[Surgical treatment of Hashimoto's thyroiditis. Personal experience]

BACKGROUND

To report personal experience in the surgical treatment of Hashimoto's thyroiditis. METHODS. Eight patients (7 females, 1 male, mean age 48 years old) referred to our Institution with diagnosis of Hashimoto's thyroiditis have been studied. All patients were evaluated by determination of serum thyroid hormones and of anti-thyreoglobulin and anti-microsomal antibodies; ultrasound and scintigraphic scans of the gland were performed in all cases and a cytological examination of fine needle aspiration (FNAC) of the nodules was evaluated. Diagnosis of Hashimoto's thyroiditis was suspected on the basis of clinical and laboratory data and was confirmed by cytology and histology on surgical specimens. Preoperative FNAC showed a Hashimoto's thyroiditis with thyroid differentiated carcinoma in 3 cases (37.5%), Hashimoto's thyroiditis in 1 case and chronic thyroiditis in 4 cases (50%). Seven patients underwent surgery, while 1 patient received a medical treatment; we performed 6 total thyroidectomies and 1 hemithyroidectomy. Histology on surgical specimens confirmed the diagnosis of Hashimoto's thyroiditis in all cases; in 3 patients an associated papillary thyroid carcinoma was found.

RESULTS

Postoperative mortality was absent; no major postoperative complications (laryngeal nerve paralysis or permanent hypocalcemia) were recorded. Only 2 mild transient hypocalcemias have been observed.

CONCLUSIONS

Total thyroidectomy is the technique of choice in surgical treatment of Hashimoto's thyroiditis, a self-immune pathology which involves the whole gland and has a high correlation with differentiated thyroid carcinoma (37.5%). Total thyroidectomy warrants a radical and definitive control of the disease, without risk of relapse, with a low incidence of major complications, in experienced hands, and anyway lower than the morbility due to reinterventions.

Transient dynamics of vulcanian explosions and column collapse

Several analytical and numerical eruption models have provided insight into volcanic eruption behaviour, but most address plinian-type eruptions where vent conditions are quasi-steady. Only a few studies have explored the physics of short-duration vulcanian explosions with unsteady vent conditions and blast events. Here we present a technique that links unsteady vent flux of vulcanian explosions to the resulting dispersal of volcanic ejecta, using a numerical, axisymmetric model with multiple particle sizes. We use observational data from well documented explosions in 1997 at the Soufrière Hills volcano in Montserrat, West Indies, to constrain pre-eruptive subsurface initial conditions and to compare with our simulation results. The resulting simulations duplicate many features of the observed explosions, showing transitional behaviour where mass is divided between a buoyant plume and hazardous radial pyroclastic currents fed by a collapsing fountain. We find that leakage of volcanic gas from the conduit through surrounding rocks over a short period (of the order of 10 hours) or retarded exsolution can dictate the style of explosion. Our simulations also reveal the internal plume dynamics and particle-size segregation mechanisms that may occur in such eruptions.

Systemic acute-phase response after laparoscopic and open cholecystectomy

BACKGROUND

Cytokines are the main mediators of inflammation and the response to trauma. The purpose of this study was to compare variations in cytokine levels following laparoscopic cholecystectomy (LC) and mini-laparotomy cholecystectomy (OC), since these two types of operations were considered to be a unique model for examining the role of local tissue injury in postoperative inflammatory reactions.

METHODS

A total of 40 patients were studied. Eighteen of them underwent LC; the remaining 22 were operated on using the open technique. Systemic concentrations of interleukin-6 (IL-6), interleukin-1 (IL-1), tumor necrosis factor (TNF), and C-reactive protein (CRP) were measured before and after the operation. In addition, we compared pre- and postoperative white blood cell (WBC) counts, postoperative body temperature, and length of postoperative hospitalization.

RESULTS

There was no difference between the two groups in IL-1 and TNF response. The rise in plasma IL-6 levels (18.86 +/- 9.61 vs 5.00 +/- 0.0 pg/ml, p < 0.0001) and CRP (8.40 +/- 5.81 vs 1.43 +/- 1.30 mg/dl, p < 0.001) were more marked after open cholecystectomy than after the laparoscopic procedure. There was no correlation between serum CRP concentrations and the other postoperative parameters.

CONCLUSION

The magnitude of the acute-phase response was less pronounced following laparoscopic cholecystectomy, consistent with a reduction in tissue trauma.

Gene expression profiling of B cell chronic lymphocytic leukemia reveals a homogeneous phenotype related to memory B cells

B cell-derived chronic lymphocytic leukemia (B-CLL) represents a common malignancy whose cell derivation and pathogenesis are unknown. Recent studies have shown that >50% of CLLs display hypermutated immunoglobulin variable region (IgV) sequences and a more favorable prognosis, suggesting that they may represent a distinct subset of CLLs which have transited through germinal centers (GCs), the physiologic site of IgV hypermutation. To further investigate the phenotype of CLLs, their cellular derivation and their relationship to normal B cells, we have analyzed their gene expression profiles using oligonucleotide-based DNA chip microarrays representative of approximately 12,000 genes. The results show that CLLs display a common and characteristic gene expression profile that is largely independent of their IgV genotype. Nevertheless, a restricted number of genes (<30) have been identified whose differential expression can distinguish IgV mutated versus unmutated cases and identify them in independent panels of cases. Comparison of CLL profiles with those of purified normal B cell subpopulations indicates that the common CLL profile is more related to memory B cells than to those derived from naive B cells, CD5(+) B cells, and GC centroblasts and centrocytes. Finally, this analysis has identified a subset of genes specifically expressed by CLL cells of potential pathogenetic and clinical relevance.

Analysis of FGFR3 gene mutations in multiple myeloma patients with t(4;14)

The t(4;14)(p16.3;q32) in multiple myeloma (MM) leads to an apparent deregulation of the FGFR3 and WHSC1/MMSET genes. FGFR3 mutations, known to be associated with genetic skeletal disorders, have also been identified in a few cases of MM (mainly cell lines) with t(4;14). We investigated FGFR3 mutations in a series of 53 MM cases; 11 cases with t(4;14) and FGFR3 overexpression were analysed using reverse transcription polymerase chain reaction, while the remaining cases were studied at DNA level. The Arg248Cys mutation, which is associated with some lethal forms of skeletal disorders, was found in one case with t(4;14). Our results indicate that FGFR3 mutations occur in only a small fraction of MM cases with t(4;14).

Deregulated FGFR3 mutants in multiple myeloma cell lines with t(4;14): comparative analysis of Y373C, K650E and the novel G384D mutations

The t(4;14)(p16.3;q32) chromosomal translocation occurs in approximately 20% of multiple myelomas (MM) and leads to the apparent deregulation of two genes located on 4p16.3: the fibroblast growth factor receptor 3 (FGFR3) and the putative transcription factor WHSC1/MMSET. Interestingly, FGFR3 mutations known to be associated with autosomal dominant human skeletal disorders have also been found in some MM cell lines with t(4;14) but their pathogenetic role in MM is still controversial. Since cell lines may represent useful models for investigating the effects of deregulated FGFR3 mutants in MM, we analysed the expression, activation, signaling pathways and oncogenic potential of three mutants identified so far: the Y373C and K650E in the KMS-11 and OPM-2 cell lines respectively, and the novel G384D mutation here identified in the KMS-18 cell line. All of the cell lines present a heterozygous FGFR3 gene mutation and transcribe the mutated allele; unlike KMS-11 and OPM-2 (which express the IIIc isoform), the KMS-18 cell line expresses prevalently the isoform IIIb. We demonstrated that, under serum-starved conditions, KMS-11 and OPM-2 cells express appreciable levels of phosphorylated FGFR3 mutants indicating a constitutive activation of the Y373C and K650E receptors; the addition of the aFGF ligand further increased the level of receptor phosphorylation. Conversely, the FGFR3 mutant in KMS-18 does not seem to be constitutively activated since it was phosphorylated only in the presence of the ligand. In all three MM cell lines, ligand-stimulated FGFR3 mutants activated the MAP kinase signaling pathway but did not apparently involve either the STAT1 or STAT3 cascades. However, when transfected in 293T cells, G384D, like Y373C and K650E, was capable of activating MAPK, STAT1 and STAT3 under serum-starved condition. Finally, a focus formation assay of NIH3T3 cells transfected with FGFR3-expressing plasmid vectors showed that Y373C and K650E (albeit at different levels) but not G384D or the wild-type receptor, can induce transformed foci. Overall, our results support the idea that FGFR3 mutations are graded in terms of their activation capability, thus suggesting that they may play a critical role in the tumor progression of MM patients with t(4;14).

Clinical relevance of microvessel density in laryngeal squamous cell carcinomas

The clinical implications of microvessel density (MVD) in head and neck tumors have not been fully elucidated. We investigated the clinicopathologic correlates and prognostic relevance of MVD in a series of 122 consecutive patients with surgically treated laryngeal squamous cell carcinoma followed-up for a mean of 79 months. MVD was evaluated after CD34 immunostaining in 3 250x microscopic fields representative of the "hot spot" area, and expressed as the mean value of the vessel counts per millimeter squared. The overall median value of the intratumoral vessel count was 69.5/mm(2). In the 20 cases we analyzed, MVD increased significantly from normal to dysplastic mucosa and infiltrating carcinoma (p = 0.0001). Nineteen carcinomas (15.6%) had MVD values that were equal to or lower than the highest MVD value (52.7/mm(2)) observed in normal mucosa samples (in which the median MVD count was 34.5/mm(2), range 16.6-52.7/mm(2), mean 35.1 +/- 11.5/mm(2)) and were therefore considered poorly vascularized. Periodic acid-Schiff (PAS) staining revealed intratumoral PAS-positive connective tissue septa in 13 cases (10.7%). The patients with poorly vascularized tumors showed a tendency toward a better prognosis, but the anatomical site, tumor extension and clinical stage were the only variables significantly associated with disease-free and overall survival.

Translocation T(4;14)(p16.3;q32) is a recurrent genetic lesion in primary amyloidosis

Primary amyloidosis is a fatal disorder characterized by low numbers of clonal plasma cells in the bone marrow and the systemic deposition of light chain fragments in the form of amyloid. The molecular pathobiology of amyloidosis is primarily unknown. Recently, a novel karyotypically undetectable t(4;14)(p16.3;q32) translocation has been identified in approximately 20% of multiple myeloma patients. The translocation leads to the apparent deregulation of two genes located on 4p16.3, the fibroblast growth-factor receptor 3 (FGFR3), and the putative transcription factor multiple myeloma SET domain (MMSET), and to the generation of IGH/MMSET hybrid transcripts. In this study, we investigated the presence of the t(4;14) translocation in 42 AL patients using a reverse transcriptase-polymerase chain reaction assay for the detection of IGH/MMSET transcripts. Chimeric transcripts were found in six patients (14%) and were consistent with a 4p16.3 breakpoint involving intron 3 and juxtaposing IGH regions to exon 4. In three of these cases, hybrid transcripts juxtaposing IGH regions to exon 5 were also observed and were probably the result of an alternative splicing skipping exon 4. Because all of the fusion transcripts (six of six) excluded exon 3, the first translated MMSET exon, only putative 5' truncated MMSET proteins could be generated. In conclusion, our results demonstrate that the t(4;14)(p16.3;q32) translocation is a recurrent genetic lesion in primary amyloidosis.

Brachial plexus injury and obstetrical risk factors

OBJECTIVE

To determine whether known historical risk factors of brachial plexus injury differ between affected neonates and healthy controls.

METHODS

The files of all 62 children with Erb's palsy who were diagnosed after birth were reviewed. The control group consisted of 124 randomly selected uninjured infants born within the same period.

RESULTS

Compared with the control group, the mothers of the neonates with brachial plexus injury were found to be significantly older (32.1+/-5.2 years vs. 28.9+/-5.8 years, P = 0.01), and had a significantly higher incidence of diabetic pregnancy (69% vs. 14.5%, P = 0.001); the infants had a significantly higher mean birth weight (3846+/-576 g vs. 3220+/-582 g, P = 0.0001) and higher incidence of birth weight > or = 4000 g (27% vs. 4.8%, P = 0.0001). Two of the infants in the study group (3.2%) were born by elective cesarean section.

CONCLUSIONS

Brachial plexus injury is associated with several non-predictable or preventable risk factors.

Prediction of Lymph Node Status by Analysis of Prognostic Factors and Possible Indications for Elective Axillary Dissection in T1 Breast Cancers

OBJECTIVE

To identify those patients with T1 breast cancers with lower risk of nodal metastases who can safely be spared axillary dissection.

DESIGN

Retrospective study.

SETTING

University hospital, Italy.

SUBJECTS

Review of clinical records and histopathological slides of 547 patients with T1 breast cancer, operated on between 1984 and 1997.

MAIN OUTCOME MEASURES

Incidence of axillary metastases in relation to age, menopausal status, diameter and grade of tumour, vascular invasion, DNA ploidy, S-phase fraction and hormone receptor state, by univariate and multivariate analysis.

RESULTS

Axillary metastases were present in 159 patients (29%). On univariate analysis, diameter of tumour 10 mm or less (pT1a/pT1b cancers), no vascular invasion, and grade 1 tumour were significantly correlated with a lower risk of nodal metastases, but only vascular invasion (p = 0.0001, odds ratio = 3.1) and diameter of tumour (p = 0.04, odds ratio = 1.6) were independent predictors on multivariate analysis. Among 34 pT1a/pT1b cancers, with low grade of tumour and no vascular invasion, only 2 (6%) had axillary metastases. When only one favourable predictive factor was associated with diameter of tumour of 10 mm or less, the incidence of axillary metastases ranged from 12% for 43 patients with grade 1 cancers to 13% for 76 patients with no vascular invasion.

CONCLUSIONS

Axillary dissection may be avoided in pT1a and pT1b breast cancers (< or = 10 mm), with low grade of tumour or no vascular invasion. T1 breast cancers 10 mm or less in diameter should be treated by a two-step approach, first wide excision of the tumour and then axillary dissection or not depending on pathological examination of the primary tumour.

Initial Experience with Laparoscopic Adjustable Gastric Banding and Pouch Dilatation: Two Cases

BACKGROUND

Late proximal pouch dilatation (LPPD) has occurred occasionally following gastric banding for morbid obesity. At present, laparoscopic conservative resetting and oversuturing of the band is considered the standard procedure for pouch dilatation without any important posterior component.

METHODS

Two cases of LPPD are presented, which occurred in our initial experience with the Lap-Band, corrected via a laparoscopic approach.

RESULTS

The reintervention was necessary in both patients, with conservative laparoscopic repositioning and oversuturing of the band in the first case and laparoscopic substitution of the gastric band in the second. We have not observed further complications, and weight loss has been maintained in a midterm outcome in both cases (30 and 18 months follow-up).

CONCLUSIONS

LPPD can be corrected with a conservative laparoscopic surgical approach, without complications and negative functional effects on mid-term outcome.

Familial medullary thyroid carcinoma (FMTC). Study of one family (treatment criteria)

AIM

The nosology of familial medullary thyroid carcinoma (FMTC) has been described as a distinct pathology, genetically determined and with autosomal dominant transmission with a gene penetrance of almost 100%. The diagnosis of this morbid condition can be made if at least four members of the same family are affected by calcitonin-secreting C-cell carcinoma.

METHODS AND RESULTS

We report the analysis of a family in which FMTC was diagnosed between 1993 and 1998. Of the five patients we confirmed as being affected by FMTC, we were able to perform a prophylactic thyroidectomy in only one case. The high possibility of lymph-node metastasis at the time of clinical diagnosis (52-75%), and the high morbidity and radio-chemo-resistance to adjuvant therapies, indicate total thyroidectomy with central lymph-node dissection.

CONCLUSION

It appears that preventive lymphadenectomy does not substantially improve survival, while pre-clinical diagnosis is of greater importance than surgery in improving survival and preventing recurrence. Total preventive thyroidectomy has been recommended in all carriers of ret genetic defects, even in families at risk with mutations of the 618 or 620 codon, because the penetrance of FMTC approaches 100%, and a 100% accordance between presence of the disease and gene carrier status is reported. This procedure would therefore represent the only possibility of achieving a 100% cure in subjects affected by familial medullary thyroid carcinoma.

IRTA1 and IRTA2, novel immunoglobulin superfamily receptors expressed in B cells and involved in chromosome 1q21 abnormalities in B cell malignancy

Abnormalities of chromosome 1q21 are common in B cell malignancies, but their target genes are largely unknown. By cloning the breakpoints of a (1;14) (q21;q32) chromosomal translocation in a myeloma cell line, we have identified two novel genes, IRTA1 and IRTA2, encoding cell surface receptors homologous to the Fc and inhibitory receptor families. Both genes are selectively expressed in mature B cells: IRTA1 in marginal zone B cells and IRTA2 in centrocytes, marginal zone B cells, and immunoblasts. As a result of the t(1;14), IRTA1 is fused to the immunoglobulin Calpha domain to produce a chimeric IRTA1/Calpha fusion protein. In tumor cell lines with 1q21 abnormalities, IRTA2 expression is deregulated. Thus, IRTA1 and IRTA2 are novel immunoreceptors implicated in B cell development and lymphomagenesis.

BCL-6 mutations are associated with immunoglobulin variable heavy chain mutations in B-cell chronic lymphocytic leukemia

The cell of origin of B-cell chronic lymphocytic leukemia (B-CLL) is still uncertain. Recent studies have indicated that a fraction of B-CLL displays somatically mutated immunoglobulin variable heavy chain (IgV(H)) genes, which suggests an origin from a post-germinal center (GC) B cell. It has been shown that the 5' noncoding region of the BCL-6 proto-oncogene is affected by mutations in normal GC B-lymphocytes and in lymphoid malignancies displaying GC/post-GC phenotype. To further explore the cellular origin of B-CLL, we have analyzed 34 cases for mutations in the BCL-6 5' noncoding region and in the IgV(H) genes. We found somatically mutated IgV(H) genes in 24 (73%) of 33 samples (average frequency, 6.5 x 10(-2)/bp) and BCL-6 mutations in 8 (24%) of 34 cases (average frequency, 0.14 x 10(-2)/bp in the mutated cases). The occurrence of BCL-6 mutations was restricted to those cases displaying IgV(H) mutations. Analysis of BCL-6 protein expression as a marker of GC phenotype showed that, regardless of the presence of IgV(H) or BCL-6 mutations, B-CLLs express BCL-6 at levels clearly below those found in normal or transformed GC B cells. These results indicate that a subset of B-CLL derives from a cell that has been exposed to the somatic hypermutation mechanism and support the hypothesis that BCL-6 mutations result from the same process that targets immunoglobulin genes.

Detection of t(4;14)(p16.3;q32) chromosomal translocation in multiple myeloma by reverse transcription-polymerase chain reaction analysis of IGH-MMSET fusion transcripts

We and others have recently identified a novel recurring t(4;14)(p16.3; q32) translocation in multiple myeloma (MM) that leads to an apparent deregulation of the FGFR3 and WHSC1/MMSET genes. Because the presence of IGH-MMSET hybrid transcripts has been found in MM cell lines with t(4;14), they may represent a specific tumor-associated marker in MM. In this study, we developed a reverse transcription-PCR (RTPCR) assay for detecting chimeric transcripts from all of the 4p16.3 breakpoints identified thus far, and we used it to investigate a representative panel of 53 MM patients and 16 patients with monoclonal gammopathy of uncertain significance; in addition, t(4;14) was investigated in all of the MM patients by means of two-color fluorescence in situ hybridization. IGH-MMSET transcripts were found in 11 of the 53 (20%) MM cases and 1 of 16 (6%) cases of monoclonal gammopathy of uncertain significance. There was complete concordance between the RT-PCR and fluorescence in situ hybridization analyses of the MM cases. The results of this study indicate that RT-PCR is a sensitive and reliable method of detecting t(4;14) and suggest that it may be useful for monitoring the disease in a significant proportion of patients.

Trophoblast giant cells express NF-kappa B2 during early mouse development

To investigate whether transcription factors of the NF-kappa B family could play a role in early mammalian development, we have analyzed the expression of nfkb1, nfkb2, c-Rel, RelA, RelB, and bcl-3 from 6.5- to 10.5-day mouse embryo implantation sites. Our study shows that nfkb2 mRNA and protein are specifically localized in trophoblast giant cells throughout the stages analyzed. Trophoblast giant cells obtained upon in vitro cultures of 7.5-day ectoplacental cones display NF-kappa B DNA-binding activity that is supershifted by the anti-NF-kappa B2 antibody. Trophoblast giant cells are embryo-derived cells that form an interface between embryonic and maternal tissues during early mouse development; they are involved in decidual remodeling and expansion of the embryonic cavity, placenta formation, and possibly avoidance of maternal immune response to the embryo. Our study suggests that NF-kappa B2 could play a role in the modulation of genes expressed in trophoblast giant cells during the course of early embryogenesis, and therefore be relevant for tissue remodeling and morphogenesis of placenta.

Immunohistochemical analysis of cyclin D1 shows deregulated expression in multiple myeloma with the t(11;14)

The t(11;14)(q13;q32) chromosomal translocation, the hallmark of mantle cell lymphoma (MCL), is recurrently found in multiple myelomas (MM) by means of conventional cytogenetics. Unlike MCL, recent molecular studies of MM-derived cell lines with t(11;14) have indicated that the breakpoints are highly dispersed over the 11q13 region; however, the fact that cyclin D1 is generally overexpressed in these cell lines suggests that this gene is the target of the translocation. To evaluate further the involvement of cyclin D1 in MM, we used immunohistochemistry and fluorescence in situ hybridization to investigate cyclin D1 expression and the presence of chromosome 11 abnormalities in a representative panel of 48 MM patients (40 at diagnosis and 8 at relapse). Cyclin D1 overexpression occurred in 12/48 (25%) of cases; combined immunohistochemistry and fluorescence in situ hybridization analyses in 39 patients showed cyclin D1 positivity in all of the cases (7/7) bearing the t(11;14), in two of the 13 cases with trisomy 11, and in one of the 19 cases with no apparent abnormalities of chromosome 11. Our data indicate that the t(11;14) translocation in MM leads to cyclin D1 overexpression and that immunohistochemical analysis may represent a reliable means of identifying this lesion in MM.

BCL10 gene mutations rarely occur in lymphoid malignancies

BCL10, a gene involved in apoptosis signalling, has recently been identified through the cloning of chromosomal breakpoints in extranodal (MALT-type) marginal zone lymphomas carrying the t(1;14)(p22;q32) translocation. BCL10 was also found mutated in these cases as well as in other types of lymphoid and solid tumors, suggesting that its inactivation may play an important pathogenetic role; however, this has been questioned by recent studies showing a lack of somatic mutations in human cancers. We report the mutation analysis of exons 1-3 of the BCL10 gene in DNAs from 228 cases of lymphoid malignancies (30 B cell chronic lymphocytic leukemias, 123 B and 45 T non-Hodgkin's lymphomas and 30 multiple myelomas). Somatic mutations were detected in four cases (approximately 2%): one small lymphocytic, one follicular and two diffuse large cell lymphomas. The mutations were all within exon 3 and have not been previously reported. Our data suggest that BCL10 mutations may play only a limited role in the pathogenesis of lymphoid neoplasms.

Lack of CD95/FAS gene somatic mutations in extranodal, nodal and splenic marginal zone B cell lymphomas

Germline CD95 (also known as FAS, APT1 and APO1) gene mutations have been associated with benign lymphoproliferative diseases and autoimmune processes. Somatic mutations have been reported in human tumours, including lymphomas. Since marginal zone B cell lymphomas usually arise in a background of chronic inflammation, often of autoimmune origin, we searched for CD95 gene mutations in an unselected series of marginal zone B cell lymphomas. The CD95/FAS full coding region, comprising exon-intron junctions, was amplified from genomic DNA by polymerase chain reaction (PCR) in 10 separate reactions. PCR products were analysed by single-strand conformation polymorphism (SSCP) and visualised by silver staining. Bands exhibiting an altered electrophoretic mobility were sequenced. Twenty-seven cases of marginal zone B cell lymphomas of whom fresh or frozen tumour material was available (18 extranodal, five splenic and four nodal) were studied. Previously described silent polymorphisms in exons 7 (C836T) and 3 (T416C) were detected in 42% and in 19% of the cases, respectively. One silent T-to-A substitution at bp 431, within exon 3, was found in one case. Our results did not reveal the presence of CD95 somatic mutations in unselected cases of marginal zone B cell lymphomas. On the basis of our data, we cannot rule out that other genes coding for proteins involved in the CD95-induced apoptotic pathway might be altered. However, this pathway does not seem to play an important role in the pathogenesis of these lymphoma subtypes.

Reduced complexity modeling and reproduction of colored textures

An unsupervised color texture synthesis-by analysis method is described. The texture is reproduced to appear perceptually similar to a given prototype by copying its statistical properties up to the second order. The synthesized texture is obtained at the output of a single-input three-output nonlinear system driven by a realization of a white Gaussian random field. Significant complexity reduction is gained by exploiting the rank deficiency of the cross power spectral density matrix of the color texture samples.

A perceptually lossless, model-based, texture compression technique

In natural scenes, still images as well as sequences, backgrounds, and objects' surfaces usually have a textural structure. Therefore, in order to efficiently code images it is crucial to investigate the texture compression problem. In this paper, a perceptually lossless, synthesis-by-analysis texture coding method is presented. The proposed approach is model based; the parameters of the model consist of a binary excitation signal and the parsimonious representation of the reconstruction filter. The estimated parameters, which allow to one synthesize, at the decoder site, a texture that is perceptually indistinguishable from the original one, are then compressed using a lossless strategy, which is based on a fast binary wavelet transformation specifically tailored to binary images. The proposed method leads to very good perceptual results superior to those of existing techniques.

Variability of polymerase chain reaction detection of the bcl-2-IgH translocation in an international multicentre study

BACKGROUND

The capacity of the polymerase chain reaction (PCR) to detect very low numbers of cells bearing a t(14;18) translocation has led to its application in assessment of the results of treatment for follicular lymphoma, and suggestions that therapy might be guided by molecular studies. To test the reliability of PCR a collaborative study was undertaken to compare results from different laboratories in Europe and North America.

METHODS

Twenty laboratories with records of publication in molecular diagnostics were sent blood from normal donors with varying numbers of t(14;18)-bearing cells added from a cell line with a translocation in the major breakpoint region (MBR) of the bcl-2 gene. Samples contained 1000, 100, 10, 1 or 0 cells per ml of whole blood and were sent blinded in duplicate. PCR methodology varied widely, with the total number of amplification cycles between 30 and 70, and 13 different primers used for the MBR region. Twelve laboratories used nested PCR and eight single round amplification.

RESULTS

The sensitivity of nested and single round PCR was similar at 100 cells/ml but below this the nested method proved significantly more sensitive. The false positive rate was 28%, with 11 samples from 9 laboratories reported as positive when no t(14;18) cells were added. PCR product size and sequence analysis showed that false positives were due to contamination from cell-line DNA rather than background translocations in the donors. There was no significant difference in false positive rates between nested and single round techniques.

CONCLUSION

The polymerase chain reaction to detect bcl-2-IgH rearrangements is presently carried out with widely disparate results. Further effort is required to bring forward a standard PCR protocol which can be re-tested in different laboratories to improve accuracy and reproducibility. The application of quantitative techniques such as real-time PCR may resolve many of the problems presently encountered.