Accelerometer-measured physical activity and its impact on sleep quality in patients suffering from restless legs syndrome

BACKGROUND

The primary symptoms of restless legs syndrome (RLS) are sleep onset insomnia and difficulty to maintain sleep. Previous studies have shown that regular physical activity can reduce the risk of developing RLS. However, the relationship between physical activity and sleep quality parameters in individuals suffering from RLS has not yet been investigated by applying accelerometry. Thus, the present study investigates the impact of physical activity (measuring both intensity levels and duration of physical activity) during the day (7-12 h, 12-18 h, 18-23 h) on sleep quality in patients suffering from idiopathic RLS by applying a real-time approach.

METHODS

In a sample of 47 participants suffering from idiopathic RLS, physical activity and sleep quality were measured over one week using accelerometers. For data analysis, physical activity levels and step counts during three periods of the day (morning, afternoon, evening) were correlated with sleep quality parameters of the subsequent night.

RESULTS

This observational study revealed that in most instances physical activity was not correlated with sleep parameters (two exceptions exist: steps taken in the morning were negatively correlated with periodic leg movements during sleep, and physical activity in the evening was negatively correlated with total sleep time). The physical activity levels of the participants in this study, however, were unexpectedly high compared to population-level data and variance in physical activity was low. The average activity was 13,817 (SD = 4086) steps and 347 (SD = 117) minutes of moderate physical activity per day in females, and 10,636 (SD = 3748) steps and 269 (SD = 69) minutes of moderate physical activity in males, respectively. Participants did not engage in any vigorous physical activity.

CONCLUSIONS

Further interventional studies are needed to investigate the daily effects of different intensities of physical activity on RLS symptoms.

Strontium-modified premixed calcium phosphate cements for the therapy of osteoporotic bone defects

In this study a premixed strontium-containing calcium phosphate bone cement for the application in osteoporotic bone defects has been developed and characterised regarding its material and in vitro properties as well as minimally invasive applicability in balloon kyphoplasty. Strontium was introduced into the cement by substitution of one precursor component, CaCO₃, with its strontium analogue, SrCO₃. Using a biocompatible oil phase as carrier liquid, a cement paste that only set upon contact with aqueous environment was obtained. Strontium modification resulted in an increased strength of set cements and radiographic contrast; and the cements released biologically relevant doses of Sr²⁺-ions that were shown to enhance osteoprogenitor cell proliferation and osteogenic differentiation. Finally, applicability of strontium-containing cement pastes in balloon kyphoplasty was demonstrated in a human cadaver spine procedure. The cement developed in this study may therefore be well suited for minimally invasive, osteoporosis-related bone defect treatment.

STATEMENT OF SIGNIFICANCE

Strontium-releasing calcium phosphate bone cements are promising materials for the clinical regeneration of osteoporosis-related bone defects since they have been shown to stimulate bone formation and at the same time limit osteoclastic bone resorption. Today clinical practice favours minimally invasive surgical techniques, e.g. for vertebral fracture treatment, posing special demands on such cements. We have therefore developed a premixed, strontium-releasing bone cement with enhanced mechanical properties and high radiographic visibility that releases biologically relevant strontium concentrations and thus stimulates cells of the osteogenic lineage. In a pilot experiment we also exemplify its excellent suitability for minimally invasive balloon kyphoplasty procedures.

Physical activity and all-cause mortality: an updated meta-analysis with different intensity categories

In a meta-analysis we investigated the effect of physical activity with different intensity categories on all-cause mortality. Many studies have reported positive effects of regular physical activity on primary prevention. This recent meta-analysis analyzed all-cause mortality with special reference to intensity categories. A computerized systematic literature search was performed in EMBASE, PUBMED, and MEDLINE data bases (1990-2006) for prospective cohort studies on physical leisure activity. Thirty-eight studies were identified and evaluated. The presentation refers to studies with 3 or 4 different intensities of regular physical activity according to a standard questionnaire. There was a significant association of lower all-cause mortality for active individuals compared with sedentary persons. For studies with three activity categories (mildly, moderately, and highly active) and multivariate-adjusted models, highly active men had a 22% lower risk of all-cause mortality (RR=0.78; 95% CI: 0.72 to 0.84) compared to mildly active men. For women, the relative risk was 0.69 (95% CI: 0.53 to 0.90). We observed similar results in moderately active persons compared to mildly active individuals (RR=0.81 for men and RR=0.76 for women). This association of activity to all-cause mortality was similar and significant in older subjects. Regular physical activity over longer time is strongly associated with a reduction in all-cause mortality in active subjects compared to sedentary persons. There is a dose-response curve especially from sedentary subjects to those with mild and moderate exercise with only a minor additional reduction with further increase in activity level.

Pressurized wet digestion in open vessels

The High Pressure Asher (HPA-S) was adapted with a Teflon liner for pressurized wet digestion in open vessels. The autoclave was partly filled with water containing 5% (vol/vol) hydrogen peroxide. The digestion vessels dipped partly into the water or were arranged on top of the water by means of a special rack made of titanium or PTFE-coated stainless steel. The HPA-S was closed and pressurized with nitrogen up to 100 bars. The maximum digestion temperature was 250 degrees C for PFA vessels and 270 degrees C for quartz vessels. Digestion vessels made of quartz or PFA-Teflon with volumes between 1.5 mL (auto sampler cups) and 50 mL were tested. The maximum sample amount for quartz vessels was 0.5-1.5 g and for PFA vessels 0.2-0.5 g, depending on the material. Higher sample intake may lead to fast reactions with losses of digestion solution. The samples were digested with 5 mL HNO(3) or with 2 mL HNO(3)+6 mL H(2)O+2 mL H(2)O(2). The total digestion time was 90-120 min and 30 min for cooling down to room temperature. Auto sampler cups made of PFA were used as digestion vessels for GFAAS. Sample material (50 mg) was digested with 0.2 mL HNO(3)+0.5 mL H(2)O+0.2 mL H(2)O(2). The analytical data of nine certified reference materials are also within the confidential intervals for volatile elements like mercury, selenium and arsenic. No cross contamination between the digestion vessels could be observed. Due to the high gas pressure, the diffusion rate of volatile species is low and losses of elements by volatilisation could be observed only with diluted nitric acid and vessels with large cross section. In addition, cocoa, walnuts, nicotinic acid, pumpkin seeds, lubrication oil, straw, polyethylene and coal were digested and the TOC values measured. The residual carbon content came to 0.2-10% depending on the sample matrix and amount.

Resolution of uncertainty of a four-stage sequential extraction procedure using analysis of variance

Sequential extraction procedures are mostly applied to soils and sediments. Investigations were made for testing the applicability of a selected extraction scheme on spoil pile material. Therefore, different spoil pile samples from uranium mining were extracted into four steps (exchangeable, reducible, oxidizable, and aqua regia soluble phase) and the contents of the elements Cr, Cu, Fe, K, Ni, and Zn were analyzed. To substitute the sequential extraction by a sequence of single extractions and thus keep uncertainties of extraction on a low level, both procedures were compared regarding conformity of their results. The effects of sample handling as well as those of analysis on the measured metal contents were determined by means of analysis of variance and sources of uncertainties were discussed.

A refined method for the meta-analysis of controlled clinical trials with binary outcome

For the meta-analysis of controlled clinical trials with binary outcome a test statistic for testing an overall treatment effect is proposed, which is based on a refined estimator for the variance of the treatment effect estimator usually used in the random-effects model of meta-analysis. In simulation studies it is shown that the proposed test keeps the prescribed significance level much better than the commonly used tests in the fixed-effects and random-effects model, respectively. Moreover, when using the test it is not necessary to choose between fixed effects and random effects approaches in advance. The proposed method applies in the same way to the analysis of a controlled multi-centre study with binary outcome, including a possible interaction between drugs and centres.

A refined method for the meta-analysis of controlled clinical trials with binary outcome

For the meta-analysis of controlled clinical trials with binary outcome a test statistic for testing an overall treatment effect is proposed, which is based on a refined estimator for the variance of the treatment effect estimator usually used in the random-effects model of meta-analysis. In simulation studies it is shown that the proposed test keeps the prescribed significance level much better than the commonly used tests in the fixed-effects and random-effects model, respectively. Moreover, when using the test it is not necessary to choose between fixed effects and random effects approaches in advance. The proposed method applies in the same way to the analysis of a controlled multi-centre study with binary outcome, including a possible interaction between drugs and centres.

Treatment of non-ulcer dyspepsia: a meta-analysis of placebo-controlled prospective studies

BACKGROUND

Dyspeptic symptoms are commonly reported complaints in clinical practice and are mostly the result of functional disorders. Empirical treatment with histamine H2-receptor blockers or gastroprokinetics for 2-4 weeks has frequently been proposed as first line management of these patients. The clinical trials which support the use of these agents, show a high variation in clinical success rate and benefit of these treatments.

METHODS

The available clinical trials were evaluated, pooled where appropriate and subjected to a meta-analysis with the principal goal to provide valid treatment recommendations for patients with non-ulcer dyspepsia. In the present meta-analysis 19 studies on gastroprokinetics (cisapride, domperidone) and 10 studies on histamine H2-receptor antagonists (cimetidine, ranitidine) were included.

RESULTS

Based on these studies, a total of 1540 patients were evaluated for histamine H2-receptor antagonists (verum n = 786, placebo n = 754) and 1235 patients for gastroprokinetics (verum n = 616, placebo n = 619). The probability for treatment success compared to placebo was 0.2026 (0.1261; 0.2791) for histamine H2-receptor antagonists and 0.4029 (0.3042; 0.5069) for gastroprokinetics.

CONCLUSIONS

Based on these data both treatments are significantly more effective than placebo in the symptomatic treatment of non-ulcer dyspepsia, with gastroprokinetics (cisapride, domperidone) being more effective than histamine H2-receptor antagonists (cimetidine, ranitidine).

On tests of the overall treatment effect in meta-analysis with normally distributed responses

For the meta-analysis of controlled clinical trials or epidemiological studies, in which the responses are at least approximately normally distributed, a refined test for the hypothesis of no overall treatment effect is proposed. The test statistic is based on a direct estimation function for the variance of the overall treatment effect estimator. As outcome measures, the absolute and the standardized difference between means are considered. In simulation studies it is shown that the proposed test keeps the prescribed significance level very well in contrast to the commonly used tests in the fixed effects and random effects model, respectively, which can become very liberal. Furthermore, just for using the proposed test it is not necessary to choose between the fixed effects and the random effects approach in advance.

High-temperature, microwave-assisted UV digestion: a promising sample preparation technique for trace element analysis

A novel, microwave-assisted, high-temperature UV digestion procedure was developed for the accelerated decomposition of interfering dissolved organic carbon (DOC) prior to trace element analysis of liquid samples such as, industrial/municipal wastewater, groundwater, and surface water, body fluids, infusions, beverages, and sewage. The technique is based on a closed, pressurized, microwave digestion device. UV irradiation is generated by immersed electrodeless Cd discharge lamps (228 nm) operated by the microwave field in the oven cavity. To enhance excitation efficiency an antenna was fixed on top of the microwave lamp. The established immersion system enables maximum reaction temperatures up to 250-280 degrees C, resulting in a tremendous increase of mineralization efficiency. Compared to open UV digestion devices, decomposition time is reduced by a factor of 5 and the maximum initial concentration of DOC can be raised by at least a factor of 50. The system's performance on a real-type sample was evaluated for the mineralization of skimmed milk (IRMM, CRM 151) and subsequent determination of trace elements using standard spectroscopic techniques. Recovery for Cd (109%), Cu (112%), Fe (99%), and Pb (96%) showed good agreement with the 95% confidence interval of the certified values.

Combined test procedures in the meta-analysis of controlled clinical trials

Concerning the actual significance level, we investigate the commonly used combined test procedures of meta-analysis, which contain the choice of the model, in which the analysis is carried out, and the commonly used tests for treatment effect in the fixed and random effects model, and some new combined test procedures, which use an alternative test statistic in the random effects model or the t-distribution as test distribution of the commonly used test statistics. A simulation study indicates that the new combined test procedures are better with respect to a prescribed significance level.

Investigation of microwave assisted drying of samples and evaporation of aqueous solutions in trace element analysis

Investigations of microwave assisted drying of sample materials and microwave assisted evaporation of aqueous sample solutions and acidic digestion residues were accomplished by means of special rotors for the microwave digestion system MULTIWAVE. To check the results obtained by microwave assisted drying, the samples were also conventionally dried at 105 degrees C in an oven. The following samples have been dried: 10 g each of meat, fish, apple, cucumber, potato, mustard, yogurt, clay and marl; 1 g each of certified reference material TORT 2 (lobster hepatopancreas), BCR 278 (mussel tissue) and BCR 422 (cod muscle); 500 g garden mould. Microwave assisted drying takes 40 min for organic samples and 30 min for inorganic material. Important is a slow increase of microwave power during the first 20 min. The results agree well with conventional drying at 105 degrees C. Losses of As, Se and Hg have been investigated for 3 CRMs. Only Se shows losses in the range of 20%. Losses of As, Be, Cd, Co, Cr, Cu, Fe, Hg, Li, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sr, Ti, Tl, V and Zn after evaporation of aqueous samples and acidic solutions after wet digestion, respectively, have been investigated. 50 mL aqueous solution was evaporated almost to dryness within 25 min. The recovery of Hg is 40-50%, of Se 90-95% and of the other elements 97-102%. 0.2 g each of TORT 2, BCR 278 and BCR 422 have been digested with 4 mL nitric acid and 1 mL hydrochloric acid by means of the microwave digestion system MULTIWAVE. The digestion residue was evaporated almost to dryness and dissolved again in 10 mL diluted nitric acid. In this case no element losses have been observed. The measured concentration of As, Cd, Cu, Fe, Mn, Hg, Pb, Mo, Ni, Se, Sr, V and Zn agree very well with the certified values. An important prerequisite for good recoveries is not to evaporate the solutions to complete dryness.

[A re-analysis of the Blue Mountain eye study on the risk of cataracts from inhaled corticosteroids. A contribution to objectifying the discussion]

By a re-analysis of the Blue Mountains Eye Study of Cumming, Mitchell and Leeder, Published in N Engl J Med 1997 (337: 8-14), there is shown in the present article, that this study does not yield a contribution to clarify the question, whether the use of inhaled corticosteroids is associated with the development of cataracts. The conclusions of the study are revealed to lead to results contradicting known risk factors.

Counteracting the negative effects of rapeseed and rapeseed press cake in pig diets

Rapeseed and rapeseed press cake were tested in four long-term experiments with a total of ninety-eight pigs. Rapeseed contained 20 and rapeseed press cake 19 mmol glucosinolates/kg DM. The proportion of the tested rapeseed products in feed amounted to 0 (control), 50, 100 and 150 g/kg diet. Moist-heat-treated rapeseed and rapeseed press cake with an extremely low glucosinolate content were also given at 150 g/kg diet. Each dietary rapeseed product level was given with 125 or 250 microgram supplementary I/kg diet. Reduced feed intake and growth retardation were found in groups receiving 150 g rapeseed products/kg diet; in the case of rapeseed the impairments were significant. Rapeseed products > or = 100g/kg diet increased the thyroid weight and decreased the serum thyroxine (T4) concentration. Higher I dosage brought the serum T4 concentration to the level of the control group and retarded thyroid enlargement. Intake of rapeseed products lowered the I content of the thyroid; however, there was no significant difference between groups given 0.9 mmol glucosinolates/kg diet and those receiving three times as much. Degrading glucosinolates by moisture and heat prevented feed intake depression and growth retardation. In the case of treated rapeseed the decreased serum T4 concentration and increased thyroid weight persisted, indicating formation of some antithyroid compounds due to myrosinase (EC 3.2.3.1) activation. A maximal glucosinolate content of 2 mmol/kg diet and additional I application are a prerequisite for using rapeseed products in pig feeding.

Total digestion of silicate containing matrices (plants, soil, sludges) using a pressure ashing device with PFA-vessels

A digestion procedure for silicate containing matrices like soil, sludge, etc. by using a commercially available pressure ashing device (Seif-Aufschlubetatechnik, Germany) with PFA (perfluoroalkoxy) sample vessels is described at the results for different matrix- and trace elements in different suitable certified standard reference materials. The advantages of this technique compared with the use of Teflon(R)-(PTFE, polytetrafluoroethylene) vessels and the open treatment in Pt-crucibles will be discussed.

Mutations in the anticodon stem affect removal of introns from pre-tRNA in Saccharomyces cerevisiae

To evaluate the role of exon domains in tRNA splicing, the anti-codon stem of proline pre-tRNAUGG from Saccharomyces cerevisiae was altered by site-directed mutagenesis of the suf8 gene. Sixteen alleles were constructed that encode mutant pre-tRNAs containing all possible base combinations in the last base pair of the anticodon stem adjacent to the anticodon loop (positions 31 and 39). The altered pre-tRNAs were screened by using an in vitro endonucleolytic cleavage assay to determine whether perturbations in secondary structure affect the intron excision reaction. The pre-tRNAs were cleaved efficiently whenever secondary structure in the anticodon stem was maintained through standard base pairing or G.U interactions. However, most of the pre-tRNAs with disrupted secondary structure were poor substrates for intron excision. We also determined the extent to which the suf8 alleles produce functional products in vivo. Each allele was integrated in one to three copies into a yeast chromosome or introduced on a high-copy-number plasmid by transformation. The formation of a functional product was assayed by the ability of each allele to suppress the +1 frameshift mutation his4-713 through four-base codon reading, as shown previously for the SUF8-1 suppressor allele. We found that alleles containing any standard base pair or G.U pair at position 31/39 in the anticodon stem failed to suppress his4-713. We could not assess in vivo splicing with these alleles because the tRNA products, even if they are made, would be expected to read a normal triplet rather than a quadruplet codon. However, all of the alleles that contained a disrupted base pair at position 31/ 39 in the anticodon stem altered the structure of the tRNA in a manner that caused frameshift suppression. Suppression indicated that splicing must have occurred to some extent in vivo even though most of the suppression alleles produced pre-tRNAs that were cleaved with low efficiency or not at all in vitro. These results have important implications for the interpretation of in vitro cleavage assays in general and for the potential use of suppressors to select mutations that affects tRNA splicing.

Enzymatic approaches to probing of RNA secondary and tertiary structure

To make strong statements about possible tertiary structure or the relative stability of regions of secondary structure, the structure-probing experiments must go further than single-hit reactions. Some elements of the environment of the RNA molecule must be altered systematically. Knowledge of the effects of ions or other interacting factors on the activity or physical parameters (e.g., NMR and melting cooperativity) of the RNA help in experimental design. For example, the copious work on tRNA(Phe) compared the crystal and solution structures and allowed the direct correlation of Mg2+ stabilization of the tertiary structure of that molecule. Figure 3 demonstrates that pre-tRNA(Leu-3) responds to Mg2+ depletion in the same manner as detected by the appearance of highly sensitive RNase cleavage sites in the D and T psi C loops. Similar experiments titrating polyamine concentrations suggested that secondary structure was more efficiently stabilized by polyamines than by Mg2+. The variation of Mg2+ concentrations has been used to gain additional information about other RNA structures. Others have used protein-RNA interactions to approach the question of the functional structure of a RNA (for examples, see Ref. 3). Thus, the ideal parameters to choose would be those known to affect the function of the RNA. The variation of Mg2+ and polyamine concentrations would minimally suggest regions of greater or lesser secondary or tertiary structure stability.

Splicing of a yeast proline tRNA containing a novel suppressor mutation in the anticodon stem

The intron-containing proline tRNAUGG genes in Saccharomyces cerevisiae can mutate to suppress +1 frameshift mutations in proline codons via a G to U base substitution mutation at position 39. The mutation alters the 3' splice junction and disrupts the bottom base-pair of the anticodon stem which presumably allows the tRNA to read a four-base codon. In order to understand the mechanism of suppression and to study the splicing of suppressor pre-tRNA, we determined the sequences of the mature wild-type and mutant suppressor gene products in vivo and analyzed splicing of the corresponding pre-tRNAs in vitro. We show that a novel tRNA isolated from suppressor strains is the product of frameshift suppressor genes. Sequence analysis indicated that suppressor pre-tRNA is spliced at the same sites as wild-type pre-tRNA. The tRNA therefore contains a four-base anticodon stem and nine-base anticodon loop. Analysis of suppressor pre-tRNA in vitro revealed that endonuclease cleavage at the 3' splice junction occurred with reduced efficiency compared to wild-type. In addition, reduced accumulation of mature suppressor tRNA was observed in a combined cleavage and ligation reaction. These results suggest that cleavage at the 3' splice junction is inefficient but not abolished. The novel tRNA from suppressor strains was shown to be the functional agent of suppression by deleting the intron from a suppressor gene. The tRNA produced in vivo from this gene is identical to that of the product of an intron+ gene, indicating that the intron is not required for proper base modification. The product of the intron- gene is a more efficient suppressor than the product of an intron+ gene. One interpretation of this result is that inefficient splicing in vivo may be limiting the steady-state level of mature suppressor tRNA.

Stable-isotope methodology in the bioavailability study of 17 alpha-methyltestosterone using gas chromatography-mass spectrometry

The application of a stable-isotope coadministration technique for estimating the relative bioavailability of 17 alpha-methyltestosterone is described. Eight healthy male subjects were administered orally a single 10-mg 17 alpha-methyltestosterone tablet together with a 10-mg 17 alpha-methyltestosterone-d3 solution. The serum concentrations of 17 alpha-methyltestosterone and 17 alpha-methyltestosterone-d3 were determined by gas chromatography-mass spectrometry with selected ion monitoring using 17 alpha-methyltestosterone-d6 as an internal standard. The extent of absorption from the tablet formulation was comparable to that from the oral solution. The stable-isotope methodology was compared with the conventional cross-over method for evaluating the bioavailability of 17 alpha-methyltestosterone.

Identification and quantification of 6 beta-hydroxydexamethasone as a major urinary metabolite of dexamethasone in man

Identification of 6 beta-hydroxydexamethasone as a major urinary metabolite of dexamethasone in man has been accomplished by nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry. Mass fragmentographic measurements revealed that more than 30% of the intravenously or orally administered dexamethasone dose was excreted in the 24-h urine as 6 beta-hydroxydexamethasone, while only a small fraction of the dose was excreted as unchanged dexamethasone and its glucuronic acid conjugate.

Influence of dioctyl sodium sulfosuccinate on the absorption of tetracycline

A pilot bioavailability study was carried out to evaluate the drug interaction and influence of dioctyl sodium sulfosuccinate (DS) on the absorption/bioavailability of tetracycline. Three tetracycline products--a fast dissolving capsule, a slow dissolving capsule and a suspension, were used in the study. DS was administered 30 minutes before tetracycline administration; and on -3, -2 and -1 day in the evening before tetracycline administration. Frequent urine samples were collected up to 48 hours and analyzed by a microbiological method. Although not statistically significant in this small study, the results suggest that there is a reduction in tetracycline bioavailability due to DS. The indiscriminate use of surface active agents to increase the dissolution rate of solid oral dosage forms in the belief that the resulting increased dissolution improves product bioavailability must be questioned.

Determination of dexamethasone in human plasma and urine by electron-impact mass spectrometry

A gas chromatographic-electron-impact mass spectrometric method for the determination of dexamethasone in biological fluids has been developed. Quantitation by isotopedilution mass spectrometry was carried out by selected-ion monitoring on the molecular ions of the tetra(trimethylsilyl) derivative of dexamethasone and of dexamethasone M+9 (m/z 680 and 689, respectively). The sensitivity, specificity, precision and accuracy of the method were demonstrated to be satisfactory for application to pharmacokinetic and bioavailability studies of dexamethasone after administration of a therapeutic dose.

Frameshift suppressor mutations outside the anticodon in yeast proline tRNAs containing an intervening sequence

Extragenic suppressors of +1 frameshift mutations in proline codons map in genes encoding two major proline tRNA isoacceptors. We have shown previously that one isoacceptor encoded by the SUF2 gene (chromosome 3) contains no intervening sequence. SUF2 suppressor mutations result from the base insertion of a G within a 3'-GGA-5' anticodon, allowing the tRNA to read a 4-base code word. In this communication we describe suppressor mutations in genes encoding a second proline tRNA isoacceptor (wild-type anticodon 3'-GGU-5') that result in a novel mechanism for translation of a 4-base genetic code word. The genes that encode this isoacceptor include SUF7 (chromosome 13), SUF8 (chromosome 8), trn1 (chromosome 1), and at least two additional unmapped genes, all of which contain an intervening sequence. We show that suppressor mutations in the SUF7 and SUF8 genes result in G-to-U base substitutions at position 39 that disrupted the normal G . C base pairing in the last base pair of the anticodon stem adjacent to the anticodon loop. These anticodon stem mutations might alter the size of the anticodon loop and permit the use of a 3'-GGGU-5' sequence within the loop to read 4-base proline codons. Uncertainty regarding the exact structure of the mature suppressor tRNAs results from the possibility that anticodon stem mutations might affect sites of intervening sequence removal. The possible role of the intervening sequence in the generation of mature suppressor tRNA is discussed. Besides an analysis of suppressor tRNA genes, we have extended previous observations of the apparent relationship between tRNA genes and repetitive delta sequences found as solo elements or in association with the transposable element TY1. Hybridization studies and a computer analysis of the DNA sequence surrounding the SUF7 gene revealed two incomplete, inverted delta sequences that form a stem and loop structure located 165 base pairs from the 5' end of the tRNA gene. In addition, sequences beginning 164 base pairs from the 5' end of the trn1 gene also exhibit partial homology to delta. These observations provide further evidence for a nonrandom association between tRNA genes and delta sequences.

Transfer RNA splicing in Saccharomyces cerevisiae. Secondary and tertiary structures of the substrates

Secondary and tertiary structures of four yeast tRNA precursors that contain introns have been elucidated using limited digestion with a variety of single-strand- and double-strand-specific nucleases. The pre-tRNAs, representing the variety of intron sizes and potential structures, were: pre-tRNALeuCAA, pre-tRNALeuUAG, pre-tRNAIleUAU, and pre-tRNAPro-4UGG. Conventional tRNA cloverleaf structure is maintained in these precursors except that the anticodon loop is interrupted by the intron. The intron contains a sequence which is complementary to a portion of the anticodon loop and allows the formation of a double helix often extending the anticodon stem. The 5' and 3' splicing cleavage sites are located at either end of this helix and are single-stranded. The intron is the most sensitive region to nuclease cleavage, suggesting that it is on the surface of the molecule and available for interaction with the splicing endonuclease. Absence of Mg2+ or spermidine renders the dihydrouridine and T psi C loops of these precursors highly sensitive to nuclease digestion. These ionic effects mimic those observed for tRNAPhe and suggest that the tRNA portion of these precursors has native tRNA structure. We propose consensus secondary and tertiary structures which may be of significance to eventual understanding of the mechanism of yeast tRNA splicing.

Transfer RNA splicing in Saccharomyces cerevisiae: defining the substrates

The primary sequences of all the tRNA precursors which contain intervening sequences and which accumulate in the Saccharomyces cerevisiae rnal mutant are presented. A combination of DNA and RNA sequence analysis has led to elucidation of the primary sequence of four hitherto uncharacterized precursors. The location of the intervening sequence has in all cases been unambiguously determined by analysis of the intermediates in the splicing reaction. Secondary structures based upon the tRNA cloverleaf are shown for all the tRNA precursors and discussed with respect to common recognition by the yeast splicing endonuclease.

Preliminary observations on dissolution and bioavailability of triamterene-hydrochlorothiazide combination products

The dissolution profiles of two brands of triamterene-hydrochlorothiazide (TRM-HCT) combination tablets and two brands of TRM-HCT combination capsules were studied using the USP paddle method at 100 rev min-1 in acid medium (0.1N). The tablets represent two products marketed in Germany, whereas the capsules represent the approved innovator's product and an unapproved generic product. The tablets dissolved almost 100 per cent in 15 min whereas the capsules dissolved less than 25 per cent in 60 min. A pilot bioavailability study was carried out in four normal healthy male volunteers. Urine samples were collected over a 48 h period and analysed for TRM, its major metabolite TRM-sulfate, and HCT using HPLC methods. The dissolution characteristics of TRM can be associated with the total drug excretion (absorption) of the product. On the other hand, the excretion (absorption) of HCT was independent of dissolution characteristics of the products. However, in TRM-HCT combination product, there appears to be a 50 per cent reduction in HCT excretion (absorption) when compared to the reported excretion (absorption) from a marketed single-entity product.

Introduction of plasma indomethacin level monitoring and evaluation of an effective threshold level in very low birth weight infants with symptomatic patent ductus arteriosus

First results are described of individually tailored indomethacin dose rates employing on-line drug level monitoring for pharmacologically induced ductal constriction in very low birth weight infants with symptomatic patent ductus arteriosus (sPDA). In addition prolonged indomethacin therapy was introduced. From our data it appears that the effective threshold indomethacin level for the induction of ductus constriction has to be about 1000 ng/ml 10 h postdosing, while ductus closure can be maintained with a dose rate that exceeds a plasma level of 500 ng/ml for at least 1 week. These maintenance levels were also effective in completely suppressing the urinary metabolite excretion rates of PGI2 and PGE2, which are potential mediators of ductal relaxation. On-line indomethacin level monitoring appears to be practically essential for prolonged indomethacin therapy to overcome the marked variation of indomethacin disposition in preterm infants with sPDA.

Stereospecific determination of D-thyroxin and L-thyroxin in serum

A new method for separate determination of D-thyroxin and L-thyroxin in the serum was applied to study the response of serum levels of these isomers and of radioimmunologically determined total T3, total T4, free T4 and TSH upon administration of 2, 4 and 6 mg of a highly purified D-thyroxin preparation in six male patients with diffuse nontoxic goiter. D- and L-thyroxin are determined separately following extraction of the hormone from the serum and formation of diastereomeric dipeptides. The separation and final determination are accomplished by means of ion-pair chromatography on reversed-phase columns using an iodine-selective catalytic detector. A significant decrease in TSH takes place during the 3-days observation period. The values of D-T4, total T3 and free T4 are highest 4 hours after administration of the tablets and get to be to initial values after 24 hours. L-T4 shows no significant change. A direct suppressive effect of D-T4 on the pituitary gland may therefore be assumed as the cause of the suppression of TSH secretion.

[Investigations concerning the mechanism of contrast damage. The significance lipophilia (author's transl)]

The damaging action on vascular endothelia of meglumin iothalamate and of meglumin ioxitalamate was tested on the rat aorta. Ioxitalamate was significantly better tolerated than iothalamate. The octanol-water-partition coefficient of various contrast media was evaluated by assessing the iodine content of the octanol phase after mixing. The coefficients found were about 100 fold lower than the coefficients computed by Levitan and Rapoport. The significance of the octanol-water-partition coefficient for endothelial injuries caused by contrast media is disputed.