Characterization of 14-3-3sigma Dimerization Determinants: Requirement of Homodimerization for Inhibition of Cell Proliferation

The seven highly conserved 14-3-3 proteins expressed in mammalian cells form a complex pattern of homo- and hetero-dimers, which is poorly characterized. Among the 14-3-3 proteins 14-3-3sigma is unique as it has tumor suppressive properties. Expression of 14-3-3sigma is induced by DNA damage in a p53-dependent manner and mediates a cell cycle arrest. Here we show that the 14-3-3sigma protein exclusively forms homodimers when it is ectopically expressed at high levels, whereas ectopic 14-3-3zeta formed heterodimers with the 5 other 14-3-3 isoforms. The x-ray structure of 14-3-3sigma?revealed 5 residues (Ser⁵, Glu²⁰, Phe²⁵, Q⁵⁵, Glu⁸⁰) as candidate determinants of dimerization specificity. Here we converted these amino-acids to residues present in 14-3-3zeta at the analogous positions. Thereby, Ser⁵, Glu²⁰ and Glu⁸⁰ were identified as key residues responsible for the selective homodimerization of 14-3-3sigma. Conversion of all 5 candidate residues was sufficient to switch the dimerization pattern of 14-3-3sigma to a pattern which is very similar to that of 14-3-3zeta. In contrast to wildtype 14-3-3sigma this 14-3-3sigma variant and 14-3-3zeta were unable to mediate inhibition of cell proliferation. Therefore, homodimerization by 14-3-3sigma is required for its unique functions among the 7 mammalian 14-3-3 proteins. As inactivation of 14-3-3sigma sensitizes to DNA-damaging drugs, substances designed to interfere with 14-3-3sigma dimerization may be used to inactivate 14-3-3sigma function for cancer therapeutic purposes.     

Glycosylation reactions — present status future directions

A short review of the present status of glycosylation reactions is presented. The reactivity of both proven and newer glycosylation methods are briefly discussed. Emphasis is placed on the control of stereochemistry and regiochemistry. As well, the identification and avoidance of side reactions is covered. Polymer-supported synthesis of oligosaccharides is noted as a promising direction for eliminating some of the problems associated with purification. It is suggested that a better understanding of the mechanism of glycosylation reactions is necessary for future improvements to stereoselectivity and regioselectivity. A key advance would be methods for enhancing the reactivity of weakly nucleophilic hydroxyls.Abbreviations BF₃ OEt₂ boron trifluoride diethyl ether complex - TMSOTf trimethylsilyl trifluorometh-anesulfonate - NIS NBS N-iodosuccinimide andN-bromosuccinimide - TfOH trifluoromethanesulfonic acid or triflic acid - AgOTf CuOTf₂ silver triflate and copper(II)triflate - Tf₂O triflic anhydride - IDCP iodonium dicollidine perchlorate - TEP triethyl phosphite - HfCp₂Cl₂ hafnium dicyclopentadienyl dichloride - Ac acetyl - Bz benzoyl - Bn benzyl - Ph phenyl - Me methyl - Et ethyl - Bu₄NOTf tetrabutylammonium triflate - Ph₂IOTf diphenyliodinium triflate - PhSeNPhth N-(phenylseleno)phthalimide - Pent 4-pentenyl - TCI trichloroactemidyl - TBDPS t-butyl diphenylsilyl - DTBP 2,6-di-t-butylpyridine - Tr trityl or triphenylmethyl Dedicated to Professor J.J. Krepinsky on the occasion of his 60th birthday     

Interkingdom Complementation Reveals Structural Conservation and Functional Divergence of 14-3-3 Proteins

The 14-3-3s are small acidic cytosolic proteins that interact with multiple clients and participate in essential cellular functions in all eukaryotes. Available structural and functional information about 14-3-3s is largely derived from higher eukaryotes, which contain multiple members of this protein family suggesting functional specialization. The exceptional sequence conservation among 14-3-3 family members from diverse species suggests a common ancestor for 14-3-3s, proposed to have been similar to modern 14-3-3ε isoforms. Structural features of the sole family member from the protozoan Giardia duodenalis (g14-3-3), are consistent with this hypothesis, but whether g14-3-3 is functionally homologous to the epsilon isoforms is unknown. We use inter-kingdom reciprocal functional complementation and biochemical methods to determine whether g14-3-3 is structurally and functionally homologous with members of the two 14-3-3 conservation groups of the metazoan Drosophila melanogaster. Our results indicate that although g14-3-3 is structurally homologous to D14-3-3ε, functionally it diverges presenting characteristics of other 14-3-3s. Given the basal position of Giardia in eukaryotic evolution, this finding is consistent with the hypothesis that 14-3-3ε isoforms are ancestral to other family members.     

Two New Species of Actinolaimidae Thorne, 1939 (Nemata: Dorylaimida) from China

Two new species of Actinolaimidae are described from China. Trachactinolaimus brevicaudatus n. sp. is 3.4-4.4 mm long; a = 40-60, b = 3.5-5.2, c = 20-21 in female and 34-39 in male; odontostyle length is 29-33 µm; spicules are 67-77 µm long; and the stoma has four onchia with numerous mural denticles. The female has a longitudinal vulva, and the male has 20 to 23 contiguous ventromedian supplements. Egtitus sinensis n. sp. is 1.7-2.2 mm long; a = 24-33, b = 3.1-3.9, c = 16-19 in female and 0.7-0.9 in male; odontostyle length is 25-29 µm; spicules are 55-56 µm long; and the prerectum 53-77 µm long. The cardia is short and blunt conoid, 13-19 µm long. The male has 12 to 13 ventromedian supplements at intervals of 2-3 µm.     

Observations on the ultrastructure of the copulatory organ of Archilopsis unipunctata (Fabricius, 1826) (Proseriata,Monocelididae)

The copulatory organ in adult specimens of Archilopsis unipunctata has been studied by transmission electron microscopy.This copulatory organ is of the conjuncta-duplex type with eversible cirrus. The seminal vesicle, lined with a nucleate epithelium, is surrounded by spirally arranged muscles. The fibres are enclosed in a sheath that is continuous with the septum of the bulbus and the basement lamina of the male canal epithelium. Distally to the seminal vesicle the bulbus is filled with the secretory cell-necks of the prostate glands. The male canal shows three different parts: seminal duct, ejaculatory duct and eversible cirrus. At the transition of seminal duct and ejaculatory duct two prostate ducts open into the lumen. The structure of the epithelium lining the different parts of the canal is described. The transition into the cirrus may be recognized by an abrupt change in the thickness, the electron density and the stratification in the basement lamina and by the disappearance of the epithelium absent indeed in the cirrus. The material found inside the cirrus-lumen is different according to the zone considered. The origin of this material and of the cirrus teeth is discussed.Abbreviations ab- apoptotic body - ba- bacteria - bb- basal bodies of cilia - bl- basement lamina - bw- body wall - c- cilia - cb- cell body - cgp- common genital porus - ci- cirrus - cip- cirrus plug - cl- lumen of cirrus - cm- circular muscles - cr- cytoplasmatic remnants - cs- cytoplasmatic sheets - ejd- ejaculatory duct - ep_ej- epithelium of ejaculatory duct - d- desmosomes - f- flagella of spermatozoa - fd- female duct - fp- female porus - gc- golgi complex - gl- glycogen particles - hd- hemidesmosomes - lm- longitudinal muscles - ly- lysosome-like body - m- muscles - m_b- muscles of the bulbus - m_c- muscles of the cirrus - m_c- muscles of the seminal vesicle - mi- mitochondria - ml- microvilli - ms- mesenchyme - n_sd- nuclei of the seminal duct - pd- prostate duct - pg- prostate glands - ri- ribosomes - s- septum - sb- secretory vesicle - sd- seminal duct - sp- spines - sv- seminal vesicle - v- vagina - vd- vas deferens     

Paravortex karlingi sp. nov. from Cerastoderma edule L., in Britain

Paravortex karlingi sp. nov. collected from the intestine of the bivalve mollusc Cerastorderma edule from the Ythan Estuary, N. E. Scotland, and elsewhere, is distinguished from a closely related species, P. cardii, also occurring in this host, on the basis of differences in habitat occupied by the two species as well as behavioural and morphological differences. P. karlingi is smaller, has fewer embryos in the gravid adult and shows a different behaviour pattern when released from the host intestine. It is also negatively phototactic whereas P. cardii is initially positively phototactic, only later becoming negatively phototactic. The occurrence of both species in Britain is briefly described.Abbreviations bc brood capsules - c core of indigestible particles - ca common atrium - ch chamber - e eye - fa female atrium - fol fibre optic light - gc gut caecum - gp genital pore - j juvenile worm - m mouth - o ovary - oe oesophagus - p pharynx - pe penis - sg shell gland - sv seminal vesicle - t testis - u uterus - vg vitelline gland - w window     

Mitotic Phosphorylation of Cdc25B Ser321 Disrupts 14-3-3 Binding to the High Affinity Ser323 Site

Cdc25B is a key regulator of entry into mitosis, and its activity and localization are regulated by binding of the 14-3-3 dimer. There are three 14-3-3 binding sites on Cdc25B, with Ser³²³ being the highest affinity binding and is highly homologous to the Ser²¹⁶ 14-3-3 binding site on Cdc25C. Loss of 14-3-3 binding to Ser³²³ increases cyclin/Cdk substrate access to the catalytic site, thereby increasing its activity. It also affects the localization of Cdc25B. Thus, phosphorylation and 14-3-3 binding to this site is essential for down-regulating Cdc25B activity, blocking its mitosis promoting function. The question of how this inhibitory signal is relieved to allow Cdc25B activation and entry into mitosis is yet to be resolved. Here, we show that Ser³²³ phosphorylation is maintained into mitosis, but phosphorylation of Ser³²¹ disrupts 14-3-3 binding to Ser³²³, mimicking the effect of inhibiting Ser³²³ phosphorylation on both Cdc25B activity and localization. The unphosphorylated Ser³²¹ appears to have a role in stabilizing 14-3-3 binding to Ser³²³, and loss of the Ser hydroxyl group appears to be sufficient to significantly reduce 14-3-3 binding. A consequence of loss of 14-3-3 binding is dephosphorylation of Ser³²³. Ser³²¹ is phosphorylated in mitosis by Cdk1. The mitotic phosphorylation of Ser³²¹ acts to maintain full activation of Cdc25B by disrupting 14-3-3 binding to Ser³²³ and enhancing the dephosphorylation of Ser³²³ to block 14-3-3 binding to this site.     

Melongosides n,o and p: steroidal saponins from seeds of solanum melongena

Three new saponins, melongosides N, O and P, have been isolated from the methanolic extract of seeds of Solanum melongena and their structures elucidated. Melongoside N is 3-O-[β-D-glucopyranosy l-(1 → 2)-β-D-glucopyranosyl]-26-O-(β-D-glucopyranosyl)-(25R)-5α-furostan-3β,22 α,26-triol, whereas melongoside O is 3-O-[β-D-glucopyranosyl-(1 → 2)β-D-glucopyranosyl]- 26-O-(β-D-glucopyranosyl)-(25R)-furost-5-en-3β,22α,26-triol and melongoside P is 3-O- [β-D-glucopyranosyl-(1 → 2)]-[α-L-rhamnopyranosyl-(1 → 3)]-β-D-glucopyranosyl)-26-O- (β-D-glucopyranosyl)-(25 R)-5α-furostan-3β,22α,26-triol.     

14-3-3 Proteins Act as Negative Regulators of the Mitotic Inducer Cdc25 in Xenopus Egg Extracts

Cdc25, the dual-specificity phosphatase that dephosphorylates the Cdc2–cyclin B complex at mitosis, is highly regulated during the cell cycle. In Xenopus egg extracts, Cdc25 is associated with two isoforms of the 14-3-3 protein. Cdc25 is complexed primarily with 14-3-3ε and to a lesser extent with 14-3-3ζ. The association of these 14-3-3 proteins with Cdc25 varies dramatically during the cell cycle: binding is high during interphase but virtually absent at mitosis. Interaction with 14-3-3 is mediated by phosphorylation of Xenopus Cdc25 at Ser-287, which resides in a consensus 14-3-3 binding site. Recombinant Cdc25 with a point mutation at this residue (Cdc25-S287A) is incapable of binding to 14-3-3. Addition of the Cdc25-S287A mutant to Xenopus egg extracts accelerates mitosis and overrides checkpoint-mediated arrests of mitotic entry due to the presence of unreplicated and damaged DNA. These findings indicate that 14-3-3 proteins act as negative regulators of Cdc25 in controlling the G₂–M transition.     

Morphological and histological study of the genital ducts ofCryptazeca monodonta (Pulmonata,Orthurethra), with special emphasis on the auxiliary copulatory organ

Summary The genital system ofCryptazeca monodonta is very similar to those reported for semidiaulic stylommatophores, but with some specific features. The fertilization pouch is simple and surrounded by subepithelial goblet gland cells. The spermoviduct has two different grooves: the oviductal channel and the spermatic groove, which run together with a blind-ending allospermiduct that opens into the lumen of the free oviduct. The vagina has a thick muscular wall with numerous pigmentary cells embedded in it. The vas deferens diverges from the spermiduct and becomes mainly glandular just before it joins the penis. This genital system is equipped with an auxiliary copulatory structure that consists of two independent and complementary organs. One of them is located just before the fusion of the free oviduct and the spermatheca stalk lumina and consists mainly of a thick mass of connective tissue. The other is a muscular sarcobellum located inside the penis. Both these organs are covered by small papillae whose connective cells are stacked. Each papilla has a solid spine on its top, which seems to be of mesenchymatous origin. As in other stylommatophores, the auxiliary copulatory organ is equipped with an adjoining gland, which inCryptazeca is next to the sarcobellum.Abbreviations ACO auxiliary copulatory organ - ag albumen gland - al allospermiduct - c connective aggregate of ACO - cc connective cells of ACO papillae - cf connective fibres - ep epiphalus - fo free oviduct - fp fertilization pouch - gl.c gland cells of sarcobellum - hd hermaphroditic duct (distal portion) - m muscle fibres - ov oviduct - p penis - pc penial caecum - pp papillae of ACO - pr prostatic gland - prm penial retractor muscle - p.sh penial sheath - s spermatheca - sc sarcobellum - SEM scanning electron micrograph - sov spermoviduct - sp spine - spd spermiduct - ss spermatheca stalk - v vagina - vd vas deferens     

Calcium exchanges in Anodonta cygnea: barriers and driving gradients

Electrical potential differences between the haemolymph and the extrapallial fluid, and between the haemolymph and the mantle cavity fluid, and ionic concentrations of calcium in the haemolymph and in extrapallial fluid were measured in vivo in Anodonta cygnea. The electrochemical potential of ionic calcium in the haemolymph is clearly above the electrochemical potential of ionic calcium in the environment and is very nearly in equilibrium with that of the extrapallial fluid. Simultaneous measurements of carbon dioxide partial pressure and pH in the extrapallial fluid showed that in this compartment ionic calcium is clearly above saturation. It is proposed that calcium deposition is regulated through the secretion of the organic matrix and by controlling the pH and the carbon dioxide partial pressure of the extrapallial fluid. An estimation of the minimum positive balance of calcium required to sustain shell growth together with the electrophysiological characterization of the mantle cavity epithelium showed that this tissue is not the route of entry of calcium into the animal.Abbreviations BW body weight - DW dry weight - E_EPF-S chemical potential difference - EPF extrapallial fluid - G_tot total conductance - I_sc short-circuit current - K_sp solubility product - MCE mantle cavity epithelium - MCF mantle cavity fluid - OME outer mantle epithelium - PCO₂ partial pressure of carbon dioxide - PVC Poly(vinyl chloride) - S shell - SEM standard error of mean - V _ic intracellular electrical potential - V _oc open-circuit voltage     

Degradation of halogenated aromatic compounds

Due to their persistence, haloaromatics are compounds of environmental concern. Aerobically, bacteria degrade these compounds by mono- or dioxygenation of the aromatic ring. The common intermediate of these reactions is (halo)catechol. Halocatechol is cleaved either intradiol (ortho-cleavage) or extradiol (meta-cleavage). In contrast to ortho-cleavage, meta-cleavage of halocatechols yields toxic metabolites. Dehalogenation may occur fortuitously during oxygenation. Specific dehalogenation of aromatic compounds is performed by hydroxylases, in which the halo-substituent is replaced by a hydroxyl group. During reductive dehalogenation, haloaromatic compounds may act as electron-acceptors. Herewith, the halosubstituent is replaced by a hydrogen atom.Abbreviations CBz chlorobenzene - DCBz dichlorobenzene - TrCBz trichlorobenzene - TCBz tetrachlorobenzene - PCBz pentachlorobenzene - HCBz hexachlorobenzene - CBA chlorobenzoic acid - BBA bromobenzoic acid - FBA fluorobenzoic acid - IBA iodobenzoic acid - CP chlorophenol - CA chloroaniline - PCBs polychlorinated biphenyls - CB chlorobiphenyl - 2,4-D 2,4-dichlorophenoxyacetic acid - 2,4,5-T 2,4,5-trichlorophenoxyacetic acid     

Experimental and comparative morphology of radula renewal in pulmonates (Mollusca,Gastropoda)

Summary The continuous renewal of the pulmonate radula and the histology and regeneration of its concomitant epithelia were studied by light and electron microscopy, autoradiography and electron microprobe analysis. The two species investigated show histological differences and the results were compared with those of a preceding study on a prosobranch radula. The radula is an intricate cuticular structure of the foregut. Only the fully grown part, which is active during feeding, lies in the buccal cavity while it is constantly renewed by the coordinated cooperation of specialized cells forming the radular sheath. The end of the sheath is occupied by cells which produce the organic matrix of the radula. In taeniogloss prosobranchs, seven multicellular cushions of small odontoblasts lie at the end of the sheath and produce the seven teeth of each cross-row. In pulmonates, the multidenticular radula is generated by numerous groups of a few voluminuous cells. Despite these histological differences, prosobranchs and pulmonates generate the radula matrix by microvilli, cytoplasmatic protrusions and apocrine secretions. The epithelia of the radular sheath contribute to the transport, tanning and mineralization of the radula. The concomitant epithelia are replaced in limited proliferation zones at the end of the radular sheath and their cells migrate anteriorly to the buccal cavity. The ultrastructure of the sheath cells and the alterations which they undergo in connection with their functions are discussed. The proliferation zone of the superior epithelium is strictly confined and the cells move together with the radula forward. In prosobranchs, the cells of the superior epithelium begin to degenerate in the middle of the radular sheath and the entire epithelium is simply extruded into the buccal cavity. In pulmonates, the opening of the radular sheath is closed by the cuticular collostylar hood which is generated by a distinct epithelium which is proved to be stationary. When leaving the proliferation zone, the superior epithelium differentiates into supporting cells and mineralizing cells; the latter cause the hardening of the radular teeth and already degenerate in the middle of the sheath. The whole superior epithelium degenerates at the border to the collostylar hood-epithelium. In Lymnaea the degeneration zone is strictly confined whereas in Cepaea the collostylar hood and its generating epithelium extend into the radular sheath and the degeneration zone ranges over a distance of 3–5 rows of teeth. The proliferation zone of the inferior epithelium extends over the posterior half of the radular sheath, but the replacement rate is much lower than in the superior epithelium. Although the inferior epithelium carries the radula, it migrates slower than the radula. Obviously the radula has to be transported actively by apical protrusions of the cells, which penetrate into the radular membrane. At the opening of the radular sheath the inferior epithelium generates the adhesive layer and degenerates. During feeding, the adhesive layer has to maintain the firm mechanical connection between radula and distal radular epithelium. Autoradiographic experiments demonstrate that the distal radular epithelium is stationary. Nevertheless, the radula is known to advance to its degeneration zone. Special attention is paid to this problem. We strongly suspect that the transport of the adhesive layer and the radula is based on pseudopodial movements of apical protrusions characteristic for the distal radular epithelium. These protrusions interdigitate with the lower face of the adhesive layer. The mechanical connection has to be maintained and so the respective structures (tonofilaments and hemi-desmosomes) have to be continually renewed. This needs a high amount of energy and obviously results in the conspicuous concentration of mitochondria near the apical surface.Abbreviations al adhesive layer - ax axon - bc buccal cavity - bce buccal cavity epithelium - bl basal layer - bla basal labyrinth - bm basal membrane - bp basal plate - bpc basal plate cell - c cilia - ch collostylar hood - che collostylar hood-epithelium - cl cuticular layer - col collostyle - cr cell remnant - cts connective tissue sheath - d desmosome - dl upper layer - dre distal radular epithelium - dz degeneration zone - fe front edge - g granula - gol dictyosome - hd hemidesmosome - hl haemolymph - ie inferior epithelium - j jaw - ma tooth matrix - mc mineralizing cell - mem membranoblast - mfb microfibrills - mfl microfilaments - mgb multigranular body - mi mitochondria - mit mitosis - ml middle layer - mt microtubuli - mv microvilli - mw membrane whirl - n nucleus - nc necrotic cluster - nf nerve fibres - nsg neurosecretory granula - o odontophor - od odontoblast - odg odontoblast group - pod pre-odontoblast - rb residual body - rer rough endoplasmatic reticulum - rm radular membrane - rt radula teeth - sc supporting cell - se superior epithelium - sj septate junction - sro subradular organ - ss secretion substance - tf tonofilaments - tsm supramedian tensor muscle - tw terminal web - v vacuole - ves vesicle     

On the spermiogenesis of Invenusta aestus (Plathelminthes,Proseriata) an ultrastructural study with implications for plathelminth phylogeny

Summary The spermiogenesis of Invenusta aestus (Coelogynoporidae) is described based on electron microscopical observations. Special attention is paid to the intercentriolar body and the anchoring apparatus of the cilia. These organelles are differentiated at the beginning of spermatid maturation and undergo striking changes during gametogenesis. The importance of the organelles mentioned for discussion of phylogenetic relationships within the Plathelminthes is considered.Abbreviations ci cilium - cy cytophore - db dense bodies - go Golgi complex - icb intercentriolar body - mi mitochondrion - mt microtubules - n nucleus - r rootlet - spo spermatogonia - spt spermatids - spy spermatocytes - tb tubular body - zd zone of differentiation     

Fine structure and formation of eggshells in marine Gastrotricha

Summary The fine structure of the gastrotrich eggshell in the hermaphroditic species Turbanella ocellata (Hummon 1974) and the parthenogenetic species Aspidiophorus sp. is described using transmission electron microscopy. The presented evidence strongly suggests that the shell is produced by the egg itself prior to oviposition in both species. The layed egg in Aspidiophorus sp. is provided with a special attachment stalk that is also preformed in the mother animal. Freshly layed eggs of T. ocellata are adhesive all around their surface and lack any specialized structures for attachment. Formation of the spiny eggshell of Aspidiophorus sp. appears to begin with a sudden release of special vesicles containing the preformed spines of the outer eggshell covering. Additional material appears to be secreted by the egg in a more gradual process after the initial vesicle release. The formation of the two fibrous layers in the eggshell of T. ocellata is less well understood and deposition of eggshell material could be seen either as a continuous process or as two separate steps, similar to the events observed for Aspidiophorus sp. For T. ocellata, Tetranchyroderma sp. and Aspidiophorus sp. it is demonstrated that formation of the cuticle occurs as an independent process from that of eggshell formation. This is significantly different from the basic mode of cuticle formation in the annelid line of evolution. The paper argues further that the data support earlier claims of a pronounced difference between the Gastrotricha-Macrodasyida and the Gastrotricha-Paucitubulatina and agree well with the postulated ties of the Gastrotricha and Nematoda. The phylogenetic importance of the eggshell fine-structure is discussed in the framework of present theories on aschelminth phylogeny.Abbreviations cus cuticular spines - cut cuticle - cov coated vesicles - cv cup-shaped vesicles - dp dense particles - ep epidermis - emb embryo - erl lacunae of smooth ER - fgb fibrous and granular bodies - fl fibrous layer - ga Golgi apparatus - gc gut cell - gv Golgi vesicles - im intercellular matrix - isp intercellular space - isl inner shell layer - ld lipid droplet - mdb medium-dense bodies - mvb multivesicular bodies - oc oocyte - od oviduct - osl outer shell layer - o egg - sv spiny vesicles - sh eggshell - st egg-stalk - sl spiny layer - sub substrate - trm trilaminate membrane - yb yolk bodies - yg yolk granule - yoc young oocyte This work was supported by NSF Grant # GB-42211 to R.M. Rieger     

Steroidal saponins of Yucca filamentosa: Yuccoside C and protoyuccoside C

Two new saponins, yuccoside C and protoyuccoside C, have been isolated from the methanolic extract of Yucca filamentosa root and their structures elucidated. Yuccoside C is 3-O-[α-d-galactopyranosyl-(1 → 2)-β-d-glucopyranosyl-(1 → 4)-β-d-glucopyranosyl]-(25S)-5β-spirostan-3β-ol, whereas protoyuccoside C is 3-O-[α-d-galactopyranosyl-(1 → 2)-β-d-glucopyranosyl-(1 → 4)-β-d-glucopyranosyl]-26-O-[β-d-glucopyranosy]-(25S)-5β-furostan-3β,22α,26-triol.     

Oogenesis and larval development of Scypha ciliata (Porifera,Calcarea)

Summary Scypha ciliata is a syconoid sponge. Its oocytes differentiate from choanocytes located near the apopyle of a flagellated chamber, and initially they remain in that location, in a trophic complex with neighbouring choanocytes. When this first growth phase is completed, the oocyte migrates to the periphery of the sponge. There it undergoes a second growth phase, in which it phagocytizes choanocytes and mesenchyme cells.Fertilization of the mature egg is assisted by a converted choanocyte, the sperm carrier cell. This cell penetrates the oocyte and transfers to it the sperm contained in a carriercell vacuole. No meiotic events have yet been observed.Cleavage is asynchronous, with holoblastic, approximately equal divisions. After the first cleavage steps the blastomeres often contain multiple nuclei. The single-layered blastoderm of the stomoblastula consists of many micromeres with flagella that project into the blastocoel, a few macromeres and four cruciform cells. There is no development of a follicle epithelium.The stomoblastula develops into the amphiblastula by inversion; with the assistance of the maternal choanocyte epithelium, the hollow sphere turns inside out, simultaneously moving out of the mesoderm and into the lumen of the adjacent flagellated chamber. In this process, the blastocoel of the stomoblastula is lost. The flagellated cells that form the wall of the amphiblastula now have their flagella extending outward; the amphiblastula also comprises four cruciform cells, macrogranular and agranular cells. The larval cavity of the amphiblastula is a newly formed structure.Abbreviations AB amphiblastula - AP apopyle - BC blastocoel - aC agranular cell - maC macrogranular cell - miC microgranular cell - CB crystalline body - CC central cavity - Ch choanocyte - fCh flat choanocyte - gCh granulate choanocyte - CM cell membrane - Co collar of choanocyte - CrC cruciform cell - DM dense material - EM electron micrograph - F flagellum - FC flagellated cell - FCm flagellated chamber - FL free larva - FV food vacuole - IR interior region - LC larval cavity - M mesenchyme - Ma macromere - MC mesenchyme cell - Mi micromere - N nucleus - Nu nucleolus - O opening - OC oocyte - P psudopodium - PC pinacocyte - PhM phase-contrast micrograph - Po pore - PP prosopyle - S sperm - SB stomoblastula - SC segmentation cavity - SCC sperm-carrier cell - SV sperm vacuole - lT large trophocyte - sT small trophocyte - V vacuole - VC vesicular cytoplasm - VM vacuole membrane     

Morphologie der Seeigelzähne

The teeth of sea-urchins are not to be compared with the other skeletal-structures of echinoderms. The tooth is constructed of two rows of calcitelements, which are connected by secondary calcareous deposits forming the functional tooth. The surface of the tooth is covered by a crust of calcit. This fundamental construction is described from Stylocidaris affinis, which belongs to the archaic Cidaridae.

---

Verzeichnis der benutzten Signaturen aO apikaler Odontoblastenherd - BG Basalgeflecht - F Flügel - H Haftrinde - HF Hauptfalte - HP Haftpunkt - K Kante - KA Kauabschnitt - KK Kaukante - L Lamellen - LB Lithoblasten - lP laterale Prismen - M Medianebene - MR Medianrinne - N Nadeln - NF Nebenfalte - P Prismen - PB prismenbildende Zellen - Pl Plumula - PP Primärplatte - PZ Plattenzähne - QF Querfalte - R Rinde - Ri Kalkrippen - Sch Schaft - sO subapikale Odontoblasten - SP Sekundärplatte - ST Steinteil - U Umbo - ZB Zellblätter - zP zentrale Prismen Mit Unterstützung der Deutschen Forschungsgemeinschaft (Beihilfe an den erstgenannten Autor).     

Xiphinema llanosum and Trophurus vultus, Two New Plant Nematode Species from Pasture Soils in Colombia

Xiphinema llanosum n. sp. and Trophurus vultus n. sp. are described and illustrated from grass soils in Llanos Orientales, Colombia. Xiphinema llanosum is a bisexual species. The female body length is 2.3-2.7 mm, odontostyle 86-96 μm, and odontophore 58-65 μm long; vulva at 42-47%; anterior ovary is absent; the anterior uterus and oviduct are similar to the posterior branch but slightly reduced; and the tail is dorsally convex-conoid with a blunt hemispherical terminus. Male body length is 2.06-2.96 mm; spicules are 40-44 μm long; and four (rarely three or five) anterior ventromedian supplementary papillae are present. Trophurus vultus females are 0.52-0.67 mm long; vulva at 56-60%; stylet is 10.5-13.5 μm long; isthmus is as long as the basal esophageal bulb; the tail is subclavate, 1.6-2.2 times anal body width long; and the terminal cuticle thickness is about one-sixth of the tail length.