THE TRANSFORMATION OF THE PLASMODIUM GALLINACEUM OOCYST IN AEDES AEGYPTI MOSQUITOES

Sporoblast and sporozoite formation from oocysts of the avian malarial parasite, Plasmodium gallinaceum, after the seventh day of infection in Aedes aegypti mosquitoes offers an interesting example of differentiation involving the appearance and modification of several cellular components. Sporoblast formation is preceded by (a) invaginations of the oocyst capsule into the oocyst cytoplasm, (b) subcapsular vacuolization and cleft formation, (c) the appearance of small tufts of capsule material on the previously noted invaginations, and (d) linear dense areas located just below the oocyst plasma membrane which predetermine the site of emerging sporozoites from the sporoblast. The subcapsular clefts subdivide the once-solid oocyst into sporoblast peninsulae. Within the sporoblast, nuclei migrate from the random distribution seen in the solid oocyst and come to lie at the periphery of the sporoblast just below the linear dense areas noted in the earlier stage. A typical nuclear fiber apparatus occurs in most of the nuclei seen in random sections at this stage although such a fiber apparatus may occasionally be seen in the solid oocyst stage. The nucleus, its associated fiber apparatus, and the overlying dense area appear to induce the onset of sporozoite budding from the sporoblast as well as the formation of the sporozoite pellicular complex and the paired organelle precursor. Several mitochondria are present in each sporozoite, in contrast to the single mitochondrion seen in the merozoites of the erythrocytic and exoerythrocytic stages of avian malaria infection. The paired organelles and associated dense inclusion bodies are formed by condensation of an irregular meshwork of membrane-bound, coarse, dense material. The nature of small, particulate cytoplasmic inclusions is described.     

ECDYSONE-MEDIATED STIMULATION OF DOPA DECARBOXYLASE ACTIVITY AND ITS RELATIONSHIP TO OVARIAN DEVELOPMENT IN AEDES AEGYPTI

Very little dopa decarboxylase activity is detectable in adult female mosquitoes Aedes aegypti which have not been allowed to engorge blood. However, when such females are injected with the molting hormone β-ecdysone a marked stimulation of this enzyme's activity is observable. No stimulation is observed in males similarly injected, nor in females injected with cholesterol or a juvenile hormone mimic. In addition, ecdysone injection initiates ovarian development in these anautogenous non-blood-fed mosquitoes. The extent of stimulation in both cases is dependent upon the amount of β-ecdysone administered. These results suggested that ecdysone may play a role in ovarian development in Aedes and led us to hypothesize that a normal blood meal may trigger the synthesis, activation, or release of this hormone endogenously. Using the radioimmune assay for ecdysone developed by Borst and O'Connor (Science [Wash. D. C.] 178:4–18.), we found that the titer of an antigenic-positive material, presumably ecdysone or a closely related analogue, substantially increased 24 h after blood feeding, thereby supporting our postulation.     

YOLK PROTEIN UPTAKE IN THE OOCYTE OF THE MOSQUITO AEDES AEGYPTI. L

Yolk proteins are thought to enter certain eggs by a process akin to micropinocytosis but the detailed mechanism has not been previously depicted. In this study the formation of protein yolk was investigated in the mosquito Aedes aegypti L. Ovaries were fixed in phosphate-buffered osmium tetroxide, for electron microscopy, before and at intervals after a meal of blood. The deposition of protein yolk in the oocyte was correlated with a 15-fold increase in 140 mµ pit-like depressions on the oocyte surface. These pits form by invagination of the oocyte cell membrane. They have a 20 mµ bristle coat on their convex cytoplasmic side. They also show a layer of protein on their concave extracellular side which we propose accumulates by selective adsorption from the extraoocyte space. The pits, by pinching off from the cell membrane become bristle-coated vesicles which carry the adsorbed protein into the oocyte. These vesicles lose the coat and then fuse to form small crystalline yolk droplets, which subsequently coalesce to form the large proteid yolk bodies of the mature oocyte. Preliminary radioautographs, and certain morphological features of the fat body, ovary, and midgut, suggest that the midgut is the principal site of yolk protein synthesis in the mosquito.     

INFECTION OF AEDES AEGYPTI LARVAE BY AXENIC CULTURES OF THE FUNGAL GENUS SMITTIUM (TRICHOMYCETES)

Spores from axenic cultures of Smittium spp., isolated from various geographical locations and from different dipteran hosts (mosquito, black fly, and chironomid larvae), were fed to mosquito larvae (Aedes aegypti). We were able to demonstrate some host specificity at the insect family level, but no significant differences in infectivity by isolates from different geographical areas. Spore germination and thallus attachment were observed in the host hindgut within 1.5 hr post spore ingestion. Preliminary studies indicate that S. culisetae has little effect on A. aegypti larvae when they are reared under conditions that promote pupation within 5–6 days. However, ingestion of large numbers of spores by 1st instar larvae growing under suboptimal nutritional conditions may produce fungal growth detrimental to larvae.     

棒孢灭蚊霉对两种蚊虫的致病性研究初报

<正> 棒孢灭蚊霉Culicinomycwe clavosporus Couch,Romney & Rao是Couch等1974年才建立的属和种,该菌在美国寄生于四斑按蚊Anopheles quadrimaculatus Say,在澳大利亚寄生于另一种按蚊A.amictushilli Woodhill and Lee(Sweeney et al.,1973);(Cooper & Sweeney,1982)。由于C.clavosporus能在人工培养基上生长和产生大量分生孢子并能保存较长时间;对人、畜的安全性方面,曾用此菌对老鼠、天竺鼠、绵羊、牛和两种野鸭进行试验,对健康均无任何影响,也没有血液和生化方面的变化,解剖观察亦未     

THE EFFECTS OF LAGENIDIUM GIGANTEUM ON AEDES ALBOPICTUS AND OTHER MOSQUITOES IN GUIZHOU, CHINA

Abstract  The mosquito fungal pathogen, Lagenidium giganteum , was used to kill mosquito larvae of Guizhou. China, in the laboratory. The infection rates in Aeds albopictus ranged 25–89%, while those in Culex quingue fasciatus 90–100%. Five additional species and one genus of mosquitoes were added to the host list of L. giganteum .     

大链壶菌对白纹伊蚊及几种其它贵州蚊虫的杀灭作用的观察(英文)

采用大链壶菌在实验室内对白纹伊蚊及其它几种贵州蚊虫的幼虫进行杀灭试验。白纹伊蚊的感染率为25—89％,而致倦库蚊的感染率可达90—100％。实验结果为大链壶菌的宿主记录新增加一个属和五个种。     

THE APPEARANCE AND STRUCTURE OF INTERCELLULAR CONNECTIONS DURING THE ONTOGENY OF THE RABBIT OVARIAN FOLLICLE WITH PARTICULAR REFERENCE TO GAP JUNCTIONS

Lanthanum tracer and freeze-fracture electron microscope techniques were used to study junctional complexes between granulosa cells during the differentiation of the rabbit ovarian follicle. For convenience we refer to cells encompassing the oocyte, before antrum and gap junction formation, as follicle cells. After the appearance of an antrum and gap junctions we call the cells granulosa cells. Maculae adherentes are found at the interfaces of oocyte-follicle-granulosa cells throughout folliculogenesis. Gap junctions are first detected in follicles when the antrum appears. In early antral follicles typical large gap junctions are randomly distributed between granulosa cells. In freeze-fracture replicas, they are characterized by polygonally packed 90-Å particles arranged in rows separated by nonparticulate A-face membrane. A particle-sparse zone surrounds gap junctions and is frequently occupied by small particle aggregates of closely packed intramembranous particles. The gap junctions of granulosa cells appear to increase in size with further differentiation of the follicle. The granulosa cells of large Graafian follicles are adjoined by small and large gap junctions; annular gap junctions are also present. The large gap junctions are rarely surrounded by a particle-free zone on their A-faces, but are further distinguished by particle rows displaying a higher degree of organization.     

蚊虫的综合防治

防蚊灭蚊是防治或消灭蚊媒病的重要环节之一。从四十年代起,由于滴滴涕、六六六等一些高效杀虫剂的广泛应用以及杀虫剂使用方法和杀虫器械的改进进,蚊虫防治有了很大的发展,在蚊媒病的防治上起了重大作用。例如有些地区,采用滴滴涕、六六六以及其他杀虫剂作室内滞留喷洒,消灭或控制了疟疾的发生。于是在国外,化学     

METABOLIC AND ULTRASTRUCTURAL CHANGES IN THE FROG OVARIAN FOLLICLE IN RESPONSE TO PITUITARY STIMULATION

Frog ovarian fragments were prevented from ovulating in vitro by the addition of actinomycin D up to 3 hr following pituitary stimulation; but addition of Actinomycin D 6 hr after stimulation was far less effective. Puromycin, on the other hand, effectively inhibited ovulation when added as late as 6 hr after pituitary stimulation. Although actinomycin D reduced uptake of uridine-³H, and puromycin reduced uptake of leucine-³H and lysine-¹⁴ by pituitary-stimulated ovarian tissue minus oocytes (OTMO) in vitro, it was found that pituitary stimulation did not significantly increase uptake of these compounds by OTMO. Radioautographs of ovarian follicles fixed 6 hr after the addition of pituitary extract and uridine-³H in vitro revealed increased RNA synthesis in the peritoneal surface epithelium, compared with unstimulated controls, while the ovarian sac epithelium showed no increase. Gross ultrastructural changes occurred in the peritoneal area of ovarian follicles following pituitary stimulation in vivo, including loss of collagen fibrils, and general disorganization of the connective tissue theca. Changes in the rough endoplasmic reticulum of the peritoneal epithelial cells, while frequently encountered, were less pronounced. None of these changes was observed in the ovarian sac area, or in the interfollicular region. The above data are consistent with the hypothesis that pituitary stimulation of the frog ovary results in increased synthesis of RNA and protein by the peritoneal epithelial cells, and that the protein may be collagenase.     

HUMAN IMPACTS HAVE SHAPED HISTORICAL AND RECENT EVOLUTION IN AEDES AEGYPTI,THE DENGUE AND YELLOW FEVER MOSQUITO

Although anthropogenic impacts are often considered harmful to species, human modifications to the landscape can actually create novel niches to which other species can adapt. These “domestication” processes are especially important in the context of arthropod disease vectors, where ecological overlap of vector and human populations may lead to epidemics. Here, we present results of a global genetic study of one such species, the dengue and yellow fever mosquito, Aedes aegypti, whose evolutionary history and current distribution have been profoundly shaped by humans. We used DNA sequences of four nuclear genes and 1504 single nucleotide polymorphism (SNP) markers developed with restriction‐site associated DNA (RAD) sequencing to test the hypothesis that Ae. aegypti originated in Africa, where a domestic form arose and spread throughout the tropical and subtropical world with human trade and movement. Results confirmed African ancestry of the species, and supported a single subspeciation event leading to the pantropical domestic form. In addition, genetic data strongly supported the hypothesis that human trade routes first moved domestic Ae. aegypti out of Africa into the New World, followed by a later invasion from the New World into Southeast Asia and the Pacific. These patterns of domestication and invasion are relevant to many species worldwide, as anthropogenic forces increasingly impact evolutionary processes.     

INDUCTION OF OVARIAN DEVELOPMENT IN AUTOGENOUS AEDES ATROPALPUS BY JUVENILE HORMONE AND 20-HYDROXYECDYSONE

Aedes atropalpus is an autogenous mosquito characterized by a first gonadotropic cycle which results in approximately 200 mature oocytes without a bloodmeal. Ovarian development is completely inhibited if these animals are decapitated or ligated between the thorax and abdomen shortly after adult emergence. Injection of 4.8 ng of 20-hydro- xyecdysone into decapitated females 12 h after eclosion restores ovarian development in all females so treated. However, the same amount of 20-hydroxyecdysone injected into isolated abdomens obtained shortly after adult emergence had no discernible effect on vitellogenesis. In contrast, all abdomens which received 0.5 ng of topically applied JH I followed by the injection of 4.8 ng 20-hydroxyecdysone produced mature oocytes. Isolated abdomens were also capable of oocyte maturation when treated with excess amounts of JH alone; JH I was the most effective followed by JH II and then JH III.

Polyacrylamide gel electrophoretic analysis of vitellin extracted from the ovaries of hormonally-treated animals did not reveal any qualitative differences compared to intact normal controls. However, less yolk protein was present in the former. This was verified by counting the number and measuring the size of ovarian follicles in individual females.