Development and evaluation of a low erosive blackcurrant juice drink. 2. Comparison with a conventional blackcurrant juice drink and orange juice

OBJECTIVE

A previous study demonstrated that an experimental low pH blackcurrant juice drink with calcium was markedly less erosive to enamel both in situ and in vitro than orange juice. Further development of the experimental blackcurrant juice drink formula has occurred and the aims of the present studies were two fold. Firstly, to confirm the low erosivity of the modified formulation and secondly, to provide more comparative data with other acidic fruit drink products.

METHOD

The study was a single centre, single blind, randomised placebo controlled 4 cell crossover design involving 12 healthy volunteers. The test drinks were orange juice, water, experimental blackcurrant juice drink with calcium and a proprietary blackcurrant juice drink. Enamel samples were retained in situ at the mid palatal regions using intraoral appliances and exposed to 250 ml volumes of the drinks 4 times per day during 15 working days. Measurements of enamel loss were made by profilometry. The same method was modelled in vitro.

RESULTS

By day 15 the mean losses of enamel in situ for orange juice, water, experimental blackcurrant juice drink with calcium and blackcurrant juice drink were 1.70, 0.05, 0.44 and 2.75 microns respectively. At all bar one measurement, the loss of enamel was significantly greater for all fruit drinks compared to water. Losses caused by the blackcurrant juice drink with calcium were significantly less than the other two fruit drinks at all time points. Losses of enamel by day 15 in the study in vitro were 13.02, 0.00, 1.78 and 39.02 microns respectively. The blackcurrant juice drink with calcium was not significantly different from water at days 3 and 6, otherwise all pairwise comparisons for differences between the 4 drinks at each time period were significant.

CONCLUSIONS

The methodologies in situ and in vitro again appear to correlate in ranking the order of erosivity of drinks. The data particularly from the study in situ allude to the very low comparative erosivity of the further modified experimental blackcurrant juice drink with calcium and support the further development of such drinks for public consumption.

Development and evaluation of a low erosive blackcurrant juice drink. 3. Final drink and concentrate, formulae comparisons in situ and overview of the concept

OBJECTIVE

Two previous studies demonstrated that a blackcurrant juice drink with added calcium produced little erosion of enamel in vitro and in situ by comparison with other low pH fruit drinks. The primary aim of this study was to demonstrate that the final formulation drink and concentrate were of similar low erosivity. Secondary aims were to provide more data on the erosivity of other fruit drink concentrates and whether erosion was influenced by anterior and posterior palate siting of enamel specimens.

METHOD

The study was a single centre, single blind, randomised placebo controlled 5 cell crossover design involving 15 volunteers. The test drinks were blackcurrant juice/calcium concentrate, blackcurrant juice/calcium drink, proprietary apple & blackcurrant juice concentrate, proprietary orange drink concentrate and water. Four enamel samples were retained in situ, 2 anterior palate and 2 mid/posterior palate, on upper removable acrylic appliances. Drinks were 250 ml volumes consumed 4 times per day during 15 working days. Concentrates were diluted 50 ml in 200 ml water. Measurements of enamel loss were made on one anterior and one posterior sample on days 2, 5, 10 and 15 by profilometry.

RESULTS

One subject approached the 20 microns erosion limit by day 10 on the orange drink and was withdrawn from that cell. Differences in mean erosion between anterior and posterior sites were variable and small. By day 15 the mean losses of enamel averaged over anterior and posterior were blackcurrant/calcium concentrate 0.28 micron, blackcurrant/calcium drink 0.35 micron, apple & blackcurrant concentrate 2.04 microns. orange concentrate 8.29 microns and water 0.08 micron. Except at day 15 for the blackcurrant/calcium drink the erosion by the blackcurrant/calcium formulations was not significantly different from water at any time point. Erosion by the apple & blackcurrant and orange concentrate drinks was highly significantly greater than the blackcurrant/calcium drinks at all but the 2 day time point for the apple & blackcurrant concentrate drink compared to the blackcurrant/calcium drink.

CONCLUSIONS

All data thus far indicate that dependant on tooth site susceptibility and the specific drink, the consumption of standard low pH fruit drinks could result in 1 mm loss of enamel in periods ranging from as little as 2 years to 20 years. Similar erosion by the low pH blackcurrant drinks with added calcium would take in excess of 100 years.

Development and evaluation of a low erosive blackcurrant juice drink in vitro and in situ. 1. Comparison with orange juice

OBJECTIVE

The aim of this study was to determine whether an experimental blackcurrant juice drink with added calcium was less erosive to enamel both in vitro and in situ compared with a proprietary orange juice product.

METHODS

The study was a single centre, blind, randomised, placebo controlled three cell crossover design. An intra oral appliance capable of retaining one enamel sample in situ was constructed and worn by 12 volunteers. The drinks under test were orange juice, the experimental blackcurrant juice drink with calcium and water. Drinks were consumed as 250 ml volumes four times during the working day under supervision for 15 days. The same methodology was modelled in vitro. Measurements of enamel loss were made by profilometry.

RESULTS

Water, the experimental blackcurrant juice drink and orange juice produced 0.19, 0.41 and 2.54 microns loss of enamel respectively in situ and 0.0, 5.2 and 22.18 microns loss of enamel respectively in vitro. All differences between pairs of drinks in situ and in vitro were statistically significant.

CONCLUSIONS

Data using this model in situ were only available for orange juice and this was therefore considered as a positive control with water a placebo control. The results have demonstrated that the experimental blackcurrant juice drink with calcium is markedly less erosive than orange juice, particularly and importantly in situ. The experimental blackcurrant juice drink has limited erosive potential to teeth and deserves further comparative investigation and development as a low pH fruit drink for public consumption.

Characterization of endotoxin and cationic liposome interaction

The objective of this study was to characterize the interaction of endotoxin with cationic liposomes used in nonviral gene delivery. Endotoxin-cationic liposome interaction was characterized using fluorescent anisotropy, and the Limulus amebocyte lysate (LAL) assay. Cellular toxicity of endotoxin-cationic liposome complex was examined using a dimethylthiazol diphenyltetrazolium bromide (MTT) assay. The effect of endotoxin on the lipid-DNA complex and subsequent transfection into COS-1 cells was also examined. A competitive interaction occurred between fluoroscein isothiocyanate (FITC)-labeled endotoxin and plasmid DNA for binding dioleoyl glycero trimethylammonium propane:dioleoyl glycero phosphoethanolamine (DOTAP:DOPE) liposomes using fluorescent anisotropy techniques. The LAL assay demonstrated no change in endotoxin activity upon interaction with liposomes. No loss of COS cell viability was detected via the MTT assay during a 5-hr exposure to endotoxin. Transient transfection studies indicate that increasing levels of endotoxin lowered activity more than 90% at 50,000 endotoxin units (EU)/ml. Endotoxin and cationic liposomes interact mainly by an electrostatic attraction. Endotoxin contamination can potentially impact transfection efficiency via competition with plasmid DNA for cationic liposome binding by increasing transfection variability at 50 EU/ml, a concentration of endotoxin contamination that can occur with small-scale plasmid preparations used for in vitro cell transfections, but would not be expected with typical GLP or GMP preparations used in clinical studies.

3Beta [N-(N',N'-dimethylaminoethane)-carbamoyl] cholesterol (DC-Chol)-mediated gene delivery to primary rat neurons: characterization and mechanism

Cationic lipid formulations consisting of 3beta [N-(N', N'-dimethylaminoethane)-carbamoyl] cholesterol (DC-Chol) and the helper lipid dioleoylphosphatidylethanolamine (DOPE) (1.5: 1 molar ratio) were prepared by solvent evaporation and sized by high pressure extrusion. Liposomes made of 1:1 molar ratio 1 ,2-dioleoyl-3-trimethyl-ammonium-propane (DOTAP)/DOPE were used as controls in the study. The two formulations were characterized and evaluated for their efficiency in transfecting SKnSH (neuroblastoma) and primary rat neuronal cell lines. DC-Chol/DOPE liposomes were more efficient at transfecting both the SKnSH and the primary rat neuronal cells and also less toxic compared to the DOTAP/DOPE liposomes. The cellular-associated signal of rhodamine-labeled DC-Chol/DOPE liposomes into SKnSH and primary rat neuronal cells was higher than the rhodamine-labeled DOTAP/DOPE liposomes. These results demonstrate that DC-Chol/DOPE cationic liposomes provide an efficient vehicle for the delivery of plasmids into SKnSH and primary neuronal cells compared to DOTAP/DOPE liposomes. DC-Chol/DOPE liposomes may provide a good non-viral candidate for transfecting primary rat neuronal cells.

Examination of various biomarkers measuring genotoxic endpoints from Barcelona airport personnel

Three different biomarkers: sister-chromatid exchanges (SCE), micronuclei (MN), and the Comet assay, were used to evaluate different kinds of genetic damage in peripheral blood lymphocytes from 34 male workers at Barcelona airport, exposed to low levels of hydrocarbons and jet fuel derivatives. The control group consisted of 11 unexposed men. We also investigated the ras p21 protein levels in plasma, in order to evaluate whether the ras gene could serve as a suitable potential marker of carcinogenic pollution in occupationally exposed cohorts. SCE and MN analyses failed to detect any statistically significant increase in the airport workers when compared with the controls, and in fact, the frequency of binucleated cells with MN in the exposed group was significantly lower than that obtained in the control. However, slight but significant differences in the mean comet length and genetic damage index were observed between the exposed and control groups when using the Comet assay. There were no statistically significant differences between both groups in p21 plasma levels. Smoking was shown to affect significantly both SCE and high frequency cells (HFC) in the exposed group.

Minimum time interval adjustment for 4-3-1 immunization rates among two-year-old children

BACKGROUND

The purpose is to determine the administrative validity of the 4-3-1 immunization rates for DPT-OPV-MMR vaccines for 2-year-old children in a community health status assessment project by accounting for premature administration of specific vaccine doses according to ACIP recommended minimal timing intervals.

METHODS

A retrospective survey of immunization certificates was made on a random sample of 1,059 kindergarten enrollees in the county, including public, private, and parochial schools. The immunization rates by the crude 4-3-1 counting method were compared with the same method adjusted for minimal time interval vaccine dosing.

RESULTS

By the crude 4-3-1 counting method, 55.5% of the students had complete immunizations by their second birthdate, and 11.8% did not meet the minimum interval recommendations on at least one of 4-3-1 vaccine series. The adjustment for minimum time interval reduced the percent in compliance with the 4-3-1 counting method by age 2 in the community to 50.7%.

CONCLUSION

The premature timing of vaccine doses is a threat to the validity of the 4-3-1 counting method. The crude 4-3-1 method over-estimates the completed immunization rates for 2-year-olds in this community-based study by about 4.8%.

A spermine-deoxycholic acid conjugate based lipid as a transfecting agent

Deoxycholic acid-spermine conjugate (DAS), which is composed of natural components (deoxycholic acid and spermine), was incorporated in liposomes and evaluated for its interaction with plasmid DNA (pDNA) and in vitro transfection efficiency. Electromicrographs demonstrated that DAS-pDNA complexes are spherical, compact and electronically dense compared to the toroidal shapes formed by the monovalent lipid 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) and pDNA. In comparison to the singly charged, non-cholesterol based lipid (DOTAP), the multivalent lipid DAS had similar transfection efficiency in two cell lines. The monovalent sterol, deoxycholic acid propyldiamine conjugate (DAP) was not effective as a transfecting agent. This suggests that multivalent facial amphiphiles such as DAS may serve as excellent candidates for non-viral gene transfer and warrant further study.

One year prospective open study of the effect of high dose inhaled steroids, fluticasone propionate, and budesonide on bone markers and bone mineral density

BACKGROUND

Inhaled corticosteroids are recognised as the most effective agents in the treatment of asthma. However, concerns have been expressed about the effects of high doses of inhaled corticosteroids on safety in relation to bone resorption and formation. This study measures the effects of two inhaled corticosteroids on bone markers and bone mineral density (BMD) over one year.

METHODS

A one year randomised, prospective, open parallel study comparing inhaled fluticasone propionate (FP), 500 micrograms twice daily in 30 patients, and budesonide (BUD), 800 micrograms twice daily in 29 patients, delivered by metered dose inhaler and large volume spacers was performed in adults with moderate to severe asthma. Biochemical markers of bone turnover (osteocalcin, procollagen type 1 C-terminal propeptide (PICP), immunoreactive free deoxypyridinoline (iFDpd), N-terminal crosslinked telopeptides of type I collagen (NTx)), BMD at the spine and femoral neck, and serum cortisol concentrations were measured at baseline and 12 months later.

RESULTS

There were no significant differences between the inhaled steroids on bone markers of bone resorption and formation or bone mineral density. Bone mineral density of the spine increased slightly in both groups over the 12 month period. Serum osteocalcin levels increased from baseline in both treatment groups (FP 16.9%, p = 0.02; BUD 14.3%, p = 0.04). PICP did not differ significantly from baseline. Both markers of bone resorption (iFDpd, NTx) varied considerably with no significant changes after one year. There was a significant correlation in percentage change from baseline between BMD of the spine and osteocalcin at 12 months (r = 0.4, p = 0.017). Mean serum cortisol levels remained within the normal range in both groups following treatment.

CONCLUSION

There was no evidence of a decrease in BMD during 12 months of treatment with high doses of either FP or BUD. The change in spine BMD correlated with the increase in osteocalcin. Studies extending over several years are needed to establish whether these findings persist.

Foam fractionation as a method to separate endotoxin from recombinant biotechnology products

The objective of this study was to evaluate the feasibility of foam fractionation for removal of contaminating endotoxin from biotechnology products, including plasmid DNA and recombinant proteins. After foam fractionation, alone and with bovine serum albumin and Triton X-100 as pro-foaming agents, FITC-labeled endotoxin remains in the bulk solution. These studies suggest that foam fractionation will be ineffective in the purification of plasmid DNA solutions, which are not surface-active and remain in the bulk solution with endotoxin. These data support the use of foam fractionation as an effective method for separating surface-active recombinant proteins, which will concentrate in the foam, away from endotoxin.

Membrane fusion and rupture in liposomes: effect of biodegradable pH-sensitive surfactants

Biodegradable pH-sensitive surfactants (BPS) are a unique family of easily metabolized compounds that demonstrate pH-dependent surface activity. These agents, in combination with other delivery systems, have demonstrated effects in enhancing transnucleic acid activity. The increased activity has been hypothesized to occur from a release of endosomal contents. Simply, the BPS delivery system containing nucleic acids enters the cell through an endocytotoic process. It encounters an acidic pH and becomes surface active leading to defects in the endosomal membrane. In the current study, an in vitro model membrane was used to better understand the liposome defect mechanisms that BPS elicit. Using this system, it is shown that BPS can induce both liposome fusion and rupture depending upon the pH and mole ratio of BPS to membrane lipids. Futhermore, liposome fusion induced by BPS was dependent on the total numbers of liposome particles while rupture was independent of interacting liposome particles. The generated data indicate that BPS agents act differently from other typical surface active agents and fuosgenic compounds. Instead of facilitating membrane fusion through the hexagonal II phase, BPS appeared to contribute and participate in the membrane fusion at different stages.

Cellular delivery is a major obstacle for oligodeoxynucleotide inhibition of telomerase activity

BACKGROUND

The ribonucleoprotein enzyme, telomerase, uses RNA as a template to add a hexanucleotide to ends of replicating chromosomes resulting in stabilization of the telomere. Telomerase activity is observed in over 85% of human primary malignancies, suggesting that it may be a new marker of cancer and raising the possibility that antitelomerase therapy may provide a new generation of cancer therapeutics.

MATERIALS AND METHODS

In this study, we evaluated phosphorothioate (PS) oligonucleotide (ODNs) inhibition of telomerase activity in intact cells and cell lysates in the SKnSH (neuroblastoma) cell line.

RESULTS

The ODNs were effective at inhibiting telomerase activity in cell lysate but demonstrated little effect when intact cells were used.

CONCLUSIONS

This study demonstrates that cellular transport may be a limiting factor with therapeutic approaches using antisense ODNs.

Computed tomography findings in an inflamed meckel diverticulum

Meckel diverticulum, the commonest congenital abnormality of the gastrointestinal tract, may be difficult to diagnose. Appearances on CT are often non-specific unless there is connection to the umbilicus or a complication has occurred. We report a case of an inflamed Meckel diverticulum seen on CT.

Ras p21 protein levels in human plasma from patients with chronic obstructive pulmonary disease (COPD) compared with lung cancer patients and healthy controls

To explore the value of an increase in ras p21 proteins in plasma as a biomarker for the carcinogenic process or for the general disease state, we have directly analysed for ras p21 proteins, plasma samples from Polish human patients with chronic obstructive pulmonary disease (COPD). They were compared with appropriate controls and also with the Polish lung cancer patients previously examined before treatment [D. Anderson, J.A. Hughes, A. Cebulska-Wasilewska, E. Nizankowska, B. Graca, Ras oncoproteins in human plasma from lung cancer patients and healthy controls, Mutat. Res. 349 (1996) 121-126]. An elevated level of ras p21 proteins was considered to be greater than 2 standard deviations (SD) above the mean negative control values. Nine out of 20 COPD patients (mean age = 65.9 years) had increased ras p21 protein levels when compared with 20 age-matched (mean age = 62.4 years) controls of the present study with a mean + 2 SD of 0.70. Eighteen out of 40 lung cancer patients (mean age = 60.1 years) had increased ras p21 protein levels compared with their concurrent controls (mean age = 40.2 years) with a mean + 2 SD of 2.53. However when compared with the age-matched controls of this present study, there were 35 out of 40 (87.5%) with increased levels. When the COPD patients and lung cancer patients were compared with 101 historical controls (age range 25-76 years, of those whose age was recorded) from unexposed healthy populations from Poland, Estonia and Spain with a mean + 2 SD of 1.83, then 4 out of 20 (20%) COPD patients and 30 out of 40 (75%) lung cancer patients had increased levels. Whether using concurrent controls, age-matched controls or historical controls, the data would suggest that an increase in ras p21 protein levels in plasma from lung cancer patients could be a possible prognostic marker or biomarker for lung cancer. COPD patients when compared with historical controls or age-matched controls had lower ras p21 protein values than cancer patients. Their ras p21 protein values might also be a biomarker for cancer. It is possible that some of these COPD patients were in the process of developing cancer or perhaps would die from COPD before cancer develops. It cannot be ruled out that the increases could be a biomarker of exposure since many of the lung cancer patients and most of the COPD patients were smokers.

Analysis of host cells associated with the Spv-mediated increased intracellular growth rate of Salmonella typhimurium in mice

The 90-kb virulence plasmid of Salmonella typhimurium encodes five spv genes which increase the growth rate of the bacteria within host cells within the first week of systemic infection of mice (P. A. Gulig and T. J. Doyle, Infect. Immun. 61:504-511, 1993). The presently described study was aimed at identifying the host cells associated with Spv-mediated virulence by manipulating the mouse host and the salmonellae. To test the effects of T cells and B cells on the Spv phenotype, salmonellae were orally inoculated into nude and SCID BALB/c mice. Relative to normal BALB/c mice, nude and SCID BALB/c mice were unaffected for splenic infection with either the Spv+ or Spv- S. typhimurium strains at 5 days postinoculation. When mice were pretreated with cyclophosphamide to induce granulocytopenia, there was a variable increase in total salmonella infection, but the relative splenic CFU of Spv+ versus Spv- S. typhimurium was not changed after oral inoculation. In contrast, depletion of macrophages from mice by treatment with cyclophosphamide plus liposomes containing dichloromethylene diphosphate resulted in equivalent virulence of Spv+ and Spv- salmonellae. To examine if the spv genes affected the growth of salmonellae in nonphagocytic cells, an invA::aphT mutation was transduced into Spv+ and Spv- S. typhimurium strains. InvA- Spv+ salmonellae were not significantly affected for splenic infection after subcutaneous inoculation compared with the wild-type strain, and InvA- Spv- salmonellae were only slightly attenuated relative to InvA+ Spv- salmonellae. Invasion-defective salmonellae still exhibited the Spv phenotype. Therefore, infection of nonphagocytes is not involved with the Spv virulence function. Taken together, these data demonstrate that macrophages are essential for suppressing the infection by Spv- S. typhimurium, by serving as the primary host cell for Spv-mediated intracellular replication and possibly by inhibiting the replication of salmonellae within other macrophages.

Interaction of oligodeoxynucleotides with mycobacteria: implications for new therapeutic strategies

The use of synthetic oligonucleotides (ONs) to systematically address new pharmacologic targets in mycobacteria would enhance the introduction of new molecular targets for drug intervention. Oligonucleotides' mechanism of action allows researchers to pursue the importance of particular proteins without the requirement of having purified samples. For this approach to be effective, mycobacteria must be able to transport ONs to their cytoplasm, and if this is not the case, the agents must be otherwise delivered. In this report, we characterize the ability of phosphorothioate (PS) and phosphorodiester (PD) ONs to interact with both Mycobacterium smegmatis and Mycobacterium tuberculosis. In addition, the use of delivery enhancer compounds, ethambutol and PAMAM dendrimer, was evaluated on the ON-mycobacteria interaction. ON interaction was demonstrated to be concentration-dependent, suggesting a possibly active component of the oligonucleotide and bacteria interaction. ON interaction could be increased by the coincubation of the bacteria with the delivery adjuvants. Treatment with ethambutol or dendrimers (fourth generation) was demonstrated to increase ON interaction with both species of mycobacteria although not to the same extent. The results of these preliminary experiments indicate that through use of the proper delivery adjuvant, ON interactions with mycobacteria can be increased. These findings may have implications for probing future antimycobacterial therapeutic targets.

Nuclear localization signal peptides enhance cationic liposome-mediated gene therapy

The use of genes as therapeutic drugs will likely involve non-viral delivery systems. While traditionally less effective for gene expression, the advantages of a non-viral delivery system include ease of production, lower toxicity, and no risk of infection. However, most non-viral systems do not incorporate a mechanism for gene transport into the nucleus. Nuclear localization signal peptides can combine the increased expression of viral delivery systems with the safety and ease of preparation of non-viral delivery systems. A novel non-viral delivery vehicle consisting of a conglomerate of a synthetic nuclear localization signal peptide derived from the SV40 virus, a luciferase encoding PGL3 plasmid, and a cationic lipid DOTAP:DOPE (1:1 w/w) liposome was transfected into SKnSH mammalian neuroblastoma cells. A three-fold increase in luciferase expression was seen with the delivery system containing a NLS peptide over cationic liposome controls. Examination of the factors that limit the rate of transgene expression can potentially lead to the discovery of new ways to improve the efficiency and efficacy of nonviral methods of gene therapy.

A method to measure clinical erosion: the effect of orange juice consumption on erosion of enamel

OBJECTIVE

Acidic soft drinks are frequently implicated in dental erosion, but there are limited supporting data. Research is problematic due to the insidious nature of erosion and accuracy in assessing tissue loss. The aim of this study was to develop and validate, using a negative control, a model to accurately measure erosion in situ due to a single aetiological agent over a relatively short time period.

METHODS

An intra-oral appliance capable of retaining an enamel sample was designed in order to assess the effect of orange juice consumption on enamel. The study was a single centre, randomized, placebo controlled, blind, crossover design.

RESULTS

Ten subjects, each consuming 11 of orange juice per day for 15 days, showed significantly more erosion on the enamel specimens than the same subjects consuming 11 of water per day over the same time period, measurements undertaken with surfometry. The same investigation was performed in vitro. Again, orange juice was significantly more erosive; indeed, it was in the order of 10 times that produced in situ. Surface microhardness testing in situ and in vitro demonstrated statistically significant differences between exposed and unexposed areas after orange juice treatment.

CONCLUSIONS

Changes produced by water either in situ or in vitro were always well within the baseline measurement parameters (+/- 0.3 micron) set down for the method and hence validated the clinical model in terms of reproducibility and accuracy in measurement. It is concluded that this method has confirmed the erosive potential of orange juice in situ. The method could have many applications to study dental erosion under highly controlled conditions and over realistic time periods.

In vitro myotoxicity of selected cationic macromolecules used in non-viral gene delivery

PURPOSE

Cationic lipid/DNA complexes have been proposed as a method of in vivo gene delivery via intravenous or intramuscular injection. A concern with using these polycationic molecules is whether they are associated with tissue toxicity at the injection site. Therefore, the objective of these studies was to investigate the myotoxic potential of selected non-viral gene delivery macromolecules (e.g., cationic lipids and polymers) with and without plasmid DNA (pDNA) in vitro.

METHODS

Myotoxicity was assessed by the cumulative release of creatine kinase (CK) over 90 minutes from the isolated rodent extensor digitorum longus muscle into a carbogenated balanced salt solution (BBS, pH 7.4, 37 degrees C) following a 15 microL injection of the test formulation. Phenytoin (Dilantin) and normal saline served as positive and negative controls, respectively.

RESULTS

The myotoxicity of plasmid DNA (pDNA, approximately 5000bp, 1 mg/ml) was not statistically different from normal saline. However, the myotoxicity of Dilantin was 16-times higher than either normal saline or pDNA (p < 0.05). Cationic liposomes were found to be less myotoxic than polylysine and PAMAM dendrimers. Polylysine's myotoxicity was found to be dependent upon concentration and molecular weight. The myotoxicity of formulations of cationic liposomes(s), lower molecular weight polylysine (25,000) and higher concentration of PAMAM dendrimers with pDNA were found to be statistically less significant than those formulations without pDNA.

CONCLUSIONS

The cationic liposomes were less myotoxic compared to the dendrimers and polylysine. Myotoxicity was dependent upon the type of cationic lipid macromolecule, concentration, molecular weight and the presence of pDNA. A possible explanation for this reduced tissue damage in cationic lipids complexed with pDNA is that the formation of complex reduces the overall positive charge of the injectable system resulting in less damage.

A comparison of air, CO2 and an air/CO2 mixture as insufflation agents for double contrast barium enema

Using CO2 for DCBE is recommended as it may decrease pain afterwards but recent studies suggest it produces inferior distension. This prospective double blind study was designed to evaluate the use of an air/CO2 mixture. We randomised 105 patients to receive air, CO2 or a 50/50 mixture as the insufflation agent in DCBE. Gases were administered from prefilled bags. Those requiring additional insufflations before over couch films were recorded. Post procedure symptoms were evaluated by questionnaire. Distension and mucosal coating were assessed independently. There was no difference in mucosal coating. Those given CO2 had significantly less immediate and delayed pain compared to air and less delayed pain compared to the 50/50 mixture. Distension with air was graded better than with the other two agents but the difference did not reach statistical significance. However 50 % of patients receiving CO2 and 40 % of those receiving the mixture required additional insufflation before over couch films as distension was considered suboptimal, compared to 17 % of those given air, which was statistically significant. Our results indicate that using CO2 causes less pain than using air or the mixture although top up insufflations are often required to maintain adequate quality distension.

Genetic effects of 1,3-butadiene on the mouse testis

1,3-Butadiene is a known male mouse germ-cell mutagen, to which humans may either be occupationally or environmentally exposed. Prolonged exposure to moderate or high doses in male mice can cause dominant lethal mutations and one report has indicated that 10 week inhalation administration of low doses can result in the production of malformed foetuses. The present study had dual purposes: (a) to attempt to clarify the suspected ability of sub-chronic (6 h/day, 5 days/wk, 10 weeks) low-dose exposure to 1,3-butadiene to induce heritable mutations in mouse male germ cells: (b) investigation of the relationships between testicular DNA damage, testicular DNA repair and foetal outcome. Adult male mice were exposed to low or moderate doses of 1,3-butadiene by inhalation sub-chronically or for a single 6 h period and either used for mating (sub-chronic exposure only) or for studies of DNA damage and repair. Litter size, dominant lethality and numbers of abnormal foetuses were determined the day preceding the normal day of parturition. Testicular DNA damage and repair were assessed by the Comet assay (for DNA damage) and the unscheduled DNA synthesis assay (for DNA repair). 1,3-Butadiene caused a statistically significant increase in dominant lethality at 125 ppm but not 12.5 ppm. No significant increase in DNA repair was found with either dose level or exposure period while only 6 h exposure to 125 ppm caused a small but significant increase in DNA damage as detected by the Comet assay. These effects demonstrate the reproductive genotoxicity of (125 ppm) 1,3-butadiene but do not confirm its ability to cause abnormalities in the offspring via the sperm. It is suggested that the relationship between 1,3-butadiene-induced DNA damage, DNA repair and heritable defects in the offspring may depend on the pattern of metabolites produced.

A comparison of male-mediated effects in rats and mice exposed to 1,3-butadiene

There is current concern that exposure of men to certain agents such as radiation and smoking can adversely affect their offspring in terms of cancer outcome. Studies in laboratory animals after radiation have supported such an association, and other studies after male exposure to radiation and various chemicals have also resulted in congenital malformations. The present study was undertaken to examine congenital malformations in offspring from males exposed to 1,3-butadiene over a lower dose range than that in an earlier mouse study and to determine if there was a species difference in sensitivity between rats and mice. An earlier extended dominant lethal study of male CD-1 mice exposed by inhalation to 12.5 ppm and 1250 ppm of 1,3-butadiene for 6 h/day, 5 days/wk, for 10 weeks produced an increase in F1 abnormalities and late deaths at 12.5 ppm and in early deaths at 1250 ppm. The present study examined the same reproductive effects after exposure of male CD-1 mice for 6 h/day, 5 days/wk, for 4 weeks to 12.5, 65 and 130 ppm of 1,3-butadiene. There was no increase in early deaths at 12.5 ppm as in the earlier study but there were statistically significant increases in early deaths at 65 and 130 ppm study and these were not dose-related. There was a non-significant increase in F1 gross abnormalities at 130 ppm and no increase in late deaths. The present study also examined male Sprague-Dawley rats after exposure to 65,400 and 1250 ppm for 6 h/day, 5 days/wk, for 10 weeks. There were no effects on early deaths, late deaths, or congenital malformations in the rat study. There was a reduction in implants at 65 ppm but this was not considered to be biologically/genetically significant as there was no corresponding increase in early deaths and the response was not dose-related. The differences observed between the rat and mouse studies would confirm the greater sensitivity to 1,3-butadiene of the mouse by comparison with the rat as reported by other workers for other parameters.

Introduction of a disulfide bond into a cationic lipid enhances transgene expression of plasmid DNA

We have introduced a convenient method of synthesis for disulfide-containing cationic lipids. The lipid, 1,2-dioleoyl-sn-glycero-3-succinyl-2-hydroxyethyl disulfide ornithine conjugate (DOGSDSO), was synthesized and used to prepare liposomes in combination with DOPE. The rationale behind the selection of the disulfide bond was to produce a lipid which could be selectively destabilized within the cytosol of the cell. The disulfide bond of DOGSDSO was shown to be cleaved by reductive media leading to destabilization of the liposome/DNA complex, thus increasing the release of pDNA compared to a non-disulfide-containing analog. The introduction of a disulfide bond increases the transfection activity using model animal cell lines. The transfection activity and toxicity of DOTAP, DOGSDSO and its analog in three cell lines were compared. The amount of transgene (e.g. luciferase) produced with the use of DOGSDSO/DOPE was greater than that of DOTAP/DOPE and up to 50 times more than that of its non-disulfide analog. The results indicate disulfide-containing cationic liposomes may act as excellent vectors for gene transfection.

Examination of ras (P21) proteins in plasma from workers exposed to benzene emissions from petrochemical plants and healthy controls

Exposure of workers to benzene and polyaromatic hydrocarbons has been documented to be at relatively high levels in the production of benzene and in the coking process at a petrochemical plant in the oil shale area in Estonia. Altogether 97 plasma samples from workers and 40 from unexposed matched referents from two samplings in different seasons were analyzed for the presence of ras (P21) proteins; of the workers 50 were exposed to benzene in the benzene production plant and 47 to polyaromatic hydrocarbons and benzene in a cokery. Proteins were separated by gel electrophoresis, transferred to a nitrocellulose membrane by Western blotting and detected by chemiluminescence, using a monoclonal antibody as the primary antibody. There were no statistically significant differences between the exposed and the referent groups. The results are thus in keeping with the lack of exposure related cytogenetic effects for this same workforce.