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Rheology describes the flow of fluids from food and plastics, to coatings, adhesives, and 3D printing inks, and is commonly denoted by viscosity alone as a simplification. While viscometers adequately probe Newtonian (constant) viscosity, most fluids have complex viscosity, requiring tests over multiple shear rates, and transient measurements. As a result, rheometers are typically large, expensive, and require additional infrastructure (e.g., gas lines), rendering them inaccessible for regular use by many individuals, small organizations, and educators. Here, we introduce a low-cost (under USD$200 bill of materials) Open Source Rheometer (OSR), constructed entirely from thermoplastic 3D printed components and off-the-shelf electromechanical components. A sample fluid rests in a cup while a micro stepping motor rotates a tool inside the cup, applying strain-controlled shear flow. A loadcell measures reaction torque exerted on the cup, and viscosity is calculated. To establish the measurement range, the viscosity of four Newtonian samples of 0.1-10 Pa.s were measured with the OSR and compared to benchmark values from a laboratory rheometer, showing under 23% error. Building on this, flow curves of three complex fluids - a microgel (hand sanitizer), foam (Gillette), and biopolymer solution (1% Xanthan Gum) - were measured with a similar error range. Stress relaxation, a transient test, was demonstrated on the biopolymer solution to extract the nonlinear damping function. We finally include detailed exposition of measurement windows, sources of error, and future design suggestions. The OSR cost is ∼1/25th that of commercially available devices with comparable minimum torque (200 µN.m), and provides a fully open-source platform for further innovation in customized rheometry., Competing Interests: Declarations. Competing interests: The authors CEO and AJH declare US utility patent US11698330B2 on fractal vane structures. The authors otherwise declare no conflict of interest., (© 2024. The Author(s).)

Montelukast, a Food and Drug Administration-approved drug for asthma and allergic rhinitis modulates leukotriene (LT) receptors and serves as a critical anti-inflammatory agent. Recent research suggests that the LT signaling pathway targeted by montelukast has broader implications for diseases such as fibrosis, cardiovascular diseases, cancer, cerebrovascular disease, and immune defense. This expanded understanding highlights montelukast's potential for repurposing in conditions involving aberrant stress mechanisms, including ocular diseases marked by inflammation, oxidative stress, ER stress, and apoptosis, among several others. This review delves into montelukast's therapeutic mechanisms across various diseases, draws parallels to ocular conditions, and examines clinical trials and associated adverse effects to underscore the unmet need for cysteinyl LT receptor antagonism by montelukast as an effective therapy for visual deficits.

An in vivo trial was conducted to determine the apparent digestibility coefficients (ADCs) of insect meals for rainbow trout, Oncorhynchus mykiss. Rainbow trout (approximately 370 g ± 23 g, mean ± SD initial weight) were stocked 25 per tank into 400-liter tanks. Fish were fed a reference diet, or 1 of 5 test diets created by blending the reference diet in a 70:30 ratio (dry-weight basis) with menhaden fish meal (MFM), 2 house cricket (Acheta domesticus) meals (cricket A and cricket B), Galleria mellonella meal, and yellow mealworm (Tenebrio molitor) meal. Diets were assigned to 3 replicate tanks of fish and fed twice daily for 14 days prior to fecal collection. Ingredients, diets, and fecal matter were analyzed in duplicate for proximate, mineral, and amino acid composition. House cricket meals were 67.3% and 69.0% protein (CP) and 16.6% and 17.1% lipid (CL), for house cricket A and B, respectively. Yellow mealworm meal contained 56.5% CP and 27.7% CL, and G. mellonella larvae meal contained 32.5% CP and 54.2% CL. Protein ADCs were 78.9 for G. mellonella larvae meal, 78.0 for yellow mealworm meal, and 76.5 for house cricket A and not different from the MFM protein ADC of 76.6, while house cricket B protein ADC was 65.8 and was significantly lower than the MFM protein ADC (F = 7.39; df = 4,14; P = 0.0049). Together, these nutritional values suggest house crickets, and yellow mealworms show promise as alternative protein sources in salmonid feeds, with the potential of G. mellonella as an alternative lipid source., (Published by Oxford University Press on behalf of Entomological Society of America 2024.)

Introduction: In the United States, over one in every ten households experiences food insecurity. Food insecurity is associated with often co-occurring adverse health consequences, including risk for obesity, type 2 diabetes, and hypertension. Within the "Food is Medicine" intervention space, Produce Prescription Programs (PRx) seek to alleviate food insecurity and improve diet and health outcomes by leveraging access to produce through healthcare organizations. Though these programs are burgeoning across the United States, research surrounding their implementation and outreach is limited., Methods: This study evaluates the implementation, reach, engagement, and retention of a PRx program piloted in two regions of Georgia (US) from 2020 to 2022. The study included 170 people living with one or more cardiometabolic conditions recruited from clinical sites in metropolitan and rural areas. The program provided pre-packaged produce boxes and nutrition education over six months. We examine participants' baseline demographics, food security status, dietary patterns, and loss to follow-up across contexts (metropolitan and rural). We employ regression analyses and model comparison approaches to identify the strongest predictors of loss to follow-up during the pilot period., Results: In the pilot period of this program, 170 participants enrolled across rural and metropolitan sites. Of these, 100 individuals (59%) remained engaged for the six-month program. While many individuals met the target criteria of living with or at-risk of food insecurity, not all lived with low or very low food security. Metropolitan participants, males, and those with children in the household had significantly higher odds of loss to follow-up compared to rural participants, females, and those without children in the household. No other significant demographic or household differences were observed., Discussion: This study demonstrates the potential of PRx programs to enhance food and nutrition security and cardiometabolic health in metropolitan and rural clinical settings. Future research should focus on addressing barriers to engagement and expanding the reach, impact, and sustainability of PRx programs across diverse contexts., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Owens, Cook, Reasoner, McLean and Webb Girard.)

At an estimated cost of $8 billion annually in the United States, revision surgeries to total joint replacements represent a substantial financial burden to the health care system and a tremendous mental and physical burden on patients and their caretakers. Fixation failures, such as implant loosening, wear, and mechanical instability of the poly(methyl methacrylate) (PMMA) cement, which bonds the implant to the bone, are the main causes of long-term implant failure. Early and accurate diagnosis of cement failure is critical for developing novel therapeutic strategies and reducing the high risk of a misjudged revision. Unfortunately, prevailing imaging modalities, notably plain radiographs, struggle to detect the precursors of implant failure and are often interpreted incorrectly. Our prior work has shown that the modification of PMMA bone cement with low concentrations of conductive fillers makes it piezoresistive and therefore self-sensing. When combined with a conductivity imaging modality such as electrical impedance tomography (EIT), it is possible to monitor load transfer across the PMMA using cost-effective, physiologically benign, non-contact, and real-time electrical measurements. Despite the ability of EIT for monitoring load transfer across self-sensing PMMA bone cement, it is unable to accurately characterize failure mechanisms. Overcoming this challenge is critical to the success of this technology in practice. Therefore, we herein expand upon our previous results by integrating machine learning techniques with EIT for cement condition characterization with the goal of establishing the feasibility of even off-the-shelf machine learning algorithms to address this important problem. We survey a wide variety of different machine learning algorithms for application to this problem, including neural networks on voltage readings of an EIT phantom for tracking the spatial position of a sample, specifying defect orientation within a sample, and classifying defect types, including cracks and delaminations. In addition, we explore the utilization of principal component analysis (PCA) for pre-treating impedance signals in each of these problems. Within the tested algorithms, our results show clear advantages of neural networks, support vector machines, and K-nearest neighbor algorithms for interpreting EIT signals. We also show that PCA is an effective addition to machine learning. These preliminary results demonstrate that the combination of smart materials, EIT, and machine learning may be a powerful instrumentation tool for diagnosing the origin and evolution of mechanical failure in joint replacements., (© 2023 Author(s). Published under an exclusive license by AIP Publishing.)

Micro-prosthetics requires the fabrication of mechanically robust and personalized components with sub-millimetric feature accuracy. Three-dimensional (3D) printing technologies have had a major impact on manufacturing such miniaturized devices for biomedical applications; however, biocompatibility requirements greatly constrain the choice of usable materials. Hydroxyapatite (HA) and its composites have been widely employed to fabricate bone-like structures, especially at the macroscale. In this work, we investigate the rheology, printability, and prosthetic mechanical properties of HA and HA-silk protein composites, focusing on the roles of composition and water content. We correlate key linear and nonlinear shear rheological parameters to geometric outcomes of printing and explain how silk compensates for the inherent brittleness of printed HA components. By increasing ink ductility, the inclusion of silk improves the quality of printed items through two mechanisms: (1) reducing underextrusion by lowering the required elastic modulus and, (2) reducing slumping by increasing the ink yield stress proportional to the modulus. We demonstrate that the elastic modulus and compressive strength of parts fabricated from silk-HA inks are higher than those for rheologically comparable pure-HA inks. We construct a printing map to guide the manufacturing of HA-based inks with excellent final properties, especially for use in biomedical applications for which sub-millimetric features are required.

Development of a refractory selective solar absorber (RSSA) is the key to unlock high-temperature solar thermal and thermochemical conversion. The fundamental challenge of RSSA is the lack of design and fabrication guidelines to simultaneously achieve omnidirectional, broadband solar absorption and sharp spectral selectivity at the desired cutoff wavelength. Here, we realize a ruthenium-carbon nanotube (Ru-CNT) nanocomposite RSSA with multiscale nanoparticle-on-nanocavity plasmonic modes. Ru conformally coated on the sidewalls of CNTs enables a spoof surface plasmon polariton mode for spectra selectivity; Ru nanoparticles formed at the tips of CNTs enable a localized surface plasmon resonance mode and plasmon hybridization for omnidirectional broadband solar absorption. The fabricated Ru-CNT RSSA has a total solar absorption (TSA) of 96.1% with sharp spectral cutoff at 2.21 μm. The TSA is maintained at over 90% for an incident angle of 56°. Our findings therefore guide full-spectrum optical and thermal control from visible to the far-infrared.

Ionic liquids (ILs) hold great potential as solvents to dissolve, recycle, and regenerate cellulosic fabrics, but the dissolved cellulose material system requires greater study in conditions relevant to fiber spinning processes, especially characterization of nonlinear shear and extensional flows. To address this gap, we aimed to disentangle the effects of the temperature, cellulose concentration, and degree of polymerization (DOP) on the shear and extensional flows of cellulose dissolved in an IL. We have studied the behavior of cellulose from two sources, fabric and filter paper, dissolved in 1-ethyl-3-methylimidazolium acetate ([C 2 C 1 Im][OAc]) over a range of temperatures (25 to 80 °C) and concentrations (up to 4%) that cover both semidilute and entangled regimes. The linear viscoelastic (LVE) response was measured using small-amplitude oscillatory shear techniques, and the results were unified by reducing the temperature, concentration, and DOP onto a single master curve using time superposition techniques. The shear rheological data were further fitted to a fractional Maxwell liquid (FML) model and were found to satisfy the Cox-Merz rule within the measurement range. Meanwhile, the material response in the non-LVE (NLVE) regime at large strains and strain rates has special relevance for spinning processes. We quantified the NLVE behavior using steady shear flow tests alongside uniaxial extension using a customized capillary breakup extensional rheometer. The results for both shear and extensional NLVE responses were described by the Rolie-Poly model to account for flow-dependent relaxation times and nonmonotonic viscosity evolution with strain rates in an extensional flow, which primarily arise from complex polymer interactions at high concentrations. The physically interpretable model fitting parameters were further compared to describe differences in material response to different flow types at varying temperatures, concentrations, and DOP. Finally, the fitting parameters from the FML and Rolie-Poly models were connected under the same superposition framework to provide a comprehensive description within the wide measured parameter window for the flow and handling of cellulose in [C 2 C 1 Im][OAc] in both linear and nonlinear regimes.

Chlorosulfonic acid and oleum are ideal solvents for enabling the transformation of disordered carbon nanotubes (CNTs) into precise and highly functional morphologies. Currently, processing these solvents using extrusion techniques presents complications due to chemical compatibility, which constrain equipment and substrate material options. Here, we present a novel acid solvent system based on methanesulfonic or p -toluenesulfonic acids with low corrosivity, which form true solutions of CNTs at concentrations as high as 10 g/liter (≈0.7 volume %). The versatility of this solvent system is demonstrated by drop-in application to conventional manufacturing processes such as slot die coating, solution spinning continuous fibers, and 3D printing aerogels. Through continuous slot coating, we achieve state-of-the-art optoelectronic performance (83.6 %T and 14 ohm/sq) at industrially relevant production speeds. This work establishes practical and efficient means for scalable processing of CNT into advanced materials with properties suitable for a wide range of applications.

Body systems once thought sterile at birth instead have complex and sometimes abundant microbial ecosystems. However, relationships between dam and calf microbial ecosystems are still unclear. The objectives of this study were to (1) characterize the various maternal and calf microbiomes during peri-partum and post-partum periods and (2) examine the influence of the maternal microbiome on calf fecal microbiome composition during the pre-weaning phase. Multiparous Holstein cows were placed in individual, freshly bedded box stalls 14 d before expected calving. Caudal vaginal fluid samples were collected approximately 24 h before calving and dam fecal, oral, colostrum, and placenta samples were collected immediately after calving. Calf fecal samples were collected at birth (meconium) and 24 h, 7 d, 42 d, and 60 d of age. Amplicons covering V4 16S rDNA regions were generated using DNA extracted from all samples and were sequenced using 300 bp paired end Illumina MiSeq sequencing. Spearman rank correlations were performed between genera in maternal and calf fecal microbiomes. Negative binomial regression models were created for genera in calf fecal samples at each time point using genera in maternal microbiomes. We determined that Bacteroidetes dominated the calf fecal microbiome at all time points (relative abundance ≥42.55%) except for 24 h post-calving, whereas Proteobacteria were the dominant phylum (relative abundance = 85.10%). Maternal fecal, oral, placental, vaginal, and colostrum microbiomes were significant predictors of calf fecal microbiome throughout pre-weaning. Results indicate that calf fecal microbiome inoculation and development may be derived from various maternal sources. Maternal microbiomes could be used to predict calf microbiome development, but further research on the environmental and genetic influences is needed.

Although the presence of bacteria has been characterized throughout the reproductive tracts of multiple species, how these bacteria may interact with the host has yet to be described. Previous reviews have described how pathogenic bacteria interact with the reproductive tract to cause infections such as metritis. This review aimed to summarize the knowledge related to pathogenic and nonpathogenic bacteria in various locations of the bovine reproductive tract and the possible mechanisms underlying host-microbe interactions during gametogenesis and early pregnancy. Lactic acid bacteria such as Lactobacillus seem to be beneficial in multiple areas of the reproductive tract: they have been associated with increased oocyte quality when in follicular fluid and secrete reactive oxygen species that are beneficial during placental angiogenesis. However, other bacteria, including Enterococcus, Staphylococcus, and Streptococcus, may modulate T helper cells that inhibit maternal recognition of pregnancy. Available data on the reproductive microbiome focus on variations in microbial communities and their associations with reproductive performance. However, research on these host-microbiome interactions may provide more insight on how bacteria affect fertility., (The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).)

Cascade-specific termination of G protein signaling is catalyzed by the RGS (regulator of G protein signaling) family members, including RGS2 . Angiotensin, vasopressin, and endothelin are implicated in preeclampsia, and RGS2 is known to inhibit G protein cascades activated by these hormones. Mutations in RGS2 are associated with human hypertension and increased risk of developing preeclampsia and its sequelae. RGS family members are known to influence maternal vascular function, but the role of RGS2 within the placenta has not been explored. Here, we hypothesized that reduced expression of RGS2 within the placenta represents a risk factor for the development of preeclampsia. Although cAMP/CREB signaling was enriched in placentas from human pregnancies affected by preeclampsia compared with clinically matched controls and RGS2 is known to be a CREB-responsive gene, RGS2 mRNA was reduced in placentas from pregnancies affected by preeclampsia. Experimentally reducing Rgs2 expression within the feto-placental unit was sufficient to induce preeclampsia-like phenotypes in pregnant wild-type C57BL/6J mice. Stimulation of RGS2 transcription within immortalized human HTR8/SVneo trophoblasts by cAMP/CREB signaling was discovered to be dependent on the activity of histone deacetylase activity, and more specifically, HDAC9 (histone deacetylase-9), and HDAC9 expression was reduced in placentas from human pregnancies affected by preeclampsia. We conclude that reduced expression of RGS2 within the placenta may mechanistically contribute to preeclampsia. More generally, this work identifies RGS2 as an HDAC9 -dependent CREB-responsive gene, which may contribute to reduced RGS2 expression in placenta during preeclampsia.

Increases in milk replacer dietary energy subsequently increase growth and weight in preweaned dairy heifers. However, the underlying effects of dietary component increases on key functional pathways have yet to be fully investigated. Elucidating these relationships may provide insights into the mechanisms through which protein and fat are partitioned for tissue growth and metabolism. We hypothesized that genes within key growth and metabolic pathways would be differentially expressed between calves fed a protein- and fat-restricted diet and calves fed a protein- and fat-enhanced diet. The objectives of this study were to (1) identify genes differentially expressed between dietary restricted calves and enhanced calves and (2) determine the key regulatory pathways influenced by these genes. Preweaned Holstein heifers (n = 12; 6 ± 0.02 d of age) were randomly assigned to 1 of 2 milk replacer diets: enhanced (28.9% crude protein, 26.2% fat; n = 6) or restricted (20.9% crude protein, 19.8% fat; n = 6). Growth measures included average daily gain and gain-to-feed ratio. After 56 d, calves were killed for tissue collection. Samples from longissimus dorsi, adipose, and liver tissues were collected and RNA was isolated for RNA sequencing analysis. The MIXED procedure of SAS (SAS Institute Inc., Cary, NC) was used to evaluate relationships of growth with dietary energy. Fixed effects included date of collection and time (day). Random effects included sire and birth weight. The RNA sequencing analysis was performed using CLC Genomics Workbench (Qiagen, Germantown, MD), and the Robinson and Smith exact test was used to identify differentially expressed genes between diets. The Protein Analysis Through Evolutionary Relationships (PANTHER) database was then used to identify functional categories of differentially expressed genes. Enhanced calves had increased growth rates and feed efficiency compared with restricted calves (average daily gain = 0.76 and 0.22, respectively; gain-to-feed ratio = 0.10 and 0.06, respectively). There were 238 differentially expressed genes in adipose, 227 in longissimus dorsi, and 40 in liver. We identified 10 genes concordant among tissues. As expected, functional analyses suggested that the majority of genes were associated with metabolic or cellular processes, predominantly cell communication and cell cycle. Overall, it appears that varying levels of dietary protein and fat influence calf growth and development through metabolic processes, including oxidative phosphorylation and glyceroneogenesis. However, protein- and fat-restricted calves appeared to experience metabolic stress at a cellular level, as evidenced by an upregulation in stress response pathways, including genes in the p53 pathway. Calves could be fed at a higher level of protein and fat to decrease the prevalence of metabolic stress at the cellular level, but evidence indicating the presence of inflammatory stress and adipose fibrosis in enhanced calves prompts further investigation of the effects of milk replacer component levels., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Background: Embryonic and fetal exposure to maternal obesity causes several maladaptive morphological and epigenetic changes in exposed offspring. The timing of these events is unclear, but changes can be observed even after a short exposure to maternal obesity around the time of conception. The hypothesis of this work is that maternal obesity influences the ovine preimplantation conceptus early in pregnancy, and this exposure will affect gene expression in embryonic and extraembryonic tissues., Results: Obese and lean ewe groups were established by overfeeding or normal feeding, respectively. Ewes were then bred to genetically similar rams. Conceptuses were collected at day 14 of gestation. Morphological assessments were made, conceptuses were sexed by genomic PCR analysis, and samples underwent RNA-sequencing analysis. While no obvious morphological differences existed between conceptuses, differentially expressed genes (≥ 2-fold; ≥ 0.2 RPKM; ≤ 0.05 FDR) were detected based on maternal obesity exposure (n = 21). Also, differential effects of maternal obesity were noted on each conceptus sex (n = 347). A large portion of differentially expressed genes were associated with embryogenesis and placental development., Conclusions: Findings reveal that the preimplantation ovine conceptus genome responds to maternal obesity in a sex-dependent manner. The sexual dimorphism in response to the maternal environment coupled with changes in placental gene expression may explain aberrations in phenotype observed in offspring derived from obese females.

Wider use and adaptation of microfluidics is hindered by the infrastructure, knowledge, and time required to build prototype systems, especially when multiple fluid operations and measurements are required. As a result, 3D printing of microfluidics is attracting interest, yet cannot readily achieve the feature size, smoothness, and optical transparency needed for many standard microfluidic systems. Herein we present a new approach to the design and construction of high-precision modular microfluidics, using standard injection-molded blocks that are modified using micromilling and assembled via elastically averaged contacts. Desktop micromilling achieves channel dimensions as small as 50 μm depth and 150 μm width and adhesive films seal channels to allow internal fluid pressure of >400 kPa. Elastically averaged connections between bricks result in a mechanical locating repeatability of ∼1 μm, enabling fluid to pass between bricks via an O-ring seal with >99.9% reliability. We demonstrated and tested block-based systems for generating droplets at rates above 9000 min -1 and COV <3%, and integrated optical sensors. We also show how blocks can be used to build easily reconfigurable interfaces with glass microfluidic devices and imaging hardware. Microfluidic bricks fabricated by FDM and SLA 3D printing cannot achieve the dimensional quality of molded bricks, yet 3D printing allows customized bricks to be integrated with standard LEGOs. Our approach enables a wide variety of modular microfluidic units to be built using a widely available, cost-effective platform, encouraging use in both research and education.

The precise arrangement of microscopic objects is critical to the development of functional materials and ornately patterned surfaces. Here, we present an acoustics-based method for the rapid arrangement of microscopic particles into organized and programmable architectures, which are periodically spaced within a square assembly chamber. This macroscale device employs two-dimensional bulk acoustic standing waves to propel particles along the base of the chamber toward pressure nodes or antinodes, depending on the acoustic contrast factor of the particle, and is capable of simultaneously creating thousands of size-limited, isotropic and anisotropic assemblies within minutes. We pair experiments with Brownian dynamics simulations to model the migration kinetics and assembly patterns of spherical microparticles. We use these insights to predict and subsequently validate the onset of buckling of the assemblies into three-dimensional clusters by experiments upon increasing the acoustic pressure amplitude and the particle concentration. The simulations are also used to inform our experiments for the assembly of non-spherical particles, which are then recovered via fluid evaporation and directly inspected by electron microscopy. This method for assembly of particles offers several notable advantages over other approaches (e.g., magnetics, electrokinetics and optical tweezing) including simplicity, speed and scalability and can also be used in concert with other such approaches for enhancing the types of assemblies achievable.

Utilizing agonist-stimulated GTPgammaS autoradiography, we analyzed the ability of preproorphanin FQ (ppOFQ) peptides to stimulate [35S]-GTPgammaS binding in adult rat brain. Orphanin FQ (OFQ) stimulated [35S]-GTPgammaS binding in a pattern similar to that described for [125I]-OFQ at the endogenous opioid receptor-like (ORL1) receptor. The ppOFQ peptides nocistatin and orphanin FQ2 (OFQ II(1-17)) had no effect, suggesting that they do not mediate their reported analgesic effects via a G(i/o)-coupled receptor (i.e. opioid or ORL1). Unlike OFQ II(1-17), high concentrations of its C-terminal extension, OFQ II(1-28), stimulated [35S]-GTPgammaS binding in a mu (mu) opioid receptor-like distribution and the effect was blocked by naloxone. To explore these observations, we evaluated the receptor binding profile of OFQ II(1-28) at the cloned ORL1 and mu opioid receptors. OFQ II(1-28) had no specific binding at either ORL1 or mu opioid receptors at concentrations up to 50 microM. This lack of affinity was not consistent with a mu-mediated effect, as suggested by preliminary observation using functional autoradiography in rat brain sections. Although behavioral studies suggest that OFQ II(1-28) possesses analgesic activity, this effect does not appear to be mediated via direct binding at the mu opioid receptor. Taken together, these findings support the view that (1) OFQ is the only ppOFQ peptide that binds to and activates the ORL1 receptor and (2) OFQ II(1-28) does not bind or stimulate [35S]-GTPgammaS binding in cells expressing the mu opioid receptor.

It is unclear how opioid selectivity and activation are regulated within the receptor core. In previous studies, the OFQ receptor was converted into a functional opioid receptor by mutating five amino acids at three sites to the corresponding residues conserved across the mu-, kappa-, and delta-opioid receptors, suggesting that these sites comprise an opioid binding pocket. To examine this hypothesis, the present study examines whether these conserved residues represent an opioid binding pocket in the context of the opioid receptors, i.e., does their removal from opioid receptors destroy opioid ligand binding? The reciprocal mutations K227A (transmembrane [TM]5), IHI290-292VQV (TM6), and I316T (TM7) were evaluated in the kappa-opioid receptor. In terms of alkaloid binding, there were no changes in affinity for mutants K227A and IHI290-292VQV. At mutant I316T, antagonist binding was unaltered, but there was a trend toward slightly decreased agonist affinity. In contrast, the binding of peptides had a more complex pattern. Again, K227A and IHI290-292VQV did not decrease the binding affinity of dynorphin-related peptides. Mutant I316T had 10- to 20-fold decreased affinity for dynorphin-related peptides, suggesting that I316 is part of a critical dynorphin recognition site. In response to alkaloid stimulation, I316T activated more G-protein(s) than wild type, and similar levels were observed in response to dynorphin stimulation. Overall, these results suggest that ligands are capable of achieving high-affinity binding through interaction with multiple sites/conformations of the receptor. These different modes of interaction have different down-stream results in terms of receptor activation and signal transduction.

A novel phenylaminotetralin (PAT) radioligand, [(3)H]-(1R, 3S)-(-)-trans-1-phenyl-3-dimethylamino-1,2,3,4-tetrahydronaphthalene ([(3)H]-[-]-trans-H(2)-PAT), is shown here to label a saturable (B(max)=39+/-6 fmol/mg protein) population of sites with high affinity (K(d)=0.13+/-0.03 nM) in guinea pig brain. Consistent with previous studies which showed that PATs stimulate catecholamine (dopamine) synthesis in rat striatum, autoradiographic brain receptor mapping studies here indicate that [(3)H]-(-)-trans-H(2)-PAT-labeled sites are highly localized in catecholaminergic nerve terminal fields in hippocampus, nucleus accumbens, and striatum in guinea pig brain. Competition binding studies with a broad range of CNS receptor-active ligands and CNS radioreceptor screening assays indicate that the pharmacological binding profile of brain [(3)H]-(-)-trans-H(2)-PAT sites closely resembles histamine H(1)-type receptors. Comparative studies using the histamine H(1) antagonist radioligand, [(3)H]mepyramine, indicate that the H(1) ligand binding profile and guinea pig brain distribution of H(1) receptors and [(3)H]-(-)-trans-H(2)-PAT sites are nearly identical; moreover, both sites have about 40-fold stereoselective affinity for (-)- over (+)-trans-H(2)-PAT. These results are discussed in light of previous studies which suggested that PATs stimulate dopamine synthesis through interaction with a novel sigma-type (sigma(3)) receptor in rodent brain; it now appears instead that PATs represent a new class of ligands for brain histamine H(1) receptors that can be stereoselectively labeled with [(3)H]-(-)-trans-H(2)-PAT., (Copyright 1999 Published by Elsevier Science B.V.)

A series of 1-phenyl-3-amino-1,2,3,4-tetrahydronaphthalenes (1-phenyl-3-aminotetralins, PATs) previously was found to stimulate tyrosine hydroxylase activity and dopamine synthesis in rat brain through interaction with a novel sigma 3 receptor. Specifically, the trans-1R,3S-(-) isomer of H2-PAT showed highest affinity for sigma 3 receptors and also produced maximal stimulation of tyrosine hydroxylase activity and dopamine synthesis, as compared to the trans-1S,3R-(+) isomer. Affinity for sigma 3 receptors and functional potency at stimulating dopamine synthesis were attenuated either by altering the position or dimethyl substitution pattern of the amino group or by hydroxylating the tetralin aromatic ring. A preliminary binding model can accommodate many PAT analogs and several non-PATs with a wide range of affinities for the sigma 3 receptor. Here, we report the synthesis and evaluation of additional analogs in order to expand previous structure-activity relationship studies. Further molecular modifications include synthesis of 1-phenyl-1-methyl-3-amino, 1-phenyl-2-amino, 1-phenyl-3-(trimethylammoniumyl), and 1-phenyl-3-(phenylalkyl) analogs, as well as ring-expanded tetrahydrobenzocycloheptenes. In general, the above modifications decreased sigma 3 receptor affinity and, in some cases, caused a reversal of the sigma 3 binding selectivity of trans- versus cis-PATs found previously. Most analogs were selective for sigma 3 receptors and showed little or no affinity for either sigma 1/sigma 2 or dopamine D1, D2, and D3 receptors. N-Phenylalkyl substituents, such as N-phenylethyl, however, endowed the 1-phenyl-3-aminotetralins with enhanced sigma 1/sigma 2 and dopamine receptor affinity while decreasing sigma 3 affinity, thus abolishing sigma 3 selectivity.

Molecular modeling studies were carried out on a series of 1-phenyl-3-amino-1,2,3,4-tetrahydronaphthalenes (phenylaminotetralins, PATs), several PAT structural analogs, and various non-PAT ligands that demonstrate a range of affinities for a novel sigma 3 receptor linked to stimulation of tyrosine hydroxylase and dopamine synthesis in rodent brain. In an effort to develop a ligand-binding model for the sigma 3 receptor, a pharmacophore mapping program (DISCO) was used to identify structural features that are common to ligands that exhibit moderate to high binding affinity for sigma 3 sites. DISCO then was utilized to propose a common pharmacophoric region that included one low-energy conformation of each compound in the training set. The resulting alignment was utilized in a comparative molecular field analysis (CoMFA) study in an attempt to correlate the steric and electrostatic fields of the molecules with the respective binding affinities at the sigma 3 receptor. A suitably predictive model was obtained from the CoMFA analysis which will be employed in the development of additional PAT analogs that could potentially display high affinity and selectivity for the sigma 3 receptor. The excluded volumes which resulted from comparing molecular volumes of active and inactive compounds were visualized to examine the limits of steric tolerance imposed by the sigma 3 receptor.

The proposed D3-selective ligand (+/-)-7-hydroxy-N,N-dipropylaminotetralin (7-OH-DPAT) inhibited tyrosine hydroxylase in vitro (IC50 = 0.6-0.7 microM) and dihydroxyphenylalanine (DOPA) accumulation in vivo (ID50 = 4.8-6.4 mg/kg) in two autoreceptor models in extrapyramidal and limbic tissue in rat forebrain, without consistent regional selectivity. Some limbic selectivity (ID50 = 10 vs. 29 mg/kg) was found in an in vivo model permitting expression of postsynaptic D3 and D2 receptor activity. The effects were partially blocked by S(-)-eticlopride alone, and fully after reserpine pretreatment. The results suggest that 7-OH-DPAT activates D3 or D2 autoreceptors, alters dopamine storage or release, and may interact with some limbic selectivity at postsynaptic D3 and D2 receptors as a partial agonist.

Certain novel 1-phenyl-3-amino-1,2,3,4-tetrahydronaphthalenes (1-phenyl-3-aminotetralins, PATs) produced stimulation (ca. 30% above basal levels) of tyrosine hydroxylase (TH) activity at 0.1 microM concentrations in rodent brain tissue. This effect on TH was blocked by the putative sigma-receptor antagonist BMY-14802, suggesting involvement of a novel neuromodulatory sigma-like receptor. Within the new phenylaminotetralin series, a correlation was found between the ability to stimulate TH and the potency to compete for binding sites labeled by (+/-)-[3H]1-phenyl-3-(N,N-dimethylamino)-6-chloro-7-hydroxy-1,2,3,4- tetrahydronaphthalene ([3H](+/-)-4). trans-Catechol analogs had low affinity for [3H]4 sites, and although they inhibited TH activity, this effect was not blocked by known sigma or dopamine antagonists. Analogs with dihydroxy substituents (catechols), as well as nitrogen substituents larger than methyl, had little affinity for [3H]4 binding sites and did not significantly affect TH activity. The pharmacology of the [3H]4 binding site is unique from that of any known sigma or dopamine receptor, thus the effects appear to be mediated by a previously uncharacterized binding site/receptor. The site has stereoselectivity for the (1R,3S)-(-)-isomer of 1-phenyl-3-(N,N-dimethylamino)-1,2,3,4-tetrahydronaphthalene; this isomer is also more active at stimulating TH. Thus, certain 1-phenyl-3-amino-1,2,3,4-tetrahydronaphthalenes appear to be selective probes of a novel receptor type that mediates sigma-like neuromodulatory activity and may have pharmacotherapeutic utility in conditions in which modulation of dopamine function is important.