On coenzyme Q orientation in membranes: A linear dichroism study of ubiquinones in a model bilayer

Summary A general approach is developed to interpret linear dichroism (LD) spectra of ubiquinones (Q _n) in host bilayers. Information is reported in terms of guest-host mutual orientation and localization. The overall orientational anisotropy of guest ubiquinone molecules is described by a basic set of limiting orientation/localization modes. Assignments of the UV transitions of the ubiquinone chromophore were obtained by the liquid crystal-linear dichroism technique and molecular orbital (CNDO/S) calculations. The LD spectra of Q _n in the bilayers provided by the lyotropic nematic mesophase exhibited by water solutions of potassium laurate and decanol were interpreted on the basis of the above assignments. The resulting experimental evidence showed a multisite distribution in the host bilayer for the aromatic heads of all the investigated Q _n derivatives except Q₀. The orientational distribution suggested by the LD spectra fits the solubilization model recently proposed by G. Lenaz [J. Membrane Biol. (1988) 104:193–209] for ubiquinone in lipid membranes. Within this model Q _n molecules are located in the midplane and their headgroups oscillate transversally across the membrane. Q ₀ instead has a single site location, close to the polar bilayer interface. Experimental evidence that the headgroup carbonyls tend to grasp the polar interface of the host bilayer was also obtained. Orientation and location distributions of Q _n guest molecules are therefore likely to result from the tendency of their aromatic heads to grasp the polar heads of the host bilayer and from the concurrent tendency of their chains to settle into the hydrocarbon host interior.abbreviations AA average absorption - OD, OD optical densities for plane polarized radiations parallel () and perpendicular () to the sample optical axis - OD OD — OD - EPR electron paramagnetic resonance - LC-LD liquid crystal-linear dichroism - LD linear dichroism - LD _r reduced linear dichroism. - MO molecular orbital - N nematic - NMR nuclear magnetic resonance - S _jj order parameters of the directions j of the transition moments of the guest chromophore - S _ii order parameters of the orientational axes i of the guest molecule with respect to the magnetic field - S _ii order parameters of the axes i of the guest molecules with respect to the bilayer axis a - S _a order parameters of the host bilayer axis a with respect to the orienting magnetic field - _j,i deflection angles between the directions j and the axes i - O _i optical factors of the i axis see Eq. (A4)] - Q_n ubiquinone whose isoprenoid chain contains n isoprenoid units Dr. A. Rossi is gratefully acknowledged for the t.e.m. reduction of the spectra. Ubiquinone homologs were kind gifts from Eisai Co., Tokyo, Japan. This work was supported by M.U.R.S.T., and C.N.R. Target Project on Biotechnology and Bioinstrumentation, Rome, Italy.     

Tubo-ovarian transplantation in the treatment of sterility. Experimental research]

Microsurgical transposition of fallopian tube and ovary has the potential of being an efficient therapeutic treatment in patients with tubal sterility. The Authors present their experience of microsurgical adnexal transplantation in rabbit by two different techniques: the first procedure by microvascular anastomosis of the ovarian vessels, the second one without vascular pedicle. Function is evaluated at various time after grafting by: exploratory laparotomy on day 30 to establish whether circulation to the grafts was still maintained; macroscopic and microscopic examination of ovaries and fallopian tubes. The microvascular techniques prove highly reliable in terms of immediate vascular patency rate but it is disappointing that 50% of the autografts has failed with blocked vessels by day 30. Perhaps this is due to the difficult techniques in anastomosing the ovarian vessels of small caliber. In spite of these outcomes the vascularized autografts were viable and functional after transplantation in contrast with the non-vascularized tubo-ovarian grafts which all failed. This experience encourages to believe that the microsurgical technique could be employed for homograft transplantation in woman with extensive ovarian and tubal damages.     

Microsurgery and laser surgery in conservative operations on the ovary. Experimental research]

In this study we compared two different conservative surgery techniques performed on 12 ovaries of female rabbits: microsurgery and CO2 Laser surgery. After the surgical procedure all the animals were investigated by a Laparotomy to evaluate the post-operative adhesion formation. Histological examinations were performed on 6 ovaries, to evaluate the possible damage to the ovarian parenchyma. We did not find significant differences between the two methods employed, particularly for the adherence formation and the parenchymal thermic damages: no post-operative adhesions were detected respectively in 3 ovaries operated on by microsurgery and 5 by laser surgery; slight adhesions were present in 2 ovaries treated with microsurgery and in 3 with laser surgery; 3 ovaries treated with microsurgery and 2 with laser surgery showed moderate adhesions. Only 2 ovaries treated with microsurgery presented severe adhesions.     

Aeration: A simple method to control vitrification and improve in vitro culture of rare australian plants

Summary Aeration of tissue cultured rare Australian plantsConostylis wonganensis S.D. Hopper (Haemodoraceae);Diplolaena andrewsii Ostenf.;Drummondita ericoides Harvey (Rutaceae);Eremophila resinosa F. Muell. (Myoporaceae);Eucalyptus ‘graniticola’ (Myrtaceae);Lechenaultia pulvinaris C. Gardner (goodeniaceae); andSowerbaea multicaulis E. Pritzel (Liliaceae) has been found to reduce vitrification in sensitive species as well as significantly improving shoot quality and transfer to soil in most study species. A simple 7-mm hole with a double-layer insert of filter paper in the polypropylene screw lids of the culture vessel decreased shoot vitrification over a 4-wk culture period. The method has implications for facilitating the tissue culture of other rare Australian plants and reducing the occurrence of this developmental abnormality.     

DNA demethylation in erythroleukaemia cells

Despite a fall in the proportion of CGs methylated, evidence has not been obtained for significant demethylation of prelabelled DNA when mouse erythroleukaemia cells are induced to differentiate. There is, however, a delay in the methylation of the DNA that is synthesised in the early period of induction, leading to its undermethylation by 30-50% and this may be a contributory cause of the observed fall in CG methylation.     

Lysis of autologous human melanoma cells by in vitro allosensitized peripheral blood lymphocytes

Summary Peripheral blood lymphocytes (PBL) of melanoma patients were sensitized in vitro with lymphocytes of a single donor or with a pool of lymphocytes of 5–20 different donors. After 6–7 days, the cytotoxic activity of the sensitized PBL was tested against cultured autologous tumor cells and lymphocytes in a ⁵¹Cr-release assay. Tumor lysis was observed in 13 of 16 cases in which patients' PBL (Pt-PBL) were stimulated by a pool of allogeneic lymphocytes and in five out of seven cases when single sensitization was performed. In no case was lysis of autologous normal lymphocytes or blasts seen. Cultivation of Pt-PBL with irradiated autologous tumor cells never led to the induction of lymphocytes cytotoxic to melanoma cells. Lysability by pool-activated autologous Pt-PBL of fresh cryopreserved tumor cells was compared to that of short-term cultured tumor cells, and no significant differences were observed. Cold-target inhibition experiments indicated that the cytotoxicity of Pt-PBL was tumor-restricted since only autologous melanoma cells but not lymphocytes were able to inhibit the reaction. These results indicate that activation of Pt-PBL is necessary in order to elicit or amplify their antitumor activity.