Distributed source imaging of alpha activity using a maximum entropy principle

OBJECTIVE

We present a method based on the distributed dipole source model to localize sources of spontaneous human brain activity, such as the alpha rhythm. The proposed method relies on the generalized maximum entropy principle and is implemented in frequency-domain.

METHODS

Several computer simulation studies of synchronous and asynchronous distributed dipole sources were carried out to test the validity of the method. The method was also applied to spontaneous electroencephalographic (EEG) recordings from human subjects to estimate the sources of alpha activity. The locations of these sources were registered with actual magnetic resonance images for anatomical visualization.

RESULTS

The simulation studies suggest the validity of the proposed method and its capability to detect distributed and fairly deep synchronous dipole sources. Results of human studies with 6 subjects suggest that the generators of alpha rhythm are mainly concentrated over the posterior regions of the cortex.

CONCLUSION

The proposed distributed source imaging method is a promising technique for localizing rhythmic brain activity.

Superpendentic index: a novel topological descriptor for predicting biological activity

A simple highly degenerating, pendenticity based, topological descriptor termed as superpendentic index has been conceptualized and its discriminating power investigated with regard to antiulcer activity. A data set consisting of 128 analogues of 4-substituted-2-guanidino thiazoles was selected for the present study. These analogues are reversible, competitive, and selective inhibitors of gastric H+,K(+)-ATPase enzyme. The value of superpendentic index of each analogue in the data set was computed and active range was identified. The biological activity assigned to each analogue using superpendentic index was subsequently compared with the reported in vitro and in vivo inhibitory activities. The accuracy of classification of analogues based on in vivo activity was found to be 82% in the active range using superpendentic index.

Estrogen-induced activation of mitogen-activated protein kinase in cerebral cortical explants: convergence of estrogen and neurotrophin signaling pathways

We have shown that estrogen elicits a selective enhancement of the growth and differentiation of axons and dendrites (neurites) in the developing CNS. We subsequently demonstrated widespread colocalization of estrogen and neurotrophin receptors (trk) within developing forebrain neurons and reciprocal transcriptional regulation of these receptors by their ligands. Using organotypic explants of the cerebral cortex, we tested the hypothesis that estrogen/neurotrophin receptor coexpression also may result in convergence or cross-coupling of their signaling pathways. Estradiol elicited rapid (within 5-15 min) tyrosine phosphorylation/activation of the mitogen-activated protein (MAP) kinases, ERK1 and ERK2, that persisted for at least 2 hr. This extracellular signal-regulated protein kinase (ERK) activation was inhibited successfully by the MEK1 inhibitor PD98059, but not by the estrogen receptor (ER) antagonist ICI 182,780, and did not appear to result from estradiol-induced activation of trk. Furthermore, we also found that estradiol elicited an increase in B-Raf kinase activity. The latter and subsequent downstream events leading to ERK activation may be a consequence of our documentation of a multimeric complex consisting of, at least, the ER, hsp90, and B-Raf. These novel findings provide an alternative mechanism for some of the estrogen actions in the developing CNS and could explain not only some of the very rapid effects of estrogen but also the ability of estrogen and neurotrophins to regulate the same broad array of cytoskeletal and growth-associated genes involved in neurite growth and differentiation.

Development of Blastocystis hominis cysts into vacuolar forms in vitro

The development of cysts of Blastocystis hominis isolated from human feces by the Ficoll-Paque concentration method and cultured in Jones' medium containing 10% horse serum is described. The morphological changes were studied by light and transmission electron microscopy at different intervals for up to 48 h. The cysts developed into a large number of vacuolar forms within 24 h, and binary fission was the only mode of reproduction observed.

Biological activity of the labdane diterpenes

Biological activity of diterpenes of the labdane skeleton, isolated from the terrestrial plants and marine sources during the last ten years has been reviewed.

Purification of a multicatalytic protease complex from developing winged bean seeds by indirect immunoaffinity chromatography

Many protease inhibitors have been characterized from leguminous seeds but very little is known about seed proteases which are supposedly regulated by these inhibitors. We have developed an indirect immunoaffinity chromatography system for the purification of cognate proteases from the same source, based on preferential high salt elution of the enzyme from a ternary complex of the protease, the inhibitor, and the anti-inhibitor IgG. Using anti-winged bean chymotrypsin inhibitor (WbCI) IgG as an affinity ligand, a multicatalytic protease complex has been purified from developing winged bean (Psophocarpus tetragonolobus) seeds. The purified preparation resolves into two large proteolytically active components when subjected to gel permeation chromatography under nondenaturing conditions, while SDS/PAGE analysis shows the presence of approximately 15 polypeptide chains in the 20- to 115-kDa range. The preparation cleaves known synthetic peptide substrates of trypsin, chymotrypsin, and V8 protease and it is only partially inhibited by a number of class-specific protease inhibitors. Western blot analysis shows the presence of WbCI in the purified preparation even after its extensive removal by the IgG-Sepharose column. The versatility of the indirect immunoaffinity chromatography system is attested by its extension to the soybean seeds.

Utility of bilateral coronary injections during complex coronary angioplasty

We describe a technique useful in complex coronary interventions wherein timed bilateral contrast injections are given in both coronary arteries. This technique is useful in chronic total occlusions in which the distal coronary vessel is not visualized except by collateral filling via the contralateral artery. This technique was applied in 12 patients; 11 with native coronary occlusion and one in whom the target site was visualized by contrast injections into a vein graft supplying competitive flow to an otherwise patent native vessel. With this technique, the distal coronary artery segment can be better visualized, which helps to aim and track the guide wire across the occluded segment.

Sequence, heterologous expression and functional characterization of tryparedoxin1 from Crithidia fasciculata

Tryparedoxin (TXN) has recently been discovered as a constituent of the complex peroxidase system in the trypanosomatid Crithidia fasciculata [Nogoceke et al. (1997) Biol. Chem. 378, 827-836] where it catalyzes the reduction of a peroxiredoxin-type peroxidase by trypanothione. Here we report on the full-length DNA sequence of the TXN previously isolated from C. fasciculata (TXN1). The deduced amino acid sequence comprises 147 residues and matches with all the peptide sequences of fragments obtained from TXN1. It shares a characteristic sequence motif YFSAxWCPPCR with some thioredoxin-related proteins of unknown function. This motif is homologous with the CXXC motif, which characterizes the thioredoxin superfamily of proteins and is known to catalyze disulfide reductions. Sequence conservations between TXNs and the typical thioredoxins are restricted to the intimate environment of the CXXC motif and three more remote residues presumed to contribute to the folding pattern of the thioredoxin-type proteins. The TXNs thus form a distinct molecular clade within the thioredoxin superfamily. TXN1 was expressed in Escherichia coli BL21 (DE3)pLysS as a C-terminally extended and His-tagged protein, isolated by chelate chromatography and characterized functionally. The recombinant product exhibited a kinetic pattern identical with, and kinetic parameters similar to those of the authentic enzyme in the trypanothione/peroxiredoxin oxidoreductase assay. The recombinant TXN1 can therefore be considered a valuable tool for the screening of specific inhibitors as potential trypanocidal agents.

In vitro encystation and excystation of Blastocystis ratti

Cysts of Blastocystis ratti were produced in vitro by culturing the parasite in Iscove's modified Dulbecco's medium (IMDM) with increasing concentrations of horse serum. Yields up to 3 x 10(6) cysts/ml of culture medium were obtained after 72 h. Encystation efficiency was time, strain and inoculum size dependent. A viability of > 70% was determined by flow cytometry employing fluorescein diacetate and propidium iodide staining. The presence of chitin as a cyst wall component was demonstrated by Calcofluor White M2R staining with which cystic stages showed blue fluorescence. The changes in morphology during excystation were examined by transmission electron microscopy. The cyst enlarged in size and some vacuoles appeared within the condensed cytoplasm. The vacuoles were full of inclusions and small glycogen aggregates. Coalescence of the vacuoles led to central body formation. Glycogen deposits were prominent throughout the excystation process. Some cysts divided by binary fission before the completion of the excystation.

Immunogenicity and protective efficacy of tuberculosis DNA vaccines encoding putative phosphate transport receptors

Using culture filtrate Ag-specific mAbs generated from mycobacteria-infected H-2b haplotype mice, we have previously identified three genes in the Mycobacterium tuberculosis genome, encoding proteins homologous to the periplasmic ATP-binding cassette phosphate-binding receptor PstS of the phosphate-specific transport system of E. coli. To define the potential vaccinal properties of these phosphate-binding proteins, female C57BL/6 mice were injected i.m. with plasmid DNA encoding PstS-1, PstS-2, or PstS-3 proteins from M. tuberculosis and immunogenicity and protective efficacy against i.v. challenge with M. tuberculosis H37Rv was analyzed. Significant levels of highly Ag-specific Abs and Th1-type cytokines IL-2 and IFN-gamma could be detected following vaccination with each of the three genes. However, only mice vaccinated with PstS-3 DNA demonstrated significant and sustained reduction in bacterial CFU numbers in spleen and lungs for 3 mo after M. tuberculosis challenge, as compared with CFU counts in mice vaccinated with control DNA. Vaccination with PstS-2 DNA induced a modest reduction in CFU counts in spleen only, whereas vaccination with PstS-1 DNA was completely ineffective in reducing bacterial multiplication. In conclusion, our results indicate that DNA vaccination is a powerful and easy method for comparative screening of potentially protective Ags from M. tuberculosis and that the PstS-3 protein is a promising new subunit vaccine candidate.

Studies with lysine N6-hydroxylase. Effect of a mutation in the assumed FAD binding site on coenzyme affinities and on lysine hydroxylating activity

The proposed FAD binding site of L-lysine N6-hydroxylase (EC 1.14.13.99) exhibits an unusual proline in a position where a highly conserved glycine is found in other FAD dependent hydroxylases. We have studied the role of this proline by mutating it to glycine in [P14G]aerA, which was expressed in Escherichia coli M15-2 and purified to homogeneity. The mutation has marked effects on the affinities of the cofactors FAD and NADPH as well as the substrate, lysine. Compared to the wild-type enzyme, the activity vs. pH profile of the mutant protein indicates a shift of the apparent pK'(a)s (7.8 and 8.7 for wild-type and 6.8 and 7.7 for the P14G-mutant enzyme) and of the activity maximum (pH 8 for wild-type and pH 7 for the P14G-mutant enzyme). While the activity of the mutant enzyme is much lower under conditions found to be optimal for the wild-type enzyme, adjustment of substrate and cofactor concentrations and pH leads to comparable activities for the mutant enzyme. These results suggest that the proline fulfils an important structural role in the proposed FAD binding site.

A recombinant measles virus expressing biologically active human interleukin-12

Suppression of cell-mediated immunity (CMI) is well-documented during and after measles. This immunosuppression is suggested to result from decreased production of interleukin-12 (IL-12), a key interleukin for CMI. In an attempt to clearly discern the role of IL-12 in measles-induced immunosuppression, a measles virus (MV) that expresses biologically active human IL-12 was generated. This was achieved by inserting the coding sequences of the two subunits (p35 and p40) of human IL-12 separated by an internal ribosome entry site in an additional transcription unit between the H and the L genes of MV. Although the IL-12-expressing MV grew slightly slower than the normal MV, it stably maintained the inserted sequences (3.2 kb) and uniformly expressed the foreign genes after 10 passages in cell culture. These findings suggest that MV is a well-suited vector for delivery of proteins of immunogenic and therapeutic importance.

A methodology for partitioning a vocabulary hierarchy into trees

Controlled medical vocabularies are useful in application areas such as medical information systems and decision-support systems. However, such vocabularies are large and complex, and working with them can be daunting. It is important to provide a means for orienting vocabulary designers and users to the vocabulary's contents. We describe a methodology for partitioning a vocabulary based on an IS-A hierarchy into small meaningful pieces. The methodology uses our disciplined modeling framework to refine the IS-A hierarchy according to prescribed rules in a process carried out by a user in conjunction with the computer. The partitioning of the hierarchy implies a partitioning of the vocabulary. We demonstrate the methodology with respect to a complex sample of the MED, an existing medical vocabulary.

Chlamydia trachomatis infection among pregnant women: prevalence and prenatal importance

BACKGROUND

Chlamydia trachomatis infection in pregnant women is suspected to result in low birth-weight and premature infants. We conducted studies to ascertain the prevalence of this infection among pregnant women in our setting and whether its presence is a risk factor for low birth-weight or prematurity.

METHODS

In the first study, 94 pregnant women between 26 and 30 weeks of gestation were screened for infection with Chlamydia trachomatis. The second investigated a cohort of 172 pregnant women presenting in spontaneous labour. The infection status was related to perinatal outcome in terms of birth-weight and gestation. In both the studies, Chlamydia trachomatis infection was diagnosed using the Chlamydiazyme test performed on endocervical swabs.

RESULTS

The prevalence of Chlamydia trachomatis infection in mid-pregnancy and at labour was 17% (16/94) and 18.6% (32/172), respectively. Women with infection were relatively older than those without it [mean (SD) age: 26.6 (4.5) years v. 24.8 (3.6) years, p = 0.01]. The mean (SD) birth-weight [2869 (611) g v. 2814 (496) g], gestation [38.5 (2.6) weeks v. 38.3 (2.0) weeks], and incidence of low birth-weight [18.7% v. 20.7%] as well as prematurity [9.4% v. 10.7%] were similar among neonates born to women with or without infection. Neonates born to infected mothers experienced purulent conjunctivitis more frequently than those born to non-infected mothers [12.5% v. 2.8%, p = 0.04].

CONCLUSION

Chlamydia trachomatis is a relatively common infection in pregnant women. However, it was not associated with either low birth-weight or prematurity.

Arene dioxides of substituted pyrenes: synthesis and X-ray structural studies

The arene dioxides of five 1-substituted pyrenes have been synthesized using dimethyldioxirane. The diasteroisomeric distribution of the dioxides has been determined. X-ray crystallographic structures of the dioxides have also been obtained. These structures show that for the cis dioxides the molecular structures show a departure from planarity, the extent of which is dependent on the substituent.

Esthesioneuroblastoma - a rarity

A young male presented with visual complaints of one year duration, epistaxis and nasal blockage of 3 months duration. He had bilateral proptosis and bitemporal hemianopia and a mass near the; roof of nasal cavity. Skull skiagram showed enlarged sella and computed tomography showed erosion of sella and a central mass. Partial excision of supra and parasellar tumour was done which on histopatho-logical examination revealed Esthesioneuroblastoma. This was followed by radiotherapy and CCNU twice, at 6 weeks interval. He is doing well after 1 year and 9 months of follow up.

Reversal of a novel multidrug resistance mechanism in human colon carcinoma cells by fumitremorgin C

We selected a human colon carcinoma cell line in increasing concentrations of mitoxantrone to obtain a resistant subline, S1-M1-3.2, with the following characteristics: profound resistance to mitoxantrone; significant cross-resistance to doxorubicin, bisantrene, and topotecan; and very low levels of resistance to Taxol, vinblastine, colchicine, and camptothecin. This multidrug resistance (MDR) phenotype, which was not reversed by verapamil or another potent P-glycoprotein (Pgp) inhibitor, CL 329,753, was dependent, in part, upon an energy-dependent drug efflux mechanism. Pgp and the multidrug resistance protein (MRP) were not elevated in the resistant cells relative to the drug-sensitive parent, suggesting that resistance was mediated by a novel pathway of drug transport. A cell-based screen with S1-M1-3.2 cells was used to identify agents capable of circumventing this non-Pgp, non-MRP MDR. One of the active agents identified was a mycotoxin, fumitremorgin C. This molecule was extremely effective in reversing resistance to mitoxantrone, doxorubicin, and topotecan in multidrug-selected cell lines showing this novel phenotype. Reversal of resistance was associated with an increase in drug accumulation. The compound did not reverse drug resistance in cells with elevated expression of Pgp or MRP. We suggest that fumitremorgin C is a highly selective chemosensitizing agent for the resistance pathway we have identified and can be used as a specific pharmacological probe to distinguish between the diverse resistance mechanisms that occur in the MDR cell.