Design of an intravenous oxygenator

The aim of this study was to design a new intravenous blood–gas exchange device and to estimate the design characteristics of the device with a dimensionless function by using a substance that can be used instead of bovine blood. In addition, the characteristics of oxygen transfer were estimated using empirical formulas and the reliability of the equations was ascertained by comparing their output with an experiment performed using bovine blood. The dimensionless function was derived using distilled water and bovine blood to estimate the oxygen transfer rate. Using the derived equations, the calculated oxygen transfer rates for bovine blood and distilled water were similar for Reynolds numbers ranging from 0.7 to 7.0. Therefore, it is possible to estimate the oxygen transfer rate in bovine blood, which is a non-Newtonian fluid, using distilled water, which is a Newtonian fluid. Moreover, it was possible to verify the related equations because the oxygen transfer rate could be estimated using the derived equations, according to the diameters of the various device modules.     

Ubiquitin and heat shock protein expression in amyotrophic lateral sclerosis

The expression of two heat shock proteins, HSP72 and p57, in addition to ubiquitin, has been studied immunocytochemically in nine amyotrophic lateral sclerosis (ALS) cases and 10 age-matched controls. HSP72 and p57 antibodies did not identify the characteristic ubiquitin-immunoreactive inclusions present in anterior horn cells in ALS spinal cord. Antibodies to HSP72, but not to p57 or ubiquitin, strongly labelled structures corresponding to polyglucosan bodies in spinal grey matter. Such immunoreactive profiles were more abundant in ALS cases, although they were also present in control material. They were sometimes identified by haematoxylin and eosin and periodic acid Schiff reaction, but were not labeled by phosphotungstic acid haematoxylin or by antibodies to glial fibrillary acidic protein. Although ubiquitin, HSP72 and p57 are stress-induced proteins, they are expressed differently and might therefore have different significance in neuronal degeneration.     

Folding and function of the myelin proteins from primary sequence data.

To explain how the myelin proteins are involved in the organization and function of the myelin sheath requires knowing their molecular structures. Except for P2 basic protein of PNS myelin, however, their structures are not yet known. As an aid to predicting their molecular folding and possible functions, we have developed a FORTRAN program to analyze the primary sequence data for proteins, and have applied this to the myelin proteins in particular. In this program, propensities for the secondary structure conformations as well as physical-chemical parameters are assigned to the amino acids and the pattern of these parameters is examined by calculating their average values, autocorrelation functions and Fourier transforms. To compare two proteins, their sequences are aligned using a unitary scoring matrix, and homologies are searched by plotting a two-dimensional map of the correlation coefficients. Comparison of the corresponding myelin basic proteins (MBP) and P0 glycoproteins (P0) for rodent and shark showed that the conserved residues included most of the amino acids which were predicted to form the alpha or beta conformations, while the altered residues were mainly in the hydrophilic and turn or coil regions. In both rodent and shark the putative extracellular domain of P0 glycoprotein displayed consecutive peaks of beta propensity similar to that for the immunoglobulins, while the cytoplasmic domain showed alpha-beta-alpha folding. To trace the immunoglobulin fold along the P0 sequence, we compared the beta propensity curve of P0 with that of the immunoglobulin M603, whose three-dimensional structure has been determined. We propose that the flat beta-sheets of P0 are orientated parallel to the membrane surface to facilitate their homotypic interaction in the extracellular space. An extra beta-fold in the extracellular domain of shark P0 compared with rodent P0 was found, and this may result in a greater attraction between the apposed extracellular surfaces and may account for a smaller extracellular space as measured by x-ray diffraction. A computer search of the myelin protein sequences for functional motifs revealed sites for N-glycosylation, phosphorylation, nucleotide binding, and certain enzyme activities. We note especially that there are potential nucleotide binding sites in proteolipid protein (PLP), MBP and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP). This is consistent with the experimental observations that PLP acts like an ionophore or proton channel when reconstituted into planar lipid bilayers, MBP binds GTP, and CNP catalyzes in vitro the hydrolysis of 2',3'-nucleotides into corresponding 2'-nucleotides.     

Differences in the abilities of human tau isoforms to promote microtubule assembly.

Three isoforms of human tau protein were compared for their abilities to induce microtubule assembly. The three isoforms, tau 3 (tau containing three microtubule-binding domains), tau 4 (tau containing four microtubule-binding domains) and tau 4L (tau containing four microtubule binding domains plus a 58-amino-acid insert near the N-terminus) were expressed in E. coli and purified using ammonium sulfate precipitation, ion exchange, and size exclusion chromatography. All three isoforms induced microtubule assembly at micromolar concentrations and showed similar critical concentrations for assembly of 0.4-0.45 microM. However, tau 4 induced microtubule formation at a rate five- to tenfold faster than either tau 3 or tau 4L. The rate of microtubule elongation seen with tau 4 was twofold greater than with tau 3 or tau 4L, suggesting that the faster rate of microtubule assembly seen with tau 4 was due, at least in part, to faster elongation. Tau 4 induced a greater number of microtubules to form at steady state than did tau 3 or tau 4L. The microtubules generated with each tau isoform had similar steady-state length distributions and were equally susceptible to cold-induced disassembly. These results indicate that the additional microtubule-binding domain in tau 4 enhances microtubule assembly, while the 58-amino-acid insert negates the stimulatory effect of the fourth microtubule-binding domain.     

Progress toward re‐engineering non‐ribosomal peptide synthetase proteins: a potential new source of pharmacological agents

Many important pharmaceutical agents, including vancomycin, bleomycin, cyclosporin, and several antibiotics, are produced by non‐ribosomal peptide synthetase (NRPS) enzymes in microorganisms. The NRPS pathway produces an extensive library of products using multienzyme complexes acting in an assembly‐line fashion. Engineering an NRPS system to produce an even greater variety of products, some of which may also have beneficial therapeutic value, would be an enormous advantage. Several approaches have been successful in generating novel NRPS products: mutational biosynthesis during which nonnatural substrates are fed to an organism; domain and module swapping between different species to generate hybrid enzymes; and rational site‐directed mutagenesis, based either on phylogeny or computational prediction, intended to switch substrate specificity and produce altered products. This review will highlight the progress in these areas and describe research in the future that will extend the capacity for re‐engineering NRPS systems. Drug Dev. Res. 66:9–18, 2006. © 2006 Wiley‐Liss, Inc.     

Spindle-cell glioblastoma or gliosarcoma?

'Gliosarcomas' have long been considered to be mixed gliomas and sarcomas. The present study failed to define criteria which clearly delineate 'gliosarcomas' from glioblastoma multiforme and suggests that 'gliosarcomas' should be considered as spindle cell glioblastomas. A total of six cases originally diagnosed as 'gliosarcomas' were compared with four cases of glioblastoma multiforme. No clinical or prognostic features were defined which would clearly separate 'gliosarcomas' from glioblastoma multiforme. Macroscopically, biopsies from 'gliosarcomas' ranged from firm, apparently well-circumscribed tumours to poorly circumscribed lesions with a soft consistency resembling glioblastoma multiforme. Histology revealed a continuous spectrum in which 'gliosarcomas' with large reticulin-rich areas of spindle cells merged with typical glioblastomas containing only small islands of spindle cells and reticulin staining. Immunocytochemistry for glial fibrillary acidic protein (GFAP); S100 protein and alpha-smooth muscle actin (ASMA) showed that the majority of cells in reticulin-poor areas of 'gliosarcoma' and glioblastomas expressed S100 protein and GFAP; many expressed ASMA and some expressed both GFAP and ASMA. Spindle cells in reticulin-rich areas of 'gliosarcomas' and glioblastomas most frequently expressed ASMA but many cells also expressed S100 protein and GFAP; some cells expressed both GFAP and ASMA. The results of this study and a review of the literature suggests that there is a clinical, radiological and pathological continuum with glioblastoma and 'gliosarcoma' at different ends of the spectrum. It is suggested, therefore, that most, if not all, 'gliosarcomas' be redesignated as spindle cell glioblastomas and not be considered as a mixture of glioma and sarcoma.