bluuebunny/crossref_metadata_2025 huggingface dataset:
ANNUAL PLANTS UNDER CYCLIC DISTURBANCE REGIME: BETTER UNDERSTANDING THROUGH MODEL AGGREGATION
Authors: Pagel Jörn , Fritzsch Katrin , Biedermann Robert , Schröder Boris
Published: January 2009

In their application for conservation ecology, “classical” analytical models and individual‐based simulation models (IBMs) both entail their specific strengths and weaknesses, either in providing a detailed and realistic representation of processes or in regard to a comprehensive model analysis. This well‐known dilemma may be resolved by the combination of both approaches when tackling certain problems of conservation ecology. Following this idea, we present the complementary use of both an IBM and a matrix population model in a case study on grassland conservation management. First, we develop a spatially explicit IBM to simulate the long‐term response of the annual plant Thlaspi perfoliatum (Brassicaceae), claspleaf pennycress, to different management schemes (annual mowing vs. infrequent rototilling) based on field experiments. In order to complement the simulation results by further analyses, we aggregate the IBM to a spatially nonexplicit deterministic matrix population model. Within the periodic environment created by management regimes, population dynamics are described by periodic products of annual transition matrices. Such periodic matrix products provide a very conclusive framework to study the responses of species to different management return intervals. Thus, using tools of matrix model analysis (e.g., loop analysis), we can both identify dormancy within the age‐structured seed bank as the pivotal strategy for persistence under cyclic disturbance regimes and reveal crucial thresholds in some less certain parameters. Results of matrix model analyses are therefore successfully tested by comparing their results to the respective IBM simulations. Their implications for an enhanced scientific basis for management decisions are discussed as well as some general benefits and limitations of the use of aggregating modeling approaches in conservation.
FIRE AND FOREST HISTORY AT MOUNT RUSHMORE
Authors: Brown Peter M. , Wienk Cody L. , Symstad Amy J.
Published: January 2009

Mount Rushmore National Memorial in the Black Hills of South Dakota is known worldwide for its massive sculpture of four of the United States' most respected presidents. The Memorial landscape also is covered by extensive ponderosa pine (Pinus ponderosa) forest that has not burned in over a century. We compiled dendroecological and forest structural data from 29 plots across the 517‐ha Memorial and used fire behavior modeling to reconstruct the historical fire regime and forest structure and compare them to current conditions. The historical fire regime is best characterized as one of low‐severity surface fires with occasional (>100 years) patches (<100 ha) of passive crown fire. We estimate that only ∼3.3% of the landscape burned as crown fire during 22 landscape fire years (recorded at ≥25% of plots) between 1529 and 1893. The last landscape fire was in 1893. Mean fire intervals before 1893 varied depending on spatial scale, from 34 years based on scar‐to‐scar intervals on individual trees to 16 years between landscape fire years. Modal fire intervals were 11–15 years and did not vary with scale. Fire rotation (the time to burn an area the size of the study area) was estimated to be 30 years for surface fire and 800+ years for crown fire. The current forest is denser and contains more small trees, fewer large trees, lower canopy base heights, and greater canopy bulk density than a reconstructed historical (1870) forest. Fire behavior modeling using the NEXUS program suggests that surface fires would have dominated fire behavior in the 1870 forest during both moderate and severe weather conditions, while crown fire would dominate in the current forest especially under severe weather. Changes in the fire regime and forest structure at Mount Rushmore parallel those seen in ponderosa pine forests from the southwestern United States. Shifts from historical to current forest structure and the increased likelihood of crown fire justify the need for forest restoration before a catastrophic wildfire occurs and adversely impacts the ecological and aesthetic setting of the Mount Rushmore sculpture.
MARKOV CHAIN MONTE CARLO METHODS FOR ASSIGNING LARVAE TO NATAL SITES USING NATURAL GEOCHEMICAL TAGS
Authors: White J. Wilson , Standish Julie D. , Thorrold Simon R. , Warner Robert R.
Published: January 2009

Geochemical signatures deposited in otoliths are a potentially powerful means of identifying the origin and dispersal history of fish. However, current analytical methods for assigning natal origins of fish in mixed‐stock analyses require knowledge of the number of potential sources and their characteristic geochemical signatures. Such baseline data are difficult or impossible to obtain for many species. A new approach to this problem can be found in iterative Markov Chain Monte Carlo (MCMC) algorithms that simultaneously estimate population parameters and assign individuals to groups. MCMC procedures only require an estimate of the number of source populations, and post hoc model selection based on the deviance information criterion can be used to infer the correct number of chemically distinct sources. We describe the basics of the MCMC approach and outline the specific decisions required when implementing the technique with otolith geochemical data. We also illustrate the use of the MCMC approach on simulated data and empirical geochemical signatures in otoliths from young‐of‐the‐year and adult weakfish,Cynoscion regalis, from the U.S. Atlantic coast. While we describe how investigators can use MCMC to complement existing analytical tools for use with otolith geochemical data, the MCMC approach is suitable for any mixed‐stock problem with a continuous, multivariate data.
RECOVERY AFTER LOCAL EXTINCTION: FACTORS AFFECTING RE‐ESTABLISHMENT OF ALPINE LAKE ZOOPLANKTON
Authors: Knapp Roland A. , Sarnelle Orlando
Published: January 2009

The introduction of fishes into naturally fishless mountain lakes often results in the extirpation of large‐bodied zooplankton species. The ability to predict whether or not particular species will recover following fish removal is critically important for the design and implementation of lake restoration efforts but is currently not possible because of a lack of information on what factors affect recovery. The objective of this study was to identify the factors influencing recovery probability in two large‐bodied zooplankton species following fish removal. We predicted that (1) Daphnia melanica would have a higher probability of recovery than Hesperodiaptomus shoshone due to differences in reproductive mode (D. melanica is parthenogenetic, H. shoshone is obligately sexual), (2) recovery probability would be a decreasing function of fish residence time due to the negative relationship between fish residence time and size of the egg bank, and (3) recovery probability would be an increasing function of lake depth as a consequence of a positive relationship between lake depth and egg bank size. To test these predictions, we sampled contemporary zooplankton populations and collected paleolimnological data from 44 naturally fishless lakes that were stocked with trout for varying lengths of time before reverting to a fishless condition. D. melanica had a significantly higher probability of recovery than did H. shoshone (0.82 vs. 0.54, respectively). The probability of recovery for H. shoshone was also significantly influenced by lake depth, fish residence time, and elevation, but only elevation influenced the probability of recovery in D. melanica. These results are consistent with between‐species differences in reproductive mode combined with the much greater longevity of diapausing eggs in D. melanica than in H. shoshone. Our data also suggest that H. shoshone will often fail to recover in lakes with fish residence times exceeding 50 years.
THE LEGACY OF MERCURY CYCLING FROM MINING SOURCES IN AN AQUATIC ECOSYSTEM: FROM ORE TO ORGANISM
Authors: Suchanek Thomas H. , Richerson Peter J. , Zierenberg R. A. , Eagles-Smith Collin A. , Slotton Darell G. , Harner E. James , Osleger David A. , Anderson Daniel W. , Cech Joseph J. , Schladow S. Geoffrey , Colwell Arthur E. , Mount Jeffrey F. , King Peggie S. , Adam David P. , McElroy Kenneth J.
Published: January 2009

Clear Lake is the site of an abandoned mercury (Hg) mine (active intermittently from 1873 to 1957), now a U.S. Environmental Protection Agency Superfund Site. Mining activities, including bulldozing waste rock and tailings into the lake, resulted in ∼100 Mg of Hg entering the lake's ecosystem. This series of papers represents the culmination of ∼15 years of Hg‐related studies on this ecosystem, following Hg from the ore body to the highest trophic levels.

A series of physical, chemical, biological, and limnological studies elucidate how ongoing Hg loading to the lake is influenced by acid mine drainage and how wind‐driven currents and baroclinic circulation patterns redistribute Hg throughout the lake. Methylmercury (MeHg) production in this system is controlled by both sulfate‐reducing bacteria as well as newly identified iron‐reducing bacteria. Sediment cores (dated with dichlorodiphenyldichlorethane [DDD], 210Pb, and 14C) to ∼250 cm depth (representing up to ∼3000 years before present) elucidate a record of total Hg (TotHg) loading to the lake from natural sources and mining and demonstrate how MeHg remains stable at depth within the sediment column for decades to millenia. Core data also identify other stresses that have influenced the Clear Lake Basin especially over the past 150 years.

Although Clear Lake is one of the most Hg‐contaminated lakes in the world, biota do not exhibit MeHg concentrations as high as would be predicted based on the gross level of Hg loading. We compare Clear Lake's TotHg and MeHg concentrations with other sites worldwide and suggest several hypotheses to explain why this discrepancy exists. Based on our data, together with state and federal water and sediment quality criteria, we predict potential resulting environmental and human health effects and provide data that can assist remediation efforts.
Wooded meadows of Estonia: conservation efforts for agricultural landscape
Authors: SAMMUL M. , KATTAI K. , LANNO K.
Published: January 2009

We provide an overview of the amount and ecological condition of wooded meadows throughout Estonia after significant changes in agriculture in the second part of 20th century. We also present the first attempt to estimate the success of recent conservation efforts for wooded meadows. Our analysis is based on recent exhaustive inventories. We found that Estonia, despite a decrease of the area in wooded meadows by two orders of magnitude during the 20th century, still has about 8400 ha remaining of which approximately 5800 ha are meadows with, at the least, an intermediate conservation value. The latter is directly dependent on mowing regime. Efforts to preserve wooded meadows include establishment of protected areas and financial support for mowing. The national conservation subsidy has been useful and supportive for wooded meadows, however the total amount of this subsidy has been small compared to the area that could be supported. The much larger funds of agri-environmental subsidies have largely not been available for wooded meadows. Moreover, there has been no record keeping about subsidisation of semi-natural grasslands using agricultural support schemes. Although the preservation of some good examples of wooded meadows in Estonia seems guaranteed, further degradation of this valuable habitat type on a national scale is very probable.;
Energy intake and growth of weanling horses in a cold loose housing system
Authors: AUTIO E. , SIHTO U. , MONONEN J.
Published: January 2009

The demand for information relating to the nutrition of horses in a cold environment is increasing with the popularity of loose housing of horses. This study examined the energy intake and growth of 10 weanling horses from November to March (22 weeks) in a loose housing system (paddock and insulated sleeping hall with deep-litter bed). The horses were measured weekly for body condition and body weight, and the feeding was adjusted according to a horses body condition. Metabolizable energy (ME) intake was compared to Finnish (MTT 2006) and Swedish (SLU 2004) nutrient requirements for 612-month-old horses. ME intake (75.5 ± 11.8 MJ d-1, mean ± SD) was on average 24.6% above the requirements. The intake varied in a non-linear fashion in the course of the winter: y = 0.086x2  0.902x + 71.5, where x is weeks from November to March (p
What is International Labor Law For?
Authors: Langille Brian A.
Published: January 2009

This Paper suggests that the answer to the question what is domestic labor law for?commonly regarded as securing justice against markets or a justified tax on market activityhas informed the search for the answer for the question what is international labor law for. This is reflected in what this Paper refers to as P2, which provides that the failure of any country to adopt humane conditions of labor is an obstacle in the way of other nations which desire to improve the conditions in their own countries. P2 envisions a race to the bottom by rational states trapped in a Prisoners Dilemma game. The author maintains that this cannot be the objective of ILO which cannot stop the race given its deficient enforcement mechanisms to ensure compliance. This Paper suggests an alternative raison detre for the ILO, which is called P1, namely social justice: universal peace can only be established if it is based upon social justice. P1 reflects what states actually seek to achieve. Following Sen, this Paper suggests that there is no tradeoff between social justice and economic efficiency. Therefore the promotion of labor rights by the ILO will contribute both to social justice and to economic success. Thus the ILO should promote international labor law so as to lead member states to pursue their self-interest which is consistent with the collective goal of humanity.
Analysis of T-helper Responses and FOXP3 Gene Expression in Patients with Japanese Cedar Pollinosis
Authors: Chikamatsu Kazuaki , Sakakura Koichi , Matsuoka Tomokazu , Endo Shuichiro , Takahashi Goro , Matsuzaki Zensei , Masuyama Keisuke
Published: January 2009

Background

Evidence has been accumulated indicating that regulatory T (T-reg) cells play a crucial role in the maintenance of peripheral T-cell tolerance to allergens. To explore the role of FOXP3, which is required for the development of T-reg cells, in allergen-specific immune responses, we examined the relationship between the alteration of FOXP3 gene expression and in vitro immune responses against allergens.

Methods

Peripheral blood mononuclear cells obtained from 19 human histocompatibility leukocyte antigens (HLA)-DPB1*0501 donors, including patients with Japanese cedar pollinosis and nonallergic healthy donors, were stimulated with Cry j 1 p61-75 peptide. On day 7, T cells were tested for peptide-specific reactivity in IFN-γ and interleukin (IL)-5 enzyme-linked immunospot (ELISPOT) assays. Real-time quantitative RT-PCR was performed to assess relative change of FOXP3 gene expression before and after in vitro stimulation. Neutralization assays using anti-glucocorticoid-induced tumor necrosis factor receptor family-related protein (GITR) and anti-IL-10 monoclonal antibody were also performed.

Results

Of 14 patients with allergic pollinosis tested, 10 responders displayed T-helper type 2 (Th2)-polarized reactivity to Cry j 1 p61-75, and 2 donors showed Th0 responses. Notably, the change of FOXP3 gene expression in donors showing peptide-specific T-helper responses was significantly lower than that in nonresponders, regardless of allergic pollinosis.

Conclusion

Our data indicate that FOXP3 is functional in nonallergic healthy donors as well as allergic patients, and FOXP3-expressing T cells may be responsible for the down-regulation of allergen-specific T-helper responses in individuals. A better understanding of the nature and specificity of FOXP3-expressing T cells in a suppressive mechanism is necessary to develop new immunotherapies against allergic rhinitis.
Construct Validation of a Low-fidelity Endoscopic Sinus Surgery Simulator
Authors: Leung Randy M. , Leung Jerry , Vescan Allan , Dubrowski Adam , Witterick Ian
Published: January 2009

Background

Before a simulator becomes widely accepted, it must be relevant, affordable, and accessible. We have developed a low-cost model emphasizing the basic skills required for endoscopic sinus surgery (ESS). It is noninvasive, free from risk of infection, and an excellent low-pressure learning opportunity. The current study was designed to assess the construct validity of our simulator.

Methods

We conducted a stratified randomized crossover-control study. Otolaryngology residents, fellows, and faculty performed predetermined tasks on the model or cadaver, and then switched. Evaluation included hand motion analysis, task time, and blinded expert review.

Results

Sixteen subjects at various levels of training participated. Cadaver performance correlated well with level of training and previous experience with ESS. However, model performance did not demonstrate statistically significant correlation.

Conclusion

Our model was unable to demonstrate clear construct validity at this time. Materials and structural modifications are in progress. Pending further validation, its low-cost construction possesses potential for integration into otolaryngology residency curricula. Assessment of the simulator's ability to improve surgical skill is also planned.
Analysis of Transnasal Endoscopic versus Transseptal Microscopic Approach for Excision of Pituitary Tumors
Authors: Higgins Thomas S. , Courtemanche Chad , Karakla Daniel , Strasnick Barry , Singh Ran Vijay , Koen Joseph L. , Han Joseph K.
Published: January 2009

Background

The traditional method of pituitary tumor excision is transseptal microscopic excision; however, the transnasal transsphenoidal endoscopic approach has shown comparable results with the transseptal microscopic approach at some institutions. The objective of this study is to compare the two types of sellar and parasellar mass resection: transnasal transsphenoidal endoscopic excision versus transseptal microscopic excision.

Methods

A retrospective cohort analysis was performed on subjects who were referred to a tertiary hospital for surgical management of sellar or parasellar masses. The two groups of patients either underwent a transnasal endoscopic approach with endoscopic excision or transseptal microscopic excision. Demographics, tumor characteristics, operative details, length of hospital stay, intraoperative and postoperative complications, level of postoperative pain, recurrence rate, use of computed tomography (CT) image guidance, and length of follow-up were gathered. The data between the two groups were then compared.

Results

The analysis included 19 subjects who underwent endoscopic excision and 29 subjects who underwent transseptal microscopic excision. Null macroadenoma was the most common sellar mass followed by prolactinoma. There were no statistical differences in rates of perioperative complications and suprasellar or cavernous sinus invasion. Patients who underwent an endoscopic approach had shorter operative times, lower estimated blood loss, less lumbar drain use, less pain, and a shorter postoperative hospital stay (p < 0.05).

Conclusion

The two approaches show similar intraoperative characteristics and immediate complication rates. Transnasal transsphenoidal endoscopic excision is a reasonable alternative to the traditional method of sellar mass excision.
A New Experimental Protocol for Preferential Differentiation of Mouse Embryonic Stem Cells into Insulin-Producing Cells
Authors: Naujok Ortwin , Francini Flavio , Picton Sally , Jörns Anne , Bailey Clifford J. , Lenzen Sigurd
Published: January 2009

Mouse embryonic stem (ES) cells have the potential to differentiate into insulin-producing cells, but efficient protocols for in vitro differentiation have not been established. Here we have developed a new optimized four-stage differentiation protocol and compared this with an established reference protocol. The new protocol minimized differentiation towards neuronal progeny, resulting in a population of insulin-producing cells with β-cell characteristics but lacking neuronal features. The yield of glucagon and somatostatin cells was negligible. Crucial for this improved yield was the removal of a nestin selection step as well as removal of culture supplements that promote differentiation towards the neuronal lineage. Supplementation of the differentiation medium with insulin and fetal calf serum was beneficial for differentiation towards monohormonal insulin-positive cells. After implantation into diabetic mice these insulin-producing cells produced a time-dependent improvement of the diabetic metabolic state, in contrast to cells differentiated according to the reference protocol. Using a spinner culture instead of an adherent culture of ES cells prevented the differentiation towards insulin-producing cells. Thus, prevention of cell attachment in a spinner culture represents a means to keep ES cells in an undifferentiated state and to inhibit differentiation. In conclusion, this study describes a new optimized four-stage protocol for differentiating ES cells to insulin-producing cells with minimal neuronal cell formation.
Mesenchymal Stem Cells Protective Effect in Adriamycin Model of Nephropathy
Authors: Magnasco Alberto , Corselli Mirko , Bertelli Roberta , Ibatici Adalberto , Peresi Monica , Gaggero Gabriele , Cappiello Valentina , Chiavarina Barbara , Mattioli Girolamo , Gusmano Rosanna , Ravetti Jean Louis , Frassoni Francesco , Ghiggeri Gian Marco
Published: January 2009

Mesenchymal stem cells (MSCs) may be of value in regeneration of renal tissue after damage; however, lack of biological knowledge and variability of results in animal models limit their utilization. We studied the effects of MSCs on podocytes in vitro and in vivo utilizing adriamycin (ADR) as a model of renal toxicity. The in vivo experimental approach was carried out in male Sprague-Dawley rats (overall 60 animals) treated with different ADR schemes to induce acute and chronic nephrosis. MSCs were given a) concomitantly to ADR in tail vein or b) in aorta and c) in tail vein 60 days after ADR. Homing was assessed with PKH26-MSCs. MSCs rescued podocytes from apoptosis induced by ADR in vitro. The maximal effect (80% rescue) was obtained with MSCs/podocytes coculture ratio of 1:1 for 72 h. All rats treated with ADR developed nephrosis. MSCs did not modify the clinical parameters (i.e., proteinuria, serum creatinine, lipids) but protected the kidney from severe glomerulosclerosis when given concomitantly to ADR. Rats given MSCs 60 days after ADR developed the same severe renal damage. Only a few MSCs were found in renal tubule-interstitial areas 1–24 h after injection and no MSCs were detected in glomeruli. MSCs reduced apoptosis of podocytes treated with ADR in vitro. Early and repeated MSCs infusion blunted glomerular damage in chronic ADR-induced nephropathy. MSCs did not modify proteinuria and progression to renal failure, which implies lack of regenerative potential in this model.
Long-Term Survival, Robust Neuronal Differentiation, and Extensive Migration of Human Forebrain Stem/Progenitor Cells Transplanted to the Adult Rat Dorsal Root Ganglion Cavity
Authors: Åkesson Elisabet , Sandelin Martin , Kanaykina Nadezda , Aldskogius Hákan , Kozlova Elena N.
Published: January 2009

Neurons in dorsal root ganglia (DRGs) transmit sensory information from peripheral tissues to the spinal cord. This pathway can be interrupted, for example, as the result of physical violence, traffic accidents, or complications during child delivery. As a consequence, the patient permanently loses sensation and often develops intractable neuropathic pain in the denervated area. Here we investigate whether human neural stem/progenitor cells (hNSPCs) transplanted to the DRG cavity can serve as a source for repairing lost peripheral sensory connections. We found that hNSPCs robustly differentiate to neurons, which survive long-term transplantation. The neuronal population in the transplants was tightly surrounded by astrocytes, suggesting their active role in neuron survival. Furthermore, 3 months after grafting hNSPCs were found in the dorsal root transitional zone (DRTZ) and within the spinal cord. The level of differentiation of transplanted cells was high in the core of the transplants whereas cells that migrated to the DRTZ and spinal cord were undifferentiated, nestin-expressing precursors. These data indicate that peripherally transplanted hNPSCs can be used for repair of dorsal root avulsion or spinal cord injuries; however, additional factors are required to guide their differentiation to the desired type of neurons. Furthermore, hNPSCs that migrate from the DRG cavity graft site to the DRTZ and spinal cord may provide trophic support for regenerating dorsal root axons, thereby allowing them to reenter the host spinal cord.
Prolonged Survival of Microencapsulated Neonatal Porcine Islet Xenografts in Immune-Competent Mice without Antirejection Therapy
Authors: Kobayashi Tsunehiro , Arefanian Hossein , Harb George , Tredget Eric B. , Rajotte Ray V. , Korbutt Gregory S. , Rayat Gina R.
Published: January 2009

Several studies have demonstrated that in vitro culture of islets prolonged islet graft survival in immune-competent mice without administration of antirejection drugs. However, we recently showed that in vitro cultured microencapsulated neonatal porcine islets (NPI) were rejected in immune-competent mice not receiving antirejection therapy. The aim of this study was to determine whether culture of microencapsulated NPI in vivo could promote long-term survival of microencapsulated NPI in immune-competent mice without administration of antirejection drugs. Microencapsulated NPI that were cultured in vitro for 7 and 50 days or transplanted initially in immune-deficient C.B.-17 SCID-BEIGE mice for 100 days (in vivo cultured) were characterized and transplanted into streptozotocin-induced diabetic immune-competent BALB/c mice. Day 50 in vitro cultured and day 100 in vivo cultured microencapsulated NPI showed significantly higher insulin and DNA content, indicating maturation of NPI compared to day 7 in vitro cultured microencapsulated NPI. Interestingly, in vivo cultured microencapsulated NPI expressed lower levels of porcine antigens compared to day 7 and day 50 in vitro cultured microencapsulated NPI. Transplantation of day 7 in vitro cultured microencapsulated NPI did not reverse diabetes in immune-competent BALB/c mouse recipients. In contrast, transplantation of day 50 in vitro cultured and in vivo cultured microencapsulated NPI into diabetic immune-competent BALB/c mice resulted in the immediate reversal of hyperglycemia within 2 days posttransplantation. However, all recipients of day 50 in vitro cultured microencapsulated NPI eventually rejected their grafts by day 15 posttransplantation, while 6 of 10 BALB/c mouse recipients of in vivo cultured microencapsulated NPI maintained normoglycemia for 100 days posttransplantation. These results show that in vivo culture of NPI in immune-deficient mice results in the modulation of NPI, which allows for their long-term survival in immune-competent mice without antirejection therapy.
Clonal Analysis of Hematopoiesis-Supporting Activity of Human Mesenchymal Stem Cells in Association with Jagged1 Expression and Osteogenic Potential
Authors: Fujita Satoshi , Toguchida Junya , Morita Yutaka , Iwata Hiroo
Published: January 2009

Human mesenchymal stem cells (hMSCs) are promising feeder cells for expanding hematopoietic stem cells (HSCs), but their potential is heterogeneous. We examined the hematopoiesis-supporting activity of hMSC at the clonal level in relation to the osteogenic potential and gene expression. Hematopoiesis-supporting activities of stably immortalized clonal hMSC lines were evaluated by the expansion of CD34+CD38- cells after 7-day coculture with human cord blood-derived CD34+ cells. Six of 16 clones expanded the numbers of CD34+CD38- cells >500-fold. These hematopoiesis-supportive clones also showed high gene expression of Jagged1, a Notch ligand, as well as high potential to deposit calcium after osteogenic induction. Thus, osteogenic hMSC clones may provide proper microenvironments for HSC expansion, ultimately conveying self-renewal signals to HSCs via the Notch pathway. However, they lost hematopoiesis-supporting activity after osteogenic differentiation. The hematopoiesis-supportive clones are potentially useful for hematopoietic microenvironment studies and as components of a coculture system for expansion of HSCs, free from contamination by xenogeneic pathogens.
Beneficial Effect of the Nonpeptidyl Low Molecular Weight Radical Scavenger IAC on Cultured Human Islet Function
Authors: Mancarella Rita , Del Guerra Silvia , Masini Matilde , Bugliani Marco , Valgimigli Luca , Pedulli Gian Franco , Paolini Moreno , Canistro Donatella , Armando Andrea , Soleti Antonio , Filipponi Franco , Mosca Franco , Boggi Ugo , Del Prato Stefano , Marchetti Piero , Lupi Roberto
Published: January 2009

We examined a possible protective effect of the nonpeptidyl low molecular weight radical scavenger IAC [bis(1-hydroxy-2,2,6,6-tetramethyl-4-piperidinyl)decanedioate di-hydrochloride] on isolated human islet cells against isolation and culture oxidative stress. Islets isolated from pancreases of nondiabetic multiorgan donors by collagenase digestion were purified by density gradient centrifugation. After the isolation, islets were either exposed or not exposed for 7 days to 10 μmol/L IAC. We found that IAC markedly reduced oxidative stress and ameliorated islets function. These results suggest that the use of IAC could be an interesting pharmacological approach for the treatment of the islets before transplantation.
Extracellular Matrix Stability of Primary Mammalian Chondrocytes and Intervertebral Disc Cells Cultured in Alginate-Based Microbead Hydrogels
Authors: Abbah S. A. , Lu W. W. , Peng S. L. , Aladin D. M. K. , Li Z. Y. , Tam W. K. , Cheung K. M. C. , Luk K. D. K. , Zhou Guang-Qian
Published: January 2009

Three-dimensional alginate constructs are widely used as carrier systems for transplantable cells. In the present study, we evaluated the chondrogenic matrix stability of primary rat chondrocytes and intervertebral disc (IVD) cells cultured in three different alginate-based microbead matrices to determine the influence of microenvironment on the cellular and metabolic behaviors of chondrogenic cells confined in alginate microbeads. Cells entrapped in calcium, strontium, or barium ion gelled microbeads were monitored with the live/dead dual fluorescent cell viability assay kit and the 1,9-dimethylmethylene blue (DMB) assay designed to evaluate sulfated glycosaminoglycan (s-GAG) production. Expression of chondrogenic extracellular matrix (ECM) synthesis was further evaluated by semiquantitative RT-PCR of sox9, type II collagen, and aggrecan mRNAs. Results indicate that Ca and Sr alginate maintained significantly higher population of living cells compared to Ba alginate (p < 0.05). Production of s-GAG was similarly higher in Ca and Sr alginate microbead cultures compared to Ba alginate microbeads. Although there was no significant difference between strontium and calcium up to day 14 of culture, Sr alginate showed remarkably improved cellular and metabolic activities on long-term cultures, with chondrocytes expressing as much as 31% and 44% greater s-GAG compared to calcium and barium constructs, respectively, while IVD cells expressed 63% and 74% greater s-GAG compared to calcium and barium constructs, respectively, on day 28. These findings indicate that Sr alginate represent a significant improvement over Ca- and Ba alginate microbeads for the maintenance of chondrogenic phenotype of primary chondrocytes and IVD cells.
Cell Surface Modification by Activated Polyethylene Glycol Prevents Allosensitization after Islet Transplantation
Authors: Wee Yu-Mee , Lim Dong-Gyun , Kim Yang-Hee , Kim Jin-Hee , Kim Song-Cheol , Yu Eunsil , Park Myung-Ok , Choi Monica Young , Park Youn-Hee , Jang Hyuk-Jai , Cho Eun-Young , Cho Myung-Hwan , Han Duck-Jong
Published: January 2009

The necessity to transplant islet tissue without the need for immunosuppressant therapy has led to the development of materials for immune modulation. Pegylation makes islets antigenically silent, protecting them from the adsorption of foreign protein and thus avoiding immune injury. The aim of this study is to determine whether pegylation of islets prolongs islet survival and function both during tissue culture and posttransplantation. We used cyanuric chloride-activated methoxy-polyethylene glycol for cell surface modification. To detect the pegylation effect on splenocytes, we measured antibody binding inhibition and abrogation of lymphocyte proliferation. To detect the pegylation effect on islet grafts, we performed rodent islet transplantation. Islet viability and function were maintained after pegylation. Pegylated islets showed a 90% decrease in antibody binding and decreased lymphocyte proliferation in a mixed lymphocyte culture. However, when pegylated islets were transplanted, no prolongation of graft survival was observed. When a subtherapeutic dose of immunosuppressant was given at the time of transplantation of pegylated islets, islet graft survival was significantly prolonged. In addition, when rats were sensitized with donor splenocytes, graft survival was prolonged by pegylation. We observed that pegylation of islets, combined with a subtherapeutic dose of immunosuppressant, protects the graft from rejection. Prolonged graft survival in sensitized recipients showed that pegylation of islets shifted the pattern of rejection from an acute humoral response to a less aggressive cellular alloresponse.
Proliferation of Hepatocyte Progenitor Cells Isolated from Adult Human Livers in Serum-Free Medium
Authors: Sasaki Kazunori , Kon Junko , Mizuguchi Toru , Chen Qijie , Ooe Hidekazu , Oshima Hideki , Hirata Koichi , Mitaka Toshihiro
Published: January 2009

Rat small hepatocytes (SHs) are committed progenitor cells that can differentiate into mature hepatocytes and can selectively proliferate in serum-free medium when they are cultured on hyaluronic acid (HA)-coated dishes. In this study we examined the separation of human SHs from adult human livers. We obtained liver tissues from the resected liver of 16 patients who underwent hepatic resections. Extracted liver specimens were clearly separate from the tumor regions with sufficient margins. Hepatic cells were isolated using the modified method of two-step collagenase perfusion. A low-speed centrifugation was performed and cells in the supernatant were finally cultured on HA-coated dishes in serum-free DMEM/F12 medium including nicotinamide, EGF, and HGF. Small-sized hepatocytes selectively proliferated to form colonies and many colonies continued growing for more than 3 weeks. The average number of cells in a colony was 38.6 ± 18.0, 79.0 ± 54.0, and 101.5 ± 115.7 at day 7, 14, and 21, respectively. About 0.04% of plated cells could form an SH colony. Immunocytochemistry showed that the cells forming a colony were positive for albumin, transferrin, keratin 8, and CD44. The results of RT-PCR showed that colony-forming cells expressed albumin, transferrin, α1-antitrypsin, fibrinogen, glutamine synthetase, many cytochrome P450s, and liver-enriched transcription factors (HNF3α, HNF4α, C/EBPα, and C/EBPβ). Furthermore, the cells expressed not only the genes of hepatic differentiated functions but also those of both hepatic stem cell marker (Thy1.1, EpCAM, AFP) and SH marker (CD44, D6.1A, BRI3). Albumin secretion into culture medium was also observed. Our results demonstrate the existence of hepatocyte progenitor cells in human adult livers, and the cells can grow in a serum-free medium on HA-coated dishes. Human SHs may be a useful source for cell transplantation as well as pharmaceutical and toxicological investigations.
Wheat proteins improve cryopreservation of rat hepatocytes
Authors: Grondin Mélanie , Hamel Francine , Averill‐Bates Diana A. , Sarhan Fathey
Published: January 2009

Hepatocytes are an important physiological model for in vitro studies of drug metabolism and toxicity. However, fresh hepatocytes are not always available and hence cyopreservation is needed to preserve large quantities until they are needed for these applications. Hepatocytes are extremely sensitive to damage induced by the freeze–thaw process, even after addition of traditional cryoprotectants such as dimethyl sulfoxide (DMSO). Furthermore, they do not proliferate in culture. We previously demonstrated that a crude wheat extract protects rat hepatocytes during cryopreservation and could provide a promising alternative to DMSO. We have considerably improved this novel cryopreservation procedure by using wheat extracts that are partially purified by either ammonium sulphate or acetone precipitation, or by using recombinant wheat freezing tolerance‐associated proteins such as WCS120, TaTIL, WCS19, and TaIRI‐2. These improved procedures enhance long‐term storage (2–12 months) and recovery of large quantities of healthy cells after cryopreservation, and maintain the differentiated functions of rat hepatocytes, compared to freshly isolated cells, as judged by viability (77–93%), adherence (77%) and metabolic functions of major cytochrome P450 isoforms CYP1A1/2, CYP2C6, CYP2D2, and CYP3A1/2. The advantage of using wheat proteins as cryopreservants is that they are non‐toxic, natural products that do not require animal serum, and are economical and easy to prepare. Biotechnol. Bioeng. 2009;103: 582–591. © 2009 Wiley Periodicals, Inc.
In silico strategy to rationally engineer metabolite production: A case study for threonine in Escherichia coli
Authors: Rodríguez‐Prados Juan‐Carlos , de Atauri Pedro , Maury Jérôme , Ortega Fernando , Portais Jean‐Charles , Chassagnole Christophe , Acerenza Luis , Lindley Nic D. , Cascante Marta
Published: January 2009

Genetic engineering of metabolic pathways is a standard strategy to increase the production of metabolites of economic interest. However, such flux increases could very likely lead to undesirable changes in metabolite concentrations, producing deleterious perturbations on other cellular processes. These negative effects could be avoided by implementing a balanced increase of enzyme concentrations according to the Universal Method [Kacser and Acerenza (1993) Eur J Biochem 216:361–367]. Exact application of the method usually requires modification of many reactions, which is difficult to achieve in practice. Here, improvement of threonine production via pyruvate kinase deletion in Escherichia coli is used as a case study to demonstrate a partial application of the Universal Method, which includes performing sensitivity analysis. Our analysis predicts that manipulating a few reactions is sufficient to obtain an important increase in threonine production without major perturbations of metabolite concentrations. Biotechnol. Bioeng. 2009;103: 609–620. © 2009 Wiley Periodicals, Inc.
Risk assessment in acute pancreatitis
Authors: Mofidi R , Patil P V , Suttie S A , Parks R W
Published: January 2009

Background

Acute pancreatitis has a variable natural history and in a proportion of patients is associated with severe complications and a significant risk of death. The various tools available for risk assessment in acute pancreatitis are reviewed.

Methods

Relevant medical literature from PubMed, Ovid, Embase, Web of Science and The Cochrane Library websites to May 2008 was reviewed.

Results and conclusion

Over the past 30 years several scoring systems have been developed to predict the severity of acute pancreatitis in the first 48–72 h. Biochemical and immunological markers, imaging modalities and novel predictive models may help identify patients at high risk of complications or death. Recently, there has been a recognition of the importance of the systemic inflammatory response syndrome and organ dysfunction.
Systematic review of endoscopic treatments for gastro-oesophageal reflux disease
Authors: Chen D , Barber C , McLoughlin P , Thavaneswaran P , Jamieson G G , Maddern G J
Published: January 2009

Background

The aim of this review was to assess the safety and efficacy of endoscopic procedures for gastro-oesophageal reflux disease.

Methods

Literature databases including Medline, Embase and PubMed were searched up to May 2006 without language restriction. Randomized controlled trials and non-randomized comparative studies with at least ten patients in each study arm, and case series studies of at least ten patients, were included.

Results

A total of 33 studies examining seven endoscopic procedures (Stretta® procedure, Bard® EndoCinch™, Wilson-Cook Endoscopic Suturing Device, NDO Plicator™, Enteryx®, Gatekeeper™ Reflux Repair System and Plexiglas®) were included in the review. Of the three procedures that were tested against sham controls (Stretta® procedure, Bard® EndoCinch™ and Enteryx®), patient outcomes in the treatment group were either as good as, or significantly better than, those of control patients in terms of heartburn symptoms, quality of life and medication usage. However, for the two procedures that were tested against laparoscopic fundoplication (Stretta® procedure and Bard® EndoCinch™), outcomes for patients in the endoscopic group were either as good as, or inferior to, those for the laparoscopic group.

Conclusion

At present there is insufficient evidence to determine the safety and efficacy of endoscopic procedures for gastro-oesophageal reflux disease, particularly in the long term.
Territorial belonging of the middle hepatic vein in living liver donor candidates evaluated by three-dimensional computed tomographic reconstruction and virtual liver resection
Authors: Radtke A , Sgourakis G , Sotiropoulos G C , Molmenti E P , Saner F H , Timm S , Malagó M , Lang H
Published: January 2009

Background

Postoperative venous congestion can lead to graft and remnant liver failure in living donor liver transplantation. This study was designed to delineate ‘territorial belonging’ of the middle hepatic vein (MHV) and to identify hepatic venous anatomy at high risk of outflow congestion.

Methods

MHV belonging patterns for right (RHL) and left (LHL) hemilivers were evaluated by three-dimensional computed tomographic reconstruction and virtual hepatectomy in 138 consecutive living liver donor candidates.

Results

The right hepatic vein (RHV) was dominant in 84·1 per cent and an accessory inferior hepatic vein (IHV) was present in 47·1 per cent of livers. Three MHV belonging types were identified for the RHL. Strong and complex MHV types A and C were associated with large RHL venous congestion. The MHV belonged to the LHL in 65·9 per cent, draining 37 per cent of this hemiliver. In virtual liver resections, left MHV type D was a risk category for small left liver remnants.

Conclusion

MHV territorial belonging types A and C were identified as high risk for RHL venous congestion. Their presence should prompt consideration of either inclusion of the MHV with the right graft or reconstruction of its tributaries, and preservation of IHV territory.
Sulphate-reducing bacteria and hydrogen sulphide in the aetiology of ulcerative colitis
Authors: Rowan F E , Docherty N G , Coffey J C , O'Connell P R
Published: January 2009

Background

The aetiology of ulcerative colitis is uncertain but may relate to environmental factors in genetically predisposed individuals. Sulphate-reducing bacteria (SRB) have been implicated through the harmful effects of hydrogen sulphide, a by-product of their respiration. Hydrogen sulphide is freely permeable to cell membranes and inhibits butyrate. This review examines the available evidence relating to SRB as a possible cause of ulcerative colitis.

Methods

A literature search was conducted using the PubMed database and search terms ‘sulphate reducing bacteria’, ‘hydrogen sulphide’, ‘ulcerative colitis’, ‘mucous gel layer’ and ‘trans-sulphuration’.

Results

Search results were scrutinized and 113 pertinent full-text articles were selected for review. Collected data related to hydrogen sulphide metabolism, SRB respiration, mucous gel layer composition and their association with ulcerative colitis.

Conclusion

There is evidence to implicate SRB as an environmental factor in ulcerative colitis. More sophisticated mucosal dissection and molecular techniques using bacteria-directed probes are required to determine an association definitively.
Randomized clinical trial of groin hernia repair with titanium-coated lightweight mesh compared with standard polypropylene mesh (Br J Surg 2008; 95: 1226–1231)
Authors: Lee Ling Hong
Published: January 2009

The Editors welcome topical correspondence from readers relating to articles published in the Journal. Responses should be sent electronically via the BJS website (www.bjs.co.uk). All letters will be reviewed and, if approved, appear on the website. A selection of these will be edited and published in the Journal. Letters must be no more than 250 words in length.
Lactide Polymerisation with Air‐Stable and Highly Active Zinc Complexes with Guanidine–Pyridine Hybrid Ligands
Authors: Börner Janna , Flörke Ulrich , Huber Klaus , Döring Artjom , Kuckling Dirk , Herres‐Pawlis Sonja
Published: January 2009

New class of air‐stable catalystsfor lactide polymerisation: Guanidine–pyridine hybrid ligands (picture, left) were used to prepare a series of zinc complexes (e.g., depicted cation [ZnL2(CF3SO3)]+, where L is the quinoline‐containing ligand with R1=R2=R3=R4=Me), in which the ligand binds through two different N‐donor atoms. The zinc complexes show high activity in ring‐opening polymerisation ofd,l‐lactide (right), giving polylactide with molecular masses up to 176 000 g mol−1and in high yield.

magnified image

The synthesis of zinc complexes of guanidine–pyridine hybrid ligands [Zn(DMEGpy)Cl2] (C1), [Zn(TMGpy)Cl2] (C2), [Zn(DMEGqu)Cl2] (C3), [Zn(TMGqu)Cl2] (C4), [Zn(DMEGpy)(CH3COO)2] (C5), [Zn(TMGpy)(CH3COO)2] (C6), [Zn(DMEGqu)(CH3COO)2] (C7), [Zn(TMGqu)(CH3COO)2] (C8), [Zn(DMEGqu)2(CF3SO3)][CF3SO3] (C9) and [Zn(TMGqu)2(CF3SO3)][CF3SO3] (C10) is reported. These zinc complexes were completely characterised and screened regarding their activity in the ring‐opening polymerisation ofd,l‐lactide. They proved to be active initiators in lactide bulk polymerisation, and polylactides with molecular weights (Mw) up to 176 000 g mol−1could be obtained. They combine high activity with robustness towards moisture and air. The influence of reaction temperature and of the anionic component of the zinc salt on the activity of the catalyst, as well as the occurrence of undesired side reactions, was investigated. By correlating these findings with the structural study on the zinc complexes we could deduce a structure–reactivity relationship for the zinc catalysts. This study was accompanied by DFT calculations. The bis‐chelate triflate complexesC9andC10, supported by quinoline–guanidine ligandsL3andL4, exhibit by far the highest reactivity. Systematic comparison of these complexes with their mono‐chelate counterparts and their bis‐guanidine analogues allows the attributes that promote polymerisation by neutral guanidine ligand systems to be elucidated: accessibility to the zinc centre and Lewis acidity.