Fate of Quasiparticles at High Temperature in the Correlated Metal Sr_{2}RuO_{4}.

We study the temperature evolution of quasiparticles in the correlated metal Sr_{2}RuO_{4}. Our angle resolved photoemission data show that quasiparticles persist up to temperatures above 200 K, far beyond the Fermi liquid regime. Extracting the quasiparticle self-energy, we demonstrate that the quasiparticle residue Z increases with increasing temperature. Quasiparticles eventually disappear on approaching the bad metal state of Sr_{2}RuO_{4} not by losing weight but via excessive broadening from super-Planckian scattering. We further show that the Fermi surface of Sr_{2}RuO_{4}-defined as the loci where the spectral function peaks-deflates with increasing temperature. These findings are in semiquantitative agreement with dynamical mean field theory calculations.

Bulk and Surface Electronic Structure of the Dual-Topology Semimetal Pt_{2}HgSe_{3}.

We report high-resolution angle-resolved photoemission measurements on single crystals of Pt_{2}HgSe_{3} grown by high-pressure synthesis. Our data reveal a gapped Dirac nodal line whose (001) projection separates the surface Brillouin zone in topological and trivial areas. In the nontrivial k-space range, we find surface states with multiple saddle points in the dispersion, resulting in two van Hove singularities in the surface density of states. Based on density-functional theory calculations, we identify these surface states as signatures of a topological crystalline state, which coexists with a weak topological phase.

New Insights and Perspectives in Fanconi Anemia Research.

Fanconi anemia is a rare, cancer-prone disease with mutations in 22 genes. The primary defect results in altered DNA repair mechanisms that fuel a severe proinflammatory condition in the bone marrow, leading to cellular depletion of the hematopoietic system and eventually to bone marrow failure. During the past three decades, a plethora of dysfunctions have been highlighted in the Fanconi anemia phenotype, but recent research allows us to glimpse an even more complex scenario where defective lipid metabolism could have important consequences in hematopoietic stem cell differentiation.

In situ strain tuning of the metal-insulator-transition of Ca2RuO4 in angle-resolved photoemission experiments.

Pressure plays a key role in the study of quantum materials. Its application in angle resolved photoemission (ARPES) studies, however, has so far been limited. Here, we report the evolution of the k-space electronic structure of bulk Ca2RuO4, lightly doped with Pr, under uniaxial strain. Using ultrathin plate-like crystals, we achieve uniaxial strain levels up to -4.1%, sufficient to suppress the insulating Mott phase and access the previously unexplored electronic structure of the metallic state at low temperature. ARPES experiments performed while tuning the uniaxial strain reveal that metallicity emerges from a marked redistribution of charge within the Ru t2g shell, accompanied by a sudden collapse of the spectral weight in the lower Hubbard band and the emergence of a well-defined Fermi surface which is devoid of pseudogaps. Our results highlight the profound roles of lattice energetics and of the multiorbital nature of Ca2RuO4 in this archetypal Mott transition and open new perspectives for spectroscopic measurements.

Rates of base excision repair are not solely dependent on levels of initiating enzymes.

The oxidized base 8-oxo-7,8-dihydroguanine (8-oxoG), the product of deamination of cytosine uracil (U), and the sites of base loss [abasic (AP) sites] are among the most frequent mutagenic lesions formed in the human genome under physiological conditions. In human cells, the enzymatic activities initiating DNA base excision repair (BER) of 8-oxoG, U and AP sites are the 8-oxoG DNA glycosylase (hOGG1), the U-DNA glycosylase (UNG) and the major hydrolytic AP endonuclease (APE/HAP1), respectively. In recent work, we observed that BER of the three lesions occurs in human cell extracts with different efficacy. In particular, 8-oxoG is repaired on average 4-fold less efficiently than U, which, in turn, is repaired 7-fold slower than the natural AP site. To discriminate whether the different rates of repair may be linked to different expression of the initiating enzymes, we have determined the amount of hOGG1, UNG and APE/HAP1 in normal human cell extracts by immunodetection techniques. Our results show that a single human fibroblast contains 123 000 +/- 22 000 hOGG1 molecules, 178 000 +/- 20 000 UNG molecules and 297 000 +/- 50 000 APE/HAP1 molecules. These limited differences in enzyme expression levels cannot readily explain the different rates at which the three lesions are repaired in vitro. Addition to reaction mixtures of titrated amounts of purified hOGG1, UNG and APE/HAP1 variably stimulated the in vitro repair replication of 8-oxoG, U and the AP site respectively and the increase was not always proportional to the amount of added enzyme. We conclude that the rates of BER depend only in part on cellular levels of initiating enzymes.

Efficient DNA base excision repair in ataxia telangiectasia cells.

Ataxia telangiectasia (A-T) cells are sensitive to a broad range of free-radical-producing and alkylating agents. Damage caused by such agents is in part repaired by base excision [base excision repair (BER)]. Two BER pathways have been demonstrated in mammalian cells: a single-nucleotide-insertion pathway and a long-patch pathway involving resynthesis of 2-10 nucleotides. Although early studies failed to detect DNA-repair defects in A-T cells exposed to ionizing radiation and radiomimetic agents, more recent experiments performed in non-dividing A-T cells and the demonstrated interaction of the A-T-mutated protein (ATM) with the BRCA1 gene product suggest that a DNA-repair defect may underlie, at least in part, the radiation sensitivity in A-T cells. We have analysed BER of a single abasic site or a single uracil in two A-T families, using an in vitro BER system. In both families, the mutation involved was homozygous and completely inactivated the ATM protein. No difference was observed between affected individuals and heterozygous or homozygous wild-type relatives in their capacity to perform DNA repair by either one-nucleotide insertion or the long-patch pathway. Hence, the putative DNA-repair defect in A-T cells, if any, does not involve BER.

Efficient repair of 8-oxo-7,8-dihydrodeoxyguanosine in human and hamster xeroderma pigmentosum D cells.

The repair of the endogenous lesion 8-oxo-7,8-dihydrodeoxyguanosine (8-oxodG) was investigated in the nucleotide excision repair mutant xeroderma pigmentosum D (XPD), using human normal or transformed XPD fibroblasts and the Chinese hamster XPD cell line UV5. In vivo repair of 8-oxodG induced by hydrogen peroxide treatment and analyzed by high-performance liquid chromatography/electrochemical detection was normal in the XPD mutant fibroblasts XP15PV and GM434, as compared to normal human fibroblasts GM970, GM5757, and GM6114. Similar results were obtained with the human SV40-transformed XPD mutant cell line GM8207 in comparison to the control cell line GM637. Repair of 8-oxodG was even slightly (2-3-fold) but reproducibly increased in Chinese hamster XPD mutant UV5 cells, as compared to parental AA8 cells. This unexpected effect was reversed by transfection in UV5 cells of a wild-type XPD cDNA and confirmed in in vitro experiments in which a plasmid substrate containing a single 8-oxoG was repaired by UV5 cell extracts. The data show that repair of 8-oxodG is normal in XPD cells, thus indicating that the neurological complications of XPD patients may not be linked to in vivo accumulation of this lesion.

Comparative repair of the endogenous lesions 8-oxo-7, 8-dihydroguanine (8-oxoG), uracil and abasic site by mammalian cell extracts: 8-oxoG is poorly repaired by human cell extracts.

The repair of the endogenous lesions 8-oxo-7,8-dihydroguanine (8-oxoG), uracil (U) and natural abasic site (AP site) was investigated using an in vitro base excision repair assay in which a plasmid substrate containing a single lesion at a defined position was repaired by mammalian cell extracts. Repair replication of an 8-oxoG/cytosine base pair performed by normal human cell extracts was approximately 5-fold less efficient than repair of a U/adenine base pair and, in turn, the latter was repaired approximately 10-fold less efficiently than an AP site placed in front of an adenine. A similar pattern of repair capacity for the three lesions was observed in Chinese hamster extracts. Repair of 8-oxoG was performed by the one nucleotide insertion pathway only. The lower repair replication ability of 8-oxoG with respect to U was linked to a lower DNA glycosylase (base removal) activity rather than to inability to process the beta-elimination cleaved strand left by the AP lyase activity associated with human oxoguanine DNA glycosylase 1. The data show that DNA repair of 8-oxoG is poor in human cells in comparison with other frequent endogenous lesions.

Analysis of repair of abasic sites in early onset breast cancer patients.

Defective DNA repair has been suggested as a possible predisposing factor for breast cancer. We have investigated the repair of the frequent endogenous lesions abasic sites in sporadic early onset breast cancer patients and matched control individuals. No significant difference was observed between the abasic site repair capacities of peripheral blood lymphocytes from cases and controls. Repair of abasic sites was also studied in tumor and surrounding normal tissues of the patients. The 2 tissues showed marked differences in histology and protein composition with a fibro-collagenous component varying from sample to sample but invariably higher in normal tissues as compared with the adjacent tumor. These differences involved the need to calculate the repair activities of tissues on the basis of cellular DNA content for comparison purposes. After doing so, tumor and normal tissues exhibited similar abasic site repair capacities, whereas lymphocytes showed a repair capacity significantly lower than tissues. We conclude that early onset sporadic breast cancer patients show no evident defect in repair of abasic sites at the level of both lymphocytes and tumor.

Leuconostoc pseudomesenteroides as a cause of nosocomial urinary tract infections.

The phenotypic and genotypic characterization of five clinical isolates of Leuconostoc pseudomesenteroides associated with nosocomially acquired urinary tract infections is described. All the strains were susceptible to chloramphenicol, clindamycin, erythromycin, gentamicin, and tetracycline; all were resistant to nalidixic acid, norfloxacin, and vancomycin; and all were intermediately affected by ampicillin and penicillin. Analysis of chromosomal DNA by pulsed-field gel electrophoresis after treatment with SmaI indicated a clonal relationship of the isolates. The results provide evidence for the possibility of nosocomial transmission of this unusual opportunistic, vancomycin-resistant pathogen.

Characterization of surface saccharides in two Corynebacterium diphtheriae strains.

Two Corynebacterium diphtheriae strains were analyzed by assays employing a battery of highly purified fluorescent lectins. From 22 lectins tested only seven with affinity to receptor molecules containing N-acetylglucosamine (D-GlcNAc), N-acetylgalactosamine (D-GalNAc), galactose (D-Gal), mannose-like (D-Man-like) and sialic acid residues showed positive fluorescent labeling. A higher reactivity of Triticum vulgaris (WGA), which binds to sialic acid and/or beta-D-GlcNAc-containing residues, and Bandeiraea simplicifolia II (BS-II), which recognizes alpha and beta-D-GlcNAc units, was shown by the sucrose-fermenting strain. Ricinus communis (RCA-I), which recognizes D-Gal units in addition to both Glycine max (SBA) and Artocarpus integrifolia (Jacaline) agglutinins that bind to D-GalNAc-containing residues, reacted preferentially with the sucrose-negative strain. Canavalia ensiformis (Con A), which recognizes D-Man-like receptors, reacted with both sucrose-fermenting and non-sucrose-fermenting C. diphtheriae biotypes. However, higher interaction was observed with the non-sucrose-fermenting strain. Fluorescence of WGA binding was significantly decreased by neuraminidase treatment suggesting the presence of an exposed sialic acid moiety on C. diphtheriae surfaces. Binding assay using radiolabeled [125I]WGA essentially confirmed the lectin fluorescence studies. N-Acetylneuraminic acid moieties were detected in whole cell hydrolysates as assessed by thin-layer and gas-liquid chromatography. The data indicate differences on the cell surface saccharide ligands between the sucrose-fermenting and the non-sucrose-fermenting C. diphtheriae strains.

The DNA helicases acting in nucleotide excision repair, XPD, CSB and XPB, are not required for PCNA-dependent repair of abasic sites.

DNA repair of abasic sites is accomplished in mammalian cells by two distinct base excision repair (BER) pathways: a single nucleotide insertion pathway and a proliferating cell nuclear antigen (PCNA)-dependent pathway involving a resynthesis patch of 2-10 nucleotides 3' to the lesion. The latter pathway shares some enzymatic components with the nucleotide excision repair (NER) pathway acting on damage induced by ultraviolet light: both pathways are strictly dependent on PCNA and several observations suggest that the polymerization and ligation phases may be carried out by common enzymatic activities (DNA polymerase delta/epsilon and DNA ligase I). Furthermore, it has been postulated that the transcription-NER coupling factor Cockayne syndrome B has a role in BER. We have investigated whether three NER proteins endowed with DNA helicase activities (the xeroderma pigmentosum D and B gene products and the Cockayne syndrome B gene product) may also be involved in repair of natural abasic sites, by using the Chinese hamster ovary mutant cell lines UV5, UV61 and 27-1. No defect of either the PCNA-dependent or the single nucleotide insertion pathways could be observed in UV5, UV61 or 27-1 mutant cell extracts, thus showing that the partial enzymatic overlap between PCNA-dependent BER and NER does not extend to DNA helicase activities.

Role of the DNA ligase III zinc finger in polynucleotide binding and ligation.

Mammalian DNA ligase III exists as two distinct isoforms denoted alpha and beta. Both forms possess a motif that is homologous to the putative zinc finger present in poly(ADP-ribose) polymerase. Here, the role of this motif in the binding and ligation of nicked DNA and RNA substrates in vitro has been examined in both isoforms. Disruption of the putative zinc finger did not affect DNA ligase III activity on nicked DNA duplex, nor did it abolish DNA ligase III-alpha activity during DNA base excision repair in a cell-free assay. In contrast, disruption of this motif reduced 3-fold the activity of both DNA ligase III isoforms on nicked RNA present in RNA/DNA homopolymers. Furthermore, whereas disruption of the motif did not prevent binding of DNA ligase III to nicked DNA duplex, binding to nicked RNA homopolymers was reduced approximately 10-fold. These results suggest that the putative zinc finger does not stimulate DNA ligase III activity on simple nicked DNA substrates, but indicate that this motif can target the binding and activity of DNA ligase III to nicked RNA homopolymer. The implications of these results to the cellular role of the putative zinc finger are discussed.

Small doses of intrathecal morphine combined with systemic diclofenac for postoperative pain control after cesarean delivery.

UNLABELLED: Postoperative pain control after cesarean delivery under spinal anesthesia is effectively obtained with morphine 0.1-0.3 mg intrathecally, although there may be dose-dependent side effects. We evaluated the quality of analgesia and the incidence of side effects with smaller doses of intrathecal morphine combined with intramuscular (i.m.) diclofenac. One hundred-twenty pregnant patients were allocated into six groups, which received the following treatments: Groups 1, 3, and 5 received 0.1, 0.05, and 0.025 mg of intrathecal morphine, respectively, plus 75 mg of i.m. diclofenac every 8 h; Groups 2, 4, and 6 received 0.1, 0.05, and 0.025 mg of intrathecal morphine, respectively, plus i.m. diclofenac on demand. Spinal anesthesia was performed with 15 mg of 0.5% hyperbaric bupivacaine. Pain scores and side effects were evaluated hourly for the first 24 h. Groups 1 and 2 had lower pain scores than Groups 3, 4, 5, and 6. However, only patients in Groups 2, 4, and 6 requested additional analgesics. Severe pruritus was more frequent in Groups 1 and 2. No patient experienced respiratory depression. We conclude that there is no advantage in using doses larger than 0.025 mg of intrathecal morphine if they are combined with systemic diclofenac. IMPLICATIONS: A multimodal approach to pain control may provide good quality analgesia while reducing drug-related side effects. In this study, a very small dose of intrathecal morphine, in association with intramuscular diclofenac, proved effective for controlling pain after cesarean delivery, with a low incidence of morphine-induced pruritus.

Involvement of XRCC1 and DNA ligase III gene products in DNA base excision repair.

DNA ligase III and the essential protein XRCC1 are present at greatly reduced levels in the xrcc1 mutant CHO cell line EM-C11. Cell-free extracts prepared from these cells were used to examine the role of the XRCC1 gene product in DNA base excision repair in vitro. EM-C11 cell extract was partially defective in ligation of base excision repair patches, in comparison to wild type CHO-9 extracts. Of the two branches of the base excision repair pathway, only the single nucleotide insertion pathway was affected; no ligation defect was observed in the proliferating cell nuclear antigen-dependent pathway. Full complementation of the ligation defect in EM-C11 extracts was achieved by addition to the repair reaction of recombinant human DNA ligase III but not by XRCC1. This is consistent with the notion that XRCC1 acts as an important stabilizing factor of DNA ligase III. These data demonstrate for the first time that xrcc1 mutant cells are partially defective in ligation of base excision repair patches and that the defect is specific to the polymerase beta-dependent single nucleotide insertion pathway.

Repair of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea-induced damage by mammalian cell extracts.

The repair of damage induced by the alkylating antitumor drug 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) was investigated using an in vitro excision repair system. Hamster cell extracts prepared from the parental CHO-9 cell line and the ERCC1 mutant 43-3B were both proficient in the repair of CCNU-induced damage. The in vitro repair of CCNU damage was faster than the repair of UV damage and plasmid substrates were rapidly and efficiently incised after incubation with either CHO-9 or 43-3B extracts. 7-Methylguanine (7-meG) and 3-methyladenine (3-meA) glycosylases were active to a similar extent in the CHO-9 and 43-3B extracts. The data indicate that most damage induced by CCNU is repaired via the ERCC1-independent base excision repair pathway, initiating with removal of chloroethylated and hydroxyethylated bases by N-glycosylases. Yet, the sensitive phenotype of 43-3B cells suggests that the ERCC1 gene product is required for the removal of a small subset of CCNU-induced lesions that are important for drug cytotoxicity.

[Pulmonary calcification in vitamin D poisoning in an infant]. / Calcificazioni polmonari in corso di intossicazione da vitamina D in un bambino.

We describe the case of a child aged 11 months with vitamin D intoxication and hypercalcemia, who developed acute renal failure and dyspnea. Chest X-rays showed interstitial changes compatible with either pulmonary alveolar proteinosis or pulmonary edema. The hypercalcemia suggested the possibility of metastatic calcifications of the lung. This hypothesis was subsequently confirmed by the progressive disappearance of pulmonary findings as calcemic levels returned to normal values... Our report emphasize the opportunity of studying the respiratory system in each patient with hypercalcemia, whichever the etiology may be.

[Infection by Mycoplasma pneumoniae. Epidemiologic investigation and statistical clinical study of 122 children admitted to the Institute of Pediatrics of the University of Florence during the period 1 January 1977 to 31 December 1983]. / L'infezione da Mycoplasma pneumoniae. Indagine epidemiologica e studio clinico statistico su 122 bambini ricoverati presso l'Istituto di Pediatria dell'Università di Firenze nel periodo 1 gennaio 1977-31 dicembre 1983.

We carried out an epidemiologic research about M. Pneumoniae infection from 1977 to 1983: determination of CF antibodies has been performed by the Bacteriology and Virology Laboratory (Prof. Lamanna, USL 10/D, Florence). Serum samples were collected by the laboratory itself and by hospitals and university departments of Florence and neighbouring communes. Our research confirms cyclic behaviour of M. Pneumoniae infection: we could follow up a 3 years long epidemic after a previous 2 years long endemic disease. We found a major sera-positive rate for M. Pneumoniae in children than in adults. In the same period we carried out a clinical-statistical study on 122 children (80 males and 42 females) admitted to the Pediatric Institute "A. Meyer" in Florence because of an infection due to M. Pneumoniae. The most affected age range sems to be included between 5 and 10 years. Pneumonia is the commonest clinical feature of M. Pneumoniae infection (85.2%): furthermore, we must point out some cases in 0-2 years-old subjects. In our patients, clinical features, X-ray findings and laboratory tests strictly agree with those reported by other authors. We treated all our patients with erythromycin: in three weeks we obtained thee normalization of clinical patterns and X-ray findings in all cases.