Electron paramagnetic resonance spectra simulation directly from molecular dynamics trajectories of a liquid crystal with a doped paramagnetic spin probe

We report simulation of EPR spectra directly and entirely from trajectories generated from molecular dynamics simulations. Results are reported for a model 3beta-DOXYL-5alpha-cholestane spin probe in a coarse-grained solvent representing a 5CB nematic host. The results are in excellent agreement with the experimental spectra. The calculated order parameters associated with the paramagnetic probe show strong correlation with the order parameter of 5CB mesogens and are in agreement with those reported in the literature. Simulation of EPR spectra entirely from molecular dynamics of real structures provides direct correlation between molecular motions and the features observed in the spectra, allowing unambiguous interpretation of the spectra. This method opens the possibility for "computer engineering" of spin-labeled materials with the desired properties, such as spin-labeled proteins, prior to experiment.

Measurement of reactive species production by nanoparticles prepared in biologically relevant media

Exposure to nanoparticles may pose a risk to health and this hypothesis is currently being investigated by toxicologists. Although the mechanism of nanoparticle toxicity has been shown to be mediated, in part, by oxidative stress, the precise mechanism and molecules involved are still unknown. In light of this, the evaluation of the oxidative potential of nanoparticles is an important consideration in measuring their toxicity. The aim of this study was to examine the use of a fluorogenic probe, 2',7'-dichlorofluorescin (DCFH), in a cell-free assay system and to assess the relationship between the results obtained with this method and with the reactive species formation observed in cells. In order to obtain a well-dispersed nanoparticle suspension, bovine serum albumin (BSA) and dipalmitoyl phosphatidyl choline (DPPC) addition in suspension medium was investigated. Both 1% BSA and 0.025% DPPC added to the medium significantly improved the stability of the nanoparticle suspension, decreasing the extent of particle agglomeration and settling over time. In a cell-free system, reactive oxygen species (ROS) production by 14nm carbon black particles (CB) suspended in DPPC was higher than that measured with the other suspensions (saline or 1% BSA). A greater ROS production was observed in MonoMac 6 cells (MM6) following treatment with 14nm CB suspended in medium containing BSA and/or DPPC compared to medium alone. In conclusion, 1% BSA and 0.025% DPPC solution was the most efficient for the preparation of a nanoparticle suspension and to measure their oxidative potential.

Phylogenetics and Mitochondrial DNA

Phylogenetic analysis can be conducted using a variety of methods, generally classified as distancebased or character-based approaches. Patterns found through phylogenetic analysis of human mitochondrial DNA (mtDNA) sequences have revealed a wealth of information in such disparate fields as the human evolution; the movement of human lineages throughout history (phylogeography); and the susceptibility of certain groups to devastating diseases. Forensic mtDNA analysis has also benefited from the use of these methods. Phylogenetic assessment of forensic mtDNA databases has revealed a consistency with published data at a depth of analysis that is not attainable with basic population genetic methods. The detailed characteristics of specific sites within a mtDNA sequence are best assessed using phylogenetic methods. These studies have identified the most informative sites for individual differentiation, while also providing quality assurance metrics to apply to individual mtDNA profiles or entire databases. Such a level of evaluation and understanding enhances the interpretation of forensic casework.

Parametrization and validation of a force field for liquid-crystal forming molecules

First principles density functional calculations have been carried out to determine the structures and conformational energies of a series of liquid-crystal fragment molecules. The calculations have been used to derive a molecular mechanics force field that describes a subset of commonly occurring liquid-crystal molecules. The force field has been used to carry out molecular dynamics simulations of the bulk phase for these fragment molecules. Computed densities and heats of vaporization are in good agreement with experimental data. These results should be useful in future molecular dynamics simulations of liquid-crystal systems.

Size-dependent proinflammatory effects of ultrafine polystyrene particles: a role for surface area and oxidative stress in the enhanced activity of ultrafines

Studies into the effects of ultrafine particles in the lung have shown adverse effects considered to be due in part to the particle size. Air pollution particles (PM(10)) are associated with exacerbations of respiratory disease and deaths from cardiovascular causes in epidemiological studies and the ultrafine fraction of PM(10) has been hypothesized to play an important role. The aim of the present study was to investigate proinflammatory responses to various sizes of polystyrene particles as a simple model of particles of varying size including ultrafine. In the animal model, we demonstrated that there was a significantly greater neutrophil influx into the rat lung after instillation of 64-nm polystyrene particles compared with 202- and 535-nm particles and this was mirrored in other parameters of lung inflammation, such as increased protein and lactate dehydrogenase in bronchoalveolar lavage. When surface area instilled was plotted against inflammation, these two variables were directly proportional and the line passed through zero. This suggests that surface area drives inflammation in the short term and that ultrafine particles cause a greater inflammatory response because of the greater surface area they possess. In vitro, we measured the changes in intracellular calcium concentration in mono mac 6 cells in view of the potential role of calcium as a signaling molecule. Calcium changes after particle exposure may be important in leading to proinflammatory gene expression such as chemokines. We demonstrated that only ultrafine polystyrene particles induced a significant increase in cytosolic calcium ion concentration. Experiments using dichlorofluorescin diacetate demonstrated greater oxidant activity of the ultrafine particles, which may explain their activity in these assays. There were significant increases in IL-8 gene expression in A549 epithelial cells after treatment with the ultrafine particles but not particles of other sizes. These findings suggest that ultrafine particles composed of low-toxicity material such as polystyrene have proinflammatory activity as a consequence of their large surface area. This supports a role for such particles in the adverse health effects of PM(10).

An IgH Enhancer That Drives Transcription through Basic Helix-Loop-Helix and Oct Transcription Factor Binding Motifs

The transcriptional enhancer (E(mu)3') of the IgH locus of the channel catfish, Ictalurus punctatus, shows strong B cell-specific activity and differs from the mammalian E(mu) enhancer in both location and structure. It occurs between the mu and delta genes and contains numerous transcription factor binding sites, predominantly octamer and muE5 motifs of consensus and variant sequences. It lacks the classical muA-muE3(CBF)-muB core array of binding motifs seen within mammalian IgH E(mu) enhancers. To determine the functionally important motifs, a series of mutant enhancers was created using sequence-targeted polymerase chain reaction. Whereas the mutation of consensus and variant octamer motifs (individually or in multiples) decreased enhancer function, mutation of a single consensus muE5 motif destroyed the function of this enhancer in mammalian plasmacytomas. Mutation of this consensus muE5 site, combined with mutations of certain octamer sites, destroyed function in catfish B cells. Experiments using artificial enhancers containing multimers of motifs or short regions of the native enhancer suggested that the minimal E(mu)3' enhancer (a) contains a consensus muE5 site and two octamer sites, (b) is B cell-specific, and (c) is active across species. The dependence of an Ig enhancer on sites that bind basic helix-loop-helix and Oct transcription factors has not previously been observed and confirms large differences in structure and function between fish and mammalian IgH enhancers.

Length variation in HV2 of the human mitochondrial DNA control region

Hair samples were typed from three individuals who exhibited length heteroplasmy in the homopolymeric cytosine stretches (C-stretch) in hypervariable region 2 (HV2). The study demonstrated that for different hairs within an individual, the HV2 C-stretch region can vary with respect to the number of cytosines and/or proportion of C-stretch length variants. Length heteroplasmy may occur regardless of the prominent length variant present in this region. Differences in the number of cytosines at the C-stretch region, or a variation in the relative amounts of heteroplasmic length variants, cannot be used to support an interpretation of exclusion.

Pinocytic loading of cytochrome c into intact cells specifically induces caspase-dependent permeabilization of mitochondria: evidence for a cytochrome c feedback loop

Previous studies introduced cytochrome c into intact cells via the disruptive techniques of microinjection or electroporation to provide support for the hypothesis that, in whole cells, cytochrome c release from mitochondria triggers caspase activation and other degradative changes. However, the types of measurements that could be undertaken with these techniques was limited. We used the simple and relatively gentle technique of pinocytic loading to demonstrate that, in intact cells, cytosolic cytochrome c specifically induced activation of caspase-3- and -9-like enzymes, and a loss of mitochondrial polarization coincident with an increase in mitochondrial permeability. Our results support the prediction from in vitro studies that activation of caspases-3 and -9 is downstream of cytochrome c release and provide the first direct evidence that, in whole cells, cytochrome c-dependent caspase-activation can exert a feedback effect to elicit mitochondrial permeabilization and collapse of the mitochondrial trans-membrane potential.

Leptin transport at the blood--cerebrospinal fluid barrier using the perfused sheep choroid plexus model

Leptin is secreted by adipose tissue and thought to regulate appetite at the central level. Several studies have explored the central nervous system (CNS) entry of this peptide across the blood-brain and blood-cerebrospinal fluid (CSF) barriers in parallel, but this is the first to explore the transport kinetics of leptin across the choroid plexus (blood-CSF barrier) in isolation from the blood-brain barrier (BBB). This is important as the presence of both barriers can lead to ambiguous results from transport studies. The model used was the isolated Ringer perfused sheep choroid plexus. The steady-state extraction of [(125)I]leptin (7.5 pmol l(-1)) at the blood face of the choroid plexus was 21.1+/-5.7%, which was greater than extraction of the extracellular marker, giving a net cellular uptake for [(125)I]leptin (14.0+/-3.7%). In addition, trichloroacetic acid precipitable [(125)I] was detected in newly formed CSF, indicating intact protein transfer across the blood-CSF barrier. Human plasma concentrations of leptin are reported to be 0.5 nM. Experiments using 0.5 nM leptin in the Ringer produced a concentration of leptin in the CSF of 12 pM (similar to that measured in humans). [(125)I]Leptin uptake at the blood-plexus interface using the single-circulation paired tracer dilution technique (uptake in <60 s) indicated the presence of a saturable transport system, which followed Michaelis-Menten-type kinetics (K(m)=16.3+/-1.8 nM, V(max)=41.2+/-1.4 pmol min(-1) g(-1)), and a non-saturable component (K(d)=0.065+/-0.002 ml min(-1) g(-1)). In addition, secretion of new CSF by the choroid plexuses was significantly decreased with leptin present. This study indicates that leptin transport at the blood-CSF barrier is via saturable and non-saturable mechanisms and that the choroid plexus is involved in the regulation of leptin availability to the brain.

Clusterin is an ATP-independent chaperone with very broad substrate specificity that stabilizes stressed proteins in a folding-competent state

We recently reported that the ubiquitous, secreted protein clusterin has chaperone activity in vitro [Humphreys et al. (1999) J. Biol. Chem. 274, 6875-6881]. In this study, we demonstrate that clusterin (i) inhibits stress-induced precipitation of a very broad range of structurally divergent protein substrates, (ii) binds irreversibly via an ATP-independent mechanism to stressed proteins to form solubilized high molecular weight complexes, (iii) lacks detectable ATPase activity, (iv) when acting alone, does not effect refolding of stressed proteins in vitro, and (v) stabilizes stressed proteins in a state competent for refolding by heat shock protein 70 (HSP70). Furthermore, we show that, at physiological levels, clusterin inhibits stress-induced precipitation of proteins in undiluted human serum. Clusterin represents the first identified secreted mammalian chaperone. However, reports from others suggest that, at least under stress conditions, clusterin may be retained within cells to exert a protective effect. Regardless of the topological site(s) of action, the demonstration that clusterin can stabilize stressed proteins in a refolding-competent state suggests that, during stresses, the action of clusterin may inhibit rapid and irreversible protein precipitation and produce a reservoir of inactive but stabilized molecules from which other refolding chaperones can subsequently salvage functional proteins.

Induction of angiogenesis by hyperplastic colonic mucosa adjacent to colon cancer

We determined whether hyperplastic mucosa adjacent to colon cancer contributes to neoplastic angiogenesis. Surgical specimens of human colon cancer (40 Dukes' stage B and 34 Dukes' stage C) were analyzed by immunohistochemistry for expression of proliferative and angiogenic molecules. The mucosa adjacent to Dukes' stage C tumors (but not Dukes' stage B tumors) had a higher Ki-67 labeling index and a higher expression of epidermal growth factor receptor and transforming growth factor-alpha than distant mucosa. The expression levels of vascular endothelial growth factor, basic fibroblast growth factor, interleukin-8, and the vascular density in the adjacent mucosa were similar to those in the tumor lesions and significantly higher than those in the distant mucosa. The expression of interferon-beta inversely correlated with the level of pro-angiogenic molecules and the vascular density. The injection of metastatic human colon cancer cells and murine colon cancer cells into the cecal wall of mice induced hyperplastic changes in the adjacent mucosa which expressed higher levels of epidermal growth factor receptor, basic fibroblast growth factor, and vascular endothelial growth factor, and lower levels of interferon-beta than did the control mucosa, which directly correlated with the degree of hyperplasia. These data suggest that metastatic human colon cancer cells can induce hyperplasia in the adjacent mucosa, which in turn produces angiogenic molecules that contribute to neoplastic angiogenesis.

In vitro toxicology of respirable Montserrat volcanic ash

OBJECTIVES

In July 1995 the Soufriere Hills volcano on the island of Montserrat began to erupt. Preliminary reports showed that the ash contained a substantial respirable component and a large percentage of the toxic silica polymorph, cristobalite. In this study the cytotoxicity of three respirable Montserrat volcanic ash (MVA) samples was investigated: M1 from a single explosive event, M2 accumulated ash predominantly derived from pyroclastic flows, and M3 from a single pyroclastic flow. These were compared with the relatively inert dust TiO(2) and the known toxic quartz dust, DQ12.

METHODS

Surface area of the particles was measured with the Brunauer, Emmet, and Teller (BET) adsorption method and cristobalite content of MVA was determined by x ray diffraction (XRD). After exposure to particles, the metabolic competence of the epithelial cell line A549 was assessed to determine cytotoxic effects. The ability of the particles to induce sheep blood erythrocyte haemolysis was used to assess surface reactivity.

RESULTS

Treatment with either MVA, quartz, or titanium dioxide decreased A549 epithelial cell metabolic competence as measured by ability to reduce 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). On addition of mannitol, the cytotoxic effect was significantly less with M1, quartz, and TiO(2). All MVA samples induced a dose dependent increase in haemolysis, which, although less than the haemolysis induced by quartz, was significantly greater than that induced by TiO(2). Addition of mannitol and superoxide dismutase (SOD) significantly reduced the haemolytic activity only of M1, but not M2 or M3, the samples derived from predominantly pyroclastic flow events.

CONCLUSIONS

Neither the cristobalite content nor the surface area of the MVA samples correlated with observed in vitro reactivity. A role for reactive oxygen species could only be shown in the cytotoxicity of M1, which was the only sample derived from a purely explosive event. These results suggest that in general the bioreactivity of MVA samples in vitro is low compared with pure quartz, but that the bioreactivity and mechanisms of biological interaction may vary according to the ash source.

Clusterin protein diversity in the primate eye

PURPOSE

The clusterin gene encodes a multi-functional protein that has been identified in different tissues, including a number of different eye tissues, primarily in the mouse and to a much lesser extent in humans. Clusterin has been implicated in a number of cellular processes such as lipid transport, membrane integrity, apoptosis, and neurodegeneration, all of which could be important to the biology of the eye. In the current communication, we provide data that confirms the expression of clusterin in a number of different human eye tissues and establishes the expression profile of this gene in monkey derived eye tissues. The issue that we sought to examine is whether a broad profile of clusterin expression in the eye is consistent in primates (monkey and human).

METHODS

The majority of our study was done using monkey eye tissues. Where possible, we have used human tissues in order to confirm published findings. Northern and western analysis was performed using tissues derived from monkey eyes. In situ hybridization and immunochemistry were carried out on human eye sections.

RESULTS

Clusterin mRNA is expressed in primate lens, cornea, limbus, sclera, orbital muscle, ciliary body, retina, RPE/choroid, and RPE cells in culture. Western analysis revealed that two major groups of clusterin exist in the eye, a high molecular weight group (>100 kDa) and a second group consisting of at least five clusterin species that are all approximately 80 kDa. Analysis of conditioned media from RPE cells cultured on permeable supports suggests that different forms of clusterin display alternative patterns of secretion.

CONCLUSIONS

Clusterin is expressed in a broad range of eye tissues in both human and monkey, suggesting that this is a characteristic feature in primates. We demonstrate for the first time that a diverse number of clusterin isoforms were observed in monkey eye tissues by western analysis. Meanwhile, the molecular size of clusterin mRNA detected in the array of tissues are identical in size, suggesting that the nature of the diversity in clusterin forms is due to post-translational modifications. In addition, new insights were made in defining clusterin expression in ciliary body, cornea, and the retinal pigment epithelium.

Ahmed glaucoma valve implant vs trabeculectomy in the surgical treatment of glaucoma: a randomized clinical trial

PURPOSE

To compare the short- and intermediate-term results of two commonly used glaucoma surgical procedures, trabeculectomy and Ahmed glaucoma valve implant.

METHODS

A randomized clinical trial was performed at two international centers. One eye each of consecutive patients requiring glaucoma surgery for intraocular pressure control was randomized to receive either trabeculectomy or the Ahmed implant.

RESULTS

Of the 117 patients, 62 were randomized to trabeculectomy and 55 to the Ahmed implant. With a mean follow-up of 9.7 months, the trabeculectomy group had statistically lower intraocular pressures at weeks 6 to 15 (12.6 mm Hg vs 16.4 mm Hg) and months 11 to 13 (11.4 mm Hg vs 17.2 mm Hg) than the Ahmed implant group. Compared with preoperative status, no statistically significant differences between groups were noted for visual acuity, visual field, lens status, and final anterior chamber depth. The cumulative probabilities of success (intraocular pressure <21 mm Hg and at least 15% reduction in intraocular pressure from preoperative level) were 83.6% for trabeculectomy and 88.1% for Ahmed implant (P =.43). However, the Ahmed implant group had a greater adjunctive medication requirement. On the last visit, 10 of the trabeculectomy eyes and 19 of the Ahmed implant eyes required at least one topical medication (P =.01). There was no statistically significant difference in the rate of complications between the two groups.

CONCLUSIONS

Lower mean intraocular pressures were noted for the trabeculectomy group. All other results, including success (as defined in this study) and frequency of complications, were comparable between the two groups.

Telomerase expression and telomere length in immortal leukocyte lines from channel catfish

Normal channel catfish leukocytes readily undergo spontaneous in vitro immortalization yielding functionally active diploid cell lines. Since telomerase activation appears to be a critical step in the establishment of immortal mammalian cells, studies were undertaken to determine if and when telomerase expression occurs during the in vitro immortalization process of channel catfish leukocytes. To this end, freshly isolated peripheral blood leukocytes (PBL) from normal fish were shown to exhibit low to undetectable levels of telomerase activity and within four days after culture initiation showed dramatic increases in telomerase activity which typically remained high for at least four weeks. This activity then declined, concomitant with decreases in cellular proliferation and increases in cell death. Cells which escaped this culture "crisis" re-expressed high levels of telomerase activity indefinitely. Although telomerase activity was expressed early in the immortalization process, clonal cell lines derived from these cultures had relatively short telomeres. These results suggest that telomerase expression in catfish leukocytes is activation-induced, and its expression does not necessarily stabilize telomere length until a critically, albeit ill-defined, short length is reached.

MHC class II A genes in the channel catfish (Ictalurus punctatus)

In order to characterize the Major histocompatibility complex (MHC) class II A genes of the channel catfish (Ictalurus punctatus) a cDNA library was screened and PCR was performed. Four different full-length cDNA sequences for MHC class II A genes were obtained from a clonal B cell line derived from an outbred fish. Two different genomic sequences and corresponding cDNAs were obtained from a presumably homozygous gynogenetic catfish. The A genes have five exons and four phase one introns. The first exon encodes the 5' untranslated region (UTR) and leader peptide; the second and third exons encode the alpha1 and alpha2 domains, respectively. The connecting peptide, transmembrane and cytoplasmic domains, as well as part of the 3' UTR, are encoded by the fourth exon and the rest of the 3' UTR is encoded by the fifth exon. Southern blot analyses using an exon three probe revealed two to four hybridizing fragments with considerable restriction fragment length polymorphisms evident among randomly selected outbred channel catfish. These findings are consistent with the presence of at least two functional polymorphic MHC class II A gene loci. An unusual aspect of the channel catfish MHC class II alpha chain is its lack of N-linked glycosylation sites.

Restoration of gap junctional intercellular communication by caffeic acid phenethyl ester (CAPE) in a ras-transformed rat liver epithelial cell line

Caffeic acid phenethyl ester (CAPE), an active ingredient of honeybee propolis, has been identified as having anti-inflammatory, anti-viral and anti-cancer properties. Since the deficiency of gap junctional intercellular communication (GJIC) has been shown to be a characteristic of most cancer cells, this study was designed to test the hypothesis that the anti-carcinogenic activity of CAPE might be related to its ability to restore GJIC in tumorigenic GJIC-deficient cells (WB-ras2 cells). The results showed that CAPE restored GJIC, phosphorylation of connexin 43 (Cx43) and its normal localization on the plasma membrane in WB-ras2 cells after 3 days at 5 microg/ml concentration. Additionally, CAPE inhibited growth in soft agar and decreased the protein level of p21(ras). The results are consistent with the hypothesis that the anti-cancer mechanism of CAPE may be mediated by its ability to restore GJIC.