长春净月潭地区土壤跳虫的生态分布

土壤动物直接参与土壤形成,它与土壤微生物的相互配合,对植物凋落物的分解起着十分重要的作用。土壤跳虫是土壤动物中最重要的类群之一。关于它的生态分布,目前国内报道不多。东北师范大学和日本九州大学合作,对长春净月潭地区的土壤跳虫进行了初步调查。     

The nature and prospects for gut membrane proteins as vaccine candidates for Haemonchus contortus and other ruminant trichostrongyloids

Substantial progress has been made in the last decade in identifying several antigens from Haemonchus contortus which, in their native form, stimulate useful levels of protective immunity (70-95% reductions in faecal egg output) in the ovine host. Much work has focussed on proteins/protein complexes expressed on the surface of the worm gut which are exposed to the blood meal, and, hence, antibody ingested with it. The antigens generally, but not in all cases, show protease activity and antibody is thought to mediate protective immunity by blocking the activity of enzymes involved in digestion within the worm. This review summarises the protective efficacy, as well as the biochemical and molecular properties, of the principal candidate antigens which are expressed in the gut of these parasites. Of course, such antigens will have to be expressed as recombinant proteins to be sufficiently cost-effective for use in a commercial vaccine and the current status of recombinant antigen expression is discussed with particular reference to conformation and glycosylation. There is a need for continued antigen definition even in the confines of gut antigens and potential targets can be selected from the rapidly expanding genome/EST datasets on the basis of predicted functional homology. Gene knockout technologies such as RNA interference have the potential to provide high throughput, rapid and inexpensive methods to define whether the protein product of a particular gene would be a suitable vaccine candidate.     

The mutation rates of di-, tri- and tetranucleotide repeats in Drosophila melanogaster

In a recent study, we reported that the combined average mutation rate of 10 di-, 6 tri-, and 8 tetranucleotide repeats in Drosophila melanogaster was 6.3 x 10(-6) mutations per locus per generation, a rate substantially below that of microsatellite repeat units in mammals studied to date (range = 10(-2)-10(-5) per locus per generation). To obtain a more precise estimate of mutation rate for dinucleotide repeat motifs alone, we assayed 39 new dinucleotide repeat microsatellite loci in the mutation accumulation lines from our earlier study. Our estimate of mutation rate for a total of 49 dinucleotide repeats is 9.3 x 10(-6) per locus per generation, only slightly higher than the estimate from our earlier study. We also estimated the relative difference in microsatellite mutation rate among di-, tri-, and tetranucleotide repeats in the genome of D. melanogaster using a method based on population variation, and we found that tri- and tetranucleotide repeats mutate at rates 6.4 and 8.4 times slower than that of dinucleotide repeats, respectively. The slower mutation rates of tri- and tetranucleotide repeats appear to be associated with a relatively short repeat unit length of these repeat motifs in the genome of D. melanogaster. A positive correlation between repeat unit length and allelic variation suggests that mutation rate increases as the repeat unit lengths of microsatellites increase.      

The role of blood pigments in the delivery of oxygen to tissues

Summary 1. The detailed manner in which the blood respiratory pigments of many invertebrates function is not well understood.2. The hemocyanins of the cephalopods studied appear to function in gas transport much like the hemoglobins of the vertebrates although these hemocyanins possess a much larger Bohr effect.3. The properties of the hemocyanins of the crustacea are fairly uniform but those of the mollusca vary considerably.4. The hemocyanins of the chitons have relatively high half-saturation oxygen pressures. They may show a normal or reverse Bohr effect, or none at all. Regardless of the direction of the effect, however, these hemocyanins are relatively insensitive to small changes of pH.5. The hemocyanins of marine snails studied have lower half-saturation pressures and all exhibited a reverse Bohr effect.6. It is suggested that:(a) the properties of the hemocyanins are related to metabolic rate, accessibility and effectiveness of the gills, and the nature of the circulatory system;(b) an important function of many invertebrate blood pigments is to maintain a large oxygen diffusion gradient across the respiratory surface;(c) the reverse Bohr effect may aid in the internal distribution of oxygen to more rapidly metabolizing snail tissues when circulation is slowed or stopped.7. A possible functional evolution of blood respiratory pigments is described.

---

Die Rolle der Blutpigmente für die Sauerstoffversorgung der Gewebe

Kurzfassung Die Art und Weise, in welcher die Hämoglobine als Sauerstoffüberträger im Wirbeltierblut funktionieren, ist wohlbekannt. Die spezifischen Eigenschaften der Wirbeltier-Hämoglobine sind wohl abgestimmt auf die physiologischen Ansprüche der betreffenden Arten und auf deren Umweltsituationen. Studien über die Hämocyanine der Arthropoden und Mollusken dagegen deuten darauf hin, da§ das Ausmaß vergleichbarer Korrelationen bei den bisher untersuchten Arten erheblich variiert. Häufig zeigen der Verlauf der Sauerstoffdissoziationskurve und dessen Veränderungen in Abhängigkeit vom pH keine augenfälligen Beziehungen zur Stoffwechselintensität, Umgebungstemperatur oder zum Sauerstoffangebot. Es wird angenommen, daß die Hämocyanine und andere Blutatmungspigmente der Wirbellosen variable Stadien in der funktionellen Evolution dieser Substanzen darstellen, wobei die Primärfunktion bei vielen Wirbellosen die Erhaltung starker Sauerstoffdiffusionsgradienten über die respiratorischen Oberflächen ist. Ladungsspannungen sowie Art und Ausmaß des Bohreffekts sind möglicherweise korreliert mit dem Wirkungsgrad und der Zugänglichkeit der Kiemen, wie auch der Natur des Kreislaufsystems.

     

Sensilla coeloconica ringed by microtrichia in host‐seeking biting midges

The distribution and morphology of antennal sensilla coeloconica in parasitic and predaceous biting midges were studied in females of Forcipomyia (feeding on the blood of frogs), Atrichopogon (feeding on haemolymph), Austroconops, Culicoides (feeding on the blood of birds and mammals) and Brachypogon (feeding on haemolymph and dissolved tissues of insects) (all: Diptera: Ceratopogonidae). A Lower Cretaceous female of Archiculicoides (Diptera: Ceratopogonidae) from Lebanese amber, which fed on the blood of unknown vertebrates, was also examined. In sensilla coeloconica ringed by microtrichia, the peg is grooved longitudinally and protrudes distinctly from the pit. We suggest that the microtrichia encircling the protruding peg form a structure resembling a picket fence in order to maintain a higher level of humidity, which facilitates the capture and transport of odour molecules through the channels in the peg wall. Sensilla coeloconica ringed by microtrichia function as very effective chemoreceptors in host‐ and prey‐seeking activity. During the evolution of Ceratopogonidae, sensilla coeloconica with a fence of microtrichia have evolved twice in groups feeding on the blood of vertebrates (i.e. in the basal lineage: Lower Cretaceous or earlier) and in the subgenus Lasiohelea of Forcipomyia (Palaeogene). Sensilla coeloconica ringed by microtrichia are described for the first time in the relict genus Austroconops.