Supercomputer-Based Ensemble Docking Drug Discovery Pipeline with Application to Covid-19

We present a supercomputer-driven pipeline for in silico drug discovery using enhanced sampling molecular dynamics (MD) and ensemble docking. Ensemble docking makes use of MD results by docking compound databases into representative protein binding-site conformations, thus taking into account the dynamic properties of the binding sites. We also describe preliminary results obtained for 24 systems involving eight proteins of the proteome of SARS-CoV-2. The MD involves temperature replica exchange enhanced sampling, making use of massively parallel supercomputing to quickly sample the configurational space of protein drug targets. Using the Summit supercomputer at the Oak Ridge National Laboratory, more than 1 ms of enhanced sampling MD can be generated per day. We have ensemble docked repurposing databases to 10 configurations of each of the 24 SARS-CoV-2 systems using AutoDock Vina. Comparison to experiment demonstrates remarkably high hit rates for the top scoring tranches of compounds identified by our ensemble approach. We also demonstrate that, using Autodock-GPU on Summit, it is possible to perform exhaustive docking of one billion compounds in under 24 h. Finally, we discuss preliminary results and planned improvements to the pipeline, including the use of quantum mechanical (QM), machine learning, and artificial intelligence (AI) methods to cluster MD trajectories and rescore docking poses.

Early identification of COVID-19 cytokine storm and treatment with anakinra or tocilizumab

OBJECTIVE

To examine outcomes among patients who were treated with the targeted anti-cytokine agents, anakinra or tocilizumab, for COVID-19 -related cytokine storm (COVID19-CS).

METHODS

We conducted a retrospective cohort study of all SARS-coV2-RNA-positive patients treated with tocilizumab or anakinra in Kaiser Permanente Southern California. Local experts developed and implemented criteria to define COVID19-CS. All variables were extracted from electronic health records.

RESULTS

At tocilizumab initiation (n = 52), 50 (96.2%) were intubated, and only seven (13.5%) received concomitant corticosteroids. At anakinra initiation (n = 41), 23 (56.1%) were intubated, and all received concomitant corticosteroids. Fewer anakinra-treated patients died (n = 9, 22%) and more were extubated/never intubated (n = 26, 63.4%) compared to tocilizumab-treated patients (n = 24, 46.2% dead, n = 22, 42.3% extubated/never intubated). Patients who died had more severe sepsis and respiratory failure and met COVID-CS laboratory criteria longer (median = 3 days) compared to those extubated/never intubated (median = 1 day). After accounting for differences in disease severity at treatment initiation, this apparent superiority of anakinra over tocilizumab was no longer statistically significant (propensity score-adjusted hazards ratio 0.46, 95% confidence interval 0.18-1.20).

CONCLUSIONS

Prompt identification and treatment of COVID19-CS before intubation may be more important than the specific type of anti-inflammatory treatment. Randomized controlled trials of targeted anti-cytokine treatments and corticosteroids should report the duration of cytokine storm in addition to clinical severity at randomization.

Supercomputer-Based Ensemble Docking Drug Discovery Pipeline with Application to Covid-19

We present a supercomputer-driven pipeline for in-silico drug discovery using enhanced sampling molecular dynamics (MD) and ensemble docking. We also describe preliminary results obtained for 23 systems involving eight protein targets of the proteome of SARS CoV-2. THe MD performed is temperature replica-exchange enhanced sampling, making use of the massively parallel supercomputing on the SUMMIT supercomputer at Oak Ridge National Laboratory, with which more than 1ms of enhanced sampling MD can be generated per day. We have ensemble docked repurposing databases to ten configurations of each of the 23 SARS CoV-2 systems using AutoDock Vina. We also demonstrate that using Autodock-GPU on SUMMIT, it is possible to perform exhaustive docking of one billion compounds in under 24 hours. Finally, we discuss preliminary results and planned improvements to the pipeline, including the use of quantum mechanical (QM), machine learning, and AI methods to cluster MD trajectories and rescore docking poses.

Nano zinc oxide - An alternate zinc supplement for livestock

AIM

This study was aimed to investigate antimicrobial and cytotoxicity effect of nano ZnO in in vitro for the application of livestock feed supplement.

MATERIALS AND METHODS

Nano ZnO was synthesized by wet chemical precipitation method using zinc acetate as a precursor and sodium hydroxide was used for reducing the precursor salt. The properties of synthesized powder were characterized using ultraviolet (UV)-visible spectroscopy, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD), respectively. In vitro antimicrobial activities were analyzed against the pathogenic bacteria in poultry Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Streptococcus aeruginosa. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was conducted to analyze the cytotoxicity effect of nano ZnO.

RESULTS

SEM showed a spherical ZnO particle in the range of 70-100 nm. The size of the particle and purity of the sample were confirmed by XRD. The nano-sized ZnO particles exhibited the UV absorption peak at 335 nm. In FTIR spectroscopy, pure ZnO nanoparticles showed stretching vibrations at 4000-5000 cm-1. ZnO nanoparticles exhibited remarkable antibacterial activity against E. coli, S. aureus, K. pneumoniae, and S. aeruginosa bacterial strains. Cell viability was significantly reduced in a dose-dependent manner in the cytotoxicity study.

CONCLUSION

From the broad-spectrum antibacterial activity and the lower cytotoxicity observed at the prescribed dose, it is concluded that nano ZnO powder is a potential alternate zinc supplement for livestock.

A protective Langerhans cell-keratinocyte axis that is dysfunctional in photosensitivity

Photosensitivity, or skin sensitivity to ultraviolet radiation (UVR), is a feature of lupus erythematosus and other autoimmune and dermatologic conditions, but the mechanistic underpinnings are poorly understood. We identify a Langerhans cell (LC)-keratinocyte axis that limits UVR-induced keratinocyte apoptosis and skin injury via keratinocyte epidermal growth factor receptor (EGFR) stimulation. We show that the absence of LCs in Langerin-diphtheria toxin subunit A (DTA) mice leads to photosensitivity and that, in vitro, mouse and human LCs can directly protect keratinocytes from UVR-induced apoptosis. LCs express EGFR ligands and a disintegrin and metalloprotease 17 (ADAM17), the metalloprotease that activates EGFR ligands. Deletion of ADAM17 from LCs leads to photosensitivity, and UVR induces LC ADAM17 activation and generation of soluble active EGFR ligands, suggesting that LCs protect by providing activated EGFR ligands to keratinocytes. Photosensitive systemic lupus erythematosus (SLE) models and human SLE skin show reduced epidermal EGFR phosphorylation and LC defects, and a topical EGFR ligand reduces photosensitivity. Together, our data establish a direct tissue-protective function for LCs, reveal a mechanistic basis for photosensitivity, and suggest EGFR stimulation as a treatment for photosensitivity in lupus erythematosus and potentially other autoimmune and dermatologic conditions.

Effectiveness of “OralDETECT”- A Spaced Repetitive Learning Method - As a Competency Assessment Tool for Early Detection of Oral Cancer

Background: Head and neck cancer is the sixth most common cancer worldwide. It is generally acknowledged that the early diagnosis of oral cancer may result in higher 5-year survival rates, less need for aggressive treatment and improved quality-of-life. There is therefore a need for a quantifiable, reliable and competency-based educational tool which can be used to train dentists and other health care providers in the early detection of oral cancers. Aim: To assess the effectiveness of “OralDETECT” spaced repetitive learning method for training dental professionals to become competent in the early detection of oral cancer. Methods: The current study involved training three dental professional groups: Oral Pathology/Oral Medicine/Oral Surgery specialists (x), Periodontists/Restorative dentists (y), General Dental Practitioners (z) and four undergraduate cohorts comprising 259 dental students from 3 different Malaysian dental schools. A structured one-day training program “OralDETECT” was conducted, consisting of a well-planned series of lectures, tests and discussions of the test answers. During the spaced discussions participants were trained on how to ask appropriate questions and look for clinical clues to arrive at the correct diagnosis of target [oral potentially malignant disorders/oral cancer (OPMD/OC)] and other nontarget lesions. The tests comprised one pretest and 4 posttests for the dental professional group, and one pretest and 3 posttests for the student groups. The overall and group mean scores were analyzed for all the tests conducted. The statistical evaluation was based on the percentage of correct answers (scores) for each test given by the participants. Repeated-measure ANOVA and post hoc Bonferroni´s test were carried out to examine the differences between test scores overall and for each group. All statistical analysis was carried out using SPSS software, where P values < 0.005 were considered significant. Results: The overall percentage of correct responses for both the dental professional and student groups increased from a minimum of 30% to above 80% from the pretest to the final posttest. There were significant differences in overall scores between all 4 posttests and the pretest for dental professional groups, and between all 3 posttests and the pretest for all student groups. The percentage of accuracy of diagnosis for the individual lesions (leukoplakia, lichen planus, erythroplakia, oral submucous fibrosis and suspicious of oral cancer) increased to > 80% for the Dental Professional groups. The percentage of diagnostic accuracy for the individual lesions also increased to > 80% (except for erythroplakia) for the student groups. Conclusion: Based on the results of our study the “OralDETECT” spaced repetitive learning method is an efficient and effective competency-based learning tool for teaching the early detection of OPMD and oral cancer among dental professionals and dental students.

Mouth Self-Examination (MSE) As a Screening Tool for Oral Potentially Malignant Disorders Among a High-Risk Indigenous Population With a Low Socioeconomic Status

Background: Oral cancer can be preceded by a group of conditions termed oral potentially malignant disorders (OPMDs). Oral cancers are associated with a 5-year survival of less than 50%, largely attributed to diagnoses at advanced stages. As pain associated with oral cancer manifests only at late stages, delay in detection often occurs. Screening has been found to aid in detection at an early stage, however it is only feasible if targeted toward high risk individuals. Mouth self-examination (MSE) is a relatively quick, inexpensive and simple to perform method of screening. Aim: To evaluate the efficacy of MSE as a screening tool for detection of oral mucosal lesions and OPMDs in a high risk indigenous population with a high prevalence of tobacco and betel quid chewing habit. Methods: Two villages were selected as the sampling frame based on prevalence of tobacco and betel quid chewing habit. Respondents were asked to check their mouth for presence of lesion or abnormalities. Education on oral cancer, including MSE was provided. Subsequently, respondents were asked to perform MSE. Finally, a comprehensive oral examination (COE) was done by a specialist and the presence of oral mucosal lesions was recorded. Results: Almost 64.5% of respondents exhibited high levels of difficulty and low mucosal visualization and retracting ability, whereas 3.0% demonstrated high attention level when performing MSE. Prevalence of oral mucosal lesions was 59.0%, whereas the prevalence of oral potentially malignant disorders (OPMDs) was 9.0%. Detection of oral lesions by respondents using MSE was lower than detection by the gold standard. Sensitivity and specificity of MSE for detection of all types of lesions were 8.6% and 95.0% respectively. When analyzing each lesion type separately, MSE was found to be most sensitive in detection of swellings (10.0%), and most specific in identifying red lesions (100.0%). For detection of OPMDs, MSE yielded a high specificity of 98.9%, with an accuracy rate of 91.8%. Conclusion: MSE is a potentially good screening tool for OPMDs and oral cancer; however, awareness level of the public on oral cancer and its associated signs and symptoms needs to be improved.

Combination of Cytopathology and DNA Ploidy Increases the Performance of Oral Epithelial Dysplasia Prediction in Oral Potentially Malignant Disorders

Background: Grading of oral epithelial dysplasia (OED) by a pathologist is currently the key guide used for treatment planning of oral potentially malignant disorders (OPMDs). Conventional oral examination (COE) clinically detects OPMDs but may not predict their risk status to transform to cancer. Therefore, there is a need for a reliable test to predict OED in OPMDs. Aim: This study was conducted to evaluate COE, liquid based cytology (Cytopath) and DNA image cytometry (Ploidy) in predicting OED in OPMDs. Methods: A total of 179 patients from Malaysia, India and Indonesia underwent COE followed by brush biopsies and scalpel biopsies. Brush-biopsy samples were analyzed for cytopathology and DNA ploidy at Dental Faculty, University of Malaya. Histopathological findings of presence/absence of OED were used as the reference standard. Calculations for sensitivity (Sn), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV) and accuracy (A) were done for individual tools and in combinations. The Youden index (Sn+Sp-1) was used as a measure of overall performance. The relevant medical ethics committees of the different research locations approved the study. Results: For COE, the sensitivity (Sn) was high (100%) and the specificity (Sp) was low (5.9%), while both Cytopath and Ploidy showed a low sensitivity (Sn) (28.6% and 22.2%) and high specificity (Sp) (94.3% and 82.3%). All 3 tools individually have high negative predictive value (NPV) for predicting presence of OED (COE-100%, Cytopath-66.7%, Ploidy-78.5%). When combining outcomes from all 3 tools, the best performance indicated by Youden index (42.1) is which defines a positive case when both COE and Cytopath show abnormal. In general, using results from at least 2 tools had better Youden indices than using these tools individually. Conclusion: COE as a screening tool by virtue of its high Sn would be a suitable first level diagnostic test, while the Cytopath and the Ploidy individually with high Sp may be used as a second level test to predict presence of OED. Combining the COE with cytopathology would be the best combination for a high performance of the tools. Cytopathology (when performed by a trained cytologist) would allow for most of the false positives from the first level test to be correctly identified as true negative at the second level. Longitudinal data are needed to assess which of these may correctly identify the malignant potential of OPMDs. Acknowledgment: Grant: High Impact Research - Ministry of Higher Education (HIR-MOHE UM000025/C3)

Synthesis, characterization and performance of bifunctional catalysts for the synthesis of menthol from citronellal

TUD-1 based catalysts containing WO₃ and Pt were synthesized and assessed in the conversion of citronellal to menthol. The hydrogenation on Pt is highest for small WO₃ particles, while their agglomeration leads to a decreased interaction and catalytic performance.

Conformational Sub-states and Populations in Enzyme Catalysis

Enzyme function involves substrate and cofactor binding, precise positioning of reactants in the active site, chemical turnover, and release of products. In addition to formation of crucial structural interactions between enzyme and substrate(s), coordinated motions within the enzyme-substrate complex allow reaction to proceed at a much faster rate, compared to the reaction in solution and in the absence of enzyme. An increasing number of enzyme systems show the presence of conserved protein motions that are important for function. A wide variety of motions are naturally sampled (over femtosecond to millisecond time-scales) as the enzyme complex moves along the energetic landscape, driven by temperature and dynamical events from the surrounding environment. Areas of low energy along the landscape form conformational sub-states, which show higher conformational populations than surrounding areas. A small number of these protein conformational sub-states contain functionally important structural and dynamical features, which assist the enzyme mechanism along the catalytic cycle. Identification and characterization of these higher-energy (also called excited) sub-states and the associated populations are challenging, as these sub-states are very short-lived and therefore rarely populated. Specialized techniques based on computer simulations, theoretical modeling, and nuclear magnetic resonance have been developed for quantitative characterization of these sub-states and populations. This chapter discusses these techniques and provides examples of their applications to enzyme systems.

Prolonged improvement of childhood onset systemic lupus erythematosus following systematic administration of rituximab and cyclophosphamide

BACKGROUND

Although the combination of cyclophosphamide and rituximab has been utilized in case reports, there are no previous reports of the long term outcome of SLE treated systematically with this regimen. We report a pilot study to evaluate the efficacy of a systematically administered course of rituximab and cyclophosphamide over an eighteen month period to provide sustained improvement in childhood onset systemic lupus erythematosus (SLE).

FINDINGS

Twelve patients with childhood onset lupus nephritis or corticosteroid resistant SLE received systematic treatment with a combination of rituximab (750 mg/M2 up to 1 gram) and cyclophosphamide (750 mg/M2: no patient exceeded 1.8 M2). Two administrations of rituximab and cyclophosphamide, two weeks apart, were administered at the start of study, six months later, and eighteen months later. Clinical data were collected and analyzed after sixty months of follow up. There was sustained improvement in all clinical parameters with a dramatic reduction in both mean SLEDAI score (10.1 to 1 at one year and 0 at five years p<0.005) and mean daily prednisone dosage (29.7 mg/day to 12.7 by one year and 7.0 mg/day at five years p<0.005), with sustained improvement in mean C3 (55.5 mg/ml to 113 at one year and 107.5 at five years p<0.001) which was maintained through sixty months of follow up. Serum immunoglobulin levels were transiently depressed but mean values were within the normal range for both IgG and IgM at one and five years. Few complications were observed (two episodes of febrile neutropenia during the first year of treatment were the only serious adverse events) and patients routinely reported sustained wellbeing.

CONCLUSIONS

This pilot study demonstrates that a systematically administered course of rituximab and cyclophosphamide over an eighteen month period provided sustained relief for patients with childhood onset SLE which was maintained over a sixty month period, while minimizing the need for corticosteroids, without excessive toxicity.

Combined heterogeneous bio- and chemo-catalysis for dynamic kinetic resolution of (rac)-benzoin

A highly efficient system for the enantiopure synthesis of benzoin was developed. The reaction system employed lipase TL from Pseudomonas stutzeri immobilized on Accurel MP1001 (Acc-LipTL) and Zr-TUD-1 (Si/Zr = 25), an acidic mesoporous silicate, for dynamic kinetic resolution of racemic benzoin in one pot.

Update on juvenile spondyloarthritis

Spondyloarthritis (SpA) encompasses a group of disorders linked by overlapping clinical manifestations and genetic predisposition. Newer classification systems developed for adults with SpA focus on identifying individuals with axial or predominantly peripheral involvement. All forms of SpA can begin during childhood, and can be considered on a continuum with adult disease. Nevertheless, there are important differences in presentation and outcome that depend on age at onset. This article highlights these differences, what has been learned about genetics and pathogenesis of SpA, and important unmet needs for future studies.

A Comparative Study of Technology and Industry Clusters of SMEs in India

This article attempts to compare the Small and Medium Enterprises (SMEs) belonging to industry and technology clusters in India. They are compared in terms of the technological efforts, nature of competition, competitive strategy, outward orientation, research and development intensity and export intensity. First part of the article gives the economics of clustering and the second part analyses the inter-cluster differences, if any, between the firms belonging to 13 clusters drawn from Mumbai and Thiruvananthapuram. The analysis reveals that the firms in the technology cluster are more outward oriented and R and D intensive compared to their counterparts in the industry cluster. They also differ in terms of the type of competitors and the competitive strategies. While the firms in the technology cluster face competition from established foreign firms, those in the industry cluster from established local firms. Process innovations are used by firms in the technology cluster whereas productivity improvements are used by firms in the industry cluster for sustaining competitive advantage. In the regression analysis, the nature of cluster, use of technology/business collaboration (Networking) and market share emerge as significant variables in explaining the R and D intensity of firms. Export intensity is explained by the R and D intensity and scale of operation.

Superflow in a toroidal Bose-Einstein condensate: an atom circuit with a tunable weak link

We have created a long-lived (≈40 s) persistent current in a toroidal Bose-Einstein condensate held in an all-optical trap. A repulsive optical barrier across one side of the torus creates a tunable weak link in the condensate circuit, which can affect the current around the loop. Superflow stops abruptly at a barrier strength such that the local flow velocity at the barrier exceeds a critical velocity. The measured critical velocity is consistent with dissipation due to the creation of vortex-antivortex pairs. This system is the first realization of an elementary closed-loop atom circuit.

Transgenic resistance by N gene of a Peanut bud necrosis virus isolate of characteristic phylogeny

The nucleocapsid protein (N) gene of a Tospovirus devastating tomato crop in the south Indian state of Tamil Nadu was cloned and characterized. The high identity of the cloned sequence to a Peanut bud necrosis virus (PBNV) tomato isolate (97.8/99.6% nucleotide/amino acid) and a PBNV peanut isolate (94.4/96.3% nucleotide/amino acid) identified the Tospovirus as an isolate of PBNV, designated PBNV Coimbatore tomato (PBNV CT) isolate. Phylogenetic analysis of PBNV CT N gene provided useful insights into the movement and evolution of PBNV within Indian Territory. The characteristic phylogeny of PBNV CT N gene implied its potential to be an efficient transgene to confer effective PBNV resistance on crop plants. The efficacy of PBNV CT N gene in conferring PBNV resistance was studied by generating tobacco (Nicotiana tabacum L. cv Wisconsin) lines transgenic to the sense or antisense version of the gene. Several transgenic lines showed transgenic mRNA and/or protein accumulation, ranging from very high to undetectable levels, accompanied by different degrees of PBNV resistance. The undetectable or very low levels of transgene transcripts in certain PBNV-resistant sense or antisense N gene transgenic lines suggested RNA-mediated resistance by post-transcriptional gene silencing (PTGS) mechanism. However, PBNV resistance of certain transgenic lines with high levels of N gene transcripts was suggestive of possible operation of RNA-mediated non-PTGS mechanism(s) of resistance in those lines. Moreover, the high levels of N protein in certain PBNV-resistant sense N gene transgenic lines suggested protein-mediated resistance. The results predict the potential of PBNV CT N gene to confer effective PBNV resistance on tomato and other economically important crops.

Observation of a 2D Bose gas: from thermal to quasicondensate to superfluid

We present experimental results on a Bose gas in a quasi-2D geometry near the Berezinskii, Kosterlitz, and Thouless (BKT) transition temperature. By measuring the density profile after time of flight and the coherence length, we identify different states of the gas. We observe that the gas develops a bimodal distribution without long range order. In this regime, the gas presents a longer coherence length than the thermal cloud; it is quasicondensed but is not superfluid. Experimental evidence indicates that we also observe the superfluid transition (BKT transition). For a sufficiently long time of flight, we observe a trimodal distribution when the gas has developed a superfluid component.

Two pathogenesis-related peroxidases in greengram (Vigna radiata (L.) wilczek) leaves and cultured cells induced by Macrophomina phaseolina (Tassi) Goid. and its elicitor

An elicitor has been isolated from Macrophomina phaseolina, the root rot and leaf blight pathogen of greengram. Suspension-cultured cells of greengram were established which responded to the fungal elicitor. When greengram leaves were inoculated with M. phaseolina two new peroxidases appeared. Similarly, two new peroxidases could be detected in suspension-cultured greengram cells when treated with the fungal elicitor. These peroxidases were purified by column chromatography and their molecular masses were 27 and 38 kDa. The new peroxidases detected in both leaves and cultured cells appear to be similar with the same molecular weights.

Shotgun optical maps of the whole Escherichia coli O157:H7 genome

We have constructed NheI and XhoI optical maps of Escherichia coli O157:H7 solely from genomic DNA molecules to provide a uniquely valuable scaffold for contig closure and sequence validation. E. coli O157:H7 is a common pathogen found in contaminated food and water. Our approach obviated the need for the analysis of clones, PCR products, and hybridizations, because maps were constructed from ensembles of single DNA molecules. Shotgun sequencing of bacterial genomes remains labor-intensive, despite advances in sequencing technology. This is partly due to manual intervention required during the last stages of finishing. The applicability of optical mapping to this problem was enhanced by advances in machine vision techniques that improved mapping throughput and created a path to full automation of mapping. Comparisons were made between maps and sequence data that characterized sequence gaps and guided nascent assemblies.

Tricuspid valve disease. Clinical evaluation, physiopathology, and management

The tricuspid and mitral valves are homologous whose function depends on coordination among components. Isolated tricuspid valve abnormalities are relatively uncommon. Rheumatic disease, chemicals, immunologic and degenerative disorders alter leaflet anatomy and may result in either stenosis, insufficiency or a combination. More often, tricuspid disorders present as a component of congenital syndromes or secondary to pulmonary vascular or let heart disease which alter geometry and function of nonleaflet components.

An acute lower limb ischaemia with an unusual cause

Acute arterial occlusion associated with an abdominal aortic aneurysm can occur as a result of acute thrombosis or embolism from a mural thrombus of the aneurysm. We report here a case of an unusual association between a seat belt injury and an acute ischaemic leg in a patient known to have an abdominal aortic aneurysm. We also demonstrate some difficult dilemma related to the use of anticoagulation in patients with multiple injuries.

Host-Specific Toxin Production by Rhizoctonia solani, the Rice Sheath Blight Pathogen

ABSTRACT Rhizoctonia solani, the rice sheath blight pathogen, produces a toxin that reproduces all symptoms of the disease. The toxin has been partially purified and it was found to be a carbohydrate containing glucose, mannose, N-acetylgalactosamine, and N-acetylglucosamine. The toxin was also detected in infected leaves. Highly virulent isolates produced more toxin than less virulent isolates. Several R. solani isolates from rice and one each from cotton and tomato produced a similar toxin. All rice cultivars tested were susceptible to the pathogen and sensitive to the toxin. Host specificity of the toxin has been demonstrated using hosts and nonhosts of the pathogen.

Emergency femoral arteriography in lower limb vascular trauma

There are difficulties in obtaining emergency arteriographic evaluation in lower limb vascular trauma even in the best centres in the world. Ten emergency room arteriograms were performed at the new Accident Service of the General Hospital, Colombo from February to October 1992 by the vascular team, using a venous cannula and improvised tubing systems. The indications were, absence of distal pulses with closed injury to the limb, previous attempts at repair, injury to the limb at more than one site and multiple shrapnel injury. A traumatic arteriovenous communication was shown in one of the arteriograms. Unnecessary exploration of the artery was prevented by the demonstration of a patent femoropopliteal segment in two cases. The average delay caused by this procedure was less than one hour, which compares well with centres in the West. Provision of an arteriogram kit at the Accident Service will help to overcome practical problems.