The use of acellular matrices for the tissue engineering of cardiac valves.

Tissue-engineering approaches to cardiac valve replacement have made considerable advances over recent years and it is likely that this application will realize clinical success in the near future. Research in this area has been driven by the inadequacy of the currently available cardiac valve prostheses for younger patients who require multiple reoperations as they grow and develop. Tissue engineering has the potential to provide a valve capable of the same growth, repair, and regeneration as a natural valve and could improve outcomes for patients of all ages. Owing to the function and physical environment of the cardiac valve, the development of tissue-engineered replacements is unusual in that the biomechanical properties of the construct must dominate the biological properties in order for the valve to be functional at the time of implantation. As a result of this, conventional tissue-engineering scaffolds based on biodegradable polymers or collagen may not at present be suitable in this situation because of their initial limited strength. Research into the use of acellular xenogeneic and allogeneic matrices for tissue-engineered heart valves has consequently become extremely popular since the biomechanical properties of the valve can potentially be preserved with an optimal decellularization technique that removes the cells without damaging the matrix. A number of acellular scaffolds have already been tested clinically both unseeded and preseeded with cells and these have met with variable results. This article reviews the concepts involved and the advantages and disadvantages of the different approaches to tissue engineering a living cardiac valve.

Serum thyroid hormones and performance of offspring in ewes receiving propylthiouracil with or without melatonin.

Two experiments were conducted during mid-gestation to examine effects in ewes of propylthiouracil (PTU) treatment alone or with melatonin on serum thyroid hormones, postpartum reproduction, and lamb performance. In the first experiment, beginning on day 0 (first day of treatment when all animals were 72.2+/-0.9 days of gestation), ewes received daily treatments (gavage) consisting of either 0mg (n=6) or 40 mg (n=6) PTU/kg body weight/day for 15 days. After 15 days, the 40 mg dosage was decreased to 20mg/kg body weight for an additional 20 days (35 days of PTU). Serum thyroxine (T4) did not differ (P>0.10) between groups through day 4; but on day 5, control females had a serum value of 67 ng/ml compared with 46 (+/-5)ng/ml for PTU-treated ewes (P=0.02). On the last day that 40 mg of PTU was administered, serum T4 averaged 67 and 7 (+/-5)ng/ml (P<0.001) in the two respective groups. Serum T4 remained low and was 80 and 1 ng/ml (P<0.001) in control and treated ewes on day 34. Serum T4 rose gradually after PTU but remained different from that observed in control ewes through day 48. Lambs from control and treated ewes had similar (P=0.46) T4 values at birth but lambs from PTU-treated ewes had lower (P=0.03) birth weights than did those from control ewes. Serum progesterone (P4) after parturition indicated a lack of cyclicity in all ewes. In the second experiment, beginning on day 0 (76.8+/-4.7 days of gestation), ewes received PTU as in Experiment 1. In addition, after 15 days of PTU, melatonin was given (i.m. injections at 5mg/day) for 30 days. Propylthiouracil decreased (P0.60) for lambs born to control and treated ewes. Female offspring of PTU+melatonin-treated dams reached puberty, became anestrus, and returned to cyclicity at similar (P>0.10) times to contemporary ewe lambs. Results indicate that 40/20mg PTU alone or with melatonin does not induce cyclicity after lambing in spring lambing ewes and has little effect on offspring performance.

Progress in the research and demonstration of Everglades periphyton-based stormwater treatment areas.

The South Florida Water Management District (District) is conducting research focused on potential advanced treatment technologies to support reduction of phosphorus (P) loads in surface water entering the remaining Everglades. Periphyton-based stormwater treatment areas (PSTA) are one of the advanced treatment technologies being researched by the District. This detailed research and demonstration project is being conducted in two phases. Basic research in field-based mesocosm experiments was conducted during the first phase within the District's Everglades Nutrient Removal Project (ENR). Studies were conducted in 24 portable PSTA mesocosms and three of the south ENR test cells. Phase 1 studies addressed the effects of system substrate (shellrock, organic peat, or sand), water depth, hydraulic loading rate, vegetation presence, depth:width ratio, and inhibition of algal growth on total phosphorus removal performance of the PSTA mesocosms. A second phase of research is currently under way, during which PSTA feasibility will be evaluated further in four field-scale constructed mesocosms totaling about 2 ha, and follow up studies within the ENR test cells and portable mesocosms will be conducted to further investigate the effects of other inorganic substrates, shallow water depth, and velocity on treatment performance. Phase 1 monitoring has determined that periphyton-dominated communities can be established in constructed wetlands within 5 months. The algal component of these periphyton plant communities is characteristic of natural Everglades periphyton. High macrophyte densities resulted from use of peat soils in PSTA mesocosms, while shellrock and sand soils promoted more desirable sparse macrophyte stands. P removal rates under the conditions of this research were relatively high considering the low influent total P concentrations tested (average 23 microg/L). PSTA mesocosms on shellrock soils were able to attain long-term average outflow total P concentrations as low as 11 microg/L. The maximum one-parameter TP first-order removal rate constant (k1) measured was 27 m/y. Minimum attainable outflow total P concentrations and mass removals appear to be the result of a balance between internal P loading from antecedent soils, uptake and burial processes in new sediments, and rainfall inputs. A different soil type (limerock) will be tested for effectiveness during Phase 2. Selected existing treatments will also be continued to look for trends over a second growing season.

Surface flow (SF) treatment wetlands as a habitat for wildlife and humans.

Water quality improvement is generally the primary objective of treatment wetlands. Creation of wildlife habitat is an inevitable outcome of these projects. However, an increasing number of treatment wetland projects have been purposely designed and operated to enhance their beneficial utility to wildlife and humans. This trend to multi-purpose treatment wetlands has broadened the basis for assessing the advantages of this natural treatment alternative. There are at least 21 treatment wetlands in the U.S. that were implemented with wildlife habitat creation and/or human use as principal goals. A number of treatment wetlands outside the U.S. also share these priorities. Hundreds of other wetlands have collected and reported quantitative data on wildlife and/or human uses. The North American Treatment Wetland Database (NADB) has been expanded to include critical wildlife habitat and human use data. This paper provides a preliminary inventory of these habitat and human use treatment wetlands, summarizes lessons learned, and identifies additional data needs.

Ecological characteristics of a natural wetland receiving secondary effluent.

The Boot wetland treatment system is a 115-acre, hydrologically altered cypress-gum wetland in Polk County, Florida. The Poinciana Wastewater Treatment Plant No. 3 has discharged secondary effluent to the bermed Boot wetland since August 1984. Before that time this natural wetland had been affected adversely by forestry, drainage, and surrounding development which contributed to dying trees and a groundcover of invasive upland plants. In accordance with the Florida Department of Environmental Protection's Wetlands Application Rule (Chapter 62-611, F.A.C.), a routine biological and water quality monitoring program has been in effect since October 1990. Components of the biological monitoring program include surveys of canopy and subcanopy, herbaceous and shrub groundcover species, benthic macroinvertebrates, fish, and nuisance mosquitoes. Effluent addition to the Boot wetland has resulted in continuous wetland inundation with atypical water depth of 2.5 to 3.0 feet for the past 15 years. Dominance and density of trees has steadily increased, upland invader species were eliminated, and stable plant, fish, and invertebrate communities were established. The long term biological data from this treatment wetland is compared to data from other natural treatment wetlands and a control wetland.

Long-term performance summary for the Boot Wetland Treatment System.

The Boot WTS is a 46.5-ha, hydrologically altered cypress-gum wetland in Polk County, Florida. Poinciana Wastewater Treatment Plant No. 3 has discharged advanced secondary treated effluent to the Boot WTS since August 1984. Comprehensive operational monitoring has been ongoing since 1990. The Boot WTS has provided consistent removal of nitrogen and phosphorus. Influent total nitrogen (TN) and total phosphorus (TP) concentrations averaged approximately 10.0 mg/L and 2.5 mg/L at an average hydraulic loading rate (HLR) of 0.2 cm/d. Wetland effluent concentrations for TN and TP averaged 1.8 mg/L and 1.2 mg/L. Available flow and water quality data were used to develop estimates of the first-order removal rate, k, for TN (14 m/y) and TP (1.8 m/y). These removal rates are within the range of values for other forested treatment wetlands. Biochemical oxygen demand (2.2 mg/L) and total suspended solids (4.9 mg/L) in the influent are near background levels for forested wetlands and are not significantly reduced with passage through the system.

Characterization of the transglutaminase-mediated large molecular weight polymer from rat liver; its relationship to apoptosis.

A large molecular weight sodium dodecyl sulfate (SDS)-insoluble polymer was isolated from rat liver and shown to be a product of transglutaminase activity by virtue of its high epsilon(gamma glutamyl)lysine content. Antiserum raised against this polymer crossreacted with another product of transglutaminase activity, the apoptotic envelope isolated from cultured hamster fibrosarcoma cells. The amino acid composition of isolated apoptotic envelopes and the SDS-insoluble polymer were found to be comparable, although not identical. Using the polymer antiserum, the apoptotic index (mg polymer protein per mg DNA) of normal and tumor tissue was determined and found to correlate with the associated transglutaminase activity. Localization of proteins involved in polymer formation in neonatal rat liver cells was found immunohistochemically to be in those cells undergoing apoptosis; these cells also stained selectively for transglutaminase. Several proteins from liver homogenate were found to crossreact with the antipolymer serum, notably proteins of 120, 80, 43 and 38 kDa.

Thermal effects on activity patterns and behavioural switching in a concourse of foragers on Stachytarpheta mutabilis (Verbenaceae) in Papua New Guinea.

1. The foraging activities of the papilionid butterflies Ornithoptera priamus poseidon and Papilio ulysses, and the solitary bee Amegilla sapiens (Apoidea, Anthophoridae) on the shrub Stachytarpheta mutabilis were studied in highland Papua New Guinea. 2. The insects' activity patterns were analysed at three sites with differing diurnal microclimate variation. O. priamus and A. sapiens foraged in the morning (after a period of basking and wing-whirring) and late afternoon when temperatures were well below daily maxima, whereas P. ulysses showed foraging peaks during the hottest part of the day. 3. Site choice by all 3 species appeared to be determined primarily by temperature, but within the limits imposed by temperature, nectar supplies probably determined which site was visited. 4. P. ulysses showed interspersed foraging and courtship behaviour, and no behavioural switching was observed for this species. At high temperatures, both O. priamus and A. sapiens ceased foraging and showed territorial and courtship behaviour. This behavioural change allowed avoidance of heat stress, and occurred even when nectar supplies were maintained at high levels. 5. Thermal effects on behavioural switching in these insects are compared with related phenomena in other bees and butterflies.

Mosquito production and hydrological capacity of southeast Florida impoundments used for wastewater retention.

In Indian River County, Florida mosquito control impoundments, larval mosquito sampling and hydrological measurements demonstrated the importance of careful consideration of these factors when developing management plans for impoundments used for wastewater retention. Discharging secondarily treated wastewater into an impoundment resulted in only minor mosquito production. However, a treatment plant failure produced extremely high Culex densities in the impoundment. Average water loss rates in impoundments studied were due to evapotranspiration (0.25 cm/day) and percolation (0.38 cm/day). Greatest percolation (0.68 cm/day) was measured when the impoundments were maximally flooded. Under the conditions of this study, the impoundments can assimilate approximately 124 cm/year of wastewater (1.52 million liters/day) over a 50 ha area without overflows.

Isolation of a herpesvirus from a bald eagle nestling.

Cloacal swabs collected from wild bald eagle nestlings (Haliaeetus leucocephalus) were tested for viruses. A virus isolated from one of these samples had a lipid coat and contained DNA. Electron microscopy confirmed that it was a herpesvirus. This appears to be the first report of a herpesvirus isolation from a wild bald eagle.

Somatic embryos from culture ovules of polyembryonic Mangifera indica L.

Ovules were aseptically removed from 2 month old fruits of 9 naturally polyembryonic cultivars and 1 monoembryonic cultivar of mango (Mangifera indica L.). Ovules were placed into culture on solid Murashige and Skoog medium that had been modified by the addition of half strength major salts and chelated iron, 6% sucrose, 400 mg/l glutamine, 100 mg/l ascorbic acid with or without the following growth regulators: 20% (v/v) CW, 1 or 2 mg/1 BA. Somatic embryogenesis occurred from the nucellus excised from the ovules of 5 of the naturally polyembryonic cultivars after 1-2 months in culture. Somatic embryogenesis was not apparently affected by the growth regulator composition of the media; however, efficient somatic embryogenesis only occurred in liquid containing 20% CW.