Altitudinal distribution limits of aquatic macroinvertebrates: an experimental test in a tropical alpine stream

1. Temperature and oxygen are recognised as the main drivers of altitudinal limits of species distributions. However, the two factors are linked, and both decrease with altitude, why their effects are difficult to disentangle. 2. This was experimentally addressed using aquatic macroinvertebrates; larvae of Andesiops (Ephemeroptera), Claudioperla, (Plecoptera), Scirtes (Coleoptera) and Anomalocosmoecus (Trichoptera), and the amphipod Hyalella in an Ecuadorian glacier‐fed stream (4100–4500 m a.s.l.). The following were performed: (i) quantitative benthic sampling at three sites to determine altitudinal patterns in population densities, (ii) transplants of the five taxa upstream of their natural altitudinal limit to test the short‐term (14 days) effect on survival, and (iii) in situ experiments of locomotory activity as a proxy for animal response to relatively small differences in temperature (5 °C vs. 10 °C) and oxygen saturation (55% vs. 62%). 3. The transplant experiment reduced survival to a varying degree among taxa, but Claudioperla survived well at a site where it did not naturally occur. In the in situ experiment, Scirtes and Hyalella decreased their activity at lower oxygen saturation, whereas Andesiops and Anomalocosmoecus did so at a low temperature. The decrease in activity from a high to a low temperature and oxygen for the five taxa was significantly correlated with their mortality in the transplant experiment. 4. Together the present experiments indicate that even relatively small differences in temperature and oxygen may produce effects explaining ecological patterns, and depending on the taxon, either water temperature or oxygen saturation, without clear interacting effects, are important drivers of altitudinal limits.     

Cloning and restriction fragment length polymorphism analysis of a cDNA for swine PIT-1, a gene controlling growth hormone expression*

A partial swine cDNA which encodes the functional domain of PIT-1 was isolated by the polymerse chain reaction (PCR). The swine PIT-1 cDNA clone is 95% identical at the protein level to the rat Pit-1 gene. Thus, Pit-l's known function in control of rat growth hormone and prolactin expression is likely to be conserved in swine. This swine cDNA clone was used to investigate genetic variability at PIT-1 in several American and Chinese breeds. Polymorphic BamIII fragments were found in pure-bred Meishan animals (n= 13), but only monomorphic fragments in five American breeds (n= 36).     

The effect of infra-red radiation on rectal temperature and respiration rate of unacclimated female new zealand white rabbits

1. 1.|An experiment was carried out to examine the effects of various levels of infra-red (i.r.) radiation on rectal temperature (RT) and respiration rate (RR) in New Zealand While rabbits.

2. 2.|A 4 × 3 × 6 factorial design was employed in which the factors were: four intensities of i.r. radiant heating of 0.0, 1.9, 2.1 and 2.4 MJ/m²/h, three replicates and six rabbits.

3. 3.|rectal temperature differed (P < 0.05) between treatments and were highest at the “high” level of i.r. radiation (1°C higher than for controls). At the “medium” and “low” levels of i.r. heating RTs were respectively 0.3 and 0.2°C higher than in controls.

4. 4.|At different levels of radiation RR were different (P < 0.05), with the highest (422.7 ± 218.1 breaths/min) at 2.4 MJ/m²/h i.r. radiant heating. This RR was almost 2.5 times that in controls, while at the “low” and “medium” i.r. levels RR values were respectively 1.5 and 2 times those of controls.

Seed germination traits of Ailanthus altissima,Phytolacca americana and Robinia pseudoacacia in response to different thermal and light requirements

Invasion of alien plant species (IAS) represents a serious environmental problem, particularly in Europe, where it mainly pertains to urban areas. Seed germination traits contribute to clarification of invasion dynamics. The objective of this research was to analyze how different light conditions (i.e., 12-hr light/12-hr darkness and continuous darkness) and temperature regimes (i.e., 15/6°C, 20/10°C and 30/20°C) trigger seed germination of Ailanthus altissima (AA), Phytolacca americana (PA) and Robinia pseudoacacia (RP). The relationship between seed germination and seed morphometric traits was also analyzed. Our findings highlight that temperature rather than light was the main environmental factor affecting germination. RP germinated at all tested temperatures, whereas at 15/6°C seeds of AA and PA showed physiological dormancy. RP had a higher germination capacity at a lower temperature, unlike AA and PA, which performed better at the highest temperatures. Light had a minor role in seed germination of the three species. Light promoted germination only for seeds of PA, and final germination percentage was 1.5-fold higher in light than in continuous darkness. Seed morphometric traits (thickness [T], area [A] and volume [V]) had a significant role in explaining germination trait variations. The results highlight the importance of increasing our knowledge on seed germination requirements to predict future invasiveness trends. The increase in global temperature could further advantage AA and PA in terms of germinated seeds, as well as RP by enhancing the germination velocity, therefore compensating for a lower germination percentage of this species at the highest temperatures.     

Endothelin-1 stimulates catalase activity through the PKCδ-mediated phosphorylation of serine 167

Our previous studies have shown that endothelin-1 (ET-1) stimulates catalase activity in endothelial cells and in lambs with acute increases in pulmonary blood flow (PBF), without altering gene expression. The purpose of this study was to investigate the molecular mechanism by which this occurs. Exposing pulmonary arterial endothelial cells to ET-1 increased catalase activity and decreased cellular hydrogen peroxide (H₂O₂) levels. These changes correlated with an increase in serine-phosphorylated catalase. Using the inhibitory peptide δV1.1, this phosphorylation was shown to be protein kinase Cδ (PKCδ) dependent. Mass spectrometry identified serine 167 as the phosphorylation site. Site-directed mutagenesis was used to generate a phospho-mimic (S167D) catalase. Activity assays using recombinant protein purified from Escherichia coli or transiently transfected COS-7 cells demonstrated that S167D catalase had an increased ability to degrade H₂O₂ compared to the wild-type enzyme. Using a phospho-specific antibody, we were able to verify that pS167 catalase levels are modulated in lambs with acute increases in PBF in the presence and absence of the ET receptor antagonist tezosentan. S167 is located on the dimeric interface, suggesting it could be involved in regulating the formation of catalase tetramers. To evaluate this possibility we utilized analytical gel filtration to examine the multimeric structure of recombinant wild-type and S167D catalase. We found that recombinant wild-type catalase was present as a mixture of monomers and dimers, whereas S167D catalase was primarily tetrameric. Further, the incubation of wild-type catalase with PKCδ was sufficient to convert wild-type catalase into a tetrameric structure. In conclusion, this is the first report indicating that the phosphorylation of catalase regulates its multimeric structure and activity.     

Effects of starvation and sucrose feeding on corpora allata of last instar larvae of Manduca sexta: in vitro activity, size, and cell number

Abstract Larvae of the tobacco hornworm moth Manduca sexta starved for the first 3 days of the last (fifth) stadium undergo a supernumerary moult. If they are provided with sucrose during the starvation period, they develop into normal pupae although pupation is delayed. The activities of the corpora allata (CA) from normal, starved, and sucrose fed larvae were followed through the fifth stadium with a radiochemical assay for Juvenile Hormone (JH) biosynthesis. An attempt was made to correlate CA-activity with CA cell number, size, and protein content.
In CA of normally fed larvae the rate of JH synthesis declined to undetectable levels by day 4 which was also the time of exposure of the dorsal vessel. In CA of starved larvae, the rate of JH synthesis at first decreased but began to increase on day 3 and reached a peak value by day 7 , at which time head capsule slippage occurred. In CA of sucrose fed larvae, the rate of biosynthesis declined as in normal larvae but the decline was extended over a longer period. Exposure of the dorsal vessel was delayed in the same manner and occurred on days 7–9. The major JH in all cases was JH-II.
The CA comprise c. 150 cells in the early fifth stadium, and this number remained constant during the fifth stadium in all three feeding regimens. In normal larvae, CA size and protein content increased several-fold during the stadium whereas in starved and sucrose-fed larvae they increased slowly and in agreement with the altered timing of developmental events. In none of the groups was the CA activity pattern correlated with morphometric changes of the CA. The rates of JH biosynthesis were not closely correlated with published JH titre curves. The in vivo mechanisms for regulation of JH production remain to be elucidated.     

From the beginning to the present state of molecular microbial pathogenesis—A tribute to Pascale Cossart

The universe of Molecular Microbial Pathogenesis is filled with many female and male stars. But there are two particularly bright shining supernovae-like stars: the late Stanley Falkow and the very lively and creative Pascale Cossart. These two outstanding luminaries, surrounded by numerous planets, do not only belong to different scientific generations but their splendor also comes from very different scientific concepts. Stanley Falkow, often referred to as the ‘Father of Molecular Microbial Pathogenesis’, made many groundbreaking contributions to this field by addressing almost all important bacterial pathogens. Pascale Cossart, who could be called in analogy the ‘Queen of Modern Molecular Microbial Pathogenesis’ by combining the Microbiology and Cell Biology, concentrates in her similarly impressive scientific work essentially on a single bacterial species which she studied and still studies in great depth: the facultative intracellular bacterial pathogen Listeria monocytogenes—and the vast majority of her most prominent publications deals with this pathogen in almost all facets. It is certainly not an exaggeration to say that she together with her co-workers and collaborators developed this model bacterium into a paradigm among the intracellular bacterial pathogens.