Mineralization budgets in sediment microcosms: Effect of the infauna and anoxic conditions

Abstract A number of sediment incubations were set up to reproduce some of the conditions used by Kristensen and Blackburn [1] and to make a comparison with their results. There were three types of microcosm: aerobic (OX), anaerobic (AN) and aerobic with Nephtys (NOX). In addition to other measurements, dissolved organic nitrogen (DON) pools and fluxes, were measured. The sediment in this experiment contained more particulate organic matter (POM). Nephtys (NOX) had the same effect as Nereis in increasing the rate of mineralization of POC and PON, compared with the OX-cores (2.1 and 2.6 times, respectively). Again, the AN-cores had a higher mineralization rate (loss of POM) than that of the OX-cores, but in addition, mineralization in NOX-cores was not significantly different from AN-cores. It was thus confirmed that anoxic mineralization could be as high, or higher, than the oxic process. Both the temporal patterns of O₂-and and CO₂-fluxes and their magnitudes were very similar to those reported earlier. This contrasts with the higher loss of POM in the present experiment. However, the loss of C in DOC (associated with the measured DON) can account for the extra POM loss. The pore-water profiles of σCO₂ and NH₄⁺ were similar to those in the earlier report, and the fluxes of σCO₂, O₂, NH₄⁺ and NO₃⁻ followed the same temporal pattern.     

Floral scent in dioeciousSalix (Salicaceae)—a cue determining the pollination system?

Floral scents of male and female inflorescences of three dioeciousSalix species were collected by head-space adsorption, and analysed by GC-MS. InSalix caprea andS. cinerea 1,4-dimethoxy benzene was the main compound, and male and female scents showed a high degree of resemblance. No dominant compound was found inS. repens and malefemale scent similarity was low. Floral scent inSalix is likely a strong orientation cue, guiding pollinators between male and female plants ensuring pollen transfer and pollination. We suggest that a high degree of male-female floral scent resemblance is coupled to a high degree of insect pollination. Floral scent does not promote reproductive isolation betweenS. caprea andS. cinerea.     

Simulation of field scale denitrification losses from soils under grass ley and barley

Denitrification losses from soils under barley and grass ley crops were simulated. The model, which includes the major processes determining inputs, transformations and outputs of nitrogen in arable soils, represents a scale compatible with information generally available in agricultural field research. The denitrification part of the model includes a field potential denitrification rate and functions for the effect of soil aeration status, soil temperature and soil nitrate content. Easily metabolizable organic matter is assumed not to limit denitrification. Simulated values were compared with denitrification measurements made during two growing seasons in the barley and grass ley treatments of a field experiment in central Sweden.Calibration revealed that the optimal parameter values describing the effect of soil aeration on denitrification rates were similar for both treatments. The response function derived agreed well with two data sets found in the literature. The potential denitrification rate constant, derived in the simulations, was higher for grass ley than for barley, which was consistent with the differences in overall rates of carbon and nitrogen turnover found between treatments.The simulated mean denitrification rates for the two seasons were within 20% of the mean of the measured values. However, simulated denitrification showed less temporal variability and a less skewed frequency distribution than measured denitrification. Some of the measured denitrification events not explained by the model could have been due to the stimulating effects of soil drying/wetting and freezing/thawing on microbial activity.     

The effect of estradiol valerate on follicular dynamics and superovulatory response in cows with Syncro-Mate-B implants

Two experiments were designed to evaluate the effect of estradiol valerate on follicular dynamics and superovulatory response in cows with Syncro-Mate-B (SMB)implants. In Experiment 1, 5 mg estradiol valerate (E(2)), injected at the same time as superstimulation treatments were initiated, resulted in fewer corpora lutea (CL), ova/embryos collected and fertilized ova (P<0.05) than if E(2) was administered with the SMB implant 7 days earlier. In Experiment 2, 31 beef cows and 26 Holstein cows were placed in one of four treatment groups. Group I (control) cows were superstimulated on Day 9 (estrus=Day 0). On Day 2, cows in Groups II, III, and IV received SMB and cows in Group III received E(2). On Day 9, cows in Group IV received E(2), and all cows were superstimulated with Folltropin. The number of CL did not differ (P>0.19) among groups. However, there were more follicles < 10 mm and fewer fertilized ova and transferable embryos (P<0.02) in Group IV cows. Ovarian ultrasonography revealed that the diameter of the largest follicle in Group III cows declined from Day 2 to Day 7 and subsequently increased until Day 13. In contrast, Groups I, II and IV were characterized by apparently linear growth between Days 2 and 13. Differences (P<0.05) were detected between Days 5 and 9. Mean diameter of the largest follicle was smaller for cows in Group III than for the remaining groups on Day 9. It was concluded that SMB did not adversely affect superovulatory response and that E(2) administration resulted in atresia of the antral follicles in the cows with SMB implants.     

Plant protoplasts and genetic engineering II

Book Review

Plant protoplasts and genetic engineering IIY.P.S. Bajaj (Ed.), (Biotechnology in Agriculture and Forestry, Vol. 9). Berlin: Springer-Verlag, 1989. 510 pages. DM398.00. ISBN 3-540-50789-2     

Affinity thermoprecipitation of trypsin using soybean trypsin inhibitor conjugated with a thermo-reactive polymer,poly(N-vinyl caprolactam)

The soybean trypsin inhibitor conjugate with a thermo-reactive water soluble polymer, poly(N-vinyl caprolactam), was successfully used for thermally induced affinity precipitation of trypsin. The validity of the developed procedure was proven by a model separation of trypsin from dilute solution containing a large excess of bovine serum albumin.     

欺骗,契约,合作的ESS

动物竞争中的欺骗、契约、合作现象是极为常见的。本文就论述与此有关的ESS。一、欺骗某些动物竞争时信号a后跟随发生行为A,如一个体不出现A则为欺骗。欺骗是相对真实     

SHOULD ETHICAL CONCERNS REGULATE SCIENCE? THE EUROPEAN EXPERIENCE WITH THE HUMAN GENOME PROJECT

... The allocation of resources can indirectly control science by defining areas undesirable for research from the point of view of society. In the United States federal funds are not available for research on human embryos. The European experience represents a new approach to control of scientific research. The project is neither prohibited nor accepted in accordance with certain ethical rules, but is followed throughout the project. This new approach originates from the complexity of the human genome project and its unpredictable consequences for man.     

Molecular characterization of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency: identification of a lys329 to glu mutation in the MCAD gene,and expression of inactive mutant enzyme protein in E. coli

Summary A series of experiments has established the molecular defect in the medium-chain acyl-coenzyme A (CoA) dehydrogenase (MCAD) gene in a family with MCAD deficiency. Demonstration of intra-mitochondrial mature MCAD indistinguishable in size (42.5-kDa) from control MCAD, and of mRNA with the correct size of 2.4 kb, indicated a point-mutation in the coding region of the MCAD gene to be disease-causing. Consequently, cloning and DNA sequencing of polymerase chain reaction (PCR) amplified complementary DNA (cDNA) from messenger RNA of fibroblasts from the patient and family members were performed. All clones sequenced from the patient exhibited a single base substitution from adenine (A) to guanine (G) at position 985 in the MCAD cDNA as the only consistent base-variation compared with control cDNA. In contrast, the parents contained cDNA with the normal and the mutated sequence, revealing their obligate carrier status. Allelic homozygosity in the patient and heterozygosity for the mutation in the parents were established by a modified PCR reaction, introducing a cleavage site for the restriction endonuclease NcoI into amplified genomic DNA containing G⁹⁸⁵. The same assay consistently revealed A⁹⁸⁵ in genomic DNA from 26 control individuals. The A to G mutation was introduced into an E. coli expression vector producing mutant MCAD, which was demonstrated to be inactive, probably because of the inability to form active tetrameric MCAD. All the experiments are consistent with the contention that the G⁹⁸⁵ mutation, resulting in a lysine to glutamate shift at position 329 in the MCAD polypeptide chain, is the genetic cause of MCAD deficiency in this family. We found the same mutation in homozygous form in 11 out of 12 other patients with verified MCAD deficiency.