What life cycle graphs can tell about the evolution of life histories

We analyze long-term evolutionary dynamics in a large class of life history models. The model family is characterized by discrete-time population dynamics and a finite number of individual states such that the life cycle can be described in terms of a population projection matrix. We allow an arbitrary number of demographic parameters to be subject to density-dependent population regulation and two or more demographic parameters to be subject to evolutionary change. Our aim is to identify structural features of life cycles and modes of population regulation that correspond to specific evolutionary dynamics. Our derivations are based on a fitness proxy that is an algebraically simple function of loops within the life cycle. This allows us to phrase the results in terms of properties of such loops which are readily interpreted biologically. The following results could be obtained. First, we give sufficient conditions for the existence of optimisation principles in models with an arbitrary number of evolving traits. These models are then classified with respect to their appropriate optimisation principle. Second, under the assumption of just two evolving traits we identify structural features of the life cycle that determine whether equilibria of the monomorphic adaptive dynamics (evolutionarily singular points) correspond to fitness minima or maxima. Third, for one class of frequency-dependent models, where optimisation is not possible, we present sufficient conditions that allow classifying singular points in terms of the curvature of the trade-off curve. Throughout the article we illustrate the utility of our framework with a variety of examples.     

Demonstration of choleragen-dependent ADP-ribosylation in whole cells and correlation with the activation of adenylate cyclase

3T3C₂ mouse fibroblasts rendered permeable to (α^?32P)NAD⁺ show cholera toxin-dependent labeling of a 45,000 m.w. protein and of a doublet of polypeptides around 52,000 m.w. These same bands are ADP-ribosylated in broken cells. Membranes prepared from pigeon erythrocytes pretreated with choleragen show a decrease in subsequent cholera toxin-specific ADP-ribosylation of a 43,000 m.w. polypeptide. Both whole cell and broken cell adenylate cyclase activation and toxin-specific ADP-ribosylation are reversed specifically by low pH and high concentrations of toxin and nicotinamide in all systems. Thus ADP-ribosylation appears to be relevant to the molecular action of choleragen in whole cells as well as in broken cells.     

Immunohistological detection of Saruplase (recombinant single-chain urokinase-type plasminogen activator) in normal rat tissue

Summary Saruplase — a recombinant single-chain urokinase-type plasminogen activator was identified immunohistochemically in normal rat tissue after intravenous administration by means of a polyclonal antibody. For this purpose, rat tissues were fixed in various ways (liquid nitrogen, ethanol, formaldehyd solution). Saruplase could be detected by the PAP method, streptavidinbiotin system and indirect immunofluorescence in the kidney (proximal tubule), liver (hepatocytes, Kupffer cells) and spleen (reticular cells). Saruplase was not localized in the rat endothelium. It is discussed that the ratspecific receptors for urokinase-type plasminogen activator on endothelial cells cannot bind Saruplase due to the extreme species specificity.     

Explaining density-dependent regulation in earthworm populations using life-history analysis

At present there is little knowledge about how density regulates population growth rate and to what extent this is determined by life-history patterns. We compared density dependent population consequences in the Nicholsonian sense based on experimental observations and life-history modeling for the earthworms Lumbricus terrestris and Eisenia fetida . Both species differ in their life-histories, L. terrestris being a relatively long-lived species with slow reproduction and occurring at low densities compared to E. fetida which has a more opportunistic strategy with a high reproductive output. E. fetida is able to colonise new habitats rapidly and may occur at relatively high population densities. Density dependency of population growth rate was estimated by incorporating density dependent effects on reproduction and growth using a modified Euler equation. The results point out that E. fetida was not as strongly impacted by density as compared to L. terrestris . Population growth rate in E. fetida was hardly affected at low and moderate density, being reduced only at high level, this compares to L. terrestris where even relatively small density effects resulted in a strong negative effect on population growth rate. Our findings indicate that density-dependent regulation in earthworms can be quantified using life-history analysis. The outcomes are in agreement with empirical field observations for populations (i.e. L. terrestris occurs ar low density, E. fetida at high density). Consideration of the potential importance of Nicholsonian density dependence for field populations of these two species in light of their known biology however produces counterintuitive conclusions. In E. fetida , although density tolerant, rapid population growth may mean this species may be subject to density dependeny regulation. In L. terrestris , although density sensitive, complex behavioural ecology (surface activity, territoriality) may limit of feedback influence on population size.     

Queuine in plants and plant tRNAs: Differences between embryonic tissue and mature leaves

In eubacterial and eukaryotic tRNAs specific for Asn, Asp, His and Tyr the modified deazaguanosinederivative queuosine occurs in position 34, the first position of the anticodon. Analysis of unfractionated tRNAs from wheat and from tobacco leaves shows that these tRNAs contain high amounts of guanosine (G) in place of queuosine (Q). This was measured by the exchange of G34 for [³H]guanine catalysed by the specific tRNA guanine transglycosylase from E. coli. Upon gel electrophoretic separation of the labeled tRNAs, seven Q-deficient tRNA species including isoacceptors are detectable. Two are identified as cytoplasmic tRNAs^Tyr and tRNA^Asp and two represent chloroplast tRNA^Tyr isoacceptors. In contrast to leaf cytoplasm and chloroplasts, wheat germ has low amounts of tRNAs with G34 in place of Q.A new enzymatic assay is described for quantitation of free queuine in cells and tissues. Analysis of queuine in plant tissues shows that wheat germ contains about 200 ng queuine per g wet weight. In wheat and tobacco leaves queuine is present, if at all, in amounts lower than 10 ng/g wet weight. The absence of Q in tRNAs from plant leaves is therefore caused by a deficiency of queuine. Tobacco cells cultivated in a synthetic medium without added queuine do not contain Q in tRNA, indicating that these rapidly growing cells do not synthesize queuine de novo.     

5 alpha-androstane-3 beta,17 beta-diol hydroxylating enzymes in stroma and epithelium of human benign prostatic hyperplasia (BPH)

As enzymatic hydroxylation of 5 alpha-androstane-3 beta,17 beta-diol (3 beta-diol) may be a factor in controlling the 5 alpha-dihydrotestosterone (DHT) content in the prostate, we were interested in activity and distribution of these enzymes in epithelium and stroma of human benign prostatic hyperplasia (BPH). The enzyme activities were measured after mechanical separation of BPH tissue from 15 patients of various ages into stroma and epithelium, and optimization of the in vitro transformation of 3 beta-diol to hydroxylated products, which were analyzed by HPLC. The main results were: (1) 3 beta-diol was hydroxylated at C-7 alpha, C-7 beta, C-6 alpha, and C-6 beta. (2) The mean Michaelis constant Km (nM +/- SEM) for hydroxylation at C-7 alpha(beta) (168 +/- 21) was significantly lower than at C-6 alpha(beta) (601 +/- 43) without differences between stroma and epithelium. (3) Hydroxylation at alpha position dominated significantly over that at beta. (4) The mean maximal metabolic rate Vmax (pmol . mg protein-1 . h-1) of hydroxylation at C-6 alpha was about 7-fold lower in stroma (3.4 +/- 0.2) than in epithelium (23.8 +/- 4.1), concerning the other hydroxylations, Vmax was about 1.6-fold lower in stroma. (5) With increasing age of the patients there was a significant decrease of the 3 beta-diol hydroxylation in stroma and epithelium. It is discussed that the significantly lower activity of 3 beta-diol hydroxylation in stroma compared to epithelium and the decrease of activity with increasing age might potentiate the DHT accumulation in stroma of BPH.     

Microcalorimetric investigation into the metabolic activity of rat caecal flora in the presence of different sugars and sugar substitutes

When adapting young rats to different sugar substitutes (sorbitol, PolydextroseR and PalatinitR), effects were seen in the caecal morphology and caecal content e.g. bacterial concentration, which did not occur when adapting rats to sugars (glucose, sucrose). For in vitro studies, anaerobic growth of caecal flora in thioglycollate medium with and without the respective substances was monitored by continuous measurement of heat production, optical density and pH. Additionally, biochemical analyses and light microscopic observations were performed in order to detect differences between adapted and non-adapted flora. In particular the microcalorimetric data furnished valuable information about alterations in bacterial metabolic activity after adaptation to sugars and sugar substitutes, and clearly indicated that all the substances tested influenced the metabolism of caecal flora.     

Effects of Heavy Metal Cations and Other Sulfhydryl Reagents on Brain Dopamine D1 Receptors: Evidence for Involvement of a Thiol Group in the Conformation of the Active Site

To investigate aspects of the biochemical nature of membrane-bound dopamine D1 receptors, rat striatal homogenates were pretreated with heavy metal cations and some other chemical agents, and their effects on D1 receptors were subsequently determined using a standard [3H](R)-(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1-N-3- benzazepine([3H]SCH 23390) binding assay. Incubation of striatal membranes with as little as 1 microM Hg2+, 10 microM Cu2+, and 10 microM Cd2+ completely prevented specific [3H]SCH 23390 binding. The effect of Cu2+, 1.5 microM, was noncompetitive in nature, whereas 3-5 microM Cu2+ afforded mixed-type inhibition. The inhibitory effect of Cu2+ was fully reversed by dithiothreitol (0.1-1 mM). Cu2+ (2 microM) did not affect the affinity of cis-flupenthixol or clozapine for remaining [3H]SCH 23390 sites. A second series of cations, Co2+ (30 microM), Ni2+ (30 microM), Mn2+ (1 mM), Ca2+ (25 mM), and Ba2+ (20 mM), inhibited specific [3H]SCH 23390 binding by 50% at the concentrations indicated. The thiol alkylating reagent N-ethylmaleimide (NEM) (0.2 mM) reduced specific binding by 70%. The effect of NEM was completely prevented by coincubation with a D1 receptor saturating concentration of SCH 23390 (20 nM) or dopamine (10 microM). The results indicated that the dopamine D1 receptor is a thiol protein and that a thiol group is essential for the ligand binding.