Alteration of monocytic cell oxidative burst caused by methacrylic monomers present in dental materials: a chemiluminescence study.

Methacrylates are present in dental composite resins used in clinical practice. Methacrylates are photo-polymerized, but this reaction is never complete, so release of uncured monomers in the periapical tissues and in biological fluids may happen and, potentially, alter the repair of pulpal and of periapical lesions by interfering with local phagocytes. The aim of this study was the evaluation of the functional activity of the monocyte-macrophage system after incubation with methacrylic monomers. The oxidative burst of two cellular systems was analysed using the chemiluminescence technique. Data were collected and statistically analysed. Monomers were found to reduce the in vitro oxidative burst of phagocytes independently from their cytotoxicity. These findings demand further evaluation of the effects of oxidative burst alteration in monocyte-macrophage function and may prompt the inclusion of the described chemiluminescence test in biocompatibility preliminary studies of dental materials.     

Rhenium(I) and ruthenium(II) complexes with a crown-linked methanofullerene ligand: synthesis, electrochemistry and photophysical characterization.

A cyclopropanation reaction has been used to prepare two methanofullerenes bearing a 2,2'-bipyridine () or pyridine () ligand separated from the fullerene through an oxyethylene macrocyclic spacer. Derivatives and were, in turn, employed to synthesize two fullerene-based ruthenium(ii) and rhenium(i) donor-acceptor dyads whose molecular structure was confirmed by (1)H NMR, (13)C NMR and exact mass determination. The UV-Vis spectrum of the dyads is the superimposition of those of appropriate model systems, indicating that ground-state electronic interactions between the constituent chromophores, in solution, are negligible, in line also with the electrochemical results. The complex voltammetric pattern was characterized by the superimposition of signals attributed to one moiety or another without significant shifts with respect to their models. Furthermore, both species undergo partial chemical degradation in the time scale of cyclic voltammetry upon their multiple reduction. Photophysical properties of and , namely, excited state interactions between the ruthenium(ii) or rhenium(i) complexes and [60]fullerene have been investigated by steady-state and time-resolved UV-Vis-NIR luminescence spectroscopy that was complemented by nanosecond laser flash photolysis in CH(2)Cl(2) solutions. All experimental findings were set into relation with the corresponding reference compounds. More precisely, excitation of the metal complexes in and gives rise to a notable steady-state and time-resolved luminescence quenching of both metal to ligand charge transfer states (i.e., [Ru(bpy)(3)](2+) and [(bpy)Re(CO)(3)(py)](+)). Conclusive evidence about the nature of the photoproducts came from nanosecond laser flash photolysis. In these experiments, only the long-lived and oxygen-sensitive [60]fullerene triplets were detected. Two pathways are envisioned for this [60]fullerene triplet formation. Firstly, intramolecular transduction of the triplet excited state energy evolving from the photoexcited metal complexes. Secondly, intersystem crossing of directly excited [60]fullerene.     

Wilson's Storm Petrels Oceanites oceanicus Recognise the Olfactory Signature of Their Mate

Chemical signals in birds have rarely been considered as recognition cues. Nevertheless, recent experiments showed that several petrel species are able to recognize their nest by smell, and in at least one species even their mate. But the use of smell may be different across the petrel species and olfactory nest recognition appears to be dependent on species’ breeding biology. To increase our knowledge of individual olfactory recognition in petrels and the relationships between breeding biology and use of smell, we tested Wilson’s storm petrels Oceanites oceanicus in Antarctica. In previous experiments, these birds failed to home if rendered anosmic, but the method employed to obtain anosmia (potentially stressing birds) and the fact that they breed in 24‐h daylight suggest that they might use visual, rather than olfactory, cues to recognize their nest. Our birds were tested in T‐maze experiments where nest odours or partner odours were presented. Wilson’s storm petrels preferred odours of their own nest and mate. Results on olfactory nest recognition confirm and complete previous results, viz. anosmic Wilson’s storm petrels do not home. Storm petrels olfactory mate recognition suggests that this ability may be widespread in burrowing petrels and implements olfactory nest recognition.     

Human and hamster procathepsin D, although equally tagged with mannose-6-phosphate, are differentially targeted to lysosomes in transfected BHK cells

BHK cells transfected with human cathepsin D (CD) cDNA normally segregate the autologous hamster cathepsin D while secreting a large proportion of the human proenzyme. In the present work, we have utilized these transfectants to examine to what extent the mannose-6-phosphate-dependent pathway for lysosomal enzyme segregation contributes to the differential sorting of human and hamster CD. We report that, in recipient control BHK cells, the rate of mannose-6-phosphate-dependent endocytosis of human procathepsin D secreted by transfected BHK cells is lower than that of hamster procathepsin D and much lower than that of human arylsulphatase A. The missorted human enzyme bears phosphorylated oligosaccharides and most of its phosphate residues are “uncovered”, like the autologous enzyme. Thus, despite both the Golgi-associated modifications of oligosaccharides, i.e. the phosphorylation of mannose and the uncovering of mannose-6-phosphate residues, which proceed on human and hamster procathepsin D with comparable efficiency, only the latter is accurately packaged into lysosomes. Ammonium chloride partially affects the lysosomal targeting of cathepsin D in control BHK cells, whereas in transfected cells, this drug strongly inhibits the maturation of human procathepsin D and slightly enhances its secretion. These data indicate that: (1) over-expression of a lysosomal protein does not saturate the Golgi-associated reactions leading to the synthesis of mannose-6-phosphate; (2) a portion of cathepsin D is targeted independently of mannose-6-phosphate receptors in the transfected BHK cells; and (3) whichever mechanism for lysosomal delivery of autologous procathepsin D is involved, this is not saturated by the high rate of expression of human cathepsin D.     

Base composition of ribosomal RNA and evolution

Summary Base composition analysis has been carried out for the two major ribosomal RNA components extracted from ribosomes of plants and animals of various taxonomic position. The high degree of change undergone by these molecules during evolution is evident from the results obtained. Moreover, the evolutionary pattern of therRNA base composition well reflects the phylogenetic relationships of the various taxonomic groups.On leave from the Facultad de Medicina, Universidad Central de Venezuela, Caracas.     

Studies on the isolation and purification of chloroplasts from Euglena gracilis

Summary A method has been developed for the isolation of chloroplasts from Euglena gracilis grown under mixotrophic conditions. This method utilizes sucrose density-gradient centrifugation in the AXII zonal rotor and allows the rapid preparation of large amounts of chloroplasts free from contaminating whole cells and other cytoplasmic materials. The majority of the isolated chloroplasts appear intact in phase contrast and electron micrographs. The purified chloroplast fraction contains DNA, the major species of which has a density of 1.682 g/cm³. The species of DNA having a density of 1.707 g/cm³ seemed to result from the presence of contaminating nuclear fragments which could be removed by isopycnic flotation.This research was supported in part by a grant from USPHS No. AM-07189 (to J. M. E.), American Cancer Society Fellowship No. PF-443 (to J.F.P.) and grant No. 2972E06 from the Office of Sponsored Research, University of Florida (to J.F.P.). Univ. of Fla. Agr. Exp. Stat. No. 4538.     

Interaction Between Histidyl Transfer Ribonucleic Acid and the First Enzyme for Histidine Biosynthesis of Salmonella typhimurium

Previous studies showed that the enzyme (phosphoribosyltransferase) which catalyzes the first step of the histidine pathway in Salmonella typhimurium plays a role in regulation of the histidine operon. Since histidyl transfer ribonucleic acid (His-tRNA) is required for repression of the histidine operon, we considered the possibility that the role of phosphoribosyltransferase might be realized through an interaction with His-tRNA. One prediction inherent in this idea is that the enzyme should interact with His-tRNA in vitro. Evidence is presented for such an interaction. Binding of (3)H-His-tRNA to purified phosphoribosyltransferase was tested on Sephadex columns and on nitrocellulose filters. The enzyme was found to have a high affinity for tRNA. Comparing the binding of (3)H-His-tRNA with that of tRNA aminoacylated with other (3)H-amino acids disclosed that the binding of the histidyl species of tRNA is favored over that of other species and is dependent upon magnesium-ion concentration.     

TOPOGRAPHY OF DNA SYNTHESIS IN THE MAMMARY GLAND OF THE C3H MOUSE AND ITS CONTROL BY OVARIAN HORMONES: AN AUTORADIOGRAPHIC STUDY

Tritium-labelled thymidine was injected 45 min before sacrifice into virgin female C3H/HeJ mice 7–23 weeks of age, as well as into 10-week-old mice which had been ovariectomized and treated daily with 1 μg of oestradiol-17β and/or 1 mg of progesterone. Autoradiographs were made of squash preparations of the mammary glands, stained by Feulgen's method. The following results were obtained: (1) During normal development of the gland, cells synthesizing DNA are abundant in terminal buds and virtually absent in duct epithelium. Hence ductal growth takes place by the addition of cells produced in the terminal end structures. (2) At 5–6 months, when mammary growth has ceased, a considerable number of cells synthesizing DNA can still be found in alveoli, though not in duct epithelium. Hence the alveolar cells constitute a renewal population in the adult virgin. Because they maintain the potentiality to divide, duct cells are a G₀ population. (3) Ovariectomy results in arrest of DNA synthesis within 3–5 days. Both oestradiol and progesterone restore DNA synthesis in alveoli but only progesterone is able to induce DNA synthesis in duct epithelium, and the differentiation of terminal buds into alveoli. This finding provides an explanation for the resumed proliferation of duct cells in pregnancy. (4) The number of cells engaged in DNA synthesis varies considerably among identical structures within the same gland. This may be due either to synchrony of cell replication and/or to fluctuations of proliferative activity in the gland.     

Hemoglobins from trout: Structural and functional properties

Summary The diversity of the structural and functional properties of the various components of trout blood may be taken as a type case of molecular adaptation to physiological requirements. Studies on this system yield, in addition, information which appears relevant to the interpretation of the behavior of mammalian hemoglobins.an invited article