Preparation of trimethylsilyl alkyne complexes of bis(pentamethylcyclopentadienyl)zirconium, (η-C5Me5)2Zr(RC≡CSiMe3), and their regioselective reactions with nitrous oxide

Benzene solutions of Cp^*₂ZrCl₂ (1) (Cp^* = η⁵-C₅Me₅) react with the alkynes Me₃SiC≡CPh, Me₃SiC≡C(c-C₅H₉) and Me₃SiC≡CCMe₃ in the presence of Na/Hg amalgam to afford high yields of the respective alkyne complexes Cp^*₂Zr(Me₃SiC≡CPh) (2), Cp^*₂Zr{Me₃SiC≡C(c-C₅H₉)} (3) and Cp^*₂Zr(Me₃SiC≡CCMe₃) (4) as crystalline compounds. Complex 2 crystallizes in the triclinic space group with a = 9.791(6), b = 10.466(6), c = 15.756(12) Å, = 86.09 (5), β = 72.09(5), γ = 72.06(4)° and Z = 2. The least-squares refinement converged to R(F) = 0.0604 and R(wF) = 0.0628 for the 3655 unique data with F_o > 4σ (F_o). Salient metrical parameters of the bound alkyne include the following: C(30)-C(31) = 1.340(9) Å; Zr-C(30) = 2.178(6) Å; Zr-C(31) = 2.219(5) Å; C(30)-C(31)-Si = 141.0(5)°; C(31)-C(30)-C(26) = 135.5(5)°. Nitrous oxide reacts with 2 or 3 to afford ((5) R = Ph; (6) R = c-C₅H₉) and 1 equiv. of N₂ via an intermediate, , which is unstable with respect to loss of dinitrogen to give the oxametallacyclobutene derivatives 5 and 6. The oxygen-atom insertion is regiospecific for the Zr-C bond that is attached to the carbyl (Ph or c-C₅H₉) substituent. Under similar conditions, complex 4, in which the alkyne is particularly labile, gives a myriad of products in its reaction with N₂O.     

Synthesis and characterization of homologous nickel(II) and palladium(II) complexes with biphosphine monoxide ligands Ph2P(CH2)nP(O)Ph2 (n = 1–3) and pTol2P(CH2)P(O)pTol2

A series of cationic nickel complexes [(η³-methally)Ni(PP(O))]SbF₆ (1–4) [PP(O) = Ph₂P(CH₂)P(O)Ph₂ (dppmO) (1), Ph₂P(CH₂)₂P(O)Ph₂ (dppeO) (2), Ph₂P(CH₂)₃P(O)Ph₂ (dpppO) (3), pTol₂P(CH₂)P(O)pTol₂ (dtolpmO) (4)] has been synthesized in good yields by treatment of [(η³-methally)NiBr]₂ with biphosphine monoxides and AgSbF₆. The ligands are coordinated in a bidentate way. Starting from [(η³-all)PdI]₂ the cationic complexes [(η³-all)PP(O))]Y (8–14). [PP(O) = dppmO, dppeO, dpppO, dtolpmO;Y = BF₄, SbF₆, CF₃SO₃, pTolSO₃] were synthesized in good yields. The coordination mode of the ligand is dependent on the backbone and the anion, revealing a monodentate coordination with dppmO for stronger coordinating anions. The intermediates [(η³-all)Pd(I)(PP(O)-κ¹-P)] (5–7) [PP(O) = dppmO (5), dppeO (6), dtolpmO (7)] were isolated and characterized. Neutral methyl complexes [(Cl)(Me)Pd(PP(O))] (15–18). [PP(O) = dppmO (15), dppeO (16), dpppO (17), dtolpmO (18)] can easily be obtained in high yields starting from [(cod)PdCl₂]. For dppmO two different routes are presented. The structure of [(Me)(Cl)Pd{;Ph₂P(CH₂-P(O)Ph₂-κ²-P,O};] · CH₂Cl₂ (15) with the chlorine atom trans to phosphorus was determined by X-ray diffraction.     

Ultrastructural study of the shell-repair membrane in the snail,Helix pomatia L.

Summary The shell-repair membrane of the snail, Helix pomatia, has been studied with the transmission electron microscope (TEM). The ultrastructure of the repair membrane, in the initial stages of calcification, revealed the presence of a fibrillar protein, proteoglycan granules, osmiophilic vesicles, and cytoplasmic dense bodies of different size and structure. The involvement of the cell constituents in the formation of calcifying centra and initial crystal formation is discussed. The amoebocytes present within the repair membrane appeared to be involved in three different functions: (1) phagocytosis, (2) release of granules, vesicles and dense bodies, and (3) secretion of a fibrillar protein. The possible lytic function of the amoebocytes is mentioned. The common features in the mineralizing process of the shell-repair membrane of the snail and the epiphyseal cartilage of the mammals were noted.This investigation was supported by a grant from the Swedish Natural Science Research Council, which is gratefully acknowledged. I am indebted to Miss Ch. Stensjö and Mrs. E. Hellmén for their technical assistance     

Two new iridoid glucosides from Gardenia jasminoides fruits

From the fruits of Gardenia jasminoides which have been employed as Chinese crude drug “Shan-zhii”, two further new iridoid glucosides, gardoside (8,10-dehydrologanic acid) and scandoside methyl ester have been isolated and their structures have been established.     

An ultrastructural study of the synaptic densities,nematosomes, neurotubules,neurofilaments and of a further three-dimensional filamentous network as disclosed by the E-PTA staining procedure

Summary After the staining of nervous tissue with phosphotungstic acid in absolute ethanol (E-PTA), a selective opacification occurs at certain specific sites, while other structures, especially the plasma and intra-cellular membranes, remain electron-lucent. Among those selectively stained sites, our studies have been focussed on: (1) The dense synaptic material consisting of several presynaptic clumps, termed projections, an intrasynaptic dense line and a subsynaptic web from which fine fibrillar wisps extend into the surrounding ground substance; (2) Neurofilaments and neurotubules, the surface of which is bristled by numerous side-arms; (3) A microfilamentous network intertwines the neurotubules, the neurofilaments and the mitochondria in the dendrites and axon, and is also connected to the E-PTA dense undercoating delineating the inner aspect of the plasma membrane and to the fine wisps emanating from the subsynaptic web. A three-dimensional microfilamentous latticework is thus formed in the nerve cell processes; (4) Dense cytoplasmic inclusions, termed nematosomes, which are usually located in the ground substance of the perikaryon among or in the vicinity of clusters of ribosomes. Tiny microfilaments emanate from the peripheral strands of these bodies. The presence of basic residues in the chains of structural proteins of which consist the subsynaptic web and the nematosome is plausible, since the specificity of the E-PTA staining procedure for the detection of basic residues has previously been put forth. The occurrence of a three-dimensional microfilamentous network in the nerve cell processes led us to hypothesize that it plays a role in translocation of materials. It may provide the motive force for the axoplasmic transport, for instance, with the neurotubules, as well as, plausibly, with the neurofilaments, serving as attachment sites and guideways.Supported by grant MA-3448 from The Medical Research Council of Canada.     

Strukturbesonderheiten der Anurenepiphyse nach prolongierter Osmierung und Anwendung der Acetylcholinesterase-Reaktion

Zusammenfassung Mit der prolongierten Osmierung nach Friend wird an den Außengliedern der pinealen Sinneszellen von Rana temporaria eine körnige Schwärzung erzielt. Diese Partikel haben einen Durchmesser von etwa 50 Å. In Analogie zu den Befunden an den retinalen Stäbchen (Eakin und Brandenburger) wird das geschwärzte Material als das Reaktionsprodukt eines Photopigments gedeutet. Weiterhin kann man mit dieser Methode in den pinealen Stützzellen 300–2500 Å große Granula darstellen, die im Golgi-Apparat entstehen. Die für Stützzellen charakteristischen Granula ermöglichen eine sichere Erkennung kleiner Stützzellanschnitte. Obwohl der Chemismus der Friendschen Reaktion nicht bekannt ist, bewährt sich diese Fixierungsmethode bei der elektiven Darstellung bestimmter Zellstrukturen. So war es möglich, den Degenerationsablauf an den Sinneszellaußengliedern und das Verhalten von Zellfortsätzen im perivaskulären Raum präziser als bisher zu untersuchen. Mit der Acetylcholinesterase-Reaktion können in der Anurenepiphyse nur Ganglienzellen und deren Neuriten elektiv hervorgehoben werden; basaler Rezeptorenfuß und die plexiformen Zonen sind dagegen negativ.

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The anuran pineal organ after prolonged osmium tetroxide fixation and in acetylcholinesterase preparations

Summary 50 Å particles are selectively demonstrated in the cytoplasmic lamellae of the outer segments of the pineal sensory cells inRana temporaria after prolonged osmium tetroxide fixation according to Friend. In analogy to the interpretations of Eakin and Brandenburger concerning the rods of the lateral eye, it is assumed that a photopigment is present in the outer segment of the anuran pineal receptors. Furthermore, 300–2500 Å granules are demonstrated in the supportive cells; these originate in the Golgi zone. The characteristic granules of supportive cells are an important feature in the demonstration of small supportive cell segments. The chemical basis of the Friend reaction is not completely understood. However, the reaction proves to be useful in the demonstration of certain cell organelles. A more precise picture of degenerating outer segments of pineal sensory cells and of the distribution of terminal processes of different pineal cell types in the perivascular spaces can be obtained by the prolonged osmium tetroxide fixation. The nerve cells of the anuran pineal organ and their axons are demonstrated selectively by the acetylcholinesterase technique. The basal feet-like processes of the receptor cells and the plexiform zones of the pineal organ are negative in acetylcholinesterase preparations.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Ultrastructure of Sarcocystis booliati Dissanaike and Poopalachelvam, 1975 from the moonrat, Echinosorex gymnurus, in Malaysia

The ultrastructure of the cyst wall and zoites of Sarcocystis booliati from the moonrat Echinosorex gymnurus, was studied with the electron microscope. The primary cyst wall was thin, smooth and filled with a finely-granular, electron-dense material. The surface of the cyst wall had a row of vesicular invaginations. The ground substance beneath the primary cyst wall did not extend into the cyst to form septae. The zoites were covered with a double-layered membrane or pellicle and had an anterior conoid, 2 conoidal rings, 22 subpellicular microtubules, about 8 rhoptries, 50–60 micronemes, scattered lipid droplets, a micropore and a posteriorly situated nucleus, in front of which was a sac-like mitochondrion with vesicular internal cristae. The distinctive features in the ultrastructure of S. booliati were the thinness of the cyst wall, the absence of cytophaneres or trabeculae and the comparatively small number of micronemes in the zoites.     

Bifurcations in Turing systems of the second kind may explain blastula cleavage plane orientation

Spontaneous pattern formation (emergence of Turing structures) may take place in biological systems as primary and secondary bifurcations to nonlinear parabolic partial differential equations describing biochemical reaction-diffusion systems. Bipolarity in mitosis and cleavage planes in cytokinesis may be related to this formation of prepatterns. Cleavage planes in early blastulas have an apparently well controlled spatial relationship to the polarity known as the animal-vegetal (A-V) axis: the mitotic spindles form perpendicular to this axis in the first two division stages, with cleavage planes going strictly through the A-V poles. The third-stage spindles are parallel to the A-V axis, and cleavage is roughly in the equatorial plane, thus separating the A-V poles. The reason for these phenomena are poorly understood with current mitosis/cytokinesis models based on intrinsic spindle properties. It is shown here by numerical simulation that a simple modification to the usual Turing equations yields selection rules which lead directly to these orientations of the prepatterns, without any further ad hoc assumptions. These results strongly support the prepattern model for mitosis and cytokinesis and the viewpoint that prepatterns play a fundamental role in nature.     

Tubuloampullar structures associated with the endoplasmic reticulum in pancreatic B-cells

Summary Unusual aggregations of ampullar dilated tubules (tubuloampullar structures, TAS) were observed in pancreatic B-cells of rats and in one case of human malignant insulinoma. The TAS were invariably associated with dilated rough endoplasmic reticulum, but lacked ribosomes. They were frequently seen to be closely associated with the Golgi apparatus. Furthermore, TAS were located mainly in degranulated areas of B-cells.Dedicated to Prof. W. Graumann on the occasion of his 65th birthdayThe expert assistance of Mrs. M. Tölken is gratefully acknowledgedThis work was supported in part by the deutsche Forschungsgemeinschaft, Re 225/7 and Kl 426/1     

Extracellular microtubule-like structures in the retina of the rainbow trout

Summary Extracellular microtubule-like structures (MLS) are described in the retina of the rainbow trout. They appear about 30 to 40 days after hatching, when the yolk-sac is consumed and the animal begins to swim and to nourish actively. They fill a widely branched system of extracellular clefts and spaces, and connect different cells and cell types, especially outer horizontal cells and bipolar cells. The MLS are not affected by the vinca alcaloid vincristine, although this drug penetrates into the MLS-filled space, as has been shown by the formation of intracellular, vincristine-induced tubulin paracrystals. The MLS are compared with other extracellular tubular structures described in other animal tissues. Their functional significance remains unclear.