Growth hormone improves growth retardation induced by rapamycin without blocking its antiproliferative and antiangiogenic effects on rat growth plate

Rapamycin, an immunosuppressant agent used in renal transplantation with antitumoral properties, has been reported to impair longitudinal growth in young individuals. As growth hormone (GH) can be used to treat growth retardation in transplanted children, we aimed this study to find out the effect of GH therapy in a model of young rat with growth retardation induced by rapamycin administration. Three groups of 4-week-old rats treated with vehicle (C), daily injections of rapamycin alone (RAPA) or in combination with GH (RGH) at pharmacological doses for 1 week were compared. GH treatment caused a 20% increase in both growth velocity and body length in RGH animals when compared with RAPA group. GH treatment did not increase circulating levels of insulin-like growth factor I, a systemic mediator of GH actions. Instead, GH promoted the maturation and hypertrophy of growth plate chondrocytes, an effect likely related to AKT and ERK1/2 mediated inactivation of GSK3β, increase of glycogen deposits and stabilization of β-catenin. Interestingly, GH did not interfere with the antiproliferative and antiangiogenic activities of rapamycin in the growth plate and did not cause changes in chondrocyte autophagy markers. In summary, these findings indicate that GH administration improves longitudinal growth in rapamycin-treated rats by specifically acting on the process of growth plate chondrocyte hypertrophy but not by counteracting the effects of rapamycin on proliferation and angiogenesis.     

Biological information on a rare pelagic fish,black ruff Centrolophus niger,caught in Icelandic waters: Distribution,feeding, and otoliths

Black ruff (Centrolophus niger) is a rare and poorly studied species found in both the Atlantic and Pacific Oceans and also in the Mediterranean Sea. It is sporadically caught south of Iceland during the annual International Ecosystem Summer Survey of the Nordic Seas. In total, 43 specimens were caught from 2009 to 2021, of which 41 specimens were caught during 2017–2021. All specimens, except one, were caught using a pelagic trawl (cod-end mesh-size: 50 mm) close to the surface (trawl depth: 0–35 m) with in situ temperature ranging from 9 to 13°C. The area south of Iceland is characterized by having warmer temperatures than other areas around the island, which might be indicative of a northern limit for the distribution of black ruff. The fish were primarily in the range of 29–46 cm with a few larger individuals up to 71 cm. Fourteen fish, caught in 2017 and 2021, were dissected to gather biological information on this species. These fish were all juveniles with no obvious sign of gonad development. Correlations between total length, fork length, and standard length are presented. Otoliths were thin and delicate with a length of ~13–16 mm, and otolith size (length, width, and area) was correlated with fish size. Much of the stomach content was at an advanced stage of digestion, but some contents could be identified and consisted of invertebrates, primarily of the orders Amphipoda and Calanoida with some unidentified fish also present.     

Patterns and rates of nucleotide substitution,insertion and deletion in the endosymbiont of ants Blochmannia floridanus

Genome reduction is a general process that has been studied in numerous symbiotic bacteria associated with insects. We investigated the last stages of genome degradation in Blochmannia floridanus, a mutualistic bacterial endosymbiont of the ant Camponotus floridanus. We determined the tempo (rates of insertion and deletion) and mode (size and number of insertion–deletion events) of the process in the last 200 000 years by analysing a total of 16 intergenic regions in several strains of this endosymbiont from different ant populations. We provide the first calculation of the reduction rate for noncoding DNA in this endosymbiont (2.2 × 10^?8 lost nucleotides/site/year) and compare it with the rate of loss in other species. Our results confirm, as it has been observed in other organisms like Buchnera aphidicola or Rickettsia spp., that deletions larger than one nucleotide can still appear in advanced stages of genome reduction and that a substitutional deletion bias exists. However, this bias is not due to a higher proportion of deletion over insertion events but to a few deletion events being larger than the rest. Moreover, we detected a substitutional AT bias that is probably responsible for the increase in the number of the small and moderate indel events in the last stages of genome reduction. Accordingly, we found intrapopulational polymorphisms for the detected microsatellites in contrast to the stability associated with these in free‐living bacteria such as Escherichia coli.     

The recombinant protein rSP03B is a valid antigen for screening dog exposure to Phlebotomus perniciosus across foci of canine leishmaniasis

The frequency of sandfly–host contacts can be measured by host antibody levels against sandfly salivary proteins. Recombinant salivary proteins are suggested to represent a valid replacement for salivary gland homogenate (SGH); however, it is necessary to prove that such antigens are recognized by antibodies against various populations of the same species. Phlebotomus perniciosus (Diptera: Psychodidae) is the main vector of Leishmania infantum (Trypanosomatida: Trypanosomatidae) in southwest Europe and is widespread from Portugal to Italy. In this study, sera were sampled from naturally exposed dogs from distant regions, including Campania (southern Italy), Umbria (central Italy) and the metropolitan Lisbon region (Portugal), where P. perniciosus is the unique or principal vector species. Sera were screened for anti‐P. perniciosus antibodies using SGH and 43‐kDa yellow‐related recombinant protein (rSP03B). A robust correlation between antibodies recognizing SGH and rSP03B was detected in all regions, suggesting substantial antigenic cross‐reactivity among different P. perniciosus populations. No significant differences in this relationship were detected between regions. Moreover, rSP03B and the native yellow‐related protein were shown to share similar antigenic epitopes, as canine immunoglobulin G (IgG) binding to the native protein was inhibited by pre‐incubation with the recombinant form. These findings suggest that rSP03B should be regarded as a universal marker of sandfly exposure throughout the geographical distribution of P. perniciosus.     

Interactive effects of temperature and habitat complexity on freshwater communities

Warming can lead to increased growth of plants or algae at the base of the food web, which may increase the overall complexity of habitat available for other organisms. Temperature and habitat complexity have both been shown to alter the structure and functioning of communities, but they may also have interactive effects, for example, if the shade provided by additional habitat negates the positive effect of temperature on understory plant or algal growth. This study explored the interactive effects of these two major environmental factors in a manipulative field experiment, by assessing changes in ecosystem functioning (primary production and decomposition) and community structure in the presence and absence of artificial plants along a natural stream temperature gradient of 5–18°C. There was no effect of temperature or habitat complexity on benthic primary production, but epiphytic production increased with temperature in the more complex habitat. Cellulose decomposition rate increased with temperature, but was unaffected by habitat complexity. Macroinvertebrate communities were less similar to each other as temperature increased, while habitat complexity only altered community composition in the coldest streams. There was also an overall increase in macroinvertebrate abundance, body mass, and biomass in the warmest streams, driven by increasing dominance of snails and blackfly larvae. Presence of habitat complexity, however, dampened the strength of this temperature effect on the abundance of macroinvertebrates in the benthos. The interactive effects that were observed suggest that habitat complexity can modify the effects of temperature on important ecosystem functions and community structure, which may alter energy flow through the food web. Given that warming is likely to increase habitat complexity, particularly at higher latitudes, more studies should investigate these two major environmental factors in combination to improve our ability to predict the impacts of future global change.     

The ecology of Lake Myvatn and the River Laxá: Variation in space and time

Ecological features of Lake Myvatn and the outflowing River Laxá show a wide range of spatial and temporal variations. The physical division of the lake into three main basins and the variation in chemical composition and temperature of the artesian springs feeding this shallow productive lake have large spatial effects. Variation in groundwater characteristics depends on percolation time and proximity to geothermal sources. Variation in precipitation is evened out by the porous volcanic soil and bedrock and the spring-water discharge is therefore very stable. A pulse of volcanic activity in 1975–1984 (the Krafla Fires) heated the groundwater entering the North Basin of the lake and changed its chemistry. Although much reduced, these effects have not disappeared yet, but overall the impact of the volcanic activity on the biota seemed minimal. Recycling of nutrients through internal loading is important and occurs on various time scales. In winter, when the lake is ice-covered, the topmost 5-cm layer of sediment pore water has a hundredfold concentration of nutrients relative to the overlying lake water. The nutrients are released during the ice-free period by sediment resuspension, diffusion, bioturbation and recycling. In spring, resuspension events sometimes lead to spikes in dissolved phosphorus and nitrogen, but there is little evidence of any major desorption of nutrients from suspended particles during such events later in the summer. In contrast to the stable groundwater, the biota show more or less regular fluctuations with no straightforward correlation with external signals. The most prominent fluctuations, those of the chironomid Tanytarsus gracilentus seem to be driven by interactions between the species and its sediment resources. Fluctuations in other invertebrates could be a consequence of the Tanytarsus cycles due to the large impact this species has on the benthic environment of this detritus-driven ecosystem. Temporal variation in epibenthic chironomids and Cladocera translates into variable production of vertebrate predators (Arctic charr, Salvelinus alpinus, and ducks), body condition and mortality of fish and sometimes into return rates of migrating adult ducks. The waterfowl show large temporal variation on a centennial scale, e.g., the invasion of the tufted duck (Aythya fuligula) which arrived by the end of the 19th century and has by now outnumbered other species. Fluctuations of Cyanobacteria (Anabaena) and the fish Gasterosteus aculeatus (three-spined stickleback) harmonize with the cycles in the benthic community. Palaeolimnological studies indicate that primary production in the South Basin became increasingly benthic as the lake depth was reduced by sedimentation (around 2 mm year^–1). Other trends include a decrease in Tanytarsus and Daphnia and an exponential increase in green algae (Cladophorales, Pediastrum) and associated organisms.     

Food selection of Tanytarsus gracilentus larvae (Diptera: Chironomidae): An analysis of instars and cohorts

Gut contents of the detritivorous Tanytarsus gracilentus larvae were studied at one site in Lake Myvatn, Iceland. Samples were collected with a sediment corer. Sediment samples were taken from the surface of the intact core before the larvae were collected. Gut contents were compared between different larval instars and cohorts, and to the surface sediment. The composition of the gut contents of all instars was different from that of the sediment surface. The first instar selected small diatoms of the genus Fragilaria, as single and paired cells, and the fourth instar selected detritus items of more variable size and origin. Apart from the third instar larvae, there were similar trends in food selectivity between the same instar of different cohorts. No major changes occurred in the composition of the surface sediment during the time of this study.