Basal body-associated nucleation center for the centrin-based cortical cytoskeletal network in Paramecium

The infraciliary lattice, a contractile cortical cytoskeletal network of Paramecium, is composed of a small number of polypeptides including centrins. Its overall pattern reflects a hierarchy of structural complexity, from assembly and bundling of microfilaments to formation of polygonal meshes arranged in a continuous network subtending the whole cell surface, with local differentiations in the shape and size of the meshes. To analyse how the geometry of this complex network is generated and maintained, we have taken two approaches. Firstly, using monoclonal antibodies raised against the purified network, we have shown that all the component polypeptides colocalize, in agreement with previous biochemical data indicating that the infraciliary lattice is formed of large complexes comprising all the component polypeptides. Secondly, by taking advantage of different experimental conditions leading to disassembly of the network, we have followed its reassembly. Cytological analysis of the process revealed 1) that the network regrows exclusively from specific infraciliary lattice organizing centers (ICLOC), precisely localized near each basal body and, 2) that the global organization is not precisely controlled by genetic information but by the basal body pattern. Finally, slight ultrastuctural differences between reassembled and control lattices suggest that the organization of the filament bundles is partly templated by that of the preexisting ones.     

The effect of polyamine biosynthesis inhibition on growth and differentiation of the phytopathogenic fungus Sclerotinia sclerotiorum

We studied the effects of several polyamine biosynthesis inhibitors on growth, differentiation, free polyamine levels and in vivo and in vitro activity of polyamine biosynthesis enzymes in Sclerotinia sclerotiorum. -Difluoromethylornithine (DFMO) and -difluoromethylarginine (DFMA) were potent inhibitors of mycelial growth. The effect of DFMO was due to inhibition of ornithine decarboxylase (ODC). No evidence for the existence of an arginine decarboxylase (ADC) pathway was found. The effect of DFMA was partly due to inhibition of ODC, presumably after its conversion into DFMO by mycelial arginase, as suggested by the high activity of this enzyme detected both in intact mycelium and mycelial extracts. In addition, toxic effects of DFMA on cellular processes other than polyamine metabolism might have occurred. Cyclohexylamine (CHA) slightly inhibited mycelial growth and caused an important decrease of free spermidine associated with a drastic increase of free putrescine concentration. Methylglyoxal bis-[guanyl hydrazone] (MGBG) had no effect on mycelial growth. Excepting MGBG, all the inhibitors strongly decreased sclerotial formation. Results demonstrate that sclerotial development is much more sensitive to polyamine biosynthesis inhibition than mycelial growth. Our results suggest that mycelial growth can be supported either by spermidine or putrescine, while spermidine (or the putrescine/spermidine ratio) is important for sclerotial formation to occur. Ascospore germination was completely insensitive to the inhibitors.     

Mollusc diversity in an Arca zebra (Mollusca: Bivalvia) community, Chacopata, Sucre, Venezuela

The diversity of a subtidal epifaunal mollusk community was studied from September, 1990 to September, 1991 in Chacopata, Sucre State, Venezuela. There were 40 species (24 bivalves and 16 gastropods). The diversity indexes (H' = 2.087, J' = 0.392, 1/D = 0.528) were low when compared with other tropical zones. Monthly diversity reached its maximum in September, 1990 (1.63 bits/ind.) and July, 1991 (1.60 bits/ind.); minimum diversity occurred in June, 1991 (0.52 bits/ind.). A Log series model applied to species abundance data showed a straight line with a diversity index alpha of 5.56. Of 40 species identified, the turkeywing Arca zebra was dominant (69% in number of individuals and 72% of biomass) followed by Pinctada imbricata, Modiolus squamosus, Chama macerophyla and Anadara notabilis. The predatory snails Phyllonotus pomum, Chicoreus brevifrons and Murex recurvirostris seemed to have trophic relationships with A. zebra. The total mean biomass in wet weight (469.20 +/- 263 g m-2, shell included) was high which indicates that A. zebra, a species with a rapid growth rate, occupies a central role in the assemblage as an efficient filter feeder that converts planktonic food into available biomass, supporting one of the most important fisheries in Venezuela.     

Oropharyngeal morphology and food habits of Micropogonias furnieri (Pisces: Sciaenidae) in the North coast of Estado Sucre,Venezuela

Morphology of the mandibular and pharyngeal region, and the feeding habits of Micropogonias furnieri were examined in 256 male and female specimens, between 28.7 and 54.3 cm total length, collected around Morro Puerto Santo, in northeast Sucre State, Venezuela (10 degrees 45'00" N-63 degrees 8'0" W), from May 1989 to April 1990. Micropogonias furnieri has a small ventral mouth; protrusible premaxillary and dentary; first branchial arches with 21 to 27 gill rakers, generally 24 to 25; and 7 to 11 pyloric caecae. The index of vacuity was low, with mean value of 7.00%. The mean intestinal index was 0.72, indicative of carnivorous species. Analysis of frequency of occurrence, indicates preference for crustaceans (45.70%), mainly crabs (34.90%), followed by polychaetes (28.00%), fishes (11.41%) and occasionally mollusks and echinoderms (4.0 and 3.9%, respectively). The diet of this species did not vary with sex.     

A comparative study of preservation and storage of Haemophilus influenzae

The aim of this study was to compare the efficacy of conservation by freezing the strains of Haemophilus influenzae at -20 degrees C and -70 degrees C. Skim milk supplemented with glucose, yeast extract and glycerol allowed highest viability of H. influenzae both at -20 degrees C and -70 degrees C from the media analyzed. Trypticase soy broth and brain heart infusion broth supplemented with glycerol, allowed excellent recovery. Use of cotton swaps as supporting material, with or without addition of cryoprotective agents, did not modify H. influenzae viability after six months of storage. Concentration of the initial inoculum positively affected viability when stored at -20 degrees C. Initial concentration did not influence survival after storage at -70 degrees C. Thawing at room temperature should not exceed 3 h as to get highest survival percentage.     

Monosynaptic GABAergic signaling from dentate to CA3 with a pharmacological and physiological profile typical of mossy fiber synapses

Mossy fibers are the sole excitatory projection from dentate gyrus granule cells to the hippocampus, where they release glutamate, dynorphin, and zinc. In addition, mossy fiber terminals show intense immunoreactivity for the inhibitory neurotransmitter GABA. Fast inhibitory transmission at mossy fiber synapses, however, has not previously been reported. Here, we show that electrical or chemical stimuli that recruit dentate granule cells elicit monosynaptic GABA(A) receptor-mediated synaptic signals in CA3 pyramidal neurons. These inhibitory signals satisfy the criteria that distinguish mossy fiber-CA3 synapses: high sensitivity to metabotropic glutamate receptor agonists, facilitation during repetitive stimulation, and NMDA receptor-independent long-term potentiation. GABAergic transmission from the dentate gyrus to CA3 has major implications not only for information flow into the hippocampus but also for developmental and pathological processes involving the hippocampus.     

端突瘿蚊属一新种记述（双翅目：瘿蚊科）

记述采自湖北省的端突瘿蚊１新种,三角端突瘿蚊Ｅｐｉｄｉｐｌｏｓｉｓ ｔｒｉａｎｇｕｌａｒｉｓ Ｍｏ ｅｔ Ｌｉｕ,ｓｐ．ｎｏｖ．。模式标本和于山东农业大学昆虫标本室。     

金边阔叶麦冬(Liriope platyphylla Wang et Tang var.variegata Hort.)的组织培养

将金边阔叶麦冬（Liriope platyphylla Wang et Tang var.variegata Hort.)不同部位外植体块,接种于附加不同激素配比的MS培养基上,实验结果表明,取自根状茎芽点,培养基为MS BA 1.5mg/L NAA 0.5mg/L的不定芽诱导率最高（100%）,长势较旺,不定芽和愈伤组织均较多,但极易造成性状分离。用MS BA 3.0mg/L NAA 0.5mg/L液体培养可以直接“芽生芽”,避免了脱分化过程,从而稳定保持嵌合性。不定芽每月可转接1次,适宜的生根培养基为1/2MS大量 IBA 0.25mg/L。试管苗在蛭石中炼苗后即可移栽。     

Comparative ecological analysis of the ostracod faunas from low- and high-polluted southwestern Spanish estuaries: a multivariate approach

The distribution and abundance of both living and total ostracod populations from the estuaries of the southwestern Spanish coast are discussed. A total of 68 species were obtained from 120 bottom samples collected in the channels, channel margins and salt marshes. Four assemblages were recognized in this area: (a) Urocythereis oblonga assemblage, with marine species well-represented in sandy substrates located near the mouths; (b) Loxoconcha rhomboidea assemblage, mainly developed in the quiet tidal channels conected with the main channels of the marine domains; (c) Loxoconcha elliptica assemblage, enclosing the most cosmopolitan and euryhaline species, very abundant in muddy sediments and low to moderate hydrodynamic conditions; and (d) Leptocythere porcellanea assemblage, only observed in the clayey-silty channel margins of the most protected ebb channels.In these transitional environments, very unfavorable conditions for the ostracod development were found in: (a) the erosional channels and channel margins; (b) most of the salt marsh samples with high subaerial exposure; and (c) sectors with high metallic pollution levels and acidic waters.     

细菌毒力基因体内表达检测技术研究进展

病原菌入侵宿主是一个及其复杂的过程。为了深入了解病原菌的致病机理,人们需要鉴定那些在感染过程中特异表达的细菌毒力基因。为此,多种体内实验模型被建立起来分析细菌在宿主体内的基因表达,它们包括了体内表达技术、信号标签突变技术、差异荧光诱导、体外转座进行基因组分析和作图技术以及体内诱导抗原技术等。文章对目前运用的这些研究方法进展进行综述,并讨论了它们的优点与不足。