Adolescent exposure to oxytocin, but not the selective oxytocin receptor agonist TGOT, increases social behavior and plasma oxytocin in adulthood.

There are indications that exposing adolescent rodents to oxytocin (OT) may have positive "trait-changing" effects resulting in increased sociability and decreased anxiety that last well beyond acute drug exposure and into adulthood. Such findings may have relevance to the utility of OT in producing sustained beneficial effects in human psychiatric conditions. The present study further examined these effects using an intermittent regime of OT exposure in adolescence, and using Long Evans rats, that are generally more sensitive to the acute prosocial effects of OT. As OT has substantial affinity for the vasopressin V1a receptor (V1aR) in addition to the oxytocin receptor (OTR), we examined whether a more selective peptidergic OTR agonist - [Thr4, Gly7]-oxytocin (TGOT) - would have similar lasting effects on behavior. Male Long Evans rats received OT or TGOT (0.5-1mg/kg, intraperitoneal), once every three days, for a total of 10 doses during adolescence (postnatal day (PND) 28-55). Social and anxiety-related behaviors were assessed during acute administration as well as later in adulthood (from PND 70 onwards). OT produced greater acute behavioral effects than TGOT, including an inhibition of social play and reduced rearing, most likely reflecting primary sedative effects. In adulthood, OT but not TGOT pretreated rats displayed lasting increases in social interaction, accompanied by an enduring increase in plasma OT. These findings confirm lasting behavioral and neuroendocrine effects of adolescent OT exposure. However, the absence of such effects with TGOT suggests possible involvement of the V1aR as well as the OTR in this example of developmental neuroplasticity.

Hormonal effects on the secretion and glycoform profile of corticosteroid-binding globulin.

Corticosteroid-binding globulin (CBG) is a plasma glycoprotein that is primarily synthesized in the liver and binds cortisol and progesterone with high affinity. In this study, a CBG secreting hepatocellular carcinoma derived cell line (HepG2) was used to investigate the hormonal regulation of hepatic CBG synthesis. HepG2 cells were grown for 72 h in 30, 300 and 3000 nM concentrations of estradiol (E2), testosterone (T), insulin, thyroxin (T4) and dexamethasone (DMZ) and the secreted CBG quantified by a novel enzyme-linked immunosorbent assay (ELISA). Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) was carried out to determine the effects of these hormones on the relative distribution of CBG glycoforms. Insulin, T4 and high concentrations of E2 decreased the secretion of CBG by HepG2 cells (p<0.05). Ethanol, the solvent used for E2, T and DMZ, also significantly attenuated CBG secretion. 2D-PAGE resolved 13-14 glycoforms of CBG produced by HepG2 cells. Insulin caused a reduction in the synthesis of more acidic, while T4 and DMZ decreased the production of more basic CBG glycoforms. Stimulation with E2 resulted in the synthesis of additional isoforms of increased acidity, which may represent a type of CBG only seen during pregnancy in vivo. Possible physiological implications of these findings are discussed.

Evaluation of biodistribution by local versus systemic administration of 99mTc-labeled pamidronate.

BACKGROUND: There is an emerging interest in utilizing local and systemic administration of bisphosphonates in orthopedics. The primary objective of this study was to use (99m)Tc-pamidronate ((99m)Tc-PAM) as a tool and compare bone and tissue uptake by local versus systemic administration. METHODS: (99m)Tc-PAM was administered intravenously (i.v.), subcutaneously (s.c.) and by direct application (d.a.) on a surgically exposed and fractured femur (d.a.#f). The animals were imaged at 2 h and 24 h after administration and then killed. Organs were harvested, and their radioactivity was estimated. Specific uptake in the right femur was compared between groups, as was systemic exposure to (99m)Tc PAM. RESULTS: Bone uptake of (99m)Tc-PAM in the i.v. and s.c. groups was 2.2 +/- 0.15 and 0.65 +/- 0.07% ID/g, respectively, at the 2 h time point. Uptake by surgically exposed right femur (d.a) was 5.15 +/- 0.26% ID/g, 134% higher than the femoral uptake by the i.v. method (P < 0.05). In the presence of exposed bone when the femur was fractured (d.a.#f), the uptake was 7.89 +/- 0.46% ID/g, a further 50% increase (P < 0.05). The uptake of (99m)Tc-PAM increased after 24 h of application to 2.4 +/- 0.15, 1.53 +/- 0.09, 7.94 +/- 0.99, and 13.2 +/- 0.80% ID/g) for i.v., s.c., d.a., and d.a.#f methods, respectively. The increases in uptake for the d.a. methods were significantly higher than for the local methods at the 24-h time point (P < 0.05). Although renal uptake was comparable with the i.v. and s.c. methods (0.22 +/- 0.03 and 0.22 +/- 0.04% ID/g), it was significantly lower with the d.a. methods (0.05 +/- 0.07 and 0.16 +/- 0.07% ID/g) (P < 0.05). The corresponding urinary excretion was 55%, 45%, 36%, and 35% of the injected dose at 24 h. CONCLUSIONS: The results indicate that the bone uptake of (99m)Tc-PAM was significantly higher (P = 0.001) and the kidney uptake significantly lower (P = 0.004) with the d.a. methods than with the i.v. or s.c. method. The findings indicate the need for further study into the potential of local administration of bisphosphonates in the presence of orthopedic indications.

Comparison of molecular mechanisms mediating cell contact phenomena in model developmental systems: an exploration of universality.

Are there universal molecular mechanisms associated with cell contact phenomena during metazoan ontogenesis? Comparison of adhesion systems in disparate model systems indicates the existence of unifying principles. Requirements for multicellularity are (a) the construction of three-dimensional structures involving a crucial balance between adhesiveness and motility; and (b) the establishment of integration at molecular, cellular, tissue, and organismal levels of organization. Mechanisms for (i) cell-cell and cell-substrate adhesion, (ii) cell movement, (iii) cell-cell communication, (iv) cellular responses, (v) regulation of these processes, and (vi) their integration with patterning, growth, and other developmental processes are all crucial to metazoan development, and must have been present for the emergence and radiation of Metazoa. The principal unifying themes of this review are the dynamics and regulation of cell contact phenomena. Our knowledge of the dynamic molecular mechanisms underlying cell contact phenomena remains fragmentary. Here we examine the molecular bases of cell contact phenomena using extant model developmental systems (representing a wide range of phyla) including the simplest i.e. sponges, and the eukaryotic protist Dictyostelium discoideum, the more complex Drosophila melanogaster, and vertebrate systems. We discuss cell contact phenomena in a broad developmental context. The molecular language of cell contact phenomena is complex; it involves a plethora of structurally and functionally diverse molecules, and diverse modes of intermolecular interactions mediated by protein and/or carbohydrate moieties. Reasons for this are presumably the necessity for a high degree of specificity of intermolecular interactions, the requirement for a multitude of different signals, and the apparent requirement for an increasingly large repertoire of cell contact molecules in more complex developmental systems, such as the developing vertebrate nervous system. However, comparison of molecular models for dynamic adhesion in sponges and in vertebrates indicates that, in spite of significant differences in the details of the way specific cell-cell adhesion is mediated, similar principles are involved in the mechanisms employed by members of disparate phyla. Universal requirements are likely to include (a) rapidly reversible intermolecular interactions; (b) low-affinity intermolecular interactions with fast on-off rates; (c) the compounding of multiple intermolecular interactions; (d) associated regulatory signalling systems. The apparent widespread employment of molecular mechanisms involving cadherin-like cell adhesion molecules suggests the fundamental importance of cadherin function during development, particularly in epithelial morphogenesis, cell sorting, and segregation of cells.

Cell adhesion during the migratory slug stage of Dictyostelium discoideum.

Prespore-specific Antigen (PsA) is selectively expressed on the surface of prespore cells at the multicellular migratory slug stage of Dictyostelium discoideum development. It is a developmentally regulated glycoprotein that is anchored to the cell membrane through a glycosyl phosphatidylinositol (GPI) anchor. We present the results of an in vitro immunological investigation of the hypothesis that PsA functions as a cell adhesion molecule (CAM), and of a ligand-binding assay indicating that PsA has cell membrane binding partner(s). This is the first evidence to implicate a direct role for a putative CAM in cell-cell adhesion during the multicellular migratory slug stage of D. discoideum development. Cell-cell adhesion assays were carried out in the presence or absence of the monoclonal antibody (mAb) MUD1 that has a single antigenic determinant: a peptide epitope on PsA. These assays showed specific inhibition of cell-cell adhesion by MUD1. Further, it was found that a purified recombinant form of PsA (rPsA), can neutralize the inhibitory effect of MUD1; the inhibitory effect on cell-cell adhesion is primarily due to the blocking of PsA by the mAb. The resistance of aggregates to dissociation in the presence of 10 mM EDTA (ethylenediamintetraacetic acid) indicates that PsA mediates EDTA-stable cell-cell contacts, and that PsA-mediated cell adhesion is likely to be independent of divalent cations such as Ca(2+) or Mg(2+).