Bayesian Machine Learning Approach to the Quantification of Uncertainties on Ab Initio Potential Energy Surfaces.

This work introduces a novel methodology for the quantification of uncertainties associated with potential energy surfaces (PESs) computed from first-principles quantum mechanical calculations. The methodology relies on Bayesian inference and machine learning techniques to construct a stochastic PES and to express the inadequacies associated with the ab initio data points and their fit. By combining high fidelity calculations and reduced-order modeling, the resulting stochastic surface is efficiently forward propagated via quasi-classical trajectory and master equation calculations. In this way, the PES contribution to the uncertainty on predefined quantities of interest (QoIs) is explicitly determined. This study is done at both microscopic (e.g., rovibrational-specific rate coefficients) and macroscopic (e.g., thermal and chemical relaxation properties) levels. A correlation analysis is finally applied to identify the PES regions that require further refinement, based on their effects on the QoI reliability. The methodology is applied to the study of singlet (11A') and quintet (25A') PESs describing the interaction between O2 molecules and O atoms in their ground electronic state. The investigation of the singlet surface reveals a negligible uncertainty on the kinetic properties and relaxation times, which are found to be in excellent agreement with the ones previously published in the literature. On the other hand, the methodology demonstrated significant uncertainty on the quintet surface, due to inaccuracies in the description of the exchange barrier and the repulsive wall. When forward propagated, this uncertainty is responsible for the variability of 1 order of magnitude in the vibrational relaxation time and of factor four in the exchange reaction rate coefficient, both at 2500 K.

Construction of a coarse-grain quasi-classical trajectory method. I. Theory and application to N2-N2 system.

This work aims to construct a reduced order model for energy transfer and dissociation in non-equilibrium nitrogen mixtures. The objective is twofold: to present the Coarse-Grain Quasi-Classical Trajectory (CG-QCT) method, a novel framework for constructing a reduced order model for diatom-diatom systems; and to analyze the physics of non-equilibrium relaxation of the nitrogen molecules undergoing dissociation in an ideal chemical reactor. The CG-QCT method couples the construction of the reduced order model under the coarse-grain model framework with the quasi-classical trajectory calculations to directly construct the reduced model without the need for computing the individual rovibrational specific kinetic data. In the coarse-grain model, the energy states are lumped together into groups containing states with similar properties, and the distribution of states within each of these groups is prescribed by a Boltzmann distribution at the local translational temperature. The required grouped kinetic properties are obtained directly by the QCT calculations. Two grouping strategies are considered: energy-based grouping, in which states of similar internal energy are lumped together, and vibrational grouping, in which states with the same vibrational quantum number are grouped together. A zero-dimensional chemical reactor simulation, in which the molecules are instantaneously heated, forcing the system into strong non-equilibrium, is used to study the differences between the two grouping strategies. The comparison of the numerical results against available experimental data demonstrates that the energy-based grouping is more suitable to capture dissociation, while the energy transfer process is better described with a vibrational grouping scheme. The dissociation process is found to be strongly dependent on the behavior of the high energy states, which contribute up to 50% of the dissociating molecules. Furthermore, up to 40% of the energy required to dissociate the molecules comes from the rotational mode, underscoring the importance of accounting for this mode when constructing non-equilibrium kinetic models. In contrast, the relaxation process is governed primarily by low energy states, which exhibit significantly slower transitions in the vibrational binning model due to the prevalence of mode separation in these states.

Enhanced B Cell Alloantigen Presentation and Its Epigenetic Dysregulation in Liver Transplant Rejection.

T cell suppression prevents acute cellular rejection but causes life-threatening infections and malignancies. Previously, liver transplant (LTx) rejection in children was associated with the single-nucleotide polymorphism (SNP) rs9296068 upstream of the HLA-DOA gene. HLA-DOA inhibits B cell presentation of antigen, a potentially novel antirejection drug target. Using archived samples from 122 white pediatric LTx patients (including 77 described previously), we confirmed the association between rs9296068 and LTx rejection (p = 0.001, odds ratio [OR] 2.55). Next-generation sequencing revealed that the putative transcription factor (CCCTC binding factor [CTCF]) binding SNP locus rs2395304, in linkage disequilibrium with rs9296068 (D' 0.578, r(2) = 0.4), is also associated with LTx rejection (p = 0.008, OR 2.34). Furthermore, LTx rejection is associated with enhanced B cell presentation of donor antigen relative to HLA-nonidentical antigen in a novel cell-based assay and with a downregulated HLA-DOA gene in a subset of these children. In lymphoblastoid B (Raji) cells, rs2395304 coimmunoprecipitates with CTCF, and CTCF knockdown with morpholino antisense oligonucleotides enhances alloantigen presentation and downregulates the HLA-DOA gene, reproducing observations made with HLA-DOA knockdown and clinical rejection. Alloantigen presentation is suppressed by inhibitors of methylation and histone deacetylation, reproducing observations made during resolution of rejection. Enhanced donor antigen presentation by B cells and its epigenetic dysregulation via the HLA-DOA gene represent novel opportunities for surveillance and treatment of transplant rejection.

Energy transfer models in nitrogen plasmas: analysis of N2(X¹Σg⁺)-N(4S(u))-e⁻ interaction.

The relaxation of N2(X¹Σg⁺) molecules in a background gas composed of N((4)S(u)) atoms and free electrons is studied by using an ideal isochoric and isothermic chemical reactor. A rovibrational state-to-state model is developed to study energy transfer process induced by free electron and atomic collisions. The required cross sections and the corresponding rate coefficients are taken from two well-known kinetic databases: NASA Ames kinetic mechanism for the description of the N2(X¹Σg⁺)-N((4)S(u)) processes and the Phys4Entry database for the electron driven processes, N2(X¹Σg⁺)-e(-). The evolution of the population densities of each individual rovibrational level is explicitly determined via the numerical solution of the master equation for temperatures ranging from 10000 to 30,000 K. It was found that the distribution of the rovibrational energy levels of N2(X¹Σg⁺) is strongly influenced by the electron driven collisional processes, which promote the excitation of the low lying vibrational levels. The macroscopic vibrational energy relaxation is governed by the molecule-atom collisions, when free electrons, initially cold are relaxing to the final heat-bath temperature. Thus, the main role of the free electrons is to ensure the equilibration of vibrational and free electron excitation, thus validating the existence of the local equilibrium T(V)-T(e). However, if electrons and heavy particles are assumed to be in equilibrium at the heat bath temperature, electron driven processes dominate the vibrational relaxation. Finally, we have assessed the validity of the Landau-Teller model for the description of the inelastic energy transfer between molecules and free electrons. In the case of free-electron temperatures lower than 10,000 K, Landau-Teller relaxation model gives an accurate description of the vibrational relaxation, while at higher temperatures the error in the predictions can be significant and the model should not be used.

Potential sources of operating room air contamination: a preliminary study.

BACKGROUND: The Neptune® surgical suction system (NSSS) and the Bair Hugger® (BH) forced-air warmer both discharge filtered exhaust or heated air into the operating room (OR), often in close proximity to a surgical site. AIM: To assess the effectiveness of this filtration, we examined the quantity and identity of microbial colonies emitted from their output ports compared with those obtained from circulating air entering the OR. METHODS: Air samples were collected from each device using industry-standard sampling devices in which a measured volume of air is impacted on to a blood agar plate at a controlled flow rate. Twelve ORs were studied. Sample plates were incubated for one week per study protocol, then interpreted for colony counts and sent for species identification. FINDINGS: The average colony count from the NSSS exhaust was not significantly different from that obtained from room air samples, however the average count from the BH output was significantly higher (P=0.0086) than room air. Genetic identification profiles revealed the presence of environmental or commensal organisms that differed depending on the source. High variability in colony counts from both devices suggests that certain NSSS and BH devices could be significant sources of OR air contamination. CONCLUSIONS: Our study showed that the BH patient warming device could be a source of airborne microbial contamination in the OR and that individual BH and NSSS units exhibit a higher output of microbial cfu than would be expected compared with incoming room air. We make simple suggestions on ways to mitigate these risks.

Oral Salmonella: malaria circumsporozoite recombinants induce specific CD8+ cytotoxic T cells.

Oral immunization with an attenuated Salmonella typhimurium recombinant containing the full-length Plasmodium berghei circumsporozoite (CS) gene induces protective immunity against P. berghei sporozoite challenge in the absence of antibody. We found that this immunity was mediated through the induction of specific CD8+ T cells since in vivo elimination of CD8+ cells abrogated protection. In vitro studies revealed that this Salmonella-P. berghei CS recombinant induced class I-restricted CD8+ cytotoxic T cells that are directed against the P. berghei CS peptide epitope spanning amino acids 242-253. This is the same peptide that previously was identified as the target of cytotoxic T lymphocytes (CTL) induced by sporozoite immunization. Salmonella-P. falciparum CS recombinants were constructed that contained either the full-length CS gene or a repeatless gene consisting of CS flanking sequences. Both of these vaccines were able to induce CD8+ CTL directed against P. falciparum CS peptide 371-390, which is identical to the target of CTL induced by sporozoites and vaccinia CS recombinants. These results directly demonstrate the ability of an intracellular bacteria such as Salmonella to induce class I-restricted CD8+ CTL and illustrate the importance of CD8+ CTL in immunity to malaria.

Ovarian cancer stem-like side-population cells are tumourigenic and chemoresistant.

BACKGROUND: Ovarian cancer is the most lethal gynaecological malignancy. Although ovarian cancer patients often respond initially to chemotherapy, they usually develop chemoresistance. We hypothesised that a small portion of ovarian cancer cells have stem-like cell properties that contribute to tumourigenesis and drug resistance. METHODS: Flow cytometry and Hoechst 33342 efflux isolated side-population (SP) cells from ascites derived from ovarian cancer patients and from mice inoculated with human ovarian cancer cell lines. The SP cells were examined for stem cell markers OCT4, NANOG, STELLAR, and ABCG2/BCRP1 by immunocytochemistry and RT-PCR. The SP cells and non-SP cells were studied for tumourigenesis and chemoresistance in vitro and in vivo. RESULTS: The SP cells expressed ABCG2/BCRP1, OCT4, STELLAR, and NANOG, detected by immunocytochemistry and RT-PCR. ABCG2/BCRP1 expression was higher in SP than in non-SP cells. Xenogeneic mice inoculated with SP cells yielded more tumours than did mice inoculated with non-SP cells. In parallel, SP cell culture resulted in extensive cell proliferation, which was markedly more than in non-SP cells. SP cells resisted chemotherapy compared with non-SP cells, both in vivo and in vitro. CONCLUSION: Ovarian cancer SP cells are tumourigenic and chemoresistant. ABCG2/BCRP1 has an important role in chemoresistance, which has implications for new therapeutic approaches.

Allospecific CD154+ T cells associate with rejection risk after pediatric liver transplantation.

Antigen-specific T cells, which express CD154 rapidly, but remain untested in alloimmunity, were measured with flow cytometry in 16-h MLR of 58 identically-immunosuppressed children with liver transplantation (LTx), to identify Rejectors (who had experienced biopsy-proven rejection within 60 days posttransplantation). Thirty-one children were sampled once, cross-sectionally. Twenty-seven children were sampled longitudinally, pre-LTx, and at 1-60 and 61-200 days after LTx. Results were correlated with proliferative alloresponses measured by CFSE-dye dilution (n = 23), and CTLA4, a negative T-cell costimulator, which antagonizes CD154-mediated effects (n = 31). In cross-sectional observations, logistic regression and leave-one-out cross-validation identified donor-specific, CD154 + T-cytotoxic (Tc)-memory cells as best associated with rejection outcomes. In the longitudinal cohort, (1) the association between CD154 + Tc-memory cells and rejection outcomes was replicated with sensitivity/specificity 92.3%/84.6% for observations at 1-60 days, and (2) elevated pre-LTx CD154 + Tc-memory cell responses were associated with significantly increased incidence (p = 0.02) and hazard (HR = 7.355) of rejection in survival/proportional hazard analysis. CD154 expression correlated with proliferative alloresponses (r = 0.835, p = 7.1e-07), and inversely with CTLA4 expression of allospecific CD154 + Tc-memory cells (r =-0.706, p = 3.0e-05). Allospecific CD154 + T-helper-memory cells, not CD154 + Tc-memory, were inhibited by increasing Tacrolimus concentrations (p = 0.026). Collectively, allospecific CD154 + T cells provide an estimate of rejection risk in children with LTx.

Temporal variation in the genetic structure of a drone congregation area: an insight into the population dynamics of wild African honeybees (Apis mellifera scutellata).

The mating system of the honeybee (Apis mellifera) has been regarded as one of the most panmictic in the animal kingdom, with thousands of males aggregating in drone congregation areas (DCAs) that virgin queens visit to mate with tens of partners. Although males from many colonies gather at such congregations, the temporal changes in the colonies contributing drones remain unknown. Yet, changes in the DCAs' genetic structure will ultimately determine population gene flow and effective population size. By repeatedly sampling drones from an African DCA over a period of 3 years, we studied the temporal changes in the genetic structure of a wild honeybee population. Using three sets of tightly linked microsatellite markers, we were able to reconstruct individual queen genotypes with a high accuracy, follow them through time and estimate their rate of replacement. The number of queens contributing drones to the DCA varied from 12 to 72 and was correlated with temperature and rainfall. We found that more than 80% of these queens were replaced by mostly unrelated ones in successive eight months sampling intervals, which resulted in a clear temporal genetic differentiation of the DCA. Our results suggest that the frequent long-range migration of colonies without nest-site fidelity is the main driver of this high queen turnover. DCAs of African honeybees should thus be regarded as extremely dynamic systems which together with migration boost the effective population size and maintain a high genetic diversity in the population.

Concanavalin A and wheat germ agglutinin receptors on Dictyostelium discoideum. Their visualization by scanning electron microscopy with microspheres.

The cellular slime mold, Dictyostelium discoideum, is a convenient model for studying cellular interactions during development. Evidence that specific cell surface components are involved in cellular interactions during its development has been obtained by Gerisch and co-workers (1, 2) using immunological techniques. Smart and Hynes (3) have shown that a cell surface protein can be iodinated on cells in aggregation phase, but not in vegetative phase, by the lactoperoxidase procedure. Recently, McMahon et al. (4), and Hoffman and McMahon have demonstrated, by SDS gel electrophoresis, considerable differences in cell surface proteins and glycoproteins of plasma membranes isolated from cells at different stages of development. Plant lectins have also been used to monitor changes in cell surface properties of D. discoideum cells during development. Weeks and co-workers (5, 6) have detected differences in the binding and agglutination of cells by concanavalin A (Con A). Gillette and Filosa (7) have shown that Con A inhibits cell aggregation and prematurely induces cyclic AMP phosphodiesterase. Capping of Con A receptors has also been reported (8). Reitherman et al. (9) have recently reported that agglutination of cells by several plant lectins and the slime mold agglutination, discoidin, changes during development. Such studies indicate that differences in surface properties exist for cells at various stages of development. However, owing to the uncertainties in the factors which contribute to lectin-induced cell agglutination (10), the molecular basis for these observations remain to be determined. In this study, we have used microspheres (11-14) coupled to either Con A or wheat germ agglutinin (WGA) as visual markers to study by scanning electron microscopy the topographical distribution of lectin receptors on D. discoideum cells fixed at different stages of development. We also describe the effect of labeling on the distribution of lectin receptors and on the morphology of the cell surface.

Biologically active chorionic gonadotropin: synthesis by the human fetus.

The kidney, and to a slight extent the liver, of human fetuses were found to synthesize and secrete the alpha subunit common to glycoprotein hormones. Fetal lung and muscle did not synthesize this protein. Since fetal kidney and liver were previously found to synthesize beta chorionic gonadotropin, their ability to synthesize bioactive chorionic gonadotropin was also determined. The newly synthesized hormone bound to mouse Leydig cells and elicited a biological response: namely, the synthesis of testosterone. These results suggest that the human fetus may participate in metabolic homeostasis during its development.

Thermally driven molecular linear motors: a molecular dynamics study.

We conduct molecular dynamics simulations of a molecular linear motor consisting of coaxial carbon nanotubes with a long outer carbon nanotube confining and guiding the motion of an inner short, capsulelike nanotube. The simulations indicate that the motion of the capsule can be controlled by thermophoretic forces induced by thermal gradients. The simulations find large terminal velocities of 100-400 nm/ns for imposed thermal gradients in the range of 1-3 K/nm. Moreover, the results indicate that the thermophoretic force is velocity dependent and its magnitude decreases for increasing velocity.

BRAF V600E mutation in Juvenile Xanthogranuloma family neoplasms of the central nervous system (CNS-JXG): a revised diagnostic algorithm to include pediatric Erdheim-Chester disease.

The family of juvenile xanthogranuloma family neoplasms (JXG) with ERK-pathway mutations are now classified within the "L" (Langerhans) group, which includes Langerhans cell histiocytosis (LCH) and Erdheim Chester disease (ECD). Although the BRAF V600E mutation constitutes the majority of molecular alterations in ECD and LCH, only three reported JXG neoplasms, all in male pediatric patients with localized central nervous system (CNS) involvement, are known to harbor the BRAF mutation. This retrospective case series seeks to redefine the clinicopathologic spectrum of pediatric CNS-JXG family neoplasms in the post-BRAF era, with a revised diagnostic algorithm to include pediatric ECD. Twenty-two CNS-JXG family lesions were retrieved from consult files with 64% (n = 14) having informative BRAF V600E mutational testing (molecular and/or VE1 immunohistochemistry). Of these, 71% (n = 10) were pediatric cases (≤18 years) and half (n = 5) harbored the BRAF V600E mutation. As compared to the BRAF wild-type cohort (WT), the BRAF V600E cohort had a similar mean age at diagnosis [BRAF V600E: 7 years (3-12 y), vs. WT: 7.6 years (1-18 y)] but demonstrated a stronger male/female ratio (BRAF V600E: 4 vs WT: 0.67), and had both more multifocal CNS disease ( BRAFV600E: 80% vs WT: 20%) and systemic disease (BRAF V600E: 40% vs WT: none). Radiographic features of CNS-JXG varied but typically included enhancing CNS mass lesion(s) with associated white matter changes in a subset of BRAF V600E neoplasms. After clinical-radiographic correlation, pediatric ECD was diagnosed in the BRAF V600E cohort. Treatment options varied, including surgical resection, chemotherapy, and targeted therapy with BRAF-inhibitor dabrafenib in one mutated case. BRAF V600E CNS-JXG neoplasms appear associated with male gender and aggressive disease presentation including pediatric ECD. We propose a revised diagnostic algorithm for CNS-JXG that includes an initial morphologic diagnosis with a final integrated diagnosis after clinical-radiographic and molecular correlation, in order to identify cases of pediatric ECD. Future studies with long-term follow-up are required to determine if pediatric BRAF V600E positive CNS-JXG neoplasms are a distinct entity in the L-group histiocytosis category or represent an expanded pediatric spectrum of ECD.

Developmental and functional biology of the primate fetal adrenal cortex.

The unique characteristics of the primate (particularly human) fetal adrenal were first realized in the early 1900s when its morphology was examined in detail and compared with that of other species. The unusual architecture of the human fetal adrenal cortex, with its unique and disproportionately enlarged fetal zone, its compact definitive zone, and its dramatic remodeling soon after birth captured the interest of developmental anatomists. Many detailed anatomical studies describing the morphology of the developing human fetal adrenal were reported between 1920 and 1960, and these morphological descriptions have not changed significantly. More recently, it has become clear that fetal adrenal cortical growth involves cellular hypertrophy, hyperplasia, apoptosis, and migration and is best described by the migration theory, i.e. cells proliferate in the periphery, migrate centripetally, differentiate during their migration to form the functional cortical zones, and then likely undergo apoptosis in the center of the cortex. Consistent with this model, cells of intermediate phenotype, arranged in columnar cords typical of migration, have been identified between the definitive and fetal zones. This cortical area has been referred to as the transitional zone and, based on the expression of steroidogenic enzymes, we consider it to be a functionally distinct cortical zone. Elegant experiments during the 1950s and 1960s demonstrated the central role of the primate fetal adrenal cortex in establishing the estrogenic milieu of pregnancy. Those findings were among the first indications of the function and physiological role of the human fetal adrenal cortex and led Diczfalusy and co-workers to propose the concept of the feto-placental unit, in which DHEA-S produced by the fetal adrenal cortex is used by the placenta for estrogen synthesis. Tissue and cell culture techniques, together with improved steroid assays, revealed that the fetal zone is the primary source of DHEA-S, and that its steroidogenic activity is regulated by ACTH. In recent years, function of the human and rhesus monkey fetal adrenal cortical zones has been reexamined by assessing the localization and ontogeny of steroidogenic enzyme expression. The primate fetal adrenal cortex is composed of three functionally distinct zones: 1) the fetal zone, which throughout gestation does not express 3 beta HSD but does express P450scc and P450c17 required for DHEA-S synthesis; 2) the transitional zone, which early in gestation is functionally identical to the fetal zone but late in gestation (after 25-30 weeks) expresses 3 beta HSD, P450scc, and P450c17, and therefore is the likely site of glucocorticoid synthesis, and 3) the definitive zone, which lacks P450c17 throughout gestation but late in gestation (after 22-24 weeks) expresses 3 beta HSD and P450scc, and therefore is the likely site of mineralocorticoid synthesis. Indirect evidence, based on effects of P450c21 deficiency and maternal estriol concentrations, indicate that the fetal adrenal cortex produces cortisol and DHEA-S early in gestation (6-12 weeks). However, controversy exists as to whether cortisol is produced de novo or derived from the metabolism of progesterone, as data regarding the expression of 3 beta HSD in the fetal adrenal cortex early in gestation are conflicting. During the 1960s, Liggins and colleagues demonstrated that in the sheep, cortisol secreted by the fetal adrenal cortex late in gestation regulates maturation of the fetus and initiates the cascade of events leading to parturition. Those pioneering discoveries provided insight into the mechanism underlying the timing of parturition and therefore were of particular interest to obstetricians and perinatologists confronted with the problems of preterm labor. However, although cortisol emanating from the fetal adrenal cortex promotes fetal maturation in primates as it does in sheep, its role in the regulation of primate parturition, unlike that in sheep

Development and regulation of growth and differentiated function in human and subhuman primate fetal gonads.

We have attempted to summarize the research on primate fetal gonadal development that has occurred over the past three decades. Many similarities exist between fetal gonadal development in human and subhuman primates; therefore, comparisons and analogies between these species can be made. Fetal gonadal development is a complex process dependent on timely maturation and differentiation of several cell types with different functions. Adequate development is important for normal sexual development and intact adult fertility potential as well as for intrauterine priming of neural centers in the central nervous system. While the fetal primate testis is active in steroidogenesis, the fetal ovary seems to be quiescent throughout most of gestation, although some ovarian steroidogenic enzymes have been demonstrated. Growth and development of both gonads are controlled during late gestation at least in part by pituitary hormones, while earlier in gestation other yet undefined regulators (placental, intragonadal) likely also are active. The main goal of this review was to demonstrate that gonadal growth and differentiation, both in males and females, is regulated by endocrine factors as well as by intragonadal, autocrine/paracrine agents. Although many parts of the puzzle are still missing it is probable that, similar to fetal development of other endocrine tissues and to events in postnatal gonads, these local regulators have important functions. Currently, primate fetal gonadal research is lacking in at least two key aspects: 1) the definition of paracrine and autocrine nonsteroidal factors that are involved in the regulation of gonadal growth and differentiation in vitro; and 2) in vivo studies in subhuman primates that might better help to clarify the biological roles of the multiple extra- and intragonadal hormones and their complex interactions. To date, the regulation of gonadal steroidogenesis has been investigated more thoroughly than the regulation of gonadal growth. Most of our knowledge stems from observations of gonadal development in anencephalics or subhuman primates after pituitary ablation. Because of the constraints of small organ size and limitation of material, studies of fetal primate gonadal development have been limited. Given such limitations, new molecular biological techniques, including polymerase chain reaction and in situ hybridization, may provide the means of addressing these questions. Further, because of these limitations, sensitive cell separation techniques need to be developed to achieve enriched primary gonadal cell cultures from individual gonads.

Effects of the transient receptor potential vanilloid 1 antagonist A-425619 on body temperature and thermoregulation in the rat.

Transient receptor potential vanilloid 1 (TRPV1) receptor antagonists have gained much attention for their potential to treat inflammatory and neuropathic pain. However, systemic administration of TRPV1 antagonists induces a period of hyperthermia, a potential liability for small molecule development. Here we characterize the effects of the TRPV1 antagonist A-425619 on body temperature (T(b)) in the rat when administered: (1) alone at different times of the circadian cycle, (2) as repeated hourly or daily treatment, (3) as pre-treatment to prevent capsaicin-induced hypothermia, (4) to capsaicin-desensitized animals, and (5) prior to a heat challenge. Changes in T(b) were compared with compound exposure data, locomotor activity, and time course of efficacy in inflammatory pain models. Without affecting locomotor activity, oral administration of A-425619 induced a transient period of hyperthermia that was followed by a period of hypothermia, a profile unique among reported TRPV1 antagonists. Repeated hourly administration of A-425619 produced an increase in T(b) similar to a single administration. A-425619 had no effect on T(b) when administered to capsaicin-desensitized rats. The duration of A-425619-induced hyperthermia, but not hypothermia, was dependent on the time of the circadian cycle when administered. Pre-treatment with A-425619 attenuated capsaicin-induced hypothermia and did not potentiate T(b) or alter thermoregulatory behavioral responses during a heat challenge. These results indicate that A-425619-induced hyperthermia is transient, circadian-dependent, not related to exposure levels, locomotor activity, or time course of analgesic action, and does not affect the ability to thermoregulate during a heat challenge.

Evidence for a structural requirement for the aggregation of platelets by collagen.

This study investigates whether soluble collagen can initiate platelet aggregation or whether a higher degree of polymerization is required. Purified rat skin collagen was prepared in four states. Soluble monomeric collagen, containing 2 muM calcium chloride, was maintained at 4 degrees C until use. A previously uncharacterized form of collagen, soluble microfibrillar collagen, was prepared from monomeric collagen containing calcium chloride by allowing it to polymerize at 23 degrees C. Viscometric and electron microscopic characterization of microfibrillar collagen indicated polymerization to ordered native filaments. Particulate native macrofibrillar collagen was prepared from monomeric collagen by allowing it to polymerize at 37 degrees C in the absence of calcium. Particulate collagen, in which the fibers were randomly associated, was prepared by salt precipitation of calcium-free monomeric collagen. Microfibrillar and native macrofibrillar collagen initiated platelet aggregation, with a lag phase of approximately 60 s. Monomeric collagen initiated aggregation with a lag phase of approximately 180 s. The duration of the lag phase for platelet aggregation initiated by monomeric collagen was independent of the dose. Salt-precipitated particulate collagen did not initiate platelet aggregation. Agents which prolong the transition from monomeric collagen to fibrillar collagen (urea, arginine) retarded or prevented the aggregation of platelets by monomeric collagen. Sodium borohydride, which stabilizes the intraand intermolecular cross-links of collagen did not affect platelet aggregation. Penicillamine, which displaces the intermolecular cross-links and binds the intramolecular cross-links of collagen, did not prevent platelet aggregation. The data suggest that an architectural requirement exists for the initiation of self-perpetuating platelet aggregation; that tropocollagen units do not fulfill this requirement; that a soluble collagen preparation, microfibrillar collagen, contains the minimal structural unit; and that cross-linkages within collagen do not play a critical role in platelet aggregation.

Hypophysiotropic and neuromodulatory regulation of adrenocorticotropin in the human fetal pituitary gland.

Synthetic human corticotropin-releasing factor (hCRF) stimulated ACTH secretion by human fetal pituitaries in superfusion and dispersed human fetal pituitary cells cultured on an extracellular matrix in static incubation from 14 to 23 wk gestational age. The action of hCRF in vitro was potentiated by arginine vasopressin (AVP) at all ages studied. 8-Br-cAMP induced a response similar to hCRF. The AVP effect on ACTH was synergistic with both CRF and 8-Br-cAMP. hCRF-mediated secretion of ACTH was noncompetitively inhibited by 24-h pretreatment, or by 3-h concomitant treatment, with dexamethasone. Neither oxytocin, catecholamines, prostaglandins, nor indomethacin exerted significant effects on ACTH secretion, either alone or in combination with hCRF or AVP during the gestational ages studied. These results support a physiologic role for CRF in the regulation of secretion by corticotropic cells as early as 14 wk gestation, by which time corticotropes and ability to secrete ACTH have been demonstrated.

Activin and inhibin in the human adrenal gland. Regulation and differential effects in fetal and adult cells.

Recent experimental data have revealed that activins and inhibins exert pivotal effects on development. As part of our studies on growth and differentiation of the human fetal adrenal gland, we examined the subunit localization, as well as the mitogenic and steroidogenic actions of activin and inhibin in human fetal and adult adrenals. All three activin and inhibin subunit proteins (alpha, beta A, and beta B) were detected in the fetal and adult adrenal cortex. Immunoreactive activin-A dimer was demonstrated in midgestation fetal and neonatal adrenals. ACTH1-24-stimulated fetal adrenal cell expression of alpha and beta A subunit messenger RNA. In addition, ACTH elicited a rise in levels of immunoreactive alpha subunit secreted by fetal and adult adrenal cells. Human recombinant activin-A inhibited mitogenesis and enhanced ACTH-stimulated cortisol secretion by cultured fetal zone cells, but not definitive zone or adult adrenal cells. Recombinant inhibin-A had no apparent mitogenic or steroidogenic effects. Thus, activin selectively suppressed fetal zone proliferation and enhanced the ACTH-induced shift in the cortisol/dehydroepiandrosterone sulfate ratio of fetal zone steroid production. These data indicate that activin-A may be an autocrine or paracrine factor regulated by ACTH, involved in modulating growth and differentiated function of the human fetal adrenal gland.