Willingness to Pay for Traceable Meat Attributes: A Meta-analysis

Several researches evaluated consumers’ Willingness To Pay (WTP) for each meat traceable attribute, generating a great deal of information in this regard, although specific to the conditions of each study. In light of this, WTP estimates for traceability characteristics differ across the literature, leading sometimes to contrasting interpretations. Seeking a full, meaningful statistical description of the findings of a collection of studies, the meta-analysis allows us to analyze consistency across studies and control for factors thought to drive variations in WTP estimates. The meta-analysis has been conducted using 23 studies that, in aggregate, report 88 valuations for WTP. Our results, aside from releasing unconditional information on the WTP for single meat traceable attributes, show how certain study-specific characteristics, like the base price and the country where the study has been conducted, have a significant impact on WTP estimatesMeta-analysis, food traceability, Willingness to Pay, Agribusiness, Agricultural and Food Policy, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, Institutional and Behavioral Economics, Production Economics, Research Methods/ Statistical Methods, Risk and Uncertainty,

Community Supported Agriculture in the urban fringe: empirical evidence for project potentiality in the metropolitan area of Naples (Italy)

Urbanisation of city-side areas effects on farm land use and organisation are analysed in this study with the objective of seeking the most effective way to implement a Community Supported Agriculture (CSA) scheme. Specifically, we used a theoretical framework to describe and assess the relationships between urbanisation and changes in farm-styles in the city belt. Our analysis is based on a case study in the protected area of the Campi Flegrei Regional Park situated in the north-western part of the Neapolitan metropolitan area, which is a peri-urban rural area with severe environmental management problems. Our results from the empirical analysis allowed us to distinguish the farms of the area into three behavioural-social groups on the basis of specific features, in order to identify the best suited type of farm for the strategic implementation of the CSA. A market scenario was predicted for each of them without any intervention

LEVERAGING PROGNOSTIC BASELINE VARIABLES TO GAIN PRECISION IN RANDOMIZED TRIALS

We focus on estimating the average treatment effect in a randomized trial. If baseline variables are correlated with the outcome, then appropriately adjusting for these variables can improve precision. An example is the analysis of covariance (ANCOVA) estimator, which applies when the outcome is continuous, the quantity of interest is the difference in mean outcomes comparing treatment versus control, and a linear model with only main effects is used. ANCOVA is guaranteed to be at least as precise as the standard unadjusted estimator, asymptotically, under no parametric model assumptions, and also is locally, semiparametric efficient. Recently, several estimators have been developed that extend these desirable properties to more general settings that allow: any real-valued outcome (e.g., binary or count), contrasts other than the difference in mean outcomes (such as the relative risk), and estimators based on a large class of generalized linear models (including logistic regression). To the best of our knowledge, we give the first simulation study in the context of randomized trials that compares these estimators. Furthermore, our simulations are not based on parametric models; instead, our simulations are based on resampling data from completed randomized trials in stroke and HIV in order to assess estimator performance in realistic scenarios. We provide practical guidance on when these estimators are likely to provide substantial precision gains, and describe a quick assessment method that allows clinical investigators to determine whether these estimators could be useful in their specific trial contexts

SENSITIVITY OF TRIAL PERFORMANCE TO DELAY OUTCOMES, ACCRUAL RATES, AND PROGNOSTIC VARIABLES BASED ON A SIMULATED RANDOMIZED TRIAL WITH ADAPTIVE ENRICHMENT

Adaptive enrichment designs involve rules for restricting enrollment to a subset of the population during the course of an ongoing trial. This can be used to target those who benefit from the experimental treatment. To leverage prognostic information in baseline variables and short-term outcomes, we use a semiparametric, locally efficient estimator, and investigate its strengths and limitations compared to standard estimators. Through simulation studies, we assess how sensitive the trial performance (Type I error, power, expected sample size, trial duration) is to different design characteristics. Our simulation distributions mimic features of data from the Alzheimer’s Disease Neuroimaging Initiative, and involve two subpopulations of interest based on a generic marker. We investigate the impact of the following design characteristics: the accrual rate, the delay time between enrollment and observation of the primary outcome, and the prognostic value of baseline variables and short-term outcomes. We apply information-based monitoring, and evaluate how accurately information can be estimated in an ongoing trial

ENHANCED PRECISION IN THE ANALYSIS OF RANDOMIZED TRIALS WITH ORDINAL OUTCOMES

We present a general method for estimating the effect of a treatment on an ordinal outcome in randomized trials. The method is robust in that it does not rely on the proportional odds assumption. Our estimator leverages information in prognostic baseline variables, and has all of the following properties: (i) it is consistent; (ii) it is locally efficient; (iii) it is guaranteed to match or improve the precision of the standard, unadjusted estimator. To the best of our knowledge, this is the first estimator of the causal relation between a treatment and an ordinal outcome to satisfy these properties. We demonstrate the estimator in simulations based on resampling from a completed randomized clinical trial of a new treatment for stroke; we show potential gains of up to 39\% in relative efficiency compared to the unadjusted estimator. The proposed estimator could be a useful tool for analyzing randomized trials with ordinal outcomes, since existing methods either rely on model assumptions that are untenable in many practical applications, or lack the efficiency properties of the proposed estimator. We provide R code implementing the estimator

VARIABLE-DOMAIN FUNCTIONAL REGRESSION FOR MODELING ICU DATA

We introduce a class of scalar-on-function regression models with subject-specific functional predictor domains. The fundamental idea is to consider a bivariate functional parameter that depends both on the functional argument and on the width of the functional predictor domain. Both parametric and nonparametric models are introduced to fit the functional coefficient. The nonparametric model is theoretically and practically invariant to functional support transformation, or support registration. Methods were motivated by and applied to a study of association between daily measures of the Intensive Care Unit (ICU) Sequential Organ Failure Assessment (SOFA) score and two outcomes: in-hospital mortality, and physical impairment at hospital discharge among survivors. Methods are generally applicable to a large number of new studies that record a continuous variables over unequal domains

The Hypotensive and bradycardic effects of mouth opening: evidence in an animal model.

Objective Previous studies in normotensive anesthetized rats (Lapi Arch.Ital.Biol 151:11-23,2013) showed that peripheral stimulation of the trigeminal nerve induced by submaximal mouth opening (mandibular extension, ME) caused prolonged (at least 80min) bradycardia, hypotension and cerebral hemodynamic changes (pial arterioles showed a characteristic response pattern consisting in a significant constriction during ME followed by a dilatation for the entire remaining observation time). Design and method In this study we assessed the in vivo effects of ME on HR, MABP and pial microcirculation in hypertensive rats. Experiments were performed in male Wistar rats weighing 250-300g (n = 8). Hypertension was induced by intraperitoneal daily injection of dexamethasone (0.03mg/kg/day) for 10 days. ME was obtained by inserting an ad hoc developed retractor between the dental arches. HR and MABP were recorded by ECG and a catheter placed in the left femoral artery and measured by a computer-assisted system. Pial arterioles were observed through a closed cranial window implanted above the left parietal cortex and visualized by an in vivo fluorescence microscopy technique to assess vessel diameter changes before (baseline), during 10min ME and thereafter until 160min. Arteriolar diameters were measured with a computer-assisted method (MIP Image program, frame by frame). Results In sham-treated (no ME) hypertensive rats (n=3) HR, MABP and pial microcirculation did not change during whole observation period. Hypertensive rats subjected to ME (n=5) showed a significant decrease of HR and MABP. HR declined by 42bpm, (p<0.01) starting from 60 min after ME up to 160min, while MABP by 18mmHg (p<0.05) starting from 20min after ME up to 100min, compared with baseline. Pial arterioles exhibited a biphasic response: the arteriolar diameter decreased by 2.94&#956;m (p<0.05) during ME, afterwards it significantly increased by 3.46&#956;m (p<0.01) starting from 20min after ME; this vasodilatation lasted for the whole observation period. Conclusions Our results suggest that ME is able to exert profound and prolonged regulatory effects on systemic arterial blood pressure and pial arteriolar tone in hypertensive rats

Long term remodeling of rat pial microcirculation after transient middle cerebral artery occlusion and reperfusion.

Objective: The aim of this study was to assess the in vivo structural and functional remodeling of pial arteriolar networks in the ischemic area of rats submitted to transient middle cerebral artery occlusion (MCAO) and different time intervals of reperfusion. Methods and results: Two closed cranial windows were implanted above the left and right parietal cortex to observe pial microcirculation by fluorescence microscopy. The geometric characteristics of pial arteriolar networks, permeability increase, leukocyte adhesion and capillary density were analyzed after 1 h or 1, 7, 14 or 28 days of reperfusion. MCAO and 1-hour reperfusion caused marked microvascular changes in pial networks. The necrotic core was devoid of vessels, while the penumbra area presented a few arterioles, capillaries and venules with severe neuronal damage. Penumbra microvascular permeability and leukocyte adhesion were pronounced. At 7 days of reperfusion, new pial arterioles were organized in anastomotic vessels, overlapping the ischemic core and in penetrating pial arterioles. Vascular remodeling caused different arteriolar rearrangement up to 28 days of reperfusion and animals gradually regained their motor and sensory functions. Conclusions: Transient MCAO-induced pial-network remodeling is characterized by arteriolar anastomotic arcades. Remodeling mechanisms appear to be accompanied by an increased expression of nitric oxide synthases

Rat pial microvascular responses to melatonin during bilateral common carotid artery occlusion and reperfusion

The present study assessed the in vivo rat pial microvascular responses induced by melatonin during brain hypoperfusion and reperfusion (RE) injury. Pial microcirculation of male Wistar rats was visualized by fluorescence microscopy through a closed cranial window. Hypoperfusion was induced by bilateral common carotid artery occlusion (BCCAO, 30 min); thereafter, pial microcirculation was observed for 60 min. Arteriolar diameter, permeability increase, leukocyte adhesion to venular walls, perfused capillary length (PCL), and capillary red blood cell velocity (V(RBC) ) were investigated by computerized methods. Melatonin (0.5, 1, 2 mg/kg b.w.) was intravenously administered 10 min before BCCAO and at the beginning of RE. Pial arterioles were classified in five orders according to diameter, length, and branchings. In control group, BCCAO caused decrease in order 2 arteriole diameter (by 17.5 ± 3.0% of baseline) that was reduced by 11.8 ± 1.2% of baseline at the end of RE, accompanied by marked leakage and leukocyte adhesion. PCL and capillary V(RBC) decreased. At the end of BCCAO, melatonin highest dosage caused order 2 arteriole diameter reduction by 4.6 ± 2.0% of baseline. At RE, melatonin at the lower dosages caused different arteriolar responses. The highest dosage caused dilation in order 2 arteriole by 8.0 ± 1.5% of baseline, preventing leakage and leukocyte adhesion, while PCL and V(RBC) increased. Luzindole (4 mg/kg b.w.) prior to melatonin caused order 2 arteriole constriction by 12.0 ± 1.5% of baseline at RE, while leakage, leukocyte adhesion, PCL and V(RBC) were not affected. Prazosin (1 mg/kg b.w.) prior to melatonin did not significantly change melatonin's effects. In conclusion, melatonin caused different responses during hypoperfusion and RE, modulating pial arteriolar tone likely by MT1 and MT2 melatonin receptors while preventing blood-brain barrier changes through its free radical scavenging action