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1.
 Photosynthetic photon flux density (PPFD) fluctuations were quantified in crops of beans (Phaseolus vulgaris L.) in the field as the canopy developed between July and October. Two different methods were used to select sunflecks and shadeflecks. Four ranges of zenith angles (60–70°, 50–60°, 40–50° and 30–40°) were selected for analysing PPFD fluctuations. At the base of the canopy, sunflecks contributed 18%, 53%, 10% and 4% during the 1st, 3rd, 5th and 7th week of growth, respectively. At a height of 20 cm above the soil surface, the respective contributions were 28% and 21% during the 6th and 7th weeks. Sunfleck lengths of 0–5 s were the most frequent, with the greatest number being found with smaller zenith angles. The proportion of short duration sunflecks increased as the growth period advanced. The number of long sunflecks decreased with time, with very few longer than 100 s by the 5th and 7th weeks. The distributions of sunfleck irradiance were similar to normal distributions and irradiance ranged in μmol m−2 s−1 from 600–900, 800–1500 and 1000–1600 respectively at zenith angles of 50–60°, 40–50° and 30–40°. A multiple regression showed that short sunflecks (<100 s) depended on zenith angle, plant height, and leaf and stem area index (L s ), whereas long sunflecks (>100 s) depended on zenith angle and L s. Shadefleck distributions were similar to those for sunflecks but there were fewer of the shortest examples and more of the longest. The best statistical distribution to describe sunflecks and shadeflecks was the gamma distribution, which could provide the basis for the future development of a good model for sunfleck and shadefleck distributions. Received: 10 November 1997 / Accepted: 2 April 1998  相似文献   

2.
Intense nanosecond pulsed electric fields (nsPEFs) have been shown to induce, on intracellular structures, interesting effects dependent on electrical exposure conditions (pulse length and amplitude, repetition frequency and number of pulses), which are known in the literature as “bioelectrical effects” (Schoenbach et al., IEEE Trans Plasma Sci 30:293–300, 2002). In particular, pulses with a shorter width than the plasma membrane charging time constant (about 100 ns for mammalian cells) can penetrate the cell and trigger effects such as permeabilization of intracellular membranes, release of Ca2+ and apoptosis induction. Moreover, the observed effects have led to exploration of medical applications, like the treatment of melanoma tumors (Nuccitelli et al., Biochem Biophys Res Commun 343:351–360, 2006). Pulsed electric fields allowing such effects usually range from several tens to a few hundred nanoseconds in duration and from a few to several tens of megavolts per meter in amplitude (Schoenbach et al., IEEE Trans Diel Elec Insul 14:1088–1109, 2007); however, the biological effects of subnanosecond pulses have been also investigated (Schoenbach et al., IEEE Trans Plasma Sci 36:414–422, 2008). The use of such a large variety of pulse parameters suggests that highly flexible pulse-generating systems, able to deliver wide ranges of pulse durations and amplitudes, are strongly required in order to explore effects and applications related to different exposure conditions. The Blumlein pulse-forming network is an often-employed circuit topology for the generation of high-voltage electric pulses with fixed pulse duration. An innovative modification to the Blumlein circuit has been recently devised which allows generation of pulses with variable amplitude, duration and polarity. Two different modified Blumlein pulse-generating systems are presented in this article, the first based on a coaxial cable configuration, matching microscopic slides as a pulse-delivery system, and the other based on microstrip transmission lines and designed to match cuvettes for the exposure of cell suspensions.  相似文献   

3.
L. Wiklicky 《Plant and Soil》1982,64(1):115-127
Summary The relationship between the EUF-nutrient fractions in the soil on the one hand and the nutrient uptake of sugar beet as well as root yield and quality (polarization, α-amino N etc.) on the other is described on the basis of results obtained over several years in surveys conducted in farmers' fields (5000–6000 fields under sugar beet per year) and in field experiments (25–35 sites per year). Statistically significant close correlations with the respective parameters were found for the following EUF nutrient fractions: EUF-NO3, EUF-P, EUF-K, EUF-Na, EUF-B and EUF-Mn. Within five years it was possible to determine the EUF-nutrient values which are required for the production of 9 t sugar/ha. These EUF values are the following: Ca: 65–70 mg/100 g at 20°C K: 11–15 mg/100 g at 20°C (depending on the clay content) Mg: 3–5 mg/100 g at 20°C Na: 2–3 mg/100 g at 20°C P: 1.4–1.6 mg/100 g at 20°C For calculation of the N fertilizer requirements of sugar beet it is suggested to use the sum of the EUF-extractable N amounts. It was found in Austria, Yugoslavia and Denmark over a period of 3 years that the EUF-N value of 1 mg/100 g soil determined between June and September was equivalent to 40 kg N/ha. If, for example, the analysed soil contains 3 mg EUF-N/100 g, 3×40=120 kg N/ha will be available to the sugar beet crop in the following year.  相似文献   

4.
The pearlfish Maurolicus imperatorius occurs above seamounts of the Emperor Seamount Chain between 30°–40° N and 168°–176° E. It forms dense aggregations at the daytime in the upper mesopelagial above the ground and disperses in the dark period of the day in the surficial layer. Judged by maturation dynamics of gonads, the spawning of this species occurs from January until April with the maximum in March. Catches of this species are characterized by expressed seasonal dynamics of size composition. Juveniles appear in catches in the end of spring-the beginning of summer. The maximum recorded SL is 68 mm. Among large fish, females dominate. The part of females is maximum in winter and minimum in spring. The age of fish with AC 46–63 mm is 265–420 days. The growth rate is abruptly retarded at the fourth month of life when the length 40–45 mm is attained. Life duration of most fish does not exceed 1.5 years, though some specimens may attain the age of two years. It is supposed that the presence of another species—M. japonicus—on the Emperor Seamount Chain may result from passive transfer in the Kuroshio waters.  相似文献   

5.
For the systematic study of the gonostomatid fishes of theDiplophos taenia species complex, a total of 698 specimens was obtained from the three oceans. Four valid species were recognized:D. taenia Günther,D. proximus Parr,D. orientalis Matsubara, andD. australis sp. nov. The diagnostic characters are 90–100 total vertebrae (TV) (37–41 abdominal (AV) +52–60 caudal vertebrae (CV)) and 103–115 IC photophores (IC) for D.taenia, 85–90 TV (36–39 AV + 48–52 CV) and 98–104 IC forD. proximus, 83–86 TV (33–35 AV + 49–52 CV) and 92–100 IC for D.orientalis, and 84–91 TV (33–37 AV+ 50–54 CV) and 99–105 IC forD. australis. In addition to the above,D. proximus has larger orbital diameter (the proportion to head length 21–28%) than the other three species (15–23%) beyond 70mm in standard length. Due to wide distribution,D. taenia shows meristic variations: the numbers of TV, IC and anal fin rays (A) are smaller at lower latitudes and larger at higher ones in all oceans, and the number of A is smaller in the Atlantic (56–71) than in the other oceans (59–72) of the same latitude. Because of these variations, identification to species level is possible only area by area. The distribution of each of the four species is also distinct:D. taenia is a cosmopolitan between about 40° N and 30° S exclusive of the eastern tropical Pacific;D. proximus is endemic to the eastern tropical Pacific;D. orientalis is limited to the North Pacific transitional zone between about 30° and 40° N; andD. australis in a transitional zone of the Southern Ocean south of 20° S.  相似文献   

6.
A two-wave technique of calciometry with the use of a fluorescence dye, fura-2/AM, was applied for examination of the effect of a protein, β-amyloid (the main component of senile plaques in Alzheimer’s disease), on calcium homeostasis in cultured neurons of the rat hippocampus; β-amyloid was added to the culture medium. In most neurons, the effect of β-amyloid appeared as a more than twofold increase in the basic calcium concentration, as compared with the control (153.4 ± 11.5 and 71.7 ± 5.4 nM, respectively; P < 0.05). The characteristics of calcium transients induced by application of hyperpotassium solution also changed; the amplitude of these transients decreased, and the duration of a part corresponding to calcium release from the cell (rundown of the transient) increased. The mean amplitude of calcium transients under control conditions was 447.5 ± 20.1 nM, while after incubation in the presence of β-amyloid this index dropped to 278.4 ± 22.6 nM. Under control conditions, the decline phase of calcium transients lasted, on average, 100 ± 6 sec, while after incubation of hippocampal cell cultures in the presence of β-amyloid this phase lasted 250 ± 10 sec. Therefore, an excess of β-amyloid influences significantly calcium homeostasis in the nerve cells by disturbing functions of the calcium-controlling systems, such as voltage-operated calcium channels of the plasma membrane and calcium stores of the mitochondria and endoplasmic reticulum. Neirofiziologiya/Neurophysiology, Vol. 40, No. 1, pp. 9–12, January–February, 2008.  相似文献   

7.
Stability and reproducibility of seeding cell performance in large-scale hybridoma cell culture has been reported by controlling only initial cell seeding density. The aim of the current study was to integrate multiple seeding cell control parameters to maintain stable and consistent cell physiological status for HAb18 cell expansion. Three parameters and their ranges were investigated, including initial cell seeding density in the range of 0.075–0.5×106 cells ml−1, “timepost” after cell passage between 8 and 36 h, and duration of subculture up to 6 months after cell revival. Cell performance was tested at the 1 L, 5 L, and 75 L scales. Desirable performance was found within the following parameter ranges: initial cell seeding density of 0.1–0.3×106 cells ml−1, “timepost” after cell passage between 14 and 22 h, and duration of subculture within 3 months of cell revival. Our results showed that cell growth rate and antibody productivity of three batches at 1 L, 5 L, and 75 L scale were found to be stably maintained within a range of 0.036–0.047 h−1 and 0.577–0.747 pg cell−1 h−1, with the positivity rate of antigen-binding activity within 97–99.75%, and the intensity of fluorescence around 200. This study may provide a simple but effective method to maintain seeding cell physiological status stable and consistent by combining seeding cell control parameters.  相似文献   

8.
Saponins are a class of compounds containing a triterpenoid or steroid core with some attached carbohydrate modules. Many saponins cause hemolysis. However, the hemolytic mechanism of saponins at the molecular level is not yet fully understood. In an attempt to explore this issue, we have studied dioscin—a saponin with high hemolytic activity—through extensive molecular dynamics (MD) simulations. Firstly, all-atom MD simulations of 8 ns duration were conducted to study the stability of the dioscin–cholesterol complex and the cholesterol–cholesterol complex in water and in decane, respectively. MM-GB/SA computations indicate that the dioscin–cholesterol complex is energetically more favorable than the cholesterol–cholesterol complex in a non-polar environment. Next, several coarse-grained MD simulations of 400 ns duration were conducted to directly observe the distribution of multiple dioscin molecules on a DPPC-POPC-PSM-CHOL lipid bilayer. Our results indicate that dioscin can penetrate into the lipid bilayer, accumulate in the lipid raft micro-domain, and then bind cholesterol. This leads to the destabilization of lipid raft and consequent membrane curvature, which may eventually result in the hemolysis of red cells. This possible mechanism of hemolysis can well explain some experimental observations on hemolysis.  相似文献   

9.
The application of the droplet vitrification cryopreservation technique to taro accessions from a range of Asia Pacific countries is presented. The optimum protocol involves excision of about 0.8 mm shoot-tips from in vitro plants, 20–40 min PVS2 exposure at 0°C followed by rapid plunge into liquid nitrogen. Thawing was done at room temperature (25°C) and shoot-tips inoculated on MS medium with 0.1 M sucrose regenerated into plantlets 4–6 weeks later. This new droplet vitrification protocol improved the mean post-thaw regeneration rates to 73–100% from 21–30% obtained with the previous cryo-vial vitrification protocol.  相似文献   

10.
Autolytic degradation of yeast RNA occurs in many foods and beverages and can impact on the sensory quality of the product, but the resulting complex mixture of nucleotides, nucleosides and nucleobases has not been properly characterised. In this study, yeast autolysis was induced by incubating cell suspensions of Saccharomyces cerevisiae at 30–60 °C (pH 7.0), and at pH 4.0–7.0 (40 °C) for 10–14 days, and the RNA degradation products formed during the process were determined by reversed-phase HPLC. Up to 95% of cell RNA was degraded, with consequent leakage into the extracellular environment of mainly 3′-, 5′- and 2′-ribonucleotides, and lesser amounts of polynucleotides, ribonucleosides and nucleobases. The rate of RNA degradation and the composition of the breakdown products varied with temperature and pH. RNA degradation was fastest at 50 °C (pH 7.0). Autolysis at lower temperatures (30 °C and 40 °C) and at pH 5.0 and 6.0 favoured the formation of 3′-nucleotides, whereas autolysis at 40 °C and 50 °C (pH 7.0) favoured 5′- and 2′-nucleotides. The best conditions for the formation of the two flavour-enhancing nucleotides, 5′-AMP and 5′-GMP, were 50 °C (pH 7.0) and pH 4.0 (40 °C), respectively.  相似文献   

11.
The combined effects of temperatures of 14, 17, 20, 22, and 25°C and salinities of 36–12‰ on embryos and larvae of the sand dollar Scaphechinus mirabilis was studied. Embryonic development is the most sensitive stage in the early ontogenesis of S. mirabilis. It is completed at a temperature of 14–20°C in a salinity range of 36–24‰ and at temperature of 22°C to 26‰. The fertilization proceeds in wider ranges of temperature and salinity. Among the swimming larvae, blastulae showed the greatest resistance to variations of these environmental factors. All the larvae survived at a temperature of 14–22°C and a salinity of 36–20‰, and more than 70% of them at 18‰. The pluteus I is the most vulnerable stage; probably this is related to the formation of the larval skeleton and transition to phytoplankton feeding. The survival of larvae at the age of 20 days was 100% at 14–22° C and a salinity of 36–24‰, most of them survived at 14–20°C and a salinity 18‰. The temperature 25 ° C is the most damaging for early development of S. mirabilis. The duration of development of that species lasts 28.5–29 days at 20°C and a salinity of 32.2–32.6‰. At 20 and 22°C, the larvae settled and completed metamorphosis more quickly if sand from the parental habitat was present. The larvae did not settle during the experiment (14 days) at 14 ° C and in the absence of sand.  相似文献   

12.
A new species, Overstreetia olsoni, is described from Atherinomorus capricornensis off Heron Island on the Great Barrier Reef off Queensland, Australia. It differs from its only known congener in that the enlarged spines of the circum-oral rows are smaller ( ≤ 4.5 × 3.5 vs ≤ 21.5 × 10.5μm), the sucker-ratio is smaller (1: 0.97–1.01 vs 1:1.8) and the eggs are larger (40–45 × 22–28 vs 34–37 × 17–22μm).  相似文献   

13.
Embryogenic tissues of Pinus nigra have been cryopreserved using a two step slow-freezing method. In the first experiment, 20 cell lines were included and the effect of the duration of cryostorage (1 h vs. 1 year) on regrowth was compared. After a short-term storage (1 h in liquid nitrogen, LN) out of 20 cell lines tested 15 showed regrowth (75%) with individual frequencies 10–100%. Long term storage (1 year in LN) resulted in regrowth of 14 cell lines (70%) while the individual frequencies reached 10–100%. One year storage had no negative influence on the fresh mass accumulation evaluated 2–3 months after thawing. Another 20 cell lines were included in the second experiment with the aim to study the correlation between cryotolerance and maturation capacity of cell lines. Between maturation capacity and cryotolerance expressed as regrowth frequencies of individual cell lines, no correlation has been found.  相似文献   

14.
Results of electrophysiological studies suggest a significant role of the lateral spinal nucleus (LSpN) in the transmission of nociceptive signals. In our study, the presence of Fos immunoreactivity and NADPH-diaphorase positivity was observed in the rat LSpN following noxious peripheral subcutaneous stimulation. Formalin-induced unilateral hindpaw stimulation in the rat caused bilateral NADPH-d reactivity and ipsilateral Fos expression in this nucleus. In the LSpN of the L3–L5 segments of stimulated rats, on average, 4.1 ± 1.2 NADPH-d-positive, NADPH-d(+), 5.1+1.8 Fos-immunoreactive, Fos(+), and 3.0 ± 1.1 double-labeled neurons per 25-μm-thick section were found unilaterally. A close anatomical relationship between NADPH-d(+) processes and Fos(+) cell nuclei in the LSpN was also observed following noxious peripheral stimulation. These neuroanatomical findings support the hypothesis that the LSpN is involved in pain processing and suggest an important role of nitric oxide-mediated signal transduction in this nucleus. Neirofiziologiya/Neurophysiology, Vol. 40, No. 1, pp. 38–42, January–February, 2008.  相似文献   

15.
HepatitisBvirus(HBV),themajorcausativeagentofchronicviralhepatitisandlivercirrhosis,isstronglyconnectedwiththedevelopmentofhepatocellularcarcinoma.OneofthemostremarkablefeaturesofHBVinfectionisthatinfectedcellsproducemultipletypesofvirusrelatedparticle…  相似文献   

16.
Early life stages of cephalopods are somewhat complex due to the life history strategy or species specificity of generalized ontogenetic patterns and processes. This work aimed to determine the time length of embryonic development at different temperatures, and if the egg size is a determinant of hatchling size in Sepiola atlantica d′Orbigny, 1839–1842. Successful hatching occurred in 98.5–100% of the eggs for each female. As seen in other coleoid cephalopods, temperature determines the amount of time for embryonic development in S. atlantica, and the obtained data were very similar to other coleoid cephalopods. Developmental times for temperatures at 13 ± 0.4°C, 18 ± 0.3°C and 16.4 ± 1.1°C were 61.8 ± 3.8, 22.6 ± 1.7 and 40.1 ± 4.8 days. The duration of embryonic development and hatchling mantle length was not strictly related. The egg volume was positively related to hatchling mantle length. Our results provide new records on the duration of embryogenesis and other information on reproductive patterns in this species. Some hatching and post-hatching behaviour are shown and discussed.  相似文献   

17.
Lipase-catalyzed synthesis of isoamyl acetate in hexane at 10–250 MPa at 80°C and 1–100 MPa at 40°C resulted in activation volumes of −12.9 ± 1.7 and −21.6 ± 2.9 cm3 mol−1, respectively. Increasing pressure from 10 to 200 MPa resulted in approximately 10-fold increase in V max at both 40 and 80°C. Pressure increased the K m from 2.4 ± 0.004 to 38 ± 0.78 mM at 40°C. In contrast, at 80°C the pressure did not affect the K m.  相似文献   

18.
In the present work, we showed that a chalcone-enriched fraction (CEF) isolated from the stem bark of a Brazilian medicinal plant, Myracrodruon urundeuva, presents neuroprotective actions on 6-hydroxydopamine (6-OHDA)-induced neuronal cell death, in rat mesencephalic cells. In the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium] assay, which is an index of cell viability, CEF (1–100 μg/ml) reversed in a concentration-dependent manner the 6-OHDA-induced cell death. While cells exposed to 6-OHDA (40 μM) showed an increased concentration of thiobarbituric acid reactive substances (TBARS), the pretreatment with CEF (10–100 μg/ml) significantly decreased the 6-OHDA-induced TBARS formation, indicative of a neuroprotection against lipoperoxidation. Furthermore, the drastic increase of nitrite levels induced by 6-OHDA, indicative of nitric oxide formation and free radicals production, was prevented by CEF. Double staining with acridine orange/ethidium bromide showed that cultures exposed to 6-OHDA (40 and 200 μM) presented an increase of apoptotic and necrotic cell numbers in a concentration-dependent manner. CEF (100 μg/ml) protected cells from apoptosis and necrosis and increased number of cells presenting a normal morphology. The immunohistochemical analysis for tyrosine hydroxylase (TH) positive neurons indicated that 6-OHDA (40 and 200 μM) caused a concentration-dependent loss of TH+ and TH− neurons. CEF protected both cells types from 6-OHDA-induced cell death. All together, our results demonstrated neuroprotective effects of chalcones, which are able to reduce oxidative stress and apoptotic injury caused by 6-OHDA. Our findings suggest that chalcones could provide benefits, along with other therapies, in neurodegenerative injuries, such as Parkinson’s disease.  相似文献   

19.
Vibrational stimulation of the tendon of the mm.gastrocnemius+soleus (100 sec–1) in rats anesthetized with chloral hydrate (400 mg/kg) resulted in the appearance of considerable Fos immunoreactivity in the lumbar spinal cord (L1-L6), as compared with that in intact animals. Total densities of Fos-immunopositive (Fos-ip) neurons in each of the examined segments were higher than 40 units per 40-μm-thick slice; the respective index reached the maximum at the L4 level (78.9 ± 2.3 cells). Most Fos-ip neurons were localized in laminae 4 to 7 of the gray matter, both ipsi- and contralaterally with respect to the side of stimulation (28.5 ± 0.6 and 28.4 ± 0.6, respectively). Single Fos-ip motoneurons were found bilaterally in the ventral horn motor nuclei. Thus, activation of muscle spindle receptors induced by vibrational stimulation applied to the Achilles tendon induces noticeable bilateral c-fos expression in spinal neuronal networks related to transmission of proprioceptive muscle-born impulsation.  相似文献   

20.
The development of Gryllus argentinus Sauss. was studied under stable laboratory conditions: the temperature of 26°C, the air humidity of 60%, and the photoperiod of 12h light: 12 h dark. The life cycle of Gryllus argentinus includes four stages: egg, pronymph, nymph, and adult. The duration of embryonic development is 18 days. The depth of egg bedding in the peat is 9.63 ± 0.12 mm (n =145), the clutch containing 2–4 eggs. A female can lay over 1100 viable eggs during the entire oviposition period. Nymphal development includes 9 instars and lasts 97 days. The duration of nymphal instars (days) is: I—5; II—6; III—6; IV—6; V—8; VI—10; VII—13; VIII—14; IX—29. The duration of the adult life is 51 days in males and 69 days, in females. In the imaginal ontogenesis of males and females, three periods can be distinguished: pre-reproductive, reproductive, and postreproductive. Males start to emit the aggressive signal on the 6th (5–8th) day (the pre-reproductive period). They enter the reproductive period (start to emit the calling song) on the 9th (8–13th) day. Females enter the reproductive period (become capable of responding to the calling song and of copulation) on the 9th (8–10th) day. Oviposition starts on the day after the first copulation. The reproductive period lasts about 40 (15–59) days in males and 58 (21–70) days in females. The post-reproductive period starts in females at the moment of finishing the egg laying period and in males, with disappearance of reproductive behavior. The period ends in the animal’s death.  相似文献   

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