Orthologs of key vertebrate neural genes are expressed during neurogenesis in the annelid Platynereis dumerilii

SUMMARY The molecular mechanisms underlying the formation and patterning of the nervous system are relatively poorly understood for lophotrochozoans (like annelids) as compared with ecdysozoans (especially Drosophila ) and deuterostomes (especially vertebrates). Therefore, we have undertaken a candidate gene approach to study aspects of neurogenesis in a polychaete annelid Platynereis dumerilii . We determined the spatiotemporal expression for Platynereis orthologs of four genes ( SoxB, Churchill, prospero / Prox , and SoxC) known to play key roles in vertebrate neurogenesis. During Platynereis development, SoxB is expressed in the neuroectoderm and its expression switches off when committed neural precursors are formed. Subsequently, Prox is expressed in all differentiating neural precursors in the central and peripheral nervous systems. Finally, SoxC and Churchill are transcribed in patterns consistent with their involvement in neural differentiation. The expression patterns of Platynereis SoxB and Prox closely resemble those in Drosophila and vertebrates—this suggests that orthologs of these genes play similar neurogenic roles in all bilaterians. Whereas Platynereis SoxC , like its vertebrate orthologs, plays a role in neural cell differentiation, related genes in Drosophila do not appear to be involved in neurogenesis. Finally, conversely to Churchill in Platynereis , vertebrate orthologs of this gene are expressed during neuroectoderm formation, but not later during nerve cell differentiation; in the insect lineage, homologs of these genes have been secondarily lost. In spite of such instances of functional divergence or loss, the present study shows conspicuous similarities in the genetic control of neurogenesis among bilaterians. These commonalities suggest that key features of the genetic program for neurogenesis are ancestral to bilaterians.     

Multiple molecular forms of rat superior cervical ganglion acetylcholinesterase: Developmental aspects in primary cell culture and during postnatal maturation in vivo

Four main molecular forms of acetylcholinesterase (AChE) can be solubilized from newborn rat superior cervical ganglia (SCG), homogenized in the presence of a high-ionic-strength, detergent-containing medium. These forms, respectively referred to as 16, 10, 6.5, and 4 S, are characterized by their sedimentation coefficients. Their relative proportions in SCG are notably different in vivo during postnatal maturation, and in culture. The 16-S AChE appears to be mainly neuronal in origin, is maintained in culture independently of original presynaptic in vivo elements, and its cellular pool is not depleted in the presence of tetrodotoxin (TTX).     

Fine‐scale Population Genetic Structure of Two Dioecious Indian Keystone Species,Ficus hispida and Ficus exasperata (Moraceae)

Although Ficus (Moraceae) is a keystone plant genus in the tropics, providing resources to many frugivorous vertebrates, its population genetic structure, which is an important determinant of its long‐term survival, has rarely been investigated. We examined the population genetic structure of two dioecious fig species (Ficus hispida and Ficus exasperata) in the Indian Western Ghats using co‐dominant nuclear microsatellite markers. We found high levels of microsatellite genetic diversity in both species. The regression slopes between genetic relationship coefficients (f_ij) and spatial distances were significantly negative in both species indicating that, on average, individuals in close spatial proximity were more likely to be related than individuals further apart. Mean parent–offspring distance (σ) calculated using these slopes was about 200 m in both species. This should be contrasted with the very long pollen dispersal distances documented for monoecious Ficus species. Nevertheless, overall population genetic diversity remained large suggesting immigrant gene flow. Further studies will be required to analyze broader scale patterns.     

Effects of experimental acidification on a lotic macroinvertebrate community

A three month experimental acidification was carried out on lotic bottom communities. Experiments were conducted under semi-natural conditions in plasticized wooden channels. Acidified communities (pH 4.0), with or without added aluminum, were compared with a reference community (pH 6.3–6.9). Added aluminum concentrations were respectively 0.2 and 0.4 mg 1^–1 in experiments performed in 1982 and 1983. Water chemistry and taxonomic composition of the macroinvertebrate communities were monitored. Under acidified conditions, results were similar, with or without added aluminum. Mean abundances of all groups of organisms were lowered. Mayflies nearly completely disappeared from the acidified channels. The only organism not affected by the acidification was Microtendipes sp. Differences in the organism response were observed: Orthocladiinae (Rheocricotopus, Parametriocnemus, Corynoneura, Thienemanniella, Nanocladius, Cricotopus) and Ephemeroptera (Baetis, Habrophlebia, Habrophlebiodes, Paraleptophlebia, Ephemerella), especially early instars, were very sensitive to low pH, Chironomini and Tanypodinae were much less sensitive, while Tanytarsini were intermediate; Oligochaeta and Nematoda were difficult to classify, their response being different from one year to another. Organisms inhabiting the surface of artificial substrates disappeared very rapidly from the system, while those buried inside had a delayed reaction to acidification. Aluminum which was mainly in the monomeric form was not responsible for community modifications. Direct action of hydrogen ions through a physiological stress seems a more credible explanation. These results, induced by a continuous experimental acidification, suggest that if this small headwater stream undergoes acidification, the resulting invertebrate community will be very simplified, with only resistant species able to cope with the acid conditions.     

Acid shock proteins of Escherichia coli

Synthesis of total cellular proteins of Escherichia coli was studied after transfer of cultures from pH 6.9 to pH 4.3. Proteins induced by such an external pH shift down were identified by mono- and bi-dimensional electrophoresis. 30 to 45 min after an acid shift, a group of at least sixteen polypeptides was markedly induced. Four of these polypeptides corresponded to the well known heat shock proteins GroEL, DnaK, HtpG and HtpM. Their pH induction was RpoH-dependent. Three other pH-induced proteins were previously identified as stress proteins induced either by osmolarity or aerobiosis or low temperature (proteins 32 (defined in this paper), C70.0 and C62.7). Seven other proteins were specifically induced after an acid shift and were called acid shock proteins (ASP). The induction of one of these proteins was RpoH-dependent, whereas that of others was RpoH-independent.     

Molecular analysis of a reciprocal translocation t(5;11)(q11;p13) in a WAGR patient

Summary Most patients with the complex association aniridia — predisposition to Wilms' tumor (WAGR syndrome) present with a de novo constitutional deletion of band 11p13. We report a patient with WAGR syndrome and a reciprocal translocation between chromosomes 5 and 11 t(5;11)(q11;p13). High resolution banding cytogenetic analysis and molecular characterization using 11p13 DNA markers showed a tiny deletion encompassing the gene for CAT but sparing the gene for FSHB. This suggests that syndromes associated with apparently balanced translocations may be due to undetectable loss of material at the breakpoint(s) rather than to breakage in the gene itself.     

Properties of the 12-O-Tetradecanoylphorbol-13-Acetate-Stimulated S6 Kinase from Rat Astroglial Cells

The S6 kinase activity of astroglial cells in primary culture stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA) has been studied. This activity was eluted as a single peak at 0.15 M NaCl from a DEAE-Sephacel column. The chromatography of this peak on phosphocellulose revealed an activity eluted at 0.15 M NaCl. This partially purified enzyme had a sedimentation coefficient of 3.7S; Km values were 2 X 10(-5) M for ATP and 10(-6) M for 40S ribosomal subunits. The optimal Mg2+ concentration requirement was 2-3 mM. Mn2+ and Co2+ could substitute for Mg2+ (optimum concentrations 1.5 and 0.8 mM, respectively), but these cations were strong inhibitors in the presence of Mg2+. The enzyme was inhibited by N-ethylmaleimide, indicating that it contained thiol groups. This S6 kinase used ATP, but not GTP, as a phosphate donor, and exhibited great specificity for S6 as phosphate acceptor. Whole histones and protamine were slightly phosphorylated whereas phosvitin, histone H1, and surprisingly the peptide Arg-Arg-Leu-Ser-Ser-Leu-Arg-Ala were not phosphorylated. The TPA-stimulated S6 kinase resembles the insulin-, fibroblast growth factor- and cyclic AMP-stimulated enzymes, suggesting that several pathways might activate the same entity.     

The complete nucleotide sequence of the colicinogenic plasmid ColA. High extent of homology with ColE1

Summary The complete nucleotide sequence of the colicinogenic plasmid ColA has been determined. The plasmid DNA consists of 6720 bp (molecular weight 4.48×10⁶). Fifteen putative biological functions have been identified using the functional map previously determined. These include 11 genes and 3 DNA sites. Nine genes encode proteins of which 3 have been fully characterized. The replication region of ColA coding for RNAI and RNAII is highly homologous to that of ColE1 andClo DF13. The same holds true for the site-specific recombination region containing palindromic symmetry and involved in stable maintenance of the plasmids. A high percentage of homology has been detected for putative mobility proteins encoded by ColA and ColE1. The exclusion proteins are also highly homologous.     

Correspondence of the monocyte antigen HMA-1 to the non-HLA antigen 9a

Monocyte-specific antibodies are detrimental to bone marrow and renal transplantation. By using human antimonocyte sera we were able to identify two monocyte-specific antigens, human monocyte antigen 1 and 2 (HMA-1 and HMA-2). The presence of HMA-1 and HMA-2 was compared with the presence of several non-HLA antigens. In panel and inhibition studies, HMA-1 corresponded to the previously described non-HLA granulocyte antigen 9a. Absorption studies showed that HMA-1 and 9a were both present on granulocytes and monocytes. The clinical relevance of these antigens is discussed.     

Extra terrestrial abiogenic organization of organic matter: The hollow spheres of the Orgueil meteorite

Fragments of the Orgueil meteorite were macerated in mineral acids (HNO₃-HF-HNO₃) to dissolve the mineral matrix and separate the acid-resistant organic residues; a routine procedure in the extraction of pollen and spores from terrestrial sediments. Numerous spherical hollow objects were found, optically resembling the brown amorphous residual organic matrix of the meteorite. Their morphology, size-distribution, and chemical composition, revealed by electron microprobe with reference to carbon and phosphorus, are described, and evaluated in connection with criteria of biogenicity. The intrinsic criteria are satisfactorily met, but the extrinsic requirement of a sedimentary environment is not met. A review of the literature concerning the meteoritic environment suggests an explanation of these spheres based on the environment of their formation. It is proposed that they are organic coatings on olivine microchondrules, magnetite and glass globules, the mineral component of which has been dissolved by the acid maceration. They could have initially resulted from the polymerization of dispersed small organic molecules condensing on the surface of the microchrondrules. The latter were injected from a volcanic nuée ardente into the dispersed cold primordial cosmic dust of hydrated silicates and organic molecules, around the meteorite parent-body. This presumably occurred before the cosmic dust accreted as the carbonaceous chondritic outer layer of the parent-body. Upsurging reducing hot gases from the nuée ardente would polymerize part of the dispersed organic matter as the insoluble brown amorphous matrix, possibly the sticking agent when the cosmic dust accreted. The spiraled form of several of the organic structures described here are suggestive of atmospheric heat microturbulences. Organic membranes and comet-form tails of spherical coatings suggest polymerization in the wake of injected microchondrules. These diverse organic structures would result in our view from the abiogenic thermal organization of organic matter in an extraterrestrial gas-solid system.

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Résumé Plusieurs fragments de la météorite d'Orgueil ont été macérés dans des acides minéraux (HNO₃, HF, HNO₃), afin de dissoudre la fraction minérale et isoler la fraction résiduelle résistant aux acides. C'est là un procédé utilisé couramment en palynologie pour extraire les grains de pollen et les spores des sédiments terrestres.De nombreux objets microscopiques, sphériques et creux, ont été mis en évidence. Ils sont optiquement similaires au résidu organique brun, amorphe, dans lequel ils sont enrobés. Leur morphologie, leur répartition en fonction de leur taille, et leur composition chimique élémentaire, analysée par la microsonde électronique, qui révèle la présence de carbone et de phosphore, sont décrites, puis évaluées en fonction des critères disponibles d'une éventuelle origine biologique. Les critères intrinsèques aux objets sont bien satisfaits, mais non le critère extrinsèque d'un environnement sédimentaire convenable.L'analyse des hypothèses qui ont été avancées pour décrire l'environnement originel de la météorite, permet de suggérer une explication de ces sphères creuses organiques, qui repose entièrement sur cet environnement à l'époque de leur formation. Ce sont des revêtements organiques à la surface de microchondrules d'olivine, de globules de verre et de magnétite, minéraux de haute température appartenant à la fraction minérale de la météorite qui a été dissoute par la macération acide.Ces coques organiques résulteraient de la polymérisation de petites molécules organiques dispersées, qui se seraient condensées à la surface de gouttelettes minérales en fusion. Ces dernières ont pu être éjectées par une nuée ardente volcanique issue du corps parent de la météorite, et projetées dans la poussière cosmique primitive froide en suspension autour de ce corps parent, composée de silicates hydratés et de petites molécules organiques.C'est ensuite seulement que cette suspension de poussière primitive aurait subi l'accrétion pour former finalement la couche extérieure froide de matière étéoritique carbonée du corps parent. En outre, des gaz réducteurs à haute température, s'élevant de la nuée ardente, ont pu polymériser en partie la matière organique en suspension, pour former la matière météoritique organique amorphe, résistant aux acides, qui a peut-être été l'agent agglomérant lors de l'accrétion.Les formes spiralées de plusieurs des structures organiques décrites ici suggèrent des microturbulences atmosphériques dûes à la chaleur. Des membranes organiques, et l'appendice en forme de queue de comète d'une sphérule, suggèrent une polymérisation organique dans le sillage de la trajectoire de microchondrules. Selon notre opinion, ces diverses structures organiques résultent donc de l'organisation abiogénique sous l'effet de la température, de matière organique préexistante, plus simple, dans un système solide-gaz extraterrestre.