Electronic hybridization of large-area stacked graphene films.

Direct, tunable coupling between individually assembled graphene layers is a next step toward designer two-dimensional (2D) crystal systems, with relevance for fundamental studies and technological applications. Here we describe the fabrication and characterization of large-area (>cm(2)), coupled bilayer graphene on SiO(2)/Si substrates. Stacking two graphene films leads to direct electronic interactions between layers, where the resulting film properties are determined by the local twist angle. Polycrystalline bilayer films have a "stained-glass window" appearance explained by the emergence of a narrow absorption band in the visible spectrum that depends on twist angle. Direct measurement of layer orientation via electron diffraction, together with Raman and optical spectroscopy, confirms the persistence of clean interfaces over large areas. Finally, we demonstrate that interlayer coupling can be reversibly turned off through chemical modification, enabling optical-based chemical detection schemes. Together, these results suggest that 2D crystals can be individually assembled to form electronically coupled systems suitable for large-scale applications.

[The study of the frequency and features of bacteria isolated in patients with non-tuberculosis respiratory disorders admitted in "M. Nasta" Institute in the first trimester 2001]. / Studiul frecventei si caracterelor florei bacteriene în pneumopatiile netuberculoase la bolnavii internati în Institutul "Marius Nasta" în primul trimestru al anului 2001.

The aim of this study was to determine the spectrum of bacteria isolated in patients with non-TB respiratory disorders, in order to find the frequency of germs isolated globally and in each of the 6 clinical syndromes: suppurations, chronic obstructive diseases exacerbations (COPD, bronchial asthma), pneumopathies, post-TB syndromes, tumors and interstitial lung diseases. We found the greatest global frequency in anaerobes (35%). This is in concordance with the high frequency of broncho-pulmonary suppurations (51% of the cases studied). In second place comes Ps. aeruginosa (18%), followed by Str. Pneumoniae (16%), H. influenzae (11%) and Klebsiella pn. (10%). Considering the germs identified in the various clinical syndromes, we found a high frequency of anaerobes associated to suppurations (51%), interstitial lung diseases (43%) and tumors (37%), while Ps. aeruginosa is first in post-TB syndromes (50%) and COPD exacerbations (21%), equal to H. influenzae. In pneumonias, Str. Pneumoniae was most frequently isolated (38%) followed by H. influenzae (25%). The susceptibility testing of strains of Klebsiella and Ps. aeruginosa revealed the increasing tendency to resistance to broad spectrum antibiotics, especially for Ps. aeruginosa, with consecutive difficulties in finding the appropriate treatment.

[The bacterial spectrum in bronchopulmonary infections]. / Spectrul bacterian al infectiilor bronhopulmonare.

UNLABELLED: This study aimed to establish the bacterial profile of bronchopulmonary infections confirmed by the cytobacteriological examination of sputum, in order to find therapeutical guidelines for empirical treatment. We included in the study 408 patients with clinical signs of bronchopulmonary infection (cough and mucopurulent sputum, fever) among which 294 hospitalised patients (5.5% of the 5280 admitted in 1997) and 114 outpatients. The sputum samples collected respecting the decontamination methods were examined cytobacteriologically (smear, culture and antibiogram). The spectrum of isolated bacteria was the following: H. influenzae--198 cases, anaerobes--54, Kl. pneumoniae--53, Ps. aeruginosa--50, S. pneumoniae--17. Analyzing the diseases for which the bacterial examination was performed, we found the following distribution: COPD--66, bacterial infections in TB patients--61, chronic suppurations--33, bronchiectasis--37, pulmonary abscess--24. We noticed the high frequency of H. influenzae and important numbers of anaerobes, Kl. pneumoniae and Ps. aeruginosa especially in COPD patients and patients with chronic suppurations. We performed antibiograms for establishing the sensitivity of bacterial samples (S. aureus, Kl. pneumoniae, Ps. aeruginosa, beta-lactamase-positive H. influenzae). Most of them were multidrug-resistant. CONCLUSIONS: 1. The cytobacteriological study of sputum may be useful for choosing the right treatment, especially for the patients with multiple antibiotic treatments and infected with multidrug resistant bacteria; 2. Knowing the bacterial spectrum in certain respiratory diseases allows the choice of empirical treatment for bronchopulmonary infections in uncomplicated cases.

[The comparative results of the antibiograms for Mycobacterium tuberculosis performed in 2 different laboratories]. / Rezultatele comparative ale antibiogramelor pentru Mycobacterium tuberculosis efectuate în doua laboratoare diferite.

The aim of this study was to appreciate the accuracy of the technique for sensitivity test for M. tuberculosis. We have tested the same bacterial strains (101) using the same drugs concentrations, by absolute concentration method, and we have compared the results obtained in two different laboratories. The concordance of the obtained results (94.05% for SM, 97.03% for INH, 99.01% for RMP, 100% for EMB) is in the limits of reproducibility obtained by other authors. The obtained results show a good technique for sensitivity test in the two laboratories.

[Acute rhinopharyngitis, acute interstitial pneumonia and parieto-frontal brain abscess with H. influenzae type B]. / Rinofaringita acuta, pneumonie acuta interstitiala si abces cerebral parieto-frontal cu H.influenzae tip B.

The paper deals with a parietal frontal cerebral abscess caused by HITB biotype I in a girl aged 8 months. First a meningitis is suspected, then a tuberculous meningitis unsuccessfully treated with ampicillin, biseptol, respectively INH, rifampicin, pyrazinamide, prednisone, phenobarbital and chloramphenicol. The patient died through a central respiratory standstill on the 17th day of disease. The anatomopathological examinations revealed a giant parietal frontal cerebral abscess. H.influenzae, (serum type B, biotype I) resistant to ampicillin, chloramphenicol, Kanamycin, rifampicin and tetracycline but sensitive to erythromycin and neomycin was also found. A pharyngeal infection with HITB was presumably the origin of the abscess.

[The comparative testing of the tuberculostatic sensitivity of M. tuberculosis strains in 2 diagnostic centers in Romania]. / Testarea comparativa a sensibilitatii la tuberculostatice a unor tulpini de M. tuberculosis în doua centre de diagnostic din tara.

The study of sensibility was carried out on 152 strains of M. tuberculosis by the method of absolute concentrations in two laboratories in Romania. The results obtained show an agreement in 71.05% of the cases. The high proportion of the disagreeing results shows the role of subjective and objective factors. The paper shows the possible modalities for correcting these factors.

Shortened insulin with enhanced in vitro potency.

After it has been shown that removal of residues B26-B30 leaves insulin with full biological activity, provided the new C-terminus is amidated (Fischer et al. (1985) Biol. Chem. Hoppe-Seyler 366, 521-525), it is demonstrated here that it does not even preclude enhancement of potency. 7 analogues of des-(B26-B30)-insulin-B25-amide were prepared by trypsin-mediated semisynthesis, the replacements being D-PheB24; HisB25, D-PheB25, TrpB25, TyrB25; D-PheB24,B25 and D-PheB24, TyrB25. Mere conversion of the configuration of B25-phenylalanine reduces in vitro potency to 0.5%. If B25-phenylalanine is, however, substituted by histidine or tyrosine activity is increased to 310 or 230, respectively. According to the features common to these two side chains, the favourable effect should be due to their ring structure with balanced aromatic and polar or H-bonding properties, respectively. The results indicate that in the complete insulin molecule the C-terminal pentapeptide modulates the subtle role that residues B24 and/or B25 play in receptor binding and activity; its presence may have a positive or negative effect. The drastic differences in activity between the shortened analogues are in no ways reflected in the CD spectra which are very similar, though clearly different from that of native insulin.

Recognition of covalent insulin-receptor complexes on viable adipocytes by anti-insulin antibodies.

Isolated rat adipocytes were photo-affinity-labelled with B2-(4-azido-2-nitrophenylacetyl)-des-PheB1-insulin or B29-(4-azido-2-nitrophenylacetyl)insulin. Four anti-insulin antibodies (3 monoclonal, 1 polyclonal) were tested for their ability to inhibit the persistent stimulation of lipogenesis caused by the covalently bound insulin [Brandenburg et al. (1980) Nature (London) 286, 821-822]. The polyclonal and 2 monoclonal antibodies, directed against the C-terminus of the B-chain, gave a significant depression, while one antibody, directed against the region A(8-10), was without effect. Under reversible conditions, without irradiation, all antibodies completely inhibited lipogenesis. For the polyclonal antibody this is shown in a dose-dependent way. It is concluded that the effective antibodies can recognize their epitope because it is accessible on the surface of the complex and does not represent part of the receptor-binding surface of insulin. This binding leads to interference with the generation and/or transmittance of the biological signal.

Structure-function relationships of shortened [LeuB25]insulins, semisynthetic analogues of a mutant human insulin.

Replacement of B25-phenylalanine by leucine in the insulin sequence causes marked inactivation. The effect of this sequence variation was studied here in des-(B26-30)-insulin. [LeuB25]des-(B26-30)-insulin and its B25-amide were prepared by trypsin-mediated semisynthesis from N-terminally protected des-(B23-30)-insulin and synthetic tripeptides. The relative lipogenic potency in isolated rat adipocytes was 8.0% for the truncated analogue with a free B25-carboxyl function, and 18.1% for the amidated analogue. Binding to cultured human IM-9 lymphocytes was 4% and 9%, respectively. Thus, both shortened insulins are markedly more active than [LeuB25]insulin. The PheB25----LeuB25 substitution in both the shortened and the full sequence has a moderate effect on the CD spectrum, indicating that the gross main chain conformation is largely retained in both molecules. Independent of the substitution an absolute increase of the circular dichroism is observed upon amidation of the B25-carboxyl group.

Time-dependence of biological activity induced by covalent insulin-receptor complexes in rat adipocytes.

Lipogenesis in isolated adipocyte preparations is stimulated when photosensitive insulin derivatives are attached covalently to specific receptors. This response was compared quantitatively with that to reversibly associated insulin, and it was shown that both covalent and reversible insulin-receptor complexes behave very similarly. The extent of stimulation of lipogenesis was studied as a function of time. Cells were incubated in buffer for various times before addition to vials containing 0 (basal) or 10 ng of monocomponent insulin/ml (maximal) and [U-3H]glucose. After 60 min, the toluene-soluble [3H]lipids were measured. The maximal stimulation induced by reversibly bound insulin was virtually constant over a period of 4 h. In contrast, adipocytes to which N alpha B2-(2-nitro-4-azidophenylacetyl)-des-PheB1-insulin had been covalently attached at the start of the experiment showed a loss of stimulation with time when incubated at 37 degrees C. This loss was decreased in the presence of lysosomotropic agents such as chloroquine at concentrations (approx. 200 microM) that had very little or no effect on the basal and maximal lipogenesis rates. A simple method was used to transform the measured rate of loss of stimulation into a rate of loss of effective units. A half-time of 80 min was calculated for the effective covalent insulin-receptor units in adipocytes at 37 degrees C at pH 7.4. This is very close to values reported by others for the internalization of covalent complexes in these cells, suggesting that this may be the causative event for the deactivation of the insulin-receptor unit. The inhibitory effect of chloroquine on the deactivation may indicate that the insulin-receptor complex can function even after internalization.

Biological action and fate of photoaffinity-labelled insulin-receptor complexes.

Covalent linking of two photoactivatable insulin derivatives, B2-(2-nitro,4-azidophenylacetyl)-des-PheB1-insulin and B29-(2-nitro,4-azidophenylacetyl)-insulin to viable rat adipocytes gives a system, which contains a fixed stoichiometry between hormone and receptor. The biological signal of prolonged lipogenesis has been used to study several aspects of insulin binding and action: the role of the site of the crosslink between insulin and receptor, recognition of bound photoinsulin by anti-insulin antibodies, the half-life of the biologically active complex, the pH-dependence of the biological signal, and the possible role of internalization. Furthermore, the effect of trypsin on the insulin receptor, as well as the insulin-receptor complex, has been investigated and a refined model of the receptor is presented.

[LeuB24]- and [LeuB25]insulins are not antagonists of lipogenesis in adipocytes.

Semisynthetic human [LeuB24]-and [LeuB25]insulins were investigated to determine whether they show antagonistic properties towards insulin-stimulated lipogenesis in isolated fat cells. In contrast to other reports, we could detect only an additive agonistic effect when constant concentrations (e.g. 0.3 ng/ml) of the analogues were mixed with varying concentrations of insulin, or when constant concentrations (e.g. 0.3 ng/ml, 0.6 ng/ml) of insulin were mixed with varying concentrations of the analogues. Similar results were obtained with mixtures of insulin and NA2-acetyl- or NA2-propionyl-des-GlyA1-insulins. These results do not support the contention that a diabetic state could be caused by either of these mutant human insulins.