New approaches to targeting RNA with oligonucleotides: inhibition of group I intron self-splicing

RNA is one class of relatively unexplored drug targets. Since RNAs play a myriad of essential roles, it is likely that new drugs can be developed that target RNA. There are several factors that make targeting RNA particularly attractive. First, the amount of information about the roles of RNA in essential biological processes is currently being expanded. Second, sequence information about targetable RNA is pouring out of genome sequencing efforts at unprecedented levels. Third, designing and screening potential oligonucleotide therapeutics to target RNA is relatively simple. The use of oligonucleotides in cell culture, however, presents several challenges such as oligonucleotide uptake and stability, and selective targeting of genes of interest. Here, we review investigations aimed at targeting RNA with oligonucleotides that can circumvent several of these potential problems. The hallmark of the strategies discussed is the use of short oligonucleotides, which may have the advantage of higher cellular uptake and improved binding selectivity compared to longer oligonucleotides. These strategies have been applied to Group I introns from the mammalian pathogens Pneumocystis carinii and Candida albicans. Both are examples of fungal infections that are increasing in number and prevalence.     

棉鼠丝虫组织化学的观察

迄今,棉鼠丝虫仍被认为是个筛选抗丝虫新药较为理想的虫种。凡对该虫有效的药物,临床上用以治疗其它丝虫病时,一般均能获得相似效果。但有关棉鼠丝虫生理及生化方面的知识,至今所知甚少。为此,我们对正常棉鼠丝虫体内组织化学进行了较为系统的观察,以期积累一些有助于了解该虫组织机能方面的资料,并为以后探讨药物的作用机制提供一些理论上的依据。     

In vitro attachment of Pneumocystis carinii from mouse and rat origin

Summary— The attachment of Pneumocystis carinii to lung cells could play a role in the pathophysiology of P carinii pneumonia. The trophozoite attaches to type I alveolar epithelial cells. Physical, chemical, and extracellular matrix factors, involved in the mouseor rat-derived P carinii attachment to fibroblastic cells in culture, were examined using a new model of in vitro adherence. The development of parasite filopodia penetrating deeply the host cell cytoplasm was observed using transmission electronic microscopy. Killed P carinii organisms were unable to attach to cultured cells. Also, parasites were unable to attach to killed target cells. The P carinii in vitro attachment was partially inhibited by cytochalasin B. In contrast, the parasite attachment was not affected when the target cell cytoskeleton was altered. In our work conditions, sialic acids were not involved in the attachment process. Present results showed that fibronectin (Fn) plays a role in the parasite attachment, and suggest that a specific Fn-binding receptor is present at the surface of mouse-derived P carinii organisms.     

Analysis of Pneumocystis carinii Cyst Wall. II. Sugar Composition

ABSTRACT. Pneumocystis carinii cysts are capable of resisting host defenses and antimicrobial drugs and are therefore thought to be responsible for relapses of P. carinii pneumonia in AIDS and other immunocompromised patients. The interaction of P. carinii with its host, and other P. carinii , might be mediated by molecules which form the outer surfaces of this organism. Carbohydrates are known to play many roles in cell-cell adhesion, and have been detected on the surface of P. carinii by lectin labeling experiments. In this study P. carinii cyst wall material was obtained from Zymolyase treatment. Alditol acetate derivatives of neutral and amino sugars or trimethylsilyl derivatives of methyl glycosides were prepared from the monosaccharides released from the sample by acid hydrolysis. Analyses were done by a combination of gas chromatography and mass spectrometry. Glucose was found to be the major sugar constituent. Mannose and galactose were present in equal ratios. A lesser amount of N-acetyl-D-glucosamine, and trace amounts of ribose and sialic acid were present in the cyst wall samples analyzed. These sugars may mediate P. carinii -host interaction and play an important protective role by creating a permeability barrier around the cyst.