New cucurbitacins from Phormium tenax and Marah oreganus

Cucurbitacins I and D and two new cucurbitacins, isocucurbitacin D and 3-epi-isocucurbitacin D, were isolated from Phormium tenax. A new cucurbitacin, dihydroisocucurbitacin B, was isolated from Marah oreganus. The acid sensitivity of the 2β-hydroxy-3-keto system found in cucurbitacin D was demonstrated.     

Phenotypic heterogeneity in 3-methylcholanthrene-induced transformation of normal rat kidney cells infected with Moloney murine leukemia virus

Normal rat kidney cells, infected with Moloney murine leukemia virus, were treated with 3-methylcholanthrene at passage 5 postinfection. Foci of transformed cells appeared after 9-11 passages following this treatment. Characterization of four different randomly isolated foci revealed a striking diversity with respect to various tested phenotypic parameters. Remarkable differences were observed among these transformed clones regarding their cell morphology, growth rate, saturation density, serum requirements, virus release and its response to rat and mouse fibroblast interferons. This study demonstrates that cell transformation by chemical-retroviral co-carcinogenesis may lead to the formation of phenotypically heterogeneous tumor cells.     

Daily rhythms of nonshivering thermogenesis in common spiny mice Acomys cahirinus under short and long photoperiods

Daily rhythms of nonshivering thermogenesis NST were studied in common spiny mice Acomys cahirinus, acclimated to different photoperiod regimes (16L:8D and 8L:16D) at a constant ambient temperature of 26°C. Noradrenaline NA (1.5 mg/kg subcutaneous) was injected at: 06:00, 12:00, 18:00 and 24:00 h (±15 min). NST was measured as the ratio between the maximal oxygen consumption (VO₂) as response to NA — VO₂NA and VO₂ measured at 26°C — VO_{2 min}. Rectal temperatures T_bNA and T_{b min} respectively were recorded at the end of VO₂ measurements. Significant variations in T_{b min}, T_bNA, and NST were revealed, under the two different photoperiod regimes. Significant differences in VO_{2 min}, NST, T_{b min} and T_bNA were also recorded within each photoperiod acclimation group. These results suggest that daily and photoperiod depended variations in the brown adipose tissue activity, presumably emerge from amount of unoccupied receptors or changes in the receptors affinity to NA.     

Floral development in bolting garlic

Garlic (Allium sativum L.) is a completely sterile plant, propagated only vegetatively. The aim of this research was to study the sequence of morphological processes occurring during floral initiation and development of a number of bolting garlic accessions from the Allium gene bank in Israel by using SEM. The garlic inflorescence is an umbel-like flower arrangement, the branches (flower clusters) of which arise from a common meristem. The numerous flowers have a distinct morphology typical of the genus Allium. Flower-stalk elongation precedes the swelling of the apical meristem and its subdivision into several centers of floral development. Within clusters, floral primordia develop unevenly. Differentiation of topsets begins after floral differentiation on the peripheral part of the apical surface, and their size, number and rate of development vary among genotypes. At least four morphological types differing in flower/topset ratio were distinguished among the 12 clones studied in this investigation. For further studies of flowering physiology and fertility restoration, only clones which can differentiate the greatest proportion of normal flowers and the least of topsets in the apical meristem should be selected. Received: 28 June 2000 / Revision accepted: 6 November 2000     

An automated computer vision and roboticsbased technique for 3-D flexible biomolecular docking and matching

The generation of binding modes between two molecules, alsoknown as molecular docking, is a key problem in rational drugdesign and biomolecular recognition. Docking a ligand, e.g.,a drug molecule or a protein molecule, to a protein receptor,involves recognition of molecular surfaces as molecules interactat their surface. Recent studies report that the activity ofmany molecules induces conformational transitions by ‘hinge-bending’,which involves movements of relatively rigid parts with respectto each other. In ligand–receptor binding, relative rotationalmovements of molecu–lar substructures about their commonhinges have been observed. For automatically predicting flexiblemolecular interactions, we adapt a new technique developed inComputer Vision and Robotics for the efficient recognition ofpartially occluded articulated objects. These type of objectsconsist of rigid parts which are connected by rotary joints(hinges). Our approach is based on an extension and generalizationof the Geometric Hashing and Generalized Hough Transform paradigmfor rigid object recognition. Unlike other techniques whichmatch each part individually, our approach exploits forcefullyand efficiently enough the fact that the different rigid partsdo belong to the same flexible molecule. We show experimentalresults obtained by an implementation of the algorithm for rigidand flexible docking. While the ‘correct’, crystal–boundcomplex is obtained with a small RMSD, additional, predictive‘high scoring’ binding modes are generated as well.The diverse applications and implications of this general, powerfultool are discussed