The Open Virtual Mirror Framework for enfacement illusions : Enhancing the sense of agency with avatars that imitate facial expressions.

Enfacement illusions are traditionally elicited by visuo-tactile stimulation, but more active paradigms become possible through the usage of virtual reality techniques. For instance, virtual mirrors have been recently proposed to induce enfacement by visuo-motor stimulation. In a virtual mirror experiment, participants interact with an avatar that imitates their facial movements. The active control over the avatar greatly enhances the sense of agency, which is an important ingredient for successful enfacement illusion induction. Due to technological challenges, most virtual mirrors so far were limited to the imitation of the participant's head pose, i.e., its location and rotation. However, stronger experiences of agency can be expected by an increase in the avatar's mimicking abilities. We here present a new open-source framework for virtual mirror experiments, which we call the Open Virtual Mirror Framework (OVMF). The OVMF can track and imitate a large range of facial movements, including pose and expressions. It has been designed to run on standard computer hardware and easily interfaces with existing toolboxes for psychological experimentation, while satisfying the requirement of a tightly controlled experimental setup. Further, it is designed to enable convenient extension of its core functionality such that it can be flexibly adjusted to many different experimental paradigms. We demonstrate the usage of the OVMF and experimentally validate its ability to elicit experiences of agency over an avatar, concluding that the OVMF can serve as a reference for future experiments and that it provides high potential to stimulate new directions in enfacement research and beyond.

Guanyl nucleotides participate in the beta-adrenergic stimulation of adenylate cyclase activity in the intermediate lobe of the rat pituitary gland.

The existence of a stimulatory guanyl nucleotide component in the intermediate lobe of the rat pituitary gland (IL) is supported by the observations that: 1) GTP was required for beta-adrenergic stimulation of adenylate cyclase activity in homogenates of IL tissue; 2) GTP, in the absence of a beta-adrenergic agonist, maximally stimulated adenylate cyclase activity in homogenates of IL tissue previously treated with cholera toxin; and 3) GTP decreased the affinity of the beta-adrenoceptor for isoproterenol, a beta-adrenergic agonist. Although when tested on fresh IL tissue, 5'-guanylyl imidodiphosphate [Gpp(NH)p], a nonhydrolyzable analog of GTP, was substantially less active than GTP in stimulating adenylate cyclase activity in the presence of isoproterenol, GTP and Gpp(NH)p each stimulated adenylate cyclase to the same degree after solubilization of IL tissue previously treated with cholera toxin. GTP and Gpp(NH)p appeared to interact at the same site in this preparation.

Stimulation of a D-2 dopamine receptor in the intermediate lobe of the rat pituitary gland decreases the responsiveness of the beta-adrenoceptor: biochemical mechanism.

In experiments using a cell-free homogenate of the intermediate lobe of the hypophysis of the rat, apomorphine, a dopaminergic agonist, diminished both basal and L-isoproterenol-stimulated adenylate cyclase activity; dopaminergic antagonists from several chemical families reversed these inhibitory effects of apomorphine. Apomorphine diminished the ability of GTP to enhance both basal and L-isoproterenol-stimulated adenylate cyclase activity but did not directly interfere with the interaction between the beta-adrenoceptor and L-isoproterenol. The affinity of the D-2 dopamine receptor in the intermediate lobe for each dopaminergic antagonist used in this study was estimated from a mathematical analysis of the data. (Endocrinology 108: 420, 1981)

[3H]spiroperidol identifies a D-2 dopamine receptor inhibiting adenylate cyclase activity in the intermediate lobe of the rat pituitary gland.

[3H]Spiroperidol ([3H]SPIRO) binds with high affinity (Kd = 0.3 nM) to cell-free homogenates of the neurointermediate lobe of the rat pituitary gland. The neurointermediate lobe contains 19.2 fmol of specific binding sites, 86% of which occur in the intermediate lobe (IL). Compounds active upon the D-2 dopamine receptor in the IL compete with [3H]SPIRO for occupancy of the specific binding site. Guanosine 5'-triphosphate decreases the affinity of agonists, but not antagonists, for the specific binding site. For each drug tested, methods derived from competitive enzyme kinetics were used to calculate the apparent affinity constants of the drug for the binding site and for the receptor regulating adenylate cyclase activity. The pharmacological properties of the specific [3H]SPIRO binding site were compared to the pharmacological properties of the D-2 dopamine receptor inhibiting adenylate cyclase activity in the IL. The similarity between the affinities determined from the binding and enzyme assays suggests that some or all of the specific [3H]SPIRO binding sites in the IL are D-2 dopamine receptors inhibiting adenylate cyclase activity.

Coordinated action of calcium ion and adenosine 3',5'-monophosphate upon the release of alpha-melanocyte-stimulating hormone from the intermediate lobe of the rat pituitary gland.

Stimulation of the release of alpha MSH from dispersed rat melanotrophs by L-isoproterenol, 8-bromo-cAMP, or cholera toxin requires calcium ion (Ca++) in the incubation medium; the stimulatory effect of each of these agents is attenuated by D-600, a Ca++ antagonist. In contrast, stimulation of the formation of cAMP by L-isoproterenol, isobutyl methylxanthine, or cholera toxin does not require Ca++ in the incubation medium. Ca++ diminishes the amount of cAMP formed by cholera toxin-treated melanotrophs. Ca++ inhibits adenylate cyclase activity and enhances cyclic nucleotide phosphodiesterase activity in cell-free homogenates of intermediate lobe tissue. A23187, a calcium ionophore, increases the accumulation of 45Ca by melanotrophs and enhances the release of alpha MSH. Furthermore, when tested upon cholera toxin-treated melanotrophs, A23187 potentiates the Ca++-induced inhibition of cAMP formation. The results indicate that Ca++ is essential for the release of alpha MSH, and that cAMP in some way enhances the effects of Ca++ upon the release process.

D-2 dopamine receptor-mediated inhibition of adenylate cyclase activity in the intermediate lobe of the rat pituitary gland requires guanosine 5'-triphosphate.

After treatment with cholera toxin, homogenates of intact intermediate lobe (IL) tissue of rat pituitary gland synthesized more cAMP than did homogenates of untreated IL tissue, and only in the presence of GTP did dopamine or apomorphine diminish the elevated adenylate cyclase activity in homogenates of cholera toxin-treated IL tissue. Furthermore, when tested on cholera toxin-treated IL tissue, 5'-guanylyl imidodiphosphate [Gpp(NH)p] and two other nonhydrolyzable analogs of GTP inhibited adenylate cyclase activity in the absence of either a dopaminergic agonist or GTP; GTP reversed the Gpp(NH)p-induced inhibition of adenylate cyclase activity. Apomorphine, a dopaminergic agonist, abolished the ability of GTP to reverse the inhibition by Gpp(NH)p; this effect of apomorphine was prevented by fluphenazine, a dopaminergic antagonist. Sodium fluoride inhibited adenylate cyclase activity to approximately the same level obtained with GTP and apomorphine. In addition, apomorphine decreased cAMP accumulation and alpha MSH release from dispersed IL cells pretreated with cholera toxin.

HIV: early virus-cell interactions.

Two entry mechanisms of HIV occur in both lymphocytes and macrophages incubated with purified virus suspensions: (a) direct fusion of the viral envelope with the cell membrane and (b) receptor-mediated endocytosis via clathrin-coated pits and vesicles. Both mechanisms are shown in detail in a time-interval series of electron micrographs. The two lipid bilayers of the viral envelope and of the cellular membrane usually fuse seamlessly within 1-3 min at 37 degrees C, but occasionally membrane ruptures occur, leading to rapid cytopathic effects, i.e., vacuolization and cytolysis only a few minutes later. In the course of virus-cell fusion, gp 120 is integrated into the cell membrane; subsequent syncytia formation was observed after 1 h of incubation. The core disintegrates and releases the viral ribonucleoprotein through the opening at the fusion site into the cytoplasm.

Alterations at the Ink4a locus in transplacentally induced murine lung tumors.

The malignant phenotype results from multiple genetic alterations, including the activation of oncogenes and inactivation of tumor suppressor genes. Activation of the Ki-ras oncogene has been implicated as an early event in the pathogenesis of lung adenocarcinomas in humans and experimental animal models. Previous studies from this laboratory have shown that, following treatment of pregnant [D2 x B6D2F(1)]F(2) or Balb/c mice with the polycyclic aromatic hydrocarbon, 3-methylcholanthrene (MC), lung tumors from the transplacentally exposed offspring exhibited a high incidence of mutations in the Ki-ras gene. The role of genetic alterations at other oncogenic or tumor suppressor loci that can mediate lung tumor initiation and/or progression have not been well characterized in either human or murine models. Using the transplacental carcinogenesis model, which results in the induction of both lung and liver tumors following in utero exposure to MC, the results of this and our previous studies show that alterations in the Ink4a locus occur in only 15 and 27% of the lung and liver tumors, respectively. Preliminary data also suggests that the type of mutation induced in the Ki-ras gene following the initial exposure to MC may influence lung tumor progression. These results imply that damage to the Ink4a gene is not a frequent pathway to malignant progression in mouse lung and liver tumors following in utero exposure to environmental carcinogens.

Actions of growth hormone-releasing factor and somatostatin on adenylate cyclase and growth hormone release in rat anterior pituitary.

The interaction of growth hormone-releasing factor (GRF) and somatostatin (SRIF) on adenylate cyclase activity and growth hormone release was investigated in pituitary homogenates and 2-day cultured rat anterior pituitary cells. GRF stimulated growth hormone release by about 3-fold (ED50 1.6 X 10(-12) M) and caused a rapid 15-fold increase in cyclic AMP production (ED50 6.0 X 10(-12) M). The increase in cyclic AMP was due to direct stimulation of adenylate cyclase by GRF, which caused a 4-fold increase in the activity of the enzyme measured in anterior pituitary homogenates. GRF-induced cyclic AMP formation and GRF-stimulated adenylate cyclase activity were maximally inhibited to the extent of about 50% by 10(-8) M somatostatin. In contrast, GRF-stimulated growth hormone release was completely inhibited by somatostatin (ID50 3.2 X 10(-11) M), suggesting a second site of action of somatostatin. These studies demonstrate that GRF stimulates growth hormone release via activation of adenylate cyclase and a rise in intracellular cyclic AMP. In addition, these findings indicate that the inhibitory action of somatostatin on growth hormone release is exerted at two levels, one at the level of adenylate cyclase affecting the production of cyclic AMP, and the other beyond the formation of the nucleotide, at a site which modulates the release of growth hormone from the cell.

6,7-Dihydroxy-2-dimethylaminotetralin (TL-99) stimulates postjunctional D-1 and D-2 dopamine receptors.

6,7-Dihydroxy-2-dimethylaminotetralin (TL-99) mimicks the ability of dopamine either to enhance adenylate cyclase activity in homogenates of goldfish retina or to inhibit adenylate cyclase activity in homogenates of the intermediate lobe (IL) of the rat pituitary gland previously treated with cholera toxin. Both the dopamine stimulated adenylate cyclase activity in the fish retina and the dopamine inhibited adenylate cyclase activity in the rat IL are associated with cells postjunctional to the dopaminergic neurons innervating these tissues. Therefore, the present data do not support the contention that TL-99 is a selective presynaptic dopamine receptor agonist.

Immunolocalization of a 22 kDa protein (IPLA7, P22) of Borrelia burgdorferi.

The monoclonal antibody LA7 was raised against the species-specific Borrelia burgdorferi lipoprotein P22 (= IPLA7), which induces antibody formation in patients with Lyme arthritis. It is composed of 194 amino acids with a calculated molecular mass of 21.8 kDa. Its gene on the linear chromosome is 582 nucleotides in length. The aim of this study was to localize the protein P22 by immune electron microscopy. Immunolabeling of Borrelia burgdorferi with LA7 and an anti-mouse immunogold conjugate proved that P22 is an outer membrane protein. This finding was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis of the outer envelope fraction, which contained 99% of the P22 proteins.

Evidence that the D-2 dopamine receptor in the intermediate lobe of the rat pituitary gland is associated with an inhibitory guanyl nucleotide component.

Stimulation of the D-2 dopamine receptor in the intermediate lobe (IL) of the rat pituitary gland diminishes both basal and isoproterenol-stimulated adenylate cyclase activity. Cholera toxin increases IL adenylate cyclase activity and reduces the ability of beta-adrenergic agonists to further enhance enzyme activity but does not alter the functioning of the D-2 dopamine receptor. Indeed, cholera toxin-treated IL tissue provides a useful experimental system to investigate the involvement of guanyl nucleotides in the functioning of the IL D-2 dopamine receptor. GTP is obligatory for dopaminergic agonists to inhibit adenylate cyclase activity of cholera toxin-treated IL tissue. Furthermore, 5'-guanylyl imidodiphosphate (Gpp[NH]p), a nonhydrolyzable analog of GTP, inhibits adenylate cyclase activity in the absence of a dopaminergic agonist. GTP reverses the Gpp(NH)p-induced inhibition of adenylate cyclase activity; apomorphine, a dopaminergic agonist, abolishes this effect of GTP. It is hypothesized that the D-2 dopamine receptor in the IL interacts with an inhibitory guanyl nucleotide component (Ni); stimulation of the D-2 dopamine receptor alters the properties of Ni so that Ni can interact with GTP and inhibit adenylate cyclase activity.

Cohort-specific rural-urban migration in Africa.

"Rural-urban migration has been modeled by both demographers and economists since the 1960s. Little regard has been given by either discipline for the other's models.... The purpose of this paper is to address this void in the African context. We examine three hypotheses: (1) that variables explaining the net urban in-migration rates vary with the age of the migrants; (2) that changes in the availability of services in urban areas [are] a factor in migration; and (3) that cohort structures (age pyramids) are also part of the explanation."

Receptor-mediated actions of corticotropin-releasing factor in pituitary gland and nervous system.

High-affinity corticotropin-releasing factor (CRF) receptors which mediate the actions of the hypothalamic peptide on adrenocorticotropic hormone (ACTH) release have been identified in the rat anterior pituitary gland. Occupancy of the pituitary receptor by CRF agonists stimulates ACTH release via activation of adenylate cyclase and cyclic adenosine monophosphate dependent protein kinase. In the regulation of ACTH secretion, the effects of CRF on the corticotroph are integrated with the stimulatory actions of cyclic adenosine monophosphate-independent stimuli such as angiotensin II, vasopressin and norepinephrine, and the inhibitory effects of glucocorticoids and somatostatin. In contrast to the major importance of the inhibitory effect of glucocorticoid feedback on ACTH secretion, somatostatin has relatively little effect on CRF-stimulated ACTH release in the normal rat corticotroph. Following adrenalectomy, the progressive elevation of plasma ACTH levels is accompanied by a concomitant decrease in pituitary CRF receptors. The postadrenalectomy loss of CRF receptors, which is prevented by dexamethasone treatment, is caused by a combination of occupancy and processing of the pituitary sites during increased secretion of the hypothalamic peptide. Recently, specific receptors for CRF have been localized in the rat and monkey brain and adrenal medulla, where they are also coupled to adenylate cyclase. Brain CRF receptors are most abundant in the cerebral and cerebellar cortices and in structures related to the limbic system and control of the autonomic nervous system. The actions of CRF on the central and peripheral nervous systems, as well as on the pituitary gland, emphasize the role of CRF as a key hormone in the integrated response to stress.

Biochemical and physiological studies of the beta-adrenoceptor and the D-2 dopamine receptor in the intermediate lobe of the rat pituitary gland: a review.

The intermediate lobe (IL) of the rat pituitary gland responds to catecholamines. Catecholamines interacting with the beta-adrenoceptor stimulate adenylate cyclase activity, enhance cyclic AMP formation and thereby trigger the release of alpha-melanocyte-stimulating hormone (alpha-MSH). Catecholamines interacting with a D-2 dopamine receptor (in the classification schema of Kebabian and Calne) diminish adenylate cyclase activity and thereby decrease the capacity of IL cells to synthesize cyclic AMP. Dopaminergic agonists also inhibit the release of alpha-MSH from IL cells. The homogeneity of the IL facilitates biochemical investigations of this tissue.