The aged hematopoietic system promotes hippocampal‐dependent cognitive decline

The aged systemic milieu promotes cellular and cognitive impairments in the hippocampus. Here, we report that aging of the hematopoietic system directly contributes to the pro‐aging effects of old blood on cognition. Using a heterochronic hematopoietic stem cell (HSC) transplantation model (in which the blood of young mice is reconstituted with old HSCs), we find that exposure to an old hematopoietic system inhibits hippocampal neurogenesis, decreases synaptic marker expression, and impairs cognition. We identify a number of factors elevated in the blood of young mice reconstituted with old HSCs, of which cyclophilin A (CyPA) acts as a pro‐aging factor. Increased systemic levels of CyPA impair cognition in young mice, while inhibition of CyPA in aged mice improves cognition. Together, these data identify age‐related changes in the hematopoietic system as drivers of hippocampal aging.     

On the origin and evolution of thermophily: reconstruction of functional precambrian enzymes from ancestors of Bacillus

Thermophily is thought to be a primitive trait, characteristic of early forms of life on Earth, that has been gradually lost over evolutionary time. The genus Bacillus provides an ideal model for studying the evolution of thermophily as it is an ancient taxon and its contemporary species inhabit a range of thermal environments. The thermostability of reconstructed ancestral proteins has been used as a proxy for ancient thermal adaptation. The reconstruction of ancestral "enzymes" has the added advantages of demonstrable activity, which acts as an internal control for accurate inference, and providing insights into the evolution of enzymatic catalysis. Here, we report the reconstruction of the structurally complex core metabolic enzyme LeuB (3-isopropylmalate dehydrogenase, E. C. 1.1.1.85) from the last common ancestor (LCA) of Bacillus using both maximum likelihood (ML) and Bayesian inference. ML LeuB from the LCA of Bacillus shares only 76% sequence identity with its closest contemporary homolog, yet it is fully functional, thermophilic, and exhibits high values for k(cat), k(cat)/K(M), and ΔG(?) for unfolding. The Bayesian version of this enzyme is also thermophilic but exhibits anomalous catalytic kinetics. We have determined the 3D structure of the ML enzyme and found that it is more closely aligned with LeuB from deeply branching bacteria, such as Thermotoga maritima, than contemporary Bacillus species. To investigate the evolution of thermophily, three descendents of LeuB from the LCA of Bacillus were also reconstructed. They reveal a fluctuating trend in thermal evolution, with a temporal adaptation toward mesophily followed by a more recent return to thermophily. Structural analysis suggests that the determinants of thermophily in LeuB from the LCA of Bacillus and the most recent ancestor are distinct and that thermophily has arisen in this genus at least twice via independent evolutionary paths. Our results add significant fluctuations to the broad trend in thermal adaptation previously proposed and demonstrate that thermophily is not exclusively a primitive trait, as it can be readily gained as well as lost. Our findings also demonstrate that reconstruction of complex functional Precambrian enzymes is possible and can provide empirical access to the evolution of ancient phenotypes and metabolisms.     

Design, synthesis, and activity of achiral analogs of 2-quinolones and indoles as non-thiol farnesyltransferase inhibitors

Beginning with the structure of tipifarnib (1), a series of inhibitors of FTase have been synthesized by transposition of the D-ring to the imidazole and subsequent modification of the 2-quinolone motif. The compounds in the new series may be achiral and have structural features that allow for analogs that are difficult or impossible to make in the tertiary carbon-based tipifarnib series. The most potent compound (4d) is 4 times more active in vitro against FTase than tipifarnib.     

Analyses of deoxycytidylate deaminase molecular forms in human-mouse and monkey-mouse somatic cell hybrids

Disc polyacrylamide gel electrophoresis (disc PAGE) analyses have revealed that mouse, human, and monkey cytosol deoxycytidylate (dCMP) deaminases differ in electrophoretic mobility, so that mixtures of mouse and human, mouse and monkey, and human and monkey enzymes can be separated. To learn whether the genes for dCMP deaminase and thymidine (dT) kinase are genetically linked, disc PAGE analyses of cytosol fractions from human-mouse and monkey-mouse somatic cell hybrids were carried out. The interspecific somatic cell hybrids were derived from the fusion of cytosol dT kinase deficient mouse cells with cytosol dT kinase-positive human and monkey cells: they contained mostly mouse chromosomes and a few primate chromosomes, including the determinant for primate cytosol dT kinase. The disc PAGE analyses demonstrated that the human-mouse and monkey-mouse somatic cell hybrids contained a dCMP deaminase activity with an electrophoretic mobility characteristic of mouse dCMP deaminase. Enzymes with electrophoretic mobilities characteristic of human and monkey dCMP deaminases were not demonstrable. These findings suggest that primate cytosol dT kinase and dCMP deaminase are coded on different chromosomes, or that the formation in hybrid cells of an active primate dCMP deaminase is suppressed. Chick-mouse somatic cell hybrids containing chick but not mouse cytosol dT kinase were also analyzed. The chick-mouse hybrid cells contained cytosol dCMP deaminase activity, but it was not possible to establish whether the enzyme was of murine or avian origin because of the similarity in electrophoretic mobility between the chick and mouse enzymes. Human and mouse cells contained low levels of mitochondrial dCMP deaminase activity. In contrast to dT kinase isozymes, however, mitochondrial and cytosol dCMP deaminases were electrophoretically indistinguishable.This investigation was aided by Grant Q-163 from the Robert A. Welch Foundation and by USPHS Grants CA-06656-12 and 1-K6-AI 2352 from the National Cancer Institute and the National Institute of Allergy and Infectious Diseases.     

Novel Haloperoxidase Reaction: Synthesis of Dihalogenated Products

The enzymatic synthesis of vicinal, dihalogenated products from alkenes and alkynes is described. The enzymatic reaction required an alkene or alkyne, dilute hydrogen peroxide, a haloperoxidase, and molar amounts of halide ions. Vicinal dichloro, dibromo, and diiodo products could be formed. A hydroxyl group on the carbon adjacent to the carbon-carbon double or triple bond lowered the halide ion concentration needed to produce the dihalo product. This reaction offers one explanation for the origin of natural, vicinal, dihalogenated products, such as those found frequently in marine microogranisms.     

Zooprophylaxis or zoopotentiation: the outcome of introducing animals on vector transmission is highly dependent on the mosquito mortality while searching

Background

Zooprophylaxis, the diversion of disease carrying insects from humans to animals, may reduce transmission of diseases such as malaria. However, as the number of animals increases, improved availability of blood meals may increase mosquito survival, thereby countering the impact of diverting feeds.

Methods

Computer simulation was used to examine the effects of animals on the transmission of human diseases by mosquitoes. Three scenarios were modelled: (1) endemic transmission, where the animals cannot be infected, eg. malaria; (2) epidemic transmission, where the animals cannot be infected but humans remain susceptible, e.g. malaria; (3) epidemic disease, where both humans and animals can be infected, but develop sterile immunity, eg. Japanese encephalitis B. For each, the passive impact of animals as well as the use of animals as bait to attract mosquitoes to insecticide was examined. The computer programmes are available from the author. A teaching model accompanies this article.

Results

For endemic and epidemic malaria with significant searching-associated vector mortality, changing animal numbers and accessibility had little impact. Changing the accessibility of the humans had a much greater effect. For diseases with an animal amplification cycle, the most critical factor was the proximity of the animals to the mosquito breeding sites.

Conclusion

Estimates of searching-associated vector mortality are essential before the effects of changing animal husbandry practices can be predicted. With realistic values of searching-associated vector mortality rates, zooprophylaxis may be ineffective. However, use of animals as bait to attract mosquitoes to insecticide is predicted to be a promising strategy.     

Deterioration of High-Moisture Corn

Two small, leaky silos were filled with normal high-moisture corn (HMC), and two with HMC severely infested by Helminthosporium maydis. Counts of mesophilic bacteria, lactobacilli, coliforms, yeasts, and molds were made on corn samples as received and periodically thereafter during 220 days of storage. Temperature and gas levels also were monitored. Sequential changes in the populations of lactobacilli, yeasts, and molds were determined during spoilage of HMC. These population changes were compared on the basis of the variables encountered in the present study as well as with the results of previous studies conducted on normal HMC stored under adequate conditions. Heavy infestation by H. maydis had no appreciable effect on HMC preservation.