On-site peer mentorship's effect on personal and professional development, stress reduction, and ease of transition into the medical education system.

CONTEXT: Mentorship aids in the transition into the medical education system, which is a demanding and stressful time for learners. The development of new medical schools to offset the physician shortage has posed a challenge in that the inaugural class of students lacks an upperclassman cohort as a resource for advice and mentorship. Mentorship has proven to have positive impacts on three domains: personal and professional development (PPD), stress reduction (SR), and ease of transition (ET) into medical school. OBJECTIVES: The purpose of this study was to identify sources of mentorship within the medical education system and compare the subjective growth of the inaugural and second classes of a newly established medical school in the three domains. METHODS: The inaugural and second classes at a newly established medical school completed an Institutional Review Board (IRB)-approved anonymous survey with questions pertaining to unidentifiable demographics, sources of mentorship, and a five-point Likert scale assessing characteristics related to the three domains. RESULTS: Twenty-three students responded to the survey. The second class (n=9) rated their growth higher in all three domains compared to the inaugural class (n=14). The inaugural class utilized the faculty mentor the most (11/14, 78.6 %). The second class utilized the on-site peer mentor the most (9/9, 100 %). Qualitative data analysis led to the emergence of three themes: (1) students utilizing their faculty mentor had the greatest growth in PPD and ET; (2) students utilizing on-site peer mentorship reporting the greatest growth in SR; and (3) informal peer mentorship utilization correlating with less growth in the three domains. CONCLUSIONS: Our study demonstrates the profound impact that mentorship has on growth in the three domains regardless of the type of mentorship utilized. The benefits, specifically with regard to SR, of an on-site peer mentorship program may not have been satisfied by other sources of mentorship.

Determination of the effect of iatrogenic blood contamination on lactate dehydrogenase and creatine kinase activity in canine cerebrospinal fluid.

BACKGROUND: Lactate dehydrogenase (LDH) and creatine kinase (CK) have differential tissue activity and isoenzyme profiles. LDH and CK exist as 5 and 3 isoenzymes, respectively, in both serum and cerebrospinal fluid (CSF). Studies have demonstrated that measuring LDH, CK, and their isoenzymes in CSF has diagnostic and prognostic values for dogs and people with neurologic disorders. OBJECTIVES: Iatrogenic blood contamination can distort the results of CSF analysis. The purpose of this study was to determine allowable thresholds of blood contamination (RBC/µL) for accurate measurement of LDH, CK, and their isoenzymes in canine CSF. METHODS: Venous blood and CSF were collected from healthy dogs. Total LDH and CK activity were measured spectrophotometrically. Isoenzyme profiles were determined using gel electrophoresis and densitometric scanning. All samples were analyzed within 6 hours of collection. A nonlinear mixed effects regression model was used to estimate the allowable thresholds of blood contamination for accurate measurement of LDH, CK, and their isoenzymes in canine CSF. RESULTS: The threshold of iatrogenic blood contamination for total LDH and total CK in healthy dogs are 6696 RBC/µL (95% CI 3879-11 187) and 5961 RBC/µL (95% CI 2939-12 085), respectively. LDH-1 is the most sensitive isoenzyme to iatrogenic blood contamination, while LDH-4 is the least sensitive. CONCLUSIONS: These results are important for the interpretation of LDH, CK, and their isoenzymes in canine CSF. Additionally, our methodology is translatable for determining thresholds of acceptable iatrogenic blood contamination in CSF for other diagnostic and prognostic biomarkers of neurologic disease.

The Effectiveness of Riparian Hedgerows at Intercepting Drift from Aerial Pesticide Application.

The primary tool used currently for preventing pesticide drift from entering streams is a no-spray buffer zone. Riparian hedgerows may provide an additional option; however, quantitative information on their effectiveness is limited. To quantify the potential benefit of riparian hedgerows for drift reduction, aerial malathion {diethyl 2-[(dimethoxyphosphorothioyl)sulfanyl]butanedioate} applications on blueberry ( L.) farms with fields adjacent to streams or ditches were monitored. Drift from fields with extensive dense woody riparian vegetation was compared with drift from fields with no dense woody riparian vegetation. Overall, total instream malathion deposition was 96.1% lower at vegetated sites compared with nonvegetated sites. Univariable models identified six variables that were significantly related to decreasing instream total malathion deposition: increasing bank canopy cover, increasing average site canopy cover, increasing canopy angle, increasing the distance between the field edge and vegetation edge, increasing the distance between the field edge and center of stream, and decreasing bank slope. For the variables most feasible for landowners to alter, the following increases could result, on average, in a 26% decrease in the total instream malathion deposition: bank canopy cover (7%), distance between field and vegetation (0.3 m), and distance between field and center of stream (0.9 m). No-spray buffer sizes needed for significant deposition reductions may be large, but for nonvegetated or minimally vegetated streams similar to those studied here, increasing bank canopy cover may give comparable advantages while allowing the use of the entire field area and conferring additional ecosystem benefits such as shading streams and improving habitat.

Pharmacokinetics and physiologic/behavioral effects of buprenorphine administered sublingually and intravenously to neonatal foals.

Buprenorphine is absorbed following sublingual administration, which would be a low-stress delivery route in foals. However, the pharmacokinetics/pharmacodynamics are not described in foals. Six healthy foals <21 days of age participated in a blinded, randomized, 3-period, 5-sequence, 3-treatment crossover prospective study. Foals received 0.01-0.02 mg/kg buprenorphine administered SL or IV with an equivalent volume of saline administered by the opposite route. Blood was collected from the cephalic vein for pharmacokinetic analysis. Physiologic parameters (HR, RR, body temperature, GI sounds), locomotion (pedometer), and behavioral data (activity level, nursing time, response to humans) were recorded. Plasma concentration of buprenorphine exceeded a presumed analgesic level (0.6 ng/ml) in five foals in the IV group and one in the SL group but only for a very brief time. Pharmacokinetic analysis following IV administration demonstrated a short elimination half-life (t1/2ß 1.95 ± 0.7 hr), large volume of distribution (6.46 ± 1.54 L/kg), and a high total clearance (55.83 ± 23.75 ml/kg/min), which differs from adult horses. Following SL administration, maximum concentrations reached were 0.61 ± 0.11 ng/ml and bioavailability was 25.1% ± 10.9%. In both groups, there were minor statistical differences in HR, RR, body temperature, locomotion, and time spent nursing. However, these differences were clinically insignificant in this single dose study, and excitement, sedation, or colic did not occur.

Rational Selection, Criticality Assessment, and Tiering of Quality Attributes and Test Methods for Analytical Similarity Evaluation of Biosimilars.

Leading regulatory agencies recommend biosimilar assessment to proceed in a stepwise fashion, starting with a detailed analytical comparison of the structural and functional properties of the proposed biosimilar and reference product. The degree of analytical similarity determines the degree of residual uncertainty that must be addressed through downstream in vivo studies. Substantive evidence of similarity from comprehensive analytical testing may justify a targeted clinical development plan, and thus enable a shorter path to licensing. The importance of a careful design of the analytical similarity study program therefore should not be underestimated. Designing a state-of-the-art analytical similarity study meeting current regulatory requirements in regions such as the USA and EU requires a methodical approach, consisting of specific steps that far precede the work on the actual analytical study protocol. This white paper discusses scientific and methodological considerations on the process of attribute and test method selection, criticality assessment, and subsequent assignment of analytical measures to US FDA's three tiers of analytical similarity assessment. Case examples of selection of critical quality attributes and analytical methods for similarity exercises are provided to illustrate the practical implementation of the principles discussed.

Exercise-induced pulmonary hemorrhage in barrel racing horses in the Pacific Northwest region of the United States.

BACKGROUND: Exercise-induced pulmonary hemorrhage (EIPH) refers to bleeding from the lungs in association with strenuous exercise. It has been documented in race horses but little information exists on EIPH in barrel racing horses. HYPOTHESIS/OBJECTIVES: Our goals were to evaluate the presence of EIPH in barrel racing horses and estimate its prevalence in the Pacific Northwest. ANIMALS: 149 barrel racing horses enrolled at events in WA (11), ID (3), and MT (33). METHODS: Observational cross-sectional study. Data collected included signalment, history of illness, respiratory disease, race division, and pre-race medications. Endoscopy was performed and tracheobronchoscopic (TBE) EIPH score was assigned based on quantity of blood in the trachea (0 = no blood to 4 = abundance of blood within the trachea). After TBE, bronchoalveolar lavage (BAL) was performed. Erythrocyte (red blood cell, RBC) counts were obtained from bronchoalveolar lavage fluid (BALF). Statistical analysis included linear and logistic regression, Fisher's exact t test, and calculation of correlation coefficient. Significance was set at P < .05. RESULTS: The prevalence of EIPH based on TBE EIPH score was 54%. When based on BALF RBC count >1,000 cells, EIPH prevalence was 66%. Race time did not significantly affect the presence of EIPH. A significant (P < .0001) positive linear relationship between the TBE and BAL erythrocyte count was identified, but its strength was poor (r2 = .15). CONCLUSIONS AND CLINICAL IMPORTANCE: EIPH occurs in over 50% of barrel racing horses in the Pacific Northwest. Precise determination of the impact of EIPH on health of barrel racers requires further study.

Monitoring Shelf Life of Pasteurized Whole Milk Under Refrigerated Storage Conditions: Predictive Models for Quality Loss.

The shelf life of pasteurized milk is generally determined through microbiological analysis. The objective of this study was to correlate microbial quality parameters then to design predictive models for shelf life of pasteurized milk. We analyzed pasteurized milk (3.9% fat) for aerobic plate counts (APCs), psychrotrophic bacteria counts (PBCs), and Bacillus spp. counts at 5, 7, 10, 13, 15, and 19 (±1 °C) to the end of storage time. We also monitored titratable acidity, pH, and, lipase, and protease activity and correlated this with APC, which is the principal index defining shelf life. Results indicate that the shelf life of pasteurized milk was 24, 36, and 72 h at 19, 15, and 13 °C respectively, as determined by APC and acidity indicators. However, milk stored at lower temperatures of 5, 7, and 10 °C had longer shelf life of 30, 24, and 12 d, respectively. A sharp increase in titratable acidity, while decrease pH were observed when APCs reached 5.0 log10 CFU/mL at all storage temperatures. Lipase and protease activities increased with storage temperature. At 5 and 7 °C, however, protease activity was very low. Therefore, we eliminated this parameter from our quality parameters as a potential spoilage indicator. PRACTICAL APPLICATION: Findings of this research are useful for monitoring the quality of commercial pasteurized milk, particularly in locations where environmental conditions make longer storage difficult. The study also provides valuable information for development of colorimetric shelf life indicators.

A pilot study of an autologous tumor-derived autophagosome vaccine with docetaxel in patients with stage IV non-small cell lung cancer.

BACKGROUND: Tumor-derived autophagosome vaccines (DRibbles) have the potential to broaden immune response to poorly immunogenic tumors. METHODS: Autologous vaccine generated from tumor cells harvested from pleural effusions was administered to patients with advanced NSCLC with the objectives of assessing safety and immune response. Four patients were vaccinated and evaluable for immune response; each received two to four doses of vaccine. Study therapy included two cycles of docetaxel 75 mg/m2 on days 1 and 29 to treat the tumor, release hidden antigens and produce lymphopenia. DRibbles were to be administered intradermally on days 14, 43, 57, 71, and 85, together with GM-CSF (50 µg/d x 6d, administered via SQ mini pump). Peripheral blood was tested for immune parameters at baseline and at each vaccination. RESULTS: Three of four patients had tumor cells available for testing. Autologous tumor-specific immune response was seen in two of the three, manifested by IL-5 (1 patient after 3 doses), and IFN-γ, TNF-α, IL-5, IL-10 (after 4 doses in one patient). All 4 patients had evidence of specific antibody responses against potential tumor antigens. All patients came off study after 4 or fewer vaccine treatments due to progression of disease. No significant immune toxicities were seen during the course of the study. CONCLUSIONS: DRibble vaccine given with GM-CSF appeared safe and capable of inducing an immune response against tumor cells in this small, pilot study. There was no evidence of efficacy in this small poor-prognosis patient population, with treatment not feasible. Trial registration NCT00850785, initial registration date February 23, 2009.

Effect of simulator orientation during skills training on performance of basic laparoscopic tasks by veterinary students.

OBJECTIVE To determine whether basic laparoscopic skills acquired during training in the horizontal plane would transfer to the vertical plane and vice versa. DESIGN Evaluation study. SAMPLE POPULATION 26 first- and second-year veterinary students with no prior laparoscopic skills training or surgical experience. PROCEDURES Participants were nonrandomly assigned to 2 groups. Group 1 (n = 15) underwent laparoscopic skills training in the horizontal plane, and group 2 (17) underwent laparoscopic skills training in the vertical plane. Following training, participants were tested on their ability to perform 5 laparoscopic tasks, first in the horizontal plane and then the vertical plane (group 1) or first in the vertical plane and then in the horizontal plane (group 2). All training and testing were performed with an augmented-reality laparoscopic simulator. RESULTS 3 participants in each group did not complete the study. For group 1, scores for 3 of the 5 tasks were significantly worse when tested in the vertical plane than when tested in the horizontal plane. For group 2, scores for 2 of the 5 tasks were significantly worse when tested in the horizontal plane than when tested in the vertical plane. For 3 tasks, the difference in scores for the training versus orthogonal plane was significantly lower for group 2 than for group 1. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that basic laparoscopic skills acquired in 1 plane frequently did not transfer to the orthogonal plane. Because veterinary surgeons may be required to treat patients in various positions, development of laparoscopic training models to simulate the vertical plane is recommended.

Statistical Approaches to Assess Biosimilarity from Analytical Data.

Protein therapeutics have unique critical quality attributes (CQAs) that define their purity, potency, and safety. The analytical methods used to assess CQAs must be able to distinguish clinically meaningful differences in comparator products, and the most important CQAs should be evaluated with the most statistical rigor. High-risk CQA measurements assess the most important attributes that directly impact the clinical mechanism of action or have known implications for safety, while the moderate- to low-risk characteristics may have a lower direct impact and thereby may have a broader range to establish similarity. Statistical equivalence testing is applied for high-risk CQA measurements to establish the degree of similarity (e.g., highly similar fingerprint, highly similar, or similar) of selected attributes. Notably, some high-risk CQAs (e.g., primary sequence or disulfide bonding) are qualitative (e.g., the same as the originator or not the same) and therefore not amenable to equivalence testing. For biosimilars, an important step is the acquisition of a sufficient number of unique originator drug product lots to measure the variability in the originator drug manufacturing process and provide sufficient statistical power for the analytical data comparisons. Together, these analytical evaluations, along with PK/PD and safety data (immunogenicity), provide the data necessary to determine if the totality of the evidence warrants a designation of biosimilarity and subsequent licensure for marketing in the USA. In this paper, a case study approach is used to provide examples of analytical similarity exercises and the appropriateness of statistical approaches for the example data.

Bioassay case study applying the maximin D-optimal design algorithm to the four-parameter logistic model.

Cell-based potency assays play an important role in the characterization of biopharmaceuticals but they can be challenging to develop in part because of greater inherent variability than other analytical methods. Our objective is to select concentrations on a dose-response curve that will enhance assay robustness. We apply the maximin D-optimal design concept to the four-parameter logistic (4 PL) model and then derive and compute the maximin D-optimal design for a challenging bioassay using curves representative of assay variation. The selected concentration points from this 'best worst case' design adequately fit a variety of 4 PL shapes and demonstrate improved robustness.

Systematic verification of bioanalytical similarity between a biosimilar and a reference biotherapeutic: committee recommendations for the development and validation of a single ligand-binding assay to support pharmacokinetic assessments.

For biosimilar drug development, it is critical to demonstrate similar physiochemical characteristics, efficacy, and safety of the biosimilar product compared to the reference product. Therefore, pharmacokinetic (PK) and immunogenicity (antidrug antibody, ADA) assays that allow for the demonstration of biosimilarity are critical. Under the auspices of the American Association of Pharmaceutical Scientists (AAPS) Ligand-Binding Assay Bioanalytical Focus Group (LBABFG), a Biosimilars Action Program Committee (APC) was formed in 2011. The goals of this Biosimilars APC were to provide a forum for in-depth discussions on issues surrounding the development and validation of PK and immunogenicity assays in support of biosimilar drug development and to make recommendations thereof. The Biosimilars APC's recommendations for the development and validation of ligand-binding assays (LBAs) to support the PK assessments for biosimilar drug development are presented here. Analytical recommendations for the development and validation of LBAs to support immunogenicity assessments will be the subject of a separate white paper.

OX40 is a potent immune-stimulating target in late-stage cancer patients.

OX40 is a potent costimulatory receptor that can potentiate T-cell receptor signaling on the surface of T lymphocytes, leading to their activation by a specifically recognized antigen. In particular, OX40 engagement by ligands present on dendritic cells dramatically increases the proliferation, effector function, and survival of T cells. Preclinical studies have shown that OX40 agonists increase antitumor immunity and improve tumor-free survival. In this study, we performed a phase I clinical trial using a mouse monoclonal antibody (mAb) that agonizes human OX40 signaling in patients with advanced cancer. Patients treated with one course of the anti-OX40 mAb showed an acceptable toxicity profile and regression of at least one metastatic lesion in 12 of 30 patients. Mechanistically, this treatment increased T and B cell responses to reporter antigen immunizations, led to preferential upregulation of OX40 on CD4(+) FoxP3(+) regulatory T cells in tumor-infiltrating lymphocytes, and increased the antitumor reactivity of T and B cells in patients with melanoma. Our findings clinically validate OX40 as a potent immune-stimulating target for treatment in patients with cancer, providing a generalizable tool to favorably influence the antitumor properties of circulating T cells, B cells, and intratumoral regulatory T cells.

Phase 1 study of stereotactic body radiotherapy and interleukin-2--tumor and immunological responses.

Preclinical models suggest that focal high-dose radiation can make tumors more immunogenic. We performed a pilot study of stereotactic body radiation therapy (SBRT) followed by high-dose interleukin-2 (IL-2) to assess safety and tumor response rate and perform exploratory immune monitoring studies. Patients with metastatic melanoma or renal cell carcinoma (RCC) who had received no previous medical therapy for metastatic disease were eligible. Patients received one, two, or three doses of SBRT (20 Gy per fraction) with the last dose administered 3 days before starting IL-2. IL-2 (600,000 IU per kilogram by means of intravenous bolus infusion) was given every 8 hours for a maximum of 14 doses with a second cycle after a 2-week rest. Patients with regressing disease received up to six IL-2 cycles. Twelve patients were included in the intent-to-treat analysis, and 11 completed treatment per the study design. Response Evaluation Criteria in Solid Tumors criteria were used to assess overall response in nonirradiated target lesions. Eight of 12 patients (66.6%) achieved a complete (CR) or partial response (PR) (1 CR and 7 PR). Six of the patients with PR on computed tomography had a CR by positron emission tomography imaging. Five of seven (71.4%) patients with melanoma had a PR or CR, and three of five (60%) with RCC had a PR. Immune monitoring showed a statistically significantly greater frequency of proliferating CD4(+) T cells with an early activated effector memory phenotype (CD3(+)CD4(+)Ki67(+)CD25(+)FoxP3(-)CCR7(-)CD45RA(-)CD27(+)CD28(+/-)) in the peripheral blood of responding patients. SBRT and IL-2 can be administered safely. Because the response rate in patients with melanoma was significantly higher than expected on the basis of historical data, we believe that the combination and investigation of CD4(+) effector memory T cells as a predictor of response warrant further study.

Amylin-mediated restoration of leptin responsiveness in diet-induced obesity: magnitude and mechanisms.

Previously, we reported that combination treatment with rat amylin (100 microg/kg.d) and murine leptin (500 microg/kg.d) elicited greater inhibition of food intake and greater body weight loss in diet-induced obese rats than predicted by the sum of the monotherapy conditions, a finding consistent with amylin-induced restoration of leptin responsiveness. In the present study, a 3 x 4 factorial design was used to formally test for a synergistic interaction, using lower dose ranges of amylin (0, 10, and 50 microg/kg.d) and leptin (0, 5, 25, and 125 microg/kg.d), on food intake and body weight after 4 wk continuous infusion. Response surface methodology analysis revealed significant synergistic anorexigenic (P < 0.05) and body weight-lowering (P < 0.05) effects of amylin/leptin combination treatment, with up to 15% weight loss at doses considerably lower than previously reported. Pair-feeding (PF) experiments demonstrated that reduction of food intake was the predominant mechanism for amylin/leptin-mediated weight loss. However, fat loss was 2-fold greater in amylin/leptin-treated rats than PF controls. Furthermore, amylin/leptin-mediated weight loss was not accompanied by the counterregulatory decrease in energy expenditure and chronic shift toward carbohydrate (rather than fat) utilization observed with PF. Hepatic gene expression analyses revealed that 28 d treatment with amylin/leptin (but not PF) was associated with reduced expression of genes involved in hepatic lipogenesis (Scd1 and Fasn mRNA) and increased expression of genes involved in lipid utilization (Pck1 mRNA). We conclude that amylin/leptin interact synergistically to reduce body weight and adiposity in diet-induced obese rodents through a number of anorexigenic and metabolic effects.

A Bayesian approach to utilizing prior data in new drug development.

In this paper we propose a Bayesian method to combine safety data collected from two separate drug development programs using the same active drug substance but for different indications, formulations, or patient populations. The objective of combining the data across the programs is to better define the level of safety risk associated with the new indication or target population. There may be adverse events (AEs) observed in the new program that represent new safety signals. Our method is to explore the AEs using data from both development programs. Our approach utilizes data collected previously to assist in analyzing safety data from the new program. It is assumed that the frequency of a certain AE follows a distribution with a parameter that characterizes the safety risk level. The parameter is assumed to follow a distribution function. In the Bayesian framework, this distribution function is called a prior distribution in the absence of data and posterior distribution when updated by real data. The key concept behind our method is to use data from the previous program to construct a posterior distribution that will in turn serve as a prior distribution for the new program. The construction of this updated prior down weights data from the previous program to emphasize the new program and thus avoids simple pooling of the data across programs. Such "soft use" of previous information minimizes the potential for undue influence of previous data on the analysis. Data from the new program are used to update the prior distribution and compute the posterior distribution for the new program. Key statistics are then calculated from the posterior distribution to quantify the risk level for the new program. We have tested the proposed approach using data from a real Phase 2 study that was conducted as part of a clinical development program for a new indication of an approved drug. The results indicate that the estimated risk level was affected both by the observed event rates and the extents of exposure across the two development programs. This approach appropriately characterizes the safety profile across the two development programs and properly contextualizes new safety signals from the new program.

Combination therapy with amylin and peptide YY[3-36] in obese rodents: anorexigenic synergy and weight loss additivity.

Circulating levels of the pancreatic beta-cell peptide hormone amylin and the gut peptide PYY[3-36] increase after nutrient ingestion. Both have been implicated as short-term signals of meal termination with anorexigenic and weight-reducing effects. However, their combined effects are unknown. We report that the combination of amylin and PYY[3-36] elicited greater anorexigenic and weight-reducing effects than either peptide alone. In high-fat-fed rats, a single ip injection of amylin (10 microg/kg) plus PYY[3-36] (1000 microg/kg) reduced food intake for 24 h (P < 0.05 vs. vehicle), whereas the anorexigenic effects of either PYY[3-36] or amylin alone began to diminish 6 h after injection. These anorexigenic effects were dissociable from changes in locomotor activity. Subcutaneous infusion of amylin plus PYY[3-36] for 14 d suppressed food intake and body weight to a greater extent than either agent alone in both rat and mouse diet-induced obesity (DIO) models (P < 0.05). In DIO-prone rats, 24-h metabolic rate was maintained despite weight loss, and amylin plus PYY[3-36] (but not monotherapy) increased 24-h fat oxidation (P < 0.05 vs. vehicle). Finally, a 4 x 3 factorial design was used to formally describe the interaction between amylin and PYY[3-36]. DIO-prone rats were treated with amylin (0, 4, 20, and 100 microg/kg.d) and PYY[3-36] (0, 200, 400 microg/kg.d) alone and in combination for 14 d. Statistical analyses revealed that food intake suppression with amylin plus PYY[3-36] treatment was synergistic, whereas body weight reduction was additive. Collectively, these observations highlight the importance of studying peptide hormones in combination and suggest that integrated neurohormonal approaches may hold promise as treatments for obesity.

Effects of prior or concurrent food restriction on amylin-induced changes in body weight and body composition in high-fat-fed female rats.

Amylin infusion reduces food intake and slows body weight gain in rodents. In obese male rats, amylin (but not pair feeding) caused a preferential reduction of fat mass with protein preservation despite equal body weight loss in amylin-treated (fed ad libitum) and pair-fed rats. In the present study, the effect of prior or concurrent food restriction on the ability of amylin to cause weight loss was evaluated. Retired female breeder rats were maintained on a high-fat diet (40% fat) for 9 wk. Prior to drug treatment, rats were either fed ad libitum or food restricted for 10 days to lose 5% of their starting body weight. They were then subdivided into treatment groups that received either vehicle or amylin (100 microgxkg(-1)xday(-1) via subcutaneous minipump) and placed under either a restricted or ad libitum feeding schedule (for a total of 8 treatment arms). Amylin 1) significantly reduced body weight compared with vehicle under all treatment conditions, except in always restricted animals, 2) significantly decreased percent body fat in all groups, and 3) preserved lean mass in all groups. These results indicate that amylin's anorexigenic and fat-specific weight loss properties can be extended to a variety of nutritive states in female rats.

The simultaneous analysis of discrete and continuous outcomes in a dose-response study: using desirability functions.

Multiple types of outcomes are sometimes measured on each animal in toxicology dose-response experiments. The potential false-positive rate from statistical tests on each endpoint may be inflated. We introduce a method of deriving a composite score that combines information from discrete and continuous outcomes through the use of desirability functions. These functions transform observed responses of any type to a 0-to-1 unitless scale. The geometric mean is used to combine the scores and then a statistical model is fit to the dose-response curve of the overall score. The overall desirability score is more sensitive to toxicity evident in only a few endpoints than other composite scores that are based on sums of components. We analyze the overall score using a nonlinear exponential model with a threshold parameter. In this example, the threshold parameter was statistically significant and its estimate was less than the lowest dose. Compared to the vehicle control, the lower overall scores at this dose group were due to lower levels of brain and blood cholinesterase (90% and 82% of control, respectively) whereas other endpoints were not altered, thus demonstrating the sensitivity of the desirability function to detect low levels of toxicity in a small number of outcomes.