The spatial arrangement of germ line cells in ovarian follicles of the mutantdicephalic inDrosophila melanogaster

Summary The pattern of intercellular connections between germ line cells has been studied in follicles of the mutantdicephalic (dic), which possess nurse cell clusters at both poles. Staining of follicles with a fluorescent rhodamine conjugate of phalloidin reveals ring canals and cell membranes and thus allows us to reconstruct the spatial organization of the follicle. Each germ line cell can be identified by the pattern of cell-cell connections which reflect the mitotic history of individual cells in the 16-cell cluster. The results indicate that in both wild-type anddicephalic cystocyte clusters one of the two cells with four ring canals normally becomes the pro-oocyte. However, in some follicles (dicephalic and wild-type) oocytes were found with fewer or more than four ring canals. Indic follicles, one or several nurse cells may become disconnected from the other cells during oocyte growth at stage 9–10. Such disconnected cells cannot later on empty their cytoplasm into the oocyte. This, in turn, might be of consequence for the determination of axial polarity of the embryo.     

Versuch einer Kausalanalyse der geotropischen Reaktionskette im Chara-Rhizoid

Summary In the initial phase of the geotropical reaction of the Chara rhizoid the growth difference postulated by Sievers (1967c) between the physically upper, slightly subapical flank and the lower one is demonstrated. In horizontal exposure the growth of the extreme cell apex is continued, while the growth of the lower flank is inhibited and that of the upper one is promoted. In the end phase the cell apex shows a damped oscillation until it finally reaches the vertical growth direction. The statoliths follow the oscillating growth of the cell tip from one flank to the opposite one until they are statistically equally redistributed in their normal position.—In vertical exposure under reduced turgor pressure the statoliths fall down into the extreme cell apex, where they inhibit the growth of this part of the cell wall, while the subapical wall grows transversally.—It is concluded that the statoliths inhibit the growth of the cell wall area which they cover.—The physical phase of the reaction chain, the susception, is the gravity-induced downward displacement of the statoliths. The physiological phase starts with the diversion of the acropetal transport of the Golgi vesicles to the upper part of the cell, which is caused by the block of statoliths (perception). The greater rate of vesicle incorporation into the upper flank in comparison to the lower one causes the subapical growth difference which results in the curvature (reaction).—In the case of the Chara rhizoid Golgi- and statolith-apparatus function as a self-regulating cellular system.

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Herrn Prof. Dr. Dr. h. c. Kurt Mothes zum 70. Geburtstag.     

Amphiphilic cationic peptides mediate cell adhesion to plastic surfaces

Four amphiphilic peptides, each with net charges of +2 or more at neutrality and molecular weights under 4 kilodaltons, were found to mediate the adhesion of normal rat kidney fibroblasts to polystyrene surfaces. Two of these peptides, a model for calcitonin (peptide 1, MCT) and melittin (peptide 2, MEL), form amphiphilic alpha-helical structures at aqueous/nonpolar interfaces. The other two, a luteinizing hormone-releasing hormone model (peptide 3, LHM) and a platelet factor model (peptide 4, MPF) form beta-strand structures in amphiphilic environments. Although it contains only 10 residues, LHM mediated adhesion to surfaces coated with solutions containing as little as 10 pmoles/ml of peptide. All four of these peptides were capable of forming monolayers at air-buffer interfaces with collapse pressures greater than 20 dynes/cm. None of these four peptides contains the tetrapeptide sequence Arg-Gly-Asp-Ser, which has been associated with fibronectin-mediated cell adhesion. Ten polypeptides that also lacked the sequence Arg-Gly-Asp-Ser but were nonamphiphilic and/or had net charges less than +2 at neutrality were all incapable of mediating cell adhesion (Pierschbacher and Ruoslahti, 1984). The morphologies of NRK cells spread on polystyrene coated with peptide LHM resemble the morphologies on fibronectin-coated surfaces, whereas cells spread on surfaces coated with MCT or MEL exhibit strikingly different morphologies. The adhesiveness of MCT, MEL, LHM, and MPF implies that many amphiphilic cationic peptides could prove useful as well defined adhesive substrata for cell culture and for studies of the mechanism of cell adhesion.     

Toll-like receptor 4 deficiency: Smaller infarcts,but nogain in function

Backgound  

It has been reported that Toll-like receptor 4 (TLR4) deficiency reduces infarct size after myocardial ischemia/reperfusion (MI/R). However, measurement of MI/R injury was limited and did not include cardiac function. In a chronic closed-chest model we assessed whether cardiac function is preserved in TLR4-deficient mice (C3H/HeJ) following MI/R, and whether myocardial and systemic cytokine expression differed compared to wild type (WT).     

A para-nitrophenol phosphonate probe labels distinct serine hydrolases of Arabidopsis

Activity-based protein profiling represents a powerful methodology to probe the activity state of enzymes under various physiological conditions. Here we present the development of a para-nitrophenol phosphonate activity-based probe with structural similarities to the potent agrochemical paraoxon. We demonstrate that this probes labels distinct serine hydrolases with the carboxylesterase CXE12 as the predominant target in Arabidopsis thaliana. The designed probe features a distinct labeling pattern and therefore represents a promising chemical tool to investigate physiological roles of selected serine hydrolases such as CXE12 in plant biology.     

Synthesis of novel acetylene-containing amino acids

Summary.  Novel synthetic procedures for the modification of non-proteinogenic acetylene-containing amino acids have been developed. The functionalization either proceeds via zinc/copper-mediated introduction of alkyl substituents, or via tungsten-catalyzed ring-closing alkyne metathesis reactions. Received March 28, 2002 Accepted October 3, 2002 Published online December 18, 2002 Acknowledgements These investigations are supported (in part) by the Netherlands Research Council for Chemical Sciences (CW) with financial aid from the Netherlands Technology Foundation (STW). Authors' address: Floris P. J. T. Rutjes, Prof. Dr., Department of Organic Chemistry, University of Nijmegen, Toernooiveld 1, NL-6525 ED Nijmegen, The Netherlands, E-mail: rutjes@sci.kun.nl  2, selected data: ¹H NMR (300 MHz, CDCl₃) δ 5.32 (d, J = 7.7 Hz, 1H), 4.44–4.40 (m, 1H), 3.76 (s, 3H), 2.75–2.73 (d, J = 5.0 Hz, 2H), 1.44 (s, 9H); ¹³C NMR (75 MHz, CDCl₃) δ 171.0, 155.0, 80.3, 74.6, 52.6, 51.9, 41.7, 28.3, 24.0; mp = 55°C.  Typical procedure for 5: zinc dust (116 mg, 1.408 mmol) was weighed into a 20 mL flask, which was repeatedly evacuated (with heating using a heat gun) and flushed with argon. Dry DMF (0.5 mL, distilled from CaH₂) and 1,2-dibromoethane (9.2 μL, 0.106 mmol) were added and the flask was heated at 80°C for 40 min. The reaction mixture was allowed to cool to room temperature, trimethylsilyl chloride (4 μL, 0.035 mmol) was added and the resulting mixture was stirred vigorously for a further 30 min under argon. Iodocyclohexane (69 μl, 0.528 mmol) was added and stirred at room temperature for 3 h more after which stirring was ceased to settle the zinc. CuCN (41 mg, 0.458 mmol) and LiCl (40 mg, 0.915 mmol) were heated to 150°C for 2 h and cooled to room temperature. Addition of DMF (1 mL) formed a soluble CuCN·2LiCl complex within 5 min. After cooling the Cu-complex to −15°C, the organozinc reagent was added dropwise followed by the bromoacetylene 2 (116 mg, 0.352 mmol). The mixture was allowed to stir overnight at room temperature. Water was added and the suspension was extracted using heptane, washed with brine, dried (MgSO₄) and concentrated. Purification using flash column chromatography (10% EtOAc in heptane) yielded 5 (100 mg, 81%) as a colorless oil. 5: IR ν 3355, 2929, 2852, 2359, 2337, 1749, 1717, 1498, 1447, 1365, 1251, 1181, 1060; ¹H NMR (300 MHz, CDCl₃) δ 5.28 (d, J = 7.7 Hz, 1H), 4.43–4.38 (m, 1H), 3.73 (s, 3H), 2.69–2.63 (m, 2H), 2.13 (m, 1H), 1.73–1.22 (m, 10H), 1.43 (s, 9H); ¹³C NMR (75 MHz, CDCl₃) δ 171.4, 155.0, 88.1, 79.9, 73.8, 52.3, 32.7, 32.7, 28.8, 28.2, 25.8, 24.6, 23.1; HRMS (EI): calculated for C₁₇H₂₇NO₄ 309.1940, found 309.1937.  A solution of the tungsten catalyst (7 mg, 10 mol%) in C₆H₅Cl (2 mL) was treated with a solution of 14 (49.0 mg, 0.120 mmol) in C₆H₅Cl (5.0 mL) under an argon atmosphere and the resulting mixture was heated at 80°C for 3 h. Evaporation followed by flash column chromatography (80% EtOAc in heptane) afforded 15 (21.0 mg, 50%; 64% after correction for starting material) and 14 (16 mg, 33%) as colorless oils. 15: [α]_D =–14.6 (c = 1, CH₂Cl₂); IR ν 3313, 2931, 2865, 2249, 1744, 1667, 1520, 1366, 1170; ¹H NMR (400 MHz, CDCl₃) δ 7.14 (d, J = 8.7 Hz, 1H), 6.08 (d, J = 8.3 Hz, 1H), 4.78 (q, J = 6.8 Hz, 1H), 4.27 (q, J = 7.9 Hz, 1H), 3.73 (s, 3H), 2.17–2.15 (m, 4H), 2.07–1.96 (m, 2H), 1.79–1.52 (m, 4H), 1.45 (s, 9H), 0.89–0.83 (m, 2H); ¹³C NMR (100 MHz, CDCl₃) δ 173.2, 171.8, 155.8, 80.4, 80.2, 79.3, 53.8, 52.5, 51.2, 32.8 (2×), 28.1, 24.6, 24.2, 18.3 (2×); HRMS (EI): calculated for C₁₈H₂₈N₂O₅