Accumulation and turnover of the classical Folch-Lees proteolipid proteins in developing and adult rat brain.

The turnover of classical Folch-Lees proteolipid proteins was studied after administration of [2,3-3H]tryptophan to both developing and adult rat brain. The animals were killed from 2h to 250 days after subcutaneous injections of [3H]tryptophan. The measured specific radioactivity in developing brain attained maximum value 24h after the administration of label, whereas the total radioactivity per brain reached a maximum 21 days after injection. The half-life of proteolipid protein from the measured specific radioactivity was 7-20 days, depending on the time-points used for the calculation, whereas calculation from total radioactivity between 28-77 and 91-257 days gave half-lives of 35-40 and 188 days respectively. In contrast, in animals injected at 40 days of age, the half-life from the whole-brain-radioactivity data was 188 days. The problem of the recycling of radioactivity for the synthesis of myelin proteins from either a general or a discrete amino acid pool is discussed.     

Possible role in uptake of water vapour by ixodid tick salivary glands

The mouth is confirmed as the site of water vapor uptake in the lone star tick, Amblyomma americanum. It was shown that the level of chloride (³⁶Cl) increased in the mouthparts of desiccated ticks. The highest levels of ³⁶Cl were found in the mouthparts, salivary glands, and gut tissue during rehydration. It is suggested that ions are secreted by the salivary glands into the mouth where water is picked up hygroscopically by the secretion. It is further suggested that the water and ions are then swallowed and absorbed from the lumen of the gut.     

Formation of sulfhydryl groups in the walls of Eimeria stiedai and E. tenella oocysts subjected to in vitro excystation.

Eimeria stiedai or Eimeria tenella oocysts were incubated in aqueous cysteine hydrochloride (cysHCl) under carbon dioxide (CO2), aqueous cysHCl under air, water under CO2 or water under air, and analyzed for sulfhydryl (-SH) groups. The cysHCl-CO2 treatment produced more -SH groups than the other treatments and was effective in allowing activation of intact and sodium hypochlorite (NaOCl)-treated E. stiedai oocysts as well as NaOCl-treated E. tenella oocysts. The CO2-cysHCl complex may act directly on the oocyst wall, especially in the micropylar region, to unmask lipid-shielded disulfide bridges, which are reduced to -SH groups. The reduction apparently disturbs the protein superstructure of the oocyst wall, promotes opening of the micropyle, and changes the impermeable state of the sporulated oocyst.     

Surface distribution of the fatty acid side chains of phosphatidylethanolamine in mixed phospholipid vesicles

A method has been developed for the selective determination of the fatty acid side chain distribution associated with the amino containing phospholipids located in the inner and outer surfaces of membranes. Using sonicated phosphatidylethanolamine/phosphatidylcholine vesicles as a model, the analysis consists of selective labeling of the outer surface amino groups with the membrane impermeable reagent 2,4,6-trinitrobenzenesulfonic acid. Outer and inner surface phosphatidylethanolamine fractions are separated by thin-layer chromatography. Analysis of methyl esters derived from these two fractions, by gas-liquid chromatography, yields the fatty acid side chain distribution. Our results show that there is no mol fraction dependence of the incorporation of any specific fatty acid side chains of egg yolk phosphatidylethanolamine into the vesicle or any preferential distribution of these side chains in the inner or outer vesicle surface. The surface distribution of the egg yolk phosphatidylethanolamine molecules in these vesicles appears to be determined by the head group packing requirements and not the fatty acid side chain composition.     

The antioxidant efficiency of vitamin C is concentration-dependent

The inhibition of autoxidation of plasma lipids by vitamin C (ascorbic acid) has been studied. The ascorbate stoichiometric factor, n, i.e., the number of peroxyl radicals trapped by each ascorbate molecule, decreases as the concentration of ascorbate increases. This is attributed to the fact that ascorbate not only acts as a radical-trapping antioxidant, but can also undergo autoxidation. The data indicate that n----2.0 as [ascorbate]----0 and that n----0 as [ascorbate]----infinity. This concentration-dependent behaviour accounts for the wide variation of n values reported in the literature. It is suggested that this autoxidative destruction of ascorbate may play a role regulating its concentration in blood plasma.     

Evolutionary Patterns of Morphology and Behavior as Inferred from a Molecular Phylogeny of New World Emballonurid Bats (Tribe Diclidurini)

A molecular phylogeny of New World emballonurid bats based on parsimony and Bayesian analyses of loci from the three different nuclear genetic transmission pathways in mammals (autosomal, X, and Y chromosomes) is well supported and independently corroborated by each individual gene tree. This is in contrast to a single most parsimonious but poorly supported tree based on morphological data, which has only one intergeneric or higher relationship shared with the molecular phylogeny. Combining the morphological and molecular data partitions results in a tree similar to the molecular tree suggesting a high degree of homoplasy and low phylogenetic signal in the morphological data set. Behavioral data are largely incomplete and likewise produce a poorly resolved tree. Nonetheless, patterns of evolution in morphology and behavior can be investigated by using the molecular tree as a phylogenetic framework. Character optimization of the appearance of dorsal fur and preferred roosting sites maps consistently and are correlated on the phylogeny. This suggests an association of camouflage for bats with unusual appearance (two dorsal stripes in Rhynchonycteris and Saccopteryx, or pale fur in Cyttarops and Diclidurus) and roosting in exposed sites (tree trunks or under palm leaves). In contrast, the ancestral states for Old and New World emballonurids are typically uniform brown or black, and they usually roost in sheltered roosts such as caves and tree hollows. Emballonuridae is the only family of bats that has a sac-like structure in the wing propatagium, which is found in four New World genera. Mapping the wing sac character states onto the phylogeny indicates that wing sacs evolved independently within each genus and that there may be a phylogenetic predisposition for this structure. Ear orientation maps relatively consistently on the molecular phylogeny and is correlated to echolocation call parameters and foraging behavior, suggesting a phylogenetic basis for these character systems.