The influence of affinity, efficacy, and slope factor on the estimates obtained by the receptorial responsiveness method (RRM): a computer simulation study

The receptorial responsiveness method (RRM) was proposed to characterize changes in the concentration of degradable agonists in the microenvironment of their receptors. The characterization is done by providing concentrations of a stable agonist for the same receptor that is equieffective with the change in concentration to be characterized. RRM is based on the analysis of concentration-effect (E/c) curves reflecting the simultaneous action of the degradable and the stable agonist. In the present study, we investigated whether dissimilar affinity and (or) efficacy of the coacting agonists as well as the steepness of the E/c curves influence the reliability of RRM. E/c curves were simulated based on the operational model and then analyzed with RRM. We found that dissimilarity in affinity of the coacting agonists did not affect the accuracy of RRM estimates. In contrast, accuracy of the estimation depended on the magnitude of the concentration to be assessed, the operational slope factor, and the operational efficacy ratio of the coacting agonists. However, our results suggest that proper choice of a stable agonist for a degradable one can help to ensure reliable results, since information about the change in concentration of a degradable agonist is otherwise difficult to obtain.     

A marked shift in the serotypes of pneumococci isolated from healthy children in Szeged, Hungary, over a 6-year period

Streptococcus pneumoniae is an important pathogen with significant morbidity and mortality rates worldwide, especially among children <5 years. Healthy carriers are the most important sources of pneumococcal infections, and the nasopharyngeal colonisation is the most prevalent among children attending communities such as day-care centres (DCCs). The conjugate pneumococcal vaccines (PCVs) were shown to have an impact on the colonisation, and so play an important role in inhibiting infections. In this study we compared the nasal carriage of healthy children attending DCCs in Szeged, Hungary in 2003/2004, when nobody was vaccinated, and in 2010, when already 1/5 of the children received PCV-7. Significant differences were observed in the serotype distribution, representing a marked shift from the previously widespread vaccine-types (mostly 6A or 14) to others (11A and 23F). The new serotypes showed higher antibiotic susceptibility. The bacterium exchange between children was clear from the pulsed-field gel electrophoresis (PFGE) patterns, and the circulation of certain international clones plays also a role in these dynamic changes.     

Bioenergetic analysis of isolated cerebrocortical nerve terminals on a microgram scale: spare respiratory capacity and stochastic mitochondrial failure

Pre-synaptic nerve terminals (synaptosomes) require ATP for neurotransmitter exocytosis and recovery and for ionic homeostasis, and are consequently abundantly furnished with mitochondria. Pre-synaptic mitochondrial dysfunction is implicated in a variety of neurodegenerative disorders, although there is no precise definition of the term 'dysfunction'. In this study, we test the hypothesis that partial restriction of electron transport through Complexes I and II in synaptosomes to mimic possible defects associated with Parkinson's and Huntington's diseases respectively, sensitizes individual terminals to mitochondrial depolarization under conditions of enhanced proton current utilization, even though these stresses are within the respiratory capacity of the synaptosomes when averaged over the entire population. We combine two novel techniques, firstly using a modification of a plate-based respiration and glycolysis assay that requires only microgram quantities of synaptosomal protein, and secondly developing an improved method for fluorescent imaging and statistical analysis of single synaptosomes. Conditions are defined for optimal substrate supply to the in situ mitochondria within mouse cerebrocortical synaptosomes, and the energetic demands of ion cycling and action-potential firing at the plasma membrane are additionally determined.     

Quantification of plant surface metabolites by matrix‐assisted laser desorption–ionization mass spectrometry imaging: glucosinolates on Arabidopsis thaliana leaves

The localization of metabolites on plant surfaces has been problematic because of the limitations of current methodologies. Attempts to localize glucosinolates, the sulfur‐rich defense compounds of the order Brassicales, on leaf surfaces have given many contradictory results depending on the method employed. Here we developed a matrix‐assisted laser desorption–ionization (MALDI) mass spectrometry protocol to detect surface glucosinolates on Arabidopsis thaliana leaves by applying the MALDI matrix through sublimation. Quantification was accomplished by spotting glucosinolate standards directly on the leaf surface. The A. thaliana leaf surface was found to contain approximately 15 nmol of total glucosinolate per leaf with about 50 pmol mm^?2 on abaxial (bottom) surfaces and 15–30 times less on adaxial (top) surfaces. Of the major compounds detected, 4‐methylsulfinylbutylglucosinolate, indol‐3‐ylmethylglucosinolate, and 8‐methylsulfinyloctylglucosinolate were also major components of the leaf interior, but the second most abundant glucosinolate on the surface, 4‐methylthiobutylglucosinolate, was only a trace component of the interior. Distribution on the surface was relatively uniform in contrast to the interior, where glucosinolates were distributed more abundantly in the midrib and periphery than the rest of the leaf. These results were confirmed by two other mass spectrometry‐based techniques, laser ablation electrospray ionization and liquid extraction surface analysis. The concentrations of glucosinolates on A. thaliana leaf surfaces were found to be sufficient to attract the specialist feeding lepidopterans Plutella xylostella and Pieris rapae for oviposition. The methods employed here should be easily applied to other plant species and metabolites.     

Ghrelin induces vasoconstriction in the rat coronary vasculature without altering cardiac peptide secretion

We administered ghrelin, a novel growth hormone-releasing hormone, to isolated perfused rat hearts, coronary arterioles, and cultured neonatal cardiomyocytes to determine its effects on coronary vascular tone, contractility, and natriuretic peptide secretion and gene expression. We also determined cardiac levels of ghrelin and whether the heart is a source of the circulating peptide. Ghrelin dose dependently increased coronary perfusion pressure (44 +/- 9%, P < 0.01), constricted isolated coronary arterioles (12 +/- 2%, P < 0.05), and significantly enhanced the pressure-induced myogenic tone of arterioles. These effects were blocked by diltiazem, an L-type Ca(2+) channel blocker, and bisindolylmaleimide (Bis), a protein kinase C (PKC) inhibitor. Interestingly, coinfusion of ghrelin with diltiazem completely restored myocardial contractile function that was decreased 30 +/- 3% (P < 0.01) by diltiazem alone. In contrast, combination of ghrelin with diltiazem or Bis did not significantly alter atrial natriuretic peptide (ANP) secretion, which was decreased 40% (P < 0.01) and 50% (P < 0.05) by these agents alone, respectively. Administration of ghrelin to cultured cardiomyocytes had no effect on ANP or B-type natriuretic peptide secretion or gene expression. Detectable amounts of low-molecular-weight ghrelin were present in cardiac tissue extracts but not in isolated heart perfusate. Thus we provide the first evidence that ghrelin has a coronary vasoconstrictor action that is dependent on Ca(2+) and PKC. Furthermore, the data obtained from diltiazem infusion suggest that ghrelin has a role in regulation of contractility when L-type Ca(2+) channels are blocked. Finally, the observation that immunoreactive ghrelin is found in cardiac tissue suggests the presence of a local cardiac ghrelin system.     

Pathological characteristics of esophago-respiratory fistulas of esophageal tumor origin

Esophago-respiratory fistulas, evolving as a result of esophageal tumors, are serious and lethal complications on account of the constant respiratory contamination and the inability to swallow. They can develop either as the complication of the end stage disease or sometimes even in the first stage of the malignancy. The objective was to reveal the characteristics of the disease. In a prospective single-center study in the period between 1984 and 2004, 243 fistulas were diagnosed. Their data were analyzed using multivariate analysis. The mean age of patients with fistula was 56.9 years, the male-to-female ratio was 4.3:1. The average time of the complaints was 5.2 months, while the time of manifestation of the fistula was 7.5 months. Dysphagia was diagnosed in 97.5% of the patients, fever in 36.9%, and cachexia in 59.5%, respectively. The average loss of weight was 10.4 kg and the average size of the tumor was 7.7 cm. Endoscopic intubation was performed in 176 cases. The average survival was 3.4 months. Patients with fistula were divided into two groups, where the characteristics of the disease were significantly different. Only in 66.3% was the fistula a late complication. In the other 33.7% of the cases the fistula was diagnosed in younger patients at the early stage of the disease, with a more aggressive, less differentiated histology. In these patients the weight loss, the grade of dysphagia and the size of the tumor were smaller, the possibilities of treatment were fewer, and survival were shorter.     

Study of career motivators affecting the emotional labour of health care professionals in oncology

In the course of their everyday work health care professionals (HCPs) often have to change their true feelings. The literature labels this performance as emotional labor. This article is presenting data on the characteristics of HCPs' most endangered by the negative consequences of emotional labor. Our simple choice question survey was conducted at Debrecen University Medical Healthcare Center with the help of 50 oncology HCPs volunteers. Nearly 90% of the HCPs examined change their true feelings in the course of work. It is very difficult to classify those threatened by the negative upshot of this emotional labor. Due to our research we found appalling differences of work motivation that were tightly interconnected with the respondents' emotional labor and their perceived role/emotional expectations. We succeeded in establishing three clusters and defining each cluster's characteristics. Figures suggest that only somewhat more than the half of the HCPs is authentic professional helper, and 45% of them does not or only slightly perceive the patients' demands concerning their work. Therefore, it is important that the work environment does not only assist the work of HCPs by professional means, but along emotional dimensions as well.