In-vitro and in-vivo assessment of nirmatrelvir penetration into CSF, central nervous system cells, tissues, and peripheral blood mononuclear cells.

Three years after SARS-CoV-2 emerged as a global infectious threat, the virus has become endemic. The neurological complications such as depression, anxiety, and other CNS complications after COVID-19 disease are increasing. The brain, and CSF have been shown as viral reservoirs for SARS-CoV-2, yielding a potential hypothesis for CNS effects. Thus, we investigated the CNS pharmacology of orally dosed nirmatrelvir/ritonavir (NMR/RTV). Using both an in vitro and an in vivo rodent model, we investigated CNS penetration and potential pharmacodynamic activity of NMR. Through pharmacokinetic modeling, we estimated the median CSF penetration of NMR to be low at 18.11% of plasma with very low accumulation in rodent brain tissue. Based on the multiples of the 90% maximal effective concentration (EC90) for SARS-CoV-2, NMR concentrations in the CSF and brain do not achieve an exposure level similar to that of plasma. A median of only 16% of all the predicted CSF concentrations in rats were > 3xEC90 (unadjusted for protein binding). This may have implications for viral persistence and neurologic post-acute sequelae of COVID-19 if increased NMR penetration in the CNS leads to decreased CNS viral loads and decreased CNS inflammation.

The Cytokine CX3CL1 and ADAMs/MMPs in Concerted Cross-Talk Influencing Neurodegenerative Diseases.

Neuroinflammation plays a fundamental role in the development and progression of neurodegenerative diseases. It could therefore be said that neuroinflammation in neurodegenerative pathologies is not a consequence but a cause of them and could represent a therapeutic target of neuronal degeneration. CX3CL1 and several proteases (ADAMs/MMPs) are strongly involved in the inflammatory pathways of these neurodegenerative pathologies with multiple effects. On the one hand, ADAMs have neuroprotective and anti-apoptotic effects; on the other hand, they target cytokines and chemokines, thus causing inflammatory processes and, consequently, neurodegeneration. CX3CL1 itself is a cytokine substrate for the ADAM, ADAM17, which cleaves and releases it in a soluble isoform (sCX3CL1). CX3CL1, as an adhesion molecule, on the one hand, plays an inhibiting role in the pro-inflammatory response in the central nervous system (CNS) and shows neuroprotective effects by binding its membrane receptor (CX3CR1) present into microglia cells and maintaining them in a quiescent state; on the other hand, the sCX3CL1 isoform seems to promote neurodegeneration. In this review, the dual roles of CX3CL1 and ADAMs/MMPs in different neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (MH), and multiple sclerosis (MS), are investigated.

An economic approach to energy budgets: HOW many resources should living organisms spare?

Ramsey's economic theory of saving (RTS) estimates how much of its commodities a nation should save to safeguard the well-being of future generations. Since RTS retains many attractive qualities such as simplicity, strength, breadth and generality, here we ask if it would be useful to investigate biophysical issues. Specifically, we focus on a biological topic that lends itself as a backdrop for the study of the imbalance between intake and expenditure, i.e., the evaluation of the multicellular living organisms' energetic requirements and constraints. Our problem is to find at each time the optimum distribution and the right balance of the cellular energy budget between consumption and storage: how much must a living organism spare to increase its chances of survival over long periods? To give an operational example, we discuss the ATP requirements in the central nervous system during the spontaneous and the evoked activity of the brain, showing that the experimentally detected values of energetic expenditure during neural computations match well with the estimations provided by RTS. Suggesting how to find the optimum allocation of the available energy between expenditure and saving at each time, RTS approaches to biological energy budgets may have a wide range of experimental applications, such as: a) optimization of the long-term survival chances of either immortalized cell cultures, or beneficial bacterial colonies and exogenous probiotic mixtures; b) eradication of detrimental biofilms, such as, e.g., heart valves' Streptococcus colonies; c) novel anti-stress and anti-ageing strategies.

Assessment of children in the autistic spectrum disorder that carry the Thr92Ala-DIO2 polymorphism.

INTRODUCTION: A polymorphism in the type 2 deiodinase (Thr92Ala-DIO2) gene has been associated with behavioral and cognitive dysfunction as well as neurodegeneration and oxidative stress in the central nervous system. OBJECTIVE: To test whether the minor allele (Ala92) frequency (MAF) is increased in children in the autism spectrum disorder (ASD), and whether carriers of the minor allele exhibit more severe symptoms and/or worse adaptive behavior. STUDY DESIGN: ASD children were evaluated at baseline and yearly throughout the study by psychologists using the following tools: autism behavior checklist, Vineland Adaptative Behaviour Scales II, non-verbal intelligence test SON-R 21/2-7, SON-R 6-40, Weschler scale for intelligence, and autism treatment evaluation checklist. SETTINGS: Academic outpatient mental health facility in Sao Paulo, Brazil. PARTICIPANTS: ASD boys and girls younger than 18 years of age. 132 consecutive ASD children, mostly boys (~ 80%); ~ 50% was classified as verbal. Exclusion criteria were coexistence of sensory and/or physical impairment, or any associated genetic syndromes. RESULTS: Median follow-up was for an uninterrupted period of 937 days (139-1375 days), which did not vary significantly among the genotypes. The MAF was 47% in ASD patients vs. 51% in a local reference population with similar ethnic background; the clinical severity and progression were not affected by the minor allele. Carriers of the minor allele exhibited higher adaptive behavior in the domains "daily living skills" and "communication", which correlated positively with the dose of the minor allele. CONCLUSION: The MAF is not different in ASD children, but carriers of the Thr92Ala-DIO2 polymorphism exhibited higher adaptive behavior.

Assessment of ionizable, zwitterionic oximes as reactivating antidotal agents for organophosphate exposure.

Since the development in the 1950's of 2-PAM (Pralidoxime), an antidote that reactivates organophosphate conjugated acetylcholinesterase in target tissues upon pesticide or nerve agent exposure, improvements in antidotal therapy have largely involved congeneric pyridinium aldoximes. Despite seminal advances in detailing the structures of the cholinesterases as the primary target site, progress with small molecule antidotes has yet to define a superior agent. Two major limitations are immediately apparent. The first is the impacted space within the active center gorge, particularly when the active center serine at its base is conjugated with an organophosphate. The reactivating nucleophile will have to negotiate the tortuous gorge terrain to access the phosphorus atom with its most nucleophilic form or ionization state, the oximate anion. A second limitation stems from the antidote crossing the blood-brain barrier sufficiently rapidly, since it is well documented that central acetylcholinesterase inhibition gives rise to cardiovascular and respiratory compromise. The associated hypoxia then leads to a sequelae of events, including poor perfusion of the brain and periphery, along with muscle fasciculation, tremors and eventually seizures. We consider both the barriers confronting and further achievements necessary to enhance efficacy of antidotes.

Simultaneous assessment of central and peripheral chemoreflex regulation of muscle sympathetic nerve activity and ventilation in healthy young men.

KEY POINTS: Central chemoreceptor stimulation, by hypercapnia (acidosis), and peripheral, by hypoxia plus hypercapnia, evoke reflex increases in ventilation and sympathetic outflow. The assumption that central or peripheral chemoreceptor-mediated sympathetic activation elicited when PCO2 increases parallels concurrent ventilatory responses is unproven. Applying a modified rebreathing protocol that equilibrates central and peripheral chemoreceptor PCO2 whilst clamping O2 tension at either hypoxic or hyperoxic concentrations, the independent ventilatory and muscle sympathetic stimulus-response properties of the central and peripheral chemoreflexes were quantified and compared in young men. The novel findings were that ventilatory and sympathetic responses to central and peripheral chemoreflex stimulation are initiated at similar PCO2 recruitment thresholds but individual specific sympathetic responsiveness cannot be predicted from the ventilatory sensitivities of either chemoreceptor reflex. Such findings in young men, if replicated in heart failure or hypertension, should temper present enthusiasm for trials targeting the peripheral chemoreflex based solely on ventilatory responsiveness to non-specific chemoreceptor stimulation. ABSTRACT: In humans, stimulation of peripheral or central chemoreceptor reflexes is assumed to evoke equivalent ventilatory and sympathetic responses. We evaluated whether central or peripheral chemoreceptor-mediated sympathetic activation elicited by increases in CO2 tension ( PCO2 ) parallels concurrent ventilatory responses. Twelve healthy young men performed a modified rebreathing protocol designed to equilibrate central and peripheral chemoreceptor PCO2 tensions with end-tidal PCO2 ( PETCO2 ) at two isoxic end-tidal PO2 ( PETO2 ) such that central responses can be segregated, by hyperoxia, from the net response (hypoxia minus hyperoxia). Ventilation and muscle sympathetic nerve activity (MSNA) were recorded continuously during rebreathing at isoxic PETO2 of 150 and 50 mmHg. During rebreathing, the PETCO2 values at which ventilation (L min-1 ) and total MSNA (units) began to rise were identified ( PETCO2 recruitment thresholds) and their slopes above the recruitment threshold were determined (sensitivity). The central chemoreflex recruitment threshold for ventilation (46 ± 3 mmHg) and MSNA (45 ± 4 mmHg) did not differ (P = 0.55) and slopes were 2.3 ± 0.9 L min-1  mmHg-1 and 2.1 ± 1.5 units mmHg-1 , respectively. The peripheral chemoreflex recruitment thresholds, at 41 ± 3 mmHg for both ventilation and MSNA were lower (P < 0.05) compared to the central chemoreflex recruitment thresholds. Peripheral chemoreflex sensitivity was 1.7 ± 0.1 L min-1  mmHg-1 for ventilation and 2.9 ± 2.6 units mmHg-1 for MSNA. There was no relationship between the ventilatory and MSNA sensitivity for either the central (r2  = 0.01, P = 0.76) or peripheral (r2  = 0.01, P = 0.73) chemoreflex. In healthy young men, ventilatory and sympathetic responses to central and peripheral chemoreceptor reflex stimulation are initiated at similar PETCO2 recruitment thresholds but individual ventilatory responsiveness does not predict sympathetic sensitivities of either chemoreflex.

A minireview of effects of green tea on energy expenditure.

In recent years, individuals have begun to tend more frequently to some natural and herbal products to be used alone or as a combination with diet and exercise for ensuring the weight loss. Green tea is the leading one of these products. In some studies, it is reported that the green tea causes an increase in thermogenesis and substrate with fat oxidation by affecting on the sympathetic nervous system. It is reported that green tea has two main components that are associated with energy expenditure. One of them is caffeine and the other is catechin content. Each of these two components has an impact on energy mechanism separately. In this minireview article, mechanisms of action and effects of caffeine and catechin, which are found in green tea composition, on energy expenditure are assessed.

Establishment of a Human Neuronal Network Assessment System by Using a Human Neuron/Astrocyte Co-Culture Derived from Fetal Neural Stem/Progenitor Cells.

Using human cell models mimicking the central nervous system (CNS) provides a better understanding of the human CNS, and it is a key strategy to improve success rates in CNS drug development. In the CNS, neurons function as networks in which astrocytes play important roles. Thus, an assessment system of neuronal network functions in a co-culture of human neurons and astrocytes has potential to accelerate CNS drug development. We previously demonstrated that human hippocampus-derived neural stem/progenitor cells (HIP-009 cells) were a novel tool to obtain human neurons and astrocytes in the same culture. In this study, we applied HIP-009 cells to a multielectrode array (MEA) system to detect neuronal signals as neuronal network functions. We observed spontaneous firings of HIP-009 neurons, and validated functional formation of neuronal networks pharmacologically. By using this assay system, we investigated effects of several reference compounds, including agonists and antagonists of glutamate and γ-aminobutyric acid receptors, and sodium, potassium, and calcium channels, on neuronal network functions using firing and burst numbers, and synchrony as readouts. These results indicate that the HIP-009/MEA assay system is applicable to the pharmacological assessment of drug candidates affecting synaptic functions for CNS drug development.

Assessment of oxidative stress biomarkers - neuroprostanes and dihomo-isoprostanes - in the urine of elite triathletes after two weeks of moderate-altitude training.

This randomized and controlled trial investigated whether the increase in elite training at different altitudes altered the oxidative stress biomarkers of the nervous system. This is the first study to investigate four F4-neuroprostanes (F4-NeuroPs) and four F2-dihomo-isoprostanes (F2-dihomo-IsoPs) quantified in 24-h urine. The quantification was carried out by ultra high pressure liquid chromatography-triple quadrupole-tandem mass spectrometry (UHPLC-QqQ-MS/MS). Sixteen elite triathletes agreed to participate in the project. They were randomized in two groups, a group submitted to altitude training (AT, n = 8) and a group submitted to sea level training (SLT) (n = 8), with a control group (Cg) of non-athletes (n = 8). After the experimental period, the AT group triathletes gave significant data: 17-epi-17-F2t-dihomo-IsoP (from 5.2 ± 1.4 µg/mL 24 h(-1) to 6.6 ± 0.6 µg/mL 24 h(-1)), ent-7(RS)-7-F2t-dihomo-IsoP (from 6.6 ± 1.7 µg/mL 24 h(-1) to 8.6 ± 0.9 µg/mL 24 h(-1)), and ent-7-epi-7-F2t-dihomo-IsoP (from 8.4 ± 2.2 µg/mL 24 h(-1) to 11.3 ± 1.8 µg/mL 24 h(-1)) increased, while, of the neuronal degeneration-related compounds, only 10-epi-10-F4t-NeuroP (8.4 ± 1.7 µg/mL 24 h(-1)) and 10-F4t-NeuroP (5.2 ± 2.9 µg/mL 24 h(-1)) were detected in this group. For the Cg and SLT groups, no significant changes had occurred at the end of the two-week experimental period. Therefore, and as the main conclusion, the training at moderate altitude increased the F4-NeuroPs- and F2-dihomo-isoPs-related oxidative damage of the central nervous system compared to similar training at sea level.

Histopathological, ultrastructural, and immunohistochemical assessment of hippocampus structures of rats exposed to TCDD and high doses of tocopherol and acetylsalicylic acid.

The effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on central nervous system consists of changing expression of estrogen receptors, whereas the result of chronic inflammatory reaction caused by dioxin is occurrence of destructive changes in various organs connected with disturbed metabolism of connective tissue and damage of cells. The aim of the study was to determine the effect of dioxins on function, ultrastructure, and cytological and histological structure of hippocampus, particularly on expression of estrogen receptors in central nervous system as well as to define protective influence of tocopherol (TCP) and acetylsalicylic acid (ASA) on the decrease in activity of proinflammatory effects in central nervous system. It was shown that TCDD contributes to destructive and inflammatory changes along with demyelization of myelin sheaths and atrophy of estrogen receptors in hippocampus. Dioxin contributes to atrophy of estrogen receptors in hippocampus, in which also destructive and inflammatory changes were found along with demyelination of myelin sheaths. Histopathological and ultrastructural image of hippocampus areas in rats, in which both TCP and ASA were used, is characterized by poorly expressed degenerative changes and smaller inflammatory reactivity. Using both TCP and ASA has a protective effect on functions of central nervous system.

CREB/TRH pathway in the central nervous system regulates energy expenditure in response to deprivation of an essential amino acid.

BACKGROUND: In the central nervous system (CNS), thyrotropin-releasing hormone (TRH) has an important role in regulating energy balance. We previously showed that dietary deprivation of leucine in mice increases energy expenditure through CNS-dependent regulation. However, the involvement of central TRH in this regulation has not been reported. METHODS: Male C57J/B6 mice were maintained on a control or leucine-deficient diet for 7 days. Leucine-deprived mice were either third intracerebroventricular (i.c.v.) injected with a TRH antibody followed by intraperitoneal (i.p.) injection of triiodothyronine (T3) or i.c.v. administrated with an adenovirus of shCREB (cAMP-response element binding protein) followed by i.c.v. injection of TRH. Food intake and body weight were monitored daily. Oxygen consumption, physical activity and rectal temperature were assessed after the treatment. After being killed, the hypothalamus and the brown adipose tissue were collected and the expression of related genes and proteins related was analyzed. In other experiments, control or leucine-deficient medium incubated primary cultured neurons were either infected with adenovirus-mediated short hairpin RNA targeting extracellular signal-regulated kinases 1 and 2 (Ad-shERK1/2) or transfected with plasmid-overexpressing protein phosphatase 1 regulatory subunit 3C (PPP1R3C). RESULTS: I.c.v. administration of anti-TRH antibodies significantly reduced leucine deprivation-stimulated energy expenditure. Furthermore, the effects of i.c.v. TRH antibodies were reversed by i.p. injection of T3 during leucine deprivation. Moreover, i.c.v. injection of Ad-shCREB (adenovirus-mediated short hairpin RNA targeting CREB) significantly suppressed leucine deprivation-stimulated energy expenditure via modulation of TRH expression. Lastly, TRH expression was regulated by CREB, which was phosphorylated by ERK1/2 and dephosphorylated by PPP1R3C-containing protein Ser/Thr phosphatase type 1 (PP1) under leucine deprivation in vitro. CONCLUSIONS: Our data indicate a novel role for TRH in regulating energy expenditure via T3 during leucine deprivation. Furthermore, our findings reveal that TRH expression is activated by CREB, which is phosphorylated by ERK1/2 and dephosphorylated by PPP1R3C-containing PP1. Collectively, our studies provide novel insights into the regulation of energy homeostasis by the CNS in response to an essential amino-acid deprivation.

Pharmacological assessment of methamphetamine-induced behavioral hyperactivity mediated by dopaminergic transmission in planarian Dugesia japonica.

The freshwater planarian Dugesia japonica has a simple central nervous system (CNS) and can regenerate complete organs, even a functional brain. Recent studies demonstrated that there is a great variety of neuronal-related genes, specifically expressed in several domains of the planarian brain. We identified a planarian dat gene, named it D. japonica dopamine transporter (Djdat), and analyzed its expression and function. Both in situ hybridization and immunofluorescence revealed that localization of Djdat mRNA and protein was the same as that of D. japonica tyrosine hydroxylase (DjTH). Although, dopamine (DA) content in Djdat(RNAi) planarians was not altered, Djdat(RNAi) planarians showed increased spontaneous locomotion. The hyperactivity in the Djdat(RNAi) planarians was significantly suppressed by SCH23390 or sulpiride pretreatment, which are D1 or D2 receptor antagonists, respectively. These results suggest that planarians have a Djdat ortholog and the ability to regulate dopaminergic neurotransmission and association with spontaneous locomotion.

A nonclinical safety assessment of MnTE-2-PyP, a manganese porphyrin.

Manganese (III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-2-PyP or BMX-010; CASRN 219818-60-7) is a manganese porphyrin compound developed as a potential drug substance for use as a radioprotective and for the ex vivo treatment of cells, tissues, and organs intended for transplantation. In preparation for an investigational new drug filing, a full good laboratory practice nonclinical safety assessment was conducted in order to evaluate the safety of MnTE-2-PyP and included the performance of in vitro genotoxicity studies, local tissue tolerance evaluation, safety pharmacology core battery studies, and single- and repeat-dose intravenous (iv) toxicity studies in mice and monkeys. The MnTE-2-PyP was determined not to be genotoxic or hemolytic, did not demonstrate flocculation or elicit adverse pharmacologic effects on respiration, the central nervous system (CNS), and had limited transitory effects on the cardiovascular system only at levels well above the therapeutic target dose. The intended iv clinical solution did not cause venous irritation in rabbits. The no observed adverse effect level (NOAEL) in mice was determined to be 10 mg/kg/day after 18 consecutive days of bolus iv dosing once daily in the morning. The NOAEL in monkeys after 14 days of bolus iv dosing in the morning was determined to be 5 mg/kg/day. At doses relevant to clinical use in humans, neither study revealed any indication of any specific target organ toxicity, including the classic heme porphyrin kidney, liver, CNS, or cardiac toxicities, or manganese toxicity. Mortality seen shortly after dosing in individual animals at higher doses was not accompanied by any organ or clinical pathology indications, suggesting a functional pharmacological-mediated effect. Based on the results of these studies, a conservative safe initial starting clinical dose of 5.0 mg (0.083 mg/kg in a 60 kg adult) was proposed for the initiation of human trials. Because of patent life issues, use of MnTE-2-PyP as a transplantation aid or radioprotective agent is not currently being pursued past the preclinical stages. It serves as a model for the clinical development of this class of drugs.

Oxidative macromolecular alterations in the rat central nervous system in response to experimentally co-induced chlorpyrifos and cold stress: a comparative assessment in aging rats.

Reactive oxygen species are generated as a result of a number of physiological and pathological processes which can promote multiple forms of oxidative damage including protein oxidation, and thereby influence the function of a diverse array of cellular processes. In our previous study we have reported that co-exposure to chlorpyrifos and cold stress in aging rats markedly influence the toxic outcome as a result of oxidative stress. In the present study, key neurochemical/enzymes were measured in order to evaluate the macromolecular alterations in response to experimentally co-induced chlorpyrifos and cold stress (15 and 20°C) either concurrently or individually in vivo for 48 h in discrete regions of brain and spinal cord of different age group rats. CPF and cold stress exposure either individually or in combination substantially increased the activity/levels of protein carbonyls, AST, ALT and decreased protein thiols, DNA, RNA and total proteins in discrete regions of CNS. Overall, the effects of co-exposure were appreciably different from either of the exposures. However, synergistic-action of CPF and cold stress at 15°C showed higher dyshomeostasis in comparison with CPF and cold stress alone and together at 20°C indicating the extent of oxidative macromolecular damage in discrete regions of brain and spinal cord. Furthermore, the present study demonstrates that macromolecular oxidative damage is highly pronounced in neonates and juveniles than the young adults.

Neuronal receptor activity-modifying protein 1 promotes energy expenditure in mice.

OBJECTIVE: Receptor activity-modifying proteins (RAMPs) 1, 2, and 3 are unusual accessory proteins that dictate the binding specificity of two G protein-coupled receptors involved in energy homeostasis: calcitonin gene-related peptide (CGRP) and amylin receptors. These proteins are expressed throughout the central nervous system (CNS), including in the brain regions involved in the regulation of energy homeostasis, but the significance of CNS RAMPs in the control of energy balance remains unknown. RESEARCH DESIGN AND METHODS: To examine the functional significance of modulating neuronal RAMP1, we assessed the effect of overexpressing human RAMP1 (hRAMP1) in the CNS on body energy balance. RESULTS: Nestin/hRAMP1 transgenic mice have a remarkably decreased body weight associated with reduced fat mass and circulating leptin levels. The transgenic mice exhibited higher energy expenditure as indicated by increased oxygen consumption, body temperature, and sympathetic tone subserving brown adipose tissue (BAT). Consistent with this, the nestin/hRAMP1 transgenic mice had elevated BAT mRNA levels of peroxisome proliferator-activated receptor γ coactivator 1α and uncoupling protein 1 and 3, and these changes can be reversed by chronic blockade of sympathetic nervous system signaling. Furthermore, metabolic response to amylin was enhanced in the nestin/hRAMP1 mice whereas the response to CGRP was blunted, possibly the result of higher expression of CGRP in the CNS. CONCLUSIONS: These data demonstrate that CNS RAMP1 plays a pivotal role in the regulation of energy homeostasis by promoting energy expenditure.

Socioeconomic status moderates associations between CNS serotonin and expression of beta2-integrins CD11b and CD11c.

One of the first steps in the development of atherogenesis is adhesion of circulating monocytes to the vascular endothelium that is stimulated by beta(2)-integrins. Stress has been associated with enhanced expression of beta(2)-integrins on monocyte cell surface (Greeson et al., 2008). Central nervous system (CNS) serotonin regulates aspects of the stress response that can influence inflammatory processes that increase risk for atherosclerosis. This study examines effects of an environmental stressor (indexed by socioeconomic status (SES)) and CNS serotonin (indexed by CSF 5HIAA level), on the expression of beta(2)-integrins (CD11a, CD11b, and CD11c) on circulating monocytes in 131 volunteers. Participants completed a protocol consisting of a lumbar puncture for assessment of CSF 5HIAA levels (day 1) followed by an experimental protocol (day 2). Blood samples for the present analyses were obtained at baseline on day 2. The interaction of SES x 5HIAA was a significant predictor of levels of CD11b and CD11c expression (p=.02, and p=.05, respectively); the mean CD11b difference between Hi and Lo SES subjects was significant (p=.003) only in those with Lo levels of 5HIAA, while SES differences in CD11b among those with Mid and Hi levels of 5HIAA did not vary statistically. The pattern of findings was similar for CD11c. The present results suggest that the combination of high environmental stress and low CNS serotonin function could contribute to atherogenesis through processes that lead to increased expression of the beta(2)-integrins CD11b and CD11c on monocyte cell surfaces.

A biomathematical modeling approach to central nervous system radioligand discovery and development.

UNLABELLED: The development of a successful PET or SPECT molecular imaging probe is a complex, time-consuming, and expensive process that suffers from high attrition. To address this problem, we have developed a biomathematical modeling approach that aims to predict the in vivo performance of radioligands directly from in silico/in vitro data. METHODS: The method estimates the in vivo nondisplaceable and total uptake of a ligand in a target tissue using a standard input function and a 1-tissue-compartment model with a parsimonious parameter set (influx rate constant K(1), efflux rate constant k(2), and binding potential BP(ND)) whose values are predicted from in silico/in vitro data including lipophilicity, molecular volume, free fraction in plasma and tissue, target density, affinity, perfusion, capillary surface area, and apparent aqueous volume in plasma and tissue. The coefficient of variation of the BP(ND) (%COV[BP(ND)]) metric, derived from Monte Carlo simulations, is used to estimate the in vivo performance of candidate compounds. A total of 28 compounds for 10 targets was evaluated using our method to predict their in vivo performance and validated against measured in vivo PET data in the Yorkshire/Danish Landrace pig. RESULTS: The predicted K(1), k(2), and BP(ND) values were generally consistent with the values estimated from in vivo PET data. The model resulted in small %COV[BP(ND)] values for widely accepted good ligands such as (11)C-flumazenil (2.02%) and (11)C-raclopride (2.55%), whereas higher values resulted from poor ligands such as (11)C-(R)-PK11195 (13.34%). Of 4 candidates for the GlyT1 transporter, the model selected (11)C-GSK931145 (2.11%) as the most promising ligand, which was consistent with historical decisions made on the in vivo PET data. CONCLUSION: A biomathematical modeling approach has the potential to predict the in vivo performance of ligands from in silico/in vitro data and aid in the development of molecular imaging probes.

Synaptic vesicle endocytosis: get two for the price of one?

Tight coupling between synaptic vesicle exocytosis and endocytosis is critical for the maintenance of neurotransmission. In this issue of Neuron, Zhu et al. reveal a surprising facet of this coupling by showing that, at low frequencies, fusion of a single vesicle leads to retrieval of two vesicles with dissimilar attributes.

Assessment of ghrelin, GHS-R, GH, and neurohormones in human fetal pituitary glands and central nervous system: an immunohistochemical study.

The aim of this work was evaluation of expression of ghrelin and GHS-R1a receptor in somatotrops and in neuronal cells of brain tissue in the process of human fetal ontogenesis. Relations were also looked for between GHRH and SS in the pituitary and in the CNS neurones of the studied fetuses. The study was based on 8 pituitaries and 8 brains from fetuses in different periods of intrauterine life. The immunocytochemical technique was used. The presence of ghrelin, GHS-R was shown in the glandular part of the pituitary and CNS during the whole period of intrauterine life. Neurohormones in the stalk of the pituitary were found in fetuses from the 32nd week of pregnancy whereas in the CNS neurones these hormones could be detected throughout the whole period of intrauterine life. The results obtained suggest that stimulation of GH secretion by ghrelin is independent of the feedback concentration and these two hormones act like signals of metabolic balance. GH release by ghrelin in fetal life is independent of somatostatin. The hypothalamic-pituitary axis which regulates pulsatile GH release from the pituitary matures functionally in the third trimester of pregnancy independent of the previous anatomical differentiation.

Chapter 8 - Nanoparticles: Transport across the olfactory epithelium and application to the assessment of brain function in health and disease.

The exciting advances within nanotechnology are beginning to be harnessed by the medical field. Nanoparticles have been used for drug delivery into the brain and have been explored for imaging, sensing, and analytical purposes. The science of nanoparticles encompasses a vast array of biological, chemical, physical, and engineering research, different aspects of which are specifically addressed in each of the chapters of this volume. Nanomaterials such as nanospheres, nanotubes, nanowires, fullerene derivatives (buckyballs), and quantum dots (Qdots) are at the forefront of scientific attention, as they provide new consumer products and advance the scientific development of novel analytical tools in medicine and in the physical sciences. This chapter will briefly survey some aspects of nanoparticle biology focusing on the following: (1) the role of olfactory nanoparticle transport into the central nervous system (CNS), both as a potential route for effective drug delivery and as a route for the passage of noxious substances into the brain proper; (2) nanoparticles as sensors of cell function and toxicity; and (3) some adverse effects of nanoparticles on the dysregulation of brain redox status.