Outpatient ENT surgery in an academic center: one and a half year's experience

OBJECTIVE/PROBLEM: Evaluation of the early phase of an ENT outpatient surgery programme.

STUDY DESIGN

Between May 1995 and December 1996, 452 ENT outpatient operations were carried out on 416 patients. In order to determine the patients' satisfaction as well as the types and frequency of complications associated with ambulatory procedures, an 18 item multiple choice questionnaire was sent to all patients.

RESULTS

Replies were received from almost 80% of the patients. The great majority of patients were satisfied with their operation and would recommend it to friends and relatives. Ten percent of the patients had to be hospitalised for longer than originally expected. The reasons for these prolonged stays are described.

CONCLUSIONS

Our results show that procedures performed on an outpatient basis do not differ from similar in patient procedures with regard to the types and frequency of complications. Medical expenses are reduced from 200-400% depending on the type of operation. In the present climate of tighter economic controls, the feasibility of lowering medical costs substantially without compromising patient care deserves our utmost attention.

Genome engineering of Toxoplasma gondii using the site-specific recombinase Cre

Site-specific DNA recombinases from bacteriophage and yeasts have been developed as novel tools for genome engineering both in prokaryotes and eukaryotes. The 38kDa Cre protein efficiently produces both inter- and intramolecular recombination between specific 34bp sites called loxP. We report here the in vivo use of Cre recombinase to manipulate the genome of the protozoan parasite Toxoplasma gondii. Cre catalyzes the precise removal of transgenes from T. gondii genome when flanked by two directly repeated loxP sites. The efficiency of excision has been determined using LacZ as reporter and indicates that it can easily be applied to the removal of undesired sequences such as selectable marker genes and to the determination of gene essentiality. We have also shown that the reversibility of the recombination reaction catalyzed by Cre offers the possibility to target site-specific integration of a loxP-containing vector in a chromosomally placed loxP target in the parasite. In mammalian systems, the Cre recombinase can be regulated by hormone and is used for inducible gene targeting. In T. gondii, fusions between Cre recombinase and the hormone-binding domain of steroids are constitutively active, hampering the utilization of this mode of post-translational regulation as inducible gene expression system.

Transformed Toxoplasma gondii tachyzoites expressing the circumsporozoite protein of Plasmodium knowlesi elicit a specific immune response in rhesus monkeys

Toxoplasma gondii tachyzoites were transformed with the coding sequence of the circumsporozoite (CS) protein of the primate malaria parasite Plasmodium knowlesi. A single inoculation of live transformed tachyzoites elicited an antibody response directed against the immunodominant repeat epitope (EQPAAGAGG)2 of the P. knowlesi CS protein in rhesus monkeys. Notably, these animals failed to show a positive serum conversion against T. gondii. Antibodies against Toxoplasma antigens were detected only after a second inoculation with a higher number of transformed tachyzoites. This boost induced an increased antibody response against the P. knowlesi CS protein associated with immunoglobulin class switching, thus demonstrating the establishment of immunological memory. These results indicate that the Toxoplasma-derived CS protein is efficiently recognized by the monkey immune system and represents an immunodominant antigen in transformed parasites.

Processing of Toxoplasma ROP1 protein in nascent rhoptries

Secretion in the obligate intracellular parasite, Toxoplasma gondii, occurs through a number of regulated compartments. Among these are the apical organelles known as rhoptries which release their contents as part of the invasion process. We are interested in the processing, targeting and ultimate function of rhoptry proteins (and have focused our analyses on rhoptry protein 1 (ROP1). In this paper, we address the issue of processing: using a number of engineered forms of the ROP1 gene (introduced into a ROP1- background), we show that ROP1 is synthesized as a pre-pro-protein that is subject to proteolytic cleavages to remove the pre-sequence and the 'pro' region, at the N-terminus. Using brefeldin A (BFA) and reduced temperature we show that this processing occurs late in the secretory pathway of the parasite. Immunolocalization studies with epitope-tagged constructs indicate that processing is apparently occurring in the nascent rhoptries of dividing parasites. The results are discussed in the context of the targeting and possible function of the ROP1 protein.

Expression, selection, and organellar targeting of the green fluorescent protein in Toxoplasma gondii

We have engineered a mutant version of the green fluorescent protein GFP (Cormack et al. Selected for bright fluorescence in E. coli. Gene 1996;173:33-38) for expression in the protozoan parasite Toxoplasma gondii. Although intact GFP was not expressed at any detectable level, GFP fusion proteins could be detected by fluorescence microscopy, flow cytometry (FACS), and immunoblotting. Both extracellular tachyzoites and T. gondii-infected host cells could readily be sorted by FACS, which should facilitate a variety of selection strategies. Several selectable markers were tested for their ability to produce stable green transgenic parasites. Fluorescence intensity was directly correlated with gene copy number and protein expression level. Weak selectable markers such as chloramphenicol acetyl transferase (CAT) driven by the SAG1 promoter, which yield multicopy insertions, are therefore most effective for selecting green fluorescent parasites-particularly when coupled to constructs which employ a strong promoter to drive GFP expression. Transformation vectors developed in the course of this work should be of general utility for the overexpression of heterologous transgenes in Toxoplasma. CAT-GFP fusion proteins were expressed in the parasite cytoplasm. GFP fusions to the P30 major surface antigen (linked on the same plasmid to a CAT selectable marker under control of various promoters) could be detected in dense granules within living cells, and were efficiently secreted into the parasitophorous vacuole. GFP fusions to the rhoptry protein ROP1 were targeted to rhoptries (specialized secretory organelles at the apical end of the parasite).

[Endonasal sequelae after hypophysectomy]

Each year, 15 transvestibular transseptal transsphenoidal hypophysectomies are performed in Lausanne. The aim of the study was to determine the complications rate of our procedure and their influence on the life quality of patients. Questionnaires were sent to 178 patients, operated between 1984 and 1995. 125 questionnaires were returned. Out of those, 73 patients accepted to undergo a control rhinoscopy. The most frequent complains were nasal obstruction and crusting (38% each), whistling while breathing through the nose (12%), and stuffiness of the upper lip or teeth (7%). Endoscopically, we detected an anterior septal perforation in 10 cases (13.7%), 8 (80%) of which were symptomatic and a posterior septal perforation in 6 cases, all of them being asymptomatic. Finally, 36% of the patients had no complains and 19% of them had an improvement of respiration after the operation. Of the whole series of 178 patients, only 5% had complications requiring an ENT follow-up for longer than 6 months after having been operated.

In control of its fate: gene regulation in Toxoplasma gondii

The intracellular protozoan parasite Toxoplasma gondii is an important opportunistic pathogen in animals and man. In parallel to its clinical significance, T. gondii is also receiving considerable attention as an attractive model organism for intracellular parasitism. Regulation of gene expression at various levels underlies the intricate interplay between the parasite and its host cell, as well as the interconversions between different life-stages. In this article we will discuss some of what is currently known about gene organization and gene regulation in T. gondii as well as some of the tools available to dissect the parasite at a molecular level.

Molecular genetic strategies in Toxoplasma gondii: close in on a successful invader

Toxoplasma gondii is an obligate intracellular parasite with an exceptional ability to invade, survive and replicate within nearly all nucleated cells. Upon differentiation into an encysted form (bradyzoites), the parasites escape the host immune defenses and thus persist long enough in man and other hosts to ensure maintenance of transmission. This protozoan parasite has long been known to cause severe congenital infections in humans and animals but has recently gained additional notoriety as an opportunistic pathogen associated with AIDS. Development of a DNA transfection system for T. gondii has provided a new tool for exploring molecular aspects of important processes such as invasion and differentiation. Additional strategies associated with genetic transformation have been devised and elaboration of even more desirable molecular tools is in progress.

Medial fractures of the femoral neck in the elderly treated by SEM bipolar prosthesis

The authors present 335 cases of medical fracture of the femoral neck in the elderly patient (mean age 80.5 years) treated by SEM type bipolar prosthesis. A total of 93 patients (28.3%) were followed-up for a total of 98 hips submitted to surgery (5 bilateral) after a mean period of 42 months, minimum 12 months, maximum 96. Clinical follow-up included these parameters: pain, movement, walking, according to Merle D'Aubigné. Radiographic follow-up consisted in standard views and maximum adduction and abduction. Pain was present in 49% of cases, although it did not significantly invalidate movement (quotients 6 and 5 in 96% of cases); in 60% of the cases there were problems with walking mostly due to the general conditions of the patient. Wear phenomena in the acetabulum were present in 32 hips (32.6%) with no correlation with clinical data. Dynamic x-rays showed that only 31% of the implants maintained intraprosthetic movement. What emerges from the study is the importance of adequate measurement of the prosthetic cupola to improve acetabular fit.

Restriction enzyme-mediated integration elevates transformation frequency and enables co-transfection of Toxoplasma gondii

This report describes the use of restriction enzyme-mediated integration (REMI) to increase the transformation frequency and allow co-transfection of several unselected constructs under the selection of a single selectable marker. We found that while BamHI (the enzyme used to originally demonstrate REMI (Schiestl, R.H. and Petes, T.D. (1991) Integration of DNA fragments by illegitimate recombination in Saccharomyces cerevisiae. Proc. Nati. Acad. Sci. USA 88, 7585-7589) increased the number of transformants by 2-5-fold over the control without added enzyme, NotI proved to be a further 29-46-times more effective in enhancing stable transformation. This simple technique was used in the transformation of three non-selective markers (two modified membrane proteins and beta-galactosidase) with a selectable construct expressing chloramphenicol acetyltransferase. Following chloramphenicol selection, four out of ten independent transformants stably acquired all four constructs with at least two expressing all four genes at the protein level. These results demonstrate that REMI may be used in the efficient stable transformation and co-transfection of this and perhaps other protozoan parasites.

Complementation of a Toxoplasma gondii ROP1 knock-out mutant using phleomycin selection

The ROP1 gene of Toxoplasma gondii encodes a rhoptry protein that has been implicated in host cell invasion by this obligate intracellular protozoan. To further explore the function of this protein, we created a ROP1 deletion mutant by transfection with a plasmid encoding the bacterial chloramphenicol acetyltransferase (cat) gene flanked by ROP1 genomic sequences. Selection for chloramphenicol resistance yielded the desired ROP1-deleted or 'knock-out' mutant. Analysis of this mutant both in vitro and in vivo shows no significant alterations in growth rate, host specificity, invasiveness or virulence and thus the ROP1 gene is not obligatory for the RH strain, at least under the conditions tested. However, electron microscopy reveals that the mutant strain's rhoptries are altered in ultrastructure; they are thinner and homogeneously electron-dense compared with the thicker and normally mottled or honeycombed appearance of wild-type rhoptries. The knock-out mutant was rescued using co-transfection of a cosmid carrying the ROP1 gene together with a plasmid encoding a new selectable marker for T. gondii, the bleomycin resistance gene (ble) from Streptoalloteichus. Southern blot analysis showed that both DNAs were stably integrated into the Toxoplasma genome, although not into the ROPI locus. The resulting strain showed wild-type levels of ROP1 expression and rescue of the ultrastructural phenotype (i.e., the rhoptries returned to their normal, mottled appearance), thus establishing a cause/effect relationship between the absence of ROP1 and the electron-opacity. These results demonstrate the utility of the reverse genetic approach in the study of Toxoplasma gene function and provide a further selectable marker for such manipulations.

A selector of transcription initiation in the protozoan parasite Toxoplasma gondii

The recent development of an efficient transfection system for the apicomplexan Toxoplasma gondii allows a comprehensive dissection of the elements involved in gene transcription in this obligate intracellular parasite. We demonstrate here that for the SAG1 gene, a stretch of six repeated sequences in the region 35 to 190 bp upstream of the first of two transcription start sites is essential for efficient and accurate transcription initiation. This repeat element shows characteristics of a selector in determining the position of the transcription start sites.

Gene replacement in Toxoplasma gondii with chloramphenicol acetyltransferase as selectable marker

A system for stable transformation of Toxoplasma gondii tachyzoites was developed that exploited the susceptibility of Toxoplasma to chloramphenicol. Introduction of the chloramphenicol acetyltransferase (CAT) gene fused to Toxoplasma flanking sequences followed by chloramphenicol selection resulted in parasites stably expressing CAT. A construct incorporating the tandemly repeated gene, B1, targeted efficiently to its homologous chromosomal locus. Knockout of the single-copy gene, ROP1, was also successful. Stable transformation should permit the identification and analysis of Toxoplasma genes important in the interaction of this opportunistic parasite with its host.

Transient transfection and expression in the obligate intracellular parasite Toxoplasma gondii

Toxoplasma gondii is a protozoan pathogen that produces severe disease in humans and animals. This obligate intracellular parasite provides an excellent model for the study of how such pathogens are able to invade, survive, and replicate intracellularly. DNA encoding chloramphenicol acetyltransferase was introduced into T. gondii and transiently expressed with the use of three vectors based on different Toxoplasma genes. The ability to introduce genes and have them efficiently and faithfully expressed is an essential tool for understanding the structure-function relation of genes and their products.

Variable effects of the conserved RNA hairpin element upon 3' end processing of histone pre-mRNA in vitro

We have studied the requirements for efficient histone-specific RNA 3' processing in nuclear extract from mammalian tissue culture cells. Processing is strongly impaired by mutations in the pre-mRNA spacer element that reduce the base-pairing potential with U7 RNA. Moreover, by exchanging the hairpin and spacer elements of two differently processed H4 genes, we find that this difference is exclusively due to the spacer element. Finally, processing is inhibited by the addition of competitor RNAs, if these contain a wild-type spacer sequence, but not if their spacer element is mutated. Conversely, the importance of the hairpin for histone RNA 3' processing is highly variable: A hairpin mutant of the H4-12 gene is processed with almost wild-type efficiency in extract from K21 mouse mastocytoma cells but is strongly affected in HeLa cell extract, whereas an identical hairpin mutant of the H4-1 gene is affected in both extracts. The hairpin defect of H4-12-specific RNA in HeLa cells can be overcome by a compensatory mutation that increases the base complementarity to U7 snRNA. Very similar results were also obtained in RNA competition experiments: processing of H4-12-specific RNA can be competed by RNA carrying a wild-type hairpin element in extract from HeLa, but not K21 cells, whereas processing of H4-1-specific RNA can be competed in both extracts. With two additional histone genes we obtained results that were in one case intermediate and in the other similar to those obtained with H4-1. These results suggest that hairpin binding factor(s) can cooperatively support the ability of U7 snRNPs to form an active processing complex, but is(are) not directly involved in the processing mechanism.

Biochemical demonstration of complex formation of histone pre-mRNA with U7 small nuclear ribonucleoprotein and hairpin binding factors

Histone RNA 3' end formation occurs through a specific cleavage reaction that requires, among other things, base-pairing interactions between a conserved spacer element in the pre-mRNA and the minor U7 snRNA present as U7 snRNP. An oligonucleotide complementary to the first 16 nucleotides of U7 RNA can be used to characterize U7 snRNPs from nuclear extracts by native gel electrophoresis. Using similar native gel techniques, we present direct biochemical evidence for a stable association between histone pre-mRNA and U7 snRNPs. Other complexes formed in the nuclear extract are dependent on the 5' cap structure and on the conserved hairpin element of histone pre-mRNA, respectively. However, in contrast to the U7-specific complex, their formation is not required for processing. Comparison of several authentic and mutant histone pre-mRNAs with different spacer sequences demonstrates that the formation and stability of the U7-specific complex closely follows the predicted stability of the potential RNA-RNA hybrid. However, this does not exclude a stabilization of the complex by U7 snRNP structural proteins.

Two-step affinity purification of U7 small nuclear ribonucleoprotein particles using complementary biotinylated 2'-O-methyl oligoribonucleotides

U7 snRNP is a low-abundance small nuclear ribonucleoprotein particle essential for 3' processing of replication-dependent histone pre-mRNA. We have developed a two-step purification of the particle from TB21 mouse mastocytoma cell nuclear extracts, with about a 20% overall yield, using affinity binding to 2'-O-methyl oligoribonucleotides. The purified particle is homogeneous with respect to RNA content. SDS/PAGE of the U7 snRNP proteins revealed a full complement of the standard core proteins (B, DD', E, F, and G) found in the majority of snRNPs. In addition, two U7-specific polypeptides of 14 kDa and 50 kDa were identified. Summation of the molecular masses of the identified components of the U7 particle yields a particle mass of 249 kDa, in approximate agreement with estimates from sucrose gradient sedimentation (261 kDa) and nondenaturing gradient PAGE (217 kDa).

Isolation of an active gene and of two pseudogenes for mouse U7 small nuclear RNA

Three U7 RNA-related sequences were isolated from mouse genomic DNA libraries. Only one of the sequences completely matches the published mouse U7 RNA sequence, whereas the other two apparently represent pseudogenes. The matching sequence represents a functional gene, as it is expressed after microinjection into Xenopus laevis oocytes. Sequence variations of the conserved cis-acting 5' and 3' elements of U RNA genes may partly explain the low abundance of U7 RNA.

Structures of four human pseudogenes for U7 small nuclear RNA

Four U7 RNA-related sequences were isolated from a human genomic DNA library. None of the sequences completely match the published human U7 RNA sequence and all of them contain features typical of reverse-transcribed pseudogenes.

Structural and functional characterization of mouse U7 small nuclear RNA active in 3' processing of histone pre-mRNA

Oligonucleotides derived from the spacer element of the histone RNA 3' processing signal were used to characterize mouse U7 small nuclear RNA (snRNA), i.e., the snRNA component active in 3' processing of histone pre-mRNA. Under RNase H conditions, such oligonucleotides inhibited the processing reaction, indicating the formation of a DNA-RNA hybrid with a functional ribonucleoprotein component. Moreover, these oligonucleotides hybridized to a single nuclear RNA species of approximately 65 nucleotides. The sequence of this RNA was determined by primer extension experiments and was found to bear several structural similarities with sea urchin U7 snRNA. The comparison of mouse and sea urchin U7 snRNA structures yields some further insight into the mechanism of histone RNA 3' processing.