A randomized, controlled trial of narrow-band imaging vs high-definition white light for adenoma detection in patients at high risk of adenomas.

AIM: The study aimed to investigate whether narrow-band imaging (NBI) can enhance adenoma detection in patients at high risk for adenomas compared with high-definition white-light endoscopy (WLE). High risk was defined as three or more adenomas at last colonoscopy, history of colorectal cancer and positive faecal occult blood test. METHOD: Two hundred and fourteen patients were randomized 1:1 to examination with NBI or WLE. The primary outcome measure was the proportion of patients with at least one adenoma detected. Secondary outcomes included total adenomas and polyps, flat adenomas, nonadenomatous polyps, advanced adenomas and patients with three or five or more adenomas. A post hoc analysis to examine the effect of endoscopist and bowel preparation was performed. RESULTS: There was no significant difference in the proportion of patients with at least one adenoma: NBI 73%vs WLE 66%, odds ratio 1.40 (95% CI 0.78-2.52), P = 0.26. There was no significant difference for any secondary outcome measure except for the number of flat adenomas which was significantly greater with NBI [comparison ratio 2.66 (95% CI 1.52-4.63), P = 0.001]. Post hoc analysis indicated that one of three endoscopists performed significantly better for adenoma detection with NBI than WLE [comparison ratio 1.92 (95% CI 1.07-3.44), P = 0.03]. Good bowel preparation was associated with significantly improved adenoma detection with NBI [comparison ratio 1.55 (95% CI 1.01-2.22), P = 0.04] but not with fair preparation. CONCLUSION: Overall NBI did not improve detection compared with WLE in a group of patients at high risk for colorectal adenomas, but specific subgroups might benefit.

Inflammation and Barrett's carcinogenesis.

Barrett's esophagus (BE) is one of the most common premalignant lesions in which normal squamous epithelium of the esophagus is replaced by metaplastic columnar epithelium. Esophageal adenocarcinoma (EA) develops through progression from BE to low- and high-grade dysplasia (LGD/HGD) and to adenocarcinoma. It is widely accepted that inflammation can increase cancer risk, promoting tumor progression. Therefore, inflammation is regarded as the seventh hallmark of cancer. In recent years, the inflammation-cancer connection of Barrett's carcinogenesis has been intensively studied, unraveling genetic abnormalities. Besides genetic alterations, inflammation is also epigenetically linked to loss of protein expression through transcriptional silencing via promoter methylation. Key mediators linking inflammation and Barrett's carcinogenesis include reactive oxygen species (ROS), NFκB, inflammatory cytokines, prostaglandins, and specific microRNAs (miRNAs). Therefore, the decipherment of molecular pathways that contain these and novel inflammatory key mediators is of major importance for diagnosis, therapy, and prognosis. The detailed elucidation of the signaling molecules involved in Barrett's carcinogenesis will be important for the development of pharmaceutical inhibitors. We herein give an overview of the current knowledge of the inflammation-mediated genetic and epigenetic alterations involved in Barrett's carcinogenesis. We highlight the role of oxidative stress and deregulated DNA damage checkpoints besides the NFκB pathway.

[Colorectal polyposis syndrome: a guide to diagnosis]. / Kolorektale Polyposen: Eine Anleitung zur Diagnostik.

Biopsies and resection specimens of the gastrointestinal tract are a major part of the routine workload in many histopathology departments, whereby polypoid lesions are generally the main focus. In addition to distinguishing non-neoplastic from neoplastic polyps and evaluating the grade of dysplasia of the latter, the pathologist should always consider the possibility of an underlying polyposis syndrome. Not only have additional hereditary polyposis syndromes been identified in recent years due to a better understanding of their genetic and epigenetic alterations but also knowledge on well known polyposes has improved, leading to subtyping of various forms according to their different genotype. It is essential for the histopathologist to understand that the conventional histomorphology of individual polyps combined with information on the number and distribution of these lesions and clinical data can provide clues regarding a possible hereditary background. Therefore, the correct histological assessment of polyps is not just about getting the diagnosis right, it might also lead to genetic screening of family members and spouses.

What is the most reliable imaging modality for small colonic polyp characterization? Study of white-light, autofluorescence, and narrow-band imaging.

BACKGROUND AND STUDY AIMS: In vivo optical diagnosis of small colorectal polyps has potential clinical and cost advantages, but requires accuracy and high interobserver agreement for clinically acceptability. We aimed to assess interobserver variability and diagnostic performance of endoscopic imaging modalities in characterizing small colonic polyps. METHODS: High quality still images of 80 polyps < 1 cm were recorded using white-light endoscopy (WLE), autofluorescence imaging (AFI) and narrow-band imaging with and without magnification (NBI and NBImag). All images were assessed for quality, prediction of polyp histology, and vascular pattern intensity (with NBI) by nine experienced colonoscopists (four experts in advanced imaging) from five UK centers. Interobserver agreement (kappa statistic), sensitivity, specificity, and accuracy were calculated compared with histopathological findings. RESULTS: Interobserver agreement for predicting polyp histology using NBImag was significantly better for experts (κ = 0.63, substantial) compared with nonexperts (κ = 0.30, fair; P < 0.001), and was moderate for all colonoscopists with WLE, AFI and NBI. Interobserver agreement for vascular pattern intensity using NBI was 0.69 (substantial) for experts and 0.57 (good) for nonexperts. NBImag had higher sensitivity than WLE (experts, 0.93 vs. 0.68, P < 0.001; nonexperts, 0.90 vs. 0.52, P < 0.001) and higher overall accuracy (experts, 0.76 vs. 0.64, P = 0.003; nonexperts 0.61 vs. 0.40, P < 0.001). AFI had worse accuracy than WLE for both expert colonoscopists (0.53 vs. 0.64, P = 0.02) and nonexperts (0.32 vs. 0.40, P = 0.04). CONCLUSIONS: Of the imaging modalities tested, NBImag appeared to have the best overall accuracy and interobserver agreement, although not adequate for in vivo diagnosis. NBI and AFI did not have better sensitivity, specificity, or accuracy compared with WLE.

Advancements in electrode design and laser techniques for fabricating micro-electrode arrays as part of a retinal prosthesis.

Retinal micro-electrode arrays (MEAs) for a visual prosthesis were fabricated by laser structuring of platinum (Pt) foil and liquid silicone rubber. A new design was created using a folding technique to create a multi-layered array from a single Pt sheet. This method allowed a reduction in both the electrode pitch, and the overall width of the array, while maintaining coplanar connection points for more stable interconnections to other components of the system. The design also included a section which could be rolled to create a cylindrical segment in order to minimise the size of the exit in the sclera after implantation. A picosecond mode-locked 532 nm laser system was investigated as a replacement for the nanosecond Q-switched 1064 nm laser currently in use. Trials showed that the ps system could produce high quality electrode tracks with a minimum pitch of 30 µm, less than 40% the pitch achievable with the ns laser. A method was investigated for the cutting of Pt foils without damaging the underlying silicone by laser machining to a depth just below the thickness of the foil. Initial samples showed promise with full penetration of the foil only occurring at cross points of the laser paths. The ps laser was also used to create roughened surfaces, in order to increase the electrochemical surface area of the electrodes. Surfaces were imaged using a scanning electron microscope, and compared to surfaces roughened with the ns laser. The ps laser was seen to offer a reduction in feature size, as well as an increase in control over the appearance of the electrode surface.

Hypoxia-inducible factor-1alpha and -2alpha are expressed in most rectal cancers but only hypoxia-inducible factor-1alpha is associated with prognosis.

The hypoxia-mediated response of tumours is a major determining factor in growth and metastasis. Understanding tumour biology under hypoxic conditions is crucial for the development of antiangiogenic therapy. Using one of the largest cohorts of rectal adenocarcinomas to date, this study investigated hypoxia-inducible factor-1alpha (HIF-1alpha) and HIF-2alpha protein expression in relation to rectal cancer recurrence and cancer-specific survival. Patients (n=90) who had undergone surgery for rectal adenocarcinoma, with no prior neoadjuvant therapy or metastatic disease, and for whom adequate follow-up data were available were selected. Microvessel density (MVD), HIF-1alpha and HIF-2alpha expressions were assessed immunohistologically with the CD34 antibody for vessel identification and the NB100-131B and NB100-132D3 antibodies for HIF-1alpha and HIF-2alpha, respectively. In a multifactorial analysis, results were correlated with tumour stage, recurrence rate and long-term survival. Microvessel density was higher across T and N stages (P<0.001) and associated with poor survival (hazard ratio (HR)=8.7, P<0.005) and decreased disease-free survival (HR=4.7, P<0.005). hypoxia-inducible factor-1alpha and -2alpha were expressed in >50% of rectal cancers (HIF-1alpha, 54%, 48/90; HIF-2alpha, 64%, 58/90). HIF-1alpha positivity was associated with both TNM stage (P<0.05) and vascular invasion (P<0.005). In contrast, no associations were demonstrated [corrected] between HIF-2alpha [corrected] and any pathological features or [corrected] outcome. The study showed an independent association between HIF-1alpha expression and advanced TNM stage with poor outcome. Our results indicate that HIF-1alpha, but not HIF-2alpha, might be used as a marker of prognosis, in addition to methods currently used, to enhance patient management.

Assessment of microvessel density and carbonic anhydrase-9 (CA-9) expression in rectal cancer.

AIM: The mechanism by which neoplasias respond to hypoxia determines their biological behavior and prognosis. Understanding the biology of tumors under hypoxic conditions is crucial for the development of anti-angiogenic therapy. Using the largest cohort of rectal adenocarcinomas to date, this study aimed to assess microvessel density (MVD) and carbonic anhydrase-9 (CA-9) expression and to correlate the results with recurrence and cancer-specific survival. MATERIALS AND METHODS: Patients (n=101) who underwent surgery for rectal adenocarcinoma without previous neoadjuvant therapy or metastatic disease were selected. MVD and CA-9 expression were assessed immunohistologically by using the CD34 antibody and the MN/CA9 M75 antibody, respectively. In a multifactorial analysis, the results were correlated with tumor stage, recurrence rate, and long-term survival. RESULTS: MVD was higher with increased T- and N-stages (p<0.01) and associated positively with poor survival (hazard ratio (HR) 1.3 per 10 vessel increase, p<0.01). CA-9 was expressed in 73% of cancers. Negative lymph node status correlated with CA-9 positivity (p<0.05), reflected in a higher rate of CA-9 positivity in earlier Dukes' stages (p<0.05). CA-9 positivity across tumor node metastasis (TNM) stages approached significance (Stage I/II: 80% CA-9 positive vs. 20% CA-9 negative; Stage III: 63% CA-9 positive vs. 37% negative, p=0.051). A trend was seen towards better cancer-specific survival in patients with CA-9 positive carcinomas (HR 0.51, p=0.07) on univariate analysis. DISCUSSION: MVD was higher in more advanced T- and N-stages and may be used as a determinant of survival in patients with rectal adenocarcinomas. CA-9 expression was seen more often in earlier Dukes' stages, possibly representing an early tumor hypoxic response. CA-9 expression by adenocarcinoma cells may confer long-term survival advantage in surgically treated rectal cancer.

Narrow band imaging with magnification for the characterization of small and diminutive colonic polyps: pit pattern and vascular pattern intensity.

BACKGROUND AND STUDY AIMS: Narrow band imaging (NBI) can accurately characterize colonic polyps using microvascular appearances. We aimed to assess whether the Kudo pit pattern classification is accurate when used with NBI (without dye-spray), and if microvascular appearances or NBI pit patterns maintain accuracy for polyp characterization at sizes < 10 mm. PATIENTS AND METHODS: 116 polyps < 10 mm in size were detected in 62 patients undergoing surveillance colonoscopy. The polyps were prospectively assessed using NBI and magnification for Kudo pit pattern (III-V neoplastic, I-II non-neoplastic) and vascular pattern intensity (VPI), a measure of microvascular density (strong VPI, neoplastic; normal or weak VPI, non-neoplastic). Sensitivity, specificity, and accuracy were calculated and compared with results from histopathology. RESULTS: The mean polyp size was 3.4 mm (range 1 - 9 mm). Overall, NBI pit pattern sensitivity, specificity, and accuracy were 0.88, 0.91, and 89.6 %, respectively. Equivalent values for VPI were 0.94, 0.89, and 91.4 %. Results were similar when polyps were subdivided into diminutive polyps (size

A comparative study of standard vs. high definition colonoscopy for adenoma and hyperplastic polyp detection with optimized withdrawal technique.

BACKGROUND: Colonoscopy has a known miss rate for polyps and adenomas. High definition (HD) colonoscopes may allow detection of subtle mucosal change, potentially aiding detection of adenomas and hyperplastic polyps. AIM: To compare detection rates between HD and standard definition (SD) colonoscopy. METHODS: Prospective, cohort study with optimized withdrawal technique (withdrawal time >6 min, antispasmodic, position changes, re-examining flexures and folds). One hundred and thirty patients attending for routine colonoscopy were examined with either SD (n = 72) or HD (n = 58) colonoscopes. RESULTS: Groups were well matched. Sixty per cent of patients had at least one adenoma detected with SD vs. 71% with HD, P = 0.20, relative risk (benefit) 1.32 (95% CI 0.85-2.04). Eighty-eight adenomas (mean +/- standard deviation 1.2 +/- 1.4) were detected using SD vs. 93 (1.6 +/- 1.5) with HD, P = 0.12; however more nonflat, diminutive (<6 mm) adenomas were detected with HD, P = 0.03. Twenty-three proximal hyperplastic polyps (0.32 +/- 0.58) were detected with SD vs. 31 (0.53 +/- 0.86) with HD, P = 0.35. Overall prevalence of proximal large (>9 mm) hyperplastic polyps was 7% (0.09 +/- 0.36). CONCLUSIONS: High definition did not lead to a significant increase in adenoma or hyperplastic polyp detection, but may help where comprehensive lesion detection is paramount. High detection rates appear possible with either SD or HD, when using an optimized withdrawal technique.

Can depth of tumour invasion predict lymph node positivity in patients undergoing resection for early rectal cancer? A comparative study between T1 and T2 cancers.

OBJECTIVE: The present study investigated the risk of lymph node metastasis according to the depth of tumour invasion in patients undergoing resection for rectal cancer. METHOD: The histology of patients undergoing oncological resection with regional lymphadenectomy for rectal cancer at St Marks Hospital from 1971 to 1996 was reviewed. Of the total number of 1549 patients, 303 patients with T(1) or T(2) rectal cancers were selected. The tumour type, grade, evidence of vascular invasion, depth of submucosal invasion (classed into 'sm1-3') were evaluated as potential predictors of lymph node positivity using univariate and multi-level logistic regression analysis. RESULTS: Tumour stage was classified as T(1) in 55 (18.2%) and T(2) in 248 (81.2%) patients. The incidence of lymph node metastasis in the T(1) group was 12.7% (7/55), compared to 19% (47/247) in the T(2) group. The node positive and negative groups were similar with regard to patient demographics, although the former contained a significantly higher number of poorly differentiated (P = 0.001) and extramural vascular invasion tumours (P = 0.002). There was no significant difference in the number of patients with sm1-3, or T(2) tumour depths within the lymph node positive and negative groups. On multivariate analysis the presence of extramural vascular invasion (odds ratio = 10.0) and tumour grade (odds ratio for poorly vs well-differentiated = 11.7) were independent predictors of lymph node metastasis. CONCLUSION: Whilst the degree of vascular invasion and poor differentiation of rectal tumours were significant risk factors for lymph node metastasis, depth of submucosal invasion was not. This has important implications for patients with superficial early rectal cancers in whom local excision is being considered.

Narrow band imaging for colonoscopic surveillance in hereditary non-polyposis colorectal cancer.

BACKGROUND: Colonoscopic surveillance for hereditary non-polyposis colorectal cancer (HNPCC) reduces death rates, but early interval cancers still occur, probably due to missed small, aggressive adenomas. Narrow band imaging (NBI), a novel endoscopic technology, highlights superficial mucosal capillaries and improves contrast for adenomas. This study examined whether a second pass with NBI in the proximal colon helped detect additional adenomas in patients with HNPCC. METHODS: 62 patients from HNPCC families (Amsterdam II or genetic criteria) attending for colonoscopic surveillance were examined twice from caecum to sigmoid-descending junction, first with high definition white light and then a second pass with NBI in a back-to-back fashion. All polyps detected were removed for histopathological analysis. RESULTS: At least one adenoma in the proximal colon was detected during the initial white light pass in 17/62 (27%). NBI detected additional adenomas in 17/62 (27%). 26/62 (42%) patients had at least one adenoma detected after both white light and NBI; absolute difference 15% (95% CI 4-25%), p = 0.004 versus white light alone. The total number of adenomas increased from 25 before NBI to 46 after NBI examination, p<0.001. The proportion of flat adenomas detected in the NBI pass, 9/21 (45%), was higher than in the white light pass, 3/25 (12%), p = 0.03. Including white light examination of the sigmoid and rectum, overall 28/62 (45%) patients had at least one adenoma detected. CONCLUSIONS: Use of NBI in the proximal colon for patients undergoing HNPCC surveillance appears to improve adenoma detection, particularly those with a flat morphology. NBI could help reduce interval cancer rates.

Molecular classification and genetic pathways in hyperplastic polyposis syndrome.

Hyperplastic Polyposis (HPPS) is a poorly characterized syndrome that increases colorectal cancer (CRC) risk. We aimed to provide a molecular classification of HPPS. We obtained 282 tumours from 32 putative HPPS patients with >or= 10 hyperplastic polyps (HPs); some patients also had adenomas and CRCs. We found no good evidence of microsatellite instability (MSI) in our samples. The epithelium of HPs was monoclonal. Somatic BRAF mutations occurred in two-thirds of our patients' HPs, and KRAS2 mutations in 10%; both mutations were more common in younger cases. The respective mutation frequencies in a set of 'sporadic' HPs were 18% and 10%. Importantly, the putative HPPS patients generally fell into two readily defined groups, one set whose polyps had BRAF mutations, and another set whose polyps had KRAS2 mutations. The most plausible explanation for this observation is that there exist different forms of inherited predisposition to HPPS, and that these determine whether polyps follow a BRAF or KRAS2 pathway. Most adenomas and CRCs from our putative HPPS patients had 'classical' morphology and few of these lesions had BRAF or KRAS2 mutations. These findings suggest that tumourigenesis in HPPS does not necessarily follow the 'serrated' pathway. Although current definitions of HPPS are sub-optimal, we suggest that diagnosis could benefit from molecular analysis. Specifically, testing BRAF and KRAS2 mutations, and perhaps MSI, in multiple polyps could help to distinguish HPPS from sporadic HPs. We propose a specific model which would have diagnosed five more of our cases as HPPS compared with the WHO clinical criteria.

Genetic determinants modulate susceptibility to pregnancy-associated tumourigenesis in a recombinant line of Min mice.

Min mice provide a good model of human familial adenomatous polyposis. Recently, we have reported on two recombinant inbred lines (I and V) and the location of a modifier (Mom3) close to Apc, which altered polyp numbers in our mice possibly by modifying the frequency of wild-type (WT) allele loss at Apc; mice with severe disease (line V) showed elevated rates of loss. We now show that in line I only, a single pregnancy caused a significant increase in adenoma multiplicity compared with virgin controls (P<0.001) and that an additional pregnancy conferred a similar risk. Pregnancy was linked to both adenoma initiation and enhanced tumour growth in line I mice, and interline crosses indicated that susceptibility to pregnancy-associated adenomas was under genetic control. We found no evidence for the involvement of oestrodial metabolizing genes or the oestrogen receptors (Esr1 and 2) in tumour multiplicity. Importantly, a significantly elevated frequency of WT allele loss at Apc was observed in adenomas from parous mice (line and backcrossed) carrying the line I Min allele relative to equivalent virgin controls (P=0.015). Our results provide the first experimental evidence for genetic determinants controlling pregnancy-associated tumourigenesis; analogous genetic factors may exist in humans.

Disease severity and genetic pathways in attenuated familial adenomatous polyposis vary greatly but depend on the site of the germline mutation.

BACKGROUND: Attenuated familial adenomatous polyposis (AFAP) is associated with germline mutations in the 5', 3', and exon 9 of the adenomatous polyposis coli (APC) gene. These mutations probably encode a limited amount of functional APC protein. METHODS AND RESULTS: We found that colonic polyp number varied greatly among AFAP patients but members of the same family tended to have more similar disease severity. 5' Mutants generally had more polyps than other patients. We analysed somatic APC mutations/loss of heterozygosity (LOH) in 235 tumours from 35 patients (16 families) with a variety of AFAP associated germline mutations. In common with two previous studies of individual kindreds, we found biallelic changes ("third hits") in some polyps. We found that the "third hit" probably initiated tumorigenesis. Somatic mutation spectra were similar in 5' and 3' mutant patients, often resembling classical FAP. In exon 9 mutants, in contrast, "third hits" were more common. Most "third hits" left three 20 amino acid repeats (20AARs) on the germline mutant APC allele, with LOH (or proximal somatic mutation) of the wild-type allele; but some polyps had loss of the germline mutant with mutation leaving one 20AAR on the wild-type allele. CONCLUSIONS: We propose that mutations, such as nt4661insA, that leave three 20AARs are preferentially selected in cis with some AFAP mutations because the residual protein function is near optimal for tumorigenesis. Not all AFAP polyps appear to need "three hits" however. AFAP is phenotypically and genetically heterogeneous. In addition to effects of different germline mutations, modifier genes may be acting on the AFAP phenotype, perhaps influencing the quantity of functional protein produced by the germline mutant allele.

Primary cutaneous mucinous carcinoma of the eyelid in a young male.

Primary cutaneous mucinous carcinoma of the eyelid is an adenocarcinoma of the eccrine glands. It is rare and locally aggressive but the prognosis following local excision, confirmed with tumour-free margins, is good. This tumour is usually described in the elderly. We present the occurrence, clinical and histological features, and management of this tumour in a young male.A 36-year-old male presented with a small cystic right lower lid lesion, which had increased in size and pigmentation over two years. He underwent excision biopsy for diagnostic purposes followed by Moh's micrographic surgical removal. The defect was repaired with an upper eyelid skin graft. A full oncological screen including whole-body computed tomography scan excluded the presence of primary mucinous carcinoma elsewhere and any metastatic spread. There has been no recurrence of tumour 18 months following excision. Ophthalmologists should be aware of the occurrence of this tumour in a younger age group than previously described. Moh's micrographic surgery is the most suitable method of treatment following exclusion of both distant primaries and metastases.

Assessing the benefit of biological valve prostheses: cumulative incidence (actual) vs. Kaplan-Meier (actuarial) analysis.

OBJECTIVE: The standard method of analysing structural valve degeneration (SVD) of biological prostheses is the Kaplan-Meier method. In order to assess SVD with regard to competing risks (e.g. death particularly in elderly patients) cumulative incidence (actual analysis) was compared to Kaplan-Meier (actuarial analysis). METHODS: We retrospectively analysed 257 patients older than 60 years, who underwent mitral valve replacement with different biological prostheses between 1974 and 2000. Reoperation-free survival was determined, both according to Kaplan-Meier and cumulative incidence analysis. RESULTS: For the total group of patients older than 60 years, the 10- and 15-year freedom from reoperation was 79+/-5 and 55+/-8%, respectively, according to Kaplan-Meier and 90+/-2 and 83+/-3% according to cumulative incidence analysis. For patients older than 65 years of age (n=170), Kaplan-Meier analysis revealed 85+/-7% freedom from reoperation at 10 years vs. 94+/-3% according to cumulative incidence analysis. For those between 60 and 65 years of age (n=87), Kaplan-Meier freedom from reoperation was 76+/-7% at 10 years and 48+/-9% at 15 years vs. 86+/-4 and 75+/-5% according to cumulative incidence analysis. CONCLUSIONS: Kaplan-Meier analysis overestimates the 10- and 15-year risk of SVD compared to cumulative incidence analysis, thus underestimating the benefit of biological valve replacement. Cumulative incidence analysis may lead to a more complete evaluation of risk and benefit and thus better patient management.

Femtosecond near-field spectroscopy: carrier relaxation and transport in single quantum wires.

Quasi-two-colour femtosecond pump and probe spectroscopy and near-field scanning optical microscopy are combined to study the carrier dynamics in single semiconductor nanostructures. In temporally, spectrally and spatially resolved measurements with a time resolution of 200 fs and a spatial resolution of 200 nm, the non-linear change in reflectivity of a single quantum wire is mapped in real space and time. The experiments show that carrier relaxation into a single quantum wire occurs on a 100 fs time scale at room temperature. Evidence is given for a transient unipolar electron transport along the wire axis on a picosecond time and 100 nm length scale.

A Piscirickettsia salmonis-like bacterium associated with mortality of white seabass Atractoscion nobilis.

Mortality among hatchery-reared juvenile white seabass Atractoscion nobilis in southern California, USA, was associated with infections by a Piscirickettsia salmonis-like organism (WSPSLO). Infected fish had no consistent external signs other than pale gills, lethargy and impaired swimming behavior. Internally, the kidney and spleen were enlarged, and some fish had livers with multiple pale foci. Smears from infected kidney, liver, and spleen stained with Wright-Giemsa had intracytoplasmic coccoid organisms, often in pairs, that ranged in size from 0.5 to 1.0 microm. Microscopic lesions included multifocal hepatic, renal, and splenic necrosis, and intralesional macrophages often contained the WSPSLO. The bacterium was isolated from infected fish on cell lines of salmonid (CHSE-214) and white seabass (WSBK) origin. The WSPSLO induced plaque formation and destroyed the cell monolayers within 10 to 14 d incubation at temperatures of 15 and 20 degrees C. The bacterium retained infectivity for cell lines up to 14 d at 4 and 13 degrees C, up to 7 d at 20 degrees C, but it was inactivated at 37 and 56 degrees C within 24 and 1 h, respectively. Freezing at -20 degrees C reduced infectivity by 100-fold. Dehydration and resuspension in distilled water completely inactivated the bacterium. In contrast, the WSPSLO retained nearly all of its infectivity for CHSE-214 cells following a 72 h period in seawater at 20 degrees C. Polyclonal rabbit antibodies made to the WSPSLO reacted specifically in indirect fluorescent antibody tests (IFAT) with the bacterium in cell cultures and smears from infected fish tissues. Tissue smears from infected salmon or CHSE-214 cells with P. salmonis reacted weakly with the anti-WSPSLO serum. Conversely, polyclonal anti-P. salmonis serum produced a weakly positive reaction with the WSPSLO from infected CHSE-214 cells. The WSPSLO as propagated in CHSE-214 cells was highly virulent for juvenile coho salmon Oncorhynchus kisutch, inducing 80% mortality within 10 d of intraperitoneal injection of 10(2.5)-50% tissue culture infectious doses per fish. We conclude that the bacterium from white seabass possesses antigenic differences from P. salmonis yet possesses virulence for salmon equal to known strains of P. salmonis.

Aortic valve replacement in children: are we on the right track?

OBJECTIVE: The choice of the ideal prosthesis for aortic valve replacement (AVR) in children is still controversial. Early degeneration of bioprostheses and the potential risks related to anticoagulation in the child have renewed the interest of many surgeons towards the Ross operation. This study concerns our 22-year experience with AVR in children. METHODS: Forty-six children, aged 4 months to 16 years (mean 11.6 years), had AVR between April 1974 and December 1996. Preoperative diagnosis revealed aortic regurgitation (AR) in 25 cases, aortic stenosis (AS) in ten, combined AS and AR in nine and LVOTO in two patients. Of the 46 patients, 26 had 37 previous procedures. Isolated AVR was performed in 19 cases, 27 children underwent 36 concomitant intracardiac procedures. Mechanical prostheses were implanted in 30 children, bioprostheses in eight, aortic homografts in three. Five patients underwent a Ross procedure. RESULTS: There was one hospital death in the latter group (2.1%). Six of seven late deaths occurred in patients who underwent complex intracardiac procedures (15.2%). Reoperation rate was 19.5% (n = 10), differentiating 16.6% for mechanical (5/30 patients) and 50% (4/8 patients) for bioprostheses. The mean follow-up period was 8.01 years, ranging from 0.45 to 21.66 years (304.04 patient-years). There was one hemorrhagic event (2.1%) due to anticoagulation, thrombosis of the mechanical valve occurred in two patients (4.2%). CONCLUSIONS: AVR can be performed with acceptable mortality rate and good long-term results in children. We perform the Ross operation only in selected cases. According to our experience, mechanical prostheses show excellent performances in children with a low incidence of complications related to anticoagulation.