn-helix domains. However, one of the predicted receiver domains of Mga1, which is at its C terminus, is not conserved in the Mga4 aa sequence. Nevertheless, a mutation in mga1 was found to be complemented for activation of the gene encoding M protein (emm) by mga4 in trans. This suggests that the aa residues of the C-terminal predicted receiver domain are not critical for activation of emm transcription.

Amino Acid Sequence↗

PubMed1996

Local infusion of FGF-saporin reduces intimal hyperplasia.

The recent conjugation of the potent ribosome-inactivating protein saporin (SAP) with basic fibroblast growth factor (FGF2) to form recombinant (r)FGF2-SAP permits increased selectivity of this mitoxin for cells exhibiting upregulated FGF receptors. Systemic administration of rFGF-SAP in therapeutic doses, however, may be associated with significant liver toxicity. In this blinded study, we used a local boundary layer infusion approach to increase local drug concentration while minimizing the risk of side effects. Six dogs underwent bilateral carotid endarterectomies. Expanded polytetrafluoroethylene infusion devices, blindly primed with rFGF2-SAP to one artery or vehicle to the contralateral vessel, were anastomosed proximal to the injured segments so that each animal served as its own control. rFGF2-SAP (2 microgram/kg/day) or vehicle (5 microl/hr) was continuously delivered for 14 days from an osmotic reservoir, through the wall of the graft infusion device. Euthanasia was carried out at 14 days and the processed arteries were blindly analyzed for intimal thickening and cellular proliferation. All dogs survived until sacrifice with no clinical side effects. Liver function tests at euthanasia were not significantly altered when compared to baseline values. Intimal area in rFGF2-SAP-treated vessels averaged 0.31 +/- 0.10 mm2 versus 0.57 +/- 0.24 mm2 in the control segments (P = 0.02), a relative reduction of 46%. Cell proliferation, however, was not significantly different at 14 days postendarterectomy (2.40 +/- 1.31% vs 2.39 +/- 0.45%). From this study it can be concluded that locally delivered rFGF2-SAP reduces intimal hyperplasia and that the boundary layer infusion strategy is an effective means for delivering high local drug concentration while minimizing systemic drug effects.

Amino Acid Sequence↗

PubMed1996

Streptococcus pyogenes infection in mice.

We inoculated 5 to 7-week-old female C3HeB/FeJ mice with Streptococcus pyogenes strain B514-Sm (type M50) by both an intranasal and intratracheal route and characterized the resulting illness. Following intranasal inoculation, the animals developed signs of illness within 1 to 8 days post-inoculation which correlated with acute, suppurative, bronchopneumonia during histopathologic analysis; however, the relationship of response to dose was non-linear, as seen previously in a small group of mice. Intratracheal inoculations were then performed to increase the quantitative reliability of the model. Following intratracheal inoculation, the animals succumbed to an illness that was indistinguishable from that seen after intranasal inoculation, and the incidence of pneumonia followed a steep dose response curve. The dose at which 50% of the animals exhibited signs of respiratory illness within 72 h was 1.0 x 10(7) colony forming units. All of the animals that appeared ill had lung lesions as determined by gross and histopathologic examination. Bacteraemia followed pneumonia in two-thirds of the intratracheally inoculated animals, indicating that the S. pyogenes had crossed tissue barriers. We hope that this model will be useful in future studies concerning the role of suspected streptococcal virulence factors in the later stages of pathogenesis of invasive S. pyogenes infection.

Animals↗

PubMed1996

Anticardiolipin antibodies: clinical consequences of "low titers".

OBJECTIVE: To clarify the implications of low levels of immunoglobulin (Ig)-G or IgM anticardiolipin antibodies. METHODS: Women who underwent clinically indicated testing for antiphospholipid antibodies were divided into four groups based on results: 1) high-positive (lupus anticoagulant or more than 19 IgG binding units of anticardiolipin antibodies; N = 131), 2) low-positive IgG (fewer than 20 IgG binding units; N 93), 3) IgM only (more than nine IgM binding units; N 97), and 4) negative (N = 153). The development of antiphospholipid antibody-related disorders was assessed for the time interval from initial antibody testing to patient interview. The median study interval for each group was at least 4 years. Forty-five percent of women had repeat testing at the time of interview. RESULTS: Women in the high-positive group were more likely to develop at least one new medical complication than those in the low-positive IgG (odds ratio [OR] 4.49, 95% confidence interval [CI] 2.01-10.03), IgM only (OR 6.00, 95% CI 2.65-13.59), and negative (OR 9.11, 95% CI 3.92-21.2) groups. In contrast, the low-positive IgG, IgM only, and negative groups had similar risks for the development of new disorders. Twelve of 129 (9.3%) women in the low-positive IgG, IgM only, or negative groups had lupus anticoagulant or more than 19 IgG binding units on retesting. Half of these women developed at least one new disorder. CONCLUSION: Women with IgM or low levels of IgG anticardiolipin antibodies comprise distinct populations from those with lupus anticoagulant or moderate to high levels of anticardiolipin antibodies. These women are not at risk for antiphospholipid antibody-related disorders beyond the risk conferred by their medical histories. However, repeat testing is warranted with new or recurrent clinical symptoms.

Adult↗

PubMed1996

Antiphospholipid antibodies and fetal death.

OBJECTIVE: To determine the type of recurrent pregnancy loss associated with antiphospholipid antibodies. METHODS: This was a retrospective analysis of women who had two or more pregnancy losses and who were tested for antiphospholipid antibodies. The specific type of pregnancy losses were determined in patients with and without antiphospholipid antibodies. RESULTS: In our highly selected referral population, 76 of 366 women (21%) tested positive for lupus anticoagulant or anticardiolipin antibodies of 20 or more immunoglobulin-G phospholipid antibody units. Pregnancy loss occurred in 280 of 333 (84%) prior pregnancies in women with and 1240 of 1479 (84%) without antiphospholipid antibodies. However, 50% of pregnancy losses in women with antiphospholipid antibodies were fetal deaths, compared with less than 15% in women who were antiphospholipid antibody-negative. More than 80% of women with antiphospholipid antibodies had at least one fetal death, compared with less than 25% of women without (P < .001). The specificity of fetal death for the presence of antiphospholipid antibodies in patients with recurrent pregnancy loss was 76%. In contrast, two or more early first-trimester losses without fetal death had a specificity of only 6% for antiphospholipid antibodies. CONCLUSION: Fetal death is more characteristic of the type of loss experienced by patients with recurrent pregnancy loss than early first-trimester pregnancy loss in women with antiphospholipid antibodies.

Abortion, Habitual↗

PubMed1996

Cyclosporin A inhibits prostaglandin E2 production by fetal amnion cells in response to various stimuli.

Use of cyclosporin A as part of an immunosuppressive regimen in pregnant transplant patients is not uncommon. Although successful pregnancies have been reported with the use of various immunosuppressive agents including cyclosporin A, the concern for fetal outcome still remains. Our purpose was to evaluate the effects of immunosuppressive cyclosporin A on prostaglandin E2 (PGE2) production by human fetal amnion. Amnion cells were isolated from term placentae obtained at elective cesarean section before the onset of labor. Cells were grown to confluence and then incubated for 16 hours with cyclosporin A (1-1000 ng/ml) in the presence and absence of interleukin 1 beta (IL-1 beta, 1 ng/ml), phorbol 12-myristate 13-acetate (PMA, 10(-7) M) and ionomycin (0.5 microM). PGE2 was measured by radioimmunoassay and cellular protein determined. IL-1 beta, PMA and ionomycin all stimulated amnion cell PGE2 production as expected. However, these stimulatory actions were attenuated by at least 50% when cells were co-incubated with cyclosporin A (1000 ng/ml). Concentrations of cyclosporin A tested included the therapeutic range (250-1000 ng/ml). Our results indicate that cyclosporin A does not stimulate amnion cell PGE2 production and is probably unrelated to preterm labor and delivery in allograft recipients.

Amnion↗

PubMed1996

Malignant schwannoma in a burn scar.

The malignant potential of a burn scar is well recognized. Epidermal malignancies predominate and sarcomas are a rare finding. The first case of a malignant schwannoma developing in a burn scar is reported, and the management discussed.

Burns↗

PubMed1996

Assembly proteins of CS1 pili of enterotoxigenic Escherichia coli.

Some strains of enterotoxigenic Escherichia coli associated with human diarrhoeal disease produce a class of pili represented by those called CS1. For the assembly of the major-pilin subunit, CooA, into pili, each of four linked genes, cooB, A, C, and D, is required. In this study, we have determined the subcellular localization of CooB, C and D, and investigated the molecular interactions of these proteins using specific antisera. CooD appears to be an integral pilus protein because it co-purifies with, and is strongly associated with, CS1 pili. In keeping with its role as an assembly protein, the CooD minor pilin (when overexpressed in CS1-piliated strains) was detected in periplasmic intermolecular complexes with the major-pilin subunit CooA. CooB is an assembly protein found exclusively in the periplasm of CS1-piliated strains. CooB also forms periplasmic intermolecular complexes with CooA, but does not constitute part of the final pilus structure. Immunoblot analysis of cell fractions showed that CooC is an outer membrane protein of CS1-piliated E. coli. Based on this information, we have proposed a model for CS1-pilus assembly which is very similar to the model for polymerization of the PapA pilin of uropathogenic E. coli. As the assembly proteins of Pap and CS1 pili are structurally unrelated, this may represent a case of convergent evolution.

Amino Acid Sequence↗

PubMed1996

Acquisition of iron from host proteins by the group A streptococcus.

To identify mammalian iron-binding proteins that can serve as iron sources for Streptococcus pyogenes, the group A streptococcus (GAS), we used a plate assay. Ferritin, hemin, hemoglobin, myoglobin, and catalase can support growth of GAS on iron-depleted medium. However, growth was not detected when iron was provided as iron-saturated transferrin or lactoferrin or bound to cytochrome c. Therefore, it appears that GAS can use the intracellular iron sources available in the human body, which is consistent with its ability to cause tissue destruction during infection.

Animals↗

PubMed1996

Iron starvation causes release from the group A streptococcus of the ADP-ribosylating protein called plasmin receptor or surface glyceraldehyde-3-phosphate-dehydrogenase.

In many pathogenic bacteria, iron starvation serves as an environmental signal that triggers the expression of virulence factors, many of which are found on the cell surface or secreted into the culture supernatant. Using the chelating agent nitrilotriacetic acid, we have established conditions for iron starvation of the important human pathogen Streptococcus pyogenes (the group A streptococcus) and determined that iron limitation results in the specific appearance of several new proteins in the culture supernatant. One of these supernatant proteins is the ADP-ribosylating protein known as streptococcal plasmin receptor (Plr) or as the streptococcal surface glyceraldehyde-3-phosphate-dehydrogenase because of its other activities. Upon iron starvation, Plr is specifically released into the culture supernatant in a time-dependent manner, and its appearance in the supernatant is not accompanied by induction of plr mRNA synthesis. Release of Plr from the bacteria may be important for the virulence of group A streptococci and the manifestation of diseases.

Adenosine Diphosphate Ribose↗

PubMed1996

Identification of isp, a locus encoding an immunogenic secreted protein conserved among group A streptococci.

The protein Mga (mga), which is required for transcription of several virulence genes of group A streptococci (GAS), including the antiphagocytic M protein, was suggested to act as the response regulator element of a bacterial two-component pathway. To investigate whether a gene encoding a cognate sensor protein is located upstream of mga, 3.1 kb of DNA 5' of the mga translational start site was cloned from serotype M6 GAS strain JRS4. Sequence analysis of this region revealed two adjacent open reading frames, a previously described orf and a new locus, isp (immunogenic secreted protein), which could encode proteins of 9 and 59 kDa, respectively. Inactivation of either open reading frame had no significant effect on transcription of the gene encoding M protein (emm) under normal growth conditions, suggesting that neither isp nor orf is involved in the Mga regulatory circuit. A protein migrating at an apparent molecular weight of 65,000 was produced when isp was transcribed and translated in vitro. The predicted isp product (Isp) contains an amino-terminal signal sequence region homologous to that found in bacterial secreted proteins, and expression of isp in Escherichia coli resulted in the presence of Isp in the periplasmic fraction. Convalescent-phase serum from a patient with an active GAS infection recognized forms of Isp both from the periplasm of E. coli and the supernatant of a GAS strain. Both isp and orf are highly conserved among strains of GAS, as shown by hybridization analyses.

Amino Acid Sequence↗

PubMed1996

Comparison of laparoscopically assisted vaginal hysterectomy with abdominal and vaginal hysterectomy.

OBJECTIVE: To define the advantages and disadvantages of laparoscopically assisted vaginal hysterectomy (LAVH). STUDY DESIGN: The first 70 cases of LAVH performed in a community hospital were compared with 70 cases of abdominal and 70 cases of vaginal hysterectomy performed by the same physicians during the same period. RESULTS: The mean operating time was 80 minutes for LAVH, 50 for abdominal hysterectomy and 40 for vaginal hysterectomy. The incidence of complications was low for all groups. Although the total mean hospital charges were higher with LAVH, those patients required the least postoperative analgesia, resumed a regular diet earlier, required the shortest hospital stay, and returned to regular activity and work earlier than the other two groups. CONCLUSION: LAVH offers specific benefits for properly selected patients.

Adult↗

PubMed1995

A comparison of meta-analytic results using literature vs individual patient data. Paternal cell immunization for recurrent miscarriage.

OBJECTIVE: To compare the meta-analytic results from published literature vs those obtained from pooling original patient data. DATA SOURCES: Individual patient data from 15 completed or ongoing trials on paternal white blood cell immunization as treatment for recurrent miscarriage were obtained through the American Society for Reproductive Immunology. STUDY SELECTION: Only randomized controlled trials were selected. Within these eight selected trials, 202 patients were from four published studies, 43 were added by the same investigators after publication, and 140 were from four unpublished trials. DATA EXTRACTION: Individual patient data were collected using a standardized form and double data entry. DATA SYNTHESIS: Using the fixed treatment effect model, we found that the effect of immunization, denoted as the relative live-birth ratio (RR), was greater by pooling summary data from published articles (RR, 1.29; 95% confidence interval [CI], 1.03 to 1.60) than by pooling all individual patient data from the same investigators (RR, 1.17; 95% CI, 0.97 to 1.37) or when individual patient data were pooled from four unpublished trials (RR, 1.01; 95% CI, 0.74 to 1.28). A similar diminishing treatment effect for the same comparisons was observed using the random treatment effect model (RR, 1.38; 95% CI, 0.89 to 1.87 using published summary data; RR, 1.18; 95% CI, 0.98 to 1.42 using individual patient data; RR, 1.01; 95% CI, 0.74 to 1.28 using unpublished trials). CONCLUSIONS: Meta-analytic results may differ depending on the use of various data sources: whether the source was from summary statistics in the literature, from individual patient data provided by trialists, or from unpublished trials.

Abortion, Habitual↗

PubMed1995

Electron transfer from cytochrome b5 to cytochrome c.

The reaction of cytochrome b5 with cytochrome c has become a very prominent system for investigating fundamental questions regarding interprotein electron transfer. One of the first computer modeling studies of electron transfer and protein/protein interaction was reported using this system. Subsequently, numerous studies focused on the experimental determination of the features which control protein/protein interactions. Kinetic measurements of the intracomplex electron transfer reaction have only appeared in the last 10 years. The current review will provide a summary of the kinetic measurements and a critical assessment of the interpretation of these experiments.

Amino Acid Sequence↗

PubMed1995

Maternal thrombocytopenia in pregnancy: time for a reassessment.

Antiplatelet autoantibodies in women with autoimmune thrombocytopenic purpura can cause fetal thrombocytopenia and serious bleeding problems. Obstetricians have used fetal scalp sampling, cordocentesis, and cesarean delivery in this disorder to avoid fetal complications such as intracranial hemorrhage. Accumulating evidence indicates that the fetal risk of intracranial hemorrhage is much lower than initially reported. Moreover, these invasive tests and treatments are costly, cause morbidity, and have little effect in preventing neonatal bleeding complications. Therefore we suggest these interventions should no longer be used in the management of maternal thrombocytopenia.

Cerebral Hemorrhage↗