The influence of suspended silt on oxygen consumption by the redbreast tilapia, Tilapia rendalli (Boulenger,1896)

The routine oxygen consumption of redbreast tilapia, Tilapia rendalli exposed to silt from the Phalaborwa Barrage was investigated under controlled laboratory conditions. Exposure of adult fish to sublethal concentrations of silt did alter routine oxygen consumption by causing increased rates (53–77% from initial) of oxygen consumption. This indicates that sublethal levels of suspended silt concentrations results in an increase in oxygen consumption by the fish due to an increase in metabolic rate associated with increased activity and stress. From the laboratory experiments, it can therefore be predicted that sublethal releases from the Phalaborwa Barrage will stress the resident fish populations. However, the extent of the impact on the fish population will depend on factors such as frequency, duration and severity of exposure as well as the species in question. Long term monitoring of the fish population below the Phalaborwa Barrage is therefore essential.     

Toxic effects of zinc and iron on the routine oxygen consumption of Tilapia sparrmanii (Cichlidae)

1. The routine oxygen consumption of Tilapia sparrmanii without the addition of any toxicants over a 72 hr period showed a decrease for the first 48 hr, but stabilised thereafter.2. Addition of zinc (98 mg l⁻¹) resulted in a drastic decrease of oxygen consumption for 3 hr. The routine oxygen consumption showed a significant decrease for the first 24 hr, while the second and third 24 hr revealed significant differences with great individual variance.3. The decrease in oxygen consumption observed after exposure to zinc, could be caused by gill damage as well as the internal action of zinc.4. An increase in oxygen consumption was noted for almost 3 hr after addition of iron (88mg l⁻¹). During the first-, second- and third 24 hr the oxygen consumption increased significantly, compared to the control values.5. The increase in routine oxygen consumption of T. sparrmanii when compared to control values after exposure to iron, could be attributed to stress and possible gill changes.6. The study revealed that after acute (72 hr) exposure to sublethal concentrations of zinc and iron, the routine oxygen consumption of T. sparrmanii was altered.     

Oxygen consumption,ammonia excretion,and filtration rate of the marine bivalve Mytilus edulis exposed to methamidophos and omethoate

In this study, the oxygen consumption, ammonia excretion, and filtration rate were monitored in Mytilus edulis in response to administration of the two pesticides, methamidophos and omethoate. Five sublethal concentrations (1, 10, 50, 100, and 200 µgL^?1) were administered over 96 h. Oxygen consumption rates increased following administration of all concentrations of methamidophos for 96 h and to the lower concentrations of omethoate (1, 10, and 50 µg L^?1) from 6 to 24 h. Over 24 h, oxygen consumption decreased significantly. Ammonia excretion rates were higher than the control after 36 h of exposure to methamidophos, while reduction was observed when M. edulis was exposed to omethoate. The O:N ratios increased when the animals were first exposed to these two pesticides and then decreased at all the concentrations. At the concentrations of 100 and 200 µgL^?1, the O:N ratio was below 30 after 72 h. The filtration rate of M. edulis decreased with the increasing concentration of pesticide exposure.     

Some factors affecting the respiration of some aquatic plants

Summary The oxygen consumption of four aquatic plants has been determined at various concentrations of dissolved oxygen and at three different temperatures.Oxygen consumption rates (mg oxygen/g dry weight per hr) at 20°C in air-saturated water were Berula erecta, 1.25; Callitriche obtusangula, 2.8; Hippuris vulgaris, 1.96; and Ranunculus pseudofluitans, 1.90.Oxygen consumption rates increased with increase in dissolved-oxygen concentration within the experimental limits of 1.2–17 p.p.m. dissolved oxygen. The relation of oxygen consumption to this range of oxygen concentrations can be described by the empirical equation R = aC ^b. Increase of temperature has been shown to increase the rates of oxygen consumption. Q₁₀ values ranging from 1.32 to 3.48 have been obtained.     

Ventilatory and behavioural responses of the marbled sole Pseudopleuronectes yokohamae to progressive hypoxia

This study identified ventilatory and behavioural responses in the marbled sole Pseudopleuronectes yokohamae under experimentally induced progressive decreases in dissolved oxygen (DO) levels. Ventilation frequency showed an increase with decreasing DO levels from normoxia to 2·75 mg O₂ l^?1, followed by a decrease in ventilation frequency at decreased DO levels from 2·00 to 0·75 mg O₂ l^?1. At DO levels below 2·00 mg l^?1, behaviours at the bottom were suppressed, whereas avoidance behaviours increased. A decrease in avoidance behaviours was observed from 1·00 to 0·75 mg O₂ l^?1. Upside‐down reversal and incapacitation at DO levels of 1·00–0·75 mg O₂ l^?1 suggested that sublethal effects on P. yokohamae were induced. The responses observed before the sublethal DO level could be interpreted as an effort to maintain oxygen uptake, reduce routine activities and facilitate avoidance. The observed DO level thresholds that induce behavioural responses, in addition to sublethal effects, indicate hypoxia‐tolerance that is important for understanding the effects of hypoxia on coastal ecosystems.     

Oxygen consumption in the rectal gland of the dogfishScyliorhinus canicula and the effects of cyclic AMP

Summary Oxygen consumption was measured in slices of dogfish (Scyliorhinus canicula) rectal gland tissue and compared with spleen and kidney. Concentrations of dibutyryl cAMP and theophylline that have previously been shown to stimulate secretion from the perfused gland and to produce a large increase in ouabain binding in this tissue, greatly increased oxygen consumption in the rectal gland but were without effect on oxygen consumption in the spleen and the kidney. Addition of theophylline alone increased rectal gland oxygen consumption and no further increase was detected on addition of cAMP at the concentration used (0.05 mmol l^–1).Ouabain (10^–4 M) significantly decreased oxygen consumption in all three tissues studied and completely abolished the increase in oxygen consumption of the rectal gland produced as a result of the addition of cAMP and theophylline.These findings are discussed in relation to the apparent specific effect of cAMP on the rectal gland and its possible mode of action in this tissue.     

Effect of sublethal doses of copper sulphate and bayluscide on survival and oxygen consumption of the snail biomphalaria alexandrina

The survival rate and oxygen consumption of Biomphalaria alexandrina snails exposed to sublethal concentrations of copper sulphate and Bayluscide were investigated. Prolonged exposure periods to the sublethal concentrations increased the percentage mortality among the exposed snails. Although the snails exposed to lower concentrations of the sublethal doses, were apparently normal, their oxygen consumption was markedly lower than the control ones. The rate of reduction of oxygen consumption by the experimental snails increased significantly at higher concentrations. The reduction of oxygen consumption was also presistent at prolonged exposure periods.     

Progeny of the maize weevil,Sitophilus zeamais,is affected by parental exposure to clove and cinnamon essential oils

The interest in and utilization of botanical insecticides, particularly essential oils, has become increasingly relevant to the control of insect pests. However, the potential ecotoxicological risks or flaws (including sublethal effects on the targeted pest generation and its subsequent progeny) of this pest control tool have been neglected frequently. Here, we evaluated the effects of sublethal exposure to clove, Syzygium aromaticum (L.) Merrill & Perry (Myrtaceae), and cinnamon, Cinnamomum verum J. Presl (Lauraceae), essential oils on adult (F0) maize weevils, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), and the physiology (e.g., body mass, respirometry, and grain consumption) and population dynamics (e.g., daily emergence and sex ratio) of their progeny. Longevities of the parents were negatively affected by the essential oils in a concentration‐dependent manner. Parental sublethal exposure to clove oil (0.17 μl cm^?2) accelerated offspring emergence but delayed the emergence of females compared to males. Parents that were sublethally exposed to clove (0.17 μl cm^?2) or cinnamon (0.35 μl cm^?2) essential oils produced heavier offspring. Parental sublethal exposure to cinnamon essential oil accelerated offspring emergence (at 0.70 μl cm^?2), delayed female emergence (at 0.17 μl cm^?2), and enhanced grain consumption (at 0.35 and 0.70 μl cm^?2) of the progeny. Thus, our findings indicate that sublethal exposure to clove and cinnamon essential oils is capable of promoting transgenerational effects in S. zeamais that can negatively impact the control efficacy of such products.     

SEASONAL VARIATION IN METABOLIC FUNCTIONS OF BRAMBLINGS

Seasonal variation in the rate of oxygen consumption during rest at different test temperatures and in the respiratory quotient (RQ) was observed in male Bramblings Fringilla montifringilla which had been caught as immature birds during autumn migration and kept under outdoor conditions for one year. Resting oxygen consumption measured from +31^o to – 4^oC during one night was significantly lower in late April and October (migratory seasons) as compared to the preceding and the following December. Because of marked seasonal changes in body weight, the significance of differences in metabolic rate between different seasons was largely dependent on the manner of expressing the rate of oxygen consumption, either per bird or as the 0–67 power of body weight (“surface coefficient”). The lower resting rate of oxygen consumption during the migratory seasons was interpreted as one possible factor responsible for allowing fat deposition by reducing total energy expenditure. This modification occurred only in birds kept under quasi-natural conditions outdoors and not in birds which were kept in cages under constant conditions of light and temperature in the laboratory.     

Microelectrode measurement of oxygen tensions in collagen-hepatocyte gels

Summary Microelectrodes have been used for the measurement of oxygen tension in various biological systems.(Silver, 1987) Although not previously reported, microelectrodes allow the direct measurement of oxygen tension profiles within collagen gels containing entrapped hepatocytes (collagcn-hepatocyte gels). These oxygen tension profiles, along with hepatocyte oxygen consumption data, allowed the estimation of a diffusion coefficient for oxygen in collagen-hepatocyte gels, D _g = 2.99 × 10^–5 cm²/s.     

Effets physiologiques de ľ atrazine à doses sublétales sur Lemna minor, VII. Incorporation ďacétate-l,2-[14C] dans les groupes de lipides et leurs acides gras

Physiological effects of sublethal doses of atrazine on Lemna minor. VII. 1,2-[¹⁴C] acetate incorporation into the groups of lipids and their fatty acids. The lipids and the fatty acids of ten-day old duckweed (Lemna minor L.), cultivated aseptically in mineral solution containing sublethal concentrations of 0,10 and 0,50 ppm (0.46 and 2.3 μM, respectively) of atrazine, were analyzed by thin-layer chromatography and gas-liquid radiochromatography after 1,2-[¹⁴C] acetate feeding. Sublethal concentrations of atrazine increased the incorporation of radioactivity in total lipids, diacylgalactosylglycerol (DGG), diacyldigalactosylglycerol (DDG), sul-folipids (SL), phosphatidylglycerol (PG), diacylglycerol (DAG) and triacylglycerol + steroll esters (TAG+SE). The incorporation of acetate-1,2-[¹⁴C] decreased in phos-phatidylcholine (PC) and in phosphatidylethanolamine (PE) in the presence of atrazine. The radioactivity increased in total Transic-hexadecenoic, linoleic and α -linolenic acids while it decreased in the other fatty acids. This indicates that the sublethal concentrations of atrazine stimulate the desaturation of fatty acids of L. minor. The radioactivity was strongly incorporated in the α -linolenic acid of DGG in the presence of atrazine. The specific radioactivity of α-linolenic acid was greater in DAG than in PG > TAG + SE > PC > PE > DGG > SL > DDG and it increased in all groupd of lipids analyzed under the influence of sublethal doses of atrazine. The labelling of Translchexadecenoic acid of PG and its specific radioactivity increased in the presence of atrazine. These changes suggest that the sublethal concentrations of atrazine stimulate especially the lipid metabolism of the chloroplasts of L. minor and they could explain the increase in the number of grana per chloroplast in treated L. minor. The results are discussed in relation to the biosynthesis of galactolipids.     

Oxygen consumption of burbot, Lota lota(L.), fed different rations of vendace, Coregonus albula L.

The oxygen consumption of adult burbot, Lota lota (L.), was examined to determine the effects of fasting and meal ration on oxygen consumption rates. The temperature (2.1 °C) was selected to represent ambient conditions for burbot in winter. The average pre‐feeding oxygen consumption rate was 29.5 mg kg^?1 h^?1. Feeding affected the oxygen consumption rates since the apparent heat increment correlated significantly with the meal ration. However, the meal ration (i.e. vendace, Coregonus albula L.) did not affect the proportion of the ingested meal energy used in the apparent heat increment. When the meal ration was increased, peak oxygen consumption ranged from 1.2 to 2.2 times higher than the fasting level. Observed low oxygen consumption values suggest that the metabolic processes of burbot are strongly reduced in low temperatures.     

Metabolic and energetic aspects of the growth of Bacillus stearothermophilus in glucose-limited and glucose-sufficient chemostat culture

With a glucose-limited chemostat culture of Bacillus stearothermophilus, increasing the incubation temperature progressively from 45°C to 63°C led to a progressive marked increase in the maintenance rates of glucose and oxygen consumption. Hence, at a fixed low dilution rate the yield values with respect to glucose and oxygen decreased substantially with increased temperature. However, the apparent Y _glucose ^max and values did not decrease but actually increased with temperature, being highest at 63°C (i.e., close to the maximum growth temperature). With glucose-sufficient cultures growing at a fixed low dilution rate (0.2 h^–1) and at their optimum temperature (55°C), glucose and oxygen consumption rates invariably were higher than that of a corresponding glucose-limited culture. Cation (K⁺ or Mg²⁺)-limited cultures expressed the highest metabolic rates and with the K⁺ limited culture this rate was found to be very markedly temperature dependent. As the temperature was increased from 45°C to 63°C the rate of glucose consumption increased 1.8-fold, and that of oxygen consumption by 3.7-fold. The culture pH value also exerted a noticeable effect on the metabolic rate of a glucose-limited culture, particularly at the extremes of pH tolerance (5.5 and 8.5, respectively). A K⁺-limited culture was less affected with respect to metabolic rate by the culture pH value though the steady state bacterial concentration, and thus the cellular K⁺ content, changed substantially. These results are discussed in relation to previous findings of the behaviour of this organism in batch culture, and to the behaviour of other thermophilic Bacillus species in chemostat culture.     

Swimming metabolism and temperature in juvenile walleye,Stizostedion vitreum vitreum

Synopsis Oxygen consumption of juvenile walleye increased between 5 and 15°C at each swimming speed between 20 and 45 cm s^–1. With further increase in temperature to 23.5°C, oxygen consumption declined. Basal oxygen consumption was estimated by extrapolation of the relationship between swimming speed and the logarithm of oxygen consumption to 0 cm s^–1. The metabolic cost of swimming, represented by the difference between total and basal oxygen consumption was independent of temperature at each swimming speed. Energy required to swim 1 km increased from 2.14 to 5.68 J g^–1 between 20 and 45 cm s^–1.     

THE EFFECT OF E TYPE PROSTAGLANDINS ON THE PROLIFERATION OF HAEMOPOIETIC STEM CELLS IN VIVO

The ability of protaglandins E₁ and E₂ to stimulate the proliferation of haemopoietic stem cells (CFU_s) was studied in vivo. PGE₂, in a dose range of 10^-4 to 10^-1μg/g body weight and PGE₁ in a dose range of 10^-5 to 10^-1μg/g body weight, produced a rapid cycling wave of CFU_s. The increase in the number of CFU_s in S phase was not followed by a rise in the femoral CFU_s content, and except for a transient increase in femoral CFU_c level, no increase in differentiation was found either. Therefore, it is proposed that haemopoiesis after PG-induced CFU stimulation is ineffective. PGE₂ did not stimulate regeneration of CFU_s in a perturbed state (after sublethal irradiation). All these findings support the idea that PGEs might represent potent stimulators of the haemopoietic stem cells acting in physiological doses. However, if acting concurrently with physiological control systems PGs lead to ineffective haemopoiesis (under normal conditions) or do not exert any measurable effect (after sublethal irradiation).     

Joint and single toxicity of Cd and Fe related to metal uptake in the mayfly Leptophlebia marginata (L.) (Insecta)

The toxic effects of Cd and Fe on the mayfly Leptophlebia marginata were tested during single and joint exposure to the metals. Data on uptake and localization of the metals were related to the following biological parameters: survival, food consumption (% gut contents) and activity (escape from prodding).The uptake of Cd by L. marginata was significantly reduced by the presence of Fe (p<0.0005).Fe²⁺- and Fe³⁺-crusts on the gills, body surface and on the gut membrane precipitated when the mayflies were exposed to either Fe alone or to Fe and Cd. This caused decreased food consumption by the mayflies.In the pigments of the eyes and the cuticle Fe²⁺ was found.Exposure to Cd led to disturbances in Cl^– and K⁺ ion balance, which were ameliorated by additional Fe-exposure due to co-precipitation processes.Exposure to Cd caused an increase in the concentrations of S and P in the mayflies.Whereas Fe caused sublethal effects (food consumption) without being taken up into the organism. Cd caused lethal effects (inactivity, death) due to disturbances of the ion balance at the membranes.     

Effect of D-amino acids on some mitochondrial functions in rat liver

Summary.  We studied the role of the D-amino acids (D-aa) D-serine, D-alanine, D-methionine, D-aspartate, D-tyrosine and D-arginine on rat liver mitochondria. The stability of D-amino acids, mitochondrial swelling, transmembrane potential and oxygen consumption were studied under oxidative stress conditions in rat liver mitochondria. In the presence of glutamate-malate all D-aas salts increased mitochondrial swelling, while in the presence of succinate plus rotenone only D-ala, D-arg and D-ser, induced mitochondrial swelling. The transmembrane potential (ΔΨ) was decreased in the presence of 1 μM Ca²⁺. The D-aas inhibited oxygen consumption in state 3. The D-aa studied exerted effects on mitochondria via an increase of free radicals production. Received January 15, 2002 Accepted April 14, 2002 Published online September 4, 2002 Acknowledgements The authors appreciated the partial economical support from Mexican grants of CONACYT (to A.S.-M. during its sabbatical) and CIC-UMSNH (2.5) and critical readings from Rafael álvarez-González. Authors' address: Alfredo Saavedra-Molina, Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio B-3. C.U., Morelia, Mich. 58030. México, Fax: 52-443-326-5788, E-mail: saavedra@zeus.umich.mx     

Production of NO and N2O by the Heterotrophic Nitrifier Alcaligenes faecalis parafaecalis under Varying Conditions of Oxygen Saturation

Production of NO and N ₂ O by the heterotrophic nitrifier Alcaligenes faecalis subsp. parafaecalis was studied during growth in batch and continuous culture on peptone-meat extract medium. Depending on oxygen saturation level, medium redox status and amount of substrate supplied, the microorganisms produced 0.002–0.25 mg NO-N h^{- 1} (g protein)^{- 1} and 0.16–2.4 mg N ₂ O-N h^{- 1} (g protein)^{- 1} . Maximum rates of nitrogen oxides production were observed during peak events initiated by sudden changes of oxygen supply in the medium and were due to combined nitrification/denitrification taking place simultaneously within the cells. Based on model simulations of enzymatic kinetics of denitrification, possible mechanisms of increased nitrogen oxides production during periods of changes in oxygen supply are suggested.     

Effect of Organic Amendments on the Oxygen Uptake of Pseudomonas putida—PAPs-1 in Chromium-Contaminated Pond Ash

In this study a Cr (VI) resistant bacterium Pseudomonas putida was isolated from pond ash and its oxygen consumption potential at different concentrations of Cr (VI) viz., 0, 100 and 200 mg kg^?1 was studied using Electrolytic Respirometry. Oxygen consumption by the bacterium was noticed up to 200 mg kg^?1 Cr (VI) concentration. To the pond ash (inoculated with and without Pseudomonas) 200 mg kg^?1 Cr (VI) was added and incorporated with different organic amendments such as farmyard manure (FYM), coir pith, paddy straw and press mud and the cumulative oxygen consumption was studied. The cumulative oxygen consumption by the bacterium was higher when the pond ash was incorporated with organic amendments. The highest oxygen consumption of 205 mg l^?1 was observed when press mud was used, which was followed by FYM (198 mg l^{? 1} ). Furthermore, the enrichment with press mud increased the nutrient content of N (57.28 mg kg^?1 ), P (5.5 mg kg^?1 ) and K (42.7 mg kg^?1 ) of the pond ash. The maximum dehydrogenase enzyme activity of 0.63 μ g TPF formed g^?1 sample h^?1 was measured when the pond ash was inoculated with Pseudomonas and enriched with press mud. The results also indicated that maximum reduction of Cr (VI) (42.5%) was observed when Pseudomonas and press mud were used. This study evaluated the possibilities of toxicity reduction and nutrient enrichment of the ash pond using a Cr (VI) resistant bacterium and organic amendments.     

Walking performance and aerobic and anaerobic metabolism of Carcinus maenas (L.) in sea water at 15°C

Walking performance of the shore crab Carcinus maenas (L.) in sea water at 15 °C was assessed. In large crabs there was an inverse relationship between fatigue time and speed; crabs ran for $\text{\$}\text{?}$10 min at 3.2 m·min^?1 and for only 2 min at 14 m·min^?1. There were linear relationships between oxygen consumption and walking speeds for small and large animals walking at up to 4 m·min^?1 Estimates of maximum oxygen consumption were proportional to W^0.13 whereas inactive consumption is proportional to W^0.44 this resulted in aerobic scope (i.e. the difference between inactive and maximal rates of oxygen consumption) remaining almost constant across a weight range of animals whereas the aerobic expansibility (maximal rates/inactive rates) declined from 7- to 4-fold with increasing size. After a 12-h period without handling (settled animals) the animals could immediately become active and reach maximal rates of oxygen consumption similar to those of animals handled 1 h before the experiment. The aerobic expansibility of these settled animals could range from 21 to 8 times their inactive rates of oxygen consumption in small and large animals respectively. After 10 min of exercise oxygen consumption and whole body lactate levels returned to pre-exercise values within 5 to 25 min. The net oxygen debts range from 16 to 64% of the net oxygen consumption increase during exercise in small and large animals respectively.Calculations of the energy gained from lactate accumulation indicated that the net aerobic energy production during walking was supplemented from 4 to 71 % by anaerobic metabolism in small and large animals respectively. With increasing animal size the decline in aerobic expansibility was offset by an increased capacity for lactate production so that the overall maximum energy production during sustained activity remained almost constant at around seven times the inactive rate. The cost of transport (the net increase in oxygen consumption per g per m) falls with increased walking speed and increased animal size.