Showing papers by "University of Colorado Boulder published in 1975"

Freeze-etching nomenclature.

Abstract: C3H/He mice chronically infected with murine cYtomegalo virus were given skin allografis fromti histoincompatible BALB/c donors. A significant inicrease in cvtomegalovirus titers occurred within 3 days after placement oJ'the graft in the spleens and kidneYs oJ' the allograft recipients as compared with control aninmals. No significant changes in virus titers were detected in the salivary gland, lung, liver, or blood ofallograJi recipients. These results indicate that the host-versus-graft reaction alone can enihance murine cvtomtiegalovirus in a chronicallY injected host atid maY help explaini the high incidence ofcvvtomegalovirus infection seen after renal and other allograft transplantation

Self-inhibition by dopaminergic neurons.

Abstract: Animals and Plants, L. E. Gilbert and P. H. Raven, Eds. (Univ. ofTexas Press, Austin, 1975), p. 3. 76. J. W. Hanover, Annu Rev. Entomol. 20,75 (1975). 77. R. H. Smith, U.S. For. Serv. Gen. Tech. Rep. PSW-I (1972); A. A. Berryman, BioScience 22, 598 (1972). 78. V. 1. Grimal'skii, L. T. Krushev, V. P. Gorlushkina, Lesn. Khoz. 12, 54 (1971); W. P. Smeljanez and L. A. Chursin, Anz. Schaedlingskd. 45, 33 (1972). 79. C. M. McKell, J. P. Blaisdell, J. R. Goodin, Eds., Wildland Shrubs-Their Biology and Utilization (General Technical Report INT-1, U.S. Forest Service, Washington, D.C., 1972). 80. C. H. A. Little, Can. J. Bot. 48, 1995 (1970). 81. S. J. Dina and L. G. Klikoff, J. Range Manage. 26, 207 (1973); J. D. Hodges and P. L. Lorio, Jr., Can. J. Bot. 47, 1651 (1969); see also Parker (84). 82. D. Otto, Arch. Forstwes. 19, 135 (1970). 83. W. Schwenke, Z. Angew. Entomol. 61, 365 (1968). 84. J. Parker, in Water Deficits and Plant Growth, T. T. Kozlowski, Ed. (Academic Press, New York, 1972), vol. 3, p. 125. 85. A. W. Naylor, in ibid., p. 241; R. E. Saunier, H. M. Hull, J. H. Ehrenreich, Plant Physiol. 43, 401 (1968). 86. T. C. R. White, Oecologia 16,279 (1974). 87. G. T. Harvey, Can. Entomol. 106, 353 (1974); see also Otto (82) and Schwenke (83). 88. T. T. Kozlowski, J. For. 67, 118 (1969); H. 0. Batzer, Environ. Entomol. 2, 727 (1973). 89. D. H. Janzen, Am. Nat. 104, 501 (1970); C. B. Huffaker, in Dynamics of Populations, P. J. denBoer and G. R. Gradwell, Eds. (Centre for Agricultural Publishing and Documentation, Wageningen, Netherlands, 1971), p. 327; J. R. Blais, For. Chron. 44 (1968).

The endotoxin-induced coagulant activity of human monocytes.

Abstract: Leucocyte suspensions, exposed to endotoxin in vitro, develop coagulant activity which has been identified as tissue factor. Pure suspensions of polymorphonuclear (PMN) neutrophils, lymphocytes and monocytes were exposed to endotoxin and tested for tissue factor activity after 4 h incubation at 37 degrees C. The results indicate that the monocyte is the cell primarily responsible for the endotoxin-induced coagulant activity of mixed leucocyte suspensions, the small amount of activity demonstrated in PMN neutrophil and in lymphocyte suspensions at high cell concentrations being accounted for by monocyte contamination of less than 1%.

Differentiation of neuroblastoma cells in culture.

Abstract: Summary 1 An elevation of the intracellular level of cyclic AMP in neuroblastoma cells by prostaglandin E1 by an inhibitor of cyclic AMP phosphodiesterase, or by analogues of cyclic AMP irreversibly induces many differentiated functions which are characteristic of mature neurones These include formation of long neurites, increase in size of soma and nucleus associated with a rise in total RNA and protein contents, increase in activities of specific neural enzymes, loss of malignancy, increase in sensitivity of adenylate cyclase to catecholamines and blockade of cells in G1-stage of the cell cycle 2 Other agents, including serum-free medium, X-irradiation, 6-thioguanine, cytosine arabinoside, methotrexate, 5-bromodeoxyuridine, nerve growth factor, glial extract and hypertonic medium can induce some of the differentiated functions which are induced by high intracellular cyclic AMP 3 Morphological differentiation and differentiated biochemical functions can each be expressed in the absence of the other 4 Many of the responses of normal embryonic nerve cells to cyclic AMP are similar to those of neuroblastoma cells 5 A working hypothesis for the malignancy of nerve cells has been proposed This states that an abnormal regulation of cyclic AMP phosphodiesterase activity which allows the expression of high amounts of this enzyme in neuroblastoma cells, may be one of the early lesions during a malignant transformation of nerve cells 6 A new experimental therapeutic model for the treatment of neuroblastoma is proposed This involves the administration of sodium butyrate followed by the injection of l-dihydroxyphenylalanine (l-dopa) and prostaglandin E1 in the presence of cyclic AMP phosphodiesterase inhibitor 7 Recent studies have elucidated the control mechanisms of some differentiated functions in neuroblastoma cells Cyclic AMP may become an important biological tool to probe the regulation and expression of many other differentiated functions in these cells In addition to neuroblastoma cells, other neuronal culture systems are now available for investigating the problems of differentiation and maturation in nerve cells

Rapid measurement of digital instantaneous frequency

Abstract: A new method is proposed for estimating the frequency domain structure of digital signals which may be characterized as having a narrow-band, rapidly time-varying spectrum. The estimated parameter is termed the digital instantaneous frequency of the input and is defined in a manner similar to that used previously to describe frequency-modulated, continuous-time signals. Instantaneous frequency estimates are derived from a spectral computation based on the use of an adaptive linear prediction filter. The proposed method differs from previous techniques in that the coefficients of this filter are continuously updated as each new input data sample is received using a simple time-domain algorithm, A derivation of the algorithm and its properties are presented. Numerical examples are included which illustrate the properties of the procedure.

Observing the states of systems with unmeasurable disturbances

Abstract: In order to estimate the state of a linear time-invariant multivariable system by using a Luenberger observer, it is generally assumed that all system inputs are measurable. This correspondence presents a simple and useful procedure for the construction of minimal-order state estimators for systems with unmeasurable disturbances.

Shear layer instability of an inviscid compressible fluid. Part 2

Abstract: The stability of parallel shear flow of an inviscid compressible fluid is investigated by a linear analysis. The extension of the Rayleigh stability criterion and Howard's semi-circle theorem to compressible flows, obtained by Lees & Lin (1946) and Eckart (1963) respectively, are each rederived by a different approach. It is then shown that a subsonic neutral solution of the stability equation may be found when the basic flow is represented by the hyperbolic-tangent velocity profile. With the aid of this solution, the unstable eigenvalues, eigenfunctions and Reynolds stress are determined by numerical methods. A brief discussion of the results follows.

Stability of Anhysteretic Remanent Magnetization in Fine and Coarse Magnetite and Maghemite Particles

Abstract: Summary Further experiments have been performed to investigate the biasing-field dependency of alternating field demagnetization curves of anhysteretic remanent magnetization as a simple test for the domain state of magnetite and maghemite particles. The biasing-field dependency in fine-grained particles was opposite to that in coarse-grained particles. The experiments were conducted on well sized synthetic specimens in the single domain, pseudo-single domain and multi-domain grain size ranges. A single domain-like biasing-field dependency was observed in equidimensional particles up to 0.2,~ in mean grain size and up to 0.4~ in elongated grains. Either the single domain/pseudo-single domain boundary lies above at least 0.2~ grain size or this field dependency test does not distinguish between single domain and pseudo-single domain states. A multidomainlike trend was observed in very coarse magnetite. The test may possibly distinguish the change from pseudo-single domain to multi-domain states. If both fine and coarse fractions are present a confusing overlap of the demagnetization curves occurs.

Recent progress in the peroxidase-labeled antibody method.

Abstract: Almost a decade has passed since the initial application of enzymes as labels in immunohistocytochemistry. During these years, the peroxidase-labeled antibody method has been used successfully by several laboratories for localizing antigens at both the light and electron microscopic levels. Recent improvements in the methodologies associated with the conjugation of peroxidase to immunoglobulin, the fixation of antigens, and the penetration of peroxidaselabeled antibodies into tissues should greatly facilitate successful application of the method.

A calculus for self-reference

Abstract: An extension of the calculus of indications (of G. Spencer Brown) is presented to encompass all occurrences of self-referential situations. This is done through the introduction of a third state in the form of indication, a state seen to arise autonomously by self-indication. The new extended calculus is fully developed, and some of its consequences for systems, logic and epistemology are discussed

Diurnal Variation of Plasma Aldosterone, Cortisol and Renin Activity in Supine Man

Abstract: In order to evaluate episodic secretion of aldosterone over the entire day, plasma aldosterone, renin activity and cortisol were measured every 10 or 30 min in normal human subjects, on both normal and sodium restricted diets, while receiving dexamethasone, on oral contraceptives and in patients with primary aldosteronism, all while supine. Peak levels of aldosterone occurred in the latter part of the sleeping hours and early in themorning in normal subjects on normal sodium diets. Aldosterone was positively correlated with cortisol in all these subjects but with renin in only 3 out of 5. When cortisol secretion was suppressed by dexamethasone, the hours of peak plasma aldosterone levels were the same, and these peak levels were not always related to renin. These data are compatible with a common determinant for ACTH and aldosterone secretion rhythms in supine man. On sodium restriction both subjects tested hadstatistically significant correlation of aldosterone with both cortisol and renin, and the 2 wom...

A variable projection method for solving separable nonlinear least squares problems

Abstract: Consider the separable nonlinear least squares problem of findinga eR n and α eR k which, for given data (y i ,t i ),i=1,2,...m, and functions ϕ j (α,t),j=1,2,...,n(m>n), minimize the functional $$r(a,\alpha ) = \left\| {y - \Phi (\alpha )a} \right\|_2^2$$ where θ(α) ij =ϕ j (α,t i ). Golub and Pereyra have shown that this problem can be reduced to a nonlinear least squares problem involvingα only, and a linear least squares problem involvinga only. In this paper we propose a new method for determining the optimalα which computationally has proved more efficient than the Golub-Pereyra scheme.

Unified theory of the onset of folding, boudinage, and mullion structure

Abstract: A mathematical study of the flow of a layered fluid shows that homogeneous pure shear aligned with the bedding is a “possible” state of motion in the sense that it is an exact solution to the governing equation. In the case of a single layer of a Newtonian material between two thick layers of different viscosity, such a state of motion is unstable to small disturbances. The growing disturbances have foldlike or pinch-and-swell form, depending on whether the applied compression is parallel or perpendicular to the layering and on whether the layer is more or less resistant to deformation than the surrounding rock. The combination of these two factors gives four distinct cases. One of these, labeled inverse folding, is of no interest because its growth rate is too small. The other three cases correspond qualitatively to folding, boudinage, and mullions. This result suggests that these three geologic structures are caused by the same mechanism: a secondary flow driven by an interfacial discontinuity in normal stress.

Placental production and foetal utilisation of lactate and pyruvate.

Abstract: APPROXIMATELY 75% of foetal oxygen consumption of sheep can be accounted for by the uptake of glucose from the umbilical circulation1–3 and catabolism of amino acids4. The contribution to foetal energy metabolism of exogenous long-chain fatty acids5 and fructose1 seems to be negligible. We report now that the placenta normally provides lactate for the foetus, in sufficient quantities to account for 25% of foetal oxidative metabolism. This finding invalidates the assumption that under normal physiological conditions there is a net flux of lactate from foetus to mother. The assumption seemed reasonable in the past because the concentration of lactate in foetal blood is greater than in maternal blood and because of the formerly prominent hypothesis that anaerobic metabolism is very active in foetal life.

Cognitive Abilities: Use of Family Data as a Control to Assess Sex and Age Differences in Two Ethnic Groups:

Abstract: Four cognitive factors were extracted from test data obtained on 997 families (3,268 individuals) in Hawaii. Factor loading profiles for the two largest ethnic groups (Caucasians and Japanese) are nearly identical, as are profiles for three different age groups. Age curves are presented for factor scores and for four specific cognitive tests. The younger respondents on the age curves are biological offspring of older respondents represented on the same curves, facilitating an unusual control for between-family variance. When the data were stratified by ethnicity, differential rates of cognitive development were indicated.

A Syndrome of Multiple Congenital Anomalies Associated With Teratogenic Exposure

Abstract: A study of 19 patients with multiple congenital anomalies described by the acronym VACTERL (Vertebral, Anal, Cardiac, Tracheoesophageal, Renal, and Limb) revealed exposure at the vulnerable period of embryogenesis to a progestogen/estrogen compound or a progestogen alone in 13 patients. These hormones were taken as a "pregnancy test," and for a variety of other reasons. Comparison of VACTERL patients with paired and matched controls, one group with chromosomal anomalies (other than Down syndrome) and another group with functional murmurs, revealed a significant difference with respect to exposure to hormonal contraceptives. The multiple anomalies of skeletal, cardiovascular, and gastrointestinal structures recapitulate the systems involved in the thalidomide syndrome, but present a variation of the pattern. Until more definitive data are available it would be prudent to emphasize the need to verify the absence of pregnancy before initiation of oral contraception and to discontinue hormonal agents as tests for pregnancy.

The equivalence of theorem proving and the interconnection problem

Abstract: A simple method of converting statements in mathematical logic to equivalent interconnection problems is demonstrated. This shows that if there exists a practical method for solving interconnection problems, then there exists a practical proof procedure for statements in mathematical logic. (In the terminology of Cook [1] and Karp [4], the interconnection problem is NP-complete.) Since such a procedure has been sought for without success for almost 100 years, we should not expect the interconnection problem to be any easier. This holds equally true for finding a method which will route a given percentage of wires.

Neoplastic differentiation: interaction of simian virus 40 and polyoma virus with murine teratocarcinoma cells in vitro.

Abstract: The host-virus interactions of Simian virus 40 (SV40) and polyoma virus (Py) with cell lines established from a teratocarcinoma were studied. The cells utilized in this study were the multipotential stem cell of the teratocarcinoma, embryonal carcinoma, and differentiated cells derived from embryonal carcinoma. Several lines of differentiated cells were established in vitro which included parietal yolk sac, epithelial, and spindle cell types. Embryonal carcinoma cells are not susceptible to infection by either SV40 or Py virus. However, differentiated cells are susceptible to infection by these viruses. The differentiated cells are permissive for Py virus replication and nonpermissive for SV40. Several continuously growing cell lines have been established from the SV40 infected cultures which express T antigen in 100% of the cells. The results indicate that undifferentiated embryonal carcinoma cells and their differentiated progeny respond quite differently to challenge with these two oncogenic DNA viruses.

The Impact of Cooperative Learning Experiences on Cross‐Ethnic Relations and Attitudes

Abstract: A field experiment examined the effects of cooperative interethnic contact on ethnic relations and attitudes in the setting of newly desegregated junior and senior high schools. Cooperative interethnic contact was induced in the experimental classrooms by means of a teaching method which emphasized the use of small interdependent student work groups composed of white, black, and Mexican-American students. Results indicated that the interethnic group method received a favorable endorsement from the teachers, produced substantially more cross-ethnic helping behavior, promoted greater relative respect and liking for Mexican-American classmates among white students, and elicited more frequent friendship choices for Mexican-Americans by whites.