Outcomes of robotic low anterior resection versus transanal total mesorectal excision for rectal cancer

Background

The quality of total mesorectal excision (TME) is regarded as a fundamental key to the oncological outcome of rectal cancer. Robotic low anterior resection (RLAR) and transanal TME (TaTME) were developed to overcome the technical challenges of conventional open TME. This study aimed to compare the short- and long-term outcomes of RLAR versus TaTME for rectal cancer.

Methods

Retrospective data from patients undergoing RLAR or TaTME at a colorectal unit in Singapore were analysed. The primary outcomes were the short-term clinical and pathological results including specimen margins and quality of TME. Secondary outcomes were recurrence, disease-free survival (DFS), and overall survival rates.

Results

A total of 80 patients who underwent either RLAR or TaTME were analysed. The TaTME group had a shorter operating time than the RLAR group (354 versus 481 min respectively; P < 0.001) and fewer stays in the high-dependency and intensive care units (38.1 versus 73.7 per cent; P = 0.010). There was a higher rate of readmissions at 30 days in the TaTME group (19.0 versus 0 per cent; P = 0.006). Specimens from TaTME had greater proximal (14.0 versus 10.0 cm; P = 0.045) and distal (2.50 versus 1.65 cm; P = 0.021) margins. Patients undergoing TaTME had borderline longer DFS (25.9 versus 15.7 months; P = 0.049). Subgroup analysis of patients with (y)pT3–4 tumours showed fewer positive circumferential resection margins with TaTME (0 versus 18.2 per cent; P = 0.019) and improved DFS (25.9 versus 15.7 months; P = 0.017).

Conclusion

Superior margins were obtained with TaTME, especially in locally advanced tumours, although TaTME was associated with a higher readmission rate compared with RLAR.

Global spectrum of population-specific common missense variation in cytochrome P450 pharmacogenes

Next-generation sequencing technology has afforded the discovery of many novel variants that are of significance to inheritable pharmacogenomics (PGx) traits but a large proportion of them have unknown consequences. These include missense variants resulting in single amino acid substitutions in cytochrome P450 (CYP) proteins that can impair enzyme function, leading to altered drug efficacy and toxicity. While most unknown variants are rare, an overlooked minority are variants that are collectively rare but enriched in specific populations. Here, we analyzed sequence variation data in 141,456 individuals from across eight study populations in gnomAD for 38 CYP genes to identify such variants in addition to common variants. By further comparison with data from two PGx-specific databases (PharmVar and PharmGKB) and ClinVar, we identified 234 missense variants in 35 CYP genes, of which 107 were unknown to these databases. Most unknown variants (n = 83) were population-specific common variants and several (n = 7) were found in important CYP pharmacogenes (CYP2D6, CYP4F2, and CYP2C19). Overall, 29% (n = 31) of 107 unknown variants were predicted to affect CYP enzyme function although further biochemical characterization is necessary. These variants may elucidate part of the unexplained interpopulation differences observed in drug response.

46 The Hidden Truth About Gender Bias in Surgery. A Systematic Review

Introduction

Gender discrimination remains pervasive in surgery, significantly impacting current and future surgeons and population health. This study analyses the gender barriers and critical retention factors for female surgeons and trainees in surgery.

Method

Five electronic databases were searched till May 2020. Titles and abstracts were sieved, followed by a full text review. Data synthesis and inductive thematic analysis were conducted using the Thomas and Harden methodology.

Result

14 articles were included, involving 528 participants. Four themes were generated–unfavourable working environment, male-dominated culture, societal pressures and progress towards gender equality. Females in surgery often faced harassment, disrespect and perceptions of incompetence, resulting in hostile work conditions, which were aggravated by the inadequate support and mentorship. The persistence of male-dominated cultures was observed, with females facing prejudice and exclusion from professional and social circles. Differential treatment and higher expectations of female surgeons also arose from entrenched societal pressures. Despite these, increased acceptance of motherhood and greater recognition of contributions by female surgeons were reported, indicating some progress in gendered culture.

Conclusions

There is a need to increase female surgical leadership and allocate resources to address the deep-rooted causes of biased surgical culture and ingrained perceptions, to achieve greater gender equality in surgery.

19 Colectomy Rate for Moderate to Severe Ulcerative Colitis with Biologics

Introduction

Biologics are recommended by both the ACG and ECCO community for the treatment of ulcerative colitis. Yet, current literature has yet to estimate the rate of colectomies after biologic therapy, and thus a pooled meta-analysis was conducted the rate of colectomies in 1month, 6 months, 1 year, 2years and five years after biologics.

Method

Medline and Embase were searched for articles examining biologics use in moderate to severe UC or acute severe UC (ASUC) from inception to 21st May 2020. Analysis of proportions were undertaken after a freeman-tukey double arcsine transformation.

Results

The pooled overall colectomy rates of ASUC and moderate to severe UC were 9% (CI: 4% - 14%) at one month, 18% (CI: 13% - 25%) at six months, 21% (CI:16% - 27%) at one year, 29% (CI:24% - 34%) at two years and 38% (CI:30% - 45%) at five years. Additionally, colectomy rates were consistently lower comparing between articles before and after 2010. At one-year, overall colectomy rate following infliximab use was at 25%, golimumab at 15%, vedolizumab at 14%, and adalimumab at 3%.

Conclusions

Colectomy rates in the era of biologics ranged from 8% to 38% and lower post-2010 showing significant improvement in management and supporting the utility of biologics in Ulcerative colitis management.

10 Complete Mesocolic Excision Produces Favorable Survival Outcomes Compared to Conventional Colectomy

Introduction

Conventional colectomy, and the Japanese Society for Cancer of the Colon and Rectum (JSCCR) D2 Lymphadenectomy (LND2), are the standards of care for the surgical management of colon cancer. Colectomy with complete mesocolic excision (CME) and JSCCR D3 Lymphadenectomy (LND3) are alternative, and more radical procedures, that provide greater lymph nodal clearance. However, controversy exists over the long-term survival benefits of CME/LND3 over non-CME colectomies (NCME)/LND2.

Method

In this study, we performed a meta-analysis to compare the survival outcomes of CME/LND3 with NCME/LND2. Medline and Embase databases were searched for articles reporting survival outcomes of both CME/LND3 and NCME/LND2, with comparisons presented using odds ratios (OR).

Results

Ten studies were included in this analysis. Overall and disease-free survival favored CME/LND3 (3-year OS: OR = 1.56; CI 1.22-2.00; p = 0.0004, 5-year OS: OR = 1.29; CI 1.02-1.64, p = 0.03, 3-year DFS: OR = 1.45; CI 1.12-1.88; p = 0.005, 5-year DFS: OR = 1.61; CI 1.14-2.28; p = 0.007). Overall and disease-free survival rates at five years were 79.8% and 85.9%, and 74.6% and 78.0%, in the CME/LND3 and NCME/LND2 groups respectively.

Conclusions

This is the first meta-analysis to demonstrate that CME/LND3 has superior long-term survival outcomes compared to NCME/LND2, hence a strong case can be made for incorporating CME/LND3 into standard care practice.

368 Perioperative Outcomes in Open versus Laparoscopic Surgery in Elderly Patients Undergoing Right Hemicolectomy

Introduction

With the global aging population, elderly patients are increasingly undergoing colorectal surgery. This study aims to evaluate postoperative outcomes in open (OS) and laparoscopic surgery (LS) for right hemicolectomy in elderly patients.

Method

We retrospectively reviewed patients aged 70 and above undergoing right hemicolectomy for malignancies at our institution. Additionally, Embase and Medline databases were reviewed, and comparative meta-analysis was conducted.

Results

84 patients were included in our cohort (OS = 34; LS = 50). No significant difference in anastomotic leak (AL) (OS = 4; LS = 2; p = 0.176), surgical site infection (SSI) (OS = 4; LS = 2; p = 0.216), and ileus (OS = 10; LS = 16; p = 0.801) was observed. LS was associated with decreased postoperative stay (p = 0.001). Additionally, LS had faster return of bowel function (ROBF) (p = 0.068) and resumption of diet (p = 0.147), albeit without significance. Overall survival (p = 0.062), and disease-free survival (p = 0.067) did not significantly differ between LS and OS.

Pooled analysis of 463 patients yielded no significant difference in AL (OR:1.15; 95%CI: 0.17-8.01; p = 0.89), SSI (OR:0.88; 95%CI: 0.44-1.76; p = 0.71), and ileus (OR:1.42; 95%CI: 0.69 – 2.92; p = 0.35). Postoperative stay (WMD:1.90 days; 95%CI: -1.81–5.61 days; p = 0.31), and ROBF (WMD:14.49 hours; 95%CI: -4.07–33.05 hours; p = 0.13) were shortened in LS, although without significance.

Conclusions

LS is associated with improved functional outcomes without an increased risk of postoperative morbidity or mortality.

20 Post-Operative Biologics and the Rate of Recurrence in Crohn’s Disease

Introduction

Post-operative recurrence after Crohn’s surgery poses a significant challenge to clinicians with an estimated of 70-90% recurrence rate. However, with the advent of biologics, reduction of recurrence after surgery has been observed in various landmark trials. Hence, we aim to quantify the rate of recurrence with post-operative biologics.

Method

Searches were done on Embase and Medline database for articles using biologics for post-operative management. A single arm meta-analysis with generalized linear mixed model and Clopper-Pearson method confidence interval was applied in the synthesis of the data on six months, one year, two year and five year.

Results

A total of 1,864 abstracts were identified, with a final total of 24 articles and 1042 patients were included in the meta-analysis. The one-year rate of recurrence for surgical, endoscopic and clinical was 3.08% (CI: 0.74% - 11.95%), 19.93% (15.81% - 24.81%) and 13.06% (CI: 8.18% - 18.92%) respectively. Correspondingly, the five-year recurrence 16.90% (CI: 9.57% - 28.11%), 84.21% (CI: 72.35% - 91.57%), 5.60% (CI: 9.92% -23.66%) respectively.

Conclusions

An observed reduction in surgical rates was reduced at five years with post-operative Crohn’s disease with biologics. Biologics therapy thus can be considered as a suitable alternative for reducing post-operative recurrence in individuals with higher risk.

295 Radiotherapy for Curative-intent Metastatic Rectal Cancer: A Systematic Review and Meta-Analysis

Introduction

The role and optimal regimen of radiotherapy in curative-intent treatment of metastatic rectal cancer is unclear and hence a single arm meta-analysis was performed.

Method

Medline, Embase and Cochrane Library databases were searched up to 16 May 2020. A Meta-analysis of binomial data was performed using a Freeman-Tukey double arcsine transformation, and pooled estimates were used to construct risk ratios and confidence intervals via the Katz-logarithmic method. Additionally, comparative meta-analysis was performed with the Mantel Haenszel model.

Results

18 studies were included. Rectal pathological complete response (pCR) was observed in 14% of tumours treated with radiotherapy (n = 57/388, CI 0.07 to 0.23). Comparative meta-analysis of cohort studies showed that treatment regimens including radiotherapy were associated with higher pT1 tumour and better oncological outcomes compared to regimens without radiotherapy. Katz-logarithmic method showed that neoadjuvant radiotherapy had a higher proportion of pN0 staging (RR = 1.81, 95% CI 1.06 to 3.09, p = 0.029) and better oncological outcomes compared to adjuvant radiotherapy, and that short course radiotherapy (SCRT) had a lower proportion of pT3 tumours (RR = 0.778, 95% CI 0.609 to 0.994, p = 0.044) and similar oncological outcomes compared to long course radiotherapy (LCRT).

Conclusions

This study supports the evidence that radiotherapy should be used in curative intent metastatic rectal cancer.

207 Laparoscopic versus Open Surgery for Locally Advanced Colon Cancer: A Retrospective Cohort Study

Introduction

While an increasing number of studies substantiate the non-inferiority of laparoscopy to open surgery for pT4 colon cancer, studies investigating its value specific to the subgroup pT4a in right hemicolectomies remain scarce.

Method

We performed a retrospective cohort analysis in National University Hospital of Singapore of patients who underwent a right hemicolectomy for pT4 colon cancer. Statistical analysis was performed using Wilcoxon rank sum test and chi square/fisher exact.

Results

In total, 65 patients had T4 colon cancer. 55 underwent right hemicolectomy and 10 underwent extended right hemicolectomy. Baseline demographics were similar in laparoscopic (n = 27) and open (n = 38) groups, with no significant difference in proportion of pT4a patients (p = 0.724). For pT4, 30-day mortality (7%, 5% respectively, p = 0.723), overall survival (p = 0.1903) and disease-free survival (p = 0.3476) did not differ significantly between laparoscopic and open groups. R0 resection rates were significantly higher in laparoscopic group (p = 0.039). pT4a subgroup analysis found similar observations. Other complications including postoperative wound infection and anastomotic bleed were not significantly different for both T4 and T4a analysis.

Conclusions

This study presented comparable safety and oncological outcomes between the two surgical methods for right hemicolectomy, suggesting laparoscopy to be a viable alternative approach for locally advanced right colon cancer.

189 Preliminary Results from an Innovative Surgical Research Group for Medical Students

Introduction

Learning research in medical school can be daunting and difficult with many lacking appropriate guidance. Particularly, research in surgery can be difficult with most clinicians tied to long hours from clinical duties, leaving medical students lost to learn the ropes for medical research.

Method

We started a surgical research group in January of 2020 under a shepherd sheep model. Shepards were senior medical students who had previous experience in research and were provided resources from consultants on statistics and research designs. Thereafter, each Shepard were paired with junior medical students (sheep) and a resident to provide clinical background. Research was then carried out small teams with minimal guidance from consultants.

Results

To date, the group has published 11 articles (median impact factor: 2.41, range: 1.89 - 3.42), 3 articles in revision and 9 articles in review.

Conclusions

We provide preliminary evidence of a successful model for building medical student research in surgery. While current analysis was limited to meta-analysis and systematic review due to the availability of data, current expansion is currently underway to expand to observational studies.

A Novel FRET Approach Quantifies the Interaction Strength of Peroxisomal Targeting Signals and Their Receptor in Living Cells

Measuring Förster–resonance–energy–transfer (FRET) efficiency allows the investigation of protein–protein interactions (PPI), but extracting quantitative measures of affinity necessitates highly advanced technical equipment or isolated proteins. We demonstrate the validity of a recently suggested novel approach to quantitatively analyze FRET-based experiments in living mammalian cells using standard equipment using the interaction between different type-1 peroxisomal targeting signals (PTS1) and their soluble receptor peroxin 5 (PEX5) as a model system. Large data sets were obtained by flow cytometry coupled FRET measurements of cells expressing PTS1-tagged EGFP together with mCherry fused to the PTS1-binding domain of PEX5, and were subjected to a fitting algorithm extracting a quantitative measure of the interaction strength. This measure correlates with results obtained by in vitro techniques and a two-hybrid assay, but is unaffected by the distance between the fluorophores. Moreover, we introduce a live cell competition assay based on this approach, capable of depicting dose- and affinity-dependent modulation of the PPI. Using this system, we demonstrate the relevance of a sequence element next to the core tripeptide in PTS1 motifs for the interaction strength between PTS1 and PEX5, which is supported by a structure-based computational prediction of the binding energy indicating a direct involvement of this sequence in the interaction.

Rare Human Missense Variants can affect the Function of Disease-Relevant Proteins by Loss and Gain of Peroxisomal Targeting Motifs

Single nucleotide variants (SNVs) resulting in amino acid substitutions (i.e., missense variants) can affect protein localization by changing or creating new targeting signals. Here, we studied the potential of naturally occurring SNVs from the Genome Aggregation Database (gnomAD) to result in the loss of an existing peroxisomal targeting signal 1 (PTS1) or gain of a novel PTS1 leading to mistargeting of cytosolic proteins to peroxisomes. Filtering down from 32,985 SNVs resulting in missense mutations within the C-terminal tripeptide of 23,064 human proteins, based on gene annotation data and computational prediction, we selected six SNVs for experimental testing of loss of function (LoF) of the PTS1 motif and five SNVs in cytosolic proteins for gain in PTS1-mediated peroxisome import (GoF). Experimental verification by immunofluorescence microscopy for subcellular localization and FRET affinity measurements for interaction with the receptor PEX5 demonstrated that five of the six predicted LoF SNVs resulted in loss of the PTS1 motif while three of five predicted GoF SNVs resulted in de novo PTS1 generation. Overall, we showed that a complementary approach incorporating bioinformatics methods and experimental testing was successful in identifying SNVs capable of altering peroxisome protein import, which may have implications in human disease.

Innovative Patient Safety Curriculum Using iPAD Game (PASSED) Improved Patient Safety Concepts in Undergraduate Medical Students

INTRODUCTION

While healthcare outcomes have improved significantly, the complex management of diseases in the hospitals has also escalated the risks in patient safety. Therefore, in the process of training medical students to be proficient in medical knowledge and skills, the importance of patient safety cannot be neglected. A new innovation using mobile apps gaming system (PAtient Safety in Surgical EDucation-PASSED) to teach medical students on patient safety was created. Students were taught concepts of patient safety followed by a gaming session using iPad games created by us. This study aims to evaluate the outcome of patient safety perception using the PASSED games created.

METHODS

An interactive iPad game focusing on patient safety issues was created by the undergraduate education team in the Department of Surgery, Yong Loo Lin School of Medicine at the National University of Singapore. The game employed the unique touched-screen feature with clinical scenarios extracted from the hospital sentinel events. Some of the questions were time sensitive, with extra bonus marks awarded if the student provided the correct answer within 10 s. Students could reattempt the questions if the initial answer was wrong. However, this entailed demerit points. Third-year medical students posted to the Department of Surgery experienced this gaming system in a cohort of 55-60 students. Baseline understanding of the students on patient safety was evaluated using Attitudes to Patient Safety Questionnaire III (APSQ-III) prior to the game. A 20 min talk on concept of patient safety using the WHO Patient Safety Guidelines was conducted. Following this, students downloaded the apps from ITune store and played with the game for 20-30 min. The session ended with the students completing the postintervention questionnaire.

RESULTS

A total of 221 3rd year medical students responded to the survey during the PASSED session. Majority of the students felt that the PASSED game had trained them to understand the processes of medical error (p < 0.001), that their understanding on patient safety issues improved (p = 0.007), and the training prepared them to prevent medical errors (p < 0.001). Many students also recognized the importance of error reporting, where they felt comfortable reporting errors committed by themselves (p < 0.001) or by other people (p < 0.001). They also felt comfortable discussing with the supervisor on medical errors (p < 0.001). Students responded that better teamwork will reduce medical errors (p = 0.003), and teaching teamwork skills will reduce medical errors (p = 0.002). After the PASSED session, students felt that patients could play an important role in preventing medical errors (p < 0.001). They felt that patient safety should be emphasized in undergraduate training (p = 0.024). The level of understanding about concepts of patient safety was also found to improve progressively from the 2nd posting to the 5th posting for both the pre-PASSED and post-PASSED intervention. The pre-PASSED scores for Posting 2 (3.59 ± 1.931), Posting 3 (4.11 ± 1.833), Posting 4 (4.84 ± 1.653), and Posting 5 (4.88 ± 1.642) were significantly higher than the post-PASSED scores for Posting 2 (4.46 ± 2.020), Posting 3 (5.17 ± 1.845), Posting 4 (5.88 ± 1.843), and Posting 5 (5.80 ± 1.843), respectively (p < 0.001).

CONCLUSION

Using iPad game (PASSED) to enhance the patient safety teaching has successfully improved the awareness and understanding of patient safety in clinical practice. This training model can be used to teach more senior medical students on the complexity of patient safety issues in medicine.

Outcomes Following Surgery for Distal Rectal Cancers: A Comparison between Laparoscopic and Open Abdomino-Perineal Resection

PURPOSE

Oncologic outcomes following laparoscopic abdomino-perineal resection (APR) for distal rectal cancer are infrequently reported. This study aims to compare the long term outcomes between laparoscopic and open APR in distal rectal cancers.

METHODS

A retrospective review of all patients who underwent APR for distal rectal cancer from May 2001 to November 2009 was performed.

RESULTS

Forty-two patients, median age 60 (24 - 86) years, formed the study group. Laparoscopic resection was attempted in 16 patients and was successful in all but one. Patients with recurrent diseases, previous abdominal operations and neoadjuvant chemoradiation were more likely to undergo open APR. There were no differences in the T-staging, number of lymph nodes harvested or the final stage of the disease between the two groups. The laparoscopic APR group had a shorter median length of hospitalization (7 vs. 10 days, p < 0.05), but longer operative duration (300 vs. 240 minutes, p > 0.05). Excluding the 9 (21.4%) patients with metastatic disease on presentation, 13 (39.4%) developed recurrence after a median follow up of 24 (4 - 107) months. Twenty (47.6%) patients died from their advanced disease subsequently while one (2.4%) died from a noncancer related cause. Analysis showed that tumour stage and circumferential resection margin positivity were associated with a poorer survival. The types of approach had no significant impact on the survival.

CONCLUSION

Laparoscopic APR for distal rectal cancer yields similar oncologic outcomes as open APR. Long-term outcome is determined by the tumour stage and circumferential resection margin and not the approach.

Post-operative health related quality of life assessment in scoliosis patients

Adolescent Idiopathic Scoliosis is a spinal deformity which affects patients' self image and confidence. Surgery is offered when the curve is more than 50 degrees based on its likelihood of progression. Studies on the radiological outcome of scoliosis correction are abundant. Therefore, it is the objective of this study to evaluate the health related quality of life in scoliosis patients who had undergone surgical correction in University Malaya Medical Center, Kuala Lumpur, Malaysia using Scoliosis Research Society-22 (SRS-22) patient questionnaire. This is a prospective evaluation of SRS-22 scores of thirty eight patients operated in our center over the past five years with a minimum follow up of one year. There were thirty two females and six males. Twenty six (68.4%) were Chinese, eight (21.1%) Malay and four (10.5%) Indian patients. The age of the patients ranged from twelve to twenty eight years, with a mean age of 18.4 +/- 3.5. Based on the King and Moe's classification, sixteen patients had King's 3 curve. The mean pre-operative Cobb angle was 68.6 degree and post-operative Cobb angle was 35.8 degree. The average curve correction was 48.5%. The overall score for SRS-22 was 4.2. The SRS-22 scores were highest for the pain domains and lowest for the functional domains. Satisfaction domain scored 4.3. The function domain scored significantly higher in those who have twenty four months or less follow up duration. Curve magnitude and the amount of correction did not significantly alter the SRS scores. In conclusion, patients were satisfied with the outcome of their operation. Although pain was common, the intensity of the pain was minimal. The amount of curve correction did not correlate with the quality of life after operation.

Cervical myelopathy caused by an exostosis of the posterior arch of C1

We report a case of vertebral osteochondroma of C1 causing cord compression and myelopathy in a patient with hereditary multiple exostosis. We highlight the importance of early diagnosis and the appropriate surgery in order to obtain a satisfactory outcome.

Use of remote sensing to detect soybean cyst nematode-induced plant stress

Integrating remote sensing and geographic information systems (GIS) technologies offers tremendous opportunities for farmers to more cost effectively manage the causes of crop stress. Initial soybean cyst nematode (SCN) population densities from 995 2-x-3-m quadrats were obtained from a soybean field near Ames, Iowa, in 2000. The percentage of sunlight reflected from each quadrat was measured weekly using a multispectral radiometer beginning in mid-May and continuing through mid-September. Aerial images were obtained at heights above the field ranging from 45 to 425 m on 12 dates during the soybean growing season. This was accomplished using color film and infrared film in conjunction with a filter to measure reflectance in the near-infrared region (810 nm). Satellite images (Landsat 7) were obtained for five dates during the 2000 growing season. Maps depicting initial SCN population densities, soybean yield, soy oil, and soy protein were generated using the GIS software program ArcView. Percentage reflectance (810 nm), aerial image intensity, and satellite image intensity data then were regressed against soybean yield, soy oil, and soy protein concentrations obtained from each geospatially referenced soybean quadrat. Percentage reflectance measurements explained up to 60% of the variation in initial SCN population densities within soybean quadrats and up to 91% of the variation in soybean yield. Aerial image and satellite image intensities explained up to 80% and 47% of the variation in soybean yield, respectively. Percentage reflectance data also explained 36% and 54% of the variation in oil and protein concentrations of the harvested soybeans, respectively. These results indicate that remote sensing coupled with GIS technologies may provide new tools to detect and quantify SCN population densities and their impacts on the quantity and quality of soybean yield.

Scoliosis in a patient with lipodystrophy--treatment difficulties and literature review

A 12 year-old Chinese schoolgirl presented with left-sided scoliosis at the age of 9 years. She has a rare defect in lipid metabolism, which is not known to be associated with spinal deformity. Her scoliotic curve deteriorated despite bracing. We report a rare occurrence of scoliosis in patient with lipodystrophy and the difficulty of using instrumented fusion in treating this condition.

Point mutations and an intragenic deletion in LIS1, the lissencephaly causative gene in isolated lissencephaly sequence and Miller-Dieker syndrome

Classical lissencephaly (smooth brain) or generalized agyria-pachygyria is a severe brain malformation which results from an arrest of neuronal migration at 9-13 weeks gestation. It has been observed in several malformation syndromes including Miller-Dieker syndrome (MDS) and isolated lissencephaly sequence (ILS). A gene containing beta-transducin like repeats, now known as LIS1, was previously mapped to the ILS/MDS chromosome region on 17p13.3. We recently localized the classical lissencephaly critical region to the LIS1 gene locus by molecular analysis of key ILS and MDS patients. We have now characterized the structure of LIS1, which consists of 11 exons, and have searched for the presence of subtle mutations in 19 ILS patients who showed no gross rearrangements of LIS1. Single strand conformational polymorphism (SSCP) analysis revealed band-shifts for three patients, each involving a different coding exon, which were not observed in their respective parental DNAs. Sequence analysis identified these de novo mutations as dA --> dG transition in exon VI at nucleotide 446, a dC --> dT transition in exon VIII at nucleotide 817, and a 22 bp deletion at the exon IX-intron 9 junction from nucleotide 988 to 1,002+7, which causes skipping of exon IX in the mature LIS1 transcript. These changes are predicted to result in an H149R amino acid substitution, an R273X premature translation termination, and abolition of amino acids 301-334, in the respective LIS1 proteins. These data thus confirm LIS1 as the gene responsible for classical lissencephaly in ILS and MDS.

Spectrometry and dosimetric evaluation of the gamma-ray emissions of 241Am

New, detailed measurements have been made of the photon spectrum of the radionuclide 241Am. Observations, recorded for a 95% confidence level over local background, provide affirmation of a number of lines previously considered to be of equivocal existence. A number of hitherto unreported emissions are similarly observed. Peak areas, expressed as a percentage of that for the 59.54 keV emission, have been ascribed to all lines of the detailed spectrum. This leads to an estimated increase in the value of exposure calculated from the measured fluence spectrum, relative to that from the 59.54 keV line, of (3.1 +/- 0.8)%, taking into account all emissions beyond the predominating 59.54 keV gamma-ray emission.

The associated X-ray spectra of Amersham caesium-137 afterloading sources

Low-energy X rays are clearly observed in the energy spectra of Amersham 137Cs afterloading sources. Examination is made of the effects of encapsulation and source train attenuation on the source spectra. Estimates of the resulting X-ray intensities are also made.

Photon absorptiometric studies of elements, mixtures and substances of biomedical interest

Photon absorptiometric measurements of several elements, mixtures and substances of biomedical interest have been performed. The 144.5 keV photons of 141Ce and the associated x-ray emissions of 203Hg at 75 keV and 137Cs at 33 keV in addition to the more commonly applied energies of 279.2 and 661.6 keV respectively, have been utilised. The concept of effective atomic numbers and the choice of tissue-equivalent substitutes has been examined with reference to the experimental findings.

Light scattering and turbidity measurements on lipid vesicles

The dynamic behaviour of model membranes in the form of sonicated liposomes in excess water was studied by means of 90 degrees C light scattering and turbidity measurements. Computer calculations based on the Rayleigh-Gans theory of light scattering were used to estimate the average size of lipid vesicles dispersed in water, taking into account the various structures of the vesicles. Normal reversible changes in the scattered light intensity and turbidity with temperature could be accounted for mainly by the changes in the refractive index of the lipid and irreversible anomalous changes were explained on the basis of fusion of smaller aggregated vesicles.