Study of gastric emptying using a ferromagnetic tracer.

A new ferromagnetic method for the measurement of gastric emptying is described. An inert tracer, magnesium ferrite, is added to a test meal. Its amount in the stomach is then measured at regular intervals by an external transducer using its ferromagnetic properties. The method is noninvasive and devoid of radiation exposure. The magnetic fields used are harmless. The feasibility, reliability, and reproducibility of the method are described. Gastric emptying was studied in 61 subjects. The shape of the gastric emptying curve conformed best to an exponential function. The mean half-time of gastric emptying was 49 +/- 17.4 min. In this limited series age and sex did not affect gastric emptying.     

Rules for biological regulation based on error minimization

The control of gene expression involves complex mechanisms that show large variation in design. For example, genes can be turned on either by the binding of an activator (positive control) or the unbinding of a repressor (negative control). What determines the choice of mode of control for each gene? This study proposes rules for gene regulation based on the assumption that free regulatory sites are exposed to nonspecific binding errors, whereas sites bound to their cognate regulators are protected from errors. Hence, the selected mechanisms keep the sites bound to their designated regulators for most of the time, thus minimizing fitness-reducing errors. This offers an explanation of the empirically demonstrated Savageau demand rule: Genes that are needed often in the natural environment tend to be regulated by activators, and rarely needed genes tend to be regulated by repressors; in both cases, sites are bound for most of the time, and errors are minimized. The fitness advantage of error minimization appears to be readily selectable. The present approach can also generate rules for multi-regulator systems. The error-minimization framework raises several experimentally testable hypotheses. It may also apply to other biological regulation systems, such as those involving protein-protein interactions.     

Impact of erythropoietin on the effects of irradiation under hypoxia

Purpose

Head and neck squamous cell carcinoma (HNSCC) represents an ideal model for assessing the impact of anemia and tumor hypoxia on the response to radiotherapy (RT). Various treatment strategies aimed at increasing tumor oxygenation in HNSCC patients have been studied and these studies have been fueled by evidence that hypoxia and, unexpectedly, erythropoietin (EPO), adversely affect the radiosensitivity of cells. The purpose of the present study was to experimentally examine the relationship between hypoxia, EPO, its receptor EPOR, EGFR and their effects on the survival and radiosensitivity of HNSCC cells underwent hypoxia.

Methods

We used Cal-166 head and neck cell line to investigate different cellular responses after RT given in oxic and hypoxic conditions, focusing on the role of EPO administration in cell proliferation and in regulating response to RT.

Results

Our results show that EPO do not evoke a physiologic response on EPOR-bearing tumor cells as assessed by cellular growth and proliferation. In addition, we present some indications that EPO could activate opposite signals related to proliferation, DNA repair and apoptosis. Among them, EGFR and AKT phosphorylation may play a role in radioresistance.

Conclusions

We concluded that the expression of the EPOR in Cal-166 cells does not seem essential for their growth and that administration of EPO does not affect RT efficacy.     

Resonance-induced multimodal body-size distributions in ecosystems

The size of an organism reflects its metabolic rate, growth rate, mortality, and other important characteristics; therefore, the distribution of body size is a major determinant of ecosystem structure and function. Body-size distributions often are multimodal, with several peaks of abundant sizes, and previous studies suggest that this is the outcome of niche separation: species from distinct peaks avoid competition by consuming different resources, which results in selection of different sizes in each niche. However, this cannot explain many ecosystems with several peaks competing over the same niche. Here, we suggest an alternative, generic mechanism underlying multimodal size distributions, by showing that the size-dependent tradeoff between reproduction and resource utilization entails an inherent resonance that may induce multiple peaks, all competing over the same niche. Our theory is well fitted to empirical data in various ecosystems, in which both model and measurements show a multimodal, periodically peaked distribution at larger sizes, followed by a smooth tail at smaller sizes. Moreover, we show a universal pattern of size distributions, manifested in the collapse of data from ecosystems of different scales: phytoplankton in a lake, metazoans in a stream, and arthropods in forests. The demonstrated resonance mechanism is generic, suggesting that multimodal distributions of numerous ecological characters emerge from the interplay between local competition and global migration.     

Aggression–impulsivity,mental pain,and communication difficulties in medically serious and medically non-serious suicide attempters

Background

Unbearable mental pain, depression, and hopelessness have been associated with suicidal behavior in general, while difficulties with social communication and loneliness have been associated with highly lethal suicide attempts in particular. The literature also links aggression and impulsivity with suicidal behavior but raises questions about their influence on the lethality and outcome of the suicide attempt.

Objectives

To evaluate the relative effects of aggression and impulsivity on the lethality of suicide attempts we hypothesized that impulsivity and aggression differentiate between suicide attempters and non-attempters and between medically serious and medically non-serious suicide attempters.

Method

The study group included 196 participants divided into four groups: 43 medically serious suicide attempters; 49 medically non-serious suicide attempters, 47 psychiatric patients who had never attempted suicide; and 57 healthy control subjects. Data on sociodemographic parameters, clinical history, and details of the suicide attempts were collected. Participants completed a battery of instruments for assessment of aggression–impulsivity, mental pain, and communication difficulties.

Results

The medically serious and medically non-serious suicide attempters scored significantly higher than both control groups on mental pain, depression, and hopelessness (p < .001 for all) and on anger-in, anger-out, violence, and impulsivity (p < .05 for all), with no significant difference between the two suicide attempter groups. Medically serious suicide attempters had significantly lower self-disclosure (p < .05) and more schizoid tendencies (p < .001) than the other three groups and significantly more feelings of loneliness than the medically non-serious suicide attempters and nonsuicidal psychiatric patients (p < .05). Analysis of aggression–impulsivity, mental pain, and communication variables with suicide lethality yielded significant correlations for self-disclosure, schizoid tendency, and loneliness. The interaction between mental pain and schizoid traits explained some of the variance in suicide lethality, over and above the contribution of each component alone.

Conclusions

Aggression–impulsivity and mental pain are risk factors for suicide attempts. However, only difficulties in communication differentiate medically serious from medically non-serious suicide attempters. The combination of unbearable mental pain and difficulties in communication has a magnifying effect on the risk of lethal suicidal behavior.     

Syphilis. Allgemeiner Teil

Ohne Zusammenfassung     

Gonorrhoe und deren Komplikationen

Ohne Zusammenfassung     

Variable intrinsic sensitivity of human tumor cell lines to raltitrexed (Tomudex) and folylpolyglutamate synthetase activity.

The cytotoxic effects of Tomudex (TX) were investigated on a panel of 15 human tumor cell lines expressing a spontaneous sensitivity to the tested agent. We determined the basal cellular amount of relevant cellular factors potentially related to the cytotoxic efficacy of or resistance to TX. We selected thymidylate synthase (TS) as the target for TX, basal reduced folates (RF), because RF may compete with TX for a common site on the TS molecule. We also tested folylpolyglutamate synthetase (FPGS) because this is the enzyme which transforms the drug into its active polyglutamated form. Results were as follows. There was a wide inter-cell line variability in IC50 values for TX and there were marked differences between cell lines for all tested biochemical parameters. No link was observed between basal cellular TS activity and TX cytotoxic efficacy. There was an inverse relationship between reduced folate cellular content and TX IC50 values; this relationship did not, however, reach statistical significance. The only significant relationship was found between basal cellular FPGS activity and TX IC50r = -0.56, p = 0.03. Tumor cells with a relatively high FPGS activity were more sensitive to TX cytotoxic effects and vice versa. Along with previous results which showed that acquired resistance to TX is accompanied by a decrease in FPGS activity, the present data are strongly indicative of a prominent role played by FPGS activity in the intrinsic sensitivity to TX. Means to up-regulate FPGS activity with pharmacological or tumor-specific genetic approaches are recommended so as to optimize TX antitumor activity.