Analysis of minimal residual disease by Ig/TCR gene rearrangements: guidelines for interpretation of real-time quantitative PCR data

Most modern treatment protocols for acute lymphoblastic leukaemia (ALL) include the analysis of minimal residual disease (MRD). To ensure comparable MRD results between different MRD-polymerase chain reaction (PCR) laboratories, standardization and quality control are essential. The European Study Group on MRD detection in ALL (ESG-MRD-ALL), consisting of 30 MRD-PCR laboratories worldwide, has developed guidelines for the interpretation of real-time quantitative PCR-based MRD data. The application of these guidelines ensures identical interpretation of MRD data between different laboratories of the same MRD-based clinical protocol. Furthermore, the ESG-MRD-ALL guidelines will facilitate the comparison of MRD data obtained in different treatment protocols, including those with new drugs.

European Society of Clinical Microbiology and Infectious Diseases: update of the diagnostic guidance document for Clostridium difficile infection

In 2009 the first European Society of Clinical Microbiology and Infectious Diseases (ESCMID) guideline for diagnosing Clostridium difficile infection (CDI) was launched. Since then newer tests for diagnosing CDI have become available, especially nucleic acid amplification tests. The main objectives of this update of the guidance document are to summarize the currently available evidence concerning laboratory diagnosis of CDI and to formulate and revise recommendations to optimize CDI testing. This update is essential to improve the diagnosis of CDI and to improve uniformity in CDI diagnosis for surveillance purposes among Europe. An electronic search for literature concerning the laboratory diagnosis of CDI was performed. Studies evaluating a commercial laboratory test compared to a reference test were also included in a meta-analysis. The commercial tests that were evaluated included enzyme immunoassays (EIAs) detecting glutamate dehydrogenase, EIAs detecting toxins A and B and nucleic acid amplification tests. Recommendations were formulated by an executive committee, and the strength of recommendations and quality of evidence were graded using the Grades of Recommendation Assessment, Development and Evaluation (GRADE) system. No single commercial test can be used as a stand-alone test for diagnosing CDI as a result of inadequate positive predictive values at low CDI prevalence. Therefore, the use of a two-step algorithm is recommended. Samples without free toxin detected by toxins A and B EIA but with positive glutamate dehydrogenase EIA, nucleic acid amplification test or toxigenic culture results need clinical evaluation to discern CDI from asymptomatic carriage.

New insights to the MLL recombinome of acute leukemias

Chromosomal rearrangements of the human MLL gene are associated with high-risk pediatric, adult and therapy-associated acute leukemias. These patients need to be identified, treated appropriately and minimal residual disease was monitored by quantitative PCR techniques. Genomic DNA was isolated from individual acute leukemia patients to identify and characterize chromosomal rearrangements involving the human MLL gene. A total of 760 MLL-rearranged biopsy samples obtained from 384 pediatric and 376 adult leukemia patients were characterized at the molecular level. The distribution of MLL breakpoints for clinical subtypes (acute lymphoblastic leukemia, acute myeloid leukemia, pediatric and adult) and fused translocation partner genes (TPGs) will be presented, including novel MLL fusion genes. Combined data of our study and recently published data revealed 104 different MLL rearrangements of which 64 TPGs are now characterized on the molecular level. Nine TPGs seem to be predominantly involved in genetic recombinations of MLL: AFF1/AF4, MLLT3/AF9, MLLT1/ENL, MLLT10/AF10, MLLT4/AF6, ELL, EPS15/AF1P, MLLT6/AF17 and SEPT6, respectively. Moreover, we describe for the first time the genetic network of reciprocal MLL gene fusions deriving from complex rearrangements.

DNA sequence analysis of the genetic environment of various blaCTX-M genes

OBJECTIVES

Over a 3 year period (2000-2003) 21 Escherichia coli, 5 Klebsiella pneumoniae, 1 Serratia marcescens and 1 Proteus mirabilis producing CTX-M-type beta-lactamase were collected from five different hospitals in Paris, France. This study was conducted to analyse the genetic environment of these 28 bla(CTX-M) genes.

METHODS

Antimicrobial susceptibility testing was performed by the disc diffusion method and MICs of various beta-lactams were determined by an agar dilution method. PCR was used to detect and sequence alleles encoding CTX-M, TEM, SHV and CMY enzymes. The genetic environment was analysed by amplification and direct sequencing using various set of PCR primers or cloning in pBK-CMV.

RESULTS

Sequence analysis revealed that these isolates contained seven different bla(CTX-M) genes: bla(CTX-M-1) (4 strains), bla(CTX-M-2) (2 strains), bla(CTX-M-3) (4 strains), bla(CTX-M-9) (1 strain), bla(CTX-M-14) (5 strains), bla(CTX-M-15) (11 strains), bla(CTX-M-24) (1 strain). TEM-1 was associated with CTX-M-type enzymes in 15 isolates. Two strains produced both CTX-M-15 and SHV-2 or CTX-M-14 and CMY-2. In 25 strains the insertion sequence ISEcp1 was located upstream of the 5' end of the bla(CTX-M) gene. Among these strains, in five isolates, ISEcp1 was disrupted by insertion sequences such as IS26 (in three of them) or IS1 or IS10. Insertion sequence IS903 was found downstream of bla(CTX-M-14) or bla(CTX-M-24). Examination of the other three bla(CTX-M) genes (two bla(CTX-M-2) and one bla(CTX-M-9)) by cloning, sequencing and PCR analysis revealed the presence of complex Class 1 integrons, In35, an integron similar to In60 and a novel integron.

CONCLUSIONS

This work further confirmed the predominant role of ISEcp1 in the mobilization of bla(CTX-M) genes of the CTX-M-1 cluster and the presence of In35, of an integron similar to In60 and a novel complex Class 1 integron.

Dissemination of CTX-M-type beta-lactamases among clinical isolates of Enterobacteriaceae in Paris, France

We analyzed 19 clinical isolates of the family Enterobacteriaceae (16 Escherichia coli isolates and 3 Klebsiella pneumoniae isolates) collected from four different hospitals in Paris, France, from 2000 to 2002. These strains had a particular extended-spectrum cephalosporin resistance profile characterized by a higher level of resistance to cefotaxime and aztreonam than to ceftazidime. The bla(CTX-M) genes encoding these beta-lactamases were involved in this resistance, with a predominance of bla(CTX-M-15). Ten of the 19 isolates produced both TEM-1- and CTX-M-type enzymes. One strain (E. coli TN13) expressed CMY-2, TEM-1, and CTX-M-14. bla(CTX-M) genes were found on large plasmids. In 15 cases the same insertion sequence, ISEcp1, was located upstream of the 5' end of the bla(CTX-M) gene. In one case we identified an insertion sequence designated IS26. Examination of the other three bla(CTX-M) genes by cloning, sequencing, and PCR analysis revealed the presence of a complex sul1-type integron that includes open reading frame ORF513, which carries the bla gene and the surrounding DNA. Five isolates had the same plasmid DNA fingerprint, suggesting clonal dissemination of CTX-M-15-producing strains in the Paris area.

Prognostic value of minimal residual disease in relapsed childhood acute lymphoblastic leukaemia

Molecular monitoring by quantitative PCR techniques of residual leukaemia cells during the first phases of treatment can predict outcome in children with acute lymphoblastic leukaemia. We did a retrospective study of 30 children who had been treated according to the ALL-REZ BFM trials to assess whether amount of minimal residual disease during the first stages of treatment for relapsed acute lymphoblastic leukaemia could predict outcome. In children with minimal residual disease of less than 10(-3) at day 36, probability of event-free survival was 0.86 (95% CI 0.77-0.95), compared with 0 in children with minimal residual disease of 10(-3) or greater (p<0.001). Our results suggest that information about molecular response to treatment can be used to predict long-term outcome in relapsed childhood acute lymphoblastic leukaemia.

The MLL recombinome of acute leukemias

Chromosomal rearrangements of the human MLL gene are a hallmark for aggressive (high-risk) pediatric, adult and therapy-associated acute leukemias. These patients need to be identified in order to subject these patients to appropriate therapy regimen. A recently developed long-distance inverse PCR method was applied to genomic DNA isolated from individual acute leukemia patients in order to identify chromosomal rearrangements of the human MLL gene. We present data of the molecular characterization of 414 samples obtained from 272 pediatric and 142 adult leukemia patients. The precise localization of genomic breakpoints within the MLL gene and the involved translocation partner genes (TPGs) was determined and several new TPGs were identified. The combined data of our study and published data revealed a total of 87 different MLL rearrangements of which 51 TPGs are now characterized at the molecular level. Interestingly, the four most frequently found TPGs (AF4, AF9, ENL and AF10) encode nuclear proteins that are part of a protein network involved in histone H3K79 methylation. Thus, translocations of the MLL gene, by itself coding for a histone H3K4 methyltransferase, are presumably not randomly chosen, rather functionally selected.

Conserved and divergent aspects of terminal patterning in the beetle Tribolium castaneum

To infer similarities and differences in terminal pattern formation in insects, we analyzed several of the key genes of this process in the beetle Tribolium castaneum. We cloned two genes of the terminal pattern cascade, namely tailless (tll) and forkhead (fkh), from Tribolium and studied their expression patterns. In addition, we analyzed the pattern of MAP kinase activation at blastoderm stage as a possible signature for torso-dependent signaling. Further, we analyzed the late expression of the previously cloned Tribolium caudal (Tc-cad) gene. Finally, we used the upstream region of Tc-tll to drive a reporter gene construct in Drosophila. We find that this construct is activated at the terminal regions in Drosophila, suggesting that the torso-dependent pathway is conserved between the species. We show that most of the expression patterns of the genes studied here are similar in Drosophila and Tribolium, suggesting conserved functions. There is, however, one exception, namely the early function of Tc-tll at the posterior pole. In Drosophila, the posterior tll expression is involved in the direct regulation of the target genes of the terminal pathway. In Tribolium, posterior Tc-tll expression occurs only for a short time and ceases before the target genes known from Drosophila are activated. Thus, we infer that Tc-tll does not function as a direct regulator of segmentation genes at the posterior end. It is more likely to be involved in the early specification of a group of "terminal" cells, which begin to differentiate only at a later stage of embryogenesis, when much of the abdominal segmentation process is complete. Thus, there appears to have been a major shift in tll function during the evolutionary transition from short germ to long germ embryogenesis.

The KMT2A recombinome of acute leukemias in 2023

Chromosomal rearrangements of the human KMT2A/MLL gene are associated with de novo as well as therapy-induced infant, pediatric, and adult acute leukemias. Here, we present the data obtained from 3401 acute leukemia patients that have been analyzed between 2003 and 2022. Genomic breakpoints within the KMT2A gene and the involved translocation partner genes (TPGs) and KMT2A-partial tandem duplications (PTDs) were determined. Including the published data from the literature, a total of 107 in-frame KMT2A gene fusions have been identified so far. Further 16 rearrangements were out-of-frame fusions, 18 patients had no partner gene fused to 5'-KMT2A, two patients had a 5'-KMT2A deletion, and one ETV6::RUNX1 patient had an KMT2A insertion at the breakpoint. The seven most frequent TPGs and PTDs account for more than 90% of all recombinations of the KMT2A, 37 occur recurrently and 63 were identified so far only once. This study provides a comprehensive analysis of the KMT2A recombinome in acute leukemia patients. Besides the scientific gain of information, genomic breakpoint sequences of these patients were used to monitor minimal residual disease (MRD). Thus, this work may be directly translated from the bench to the bedside of patients and meet the clinical needs to improve patient survival.

Prevalence and pathogenicity of binary toxin-positive Clostridium difficile strains that do not produce toxins A and B

Clostridium difficile causes antibiotic-associated diarrhoea and pseudomembranous colitis. The main virulence factors of C. difficile are the toxins A (TcdA) and B (TcdB). A third toxin, called binary toxin (CDT), can be detected in 17% to 23% of strains, but its role in human disease has not been clearly defined. We report six independent cases of patients with diarrhoea suspected of having C. difficile infection due to strains from toxinotype XI/PCR ribotype 033 or 033-like, an unusual toxinotype/PCR ribotype positive for CDT but negative for TcdA and TcdB. Four patients were considered truly infected by clinicians and were specifically treated with oral metronidazole. One of the cases was identified during a prevalence study of A(-)B(-)CDT(+) strains. In this study, we screened a French collection of 220 nontoxigenic strains and found only one (0.5%) toxinotype XI/PCR ribotype 033 or 033-like strain. The description of such strains raises the question of the role of binary toxin as a virulence factor and could have implications for laboratory diagnostics that currently rarely include testing for binary toxin.

Activation of the HIF pathway in childhood ALL, prognostic implications of VEGF

Hypoxia-inducible factor 1 (HIF-1) controls angiogenesis and glycolysis, two leading characteristics of solid tumor invasion, metastasis, and lethality. Increased angiogenesis is also found in the bone marrow (BM) of leukemias. Less is known in leukemia about the role of HIF-1 and vascular endothelial growth factor (VEGF), the most important proangiogenic target gene of HIF-1. We show by immunohistochemistry that the oxygen-regulated component of HIF-1 (HIF-1alpha) is overexpressed in clusters of leukemic cells in BM specimens of childhood acute lymphoblastic leukemia (ALL) and absent in biopsies of normal BM. Half the HIF-1alpha-positive ALL biopsies exhibited VEGF coexpression. Among 96 children with relapsed ALL, diagnostic BM aspirates with high VEGF mRNA levels were associated with a significantly lower probability of event-free survival at 3 years (0.31+/-0.08 vs 0.65+/-0.07, P=0.003). Those with poor molecular response to therapy (evaluated by MRD assessment) had 2.2-fold higher VEGF levels than those responding well to chemotherapy (P=0.005). In conclusion, the data demonstrate activation of the HIF pathway in the BM of ALL patients and indicate that the expression of HIF target genes, such as VEGF, play an important role in leukemia progression, therapy response, and outcome.

On the in vivo deformation of the mitral valve anterior leaflet: effects of annular geometry and referential configuration

Alteration of the native mitral valve (MV) shape has been hypothesized to have a profound effect on the local tissue stress distribution, and is potentially linked to limitations in repair durability. The present study was undertaken to elucidate the relation between MV annular shape and central mitral valve anterior leaflet (MVAL) strain history, using flat annuloplasty in an ovine model. In addition, we report for the first time the presence of residual in vivo leaflet strains. In vivo leaflet deformations were measured using sonocrystal transducers sutured to the MVAL (n = 10), with the 3D positions acquired over the full cardiac cycle. In six animals a flat ring was sutured to the annulus and the transducer positions recorded, while in the remaining four the MV was excised from the exsanguinated heart and the stress-free transducer positions obtained. In the central region of the MVAL the peak stretch values, referenced to the minimum left ventricular pressure (LVP), were 1.10 ± 0.01 and 1.31 ± 0.03 (mean ± standard error) in the circumferential and radial directions, respectively. Following flat ring annuloplasty, the central MVAL contracted 28% circumferentially and elongated 16% radially at minimum LVP, and the circumferential direction was under a negative strain state during the entire cardiac cycle. After valve excision from the exsanguinated heart, the MVAL contracted significantly (18 and 30% in the circumferential and radial directions, respectively), indicating the presence of substantial in vivo residual strains. While the physiological function of the residual strains (and their associated stresses) are at present unknown, accounting for their presence is clearly necessary for accurate computational simulations of MV function. Moreover, we demonstrated that changes in annular geometry dramatically alter valvular functional strains in vivo. As levels of homeostatic strains are related to tissue remodeling and homeostasis, our results suggest that surgically introduced alterations in MV shape could lead to the long term MV mechanobiological and microstructural alterations that could ultimately affect MV repair durability.

Guidance document for prevention of Clostridium difficile infection in acute healthcare settings

SCOPE

Clostridium difficile infection (CDI) is the most important infective cause of healthcare-associated diarrhoea in high income countries and one of the most important healthcare-associated pathogens in both Europe and the United States. It is associated with high morbidity and mortality resulting in both societal and financial burden. A significant proportion of this burden is potentially preventable by a combination of targeted infection prevention and control measures and antimicrobial stewardship. The aim of this guidance document is to provide an update on recommendations for prevention of CDI in acute care settings to provide guidance to those responsible for institutional infection prevention and control programmes.

METHODS

An expert group was set up by the European society of clinical microbiology and infectious diseases (ESCMID) Study Group for C. difficile (ESGCD), which performed a systematic review of the literature on prevention of CDI in adults hospitalized in acute care settings and derived respective recommendations according to the GRADE approach. Recommendations are stratified for both outbreak and endemic settings.

QUESTIONS ADDRESSED BY THE GUIDELINE AND RECOMMENDATIONS

This guidance document provides thirty-six statements on strategies to prevent CDI in acute care settings, including 18 strong recommendations. No recommendation was provided for three questions.

Identification and characterization of an Epstein-Barr virus nuclear antigen 2-responsive cis element in the bidirectional promoter region of latent membrane protein and terminal protein 2 genes

Epstein-Barr virus (EBV) transforms resting B cells in vitro very efficiently. The nuclear viral protein EBV nuclear antigen 2 (EBNA2) is absolutely required for this process and also acts as a transcriptional activator of cellular and viral genes. As shown previously, EBNA2 transactivates the promoters of the viral latent membrane proteins. It interacts indirectly with an EBNA2-responsive cis element of the terminal protein 1 (TP1) promoter. To identify the sequences mediating EBNA2 transactivation of the bidirectional promoter region driving expression of the latent membrane proteins LMP and TP2 in opposite directions, we assayed the effects of EBNA2 on the activities of promoter deletion and site-directed mutants of TP2 and LMP promoter luciferase reporter gene constructs by cotransfections into EBNA2-negative Burkitt's lymphoma cells. We were able to delineate an 80-bp EBNA2-responsive region (EBNA2RE) between -232 and -152 relative to the LMP RNA start site which could also mediate EBNA2-dependent activation on a heterologous promoter. Sequences of 20 and 32 bp located at the 5' and 3' ends, respectively, of the EBNA2RE were both essential for EBNA2 responsiveness. Full transactivation of the LMP and TP2 promoters seemed to require 20 bp of 5' adjacent sequences in addition to the 80-bp element. Electrophoretic mobility shift assays revealed specific protein-DNA complexes formed at the EBNA2RE. Oligonucleotides from -181 to -152 and -166 to -132 relative to the LMP RNA start site visualized one B-cell and one B-cell-plus-HL60-specific retarded protein-DNA complex, respectively. Additionally, an oligonucleotide from -253 to -210 revealed two specific protein-DNA complexes with nuclear extracts from different B and non-B cells, suggesting also the binding of ubiquitously expressed proteins on the EBNA2RE. Thus, these experiments defined a 80-bp cis element sufficient for conferring EBNA2 inducibility and demonstrated specific interactions of cellular proteins at DNA sequences within the EBNA2RE, which are critical for transactivation by EBNA2.

Identification of a genetically defined ultra-high-risk group in relapsed pediatric T-lymphoblastic leukemia

In the search for genes that define critical steps of relapse in pediatric T-cell acute lymphoblastic leukemia (T-ALL) and can serve as prognostic markers, we performed targeted sequencing of 313 leukemia-related genes in 214 patients: 67 samples collected at the time of relapse and 147 at initial diagnosis. As relapse-specific genetic events, we identified activating mutations in NT5C2 (P=0.0001, Fisher's exact test), inactivation of TP53 (P=0.0007, Fisher's exact test) and duplication of chr17:q11.2-24.3 (P=0.0068, Fisher's exact test) in 32/67 of T-ALL relapse samples. Alterations of TP53 were frequently homozygous events, which significantly correlated with higher rates of copy number alterations in other genes compared with wild-type TP53 (P=0.0004, Mann–Whitney's test). We subsequently focused on mutations with prognostic impact and identified genes governing DNA integrity (TP53, n=8; USP7, n=4; MSH6, n=4), having key roles in the RAS signaling pathway (KRAS, NRAS, n=8), as well as IL7R (n=4) and CNOT3 (n=4) to be exclusively mutated in fatal relapses. These markers recognize 24/49 patients with a second event. In 17 of these patients with mostly refractory relapse and dire need for efficient treatment, we identified candidate targets for personalized therapy with p53 reactivating compounds, MEK inhibitors or JAK/STAT-inhibitors that may be incorporated in future treatment strategies.

Durability of left ventricular assist devices: Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) 2006 to 2011

OBJECTIVES

The present study compared the interval until device exchange or death from pump-related failure in patients with pulsatile versus continuous flow left ventricular assist devices.

METHODS

Data from Interagency Registry for Mechanically Assisted Circulatory Support (June 23, 2006, to March 31, 2011) compared the durability of implanted pulsatile and continuous flow left ventricular assist devices. The durability issues included pump replacement for infection, thrombosis-hemolysis, driveline failure, or pump drive unit failure, and death from driveline or pump drive unit failure.

RESULTS

A total of 3302 left ventricular assist devices were implanted (486 pulsatile, 2816 continuous flow) and 98 pump exchanges or deaths from durability issues (46 pulsatile, 52 continuous flow; 3% of implants). The interval to device issue was greater for the continuous flow than for the pulsatile devices (P < .001). A comparisons of the causes for pump exchange or pump-related death showed (1) greater freedom from pump failure in the continuous flow compared with the pulsatile left ventricular assist devices (10 events/2816 continuous flow implants vs 39 events/486 pulsatile implants; P < .0001); (2) similar exchange or pump-related death for driveline failure (1/486 pulsatile vs 7/2816 continuous flow; P = .82); (3) similar exchange or pump-related death for thrombosis-hemolysis (2/486 pulsatile vs 28/2816 continuous flow; P = .25); and (4) fewer exchanges or pump-related deaths from infection in continuous flow left ventricular assist devices (4/486 pulsatile vs 7/2816 continuous flow; P = .034). Competing outcomes analysis corroborated this finding, with 54% of continuous flow versus 23% of pulsatile patients alive and receiving support at 12 months after implantation.

CONCLUSIONS

The Analysis of Interagency Registry for Mechanically Assisted Circulatory Support data showed greater durability for continuous flow than for pulsatile left ventricular assist devices. Even longer durations of support can be expected if pump durability continues to improve.

Tissue-specific induction of mutations by streptozotocin in vivo

Streptozotocin has been reported to induce DNA damage in mouse liver although malignant tumors were not induced in this organ. DNA damage had not yet been monitored in the mouse kidney which was the tumor target organ in two mouse studies. In order to elucidate target organ specificity of genotoxicity and of tumorigenesis, we investigated the induction of DNA damage (microgel electrophoresis assay) and mutations (LacI transgenic mouse mutation assay) in the liver and kidney of male C57BL/6 mice. Our results show that the microgel electrophoresis assay was more sensitive and revealed the genotoxic potential of streptozotocin at lower doses than the mutation assay. It was, however, less specific in that DNA damage was induced both in target and non-target tissues of carcinogenesis at a similar potency. In contrast, the mutation analysis revealed the kidney to be more sensitive when the induced mutation frequencies are expressed as a multiple of the respective spontaneous rates. We conclude, therefore, that the carcinogenic organotropy of streptozotocin correlates better with its tissue-specific mutagenicity than with its pattern of inducing DNA damage when the two in vivo genotoxicity assays mentioned above are used. A combined use of the microgel electrophoresis assay and the transgenic mouse mutation assay is proposed for investigations of tissue-specific genotoxicity.

On the biomechanical role of glycosaminoglycans in the aortic heart valve leaflet

While the role of collagen and elastin fibrous components in heart valve valvular biomechanics has been extensively investigated, the biomechanical role of the glycosaminoglycan (GAG) gelatinous-like material phase remains unclear. In the present study, we investigated the biomechanical role of GAGs in porcine aortic valve (AV) leaflets under tension utilizing enzymatic removal. Tissue specimens were removed from the belly region of porcine AVs and subsequently treated with either an enzyme solution for GAG removal or a control (buffer with no enzyme) solution. A dual stress level test methodology was used to determine the effects at low and high (physiological) stress levels. In addition, planar biaxial tests were conducted both on-axis (i.e. aligned to the circumferential and radial axes) and at 45° off-axis to induce maximum shear, to explore the effects of augmented fiber rotations on the fiber-fiber interactions. Changes in hysteresis were used as the primary metric of GAG functional assessment. A simulation of the low-force experimental setup was also conducted to clarify the internal stress system and provide viscoelastic model parameters for this loading range. Results indicated that under planar tension the removal of GAGs had no measureable affect extensional mechanical properties (either on- or 45° off-axis), including peak stretch, hysteresis and creep. Interestingly, in the low-force range, hysteresis was markedly reduced, from 35.96±2.65% in control group to 25.00±1.64% (p<0.001) as a result of GAG removal. Collectively, these results suggest that GAGs do not play a direct role in modulating the time-dependent tensile properties of valvular tissues. Rather, they appear to be strongly connected with fiber-fiber and fiber-matrix interactions at low force levels. Thus, we speculate that GAGs may be important in providing a damping mechanism to reduce leaflet flutter when the leaflet is not under high tensile stress.

Potential of LightCycler technology for quantification of minimal residual disease in childhood acute lymphoblastic leukemia

A certain quantity of residual leukemic cells at several time points during chemotherapy of childhood acute lymphoblastic leukemia (ALL) was proved to predict outcome. Future childhood ALL treatment will take minimal residual disease (MRD) into consideration for stratification aiming at an individualization of chemotherapeutic regimens. Recently, the first quantitative real-time PCR assay for MRD detection was described using T cell receptor and immunoglobulin gene rearrangements as clonal markers. Quantitative real-time PCR was performed with TaqMan technology. Here, we present for the first time the potential of LightCycler real-time PCR technology to quantify MRD. We compare and assess different approaches for real-time PCR quantification of leukemic cells, based either on clone-specific primers and general fluorescence detection with SYBR Green, TaqMan probe or hybridization probes, or based on general PCR amplification and clone-specific detection with hybridization probes. MRD quantification with LightCycler real-time PCR technology is a sensitive, specific and incomparably rapid method that needs no post-PCR handling, hence eliminating contamination risk and saving time. Working towards the establishment of MRD quantification in routine diagnostics and towards treatment strategies based on these results, LightCycler quantitative PCR seems to be a promising new technique that makes results immediately available for treatment decisions.

Rupture of the diaphragm caused by blunt trauma

Our experience with 27 patients who sustained traumatic laceration of the diaphragm caused by blunt forces is described. Automobile accident were the most frequent cause of rupture and young adult males the most vulnerable. The left hemidiaphragm is most frequently injured, but with sufficient force significant tears in the right hemidiaphragm will occur. Most of these patients sustained injury to multiple organ systems. The preoperative diagnosis of traumatic diaphragmatic hernia is based on a high index of suspicion, close and continued observation of the patient, and correct interpretation of roentgenograms of the chest. The mortality rate is high, owing to the magnitude of the injuries.