Effects of stocking density and food density on survival,growth and yield of laboratory-reared larvae of sea bream Archosargus rhomboidalis (L.) (Sparidae)*

Growth and survival of sea bream, Archosargus rhomboidalis (L.) larvae were affected by both abundance of eggs that were initially stocked in 75 1 rearing systems and by the concentration of copepod nauplii and copepodites that were fed to larvae. Stocking levels were 2, 4, 8,16 or 32 per litre while food abundance was maintained at approximately 100, 500, 1500 or 3000 per litre. Experiments were of 16 days duration at 26° C. Survival was best, often exceeding 60%, when food levels were 1500 or 3000 per litre and when stocking density did not exceed 8 eggs per litre. Growth was best at the lowest stocking densities and highest food levels. The highest total yields in wet weight occurred at 8 per litre stock density and 3000 per litre food level. Mean wet weight per survivor and yield per stocked egg were greatest at the lowest stocking densities and highest food levels. A 500 per litre food level was marginal for growth and survival, and 100 per litre produced significant survival only at the 2 per litre stocking density. Two experiments at 6000 and 10 000 per litre food levels at 4 per litre stock density gave the best observed growth, and survival as good as in any other experiments. Possible relations between sea bream larvae and their food supply in the natural environment are discussed. Results also are discussed in terms of their possible contribution to aquaculture efforts.     

High rate anaerobic digestion of piggery manure with polyurethane sponges as support material

Summary The use of polyurethane foam sponges to colonize methanogenic associations for the digestion of piggery manure has been investigated. Fermentors containing polyurethane pads as colonization matrix reached a biogas production rate of ca. 2.0 litres per litre reactor per day (30–33°C), hydraulic retention time 7.5 daysl and a biogas yield of 16 litres per litre piggery manure (7–9% TS). Corresponding control fermentors containing no pads reached a gas production rate of 1.3 litres per litre reactor per day and only about 10 litres biogas per litre piggery manure.     

Most probable number methodology for quantifying dilute concentrations and fluxes of Escherichia coli O157:H7 in surface waters

Aims:  To better understand the transport and enumeration of dilute densities of Escherichia coli O157:H7 in agricultural watersheds, we developed a culture-based, five tube-multiple dilution most probable number (MPN) method.
Methods and Results:  The MPN method combined a filtration technique for large volumes of surface water with standard selective media, biochemical and immunological tests, and a TaqMan confirmation step. This method determined E. coli O157:H7 concentrations as low as 0·1 MPN per litre, with a 95% confidence level of 0·01–0·7 MPN per litre. Escherichia coli O157:H7 densities ranged from not detectable to 9 MPN per litre for pond inflow, from not detectable to 0·9 MPN per litre for pond outflow and from not detectable to 8·3 MPN per litre for within pond. The MPN methodology was extended to mass flux determinations. Fluxes of E. coli O157:H7 ranged from <27 to >10⁴ MPN per hour.
Conclusion:  This culture-based method can detect small numbers of viable/culturable E. coli O157:H7 in surface waters of watersheds containing animal agriculture and wildlife.
Significance and Impact of the Study:  This MPN method will improve our understanding of the transport and fate of E. coli O157:H7 in agricultural watersheds, and can be the basis of collections of environmental E. coli O157:H7.     

Effect of Penicillamine in Promoting Lead Excretion

A spectrochemical study of the urine and blood of 14 subjects exposed to lead in their work for several years, but without obvious signs of intoxication, was carried out to determine the porphyrin and lead content before and after a provocative dose of 0.9 g. penicillamine, administered on a single day.The average total urinary porphyrin excretion before administration of penicillamine was 0.506 mg. per litre (normal value = 0.274), and after penicillamine administration 0.386 mg. per litre (normal value = 0.274). The average lead excretion before administration of penicillamine was less than 0.013 mg. per litre (normal value = 0.031) and after administration of penicillamine 0.367 mg. per litre (normal value = 0.047).The average erythrocyte porphyrin content was 76.8 μg. % before and 76.95 μg. % after administration of penicillamine—values approximately thrice normal. Blood lead content before administration of penicillamine averaged 7.61 μg. % and after penicillamine 5.68 μg. %.Lead excretion in exposed persons before penicillamine administration was less than in apparently normal persons, while porphyrin levels were higher. The effect of penicillamine is shown by a definite increase in lead excretion (average = 0.406 mg. lead per gram penicillamine administered) and a decrease in porphyrin excretion in the 14 subjects.     

Toxicity of a mixture of polychlorinated organic compounds towards an unacclimated methanogenic consortium

Summary The toxicity of a mixture of polychlorinated aliphatic compounds towards an unacclimated methanogenic consortium was assayed in carrier-free, continuously-stirred batch experiments. Results obtained indicate that a 50 % inhibition of methanogenesis occurs at 3.3 mg toxic mixture per litre mixed liquor and that at 100 mg toxic mixture per litre mixed liquor, the inhibition of methanogenesis is complete.     

Comparative inhibition ofAcetobacterium wieringae by two non-ionic surfactants: Tween 20 and ATPlus 258

Summary The effect of two non-ionic surfactants, Tween 20 and ATPlus 258 was assayed on the growth ofAcetobacterium wieringae on fructose. Both surfactants proved to inhibit the growth ofA. wieringae, already at 100 mg per litre. At 1000 mg per litre, the growth ofA. wieringae was inhibited by 41% by Tween 20 and completely by ATPlus 258. The production of the fermentation end-metabolite, acetic acid, followed the same inhibition pattern.     

Comparative study of reactor performance for the resolution of d,l-amino acids

The racemic resolution of l-valine and l-serine by fungal aminoacylase has been evaluated by comparing the performance of various reactor configurations including an anion exchange nylon tangential flow membrane reactor, a tubular reactor with aminoacylase adsorbed onto DEAE-Sephadex as support and a continuous stirred tank reactor with enzyme recycling using a flat ultrafiltration module (CSTR/UF). Among the substrates tested, the N-chloroacetyl-d,l-amino acids were the preferred substrates, showing the highest catalytic efficiency (V_m/K_m).Optimum reactor operational conditions obtained in discontinuous assays were selected to study the behaviour of the reactors in a continuous mode. DEAE-Sephadex loaded six-fold more enzyme than anion exchange nylon (60 and 10 gE/litre, respectively, related to reactor volume), whereas enzyme concentration within the CSTR/UF reactor was limited only by enzyme solubility.The tangential flow membrane reactor configuration with a 10 g/litre enzyme concentration produced higher productivity values (0·35 kg l-valine/litre per day, and 80% conversion degree) and operational stability (t = 161 days) than the CSTR/UF reactor (0·24 kg l-valine/litre per day, and 80% conversion degree) performing with the same enzyme concentration. The tubular reactor with the enzyme adsorbed onto DEAE-Sephadex (60 g/litre enzyme load) showed higher productivity values (1·9 kg l-valine/litre per day, and 80% conversion degree) and operational stability (t = 70 days) than the CSTR/UF reactor (1·05 kg l-valine/litre per day, and 80% conversion degree). However, the CSTR/UF reactor was the preferred configuration, as it had the highest enzyme load and productivity (1·95 kg l-valine/litre per day of reactor volume, and 80% conversion degree), a half-life of 55 days at 50°C, and the possibility of easy continuous enzyme addition.     

Growth and spore formation in Bacillus thuringiensis at high substrate concentrations

The work was aimed at studying the effect exerted by elevated concentrations of glucose, yeast extract and acetate on the growth of Bacillus thuringiensis subsp. galleriae, strain 69-6, and on the formation of spores and crystals by it. Glucose concentrations from 30 to 100 g per litre did not prevent spore formation. Yeast extract inhibited spore formation to a greater extent and stopped it almost completely at a concentration of 20 g per litre. Acetate at a concentration of 1.0 to 10 g per litre delayed spore formation and produced a less action on crystal formation, so that those processes were uncoupled in time.     

Anaerobic treatment of baker's yeast wastewater: I. Start-up and sodium molybdate addition

The anaerobic treatment of baker's yeast wastewater was studied using an anaerobic biological contact reactor (AnRBC) and a fixed-film reactor. The AnRBC had an active biomass developed within the reactor before this study commenced; however, the fixed-film reactor was started without attached biomass in a support structure. The gas production rates obtained for the AnRBC were between 0·55 and 0·61 litre methane per litre reactor per day. However, a gas production rate of only 0·46 litre methane per litre reactor per day was achieved after a four-month operating period for the fixed-film reactor. Higher chemical oxygen demand reduction was also found in the AnRBC. The results indicated that the presence of high sulfate concentration in baker's yeast wastewater affected teh start-up process. The reactor with fully developed active biomass was less susceptible to sulfate inhibition and showed improved anaerobic digestion. Results indicate that the reactor should be innoculated by feeding nutrient-balanced substrate before it was subjected to the digestion of baker's yeast wastewater. The fixed-film reactor was also fed with the substrate contianing sodium molybdate, an inhibitor of sulfate-reducing bacteria. The results indicated that both methanogenic and sulfate-reducing bacteria were inhibited.     

Ouabain-insensitive net sodium influx in erythrocytes of normotensive and essential hypertensive humans

The Na+ content of erythrocytes is elevated in people with essential hypertension. There is conflicting evidence about its cause. The present study was designed to investigate whether the increase in content is due to a defect in a ouabain-resistant Na+ flux. Net Na+ influx was determined from the increase in Na+ content of erythrocytes during incubation in the presence of ouabain. Na+ content of erythrocytes from 24 normotensive Caucasian subjects with no known family history of hypertension was 6.9 +/- 1.3 mmol per litre of cells. It was 7.9 +/- 2.0 mmol per litre of cells in 18 subjects with essential hypertension. The difference was less and not significant when the two non-Caucasian subjects of the hypertensive group were excluded. Net Na+ influx was 1.83 mmol/h per litre of cells in the normotensive group. In eight subjects it was measured on a second occasion after an interval of several months. The coefficient of a variation of the duplicate tests was 2.4%. Net Na+ influx was significantly higher in the hypertensive group, the value was 2.18 +/- 0.15 mmol/h per litre of cells. In 11 of these subjects, Na+ influx was measured on a second occasion. The coefficient of variation was 6.2%, significantly greater than in the control group. In some of these subjects Na+ influx was within the normal range on one of the two occasions. When the groups were compared with use of the mean values from the duplicate tests, net Na+ influx was elevated in 17 of the 18 hypertensive subjects. The findings are discussed with reference to previous work and in relation to the established facilitatory effects of an increased intracellular Na+ concentration on excitable cells that influence blood pressure.     

Characteristic Stimulation by Ethylene of Respiration in Dutch Iris Bulbs

The low steady-state basic respiration of iris bulbs (Iris bollandica cv.‘Wedgwood') at 30°C can be enhanced by ethylene. When ethylene is administered continuously a lag period of 4 hours is followed by an increase in the rate of respiration showing two peaks, one after 24 hours and the other after 3 to 4 days. Thereafter, the respiration rate decreases gradually, notwithstanding the presence of ethylene. Concentrations of less than 0.05 microlitre ethylene per litre have no effect, and the maximum effect is observed at concentrations of 3 microlitre per litre and higher. Between 0.2 and 2 microlitre ethylene per litre the peak values of the first maximum are linearly proportional to the logarithm of the ethylene concentration applied. The characteristics of the respiratory response in iris bulbs are probably similar to those described for potato tubers and non-climacteric fruits.     

Implantation of an ultrasonic indicator into the pudendal artery to study the blood flow volume in the cow mammary gland

The cow mammary gland blood flow was found to equal 601.8 litres per a litre of milk at a daily yield 5 litres, whereas at a decreased daily yield (3.7 l/day) the blood flow was equal 452 litres per every litre of milk.     

Human tissue-type plasminogen activator. Production in continuous serum-free cell culture and rapid purification.

A simplified procedure for the production and purification of human tissue-type plasminogen activator (t-PA) is described. Bowes-melanoma cells were maintained in continuous serum-free culture. The cell nutrient consisted of Dulbecco's modified Eagle's medium (DMEM) supplemented with insulin (5 mg/litre), transferrin (5 mg/litre), progesterone (1 nM), cortisol (10 nM), aprotinin (2 X 10(4) units/litre) and a mixture of trace elements. t-PA accumulated in the culture medium at a rate of 40 units/day per ml and was harvested every third day. Cell losses during each harvest, leading to a steady decline of enzyme yields, were compensated for by treating the cells with 5% (v/v) fetal-bovine serum in DMEM every 6-8 weeks. t-PA was rapidly purified by a combination of cation-exchange chromatography and gel filtration. The procedure yielded mainly single-chain t-PA of a specific activity of 80 000 to 100 000 units/mg.     

Wastewater reuse in agriculture and the risk of intestinal nematode infection

The increasing use of wastewater for crop irrigation in arid and semi-arid zones means that wastewater parasitology is becoming on important research area. The World Health Organization's (WHO) current guideline states that only treated wastewater containing no more than one human intestinal nematode egg per litre should be used for irrigation. This guideline was based on very limited epidemiological evidence. In this article Rachel Ayres, Rebecca Stott, Duncan Mara and Donald Lee describe their recent work in Yorkshire and northeast Brazil and suggest that their results may be the first evidence for relaxing the WHO guideline for restricted irrigation to no more than ten intestinal nematode eggs per litre.     

Isolation and characterisation of catechol-like siderophore from cowpea Rhizobium RA-1

Cowpea Rhizobium RA-1 produced a catechol-like siderophore. Secondary hydroxamic acids were not detected. Bioassay of the siderophore exhibited a distinct zone of growth of cowpea rhizobia. One litre of culture filtrate gave 6.2 mg of catechol-like siderophore. Glycine and threonine were detected in the siderophore. Maximum production of siderophore was found at 36 h of growth of cowpea Rhizobium RA-1.Abbreviations 2,3-DHBA 2,3-dihydroxy benzoic acid - EDTA ethylenediamine tetraacetic acid     

A radioimmunoassay for duck serum ferritin

Development and optimization of a radioimmunoassay for duck serum ferritin described. 125I-labelled ferritin and rabbit anti-ferritin antibody are used together with goat anti-rabbit gamma globulin as separating agent for the bound and free fractions. The assay has a working range of up to 500 micrograms of ferritin per litre and a sample requirement of 50 microliter of serum. The assay requires a 24 h period and has a sensitivity of 10 micrograms of ferritin per litre.     

The effect of medium composition on the production of valine byCorynebacterium 9366-EMS/184

The auxotrophic mutantCorynebacterium 9366-EMS/184, requiring isoleuoine accumulates about 22 g of L-valine per litre after a 96 h cultivation in a medium containing 15% sucrose and 1% ammonium acetate.     

以浮游植物评价达赉湖水质污染及营养水平

1987—1988年在30个样点,四季采样,对达赉湖的浮游植物进行了种类组成,生物量、种群数量、优势种、污染指示种、硅藻指数、综合指数等群落生态学的初步研究,应用后五项参数对达赉湖水质污染及营养水平进行了评价。达赉湖浮游植物年均值达54.7×106个/L(细胞数,或个体数为2.3×106个/L),硅藻指数为149.3,综合指数为5.6。群落组成中污染指示种占65%,春季以绿藻的十字藻、卵囊藻为优势种,其它3个季节均以蓝藻中的微囊藻、鱼腥藻、腔球藻占优势,表明达赉湖已受到中等程度污染,属于蓝、绿藻型富营养湖。       

Formation ofdl-Alanine byCorynebacterium sp. 9366-EMS/270

After a 4-d cultivation in a medium containing 7.5% glucose, 0.6% ammonium nitrate and 0.5% peptone, the leaky mutant Corynebacterium sp. 9366-EMS/270 stimulated in its growth by arginine, was found to accumulate 12.2 g DL-alanine per litre medium.     

Temperature-induced production of recombinant human insulin in high-cell density cultures of recombinant Escherichia coli

The construction of expression vectors encoding either the human insulin A- or B-chains fused to a synthetic peptide and the temperature-induced expression of the recombinant genes in Escherichia coli are reported. Using this two-chain approach we also describe the separate isolation of the insulin A- and B-chains from inclusion bodies and their subsequent assembly into native human insulin. The production of the insulin fusion proteins were carried out in high-cell density fed-batch cultures using a synthetic medium with glucose as sole carbon and energy source. The expression of the recombinant genes by temperature-shift in high-cell density cultures of recombinant E. coli resulted in product yields of grams per litre of culture broth, e.g. 4.5 g of insulin B-chain fusion protein per litre of culture broth. This translates into an expression yield of about 800 mg of the insulin B-chain per litre of culture. Under similar cultivation conditions the expression yield of the insulin A-chain corresponds to approximately 600 mg per litre of culture. The metabolic burden imposed on the recombinant cells during temperature-induced production of insulin fusion proteins in high-cell density cultures is reflected in an increased respiratory activity and a reduction of the biomass yield coefficient with respect to glucose.