Sodium and potassium relations of Spergularia marina following N and P deprivation: results of short-term growth studies

In this, we consider the coordination of plant growth and ion acquisition, reporting the short-term adjustments of growth and K⁺ and Na⁺ relations which follow when plants are subject to a sudden deprivation of N and P. The plant used for the experiments, Spergularia marina (L.) Grieseb., is a small coastal halophyte, and the growth medium was 0.2 × modified seawater. By considering nutrients whose availability has not been changed, we report on an aspect of organismal integration which has received little attention either experimentally or in mathematical models. The studies are limited to the first 60 h after N and P deprivation in order to consider changes that, if they are not primary responses, are not temporally remote, passive adjustments. For growth analyses, plants were used approximately 30 days after germination and 16 days after transfer to solution culture. Random harvests were made at hourly invervals, and after 12 h, one-half of the plants were transferred to cultures without N or P. Tissue analyses were used to calculate relative growth rates, relative accumulation rates and net uptake rates. For comparison, isotope uptake studies using ⁴²K⁺ and ²²Na⁺ were conducted at 12, 36 and 60 h after deprivation. The effects on growth and biomass allocation were very rapid, detectable within 13 h. K⁺ transport also responded quickly, and from the beginning of the study, there was essentially no net translocation of K⁺ to the shoot. Isotope studies confirmed the responsiveness, with translocation reduced 33 and 90% after 12 and 36 h, respectively. Though Na⁺ adjustments were slower, they were coordinated with growth such that tissue concentrations in the N and P-deprived plants were comparable to those in the controls. We conclude that N and C are insufficient elements on which to build mathematical models useful to environmental physiologists. At a minimum, the incorporation of K⁺ relations in growth models would both allow the development of the osmotic potential needed to drive cell expansion, and provide a means to probe –experimentally as well as mathematically – the coordinating mechanisms of plant growth and resource management.     

SPERMATOGENESIS IN COLEOCHAETE PULVINATA (CHAROPHYCEAE): EARLY BLEPHAROPLAST DEVELOPMENT

Transmission electron microscopy of serial thin sections was used to reconstruct several early developmental stages of the blepharoplast in Coleochaete pulvinata spermatids. These were compared to published studies of blepharoplast development in Charales and the closest relatives of charophycean green algae among embryophytes, i.e., hornworts and liverworts. Bicentriolar centrosomes such as occur in bryophytes and fern allies were not observed in Coleochaete. Centriole replication in C. pulvinata was orthogonal as in Charales. The resulting two daughter centrioles were oriented perpendicularly and joined proximally by electron-dense material. Their orthogonal relationship was maintained throughout blepharoplast development by a massive, banded connective which appeared early. In spermatids of hornworts and liverworts, a multilayered structure (MLS) develops in association with two centrioles destined to become flagellar basal bodies. When the MLS of these lower land plants is sectioned at right angles to the long axis of the microtubular layer, the MLS is observed to lie beneath cross sections of both centrioles. In contrast, when developing MLSs of C. pulvinata and Charales are similarly sectioned, they occur beside a cross section of just one of the two centrioles. In C. pulvinata (as in other charophytes), MLS lamellae are oriented at a 90-degree angle to the long axis of the S₁ microtubules from the beginning. This contrasts with the 40–45 degree angle between the MLS lamellae and S₁ microtubules universally reported for archegoniates. In early C. pulvinata spermatids, spline microtubules are closely associated with an anterior mitochondrion having a low stromal density and few cristae. An anterior mitochondrion is typically associated with blepharoplast development in hornworts and liverworts, but has not previously been reported to occur in Coleochaete or any other charophycean alga. In Coleochaete, as in hornworts and liverworts, but unlike Charales, structure of mature blepharoplasts reflects early blepharoplast ontogeny. Very little change in positional relationships among blepharoplast components (flagella, connective, MLS) occurs during development. These character-state differences are of importance in cladistic analyses of charophycean algae and lower land plants.     

Fast optimal genome tiling with applications to microarray design and homology search.

In this paper, we consider several variations of the following basic tiling problem: given a sequence of real numbers with two size-bound parameters, we want to find a set of tiles of maximum total weight such that each tiles satisfies the size bounds. A solution to this problem is important to a number of computational biology applications such as selecting genomic DNA fragments for PCR-based amplicon microarrays and performing homology searches with long sequence queries. Our goal is to design efficient algorithms with linear or near-linear time and space in the normal range of parameter values for these problems. For this purpose, we first discuss the solution to a basic online interval maximum problem via a sliding-window approach and show how to use this solution in a nontrivial manner for many of the tiling problems introduced. We also discuss NP-hardness results and approximation algorithms for generalizing our basic tiling problem to higher dimensions. Finally, computational results from applying our tiling algorithms to genomic sequences of five model eukaryotes are reported.     

Dog-DAT: a direct agglutination test using stabilized, freeze-dried antigen for the serodiagnosis of canine visceral leishmaniasis

Abstract We have evaluated the use of an improved direct agglutination test (DAT) based on stable, freeze-dried antigen for the detection of anti- Leishmania antibodies in canine serum samples. With a cut-off value of 1:640, the sensitivity of the DAT was shown to be 100% and the specificity of the test was 98.8%.     

黄精凝集素Ⅱ分子稳定性与生物学活性研究

黄精凝集素Ⅱ分子稳定性与生物学活性研究鲍锦库,曾仲奎,周红（四川大学生物系,成都,６１００６４）本文在黄精凝集素Ⅱ纯化及性质研究的基础上,应用多种变性条件,研究其分子特性,同时对分子的巯基和色氨酸进行修饰,研究该凝集素分子保持其生物学活性与这些基团的...     

A NEW SPECIES OF GENUS HABROPHLEBIODES ULMER (EPHEMEROPTERA: LEPTOPHLEBIIDAE)

Abstract  The present paper deals with a new species Habrophlebiodes zijinensis sp. nov. collected in Nanjing, Jiangsu Povince, China.     

Chaperone SecB: Conformational changes demonstrated by circular dichroism

The chaperone SecB, which is involved in protein export inEscherichia coli, is shown by circular dichroism measurements to contain a high content of-pleated sheets. Prediction of the secondary structure of SecB is in good agreement with the observed content of-sheet. In accordance with the previous studies in which changes in conformation were assessed indirectly [Randall (1992),Science 257, 241–245], here we show that the conformation of SecB changes with the concentration of salt in the milieu and also when SecB interacts with a peptide ligand.Abbreviations ANS 1-anilino-naphthalene-8-sulfonate - CD circular dichroism - NMR nuclear magnetic resonance - CCA convex constraint analysis     

Seasonal ectomycorrhizal fungal biomass development on loblolly pine (Pinus taeda L.) seedlings

Ergosterol, a membrane sterol found in fungi but not in plants, was used to estimate live mycelial biomass in ectomycorrhizae. Loblolly pine (Pinus taeda L.) seeds were sown in April 1993 and grown with standard nursery culture practices. Correlations between total seedling ergosterol and visual assessment of mycorrhizal colonization were high during July and August but low as ectomycorrhizal development continued into the growing season. Percentages of mycelial dry weight over lateral roots decreased from 9% in July to 2.5% in November because seedling lateral root dry weight accumulated faster than mycelial dry weight. Total ergosterol per seedling increased from July through February. As lateral root dry weight ceased to increase during winter months, ectomycorrhizal mycelia became the major carbohydrate sink of pine seedlings. No distinctive seasonal pattern of soil ergosterol content was observed. The impact of ectomycorrhizal fungi on plant carbohydrate source-sink dynamics can be quantitatively estimated with ergosterol analysis but not with conventional visual determination.     

Effects of estradiol-17β in the male xenopus laevis: Isolation and translation of cytoplasmic messenger rna populations

Summary Total Xenopus liver cytoplasmic RNA isolated following long-term estrogen administration (14 days) was fractioned using Sepharose 4B chromatography. One of the Sepharose 4B peaks was shown to contain RNA with a molecular weight reported for vitellogenin mRNA (34S). The presence of estrogeninduced vitellogenin mRNA in the peak 5 RNA was determined by translation of the RNA in the oocyte and analysis of the oocyte translational products by immunoprecipitation with anti-vitellogenin.Sepharose 4B peaks 2 and 3 were also observed to contain estrogen induced mRNA populations sedimenting between 9-18S. These findings suggest that Sepharose 4B chromatography might prove useful in separating different mRNA populations following estrogen-induced gene activation.     

Synthesis of (±)-16-thioketal and 16-keto prostaglandins

The synthesis of ((±)-16-thioketal and 16-keto PGE₂ methyl ester ( and ) is herein described.