Reproductive Competition in Colonies of the Ant Leptothorax gredleri

Colonies of the ant, Leptothorax (s. str.) gredleri may contain several inseminated female reproductives of which typically only one is laying eggs. Observations suggest that “functional monogyny” is caused by aggressive interactions among nestmate queens. Only the most dominant queen reproduces. Subordinate queens either leave the colony to found their own nests solitarily or by budding, or stay in the nest without reproducing, but may eventually replace the dominant queen. The interrelations of life history of L. gredleri, population structure and habitat characteristics are examined.     

Presynaptic Nicotinic Receptors Stimulate Increases in Intraterminal Calcium of Chick Sympathetic Neurons in Culture

Abstract: Stimulation of chick sympathetic neurons in culture by the cholinergic agonists acetylcholine, nicotine, and 1,1-dimethyl-4-phenylpiperazinium (all at 10–1,000 µmol/L) induced concentration-dependent increases of free calcium levels measured by fura 2 fluorescence in neuronal processes. The response evoked by acetylcholine had both nicotinic and muscarinic components, whereas that induced by 1,1-dimethyl-4-phenylpiperazinium was purely nicotinic. Tetrodotoxin (0.3 µmol/L) blocked completely the increase of intraterminal free calcium level evoked by electrical stimulation. On the other hand, stimulation with 1,1-dimethyl-4-phenylpiperazinium still evoked 20–25% of the control response in the presence of tetrodotoxin. The concentration-response relationship of 1,1-dimethyl-4-phenylpiperazinium stimulation did not differ in the absence and in the presence of tetrodotoxin. The nicotinic antagonists d -tubocurarine (10 µmol/L) and mecamylamine (10 µmol/L), but not α-bungarotoxin (125 nmol/L), prevented the increase of intraterminal free calcium level evoked by 1,1-dimethyl-4-phenylpiperazinium (100 µmol/L) in the presence of tetrodotoxin. These observations indicate the presence of nicotinic receptors on neuronal processes that increase the intraterminal concentration of free calcium and probably modulate transmitter release. Their pharmacological properties are similar to those of nicotinic receptors located on neuronal cell bodies.     

Spider biodiversity potential of an ungrazed and a grazed inland salt meadow in the National Park 'Neusiedler See-Seewinkel' (Austria): implications for management (Arachnida: Araneae)

To assess the biodiversity potential of an ungrazed and a grazed inland salt meadow in the Seewinkel (Eastern Austria), spider assemblages were recorded by pitfall trapping for 1 year. Both species assemblages consisted, to a large extent, of rare species of conservation interest. The species assemblage of the grazed site was dominated by Pardosa agrestis, but highly specific halotopobiontic species also occurred in higher numbers. Halotolerant species were also present in the ungrazed meadow, but their individual number was much lower. The species composition of this site reflects the more balanced microclimatical situation of the high sward. Comparison of the two assemblages with 207 other meadow spider assemblages of Central Europe shows a separated position, especially of the grazed site assemblage. High similarities with assemblages of meadows with a similar vegetation structure indicate a high importance of management. Considering the high proportion of rare species on both sites, the best management of the salt meadow and pan shores of the Seewinkel should combine areas of light grazing with ungrazed areas. However, the proportion of these parts and the intensity of grazing still remains to be determined by quantitative experiments.     

l-NNA inhibits the histochemical NADPH-d reaction in rat spinal cord neurons

In nerve tissue the histochemical nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) reaction is considered a suitable marker for nitric oxide synthase (NOS) activity. We have previously shown that the NOS-specific inhibitorl-nitroarginine (l-NNA) can block NADPH-d staining in intermediolateral (IML) neurons of the rat spinal cord; such a reaction might serve as a control for the presence of a NOS-related catalytic activity, i.e.,l-NNA-dependent NO synthesis in these neurons. However,l-NNA inhibition of neuronal NADPH-d is inconsistent and is therefore disputed by others. This prompted us to reinvestigate the reaction conditions to provide a standardized protocol for inhibition experiments. In IML neurons of formaldehyde-fixed spinal cord tissue, inhibition of NADPH-d reaction was tested by preincubation of frozen sections with the flavin-binder diphenylene iodonium chloride (DPI, 10 M-1 mM) which blocked the NADPH-d reaction in a concentration-dependent way, suggesting an inverse relationship of inhibitor concentration and final reaction product generated. Preincubation with the NOS-specific inhibitorl-NNA in glycine-NaOH buffer (pH 8.5–9.5) but notl-nitroarginine methyl ester (l-NAME) revealed a concentration-dependent blocking effect on neuronal NADPH-d comparable to the effects seen with DPI, suggesting the existence of al-NNA sensitive NADPH-d activity. Blocking withl-NNA (100 M-10 mM) was prevented by excessl-arginine (10–100 mM), suggesting competitive binding sites. NADPH-d staining was not inhibited by 7-nitro indazole, another NOS inhibitor. Thus, in formaldehyde-fixed nervous tissue both DPI andl-NNA inhibit the NOS-associated catalytic NADPH-d activity, thereby preventing NADPH-dependent conversion of nitroblue tetrazolium to formazan.Presented in the Workshop Detection of NO-synthases at the XXXVI Symposium of the Society for Histochemistry on Oxy Radicals, 20–23 September 1994, Heidelberg, Germany     

Modification of sodium inactivation in myelinated nerve by Anemonia toxin II and iodate. Analysis of current fluctuations and current relaxations

(1) Na+ currents and Na+ current fluctuations were measured in single myelinated nerve fibres of Rana esculenta under voltage-clamp conditions. The process of Na+ inactivation was modified by external treatment with 7 microM Anemonia Toxin II or by internal application of 20 or 40 mM IO3(-). (2) At depolarization of 24 and 32 mV the spectral density of Na+ current fluctuations could be described as the sum of two contributions, Sh(f) and Sm(f), representing the spectrum from fluctuations of the inactivation (h) and activation (m) gates, respectively. At higher depolarizations of 40 and 48 mV the low frequency (h) fluctuations could be better fitted by the sum, Sh1(f)+Sh2(f), of two separate Lorentzian functions. (3) The Na+ current and the variance of Na+ current fluctuations between 150 and 450 ms after depolarization are increased by one order of magnitude after application of Anemonia Toxin II or IO3(-). (4) The kinetics of Na+ current inactivation were described as A1 x exp(-t/tau h1) + A2 x exp(-t/tau h2) + B. The constant, tau h1, of fast Na+ inactivation was the same in normal and modified nerve fibres. The slow inactivation time constant, tau h2, increased with increasing depolarizations in modified fibres but decreased under control conditions. In all cases tau h2 showed a similar voltage dependence as the time constant found by fitting the low frequency fluctuations of Na+ current with one Lorentzian function, Sh(f). (5) It is concluded that Anemonia Toxin II and IO3(-) modify a fraction of Na+ channels in an all-or-none manner. A lower limit of the number of modified Na+ channels is estimated from the Na+ current and the variance Na+ current fluctuations. 7 microM external Anemonia Toxin II modifies more than 17% and 20 or 40 mM internal IO3(-) more than 8% of all Na+ channels. The inactivation gates in modified channels experience an electric field different from that in normal fibres.     

A unique pattern of toxic synthesis in pentitol catabolism: Implications for evolution

Summary All of ourEscherichia coli C mutants blocked in the first step of D-arabitol catabolism (D-arabitol dehydrogenase) became unable to grow in the presense of D-arabitol. We have shown that this sensitivity is eliminated by a defect in the second enzyme of the pathway (D-xylulokinase), leading to a pattern of toxicity and its relief which has not been previously reported. We have found a similar pattern of toxicity and its relief in the closely related ribitol pathway. The evolutionary significance of these findings is discussed.     

Studies on dissimilatory sulfate-reducing bacteria that decompose fatty acids

Three strains (2ac9, 3ac10 and 4ac11) of oval to rodshaped, Gram negative, nonsporing sulfate-reducing bacteria were isolated from brackish water and marine mud samples with acetate as sole electron donor. All three strains grew in simple defined media supplemented with biotin and 4-aminobenzoic acid as growth factors. Acetate was the only electron donor utilized by strain 2ac9, while the other two strains used in addition ethanol and/or lactate. Sulfate served as electron acceptor and was reduced to H₂S. Complete oxidation of acetate to CO₂ was shown by stoichiometric measurements with strain 2ac9 in batch cultures using sulfate, sulfite or thiosulfate as electron acceptors. With sulfate an average growth yield of 4.8 g cell dry weight was obtained per mol of acetate oxidized; with sulfite or thiosulfate the growth yield on acetate was about twice as high. None of the strains contained desulfoviridin. In strain 2ac9 cytochromes of the b- and c-type were detected. Strain 2ac9 is described as type strain of the new species and genus, Desulfobacter postgatei.     

A new anaerobic,sporing, acetate-oxidizing,sulfate-reducing bacterium,Desulfotomaculum (emend.) acetoxidans

Archives of Microbiology - A new strictly anaerobic, polarly flagellated, sporing, acetate-oxidizing, sulfate-reducing bacterium was isolated from anaerobic fresh or sea water mud samples. The...