Schistosoma mansoni: Ultrastructure of early transformation of skin- and shear-pressure-derived schistosomules

Against the background of cercarial fine structure, ultrastructural changes were compared in schistosomules of Schistosoma mansoni 30 min and 1 hr after their production in vivo by skin penetration and in vitro by shear pressure. The same developmental pattern was observed in schistosomules of both derivations. In vitro schistosomules, however, developed more slowly, resembled cercariae more closely, and varied less among organisms than did in vivo schistosomules. The greatest morphological changes were observed in the 1-hr in vivo schistosomules. These were as follows: (1) in tegument, formation of transient microvilli, a hepatalaminate outer membrane and accented surface invaginations, loss of glycocalyx, movement outward of cyton vesicles via bridges, accumulation of multilaminate bodies around bridge openings; (2) in the anterior organ (oral sucker), movement of head gland vesicles via the ducts into tegument followed by collapse of the gland fundus, disappearance of the circumfundal cells and two large support cells, and the appearance in these areas of membranes and parenchymal cells; (3) secretion of the acetabular gland contents, collapse of the glands and replacement by membranes and parenchymal cells; (4) peristaltic activity of the digestive tract as shown by alternate areas of lumen constriction and dilation; (5) loss of bladder and contraction of the small aboral collecting tubules; and (6) conversion of heterochromatic parenchymal cell nuclei to euchromatic. In contrast, the 1-hr in vitro shear schistosomules resembled 30-min in vivo schistosomules, retaining many cercarial features.     

Regulatory properties of a partially purified preparation of pyruvate kinase from Fasciola hepatica

It possesses sigmoid kinetics with PEP; FBP activation changes the relationship to a rectangular hyperbola. The enzyme is inhibited by malate, which competes with PEP; FBP relieves the inhibition slightly. ATP and bicarbonate ions are also inhibitory at high concentrations. ATP inhibition is mixed-competitive with PEP; bicarbonate inhibition is non-competitive. It is suggested that pyruvate kinase may regulate both lactate and acetate production by moderating the size of the cytosolic pyruvate pool.     

Natural chelators in sea water: Detoxification of Zn2+ by brown algal polyphenols

We have examined growth responses of several species of marine phytoplankton, cultured with and without heavy metal stress, to supplements of polymeric polyphenols from the brown algae Ascophyllum nodosum (L.) Le Jol. and Fucus vesiculosus L. In the absence of additional heavy metals. supplements of up to 4000 μg. 1 of polyphenols had a small effect on initial growth rates for three of these microalgae and had no effect on maximum cell densities for four species. One very common, heavy metal-sensitive diatom, Skeletonema costatum (Grev.) Cl., showed significantly increasing maximum cell density in the cultures, with increasing addition of polyphenols to the medium. The toxicity of Zn²⁺ (0.5–2.0 mg·1 ¹) to cultures of the diatom Phaeodactylum tricornutum Bohlin was relieved by supplements (100–200 μg·1 ¹) of the brown algal polyphenols. Exudation of these polyphenols from brown seaweeds may contribute to the natural chelating capacity of inshore sea water.     

Reconstitution of acetylcholine receptor from Torpedo californica with highly purified phospholipids: Effect of α-tocopherol,phylloquinone, and other terpenoid quinones

Acetylcholine receptor from $\text{Torpedo californica}$ can be incorporated by the cholate dialysis procedure into liposomes prepared with crude soybean phospholipids (asolectin). Vesicles reconstituted with asolectin depleted of neutral lipids or with a mixture of pure phospholipids, are less active in catalyzing carbamylcholine-sensitive Na⁺ flux. Inclusion of α-tocopherol or certain quinones such as coenzyme Q₁₀ or vitamin K₁ during reconstitution yields vesicles with carbamylcholine-sensitive Na⁺ flux which, under optimal conditions, was considerably higher than that observed with vesicles reconstituted with crude phospholipid mixtures.     

Genetic polymorphism of the major parotid salivary glycoprotein (Gl) with linkage to the genes for Pr,Db, and Pa

Genetic polymorphism of the major glycoprotein (Gl) found in parotid saliva is determined by autosomal inheritance of one unexpressed and four expressed alleles. This hypothesis is supported by studies in 41 white families including 146 children. For 143 randomly collected salivas from whites and 82 randomly collected salivas from blacks, maximum likelihood estimates of the gene frequencies are as follows: for whites, Gl ¹=0.742, Gl ²=0.040, Gl ³=0.155, Gl ⁴=0.017, Gl ⁰=0.046; for blacks, Gl ¹=0.459, Gl ²=0.050, Gl ³=0.337, Gl ⁴=0.044, Gl ⁰=0.110. There is strong evidence for linkage of Gl/Pr (seven families, lod score at =0 is 5.24) and Gl/Db (eight families, lod score at =0 is 4.45). The allelic products of Gl show evidence for linkage disequilibrium with the products of the Pr, Db, and Pa loci (P<0.0005). On the basis of varying degrees of linkage disequilibrium, Gl may be closer to Db than to Pr or Pa and on the outside of Db with respect to Pr or Pa. Amino acid analyses of Gl 1 and Gl 4 proteins show strong resemblances in composition to the major basic glycoprotein and the acidic proline-rich proteins of parotid saliva described by other workers. The polymorphic forms of the Gl proteins show microheterogeneity due to variability in charge and molecular weight. The electrophoretic polymorphism appears to be determined by apparent differences in molecular weights between the Gl proteins.This study was supported by a grant from the National Institutes of Dental Research (DEO 3658-12) and in part by NIH Grant GM 15422 and NIH Training Grant GM 00398. Paper No. 2242 of the Laboratory of Genetics, University of Wisconsin, Madison, Wisconsin 53706.     

ULTRASTRUCTURE OF GLANDULAR TRICHOMES OF LEAVES OF NICOTIANA TABACUM L., cv XANTHI

Electron microscopy confirms previous light microscope observations that tobacco leaf trichomes are glandular and that there are two different types. Both the tall trichome (multicellular stalk, unicellular or multicellular head) and the short trichome (unicellular stalk; multicellular head) exhibit characteristics common to gland cells—a dense cytoplasm, numerous mitochondria, and little vacuolation. The tall trichome contains structurally well developed chloroplasts and an elaborate network of endoplasmic reticulum. The short trichome contains undifferentiated plastids and endoplasmic reticulum which parallels the nucleus and plasmalemma. Few dictyosomes are seen either in the short trichome or in the tall trichome. The short trichome appears to undergo structural changes concurrently with the appearance of secretory product within the cells. The most noticeable change is the formation of the extraplasmic space between the cell wall and the plasmalemma. Electron dense secretory product is observed between the plasmalemma and the cell wall and within the intercellular spaces.     

ATP synthesis in a succinate decarboxylase system from Fasciola hepatica mitochondria

Köhler P. B.,Ryant C. and Behm Carolyn A. 1978. ATP synthesis in a succinate decarboxylase system from Fasciola hepatica mitochondria. International Journal for Parasitology8: 399–404. Succinate decarboxylation was measured by the formation of ¹⁴CO₂ from 1,4-¹⁴C-succinate in a particle free, dialysed mitochondrial extract from liver fluke. It has an absolute requirement for Mg²⁺ and CoA. ATP, ADP and inorganic phosphate are essential for optimal activity. Ap₅A, an inhibitor of adenylate kinase, and glutathione are also necessary. GTP supports decarboxylation as well as ATP, provided ADP is also present. The formation of CO₂ and propionate greatly exceeds the amount of ATP and CoA initially present in the reaction mixture. A net, substrate-level phosphorylation of ADP occurs, the amount of ATP formed being equivalent to the production of CO₂ or propionate. This system is inhibited in flukes incubated in vitro with mebendazole.It is concluded that ATP is required to spark the fermentation system when succinate is the initial substrate and intermediate substrates are absent; that the terminal step in propionate formation is catalysed by a transferase which transfers CoA from propionyl CoA to succinate; and that ATP formation is coupled to the decarboxylation of methylmalonyl-CoA. A reaction scheme is presented.     

Kinetics and morphology of glucose-limited cultures of moulds grown in a chemostat and on solid media

The affinity (K _s value) of Geotrichum candidum for glucose determined from chemostat cultures was ca. 1 mg/l. K _s values for glucose were also estimated from the radial growth rates of colonies of G. candidum and Neurospora crassa grown on media solidified with agar or silica gel. An assessment is made of the use of colony radial growth rate to determine substrate affinities. The length of apical and intercalary hyphal comparte ments, internode length and the diameter of leading hyphaat the margin of colonies grown on solid media were all reduced at low glucose concentrations.     

Bile acids. XL. Methyl 3beta, 7beta-dihydroxy-5alpha-cholanate. An example of dehydrogenation with Raney nickel

The bile acid derived from hydrogenolysis of methyl 6-oxo-3α, 7β-dihydroxy-5α-cholanate-6-ethylenethioketal with Raney nickel has been shown to be 3β, 7β-dihydroxy-5α-cholanic acid (VI). On extended reflux with Raney nickel the original C-3 hydroxyl group is dehydrogenated and the 3-oxo-derivative reduced principally to the equatorial 3β-o1. The positions and configurations of the hydroxyl groups were determined by reduction of the derived monohydroxy mono-oxo derivatives to the known monohydroxy acids. The materials (VI) has been synthesized from 3β-hydroxy-7-oxo-5α-cholanic acid by reduction with sodium and alcohol. Physical properties support the assigned structure.