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1.
C. Lydersen K. M. Kovacs M. O. Hammill 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(2):81-88
In this study we measured growth and milk intake and calculated energy intake and its allocation into metabolism and stored
tissue for hooded seal (Cystophora cristata) pups. In addition, we measured mass loss, change in body composition and metabolic rate during the first days of the postweaning
fast. The mean body mass of the hooded seal pups (n = 5) at the start of the experiments, when they were new-born, was 24.3 ± 1.3 kg (SD). They gained an average of 5.9 ± 1.1.
kg · day−1 of which 19% was water, 76% fat and 5% protein. This corresponds to an average daily energy deposition of 179.8 ± 16.0 MJ.
The pups were weaned at an average body mass of 42.5 ± 1.0 kg 3.1 days after the experiment was initiated. During the first
days of the postweaning fast the pups lost an average of 1.3 ± 0.5␣kg of body mass daily, of which 56% was water, 16% fat
and 28% protein. During the nursing period the average daily water influx for the pups was 124.6 ± 25.8 ml · kg−1. The average CO2 production during this period was 1.10 ± 0.20 ml · g−1 · h−1, which corresponds to a field metabolic rate of 714 ± 130 kJ · kg−1 · day−1, or 5.8 ± 1.1 times the predicted basal metabolic rate according to Kleiber (1975). During the postweaning fast the average
daily water influx was reduced to 16.1 ± 6.6 ml · kg−1. The average CO2 production in␣this period was 0.58 ± 0.17 ml · g−1 · h−1 which corresponds to a field metabolic rate of 375 ± 108 kJ · kg−1 · day−1 or 3.2 ± 0.9 times the predicted basal metabolic rate. Average values for milk composition were 33.5% water, 58.6% fat and
6.2% protein. The pups drank an average of 10.4 ± 1.8␣kg of milk daily, which represents an energy intake of 248.9 ± 39.1
MJ · day−1. The pups were able to store 73.2 ± 7.7% of this energy as body tissue.
Accepted: 15 August 1996 相似文献
2.
Bradshaw SD Bradshaw FJ 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(2):183-192
Rates of protein turnover and synthesis were measured in wild-caught Honey possums (Tarsipes rostratus) in the southwest of Western Australia and compared between males and females with and without pouch young. Possums were
injected with 50 μg of 15N-glycine and ammonia collected within 24 h was used as the nitrogen end-product in a single-injection protocol. The overall
mean rate of protein synthesis measured was 7.7 ± 0.5 g kg−0.75 day−1, which falls within the range of values reported for other marsupial species. Whole body rates of nitrogen flux and protein
synthesis did not vary significantly between males and females with and without young, but females with pouch young showed
significantly lower rates of protein synthesis when expressed in relation to metabolic body size. This difference was no longer
apparent, however, if the mass of the females was corrected for the estimated mass of the young in the pouch averaging 9.3 ± 1.6 g kg−0.75 day−1 and suggesting that the young should not be considered as part of the metabolic body pool. Whole body rates of protein degradation
were significantly reduced in females carrying pouch young, suggesting that protein may be being diverted from the pool to
milk production. Calculations indicate that the daily fraction of the female’s nitrogen synthesis rate that needs to be diverted
to pouch young to sustain their growth is less than 5%, and may not be detectable with the current methodology. 相似文献
3.
Delorme M Thomas DW 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(2):123-132
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 相似文献
4.
Dawson TJ McTavish KJ Munn AJ Holloway J 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2006,176(1):45-53
The Eastern Grey Kangaroo (Macropus giganteus) occurs mostly in the wetter regions of eastern Australia. However, in the past 30–40 years it has moved into more arid regions
(rainfall<250 mm), thus increasing its overlap zone with the xeric adapted Red Kangaroo (Macropus rufus). An increased access to water (supplied for domestic stock) may explain this range extension, but changes in the availability
of preferred feed could also be involved. The water use, drinking patterns and thermoregulatory behaviour of these two species
of kangaroo have been examined in a semi-free range study, during summer at an arid rangeland site. Foraging was largely nocturnal
in both species and during the day they behaved to reduce heat loads. This was especially so for M. giganteus, which showed greater shade seeking. However, it still used more water (72±2.6 mL kg−1 day−1, mean ± SE) than M. rufus (56±7.6 mL kg−1 day−1) and drank twice as frequently. Although M. giganteus produced a less concentrated urine (1422±36 mosmol kg−1) than M. rufus (1843±28 mosmol kg−1), kidney physiology did not explain all of the differences in water metabolism between the species. Water from the feed and
faecal water retention also appear to be involved. Broadly, a better access to reliable water and the utilisation of mesic
microhabitats has enabled M. giganteus to make inroads into the changing rangelands of eastern Australia. However, changes in the vegetation, due to stock grazing,
have also favoured M. giganteus, which is a grass eating specialist. 相似文献
5.
Mutay Aslan Gultekin Yucel Hakan Bozcuk Burhan Savas 《Cancer immunology, immunotherapy : CII》1998,47(3):176-181
Secondary infections related to neutropenia and functional defects of phagocytes are common consequences in patients treated
for cancer. The hematopoietic colony-stimulating factors (CSF) have been introduced into clinical practice as additional supportive
measures that can reduce the incidence of infectious complications in patients with cancer and neutropenia. The aim of this
study was to determine the role of␣granuolcyte/macrophage(GM)-CSF and granulocyte(G)-CSF in enhancing in vivo human neutrophil
function. A luminol-dependent chemiluminescence assay was developed to evaluate whether the repair in neutropenia accompanies
the ability of neutrophils to function. A dose of 5 μg G-CSF kg−1 day−1 [recombinant human (rHu) G-CSF; filgrastim] or 250 μg GM-CSF m−2 day−1 (rHu GM-CSF; molgramostim) was administered subcutaneously once daily to 12 metastatic cancer patients being treated with
different cytotoxic regimens. All injections of CSF were given after the initiation of neutropenia and continued until the
occurrence of an absolute neutrophil recovery. rHu GM-CSF and rHu G-CSF, administered once daily at the 250 μg m−2 day−1 and 5 μg kg−1 day−1 level, were effective in increasing the absolute neutrophil count and neutrophil function, as measured by an automated chemiluminescence
system.
Received: 26 February 1998 / Accepted: 21 May 1998 相似文献
6.
D. Moro S. D. Bradshaw 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(6):419-428
The coexistence of the Lakeland Downs short-tailed mouse Leggadina lakedownensis and house mouse Mus domesticus on Thevenard Island, in the arid north of Western Australia, prompted a study to compare their seasonal water and sodium
metabolism using tritiated water and sodium-22 as tracers. Fractional water influx rates for M. domesticus (40.3 ± 1.6% total body-water day−1) were significantly higher than those for L. lakedownensis (25.3 ± 1.2% total body-water day−1). Water effluxes were higher in both species of mouse after the passage of a cyclonic storm near the study site. Water flux
differences remained significant between species when turnover rates were scaled with body mass. A comparison of water influx
rates of M. domesticus with those predicted for field populations of other eutherian rodents showed that rates for M. domesticus on Thevenard Island were higher than expected. In contrast, water influx rates for L. lakedownensis did not differ significantly from expected values for a desert rodent. Rates of sodium influx for M. domesticus (41.7 ± 3.6 mmol kg−1 day−1) were over twice those of L. lakedownensis (19.7 ± 4.8 mmol kg−1 day−1), and were reflected in the significantly higher concentrations of sodium ingested in the diet, and excreted in the urine,
of M. domesticus. Furthermore, the rate of water influx was positively correlated with the rate of sodium influx in M. domesticus, suggesting that they were obtaining both water and sodium from the one dietary source. There was no evidence to suggest
that mice of either species were experiencing water or sodium stress, because water and sodium influxes and effluxes remained
in balance. These results suggest that M. domesticus on Thevenard Island had a higher-than-expected daily water requirement, and may represent a mesic deme of house mice that
have yet to adapt to the island environment.
Accepted: 9 May 1999 相似文献
7.
Phase I trial of interleukin-2 and high-dose arginine butyrate in metastatic colorectal cancer 总被引:4,自引:0,他引:4
Douillard JY Bennouna J Vavasseur F Deporte-Fety R Thomare P Giacalone F Meflah K 《Cancer immunology, immunotherapy : CII》2000,49(1):56-61
Interleukin-2 (IL-2) and sodium butyrate allow rats to be cured of peritoneal carcinomatosis from colon cancer. We performed
a phase I trial of IL-2 and high-dose arginine butyrate (ArgB) in patients with advanced metastatic colorectal cancer. Patients and methods: From April to July 1997, six patients were included in the trail; they had a median age of 52 years, four had a performance
status of 0, two had a performance status of 1 with normal biological functions. All patients had received at least two prior
lines of chemotherapy. A fixed dose of 18 MIU/m2 IL-2,was administered by subcutaneous injection and ArgB was delivered via continuous intravenous infusion on days 1–6 with
escalating doses starting at 2 g kg−1 day−1. Results: The planned dose escalation was not possible because of toxicities. A daily ArgB dose of 2 g/kg was delivered for nine cycles.
Level 2 (4 g/kg) could not be delivered in three of the six patients because of liver toxicity. The dose-limiting toxicities
were fatigue and liver function disturbances. The maximum tolerated dose for ArgB was 3 g kg−1 day−1, in combination with IL-2 at 12 MIU m2 day−1. No clinical response was seen. Pharmacokinetic analysis showed large intra- and interindividual variations. Conclusion: This schedule with a high dose of ArgB proved to be highly toxic with liver insufficiency. We will be running another trial
with lower doses of ArgB calculated from the schedule used in the experimental model, starting at a dose of 20 mg kg−1 day−1 for ArgB and 200 000 UI kg−1 day−1 IL-2, every 8 h.
Received: 13 May 1999 / Accepted: 28 October 1999 相似文献
8.
Bradshaw SD Bradshaw FJ 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(8):569-580
A method is described, based on the simultaneous turnover of both stable (18O) and radioactive isotopes (3H and 22Na), whereby the daily nectar and pollen intake of free-ranging marsupial honey possums (Tarsipes rostratus) may be estimated. The field metabolic rate is measured using doubly labelled water and nectar intake is estimated independently
from the measured water and sodium fluxes. The method assumes that free-water intake is negligible (but may be accounted for
if not the case), that virtually all dietary sodium is derived from nectar rather than from pollen, and that the animals are
in energetic balance over the period of measurement. These assumptions have been tested and found to be robust, except during
periods of heavy rain when significant intakes of free-water were recorded. Leaching experiments with pollen grains suggest
that less than 10% of the sodium ingested by honey possums is derived from pollen and calculations thus assumed a 90%:10%
split between nectar and pollen. Nectar intake averaged 5.9 ± 0.6 ml · day−1 and regressing nectar intake on daily change in body mass predicts an intake of approximately 7 ml · day−1 nectar to maintain balance for a 9 g honey possum. Estimates of pollen intake averaged 660 ± 156 mg · day−1 and a similar regression analysis of the data predicts that a daily intake of approximately 1 g pollen would be needed to
maintain mass balance of honey possums. Estimated nectar and pollen intakes did not differ significantly between males and
females, but nectar intake was higher in winter compared with dry periods of the year. The sugar content of nectar falls during
winter, however, and the overall energy derived from nectar thus remains roughly constant. Estimates of pollen and nectar
intake for individual animals were not significantly correlated, suggesting that honey possums forage selectively for these
two food items.
Accepted: 19 August 1999 相似文献
9.
Bradshaw FJ Bradshaw SD 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2001,171(1):59-67
A nitrogen balance feeding trial was carried out with the marsupial honey possum, Tarsipes rostratus, using four pollen-honey diets varying in nitrogen content from 9.4 mg · g−1 to 2.3 mg · g−1 dry matter. The dietary maintenance nitrogen requirement (MNR) was determined by regression analysis as 89 ± 21 mg N · kg−0.75 · day−1 and the truly digestible MNR was 79 mg N · kg−0.75 · day−1.. Regressing nitrogen balance on daily nitrogen intake separately for ten males and seven females revealed that the slopes
of the fitted lines did not vary significantly, but the difference in the intercepts approached significance. This suggests
that the MNR for females may be lower than that of males. The nitrogen digestibility of the diet was 76% and the biological
value (BV) was 58%. A comparison of the MNR of the honey possum with that of other marsupials shows that it is indeed much
lower than that of herbivorous macropodid marsupials and is close to that of the sap- and gum-feeding sugar glider, Petarurus breviceps. The endogenous urinary nitrogen excretion (EUN) of the honey possum was 42 mg N · kg−0.75 · day−1 and a regression analysis with other published data showed that the EUN per unit basal heat production is significantly lower
than that of eutherian mammals. Measurements of the actual feeding rates of animals in the field, taken together with the
low MNR, do not lend support to the hypothesis that the honey possum exhibits a reduced rate of reproduction due to a deficiency
in dietary nitrogen. It is possible that the quality of nitrogen provided by pollen, as reflected in its composition of essential
amino acids, may be a limiting factor.
Accepted: 15 September 2000 相似文献
10.
Kanesa May Duncan 《Environmental Biology of Fishes》2006,76(2-4):139-149
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. 相似文献
11.
C. Lydersen K. M. Kovacs M. O. Hammill I. Gjertz 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(7):405-411
In this study we measure energy intake via milk in nursing bearded seal (Erignathus barbatus) pups and determine how this energy is allocated into metabolism and storage of new tissues. This was accomplished using
longitudinal mass gain records and the doubly labelled water technique on nursing pups in combination with cross-sectional
data on changes in milk composition from bearded seal mothers. The pups (n=3) were all less than a week old at the start of the experiments. Pups gained 3.3±0.4 kg·day-1 of which 50% was fat, 14% protein and 36% water. Average daily water influx for the pups was 69.5±9.0 ml · kg-1· day-1. Average CO2 production during the study period was 0.99±0.10 ml·g-1·h-1, which corresponds to a field metabolic rate of 642±67 kJ·kg-1· day-1, or 6.0±0.5 times the predicted basal metabolic rate according to Kleiber (1975). The pups drank an average of 7.6±0.5 kg
of milk daily. This corresponds to a daily energy intake of 154±8 MJ, 47±14% of which was stored as new body tissue. Despite
this high energy intake bearded seal pups do not get as fat as do other nursing phocids. This is in part due to their larger
body size but also due to their very active aquatic lifestyle and the lower and more consistent fat content of the milk compared
to other phocid species. Bearded seal mothers forage during lactation and may also be involved in teaching their pups to feed
independently. All these data suggest that the lactation strategy of bearded seals differs from the phocid norm. 相似文献
12.
Juan Fuentes F. B. Eddy 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(6):438-443
Drinking in Atlantic salmon (Salmo salar) juveniles was investigated in fresh water and following transfer to sea water. There was a significant effect of fish size
on drinking, and smolts (20–30 g) imbibed about ten times less water than alevins of 0.2–0.3 g. Freshwater smolts drank at
a rate of 0.15 ± 0.03 ml · kg−1 · h−1 and administration of doses of 10 or 20 mg · kg−1 of papaverine (stimulator of the renin- angiotensin system RAS) or [Asn1, Val5]-Angiotensin II (0.4 μmol · kg−1) resulted in significant increases in drinking, while administration of the angiotensin converting enzyme inhibitor, enalapril
(50 mg · kg−1) had no effect on drinking. Transfer of Atlantic salmon smolts to 1/3, 2/3 and full strength sea water resulted in significant
increases in drinking to 1.06 ± 0.12, 1.24 ± 0.0.16 and 3.89 ± 0.28 ml · kg−1 · h−1, respectively. In sea water, stimulation of the endogenous RAS by administration of papaverine (20 mg · kg−1) resulted in a 20% increase in drinking, while administration of enalapril to doses of 50 and 200 mg · kg−1 lowered drinking to 1.99 ± 0.48 and 0.32 ± 0.06 ml · kg−1 · h−1, respectively. All treatments were without effect on blood plasma levels of Na+ and Cl− in fresh water, while in sea water smolts both stimulation and inhibition of drinking resulted in hemoconcentration of Na+ and Cl−. The role of the renin angiotensin system in control of drinking and hydromineral balance in Atlantic salmon is discussed.
Accepted: 27 February 1997 相似文献
13.
John A. Hawley Garry S. Palmer Timothy D. Noakes 《European journal of applied physiology and occupational physiology》1997,75(5):407-412
This study compared the effects of supplementing the normal diets of six trained cyclists [maximal oxygen uptake O2max) 4.5 (0.36)l · min−1; values are mean (SD)] with additional carbohydrate (CHO) on muscle glycogen utilisation during a 1-h cycle time-trial (TT).
Using a randomised crossover design, subjects consumed either their normal diet (NORM) for 3 days, which consisted of 426
(137) g · day−1 CHO [5.9 (1.4) g · kg−1 body mass (BM)], or additional CHO (SUPP) to increase their intake to 661 (76) g · day−1 [9.3 (0.7) g · kg−1 BM]. The SUPP diet elevated muscle glycogen content from 459 (83) to 565 (62) mmol · kg−1 dry weight (d.w.) (P < 0.05). However, despite the increased pre-exercise muscle glycogen stores, there was no difference in the distance cycled
during the TT [40.41 (1.44) vs 40.18 (1.76) km for NORM and SUPP, respectively]. With NORM, muscle glycogen declined from
459 (83) to 175 (64) mmol · kg−1 d.w., whereas with SUPP the corresponding values were 565 (62) and 292 (113) mmol · kg−1 d.w. Accordingly, both muscle glycogen utilisation [277 (64) vs 273 (114) mmol · kg−1 d.w.] and total CHO oxidation [169 (20) vs 165 (30) g · h−1 for NORM and SUPP, respectively] were similar. Neither were there any differences in plasma glucose or lactate concentrations
during the two experimental trials. Plasma glucose concentration averaged 5.5 (0.5) and 5.6 (0.6) mmol · l−1, while plasma lactate concentration averaged 4.4 (1.9) and 4.4 (2.3) mmol · l−1 for NORM and SUPP, respectively. The results of this study show that when well-trained subjects increase the CHO content
of their diet for 3 days from 6 to 9 g · kg−1 BM there is only a modest increase in muscle glycogen content. Since supplementary CHO did not improve TT performance, we
conclude that additional CHO provides no benefit to performance for athletes who compete in intense, continuous events lasting
1 h. Furthermore, the substantial muscle CHO reserves observed at the termination of exercise indicate that whole-muscle glycogen
depletion does not determine fatigue at this exercise intensity and duration.
Accepted: 25 November 1996 相似文献
14.
Anaerobic co-digestion of dairy manure with mulched switchgrass for improvement of the methane yield
The owners of farm-scale anaerobic digesters are relying on off-farm wastes or energy crops as a co-digestion feedstock with
animal manure in order to increase their production of methane and thus revenues. Switchgrass represents an interesting feedstock
for Canadian digesters owners as it is a high-yielding low-maintenance perennial crop, well adapted to northern climate. Methane
potential assays in batch tests showed methane production of 19.4 ± 3.6, 28.3 ± 1.7, 37.3 ± 7.1 and 45.7 ± 0.8 L kg−1, for raw manure, blended manure, manure and mulched switchgrass, manure and pretreated switchgrass, respectively. Two 6-L
lab-scale anaerobic digesters were operated for 130 days in order to assess the benefit of co-digesting switchgrass with bovine
manure (digester #2), at a 20% wet mass fraction, compared with a manure-only operation (digester #1) The digesters were operated
at an hydraulic retention time of 37 ± 6 days and at loads of 2.4 ± 0.6 and 2.6 ± 0.6 kg total volatile solids (TVS) L−1 day−1 for digesters #1 (D1) and #2 (D2), respectively. The TVS degradation reached 25 and 39%, which resulted in a methane production
of 1.18 ± 0.18 and 2.19 ± 0.31 L day−1 for D1 and D2, respectively. The addition of 20% on a wet mass ratio of switchgrass to a manure digester increased its methane
production by 86%. The co-digestion of switchgrass in a 500 m3 manure digester could yield up to 10.2 GJ day−1 of purified methane or 1.1 MWh day−1 of electricity. 相似文献
15.
Effects of the burrowing mayfly,Hexagenia, on nitrogen and sulfur fractions in lake sediment microcosms 总被引:1,自引:1,他引:0
Effects of the burrowing mayfly, Hexagenia, on nitrogen and sulfur fractions of sediment, and overlying water were determined. Laboratory microcosms were used to reproduce
the benthic environment. The activities of Hexagenia increased sediment Eh (1.98 ± 0.486 (22) mV · day −1), and decreased pH in sediment (−0.007 ± 0.001 (22) day −1) and overlying water(-0.024 ± 0.004 (10) day−1). In the control, Eh decreased and pH did not change. The presence of Hexagenia also markedly increased ammonia in sediment (5.46 ± 0.14 (22) ppm N · day−1) and overlying water (0.792 ± 0.154 (10) ppm N · day−1), while the control did not change. In addition, the sulfate fraction of sediment (0.177 ± 0.006 (17)% dry mass) and water
(50.0 ± 4.9 (5) mg · I−1) in microcosms with Hexagenia was greater than that of the control (0.151 ± 0.005 (16)% dry mass; 14.7 ± 1.71 (3) mg · 1−1) at the termination of the experiment. Hexagenia may also stimulate the mineralization of carbon-bonded sulfur. The general role of Hexagenia in altering sediment chemistry is discussed. 相似文献
16.
Pass GJ Foley WJ 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(3):185-192
The effect of the phenolic glycoside, salicin, on food intake of the common brushtail possum (Trichosurus vulpecula) was studied in a series of feeding experiments. Increasing the concentration of salicin in a diet of fruits and cereals
led to significant reductions of food intake in the short term (6 days). After prolonged (20 days) exposure to salicin, food
intake (19 g kg−0.75 day−1) was still reduced relative to controls (31 g kg−0.75 day−1) but not reduced to the same extent as in the short-term experiments. Nonetheless, over these 20 days, common brushtail possums
regulated their intake of salicin so as not to exceed a threshold limit of 1.9 ± 0.1 g kg−0.75 day−1. Manipulative experiments sought to determine whether this threshold intake was in response to pre-ingestive factors (taste)
or the post-ingestive consequences of ingesting salicin. Dietary salicin (0.17–5.0% DM) had no significant effect on nitrogen
balance or urea metabolism and injection of a specific serotonin receptor antagonist, ondansetron, did not lead to increases
in salicin intake as has been found for some other plant secondary metabolites. Similarly, administration of 1.3 g salicin
by gavage had no significant effect on the subsequent intake of salicin compared to controls that were gavaged with water.
We concluded that pre-ingestive factors were responsible for common brushtail possums limiting their intake of salicin-rich
diets rather than any measurable post-ingestive consequence of feeding.
Accepted: 7 December 1999 相似文献
17.
Sandy clay loam soil was contaminated with 5000 mg kg−1 diesel, and amended with nitrogen (15.98 atom% 15N) at 0, 250, 500, and 1000 mg kg−1 to determine gross rates of nitrogen transformations during diesel biodegradation at varying soil water potentials. The observed
water potential values were −0.20, −0.47, −0.85, and −1.50 MPa in the 0, 250, 500, and 1000 mg kg−1 nitrogen treatments respectively. Highest microbial respiration occurred in the lowest nitrogen treatment suggesting an inhibitory
osmotic effect from higher rates of nitrogen application. Microbial respiration rates of 185, 169, 131, and 116 mg O2 kg−1 soil day−1 were observed in the 250, 500, control and 1000 mg kg−1 nitrogen treatments, respectively. Gross nitrification was inversely related to water potential with rates of 0.2, 0.04,
and 0.004 mg N kg−1 soil day−1 in the 250, 500, and 1000 mg kg−1 nitrogen treatments, respectively. Reduction in water potential did not inhibit gross nitrogen immobilization or mineralization,
with respective immobilization rates of 2.2, 1.8, and 1.8 mg N kg−1 soil day−1, and mineralization rates of 0.5, 0.3, and 0.3 mg N kg−1 soil day−1 in the 1000, 500, and 250 mg kg−1 nitrogen treatments, respectively. Based on nitrogen transformation rates, the duration of fertilizer contribution to the
inorganic nitrogen pool was estimated at 0.9, 1.9, and 3.2 years in the 250, 500, and 1000 mg kg−1 nitrogen treatments, respectively. The estimation was conservative as ammonium fixation, gross nitrogen immobilization, and
nitrification were considered losses of fertilizer with only gross mineralization of organic nitrogen contributing to the
most active portion of the nitrogen pool. 相似文献
18.
Hidenobu Kunii 《Ecological Research》1988,3(3):305-318
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. 相似文献
19.
Susumu S. Abe Takashi Kotegawa Taisuke Onishi Yoshinori Watanabe Toshiyuki Wakatsuki 《Ecological Research》2012,27(1):219-227
This study investigated the influence of mound-building termites on soil particle dynamics on the land surface and in soil-forming
processes by examining the amount of soil particles in mound structures of Macrotermes bellicosus in a highly weathered Ultisol of tropical savanna. Soil particle turnover via the mounds was estimated using particle stock
data and soil turnover data from previous studies. A 4-ha study plot with six mounds of relatively uniform shape and size
was investigated. Soil mass constituting the mounds was 6,166 ± 1,581 kg mound−1 within which the mound wall and nest body accounted for 5,002 ± 1,289 and 1,164 ± 293 kg, respectively. The mound wall contained
a significantly larger amount of clay (252 ± 9.97 g kg−1) balanced with a lower sand content (676 ± 26.5 g kg−1) than in the adjacent surface (Ap1) horizon, (46.4 ± 12.8 g clay kg−1; 866 ± 83.2 g sand kg−1); the nest body had much higher clay content (559 ± 51.0 g kg−1) but less sand (285 ± 79.2 g kg−1) than the mound wall. As a result, the mounds of M. bellicosus accumulated clay of 2,874 ± 781 kg ha−1 (corresponding to 2.52% of clay stock in the Ap1 horizon) along with an estimated clay turnover rate of 169 kg ha−1 year−1. These findings suggest a positive feedback effect from termite mound-building activity on soil particle dynamics in tropical
savanna ecosystems: M. bellicosus preferentially use subsoil material for mound construction, resulting in relocation of illuvial clay in the subsoil to the
land surface where clay eluviation from the surface soil and its illuviation in the subsoil are major soil-forming processes. 相似文献
20.
Simultaneous nutrients and carbon removal during pretreated swine slurry degradation in a tubular biofilm photobioreactor 总被引:1,自引:0,他引:1
Ignacio de Godos Cristina González Eloy Becares Pedro A. García-Encina Raúl Muñoz 《Applied microbiology and biotechnology》2009,82(1):187-194
The biodegradation potential of an innovative enclosed tubular biofilm photobioreactor inoculated with a Chlorella sorokiniana strain and an acclimated activated sludge consortium was evaluated under continuous illumination and increasing pretreated
(centrifuged) swine slurry loading rates. This photobioreactor configuration provided simultaneous and efficient carbon, nitrogen,
and phosphorous treatment in a single-stage process at sustained nitrogen and phosphorous removals efficiencies ranging from
94% to 100% and 70–90%, respectively. Maximum total organic carbon (TOC), NH4
+, and PO4
3− removal rates of 80 ± 5 g C mr
−3 day−1, 89 ± 5 g N mr
−3 day−1, and 13 ± 3 g P mr
−3 day−1, respectively, were recorded at the highest swine slurry loadings (TOC of 1,247 ± 62 mg L−1, N–NH4
+ of 656 ± 37 mg L−1, P–PO4
3+ of 117 ± 19 mg L−1, and 7 days of hydraulic retention time). The unusual substrates diffusional pathways established within the phototrophic
biofilm (photosynthetic O2 and TOC/NH4
+ diffusing from opposite sides of the biofilm) allowed both the occurrence of a simultaneous denitrification/nitrification
process at the highest swine slurry loading rate and the protection of microalgae from any potential inhibitory effect mediated
by the combination of high pH and high NH3 concentrations. In addition, this biofilm-based photobioreactor supported efficient biomass retention (>92% of the biomass
generated during the pretreated swine slurry biodegradation). 相似文献