Truncated N-terminal fragments of huntingtin with expanded glutamine repeats form nuclear and cytoplasmic aggregates in cell culture

Huntington's disease (HD) is a progressive neurodegenerative disorder caused by an expanding CAG repeat coding for polyglutamine in the huntingtin protein. Recent data have suggested the possibility that an N-terminal fragment of huntingtin may aggregate in neurons of patients with HD, both in the cytoplasm, forming dystrophic neurites, and in the nucleus, forming intranuclear neuronal inclusion bodies. An animal model of HD using the short N-terminal fragment of huntingtin has also been found to have intranuclear inclusions and this same fragment can aggregate in vitro . We have now developed a cell culture model demonstrating that N-terminal fragments of huntingtin with expanded glutamine repeats aggregate both in the cytoplasm and in the nucleus. Neuroblastoma cells transiently transfected with full-length huntingtin constructs with either a normal or expanded repeat had diffuse cytoplasmic localization of the protein. In contrast, cells transfected with truncated N-terminal fragments showed aggregation only if the glutamine repeat was expanded. The aggregates were often ubiquitinated. The shorter truncated product appeared to form more aggregates in the nucleus. Cells transfected with the expanded repeat construct but not the normal repeat construct showed enhanced toxicity to the apoptosis- inducing agent staurosporine. These data indicate that N-terminal truncated fragments of huntingtin with expanded glutamine repeats can aggregate in cells in culture and that this aggregation can be toxic to cells. This model will be useful for future experiments to test mechanisms of aggregation and toxicity and potentially for testing experimental therapeutic interventions.      

Biological effects of recombinant human granulocyte colony-stimulating factor in patients with untreated acute myeloid leukemia

Hematopoietic growth factors are being administered to patients with acute myeloid leukemia (AML) both to shorten the duration of chemotherapy-induced neutropenia and in an attempt to increase cytotoxicity of cell cycle-specific agents. However, limited information is available concerning the effects of growth factors in AML patients. To examine the in vivo effects of recombinant human granulocyte colony-stimulating factor (G-CSF) on AML cells, laboratory studies were performed before and after a 72-hour intravenous infusion of G-CSF (10 micrograms/kg/d) administered to 28 untreated AML patients. Twenty-seven patients (96%) showed increases in at least one of the following parameters after G-CSF: blood blasts, bone marrow (BM) blasts, leukemia cells in S phase or interphase cells with leukemia- specific markers shown by fluorescence in situ hybridization. The median paired change in absolute blast count was +2.7 x 10(9)/L (P = .0001) after G-CSF, as compared with 0.0 during the 72 hours before initiation of G-CSF. The median percentage of BM leukemia cells in S phase increased from 6.0% to 10.7% after G-CSF (median change, %5.9%; P = .009). Interphase BM cells with trisomy 8 or monosomy 7 increased in 6 of 6 patients with these abnormalities (P = .02) with a median percent increase of 47%. Blood neutrophil counts also increased during G-CSF (median paired change, +2.8 x 10(9)/L; P < .0001). Trisomy 8 or monosomy 7 was shown by fluorescence in situ hybridization in post-G- CSF blood neutrophils from 4 of 6 patients but was also present in neutrophils before G-CSF. We conclude that the percentage of leukemia cells in S phase increases and that leukemia cell populations undergo expansion during short-term administration of G-CSF in almost all AML patients.     

mdx muscle pathology is independent of nNOS perturbation

In skeletal muscle, neuronal nitric oxide synthase (nNOS) is anchored to the sarcolemma via the dystrophin-glycoprotein complex. When dystrophin is absent, as in Duchenne muscular dystrophy patients and in mdx mice, nNOS is mislocalized to the interior of the muscle fiber where it continues to produce nitric oxide. This has led to the hypothesis that free radical toxicity from mislocalized nNOS may contribute to mdx muscle pathology. To test this hypothesis directly, we generated mice devoid of both nNOS and dystrophin. Overall, the nNOS- dystrophin null mice maintained the dystrophic characteristics of mdx mice. We evaluated the mice for several features of the dystrophic phenotype, including membrane damage and muscle morphology. Removal of nNOS did not alter the extent of sarcolemma damage, which is a hallmark of the dystrophic phenotype. Furthermore, muscle from nNOS-dystrophin null mice maintain the histological features of mdx pathology. Our results demonstrate that relocalization of nNOS to the cytosol does not contribute significantly to mdx pathogenesis.      

Autophagy and adaptive immunity

Autophagy plays an important role in maintaining intracellular homeostasis by promoting the transit of cytoplasmic material, such as proteins, organelles and pathogens, for degradation within acidic organelles. Yet, in immune cells, autophagy pathways serve an additional role in facilitating intracellular surveillance for pathogens and changes in self. Autophagy pathways can modulate key steps in the development of innate and adaptive immunity. In terms of adaptive immunity, autophagy regulates the development and survival of lymphocytes as well as the modulation of antigen processing and presentation. Specialized forms of autophagy may be induced by some viral pathogens, providing a novel route for major histocompatibility complex (MHC) class I antigen presentation and enhanced CD8⁺ T-cell responses. Autophagy induction in target cells also increases their potential to serve as immunogens for dendritic cell cross-presentation to CD8⁺ T cells. The requirement for autophagy in MHC class II presentation of cytoplasmic and nuclear antigens is well established, yet recent studies also point to a critical role for autophagy in modulating CD4⁺ T-cell responses to phagocytosed pathogens. Autophagy pathways can also modulate the selection and survival of some CD4⁺ T cells in the thymus. However, much still remains to be learned mechanistically with respect to how autophagy and autophagy-linked genes regulate pathogen recognition and antigen presentation, as well as the development and survival of immune cells.     

Evaluation of antibacterial,antifungal and modulatory activity of methanol and ethanol extracts of Padina sanctae-crucis

Background

Multi-resistantmicroorganisms such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Candida tropicalis e Candida krusei are the main causes of microbial infections. Padina sanctae-crucis is a seaweed often used to check the contamination of ecosystems by materials such as heavy metals, but studies of the antimicrobial activity of the same seaweed were not found.

Methods

The tests for the minimum inhibitory concentration and modulation of microbial resistance, with the use of ethanolic and methanolic extracts of Padina Sanctae-cruces combined with drugs of the class of aminoglycosides and antifungal were used to evaluate the activity against the cited microorganisms.

Results

Was observed a modulation of antibiotic activity between the natural products and the E. coli and S. aureus strains, indicating a synergism and antagonism respectively.

Conclusions

The results showed a moderate modulatory effect against some microorganisms studied.