Association between exposure to anaesthesia and surgery and long-term cognitive trajectories in older adults: report from the Mayo Clinic Study of Aging.

BACKGROUND: The link between exposure to general anaesthesia and surgery (exposure) and cognitive decline in older adults is debated. We hypothesised that it is associated with cognitive decline. METHODS: We analysed the longitudinal cognitive function trajectory in a cohort of older adults. Models assessed the rate of change in cognition over time, and its association with exposure to anaesthesia and surgery. Analyses assessed whether exposure in the 20 yr before enrolment is associated with cognitive decline when compared with those unexposed, and whether post-enrolment exposure is associated with a change in cognition in those unexposed before enrolment. RESULTS: We included 1819 subjects with median (25th and 75th percentiles) follow-up of 5.1 (2.7-7.6) yr and 4 (3-6) cognitive assessments. Exposure in the previous 20 yr was associated with a greater negative slope compared with not exposed (slope: -0.077 vs -0.059; difference: -0.018; 95% confidence interval: -0.032, -0.003; P=0.015). Post-enrolment exposure in those previously unexposed was associated with a change in slope after exposure (slope: -0.100 vs -0.059 for post-exposure vs pre-exposure, respectively; difference: -0.041; 95% confidence interval: -0.074, -0.008; P=0.016). Cognitive impairment could be attributed to declines in memory and attention/executive cognitive domains. CONCLUSIONS: In older adults, exposure to general anaesthesia and surgery was associated with a subtle decline in cognitive z-scores. For an individual with no prior exposure and with exposure after enrolment, the decline in cognitive function over a 5 yr period after the exposure would be 0.2 standard deviations more than the expected decline as a result of ageing. This small cognitive decline could be meaningful for individuals with already low baseline cognition.

Tomato mottle wrinkle virus, a recombinant begomovirus infecting tomato in Argentina.

Begomoviruses seriously threaten tomato production in South America. Here, we present the molecular characterization of a novel tomato-infecting begomovirus isolated in Argentina and demonstrate its infectivity. After cloning and sequencing the complete genome of this new virus, pairwise genetic distance and phylogenetic analyses revealed that it is a novel virus that is closely related to other begomoviruses found in Argentina, Brazil and Bolivia. We have proposed naming the virus tomato mottle wrinkle virus (ToMoWrV), based on symptoms produced upon its biolistic inoculation into tomato plants. Recombination analysis revealed that ToMoWrV is a recombinant, with parental sequences likely belonging to the South American begomoviruses soybean blistering mosaic virus (SoBlMV) and tomato yellow vein streak virus (ToYVSV).

Sequence analysis of Indian iris yellow spot virus ambisense genome segments: evidence of interspecies RNA recombination.

The nucleotide sequence of M- and S-RNA segments of an Indian iris yellow spot virus (IYSV) were determined. Sequence comparisons showed that both of these sequences shared less than 95 % identity with those other known IYSV isolates. Phylogenetic analysis revealed that the S- and M-RNA sequences of known IYSV isolates clustered with those of the tospoviruses, tomato yellow ring virus, polygonum ringspot virus and hippeastrum chlorotic ringspot virus. Further, multiple recombination detection methods detected inter- and intra-species recombination events that clustered primarily within the intergenic regions of S- and M-RNA, suggesting that these are possibly recombination hotspots in IYSV and closely related tospoviruses.

Virological and immunological factors associated with HIV-1 differential disease progression in HLA-B 58:01-positive individuals.

Molecular epidemiology studies have identified HLA-B 58:01 as a protective HIV allele. However, not all B 58:01-expressing persons exhibit slow HIV disease progression. We followed six HLA-B 58:01-positive, HIV subtype C-infected individuals for up to 31 months from the onset of infection and observed substantial variability in their clinical progression despite comparable total breadths of T cell responses. We therefore investigated additional immunological and virological factors that could explain their different disease trajectories. Cytotoxic T-lymphocyte (CTL) responses during acute infection predominantly targeted the TW10 and KF9 epitopes in p24(Gag) and Nef, respectively. Failure to target the TW10 epitope in one B 58:01-positive individual was associated with low CD4(+) counts and rapid disease progression. Among those targeting TW10, escape mutations arose within 2 to 15 weeks of infection. Rapid escape was associated with preexisting compensatory mutations in the transmitted viruses, which were present at a high frequency (69%) in the study population. At 1 year postinfection, B 58:01-positive individuals who targeted and developed escape mutations in the TW10 epitope (n = 5) retained significantly higher CD4(+) counts (P = 0.04), but not lower viral loads, than non-B 58:01-positive individuals (n = 17). The high population-level frequency of these compensatory mutations may be limiting the protective effect of the B 58:01 allele.

NASP: a parallel program for identifying evolutionarily conserved nucleic acid secondary structures from nucleotide sequence alignments.

SUMMARY: Many natural nucleic acid sequences have evolutionarily conserved secondary structures with diverse biological functions. A reliable computational tool for identifying such structures would be very useful in guiding experimental analyses of their biological functions. NASP (Nucleic Acid Structure Predictor) is a program that takes into account thermodynamic stability, Boltzmann base pair probabilities, alignment uncertainty, covarying sites and evolutionary conservation to identify biologically relevant secondary structures within multiple sequence alignments. Unique to NASP is the consideration of all this information together with a recursive permutation-based approach to progressively identify and list the most conserved probable secondary structures that are likely to have the greatest biological relevance. By focusing on identifying only evolutionarily conserved structures, NASP forgoes the prediction of complete nucleotide folds but outperforms various other secondary structure prediction methods in its ability to selectively identify actual base pairings. AVAILABILITY: Downloable and web-based versions of NASP are freely available at http://web.cbio.uct.ac.za/~yves/nasp_portal.php CONTACT: yves@cbio.uct.ac.za SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Genomic sequence analysis of four new chrysanthemum virus B isolates: evidence of RNA recombination.

Chrysanthemums worldwide suffer from a high incidence of infection with chrysanthemum virus B (CVB), a member of the genus Carlavirus, family Betaflexiviridae. Three major lineages or strains of this virus have been found in India, but none have been characterized beyond the genetic variation they display in their coat protein genes. Here, we describe the analysis of four near-complete genome sequences (from the three lineages) representing the genetic diversity of these strains. Ranging in size from 8815 to 8855 nucleotides (excluding the polyA tail), these four isolates have a genome organization very similar to that of the recently reported Japanese isolate of CVB, with which they share between 70 and 73% genome-wide sequence identity. We present further evidence that recombination may feature quite prominently in the evolution of CVB.

Differential disease phenotype of begomoviruses associated with tobacco leaf curl disease in Comoros.

In the 2000s, tobacco plantations on the Comoros Islands were afflicted with a previously unobserved tobacco leaf curl disease characterised by symptoms of severe leaf curling and deformation. Previous molecular characterization of potential viral pathogens revealed a complex of African monopartite tobacco leaf curl begomovirus (TbLCVs). Our molecular investigation allowed the characterization of a new monopartite virus involved in the disease: tomato leaf curl Namakely virus (ToLCNamV). Agroinoculation experiments indicated that TbLCVs and tomato leaf curl viruses (ToLCVs) can infect both tomato and tobacco but that infectivity and symptom expression fluctuate depending on the virus and the plant cultivar combination.

Creating a model to predict time intervals from induction of labor to induction of anesthesia and delivery to coordinate workload.

BACKGROUND: Induction of labor continues to become more common. We analyzed induction of labor and timing of obstetric and anesthesia work to create a model to predict the induction-anesthesia interval and the induction-delivery interval in order to co-ordinate workload to occur when staff are most available. METHODS: Patients who underwent induction of labor at a single medical center were identified and multivariable linear regression was used to model anesthesia and delivery times. Data were collected on date of birth, race/ethnicity, body mass index, gestational age, gravidity, parity, indication for labor induction, number of prior deliveries, time of induction, induction agent, cervical dilation, effacement, and fetal station on admission, date and time of anesthesia administration, date and time of delivery, and delivery type. RESULTS: A total of 1746 women met inclusion criteria. Associations which significantly influenced time from induction of labor to anesthesia and delivery included maternal age (anesthesia P <0.001, delivery P =0.002), body mass index (both P <0.001), prior vaginal delivery (both P <0.001), gestational age (anesthesia P <0.001, delivery P <0.018), simplified Bishop score (both P <0.001), and first induction agent (both P <0.001). Induction of labor of nulliparous women at 02:00 h and parous women at 04:00 or 05:00 h had the highest estimated probability of the mother having her first anesthesia encounter and delivering during optimally staffed hours when our institution's specialty personnel are most available. CONCLUSIONS: Time to obstetric and anesthesia tasks can be estimated to optimize induction of labor start times, and shift anesthesia and delivery workload to hours when staff are most available.

Widely conserved recombination patterns among single-stranded DNA viruses.

The combinatorial nature of genetic recombination can potentially provide organisms with immediate access to many more positions in sequence space than can be reached by mutation alone. Recombination features particularly prominently in the evolution of a diverse range of viruses. Despite rapid progress having been made in the characterization of discrete recombination events for many species, little is currently known about either gross patterns of recombination across related virus families or the underlying processes that determine genome-wide recombination breakpoint distributions observable in nature. It has been hypothesized that the networks of coevolved molecular interactions that define the epistatic architectures of virus genomes might be damaged by recombination and therefore that selection strongly influences observable recombination patterns. For recombinants to thrive in nature, it is probably important that the portions of their genomes that they have inherited from different parents work well together. Here we describe a comparative analysis of recombination breakpoint distributions within the genomes of diverse single-stranded DNA (ssDNA) virus families. We show that whereas nonrandom breakpoint distributions in ssDNA virus genomes are partially attributable to mechanistic aspects of the recombination process, there is also a significant tendency for recombination breakpoints to fall either outside or on the peripheries of genes. In particular, we found significantly fewer recombination breakpoints within structural protein genes than within other gene types. Collectively, these results imply that natural selection acting against viruses expressing recombinant proteins is a major determinant of nonrandom recombination breakpoint distributions observable in most ssDNA virus families.

Characterization of tomato yellow vein streak virus, a begomovirus from Brazil.

Tomato yellow vein streak virus (ToYVSV) is a tentative begomovirus (Family Geminiviridae) species that seriously affects tomato and potato production in Brazil. Here, we have determined the genomic and biological characteristics of a ToYVSV isolate (Ba3) from a potato plant sampled in Rio Grande do Sul State, Brazil. The DNA-A nucleotide sequence of Ba3 and another previously reported ToYVSV isolate share 89.7% sequence identity. These ToYVSV isolates should be classified as a new species in that they are most closely related to Soybean blistering mosaic virus with which they share only approximately 80% identity. Cloned constructs containing 1.5 mer copies of the ToYVSV genomic components were found, by biolistic bombardment, to be infectious in at least 11 plant species in 2 families (Solanaceae and Malvaceae). Symptoms on tomato and potato plants were identical to those originally observed on field-infected plants. ToYVSV was also sap-transmissible from Nicotiana benthamiana to N. benthamiana and tomato, but not to potato plants.

Comparative analysis of American Dengue virus type 1 full-genome sequences.

Dengue virus (DENV; Genus Flavivirus, Family Flaviviridae) has been circulating in Brazil since at least the mid-1980s and continues to be responsible for sporadic cases of Dengue fever and Dengue hemorrhagic fever throughout this country. Here, we describe the full genomes of two new Brazilian DENV-serotype 1 (DENV-1) variants and analyze these together with all other available American DENV-1 full-genome sequences. Besides confirming the existence of various country-specific DENV-1 founder effects that have produced a high degree of geographical structure in the American DENV-1 population, we also identify that one of the new viruses is one of only three detectable intra-American DENV-1 recombinants. Although such obvious evidence of genetic exchange among epidemiologically unlinked Latin American DENV-1 sequences is relatively rare, we find that at the population-scale there exists substantial evidence of pervasive recombination that most likely occurs between viruses that are so genetically similar that it is not possible to reliably distinguish and characterize individual recombination events.

Inhibitors of protein synthesis and RNA synthesis prevent neuronal death caused by nerve growth factor deprivation.

We have developed an experimental paradigm to study the mechanism by which nerve growth factor (NGF) allows the survival of sympathetic neurons. Dissociated sympathetic neurons from embryonic day-21 rats were grown in vitro for 7 d in the presence of NGF. Neurons were then deprived of trophic support by adding anti-NGF antiserum, causing them to die between 24 and 48 h later. Ultrastructural changes included disruption of neurites, followed by cell body changes characterized by an accumulation of lipid droplets, changes in the nuclear membrane, and dilation of the rough endoplasmic reticulum. No primary alterations of mitochondria or lysosomes were observed. The death of NGF-deprived neurons was characterized biochemically by assessing [35S]methionine incorporation into TCA precipitable protein and by measuring the release of the cytosolic enzyme adenylate kinase into the culture medium. Methionine incorporation began to decrease approximately 18 h post-deprivation and was maximally depressed by 36 h. Adenylate kinase began to appear in the culture medium approximately 30 h after deprivation, reaching a maximum by 54 h. The death of NGF-deprived neurons was entirely prevented by inhibiting protein or RNA synthesis. Cycloheximide, puromycin, anisomycin, actinomycin-D, and dichlorobenzimidazole riboside all prevented neuronal death subsequent to NGF deprivation as assessed by the above morphologic and biochemical criteria. The fact that sympathetic neurons must synthesize protein and RNA to die when deprived of NGF indicates that NGF, and presumably other neurotrophic factors, maintains neuronal survival by suppressing an endogenous, active death program.

Combined spinal/caudal catheter anesthesia: extending the boundaries of regional anesthesia for complex pediatric urological surgery.

BACKGROUND: Spinal anesthesia (SA) is an established anesthetic technique for short outpatient pediatric urological cases. To avoid general anesthesia (GA) and expand regional anesthetics to longer and more complex pediatric surgeries, the authors began a program using a combined spinal/caudal catheter (SCC) technique. STUDY DESIGN: The authors retrospectively reviewed the charts of all patients scheduled for surgery under SCC between December 2016 and April 2018 and recorded age, gender, diagnosis, procedure, conversion to GA/airway intervention, operative time, neuraxial and intravenous medications administered, complications, and outcomes. The SCC technique typically involved an initial intrathecal injection of 0.5% isobaric bupivacaine followed by placement of a caudal epidural catheter. At the discretion of the anesthesiologist, patients received 0.5 mg per kilogram of oral midazolam approximately 30 min prior to entering the operating room. One hour after the intrathecal injection, 3% chloroprocaine was administered via the caudal catheter to prolong the duration of surgical block. Intra-operative management included either continuous infusion or bolus dosing of dexmedetomidine, as needed, for patient comfort and to optimize surgical conditions. Prior to removal of caudal catheter in the post-anesthesia care unit, a supplemental bolus dose of local anesthesia was given through the catheter to provide prolonged post-operative analgesia. RESULTS: Overall, 23 children underwent attempted SCC. SA was unsuccessful in three patients, and surgery was performed under GA. The remaining 20 children all had successful SCC placement. There were 11 girls and nine boys, with a mean age of 16.5 months (3.3-43.8). Surgeries performed under SCC included seven ureteral reimplantations, two ureterocele excisions/reimplantations, two megaureter repairs, four first-stage hypospadias repairs, one distal hypospadias repair, one second-stage hypospadias repair, two feminizing genitoplasties, and one open pyeloplasty. Average length of surgery was 109 min (range 63-172 min). Pre-operative midazolam was given in 13/20 (65%). All SCC patients were spontaneously breathing room air during the operation, and there were no airway interventions. Only one SCC patient received opioids intra-operatively. There were no intra-operative or perioperative complications. DISCUSSION: This pilot study shows that the technique of SCC allows one to do more complex urologic surgery under regional anesthesia than what would be possible under pure SA alone. The main limitations of the study include the relatively small number of patients and the small median length of the operative procedures. As a proof of concept, however, this does show that complex genital surgery bladder level procedures such as ureteral reimplantation can be performed under regional anesthesia. CONCLUSION: SCC allows for more complex surgeries to be performed exclusively under regional anesthesia, thus obviating the need for airway intervention, minimizing or eliminating the use of opioids, and thus avoiding known and potential risks associated with GA. The latter is of particular importance given current concerns regarding hypothetical neurocognitive effects of GA on children aged below 3 years.

Need for additional anesthesia after single injection spinal analgesia for labor: a retrospective cohort study.

BACKGROUND: There is little information about the use and efficacy of single injection spinal blocks for labor analgesia; specifically, how frequently subsequent analgesia or anesthesia is needed. This study determined how frequently an additional anesthetic intervention was needed in women who received single injection spinal analgesia. METHODS: This retrospective study examined electronic medical records to find all single injection spinal analgesic blocks for labor analgesia over a 14-year (2003-2016) period. Patient and block characteristics and patient outcomes were recorded. The primary outcome was need for an additional anesthetic intervention following single injection spinal for labor analgesia. RESULTS: Four-hundred-and-twenty-eight patients received single injection spinal blocks for labor and 60 (14.0%) needed an additional anesthetic either for labor analgesia (n=49) or an unexpected procedure (n=11). Two of these (0.5%) required general anesthesia. Parity of zero (nulliparous), a low cervical dilation at the time of the spinal injection, and induction of labor status, were associated with an increased risk of needing an additional anesthetic intervention. CONCLUSIONS: This retrospective review provides evidence that single injection spinal anesthesia may be used for multiparous women with spontaneous labor and more advanced cervical dilation.

First Report of Maize streak virus Field Infection of Sugarcane in South Africa.

Prior to the introduction of highly resistant sugarcane varieties, Sugarcane streak virus (SSV) caused serious sugar yield losses in southern Africa. Recently, sugarcane plants with streak symptoms have been identified across South Africa. Unlike the characteristic fine stippling and streaking of SSV, the symptoms resembled the broader, elongated chlorotic lesions commonly observed in wild grasses infected with the related Maize streak virus (MSV). Importantly, these symptoms have been reported on a newly released South African sugarcane cultivar, N44 (resistant to SSV). Following a first report from southern KwaZulu-Natal, South Africa in February 2006, a survey in May 2007 identified numerous plants with identical symptoms in fields of cvs. N44, N27, and N36 across the entire South African sugarcane-growing region. Between 0.04 and 1.6% of the plants in infected fields had streak symptoms. Wild grass species with similar streaking symptoms were observed adjacent to one of these fields. Potted stalks collected from infected N44 plants germinated in a glasshouse exhibited streak symptoms within 10 days. Virus genomes were isolated and sequenced from a symptomatic N44 and Urochloa plantaginea plants collected from one of the surveyed fields (1). Phylogenetic analysis determined that while viruses from both plants closely resembled the South African maize-adapted MSV strain, MSV-A4 (>98.5% genome-wide sequence identity), they were only very distantly related to SSV (~65% identity; MSV-Sasri_S: EU152254; MSV-Sasri_G: EU152255). To our knowledge, this is the first confirmed report of maize-adapted MSV variants in sugarcane. In the 1980s, "MSV strains" were serologically identified in sugarcane plants exhibiting streak symptoms in Reunion and Mauritius, but these were not genetically characterized (2,3). There have been no subsequent reports on the impact of such MSV infections on sugarcane cultivation on these islands. Also, at least five MSV strains have now been described, only one of which, MSV-A, causes significant disease in maize and it is unknown which strain was responsible for sugarcane diseases on these islands in the 1980s (2,3). MSV-A infections could have serious implications for the South African sugar industry. Besides yield losses in infected plants due to stunting and reduced photosynthesis, the virus could be considerably more difficult to control than it is in maize because sugarcane is vegetatively propagated and individual plants remain within fields for years rather than months. Moreover, there is a large MSV-A reservoir in maize and other grasses everywhere sugarcane is grown in southern Africa. References: (1) B. E. Owor et al. J Virol. Methods 140:100, 2007. (2) M. S. Pinner and P. G. Markham. J. Gen. Virol. 71:1635, 1990. (3) M. S. Pinner et al. Plant Pathol. 37:74, 1998.

Increase in taxonomic assignment efficiency of viral reads in metagenomic studies.

Metagenomics studies have revolutionized the field of biology by revealing the presence of many previously unisolated and uncultured micro-organisms. However, one of the main problems encountered in metagenomic studies is the high percentage of sequences that cannot be assigned taxonomically using commonly used similarity-based approaches (e.g. BLAST or HMM). These unassigned sequences are allegorically called « dark matter ¼ in the metagenomic literature and are often referred to as being derived from new or unknown organisms. Here, based on published and original metagenomic datasets coming from virus-like particle enriched samples, we present and quantify the improvement of viral taxonomic assignment that is achievable with a new similarity-based approach. Indeed, prior to any use of similarity based taxonomic assignment methods, we propose assembling contigs from short reads as is currently routinely done in metagenomic studies, but then to further map unassembled reads to the assembled contigs. This additional mapping step increases significantly the proportions of taxonomically assignable sequence reads from a variety -plant, insect and environmental (estuary, lakes, soil, feces) - of virome studies.

Effect of oral contraceptives on the mammary glands of Rhesus monkeys: a preliminary report.

PIP: To determine the relationship of oral contraceptive use and breast cancer, 96 rhesus monkeys were administered either Enovid-E (2.5 mg norethynodrel and .1 mg mestranol) or Ovulen (1 mg ethynodiol diacetate and .1 mg mestranol) cyclically for 5 years at doses of 1, 10 and 50 times the human dose. The animals' progress was compared with a control group of 32 monkeys. General physical and mammary gland examinations were conducted before treatment and monthly thereafter. During the 5 year study period none of the treated animals demonstrated clinical evidence of mammary gland lesions, no deaths from breast malignancy occurred, and no palpable breast nodules were found.^ieng

Discovery of parvovirus-related sequences in an unexpected broad range of animals.

Our knowledge of the genetic diversity and host ranges of viruses is fragmentary. This is particularly true for the Parvoviridae family. Genetic diversity studies of single stranded DNA viruses within this family have been largely focused on arthropod- and vertebrate-infecting species that cause diseases of humans and our domesticated animals: a focus that has biased our perception of parvovirus diversity. While metagenomics approaches could help rectify this bias, so too could transcriptomics studies. Large amounts of transcriptomic data are available for a diverse array of animal species and whenever this data has inadvertently been gathered from virus-infected individuals, it could contain detectable viral transcripts. We therefore performed a systematic search for parvovirus-related sequences (PRSs) within publicly available transcript, genome and protein databases and eleven new transcriptome datasets. This revealed 463 PRSs in the transcript databases of 118 animals. At least 41 of these PRSs are likely integrated within animal genomes in that they were also found within genomic sequence databases. Besides illuminating the ubiquity of parvoviruses, the number of parvoviral sequences discovered within public databases revealed numerous previously unknown parvovirus-host combinations; particularly in invertebrates. Our findings suggest that the host-ranges of extant parvoviruses might span the entire animal kingdom.

Biodegradable polymeric stents for vascular application in a porcine carotid artery model: English version.

Over the past years the development of biodegradable polymeric stents has made great progress; nevertheless, essential problems must still be solved. Modifications in design and chemical composition should optimize the quality of biodegradable stents and remove the weaknesses. New biodegradable poly-L-lactide/poly-4-hydroxybutyrate (PLLA/P4HB) stents and permanent 316L stents were implantedendovascularly into both common carotid arteries of 10 domestic pigs. At 4 weeks following implantation, computed tomography (CT) angiography was carried out to identify the distal degree of stenosis. The PLLA/P4HB group showed a considerably lower distal degree of stenosis by additional oral application of atorvastatin (mean 39.81 ± 8.57 %) compared to the untreated PLLA/P4HB group without atorvastatin (mean 52.05 ± 5.80 %). The 316L stents showed no differences in the degree of distal stenosis between the group treated with atorvastatin (mean 44.21 ± 2.34 %) and the untreated group (mean 35.65 ± 3.72 %). Biodegradable PLLA/P4HB stents generally represent a promising approach to resolving the existing problems in the use of permanent stents. Restitutio ad integrum is only achievable if a stent is completely degraded.

Early in vivo experience with tissue-engineered trileaflet heart valves.

BACKGROUND: Tissue engineering is a new approach in which techniques are being developed to transplant autologous cells onto biodegradable scaffolds to ultimately form new functional autologous tissue. Workers at our laboratory have focused on tissue engineering of heart valves. The present study was designed to evaluate the implantation of a whole trileaflet tissue-engineered heart valve in the pulmonary position in a lamb model. METHODS AND RESULTS: We constructed a biodegradable and biocompatible trileaflet heart valve scaffold that was fabricated from a porous polyhydroxyalkanoate (pore size 180 to 240 microm; Tepha Inc). Vascular cells were harvested from ovine carotid arteries, expanded in vitro, and seeded onto our heart valve scaffold. With the use of cardiopulmonary bypass, the native pulmonary leaflets were resected, and 2-cm segments of pulmonary artery were replaced by autologous cell-seeded heart valve constructs (n=4). One animal received an acellular valved conduit. No animal received any anticoagulation therapy. Animals were killed at 1, 5, 13, and 17 weeks. Explanted valves were examined histologically with scanning electron microscopy, biochemically, and biomechanically. All animals survived the procedure. The valves showed minimal regurgitation, and valve gradients were <20 mm Hg on echocardiography. The maximum gradient was 10 mm Hg with direct pressures. Macroscopically, the tissue-engineered constructs were covered with tissue, and there was no thrombus formation on any of the specimens. Scanning electron microscopy showed smooth flow surfaces during the follow-up period. Histological examination demonstrated laminated fibrous tissue with predominant glycosaminoglycans as extracellular matrix. 4-Hydroxyproline assays demonstrated an increase in collagen content as a percentage of native pulmonary artery (1 week 45.8%, 17 weeks 116%). DNA assays showed a comparable number of cells in all explanted samples. There was no tissue formation in the acellular control. CONCLUSIONS: Tissue-engineered heart valve scaffolds fabricated from polyhydroxyalkanoates can be used for implantation in the pulmonary position with an appropriate function for 120 days in lambs.