Mandibuloacral dysplasia is caused by a mutation in LMNA-encoding lamin A/C

Mandibuloacral dysplasia (MAD) is a rare autosomal recessive disorder, characterized by postnatal growth retardation, craniofacial anomalies, skeletal malformations, and mottled cutaneous pigmentation. The LMNA gene encoding two nuclear envelope proteins (lamins A and C [lamin A/C]) maps to chromosome 1q21 and has been associated with five distinct pathologies, including Dunnigan-type familial partial lipodystrophy, a condition that is characterized by subcutaneous fat loss and is invariably associated with insulin resistance and diabetes. Since patients with MAD frequently have partial lipodystrophy and insulin resistance, we hypothesized that the disease may be caused by mutations in the LMNA gene. We analyzed five consanguineous Italian families and demonstrated linkage of MAD to chromosome 1q21, by use of homozygosity mapping. We then sequenced the LMNA gene and identified a homozygous missense mutation (R527H) that was shared by all affected patients. Patient skin fibroblasts showed nuclei that presented abnormal lamin A/C distribution and a dysmorphic envelope, thus demonstrating the pathogenic effect of the R527H LMNA mutation.     

Synthesis and evaluation of the cardiovascular effects of two, membrane impermeant, macromolecular complexes of dextran-testosterone

The incidence of cardiovascular disease is greater in men than in premenopausal women. Testosterone has been considered a significant risk factor for cardiovascular disease, but testosterone's mechanism of action and its cellular site of action are still not clear. However, it is likely that non-genomic extracellular effects of the hormone are involved. With the aim of providing further information about this phenomenon, two membrane impermeant, macromolecular complexes of testosterone were synthesized and their cardiovascular effects were evaluated. We covalently bound testosterone (through carbon 3 or C-17 functional groups) to dextran (2 MDa) and evaluated its effects on isolated and perfused rat hearts (Langerdorff model). Our results showed that the macromolecular complexes increased vascular resistance similarly to free testosterone and blocked adenosine-induced vasodilatation. These effects were exerted rapidly and possibly through a non-genomic mechanism. Blockade of C-3 or C-17 functional groups by binding to macromolecular dextran induced no qualitative and/or quantitative changes in testosterone-induced effects.     

Ionic network at the C-terminus of the beta-glycosidase from the hyperthermophilic archaeon Sulfolobus solfataricus: Functional role in the quaternary structure thermal stabilization

Biochemical, crystallographic, and computational data support the hypothesis that electrostatic interactions are among the dominant forces in stabilizing hyperthermophilic proteins. The thermostable beta-glycosidase from the hyperthermophile Sulfolobus solfataricus (Ssbeta-gly) is an interesting model system for the study of protein adaptation to high temperatures. The largest ion-pair network of Ssbeta-gly is located at the tetrameric interface of the molecule; in this paper, key residues in this region were modified by site-directed mutagenesis and the stability of the mutants was analyzed by kinetics of thermal denaturation. All mutations produced faster enzyme inactivation, suggesting that the C-terminal ionic network prevents the dissociation into monomers, which is the limiting step in the mechanism of Ssbeta-gly inactivation. Moreover, the calculated reaction order showed that the mechanism of inactivation depends on the mutation introduced, suggesting that intermediates maintaining enzymatic activity are produced during the inactivation transition of some, but not all, mutants. Molecular models of each mutant allow us to rationalize the experimental evidence and give support to the current theories on the mechanism of ion pair stabilization in proteins from hyperthermophiles.     

Histological process and dynamics of germ cell degeneration in pejerrey Odontesthes bonariensis larvae and juveniles during exposure to warm water

Elevated temperature causes degeneration and disappearance of the germ cells in the males of scrotal mammals. It was recently shown that heat-induced germ cell degeneration occurs also in fish but, unlike in mammals, it occurs not only in males but also in females. The purpose of this study was to clarify the histological process and dynamics of heat-induced germ cell disappearance in pejerrey Odontesthes bonariensis larvae and juveniles. Monosex and mixed-sex fish produced by thermal manipulation of sex (temperature-dependent sex determination) were subjected to 29 degrees C for periods between 1 and 12 weeks, and used to analyze, by histological methods, the changes in gonadal size and the number of normal and degenerating germ cells. Groups exposed to 29 degrees C for 8-12 weeks were subsequently transferred to 24 degrees C to verify if any gonadal damage would be permanent. Germ cell degeneration, histologically characterized by nuclear pyknosis or eosinophilia and cytoplasmic eosinophilia, was observed with increasing frequency at higher temperatures (29>24> 17 degrees C) and more in males than in females. Clear degenerative changes in the germinal epithelium usually began within one week of exposure to 29 degrees C and appeared clearer in females than in males. Complete loss of germ cells was observed only in individuals exposed for periods of 8-12 weeks to 29 degrees C but no treatment produced 100% sterile fish. Germ cells that remained in the gonads after exposure to 29 degrees C retained the capacity to rapidly recolonize germ cell-depleted areas, suggesting that the associated somatic cells in the gonads are little or not affected by this temperature.     

Effects of crude extracts of Agaricus blazei on DNA damage and on rat liver carcinogenesis induced by diethylnitrosamine

The effects of crude extracts of the mushroom Agaricus blazei Murrill (Agaricaceae) on both DNA damage and placental form glutathione S-transferase (GST-P)-positive liver foci induced by diethylnitrosamine (DEN) were investigated. Six groups of adult male Wistar rats were used. For two weeks, animals of groups 3 to 6 were treated with three aqueous solutions of A. blazei (mean dry weight of solids being 1.2, 5.6, 11.5 and 11.5 mg/ml, respectively). After this period, groups 2 to 5 were given a single ip injection 200 mg/kg DEN and groups 1 and 6 were treated with 0.9% NaCl. All animals were subjected to 70% partial hepatectomy at week five and sacrificed 4, 24 and 48 h or 8 weeks after DEN or 0.9% NaCl treatments (10th week after the beginning of the experiment). The alkaline comet assay and GST-P-positive liver foci development were used to evaluate the influence of the mushroom extracts on liver cell DNA damage and on the initiation of liver carcinogenesis, respectively. Previous treatment with the highest concentration of A. blazei (11.5 mg/ml) significantly reduced DNA damage, indicating a protective effect against DEN-induced liver cytotoxicity/genotoxicity. However, the same dose of mushroom extract significantly increased the number of GST-P-positive liver foci.     

Physicochemical and biological study of selected hydrophobic polyethylenimine-based polycationic liposomes and their complexes with DNA

Non-viral gene therapy is based on the development of efficient and safe gene carrier systems able to transfer DNA into cells. Polyethylenimine (PEI), the most promising non-viral vector, with its high cationic-charge-density potential is able (1) to compact DNA in complexes (polyplexes) smaller than those formed by liposomes (lipoplexes) and (2) to destabilize the endosomal membrane by a 'proton sponge' effect. Several PEI's hydrophobic modifications were reported in the last several years but in some cases a reduced transfection efficiency was observed. The mechanism underlying this phenomenon is not well understood so far. In order to extensively investigate these mechanisms, we reported a physicochemical and biological study of selected hydrophobic PEI's derivatives grafted with chains of different length and percentages of substitution able to form vesicles (polycationic liposomes) and to bind DNA. Their properties were studied by means of dynamic light scattering, freeze-fracture microscopy, potentiometric titrations, gel retardation assays, polyanion exchange reactions, toxicity assays, in vitro transfections, and fluorescence microscopy. Our results indicate that even if polyplexes are able to pass through the cellular membrane, the stability of PEI's hydrophobic polyplexes likely explain their different transfection efficiency in vitro.     

Defining the response of a microorganism to temperatures that span its complete growth temperature range (-2°C to 28°C) using multiplex quantitative proteomics

The growth of all microorganisms is limited to a specific temperature range. However, it has not previously been determined to what extent global protein profiles change in response to temperatures that incrementally span the complete growth temperature range of a microorganism. As a result it has remained unclear to what extent cellular processes (inferred from protein abundance profiles) are affected by growth temperature and which, in particular, constrain growth at upper and lower temperature limits. To evaluate this, 8-plex iTRAQ proteomics was performed on the Antarctic microorganism, Methanococcoides burtonii. Methanococcoides burtonii was chosen due to its importance as a model psychrophilic (cold-adapted) member of the Archaea, and the fact that proteomic methods, including subcellular fractionation procedures, have been well developed. Differential abundance patterns were obtained for cells grown at seven different growth temperatures (-2°C, 1°C, 4°C, 10°C, 16°C, 23°C, 28°C) and a principal component analysis (PCA) was performed to identify trends in protein abundances. The multiplex analysis enabled three largely distinct physiological states to be described: cold stress (-2°C), cold adaptation (1°C, 4°C, 10°C and 16°C), and heat stress (23°C and 28°C). A particular feature of the thermal extremes was the synthesis of heat- and cold-specific stress proteins, reflecting the important, yet distinct ways in which temperature-induced stress manifests in the cell. This is the first quantitative proteomic investigation to simultaneously assess the response of a microorganism to numerous growth temperatures, including the upper and lower growth temperatures limits, and has revealed a new level of understanding about cellular adaptive responses.