Dynamic rearrangement of the filamentous actin network occurs during zoosporogenesis and encystment in the oomycete phytophthora cinnamomi

The organization of filamentous actin (F-actin) in living cells of the oomycete Phytophthora cinnamomi was determined during zoosporogenesis and zoospore encystment by microinjecting sporangia with fluorescently labeled phalloidin and observing resultant fluorescence by confocal microscopy. In multinucleate sporangia prior to the induction of cleavage, phalloidin labeling took the form of plaques which occurred mainly in the periphery of the sporangia. After induction of cleavage, phalloidin labeling showed that the plaques disappeared and that F-actin began to accumulate along the developing cleavage planes and around nuclei and water expulsion vacuoles. F-actin labeling was also observed near the plasma membrane in zoospores and young cysts but reverted to the plaque form in older cysts. Localization of F-actin close to the developing cleavage planes is consistent with the idea that actin microfilaments function in the positioning and expansion of the cleavage membranes. Observations of plaques of actin in living sporangia provide evidence that plaques are not aldehyde-induced fixation artifacts. Copyright 1998 Academic Press.     

Dermatan sulfate is the predominant antithrombotic glycosaminoglycan in vessel walls: implications for a possible physiological function of heparin cofactor II

The role of different glycosaminoglycan species from the vessel walls as physiological antithrombotic agents remains controversial. To further investigate this aspect we extracted glycosaminoglycans from human thoracic aorta and saphenous vein. The different species were highly purified and their anticoagulant and antithrombotic activities tested by in vitro and in vivo assays. We observed that dermatan sulfate is the major anticoagulant and antithrombotic among the vessel wall glycosaminoglycans while the bulk of heparan sulfate is a poorly sulfated glycosaminoglycan, devoid of anticoagulant and antithrombotic activities. Minor amounts of particular a heparan sulfate (< 5% of the total arterial glycosaminoglycans) with high anticoagulant activity were also observed, as assessed by its retention on an antithrombin-affinity column. Possibly, this anticoagulant heparan sulfate originates from the endothelial cells and may exert a significant physiological role due to its location in the interface between the vessel wall and the blood. In view of these results we discuss a possible balance between the two glycosaminoglycan-dependent anticoagulant pathways present in the vascular wall. One is based on antithrombin activation by the heparan sulfate expressed by the endothelial cells. The other, which may assume special relevance after vascular endothelial injury, is based on heparin cofactor II activation by the dermatan sulfate proteoglycans synthesized by cells from the subendothelial layer.     

Protein import, replication, and inheritance of a vestigial mitochondrion

Mitochondrial remnant organelles (mitosomes) that exist in a range of "amitochondrial" eukaryotic organisms represent ideal models for the study of mitochondrial evolution and for the establishment of the minimal set of proteins required for the biogenesis of an endosymbiosis-derived organelle. Giardia intestinalis, often described as the earliest branching eukaryote, contains double membrane-bounded structures involved in iron-sulfur cluster biosynthesis, an essential function of mitochondria. Here we present evidence that Giardia mitosomes also harbor Cpn60, mtHsp70, and ferredoxin and that despite their advanced state of reductive evolution they have retained vestiges of presequence-dependent and -independent protein import pathways akin to those that operate in mammalian mitochondria. Although import of IscU and ferredoxin is still reliant on their amino-terminal presequences, targeting of Giardia Cpn60, IscS, or mtHsp70 into mitosomes no longer requires cleavable presequences, a derived feature from their mitochondrial homologues. In addition, we found that division and segregation of a single centrally positioned mitosome tightly associated with the microtubular cytoskeleton is coordinated with the cell cycle, whereas peripherally located mitosomes are inherited into daughter cells stochastically.     

Effect of age on the orientation of the auricular activation vector in pig

The effects of cardiac maturation on the orientation of the auricular activation mean vectors (AP and SAP) in Landrace X White Belgian pigs has been analyzed. The magnitudes of AP and SAP vectors undergo a significant increase between 5 and 20 days of age. On the contrary, physical maturation does not appear to have any effect on the sequence of auricular activation in pigs, since in all the age groups analyzed, the same orientation for P vectors on the horizontal plane and in space was maintained. Both vectors indicated that the auricular activation front was predominantly directed towards the left, caudally and ventrally. It should be noted that in a high percentage of individuals of 1 to 5 days of age, the auricular activation vector goes towards the left and cranially.     

Histological development of the digestive system of Mayan cichlid Cichlasoma urophthalmus (Günther 1862)

The ontogeny of the digestive tract in Cichlasoma urophthalmus was studied by means of optical microscopy from hatching to 30 days post‐hatching (dph; 855 degree days, dd). The development of the digestive system in this precocial species was a very intense and asynchronous process, which proceeded from both distal ends interiorly. At hatching, the digestive tract consisted of a straight tube with a smooth lumen dorsally attached to the yolk‐sac. The digestive accessory glands were already differentiated and eosinophilic zymogen granules were visible in the exocrine pancreas. At the onset of exogenous feeding between 5 and 6 dph (142.5–171.0 cumulative thermal units, CTU), the buccopharynx, oesophagus, intestine, liver and pancreas were almost completely differentiated, with the exception of the gastric stomach that completed its differentiation between 11 and 14 dph (313.5–399.0 CTU). The development of gastric glands at 14 dph and the differentiation of the stomach in the fundic, cardiac and pyloric regions at 19 dph (541.5 CTU) were the last major events in digestive tract development and designated the onset of the juvenile period. Remnants of yolk were still detected until 16 dph (456.0 CTU), indicating a long period of mixed nutrition that lasted between 10 and 11 days (285.0–313.5 CTU). The results of the organogenesis of larvae complement previous data on the functionality of the digestive system and represent a useful tool for establishing the functional systemic capabilities and physiological requirements of larvae to ensure optimal welfare and growth under aquaculture conditions, which might be useful for improving current larval rearing practices for this cichlid species.     

Natural hybridisation among Quercus glabrescens,Q. rugosa and Q. obtusata (Fagaceae): Microsatellites and secondary metabolites markers

• Natural hybridisation has significant ecological, genetic and evolutionary consequences altering morphological and chemical characters of individuals. Quercus glabrescens, Q. rugosa and Q. obtusata are white oak species well separated by their morphological characters when they occur in allopatry in Mexican temperate forests. However, in sympatry, individuals with atypical morphology have been observed, suggesting hybridisation events.
• In this study, we determined, with microsatellites and secondary metabolites, if interspecific gene flow occurs when these three oak species coexist in sympatry. In total, 180 individuals belonging to seven populations [three allopatric (one for each parental species) and four sympatric sites] were analysed.
• Allopatric populations represent well‐defined genetic groups and the sympatric populations showed genetic evidence of hybridisation between Q. glabrescens × Q. rugosa and Q. glabrescens × Q. obtusata. The hybridisation percentage varied between sites and combination of involved species. We registered the presence of unique flavonoid compounds for Q. glabrescens (caffeic acid and flavonol 2), Q. rugosa (flavonol 5) and Q. obtusata (flavonol 1). Three compounds (quercetin rhamnoside, flavonol 3 and alkyl coumarate) were expressed in all taxa. Finally, the hybrid genotypes identified in this study (Q. glabrescens × Q. rugosa and Q. glabrescens × Q. obtusata) showed specific chemical profiles, resulting from a combination of those of their parental species.
• These results show that hybridisation events between these oak species alter chemical expression of secondary metabolites, creating a mosaic of resources and conditions that provide the substrate for different combinations of foliar‐associated species such as herbivores, endophytic fungi or epiphyte plants.

     

Glucose-6-phosphate dehydrogenase deficiency in northern Mexico and description of a novel mutation

Glucose-6-phosphate dehydrogenase deficiency (G6PD) is the most common enzyme pathology in humans; it is X-linked inherited and causes neonatal hyperbilirubinaemia, chronic nonspherocytic haemolytic anaemia and drug-induced acute haemolytic anaemia. G6PD deficiency has scarcely been studied in the northern region of Mexico, which is important because of the genetic heterogeneity described in Mexican population. Therefore, samples from the northern Mexico were biochemically screened for G6PD-deficiency, and PCR-RFLPs, and DNA sequencing used to identify mutations in positive samples. The frequency of G6PD deficiency in the population was 0.95% (n = 1993); the mutations in 86% of these samples were G6PD A^?202A/376G , G6PD A^?376G/968C and G6PD Santamaria^376G/542T . Contrary to previous reports, we demonstrated that G6PD deficiency distribution is relatively homogenous throughout the country (P = 0.48336), and the unique exception with high frequency of G6PD deficiency does not involve a coastal population (Chihuahua: 2.4%). Analysis of eight polymorphic sites showed only 10 haplotypes. In one individual we identified a new G6PD mutation named Mexico DF^193A>G (rs199474830), which probably results in a damaging functional effect, according to PolyPhen analysis. Proteomic impact of the mutation is also described.