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1.
Frank Triska Catherine M. Pringle John H. Duff Ronald J. Avanzino Gary Zellweger 《Biogeochemistry》2006,81(2):145-157
Soluble reactive phosphorus (SRP) transport/retention was determined in two rain forest streams (Salto, Pantano) draining La Selva Biological Station, Costa Rica. There, SRP levels can be naturally high due to groundwater enriched by geothermal activity within the surfically dormant volcanic landscape, and subsequently discharged at ambient temperature. Combined field and laboratory approaches simulated high but natural geothermal SRP input with the objective of estimating the magnitude of amended SRP retention within high and low SRP settings and determining the underlying mechanisms of SRP retention. First, we examined short-term SRP retention/transport using combined SRP-conservative tracer additions at high natural in situ concentrations. Second, we attempted to observe a DIN response during SRP amendment as an indicator of biological uptake. Third, we determined SRP release/retention using laboratory sediment assays under control and biologically inhibited conditions. Short-term in situ tracer-SRP additions indicated retention in both naturally high and low SRP reaches. Retention of added SRP mass in Upper Salto (low SRP) was 17% (7.5 mg-P m−2 h−1), and 20% (10.9 mg-P m−2 h−1) in Lower Salto (high SRP). No DIN response in either nitrate or ammonium was observed. Laboratory assays using fresh Lower Salto sediments indicated SRP release (15.4 ± 5.9 μg-P g dry wt.−1 h−1), when incubated in filter sterilized Salto water at ambient P concentration, but retention when incubated in filter sterilized river water amended to 2.0 mg SRP l−1 (233.2 ± 5.8 μg-P g dry wt.−1 h−1). SRP uptake/release was similar in both control- and biocide-treated sediments indicating predominantly abiotic retention. High SRP retention even under biologically saturated conditions, absence of a DIN response to amendment, patterns of desorption following amendment, and similar patterns of retention and release under control and biologically inhibited conditions all indicated predominantly abiotic P flux. 相似文献
2.
Luki Subehi Takehiko Fukushima Yuichi Onda Shigeru Mizugaki Takashi Gomi Ken’ichirou Kosugi Shinya Hiramatsu Hikaru Kitahara Koichiro Kuraji Tomomi Terajima 《Limnology》2010,11(2):115-124
Despite continued interest in stream water temperature (Tw) analysis, there are few studies of Tw response to rainfall events
at forested watersheds. We examined 61 sets of data on Tw for 21 rainfall events at 16 watersheds with various slope gradients
(from 0.08 to 0.56) in four regions of Japan from June 2004 to December 2005. The investigation focused on the changes of
specific discharge (ΔQs) and ΔTw at medium-sized watersheds (0.5–100 ha). The results clearly demonstrated different flow
patterns expressed by Qs vs. Tw hysteretic loops. Those were clockwise in Period I (April–September) and counterclockwise
in Period II (October–March), except for lower slope gradient at Aichi, where counterclockwise loops were observed in both
periods. These differences in hysteretic loops could be explained by the differences in Tw and in response times to rainfall
between surface/subsurface and groundwater flows. The response times were probably determined by the slope gradient and the
vertical level of groundwater. We also found that the changes in air temperature (ΔTa) influenced ΔTw to a lesser degree than
Qs. The average rainfall intensities in Period I and Period II (9.3 ± 1.7 and 5.4 ± 0.2 mm/h, respectively) affected the average
values of ΔQs and ΔTw (6.62 ± 4.08 mm/h and 1.7 ± 0.4°C; 0.85 ± 0.68 mm/h and 0.9 ± 0.3°C, respectively). This indicates that
slope gradient and Qs influenced ΔTw by changing the relative proportions of flow paths. In addition, the water table changes
influenced the percentage of groundwater flow to the stream. 相似文献
3.
A pioneering limnological investigation was carried out in Bhutan in a small peat bog in the Trashiyangtse district (1950 m
above sea level) from February 2000 to January 2002. The sampled pond water had low transparency (55.0–95.0 cm), was typically
acidic (pH 5.69–6.58) with soft water (alkalinity, 11.0–36.0 mg/l; total hardness, 10.0–34.0 mg/l), and had low to moderate
specific conductivity (17.0–62.0 μS/cm). Further, moderate Na (2.0–6.8 mg/l), K (1.8–13.5 mg/l), sulphate (0.85–2.99 mg/l),
and silicate (2.5–15.0 mg/l) concentrations as well as low nutrient levels such as phosphate (0.006–0.170 mg/l) and nitrate
(0.003–0.180 mg/l) characterize the water in the peat bog. The recorded net plankton comprised 27 species of phytoplankton
and 49 species of zooplankton, with the latter indicating greater homogeneity and breaking down into Rotifera (23 species)
> Cladocera (13 species) > Rhizopoda (8 species) > Copepoda (3 species) > Ostracoda = Nematoda (1 species each). On the other
hand, the net plankton density ranged between 93 and 692 number/l (n/l) with numerical dominance by phytoplankton (68.5% ±
12%), of which Chlorophyceae were predominant (90 ± 63 n/l). Zooplankton showed moderately high diversity (2.745 ± 0.293)
and evenness (0.925 ± 0.049) and exhibited almost equal abundance of four recorded groups, namely Cladocera (20 ± 15 n/l)
> Rotifera (15 ± 6 n/l) > Copepoda (14 ± 7 n/l) > Rhizopoda (14 ± 4 n/l). While no significant impact of abiotic factors was
recorded on zooplankton density, rainfall alone was the most important factor that influenced net plankton and various groups
of phytoplankton. Comments on some comparative limnological attributes are also made with similar as well as different habitats
in the nearby Himalayan countries. 相似文献
4.
Rodrigo S. P. de Skowronski Paula F. Gheller Sandra Bromberg Carlos J. David Mônica A. V. Petti Thaïs N. Corbisier 《Polar Biology》2009,32(6):839-851
The spatial and temporal variation of microphytobenthic biomass in the nearshore zone of Martel Inlet (King George Island,
Antarctica) was estimated at several sites and depths (10–60 m), during three summer periods (1996/1997, 1997/1998, 2004/2005).
The mean values were inversely related to the bathymetric gradient: higher ones at 10–20 m depth (136.2 ± 112.5 mg Chl a m−2, 261.7 ± 455.9 mg Phaeo m−2), intermediate at 20–30 m (55.6 ± 39.5 mg Chl a m−2, 108.8 ± 73.0 mg Phaeo m−2) and lower ones at 40–60 m (22.7 ± 23.7 mg Chl a m−2, 58.3 ± 38.9 mg Phaeo m−2). There was also a reduction in the Chl a/Phaeo ratio with depth, from 3.2 ± 3.2 (10–20 m) to 0.7 ± 1.0 (40–60 m), showing a higher contribution of senescent phytoplankton
and/or macroalgae debris at the deeper sites and the limited light flux reaching the bottom. Horizontal differences found
in the biomass throughout the inlet could not be clearly related to hydrodynamics or proximity to glaciers, but with sediment
characteristics. An inter-summer variation was observed: the first summer presented the highest microphytobenthic biomass
apparently related to more hydrodynamic conditions, which causes the deposition of allochthonous material. 相似文献
5.
Naushad SM Reddy CA Rupasree Y Pavani A Digumarti RR Gottumukkala SR Kuppusamy P Kutala VK 《Cell biochemistry and biophysics》2011,61(3):715-723
The aim of this case–control study is to explore the role of aberrations in xenobiotic metabolism in inducing oxidative DNA
damage and altering the susceptibility to breast cancer. Cytochrome P4501A1 (CYP1A1) m1 (OR: 1.41, 95% CI 1.08–1.84), CYP1A1
m4 (OR: 5.13, 95% CI 2.68–9.81), Catecholamine-O-methyl transferase (COMT) H108L (OR: 1.49, 95% CI 1.16–1.92), and glutathione S-transferase (GST) T1 null (OR: 1.68, 95% CI 1.09–2.59) variants showed association with breast cancer risk. Reduced folate
carrier 1 (RFC1) 80A/CYP1A1 m1/CYP1A1 m4 and RFC1 80A/thymidylate synthase (TYMS) 5′-UTR 2R/methionine synthase (MTR) 2756G/COMT
108L genetic combinations were found to inflate breast cancer risk under the conditions of low dietary folate (345 ± 110 vs.
379 ± 139 μg/day) and low plasma folate (6.81 ± 1.25 vs. 7.09 ± 1.26 ng/ml) by increasing plasma 8-oxo-2′-deoxyguanosine (8-oxodG).
This increase in 8-oxodG is attributed to low methionine (49.38 ± 23.74 vs. 53.90 ± 23.85 μmol/l); low glutathione (378 ± 242
vs. 501 ± 126 μmol/l) and GSTT1 null variant; and hypermethylation of CpG island of extracellular-superoxide dismutase (EC-SOD)
(92.78 ± 11.49 vs. 80.45 ± 9.86%), which impair O-methylation of catechol estrogens to methoxy estrogens, conjugation of glutathione to semiquinones/quinones and free radical
scavenging respectively. Our results suggest cross-talk between one-carbon metabolism and xenobiotic metabolism influencing
oxidative DNA damage and susceptibility to breast cancer. 相似文献
6.
Seema Jain Priyamvada Sharma Shobha Kulshreshtha Govind Mohan Saroj Singh 《Biological trace element research》2010,133(2):162-170
Pre-eclampsia is the most common medical complication of pregnancy associated with increased maternal and infant mortality
and morbidity. Its exact etiology is not known, although several evidences indicate that various elements might play an important
role in pre-eclampsia. This study was carried out to analyze and to compare the concentration of calcium, magnesium, and zinc
in the serum of women with pre-eclampsia and in normal pregnant women. Fifty clinically diagnosed patients with pre-eclampsia
(25 with mild and 25 with severe pre-eclampsia) and 50 normal pregnant controls were enrolled in this study. The serum calcium,
magnesium, and zinc levels were estimated with an atomic absorption spectrophotometer. The mean serum levels of calcium, magnesium,
and zinc in normal pregnant group were 2.45 ± 0.18 mmol/L, 0.79 ± 0.13 mmol/L, and 15.64 ± 2.4 μmol/L, respectively, while
in mild pre-eclamptic group, these were 2.12 ± 0.15 mmol/L, 0.67 ± 0.14 mmol/L, and 12.72 ± 1.7 μmol/L, respectively. Serum
levels in severe pre-eclamptic group were 1.94 ± 0.09 mmol/L, 0.62 ± 0.11 mmol/L, and 12.04 ± 1.4 μmol/L, respectively. These
results indicate that reduction in serum levels of calcium, magnesium, and zinc during pregnancy might be possible contributors
in etiology of pre-eclampsia, and supplementation of these elements to diet may be of value to prevent pre-eclampsia. 相似文献
7.
Tumor cells have a high tolerance for acidic and hypoxic microenvironments, also producing abundant lactic acid through accelerated
glycolysis in the presence or absence of O2. While the accumulation of lactate is thought to be a major contributor to the reduction of pH-circumscribing aggressive
tumors, it is not known if other endogenous metabolic products contribute this acidity. Furthermore, anaerobic metabolism
in cancer cells bears similarity to homo-fermentative lactic acid bacteria, however very little is known about an alternative
pathway that may drive adenosine triphosphate (ATP) production independent of glycolysis. In this study, we quantify over
40 end-products (amines, acids, alcohols, aldehydes, or ketones) produced by malignant neuroblastoma under accelerated glycolysis
(+glucose (GLU) supply 1–10 mM) ± mitochondrial toxin; 1-methyl-4-phenylpyridinium (MPP+) to abate aerobic respiration to delineate differences between anaerobic vs. aerobic cell required metabolic pathways. The
data show that an acceleration of anaerobic glycolysis prompts an expected reduction in extracellular pH (pHex) from neutral to 6.7 ± 0.006. Diverse metabolic acids associated with this drop in acidity were quantified by ionic exchange
liquid chromatography (LC), showing concomitant rise in lactate (Ctrls 7.5 ± 0.5 mM; +GLU 12.35 ± 1.3 mM; +GLU + MPP 18.1 ± 1.8 mM),
acetate (Ctrl 0.84 ± 0.13 mM: +GLU 1.3 ± 0.15 mM; +GLU + MPP 2.7 ± 0.4 mM), fumarate, and a-ketoglutarate (<10 μM) while a
range of other metabolic organic acids remained undetected. Amino acids quantified by o-phthalaldehyde precolumn derivatization/electrochemical detection–LC show accumulation of l-alanine (1.6 ± .052 mM), l-glutamate (285 ± 9.7 μM), l-asparagine (202 ± 2.1 μM), and l-aspartate (84.2 ± 4.9 μM) produced during routine metabolism, while other amino acids remain undetected. In contrast, the
data show no evidence for accumulation of acetaldehyde, aldehydes, or ketones (Purpald/2,4-dinitrophenylhydrazine—Brady's
reagent), acetoin (Voges–Proskauer test), or alcohols (NAD+-linked alcohol dehydrogenase). In conclusion, these results provide preliminary evidence to suggest the existence of an active
pyruvate–alanine transaminase or phosphotransacetylase/acetyl-CoA synthetase pathway to be involved with anaerobic energy
metabolism of cancer cells. 相似文献
8.
Mitchell K. Taylor Jeff Laake Philip D. McLoughlin H. Dean Cluff Erik W. Born Aqqalu Rosing-Asvid François Messier 《Polar Biology》2008,31(4):491-499
We estimated demographic parameters and current harvest risks for a population of polar bears (Ursus maritimus Phipps) inhabiting northern Smith Sound and Kane Basin, Canada and Greenland. Our demographic analysis included a detailed
assessment of age- and sex-specific survival and recruitment from 141 marked polar bears, using information contained within
the standing age distribution of captures and mark-recapture analysis. Total survival rates
for females were: 0.374 ± 0.180 (cubs), 0.686 ± 0.157 (ages 1–4), and 0.967 ± 0.043 (ages 5+). Mean litter size was 1.67 ± 0.08
cubs. Females did not reproduce until at least age 6, which is late compared to other populations of polar bears. The model-averaged,
mark–recapture estimate of mean abundance (±1 SE) for years 1994–1997 was 164 ± 35 bears. We incorporated demographic parameters
and their variances into a harvest risk analysis (i.e., a stochastic, harvested population viability analysis, PVA). Results
suggest that polar bears in the region were severely over-harvested during the mark–recapture interval (1992–1997). The current
status of the population is unknown. 相似文献
9.
Two simple, economical, rapid, precise, and accurate methods for simultaneous determination of olmesartan medoxomil and hydrochlorothiazide
in combined tablet dosage form have been developed. The first method is based on ratio spectra derivative spectrophotometry,
and the second method is zero-crossing difference spectrophotometry. The amplitudes in the first derivative of the corresponding
ratio spectra at 231.0 and 271.0 nm were selected to determine olmesartan medoxomil and hydrochlorothiazide, respectively.
Measurements of absorbance were carried out at zero-crossing wavelengths 257.8 and 240.2 nm for olmesartan medoxomil and hydrochlorothiazide
by zero-crossing difference spectrophotometric method. Beer’s law is obeyed in the concentration range of 08–24 μg/mL for
olmesartan medoxomil (OLM) and 05–15 μg/mL for hydrochlorothiazide (HCT) by ratio spectra derivative and 05–30 μg/mL for OLM
and HCT by zero-crossing difference spectrophotometric method. The results of the assay were found to be 100.46 ± 0.95 for
OLM and 100.4 ± 0.27 for HCT by ratio spectra derivative and 99.06 ± 1.14 for OLM and 100.05 ± 0.90 for HCT by zero-crossing
difference spectrophotometric method. These methods passes F test and t test. Both methods were validated statistically and by performing recovery study. 相似文献
10.
《Harmful algae》2014
A two-year study was conducted to explore summer development of macroalgae and their total phosphorus and nitrogen content at three stations in a broad and clear French carbonate river. Water discharge, temperature and insolation, each with a different time lag, as well as substrates and nutrients were examined in order to explain macroalgal biomass variability. Twenty-four macroalgae genera were recorded with Spirogyra, Cladophora, Vaucheria and Oedogonium as abundant. Through redundancy analysis the macroalgal community composition exhibited significant differences, between the sampling sites and also from one year to the next. Water discharge (time-lag = 5 days) and temperature (time-lag = 20 days) both significantly explained macroalgal biomass variability, highlighting differences in the time lag of the macroalgal community's ecological response to environmental changes. Spatial segregation was observed within the wide riverbed due to habitat variability, allowing co-occurrence in the development of ecologically different taxa within each sampling site. The high nitrate concentrations as compared with the particular low phosphorus concentrations led to especially high DIN/SRP ratios (248 ± 103, n = 18). The N/P ratios in algal tissues were high (25 ± 16, n = 26) and indicated P-limitation. The differences in DIN/SRP and N/P ratios suggest additional nutrient sources than open water such as groundwater inputs. 相似文献
11.
Ierecê L. Rosa Tacyana P. R. Oliveira Frederico M. Osório Luiz E. Moraes André L. C. Castro Glaura M. L. Barros Rômulo R. N. Alves 《Biodiversity and Conservation》2011,20(9):1951-1971
Seahorses (Hippocampus spp.) are globally threatened by overexploitation and habitat destruction; they are also regarded as susceptible to heavy
exploitation due to some of their life-history traits. From an economic perspective, they are fishes with high monetary value
and marketability. Seahorses are now listed in Appendix II of CITES (Convention on International Trade in Endangered Species
of Wild Fauna and Flora), to ensure that the international trade is not detrimental to the survival of wild populations; the
effectiveness evaluation of these international controls needs comparable monitoring data, including evaluation of spatial
and temporal trends. This study assesses the seahorse trade in Brazil, aiming to detect trends in catch levels, volumes and
prices. Our main findings were: the dried trade was unregulated, without formal records, and primarily domestic, although
records of unreported exports existed; it was primarily sustained by incidental captures in trawl nets. The live seahorse
trade was mainly destined for exports, and regulated through national quotas. Between 2002 and 2009, mean prices for dried
seahorses ranged from US$1.06 ± 0.46 (level 1 traders) to US$1.06 ± 0.46 (level 1 traders) to US2.78 ± 0.68 (end-sellers) each, while mean prices for each live
seahorse traded on the domestic market (1997–2009) ranged from US$1.13 ± 0.02 (level 1 traders) to US$1.13 ± 0.02 (level 1 traders) to US10.08 ± 1.71 (retailers).
Mean declared export price (2006–2008) was 15.57 ± 10.87. Enhanced implementation of the CITES listing in Brazil will require
further research, and additional measures to address both direct and indirect fishing pressure on seahorse populations. 相似文献
12.
A study was conducted in Mona Lake, a small eutrophic lake located in western Michigan (USA) to address the temporal and spatial
variability of external and internal phosphorus loading. External P load varied among subbasins, which was mostly related
to discharge, but also to land use. Black Creek, which drains lands with natural cover and agriculture, accounted for the
majority of flow, and total phosphorus (TP) and soluble reactive phosphorus (SRP) load, to Mona Lake. However, the relative
contribution of SRP load was greater in Little Black Creek, which flows through a mostly urbanized subbasin, than in Black
Creek. The relative importance of internal loading was strongly related to season, as internal TP loads contributed only ∼9%
of the overall P load in April 2005, but ∼68–82% of the overall P load in the summer and early fall seasons. Internal TP and
SRP loading was greater under anaerobic than aerobic conditions. Mean anaerobic TP release rates ranged from 0.80 to 15.56 mg P m−2 d−1, varying with site and season. Spatial variability in both internal phosphorus loading and sediment P concentration was also
evident. By taking into account the spatial and temporal variability of different loading sources, management practices can
be targeted to optimize nutrient source control strategies. 相似文献
13.
《Process Biochemistry》2004,39(11):1519-1524
Changes in pyruvate and ascorbate production and antioxidant enzyme activities together with lipid peroxidation levels in Fusarium equiseti were investigated in relation to changes in the concentrations of glucose and maltose as carbon sources in the range of 5–25 g/l in Armstrong Fusarium Medium (AFM). The highest pyruvate concentration obtained at 20 g/l maltose was 67.5 ± 0.69 μg/ml while ascorbic acid reached a maximum value at 25 g/l glucose of 1866±26.1 μg/ml The maximum superoxide dismutas (SOD) activities related to increased pyruvate production were determined in AFM medium containing 20 g/l glucose as 41.49±0.65 and maltose as 61.12±0.8 IU/mg. Catalase (CAT) activity variations showed coherence with SOD activity in a medium containing maltose and reached 219.11±2.8 IU/mg while they were decreased with increasing glucose concentration. glutathione peroxidase (GSH-Px) activities in F. equiseti did not change significantly with glucose and maltose concentration and were determined to be 1.21±0.22 and 1.67±0.15 IU/mg, respectively. Minimum lipid peroxidation levels for each carbon source were determined in both 20 g/l maltose and glucose concentrations as 0.9 and 1.62 nmol MDA/g wet weight. 相似文献
14.
Andres Meos Tiiu Jüriado Vallo Matto Ain Raal 《Biological trace element research》2011,140(2):244-251
Trace metal contamination is a major environmental and health problem virtually in all countries. The present study was aimed
to estimate the lead content of pot marigold (Calendula officinalis L.) inflorescences and leaves collected from a nonpolluted test field. The lead content in dry pot marigold inflorescences
was 9.34 ± 0.79 μg/g, in dry leaves 11.57 ± 0.47 μg/g, and in soil 0.649 ± 0.012 μg/g. The distance of pot marigold collection
beds (30–220 m from the motorway) had no effect on lead content. There was a strong positive correlation between the amount
of precipitations and lead content of pot marigold leaves but not inflorescences indicating the soil as primarily the source
of increased lead content. In conclusion, no effect of motorway vicinity was found for pot marigold inflorescences or leaves
lead content; however, as a precaution, it is not recommended to collect the plants during or just after showers. 相似文献
15.
The most-probable-number enumeration of dichlobenil and 2,6-dichlorobenzamide (BAM) degrading microbes in Finnish aquifers 总被引:2,自引:0,他引:2
Veera Pukkila Juhani Gustafsson Jari Tuominen Anri Aallonen Merja H. Kontro 《Biodegradation》2009,20(5):679-686
In groundwater subsurface deposits and a topsoil from five aquifers having 2,6-dichlorobenzamide (BAM) in water, we determined
the most-probable-number (MPN) of 2,6-dichlorobenzonitrile (dichlobenil) and metabolite BAM degrading microorganisms. Dichlobenil
and BAM were combined nitrogen sources in the MPN tubes, which were scored positive at concentrations <75% after 1 month incubation.
Aerobic and anaerobic microbes degrading dichlobenil and BAM were common in samples in low numbers of 3.6–210 MPN g dw−1. Additional degradation occurred in high MPN dilutions of some samples, the microbial numbers being 0.11–120 × 105 MPN g dw−1. The strains were isolated from low and high dilutions of one deposit, and degradation in pure cultures was confirmed by
HPLC. According to the 16S rDNA sequencing, strains were from genera Zoogloea, Pseudomonas, Xanthomonas, Rhodococcus, Nocardioides, Sphingomonas, and Ralstonia. Dichlobenil (45.5 ± 18.3%) and BAM (37.6 ± 14%) degradation was low in the MPN tubes. Despite of microbial BAM degradation
activity in subsurface deposits, BAM was measured from groundwater. 相似文献
16.
Hong-qun Zhang Ning Li Zheng Zhang Shan Gao Hong-yin Yin Dong-mei Guo Xibao Gao 《Biological trace element research》2009,131(1):25-32
Sera of 890 healthy Jinan residents were chosen randomly, and the concentrations of serum Zn and Cu were detected by atomic
absorption spectrometry. The mean serum Zn and Cu concentrations and Zn/Cu were 1.32 ± 0.49 mg/l, 0.99 ± 0.26 mg/l, and 1.41 ± 0.56,
respectively. Significantly higher levels of serum Zn and Zn/Cu but lower serum Cu were found in the men. Descending tendency
of serum Zn and Zn/Cu was observed with social-economic status and age but not significant. Alcohol consumption produced higher
level of serum Zn and Zn/Cu but lower Cu concentration. Smoking caused significant lower level in serum Cu concentration but
no significance in serum Zn and Zn/Cu. Serum Zn and Zn/Cu were normal only when hours of sleep a night were kept within 7–9 h.
Higher level of serum Zn and Cu concentrations and Zn/Cu were observed in individuals with regular physical exercise, but
still no significant difference existed. No clear relationship between educational levels with serum Zn and Cu concentrations
and Zn/Cu was observed. 相似文献
17.
Kailiang Hu Yuguang Meng Hao Lei Shuyi Zhang 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(1):117-123
Cerebral blood flow (CBF) of a vespertilionid bat, Miniopterus fuliginosus (M. f.), and a pteropodid bat, Rousettus leschenaultii (R. l.) was measured non-invasively during induced hypothermia (37–10°C for M. f. and 37–24°C for R. l.) with perfusion-weighted magnetic resonance imaging. In both species, the average CBF was found to decrease with rectal temperature.
The patterns of hypothermia-induced regional CBF changes, however, were different between the two species. In the pteropodid
bat, the extent of CBF decrease at lower rectal temperature was similar in the cortex and thalamus, resulting in an unchanged
thalamus/cortex CBF ratio. In contrast, the thalamus/cortex CBF ratio in the vespertilionid species increased progressively
with decreasing rectal temperature (1.52 ± 0.14 at 37 ± 1°C vs. 2.28 ± 0.29 at 10 ± 1°C). These results suggest that the manner
in which the two bat species cope with low body temperature may be reflected by a differential CBF regulation between thalamus
and cortex. 相似文献
18.
Masahiko Hirata Nobumi Hasegawa Kangoro Nogami Tatsunobu Sonoda 《Journal of Ethology》2009,27(3):437-445
This 4-year study monitored maintenance behavior of beef cattle (Japanese Black) foraging in a young Chamaecyparis obtusa (an evergreen conifer) plantation in southwestern Japan. The animals spent 551 ± 8 min (mean ± SE) per day grazing, 436 ± 4 min
ruminating, 313 ± 9 min resting, 44 ± 2 min moving, and 96 ± 4 min on other activities. Grazing activity was high during 0600–1800 h
and low during 2200–0600 h. Ruminating activity was high during 2200–0600 h and low during 0600–1800 h. Resting activity was
high during 2200–0600 h and low for the remainder of the day. Air temperature was not a dominant factor determining the daily
duration of grazing, rumination, or resting. The activity of the animals was usually synchronized, with the degree of synchronization
being highest in grazing followed by ruminating and resting. Daily liveweight change of the animals was positively related
with daily ruminating time, i.e., animals gained more when they ruminated longer. The maintenance behavior of cattle in the
young tree plantation, as compared with that on grasslands, is characterized by (1) high grazing activity around midday, (2)
low ruminating activity in the daytime, and (3) midday adjustment of the daily total grazing time. Daily rumination time may
be used as an indicator of animal performance on the bases of a herd (not individual animals) and a period of 2–15 weeks (not
individual days). 相似文献
19.
Gigartina skottsbergii is a commercially important carrageenan producer that has been suffering severe extraction pressure in Chile’s Magellan Region
and Cape Horn Archipelago since 1998. In order to create baseline information for its cultivation and repopulation, we studied
the effects of agricultural fertilizers on growth of G. skottsbergii early developmental stages. The culture media utilized were: a) seawater + Bayfoland, b) seawater + Superphosphate, c) seawater
+ Urea, d) seawater + Provasoli and e) seawater as a control. The culture conditions were: a) 12L:12D photoperiod; b) temperature
8 ± 1°C and c) irradiance at 45 μmol photons m−2 s−1. After 60 days, higher relative growth rates between treatments were observed; the treatments that included Bayfoland and
Provasoli showed greater growth (382 ± 55 and 378 ± 50 μm, respectively,) compared to Superphosphate (88 ± 16 μm), control
(78 ± 10 μm) and Urea (70 ± 11 μm) treatments, after 81 days. The Urea treatment and the control had inhibitory effects on
G. skottsbergii germlings growth and survival, as evidenced by progressive loss of pigmentation and death after 60 days. These results showed
that Bayfoland was an excellent alternative to develop cultures. 相似文献
20.
L. Charpy M. Rodier A. Couté C. Perrette-Gallet C. Bley-Loëz 《Coral reefs (Online)》2010,29(3):771-783
Closure of the Clipperton Island atoll (10°17′ N 109°13′ W), now a meromictic lake, is estimated to have occurred between
1839 and 1849. It was still closed in 2005. Brackish waters in the upper layer (0–10 m) were oxygenated, while saline waters
in the deep layer (>20 m) were anoxic. Allowing for the methodological difficulties of earlier measurements, the physical
characteristics of the lagoon did not seem to have changed significantly since the last expedition (1980). The intermediate
layer between brackish and saline waters was characterized by a strong density gradient and a temperature inversion of up
to 1.6°C. Microbial activity, water exchange between the deep layer and surrounding oceanic waters and the geothermal flux
hypothesis are discussed. The low DIN and SRP concentrations observed in the upper layer, despite high nutrient input by seabird
droppings, reflect the high nutrient uptake by primary producers as attested by the elevated overall gross primary production
(6.6 g C m−2 day−1), and high suspended photosynthetic biomass (2.23 ± 0.23 μg Chl a l−1) and production (263 ± 27 μg C l−1 day−1). Phytoplankton composition changed in 67 years with the advent of new taxa and the disappearance of previously recorded
species. The freshwater phytoplanktonic community comprised 43 taxa: 37 newly identified during the expedition and 6 previously
noted; 16 species previously found were not seen in 2005. The closure of the lagoon, combined with the positive precipitation–evaporation
budget characteristic of the region, has induced drastic changes in lagoon functioning compared with other closed atolls. 相似文献