A statistical table for the degree of coexistence between two species

Summary The well known Jaccard's association coefficient has been calculated on perfectly random infinite samples of different n size and a statistical table with the corresponding probability values is presented.The drawing for this paper has been prepared by Mr. Armin Coray with a grant of the Swiss National Science Foundation (No. 3.5.581.-0.75)     

Modal analysis of renewal models for spontaneous single neuron discharge

Three renewal process models of neural discharge were briefly discussed, and their modal properties were analyzed. Examples of numerical solutions for the p · d · f's of each model were presented, and they conformed with the analytical results, demonstrating that one of the models, Model 2, generates multimodal interresponse time p · d · f's. Several areas of comparison with real data were indicated.Supported in part by a grant from the Alfred P. Sloan Foundation to the Department of Theoretical Biology, and by Research Grant No. NSF-GP-16071 from the Division of Mathematical, Physical and Engineering Sciences of the National Science Foundation to the Department of Statistics, University of Chicago.     

Rudimentary locus of Drosophila melanogaster: Partial purification of a carbamylphosphate synthase-aspartate transcarbamylase-dihydroorotase complex

Glutamine-dependent CPSase, ATCase, and DHOase from Drosophila, the first three enzymes in pyrimidine biosynthesis, show coordinate variation in activity throughout development. The three activities were highest in first instar larvae and decreased as development proceeded. The three activities cosediment in sucrose gradients as a single peak with a relative sedimentation coefficient of approximately 30S. CPSase, ATCase, and DHOase copurify during (NH₄) ₂SO₄ fractionation and during DEAE-cellulose and hydroxylapatite chromatography.This work was supported by a grant from the National Science Foundation (No. PCM75-22802). In addition, Stuart I. Tsubota was a NIH Predoctoral Trainee (No. 5T32-GM07 127) and Susan E. Germeraad was a Cystic Fibrosis Foundation Postdoctoral Fellow.     

Dynamical synaptic plasticity: a model and connection to some experiments

 Using a modified version of a phenomenological model for the dynamics of synaptic plasticity, we examine some recent experiments of Wu et al. [(2001) J Physiol 533:745–755]. We show that the model is quantitatively consistent with their experimental protocols producing long-term potentiation (LTP) and long-term depression (LTD) in slice preparations of rat hippocampus. We also predict the outcome of similar experiments using different frequencies and depolarization levels than reported in their results. Received: 3 September 2002 / Accepted in revised form: 22 October 2002 / Published online: 24 February 2003 Correspondence to: H.D.I. Abarbanel (e-mail: hdia@jacobi.ucsd.edu) Acknowledgements. We are very grateful to A. Selverston and D. Feldman for conversations about this work. This work was partially supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Engineering and Geosciences, under grants No. DE-FG03-90ER14138 and No. DE-FG03-96ER14592, by a grant from the National Science Foundation, NSF PHY0097134, by a grant from the Army Research Office, DAAD19-01-1-0026, by a grant from the Office of Naval Research, N00014-00-1-0181, and by a grant from the National Institutes of Health, NIH R01 NS40110-01A2. This work was also partially supported by M. Ciencia y Tecnologa BFI2000-0157 (R.H.).     

The larval retreat and feeding net of macronema carolina banks (Trichoptera: Hydropsychidae)

Larvae of the caddisfly Macronema carolina, which is widely distributed in the eastern United States, construct chambers on and in the bark and outermost wood of submerged tree limbs in large streams. Each chamber consists of two main parts, a feeding chamber and a larval retreat. A feeding net 10–11 mm² in area is spun diagonally across the inside of the open ended, tubular feeding chamber, the anterior end of which opens directly into the current. This feeding net has a very fine mesh with openings of approximately 5 × 40 μ and is used to strain microseston (fine particulate organic matter, phytoplankton and bacteria) upon which the larva grazes while situated in a retreat opening into the side of the feeding chamber. This larval retreat has a small opening posteriorly which is apparently used as an exit for feces and water passing over the gills. We propose that the Holarctic distribution of Macronema spp., as inhabiting large streams, may be influenced more by feeding habits of the species, than the conventional water quality parameters often used by aquatic biologists to account for distribution. This research was supported by a grant from the National Science Foundation (U.S.A.). This research was supported by a grant from the National Science Foundation (U.S.A.).     

Ultrastructural changes in nurse and follicle cells during late stages of oogenesis in Drosophila melanogaster

Summary During stages 11 and 12, follicle cells surrounding the nurse cells produce lysosomes which presumably aid in the breakdown of the nurse cells. Accompanying a DNA reduction in nurse cell nuclei are several characteristic morphological changes including the appearance of intranuclear rod-like structures and nuclear granules about 300 Å in diameter. Similarities between structures seen in Drosophila nurse cell nuclei and those seen in other organisms are discussed.This research was supported by U. S. Public Health Service Grants 5TIGM903-3 and 1-F1-GM-33, 385-01 and National Science Foundation grant GB-7457.     

N-1-napthylphthalamic-acid-binding activity of a plasma membrane-rich fraction from maize coleoptiles

Summary Plasma membrane-rich fractions were prepared from maize coleoptiles by low-shear homogenization and differential and sucrose-gradient centrifugation. Plasma membrane fragments were identified using a specific cytochemical stain based on phosphotungstic acid prepared in chromic acid. In a comparison of 10 different cell fractions of varying plasma membrane content, the N-1-napthylphthalamic-acid (NPA)-binding activity of the fractions was directly proportional to the content of plasma membrane. The NPA binding appears to be strong K _M between 10^-8 and 10^-7 M) but non-covalent. NPA is known to inhibit auxin transport efficiently and quickly. Thus, the results are consistent with the localization of auxin transport sites at the plasma membrane of plant cells.Purdue University Agricultural Experiment Station Journal Paper No. 4355. This work was supported in part by a grant from the National Science Foundation GB-23183.Supported by National Science Foundation Postdoctoral Fellowship.     

Particle aggregation and phagotrophy by Ochromonas

Summary Ochromonas danica creates a current with its flagella which forces fluid and particles to flow toward the front and over the sides of the phytoflagellate. It is able to aggregate particles including bacteria by this action, trap them at its surface, and engulf them. Aggregation and phagocytic activity requires live, metabolically active cells. This type of biological activity may permit O. danica and similar organisms to sample their environment and extract particles.Aided by grant GB 20825 from the National Science Foundation and 5-S05-RR-07064-06 from the National Institutes of Health.     

An analysis of neutral-alleles and variable-environment diffusion models

Three diffusion models are formulated for the evolution of a diploid population with K alleles at one locus with completely symmetric mutation and random genetic drift, a variable-environment, and all the above mechanisms. For the diallelic case, the transient behavior is studied by solving the corresponding diffusion equations by an asymptotic method valid for short time intervals. The transient behavior of the three models is compared for the case when their stationary distributions are identical. The expected amount of heterozygosity is computed using the asymptotic solution and is compared to an exact result. The asymptotic results are extended to the general case with K alleles at the locus for the symmetric mutation and variable-environment models.Research supported by the National Science Foundation under Grant MCS 79-01718     

Spike timing dependent synaptic plasticity in biological systems

 Association of a presynaptic spike with a postsynaptic spike can lead to changes in synaptic efficacy that are highly dependent on the relative timing of the pre- and postsynaptic spikes. Different synapses show varying forms of such spike-timing dependent learning rules. This review describes these different rules, the cellular mechanisms that may be responsible for them, and the computational consequences of these rules for information processing and storage in the nervous system. Received: 16 January 2002 / Accepted: 3 June 2002 Acknowledgements. This research is supported in part by a National Science Foundation grant IBN 98-08887 (awarded to PDR), and by National Institutes of Health grants R01-MH49792 (awarded to CCB), R01-MH60996 (awarded to CCB), and R01-MH60996 (awarded to PDR). Correspondence to: P. D. Roberts (e-mail: robertpa@ohsu.edu)     

The cell content and secretion of water-soluble vitamins by several freshwater algae

Three green algae, Chlamydomonas reinhardii, Chlorella vulgaris and Scenedesmus obliquus, and one blue-green alga, Anabaena cyclindrica, were grown in chemically defined media. All the algac examined contained folates, -carotene and vitamins C and E; several of the B-vitamins and vitamin A were found in varying amounts in some but not in all the algae examined. All the green algae secreted significant amounts of folate and biotin and all but Scenedesmus secreted pantothenate into their growth medium; Anabaena secreted folate and pantothenate.This work was done with the support of grant BMS 74-08918 from the National Science Foundation     

Effect of trehalose on the spawn storage in some edible mushroom fungi (2): Effect on preservation in the freezer

 We describe the effects of trehalose on spawn storage in a home freezer (average temperature, −16°C) where edible fungi usually do not survive. When the mycelia of Lentinula edodes were stored in a freezer for 3 days, the survival rate of mycelia cultivated on 2% glucose medium was 30%, whereas those on media containing 2% and 5% trehalose were 50% and 60%, respectively. Addition of trehalose to the culture was more effective in Pleurotus ostreatus. These results suggest that trehalose played the role of a stress protectant against freezing, because the mycelia cultured on a trehalose medium grew more rapidly and produced more fruiting bodies compared to those cultured on glucose. Received: February 6, 2002 / Accepted: October 1, 2002 Acknowledgments This work was partially supported by a Grant in Aid for Scientific Research (c) (2) No. 12660156 from the Japan Society for the Promotion of Science. We also gratefully acknowledge a grant from Hokuto Foundation for the Promotion of Biological Science. Correspondence to:T. Terashita     

Induction and genetics of two alpha-galactosidase activities in Saccharomyces cerevisiae

Summary The induction of -galactosidase of Saccharomyces cerevisiae was investigated. We have demonstrated the existence of inducible internal and external -galactosidase activities and have studied the relationship between the two -galactosidases by examining a mutant strain which lacks both the internal and external activities. The mutant possesses a mutation in a single locus (mel 1-1) which does not affect the synthesis of the other galactose pathway enzymes or the ability of the yeast to grow on media containing only galactose as the carbon source. Genetic studies of the mutant indicate that mel 1-1 is recessive and allelic to the wild type allele for melibiose fermentation Mel 1.This investigation was supported in part by Grant No. AM15325 from the National Institutes of Arthritis, Metabolism and Digestive Diseases, and a grant from the Office of Research Administration, University of Hawaii. R.G. Buckholz was a National Science Foundation Pre-Doctoral Fellow during part of this study     

Intracellular development of a large DNA bacteriophage lytic for Caulobacter crescentus

Summary The cytological alterations accompanying Cb 13 infection of Caulobacter crescentus CB13 cells were followed by electron microscopic examination of sections of cells fixed at various stages of the infection. During the first half of the latent period, the cells appear unaltered. In the second half, the nucleoplasm migrates to the cell periphery and becomes more discrete than the nucleoplasm of uninfected cells. Phage particles appear within the migrated nucleoplasm. The only further alteration apparent in the sections is the absence of the lysozyme-versenesoluble layer of the cell wall of phage-lysed cells.This work was supported by National Science Foundation grant GB-2872.Dedicated to Professor C. B. van Niel on the occasion of his 70th birthday.     

Light and electron microscopic detection of (3 Gal β1,4 GlcNAc β1) sequences in asparagine-linked oligosaccharides with the Datura stramonium lectin

Summary The Datura stramonium lectin recognizes with high affinity the disaccharide N-acetyllactosamine (Gal 1,4 GlcNAc). We have developed a highly specific cytochemical affinity technique in which an ovomucoid-gold complex serves as second step reagent for the visualization of this lectin bound to reactive sequences present in tissue sections. The lectin binding sites were detected in semithin and ultrathin sections of aldehyde-fixed and low temperature Lowicryl K4M embedded tissues. For light microscopical labeling the photochemical silver reaction for signal amplification was required. The application of this technique for the detection of N-acetyllactosamine containing asparagine-linked oligosaccharides in various intracellular organelles and the plasma membrane is demonstrated.This study was supported by the Swiss National Science Foundation grant nr. 31-26273.89 (to J.R.) and GM 29470 from the National Institutes of Health (to I.J.G.). Dr. G. Egea was a recipient of a European Molecular Biology Organization long term fellowship.     

A note on the fine structure of the Ochromonas danica “tail”

Summary The fine structure of the Ochromonas danica tail is detailed. The microtubules, microtubule anchoring structures, posterior swelling, surface vesicles, and in some instances cup shape of the tail end are described and used to explain the behavior of the organism when attached to surfaces.Aided by a grant GB 20825 from the National Science Foundation.     

Immunohistochemical evidence for the presence of tryptophan hydroxylase in the brains of insects as revealed by sheep anti-tryptophan hydroxylase polyclonal antibody

Immediately following the discovery of tryptophan hydroxylase in Drosophila, we demonstrated the presence of tryptophan hydroxylase in the brain of the beetle Harmonia axyridis (Coleoptera: Coccinellidae). However, whether tryptophan hydroxylase is present in the brains of other insects is still a matter of discussion. In the current study, sheep anti-tryptophan hydroxylase polyclonal antibody has been applied to test for tryptophan hydroxylase immunoreactivity in a broader taxonomic range of insect brains, including holometabolous and hemimetabolous insects: one species each of Coleoptera, Hymenoptera, Diptera, and Blattaria, and two species of Lepidoptera. All species show consistent tryptophan hydroxylase immunoreactivity with distribution patterns matching that of serotonin. The immuno-positive results of such an antibody in brains from diverse orders of insects suggest that specific tryptophan hydroxylase responsible for central serotonin synthesis is probably present in the brains of all insects. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. This work was supported by grants from the National Natural Science Foundation of China (grant no. 30470546) and the Natural Science Foundation of Jilin Province (grant no. 20030550–7).     

The peroxidase-glucose oxidase system: A new method to determine glucose liberated by carbohydrate degrading soil enzymes

This paper describes a new, accurate method for determination of glucose in soil enzyme assays. The low limit of detection of glucose by the peroxidase-glucose oxidase (PGO) system is 0.004 mg glucose · g soil⁻¹. Comparisons of PGO with the anthrone and phenol-sulfuric acid methods revealed no differences in the detection of glucose standard solutions. By eliminating the use of large volumes of H₂SO₄, the PGO system reduces laboratory hazards. A portion of this work was supported by National Science Foundation Grant DEB-8004172 and a grant from the Miami University Faculty Research Committee.     

Electron microscope studies on collagen

Summary The present paper describes the effect of intensive tryptic digestion of native tropocollagen (TC) macromolecules in solution. Contrary to earlier investigations it has been found that the trypsin treatment results in a fragmentation of the TC molecules. The addition of ATP to solutions exposed to the enzyme yields SLS fragments, 2250 Å in length. Comparison between these and normal SLS type aggregates shows that the scission occurs in a well-defined locus adjacent to the -1/2-line seen after positive staining. The significance of this finding is discussed.This study was supported by grant NB-02215-04 from the National Institute of Neurological Diseases and Blindness, Public Health Service, U.S.A. and a Student research fellowship from the Norwegian Research Council for Science and the Humanities. This aid is gratefully acknowledged.I am indebted to Mrs. J. Line Vaaland and Mr. B. V. Johansen for technical assistance.