Induction of Antibiotic Resistance in Paramecium tetraurelia by the Bacterial Gene APH-3'-II

We have generated a transformation marker for Paramecium using a Paramecium expression vector (pPXV) and the open reading frame (ORF) of the bacterial antibiotic resistance gene aminoglycoside 3'-phosphotransferase-II (APH-3'-II or neo^r) from the transposon Tn5. The expression vector contained a small multiple cloning site between the 5' and 3' non-coding regions of the calmodulin gene, and Tetrahymena telomere sequences for the stability of the plasmid in Paramecium. After the neo^r ORF was inserted, the plasmid was referred to as pPXV-NEO. Delivery of approximately 10–20 picoliters of linearized PXV-NEO at > 2000 copies/pl into the macronucleus effected 100% transformation. Southern and Northern blot hybridization showed the presence of neo^r-specific DNA and RNA, respectively, in all of the transformed clones but not in the untransformed clones. The degree of resistance to G-418, and the concentrations of neo^r-specific DNA and neo^r-specific RNA in the clones were proportional to the concentration of the vector injected. We have demonstrated that when the linearized plasmid was injected into the macronucleus, the prokaryotic sequence conferred an antibiotic resistance to Paramecium despite codon-usage differences.     

使用非侵入的神经影像方法解码人类思维

随着神经影像技术的发展,“读脑机器”在不久的将来可能会变成现实。在众多实现“读脑机器”的技术中,使用基于血氧水平依赖的脑功能磁共振技术的神经解码方法则是非常有希望的一种技术。在本报告中,我们结合我们实验室最近开展的两个研究工作,说明了使用功能磁共振技术进行神经解码的一般方法及其应用。本领域的发展很快,所有的这些工作让我们对发明“读脑机器”充满了期待。但是,与此同时,我们也应该看到目前还存在着很多技术的局限和挑战。本报告的最后,我们也对这些局限和挑战进行了一些讨论。     

The Application of Autoradiography to Developmental Studies in the Hydrozoa

The uptake of isotopically labelled nucleotides and amino acidshas been studied in five species of hydrozoans. In three speciesthe label was introduced both through immersion in a mediumcontaining the labeled compound and by injecting the labeledcompound into the gastrovascular cavity. In the remaining twospecies the label was introduced by immersion only. The comparisonof soaked and injected specimens clearly indicates that injectionis the method of choice whenever the injection of compoundsinto the gastrovascular cavity is possible. The relative easewith which labeled compounds were absorbed can be correlatedwith the ultrastructure of the epidermal and gastrodermal cellsurfaces and their associated extracellular coats. The use ofthese autoradiographic techniques is illustrated by the useof injected tritiated thymidine and tritiated uiidine to followthe replacement cycle of the zymogenic secretory cell in Hydra,and the use of immersion to introduce tritiated thymidine intothe planula larva of Pennaria.     

The Life Cycle of Cryptosporidium baileyi n. sp. (Apicomplexa, Cryptosporidiidae) Infecting Chickens

ABSTRACT. The life cycle and morphology of a previously undescribed species of Cryptosporidium isolated from commercial broiler chickens is described. The prepatent period for Cryptosporidium baileyi n. sp. was three days post oral inoculation (PI) of oocysts, and the patent period was days 4–24 PI for chickens inoculated at two days of age and days 4–14 for chickens inoculated at one and six months of age. During the first three days PI, most developmental stages of C. baileyi were found in the microvillous region of enterocytes of the ileum and large intestine. By day 4 PI, most parasites occurred in enterocytes of the cloaca and bursa of Fabricius (BF). Mature Type I meronts with eight merozoites first appeared 12 h PI and measured 5.0 × 4.9 μm. Mature Type II meronts with four merozoites and a large granular residuum first appeared 48 h PI and measured 5.1 × 5.1 μm. Type I meronts with eight short merozoites and a large homogeneous residuum first appeared 72 h PI and measured 5.2 × 5.1 μm. Microgamonts (4.0 × 4.0 μm) produced 16 micro-gametes that penetrated into macrogametes (4.7 × 4.7 μm). Macrogametes gave rise to two types of oocysts that sporulated within the host cells. Most were thick-walled oocysts (6.3 × 5.2 μm), the resistant forms that passed unaltered in the feces. Some were thin-walled oocysts whose wall (membrane) readily ruptured upon release from the host cell. Sporozoites from thin-walled oocysts were observed penetrating enterocytes in mucosal smears. The presence of thin-walled, autoinfective oocysts and the recycling of Type I meronts may explain why chickens develop heavy intestinal infections lasting up to 21 days. Oocysts of C. baileyi were inoculated orally into several animals to determine its host specificity. Cryptosporidium baileyi did not produce infections in suckling mice and goats or in two-dayold or two-week-old quail. One of six 10-day-old turkeys had small numbers of asexual stages only in the BF. Four of six one-day-old turkeys developed mild infections only in the BF, and sexual stages of the parasite were observed in only one of the four. All seven one-day-old ducks and seven two-day-old geese developed heavy infections only in the BF with all known developmental stages present.     

An analysis of anemotactic flight in female moths stimulated by host odour and comparison with the males' response to sex pheromone

ABSTRACT. The flight pattern of mated female navel orangeworm moths, Amyelois transitella (Walker), responding to odour from potential larval hosts is zigzagging upwind flight. However, at times these moths are capable of flying nearly directly upwind towards the odour source (track angles near 0). This response indicates that these females are capable of very accurate anemotactic control of their heading or course angle, since small angular errors in this measure would translate into larger deviations from direct upwind flight. Males of this species exhibit flight patterns similar to those of females, including track angles clustered about 0 when flying upwind to a source of the female-produced pheromone, but under these experimental conditions they flew with a higher average airspeed than the females. When females lose contact with an odour plume they initiate a well-defined programme of cross-wind counterturning or casting, which may normally increase their chances of retrieving contact with that plume when the wind direction shifts. The resultant track angles of females increase significantly by 0.8 s after plume loss, indicating that the female has initiated changes in both her course angle and airspeed. By 1 s after plume loss the females' track angles are no longer unimodally distributed about 0, but are bimodally distributed about -90 and +90. Males responded more rapidly to the loss of a pheromone plume, demonstrating a significant change in track angle 0.4 s after plume loss. Overall, female and male A.transitella exhibited remarkably similar anemotactic flight manoeuvres during upwind flight to odour sources as well as after plume loss.