Cytosine deaminations catalyzed by DNA cytosine methyltransferases are unlikely to be the major cause of mutational hot spots at sites of cytosine methylation in Escherichia coli.

Sites of cytosine methylation are hot spots for Cto T mutations in Escherichia coli DNA. We have developed a genetic reversionassay that allows direct selection of C to T mutations at a site of methylation.Because the mutant gene is on a plasmid, this system can be used to studymutational effects of biochemical agents in vitro as well as in vivo. Using thissystem we show that in vitro an E. coli methyltransferase can cause C to Udeaminations at a site of methylation. Reaction conditions that are known toinhibit a side reaction of the methyltransferase also suppress reversionfrequency, suggesting that this side reaction is required for deamination.Furthermore, a mutation in the enzyme that eliminates its catalytic activity butnot its ability to bind DNA eliminates the ability of the enzyme to cause C to Udeaminations. Despite this, in vivo experiments strongly suggest thatenzyme-catalyzed deaminations of cytosine do not play a major role in makingmethylation sites in E. coli hot spots for mutations. For example, althoughuracil-DNA glycosylase (Ung) suppresses the occurrence of mutations due to C toU deaminations, the frequency of C to T mutations at a methylation site remainshigh in ung+ cells. Furthermore, the reversion frequencies in ung+ and ung-cells are quite similar.     

Short colon variant

A one day old neonate with a short colon, associated exomphalos minor; bifid scrotum and ileovesical fistula is reported.     

Platelet glycoprotein IIb/IIIa inhibition using eptifibatide with primary coronary stenting for acute myocardial infarction: a 30-day follow-up study.

The results of primary coronary stenting for acute myocardial infarction (AMI) have been reported to improve significantly with the concomitant administration of platelet glycoprotein IIb/IIIa inhibitor abciximab. There are, however, no data available with the use of eptifibatide, a more cost-effective, small-molecule GP IIb/IIIa blocker with a shorter half-life. In a prospective multicenter feasibility and efficacy study, we assigned 55 consecutive patients with AMI being taken up for primary stenting to receive eptifibatide just before the procedure (two boluses of 180 microg/kg 10 min apart and a 24-hr infusion of 2 microg/kg/min). Clinical outcomes were evaluated at 30 days after the procedure. The angiographic patency of the vessel with TIMI flow rates, TIMI myocardial perfusion (TMP) grade, and corrected TIMI frame counts were assessed at the end of procedure and before hospital discharge. At 30 days, the primary endpoint, a composite of death, myocardial infarction, and urgent target vessel revascularization (TVR) was seen in 12.7% of patients. The TIMI 3 and TMP grade 3 flow, which was seen in 93% and 86% of patient, respectively, at the end of the procedure, declined to 86% and 78%, respectively (P < 0.05) before hospital discharge. Corrected TIMI frame counts also decreased from 25.7 +/- 7.2 to 22.9 +/- 6.8 (P < 0.05). There were five (9.1%) instances of subacute thrombosis (SAT) presenting as AMI, needing urgent TVR in all, within 3-5 days of the primary procedure. No excessive bleeding complication, directly attributable to the use of eptifibatide, was observed. The study was terminated prematurely because of an unacceptable SAT rate. Administration of eptifibatide along with primary stenting for AMI is associated with a high TIMI 3 and TMP grade 3 flow acutely. However, these flows decline significantly before hospital discharge and lead to a high rate of SAT. The dosage and duration of infusion of eptifibatide in this setting needs further evaluation.     

(R)-2-Phenylpyrrolidine Substituted Imidazopyridazines: A New Class of Potent and Selective Pan-TRK Inhibitors

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Selective coronary angiography via antegrade venous route in congenital cyanotic heart disease

An antegrade venous technique was utilised to perform selective coronary angiography in cyanotic infants and children. The procedure was successful in 88% (37/42) cases and excellent quality angiograms were recorded. The importance of proper catheter selection and details of the technique are discussed. © 1993 Wiley-Liss, Inc.     

Functional characterization of novel rare CYP2A6 variants and potential implications for clinical outcomes

CYP2A6 activity, phenotyped by the nicotine metabolite ratio (NMR), is a predictor of several smoking behaviors, including cessation and smoking‐related disease risk. The heritability of the NMR is 60–80%, yet weighted genetic risk scores (wGRSs) based on common variants explain only 30–35%. Rare variants (minor allele frequency <1%) are hypothesized to explain some of this missing heritability. We present two targeted sequencing studies where rare protein‐coding variants are functionally characterized in vivo, in silico, and in vitro to examine this hypothesis. In a smoking cessation trial, 1687 individuals were sequenced; characterization measures included the in vivo NMR, in vitro protein expression, and metabolic activity measured from recombinant proteins. In a human liver bank, 312 human liver samples were sequenced; measures included RNA expression, protein expression, and metabolic activity from extracted liver tissue. In total, 38 of 47 rare coding variants identified were novel; characterizations ranged from gain‐of‐function to loss‐of‐function. On a population level, the portion of NMR variation explained by the rare coding variants was small (~1%). However, upon incorporation, the accuracy of the wGRS was improved for individuals with rare protein‐coding variants (i.e., the residuals were reduced), and approximately one‐third of these individuals (12/39) were re‐assigned from normal to slow metabolizer status. Rare coding variants can alter an individual’s CYP2A6 activity; their integration into wGRSs through precise functional characterization is necessary to accurately assess clinical outcomes and achieve precision medicine for all. Investigation into noncoding variants is warranted to further explain the missing heritability in the NMR.

Study Highlights

• WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC?

Common CYP2A6 variants (minor allele frequency >1%) explain 30–35% of the variation in CYP2A6 activity, despite high heritability estimates (60–80%) in the CYP2A6 activity biomarker measure. One hypothesis is that rare coding variants (minor allele frequency <1%) may explain a portion of the missing heritability from pharmacogenes, including CYP2A6.

• WHAT QUESTION DID THIS STUDY ADDRESS?

What is the relative contribution of rare coding variants in explaining variation in CYP2A6 activity? How necessary is the incorporation of rare coding variants in predicting individual metabolic status, and consequent tailoring of treatment?

• WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE?

Rare coding variants may explain only a small fraction of the variation on a population level; however, their role may be important on an individual level, altering the predicted metabolic status in a third of the individuals with these rare coding variants.

• HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE?

Evaluating rare coding variants in pharmacogenes, such as CYP2A6, will be valuable in enhancing the investigation of CYP2A6’s influence on tobacco addiction and disease pathogenesis, by providing a more accurate reflection of the phenotypic metabolic status through improved genetic assessments.     

Pitfalls of radiation survey after brachytherapy implant removal preceding Tl-201 study

An unexpected elevated postimplant radiation survey is described in an elderly patient with an interstitial low-dose-rate iridium-192 (Ir-192) needle implant for endometrial cancer. The elevated activity was related to prolonged clearance of Tl-201 from a cardiac study that had been performed 7 days earlier. The Tl-201 accumulated in the soft tissue, particularly the colon, resulting in increased survey readings over the abdomen and raising concern that an Ir-192 source remained within the patient. This case shows that delayed excretion of a diagnostic radionuclide agent can cause elevated activity high enough to confound postradiotherapy implant survey readings. The estimated surface exposure from a single iridium source left in the pelvis was determined using a phantom study. Possible factors causing decreased excretion of Tl-201 in a patient with heart disease, arteriosclerotic vascular disease, previous pelvic radiation therapy, and a brachytherapy procedure are discussed. A preloading radiation survey is recommended in patients who have had previous nuclear medicine studies involving radionuclides with long half-lives.     

Development of a database of critically evaluated flavonoids data: application of USDA's data quality evaluation system

The USDA Special Interest Database for flavonoid content of selected foods contains 26 most abundant compounds within 5 predominant subclasses of flavonoids–flavonols, flavones, flavanones, flavan-3-ols, and anthocyanidins. All the data were evaluated for 5 quality evaluation categories (sampling plan, sample handling, analytical method, analytical quality control and number of samples), using the data quality evaluation system developed by the USDA scientists. Confidence Codes (A–through D) were then assigned to every value. The database contains acceptable values for 225 selected foods. Only 97 sources out of approximately 475 collected included acceptable analytical data. The overall quality of data was good with 64% of the observations receiving A or B confidence codes; the flavan-3-ols subclass received better ratings than other subclasses. While this is the first comprehensive database for flavonoids in foods, the majority of data came from Europe and countries other than the US. Due to the observed variability in the values it will be important to have data for US foods. The evaluation of data quality helps set priorities and further identifies the foods to be analyzed as well as areas to improve data quality. Furthermore, release of data quality confidence codes with data provides necessary information to investigators to assess the impact of flavonoid intake on risk of various chronic diseases.