Existence of Three Subtypes of Bradykinin B2 Receptors in Guinea Pig

We describe the binding of [3H]bradykinin to homogenates of guinea pig brain, lung, and ileum. Analysis of [3H]bradykinin binding kinetics in guinea pig brain, lung, and ileum suggests the existence of two binding sites in each tissue. The finding of two binding sites for [3H]bradykinin in ileum, lung, and brain was further supported by Scatchard analysis of equilibrium binding in each tissue. [3H]Bradykinin binds to a high-affinity site in brain, lung, and ileum (KD = 70-200 pM), which constitutes approximately 20% of the bradykinin binding, and to a second, lower-affinity site (0.63-0.95 nM), which constitutes the remaining 80% of binding. Displacement studies with various bradykinin analogues led us to subdivide the high- and lower-affinity sites in each tissue and to suggest the existence of three subtypes of B2 receptors in the guinea pig, which we classify as B2a, B2b, and B2c. Binding of [3H]bradykinin is largely to a B2b receptor subtype, which constitutes the majority of binding in brain, lung, and ileum and represents the lower-affinity site in our binding studies. Receptor subtype B2c constitutes approximately 20% of binding sites in the brain and lung and is equivalent to the high-affinity site in brain and lung. We suggest that a third subtype of B2 receptor (high-affinity site in ileum), B2a, is found only in the ileum. All three subtypes of B2 receptors display a high affinity for bradykinin, whereas they show different affinities for various bradykinin analogues displaying agonist or antagonist activities.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lan-1: A Human Neuroblastoma Cell Line With M1 and M3 Muscarinic Receptor Subtypes Coupled to Intracellular Ca2+ Elevation and Lacking Ca2+ Channels Activated by Membrane Depolarization

The LAN-1 clone, a cell line derived from a human neuroblastoma, possesses muscarinic receptors. The stimulation of these receptors with increasing concentrations of carbachol (CCh; 1-1,000 microM) caused a dose-dependent increase of the intracellular free Ca2+ concentration ([Ca2+]i). This increase was characterized by an early peak phase (10 s) and a late plateau phase. The removal of extracellular Ca2+ reduced the magnitude of the peak phase to approximately 70% but completely abolished the plateau phase. The muscarinic-activated Ca2+ channel was gadolinium (Gd3+) blockade and nimodipine and omega-conotoxin insensitive. In addition, membrane depolarization did not cause any increase in [Ca2+]i. The CCh-induced [Ca2+]i elevation was concentration-dependently inhibited by pirenzepine and 4-diphenylacetoxy-N-methylpiperidine methiodide, two rather selective antagonists of M1 and M3 muscarinic receptor subtypes, respectively, whereas methoctramine, an M2 antagonist, was ineffective. The coupling of M1 and M3 receptor activation with [Ca2+]i elevation does not seem to be mediated by a pertussis toxin-sensitive guanine nucleotide-binding protein or by the diacylglycerol-protein kinase C system. The mobilization of [Ca2+]i elicited by M1 and M3 muscarinic receptor stimulation seems to be dependent on an inositol trisphosphate-sensitive intracellular store. In addition, ryanodine did not prevent CCh-induced [Ca2+]i mobilization, and, finally, LAN-1 cells appear to lack caffeine-sensitive Ca2+ stores, because the methylxanthine was unable to elicit intracellular Ca2+ mobilization, under basal conditions, after a subthreshold concentration of CCh (0.3 microM), or after thapsigargin.     

AT1 Angiotensin Receptors Mobilize Intracellular Calcium in a Subclone of NG108–15 Neuroblastoma Cells

The effects of angiotensin II (AII) and related peptides on the mobilization of internal Ca2+ were studied in a subclone of NG 108-15 cells. The subclone, C1, was prepared by fluorescence-activated cell cloning using a rapid response kinetics and a large response magnitude following stimulation by AII as the selection criteria. Angiotensin I, AII, and angiotensin III (AIII) stimulated Ca2+ mobilization in the C1 cells in a concentration-dependent manner (1 nM-100 microM), yielding EC50 values of 437 +/- 80 nM (n = 4; slope = 1.6 +/- 0.3), 57 +/- 8 nM (n = 12; slope = 1.5 +/- 0.3), and 36 +/- 5 nM (n = 7; slope = 1.4 +/- 0.3), respectively. AIII was significantly more potent than AII (p less than 0.05). In contrast, Des-Phe8-AII, AII-hexapeptide (AII 3-8), and p-NH2-Phe6-AII (1-10 microM) were inactive as agonists. Although the effects of AII and AIII in C1 and parent NG108-15 cells were totally inhibited by the AT1 receptor-selective nonpeptide antagonist, DUP-753 (0.3-1 microM), the AT2-selective antagonists, EXP-655 and CGP42112A (1-10 microM), failed to block the effects of AII. DUP-753 (0.3-100 nM) produced dextral shifts of the AII-induced concentration-response curves and yielded an estimated affinity constant (pA2) of 8.5 +/- 0.2 (n = 16) using single-point analysis involving different concentrations of DUP-753. These data compared well with those obtained for the inhibition of AII-induced aortic contractions by DUP-753 (pA2 = 8.5) reported previously by others.(ABSTRACT TRUNCATED AT 250 WORDS)     

Brazilian vegetation on maps

The development and current status of mapping the vegetation of Brazil is discussed. This includes the manner of portraying the vegetation on maps, especially with regard to physiognomy and structure, the floristic composition and ecological relations. A slow beginning has given way to a rapid though uneven development. Recent government efforts tend to correct this.     

Pollenanalytical research in the Grisons (Switzerland)

In the first part, an overview of the history of palynological researeh in Switzerland and particularly in the Grisons is given, with a map showing all investigated areas in the Grisons. The second part deals with the significance of the pollenanalytical research in the Grisons, namely, the history of vegetation during the Late and Post Glacial, climatic fluctuations and applications in geomorphology, archaeology and forestry research. Finally, some results concerning the history of vegetation during the Late and Post Glacial are discussed.I would like to thank my colleague H. Holzhauser for his help with the drawing of the figures.     

Abnormal dorsal light response in teleost fish after intraocular injection of 6-hydroxydopamine

Following unilateral intraocular injection with 6-hydroxydopamine to the right eye, Midas cichlids displayed an acute abnormal dorsal light response, in favour of the right eye. This condition was reversed immediately by dopamine or dopamine receptor agonists delivered by intraocular injection but this recovery was not sustained, Retinal dopamine production reappeared gradually from day 30 post-6-hydroxydopamine treatment, and coincided with the fish beginning to adopt a normal dorsal light reaction. Dopamine production recovered completely at day 45 post-6-hydroxydopamine injection and coincided with complete recovery of the normal dorsal light reaction. These observations suggest a role for intraocular dopamine in maintenance of the visual part of the normal dorsal light reaction.     

Ultrastructural characterization of atrial natriuretic peptide receptors (ANP-R) mRNA expression in rat kidney cortex

Atrial natriuretic peptide (ANP) and two complementary peptides named brain natriuretic peptide and C-type natriuretic peptide are involved in diuresis, natriuresis, hypotension and vasorelaxation. Their actions are mediated by highly selective and specific ANP receptors. Three subtypes have been characterized and cloned: ANP receptor A, ?B and ?C. In the present study, the mRNA for each subtype was detected by ultrastructural in situ hybridization on ultrathin sections of Lowicryl-embedded tissue and frozen tissue. The distribution of mRNA (visualized by gold particles) for each subtype was found to differ in different cells of the nephron. The three subtypes of this receptor family were expressed in all the parts of the nephron, but their expression levels were different. The ANPR-A mRNA was the most abundant in cells of glomerulus, proximal and distal tubules. The subtype C was the least expressed mRNA in glomerulus. In contrast, the subcellular localization of the three mRNAs was similar; they were found in the cytoplasmic matrix and the euchromatin of the nucleus. In conclusion, the differential expression of these mRNAs in kidney cortex indicates that these three peptides act directly in differing parts of nephron regions which are the glomerulus, the proximal and distal tubules.     

Vegetation maps based on remote sensing are informative predictors of habitat selection of grassland birds across a wetness gradient

Vegetation is a major environmental factor influencing habitat selection in bird species. High resolution mapping of vegetation cover is essential to model the distribution of populations and improve the management of breeding habitats. However, the task is challenging for grassland birds because microhabitat variations relevant at the territory scale cannot be measured continuously over large areas to delineate areas of higher suitability. Remote sensing may help to circumvent this problem. We addressed this issue by using SPOT 5 imagery and phytosociological data. We mapped grassland vegetation in a floodplain using two methods. We (i) mapped the continuous Ellenberg index of moisture and (ii) identified 5 vegetation classes distributed across the wetness gradient. These two methods produced consistent output maps, but they also provided complementary results. Ellenberg index is a valuable proxy for soil moisture while the class approach provided more information about vegetation structure, and possibly trophic resources. In spite of the apparent uniformity of meadows, our data show that birds do not settle randomly along the moisture and vegetation gradients. Overall birds tend to avoid the driest vegetation classes, i.e. the highest grounds. Thus, vegetation maps based on remote sensing could be valuable tools to study habitat selection and niche partition in grassland bird communities. It is also a valuable tool for conservation and habitat management.