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At least 307 records · Page 17Linked to original sources
PubMed1996

Molecular genetic tests as a guide to surgical management of familial adenomatous polyposis.

BACKGROUND: In familial adenomatous polyposis the only curative treatment is colectomy, and the choice of operation lies between restorative proctocolectomy (RPC) and colectomy with ileorectal anastomosis (IRA). The RPC procedure carries a higher morbidity but, unlike IRA, removes the risk of subsequent rectal cancer. Since the course of familial adenomatous polyposis is influenced by the site of mutation in the polyposis gene, DNA analysis might be helpful in treatment decisions. METHODS: We evaluated the incidence of rectal cancer in polyposis patients who had undergone IRA, and examined whether the requirement for subsequent rectal excision because of cancer or uncontrollable polyps was related to the site of mutation. FINDINGS: Between 1956 and mid-1995, 225 patients registered at the Netherlands Polyposis Registry had undergone IRA. In 87 of them, a pathogenetic mutation was detected. 72 patients had a mutation located before codon 1250 and 15 patients after this codon. The cumulative risk of rectal cancer 20 years after surgery was 12%, and at that time 42% had undergone rectal excision. The risk of secondary surgery was higher in patients with mutations in the region after codon 1250 than in patients with mutations before this codon (relative risk 2.7, p < 0.05). INTERPRETATION: On this evidence, IRA should be the primary treatment for polyposis in patients with mutations before codon 1250, and RPC in those with mutations after this codon.

Adenomatous Polyposis Coli↗
PubMed2006

Using spectroscopic data on imidazolium cation conformations to test a molecular force field for ionic liquids.

A molecular force field for the computer simulation of ionic liquids is evaluated a posteriori by confrontation against Raman spectroscopic data, published after the force field had been formulated. Specifically, the terms in the force field describing the conformational aspects of dialkylimidazolium cations, which were specifically developed for these compounds using high level ab initio calculations, are those affecting the distribution of conformers in simulated ionic liquids. Those distributions are compared with analyses of the liquid-phase Raman spectra, and the features of a series of dihedral torsions along the alkyl side chains in 1-alkyl-3-methylimidazolium cations in several ionic liquids are discussed.

Journal Article↗
PubMed2001

Quality control in molecular genetic testing.

DNA-based testing for genetic diseases has developed from nothing into a principal part of laboratory medicine over the past 15 years. In the rush to bring these powerful new technologies into medical use, issues of quality have not always been given sufficient attention. Efforts are now being made to assess the quality of the output of genetic testing laboratories, and the results show that there is room for improvement.

Accreditation↗
PubMed2005

Kinetics of fluorescence quenching for electron transfer and for energy transfer: molecular dynamics tests for spherical molecules.

The Smoluchowski approach to description of fluorescence quenching is tested by comparing the theory with computer simulations for the case of spherical molecules. The distance dependent sink terms describing the electron transfer mechanism and the Forster model for the energy transfer are considered. It is shown that the agreement between the rate coefficient from the model and from simulations depends on the strength of the solute-solvent interactions as well as on the speed of reaction itself. Comparing results of simulations for different quencher concentrations we estimate the strength of quencher concentration dependence effect and the range of times the effect may be significant. In the long time limit the increase in quencher concentration decreased the rate coefficient.

Journal Article↗
PubMed2003

Glucose uptake in enterocytes: a test for molecular targets of okadaic acid.

The main diarrheic shellfish poisoning (DSP) toxin is okadaic acid (OA). Although OA is a protein phosphatase 1 and 2A inhibitor less is known about the involvement of the toxin in diarrhea. The initial statement was that OA, by altering the phosphorylation state of proteins, might modify glucose uptake and consequently ionic and water reabsorption across the small intestine. This report presents studies of glucose transport in isolated rabbit enterocytes by using a fluorescent derivative of D-glucose. The dye allowed examining the relation between the toxic effect of OA and cellular mechanisms involved in glucose transport. The central findings are: (i) OA potentiates decrease on glucose uptake due to protein kinase A (PKA) inhibitors such as H89; and (ii) the increase of sugar uptake induced by the protein kinase C (PKC) inhibitor chelerythrine is enhanced by OA. Importance of this work is justified by the need to determine molecular targets of diarrheic toxins in intestinal cells.

4-Chloro-7-nitrobenzofurazan↗
PubMedDate not supplied

Implications of molecular diagnostic testing in families with hereditary pancreatitis.

Hereditary Pancreatitis (HP), is an autosomal dominant trait, which presents with recurrent attacks of abdominal pain, and is the most common cause of chronic relapsing pancreatitis in children. In addition to recurring episodes of intense epigastric pain, patients have nausea, vomiting, and anorexia, and typically show elevated serum amylase levels during the acute episode that can rapidly decline in convalescence. Complications of long-standing disease include features of chronic pancreatitis, such as pancreatic pseudo-cyst, exocrine and endocrine failure, parenchymal calcification, and pancreatic cancer. A large family from Virginia, which was originally studied by Katwinkle and Lapey in 1973, was re-ascertained through a new proband. Linkage studies in this family mapped the gene to the 7q35 region, with similar results being reported simultaneously by two other groups. A pathogenic G to A transition mutation in exon 3 of the cationic trypsinogen (CT) gene, which had previously been mapped to this region, was found both in our family as well as other families from North America. Many other conditions can produce abdominal symptoms that are often mis-attributed to the disease in HP families. An affected member of our family in whom the mutation was confirmed by direct sequencing of exon 3 of the cationic trypsinogen gene requested diagnostic testing on his 4-year-old son because of onset of severe abdominal pain and vomiting. Screening for the mutation in this child did not reveal the pathogenic G to A change. These results prevented unnecessary invasive diagnostic procedures and treatment in this child. The pre-symptomatic testing of high risk individuals could, thus, have a significant impact on the well being of both affected and normal family members.

Adult↗
PubMed1999

Frequency of problems during clinical molecular-genetic testing.

Concerns have been raised about the quality of DNA-based genetic testing, but few data are available on the problems that occur during clinical genetic testing. We sought to determine the frequency and severity of such problems in US laboratories. Problems were defined as events that could or did impair patient care significantly. Data on the frequency and severity of adverse events during genetic testing were collected from laboratories by anonymous mail questionnaire and detailed on-site inspection. The surveyed laboratories (n = 42) reported significant problems in 0.33% of tests performed; the corresponding value in the inspected laboratories (n = 2) was 0.38%. Sixty percent of problems occurred in the pretest phase, 32% in the laboratory phase, and 8% in the posttest phase or multiple phases. The average level of actual harm resulting from these problems was low. Moderate or high levels of harm occurred in only 0.008% of total cases. No lawsuits, judgments, or disciplinary actions were taken against the laboratories in 277,000 tests performed. The overall frequency of problems in a given laboratory did not correlate with laboratory age, test volume, accreditation status, proficiency testing performance, or institution type (academic, private nonprofit, private for profit). In conclusion, significant problems during genetic testing occur infrequently (< 0.5% in most laboratories), and problems resulting in moderate or high levels of harm to patients are rare (0.008%).

Adult↗
PubMed2006

Testing the molecular clock: molecular and paleontological estimates of divergence times in the Echinoidea (Echinodermata).

The phylogenetic relationships of 46 echinoids, with representatives from 13 of the 14 ordinal-level clades and about 70% of extant families commonly recognized, have been established from 3 genes (3,226 alignable bases) and 119 morphological characters. Morphological and molecular estimates are similar enough to be considered suboptimal estimates of one another, and the combined data provide a tree that, when calibrated against the fossil record, provides paleontological estimates of divergence times and completeness of their fossil record. The order of branching on the cladogram largely agrees with the stratigraphic order of first occurrences and implies that their fossil record is more than 85% complete at family level and at a resolution of 5-Myr time intervals. Molecular estimates of divergence times derived from applying both molecular clock and relaxed molecular clock models are concordant with estimates based on the fossil record in up to 70% of cases, with most concordant results obtained using Sanderson's semiparametric penalized likelihood method and a logarithmic-penalty function. There are 3 regions of the tree where molecular and fossil estimates of divergence time consistently disagree. Comparison with results obtained when molecular divergence dates are estimated from the combined (morphology + gene) tree suggests that errors in phylogenetic reconstruction explain only one of these. In another region the error most likely lies with the paleontological estimates because taxa in this region are demonstrated to have a very poor fossil record. In the third case, morphological and paleontological evidence is much stronger, and the topology for this part of the molecular tree differs from that derived from the combined data. Here the cause of the mismatch is unclear but could be methodological, arising from marked inequality of molecular rates. Overall, the level of agreement reached between these different data and methodological approaches leads us to believe that careful application of likelihood and Bayesian methods to molecular data provides realistic divergence time estimates in the majority of cases (almost 80% in this specific example), thus providing a remarkably well-calibrated phylogeny of a character-rich clade of ubiquitous marine benthic invertebrates.

Animals↗
PubMedDate not supplied

Effectiveness of sequencing connexin 26 (GJB2) in cases of familial or sporadic childhood deafness referred for molecular diagnostic testing.

PURPOSE: Hearing loss is a common congenital disorder that is frequently associated with mutations in the GJB2 gene encoding the connexin 26 protein (Cx26). We sought to evaluate the effectiveness of direct DNA sequencing for detection of Cx26 mutations as a clinical diagnostic test. METHODS: We designed a clinical assay using a three-step polymerase chain reaction (PCR)-based DNA sequencing strategy to detect all possible mutations in the open reading frame and flanking sequences of Cx26. The results of the first 324 cases of childhood deafness referred for diagnostic testing were analyzed. RESULTS: A total of 127 of the 324 (39.2%) cases had at least one mutant Cx26 allele (36.1% of sporadic cases, 70% of familial cases). Of these 127 case, 57 (44.8%) were homozygotes or compound heterozygotes. Thirty-four different mutations were identified, including 10 novel mutations, 6 of which (T8M, K15T, R32L, M93I, N206S, and 511-512insAACG) may be pathogenic. We also provide new evidence on the pathogenicity or nonpathogenicity of 12 previously reported mutations, and clarify the confusing nomenclature of the 313-326del14 mutation. CONCLUSION: A simple and rigorous method for efficient PCR-based sequence analysis of Cx26 is a sensitive clinical assay for evaluating deaf children. Its widespread use is likely to identify additional pathogenic mutations and lead to a better understanding of the clinical significance of previously identified mutations.

Alleles↗
PubMed1991

Comparison of ultracentrifugation and polyethylene glycol precipitation for concentration of hepatitis B virus (HBV) DNA for molecular hybridisation tests and the relationship of HBV-DNA to HBe antigen and anti-HBe status.

A 32P-labelled DNA probe was used to examine 50 hepatitis B surface antigen (HBsAg)-positive sera for the presence of hepatitis B virus (HBV) DNA. HBV-DNA was detected in all 21 HBeAg-positive samples, in one out of 21 anti-HBe-positive samples and in three out of eight HBeAg- and anti-HBe-negative samples. The results of this DNA hybridisation test correlated well with HBeAg status and could be used to determine infectivity in HBeAg- and anti-HBe-negative samples. Ultracentrifugation was marginally superior to polyethylene glycol precipitation for concentrating HBV-DNA from serum.

Chemical Precipitation↗
PubMed2005

Ichthyosis bullosa of Siemens: its correct diagnosis facilitated by molecular genetic testing.

Ichthyosis bullosa of Siemens (IBS, MIM 146800) is a unique congenital ichthyosis characterized by mild epidermal hyperkeratosis over flexural areas, blister formation and the development of superficially denuded areas of hyperkeratotic skin. It is clinically difficult to distinguish severe IBS from mild bullous congenital ichthyosiform erythroderma (BCIE, MIM 113800). In the current literature, 19 IBS families with keratin 2e (K2e) mutations have been reported, despite only five IBS families having been reported before the first identification of K2e mutation in 1994. We studied four patients from three Japanese IBS families. They had previously been misdiagnosed as having BCIE before the correct diagnosis was made after mutation detection. To detect the pathogenic mutations, we performed direct sequencing of the entire coding regions of KRT2E encoding K2e in the patients and healthy family members. K2e mutations, a 1469T-->C transition (L490P) and a 1477G-->A transition (E493K) within the conserved 2B helix termination motif of the rod domain were detected in the families and the definite diagnosis of IBS was made in the four cases. The present results indicate that IBS is not such a rare entity as was previously thought, and accurate diagnosis is now available by mutation analysis.

Adult↗