Four-urn catenary model for excretion

A chain-like arrangement of four urns (a catenary system) into which different color balls (white, corresponding to radio atoms, and black, corresponding to stable atoms) are being transferred is used to simulate the transport of atoms down the GI tract of man and animals. Into the first urn (stomach) are placedw _o white balls andr black balls while in the 2nd (small intestines) and 3rd (large intestines) urn, onlyr blacks are put in, with no whites. A sample of sizer is transferred from the 1st, 2nd and 3rd urns to the 2nd, 3rd and 4th (infinite universe) urns. From the random variable difference equations the first and second moments for the distribution of the number of radio atoms present in each urn are obtained. The variance of the contents of radioatoms in the excretion urn is Research sponsored by the Office of Health and Environmental Research, U.S. Department of Energy under contract W-7405-eng-26 with the Union Carbide Corporation.     

A reinforcement depletion urn problem—II. Application and generalization

The urn model discussed in part is generalized so that the random depletion of balls from the urn in any cycle is not necessarily the same as the reinforcement in that cycle. This model is applied to an urn containing balls of three colors (white, red, black) for which the black balls always receive reinforcements, whereas there is only one cycle in which red balls are added. Experimental data are considered in which red balls correspond to radioactive iodine atoms, black balls to stable iodine atoms and white balls to empty space, all relating to the thyroid gland. Half-life periods for the radioactive iodine in relation to the time of uptake (ten years, fifteen years, etc.) are considered.     

Continuous ethanol production by a flocculent strain of Zymomonas mobilis

Summary Cell retention and ethanol production using the flocculent bacterium Zymomonas mobilis NRRL B-12526 were studied in three bioreactor configurations. The flocculent growth characteristic of this strain and a special reactor design were combined to achieve relatively high cell concentrations in a continuous bioreactor for the conversion of glucose to ethanol.Research sponsored by the Office of Energy Research, U.S. Department of Energy, under contract W-7405-eng-26 with the Union Carbide Corporation.     

Dibenzothiophene sulfur can serve as the sole electron acceptor during growth by sulfate-reducing bacteria

Summary Three species of Sulfate-Reducing Bacteria (SRB) were able to grow using dibenzothiophene (DBT) as their sole source of sulfur and sole electron acceptor. Desulfotomaculum orientis and Desulfovibrio desulfuricans were grown at 30°C while Thermodesulfobacterium commune was grown at 60°C, in media containing lactate and citrate. Hydrogen sulfide was the product of dissimilatory sulfur reduction.Research supported by the Office of Oil and Gas Processing of Fossil Energy, U.S. Department of Energy under contract DE-AC05-84OR21400 with Martin Marietta Energy Systems Inc.     

On a two urn model of Polya-type

A two urn Polya-type scheme is considered in whichr black balls (corresponding to the stable form of an element) are added to urn one at every stage and the same number of balls are removed at random at every stage from the same urn. In between these two operations, which form a stage or iteration, a fixed number of balls is exchanged at random between urns one and two. Urn one has a given initial number of white balls (corresponding to a radioactive form of the same element). The problem of interest is to study the stochastic aspect of the number of white balls remaining in urn one (and/or urn two) aftern iterations.     

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.).     

Hexokinase isozyme variability in Drosophila robusta

Several isozymes of hexokinase have been found in Drosophila robusta. These have been defined in this paper in several dimensions, including genetic variation, ontogenic variation, tissue-organ variation, and substrate specificity.The work reported in this paper was supported in part by USPHS grant AM 09381, USPHS Career Development Award 1-K3-AM 7959 (GJB), and by Contract AT (11-1)-1152, Atomic Energy Commission, and in part by the Research and Development Command, Office of the Surgeon General, Department of the Army, under Contract DA-49-193-MD-2855 with the Department of Medicine, University of Michigan. This is contribution No. 662 from the Army Research Program on Malaria.     

A simple fractionation of chicken egg yolk yields a protein component that stimulates cell proliferation and differentiation in primary avian tendon cells

Summary An easily prepared and stable protein fraction from chick egg yolk promotes cell division (40 h generation time) and expression of procollagen (60% of total protein synthesis) in primary avian tendon cells in a serum-free medium. The activity of this yolk fraction (YF) is proteinaceous as reflected by its sensitivity to protease treatment. Yolk fraction is resolved into four major components on sodium dodecyl sulfate polyacrylamide gel electrophoresis with apparent molecular weights of 82,70,42,35 (× 10⁻³). Under nondenaturing conditions, YF runs as a mixture of high molecular weight aggregates on Sephacryl G-200. We postulate that the active part of YF could be the in ovo growth promoter for embryonic chick tendon cells. This work was supported in part by National Institutes of Health grant CA 37958 and in part by the Office of Health and Environmental Research, Office of Energy Research, U.S. Department of Energy, under Contract DE-AC03-76SF00098.     

The aggregation states of spinach phosphoribulokinase

Phosphoribulokinase (PRK; EC 2.1.7.19) is active in illuminated chloroplasts and inactive in darkened chloroplasts. This regulatory mechanism is mediated by thioredoxin-dependent reduction of a kinase disulfide in vivo. Extracts of spinach (Spinacia oleracea L.) leaves in the presence of 10 mM dithiothreitol contain a single 80-kDa form of PRK as judged by gel filtration. Gel filtration of thiol-free extracts of light-harvested tissue shows the presence of two inactive forms of PRK, the 80-kDa form and an aggregate (> 550 kDa) form, but treatment of both forms with dithiothreitol restores kinase activity. Gel filtration following extraction of dark-harvested tissue in the absence of dithiotreitol demonstrates the presence of only the heavier form. Inclusion of 400 mM (NH₄)₂SO₄ in the homogenization buffer during extraction of light-harvested tissue suppresses the formation of the high-M _r form of PRK, but does not eliminate the aggregate form observed in extracts of dark-harvested leaves. However, prolonged treatment of extracts from dark-harvested tissue with 400 mM (NH₄)₂SO₄ results in conversion of the high-M _r form of phosphoribulokinase to the low-M _r form. The data are consistent with the heavier form of phosphoribulokinase being the normal in-vivo aggregation state in the dark, while the lighter form is the normal aggregation state in the light.This research was sponsored jointly by the science and education administration of the U.S. Department of Agriculture under Grant No. 88-37130-3722 from the Competitive Research Grants Office and by the Office of Health and Environmental Research, U.S. Department of Energy under Contract DE-AC05-84OR21400 with Martin Marietta Energy Systems Inc., Oak Ridge, Tenn., USA. The author is Postdoctoral Investigator supported by the U.S. Department of Agriculture through Subcontract No. 88-37130-3722 from the Biology Division of Oak Ridge National Laboratory to the University of Tennessee.     

Structure and function of the photosynthetic reaction center fromRhodobacter sphaeroides

The three-dimensional structure of the photosynthetic reaction center fromRhodobacter sphaeroides is described. The reaction center is a transmembrane protein that converts light into chemical energy. The protein has three subunits: L, M, and H. The mostly helical L and M subunits provide the scaffolding and the finely tuned environment in which the chromophores carry out electron transfer. The details of the protein-chromophore interactions are from studies of a trigonal crystal form that diffracted to 2.65-Å resolution. Functional studies of the multi-subunit complex by site-specific replacement of key amino acid residues are summarized in the context of the molecular structure.This work was supported in part by the U.S. Department of Energy, Office of Health and Environmental Research, under Contract No. W-31-109-ENG-38 and by Public Health Service Grant GM36598.     

Accumulation of Cu++ onto modified bone-gelatin beads

1 Summary Cu²⁺ adsorbs onto modified bone gelatin beads as a function of pH. The amount of Cu²⁺ adsorbed is similar to that which has been shown to be adsorb onto other biological materials including bacterial biomass. Langmuir adsorption isotherms were fitted to this data and both the asymptotic maximum solid-phase concentration and the equilibrium constant for these isotherms are presented as a function of the solution pH. The adsorption rate for a typical set of experimental conditions is presented.Research supported by the Office of Basic Energy Scineces, Divisions of Engineering and Geosciences. U.S. Department of Energy under contract DE-AC05-84OR21400 with Martin Marietta Energy Systens, Inc.     

Botryococcus braunii carbon/nitrogen metabolism as affected by ammonia addition

Carbon metabolism in photosynthesizing and respiring cells of Botryococcus braunii was radically changed by the presence of 1 mM NH₄Cl in the medium, when the so-called resting state previously had been subjected to a nitrogen-deficient medium. Ammonia addition to the algae photosynthesizing with ¹⁴C-labelled HCO ₃ ^- almost completely inhibited the synthesis of ¹⁴C-labelled botryococcenes and other hexane-extractable compounds, and also inhibited the formation of insoluble compounds; however, it resulted in a large increase in the synthesis of alanine, glutamine, other amino acids, and especially of 5-aminolevulinic acid. Total CO₂ fixation decreased about 60% and O₂ evolution decreased more than 50%.CO₂ fixation in the dark with ammonia present led to labelled products derived from phosphoenolpyruvate carboxylation, such as glutamine, glutamate, and malate. Respiratory uptake of O₂ increased by about 70%.The inhibition of terpenoid synthesis and increased synthesis of C₅ amino acids by Botryococcus upon ammonia addition indicates 1) a diversion of acetyl coenzyme A from synthetic pathways leading to terpenoids and 2) increased operation of pathways leading to the synthesis of amino acids, especially 5-aminolevulinic acid, a precursor to chlorophyll biosynthesis.This work was supported in part by the Office of Energy Research, Office of Basic Energy Sciences, Biological Energy Research Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098, in part by a grant from SOHIO, and, in part, by a grant from the Japan-U.S. Cooperative Science Program (The Japan Society for the Promotion of Science, National Science Foundation, Division of International Programs)     

Analysis of tracer experiments in non-conservative steady-state systems

A method is developed for finding the transfer and localization rates and the volumes ofN compartment steady-state biological systems from experimental results. It is shown that a complete solution for certain systems in which the rates and volumes remain constant and in which there is access to all compartments can be obtained by using a single radioactive tracer. The information obtainable from experiments wherein some compartments are not accessible is analyzed for mammillary and catenary systems. Conservative systems are handled as special cases in which the localization is zero while anisotropic membranes separating compartments are shown to introduce no additional mathematical difficulty whenever all compartments are accessible. The limitations on the use of this method of multi-compartment tracer analysis are briefly discussed. Research supported by the Atomic Energy Commission, Contract AT (30-1)-1551.     

An urn model study of variability within a compartment

Formulas are derived for the mean and variance of the number of radioactive atoms present in a compartment (or urn). Initally,n ₁ radioactive atoms andb stable atoms are placed in the urn; and subsequently,r stable atoms are added and an equal number,r, of a random mixture of stable and radioactive atoms is removed per unit time. The expected number of radioactive atoms,E(t), present at timet is, as expected,n ₁ e^−λt where λ=(r/Δt)/(b+r+n ₁). The relative variance, σ²(t)/n ₁ ² , vanishes to zero forr=1, atoms per unit time and for a large number ofn ₁ radioactive atoms; but for a large number of bothr andn ₁ atoms the relative variance is ∼e ^−λt , equal to the fractional retention, fort>1/λ. Thus in studies where radionuclides are injected into animals and a single compartment represents the data, if a large variance is observed it might be due to the fact that large numbers of atoms are transferred out in unit time. When a small variance is observed, this is probably due to the fact that few atoms are transferred in smaller units of time (such that λ is the same in both cases). Research sponsored by the Energy Research and Development Administration under contract with Union Carbide Corporation.     

The use of radioactive iodine in the treatment of Graves disease

Fifty patients with uncomplicated Graves' disease were treated with radioactive iodine (I(131)). Twenty-six patients who were followed for one year or longer are the basis of this report. Twenty-five are now euthyroid; only one is not completely well. The total dose of radioiodine administered varied from 0.5 to 10 millicuries. The average length of time necessary for return to a euthyroid state was from three to four months. Hypometabolism developed in three patients, and in one the signs and symptoms of myxedema developed. No other complications ensued. One patient who apparently relapsed had complete return to normal after further iodine administration. The determination of the uptake of radioactive iodine by the thyroid gland is a useful diagnostic procedure in differentiating conditions simulating hyperthyroidism.Following treatment with radioactive iodine, the thyroid gland becomes smaller, the uptake of iodine by the gland is reduced, and the level of organic iodine in the plasma becomes normal. In acute thyroiditis, in spite of a high basal metabolic rate, high content of organic iodine in the plasma and other evidences of "hyperthyroidism," the uptake of I(131) has been very low.     

Genetic variation for prolidase (PEP-4) in the mouse maps near the gene for glucosephosphate isomerase (GPI-1) on chromosome 7

An inherited electrophoretic variant of prolidase (EC 3.4.13.9), also called peptidase 4 (PEP-4), has been discovered among inbred strains of mice. Analysis of progeny from reciprocal backcrosses established that the electrophoretic forms are expressed codominantly and that Pep-4 is located between the genes for glucosephosphate isomerase (Gpi-1) and pink-eyed dilution (p) on chromosome 7. These data define a region of conserved gene linkage between mouse chromosome 7 and human chromosome 19, as originally indicated by somatic cell hybrid studies, and imply that human prolidase (PEPD) is located in the region of human chromosome 19 pter q13.Research sponsored by the Office of Health and Environmental Research, U.S. Department of Energy, under Contract W-7405-eng-26 with the Union Carbide Corporation.By acceptance of this article, the publisher or recipient acknowledges the right of the U.S. Government to retain a nonexclusive, royalty-free license in and to any copyright covering the article.     

Collagen-fibronectin interactions in normal and rous sarcoma virus-transformed avian tendon cells: Possible mechanisms for increased extracellular matrix turnover after transformation

Summary Using gelatin, casein, and fibronectin as substrates and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), we have identified protein-degrading enzymes in both normal and Rous sarcoma virus-transformed primary avian tendon cells. Although there are some consistent differences in the profile of the gelatinolytic activities (mainly metalloproteinases) between normal and transformed cells, the amounts of fibronectin-degrading activities seem to be comparable. In vitro studies reported here demonstrate that the degradation of fibronectin is partially and specifically inhibited by gelatin and collagen. We therefore propose that the abundant collagen present in normal tendon cells protects fibronectin against degradation. Conversely, in transformed cells, where collagen levels are drastically reduced, fibronectin may be more accessible to degradation. Thus differences in the steady-state levels of fibronectin on normal and transformed cells may be, at least in part, a consequence of changes in collagen levels. This work was supported by the Office of Health and Environmental Research, Office of Energy Research, U.S. Department of Energy, Washington, D.C., under contracts DE-AC03-76-SF00098 and DE-AC03-76-SF01012.     

p-Nitrophenyl-β-d-xyloside modulates proteoglycan synthesis and secretory differentiation in mouse mammary epithelial cell cultures

Summary Primary cultures of mouse mammary epithelial cells synthesize significant quantities of chondroitin and heparan sulfate proteoglycans (16). Long term treatment of such cultures with p-nitrophenyl-β-D-xylopyranoside leads to a 10–20 fold increase in the synthesis and secretion of free chondroitin sulfate glycosaminoglycan (GAG) chains and assembly of a cell-associated matrix that is relatively enriched in heparan sulfate proteoglycan. This modulation of cell-synthesized proteoglycans leads to significant changes in cell morphology and cellular differentiation. Notably cells cultured on plastic culture dishes change from being flattened to cuboidal. The synthesis of the milk proteins α1, α2, and β-casein is also increases as is the formation of fat droplets and fat droplet membrane components. Promotion of differentiation increases with increasing xyloside concentration in the range 0–1.5 mM, but there may be a block in secretion at higher xyloside concentrations. While the detailed mechanisms remain to be elucidated, we conclude that the composition of proteoglycans incorporated into the matrix (and possibly the glycosaminoglycans secreted into the medium), may play a significant role in maintaining the phenotypic characteristics of terminally differentiated mammary epithelial cells. This research was supported by the Office of Health and Environmental Research, Office of Energy Research, U.S. Dept. of Energy under contract No. DEAC-03-76SF00098 and by National Institutes of Health Grant CA44398-01 (G. Parry) Editor's Statement Exogenous elements of extracellular matrix affect expression of cultured mammary cell function. This work reports manipulation of cell-derived endogenous matrix elements and shows correlative changes in cell functions.     

The muc+ gene of plasmid pKM101 prevents respiration shutoff in far ultraviolet-irradiated Salmonella typhimurium

Summary The plasmid pKM101 is known to protect Escherichia coli and Salmonella typhimurium against killing by far UV irradiation and to enhance UV-induced mutagenesis. The muc ⁺ gene of the plasmid is responsible for both of these effects. This paper shows that respiration of S. typhimurium shuts off about an hour after UV irradiation and that pKM101 prevents the shutoff. Plasmids which contained Tn5 translocatable elements, either in (and having produced a muc mutation) or flanking the muc ⁺ gene, have been introduced into S. typhimurium. The muc mutant plasmid, which does not protect its host against UV killing and does not enhance UV induced mutagenesis, also does not protect against UV induced respiration shutoff. Like-wise, plasmids in which the Tn5 translocatable elements flank the nuc ⁺ gene protect against shutoff of respiration. Thus the muc ⁺ gene of pKM101 is responsible for protection against UV induced shutoff of respiration in S. typhimurium.Research sponsored by the Office of Health and Environmental Research, U.S. Department of Energy, under contract W-7405-eng-26 with the Union Carbide Corporation and by the National Science Foundation under grant No. PCM 7908647 with the University of Tennessee, Knoxville     

Solubilization of coal by an extracellular product fromStreptomyces setonii 75Vi2

Summary Several low-ranked coals were solubilized when placed on the surface of agar cultures ofStreptomyces viridosporous T7A andS. setonii 75Vi2. When grown in submerged cultureS. setonii 75Vi2 produced an extracellular component that was capable of solubilizing coals. The extracellular coal solubilizing component had a molecular weight of <10000 and was heat stable since, after 1h at 121°C, only 30–40% of the activity was lost. Treatment with any of three proteases also appeared to be ineffective in decreasing activity. These results suggest that coal solubilization byS. setonii 75Vi2 is nonenzymatic.Research supported by the Fossil Energy Advances Research and Technology Program, managed by the Pittsburg Energy Technology Center, U.S. Department of Energy, under Contract No. DE-AC05-840R21400 with Martin Marietta Energy Systems, Inc.