Dose-dependent response of prefrontal transcranial direct current stimulation on the heart rate variability: An electric field modeling study.

Transcranial direct current stimulation (tDCS) of the prefrontal cortex (PFC) modulates the autonomic nervous system by activating deeper brain areas via top-down pathway. However, effects on the nervous system are heterogeneous and may depend on the amount of current that penetrates. Therefore, we aimed to investigate the variable effects of tDCS on heart rate variability (HRV), a measure of the functional state of the autonomic nervous system. Using three prefrontal tDCS protocols (1.5, 3 mA and sham), we associated the simulated individual electric field (E-field) magnitude in brain regions of interest with the HRV effects. This was a randomized, double-blinded, sham-controlled and within-subject trial, in which healthy young-adult participants received tDCS sessions separated by 2 weeks. The brain regions of interest were the dorsolateral PFC (DLPFC), anterior cingulate cortex, insula and amygdala. Overall, 37 participants were investigated, corresponding to a total of 111 tDCS sessions. The findings suggested that HRV, measured by root mean squared of successive differences (RMSSD) and high-frequency HRV (HF-HRV), were significantly increased by the 3.0 mA tDCS when compared to sham and 1.5 mA. No difference was found between sham and 1.5 mA. E-field analysis showed that all brain regions of interest were associated with the HRV outcomes. However, this significance was associated with the protocol intensity, rather than inter-individual brain structural variability. To conclude, our results suggest a dose-dependent effect of tDCS for HRV. Therefore, further research is warranted to investigate the optimal current dose to modulate HRV.

Dose-dependent incidence of agranulocytosis in patients treated with methimazole and propylthiouracil.

Agranulocytosis is a serious adverse effect of methimazole (MMI) and propylthiouracil (PTU), and although there have been reports suggesting a dose-dependent incidence in relation to both drugs, the evidence has not been conclusive. The objective of our study was to determine whether the incidences of agranulocytosis induced by MMI and PTU exhibit dose-dependency. The subjects were 27,784 patients with untreated Graves' disease, 22,993 of whom were on an antithyroid drug treatment regimen for more than 90 days. Within this subset, 18,259 patients had been treated with MMI, and 4,734 had been treated with PTU. The incidence of agranulocytosis according to dose in the MMI group was 0.13% at 10 mg/day, 0.20% at 15 mg/day, 0.32% at 20 mg/day, and 0.47% at 30 mg/day, revealing a significant dose-dependent increase. In the PTU group, there were 0 cases of agranulocytosis at doses of 125 mg/day and below, 0.33% at 150 mg/day, 0.31% at 200 mg/day, and 0.81% at 300 mg/day, also revealing a significant dose-dependent increase. The incidence of agranulocytosis at MMI 15 mg and PTU 300 mg, i.e., at the same potency in terms of hormone synthesis inhibition, was 0.20% and 0.81%, respectively, and significantly higher in the PTU group. Our findings confirm a dose-dependent increase in the incidence of agranulocytosis with both drugs, but that at comparable thyroid hormone synthesis inhibitory doses PTU has a considerably higher propensity to induce agranulocytosis than MMI does.

Sevoflurane dose and postoperative delirium: a prospective cohort analysis.

BACKGROUND: Recent trials are conflicting as to whether titration of anaesthetic dose using electroencephalography monitoring reduces postoperative delirium. Titration to anaesthetic dose itself might yield clearer conclusions. We analysed our observational cohort to clarify both dose ranges for trials of anaesthetic dose and biological plausibility of anaesthetic dose influencing delirium. METHODS: We analysed the use of sevoflurane in an ongoing prospective cohort of non-intracranial surgery. Of 167 participants, 118 received sevoflurane and were aged >65 yr. We tested associations between age-adjusted median sevoflurane (AMS) minimum alveolar concentration fraction or area under the sevoflurane time×dose curve (AUC-S) and delirium severity (Delirium Rating Scale-98). Delirium incidence was measured with 3-minute Diagnostic Confusion Assessment Method (3D-CAM) or CAM-ICU. Associations with previously identified delirium biomarkers (interleukin-8, neurofilament light, total tau, or S100B) were tested. RESULTS: Delirium severity did not correlate with AMS (Spearman's ρ=-0.014, P=0.89) or AUC-S (ρ=0.093, P=0.35), nor did delirium incidence (AMS Wilcoxon P=0.86, AUC-S P=0.78). Further sensitivity analyses including propofol dose also demonstrated no relationship. Linear regression confirmed no association for AMS in unadjusted (log (IRR)=-0.06 P=0.645) or adjusted models (log (IRR)=-0.0454, P=0.735). No association was observed for AUC-S in unadjusted (log (IRR)=0.00, P=0.054) or adjusted models (log (IRR)=0.00, P=0.832). No association of anaesthetic dose with delirium biomarkers was identified (P>0.05). CONCLUSION: Sevoflurane dose was not associated with delirium severity or incidence. Other biological mechanisms of delirium, such as inflammation and neuronal injury, appear more plausible than dose of sevoflurane. CLINICAL TRIAL REGISTRATION: NCT03124303, NCT01980511.

Pharmacokinetics of the novel 5-HT4 receptor agonist, DA-6886, in dogs.

The pharmacokinetics of a new 5-hydroxytryptamine receptor 4 agonist, DA-6886, intended for the treatment of constipation-predominant irritable bowel syndrome, were evaluated in beagle dogs following both intravenous and oral administration of DA-6886 (1-10 mg/kg). The study also examined the effects of gender and food on the pharmacokinetics of DA-6886 in dogs.DA-6886 demonstrated dose-proportional area under the plasma concentration-time curve (AUC) values and dose-independent clearance (21.0-24.6 mL/min/kg) after administration via both routes. The steady-state volume of distribution (Vss) for DA-6886 was dose-independent and relatively large (6.76-8.57 L/kg), aligning with its observed high distribution in rat tissues.No significant differences were observed in the pharmacokinetics of DA-6886 between male and female dogs. Post oral administration, extent of absolute oral bioavailability (BA) was relatively high (48.2-96.1%) in contrast to the rates observed in rats (18.9-55.0%).Dogs that were fed exhibited a significantly lower Cmax and a delayed Tmax in comparison to those that were fasted. However, the AUC values were similar between the two groups. The extended stomach transit time in the fed state may account for this delayed absorption of DA-6886 without substantial changes in AUC.

Glucose levels show independent and dose-dependent association with worsening acute pancreatitis outcomes: Post-hoc analysis of a prospective, international cohort of 2250 acute pancreatitis cases.

BACKGROUND: Metabolic risk factors, such as obesity, hypertension, and hyperlipidemia are independent risk factors for the development of various complications in acute pancreatitis (AP). Hypertriglyceridemia dose-dependently elicits pancreatotoxicity and worsens the outcomes of AP. The role of hyperglycemia, as a toxic metabolic factor in the clinical course of AP, has not been examined yet. METHODS: We analyzed a prospective, international cohort of 2250 AP patients, examining associations between (1) glycosylated hemoglobin (HbA1c), (2) on-admission glucose, (3) peak in-hospital glucose and clinically important outcomes (mortality, severity, complications, length of hospitalization (LOH), maximal C-reactive protein (CRP)). We conducted a binary logistic regression accounting for age, gender, etiology, diabetes, and our examined variables. Receiver Operating Characteristic Curve (ROC) was applied to detect the diagnostic accuracy of the three variables. RESULTS: Both on-admission and peak serum glucose are independently associated with AP severity and mortality, accounting for age, gender, known diabetes and AP etiology. They show a dose-dependent association with severity (p < 0.001 in both), mortality (p < 0.001), LOH (p < 0.001), maximal CRP (p < 0.001), systemic (p < 0.001) and local complications (p < 0.001). Patients with peak glucose >7 mmol/l had a 15 times higher odds for severe AP and a five times higher odds for mortality. We found a trend of increasing HbA1c with increasing LOH (p < 0.001), severity and local complications. CONCLUSIONS: On-admission and peak in-hospital glucose are independently and dose-dependently associated with increasing AP severity and mortality. In-hospital laboratory control of glucose and adequate treatment of hyperglycemia are crucial in the management of AP.

Dose dependency of γ-H2AX formation in the rat urinary bladder treated with genotoxic and nongenotoxic bladder carcinogens.

We previously reported that immunostaining for γ-H2AX, a biomarker of DNA damage, in the rat urinary bladder is useful for early detection of bladder carcinogens in 28-day toxicity studies. Here, we aimed to examine the dose dependency of γ-H2AX formation in the urinary bladder of rats. Male F344 rats (aged 6 weeks) were orally administered N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN; 0%, 0.0001%, 0.001%, 0.01%, 0.02%, or 0.05% in drinking water), a genotoxic bladder carcinogen, and melamine (0%, 0.3%, 1.0%, or 3.0% in the diet), a nongenotoxic bladder carcinogen, for 2 days or 4 weeks. Immunohistochemical analysis showed that γ-H2AX- and Ki67-positive epithelial cells in the bladder urothelium were significantly increased, with a clear dose dependency, in both BBN- and melamine-treated groups. Additionally, γ-H2AX formation was detected from the lower-dose group, without increased Ki67 expression or histopathologic findings. The ratios of γ-H2AX-positive cells at week 4 in both BBN- and melamine-treated groups were higher than those on day 2, indicating the time-dependent increase in γ-H2AX formation. Immunofluorescence double-staining revealed that γ-H2AX single-positive cells without Ki67 expression were often found in the urothelium of BBN-treated rats, whereas most γ-H2AX-positive cells were Ki67-positive in the melamine group. Our results demonstrated that γ-H2AX formation in the urinary bladder increased in a clear dose-dependent manner and that γ-H2AX immunostaining has the potential to detect bladder carcinogens after a 2-day administration. Furthermore, the association of genotoxic mechanisms in bladder carcinogenesis could be determined by analyzing the colocalization of γ-H2AX and Ki67 in the urothelium.

In vitro toxicity assessment of respirable solid surface composite sawing particles.

Solid surface composites (SSCs) are a class of popular construction materials composed of aluminum trihydrate and acrylic polymers. Previous investigations have demonstrated that sawing SSC releases substantial airborne dusts, with a number-based geometric mean diameter of 1.05 µm. We reported that in mice, aspiration exposure to airborne SSC dusts induced symptoms of pulmonary inflammation at 24-h postexposure: neutrophilic influx, alveolitis, and increased lactate dehydrogenase (LDH) and pro-inflammatory cytokine levels in lavage fluid. The particles appeared to be poorly cleared, with 81% remaining at 14-day postexposure. The objective of this study was to determine the toxicity specifically of respirable particles on a model of human alveolar macrophages (THP-1). The relative toxicities of subfractions (0.07, 0.66, 1.58, 5.0, and 13.42 µm diameter) of the airborne particles were also determined. THP-1 macrophages were exposed for 24 h to respirable particles from sawing SSC (0, 12.5, 25, 50, or 100 µg/ml) or size-specific fractions (100 µg/ml). Exposure to respirable SSC particles induced THP-1 macrophage toxicity in a dose-dependent manner. Viability was decreased by 15% and 19% after exposure to 50 and 100 µg/ml SSC, respectively, which correlated with increased cell culture supernatant LDH activity by 40% and 70% when compared to control. Reactive oxygen species (ROS) production and inflammatory cytokines were increased in a dose-dependent manner. A size-dependent cytotoxic effect was observed in the cells exposed to subfractions of SSC particles. SSC particles of 0.07, 0.66, and 1.58 µm diameter killed 36%, 17%, and 22% of cells, respectively. These results indicate a potential for cytotoxicity of respirable SSC particles and a relationship between particle size and toxicity, with the smallest fractions appearing to exhibit the greatest toxicity.

Diagnosis of osteoporosis in statin-treated patients is dose-dependent.

OBJECTIVE: Whether HMG-CoA-reductase inhibition, the main mechanism of statins, plays a role in the pathogenesis of osteoporosis, is not entirely known so far. Consequently, this study was set out to investigate the relationship of different kinds and dosages of statins with osteoporosis, hypothesising that the inhibition of the synthesis of cholesterol could influence sex-hormones and therefore the diagnosis of osteoporosis. METHODS: Medical claims data of all Austrians from 2006 to 2007 was used to identify all patients treated with statins to compute their daily defined dose averages of six different types of statins. We applied multiple logistic regression to analyse the dose-dependent risks of being diagnosed with osteoporosis for each statin individually. RESULTS: In the general study population, statin treatment was associated with an overrepresentation of diagnosed osteoporosis compared with controls (OR: 3.62, 95% CI 3.55 to 3.69, p<0.01). There was a highly non-trivial dependence of statin dosage with the ORs of osteoporosis. Osteoporosis was underrepresented in low-dose statin treatment (0-10 mg per day), including lovastatin (OR: 0.39, CI 0.18 to 0.84, p<0.05), pravastatin (OR: 0.68, 95% CI 0.52 to 0.89, p<0.01), simvastatin (OR: 0.70, 95% CI 0.56 to 0.86, p<0.01) and rosuvastatin (OR: 0.69, 95% CI 0.55 to 0.87, p<0.01). However, the exceeding of the 40 mg threshold for simvastatin (OR: 1.64, 95% CI 1.31 to 2.07, p<0.01), and the exceeding of a 20 mg threshold for atorvastatin (OR: 1.78, 95% CI 1.41 to 2.23, p<0.01) and for rosuvastatin (OR: 2.04, 95% CI 1.31 to 3.18, p<0.01) was related to an overrepresentation of osteoporosis. CONCLUSION: Our results show that the diagnosis of osteoporosis in statin-treated patients is dose-dependent. Thus, osteoporosis is underrepresented in low-dose and overrepresented in high-dose statin treatment, demonstrating the importance of future studies' taking dose-dependency into account when investigating the relationship between statins and osteoporosis.

Mortality Risk Following Application of a Paclitaxel-Coated Stent in Femoropopliteal Lesions.

PURPOSE: To examine if endovascular therapy (EVT) with paclitaxel-coated stents increases the mortality risk in patients with symptomatic lower limb peripheral artery disease (PAD). MATERIALS AND METHODS: A retrospective analysis was conducted of paclitaxel-coated stent use in the femoropopliteal segment of 1535 symptomatic (Rutherford category 2 to 4) patients treated between January 2010 and December 2016 at 4 hospitals in Japan. The risk of all-cause mortality was examined between the 285 patients (mean age 73±8 years; 213 men) treated with a paclitaxel-coated stent (PTX-coated group) and 1250 patients (mean age 73±9 years; 872 men) not exposed to a paclitaxel-coated device (PTX-free group) during EVT. Propensity score matching was employed to balance baseline characteristics. Cox proportional hazards models stratified on the quintiles of the propensity score were used to investigate paclitaxel-coated stent use and mortality risk as well as interactions among baseline variables and the main outcome. Interactions between a PXT-coated stent and subgroups of the PTX-free group (bare stent and angioplasty) were also investigated, as was the impact of paclitaxel dose on mortality risk. The results of regression analysis are reported as the hazard ratio (HR) and 95% confidence interval (CI). RESULTS: The 3-year overall survival estimates were 86.4% in the PTX-coated group vs 87.7% in the PTX-free group; the corresponding 5-year estimates were 77.5% vs 73.7%, respectively. There was no significant difference in all-cause mortality between the 2 groups (HR 0.89, 95% CI 0.66 to 1.19, p=0.41). The cause of death also showed no remarkable difference between the groups. Chronic renal failure (p=0.044) and arterial calcification (p=0.022) demonstrated a significant interaction effect on the association of the use of a PTX-coated stent with all-cause mortality. No subgroup demonstrated that the use of a paclitaxel-coated stent was associated with an increased risk of all-cause mortality. A dose dependency was not evident. CONCLUSION: Mortality risk following application of a PTX-coated stent did not increase over 5 years, irrespective of the dose. A PTX-coated stent for femoropopliteal lesions in PAD patients is a safe treatment option.

Beneficial and deleterious effects of cannabinoids in the brain: the case of ultra-low dose THC.

This article reviews the neurocognitive advantages and drawbacks of cannabinoid substances, and discusses the possible physiological mechanisms that underlie their dual activity. The article further reviews the neurocognitive effects of ultra-low doses of ∆9-tetrahydrocannabinol (THC; 3-4 orders of magnitude lower than the conventional doses) in mice, and proposes such low doses of THC as a possible remedy for various brain injuries and for the treatment of age-related cognitive decline.

Dose-dependency of the cardiovascular risks of non-steroidal anti-inflammatory drugs.

Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used to treat pain and inflammatory conditions such as arthritis. However, both arthritis and many NSAIDs increase cardiovascular (CV) risks. The dose-dependency of the elevated CV risks of NSAIDs has not been well-studied. We tested the hypothesis that low but still effective doses of these drugs are void of CV side effects. As the model drug, we chose diclofenac because of its known high CV toxicity, as markers of CV risks, we assessed concentrations of cytochrome P450-mediated metabolites of arachidonic acid (ArA), and we used adjuvant arthritis as an experimental model of arthritis. Following 7 daily doses (2.5-15 mg/kg), the effective dosage range of diclofenac was identified (> 5 mg/kg/day). While 7 consecutive days of low therapeutic doses did not alter the CYP-mediated ArA metabolism, the highest dose of 15 mg/kg/day caused imbalances in ArA metabolic profiles toward cardiotoxicity by increasing the ratio of cardiotoxic 20-hydroxyeicosatetraenoic acid over cardioprotective epoxyeicosatrienoic acids. This is suggestive of dose-dependency of NSAID cardiotoxicity, and that low therapeutic doses may be void of CV side effects. Human studies are needed to examine the safety of low but effective doses of NSAIDs.

Faim2 contributes to neuroprotection by erythropoietin in transient brain ischemia.

Delayed cell death in the penumbra region of acute ischemic stroke occurs through apoptotic mechanisms, making it amenable to therapeutic interventions. Fas/CD95 mediates apoptotic cell death in response to external stimuli. In mature neurons, Fas/CD95 signaling is modulated by Fas-apoptotic inhibitory molecule 2 (Faim2), which reduces cell death in animal models of stroke, meningitis, and Parkinson disease. Erythropoietin (EPO) has been studied as a therapeutic strategy in ischemic stroke. Erythropoietin stimulates the phosphatidylinositol-3 kinase/Akt (PI3K/Akt) pathway, which regulates Faim2 expression. Therefore, up-regulation of Faim2 may contribute to neuroprotection by EPO. Male Faim2-deficient mice (Faim2-/- ) and wild-type littermates (WT) were subjected to 30 min of middle cerebral artery occlusion (MCAo) followed by 72 h of reperfusion. EPO was applied before (30 min) and after (24 and 48 h) MCAo. In WT mice application of EPO at a low dose (5000 U/kg) significantly reduced stroke volume, whereas treatment with high dose (90 000 U/kg) did not. In Faim2-/- animals administration of low-dose EPO did not result in a significant reduction in stroke volume. Faim2 expression as measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR) increased after low-dose EPO but not with high dose. An extensive phenotyping including analysis of cerebral vessel architecture did not reveal confounding differences between the genotypes. In human post-mortem brain Faim2 displayed a differential expression in areas of penumbral ischemia. Faim2 up-regulation may contribute to the neuroprotective effects of low-dose erythropoietin in transient brain ischemia. The dose-dependency may explain mixed effects of erythropoietin observed in clinical stroke trials.

Dose-dependency of multiple free radical-scavenging activity of edaravone.

BACKGROUND: Edaravone is a powerful free radical scavenger that is in clinical use. However, data concerning its dose-response relationship against multiple free radicals remain sparse. The purpose of the present study was to demonstrate the dose-dependency of direct scavenging activity of edaravone against multiple free radical species. MATERIALS AND METHODS: Free radical-scavenging activities of edaravone against six free radical species were evaluated by electron spin resonance spectroscopy using spin-trapping method. RESULTS: Edaravone scavenged the following free radicals in dose-dependent manners with reaction rate constants (kedaravone) or 50% inhibitory concentration (IC50) as indicated: hydroxyl radical (kedaravone = 5.2 × 1010 M-1 s-1), superoxide anion (kedaravone/kG-CYPMPO = 0.63), tert-butyl peroxyl radical (kedaravone/kG-CYPMPO = 8.8), ascorbyl free radical (IC50 = 0.17 ± 0.06 mM), 2,2-diphenyl-1-picrylhydrazyl (DPPH, IC50 = 4.7 ± 0.3 µM), and nitric oxide (kedaravone = 7.0 × 103 M-1 s-1). CONCLUSIONS: The dose-dependent scavenging activities of edaravone against multiple free radical species were clearly illustrated. It is speculated that edaravone acts as antioxidant by dose-dependently scavenging multiple free radical species along the chain reactions of oxidative stress in surgery.

Dose-dependent pharmacokinetics and tentative identification of urine metabolites from an isosteviol derivative with anti-hepatitis B activity in rats.

Compound 1 (ent-16-oxobeyeran-19-N-methylureido) is a semisynthetic isosteviol derivative that shows anti-hepatitis B virus activity in Huh7 cells by affecting viral DNA transcription and the Toll-like receptor 2/nuclear factor-κB signaling pathway. Thus, the pharmacokinetics and metabolite identification were studied as part of the discovery and development process of compound 1. The pharmacokinetics was evaluated after administration to rats at an intravenous dose of 2 mg/kg, and oral doses of 2, 5 and 10 mg/kg. Plasma concentrations were determined using LC-MS/MS. Moreover, urine samples from rats dosed at 10 mg/kg were scanned for metabolites using UPLC-QTOF-MS/MS. Results for the intravenously administered dose of 2 mg/kg showed that the area under the concentration-time curve was 65,223.31 ± 4269.80 ng min/mL, and the systemic clearance was 0.031 ± 0.0021 L/min. Oral pharmacokinetic parameters were dose-dependent, showing nonproportional increases in the oral AUCs with respective values of 4371.62 ± 3084.81, 22,472.75 ± 9103.33 and 135,141.83 ± 38,934.03 ng min/mL for 2, 5 and 10 mg/kg. The bioavailability was low at 1.5% for 2 mg/kg dose, and at 1.1% for both 5 and 10 mg/kg doses. Metabolites excreted in the urine indicate possible N-oxidation and glucuronide conjugation.

Dose-dependent effect of parathyroid hormone on fracture healing and bone formation in mice.

BACKGROUND: Parathyroid hormone (PTH) is the only clinically approved osteoanabolic drug for osteoporosis treatment. However, PTH is not established for the treatment of fracture healing, and doses of PTH diverge significantly between different studies. We hypothesized that the effect of PTH on promoting fracture healing and bone formation is dose dependent. MATERIALS AND METHODS: In vivo, mice were treated with PTH (10, 40, and 200 µg/kg) in a closed femoral fracture model. Fracture healing was analyzed after 4 weeks. The fourth lumbar vertebra was analyzed to assess systemic effects. In addition, osteoblasts from calvaria of mice were treated in vitro with PTH doses of 10-5-50 nM, and their differentiation was analyzed after 26 days. RESULTS: In vivo, PTH dose-dependently stimulated bone formation in the fracture callus and the vertebral body. However, PTH treatment did not increase biomechanical stiffness of the fractured femora in a dose-dependent manner. The increased bone formation in the 200 µg/kg group was associated with a depletion of osteoclasts, indicating diminished bone remodeling. Of interest, in vitro, we observed diminished mineralization with the highest doses of PTH in osteoblast cultures. CONCLUSIONS: PTH dose-dependently stimulates bone formation in vivo. However, during fracture healing, this did not result in a dose-dependent increase of the mechanical stiffness of the fracture callus. Taken together, our in vivo and in vitro data indicate that the dose-dependent effects of PTH during fracture healing are based on the actions on multiple cell types, thereby influencing not only bone formation but also osteoclastic callus remodeling.

Modeling Rabbit Responses to Single and Multiple Aerosol Exposures of Bacillus anthracis Spores.

Survival models are developed to predict response and time-to-response for mortality in rabbits following exposures to single or multiple aerosol doses of Bacillus anthracis spores. Hazard function models were developed for a multiple-dose data set to predict the probability of death through specifying functions of dose response and the time between exposure and the time-to-death (TTD). Among the models developed, the best-fitting survival model (baseline model) is an exponential dose-response model with a Weibull TTD distribution. Alternative models assessed use different underlying dose-response functions and use the assumption that, in a multiple-dose scenario, earlier doses affect the hazard functions of each subsequent dose. In addition, published mechanistic models are analyzed and compared with models developed in this article. None of the alternative models that were assessed provided a statistically significant improvement in fit over the baseline model. The general approach utilizes simple empirical data analysis to develop parsimonious models with limited reliance on mechanistic assumptions. The baseline model predicts TTDs consistent with reported results from three independent high-dose rabbit data sets. More accurate survival models depend upon future development of dose-response data sets specifically designed to assess potential multiple-dose effects on response and time-to-response. The process used in this article to develop the best-fitting survival model for exposure of rabbits to multiple aerosol doses of B. anthracis spores should have broad applicability to other host-pathogen systems and dosing schedules because the empirical modeling approach is based upon pathogen-specific empirically-derived parameters.

Inter-individual variability in cortical excitability and motor network connectivity following multiple blocks of rTMS.

The responsiveness to non-invasive neuromodulation protocols shows high inter-individual variability, the reasons of which remain poorly understood. We here tested whether the response to intermittent theta-burst stimulation (iTBS) - an effective repetitive transcranial magnetic stimulation (rTMS) protocol for increasing cortical excitability - depends on network properties of the cortical motor system. We furthermore investigated whether the responsiveness to iTBS is dose-dependent. To this end, we used a sham-stimulation controlled, single-blinded within-subject design testing for the relationship between iTBS aftereffects and (i) motor-evoked potentials (MEPs) as well as (ii) resting-state functional connectivity (rsFC) in 16 healthy subjects. In each session, three blocks of iTBS were applied, separated by 15min. We found that non-responders (subjects not showing an MEP increase of ≥10% after one iTBS block) featured stronger rsFC between the stimulated primary motor cortex (M1) and premotor areas before stimulation compared to responders. However, only the group of responders showed increases in rsFC and MEPs, while most non-responders remained close to baseline levels after all three blocks of iTBS. Importantly, there was still a large amount of variability in both groups. Our data suggest that responsiveness to iTBS at the local level (i.e., M1 excitability) depends upon the pre-interventional network connectivity of the stimulated region. Of note, increasing iTBS dose did not turn non-responders into responders. The finding that higher levels of pre-interventional connectivity precluded a response to iTBS could reflect a ceiling effect underlying non-responsiveness to iTBS at the systems level.

Dose-dependent model of caffeine effects on human vigilance during total sleep deprivation.

Caffeine is the most widely consumed stimulant to counter sleep-loss effects. While the pharmacokinetics of caffeine in the body is well-understood, its alertness-restoring effects are still not well characterized. In fact, mathematical models capable of predicting the effects of varying doses of caffeine on objective measures of vigilance are not available. In this paper, we describe a phenomenological model of the dose-dependent effects of caffeine on psychomotor vigilance task (PVT) performance of sleep-deprived subjects. We used the two-process model of sleep regulation to quantify performance during sleep loss in the absence of caffeine and a dose-dependent multiplier factor derived from the Hill equation to model the effects of single and repeated caffeine doses. We developed and validated the model fits and predictions on PVT lapse (number of reaction times exceeding 500 ms) data from two separate laboratory studies. At the population-average level, the model captured the effects of a range of caffeine doses (50-300 mg), yielding up to a 90% improvement over the two-process model. Individual-specific caffeine models, on average, predicted the effects up to 23% better than population-average caffeine models. The proposed model serves as a useful tool for predicting the dose-dependent effects of caffeine on the PVT performance of sleep-deprived subjects and, therefore, can be used for determining caffeine doses that optimize the timing and duration of peak performance.

Characterization of Vagus Nerve Stimulation (VNS) Dose-Dependent Effects on EEG Power Spectrum and Synchronization.

This study investigates the dose-dependent EEG effects of Vagus Nerve Stimulation (VNS) in patients with drug-resistant epilepsy. This research examines how varying VNS intensities impacts EEG power spectrum and synchronization in a cohort of 28 patients. Patients were categorized into responders, partial-responders, and non-responders based on seizure frequency reduction. The methods involved EEG recordings at incremental VNS intensities, followed by spectral and synchronization analysis. The results reveal significant changes in EEG power, particularly in the delta and beta bands across different intensities. Notably, responders exhibited distinct EEG changes compared to non-responders. Our study has found that VNS intensity significantly influences EEG power topographic allocation and brain desynchronization, suggesting the potential use of acute dose-dependent effects to personalized VNS therapy in the treatment of epilepsy. The findings underscore the importance of individualized VNS dosing for optimizing therapeutic outcomes and highlight the use of EEG metrics as an effective tool for monitoring and adjusting VNS parameters. These insights offer a new avenue for developing individualized VNS therapy strategies, enhancing treatment efficacy in epilepsy.

Aripiprazole dose associations with metabolic adverse effect: Results from a longitudinal study.

OBJECTIVE: Weight gain, blood lipids and/or glucose dysregulation can follow aripiprazole treatment onset. Whether aripiprazole dosage is associated with an increase in these metabolic parameters remains uncertain. The present study investigates aripiprazole dose associations with weight change, blood glucose, lipids, and blood pressure. METHODS: 422 patients taking aripiprazole for a minimum of three weeks to one year were selected from PsyMetab and PsyClin cohorts. Associations between aripiprazole dose and metabolic outcomes were examined using linear mixed-effect models. RESULTS: Aripiprazole dose was associated with weight change when considering its interaction with treatment duration (interaction term: -0.10, p < 0.001). This interaction resulted in greater weight gain for high versus low doses at the beginning of the treatment, this result being overturned at approximately five months, with greater weight increase for low versus high doses thereafter. LDL and HDL cholesterol levels were associated with aripiprazole dose over five months independently of treatment duration, with an average of 0.06 and 0.02 mmol/l increase for each 5 mg increment, respectively (p = 0.033 and p = 0.016, respectively). Furthermore, mean dose increases were associated with greater odds (+30 % per 5 mg increase) of clinically relevant weight gain (i.e., ≥7 %) over one year (p = 0.025). CONCLUSION: Aripiprazole dose was associated with one-year weight changes when considering its interaction with treatment duration. Increasing its dose could lead to metabolic worsening over the first five months of treatment, during which minimum effective doses should be particularly preferred.