Changes in the population dynamics of Keratella cochlearis (Gosse), Kellicottia longispina (Gosse) and Polyarthra vulgaris Carlin in a fertilized enclosure

The population dynamics of phytoplankton and zooplankton in a fertilized enclosure were studied from April 1977 to June 1978. During the first spring period, the rotifers Keratella cochlearis, Kellicottia longispina, and Polyarthra vulgaris were scarce. During the following spring, all three species were abundant. An attempt is made to explain these differences. Food resource competition from cladocerans, and the low food quality and possible inhibitory effects of Coccomyxa sp. were found to be the most likely factors limiting the growth of these rotifers during the first spring period.     

Ultrastructure and histochemistry,of the stomach of Asplanchna sieboldi

Stomach cells of female Asplanchna sieboldi are specialized for absorption and intracellular digestion of nutrients. Evidence is presented to show that electron-opaque colloidal substances, present in the medium and within digestive vacuoles of the prey (Paramecium), are taken up by the stomach cells at the apical cell membrane and sequestered within food vacuoles which contain hydrolases working in both the acid and alkaline pH range. The stomach cells are also implicated in the absorption of molecules below the resolving power of the electron microscope. In rotifers possessing a complete digestive tract, this task is presumed to be handled by the intestine.     

Food composition of Clarias gariepinus (= C. lazera) (Cypriniformes,Clariidae) in Lake Kinneret (Israel)

The feeding behaviour of the freshwater piscivore, Clarias gariepinus (C. lazera) (C & V 1840) was studied over two periods: 1973–1975 and 1981–1982, in Lake Kinneret (Israel). The total number of fish analysed was 264 and their sizes (SL) and weights varied between 238 and 830 mm (146 to 5728 g). More than fifty species of plants and animals from the plankton, benthos and nekton of Lake Kinneret were identified in the intestines of C. gariepinus. Preyed fish were the most abundant food component (81%) and constituted the highest biomass, with Mirogrex terraesanctae representing the majority (although other species were also found). The potential impact of piscivory in the Kinneret ecosystem is considered.     

褐稻虱取食试验及防治探讨

本文用茚三酮法, 以褐稻虱Nilaparvata lugens(stal)排泄的蜜露面积来测定其相对取食量.试验表明:取食量随虫期增大, 逐日取食分布各虫期呈现明显的峰期(图3);发育历期与累积取食量成幂函数关系: N(t)=0.0531t^2.298式中N(t)=累积取食量, t=发育历期(天);褐稻虱各虫期取食率的变化;若以一龄若虫为1计算, 一一四龄若虫取食量比分别为1:1.66:2.10:3.16:10.26, 成虫为73.19;羽化后8天, 短翅型雌虫日均取食量比长翅型雄虫大6.33倍;按褐稻虱的取食行为, 化学防治适期以世代成虫初见期为宜.     

胆碱能神经对人餐后神经降压素释放的影响

本文比较了6名健康成人进食、餐前肌注阿托品以及单纯咀嚼食物后的血浆神经降压素样免疫活性物质(NTLI)水平的变化,以探讨胆碱能神经对神经降压素释放的影响。用放射免疫测定法分别测定NTLI和胰多肽(PP)的含量,以便同时比较两者释放的状态。6人的基础血浆NTLI和PP的水平平均分别为15.7±2.4和16.6±9 7pmol/L。进食后,血浆NTLI和PP水平均显著增高,并呈双相反应。第一个血浆NTLI高峰平均为60.7±13.2pmol/L,出现于餐后的20min。餐后90min,又出现另一个高峰,其平均水平为58.8±8.2pmol/L。在进食前肌注阿托品1mg,餐后的第一个血浆NTLI高峰消失,而第二个高峰仍存在。单纯咀嚼食物后,血浆PP水平明显增高,而对NTLI的释放无刺激作用。本文结果提示,餐后早期的神经降压素释放的调节是由非迷走胆碱能神经参与的,而后期的释放不受胆碱能神经的影响。     

Performance of nymphal and adult Nezara viridula on selected alternate host plants

Laboratory studies with the southern green stink bug, Nezara viridula (L.) (Hemiptera: Pentatomidae), feeding on seeds or fruits of some alternate host plants, demonstrated differences in nymphal survival and development time, and body weight at adult emergence. Lowest mortalities (25%) were observed for nymphs on fruits of dakota mustard [Brassica kaber (DC.)] and siberian motherwort (Leonurus sibiricus L.). On fruits of castor bean (Ricinus communis L.) nymph mortality was ca. 60%, and on mature seeds of L. sibiricus ca. 75%. Total development time from second instar to adult ranged from ca. 26 days on B. kaber to ca. 42 days on R. communis. Fresh body weight at adult emergence was greatest for nymphs on L. sibiricus and lowest on R. communis. Adult survival after 30 days and mean longevity was greater on L. sibiricus than on the remaining foods, being drastically reduced on R. communis. In general, reproductive performance on all foods was similar, except R. communis, on which no female reproduced. Female weight gain of N. viridula was generally greater on L. sibiricus On R. communis, adults lost weight during their first week and showed the lowest weight gain at the end of day 29. Field observations coupled with these laboratory studies suggest that in the Warta area (northern Paraná state, Brazil, 23° 11 S), L. sibiricus and B. kaber are important alternate food plants in the seasonal phenology of N. viridula. R. communis, however, is of poor nutritional quality, serving primarily as a refuge.

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Résumé L'alimentation au laboratoire de N. viridula avec les graines et les fruits de diverses plantes a entraîné différentes mortalités larvaires, différentes vitesses de développement et des différences dans les poids des adultes à l'émergence. Les mortalités les plus faibles (25%) on été observées avec les fruits de Brassica kaber DC. et de Leonurus sibiricus L.Avec les fruits de Ricinus communis L., la mortalité larvaire était de 60%; sur graines mûres de L. sibiricus, elle était de 75%. La durée du développement du second stade à l'adulte a varié de 26 jours sur B. kaber à 42 jours sur R. communis. Le poids frais des adultes à l'émergence était le plus élevé avec L. sibiricus et le plus faible avec de R. communis. La longévité des adultes au-delà de 30 jours était la plus élevée avec L. sibiricus, et était fortement réduite avec R. communis. Dans l'ensemble, la reproduction était de même importance avec les différents aliments, à l'exception de R. communis avec lequel les femelles ne se reproduisaient pas. Le gain de poids des femelles était généralement supérieur avec L. sibiricus; avec R. communis les adultes ont perdu du poids pendant la première semaine et ont présenté le plus faible gain à la fin du 29ème jour.Des observations dans la nature, associées à ces expériences de laboratoire, laissent supposer que dans la zone de Warta (au Nord de l'état de Paraná, 23° 11 S, au Bresil), L. sibiricus et B. kaber sont des plantes hôtes alternatives importantes dans la phénologie saisonnière de N. viridula. Cependant, R. communis, de faible valeur alimentaire, sert avant tout de refuge.

     

Strand targeting signal(s) for in vivo mutation avoidance by post-replication mismatch repair in Escherichia coli

Summary The involvement of GATC sites in directing mismatch correction for the elimination of replication errors in Escherichia coli was investigated in vivo by analyzing mutation rates for a gene carried on a series of related plasmids that contain 2, 1 and 0 such sites. This gene encoding chloramphenicol acetyl transferase (Cat protein) was inactivated by a point mutation. In vivo mutations restoring resistance to chloramphenicol were scored in mismatch repair proficient (mut ⁺) and deficient (mutHLS^-) strains. In mut ⁺ cells, reduction of GATC sites from 2 to 0 increased mutation rates approximately 10-fold. Removal of the GATC site distal to the cat ^- mutation increased the rate of mutation less than 2-fold, indicating that mismatch repair can proceed normally with a single site. The mutation rate increased 3-fold after removal of the GATC site proximal to the mutation. In the absence of a GATC site, mutL^- and mutS^- strains exhibited a 2- to 3-fold increased mutation rate as compared to isogenic mutH^- and mut ⁺ strains. This indicates that 50%–70% of replication errors can be corrected in a mutLS-dependent way in the absence of any GATC site to target mismatch correction to newly synthesized DNA strands. Other strand targeting signals, possibly single strand discontinuities, might be used in mutLS-dependent repair     

The loci of perception for phytochrome control of internode growth in light-grown mustard: Promotion by low phytochrome photoequilibria in the internode is enhanced by blue light perceived by the leaves

Under continuous white light (WL), extension growth of the first internode in Sinapis alba L. was promoted by low red (R): far-red (FR) ratios reaching the stem and-or the leaves. Conversely, the growth promotion by end-of-day light treatments was only triggered by FR perceived by the leaves and cotyledons, while FR given to the growning internode alone was tatally ineffective. Continuous WL+FR given to the internode was also in-effective if the rest of the shoot remained in darkness. Both the background stem growth, and the growth promotion caused by either an end-of-day FR pulse or continuous WL+FR given to the internode, increased with increasing fluence rates of WL given to the rest of the shoot. The increase by WL of the growth-stimulatory effect of low phytochrome photoequilibria in the internode appears to be mediated by a specific blue-light-absorbing photoreceptor, as blue-deficient light from sodium-discharge lamps, or from filtered fluorescent tubes, promoted background stem growth similarly to WL but did not amplify the response to the R:FR ratio in the internode. Supplementing the blue-deficient light (94 mol·m^-2·s^-1) with low fluence rates of blue (<9 mol·m^-2·s^-1) restored the promotive effect of low R:FR reaching the internode.Abbreviations BL blue light - FR far-red light - PAR photosynthetically active radiation - Pfr/P ratio between the FR-absorbing form and total phytochrome - R red light - SOX low-pressure sodium lamp - WL white light Supported by the Consejo Nacional de Investigaciones Cientificas y Técnicas (República Argentina) and the ORS scheme (UK)     

Importance of communal foraging grounds outside the reed marsh for breeding great reed warblers

Foraging habitat selection of breeding great reed warblers was studied at a shore of Lake Biwa. The foraging grounds of parent warblers during the nesting period were not restricted to the breeding territory of the reed marsh, their nestling habitat. The paddy field outside the reed marsh was used communally by them throughout the breeding season. Females with early stage nestlings did not visit the paddy field whereas when nestlings were older than 3 days, more than half of their total food was collected there. Females with nests adjacent to the paddy field tended to exploit the paddy field more often than those with nests distant from it. Monogamously mated females tended to exploit the paddy field more often than polygynously mated females. Food collected in the paddy field was larger than that in the reed marsh and parent birds were prepared to travel longer distances to exploit the rich source of food in the paddy field. The importance of the communal foraging ground outside the reed marsh as a background of the polygynous mating system of this species is discussed.     

Inhibited growth of common enteropathogenic bacteria in lactic-fermented cereal gruels

A natural lactic fermentation of mixtures of water and whole flour of either maize or high-tannin sorghum was obtained either before or after cooking to a weaning gruel: The preparations had a final pH of about 3.8 (range 3.67 to 4.00) and a ratio of lactic acid to acetic acid of 91 (w/w). The growth of added (about 10⁷ c.f.u./g gruel) Gram-negative intestinal pathogenic bacteria, enterotoxigenicEscherichia coli, Campylobacter jejuni, Shigella flexneri andSalmonella typhimurium, was strongly inhibited in the sour gruels, and the effect could primarily be explained by the low pH caused by the formation of lactic and acetic acids during the fermentation process. Of the added Gram-positive bacteria,Bacillus cereus andStaphylococcus aureus showed similar inhibited growth up to 7h after inoculation in the sour gruels. The strain ofStaphylococcus, however, showed only a continued reduction in growth in the fermented gruel samples, which had a viable lactic bacteria culture indicating the presence of a bacteriocin. This implies that a low pH (< 4.0) alone is not sufficient to sustain the inhibition of the growth ofStaphylococcus aureus. The survival studies were carried out at optimal temperatures for each respective enteropathogen.