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PubMed1992

Effects of mutagen-sensitive mus mutations on spontaneous mitotic recombination in Aspergillus.

Methyl methane-sulfonate (MMS)-sensitive, radiation-induced mutants of Aspergillus were shown to define nine new DNA repair genes, musK to musS. To test mus mutations for effects on mitotic recombination, intergenic crossing over was assayed between color markers and their centromeres, and intragenic recombination between two distinguishable adE alleles. Of eight mutants analyzed, four showed significant deviations from mus+ controls in both tests. Two mutations, musK and musL, reduced recombination, while musN and musQ caused increases. In contrast, musO diploids produced significantly higher levels only for intragenic recombination. Effects were relatively small, but averages between hypo- and hyperrec mus differed 15-20-fold. In musL diploids, most of the rare color segregants resulted from mitotic malsegregation rather than intergenic crossing over. This indicates that the musL gene product is required for recombination and that DNA lesions lead to chromosome loss when it is deficient. In addition, analysis of the genotypes of intragenic (ad+) recombinants showed that the musL mutation specifically reduced single allele conversion but increased complex conversion types (especially recombinants homozygous for ad+). Similar analysis revealed differences between the effects of two hyperrec mutations; musN apparently caused high levels solely of mitotic crossing over, while musQ increased various conversion types but not reciprocal crossovers. These results suggest that mitotic gene conversion and crossing over, while generally associated, are affected differentially in some of the mus strains of Aspergillus nidulans.

Aspergillus nidulans↗
PubMed1999

Histidine 179 mutants of GTP cyclohydrolase I catalyze the formation of 2-amino-5-formylamino-6-ribofuranosylamino-4(3H)-pyrimidinone triphosphate.

GTP cyclohydrolase I catalyzes the conversion of GTP to dihydroneopterin triphosphate. The replacement of histidine 179 by other amino acids affords mutant enzymes that do not catalyze the formation of dihydroneopterin triphosphate. However, some of these mutant proteins catalyze the conversion of GTP to 2-amino-5-formylamino-6-ribofuranosylamino-4(3H)-pyrimidinone 5'-triphosphate as shown by multinuclear NMR analysis. The equilibrium constant for the reversible conversion of GTP to the ring-opened derivative is approximately 0.1. The wild-type enzyme converts the formylamino pyrimidine derivative to dihydroneopterin triphosphate; the rate is similar to that observed with GTP as substrate. The data support the conclusion that the formylamino pyrimidine derivative is an intermediate in the overall reaction catalyzed by GTP cyclohydrolase I.

Catalytic Domain↗
PubMed2005

Chemical conversion of nitrate and nitrite to nitrous oxide for nitrogen and oxygen isotopic analysis in freshwater and seawater.

We present a novel method for nitrogen and oxygen natural isotopic abundance analysis of nitrate and nitrite of seawater and freshwater at environmental concentrations. The method involves the reduction of nitrate to nitrite using spongy cadmium with further reduction to nitrous oxide using sodium azide in an acetic acid buffer. For separate nitrite analysis, the cadmium reduction step is simply bypassed. Nitrous oxide is purged from the water sample and trapped cryogenically using an automated system with subsequent release into a gas chromatography column. The isolated nitrous oxide is then analyzed on a continuous flow isotope ratio mass spectrometer via an open split. This paper describes the basic protocol and reaction conditions required to obtain reproducible natural abundance level nitrogen and oxygen isotopic ratios from nitrate, nitrite, or both, and the results obtained to support these conclusions. A standard deviation less than 0.2 per thousand for nitrogen and 0.5 per thousand for oxygen was found for nitrate samples ranging in concentration from 40 to 0.5 microM (better for nitrite), with a blank of 2 nmol for 50-mL samples. Nitrogen and oxygen isotopic fractionation and oxygen atom exchange were consistent within each batch of analysis. There was no interference from any seawater matrixes. Only one other method published to date can measure the nitrate oxygen isotopic abundance in seawater and none that do so for nitrite alone in the presence of nitrate. This method may prove to be simpler, faster, and obtain isotopic information for lower concentrations of nitrate and nitrite than other methods.

Journal Article↗
PubMed1978

Analysis of the registry of toxic effects of chemical substances (RTECS) files and conversion of the data in these files for input to the environmental chemicals data and information network (ECDIN).

A data bank for environmental chemicals, ECDIN, is being developed at the Joint Research Centre of the European Communities in cooperation with universities and research institutes in the nine member states as a part of the Environmental Research Programme of the EC. During the pilot phase of the project, data from the Registry of Toxic Effects of Chemical Substances have been incorporated into the data bank. Conversions of the data into ECDIN input format was necessary before inclusion of the toxicity data in ECDIN, and the computer programs used for this format conversion have produced various statistics for the contents of the RTECS files. Analyses of the data in three editions of RTECS are presented.

Environmental Pollutants↗
PubMed2006

A new type of bacterial sulfatase reveals a novel maturation pathway in prokaryotes.

Sulfatases are a highly conserved family of enzymes found in all three domains of life. To be active, sulfatases undergo a unique post-translational modification leading to the conversion of either a critical cysteine ("Cys-type" sulfatases) or a serine ("Ser-type" sulfatases) into a Calpha-formylglycine (FGly). This conversion depends on a strictly conserved sequence called "sulfatase signature" (C/S)XPXR. In a search for new enzymes from the human microbiota, we identified the first sulfatase from Firmicutes. Matrix-assisted laser desorption ionization time-of-flight analysis revealed that this enzyme undergoes conversion of its critical cysteine residue into FGly, even though it has a modified (C/S)XAXR sulfatase signature. Examination of the bacterial and archaeal genomes sequenced to date has identified many genes bearing this new motif, suggesting that the definition of the sulfatase signature should be expanded. Furthermore, we have also identified a new Cys-type sulfatase-maturating enzyme that catalyzes the conversion of cysteine into FGly, in anaerobic conditions, whereas the only enzyme reported so far to be able to catalyze this reaction is oxygen-dependent. The new enzyme belongs to the radical S-adenosyl-l-methionine enzyme superfamily and is related to the Ser-type sulfatase-maturating enzymes. This finding leads to the definition of a new enzyme family of sulfatase-maturating enzymes that we have named anSME (anaerobic sulfatase-maturating enzyme). This family includes enzymes able to maturate Cys-type as well as Ser-type sulfatases in anaerobic conditions. In conclusion, our results lead to a new scheme for the biochemistry of sulfatases maturation and suggest that the number of genes and bacterial species encoding sulfatase enzymes is currently underestimated.

Amino Acid Motifs↗
PubMed2005

The first picoseconds in bacterial photosynthesis--ultrafast electron transfer for the efficient conversion of light energy.

In this Minireview, we describe the function of the bacterial reaction centre (RC) as the central photosynthetic energy-conversion unit by ultrafast spectroscopy combined with structural analysis, site-directed mutagenesis, pigment exchange and theoretical modelling. We show that primary energy conversion is a stepwise process in which an electron is transferred via neighbouring chromophores of the RC. A well-defined chromophore arrangement in a rigid protein matrix, combined with optimised energetics of the different electron carriers, allows a highly efficient charge-separation process. The individual molecular reactions at room temperature are well described by conventional electron-transfer theory.

Bacterial Physiological Phenomena↗
PubMed2005

Inhibition of parathyroid hormone: a dose equivalency study of paricalcitol and doxercalciferol.

INTRODUCTION: Paricalcitol and doxercalciferol are effective in reducing parathyroid hormone PTH concentrations in patients with secondary hyperparathyroidism. The purpose of this study was to determine the relative dose of doxercalciferol (compared to paricalcitol) required to maintain equivalent PTH concentrations in dialysis patients. METHODS: Chronic hemodialysis patients treated with a stable dose of paricalcitol for at least 3 months were randomized to receive doxercalciferol at either 35, 50, or 65% of the paricalcitol dose for 6 weeks. Serum iPTH, calcium, phosphorus, and albumin were determined at baseline and monitored every 2 weeks. A linear regression analysis of percent change in iPTH values by dose group was performed to determine the conversion factor. RESULTS: 27 patients were enrolled. Initial iPTH, adjusted serum calcium, serum phosphorus, and CaxP were similar among the treatment groups. Linear regression analysis demonstrated a conversion factor of 0.57 for the dose of doxercalciferol relative to paricalcitol resulting in equivalent suppression of iPTH. Corrected serum calcium, phosphorus, CaxP product, as well as incidence of hypercalcemia, hyperphosphatemia and CaxP >50 were similar for all groups. CONCLUSION: In patients on a maintenance dose of paricalcitol, dosing doxercalciferol at 55-60% of the paricalcitol dose results in comparable inhibition of PTH.

Adult↗
PubMed2005

Assessment of the quality of interaction in distance learning programmes utilising the Internet (WebCT) or interactive television (ITV).

INTRODUCTION: This study focuses on the quality of interaction in interactive TV (ITV), WebCT bulletin boards (BBs) and chat rooms (CRs) and addresses the question of how effectively new collaborative electronic technologies have been married with new pedagogical ideas to create effective learning for distance education students. METHODS: Fifteen (out of 68) BB, 14 (out of 32) CR and 13 (out of 25) ITV conversations were randomly selected for coding using a modified exchange structure analysis. The roles that students and lecturers took in the conversations were determined from this. RESULTS: The percentage of turns made by lecturers as opposed to students was 51% in CRs, 14% in BBs and 68% in ITV. The percentage of turns spent on actual coursework was 73% in CRs, 89% in BBs and 82% in ITV. Comparisons between tutors' and students' roles within as well as between ITV, BBs and CRs were all statistically significant with P < 0.05. In CRs the main roles of both students and lecturers were those of elaborators, inquirers and explainers. In BBs the main roles of students and lecturers were those of explainers and evaluators. In ITV sessions students' main roles were those of elaborators and explainers, whereas lecturers' main roles were those of lecturers, elaborators, inquirers and evaluators. CONCLUSION: In terms of creating a constructivist and active learning community that can operate within a distance learning paradigm, WebCT appears superior to ITV.

Education, Distance↗
PubMed1993

Decreased sex hormone-binding globulin predicts noninsulin-dependent diabetes mellitus in women but not in men.

Sex hormones may influence risk factors for noninsulin-dependent diabetes mellitus (NIDDM). Decreased sex hormone-binding globulin (SHBG; an indirect measure of androgenicity) is associated with hyperinsulinemia and insulin resistance. We measured SHBG concentrations in 58 subjects who later converted to diabetes and 107 subjects who remained normoglycemic throughout the 8 yr of follow-up of the San Antonio Heart Study, a population-based study of diabetes and cardiovascular disease. Among premenopausal women, SHBG concentrations (nanomoles per L) were significantly lower in converters than in nonconverters (41.6 +/- 12.4 vs. 74.4 +/- 10.0; P = 0.004), but corresponding differences were not observed in postmenopausal women or in men. Since, however, analysis of variance suggested no significant interaction between menopausal status and conversion to NIDDM, we pooled pre- and postmenopausal women. Subsequent analysis indicated that SHBG concentrations predicted the development of NIDDM in women independently of glucose and insulin concentrations. We conclude that increased androgenicity, as assessed by decreased SHBG concentrations, is an important independent risk factor for NIDDM in women.

Adult↗
PubMed1997

Prognostic factors in the outcome of supracondylar femoral osteotomy for lateral compartment osteoarthritis of the knee.

OBJECTIVE: To identify the demographic and operative factors that determine outcome in supracondylar femoral osteotomy for lateral compartment osteoarthritis of the knee. DESIGN: Clinical and radiologic review of a nonrandomized, consecutive one-surgeon series. SETTING: A university-affiliated, elective surgical referral centre. PATIENTS: Forty-nine consecutive patients with unicompartmental osteoarthritis of the knee, involving the lateral compartment, and of sufficient severity that the alternative surgical procedure would be total knee replacement. INTERVENTION: Supracondylar varus osteotomy stabilized with a blade plate. MAIN OUTCOME MEASURES: Knee function measured by the Knee Society Score and time to conversion to total knee replacement. RESULTS: A Knee Society Score greater than 80 was obtained in 81% of patients, but in the function portion of the measurement only 30% had a similar score. After discarding the patients who died, life-table analysis demonstrated the predicted survival before conversion to total knee replacement to be 87% at 7 years. There was no correlation with patient age or sex, femorotibial angulation, amount of correction or time after the intervention. Removal of the fixation device improved the clinical result. CONCLUSION: The role of supracondylar femoral osteotomy remains poorly defined, but the procedure can delay total knee replacement for considerable time in appropriate patients.

Adult↗
PubMed1984

Familial hyperproinsulinemia. Two cohorts secreting indistinguishable type II intermediates of proinsulin conversion.

Familial hyperproinsulinemia, a hereditary syndrome in which individuals secrete high amounts of 9,000-mol wt proinsulin-like material, has been identified in two unrelated cohorts. Separate analysis of the material from each of the two cohorts had suggested that the proinsulin-like peptide was a conversion intermediate in which the C-peptide remained attached to the insulin B-chain in one case, whereas it was a conversion intermediate in which the C-peptide remained attached to the insulin A-chain in the other. To reinvestigate this apparent discrepancy, we have now used chemical, biochemical, immunochemical, and physical techniques to compare in parallel the structures of the immunoaffinity chromatography-purified, proinsulin-like peptides isolated from the serum of members of both families. Our results show that affected individuals in both cohorts secrete two-chained intermediates of proinsulin conversion in which the COOH-terminus of the C-peptide is extended by the insulin A-chain and from which the insulin B-chain is released by oxidative sulfitolysis. Analysis of the conversion intermediates by reverse-phase high-performance liquid chromatography using two different buffer systems showed that the proinsulin-related peptides from both families elute at a single position very near that of the normal intermediate des-Arg31, Arg32-proinsulin. Further, treatment of these peptides with acetic anhydride prevented trypsin-catalyzed cleavage of the C-peptide from the insulin A-chain, a result demonstrating the presence of Lys64 and the absence of Arg65 in both abnormal forms. We conclude that individuals from both cohorts with familial hyperproinsulinemia secret very similar or identical intermediates of proinsulin conversion in which the C-peptide remains attached to the insulin A chain and in which Arg65 has been replaced by another amino acid residue.

Acetic Anhydrides↗
PubMed1999

Redistribution of MAP2 immunoreactivity in the neurohypophysial astrocytes of adult rats during dehydration.

The low-molecular-weight microtubule-associated protein-2 (LMW MAP2) is expressed in immature and developing brains, and decreases its content dramatically along with maturation of the central nervous system. In our previous studies, we demonstrated through western blots and dual-labeling immunohistochemistry that LMW MAP2 is expressed in the pituicytes, modified astrocytes of the neurohypophysis in adult rats. The present study aimed to examine changes in the MAP2 immunoreactivity within pituicyte in adult rats under various hydration states using quantitative morphometrical analysis to demonstrate in vivo shape conversion of the pituicyte morphology. In well-hydrated control rats, light microscopic observation revealed that MAP2-stained pituicytes ramified long and well-branched processes. At electron microscopic level, MAP2 immunoreactivity was found in the fine process and cell body of all pituicyte cytoplasm, but not in the axonal terminals containing neurosecretory vesicles. The quantitative analysis demonstrated that the cell size and perimeter of MAP2-stained pituicytes were significantly greater as compared with those of cells stained with glial fibrillary acidic protein (GFAP). When the rats were dehydrated with water deprivation or drinking of 2% saline solution, the process of MAP2-stained pituicytes was less branched due to retracting their cellular processes as compared with those of well-hydrated control and rehydrated rats. The quantitative analysis further demonstrated that water deprivation significantly reduced the cell size, perimeter and length of cellular processes of MAP2-stained pituicytes as compared with those of control. The present finding indicates that MAP2 staining is better method for investigating in vivo shape conversion of the pituicyte morphology than GFAP one. Moreover, the finding that hydration states significantly and reversibly alter in vivo pituicyte shape supports the hypothesis that the plastic shape conversion of pituicyte morphology is responsible for morphological plasticity in the neurohypophysis.

Animals↗
PubMed2002

[A newly developed maneuver, field change conversion (FCC), improved evaluation of the left ventricular volume more accurately on quantitative gated SPECT (QGS) analysis].

PURPOSE: To investigate whether a newly developed maneuver that reduces the reconstruction area by a half more accurately evaluates left ventricular (LV) volume on quantitative gated SPECT (QGS) analysis. METHODS: The subjects were 38 patients who underwent left ventricular angiography (LVG) followed by G-SPECT within 2 weeks. Acquisition was performed with a general purpose collimator and a 64 x 64 matrix. On QGS analysis, the field magnification was 34 cm in original image (Original: ORI), and furthermore it was changed from 34 cm to 17 cm to enlarge the re-constructed image (Field Change Conversion: FCC). End-diastolic volume (EDV) and end-systolic volume (ESV) of the left ventricle were also obtained using LVG. RESULTS: EDV was 71 +/- 19 ml, 83 +/- 20 ml and 98 +/- 23 ml for ORI, FCC and LVG, respectively (p < 0.001: ORI versus LVG, p < 0.001: ORI versus FCC, p < 0.001: FCC versus LVG). ESV was 28 +/- 12 ml, 34 +/- 13 ml and 41 +/- 14 ml for ORI, FCC and LVG, respectively (p < 0.001: ORI versus LVG, p < 0.001: ORI versus FCC, p < 0.001: FCC versus LVG). CONCLUSION: FCC was better than ORI for calculating LV volume in clinical cases. Furthermore, FCC is a useful method for accurately measuring the LV volume on QGS analysis.

Aged↗
PubMed1997

Proinsulin and its conversion intermediates in human pancreas and isolated islet tissue: kinetics and steady-state analysis.

In non-insulin-dependent diabetes, circulating insulin-related immunoreactivity (IRI) is often composed of a higher fraction of the incompletely converted forms proinsulin and des-31,32 proinsulin. The present study describes an immunoadsorption method for measuring the proportions of proinsulin, its two split products, and insulin in human pancreatic tissue and for determining their rates of formation in human isolated islets. The method uses two junction-specific monoclonal proinsulin antibodies in a protein G fractionation; it is validated by > or = 90% specificity and recovery. The peptide contents measured in tissue extracts were comparable to those determined in a previously developed immunoradiometric assay. In the nine tissue extracts from nondiabetic donor organs, 97% of IRI corresponded to insulin, 1% to proinsulin, 2% to the des-31,32 proinsulin conversion product, and 0.1% to des-64,65 proinsulin. Two samples from non-insulin-dependent diabetics under sulfonylurea treatment contained a fourfold lower content of IRI but the peptide distribution was comparable except for a low percentage (0.3) of proinsulin in one case. In pulse-chase experiments on three-preparations of human islets isolated from nondiabetic donors, proinsulin represented the major (> 90%) IRI that was synthesized at the end of the 30-min pulse; a subsequent 90-min chase at either 2.5 or 10 mM glucose resulted in conversion of 75% of proinsulin to des-31,32 (20%) and des-64,65 (2%) intermediates and to insulin (50%); after a 180-min chase, 88% of proinsulin was converted to insulin, but 10% remained present as proinsulin. In a pulse-chase experiment on islets isolated from tissue with a high proportion of des-31,32 intermediate (5% instead of 2%), the conversion process was slower (45% after 90 min and 70% after 180 min) and resulted in a higher fraction of des-31,32 intermediate, suggesting that the elevated tissue content in this intermediate is caused by a reduced PC2 converting activity. These data confirm that des-31,32 proinsulin represents the major conversion intermediate in normal human islets and indicate the existence of slow converters, possibly as a result of decreased enzymatic processing of the prohormone's AC junction.

Adolescent↗
PubMed2005

Identification of novel mutations in patients with Shwachman-Diamond syndrome.

Shwachman-Diamond syndrome (SDS) is a rare autosomal recessive disease, mainly characterized by exocrine pancreatic insufficiency, hematological dysfunction and skeletal abnormalities. The SDS disease locus was mapped to chromosome 7q11 and disease-associated mutations were reported in the Shwachman-Bodian-Diamond syndrome (SBDS) gene. SBDS is a member of a highly conserved protein family with putative orthologs in diverse species including archaea and eukaryotes. It is widely expressed in many tissues and its function is still unknown. In the present study we analyzed the genotype of 15 unrelated Italian SDS patients. After sequencing the whole coding region we were able to complete all genotypes of the SDS patients tested. A total of eleven distinct mutations were identified. The most frequent mutations are due to gene conversion events between SBDS and its unprocessed pseudogene, named SBDSP. We described four new gene conversions involving exon 2 and three novel mutations that are not a result of gene conversion events. In two out of the fifteen cases, the family analysis evidenced an apparently unexpected inheritance of SDS alleles between parents and affected children. In the first case we found a new large gene conversion event, that caused the failure of the amplification of the father's allele and in the second what could be explained as a de novo gene conversion. Both cases have important implications for genetic counseling and molecular genetic analysis. In a disorder caused by gene conversions of variable extension these findings emphasize the necessity of testing patient's parents and the significance of the choice of primers.

Adolescent↗
PubMed1992

[Current status of forensic breath alcohol analysis].

1) As long as the requirements mentioned in the expert opinion of the BGA concerning the analyzers and measuring systems are not fulfilled, the measuring results can only be used as pretest results. At the present time there are not any analyzers available on the world market, which fulfill all requirements! 2) Even if all requirements would be fulfilled, there still arise many doubts concerning the actual probative force of breath alcohol analysis. They are essentially based on inadequate knowledge of physiological and pathological influences. 3) If presuppositions mentioned under 1) and 2) are disregarded, it should be possible to lay down analogic results from the BAK-limits to breathalcohol concentrations, but problems will always appear, if conversions to another time (than the analysis time) or comparisons with BAK-values are to be effected. The dimension and their difficulties for the forensic and legal expert opinion are not yet in sight.

Alcoholic Intoxication↗
PubMed1994

Chronic immunosuppression of the renal transplant patient.

The advent of potent immunosuppressive drugs to prevent rejection has led to a phenomenal improvement in renal transplant results increasing spectacularly the number of transplant recipients to arrive in the transplant clinic who remain for many years. This has engendered a series of questions about the most appropriate cyclosporine dosing for these patients that prevents rejection while avoiding toxicity. Three separate issues were analyzed: the most appropriate combination strategy with cyclosporine as a base "double" or "triple" therapy; the possibility of conversion from regimens containing cyclosporine to those devoid of it; and the optimal cyclosporine dose for a maintenance regimen. A meta-analysis of seven individual prospective and randomized trials of double versus triple therapy encompassing 1,080 patients revealed no statistical difference between the two regimens in terms of graft survival at 1 or 5 yr, patient survival, the rejection rate per patient, or the infection rate. In an analysis of 17 separate studies in which conversion away from cyclosporine was attempted, in 629 individuals with 702 individuals left on cyclosporine as controls, a significant risk of acute rejection (P < 0.001) was found in the withdrawn group without evidence of improved graft survival. Certain factors such as previous rejection, race, and degree of reactivity predicted even more rejection in the withdrawn group. Analyzing six separate studies of renal transplant recipients maintained on cyclosporine for up to 5 yr with renal functional stability, one can conclude that a dose of approximately 4.0 mg/kg per day is optimal. Because of variant pharmacokinetics or concomitant medicines, blood levels can confirm a therapeutic concentration with this target dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical Trials as Topic↗
PubMed1997

Analysis of forces developed during root canal preparation with the balanced force technique.

The aim of this study was to examine the forces and torque developed during root canal preparation with the balanced force technique using a recently described force-analyser device. A tooth was placed in a holder within the Endograph and forces and torques exerted were recorded. These parameters, which can be studied during preparation (on-line) or stored and examinated subsequently (off-line) generated endograms, which showed the forces generated with time. In addition, the endograms of preparations performed by students and endodontists, as well as deliberately induced failures in preparation technique (broken instruments), were compared. The values for the forces and torques depended on the size of the instruments and were related to the phase of the preparation. For the endodontists, the vertical and horizontal forces varied, respectively, from 0.08 +/- 0.01 kg for a size 15 to 0.65 +/- 0.10 kg for a size 45, and from 0.01 +/- 0.005 kg for a size 15 to 0.4 +/- 0.1 kg for a size 40. The torque varied from 0.08 +/- 1 kg mm-1 for a size 15 to 1.6 +/- 0.4 kg mm-1 for a size 45. With the endograms used as a reference, the relation between the developed vertical forces and the torque became more similar between the groups of endodontists and students. The Endograph provides a new approach to the analysis of preparation technique because it depicts the relationships between the different parameters of the preparation.

Amplifiers, Electronic↗