X-ray crystal structure of galabiose, O-alpha-D-galactopyranosyl-(1---4)-D-galactopyranose

O-alpha-D-Galactopyranosyl-(1---4)-D-galactopyranose, C12H22O11, Mr = 342.30, crystallises in the orthorhombic space group P2(1)2(1)2(1), and has alpha = 5.826(1), b = 13.904(3), c = 17.772(4) A, Z = 4, and Dx = 1.579 g.cm-3. Intensity data were collected with a CAD4 diffractometer. The structure was solved by direct methods and refined to R = 0.063 and Rw = 0.084 for 2758 independent reflections. The glycosidic linkage is of the type 1-axial-4-axial with torsion angles phi O-5' (O-5'-C-1'-O-1'-C-4) = 98.1(2) degrees, psi C-3 (C-3-C-4-O-1'-C-1') = -81.9(3) degrees, phi H (H-1'-C-1'-O-1'-C-4) = -18 degrees, and psi H (H-4-C-4-O-1'-C-1') = 35 degrees. The conformation is stabilised by an O-3 . . . O-5' intramolecular hydrogen-bond with length 2.787(3) A and O-3-H . . . O-5' = 162 degrees. The glycosidic linkage causes a folding of the molecule with an angle of 117 degrees between the least-square planes through the pyranosidic rings. The crystal investigated contained 56(1)% of alpha- and 44(1)% of beta-galabiose as well as approximately 70% of the gauche-trans and approximately 30% of the trans-gauche conformers about the exocyclic C-5'-C-6' and C-5-C-6 bonds. The crystal packing is governed by hydrogen bonding that engages all oxygen atoms except the intramolecular acceptor O-5' and the glycosidic O-1' oxygen atoms.     

Behaviour of drifting insect larvae

The larval drift behaviour of 23 species representing Ephemeroptera, Plecoptera and Trichoptera was investigated in the laboratory using different current regimes. Mayfly nymphs often performed swimming, while caddis larvae were reluctant to do so. Stonefly nymphs were intermediate. In mayflies swimming seemed to be used to reach the substrate as soon as possible. In contrast most stonefly nymphs by swimming prolonged the time spent in the water column. Modes of swimming and sinking posture differed markedly between the orders. Living passively sinking animals often reached bottom faster than dead control specimens, so consequently behaviour did not always express itself in activity. Some caddis larvae spun adherent anchor lines. Differences among taxa seemed more important in explaining swimming activity compared to preferred habitats (as stream, river and lake) in each species. However, observed differences among closely related species indicated subtle differences related to microhabitat to be of profound importance in explaining the alternative behavioural strategies used.     

Recognition of peat-forming plant communities from their peat deposits in two south Swedish bog complexes

Peat samples, 3 015 from 103 boring points, on two mires (Åkhult mire, Store Mosse mire) south Sweden, have been subjected to macrofossil analysis. Based on plant remains, 9 peat groups were distinguished in the field. A further classification using phytosociological methods revealed 29 peat types. The affinities between the peat types were determined from TABORD classification and a Reciprocal Averaging ordination. The primary floristic differentiation is correlated with a gradient from treeless-to wooded stands, which coincides largely with the mire expanse-mire margin gradient. The poor-rich gradient seems to parallel the treeless-wooded gradient as well and may reflect the natural conditions in this mire before it was affected by man. The hummock-mud-bottom gradient is easy to distinguish in peat, formed by bog communities, but is not distinct in peat formed by fen communities and impossible to detect in peat dominated by wood remains. The amount of identifiable remains depends on the decomposition, which is determined by (1) the period of time the plant litter stays in the acrotelm, and (2) the nutrient status. The decomposition is greatest in fen-peat with abundant wood remains. This probably depends on a good supply of oxygen caused by greater horizontal water movements and better nutrient status.     

Cell cycle traverse and protein metabolism in human NHIK 3025 cells: the role of anchorage

We have studied the effect of cell anchorage on the human cell line NHIK 3025 in vitro, to see whether the growth regulating effect of cell anchorage primarily affected DNA division cycle or mass growth cycle. It was found that cell to cell anchorage had the same effect on cell cycle progression as anchorage to a solid surface, which indicates that it is anchorage per se and not cell shape that is important for growth control in NHIK 3025 cells. When NHIK 3025 cells were grown without attachment to a solid surface, both G1 and cell cycle duration was prolonged by 6 h, which means that the prolonged cell cycle was due to a prolonged G1. During the first part of the cell cycle the rate of protein synthesis and degradation was constant, and at the same level in cells grown with and without attachment. This means that the prolonged G1 was not due to a reduced protein accumulation or mass growth. Towards the end of the cell cycle protein accumulation was reduced. This effect was either due to a size control before cell division or a secondary effect of the prolonged G1. We therefore conclude that cell anchorage as a growth regulator primarily affects the DNA/cell division cycle.     

Single-file diffusion through the Ca2+-activated K+ channel of human red cells

Summary We have examined the effect of internal and external pH on Na⁺ transport across toad bladder membrane vesicles. Vesicles prepared and assayed with a recently modified procedure (Garty & Asher, 1985) exhibit large, rheogenic, amiloridesensitive fluxes. Of the total²²Na uptake measured 0.5–2.0 min after introducing tracer, 80±4% (mean±se,n=9) is blocked by the diuretic with aK ₁ of 2×10^–8 m. Thus, this amiloridesensitive flux is mediated by the apical sodium-selective channels. Varying the internal (cytosolic) pH over the physiologic range 7.0–8.0 had no effect on sodium transport; this result suggests that variation of intracellular pHin vivo has no direct apical effect on modulating sodium uptake. On the other hand,²²Na was directly and monotonically dependent on external pH. External acidification also reduced the amiloride-sensitive efflux across the walls of the vesicles. This inhibition of²²Na efflux was noted at external Na⁺ concentrations of both 0.2 m and 53mm.These results are different from those reported with whole toad bladder. A number of possible bases for these differences are considered and discussed. We suggest that the natriferic response induced by mucosal acidification of whole toad urinary bladder appears to operate indirectly through one or more factors, presumably cytosolic, present in whole cells and absent from the vesicles.     

The putative dopamine autoreceptor agonist B-HT 920 decreases nigral dopamine cell firing rate and prolactin release in rat

Recent behavioural and biochemical investigations have suggested that the alpha-2 receptor agonist B-HT 920 is also a centrally acting dopamine (DA) agonist with a selectivity for autoreceptors. It is presently demonstrated that B-HT 920, in contrast to the structurally related alpha-2 agonist B-HT 933, effectively reduces the firing rate of nigral DA neurons both after intravenous and microiontophoretic administration. Furthermore, B-HT 920, but not B-HT 933, decreases plasma levels of prolactin in reserpine pretreated rats. The electrophysiological as well as the neuroendocrine effects of the drug were antagonised by DA antagonists but not by alpha-2 receptor antagonists. The data support the contention that B-HT 920 acts as an agonist at central DA autoreceptors. Furthermore, they reinforce the hypothesis that lactotroph DA receptors are more similar to DA autoreceptors than to postsynaptic DA receptors in the brain.     

An estimate of pollen carryover by ants in a natural population of Scleranthus perennis L. (Caryophyllaceae)

Summary Pollen carryover by ants was estimated in a natural population of Scleranthus perennis L. (Caryophyllaceae) using fluorescent dye as a pollen analogue.A highly significant exponential decrease in deposition of dye grains in a sequence of flowers visited by the main flowr visitor, Formica (S.) rufibarbis F., was observed with most grains being deposited in the first few flowers visited. At most 12 flowers were visited in a sequence.The mean between-flower transfer distance was estimated to be 6.2 cm, within-plant pollen transfers being recorded as zero. When all within-plant movements were excluded the mean was 22.5 cm. The distribution of transport distances differed from what I observed for honey-bees which occasionally foraged on dense stands of S. perennis. Calculations made on the deposition of dye grains transferred by ants showed that 7% of the dye grains deposited in the first flower visited after the dye source may reach a flower situated c. 30 cm from the dye source.     

Radioimmunoassay for determination of indole-3-acetic acid in fungi and plants

A radioimmunoassay technique for indole-3-acetic acid is described. The method has successfully been used to measure extractable indole-3-acetic acid in fungal and plant materials and is able to detect as little as 0.3 pmol. As non-radioactive antigen the methyl ester of indole-3-acetic acid is used and the radioactive antigen is tritiated. An acid-catalyzed esterification of indole-3-acetic acid is used for conversion into methyl ester. The measuring range of the assay is 0.3–10 pmol. In the assay, separation of free and bound fractions is achieved by dextran-coated charcoal, leaving the bound fraction in the supernatant.     

Animal community structure as a function of stream size

The species-area relationship of the island biogeography theory was calculated for macroinvertebrates in 22 coastal, adjacent streams. A z-value of 0.19 was obtained. The low z-value was probably a consequence of the short distances between streams as well as high dispersal rates. In addition, a cluster analysis based on the dissimilarity of species assemblages showed that stream size was of prime importance in categorizing the streams. To a smaller extent water quality affected the community structure in the streams.