The effect of explicit counterion binding on the transference number of polyelectrolyte solutions.

Polyelectrolyte solutions have been proposed as a method to improve the efficiency of lithium-ion batteries by increasing the cation transference number because the polymer self-diffusion coefficient is much lower than that of the counterion. However, this is not necessarily true for the polymer mobility. In some cases, negative transference numbers have been reported, which implies that the lithium ions are transporting to the same electrode as the anion, behavior that is often attributed to a binding of counterions to the polyion. We use a simple model where we bind some counterions to the polymer via harmonic springs to investigate this phenomenon. We find that both the number of bound counterions and the strength of their binding alter the transference number, and, in some cases, the transference number is negative. We also investigate how the transference number depends on the Manning parameter, the ratio of the Bjerrum length to charge separation along the chain. By altering the Manning parameter, the transference number can almost be doubled, which suggests that charge spacing could be a way to increase the transference number of polyelectrolyte solutions.

School age outcome of hospitalisation with respiratory syncytial virus infection of prematurely born infants.

BACKGROUND: Hospitalisation due to respiratory syncytial virus (RSV) infection in the first 2 years after birth has been associated with increased healthcare utilisation and associated costs up to 5 years of age in children born prematurely at less than 32 weeks of gestation who developed bronchopulmonary dysplasia (BPD). A study was undertaken to determine whether hospitalisation due to RSV infection in the first 2 years was associated with increased morbidity and lung function abnormalities in such children at school age, and if any effects were influenced by age. METHODS: Healthcare utilisation and cost of care in years 5-7 were reviewed in 147 children and changes in healthcare utilisation between 0 and 8 years were assessed also using results from two previous studies. At age 8-10 years, 77 children had their lung function assessed and bronchial hyper-responsiveness determined. RESULTS: Children hospitalised with RSV infection (n = 25) in the first 2 years had a greater cost of care related to outpatient attendance than those with a non-respiratory or no admission (n = 72) when aged 5-7 years (p = 0.008). At 8-10 years of age, children hospitalised with RSV infection (n = 14) had lower forced expiratory volume in 0.75 s (FEV(0.75)) (p = 0.015), FEV(0.75)/forced vital capacity (p = 0.027) and flows at 50% (p = 0.034) and 75% (p = 0.006) of vital capacity than children hospitalised for non-RSV causes (n = 63). Healthcare utilisation decreased with increasing age regardless of RSV hospitalisation status. CONCLUSIONS: In prematurely born children who had BPD, hospitalisation due to RSV infection in the first 2 years is associated with reduced airway calibre at school age.

Use of plants for toxicity assessment of estuarine ecosystems.

Estuarine ecosystems are being rapidly degraded by environmental toxicants from municipal and industrial wastes, agricultural runoff, recreational boating, shipping, and coastal development, ranking them as the most anthropogenically degraded habitat types on earth. Toxicity tests are used to establish links between adverse ecological effects and the toxicity of environmental chemicals. However, most toxicity tests used for regulating the release of chemicals into the environment have used animals as test species, with the erroneous assumption that toxicant levels protective of fish or invertebrates are also protective of plants. Most plant toxicity tests have used terrestrial crop plants, whereas the few aquatic test species used have been primarily freshwater algae. Even though estuarine and marine vascular plants are highly vulnerable to environmental chemicals, phytotoxicity studies using native coastal plants have been limited, and no such studies are required for testing by regulating agencies. The relevance of toxicity tests of estuarine sediments and of wastes entering the estuary should depend on the use of estuarine and marine plant species. This review summarizes toxicity testing of marine plants used in biomonitoring, phytotoxicity, biotransformations of toxicants, bioaccumulation, and phytoremediation. Challenges to marine plant testing are discussed and include developing standard test protocols, identifying species with minimal salinity and toxicant interaction, defining and choosing a suitable sediment for sediment-bound toxicant testing, selecting endpoints with low variability, producing viable seeds, and culturing test plants. Progress in acquiring a suitable database is being made, but at a rate that is inadequate to create the sound, scientific foundation needed for safeguarding our estuarine ecosystems in the near future.

Comparison of once- and twice-daily clarithromycin in the treatment of adults with severe acute lower respiratory tract infections.

BACKGROUND: Although the modified-release (MR) formulation of clarithromycin has demonstrated bioequivalence to the immediate-release (IR) formulation and thus can be prescribed for lower respiratory tract infections (LRTIs), a MEDLINE search from 1995 through 1998 and information on file with the manufacturer indicate that no data are available on the effectiveness of this new formulation in the treatment of severe LRTIs such as community-acquired pneumonia. OBJECTIVE: This study was designed to compare clinical success rates (percentage of patients with clinical cure or improvement) with once- and twice-daily regimens of clarithromycin in the treatment of patients with severe, acute LRTIs requiring oral antibiotic therapy. METHODS: In this multicenter, investigator-blinded, randomized, parallel-group study, adult patients with clinical evidence suggesting severe, acute LRTI were recruited from 22 general practices in the United Kingdom. Patients were randomly allocated to receive either clarithromycin 500 mg BID (IR tablets) or clarithromycin 1 g OD (two 500-mg MR tablets) for 7 to 14 days. The outcome measures were resolution of or improvement in clinical signs and symptoms (including resolution of cough), unscheduled visits for the same symptom, days to resumption of normal activities, and improvements in quality of life (assessed using the EQ-5D version of the EuroQoL questionnaire). Clinical, microbiologic, and serologic assessments were performed before, during, and after treatment. Efficacy and safety data were analyzed on an intent-to-treat basis. RESULTS: One hundred sixty men (n = 83) and women (n = 77) between the ages of 19 and 88 years took part in the study, 78 receiving clarithromycin 500 mg BID and 82 receiving clarithromycin 1 g OD. At 4 weeks after the start of treatment, the high clinical success rates were comparable between groups: 84.6% with clarithromycin 500 mg BID and 90.2% with clarithromycin 1 g OD. No significant differences in outcome measures were noted between the 2 regimens. Both treatments were well tolerated, with taste disturbance being the most commonly reported adverse event (10.6% vs 6.1% with clarithromycin 500 mg BID and 1 g OD, respectively). CONCLUSIONS: The 2 clarithromycin regimens were equally efficacious and well tolerated in the treatment of severe, acute LRTIs. However, caution should be exercised in applying these results to the general population, because the study excluded certain categories of patients who would normally be treated. In addition, the small sample size may have obscured clinically significant differences between the 2 regimens.

Life-cycle toxicity of bis(tributyltin) oxide to the sheepshead minnow (Cyprinodon variegatus).

The effects of tributyltin (TBT) to the life cycle of the estuarine fish Cyprinodon variegatus were examined in a 180-day flow-through exposure. The study was initiated with embryos less than 24 h postfertilization and monitored through hatch, maturation, growth, and reproduction under continuous exposure to mean measured TBT concentrations of 5.4, 3.2, 1.3, 0.66, and 0.41 microg TBT/L. Progeny isolated at the onset of reproduction by the parental generation (F0) were monitored for survival as embryos, survival as fry/juveniles, and growth 30 days postisolation. TBT, at a concentration of 5.4 microg/L, significantly reduced embryo survival of the F0 generation sheepshead minnows. By day 145 of the exposure, significant effects to the survival of this generation increased and included all test concentrations >/=0.66 microg/L. Survival of 0.66 microg/L was reduced 59% relative to control survival by termination of the F0 generation. Growth of F0 generation organisms as measured by standard length was significantly reduced only on day 90 at 3.2 microg/L, however no significant reductions of wet or dry weight related to treatment concentration were detected. Due to complete mortality of organisms exposed to 5.4 microg/L by study day 7, effects to fecundity and progeny were monitored at measured concentrations of 3.2, 1.3, 0.66, and 0.41 microg TBT/L. Fecundity, as measured by the production of viable eggs produced per female per day, was unaffected by any of the test treatments. All F1 generation embryos isolated from treatment chambers into 3.2 microg/L died. Survival, standard length, wet and dry weight of the F1 generation at the remaining treatment concentrations were unaffected. The results of this study indicate that exposure to TBT reduced survival of the F0 generation sheepshead minnow and establishes the lowest observed effect concentration (LOEC) as 0.66 microg TBT/L, and the no observed effect concentration (NOEC) as 0.41 microg TBT/L for this species.http://link.springer-ny. com/link/service/journals/00244/bibs/37n2p258.html

The effect of monovalent cations on the self-association of cytidylyl-(3-5')-guanosine and guanylyl-(3'5')-cytidine in aqueous solution.

The hydrogen-bonding, base stacking, and formation of extended aggregates has been investigated for salts of guanylyl-3'-5')-cytidine, GpC, and cytidylyl-(3'-5')- guanosine, CpG, in which the cation was Na+, K+, or tetramethylammonium (TMA+). Variable temperature studies were done at 2-70 degrees C on aqueous solutions at pD4 and 8 using 1H NMR and FTIR. At low temperatures it has been found that at pD 8 both GpC and CpG form Watson-Crick dimers which stack upon each other to form larger species. A slight cation effect is observed below 35 degrees C which has the order: TMA+ > Na+ > K+. This order suggests that the cations are interacting with the phosphate and interactions with the bases are unlikely. The 1H NMR spectrum for TMACpG at pD 4 has been assigned and exhibits chemical shift differences from those at pD 8 which are consistent with protonation of the N3 of the cytidine residue. Based on NMR line broadening, CpG at pD 4 has a greater degree of self-association at low temperature than it or GpC have at pD 8. A different type of hydrogen bonding and self-association occur in CpG at pD 4 compared to pD 8, but the structures are uncertain. Due to hemi-protonation of the cytidine N3, parallel G-G/C-C+ base paired dimers or G-tetrads may be forming.

Prevention of atmospheric contamination during isoflurane sedation.

With a view to minimising staff exposure to exhaled isoflurane which had been used for sedation, we assessed the efficacy of either activated charcoal adsorption or active or passive mechanical scavenging systems in intensive care units (ICUs). Personal monitoring revealed minimal exposure of staff to the sedating agent. Infra-red analyses of ambient air rarely showed isoflurane levels greater than 26 ppm, with mean concentrations of around 1 ppm. Small spillages during vaporiser filling were of no polluting significance. The activated charcoal adsorbers functioned highly efficiently for at least 12-hour periods. With simple scavenging techniques, atmospheric isoflurane contamination during sedation with the agent remains well within an acceptable range and is unlikely to pose a health risk to nursing and medical staff.

Stability of a commercially prepared fish oil (omega-3 fatty acid) laboratory rodent diet.

There is evidence that highly unsaturated omega-3 fatty acids present in fish oils can provide a cancer-protective effect; however, when added to laboratory rodent formulations, these fatty acids are subject to rapid and/or extensive oxidation and other chemical changes by exposure to air, light, or heat during processing of pellets or when stored for various lengths of time. An animal diet with 16% refined fish oil and 4% corn oil was commercially prepared with antioxidants (butylated hydroxytoluene and butylated hydroxyquinone in addition to alpha-tocopherol) present, and precautions were taken to prevent oxidation at all stages of production and handling. Fatty acid composition of dried powdered diet as well as freshly processed dried pellets was analyzed from four lots at the beginning and end of a 45-day feeding period. Additionally, fatty acid analyses were carried out on pellets dried by both vacuum and air techniques, and pellets were left exposed to air at room temperature for 96 hours. No statistical difference in overall fatty acid composition was observed among lots due to pelletization or drying procedures. Moreover, 4 days of exposure of pellets to air at ambient temperatures and 45 days of freezer storage had no significant effect on their fatty acid composition. It would appear that rodent diets containing omega-3 fatty acids can be reliably prepared commercially and safely substituted for diets prepared manually and in bulk on a weekly basis.

A multicentre, hospital study of the efficacy and safety of terazosin and its effects on the plasma cholesterol levels of patients with essential hypertension.

The safety, efficacy and the effect on the plasma total cholesterol of once-daily terazosin hydrochloride administered either as monotherapy or in combination with other antihypertensive therapy were evaluated in patients with mild-moderate uncontrolled essential hypertension in this U.K., open, multicentre hospital, 3-month study. Patients initially received 1 mg of terazosin as monotherapy or in addition to their current antihypertensive therapy followed by dose titration, if necessary, to a maximum of 10 mg over the first 6 weeks depending upon blood pressure control. Patients then continued treatment for a further 6 weeks on their optimum dosage. There were highly significant mean reductions in systolic and diastolic blood pressures at the end of 12 weeks for 439 patients of 18.5 and 14.0 mmHg (P less than 0.001), respectively, and were similar to the reductions shown when subgrouping the patients into either those 197 patients who were treated with terazosin as monotherapy (17.6/13.7 mmHg, P less than 0.001) or those 242 patients treated with terazosin in combination with other antihypertensive agents (19.3/14.2 mmHg, P less than 0.001). In addition, in a sub-group of 132 patients who had their mean total cholesterol measured at the end of 12 weeks' treatment, there was a significant reduction of -0.4 mmol/l (P less than 0.01). A similar significant mean reduction for total cholesterol was also shown when this subgroup was divided into those 50 patients who were treated with terazosin as monotherapy (-0.56 mmol/l, P less than 0.01), but not for those 82 patients treated with terazosin in combination with other antihypertensive agents (-0.3 mmol/l, P greater than 0.05 less than 0.1). No serious toxicity or safety problems were observed. Once daily administration of terazosin, either as monotherapy or in combination with other antihypertensive agents, proved to be safe and effective in reducing the blood pressure of patients with uncontrolled mild-moderate essential hypertension and favourably reduced the total plasma cholesterol level.

A multicentre, hospital study of the efficacy and safety of terazosin and its effects on the plasma cholesterol levels of patients with untreated essential hypertension.

The safety, efficacy and the effect on the plasma total cholesterol of once-daily terazosin hydrochloride administered as monotherapy was evaluated in 69 patients with mild-moderate untreated essential hypertension in this open, hospital, multi-centre, 3 month study. Patients initially received 1 mg of terazosin followed by dose titration, if necessary, to a maximum of 10 mg over the first six weeks depending upon blood pressure control. Patients then continued treatment for a further six weeks on their optimum dosage. At the end of 12 weeks' treatment, there were highly significant mean reductions in systolic and diastolic blood pressures of 14.5 and 12.9 mmHg (P less than 0.001), respectively, as well as a significant reduction in the mean total cholesterol of -0.56 mmol/l (-9.5%, P less than 0.01). No serious toxicity or safety problems were observed. Once daily administration of terazosin proved to be safe and effective in reducing the blood pressure of patients with mild-moderate essential hypertension and favourably reduced the total plasma cholesterol level.

Carcinogenic effects of some polycyclic aromatic hydrocarbons on the Japanese medaka and guppy in waterborne exposures.

In this paper, we review studies on the carcinogenic effects of two polycyclic aromatic hydrocarbons (PAHs), benzo(a)pyrene (BaP) and 7,12-dimethylbenz(a)anthracene (DMBA), on the Japanese medaka (Oryzias latipes) and the guppy (Poecilia reticulata). Exposure media were prepared by adding PAHs to water, with and without dimethylformamide (DMF) as a carrier, and passing this solution through various sized filters. The low exposure medium was a 0.45 micron filtrate without DMF that contained less than 5 micrograms L-1 PAH. The intermediate medium was a DMF-mediated 0.45 micron filtrate which contained 30-50 micrograms L-1 of PAH. The high medium was a DMF-mediated glass-fibre filtrate which contained 150-250 micrograms L-1 of PAH. Young fish specimens (6-10 d old) were given a 6 h exposure once weekly for 2 to 4 wk. Both BaP and DMBA induced hepatic neoplasms in the two species, with the medaka being more sensitive than the guppy, and DMBA being a stronger carcinogen than BaP. Liver neoplasms almost exclusively developed after exposure to BaP and the neoplasms were limited to the high concentration exposure, whereas DMBA caused a substantial number of extrahepatic neoplasms as well as hepatic ones, especially in the medaka. Furthermore, all three concentrations of DMBA induced hepatic neoplasms in the medaka and all but the low concentration induced neoplasms in the guppy. These studies demonstrate the carcinogenic effects of two waterborne PAHs on two small fish species following brief exposures to very low concentrations, and support the contention that environmental PAHs can contribute to the occurrence of cancer in wild fishes.

Dose-related carcinogenic effects of water-borne benzo[a]pyrene on livers of two small fish species.

Benzo[a]pyrene (BaP) administered by water-borne exposures caused dose-related carcinogenic effects in livers of two small fish species, the Japanese medaka (Oryzias latipes) and the guppy (Poecilia reticulata). Medaka and guppies each were given two 6-h exposures. The first exposure was conducted on 6- to 10-day-old specimens. The second exposure was given 7 days later. The tests incorporated five treatment groups: (1) control, (2) carrier (dimethylformamide) control, (3) low BaP dose (not detectable--4 ppb), (4) intermediate BaP dose (about 8-47 ppb BaP), and (5) high BaP dose (200-270 ppb). Following the high-dose exposure, hepatocellular lesions classified as foci of cellular alteration (altered foci), adenomas, and hepatocellular carcinomas occurred in both species. In medaka, the lesions appeared to develop sequentially with the appearance of altered foci followed by adenomas and then hepatocellular carcinomas. Most lesions in guppies, however, were classified as altered foci although a few adenomas occurred in the early (24-week) sample and hepatocellular carcinomas occurred in the late (52-week) sample. When total lesions were combined, medaka had an 11% incidence at 24 weeks after the initial exposure and 36% incidence at 36 weeks. In guppies, 8% had liver lesions at 24 weeks, 19% at 36 weeks, and 20% at 52 weeks. A single extrahepatic neoplasm, a capillary hemangioma in a gill filament, occurred in a medaka from the 36-week high-dose sample. The results suggest that the medaka and guppy are capable of metabolizing water-borne BaP to carcinogenic metabolites which initiate hepatic tumor development.