On the mechanism by which dopamine inhibits prolactin release in the anterior pituitary

An $\text{in}$$\text{vitro}$ perfusion system was used to assess the effects of chloride channel blockers, dopamine (DA) receptor agonists and antagonists, and GABA receptor agonists and antagonists on prolactin release from the mouse anterior pituitary. Dopamine and muscimol inhibited prolactin release ($\text{IC}{}_{50}{}^1\text{= 6 × 10}{}^{\mathrm{?8}}\text{M and}\text{10}{}^{\mathrm{?5}}\text{M}$ respectively). The GABA receptor antagonist bicuculline blocked the inhibition of prolactin release by muscimol but not dopamine. The dopamine receptor antagonist chlorpromazine blocked the dopamine- but not muscimol-induced inhibition of prolactin release. Haloperidol, however, reversed both the muscimol and dopamine induced inhibition of prolactin release. Furthermore, the chloride channel blocker picrotoxinin blocked the inhibition of prolactin release elicited by both dopamine and muscimol. These later results suggest that the anterior pituitary dopamine receptor which mediates the inhibition of prolactin release may be coupled to a picrotoxinin sensitive chloride ionophore and that haloperidol may affect the function of both DA and GABA receptors in the anterior pituitary.     

Influence of the composition of the fusion medium on the yield of electrofused yeast hybrids

Abstract Electrofusion between cells of yeast strains with different genetic markers in isotonic sorbitol solutions leads to high yields of hybrids when 0.1 mM Ca²⁺ and 0.5 mM Mg²⁺ salts are aded. On average, 1000–2000 hybrids are obtained when electrofusion is performed (in a helical chamber) compared to a yield of about 40–120 in the absence of these bivalent cations. A further increase in yield can be achieved by the addition of 1 mg/ml albumin, which results in up to 4000 hybrids per experimental run. The entire fusion process leads to very reproducible results in the presence of these substances.     

The Legal Regulation of Floats and Gliders—In Quest of a New Regime?

This article analyzes the legal status of unmanned instruments (particularly, floats and gliders) for observation purposes in the ocean environment. These new kinds of instruments are being deployed by the thousands into the oceans, not the least as part of the Argo Project of the International Oceanographic Commission. Their uncontrolled drifting has raised legal questions, especially when such instruments enter waters subject to the jurisdiction of foreign states. The authors argue that the current international legal framework is insufficient to address the pertinent issues, and that a new legal regime is needed.     

Energetics and intermediates of the assembly of Protein OmpA into the outer membrane of Escherichia coli

OmpA is a major protein of the outer membrane of Escherichia coli. It is made as a larger precursor, pro-OmpA, which requires a membrane potential for processing. We now show that pro-OmpA accumulates in the cytoplasm of cells treated with carbonyl cyanide m-chlorophenylhydrazone, an uncouple which lowers the membrane potential. Upon restoration of the potential, this pro-OmpA is secreted, processed, and assembled into the outer membrane. Pro-OmpA made in vitro is also recovered with the postribosomal supernatant. It is efficiently processed to OmpA by liposomes which have bacterial leader peptidase that is exclusively internally oriented. These experiments show that: (i) the insertion of pro-OmpA into the plasma membrane is not coupled to its synthesis; (ii) insertion is promoted by the transmembrane electrochemical potential; (iii) pro-OmpA can cross a bilayer spontaneously; and (iv) pro-OmpA is processed by the same leader peptidase which converts M13 procoat to coat.     

Environmental Particulate (PM2.5) Augments Stiffness-Induced Alveolar Epithelial Cell Mechanoactivation of Transforming Growth Factor Beta

Dysfunctional pulmonary homeostasis and repair, including diseases such as pulmonary fibrosis (PF), chronic obstructive pulmonary disease (COPD), and tumorigenesis have been increasing over the past decade, a fact that heavily implicates environmental influences. Several investigations have suggested that in response to increased transforming growth factor - beta (TGFβ) signaling, the alveolar type II (ATII) epithelial cell undergoes phenotypic changes that may contribute to the complex pathobiology of PF. We have previously demonstrated that increased tissue stiffness associated with PF is a potent extracellular matrix (ECM) signal for epithelial cell activation of TGFβ. The work reported here explores the relationship between tissue stiffness and exposure to environmental stimuli in the activation of TGFβ. We hypothesized that exposure of ATII cells to fine particulate matter (PM2.5) will result in enhanced cell contractility, TGFβ activation, and subsequent changes to ATII cell phenotype. ATII cells were cultured on increasingly stiff substrates with or without addition of PM2.5. Exposure to PM2.5 resulted in increased activation of TGFβ, increased cell contractility, and elongation of ATII cells. Most notably, on 8 kPa substrates, a stiffness greater than normal but less than established fibrotic lung, addition of PM2.5 resulted in increased cortical cell stiffness, enhanced actin staining and cell elongation; a result not seen in the absence of PM2.5. Our work suggests that PM2.5 exposure additionally enhances the existing interaction between ECM stiffness and TGFβ that has been previously reported. Furthermore, we show that this additional enhancement is likely a consequence of intracellular reactive oxygen species (ROS) leading to increased TGFβ signaling events. These results highlight the importance of both the micromechanical and biochemical environment in lung disease initiation and suggest that individuals in early stages of lung remodeling during fibrosis may be more susceptible than healthy individuals when exposed to environmental injury adjuvants.     

Co‐occurrence patterns of trees along macro‐climatic gradients and their potential influence on the present and future distribution of Fagus sylvatica L.

Aim During recent and future climate change, shifts in large‐scale species ranges are expected due to the hypothesized major role of climatic factors in regulating species distributions. The stress‐gradient hypothesis suggests that biotic interactions may act as major constraints on species distributions under more favourable growing conditions, while climatic constraints may dominate under unfavourable conditions. We tested this hypothesis for one focal tree species having three major competitors using broad‐scale environmental data. We evaluated the variation of species co‐occurrence patterns in climate space and estimated the influence of these patterns on the distribution of the focal species for current and projected future climates. Location Europe. Methods We used ICP Forest Level 1 data as well as climatic, topographic and edaphic variables. First, correlations between the relative abundance of European beech (Fagus sylvatica) and three major competitor species (Picea abies, Pinus sylvestris and Quercus robur) were analysed in environmental space, and then projected to geographic space. Second, a sensitivity analysis was performed using generalized additive models (GAM) to evaluate where and how much the predicted F. sylvatica distribution varied under current and future climates if potential competitor species were included or excluded. We evaluated if these areas coincide with current species co‐occurrence patterns. Results Correlation analyses supported the stress‐gradient hypothesis: towards favourable growing conditions of F. sylvatica, its abundance was strongly linked to the abundance of its competitors, while this link weakened towards unfavourable growing conditions, with stronger correlations in the south and at low elevations than in the north and at high elevations. The sensitivity analysis showed a potential spatial segregation of species with changing climate and a pronounced shift of zones where co‐occurrence patterns may play a major role. Main conclusions Our results demonstrate the importance of species co‐occurrence patterns for calibrating improved species distribution models for use in projections of climate effects. The correlation approach is able to localize European areas where inclusion of biotic predictors is effective. The climate‐induced spatial segregation of the major tree species could have ecological and economic consequences.     

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