Non-marine Teredolites from the Middle Eocene of southern England

Middle Eocene, non-marine sediments from southern England contain examples of Teredolites borings in two contrasting palaeoenvironmental settings, viz.: (A) as in situ borings in an allochthonous lignite in an abandoned river channel and (B) as bored logs in cross-bedded fluvial sandstones of probable point-bar origin. The lignite is 0.30 m thick, of which the upper 0.20 m is intensely bored. Rounded pebbles of ?charcoal at its base also show small borings. A log in a fluvial sandstone shows densely-packed. radial club-shaped borings. now filled with sandstone. The wood substrate has subsequently been oxidized away. To our knowledge, this is the first detailed account of Teredolites from an ancient freshwater setting.     

A comparison of the actions of trypsin and pepsin on porcine immunoglobulin M and their effects on biological activity

The action of trypsin at 55 degree C and pH 8.3 on pig IgM anti-Salmonella has been compared with the action of pepsin at 37 degree C and pH 4.6. Both processes cause the gradual removal of Fab arms and Cmu2 domains to produce eventually an (Fc)5 fragment. However, during tryptic digestion Fab arms are preferentially removed from the same subunit, whereas peptic digestion causes random removal from any subunit. At intermediate stages of digestion both processes produce partially fragmented molecules which consist of an (Fc)5 portion still attached to limited numbers of Fab arms. Both processes cause a gradual decrease in the ability of molecules to agglutinate Salmonella, but complement fixation by the complexes declines much more rapidly. A stage is reached where molecules having four Fab arms can still agglutinate but there is no complement fixation. However, the remaining arms on the tryptic molecules are distributed in pairs on the same subunit, whereas those on the peptic molecules are distributed randomly. Hence the number of remaining Fab arms, rather than their distribution, appears to be the critical factor which influences biological activity. A possible explanation for this is discussed.     

Changes in the levels of wheat- and barley-germ agglutinin during embryogenesis in vivo,in vitro and during germination

Radioimmunoassay has been used to measure levels of wheat-germ agglutinin and barley-germ agglutinin during embryogenesis and germination. The two lectins exhibited similar patterns of accumulation during grain maturation in vivo and both decreased to low levels after imbibition of harvest-ripe grains for 3 d. Precocious germination of immature wheat and barley embryos excised and cultured in vitro could be prevented either by inclusion of abscisic acid or mannitol in the culture medium. Changes in the level of wheat-germ agglutinin induced by in vitro culture depended on the maturation stage of the embryo. No direct correlation was found between application of exogenous abscisic acid and accumulation of the lectin.     

Do colonic bacteria contribute to cholesterol gall-stone formation? Effects of lactulose on bile.

Ten healthy middle-aged women volunteered for a study to test the effect of lactulose--a synthetic, non-absorbable disaccharide--on the colonic metabolism of bile acids and on bile lipid composition. Lactulose (60 g daily in eight cases, 39 g daily in two) was taken as a proprietary syrup for six weeks, and bile was collected by duodenal intubation before and immediately after six weeks. All subjects showed a fall in the percentage of the 7-alpha-dehydroxylated bile acid deoxycholic acid (mean 28.4 +/- SEM 3.7 to 15.6 +/- 2.4; p less than 0.002) and a rise in the percentage of the primary bile acid chenodeoxycholic acid (mean 33.2 +/- 42.9 +/- 2.9; p less than 0.001). The percentage of cholic acid rose in eight subjects but mean values did not differ significantly. Bile was initially super-saturated with cholesterol in most subjects and became less saturated with cholesterol in all but one (mean saturation index 1.40 +/- 0.11 to 1.19 +/- 0.07; p less these 0.005). These data support the theory colonic bacteria contribute to cholesterol gall-stone formation.     

Effect of different disintegration techniques and media on yield and appearance of isolated nuclei

Cell nuclei have been released from various plant tissues (barley leaves, roots and embryos, tobacco leaves and tissue cultures,Vicia faba roots,Arabidopsis thaliana leaves) by several homogenization methods and the optimal method was established for each tissue. The effect of the composition of isolation medium on the yield and appearance of isolated nuclei was also studied. Longer incubation withn-octanol increases the yield considerably in most cases. Low concentrations of osmoticum increase the yield and their adverse effect on the integrity of nuclei is of little significance. Gum arabic has a favourable effect on nuclei isolation from roots only.     

Spectrophotometric determination of inorganic phosphate in the presence of thiol compounds

A spectrophotometric method for inorganic phosphate determination in the presence of thiol compounds is described. Thiol compounds, which interfere with the measurement of inorganic phosphate by a modification of the method of Gomori, are removed by carboxymethylation by iodoacetate prior to the formation and reduction of phosphomolybdate complex. A linear standard curve is obtained by this method, and the method is suitable for the assay of a phosphate-releasing enzyme when the measurement must be performed in the presence of thiol compounds.     

Hypophysiotrophic thyrotropin releasing hormone (TRH) synthesizing neurons. Ultrastructure, adrenergic innervation and putative transmitter action

The neuropeptide thyrotropin releasing hormone (TRH) is capable of influencing both neuronal mechanisms in the brain and the activity of the pituitary-thyroid endocrine axis. By the use of immunocytochemical techniques, first the ultrastructural features of TRH-immunoreactive (IR) perikarya and neuronal processes were studied, and then the relationship between TRH-IR neuronal elements and dopamine-beta-hydroxylase (DBH) or phenylethanolamine-N-methyltransferase (PNMT)-IR catecholaminergic axons was analyzed in the parvocellular subnuclei of the hypothalamic paraventricular nucleus (PVN). In control animals, only TRH-IR axons were detected and some of them seemed to follow the contour of immunonegative neurons. Colchicine treatment resulted in the appearance of TRH-IR material in parvocellular neurons of the PVN. At the ultrastructural level, immunolabel was associated with rough endoplasmic reticulum, free ribosomes and neurosecretory granules. Non-labelled axons formed synaptic specializations with both dendrites and perikarya of the TRH-synthesizing neurons. TRH-IR axons located in the parvocellular units of the PVN exhibited numerous intensely labelled dense-core and fewer small electron lucent vesicles. These axons were frequently observed to terminate on parvocellular neurons, forming both bouton- and en passant-type connections. The simultaneous light microscopic localization of DBH or PNMT-IR axons and TRH-synthesizing neurons demonstrated that catecholaminergic fibers established contacts with the dendrites and cell bodies of TRH-IR neurons. Ultrastructural analysis revealed the formation of asymmetric axo-somatic and axo-dendritic synaptic specializations between PNMT-immunopositive, adrenergic axons and TRH-IR neurons in the periventricular and medial parvocellular subnuclei of the PVN. These morphological data indicate that the hypophysiotrophic, thyrotropin releasing hormone synthesizing neurons of the PVN are directly influenced by the central epinephrine system and that TRH may act as a neurotransmitter or neuromodulator upon other paraventricular neurons.