Lycopene modulates initiation of N-nitrosodiethylamine induced hepatocarcinogenesis: Studies on chromosomal abnormalities,membrane fluidity and antioxidant defense system

Oxidative damage due to free radicals generated during nitrosamine metabolism has been suggested as one of the major cause for the initiation of hepatocarcinogenesis. Lycopene, is a well known antioxidant and have promising preventive potentials, however the mechanism of action remain hypothetical and unclear. To investigate the involvement of lycopene extracted from tomatoes (LycT) against oxidative stress induced deleterious effect of N-nitrosodiethylamine (NDEA) on cellular macromolecules, female Balb/c mice were divided in four groups: Control, NDEA (cumulative dose of 200 mg NDEA/kg body weight injected intraperitoneally in 8 weeks), LycT (5 mg/kg body weight given orally on alternate days, throughout the study) and LycT + NDEA (co-administration of LycT and NDEA). NDEA treatment commenced after 2 weeks of LycT administration. At the end of NDEA exposure i.e., at 10th week, enhanced activities of hepatic phase I enzymes, levels of reactive oxygen species (ROS), lipid peroxidation (LPO) was observed in NDEA group which may have contributed in chromosomal aberrations, enhanced micronucleated cell score, membrane fluidity and serum liver marker enzymes. A significant decrease in enzymatic and non-enzymatic antioxidant system could delineate the mechanism behind such NDEA insults. LycT pre-treatment to NDEA challenged group showed lower chromosomal abnormalities, micronucleated cells score, ROS, LPO levels and liver enzymes. Lycopene aids in normalizing the membrane fluidity and enhancing the activity of antioxidant enzymes and reduced glutathione which could account for the reduced oxidative damage in LycT + NDEA group. It seemed that lycopene supplementation target multiple dys-regulated pathways during initiation of carcinogenesis. Thus, dietary supplementation with lycopene can serve as an alternate measure to intervene the initiation of carcinogenesis.     

Cadmium and zinc influx characteristics by intact corn (Zea mays L.) seedlings

Summary Cadmium and zinc uptake parameters were determined for intact corn (Zea mays L.) seedlings grown for 15 and 22 in nutrient solutions containing levels of Cd and Zn that were similar to those found in soil solutions. Uptake of both elements was assumed to follow Michaelis-Menten kinetics. Calculations were based on the concentrations of free ionic Cd (Cd²⁺) and Zn (Zn²⁺) rather than the total solution concentration. Rates of Zn uptake were measured by determining depletion of Zn for periods of up to 30 h from solutions containing initial concentrations of 1.5 and 10μmol Zn 1⁻¹. Depletion curves suggested that Zn uptake characteristics were similar at both levels of Zn in solution. The Imax for Zn uptake decreased from 550 to 400 pmol m⁻² root surface s⁻¹ between 16 and 22 d of growth while Km decreased from 2.2 to 1.5 μmol Zn²⁺ 1⁻¹. Cadmium uptake parameters were measured by controlling Cd²⁺ activities in nutrient solution betwen 6.3 to 164 nmol l⁻¹ by continuous circulation of nutrient solution through a mixed-resin system. Imax for Cd uptake was 400 pmol m⁻² root surface s⁻¹ at 15 and 22 d of growth. The magnitude of Km increased from 30 to 100 nmol Cd²⁺ 1⁻¹ during this time period. The Km value suggests that corn is efficient for Cd uptake. The results of these uptake studies are consistent with the observed uptake of Zn and Cd by corn seedlings in soils.     

Enhancement of growth and polysaccharide production in suspension cultures of protocorm-like bodies from Dendrobium huoshanense by the addition of putrescine

Putrescine at 0.6 mM stimulated protocorm-like body growth and polysaccharide synthesis in suspension cultures of Dendrobium huoshanense. The specific growth rate of protocorm-like body increased from 0.047 to 0.056 day⁻¹, and the maximum dry weight and polysaccharide production reached 33.2 and 2.94 g l⁻¹, respectively, while they were 24.6 and 2.12 g l⁻¹, respectively, in the control. The administration of polyamine inhibitor, α-dl-difluoromethylarginine, at 1 mM, decreased protocorm-like body growth and polysaccharide production to 21.4 and 1.76 g l⁻¹, respectively.     

Reclamation of an activated-sludge microbial consortium by selective biostimulation

Our previous study showed that an activated-sludge process broke down at the phenol-loading rate of 1.5 g l⁻¹ day⁻¹, when non-flocculating bacteria (called R6T and R10) overgrew the sludge, resulting in a sludge washout. In this study, we attempted to circumvent this breakdown problem by reclaiming the consortium structure. Activated sludge was fed phenol, and the phenol-loading rate was increased stepwise from 0.5 g l⁻¹ day⁻¹ to 1.0 g l⁻¹ day⁻¹ and then to 1.5 g l⁻¹ day⁻¹. Either galactose or glucose (at 0.5 g l⁻¹ day⁻¹) was also supplied to the activated sludge from the phenol-loading rate of 1.0 g l⁻¹ day⁻¹. Pure culture experiments have suggested galactose to be a preferential substrate for a floc-forming bacterium (R6F) that predominantly degrades phenol under low phenol-loading conditions. Supplying galactose allowed sustainment of the R6F population and suppression of the overgrowth of R6T and R10 at the phenol-loading rate of 1.5 g l⁻¹ day⁻¹. This measure allowed the activated-sludge process to treat phenol at a phenol-loading rate up to 1.5 g l⁻¹ day⁻¹, although it broke down at 2.0 g l⁻¹ day⁻¹. In contrast, supplying glucose reduced the R6F population and allowed the activated-sludge process to break down at the phenol-loading rate of 1.0 g l⁻¹ day⁻¹. This study demonstrated that reclamation of the activated-sludge consortium by selective biostimulation of the floc-forming population improved the phenol-treating ability of the process. Received: 13 January 2000 / Received revision: 10 March 2000 / Accepted: 7 April 2000     

Lycopene Protects against Hypoxia/Reoxygenation-Induced Apoptosis by Preventing Mitochondrial Dysfunction in Primary Neonatal Mouse Cardiomyocytes

Background

Hypoxia/reoxygenation(H/R)-induced apoptosis of cardiomyocytes plays an important role in myocardial injury. Lycopene is a potent antioxidant carotenoid that has been shown to have protective properties on cardiovascular system. The aim of the present study is to investigate the potential for lycopene to protect the cardiomyocytes exposed to H/R. Moreover, the effect on mitochondrial function upon lycopene exposure was assessed.

Methods and Findings

Primary cardiomyocytes were isolated from neonatal mouse and established an in vitro model of H/R which resembles ischemia/reperfusion in vivo. The pretreatment of cardiomyocytes with 5 µM lycopene significantly reduced the extent of apoptosis detected by TUNEL assays. To further study the mechanism underlying the benefits of lycopene, interactions between lycopene and the process of mitochondria-mediated apoptosis were examined. Lycopene pretreatment of cardiomyocytes suppressed the activation of the mitochondrial permeability transition pore (mPTP) by reducing the intracellular reactive oxygen species (ROS) levels and inhibiting the increase of malondialdehyde (MDA) levels caused by H/R. Moreover, the loss of mitochondrial membrane potential, a decline in cellular ATP levels, a reduction in the amount of cytochrome c translocated to the cytoplasm and caspase-3 activation were observed in lycopene-treated cultures.

Conclusion

The present results suggested that lycopene possesses great pharmacological potential in protecting against H/R-induced apoptosis. Importantly, the protective effects of lycopene may be attributed to its roles in improving mitochondrial function in H/R-treated cardiomyocytes.     

Estimation of daily energetic requirements in young scalloped hammerhead sharks, Sphyrna lewini

Juvenile scalloped hammerhead sharks, Sphyrna lewini, are apex predators within their nursery ground in Kāne‘ohe Bay, Ō‘ahu, Hawai‘i. Understanding daily maintenance requirements of a top-level predator is an important step toward understanding its ecological impact within a nursery ecosystem. Juvenile S. lewini were fed a range of daily ration levels to examine the effect of feeding rate on growth and gross conversion efficiency. The von Bertalanffy growth model yielded the best fit to the data, predicting a maintenance ration of 115 kJ kg⁻¹ day⁻¹ (3.4% body weight (BW) day⁻¹) and a maximum growth rate of 38 kJ kg⁻¹ day⁻¹. This finding is in agreement with the previous prediction of high energetic requirements for S. lewini. In combination with the hypothesized food limitation within Kāne‘ohe Bay, this result may explain the observed high mortality rates of S. lewini. Gross conversion efficiency, K ₁, ranged from −36% to 34%, with maximum efficiency at feeding levels of 5.1% BW day⁻¹. The growth conversion efficiency of S.␣lewini is similar to that of lemon sharks and teleost fishes. Growth rates of juvenile S. lewini are possibly restricted by their high metabolic rate, limited food availability and foraging inexperience. By directly examining the effect of ration size on growth and food conversion, it was possible to resolve discrepancies between earlier studies, which used respiratory metabolism and gut content analyses.     

Seasonal growth and biomass ofTrapa japonica Flerov in Ojaga-Ike Pond,Chiba, Japan

In order to determine the seasonal growth and biomass ofTrapa japonica Flerov, field observations were carried out at Ojaga-ike Pond, Chiba, Japan, during 1979 and 1980. In spring, the plant showed exponential growth (c. 0.080 g g⁻¹ day⁻¹) and shoot elongation was as rapid as 10 cm day⁻¹. The plant attained its maximum biomass (380.5±35.1 g m⁻²) in late August, and about 50% of this was concentrated in the topmost 30-cm stratum (645.7±33.1 g m⁻³); maximum total stem length exceeded 6m. The plant produced large (500–800 mg per fruit), but small numbers of nut-like fruit (maximum, 5 fruits per rosette). Defoliation occurred almost linearly with time at a rate of 30.6 leaves m⁻² day⁻¹; annual net leaf production was estimated to be about twice as large as the seasonal maximum leaf biomass. While the number of leaves per rosette showed moderate seasonal change, rosette density, rosette area and leaf dry weight changed considerably during the year. From the negative log-log correlation between mean total leaf dry weight per rosette and rosette density, density-dependent rosette growth was assumed. The cause of the wide spread of this species in aquatic habitats is briefly discussed in terms of its seed size and morphology.     

Comparative analysis of the digestive efficiency and nitrogen and energy requirements of the phyllostomid fruit-bat (Artibeus jamaicensis) and the pteropodid fruit-bat (Rousettus aegyptiacus)

Nitrogen (N) and energy (E) requirements of the phyllostomid fruit bat, Artibeus jamaicensis, and the pteropodid fruit bat Rousettus aegyptiacus, were measured in adults that were fed on four experimental diets. Mean daily food intake by A. jamaicensis and R. aegyptiacus ranged from 1.1–1.6 times body mass and 0.8–1.0 times body mass, respectively. Dry matter digestibility and metabolizable E coefficient were high (81.1% and 82.4%, respectively) for A. jamaicensis and (77.5% and 78.0%, respectively) for R. aegyptiacus. Across the four diets, bats maintained constant body mass with mean metabolizable E intakes ranging from 1357.3 kJ · kg^−0.75 · day⁻¹ to 1767.3 kJ · kg^−0.75 · day⁻¹ for A. jamaicensis and 1282.6–1545.2 kJ · kg^−0.75 · day⁻¹ for R. aegyptiacus. Maintenance E costs were high, in the order of 3.6–5.4 times the basal metabolic rate (BMR). It is unlikely that the E intakes that we observed represent a true measure of maintenance E requirements. All evidence seems to indicate that fruit bats are E maximizers, ingesting more E than required and regulating storage by adjusting metabolic output. We suggest that true maintenance E requirements are substantially lower than what we observed. If it follows the eutherian norm of two times the BMR, fruit bats must necessarily over-ingest E on low-N fruit diet. Dietary E content did affect N metabolism of A. jamaicensis. On respective low- and high-E diets, metabolic fecal N were 0.492 mg N · g⁻¹ and 0.756 mg N · g⁻¹ dry matter intake and endogenous urinary N losses were 163.31 mg N · kg^−0.75 · day⁻¹ and 71.54 mg N · kg^−0.75 · day⁻¹. A. jamaicensis required 332.3 mg · kg^−0.75 · day⁻¹ and 885.3 mg · kg^−0.75 · day⁻¹ of total N on high- and low-E diets, respectively, and 213.7 mg · kg^−0.75 · day⁻¹ of truly digestible N to achieve N balance. True N digestibilities were low (29% and 49%) for low- and high-E diets, respectively. For R. aegyptiacus, metabolic fecal N and endogenous urinary N losses were 1.27 mg N · g⁻¹ dry matter intake and 96.0 mg N · kg^−0.75 · day⁻¹, respectively, and bats required 529.8 mg · kg^−0.75 · day⁻¹ (total N) or 284.0 mg · kg^−0.75 · day⁻¹ (truly digestible N). True N digestibility was relatively low (50%). Based on direct comparison, we found no evidence that R. aegyptiacus exhibits a greater degree of specialization in digestive function and N retention than A. jamaicensis. When combined with results from previous studies, our results indicate that all fruit bats appear to be specialized in their ability to retain N when faced with low N diet. Accepted: 24 November 1998     

Osmotic adjustment inSorghum bicolor (L. Moench) grown under moisture stress in soil and osmotically modified solution cultures

Sorghum (Sorghum bicolor L. Moench) plants were grown in solution culture and stressed at three rates of decreasing leaf water potential (−0.123, −0.068 and −0.029 MPa day⁻¹) achieved by the incremental addition of an osmoticum, polyethylene glycol (PEG) 6000 to the solutions. Plants were also grown in soil and given different amounts of water which resulted in rates of decreasing leaf water potentials of −0.130 and −0.073 MPa day⁻¹. The rate of stress and the culture system influenced the accumulation of solutes in the cell, but not cell volume. A rapid stress (−0.123 and −0.130 MPa day⁻¹) to approximately −1.6 MPa leaf water potential resulted in 0.75 and 0.16 MPa of osmotic adjustment in the PEG and soil culture respectively. At moderate stress (−0.068 and −0.073 MPa day⁻¹) respective values were 1.68 and 0.58 MPa. There were some visual symptoms in the solution grown plants characteristic of uptake of high molecular weight PEG. However the relative growth rates of these plants were equal to or greater than those of the soil grown plants. In view of the differences in plant water status of soil and PEG solution cultured plants it was concluded that the use of the latter system would not be entirely suitable for some studies of drought resistance in sorghum, as related to crop performance in the field.     

Microbial degradation of tetraethyl lead in soil monitored by microcalorimetry

Sieved agricultural soil samples were treated with the anti-knock agent tetraethyl lead (Et₄Pb), and the resulting effects were analyzed by microcalorimetry. Et₄Pb additions resulted in an increase of the heat production rate, provided that oxygen was present and that the soil was not autoclaved. The increased heat production rate was accompanied by degradation of Et₄Pb, as verified by speciation analysis (GC-MS) of the remaining Et₄Pb and its ionic degradation products (triethyl lead and diethyl lead cations). Conclusive evidence was obtained that these transformations were mediated mainly by microbes. At an initial Et₄Pb concentration of 2 g Pb/kg dry weight the biodegradation rate was about 780 μmol day⁻¹ kg dry weight⁻¹, whilst the chemical decomposition was only 50 μmol day⁻¹ kg dry weight⁻¹. A fivefold rise of the initial Et₄Pb concentration resulted in a decrease of the biodegradation rate to 600 μmol day⁻¹ kg dry weight⁻¹ and an increase of the chemical decomposition to 200 μmol day⁻¹ kg dry weight⁻¹. The biodegradation rate was not influenced by the addition of glucose, which means that no indication for a cometabolic attack of Et₄Pb was found. Received: 25 February 1997 / Received revision: 22 April 1997 / Accepted: 27 April 1997     

Lycopene Inhibits Ischemia/Reperfusion-Induced Neuronal Apoptosis in Gerbil Hippocampal Tissue

Plant lycopene exhibits antioxidant activity in animal tissues. Transient cerebral ischemia/reperfusion in Mongolian gerbils resulted in delayed neuronal death in hippocampal regions. We examined the antioxidant effects of lycopene because we expected lycopene to attenuate ischemia-related neuronal damage by controlling apoptosis at the gene level. The gerbils were divided into two groups: the normal feeding (control) group that received normal market food (MF) and the lycopene group that received MF containing lycopene (5 mg in 100 g MF food). After 1.5–2.0 months (when body weight were 60–65 g), the lycopene level was 38.2 ± 17.6 ng/ml in serum and 11.9 ± 4.0 μg/g-wet weight tissue in the liver. Levels of B cell leukemia-2, an apoptosis-suppressing protein, decreased in control animal brains 1, 3, and 7 days after surgery, whereas the levels increased in lycopene-treated animal brains. Moreover, cysteinyl aspartate-specific protease-3 activity increased gradually after ischemia, but was suppressed in the lycopene-treated animal brains 7 days after surgery. Finally, hippocampal superoxide dismutase (SOD) activity decreased in the control group 3 h after ischemia and, gradually increased thereafter, whereas it was significantly elevated in the lycopene group. Thus, orally administered lycopene is accumulated in the body, and provided protections against ischemia/reperfusion-induced brain injury by inducing an increase in SOD activity and inhibiting apoptosis.     

Effects of interaction between65Zn,cadmium, and copper in rats

Distribution and retention of zinc in the presence of cadmium and copper was studied in rats exposed repeatedly to these metals. The experiment was performed on white rats of the Wistar strain. The animals were divided into four groups/five rats each: 1)⁶⁵ZnCl₂; 2)⁶⁵ZnCl₂+CdCl₂; 3)⁶⁵ZnCl₂+CuCl₂; and 4) control group. Rats were administered sc every other day for two weeks:⁶⁵ZnCl₂−5 mg Zn/kg; CdCl₂−0,3 Cd/kg; and CuCl₂−2 mg Cu/kg. The zinc content was measured in rat tissues by γ-counting. Effect of Cd and Cu on subcellular distribution of zinc in the kidney and liver and on the level of metallothionein were also examined. Whole body retention of zinc under the influence of cadmium was lower than that observed in animals treated with zinc alone. However, copper increased twofold the whole body retention of zinc. Cadmium elevated the accumulation of zinc only in the kidneys nuclear fraction and liver soluble fraction. In the kidneys and liver, copper elevated the accumulation of zinc, in the nuclear, mitochondrial, and soluble fractions. The level of metallothionein-like proteins (MT) in the kidneys after a combined supply of zinc and copper was significantly increased with respect to the group of animals treated with zinc alone. These results indicated complex interactions between cadmium, copper, and zinc that can affect the metabolism of each of the metals.     

Dose-related steady states of fat loss in long-term leptin-treated <Emphasis Type="Italic">ob/ob</Emphasis> mice: Leptin resistance or desensitization versus counterregulatory signaling

We tried to unravel why leptin’s fat store depleting action levels off in the course of long-term applications. Supplying leptin by minipump infusion for 2 months to ob/ob mice at rates between 115 pmol day⁻¹ and 460 pmol day⁻¹ resulted in stable plasma leptin levels between 0.2 ng ml⁻¹ and 8 ng ml⁻¹. Initial treatment effects were leptin dose-dependent reductions in food intake and body mass, especially in fat content, followed by re-increases of food intake to levels only 4–18% below pre-treatment levels. Decreased body mass subsequently stabilized dose-dependently with body fat contents between 4% and 33% showing that total fat depletion was not a precondition for the progressive reduction of leptin-induced anorexia. Oxygen consumption measurements excluded contributions of enhanced energy dissipation to fat depletion. Plasma insulin concentrations declined from excessively high pre-treatment levels to steady, leptin dose-dependent levels within the normal range. Temporary anorexia in response to repeated additional 1-day leptin injections (100 pmol g⁻¹ day⁻¹) remained unchanged throughout long-term leptin infusion. Among various alternatives considered to explain the adipostatic equilibrium attained at new, dose-dependent levels under long-term leptin treatment, interaction between the leptin signal and at least one counteracting signal increasing with fat depletion is proposed as the most plausible working hypothesis.     

Transfer of Cl from herbage into tissues and milk products of dairy cattle and pigs

Cl-36 is an important component of nuclear waste. The concentrations of stable chlorine (Cl) in pig and cow tissues were measured to provide information which can be used to parameterize models of ³⁶Cl transfer into agricultural animals. The concentration of stable Cl in cows’ milk was 1.0 ± 0.2 g L⁻¹, in cow muscle it was 0.7 ± 0.2 g kg⁻¹ wet mass (wm) and in pig muscle 0.4 ± 0.1 g kg⁻¹ wm. The concentration of stable Cl in cow and pig liver was 0.9 ± 0.3 g kg⁻¹ wm, which was about two-fold higher than that in the kidney and lung. Due to homeostatic control, stable Cl concentrations in animal tissues are not related to the amount ingested daily in herbage at intake rates in the normal physiological range of up to 188 g day⁻¹ for cows and up to 40 g day⁻¹ for pigs. Therefore, the commonly used transfer coefficient is not suitable for use in quantifying the transfer of ³⁶Cl to milk and meat. Since the metabolism of stable Cl and ³⁶Cl in an animal’s body is identical, the average equilibrium ratios of ³⁶Cl to stable Cl in the daily ration (³⁶Cl (g kg⁻¹)/Cl (g kg⁻¹)) and animal tissues will be the same. We therefore conclude that the average equilibrium Cl isotopic ratio in the dietary daily intake should be used to predict the contamination of meat and milk with ³⁶Cl.     

Effects of lycopene on the initial state of atherosclerosis in New Zealand White (NZW) rabbits

Background

Lycopene is the main carotenoid in tomatoes, where it is found in high concentrations. Strong epidemiological evidence suggests that lycopene may provide protection against cardiovascular diseases. We therefore studied the effects of lycopene on diet-induced increase in serum lipid levels and the initiation of atherosclerosis in New Zealand White (NZW) rabbits.

Methodology/Principal Findings

The animals, divided into four groups of 9 animals each, were fed either a standard diet, a high-cholesterol diet containing 0.5% cholesterol, a high-cholesterol diet containing placebo beadlets, or a high-cholesterol diet plus 5 mg/kg body weight/day of lycopene (in the form of lycopene beadlets), for a period of 4 weeks. We found significantly elevated lycopene plasma levels in the animal group treated with lycopene beadlets. Compared to the high-cholesterol and the placebo group, this was associated with a significant reduction of 50% in total cholesterol and LDL cholesterol serum levels in the lycopene group. The amount of cholesteryl ester in the aorta was significantly decreased by lycopene. However, we did not observe a significant decrease in the extent of aortic surface lipid accumulation in the lycopene group. In addition, no differences in the intima-media thickness among groups were observed. Endothelial-dependent and endothelial-independent vasodilation in isolated rabbit aortic and carotid rings did not differ among any of the animal groups.

Conclusions

Lycopene supplementation for 4 weeks increased lycopene plasma levels in the animals. Although we found strongly reduced total and LDL cholesterol serum levels as well as significantly lower amounts of cholesteryl ester in the aortae in the lycopene-treated group, no significant differences in initial lesions in the aortae were detected.     

Functional Characterization of the Microbial Community in Geothermally Heated Marine Sediments

The microbial population of geothermally heated sediments in a shallow bay of Vulcano Island (Italy) was characterized with respect to metabolic activities and the putatively catalyzing hyperthermophiles. Site-specific anoxic culturing media, most of which were amended with combinations of electron donors (glucose or carboxylic acids) and acceptors (sulfate), were used for selective enrichment of metabolically defined subpopulations. The mostly archaeal chemoautotrophs produced formate at rates of 3.25 and 0.46 fmol cell⁻¹ day⁻¹ with and without sulfate, respectively. The glucose fermenting heterotrophs produced acetate (18 fmol cell⁻¹ day⁻¹) and lactate (2.6 fmol cell⁻¹ day⁻¹) and were identified as predominantly Thermus sp. and coccoid archaea. These archaeal cells also metabolized lactate (5.6 fmol cell⁻¹ day⁻¹), but neither formate nor acetate. The heterotrophic culture enriched on formate/acetate/propionate/sulfate utilized mainly formate (27 fmol cell⁻¹ day⁻¹) and lactate (89–195 fmol cell⁻¹ day⁻¹), and consumed sulfate (38–68 fmol cell⁻¹ day⁻¹). These formate or lactate consuming sulfate reducers were dominated by Archaeoglobales (7% in situ) and unidentified Archaea. The in situ benthic community comprised 15% Crenarchaeota, a significant group only in the autotrophic cultures, and 3% Thermus sp., the putatively predominant group involved in fermentative metabolism. The role of Thermoccales (4% in situ) remained undisclosed in our experiments. This first comprehensive data set established plausible links between several groups of hyperthermophiles in shallow marine hydrothermal systems, their metabolic function within the benthic microbial community, and biogeochemical turnover rates.     

Increase of lycopene production by supplementing auxiliary carbon sources in metabolically engineered <Emphasis Type="Italic">Escherichia coli</Emphasis>

In the fed-batch culture of glycerol using a metabolically engineered strain of Escherichia coli, supplementation with glucose as an auxiliary carbon source increased lycopene production due to a significant increase in cell mass, despite a reduction in specific lycopene content. l-Arabinose supplementation increased lycopene production due to increases in cell mass and specific lycopene content. Supplementation with both glucose and l-arabinose increased lycopene production significantly due to the synergistic effect of the two sugars. Cell growth by the consumption of carbon sources was related to endogenous metabolism in the host E. coli. Supplementation with l-arabinose stimulated only the mevalonate pathway for lycopene biosynthesis and supplementation with both glucose and l-arabinose stimulated synergistically only the mevalonate pathway. In the fed-batch culture of glycerol with 10 g l⁻¹ glucose and 7.5 g l⁻¹ l-arabinose, the cell mass, lycopene concentration, specific lycopene content, and lycopene productivity after 34 h were 42 g l⁻¹, 1,350 mg l⁻¹, 32 mg g cells⁻¹, and 40 mg l⁻¹ h⁻¹, respectively. These values were 3.9-, 7.1-, 1.9-, and 11.7-fold higher than those without the auxiliary carbon sources, respectively. This is the highest reported concentration and productivity of lycopene.     

Adequacy of food rations in soldiers during exercise in hot, day-time conditions assessed by doubly labelled water and energy balance methods

The energy requirements of people doing physical work in hot climates are not clearly understood. In particular, we know little about the combined effects of heat stress and muscular work on energy requirements. During military exercises in the African bush soldiers are supplied with standard rations, the adequacy of which is unknown. We have now assessed the adequacy of these food and water rations in 12 male Zimbabwean soldiers during 12 days of strenuous, heat-stress exercise in the field. We used two methods to measure energy expenditure: the double-labelled water method (DLW) and the energy balance method (i.e. comparing dietary energy with changes, if any, in body energy stores). Two groups were studied: one group (eight subjects) carried out field exercises; the control group consisted of four soldiers doing normal work. Mean daily energy expenditure as assessed by the DLW method was [mean (SE)] 23 (1.5) MJ · day⁻¹ for the field group and 14 (0.5) MJ · day⁻¹ for the control group (P<0.001). By the energy balance method, daily energy expenditure was calculated to be 26 (0.7) MJ · day⁻¹ and 15.5 (0.4) MJ · day⁻¹ for the field group and control group, respectively. Body mass loss was 3 (0.1) kg [4.6 (0.3)% of body mass] for the field group, but the control group gained 1.1 (0.1) kg. Mean daily fluid intake was 11 (0.5) 1 · day⁻¹, suggesting that the standard ration supplied was inadequate. Body mass loss was caused by both the energy deficit and total body water loss. These results suggest strenuous work in hot, dry field conditions imposes extra energy requirements. Accepted: 21 January 1997     

Changes in morphological, photosynthetic and physiological responses of Mono Maple seedlings to enhanced UV-B and to nitrogen addition

In the southeast of the Qinghai-Tibetan Plateau of China, Mono Maple is a common species in reforestation processes. The paper mainly investigated the changes in morphological, photosynthetic and physiological responses of Mono Maple seedlings to UV-B radiation, nitrogen supply and their combination. The experimental design included two levels of UV-B treatments (ambient UV-B, 11.02 KJ m⁻² day⁻¹; enhanced UV-B, 14.33 KJ m⁻² day⁻¹) and two nitrogen levels (0; 20 g N m⁻² a⁻¹)—to determine whether the adverse effects of UV-B on plants are eased by nitrogen supply. Enhanced UV-B caused a marked decline in growth parameters, net photosynthetic rate, and photosynthetic pigments, whereas it induced an increase in reaction oxygen species (hydrogen peroxide accumulation and the rate of superoxide radical production) and malondialdehyde content. Enhance UV-B also induced an increase in antioxidant compounds of Mono Maple, such as UV-B absorbing compounds, proline content, and activities of antioxidant enzymes (peroxidase, superoxide dimutase and catalase). On the other hand, nitrogen supply caused an increase in some growth parameters, net photosynthetic rate, photosynthetic pigments and antioxidant compounds (peroxidase, proline content and UV-B absorbing compounds), and reduced the content of reaction oxygen species (H₂O₂ accumulation, the rate of O₂⁻ production) and malondialdehyde content under ambient UV-B. However, under enhanced UV-B, nitrogen supply inhibited some growth parameters, and increased H₂O₂ accumulation, the rate of O₂⁻ production and MDA content, though proline content, UV-B absorbing compounds and activities of POD and SOD increased. These results implied that enhanced UV-B brought harmful effects on Mono Maple seedlings and nitrogen supply made plants more sensitive to enhanced UV-B, though increased some antioxidant activity.     

Characteristics of cadmium accumulation and tolerance in <Emphasis Type="Italic">Rorippa globosa</Emphasis> (Turcz.) Thell., a species with some characteristics of cadmium hyperaccumulation

Characteristics of cadmium (Cd) accumulation and tolerance in Rorippa globosa (Turcz.) Thell., a species with some characteristics of cadmium hyperaccumulation were further investigated and compared with a closely related species, Rorippa islandica. The results showed that there was no phytotoxicity for R. globosa leaves or reduction in biomass when treated with 25 μg Cd g⁻¹, although the concentration of Cd accumulated in the leaves was up to 218.9 μg Cd g⁻¹ dry weight (DW). On the contrary, Cd toxicity was observed in R. islandica leaves by way of determining changes in fresh weight (FW), malondialdehyde (MDA) level and chlorophyll content while treated with 25 μg Cd g⁻¹ DW. R. globosa had stronger self-protection ability than R. islandica to adapt to oxidative stress caused by Cd. Application of Cd significantly increased the activity of superoxide dismutase (SOD) in leaves, the activity of peroxidase (POD) in roots, and the activity of catalase (CAT) in leaves and roots of R. globosa. By contrast, in R. islandica, the activity of antioxidant enzymes was inhibited or unchanged by various Cd treatments. However, R. globosa leaves had higher activity of antioxidant enzymes such as SOD and POD than that of R. islandica. The antioxidative defense systems in R. globosa might play an important role in Cd tolerance. The Cd treatments significantly induced the synthesis of phytochelatins (PCs) in the two species. Leaf PCs and Cd accumulation by R. globosa were much greater than those by R. islandica, but root PCs and Cd accumulation by R. islandica were much greater than those by R. globosa, suggesting that PCs in leaves may be a biomarker of Cd hyperaccumulation, and the synthesis of PCs may be related to an increase in the uptake of Cd ions into the cytoplasm, not the primary mechanism for Cd tolerance.