Organismal differences in post-translational modifications in histones H3 and H4

Post-translational modifications (PTMs) of histones play an important role in many cellular processes, notably gene regulation. Using a combination of mass spectrometric and immunobiochemical approaches, we show that the PTM profile of histone H3 differs significantly among the various model organisms examined. Unicellular eukaryotes, such as Saccharomyces cerevisiae (yeast) and Tetrahymena thermophila (Tet), for example, contain more activation than silencing marks as compared with mammalian cells (mouse and human), which are generally enriched in PTMs more often associated with gene silencing. Close examination reveals that many of the better-known modified lysines (Lys) can be either methylated or acetylated and that the overall modification patterns become more complex from unicellular eukaryotes to mammals. Additionally, novel species-specific H3 PTMs from wild-type asynchronously grown cells are also detected by mass spectrometry. Our results suggest that some PTMs are more conserved than previously thought, including H3K9me1 and H4K20me2 in yeast and H3K27me1, -me2, and -me3 in Tet. On histone H4, methylation at Lys-20 showed a similar pattern as H3 methylation at Lys-9, with mammals containing more methylation than the unicellular organisms. Additionally, modification profiles of H4 acetylation were very similar among the organisms examined.     

Complex formation by 3 H-aldosterone in rat kidney and liver

Low molecular weight polar complexes were shown to be formed $\text{in vivo}$ from ³H-aldosterone in both kidney and liver subcellular fractions, the majority being present in the cytosol fractions. Significant differences were observed between the quantities of polar complexes present in kidney subcellular fractions from intact and adrenalectomized male rats and also between the quantities of these kidney polar complexes from spironolactone treated male rats. ³H-aldosterone macro-molecule complexes were shown to exist in appreciable quantities only in the kidney cytosol fractions of adrenalectomized male rats. These gel filtration studies also showed the ³H-aldosterone labeled macromolecule complexes to consist of two protein peaks; one of high molecular weight and the other of lower molecular weight (～50,000 mol. wt.). The amount of ³H-aldosterone labeled protein complexes in kidney cytosol was greatly reduced when adrenalectomized rats were pretreated $\text{in vivo}$ with spironolactone.     

Adrenergic desensitization in leukocytes of normal and asthmatic subjects.

Cyclic AMP was measured in leukocytes of normal and asthmatic subjects before and after one week of treatment with equal amounts of ephedrine. During the control and placebo periods, the measurements of cyclic AMP in leukocytes of asthmatic subjects were similar to those of normal individuals. After one week of treatment with ephedrine, both groups exhibited suppression of the leukocyte cyclic AMP response to adrenergic stimulation in vitro: however, the suppression of response was significantly greater in asthmatic subjects (p less than .u1). Subcutaneous administration of epinephrine was followed by further suppression of the leukocyte cyclic AMP response to in vitro stimulation which was similar in both groups during all treatment periods. The results indicate that in vivo exposure to adrenergic medications is followed by desensitization of the leukocyte responses to subsequent adrenergic stimulation in vitro. After administration of small doses of medication, the severity and/or duration of desensitization is significantly greater in asthmatic leukocytes.     

Structural and functional connectivity of marine fishes within a semi-enclosed Newfoundland fjord

The interplay between structural connectivity ( i.e. habitat continuity) and functional connectivity ( i.e. dispersal probability) in marine fishes was examined in a coastal fjord (Holyrood Pond, Newfoundland, Canada) that is completely isolated from the North Atlantic Ocean for most of the year. Genetic differentiation was described in three species (rainbow smelt Osmerus mordax , white hake Urophycis tenuis and Atlantic cod Gadus morhua ) with contrasting life histories using seven to 10 microsatellite loci and a protein-coding locus, Pan I ( G. morhua ). Analysis of microsatellite differentiation indicated clear genetic differences between the fjord and coastal regions; however, the magnitude of difference was no more elevated than adjacent bays and was not enhanced by the fjord's isolation. Osmerus mordax was characterized by the highest structure overall with moderate differentiation between the fjord and St Mary's Bay ( F _ST c. 0·047). In contrast, U. tenuis and G. morhua displayed weak differentiation ( F _ST < 0·01). Nonetheless, these populations did demonstrate high rates (< 75%) of Bayesian self-assignment. Furthermore, elevated differentiation was observed at the Pan I locus in G. morhua between the fjord and other coastal locations. Interestingly, locus-specific genetic differentiation and expected heterozygosity were negatively associated in O. mordax , in contrast to the positive associations observed in U. tenuis and G. morhua . Gene flow in these species is apparently unencumbered by limited structural connectivity, yet the observed differentiation suggests that population structuring exists over small scales despite high dispersal potential.     

Embryogenesis in the Presence of Blockers of Mechanosensitive Ion Channels

Certain developmental events are thought to be controlled by mechanical tension, but the nature of the transduction mechanism for sensing and responding to tension changes is unknown. A good candidate for such a sensing system would be stretch-activated (SA) ion channels, a type of mechanosensitive (MS) ion channel found in many preparations including the oocytes or embryos of ascidians, fish, and amphibians. To test the hypothesis that SA channel activation is important for early embryogenesis, we treated amphibian and ascidian eggs and embryos with inhibitors of MS ion channels. Xenopus laevis eggs and embryos were treated with gadolinium (Gd³⁺) concentrations up to 100 times the K_d for SA channel inhibition. Boltenia villosa eggs and embryos were exposed to three agents (Gd³⁺, tubocurarine, and gallamine) which are known to block SA channels in other organisms. None of these drugs interfered with morphogenesis in a manner that would suggest SA channel activity is critical to early embryogenesis.     

A 31P-NMR study of the intact liver fluke Fasciola hepatica

³¹P-NMR techniques offer a useful method of studying changes in the metabolism of intact parasitic worms. The liver flukes, Fasciola hepatica, provide good quality ³¹P high resolution NMR spectra for at least 6 h under anaerobic conditions. The levels of ATP remain constant throughout this period. There is no signal for phosphocreatine or phosphoarginine. In contrast to the findings in mammalian tissues, there is a distinct peak for the terminal phosphate of ADP. A number of signals are observed in the phosphodiester region of the spectrum the largest of which is identified as l-α-glycerophosphoryl choline. Serotonin (5-hydroxytryptamine) causes an appreciable increase in the levels of sugar phosphates when the flukes are incubated in the absence of glucose. The addition of glucose also causes a marked increase in the signals for the hexose phosphate.     

Lymphatic Clearance of the Brain: Perivascular,Paravascular and Significance for Neurodegenerative Diseases

The lymphatic clearance pathways of the brain are different compared to the other organs of the body and have been the subject of heated debates. Drainage of brain extracellular fluids, particularly interstitial fluid (ISF) and cerebrospinal fluid (CSF), is not only important for volume regulation, but also for removal of waste products such as amyloid beta (Aβ). CSF plays a special role in clinical medicine, as it is available for analysis of biomarkers for Alzheimer’s disease. Despite the lack of a complete anatomical and physiological picture of the communications between the subarachnoid space (SAS) and the brain parenchyma, it is often assumed that Aβ is cleared from the cerebral ISF into the CSF. Recent work suggests that clearance of the brain mainly occurs during sleep, with a specific role for peri- and para-vascular spaces as drainage pathways from the brain parenchyma. However, the direction of flow, the anatomical structures involved and the driving forces remain elusive, with partially conflicting data in literature. The presence of Aβ in the glia limitans in Alzheimer’s disease suggests a direct communication of ISF with CSF. Nonetheless, there is also the well-described pathology of cerebral amyloid angiopathy associated with the failure of perivascular drainage of Aβ. Herein, we review the role of the vasculature and the impact of vascular pathology on the peri- and para-vascular clearance pathways of the brain. The different views on the possible routes for ISF drainage of the brain are discussed in the context of pathological significance.     

Substantial sulfatide deficiency and ceramide elevation in very early Alzheimer's disease: potential role in disease pathogenesis

In addition to pathology in the gray matter, there are also abnormalities in the white matter in Alzheimer's disease (AD). Sulfatide species are a class of myelin-specific sphingolipids and are involved in certain diseases of the central nervous system. To assess whether sulfatide content in gray and white matter in human subjects is associated with both the presence of Alzheimer's disease (AD) pathology as well as the stage of dementia, we analyzed the sulfatide content of brain tissue lipid extracts by electrospray ionization mass spectrometry from 22 subjects whose cognitive status at time of death varied from no dementia to very severe dementia. All subjects with dementia had AD pathology. The results demonstrate that: (i) sulfatides were depleted up to 93% in gray matter and up to 58% in white matter from all examined brain regions from AD subjects with very mild dementia, whereas all other major classes of lipid (except plasmalogen) in these subjects were not altered in comparison to those from age-matched subjects with no dementia; (ii) there was no apparent deficiency in the biosynthesis of sulfatides in very mild AD subjects as characterized by the examination of galactocerebroside sulfotransferase activities in post-mortem brain tissues; (iii) the content of ceramides (a class of potential degradation products of sulfatides) was elevated more than three-fold in white matter and peaked at the stage of very mild dementia. The findings demonstrate that a marked decrease in sulfatides is associated with AD pathology even in subjects with very mild dementia and that these changes may be linked with early events in the pathological process of AD.