Local cOinage and Hospital Equipment Index (Lo Hei): projectile distance of Singapore coinage and healthcare-related equipment in a 3T magnetic resonance imaging scanner

INTRODUCTION

Modern magnetic resonance imaging (MRI) scanners utilise superconducting magnets that are permanently active. Patients and healthcare professionals have been known to unintentionally introduce ferromagnetic objects into the scanning room. In this study, we evaluated the projectile risk of Singapore coinage as well as some common healthcare equipment within a 3 T MRI scanner.

METHODS

A rig termed 'Object eNtry Guidance and Linear Acceleration Instrument' (ONG LAI) was custom-built to facilitate safe trajectory of the putative ferromagnetic objects. A ballistic gel target was utilised as a human tissue surrogate to estimate tissue penetration. The point at which objects would self-propel towards the scanner was named 'Huge Unintended Acceleration Towards Actual Harm (HUAT AH)'.

RESULTS

Singapore third-series coins (10-cent to 1-dollar coins) are highly ferromagnetic and would accelerate towards the MRI scanner from more than one metre away. Cannulas with their needles are ferromagnetic and would self-propel towards the scanner from a distance of 20 cm. Standard surgical masks are ferromagnetic and may lose their sealing efficacy when they are worn too close to the magnet. Among the tested objects, a can of pineapple drink (Lee Pineapple Juice) had the highest HUAT AH at a distance of more than 1.5 m.

CONCLUSION

Some local coinage and commonly found objects within a healthcare setting demonstrate ferromagnetic activity with projectile potential from a distance of more than 1 m. Patients and healthcare professionals should be cognisant of the risk associated with introducing these objects into the MRI scanning room.

Revolutionizing the Management of Large-Core Ischaemic Strokes: Decoding the Success of Endovascular Therapy in the Recent Stroke Trials

Endovascular therapy (EVT) has revolutionized the management of acute ischaemic strokes with large vessel occlusion, with emerging evidence suggesting its benefit also in large infarct core volume strokes. In the last two years, four randomised controlled trials have been published on this topic-RESCUE-Japan LIMIT, ANGEL-ASPECT, SELECT2 and TENSION, with overall results showing that EVT improves functional and neurological outcomes compared to medical management alone. This review aims to summarise the recent evidence presented by these four trials and highlight some of the limitations in our current understanding of this topic.

Leveraging AI in Postgraduate Medical Education for Rapid Skill Acquisition in Ultrasound-Guided Procedural Techniques

Ultrasound-guided techniques are increasingly prevalent and represent a gold standard of care. Skills such as needle visualisation, optimising the target image and directing the needle require deliberate practice. However, training opportunities remain limited by patient case load and safety considerations. Hence, there is a genuine and urgent need for trainees to attain accelerated skill acquisition in a time- and cost-efficient manner that minimises risk to patients. We propose a two-step solution: First, we have created an agar phantom model that simulates human tissue and structures like vessels and nerve bundles. Moreover, we have adopted deep learning techniques to provide trainees with live visualisation of target structures and automate assessment of their user speed and accuracy. Key structures like the needle tip, needle body, target blood vessels, and nerve bundles, are delineated in colour on the processed image, providing an opportunity for real-time guidance of needle positioning and target structure penetration. Quantitative feedback on user speed (time taken for target penetration), accuracy (penetration of correct target), and efficacy in needle positioning (percentage of frames where the full needle is visualised in a longitudinal plane) are also assessable using our model. Our program was able to demonstrate a sensitivity of 99.31%, specificity of 69.23%, accuracy of 91.33%, precision of 89.94%, recall of 99.31%, and F1 score of 0.94 in automated image labelling.

Clinical Utility of 18Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (18F-FDG PET/CT) in Multivisceral Transplant Patients

Multivisceral transplant (MVTx) refers to a composite graft from a cadaveric donor, which often includes the liver, the pancreaticoduodenal complex, and small intestine transplanted en bloc. It remains rare and is performed in specialist centres. Post-transplant complications are reported at a higher rate in multivisceral transplants because of the high levels of immunosuppression used to prevent rejection of the highly immunogenic intestine. In this study, we analyzed the clinical utility of 28 ¹⁸F-FDG PET/CT scans in 20 multivisceral transplant recipients in whom previous non-functional imaging was deemed clinically inconclusive. The results were compared with histopathological and clinical follow-up data. In our study, the accuracy of ¹⁸F-FDG PET/CT was determined as 66.7%, where a final diagnosis was confirmed clinically or via pathology. Of the 28 scans, 24 scans (85.7%) directly affected patient management, of which 9 were related to starting of new treatments and 6 resulted in an ongoing treatment or planned surgery being stopped. This study demonstrates that ¹⁸F-FDG PET/CT is a promising technique in identifying life-threatening pathologies in this complex group of patients. It would appear that ¹⁸F-FDG PET/CT has a good level of accuracy, including for those MVTx patients suffering from infection, post-transplant lymphoproliferative disease, and malignancy.

What you need to know about: imaging in patients with renal failure

Contrast-enhanced medical imaging is commonly requested in clinical practice. Contrast media provide better differentiation of tissue enhancement, improves the soft tissue contrast resolution, and enhances the ability to study the physiology and function of the organs and/or systems. However, contrast media may cause complications, especially in patients with renal failure. This article discusses the use of contrast media in common imaging modalities and the relationship between contrast media and renal function. Administration of iodinated contrast media in computed tomography may cause contrast-associated acute kidney injury; the risk factors and preventive strategies for this are elaborated in this article. Administration of gadolinium-based contrast media in magnetic resonance imaging may lead to nephrogenic systemic fibrosis. Therefore, precautions should be taken when planning for medical imaging for patients with pre-existing acute kidney injury or end-stage chronic kidney disease, for whom contrast media administration in computed tomography or magnetic resonance imaging may be relatively contraindicated. Alternatively, ultrasound contrast agents can be safely used in patients with acute kidney injury or chronic kidney disease. Clinical teams should discuss these patients with radiologists, taking into account the risk-benefits of contrast media, to determine the optimal imaging protocol or modality to answer the clinical query.

Mindfulness-based therapy for smoking cessation and mental health: a randomised controlled trial

INTRODUCTION

Effective smoking cessation programmes are essential for assisting smokers in quitting, indirectly lowering mortality and morbidity associated with smoking. Numerous studies have indicated positive outcomes when using mindfulness treatment (MT) to treat psychological or behavioural health issues. Although to date, no study has looked at the effectiveness of online MT for quitting smoking while addressing mental health, particularly among the Asian population. Therefore, this study compares the efficiency of online MT to traditional counselling therapy (CT) in aiding smoking cessation programmes while also addressing mental health.

MATERIALS AND METHODS

A randomised control study with a two-group, single-blind design and baseline evaluation was selected. Social media sites were used to advertise for participants, who were then admitted after meeting the requirements. Participants who met the eligibility requirements were randomly split into two groups. Each group received a total of three sessions of online therapy (MT or CT), once every two weeks, as well as one phone call per week as reinforcement. At the beginning and end of the intervention, participants completed questionnaires (1st week and 5th week). Generalized Estimating Equation (GEE) statistical analysis was used to analyse all the variables.

RESULTS

The MT group experienced a statistically significant decrease in cigarette consumption (β: -3.50, 95% Wald CI: - 4.62, -2.39) compared to the CT group over time. Furthermore, the MT group demonstrated significant improvements in their scores for the AAQ-2, anxiety, stress, depression and mindfulness compared to the CT group.

CONCLUSION

Online MT is more successful at assisting smokers in lowering their daily cigarette intake and supporting their mental health during the smoking cessation process. Further longitudinal comparisons of the effectiveness of online MT should be undertaken using online platforms in future studies.

Combined balloon guide catheter, aspiration catheter, and stent retriever technique versus balloon guide catheter and stent retriever alone technique: a systematic review and meta-analysis

BACKGROUND

The use of a combination of balloon guide catheter (BGC), aspiration catheter, and stent retriever in acute ischemic stroke thrombectomy has not been shown to be better than a stent retriever and BGC alone, but this may be due to a lack of power in these studies. We therefore performed a meta-analysis on this subject.

METHODS

A systematic literature search was performed on PubMed, Scopus, Embase/Ovid, and the Cochrane Library from inception to October 20, 2021. Our primary outcomes were the rate of successful final reperfusion (Treatment in Cerebral Ischemia (TICI) 2c-3) and first pass effect (FPE, defined as TICI 2c-3 in a single pass). Secondary outcomes were 3 month functional independence (modified Rankin Scale score of 0-2), mortality, procedural complications, embolic complications, and symptomatic intracranial hemorrhage (SICH). A meta-analysis was performed using RevMan 5,4, and heterogeneity was assessed using the I² test.

RESULTS

Of 1629 studies identified, five articles with 2091 patients were included. For the primary outcomes, FPE (44.9% vs 45.4%, OR 1.04 (95% CI 0.90 to 1.22), I²=57%) or final successful reperfusion (64.5% vs 68.6%, OR 0.98 (95% CI 0.81% to 1.20%), I²=85%) was similar between the combination technique and stent retriever only groups. However, the combination technique had significantly less rescue treatment (18.8% vs 26.9%; OR 0.70 (95% CI 0.54 to 0.91), I²=0%). This did not translate into significant differences in secondary outcomes in functional outcomes, mortality, emboli, complications, or SICH.

CONCLUSION

There was no significant difference in successful reperfusion and FPE between the combined techniques and the stent retriever and BGC alone groups. Neither was there any difference in functional outcomes, complications, or mortality.

The Role of Interventional Radiology in the Diagnosis and Treatment of Pulmonary Arteriovenous Malformations

Pulmonary arteriovenous malformations (PAVMs) are uncommon, predominantly congenital direct fistulous connections between the pulmonary arteries and pulmonary veins, resulting in a right to left shunt. Patients with PAVMs are usually asymptomatic with lesions detected incidentally when radiological imaging is performed for other indications. In this review, we discuss the classification and radiological features of PAVMs as well as their treatment and follow-up options, with a particular focus on percutaneous endovascular techniques and the evolution of the available equipment for treatment.

SIroliMus coated angioPlasty versus plain balloon angioplasty in the tREatment of dialySis acceSs dysfunctION (IMPRESSION): study protocol for a randomized controlled trial

Background

Percutaneous transluminal angioplasty is the current standard treatment for arteriovenous fistula (AVF) stenosis. The mid- and long-term patency with plain balloon angioplasty (PBA) is however far from satisfactory. While paclitaxel-coated balloon angioplasty has been shown to be superior to PBA, concern over its safety profile has recently arisen after a reported possible increased mortality risk with a meta-analysis of large lower limb studies. An angioplasty balloon with a new type of drug coating, the sirolimus-coated balloon (SCB), has been proven to improve patency in the coronary arteries. However, its effect on AV access has yet to be studied.

Methods/design

This is an investigator-initiated, prospective, multicenter, double-blinded, randomized controlled clinical trial to assess the effectiveness of SCB compared to PBA in improving the patency of AVF after angioplasty. A total of 170 patients with mature AVF that requires PTA due to AVF dysfunction will be randomly assigned to treatment with a SCB or PBA at a 1:1 ratio, stratified by location of AVF and followed up for up to 1 year. The inclusion criteria include [1] adult patient aged 21 to 85 years who requires balloon angioplasty for dysfunctional arteriovenous fistula [2]; matured AVF, defined as being in use for at least 1 month prior to the angioplasty; and [3] successful angioplasty of the underlying stenosis with PBA, defined as less than 30% residual stenosis on digital subtraction angiography (DSA) and restoration of thrill in the AVF on clinical examination. The exclusion criteria include thrombosed or partially thrombosed access circuit at the time of treatment, presence of symptomatic or angiographically significant central vein stenosis that requires treatment with more than 30% residual stenosis post angioplasty, and existing stent placement within the AVF circuit. The primary endpoint of the study is access circuit primary patency at 6 months. The secondary endpoints are target lesion primary patency; access circuit-assisted primary patency; access circuit secondary patency at 3, 6, and 12 months; target lesion restenosis rate at 6 months; total number of interventions; complication rate; and cost-effectiveness. The trial is supported by Concept Medical.

Discussion

This study will evaluate the clinical efficacy and safety of SCB compared to PBA in the treatment of AVF stenosis in hemodialysis patients.

Trial registration

ClinicalTrials.govNCT04409912. Registered on 1 June 2020

The effectiveness of the Safety in Interventional Radiology (SIR) Shield in reducing droplet transmission and its effect on image quality and radiation dose

Objective:

To evaluate the efficacy of a barrier shield in reducing droplet transmission and its effect on image quality and radiation dose in an interventional suite.

Methods:

A human cough droplet visualisation model in a supine position was developed to assess efficacy of barrier shield in reducing environmental contamination. Its effect on image quality (resolution and contrast) was evaluated via image quality test phantom. Changes in the radiation dose to patient post-shield utilisation was measured.

Results:

Use of the shield prevented escape of visible fluorescent cough droplets from the containment area. No subjective change in line-pair resolution was observed. No significant difference in contrast-to-noise ratio was measured. Radiation dosage to patient was increased; this is predominantly attributed to the increased air gap and not the physical properties of the shield.

Conclusion:

Use of the barrier shield provided an effective added layer of personal protection in the interventional radiology theatre for aerosol generating procedures.

Advances in knowledge:

This is the first time a human supine cough droplet visualisation has been developed. While multiple types of barrier shields have been described, this is the first systematic practical evaluation of a barrier shield designed for use in the interventional radiology theatre.

SIR HELMET (Safety In Radiology HEalthcare Localised Metrological EnviromenT): a low-cost negative-pressure isolation barrier for shielding MRI frontline workers from COVID-19 exposure

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Low cost reusable acrylic and silicone rubber barrier shield design.

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Localised negative pressure environment simulating isolation rooms.

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Does not affect MRI image quality even on the most sensitive sequences.

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Additional personal protective equipment for frontline healthcare professionals.

Preparing IR for COVID-19: The Singapore Experience

This paper describes country-wide special measures undertaken for interventional radiology staff during the current coronavirus disease 2019 (COVID-19) pandemic. Although each interventional radiology service around the world faces unique challenges, the principles outlined in this article will be useful when designing or strengthening individual practices and integrating them within wider hospital and national measures. Moving beyond the current outbreak, these measures will be useful for any future infectious diseases which are likely to arise.

Eye preservation tectonic graft using glycerol-preserved donor cornea

AIMS

To report the surgical outcome of tectonic graft using glycerol-preserved donor corneas to treat perforated keratitis.

METHODS

The medical records were reviewed of all patients treated for perforated keratitis using glycerol-preserved corneas at a single institution between 1 July 2004 and 31 June 2010. The clinical features, precipitating factors, adjuvant therapies, and therapeutic outcomes were analyzed. Success was defined as re-epithelialization of the ocular surface without evisceration.

RESULTS

Fourteen eyes from 14 patients (6 male and 8 female) were included. Age ranged from 58 to 84 years (average, 70.71 ± 8.52 years) and the follow-up time ranged from 7 to 56 months (mean, 25.35 ± 16.84 months). The culture results showed five bacterial infections, five cases of fungal keratitis, and one mixed infection; the culture results were negative for three patients. Satisfactory anatomical integrity was obtained in eight grafts (57.14%) that healed with neovascularization. Six grafts (48.85%) showed delayed re-epithelialization and were repaired with conjunctival flaps to maintain ocular surface integrity. Three patients developed secondary glaucoma and received trans-scleral cyclophotocoagulation. Thirteen patients had satisfactory anatomical integrity without evisceration or exenteration, while one patient received evisceration at 39-month follow-up because of intractable glaucoma.

CONCLUSIONS

Glycerol-preserved donor corneas combined with anterior vitrectomy with or without conjunctival flaps may be effective substitutes for evisceration surgery in patients with perforated keratitis.

Nucleotide-binding oligomerization domain-1 and epidermal growth factor receptor: critical regulators of beta-defensins during Helicobacter pylori infection

Host-pathogen interactions that allow Helicobacter pylori to survive and persist in the stomach of susceptible individuals remain unclear. Human beta-defensins (hBDs), epithelial-derived antimicrobial peptides are critical components of host-defense at mucosal surfaces. The role of H. pylori-mediated NF-kappaB and epidermal growth factor receptor (EGFR) activation on beta-defensin expression was investigated. Transient transfection studies utilizing beta-defensin promoter constructs were conducted in gastric cells with contribution of individual signaling events evaluated by the addition of specific inhibitors, small interference nucleotide-binding oligomerization domain 1 (NOD1) RNA or plasmids encoding Vaccinia virus proteins that interrupt interleukin-1 and Toll-like receptor signaling. The role of individual MAPK pathways was further delineated in HEK-293 cells expressing conditional MAPK mutants. We found hBD2 expression exclusively dependent on the presence of the bacterial cag pathogenicity island, with NOD1 a critical host sensor. Impairment of murinebeta-defensin 4 (an orthologue of hBD2) expression in NOD1-deficient mice 7-days post-infection further confirmed the role of this cytoplasmic pattern-recognition receptor in eliciting host innate immunity. In contrast to hBD2, hBD3 expression was NOD1-independent but EGFR and ERK pathway-dependent. Importantly, Toll-like receptor signaling was not implicated in H. pylori-mediated hBD2 and hBD3 gene expression. The divergent signaling events governing hBD2 and hBD3 expression suggest temporal functional variation, such that hBD2 may contribute to antimicrobial barrier function during the inflammatory phase with hBD3 playing a greater role during the repair, wound healing phase of infection.

Identification of virus-specific vesicles in Giardiavirus-infected Giardia lamblia

Giardiavirus (GLV), which infects the parasitic protozoan Giardia lamblia, is a nonsegmented double-stranded (ds) ribonucleic acid (RNA) virus. We previously purified two distinct types of related GLV from infected G. lamblia, and showed differential export of one of the viruses from infected cells. In the present study, fractionation of cell lysate was performed, revealing the presence of viruses in the membranous fraction. Distribution of viral antigens in the infected cells was examined by immunocytochemistry. The signal was enriched in certain regions of the cytoplasm, suggesting that a portion of GLV is confined to certain cellular compartments. A significantly reduced signal was also detected in the nuclei. We directly observed the viruses in the infected cells by electron microscopy. Consistent with previous observations, virus-like particles were clearly observed in some membranous vesicles in the cytoplasm at 48 h postinfection, and virus-like particles were again seen in the cytoplasm and then in the nuclei toward the late phase of virus infection. The virus-associated vesicles and some electron-dense nuclear structures were only observed in virus-infected cells, suggesting that virus infection may induce ultrastructural alteration of G. lamblia.

Human babesiosis in Taiwan: asymptomatic infection with a Babesia microti-like organism in a Taiwanese woman

An asymptomatic Babesia infection was confirmed by laboratory diagnoses. The intraerythrocytic protozoan (designed TW1) isolated from a 51-year-old Taiwanese woman appeared to be morphologically consistent with small-form piroplasm, and measurements indicated that it had a body size of 1.5 to 2.5 microm in diameter. The typical features of ring, binary, and tetrad forms were observed in Giemsa-stained thin blood smears. A persistent and low-grade parasitemia was established after hamster inoculation. Indirect immunofluorescent-antibody reactivities indicate that this strain (TW1) of Babesia was serologically related to, but not identical to, the Babesia species (B. microti) that infects rodents. Antibody titers in the patient's sera combined with the clinical symptoms suggested that the present case was a chronic and subclinical babesial infection. A neighborhood human serologic survey indicated that the infection may have been acquired accidentally from an infected rodent and localized within the same family. Indeed, rodents from areas around the neighborhood were trapped, and a high prevalence (83%) of babesial infection was observed. The possible vector responsible for the transmission remains to be identified.

Use of the ProSpecT microplate enzyme immunoassay for the detection of pathogenic and non-pathogenic Entamoeba histolytica in faecal specimens

A commercial microplate enzyme immunoassay (ProSpecT EIA; Alexon Inc., Sunnyvale, CA 94089, USA) was compared with conventional microscopy for the diagnosis of Entamoeba histolytica infection. Using specimens known to be infected, the sensitivity of the ProSpecT EIA was 78% and its specificity was 99%. No cross reaction with other intestinal parasites was observed. The ProSpecT EIA and conventional microscopy (using merthiolate-iodine-formaldehyde direct wet mounts and concentration techniques) were then used to detect E. histolytica infections in 431 patients in a mental hospital in Taiwan. Using single stool specimens, microscopy detected infection in 10.9% of the patients, compared with 16.9% detected by ProSpecT EIA. The latter method was simple and quick, but more expensive, and could be used to complement microscopy if a prompt diagnosis is desired clinically. However, ProSpecT EIA cannot differentiate between pathogenic E. histolytica and non-pathogenic strains (= E. dispar), which limits its usefulness.

Separation and characterization of two related giardiaviruses in the parasitic protozoan Giardia lamblia

Giardiavirus encapsidates a 6.2-kb double-stranded (ds) RNA within a capsid that consists of a major 100-kDa capsid protein (p100) and a minor 190-kDa protein (p190). In this study, two nonhomologous 6.2-kb ds RNAs cohabiting in Giardia lamblia trophozoites were found to be separately encapsidated into two distinct virions, one (designated GLV[p100]) whose capsid consists of p100 and p190, and the other (designated GLV[p95]) whose capsid consists of a 95-kDa protein (p95) and a minor p190-equivalent protein. Both types of virions were enriched in the membranous fraction of a lysate from virus-infected G. lamblia cells. Separation of these virions was achieved by CsCl gradient centrifugation following osmotic rupture of the viral particles. By these treatments, the 6.2-kb ds RNA was removed from GLV[p100] whereas that in GLV[p95] remained unchanged, and the two 6.2-kb ds RNAs that had been purified by this protocol displayed differential hybridization properties to viral cDNA probes. Western blotting and peptide mapping experiments show that p100 and p95 were closely related proteins, but each had distinct amino acid sequences. Virus purification and pulse-chase experiments show that GLV[p100] was selectively secreted into the medium whereas GLV[p95] remained within the trophozoites of G. lamblia toward the late phase of cell growth. Secretion of GLV[p100] was not inhibited by Brefeldin A. These findings demonstrate the cohabitation of multiple Giardiavirus species in G. lamblia.

Identification of a satellite double-stranded RNA in the parasitic protozoan Trichomonas vaginalis infected with T. vaginalis virus T1

Co-infection by a 0.5-kb small double-stranded (ds) RNA together with Trichomonas vaginalis virus (TVV) genomic 4.6-kb dsRNA is commonly observed in a number of T. vaginalis isolates. By molecular cloning and primer extension experiments, the 497-bp cDNA sequence of a 0.5-kb dsRNA co-infecting with TVV-T1 in T vagina/is T1 isolate was elucidated. Consistent with the replication cycle of a typical dsRNA virus, a plus-strand viral RNA beginning at +1 of the 0.5-kb dsRNA was identified in infected T. vaginalis T1 cells by primer extension and Northern hybridization studies. The 0.5-kb dsRNA was separately encased in TVV capsids from the viral genomic dsRNA, as shown by protein analysis and electron microscopic examination of viral particles purified by multiple rounds of CsCl gradient centrifugation. The riboprobes transcribed from a cloned cDNA of the 0.5-kb dsRNA exhibited strong hybridization to a small dsRNA in a T vaginalis T9 isolate, which harbors a TVV-T9 distantly related to TVV-T1, but the same probes showed very little hybridization to the viral genomic dsRNA of both TVV-T1 and TVV-T9. Very little sequence homology between the 0.5-kb dsRNA and the 4.6-kb dsRNA in TVV-T1 was found by computer-assisted analysis, suggesting that the small dsRNA in T. vaginalis T1 is not derived from the genome of TVV-T1 or other distantly related T. vaginalis viruses. These results suggest that the small dsRNAs in T vaginalis are satellite RNAs of T. vaginalis virus.

Molecular cloning and characterization of a ras-related gene of ran/tc4/spi1 subfamily in Giardia lamblia

The significance of Ras-like proteins in the protozoa is relatively unexplored. In this report, a gene encoding a Ras-like nuclear (Ran) protein was identified in Giardia lamblia by a polymerase chain reaction-based cloning strategy. The sequence analyses suggest that the gene was intronless, and had short 5'-untranslated leader sequences in the corresponding mRNA up to -2, -4, or -29 bases upstream of the first initiation codon. The full-length cDNA sequence predicted a protein comprising 226 amino acids, in which the highly conserved functional motifs of the Ras superfamily were all preserved. This protein showed 52% identity to human TC4 and 50% identity to yeast Spi1 proteins, suggesting that it is closely related to the Ran proteins, and it was therefore designated gRan. gRan produced from recombinant Escherichia coli exhibited GTP binding activity by an overlay assay. In good agreement with the predicted size of gRan, a 27-kDa protein was identified in a lysate of G. lamblia by Western blotting using antiserum raised against recombinant gRan. The protein was further localized in both nuclei of G. lamblia by immunofluorescence staining. Recombinant gRan exhibited low affinity for GTP with a Kd value of 16.8 microM. The affinity was enhanced to a Kd value of 2.2 microM in the presence of 10 mM Mg2+. The intrinsic GTPase activity of gRan was observed only in the presence of 10 mM Mg2+ and had an estimated Km of 5.6 microM and a Kcat of 0.33/h. These observations demonstrate the presence of Ras-like proteins in the most primitive eukaryotic cells, G. lamblia, and infer that the Ran protein may play a functional role in the nuclei of this organism.

Giardiavirus enters Giardia lamblia WB trophozoite via endocytosis

As part of our continuing effort in the study of Giardiavirus life cycle, the early events of Giardia lamblia virus (GLV) infection in the trophozoites of G. lamblia WB strain were examined. Electron microscopy showed that GLV particles were initially localized on plasma membrane. As time progresses, GLV was translocated to the peripheral vacuole and then spread to the cytoplasm. Inhibitors of endocytosis such as sodium azide, chloroquine, or ammonium chloride disrupted viral infection when the drug was added simultaneously with the infecting GLV. The inhibitory effect was reduced when sodium azide or chloroquine was added at various intervals after infection. When cells infected for 1 hr were examined by immunofluorescence staining, sodium azide greatly reduced GLV staining signal in general while chloroquine restricted the staining signal to a few bright spots. Significantly more GLV was found in the peripheral vacuoles of chloroquine-treated cells than untreated controls by semiquantitative electron microscopy. In contrast, only a reduced amount of GLV was found in the peripheral vacuoles of sodium azide-treated cells. These results suggest that sodium azide reduces the internalization of infecting GLV, while chloroquine confines the virus in the peripheral vacuoles and, consequently, leads to nonproductive infection. We conclude from these observations that the entry of GLV into the susceptible WB cells in the event of infection is most likely mediated by endocytosis.

The course of giardiavirus infection in the Giardia lamblia trophozoites

The subcellular distribution of Giardia lamblia virus RNA in infected G. lamblia trophozoites was examined by in situ hybridization using biotinylated DNA probe and riboprobe. In G. lamblia Portland I strain, which is chronically infected by G. lamblia viruses, the viral RNA was detected in the cytoplasm as well as in the twin nuclei. When riboprobe was used to examine the course of virus infection in WB strain, accumulation of viral RNA was detected only in the cytoplasm prior to the first 72 hr of infection. Using DNA probe, further accumulation of viral RNA in increasing number of cells occurred after the 72nd hr of infection, with the RNA found in both the cytoplasm and nuclei. Eventually, the cell nuclei showed damaged morphology that deteriorated rapidly toward the final stage of infection. These observations indicate that early phase of viral RNA replication may take place in the cytoplasm of infected G. lamblia, but the nuclei are also involved during the late phase of viral replication.