bluuebunny/crossref_metadata_2025 huggingface dataset:
Longitudinal data on telomere length in leukocytes from newborn baboons support a marked drop in stem cell turnover around 1 year of age
Authors: Baerlocher Gabriela M. , Rice Karen , Vulto Irma , Lansdorp Peter M.
Published: December 2006

Stem cells of various tissues are typically defined as multipotent cells with ‘self‐renewal’ properties. Despite the increasing interest in stem cells, surprisingly little is known about the number of times stem cells can or do divide over a lifetime. Based on telomere‐length measurements of hematopoietic cells, we previously proposed that the self‐renewal capacity of hematopoietic stem cells is limited by progressive telomere attrition and that such cells divide very rapidly during the first year of life. Recent studies of patients with aplastic anemia resulting from inherited mutations in telomerase genes support the notion that the replicative potential of hematopoietic stem cells is directly related to telomere length, which is indirectly related to telomerase levels. To revisit conclusions about stem cell turnover based on cross‐sectional studies of telomere length, we performed a longitudinal study of telomere length in leukocytes from newborn baboons. All four individual animals studied showed a rapid decline in telomere length (∼2–3 kb) in granulocytes and lymphocytes in the first year after birth. After 50–70 weeks the telomere length appeared to stabilize in all cell types. These observations suggest that hematopoietic stem cells, after an initial phase of rapid expansion, switch at around 1 year of age to a different functional mode characterized by a markedly decreased turnover rate.
Design and synthesis of compounds that extend yeast replicative lifespan
Authors: Yang Hongying , Baur Joseph A. , Chen Allen , Miller Christine , Sinclair David A.
Published: December 2006

This past decade has seen the identification of numerous conserved genes that extend lifespan in diverse species, yet the number of compounds that extend lifespan is relatively small. A class of compounds called STACs, which were identified as activators of Sir2/SIRT1 NAD+‐dependent deacetylases, extend the lifespans of multiple species in a Sir2‐dependent manner and can delay the onset of age‐related diseases such as cancer, diabetes and neurodegeneration in model organisms. Plant‐derived STACs such as fisetin and resveratrol have several liabilities, including poor stability and relatively low potency as SIRT1 activators. To develop improved STACs, stilbene derivatives with modifications at the 4’ position of the B ring were synthesized using a Horner‐Emmons‐based synthetic route or by hydrolyzing deoxyrhapontin. Here, we describe synthetic STACs with lower toxicity toward human cells, and higher potency with respect to SIRT1 activation and lifespan extension in Saccharomyces cerevisiae. These studies show that it is possible to improve upon naturally occurring STACs based on a number of criteria including lifespan extension.
Reduced Mortality: The Unexpected Impact of a Telephone‐Based Care Management Intervention for Older Adults in Managed Care
Authors: Alkema Gretchen E. , Wilber Kathleen H. , Shannon George R. , Allen Douglas
Published: December 2006

Objective.This analysis evaluated mortality over 24 months for Medicare managed care members who participated in the Care Advocate Program (CA Program) designed to link those with high health care utilization to home‐ and community‐based services.

Data Source.Secondary data from the CA Program, part of the California HealthCare Foundation's Elders in Managed Care Initiative.

Study Design.Randomized‐control trial in which participants (N=781) were randomly assigned to intent‐to‐treat (ITT) and control groups. ITT group received telephonic social care management and 12 months of follow‐up. Various multivariate analyses were used to evaluate mortality risk throughout multiple study periods controlling for sociodemographic characteristics, health status, and health care utilization.

Population Studied.Older adults (65+) enrolled in a Medicare managed care plan who had high health care utilization in the previous year.

Principal Findings.ITT group had a significantly lower odds of mortality throughout the study (OR=0.55;p=.005) and during the care management intervention (OR=0.45;p=.006), whereas differential risk in the postintervention period was not statistically significant. Other significant predictors of mortality were age, gender, three chronic conditions (cancer, heart disease, and kidney disease), and emergency room utilization.

Conclusions.Findings suggest that the care advocate model of social care management affected mortality while the program was in progress, but not after completion of the intervention phase. Key model elements accounted for the findings, which include individualized targeting, assessment, and monitoring; consumer choice, control, and participant self‐management; and bridging medical and social service delivery systems through direct linkages and communication.
The Political Economy of Government‐Issued Longevity Bonds
Authors: Brown Jeffrey R. , Orszag Peter R.
Published: December 2006

Abstract

This article explores the trade‐offs associated with government issuance of longevity bonds as a way of stimulating private annuity supply in the presence of aggregate mortality risk. We provide new calculations suggesting a 5 percent chance that aggregate mortality risk could ex post raise annuity costs for private insurers by as much as 5–10 percentage points, with the most likely effect based on historical patterns toward the lower end of that range. While we suspect that aggregate mortality risk does exert some upward pressure on annuity prices, evidence from private market pricing suggests that, to the extent that private insurers are accurately pricing this risk, the effect is less than 5 percentage points. We discuss ways that the private market can spread this risk, while emphasizing that the government has the unique ability to spread aggregate risk across generations. We note factors that might hamper such an efficient allocation of risk, including potential political incentives for the government to shift more than the optimal amount of risk onto future generations, and the possibility that government fiscal policy might allocate risk less efficiently within each generation than would private markets. We also discuss how large‐scale longevity bond issuance might affect government borrowing costs, as well as political economy aspects of how the proceeds from such a bond issuance might be used.
State Budgetary Processes and Reforms: The California Story
Authors: MUSSO JULIET , GRADDY ELIZABETH , GRIZARD JENNIFER
Published: December 2006

This paper analyzes state budgetary processes and reforms to inform California budgetary policy. We consider key institutional provisions, including budget periodicity, tax and expenditure limitations, balanced budget and reserve requirements, and supermajority vote requirements, and analyze the extent to which changes are likely to advance procedural norms. Our analysis suggests that empirically unproven assumptions and poorly articulated linkages between budgetary processes and outcomes have undermined the state's ability to understand the budgetary problem and identify effective reforms. We recommend a focus on procedural norms and related reforms that promote effective budgeting processes as a less partisan framework for reform.
Performance‐Based Budgeting: The Contribution of the Program Assessment Rating Tool
Authors: MULLEN PATRICK R.
Published: December 2006

Under the President's Management Agenda for performance and budget integration, the Office of Management and Budget (OMB) designed the Program Assessment Rating Tool (PART) to breath new life into performance‐based budgeting as envisioned by the Government Performance and Results Act (GPRA). This article discusses what PART is designed to do and how the PART process works. Based on recent Government Accountability Office (GAO) reports addressing implementation of PART in the last four fiscal years, the article answers such questions as: Has PART made a difference in program operations? What is the relationship between PART and GPRA? Has progress been made in improving the evidence base for PART assessments? How well does PART assess programs related to a common goal? What has been congressional reaction to the PART process? Are PART and performance budgeting making a difference in government?
Family Businesses Can Out–Compete: As Long as They Are Willing to Question the Chosen Path
Authors: Ensley Michael
Published: December 2006

This commentary extends the discussion of whether CEO tenure will lead to strategies that have a longer–term orientation by examining the moderating role of task conflict which may either foster a decision–making context in which a long–term orientation represents a superior approach to decision making, or foster one which leads to strategic inertia, depending upon its intensity. The findings indicate that family firms that persist with the same CEO tend to persist with the same strategy when the level of executive team task conflict is high.
Interorganizational Familiness: How Family Firms Use Interlocking Directorates to Build Community–Level Social Capital
Authors: Lester Richard H. , Cannella Albert A.
Published: December 2006

We draw on the concept of community–level social capital and apply it to the situation of a family–controlled public corporation. While traditional agency theory argues that agency costs are minimized in a family–controlled business (FCB) due to an improved alignment of owner and manager interests, we argue instead that FCBs endure additional agency costs uniquely related to the family firm organizational structure. To mitigate these additional costs, we propose that FCBs use board interlocks to build and maintain community–level social capital. That is, the intercorporate network of FCBs generates shared understandings, values, problem solving techniques, and approaches to dealing with family issues. Further, the network generates a level of social support for family business owners and managers grappling with challenges endemic to family control of public corporations. We generate a number of propositions that can be used in future research to test the theory developed here. We conclude with the assertion that the community–level social capital generated by the network of FCBs is an important reason for the survival and persistence of individual family firms, despite the existence of additional family–related costs.
How Family Firms Solve Intra–Family Agency Problems Using Interlocking Directorates: An Extension
Authors: Chua Jess H. , Steier Lloyd P. , Chrisman James J.
Published: December 2006

This commentary makes two contributions to a better understanding of interlocking directorates in family firms. First, we compare agency costs in family and nonfamily firms. Second, we present additional propositions on how interlocking directorates address agency issues in family firms.
The Complicating Factor of Life Cycles in Corporate Venturing
Authors: Hoy Frank
Published: December 2006

Does family matter in corporate venturing? Converting the question, can a family firm survive without corporate venturing? Life cycle theory contends that it is normal for an organization to form, grow, mature, decline, and die. Long–term survival, especially through multiple generations, would require renewal through innovation to avoid decay and death. Strategic corporate venturing may be the answer for many family firms. To innovate and prosper, a family enterprise must contend with multiple life cycles, rarely synchronized, any one of which may be in a decline stage at any point in time. This commentary examines how life cycles complicate the ability of families to plan strategically for corporate entrepreneurship.
Are We Family and Are We Treated as Family? Nonfamily Employees’ Perceptions of Justice in the Family Firm
Authors: Barnett Tim , Kellermanns Franz W.
Published: December 2006

The importance of justice perceptions in fostering positive job attitudes and value–creating behaviors in organizations is well established in the literature. Despite this, only a handful of studies have addressed justice in family firms, and none have presented a theoretical model illustrating how nonfamily employees’ justice perceptions may be influenced by family involvement in family firms. Here, we suggest that the level of family influence impacts the justice perceptions of nonfamily employees primarily through its effect on the human resource (HR) practices within family firms. Specifically, we propose that low levels of family influence tend to have little impact on the fairness of HR practices, that moderate levels of family influence tend to have positive effects on the fairness of HR practices, and that high levels of family influence tend to have negative effects on the fairness of HR decision processes and outcomes. Accordingly, we present and provide a conceptual support for a model that outlines the proposed relationships among family influence, family firms’ HR practices, and the justice perceptions of nonfamily employees.
Morphological Control of Centimeter Long Aluminum‐Doped Zinc Oxide Nanofibers Prepared by Electrospinning
Authors: Lin Dandan , Pan Wei , Wu Hui
Published: December 2006

Centimeter long aluminum‐doped zinc oxide (AZO) nanofibers were prepared by electrospinning from polyvinyl alcohol (PVA) aqueous solutions, and the fibers with controlled morphology were expected to have potential applications in gas‐sensing and optoelectronic devices. In our research, the diameter and morphology of the nanofibers can be controlled by the applied voltage, the concentration of PVA, and the aluminum (Al) dopant. The introduction of Al resulted in a decrease of the zinc oxide lattice constant by 0.41% and uniform distribution of the nanofiber diameters. Possible mechanisms were proposed to discuss the variations of diameter and morphology.
High‐Temperature Electrical Transport and Thermoelectric Power of Partially Substituted Ca3Co4O9‐Based Ceramics
Authors: Lin Yuan‐Hua , Nan Ce‐Wen , Liu Yuheng , Li Jingfeng , Mizokawa T. , Shen Zhijian
Published: December 2006

We present high‐temperature electrical transport and thermoelectric power of K and/or La‐doped Ca3Co4O9‐based ceramics. Temperature and doping dependence of electrical transport properties indicate that both K and La substitutions can increase electrical conductivity at a high temperature, which are mainly related to an increase in carrier concentration and carrier mobility. A metallic‐to‐semiconducting transition temperature (T*) can be observed and shifts to a lower temperature as the doping content increases. However, activation energy is almost independent of the doping. All of the samples show positive thermoelectric power, and the temperature dependence of the thermoelectric power exhibits a simple linear behavior at T>T*. Our experimental data indicate that all of the Ca3Co4O9‐based ceramic samples exhibit large thermoelectric power (∼120 to 180 μV/K).
Influence of cyclosporin A on quality of bone around integrated dental implants: a radiographic study in rabbits
Authors: Sakakura Celso Eduardo , Marcantonio Elcio , Wenzel Ann , Scaf Gulnara
Published: December 2006

Objectives: To evaluate the influence of cyclosporin A (CsA) administration on bone around integrated dental implants assessed by a bone quality index and by quantitative subtraction radiography.

Material and methods: A total of 36 machine surface commercial implants were placed in 18 adult rabbits. After a 3‐month healing period without any disturbance, the animals were randomly divided into three groups of six animals each. Group A was sacrificed at this time. CsA was injected subcutaneously in an immunosuppressive dose of 10 mg/kg/day in a test group (Group T), and a Group B served as a control, receiving only vehicle. After 3 months of cyclosporin administration, the animals of both Groups B and T were sacrificed. Radiographs were obtained at implant surgery and at the day of sacrifice with a CMOS sensor. Bone quality around the implants was compared between the groups using a bone quality index and quantitative subtraction radiography.

Results: The bone analysis showed that in Group T, the bone quality changed dramatically from a dense cortical to a loose trabecular bone structure (P<0.0001, χ2 test) while in Groups A and B there were no significant differences. Quantitative digital subtraction radiography showed significantly (P<0.05) lower gray shade values (radiographic density) in a region of bone formation around the implants in Group T (118±12) than in Groups A (161±6) and B (186±10).

Conclusion: Within the limits of this study, CsA administration has a negative effect on the quality of bone around integrated dental implant.
Bone formation after sinus augmentation with engineered bone
Authors: Zizelmann Christoph , Schoen Ralf , Metzger Marc Christian , Schmelzeisen Rainer , Schramm Alexander , Dott Britta , Bormann Kai‐Hendrik , Gellrich Nils Claudius
Published: December 2006

Objectives: The aim of the following investigation was to quantify the resorption rate of tissue‐engineered bone grafts in the maxillary sinus using volume measurements.

Material and methods: Sinus floor augmentation using autologous bone grafts from the iliac crest (n=17, group 1) was compared with commercially produced transplants of human cells seeded on polyglycolid–polylactid (PLGA) scaffolds (Oral Bone®) (n=14, group 2).

Results: The total resorption rate for autologous transplants 3 months post operation was 29%, while the tissue‐engineered bone showed a resorption rate of 90%.

The autologous bone had a bone density of up to 266–551 Hounsfield units (HU), while sufficient mineralization of tissue‐engineered bone was found in only one case (152 HU).

Conclusion: In this clinical study, the use of autologous cancellous bone grafts in sinus augmentation was more reliable than scaffolds containing cultured osteoblasts. Further tissue‐engineered bone transplants should be examined to draw general conclusions about the use of tissue‐engineered grafts compared with autologous bone grafts for maxillary sinus augmentation.
Pim‐1 induced polyploidy but did not affect megakaryocytic differentiation of K562 cells and CD34+ cells from cord blood
Authors: Jung Yun‐Jae , Chae Hee‐Chung , Seoh Ju‐Young , Ryu Kyung‐Ha , Park Hae‐Kyung , Kim Young‐Ju , Woo So‐Youn
Published: December 2006

In a previous study, we determined the gene expression profile of both megakaryocytic and non‐megakaryocytic lineage cells via serial analysis of gene expression and microarray methods, and demonstrated that Pim‐1 was expressed more abundantly in megakaryocytic lineage cells. In this study, we knocked down Pim‐1 in K562 cells, as well as in CD34+ cells from cord blood, via RNA interference, in order to analyze the effects of Pim‐1 expression on the megakaryocytic differentiation of these cells. We then additionally overexpressed the Pim‐1 genes in K562 cells, and conducted a comparison of these effects with those of RNAi cells on the course of megakaryocytic differentiation. The results of this study revealed that Pim‐1 knockdown exerted no effects on commitment or differentiation toward megakaryocytic lineage, as evidenced by the detected CD41+ or CD61+ cells, or on the number of megakaryocytic colony forming units. However, Pim‐1 knockdown was found to elicit a reduction in CD41+ cells with >4n DNA content, and a concomitant increase in the fraction of cells achieving a ploidy of >4n in the Pim‐1 overexpressing population of K562 cells. Collectively, the findings of these studies indicate that the expression of Pim‐1 expression is both necessary and sufficient for polyploidization, but is not critical to cytoplasmic differentiation on megakaryopoiesis.
Severe periodontal damage by an ultrasonic endodontic device: a case report
Authors: Walters John D. , Rawal Swati Y.
Published: December 2006

Abstract –  Heat produced within a root canal during use of an ultrasonic instrument can be conducted through the dentin into periodontal ligament, bone and soft tissue. If severe in intensity or long in duration, it can induce damage to these tissues. This report describes a case in which an ultrasonic endodontic instrument apparently induced severe damage to alveolar bone, gingiva and nasal mucosa in a 42‐year‐old female. Overheating of a maxillary central incisor caused necrosis of soft tissue and bone on the facial and mesial aspects and triggered a protracted inflammatory response in the adjacent nasal cavity. To relieve the severe discomfort associated with this damage, the patient chose to have her maxillary incisors extracted and replaced by a removable partial denture. A defect in the soft tissue and bone was present at a follow‐up visit 10 months after the extractions. While morbidity of this nature is rare, this case reinforces the need to maintain adequate cooling of ultrasonic instruments.
Tomato Fruit Development and Ripening Are Altered by the Silencing of LeEIN2 Gene
Authors: Zhu Hong‐Liang , Zhu Ben‐Zhong , Shao Yi , Wang Xiao‐Guang , Lin Xi‐Jin , Xie Yuan‐Hong , Li Ying‐Cong , Gao Hong‐Yan , Luo Yun‐Bo
Published: December 2006

Loss‐of‐function ethylene insensitive 2 (EIN2) mutations showed ethylene insensitivity in Arabidopsis, which indicated an essential role of EIN2 in ethylene signaling. However, the function of EIN2 in fruit ripening has not been investigated. To gain a better understanding of EIN2, the temporal regulation of LeEIN2 expression during tomato fruit development was analyzed. The expression of LeEIN2 was constant at different stages of fruit development, and was not regulated by ethylene. Moreover, LeEIN2‐silenced tomato fruits were developed using a virus‐induced gene silencing fruit system to study the role of LeEIN2 in tomato fruit ripening. Silenced fruits had a delay in fruit development and ripening, related to greatly descended expression of ethylene‐related and ripening‐related genes in comparison with those of control fruits. These results suggested LeEIN2 positively mediated ethylene signals during tomato development. In addition, there were fewer seeds and locules in the silenced fruit than those in the control fruit, like the phenotype of parthenocarpic tomato fruit. The content of auxin and the expression of auxin‐regulated gene were declined in silenced fruit, which indicated that EIN2 might be important for crosstalk between ethylene and auxin hormones.

(Managing editor: Li‐Hui Zhao)
Comparative Studies on the Allelopathic Effects of Ulva pertusa Kjellml, Corallina pilulifera Postl et Ruprl, and Sargassum thunbergii Mertl O. Kuntze on Skeletonema costatum (Grev.) Cleve
Authors: Wang Ren‐Jun , Xiao Hui , Zhang Pei‐Yu , Qu Liang , Cai Heng‐Jiang , Tang Xue‐Xi
Published: December 2006

In the present study, we evaluated the allelopathic effects of three macroalgae, namely Ulva pertusa Kjellml, Corallina pilulifera Postl et Ruprl, and Sargassum thunbergii Mertl O. Kuntze, on the growth of the microalga Skeletonema costatum (Grev.) Creve using culture systems in which the algae coexisted. The effects of the macroalgal culture medium filtrate on S. costatum were also investigated. Moreover, isolated co‐culture systems were built to confirm the existence of allelochemicals and preclude growth inhibition by direct contact. The coexistence assay data demonstrated that the growth of S. costatum was strongly inhibited when fresh tissues, dry powder and aqueous extracts were used; the allelochemicals were lethal to S. costatum at relatively higher concentrations. The effects of the macroalgal culture medium filtrate on the microalga showed both species specificity and complexity. The inhibitory effect of fresh macroalgal tissue and culture medium filtrate on the microalga was due to the alleochemicals released by the macroalgae. The results of the present study show that the allelopathic effects of macroalgae on the microalga are complex. The present study could shed light onto the basis of the interaction between macro‐and microalgae.

(Managing editor: Ping He)
CO2 Exchange and Chlorophyll Fluorescence of Phospho‐enolpyruvate Carboxylase Transgenic Rice Pollen Lines
Authors: Ling Li‐Li , Lin Hong‐Hui , Ji Ben‐Hua , Jiao De‐Mao
Published: December 2006

To elucidate the photosynthetic physiological characteristics and the physiological inherited traits of rice (Oryza sativa L.) hybrids and their parents, physiological indices of photosynthetic CO2 exchange and chlorophyll fluorescence parameters were measured in leaves of the maize phosphoenolpyruvate carboxylase (PEPC) transgenic rice as the male parent, sp. japonica rice cv. 9516 as the female parent, and the stable JAAS45 pollen line. The results revealed that the PEPC gene could be stably inherited and transferred from the male parent to the JAAS45 pollen line. Moreover, the JAAS45 pollen line exhibited high levels of PEPC activity, manifesting higher saturated photosynthetic rates, photosynthetic apparent quantum yield (AQY), photochemical efficiency of photosystem II and photochemical and non‐photochemical quenching, which indicated that the JAAS45 pollen line has a high tolerance to photo‐inhibition/photo‐oxidation under strong light and high temperature. Furthermore, JAAS45 was confirmed to still be a C3 plant by δ13C carbon isotope determination and was demonstrated to have a limited photosynthetic C4 microcycle by feeding with exogenous C4 primary products, such as oxaloacetate or malate, or phosphoenolpyruvate. The present study explains the physiological inherited properties of PEPC transgenic rice and provides an expectation for the integration of traditional breeding and biological technology.

(Managing editor: Ping He)
Cloning, E. coli Expression and Molecular Analysis of Amorpha‐4,11‐Diene Synthase from a High‐Yield Strain of Artemisia annua L.
Authors: Li Zhen‐Qiu , Liu Yan , Liu Ben‐Ye , Wang Hong , Ye He‐Chun , Li Guo‐Feng
Published: December 2006

Increasing demand of artemisinin in the treatment of malaria has placed substantial stress on the total artemisinin supplies world‐wide, so more attention has been paid to increasing the content of artemisinin in the Artemisia annua L. plant. In this study, amorpha‐4,11‐diene synthase (ADS) cDNA (ads1) and genomics gene (gads1) were cloned from a high‐yield A. annua strain 001. The activity of ADS1 was confirmed by heterogeneous overexpression of ads1 and in vitro enzymatic incubation. Reverse transcript‐polymerase chain reaction results demonstrated that ads1 expressed in leaves, flowers and young stems, but not in roots. This organ‐specific expression pattern of ads1 is consistent with that of artemisinin accumulation in the plant. The gads1 has a complex organization including seven exons and six introns, and belongs to class III terpene synthase. DNA gel blotting revealed that the ADS gene has at least four copies in the genome of strain 001. The higher copy numbers might be one of the reasons for its high artemisinin content.

(Managing editor: Wei Wang)
Pollen and Resource Limitation in Veratrum nigrum L. (Liliaceae), an Andromonoecious Herb
Authors: Liao Wan‐Jin , Song Qing‐Fa , Zhang Da‐Yong
Published: December 2006

Pollen limitation and resource limitation were invoked to account for the pattern that flowering plants produce more flowers and ovules than fruits and seeds. This study aimed to determine their relative importance in Veratrum nigrum, a self‐compatible, perennial, andromonoecious herb. In order to determine whether female production was limited by pollen grains on stigmas or by available resources, we performed supplemental hand pollination in three populations, male‐flower‐bud removal in three other populations, and emasculation of hermaphroditic flowers in still another population, resulting in a total of seven populations experimentally manipulated. Across the three populations, supplemental hand pollination did not significantly increase fruit set, seed number per fruit, and total seed production per individual, nor did emasculation of hermaphroditic flowers. Taken together, our results suggest that pollen grains deposited on stigmas were abundant enough to fertilize all the ovules. Male‐flower‐bud removal significantly increased the mean size of hermaphroditic flowers in all three populations. Female reproductive success was increased in one population, but not in the other two populations possibly due to heavy flower/seed predation. We concluded that the female reproductive success of V. nigrum was not limited by pollen grains but by available resources, which is consistent with Bateman's principle. Furthermore, the female reproduction increase of male‐flower‐bud removal individuals might suggest a trade‐off between male and female sexual functions.

(Managing editor: Wei Wang)
Complementation and Expression Analysis ofSoRab1AandSoRab2Ain Sugarcane Demonstrates Their Functional Diversification
Authors: Zhang Jia‐Ming , Sylvester Anne W , Li Ding‐Qin , Sun Xue‐Piao
Published: December 2006

Mammalian and plant Rab1 and Rab2 are small GTPases that regulate vesicle trafficking in the endoplasmic reticulum (ER) to Golgi compartments. Little is known about their functional diversification or potential interaction. We cloned sugarcane(Saccharum officinarumL.)Rab1AandRab2Agenes and studied their functional differences by expression and complementation experiments. We found differential expression of the two genes during sugarcane leaf development:SoRab2Aexpression declined from the dividing base to the maturing tip of the growing leaves, whereasSoRab1Awas constitutively expressed, suggesting that SoRab2A is required for cell division and expansion and SoRab1A is required for cells at all developmental stages. We used a yeast temperature sensitiveypt1‐A136Dmutant strain to further investigate these shared and unique functions. Ypt1 is a small GTPase that regulates vesicle transport in the same cellular location as Rab1 and Rab2. NeitherSoRab1AnorSoRab2Aalone could restore the growth of the mutant at restrictive temperatures whenSoRab1AandSoRab2Awere transformed separately. However,SoRab1Atransformants maintained normal morphology and viability at non‐permissive temperature, and resumed growth when returned to permissive temperature, whereasSoRab2Atransformants died at non‐permissive temperature, suggesting that SoRab1A function is required for a cell's viability. Mutant growth was fully restored whenSoRab1AandSoRab2Awere co‐transformed, indicating thatSoRab1AandSoRab2Acomplement each other and they both are needed to restore the function ofypt1‐A136D.These results demonstrate thatSoRab1AandSoRab2Aserve distinct but overlapping functions, mostly by regulating the transportation of different sets of proteins.

(Managing editor: Li‐Hui Zhao)
Ecophysiological Response of Plants to Combined Pollution from Heavy‐duty Vehicles and Industrial Emissions in Higher Humidity
Authors: Cui Hong‐Xia , Jiang Gao‐Ming , Niu Shu‐Li , Jiang Chuang‐Dao , Liu Mei‐Zhen , Yu Shun‐Li , Gao Lei‐Ming
Published: December 2006

Pollution can be aggravated in industrial areas if traffic exhausts are mixed with industrial emissions under high humidity conditions. Plants growing in such environments may suffer from severe stress. The impact of vehicle emissions on urban vegetation in an industrial area in Qingdao, China, was investigated by studying seven plant species at visible, physiological and chemical levels. The traits of plant species in certain environmental conditions were compared between a clear area, Badaguan (BDG), and polluted area, Roadside (RS). We found that foliar sulfur uptake for all species was not significantly high at RS compared with BDG, although the sulfur content of atmosphere and surface soils at RS were much higher than those at BDG. For Ailanthus altissima Swingle, the content of foliar pigment and net photosynthesis rate (PN) decreased by 20%. Meanwhile, leaves became incrassate and no visible leaf damage was noted, suggesting this species could adapt well to pollution. A 50% decrease in PN occurred in Hibiscus syriacus L., but there was no statistical change in content of chlorophyll a and b and water uptake. Also, thickened leaves may prevent the pollutant from permeation. Foliar water content was still at a low level, although a water compensation mechanism was established for Fraxinus chinensis Rosb. reflected by low water potential and high water use efficiency. More adversely, a 65% decrease in PN happened inevitably with the significant decomposition of photosynthetic pigments, which exhibited visible damage. We also noted in one evergreen species (Magnolia grandiflora L.) that water absorption driven by low water potential should be helpful to supply water loss induced by strong stomatal transpiration and maintain normal growth. Furthermore, photosynthetic pigment content did not decline statistically, but supported a stable net assimilation. Two herbaceous species, Poa annua L. and Ophiopogon japonicus Ker‐Gawl., were very tolerant to adverse stress compared to other woody species, especially in assimilation through a compensatory increase in leaf area. A more remarkable decline in PN (decrease 80%) was noted in the exotic but widespread species, Platanus orientalis L., with serious etiolation and withering being exhibited on the whole canopy. Our results suggested, special for woody species, that most native species are more tolerant to pollution and therefore should to be broadly used in a humid urban industrial environment with heavy‐duty vehicle emissions.

(Managing editor: Ya‐Qin Han)
Covalent Attachment of Lactase to Low‐Density Polyethylene Films
Authors: Goddard J.M. , Talbert J.N. , Hotchkiss J.H.
Published: December 2006

ABSTRACT:  Polymer films to which bioactive compounds such as enzymes are covalently attached offer potential for in‐package processing of food. β‐galactosidase (lactase) was covalently attached to surface‐functionalized low‐density polyethylene films. A two‐step wet chemical functionalization introduced 15.7 nmol/cm2 primary amines to the film surface. Contact angle, dye assays, X‐ray photoelectron spectroscopy, and appropriate protein assays were used to characterize changes in film surface chemistry after each step in the process of attachment. Glutaraldehyde was used to covalently attach lactase to the surface at a density of 6.0 μg protein per cm2 via reductive amination. The bond between the covalently attached lactase and the functionalized polyethylene withstood heat treatment in the presence of an ionic denaturant with 74% enzyme retention, suggesting that migration of the enzyme into the food product would be unlikely. The resulting polyethylene had an enzyme activity of 0.020 lactase units (LU)/cm2 (approximately 4500 LU/g). These data suggest that enzymes that may have applications in foods can be covalently attached to inert polymer surfaces, retain significant activity, and thus have potential as a nonmigratory active packaging materials.
Trans‐Cinnamaldehyde from Cinnamomum zeylanicum Bark Essential Oil Reduces the Clindamycin Resistance of Clostridium difficile in vitro
Authors: Shahverdi A.R. , Monsef‐Esfahani H.R. , Tavasoli F. , Zaheri A. , Mirjani R.
Published: December 2006

ABSTRACT:  Therapy with antimicrobial drugs, such as clindamycin, that perturb the intestinal flora but fail to inhibit growth of other microorganisms can permit the proliferation of Clostridium difficile and the elaboration of exotoxin. Therefore, there has been increasing interest in the use of inhibitors of antibiotic resistance for use in combination therapy. The essential oil of Cinnamomum zeylanicum bark enhanced the bactericidal activity of clindamycin and decreased the minimum inhibitory concentration of clindamycin required for a toxicogenic strain of C. difficile. Thin‐layer chromatography (TLC) analysis of the essential oil separated a fraction (Rf= 0.54) that was the most effective at enhancing the clindamycin antimicrobial activity. Using gas liquid chromatography and known standards, the active fraction was identified as trans‐cinnamaldehyde (3‐phenyl‐2‐Propenal). Combinations of clindamycin and trans‐cinnamaldehyde were tested to determine the fractional inhibitory concentration (FIC) index by conventional checkerboard titration. The FIC index for C. difficile was found to be 0.312, which confirmed the synergistic actions of clindamycin and trans‐cinnamaldehyde. The presence of 20 μg/mL of trans‐cinnamaldehyde decreased the MIC of clindamycin for C. difficile 16‐fold, from 4.0 to 0.25 μg/mL. These results signify that low concentrations of trans‐cinnamaldehyde elevate the antimicrobial action of clindamycin, suggesting a possible clinical benefit for utilizing these natural products for combination therapy against C. difficile.
Searching for New Mathematical Growth Model Approaches for Listeria monocytogenes
Authors: Valero A. , Hervás C. , García‐Gimeno R.M. , Zurera G.
Published: December 2006

ABSTRACT:  Different secondary modeling approaches for the estimation of Listeria monocytogenes growth rate as a function of temperature (4 to 30 °C), citric acid (0% to 0.4% w/v), and ascorbic acid (0% to 0.4% w/v) are presented. Response surface (RS) and square‐root (SR) models are proposed together with different artificial neural networks (ANN) based on product functions units (PU), sigmoidal functions units (SU), and a novel approach based on the use of hybrid functions units (PSU), which results from a combination of PU and SU. In this study, a significantly better goodness‐of‐fit was obtained in the case of the ANN models presented, reflected by the lower SEP values obtained (< 24.23 for both training and generalization datasets). Among these models, the SU model provided the best generalization capacity, displaying lower RMSE and SEP values, with fewer parameters compared to the PU and PSU models. The bias factor (Bf) and accuracy factor (Af) of the mathematical validation dataset were above 1 in all cases, providing fail‐safe predictions. The balance between generalization properties and the ease of use is the main consideration when applying secondary modeling approaches to achieve accurate predictions about the behavior of microorganisms.
Development of Reformative Surgery Method Using Partial Freezing for the Liver
Authors: Takahashi M. , Nomura S. , Jindai M. , Shibata S. , Zhu X. , Watanabe Y. , Kawachi K. , Okabe N.
Published: December 2006

To minimize surgical stresses including blood loss and operation time to the patients during hepatic resection, we studied the feasibility of a combination of a partial liver freezing technique and shape-memory alloy, which also enables a free-designed resection curve. In this surgical procedure, the region surrounding a tumor in the liver is frozen to excise and prevent hemorrhage. The liver was frozen by a Peltier module. The effects of cooling rate and freezing temperature on the excision force that arise between a scalpel and the liver are carried out experimentally as a basic research for partial freezing surgical procedures. A porcine liver was used as a liver sample. The physical properties were estimated by using the finite element method based on the heat transfer characteristics of the liver. Isolation of the liver was conducted using a scalpel attached to the end-effector of a 3 degrees of freedom robot. In the experiments, the minimum excision force was obtained at a temperature between 272K and 275K; therefore, it is preferable that the liver be excised within this temperature range. Lowering of the cooling rate decreases the excision force even if the temperature of the liver remains unchanged. The lower the temperature of the liver is, the larger the increment rate of excision force is with regard to the cooling rate.
Fiber Kinematics of Small Intestinal Submucosa Under Biaxial and Uniaxial Stretch
Authors: Gilbert Thomas W. , Sacks Michael S. , Grashow Jonathan S. , Woo Savio L.-Y. , Badylak Stephen F. , Chancellor Michael B.
Published: December 2006

Improving our understanding of the design requirements of biologically derived collagenous scaffolds is necessary for their effective use in tissue reconstruction. In the present study, the collagen fiber kinematics of small intestinal submucosa (SIS) was quantified using small angle light scattering (SALS) while the specimen was subjected to prescribed uniaxial or biaxial strain paths. A modified biaxial stretching device based on Billiar and Sacks (J. Biomech., 30, pp. 753–7, 1997) was used, with a real-time analysis of the fiber kinematics made possible due to the natural translucency of SIS. Results indicated that the angular distribution of collagen fibers in specimens subjected to 10% equibiaxial strain was not significantly different from the initial unloaded condition, regardless of the loading path (p=0.31). Both 10% strip biaxial stretch and uniaxial stretches of greater than 5% in the preferred fiber direction led to an increase in the collagen fiber alignment along the same direction, while 10% strip biaxial stretch in the cross preferred fiber direction led to a broadening of the distribution. While an affine deformation model accurately predicted the experimental findings for a biaxial strain state, uniaxial stretch paths were not accurately predicted. Nonaffine structural models will be necessary to fully predict the fiber kinematics under large uniaxial strains in SIS.
A Penetration-Based Finite Element Method for Hyperelastic 3D Biphasic Tissues in Contact. Part II: Finite Element Simulations
Authors: Ün Kerem , Spilker Robert L.
Published: December 2006

The penetration method allows for the efficient finite element simulation of contact between soft hydrated biphasic tissues in diarthrodial joints. Efficiency of the method is achieved by separating the intrinsically nonlinear contact problem into a pair of linked biphasic finite element analyses, in which an approximate, spatially and temporally varying contact traction is applied to each of the contacting tissues. In Part I of this study, we extended the penetration method to contact involving nonlinear biphasic tissue layers, and demonstrated how to derive the approximate contact traction boundary conditions. The traction derivation involves time and space dependent natural boundary conditions, and requires special numerical treatment. This paper (Part II) describes how we obtain an efficient nonlinear finite element procedure to solve for the biphasic response of the individual contacting layers. In particular, alternate linearization of the nonlinear weak form, as well as both velocity-pressure, v‐p, and displacement-pressure, u‐p, mixed formulations are considered. We conclude that the u‐p approach, with linearization of both the material law and the deformation gradients, performs best for the problem at hand. The nonlinear biphasic contact solution will be demonstrated for the motion of the glenohumeral joint of the human shoulder joint.
The Deformation of an Erythrocyte Under the Radiation Pressure by Optical Stretch
Authors: Liu Yong-Ping , Li Chuan , Liu Kuo-Kang , Lai Alvin C. K.
Published: December 2006

In this paper, the mechanical properties of erythrocytes were studied numerically based upon the mechanical model originally developed by Pamplona and Calladine (ASME J. Biomech. Eng., 115, p. 149, 1993) for liposomes. The case under study is the erythrocyte stretched by a pair of laser beams in opposite directions within buffer solutions. The study aims to elucidate the effect of radiation pressure from the optical laser because up to now little is known about its influence on the cell deformation. Following an earlier study by Guck et al. (Phys. Rev. Lett., 84, p. 5451, 2000; Biophys. J., 81, p. 767, 2001), the empirical results of the radiation pressure were introduced and imposed on the cell surface to simulate the real experimental situation. In addition, an algorithm is specially designed to implement the simulation. For better understanding of the radiation pressure on the cell deformation, a large number of simulations were conducted for different properties of cell membrane. Results are first discussed parametrically and then evaluated by comparing with the experimental data reported by Guck et al. An optimization approach through minimizing the errors between experimental and numerical data is used to determine the optimal values of membrane properties. The results showed that an average shear stiffness around 4.611×10-6Nm−1, when the nondimensional ratio of shear modulus to bending modulus ranges from 10 to 300. These values are in a good agreement with those reported in literature.
Validation of CFD Simulations of Cerebral Aneurysms With Implication of Geometric Variations
Authors: Hoi Yiemeng , Woodward Scott H. , Kim Minsuok , Taulbee Dale B. , Meng Hui
Published: December 2006

Background. Computational fluid dynamics (CFD) simulations using medical-image-based anatomical vascular geometry are now gaining clinical relevance. This study aimed at validating the CFD methodology for studying cerebral aneurysms by using particle image velocimetry (PIV) measurements, with a focus on the effects of small geometric variations in aneurysm models on the flow dynamics obtained with CFD. Method of Approach. An experimental phantom was fabricated out of silicone elastomer to best mimic a spherical aneurysm model. PIV measurements were obtained from the phantom and compared with the CFD results from an ideal spherical aneurysm model (S1). These measurements were also compared with CFD results, based on the geometry reconstructed from three-dimensional images of the experimental phantom. We further performed CFD analysis on two geometric variations, S2 and S3, of the phantom to investigate the effects of small geometric variations on the aneurysmal flow field. Results. We found poor agreement between the CFD results from the ideal spherical aneurysm model and the PIV measurements from the phantom, including inconsistent secondary flow patterns. The CFD results based on the actual phantom geometry, however, matched well with the PIV measurements. CFD of models S2 and S3 produced qualitatively similar flow fields to that of the phantom but quantitatively significant changes in key hemodynamic parameters such as vorticity, positive circulation, and wall shear stress. Conclusion. CFD simulation results can closely match experimental measurements as long as both are performed on the same model geometry. Small geometric variations on the aneurysm model can significantly alter the flow-field and key hemodynamic parameters. Since medical images are subjected to geometric uncertainties, image-based patient-specific CFD results must be carefully scrutinized before providing clinical feedback.
Correspondence of Low Mean Shear and High Harmonic Content in the Porcine Iliac Arteries
Authors: Himburg Heather A. , Friedman Morton H.
Published: December 2006

Background. Temporal variations in shear stress have been suggested to affect endothelial cell biology. To better quantify the range of dynamic shear forces that occur in vivo, the frequency content of shear variations that occur naturally over a cardiac cycle in the iliac arteries was determined. Method of Approach. Computational fluid dynamic calculations were performed in six iliac arteries from three juvenile swine. Fourier analysis of the time-varying shear stress computed at the arterial wall was performed to determine the prevalence of shear forces occurring at higher frequencies in these arteries. Results. While most of each artery experienced shear forces predominantly at the frequency of the heart rate, the frequency spectra at certain regions were dominated by shear forces at higher frequencies. Regions whose frequency spectra were dominated by higher harmonics generally experienced lower mean shear stress. The negative correlation between shear and dominant harmonic was significant (p=0.002). Conclusions. Since lesion development typically occurs in regions experiencing low time-average shear stress, this result suggests that the frequency content of the shear exposure may also be a contributing factor in lesion development. A better understanding of the vascular response to shear components of different frequencies might help rationalize the notion of "disturbed flow" as a hemodynamic entity.