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41.
The photosynthetic behaviour ofDunaliella viridis has been studied under a combination of three variables: irradiance (0–900 mol m–2 s–1), temperature (15, 23, 31, 38, 42 °C) and nitrogen concentration (0.05, 0.5, 1.5, 5, 10 mM NO
3
-
) at a salinity of 2 M NaCl.The highest rates of photosynthesis have been found at 31 °C and a nitrate concentration of 10 mM. There exists a synergistic effect between temperature and nitrogen availability on the photosynthesis ofD. viridis; under nitrogen deficiency oxygen evolution is low, even null at high temperature. The interaction between these two variables of control occurs in a multiplicative way. There is also a general increase in photosynthetic pigments following the increase in nitrogen concentration in the culture medium. The normalization of net photosynthesis data in relation to chlorophylla shows that nitrogen concentration makes an indirect control of the photosynthetic rate ofD. viridis through the variation of pigment concentration. 相似文献
42.
Elyse Bissonnette Ouhida Benrezzak Prometeo Madarnas Carlos Brailovsky Vijai N. Nigam 《Cancer immunology, immunotherapy : CII》1988,27(3):272-277
Summary Three synthetic glycolipids, maltose tetrapalmitate (MTP), maltose hexastearate (MHS), and maltose hexalinoleate (MHL) prepared as nontoxic lipid A analogs, and Escherichia coli lipopolysaccharide (LPS) were assayed for their mitogenic activity using spleen lymphocytes in nine inbred mouse strains and three F1 hybrids. The MTP and LPS were also assayed for their ability to enhance plaque-forming cell (PFC) responses using sheep red blood cells as the antigen in th same inbred mouse strains and F1 hybrids, The mitogenic activity of synthetic glycolipids was several fold lower than that of LPS and MHL was inferior to MTP and MHS. DBA/2J was the most responsive strain for MTP and DBA/1J and C3H/HeJ the least. The mitogenic activity of MTP was generally in agreement with the PFC response stimulation by it. Lowdose cyclophosphamide treatment of mice synergized MTP for PFC response augmentation. Genetic studies on MTP mitogenicity revealed that 90% of responder DBA/2J X nonresponder C3H/HeJ F1 hybrids had intermediate mitogenic activity. Among F2, 73% had intermediate-high activity and 27% were nonmitogenic. Among F1 X C3H/HeJ backcrosses 11% had high, 56% intermediate, and 33% had no mitogenic activity, whereas, for the F1 X DBA/2J backcross, 14% had high, 36% intermediate, and 50% low or negligible activity. The data favored a single gene for MTP activation of immune cells.This work was supported, in part, by a grant from the National Cancer Institute of Canada, and by grant from the Cancer Research Society Inc. 相似文献
43.
H Suzuki Y Kondo A D Carlos J C Seidel 《The Journal of biological chemistry》1988,263(22):10974-10979
The effects of ionic strength, MgATP, and phosphorylation on the degradation rates of heavy meromyosin (HMM) by papain have been compared to their effects on the sedimentation coefficient (s20,w) to determine the relationship of the degradation rate to the equilibrium between the flexed and the extended forms (Suzuki, H., Stafford, W. F., Slayter, H. S., and Seidel, J. C. (1985) J. Biol. Chem. 260, 14810-14817). At 0.025 M NaCl, where HMM is predominantly in the flexed form, MgATP, Mg-adenylyl imidodiphosphate or MgADP reduce kH by 80-90%. MgATP exerts its optimal effect at this ionic strength, where at least 70% of HMM is flexed in the presence or absence of MgATP, suggesting that nucleotides reduce kH by decreasing the proteolytic susceptibility of the flexed form. At 0.5 M NaCl, where HMM is in the extended form, MgATP has no effect on kH. At low ionic strengths phosphorylation decreases kH but increases it in the presence of MgATP. Plots of kH against s20,w determined at various ionic strengths are linear, the data for phosphorylated and dephosphorylated HMM falling on the same line. Thus, raising the ionic strength or phosphorylating the 20-kDa light chain appears to alter kH by increasing the fraction of HMM in the extended form. The degradation rate of the 20-kDa light chain (kL) of dephosphorylated HMM responds to changes in ionic strength in essentially the same way as does kH, suggesting that the response of kL to changes in ionic strength can also be attributed to conversion of HMM to the extended form. However, kL for phosphorylated HMM measured in the presence of MgATP exhibits very little dependence on ionic strength. 相似文献
44.
Richard C. Leegood Carlos A. Labate Steven C. Huber H. Ekkehard Neuhaus Mark Stitt 《Planta》1988,176(1):117-126
Glycerol induced a limitation on photosynthetic carbon assimilation by phosphate when supplied to leaves of barley (Hordeum vulgare L.) and spinach (Spinacia oleracea L.). This limitation by phosphate was evidenced by (i) reversibility of the inhibition of photosynthesis by glycerol by feeding orthophosphate (ii) a decrease in light-saturated rates of photosynthesis and saturation at a lower irradiance, (iii) the promotion of oscillations in photosynthetic CO2 assimilation and in chlorophyll fluorescence, (iv) decreases in the pools of hexose monophosphates and triose phosphates and increases in the ratio of glycerate-3-phosphate to triose phosphate, (v) decreased photochemical quenching of chlorophyll fluorescence, and increased non-photochemical quenching, specifically of the component which relaxed rapidly, indicating that thylakoid energisation had increased. In barley there was a massive accumulation of glycerol-3-phosphate and an increase in the period of the oscillations, but in spinach the accumulation of glycerol-3-phosphate was comparatively slight. The mechanism(s) by which glycerol feeding affects photosynthetic carbon assimilation are discussed in the light of these results.Abbreviations Chl
chlorophyll
- C
i
intercellular concentration of CO2
- P
phosphate
- PGA
glycerate-3-phosphate
- Pi
orthophosphate
- triose-P
sum of glyceraldehyde-3-phosphate and dihydroxyacetone phosphate 相似文献
45.
We studied the behavior of the Poeciliid fishGambusia affinis after the introduction of 3 substances into their tank: a homogenization ofGambusia affinis, a homogenization of the Anabantid fishBetta splendens, and a blank made of distilled water. The response of the fish was measured as a change in their spatial distribution in
the tank after the introduction of the substance. Two sizes of fish were used, and theGambusia homogenization produced clear alarm reactions in both, the fish fleeing to the bottom of the tank. This is one of a few examples
available of recognition of alarm substances in non-ostariophysian fish. In addition, we found that the small fishes that
had recently been exposed to the alarm substance stayed in an ‘alert state’, in which they had an increased sensitivity to
mechanical and visual fright stimuli. 相似文献
46.
47.
Summary In this paper the effect of temperature and pH on the settling behaviour of a flocculent strain ofZymomonas mobilis is studied by using the old fashioned batch settling technique. Plots are given to show the influence of the above mentioned parameters on the settling curve behaviour. 相似文献
48.
The sperm nuclei of Aulacomya ater, family Mitylidae, contain three proteins (X, Aa5 and Aa6) which are specific to this cell type coexisting with a set of five somatic-type histones. Information about the chromatin structure resulting from this kind of association is scarce. Therefore, we have probed the structure of this sperm chromatin through digestion with micrococcal nuclease in combination with salt fractionation. The data obtained have allowed us to propose a nucleosomal arrangement for this chromatin. However, two types of nucleosomes would be present in agreement with their protein components. 相似文献
49.
Accuracy and direction of error in the sexing of the skeleton: implications for paleodemography 总被引:1,自引:0,他引:1
R S Meindl C O Lovejoy R P Mensforth L Don Carlos 《American journal of physical anthropology》1985,68(1):79-85
Determinations of sex by subjective assessment of the skulls from a skeletal series of known sex were compared to fully independent assessments based on pelves of the same specimens. Within-sex correlations of cranial and pelvic morphologies measured on an android-gynecoid scale were smaller than expected. Subjective assessment by means of the skull compared favorably to that of the linear discriminant functions of Giles and Elliot; however, the direction of error was similar for both procedures. Of course, estimations based on the pelves were generally superior to both in terms of frequency and overall bias of error. The bias of sex estimation for paleodemographic purposes is contingent upon completeness of skeletal remains. 相似文献
50.
Glucocorticoids Potentiate the Prostaglandin E1 -Mediated Cyclic AMP Formation by a Cultured Murine Neuroblastoma Clone 总被引:2,自引:2,他引:0
The effect of steroid hormones on the prostaglandin E1 (PGE1)-mediated cyclic AMP formation by murine neuroblastoma clone N1E-115 was studied. Dexamethasone at submicromolar concentrations and corticosterone at micromolar concentrations (steroids with glucocorticoid activity) were able to modify the PGE1-mediated response whereas testosterone, progesterone, and estradiol each at 10 microM had no effect. Glucocorticoids added to the culture medium of N1E-115 cells produced an increase in the maximal response to PGE1 only after long-term (greater than or equal to 4 h) incubation with the hormone. Inhibitors of protein and RNA synthesis blocked this effect of glucocorticoids. Basal activity of adenylate cyclase in treated cells was twofold higher than that in control cells, and this enzyme seemed to be the primary target for the hormone action, since the activity of 3':5'-cyclic AMP phosphodiesterase and the binding of [3H]PGE1 to its receptors were not altered by glucocorticoid treatment. Our results indicate that glucocorticoids modulate receptor-mediated responses in cells of neural origin through a mechanism that involves induction of protein synthesis. 相似文献