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1.
Phytoplanktonic populations were studied in Tazenat lake by three methods:
A comparison of the results obtained gives an insight into the utilisation and transformation of energy by the biota of the lake 相似文献
| – | Primary production using 14C technic |
| – | Standing crop estimation |
| – | Amount of chlorophyll a |
2.
Being able to carry zidovudine (AZT) at known concentrations into CD4+/CD38+ and CD14+ cells permits:
Further studies are necessary in order to:
相似文献
| – | - to reduce the drug dosage and to increase the interval for administration (until 1 dose I.V. every week); |
| – | - to modulate the drug concentration into the CD4+/CD38 an CD14+ cells in relation to the in vitro determined HIV sensitiveness; |
| – | - to eliminate haematological, medullary and general toxicity; |
| – | - to be able to treat severely hill patients. |
| – | - To find out the better phase to start the therapy; |
| – | - To use several drugs with different mechanisms of action in order to slow down as much as possible the presence of resistant viral strains. |
| – | - As for other drugs which are beginning to be used with artificial vehicles, futher studies are required to improve the selectivity and safety of LIPOAZT for the target cells including macrophages. |
3.
Culture studies with healthy and virus-infected isolates of Ectocarpus siliculosus, Feldmannia simplex and F. irregularis gave the following results:
相似文献
| – | Virus particles are produced in deformed reproductive organs (sporangia or gametangia) of the hosts and are released into the surrounding seawater. |
| – | Their infective potential is lost after several days of storage under laboratory conditions. |
| – | New infections occur when gametes or spores of the host get in contact with virus particles. The virus genome enters all cells of the developing new plant via mitosis. |
| – | Virus expression is variable, and in many cases the viability of the host is not impaired. Infected host plants may be partly fertile and pass the infection to their daughter plants. |
| – | Meiosis of the host can eliminate the virus genome and generate healthy progeny. |
| – | The genome of the Ectocarpus virus consists of dsDNA. Meiotic segregation patterns suggest an intimate association between virus genome and host chromosomes. |
| – | An extra-generic host range has been demonstrated for the Ectocarpus virus. |
| – | Field observations suggest that virus infections in ectocarpalean algae occur on all coasts of the world, and many or all Ectocarpus and Feldmannia populations are subject to contact with virus genomes. |
4.
Rolf Bergmann 《Antonie van Leeuwenhoek》1989,55(2):143-152
Thiolutin was found to inhibit the utilization of glucose and other growth substrates in Escherichia coli. The inhibition was detected by a sharp drop of the respiration rate after addition of the antibiotic. The actual function affected was allocated to the cytoplasmic membrane of the bacterial cells by the following evidence:
It was concluded that the transport of certain substrates across the membrane was inhibited. 相似文献
| – | - spheroplasts were affected like intact cells, |
| – | - individual reactions of either the electron transport chain or the glycolytic pathway were not inhibited, |
| – | - glucose consumption in the culture stopped and the cells accumulated guanosine tetraphosphate as under starvation conditions, |
| – | - activation of the cell's apo-glucose dehydrogenase restored respiration via bypassing the glucose phosphotransferase system. |
5.
R. Durand 《Mycopathologia》1976,60(1):3-16
The present review describes the effects of light on reproductive processes in fungi, mainly when action spectra are available.The study of these has resulted in three kinds of photoresponses observable in fungi:
相似文献
| – | responses only to UV light (230–380 nm) |
| – | responses to NUV and blue light (300–520nm) |
| – | responses to great wavelengths of the visible spectrum. The photomorphogenetic processes on the control of these same photoreceptor pigments are reviewed. |
6.
Structure and osmoregulatory functions of the intestinal folds in the seawater eel,Anguilla anguilla
Valérie Simonneaux Willy Humbert Raymond Kirsch 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,158(1):45-55
| 1. | The epithelium of the anterior intestine in the seawater eel shows very high and narrow folds whose composition and possible role in osmotic regulation were studied. |
| 2. | The enterocytes present a basal labyrinth: numerous mitochondria more or less surrounded by infoldings of the basal membrane. In the intestinal folds, the serosal tissue contains lymphocytes, fibrocytes, enterochromaffin cells, capillaries, smooth muscle fibers and collagen fibers. The tissue is less dense at the tip than at the base of the folds. |
| 3. | X-ray microanalyses and electrophysiological studies showed that the serosal, spaces are diffusive compartments sustaining ionic gradients. Na+ and Cl– activity decreased and K+ activity increased from the base to the tip of the intestinal folds. |
| 4. | Na+ or Cl– gradients are abolished when the co-ion is removed from the bathing solutions. Serosal ouabain has no reproducible effects on the ion gradients, making it impossible to determine whether these gradients result from the activity of the Na+–K+ pump. K+ gradients decreased with serosal barium and increase with mucosal barium. |
| 5. | The ion distribution in the serosal compartments together with ultrastructural characteristics are discussed. It is suggested that water absorption occurs involving a basal ion recycling mechanism. |
7.
James S. Clark 《Biogeochemistry》1990,11(1):1-22
Path analysis was used to determine the importance of long-term disturbance regime and the relative importances of correlations among vegetation patterns, disturbance history, and nitrogen (N) mineralization in old-growth forests of northwestern Minnesota. Leaf biomass (estimated by allometric equations), fire history (from fire scars on Pinus resinosa trees), and N mineralization rates (estimated from incubationsin situ) were determined from sample plots dominated by
相似文献
| – | Betula papyrifera, Populus tremuloides, andP. grandidentata |
| – | a mixture ofAcer saccharumandTilia americana, or |
| – | Quercus borealis andOstrya virginiana. |
8.
9.
Sources,fates, and impacts of nitrogen inputs to terrestrial ecosystems: review and synthesis 总被引：1，自引：0，他引：1
The relative importance of nitrogen inputs from atmospheric deposition and biological fixation is reviewed in a number of diverse, non-agricultural terrestrial ecosystems. Bulk precipitation inputs of N (l–l2 kg N ha–1 yr–1) are the same order of magnitude as, or frequently larger than, the usual range of inputs from nonsymbiotic fixation (< 1=" –=" 5=" kg=" n=">–1 yr–1), especially in areas influenced by industrial activity. Bulk precipitation measurements may underestimate total atmospheric deposition by 30–40% because they generally do not include all forms of wet and dry deposition. Symbiotic fixation generally ranges from 10–160 kg N ha–1 yr–1) in ecosystems where N-fixing species are present during early successional stages, and may exceed the range under unusual conditions.Rates of both symbiotic and nonsymbiotic fixation appear to be greater during early successional stages of forest development, where they have major impacts on nitrogen dynamics and ecosystem productivity. Fates and impacts of these nitrogen inputs are important considerations that are inadequately understood. These input processes are highly variable in space and time, and few sites have adequate comparative information on both nitrogen deposition and fixation.
相似文献
| – | - more intensive studies of total atmospheric deposition, especially of dry deposition, are needed over a wide range of ecosystems; |
| – | - additional studies of symbiotic fixation are needed that carefully quantify variation over space and time, examine more factors regulating fixation, and focus upon the availability of N and its effects upon productivity and other nutrient cycling processes; |
| – | - process-level studies of associative N-fixation should be conducted over a range of ecosystems to determine the universal importance of rhizosphere fixation; |
| – | - further examination of the role of free-living fixation in wood decomposition and soil organic matter genesis is needed, with attention upon spatial and temporal variation; and |
| – | - investigations of long-term biogeochemical impacts of these inputs must be integrated with process-level studies using modern modelling techniques. |
10.
Gareth Rice Roland Clift Richard Burns 《The International Journal of Life Cycle Assessment》1997,2(1):53-59
Twelve of the main European LCA software packages currently available are examined wirh the aim of establishing which are
the most appropriate for LCAs on industrial processes. The packages performances are assessed in terms of
The review concludes with a Specification Table which summarises the facilities available on each software package.
The general conclusion from this study is that for industrially based LCAs, there are four packages which may offer advantages
over the rest. These are The Boustead Model, The Ecobilan Group’s TEAM™, PEMS 3.0 and SimaPro 3.1. 相似文献
| – | • Volume of Data |
| – | • WindowsTM environment |
| – | • Network Capabilities |
| – | • Impact Assessment |
| – | • Graphical representation of the inventory results |
| – | • Sensitivity analysis |
| – | • Units |
| – | • Cost |
| – | • User Support |
| – | • Flow Diagrams |
| – | • Burdens allocation |
| – | • Transparency of data |
| – | • Input & output parameters |
| – | • Demo version |
| – | • Quality of data |
11.
The active reaction upon stimulation of the femoral chordotonal organ in stick insects is known to control velocity and endpoint of flexion movements of the femur-tibia joint (Bässler 1988). This article presents evidence that spiking interneurones in the ventral anterior median part of the adjacent ganglion participate in the generation of the active reaction as well as non-spiking interneurones in the dorsal lateral region do. Three different kinds of experiments lead to this conclusion:
相似文献
| – | - Ablation of the ventral anterior median part of the metathoracic ganglion ofExtatosoma did not qualitatively alter the resistance reflex in the inactive animal but abolished the active reaction. |
| – | - Recordings from spiking interneurones in the same region of the prothoracic ganglion ofCarausius show that some of these neurones responded to a chordotonal organ stimulus in a way, which depended on the behavioural state of the animal. |
| – | - Some non-spiking interneurones, which mediate the resistance reflex in the inactive animal, respond differently during an active reaction. |
12.
Impact of phosphorus supply on root exudation, aerenchyma formation and methane emission of rice plants 总被引：2，自引：0，他引：2
This study evaluated the impact of P supply on rice plant development and the methane budget of rice fields by 2 different approaches: (1) root growth, exudation and aerenchyma formation were recorded in an experiment with hydroponic solution; (2) dissolved CH4 concentration and CH4 emission were investigated in a pot experiment. In both approaches, we used three different cultivars and three levels of P supply. In the experiment with solution culture (0.5 ppm, 5 ppm, and 10 ppm P), root exudation ranged between 0.5 to 36.7 mol C plant–1 h–1 and increased steadily with plant growth at given P level. Low P supply resulted in
However, root exudation did not differ among treatments when related to the dry weight of roots. Thus, high exudation rates were caused by larger root biomass and not by higher activity of the root tissue.The pot experiment was conducted with a P-deficient soil that was either left without amendment or fertilized by 25 and 50 mg P kg
soil
–1
, respectively. Low P supply resulted in
相似文献
| • | depressed shoot growth but increased root growth in culture solution |
| • | increments in the root/shoot ratio by factors of 1.4 to 1.9 at flowering stage |
| • | enhanced the development of root aerenchyma, and |
| • | stimulation of root exudation per plant by factors of 1.3–1.8 as compared to medium P |
| • | supply and by factors of 2.1–2.4 as compared to high P supply. |
| • | higher CH4 concentrations in soil solution; i.e., at flowering stage the soil solution concentrations were 34–50 M under P deficiency and 10–22 M under ample P supply and · significant increases of CH4 emission rates during the later stages of plant growth. |
| • | These findings reflect a chain of response mechanisms to P stress, that ultimately lead to higher methane emission rates. |
13.
Peter Krippeit-Drews Gisela Drews Kai Graszynski 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1989,159(1):43-49
| 1. | Transepithelial potential differences (PDte) and acidification rates of the bath chamber were measured on isolated perfused posterior gills of the fiddler crabUca tangeri adapted to dilute seawater. |
| 2. | The PDte decreased to almost zero when Na+ was substituted by choline or when ouabain was added to the perfusion saline in high concentrations (10 mmol·l–1). Thus, the rheogenic NaCl-transport across the gill epithelium seems to be totally Na+-dependent. |
| 3. | When Cl– was replaced by gluconate, a bath positive PDte occurred which was insensitive to ouabain. This PDte could also be observed when, in addition to Cl– removal, Na+ was replaced by TMA+. |
| 4. | Bath acidification under normal conditions could be abolished by ouabain, indicating that there is H+ excretion via electrically silent Na+/H+ exchange. In contrast, bath acidification under Cl–-free conditions is only partially blocked by ouabain. |
| 5. | It is concluded that under Cl–-free conditions a rheogenic H+-pump in the apical membrane is responsible for the ouabain-insensitive bath acidification as well as for the PDte. |
14.
J. Pernberg H. Machemer 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1989,164(4):551-562
| 1. | Properties of the membrane currents ofDidinium nasutum have been investigated under voltage clamp in different solutions and after deciliation. |
| 2. | Theearly transient Ca2+ inward current activates in a voltage-dependent manner. Inactivation is both Ca2+ -dependent and voltage-dependent. |
| 3. | Alate Ca2+ current rises with time to peak > 50 ms and decays in the order of seconds. |
| 4. | Activation and inactivation of the late Ca2+ current is voltage-dependent. |
| 5. | The delayed outward current is activated by voltage. The kinetics of this K+ current, but not its amplitude, are enhanced in the presence of intracellular EGTA. |
| 6. | The two voltage-dependent Ca2+ channels are located in the cilia, whereas all K+ channels are restricted to the somatic membrane. |
15.
3DFS is a 3D flexible searching system for lead discovery. Version 1.0 of 3DFS was published recently (Wang, T.; Zhou, J. J. Chem. Inf. Comput. Sci., 1998, 38, 71–77). Here version 1.2 represents a substantial improvement over version 1.0. There are six major changes in version 1.2 compared to version 1.0.
Besides the above, this paper supplies:
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1007/s0089490050231 相似文献
| 1. | A new rule of aromatic ring recognition. |
| 2. | The inclusion of multiple-type atoms and chains in queries. |
| 3. | The inclusion of more spatial constraints, especially the directions of lone pairs. |
| 4. | The improvement of the query file format. |
| 5. | The addition of genetic search for flexible search. |
| 6. | An output option for generating MOLfiles of hits. |
| 1. | More query examples. |
| 2. | A comparison between genetic search and Powell optimization. |
| 3. | More detailed comparison between 3DFS and Chem-X. |
| 4. | A preliminary application of 3DFS to K+ channel opener studies. |
16.
Micropropagated bananas derived from Banana Bunchy-Top Virus (BBTV) infected plants, but displaying no symptoms of the disease, were established in the field. They were grown for three years and produced a plant crop and ratoon crops. No disease symptoms were observed. There was uncertainty as to whether
To resolve this question, suckers from these plants and non-infected controls were established in pots and infected with aphids, Pentalonia nigronervosa Coq, collected from BBTV-infected plants. All plants produced characteristic Banana Bunchy-Top Disease (BBTD) symptoms in five months. In addition, samples collected from the original symptomless field plants were tested by DAS-ELISA using a polyclonal antibody specific for BBTV. No detectable levels of virus were found in any of the samples. These studies support the view that the symptomless plants were virus free and not symptomlessly infected or BBTV-resistant somaclones generated from micropropagation. Nevertheless there continues to be a need for caution in dissemination of micropropagated bananas, especially when obtained from regions where BBTV is known to occur. 相似文献
| – | micropropagation eliminated the virus from the material, |
| – | the plants were symptomlessly infected, or |
| – | the plants were somaclonal variants that suppress symptom expression. |
17.
J. van der Blom 《Insectes Sociaux》1992,39(3):237-249
Studies on the division of labour in honeybees have mainly been focused on behaviour that is performed by workers of different ages or genetic background. However, little is yet known about behavioural differenceswithin groups of honeybee workers. The aim of this paper is to establish whether queen attendance in honeybee colonies is a function of specialists among the workers within one age cohort in colonies with a natural number of partilines. Furthermore, I want to assess whether the duration of contact of individual workers with the queen is correlated with their involvement in other behaviour and, in the long term, with their differentiation into laying and non-laying workers after the colony becomes queenless.The individual involvement in queen attendance was studied by investigation of three parameters:
I hardly found any indications that there is a significance differentiation for queen attendance. 相似文献
| – | the number of separate bouts of performing the behaviour |
| – | the total duration of queen-worker contact |
| – | the constancy of the relative individual involvement. |
18.
In this report we describe the most suitable protocol for callus formation and plant regeneration for cotton. We screened 15 cotton (Gossypium hirsutum L.) genotypes for metal resistance and two of them, Nazilli M-503 (M503) Nazilli 143 (N-143) selected as Cd, Cu and Ni resistant. The cotyledonary nodes from these genotypes were the best explants for regeneration of shoots (more than 90 %) and roots (50 to 70 %). Shoot apex also gave good shoot regeneration (more than 90 %) but their root regeneration efficiency was low (35 %). These results show that Murashige and Skoog (MS) media containing 0.44 μM naphthaleneacetic acid (NAA) and 0.98 μM indole-3-butyric acid (IBA) was the most suitable recipe for getting high shoot and root regeneration from cotyledonary nodes of N-143 and M503 cotton genotypes.Abbreviations
This work was supported by the Textile Industry grant No. F000301 given to A.R. Memon. 相似文献
| 2,4 D | 2,4-dichlorophenoxyacetic acid |
| BAP | 6-benzylaminopurine |
| GA | gibberellic acid |
| IBA | indole-3-butyric acid |
| MS medium | Murashige and Skoog medium |
| NAA | naphthaleneacetic acid |
19.
Oncostatin M, a multifunctional cytokine 总被引：6，自引：0，他引：6
20.
Donald A. Briscoe Gary Fiskum Anne L. Holleran Joanne K. Kelleher 《Molecular and cellular biochemistry》1994,136(2):131-137
Metabolic characteristics of experimental hepatoma cells include elevated rates of glycolysis and lipid synthesis. However, pyruvate derived from glucose is not redily oxidized, and the source of acetly CoA for lipid synthesis in As-39D cells has not been characterized. In this study ketone bodies were examined as a possible source of acetyl CoA in AS-30D hepatoma cells.The major findings were:
相似文献
| 1. | Acetoacetate was utilized by AS-30D cells, with14C-lipid and14CO2 as major products of [3-14C] acetoacetate. |
| 2. | Lipid synthesis from acetoacetate was dependent on the presence of glucose in the medium. |
| 3. | Acetoacetate supported rapid respiration by AS-30D mitochondria in the presence of 0.1 mM malate. |
| 4. | Succinly CoA acetoacetyl CoA transferase activity in AS-30D mitochondria was approximately 40 fold greater than that found in rat liver mitochondria. |
| 5. | Addition of acetoacetate, but not -hydroxybutyrate decreased conversion of [1-14C] acetate to14CO2, presumably by diluting the specific radioactivity of the acetyl CoA derived from the acetate tracer. |
| 6. | In the presence of glucose, approximately one fourth of acetoacetate utilized was converted to lipid. This result is consistent with elevated lipogenesis postulated by the truncated TCA cycle hypothesis. These data demonstrate for the first time the flux of acetoacetate carbon to lipid and CO2 in hepatoma cells and suggest that increases in the ambient concentration of acetoacetate, occurring in fasting or malignant cachexia, could produce increases in the utilization of this ketone body by hepatoma cells containing 3-oxyacid CoA transferase activity. |