Beam implementation in a nonorthogonal coordinate system: application to the scattering from random rough surfaces

The C method is known to be one of the most efficient and versatile tools established for modeling diffraction gratings. Its main advantage is the use of a coordinate system in which the boundary conditions apply naturally and are, ipso facto, greatly simplified. In the context of scattering from random rough surfaces, we propose an extension of this method in order to treat the problem of diffraction of an arbitrary incident beam from a perfectly conducting (PEC) rough surface. For that, we were led to revisit some numerical aspects that simplify the implementation and improve the resulting codes.

Behaviour of Campylobacter jejuni in experimentally contaminated bottled natural mineral water

AIMS

The main objective of the present study was to estimate the survival of microaerophilic Campylobacter jejuni in filtered natural mineral water at 4 degrees C and 25 degrees C. The influence of the presence of biodegradable organic matter was tested, assuming that the bacterial contamination of a bottled natural mineral water could be associated with contamination by organic matter.

METHODS AND RESULTS

Washed Campylobacter cultures were inoculated in natural mineral water and sterile natural mineral water, and incubated in the dark at 4 degrees C and 25 degrees C. The effect of temperature, the biodegradable organic matter added, incubation atmosphere and autochthonous microflora were tested on the cultivability of Camp. jejuni.

CONCLUSIONS

The survival of Camp. jejuni in natural mineral water was better at 4 degrees C than at 25 degrees C, and the presence of organic matter led to a deceleration in the loss of cultivability and to the multiplication of Camp. jejuni in natural mineral water.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study highlighted the fact that, in the event of dual contamination of a bottled natural mineral water (Campylobacter and biodegradable organic matter), the pathogen could survive (and even grow) for a relatively long time, especially at low temperature and in spite of the presence of oxygen.

Localization of light in a lamellar structure with left-handed medium : the Light Wheel

A rigorous analysis of the contra-directional coupling between a left-handed waveguide and a right-handed waveguide shows that such a structure supports twin modes with complex (conjugate) propagation constants. Using evanescent coupling or a source inside one of the waveguides, the twin modes can be excited. In this case, light rotates inside the lamellar structure forming an exotic mode : the light wheel. The structure can finally be seen as a new type of cavity and can be used for beam reshaping.

Involvement of NR2A- or NR2B-containing N-methyl-D-aspartate receptors in the potentiation of cortical layer 5 pyramidal neurone inputs depends on the developmental stage

In the cortex, N-methyl-D-aspartate receptors (NMDARs) play a critical role in the control of synaptic plasticity processes. We have previously shown in rat visual cortex that the application of a high-frequency stimulation (HFS) protocol used to induce long-term potentiation in layer 2/3 leads to a parallel potentiation of excitatory and inhibitory inputs received by cortical layer 5 pyramidal neurones without changing the excitation/inhibition balance of the pyramidal neurone, indicating a homeostatic control of this parameter. We show here that the blockade of NMDARs of the neuronal network prevents the potentiation of excitatory and inhibitory inputs, and this result leaves open to question the role of the NMDAR isoform involved in the induction of long-term potentiation, which is actually being strongly debated. In postnatal day (P)18-23 rat cortical slices, the blockade of synaptic NR2B-containing NMDARs prevents the induction of the potentiation induced by the HFS protocol, whereas the blockade of NR2A-containing NMDARs reduced the potentiation itself. In P29-P32 cortical slices, the specific activation of NR2A-containing receptors fully ensures the potentiation of excitatory and inhibitory inputs. These results constitute the first report of a functional shift in subunit composition of NMDARs during the critical period (P12-P36), which explains the relative contribution of both NR2B- and NR2A-containing NMDARs in synaptic plasticity processes. These effects of the HFS protocol are mediated by the activation of synaptic NMDARs but our results also indicate that the homeostatic control of the excitation/inhibition balance is independent of NMDAR activation and is due to specialized recurrent interactions between excitatory and inhibitory networks.

The genotype 3-specific hepatitis C virus core protein residue phenylalanine 164 increases steatosis in an in vitro cellular model

BACKGROUND AND AIMS

The prevalence and severity of liver steatosis are higher in patients infected with genotype 3 hepatitis C virus (HCV) than in patients infected with other genotypes. HCV core protein is known to affect lipid metabolism, inducing lipid droplet accumulation both in vitro and in vivo. An in vitro cellular model was used to investigate whether an HCV core protein with residues specific to genotype 3 increased this phenomenon.

METHODS

Sequence comparisons for HCV core protein domain II, which is known to interact with lipid droplets, identified the phenylalanine (F) residue at position 164 as the only residue specific to genotype 3. The area covered by lipid droplets in sections of cells producing a wild-type genotype 1a HCV core protein was compared with that in cells producing a Y164F mutant protein.

RESULTS

Cumulative lipid droplet area was significantly greater in sections of cells producing the Y164F mutant HCV core protein than in cells producing the wild-type protein (p<0.001). The frequency of cell sections containing more than 3 mum(2) of lipid droplets, in particular, was higher for the mutant than for the wild-type protein.

CONCLUSION

The data provide a molecular explanation for HCV genotype 3-specific lipid accumulation. This difference between genotypes may be due to phenylalanine having a higher affinity for lipids than tyrosine (Y). These observations provide useful information for further studies of the mechanisms involved in HCV-induced steatosis.

What factors influence healthcare professionals' opinion and attitude regarding information for patients about hospital infection?

Although informing patients about medical risks is said to decrease the number of malpractice claims, most inpatients receive no information about hospital infection. Using a self-administered questionnaire, we surveyed 1270 healthcare workers randomly selected from 22 French hospitals to assess their opinion on information for patients about hospital infection risks, and their practice of informing patients with, or without, hospital infection. The influence of healthcare worker characteristics on opinion and practice was assessed using logistic regression. Response rate was 87.2%. Although 85.4% supported giving more information, only 17.0% routinely informed non-infected patients and 31.6% informed infected patients about infection. Attitudes were influenced by healthcare worker characteristics and environmental factors. Knowledge of obligations influenced practice when informing non-infected patients, but not those with hospital-acquired infection. Further research is needed to help healthcare professionals improve risk communication and disclosure of hospital infection.

Increased incidence of disease transformation and development of MDS/AML in Waldenstrom's macroglobulinemia (WM) patients treated with nucleoside analogues

8018

Background: WM is an indolent B-cell lymphoma. NA are widely used in the treatment of WM, and are considered as appropriate first line agents for the treatment of WM (Gertz et al, Semin Oncol 2003; Treon et al, Blood 2006). Increased incidences of disease transformation and development of MDS/AML have been observed among patients with indolent B-cell malignancies receiving NA. We therefore sought to delineate the incidence for these events in a large population of WM patients treated at our institution. Methods: 326 previously treated patients with the consensus panel definition of WM, who received treatment with (n=173) or without (n=153) a NA were included in this analysis. Baseline characteristics between NA and non-NA treated patients were not significantly different and were as follows: median age 59 years; male/female ratio 1.4; median B2M 2.9 mg/L; serum IgM 3,000 mg/dL; BM involvement 40%; Hct 34%; WBC 5,100/ul, and PLT count 243,000/ul. For patients receiving NA, treatment consisted of either fludarabine (n=117; 68%), cladribine (n=48; 27%) or both (n=8; 5%). For non-NA treated patients, therapy included chlorambucil, rituximab, CVP, CHOP, thalidomide, and cyclophosphamide alone or in combination with rituximab, and alemtuzumab. Median follow-up of patients was 64 (range 10–270) months. Results: Among NA treated patients, 10 (5.7%) patients had transformation to an aggressive NHL (to DLBCL) (n=7; 4%) or developed MDS/AML (n=3; 1.7%). Disease transformation and development of MDS/AML occurred at a median time of 48 (range 7–114), and 48 (range 38–52) months following NA treatment, respectively. In contrast, among non-NA treated patients, only 1 patient demonstrated disease transformation (to DLBCL) at 10 months and no patients developed AML/MDS (p=0.025). Conclusions: These data demonstrate an increased incidence of disease transformation and development of MDS/AML among WM patients treated with NA.

No significant financial relationships to disclose.

Human osteosarcoma cells express functional receptor activator of nuclear factor-kappa B

RANK, RANK ligand (RANKL) and osteoprotegerin (OPG) are the key regulators of bone metabolism, both in normal and pathological conditions. Previous data have demonstrated that human osteosarcoma biopsies express RANKL as well as OPG, and functional RANK is expressed in a murine osteosarcoma cell line. As RANK expression in human osteosarcoma remains controversial, the aim of the present study was to analyse its expression in vitro in human osteosarcoma cell lines, ex vivo using pathological tissues, and then to determine its functionality in terms of signal transduction pathways modulated by RANKL. RT-PCR analysis and immunohistochemistry experiments revealed that RANK is expressed at both transcriptional and protein levels in MNNG/HOS, Saos-2 and MG-63 human osteosarcoma cell lines, in contrast to the U-2 OS osteosarcoma cell line and human osteoblasts, which were negative. RANK was also expressed in 57% of osteosarcoma biopsies. Furthermore, western blot experiments clearly demonstrated the functionality of RANK. Thus, RANKL significantly induced the phosphorylation of ERK1/2, p38 and IkappaB in RANK-positive osteosarcoma cells. This study is the first report of functional RANK expression in human osteosarcoma cells: this strengthens the involvement of the RANK-RANKL-OPG axis in primary bone tumour biology and identifies novel therapeutic approaches targeting RANK-positive osteosarcoma.

Functional compartmentalization following induction of long-term graft survival with pregraft donor-specific transfusion

Long-term survival is achieved in rat recipients by pre-graft donor-specific blood transfusion. We characterized the immune compartments in long-term survivors and analyzed them for capacity to transfer tolerance and protect against chronic rejection. Splenocytes and spleen T cells from treated recipients transferred long-term graft survival to 100% of secondary recipients. In contrast, blood transferred graft survival to only 50% of recipients whereas blood T cells had no effect. An unaltered TCR repertoire, an increase in suppressive CD4+CD25+ T cells, a decrease in antidonor T-cell proliferative response and normal perforin-granzyme levels were the hallmarks of the spleen T cells. Blood T cells were characterized by a strongly altered CD8+ repertoire, normal CD4+CD25+ T cell number with unchanged antidonor T-cell proliferative response, an activated T-cell phenotype and an increase in perforin-granzyme levels. However, following the transfer of blood or spleen cells into secondary recipients, all grafts displayed chronic rejection. These findings provide evidence that distinct compartments play critical roles in DST recipients. Regulatory cells do not accumulate in blood, which appears to be a reservoir for cytotoxic T cells. Spleen T cells, which display a regulatory-like profile and transfer graft survival, are not able to prevent chronic rejection.

Engineering cartilage with human nasal chondrocytes and a silanized hydroxypropyl methylcellulose hydrogel

Tissue engineering strategies, based on developing three-dimensional scaffolds capable of transferring autologous chondrogenic cells, holds promise for the restoration of damaged cartilage. In this study, the authors aimed at determining whether a recently developed silanized hydroxypropyl methylcellulose (Si-HPMC) hydrogel can be a suitable scaffold for human nasal chondrocytes (HNC)-based cartilage engineering. Methyltetrazolium salt assay and cell counting experiments first revealed that Si-HPMC enabled the proliferation of HNC. Cell tracker green staining further demonstrated that HNC were able to form nodular structures in this three-dimensional scaffold. HNC phenotype was then assessed by RT-PCR analysis of type II collagen and aggrecan expression as well as alcian blue staining of extracellular matrix. Our data indicated that Si-HPMC allowed the maintenance and the recovery of a chondrocytic phenotype. The ability of constructs HNC/Si-HPMC to form a cartilaginous tissue in vivo was finally investigated after 3 weeks of implantation in subcutaneous pockets of nude mice. Histological examination of the engineered constructs revealed the formation of a cartilage-like tissue with an extracellular matrix containing glycosaminoglycans and type II collagen. The whole of these results demonstrate that Si-HPMC hydrogel associated to HNC is a convenient approach for cartilage tissue engineering.

Clinical operational tolerance after kidney transplantation

Induction of allograft-specific tolerance and the detection of a "tolerance" state in recipients under immunosuppression with long-term stable graft function are major challenges in transplantation. Clinical "operational tolerance," defined as stable and acceptable graft function without immunosuppression for years, is a rare event. There is no report on the clinical history of such patients. In this article, we report on the medical history of 10 kidney recipients who display an immunosuppressive drug-free "operational tolerance" for 9.4 +/- 5.2 years. Clinical factors that may favor such a tolerant state are underlined. Firstly, most of the patients interrupted immunosuppression over a long time period (until 4 years), which mimics the procedure of intentional immunosuppression weaning following liver transplantation. Secondly, donor age was younger (median 25 years) than the one of the general transplanted population, suggesting that graft quality is one of the conditions favoring "operational tolerance." Moreover, the "operationally tolerant" recipients may be 'low responders' to blood transfusions (PRA 6 +/- 5.4%, six blood transfusions). We also show that "operational tolerance" occurs in the presence of anti-donor class II antibodies, as assessed in two patients. Finally, two patients degraded their renal function 9 to 13 years after treatment withdrawal, however only one presented histological lesions of chronic rejection.

High-performance liquid chromatographic assay with UV detection for measurement of dihydrouracil/uracil ratio in plasma

A rapid, robust and sensitive HPLC method for analysis of uracil (U) and dihydrouracil (UH2) in plasma was developed using solid phase extraction and ultraviolet detection. Separation was achieved with a SymmetryShield RP18 column and an Atlantis dC18 column using a 10 mM potassium phosphate buffer as mobile phase. Compounds were eluted within 15 min without interference. Recovery was 80.4 and 80.6% for U and UH2. Calibration curves were linear from 2.5 to 80 ng/mL for U and 6.75 to 200 ng/mL for UH2. The LLQ was, respectively, 2.5 ng/mL for U, and 6.75 ng/mL for UH2. Within-run and between-run precision were less than 5.94% and inaccuracy did not exceed 7.80%. The overall procedure has been applied to correlate UH2/U ratio with dihydropyrimidine dehydrogenase activity in 165 cancer patients.

Phosphohistone H3 labelling for histoprognostic grading of breast adenocarcinomas and computer-assisted determination of mitotic index

BACKGROUND

Microscopic evaluation of mitotic figures is a routine procedure in the assessment of the histoprognostic grade of tumours. Nevertheless, their count may be fraught with difficulties. As histone H3 phosphorylation at serine 10 is closely linked to chromosomal condensation, a new monoclonal antibody directed to phosphorylated histone H3 (PPH3) was recently proposed to detect mitotic cells.

AIM

To test the reliability of this antibody in detecting and counting mitotic figures in sections of breast adenocarcinomas, because of the importance of mitotic count in histoprognostic grading.

METHODS

The pattern of PPH3 staining in formalin-fixed paraffin wax-embedded tissues, including normal tissues and a series of 39 breast adenocarcinomas, was examined. A new computer-assisted method was also developed for determining the mitotic index.

RESULTS AND CONCLUSIONS

In all tissues tested, PPH3-labelled mitotic figures were easily detected, allowing a rapid identification of the area of highest mitotic activity. In breast carcinomas, a strong correlation was observed between PPH3-stained and haematoxylin and eosin-stained mitotic counts (r = 0.86, p<0.0001). Counting of prophase nuclei that coexpress cyclin B1, a marker of the G2/M phase, was possible by PPH3 staining; its accuracy led us to reconsider the tumour grade in three cases. Finally, an automatic computer-assisted method was designed for assessing mitotic index with confocal microscopy and image-analysis software.

[Elderly abuse]

Elderly abuse is still far too much ignored. A better understanding of this problem allows us to a better answer proposing an appropriate coping as well as a preventing action. This article describe this society phenomenon with is worth looking at by every health professional. Identifying such situation as elderly abuse is a very tricky process, anyway, some risk factors bound to the victims, the authors or environment can lead us to watch situations that can need to be surrounded. Elderly abuse includes physical, psychological, financial, civilian, medical abuse and neglecting. One of the reasons of the taboo around the problem is the victim's silence connected to their fears and feelings and also the circle's attitude. An acute perception of this phenomenon can lead to adequate prevention and coping. In these conditions, the " Centre d'Aide aux Personnes Agées Maltraitées" (CAPAM) can develop its listening attitude as well as pluridisciplinar team actions.

The transcription factor RFX3 directs nodal cilium development and left-right asymmetry specification

There are five members of the RFX family of transcription factors in mammals. While RFX5 plays a well-defined role in the immune system, the functions of RFX1 to RFX4 remain largely unknown. We have generated mice with a deletion of the Rfx3 gene. RFX3-deficient mice exhibit frequent left-right (LR) asymmetry defects leading to a high rate of embryonic lethality and situs inversus in surviving adults. In vertebrates, specification of the LR body axis is controlled by monocilia in the embryonic node, and defects in nodal cilia consequently result in abnormal LR patterning. Consistent with this, Rfx3 is expressed in ciliated cells of the node and RFX3-deficient mice exhibit a pronounced defect in nodal cilia. In contrast to the case for wild-type embryos, for which we document for the first time a twofold increase in the length of nodal cilia during development, the cilia are present but remain markedly stunted in mutant embryos. Finally, we show that RFX3 regulates the expression of D2lic, the mouse orthologue of a Caenorhabditis elegans gene that is implicated in intraflagellar transport, a process required for the assembly and maintenance of cilia. In conclusion, RFX3 is essential for the differentiation of nodal monocilia and hence for LR body axis determination.

Metatarsal giant cell tumors and giant cell reparative granuloma are similar entities

Light and electron microscopic investigations and studies of the resorption ability in vitro of giant cells were done in two patients with giant cell osteolytic lesions of metatarsal bone. Giant cells harvested from both patients were similar in morphologic features and ability to resorb dentin. After other diagnoses of osteolytic lesions of metatarsal bone were ruled out, one lesion was considered a giant cell reparative granuloma and the other a true giant cell tumor of bone. Clinical, radiologic, ultrastructural, functional studies, and data in the literature, indicated that giant cell reparative granuloma only can be differentiated from giant cell tumor by younger age at diagnosis and the occurrence of giant cell clusters. All other features (cortical erosion, high rate of recurrence, hemorrhage areas, predominant intercellular collagenous substance) are characteristic of both lesions. If these two giant cell lesions are different entities, more accurate means are needed to distinguish them.

Light transmission by subwavelength square coaxial aperture arrays in metallic films

Using the Fourier modal method, we study the enhanced transmission exhibited by arrays of square coaxial apertures in a metallic film. The calculated transmission spectrum is in good agreement with FDTD calculations. We show that the enhanced transmission can be explained when we consider a few guided modes of a coaxial waveguide.

Is t(14;18)(q32;q21) a constant finding in follicular lymphoma? An interphase FISH study on 63 patients

The translocation (14;18)(q32;q21) is the hallmark of follicular lymphoma (FL). However, conventional cytogenetics and PCR techniques fail to detect it in at least 10% of cases. In order to evaluate the true incidence of this translocation in FL, we analyzed 63 patients with FL, and 17 patients with diffuse large cell lymphoma (DLCL) corresponding to suspected FL transformations using interphase fluorescence in situ hybridization (FISH). Colocalized signals related to the translocation were observed in 19-92% of cells (median = 51%), corresponding to positivity over the threshold in all (63/63) cases. Similarly, 16/17 possibly secondary DLCL displayed the translocation. Although some cytogenetic changes might be missed by this FISH assay (such as rare insertion, or translocations with other chromosomal partners), our results stress t(14;18)(q32;q21) as an almost constant finding in FL. Our sensitive interphase FISH assay should be of great value to define FL more accurately, namely in patients included into therapeutic trials. Furthermore, this approach could be of interest in (re)defining some types of FL, especially the grade 3 FL which frequently lack t(14;18).

On-line measurement of texture, thickness and plastic strain ratio using laser-ultrasound resonance spectroscopy

Laser-ultrasound resonance spectroscopy, a non-contact ultrasonic technique, was used to determine reliably and rapidly the crystallographic texture, the average plastic strain ratio, and the thickness of sheet metal on the production line. As with laser-ultrasonics, a short laser pulse is used to generate a wide-band pulse of ultrasound and a laser interferometer is used for its detection. In this paper, a large number of echoes are collected and analyzed together using Fourier techniques to measure the natural resonance frequencies in the thickness of the sheet. One longitudinal and two shear resonance frequencies were measured together with their harmonics. From these frequencies, two crystallographic orientation distribution coefficients, W(400) and W(420), are obtained, as well as a highly accurate measurement of the sheet thickness that is corrected for changes in ultrasonic velocity caused by texture variations. Using these coefficients, the average and in-plane twofold and fourfold variations of the plastic strain ratio, respectively r delta(2)r, and delta(4)r, can be evaluated. These parameters are indications of the formability of metals sheets, which is of industrial interest. Measurements on 1 mm thick, low carbon steel sheets have shown the following measurement accuracies: r to within +/-0.08, delta(2)r, and delta(4)r to within +/-0.1, and thickness to better than +/-1 microm. On-line tests at LTV Steel Company showed that the sensitivity of the apparatus is sufficient to detect systematic variations in texture along the length of similar production coils and that the on-line repeatability for r was of order +/-0.02.

Polydnavirus replication: the EP1 segment of the parasitoid wasp Cotesia congregata is amplified within a larger precursor molecule

Polydnaviruses are unique viruses: they are essential for successful parasitism by tens of thousands of species of parasitoid wasps. These viruses are obligatorily associated with the wasps and are injected into the host during oviposition. Molecular analyses have shown that each virus sequence in the segmented polydnavirus genome is present in the wasp DNA in two forms: a circular form found in the virus particles and an integrated form found in the wasp chromosomes. Recent studies performed on polydnaviruses from braconid wasps suggested that the circular forms were excised from the chromosome. The different forms of the EP1 circle of Cotesia congregata polydnavirus during the pupal-adult development of the parasitoid wasp were analysed. Unexpectedly, an off-size fragment formerly used to diagnose the integration of the EP1 sequence into wasp genomic DNA was found to be amplified in female wasps undergoing virus replication. The EP1 sequence is amplified within a larger molecule comprising at least two virus segments. The amplified molecule is different from the EP1 chromosomally integrated form and is not encapsidated into virus particles. These findings shed light on a new step towards EP1 circle production: the amplification of virus sequences preceding individual circle excision.

Integrin up-regulation in chronic liver disease: relationship with inflammation and fibrosis in chronic hepatitis C

In 94 patients with chronic hepatitis C, the pattern of integrin expression was correlated with firstly, the histological activity index, necro-inflammatory grade, and stage of fibrosis; secondly, the expression of inflammatory markers including ICAM-1; and thirdly, the extent and intensity of laminin deposition in the perisinusoidal matrix. Immunohistochemical results were evaluated according to a semi-quantitative scoring system or by image analysis. Increased beta1 expression was observed in 88.2% of cases. The expression of alpha1 and alpha5 was increased in 55% and 58.5% of cases, respectively. alpha6 chain was detected in 78.7% of cases. There were no statistically significant differences in integrin expression level according to Knodell's score, inflammatory grade, or stage of fibrosis. ICAM-1 expression was higher in patients with high scores for beta1 expression, but the differences were not statistically significant. There were significantly more patients with high scores for beta1 expression among those with continuous perisinusoidal deposition of laminin. Moreover, a close statistical correlation was observed between alpha6 induction and perisinusoidal laminin deposition (p<0.001). The results suggest that integrin up-regulation in chronic hepatitis C is more closely related to the fibrotic process than to the inflammatory lesions. This reinforces the idea that integrin induction in chronic liver disease is part of a coordinated process involved in the progression of liver fibrosis.

Apolipoprotein B48 glycosylation in abetalipoproteinemia and Anderson's disease

BACKGROUND & AIMS

Abetalipoproteinemia and Anderson's disease are hereditary lipid malabsorption syndromes. In abetalipoproteinemia, lipoprotein assembly is defective because of mutations in the microsomal triglyceride transfer protein. Here, we evaluated the intracellular transport of apolipoprotein B48 to localize the defect in Anderson's disease.

METHODS

Asparagine-linked oligosaccharide processing of apolipoprotein B48 in normal and affected individuals was determined by the endoglycosidase H and F sensitivities of the protein after metabolic labeling of intestinal explants in organ culture. Cell ultrastructure was evaluated with electron microscopy.

RESULTS

In Anderson's disease as in normal individuals, there was a time-dependent transformation of high mannose endoglycosidase H-sensitive oligosaccharides, of endoplasmic reticulum origin, to complex endoglycosidase H-resistant oligosaccharides, added in the Golgi network. In contrast, despite the translocation of apolipoprotein B48 into the endoplasmic reticulum in patients with abetalipoproteinemia and in biopsies treated with Brefeldin A, which blocks anterograde transport between the endoplasmic reticulum and the Golgi network, there was no transformation of endoglycosidase H-sensitive oligosaccharides.

CONCLUSIONS

In abetalipoproteinemia and Anderson's disease, apolipoprotein B48 is completely translocated into the endoplasmic reticulum, but only in Anderson's disease is the protein transported to the Golgi apparatus. This suggests that Anderson's disease is caused by a post-Golgi cargo-specific secretion defect.

High-performance liquid chromatographic assay with ultraviolet detection for quantification of dihydrofluorouracil in human lymphocytes: application to measurement of dihydropyrimidine dehydrogenase activity

The anticancer drug 5-fluorouracil (5FU) undergoes extensive biotransformation to 5-dihydrofluorouracil (5FUH2) by the enzyme dihydropyrimidine deshydrogenase (DPD). A new HPLC method with direct UV detection for the determination of 5FUH2 in peripheral lymphocytes has been developed to detect DPD deficiency in patients treated with 5FU-based therapy. The method has been shown to be valid over the 5FUH2 concentration range of 1.14-37.88 nmol/ml. Optimal enzymatic conditions for DPD activity measurement were studied: incubation time, protein and 5FU concentrations. The assay was successfully cross-validated with the existing method using HPLC with radiochemical detection.

[Subfascial lipomatous tumors: management in a series of 37 consecutive cases]

PURPOSE OF THE STUDY

The prognosis of subfascial lipomatous soft tissue tumors depends greatly on their histological type ranging from benign lipomas that cause little local or general problems to the severe prognosis of liposarcomas that exhibit both local and distant extension. However, the clinical presentation of the two types of tumors may be similar and thus quite misleading, sometimes leading to inappropriate management and severe consequences. The main objective of this study was to determine whether the preoperative work-up in patients treated for musculoskeletal tumors within our recruitment zone is adequate, allowing appropriate therapeutic decisions. In addition, we wanted to know what explorations are most pertinent for the differential diagnosis between benign and malignant subfascial lipomatous soft tissue tumors.

MATERIAL AND METHODS

Thirty-seven patients with subfascial tumors were included in this study. There were 16 with benign lipomas and 21 with liposarcomas. All the patients with benign lipomas but only 9 (43%) of those with liposarcoma had received initial care within our recruitment zone before final diagnosis. Two cases had been referred after biopsy and 1 after resection by morcellation; the 9 others were secondary referrals after tumor recurrence. Only 5 of these 12 referred patients had had an MRI exploration prior to surgery, 2 with an erroneous interpretation. An MRI series was obtained for all the patients with benign lipoma and for the 9 with liposarcomas who attended our units directly. A biopsy was also obtained in case of suspected liposarcoma. Two radiologists blinded to the final diagnosis reviewed the available MRI to assess their diagnostic value for subfascial lipomatous soft tissue tumors.

RESULTS

No case of recurrence, after marginal resection (10 cases) was noted for lipomas. Six are under observation with regular MRI (with no change in size or signal). Four patients with liposarcoma died from their disease (19%) and 2 who had undergone "curative" resection had a recurrence (12%). Incorrect or imprecise (incomplete, incorrectly interpreted or no MRI) preoperative diagnosis led to additional morbidity with 3.4 surgical procedures (mean per patient) compared with 1 in patients who had had undergone a complete work-up and whose diagnosis was established after multidisciplinary discussions. Among the diagnostic elements available before pathology, only MRI findings had diagnostic value for subfascial lipomatous soft tissue tumors: for benign lipoma positive predictive value=92% and negative predictive value=93%.

DISCUSSION

The clinical course of the benign lipomas and the sarcomas in this series confirm the radically different prognosis of these two tumors, both in terms of local extension and survival. Inadequate management in the initial diagnostic stages-i.e. lack of MRI with contrast injection, biopsy and multidisciplinary interpretation prior to treatment-raises the risk of higher morbidity, particularly a significantly greater number of reoperations, and progression to a higher grade of malignancy for two tumors. Our retrospective analysis enabled us to develop a decision making tree for patients with subfascial lipomatous tumors. Prospective validation will be necessary.

Prolonged, but not acute, glutathione depletion promotes Fas-mediated mitochondrial permeability transition and apoptosis in mice

Glutathione depletion either decreased or increased death-receptor-mediated apoptosis in previous studies. Comparison of the durations of glutathione depletion before death-receptor stimulation in these studies might suggest a different effect of prolonged versus acute thiol depletion. We compared the effects of the prolonged glutathione depletion caused by a sulfur amino acid-deficient (SAA(-)) diet and the acute depletion caused by a single dose of phorone on hepatic apoptosis triggered by the administration of an agonistic anti-Fas antibody. The chronic SAA(-) diet did not affect hepatic Fas or Bcl-XL, but increased p53 and Bax, and exacerbated Fas-mediated mitochondrial membrane depolarization, electron-microscopy-proven outer mitochondrial membrane rupture, cytochrome c translocation to the cytosol, and caspase 3 activation. These effects were prevented by cyclosporin A, an inhibitor of mitochondrial permeability transition. The SAA(-) diet increased internucleosomal DNA fragmentation, the percentage of apoptotic hepatocytes, serum alanine transaminase (ALT) activity, and mortality after Fas stimulation. Despite a similar decrease in hepatic glutathione, administration of a single dose of phorone 1 hour before the anti-Fas antibody did not change p53 or Bax, and did not enhance Fas-induced mitochondrial permeability transition and toxicity. However, 4 repeated doses of phorone (causing more prolonged glutathione depletion) increased Bax and Fas-mediated toxicity. In conclusion, a chronic SAA(-) diet, but not acute phorone administration, increases p53 and Bax, and enhances Fas-induced mitochondrial permeability transition and apoptosis. Thiol depletion could cause oxidative stress that requires several hours to increase p53; the latter induces Bax, which translocates to mitochondria after Fas stimulation.

Pitx3 activates mouse tyrosine hydroxylase promoter via a high-affinity binding site

Tyrosine hydroxylase (TH) is the rate-limiting enzyme of dopamine and (nor)adrenaline biosynthesis. Regulation of its gene expression is complex and different regulatory mechanisms appear to be operative in various neuronal lineages. Pitx3, a homeodomain-containing transcription factor, has been cloned from neuronal tissues and, in the CNS, mouse Pitx3 is exclusively expressed in midbrain dopaminergic (MesDA) neurons from embryonic day 11 (E11). TH appears in these neurons at E11.5, consistent with a putative role of Pitx3 in TH transcription. We show that Pitx3 activates the TH promoter through direct interaction with a single high-affinity binding site within the promoter and that this site is sufficient for Pitx3 responsiveness. In contrast, we did not observe an effect of Nurr1, an orphan nuclear receptor essential for normal development of MesDA neurons, on TH promoter activity. Pitx3 activation of TH promoter activity appears to be cell-dependent suggesting that Pitx3 action may be modulated by other(s) regulatory mechanism(s) and factor(s).

Natural antibodies to factor VIII

Anti-factor VIII antibodies represent a unique model to study the relationship between natural autoreactivity (natural antibodies to factor VIII of healthy individuals), disease-associated autoimmunity ("spontaneous" factor VIII inhibitors of patients with anti-factor VIII autoimmune disease) and antigen-driven immune responses (immune inhibitors in multitransfused patients with hemophilia A) to a single human protein antigen. Although natural and disease-associated anti-factor VIII antibodies are not readily distinguished based on the comparison of their isotypic distribution and epitope mapping, available studies of cross-reacting idiotypes suggest that factor VIII inhibitors in patient's plasma encompass two populations of anti-factor VIII antibodies. Some antibodies result from the clonal expansion of B lymphocytes that exist before treatment with factor VIII and secrete anti-factor VIII antibodies with properties similar to those of natural anti-factor VIII antibodies present in healthy individuals; other inhibitors are produced by B cell clones that have undergone affinity maturation and hypermutation of the V regions of the antibodies they produce. The implications for the treatment of patients with anti-factor VIII inhibitors are discussed.

Mechanisms for experimental buprenorphine hepatotoxicity: major role of mitochondrial dysfunction versus metabolic activation

BACKGROUND/AIMS

Although sublingual buprenorphine is safely used as a substitution drug in heroin addicts, large overdoses or intravenous misuse may cause hepatitis. Buprenorphine is N-dealkylated to norbuprenorphine by CYP3A.

METHODS

We investigated the mitochondrial effects and metabolic activation of buprenorphine in isolated rat liver mitochondria and microsomes, and its toxicity in isolated rat hepatocytes and treated mice.

RESULTS

Whereas norbuprenorphine had few mitochondrial effects, buprenorphine (25-200 microM) concentrated in mitochondria, collapsed the membrane potential, inhibited beta-oxidation, and both uncoupled and inhibited respiration in rat liver mitochondria. Both buprenorphine and norbuprenorphine (200 microM) underwent CYP3A-mediated covalent binding to rat liver microsomal proteins and both caused moderate glutathione depletion and increased cell calcium in isolated rat hepatocytes, but only buprenorphine also depleted cell adenosine triphosphate (ATP) and caused necrotic cell death. Four hours after buprenorphine administration to mice (100 nmol/g body weight), hepatic glutathione was unchanged, while ATP was decreased and serum transaminase increased. This transaminase increase was attenuated by a CYP3A inducer and aggravated by a CYP3A inhibitor.

CONCLUSIONS

Both buprenorphine and norbuprenorphine undergo metabolic activation, but only buprenorphine impairs mitochondrial respiration and ATP formation. The hepatotoxicity of high concentrations or doses of buprenorphine is mainly related to its mitochondrial effects.

Analysis of foodborne disease in Belgium in 1997

Foodborne disease represents a major problem for public health in industrialized countries, albeit with a low lethality. Foodborne diseases are defined as a group of viral, bacterial or parasitic gastrointestinal infections transmitted by means of food. Proper food-hygiene practices and surveillance of individual diseases and in particular outbreaks are the first steps in targeting their prevention. The incidence of this illness is difficult to estimate. In the Netherlands a yearly incidence of gastrointestinal infections of 500 per 1,000 inhabitants is estimated, of which most are foodborne. To set up priorities in the actions to undertake, to establish the most frequent risks, to develop preventive efforts and to answer to international requirements, accurate data on foodborne disease from Belgium are required. In order to co-ordinate the initiatives in the Belgian context, a working group was set up in 1995. In 1997 a total of 2,013 persons with foodborne disease were identified as part of 140 outbreaks, 22 of which occurred with 10 cases or more. Salmonella Enteritidis (88 outbreaks) was identified as the main pathogen in foodborne disease, followed by S. Typhimurium (11), S. Hadar (4). Eggs and meat products were identified as the main food-items involved, although it remains difficult to obtain proper intervention studies allowing to identify the specific cause(s). In 1997, a total of 12,732 human Salmonella isolates and 5,617 Campylobacter isolates were identified by the respective national reference laboratories. Salmonella isolates from Belgium accounted in 1997 for more than a fifth of all Salmonella isolates in the EU. The final objective of the working group is the implementation of a surveillance system for all risk factors concerned with the development of food-related illness, including an early warning system and an efficient analysis of microbiological criteria relating to human health, food and food production, including livestock. An essential element of this surveillance is communication of the results, risks and measures for prevention between all the departments, institutions and public health authorities concerned.

Idiotypic regulation of anti-factor VIII antibodies

This review focuses on the relationship between natural autoreactivity, autoimmunity in disease and antigen-driven immune responses to factor VIII and on idiotype-mediated immune regulation of anti-factor VIII antibodies in health and disease.

Prevention of acute rejection with antithymocyte globulin, avoiding corticosteroids, and delaying cyclosporin after renal transplantation

BACKGROUND

Despite their well-known side-effects, corticosteroids (Cs) are currently used after kidney transplantation. Avoidance of Cs may improve patient quality of life and eventual long-term survival. We report on a regimen using antithymocyte globulin (ATG) and mycophenolate mofetil (MMF) for induction, and cyclosporin (CsA) plus MMF for maintenance treatment of recipients of primary kidney transplantation.

METHODS

We studied 11 consecutive, non-sensitized renal transplant patients (nine cadaver and two living donors). Initial immunosuppression consisted of ATG (1.5 mg/kg/day, i.v.) given for 10 days and MMF (1.0 g/b.i.d.). CsA (8 mg/kg, in two divided doses) was started on post-operative day 11. Cs were only allowed in the case of MMF discontinuation, for the treatment of acute rejection, and in the event of recurrence of the primary glomerulonephritis.

RESULTS

All patients completed the entire 10-day ATG course. Main side-effects included fever (>38 degrees C) and serum sickness, observed in 73 and 27% of the patients respectively. The incidence of acute rejection was 27% (three of 11 patients). In two patients with acute rejection, serum sickness was concomitantly diagnosed and renal histology was partially compatible with immune-complex disease. The remaining patient had two episodes of low-grade rejection. All rejection episodes were rapidly reversed. Two patients (18%) were treated with ganciclovir for cytomegalovirus (CMV) infection. Two patients (18%) are currently receiving Cs for recurrence of the native glomerulonephritis and two rejection episodes respectively. All patients are currently alive with functioning kidneys (average follow-up of 8.4 months; average creatinine level of 128 micromol/l).

CONCLUSION

This pilot study suggests that ATG induction in combination with MMF and delayed introduction of CsA, in the absence of Cs, is not well tolerated in recipients of kidney transplants. An earlier introduction of calcineurin inhibitors and/or a shorter course of ATG may reduce the incidence of fever and serum sickness secondary to ATG.

Factor VIII inhibitor with catalytic activity towards factor VIII

Hemophilia A is an X chromosome-linked recessive disorder resulting in defective or deficient factor VIII (FVIII) molecules, which, in its severe form, is a life-threatening, crippling hemorrhagic disease. Infusion of purified FVIII to patients with severe hemophilia A results in approximately 25% of the cases in the emergence of anti-FVIII antibodies (inhibitors) that are known to neutralize the procoagulant activity of FVIII by steric hindrance. We recently reported on the proteolysis of FVIII by alloantibodies in the plasma of two high responder patients with severe hemophilia A, demonstrating a new mechanism by which FVIII inhibitors may prevent the pro-coagulant function of FVIII. Hemophilia is the first model in which a direct link between the hydrolysis of the target molecule and the occurrence of clinical manifestations has been established. It also represents the first example in humans, of the induction of catalytic antibodies following the exogenous administration of an antigen. The characterization of FVIII inhibitors as site-specific proteases may provide new approaches to the treatment of inhibitors.

Cytochrome P450-generated reactive metabolites cause mitochondrial permeability transition, caspase activation, and apoptosis in rat hepatocytes

Although cytochrome P-450 (CYP)-generated reactive metabolites can cause hepatocyte apoptosis, the mechanism of this effect is incompletely understood. In the present study, we assessed the hepatotoxicity of skullcap, a diterpenoid-containing herbal remedy. Male rat hepatocytes were incubated for 2 hours with skullcap diterpenoids (100 microg/mL). This treatment decreased cell glutathione and protein thiols and increased cell [Ca(2+)]. This activated Ca(2+)-dependent tissue transglutaminase, forming a cross-linked protein scaffold, and also opened the mitochondrial permeability transition pore, causing outer mitochondrial membrane rupture, increased cytosolic cytochrome c, activation of procaspase 3, internucleosomal DNA fragmentation, and ultrastructural features of apoptosis. Cell death was increased by a CYP3A inducer (dexamethasone) or a sulfur amino acid-deficient diet increasing glutathione depletion. In contrast, cell death was prevented by decreasing CYP3A activity (with troleandomycin), preventing glutathione depletion (with cysteine or cystine), blocking Ca(2+)-modulated events (with calmidazolium), preventing mitochondrial permeability transition (with cyclosporin A), or inhibiting caspase 3 (with acetyl-Asp-G u-Va-Asp-a dehyde). Both calmidazolium and cyclosporin A also prevented the increase in cytosolic cytochrome c and procaspase 3 activation. In conclusion, CYP3A activates skullcap diterpenoids into reactive metabolites that deplete cellular thiols and increase cell [Ca(2+)]. This activates Ca(2+)-dependent transglutaminase and also opens the mitochondrial permeability transition pore, causing outer mitochondrial membrane rupture, cytochrome c release, and caspase activation. Preventing mitochondrial permeability transition pore opening and/or caspase activity blocks apoptosis, showing the fundamental role of these final events in metabolite-mediated hepatotoxicity.

Salvage extended-field irradiation in follicular non-Hodgkin's lymphoma after failure of chemotherapy

PURPOSE

To evaluate the efficacy of total abdominopelvic (TAI) and total body irradiation (TBI) in heavily pretreated follicular non-Hodgkin's lymphoma (NHL).

PATIENTS AND METHODS

From 1983 to 1998, 34 patients received TAI (n = 22) or TBI (n = 12). All had Stage III or IV, Class B, C, D NHL in the working formulation and failed after receiving 1-5 regimens of chemotherapy. TAI was given at 20 Gy over a 3-week period. TBI was delivered in two successive half-body irradiations of 15 Gy over a 2-week period with a 4-week interval between each.

RESULTS

Mean follow-up from TAI or TBI was 120 months (range, 6-180). Seventy-six percent of patients achieved complete response and 24% partial response. Median survival was 62 months, 5-year and 10-year overall survival was 59% and 41%, and disease-free survival was 56% and 30%, respectively. Grade III or IV toxicity was gastrointestinal in 38% of patients and hematologic in 30%. No toxic death or delayed complications were observed.

CONCLUSION

Extended-field irradiation is feasible and efficient after failure of chemotherapy in follicular NHL.

Antibodies to the FVIII light chain that neutralize FVIII procoagulant activity are present in plasma of nonresponder patients with severe hemophilia A and in normal polyclonal human IgG

We have analyzed the properties of anti-factor VIII (FVIII) immunoglobulin (Ig) G recovered by affinity chromatography on FVIII-Sepharose from the IgG fraction of the plasma of healthy individuals and nonresponder patients with hemophilia A. Affinity-purified anti-FVIII antibodies were found to neutralize FVIII activity and to bind to FVIII with an affinity similar to that of anti-FVIII IgG that had been affinity-purified from the plasma of inhibitor-positive hemophilia patients and of patients with anti-FVIII autoimmune disease. The antibodies also exhibited patterns of reactivity with thrombin-digested FVIII similar to those of FVIII inhibitors and preferentially recognized epitopes located in the light chain of FVIII. These observations suggest that FVIII inhibitors occurring in hemophilia A and in patients with anti-FVIII autoimmune disease originate from the expansion of preexisting natural anti-FVIII clones that exhibit FVIII-neutralizing properties.

IgG-secreting lymphoplasmacytoid leukaemia: a B-cell disorder with extensively mutated VH genes undergoing Ig isotype-switching frequently associated with trisomy 12

We investigated 16 patients with elevated serum monoclonal IgG and a leukaemic B-cell lymphocytic disorder different from multiple myeloma. Their clinical history was that of a non-aggressive disease with dominant splenomegaly and long survival. Whereas abnormal blood and bone marrow cells were predominantly small lymphocytes with a few lymphoplasmacytoid cells, histopathological features included a lymphoplasmacytic infiltrate in eight cases. Most frequently, abnormal blood cells displayed a CD19+CD5-CD23+/- immunophenotype different from that of chronic lymphocytic leukaemia, except in two cases with a CD19+CD5+CD23+ phenotype. Interestingly, a coexistent serum monoclonal IgM and/or surface IgMG+ with identical light chain was identified in 10 patients, whereas in the remaining six patients only IgG expression was determined. VH gene analysis was performed in eight patients to investigate the clonal origins of tumour cells. All cases utilized the VH3 family, with evidence of extensive somatic mutations and intraclonal homogeneity in all cases. VH gene analysis indicated a clonal relationship between cells expressing IgM and IgG, with one case being biclonal. Cytogenetic evaluation showed a high incidence of trisomy 12 (60%) and 13q14 deletion (40%). In conclusion, we have described an unusual subset of low-grade lymphoma with high-serum IgG and frequent lymphoplasmacytoid features in which tumour cells derive from post-follicular memory B cells undergoing isotype switching with some cases arrested at both the IgM and IgG stage and others as IgG-positive cells only.

Opening of the mitochondrial permeability transition pore causes matrix expansion and outer membrane rupture in Fas-mediated hepatic apoptosis in mice

Although Fas stimulation has been reported to cause outer mitochondrial membrane rupture in Jurkat cells, the mechanism of this effect is debated, and it is not known if outer membrane rupture also occurs in hepatocyte mitochondria. We studied the in vivo effects of Fas stimulation on ultrastructural lesions and mitochondrial function in mice. Four hours after administration of an agonistic anti-Fas antibody (8 microg/animal), caspase activity increased 5.4-fold. Nuclear DNA showed internucleosomal fragmentation, whereas supercoiled mitochondrial DNA was replaced by circular and linear forms. Mitochondrial cytochrome c was partly released into the cytosol. Ultrastructurally, mitochondrial lesions were observed in both apoptotic hepatocytes (with nuclear chromatin condensation/fragmentation) and nonapoptotic hepatocytes (without nuclear changes). In nonapoptotic cells, outer mitochondrial membrane rupture allowed herniation of the inner membrane and matrix through the outer membrane gap. In apoptotic hepatocytes, the matrix became electron-lucent and no longer protruded through the outer membrane gap. Mitochondria clustered around the nucleus, whereas rough endoplasmic reticulum cisternae became peripheral. In liver mitochondria isolated after Fas stimulation, the membrane potential decreased, whereas basal respiration increased. Pretreatment with either z-VAD-fmk (an inhibitor of caspases) or cyclosporin A (a permeability transition inhibitor) totally or mostly prevented mitochondrial outer membrane rupture, membrane potential decrease, cytochrome c release, and apoptosis. In conclusion, in vivo Fas stimulation causes caspase activation, mitochondrial permeability transition (decreasing the membrane potential and increasing basal respiration), mitochondrial matrix expansion (as shown by matrix herniation), outer mitochondrial membrane rupture, and cytochrome c release.

Highly altered V beta repertoire of T cells infiltrating long-term rejected kidney allografts

Chronic rejection represents a major cause of long-term kidney graft loss. T cells that are predominant in long-term rejected kidney allografts (35 +/- 10% of area infiltrate) may thus be instrumental in this phenomenon, which is likely to be dependent on the indirect pathway of allorecognition only. We have analyzed the variations in T cell repertoire usage of the V beta chain at the complementary determining region 3 (CDR3) level in 18 human kidney grafts lost due to chronic rejection. We observed a strongly biased intragraft TCR V beta usage for the majority of V beta families and also a very high percentage (55%) of V beta families exhibiting common and oligoclonal V beta-C beta rearrangements in the grafts of patients with chronic rejection associated with superimposed histologically acute lesions. Furthermore, V beta 8 and V beta 23 families exhibited common and oligoclonal V beta-J beta rearrangements in 4 of 18 patients (22%). Several CDR3 amino acid sequences were found for the common and oligoclonal V beta 8-J beta 1.4 rearrangement. Quantitative PCR showed that biased V beta transcripts were also overexpressed in chronically rejected kidneys with superimposed acute lesions. In contrast, T lymphocytes infiltrating rejected allografts with chronic rejection only showed an unaltered Gaussian-type CDR3 length distribution. This pattern suggests that late graft failure associated with histological lesions restricted to Banff-defined chronic rejection does not involve T cell-mediated injury. Thus, our observation suggests that a limited number of determinants stimulates the recipient immune system in long-term allograft failure. The possibility of a local response against viral or parenchymatous cell-derived determinants is discussed.

Interaction of anti-HLA antibodies with pig xenoantigens

BACKGROUND

Many patients with renal failure are condemned to long-term dialysis with little prospect of transplantation because they are highly sensitized with immunoglobulin G (IgG) directed against class I human leukocyte antigens (HLA) of virtually all donors. Xenotransplantation could represent an attractive solution providing their alloantibodies (alloAb) do not recognize porcine motifs. Hitherto there has been no in vivo demonstration of any cross-reactivity and the objective of this work was to investigate this problem using a technique of extracorporeal pig kidney perfusion as a model of clinical xenografting.

METHODS

Pig kidneys were perfused ex vivo with plasma from both a group of highly sensitized patients and healthy individuals. Sequential plasma samples were analyzed for the titer of anti-Galalpha1-3Gal antibody (Ab) (major natural xenoreactive Ab) by enzyme-linked immunosorbent assay and anti-HLA class I Ab against a cell panel. At the end of perfusion, kidneys were perfused with a citric acid buffer to elute bound Ab.

RESULTS

Galalpha1-3Gal Ab were shown to decrease rapidly in the plasma (in less than 10 min) and then reached a plateau. A fractional decrease in anti-HLA Ab was also found in some of the perfused plasma samples. Anti-Gal Ab were readily detected in all citric acid perfusates and anti-HLA Ab in 8 of 10. The HLA specificities of eluted Ab were mainly concordant with the originally designated specificities for each patient.

CONCLUSION

Anti-HLA class I Ab presumably cross-react with pig class I homologues. However, some plasma samples did not cross-react, suggesting that negatively cross-matched pig kidneys could be identified in the pig population for xenotransplantation in these patients. Further studies are required to precisely describe these cross-reactivities and to understand their functional significance in xenotransplantation.

Catalytic activity of antibodies against factor VIII in patients with hemophilia A

Hemophilia A is an X chromosome-linked recessive disorder resulting in defective or deficient factor VIII (FVIII) molecules, which, in its severe form, is a life-threatening and crippling hemorrhagic disease. Infusion of homologous FVIII to patients with severe hemophilia A results, in 25% of patients, in the emergence of alloantibodies against FVIII (inhibitors)( ref. 1) that inhibit FVIII procoagulant activity by steric hindrance of the interaction of FVIII either with stabilizing molecules, with molecules essential for its activity or with activating molecules. Here, we report on the proteolysis of FVIII by alloantibodies of two patients with severe hemophilia A, demonstrating a previously unknown mechanism by which FVIII inhibitors may prevent the pro-coagulant function of FVIII. The kinetic parameters of FVIII hydrolysis indicate a functional role for the catalytic immune response in the inactivation of FVIII in vivo. The characterization of alloantibodies against FVIII as site-specific proteases may provide new approaches to the treatment of FVIII inhibitors.