Effects of temperature on the energy budgets of Hydra pseudoligactis

Summary Dry matter, nitrogen, and energy budgets were determined for laboratory cultures of Hydra pseudoligactis reared at 10, 15, 20, and 25° C, and fed freshly collected zooplankton. Maximum specific feeding rates increased from 0.24 to 0.91 (KJ food/KJ Hydra) with increasing rearing temperature. The corresponding growth rates increased from 0.14 to 0.29 but gross (growth/ingestion), net (growth/(ingestion-egestion)), and assimilation (gross/net) efficiencies decreased with increasing temperatures. The requisite food densities to maintain maximum ingestion rates (when permitted to feed for 3 hrs day^-1) increased from 0.0056 to 0.021 KJ of zooplankton/KJ of Hydra. The combination of increasing energy requirements, decreasing food supply, and efficiencies of food utilization, with increasing water temperatures may contribute to the rapid declines of Hydra populations that are often observed in temperate lakes.Financial support was provided by the Youngstown State University Research Council, Grant Number 287 and a Grand-in-Aid of Research to W.C. from Sigma Xi, The Scientific Research Society of North America. George Mateja and Karen Gates helped with the laboratory and field work. The Mahoning Valley Sanitary District, Mr. John Tucker, Chief Engineer, provided facilities and access to Meander Creek Reservoir. The figures were prepared by Ms. Susan Geer, Youngstown State University Media Center     

Genetic and Molecular Analysis of cglB, a Gene Essential for Single-Cell Gliding in Myxococcus xanthus

Gliding movements of individual isolated Myxococcus xanthus cells depend on the genes of the A-motility system (agl and cgl genes). Mutants carrying defects in those genes are unable to translocate as isolated cells on solid surfaces. The motility defect of cgl mutants can be transiently restored to wild type by extracellular complementation upon mixing mutant cells with wild-type or other motility mutant cells. To develop a molecular understanding of the function of a Cgl protein in gliding motility, we cloned the cglB wild-type allele by genetic complementation of the mutant phenotype. The nucleotide sequence of a 2.85-kb fragment was determined and shown to encode two complete open reading frames. The CglB protein was determined to be a 416-amino-acid putative lipoprotein with an unusually high cysteine content. The CglB antigen localized to the membrane fraction. The swarming and gliding defects of a constructed DeltacglB mutant were fully restored upon complementation with the cglB wild-type allele. Experiments with a cglB allele encoding a CglB protein with a polyhistidine tag at the C terminus showed that this allele also promoted wild-type levels of swarming and single-cell gliding, but was unable to stimulate DeltacglB cells to move. Possible functions of CglB as a mechanical component or as a signal protein in single cell gliding are discussed.     

Kinetic and Energetic Model for the Primary Processes in Photosystem II

A detailed model for the kinetics and energetics of the exciton trapping, charge separation, charge recombination, and charge stabilization processes in photosystem (PS) II is presented. The rate constants describing these processes in open and closed reaction centers (RC) are calculated on the basis of picosecond data (Schatz, G. H., H. Brock, and A. R. Holzwarth. 1987. Proc. Natl. Acad. Sci. USA. 84:8414-8418) obtained for oxygen-evolving PS II particles from Synechococcus sp. with ~80 chlorophylls/P₆₈₀. The analysis gives the following results. (a) The PS II reaction center donor chlorophyll P₆₈₀ constitutes a shallow trap, and charge separation is overall trap limited. (b) The rate constant of charge separation drops by a factor of ~6 when going from open (Q-oxidized) to closed (Q-reduced) reaction centers. Thus the redox state of Q controls the yield of radical pair formation and the exciton lifetime in the Chl antenna. (c) The intrinsic rate constant of charge separation in open PS II reaction centers is calculated to be ~2.7 ps^-1. (d) In particles with open RC the charge separation step is exergonic with a decrease in standard free energy of ~38 meV. (e) In particles with closed RC the radical pair formation is endergonic by ~12 meV. We conclude on the basis of these results that the long-lived (nanoseconds) fluorescence generally observed with closed PS II reaction centers is prompt fluorescence and that the amount of primary radical pair formation is decreased significantly upon closing of the RC.     

Influence of chirality,amino acid sequence,and protecting groups on the intramolecular interaction behavior of dipeptide and tripeptide derivatives

The intramolecular interaction of protected dipeptides and tripeptides containing the amino acid units Ala, Phe, and Val was studied by means of ir spectroscopy. The NH and CO regions of the compounds dissolved in carbon tetrachloride clearly show the existence of different intramolecular hydrogen bonds. Using solvents with higher polarity such as chloroform and methylene chloride, the association bands disappear. Investigating the substances with the same amino acid sequence but opposite chirality of the central C atom in the peptide chain, we observed different band shapes in the CO and NH regions. Large effects were found when the chirality of the Phe unit in the second position was changed. This is probably due to the steric hindrance originated by the rotation of the aromatic ring in the side chain. The protecting groups, Z (benzyloxycarbonyl) or Boc (tert-butyloxycarbonyl) residues at the N-terminal group and methyl- or tert-butyl esters at the C-terminal group, influence the solubility of the substances in nonpolar solvent, as well as the NH and CO association band profiles in the methylene chloride solutions. The consequences of changing the sequence of the amino acids are discussed for the tripeptide derivatives. Besides a qualitative discussion, some quantitative considerations concerning the intramolecular interaction are also given to illustrate the different stabilities of the associates. © 1996 John Wiley & Sons, Inc.     

Comparative morphology of the head of selected sporophagous and non‐sporophagous aleocharinae (Coleoptera: Staphylinidae): Musculature and hypopharynx‐prementum complex

To investigate whether specialization to spore‐ (or pollen‐) feeding in advanced Aleocharinae is mirrored by their head anatomy, we compiled and compared synchrotron X‐ray micro‐tomography datasets for 11 Aleocharinae in conjunction with previous data for two aleocharine and six outgroup species (two nonstaphylinids, four staphylinids). We describe the presence/absence of head muscles and investigate the variability of points of origin by character mapping analyses. Monophyly of Aleocharinae is supported by the absence of M. 48 (M. tentoriobuccalis anterior), and by changes in the origins of Mm. 1, 2, 17, 18, 28, 29, 30. Within Aleocharinae the origins of the labial muscles (Mm. 28–30) have shifted posteriorly to the gula, which might enhance the movement posterad of the hypopharynx and partly compensate for the loss of M. 48. We also analyzed the general organization of the hypopharynx‐prementum complex and the fine structure of the mandibles through SEM studies. In the absence of grinding mandibular molae like those of most mycophagous Coleoptera, seven aleocharine species studied have evolved “pseudomolae” at the ventral side of the mandibles that replace true molae as secondary grinding surfaces. In these species, the hypopharynx is elevated and displaced anteriorly, bearing a bowl‐like depression on its surface that functions as a mortar where spores are ground between the hypopharynx and the mandibles. Two of these species are not yet known to feed on spores or pollen. Another species (Oxypoda alternans) is thought to feed on fungus material but bears no pseudomolae on its mandibles. J. Morphol. 271:910–931, 2010. © 2010 Wiley‐Liss, Inc.     

Investigation of the reaction of peroxynitrite with propofol at acid pH: predominant production of oxidized, nitrated, and halogenated derivatives.

We reported here the reaction, in acidic conditions, of peroxynitrite (ONOO(-)) with the anaesthetic agent propofol (2,6-diisopropylphenol, PPF). The most interesting finding is that peroxynitrite is able to nitrate and to oxidize propofol leading to 4-nitropropofol, quinone, and diphenylquinone as the major products. More surprisingly, we also found that peroxynitrite is capable of halogenating propofol in the presence of halide ions, suggesting the formation of nitrosyl chloride (NOCl) or nitryl chloride (NO(2)Cl) from the reaction of peroxynitrite with chloride ions. A significant enhancement of the halogenation yield is observed with a simultaneous decrease of the yields of the other products in the presence of methanol or hydrogen peroxide. Increased halogenation of PPF probably results from the formation of peroxynitrate (O(2)NOO(-)), that further oxidizes chloride ions in hypochlorous acid (HOCl) or molecular chlorine (Cl(2)). Spontaneous decay of peroxynitrate is relatively slow in acidic medium, thus explaining the decrease of the yields of the other products. By direct EPR techniques, we also observed that this reaction occurs via a radical pathway.     

Low diversity but high differentiation: the population genetics of Aglaope infausta (Zygaenidae: Lepidoptera)

Aim Aglaope infausta is a thermophilous Zygaenid of Atlanto-Mediterranean origin, distributed in Portugal, Spain, France and north-western Italy reaching its north-eastern distribution limit in western Germany. The local, regional and inter-regional genetic structure of this species is studied in this analysis. Location and methods The allozymes of 456 individuals from 12 populations (11 from western Germany and one from southern Portugal) were studied by electrophoresis. Results Six of the 19 loci analysed were monomorphic. Genetic differentiation between populations was high (F_ST: 0.404), while the mean genetic diversity was low (H_e: 3.4%). Most (96.5%) of the genetic variance between populations was between the Portuguese and the German samples, but also the differentiation within Germany was considerable (F_SR: 0.101). In Germany, A. infausta occurs in two major regions (middle Rhine and Nahe) that are geographically separated, and 55.5% of the genetic variance was found between these two regions. The populations of both areas do not differ in their genetic diversity, but those of the middle Rhine have significantly higher genetic distances among them than the Nahe populations (0.020 and 0.015, respectively). F_ST was also higher in the middle Rhine region than in the Nahe region (0.089 and 0.045, respectively). Main conclusions Aglaope infausta shows a very low level of genetic heterogeneity for a lepidopteran species. However, this genetic poverty is not affecting the species’ viability. During the ice ages, differentiation into two genetic lineages occurred, most probably in a south-western and a south-eastern differentiation centre in Iberia. The gap in the distribution range in Germany is clearly reflected in the genetic structure. This differentiation must have developed relatively quickly because western Germany most probably was colonized during the climatic optimum 6000 years ago.     

Renal dysfunction induced by cadmium: biomarkers of critical effects

Cadmium (Cd) is cumulative poison which can damage the kidneys after prolonged exposure in the industry or the environment. Renal damage induced by Cd affects primarily the cellular and functional integrity of the proximal tubules, the main site of the renal accumulation of the metal. This results in a variety of urinary abnormalities including an increased excretion of calcium, amino acids, enzymes and proteins. These effects have been documented by a large number of studies conducted during more than two decades in experimental animals and in populations environmentally or occupationally exposed to Cd. There is now a general agreement to say that the most sensitive and specific indicator of Cd-induced renal dysfunction is a decreased tubular reabsorption of low molecular weight proteins, leading to the so-called tubular proteinuria. beta2-microblobulin, retinol-binding protein and alpha1-microglobulin are the microproteins the most commonly used for screening renal damage in populations at risk. Tubular dysfunction develops in a dose-dependent manner according to the internal dose of Cd as assessed on the basis of Cd levels in kidney, urine or in blood. Depending on the sensitivity of the renal biomarker and the susceptibility of the exposed populations, the thresholds of urinary Cd vary from 2 to 10 microg/g creatinine. The thresholds associated with the development of the microproteinuria, the critical effect predictive of a decline of the renal function, is estimated around 10 microg/g creatinine for both occupationally and environmentally exposed populations. Much lower thresholds have been reported in some European studies conducted on the general population. These low thresholds, however, have been derived from associations whose causality remains uncertain and for urinary protein increases that might be reversible. Cd-induced microproteinuria is usually considered as irreversible except at the incipient stage of the intoxication where a partial or complete reversibility has been found in some studies.