Loss of gametophytic self-incompatibility with evolution of inbreeding depression

Gametophytic self-incompatibility (SI) in plants is a widespread mechanism preventing self-fertilization and the ensuing inbreeding depression, but it often evolves to self-compatibility. We analyze genetic mechanisms for the breakdown of gametophytic SI, incorporating a dynamic model for the evolution of inbreeding depression allowing for partial purging of nearly recessive lethal mutations by selfing, and accounting for pollen limitation and sheltered load linked to the S-locus. We consider two mechanisms for the breakdown of gametophytic SI: a nonfunctional S-allele and an unlinked modifier locus that inactivates the S-locus. We show that, under a wide range of conditions, self-compatible alleles can invade a self-incompatible population. Conditions for invasion are always less stringent for a nonfunctional S-allele than for a modifier locus. The spread of self-compatible genotypes is favored by extremely high or low selfing rates, a small number of S-alleles, and pollen limitation. Observed parameter values suggest that the maintenance of gametophytic SI is caused by a combination of high inbreeding depression in self-incompatible populations coupled with intermediate selfing rates of the self-compatible genotypes and sheltered load linked to the S-locus.     

Exact tests of goodness of fit of log-linear models for rates

We propose Metropolis-Hastings sampling methods for estimating the exact conditional p-value for tests of goodness of fit of log-linear models for mortality rates and standardized mortality ratios. We focus on two-way tables, where the required conditional distribution is a multivariate noncentral hypergeometric distribution with known noncentrality parameter. Two examples are presented: a 2 x 3 table, where the exact results, obtained by enumeration, are available for comparison, and a 9 x 7 table, where Monte Carlo methods provide the only feasible approach for exact inference.     

三角梅属植物的生物学研究进展

三角梅属(Bougainvil lea)属于紫茉莉科(Nyctaginaceae), 有14个种。该文综述了三角梅属植物的生物学特性, 展望了该属植物在增进人类健康、丰富精神生活以及保护环境等方面的应用前景。三角梅属植物因其苞片的形态色彩以及植株形态的变化而具有独特的观赏价值。三角梅属植物不仅作为花卉备受关注, 近年来, 有关三角梅其它应用价值的研究使人们对其有了新的认识。从三角梅叶片中分离得到具有类胰岛素功能的松醇(D-pini tol )对替代胰岛素治疗糖尿病以及减轻胰岛素疗法带来的副作用具有重要意义。研究还表明, 三角梅叶片和根中至少含有2种抗病毒蛋白——BAPI和 Bouganin, 它们对于多种植物病毒具有不同程度的抑制作用。这些研究结果对于开发低毒高效的生物农药具有十分积极的意义。三角梅还是研究甜菜色素代谢的重要模式植物之一, 其甜菜色素的种类和含量之丰富为开发安全的天然食用色素开辟了广阔的前景。这些相关研究展示了三角梅作为资源植物的多元价值, 为进一步开发三角梅的观赏、医药、生物农药价值和作为天然食用色素以及发挥环境修复作用提供了充分的科学依据。     

三角梅属植物的生物学研究进展

三角梅属（Bougainvillea）属于紫茉莉科（Nyctaginaceae）,有14个种。该文综述了三角梅属植物的生物学特性,展望了该属植物在增进人类健康、丰富精神生活以及保护环境等方面的应用前景。三角梅属植物因其苞片的形态色彩以及植株形态的变化而具有独特的观赏价值。三角梅属植物不仅作为花卉备受关注,近年来,有关三角梅其它应用价值的研究使人们对其有了新的认识。从三角梅叶片中分离得到具有类胰岛素功能的松醇（D-pinitol）对替代胰岛素治疗糖尿病以及减轻胰岛素疗法带来的副作用具有重要意义。研究还表明,三角梅叶片和根中至少含有2种抗病毒蛋白——BAPI和Bouganin,它们对于多种植物病毒具有不同程度的抑制作用。这些研究结果对于开发低毒高效的生物农药具有十分积极的意义。三角梅还是研究甜菜色素代谢的重要模式植物之一,其甜菜色素的种类和含量之丰富为开发安全的天然食用色素开辟了广阔的前景。这些相关研究展示了三角梅作为资源植物的多元价值,为进一步开发三角梅的观赏、医药、生物农药价值和作为天然食用色素以及发挥环境修复作用提供了充分的科学依据。     

Thresholds of bifurcation of the degree of circular polarization of the bremsstrahlung-generated pump field harmonics in plasma

It is established that, for a Maxwellian plasma in a monochromatic pump field, the phenomenon of bifurcation of the degree of circular polarization of the field harmonics is of a universal nature. A general equation determining the thresholds for this phenomenon for arbitrary harmonics is derived, and a set of its solutions is presented for illustrative purposes.     

Radioiodination of the stable metabolic fragment of bradykinin, RPPGF

Arg-Pro-Pro-Gly-Phe (RPPGF, BK[1–5]), is a stable metabolite of the peptide hormone bradykinin. Considering the short half-life of bradykinin (BK, 15 secs), RPPGF has been used as a marker for BK’s endogenous generation. A lack of a radioiodinated RPPGF has precluded the development of a radioimmunoassay for this peptide. The present study describes a two-step reaction that allows for the incorporation of ¹²⁵I into the aromatic ring of the phenylalanine of RPPGF. This radioiodinated analog is recognized by an antibody to RPPGF, demonstrating its utility for the development of a radioimmunoassay for measurements of RPPGF, a stable metabolic product of bradykinin.     

Effects of dominance on the probability of fixation of a mutant allele

We consider whether the fixation probability of an allele in a two-allele diploid system is always a monotonic function of the selective advantage of the allele. We show that while this conjecture is correct for intermediate dominance, it is not correct in general for either overdominant or underdominant alleles, and that for some parameter ranges the fixation probability can initially decrease and then increase as a function of the amount of selection. We have partial results that characterize the ranges of parameters for which this happens.      

Genetic mapping of ossification of the posterior longitudinal ligament of the spine.

Ossification of the posterior longitudinal ligament of the spine (OPLL) is recognized as a common disorder among Japanese and throughout Asia. Estimates of its prevalence are in the range of 1. 9%-4.3%. Although its etiology is thought to involve a multiplicity of factors, epidemiological and family studies strongly implicate genetic susceptibility in the pathogenesis of OPLL. In this study we report an identification of a predisposing locus for OPLL, on chromosome 6p, close to the HLA complex. The evidence for this localization is provided by a genetic-linkage study of 91 affected sib pairs from 53 Japanese families. In this sib-pair study, D6S276, a marker lying close to the HLA complex, gives evidence for strongly significant linkage (P = .000006) to the OPLL locus. A candidate gene in the region, that for collagen 11A2, was analyzed for the presence of molecular variants in affected probands. Of 19 distinct variants identified, 4 showed strong statistical associations with OPLL (highest P = .0004). These observations of linkage and association, taken together, show that a genetic locus for OPLL lies close to the HLA region, on chromosome 6p.     

Thermostability of Proteases and Lipases from a Number of Species of Psychrotrophic Bacteria of Dairy Origin

Proteases and lipases from a number of different species of psychrotrophic bacteria isolated from dairy products are resistant to heat treatments of 77°C for a holding time of 17 s and 140°C for a holding time of 5s. A further treatment combining the 77°C for 17 s heating process with a heat treatment involving a temperature of 55°C for 1 h was also examined. The proteases and, to a lesser extent, the lipases were also resistant to the treatments in combination. The resistance of proteases and lipases to inactivation by a treatment of 55°C for 1 h varied between and within species. Therefore, this treatment may not have a widespread practical application.     

Design and characterization of a plasmid vector system capable of rapid generation of antibodies of multiple isotypes and specificities

We present a detailed method for constructing a vector system composed of plasmids encoding immunoglobulin genes that have been constructed in such a fashion so as to allow for the generation and secretion of antibodies of multiple specificities and isotypes via a rapid and easy cloning-and-ligation scheme. Restriction sites within each plasmid allow for the removal of variable domains, constant domains, leader sequences, or the entire immunoglobulin gene. Degenerate primers are used to clone variable regions from hybridoma cDNAs, allowing for the creation of antibodies with varying binding specificities. Sequence-specific primers are used to clone antibody constant domains, allowing for the creation of antibodies of multiple isotypes from a variety of lineages. A high-efficiency leader sequence has been inserted into the start of each gene to improve secretion. Antibodies constructed through this system are efficiently secreted by transfected cells, and are fully functional in antigen-specific binding assays.     

The role of phadiatop in the screening of respiratory allergy

Phadiatop is a new in vitro screening test for respiratory allergy. This test, based on the RAST procedure, detects in serum, the presence of specific IgE to a mixture of common inhalent allergens. Among 70 patients (26 children and 44 adults) consulting for respiratory syndrome, Phadiatop was positive in 31 cases. There were a good correlation between this new test and skin tests (59% for adults and 92% for children), total IgE (70% for adults and 65% for children) and RAST (93% for adults and 96% for children). Phadiatop, with a specificity of 100%, a sensitivity of 82% (76% for adults and 92% for children) and an efficiency of 90% (86% for adults and 96% for children), is a more accurate test than total IgE and could be an excellent in vitro screening test for respiratory allergy.     

Evaluation of antifungal activity of antimycotics by automatic analyzing system

Antifungal activity of several antimycotics has been evaluated using an automatic analyzing system (AAS), which is composed of a specially designed reaction vessel, microscopic observation system, image analyzing system, and computer program for automatic tracing of hypha growth. The agar plate was prepared on the ceiling of the reaction vessel, and spore mass of a fungus (Aspergillus niger) was inoculated onto it. After the preincubation at 28 °C for 24 h the reaction vessel was set on a microscope stage and connected to the liquid flow system. An appropriate hypha was selected for the measurement of growth process during the following steps: first contact with saline for 30 min for the adaptation, the second contact with same saline for 30 min, contact with saline containing an antimycotic substance for 60 min, and contact with flushing saline for 60 min. During a sequence of these steps, the apical tip of a growing hypha displayed on a TV monitor was followed automatically. The dynamic response of hypha to an agent was analyzed by several parameters. Morphological changes of the hypha caused by respective agents were recorded on VTR for further analysis. By using this system, the antifungal activity of antimycotics could be quantitatively determined within several hours.     

Purification and mechanism of action of a plant galactokinase]

The previously described galactokinase from Fenugreek seeds, has been purified by affinity chromatography on a column of galactosamine-CH Sepharose. This material ensures a more specific fixation than does ATP-Sepharose. A 400 fold purification was achieved in a single step, with a 80 per cent yield. Km's for galactose and for Mg/ATP2- complex were respectively 0.54 x 10-3 M and 5, 10-3 M. Galactose-1-phosphate is a competitive inhibitor of galactose while the inhibition for Mg-ATP2- is not a competitive one. The Mg-ADP complex is a non-competitive inhibitor of both galactose and Mg-ATP2-. Moreover, the Km of the enzyme for M-ATP2- complex is modified when 2-deoxy- and 6-deoxy-galactose are used instead of galactose. These results are consistent with an ordered sequential mechanism for this galactokinase: galactose binds to the enzyme before Mg-ATP2-, and galactose-1-phosphate is the last reaction product liberated. The affinity of the kinase for 6-deoxygalactose is lower than for 2-deoxygalactose. This observation reveals the importance of the hydroxyl in C6 position for the binding on the enzyme.     

Direct Detection of Membrane-Inserting Fragments Defines the Translocation Pores of a Family of Pathogenic Toxins

Large clostridial toxins (LCTs) are a family of homologous proteins toxins that are directly responsible for the symptoms associated with a number of clostridial infections that cause disease in humans and in other animals. LCTs damage tissues by delivering a glucosyltransferase domain, which inactivates small GTPases, across the endosomal membrane and into the cytosol of target cells. Elucidating the mechanism of translocation for LCTs has been hampered by difficulties associated with identifying marginally hydrophobic segments that insert into the bounding membrane to form the translocation pore. Here, we directly measured the membrane-insertion partitioning propensity for segments spanning the putative pore-forming region using a translocon-mediated insertion assay and synthetic peptides. We identified membrane-inserting segments, as well as a conserved and functionally important negatively charged residue that requires protonation for efficient membrane insertion. We provide a model of the LCT pore, which provides insights into translocation for this enigmatic family of α-helical translocases.     

High-throughput quantification of hydroxyproline for determination of collagen

An accurate and high-throughput assay for collagen is essential for collagen research and development of collagen products. Hydroxyproline is routinely assayed to provide a measurement for collagen quantification. The time required for sample preparation using acid hydrolysis and neutralization prior to assay is what limits the current method for determining hydroxyproline. This work describes the conditions of alkali hydrolysis that, when combined with the colorimetric assay defined by Woessner, provide a high-throughput, accurate method for the measurement of hydroxyproline.     

Modeling of the enzymatic kinetic synthesis of cephalexin--influence of substrate concentration and temperature

During enzymatic kinetic synthesis of cephalexin, an activated phenylglycine derivative (phenylglycine amide or phenylglycine methyl ester) is coupled to the nucleus 7-aminodeacetoxycephalosporanic acid (7-ADCA). Simultaneously, hydrolysis of phenylglycine amide and hydrolysis of cephalexin take place. This results in a temporary high-product concentration that is subsequently consumed by the enzyme. To optimize productivity, it is necessary to develop models that predict the course of the reaction. Such models are known from literature but these are only applicable for a limited range of experimental conditions. In this article a model is presented that is valid for a wide range of substrate concentrations (0-490 mM for phenylglycine amide and 0-300 mM for 7-ADCA) and temperatures (273-298 K). The model was built in a systematic way with parameters that were, for an important part, calculated from independent experiments. With the constants used in the model not only the synthesis reaction but also phenylglycine amide hydrolysis and cephalexin hydrolysis could be described accurately. In contrast to the models described in literature, only a limited number (five) of constants was required to describe the reaction at a certain temperature. For the temperature dependency of the constants, the Arrhenius equation was applied, with the constants at 293 K as references. Again, independent experiments were used, which resulted in a model with high statistic reliability for the entire temperature range. Low temperatures were found beneficial for the process because more cephalexin and less phenylglycine is formed. The model was used to optimize the reaction conditions using criteria such as the yield on 7-ADCA or on activated phenylglycine. Depending on the weight of the criteria, either a high initial phenylglycine amide concentration (yield on 7-ADCA) or a high initial 7-ADCA concentration (yield on phenylglycine amide) is beneficial.     

Assessment of potential indigenous plant species for the phytoremediation of arsenic-contaminated areas of Bangladesh

Soil and water contaminated with arsenic (As) pose a major environmental and human health problem in Bangladesh. Phytoremediation, a plant-based technology, may provide an economically viable solution for remediating the As-polluted sites. The use of indigenous plants with a high tolerance and accumulation capacity for As may be a very convenient approach for phytoremediation. To assess the potential of native plant species for phytoremediation, plant and soil samples were collected from four As-contaminated (groundwater) districts in Bangladesh. The main criteria used for selecting plants for phytoremediation were high bioconcentration factors (BCFs) and translocation factors (TFs) of As. From the results of a screening of 49 plant species belonging to 29 families, only one species of fern (Dryopteris filix-mas), three herbs (Blumea lacera, Mikania cordata, and Ageratum conyzoides), and two shrubs (Clerodendrum trichotomum and Ricinus communis) were found to be suitable for phytoremediation. Arsenic bioconcentration and translocation factors > 1 suggest that these plants are As-tolerant accumulators with potential use in phytoextraction. Three floating plants (Eichhornia crassipes, Spirodela polyrhiza, and Azolla pinnata) and a common wetland weed (Monochoria vaginalis) also showed high BCF and TF values; therefore, these plants may be promising candidates for cleaningup As-contaminated surface water and wetland areas. The BCF of Oryza sativa, obtained from As-contaminated districts was > 1, which highlights possible food-chain transfer issues for As-contaminated areas in Bangladesh.     

Identifying combinations of cancer markers for further study as triggers of early intervention

In many long-term clinical trials or cohort studies, investigators repeatedly collect and store tissue or serum specimens and later test specimens from cancer cases and a random sample of controls for potential markers for cancer. An important question is what combination, if any, of the molecular markers should be studied in a future trial as a trigger for early intervention. To answer this question, we summarized the performance of various combinations using Receiver Operating Characteristic (ROC) curves, which plot true versus false positive rates. To construct the ROC curves, we proposed a new class of nonparametric algorithms which extends the ROC paradigm to multiple tests. We fit various combinations of markers to a training sample and evaluated the performance in a test sample using a target region based on a utility function. We applied the methodology to the following markers for prostate cancer, the last value of total prostate-specific antigen (PSA), the last ratio of total to free PSA, the last slope of total PSA, and the last slope of the ratio. In the test sample, the ROC curve for last total PSA was slightly closer to the target region than the ROC curve for a combination of four markers. In a separate validation sample, the ROC curve for last total PSA intersected the target region in 77% of bootstrap replications, indicating some promise for further study. We also discussed sample size calculations.     

Comparison of models of insulin release

A model for insulin secretion with a storage and a labile compartment, as well as a provisionary factor, is combined with a signal model in which the signal can be the difference between an excitation and an inhibition, or the difference in concentrations inside and outside some cell components. The model, using a single set of values for the parameters, accounts in a semiquantitative manner for all of the regularly appearing features of the insulin secretion from thein vitro perfused pancreas to a wide range of patterns of glucose and tolbutamide stimulation. Among the features which can be accounted for are: early and late secretion of insulin as a function of glucose in terms of a single parameter; the apparent depletion and recovery during a pulsed pattern of stimulation by tolbutamide; the hypersecretion following a short period of rest during a prolonged stimulation by glucose; the negative spike which occurs when the concentration of glucose, which has been maintained for a period of time, is suddenly reduced to a lower level; and the appropriate responses to slow and fast ramp functions of glucose concentration.     

Range of action of moth sex-attractant sources

Observations and experiments which indicate the range of attraction of a sex-attractant source are distinguished from those which show its range of stimulation or sampling range. Published evidence of these ranges for lepidopteran sex-attractant sources is reviewed. In particular, evidence for the values of these three parameters for traps containing 100 g of synthetic sex-pheromone of the pea moth, Cydia nigricana (F.), is presented, including the results of a timed mark and recapture experiment. It is concluded that for C. nigricana the ranges of attraction, stimulation and the daily sampling range for such a source placed in a cereal crop are at least 200, 500 and 500 m respectively.