Showing papers by "University of Colorado Boulder published in 1968"

Measurement of Umbilical Arterial Blood Flow to the Sheep Placenta and Fetus in Utero: DISTRIBUTION TO COTYLEDONS AND THE INTERCOTYLEDONARY CHORION

Abstract: A method of estimating the magnitude and distribution of umbilical blood flow by means of radioactive microspheres in sheep fetuses in utero is described. Simultaneous measurements of total umbilical flow by this method and the steady-state diffusion technique showed agreement within ±11%. In 11 fetuses of 90 to 150 days gestational age, the distribution of umbilical flow to the intercotyledonary chorion was 6.2±0.8% of the total. This information has been used to estimate the effect of venous admixture of cotyledonary and noncotyledonary blood on the umbilical vein-uterine vein concentration difference of inert molecules with flow-limited transplacental clearance.

Plasma Volume Expansion Resulting from Interference with Adrenergic Function in Normal Man

Abstract: Guanethidine was administered to 10 normal subjects in order to examine the effects of reduced adrenergic function on plasma volume. An increase in the plasma volume was observed averaging 21.4% after 1 week, and 12.1% and 13.1% after 2 and 3 weeks of drug administration. A similar change in plasma volume resulted when alphaadrenergic blockade was produced with phenoxybenzamine. These changes occurred in the absence of sodium retention and were associated with attenuation of forearm venous sympathetic reflexes and a rise in forearm venous compliance. The increase in venous compliance which was observed was proportional to the changes in plasma volume in these subjects. Thus, the sympathetic nervous system through its control of venous resistance may provide a means whereby the blood volume can be regulated.

Representation of the Magnetization Characteristic of DC Machines for Computer Use

Abstract: The calculation of flux densities in dc machines using digital computers requires a representation of the magnetization curve of the materials either as H = f1(B) or B = f2(H). A figure of merit of the approximation is defined. The representation can be achieved by the use of simple algebraic or transcendental functions. For satisfactory fit, however, the B-H characteristic has to be subdivided into several parts. As a better alternative a numerical method is proposed in which the magnetization curve is subdivided into a large number of sections. A method of linear interpolation is then employed. A computer program to accomplish this task is described.

A Rationale for a Science Museum

Abstract: There is an increasing need to develop public understanding of science and technology. The fruits of science and the products of technology continue to shape the nature of our society and to influence events which have a world-wide significance. Yet the gulf between the daily lives and experience of most people and the complexity of science and technology is widening. Remarkably few individuals are familiar with the details of the industrial processes involved in their food, their medicine, their entertainment or their clothing. The phenomena of basic science which have become the raw material of invention are not easily accessible by the direct and unaided observation of nature yet they are natural phenomena which have, for one segment of society, become as intriguing and as beautiful as a butterfly or a flower.

Enzyme activities and ethanol preference in mice

Abstract: Alcohol dehydrogenase and aldehyde dehydrogenase, the two principal enzymes of alcohol metabolism, were assayed in the livers of the inbred mouse strains C57BL/6J and DBA/2J. Previous work has shown that animals of various C57BL substrains prefer a 10% ethanol solution to water in a two-bottle preference test, and that animals of various DBA/2 substrains avoid alcohol. In the present study, C57BL/6J mice were found to have 300% more aldehyde dehydrogenase activity than DBA/2J mice and 30% more alcohol dehydrogenase activity. The F1 generation is intermediate to the parents in preference for the 10% alcohol solution and is also found to possess intermediate levels of alcohol and aldehyde dehydrogenase activity. These experiments suggest a systematic relationship between the behavioral trait of ethanol preference and the activity of aldehyde dehydrogenase and a similar but much less pronounced relationship with alcohol dehydrogenase.

The Gunn effect under imperfect cathode boundary conditions

Abstract: The usual assumption in the theory of the Gunn effect of a well-behaved cathode is replaced by a more general set of boundary conditions adapted to the treatment of cathode contacts with some interface resistance. The treatment is in terms of a "control characteristic": that is, the current-field characteristic of the cathode interface itself. For contacts with an interface resistance, the control characteristic lies at least partially below the bulk current-field characteristic. This leads to the primary nucleation of depletion rather than accumulation layers. Depending on the detailed shape of the control characteristic and the location of its crossover point (if any) with the bulk characteristic, a large variety of device behavior can be explained. Examples are Gunn's preoscillation cathode fall, Kennedy's prethreshold amplification behavior, the occurrence of excessive threshold fields for the onset of oscillations, and oscillations with lower amplitude and higher frequency than for well-behaved transit time oscillations, despite good doping homogeneity.

The Magnetic Properties of Naturally Occurring Goethite

Abstract: Summary It has been found that goethite acquires a thermoremanent magnetization (TRM) when cooled in the presence of a magnetic field from 120°C. It is believed that this TRM is due to the presence of antiferromagnetism in goethite with a Neel temperature of 120°C. A few spins have no mates because of small grain size or the presence of imperfections and impurities. This TRM is related to antiferromagnetism. Similarly, hematite acquires a TRM at its Neel temperature which is due to unbalanced spins. In addition hematite is known to have a ‘parasitic ferromagnetism’. Hematite derived from heating goethite above 350°C showed two different types of behaviour. Hematite composed of particles less than 1/2μ diameter showed no spontaneous magnetization, but did show a weak thermoremanence whereas hematite composed of larger particles developed a spontaneous magnetization. These observations indicate that parasitic ferromagnetism exists only in grains larger than 1/2μ.

Metabolism of lactose by Staphylococcus aureus and its genetic basis.

Abstract: THE METABOLISM OF LACTOSE WAS FOUND TO BE CONTROLLED BY THREE GENES: a gene for the synthesis of a beta-galactosidase attacking only phosphorylated galactosides; a gene for a protein permitting concentration of phosphorylated galactosides which probably acts by transferring phosphates to them; and a gene regulating the first two structural genes. The three genes are closely linked and may have the same order as in Escherichia coli. Galactose-6-phosphate was found to be a better inducer of lactose utilization than is galactose or any other inducer. The inhibition of induction by isopropylthiogalactoside was found to occur at the level of the protein permitting the concentration of galactoside phosphates.

Changes in cell wall polysaccharides associated with growth.

Abstract: Changes in the polysaccharide composition of Phaseolus vulgaris, P. aureus, and Zea mays cell walls were studied during the first 28 days of seedling development using a gas chromatographic method for the analysis of neutral sugars. Acid hydrolysis of cell wall material from young tissues liberates rhamnose, fucose, arabinose, xylose, mannose, galactose, and glucose which collectively can account for as much as 70% of the dry weight of the wall. Mature walls in fully expanded tissues of these same plants contain less of these constituents (10%-20% of dry wt). Gross differences are observed between developmental patterns of the cell wall in the various parts of a seedling, such as root, stem, and leaf. The general patterns of wall polysaccharide composition change, however, are similar for analogous organs among the varieties of a species. Small but significant differences in the rates of change in sugar composition were detected between varieties of the same species which exhibited different growth patterns. The cell walls of species which are further removed phylogenetically exhibit even more dissimilar developmental patterns. The results demonstrate the dynamic nature of the cell wall during growth as well as the quantitative and qualitative exactness with which the biosynthesis of plant cell walls is regulated.

Three Particle Effects in the Pair Distribution Function for Helium-4 Gas

Abstract: The diagonal elements of the three-particle density matrix for ${\mathrm{He}}^{4}$ have been formulated in terms of Wiener functional integrals in order to compute both that part of the pair distribution function linear in the density and the third virial coefficient. The three-particle interaction energy was taken to be a sum of Lennard-Jones (12-6) potentials between pairs of particles. Evaluation of the Wiener integrals was carried out by a Monte Carlo sampling technique to yield the pair distribution function and third virial coefficient for temperatures from 273 to 5\ifmmode^\circ\else\textdegree\fi{}K. Comparison of the linear portion of the density expansion of the pair distribution function gave qualitative agreement with experimental values for the pair distribution function in liquid ${\mathrm{He}}^{4}$ measured by neutron diffraction. The values of the third virial coefficient calculated by this method are consistently smaller than the experimental values and consistently larger than the classical values of this quantity over the given temperature range.

Effects of p-chlorophenylalanine on conditioned avoidance learning

Abstract: A single injection of p-chlorophenylalanine enhanced the performance of two strains of rats in a conditioned avoidance task. The enhancement was especially evident at low UCS intensities for one strain and at high UCS intensities for the other strain. Chronic p-chlorophenylalanine treatment retarded the performance of rats and mice in conditioned avoidance tasks.

The effects of enucleation on the cytoplasmic membranes of amoeba proteus

Abstract: The dependence of cytoplasmic membranes upon the nucleus was studied by examining enucleated amebae with the electron microscope at intervals up to 1 wk after enucleation. Amebae were cut into two approximately equal parts, and the fine structure of the enucleated portions was compared with that of the nucleated parts and starved whole cells which had been maintained under the same conditions. Golgi bodies were diminished in size 1 day after enucleation and were not detected in cells enucleated for more than 2 days. The endoplasmic reticulum of enucleated cells appeared to increase in amount and underwent changes in its morphology. The sparsely scattered short tubules of granular endoplasmic reticulum present in unmanipulated amebae from stock cultures were replaced in 1–3-day enucleates by long narrow cisternae. In 3–7-day enucleates, similar cisternae of granular endoplasmic reticulum encircled areas of cytoplasm partially or completely. It was estimated that in most cases hundreds of these areas encircled by two rough membranes were formed per enucleated cell. The number of ribosomes studding the surface of the endoplasmic reticulum decreased progressively with time after enucleation. In contrast, the membranes of nucleated parts and starved whole cells did not undergo these changes. The possible identification of membrane-encircled areas as cytolysomes and their mode of formation are considered. Implications of the observations regarding nuclear regulation of the form of the Golgi apparatus and the endoplasmic reticulum are discussed.

Position Operators and Localizability of Quantum Systems Described by Finite- and Infinite-Dimensional Wave Equations

Abstract: The principles of quantum mechanics impose certain restrictions on acceptable position operators. The probability density as derived from the position operator should agree with the fourth component of the current vector. The various relativistic wave equations are reexamined from the point of view of this consistency test. These and the group theoretical considerations lead to the conclusion that only a Dirac particle can be considered to be elementary. The position operator of the infinite-dimensional theories is investigated and the advantages of theories using the unitary representations of the Lorentz group are discussed.

Electron Paramagnetic Resonance Absorption in Oxygen with the HCN Laser

Abstract: Paramagnetic resonance absorption between the $N=3$, $J=4$, $M=\ensuremath{-}4$ and $N=5$, $J=5$, $M=\ensuremath{-}4$ levels of ground state ${\mathrm{O}}_{2}$ was observed at the HCN laser frequency of 890 759 \ifmmode\pm\else\textpm\fi{} 3 MHz in a magnetic field of 16 418 \ifmmode\pm\else\textpm\fi{} 1 G. This is the first observation of absorption in a gaseous sample in which laser electron-paramagnetic-resonance techniques were used.

Clonal growth of differentiated rabbit cartilage cells.

Abstract: Single cell suspensions have been prepared from rabbit cartilage by collagenase digestion in the presence of fetal bovine serum. When inoculated into medium F12 supplemented with 5% fetal bovine serum and 5% rabbit serum, the cartilage cell suspensions yield large healthy colonies of epithelial-like cells with an average plating efficiency of 47%. At the end of a 14 day incubation period, the centers of many of the colonies are thickened into multilayered aggregates. Such colonies exhibit serveral cartilage-like properties, including metachromatic staining with toluidine blue, dense brown staining with bismark brown, bright green staining with alcian green, and a refractile matrix which can be seen with the phase contrast microscope to surround the living cells. Similar properties have also been observed in second and third passage subcultures.

The Blochmann bodies: hereditary intracellular symbionts of insects.

Abstract: Summary The term ‘Blochmann body’ was originated by Wheeler in 1889 for bacteria-like particles in the cytoplasm of cockroach eggs. These particles can be traced during embryonic development to definitive somatic cells, the mycetocytes. These and similar particles of other insects have so far not been cultivated in bacteriological media nor injected into host animals to produce either pathological or benign infections. Their structure and composition indicate them to be evolutionary descendants of free-living micro-organisms; operationally, they appear to belong to the class of cell particles designated by Lederberg (1952) as plasmids. Genetic studies have shown the Blochmann bodies to be transmitted through the maternal line. Their presence in the egg cytoplasm at some stage in oocyte development is easily demonstrated, but studies by a number of workers have so far yielded a variety of conflicting claims or suggestions as to how the particles get into the germ cells or oocytes. The Blochmann particles of cockroaches, besides existing in the mycetocytes and eggs, occur embedded in a dense tangle of microvilli which are extensions of the plasma membrane of young oocytes. Essentially particle-free strains of cockroaches can be produced by feeding aureo-mycin or high levels of urea, or by withholding manganese. The effect is produced only by treating females, and is delayed one generation. In generations following the first (symbiont-free) generation, the Blochmann symbionts gradually reappear, suggesting that elimination was not absolute. Blochmann bodies in both the mycetocytes and the ovarioles of the cockroach carry out oxidative metabolism, as indicated by their ability to reduce tetrazolium. Glycolysis has not been demonstrated. The generalization that symbionts of the Blochmann type represent an adaptation to compensate for dietary deficiencies is inapplicable, since deficiencies have not been demonstrated for the diets of cockroaches, weevils, or homopterans—the major insect groups in which the symbionts occur. The symbionts of cockroaches and homopterans appear to be involved in the utilization of nitrogenous waste products in synthetic metabolism. In most instances the Blochmann bodies lack the central nucleoid body characteristic of the growing phase of free-living bacteria, thus resembling the Kappa and Mu particles of Paramecium and the endosymbiont of the protozoan Crithidia oncopelti. Both histochemical tests and electron-microscope studies indicate a DNA component that is widely dispersed within the particle. Blochmann bodies are without internal cristae. The cockroach symbionts contain muramic acid, a diagnostic feature of the cell wall of bacteria. Response to various nuclear and cytoplasmic reagents is intermediate between those of typical mitochondria and free-living bacteria. The envelopes of the Blochmann particles are generally thinner than those of free-living bacteria. The function of plasmids of the Blochmann type may be that they, like the bacteroids of the Rhixobium-legume symbiosis, extend the range of metabolic potential of the host cell by a process of mutual host-symbiont adjustment. Possible roles could be subsumed under the headings of bacteria-like, mitochondria-like, or nucleus-like functions.

On asymptotic expansions of electronic terms of the molecular ion H2

Abstract: The behaviour of electronic terms and wave functions of the molecular ion H2+ for large internuclear separations is considered. Comparisons of asymptotic formulae with numerical calculations are presented.

Smallpox vaccination of eczema patients with a strain of attenuated live vaccinia (CVI-78).

Abstract: A group of 1,009 patients suffering from eczema or other skin disorders have received elective vaccination with the CVI-78 strain of vaccinia. The vaccine is attenuated by repeated passages through chick embryos; its infectivity titer is 8.4 (TCID 50 /ml). It is free of bacteria and known viruses, including avian leukosis virus. It was administered by one of two routes (multiple pressure or subcutaneously) with a minimal dose of 1,000 TCID 50 and a maximal dose of 30,000 TCID 50 . Local and systemic reactions and temperature elevations in these eczematous patients were significantly less marked than those experienced with a standard strain of vaccinia in normal children. No virus dissemination or other complications occurred, except for two instances of mild erythema multiforme. Seroconversion was noted in all 387 patients tested to date. Multiple pressure revaccinations with a standard strain 1 to 6 months later resulted in marked modification of the vaccination reaction without systemic reactions. It would appear that the CVI-78 strain of vaccinia virus is effective and safe for elective primary vaccination of children suffering from eczema.

Pharmacogenetic correlates of pentylenetetrazol and electroconvulsive seizure thresholds in mice.

Abstract: DBA/2J mice, susceptible to audiogenic seizures, were found to be more susceptible to pentylenetetrazol- and electrically-induced seizures than either C57BL/6J or F1 hybrid mice, which are resistant to audiogenic seizures Reserpine increased susceptibility to both pentylenetetrazol and electroconvulsive seizures in C57BL/6J, DBA/2J and F1 hybrid mice 5-hydroxytrptophan, iproniazid and amino-oxyacetic acid decreased seizure susceptibility in all groups of mice These results were interpreted to mean that DBA/2J mice are more susceptible to seizures than C57BL/6J or F1 hybrid mice regardless of the agents used to induce the seizures, and that levels of 5-HT, NE and GABA are important in determining seizure thresholds