Showing papers by "University of California, Davis published in 1968"

Polychlorinated biphenyls in the global ecosystem.

Abstract: Polychlorinated biphenyls are widely dispersed in the global ecosystem, and are powerful inducers of hepatic enzymes which degrade oestradiol. Together with other chlorinated biocides, such as DDT, they could account for a large part of the aberration in calcium metabolism which has been observed in many species of birds since the Second World War.

Prosthecomicrobium and Ancalomicrobium: New Prosthecate Freshwater Bacteria

Abstract: Direct microscopic examination of natural freshwater samples reveals a variety of small microorganisms having elaborate cellular appendages. Several strains have been isolated from crude cultures containing low concentrations of organic nutrients. All of the isolates are procaryotic. They are aerobic chemoorganotrophs that require vitamins for growth. Because they cannot be assigned to any of the existing bacterial genera, two new genera are proposed: Ancalomicrobium for organisms which have several long appendages and which reproduce by budding; Prosthecomicrobium for organisms which have many short appendages tapering toward a blunt tip and which reproduce by binary fission. Gas vacuoles have been found in strains of each genus. The term prostheca is proposed for the rigid appendages of procaryotic cells bounded by the cell wall, and is defined to include the structures on these new bacteria, as well as the stalks of the caulobacters and the hyphae of the hyphomicrobia.

A system for expressing net energy requirements and feed values for growing and finishing beef cattle.

Abstract: E ARLY in 1963 the authors introduced a net energy system designed for use in the growing and finishing phase of the beef cattle industry (Lofgreen, 1963a, b, c). The system separated the requirements for maintenance from that for body weight gain and expressed a net energy value of the feed for these two functions. Such a system of expression was suggested to the Nutrition Committee of the National Research Council and was included in the first printing of the N.R.C. Bulletin of suggested energy terminOlogy as an errata sheet replacing the original terminology (Harris, 1962). For the past 4 years the suggested method has been tested under various conditions at this station, in commercial feedlots, and by nutrition consultants working with the cattle feeding industry and its adaptability to practice has been demonstrated. I t is the purpose of this paper to present the proposed system in the scientific literature, describe the experimental data upon which it is based, and discuss its application. The terminology used herein is that suggested in the first revision of the N.R.C. Bulletin on energy terms (Harris, 1966).

The Genetics of Inbreeding Populations

Abstract: Publisher Summary This chapter discusses the effects of inbreeding in terms of genetic models of steadily increasing complexity. It correlates theoretical effects with observations and measurements that show that inbreeding populations contain large amounts of genetic variability and that this variability is organized into highly integrated and flexible systems. The observed structure of inbreeding populations results from an appropriate integration of inbreeding into the constellation of genetic and ecological factors that are involved in the regulation of variability and maintenance of flexibility. An understanding of the genetic structure of inbreeding species derives from the combining analyses of theoretical models with studies on experimental and natural populations. Inbreeding can arise in populations either as a result of various mechanisms that affect the mating system, or from restrictions in actual or effective population size. The theoretical effects of inbreeding are introduced in terms of single-locus population models in which population size is assumed sufficiently large to avoid sampling effects and in which it is assumed that selective values, mating system parameters, and other population parameters are constant in all environments. The effects on population structure of linkage and epistatic interactions among different polymorphisms are considered in terms of multilocus genetic models involving deviations from a fixed optimum, heterotic models, and mixed optimum-heterotic models.

Adsorption rate constants from chromatography

Abstract: A new method for determining adsorption equilibrium constants, rate constants, and intraparticle diffusivities is described and applied for the adsorption of ethane, propane, and n-butane on silica gel. The method rests upon recently developed theory for relating the moments of the effluent concentration wave from a bed of adsorbent particles to the rate constants associated with the various steps in the overall adsorption process. It is necessary to operate at concentrations of adsorbable gas such that the adsorption isotherm is linear. However, it is possible to take into account effects of longitudinal dispersion and diffusion to the particle surface as well as the intraparticle processes of diffusion and adsorption on the pore surface. The method gave reasonable values for intraparticle diffusivities and adsorption rate constants. Intraparticle diffusion was a major resistance for all particle sizes studied and for the largest size (R = 0.50 mm.) this step controlled the overall rate. From the constants determined chromatographically it is possible to predict breakthrough curves for the adsorption of these hydrocarbons on silica gel. The predicted curves agree well with experimentally established breakthrough curves.

Stomatal Opening: Role of Potassium Uptake by Guard Cells

Abstract: Stomata in isolated epidermal strips open in response to light plus air free of carbon dioxide when the strips are floated on potassium chloride solutions of low concentrations. This opening depends on the stimulation of active accumulation of potassium in quantities sufficient to account for the observed changes in solute potential of the guard cells.

Stomatal Opening in Isolated Epidermal Strips of Vicia faba. II. Responses to KCl Concentration and the Role of Potassium Absorption

Abstract: The stimulation by KCl of stomatal opening in isolated epidermal strips of Vicia faba was examined. In dark + normal air the opening response was maximal at 100 mm KCl while in light + CO(2)-free air it was maximal at about 10 mm KCl. CO(2)-free air was more influential than light in reducing the KCl concentration required for maximal opening. K(+) was essential while Cl(-) seemed to be of secondary importance in these processes.The use of (86)Rb(+) as a tracer for K(+) showed that the increase in stomatal aperture under various conditions was well correlated with K(+) uptake. The estimated amount of K(+) taken up by guard cells, along with a counter ion, was sufficient to account for the changes in solute potential associated with opening. It is suggested that the absorption of extracellular solutes, such as K(+), may be the primary mechanism of stomatal opening. Both opening and K(+) absorption are stimulated by light + CO(2)-free air.The increase in stomatal aperture was also well correlated with the decrease in stainable starch in guard cells under all conditions. It is suggested that this is a secondary change, although perhaps closely linked to K(+) absorption.

Ruminant-like digestion of the langur monkey.

Abstract: The adaptation of langur monkeys to a laboratory environment has made possible a detailed investigation of their digestive physiology. The diverticular form of the langur stomach permits a bacterial fermentation of the leafy diet, which results in important contributions to the nutrition of these primates. The demonstration of a ruminant-like digestion in langurs extends the known taxonomic distribution of this digestive adaptation.

Diacetyl Biosynthesis in Streptococcus diacetilactis and Leuconostoc citrovorum

Abstract: Pyruvate was shown to be the precursor of diacetyl and acetoin in Streptococcus diacetilactis, but dialyzed cell-free extracts of S. diacetilactis and Leuconostoc citrovorum that had been treated with anion-exchange resin to remove coenzyme A (CoA) formed only acetoin from pyruvate in the presence of thiamine pyrophosphate (TPP) and Mg++ or Mn++ ions. The ability to produce diacetyl was restored by the addition of acetyl-CoA. Acetyl-phosphate did not replace the acetyl-CoA. Neither diacetyl nor acetoin was formed when the otherwise complete reaction system was modified by using boiled extract or by omitting the extract, pyruvate, TPP, or the metal ions. Free acetaldehyde was not involved in the biosynthesis of diacetyl or acetoin from pyruvate, dialyzed cell-free extracts of the bacteria produced only acetoin (besides CO2) from α-acetolactate, and acetoin was not involved in the biosynthesis of diacetyl. Only one of the optical isomers present in racemic α-acetolactate was attacked by the extracts, and there was no appreciable spontaneous decarboxylation of the α-acetolactate at the pH (4.5) used in experiments.

Characterization of Methanobacterium mobilis, sp. n., isolated from the bovine rumen.

Abstract: A methanogenic bacterium, present in bovine rumen contents at concentrations of approximately 2 x 10(8) cells per ml, has been isolated in pure culture. The organism is a strictly anaerobic, weakly motile, nonsporeforming, gram-negative rod (0.7 mu x 1.5 to 2.0 mu) with rounded ends. There is a single polar flagellum. The organism grows at temperatures between 30 and 45 C, with an optimum at 40 C, and at pH values between 5.9 and 7.7, with optimal growth between pH 6.1 and 6.9. Of the 17 substrates tested, only formate and H(2) plus CO(2) supported growth. An unidentified, heat-stable factor(s) was required by the organism. The factor, which was not one of the common ones, was present in rumen fluid, mixed rumen bacteria, and yeast extract. On the basis of colony morphology, Gram reaction, and motility, the organism is classified as a new species of methanogenic bacterium, and the name Methanobacterium mobilis sp. n. is proposed.

Some effects of energy-transfer inhibitors and of Ca++-free or K+-enhanced media on the release of luteinizing hormone (LH) from the rat pituitary gland in vitro.

Abstract: The hypothalamic extract-stimulated release of luteinizing hormone (LH) from the rat pituitary incubated in vitro was found to be dependent upon the presence of Ca++ in the medium. When the K+ concentration of the medium was increased to 59 HIM the release of LH was much stimulated as compared to controls in 5.9 HIM K+. When hypothalamic extract and 59 mM K+ when both present the stimulatory effects on LH release were additive. The 59 mM K+- stimulated release of LH was also dependent upon the presence of Ca++. However, absence of Ca++ did not inhibit, nor did excess K+ stimulate, the incorporation of 14C-leucine into LH. At concentrations of dinitrophenol and oligomycin where 75% of the incorporation of 14C-leucine into LH was inhibited the release of LH was not affected. These results indicate that the synthesis and release of LH are separate phenomena. (Endocrinology 82: 225, 1968)

Regulation of Starch Biosynthesis in Plant Leaves: Activation and Inhibition of ADPglucose Pyrophosphorylase

Abstract: The ADPglucose pyrophosphorylases of 7 plant-leaf tissues were partially purified and characterized. In all cases the enzymes showed stability to heat treatment at 65° for 5 minutes in the presence of 0.02 m phosphate buffer, pH 7.0. The leaf ADPglucose pyrophosphorylases were activated 5 to 15-fold by 3-phosphoglycerate. Fructose-6-phosphate and fructose 1, 6-diphosphate stimulated ADPglucose pyrophosphorylase to lesser extents. The A 0.5 (conc of activator required to give 50% of the observed maximal activation) of 3-phosphoglycerate for the barley enzyme was 7 × 10 −6 m while for the sorghum enzyme it was 3.7 × 10 −4 m. Inorganic phosphate proved to be an effective inhibitor of ADPglucose synthesis. The I 0.5 (conc of inhibitor that gave 50% inhibition of activity for the various leaf enzymes varied from 2 × 10 −5 m (barley) to 1.9 × 10 −4 m (sorghum). This inhibition was reversed or antagonized by the activator 3-phosphoglycerate. These results form the basis for an hypothesis of the regulation of leaf starch biosynthesis.

Cytogenetic analysis of the tomato genome by means of induced deficiencies

Abstract: Cytological studies of 74 deficiencies of tomato chromosomes induced by radiation and identified by the pseudo-dominant technique reveal the loci of 35 genes on 18 of the 24 arms of the complement. These findings integrated with data obtained from various trisomic types establish centromere positions, orientation of linkage groups, and markers on all but three of the arms. The prospects of obtaining a specific kind of deficiency for a given region were found to depend on : (1) kind of radiation applied, (2) (non-random) breakage frequency in different parts of the chromosome, (3) stability of broken ends, (4) tolerance of deficiency in different parts of the genome, and (5) relative vigor of the mutant homozygote used to detect the deficiency. Aspects of the frequently observed non-homologous pairing phenomenon are presented and discussed. Marker genes whose loci are known appear to be non-randomly distributed between and within chromosomes. Chromosome exchanges as determined by genetic crossing over and cytologically observed chiasmata are likewise non-randomly distributed between and within chromosomes.

Malo-lactic fermentation.

Abstract: Publisher Summary This chapter discusses the biochemistry and metabolism of bacteria causing malo-lactic fermentation, and also the application of this knowledge to control malo-lactic fermentation. Malo-lactic fermentation is necessary not only to deacidify some wines and to stabilize others, but also to improve some wines apparently by addition of certain products of metabolism, which make the flavor more complex. Natural malo-lactic fermentation can be encouraged by use of low levels of sulfur dioxide (less than 50 mg./liter), delay in addition of acidifying or fining agents, and storage at warmer temperatures. Aeration can stimulate malo-lactic fermentation. Malo-lactic fermentation is most likely to occur under conditions, which also favor wine spoilage. It is nearly impossible to obtain malo-lactic fermentation in wines with very high acidity -approaching pH 3.0. In regions producing these wines, it is often legal to increase the pH by addition of chemicals, by amelioration with water, or by ion exchange. Further, deacidification can then be made by malo-lactic fermentation. Increase in pH can also be obtained by blending the wine with another wine, which has undergone malo-lactic fermentation and has less acidity. The pH of the blended wine may then allow further malo-lactic fermentation.

Symmetrical gaits of dogs in relation to body build

Abstract: Symmetrical gaits of 37 breeds of dogs were analyzed. Usual walking and trotting gaits resemble those of other carnivores of similar size and conformation. Only certain long-legged dogs pace – usually at the fast walk or slow run. At the moderate walk, long-legged dogs tend to use lateral-couplets gaits, whereas short-legged breeds tend to use single-foot gaits. Many dogs must turn the axis of the body slightly from the line of travel at the trot to prevent interference between fore and hind feet. The relative duration with the ground made by fore and hind feet is discussed, usual support-sequences of the varicus gaits are presented, and the amount of variation is shown.

The kinetics of the reversible inhibition of heart lactate dehydrogenase through the formation of the enzyme–oxidized nicotinamide–adenine dinucleotide–pyruvate compound

Abstract: The inhibition of lactate dehydrogenase at high pyruvate concentration was studied in three ways. First, a rapid decrease in the rate of the enzyme reaction was observed; secondly, the rate of formation of a pyruvate–NAD+ compound was followed by the change in E325; thirdly, the rate of quenching of the protein fluorescence was measured. The data obtained at pH6·0 at different temperatures and ionic strengths as functions of pyruvate, NAD+ and enzyme concentrations show that the extent of inhibition can be correlated with the reversible formation of a compound between pyruvate and enzyme-bound NAD+. It is suggested that the detailed kinetic analysis of the formation of this abortive ternary compound will give pertinent information about properties of the enzyme–NAD+ compound involved in the normal catalytic process.

Biology as an autonomous science.

Abstract: The goal of science is the systematic organization of knowledge about the universe on the basis of explanatory principles that are genuinely testable. The starting point of science is the formulation of statements about objectively observable phenomena. Common sense knowledge also provides information about the world. The distinction between science and common sense knowledge is based upon the joint presence in science of at least three distinctive characteristics. First, science seeks to organize knowledge in a systematic way by exhibiting patterns of relations among statements concerning facts which may not appear obviously as mutually related.

Chromatographic study of surface diffusion

Abstract: A new method, based upon chromatography, was used to measure surface diffusion coefficients for ethane, propane, and n-butane on silica gel. The diffusivities correspond to very low surface coverages (fraction of a monolayer of the order of 10−4) and hence should represent limiting values. A survey of available surface diffusion information, all at higher coverages, indicated that the results reported here are at the lower end of the range of diffusivities. The activation energy and heat of adsorption, for example, for n-butane, were 4.4 and −7.8 k cal./mole, respectively. Surface diffusion was a significant fraction of the total intraparticle mass transport, in part because in the small pores in silica gel gas phase diffusion was solely by the Knudsen mechanism. For propane, surface migration was 73% of the total transport at 50°C. and 61.5% at 125°C.