Hyposialylation of neprilysin possibly affects its expression and enzymatic activity in hereditary inclusion-body myopathy muscle

Autosomal recessive hereditary inclusion-body myopathy (h-IBM) is caused by mutations of the UDP- N -acetylglucosamine 2-epimerase/ N -acetylmannosamine kinase gene, a rate-limiting enzyme in the sialic acid metabolic pathway. Previous studies have demonstrated an abnormal sialylation of glycoproteins in h-IBM. h-IBM muscle shows the abnormal accumulation of proteins including amyloid-β (Aβ). Neprilysin (NEP), a metallopeptidase that cleaves Aβ, is characterized by the presence of several N-glycosylation sites, and changes in these sugar moieties affect its stability and enzymatic activity. In the present study, we found that NEP is hyposialylated and its expression and enzymatic activity reduced in all h-IBM muscles analyzed. In vitro , the experimental removal of sialic acid by Vibrio Cholerae neuraminidase in cultured myotubes resulted in reduced expression of NEP. This was most likely because of a post-translational modification consisting in an abnormal sialylation of the protein that leads to its reduced stability. Moreover, treatment with Vibrio Cholerae neuraminidase was associated with an increased immunoreactivity for Aβ mainly in the form of distinct cytoplasmic foci within myotubes. We hypothesize that, in h-IBM muscle, hyposialylated NEP has a role in hampering the cellular Aβ clearing system, thus contributing to its abnormal accumulation within vulnerable fibers and possibly promoting muscle degeneration.     

Lakeside cemeteries in the Sahara: 5000 years of holocene population and environmental change

Background

Approximately two hundred human burials were discovered on the edge of a paleolake in Niger that provide a uniquely preserved record of human occupation in the Sahara during the Holocene (∼8000 B.C.E. to the present). Called Gobero, this suite of closely spaced sites chronicles the rapid pace of biosocial change in the southern Sahara in response to severe climatic fluctuation.

Methodology/Principal Findings

Two main occupational phases are identified that correspond with humid intervals in the early and mid-Holocene, based on 78 direct AMS radiocarbon dates on human remains, fauna and artifacts, as well as 9 OSL dates on paleodune sand. The older occupants have craniofacial dimensions that demonstrate similarities with mid-Holocene occupants of the southern Sahara and Late Pleistocene to early Holocene inhabitants of the Maghreb. Their hyperflexed burials compose the earliest cemetery in the Sahara dating to ∼7500 B.C.E. These early occupants abandon the area under arid conditions and, when humid conditions return ∼4600 B.C.E., are replaced by a more gracile people with elaborated grave goods including animal bone and ivory ornaments.

Conclusions/Significance

The principal significance of Gobero lies in its extraordinary human, faunal, and archaeological record, from which we conclude the following:

1. The early Holocene occupants at Gobero (7700–6200 B.C.E.) were largely sedentary hunter-fisher-gatherers with lakeside funerary sites that include the earliest recorded cemetery in the Sahara.
2. Principal components analysis of craniometric variables closely allies the early Holocene occupants at Gobero with a skeletally robust, trans-Saharan assemblage of Late Pleistocene to mid-Holocene human populations from the Maghreb and southern Sahara.
3. Gobero was abandoned during a period of severe aridification possibly as long as one millennium (6200–5200 B.C.E).
4. More gracile humans arrived in the mid-Holocene (5200–2500 B.C.E.) employing a diversified subsistence economy based on clams, fish, and savanna vertebrates as well as some cattle husbandry.
5. Population replacement after a harsh arid hiatus is the most likely explanation for the occupational sequence at Gobero.
6. We are just beginning to understand the anatomical and cultural diversity that existed within the Sahara during the Holocene.

     

Influence of the anionic ligands on the anticancer activity of Ru(II)-dmso complexes: Kinetics of aquation and in vitro cytotoxicity of new dicarboxylate compounds in comparison with their chloride precursors

We performed extensive studies on the kinetics of hydrolysis of a series of Ru(II)-dmso complexes containing dicarboxylate ligands, such as oxalate, malonate, succinate and 1,1-cyclobutane dicarboxylate (cbdc), derived from anticancer-active Ru(II)-dmso-Cl precursors. The in vitro antitumor activity of those compounds in comparison with their chloride precursors was evaluated against two tumor cell lines, the human KB oral carcinoma and the murine B16-F10 melanoma. The aim of this study was to assess how the nature of the anionic ligands (i.e. dicarboxylates vs. chlorides) affects the chemical behavior and the in vitro antitumor activity of Ru(II)-dmso complexes. Among the tested compounds only one complex, the dimer [fac-Ru(dmso-S)(3)(H(2)O)(mu-cbdc)](2) (5), exhibited moderate activity against both cell lines. Interestingly, this compound is the most kinetically stable in aqueous solution among those investigated. Despite the moderate in vitro activity, in an in vivo test, complex 5 exhibited no activity against both the primary tumor growth and the formation of spontaneous metastases on the MCa mammary carcinoma model.     

The intrinsic resistance of female hearts to an ischemic insult is abrogated in primary cardiac hypertrophy

Important sex differences in cardiovascular disease outcomes exist, including conditions of hypertrophic cardiomyopathy and cardiac ischemia. Studies of sex differences in the extent to which load-independent (primary) hypertrophy modulates the response to ischemia-reperfusion (I/R) damage have not been characterized. We have previously described a model of primary genetic cardiac hypertrophy, the hypertrophic heart rat (HHR). In this study the sex differences in HHR cardiac function and responses to I/R [compared to control normal heart rat (NHR)] were investigated ex vivo. The ventricular weight index was markedly increased in HHR female (7.82 +/- 0.49 vs. 4.80 +/- 0.10 mg/g; P < 0.05) and male (5.76 +/- 0.22 vs. 4.62 +/- 0.07 mg/g; P < 0.05) hearts. Female hearts of both strains exhibited a reduced basal contractility compared with strain-matched males [maximum first derivative of pressure (dP/dt(max)): NHR, 4,036 +/- 171 vs. 4,258 +/- 152 mmHg/s; and HHR, 3,974 +/- 160 vs. 4,540 +/- 259 mmHg/s; P < 0.05]. HHR hearts were more susceptible to I/R (I = 25 min, and R = 30 min) injury than NHR hearts (decreased functional recovery, and increased lactate dehydrogenase efflux). Female NHR hearts exhibited a significantly greater recovery (dP/dt(max)) post-I/R relative to male NHR (95.0 +/- 12.2% vs. 60.5 +/- 9.4%), a resistance to postischemic dysfunction not evident in female HHR (29.0 +/- 5.6% vs. 25.9 +/- 6.3%). Ventricular fibrillation was suppressed, and expression levels of Akt and ERK1/2 were selectively elevated in female NHR hearts. Thus the occurrence of load-independent primary cardiac hypertrophy undermines the intrinsic resistance of female hearts to I/R insult, with the observed abrogation of endogenous cardioprotective signaling pathways consistent with a potential mechanistic role in this loss of protection.     

NMR solution structure of Cn12, a novel peptide from the Mexican scorpion Centruroides noxius with a typical beta-toxin sequence but with alpha-like physiological activity.

Cn12 isolated from the venom of the scorpion Centruroides noxius has 67 amino-acid residues, closely packed with four disulfide bridges. Its primary structure and disulfide bridges were determined. Cn12 is not lethal to mammals and arthropods in vivo at doses up to 100 microg per animal. Its 3D structure was determined by proton NMR using 850 distance constraints, 36 phi angles derived from 36 coupling constants obtained by two different methods, and 22 hydrogen bonds. The overall structure has a two and half turn alpha-helix (residues 24-32), three strands of antiparallel beta-sheet (residues 2-4, 37-40 and 45-48), and a type II turn (residues 41-44). The amino-acid sequence of Cn12 resembles the beta scorpion toxin class, although patch-clamp experiments showed the induction of supplementary slow inactivation of Na(+) channels in F-11 cells (mouse neuroblastoma N18TG-2 x rat DRG2), which means that it behaves more like an alpha scorpion toxin. This behaviour prompted us to analyse Na(+) channel binding sites using information from 112 Na(+) channel gene clones available in the literature, focusing on the extracytoplasmic loops of the S5-S6 transmembrane segments of domain I and the S3-S4 segments of domain IV, sites considered to be responsible for binding alpha scorpion toxins.     

Salinity induced differences in growth,ion distribution and partitioning in barley between the cultivar Maythorpe and its derived mutant Golden Promise

Dry matter changes and ion partitioning in two near isogenic barley cultivars Maythorpe (relatively salt sensitive) and Golden Promise (relatively salt tolerant) were studied in response to increasing salinity. Although the growth of both cultivars was significantly reduced by exposure to NaCl, the effect was greater in Maythorpe, whilst Golden Promise maintained an increased ratio of young to old leaf blade. Golden Promise maintained significantly lower Na⁺ concentrations in young expanding tissues compared with Maythorpe. Partitioning of Cl^– was evident in that both varieties maintained lower Cl^– concentrations in mesophyll than in epidermal cells. Golden Promise maintained higher K⁺/Na⁺ and Ca²⁺/Na⁺ ratios in young leaf blade and young sheath tissues than Maythorpe when exposed to salt. Differences in ion partitioning and the maintenance of higher K⁺ and Ca²⁺ to Na⁺ ratios, especially in young growing and recently expanded tissues, would appear to be important mechanisms contributing to the improved salt tolerance of Golden Promise.     

Relaxometric evaluation of novel manganese(II) complexes for application as contrast agents in magnetic resonance imaging

Three novel Mn(II) complexes bearing benzyloxymethyl functionalities are reported and their ability to enhance water (1H and 17O) relaxation times is investigated in detail. Two of them contain one coordinated water molecule and display relaxivity values only slightly smaller than those shown by the most clinically used contrast agents (e.g. [Gd(DTPA)(H2O)]2-). Moreover, in these Mn(II) chelates the exchange rate of the coordinated water is ca. one order of magnitude higher if compared to the exchange rates previously reported for Gd(III) complexes with octadentate ligands. The occurrence of such fast exchange rates of the coordinated water is exploited in the formation of macromolecular adducts with human serum albumin to attain systems displaying relaxivity values in the upper range of those so far reported for analogous Gd(III) systems. These results strongly support the view that Mn(II) complexes, in spite of the lower effective magnetic moment, can be considered as viable alternatives to the currently used Gd(III) complexes as contrast agents for MRI applications.