颗石藻Pleurochrysis carterae抗捕食特征

颗石藻Pleurochrysis carterae是沿海水域中常见钙化微藻,易形成高密度水华,也是养殖环境致害种之一。抗捕食防御能力可能是其种群增殖优势的一个重要原因。以卤虫作为捕食者,分析了颗石藻P.carterae抗捕食现象,以及在捕食压力下的重要生理生化响应特征,以期为颗石藻P.carterea抗捕食机制研究及其高密度增殖机理提供参考。研究结果显示:(1)当颗石藻P.carterae比例增加时,卤虫对微藻的摄食率显著降低,且存活率显著下降,显示该藻具抗捕食能力。(2)以卤虫饵料微藻球等鞭金藻(Isochrysis galbana)为对照,比较研究发现,相同的捕食压力下,饵料金藻的叶绿素荧光参数(电子传递速率ETR和最大量子产率Fv/Fm)显著降低,但颗石藻P.carterae的ETR和Fv/Fm没有显著变化,显示颗石藻P.carterae对卤虫抗捕食作用。(3)相对于没有捕食压力的对照组,捕食压力下,饵料金藻I.galbana的脂类组成没有显著差异。但是,颗石藻P.carterae的脂类组成则发生了显著变化,主要表现在对细胞叶绿体有重要作用的单半乳糖甘油二酯(MGDG),双半乳糖甘油二酯(DGDG),磷脂酰甘油二酯(PG)含量上升,与促细胞分裂相关的二酰甘油(DAG)和磷脂酰肌醇(PI)也上升。这些脂类代谢物的变化可能在其种群水平上抵抗捕食并实现种群增殖中发挥作用。(4)培养介质中磷的状态对颗石藻P.carterae细胞二甲基巯基丙酸(Dimethyl sulfonio propionate,DMSP)含量有显著影响,且影响颗石藻P.carterae对卤虫的致害效应:缺磷条件下生长的颗石藻P.carterae首先使卤虫受害。当培养液中仅以ATP为磷源时,颗石藻P.carterae的卤虫致害效应则降低。研究证明,颗石藻P.carterae具有抗捕食能力,细胞的脂类代谢物质以及DMSP可能在抗捕食防御中发挥作用。     

Serial reconstruction of the mitochondrial reticulum in the coccolithophorid,Pleurochrysis carterae (Prymnesiophyceae)

Summary A serial reconstruction of the chondriome ofPleurochrysis carterae (Braarudet Fagerland) Christensen has revealed a single, reticulated mitochondrion branching throughout the cell. The occurrence of a single mitochondrion in unicellular algae is briefly reviewed and its phylogenetic significance is discussed.     

Purified NAD(P)H-quinone oxidoreductase enhances the mutagenicity of dinitropyrenes in vitro

The effect of highly purified rat liver cytosolic NAD(P)H-quinone oxidoreductase [EC 1.6.99.2] on the mutagenicity of 1,3- 1,6- and 1,8-dinitropyrene (DNP) was studied in the Ames Salmonella typhimurium mutagenicity assay. NAD(P)H-quinone oxidoreductase over the range of 0.02–0.8 μ g/plate (38–1500) units increased up to threefold the mutagenicity of all three DNPs in S. typhimurium TA 98. In TA98NR, a strain deficient in “classical” nitroreductase, the mutagenicity of 1,6- and 1,8-DNP was essentially unchanged, whereas that of 1,3-DNP was markedly reduced. NAD(P)H-quinone oxidoreductase enhanced the mutagenicity of 1,6- and 1,8-DNP to approximately equivalent extents in TA98NR and TA98. The mutagenicity of 1,3-DNP in TA98NR was potently enhanced by the addition of NAD(P)H-quinone oxidoreductase in a dose-responsive manner. In the presence of 0.8 μg NAD(P)H-quinone oxidoreductase, 1,3-DNP displayed a mutagenic response in TA98NR that was comparable to that obtained in TA98. NAD(P)H-quinone oxidoreductase was found to increase the mutagenicity of 1,6- but not 1,3- or 1,8-DNP to mutagenic intermediates in TA98/1,8-DNP₆, a strain deficient in O-acetyltransferase activity. The results suggest that NAD(P)H-quinone oxidoreductase not only catalyzes reduction of the parent DNP but also that of partially reduced metabolites generated from that DNP. Such reductive metabolism may lead to increased formation of the penultimate mutagenic species.     

Reduction in Ames Salmonella mutagenicity of mainstream cigarette smoke condensate by tobacco protein removal

The mutagenic activity of cigarette smoke condensates (CSC) made from tobacco before and after removal of protein was assessed by the Ames Salmonella assay in bacterial strains TA98 and TA100. Removal of protein and peptides from flue-cured tobacco via water extraction followed by protease digestion reduced the mutagenicity of the resultant CSC by 80% in the TA98 strain and 50% in the TA100 strain. Similarly, reductions of 81% in TA98 and 54% in TA100 were seen following water extraction and protease digestion of burley tobacco. The significant reductions in Ames mutagenicity following protein removal suggest that protein pyrolysis products are a principal contributor to the genotoxicity of CSC as measured in this assay.     

Polymorphism and size-pairing in the harvester antPogonomyrmex badius: a test of the ecological release hypothesis

Summary The role of caste polymorphism in the foraging strategy ofPogonomyrmex badius was studied in the field by measuring food items collected by foragers, and correlating food item size variables with forager size variables. The diet ofP. badius included seeds and insects. In two colonies examined, these food types comprised different proportions of the diet sample.Although some forager size variables showed close or significant correlations with food item size variables, we could identify no overall significant relationship between worker size and seed or prey size. Polymorphism inP. badius may be associated with omnivory. However, since minor workers serve as foragers and represent a portion of the total worker size variation, dietary expansion through caste proliferation appears to be only one aspect of the functional significance of polymorphism in this species.     

Two types of antimutagenic effects of gallic and tannic acids towards N-nitroso-compounds-induced mutagenicity in the amesSalmonella Assay

The frequency ofhis ⁺ revertants induced by N-methyl-N-nitrosourea (MNU) and N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) in the strain TA100 ofSalmonella typhimurium was decreased by gallic and tannic acid. In weak buffer solutions, the inhibition effects of gallic acid towards MNU and MNNG mutagenicity was caused primarily by a decrease of pH in the incubation mixtures. At adjusted pH (pH 5.0 and 6.5), the antimutagenic effects are largely the result of an interaction between MNU or MNNG with phenolic acids outside the cells.     

Antimutagenic properties of a polyphenol-enriched extract derived from sesame-seed perisperm

A polyphenolic mixture derived from sesame-seed perisperm (SSP) strongly reduced the mutagenicity of hydrogen peroxide (H₂O₂), sodium azide (NaN₃), and benzo[a]pyrene (BaP) in strains TA100 and/or TA98 of Salmonella typhimurium. It exhibited desmutagenic activity against H₂O₂, BaP in TA98 and/or TA100 and biomutagenic activity (apparently by affecting the DNA-repair system) against NaN₃ in strain TA100. According to in vitro experiments the polyphenolic mixture inhibited the activity of the CYP1A1 (EROD) enzyme responsible for the activation of BaP in the Ames’ test, as well as that of the cytosolic enzyme GST.A cytosolic fraction from liver of male Wistar rats treated with either 20% SSP in the food, or 3 mg or 6 mg of polyphenolic mixture/20 g food/day for a time period of 8 weeks reduced the mutagenic potential of BaP in strains TA100 and TA98, with the cytosolic fraction from rats treated with SSP causing the strongest reduction. Furthermore, a microsomal fraction from the 20% SSP-treated rats inhibited the mutagenicity of BaP in strains TA100 (26.3%) and TA98 (23%). In contrast, a microsomal fraction from rats treated with 3 mg of polyphenolic mixture stimulated the mutagenicity of BaP in TA100 but reduced it in TA98, while for the microsomal fraction from rats treated with 6 mg of polyphenolic mixture, these effects on TA100 and TA98 were reversed.     

Yeast communities of the cactusPilosocereus arrabidae as resources for larval and adult stages ofDrosophila serido

The feeding behavior ofDrosophila serido on the yeast communities of necrotic stem tissue ofPilosocereus arrabidae were studied in a sand dune ecosystem of Rio de Janeiro, Brazil. The prevalence of cactophilic yeasts includingPichia barkeri, Candida sonorensis andGeotrichum sp. in the crops and external surfaces ofD. serido reflected its association with the cactus habitat. The effective number of yeasts vectored on the surface of flies was higher than that in the crops. Also overlap between the yeasts from stems and from crops was partial suggesting selective feeding by the flies in the substrates visited. The females had a higher effective number of yeast species and a lower similarity than males with the yeast community ofP. arrabidae. This was probably related to the search for oviposition sites by females. The presence ofPichia thermotolerans-like andPichia amethionina varpachycereana in the flies, but not inP. arrabidae stems, indicated thatD. serido was not limited to this cactus species. The larvae and adults lived in different patches with the adults feeding in patches with higher yeast species richness. The larvae had a narrower feeding niche and higher overlap withP. arrabidae, and preferredP. barkeri andPichia cactophila as food. Adult flies fed on patches with the most frequent yeasts except forP. cactophila. Pichia caribaea was found in higher frequency in the adult crops than in the stems. Our data suggested that there was food selection and diet partitioning between adult and larval stages ofD. serido.     

Mutagenicity,sister chromatid exchange inducibility andin vitro cell transforming ability of particulates from Athens air

Airborne particulates were collected over a period of twelve months by the use of Hi-Vol samplers in the basin of Athens, Greece. N-Hexane extracts were tested in a battery ofin vitro tests for their ability to induce mutation in bacteria as well as mutation, sister chromatid exchange and morphological transformation in cultured mammalian cells. Positive results were found for mutagenicity withSalmonella strain TA98 in the Ames assay, for sister chromatid exchange induction in CHO cells and for transformation in BALB/c 3T3 cells in culture. They also showed weak non-doserelated induction of ouabain resistance in BALB/c 3T3 cells. The contribution of oxidizing and nitrating agents found in the Athens atmosphere, together with sunlight UV irradiation in the formation of direct acting mutagens and potential carcinogens from ambient polycyclic aromatic hydrocarbons, is suggested.Abbreviations FCS fetal calf serum - FPG fluorescent-plus-Giemsa technique - oua^R ouabain resistant - PAH polycyclic aromatic hydrocarbon - SCE sister chromatid exchange - TSP total suspended particulate     

Antimutagenic activity of soybeans fermented with basidiomycetes in Ames/Salmonella test

Soybeans fermented with either Phellinus igniarius or Agrocybe cylindracea inhibited the mutagenicity of the directly-acting mutagens: 4-nitro-o-phenylenediamine on Salmonella typhimurium strain TA 98 and NaN₃ on S. typhimurium strain TA 100; and indirectly-acting mutagens, 2-aminofluorene using strain TA 98 and benzo[a]pyrene using strain TA 100, in the presence of a supernatant solution from mammalian hepatic microsomes.     

The survival of different vibrios in association with a laboratory culture of the red-tide-causing organism Amphidinium carterae

The survival of different vibrios in association with a red-tide-causing organism Amphidinium carterae was studied in the laboratory. Vibrio alginolyticus and V. harveyi could not survive beyond 14 days in an actively growing culture of A. carterae. On the other hand, V. parahaemolyticus could be detected up to 40 days.     

Inhibitory effects of microalgae on the activation of hyaluronidase

The inhibitory effects of seven microalgae, Nostoc flagelliforme, Spirulina platensis, Porphyridium purpureum, Rhodosorus marinus,Chlorella pyrenoidosa, Dunaliella salina and Pleurochrysiscarterae on the activation of hyaluronidase were evaluated. Theinhibitory effect of the ethanol-insoluble fraction of each water extract frommicroalgae was stronger than that of the ethanol-soluble fraction. The50% inhibitory concentration (IC₅₀) of the ethanol-insolublefraction of S. platensis, P. purpureum, R. marinus, C.pyrenoidosa, D. salina and P. carterae was 0.15, 0.18, 0.26,0.94, 0.15 and 0.41 mg mL^-1, respectively. The IC₅₀ ofN .flagelliforme was not calculated, because there was no detectableinhibitory effect of this alga. The IC₅₀ of disodium cromoglycate(DSCG) used as the anti-allergic medicine was 0.14 mg mL^-1. The IC₅₀ of S. platensis, P. purpureum and D. salinawere almost the same as that of DSCG. This suggests that theethanol-insoluble fraction of S. platensis, P. purpureum and D. salina might be an anti-allergic substance. The ethanol-insoluble fractionof S. platensis and D. salina was ultrafiltered through a membranehaving a molecular exclusion limit of 20 kDa. The IC₅₀ of theresidue was stronger than that of the filtrate. These results suggest that theanti-allergic substance(s) of these microalgae may be polysaccharides.     

The mechanical significance of the occlusal geometry of great ape molars in food breakdown

Analyses of dental function are an essential component of the study of human evolution. However, with few exceptions, they have utilized the traditional analogizing method of comparative anatomy, and have assumed rather than demonstrated that proposed adaptive characters confer a performance benefit. Since food reduction is a mechanical process, it is appropriate to measure performance using mechanical parameters, specifically the ability of a given morphology to induce failure in food particle by either of the two major regimes: crush and shear, corresponding to simple stresses (tensile and compressive) and shear stress, respectively. We apply finite elements stress analysis to model the relationship between the angulation of the intercuspal occlusal surfaces in a “puncture crushing” mode of mastication. On the basis of morphological data acquired from sectioned great ape molars, we have predicted the nature, magnitude and distribution of stress in a standard food particle by models representing each morphotype. Results indicate that the blunt-cusped molars ofHomo, the gradually-sloping supporting (buccal) cusps but high-angled guiding (lingual) cusps of the lower molars ofPan, and the high angled occlusal surfaces ofGorillaare all more likely to fracture small food particles by shear, while the gradually sloping occlusal surfaces ofPongomolars are more likely to break them down by “crush”. Mechanisms of food failure induced by molars ofPanandHomowill vary according to the orientation of the tooth–food contacting surfaces, which in turn will vary according to the size of the food particle. These genera may be able to break food down either by shear or by “crush”.     

Antigenotoxic potential of glucomannan on four model test systems

Antimutagenic, anticlastogenic, and bioprotective effect of polysaccharide glucomannan (GM) isolated fromCandida utilis was evaluated in four model test systems. The antimutagenic effect of GM against 9-aminoacridine (9-AA)- and sodium azide (NaN₃)-induced mutagenicity was revealed in theSalmonella typhimurium strains TA97 and TA100, respectively. GM showed anticlastogenic effect against N-nitroso-N-methylurea (NMU) induced chromosome aberrations in theVicia sativa assay. The bioprotective effect of GM co-treated with methyl-methane-sulphonate (MMS) was also established inChlamydomonas reinhardtii repair deficient strainsuvs10 anduvs14. The statistically significant antimutagenic potential of GM was not proved against 4-nitro-quinoline-1-oxide (4-NQO)-induced mutagenicity inSaccharomyces cerevisiae D7 assay. It may be due to bioprotectivity of -mannan and -glucan, which are integral part ofS. cerevisiae cell walls. Due to the good water solubility, low molecular weight (30 kDa), antimutagenic/anticlastogenic, and bioprotective activity against chemical compounds differing in mode of action, GM appears to be a promising natural protective (antimutagenic) agent.     

Evaluation of Toxicity of <Emphasis Type="Italic">Cercospora piaropi</Emphasis> in a Mycoherbicide Formulation by Using Bacterial Bioluminescence and the Ames Mutagenicity Tests

An evaluation of the potential hazards associated with mutagenicity and acute toxicity of a mycoherbicide formulation based on the fungal pathogen Cercospora piaropi was performed. Neither the mycoherbicide nor any of its components were mutagenic to Salmonella typhimurium TA98 and TA100 with or without metabolic activation. Both the C. piaropi and the mycoherbicide formulation were shown to be moderately toxic with a bacterial bioluminescence assay. No acute toxicity was found in water samples taken from tanks after treatment of water hyacinth with the mycoherbicide.     

Enhancement of the mutagenicity of IQ and MeIQ by nitrite in the Salmonella system.

The fried food mutagens IQ, MeIQ, Glu-P-1 and Trp-P-2 were treated with nitrite at pH 3.0 for 1 h at 37 degrees C. The resulting reaction mixtures were tested for mutagenicity towards Salmonella typhimurium TA97, TA98, TA100 and TA1535. Glu-P-1 and Trp-P-2 were readily converted to weak or non-mutagenic deaminated compounds, whereas IQ and MeIQ were converted to extremely strong mutagenic derivatives in both the presence and the absence of rat liver S9 mix. The mutagenicity of MeIQ in TA98 was enhanced by nitrite up to 3-fold, while that of nitrosated MeIQ was further enhanced by S9 mix up to 15-fold. The nitrosation products of MeIQ were resolved into 7 bands by TLC on silica gel plate. Bands I, III, V and VI were highly mutagenic to both TA98 and TA100. The experimental results suggest that the non-enzymatic formation of direct-acting mutagens from indirect-acting mutagens such as IQ or MeIQ might be physiologically important, especially with regard to the etiology of human gastrointestinal tract tumors.     

Mutagenic activity of the glutathione S-transferase substrate 1-chloro-2,4-dinitrobenzene (CDNB) in the Salmonella mutagenicity assay

The mutagenicity of the commonly used glutathione S-transferase substrates 1-chloro-2,4-dinitrobenzene (CDNB) and 1,2-dichloro-4-nitrobenzene (DCNB) was investigated in the Salmonella mutagenicity assay. CDNB induced a concentration-dependent mutagenic response in Salmonella typhimurium strain TA98. Incorporation of an activation system derived from Aroclor 1254-induced rats did not influence mutagenic response. Under the same conditions DCNB failed to display mutagenic activity. The mutagenic activity of CDNB was attenuated in bacterial strains under-expressing nitroreductase or O-acetylase activity but, in contrast, it was exaggerated in an O-acetylase over-expressing strain. It is inferred that CDNB exhibits a mutagenic response following reduction of the nitro-group to the hydroxylamine, which is further acetylated to form the acetoxy derivative that presumably breaks down spontaneously to generate the nitrenium ion, the likely ultimate mutagen.     

Assessing the Mutagenic Potential of Surface Sediments from Beijing Guanting Reservoir to Salmonella typhimurium

Mutagenicity of organic extracts from Beijing Guanting Reservoir sediments was investigated with TA98 and TA100 of Salmonella typhimurium. TA98 and TA100 were employed to detect frameshift mutation and base-pair substitution mutation, respectively. For TA100, no positive result was found, while TA98 was more sensitive and pro-mutagenic frameshift mutagens were mainly detected in sediments. Sediments from northern and southern Guanting Reservoir were at potential mutagenic risk. No mutagenicity was found in the sediments from the entrance of the tributaries, but strong mutagenicity was observed in the sediments from the outlet of the reservoir. Chemical analysis was also performed, and poor correlation was found between mutagenicity and organochlorine pesticides (OCPs). However, significant positive correlation was found for polycyclic aromatic hydrocarbons (PAHs) (r = 0.603–0.946), which showed that PAHs were dominated for the tested mutagenicity in the sediments. Polychlorinated biphenyls (PCBs) might induce mutagenicity or promote the mutagenicity of other substances.     

In vitro susceptibility ofPityrosporum ovale (Malassezia furfur) to human androgenic steroids

Cells ofPityrosporum ovale that colonize human pilosebaceous units are constantly exposed to cutaneous androgenic steroids. The aim of our study was to find out whetherP. ovale is susceptible to these hormones. Three strains ofP. ovale were grown in vitro in the presence of various concentrations oftestosterone, dehydroepiandrosterone, androstenedione, androstanedione, 5--dihydrotestosterone andprogesterone (10, 100, and 1000 µg/ml; agar dilution assays). In addition, three strains ofCandida albicans were also exposed to equal concentrations of the same androgens. As a result, allP. ovale strains were suppressed by 1000 µg/mlandrostenedione, which was the strongest inhibitor. The other androgenic steroids also significantly reducedP. ovale growth at different concentrations, depending on the hormone used and the strain tested.Progesterone was inhibitory at the highest concentration for oneP. ovale strain only.Candida albicans was not affected by any of the androgens. These findings demonstrate an in vitro susceptibility ofP. ovale to high concentrations of human androgenic steroids. A relevance of this interaction for the in vivo fungus-host relation is not apparent.