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1.
Diversity of lactic acid bacteria and yeasts in Airag and Tarag,traditional fermented milk products of Mongolia 总被引:2,自引:1,他引:1
Koichi Watanabe Junji Fujimoto Masae Sasamoto Jamyan Dugersuren Tseveendori Tumursuh Shirchin Demberel 《World journal of microbiology & biotechnology》2008,24(8):1313-1325
We used culture- and molecular-biology-based methods to investigate microbial diversity in the traditional Mongolian fermented
milks “Airag” (fermented mare’s milk) and “Tarag” (fermented milk of cows, yaks, goats, or camels). By rRNA or functional
gene sequencing, we identified 367 lactic acid bacteria (LAB) strains and 152 yeast strains isolated from 22 Airag and 31
Tarag samples. The total concentration of LAB in Airag (107.78 ± 0.50 c.f.u. ml–1; mean ± SD) was significantly lower (P < 0.01) than in Tarag (108.35 ± 0.62 c.f.u. ml−1), whereas the total concentration of yeasts in Airag (107.41 ± 0.61 c.f.u. ml-1) was significantly higher (P < 0.01) than in Tarag (105.86 ± 1.29 c.f.u. ml-1). Lactobacillus helveticus and Lactobacillus kefiranofaciens were isolated from Airag as the predominant LAB strains at levels of about 107 c.f.u. ml−1, whereas Lactobacillus delbrueckii subsp. bulgaricus, L. helveticus, and Streptococcus thermophilus were the predominant isolates from Tarag at about 107 c.f.u. ml−1. The lactose-fermenting Kluyveromyces marxianus was isolated predominantly from Airag as its major alcoholic fermentation component. Non-lactose-fermenting yeasts such as
Saccharomyces cerevisiae, Issatchenkia orientalis, and Kazachstania unispora were the predominant isolates from Tarag, at about 105 c.f.u. ml−1. The apparent geographic differences in the L. kefiranofaciens and S. thermophilus contents of Tarag strongly suggested that differences among the animal species from which the milk was sourced, rather than
geographic distances, were the most important factors influencing the diversity of the microbial composition of traditional
fermented milks in Mongolia. 相似文献
2.
The use of clove oil as a potential anaesthetic for freshwater amphipods was examined at 20 °C. Individuals of Gammarus minus, a common species in southern Illinois, USA, spanning the entire body size range (4.3–14.3 mm), were used to test four anaesthetic
concentrations varying from 1.48 × 10−4 ml ml−1 to 5.9 × 10−4 ml ml−1. Small-bodied individuals (mean size = 5.4 mm ± 0.27SE) were used to test additional concentrations, up to 14.7 × 10−4 ml ml−1, a 10-fold span, to identify potential lethal concentrations. At the lowest concentration, time to anaesthesia and recovery
was constant at all body sizes. For the three next higher concentrations, time to anaesthesia decreased with increasing concentration
while recovery time increased. Activity of amphipods was not affected by the ethanol carrier. In addition, activity did not
differ between amphipods that had recovered from anaesthesia and unexposed amphipods. At clove oil concentrations of 8.84
× 10−4 ml ml−1 and 14.7 × 10−4 ml ml−1, mortality was 7 and 40%, respectively, indicating, that 5.9 × 10−4 ml ml−1 was a safe working concentration. No mortality was observed with Gammarus acherondytes, a federally endangered cave amphipod on which the protocol with 80 μl of stock was used in the field. The method enabled
us to obtain information on the endangered amphipod which normally would have required the sacrifice of individuals. Thus,
research can continue on species for which population numbers are low and for which basic information is needed to formulate
meaningful recovery plans. 相似文献
3.
Butler DG 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(7):733-742
Pekin ducks (Anas platyrhynchos) were bilaterally adrenalectomized (biADX), injected with 1 mg of triamcinolone (TRIAM) kg bw−1 im and given 0.9% saline drinking water during a 24 h recovery period followed by chemical sympathectomy with 6OH DOPA 3 h
before the start of experimental observations. Baseline plasma dopamine (DA) concentrations decreased from 283 ± 88.5 pmol ml−1 to 42.4 ± 11.1 pmol ml−1; epinephrine (E) from 142 ± 46 pmol ml−1 to 18.4 ± 9.2 pmol ml−1 and norepinephrine (NE) from 742 ± 84 pmol ml−1 to 406 ± 38 pmol ml−1 1 day after biADX + TRIAM but before chemical sympathectomy. Baseline MABP increased from 132 ± 3.2 mmHg to 209 ± 14.3 mmHg
(P < 0.05) in response to TRIAM. After chemical sympathectomy with 6OH DOPA there was an additional 90% decrease in plasma NE
to 42 ± 9.4 pmol ml−1 and a concurrent 60% decrease in MABP to 83.4 ± 6.9 mmHg (P < 0.05). Nasal fluid secretion was maintained by the continuous infusion of hypertonic saline (1,000 mosmol kg H2O−1 at a rate of 0.3 ml kg−1 min−1). Rates of nasal fluid secretion and fluid electrolyte concentrations were unchanged following biADX + TRIAM + 6OH DOPA.
Angiotensin II (ANG II; dose 1 μg kg bw−1 i.v.), attenuated nasal fluid secretion showing that the response to ANG II was not NE- dependent. Plasma NE concentrations
decreased following Tyramine i.v. (33 ± 8.5 pmol ml−1) there being no vasopressor response. This is the first report of the ANG II induced attenuation of duck salt gland secretion
in the absence of measurable E and NE. 相似文献
4.
Limnological characteristics of the freshwater ecosystems of Byers Peninsula, Livingston Island, in maritime Antarctica 总被引:2,自引:0,他引:2
M. Toro A. Camacho C. Rochera E. Rico M. Bañón E. Fernández-Valiente E. Marco A. Justel M. C. Avendaño Y. Ariosa W. F. Vincent A. Quesada 《Polar Biology》2007,30(5):635-649
A limnological survey of 15 lakes and 6 streams was carried out on Byers Peninsula (Livingston Island, South Shetland Islands,
Antarctica) during austral summer 2001–2002. Most of the surface waters had low conductivities (20–105 μS cm−1) and nutrients (total phosphorus 0.01–0.24 μM), but some coastal lakes were enriched by nutrient inputs from seal colonies
and marine inputs. Plankton communities in the lakes contained picocyanobacteria (102–104 cells ml−1), diatoms, chrysophytes and chlorophytes, and a large fraction of the total biomass was bacterioplankton. Zooplankton communities
were dominated by Boeckella poppei and Branchinecta gainii; the benthic cladoceran Macrothrix ciliata was also recorded, for the first time in Antarctica. The chironomids Belgica antarctica and Parochlus steinenii, and the oligochaete Lumbricillus sp., occurred in stream and lake benthos. The phytobenthos included cyanobacterial mats, epilithic diatoms and the aquatic
moss Drepanocladus longifolius. These observations underscore the limnological richness of this seasonally ice-free region in maritime Antarctica and its
value as a long-term reference site for monitoring environmental change. 相似文献
5.
We evaluated the combined effects of algal (Chlorella vulgaris) food levels (low, 0.5 × 106 (or 2.9 μg C ml−1); and high, 1 × 106 cells ml−1 (or 5.8 μg C ml−1)) and zinc concentrations (0, 0.125, and 0.250 mg l−1 of ZnCl2) on the competition between two common planktonic rotifers Anuraeopsis fissa and Brachionus rubens using their population growth. Median lethal concentration data (LC50) (mean ± 95% confidence intervals) showed that B. rubens was more resistant to zinc (0.554 ± 0.08 mg l−1) than A. fissa (0.315 ± 0.07 mg l−1). A. fissa when grown alone or with Zn was always numerically more abundant than B. rubens. When grown in the absence of zinc, under low- and high-food levels, the peak abundances of A. fissa varied from 251 ± 24 to 661 ± 77 ind. ml−1, respectively, and the corresponding maxima for B. rubens were 52 ± 3 and 102 ± 18 ind. ml−1. At a given food level, competition for food reduced the peak abundances of both rotifers considerably. Increase in Zn concentration
also lowered the rotifer abundances. The impact of zinc on competition between the two-rotifer species was evident at low-food
level, mainly for A. fissa. At zinc concentrations of 0 and 0.125 mg l−1, the populations of both rotifers continued to grow for about 10 days, but thereafter B. rubens began to decline. Role of zinc on the competitive outcome of the two species is discussed in relation to the changing algal
densities in natural water bodies. 相似文献
6.
C. Schirlo A. Bub C. Reize A. Bührer J. Kohl E. A. Koller 《European journal of applied physiology and occupational physiology》1997,75(2):124-131
To investigate the role of fluid shifts during the short-term adjustment to acute hypobaric hypoxia (AHH), the changes in
lower limb (LV) and forearm volumes (FV) were measured using a strain-gauge plethysmograph technique in ten healthy volunteers
exposed to different altitudes (450 m, 2500 m, 3500 m, 4500 m) in a hypobaric chamber. Arterial blood pressure, heart rate,
arterial oxygen saturation (S
aO2), endtidal gases, minute ventilation and urine flow were also determined. A control experiment was performed with an analogous
protocol under normobaric normoxic conditions. The results showed mean decreases both in LV and FV of −0.52 (SD 0.39) ml · 100
ml−1 and −0.65 (SD 0.32) ml · 100 ml−1, respectively, in the hypoxia experiments [controls: LV −0.28 (SD 0.37), FV −0.41 (SD 0.47) ml · 100 ml−1]. Descent to normoxia resulted in further small but not significant decreases in mean LV [−0.02 (SD 0.11) ml · 100 ml−1], whereas mean FV tended to increase slightly [ + 0.02 (SD 0.14) ml · 100 ml−1]; in the control experiments mean LV and FV decreased continuously during the corresponding times [−0.19 (SD 0.31), −0.18
(SD 0.10) ml · 100 ml−1, respectively]. During the whole AHH, mean urine flow increased significantly from 0.84 (SD 0.41) ml · min−1 to 3.29 (SD 1.43) ml · min−1 in contrast to the control conditions. We concluded that peripheral fluid volume shifts form a part of the hypoxia-induced
acute cardiovascular changes at high altitude. In contrast to the often reported formation of peripheral oedema after prolonged
exposure to hypobaric hypoxia, the results provided no evidence for the development of peripheral oedema during acute induction
to high altitude. However, the marked increase in interindividual variance in S
aO2 and urine flow points to the appearance of the first differences in the short-term adjustment even after 2 h of acute hypobaric
hypoxia.
Accepted: 27 August 1996 相似文献
7.
Nigel J. Adams Berry Pinshow Leonard Z. Gannes 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(6):444-450
We used tritium-labeled water to measure total body water, water influx (which approximated oxidative water production) and
water efflux in free-flying tippler pigeons (Columba livia) during flights that lasted on average 4.2 h. At experimental air temperatures ranging from 18 to 27 °C, mean water efflux
by evaporation and excretion [6.3 ± 1.3 (SD) ml · h−1, n = 14] exceeded water influx from oxidative water and inspired air (1.4 ± 0.7 ml · h−1, n = 14), and the birds dehydrated at 4.9 ± 0.9 ml · h−1. This was not significantly different from gravimetrically measured mass loss of 6.2 ± 2.1 g · h−1 (t = 1.902, n = 14, P>0.05). This flight-induced dehydration resulted in an increase in plasma osmolality of 4.3 ± 3.0 mosmol · kg−1 · h−1 during flights of 3–4 h. At 27 °C, the increase in plasma osmolality above pre-flight levels (ΔP
osm = 7.6±4.29 mosmol · kg−1 · h−1, n = 6) was significantly higher than that at 18 °C (ΔP
osm = 0.83±2.23 mosmol · kg−1 · h−1, (t = 3.43, n = 6, P < 0.05). Post-flight haematocrit values were on average 1.1% lower than pre-flight levels, suggesting plasma expansion. Water
efflux values during free flight were within 9% of those in the one published field study (Gessaman et al. 1991), and within
the range of values for net water loss determined from mass balance during wind tunnel experiments (Biesel and Nachtigall
1987). Our net water loss rates were substantially higher than those estimated by a simulation model (Carmi et al. 1992) suggesting
some re-evaluation of the model assumptions is required.
Accepted: 8 April 1997 相似文献
8.
Ten accessions belonging to the Brassica oleracea subspecies alba and rubra, and to B. oleracea var. sabauda were used in this study. Protoplasts were isolated from leaves and hypocotyls of in vitro grown plants. The influence of selected factors on the yield, viability, and mitotic activity of protoplasts immobilized
in calcium alginate layers was investigated. The efficiency of protoplast isolation from hypocotyls was lower (0.7 ± 0.1 × 106 ml−1) than for protoplasts isolated from leaf mesophyll tissue (2 ± 0.1 × 106 ml−1). High (70–90%) viabilities of immobilized protoplasts were recorded, independent of the explant sources. The highest proportion
of protoplasts undergoing divisions was noted for cv. Reball F1, both from mesophyll (29.8 ± 2.2%) and hypocotyl (17.5 ± 0.3%)
tissues. Developed colonies of callus tissue were subjected to regeneration and as a result plants from six accessions were
obtained. 相似文献
9.
Sperling JB Grigg GC Beard LA Limpus CJ 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(7):779-786
Oxygen equilibrium curves and other respiratory-related variables were determined on blood from the flatback turtle (Natator depressus) and, for comparison, on some samples from the loggerhead turtle (Caretta caretta). The oxygen carrying capacity of the flatback turtle, 4.9–8.7 mmol l−1 (n = 49), is at the high end of the range in diving reptiles. Oxygen affinity (P50) was similar in both species at 5% CO2, ranging from 37 to 55 mmHg (43 mmHg ± 5.3 SD, n = 24, 25°C, pH 7.17) in flatbacks and 43–49 mmHg in loggerheads (46 mmHg ± 2.0 SD, n = 7, 25°C, pH 7.13), whereas at 2% CO2, flatbacks had a higher oxygen affinity. The curves differed in sigmoidicity, with Hill n coefficients of 2.8 and 1.9 in flatbacks and loggerheads, respectively. The Bohr effect was small in both the species, consistent
with results from other sea turtles. Lactate levels were high, perhaps because the samples were taken from turtles coming
ashore to lay eggs. Flatbacks are rarely found in waters deeper than 45 m. It is suggested that they have a respiratory physiology
particularly suited to sustain prolonged shallow dives. 相似文献
10.
Buatong Jirayu Phongpaichit Souwalak Rukachaisirikul Vatcharin Sakayaroj Jariya 《World journal of microbiology & biotechnology》2011,27(12):3005-3008
The aim of this work was to select endophytic fungi from mangrove plants that produced antimicrobial substances. Minimal inhibitory
concentrations (MIC) and minimal bactericidal concentrations (MBC) or minimal fungicidal concentrations (MFC) of crude extracts
from 150 isolates were determined against potential human pathogens by a colorimetric microdilution method. Ninety-two isolates
(61.3%) produced inhibitory compounds. Most of the extracts (28–32%) inhibited Staphylococcus aureus (MIC/MBC 4–200/64–200 μg ml−1). Only two extracts inhibited Pseudomonas aeruginosa (MIC/MBC 200/>200 μg ml−1). 25.5 and 11.7% inhibited Microsporum gypseum and Cryptococcus neoformans (MIC/MFC 4–200/8–200 μg ml−1 and 8–200/8–200 μg ml−1, respectively), while 7.5% were active against Candida albicans (MIC/MFC 32–200/32–200 μg ml−1). None of the extracts inhibited Escherichia coli. The most active fungal extracts were from six genera, Acremonium, Diaporthe, Hypoxylon, Pestalotiopsis, Phomopsis, and Xylaria as identified using morphological and molecular methods. Phomopsis sp. MA194 (GU592007, GU592018) isolated from Rhizophora apiculata showed the broadest antimicrobial spectrum with low MIC values of 8–32 μg ml−1against Gram-positive bacteria, yeasts and M. gypseum. It was concluded that endophytic fungi from mangrove plants are diverse, many produce compounds with antimicrobial activity
and could be suitable sources of new antimicrobial natural products. 相似文献
11.
Phylogenetic and Physiological Diversity of Bacteria Isolated from Puruogangri Ice Core 总被引:2,自引:0,他引:2
The microbial abundance, the percentage of viable bacteria, and the diversity of bacterial isolates from different regions
of a 83.45-m ice core from the Puruogangri glacier on the Tibetan Plateau (China) have been investigated. Small subunit 16S
rRNA sequences and phylogenetic relationships have been studied for 108 bacterial isolates recovered under aerobic growth
conditions from different regions of the ice core. The genomic fingerprints based on ERIC (enterobacterial repetitive intergenic
consensus)-polymerase chain reaction and physiological heterogeneity of the closely evolutionary related bacterial strains
isolated from different ice core depths were analyzed as well. The results showed that the total microbial cell, percentages
of live cells, and the bacterial CFU ranged from 104 to 105 cell ml−1 (Mean, 9.47 × 104; SD, 5.7 × 104, n = 20), 25–81%, and 0–760 cfu ml−1, respectively. The majority of the isolates had 16S rRNA sequences similar to previously determined sequences, ranging from
92 to 99% identical to database sequences. Based on their 16S rRNA sequences, 42.6% of the isolates were high-G + C-content
(HGC) gram-positive bacteria, 35.2% were low-G + C (LGC) gram-positive bacteria, 16.6% were Proteobacteria, and 5.6% were CFB group. There were clear differences in the depth distribution of the bacterial isolates. The isolates
tested exhibited unique phenotypic properties and high genetic heterogeneity, which showed no clear correlation with depths
of bacterial isolation. This layered distribution and high heterogeneity of bacterial isolates presumably reflect the diverse
bacterial sources and the differences in bacteria inhabiting the glacier’s surface under different past climate conditions. 相似文献
12.
Hans Mose Jensen Lorna Pedersen AnnDorte Burmeister Benni Winding Hansen 《Polar Biology》1999,21(5):269-278
The distribution of phytoplankton biomass and primary production were studied during summer 1993 at 16 stations from 65 to
72°N off West Greenland, ranging more than 900 km. Hydrography, nutrients and chlorophyll a profiles revealed a significant change in structure from south to north. Nitrate was depleted in the euphotic zone at most
stations except close to the ice edge (West Ice) or close to outflow from large glaciers. The vertical distribution of phosphate
followed that of nitrate, but was never depleted. Despite two stations with relatively high surface concentrations, silica
showed the same distribution as the other two nutrients. In the south, chlorophyll a concentration and primary production were lower than north of Disko Bay (69°N), associated with a well-mixed versus a salinity-generated
stratification, respectively. In Vaigat, a high-production station was identified, (st. 910, 69°52′69N–51°30′61W) with a chlorophyll a concentration in the euphotic zone of >13 μg l−1 and an area primary production of 3.2 g C m−2 day−1. This is seldom encountered in arctic waters and was presumably due to nutrient-rich melt-water originating from the Iluliíssat
Glacier. The overall primary production for the studied area was 67–3207 mg C m−2 day−1 (mean ± SD=341± 743 mg C m−2 day−1), which is within the range of the few results published for West Greenland and eastern Canadian Arctic waters.
Accepted: 24 October 1998 相似文献
13.
Effects of temperature, and availability of nitrogen and phosphorus on the abundance of Anabaena and Microcystis in Lake Biwa, Japan: an experimental approach 总被引:23,自引:0,他引:23
Under optimal nutrient conditions, both Microcystis sp. and Anabaena sp. isolated from Lake Biwa grew optimally at 28–32°C but differed in maximal growth rates, phosphate uptake kinetics, maximal
phosphorus quotas, and growth responses to nitrogen and phosphorus limitation. The maximal growth rates of Microcystis and Anabaena were 1.6 and 1.25 divisions day−1, respectively. With phosphate and nitrate in the growth-limiting range, the growth of Microcystis was optimal at an N : P ratio of 100 : 1 (by weight) and declined at lower (nitrogen limitation) and higher (phosphorus limitation)
ratios. In contrast, Anabaena growth rates did not change at N : P ratios from 1000 : 1 to 10 : 1. Starting with cells containing the maximal phosphorus
quota, Microcystis growth in minus-phosphorus medium ceased in 7–9 days, compared with 12–13 days for Anabaena. The phosphate turnover time in cultures starved to their minimum cell quotas was 7.9 min for Microcystis and 0.6 min for Anabaena. Microcystis had a higher K
s (0.12 μg P l−1 10−6 cells) and lower V
max (9.63 μg P l−1 h−1 10−6 cells), than Anabaena (K
s 0.02 μg P l−1 h−1 10−6 cells; V
max 46.25 63 μg P l−1 h−1 10−6 cells), suggesting that Microcystis would not be able to grow well in phosphorus-limited waters. We conclude that in spite of the higher growth rate under ideal
conditions, Microcystis does not usually bloom in the North Basin because of low availability of phosphorus and nitrogen. Although Anabaena has an efficient phosphorus-uptake system, its main strategy for growth in low-phosphorus environments may depend on storage
of phosphorus during periods of abundant phosphorus supply, which are rare in the North Basin.
Received: July 31, 2000 / Accepted: October 18, 2000 相似文献
14.
Blue-green algal blooms formed by Microcystis and Oscillatoria often occur in shallow eutrophic lakes, such as Lake Taihu (China) and Lake Kasumigaura (Japan). Growth characteristics
and competitions between Microcystis aeruginosa and Oscillatoria mougeotii were investigated using lake simulator systems (microcosms) at various temperatures. Oscillatoria was the superior competitor, which suppressed Microcystis, when temperature was <20°C, whereas the opposite phenomenon occurred at 30°C. Oscillatoria had a long exponential phase (20 day) and a low growth rate of 0.22 day−1 and 0.20 day−1 at 15°C and 20°C, respectively, whereas Microcystis had a shorter exponential phase (2–3 days) at 30°C and a higher growth rate (0.86 day−1). Interactions between the algae were stronger and more complex in the lake simulator system than flask systems. Algal growth
in the lake simulator system was susceptible to light attenuation and pH change, and algae biomasses were lower than those
in flasks. The outcome of competition between Microcystis and Oscillatoria at different temperatures agrees with field observations of algal communities in Lake Taihu, indicating that temperature
is a significant factor affecting competition between Microcystis and Oscillatoria in shallow, eutrophic lakes. 相似文献
15.
Optical fractionation of chlorophyll and primary production for coastal waters of the Southern Ocean 总被引:1,自引:1,他引:0
Our objective was to quantify the potential variability in remotely sensed chlorophyll a (Chl a) and primary productivity in coastal waters of the Southern Ocean. From data collected throughout the springs/summers of
1991–1994, we calculated the proportion of water column Chl a and primary productivity within the upper optical attenuation length (K −1
par) and the satellite-weighted depth. The temporal variability was resolved every 2–3 days and was observed to be greater within
years than between years. Three-year averages (n=223) revealed that 10.2 ± 3.6% of total Chl a and 14.8 ± 6.5% of production occurred within satellite-weighted depth in predominantly Case I waters. The average values
were twice as high within K −1
par, 24.1 ± 8% of total Chl a and 34 ± 9% of production respectively. Masked in these long-term averages are very large changes occurring on short time
scales of seasonal blooms. We observed that the patterns of Chl a vertical distribution within blooms are also subject to taxonomic influence and dependent upon the physiological state of
the phytoplankton. Highest proportions of water column Chl a in the first optical depth were measured during the rapid onset of surface cryptophyte blooms each year, i.e. 50% within
K −1
par and 30% above the satellite-weighted depth. Lowest fractions, 6% and 2% of biomass within K −1
par and satellite-weighted depth respectively, were associated with peak bloom conditions independent of taxonomy. Our analyses
suggest that satellite-dependent models of Chl a and subsequent chlorophyll-dependent primary production will be challenging to develop for the near-shore Southern Ocean,
especially given the potentially high natural variability in the vertical distribution of Chl a driven by physical forcing, the photoadaptive abilities of polar phytoplankton, and taxonomic influences.
Accepted: 27 August 1999 相似文献
16.
Borgwardt N Culik BM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(2):100-106
Open-flow oxygen and carbon dioxide respirometry was used in Neumünster Zoo (Germany) to examine the energy requirements
of six Asian small-clawed otters (Amblonyx cinerea) at rest and swimming voluntarily under water. Our aim was to compare their energy requirements with those of other warm-blooded
species to elucidate scale effects and to test whether the least aquatic of the three otter species differs markedly from
these and its larger relatives. While at rest on land (16 °C, n = 26), otters (n = 6, mean body mass 3.1 ± 0.4 kg) had a respiratory quotient of 0.77 and a resting metabolic rate of 5.0 ± 0.8 Wkg−1(SD). This increased to 9.1 ± 0.8 Wkg−1 during rest in water (11–15 °C, n = 4) and to 17.6 ± 1.4 Wkg−1 during foraging and feeding activities in a channel (12 °C, n = 5). While swimming under water (n = 620 measurements) in an 11-m long channel, otters preferred a speed range between 0.7 ms−1 and 1.2 ms−1. Transport costs were minimal at 1 ms−1 and amounted to 1.47 ± 0.24 JN−1 m−1 (n = 213). Metabolic rates of small-clawed otters in air were similar to those of larger otter species, and about double those
of terrestrial mammals of comparable size. In water, metabolic rates during rest and swimming were larger than those extrapolated
from larger otter species and submerged swimming homeotherms. This is attributed to high thermoregulatory costs, and high
body drag at low Reynolds numbers.
Accepted: 21 December 1998 相似文献
17.
We discuss the energetics of a cladoceran, Simocephalus vetulus at different temperatures (8.0 ± 1.0, 15.0 ± 1.0, 21.0 ± 1.0 and 28.0 ± 1.0 °C) and food (Chlamydomonas sp.) concentrations (25 × 103, 50 × 103, 75 × 103 and 100 × 103 cells ml−1). Increase in temperature accelerated ingestion and, to some extent, oxygen consumption. The study revealed a high reproduction
efficiency in S. vetulus. Net growth efficiency (ECI) was higher (13.17–41.18%) in pre-adults than in adults (2.71–8.40%). The assimilated energy
(A) increased with increasing food concentration at all temperatures. Assimilation efficiency (AD) decreased with increasing
food concentrations. The energy used for growth (P) was nearly constant at all food levels because the egested energy increased
and assimilation efficiency decreased as food concentration increased. 相似文献
18.
Sediment in the littoral zone of lakes is frequently disturbed by wave action or bioturbation, resulting in sediment resuspension.
In undisturbed sediment, methanotrophic bacteria efficiently reduce the diffusive flux of methane into the water column. In
a microcosm study, the resuspension of littoral sediment was simulated in sediment cores for a winter (n = 3) and a summer situation (n = 3). The erosion of surface sediment resulted in a large flux of methane into the overlying water (207 ± 176 μmol h−1 m−2 in winter and 73 ± 18 μmol h−1 m−2 in summer). Only a minor part (16 ± 7%) of the methane released was oxidized by methanotrophic bacteria, whereas the major
part escaped into the water column. Only 6–16% of the littoral zone has to be resuspended to reach the same flux as from undisturbed
littoral sediment. For the daily flux, a sediment resuspension has to last 1–4 h to reach the undisturbed daily flux. The
study reveals the important role of sediment resuspension in the littoral methane cycle as an intense but variable source
of methane of largely unknown magnitude. 相似文献
19.
Suzuki M Endo N Nakano Y Kato H Kishiro T Asahina K 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2008,178(2):149-156
This study examined the distribution pattern of aquaporin-2 (AQP2), relative medullary thickness (RMT) and urine properties
in the bottlenose dolphin Tursiops
truncatus and Baird’s beaked whale Berardius bairdii. Immunohistochemical studies revealed that AQP2 was localized in the collecting tubules/ducts of both species’ renicules,
as in terrestrial mammals. The collecting ducts with AQP2 were thinner and arranged more densely in the dolphin than in the
whale. RMT values in the renicule were moderate in both species, but were significantly higher in the dolphin (6.0 ± 0.9)
than the whale (4.9 ± 0.7). Urine of the bottlenose dolphin is comparatively concentrated (osmolality: 1715.7 ± 279.4 mOsm kg−1, Na+: 490.1 ± 87.9 mmol l−1, Cl−: 402.7 ± 79.6 mmol l−1, K+: 80.7 ± 25.8 mmol l−1, urea nitrogen: 703.5 ± 253.9 mmol l−1), while urine of the dead Baird’s beaked whale is less concentrated (osmolality: 837.5 ± 293.8 mOsm kg−1, Na+: 192.9 ± 81.5 mmol l−1, Cl−: 159.9 ± 71.4 mmol l−1, K+: 44.3 ± 29.5 mmol l−1, urea nitrogen: 270.7 ± 120.3 mmol l−1). These data suggest it is possible that the differences in these renal morphological features may be related in some way
to the difference in urine composition between the species, although further studies are necessary.
M. Suzuki and N. Endo are equal contributors to this study. 相似文献
20.
Herbert R. L. Drouin 《European biophysics journal : EBJ》1999,28(7):600-604
A new ion-selective liquid membrane microelectrode, based on the neutral carrier 1,1′-bis(2,3-naphtho-18-crown-6), is described
that shows the dependence of EMF on the activity of divalent putrescine cations a
Put, with the linear slope s
Put = 26 ± 3 mV/decade (mean ± SD, N = 18), in the range 10−4–10−1 M at 25 ± 1 °C. Values of potentiometric putrescine cation selectivity coefficients of logK
Pot
Put
j
(mean ± SD, N) are obtained by the separate solution method for the ions K+ (1.0 ± 0.4, 10), Na+ (−1.2 ± 0.4, 8), Ca2+ (−2.3 ± 0.5, 10) and Mg2+ (−2.5 ± 0.5, 7). The microelectrode can be applied for the direct analysis of the activities of free divalent putrescine
cations in the range 5 × 10−4 to 10−1 M in an extracellular ionic environment. Established analytical methods, e.g. high performance liquid chromatography, determine
the total concentration of the derivatives of free and bound putrescine.
Received: 20 December 1998 / Revised version: 7 May 1999 / Accepted: 27 May 1999 相似文献