The contradictory effect of the methoxy-substituent in palladium-catalyzed ethylene/methyl acrylate cooligomerization.

Two new nonsymmetric bis(aryl-imino)acenaphthene ligands (Ar,Ar'-BIAN) and one symmetric Ar2-BIAN were studied. The three ligands share the presence of at least one methoxy group on one of the two aryl rings. These ligands were used for the synthesis of neutral and monocationic palladium(ii) complexes of general formula [Pd(CH3)Cl(N-N)] and [Pd(CH3)(L)(N-N)][PF6] (N-N = Ar,Ar'-BIAN, Ar2-BIAN; L = CH3CN, dmso). Due to the nonsymmetric nature of the ligands and their coordination to palladium in a nonsymmetric chemical environment, cis and trans isomers are possible for the three series of complexes with Ar,Ar'-BIANs. Both a detailed NMR investigation in solution and the X-ray characterization in the solid state point out that the trans isomer is the preferred species for the neutral derivatives, whereas for the cationic compounds a decrease in the stereoselectivity of the coordination is observed. One of the new Ar,Ar'-BIANs differs from an already reported nonsymmetric α-diimine for the replacement, on one aryl ring, of a methyl group with a methoxy substituent, thus allowing a comparison of the structural features of the relevant complexes. The monocationic complexes were tested as precatalysts for the ethylene/methyl acrylate copolymerization under mild reaction conditions. Despite the structural similarities observed in solution with the already known precatalysts, the present compounds demonstrated a remarkable decrease in the productivity values associated with a higher affinity for the polar monomer.

Palladium complexes with simple iminopyridines as catalysts for polyketone synthesis.

Four iminopyridines (N-N') differing in the nature of the substituents on the iminic carbon and on the ortho positions of the aryl ring (H or CH3) on the iminic nitrogen were used for the synthesis of neutral and monocationic palladium(ii) complexes of general formulae [Pd(CH3)Cl(N-N')] and [Pd(CH3)(NCCH3)(N-N')][PF6]. The detailed NMR characterization in solution highlighted that: (i) for both series of complexes, the Pd-CH3 signal is progressively shifted to a lower frequency on increasing the number of methyl groups on the ligand skeleton; (ii) for the neutral derivatives, the chemical shift of the (15)N NMR signals, determined through {(1)H,(15)N}-HMBC spectra, is significantly affected by the coordination to palladium; (iii) the coordination induced shift (CIS) of the nitrogen atom trans to the CH3 ligand is smaller than the other. The structure in the solid state for the neutral derivatives with all the four ligands was solved, pointing out that: (iv) the Pd-C bond distance increases with the basicity of the nitrogen-donor ligand; (v) the Pd-N bond distance correlates well with the CIS value. The combining of the solution and solid state structural features allows stating that: (vi) the Pd-CH3 singlet is a good probe for the electron donor capability of the ligand; (vii) the CIS value might be used as a probe for the strength of the Pd-N bond. All monocationic complexes generated active catalysts for the CO/vinyl arene copolymerization, leading to prevailingly syndiotactic polyketones. The catalyst performances, both in terms of catalyst productivity and polymer molecular weight, correlate well with the precatalyst structural features.

Limbal fibroblast conditioned media: a non-invasive treatment for limbal stem cell deficiency.

PURPOSE: Limbal fibroblasts are known to regulate the maintenance and differentiation of the corneal epithelium including the limbal epithelial stem cells. This study examined the effect of limbal fibroblast conditioned media in a mouse model of limbal stem cell deficiency. METHODS: Limbal stem cell deficiency was created in C57/Bl6 mice by performing a limbus to limbus epithelial debridement. The mice were treated topically for 3 weeks with conditioned media derived from human limbal fibroblasts. The control mice were treated with skin fibroblast conditioned media or Dulbecco's serum-free medium. RESULTS: The mice treated with limbal fibroblast conditioned media demonstrated substantial growth of corneal type epithelial cells on the corneal surface with less conjunctival goblet cells. By contrast, the control treated corneas were found to be covered primarily by conjunctival type epithelium. CONCLUSIONS: Cell culture media conditioned by limbal fibroblasts appear to contain factor(s) that are therapeutically beneficial in a model of limbal stem cell deficiency. The current results further support the notion that the essential limbal stem cell niche is provided by limbal fibroblasts and suggest a new, non-invasive option in the treatment of limbal stem cell deficiency.

[Evaluation of the three-dimensional stability using dental casts after orthognathic surgery]. / Valutazione gipsometrica della stabilità dimensionale dopo interventi di chirurgia ortognatodontica.

BACKGROUND: The increasingly frequent use of orthognathic surgery raises several questions on the results of operations, the resulting morphological and functional modifications, and the long-term three dimensional stability of the arches after surgery. In order to answer these questions a study was carried out using pre- and postoperative casts of the arches in a group of patients to evaluate the three dimensional stability of the correction. METHODS: Thirty-nine patients with different forms of malocclusion were selected who had undergone orthognathodontic surgery at least one year earlier. Twenty-seven patients (69.2%) received postoperative orthodontic treatment, including 9 who had undergone lower jaw surgery (33.3%), 3 maxillary surgery (11.1%) and 15 undergoing combined surgery (55.6%). Twelve patients (30.8%) did not receive postoperative orthodontic surgery, including 2 who had undergone lower jaw surgery (16.6%), 5 maxillary surgery (41.7%) and 5 undergoing combined surgery (41.7%). The two-dimensional reproductions of dental casts were studied using electronic image processing. Five different techniques were used (Bolton, Lundström, Howes, Staley and Reinhardt) to evaluate the dental arches. The study also evaluated whether any difference in results could be ascribed to use or absence of pre or postoperative orthodontic treatment. RESULTS: The results indicate that protocols and surgical techniques used produce dental arches that are three-dimensionally stable and the use of orthodontic treatment gives greater stability one year after surgery compared to cases treated with surgery alone. CONCLUSIONS: Major maxillary surgery should always be considered when assessing the possible solutions to malocclusions in order to correct anomalous bone formation with a reduced risk of recidivation of the correction.

[Equilibrium and orthognathodontic surgery: correlations in a group of patients undergoing treatment]. / Posturologia e chirurgia ortognatodontica. Correlazioni in un gruppo di pazienti trattati.

BACKGROUND: The aim of this study was to evaluate the main parameters provided by the static stabilometric test (mean X, mean Y, mean velocity, length of tracing, standard deviation of velocity, ellipse area) in the follow-up of patients suffering from skeletal occlusive pathology undergoing orthognathodontic surgery to confirm the re-establishment of postural equilibrium. METHODS: Fifteen patients with skeletal dysgnathia were correlated with a group of 10 healthy subjects. The same parameters were analysed in the dysgnathic subjects at 6 and 12 months after surgical correction. The patients enrolled in this study underwent surgery at the Division of Maxillofacial surgery of Turin University. Student's "t"-test and multivariate statistical analysis (Cox regression) were used for the statistical analysis of results. RESULTS: A significant variability was noted in some of the main parameters analysed (mean X, mean Y, tracing length) between the two populations (healthy and dysgnathic) compared to visual signs (eyes opened-closed). The change in stabilometric values within the group of dysgnathic patients was highly significant 6 and 12 months after surgery, not only in terms of visual signs but also the cervical component (retroflexion of the head), above all the value of mean Y (p = 0.001). CONCLUSIONS: An analysis of these results shows that static stabilometry can be a valuable aid both during the preoperative evaluation and during the follow-up in patients undergoing jaw surgery since it can quantify the improvement of body balance.

Similarities of essential and spontaneous hypertension. Volume and number of blood cells.

Spontaneously hypertensive rats have long been used as an animal counterpart of human essential hypertension. The validation of this strain as a model rests mainly on the "clinical" similarity of the two syndromes, but it has scarcely been founded on numerical comparison of measurable parameters. We investigated three hematological indexes previously recognized to be altered in spontaneously hypertensive rats: the single-cell volume of erythrocytes, the single-cell volume of platelets, and the erythrocyte number. Erythrocyte volume was lower by 7%, platelet volume was higher by 12%, and erythrocyte count was higher by 22% in spontaneously hypertensive rats in comparison with Wistar-Kyoto controls. More unexpectedly, it was found that erythrocyte volume is lower by 2%, platelet volume is higher by 3%, and erythrocyte number is higher by 6% in essential hypertensive subjects when compared with normotensive healthy subjects. These results, combined with previously reported blood cell alterations in subjects and rats, reinforce the evidence of a biological similarity between essential and spontaneous hypertension.

Separation of steryl esters by reversed-phase liquid chromatography.

Thirty steryl esters composed of ten different fatty acids and 14 sterols as well as two wax esters were analyzed by reversed-phase liquid chromatography on a Zorbax ODS column at 205 nm using acetonitrile-isopropanol 60:40 (v/v) as a mobile phase. Contributions (sigma values) of individual double bonds and alkyl groups in the steryl ester were determined from the relative retention values for steryl esters with and without the feature. A double bond and an alkyl group had a greater effect on the retention time of a steryl ester when present in the fatty acid rather than in the sterol moiety. The sigma value can be used to obtain structural information about a steryl ester. Separation of a complex mixture of steryl esters found in corn oil was achieved using this technique.