Oxidation of glycine by Phaseolus leghaemoglobin with associated catabolic reactions at the haem.

Leghaemoglobin from the root nodules of kidney bean (Phaseolus vulgaris) reacts in alkaline glycine solutions as a glycine oxidase in a reaction that may also be regarded as a coupled oxidation. Leghaemoglobin is reduced to the ferrous form by glycinate, the oxygen complex is formed, and finally the haem is attacked to yield a green reaction product. Glycine is simultaneously oxidized to glyoxylate, and hydrogen peroxide is generated. The initial velocity of the formation of the green product is proportional to the concentrations of leghaemoglobin and glycine, and the optimum pH for the reaction is 10.2. The green product is not formed if carbon monoxide, azide of imidazole is bound to the haem, whereas oxidation of glycine to glyoxylate is not inhibited by azide and not essentially by carbon monoxide. Haem breakdown is activated by digestion of leghaemoglobin by carboxypeptidase, and partly inhibited by catalase and superoxide dismutase.     

Equipoise, knowledge and ethics in clinical research and practice

It is widely maintained that a clinical trial is ethical only if some form of equipoise between the treatments being compared obtains. To be in equipoise between two treatments A and B is to be cognitively indifferent between the statement 'A is strictly more effective than B' and its negation. It is natural to claim that equipoise regarding A and B is necessary for randomised assignment to treatments A and B to be beneficent and non-maleficent and is sufficient for such an assignment to be fair. Cashing this out precisely is difficult, and various forms of equipoise have been discussed which consider whose equipoise is relevant to the decision. This is to make judgement of equipoise something to be managed socially, while its prima facie significance is supposedly cognitive. Recent reconstructions of equipoise-like concepts in epistemology give clues about how to understand equipoise cognitively. In this paper I examine some of this work and discuss how successful it has been. I suggest that while this work is promising, it still has far to go, and that while equipoise remains the best theory we have of the cognitive justification for clinical trials, it is nonetheless incoherent.     

Failure to Maintain Glycolysis in Anoxic Nerve Terminals

Synaptosomal glycolysis is stimulated eight- to 10-fold when the respiratory chain is inhibited by cyanide or by anoxia. However, the stimulation is transient and after 15 min declines toward the preanoxic rate. The decline is not seen when Ca2+ is absent or when the respiratory chain is inhibited by rotenone. The decline in glycolysis is reversible, is not due to substrate exhaustion, and is the cause, rather than the effect, of lowered synaptosomal ATP/ADP ratios. The failure to maintain glycolysis when the terminal oxidase of the respiratory chain is inhibited may have relevance to the sensitivity of the brain to anoxic damage.     

Coalescent-based DNA barcoding: multilocus analysis and robustness

DNA barcoding is the assignment of individuals to species using standardized mitochondrial sequences. Nuclear data are sometimes added to the mitochondrial data to increase power. A barcoding method for analysing mitochondrial and nuclear data is developed. It is a Bayesian method based on the coalescent model. Then this method is assessed using simulated and real data. It is found that adding nuclear data can reduce the number of ambiguous assignments. Finally, the robustness of coalescent-based barcoding to departures from model assumptions is studied using simulations. This method is found to be robust to past population size variations, to within-species population structures, and to designs that poorly sample populations within species. Supplementary Material is available online at www.liebertonline.com/cmb.     

Analytical studies of injury criteria for the thorax

The viscous criterion is a recently developed criterion to assess injury severity of the human thorax. In the viscous criterion, the peak viscous response, which is defined as the maximum product of deformation velocity and compression of an object, is proposed as a predictor of injury risk. However, the physical meaning of the criterion is not very clear. In this paper, the mathematical properties of the viscous criterion are analyzed. A mechanical thorax model is then used to relate the criterion to the physical quantities of the model using energy concepts. It is found that the so-called peak viscous response is strongly related to the peak energy storing rate of the thorax which is not related to the viscosity of the thorax. It is also shown that the viscous response of the thorax is given by the integral of the velocity squared with respect to time. The analysis is further expanded to a more general case to result in four criteria based upon the energy concepts. A hypothesis for injury assessment is proposed by using the four criteria.     

A scheme for binocular depth perception suggested by neurophysiological evidence

A scheme suggested by neurophysiological evidence is proposed to account for the perceptual phenomena related to binocular stereopsis, especially those observed with Julesz' random stereograms. In the scheme, monocular local features are extracted first. Then the correspondence between the left and right local features is searched for. The correspondence is not one-to-one in general. Thus a sort of direction column due to Blakemore is formed. Each unit in the column is binocular and the receptive field belonging to one eye is located in the same part of the visual field as long as the unit belongs to the same column. However, the receptive fields belonging to the other eye are horizontally displaced to one another. That is, each unit is characterized by binocular disparity. If the correspondence is not one-to-one, then several units belonging to the same column respond simultaneously. Binocular stereopsis can be established if one-to-one correspondence is determined to yield global three dimensional regions. The determination of one-to-one correspondence is carried out through a sort of laterally interacting circuitry in the disparity domain. After the determination of local correspondence, three dimensional global regions are formed by detecting the boundary and by filling-in occluded regions. The results of computer simulation are presented regarding Julesz' stereograms with various types of perturbation. Furthermore, the case of random-dot stereogram in which there is a size difference between the left and right images is simulated. Finally, the computer simulation related to the hysteresis in binocular depth perception is carried out.     

Genetic Control of Phosphorus Assimilation in NEUROSPORA CRASSA: Dose-Dependent Dominance and Recessiveness in Constitutive Mutants

Mutants called nuc-1c, constitutive for alkaline phosphatase synthesis, were isolated and mapped very close to nuc-1 mutants in which this enzyme is not expressed. nuc-1 is epistatic to nuc-1c. nuc-1c acts only if it is cis to normal nuc-1 function. The preparation of partial diploids heterozygous for various nuc-1 alleles is described; nuc-1c is dominant to nuc-1+, which in turn is dominant to nuc-1. In heterocaryons with nuc-1+, nuc-1c is dominant when it is present in high proportion, but essentially recessive if it is present in low proportions. In heterocaryons with nuc-1, nuc-1c is again dominant when present in high proportions, but in low proportions it "complements" to give essentially normal repressibility. A model of regulation consistent with these findings is presented.     

国内某低品位难选铜矿的生物浸出研究

目的:微生物湿法冶金技术是一种有效回收难处理常规选矿方法难以处理的复杂矿中金属的方法,本研究旨在利用该工艺处理国内某低品位(0.67%)难选铜矿,提高铜的回收率。方法:首先,从某矿山富集得到中温富集物,其次,对该矿石进行生物浸出,同时优化浸出过程工艺参数。结果:所富集得到的中温富集物最适生长温度为30℃,最适pH值为1.9。在摇瓶中浸出难选铜矿时,最佳摇床转速为180 r/min,最优充气强度为360 mL/min,10天内难选铜矿中铜的浸出率可以达到92%。结论:该中温富集物具有较好地浸出难选铜矿的能力。     

The kinetics of hemolytic plaque formation. III. Inhibition of plaques by antigen.

Equations are presented which can be used to describe the inhibition of plaques by multifunctional antigen which binds γG antibody bivalently. The interaction is treated as a bimolecular reaction which is irreversible within the time of the experiment. It is shown that under these conditions the characteristics of the inhibition curve, and their relationship to kinetic and thermodynamic parameters are strongly dependent upon how antibody interacts with RBCs. When the epitope coating is dense, multivalent attachment of antibody is likely and the interaction is considered irreversible. When the epitope coating is sparse, only rapid, reversible univalent attachment is considered and local equilibrium is assumed to hold.The first case leads to an abrupt inhibition curve whose position is determined by the forward rate constant and RBC density. The second case leads to broad asymmetric curves. For this situation the relation between the extent of inhibition and the affinity of the population is generally complicated and reliable affinity information is difficult to obtain. This is contrasted to results obtained previously for unifunctional inhibitors from which reliable affinity information can, in principle, be obtained. The results emphasize the need for carefully designed experiments if affinity information is to be obtained from inhibition studies.     

Cysteinesulfonate and beta-sulfopyruvate metabolism. Partitioning between decarboxylation, transamination, and reduction pathways

L-Cysteinesulfonate (L-cysteate) is present in plasma, urine, and tissues in concentrations comparable to that of L-cysteinesulfinate, the primary oxidative metabolite of L-cysteine. Although cysteinesulfonate is known to be decarboxylated to taurine by cysteinesulfinate decarboxylase, the occurrence and importance of other metabolisms has not been examined. The present studies indicate that cysteinesulfonate partitions in vivo between decarboxylation and transamination; the latter reaction is catalyzed by aspartate aminotransferase and yields beta-sulfopyruvate. Whereas beta-sulfinylpyruvate, the product of cysteinesulfinate transamination, decomposes spontaneously, beta-sulfopyruvate is stable and is reduced by malate dehydrogenase to beta-sulfolactate. When L-[1-14C]cysteinesulfonate is given to mice, 60-75% is decarboxylated to taurine and about 25% is excreted in the urine as beta-sulfolactate. beta-Sulfo[1-14C] pyruvate is found to partition about equally between beta-sulfolactate and cysteinesulfonate formation; greater than 90% of the latter is decarboxylated. Parenterally administered beta-sulfo[1-14C]lactate is mostly excreted in the urine, but 12% is metabolized via beta-sulfopyruvate and cysteinesulfonate to 14CO2 and taurine. beta-Sulfopyruvate is not excreted, and only traces of sulfoacetate, perhaps formed by oxidative decarboxylation, are detected. These studies establish that cysteinesulfonate, beta-sulfopyruvate, and beta-sulfolactate are reversibly interconverted in vivo. Since only cysteinesulfonate is directly metabolized to CO2, the rate of 14CO2 formation from L-[1-14C]cysteinesulfonate is a valid measure of total cysteinesulfinate decarboxylase activity in vivo; use of this assay permits inhibitor effects to be accurately determined in intact mice. Thus, whereas in vitro assays indicate that beta-methyleneaspartate inhibits brain, liver, and kidney cysteinesulfinate decarboxylase by 0, greater than 60, and 90%, respectively, in vivo studies with L-[1-14C]cysteinesulfonate show net metabolic inhibition is about 40%.     

Site of graviperception in roots: a re-examination

Two lines of evidence have been cited to support the assertion that the root cap is the sole site of graviperception in the root. The first evidence is based on surgical removal of the cap, which abolishes the response to gravity. This is sufficient to conclude that the cap is involved in gravitropism, but not to conclude that the cap is the site of graviperception. The second is based on the results of centrifugation experiments, in which different parts of the plant are subjected to different centrifugal forces. The data from such experiments have been cited to support the conclusion that the perception of gravity is limited to the rootcap. However, these data actually support the conclusion that gravity is perceived throughout the root tip, and not only in the root cap. We believe that the data support the conclusion that the root cap is involved in root gravitropism, but that there is inadequate evidence to conclude that the cap is the sole site of graviperception.     

Characterization of two different Ly-1+ T cell populations that mediate delayed-type hypersensitivity

This paper describes two functionally different T cell populations that mediate delayed-type hypersensitivity (DTH) reactions in contact-sensitized mice. Both of these T cells are Ly-1+, Qa-2-, and Vicia villosa lectin nonadherent. One of these T cell subpopulations is responsible for the classical 24- to 48-hr component of DTH reactions, is induced 3 to 4 days after immunization, is H-2 restricted, is sensitive to irradiation and to antigen-specific T cell-derived suppressor factors, and is found in nylon wool-nonadherent as well as nylon wool-adherent populations. In contrast, the T cell population that is responsible, via an antigen-specific T cell factor, for a recently described early component of DTH, which is an obligatory initial step for expression of DTH, is induced within 24 hr after immunization, requires much less antigen for immunization, is not H-2 restricted, is not sensitive to irradiation nor to T suppressor factors, and is found exclusively in the nylon wool-nonadherent fraction. These results support a new formulation of DTH. According to this formulation, Ly-1+ T cells produce an antigen-specific, tissue-sensitizing, mast cell-activating factor, and via this factor induce the early component of DTH, which is an obligatory first step in which local antigen challenge induces increased local vascular permeability. This required opening of gaps between endothelial cells is due to T cell factor-dependent release of the vasoactive amine serotonin from cells such as mast cells. This first step allows the second, H-2-restricted, Ly-1+ T cell population to enter the reaction site, and to then be triggered by antigen to release lymphokines that attract the subsequent influx of blood-borne, bone marrow-derived leukocytes to constitute the classical delayed-in-time component of DTH reactions.     

Characterisation of PduS, the pdu metabolosome corrin reductase, and evidence of substructural organisation within the bacterial microcompartment

PduS is a corrin reductase and is required for the reactivation of the cobalamin-dependent diol dehydratase. It is one component encoded within the large propanediol utilisation (pdu) operon, which is responsible for the catabolism of 1,2-propanediol within a self-assembled proteinaceous bacterial microcompartment. The enzyme is responsible for the reactivation of the cobalamin coenzyme required by the diol dehydratase. The gene for the cobalamin reductase from Citrobacter freundii (pduS) has been cloned to allow the protein to be overproduced recombinantly in E. coli with an N-terminal His-tag. Purified recombinant PduS is shown to be a flavoprotein with a non-covalently bound FMN that also contains two coupled [4Fe-4S] centres. It is an NADH-dependent flavin reductase that is able to mediate the one-electron reductions of cob(III)alamin to cob(II)alamin and cob(II)alamin to cob(I)alamin. The [4Fe-4S] centres are labile to oxygen and their presence affects the midpoint redox potential of flavin. Evidence is presented that PduS is able to bind cobalamin, which is inconsistent with the view that PduS is merely a flavin reductase. PduS is also shown to interact with one of the shell proteins of the metabolosome, PduT, which is also thought to contain an [Fe-S] cluster. PduS is shown to act as a corrin reductase and its interaction with a shell protein could allow for electron passage out of the bacterial microcompartment.     

Risk avoidance and nesting strategies

Gillespie (1974,1975) has shown that selection will tend to minimize variance in offspring number. It is shown that this effect is due to selection maximizing the average number of surviving offspring when there is density-dependent survival, and that it is unnecessary to invoke principles such as minimizing the variability of fitness (Real, 1980). The effect of this principle of selecting for laying several small clutches rather than one large clutch when there is predation on whole clutches is investigated. It is found that the selection pressure is weak, contrary to the conclusion of Rubenstein (1982), and is unlikely to be of evolutionary importance.     

Two types of hormone-responsive adenylate cyclase in the rat liver

We have demonstrated the existence of two types of hormone-responsive adenylate cyclase in the isolated perfused rat liver. One, less abundant, is linked to glycogenolysis and the other is not. Glucagon stimulates mainly the glycogenolysis-linked fraction and, to a lesser extent, the fraction which is not linked to glycogenolysis. The suppressive effect of insulin is specific for the glucagon-responsive adenylate cyclase and is inhibited by 3-isobutyl-1-methylxanthine (IBMX). However, this mechanism can explain only partly the ability of insulin to suppress glycogenolysis, and is not observed when cAMP is increased sufficiently by glucagon. Secretin-responsive adenylate cyclase is not linked to glycogenolysis and is suppressed specifically by oxymetazoline. The capacity of this suppressive effect is large and not inhibited by IBMX. These results suggest that there is a functional compartmentalization of cAMP within the hepatocyte or among hepatocytes.     

A transient histone hyperacetylation signal marks nucleosomes for remodeling at the PHO8 promoter in vivo.

Chromatin remodeling of the yeast PHO8 promoter requires the SAGA histone acetyltransferase complex. We report here that SAGA is necessary and sufficient to establish an activator-dependent hyperacetylation peak over the PHO8 promoter that is restricted to those nucleosomes that are remodeled upon activation. This local hyperacetylated state is observed upon activation in the absence of the SWI/SNF complex when the remodeling process is frozen subsequent to activator binding. Hyperacetylation is lost, however, if remodeling is permitted to go to completion. Thus, a transient histone hyperacetylation signal is shown to be a prerequisite for, and determinant of, the domain of nucleosome remodeling in vivo.     

Aspects of the Clausius-Shannon Identity: Emphasis on the components of transitive information in linear,branched and composite physical systems

In this paper I consider how information is required to specify various systems. It is shown that the transitive information of any physical system, is distributed among three distinct components. One of these, the selective component, is required to specify the elemental parts of the system. Another, the connective component, is required to specify the macrostructure of the system; that is the way the parts are put together. And a third, the conformative component, is required to specify the intrinsic complexion or microstructure of the system. An interesting method for analyzing branched systems which takes account of connective ambiguity is described in some detail. The relationship between information and entropy, known as the Clausius-Shannon Identity, is then discussed with reference to selected thermodynamic models: and that aspect of information which is often overlooked, namely the distinction, between transitive and intransitive information is highlighted. The applications (or perhaps more correctly, the limitations of applying this treatment) to problems of biological interest are also indicated.     

Darwinian selection leads to Gaia

The Gaia hypothesis, in its strongest form, states that the Earth's atmosphere, oceans, and biota form a tightly coupled system that maintains environmental conditions close to optimal for life. According to Gaia theory, optimal conditions are intrinsic, immutable properties of living organisms. It is assumed that the role of Darwinian selection is to favor organisms that act to stabilize environmental conditions at these optimal levels. In this paper, an alternative form of Gaia theory based on more traditional Darwinian principles is proposed. In the new approach, environmental regulation is a consequence of population dynamics, not Darwinian selection. The role of selection is to favor organisms that are best adapted to prevailing environmental conditions. However, the environment is not a static backdrop for evolution, but is heavily influenced by the presence of living organisms. The resulting co-evolving dynamical process eventually leads to the convergence of equilibrium and optimal conditions. A simple Daisyworld model is used to illustrate this convergence phenomenon. Sensitivity analysis of the Daisyworld model suggests that in stable ecosystems, the convergence of equilibrium and optimal conditions is inevitable, provided there are no externally driven shocks to the system. The end result may appear to be the product of a cooperative venture, but is in fact the outcome of Darwinian selection acting upon "selfish" organisms.     

Strong-polar mutations in the transferase gene of the galactose operon in E.coli

Summary A class of mutations in the transferase gene of the galactose operon in E. coli is described, which is strongly polar for the synthesis of kinase. The latter enzyme is made only to the extent of about 0.1% of the amount made in the induced wildtype. This amount is not dependent on the map position of the mutations and the residual synthesis is non-inducible. The mutants thus resemble 0° mutants in the same operon.Epimerase, which is coded for by the gene proximal to the transferase gene with respect to the operator, is made in normal amounts and its synthesis is normally inducible.The mutants do not seem to belong either to the nonsense or to the frameshift class on the basis of reversion pattern, suppressibility, and degree of polarity. The possible nature of the mutations is discussed.