Uptake of [2-14C]abscisic acid and distribution of 14C in apple embryos

Pyrus malus L. var. Golden delicious embryos were incubated with (±)-[2-¹⁴C]abscisic acid (ABA) (10^-5 M, 355 kBq mol^-1). After incubations of various durations, the radioactivity was measured in whole embryos, cotyledons, and embryonic axes.With either 48-h or 16-d incubation periods, the uptake of [¹⁴C]ABA depended upon the mode of culture used. The lowest values corresponded to the absorption by the embryonic axis, the highest to the absorption by the distal parts of the two cotyledons. The cotyledons accumulated the main part of the radioactivity under all conditions. Dormant and almost completely after-ripened embryos cultivated for 4 d showed no significant differences in the radioactivity uptake for identical modes of culture. There was a linear relationship between exogenous ABA concentrations (0.5 to 3.10^-5 M) and ABA uptake for embryos cultivated for 4 d with the distal parts of the cotyledons immersed in the medium.Abbreviations ABA abscisic acid. RM, RM⁺, C/2 M, and CM are different modes of embryo cultures: embryonic axis immersed alone (RM), together with the proximal parts of the cotyledons (RM⁺); distal parts of the cotyledons immersed alone (CM); embroyo flat on the medium, the root and the external surface of one cotyledon being in contact with the medium (C/2 M) - PP proximal parts of the cotyledons - DP distal parts of the cotyledons     

Uptake and utilization of14C-glycine by embryos ofSebastes melanops

Synopsis The ability of embryos of the viviparous scorpaenidSebastes melanops to take up nutrients from an exogenous substrate was demonstrated by incubating embryos at various stages of development (18–30 days after fertilization) in¹⁴C-labeled glycine for 24 h. Uptake was highest for embryos at the latest stages (28–30 days) and increased at a linear rate during the incubation period. Nutrient uptake was not time dependent in embryos at the early stages (18–22 days). Nutrient utilization byS. melanops embryos was measured by the oxidation of¹⁴C-labeled glycine to¹⁴CO₂. The amount of respired¹⁴CO₂ by the oldest embryos increased significantly at a linear rate over the 24 h incubation period. There was no evidence of nutrient utilization by the youngest embryos. The developmental changes we observed in the uptake and utilization of exogenous glycine are supported by our previous findings that the oldest embryos have fully developed mouths and guts, and require additional nutrition from intraovarian sources at this stage of development.     

Binding of [14C] DDT by submitochondrial particles

1. Binding of [14C] DDT by submitochondrial particles and by liposomes prepared from lipids extracted from the particles was studied by the discontinuous sucrose gradient method. 2. Binding of the insecticide was a biphasic linear function of the biomembrane- and liposome-concentration with a break in the binding curve occurring at identical concentrations of phospholipid for both the biomembrane and vesicle. The biphasic binding curve is interpreted in terms of decreased availability of binding sites as a result of particle-particle interaction. 3. [14C] DDT was bound mainly by the membrane lipids and only negligible binding was detected for the delipidated membrane. 4. A 100-200-fold excess of unlabeled DDT had no effect on the binding of [14C] DDT and a 600-fold excess of unlabeled DDT reduced the binding by 20% suggesting that binding of [14C] DDT by lipids was nonspecific. 5. These results are discussed in relation to the strong inhibition by DDT of mitochondrial bioenergetics.     

Serum and liver enzyme changes in rats after short term exposure to dichlorvos

Rat serum and liver ICDH, OCT, GOT and GPT activities are significantly elevated 2-6 hr after i.p. injections of single doses (2.5 mg/kg body wt) of dichlorvos. ICDH, OCT, GOT and GPT activities are significantly increased in serum and liver of rats receiving daily injections (0.25 mg/kg body wt) for 7 days. Although liver SD is significantly elevated in the single and repeated dosage study, serum SD appears unaffected at these levels of dichlorvos toxicity. Changes in serum OCT activity estimations maybe a useful single parameter for screening pesticides for potential hepatotoxic effects in humans and farm animals.     

Uptake of Glucose-1-14C by Pullularia pullulans

Pullularia pullulans cells were grown in a medium containing yeast extract, malt extract, glucose, and nutrient salts, in addition to glucose-1-(14)C. The lipids extracted from the cells were fractionated by use of a single column packed with silicic acid. Of the total radioactive carbon added to the culture medium, the neutral lipid fractions contained 24.8%, whereas the phospholipid portions contained only 2.1%. The largest amount (16.5%) of (14)C among the neutral lipids was found in the fraction containing the free sterols. Among the phospholipids, the largest amount (1.1%) was found in phosphatidylserine and phosphatidylethanolamine. The second largest amount (9.6%) of the total (14)C used was found in trehalose, followed by carbon dioxide (7.3%).     

Uptake of [14C]oxamniquine by Schistosoma mansoni

The uptake and retention of drug-related material by Schistosoma mansoni was studied in the mouse host following a single oral or intramuscular dose (50 mg/kg) of [14C]oxamniquine. Male worms took up more labelled material than did female worms but the amount in each particular sex of worm was found to be similar after both routes of administration. Exposure of worms was therefore independent of the route of administration. Six days after drug administration, at the time of an hepatic shift, significantly more drug-related material was present in male worms than in female worms. Examination of worms recovered from mice 4 h after treatment showed that metabolites of oxamniquine constituted 70--90% of the drug-related material present in the worms. Both sexes of worms were able to take up metabolites of oxamniquine in vitro.     

Effects of anionic polyacrylamide on maize growth: a short term 14C labeling study

Plant and Soil - Various anionic polyacrylamide polymers (PAMs) are frequently used to improve soil properties and reduce erosion. However, the effects of their application on plant growth remain...     

Uptake and K+-stimulated release of [14C]glycine from frog retinal synaptosomal fractions

The uptake of [¹⁴C]glycine and the effect of depolarizing potassium concentrations on its release was investigated in the whole frog retina and its synaptosomal fractions. The uptake of [¹⁴C]glycine in retina and synaptosomal fractions was found to be saturable as well as energy and Na⁺-dependent. TheK _m value for glycine uptake was found to be 46 M for P₂ fraction and 100 M for P₁ fraction, with aV _max of 3.5 and 3.8 nmol/mg protein/min respectively. The release of [¹⁴C]glycine from P₁ and P₂ synaptosomal fractions was markedly increased by raising potassium concentration in the medium, in a partially Ca²⁺-dependent manner. Evoked glycine release was 50% reduced when calcium was omitted from the medium. The K⁺-stimulated release of glycine from P₂ fraction was significantly reduced in the presence of TTX. The cellular origin of the P₁ and P₂ synaptosomal fractions releasing glycine is discussed.     

Uptake of C14-atrazine by prairie grasses in a phytoremediation setting

Agrochemicals significantly contribute to environmental pollution. In the USA, atrazine is a widely used pesticide and commonly found in rivers, water systems, and rural wells. Phytoremediation can be a cost-effective means of removing pesticides from soil. The objective of this project was to investigate the ability of prairie grasses to remove atrazine. ¹⁴C-labeled atrazine was added to sterilized sand and water/nutrient cultures, and the analysis was performed after 21 days. Switchgrass and big bluestem were promising species for phytoremediation, taking up about 40% of the applied [¹⁴C] in liquid hydroponic cultures, and between 20% and 33% in sand cultures. Yellow Indiangrass showed low resistance to atrazine toxicity and low uptake of [¹⁴C] atrazine in liquid hydroponic cultures. Atrazine degradation increased progressively from sand to roots and leaves. Most atrazine taken up by prairie grasses from sand culture was degraded to metabolites, which accounted for 60–80% of [¹⁴C] detected in leaves. Deisopropylatrazine (DIA) was the main metabolite detected in sand and roots, whereas in leaves further metabolism took place, forming increased amounts of didealkylatrazine (DDA) and an unidentified metabolite. In conclusion, prairie grasses achieved high atrazine removal and degradation, showing a high potential for phytoremediation.     

Timekeeping by frog embryos, in normal development and after heat shock

(1) Timekeeping refers to the uniformity of development in time. The precision of timekeeping is measured by the extent to which embryos, within an initially synchronous population, come to diverge in the course of their development. (2) Divergence is measured as the variation in the stage of development reached between embryos allowed to develop for a fixed period of time. The lower the variation the better the timekeeping. (3) Divergence among frog embryos that started development at the same time is hardly measurable after approx. 100 h of development. This striking uniformity indicates good timekeeping. (4) Timekeeping is not impaired among the survivors following heat shocks that retard development and disturb and curtail morphogenesis. (5) The immediate effect of heat shock is a stoppage of development, the duration of which is the same for all embryos in the same treatment batch. The embryos react to heat shock by rescheduling their development with the interpolation of a rest, the duration of which is controlled to the same precision as normal development. The postponement of development, without impairment of timekeeping, implies dis-engagement of the processes of morphogenesis from, and their subsequent re-engagement with, an enduring rate-determining activity unaffected by heat shock. (6) We have searched for embryos whose rate of development was disturbed by heat shock to run slower or faster than the norm. We have found none. It seems that the (temperature-compensated) rate of development is invariant up to the moment of failure, or a change is immediately lethal.     

Gonadal toxicity of short term chronic endosulfan exposure to male rats

Endosulfan was studied for its effect on rat testicular toxicity in relation to the enzymes of androgen biosynthesis, viz. 3 beta-hydroxysteroid dehydrogenase (EC 1.1.1.145, 3 beta-HSD) and 17 beta-hydroxysteroid dehydrogenase (EC 1.1.1.64, 17 beta-HSD); cytosolic conjugation enzyme, glutathione-S-transferase (EC 2.5.1.18); and testicular as well as serum testosterone levels at the dose levels of 2.5, 5.0, 7.5 and 10 mg/kg body weight fed orally for 7 and 15 days. Organ and body weights of the treated animals did not change significantly, however, the testicular protein contents were found to be increased appreciably after 7 days treatments. The activity profile of cytosolic conjugation enzyme showed much remained low during 7 days treatment, however, the two steroidogenic enzymes showed much individual variations in response to endosulfan treatments. An overall varied response with respect to testosterone biosynthesis and its secretion to serum was observed suggesting nevertheless, a profound hormonal imbalance caused by this insecticide to male gonads on short term chronic exposures.     

Cellular reactions induced by chronic exposure to 14C beta-rays

In V-79 cells the Effects of chronic exposure on induction of chromosome aberrations and abnormal metaphases as well as on efficiency of subsequent exposure to 2 Gy gamma-rays were investigated. It was found that chronic exposure increased the yield of chromosome aberrations as well as abnormal metaphases (spread-metaphases and apoptotic metaphases). In spite of the level of damages in cells, the chronic beta-exposure protected cells against the additional induction of chromosomal aberrations by subsequent exposure to higher acute dose of gamma-irradiation. Cytogenetic adaptive response was retained in the surviving progeny of irradiated cells which were cultured in free medium during 40, 70 days or one year after chronic exposure. At this time the level of residual chromosome aberrations, colony forming ability and distribution of the cells by the number of chromosomes were almost the same as in unirradiated cells. However, the high level of abnormal metaphases and half as much of cells in colony in the surviving progeny of irradiated cells in comparison with unirradiated cell, allow us to suggest that the chronic exposure induced the selection of adaptive forms in condition of the higher level of radiation.     

Neural integration by short term potentiation

Neurophysiological studies in the oculomotor system suggest that an integrative operation is required in order to derive an eye position signal from a command signal which usually correlates with eye velocity. Several proposed models for a neural integrator are examined. All these models incorporate some form of positive feedback as a basic mechanism. Based on the performance of the models, we argue that such a scheme require extreme high precision in order to work properly. A new model based on potentiation phenomena in synaptic transmission is proposed and is shown to be free from the deficits of most previous models. The proposed model also accounts for various neural behaviors in a very natural way. A possible implementation of the model is also discussed in the context of the vestibulo-ocular reflex (VOR).