Standardization and Normalization of Data from Laser Ablation Inductively Coupled Plasma Mass Spectrometry

Laser ablation inductively coupled plasma mass spectrometry is a useful technique for the precise determination of major, minor and trace element distributions or isotope ratios in solid samples and biological tissue sections. However, measured ion intensities of selected mass-to-charge ratios, may vary considerably from run to run and might also underlie non-linear drift within a run. Therefore, beside the calibration of the measurement, normalization of ion intensities to a reference such as an internal standard is necessary. Other strategies use an endogenous reference element of which a homogenous distribution in the sample is assumed, or derive a more complex reference parameter from a given dataset. Generally, normalization methods depend on the experimental setup and sample material and are usually based on one or few isotopes or the total ion current. This chapter reports different normalization methods that either used a separate reference value for each data point – constituting a pixel in the isotope image – or used a constant normalization factor per measurement run. In conclusion, normalization is essential to minimize deviations of element concentrations due to measurement-related fluctuations. Normalization and definition of an area of interest are powerful tools to obtain high-contrast isotope images with absolute element concentrations

Sleep Deprivation Increases Cerebral Serotonin 2A Receptor Binding in Humans

STUDY OBJECTIVES: Serotonin and its cerebral receptors play an important role in sleep-wake regulation. The aim of the current study is to investigate the effect of 24-h total sleep deprivation on the apparent serotonin 2A receptor (5-HT(2A)R) binding capacity in the human brain to test the hypothesis that sleep deprivation induces global molecular alterations in the cortical serotonergic receptor system. DESIGN: Volunteers were tested twice with the subtype-selective radiotracer [(18)F]altanserin and positron emission tomography (PET) for imaging of 5-HT(2A)Rs at baseline and after 24 h of sleep deprivation. [(18)F]Altanserin binding potentials were analyzed in 13 neocortical regions of interest. The efficacy of sleep deprivation was assessed by questionnaires, waking electroencephalography, and cognitive performance measurements. SETTING: Sleep laboratory and neuroimaging center. PATIENTS OR PARTICIPANTS: Eighteen healthy volunteers. INTERVENTIONS: Sleep deprivation. MEASUREMENTS AND RESULTS: A total of 24 hours of sleep deprivation led to a 9.6% increase of [(18)F]altanserin binding on neocortical 5-HT(2A) receptors. Significant region-specific increases were found in the medial inferior frontal gyrus, insula, and anterior cingulate, parietal, sensomotoric, and ventrolateral prefrontal cortices. CONCLUSIONS: This study demonstrates that a single night of total sleep deprivation causes significant increases of 5-HT(2A)R binding potentials in a variety of cortical regions although the increase declines as sleep deprivation continued. It provides in vivo evidence that total sleep deprivation induces adaptive processes in the serotonergic system of the human brain. CITATION: Elmenhorst D; Kroll T; Matusch A; Bauer A. Sleep Deprivation Increases Cerebral Serotonin 2A Receptor Binding in Human

Acute ethanol application increases A1 adenosine receptor availability in the human brain

The fatiguing and sedating effects of alcohol in humans are supposed to be mediated partially by the inhibitory actions of cerebral adenosine, the main degradation product of ATP. Ethanol is known to increase extracellular adenosine several fold in the brain of rats by an increase in adenosine formation and a decrease of adenosine uptake. Interestingly, it has recently been reported that cerebral A1 adenosine receptor (A1AR) availability measured with [11C]MPDX was increased after ethanol exposure in rats. In the present pilot study we investigated the impact of acute ethanol exposure on A1AR availability in the human brain by the use of PET and the highly selective radioligand [18F]CPFPX. This method has been proved suitable for quantifying A1AR densities in the human brain. A bolus plus constant infusion for steady state quantification allows investigating acute drug interactions like the occupancy of A1AR by caffeine. In this ongoing study we administered 40 g of ethanol (corresponding to 1 L of beer, n=3) or placebo (n=1) during the steady state period of the PET experiment in healthy volunteers. Ethanol was diluted in 1 L of isotonic NaCl solution and infused intravenously between 80 and 110 min of the 140 min PET scan. Blood alcohol concentration peaked individually between 0.65 and 0.98 mg/mL 30 min after start of the infusion. Arterialized venous blood samples were collected to determine the distribution volume (VT) of [18F]CPFPX by calculating the ratio of the concentrations between tissue and plasma during steady state. The timespan of this ratio represented either baseline (60 to 80 min) or ethanol condition (120 and 140 min). The distribution volumes of various cortical and subcortical regions remained basically constant before and after placebo exposure (relative difference 3%). In contrast, distribution volumes in the ethanol group increased quickly by on average 29%. Our preliminary data exhibit for the first time a rapid increase in cerebral A1AR availability following acute intravenous ethanol application in humans

Imaging of adenosine receptors

Over the last decades adenosine receptor ligands, agonists as well as antagonists, have been developed. The requirements for compounds suitable for non-invasivein vivo imaging of adenosine receptors (radiopharmaceuticals, radiotracers) with positron emission tomography (PET) are in several aspects different from thosefor therapeutic drugs. This difference will be elucidated for radiotracers involved in human neurotransmission research.In humans theA1 adenosine receptor (A1AR) shows themost abundant distribution and highest concentrations in brain cortical and subcortical areas, whereas theA2Aadenosine receptor (A2AAR) can be found in selected regions like striatum, nucleus accumbens, olfactory tubercle. A2B adenosine receptors (A2BAR) and A3 adenosinereceptors (A3ARs) are expressed in low levels in the brain.Most of the imaging probes therefore target the A1AR and A2AAR. The talk will give an overview of currentlyused imaging probes and applications. The neuroreceptor imaging technique has been used for example to investigate physiological mechanisms of the sleep wakeregulation or pathophysiological conditions like cerebral ischemia, ethanol intoxication, epilepsy or Alzheimer’s disease in humans and animal models. Pharmacokineticanalysis of PET experiments allow additionally to investigate drug action in the human brain, like for example the impact of caffeine on A1AR availability

Divergent Effects of the Nonselective Adenosine Receptor Antagonist Caffeine in Pre-Manifest and Motor-Manifest Huntington’s Disease

There is a controversy about potentially positive or negative effects of caffeine consumption on onset and disease progression of neurodegenerative diseases such as Huntington’s Disease (HD). On the molecular level, the psychoactive drug caffeine targets in particular adenosine receptors (AR) as a nonselective antagonist. The aim of this study was to evaluate clinical effects of caffeine consumption in patients suffering from premanifest and motor-manifest HD. Data of the global observational study ENROLL-HD were used, in order to analyze the course of HD regarding symptoms onset, motor, functional, cognitive and psychiatric parameters, using cross-sectional and longitudinal data of up to three years. We split premanifest and manifest participants into two subgroups: consumers of >3 cups of caffeine (coffee, cola or black tea) per day (>375 mL) vs. subjects without caffeine consumption. Data were analyzed using ANCOVA-analyses for cross-sectional and repeated measures analysis of variance for longitudinal parameters in IBM SPSS Statistics V.28. Within n = 21,045 participants, we identified n = 1901 premanifest and n = 4072 manifest HD patients consuming >3 cups of caffeine/day vs. n = 841 premanifest and n = 2243 manifest subjects without consumption. Manifest HD patients consuming >3 cups exhibited a significantly better performance in a series of neuropsychological tests. They also showed at the median a later onset of symptoms (all p < 0.001), and, during follow-up, less motor, functional and cognitive impairments in the majority of tests (all p < 0.050). In contrast, there were no beneficial caffeine-related effects on neuropsychological performance in premanifest HD mutation carriers. They showed even worse cognitive performances in stroop color naming (SCNT) and stroop color reading (SWRT) tests (all p < 0.050) and revealed more anxiety, depression and irritability subscores in comparison to premanifest participants without caffeine consumption. Similarly, higher self-reported anxiety and irritability were observed in genotype negative/control group high dose caffeine drinkers, associated with a slightly better performance in some cognitive tasks (all p < 0.050). The analysis of the impact of caffeine consumption in the largest real-world cohort of HD mutation carriers revealed beneficial effects on neuropsychological performance as well as manifestation and course of disease in manifest HD patients while premanifest HD mutation carrier showed no neuropsychological improvements, but worse cognitive performances in some tasks and exhibited more severe signs of psychiatric impairment. Our data point to state-related psychomotor-stimulant effects of caffeine in HD that might be related to regulatory effects at cerebral adenosine receptors. Further studies are required to validate findings, exclude potential other unknown biasing factors such as physical activity, pharmacological interventions, gender differences or chronic habitual influences and test for dosage related effects

Bioimaging mass spectrometry of trace elements – recent advance and applications of LA-ICP-MS: A review

Bioimaging using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) offers the capability to quantify trace elements and isotopes within tissue sections with a spatial resolution ranging about 10–100 μm. Distribution analysis adds to clarifying basic questions of biomedical research and enables bioaccumulation and bioavailability studies for ecological and toxicological risk assessment in humans, animals and plants. Major application fields of mass spectrometry imaging (MSI) and metallomics have been in brain and cancer research, animal model validation, drug development and plant science. Here we give an overview of latest achievements in methods and applications. Recent improvements in ablation systems, operation and cell design enabled progressively better spatial resolutions down to 1 μm. Meanwhile, a body of research has accumulated covering basic principles of the element architecture in animals and plants that could consistently be reproduced by several laboratories such as the distribution of Fe, Cu, Zn in rodent brain. Several studies investigated the distribution and delivery of metallo-drugs in animals. Hyper-accumulating plants and pollution indicator organisms have been the key topics in environmental science. Increasingly, larger series of samples are analyzed, may it be in the frame of comparisons between intervention and control groups, of time kinetics or of three-dimensional atlas approaches