Dilution and acidification effects during the spring flood of four Swedish mountain brooks

The seasonal variation in water chemistry was followed during 1980 and 1981 in four mountain brooks in the southern part of Swedish Lapland. In the area investigated the soil is calcareous and the brook water is very well buffered during the major part of the year, with alkalinity varying between 0.4 and 1.0 milliequivalents per liter and with pH values about 7.5. These years the snow had a pH of approximately 5.2, which was considerably higher than has been reported from adjacent areas in the lower, coniferous region. During snowmelt the water discharge increased drastically, and although the net transport of bicarbonate increased, alkalinity showed low values due to dilution with meltwater. pH decreased, but not further than to 6.3–6.5, far from values reported in 1979 (pH less than 5), apparently due to the comparatively clean snow. A slight deficit in alkalinity, as compared to the nonmarine calcium and magnesium content, points to an acidification impact on the area. During maximum runoff some chemical variables, like aluminium, iron, nitrogen and phosphorus, behaved reversely to what might be expected during dilution and reached maxima in concentrations. It is concluded that the extreme runoff characteristics of high mountain areas make brook water more sensitive to acid precipitation than might be expected when regarding only the calcareous properties of soil and bedrock.     

A histochemically demonstrable thiaminepyrophosphatase activity in the sinusoidal endothelium of the liver

Summary A new histochemically demonstrable thiaminepyrophosphatase activity in liver tissue is described. It appears to be localized solely to the cytosomes of the sinusoidal endothelium. The activity, which requires high concentration of lead ion for its demonstration, has a high degree of substrate specificity. It resists formaldehyde fixation, ethanol and many inhibitors. The optimum pH is at pH 6.This study was supported in part by a grant from the Swedish Medical Research Council.     

A comparison between histochemically demonstrable Golgi-associated and bile canalicular TDP-ase activity in liver

Summary Histochemically demonstrable Golgi-associated TDP-ase activity in liver cells from cat, chicken, rat and frog has been investigated.This activity is highly substrate-specific, insensitive to aldehyde fixation, ethanol, acetate, lead and most enzyme inhibitors. It is stimulated by divalent manganese, calcium, magnesium and cobalt and optimum pH is at pH 6 to 7.The characteristics are identical for all four species but significant differences exist at a comparison with bile canalicular activity, Golgi-associated activity in other cells and biochemical findings.This study was supported in part by a grant from the Swedish Medical Research Council.     

Sandwich Embedding of Monolayers of Cells in Epoxy Resin for Ultrathin Sectioning

In this procedure for embedding monolayers of cells, the usual glass slides are replaced by plates of resin 1-1.5 mm thick. Unlike the open-face embedding technique, the present procedure uses only a few drops of unpolymerized resin, which are applied to the fixed and dehydrated cells. During polymerization this small amount of liquid resin spreads across a relative large area, leaves the cells covered by a very thin layer, and permits phase contrast observations through it. Ultrathin sections of a particular cell encircled by a rotary scriber can be obtained by sectioning the resin slide, which has been trimmed and mounted directly in the specimen holder of the ultramicrotome.     

Mechanism of intestinal formation of deoxycholic acid from cholic acid in humans: evidence for a 3-oxo-delta 4-steroid intermediate

12 alpha-Hydroxy-3-oxo-4-cholenoic acid coupled to an adenosine nucleotide has been shown to be a metabolite of cholic acid in the intestinal anaerobic bacteria, Eubacterium species VPI 12708 (1987. J. Biol. Chem. 262: 4701-4707) and it has been suggested that this may be an intermediate in the conversion of cholic acid into deoxycholic acid. The possibility that the intestinal conversion of cholic acid into deoxycholic acid involves a 3-oxo-delta 4-steroid as an intermediate has been studied in the present work by use of [3 beta-3H]- and [5-3H]-labeled cholic acid. Whole cells as well as cell extracts of Eubacterium sp. VPI 12708 catalyzed conversion of [3 beta-3H] + [24-14C]cholic acid into deoxycholic acid with loss of about 50% of 3H label. When unlabeled chenodeoxycholic acid (20 microM) was added along with [3 beta-3] + [24-14C]cholic acid, then approximately 85% of the [3 beta-3H]-labeled was lost from deoxycholic acid. After administration of the same mixture to two healthy volunteers, deoxycholic acid could be isolated that had lost 81 and 84%, respectively, of the 3H label. Conversion of a mixture of [5-3H]- and [24-14C]labeled cholic acid by the above intestinal bacteria or cell extracts led to loss of 79-94 of the [5-3H] label.(ABSTRACT TRUNCATED AT 250 WORDS)     

Trade-off among antiherbivore defences in a south american blackberry (Rubus bogotensis)

Summary The idea of trade-offs among antiherbivore defences in plants is examined using data from a South American blackberry (Rubus bogotensis). Two distinct morphs of R. bogotensis, one with glandular trichomes and one without, were compared with respect to leaf toughness, number of prickles and prickle length. The two morphs were sympatric and grew under similar environmental conditions. The morph lacking trichomes had significantly tougher leaves and also tended to have more and longer prickles. Bioassay showed that Ithomiid larvae fed to a lesser extent on tough leaves than on more tender ones. Correlations between antiherbivore defences within each phenotype revealed three significant or almost significant negative relationships. The comparisons support the hypothesis that trade-offs exist among antiherbivore defences.     

Fungal protoplasts as tools for studies on protein secretion

Summary Protoplasts were prepared from mycelium of Aspergillus niger N-402. Sucrose was used to induce the synthesis and secretion of invertase. Protoplasts secreted 2 forms of invertase, different to those secreted by the mycelium. ¹⁴C mannose was shown to be taken up by protoplasts and incorporated into secreted proteins.     

Identification of some major cytokinins in Phaseolus vulgaris and their distribution

The determination of the various endogenous cylokinins and their distribution among organs is important in understanding their role in growth and development in the intact plant. Cytokinins in young plants of Phaseolus vulgaris were purified by immunoaffinity chromatography and HPLC, and characterised by UV spectra. Zeatin nucleotide (zeatin riboside-5'-monophosphate) and isopentenyladenine nucleotide (isopentenyladenosne-5'-monopnosphate) were the most abundant cytokinins in all organs. Their identities were confirmed by GC-MS. The levels of zeatin, zeatin riboside, isopentenyladenine and isopentenyladenosine never exceeded 5% of the nucleotides, as assessed by a methodology that preserves cytokinin nucleotides. Three extraction methods were compared with qualitatively similar results, though differing in their suppression of nucleotidase activity. Cytokinin nucleotide levels were greater in the stems and petioles than in the roots and leaves on a per gram fresh weight basis, and were greater in the stems than in the other organs on a per plant basis. Levels of the zeatin and isopentenyladenine nucleotides were about equal in the stems and leaves, but in the petioles the zeatin nucleotide levels were about twice the level of isopentenyladenine nucleotide, while in the roots they were about half the isopentenyladenine nucleotide level. The importance of considering the cytokinin form is emphasised.