Hyperhomocysteinemia: marker of systemic atherosclerosis in peripheral arterial disease.

AIM: Patients suffering from peripheral arterial disease (PAD) are increasingly described as having hyperhomocysteinemia more than in patients with coronary artery or cerebrovascular disease. Cases of symptomatic PAD usually present with associated coronary artery or cerebrovascular disease and renal artery disease. It can thus be postulated that multilocular atherosclerosis is linked to hyperhomocysteinemia and that the extent of atherosclerosis has a possible correlation with homocysteine concentrations. The aim of this study was to ascertain whether fasting total homocysteine concentrations in patients with PAD are associated with the extent and the localization of systemic atherosclerosis in cerebrovascular, coronary and/or renal vascular zones. METHODS: A total of 183 patients with PAD, Fontaine stages II-IV, were divided into 2 groups: Group A contained patients with isolated PAD (n=98) and Group B patients with systemic atherosclerosis in PAD (n=85). Characterization of vascular disease in various vascular zones was indication-adapted using non-invasive and/or invasive METHODS: Patients with renal insufficiency were excluded from the study. RESULTS: Homocysteine concentrations were significantly lower in patients with isolated PAD than in patients with additional systemic atherosclerosis (10.1+/-4.4 vs 16.7+/-7.04 micromol/l, p<0.0001). There were no differences in localization or extent of concomitant systemic atherosclerosis. Logistic regression analysis indicated that elevated plasma homocysteine and decreasing ABPI served independently as significant risk indicators for systemic atherosclerosis in patients with PAD (p<0.0001). CONCLUSION: Hyperhomocysteinemia is a precursoral marker of systemic atherosclerosis and thus a prognostic indicator of cardiovascular morbidity and mortality in PAD.

Nuclear lamins: their structure, assembly, and interactions.

Nuclear lamins are intermediate filament-type proteins that are the major building blocks of the nuclear lamina, a fibrous proteinaceous meshwork underlying the inner nuclear membrane. Lamins can also be localized in the nuclear interior, in a diffuse or spotted pattern. Nuclei assembled in vitro in the absence of lamins are fragile, indicating that lamins mechanically stabilize the cell nucleus. Available evidence also indicates a role for lamins in DNA replication, chromatin organization, spatial arrangement of nuclear pore complexes, nuclear growth, and anchorage of nuclear envelope proteins. In this review we summarize the current state of knowledge on the structure, assembly, and possible functional roles of nuclear lamins, emphasizing the information concerning the ability of nuclear lamins to self-assemble into distinct oligomers and polymers.

The preprotein translocation channel of the outer membrane of mitochondria.

The preprotein translocase of the outer membrane of mitochondria (TOM complex) facilitates the recognition, insertion, and translocation of nuclear-encoded mitochondrial preproteins. We have purified the TOM complex from Neurospora crassa and analyzed its composition and functional properties. The TOM complex contains a cation-selective high-conductance channel. Upon reconstitution into liposomes, it mediates integration of proteins into and translocation across the lipid bilayer. TOM complex particles have a diameter of about 138 A, as revealed by electron microscopy and image analysis; they contain two or three centers of stain-filled openings, which we interpret as pores with an apparent diameter of about 20 A. We conclude that the structure reported here represents the protein-conducting channel of the mitochondrial outer membrane.

Making heads and tails of intermediate filament assembly, dynamics and networks.

Thus far, intermediate filaments (IFs) have been the least understood of the three cytoskeletal filament systems with regard to their structure, assembly, network formation, and dynamics. This picture is now slowly but definitely changing, as recent in vivo and in vitro experiments, including generation of transgenic animals, have yielded important new data shedding light on the following areas: the molecular architecture of IFs; the role of the highly variable end domains during IF assembly and network formation; the factors that govern whether IF proteins are involved in de novo filament formation or are incorporated into a pre-existing IF network; and the effects of post-translational modifications, such as phosphorylation and glycosylation of IF polypeptides, on filament assembly, dynamics and turnover.

The rod domain of NF-L determines neurofilament architecture, whereas the end domains specify filament assembly and network formation.

Neurofilaments, assembled from NF-L, NF-M, and NF-H subunits, are the most abundant structural elements in myelinated axons. Although all three subunits contain a central, alpha-helical rod domain thought to mediate filament assembly, only NF-L self-assembles into 10-nm filaments in vitro. To explore the roles of the central rod, the NH2-terminal head and the COOH-terminal tail domain in filament assembly, full-length, headless, tailless, and rod only fragments of mouse NF-L were expressed in bacteria, purified, and their structure and assembly properties examined by conventional and scanning transmission electron microscopy (TEM and STEM). These experiments revealed that in vitro assembly of NF-L into bona fide 10-nm filaments requires both end domains: whereas the NH2-terminal head domain promotes lateral association of protofilaments into protofibrils and ultimately 10-nm filaments, the COOH-terminal tail domain controls lateral assembly of protofilaments so that it terminates at the 10-nm filament level. Hence, the two end domains of NF-L have antagonistic effects on the lateral association of protofilaments into higher-order structures, with the effect of the COOH-terminal tail domain being dominant over that of the NH2-terminal head domain. Consideration of the 21-nm axial beading commonly observed with 10-nm filaments, the approximate 21-nm axial periodicity measured on paracrystals, and recent cross-linking data combine to support a molecular model for intermediate filament architecture in which the 44-46-nm long dimer rods overlap by 1-3-nm head-to-tail, whereas laterally they align antiparallel both unstaggered and approximately half-staggered.

Effect of MAP2, MAP2c, and tau on kinesin-dependent microtubule motility.

By making use of DIC video microscopy to monitor microtubule motility we have studied the effect of several MAPs (MAP2, MAP2c, tau) on microtubule-kinesin interactions and microtubule gliding. Of the three MAPs tested, MAP2 interferes most strongly with kinesin-dependent microtubule motility.

Aluminum fluoride, microtubule stability, and kinesin rigor.

Aluminum fluoride may be used both to stabilize microtubules and to induce strong binding of kinesin, thus circumventing the need for taxol and AMP-PNP in kinesin preparations.

Adaptive variation in environmental and genetic sex determination in a fish.

Two general mechanisms of sex determination have been identified among gonochoristic vertebrates: environmental sex determination where offspring become male or female in response to an environmental factor(s) during development (for example, some fishes and reptiles); and genetic sex determination where sex is determined by genotype at conception (as in birds and mammals). How do these sex-determining systems evolve? Direct evidence is virtually non-existent because the sex-determining systems of most species appear to have little genetic variation. Here we provide the first evidence of adaptive variation in environmental and genetic sex determination within a species. We show that in a fish with temperature-dependent sex determination, populations at different latitudes compensate for differences in thermal environment and seasonality by adjusting the response of sex ratio to temperature, and by altering the level of environmental as opposed to genetic control. The adjustments observed are precisely those predicted by adaptive sex ratio theory.