Small angle neutron scattering on an absolute intensity scale and the internal surface of diatom frustules from three species of differing morphologies.

The internal nanostructure of the diatoms Cyclotella meneghiniana, Seminavis robusta and Achnanthes subsessilis was investigated using small angle neutron scattering (SANS) to examine thin biosilica samples, consisting of isotropic (powder) from their isolated cell walls. The interpretation of SANS data was assisted by several other measurements. The N2 adsorption, interpreted within the Branuer-Emmet-Teller isotherm, yielded the specific surface area of the material. Fourier transform infrared (FTIR) and Raman spectroscopy indicates that the isolated material is amorphous silica with small amounts of organic cell wall materials acting as a filling material between the silica particles. A two-phase (air and amorphous silica) model was used to interpret small angle neutron scattering data. After correction for instrumental resolution, the measurements on two SANS instruments covered an extended range of scattering vectors 0.0011 nm(-1) < q < 5.6 nm(-1), giving an almost continuous SANS curve over a range of scattering vectors, q, on an absolute scale of intensity for each sample. Each of the samples gave a characteristic scattering curve where log (intensity) versus log (q) has a -4 dependence, with other features superimposed. In the high-q regime, departure from this behaviour was observed at a length-scales equivalent to the proposed unitary silica particle. The limiting Porod scattering law was used to determine the specific area per unit of volume of each sample illuminated by the neutron beam. The Porod behaviour, and divergence from this behaviour, is discussed in terms of various structural features and the proposed mechanisms for the bio-assembly of unitary silica particles in frustules.

Thermal fluctuations of haemoglobin from different species: adaptation to temperature via conformational dynamics.

Thermodynamic stability, configurational motions and internal forces of haemoglobin (Hb) of three endotherms (platypus, Ornithorhynchus anatinus; domestic chicken, Gallus gallus domesticus and human, Homo sapiens) and an ectotherm (salt water crocodile, Crocodylus porosus) were investigated using circular dichroism, incoherent elastic neutron scattering and coarse-grained Brownian dynamics simulations. The experimental results from Hb solutions revealed a direct correlation between protein resilience, melting temperature and average body temperature of the different species on the 0.1 ns time scale. Molecular forces appeared to be adapted to permit conformational fluctuations with a root mean square displacement close to 1.2 Å at the corresponding average body temperature of the endotherms. Strong forces within crocodile Hb maintain the amplitudes of motion within a narrow limit over the entire temperature range in which the animal lives. In fully hydrated powder samples of human and chicken, Hb mean square displacements and effective force constants on the 1 ns time scale showed no differences over the whole temperature range from 10 to 300 K, in contrast to the solution case. A complementary result of the study, therefore, is that one hydration layer is not sufficient to activate all conformational fluctuations of Hb in the pico- to nanosecond time scale which might be relevant for biological function. Coarse-grained Brownian dynamics simulations permitted to explore residue-specific effects. They indicated that temperature sensing of human and chicken Hb occurs mainly at residues lining internal cavities in the ß-subunits.

Early and late complications after pancreatic necrosectomy.

BACKGROUND: Surgery for pancreatic necrosis is associated with a high morbidity and mortality. The aim of this study was to review the incidence of early and late complications after pancreatic necrosectomy in a large contemporary series of patients. METHODS: The clinical outcomes of 88 patients who underwent pancreatic necrosectomy between 1997 and 2003 were reviewed. RESULTS: The median age was 55.5 (range, 18-85) years, 54 (61%) were males, 68 (77%) had primary pancreatic infection, 71 (81%) had >50% necrosis, and the median admission Acute Physiology and Chronic Health Evaluation score was 9 (range, 1-21). Median time to surgery was 31 (range, 1-161) days; 47 patients underwent minimally invasive necrosectomy and 41 open necrosectomy; 81 (92%) of patients had complications postoperatively, and 25 (28%) died. Multiorgan failure (odds ratio = 3.4, P = .05) and hemorrhage (odds ratio = 6.1, P = .03) were the only independent predictors of mortality. During a median follow-up of 28.9 months, 39 (62%) of 63 surviving patients had one or more late complications: biliary stricture in 4 (6%), pseudocyst in 5 (8%), pancreatic fistula in 8 (13%), gastrointestinal fistula in 1 (2%), delayed collections in 3 (5%), and incisional hernia in 1 (2%); intervention was required in 10 (16%) patients. Sixteen (25%) of 63 surviving patients developed exocrine insufficiency, and 19 (33%) of 58 without prior diabetes mellitus developed endocrine insufficiency. CONCLUSIONS: Almost all patients undergoing necrosectomy developed significant early or late complications or both. Multiorgan failure and postoperative hemorrhage were independent predictors of mortality. Long-term follow-up was important because 62% developed complications, and 16% of those with complications required surgical or endoscopic intervention.

Positron emission tomography does not add to computed tomography for the diagnosis and staging of pancreatic cancer.

BACKGROUND: Positron emission tomography (PET) has been proposed for pancreatic cancer diagnosis and staging. METHODS: 112 patients with suspected pancreatic cancer underwent 18F-fluoro-2-deoxy-D-glucose gamma camera PET and computed tomography (CT), of whom 62 also had laparoscopic ultrasonography and 70 underwent abdominal exploration for potential resection. The final diagnosis was malignancy in 78 and benign disease in 34 patients (25 with chronic pancreatitis). RESULTS: The diagnostic sensitivity and specificity for PET were 73 and 60% compared to 89 and 65% for CT respectively (Cohen's kappa = 0.59). In 30 patients CT was equivocal with cancer in 14 and benign disease in 16. PET correctly diagnosed 13 of these patients (cancer in 6 and benign disease in 7), interpreted 4 as equivocal (cancer in 3 and benign disease in 1) but was incorrect in the remaining 13 patients (cancer in 5 and benign disease in 8). The sensitivity and specificity for detecting small volume metastatic disease were 20 and 94% for CT and 22 and 91% for PET, respectively. CONCLUSION: PET had a similar accuracy to that of CT for imaging pancreatic cancer but it did not provide any additional information in patients with equivocal CT findings and currently would seem of little benefit for the staging of pancreatic cancer.

Fungal infection but not type of bacterial infection is associated with a high mortality in primary and secondary infected pancreatic necrosis.

INTRODUCTION: Knowledge of microbiology in the prognosis of patients with necrotizing pancreatitis is incomplete. AIM: This study compared outcomes based on primary and secondary infection after surgery for pancreatic necrosis. METHOD: From a limited prospective database of pancreatic necrosectomy, a retrospective case note review was performed (October 1996 to April 2003). RESULTS: 55 of 73 patients had infected pancreatic necrosis at the first necrosectomy. 25 of 47 patients had resistant bacteria to prophylactic antibiotics (n = 21) or did not receive prophylactic antibiotics (n = 4), but this was not associated with a higher mortality (9 of 25) compared to those with sensitive organisms (4 of 22). Patients with fungal infection (n = 6) had a higher initial median (95% CI) APACHE II score compared to those without (11 (9-13) verus 8.5 (7-10), p = 0.027). Five of six patients with fungal infection died compared to 13 of 47 who did not (p = 0.014). With the inclusion of secondary infections 21 (32%) of 66 patients had fungal infection with 10 (48%) deaths compared to 11 (24%) of 45 patients without fungal infection (p = 0.047). CONCLUSION: Whether associated with primary or secondary infected pancreatic necrosis, fungal but not bacterial infection was associated with a high mortality.

Pancreatic hamartoma.

Pancreatic hamartoma is a rare benign lesion and may be mistaken for a malignancy, as demonstrated by two cases. The first case was a 29-year-old man who presented with a 7-month history of intermittent upper abdominal pain, nausea and vomiting and a 15-kg weight loss. CT and MRI revealed a mass in the head of the pancreas. The second case was a 62-year-old man who presented with a 2-year history of intermittent abdominal pain, vomiting and a 25-kg weight loss. Although positron emission tomography was normal, CT revealed thickening of the duodenal wall and endoluminal ultrasonography revealed a tumour in the head of the pancreas. Both patients recovered from uneventful Kausch-Whipple pancreatoduodenectomy (in the first patient, it was pylorus-preserving), and in each case the histological diagnosis was hamartoma. Pancreatic hamartoma can present with vague, non-specific symptoms which, despite modern diagnostic tools, can be difficult to diagnose. Surgical resection with histopathological examination is required to confirm the diagnosis.

Influence of opioid use on surgical and long-term outcome after resection for chronic pancreatitis.

BACKGROUND: The outcome of pancreatic resection for chronic pancreatitis in patients with preoperative opioid use is not well described. METHODS: During 1997 to 2003, 112 of 231 patients referred with chronic pancreatitis underwent pancreatic resection. The outcome of patients who had preoperative opioid use (N=46) was compared with those without (N=66). RESULTS: Patients who used opioids presented at a younger age and had a younger age of symptom onset, longer symptom duration, more hospitalizations, a higher frequency of diabetes mellitus, a higher pain score, and more restriction in daily activity (all P<.05). Twenty-one (46%) patients with opioid use had a total pancreatectomy compared with 9 (14%) without opioid use (P=.0002); the 21 patients also had a higher frequency of postoperative bleeding and early reoperation (8 vs 2, P<.02; 11 vs 3, P=.003, respectively). Mortality and overall morbidity was not significantly different between the 2 groups (4 vs 1, 27 vs 34, respectively). Pain scores improved postoperatively in both groups (P=.001) and was not significantly different between the groups from 12 months onward (median follow-up of 12 months, range, 3-60 months). Twenty percent of patients who used preoperative opioids however reverted to morphine use compared with 6% of patients who had not used opioids. CONCLUSIONS: Patients who used opioids had more advanced disease than patients without opioid use, accounting for part of the postoperative morbidity. Although long-term pain relief was comparable between the 2 groups, maintaining opioid withdrawal was more problematic in those with preoperative opioid use. Earlier referral for resection may be warranted in this group of patients.

Hereditary pancreatic endocrine tumours.

The two main types of hereditary pancreatic neuroendocrine tumours are found in multiple endocrine neoplasia type 1 (MEN-1) and von Hippel-Lindau disease (VHL), but also in the rarer disorders of neurofibromatosis type 1 and tuberous sclerosis. This review considers the major advances that have been made in genetic diagnosis, tumour localization, medical and surgical treatment and palliation with systemic chemotherapy and radionuclides. With the exception of the insulinoma syndrome, all of the various hormone excess syndromes of MEN-1 can be treated medically. The role of surgery however remains controversial ranging from no intervention (except enucleation for insulinoma), intervening for tumours diagnosed only by biochemical criteria, intervening in those tumours only detected radiologically (1-2 cm in diameter) or intervening only if the tumour diameter is > 3 cm in diameter. The extent of surgery is also controversial, although radical lymphadenectomy is generally recommended. Pancreatic tumours associated with VHL are usually non-functioning and tumours of at least 2 cm in diameter should be resected. Practice guidelines recommend that screening in patients with MEN-1 should commence at the age of 5 years for insulinoma and at the age of 20 years for other pancreatic neuroendocrine tumours and variously at 10-20 years of age for pancreatic tumours in patients with VHL. The evidence is increasing that the life span of patients may be significantly improved with surgical intervention, mandating the widespread use of tumour surveillance and multidisciplinary team management.

Shear-induced alignment of self-associated hemoglobin in human erythrocytes: small angle neutron scattering studies.

Small angle neutron scattering (SANS) was performed on suspensions of actively metabolising human erythrocytes in the constant shear field induced by a Couette cell. The SANS pattern recorded on a two-dimensional detector was a function of the shear rate; at zero shear, the SANS pattern had radial symmetry around the direction of the beam. The radial average of the SANS pattern consisted of a broad intensity maximum superimposed on a decay. The intensity maximum at q = 0.1 A(-1) was attributed to isotropically oriented self-associated complexes of the tetrameric oxygen transport protein hemoglobin inside the erythrocytes. A flow curve of the cell suspension was used to identify at what shear rate a suspension of uniaxially oriented ellipsoidal cells is produced. The radial symmetry of the SANS patterns persisted until the shear rate was sufficient to produce a suspension of uniaxially oriented ellipsoidal cells. Again, an intensity maximum was present in directions parallel and orthogonal to the shear axis, but this intensity maximum was superimposed upon quite different intensity decays in each direction from that of the primary neutron beam. The angular range of the SANS instrument was limited, however the results from shear-induced structural changes is consistent with a model that involves hemoglobin complexes that are aligned with respect to the plasma membranes of the elongated cells.

Minimally invasive retroperitoneal pancreatic necrosectomy.

INTRODUCTION: Open surgery for pancreatic necrosis is associated with considerable morbidity and mortality. We report the results of a recently developed minimally invasive technique that we adopted in 1998. METHODS: A descriptive explanation of the approach is given together with the results of a retrospective analysis of patients who underwent a minimally invasive retroperitoneal pancreatic necrosectomy (MIRP) between August 1998 and April 2002. PATIENTS: There were 24 patients with a median (range) age of 61 (29-75) years. The initial median (range) APACHE II score was 8 (2-21). All patients had infected pancreatic necrosis with at least 50% pancreatic necrosis. In three patients it was not possible to complete the first MIRP because of technical reasons. RESULTS: A total of 88 procedures were performed with a median (range) of 4 (0-8) per patient. Twenty-one (88%) patients developed 36 complications during the course of their illness. Five patients required an additional open procedure: 2 for subsequent distant collections, 2 for bleeding and 1 for persisting sepsis and a distant abscess. Six (25%) patients who had MIRP died. The median (range) post-operative hospital stay was 51 (5-200) days. CONCLUSIONS: MIRP is a new technique that has shown promising results, and could be preferable to open pancreatic necrosectomy in selected patients. However, unresolved issues remain to be overcome and the exact role of MIRP in the management of pancreatic necrosis has yet to be defined.

Radiology and the Cancer Services Collaborative--an opportunity awaits.

The principles and methodologies used by the Cancer Services Collaborative (CSC) are particularly relevant for radiology departments. A radiology project looking at the provision of barium enema examinations is used to highlight how the principles can be applied to a radiology department. Advice on how to access available CSC literature is offered. The CSC principles and methodologies are an important part of the NHS modernization agenda, and offer an exciting vehicle to improve patient care. It is important that radiologists understand the opportunities offered and the challenges posed by the modernization agenda.

Endorectal magnetic resonance imaging of a rectal duplication cyst.

A case of a duplication cyst of the rectum is presented. This case highlights the potential role of endoluminal magnetic resonance imaging in the diagnosis of this uncommon condition. Alternative imaging modalities and differential diagnoses are discussed.

Unravelling the helix--a physician's guide to spiral computed tomography.

The introduction of spiral technology to computed tomography (CT) scanners in the late 1980s has revolutionised the field of CT. Spiral CT offers definite practical benefits over conventional scanners and has expanded the role of CT through the development of new scanning techniques. CT scanning now rivals magnetic resonance imaging in many areas of investigation, and for some situations is the clear investigation of choice. This review is aimed at those clinicians who have access to spiral scanning services but wish to have a greater understanding of the technique and its clinical applications. The concept of spiral CT, and the differences between spiral and conventional scanning are discussed. The various clinical applications of the technique are illustrated.

CT scanning of the paranasal sinuses--the effect of reducing mAs.

High quality CT scans are required prior to fibreoptic endoscopic sinus surgery (FESS) surgery and in many institutions such scans are performed using a high mAs technique. Consequently, the investigation imparts a radiation dose to the patient and in particular to the eye. Such a radiation dose is a possible source of morbidity. We believe that the mAs, and consequently the radiation dose, can be considerably reduced without affecting scan quality. The present study compares the quality of sinus CT scans performed at two mAs values, 40 and 60. Scan quality was assessed in terms of the ability to visualize clearly important anatomical structures and in terms of overall perceived quality. We show that mAs values as low as 40 can be used without adversely affecting the diagnostic quality of the examination.