Pituitary adenylate cyclase activating peptide (PACAP) in guinea-pig lung: distribution and dilatory effects.

The lower airways of guinea-pigs were analyzed for pituitary adenylate cyclase activating peptide (PACAP) using immunocytochemistry. In the trachea a moderate supply of PACAP-immunoreactive nerve fibers occurred around smooth muscle bundles, glands and small blood vessels. In the lung, PACAP-immunoreactive nerve fibers were distributed around small glands and bronchi. A rich supply of PACAP immunoreactive nerve fibers was found around blood vessels in the lungs. PACAP-suppressed smooth muscle responses were analysed using isolated circular segments of trachea, pulmonary arteries and aorta of guinea-pigs. In both airways and arteries PACAP caused a concentration-dependent relaxation of precontracted segments. The maximal relaxation effects were more pronounced in the airways than in the arteries while the order of potency was aorta greater than pulmonary artery greater than trachea. The effect of PACAP was compared to those of acetylcholine (ACh) and vasoactive intestinal peptide (VIP). In the pulmonary artery the vasomotor responses expressed as maximal dilatation had the order: ACh greater than VIP = PACAP while the order of potency was PACAP = VIP greater than ACh. In the trachea, PACAP was slightly more potent than VIP. The relaxatory responses to PACAP in the trachea and the intrapulmonary arteries were unaffected by pretreatment with atropine, prazosin, yohimbine, propranolol, mepyramine, cimetidine and Spantide. Removal of the endothelium abolished PACAP-induced vascular relaxation. Conceivably, PACAP-containing nerve fibers play a role in the regulation of airway resistance and local blood flow.     

Leafminers help us understand leaf hydraulic design

Leaf hydraulics of Aesculus hippocastanum L. were measured over the growing season and during extensive leaf mining by the larvae of an invasive moth (Cameraria ohridella Deschka et Dimic) that specifically destroy the palisade tissue. Leaves showed seasonal changes in hydraulic resistance (R_lamina) which were related to ontogeny. After leaf expansion was complete, the hydraulic resistance of leaves and the partitioning of resistances between vascular and extra‐vascular compartments remained unchanged despite extensive disruption of the palisade by leafminers (up to 50%). This finding suggests that water flow from the petiole to the evaporation sites might not directly involve the palisade cells. The analysis of the temperature dependence of R_lamina in terms of Q₁₀ revealed that at least one transmembrane step was involved in water transport outside the leaf vasculature. Anatomical analysis suggested that this symplastic step may be located at the bundle sheath where the apoplast is interrupted by hydrophobic thickening of cell walls. Our findings offer some support to the view of a compartmentalization of leaves into well‐organized water pools so that the transpiration stream would involve veins, bundle sheath and spongy parenchyma, while the palisade tissue would be largely by‐passed with the possible advantage of protecting cells from short‐term fluctuations in water status.     

Faster returns on ‘leaf economics’ and different biogeochemical niche in invasive compared with native plant species

Plant‐invasive success is one of the most important current global changes in the biosphere. To understand which factors explain such success, we compared the foliar traits of 41 native and 47 alien‐invasive plant species in Oahu Island (Hawaii), a location with a highly endemic flora that has evolved in isolation and is currently vulnerable to invasions by exotic plant species. Foliar traits, which in most cases presented significant phylogenetic signal, i.e. closely related species tended to resemble each other due to shared ancestry, separated invasive from native species. Invasive species had lower leaf mass per area and enhanced capacities in terms of productivity (photosynthetic capacity) and nutrient capture both of macro‐ (N, P, K) and microelements (Fe, Ni, Cu and Zn). All these differences remain highly significant after removing the effects of phylogenetic history. Alien‐invasive species did not show higher efficiency at using limiting nutrient resources, but they got faster leaf economics returns and occupied a different biogeochemical niche, which helps to explain the success of invasive plants and suggests that potential increases in soil nutrient availability might favor further invasive plant success.     

Enhancement of Antigenic Site Detection with Gold Labeled Secondary and Tertiary Antibodies Using the Immunogold-Silver Staining Method

We report a modification of the immunogold-silver staining method (IGSS) for localizing hepatic phosphoenolpyruvate carboxykinase (PEPCK) in tissue sections, and we compare the efficacy of localizing the primary antibody with either a 5 nm gold labeled secondary antibody or 5 nm gold labeled secondary and tertiary antibodies. Light microscope examination of 10 μm frozen sections demonstrated that the use of combined secondary and tertiary gold labeled antibodies was superior to using a secondary gold labeled antibody alone. The increased labeling density (number of colloidal gold particles/antigenic site/cell) achieved by combined gold labeled antibodies was confirmed by electron microscopy. The increased labeling density resulted in a two-thirds reduction in the time needed for the IGSS physical development of the silver shells and less background. We achieved intense specific staining of hepatocytes expressing PEPCK while minimizing background staining. The use of combined secondary and tertiary gold labeled antibodies enhances the signal-to-noise ratio, achieves high resolution and is a suitable method for use in both light and electron microscopy.     

Morphometric analysis of hepatocytes from rats subjected to compound 48/80-induced anaphylactic shock

Morphometric and biochemical techniques were used to analyze hepatic glycogen, endoplasmic reticulum, and mitochondrial matrix granules in rats treated with compound 48/80 to induce an anaphylactic-like state of shock. Thirty minutes after insult there was a significant decrease in glycogen and mitochondrial matrix granules, an increase in rough endoplasmic reticulum (RER), and no change in smooth endoplasmic reticulum (SER). Less glycogen in experimental rats substantiated a previously described glycogenolytic response to compound 48/80. The decrease in matrix granules implies a loss and/or shift in intramitochondrial calcium as occurs in epinephrine-induced glycogenolysis in the rat. Since other glycogenolytic agents, e.g. glucagon, and starvation stimulate an increase in SER presumably from RER, the present morphological data suggest the increase in RER may precede proliferation of SER from RER.