Die Feinstruktur der Sehkolben und der Lamellarkörper von Parotoplana capitata (Plathelminthes,Proseriata)

Zusammenfassung Die Ultrastruktur der intracerebralen Sehkolben und die der potentiell photoreceptorischen Lamellarkörper aus der Cerebralregion von Parotoplana capitata werden dargestellt. Die Konfiguration der Rhabdomeren der Sehkolben zeigt eine deutliche Terzettbildung. Zwischen die Cilien der Lamellarkörper schieben sich einige Mikrovilli. Die Bedeutung der pigmentfreien Sehkolben und der Lamellarkörper in evolutiver Hinsicht wird diskutiert. Der Mangel von Pigmentgranula in der Mantelzelle der Sehkolben bildet eine Autapomorphie der Proseriata Lithophora. Ciliäre Lamellarkörper repräsentieren vermutlich eine Autapomorphie des Teiltaxons Parotoplaninae.

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Fine structure of visual clubs and lamellate bodies in Parotoplana capitata (Plathelminthes, Proseriata)

Summary The ultrastructure of intracerebral visual clubs and the fine structure of presumed photoreceptive lamellate bodies from the cerebral region of Parotoplana capitata are described. The rhabdomeric elements of the visual clubs exhibit a tripartite configuration. Some microvilli are mingled with the cilia of the lamellate bodies. The evolutionary aspects of the visual clubs and of the lamellate bodies are discussed. The absence of pigment granules within the mantle cell of the visual clubs form an autapomorphy of the Proseriata Lithophora. Ciliary lamellate bodies represent an autapomorphy of the subordinated taxon Parotoplaninae.

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Abkürzungen bk Basalkörper - cm ciliäre Mikrotubuli - cw Cilienwurzel - gk Gehirnkapsel - la Lamellen des Membranwirtels - mc Mantelzelle - mi Mitochondrium - mv Mikrovilli - nl Zellkern des Lamellarkörpers - nm Zellkern der Mantelzelle - nr Zellkern der Receptorzelle - rc Receptorzelle - rh Rhabdomeren Die Studie wurde in der Arbeitsstelle zur Erforschung der Mikrofauna des Meeresbodens der Akademie der Wissenschaften und der Literatur Mainz in Göttingen angefertigt. Für technische Assistenz danke ich Frau E. Hildenhagen-Brüggemann, Frau M. Frixe und Herrn B. Baumgart     

Membrane geometry of “open” prolamellar bodies

Summary The open type of prolamellar body in etiplasts was examined by electron microscopy to characterise its three-dimensional organisation. As in more compact forms of prolamellar body, its basic geometric unit is a tetrahedrally branched tubule. In the open type, these lie smoothly confluent with one another at the vertices of 5- and 6-membered rings which circumscribe the faces of three kinds of polyhedra: pentagonal dodecahedra (with 12 pentagonal faces), 14-hedra (2 opposite hexagonal faces joined by two circlets of six pentagonal faces), and 15-hedra (3 hexagonal and 12 pentagonal faces). These polyhedra join confluently in their turn, sharing faces with one another in at least one recognisable superstructure which accounts for the appearance of open prolamellar bodies in many ultrathin sections. In this organisation, columns of pentagonal dodecahedra are arranged at 120 ° to one another in the x-y-plane of the lattice. They do not fill the plane but intersect so as to delimit voids in the form of hexagonally arranged 14-hedra (with hexagonal rings in the x-y-plane). Strata of this type alternate with strata made of face-sharing 15-hedra (with their hexagonal rings normal to x-y), which also delimit 14-hedra. The 14-hedra thus lie in register in the z-axis in hexagonally arranged columns, normal to the alternating strata. Other possible organisations cannot be excluded and local variations and dislocations certainly occur, but many micrographs that display elements of symmetry in open prolamellar bodies can be matched to thin slices through such a model. Its geometry is like that of the cages of water molecules in type IV (sensu Jeffrey=type IIIsensu O'Keeffe) clathrate-hydrates, point group P6/mmm, but about two orders of magnitude larger.     

Interspecific variability of telomeric DNA length in some Siberian and endemic Baĭkal planarians (Plathelminthes, Tricladida)

The length of the telomeric DNA in nine species of planarians inhabiting Lake Baikal and one Siberian species from Baikal rivers was determined using Southern hybridization. According to preliminary estimations, it varied in the range of 25-30 kb (Rimacephalus arecepta, Rimacephalus pulvinar, Sorocelis hepatizon, Sorocelis nigrofasciata, Protocotylus sp., Baikalobia guttata, Bdellocephala baikalensis, Phagocata sibirica) and 50 kb (Baikaloplana valida, Baikalobia copulatrix). It is the first estimation of the values of telomeric region lengths for Baikal free-living flat worms.     

Culture of Poecilia reticulata (Pisces: Poecilidae) in tropical water bodies, Veracruz, México

Poecilia reticulata, also known as guppy, is the most popular fish in the aquarium environment. Guppys are viviparous fish with high tolerance to extreme temperatures. The development of the offspring takes between 25 and 30 days. We developed a technology for raising guppys, which outlines infrastructure and devices for reproduction, nursery, feeding, and commercialization, evaluating the financial and technical feasibility of this technology in a case study. The complete reproductive cycle occured in floating cages with 1 mm mesh and the method was tested in a tropical lagoon in Mexico. Water quality was monitored throughout the study period (temperature, dissolved oxygen and pH levels). A marketing survey was carried out at all existing aquarium shops in Veracruz City. Data collected depict quantities demanded and offered for each species by season, place of origin, and resistance to handling. The hydrobiological characteristics were: average temperature 31.4 degrees C, dissolved oxygen 4.5 mgl(-1), and pH level 6.8. With these values we built a production function, and used it to evaluate profitability. We estimate a benefit/cost ratio of 1.16, with a net annual income of US$257.67. The system may provide two permanent jobs.     

Growth factors in asexually reproducing catenulida and macrostomida (Plathelminthes)?

Summary The occurrence and localization of immuno-reactivity (IR) to epidermal growth factor receptor (EGF-r), epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF), revealed by the present study, indicate growth-factor-like substances in the asexually reproducing flatworms,Stenostomum leucops andMicrostomum lineare. IR to all three antibodies occurs in the nervous system. Differences in the number of positive cells and intensity of IR during asexual development of new individuals were observed. By confocal scanning laser microscopy, immunopositive growth cones of nerve fibres were seen in developing zooids, and weakly or unstained perikarya were observed in close contact with the positive nerve fibres. Antibodies to the growth factors EGF-r, EGF and bFGF as well as to the neuroactive substances 5-HT and RF-amide had a negative influence on the growth and asexual reproduction of culturedS. leucops. No significant differences in the influence of antibodies to growth factors and antibodies to the neuroactive substances were observed.     

Redescription of “Nesticus” citrinus (Taczanowski, 1874) (Araneae,Araneoidea) from French Guyana

“Nesticus” citrinus, a species originally placed in Theridion is redescribed based on the syntype series composed by 7 females and a lectotype is designated. All syntypes have broken emboli in their epigynes. Taxonomic position of “Nesticus” citrinus is briefly discussed and its belonging to Nesticidae is doubted.     

On the status of “Urotherium antiquum” (Ameghino) (Xenarthra,Glyptodontidae)

Within the Late Neogene Glyptodontidae of the Pampean region of Argentina, “Urotherium antiquum” was described on the basis of some associated osteoderms of the dorsal carapace, which in addition include a partial skull and left hemimandible. The diagnostic characters are located on the exposed surface of the osteoderms of the dorsal carapace which somewhat resembles those of the Pleistocene genus Neuryurus. Although the relationship of “U. antiquum” to the remaining Glyptodontidae has never been clarified, some cladistic analyses suggest a close phylogenetic affinity with the clade composed of Plohophorus + (Glyptodon + Doedicurus). A careful comparison of “U. antiquum” to well-characterized taxa with similar stratigraphic and geographic provenance reveals that no significant skull differences are observed from Plohophorus figuratus Ameghino. It seems likely that the alleged ornamentation pattern that characterizes this species was produced by a taphonomic alteration of the exposed surface of the osteoderms, a process broadly distributed in glyptodonts having a “rosette” ornamentation pattern. Finally, some characters present in the osteoderms of the type specimen of “U. antiquum” suggest that it may be a juvenile specimen. In summary, “U. antiquum” should be considered a junior synonym of P. figuratus.     

Sperm epidermal growth factor receptor (EGFR) mediates α7 acetylcholine receptor (AChR) activation to promote fertilization

To attain fertilization the spermatozoon binds to the egg zona pellucida (ZP) via sperm receptor(s) and undergoes an acrosome reaction (AR). Several sperm receptors have been described in the literature; however, the identity of this receptor is not yet certain. In this study, we suggest that the α7 nicotinic acetylcholine receptor (α7nAChR) might be a sperm receptor activated by ZP to induce epidermal growth factor receptor (EGFR)-mediated AR. We found that isolated ZP or α7 agonists induced the AR in sperm from WT but not α7-null spermatozoa, and the induced AR was inhibited by α7 or EGFR antagonists. Moreover, α7-null sperm showed very little binding to the egg, and microfluidic affinity in vitro assay clearly showed that α7nAChR, as well as EGFR, interacted with ZP3. Induction of EGFR activation and the AR by an α7 agonist was inhibited by a Src family kinase (SFK) inhibitor. In conclusion we suggest that activation of α7 by ZP leads to SFK-dependent EGFR activation, Ca(2+) influx, and the acrosome reaction.     

A new in vivo model for luteolysis using systemic pulsatile infusions of PGF(2α)

A new in vivo model for studying luteolysis was developed in sheep to provide a convenient method for collecting corpora lutea for molecular, biochemical, and histological analysis during a procedure that mimics natural luteolysis. It was found that the infusion of prostaglandin F(2α) (PGF(2α)) at 20 μg/min/h into the systemic circulation during the mid luteal phase of the cycle allowed sufficient PGF(2α) to escape across the lungs and thus mimic the transient 40% decline in the concentration of progesterone in peripheral plasma seen at the onset of natural luteolysis in sheep. Additional 1h-long systemic infusions of PGF(2α), given at physiological intervals, indicated that two infusions were not sufficient to induce luteolysis. However, an early onset of luteolysis and estrus was induced in one out of three sheep with three infusions, two out of three sheep with four infusions, and three out of three sheep with five infusions. Reducing the duration of each systemic infusion of PGF(2α) from 1h to 30 min failed to induce luteolysis and estrus even after six systemic infusions indicating that, not only are the amplitude and frequency of PGF(2α) pulses essential for luteolysis, but the actual duration of each pulse is also critical. We conclude that a minimum of five systemic pulses of PGF(2α), given in an appropriate amount and at a physiological frequency and duration, are required to mimic luteolysis consistently in all sheep. The five pulse regimen thus provides a new accurate in vivo model for studying molecular mechanisms of luteolysis.     

No need to replace an “anomalous” primate (Primates) with an “anomalous” bear (Carnivora,Ursidae)

By means of mitochondrial 12S rRNA sequencing of putative “yeti”, “bigfoot”, and other “anomalous primate” hair samples, a recent study concluded that two samples, presented as from the Himalayas, do not belong to an “anomalous primate”, but to an unknown, anomalous type of ursid. That is, that they match 12S rRNA sequences of a fossil Polar Bear (Ursus maritimus), but neither of modern Polar Bears, nor of Brown Bears (Ursus arctos), the closest relative of Polar Bears, and one that occurs today in the Himalayas. We have undertaken direct comparison of sequences; replication of the original comparative study; inference of phylogenetic relationships of the two samples with respect to those from all extant species of Ursidae (except for the Giant Panda, Ailuropoda melanoleuca) and two extinct Pleistocene species; and application of a non-tree-based population aggregation approach for species diagnosis and identification. Our results demonstrate that the very short fragment of the 12S rRNA gene sequenced by Sykes et al. is not sufficiently informative to support the hypotheses provided by these authors with respect to the taxonomic identity of the individuals from which these sequences were obtained. We have concluded that there is no reason to believe that the two samples came from anything other than Brown Bears. These analyses afforded an opportunity to test the monophyly of morphologically defined species and to comment on both their phylogenetic relationships and future efforts necessary to advance our understanding of ursid systematics.     

Bacterial production and refolding from inclusion bodies of a “Weak” toxin, a disulfide rich protein

The gene for the “weak” toxin of Naja kaouthia venom was expressed in Escherichia coli. “Weak” toxin is a specific inhibitor of nicotine acetylcholine receptor, but mechanisms of interaction of similar neurotoxins with receptors are still unknown. Systems previously elaborated for neurotoxin II from venom of the cobra Naja oxiana were tested for bacterial production of “weak” toxin from N. kaouthia venom. Constructs were designed for cytoplasmic production of N. kaouthia “weak” toxin in the form of a fused polypeptide chain with thioredoxin and for secretion with the leader peptide STII. However, it became possible to obtain “weak” toxin in milligram amounts only within cytoplasmic inclusion bodies. Different approaches for refolding of the toxin were tested, and conditions for optimization of the yield of the target protein during refolding were investigated. The resulting protein was characterized by mass spectrometry and CD and NMR spectroscopy. Experiments on competitive inhibition of ¹²⁵I-labeled α-bungarotoxin binding to the Torpedo californica electric organ membranes containing the muscle-type nicotine acetylcholine receptor (α1₂β1_γδ) showed the presence of biological activity of the recombinant “weak” toxin close to the activity of the natural toxin (IC₅₀ = 4.3 ± 0.3 and 3.0 ± 0.5 µM, respectively). The interaction of the recombinant toxin with α7 type human neuronal acetylcholine receptor transfected in the GH₄C₁ cell line also showed the presence of activity close to that of the natural toxin (IC₅₀ 31 ± 5.0 and 14.8 ± 1.3 µM, respectively). The developed bacterial system for production of N. kaouthia venom “weak” toxin was used to obtain ¹⁵N-labeled analog of the neurotoxin.     

Spirochete round bodies Syphilis, Lyme disease & AIDS: Resurgence of “the great imitator”?

We advocate investigation of spirochete cyclical symbioses (e.g.,Borrelia sp.,Leptospira sp., Treponema sp.) given the newly established verification of a developmental history in these gram-negative motile helical eubacteria, both in pure culture and in mammals. Symbiotic spirochetes can be compared to free-living relatives for their levels of integration (behavioral, metabolic, gene product or genetic levels), Detailed research that correlates life histories of symbiotic spirochetes to changes in the immune system of associated vertebrates is sorely needed. Genome analyses show that in necrotrophic symbioses (Borrelia andTreponema sp.) of humans and other primates, integration of the bionts occurs at the gene product and genetic level. Spirochete round bodies (also called cysts, L-forms and sphaeroplasts) can be induced by many types of unfavorable conditions (e.g., threats of starvation, desiccation, oxidation, penicillin and other antibiotics). Reversion to familiar helical, motile active swimmers by placement of pure cultures into favorable environments in some cases can be controlled. These observations are supported by a European literature, especially Russian, apparently unknown to American medicine and medical research.     

Bis(heptalene) “submarine” metal dimer sandwich compounds (C12H10)2M2 (M = Ti, V, Cr, Mn, Fe, Co, Ni)

The bis(heptalene)dimetal complexes (C₁₂H₁₀)₂M₂ of the first row transition metals from Ti to Ni are predicted by density functional theory to exhibit “submarine” sandwich structures with a pair of metal atoms sandwiched between the two heptalene rings. For the early transition metal derivatives (C₁₂H₁₀)₂M₂ (M = V, Cr) there are two types of such structures. In one structural type the metals are sandwiched between two heptahapto heptalene rings with metal-metal distances (3.5–3.8 Å) too long for direct metal-metal bonding. The other type of (C₁₂H₁₀)₂M₂ (M = V, Cr, Mn) structure has a pair of bonded metal atoms sandwiched between a fully bonded heptalene ligand and a heptalene ligand bonded to the metals only through an eight-carbon heptafulvene subunit, leaving an uncomplexed cis-1,3-diene unit. The formal metal-metal bond orders in these latter structures are 3, 2, and 1 for M = V, Cr, and Mn with predicted bond lengths of 2.5, 2.7, and 2.8 Å, respectively. For (C₁₂H₁₀)₂Fe₂ a singlet structure with each iron atom sandwiched between a hexahapto and a tetrahapto heptalene ring is energetically preferred over an alternate structure with ferrocene-like iron atoms sandwiched between two pentahapto heptalene rings. Partial bonding of each heptalene ring to the metal atoms occurs in the late transition metal derivatives (C₁₂H₁₀)₂M₂ (M = Co, Ni). This leads to an unsymmetrical structure for the cobalt derivative and a structure for the nickel derivative with each nickel atom sandwiched between a trihapto ligand and a tetrahapto ligand.

The spermatozoa of three species of Xenotrichulidae (Gastrotricha,Chaetonotida): the two “dünne Nebengeisseln” of spermatozoa in Heteroxenotrichula squamosa are peculiar para-acrosomal bodies

The spermatozoa of xenotrichulid gastrotrichs have been studied with the aim of supplying further characters for the phylogenetic analysis of Gastrotricha and to assess the reported biflagellarity of Heteroxenotrichula squamosa. Three species have been examined, belonging to the two hermaphroditic genera of xenotrichulids. The spermatozoa are filiform cells characterized by a scarcely condensed nucleus followed by a single mitochondrion and a flagellum with large accessory fibers. These show an obliquely striated cortex and a core containing some dense material. In Heteroxenotrichula squamosa and Xenotrichula punctata there is also a simple acrosome flanked by two para-acrosomal bodies which are curious long extracellular structures formed by a pile of electron-dense disks connected by thin threads. Xenotrichula intermedia lacks both acrosome and paraacrosomal bodies. The sperm model of xenotrichulids is very different from that of the Macrodasyida and Chaetonotida so far studied, thus supporting an isolated position of the family. The oblique striation of the tail's accessory fibers is similar in to the one period and inclination of the strated cylinder of macrodasyid gastrotrichs, thus being the only spermatological character shared by the two gastrotrich taxa.     

Cytoplasmic virus-like particles associated with the nucleolus in wheat,similar to “S bodies” and retroposon particles

Summary Wheat roots from germinating seedlings of Chinese spring wheatTriticum aestivum grown for 36 hours at 20°C were examined by conventional thin-section electron microscopy. Virus-like particles were seen inside a large cytoplasmic intrusion into the nucleus having the appearence of a nucleolar vacuole. The particles were isometric and about 50 nm in diameter with a membrane-like coat and a small core. The cytoplasmic intrusion was bounded by nuclear envelope with pores apparent where it abutted nucleoplasm. The particles are similar to previously reported solitary particles S bodies from a range of plants but are also similar in size and morphology to the retroposon particles associated with copia like elements in other organisms. The position of the virus-like particles in the young wheat roots is discussed in relation to interactions with components of the cell skeleton.