A comparative ecological investigation of two related mayfly nymphs

Zusammenfassung Heptagenia sulphurea wird auf Steinen, H. fuscogrisea in der Vegetation von Fließgewässern gefunden (Fig. 2).In Experimenten wählte H. sulphurea Steine und groben Kies. H. fuscogrisea wählte Batrachium als Substrat, nur ein geringer Anteil der Larven fand sich auf Callitriche (Fig. 3).Die Zeit, die zwischen Loslassen und erneutem Anhaften auf dem Substrat im strömenden Milieu verstreicht, war unterschiedlich bei den zwei Spezies. Die auf Steinen lebende Art reagierte schneller als die aus der Vegetation. H. sulphurea verhielt sich, wenn sie von der Strömung ergriffen worden war, ziemlich passiv, doch trug die turbulente Strömung das Tier dem Substrat zu, so hatte es gewöhnlich sicheren Halt.Im Strömungsaquarium bevorzugt H. sulphurea die strömungsexponierten Bereiche, aber viele waren auch im ruhigen Wasser (Fig. 5).Wurde H. fuscogrisea von der Strömung ergriffen, so führte sie Schwimmbewegungen aus. Erreicht sie eine Haltmöglichkeit an strömungsexponiertem Platz, so wird sie oft weitergetragen. Die Tiere lassen sie meist in ruhigem Wasser nieder.Im Strömungsaquarium bevorzugt H. fuscogrisea überwiegend die Regionen ruhigen Wassers (Fig. 5).Die Zeit zwischen Loslassen und Festsetzen war deutlich durch die Temperatur beeinflußt (Fig. 6).Der dichte Haarbesatz an der hinteren Kante der Femur von H. sulphurea wird als Anpassung an das Leben in der Strömung angesehen, weil er die Wirbelbildung herabsetzen kann. Der Haarbesatz entlang der Tibia bei H. fuscogrisea wird als Anpassung zum Schwimmen angesehen, zu dem these Spezies befähigt ist, wenn sie von der Strömung ergriffen wird (Fig. 8).Die Spezies von Steinen ist etwas mehr abgeflacht als die aus der Vegetation (Fig. 7).     

Stochastic modelling of a single ion channel: interdependence of burst length and number of openings per burst

Previous modelling of single channel behaviour based on Markov processes has been concerned mainly with means and marginal distributions of particular quantities. The present study derives the joint distribution, conditional distributions, and associated mean values for the burst length (T) and the number (N) of openings per burst in two simple three-state models in which bursting is possible, one for an agonist-only and one for a channel blocking mechanism. In both models the conditional mean burst length (E(T/N = r)) increases linearly as a function of the number of openings per burst, while the conditional mean number of openings per burst (E(N/T = x)) is a nonlinear strictly increasing function of burst length, which is asymptotically linear for large burst length. The asymptotic intercept for each model is shown to be less than, equal to, or greater than unity according as mean channel closed-time is less than, equal to, or greater than mean open-time. For parameter values typical of the nicotinic receptor, this intercept is less than unity for the agonist-only model and greater than unity for the blocking model. As a result of the dependence between the number of openings per burst and burst length, it is shown that experimental estimates of the unconditional mean number of openings per burst may be biased if bursts of only short duration are collected.     

Enhanced production of human gamma-interferon in nylon column-fractionated cell cultures

The production of human gamma-interferon (HuIFN-gamma) in unfractionated and nylon wool column-fractionated leukocyte cell cultures stimulated with PMA and PHA was investigated. Production was studied with normal and reduced autologous serum protein levels in 96-hr spinner cultures. A 10- to 15-fold enhancement of production and a 50-fold increase in specific activity of crude HuIFN-gamma was demonstrated in nylon column-fractionated/reduced serum cell cultures. Kinetic analysis revealed a production rate maximum within 6 hr of induction in unprocessed cell cultures, whereas production occurred at an essentially constant rate for 48 hr in fractionated cell cultures.     

New Approaches for Absolute Quantification of Stable‐Isotope‐Labeled Peptide Standards for Targeted Proteomics Based on a UV Active Tag

Targeted proteomics depends on the availability of stable isotope labeled (SIL) peptide standards, which for absolute protein quantification need to be absolutely quantified. In the present study, three new approaches for absolute quantification of SIL peptides are developed. All approaches rely on a quantification tag (Qtag) with a specific UV absorption. The Qtag is attached to the peptide during synthesis and is removed by tryptic digestion under standard proteomics workflow conditions. While one quantification method (method A) is designed to allow the fast and economic production of absolutely quantified SIL peptides, two other methods (methods B and C) are developed to enable the straightforward re‐quantification of SIL peptides after reconstitution to control and monitor known problems related to peptide solubility, precipitation, and adhesion to vials. All methods yield consistent results when compared to each other and when compared to quantification by amino acid analysis. The precise quantitation methods are used to characterize the in vivo specificity of the H3 specific histone methyltransferase EZH2.     

Alternative reproductive tactics are associated with sperm performance in invasive round goby from two different salinity environments

During male–male competition, evolution can favor alternative reproductive tactics. This often results in a dominant morph that holds a resource, such as a nest for egg laying, which competes with a smaller sneaker morph that reproduces by stealing fertilizations. The salinity environment can influence male growth rates, for example, via osmoregulatory costs, which in turn may influence the use of sneaker tactics for small males competing for mating opportunities. Salinity can also affect sperm directly; however, little is known of how salinity influences sneaker tactics through sperm performance. We sampled males of the invasive round goby (Neogobius melanostomus) from two environments, a freshwater river and a brackish estuary. This fish has two male morphs: nest‐holding dark males and non‐nest‐holding light males. We examined the role of water salinity of 0, 8, and 16 on sperm performance and found that for estuarine males, a salinity of 0 reduced sperm velocity compared to a salinity of 8 and 16. Riverine males had low velocity in all salinities. Sperm viability also decreased by over 30% in 0 salinity, compared to 8 and 16, for fish from both environments. Gobies produce ejaculate contents in specialized glands that could in theory shield sperm in an adverse environment. However, gland contents did not improve sperm performance in our tests. Body mass and age estimates indicate that riverine males invested more in somatic growth compared to estuarine males. Estuarine light morph males had a high enough gonadosomatic index to indicate sneaker tactics. We propose that when sperm performance is low, such as for the riverine males, sneaker tactics are ineffective and will be selected against or phenotypically suppressed. Instead, we interpret the increased investment in somatic growth found in riverine males as a life‐history decision that is advantageous when defending a nest in the next reproductive season.