A noncognate aminoacyl-tRNA synthetase that may resolve a missing link in protein evolution

Efforts to delineate the advent of many enzymes essential to protein translation are often limited by the fact that the modern genetic code evolved before divergence of the tree of life. Glutaminyl-tRNA synthetase (GlnRS) is one noteworthy exception to the universality of the translation apparatus. In eukaryotes and some bacteria, this enzyme is essential for the biosynthesis of Gln-tRNAGln, an obligate intermediate in translation. GlnRS is absent, however, in archaea, and most bacteria, organelles, and chloroplasts. Phylogenetic analyses predict that GlnRS arose from glutamyl-tRNA synthetase (GluRS), via gene duplication with subsequent evolution of specificity. A pertinent question to ask is whether, in the advent of GlnRS, a transient GluRS-like intermediate could have been retained in an extant organism. Here, we report the discovery of an essential GluRS-like enzyme (GluRS2), which coexists with another GluRS (GluRS1) in Helicobacter pylori. We show that GluRS2's primary role is to generate Glu-tRNAGln, not Glu-tRNAGlu. Thus, GluRS2 appears to be a transient GluRS-like ancestor of GlnRS and can be defined as a GluGlnRS.     

Epidermal langerhans cell depletion after artificial ultraviolet B irradiation of human skin in vivo: apoptosis versus migration

Ultraviolet B radiation can suppress cellular immunity. One of the mechanisms related to this immunosuppression is the disappearance of Langerhans cells from the epidermis. The aim of this study was to establish the mechanism of ultraviolet B-induced Langerhans cell disappearance in healthy individuals. The two most likely mechanisms for Langerhans cell disappearance are apoptosis and migration. Apoptosis was assessed in vivo by exposing buttock skin of 10 healthy volunteers to six minimal erythema doses of ultraviolet B. Only very few apoptotic Langerhans cells could be observed in sections from the ultraviolet B-exposed skin. Migration of Langerhans cells cannot be established in skin sections and suction blisters were therefore raised in an attempt to trap migrating Langerhans cells in the sub-basal membrane blister fluid. Blisters were raised on the flexor side of the lower arm of 30 healthy volunteers at several time points after exposure of the skin to six minimal erythema doses of ultraviolet B. Blister fluid was collected and blister roofs were removed to check for Langerhans cell disappearance. Langerhans cells were detected in the blister fluid of the ultraviolet B-exposed skin and not of the unexposed skin. The number of Langerhans cells in the blister fluid peaked at about 18 h after ultraviolet exposure, which coincided with the largest depletion of Langerhans cells in the blister roof. A fraction (20-30%) of the Langerhans cells in the blister fluid stained positive for DNA damage (cyclobutyl pyrimidine dimers), showing that they originated from the epidermis. Ultraviolet B-induced Langerhans cell disappearance appears to be mainly attributable to migration.     

In vivo animal functional MRI: improved image quality with a body-adapted mold

PURPOSE: To reduce functional magnetic resonance imaging (fMRI) susceptibility distortion at the air/tissue interphase in animal experiments. MATERIALS AND METHODS: We investigated the applicability of a body-adaptable flexible mold consisting of a fast-setting alginate. This technique was implemented for subcutaneous growing tumors in rats and for the brains of monkeys. RESULTS: The T(2)*-weighted gradient-echo, echo-planar imaging (GE-EPI) data obtained with the body-adapted mold showed a reduction of susceptibility artifacts and improved image quality. With both rat tumor and monkey brain, an optimized match with the anatomical T(1) images was possible. CONCLUSION: The present mold methodology is a rapid, easy, and inexpensive way to reduce magnetic susceptibility during animal GE-EPI.     

Effect of radiologic contrast media on cell volume regulatory mechanisms in human red blood cells

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate cell volume regulation in human red blood cells (RBCs) after incubation in solutions of three contrast media: iohexol (830 mOsm), ioxaglate (520 mOsm), and iodixanol (300 mOsm). MATERIALS AND METHODS: Whole blood sampled from six healthy subjects was exposed to Ringer solutions containing 25% or 5% vol/vol iohexol (final osmolality, 440 or 340 mOsm, respectively), ioxaglate (final osmolality, 395 or 335 mOsm, respectively), iodixanol (final osmolality, 330 or 315 mOsm, respectively), or NaCl (control solutions with the same osmolality as that of the contrast media). In some experiments, control RBCs were subjected to a hyposmotic solution (100 mOsm). RBC volumes were obtained with a Coulter counter. RESULTS: The RBCs showed normal regulatory cell shrinkage after hyposmotically induced swelling. All 25% vol/vol contrast material solutions and their control solutions induced RBC shrinkage (range, 6% +/- 1 [standard error] to 22% +/- 3). The same was true for cells exposed to 5% vol/vol contrast material (range, 4% +/- 1 to 7% +/- 1). The shrinkage phase was followed by cell swelling (10% +/- 2 to 20% +/- 2 for 25% contrast material and their control solutions and 8% +/- 1 to 15% +/- 2 for 5% contrast material and their control solutions). No contrast material-exposed RBCs increased their volumes to the level reached with their control solutions. CONCLUSION: RBCs exposed to hyperosmotic iohexol, ioxaglate, or iodixanol solutions shrank and then swelled. The degree of shrinkage and subsequent swelling could not be explained simply with the osmolality of the test solutions. Physicochemical properties of the contrast media must be involved, putatively affecting electrolyte fluxes over the RBC membrane. Possible targets of these effects are the K+/Cl- symporter, K+ channels, and the Na+/K+/Cl- symporter.     

Phase 1 study to identify tumour hypoxia in patients with head and neck cancer using technetium-99m BRU 59-21

The aim of this study was to assess the safety and biodistribution of technetium-99m BRU 59-21, a novel radioactively labelled 2-nitro-imidazole hypoxic marker, in head and neck cancer patients and to correlate uptake with pimonidazole staining. (99m)Tc-BRU 59-21 was administered intravenously (mean dose 824 MBq, range 780-857 MBq) to ten head and neck cancer patients scheduled for primary surgery, and whole-body images and SPET scans were then obtained. Uptake of radioactivity in the regions of interest was determined and tumour to normal tissue ratios were calculated after correlative evaluation with MRI/CT. Twelve to 16 h before surgery (up to 2 weeks after the scan), patients received pimonidazole intravenously. Tumour sections were stained immunohistochemically for pimonidazole binding. No serious adverse events were reported. In five patients there were ten adverse events, which were mild in intensity and resolved completely without intervention. Uptake of (99m)Tc-BRU 59-21 was observed in eight of the ten primary tumours. Tumour to normal tissue ratios on the SPET scans for primary tumour and lymph nodes increased from 1.8 (range 0.9-2.7) to 2.1 (range 0.8-3.7) between 30 min and 3 h post injection. Tumour to normal tissue ratios in the primary tumour were significantly correlated with pimonidazole staining for SPET scans performed 30 min and 3 h post injection ( P=0.016 and P=0.037, respectively). When primary tumour and involved lymph nodes were considered in conjunction, correlation between the tumour to normal tissue ratio and pimonidazole staining was observed for early ( P<0.001) but not for late SPET scans ( P=0.076). However, late scans showed better tumour delineation than early scans. Administration of (99m)Tc-BRU 59-21 in head and neck cancer patients appears to be safe and feasible. Uptake and retention in tumour tissue was observed, suggestive of tumour hypoxia, and this was supported by correlations with staining for the hypoxic marker pimonidazole.     

The Effect of Brochures and Audiotape on Efficacy and Tolerability of Venlafaxine in Depressed Outpatients: A Single-Blind Parallel Study in General Practice

OBJECTIVE: The possible positive effects of brochures and an audiotape containing information on efficacy and tolerance on side effects, dropout rate, and clinical outcome of treatment with venlafaxine were studied in 1048 depressed outpatients (as clinically judged by the general practitioner; 740 women and 308 men), aged 18 to 85 years. METHOD: The study was of a single-blind, parallel-group design. All 4 groups were verbally informed: one group received only verbal information, a second group additionally received brochures, a third group additionally received information on audiotape, and a fourth group additionally received brochures and information on audiotape. There were 5 study visits, the first at baseline (week 0), followed by a visit at weeks 1, 2, 4, and 6. At each study visit, the Clinical Global Impressions scale, Zung Depression Scale, Quality of Life Scale, and State-Trait Anxiety Inventory were completed. The Patient's and Investigator's Subjective Ratings of Tolerance and Efficacy were completed at the final study visit. RESULTS: The brochures and audiotape reduced the dropout rate due to lack of efficacy (p =.01 and p =.04, respectively). In addition, the percentage of patients reporting side effects was lower in the group that received brochures than in the group that received only verbal information (p =.05). Additional information had no effect on efficacy measures. CONCLUSION: Supplying patients with education in the form of brochures and/or audiotape containing information on efficacy and tolerance of the drug reduces the dropout rate due to lack of efficacy. For the reduction of side effects, brochures in particular seem suitable. Information on audiotape or written information seems to lengthen the period that patients wait for the possible beneficial action of the medication. To reduce the dropout rate, it may be recommended that patients receive, in addition to brochures, spoken information on audiotape or compact disc.     

Radiation-induced effects on gene expression: an in vivo study on breast cancer.

BACKGROUND AND PURPOSE: Breast cancer is diagnosed worldwide in approximately one million women annually and radiation therapy is an integral part of treatment. The purpose of this study was to investigate the molecular basis underlying response to radiotherapy in breast cancer tissue. MATERIAL AND METHODS: Tumour biopsies were sampled before radiation and after 10 treatments (of 2 Gray (Gy) each) from 19 patients with breast cancer receiving radiation therapy. Gene expression microarray analyses were performed to identify in vivo radiation-responsive genes in tumours from patients diagnosed with breast cancer. The mutation status of the TP53 gene was determined by using direct sequencing. RESULTS AND CONCLUSION: Several genes involved in cell cycle regulation and DNA repair were found to be significantly induced by radiation treatment. Mutations were found in the TP53 gene in 39% of the tumours and the gene expression profiles observed seemed to be influenced by the TP53 mutation status.     

A phase I and pharmacokinetic study of ecteinascidin-743 on a daily x 5 schedule in patients with solid malignancies.

PURPOSE: The purpose of this study was to (a) assess the feasibility of administering ecteinascidin-743 (ET-743), a novel DNA minor-groove disrupting agent of marine origin, administered as a daily i.v. infusion for 5 days every 3 weeks; (b) recommend a dose for Phase II studies; (c) characterize its pharmacokinetic behavior; and (d) seek preliminary evidence of anticancer activity. EXPERIMENTAL DESIGN: Patients with advanced solid malignancies were treated with escalating doses of ET-743 as a daily 1-h i.v. infusion for 5 days every 3 weeks. Plasma and urine were sampled on both days 1 and 5 of the first course. Pharmacokinetic parameters were related to the principal toxicities. RESULTS: Forty-two patients were treated with 118 courses of ET-743 at doses ranging from 6 to 380 microg/m(2)/day. Elevations in hepatic transaminases were common at ET-743 dose levels > or =216 microg/m(2)/day, resolved rapidly, and were never dose limiting nor cumulative. Instead, hematological toxicity was the principal toxicity that precluded dose escalation. The maximum tolerated dose of ET-743 that could be administered repetitively was 325 microg/m(2)/day. Antitumor activity was noted in three patients with leiomyosarcoma and primary peritoneal and ovarian carcinomas. The pharmacokinetics of ET-743 were dose independent, and drug accumulation over the 5 days of treatment was modest, with the ratio of the area under the plasma-versus-time curve on day 5 to that on day 1 averaging 2.05. The volume of distribution at steady state was large (mean, 1037 liters/m(2)), and the mean terminal half life on day 5 was 26.81 h. CONCLUSIONS: The maximum tolerated dose of ET-743 that can be administered repetitively is 325 microg/m(2)/day daily x 5 every 3 weeks, which is recommended for disease-directed clinical trials. The acceptable toxicity profile of ET-743 on the divided-dose schedule evaluated in this trial, as well as the generally superior antitumor activity associated with divided-dose schedules in preclinical studies, provides a rationale for further evaluation of ET-743 on this administration schedule.     

Coca chewing among high altitude natives: Work and muscular efficiencies of nonhabitual chewers

The leaves of the coca plant (Erythroxylum sp.) have long been chewed by natives of the highland Andes. Folk belief is that the mild stimulant effect is indispensable as an ergogenic aid for strenuous work activities in a high altitude environment. This study explored the exercise responses of 23 nonhabitual coca chewing males who were asked to pedal a bicycle ergometer through a series of submaximal and maximal workloads both with and without coca chewing. The protocol of the exercise test was specifically designed to allow for the determination of work and muscular efficiencies during to submaximal work. The subjects showed no differences between the coca and control work protocols for VO₂max (1/min), VCO₂max (1/min), or maximal work output (watts). Further, there were no differences between coca and control work protocols in oxygen saturation (%), pulmonary ventilation (1/min), or respiratory exchange ratio (VCO₂/VO₂) at any level of work. Coca chewing caused subjects to have a higher heart rate (bpm) and lower oxygen pulse (ml/beat) for most submaximal workloads and higher ventilatory equivalents (VE/VO₂ and VE/VCO₂) above 50% of VO₂max. Although there was a tendency for higher gross efficiencies (GE) during the coca exercise test at lower relative work levels, between 30–40% of the VO₂max, this difference did not reach significance. Mean net efficiency (NE) was higher (P=0.018) at a relative work level of ～32% of the VO₂max for exercise with coca (23.2% vs. 20.8%). This difference was not apparent at any other work level. The mean delta efficiency (DE) was significantly lower (P = 0.012) for exercise with coca (26.7%) than for exercise without coca (28.2%). These efficiency differences suggest a muscle metabolic effect for coca chewing at low workloads whereby less oxygen is consumed by the muscle to perform a given work task. Howeve, given the difficulty of interpreting efficiency values, it is not entirely clear if the differences are indicative of a work performance benefit for coca chewing. © 1995 Wiley-Liss, Inc.