Epigenetic toxicology as toxicant-induced changes in intracellular signalling leading to altered gap junctional intercellular communication

Communication mechanisms [extra-, intra-, and gap junctional inter-cellular communication (GJIC)] control, from the fertilized egg, through embryogenesis to maturity and aging, whether a cell proliferates, differentiates, dies by apoptosis, or if differentiated, adaptively responds to endogenous and exogenous signals. From the egg to the 100 trillion cells in the human body, health is maintained when these communication processes between stem, progenitor and terminally differentiated cells are integrated. Each cell choice involves 'epigenetic' mechanisms to alter the expression of genes at the transcriptional, translational or post-translational levels. Disruption of the communication mechanisms can be either adaptive or maladaptive. Modulation of extra-cellular communication, either by genetic imbalances of growth factors, hormones or neurotransmitters or by environmental, exogenous chemicals can trigger signal transducing intra-cellular mechanisms. These intra-cellular signals can modulate gene expression at the transcriptional, translational or post-translational levels while also modulating GJIC. Untimely or chronic disruption of GJIC during embryonic or fetal development could lead to embryonic lethality or teratogenesis. By modulation of GJIC, homeostatic control of cell growth, differentiation or apoptosis could lead to specific diseases, such as neurological, cardiovascular, reproductive or endocrinological dysfunction. Chemical modulation or oncogene down-regulation of GJIC in initiated tissues has been shown to lead to tumor promotion. Genetic syndromes carrying a mutated gap junction gene, together with some transgenic and knock-out gap junction gene mice, provide evidence for the importance of this organelle found only in metazoans. Implications for 'thresholds' to toxicants and for risk assessment are evident.

Functional and molecular characterization of teleost leukocytes

The coupling of immunologically relevant in vitro assay systems, cell separation techniques, and the development of distinct clonal leukocyte lines has established the existence of T, B, natural killer, and accessory cell equivalents in teleosts. B cells are directly defined by monoclonal antibodies to teleost immunoglobulin (Ig) and identification of Ig H and L chain genes. As in mammals, fish B cells show Ig H-chain gene rearrangements, allelic exclusion, produce both membrane-bound and secreted forms of Ig, and transduce intracellular proliferative signals upon anti-Ig cross-linking. It has also been found that some fish B cells express a unique chimeric Ig chain with sequence homology to mammalian Ig delta. Teleost T cells are still indirectly defined as sIg- lymphocytes due to a lack of definitive surface markers. These mIg- lymphocytes are the responding cells in mixed leukocyte cultures, proliferate specifically to autologously processed and presented antigen, provide helper function for in vitro antibody responses, and produce interleukin-like factors upon activation. Recent identification of teleost T-cell receptor alpha and beta genes has now permitted the unequivocal genetic demonstration that some of these mIg- cells are bona fide T cells. It is anticipated that such long-term clonal cell lines will be indispensable tools for dissecting the physiology, biochemistry and molecular biology of teleost immune responses.

Towards an ecological audiology: stereophonic listening chamber and acoustic environmental tests

An acoustic laboratory for reproduction of speech and acoustic environments is presented along with two sound field tests. Its design has been inspired by the LEDE (Living End Dead End) principle for construction of radio and music control rooms. The equipment and the 12 loudspeakers can simultaneously reproduce several stereophonic and monophonic recordings. The interesting feature is that the delayed first reflex in the LEDE room allows for a realistic perception of the recording room. A preliminary presentation of two newly developed tests for sound field listening is given. In DSIN. Directional Speech In Noise, the JFC (just follow conversation) threshold for continuous discourse is determined in 12 directions in quiet and in noise from +/- 60 degrees azimuth. In SEIT (Sound Environmental Identification Test), stereophonic acoustic environments are presented and the subject is asked to identify specific components and to characterize each environment as closely as possible. Results from tests with normal hearing subjects and examples of results with hearing impaired subjects are presented. The potential of the technique for use in aural rehabilitation, functional definition of auditory communication and quality assessment of hearing aids is discussed. It is pointed out that the term ecological audiology is suitable for describing the interaction between the communicating individual and the environment in a broad sense.

Control of the human cell cycle by a bacterial protein, gapstatin

The oral gram-negative bacterium Actinobacillus actinomycetemcomitans is a major pathogen in human periodontal disease. Saline extraction releases a range of surface-associated components from this bacterium, including one which exhibits potent anti-proliferative activity as assessed by its capacity to inhibit DNA synthesis by human and other mammalian cells. Cultures incubated with this bacterial fraction for a prolonged period comprise a high proportion of cells containing a 4n level of DNA. Studies using hydroxyurea-synchronized cultures showed that cells treated with the surface-associated fraction were arrested in the G2 phase of the cell cycle and did not enter mitosis. This G2/M blockade was observed only when the bacterial fraction was added to the cells during early S phase. Our data also suggest that the active bacterial component binds to surface receptors expressed by the human cells and may act by a novel mechanism which involves down-regulation of cyclin B1 expression. The anti-proliferative activity of the bacterial fraction, purified by a combination of ammonium sulphate precipitation, HPLC anion exchange and gel filtration, has been shown to be an 8 kDa protein, which we have called gapstatin. Purified gapstatin was shown to be responsible for the the inhibitory effects of the surface-associated fraction on mammalian cells.

Characterization of type IV pilus genes in Pseudomonas syringae pv. tomato DC3000

Many strains of Pseudomonas syringae produce retractile pili that act as receptors for lytic bacteriophage phi 6. As these are also characteristics of type IV pili, it was postulated that P. syringae may possess genes for type IV pilus biogenesis. A cosmid clone bank of P. syringae pv. tomato DC3000 genomic DNA was used to complement a mutant of Pseudomonas aeruginosa defective in the PilD (XcpA) prepilin peptidase gene by selection for restoration of extracellular protein secretion, a function also known to require PilD. A cosmid able to complement this mutant was also able to complement mutations in the pilB and pilC genes, suggesting that, if the organization of these genes is similar to that of P. aeruginosa, the cosmid may contain the P. syringae pilA. This was confirmed by sequencing a region from this plasmid that was shown to hybridize at low stringency to the P. aeruginosa pilA gene. The deduced P. syringae PilA polypeptide possesses the characteristic properties of the type IV pilins. Heterologous expression of the P. syringae pilA in P. aeruginosa was also shown, conferring not only phi 6 phage sensitivity to P. aeruginosa pilA mutants but also sensitivity to PO4, a lytic bacteriophage specific for the pilus of P. aeruginosa. This suggests that additional components might be present in the mature pilus of P. aeruginosa that are the true receptors for this phage. Chromosomal mutations in P. syringae pv. tomato DC3000 pilA and pilD genes were shown to abolish its sensitivity to bacteriophage phi 6. To determine the importance of P. syringae pilus in plant leaf interactions, these mutations were tested under laboratory and field conditions. Although little effect was seen on pathogenicity, culturable leaf-associated population sizes of the pilA mutant were significantly different from those of the wild-type parent. In addition, the expression of the DC3000 pilA gene appears to contribute to the UV tolerance of P. syringae and may play a role in survival on the plant leaf surface.

An item response theory analysis of the Conners Teacher's Rating Scale

We used an item response theory (IRT) measurement model to examine the 28-item Conners Teacher's Rating Scale (CTRS) for the diagnosis of attention-deficit/hyperactivity disorder (ADHD). Using an Israeli sample of 453 pairs of respondents (parents and teachers), we broke down our sample into nonclinical (n = 306) and clinical (n = 147) subsamples. IRT analyses based on a rating scale model revealed structural inadequacies involving the apparent inappropriateness of the 4-point Likert-type scale used by the CTRS. Additionally, IRT analyses were able to shed light on differences in the structure of the latent trait for the ADHD variable as measured by the CTRS for all four groups of respondents. Implications for the diagnosis and treatment of ADHD are presented.

Cellular microbiology: cycling into the millennium

Cellular microbiology is a newly developing science born from the realization that many different aspects of eukaryotic cell biology are targeted by microbial virulence mechanisms. One example of this is the emerging evidence that several bacteria can interfere, directly or indirectly, with the eukaryotic cell cycle. This article discusses the cell-cycle effects of bacterially generated molecules, their role in virulence and their possible therapeutic potential.

Management of parvovirus infection in pregnancy and outcomes of hydrops: a survey of members of the Society of Perinatal Obstetricians

OBJECTIVE

Our purpose was to investigate the evaluation and management of parvovirus infection during pregnancy.

STUDY DESIGN

Surveys were mailed to members of the Society of Perinatal Obstetricians residing in the United States and Canada in July 1997. They were asked about their evaluation and management of parvovirus infection, including whether they repeated and confirmed serologic studies, what their initial and follow-up evaluations included, whether they had had any cases of parvovirus-associated hydrops in the past 2 years, and if so, what were the management and outcomes of the hydropic fetuses.

RESULTS

Surveys were mailed to 1623 members of the Society of Perinatal Obstetricians and 541 completed surveys were returned. Sixty-eight percent of the respondents repeated and confirmed serologic studies. Eighty-nine percent used ultrasonography in their initial management of pregnant patients with recent parvovirus infection, 7.5% used amniocentesis for polymerase chain reaction, and 2% used fetal blood sampling. The outcomes of the 539 cases of parvovirus-induced hydrops included spontaneous resolution in 34%, death without intrauterine transfusion in 30%, resolution after intrauterine transfusion in 29%, death after intrauterine transfusion in 6%, and pregnancy termination in 1%. Almost all cases of nonimmune hydrops reported occurred between 16 and 32 weeks.

CONCLUSIONS

Approximately one third of the cases of parvovirus-induced nonimmune hydrops resolved spontaneously, whereas 83.5% of hydropic fetuses transfused survived.

Response of single species biofilms and microcosm dental plaques to pulsing with chlorhexidine

The aim of this study was to determine the effect of pulsing chlorhexidine gluconate, at concentrations commonly used in mouthwashes, on Streptococcus sanguis biofilms and microcosm dental plaques in vitro. Biofilms were grown on bovine enamel and nutrients were supplied in the form of artificial saliva. Pulsing experiments were carried out on steady-state biofilms using 0.05 or 0.2% chlorhexidine solutions delivered twice daily for 1 min. In a separate study, the enamel discs on which the biofilms were formed were pre-treated with chlorhexidine and pulsed directly after inoculation and then at regular intervals. With both concentrations of chlorhexidine used, a c.2 log10 reduction in the viable counts of S. sanguis was achieved with the initial pulse, but as pulsing continued, the bacterial population recovered, albeit not to the previous level. A c.1 log10 reduction in the total viable counts of the microcosm plaques was seen after the first pulse with 0.2% chlorhexidine. The total count then recovered rapidly and, after the fifth pulse, the total viable counts were not significantly different from those before pulsing. The total counts then remained at a similar level throughout the course of the experimental runs. Pre-treatment of the enamel discs with 0.2% chlorhexidine before inoculation produced viable counts of c.10(5) cfu/mm2, a 1 log10 reduction compared with untreated discs. After pulsing with 0.2% chlorhexidine at 8 h, a 3 log10 reduction was seen in the total aerobic and anaerobic counts, but again the viable counts subsequently increased despite twice-daily chlorhexidine pulsing. Regardless of the nature of the biofilm, pulsing initially achieved substantial kills, but the viability of the biofilms subsequently increased despite continued pulsing. Chlorhexidine was effective at reducing the viability of microcosm plaques when it was applied to the substratum before exposure to bacteria and subsequently pulsed on to the biofilms.

Data-driven quality improvement for HMO patients: one agency's experience with OASIS and OBQI

The authors determined whether a home health agency could use Outcome Assessment and Information Set (OASIS) items and the Outcome-Based Quality Improvement (OBQI) model to enhance outcomes for health maintenance organization (HMO) patients. After an initial baseline period and four quarters of quality improvement activities, Improvement and Stabilization scores showed few significant changes. When the results were reviewed, investigators considered both the HMO authorization patterns and challenges encountered in using the OASIS-OBQI paradigm.

Influence of growth mode and sucrose on susceptibility of Streptococcus sanguis to amine fluorides and amine fluoride-inorganic fluoride combinations

This study evaluated the susceptibility to amine fluorides (AmFs) of planktonic and biofilm cultures of Streptococcus sanguis grown with and without sucrose. Cultures were incubated with AmFs (250 mg of fluoride liter-1) for 1 min. The susceptibility of biofilms was less than that of the planktonic form and was further decreased by growth in the presence of sucrose.

Transjugular intrahepatic portosystemic shunts and liver transplantation in patients with refractory hepatic hydrothorax

Hepatic hydrothorax is a relatively infrequent but potentially serious complication of cirrhosis resulting from the accumulation of ascitic fluid in the chest cavity. Medical management is initially directed at controlling ascites formation, but invasive therapeutic procedures may be required if symptoms persist. The aim of this study was to report on the long-term efficacy and safety of transjugular intrahepatic portosystemic shunt (TIPS) placement to reduce portal hypertension in 12 consecutive subjects with refractory hepatic hydrothorax. Most subjects had evidence of advanced cirrhosis of varying causes (Child-Pugh class A, 1; B, 5; C, 6). Mean subject age was 54 years, and subjects were followed up for a mean of 173 days (range, 7-926 days). The portosystemic pressure gradient after TIPS was reduced to <12 mmHg in all cases. Periprocedural morbidity was noted in 2 subjects, and 30-day survival after TIPS placement was 75%. Overall, 58% of subjects experienced either a complete or partial response following TIPS placement. Subject response did not correlate with age, baseline creatinine clearance, or Child-Pugh score. Cumulative subject survival was 42%, and 4 of the 5 long-term survivors required eventual liver transplantation. Subject age >65 years was associated with early mortality after TIPS placement, but this trend was not statistically significant. All 4 subjects undergoing liver transplantation required perioperative pleural fluid drainage, but only 1 subject has experienced recurrent effusion. We conclude that TIPS may be a safe and effective temporizing treatment for carefully selected patients with refractory hepatic hydrothorax. However, patient survival is limited after TIPS and is primarily determined by availability of liver transplantation.

Composition and susceptibility to chlorhexidine of multispecies biofilms of oral bacteria

Using a constant-depth film fermentor, we have grown a six-membered biofilm community with a bacterial composition similar to that found in supragingival dental plaque. Cryosectioning revealed the distribution of bacteria throughout the biofilm. Exposure to 0.2% chlorhexidine for up to 5 min had little effect on biofilm viability.

A study of the uptake of toluidine blue O by Porphyromonas gingivalis and the mechanism of lethal photosensitization

The purpose of the study was to determine the distribution of the photosensitizer toluidine blue O (TBO) within Porphyromonas gingivalis and the possible mechanism(s) involved in the lethal photosensitization of this organism. The distribution of TBO was determined by incubating P. gingivalis with tritiated TBO (3H-TBO) and fractionating the cells into outer membrane (OM), plasma membrane (PM), cytoplasmic proteins, other cytoplasmic constituents and DNA. The percentage of TBO in each of the fractions was found to be, 86.7, 5.4, 1.9, 5.7 and 0.3%, respectively. The involvement of cytotoxic species in the lethal photosensitization induced by light from a heliumneon (HeNe) laser and TBO was investigated by using deuterium oxide (D2O), which prolongs the lifetime of singlet oxygen, and the free radical and signlet oxygen scavenger L-tryptophan. There were 9.0 log10 and 2 log10 reductions in the presence of D2O and H2O (saline solutions), respectively, at a light dose of 0.44 J (energy density = 0.22 J/cm2), suggesting the involvement of singlet oxygen. Decreased kills were attained in the presence of increasing concentrations of L-tryptophan. The effect of lethal photosensitization on whole cell proteins was determined by measuring tryptophan fluorescence, which decreased by 30% using 4.3 J (energy density = 4.3 J/cm2) of light. Effects on the OM and PM proteins were determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. There was evidence of change in the molecular masses of several PM proteins and OM proteins compared to controls. There was evidence of damage to the DNA obtained from irradiated cells. Scanning electron microscopic studies showed that there was coaggregation of P. gingivalis cells when sensitized and then exposed to laser light. These results suggest that lethal photosensitization of P. gingivalis may involve changes in OM and/or PM proteins and DNA damage mediated by singlet oxygen.

Commensal communism and the oral cavity

The world we live in contains unimaginable numbers of bacteria, and these and other single-celled creatures represent the major diversity of life on our planet. During the last decade or so, the complexity and intimacy of the interactions which occur between bacteria and host eukaryotic cells during the process of infection have begun to emerge. The study of such interactions is the subject of the new discipline of cellular microbiology. This intimacy of bacteria/host interactions creates a major paradox. The average human being is 90% bacteria in terms of cell numbers. These bacteria constitute the commensal or normal microflora and populate the mucosal surfaces of the oral cavity, gastrointestinal tract, urogenital tract, and the surface of the skin. In bacterial infections, much of the pathology is due to the release of a range of bacterial components (e.g., modulins such as lipopolysaccharide, peptidoglycan, DNA, molecular chaperones), which induce the synthesis of the local hormone-like molecules known as pro-inflammatory cytokines. However, such components must also be constantly released by the vast numbers of bacteria constituting the normal microflora and, as a consequence, our mucosae should constantly be in a state of inflammation. This is patently not the case, and a hypothesis is forwarded to account for this "commensal paradox", namely, that our commensal bacteria and mucosal surfaces exist in a state of bio-communism, forming a unified "tissue" in which interactions between bacteria and epithelia are finely balanced to ensure bacterial survival and prevent the induction of damaging inflammation. Evidence is emerging that bacteria can produce a variety of proteins which can inhibit the synthesis/release of inflammatory cytokines. The authors predict that such proteins are simply one part of an extensive signaling system which occurs between bacteria and epithelial cells at mucosal surfaces such as those found in the oral cavity.

Measuring individual differences in change with multidimensional Rasch models

Item response models have been developed to explore change measurement, including those proposed by Fischer and his colleagues (e.g., Fischer & Pazer, 1991; Fischer & Ponocny, 1994), Andersen (1985) and Embretson (1991). In this article, we propose another multidimensional Rasch model, the multidimensional random coefficient multinomial logit (MRCML) model (Adams, Wilson, & Wang, 1997). All these models are briefly reviewed and compared. The MRCML can be applied to not only polytomous items but also investigation of variations in item difficulties. Based on variations in difficulties across occasions and items, five kinds of models are proposed. Some simulation studies were conducted to examine parameter recovery of the MRCML model under various testing situations. All the parameters were recovered very well. A real data set was analyzed to show applications of the MRCML to measuring individual differences in change.

The Escherichia coli chaperonin 60 (groEL) is a potent stimulator of osteoclast formation

Chaperonins (cpns) are intracellular oligomeric protein complexes that fold and refold proteins in a catalytic manner and aid in the transmembrane transport of cellular proteins. We reported previously that the lipopolysaccharide-free recombinant cpn60 of Escherichia coli (groEL) is able to stimulate the breakdown of murine calvarial bone in culture and showed that such resorption is potently inhibited by an inhibitor of the enzyme cyclo-oxygenase and to a lesser extent by inhibitors of 5-lipoxygenase. In this study, we have investigated the effects of groEL on the resorptive activity and formation of osteoclasts in culture. In low density, osteoclast-containing cultures from neonatal rats incubated for 24 or 96 h on dentine discs, groEL (1-1000 ng/ml) stimulated resorption pit formation up to 4-fold, but this effect was essentially dependent on cell number. Using 12-day cultures of mouse bone marrow to assess osteoclast recruitment, groEL (1-1000 ng/ml) caused a dramatic dose-dependent stimulation of the formation of tartrate-resistant acid phosphatase-positive multinucleated cells and the resorption of the dentine on which bone marrow cells were cultured. Osteoclast formation elicited by groEL was almost completely abolished by indomethacin, an inhibitor of cyclo-oxygenase, but was unaffected by inhibitors of 5-lipoxygenase, suggesting that prostaglandins but not leukotrienes may mediate the action of groEL on osteoclastogenesis. It is possible that bacterial cpn60s such as groEL may play a role in the osteolysis associated with bone infections. Whether endogenous ("self") chaperonins have a role in other bone loss disorders, such as osteoporosis, is an intriguing possibility.

Homogeneous Escherichia coli chaperonin 60 induces IL-1 beta and IL-6 gene expression in human monocytes by a mechanism independent of protein conformation

Escherichia coli chaperonin (cpn) 60 (groEL) is a protein-folding oligomer lacking tryptophan residues that copurifies with tryptophan-containing proteins and peptides. Cpn 60 is a major immunogen in infectious diseases, and evidence suggests that groEL and mycobacterial cpn 60s can induce cytokine synthesis, stimulate cytokine-dependent bone resorption, and up-regulate expression of vascular endothelial cell adhesion molecules. Whether such activities are due to the cpn 60 or to the copurifying/contaminating proteins/peptides has not been determined. Here we report a method for removing the protein contaminants of groEL and demonstrate that this, essentially homogeneous, groEL remains a potent inducer of human monocyte IL-1beta and IL-6 production. Contaminating peptides had no cytokine-inducing activity and did not synergize with purified groEL. The LPS inhibitor polymyxin B and the CD14-neutralizing Ab MY4 had no inhibitory action on groEL demonstrating that activity is not due to LPS contamination. Heating groEL had no effect on its capacity to stimulate human monocytes to secrete IL-6. Proteolysis of groEL with trypsin, sufficient to produce low molecular mass peptides, also had no inhibitory effect. Thus, we conclude that groEL is a potent inducer of monocyte proinflammatory cytokine production, which acts through the binding of nonconformational peptide domains that are conserved after proteolysis. These data suggest that if groEL was released from bacteria it could induce prolonged tissue pathology by virtue of its cytokine-inducing activity and its resistance to proteolytic inhibition of bioactivity.