Fine-root mortality rates in a temperate forest: estimates using radiocarbon data and numerical modeling.

* We used an inadvertent whole-ecosystem 14C label at a temperate forest in Oak Ridge, Tennessee, USA to develop a model (Radix1.0) of fine-root dynamics. Radix simulates two live-root pools, two dead-root pools, non-normally distributed root mortality turnover times, a stored carbon (C) pool, and seasonal growth and respiration patterns. * We applied Radix to analyze measurements from two root size classes (< 0.5 and 0.5-2.0 mm diameter) and three soil-depth increments (O horizon, 0-15 cm and 30-60 cm). * Predicted live-root turnover times were < 1 yr and approximately 10 yr for short- and long-lived pools, respectively. Dead-root pools had decomposition turnover times of approximately 2 yr and approximately 10 yr. Realistic characterization of C flows through fine roots requires a model with two live fine-root populations, two dead fine-root pools, and root respiration. These are the first fine-root turnover time estimates that take into account respiration, storage, seasonal growth patterns, and non-normal turnover time distributions. * The presence of a root population with decadal turnover times implies a lower amount of belowground net primary production used to grow fine-root tissue than is currently predicted by models with a single annual turnover pool.

Differential expression of placental lactogen-II and prolactin-like protein-A in the rat chorioallantoic placenta.

The rat chorioallantoic placenta is comprised of two morphologically distinct regions: the junctional zone and the labyrinth zone. The purpose of this investigation was to determine the relative contributions of trophoblast cells in each of these regions to the expression of placental lactogen-II (PL-II) and PRL-like protein-A (PLP-A) during development, mRNA expression was estimated by Northern blot analysis, whereas, protein expression was estimated by electrophoresis, immunoblotting, and immunocytochemical analyses. The immunochemical analyses used antipeptide antisera directed to amino acids 56-70 of PL-II and amino acids 152-164 of PLP-A. Northern and immunoblotting analyses indicated that both PL-II mRNA and protein expression were maximal in the junctional zone on day 13 of gestation and declined as gestation proceeded. In contrast, PL-II mRNA and protein expression in the labyrinth zone were low on day 13 and increased as gestation advanced. PL-II was specifically localized to giant cells. At midgestation, PL-II-positive giant cells were identified bordering the uterine decidua in the junctional zone and choriovitelline placenta. As gestation advanced. PL-II-positive cells were also localized to the labyrinth zone. Immunoreactivity was restricted to the cytoplasm of PL-II-positive cells. PLP-A mRNA and protein were predominantly expressed in the junctional zone of the chorioallantoic placenta. Expression of PLP-A increased as gestation advanced. PLP-A was specifically localized to giant and spongiotrophoblast cells of the junctional zone. Immunoreactivity was found in both cytoplasmic and nuclear compartments of PLP-A-positive cells. In summary, PL-II expression shifts from the junctional to the labyrinth zone during pregnancy, whereas PLP-A is predominantly expressed in the junctional zone during the latter third of pregnancy. Both hormones are produced by giant cells of the junctional zone, but only PL-II is expressed by choriovitelline and labyrinthine trophoblast cells. PLP-A is also expressed by spongiotrophoblast cells of the junctional zone. These findings provide insights into the process of placental morphogenesis.

Analysis of candidate genes in the CLN6 critical region using in silico cloning.

CLN6, the gene for variant late infantile neuronal ceroid lipofuscinosis, was mapped to a 4 cM region on chromosome 15q22-23. Subsequently the critical region was narrowed to less than 1 cM between microsatellite markers D15S988 and D15S1000 by additional marker typing in an expanded family resource. A physical map was constructed across this region using YAC and PAC clones and sequence was generated from two PAC clones. This sequence was analysed together with overlapping sequence generated by the Human Genome Project to identify genes within the region using an in silico cloning approach. In all, 29 genes have been identified and 18 have been analysed for mutations by direct sequencing. This powerful new approach will lead to the identification of CLN6.

Toxoplasmosis in black-faced kangaroos (Macropus fuliginosus melanops).

An epizootic of toxoplasmosis among captive black-faced kangaroos (Macropus fuliginosus melanops) is reported. Eight of 25 adult kangaroos had antibodies to Toxoplasma gondii. Serologic data indicated recent exposure to T. gondii in six kangaroos. Two kangaroos had high T. gondii antibody titers (greater than or equal to 16,384) in the modified agglutination test and their infants died when less than 7 months old. Toxoplasma gondii tachyzoites were found in several organs of one infant kangaroo (joey) that died at about 82 days of age and numerous cysts were seen in skeletal muscles of the other joey that died at about 7 months of age. Adult kangaroos had subclinical infections. The modified agglutination test and the dye test were more sensitive than the indirect hemagglutination and latex agglutination tests for the detection of T. gondii antibodies in kangaroo sera.

Creation of hydrophilic nitric oxide releasing polymers via plasma surface modification.

Herein, we describe the surface modification of an S-nitrosated polymer derivative via H2O plasma treatment, resulting in polymer coatings that maintained their nitric oxide (NO) releasing capabilities, but exhibited dramatic changes in surface wettability. The poly(lactic-co-glycolic acid)-based hydrophobic polymer was nitrosated to achieve a material capable of releasing the therapeutic agent NO. The NO-loaded films were subjected to low-temperature H2O plasma treatments, where the treatment power (20-50 W) and time (1-5 min) were varied. The plasma treated polymer films were superhydrophilic (water droplet spread completely in <100 ms), yet retained 90% of their initial S-nitrosothiol content. Under thermal conditions, NO release profiles were identical to controls. Under buffer soak conditions, the NO release profile was slightly lowered for the plasma-treated materials; however, they still result in physiologically relevant NO fluxes. XPS, SEM-EDS, and ATR-IR characterization suggests the plasma treatment resulted in polymer rearrangement and implantation of hydroxyl and carbonyl functional groups. Plasma treated samples maintained both hydrophilic surface properties and NO release profiles after storage at -18 °C for at least 10 days, demonstrating the surface modification and NO release capabilities are stable over time. The ability to tune polymer surface properties while maintaining bulk properties and NO release properties, and the stability of those properties under refrigerated conditions, represents a unique approach toward creating enhanced therapeutic biopolymers.

Fine-root turnover patterns and their relationship to root diameter and soil depth in a 14C-labeled hardwood forest.

Characterization of turnover times of fine roots is essential to understanding patterns of carbon allocation in plants and describing forest C cycling. We used the rate of decline in the ratio of 14C to 12C in a mature hardwood forest, enriched by an inadvertent 14C pulse, to investigate fine-root turnover and its relationship with fine-root diameter and soil depth. Biomass and Delta14C values were determined for fine roots collected during three consecutive winters from four sites, by depth, diameter size classes (< 0.5 or 0.5-2 mm), and live-or-dead status. Live-root pools retained significant 14C enrichment over 3 yr, demonstrating a mean turnover time on the order of years. However, elevated Delta14C values in dead-root pools within 18 months of the pulse indicated an additional component of live roots with short turnover times (months). Our results challenge assumptions of a single live fine-root pool with a unimodal and normal age distribution. Live fine roots < 0.5 mm and those near the surface, especially those in the O horizon, had more rapid turnover than 0.5-2 mm roots and deeper roots, respectively.

Passive nighttime warming facility for forest ecosystem research.

A nighttime warming experiment is proposed. Over the last four decades a significant rise in nighttime minimum temperature has been determined from analysis of meteorological records from a global distribution of locations. The experiment involves nighttime deployment of infrared (IR) reflecting curtains around four sides of a forest canopy and across the top of the forest to mimic the top-down warming effect of cloud cover. The curtains are deployed with cable and pulley systems mounted on a tower and scaffolding structure built around the selected forest site. The trunk space is not enclosed except as an optional manipulation. The curtains reflect long-wave radiation emitted from the forest and ground back into the forest warming the trees, litter, and soil. Excellent infrared reflection can be obtained with commercially available fabrics that have aluminum foil bonded to one side. A canopy warming of 3 to 5 degrees C is expected on cloudless nights, and on cloudy nights, a warming of 1 to 3 degrees C is anticipated relative to a control plot. The curtains are withdrawn by computer control during the day and also at night during periods with precipitation or excessive wind. Examples of hypothesized ecosystem responses to nighttime warming include: (1) increase in tree maintenance respiration (decreasing carbon reserves and ultimately tree growth), (2) increase in the length of the growing season (increasing growth), (3) increase in soil respiration, (4) increase in litter decomposition, (5) increase in mineralization of N and other nutrients from soil organic matter, (6) increase in nutrient uptake (increasing growth), and (7) increase in N immobilization in litter. Hypothesis 1 has the opposite consequence for tree growth to Hypotheses 2 and 6, and thus opposite consequences for the feedback regulation that vegetation has on net greenhouse gas releases to the atmosphere. If Hypothesis 1 is dominant, warming could lead to more warming from the additional CO(2) emissions. Site-specific meteorological, ecophysiological, and phenological measurements are obtained in the warming treatment and in a carefully selected control plot to investigate site-specific hypotheses. Measurements made on both plots for a baseline period and during the period of curtain deployment provide data to test the hypotheses statistically by the "before-after-control-impact" method applicable to unreplicated experiments. The enclosure has a modular design that can be adapted and combined with other forest-scale manipulation experiments such as free air CO(2) enrichment and throughfall displacement.

Structure of the highly conserved HERC2 gene and of multiple partially duplicated paralogs in human.

Recombination between chromosome-specific low-copy repeats (duplicons) is an underlying mechanism for several genetic disorders. Recently, a chromosome 15 duplicon was discovered in the common breakpoint regions of Prader-Willi and Angelman syndrome deletions. We identified previously the large HERC2 transcript as an ancestral gene in this duplicon, with approximately 11 HERC2-containing duplicons, and demonstrated that recessive mutations in mouse Herc2 lead to a developmental syndrome, juvenile development and fertility 2 (jdf2). We have now constructed and sequenced a genomic contig of HERC2, revealing a total of 93 exons spanning approximately 250 kb and a CpG island promoter. A processed ribosomal protein L41 pseudogene occurs in intron 2 of HERC2, and putative VNTRs occur in intron 70 (28 copies, approximately 76-bp repeat) and 3' exon 40 through intron 40 (6 copies, approximately 62-bp repeat). Sequence comparisons show that HERC2-containing duplicons have undergone several deletion, inversion, and dispersion events to form complex duplicons in 15q11, 15q13, and 16p11. To further understand the developmental role of HERC2, a highly conserved Drosophila ortholog was characterized, with 70% amino acid sequence identity to human HERC2 over the carboxy-terminal 743 residues. Combined, these studies provide significant insights into the structure of complex duplicons and into the evolutionary pathways of formation, dispersal, and genomic instability of duplicons. Our results establish that some genes not only have a protein coding function but can also play a structural role in the genome.

Transcript map and comparative analysis of the 1.5-Mb commonly deleted segment of human 5q31 in malignant myeloid diseases with a del(5q).

Loss of a whole chromosome 5, or a del(5q), are recurring abnormalities in malignant myeloid diseases. In previous studies, we defined a commonly deleted segment (CDS) of 1.5 Mb between D5S479 and D5S500 in patients with a del(5q), and we established a P1 artificial chromosome-based contig encompassing this interval. To identify candidate tumor suppressor genes (TSGs), we developed a transcript map of the CDS. The map contains 18 genes and 12 expressed sequence tags/UniGenes. Among the 18 genes are 10 genes that were previously cloned and 8 novel genes. The newly identified genes include CDC23, which encodes a component of the anaphase-promoting complex; RAB6KIFL, which encodes a kinesin-like protein involved in organelle transport; and KLHL3, which encodes a human homologue of the Drosophila ring canal protein, kelch. We determined the intron/exon organization of 14 genes and eliminated each gene as a classical TSG by mutation analysis. In addition, we established a single-nucleotide polymorphism map as well as a map of the mouse genome that is syntenic to the CDS of human 5q31. The development of a transcription map will facilitate the molecular cloning of a myeloid leukemia suppressor gene on 5q.