Abstract IA20: Challenges, opportunities, and lessons learned in the bench-to-bedside translation of xenopatient studies

Progress in oncology drug development has been hampered by a lack of preclinical models that reliably predict clinical activity of novel compounds in cancer patients. This is thought to be largely due to the inability of cell culture and cell line xenograft models to faithfully recapitulate the complex genetic and histologic heterogeneity of tumors. Patient-derived xenograft (PDX) models, the topic of this meeting, have been shown to be biologically stable when passaged in mice in terms of global gene expression patterns, mutational status, drug responsiveness, and tumor architecture, thus providing an opportunity for more efficient and effective preclinical drug development. Potential applications include initial drug activity screening, biomarker development, assessment of combination strategies, and more recently, testing of immunotherapy strategies in humanized PDX models. With escalating concerns over heterogeneity between primary and metastatic sites and within the tumor itself, PDX models may also provide a platform for studying the evolution of heterogeneity, particularly within the context of drug resistance mechanisms. Despite all of the theoretical advantages of these models and potential novel applications, academic labs, which operate on a smaller scale than industry, must continue to refine and assess the opportunities and limitations of PDX models in order to ensure the greatest bench-to-bedside translation of novel therapies. Our group has been working with PDX models over the last seven years and has developed a large and robust bank of PDX models of which the majority has undergone full genomic annotation. In this session on practical applications of PDX models, specific examples will be presented that represent distinct scenarios of preclinical development within the context of the opportunities, challenges, and lessons learned in utilizing these models in xenopatient trials. There is no doubt that PDX models represent a more clinically relevant platform for oncology drug development, but it will be important to recognize their strengths and weaknesses in order to fully exploit their potential in the drug development process. This is particularly important for academic labs where partnerships with industry are valuable and resources may be limited.

Citation Format: S. Gail Eckhardt, Todd Pitts, Aik Choon Tan, Stacey Bagby, John Arcaroli, Anna Capasso, Kit Wong, Peter Klauck, Wells Messersmith, S Lindsey Davis, Christopher Lieu, Stephen Leong, Jennifer Diamond, John Tentler. Challenges, opportunities, and lessons learned in the bench-to-bedside translation of xenopatient studies. [abstract]. In: Proceedings of the AACR Special Conference: Patient-Derived Cancer Models: Present and Future Applications from Basic Science to the Clinic; Feb 11-14, 2016; New Orleans, LA. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(16_Suppl):Abstract nr IA20.

Abstract PR03: Characterizing the immune context of responses to immunotherapy in humanized patient derived xenograft models of CRC

Introduction: Inhibiting the activity of the epidermal growth factor receptor (EGFR) with monoclonal antibodies has been utilized as a therapeutic strategy for patients with metastatic colorectal cancer (CRC), leading to improved clinical results alone and in combination with standard chemotherapy. Many systematic reviews and metanalyses were performed to better understand the role of EGFR inhibition in CRC, revealing that KRAS exon 2 mutations and furthermore exons 3 and 4 and NRAS exons 2, 3, and 4 were predictive of non-responsiveness to these agents. Concurrent with these results has been the development of immunotherapy targeting immune regulatory checkpoints such as CTLA-4 and PD-1 that have initiated a new era in the treatment of cancer. In order to gain a better biological understanding of the context of immune responses and facilitate preclinical evaluation of cancer immunotherapy, we developed a hematopoietic humanized mouse model utilizing patient-derived CRC xenograft tumor models to assess immune therapy for RAS mutant CRC. Not only could evaluation of humanized RAS mutant PDX models provide additional information on the potential for clinical activity of immune therapies, but could also improve the understanding of immune responses to RAS mutant cancers. We therefore hypothesize that humanized RAS mutant colorectal PDX models can be used to evaluate the preclinical activity of immune targeted agents for treatment of RAS mutant colorectal cancer.

Methods: Humanized BRG mice developed from the BALB/cRag2-/-IL2Rγc-/- (BRG) strain which is known to accept human hematopoietic stem cells, have been used to enhance engraftment. BRG newborn pups were humanized through transplantation of approximately 1x105 CD34+ cells purified from umbilical cord blood. The mice were evaluated for chimerism at 8 and 12 weeks. At 14 weeks, tumor tissue from established PDX models were implanted on the right and left flank of humanized mice. The tumor was selected among a cluster within the “immune-enriched” subtype (C2) based upon the RNAseq characterization of the models. When the average tumor size reached a volume of approximately ~150-300 mm3, the mice were randomized into either vehicle or nivolumab treatment groups. Mice were monitored daily for signs of toxicity and weighed twice weekly. They were treated with nivolumab (30 mg/kg) twice a week by intraperitoneal injection for 15 days. Tumor size was evaluated twice weekly by caliper measurements using the following equation: tumor volume= (length × width2) × 0.52. At the end of the treatment, mice were euthanized while sera, lymph nodes, spleen, bone marrow and tumors were collected for further investigation.

Results: Humanized RAS mutant CRC PDX models were successfully established in vivo. While no differences were observed in tumor growth among the control and treated arms, we were able to detect differences in PD1 expression among treated versus control mice, with lower expression in the nivolumab treated group. We also observed higher numbers of T cells in the lymph nodes of nivolumab treated mice, suggesting T cell expansion. Interestingly, we also observed an increase of T cells in the spleen and blood and late occupancy of T cells in the bone marrow. Two of the treated mice exhibited identifiable TILs that were comprised of a majority of CD4+ T cells with an activated phenotype (CD69+).

Conclusions: Humanized KRAS mutant CRC PDX models were successfully established and tumor engraftment occurred in all humanized mice with nivolumab-treated mice demonstrating the development of lymph nodes that were populated by activated T cells. These preliminary results demonstrate that human immunity and PD-1 expressing T cells exist in these models and provide the basis for planned immunotherapy combination studies.

This abstract is also being presented as Poster A23.

Citation Format: Anna Capasso, Julie Lang, Todd M. Pitts, S. Lindsey Davis, Chris H. Lieu, Stacey M. Bagby, Aik Choon Tan, John J. Tentler, Jill E. Slansky, Roberta Pelanda, S. Gail Eckhardt. Characterizing the immune context of responses to immunotherapy in humanized patient derived xenograft models of CRC. [abstract]. In: Proceedings of the AACR Special Conference: Patient-Derived Cancer Models: Present and Future Applications from Basic Science to the Clinic; Feb 11-14, 2016; New Orleans, LA. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(16_Suppl):Abstract nr PR03.

Combined inhibition of MEK and Aurora A kinase in KRAS/PIK3CA double-mutant colorectal cancer models

Aurora A kinase and MEK inhibitors induce different, and potentially complementary, effects on the cell cycle of malignant cells, suggesting a rational basis for utilizing these agents in combination. In this work, the combination of an Aurora A kinase and MEK inhibitor was evaluated in pre-clinical colorectal cancer models, with a focus on identifying a subpopulation in which it might be most effective. Increased synergistic activity of the drug combination was identified in colorectal cancer cell lines with concomitant KRAS and PIK3CA mutations. Anti-proliferative effects were observed upon treatment of these double-mutant cell lines with the drug combination, and tumor growth inhibition was observed in double-mutant human tumor xenografts, though effects were variable within this subset. Additional evaluation suggests that degree of G2/M delay and p53 mutation status affect apoptotic activity induced by combination therapy with an Aurora A kinase and MEK inhibitor in KRAS and PIK3CA mutant colorectal cancer. Overall, in vitro and in vivo testing was unable to identify a subset of colorectal cancer that was consistently responsive to the combination of a MEK and Aurora A kinase inhibitor.

Antitumor activity of the MEK inhibitor TAK-733 against melanoma cell lines and patient-derived tumor explants

The goal of this study was to investigate the activity of the selective MEK1/2 inhibitor TAK-733 in both melanoma cell lines and patient-derived melanoma xenograft models. In vitro cell proliferation assays using the sulforhodamine B assay were conducted to determine TAK-733 potency and melanoma responsiveness. In vivo murine modeling with eleven patient-derived melanoma explants evaluated daily dosing of TAK-733 at 25 or 10 mg/kg. Immunoblotting was performed to evaluate on-target activity and downstream inhibition by TAK-733 in both in vitro and in vivo studies. TAK-733 demonstrated broad activity in most melanoma cell lines with relative resistance observed at IC50 > 0.1 μmol/L in vitro. TAK-733 also exhibited activity in 10 out of 11 patient-derived explants with tumor growth inhibition ranging from 0% to 100% (P < 0.001-0.03). Interestingly, BRAF(V600E) and NRAS mutational status did not correlate with responsiveness to TAK-733. Pharmacodynamically, pERK was suppressed in sensitive cell lines and tumor explants, confirming TAK-733-mediated inhibition of MEK1/2, although the demonstration of similar effects in the relatively resistant cell lines and tumor explants suggests that escape pathways are contributing to melanoma survival and proliferation. These data demonstrate that TAK-733 exhibits robust tumor growth inhibition and regression against human melanoma cell lines and patient-derived xenograft models, suggesting that further clinical development in melanoma is of scientific interest. Particularly interesting is the activity in BRAF wild-type models, where current approved therapy such as vemurafenib has been reported not to be active.

Triple-negative breast cancer: bridging the gap from cancer genomics to predictive biomarkers

Triple-negative breast cancer (TNBC) represents a challenge clinically due to a lack of response to hormonal and HER2-targeted agents coupled with an aggressive disease course. As the biology of this breast cancer subtype is better understood, it is clear that TNBC is a heterogeneous disease and one targeted therapy is unlikely to be active in all patients. Biomarkers predictive of response to treatment are thus of great importance in TNBC. This review outlines studies evaluating biomarkers predictive of response to neoadjuvant chemotherapy and to targeted therapies in the advanced setting. The development of validated biomarkers in conjunction with novel targeted therapies represents an opportunity to improve patient outcomes in TNBC.

Targeting nuclear kinases in cancer: development of cell cycle kinase inhibitors

Cellular proliferation is a tightly controlled set of events that is regulated by numerous nuclear protein kinases. The proteins involved include checkpoint kinases (CHK), cyclin-dependent kinases (CDK), which regulate the cell cycle and aurora kinases (AURK) and polo-like kinases (PLK), which regulate mitosis. In cancer, these nuclear kinases are often dysregulated and cause uncontrolled cell proliferation and growth. Much work has gone into developing novel therapeutics that target each of these protein kinases in cancer but none have been approved in patients. In this review we provide an overview of the current compounds being developed clinically to target these nuclear kinases involved in regulating the cell cycle and mitosis.

Abstract B48: A first-in-human Phase I study of the novel cancer stem cell (CSC) targeting antibody OMP-52M51 (anti-Notch1) administered intravenously to patients with certain advanced solid tumors

Background: The Notch pathway plays a central role in embryonic development, the regulation of stem and progenitor cells, and is implicated centrally in many forms of human cancer. Notch1 is known to be frequently activated in certain solid tumor types. OMP-52M51 is a humanized IgG2 antibody that inhibits the signaling function of the Notch1 receptor. Mouse xenograft studies using minimally-passaged, patient-derived xenografts have shown that OMP-52M51 impedes tumor growth and selectively eliminates CSCs in a range of tumor types particularly in tumors with activated Notch1 signaling. In these models, anti-Notch1 antibody also has anti-angiogenic effects leading to tumor growth inhibition. As such, OMP-52M51 is a novel anti-cancer agent that inhibits tumor growth through direct actions on tumor cells, including CSCs, and effects on tumor angiogenesis.

Methods: A phase I dose escalation and expansion study was initiated in patients with certain advanced solid tumor indications (cholangiocarcinoma, breast, colorectal, esophageal, gastric, and small cell lung cancers) that have frequencies of Notch1 activation of 12-29% (AACR 2013; #3728). OMP-52M51 was administered intravenously to study safety, pharmacokinetics (PK), pharmacodynamics (PD), preliminary efficacy, and to determine the maximum tolerated dose (MTD). The trial has a Notch1 IHC biomarker selected expansion cohort to test for single-agent response rate.

Results: Ten patients have been enrolled in 4 dose-escalation cohorts at doses of 0.25, 0.5, 1, and 2.5mg/kg administered every 4 weeks (Q4W). The most frequently reported drug-related adverse events were: mild to moderate diarrhea (56%), rash (22%), and nausea (22%). One patient developed grade 3 diarrhea for 24 hours controlled with Imodium. No dose-limiting toxicities (DLTs) have occurred and dose escalation continues. The PK of OMP-52M51 in patients is characterized by dose-dependent clearance. One patient with colorectal cancer has prolonged stable disease for &gt;100 days with a decline in CEA tumor marker. Biomarker analyses for Notch pathway modulation and activation are ongoing.

Conclusions: OMP-52M51 is generally well tolerated. Dose escalation continues and updated results will be presented.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B48.

Citation Format: S. Lindsey Davis, Patricia LoRusso, Lu Xu, Ann M. Kapoun, Jakob Dupont, Pamela Munster, S. Gail Eckhardt, Amita Patnaik. A first-in-human Phase I study of the novel cancer stem cell (CSC) targeting antibody OMP-52M51 (anti-Notch1) administered intravenously to patients with certain advanced solid tumors. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B48.

The development of regorafenib and its current and potential future role in cancer therapy

Regorafenib is a novel multikinase inhibitor that has demonstrated broad antitumor activity across various solid tumor types, in preclinical and clinical studies. Preclinical data show inhibitory activity of angiogenic, stromal and oncogenic tyrosine kinases through the targeting of vascular endothelial growth factor receptors 1, 2 and 3, tyrosine-protein kinase receptor TIE-2, platelet-derived growth factor receptor β, fibroblast growth factor receptor 1, proto-oncogene tyrosine-protein kinase receptor Ret, mast/stem cell growth factor receptor Kit, RAF proto-oncogene serine/threonine-protein kinase and wild-type and V600E mutant serine/threonine-protein kinase B-raf. Phase I trials have shown that the drug is relatively well tolerated at doses of 160 mg daily on a 3-weeks-on/1-week-off schedule, or 100 mg daily on a continuous schedule, with adverse effects typical of other multikinase inhibitors. Phase II studies demonstrated clinical benefit in a variety of tumor types, mostly associated with prolonged stable disease. Phase III studies include the CORRECT trial, which ultimately led to FDA approval of the drug in the setting of metastatic colorectal cancer previously treated with standard therapies. There is still much work to be done to determine the role of regorafenib in the future of cancer therapy. This review will focus on the development of regorafenib, from early preclinical work through phase I, II and III trials, as well as highlighting the current role and potential future directions of this novel agent.

Understanding soaring bird migration through interactions and decisions at the individual level

Many soaring bird species migrate southwards in autumn from their breeding grounds in Europe and Central Asia towards their wintering grounds. Our knowledge about interactions between migrating birds, thermal selection during migration and mechanisms that lead to flocking or convergent travel networks is still very limited. To start investigating these aspects we developed an individual-based simulation model that describes the local interactions between birds and their environment during their migratory flight, leading to emergent patterns at larger scales. The aim of our model is to identify likely decision rules with respect to thermal selection and navigation. After explaining the model, it is applied to analyse the migration of white storks (Ciconia ciconia) over part of its migration domain. A model base-run is accompanied by a sensitivity analysis. It appears that social interactions lead to the use of fewer thermals and slight increases in distance travelled. Possibilities for different model extensions and further model application are discussed.

Botulinum toxin abolishes sweating via impaired sweat gland responsiveness to exogenous acetylcholine

BACKGROUND

Botulinum toxin A (BTX) disrupts neurotransmitter release from cholinergic nerves. The effective duration of impaired sweat secretion with BTX is longer relative to that of impaired muscle contraction, suggesting different mechanisms in these tissues.

OBJECTIVES

The aim of this study was to test the hypothesis that BTX is capable of altering sweating by reducing the responsiveness of the sweat gland to acetylcholine.

METHODS

BTX was injected into the dorsal forearm skin of healthy subjects at least 3 days before subsequent assessment. On the day of the experiment, intradermal microdialysis probes were placed within the BTX-treated area and in an adjacent untreated area. Incremental doses of acetylcholine were administered through the microdialysis membranes while the sweat rate (protocol 1; n = 8) or a combination of sweat rate and skin blood flow (protocol 2; n = 8) were assessed.

RESULTS

A relative absence of sweating was observed at the BTX site for both protocols (protocol 1: 0.05 +/- 0.09 mg cm(-2) min(-1); protocol 2: 0.03 +/- 0.04 mg cm(-2) min(-1), both at the highest dose of acetylcholine), while the sweat rate increased appropriately at the control sites (protocol 1: 0.90 +/- 0.46 mg cm(-2) min(-1); protocol 2: 1.07 +/- 0.67 mg cm(-2) min(-1)). Cutaneous vascular conductance increased to a similar level at both the BTX and control sites.

CONCLUSIONS

These results demonstrate that BTX is capable of inhibiting sweat secretion by reducing the responsiveness of the sweat gland to acetylcholine, while not altering acetylcholine-mediated cutaneous vasodilatation.

Modeling Uhthoff's phenomenon in MS patients with internuclear ophthalmoparesis

OBJECTIVE

The goal of this investigation was to demonstrate that internuclear ophthalmoparesis (INO) can be utilized to model the effects of body temperature-induced changes on the fidelity of axonal conduction in multiple sclerosis (Uhthoff's phenomenon).

METHODS

Ocular motor function was measured using infrared oculography at 10-minute intervals in patients with multiple sclerosis (MS) with INO (MS-INO; n = 8), patients with MS without INO (MS-CON; n = 8), and matched healthy controls (CON; n = 8) at normothermic baseline, during whole-body heating (increase in core temperature 0.8 degrees C as measured by an ingestible temperature probe and transabdominal telemetry), and after whole-body cooling. The versional disconjugacy index (velocity-VDI), the ratio of abducting/adducting eye movements for velocity, was calculated to assess changes in interocular disconjugacy. The first pass amplitude (FPA), the position of the adducting eye when the abducting eye achieves a centrifugal fixation target, was also computed.

RESULTS

Velocity-VDI and FPA in MS-INO patients was elevated (p < 0.001) following whole body heating with respect to baseline measures, confirming a compromise in axonal electrical impulse transmission properties. Velocity-VDI and FPA in MS-INO patients was then restored to baseline values following whole-body cooling, confirming the reversible and stereotyped nature of this characteristic feature of demyelination.

CONCLUSIONS

We have developed a neurophysiologic model for objectively understanding temperature-related reversible changes in axonal conduction in multiple sclerosis. Our observations corroborate the hypothesis that changes in core body temperature (heating and cooling) are associated with stereotypic decay and restoration in axonal conduction mechanisms.

What would the world be like without animals for food, fiber, and labor? Are we morally obligated to do without them?

Numerous animal rights and animal liberation theorists have concluded that nonhuman animals have moral standing and noninterference rights. Therefore, they say that humans are morally obligated to stop using animals for food, fiber, labor, and research. I disagree with that conclusion for at least 2 reasons. First, it has been suggested that food production models are possible using large herbivores that might actually cause less harm (kill) to animals than a vegan food production model. This is because intensive crop production used to produce food for a vegan diet kills (harms) far more animals of the field than extensive agriculture (pasture production). So, a combined food production system that includes crops and pasture harvested by large herbivores to be used for human food may kill fewer animals than would a vegan-crop model. Second, pragmatically, it is improbable that all peoples of the world could ever be convinced that they must give up animals. In fact, it may be unethical to try to do that, because in poor countries, these animals are essential to the survival of the human populations. But what about the richer nations? Maybe they will or should be convinced to do without animals because of the moral strength of the animal rights and animal liberation theories. However, I believe that there are far too many obstacles for that to happen. What then are we morally obligated to do about animals? I suggest that animals do have moral standing, and that we are morally obligated to recognize their unique species-specific natures and treat them accordingly. That would mean treating animals according to their physical and behavioral needs or telos. That, I believe, is the most likely outcome of the conversation about animal rights.

Infective endocarditis caused by USA300 methicillin-resistant Staphylococcus aureus (MRSA)

We report seven cases of infective endocarditis caused by USA300 methicillin-resistant Staphylococcus aureus (MRSA) at an urban, tertiary care, academic institution. Five strains were community associated and two were healthcare associated. All patients were injection drug users. Staphylococcus aureus isolates were characterised as USA300-type MRSA using pulsed-field gel electrophoresis. Five cases were right-sided endocarditis and two cases were left-sided. The mean length of in-hospital antimicrobial therapy was 23 days and the mean length of total antibiotic therapy was 55 days. Complications included heart failure resulting in valve replacement in one patient as well as death in that patient. As USA300 strains of MRSA continue to increase in prevalence, clinicians must be aware of the increasing spectrum of illness in considering management and prevention strategies.

Epidemiology and outcomes of community-associated methicillin-resistant Staphylococcus aureus infection

Over a 2-year period (2003 to 2005) patients with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) and community-acquired methicillin-susceptible Staphylococcus aureus (CA-MSSA) infections were prospectively identified. Patients infected with CA-MRSA (n = 102 patients) and CA-MSSA (n = 102 patients) had median ages of 46 and 53 years, respectively; the most common sites of infection in the two groups were skin/soft tissue (80 and 93%, respectively), respiratory tract (13 and 6%, respectively), and blood (4 and 1%, respectively). Fourteen percent of patients with CA-MRSA infections and 3% of patients with CA-MSSA infections had household contacts with similar infections (P < 0.01). Among the CA-MRSA isolates, the pulsed-field gel electrophoresis (PFGE) groups detected were USA300 (49%) and USA100 (13%), with 27 PFGE groups overall; 71% of the isolates were staphylococcal chromosome cassette mec (SCCmec) type IV, 29% were SCCmec type II, and 54% had the Panton-Valentine leucocidin (PVL) gene. Among the CA-MSSA isolates there were 33 PFGE groups, with isolates of the USA200 group comprising 11%, isolates of the USA600 group comprising 11%, isolates of the USA100 group comprising 10%, and isolates of the PVL type comprising 10%. Forty-six and 18% of the patients infected with CA-MRSA and CA-MSSA, respectively, were hospitalized (P < 0.001). Fifty percent of the patients received antibiotic therapy alone, 5% received surgery alone, 30% received antibiotics and surgery, 3% received other therapy, and 12% received no treatment. The median durations of antibiotic therapy were 12 and 10 days in the CA-MRSA- and CA-MSSA-infected patients, respectively; 48 and 56% of the patients in the two groups received adequate antimicrobial therapy, respectively (P < 0.001). The clinical success rates of the initial therapy in the two groups were 61 and 84%, respectively (P < 0.001); recurrences were more common in the CA-MRSA group (recurrences were detected in 18 and 6% of the patients in the two groups, respectively [P < 0.001]). CA-MRSA was an independent predictor of clinical failure in multivariate analysis (odds ratio, 3.4; 95% confidence interval, 1.7 to 6.9). In the community setting, the molecular characteristics of the S. aureus strains were heterogeneous. CA-MRSA infections were associated with a more adverse impact on outcome than CA-MSSA infections.

A 2.5-Mb contig constructed from Angus, Longhorn and horned Hereford DNA spanning the polled interval on bovine chromosome 1

The polled locus has been mapped by genetic linkage analysis to the proximal region of bovine chromosome 1. As an intermediate step in our efforts to identify the polled locus and the underlying causative mutation for the polled phenotype, we have constructed a BAC-based physical map of the interval containing the polled locus. Clones containing genes and markers in the critical interval were isolated from the TAMBT (constructed from Angus and Longhorn genomic DNA) and CHORI-240 (constructed from horned Hereford genomic DNA) BAC libraries and ordered based on fingerprinting and the presence or absence of 80 STS markers. A single contig spanning 2.5 Mb was assembled. Comparison of the physical order of STSs to the corresponding region of human chromosome 21 revealed the same order of genes within the polled critical interval. This contig of overlapping BAC clones from horned and polled breeds is a useful resource for SNP discovery and characterization of positional candidate genes.

Heat stress enhances arterial baroreflex control of muscle sympathetic nerve activity via increased sensitivity of burst gating, not burst area, in humans

The relationship between muscle sympathetic nerve activity (MSNA) and diastolic blood pressure has been used to describe two sites for arterial baroreflex control of MSNA. By determining both the likelihood of occurrence for sympathetic bursts and the area of each burst for a given diastolic blood pressure, both a 'gating' and an 'area' control site has been described in normothermic humans. Assessing the effect of heat stress on these mechanisms will improve the understanding of baroreflex control of arterial blood pressure under this thermal condition. Therefore, the purpose of this study was to test the hypothesis that heat stress enhances arterial baroreflex control of burst gating and area. In 10 normotensive subjects (age, 32+/-2 years; mean+/-s.e.m.), MSNA (peroneal) was assessed using standard microneurographic techniques. Five minute periods of data were examined during normothermic and whole-body heating conditions. The burst incidence (i.e. number of sympathetic bursts per 100 cardiac cycles) and the area of each burst were determined for each cardiac cycle and were placed into 3 mmHg intervals of diastolic blood pressure. During normotheric conditions, there was a moderate, negative relationship between burst incidence and diastolic blood pressure (slope=-2.49+/-0.38; r(2)=0.73+/-0.06; mean+/-s.e.m.), while area per burst relative to diastolic blood pressure exhibited a less strong relationship (slope=-1.13+/-0.46; r(2)=0.45+/-0.09). During whole-body heating there was an increase in the slope of the relationship between burst incidence and diastolic blood pressure (slope=-4.69+/-0.44; r(2)=0.84+/-0.03) compared to normothermia (P<0.05), while the relationship between area per burst and diastolic blood pressure was unchanged (slope=-0.92+/-0.29; r(2)=0.41+/-0.08) (P=0.50). The primary finding of this investigation is that, at rest, whole-body heating enhanced arterial baroreflex control of MSNA through increased sensitivity of a 'gating' mechanism, as indicated by an increase in the slope of the relationship between burst incidence and diastolic blood pressure. This occurrence is likely to afford protection against potential decreases in arterial blood pressure in an effort to preserve orthostatic tolerance during heat stress.

Team approach to teaching participatory group process involving natural resources and agriculture

Contemporary issues are defined by people who share diverse and often strongly defended views about the topic. In Oregon, citizens are increasingly being asked or expected to participate in complex decisions that require a consensus. Rather than teach one professor's synthesis of a contemporary natural resource issue, faculty from six disciplines coach group process, interactive learning skills, and systems thinking as a way to address complex issues from multiple perspectives. Students learn by grappling with a natural resource issue of their choice within groups based on a diversity among majors, degree status, and gender. Students define situation (S), brainstorm new or different targets (T), and analyze two or more pathways (P), using an STP learning and action process. Exploring potential pathways involves defining possible consequences, stakeholder views, feasibility (ecological, social, economic, and political), and planning that includes expected behavior of the improved system over time. Students present their topics and improvements showing systemic relationships, systematic analysis, and integration of scientific facts and secondary data at midterm and during finals. Reflective learning is fostered throughout the course with prompted questions in a journal notebook. Grading criteria promote meaningful inquiry and participation in group process combined with integration of scientific facts and reflective learning.

Exogenous nitric oxide inhibits sympathetically mediated vasoconstriction in human skin

Two experiments were performed to identify whether nitric oxide (NO) inhibits sympathetically mediated vasoconstriction in human skin. In eight subjects increasing doses of sodium nitroprusside (SNP; 8.4 x 10(-6)-8.4 x 10(-3)m) were administered via intradermal microdialysis. At each dose of SNP, cutaneous vasoconstrictor responsiveness was assessed during a 3 min whole-body cold stress. The relative reduction in forearm cutaneous vascular conductance (CVC) during the cold stress was significantly attenuated for SNP doses greater than 8.4 x 10(-4)m (control: 63.0 +/- 4.1%, SNP 8.4 x 10(-6)m: 57.1 +/- 4.7%, SNP 8.4 x 10(-5)m: 57.0 +/- 3.6%, SNP 8.4 x 10(-4)m: 44.5 +/- 5.4% and SNP 8.4 x 10(-3)m: 28.8 +/- 7.9%). The second experiment was performed to identify whether this response was due to NO attenuating sympathetically mediated vasoconstriction or due to a non-specific effect of an elevated CVC secondary to SNP administration. In seven subjects forearm CVC during a whole-body cold stress was assessed at two sites: at a site dilated via microdialysis administration of SNP and at a site dilated with isoproterenol (ISO). CVC was not different between sites prior to (SNP: 0.42 +/- 0.11; ISO: 0.46 +/- 0.11 AU mmHg(-1) (AU, arbitrary units), P > 0.05) or following drug infusion (SNP: 1.36 +/- 0.21; ISO: 1.27 +/- 0.23 AU mmHg(-1), P > 0.05). The reduction in CVC during the subsequent cold stress was significantly less at the SNP site (38.1 +/- 6.2%) relative to the ISO site (65.0 +/- 5.5%; P= 0.007). These data suggest NO is capable of inhibiting sympathetically mediated vasoconstriction in the cutaneous vasculature.

Defining a middle ground for philosophers and production: bioethics

From the perspective of most animal scientists and producers, animal agriculture has become increasingly contentious over the last 10 to 20 years. Furthermore, our critics seem to be extremists whose views are biased and unreasonable. But guess what? The critics say the same thing about animal producers and scientists (us). So where is the middle ground and how do we get there? Should we even worry about trying to define the middle ground? Are these contentious issues a fad that will go away? Are these "extremist" critics so far outside reason that they will be ignored by society? Ignoring "them" is not likely to work because we have seen society changing its mind (developing a new social ethic) with regard to farm animals, in part because of what these critics are saying. As a result, it is vitally important for us to know and understand what is happening and why. For example, there isn't just one voice among the critics. There is actually a spectrum of opinion among the group which conventional agriculturalists usually call their critics. The WCC-204 committee generally agrees that the key to finding the middle ground between what is perceived as a polarized set of issues between "us" (animal scientists and producers) and "them" (philosopher critics) is for both sides to learn about the reasons why each side says what they do. Only then can all parties rationally begin to identify where the middle ground lies.

Pharmacokinetic and pharmacodynamic issues in the treatment of bacterial infectious diseases

This review outlines some of the many factors a clinician must consider when selecting an antimicrobial dosing regimen for the treatment of infection. Integration of the principles of antimicrobial pharmacology and the pharmacokinetic parameters of an individual patient provides the most comprehensive assessment of the interactions between pathogen, host, and antibiotic. For each class of agent, appreciation of the different approaches to maximize microbial killing will allow for optimal clinical efficacy and reduction in risk of development of resistance while avoiding excessive exposure and minimizing risk of toxicity. Disease states with special considerations for antimicrobial use are reviewed, as are situations in which pathophysiologic changes may alter the pharmacokinetic handling of antimicrobial agents.

Total mercury concentrations in lakes and fish of western Maryland, USA

The purpose of this study was to quantify total mercury concentrations in three species of fish in three lakes of western Maryland: Piney Creek reservoir, Deep Creek Lake, and Lake Habeeb. We measured total mercury concentrations in water from each lake and muscle tissue from 119 fish collected in fall 2000: 15 largemouth bass (Micropterus salmoides), 15 yellow perch (Perca flavescens), and 15 bluegill (Lepomis macrochirus) from the Piney Creek reservoir; 15 largemouth bass, 15 yellow perch, and 14 bluegill from Deep Creek Lake; and 15 largemouth bass and 15 bluegill from Lake Habeeb. Average total mercury concentrations (+/- SD) in surface waters were 0.96 +/- 0.03 ng L(-1) for the Piney Creek reservoir, 0.56 +/- 0.07 ng L(-1) for Deep Creek Lake, and 0.40 +/- 0.05 ng L(-1) for Lake Habeeb. These water quality differences were sometimes reflected in the total mercury concentration in fish muscle tissue. Total mercury concentrations in bluegill (0.05 +/- 0.02 microg g(-1)) and largemouth bass (0.10 +/- 0.03 microg g(-1)) from Lake Habeeb were significantly (p < 0.001) lower than the total mercury concentrations in bluegill and largemouth bass from the Piney Creek reservoir (bluegill: 0.13 +/- 0.04 microg g(-1) and largemouth bass: 0.37 +/- 0.18 microg g(-1)) and Deep Creek Lake (bluegill: 0.11 +/- 0.04 microg g(-1) and largemouth bass: 0.30 +/- 0.09 microg g(-1)). Yellow perch from the Piney Creek reservoir had significantly higher total mercury concentrations than yellow perch from Deep Creek Lake (0.20 +/- 0.08 microg g(-1) versus 0.13 +/- 0.04 microg g(-1)). In contrast, total mercury concentrations in largemouth bass from the Piney Creek reservoir and Deep Creek Lake were not significantly different. With the exception of largemouth bass from Lake Habeeb and yellow perch from Deep Creek Lake, there were relatively strong (r(2) > 0.39-0.79) log-log relationships between the size (weight and length) of the fish and total mercury concentrations in muscle tissue. The largest largemouth bass (> 800 g and > 38 cm) from both Deep Creek Lake and the Piney Creek reservoir had total mercury concentrations that exceeded the consumption advisory of 0.5 microg g(-1) that is used by many states and Canada. In contrast, total mercury concentrations in largemouth bass from Lake Habeeb did not exceed this consumption advisory. Our results suggest that fish consumption advisories are needed for largemouth bass in the Piney Creek reservoir and Deep Creek Lake.

Phenotypic and genetic correlations among floral traits in two species of Thalictrum

The evolution of dioecy in plants is expected to be followed by sex-specific selection, leading to sexual dimorphism. The extent of the response to selection depends on the genetic covariance structure between traits both within and between the sexes. Here I describe an investigation to determine phenotypic and genetic correlations between reproductive traits within cryptically dioecious Thalictrum pubescens and within morphologically dioecious T. dioicum. Females of T. pubescens produce flowers having stamens and pistils, appearing hermaphroditic. Genetic correlations were estimated as family-mean correlations among paternal half-sib families. Positive phenotypic and genetic correlations between parts of the same reproductive organs, as the anther and filament of the stamen, indicate developmental associations between these traits in both species. Negative genetic correlations were detected between pistil number and size of reproductive organs in T. dioicum and showed the same direction, but not significance, in T. pubescens. There was a negative phenotypic correlation between the number of stamens and the number of pistils within female flowers of T. pubescens. Within T. pubescens, there was a positive genetic correlation between the number of stamens in males and the number of pistils in females, indicating that floral evolution in males and females may not be independent in this species.

Effects of past abuse experiences on children's eyewitness memory

Relations between child maltreatment and children's eyewitness memory were examined. A matched sample of abused and nonabused 3- to 10-year-old children (n = 70) participated in a play session with an unfamiliar adult and were interviewed about the interaction 2 weeks later. Consistent with results from previous research, older compared to younger children's reports were more complete and accurate. Abused and nonabused children performed similarly with several exceptions: Nonabused children were more accurate in answering specific questions, made fewer errors in identifying the unfamiliar adult in a photo identification task, and (at least for younger boys) freely recalled more information. Most effects remained when group differences in IQ and behavioral symptomology were statistically controlled. Importantly, abused and nonabused children did not differ in their accuracy or suggestibility in response to questions that were relevant to abusive actions. Among abused children, however, those who suffered more severe sexual abuse made more omission errors to specific abuse-relevant questions. Contributions to psychological theory and legal implications for understanding children's eyewitness memory and testimony are discussed.

SdrG, a fibrinogen-binding bacterial adhesin of the microbial surface components recognizing adhesive matrix molecules subfamily from Staphylococcus epidermidis, targets the thrombin cleavage site in the Bbeta chain

Staphylococcus epidermidis is an important opportunistic pathogen and is a major cause of foreign body infections. We have characterized the ligand binding activity of SdrG, a fibrinogen-binding microbial surface component recognizing adhesive matrix molecules from S. epidermidis. Western ligand blot analysis showed that a recombinant form of the N-terminal A region of SdrG bound to the native Bbeta chain of fibrinogen (Fg) and to a recombinant form of the Bbeta chain expressed in Escherichia coli. By analyzing recombinant truncates and synthetic peptide mimetics of the Fg Bbeta chain, the binding site for SdrG was localized to residues 6-20 of this polypeptide. Recombinant SdrG bound to a synthetic 25-amino acid peptide (beta1-25) representing the N terminus of the Fg Bbeta chain with a KD of 1.4 x 10(-7) m as determined by fluorescence polarization experiments. This was similar to the apparent K(D) (0.9 x 10(-7) m) calculated from an enzyme-linked immunosorbent assay where SdrG bound immobilized Fg in a concentration-dependent manner. SdrG could recognize fibrinopeptide B (residues 1-14), but with a substantially lower affinity than that observed for SdrG binding to synthetic peptides beta1-25 and beta6-20. However, SdrG does not bind to thrombin-digested Fg. Thus, SdrG appears to target the thrombin cleavage site in the Fg Bbeta chain. In fact, SdrG was found to inhibit thrombin-induced fibrinogen clotting by interfering with fibrinopeptide B release.