Long-chain n−3 polyunsaturated fatty acid production by members of the marine protistan group the thraustochytrids: screening of isolates and optimisation of docosahexaenoic acid production

Following an isolation programme for thraustochytrids (marine fungoid protists) from three different locations, 57 isolates were screened for biomass, oil and docosahexaenoic acid production (DHA). Although a common fatty acid profile for the thraustochytrid isolates emerged, there was considerable variation in the DHA content of the oil. In some isolates from a cold temperate environment, DHA represented almost 50% of the total fatty acids present. Although isolates from a sub-tropical environment produced higher levels of biomass, with up to 37% (w/w) oil, the DHA fraction of the fatty acids was low. Cool temperate isolates gave intermediate values. Studies to optimise biomass and DHA production by manipulation of growth medium composition were carried out on a tropical strain. Results indicated that medium with a high C:N ratio stimulated DHA production. The use of such media in bioreactor cultivations gave maximum biomass, lipid and DHA content of 14 g l⁻¹, 78 and 25% (w/w), respectively. Optimum DHA production was 2.17 g l⁻¹ after 107 h cultivation.     

Biochemical aspects of egg hatch in endo- and ectoparasites: potential for rational drug design.

Control of parasites through rational drug design requires a thorough understanding of the parasite's lifecycle encompassing the biochemical and physiological processes which contribute to normal parasite homeostasis. The hatching of parasite eggs for example, represents an important process in the development of a parasitic infection. Previous studies in helminths have indicated that secreted enzymes often facilitate successful endoparasite egg hatch. In contrast, there are relatively few examples demonstrating a role for secreted enzymes in the egg hatching process of insects. An analysis of this process in the ectoparasite Lucilia cuprina suggests a role for secreted enzymes in the hatching of sheep blowfly eggs. Characterisation of the proteases collected at the time of egg hatch indicates the presence of serine proteases. Further purification and characterisation of these proteases may enable the design of specific inhibitors to interfere with the egg hatch process and therefore provide a novel means of control.     

Hypercholesterolemia increases mitochondrial oxidative stress and enhances the MPT response in the porcine myocardium: beneficial effects of chronic exercise

Hypercholesterolemia has been suggested to have direct negative effects on myocardial function due to increased reactive oxygen species (ROS) generation and increased myocyte death. Mitochondrial permeability transition (MPT) is a significant mediator of cell death, which is enhanced by ROS generation and attenuated by exercise training. The purpose of this study was to investigate the effect of hypercholesterolemia on the MPT response of cardiac mitochondria. We tested the hypothesis that familial hypercholesterolemic (FH) pigs would have an enhanced MPT response and that exercise training could reverse this phenotype. MPT was assessed by mitochondrial swelling in response to 10-100 μM Ca(2+). FH pigs did show an increased MPT response to Ca(2+) that was associated with decreases in the expression of the putative MPT pore components mitochondrial phosphate carrier (PiC) and cyclophilin-D (CypD). FH also caused increased oxidative stress, depicted by increased protein nitrotyrosylation, as well as decreased levels of reduced GSH in cardiac mitochondria. Expression of the mitochondrial antioxidant enzymes manganese superoxide dismutase (MnSOD), thioredoxin-2 (Trx2), and peroxiredoxin-3 (Prx3) was greatly reduced in the FH pigs. In contrast, cytosolic catalase expression and activity were increased. However, chronic exercise training was able to normalize the MPT response in FH pigs, reduce mitochondrial oxidative stress, and return MnSOD, Trx2, Prx3, and catalase expression/activities to normal. We conclude that FH reduces mitochondrial antioxidants, increases mitochondrial oxidative stress, and enhances the MPT response in the porcine myocardium, and that exercise training can reverse these detrimental alterations.     

The Rho kinase inhibitor Y-27632 increases erythrocyte deformability and low oxygen tension-induced ATP release

Low oxygen (O(2)) tension and mechanical deformation are stimuli for ATP release from erythrocytes. It has been shown previously that rabbit erythrocytes made less deformable with diamide, a thiol cross-linking agent, release less ATP in response to low O(2) tension, suggesting a link between these two stimuli. In nonerythroid cells, activation of the Rho/Rho kinase signaling pathway has been reported to decrease cell deformability by altering Rho kinase-dependent cytoskeleton-protein interactions. We investigated the hypothesis that the Rho kinase inhibitor Y-27632 would increase erythrocyte deformability and thereby increase low O(2) tension-induced ATP release from erythrocytes. Here we show that Y-27632 (1 μM) increases erythrocyte deformability (5%) and increases low O(2) tension-induced ATP release (203%) from healthy human erythrocytes. In addition, we found that, when erythrocytes were made less deformable by incubation with diamide (100 μM), Y-27632 restored both deformability and low O(2) tension-induced ATP release to levels similar to those measured in the absence of diamide. These findings suggest that the Rho kinase inhibitor Y-27632 is able to reverse the diamide-induced decrease in erythrocyte deformability and rescue low O(2) tension-induced ATP release. These results further support a link between erythrocyte deformability and ATP release in response to low O(2) tension.     

Evolution of human immunodeficiency virus type 1 in a patient with cross-reactive neutralizing activity in serum

Analysis of longitudinally obtained HIV-1 env sequences from an individual with reported cross-reactive neutralizing activity revealed that the majority of viral variants obtained from serum between 4 and 7 years after seroconversion were unable to persist in peripheral blood. Here we show that these viral variants were more sensitive to autologous serum neutralization, had shorter envelopes with fewer potential N-linked glycosylation sites, and showed lower replication kinetics than successfully evolving HIV-1 variants. These data reflect the host selection pressures on phenotypic characteristics of HIV-1 and illustrate in detail the dynamic interaction between HIV-1 and its host's humoral immune responses.     

AMPK and substrate availability regulate creatine transport in cultured cardiomyocytes

Profound alterations in myocellular creatine and phosphocreatine levels are observed during human heart failure. To maintain its intracellular creatine stores, cardiomyocytes depend upon a cell membrane creatine transporter whose regulation is not clearly understood. Creatine transport capacity in the intact heart is modulated by substrate availability, and it is reduced in the failing myocardium, likely adding to the energy imbalance that characterizes heart failure. AMPK, a key regulator of cellular energy homeostasis, acts by switching off energy-consuming pathways in favor of processes that generate energy. Our objective was to determine the effects of substrate availability and AMPK activation on creatine transport in cardiomyocytes. We studied creatine transport in rat neonatal cardiomyocytes and HL-1 cardiac cells expressing the human creatine transporter cultured in the presence of varying creatine concentrations and the AMPK activator 5-aminoimidazole-4-carboxamide-1-β-d-ribonucleoside (AICAR). Transport was enhanced in cardiomyocytes following incubation in creatine-depleted medium or AICAR. The changes in transport were due to alterations in V(max) that correlated with changes in total and cell surface creatine transporter protein content. Our results suggest a positive role for AMPK in creatine transport modulation for cardiomyocytes in culture.     

Animal vocal sequences: not the Markov chains we thought they were

Many animals produce vocal sequences that appear complex. Most researchers assume that these sequences are well characterized as Markov chains (i.e. that the probability of a particular vocal element can be calculated from the history of only a finite number of preceding elements). However, this assumption has never been explicitly tested. Furthermore, it is unclear how language could evolve in a single step from a Markovian origin, as is frequently assumed, as no intermediate forms have been found between animal communication and human language. Here, we assess whether animal taxa produce vocal sequences that are better described by Markov chains, or by non-Markovian dynamics such as the ‘renewal process’ (RP), characterized by a strong tendency to repeat elements. We examined vocal sequences of seven taxa: Bengalese finches Lonchura striata domestica, Carolina chickadees Poecile carolinensis, free-tailed bats Tadarida brasiliensis, rock hyraxes Procavia capensis, pilot whales Globicephala macrorhynchus, killer whales Orcinus orca and orangutans Pongo spp. The vocal systems of most of these species are more consistent with a non-Markovian RP than with the Markovian models traditionally assumed. Our data suggest that non-Markovian vocal sequences may be more common than Markov sequences, which must be taken into account when evaluating alternative hypotheses for the evolution of signalling complexity, and perhaps human language origins.     

Immunization of sheep against infection with larvae of the blowfly Lucilia cuprina

Sheep were repeatedly exposed to a second stage excretory-secretory antigen preparation of Lucilia cuprina by intradermal injection (S group) or intranasal aerosol (I group) in an attempt to induce immunity to the larvae. Hypersensitivity responses to the injections were monitored and correlated with larval numbers at subsequent challenge. Intradermal injections showed that the immediate or IgE-mediated and the intermediate or Arthus response were the major skin hypersensitivity reactions to the larval antigens. At challenge there was no significant reduction in larval numbers between the S and the control group, however the Arthus reaction did show some correlation with larval recoveries in the S group. There was a significant reduction in larval numbers (P < 0.005 Mann-Whitney U Test) between the I and the control group. In addition, the animals which showed respiratory hypersensitivity to the aerosol during the immunization period had the lowest larval recoveries. The results of a second challenge in the I group did not show continued protection. It is suggested that the protective response was suppressed by exposure to antigens at the first challenge infection. Exudate samples recovered during the infection were analysed for protein amount and the results were correlated with larval survival. They suggested that two separate mechanisms of resistance are operating in this experiment. The first occurs early in the infection, is probably associated with immediate hypersensitivity, and may control the initiation of protein leakage. The second occurs later in the infection and may result in the leakage of proteins able to control larval survival.