Production of molecular hydrogen with immobilized cells ofRhodospirillum rubrum

Summary Cells ofRhodospirillum rubrum have been immobilized in various gels and tested for photobiological hydrogen production. Agar proved to be the best immobilizing agent with respect to production rates as well as stability. Agar immobilized cells were also superior compared to liquid suspension cultures. Growth conditions of the cells prior to immobilization, e.g. cell age, light intensity or nutrient composition, were of primary importance for the activity in the later immobilized state. A reactor with agar immobilized cells has been operated successfully over 3000 h with a loss of the activity of about 60%. Mean rates for hydrogen production for immobilized cells in this work during the first 60 to 70 hours after immobilization were in the range of 18 to 34 μl H₂ mg⁻¹ d.w. h⁻¹ and thus by a factor of up to 2 higher than liquid cultures under the same conditions. Maximal rates of hydrogen production (57 μl H₂ ml⁻¹ immobilized cell suspension) were reached in agar gel beads with cells immobilized after 70 h growth in liquid culture in the light and a cell density of 1.0 mg ml⁻¹, 70 h after immobilization.     

Metabolic,physiological and kinetic aspects of the alcoholic fermentation of whey permeate by Kluyveromyces fragilis NRRL 665 and Kluyveromyces lactis NCYC 571

Optimum growth conditions for the fermentation of non-concentrated whey permeate by Kluyveromyces fragilis NRRL 665 have been defined. Use of 3.75 g yeast extract l^?1, a growth temperature of 38°C and a pH of 4.0 allowed a maximum productivity of 5.23 g ethanol l^?1 h^?1 in continuous culture with a yield 91% of theoretical. Complete batch fermentation of permeate with 100 g lactose l^?1 was possible with a maximum specific growth rate of 0.276 h^?1 without any change in ethanol yield. Fermentation of concentrated permeate resulted, however, in a general decrease of specific substrate consumption rate, demonstrated by the inability to completely convert an initial 90 or 150 g lactose l^?1 in continuous culture, even at dilution rates as low as 0.05 and 0.08 h^?1, respectively. The decrease could be related to substrate inhibition, to an increase in osmotic pressure caused by lactose and salts, and to ethanol inhibition of both alcohol and biomass yield. The decrease in specific productivity could be counterbalanced by use of high cell density cultures, obtained by cell recycle of K. fragilis. Fermentation of a non-concentrated permeáte at a dilution rate of 1 h^?1 resulted in a productivity of 22 g l^?1 h^?1 at 22 g ethanol l^?1. Cell recycle using flocculating Kluyveromyces lactis NCYC 571 was also tested. With this strain a productivity of 9.3 g l^?1 h^?1 at 45 g product l^?1 was attained at a dilution rate of 0.2 h^?1, with an initial lactose concentration of 95 g l^?1.     

Myocardial S-adenosylhomocysteine hydrolase is important for adenosine production during normoxia

(1) The coronary vasodilator adenosine can be formed in the heart by breakdown of AMP or S-adenosylhomocysteine (SAdoHcy). The purpose of this study was to get insight into the relative importance of these routes of adenosine formation in both the normoxic and the ischemic heart. (2) A novel HPLC method was used to determine myocardial adenosine and SAdoHcy. Accumulation of SAdoHcy was induced in isolated rat hearts by perfusion with L-homocysteine thiolactone or L-homocysteine. The release of adenosine, inosine, hypoxanthine, xanthine and uric acid was determined. Additional in vitro experiments were performed to determine the kinteic parameters of S-adenosylhomocysteine hydrolase. (3) During normoxia the thiolactone caused a concentration-dependent increase in SAdoHcy. At 2000 μM of the thiolactone an SAdoHcy accumulation of 0.49 nmol/min per g wet weight was found during normoxia. L-Homocysteine (200 μM) caused an increased of 0.37 and 4.17 nmol SAdony/soc per g wet weight during normaxia and ischemia, respectively. (4) The adenosine concentration in ischemic hearts was significantly lower when homocysteine was infused (6.2 vs. 115 nmol/g; P < 0.05). Purine release was increased 4-fold during ischemia. (5) The K_m for hydrolysis of SAdoHcy was about 12 μM. At in vitro conditions favoring near-maximal SAdoHcy synthesis (72 μM adenosine, 1.8 mM homocysteine), the synthesis rate in homogenates was 10 nmol/min per g wet weight. (6) From the combined in vitro and perfusion studies, we comclude that S-adenosylhomocysteine hydrolase can contribute significantly to adenosine production in normoxic rat heart, but not during ischemia.     

Saccharin induces morphological changes and enhances prolactin production in GH4C1 cells

Summary The artificial sweetener saccharin inhibits binding of epidermal growth factor (EGF) to cultured rat pituitary tumor cells (GH₄C₁ cells). Saccharin also causes morphological alterations in these cells, resulting in pronounced elongation, stretching, and firmer attachment of cells to the culture dishes. These alterations in cell shape are similar to those observed after treatment of GH₄C₁ cells with EGF and with thyrotropin-releasing hormone (TRH), both of which enhance prolactin (PRL) production in these cells. After assaying for PRL in saccharin-treated cultures, it was observed that this sweetener is also capable of stimulating PRL production two-to sixfold in a dose-dependent manner. Enhancement of PRL production can be observed at 0.5 mM saccharin, yet this is 10 times less than the saccharin concentration required to alter cell shape. These effects of saccharin on cell morphology and on PRL production are reversible in GH₄C₁ cell cultures. When added to cultures along with maximal concentrations of EGF or TRH, the effects of saccharin on PRL production are additive, suggesting that the actions of saccharin are mediated by a somewhat different pathway from that of the peptide hormones. Pulse labeling studies indicate that the enhancement of PRL production is highly specific inasmuch as saccharin was found to decrease the overall rate of protein synthesis in these cells. Saccharin also causes a decrease in the rate of DNA synthesis under these treatment conditions. Mitomycin C, which similarly inhibited DNA synthesis, had no effect on cell morphology or PRL production. This investigation was supported by a Faculty Research Grant from Wheaton College     

Nutrient addition experiments in Lago Jacaretinga,Central Amazon,Brazil: 2. The effect of humic and fulvic acids

Enrichment experiments consisting of additions of nutrients (nitrogen and phosphorus) and humic and fulvic acids were carried out using natural phytoplankton assemblages from Lago Jacaretinga, Central Amazon, Brazil. The addition of nutrients resulted in greatly stimulated primary production whereas addition of humic and fulvic acids had no effect. When both nutrients and humic and fulvic acids were added in combination, algal community response was identical to treatments in which only nutrients had been added. The result contrasts with previous phytoplankton culture studies in which the addition of humic material to the culture media increased production. Comparison of absorbance spectra indicated a severe reduction in the quantity and quality of light in Amazonian black waters relative to that in white waters.     

Foraminifera and meiofauna on an intertidal mudflat,Cornwall, England: Populations; respiration and secondary production; and energy budget

A rich and varied meiofauna inhabits a Cornish mudflat near the mouth of the Tamar River in southwestern England. Population densities range from 117 to 943 individuals · g^–1 (wet) sediment (1.4–11.4 × 10⁶ individuals · m^–2), with foraminifera, harpacticoid copepods and nematodes appearing in nearly equal numbers and comprising most of the meiofauna. Seasonally, meiofaunal numbers rise and fall with solar radiation and vary inversely with river discharge. Two species, the atestate allogromiid A and the calcareous Haynesina germanica (Ehrenberg), far outnumber other foraminifera; their population densities and growth rates reach maxima in spring and summer.Monthly rates of sediment respiration are locally variable, but clearly increase from winter (4.13 ml O₂ · m^–2 · h^–1 in December) to spring (38.87 ml O₂ · m^–2 · h^–1 in April). Experiments and calculations ascribe approximately 30% of this total to the meiofauna (including microfauna and microflora), 50% to bacteria and less than 20% to chemical oxidation. A tentative energy budget for the mudflat suggests that secondary production by meiofauna is small as compared with coastal environments elsewhere, and that meiofaunal production (426 Kcal · m^–2 · y^–1) is nearly twice meiofaunal respiration (252 Kcal · m^–2 · yr^–1).     

Biomass and production of Argyrodiaptomus furcatus,a tropical calanoid copepod in Broa Reservoir,southern Brazil

The biomass and the production of Argyrodiaptomus furcatus (Sars), the most abundant copepod in Broa Reservoir (São Carlos, São Paulo State), were estimated, determining in the laboratory the development time and the quantity of organic carbon and establishing the relationship between these two parameters. The daily production was calculated from P = B(1- e^gt) and the annual production was obtained by integrating daily production against time. The maximum production of Argyrodiaptomus furcatus in the reservoir depends on the region considered and on the period of the year. The maximum production was 45.15 mg C m^–3d^–1 in March, 1976 at station II, region of macrophytes and 6.74 mg C m^–3d^–1 at station IV, near the dam. The mean production for the year is 6.26 mg C m^–3d^–1 at station II and 1.43 mg C m^–3d^–1 at station IV.     

14C-Metabolism in cultured cotyledon explants of radiata pine

Excised cotyledons of radiata pine ( Pinus radiata D. Don), cultured under shootforming (plus cytokinin) and elongating (minus cytokinin) conditions, were incubated in ¹⁴C-glucose, ¹⁴C-acetate or ¹⁴C-bicarbonate at different stages of growth and differentiation. ¹⁴CO₂ was produced when the cotyledons were fed ¹⁴C-glucose and ¹⁴C-acetate (no measurement was made for ¹⁴C-bicarbonate feeding). Label from these precursors was incorporated into ethanol-soluble and -insoluble fractions. The largest percentage of radioactivity was associated with the ethanol-soluble portion, which was further fractionated into lipids, amino acids, organic acids and sugars. The amount of label and the pattern of labelling associated with each of the above classes of metabolites varied with time in culture and morphogenetic behaviour of the cotyledons. In general, there was a tendency towards a high rate of incorporation of label in elongating cotyledons during the period of rapid elongation. On the other hand, a high rate of incorporation of label in shoot-forming cotyledons coincided with the period of meristematic tissue formation. The data obtained support the hypothesis that organized development in vitro involves a shift in metabolism, which precedes and is coincident with the initiation of the process.