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Biomedical subjects

M Miller

Publications and source records attributed to M Miller.

At least 181 records · Page 10Linked to original sources
PubMed1999

Infection with Helicobacter pylori is not a major independent risk factor for stable coronary heart disease: lack of a role of cytotoxin-associated protein A-positive strains and absence of a systemic inflammatory response.

BACKGROUND: There is controversy about the association between Helicobacter pylori infection and manifestations of coronary heart disease (CHD), the potential role of the more virulent H pylori strains, and whether or not a positive serostatus is related to increased levels of markers of systemic inflammation. METHODS AND RESULTS: We assessed the prevalence of an infection with H pylori and in particular the anti-cytotoxin-associated protein A (CagA) antibody response of the more virulent strains expressing CagA in 312 patients with stable CHD and in 479 control subjects. Serological prevalence of H pylori infection (IgG titer) was significantly higher in patients than in control subjects after adjustment for age and sex (44.2% versus 31.3%, P<0.001). After adjustment for various covariates in multiple logistic regression, the odds ratio (OR) for CHD was 1.3 (95% CI, 0.9 to 1.9) given a positive IgG serostatus. The prevalence of CagA-positive strains was 27.9% in patients and 21.7% in control subjects (P=0.076 adjusted for age and sex). The OR for CHD in the fully adjusted model was 1.1 (95% CI, 0.7 to 1.7). None of the inflammatory markers (C-reactive protein, fibrinogen, plasma viscosity, or leukocytes) was significantly different according to serostatus. CONCLUSIONS: In this large case-control study, the association of H pylori infection with stable CHD was strongly reduced and was no longer statistically significant after controlling for potential confounders. We also found no independent association between the more virulent strains and CHD. In addition, a positive serostatus was not associated with a systemic inflammatory response. Thus, these data do not support the hypothesis that infection with H pylori might be a major risk factor for stable CHD.

Aged↗
PubMed1999

Interaction of macrophage-stimulating protein with its receptor. Residues critical for beta chain binding and evidence for independent alpha chain binding.

Macrophage-stimulating protein (MSP) and hepatocyte growth factor/scatter factor (HGF/SF) are plasminogen-related growth and motility factors that interact with cell-surface protein tyrosine kinase receptors. Each one is a heterodimeric protein comprising a disulfide-linked alpha chain and a serine protease-like beta chain. Despite structural similarities between MSP and HGF, the primary receptor binding site is located on the alpha chain of HGF/SF but on the beta chain of MSP. To obtain insight into the structural basis for MSP beta chain binding, beta chain structure was modeled from coordinates of an existing model of the HGF beta chain. The model revealed that the region corresponding to the S1 specificity pocket in trypsin is filled by the Asn(682)/Glu(648) interacting pair, leaving a shallow cavity for possible beta chain interaction with the receptor. Mutants in this region were created, and their binding characteristics were determined. A double mutation of Asn(682)/Glu(648) caused diminished binding of the beta chain to the MSP receptor, and a single mutation of neighboring Arg(683) completely abolished binding. Thus, this region of the molecule is critical for binding. We also found that at equimolar concentrations of free alpha and beta chains, alpha chain binding to receptor was detectable, at levels considerably lower than beta chain binding. The EC(50) values determined by quantitative enzyme-linked immunosorbent assay are 0.25 and 16.9 nM for beta and alpha chain, respectively. The data suggest that MSP has two independent binding sites with high and low affinities located in beta and alpha chain, respectively, and that the two sites together mediate receptor dimerization and subsequent activation.

Amino Acid Sequence↗
PubMed1999

Use of the oral neuraminidase inhibitor oseltamivir in experimental human influenza: randomized controlled trials for prevention and treatment.

CONTEXT: Influenza virus neuraminidase is thought to be essential for virus replication in humans; however, to date, available neuraminidase inhibitors are limited to zanamivir, which is topically administered. OBJECTIVE: To determine the safety, tolerability, and antiviral activity of oral neuraminidase inhibitor oseltamivir (GS4104/Ro64-0796) for prevention and the early treatment of influenza in experimentally infected humans. DESIGN: Two randomized, double-blind, placebo-controlled trials conducted between June and July 1997. SETTING: Individual hotel rooms; 2 large US university medical schools. PARTICIPANTS: A total of 117 healthy adult volunteers (aged 18-40 years; median age, 21 years) who were susceptible (hemagglutination-inhibition antibody titer < or =1:8). INTERVENTIONS: All subjects were inoculated intranasally with influenza A/Texas/36/91 (H1N1) virus. For the prophylaxis study, oral oseltamivir (100 mg once daily [n = 12], 100 mg twice daily [n = 12], or matching placebo [n = 13], starting 26 hours before virus inoculation) was administered. For the treatment study, the same drug was given (20 mg, 100 mg, or 200 mg twice daily, 200 mg once daily, or matching placebo [n = 16], in each group starting 28 hours after inoculation). All regimens were continued for 5 days. MAIN OUTCOME MEASURES: Comparing placebo groups with pooled treatment groups, for prophylaxis, outcomes included frequency of infection and viral shedding; for treatment, viral shedding in titers. RESULTS: In the prophylaxis study, 8 (67%) of 12 placebo and 8 (38%) of 21 oseltamivir recipients became infected (P = .16; efficacy, 61%); 6 (50%) placebo compared with 0 oseltamivir recipients shed virus (P<.001; efficacy, 100%), and 33% of placebo but no oseltamivir recipient had infection-related respiratory illness (P<.01). Among infected subjects in the treatment study (n = 69), the viral titer area under the curve of the combined oseltamivir groups (n = 56) was lower (median [interquartile range [IQR]], 80 [23-151] vs 273 [79-306] log10 tissue culture-infective doses50 per milliliter x hour; P = .02) than the placebo group (n = 13), and the median (IQR) duration of viral shedding with therapy was reduced from 107 (83-131) to 58 (35-59) hours (P = .003). Oseltamivir treatment also reduced symptom scores (median [IQR] score-hours, 225 [97-349] vs 400 [189-645]; P = .05), and nasal proinflammatory cytokine levels. Transient mild to moderate nausea after dosing was observed in 15 (17%) of 88 oseltamivir and 2 (7%) of 29 placebo recipients (95% confidence interval for difference, -11% to 68%), which was largely prevented by ingestion with food. CONCLUSIONS: In these trials, prophylaxis and early treatment with oral oseltamivir were both associated with significant antiviral and clinical effects in experimental human influenza.

Administration, Oral↗
PubMed1999

Giving triglycerides their due.

Often considered less important than other serum lipids, triglycerides are nevertheless an independent risk factor for coronary artery disease. Treatment may be indicated even when triglyceride levels are only mildly elevated and cholesterol readings are within the normal range. Detailed lipoprotein profiles, now clinically available, may guide decision making in such cases.

Adult↗
PubMed1999

Host-cell positive transcription elongation factor b kinase activity is essential and limiting for HIV type 1 replication.

HIV-1 gene expression and viral replication require the viral transactivator protein Tat. The RNA polymerase II transcriptional elongation factor P-TEFb (cyclin-dependent kinase 9/cyclin T) is a cellular protein kinase that has recently been shown to be a key component of the Tat-transactivation process. For this report, we studied the requirement for P-TEFb in HIV-1 infection, and we now show that P-TEFb is both essential and limiting for HIV-1 replication. Attenuation of P-TEFb kinase activity either by expression of a dominant-negative cyclin-dependent kinase 9 transgene or through the use of small-molecule inhibitors suppresses HIV-1 gene expression and HIV-1 replication. Inhibition of HIV-1 replication is affected in a manner consistent with a direct and specific effect on P-TEFb and the known functional role of P-TEFb in Tat-activated transcription. Tat-activated expression of HIV-1 genes seems uniquely dependent on P-TEFb, as inhibition of P-TEFb activity and HIV-1 replication can be achieved without compromising cell viability or RNA polymerase II-dependent cellular gene transcription. Selective inhibition of the P-TEFb kinase may therefore provide a novel approach for developing chemotherapeutic agents against HIV-1.

Cell Line↗
PubMed1999

Role of configurational gating in intracomplex electron transfer from cytochrome c to the radical cation in cytochrome c peroxidase.

Electron transfer within complexes of cytochrome c (Cc) and cytochrome c peroxidase (CcP) was studied to determine whether the reactions are gated by fluctuations in configuration. Electron transfer in the physiological complex of yeast Cc (yCc) and CcP was studied using the Ru-39-Cc derivative, in which the H39C/C102T variant of yeast iso-1-cytochrome c is labeled at the single cysteine residue on the back surface with trisbipyridylruthenium(II). Laser excitation of the 1:1 Ru-39-Cc-CcP compound I complex at low ionic strength results in rapid electron transfer from RuII to heme c FeIII, followed by electron transfer from heme c FeII to the Trp-191 indolyl radical cation with a rate constant keta of 2 x 10(6) s-1 at 20 degrees C. keta is not changed by increasing the viscosity up to 40 cP with glycerol and is independent of temperature. These results suggest that this reaction is not gated by fluctuations in the configuration of the complex, but may represent the elementary electron transfer step. The value of keta is consistent with the efficient pathway for electron transfer in the crystalline yCc-CcP complex, which has a distance of 16 A between the edge of heme c and the Trp-191 indole [Pelletier, H., and Kraut, J. (1992) Science 258, 1748-1755]. Electron transfer in the complex of horse Cc (hCc) and CcP was examined using Ru-27-Cc, in which hCc is labeled with trisbipyridylruthenium(II) at Lys-27. Laser excitation of the Ru-27-Cc-CcP complex results in electron transfer from RuII to heme c FeII with a rate constant k1 of 2.3 x 10(7) s-1, followed by oxidation of the Trp-191 indole to a radical cation by RuIII with a rate constant k3 of 7 x 10(6) s-1. The cycle is completed by electron transfer from heme c FeII to the Trp-191 radical cation with a rate constant k4 of 6.1 x 10(4) s-1. The rate constant k4 decreases to 3.4 x 10(3) s-1 as the viscosity is increased to 84 cP, but the rate constants k1 and k3 remain the same. The results are consistent with a gating mechanism in which the Ru-27-Cc-CcP complex undergoes fluctuations between a major state A with the configuration of the hCc-CcP crystalline complex and a minor state B with the configuration of the yCc-CcP complex. The hCc-CcP complex, state A, has an inefficient pathway for electron transfer from heme c to the Trp-191 indolyl radical cation with a distance of 20.5 A and a predicted value of 5 x 10(2) s-1 for k4A. The observed rate constant k4 is thus gated by the rate constant ka for conversion of state A to state B, where the rate of electron transfer k4B is expected to be 2 x 10(6) s-1. The temperature dependence of k4 provides activation parameters that are consistent with the proposed gating mechanism. These studies provide evidence that configurational gating does not control electron transfer in the physiological yCc-CcP complex, but is required in the nonphysiological hCc-CcP complex.

2,2'-Dipyridyl↗
PubMed1999

Actinobacillus actinomycetemcomitans immunosuppressive protein is a member of the family of cytolethal distending toxins capable of causing a G2 arrest in human T cells.

We have previously shown that Actinobacillus actinomycetecomitans produces an immunosuppressive factor (ISF) capable of impairing human lymphocyte function by perturbing cell cycle progression. We now report that ISF is the product of the cdtB gene, one of three genes encoding the family of cytolethal distending toxins (Cdt). The ISF polypeptide exhibits >/=95% identity with Hemophilus ducreyi CdtB protein and </=60% homology with Escherichia coli or Campylobacter jejuni CdtB. Pretreatment of PHA-activated lymphocytes with 5-25 ng ISF results in G2 arrest of CD4+ and CD8+ T cells. Similarly, treatment of HeLa cells results in G2 arrest and cell elongation and distension. However, lymphocytes are at least 5 times more sensitive to ISF than HeLa cells and do not undergo the elongation and distension that characterizes interactions of Cdts with cell lines. ISF-treated lymphocytes express normal cyclin A and B1 levels, but contain reduced levels of cell cycle-dependent kinase-1 (Cdk1). Additionally, the majority of Cdk1 is in the hyperphosphorylated, inactive, form. In contrast, PHA-induced G2 cells contain elevated levels of the hypophosphorylated, active Cdk1. Failure of ISF-treated cells to dephosphorylate Cdk1 is not associated with decreased availability of Cdc25. These studies suggest that the CdtB protein alone is capable of inducing G2 arrest in lymphocytes and cell cycle arrest, elongation, and distension of HeLa cells. Our studies also suggest that lymphocytes may be primary targets for A. actinomycetemcomitans CdtB (ISF) and possibly for other Cdt family members as well. Thus, Cdts may function to impair host immunity and contribute to the pathogenesis of disease associated with Cdt-producing organisms.

Aggregatibacter actinomycetemcomitans↗
PubMed1999

Novel mutations of the MET proto-oncogene in papillary renal carcinomas.

Hereditary papillary renal carcinoma (HPRC) is characterized by multiple, bilateral papillary renal carcinomas. Previously, we demonstrated missense mutations in the tyrosine kinase domain of the MET proto-oncogene in HPRC and a subset of sporadic papillary renal carcinomas. In this study, we screened a large panel of sporadic papillary renal carcinomas and various solid tumors for mutations in the MET proto-oncogene. Summarizing these and previous results, mutations of the MET proto-oncogene were detected in 17/129 sporadic papillary renal carcinomas but not in other solid tumors. We detected five novel missense mutations; three of five mutations were located in the ATP-binding region of the tyrosine kinase domain of MET. One novel mutation in MET, V1110I, was located at a codon homologous to an activating mutation in the c-erbB proto-oncogene. These mutations caused constitutive phosphorylation of MET when transfected into NIH3T3 cells. Molecular modeling studies suggest that these activating mutations interfere with the intrasteric mechanism of tyrosine kinase autoinhibition and facilitate transition to the active form of the MET kinase. The low frequency of MET mutations in noninherited papillary renal carcinomas (PRC) suggests that noninherited PRC may develop by a different mechanism than hereditary papillary renal carcinoma.

3T3 Cells↗