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61.
鄱阳湖水生维管束植物生物量及其合理开发利用的初步建议 总被引:15,自引:2,他引:13
用4种不同的计算方法测定了鄱阳湖水生维管束植物的生物量。根据22个断面,199个采集点,398个样方的测定结果,得出鄱阳湖水生维管束植物的年生产量为431.76万吨(湿重),即相当于5.44×10~(-15)焦耳(能量)。其中,马来眼子菜、苦草和黑藻等3种合计约占总生物量的71.46%。全湖可供草食性鱼类食用的水生维管束植物约占总量的86.9%。文中还对4个植物带和9个群丛生物量的分布规律进行了讨论。提出了人工增殖草食性鱼类,调整湖中植被组成,保护和种植水生经济植物等合理开发利用鄱阳湖水生植物资源的初步建议。 相似文献
62.
Summary The popliteal lymph nodes were removed from young rats of various ages five days after a single immunization with TNP-KLH in the hind footpads. Cryostat sections of the lymph nodes were investigated by means of enzyme and immunohistochemical techniques at the light-microscopical level.The presence and localization of anti-TNP antibody-containing cells were examined using a new technique to visualize specific antibodies. Moreover, the development of the lymph nodes following exogenous antigenic stimulation was compared with that of unstimulated lymph nodes.Specific antibody-containing cells could not be found before day 15 after birth, in rats immunized at day 10. From that time these lymphoid cells were located primarily at the border between cortex and medulla. Younger popliteal lymph nodes showed only aspecific immunoglobulin-containing lymphoid cells. With age, the number of specific antibody-containing cells tended to increase. These cells were more mature, according to morphological criteria and were located nearer the medulla.The first primary follicles were seen at day 19, as was the case in unstimulated animals. The first secondary follicles, containing germinal centers, were detected at day 23, whereas in unstimulated popliteal lymph nodes they were never found.Trapping of immune complexes could not be demonstrated before day 33 after birth. The later appearance of this phenomenon might be a consequence of the techniques applied to demonstrate specific antibody-containing cells.Abbreviations PLN
popliteal lymph node
- FDC
follicular dendritic cell
- IDC
interdigitating cell
- HEV
high endothelial venule
- TNP
trinitrophenyl
- KLH
keyhole limpet hemocyanin
- PBS
phosphate-buffered saline
- GCPC
germinal center precursor cell
-
sIg
surface immunoglobulin
-
cIg
cytoplasmic immunoglobulin 相似文献
63.
Abstract: Primary cultures were prepared from newborn rat brain. After 16-18 days, they consisted mainly of mature and immature astrocytes and oligodendrocytes, as judged by immunohistochemistry. To study the metabolism of ethanolamine glycerophospholipids, the cells were incubated with 1-[1-3 H]alkyl- sn -glycero-3-phosphoethanolamine (1-alkyl-GPE), for 1–20 h. Five main products were formed: 1-alkyl-2-acyl-GPE; 1-alkyl-2-acyksn-glycero-3-phosphocholine (1-alkyl-2-acyl-GPC); 1-alkenyl-2-acyl-GPE (ethanolamine plasmalogen); 1-alkenyl-2-acyl-GPC (choline plasmalogen); and 1-alkyl-glycerol. Acylation of the substrate was the main reaction during the first 3 h of incubation, whereas desaturation to plasmaiogen reached a maximum after 12 h. Greater amounts of radioactivity were observed in the phosphatidylcholine fraction after longer incubation times. Only small amounts of choline plasmalogen were observed. The phosphatidylethanolamine fraction consisted of 26.5% diacyl-, 27.5% alkyl-acyl-, and 46.0% alkenyl-acyl- compounds, whereas the corresponding data for the phosphatidylcholine fraction were 78.5, 16.4, and 5.1%, respectively, after 20 h of incubation. Hydrolysis of the substrate to 1-alkyl-glycerol was a minor reaction. 相似文献
64.
B. Edwin Blaisdell 《Journal of molecular evolution》1983,19(2):122-133
Summary Coding sequences of eucaryotic nuclear DNA were characterized by an excess of short runs and a deficit of long runs of weak
and of strong hydrogen bonding bases; non-coding sequences by a deficit of short runs and an excess of long runs, in the same
of purines and of pyrimidines. The conservation of these attributes across DNA sequences coding for proteins of widely different
function, across widely different eucaryotic species for the same protein and across related genes that diverged a long time
ago and that now show large differences in base and, if coding, amino acid sequence suggested that these attributes have survival
value. It was concluded that these attributes constitute probalistic constraints on th primary structure (base sequence) of
both coding and non-coding DNA. 相似文献
65.
B. Peco 《Plant Ecology》1989,83(1-2):269-276
Pasture vegetation in an open woodland of Quercus rotundifolia subjected to periodic ploughing was sampled in spring during 8 consecutive years. The frequency of herbaceous species was recorded in a total of 69 permanent plots located on 5 adjacent sites with similar lithology, slope and orientation but differing in age since previous ploughing.Vegetation dynamics expressed as trajectories of permanent plots in a non-metric multidimensional scaling space has been modelled in terms of evironmental variables. By fitting a generalized linear model, the dynamics are shown to be related to years since last ploughing, geographical location of plots, total annual rainfall and November rainfall. Meteorological patterns of the sampling period are also described.Abbreviations GLM =
Generalized Linear Model
- NMDS =
Non-metric Multi-Dimensional Scaling
- UPGMA =
Unweighted Pair-Group Method using Arithmetic Averages 相似文献
66.
Shiro Tsuyuzaki 《Ecological Research》1989,4(2):167-173
In 1987, a study on buried seed populations was conducted in the crater basin of Mt. Usu, a volcano located in northern Japan,
where the vegetation had beeen almost completely destroyed by eruptions in 1977 and 1978. The former vegetation had consisted
of grassland and broad-leaved forest. In the areas formerly occupied by this grassland and forest, 2128.0 and 1985.3 seeds
per square meter, respectively, were extracted from 12 blocks of the former topsoil using a floattion method. This revealed
that many seeds were still viable even after ten years of burial under thick volcanic deposits. The seeds were distributed
more in sandy soil than in rocky soil of the former topsoil. Twenty-five species, most of which favored grassland, were detected
in both the former grassland and forest. From comparison of α-and β-diversities between the grassland and forest, the structure
of the buried seed population was considered likely to have been more diverse in the forest than in the grassland. The determinants
of composition of the buried seed populations were discussed with reference to the former vegetation and soil characteristics. 相似文献
67.
The authors examined relationships between Kira's warmth index (WI) and four other important thermal indices: the sums of
daily mean temperatures above 5°C and 10°C, Thornthwaite's potential evapotranspiration (PE) and Holdridge's annual biotemperature.
The thermal records of 671 meteorological stations evenly located all over China were used to make these comparisons. Close
correlations were found within the four relationships, and accordingly WI was used to analyse the thermal distributions of
the main vegetation types. Vegetation types around the 671 stations were read from a vegetation map with a scale of 1/4000000.
Vegetation types at 269 stations corresponded to the natural or seminatural vegetation, and 29 vegetation types were distinguished
by arranging the 269 data into the same or similar types. The geographical distribution of these 29 types and the corresponding
main climatic features were described. The relations between WI and distribution of these vegetation types were discussed
in detail. As a result, WI values (°C month) corresponding to the vegetation zones could be summarized as follows: (1) arctic
or alpine vegetation zone: 0–15; (2) boreal or subalpine vegetation zone: 15-(50–55); (3) cool-temperate vegetation zone:
(50–55)–(80–90); (4) warm-temperate vegetation zone: (80–90)–(170–180). These values almost coincided with Kira's values.
Chinese postgraduate student in Japan sent by the Chinese Government. 相似文献
68.
Primary production of phytoplankton and secondary production of a daphnid and a chaoborid were studied in a small eutrophic
pond. The gross primary production of phytoplankton was 290 gC m−2 per 9 months during April–December. Regression analysis showed that the gross primary production was related to the incident
solar radiation and the chlorophylla concentration and not to either total phosphorus or total inorganic nitrogen concentration. The mean chlorophylla concentration (14.2 mg m−3), however, was about half the expected value upon phosphorus loading of this pond. The mean zooplankton biomass was 1.60
g dry weight m−2, of whichDaphnia rosea and cyclopoid copepods amounted to 0.69 g dry weight m−2 and 0.61 g dry weight m−2, respectively. The production ofD. rosea was high during May–July and October and the level for the whole 9 months was 22.6 g dry weight m−2.Chaoborus flavicans produced 10 complete and one incomplete cohorts per year. Two consecutive cohorts overlapped during the growing season. The
maximum density, the mean biomass, and the production were 19,100 m−2, 0.81 g dry weight m−2, and 11.7 g dry weight m−2yr−1, respectively. As no fish was present in this pond, the emerging biomass amounted to 69% of larval production. The production
ofC. flavicans larvae was high in comparison with zooplankton production during August–September, when the larvae possibly fed not only
on zooplankton but also algae. 相似文献
69.
Characterization of Opioid Receptors in Cultured Neurons 总被引:1,自引:1,他引:0
Pierre J.-J. Vaysse R. Suzanne Zukin Kay L. Fields John A. Kessler 《Journal of neurochemistry》1990,55(2):624-631
The appearance of mu-, delta-, and kappa-opioid receptors was examined in primary cultures of embryonic rat brain. Membranes prepared from striatal, hippocampal, and hypothalamic neurons grown in dissociated cell culture each exhibited high-affinity opioid binding sites as determined by equilibrium binding of the universal opioid ligand (-)-[3H]bremazocine. The highest density of binding sites (per mg of protein) was found in membranes prepared from cultured striatal neurons (Bmax = 210 +/- 40 fmol/mg protein); this density is approximately two-thirds that of adult striatal membranes. By contrast, membranes of cultured cerebellar neurons and cultured astrocytes were devoid of opioid binding sites. The opioid receptor types expressed in cultured striatal neurons were characterized by equilibrium binding of highly selective radioligands. Scatchard analysis of binding of the mu-specific ligand [3H]D-Ala2,N-Me-Phe4,Gly-ol5-enkephalin to embryonic striatal cell membranes revealed an apparent single class of sites with an affinity (KD) of 0.4 +/- 0.1 nM and a density (Bmax) of 160 +/- 20 fmol/mg of protein. Specific binding of (-)-[3H]bremazocine under conditions in which mu- and delta-receptor binding was suppressed (kappa-receptor labeling conditions) occurred to an apparent single class of sites (KD = 2 +/- 1 nM; Bmax = 40 +/- 15 fmol/mg of protein). There was no detectable binding of the selective delta-ligand [3H]D-Pen2,D-Pen5-enkephalin. Thus, cultured striatal neurons expressed mu- and kappa-receptor sites at densities comparable to those found in vivo for embryonic rat brain, but not delta-receptors. 相似文献
70.
Bernard J. Van Vliet Arie H. Mulder Anton N. M. Schoffelmeer 《Journal of neurochemistry》1990,55(4):1274-1280
The receptors mediating the inhibition of D1 dopamine receptor-stimulated adenylate cyclase by opioids were examined in primary cultures of rat neostriatal neurons. Adenylate cyclase activity was dose-dependently increased by the selective D1 dopamine receptor agonist SKF 38393 (EC50 = 0.05 microM). This stimulation was fully antagonized by the selective D1 dopamine receptor antagonist SCH 23390 (1 microM). SKF 38393 (1 microM)-stimulated adenylate cyclase activity was strongly reduced (by almost 60%) by the highly selective mu-agonist [D-Ala2, MePhe4, Gly-ol5]-enkephalin (DAGO; EC50 = 0.006 microM) and high concentrations of the selective delta-agonist [D-Ser2(O-tert-butyl), Leu5]-enkephalyl-Thr6 (DSTBU-LET; EC50 = 0.13 microM) but not by the selective delta-agonist [D-penicillamine2, D-penicillamine5]enkephalin (DPDPE). D1 dopamine receptor-stimulated adenylate cyclase activity was also slightly reduced (by approximately 20%) by high concentrations of the kappa-agonist U50,488 (EC50 = 0.63 microM). The inhibitory effects of submaximally effective concentrations of DAGO, DSTBULET, and U50,488 were equally well antagonized by the mu-opioid receptor-selective antagonist naloxone (EC50 of approximately 0.1 microM). Neither the irreversible delta-ligand fentanyl isothiocyanate (1 microM) nor the reversible delta-antagonist ICI 174864 (1 microM) reversed the inhibitory effects of DSTBULET. The inhibitory effects of DAGO and U50,488 were equally well reversed by high concentrations (greater than 0.1 microM) of the kappa-opioid receptor-selective antagonist norbinaltorphimine. The effect of DAGO (1 microM) was already detectable after 1 day in culture, whereas DPDPE (1 microM) had no effect even after 28 days in culture. These data indicate that an homogeneous population of mu-opioid receptors coupled as inhibitors to D1 dopamine receptor-stimulated adenylate cyclase is expressed in rat neostriatal neurons in primary culture. 相似文献