播种季节对玉米生长发育及干物质生产和分配的影响

1996－1997年,在蒙自坝对春、夏、秋、冬四季玉米的生长发育和干物质生产与分配进行了系统研究,结果表明：1冬玉米生育最长达171天,而夏玉米只有101天。2．春玉米花丝期的生产了较多的干物质,其它的则是花线期后生产的干物质更多,干物质生产量与日照时数和LAI的乘积正相关。3．灌浆期籽粒重占总增重的比例与各季玉米灌浆期≥10℃的积温正相关。4．春玉米籽生产除灌浆期的光合产物外,动用了前期贮存物的11．1％,其他玉米完全依赖于灌浆期的光合产物,并且不同比例光合产物贮存于营养体中。说明其玉米的产量受限于灌浆期的光合产物,其它玉米则受库容小或运输不畅的限制。     

Generation of human anti-MUC3 IgG antibodies after in vitro immunization of naive peripheral blood B-lymphocytes

It has been demonstrated that IgG antibodies can be generated to self-antigen peptides as well as against viral antigens by an antigen-specific in vitro immunization system of resting human peripheral B-lymphocytes. Using a synthetic peptide from the consensus variable tandem-repeat region of the MUC3 mucin (TSSITTTGTTSHSTPSP) as the B cell epitope, we immunized blood donor B-lymphocytes in vitro and tested for MUC3-specific antibodies by ELISA. After the primary activation step all antibodies were IgM. At the end of the secondary immunization step we obtained 1.8% (21/1138) of the cultures with IgG-switched antibodies. In a competitive inhibition ELISA using the MUC1, MUC2, MUC3, MUC4 and PIP2 peptides, only one culture (F8.1) gave satisfactory specific inhibition. Using this antibody in fluorometric studies, it stained cells from two colon carcinoma cell lines predominantly in the cytoplasm, whereas those from a breast cancer cell line stained predominantly the cell surface. In a preliminary immunohistological evaluation with formalin-fixed sections, the antibody appeared to moderately stain colon sections, but not breast sections or lymph node. This method of in vitro immunization may be a useful tool in generating IgG antibodies specific to self-antigens and could find applications in tumour targeting and immunotherapy. Received: 12 October 2000 / Accepted: 11 January 2001     

Improved plant-based production of E1 endoglucanase using potato: expression optimization and tissue targeting

Optimization of Acidothermus cellulolyticus endoglucanase (E1) gene expression in transgenic potato (Solanum tuberosum L.) was examined in this study, where the E1 coding sequence was transcribed under control of a leaf specific promoter (tomato RbcS-3C) or the Mac promoter (a hybrid promoter of mannopine synthase promoter and cauliflower mosaic virus 35S promoter enhancer region). Average E1 activity in leaf extracts of potato transformants, in which E1 protein was targeted by a chloroplast signal peptide and an apoplast signal peptide were much higher than those by an E1 native signal peptide and a vacuole signal peptide. E1 protein accumulated up to 2.6% of total leaf soluble protein, where E1 gene was under control of the RbcS-3C promoter, alfalfa mosaic virus 5-untranslated leader, and RbcS-2A signal peptide. E1 protein production, based on average E1 activity and E1 protein accumulation in leaf extracts, is higher in potato than those measured previously in transgenic tobacco bearing the same transgene constructs. Comparisons of E1 activity, protein accumulation, and relative mRNA levels showed that E1 expression under control of tomato RbcS-3C promoter was specifically localized in leaf tissues, while E1 gene was expressed in both leaf and tuber tissues under control of Mac promoter. This suggests dual-crop applications in which potato vines serve as enzyme production `bioreactors' while tubers are preserved for culinary applications.     

Analysis of the genome of an alkaliphilic Bacillus strain from an industrial point of view

Bacillus species and other microbes with pH optima for growth higher than pH 9 are defined as alkaliphiles. A large number of alkaliphilic Bacillus strains producing useful enzymes, have been isolated from various environments. Some of these enzymes, such as proteases and cellulases from alkaliphilic Bacillus strains, have been commercialized and have brought great advantages to industry and domestic life. To support further development of the enzyme industry, we initiated analysis of the genome of Bacillus halodurans C-125, which is 4.25 Mb in size, and constructed a physical and genetic map for comparison with the Bacillus subtilis chromosome. Systematic sequencing of the whole genome of Bacillus halodurans C-125 has been automated since the beginning of May 1998, and sequencing of 98% of the whole genome has been done so far. Through genome analysis, it became apparent that the genome organization of alkaliphilic Bacillus halodurans C-125 is totally different from that of B. subtilis orthologues. Received: July 11, 1999 / Accepted: December 27, 1999     

Application of Live Monocells from Macroalgae to Shellfish Seed Production

Monocells were isolated from several macroalgae, Porphyra yezoensis, Undaria pinnatifida, and Laminaria japonica, by digestion with alga-tool enzymes. The monocells were then used to feed the parents or larvae of bay scallop Argopecten irradians, blood cockle Arca inflata, and abalone Haliotis discus juveniles. Results showed that the parents of bay scallop and blood cockle fed with Porphyra monocells could mature and discharge eggs and spermatozoa and their larvae could metamorphose; the survival rate of abalone juveniles fed with isolated cells from Laminaria and Undaria increased by 100% compared with that of those fed with artificial food. Received October 2, 1997; accepted December 18, 1998.     

Effect of isopropyl myristic acid ester on the physical characteristics and in vitro release of etoposide from PLGA microspheres

The purpose of this paper was to study the effect of the isopropyl myristic acid ester (IPM) on the physicochemical characteristics of etoposide-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres-specifically, the effects on the size and drug loading of the microspheres, the polymer matrix and surface morphology, and the release of etoposide from the microspheres. The experiment was structured to examine 2 IPM concentrations (25% and 50%) and 1 control (no IPM) at 2 different etoposide-loading percentages (10% and 5%). The microspheres were prepared using a single-emulsion solvent-extraction procedure. Samples from each batch of microspheres were then analyzed for size distribution. drug-loading efficiency, surface characteristics, in vitro release, and in vitro microsphere degradation. The incorporation of 50% IPM significantly increased (P<05) the size of the microspheres when compared with the control and 25% IPM microspheres. However, incorporation of 25% or 50% IPM did not change (P>.05) the drug-loading efficiency in comparison with the microspheres prepared without IPM. The microspheres containing 50% IPM were shown to significantly increase (P<.05) the release of etoposide from the microspheres at both etoposide concentrations. The microspheres prepared incorporating 25% IPM and 5% etoposide increased the in vitro release (P<.05) in comparison with the microspheres prepared without IPM. The 5% etoposide-PLGA microspheres showed a smooth, nonporous surface that changed to a dimpled. nonporous surface after addition of 25% IPM. During the in vitro degradation study, the IPM-containing microspheres slowly became porous but retained their structural integrity throughout the experiment.     

In vitro axial preload application during spine flexibility testing: towards reduced apparatus-related artefacts

Presently, there is little consensus about how, or even if, axial preload should be incorporated in spine flexibility tests in order to simulate the compressive loads naturally present in vivo. Some preload application methods are suspected of producing unwanted “artefact” forces as the specimen rotates and, in doing so, influencing the resulting kinematics. The objective of this study was to quantitatively compare four distinct types of preload which have roots in contemporary experimental practice. The specific quantities compared were the reaction moments and forces resulting at the intervertebral disc and specimen kinematics. The preload types incorporated increasing amounts of caudal constraint on the preload application vector ranging from an unconstrained dead-load arrangement to an apparatus that allowed the vector to follow rotations of the specimen. Six human cadaveric spine segments were tested (1-L1/L2, 3-L2/L3, 1-L3/L4 and 1-L4/L5). Pure moments were applied to the specimens with each of the four different types of compressive preload. Kinematic response was measured using an opto-electronic motion analysis system. A six-axis load cell was used to measure reaction forces and moments. Artefact reaction moments and shear forces were significantly affected by preload application method and magnitude. Unconstrained preload methods produced high artefact moments and low artefact shear forces while more constrained methods did the opposite. A mechanical trade-off is suggested by our results, whereby unwanted moment can only be prevented at the cost of shear force production. When comparing spine flexibility studies, caution should be exercised to ensure preload was applied in a similar manner for all studies. Unwanted moments or forces induced as a result of preload application method may render the comparison of two seemingly similar studies inappropriate.     

Do hornets have zombie workers?

Colonies of the European hornet, Vespa crabro, are typically founded by a single queen mated to a single male. From the resulting colony relatedness pattern we predicted strong worker-queen conflict over male production where both the workers and the queen attempt to produce the colony's males. To test for this conflict, male production was studied in 15 hornet nests using a combination of DNA microsatellite analysis (282 males), worker ovary dissections (500 workers from eight nests) and 50 h of observation (four nests). In contrast to our prediction, the data show that hornet males are queens' sons, that workers never attempt to lay eggs, rarely have activated ovaries, and that there is no direct aggression between the queen and the workers. This contrasts with other data for vespine wasps, which support relatedness predictions. Dolichovespula arenaria has the same kin structure as V. crabro and workers produce males in many colonies. The similarity between these two species makes it difficult to explain why workers do not reproduce in V. crabro. Self-restraint is expected if worker reproduction significantly reduces colony productivity but there is no obvious reason why this should be important to V. crabro but not to D. arenaria. Alternatively, queen control may be important. The absence of expressed queen-worker conflict rules out physical control. Indirect pheromonal control is a possibility and is supported by the occurrence of royal courts and queen pheromone in Vespa but not Dolichovespula. Pheromonal queen control is considered evolutionarily unstable, but could result from a queen-worker arms race over reproductive control in which the queen is ahead. The genetic data also revealed diploid males in one colony, the first example in the vespine wasps, and two colonies with double matrilines, suggesting that occasional usurpation by spring queens occurs.     

GRAZING OPTIMIZATION,NUTRIENT CYCLING,AND SPATIAL HETEROGENEITY OF PLANT‐HERBIVORE INTERACTIONS: SHOULD A PALATABLE PLANT EVOLVE?

Abstract.— Can the evolution of plant defense lead to an optimal primary production? In a general theoretical model, Loreau (1995) and de Mazancourt et al. (1998, 1999) have shown that herbivory could increase primary production up to a moderate rate of grazing intensity through recycling of a limiting nutrient, provided several conditions are fulfilled. In the present paper, we assume: (1) grazing intensity is controlled by plants through their level of palatability; and (2) plant fitness is determined by its productivity. We explore the conditions under which such an optimal production may be reached through natural selection. We model two competing plant types that differ only in palatability and are distributed in a patchy landscape determined by the plant‐herbivore interaction. Patch size is determined by herbivore behavior: herbivores recycle nutrient homogeneously within patches, but recycle nutrient proportionally to consumption between patches. The model shows that a strategy of intermediate palatability can be adaptive in response to a small herbivore that lives on and recycles nutrient around one or a few individual plants. For moderately small herbivores, plant palatability may evolve towards one of two local convergent strategies, depending on the initial conditions. For medium‐ to large‐sized herbivores, the nonpalatable strategy is always selected. We discuss the functional and evolutionary implications of these results, and suggest that the traditional dichotomy describing antagonistic and mutualistic interactions may be misleading.