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The Fukushima Dai-ichi nuclear power plant accident released limited amounts of actinides on soils of Japan. Characterisation of these particles is essential to determine the fate of actinides in the environment. The method presented in this paper, based on α-tracks detections, microscope observations and mass-spectrometry measurements, was designed to identify and characterize actinide-bearing particles in soil samples. The method was tested on a road dust sample collected in the main radioactive plume of the Fukushima region. Accordingly, α-tracks detection was demonstrated to provide a powerful technique to localise these particles and prepare their morphological, elemental and isotopic characterization. [ABSTRACT FROM AUTHOR]

A study was made of the bulk-leaf water relations of selected species of epiphytic bromeliads growing in their natural habitat in Trinidad (West Indies). Field measurements were made during the rainy season at three forest sites centred on the wetter part of the island. The epiphytic bromeliads were sampled in situ using modified rock-climbing techniques at 4- to 6-h intervals during complete day-nigh cycles. Eleven species were studied that differed in their photosynthetic pathways and habitat preferences. The C species among the epiphytic bromeliads characteristically showed maximum values of xylem tension (measured with the pressure chamber) during the day, whereas the species with crassulacean acid metabolism (CAM) attained maximum values towards the end of the night. In addition, the CAM species showed large nocturnal increases in leaf-cell-sap osmotic pressure and titratable acidity. These nocturnal increases showed mean values of 0.601 MPa and 289 mol H m, respectively, for four species sampled at an exposed forest clearing (250 m), where CAM species were well represented. At the other two sites, a lowland forest (60 m) and a ridge forest (740 m), CAM bromeliads were found in the forest canopy, but in the lowest strata all the bromeliads were C species. This species distribution was associated with a marked vertical stratification of microlimate, the forest canopy being characterized by much bigger day-night changes in temperature and water-vapour-pressure deficit than the undergrowth. The C-CAM intermediate Guzmania monostachia var. monostachia showed significant nocturnal acidification in the forest clearing but not in the understory of the lowland forest. Taken as a whole, the C and CAM bromeliads were very similar in the range of values observed for xylem tension and osmotic pressure, as well as in aspects of their leaf anatomy. However, epidermal trichomes covered a large percentage of the leaf surface area in xeromorphic species (e.g. Tillandsia utriculata), whereas they were poorly developed in shade-tolerant species (e.g. G. lingulata var. lingulata). The absolute values of sylem tension and osmotic pressure were low for all species. Mean minimum xylem tension during the day-night cycles was in the range of 0.18-0.23 MPa and mean maximum in the range 0.41-0.53 MPa; during periods of rain, xylem tension reached a mean minimum of 0.12 MPa. Mean minimum osmotic pressure was in the range 0.449-0.523 MPa. Such between-site and between-species differences as were observed in the water relations of the bromeliads could be related to the microclimatic conditions prevailing in the various epiphytic habitats. [ABSTRACT FROM AUTHOR]

The effects of calcitonin, vasoactive intestinal peptide (VIP), parathyroid hormone (PTH) and isoprenaline on intracellular cAMP accumulation were determined in the distal tubule (DCT) microdissected from collagenase-treated rabbit kidney. In DCTb (the initial 'bright' portion) calcitonin (10 ng/ml) elicited a highly reproducible response 203.7±19.1 fmol cAMP mm 4 min (SE, N=13) whereas VIP-induced cAMP accumulation was less and more variable from one experiment to another (1 μM, 97.2±17.8 fmol mm 4 min, SE, N=12). When used in combination, these two agonists were non-additive, indicating stimulation of a single pool of cAMP in DCTb. In DCTg, ('granular') which consists of at least two cell types, PTH (100 nM) elicited a marked, reproducible accumulation of cAMP (154.3±27.0 fmol mm 4 min; SE, N=5). Isoprenaline (1 μM) and VIP (1 μM) induced much smaller increases in cAMP levels 20.9±2.7 and 29.4±4.1 fmol mm 4 min (SE, N=5) respectively, and, when used in combination, were non-additive, demonstrating that VIP and isoprenaline are active on the same cell type. In DCTb, prostaglandin E (PGE) inhibited both calcitoninand VIP-stimulated cAMP accumulation (calcitonin 57.8±2.7% inhibition, SE, N=16; VIP, 80.6±2.1% inhibition, SE, N=5). The EC values for calcitonin were 1.21±0.33 ng/ml and 1.83±0.25 ng/ ml (SD, N=3) in the absence and presence of PGE (300 nM) respectively with an IC for PGE of 26.3±6.3 nM (SE, N=4). In contrast, no effects of PGE were seen in DCTg vis à vis PTH, isoprenaline or VIP. The percentage inhibition of calcitonin-stimulated cAMP accumulation by PGE was of the same order in the presence of isobutylmethylxanthine (an inhibitor of all types of phosphodiesterase), Ro 20-1724 (inhibitor of low- K cAMP-specific phosphodiesterase) or in the absence of inhibitor. Preincubation of DCTb with pertussis toxin for up to 8 h in different experimental conditions did not relieve the inhibition by PGE. Protein kinase C activation by phorbol ester did not attenuate calcitonin responses. These data demonstrate that the inhibition by PGE of cAMP production is restricted to the initial portion (DCTb) of the distal convoluted tubule and is effective on both calcitonin and VIP responses. When tested in the presence of Ro 20-1724, ionomycin, A-adenosine, α-adrenergic and muscarinic agonists were without effect on calcitoninand PTH-stimulated cAMP accumulation in DCTb and DCTg respectively. [ABSTRACT FROM AUTHOR]

Specific I-labelled vasoactive intestinal peptide (VIP) binding was determined in feline renal cortical and medullary plasma membranes. For the cortex, Scatchard analysis of the data resulted in a curvilinear plot with a high-affinity site K of 8.4±2.6 nmol l (SE, n=6) and a second low-affinity site K 204 ± 16 nmol l with binding site concentrations ( B) of 385±44.5 and 2710±181.3 fmol mg protein respectively. Conversely a similar analysis of the results obtained for outer medullary membranes gave a single site with a K of 1.2±0.2 nmol l (SE, n=4) and B of 157.8±24.7 fmol mg. Inner medullary membrane binding data. Gave a single site of lower affinity ( K= 62.5±21.6 nmol l; n=3). Structurally related peptides, glucagon and secretin, were ineffective (up to 1 μmol l) in displacing VIP from specific sites in both cortex and medulla. Porcine PHI 1-27 (a peptide having N-terminal histidine and C-terminal isoleucine) and a VIP antagonist [4-Cl- D-PheLeu]VIP both displaced I-VIP from cortical and medullary membrane binding sites with IC values of 43.0 nmol l and 1.3 μmol l (cortex) and 132.0 nmol l and 1.5 μmol l (medulla) respectively. The localisation of specific VIP binding sites in feline kidney was investigated further by in vitro autoradiography. A high density of binding sites was visible at the cortico-medullary boundary as well as in the outer stripe of the outer medulla and in radial structures projecting into the cortex. There was a moderate density of binding sites in the superficial cortex. In addition the distribution of tubular VIP-sensitive adenylate cyclase was determined in microdissected nephron segments. In the presence of 10 μmol l GTP, 1 μmol l VIP effected marked stimulations over basal adenylate cyclase activity in medullary collecting tubules (4.7-fold), the 'bright' and 'granular' portions of the distal convoluted tubule (4.1- and 2.2-fold respectively) and in the pars recta of the proximal tubule (2.7-fold). Thus VIP-responsive adenylate cyclase has a discrete localisation in the feline nephron, which appears to correlate with specific binding sites as defined by autoradiography. [ABSTRACT FROM AUTHOR]

Colonic function in rats was investigated up to 14 days following exposure to whole-body gamma irradiation (8 Gy) using a combination of in vivo and in vitro approaches. Water and electrolyte fluxes were measured in vivo under anesthesia by insertion of an agarose cylinder into the descending colon. Short-circuit current responses (Isc; basal, agonist-stimulated) of distal colon were measured in vitro as were mannitol and sodium fluxes. Water and electrolyte absorption (Na, Cl) was markedly reduced at four days after irradiation but returned to normal at seven days. Potassium secretion was increased from one to seven days after exposure. There were no differences in basal Isc, Na, or mannitol fluxes at four days but responses to secretagogues (5-hydroxytryptamine, forskolin, carbachol) were attenuated. No morphological alterations were associated with these functional modifications. [ABSTRACT FROM AUTHOR]