Oxygen consumption and energy metabolism of the early mouse embryo

Oxygen consumption of preimplantation and early postimplantation mouse embryos has been measured using a novel noninvasive ultramicrofluorescence technique, based on an oil-soluble, nontoxic quaternary benzoid compound pyrene, whose fluorescence is quenched in the presence of oxygen. Pyruvate and glucose consumption, lactate production, and glycogen formation from glucose were also measured. Preimplantation mouse embryos of the strain CBA/Ca × C57BL/6 were cultured in groups of 10–30 in 2 μl of modified M2 medium containing 1 mmol l⁻¹ glucose, 0 mmol l⁻¹ lactate, and 0.33 mmol l⁻¹ pyruvate, for between 4–6 hr. Day 6.5 and 7.5 embryos were cultured singly in 40 μl M2 medium for between 2–3 hr. Oxygen consumption was detected at all stages of development, including, for the first time, in the early postimplantation embryo. Consumption remained relatively constant from zygote to morula stages before increasing in the blastocyst and day 6.5–7.5 stages. When expressed as QO₂ (μl/mg dry weight/hr), oxygen consumption was relatively constant from the one-cell to morula stages before increasing sharply at the blastocyst stage and declining to preblastocyst levels on days 6.5 and 7.5. Pyruvate was consumed during preimplantation stages, with glucose uptake undetectable until the blastocyst stage. Glucose was the main substrate consumed by the 6.5 and 7.5 day embryo. The proportions of glucose accounted for by lactate appearance were 81%, 86%, and 119% at blastocyst, day 6.5, and day 7.5 stages, respectively. The equivalent figures for glucose incorporated into glycogen were 10.36%, 0.21%, and 0.19%, respectively. The data are consistent with a switch from a metabolism dependent on aerobic respiration during early preimplantation stages to one dependent on both oxidative phosphorylation and aerobic glycolysis at the blastocyst stage, a pattern which is maintained on days 6.5 and 7.5. Our technique for measuring oxygen consumption may have diagnostic potential for selecting viable embryos for transfer following assisted conception techniques in man and domestic animals. © 1996 Wiley-Liss, Inc.     

Mango powdery mildew Oidium mangiferae an alternative food for the predatory mites Typhlodromus mangiferus and Typhlodromips swirskii (Phytoseiidae) in absence or presence increasing prey density of Oligonichus mangiferus (Tetranychidae) in Egypt

The predacious mites, Typhlodromus mangiferus Zaher and El-Borolossy and Typhlodromips swirskii (Athias-Henriot), reproduced successfully on mango powdery mildew Oidium mangiferae Berthet in absence or presence of spider mite prey Oligonichus mangiferus (Rahman and Sapra) under laboratory conditions of 25 ± 1°C and 60–65% R.H. Adult female of both predators consumed protonymphs of O. mangiferus at different experimental densities. The consumption rate increased with increasing prey densities up to 25 protonymphs/female/day and decreased significantly at 35 and 50 protonymphs/female/day for the two predatory mites. Addition of powdery mildew conidia to each prey density significantly reduced consumption of spider mites at 35 and 50 protonymphs/female/day. Mean eggs/female/day by T. swirskii and T. mangiferus was 0.30 and 0.72 when reared on powdery mildew conidia compared with 1.64 and 1.57 when fed on powdery mildew and tetranychid prey, respectively. This increase in reproduction would have compensated the reduction in protonymph prey consumption due to the presence of mildew conidia. Mite–mildew interactions are discussed.     

Morphine release and displacement by naloxone in vivo in morphine naive and withdrawn rats

Male Long-Evans rats, implanted in the lateral cerebroventricle with chronic indwelling push-pull cannulae, were perfused (10 μl/min) for 120 min: 20 min with 1.5 × 10^?6M morphine in sterile isotonic saline containing 2.3 mM CaCl₂ (vehicle); 40 min with vehicle; 20 min with 1.5 × 10^?6M morphine; 10 min with vehicle and 30 min with 1 × 10^?6M naloxone in vehicle. These rats and drug-naive rats were implanted s.c. with 2 × 50 mg morphine pellets. After 72 hr the pellets were removed and 18–24 hr later the above perfusion procedure was repeated. The amount of morphine collected in the perfusate during the washout with naloxone was elevated, compared to the amount collected during the corresponding time of the washout with vehicle for both naive and withdrawn groups. The enhanced morphine release during the washout with naloxone did not differ significantly between the naive and withdrawn rats. However, significantly less morphine was recovered in the perfusate collected during the vehicle washout from the withdrawn rats, compared to that collected from the naive rats. The data suggest that $\text{in vivo}$ morphine is specifically bound to receptors and is sensitive to naloxone displacement. It is also concluded that morphine is differentially taken up or otherwise disposed of by brains of rats which are in opiate withdrawal.     

ENDOGENOUS LEVELS OF INDOLE-3-ACETIC ACID IN SYNCHRONOUS CULTURES OF CHLORELLA PYRENOIDOSA12

Endogenous levels of indole-3-acetic acid were mesaured in synchronous cultures of Chlorella pyrenoidosa (TX-7-11-05). The cultures were synchronized by alternating light:dark periods of 15:9 hr at a temperature of 40 ± 1 C. After 2 synchronous cycles the cultures were exposed to a low light treatment of 350 ± 100 ft-c. The time to incipient cell division under these conditions was 6 hr and 15 min. Samples were taken at 3 sampling periods during the low light treatment period:low light 0 hr (LL0); low light 3 hr (LL3); and low light 6:15 hr (LL6:15). The algal extracts were analyzed by a fluorometric procedure which measured the indole-α-pyrone product formed by the action of the trifluoracetic acid-acetic anhydride reagent with IAA. The IAA levels increased gradually from the autospore stage (5.19 μg × 10^?4/mg dry wt) to the adolescent stage (7.13 μg × 10^?4/mg dry wt) and more rapidly when approaching the ripened adult stage (14.55 μg × 10^?4/mg dry wt). The mean percentage increase from autospore to adolescent was 36.9%, and from adolescent to ripened adult 104.6%. The total percentage increase from autospore to adult was 180.3%. Levels of IAA were 2 times higher just prior to division than in the autospore stage.     

Replacement of media in cell culture alters oxygen toxicity: Possible role of lipid aldehydes and glutathione transferases in oxygen toxicity

Replacement of media in cell cultures during exposure to hyperoxia was found to alter oxygen toxicity. Following 100 hr of exposure to 95% or 80% O₂, the surviving fraction (SF) of Chinese hamster fibroblasts, as assayed by clonogenicity, was less than 1 × 10^?3 when the culture media was replaced only at the onset of the O₂ exposure. Media replacement every 24 hr throughout the hyperoxic exposure resulted in SFs of 1.7 × 10^?1 (95% O₂) and 1.9 × 10^?1 (80% O₂) at 95 hr. Cellular resistance to and metabolism of 4-hydroxy-2-nonenal (4HNE), a cytotoxic byproduct of lipid peroxidation, was examined in cells 24 hr following exposure to 80% O₂ for 144 hr with media replacement. These O₂-exposed cells were resistant to 4HNE, requiring 2.6 times as long in 80 μM 4HNE to reach 30% survival as compared to density-matched normoxia control. Furthermore, during 40 and 60 min of exposure to 4HNE, the O₂-preexposed cells metabolized greater quantities of 4HNE (fmole/cell) relative to control. The activity of glutathione S-transferase (GST), an enzyme believed to be involved with the detoxification of 4HNE, was significantly increased in the O₂-preexposed cells compared with controls. Catalase activity was significantly increased, but no change was found in total glutathione content, glutathione peroxidase, manganese superoxide dismutase, and copper-zinc superoxide dismutase activities at the time of 4HNE treatment in the O₂-preexposed cells relative to density-matched control. The results demonstrate that in vitro tolerance to the cytotoxic effects of hyperoxia can be achieved through media replacement during O₂ exposure. Tolerance to oxygen toxicity conferred resistance to the cytotoxic effects of 4HNE, possibly through GST-catalyzed detoxification. These results provide further support for the hypothesis that toxic aldehydic byproducts of lipid peroxidation contribute to hyperoxic injury.     

Functional organization and plasticity of the photosynthetic unit of the cyanobacterium Anacystis nidulans

Anacystis nidulans grown under high and low light, 100 and 10 μE m^?2 s^?1, respectively, was analyzed with respect to chlorophyll/P700, phycobiliproteins/P700, chlorophyll/cell, and oxygen evolution parameters. The photosynthetic unit sizes of this cyanobacterium, measured as the ratio of total chromophores (chlorophyll and bilin) to P700, were shown to be similar to those of higher plants and green algae. High light grown cells possessed a photosynthetic unit consisting of a core of 157 ± 6 chlorophyll a molecules per P700 associated with a light harvesting system of 95 ± 3.5 biliprotein chromophores. Low light grown cells had substantially more biliprotein chromophores per P700 (125 ± 3.1) than high light cells, but showed no significant difference in the numbers of chlorophyll a molecules per P700 (149 ± 4). Analyses of aqueous biliprotein extracts indicate that low light grown cells produce proportionately more phycocyanin relative to allophycocyanin than high light cells. Calculations of the molecular weight of biliproteins per P700 suggest that there is less than one phycobilisome per reaction center I under both growth conditions. Differences in chlorophyll/cell ratios and oxygen evolution characteristics were also observed. High light cells contain 6.3 × 10^?12 mg chlorophyll cell^?1, while low light grown cells contain 12.8 × 10^?12 mg chlorophyll cell^?1. Photosynthetic oxygen evolution rate vs. light intensity curves indicate that high light grown cells reach maximal levels of oxygen evolution at higher light intensity than low light grown cells. Maximal rates of oxygen evolution were 16.6 μmol oxygen min^?1 (mg chlorophyll)^?1 for high and 8.4 μmol oxygen min^?1 (mg chlorophyll)^?1 for low light cells. Maximal oxygen evolution rates per cell were equivalent for both cell types, although the amount of P700 per cell was lower in high light cells. High light grown cells are therefore capable of producing more oxygen per reaction center I than low light grown cells.     

Risk Assessment for Natural Uranium in Subsurface Water of Punjab State,India

Traces of uranium were measured by laser fluorimeter in 235 subsurface water samples collected from four districts of Punjab state in India. The concentration of U in water samples ranged between <2–644 μg/L with a mean value of 73.1 μg/L. The radiological risk was observed to be in the range of 5.55 × 10^?6–1.78 × 10^?3 with a mean value of 2.03 × 10^?4, which is around 22% more than the maximum acceptable level (l.67 × 10^?4) as per guidelines of India's Atomic Energy Regulatory Board. The mean of chemical toxicity risk, expressed as life time average daily dose (LADD) was worked out to be 5.56 μg/kg/day with a range of 0.15–48 μg/kg/day by considering a bodyweight of 51.5 ± 8.5 kg, water ingestion rate of 4.05 L/d, and life expectancy of 63.7 yrs for an adult Indian reference man and compared with the reference dose (4.53 μg/kg/day). The average exposure level of U was comparatively high and the chemical toxicity was expected to be more. The mean of hazard quotient (LADD/ RfD) for all four districts was found to be greater than 1, indicating that groundwater may not be suitable for consumption from a chemical toxicity point of view.     

Implications of Using Steady-State Conditions in Estimating Dermal Uptake of Volatile Compounds in Municipal Drinking Water: An Example of THMs

Dermal exposure to volatile compounds (VC) in municipal water while showering is typically estimated using a steady-state condition between VC in water impacting on skin and skin exposed to water. The lag times to achieve steady-state between VC and skin can vary in the range of 7.5–218.3 min, while shower duration is often less than these values. Estimates of dermal exposure to VC using steady-state while showering may misinterpret exposure. This study developed models and estimated exposure to some disinfection byproducts (DBPs) through dermal pathway by considering lag times while showering. Dermal uptakes of VC were compared using different approaches. In the proposed approach, uptakes of trihalomethanes were estimated between 9.55 × 10^?10–1.43 × 10^?8 mg/cm² of skin during the lag times from exposure to water with trihalomethanes of 50 μg/L. These values were higher than the steady-state estimates (1.37 × 10^?10–4.34 × 10^?9 mg/cm²), and lower than the average exposure analysis (4.12 × 10^-8–1.93 × 10^?6 mg/cm²). Using the Drinking Water Surveillance Program data in Ontario, chronic daily intakes of trihalomethanes were estimated to be 9.40 × 10^?7 (1.85 × 10^?7–1.65 × 10^?6), 3.89 × 10^?6 (7.11 × 10^?7–2.33 × 10^?5), and 1.40 × 10^?6 (4.0 × 10^?7–1.77 × 10^?6) mg/kg/day in Toronto, Ottawa, and Hamilton, respectively. The findings can be useful in understanding THMs exposure and risk through dermal pathway.     

Abnormality of 2-deoxyglucose uptake kinetics in fibroblasts at low concentrations

2-deoxyglucose uptake rates at low sugar concentrations (less than 500 μM) appeared to be lower than those predicted by the Michaelis-Menten model which correctly described higher concentrations. This phenomenon which we will call concentration-dependent transport lag, was also observed for L-glucose uptake which suggest that this phenomenon is carrier-independent. A model involving the perimembrane space is developed which, for L-glucose, gives k₁ = 0.931 ± 0.072 × 10^?6 l. mg protein^?1. minute^?1, k₂ = 2.97 ± 0.19 × 10^?7 l. mg protein^?1. minute^?1 and So = 88,8 ± 4,3 μM; where k₁ is the diffusion constant in the cell membrane, k₂ is the diffusion constant in the perimembrane space and S_o the sugar concentration required in the external medium in order to provide an équivalent sugar concentration in the transport carrier area.     

Effects and mechanisms of ghrelin on cardiac microvascular endothelial cells in rats

Ghrelin is thought to directly exert a protective effect on the cardiovascular system, specifically by promoting vascular endothelial cell function. Our study demonstrates the ability of ghrelin to promote rat CMEC (cardiac microvascular endothelial cell) proliferation, migration and NO (nitric oxide) secretion. CMECs were isolated from left ventricle of adult male Sprague—Dawley rat by enzyme digestion and maintained in endothelial cell medium. Dil‐ac‐LDL (1,1′‐dioctadecyl‐3,3,3′,3′‐ tetramethylindocarbocyanine‐labelled acetylated low‐density lipoprotein) intake assays were used to identify CMECs. Cells were split into five groups and treated with varying concentrations of ghrelin as follows: one control non‐treated group; three ghrelin dosage groups (1×10^?9, 1×10^?8, 1×10^?7 mol/l) and one ghrelin+PI3K inhibitor group (1×10^?7 mol/l ghrelin+20 μmol/l LY294002). After 24 h treatment, cell proliferation capability was measured by MTT [3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl‐2H‐tetrazolium bromide] assay and Western blot for PCNA (proliferating cell nuclear antigen) protein expression. Migration of CMECs was detected by transwell assays, and NO secretion of CMECs was measured via nitrate reduction. Protein expression of AKT and phosphorylated AKT in CMECs was measured by Western blot after exposure to various concentrations of ghrelin and the PI3K inhibitor LY294002. Our results indicate that ghrelin significantly enhanced cell growth at concentrations of 10^?8 mol/l (0.271±0.041 compared with 0.199±0.021, P=0.03) and 10^?7 mol/l (0.296±0.039 compared with 0.199±0.021, P<0.01). However, addition of the PI3K/AKT inhibitor LY294002 inhibited the ghrelin‐mediated enhancement in cell proliferation (0.227±0.042 compared with 0.199±0.021, P=0.15). At a concentration between 10^?8 and 10^?7 mol/l, ghrelin caused a significant increase in the number of migrated cells compared with the control group (126±9 compared with 98±7, P=0.02; 142±6 compared with 98±7, P<0.01), whereas no such change could be observed in the presence of 20 μmol/l of the PI3K/Akt inhibitor LY294002 (103±7 compared with 98±7, P=0.32). Ghrelin treatment significantly enhanced NO production in a dose‐dependent fashion compared with the untreated control group [(39.93±2.12) μmol/l compared with (30.27±2.71) μmol/l, P=0.02; (56.80±1.98) μmol/l compared with (30.27±2.71) μmol/l, P<0.01]. However, pretreatment with 20 μmol/l LY294002 inhibited the ghrelin‐stimulated increase in NO secretion [(28.97±1.64) μmol/l compared with (30.27±2.71) μmol/l, P=0.37]. In summary, we have found that ghrelin treatment promotes the proliferation, migration and NO secretion of CMECs through activation of PI3K/AKT signalling pathway.     

Production of microbial protein from tree bark by Phanerochaete chrysosporium

Phanerochaete chrysosporium was grown in fermentors on NaOH-extracted maple, pine, and cedar barks at the optimum substrate concentration of 1% (w/v). The yields (mg protein/liter) on maple, pine, and cedar were 1500, 1200, and 880, respectively, which are probably due to the different lignin contents of the barks. Lignin is not utilized. The productivities at 30°C obtained for pine (4.07 × 10^?2 g protein/liter hr) and cedar (2.63 × 10^?2 g protein/liter hr) barks were greater than for maple (2.63 × 10^?2 g protein/liter hr). The substrate (bark) was the limiting component of the fermentation. Over the 26–38°C temperature range protein productivity increased by a factor of three (1.55 × 10^?2 vs. 4.61 × 10^?2 g protein/liter hr) for maple bark. Low agitation rates resulted in an overproduction of cellulase and reduced levels of microbial protein.     

Isolation and respiratory measurements on a single large mitochondrion

Mitochondria ranging in size from 5–8 μm were produced by feeding Cuprizone to mice weaned at 17 days. A small piece of liver was disrupted and a single large mitochondrion isolated with a suction capillary and a micromanipulator and placed in a microchamber attached to a sensitive oxygen electrode. The mitochondrion showed a respiratory rate of 1.4 × 10^?10 μatoms 0/min and a respiratory ratio with and without ADP of 3.7 with succinate. The respiratory ratio is the same as that obtained with normal mitochondria measured in the same apparatus. The respiratory rate of a 7 μm mitochondrion is estimated to be 1.3 × 10^?4 μatoms 0/min/cm² of inner membrane surface area which is very similar to the rate of 0.7 × 10^?4 μatoms 0/min/cm² estimated for a normal mitochondrion.     

Performance study of perfusion cultures for the production of single-chain urokinase-type plasminogen activator (scu-PA) in a 2.5 l spin-filter bioreactor

A perfusion-control strategy based on cellular consumption rates of oxygen and glucose was established for the production of single-chain urokinase-type plasminogen activator (scu-PA). Employing this strategy, the influences of microcarrier types and the culture media on culture performances were evaluated. In the control perfusion culture, which used a solid microcarrier and a 1% fetal bovine serum (FBS) medium, viable cell density reached 3.1?×?10⁷?cells?ml^?1. However, formation of large, heterogeneous aggregates (500–1,000?μm) resulted in a gradual decrease in viable cell density to less than 1.0?×?10⁷?cells?ml^?1. Accordingly, declines in the production of urokinase-type plasminogen activator (u-PA) and in the scu-PA portion of u-PA were observed. In the serum-free media, cell growth and u-PA production were suppressed 2–3?times, but were significantly enhanced when a porous microcarrier, Cultispheer G, was used. The cell-growth profile showed a continuous increase in cell density, reaching 5.1?×?10⁷?cells?ml^?1, and the production of u-PA remained stable throughout the culture (1586?±?247?IU?ml^?1). The values of all the parameters associated with cell growth and u-PA production were fairly comparable to or even higher than those in the control culture. Moreover, a 13% higher scu-PA portion of u-PA was observed in the serum-free culture, regardless of the microcarrier type, compared with scu-PA portion of u-PA in the control culture.     

Ultramicroassay for plasma renin concentration in the rat using the antibody-trapping technique

Using the antibody-trapping technique, picogram quantities of angiotensin-I generated during 24 hr of incubation at 37°C were stable and fully protected against peptidases. The method employs purification of angiotensin-I antisera on DEAE-cellulose and purification of renin substrate by affinity chromatography using specific antirenin antibodies in order to remove endogenous renin. The assay was performed in a single tube without a transfer step in a total volume of 30 μl at pH 6,5 with incubation for 24 hr at 37°C. With a normal rat plasma renin concentration of 5 × 10^?4 GU ml^?1, the detection limit was 10 nl or a total of 5 × 10^?9 GU. In the range 20–125 nl, precision was ±10%.     

Electrogenerated chemiluminescence reaction of lucigenin with isatin at a platinum electrode

The electrogenerated chemiluminescence (ECL) reaction of lucigenin with isatin was investigated at a platinum electrode in a neutral aqueous solution. The ECL intensity of lucigenin at ?0.65 V was greatly enhanced by isatin, and the ECL intensity was about 50 times higher than that of lucigenin without isatin. The enhanced ECL was believed to be produced by the chemiluminescence reaction between reduced lucigenin and superoxide anion that was generated by the reaction of electrochemically reduced isatin with dissolved oxygen. The conditions for the determination of isatin were optimized. Under the optimized condition, the enhanced ECL intensity vs. isatin concentration was linear in the range 4.8 × 10^?7?1.9 × 10^?5 g/mL; with a detection limit of 3.3 × 10^?8 g/mL, and the relative standard derivation 1.0 × 10^?6 g/mL isatin was 3.8%. Copyright © 2004 John Wiley & Sons, Ltd.     

Respiration,energy balance and development during growth and starvation of Carcinus maenas L. larvae (Decapoda:Portunidae)

In all larval stages of Carcinus maenas L. oxygen consumption was measured at three temperatures (12,18,25 °C). Values increased during development and were in the range of 0.037 ± 0.01 (zoea-1, 12°C, $\text{x}\text{?}\text{± 95\% CL}$) to 0.734 ± 0.047 μl O₂ · h^?1 · ind^?1 (megalopa, 25 °C). Growing larvae showed temperature dependent trends in weight specific respiration rates (referred to dry wt; DW), with values between ≈2.4 and 9.4 μl O₂· h^?1·mg DW^?1. Increase in oxygen consumption of megalops did not differ much at temperatures between 18 and 25 °C. This points to an exceptional physiological position of this stage. Fed zoea-1 of C. maenas (18 °C) revealed growth rates in terms of 40% DW, 20% carbon (C), 30% nitrogen (N) and 65% hydrogen (H). At the same time larvae gained individual energy by 13% (J · ind^?1), while weight specific energy dropped by ≈ 19% (J · mg DW^?1) during the first day and remained constant until the moult. Starved zoea-1 of C. maenas (18 ° C) gained ≈ 20 % in DW through the first day, probably caused by inorganic salts which enter the organism after the moult of the prezoea. DW dropped to ≈ 25 % of initial value, when starvation continued. Single components decreased by ≈50% (C), 54% (N), 57% (J · ind^?1). Weight specific energy (J · mg DW^?1) decreased by 40% during the first 4 days of starvation, remaining constant thereafter. Individual respiration rate (R) dropped by 61 %, weight specific respiration rate (QO₂) by 55 %. Individual energy loss in starved zoea-1 was 0.077 J over a period of 11 days. In this period ≈ 9.3 μl O₂·ind^?1 were consumed. Thus effective oxygen capacity was lower than in growing larvae. It dropped to 5.3 J·mlO₂^?1 after 4 days and remained constant if starvation continued, i.e. 65 % of possible energy loss occurred during the first 4 days. Decrease in requirement for oxygen and its effective capacity were both recognized as independent components of survival during starvation. Partitioning of energy through individual larval development of C. maenas was investigated for all five larval stages. The cumulative budget could be calculated: consumption (C) = 28.23 J, growth (G) = 0.92 J, exoskeleton (Ex) = 0.20 J, metabolism (M) = 5.30 J, egestion and excretion (E) = 21.82 J. Mean gross and net growth efficiency were, K₁ = 3.3% and K₂ = 14.8%, respectively.     

Photobleaching recovery studies of membrane events accompanying lectin stimulation of rabbit lymphocytes.

Fluorescence photobleaching recovery methods reveal marked changes in lateral mobilities of rabbit lymphocyte membrane components during the course of stimulation with succinyl concanavalin A (S Con A). The diffusion constant of S Con A receptors on T lymphocytes falls from 1.6×10^?10 cm²/sec to 6.5×10^?11 cm²/sec within 4 hr after stimulation, remains constant for 14 hr, and returns to its former value. The mobility of B cell receptors similarly falls from 1.4×10^?10 cm²/sec to 5.5×10^?11 cm²/sec but regains its unstimulated value much more slowly. In contrast, a fluorescent phospholipid analog shows constant mobilities of 1.9×10^?8 cm²/sec and 1.5×10^?8 cm²/sec in T and B cells, respectively, throughout the experiment.     

Calorific values of Chlorella vulgaris (Trebouxiophyceae) as a function of different phosphorus concentrations

Quantification of the calorific content of microalgae is critical in studies of energy flow, trophic partitioning, plant/herbivore interactions in aquaculture and biomass production for biofuels. We investigated the calorific value and biochemical composition of Chlorella vulgaris at different phosphorus (P) concentrations (6.0 × 10^?7, 2.3 × 10^?6 and 2.3 × 10^?4 mol L^?1 P). As expected, the control (2.3 × 10^?4 mol L^?1 P) supported better growth than P limited treatments. Biomolecules like total carbohydrates and lipids accumulated under P limitation, which significantly correlated with high calorific values. Lipid class composition showed that triacylglycerols were the most accumulated under P limited conditions. The calorific value reported under control conditions (13.78 kJ g^?1) was less than those obtained under P limitation (30.47–33.07 kJ g^?1). The highest calorific value with less growth retardation was obtained at 2.3 × 10^?6 mol L^?1 P.     

RESPIRATION BY CULTIVATED ASTROCYTES AND NEURONS FROM THE CEREBRAL HEMISPHERES

-Rates of oxygen uptake were measured in chick and/or rat astrocytes and neuronal cells cultivated for 2–4 weeks in Falcon flasks or Rose chambers. All the preparations were found to have respiratory rates between 0.4 and 0.8 × 10^?5μl/h O₂ per cell. Based upon measurements of cell diameters these values were recalculated to about 570 μmol/g wet wt. for the neuronal cells and 130 μmol/g wet wt. for the glial cells. The results are compared with previous data of oxygen uptake by neurons and glial cells separated by other procedures.