Women of Belize: Gender and Change in Central America

Women of Belize: Gender and Change in Central America. Irma McClaurin. New Brunswick, NJ: Rutgers University Press, 1996.218 pp.     

The effect of calcium on the respiratory responses of mung bean mitochondria.

Purified mung bean hypocotyl mitochondria were examined for their capacity to carry out respiration-dependent accumulation of calcium. The addition of 0.1-1.0 mM calcium to mung bean mitochondria supplemented with succinate gave no stimulation of state 4 respiration even in the presence of inorganic phosphate and the ionophoretic antibiotic A-23187. Even at high calcium concentrations, no transient changes in the respiratory activity occurred and subsequent addition of ADP initiated a further state 3 response. Although the additions of calcium resulted in a rapid H+ ejection, it was insensitive to lanthanum and uncoupling agents. Similarly, additions of calcium failed to initiate any transient changes in the oxidation-reduction states of either pyridine nucleotides or cytochrome b. Direct spectrophotometric recordings of absorbance changes of murexide revealed no respiration-linked calcium transport. It is proposed that although mung bean mitochondria possess a respiration-linked electrochemical potential gradient it would appear that this potential cannot be expressed as calcium transport even at high ion concentrations, probably due to a low calcium membrane permeability.     

On continuous-time capture-recapture in closed populations

Schofield et al. (2018, Biometrics 74, 626–635) presented simple and efficient algorithms for fitting continuous-time capture-recapture models based on Poisson processes. They also demonstrated by real examples that the standard method of discretizing continuous-time capture-recapture data and then fitting traditional discrete-time models may lead to information loss in population size estimation. In this article, we aim to clarify that key to the approach of Schofield et al. (2018) is the Poisson model assumed for the number of captures of each individual throughout the study, rather than the fact of data being collected in continuous time. We further show that the method of data discretization works equally well as the method of Schofield et al. (2018), provided that a Poisson model is applied instead of the traditional Bernoulli model to the number of captures for each individual on each sampling occasion.     

Involvement of iron in the biogenesis of the cyanide-insensitive respiration in the yeast Saccharomycopsis lipolytica

The involvement of iron in the biogenesis of the cyanide-insensitive respiration in the yeast Saccharomycopsis lipolytica has been established on the following basis: (1) endogenous metal chelation by either benzyl- or salicylhydroxamic acid, EDTA or nitrilotriacetate prevented the biogenesis of the cyanide-insensitive respiratory pathway in S. lipolytica. (2) Addition of Fe(III) during the biogenesis increased both the rate of the appearance of the alternative respiratory pathway and its extent. Neither Fe(II), nor Co(II), Cu(II), Al(III), La(III), Mn(II) or Mg(II) could substitute for Fe(III). (3) The biogenesis of the alternative respiratory pathway could be dissociated into two steps: (a) a first one, slow, cycloheximide-sensitive, temperature-dependent, iron-independent, leading to cells still fully cyanide-sensitive, presumably involving the de novo biosynthesis of an inactive protein moiety and (b) a second step, fast, iron-dependent, temperature-independent, cycloheximide-insensitive, leading to cells with a cyanide-insensitive respiration, presumably the activation by iron of the inactive precursor.     

Attempted asymmetric electrochemical reductions in magnetic fields

Because of negative, ambiguous or controversial results claimed by previous investigators studying the potential efficacy of magnetic fields in directing asymmetric syntheses and because of its potential importance as regards the origin of optical activity, we have attempted to confirm a recent report by Takahashiet al. (1986), who claimed that phenylglyoxylic acid (XIX) may be reduced electrochemically at a mercury cathode placed in a magnetic field of 0.168 T to optically active mandelic acid (XX), with optical yields favoring the S(+)-XX enantiomer as high as 25%. We have found that the complete reduction of XIX in pH 3.8 acetate buffer at a mercury cathode in magnetic fields of either 0.14 or 7.05 T leads only to racemic XX products. The earlier literature describing attempted absolute asymmetric syntheses in magnetic, electric and gravitational fields is briefly and critically reviewed.