Effect of chilling on the diurnal rhythm of enzymes involved in protection against oxidative stress in a chilling-tolerant and a chilling-sensitive maize genotype

The effect of chilling on diurnal changes in activity of adenosine 5'-phosphosulfate sulfotransferase, glutathione reductase (EC 1.6.4.2) and glutathione transferase (EC 2.5.1.18) was analysed in the second leaf of Z 7, a chilling-tolerant, and Penjalinan, a chilling-sensitive maize (Zea mays L.) genotype. Nitrate reductase (EC 1.6.6.1) was measured for comparison. All enzyme activities examined changed with a typical diurnal rhythm in both genotypes cultivated at 25°C. Adenosine 5'-phosphosulfate sulfotransferase and nitrate reductase activity peaked during the light period, then decreased and reached lowest levels at the end of the dark period. Glutathione reductase activity increased in the dark and decreased during the light period. Maximum glutathione transferase activities were measured in the middle of the light period, minimal ones in the middle of the dark period. At 12°C these diurnal changes were eliminated in all enzymes examined of both genotypes.
The average adenosine 5'-phosphosulfate sulfotransferase and glutathione reductase activity were higher in the chilling-tolerant Z 7 than in the sensitive Penjanilan at 12°C in the light. Increased levels of both enzymes may contribute in establishing increased levels of cysteine and reduced glutathione in the chilling-tolerant Z 7. Indeed it has been shown before that the chilling-tolerant maize genotypes contain higher levels of both compounds at low temperatures than chilling-sensitive ones.     

Application of Reference Data for Assessing and Restoring Headwater Ecosystems

Attributes of 25 headwater streams and their associated wetlands were quantitatively sampled in the inner coastal plain of eastern North Carolina. Data from these sites were used to construct and test one functional assessment model (biogeochemical cycling) using the hydrogeomorphic (HGM) approach. Of the 25 sites sampled, 16 unaltered sites were used to establish standards against which field indicators could be compared (indexed). Nine altered sites were used to examine the sensitivity of the model to assess the types of alterations typically inflicted upon headwater ecosystems in eastern North Carolina: channelization, logging, construction of cross-floodplain ditches to shunt water directly from uplands to the main stream channel, and conversion of stream floodplains and buffer zones to cropland. Of 30 field indicators measured that potentially could be used to model alterations to hydrologic regime and biomass stocks, we found six were robust in assessing conditions related to biogeochemical cycling. Hydrologic indicators used in the model included: (1) presence/absence of channelization, (2) presence/absence of cross-floodplain ditches, and (3) a measure of buffer condition (using width and quality). Biomass indicators included: (4) total basal area of trees, (5) percent litter cover, and (6) volume of coarse woody debris. Our preliminary biogeochemical cycling model using these six variables was sensitive to alterations in nine altered sites and to a suite of hypothetical restorations of the most altered site. However, in order to improve accuracy of our preliminary model, it should be validated with studies designed to measure how alterations of various types and magnitudes affect biogeochemical processes.     

Remembering Our Indian School Days: The Boarding School Experience

Remembering Our Indian School Days: The Boarding School Experience. Heard Museum, Phoenix. November 2000-05     

The mechanism of the cryoprotective effect of glycerol in beetles tolerant to freezing

The mechanism of the cryoprotective effect of glycerol has been studied experimentally on freezetolerant Pytho depressus beetles. The lowest tolerated temperature of the beetles was determined as a function of their pre-freezing glycerol concentration. The temperatures, at which the potentially harmful non-penetrating solutes would reach the injurious level in the frozen body fluid were estimated for solutions with different pre-freezing concentrations of glycerol, assuming a colligative effect of glycerol. The lowest tolerated temperature of the beetles ranged from ?7.5 C for beetles lacking glycerol to ?27 C for beetles having a pre-freezing glycerol concentration of 1500 mmolal in their body fluid. The estimated temperatures fitted these observations almost perfectly. Thus, the results support the view that the cryoprotective effect of glycerol in freeze-tolerant beetles is based on the colligative properties of the substance.     

The positive correlation between avian species richness and human population density in Britain is not attributable to sampling bias

Aim  To assess whether spatial variation in sampling effort drives positive correlations between human population density and species richness.
Location  British 10 × 10 km squares.
Methods  We calculated three measures of species richness from atlas data of breeding birds in Britain: total species richness, species richness standardised for sampling effort, and the number of species only recorded in supplementary casual records in a manner not standardised for survey effort. We then assessed the form of the relationship between these richness estimates and human population density, both with and without taking spatial autocorrelation into account.
Results  Both total and standardised species richness exhibit similar species richness–human population density relationships; species richness generally increases with human population density, but decreases at the very highest densities. Supplementary species richness is very weakly correlated with human population density.
Main conclusions  In this example, sampling effort only slightly influences the form of species richness–human population density relationships. The positive correlation between species richness and human population density and any resultant conservation conflicts are thus not artefactual patterns generated by confounding human density and sampling effort.     

Cyclic insulin-regulated aminopeptidase (IRAP)/AT4 receptor ligands.

The angiotensin IV receptor (AT4 receptor) is the insulin-regulated aminopeptidase enzyme (IRAP, EC 3.4.11.3). This membrane-spanning enzyme belongs to the M1 family of zinc-dependent metallo-peptidases. It has been proposed that AT4 receptor ligands exert their physiological effects by binding to the active site of IRAP and thereby inhibiting the catalytic activity of the enzyme. The biological activity of a large series of linear angiotensin IV analogs was previously disclosed. Herein, the synthesis and biological evaluation of a series of angiotensin IV analogs, encompassing macrocyclic ring systems of different sizes, are presented. It is demonstrated that disulfide cyclizations of angiotensin IV can deliver ligands with high IRAP/AT4 receptor affinity. One ligand, with an 11-membered ring system (4), inhibited human IRAP and aminopeptidase N (AP-N) activity with similar potency as angiotensin IV but was considerably more stable than angiotensin IV toward enzymatic degradation. The compound provides a promising starting point for further optimization toward more drug-like derivatives. The cyclic constrained analogs allowed us to propose a tentative bioactive conformation of angiotensin IV and it seems that the peptide adopts an inverse gamma-turn at the C-terminal.     

IADS, a decomposition product of DIDS activates a cation conductance in Xenopus oocytes and human erythrocytes: new compound for the diagnosis of cystic fibrosis.

DIDS (4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid) is a commonly used blocker of plasma membrane anion channels and transporters. We observed that DIDS undergoes decomposition while stored in DMSO (dimethyl sulfoxide) forming a biologically active compound. One decomposition product, called IADS, was identified and synthesized. Voltage-clamp and patch clamp experiments on Xenopus laevis oocytes and human erythrocytes revealed that IADS is able to activate a plasma membrane cation conductance in both cell types. Furthermore, we found that IADS induces hemolysis in red blood cells of healthy donors but fails to hemolyze erythrocytes of donors with cystic fibrosis. Thus, IADS stimulated activation of a cation conductance could form the basis for a novel diagnostic test of cystic fibrosis.     

COMPARATIVE CYTOLOGY OF ULOTHRIX AND STIGEOCLONIUM1

This investigation describes the cytology of the ulotrichalean genera Ulothrix and Stigeoclonium. Cellular organization is similar to the degree that interphase cells of the 2 genera cannot be distinguished with certainly. In Stigeoclonium, the nuclear envelope becomes disrupted at the end of prophase, and centrioles enter the nucleoplasm. At metaphase the nuclear envelope is again intact, and some of the spindle tubules appear to be contiguous with the nuclear envelope. The spindle in Ulothrix is essentially open with, no attachment of spindle tubules to the nuclear envelope and with, centrioles on the spindle-cytoplasm interface at the spindle poles. Spindle poles are blunt in Stigeoclonium and pointed in Ulothrix. Cytokinesis is by cell plate formation in both genera, but there is no phragmoplast.     

The phenoloxidases of the Ascomycete Podospora anserina

Summary In order to learn the internal conditions for the production of the various phenoloxidases produced by the Ascomycete Podospora anserina the wild strain has been grown under controlled conditions in a fermenter for a period of 34 days. Samples were withdrawn at regular intervals and assayed for mycelial yield and intra- and extracellular phenoloxidase production.Maximal yield was obtained at the following age of the culture: Mycelial production 9 d, tyrosinase 4 d, the high molecular weight laccase I between 9 and 19 d. The low molecular weight laccases II and III, initially present in medium concentrations, dropped to an early minimum after 4 days, followed by an increase with a maximum in the late autolytic phase.The changes in the phenoloxidase spectrum and the antiparallel production curve for the high molecular weight against the low molecular weight laccases are discussed in relation to the earlier observed genetical and physiological control of phenoloxidase synthesis and in relation to the possibility of laccase I being composed of active subunits of low molecular weight laccases.With support of the Deutsche Forschungsgemeinschaft, Bad Godesberg (Germany).