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.     

Ordination as a tool for analyzing complex data sets

Summary Ordination has proven to be a useful tool for examining relationships between environment and vegetation in data sets with a simple underlying environmental strueture. Complex data sets have proven much less tractable. A strategy is offered for dealing with complex data sets based on progressive removal of sets of stands along identified gradients, and subsequent reordination. This strategy is demonstrated using forests of the North Carolina piedmont.The author gratefully acknowledges the continuing collaboration of Dr. Norman L. Christensen of Duke University. This research was supported by National Science Foundation grants DEB-7708743 and DEB-7804043 to R.K.P. and DEB-7707532 and DEB-7804041 to N.L.C.     

Epilithic periphyton and detritus studies in a subalpine stream

The accumulation of epilithic periphyton in Ward Creek, a permanent stream within the Lake Tahoe basin, California, was measured weekly at three stations from July through September, 1972. Subsamples were analyzed for total carbon and adenosine triposphate content. The mean total carbon content at three stations over the period of investigation was 0.508 ± 0.263 mg carbon cm^–2. Live biomass, as estimated from ATP measurements, averaged 0.121 ± 0.115 mg carbon cm 2. It was estimated that approximately 76% of the organic carbon accumulating on rock substrates was present as detritus. Scanning electron microscopy of rock substrates suggested that much of this detrital accumulation may consist of diatom stalk materials.This work was supported by a grant from the National Science Foundation/RANN GI-22. C. R. Goldman, Principal Investigator.     

Partitioning of reduced nitrogen derived from exogenous nitrate in maize roots: Initial priority for protein synthesis

Summary When roots of five day-old maize seedlings were exposed to¹⁵N-nitrate, a constant (25–29%) proportion of the reduced¹⁵N derived from the entering¹⁵N-nitrate accumulated as insoluble¹⁵N nitrogen. Constancy was established by two hours and lasted through 12 hours at ambient¹⁵N-nitrate concentrations of 0.05 mM to 20.0 mM. Even when little¹⁵N nitrate had been reduced (<2 moles), there was a linear relationship between accumulation of insoluble¹⁵N (but not accumulation or translocation of soluble reduced¹⁵N) and total reduced¹⁵N. It is proposed that protein synthesis from the entering nitrate occurs in close association with nitrate reduction.Paper No. 9764 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC, 27695-7619, USA. This research was supported by Grant No. PCM-8118661 from the National Science Foundation.Use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the product's name or criticisms of similar ones not mentioned.     

Gramicidin-D-stimulated influx of monovalent cations into plant roots

Summary Gramicidin D and nigericin were found to stimulate K⁺ influx into oat roots. Valinomycin and nonactin had little effect on K⁺ influx. The region of the root most sensitive to gramicidin was the elongation zone. Monocot roots were more sensitive to gramicidin than dicot roots. At 0.2 mM KCl, gramicidin stimulated K⁺ influx by 4- to 8fold over a 30-min absorption period. Although a gramicidin response is detectable within one minute, maximum stimulation occurred after a slight (approximately 2-min) lag period. The gramicidin effect was much greater at 0.2 mM KCl than at 20 mM KCl. Respiratory inhibitors reduced the gramicidin-stimulated K⁺ influx by 50–80%. The results are discussed in terms of possible mechanisms of action of the various ionophores on ion transport in roots.This work was supported by National Science Foundation Grants GB-5549 and GB-12674 and by the Illinois Agriculture Experiment Station.     

Control of relative growth rate by application of the relative addition rate technique to a traditional solution culture system

The relative addition rate (RAR) technique allows the nutritional control of plant relative growth rate (RGR) by the provision of nutrients at exponential supply rates. The technique, however, was developed with technologically sophisticated aeroponic systems. In this paper, we report on experiments used to adapt the RAR technique to a conventional solution culture system. A background concentration requirement of 36 μM nitrogen (N), with other nutrients supplied in proportion to N, was necessary to produce a constant RGR of Triticum aestivum L. (wheat) at a low RAR. Solution pH changes were reduced by increasing the percentage of NH₄ in the nitrogen supply, but the plants exhibited dry weight reductions and symptoms of toxicity above 30% NH₄. For wheat, a ratio of 25/75 NH₄/NO₃ was optimum for minimizing pH changes within the nontoxic range. A test of the effectiveness of the RAR technique using this background concentration and NH₄/NO₃ ratio showed that RGR increased with RAR with a linear slope of 0.55 and an intercept of 0.07 d^-1. Although the relationship between growth rate and nutrient supply was less than the one-to-one dependence of RGR on RAR that has been obtained with more sophisticated apparatus, application of the RAR technique to a conventional solution culture system still affords considerable control of RGR and presents a simple method for growing plants at different levels of nutrient stress and at distinct RGRs.     

Biochemical genetics of Fundulus heteroclitus (L.). IV. Spatial variation in gene frequencies of Idh-A,Idh-B, 6-Pgdh-A,and Est-S

The spatial variation in gene frequencies of four unlinked polymorphic loci was studied in the teleost Fundulus heteroclitus. Three loci (Idh-A, Idh-B, and Est-S) exhibit significant north-south clinal variation in allelic frequencies along the Atlantic Coast of North America, while a fourth locus (6-Pgdh-A) shows a modest clinal variation. These data, together with our previous data for Ldh-B, Mdh-A, Gpi-B, and Pgm-A, reveal a pattern of low gene diversity in the colder northern extremes of the species range and high gene diversity in warmer southern latitudes.This work was supported by Grants DEB76-19877 and DEB79-12216 from the National Science Foundation and by Grant P60-80-04 from the State of Maryland. REC and RVB were supported by NIH Training Grant GM07231 to the Department of Biology.Contribution No. 1104 from the Department of Biology, The Johns Hopkins University.     

Hypoxylon rubiginosum: Cytology of the ascus and surface morphology of the ascospore

Summary The haploid chromosome number ofHypoxylon rubiginosum is 5. The ascospore is uninucleate when formed, becoming binucleate following a mitosis. One of the nuclei subsequently disintegrates. Maturing ascospores are uninucleate.The morphology of the ascospore, as revealed by the scanning electron microscope, is described. The outer wall layer — the perisporium — shows heretofore undescribed surface fibrils. The possible significance of the fibrils is discussed.Paper No. 3205. Washington State University College of Agriculture Project 1767. This study was supported in part by National Science Foundation Grants GB-5219 and GB-8004.     

The scatter of intracellular ionic concentration in the lobster circumesophageal axon

Summary The intracellular potassium and sodium concentrations of the lobster circumesophageal axon was measured with an ultramicro integrative flame photometer. The average concentration of 376.1 mM/l vol for potassium and 63.8 mM/l vol for sodium that was determined was correlated with electrophysiological data. The large scatter of the concentration in individual axons is compared with measurements by other investigators and is discussed.The work of the Laboratory of Neurophysiology is supported in part by grants from the Muscular Dystrophy Associations of America; by Public Health Service Research Grants (NB 03728) and Training Grant (NB 05328), from the National Institute of Neurological Diseases and Stroke; and from the National Science Foundation (GB 6988X). Dr. Freeman was a Postdoctoral Trainee Fellow In Neurophysiology.     

Cultivation of microvascular endothelial cells from human preputial skin

Summary A procedure is described for the isolation and cultivation of microvascular endothelium from human skin. Neonatal foreskins are pooled, washed, minced, and dissociated by a mixture of collagenase and dispase. Microvascular endothelium, liberated in the form of intact capillary fragments, is incompletely separated from fibroblasts and epidermal cells by sieving through nylon mesh, followed by velocity sedimentation on 5% bovine serum albumin. The endothelium-enriched fraction has been maintained in primary culture for up to 3 weeks. The resulting epithelioid colonies have been characterized morphologically by both light and transmission electron microscopy and manifest all of the structural features that distinguish other, large-vessel endothelia in culture. In addition, immunohistochemical studies using an indirect fluorescent antibody technique demonstrate that these cells contain the endothelium-specific product, Factor VIII antigen. This work was supported by National Institutes of Health Grants AM18904 and AM20571, the RGK Foundation, the Charlotte and Sidney Lifschultz Foundation, the Juvenile Diabetes Foundation, and the South Carolina Geenral Medical Faculty Research Appropriation.     

Sympodiomyces gen. n., a yeast-like organism from southern marine waters

Sympodiomyces gen. n. is described with the single speciesSympodiomyces parvus sp. n. The distinguishing characteristic of this yeast-like genus is the method of asexual reproduction: conidia are produced on a conidiophore that develops sympodially. A sexual stage has not been observed, therefore the genus is placed among the Fungi Imperfecti, family Cryptococcaceae.Contribution No. 1364 from the Rosenstiel School of Marine and Atmospheric Science, University of Miami, Florida.The authors gratefully acknowledge Dr. Jan Kohlmeyer, Univ. of North Carolina, Morehead City, North Carolina; Dr. R. T. Moore, North Carolina State Univ. at Raleigh; Dr. H. J. Phaff, Univ. of California at Davis; Miss W. Ch. Slooff and Mr. D. Yarrow, CBS, Delft, Netherlands; Dr. K.Tubaki, Institute for Fermentation, Osaka, Japan; and Dr. J. A. von Arx, C.B.S., Baarn, for examining cultures ofS. parvus. Dr. D. P. Rogers, Univ. of Illinois, Urbana, Ill, prepared the generic Latin diagnosis. Mr. Steven Y. Newell and Mr. A. Weiner, Univ. of Miami, assisted in obtainingEltanin collections. This study was supported by the National Science Foundation through the Office of Antarctic Programs Grant No. GA 13675.     

Isozyme genotype-environment relationships in natural populations of the harvester ant,Pogonomyrmex barbatus,from Texas

Three different allelic isozyme systems (two esterases, ESH and ESR, and a malic dehydrogenase, MDH) were analyzed in population samples of a species of ant, Pogonomyrmex barbatus, from Texas. Allelic frequencies were determined for several collection localities, and a number of significant differences were found. Principal component analysis was used to compare the patterns of variability of the allelic frequencies with environmental factors. Significant correlation was particularly evident with respect to weather and the pattern of variability in both esterases, and it is therefore suspected that natural selection is important in determining the allele frequency patterns. Observed and expected genotypic proportions were found in good agreement, generally, but in some localities homozygotes appeared in significantly greater numbers than expected. Heterotic selective maintenance was thus not indicated. Correlation found between patterns of variability in the enzyme systems themselves was consistent with the hypothesis that all three enzyme systems were affected by the environmental factors.Supported in part by USPHS Research Grants No. GM 15769, GM 11609, and GM 11546 and Texas A & I University Faculty Research Grant No. 449-N-68. The field work and laboratory analyses in this investigation were done while the senior author was at the University of Texas, and the data were analyzed at North Carolina State University. The computing was supported by Grant FR-00011 of the National Institutes of Health. Paper number 2784 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, North Carolina.     

Heat stability studies at the α-glycerophosphate dehydrogenase locus in populations of Drosophila melanogaster

The level of hidden variation in populations of Drosophila melanogaster at the Gpdh ⁺ locus was determined by thermal stability studies of the protein. The results indicate a lack of variation using these methods both in and between the two common electrophoretic variants. It is suggested that -GPDH is conserved in primary structure, which may be related to its critical role in flight muscle metabolism.This investigation was supported by NIH Research Grants No. GM-11546 and GM-23617. Paper No. 5262 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, North Carolina 27607.     

Responses of plant growth rate to nitrogen supply: a comparison of relative addition and N interruption treatments

This paper investigates the effects of uptake of nitrate and the availability of internal N reserves on growth rate in times of restricted supply, and examines the extent to which the response is mediated by the different pools of N (nitrate N, organic N and total N) in the plant. Hydroponic experiments were carried out with young lettuce plants (Lactuca sativa L.) to compare responses to either an interruption in external N supply or the imposition of different relative N addition rate (RAR) treatments. The resulting relationships between whole plant relative growth rate (RGR) and N concentration varied between linear and curvilinear (or possibly bi-linear) forms depending on the treatment conditions. The relationship was curvilinear when the external N supply was interrupted, but linear when N was supplied by either RAR methods or as a supra-optimal external N supply. These differences resulted from the ability of the plant to use external sources of N more readily than their internal N reserves. These results show that when sub-optimal sources of external N were available, RGR was maintained at a rate which was dependent on the rate of nitrate uptake by the roots. Newly acquired N was channelled directly to the sites of highest demand, where it was assimilated rapidly. As a result, nitrate only tended to accumulate in plant tissues when its supply was essentially adequate. By comparison, plants forced to rely solely on their internal reserves were never able to mobilize and redistribute N between tissues quickly enough to prevent reductions in growth rate as their tissue N reserves declined. Evidence is presented to show that the rate of remobilization of N depends on the size and type of the N pools within the plant, and that changes in their rates of remobilization and/or transfer between pools are the main factors influencing the form of the relationship between RGR and N concentration.     

Modeling insect dispersal and estimating parameters when mark-release techniques may cause initial disturbances

We consider the problem of quantitatively modeling movements of marked flea beetles in cultivated arrays of the cole crop, collards (Brassica oleraceae). Methods for the estimation of temporally and spatially dependent parameters in general dispersal models are outlined and a summary of our findings using these methods with flea beetle data is given.This research was supported in part by the National Science Foundation under NSF # MCS-8205335 and by the U.S. Air Force Office of Scientific Research under contract AFOSR 81-0198. Part of the research was carried out while this author was a Visiting Professor in the Department of Mathematics at Southern Methodist UniversityThis research was supported in part by the National Science Foundation under NSF # DEB-8207117This research was supported in part by the National Science Foundation under NSF # MCS-8200883. Part of the research was carried out while the first and third authors were visitors at the Institute for Computer Applications in Science and Engineering (ICASE), NASA Langley Research Center, Hampton, Virginia which is operated under NASA contracts NAS1-15810 and NAS1-16394     

An integrated tracer kinetics system for studying carbon uptake and allocation in plants using continuously produced11CO2

Summary An integrated approach to study the effects of environmental factors on plants is described. The central theme of the system is the use of CO₂ labelled with¹¹C supplied continuously to the plant and following the emitted radiation in vivo in the leaf, the phloem and the various sinks. The system consists of six components and with minor changes can be used for other tracers such as¹³N for nitrogen fixation studies. Because of the short half life of the isotope, several experiments can be carried out on the same plant under the same environmental conditions without disturbing the plant. A host of ecologically, agriculturally and genetically important questions can be answered using this technique.Research supported jointly by the National Science Foundation Ecosystems Studies Program (DEB-22165) and the U.S. Department of Energy Office of Carbon Dioxide and Climate Research (DEA 101-81ER60012). We also acknowledge the NSF Biological Research Resources Program (DEB80-21312) for support of the Duke University Phytotron     

Genetic mapping of aminoglycoside and fusidic acid resistant mutations in Bacillus subtilis

Summary Mutations governing resistance to neamine, neomycin, kanamycin and fusidic acid have been mapped within the ribosomal region of theBacillus subtilis genome using PBS1-mediated transduction. The probable order of these closely linked markers is: This work was supported by a predoctoral training grant, GM-1290, from the National Institutes of Health, administered by the Department of Microbiology, N.Y.U. School of Medicine, and by a research grant from the National Science Foundation, GB-16782, awarded to I.S.     

Cat-2 gene expression

Summary Poly(A)⁴ RNA was isolated from maize scutella of different stages of post-germinative development and translated in vitro in a rabbit reticulocyte translation system. Immunoprecipitation of the translation products with CAT-2-specific antibody was used to quantitate the relative levels of translatable CAT-2 mRNA at each stage. The results show a close correlation between the developmental profile of Cat2 gene expression and the profile of CAT-2 mRNA levels. Evidence that the levels of CAT-2 mRNA are regulated by a temporal regulatory gene (Car1) is presented and the possible mechanism(s) of this regulation discussed.This work was supported by Research Grants No. GM22733 and No. GM33817 from the U.S. National Institutes of Health, Public Health Service to J.G.S. This is paper No. 9933 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695, USA     

Effects of cycloheximide and kinetin pretreatments on responses of susceptible and resistant Avena leaf protoplasts to the phytotoxin victorin

Avena leaf protoplasts from varieties susceptible (cv. Park)and resistant (cv. Victory) to victorin incorporate the labelfrom ³H-L-leucine, ³H-uridine and ³H-thymidine into trichloroaceticacid-insoluble materials at comparable rates. When incubatedin the presence of the toxin, susceptible protoplasts beginto lyse after a short period of time; the effect on resistantprotoplasts is minimal. Victorin also significantly reducesincorporation of label from leucine and to a lesser extent fromuridine and thymidine into susceptible protoplasts but has anegligible effect on resistant protoplasts. Pretreatment ofsusceptible leaves with cycloheximide but not kinetin protectsagainst the subsequent action of victorin on apparent proteinsynthesis and lysis of protoplasts. ¹Permanent address: Institut National de la Recherche Agronomique,Station de Physiologie et Biochemie Végétales,"La Grande Ferrade", Centre de Recherches de Bordeaux, 33 Pont-de-la-Maye,Bordeaux, France. ²School of Forestry and Environmental Studies, Yale University. ³Supported by grant GI-32958 of the RANN program of the NationalScience Foundation to A. W. Galston. We are indebted to WhitneyAdams, jr. for expert assistance. (Received April 10, 1976; )     

Weaving New Worlds: Southeastern Cherokee Women and Their Basketry

Weaving New Worlds: Southeastern Cherokee Women and Their Basketry. Sarah H. Hill. Chapel Hill: University of North Carolina Press, 1997. 414pp.