Evolution of spore release mechanisms in the saprolegniaceae (Oomycetes): evidence from a phylogenetic analysis of internal transcribed spacer sequences

Classical studies on spore release within the Saprolegniaceae (Oomycetes) led to the proposition that different mechanisms of sporangial emptying represent steps in an evolutionary transition series. We have reevaluated this idea in a phylogenetic framework using internal transcribed spacer sequences of four genera. These data were compared with the response to osmotic stress exhibited by each taxon. Saprolegnia emerges as the most basal genus, sister to Achlya, Thraustotheca, and Dictyuchus. Achlya and Thraustotheca are most closely related, while Dictyuchus appears to have evolved along a separate evolutionary lineage. The resulting phylogenetic framework is consistent with the idea that the mechanism of sporangial emptying exhibited by Saprolegnia represents the plesiomorphic condition from which the other mechanisms were derived independently. These alternative mechanisms of spore release may have resulted from a small number of mutations that inhibited axonemal development and altered the temporal and spatial expression of lytic enzymes that degrade the sporangial wall. Copyright 1998 Academic Press.     

Enantioselective metabolism of primaquine by human CYP2D6

Given the threat of resistance of human malaria parasites, including to artemisinin derivatives, new agents are needed. Chloroquine (CQ) has been the most widely used anti-malarial, and new analogs (CQAns) presenting alkynes and side chain variations with high antiplasmodial activity were evaluated. Six diaminealkyne and diaminedialkyne CQAns were evaluated against CQ-resistant (CQ-R) (W2) and CQ-sensitive (CQ-S) (3D7) Plasmodium falciparum parasites in culture. Drug cytotoxicity to a human hepatoma cell line (HepG2) evaluated, allowed to calculate the drug selectivity index (SI), a ratio of drug toxicity to activity in vitro. The CQAns were re-evaluated against CQ-resistant and -sensitive P. berghei parasites in mice using the suppressive test. Docking studies with the CQAns and the human (Hss LDH) or plasmodial lactate dehydrogenase (Pf LDH) enzymes, and, a β-haematin formation assay were performed using a lipid as a catalyst to promote crystallization in vitro. All tested CQAns were highly active against CQ-R P. falciparum parasites, exhibiting half-maximal inhibitory concentration (IC50) values below 1 μΜ. CQAn33 and CQAn37 had the highest SIs. Docking studies revealed the best conformation of CQAn33 inside the binding pocket of Pf LDH; specificity between the residues involved in H-bonds of the Pf LDH with CQAn37. CQAn33 and CQAn37 were also shown to be weak inhibitors of Pf LDH. CQAn33 and CQAn37 inhibited β-haematin formation with either a similar or a 2-fold higher IC50 value, respectively, compared with CQ. CQAn37 was active in mice with P. berghei, reducing parasitaemia by 100%. CQAn33, -39 and -45 also inhibited CQ-resistant P. berghei parasites in mice, whereas high doses of CQ were inactive. The presence of an alkyne group and the size of the side chain affected anti-P. falciparum activity in vitro. Docking studies suggested a mechanism of action other than Pf LDH inhibition. The β-haematin assay suggested the presence of an additional mechanism of action of CQAn33 and CQAn37. Tests with CQAn34, CQAn37, CQAn39 and CQAn45 confirmed previous results against P. berghei malaria in mice, and CQAn33, 39 and 45 were active against CQ-resistant parasites, but CQAn28 and CQAn34 were not. The result likely reflects structure-activity relationships related to the resistant phenotype.     

Somatosensory areas S2 and PV project to the superior colliculus of a prosimian primate, Galago garnetti

As part of an effort to describe the connections of the somatosensory system in Galago garnetti, a small prosimian primate, injections of tracers into cortex revealed that two somatosensory areas, the second somatosensory area (S2) and the parietal ventral somatosensory area (PV), project densely to the ipsilateral superior colliculus, while the primary somatosensory area (S1 or area 3b) does not. The three cortical areas were defined in microelectrode mapping experiments and recordings were used to identify appropriate injection sites in the same cases. Injections of wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) were placed in S1 in different mediolateral locations representing body regions from toes to face in five galagos, and none of these injections labeled projections to the superior colliculus. In contrast, each of the two injections in the face representation of S2 in two galagos and three injections in face and forelimb representations of PV in three galagos produced dense patches of labeled terminations and axons in the intermediate gray (layer IV) over the full extent of the superior colliculus. The results suggest that the higher-order somatosensory areas, PV and S2, are directly involved in the visuomotor functions of the superior colliculus in prosimian primates, while S1 is not. The somatosensory inputs appear to be too widespread to contribute to a detailed somatotopic representation in the superior colliculus, but they may be a source of somatosensory modulation of retinotopically guided oculomotor instructions.     

Clinical validity of outcome pain measures in naturally occurring canine osteoarthritis

ABSTRACT: BACKGROUND: The conceptual validity of kinetic gait analysis and disability outcome assessment methods has guided their use in the assessment of pain caused by osteoarthritis (OA). No consensus on the best clinical methods for pain evaluation in canine OA exists, particularly, when evaluating treatments where a smaller treatment effect is anticipated than with pharmacological pain killers. This study thus aimed at determining the technical validity of some clinical endpoints on OA pain in dogs using the green-lipped mussel (GLM)-enriched diet. Twenty-three adult dogs with clinical OA completed the prospective controlled study. All the dogs were fed a balanced diet over a 30-day control period followed by a GLM-enriched diet over a 60-day period. The kinetic gait analysis parameter (PVFBW, peak vertical force adjusted for body weight change), electrodermal activity (EDA), and a standardized multifactorial pain questionnaire (MFQ) were performed on day (D) 0 (inclusion), D30 (start) and D90 (end). The owners completed a client-specific outcome measures (CSOM) instrument twice a week. Motor activity (MA) was continuously recorded in seven dogs using telemetered accelerometric counts. We hypothesized that these methods would produce convergent results related to diet changes. A Type I error of 0.05 was adjusted to correct for the multiplicity of the primary clinical endpoints. RESULTS: Neither the EDA nor the MFQ were found reliable or could be validated. Changes in the PVFBW (Padj = 0.0004), the CSOM (Padj = 0.006) and the MA intensity (Padj = 0.02) from D0 to D90 suggested an effect of diet(s). Only the PVFBW clearly increased after the GLM-diet (Padj = 0.003). The CSOM exhibited a negative relationship with the PVFBW (P = 0.02) and MA duration (P = 0.02). CONCLUSIONS: The PVFBW exhibited the best technical validity for the characterization of the beneficial effect of a GLM-enriched diet. The CSOM and MA appeared less responsive following a GLM-diet, but these measures appeared complementary to gait analysis. Apparently, the CSOM provides the capacity to rely on pain OA assessment influenced by both lameness quantification (PVFBW) and physical functioning (MA).     

Structural and gene expression analyses of uptake hydrogenases and other proteins involved in nitrogenase protection in Frankia

The actinorhizal bacterium Frankia expresses nitrogenase and can therefore convert molecular nitrogen into ammonia and the by-product hydrogen. However, nitrogenase is inhibited by oxygen. Consequently, Frankia and its actinorhizal hosts have developed various mechanisms for excluding oxygen from their nitrogen-containing compartments. These include the expression of oxygen-scavenging uptake hydrogenases, the formation of hopanoid-rich vesicles, enclosed by multi-layered hopanoid structures, the lignification of hyphal cell walls, and the production of haemoglobins in the symbiotic nodule. In this work, we analysed the expression and structure of the so-called uptake hydrogenase (Hup), which catalyses the in vivo dissociation of hydrogen to recycle the energy locked up in this ‘waste’ product. Two uptake hydrogenase syntons have been identified in Frankia: synton 1 is expressed under free-living conditions while synton 2 is expressed during symbiosis. We used qPCR to determine synton 1 hup gene expression in two Frankia strains under aerobic and anaerobic conditions. We also predicted the 3D structures of the Hup protein subunits based on multiple sequence alignments and remote homology modelling. Finally, we performed BLAST searches of genome and protein databases to identify genes that may contribute to the protection of nitrogenase against oxygen in the two Frankia strains. Our results show that in Frankia strain ACN14a, the expression patterns of the large (HupL1) and small (HupS1) uptake hydrogenase subunits depend on the abundance of oxygen in the external environment. Structural models of the membrane-bound hydrogenase subunits of ACN14a showed that both subunits resemble the structures of known [NiFe] hydrogenases (Volbeda et al. 1995), but contain fewer cysteine residues than the uptake hydrogenase of the Frankia DC12 and Eu1c strains. Moreover, we show that all of the investigated Frankia strains have two squalene hopane cyclase genes (shc1 and shc2). The only exceptions were CcI3 and the symbiont of Datisca glomerata, which possess shc1 but not shc2. Four truncated haemoglobin genes were identified in Frankia ACN14a and Eu1f, three in CcI3, two in EANpec1 and one in the Datisca glomerata symbiont (Dg).     

Reduced susceptibility to eccentric exercise-induced muscle damage in resistance-trained men is not linked to resistance training-related neural adaptations

The purpose of this study was to examine the acute effects of maximal concentric vs. eccentric exercise on the isometric strength of the elbow flexor, as well as the biceps brachii muscle electromyographic (EMG) responses in resistance-trained (RT) vs. untrained (UT) men. Thirteen RT men (age: 24 ± 4 years; height: 180.2 ± 7.7 cm; body weight: 92.2 ± 16.9 kg) and twelve UT men (age: 23 ± 4 years; height: 179.2 ± 5.0 cm; body weight: 81.5 ± 8.6 kg) performed six sets of ten maximal concentric isokinetic (CON) or eccentric isokinetic (ECC) elbow flexion exercise in two separate visits. Before and after the exercise interventions, maximal voluntary contractions (MVCs) were performed for testing isometric strength. In addition, bipolar surface EMG signals were detected from the biceps brachii muscle during the strength testing. Both CON and ECC caused isometric strength to decrease, regardless of the training status. However, ECC caused greater isometric strength decline than CON did for the UT group (p = 0.006), but not for the RT group. Both EMG amplitude and mean frequency significantly decreased and increased, respectively, regardless of the training status and exercise intervention. Resistance-trained men are less susceptible to eccentric exercise-induced muscle damage, but this advantage is not likely linked to the chronic resistance training-induced neural adaptations.     

Somatosensory areas S2 and PV project to the superior colliculus of a prosimian primate,Galago garnetti

As part of an effort to describe the connections of the somatosensory system in Galago garnetti, a small prosimian primate, injections of tracers into cortex revealed that two somatosensory areas, the second somatosensory area (S2) and the parietal ventral somatosensory area (PV), project densely to the ipsilateral superior colliculus, while the primary somatosensory area (S1 or area 3b) does not. The three cortical areas were defined in microelectrode mapping experiments and recordings were used to identify appropriate injection sites in the same cases. Injections of wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) were placed in S1 in different mediolateral locations representing body regions from toes to face in five galagos, and none of these injections labeled projections to the superior colliculus. In contrast, each of the two injections in the face representation of S2 in two galagos and three injections in face and forelimb representations of PV in three galagos produced dense patches of labeled terminations and axons in the intermediate gray (layer IV) over the full extent of the superior colliculus. The results suggest that the higher-order somatosensory areas, PV and S2, are directly involved in the visuomotor functions of the superior colliculus in prosimian primates, while S1 is not. The somatosensory inputs appear to be too widespread to contribute to a detailed somatotopic representation in the superior colliculus, but they may be a source of somatosensory modulation of retinotopically guided oculomotor instructions.     

Short-term variations of mycosporine-like amino acids in the carrageenan-producing red macroalga Mazzaella laminarioides (Gigartinales,Rhodophyta) are related to nitrate availability

Journal of Applied Phycology - The effect of solar UV radiation exposure and NO3– supply on mycosporine-like amino acids (MAAs) accumulation in the carrageenan-producing red macroalga...