Biomedical Science Medical and Health News Headlines

Probing the influence of myelin and glia on the tensile properties of the spinal cord.

Biomech Model Mechanobiol. 2008 Aug 23;

Authors: Shreiber DI, Hao H, Elias RA

Although glia have been historically classified as the structurally supporting cells of the central nervous system, their role in tissue mechanics is still largely unstudied. The influence of myelin and glia on the mechanical properties of spinal cord tissue was examined by testing embryonic day 18 chick embryo spinal cords in uniaxial tension following disruption of the glial matrix using either ethidium bromide (EB) or an antibody against galactocerebroside (alphaGalC) in the presence of complement. Demyelination was confirmed by myelin basic protein immunoreactivity and quantified using osmium tetroxide staining. A substantial loss of astrocytes and oligodendrocytes concurrent with demyelination was observed following EB injection but not alphaGalC injection. No morphological changes were observed following injection of saline or IgG with complement as controls for EB and alphaGalC. Demyelinated spinal cords demonstrated significantly lower stiffness and ultimate tensile stress than myelinated spinal cords. No significant differences were observed in the tensile response between the two demyelinating protocols. The results demonstrate that the glial matrix provides significant mechanical support to the spinal cord, and suggests that myelin and cellular coupling of axons via the glial matrix in large part dictates the tensile response of the tissue.

PMID: 18719957 [PubMed - as supplied by publisher]

Changes in PDGF concentration in surgically treated colorectal carcinoma.

Adv Med Sci. 2008;53:37-41

Authors: Mantur M, Snarska J, Sidorska A, Ostrowska H, Kruszewska-Wnorowska K, Wojszel J

Purpose: The aim of the present study was to asses the effect of tumor advancement, differentiation grade and surgery treatment on PDGF- AB level and platelet (PLT) count depending on the site of blood collection.Material and methods: The study included 38 patients submitted to surgical treatment due to diagnosis of colorectal cancer (CRC) without remote metastasis: G2- 20 patients and group G3- 18 patients. The control group consisted of 24 healthy subjects. In CRC patients the blood samples was collected three times: 1) before surgery, 2) intrasurgically and 3) 90 days after surgery. Serum PDGF- AB concentration was determined by ELISA- Kit reagents.Results: PDGF concentration in all the patients was several times higher than in the control group, irrespective of tumor differentiation grade and the site of blood collection. However the level of PDGF- AB in intraoperatively collected arterial blood and venous blood in group G3 (arterial blood- 379.9+/-12.1 ng/ml; venous blood- 398.4+/-13.2 ng/ml) was significantly higher than in group G2 (arterial blood- 169.4+/-88.6 ng/ml; venous blood- 194.2+/-84.0 ng/ml). No significant differences were observed between venous and arterial blood. No correlation was found between the PLT count and PDGF- AB concentration.Conclusion: High blood PDGF- AB concentration in CRC patients but no significant positive correlation observed between the PLT count and PDGF-AB suggest its neoplastic origin beside PLT. Determination of this factor in blood serum may have an important implication in early diagnosis of CRC, which is the second most common malignant neoplasm with high recurrence rates.

PMID: 18715835 [PubMed - in process]

Stimulation by lithium of the interaction between the transcription factor CREB and its coactivator TORC.

Biosci Rep. 2008 Aug 22;

Authors: Heinrich A, Böer U, Tzvetkov M, Oetjen E, Knepel W

Lithium salts are clinically important drugs used to treat bipolar mood disorder. The mechanisms accounting for the clinical efficacy are not completely understood. Chronic treatment with lithium is required to establish mood stabilization, suggesting the involvement of neuronal plasticity processes. CREB (cAMP response element binding protein) is a transcription factor known to mediate neuronal adaptation. Recently, the CREB-coactivator TORC (transducer of regulated CREB) has been identified as a novel target of lithium and shown to confer an enhancement by lithium of cAMP-induced CREB-directed gene transcription. TORC is sequestered in the cytoplasm and its nuclear translocation controls CREB activity. In the present study, the effect of lithium on TORC function was investigated. Lithium did affect neither the nuclear translocation of TORC nor TORC1 transcriptional activity, but increased the promoter occupancy by TORC1 as revealed by chromatin immunoprecipitation assay. In a mammalian two-hybrid assay as well as in a cell-free GST pull-down assay, lithium enhanced the CREB-TORC1 interaction. Magnesium ions strongly inhibited the interaction between GST-CREB and TORC1 and this effect was reversed by lithium. Thus, our data suggest that, once TORC has entered the nucleus, lithium as a cation directly stimulates the binding of TORC to CREB, leading to an increase in cAMP-induced CREB target gene transcription. This novel mechanism of lithium action is likely to contribute to the clinical mood stabilizing effect of lithium salts.

PMID: 18717645 [PubMed - as supplied by publisher]

Dinucleotide-sensing proteins: linking signaling networks and regulating transcription.

Sci Signal. 2008;1(33):pe38

Authors: Lamb HK, Stammers DK, Hawkins AR

Differential binding of dinucleotides to key regulatory proteins can modulate their interactions with other proteins and, in some cases, can signal fluctuations in the cellular redox state, to produce changes in transcription and physiological state. The dinucleotide-binding proteins human HSCARG and yeast transcription repressor Gal80p are examples that offer exciting glimpses into the potential for dinucleotide-sensing proteins to couple fluctuations in dinucleotide ratios to changes in transcription and to act as networking agents linking different classes of signaling molecules.

PMID: 18714085 [PubMed - in process]