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In many species highly expressed genes (HEGs) over-employ the synonymous codons that match the more abundant iso-acceptor tRNAs. Bacterial transgene codon randomization experiments report, however, that enrichment with such "translationally optimal" codons has little to no effect on the resultant protein level. By contrast, consistent with the view that ribosomal initiation is rate limiting, synonymous codon usage following the 5' ATG greatly influences protein levels, at least in part by modifying RNA stability. For the design of bacterial transgenes, for simple codon based in silico inference of protein levels and for understanding selection on synonymous mutations, it would be valuable to computationally determine initiation optimality (IO) scores for codons for any given species. One attractive approach is to characterize the 5' codon enrichment of HEGs compared with the most lowly expressed genes, just as translational optimality scores of codons have been similarly defined employing the full gene body. Here we determine the viability of this approach employing a unique opportunity: for Escherichia coli there is both the most extensive protein abundance data for native genes and a unique large-scale transgene codon randomization experiment enabling objective definition of the 5' codons that cause, rather than just correlate with, high protein abundance (that we equate with initiation optimality, broadly defined). Surprisingly, the 5' ends of native genes that specify highly abundant proteins avoid such initiation optimal codons. We find that this is probably owing to conflicting selection pressures particular to native HEGs, including selection favouring low initiation rates, this potentially enabling high efficiency of ribosomal usage and low noise. While the classical HEG enrichment approach does not work, rendering simple prediction of native protein abundance from 5' codon content futile, we report evidence that initiation optimality scores derived from the transgene experiment may hold relevance for in silico transgene design for a broad spectrum of bacteria.

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The aim of this article is to document the incidence and appearances of the pyramidal lobe of the thyroid gland, and discuss the clinical relevance of this entity in sonographic practice. A prospective study was undertaken over a period of 10 months. A total of 416 consecutive patients attending head and neck ultrasound lists were scanned by a single experienced radiologist or an advanced practitioner sonographer. At the time of reporting, the presence of a pyramidal lobe was recorded. The anatomical morphology was classified into five subgroups devised for the purposes of the study. Appearances were documented in both normal and pathological glands. Of the total number of patients scanned, 90 patients were found to have pyramidal lobes, giving an overall incidence of 21%. In all, 51% were found to originate from the right of the isthmus, 46% from the left and 2% from the midline. One patient had two pyramidal lobes. A significant number of patients having routine neck ultrasounds have an incidental finding of a pyramidal lobe. Ultrasound is an effective modality for the demonstration and classification of the pyramidal lobe, as well as identification of pathology. It is important for radiologists to be aware of this normal variation, as it may be the site of primary or recurrent thyroid pathology. Radiologists should report it where relevant to ensure adequate surgical treatment of pathological glands.

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This case illustrates the surgical use of wire localization, a well tried technique from a different field of surgery, in the removal of an ultrasound-detected, impalpable deep lower cervical lymph node in a high-risk patient. A localization needle with an echogenic tip was placed freehand under ultrasound guidance, immediately before surgery. The imaging and marking of the impalpable cervical lymph node resulted in a precise surgical dissection and a reduction in operating time whilst minimizing risks to the patient and staff.

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AIM: To determine the accuracy of multidetector row CT renal angiography in the preoperative evaluation of live kidney donors, and to identify potential pitfalls when reporting. METHODS: Between July 1998 and June 2003, 74 consecutive live renal donors underwent contrast-enhanced multidetector row CT renal angiography before donor nephrectomy. The operative notes and radiological reports of all cases were reviewed retrospectively. Where a significant discrepancy was identified, the archived images were reviewed by two radiologists in the light of the intraoperative findings. RESULTS: A total of 12 discrepancies were identified in 11 of the 74 cases (15%). In the preoperative CT angiography reports, 4 accessory arteries, 6 early-branching renal arteries, 1 duplicated renal vein and 1 accessory ureter were not identified; 9 of these were evident on review, but were not detected at the time of reporting. In 3 cases (1 accessory artery, the duplicated renal vein and the accessory ureter), the anomaly was not visible on review of the CT angiographic data, even with the benefit of hindsight. Surgical feedback during the study period resulted in modifications to CT technique and improved performance. CONCLUSION: In the majority of cases, there was good correlation between preoperative CT renal angiography and operative findings. Most discrepancies were due either to an oversight by the reporting radiologist, or failure to fully appreciate the potential surgical significance of certain findings. Regular surgical feedback plays a valuable role in improving reporting accuracy and maintaining imaging standards.

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A case of spontaneous recurrent haemarthrosis of the knee presenting 3 months after the unicondylar knee replacement is described. Femoral arteriography demonstrated hypertrophy of the saphenous branch of descending genicular artery with a prominent vascular blush in the region of posteromedial aspect of the popliteal fossa thought to represent a hypertrophic vascular mass of synovium. Therapeutic embolisation of the saphenous branch of descending genicular artery was performed using three fibred platinum coils with satisfactory clinical results. Since the embolisation, the haemarthrosis has not recurred. To our knowledge, this therapeutic procedure used to treat recurrent haemarthrosis following unicondylar knee arthroplasty has not been previously described in the literature.

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Self-expanding stents can be used in the palliative management of strictures in the oesophagus, gastric outlet, bile duct and lower gastrointentinal tract [1-4]. Successful stent deployment depends on satisfactory positioning of the assembly device across the stricture. Previous reconstructive surgery may prevent precise endoscopic stent placement. This case report describes percutaneous transthoracic stenting of gastric outlet obstruction due to malignant external compression three years after oesophagectomy. Lyburn, I. (2001). Clinical Radiology56, 82-83.

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Oral motor dysfunction is common in children with neurological impairment. Nutritional advice depends upon an accurate assessment of feeding potential in these cases. Videofluoroscopic assessment of oral motor function has been the accepted "gold standard" investigation for several years but has significant drawbacks, including the time constraints set by the use of ionizing radiation and the problems posed by the cumbersome equipment needed in mimicking the child's normal feeding situation. Ultrasonography (US) has been suggested as an alternative or additional investigation of oral motor function in children with neurological impairment. We prospectively evaluated a scoring system derived from US assessment of oral motor function in 32 malnourished disabled children with feeding problems by comparing them with a group of matched control children without neurological impairment. US imaging provided useful information with regard to the oral cavity and the soft tissue structures, capturing the salient features of tongue/hyoid/palate activity and bolus transport across the tongue and through the hypopharyngeal area. The mean percentage score obtained by US assessment of oral motor function in children with neurological impairment was 54.3 +/- 23.2 and from children without neurological impairment 91.9 +/- 12.7 (p < 0.0001). Scores for the oral and pharyngeal phases of swallowing were also very significantly lower than that in the control group, both phases being equally impaired in the disabled children. This study has demonstrated that a scoring system based on US assessment of different components of oral motor activity detects statistically significant differences in the feeding capabilities of children with neurological impairment.

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High resolution ultrasound is a promising technique in the assessment of laryngeal carcinoma, yet few published studies have appeared concerning its use. We set out to assess if ultrasound could correctly identify the site and size of known lesions, if unsuspected extralaryngeal spread or nodal involvement could be shown and if the results could be used to influence patient management. Fourteen patients with advanced laryngeal cancer (Stage T2 or above) were prospectively evaluated by systematic ultrasound technique, with the sonologist blind to the clinical findings. The results were correlated with clinical assessment and with histopathological findings in six patients who subsequently underwent surgery. Eleven of 14 tumours were visible on ultrasound and the site and size correctly identified in each. Unsuspected extralaryngeal spread was found in four cases increasing the tumour stage to T4; spread to the pre-epiglottic space was also shown in four cases. Nodal staging was correctly raised in two cases and incorrectly in one. Patient management was significantly influenced in 8/14 cases. Ultrasound can identify the majority of laryngeal tumours of Stage T2 and above, and detect extralaryngeal spread. Small tumours may not be visible but in this preliminary study, ultrasound complemented the clinical assessment and was useful in patient management.

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We report a case of a patient with sickle cell disease who presented with mesenteric nodes and pulmonary TB and who subsequently relapsed on triple therapy and presented with disseminated tuberculous osteomyelitis and cervical lymphadenopathy. We emphasize the difficulty of establishing the diagnosis at all stages of presentation.

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One hundred consecutive legs in 74 patients presenting with recurrent varicose veins were investigated by varicography. Forty recurrences occurred at the groin, 80 in the thigh and 97 in the calf. Within each group different anatomical variations were encountered, and we describe the frequency of these and of certain commonly observed combinations. We also suggest possible causes, and discuss how the results of varicography may assist in surgical management.

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The diagnostic quality of intravenous subtraction aorto-iliac arteriograms was assessed in 60 patients randomly allocated to receive either hyoscine butylbromide or glucagon as an inhibitor of bowel peristalsis. The examinations in patients receiving hyoscine butylbromide showed statistically significantly less artefact due to bowel movement than those receiving glucagon. Furthermore, glucagon is 20 times more expensive than hyoscine butylbromide. Neither drug produced significant ECG changes or side effects. We conclude that intravenous hyoscine butylbromide should be used routinely, except where specifically contra-indicated, in all patients undergoing IV-DSA of the aorto-iliac segments.

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