Imaging real-time aggregation of amyloid beta protein (1-42) by atomic force microscopy

Amyloid beta protein (AbetaP) is the major fibrillar constituent of senile plaques. However, no causative role for AbetaP-fibers in Alzheimer's disease (AD) pathology is established. Globular AbetaPs are continuously released during normal cellular metabolism at pico- to nano-molar concentration. We used atomic force microscopy (AFM) to examine aggregation of freshly prepared AbetaP(1-42) and to examine the role of AbetaP concentration, imaging medium (air, water, or PBS) and agonists/antagonists on AbetaP-fibrillogenesis. At even very high and non-physiological AbetaP concentrations, 24-48 h of real-time AFM imaging (a) in water show only multiple layers of globular aggregates and no fibrils and (b) in PBS show mainly the globular structures and some short fibrils. On-line addition of Zn, an agonist for AbetaP-fibrillogenesis, induced a slow but non-fibrillar aggregation of globular AbetaPs. EDTA, a chelator of Zn and calcium (a modulator of AbetaP-mediated toxicity) induced a reversible change in the Zn-mediated aggregation. These results strongly suggest that no AbetaP-fibers are formed for the physiologically relevant concentration and thus the plaque-associated fibers may not account for the AD pathophysiology.     

Development of cloning vectors and transformation methods for<Emphasis Type="Italic"> Amycolatopsis</Emphasis>

The genus Amycolatopsis is of industrial importance, as its species are known to produce commercial antibiotics. It belongs to the family Pseudonocardiaceae and has an eventful taxonomic history. Initially strains were identified as Streptomyces, then later as Nocardia. However, based on biochemical, morphological and molecular features, the genus Amycolatopsis, containing seventeen species, was created. The development of molecular genetic techniques for this group has been slow. The scarcity of molecular genetic tools including stable plasmids, antibiotic resistance markers, transposons, reporter genes, cloning vectors, and high efficiency transformation protocols has made progress slow, but efforts in the past decade have led to the development of cloning vectors and transformation methods for these organisms. Some of the cloning vectors have broad host range (pRL series) whereas others have limited host range (pMEA300 and pMEA100). The cloning vector pMEA300 has been completely sequenced, while only the minimal replicon (pA-rep) has been sequenced from pRL plasmids. Direct transformation of mycelia and electroporation are the most widely applicable methods for transforming species of Amycolatopsis. Conjugational transfer from Escherichia coli has been reported only in the species A. japonicum, and gene disruption and replacements using homologous recombination are now possible in some strains. Electronic Publication     

Identification of novel Cryptosporidium genotypes from the Czech Republic

Isolates of Cryptosporidium from the Czech Republic were characterized from a variety of different hosts using sequence and phylogenetic analysis of the 18S ribosomal DNA and the heat-shock (HSP-70) gene. Analysis expanded the host range of accepted species and identified several novel genotypes, including horse, Eurasian woodcock, rabbit, and cervid genotypes.     

A predictive aggregate transport model for microfiltration of combined macromolecular solutions and poly-disperse suspensions: model development

A methodology, called the aggregate transport model, is presented that can a priori predict both the pressure-independent permeation flux and yield of target species for the microfiltration of poly-disperse solutions. The model captures the phenomenon of critical shear rate. Beyond the critical shear rate (expressed as a ratio of shear rate to permeation flux), the transmission of proteins drops sharply as a result of cake classification. The widely reported benefits of operating at uniform transmembrane pressure and constant wall concentration follow from this method. The methodology is general in nature and can be used predictively to obtain an optimal balance between flux and yield of target species during the microfiltration of many commercial poly-disperse suspensions. In the accompanying paper we test this model for microfiltration of transgenic whole goat milk.     

Successful development of viable blastocysts from enhanced green fluorescent protein transgene-microinjected mouse embryos: comparison of culture media

To improve efficiency of transgenesis, we compared M16 and CZB embryo culture media, supporting development to blastocysts of FVB/N mouse pronuclear-eggs, microinjected with enhanced green fluorescent protein (EGFP) transgene. When EGFP-injected-eggs were cultured (120 hr), blastocyst development was significantly (P < 0.03) higher in M16 medium (72.5 +/- 2.4%) than that in CZB (13.2 +/- 4.3%) or CZBG (CZB with 5.6 mM glucose at 48 hr culture) (62.1 +/- 3.7%) media. Blastocyst development of noninjected embryos was higher in M16 (92.0 +/- 2.6%) and CZBG (83.9 +/- 3.9%) media than in CZB (31.9 +/- 2.8%) medium (P < 0.0001). However, percentages of morulae at 72 hr were comparable in all treatments. Developed blastocysts were better in M16 than in CZB or CZBG media. Consistent with this, mean cell number per blastocyst, developed from injected embryos, was significantly (P < 0.002) higher in M16 medium (79.6), than those in CZB (31.3) or CZBG media (60.7); similar with noninjected embryos. Cell allocation to trophectoderm (TE) and inner cell mass (ICM), i.e., TE:ICM ratio, for injected blastocysts in M16 (3.0) was less than (P < 0.05) those in CZB (4.2) and CZBG (4.4) media; similar with noninjected blastocysts. Moreover, blastocysts, developed in M16 and CZBG media, hatched, attached, and exhibited trophoblast outgrowth; 18% of them showed EGFP-expression. Importantly, blastocysts from M16 medium produced live transgenic "green" pups (11%) following embryo transfer. Taken together, our results indicate that supplementation of glucose, at 48 hr of culture (CZBG), is required for morula to blastocyst transition; M16 medium, containing glucose from the beginning of culture, is superior to CZB or CZBG for supporting development of biologically viable blastocysts from EGFP-transgene-injected mouse embryos.     

Glioma inhibition by HGF/NK2, an antagonist of scatter factor/hepatocyte growth factor

Strategies that antagonize growth factor signaling are attractive candidates for the biological therapy of brain tumors. HGF/NK2 is a secreted truncated splicing variant and potential antagonist of scatter factor/hepatocyte growth factor (SF/HGF), a multifunctional cytokine involved in the malignant progression of solid tumors including glioblastoma. U87 human malignant glioma cells that express an autocrine SF/HGF stimulatory loop were transfected with the human HGF/NK2 cDNA and clonal cell lines that secrete high levels of HGF/NK2 protein (U87-NK2) were isolated. The effects of HGF/NK2 gene transfer on the U87 malignant phenotype were examined. HGF/NK2 gene transfer had no effect on 2-dimensional anchorage-dependent cell growth. In contrast, U87-NK2 cell lines were approximately 20-fold less clonogenic in soft agar and approximately 4-fold less migratory than control-transfected cell lines. Intracranial tumor xenografts derived from U87-NK2 cells grew much slower than controls. U87-NK2 tumors were approximately 50-fold smaller than controls at 21 days post-implantation and HGF/NK2 gene transfer resulted in a trend toward diminished tumorigenicity. This report shows that the predominant effect of transgenic HGF/NK2 overexpression by glioma cells that are autocrine for SF/HGF stimulation is to inhibit their malignant phenotype.     

Phylogenetic relationships of Cryptosporidium parasites based on the 70-kilodalton heat shock protein (HSP70) gene

We have characterized the nucleotide sequences of the 70-kDa heat shock protein (HSP70) genes of Cryptosporidium baileyi, C. felis, C. meleagridis, C. muris, C. serpentis, C. wrairi, and C. parvum from various animals. Results of the phylogenetic analysis revealed the presence of several genetically distinct species in the genus Cryptosporidium and eight distinct genotypes within the species C. parvum. Some of the latter may represent cryptic species. The phylogenetic tree constructed from these sequences is in agreement with our previous results based on the small-subunit rRNA genes of Cryptosporidium parasites. The Cryptosporidium species formed two major clades: isolates of C. muris and C. serpentis formed the first major group, while isolates of C. felis, C. meleagridis, C. wrairi, and eight genotypes of C. parvum formed the second major group. Sequence variations were also observed between C. muris isolates from ruminants and rodents. The HSP70 gene provides another useful locus for phylogenetic analysis of the genus Cryptosporidium.     

Cryptosporidium spp. in domestic dogs: the "dog" genotype

Genetic and phylogenetic characterization of Cryptosporidium isolates at two loci (18S rRNA gene and heat shock gene) from both Australian and United States dogs demonstrated that dog-derived Cryptosporidium isolates had a distinct genotype which is conserved across geographic areas. Phylogenetic analysis provided support for the idea that the "dog" genotype is, in fact, a valid species.