Coaxial stacking of helixes enhances binding of oligoribonucleotides and improves predictions of RNA folding

An RNA model system consisting of an oligomer binding to a 4-nt overhang at the 5' end of a hairpin stem provides thermodynamic parameters for helix-helix interfaces. In a sequence-dependent manner, oligomers bind up to 1000-fold more tightly adjacent to the hairpin stem than predicted for binding to a free tetramer at 37 degrees C. For the interface (/) in [formula: see text] additional free energy change, delta delta G 37 degrees, for binding is roughly the nearest-neighbor delta G 37 degrees for propagation of an uninterrupted helix of equivalent sequence, CGGC. When X and Z are omitted, the delta delta 37 degrees is even more favorable by approximately 1 kcal/mol (1 cal = 4.184J). On average, predictions of 11 RNA secondary structures improve from 67 to 74% accuracy by inclusion of similar stacking contributions.

Protein-dependent translocation of aminophospholipids and asymmetric transbilayer distribution of phospholipids in the plasma membrane of ram sperm cells

We have investigated the transbilayer movement of phospholipids in the plasma membrane of ram sperm cells using spin- and fluorescence-labeled lipid analogues. After incorporation into the outer leaflet, phosphatidylcholine (PC) and sphingomyelin (SM) moved slowly to the inner cytoplasmic leaflet, whereas phosphatidylserine (PS) and phosphatidylethanolamine (PE) rapidly disappeared from the exoplasmic monolayer. Variation of the initial velocity of the relocation kinetics vs the amount of analogue incorporated into the membrane suggests a saturability of the transbilayer movement of aminophospholipids. ATP depletion or pretreatment with N-ethylmaleimide of ram sperm cells reduced the fast inward motion of PS and PE, indicating a protein-mediated aminophospholipid translocation. The results suggest for the plasma membrane of ram sperm cells the presence of an aminophospholipid translocase and an asymmetric transversal lipid distribution with aminophospholipids preferentially located in the inner leaflet and choline-containing phospholipids in the outer leaflet. The relevance of the transversal segregation of phospholipids for membrane fusion processes occurring during fertilization is discussed.

[Circadian aspects of acetylsalicylic acid induced injury and protective effect of ranitidine on the the upper gastrointestinal tract]

Circadian Aspects of Acetylsalicylic Acid Induced Injury and Protective Effect of Ranitidine on the Upper Gastrointestinal Tract. In a randomised parallel double-blind study the gastric and duodenal effects of 300 mg acetylsalicylic acid (ASA, CAS 50-78-2) daily in the presence and absence of 150 mg ranitidine (Zantic, CAS 66357-35-5) daily was evaluated in 32 healthy volunteers undergoing upper gastrointestinal endoscopy. Drugs were taken over a period of 7 days either at 8 a.m. (n = 16) or at 8 p.m. (n = 16). Endoscopic controls were performed at entry and repeated after 7 days of treatment. At entry both groups showed comparable mucosal damages: 8 a.m. group: ASA/placebo 0.8 +/- 0.1 (stomach) and 0.1 +/- 0.1 (duodenum): ASA/ranitidine 1.0 +/- 0.0 (stomach) and 0.07 +/- 0.06 (duodenum). 8 p.m. group: ASA/placebo 0.9 +/- 0.06 (stomach) and 0.1 +/- 0.09 (duodenum). ASA/ranitidine 0.8 +/- 0.08 (stomach) and 0.07 +/- 0.06 (duodenum). After 7 days of treatment the lesions score increased in the ASA/Placebo group in the 8 a.m. group to 9.1 +/- 1.1 (stomach) and 2.7 +/- 1.0 (duodenum), and in the 8 p.m. group to 10.9 +/- 1.1 (stomach) and to 3.9 +/- 0.9 duodenum). The corresponding values in the ASA/ranitidine group were 2.6 +/- 0.8 (stomach) and 0.2 +/- 0.08 (duodenum) (8 a.m.) and 4.8 +/- 0.8 (stomach) and 0.3 +/- 0.1 (duodenum) (8 p.m.). There was no statistical difference between the morning- and the evening dose of ASA. In addition, ranitidine protection was also time-independent.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of ibuprofen lysinate and acetylsalicylic acid on gastric and duodenal mucosa. Randomized single-blind placebo-controlled endoscopic study in healthy volunteers

Acetylsalicylic acid (ASA, CAS 50-78-2) and ibuprofen (IB) are commonly used over-the-counter drugs for short-term treatment of pain of different origin. Ibuprofen lysinate (IBL, CAS 57469-76-8) is a water soluble form of ibuprofen for rapid absorption. This single blind, randomized, controlled study compared the incidence and severity of irritation of gastric and duodenal mucosa in normal healthy subjects (n = 45) following administration of IBL (Dolormin) 800 mg/d, ASA 2000 mg/d or placebo for 3 consecutive days. Gastric and duodenal mucosal injury were assessed endoscopically using a severity scale of 0-4 for mucosal erosions and mucosal hemorrhages. Mean gastric hemorrhage and erosion scores for ASA and IBL were significantly higher than those for placebo. In addition, ASA was found to be significantly more irritating to gastric mucosa than IBL, in both the incidence and severity of gastric erosions. No duodenal hemorrhages were detected in this study. The incidence of duodenal erosions was significantly higher in the ASA group (64%) than in both the IBL (6%) and placebo groups (0%) which were not significantly different. Only one subject (in the placebo group) reported an adverse experience (mild headache) during the study. The data suggest that both active treatments are more injurious to the gastric mucosa than placebo when given for 3 days to normal healthy volunteers, but that IBL 800 mg/d is significantly less injurious to the gastric and duodenal mucosa than ASA 2000 mg/d.

Effect of exercise supplementation during adenosine infusion on hyperemic blood flow and flow reserve

Physical stress might modulate myocardial blood flow in near-maximally dilated coronary arteries by increasing coronary perfusion pressure, myocardial contractility, and heart rate. The net effect of these changes on hyperemic blood flows has not yet been defined in humans. To quantify the effect of physical exercise on pharmacologically induced hyperemia, myocardial blood flow was measured in 11 healthy volunteers. Measurements were performed with positron emission tomographic imaging with nitrogen-13 ammonia at rest, during intravenous (i.v.) adenosine administration (140 micrograms.kg-1.min-1 over 6 minutes), and during i.v. adenosine administration plus supine bicycle exercise with a maximal workload of 125 W. Myocardial blood flow was quantified by using a previously validated graphic analysis. Heart rate, systolic blood pressure, rate-pressure product, and mean aortic blood pressures were significantly higher during combined physical and pharmacologic stress than during pharmacologic stress alone. However, myocardial blood flow decreased from 2.6 +/- 0.4 to 2.2 +/- 0.4 ml.min-1.gm-1 with the addition of physical stress (p < 0.05). This decline was associated with a significant increase in coronary vascular resistance (35 +/- 6 vs 52 +/- 13 mm Hg.ml-1.gm.min; p < 0.05). Accordingly, myocardial flow reserve declined, from 5.0 +/- 0.9 to 4.3 +/- 1.0, with exercise supplementation (p < 0.05). Exercise in addition to pharmacologic stress increases coronary vascular resistance and thus significantly decreases hyperemic myocardial blood flow and flow reserve. This decrease results most likely from an increase in extravascular restrictive forces caused by higher ventricular pressures and contractility during physical stress.

Human papillomavirus DNA in oral squamous cell carcinomas and normal mucosa

Human papillomavirus (HPV) infections in oral carcinomas and normal oral mucosa were studied by consensus primer screening and typing for HPV types 6/11, 16 and 18 DNA. After polymerase chain reaction (PCR) the DNA species of interest were identified by Southern blot hybridization with digoxigenin-labeled oligonucleotide probes. Frozen tissue and scrapings were equally suitable for HPV testing and yielded high HPV detection rates in carcinomas. By comparison, HPV analysis of paraffin-embedded material was much less efficient. HPV were demonstrated in 61.5% (16/26) of oral squamous cell carcinomas, high risk HPV 16 and 18 being the preferential types. The frequency of HPV detection in non-neoplastic mucosa of tumor patients decreased clearly with increasing distance from the tumor (range 26.9-3.8%) suggesting focal HPV infections. In contrast, normal buccal mucosa of a group of healthy volunteers contained HPV DNA only in 1% (1/97).

On the validity of lipid dequenching assays for estimating virus fusion kinetics

Octadecylrhodamine (R18) has often been used to measure membrane fusion of enveloped viruses by fluorescence dequenching. In order to see whether non-specific R18 exchange between non-fused membranes occurs we have measured fusion of influenza virus with erythrocyte membranes by utilizing dequenching of the non-exchangeable lipid analogue N-(lissamine-rhodamine B-sulfonyl)diacylphosphatidylethanolamine (N-Rh-PE). Rather low concentration of N-Rh-PE (< 0.1 mol%) were required to assess fusion since self-quenching in the influenza virus membrane was more efficient in comparison to R18. For both markers we observed the same kinetics as well as the same extent of fluorescence dequenching upon triggering low pH-induced fusion. Non-specific marker transfer was not observed. Haemolysis was not affected by either type of fluorophore. Our results confirm that R18 is a valuable tool to investigate membrane fusion of enveloped viruses in a quantitative manner. Differences in the efficiency of self-quenching of both markers are discussed.

Incorporation of phospholipid analogues into the plasma membrane affects ATP-induced vesiculation of human erythrocyte ghosts

The influence of various spin-labelled phospholipid analogues on the ATP-dependent vesiculation of human erythrocyte ghosts at 37 degrees C was investigated by monitoring the acetylcholinesterase activity. After incorporation of analogues into the outer leaflet a decline of endocytic vesiculation was observed. However, suppression was arrested after about 20 min when ghosts have been labelled with a phosphatidylserine analogue known to redistribute rapidly to the inner leaflet. These data suggest that vesiculation of erythrocyte ghosts is affected by differential expansion of the inner and outer leaflet.

Short report: long-term management of peptic ulcer disease with ranitidine in Germany

One hundred and twenty-five patients with duodenal ulcer disease were given continuous ranitidine therapy after initial acute healing. Cumulative remission rates indicated that 95% of patients were ulcer-free after 1 year, 89% at 2 years, 81% at 3 years, 70% at 4 years and 60% at 5 and 6 years. Nine patients had a second recurrence after healing of the first. No patient developed an ulcer complication. These results support the view that long-term continuous ranitidine therapy prevents ulcer recurrence and complications.

[p53 alterations and HPV status in oral squamous cell carcinomas]

Immunohistochemical examination of p53 protein accumulation, analysis of the p53 gene using amplification of the exons 5-8 followed by TGGE, and PCR based HPV typing were carried out on 40 oral squamous cell carcinomas. 28 of 40 oral carcinomas (70%) contained DNA of the oncogenic HPV types 16 and 18. A p53 accumulation was present in 20 of 37 tumors (54%). Mutations of the p53 gene were detected in 15 of 39 carcinomas (38%). 15 of 20 oral carcinomas with abnormal p53 expression and 11/15 tumors with mutations of the p53 gene were HPV positive. Our results demonstrate a frequent occurrence of p53 abnormalities in HPV positive oral squamous cell carcinomas. This pattern is divergent from HPV related genital carcinomas and could reflect differences in the etiology of squamous cell carcinomas of different sites.

Rapid determination of the transbilayer distribution of NBD-phospholipids in erythrocyte membranes with dithionite

The assessment of the transverse distribution and mobility of NBD-labelled phospholipid analogues in biological membranes by selective chemical destruction of fluorescent label in the outer monolayer with dithionite has been investigated using resealed erythrocyte ghosts as a model system. The distribution of those analogues can be determined in < 30 s directly in the cell suspension provided the permeation of dithionite across the membrane is suppressed. The results were compared with data on translocation of either NBD- or spin-labelled phospholipid analogues obtained with the technique of back exchange to BSA. It is shown that the passage of dithionite can be mediated by anion-transport systems such as band 3 which is inhibited by DIDS. Appropriate conditions for the applicability of the assay were elucidated also using resealed ghosts having fluorescent NBD-taurine in the intracellular lumen. The application of the assay to measure fast translocation processes, e.g. those mediated by the aminophospholipid translocase, is described.

Nizatidine in therapy and prevention of non-steroidal anti-inflammatory drug-induced gastroduodenal ulcer in rheumatic patients

Two hundred and sixty-nine patients with various rheumatic disorders who had been treated with non-steroidal anti-inflammatory drugs (NSAID) for at least 3 weeks were enrolled in this randomized double-blind multicentre trial. Entry criteria were the presence of an ulcer in the gastric and/or duodenal mucosa (> 3 mm and < 20 mm in diameter) and dyspeptic symptoms. The patients were treated with 150 mg nizatidine nocte (n = 86), 2 x 150 mg/d (n = 93) and 2 x 300 mg/d (n = 90) nizatidine. All patients continued to take their original NSAID medication. The three nizatidine groups were well matched with respect to important patient characteristics. After 8 weeks of treatment more than 90% of gastric and duodenal ulcers (DU) had healed under all three nizatidine dosages. There was a tendency to higher healing rates in the case of gastric ulcers after 4 weeks following the higher dose of nizatidine. Erosion, in the stomach and duodenum as well as oesophagitis, improved to a similar degree with all nizatidine doses. There were similar improvements in clinical symptoms such as epigastric pain, heartburn etc. Consumption of additional antacids were similar in all three groups. In the subsequent prevention trial, 237/221 patients were followed for 3/6 months. In addition to their continued antirheumatic medication 116/107 received nizatidine 150 mg nocte and 121/114 patients 2 x 150 mg nizatidine daily. The cumulative relapse rates within 6 months averaged 5.5% in the low and 1.8% in the high dose group (NS). The safety of nizatidine was assessed as good in both the therapeutic and the preventive trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Transmembrane mobility and distribution of phospholipids in the membrane of mouse beta-thalassaemic red blood cells

Using spin-labelled lipid analogues, the transmembrane mobility and distribution of phospholipids in normal and beta-thalassaemic murine red blood cells were investigated. The velocities of spin-labelled phosphatidylserine (PS*) and spin-labelled phosphatidylethanolamine (PE*) active transport into the inner leaflet were not significantly different between normal and pathological cells. The stationary distribution of PE* in thalassaemic erythrocytes (79.5 +/- 2.0% inside) differed from that of control cells (91.1 +/- 1.6% inside), while that of PS* was unaffected. In thalassaemic cells the passive diffusion of spin-labelled phosphatidylcholine (PC*) was accelerated 4-fold and its stationary distribution was shifted to 34.5 +/- 2.3% inside compared to 19.5 +/- 1.6% in control cells. Spin-labelled sphingomyelin (SM*), which showed no inward movement in normal cells, diffused partially towards the inner leaflet of thalassaemic erythrocyte membranes. These results indicate that modifications of the transverse lipid organisation in beta-thalassaemic red blood cells are due to changes in passive diffusion movements, and not to changes in aminophospholipid translocase activity.

[Circadian dependency of ibuprofen gastropathy and the protective effect of ranitidine. An endoscopic, controlled double-blind pilot study]

Circadian Dependency of Ibuprofen Gastropathy and Protective Effect of Ranitidine/An endoscopic, controlled double-blind pilot study. In a randomized parallel double-blind study, the gastric and duodenal effects of 600 mg S(+)-ibuprofen (CAS 15687-27-1) daily in the presence and absence of 300 mg ranitidine (CAS 66357-35-5) was evaluated in 20 healthy volunteers undergoing upper GI-endoscopy. Drugs were taken over a period of 7 days either at 8 a.m. (n = 10) or at 8 p.m. (n = 10). Endoscopic controls were performed at entry and repeated after 7 days of treatment. A damage score according to Lanza et al. was used. At entry both groups showed comparable mucosal damages. 8 a.m.-group: ibuprofen/placebo (stomach) 0.9 +/- 0.1 and 0.0 +/- 0.0 (duodenum); ibuprofen/ranitidine 0.8 +/- 0.1 (stomach) and 0.1 +/- 0.1 (duodenum). 8 p.m.-group: ibuprofen/placebo 0.9 +/- 0.1 (stomach) and 0.2 +/- 0.1 (duodenum); ibuprofen/ranitidine 0.9 +/- 0.1 (stomach) and 0.1 +/- 0.1 (duodenum). After 7 days of treatment the lesion score increased in the ibuprofen/placebo-group in the 8 a.m.-group to 3.2 +/- 1.2 (stomach) and to 0.7 +/- 0.5 (duodenum), and in the 8 p.m.-group to 8.4 +/- 1.9 (stomach) and to 2.9 +/- 1.2 (duodenum). The corresponding values in the ibuprofen/ranitidine-group were 1.8 +/- 0.8 (stomach) and 0.1 +/- 0.1 (duodenum) (8 a.m.-group) as well as 5.1 +/- 1.4 (stomach) and 0.1 +/- 0.1 (duodenum) (8 p.m.-group). The difference between the morning and the evening dose of ibuprofen as well as ranitidine protection reached statistical significance when the corresponding data were pooled (p < 0.05). Our data suggest that the gastrolesive effects of S(+)-ibuprofen are dependent of the time of drug ingestion; protection by ranitidine, however, was time-independent.

Early neuroleptic intervention in schizophrenia: are prodromal symptoms valid predictors of relapse?

All recently completed controlled two-year studies on intermittent, early neuroleptic intervention treatment have failed to compare favourably with studies on maintenance treatment concerning relapse prevention. The reason for this failure is still unclear. Therefore the implicit, but as yet unproven, hypothesis that a relapse can be predicted from prodromal symptoms was tested from the perspective of our German multicentre study. Results demonstrate that this is not the case. Possible reasons for and clinical implications of this negative finding are discussed.

[Cryopreservation of embryos in the in vitro fertilization/embryo transfer program]

An ultra-rapid method for cryopreservation of human embryos, using 1,2-propane-diol, was developed. 280 spare embryos obtained in the IVF program were frozen by this method. 91 embryos were thawed and 68 of them (74.7%) survived the procedure with more than half the blastomeres intact. 65 embryos were transferred in 28 cycles. Two pregnancies developed (7.1%), one of which ended by the birth of a healthy girl (the first birth after transfer of a frozen/thawed embryo in the Czech Republic). The other pregnancy is ongoing.

[Circadian aspects of diclofenac gastroduodenopathy and the protective effect of roxatidine]

The gastrointestinal side-effect profile of non-steroidal anti-inflammatory drugs should follow a circadian rhythm. In a randomized, parallel, double-blind study the gastric duodenal effects of 100 mg diclofenac retard daily in the presence and absence of 150 mg roxatidine was evaluated in 20 healthy volunteers undergoing upper GI-endoscopy. Drugs were taken over a period of 14 days either at 8 a.m. (n = 10) or at 8 p.m. (n = 10). Endoscopic controls were performed at entry and repeated after 14 days of treatment. A damaging score according to Lanza et al. was used. At entry both groups showed comparable mucosal damages: 8 a.m.-group: placebo 0.9 +/- 0.1 (+SEM), roxatidine 0.9 +/- 0.1; 8 p.m.-group: placebo 1.0 +/- 0.0, roxatidine 0.9 +/- 0.1. After 14 days of treatment the lesion score increased in the diclofenac retard/placebo-group in the 8 a.m.-group to 7.6 +/- 1.9 and in the 8 p.m.-group to 7.2 +/- 1.1. The corresponding values in the diclofenac/roxatidine-group were 2.1 +/- 0.9 (8 a.m.-group) and 1.4 +/- 0.4 (8 p.m.-group). This protection afforded by roxatidine was significant when compared with placebo (p < 0.05). Our data suggest that the gastrolesive effects of diclofenac retard are independent of the time of drug ingestion; in addition protection by roxatidine was also time-independent.

[A comparison of the gastroduodenal tolerance of ticlopidine and acetylsalicylic acid]

Changes in the gastroduodenal mucosa caused by 250 mg ticlopidine twice daily (group 1; n = 12) or 300 mg aspirin daily (group 2; n = 12) were compared in a randomized double-blind trial of 24 healthy men, aged 20 to 35 years. An oesophago-gastroduodenoscopy was performed before and after either drug had been taken for 7 days. Results were tabulated according to a uniform scoring system (normal mucosa, erythema, petechiae, erosions, ulcer, and blood in the lumen). Both groups had identical scores at the start of the trial (group 1: 0.9 +/- 0.1; group 2: 0.8 +/- 0.1). After the seven days, the score in group 2 had risen to 9.7 +/- 1.5 (median 9.0), while it had hardly changed in group 1 (1.7 +/- 0.5; median 1.0), a statistically significant difference (P < 0.05). The data indicate that ticlopidine is better tolerated by the gastroduodenal mucosa than low dosage aspirin.

Mathematical modelling of lipid transbilayer movement in the human erythrocyte plasma membrane

A model is presented to simulate transverse lipid movement in the human erythrocyte membrane. The model is based on a system of differential equations describing the time-dependence of phospholipid redistribution and the steady state distribution between the inner and outer membrane monolayer. It takes into account several mechanisms of translocation: (i) ATP-dependent transport via the aminophospholipid translocase; (ii) protein-mediated facilitated and (iii) carrier independent transbilayer diffusion. A reasonable modelling of the known lipid asymmetry could only be achieved by introducing mechanism (iii). We have called this pathway the compensatory flux, which is proportional to the gradient of phospholipids between both membrane leaflets. Using realistic model parameters, the model allows the calculation of the transbilayer motion and distribution of endogenous phospholipids of the human erythrocyte membrane for several biologically relevant conditions. Moreover, the model can also be applied to experiments usually performed to assess phospholipid redistribution in biological membranes. Thus, it is possible to simulate transbilayer motion of exogenously added phospholipid analogues in erythrocyte membranes. Those experiments have been carried out here in parallel using spin labeled lipid analogues. The general application of this model to other membrane systems is outlined.

Influence of age and hemodynamics on myocardial blood flow and flow reserve

BACKGROUND

Aging is associated with changes of the systolic blood pressure that may increase cardiac work and myocardial blood flow at rest and reduce the myocardial flow reserve. This might be misinterpreted as age-related impairment of the coronary vasodilator capacity.

METHODS AND RESULTS

Myocardial blood flow was quantified at rest and after administration of intravenous dipyridamole in 40 healthy volunteers (12 women and 28 men) with 13N-ammonia and positron emission tomography. Eighteen of the normal subjects were less than and 22 were older than 50 years (31 +/- 9 versus 64 +/- 9 years). The resting rate-pressure product was lower in the younger than in the older subjects (6895 +/- 1070 versus 8634 +/- 1890; P < 0.01). Myocardial blood flow at rest averaged 0.76 +/- 0.17 mL.min-1.g-1 in the younger volunteers and 0.92 +/- 0.25 mL.min-1.g-1 in the older volunteers (P < 0.05). Hyperemic blood flows did not differ between younger and older subjects (3.0 +/- 0.8 versus 2.7 +/- 0.6 mL.min-1.g-1; P = NS); however, minimal coronary resistance was higher in the older subjects. Corrected for indexes of coronary driving pressure, hyperemic flow was lower in older than in younger normal subjects. The higher resting blood flows combined with similar hyperemic flows resulted in a lower myocardial flow reserve in the older than in the younger normal subjects (4.1 +/- 0.9 versus 3.0 +/- 0.70; P < 0.0001). The flow reserve was more closely correlated with resting than with hyperemic blood flows.

CONCLUSIONS

Aging does not alter significantly dipyridamole-induced hyperemic flows; although coronary vascular resistance after dipyridamole was somewhat increased in older subjects. The gradual decline of the myocardial blood flow reserve correlates with an age-related increase of baseline myocardial work and blood flow. These findings suggest that the reduced flow reserve with age is primarily due to increased cardiac work and blood flow at rest rather than to an abnormal vasodilator capacity.

Synergism and antagonism between N-methyl-N'-nitro-N-nitroso-guanidine and 9-aminoacridine in mutation induction in Escherichia coli K12

When bacteria were treated simultaneously with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and low concentrations of 9-aminoacridine (9AA), the yield of frameshift mutations was much greater than that expected on the basis of independent action of both mutagens. In combination with a high concentration of 9AA, however, MNNG had an antagonistic effect upon the induction of frameshift mutations. There was no synergistic interaction between the two mutagens in bacteria in which the adaptive response to methylating agents had been induced. 9AA not only induced frameshift mutations, but also caused a small increase in reversions of a nonsense (ochre) mutation and, in combination with low MNNG concentrations, it had a small synergistic effect.