Large-Area Epitaxial Mott Insulating 1T-TaSe2 Monolayer on GaP(111)B.

Two-dimensional Mott materials have recently been reported in the dichalcogenide family with high potential for Mottronic applications. Nevertheless, their widespread use as a single or few layers is hampered by their limited device integration resulting from their growth on graphene, a metallic substrate. Here, we report on the fabrication of 1T-TaSe2 monolayers grown by molecular beam epitaxy on semiconducting gallium phosphide substrates. At the nanoscale, the charge density wave reconstruction and a moiré pattern resulting from the monolayer interaction with the substrate are observed by scanning tunneling microscopy. The fully open gap unveiled by tunneling spectroscopy, which can be further manipulated by the proximity of a metal tip, is confirmed by transport measurements from micrometric to millimetric scales, demonstrating a robust Mott insulating phase at up to 400 K.

Iuliacumite: A Novel Chemical Short-Range Order in a Two-Dimensional Wurtzite Single Monolayer InAs1-xSbx Shell on InAs Nanowires.

A chemical short-range order is found in single monolayer InAs1-xSbx shells, which inherit a wurtzite structure from the underlying InAs nanowire, instead of crystallizing in the energetically preferred zincblende structure. The chemical order is characterized by an anticorrelation ordering vector in the ⟨112̅0⟩ direction and arises from strong Sb-Sb repulsive interactions along the atomic chains in the ⟨112̅0⟩ direction.

Quantification of zidovudine and its monophosphate in cell extracts by on-line solid-phase extraction coupled to liquid chromatography.

A simple and rapid analytical method for the simultaneous quantification of zidovudine (AZT) and its monophosphate (AZTMP) in cell extracts has been developed using high-performance liquid chromatography (HPLC) with on-line solid-phase extraction and 2-aminoethyl-3'-azido-2',3'-dideoxythymidin-5'-yl phosphodiester sodium salt as internal standard (IS). The cell extract samples were directly injected on a short reversed-phase precolumn using an aqueous buffer containing an ion-pairing reagent as a mobile phase. Under these conditions, the analytes were retained on the precolumn whereas the proteins were discarded. The analytes were then transferred onto the analytical column by increasing the strength of the eluent. The calibration curve was linear over a concentration range of 0.5-100 microg/ml. Inter- and intra-day accuracy and precision results satisfied the accepted criteria for bioanalytical validation. This method was used to study the decomposition pathway of a model pronucleotide in an in vitro approach.

Diastereoisomeric resolution of a pronucleotide using solid phase extraction and high performance liquid chromatography: application to a stereoselective decomposition kinetic in cell extracts.

A stereospecific HPLC methodology has been developed for the diastereoisomeric resolution of a mononucleotide prodrug in cell extracts. This method involves the use of solid phase extraction on a C18 cartridge. Diastereoisomers and internal standard resolutions were performed on a cellulose based chiral column (Chiralcel OD-H) used in the normal phase mode. The method was validated in terms of specificity, recovery, linearity (diasteroisomers mixture concentration: 3-60 micromol L(-1)), precision and accuracy and detection limit (1.67 and 1.33 micromol L(-1) for first and second eluted diastereoisomer). This method was applied to the determination of the apparent rate constants of disappearance and half-lives of each stereoisomers. This permits to conclude to the stereoselectivity of the enzymatic activity involved in the decomposition pathway of 2.

Mononucleoside phosphotriester derivatives with S-acyl-2-thioethyl bioreversible phosphate-protecting groups: intracellular delivery of 3'-azido-2',3'-dideoxythymidine 5'-monophosphate.

The synthesis, in vitro anti-HIV-1 activity, and decomposition pathways of several mononucleoside phosphotriester derivatives of 3'-azido-2',3'-dideoxythymidine (AZT) incorporating a new kind of carboxylate esterase-labile transient phosphate-protecting group, namely, S-acyl-2-thioethyl, are reported. All the described compounds showed marked antiviral activity in thymidine kinase-deficient CEM cells in which AZT was virtually inactive. The results strongly support the hypothesis that such pronucleotides exert their biological effects via intracellular delivery of the 5'-mononucleotide of AZT. This point was corroborated by decomposition studies in cell extracts and culture medium.

Comparative evaluation of seven oligonucleotide analogues as potential antisense agents.

12-Mer analogues, representative of seven different classes of structurally modified oligonucleotides and complementary to the same target, have been compared for their binding affinity for both single-stranded DNA and RNA, resistance to hydrolysis by nucleases in culture medium (RPMI 1640 + 10% inactivated fetal calf serum), and inhibition of HIV-1 replication in de novo infected MT4 T lymphocytes. The viral target was the splice acceptor site of the premessenger coding for the regulatory protein tat. The oligo(2'-O-alkyl)ribonucleotides (beta-2'O-allyl-RNA and beta-2'OMe-RNA) were shown to form the most stable hybrids with complementary RNA strands whereas the alpha-anomeric oligodeoxynucleoside phosphorothioate analogue displayed the highest stability in the culture medium. All the modified oligonucleotides examined in the present study exhibited a sequence-nonspecific inhibitory effect on HIV-1 replication, the phosphorothioate analogues being the most active ones (ED50 < 1 microM).

"On-line internal surface reversed-phase cleaning": the direct HPLC analysis of crude biological samples. Application to the kinetics of degradation of oligonucleotides in cell culture medium.

An "on-line" HPLC analysis of crude biological samples is described. A precolumn of internal surface reversed-phase material allows the passage of proteins and other unwanted products while retaining analytes which are transferred, concentrated and chromatographed on a conventional reverse-phase or ion-exchange HPLC column. This protocol allows precise kinetics of the degradation of an oligonucleotide in cell culture to be obtained without radiolabeling or sample preparation.

Intracellular delivery of nucleoside monophosphates through a reductase-mediated activation process.

On the basis of three different models (namely: ddU, AZT and PMEA), mononucleotide phosphotriester derivatives were designed to be able to liberate the corresponding monophosphate (or phosphonate) inside the cell through a reductase-mediated activation process. It was demonstrated that the use of bis[S-(2-hydroxyethylsulfidyl)-2-thioethyl] esters of ddUMP (11), AZTMP (12) and PMEA (17) resulted in intracellular delivery of the parent monophosphate (or phosphonate). This point was corroborated by observation of an anti-HIV effect of, 11 in various cell lines, for 12 in CEM TK- cells and by the enhanced activity observed for 17. Furthermore, the reported decomposition data in cell extracts fully confirm the validity of this approach and show unambiguously the potential for intracellular reductase-mediated activation of the starting drug.

5'-Hydrogenphosphonates of anti-HIV nucleoside analogues revisited: controversial mode of action.

The monomeric and symmetrical dimeric 5'-hydrogenphosphonate derivatives of AZT were prepared and evaluated for their inhibitory properties against HIV-1 in several cell lines. The synthesis of the compounds was achieved by reaction of AZT with in situ prepared phosphorus tris(imidazolide) or with phosphonic acid in the presence of pivaloyl chloride. The two title compounds showed in vitro anti-HIV activity similar to (but not better than) that of AZT in three cell lines which were not deficient in thymidine kinase. On the other hand they were inactive in CEM-TK- cells. Pharmacokinetic studies in several media corroborate the assumption that these compounds must not be considered as 'true antiviral agents', but that they act by releasing their nucleoside entity.

SATE pronucleotide approaches: an overview.

This review depicts in vitro and in vivo results obtained with nucleotide prodrugs (pronucleotides) bearing S-acyl-2-thioethyl (SATE) groups as esterase-labile phosphate protections. New developments are illustrated by the design of mononucleoside mixed phosphoester derivatives leading to the selective intracellular delivery of the corresponding 5'-mononucleotide through two different enzyme-mediated activation steps.

The effects of high-intensity and low-intensity cycle ergometry in older adults with knee osteoarthritis.

BACKGROUND: People with osteoarthritis (OA) of the knee experience pain and deconditioning that lead to disability. This study challenged the clinical belief that repetitive lower extremity exercise is not indicated in persons with knee OA. The effects of high-intensity and low-intensity stationary cycling on functional status, gait, overall and acute pain, and aerobic capacity were examined. METHODS: Thirty-nine adults (71+/-6.9 years old) with complaints of knee pain and diagnosis of OA were randomized to either a high-intensity (70% heart rate reserve [HRR]) or low-intensity (40% HRR) exercise group for 10 weeks of stationary cycling. Participants cycled for 25 minutes, 3 times per week. Before and after the exercise intervention they completed the Arthritis Impact Measurement Scale 2 for overall pain assessment, underwent timed chair rise, 6-minute walk test, gait, and graded exercise treadmill tests. Acute pain was reported daily with a visual analog scale and the Western Ontario and McMaster Universities Osteoarthritis Index scale. RESULTS: Analysis of variance revealed that participants in both groups significantly improved in the timed chair rise, in the 6-minute walk test, in the range of walking speeds, in the amount of overall pain relief, and in aerobic capacity. No differences between groups were found. Daily pain reports suggested that cycling did not increase acute pain in either group. CONCLUSIONS: Cycling may be considered as an alternative exercise modality for patients with knee OA. Low-intensity cycling was as effective as high-intensity cycling in improving function and gait, decreasing pain, and increasing aerobic capacity.

New insights regarding the potential of the pronucleotide approach in antiviral chemotherapy.

The rationale for a pronucleotide approach based on the use of phosphotriesters which incorporate enzyme-mediated bio-labile protection is discussed in detail. Among the studied bio-labile phosphate protecting groups, the S-acyl-2-thioethyl (SATE) groups appeared the most promising as exemplified in cell culture systems in the case of the pronucleotides of 3'-azido-3'-deoxythymidine, 2',3'-didehydro-3'-deoxythymidine, 2',3'-dideoxyadenosine and acyclovir In vivo implementations of such bis(SATE) pronucleotides have been planned for future animal studies.

Kinetics study of the biotransformation of an oligonucleotide prodrug in cells extract by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

The fate of a dodecathymidine prodrug in cell extract was monitored by MALDI-TOF MS. This technique allows a facile identification and a relative quantification of metabolites produced. We showed that the relative peak intensities were similar to the relative metabolite proportions that permitted the determination of their half-lives. The oligonucleotide prodrug was fully metabolized to yield the T12 phosphorothioate likely through a carboxyesterase mediated mechanism.

SATE (aryl) phosphotriester series. II. Stability studies and physicochemical parameters.

The stability of phosphotriester derivatives of 3'-azido-2',3'-dideoxythymidine (AZT) bearing a S-pivaloyl-2-thioethyl (tBuSATE) group and various aryl residues derived from L-tyrosine was evaluated in biological media. The results demonstrate that such compounds give rise to intracellular delivery of the parent mononucleotide through esterase and phosphodiesterase hydrolytic steps, successively.

Design of new mononucleotide prodrugs: aryl (SATE) phosphotriester derivatives.

Synthesis, biological activities and decomposition kinetics of novel phosphotriester derivatives of 3'-azido-2',3'-dideoxythymidine (AZT) bearing a S-tButyl-2-thioethyl (tBuSATE) group and L-tyrosinyl residues are reported. All the derivatives appeared to be potent inhibitors of HIV-1 replication in various cell culture experiments. The proposed decomposition process of these mixed phosphotriesters may involve successively an esterase and then a phosphodiesterase activation.

Direct MALDI-TOF MS analysis of oligonucleotides on solid support through a photolabile linker.

MALDI-TOF mass spectrometry was used to analyze oligonucleotides still anchored to long-chain alkylamine controlled-pore glass (LCAA-CPG) through a photolabile linker. This technique is useful to follow supported chemical reactions in real time and monitor by-products formation.

[Primitive cutaneous neuroendocrine carcinomas or Merkel's tumor. Clinical and therapeutic aspects in 22 patients]. / Carcinomes neuroendocrines cutanés primitifs ou tumeurs de Merkel. Aspects cliniques et thérapeutiques chez 22 malades.

INTRODUCTION: Primitive cutaneous neuroendocrine carcinoma (PCNC) is a rare tumor with poor prognosis. Surgery is the treatment of choice, but radiotherapy is taking a larger place in the management of these patients. METHODS: The files of 22 patients were studied retrospectively over a period of 14 years. RESULTS: The study included 17 women and 5 men with a mean age of 75.5 years. The localization of the tumor was the cephalic extremity in 12 cases. At the initial stage, the tumor in 3 of the 22 patients was of glandular or visceral localization. Thirteen stage I patients were treated surgically. Adjuvant radiotherapy was performed in 10 of these patients and only one relapsed (incomplete initial exeresis). The other three relapsed. Exclusive radiotherapy led to complete response in 4 patients who could not undergo surgery and in 2 with local relapses. Seven patients exhibited glandular involvement and 6 of them died (median 7 months) after the adenopathy had been discovered. DISCUSSION: Our series illustrates the clinical characteristics of this tumor of the elderly, which is predominantly cephalic and of rapid progression. From a therapeutic point of view, our results underline the benefit of radiotherapy as adjuvant to surgery. When surgery is impossible, and in the case of local relapse, radiotherapy gives good results.

[Ambulatory skin grafting in leg ulcers: a feasibility study of 34 patients]. / Greffe cutanée ambulatoire des ulcères de jambe: étude de faisabilité chez 34 malades.

OBJECTIVES: Despite the advent of modern dressings, management of leg ulcers remains a long costly process, particularly if no etiological treatment is possible. Autologous skin grafting is more and more widely used in this indication. The aim of this open single center noncomparative study was to analyze the feasibility of ambulatory procedures for skin grafting and the incidence of ambulatory care in a medical nursing clinic as an alternative to traditional hospitalization on total cost in this pathological condition. PATIENTS AND METHODS: Thirty-nine grafts were performed in 34 consecutive patients. No selection was made for etiology or duration of the leg ulcers. Three grafting techniques were used after debridement-cleansing: flap grafts for medium sized ulcers (29 cases), mesh grafts for large ulcers (6 cases) and patch grafts for small ulcers or ulcers with irregular contours (4 cases). The dressing was opened on day 5, nursing care was provided every 2 days and daily in case of infection. Percentage of healing was evaluated clinically on days 5, 15 and 30 then at months 3, 6 and 12. Photographs were taken. RESULTS: Four patients were lost to follow-up and one died. Among the 34 grafts assessed at 6 months, we obtained total healing in 56 p. 100, 75 p. 100 healing in 6 p. 100, 50 p. 100 healing in 9 p. 100 and failure in 29 p. 100. Healing rates were those expected for arterial ulcers and necrotic angiodermas. For venous leg ulcers, the rate of total healing was only 30 p. 100 at 6 months and 43 p. 100 at 1 year. Outcome depended on duration of the lesion and not on the type of skin graft or patient age. DISCUSSION: This prospective study reports outcome of ambulatory skin grafting in a large representative sample of patients with leg ulcers of various etiologies. The less favorable outcome for venous ulcers can be explained by the duration of the ulcerations and infection in these often neglected lesions. The risk of graft displacement, contact eczema, and infection must be recognized for early treatment. There were no cases with general complications. This ambulatory technique has the enormous advantage of limiting the risk of hospital-related problems in this elderly population and of reducing overall cost of care for leg ulcers, and finally of limiting the risk of recurrence by regular post-graft follow-up in a specialized center and by treatment of the causal disease.

[Enoxaparin-induced cutaneous necrosis localized on insulin lipodystrophies]. / Nécroses cutanées à l'enoxaparine localisées sur des zones de lipodystrophie insulinique.

INTRODUCTION: Low-molecular weight heparin-induced cutaneous necrosis is exceptional. Pathogenesis remains unclear. We report an exceptional case with elective localization of the necrotic areas in insulin lipodystrophic tissue. CASE REPORT: A 69-year old patient developed areas of skin necrosis after starting enoxaparin therapy. These areas were located far from the points of injection and focalized on skin areas where the patient had been injecting insulin daily for the last four years. These areas had an aspect of insulin lipodystrophy. Biopsy specimens showed leukocytoclastic vasculitis. There were no associated biological anomalies. One month later, prick-tests were made with different low-molecular weight heparins and calcium heparinate in a lipodystrophic area together with an enoxaparin control test in healthy skin. The only positive test was for enoxaparin in an insulin lipodystrophic area (hard erythema at 24 hours). Histology at 72 hours demonstrated leukocytoclastic vasculitis. DISCUSSION: Six cases of cutaneous necrosis induced by low-molecular weight heparin have been reported, including three cases with enoxaparin. Two pathophysiological mechanisms could be involved: (i) localized heparin-dependent platelet aggregation, or (ii) vasculitis induced by type III hypersensitivity reaction. In our case, the leukocytoclastic aspect of the vasculitis was compatible with an immune complex hypersensitivity reaction. The localization of the necrotic areas would be explained by enoxaparin-induced preferential deposit of immune complexes in the vascular turbulences present in lipodystrophic areas.

[Paraneoplastic pemphigus with tracheobronchial involvement]. / Pemphigus paranéoplasique avec atteinte trachéo-bronchique.

BACKGROUND: Paraneoplastic pemphigus is a bullous skin disease with characteristic polymorphous clinical presentation and precise histological and immunological features. We report a case of paraneoplastic pemphigus associated with chronic lymphoid leukemia involving the tracheobronchial epithelium. CASE REPORT: A patient with chronic lymphoid leukemia developed pluriorificial lesions. There were several conjunctival, buccal and genital erosions associated with erosive plaques on the trunk, Nikolski's sign and bullous lesions suggestive of paraneoplastic pemphigus. Histology examination of a bulla showed intraepidermal blistering and suprabasal acantholysis. Direct immunofluorescence evidenced intercellular IgG and C3 deposits. Search for anti-intercellular substance antibodies was positive with fluorescence on specific paraneoplastic pemphigus substrates. At immunotransfer, the serum recognized several bands corresponding to 250, 230, 210 and 190 kD antigens, confirming the diagnosis of paraneoplastic pemphigus. Several days later, the patient's general condition deteriorated with bronchorrhea. Bronchial endoscopy visualized ulceronecrotic plaques. Tracheal biopsy evidenced acantholytic cells and intraepithelial cleavage. General corticosteroid therapy was initiated and led to improvement of the skin lesions but the patient died rapidly from pneumonia. Autopsy confirmed the presence of epithelial cleavage and acantholysis involving the trachea and bronchi. DISCUSSION: This case illustrates the difficulty of diagnosing paraneoplastic pemphigus in the early stages. The pluriorificial lesions were suggestive of a Stevens-Johnson syndrome. Besides the genital, conjunctival and buccal mucosa, other mucosa can be involved. In our case, despite the absence of an immunological element, histology was highly suggestive of specific tracheobronchial localizations. The presence of such lesions, which should be searched for in all cases with bronchopulmonary manifestations, worsens the prognosis.