Showing papers by "University of California, Davis published in 1973"

On the Equivalence of Control Systems and the Linearization of Nonlinear Systems

Abstract: Given two control systems where the control enters linearly, a necessary and sufficient condition is derived that these systems be locally diffeomorphic, i.e., that there exist a local diffeomorphism between the state spaces which carries a trajectory of the first system for each control into the trajectory of the second system for the same control. As a corollary we derive necessary and sufficient conditions for a system to be locally diffeomorphic to a linear system.

Taxonomy of the marine, luminous bacteria

Abstract: One hundred and seventy-three strains of marine, luminous bacteria isolated from sea water, surfaces and intestines of fish, as well as from the luminous organs of fish and squid were submitted to an extensive phenotypic characterization A numerical analysis of the results grouped these strains into four clusters which were formed on the basis of overall phenotypic similarity One cluster, which was given the designationBeneckea harveyi, consisted of strains which had a moles% GC content in their DNAs of 465±13 and a single, sheathed, polar flagellum when grown in liquid medium Most of these strains had unsheathed, peritrichous flagella in addition to the sheathed, polar flagellum when grown on solid medium The two phenotypically similar clusters which were assigned the species designationsPhotobacterium phosphoreum andP mandapamensis consisted of strains which had 1–3 unsheathed, polar flagella and moles % GC contents in their DNAs of 415±07 and 429±05, respectively The cluster designatedP fischeri contained strains having 2–8 sheathed, polar flagella and a moles % GC content of 398±11 These four species could be further distinguished on the basis of a number of nutritional properties as well as other phenotypic traits The assignment of the luminous, marine bacteria to four species was supported by differences in the properties of the luminous system as well as differences in the pattern of regulation of spartokinase activity which are discussed The speciesB harveyi was found to be phenotypically similar to a number of previously characterized, non-luminous strains ofBeneckea which should probably be assigned to this species

Genetic differentiation, sympatric speciation, and the origin of a diploid species of stephanomeria.

Abstract: A B S T R A C T Evidence is presented that a geographically peripheral population of the annual Stephanomeria exigua ssp. coronaria (Compositae), a widespread and ecologically diverse species, has recently given rise by a process of sympatric speciation to a diploid species presently designated "Malheurensis." The new species comprises less than 250 individuals and is found only at a single locality in eastern Oregon where it grows interspersed with its parental population. Stephanomeria exigua ssp. coronaria is an obligate outcrosser and "Malheurensis" is highly self-pollinating. Reproductive isolation is maintained by differences in breeding system, a crossability barrier that reduces seed set following cross-pollination between them, and reduction in hybrid fertility caused by chromosomal structural differences. They are very similar morphologically. Electrophoretic analyses of seven enzyme systems demonstrate that all the alleles but one at the controlling 13 gene loci in "Malheurensis" are identical to alleles in ssp. coronaria. The new species displays certain maladapted features including loss of the specific requirements for seed germination characteristic of the progenitor population of ssp. coronaria. The origin of "Malheurensis" appears to be an exception to the theory of geographical speciation because spatial isolation is not necessary at any time for the origin or establishment of its reproductive isolating barriers. The nature of these barriers plus the genetic homogeneity of the species are compatible with the hypothesis that it derives from a single progenitor individual. Very little genetic change is involved initially in this mode of speciation.

Genetic variation in tridacna maxima, an ecological analog of some unsuccessful evolutionary lineages.

Abstract: The adaptive strategies of populations are very important elements in the ecological structure of the biosphere. By adaptive strategy is meant a suite of population parameters that is adaptive to the temporal and spatial structure and variability of an environmental regime (see Levins, 1968). In any given range of environments, communities will tend to be composed of species with the particular set of strategies appropriate to the regime. Thus the structure and function of community and of provincial ecosystems reflect to a considerable extent the properties of the environment, varying in such factors as species diversity, pattern of trophic linkages, and proportion of consumers vs. recuperators. The extent to which Mendelian populations follow genetic strategies that contribute importantly to their overall adaptive strategies is still an open question. Adaptive strategies are simply the products of the evolution of a variety of parameters along adaptive pathways that lead to harmonious, advantageous assemblages of population characteristics in a given range of environmental regimes. It seems reasonable that the genetic system itself, which influences the pattern of reproduction, of recombination, and of functional variation in important ways, should reflect population features so that characteristic genetic systems might be favored in certain environmental regimes. Theoretical suggestions to this effect have been made by Carson (1960), Levins (1968), Grassle (1967), Bretsky and Lorenz (1969, 1970) and others. In the fossil record, which is bestpreserved in shallow marine sediments, it is possible to infer changing sequences of adaptive strategies in communities, in provinces, and at times in the entire marine biosphere, presumably in response to important changes in the ancient shallow marine environments (Valentine and Moores, 1970, 1972; Valentine, in press). At times these changes are associated with major waves of extinction, which have swept away high proportions of the marine biota episodically (Newell, 1952, 1956, 1967; Harland et al., 1967; Valentine, 1969). Hypotheses to account for these extinctions are legion, ranging from reliance on occasional extraterrestrial catastrophes to the regular operation of ecological diversity regulators such as are at work today. One current hypothesis is that the extinctions result from the failure of genetic strategies to meet population requirements in changing environments. This hypothesis has far-reaching implications and has stimulated the research on which this report is based.

Functions to Predict Effects of Crop Water Deficits

Abstract: A well-advanced research program is aimed at quantitative prediction of relations between principal crops and water. Goals are to: (1) estimate functional relations between crop yield Y and water at all water supply levels; water being defined as seasonal depths of both evapotranspiration ET and irrigation IRR ; and (2) optimize water management by maximizing profit or water use efficiency or other objective. Davis, Calif. field and lysimeter studies with corn show: (1) the Y versus ET function is linear, provided unavoidable ET deficits from limited irrigation water coincide with those crop growth stages that influence yield the least; and (2) the Y versus IRR function is convex, reflecting decreasing irrigation efficiency (percentage of IRR utilized ET ) as actual crop ET approaches fulfillment of maximum requirements. When IRR equals zero the two functions become one, and ET derives entirely from stored soil water and rainfall.

Propagation Modes, Equivalent Circuits, and Characteristic Terminations for Multiconductor Transmission Lines with Inhomogeneous Dielectrics

Abstract: The theory of wave propagation on Iossless multiconductor transmission lines with inhomogeneous dielectrics is developed using matrix analysis. The treatment is concise and complete and has the advantage of identifying propagation modes in a way that permits straightforward physical interpretation. The equivalent circuit for the general line is derived and its application to the solution of wave problems with reflections is demonstrated. Special consideration is given to the problem of characteristically terminating a multiconductor line, i.e., terminating without reflections. The realizability of such a characteristic termination network is discussed, and proofs of realizability are given for the important cases of all lines with homogeneous dielectrics and all three-conductor lines, regardless of dielectric inhomogeneities. Symmetric three-conductor lines are discussed to exemplify the general theory, and an application to the problem of mode conversion on symmetric and asymmetric shielded strip lines is given.

Potential genetic resources in tomato species: clues from observations in native habitats.

Abstract: Interspecific hybridization is playing an increasingly important role in the breeding of improved cultivars of higher plants. Lycopersicon is a good example of a genus in which the cultivated species (L. esculentum Mill.) is being improved in this fashion. The advantages offered by the tomato species for this purpose are: a. All species can be readily grown for experimental purposes, and L. esculentum is widely cultivated under a wide range of environmental conditions. b. Excellent sources of germ plasm now exist in the wild species as well as in modern and primitive cultivars of L. esculentum. c. All of the wild species can be hybridized with L. esculentumn, albeit requiring special aids in certain combinations; fertility and viability of the hybrid generations permit the intended gene transfers. All species have 12 pairs of chromosomes, which are essentially homologous. d. The cultivated species is well known genetically; its chromosomes have been mapped cytologically and genetically; it behaves as a basic diploid (27, 28).

Effect of hydrocolloids on oral viscosity and basic taste intensities

Abstract: . This study determined the effects of low concentrations of five food hydrocolloids on the taste intensities of aqueous solutions of sucrose, citric acid, sodium chloride, saccharin, and caffeine. The effects of the taste compounds on both oral and Brookfield viscosities were also measured. In general, sourness of citric acid and bitterness of caffeine were suppressed, while sweetness of saccharin was enhanced. Among the basic tastes, sourness was affected the most and saltiness the least. Except for sucrose, modification of taste intensity was independent of viscosity, and appeared to be related to the physicochemical properties of the hydrocolloid and the taste compound. About 16 cps were needed to reduce significantly the sweetness of sucrose. The taste compounds altered oral and physical viscosities differentially depending on the specific gum/taste combination. Generally, viscosity was reduced by the addition of all taste compounds except sucrose which increased the physical viscosity.

Damage to microsomal membrane by lipid peroxidation.

Abstract: Alterations of microsomal membrane integrity were examined during lipid peroxidation. Loss of membrane-bound NADPH cytochromec reductase activity and protein release into the aqueous phase were related to disruption of the lipophilic region of the membrane. Formation of fluorescent products in the lipid phase of the membrane occurred only in the presence of peroxidation products. Changes in the membrane lipid phase during peroxidation included a decrease in the reactive amino groups of the phospholipids and a decrease in detectable phosphatidyl ethanolamine. In an ultrafiltration continuous flow chamber, peroxidized microsomal membranes were hydrolyzed to a lesser degree by solubilized lysosomal cathepsins and to a greater degree by lysosomal nucleases than were nonperoxidized membranes.

Momentum and mass transfers in the surface boundary layer

Abstract: Results are presented from six micrometeorological studies conducted over a grass turf at Davis, California, in 1966 and 1967. Highly reliable surface drag and evaporation data from very sensitive lysimeters of 6·1 m diameter afforded excellent opportunity to evaluate several parameters important to aerodynamic-prediction equations. For the six studies the mean von Karman constant, k, ranged from 0·40 to 0·44, strongly supporting continued acceptance of k at around 0·42. The Monin-Obukhov (1954) universal ϕM function was found to vary as ∣Ri∣−1/3 under near-free convection, indicating significantly greater diabatic profile effects than suggested in the form of the KEYPS profile as given by Sellers (1965). Empirical relationships providing excellent fit to experimental data for the range −3·5 < Ri < 0·3, were ϕM = (1–16 Ri)−1/3 and ϕM = (1 + 16Ri)1/3 respectively for unstable and stable conditions. For ϕw corresponding expressions were ϕw = ·885 (1–22 Ri)−.40 and ϕw = ·885 (1+34 Ri).40. The ratio KW/KM showed a systematic drop from 1·13 at neutral to a value around 0·75 under strongly stable conditions, which conflicts with recent reports of no change of KH/KM within a wide range of stable conditions (Laykhtman and Panomareva 1969; Webb 1970; Oke 1970). The UCD results are in general agreement with the literature in that KW/KM systematically increased with increasing instability. In the range 0 > Ri > −2·0, KW/KM increased from 1·13 to 1·6. No expressions relating ϕM and ϕW or KW/KM to z/L are presented due to uncertainties in Davis z/L data. However, use of Davis Ri data in several published z/L (Ri) relationships, allowed a limited comparison with results of previous studies.

Enzyme differentiation and phylogeny in clarkia franciscana, c. rubicunda and c. amoena.

Abstract: When chromosomal reorganization in annual plants results in rapid speciation, the derivative species closely resemble their parents in morphological features and often in ecological tolerances. This suggests that divergence at the genetic level, i.e., the establishment of new alleles, is a much slower process than the erection of reproductive isolating barriers. The extent of genetic divergence at large numbers of loci can be established by gel electrophoresis of enzymes and other proteins. Several species of Clarkia furnish some of the most intensively studied examples of rapid speciation in annual plants (Lewis, 1962, 1966). In order to investigate the genetic consequences of rapid speciation, electrophoretic studies of enzyme differentiation were initiated in Clarkia franciscana, C. rubicunda and C. amoena. Clarkia franciscana consists of a single population on a serpentine outcrop in San Francisco, California, and occurs near the northern periphery of the distribution of C. rubicunda. Clarkia amoena replaces C. rubicunda just north of San Francisco Bay and is found northward to British Columbia. The three species are closely similar morphologically but hybrids between any two of them have very low fertilities caused by meiotic irregularities attributed to gross chromosomal structural differences (Lewis and Raven, 1958a). Clarkia fransiscana is morphologically uniform and highly self-pollinating, and has been observed (ibid.) to fluctuate in numbers from 600 to 4000 individuals in different years. In contrast, both of the other Clarkias generally outcross, consist of large numbers of populations, and are morphologically and ecologically variable. On the basis of distributions, overall variabilities, cytogenetic studies and other evidence, Lewis and Raven proposed that C. amoena is an ancient species and gave rise to C. rubicunda which, in turn, is the progenitor of C. franciscana. The latter species is thought to have originated relatively recently, perhaps at its present site, as a consequence of rapid reorganization of chromosomes brought about by forced inbreeding among surviving individuals of a population of C. rubicunda which had been subjected to a sudden, severe environmental stress such as early-season drought.

Fluorescent products from reaction of peroxidizing polyunsaturated fatty acids with phosphatidyl ethanolamine and phenylalanine.

Abstract: Fluorescent chromophores produced by reaction of peroxidizing arachidonic acid or methyl docosahexaenoate with synthetic dipalmityl phosphatidyl ethanolamine were lipid soluble, and those from reaction with phenylalanine were water soluble. In all reaction systems that contained polyunsaturated fatty acid and only one amine compound, the development of fluorescence was linearly related to oxygen absorption for 12–24 hr (p<0.001) and to the amount of thiobarbituric acid reacting materials until the rate of oxygen absorption decreased. The fluorochromes typically had maximum excitation at 360 nm and maximum emission at 430–440 nm, indicating that they were conjugated Schiff bases with the general structure R−N=C−C=C−N−R, where R represents the amino acid phenylalanine or the phospholipid phosphatidyl ethanolamine. The fluorochromes were similar to those extracted from isolated age pigments and tissues of animals that are aged, vitamin E-deficient, or stressed with highly unsaturated lipid diets.

Purification and Some Properties of Two Polyphenol Oxidases from Bartlett Pears

Abstract: Two polyphenol oxidases (enzymes A and B) from Bartlett pear (Pyrus communis) peelings were purified to electrophoretic homogeneity according to polyacrylamide gel by a combination of Sephadex gel filtration, diethylaminoethyl cellulose chromatography and hydroxyl apatite chromatography. While the two enzymes differ electrophoretically at pH 9.3, chromatographically on hydroxyl apatite, and in the effect of ionic strength on activity, they are similar with respect to chromatography on diethylaminoethyl cellulose, substrate specificity, pH activity relations, inhibition by p-coumaric and benzoic acids, and heat stability. The two enzymes are o-diphenol oxidases with no detectable monophenolase or laccase activities. Pyrocatechol, 4-methyl catechol, chlorogenic acid, and d-catechin are good substrates of the enzymes with K(m) values in the range of 2 to 20 mm. Dependences of activity on oxygen and chlorogenic acid concentrations indicate a sequential mechanism for binding of these substrates to enzyme B. V(max) and K(m) values for oxygen and chlorogenic acid were 103 mumoles O(2) uptake per minute per milligram of enzyme, 0.11 mm and 7.2 mm, respectively, for enzyme B at pH 4.0. Both enzymes had maximum activity at pH 4.0 on chlorogenic acid. K(m) values for chlorogenic acid were independent of pH from 3 to 7; the V(max) values for both enzymes gave bell-shaped curves as a function of pH. p-Coumaric acid is a simple, linear noncompetitive inhibitor with respect to chlorogenic acid at pH 6.2 with K(i) values of 0.38 and 0.50 mm for enzymes A and B, respectively. Benzoic acid is a linear competitive inhibitor with respect to chlorogenic acid at pH 4.0 with K(i) values of 0.04 and 0.11 mm for enzymes A and B, respectively.

Protein kinases: aspects of their regulation and diversity.

Abstract: Publisher Summary This chapter discusses the protein kinases, aspects of their regulation, and their diversity. Studies of protein kinases have become intimately associated with an understanding of the function of cyclic AMP. In the past few years, it has been observed that hormones, interacting with specific receptors on the cell surface, modulate adenyl cyclase activity. The resultant changes in intracellular cyclic AMP concentrations evoke the physiological responses distinctive of each hormone-target cell interaction. The cyclic nucleotide binds to a specific receptor protein that interacts at the promoter region of the operon and, in consequence, modulates the rate of synthesis of specific species of messenger RNA. Moreover, glycogenolysis is a common feature of most mammalian tissues and, therefore, caution must be used in expanding the interpretation of the enzyme distribution data to account for the hormonal regulation of other metabolic processes. Recently, no correlation was found in the developmental patterns in skeletal muscle, liver, and heart, between cyclic AMP-dependent protein kinase and the glycogenolytic enzymes phosphorylase and phosphorylase kinase.

Mechanisms of Ion Transport through Plant Cell Membranes

Abstract: Publisher Summary Plant cells exhibit unique features of ion transport. Historically, transport investigations have been confined largely to the characterization of the kinetics of the passage of a plethora of substances through biological membranes. This chapter discusses the transport of ions in Neurospora, describes the asexual part of the growth cycle of Neurospora, and identifies the developmental stages that have been used for transport studies. The chapter also discusses the properties of a variety of transport systems characterized in Neurospora. The characteristics of ion transport in roots include its competence in coping with spatial and temporal variations, high affinity for nutrient ions, great selectivity, and maintenance of a state of nonequilibrium with an ambient medium. Evidence for passive, diffusional movements of ions across uninjured plasmalemmas of the cells of higher plants in a state of active absorption is neither extensive nor firm; this favors the view that active transport agents or carriers must mediate the movement of ions across these membranes. The chapter presents evidence, mainly kinetic, for carrier-mediated transport to deduce certain properties of active agents or carriers, especially those related to the specificity or selectivity of ion transport.

Effect of Weak Acids on Amino Acid Transport by Penicillium chrysogenum: Evidence for a Proton or Charge Gradient as the Driving Force

Abstract: A variety of weak acids at and below their pKa are potent inhibitors of transport in Penicillium chrysogenum. The effective compounds include sorbate, benzoate, and propionate (common antifungal agents), indoleacetate (a plant hormone), acetylsalicylate (aspirin), hexachlorophene, and a yellow pigment produced by the mycelia under nutrient-deficient conditions, as well as the classical uncouplers 2,4-dinitrophenol, p-nitrophenol, and azide. The results suggest that a proton gradient or charge gradient is involved in energizing membrane transport in P. chrysogenum. The unionized form of the weak acids could discharge the gradient by diffusing through the membrane and ionizing when they reach an interior compartment of higher pH. Experiments with 2,4-dinitrophenol and p-nitrophenol established that the ionized species are not absorbed by the mycelium to any great extent. The transport inhibitors also caused a decrease in cellular adenosine 5′-triphosphate (ATP) levels, but there was no constant correlation between inhibition of transport and suppression of cellular ATP. A decrease in aeration of the mycelial suspension had the same effect on transport and ATP levels as the addition of a weak organic acid. The effects on transport rates and ATP levels were reversible. The instantaneous inhibition of [14C]l-leucine transport by NH4− (and vice-versa) in nitrogen-starved mycelia at pH values of 7 or below can be explained by competition for a common energy-coupling system. The inhibition is not observed in carbon-starved mycelia in which the NH4+ transport system is absent or inactive (but the general amino acid transport is fully active), or in iodoacetate-treated mycelia in which the NH4+ transport system has been differentially inactivated. At pH values greater than 7.0, NH3 and HPO42− inhibit transport, presumably by discharging the membrane proton or charge gradient. Aniline counteracts the inhibitory effect of NH3 and HPO42− possibly by acting as a proton reservoir or buffer within the membrane.