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61.
Summary Two techniques for phenotyping the human placental alkaline phosphatase system were developed: high-voltage agarose-gel electrophoresis
and thin-layer separator isoelectric focusing on agarose. These methods enabled a more rapid and sensitive phenotyping of
all common phenotypes than the traditionally employed starch-gel electrophoresis. An extended polymorphism of placental alkaline
phosphatase was revealed by isoelectric focusing. The existence of two suballeles of Pl1 allele and two suballeles of Pl2 allele was postulated. 相似文献
62.
Light- and CO2-saturated photosynthesis of nonhardened rye (Secale cereale L. cv. Musketeer) was reduced from 18.10 to 7.17 mol O2·m–2·s–1 when leaves were transferred from 20 to 5°C for 30 min. Following cold-hardening at 5°C for ten weeks, photosynthesis recovered to 15.05 mol O2·m–2·s–1,comparable to the nonhardened rate at 20°C. Recovery of photosynthesis was associated with increases in the total activity and activation of enzymes of the photosynthetic carbon-reduction cycle and of sucrose synthesis. The total hexose-phosphate pool increase by 30% and 120% for nonhardened and cold-hardened leaves respectively when measured at 5°C. The large increase in esterified phosphate in coldhardened leaves occurred without a limitation in inorganic phosphate supply. In contrast, the much smaller increase in esterified phosphate in nonhardened leaves was associated with an inhibition of ribulose-1,5-bisphosphate carboxylase/oxygenase and sucrose-phosphate synthase activation. It is suggested that the large increases in hexose phosphates in cold-hardened leaves compensates for the higher substrate threshold concentrations needed for enzyme activation at low temperatures. High substrate concentrations could also compensate for the kinetic limitations imposed by product inhibition from the accumulation of sucrose at 5°C. Nonhardened leaves appear to be unable to compensate in this fashion due to an inadequate supply of inorganic phosphate.Abbreviations DHAP
dihydroxyacetone phosphate
- Fru6P
fructose-6-phosphate
- Fru 1,6BP
fructose-1,6-bisphosphate
- Fru1,6BPase
fructose-1,6-bisphosphatase
- Glc6P
glucose-6-phosphate
- PGA
3-phosphoglycerate
- PPFD
photosynthetic photon flux density
- CH
cold-hardened rye grown at 5°C
- NH
nonhardened rye grown at 24°C
- Rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase
- RuBP
ribulose-1,5-bisphosphate
- SPS
sucrose-phosphate synthase
- UDPGlc
uridine 5-diphosphoglucose
This work was supported by operating grants from the Swedish Natural Sciences Research Council to G.Ö. and P.G. 相似文献
63.
Margus Vilbas Toomas Esperk Triin Edovald Ants Kaasik Tiit Teder 《Journal of Insect Conservation》2016,20(6):1059-1067
Female oviposition decisions in insects may strongly affect offspring growth and survival, and thus determine population performance. In this study, we examined oviposition site selection in the xerophilous ecotype of the endangered myrmecophilous butterfly Phengaris (=Maculinea) alcon (Lepidoptera, Lycaenidae) in Estonia, at the northern distribution margin of both the butterfly and its host plant, Gentiana cruciata L. Egg distribution on individual host plants appeared to be highly uneven: plants carrying high egg loads contrasted to a high proportion of host plants without any or with a few eggs. Host plant use for oviposition was strongly dependent on plant characteristics and environmental context. Host plant height relative to the surrounding vegetation rather than the absolute height of host plants was a key factor determining the use of particular host plant individuals for oviposition. In particular, plants protruding above surrounding vegetation had a higher probability of being used for oviposition, and carried more eggs. Additionally, the number of eggs laid on individual host plants was positively associated with the presence of flowers and the number of shoots. More aggregated host plants received fewer eggs than those with less conspecifics around. Feeding damage by wild herbivores, found in a substantial proportion of the butterfly’s host plants, strongly reduced the number of eggs on individual plants. Our results underline the need to assure that butterfly’s host plants do not become overgrown by surrounding vegetation. Best practices for opening vegetation around host plants may need further studies that explicitly account for butterfly’s host ants—their abundance in relation to vegetation height and their response to opening vegetation. 相似文献
64.
Blanckenhorn WU Dixon AF Fairbairn DJ Foellmer MW Gibert P van der Linde K Meier R Nylin S Pitnick S Schoff C Signorelli M Teder T Wiklund C 《The American naturalist》2007,169(2):245-257
A prominent interspecific pattern of sexual size dimorphism (SSD) is Rensch's rule, according to which male body size is more variable or evolutionarily divergent than female body size. Assuming equal growth rates of males and females, SSD would be entirely mediated, and Rensch's rule proximately caused, by sexual differences in development times, or sexual bimaturism (SBM), with the larger sex developing for a proportionately longer time. Only a subset of the seven arthropod groups investigated in this study exhibits Rensch's rule. Furthermore, we found only a weak positive relationship between SSD and SBM overall, suggesting that growth rate differences between the sexes are more important than development time differences in proximately mediating SSD in a wide but by no means comprehensive range of arthropod taxa. Except when protandry is of selective advantage (as in many butterflies, Hymenoptera, and spiders), male development time was equal to (in water striders and beetles) or even longer than (in drosophilid and sepsid flies) that of females. Because all taxa show female-biased SSD, this implies faster growth of females in general, a pattern markedly different from that of primates and birds (analyzed here for comparison). We discuss three potential explanations for this pattern based on life-history trade-offs and sexual selection. 相似文献
65.
66.
Lindsey J. Organtini Andrew B. Allison Tiit Lukk Colin R. Parrish Susan Hafenstein 《Journal of virology》2015,89(3):1909-1912
Canine parvovirus type 2 (CPV-2) emerged in 1978 and spread worldwide within 2 years. Subsequently, CPV-2 was completely replaced by the variant CPV-2a, which is characterized by four specific capsid (VP2) mutations. The X-ray crystal structure of the CPV-2a capsid shows that each mutation confers small local changes. The loss of a hydrogen bond and introduction of a glycine residue likely introduce flexibility to sites that control interactions with the host receptor, antibodies, and sialic acids. 相似文献
67.
Pulmonary function in normal subjects following exercise at cold ambient temperatures 总被引:1,自引:0,他引:1
Kenneth R. Chapman Laurie J. Allen Tiit T. Romet 《European journal of applied physiology and occupational physiology》1990,60(3):228-232
We measured pulmonary function in 12 healthy volunteers before and at 5-min intervals for 30 min following treadmill exercise of 30 min duration performed under control (20 degrees C) and cold (-11 degrees C) ambient temperatures. Post-run changes in forced vital capacity (FVC), residual volume (RV) and peak expiratory flow rate were similar between the two temperature conditions. FVC decreased slightly but significantly 5 min post-run (-0.25 +/- 0.20 l and -0.21 +/- 0.20 l, for control and cold conditions respectively) and returned to baseline by 30 min. RV increased significantly post-exercise (+0.07 +/- 0.09 l and +0.14 +/- 0.1 l, control and cold respectively) and remained elevated for 30 min. Forced expired volume in 1 s was not significantly different following either run. Post-exercise, maximum mid-expiratory flow rate and flows at 50% and 25% of vital capacity were not significantly different between warm and cold conditions. These data suggest that changes in lung volumes following exercise under cold ambient conditions are similar to changes seen following warm exercise of similar duration. In non-asthmatics, moderate exertion under cold ambient conditions does not appear to cause clinically significant decreases in expiratory flow rates as compared to similar exertion under warm conditions. 相似文献
68.
Summary Acetylcholinesterase (AChE, EC 3.1.1.7) and choline acetyltransferase (CAT, EC 2.3.1.6) activities where studied in the early development of the chick embryo. A sharp increase in AChE activity occurred in the gastrulating embryo. The highest AChE activity was associated with hypoblast cells. By sucrose density gradient centrifugation three molecular forms of AChE with sedimentation coefficients 4.7 S, 6.8 S and 10.9 S were determined. During the gastrulation there was no remarkable change in the activity of CAT. A two-fold decrease in the CAT activity occurred at the end of gastrulation. 相似文献
69.
70.
An advanced radiogasometric method for the study of plant leaf CO2 exchange is presented. The method enables determination of the rates of CO2 fixation, photorespiration and respiration in the light under steady‐state photosynthesis and discrimination between primary and stored photosynthates as substrates of photorespiratory and respiratory decarboxylations. The method is based on the analysis of the time curves of 14CO2 evolution from labeled primary and stored photosynthates in leaves previously exposed to 14CO2. The molar rates of different decarboxylation reactions are calculated from the initial slopes of the curves taking into account the specific radioactivity of CO2 fed to leaves and/or evolved from leaves. To estimate the contribution of primary and stored photosynthates, the measurements of 14CO2 evolution are performed after feeding plant leaves for different periods with 14CO2. Photorespiration and respiration are distinguished on the basis of data obtained from measurements of 14CO2 evolution under normal (210 ml l−1) and low (15 ml l−1) concentrations of oxygen. A principally new method for the determination of the rate of intracellular refixation of respiratory CO2 has been developed. The method is based on the measurements of 14CO2 evolution from leaves into the medium of very high concentrations (30 ml l−1) of 12CO2, where the probability of refixation of 14CO2 evolved inside the cell is close to zero. The results obtained were comparable with the data derived from parallel refixation measurements by means of gasometric methods. As an example of application, the data on CO2 exchange in leaves of two contrasting groups of C3‐species, differing in the ability of starch accumulation, are presented. 相似文献