Epigenetic alterations in folate transport genes in placental tissue from fetuses with neural tube defects and in leukocytes from subjects with hyperhomocysteinemia

The objectives of this study were to identify tissue-specific differentially methylated regions (T-DMR’s) in the folate transport genes in placental tissue compared with leukocytes, and from placental tissues obtained from normal infants or with neural tube defects (NTDs). Using pyrosequencing, we developed methylation assays for the CpG islands (CGIs) and the CGI shore regions of the folate receptor α (FOLR1), proton-coupled folate transporter (PCFT) and reduced folate carrier 1 (RFC1) genes. The T-DMRs differed in location for each gene and the difference in methylation ranged between 2 and 54%. A higher T-DMR methylated fraction was associated with a lower mRNA level of the FOLR1 and RFC1 genes. Methylation fractions differed according to RFC1 80G > A genotype in the NTD cases and in leukocytes from subjects with high total plasma homocysteine (tHcy). There were no differences in methylated fraction of folate transporter genes between NTD cases and controls. We suggest that T-DMRs participate in the regulation of expression of the FOLR1 and RFC1 genes, that the RFC1 80G > A polymorphism exerts a gene-nutrition interaction on DNA methylation in the RFC1 gene, and that this interaction appears to be most prominent in NTD-affected births and in subjects with high tHcy concentrations.     

Comparison of complex modeling strategies for prediction of a binary outcome based on a few,highly correlated predictors

Motivated by a clinical prediction problem, a simulation study was performed to compare different approaches for building risk prediction models. Robust prediction models for hospital survival in patients with acute heart failure were to be derived from three highly correlated blood parameters measured up to four times, with predictive ability having explicit priority over interpretability. Methods that relied only on the original predictors were compared with methods using an expanded predictor space including transformations and interactions. Predictors were simulated as transformations and combinations of multivariate normal variables which were fitted to the partly skewed and bimodally distributed original data in such a way that the simulated data mimicked the original covariate structure. Different penalized versions of logistic regression as well as random forests and generalized additive models were investigated using classical logistic regression as a benchmark. Their performance was assessed based on measures of predictive accuracy, model discrimination, and model calibration. Three different scenarios using different subsets of the original data with different numbers of observations and events per variable were investigated. In the investigated setting, where a risk prediction model should be based on a small set of highly correlated and interconnected predictors, Elastic Net and also Ridge logistic regression showed good performance compared to their competitors, while other methods did not lead to substantial improvements or even performed worse than standard logistic regression. Our work demonstrates how simulation studies that mimic relevant features of a specific data set can support the choice of a good modeling strategy.     

Population structure of Placostylus hongii (Gastropoda: Paryphantidae) on the Poor Knights Islands

Abstract

Populations of the native land snail Placostylus hongii (Lesson, 1830) on the Poor Knights Islands were investigated during visits in 1976, 1977, and 1978. Marking and recapture of individual snails showed that linear growth of the shell ceased when a lip was formed around the outer margin of the aperture. Measurements of snails suggested that increase in outer lip width was a good indication of age, but that the rate of lip thickening varied between populations. Large Placostylus showed a restricted range of movement. Both tagging studies and random sampling revealed that mortality was size specific. Most small snails (<60 mm shell length) located were dead, whereas most larger snails were alive. Population densities of living snails averaged 2.2 individuals per 0.25 m² in the study area. The local distribution was patchy owing to the tendency of snails to be associated with specific features of the vegetation.     

Adaptation of oysters to life on soft substrates

In spite of their sessile nature, oysters of the genera Crassostrea, Ostrea and their allies are adapted to live on soft muddy bottoms. To provide them with secure attachment and to keep the animal above the surface of the mud, these soft-bottom oysters employ two basic strategies. They tend to be gregarious in their settlement, thereby providing one another with surfaces for attachment, and they form lightweight shells. In addition to these common characteristics, these oysters have followed different morphological pathways to live successfully on soft muddy bottoms. There are at least four types of morphologies: (1) relay-type succession (shells pile up on one another over many generations); (2) konbo-type elongation (both valves grow vertically upwards, the dorsal hinge remaining at the base, near the umbo); (3) cone-type elongation (the attached valve grows upwards and the free valve acts as a lid); and (4) lightweight recliners (bulky shells with lightweight fabrics and cavities within them). Judging from the variety of taxa that have adopted it and the sizes of their populations, the relay-type is the most successful of these strategies. Recliners were particularly common during the Mesozoic. The relay-type appeared in the Late Jurassic, becoming the dominant adaptive strategy during the Cenozoic.     

Phylogenetic implications and diagenetic stability of macromolecules from pleistocene and recent shells of Mercenaria mercenaria (mollusca,bivalvia)

The phylogeny and diagenesis of Pleistocene and Recent bivalves were studied immunologically by use of a conventional antiserum elicited against an EDTA‐soluble macromolecular extract from shells of the modern bivalve mollusc Mercenaria mercenaria. ELISA tests of the antiserum with shell fragments of a wide range of modern bivalves gave taxonomically significant results. The antiserum reacted with palaeoheterodonts and heterodonts but not with representatives of other bivalve subclasses. This phylogenetic reactivity was also apparent in tests with fossil shells, although the specificity and overall strength of the reaction were both reduced. Absorption of the antiserum with etched shell powders of various (palaeo)heterodonts yielded more specific antibody preparations.

Investigations of shell matrix diagenesis, using the anti‐Mercenaria serum, demonstrated that small amounts of original determinants could be detected even in fossils over one million years old. The reactivity of the serum with extracts of fossil Mercenaria decreased with sample age. The relationship between serum reactivity and the degree of amino acid racemization was almost linear. Clearly, the various determinants to which antibodies were elicited were being destroyed at different rates.     

Sexual maturity in young Dreissena polymorpha from Lake Como (N. Italy)

Summary

The reproductive biology of the zebra mussel Dreissena polymorpha was studied during 1999 in a natural population living in Lake Como (N. Italy), with particular reference to the differences in behavior between young and adult mussels. Histological analysis of gonads was used to study the gametogenic cycles and to evaluate when the young reached sexual maturity. Signs of active gametogenesis were detected in ≥4 mm shell length mussels. Mature gametes and the first spawning events were observed in ≥5 mm males and in ≥6 mm females. The gonad feature of ≥7 mm mussels was similar to that of the adults. Size frequency distributions revealed that the new generation (0⁺) first spawned in the year following birth, but only after winter. The length of larval time seemed to vary greatly depending on the spawning period, in addition to the environmental conditions. The first settled mussels ≥500 μm in shell length were observed 3–4 months after the first depositions. Water temperature seemed to be the most important factor which regulated sexual phenomena of both young and adult mussels. Its role in the onset of the spawning events was confirmed, but it is important to point out that temperature is not enough to trigger reproduction since gamete release is impossible without sufficient energy, especially for young mussels.     

Comparison of a modified shell vial culture procedure with conventional mouse inoculation for rabies virus isolation

Rabies is a neurotropic disease that is often lethal. The early diagnosis of rabies infection is important and requires methods that allow for the isolation of the virus from animals and humans. The present study compared a modified shell vial (MSV) procedure using 24-well tissue culture plates with the mouse inoculation test (MIT), which is considered the gold standard for rabies virus isolation. Thirty brain samples (25 positive and 5 negative by the fluorescent antibody test) obtained from different animal species at the National Institute of Hygiene Rafael Rangel in Caracas, Venezuela, were studied by the MIT and MSV assays. Nine samples (36%) were positive at 24 h, 10 (40%) were positive at 48 h and six (24%) were positive at 72 h by the MSV assay. With the MIT assay, 76% were positive at six days post inoculation and 12% were positive at 12 and 18 days post inoculation. One sample that was negative according to the MSV assay was positive with MIT on the 12th day. The MSV procedure exhibited a sensitivity of 96.2%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value 80%. This procedure allowed for rapid rabies virus detection. MIT can be employed as an alternative method in laboratories without tissue culture facilities.     

Catalogue et affinités géographiques des Odonata des îles voisines de Madagascar (Insecta: Pterygota)

Une analyse bibliographique exhaustive révèle que 71 espèces et sous-espèces d’Odonates sont présentes sur l’ensemble des îles voisines de Madagascar appartenant aux archipels des Mascareignes, des Comores et des Seychelles. Le taux d’endémisme maximal pour l’ensemble des îles voisines de Madagascar est de 34 %. Le taux d’endémisme est sensiblement plus important dans les Mascareignes (34 %) qu’aux Comores (23 %) ou aux Seychelles (19 %). Le peuplement odonatologique y est dominé par les Libellulidae (36 taxons) et les Coenagrionidae (18 taxons). Chaque archipel possède au moins un des 23 taxons endémiques présents sur ces îles. Les Seychelles comptent deux genres monospécifiques endémiques: Allolestes et Leptocnemis. Les Mascareignes abritent deux genres endémiques: Thalassothemis et Coenagriocnemis. Ce dernier a subi une radiation évolutive au sein de l’archipel. Les îles voisines de Madagascar se caractérisent par une radiation évolutive des genres Hemicordulia et Gynacantha à l’échelle de la région. Les affinités géographiques sont principalement afro-tropicales. La colonisation à partir de l’Afrique est le fait de taxons particuliers qui ne sont pas un échantillon aléatoire de l’ensemble du pool continental. Sur l’ensemble des îles voisines de Madagascar, la richesse spécifique des peuplements d’Odonates d’affinité africaine est maximale sur les îles proches du continent.     

Strategic Management of an Invasive Ant‐scale Mutualism Enables Recovery of a Threatened Tropical Tree Species

Mutualisms between invasive ants and honeydew‐producing insects can have widespread negative effects on natural ecosystems. This is becoming an increasingly serious problem worldwide, causing certain ecosystems to change radically. Management of these abundant and influential mutualistic species is essential if the host ecosystem is to recover to its former non‐invaded status. This negative effect is particularly prevalent on some tropical islands, including Cousine Island, Seychelles. On this island, the invasive ant Pheidole megacephala has caused serious indirect damage to the threatened native Pisonia grandis trees via a mutualism with an invasive scale insect, Pulvinaria urbicola. We aimed to suppress the ant, thereby decoupling the mutualism and enabling recovery of the Pisonia trees. We treated all areas where ant pressure was high with a selective formicidal bait, which was deployed in custom‐made bait stations designed to avoid risk of treatment to endemic fauna. In the treated area, ant foraging activity was reduced by 93 percent and was followed by a 100 percent reduction in scale insect density. Abundance of endemic herbivorous insects and herbivorous activity increased significantly, however, after the decline in mutualistic species densities. Despite the native herbivore increase, there was considerable overall improvement in Pisonia shoot condition and an observed increase in foliage density. Our results demonstrate the benefit of strategic management of highly mutualistic alien species to the native Pisonia trees. It also supports the idea that area‐wide suppression is a feasible alternative to eradication for achieving positive conservation management at the level of the forest ecosystem.