Spatially localized interactive neural populations—II: Stability and dynamics of excitatory sets

The stability characteristics and dynamical behavior of a system of mutually excitatory neurons in close spatial proximity are investigated with a mathematical model. The model predicts the existence of uniform, intermediate levels of activity other than those of no activity and maximal activity. The model also, yeilds a good explanation of data obtained from periglomerular neurons in the olfactory bulb of the cat. This paper is based on a dissertation submitted by the author to Rensselaer Polytechnic Institute in partial fulfillment of the requirements for the degree of Doctor of Philosophyy. This work was supported in part by a Fellowship sponsored by the IBM Corporation and in part by the National Science Foundation under Grant MCS75-08328.     

Oscillatory coexistence in a food chain model with competing predators

A food chain model with two predators feeding on a single prey in a chemostat is studied. Using a multiparameter bifurcation analysis, we find parameters values for which there is stable oscillatory coexistence of the predators. It is also shown how these coexistent states provide a transition between two possible states of competitive exclusion. It is shown that the competitive exclusion principle need not hold if one or more of the predators has oscillatory behavior in the absence of other predators.This work was partially supported by National Science Foundation Grant MCS 83-01881     

Effect of high nonexchangeable aluminium on nitrogen and phosphorus availability in a humus-rich acid forest soil

The effect of high nonexchangeable aluminum on availability of nitrogen (N) and phosphorus (P) was studied in a Cryptopodzolic soil (Cademario) derived from mica schist in southern Switzerland. The research involved a greenhouse pot experiment comparing growth of barley on soil samples of three soil layers (10- to 25-, 40- to 60- and 70- to 90 cm) of the Cademario profile, representing a range of Al and organic matter properties, with the 10- to 40 cm layer of a profile of an acidic brown earth (Haplumbrept), derived from cherty limestone. The experiment, which included four nutrient treatments [check, N₀ (PKS), P₀ (NKS) and full (NPKS)], lime and no lime treatments and four replicates, was supplemented by soil chemical analysis. Results showed that liming alone produced greater yield responses in the Cademario soil than N or P added singly or together. On unlimed soils, barley yield for check, N₀, and P₀ treatments showed a positive linear relation with exchangeable Ca of soils and a negative linear relation with organically-complexed Al. Failure of liming to influence P_av, especially when combined with P fertilization, suggests that P was quickly absorbed on highly active surfaces formed from initially exchangeable Al.This research is a cooperative effort of the Arizona Agricultural Experiment Stations, Journal Article No. 7100 and the Swiss Federal Institute for Forest, Snow and Landscape; it was supported by the National Science Foundation, USA, Grant No. INT-8304490, and the Swiss National Science Foundation, Grant No. 2.919-803.This research is a cooperative effort of the Arizona Agricultural Experiment Stations, Journal Article No. 7100 and the Swiss Federal Institute for Forest, Snow and Landscape; it was supported by the National Science Foundation, USA, Grant No. INT-8304490, and the Swiss National Science Foundation, Grant No. 2.919-803.     

Global dynamics of a selection model for the growth of a population with genotypic fertility differences

A population growth model is considered for a one locus two allele problem with selection based entirely on fertility differences. A local stability analysis is carried out for the critical points — which include possible polymorphic states — of the resulting nonlinear differential equations. The methods of dynamical systems theory are applied to obtain limiting genotypic proportions for every initial state. Thus the results are global and there are no periodic solutions.Research for this paper was partially supported by the National Science and Engineering Research Council of Canada Grant NSERC A-8130Research for this paper was partially supported by the National Science and Engineering Research Council of Canada Grant NSERC A-4823Research supported by NSF Grant MCS 7901069. A portion of the work was carried out while the author was a Visiting Professor at the University of Utah, Salt Lake City, Utah     

Optimal motor control may mask sensory dynamics

Properties of neural controllers for closed-loop sensorimotor behavior can be inferred with system identification. Under the standard paradigm, the closed-loop system is perturbed (input), measurements are taken (output), and the relationship between input and output reveals features of the system under study. Here we show that under common assumptions made about such systems (e.g. the system implements optimal control with a penalty on mechanical, but not sensory, states) important aspects of the neural controller (its zeros mask the modes of the sensors) remain hidden from standard system identification techniques. Only by perturbing or measuring the closed-loop system “between” the sensor and the control can these features be exposed with closed-loop system identification methods; while uncommon, there exist noninvasive techniques such as galvanic vestibular stimulation that perturb between sensor and controller in this way. This work was supported by the National Science Foundation under Grant No. 0543985, and by the National Institutes of Health under Grant No. 2RO1 NS35070.     

Interpolation coding: A representation for numbers in neural models

A central task of perception can be defined as one of computing hierarchies of invariants. One way of representing such invariants in intermediate levels of abstraction in this hierarchy is to use discrete units. These have been termed value units. A problem with such an encoding is that there has not been a good way to represent accurate numerical quantities using these units. This paper remedies the deficiency by describing a scheme that interpolates values between units representing fixed numerical quantities. The scheme has nice properties: it extends across functional mappings and it allows different sources of evidence to be combined.This work was supported in part by the National Science Foundation under Grant DCR-8405720 and the National Institutes of Health under Public Health Service Grant 1R01NS22407-01     

The sampling theory of neutral alleles and an urn model in population genetics

The behaviour of a Pólya-like urn which generates Ewens' sampling formula in population genetics is investigated. Connections are made with work of Watterson and Kingman and to the Poisson-Dirichlet distribution. The order in which novel types occur in the urn is shown to parallel the age distribution of the infinitely many alleles diffusion model and consequences of this property are explored. Finally the urn process is related to Kingman's coalescent with mutation to provide a rigorous basis for this parallel.This research was partially supported by the Sloan Foundation under Grant 85-6-14 and by the National Science Foundation     

Retinal responses inNautilus

Summary Electrical responses (ERG) were recorded from the retinal surface of the eye ofNautilus pompilius. Brief light flashes and step changes in intensity were used to explore linear and nonlinear response properties. The linear responses could be fitted well with cascaded exponential decay processes and a time delay. Nonlinear phenomena included a saturating amplitude of response with increased light intensity, and shape changes induced by adaptation and by background illumination.This study, of the R/V Alpha Helix Southeastern Asia Expedition, was supported by the National Science Foundation under Grants OFS74-01830 and OCE74-02888 to Scripps Institution of Oceanography. It was also supported by the National Science Foundation Grant BMS75-01149 to Iowa State University. — We would like to thank Walter Schneider for his technical assistance while on shipboard. This work would not have been possible without the help and hospitality of the wonderful people of Bindoy, Negros Oriental, The Republic of the Philippines.     

Determination of the ionization potential and the electron affinity of various biologically active substances by polarography

The electron affinity and ionization potential of various biological substances were measured by polarography and compared with their effect on growth ofE. coli.This research was supported by the National Science Foundation, Grant GM 10383, the Josephine B. Crane Foundation, and the Thayer Lindsley Foundation.     

Introduction to special issue on RNA

In this introduction to the special issue on RNA, we provide a brief overview of some of the novel and exciting biological discoveries concerning diverse roles played by RNA, and subsequently we give a rapid summary of some algorithmic aspects of RNA structure and alignment. Each of the contributions to this special issue is briefly described. This work is funded in part by the National Science Foundation under Grant No. DBI-0543506.     

Further observations on dividing and non-dividing cnidoblasts in the regenerating isolated gastrodermis of Hydra

Summary Cnidoblasts derived from the dedifferentiation of gland cells in the regenerating isolated gastrodermis of Hydra are capable of nuclear and cytoplasmic division. The daughter cell containing the nematocyst apparently develops normally. The fate of the other daughter cell remains obscure, but it is believed that it is also capable of developing a nematocyst. Only a single bi-nucleated cnidoblast was observed and it was in the process of degeneration. It is suggested that at least in the present system, cnidoblasts are derived not only from interstitial cells but also from pre-existing cnidoblasts.This investigation was supported by the National Science Foundation Grant No. GB 8384.With the technical assistance of Linda Bookman.     

A recovery-relapse epidemic model with spatial diffusion

An epidemic model of an infectious phenomenon is analyzed. The model allows for an age-dependency to describe the phases of incubation, recovery, and relapse, and for a spatial dependency to describe diffusion of the population in geographical space.Supported in part by the National Science Foundation Grant NSF MCS 7903047     

Altered secretion of kidney lysosomal enzymes in the mouse pigment mutants ruby-eye,ruby-eye-2-J,and maroon

Melanosomes and lysosomes share structural and biosynthetic properties. Three mouse pigment mutants, ruby-eye, ruby-eye-2-J, and maroon, have abnormally high concentrations of kidney lysosomal enzymes. Concentrations of kidney nonlysosomal enzymes and of liver and serum lysosomal enzymes are normal. By light microscopy the mutants have normal kidney lysosome morphology. It does not appear that the mutant genes cause an increased rate of production of lysosomes since the increased kidney -glucuronidase concentration is not accompanied by a corresponding increase in rate of synthesis. The common defect in all mutants is a decreased rate of secretion of lysosomal enzymes from kidney into urine. Eight mouse pigment mutants are now known which affect both melanosome and lysosome function. They should serve as useful models for the study of the biogenesis, structure, and processing of these and other subcellular organelles.This work was supported in part by United States Public Health Service Research Grant GM-19521 and by National Science Foundation Grant PCM77-24804. E. K. N. was supported in part by United States Public Health Service Grant GM07093-03. F. W. was a high school student in the summer program supported by National Science Foundation Grant SP177-26980.     

Biochemical genetics of Fundulus heteroclitus (L.). III. Inheritance of isocitrate dehydrogenase (Idh-A and Idh-B), 6-phosphogluconate dehydrogenase (6-Pgdh-A), and serum esterase (Est-S) polymorphisms

Starch gel electrophoresis has shown that natural populations of Fundulus heteroclitus have variants at four enzyme-coding loci: Idh-A, Idh-B, 6-Pgdh-A, and Est-S. Analysis of the phenotypic distribution of the F₁ generation suggests that each of the variants segregates as autosomally inherited codominant alleles. Tissue specificity and intracellular localization were also determined for the IDH and 6PGDH isozymes.This work was supported by Grants DEB 76-19877 and DEB 79-12216 from the National Science Foundation and by Grant P60-80-04 from the State of Maryland. RVB and REC were supported by NIH Training Grant GM07231 to the Department of Biology.Contribution No. 1103 from the Department of Biology, The Johns Hopkins University.     

Screening and breeding of high taxol producing fungi by genome shuffling

To apply the fundamental principles of genome shuffling in breeding of taxol-producing fungi, Nodulisporium sylviform was used as starting strain in this work. The procedures of protoplast fusion and genome shuffling were studied. Three hereditarily stable strains with high taxol production were obtained by four cycles of genome shuffling. The qualitative and quantitative analysis of taxol produced was confirmed using thin-layer chromatography (TLC), high performance liquid chromatography (HPLC) and LC-MS. A high taxol producing fungus, Nodulisporium sylviform F4-26, was obtained, which produced 516.37 μg/L taxol. This value is 64.41% higher than that of the starting strain NCEU-1 and 31.52%―44.72% higher than that of the parent strains.     

In vitro culture of ovaries of a viviparous gall midge

Summary Ovaries of the viviparous pedogenetic gall midgeHeteropeza pygmaea can be cultured in hemolymph obtained from X-ray-sterilized larvae of the same species. In this culture medium, formation of follicles is essentially the same as in vivo, and sometimes female larvae develop from these follicles. The ovaries of such larvae, in their turn, have been cultured in vitro to produce larvae. In this way, in vitro development from oogonium to larva has been maintained for several generations. When using hemolymph obtained from larvae grown under different conditions, the in vitro cultured ovaries produce a second type of egg which probably is male-determined. Ovarian development in vitro has been studied with differential interference contrast optics and time-lapse cinemicrography. This work was supported by the Swiss National Science Foundation Grant No. 3.2010.73.     

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     

A review of important concepts in the trophic organization of pelagic ecosystems

The physical environment has an important influence on the size composition of primary producers in plankton communities. This effect is transmitted through the trophic structure by size selective feeding processes at each level. A pictorial representation of trophic organization in pelagic ecosystems is presented which illustrates the complex involvement of individual species in the food web and the dynamic nature of ecosystem development along alternate pathways.This research was supported in full by the National Science Foundation, Grant No. NSF OCE76-02035.     

The prolactin cell of the white-crowned sparrow,Zonotrichia leucophrys pugetensis

Summary The anterior pituitaries from a series of female White-crowned Sparrows,Zonotrichia leucophrys pugetensis, in the periods of oviposition, incubation, and brooding under natural conditions, have been investigated by electron microscopy. The prolactin cells occur in cephalic lobe and are characterized by large (ca. 300–600 m), polymorphic electron-dense secretory granules and an extremely well developed, lamellated endoplasmic reticulum. During incubation and brooding it is only these prolactin cells that are in an activated secretory phase, as indicated by increase in number and size, extremely well developed endoplasmic reticulum, decrease in number of mature secretory granules, and by active formation of granules in the enlarged Golgi apparatus. In the late stages of brooding, and post-breeding, the prolactin cells regress with involution of the endoplasmic reticulum and Golgi apparatus, reaccumulation of granules, and the appearance of lysosomes.The gonadotropes of both the cephalic and caudal lobes undergo progressive morphologic changes through the course of the breeding period. They are numerous and active in the ovulating bird. They undergo gradual regression during the periods of incubation and brooding to become typical broody cells.This investigation was supported by Grant No. GF-33334, U.S.-Japan Cooperative Science Program of the National Science Foundation and by Grant No. GB-28080X, also from the National Science Foundation, to Professor Farner; and by Grant No. 5R040 Japan-U.S. Cooperative Science Program of Japan Association of Science Promotion, to Professor Mikami.     

Present status and future prospects for the hybridoma technology

Summary A somatic cell genetic technique has recently been developed that makes it possible to obtain very large amounts of homogeneous antibodies and to replenish the supply of the exact same antibodies whenever they are needed. This hybridoma technology has already contributed to major scientific advances and will surely improve the diagnosis and treatment of many diseases. Because the technology itself is relatively simple and inexpensive, it has captured the attention of basic scientists, clinicians, and industrial managers and investors. This work was supported by National Institutes of Health Grants AI 10702 and AI 5231, National Science Foundation Grant PCM77-25635, and American Cancer Society Grant NP-317.