T-cell papulosis associated with B-cell malignancy: a distinctive clinicopathologic entity.

BACKGROUND: A distinctive eruption referred to as 'insect bite-like reaction' or 'eosinophilic dermatosis of haematological malignancy' has been described during the course of haematological B-cell malignancies (BCM). However, its clinical evolution, histopathological features and pathogenesis remain unclear. OBJECTIVES: To characterize this eruption and to investigate its pathogenesis and relationship with the underlying BCM. METHODS: In this multicenter retrospective study of the French Study Group on Cutaneous Lymphomas, 37 patients with a BCM and a cutaneous eruption consisting in chronic and/or recurrent papules, papulo-vesicles and/or nodules were included. Clinical, histopathological, immunohistochemical and molecular data were reviewed. RESULTS: No significant insect bite history or seasonal predominance was recorded. Patients had pruritic papules (81%), papulo-vesicles (43%) and nodules (38%), often predominated in the head and neck region (84%), without complete remission periods in most cases (57%). The predominant associated BCM was chronic lymphocytic leukaemia (73%). Histological and immunohistochemical review showed a dense dermal lymphocytic infiltrate predominantly composed of T lymphocytes (100%), with frequent eosinophils (77.6%); a perivascular and periadnexal (most often folliculotropic) pattern (77.6%), sometimes suggestive of a folliculotropic mycosis fungoides; clusters of tumour B cells were identified in 47% of cases using appropriate phenotyping markers. In 10/14 cases (71.4%) tested for B-cell IgH gene rearrangement, a B-cell clone was identified in skin lesions (identical to the blood clone in nine cases), whereas no T-cell clone was present. CONCLUSION: We propose the denomination 'T-cell papulosis associated with B-cell malignancy' (TCP-BCM) for this distinctive eruption. Although resulting in various histopathological pictures, it can be easily recognized by clinicians and may be identified by informed pathologists relying on some key features. An extravasation of tumour B cells with skin-homing properties associated with a secondary, predominant, T-cell immune reaction could explain the clinicopathologic aspect and the prolonged regressive and recurrent course of the disease.

Relationships between body dimensions, body weight, age, gender, breed and echocardiographic dimensions in young endurance horses.

BACKGROUND: The heart's physiological adaptation to aerobic training leads to an increase in heart chamber size, and is referred to as the Athlete's heart. However, heart dimensions are also related to body weight (BWT), body size, growth and (in some species) breed. There are few published data on the relationships between heart dimensions and growth or aerobic training in Arabian and Arabian-related endurance horses. Therefore the objective of the present study was to describe the influence of body dimensions (body length (BL), thoracic circumference (TC), withers height (WH)), BWT, age, gender, breed (purebred Arabians, part-bred Arabians, Anglo-Arabians, and Others) and the initiation of endurance training on echocardiographic measurements in competition-fit endurance horses aged 4 to 6 years. RESULTS: Most left atrial (LA) and left ventricular (LV) dimensions increased with age, whereas LA and LV functional indices did not. Although there was no gender difference for LV dimensions, females had larger LA dimensions. In terms of breed, Anglo-Arabians had the largest LV dimensions. Regression models indicated that the included explanatory factors had a weak influence on heart dimensions. Age, body dimensions, breed and gender showed the most consistent influence on LA dimensions, whereas BWT, breed and kilometres covered in competition showed the most consistent influence on LV dimensions. CONCLUSION: The increase in echocardiographic dimensions with age indicates on-going growth in our population of 4 to 6 year-old horses. We also observed small changes associated with the initiation of endurance training. Morphometric dimensions had a greater influence on LA dimensions, whereas LV dimensions were also influenced (albeit weakly) by parameters associated with exercise intensity. These results may therefore reflect early adaptations linked to the initiation of endurance training.

Are Gadolinium-Enhanced MR Sequences Needed in Simultaneous 18F-FDG-PET/MRI for Tumor Delineation in Head and Neck Cancer?

BACKGROUND AND PURPOSE: PET/MRI with 18F-FDG has demonstrated the advantages of simultaneous PET and MR imaging in head and neck cancer imaging, MRI allowing excellent soft-tissue contrast, while PET provides metabolic information. The aim of this study was to evaluate the added value of gadolinium contrast-enhanced sequences in the tumor delineation of head and neck cancers on 18F-FDG-PET/MR imaging. MATERIALS AND METHODS: Consecutive patients who underwent simultaneous head and neck 18F-FDG-PET/MR imaging staging or restaging followed by surgery were retrospectively included. Local tumor invasion and lymph node extension were assessed in 45 head and neck anatomic regions using 18F-FDG-PET/MR imaging by 2 rater groups (each one including a radiologist and a nuclear medicine physician). Two reading sessions were performed, one without contrast-enhanced sequences (using only T1WI, T2WI, and PET images) and a second with additional T1WI postcontrast sequences. The results were compared with the detailed histopathologic analysis, used as reference standard. The κ concordance coefficient between the reading sessions and sensitivity and specificity for each region were calculated. RESULTS: Thirty patients were included. There was excellent agreement between the contrast-free and postgadolinium reading sessions in delineating precise tumor extension in the 45 anatomic regions studied (Cohen κ = 0.96, 95% CI = [0.94-0.97], P < .001). The diagnostic accuracy did not differ between contrast-free and postgadolinium reading sessions, being 0.97 for both groups and both reading sessions. For the 2 rater groups, there was good sensitivity for both contrast-free (0.83 and 0.85) and postgadolinium reading sessions (0.88 and 0.90, respectively). Moreover, there was excellent specificity (0.98) for both groups and reading sessions. CONCLUSIONS: Gadolinium chelate contrast administration showed no added value for accurate characterization of head and neck primary tumor extension and could possibly be avoided in the PET/MR imaging head and neck workflow.

Nuclear localization of aspartate transcabamoylase in Saccharomyces cerevisiae.

The cytochemical technique using the in situ precipitation of orthophosphate ions liberated specifically by the aspartate carbamoyltransferase (ATCase) (EC 2.1.3.2) reaction indicated that in Saccharomyces cerevisiae this enzyme is confined to the nucleus. This observation is in accordance with the result reported by Bernhardt and Davis (1972), Proc. Natl. Acad. Sci. U. S. A. 69:1868-1872) on Neurospora crassa. The nuclear compartmentation was also observed in a mutant strain lacking proteinase B activity. This finding indicates that this proteinase is not involved in the nuclear accumulation of ATCase, and that the activity observed in the nucleus corresponds to the multifunctional form associated with the uracil path-specific carbamoylphosphate synthetase and sensitive to feedback inhibition by UTP. In a ura2 strain transformed by nonintegrated pFL1 plasmids bearing the URA2-ATCase activity encoding gene, the lead phosphate precipitate was observed predominantly in the cytoplasm. This finding enhances the reliability of the technique used by eliminating the possibility of an artifactual displacement of an originally cytoplasmic reaction product during the preparation of the material for electron microscopy. On the other hand, nuclei isolated under hypoosmotic conditions do not exhibit the ATCase activity that is recovered in the cytosolic fractions after differential centrifugation of the lysate in Percoll gradient. A release of the protein from the nuclei during the lysis step, consistent with its nucleoplasmic localization, is postulated.

Prevalence of West Nile virus neutralizing antibodies in wild birds from the Camargue area, southern France.

The Camargue area of southern France experienced the re-emergence of West Nile Virus (WNV) in the late summer of 2000 and 2004. Immediately preceding the 2004 outbreak, samples were collected from 432 birds of 32 different species captured in mist nets and from 201 Cattle Egret (Bubulcus ibis) nestlings sampled in their nests between 1 April and 12 June 2004. West Nile virus neutralizing titers of >/=40 were detected in 4.8% (95% confidence limit, 2.9-7.5%) of the adult birds and in 1.6% (0.3-4.6%) of the egret nestlings. Migratory passerines had a higher prevalence of WNV neutralizing antibodies (7.0%) than did resident and short-distance migratory passerines (0.8%), suggesting exposure to WNV or a related flavivirus during overwintering in Africa.

Picosecond dynamics of T and R forms of aspartate transcarbamylase: a neutron scattering study.

E. coli aspartate transcarbamylase (ATCase) is a 310 kDa allosteric enzyme which catalyses the first committed step in pyrimidine biosynthesis. The binding of its substrates, carbamylphosphate and aspartate, induces significant conformational changes. This enzyme shows homotropic cooperative interactions between the catalytic sites for the binding of aspartate. This property is explained by a quaternary structure transition from T state (aspartate low affinity) to R state (aspartate high affinity) accompanied by a 5% increase of radius of gyration of ATCase. The same quaternary structure change is observed upon binding of the bisubstrate analogue PALA (N-(phosphonacetyl)-L-aspartate. Owing to the large incoherent neutron scattering cross-section of the hydrogen atom and the abundance of this element in proteins, inelastic neutron scattering gives a global view of protein dynamics as sensed via the individual motions of its hydrogen atoms. We present neutron scattering results of the local dynamics (few angstroms), at short time (few tens of picoseconds), of ATCase in T and R forms. Compared to the T form, we observe an increased mobility of the protein in the R form that we associate to an increase of accessible surface area to the solvent. Beyond this specific result, this highlights the key role of the accessible surface area (ASA) in dynamic contribution to inelastic neutron data in the picosecond time scale. In particular, we want to stress out (i) that a difference at the picosecond time scale does not allow to conclude to a difference in the dynamics at a longer time scale and to address whether the T state is looser than the R state (ii) how challenging is, any comparison in terms of general dynamics (tense or relaxed) between dynamic values deduced from experimental neutron data on proteins with different sequences and therefore ASA. This caveat holds particularly when comparing dynamics of a mesophile with the corresponding extremophile.

[Liver steatosis and in-out of phase MR imaging: theory and clinical applications at 3T]. / Stéatose hépatique et séquence phase-opposition de phase: aspects théoriques et applications pratiques à 3T.

Liver steatosis may evolve into steatohepatitis then cirrhosis with related complications. It may also contribute to hepatocellular failure, sometimes fatal after major hepatectomy, especially in the setting of liver transplantation with living donor. Imaging must allow non-invasive detection and accurate quantification. In and out of phase MR imaging routinely performed in clinical practice is a simple and robust means of achieving these goals. In this article, we will review the histological, pathophysiologic, and clinical features of liver steatosis and the key points of in and out of phase pulse sequences and underlying physical principles. The T2* relaxation, cause of a loss of signal between both echo times must be taken into account. Echo times must be known for image interpretation, and optimized, especially at 3T. Finally, the T1 of lipids and water is different and causes T1 effects that may lead to quantification errors while being advantageous for image interpretation. The combination of these factors allows detection and quantification of liver steatosis in routine clinical practice.

Kinetic parameters of aspartate transcarbamylase in human normal and tumoral cell lines.

The kinetic parameters of aspartate transcarbamylase activity were determined in dialyzed extracts coming from ten different human normal and tumoral cell lines (three fibroblasts, four melanomas, and three colorectal carcinomas). Specific activities do not correlate with the malignant character of the cells but rather with the fact that the cells divide actively or not. Growth curves show large variations in the cell sensitivity to N-(phosphonacetyl)-L-aspartate (PALA). However, no differences in substrate affinity or PALA sensitivity of the aspartate transcarbamylase activities present in the corresponding cell extracts could be detected. Thus, the different human cell susceptibilities to PALA do not result from an intrinsic property of aspartate transcarbamylase. Cell death under the influence of PALA does not correlate with the tumoral or normal character of the cells.

A hair on the tongue.

INTRODUCTION: Human hairs are generally localized on the cutaneous part of the head, neck, torso, armpits, pubis and limbs. Sometimes it can be found in an unusual localization and is then called heterotopic. OBSERVATION: A 30-year-old man presented with a hair in the middle of the dorsum of the tongue. It was decided to perform an excision under local anesthesia. DISCUSSION: Few reports exist that describe hair growing on mucosa. Only one other case has been published concerning the tongue.

Modification of the structural and redox properties of cytochrome c by heteropolytungstate binding.

Complex formation between horse heart ferricytochrome c and large three-dimensional polyanions has been investigated, in order to study the influence of surface electrostatic interactions on the structural and redox properties of cytochrome c. Cytochrome c binds the large heteropolytungstates (NaSb9W21O86)18- and (KAs4W40O140)27- with a 1/1 polyanion/cytochrome c ratio, and the smaller ion (SiW11O39)8- with a 2/1 ratio. Upon complexation, cytochrome c undergoes structural changes that are dependent on the size and charge of the polyanion, and on the pH and ionic strength of the medium. Three different forms of complexed cytochrome c have been characterized by optical and EPR spectroscopies, in the pH range 6.5-8: an N form, close to the native structure, an A form, analogous to cytochrome c in acidic medium, and a novel B form in which the heme pocket is open but the iron remains low-spin. The redox potential of cytochrome c is lowered to 250-220 mV (vs. NHE) in the N form, and to 80 mV in the B form.

Polytungstate binding to metmyoglobin: an access to various structural forms of the protein.

Complex formation between metMb and three heteropolytungstates, offering various sizes and charges, has been studied in the pH range 6-8. 1:1 complexes are formed with (KAs4W40O140)27- and (NaSb9W21O86)18-, with an association constant of 10(6) and 4 x 10(5) M-1 respectively, at pH 7.3 and 10 mM ionic strength. Resulting structural changes of the metMb moiety have been investigated by absorption, CD and EPR spectroscopies. Besides an acid-denatured-like form, obtained at a pH as high as 6.5 with the largest polyanion, the formation of an hemichrome is generally observed. It can be reduced to the hemochrome, whereas the complexation of deoxyMb by the polytungstates leaves the deoxy structure unaltered.

Incorporation of amino acid analogs during the biosynthesis of Escherichia coli aspartate transcarbamylase.

Amino acid-requiring mutants capable of producing derepressed levels of aspartate transcarbamylase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2) were obtained and used for the incorporation in this enzyme of eight different amino acid analogs. These amino acid replacements enabled the biosynthesis of a series of modified aspartate transcarbamylases altered in their catalytic or regulatory properties. The enzyme in which phenylalanine was rereplaced by 2-fluorophenylalanine was purified to homogeneity and appeared to have the same specific activity as normal asparate transcarbamylase but lacking both homotropic and heterotropic interactions.

X-ray scattering titration of the quaternary structure transition of aspartate transcarbamylase with a bisubstrate analogue: influence of nucleotide effectors.

The regulation of aspartate transcarbamylase (ATCase) involves various conformational changes, including a large quaternary structure rearrangement. This is directly related to a major change in its solution X-ray scattering curve upon binding the bisubstrate analogue N-(phosphonacetyl)-L-aspartate (PALA), allowing us to monitor directly the amount of the different quaternary structures present in solution. Data were analysed by singular vector decomposition without any prior assumption as to the number of quaternary structure states. Scattering curves in the presence of variable concentrations of PALA, alone or with saturating CTP or ATP, can be accounted for with only two states. Consequently the method gives the fraction of molecules in either state. Whereas CTP slightly decreases the proportion of molecules in the R state, ATP has no detectable effect, whatever the amount of PALA ligated to ATCase. The requirement for only two quaternary structures, suggesting a concerted transition, promoted us to test the ability of the classical model, proposed by Monod, Wyman and Changeux, to account for our data. By and large, it is satisfactory as regards the homotropic effect of PALA and the observed effect of CTP, although it remains incompatible with some other observations, which support the involvement of more indirect mechanisms in the inhibitory properties of CTP. But ATP does not directly influence the T to R transition and consequently must act by a totally different mechanism.

Structure-function relationship in allosteric aspartate carbamoyltransferase from Escherichia coli. I. Primary structure of a pyrI gene encoding a modified regulatory subunit.

In a previous article, we have identified a lambda bacteriophage directing the synthesis of a modified aspartate carbamoyltransferase lacking substrate-co-operative interactions and insensitive to the feedback inhibitor CTP. These abnormal properties were ascribed to a mutation in the gene pyrI encoding the regulatory polypeptide chain of the enzyme. We now report the sequence of the mutated pyrI and show that, during the generation of this pyrBI-bearing phage, six codons from lambda DNA have been substituted for the eight terminal codons of the wild-type gene. A model is presented for the formation of this modified pyrI gene during the integrative recombination of the parental lambda phage with the Escherichia coli chromosome. An accompanying paper emphasizes the importance of the carboxy-terminal end of the regulatory chain for the homotropic and heterotropic interactions of aspartate carbamoyltransferase.

Structure-function relationship in allosteric aspartate carbamoyltransferase from Escherichia coli. II. Involvement of the C-terminal region of the regulatory chain in homotropic and heterotropic interactions.

The modified aspartate transcarbamylase (ATCase) encoded by the transducing phage described by Cunin et al. has been purified to homogeneity. In this altered form of enzyme (pAR5-ATCase) the last eight amino acids of the C-terminal end of the regulatory chains are replaced by a sequence of six amino acids coded for by the lambda DNA. This modification has very informative consequences on the allosteric properties of ATCase. pAR5-ATCase lacks the homotropic co-operative interactions between the catalytic sites for aspartate binding and is "frozen" in the R state. In addition, this altered form of enzyme is insensitive to the physiological feedback inhibitor CTP, in spite of the fact that this nucleotide binds normally to the regulatory sites. Conversely, pAR5-ATCase is fully sensitive to the activator ATP. However, this activation is limited to the extent of the previously described "primary effect" as expected from an ATCase form "frozen" in the R state. These results emphasize the importance of the three-dimensional structure of the C-terminal region of the regulatory chains for both homotropic and heterotropic interactions. In addition, they indicate that the primary effects of CTP and ATP involve different features of the regulatory chain-catalytic chain interaction area.

Quaternary structure changes in aspartate transcarbamylase studied by X-ray solution scattering. Signal transmission following effector binding.

The result of binding the effectors ATP and CTP to aspartate transcarbamylase was studied by X-ray solution scattering. Binding of substrate analogues produces a substantial change in the solution scattering curve, allowing us to monitor the proportion of the different quaternary structure states present in solution. In the initial solution this ratio was made roughly unity by adding either carbamyl phosphate and succinate, or N-(phosphonacetyl)-L-aspartate (PALA). ATP or CTP were then added, and their effect on the proportion of the different quaternary structure states was followed. When using carbamyl phosphate and succinate (weakly bound), ATP or CTP had a clear effect, as observed previously by monitoring the sedimentation rate (Changeux et al., 1968). However, when PALA (strongly bound) was used, the effect of CTP was very much smaller, and that of ATP was undetectable. This result supports the explanation by Tauc et al. (1982), that nucleotides act mostly through changing the affinity of the active sites for substrate, and only to a small extent by directly modifying the quaternary structure equilibrium in the case of CTP.

Allosteric regulation of carbamoylphosphate synthetase-aspartate transcarbamylase multifunctional protein of Saccharomyces cerevisiae: selection, mapping and identification of missense mutations define three regions involved in feedback inhibition by UTP.

The positive screening procedure previously described was used in order to select, clone and characterize mutants defective in negative feedback control by UTP of the yeast carbamoylphosphate synthetase-aspartate transcarbamylase protein (CPSase-ATCase). The selection procedure was improved by adding a general mapping method for dominant mutations in order to avoid sequencing the whole URA2 allele (7 kb). All 16 mutants obtained carry missense mutations leading to single amino acid replacements: five of them are located in the CPSase domain while the other 11 are in the ATCase domain. In these 16 mutants, ATCase is no longer inhibited by UTP although CPSase retains full sensitivity to the effector, suggesting that the regulation of the two activities involve distinct mechanisms. Amino acid replacements in the ATCase domain were located on a three-dimensional model structure of the yeast ATCase domain. They are clustered in two regions of this domain which must be directly involved in the feedback process.

Allosteric regulation and substrate channeling in multifunctional pyrimidine biosynthetic complexes: analysis of isolated domains and yeast-mammalian chimeric proteins.

The initial steps of pyrimidine biosynthesis in yeast and mammals are catalyzed by large multifunctional proteins of similar size, sequence and domain structure, but appreciable functional differences. The mammalian protein, CAD, has carbamyl phosphate synthetase (CPSase), aspartate transcarbamylase (ATCase) and dihydroorotase (DHOase) activities. The yeast protein, ura2, catalyzes the first two reactions and has a domain, called pDHO, which is homologous to mammalian DHOase, but is inactive. In CAD, only CPSase is regulated, whereas both CPSase and ATCase in the yeast protein are inhibited by UTP. These functional differences were explored by constructing a series of mammalian yeast chimeras. The isolated ATCase domain is catalytically active, but is not regulated. The inclusion of the yeast sequences homologous to the mammalian regulatory domain (B3) and the intervening pDHO domain did not confer regulation. Chimeric proteins in which the homologous regions of the mammalian protein were replaced by the corresponding domains of ura2 exhibited full catalytic activity, as well regulation of the CPSase, but not the ATCase, activities. The yeast B3 subdomain confers UTP sensitivity on the mammalian CPSase, suggesting that it is the locus of CPSase regulation in ura2. Taken together, these results indicate that there are regulatory site(s) in ura2. Channeling is impaired in all the chimeric complexes and completely abolished in the chimera in which the pDHO domain of yeast is replaced by the mammalian DHO domain.

The activation of Escherichia coli aspartate transcarbamylase by ATP. Specific involvement of helix H2' at the hydrophobic interface between the two domains of the regulatory chains.

The regulatory chain of E. coli aspartate transcarbamylase (E.C. 2.1.3.2) is folded into two domains. The allosteric domain harbours the regulatory site where the activator ATP and the inhibitors CTP and UTP bind competitively. The zinc domain ensures the contact with the catalytic chains. The interface between these two domains is hydrophobic, and involves the carboxy-terminal part of the helix H2' of the allosteric domain and several residues of the zinc domain. This structural feature mediates the transmission of the ATP regulatory signal. In the present work, site-directed mutagenesis and molecular modelling were used to investigate the role of specific amino acid residues in this process. The modifications of the hydrophobic core which are expected to alter the position of helix H2' reduce or abolish the sensitivity of the enzyme to ATP. The properties of the mutants and the results of modelling are fully consistent and suggest that a movement of helix H2' is part of the mechanism of activation by ATP. A model is proposed to account for the transmission of the ATP signal from the regulatory site to the interface between the regulatory and catalytic chains.

Co-operative interactions between the catalytic sites in Escherichia coli aspartate transcarbamylase. Role of the C-terminal region of the regulatory chains.

In aspartate transcarbamylase (ATCase) each regulatory chain interacts with two catalytic chains each one belonging to a different trimeric catalytic subunit (R1-C1 and R1-C4 types of interactions as defined in Fig. 1). In order to investigate the interchain contacts that are involved in the co-operative interactions between the catalytic sites, a series of modified forms of the enzyme was prepared by site-directed mutagenesis. The amino acid replacements were devised on the basis of the previously described properties of an altered form of ATCase (pAR5-ATCase) which lacks the homotropic co-operative interactions between the catalytic sites. The results obtained (enzyme kinetics, bisubstrate analog influence and pH studies) show that the R1-C4 interaction is essential for the establishment of the enzyme conformation that has a low affinity for aspartate (T state), and consequently for the existence of co-operativity between the catalytic sites. This interaction involves the 236-250 region of the aspartate binding domain of the catalytic chain (240s loop) and the 143-149 region of the regulatory chain which comprises helix H3'.