Carbonic acid as the host signal for the development of parasitic stages of nematodes

Petronijevic T., Rogers W. P. and Sommerville R. I. 1985. Carbonic acid as the host signal for the development of parasitic stages of nematodes. International Journal for Parasitology15: 661–667. This paper gives results on which may be based an identification of the component of the system CO₂ + H₂O ai H₂CO₃ ai H⁺ HCO₃^? which acts as the stimulus from the animal host for some nematodes. Using infective juveniles of Nematospiroides dubius and Haemonchus contortus, the effects on exsheathment of (1) low pCO₂ values, (2) the presence of carbonic anhydrase in the stimulating medium, and (3) the inhibition of carbonic anhydrase within the juveniles have been examined. The results lead to the suggestion that it is the “readily available” undissociated H₂CO₃, or H₂CO₃ + HCO₃^? which is the critical factor in the stimulus for development. The wide range of [H⁺]s over which “readily available” H₂CO₃ is present in physiological environments suggests that this host signal may be important for infection with many species.     

Tb3+ binding to bovine prothrombin and bovine prothrombin fragment 1

The binding of Tb3+ to bovine prothrombin and the amino-terminal 156 residues of prothrombin (F-1) was studied. On the basis of various Tb3+ emission properties, three classes of Tb3+-binding sites were described. The first class contained three high affinity sites in the F-1 region. These sites were filled noncooperatively and were saturated with Tb3+ before the other classes of sites started to fill. Ho3+ quenching of Tb3+ emission showed that these sites were in close proximity to one another (estimated distances 6-12 A). The second class of sites contained three lower affinity sites, also in the F-1 region. These sites bound Tb3+ in a stoichiometric manner and saturated prior to metal binding to the final class of sites. The number of protein ligands binding Tb3+ in the high affinity sites decreased as this second set of sites was filled. Ho3+ quenching of Tb3+ emission suggested that these sites were closely spaced and/or close to the first set of sites. The third class of sites contained 4-6 low affinity sites unique to prothrombin (not in the F-1 region). These sites were not studied extensively, but Tb3+ did not appear to bind stoichiometrically and did not saturate these sites in a manner similar to the other two classes of sites. The emission properties of Tb3+ bound to F-1 were different in KCl versus NaCl containing buffer while the emission properties of Tb3+ bound to prothrombin were not. Optimum conditions for studying lanthanide binding to F-1 (i.e. when Tb3+ bound to F-1 showed emission properties similar to Tb3+ bound to prothrombin) were when F-1 experiments were done at low F-1 concentrations in buffer containing 0.1 M KCl.     

Specific interaction of proteins with 5 S RNA and tRNA in the 42 S storage particle of Xenopus oocytes

During early oogenesis in amphibia, most of the 5 S RNA and tRNA is stored in a ribonucleoprotein particle that sediments at 42 S. In Xenopus laevis the 42 S particle contains two major proteins: of M_r 48 000 (P48) and 43 000 (P43). It is shown that heterogeneity in composition of the 42 S particle reflects a changing situation whereby initially, both 5 S RNA and tRNA are complexed with P48 (1 molecule 5 S RNA: 1 molecule P48; 2 or 3 molecules tRNA: 1 molecule P48), but later, tRNA becomes increasingly associated with P43 (in a 1:1 ratio) although 5 S RNA remains complexed with a cleavage product of P48. These changes relate to the eventual utilization of the excess 5 S RNA and tRNA in ribosome assembly and protein synthesis.     

Molting in a parasitic nematode, Phocanema decipiens—VII. The mode of action of the ecdysial hormone

The cycle of aminopeptidase activity demonstrated by histochemical methods in the activated excretory gland could not be detected in homogenates. In the electron microscope, the secretory granules in dormant glands were dense and irregular in shape and the mitochondria elongate, relatively dense, and with a crenellated outer membrane. The excretory gland was activated when the neuroendocrine system was stimulated by farnesyl methyl ether. In activated glands the secretory granules became larger, less dense and the membranes began to fuse with membranes of the ductules which ramify through the gland. The mitochondria became swollen. Aminopeptidase activity was displayed by a large uniformly less dense granules but not by the denser granules, and was seen in the endoplasmic reticulum, Golgi apparatus and in the lumen of the ducts. It is suggested that the ecdysial hormone from the neurosecretory cells sets in train a sequence of events which leads to entry of water into the gland and consequent activation of the enzyme in the granules, and to changes in the membranes of the granules which facilitate fusion with the membrane lining the ducts.     

我国微茎类吸虫研究:ⅩⅢ.微茎类吸虫成虫结构特征排序

对我国52种微茎类吸虫的18项成虫形态学特征进行主成分分析,结果表明:卵巢位置、子宫延伸位置等7项性状对第一主成分贡献较大,提示描述器官位置的指标是重要的分类依据。52个虫种在前三个主成分上的排序图显示应将其划分成4个亚科。     

Gyrodactylus gemini n. sp. (Monogenea: Gyrodactylidae), a parasite of Semaprochilodus taeniurus (Steindachner) from the Venezuelan Amazon

Gyrodactylus gemini n. sp. (Monogenea, Gyrodactylidae) is described from the surface of the body and fins of the fish Semaprochilodus taeniurus (Steindachner) imported into Britain from the Venezuelan Amazon. The new species differs from other species of the genus, including those described from South and Central America, by having: (i) stout hamuli with straight shafts and diverging roots; (ii) marginal hooks with the sickle length larger than the width; (iii) a dorsal bar without a medial constriction; (iv) a rectangular ventral bar with short processes; (v) a triangular ventral bar membrane; and, most obviously, (vi) at least two generations which can develop two embryos simultaneously. This is the first known species of the genus Gyrodactylus from the Venezuelan Amazon and the first record of the subgenus Gyrodactylus (Gyrodactylus) from South America.     

柱萤叶甲属研究（Ⅰ）鞘翅具黑色刻点的种类记述（鞘翅目：叶甲科）

本文就萤叶甲亚科中柱萤叶甲属鞘翅具黑色刻点的种类进行研究,共记述４种,我国已记录３种,其中１种为新种。     

我国微茎类吸虫的研究Ⅻ.类茎属及多黄属二新种报道：复殖目：微茎科

本文报道在湛江市附近海域海鸟体内获得的两种吸虫,经鉴定为新种,命名为巨口类茎吸虫,新种Ｍｉｃｒｏｐｈａｌｌｏｉｄｅｓ ｍａｃｒｏｓｔｏｎｒｓ ｓｐ．ｎｏｖ．,珊瑚多黄吸虫,新种Ｍｕｌｔｉｖｉｔｅｌｌｕｓ ｃｏｒａｌｉｕｓ ｓｐ．ｎｏｖ．     

The functional morphology of the alimentary canal of larval stages of the parasitic copepod Lepeophtheirus salmonis

The functional morphology of the alimentary canal of copepodite and chalimus stages of Lepeophtheirus salmonis (Krøyer, 1837) is described and compared with that found in other copepods studied to date.
The buccal cavity passes into a gut comprising three major regions: foregut (oesophagus), midgut and hindgut. The foregut and hindgut both posscss a cuticular lining whereas the midgut is lined with specialized epithelial cells. The midgut is divided into three recognizable zones, namely anterior midgut caecum, anterior midgut and posterior midgut. Three main types of epithelial cell are recognizable in the midgut: vesicular cells, microvillous cells and basal cells which correspond to the cell types normally described in other parasitic and free-living copepod species.
Digestion is thought to occur in the midgut and be mediated by the epithelial cells that line it. Although several glands appear to discharge into the area of the buccal cavity, none was seen to interface to any other area of the gut. There was no evidence for the involvement of commensal gut bacteria in food digestion.