A new internal perfusion method for transport studies in squid giant axons

A new internal perfusion method has been developed which allows control of the internal solute composition in squid axons. The superiority of this technique compared to the old perfusion methods is shown by the experiments performed which have reproduced, both qualitatively and quantitatively, the Na+ and Ca2+ fluxes observed in intact and dialyzed axons. Compared with the internal dialysis, the perfusion method has the advantage that the permeability barrier give by the porous capillary has been eliminated. This allows the introduction into the axon of solutes with very high molecular weight, at the same time that a fast and reliable internal control can be achieved.     

Spongelike alginate nanoparticles as a new potential system for the delivery of antisense oligonucleotides.

The aim of this study was to design a new antisense oligonucleotide (ON) carrier system based on alginate nanoparticles and to investigate its ability to protect ON from degradation in the presence of serum. Pharmacokinetics and tissue distribution of ON-loaded nanoparticles have been determined after intravenous administration. An original and dynamic process for ON loading into polymeric nanoparticles has been applied. It is based on the diffusion of ON or ON/polylysine complex into the nanoparticle or the alginate gel, respectively. Indeed, the single coincubation of ON with nanoparticles led, within a few days, to an extremely efficient association. The diffusion kinetic of ON was shown to be dependent on several parameters, incubation temperature, ON concentration, presence or absence of polylysine, polylysine molecular weight, and nanoparticle preparation procedure. This new alginate-based system was found to be able to protect [33P]-radiolabeled ON from degradation in bovine serum medium and to modify their biodistribution, as an important accumulation of radioactivity was observed in the lungs, in the liver, and in the spleen after intravenous administration into mice. ON may be associated efficiently with calcium alginate in a colloidal state. Such nanosponges are promising carriers for specific delivery of ON to lungs, liver, and spleen.     

Winter food availability limits winter survival of Mongolian gerbils (<Emphasis Type="Italic">Meriones unguiculatus</Emphasis>)

Food availability is important to the dynamics of animal social organizations or populations. However, the role of winter food availability in animal population dynamics is still controversial. We carried out an experimental study to test Lack’s hypothesis that reduced food in winter limits survival and spring numbers of breeding individuals of social groups, using the Mongolian gerbil (Meriones unguiculatus) as model species. We established 24 gerbil social groups in 24, 10 × 10 m, pens in September 2008. We provided wheat seeds as supplemental food in 12 enclosures from September 2008 to March 2009; the other 12 enclosures, not provided with supplemental food, served as controls. We live-trapped gerbils at a 2-week interval from September to April. Supplemental food during winter increased biweekly survival by 10% relative to that in control groups. Only four control social groups survived to the end of our study whereas all 12 food-supplemented social groups survived through our study period. Supplemental food also increased cumulative numbers of recruits and group sizes of gerbils. We conclude that winter food availability limits winter survival and spring social groups or population sizes of Mongolian gerbils.     

Reply to Hussey et al.: The requirement for accurate diet-tissue discrimination factors for interpreting stable isotopes in sharks

Carbon and nitrogen stable isotope analyses have improved our understanding of food webs and movement patterns of aquatic organisms. These techniques have recently been applied to diet studies of elasmobranch fishes, but isotope turnover rates and isotope diet–tissue discrimination are still poorly understood for this group. We performed a diet switch experiment on captive sandbar sharks (Carcharhinus plumbeus) as a model shark species to determine tissue turnover rates for liver, whole blood, and white muscle. In a second experiment, we subjected captive coastal skates (Leucoraja spp.) to serial salinity reductions to measure possible impacts of tissue urea content on nitrogen stable isotope values. We extracted urea from spiny dogfish (Squalus acanthias) white muscle to test for effects on nitrogen stable isotopes. Isotope turnover was slow for shark tissues and similar to previously published estimates for stingrays and teleost fishes with low growth rates. Muscle isotope data would likely fail to capture seasonal migrations or diet switches in sharks, while liver and whole blood would more closely reflect shorter term movement or shifts in diet. Nitrogen stable isotope values of skate blood and skate and dogfish white muscle were not affected by tissue urea content, suggesting that available diet–tissue discrimination estimates for teleost fishes with similar physiologies would provide accurate estimates for elasmobranchs.     

Effect of dilution rate on eicosapentaenoic acid productivity ofPhaeodactylum tricornutum utex 640 in outdoor chemostat culture

Summary Eicosapentaenoic acid (EPA) volumetric productivity from an outdoor chemostat culture ofPhaeodactylum tricornutum UTEX 640 in a 50-l tubular photobioreactor varies with dilution rate, reaching a maximum of 47.8 mg l^–1 d^–1 at D=0.36 d^–1. Continuous culture at high dilution rates' is proposed as the most adequate operating mode to maximize polyunsaturated fatty acid production.     

L-thyroxine and L-triiodothyronine in the cerebral tissues of the adult rat. Effect of hypothyroidism]

The L-thyroxine and L-triiodothyronine concentrations in several brain areas (cerebral cortex, brain stem, hypothalamus, total brain and hypophysis) in normal and hypothyroid rats have been studied. Results show that L-thyroxine values at tissue level are inferior in the hypothyroid group, although non-significant with respect to the control group, whereas L-triiodothyronine presents values similar to the hypothyroid group and its control in all the brain regions studied with the exception of hypophysis. These results show that in hypothyroid situations exist a compensatory mechanism for maintaining the adequate L-triiodothyronine levels in several brain areas, although the serum levels are strongly decreased in hypothyroid animals.     

Effect of strontium and magnesium on blood calcium]

Twenty four male Wistar rats weighing 250 +/- 10 g, in three groups of 8 rats each, were used. Group A was used as control and the content of its drinking water was 6.5 mg/l Ca; 2.4 mg/l Mg. The drinking water of groups B and C was supplemented with 20 mM (SrCl2) and 20 mM (MgCl2), respectively. Once the 20 days of mineral supplementation had passed, arterial blood was extracted by puncture in the abdominal aorta. In the serum obtained after centrifugation, Ca, Mg, Sr and the total proteins (TP) were determined. Afterwards the serum was subjected to ultrafiltration. Concentrations of Ca, Mg and TP were measured in the obtained ultrafiltrates (u), with the above described techniques. The pH was measured before and after the ultrafiltration. The TP decreased significantly both in group B (supplemented with Sr), and in group C (supplement with Mg). Increases in Ca were found in group B and in Mg in group C. The Mg/Ca ratio increased 10% after the supplementation with Mg. At the ultrafiltrate a significant increase in Cau after supplementation with Sr and with Mg was observed. The Mgu/Cau ratio decreased 14% in the group supplemented with Sr and 38% after the supplementation with Mg. In conclusion, the supplementation with Sr (20 mM) in rats increases the Cau and could have the effect of reducing protein synthesis. These facts should be borne in mind when Sr is used for therapeutical purposes.     

Interferon inhibits DNA Synthesis induced in Mouse Lymphocyte Suspensions by Phytohaemagglutinin or by Allogeneic Cells

IN addition to its well known antiviral activity, interferon has recently been shown to inhibit the multiplication of tumour and mammalian cells in cell culture^1–6. We report here the inhibition by interferon of DNA synthesis induced in mouse spleen lymphocytes by the non-viral stimuli phytohaemagglutinin (PHA) and allogeneic lymphocytes. These findings are in accord with our contention that interferon affects cell function and, furthermore, they suggest that by acting on lymphocytes, interferon plays a role in the immunological response of the host.