The relevance of rooted vascular plants as indicators of estuarine sediment quality

Toxicity assessments and numerical quality assessment guidelines for estuarine sediments are rarely based on information for aquatic plants. The effect of this lack of information on contaminated sediment toxicity evaluations is largely unknown. For this reason, the toxicities of whole sediments collected from 15 sites in three urbanized Florida bayou-estuaries were determined for the benthic invertebrates Mysidopsis bahia and Ampelisca abdita and the plants Scirpus robustus Pursh (saltmarsh bulrush) and Spartina alterniflora Loisel (saltmarsh cordgrass). The results of the bioassays, conducted for 7 to 28 days, were compared for interspecific differences and to effects-based, sediment quality assessment guidelines. A variety of inorganic and organic analytes were detected in the estuarine sediments, and concentrations of as many as 7 analytes exceeded the sediment guidelines at the 15 sampling locations. Toxicity occurred at 2 of the 15 sampling stations based on invertebrate survival. Twelve of the 15 sediments had either a significant stimulatory or inhibitory effect on early seedling growth relative to a reference sediment (p < 0.05). The phytoresponse was specific to the location, test species, and plant tissue. There was no consistent trend between the sensitivities of the plants and invertebrates exposed to the sediments collected from the same sites. Of the 12 sediments that significantly affected seedling growth, 10 were not acutely toxic to the invertebrates. Consequently, the plant test species provided information that would have been missing if only animal test species were used. For this reason, the phytotoxicity database needs to be expanded for contaminated sediments to further evaluate interspecific sensitivities and to provide perspective on the environmental relevancy of proposed sediment quality criteria and effects-based assessment guidelines for which this information is usually missing. However, additional test method development and field validation are needed to support this effort, which includes the identification of sensitive plant test species, response parameters, and the chemical and physical sediment factors that influence plant growth.

Hospital discharge after ambulatory knee arthroscopy: A comparison of epidural 2-chloroprocaine versus lidocaine

BACKGROUND AND OBJECTIVES

This prospective, randomized, double-blind study compares the efficacy of epidural 2-chloroprocaine and lidocaine for attaining hospital discharge criteria after ambulatory knee arthroscopy. We hypothesized that 2-chloroprocaine would facilitate earlier discharge than lidocaine.

METHODS

American Society of Anesthesiologists (ASA) I and II patients were randomized to receive equipotent doses of epidural 3% 2-chloroprocaine or 1.5% lidocaine, both without epinephrine. Time to block resolution and discharge were compared between groups, along with the need for epidural reinjection, surgical times, and postoperative back pain.

RESULTS

Twenty-seven patients completed the study, 13 in the 2-chloroprocaine group and 14 in the lidocaine group. The 2-chloroprocaine group was ready for discharge significantly earlier than the lidocaine group (130 +/- 17 min [range, 105 to 160] v 191 +/- 32 min [range 144 to 251]; P <.0001, 90% power). The lidocaine group required more epidural reinjections. Anesthesia-related side effects were similar in both groups.

CONCLUSIONS

Epidural 3% 2-chloroprocaine without epinephrine is an advantageous choice for ambulatory knee arthroscopy. It enables readiness for discharge an hour sooner than 1.5% lidocaine, requires fewer reinjection interventions, and may reduce delayed discharge secondary to prolonged time to void. This clinical study shows the superiority of epidural 3% 2-chloroprocaine over 1.5% lidocaine for expediting hospital discharge after ambulatory surgery.

Dredging impact on an urbanized Florida bayou: effects on benthos and algal-periphyton

Environmental effects of dredging events have been uncommonly reported for shallow, residential estuaries characteristic of the Gulf of Mexico region. The objective of this study was to determine the impact of hydraulic dredging on an urbanized estuary. Physicochemical quality, benthic community composition, whole sediment toxicity, periphytic algal community composition and trace metal tissue quality were determined prior to and after dredging. The effects on surface water pH, dissolved oxygen, and temperature were negligible but photosynthetically active radiation was decreased at several stations. Dredging significantly reduced benthic diversity and density (P < 0.05). However, the sediments were not acutely toxic to the epibenthic, Americamysis bahia (formerly Mysidopsis bahia); survival averaged 93% (post-dredging) and to 98% (pre-dredging). There were several post-dredging taxonomic structural changes in the diatom-dominated, periphyton community but differences in mean density and three diversity indices were not significant. Trace metal concentration in periphyton after dredging were reduced from an average of 4-65% and significantly for mercury, zinc and chromium in several areas. It was concluded that the environmental impact of small-scale dredging events in urbanized near-coastal areas, based on the selected parameters, are likely to be localized and of short-term environmental consequence. The choice of the target biota, response parameters and chemical analysis are important considerations in the environmental impact assessment of these periodic episodic events.

Spread rate for a nonlinear stochastic invasion

Despite the recognized importance of stochastic factors, models for ecological invasions are almost exclusively formulated using deterministic equations [29]. Stochastic factors relevant to invasions can be either extrinsic (quantities such as temperature or habitat quality which vary randomly in time and space and are external to the population itself) or intrinsic (arising from a finite population of individuals each reproducing, dying, and interacting with other individuals in a probabilistic manner). It has been long conjectured [27] that intrinsic stochastic factors associated with interacting individuals can slow the spread of a population or disease, even in a uniform environment. While this conjecture has been borne out by numerical simulations, we are not aware of a thorough analytical investigation. In this paper we analyze the effect of intrinsic stochastic factors when individuals interact locally over small neighborhoods. We formulate a set of equations describing the dynamics of spatial moments of the population. Although the full equations cannot be expressed in closed form, a mixture of a moment closure and comparison methods can be used to derive upper and lower bounds for the expected density of individuals. Analysis of the upper solution gives a bound on the rate of spread of the stochastic invasion process which lies strictly below the rate of spread for the deterministic model. The slow spread is most evident when invaders occur in widely spaced high density foci. In this case spatial correlations between individuals mean that density dependent effects are significant even when expected population densities are low. Finally, we propose a heuristic formula for estimating the true rate of spread for the full nonlinear stochastic process based on a scaling argument for moments.

Modeling and analysis of stochastic invasion processes

In this paper we derive spatially explicit equations to describe a stochastic invasion process. Parents are assumed to produce a random number of offspring which then disperse according to a spatial redistribution kernel. Equations for population moments, such as expected density and covariance averaged over an ensemble of identical stochastic processes, take the form of deterministic integro-difference equations. These equations describe the spatial spread of population moments as the invasion progresses. We use the second order moments to analyse two basic properties of the invasion. The first property is 'permanence of form' in the correlation structure of the wave. Analysis of the asymptotic form of the invasion wave shows that either (i) the covariance in the leading edge of the wave of invasion asymptotically achieves a permanence of form with a characteristic structure described by an unchanging spatial correlation function, or (ii) the leading edge of the wave has no asymptotic permanence of form with the length scales of spatial correlations continually increasing over time. Which of these two outcomes pertains is governed by a single statistic, phi which depends upon the shape of the dispersal kernel and the net reproductive number. The second property of the invasion is its patchy structure. Patchiness, defined in terms of spatial correlations on separate short (within patch) and long (between patch) spatial scales, is linked to the dispersal kernel. Analysis shows how a leptokurtic dispersal kernel gives rise to patchiness in spread of a population.

Venous thromboembolism and oral contraceptive use: a methodological study of diagnostic suspicion and referral bias

BACKGROUND

In studies of oral contraceptive oral contraceptive use and risk of venous thromboembolism, bias related to heightened diagnostic suspicion and preferential referral of oral contraceptive users has been an issue. The aim of our study was to determine the presence and potential impact of diagnostic suspicion and referral bias.

METHODS

We conducted a case/non-case study in 21 regional study centers in Germany and, in parallel, a conventional case-control study using the same cases but randomly selected population controls from the same areas. Women with symptoms compatible with venous thromboembolism were included in the study between 1994 and 1999, and classified as cases or non-cases (first reference group) according to the diagnostic work-up (case/non-case study). A second reference group consisted ofpopulation controls (conventional case-control study as an internal comparison for the case/non-case study): 606 cases, 462 non-cases and 2942 population controls aged 15-49 years. Adjusted unconditional regression analyses were performed.

RESULTS

Adjusted odds ratios for venous thromboembolism in oral contraceptive users were systematically higher in the classical case-control study compared to the case/non-case approach (using the same cases) across all subgroup analyses (e.g. for idiopathic cases, the odds ratio was 67% higher in the case-control study: 4.33 (95% confidence interval (CI) 3.27-5.74) versus 2.60 (95% CI 1.75-3.88)). We found a significantly increasing trend of oral contraceptive use in four categories of increasingly sophisticated diagnostic tests that were applied to 1067 women with a suspicion of venous thromboembolism, irrespective of the outcome. Stratified analysis showed the diagnostic level to be a confounder.

CONCLUSION

In our population-based study with the possibility of internal comparison, we found clear evidence that diagnostic suspicion and referral bias does play an important role in case-control studies of venous thromboembolism risk among oral contraceptive users. This underlines the importance of making an effort to avoid this bias when designing a new study.

Secondary data analysis: new perspective for adolescent research

Adolescents are at high risk for preventable health problems, but realities of research funding and obtaining data from large samples make it difficult for many researchers to answer important questions. Secondary analysis of existing data sets is described as a reasonable alternative in spite of its limitations. Methods and available resources are identified along with suggestions for research priorities with adolescents.

Invasion speeds in fluctuating environments

Biological invasions are increasingly frequent and have dramatic ecological and economic consequences. A key to coping with invasive species is our ability to predict their rates of spread. Traditional models of biological invasions assume that the environment is temporally constant. We examine the consequences for invasion speed of periodic and stochastic fluctuations in population growth rates and in dispersal distributions.

Randomized clinical trial of the effect of semi-occlusive dressings on the microflora and clinical outcome of acute facial wounds

This study investigated whether treatment with occlusive, hydroactive polyurethane dressings affects the microflora and clinical outcome of acute wounds. A randomized, controlled trial was performed on 60 patients with acute facial lacerations. Following primary closure, patients were provided with either a dry-gauze dressing or a hydroactive polyurethane dressing (Cutinova Thin). The wounds were assessed clinically and microbiologically prior to closure, then after 5, 28 and 56 days. The dressing, which was removed at day 5, was also sent for microbiological culture. Wounds treated with the polyurethane dressing showed improved comfort and contour (p < 0.04), less erythema (p < 0.03) and less potential for scarring (p < 0.01) at day 5. At day 28 and day 56, there were no significant differences in the clinical assessment between the test and control groups (p > 0.05). A total of 518 isolates were recovered from the patients during the study. Mean number of isolates and bacterial growth density were calculated in both groups. A similar range of microorganisms were obtained from both treatment groups with no clear difference in organism colonization. This study shows the potential usefulness of facial wounds as a human model for studying acute wound healing responses and anti-scarring therapy. While short-term, clinical benefits of occlusive dressings were evident in the management of acute wounds, these data clearly show that all studies of scarring following acute wounding should extend over at least 3 months post-injury to allow for spontaneous improvement to occur.

Wetland plant seedlings as indicators of near-coastal sediment quality: interspecific variation

The toxicities of whole sediments collected from an urbanized Florida bayou-estuary were determined for the epibenthic mysid, Mysidopsis bahia, and the infaunal amphipod, Ampelisca abdita. In addition, the phytotoxicities of the same sediments were evaluated using rooted macrophytes, Scirpus robustus Pursh and Spartina alterniflora Loisel. The results of the 24 bioassays conducted for 7-28 days, were compared for interspecific differences. Toxicity to the benthic invertebrate species was predicted to be likely in all cases, based on comparison to effects-based sediment quality assessment guidelines. However, acute toxicity was uncommon and occurred at only one of the six sampling stations. In contrast, several sediments were either significantly phytostimulatory or phytoinhibitory (P < 0.05) relative to a reference estuarine sediment. The results show the importance of considering interspecific variation and phytoassessment in contaminated sediment evaluations. Phytoassessment, the focus of this research, provided useful information that would have been missing if only the animal test species were used. For this reason, the phytotoxicity data base needs to be increased to better evaluate the relevance of most current contaminated sediment evaluations for coastal areas and also to determine the realism of proposed numerical sediment quality assessment guidelines and criteria.

Macrorestriction fingerprinting of "Streptococcus milleri" group bacteria by pulsed-field gel electrophoresis

Although isolates of the "Streptococcus milleri" group (SMG) of bacteria are regarded as members of the commensal microflora of the body, they are frequently encountered in purulent infections from a range of body sites. The genetic diversity of 91 epidemiologically unrelated SMG isolates (including 37 commensal strains and 49 disease-associated strains) was analyzed by macrorestriction fingerprinting (MF). The genomes were digested with SmaI and ApaI independently, and fragments were resolved by pulsed-field gel electrophoresis. Similarities between banding profiles were determined, and strains were clustered on this basis into dendrograms. In common with other commensal species that have been examined by MF, considerable genetic diversity was revealed. In addition, the clustering of strains tended to support the current taxonomic position of this heterogeneous group. The present study has shown that MF is a powerful tool for characterization of SMG strains and that its use is likely to be of great value in epidemiological and population genetic studies of this group of bacteria.

Electron capture dissociation for structural characterization of multiply charged protein cations

For proteins of < 20 kDa, this new radical site dissociation method cleaves different and many more backbone bonds than the conventional MS/MS methods (e.g., collisionally activated dissociation, CAD) that add energy directly to the even-electron ions. A minimum kinetic energy difference between the electron and ion maximizes capture; a 1 eV difference reduces capture by 10(3). Thus, in an FTMS ion cell with added electron trapping electrodes, capture appears to be achieved best at the boundary between the potential wells that trap the electrons and ions, now providing 80 +/- 15% precursor ion conversion efficiency. Capture cross section is dependent on the ionic charge squared (z2), minimizing the secondary dissociation of lower charge fragment ions. Electron capture is postulated to occur initially at a protonated site to release an energetic (approximately 6 eV) H. atom that is captured at a high-affinity site such as -S-S- or backbone amide to cause nonergodic (before energy randomization) dissociation. Cleavages between every pair of amino acids in mellitin (2.8 kDa) and ubiquitin (8.6 kDa) are represented in their ECD and CAD spectra, providing complete data for their de novo sequencing. Because posttranslational modifications such as carboxylation, glycosylation, and sulfation are less easily lost in ECD than in CAD, ECD assignments of their sequence positions are far more specific.

Immunisation against varicella in end stage and pre-end stage renal failure. Trans-Pennine Paediatric Nephrology Study Group

OBJECTIVES

To investigate the seroconversion rate and duration of persistence of protective antibody titres after varicella immunisation in children with renal failure.

DESIGN

32 children (25 end stage and 7 pre-end stage renal failure) were immunised using 2 x 2,000 plaque forming unit doses of varicella vaccine 3 months apart. Varicella antibody titres were measured by enzyme linked immunosorbent assay.

RESULTS

All children initially seroconverted after immunisation. At a mean follow up of 20.3 months, 23 of 28 had protective antibody titres, 4 children having died of unrelated causes. Two children required a third booster dose. 11 children underwent renal transplantation; 10 had protective titres at the time of transplantation and, at a mean of 23.4 months after immunisation, 6 currently have protective titres. Minor side effects occurred after 11 vaccine doses in 9 children. No child developed varicella, despite 10 clear episodes of exposure to the wild-type virus.

CONCLUSIONS

Varicella immunisation in children with end stage and pre-end stage renal failure results in a high rate of seroconversion and persistence of protective antibody titres. More widespread use of the vaccine before renal transplantation is recommended.

Isolation and identification of Candida from the oral cavity

A number of methods of sampling the oral cavity for the presence of candida have been developed. Such techniques play an important role in the diagnosis and management of oral candidosis. In the past, identification of candida isolated from the oral cavity has usually been limited to the genus Candida or to the species C. albicans. However, with the recognition that Candida species differ in the production of putative virulence factors and sensitivity to antifungal agents, greater emphasis has been placed on identification of isolates to species level. As a result a range of commercially available systems for yeast identification can now be used in conjunction with traditional identification procedures.

Bladder augmentation surgery--what about the malignant risk?

Augmentation cystoplasty has become a common surgical treatment for the neuropathic bladder. However, malignancy in bladder augmentations has been well-described and in time is estimated to occur in 1.3% of cases. We surveyed 36 paediatric surgeons from the UK with a special interest in paediatric urology to ascertain how many bladder augmentations were being performed in children each year and whether the surgeons were warning patients/parents of the malignant risks involved with this surgery. Over 150 bladder augmentations were being performed in the UK each year. Surgeons surveyed were concerned about the malignant risks and nearly all agreed that a Central Registry of patients with bladder augmentations should be established to keep track of developments.

The Transnational Study on Oral Contraceptives and the Health of Young Women. Methods, results, new analyses and the healthy user effect

The results of the Transnational Study on Oral Contraceptives and the Health of Young Women studies are reviewed, potential biases shown, and new analyses are presented. The initial finding was a slight increase in the risk of venous thromboboembolism (VTE) when users of third generation OC (containing the progestins desogestrel and gestodene) were compared with users of older (second generation) OC [odds ratio (OR) of 1.5; 95% confidence interval (CI) 1.0, 2.1]. In order to account for potential biases in the study, new analyses were performed. A quadratic spline technique comparing first users of OC with never-users found that risk of VTE is highest in the first year of OC use, but showed no difference between the two generations of OC upon adjustment. An analysis of a new dataset which now included full information on the past exposure history of all study subjects with a Cox regression model with time-dependent covariates produced an OR of 0.8 (0.5, 1.3) for the comparison of current users of third generation OC with current users of second generation OC. The results of the newer analyses with more refined techniques and with an enhanced dataset which includes data collected on the past exposures of all study subjects indicates that bias, particularly that introduced by healthy user cohorts, accounts for the results initially shown for VTE within the Transnational Study.

Deoxyribonucleic acid typing methods for medically important microorganisms

The ability to type microorganisms to a sub-species level plays an essential role in the diagnosis, treatment and control of human infection. Traditionally, differentiation of microorganisms has involved analysis of phenotypic markers. However, these methods are not universally applicable to all microorganisms, and results may be influenced by environmental factors. Recent developments in DNA analysis, together with the limitations of phenotypic methods, have resulted in an increasing use of procedures based on DNA analysis for the typing of clinically important microorganisms. The aim of this review is to provide an overview of the advantages and disadvantages of the genetic typing techniques currently available.