Heat flows in rock cracks naturally optimize salt compositions for ribozymes.

Catalytic nucleic acids, such as ribozymes, are central to a variety of origin-of-life scenarios. Typically, they require elevated magnesium concentrations for folding and activity, but their function can be inhibited by high concentrations of monovalent salts. Here we show that geologically plausible high-sodium, low-magnesium solutions derived from leaching basalt (rock and remelted glass) inhibit ribozyme catalysis, but that this activity can be rescued by selective magnesium up-concentration by heat flow across rock fissures. In contrast to up-concentration by dehydration or freezing, this system is so far from equilibrium that it can actively alter the Mg:Na salt ratio to an extent that enables key ribozyme activities, such as self-replication and RNA extension, in otherwise challenging solution conditions. The principle demonstrated here is applicable to a broad range of salt concentrations and compositions, and, as such, highly relevant to various origin-of-life scenarios.

Repeated cures with paracetamol worsen sarcopenia in old rats with suboptimal food intake.

The availability of all amino acids is of prime importance to prevent the ageing-associated decrease in skeletal muscle mass i.e. sarcopenia. Cysteine is the precursor of sulfate and glutathione that are both utilized in the liver to detoxify paracetamol (APAP). Cysteine availability could become limiting under repeated cures with APAP, especially when food intake is suboptimal. The aim of the study was to determine whether repeated cures with APAP could worsen sarcopenia. Twenty-two-month-old male Wistar rats received 3 two-week-long cures of APAP (1% of the diet) intercalated with washout periods of two weeks (APAP group). They were compared to untreated control rats euthanatized prior to the experiment (CT group) and rats pair-fed to the APAP group (PF group). Skeletal muscle mass and protein metabolism, as well as plasma amino acids and glutathione were assessed at the end of the third cure. APAP cures reduced food intake by 33, 23 and 33 % during the successive cures leading to an overall body weight loss of 8%. APAP rats lost lean mass during the experiment (-11%). This loss tended (P = 0.09) to be higher than in the PF group (-9%). The mass of hind limb muscles and the absolute synthesis rate of muscle proteins were 13 and 17% lower in the APAP group than the PF group, respectively. Plasma free cyst(e)ine (i.e. all free forms of cysteine not bound to proteins) and glutathione were 25% lower in the APAP group than the PF group. Repeated cures with APAP worsened sarcopenia in old rats with suboptimal food intake likely as a consequence of the APAP-induced shortage in cysteine/glutathione. Clinical studies are needed to clarify the effect of repeated treatments with paracetamol on skeletal muscle mass in older persons having suboptimal or insufficient dietary intakes.

Skeletal muscle wasting occurs in adult rats under chronic treatment with paracetamol when glutathione-dependent detoxification is highly activated.

The use of glutathione (GSH) and sulfate for the detoxification of paracetamol (acetaminophen, APAP) could occur at the expense of the physiological uses of cysteine (Cys). Indeed GSH and sulfate both originate from Cys. Significant APAP-induced Cys loss could generate alterations in GSH and protein metabolisms leading to muscle wasting. The study aimed to investigate the effects of chronic treatment with APAP on whole-body and tissue homeostasis (mass, GSH, proteins, and nitrogen balance) in relation to sulfur losses through APAP-detoxification pathways. Adult male Wistar rats were fed 0% APAP, 0.5% APAP or 1% APAP diets for 17 days. APAP doses were respectively around and largely above the threshold of sulfation saturation for rats. During the last days, the rats were placed in metabolic cages in order to quantify N balance and urinary APAP metabolites. Gastrocnemius muscle mass, protein and GSH contents, N balance and plasma free cyst(e)ine were 8% (P=0.02), 7% (P=0.03), 26% (P=0.01), 37% (P=0.01), and 33% (P=0.003) lower in the 1% APAP group than in the 0% APAP group, respectively. There was no significant difference in these parameters between the 0.5% APAP group and the 0% APAP group. Muscle wasting occurred when the detoxification of APAP through the GSH-dependent pathway was highly activated. Muscle protein synthesis could have been reduced due to a shortage in Cys and/or an increase in protein degradation in response to intra-muscular oxidative stress. Hence, without dietary sulphur amino acid increase, peripheral bioavailability of Cys and muscle GSH are potential players in the control of muscle mass under chronic treatment with APAP, an analgesic medication of widespread use, especially in the elderly.

Usability of an adaptive computer assistant that improves self-care and health literacy of older adults.

OBJECTIVES: We developed an adaptive computer assistant for the supervision of diabetics' self-care, to support limiting illness and need for acute treatment, and improve health literacy. This assistant monitors self-care activities logged in the patient's electronic diary. Accordingly, it provides context-aware feedback. The objective was to evaluate whether older adults in general can make use of the computer assistant and to compare an adaptive computer assistant with a fixed one, concerning its usability and contribution to health literacy. METHODS: We conducted a laboratory experiment in the Georgia Tech Aware Home wherein 28 older adults participated in a usability evaluation of the computer assistant, while engaged in scenarios reflecting normal and health-critical situations. We evaluated the assistant on effectiveness, efficiency, satisfaction, and educational value. Finally, we studied the moderating effects of the subjects' personal characteristics. RESULTS: Logging self-care tasks and receiving feedback from the computer assistant enhanced the subjects' knowledge of diabetes. The adaptive assistant was more effective in dealing with normal and health-critical situations, and, generally, it led to more time efficiency. Subjects' personal characteristics had substantial effects on the effectiveness and efficiency of the two computer assistants. CONCLUSIONS: Older adults were able to use the adaptive computer assistant. In addition, it had a positive effect on the development of health literacy. The assistant has the potential to support older diabetics' self care while maintaining quality of life.

Virtual reality treatment versus exposure in vivo: a comparative evaluation in acrophobia.

The aim of the present study was to evaluate the effectiveness of low-budget virtual reality (VR) exposure versus exposure in vivo in a between-group design in 33 patients suffering from acrophobia. The virtual environments used in treatment were exactly copied from the real environments used in the exposure in vivo program. VR exposure was found to be as effective as exposure in vivo on anxiety and avoidance as measured with the Acrophobia Questionnaire (AQ), the Attitude Towards Heights Questionnaire (ATHQ) and the Behavioral Avoidance Test (BAT). Results were maintained up to six months follow-up. The present study shows that VR exposure can be effective with relatively cheap hardware and software on stand-alone computers currently on the market. Further studies into the effectiveness of VR exposure are recommended in other clinical groups as agoraphobics and social phobics and studies in which VR exposure is compared with more emerging virtual worlds as presented in CAVE-type systems.

Research on presence in virtual reality: a survey.

Virtual Reality (VR) is starting to be used in psychological therapy around the world. However, a thorough understanding of the reason why VR is effective and what effect it has on the human psyche is still missing. Most research on this subject is related to the concept of presence. This paper gives an up-to-date overview of research in this diverse field. It starts with the most prevailing definitions and theories on presence, most of which attribute special roles for the mental process of attention and for mental models of the virtual space. A review of the phenomena thought to be effected by presence shows that there is still a strong need for research on this subject because little conclusive evidence exists regarding the relationship between presence and phenoma such as emotional responses to virtual stimuli. An investigation shows there has been substantial research for developing methods for measuring presence and research regarding factors that contribute to presence. Knowledge of these contributing factors can play a vital role in development of new VR applications, but key knowledge elements in this area are still missing.

Virtual reality treatment in acrophobia: a comparison with exposure in vivo.

The aim of the present study was to evaluate the effectiveness of low-budget virtual reality exposure versus exposure in vivo in a within-group design in 10 individuals suffering from acrophobia. Virtual reality exposure was found to be at least as effective as exposure in vivo on anxiety and avoidance as measured with the Acrophobia Questionnaire (AQ), and even more effective on the Attitude towards Heights Questionnaire (AHQ). The present study shows that virtual reality exposure can be effective with relatively cheap hardware and software on stand-alone computers currently on the market. Further studies are recommended, in which virtual reality exposure is compared with in vivo exposure in a between-group design, thus enabling investigation of the long-term effects of virtual reality treatment.

Evaluation of a filmless radiology pilot--a preliminary report.

The development of the Multimedia Electronic Medical Record System (MEMRS) promises new opportunities to significantly reduce the routine use of film as the medium for viewing radiological medical images. The effect of this change to digital media on physician workflow and the perceived value and utility of medical images is an area of ongoing investigation. In this study we examined oncology clinicians use of medical images in a MEMRS. We conducted observational studies of clinicians during a filmless radiology pilot study in which a filmless environment was simulated but the actual film was available on request. This observational study was the first step in a comprehensive evaluation designed to elucidate the issues surrounding the implementation of a filmless radiology environment. We identified and examined several of these issues, including physician concern regarding the utility of digital images for clinical use and comparison with film, the need to address the effects of image compression with clinicians, and the workflow changes necessary to incorporate digital image use into a clinical practice.

Effects of azetidine-2-carboxylic acid on treatments of hepatoma cells with single or fractionated X-ray irradiations and on thermal radiosensitization in normal and thermotolerant cells.

The amino acid analog azetidine-2-carboxylic acid (azetidine) is a potent sensitizer to both hyperthermia and ionizing radiation. Incubation of H35 hepatoma cells with 2.5 mM azetidine before or after treatments with X-rays causes a time- and sequence-dependent enhancement of cell killing. Exposure of cells to 1-1.5 mM azetidine for 96 h in combination with repeated doses of 3 Gy X-rays at 24 h intervals causes an enhanced reduction of the surviving cell population due to both radiosensitization and an additional growth inhibition. Azetidine does not prevent the induction of thermotolerance after a heat shock. This thermotolerance proportionally reduces thermal radiosensitization but does not seem to affect azetidine radiosensitization. It is suggested that thermal radiosensitization and azetidine radiosensitization operate by different mechanisms.

NADPH-oxidase-dependent superoxide production by myocyte-derived H9c2 cells: influence of ischemia, heat shock, cycloheximide and cytochalasin D.

Extracellular oxygen radicals produced by H9c2 rat heart cells in monolayer cultures during ischemia and subsequent reoxygenation were monitored using the luminol-horseradish peroxidase-enhanced chemiluminescence technique. As expected, the photon count diminishes during ischemia but again rapidly attains normal values following reoxygenation. In the presence of superoxide dismutase, this photon emission is repressed, as is also the case in the presence of diphenylene iodonium, a specific inhibitor of NADPH-oxidase activity. Thus, the conclusion seems justified that H9c2 rat heart cells in monolayer cultures produce superoxide radicals extracellularly due to an NADPH oxidase-like action. In order to characterize this extracellular superoxide-generating system, we determined its sensitivity to increased temperatures, inhibition of protein synthesis and perturbations of cytoskeletal structures. Heat shocks result in a delayed inactivation of the NADPH oxidase activity followed by recovery, the kinetics of which depend on the imposed heat shock temperature. This inactivation is independent of protein synthesis and actin cytoskeletal structures, but the recovery of the enzyme's activity is dependent on these entities.

Is heat shock protein re-induction during tolerance related to the stressor-specific induction of heat shock proteins?

The existence of stressor-specific induction programs of heat shock proteins (hsps) leads us to analyze the possible occurrence of a stressor-specific tolerance induced by either heat shock, arsenite, or cadmium. As a measure of this tolerance re-induction of hsps was studied. In this paper, we tested whether the refractory state is either valid for each specific hsp (implying independent regulation of every member of the heat shock protein family) or extends from small subsets of the hsp-family to even larger groups of proteins (indicating a more common denominator in their regulation). (re-)induction of hsps does not seem to be regulated at the level of each individual hsp since differences in induced synthesis of hsps between two stressor conditions are not supplemented systematically upon the sequential application of the two stressors. The most notable example in this respect is hsp60. A pretreatment with cadmium, which hardly induces synthesis of this hsp, does induce a tolerance to (re)-induction by heat shock, which normally induces hsp60. This suggests the existence of a more common denominator regulating the coordinate expression of at least some hsps. From our data we conclude that the degree, but not the pattern, of hsp re-induction is influenced by the type of stressor used in the pretreatment. The pattern of hsps induced by a secondary applied stressor still shows most of its stressor-specificity and seems to be independent of any pretreatment. The possible implications of stressor-specificity are discussed.

Epidermal growth factor stimulates phosphorylation of eukaryotic initiation factor 4B, independently of protein kinase C.

We demonstrate that exposure of human epidermoid carcinoma A431 cells to epidermal growth factor (EGF) results in phosphorylation of eIF-4B within minutes after addition of EGF. The EGF-induced phosphorylation of eIF-4B is not caused by the EGF receptor tyrosine kinase itself, since no tyrosine-phosphorylated eIF-4B could be detected upon immunoprecipitation using an anti-phosphotyrosine antibody. Enhanced phosphorylation of eIF-4B was also detected upon exposure of the cells to phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC), suggesting that eIF-4B may be a substrate of PKC. However, down-regulation of PKC did not influence the EGF-induced eIF-4B phosphorylation, which indicates that eIF-4B is phosphorylated by an as yet unknown kinase, activated early in the EGF-induced signal transduction cascade.

Clinical utility of an enhanced human immunodeficiency virus type 1 p24 antigen capture assay.

The presence of p24 core antigen in the serum of individuals with human acquired immunodeficiency syndrome has been used as one of the important prognostic markers of HIV-1 infection and also as an end point in evaluating antiviral drugs and vaccines. Unfortunately the majority of p24 antigen present in serum exists as an antigen-antibody complex and is not detected with the commercial kits currently available to measure p24 antigen. In this study, we report a simple procedure utilizing treatment of serum samples with glycine buffer (pH 1.85) to dissociate antigen-antibody complexes prior to assaying for p24 antigen. A 300% increase in the number of p24-reactive samples and a 3- to 12-fold increase in the quantity of antigen detected were observed when samples were pretreated with 1.5 M glycine buffer (pH 1.85) for 1 hr. Glycine treatment of samples did not result in non-specific positive tests and samples previously shown to be reactive remained positive. In reconstruction experiments the release of antigen was found to be inversely proportional to the amount of p24 antibody present in the serum. The percentage of HIV-1-infected patients positive for p24 antigen was clearly a function of CD4 count. Forty-nine percent of patients with more than 500 CD4 cells and 100% of patients with less than 200 CD4 were p24 positive.(ABSTRACT TRUNCATED AT 250 WORDS)

Separation of translationally active mRNAs by reversed-phase ion-pair high-performance liquid chromatography.

An ion-pair high-performance liquid chromatographic method on C4 columns was developed for the separation of mRNAs. The addition of methylmercuric hydroxide markedly influenced the separation according to length of these molecules. A method is given to recover minute amounts of translatable mRNA from the organic phase. The resolution of mRNAs improved with increasing pore size of the column support.

Short-term exposure to cadmium modifies phosphorylation of gill proteins in the sea mussel.

1. Sea mussels were exposed to cadmium for short periods of time. The excised gills were incubated with radioactive orthophosphate. The gill proteins were separated by 1- and 2-dimensional gel electrophoresis and the phosphorylation state of the proteins was determined by image analysis of autoradiographs. 2. 1-Dimensional gel electrophoresis revealed that exposure of the animals to cadmium stimulated phosphorylation of the gill proteins in a cadmium concentration-dependent manner. 3. 2-Dimensional gel electrophoresis showed that cadmium differentially affected the phosphorylation of various proteins. Major alterations were observed in the basic, high mol. wt proteins and in the acidic, low mol. wt polypeptides.

Synthesis of stress proteins under normal and heat shock conditions in gill tissue of sea mussels (Mytilus edulis) after chronic exposure to cadmium.

1. Sea mussels were exposed to 16.5 micrograms Cd/1 under semi-field conditions for almost one year. The isolated gills were incubated with 35S-methionine or -cysteine. 2. Chronic exposure to cadmium neither altered the rate of amino acid incorporation nor induced expression of heat shock proteins in the gills. 3. Heat shock imposed after chronic exposure to cadmium resulted in an increased synthesis of heat shock proteins, especially those of high molecular weight. 4. Synthesis of cadmium-binding, low molecular weight proteins was observed at any point of the exposure time. Their cadmium-binding capacity and rate of synthesis, after the initial increase, remained unchanged throughout the exposure.

Autoregulation of the glomerular filtration rate and the single-nephron glomerular filtration rate despite inhibition of tubuloglomerular feedback in rats chronically volume-expanded by deoxycorticosterone acetate.

Tubuloglomerular feedback (TGF) function and autoregulation (renal blood flow RBF; glomerular filtration rate, GFR; single-nephron glomerular filtration rate, SNGFR) were examined in rats chronically treated with deoxycorticosterone acetate (DOCA) and given isotonic saline to drink. DOCA treatment depressed arterial plasma renin activity, expanded plasma volume by 25% and increased arterial blood pressure. Autoregulation of RBF and GFR was maintained in the DOCA animals above 90 mm Hg and 110 mm Hg respectively, whereby both GFR and RBF were lower than in controls. Micropuncture experiments demonstrated the absence of TGF in the DOCA animals. There was no difference between SNGFR values measured in the distal and proximal tubules, nor was there a significant response of SNGFR when loops of Henle were perfused with Ringer's solution at 20 nl/min. Loop perfusion in control rats with tubular fluid collected in DOCA rats elicited a normal TGF response, showing that TGF inhibition in the DOCA animals is due to changes in the function of the juxtaglomerular apparatus. In contrast to control rats, proximal SNGFR was perfectly autoregulated. These results suggest that TGF is not primarily responsible for autoregulation and that the vasodilatation normally resulting from acute TGF interruption is therefore compensated by some other mechanism such that RBF and GFR are lower than in controls.