bluuebunny/crossref_metadata_2025 huggingface dataset:
Insulin Regulates Islet α-Cell Function by Reducing KATP Channel Sensitivity to Adenosine 5′-Triphosphate Inhibition
Authors: Leung Yuk M. , Ahmed Ishtiaq , Sheu Laura , Gao Xiaodong , Hara Manami , Tsushima Robert G. , Diamant Nicholas E. , Gaisano Herbert Y.
Published: February 2006

Glucose regulates pancreatic islet α-cell glucagon secretion directly by its metabolism to generate ATP in α-cells, and indirectly via stimulation of paracrine release of β-cell secretory products, particularly insulin. How the cellular substrates of these pathways converge in the α-cell is not well known. We recently reported the use of the MIP-GFP (mouse insulin promoter-green fluorescent protein) mouse to reliably identify islet α- (non-green cells) and β-cells (green cells), and characterized their ATP-sensitive K+ (KATP) channel properties, showing that α-cell KATP channels exhibited a 5-fold higher sensitivity to ATP inhibition than β-cell KATP channels. Here, we show that insulin exerted paracrine regulation of α-cells by markedly reducing the sensitivity of α-cell KATP channels to ATP (IC50 = 0.18 and 0.50 mm in absence and presence of insulin, respectively). Insulin also desensitized β-cell KATP channels to ATP inhibition (IC50 = 0.84 and 1.23 mm in absence and presence of insulin, respectively). Insulin effects on both islet cell KATP channels were blocked by wortmannin, indicating that insulin acted on the insulin receptor-phosphatidylinositol 3-kinase signaling pathway. Insulin did not affect α-cell A-type K+ currents. Glutamate, known to also inhibit α-cell glucagon secretion, did not activate α-cell KATP channel opening. We conclude that a major mechanism by which insulin exerts paracrine control on α-cells is by modulating its KATP channel sensitivity to ATP block. This may be an underlying basis for the proposed sequential glucose-insulin regulation of α-cell glucagon secretion, which becomes distorted in diabetes, leading to dysregulated glucagon secretion.
A Novel Cytochrome P450, Zebrafish Cyp26D1, Is Involved in Metabolism of All-trans Retinoic Acid
Authors: Gu Xingxing , Xu Fang , Song Wei , Wang Xiaolin , Hu Ping , Yang Yumin , Gao Xiang , Zhao Qingshun
Published: February 2006

Retinoid signaling is essential for development of vertebrate embryos, and its action is mainly through retinoic acid (RA) binding to its RA receptors and retinoid-X receptors, while the critical concentration and localization of RA in embryos are determined by the presence and activity of retinal dehydrogenases (for RA synthesis) and cytochrome P450 RAs (Cyp26s) (for degradation of RA). Previously, we identified a novel cyp26 gene (cyp26d1) in zebrafish that is expressed in hindbrain during early development. Using reverse-phase HPLC analyses, we show here that zebrafish Cyp26D1 expressed in 293T cells could metabolize all-trans RA, 9-cis RA, and 13-cis RA, but could not metabolize retinol or retinal. The metabolites of all-trans RA produced by Cyp26D1 were the same as that produced by Cyp26A1, which are mainly 4-hydroxy-all-trans-RA and 4-oxo-all-trans-RA. Performing mRNA microinjection into zebrafish embryos, we demonstrated that overexpression of Cyp26D1 in embryos not only caused the distance between rhombomere 5 and the first somite of the injected embryos to be shorter than control embryos but also resulted in left-right asymmetry of somitogenesis in the injected embryos. These alterations were similar to those caused by the overexpression of cyp26a1 in zebrafish embryos and to that which resulted from treating embryos with 1 μm 4-diethylamino-benzaldehyde (retinal dehydrogenase inhibitor), implying that cyp26d1 can antagonize RA activity in vivo. Together, our in vitro and in vivo results provided direct evidence that zebrafish Cyp26D1 is involved in RA metabolism.
Differentiation of Amphetamine/Methamphetamine and Other Cross-Immunoreactive Sympathomimetic Amines in Urine Samples by Serial Dilution Testing
Authors: Woodworth Alison , Saunders Al N , Koenig John W , Moyer Thomas P , Turk John , Dietzen Dennis J
Published: February 2006

Background: Immunoassay-based screening for amphetamines has a variable positive predictive value (PPV) for detecting amphetamine abuse. The lack of immunoassay specificity necessitates confirmatory testing by gas chromatography–mass spectrometry (GC/MS), but the technical complexity and expense of GC/MS limit its availability. Physicians may make decisions regarding patient disposition based on unverified results. In this study we assessed the utility of using dose–response properties to distinguish urine samples containing amphetamines from samples containing cross-immunoreactive species.

Methods: Urine was supplemented with known concentrations of amphetamine, methamphetamine, methylenedioxymethamphetamine (MDMA), or pseudoephedrine. Using a series of dilutions, we determined the maximum change in rate over the fractional change in concentration for each compound in the Emit® II amphetamine/methamphetamine immunoassay. Patient urine samples that screened positive for amphetamines were diluted 1:1, 1:10, and 1:20, and maximum slope estimates within the dynamic assay range were determined. An optimal slope cutoff that differentiated samples containing (meth)amphetamine from those containing cross-reacting species was determined by ROC analysis.

Results: The slope of the dose response was largest for amphetamine and methamphetamine, followed by MDMA and pseudoephedrine. The optimum slope cutoff for identifying patient specimens containing (meth)amphetamine was 320 (sensitivity, 96%; specificity, 90%; PPV, 92%). High concentrations of less reactive compounds may mask low concentrations of amphetamines.

Conclusions: Use of the slope of the dose–response relationship in patient urine specimens can enhance the PPV of presumptive positive immunoassay results but does not exclude the presence of low amphetamine concentrations in samples containing high concentrations of cross-reactive species.
Transparenz haptischer Telepräsenzsysteme mit konstanter Zeitverzögerung (Transparency of Haptic Telepresence Systems with Constant Time Delay)
Authors: Hirche Sandra , Buss Martin
Published: February 2006

In diesem Artikel wird untersucht, wie sich Kommunikationslatenzen zusammen mit einer passivitätsbasierten Regelungsstrategie auf die Performanz, gemessen als Transparenz, eines haptischen Telepräsenzsystems auswirken. Die gefühlte mechanische Impedanz, im Speziellen deren physikalische Parameter Masse, Steifigkeit und Dämpfung, werden als Funktion der Kommunikationslatenz und der Regelungsparameter hergeleitet und mit der Umgebungs-Impedanz verglichen. Die Ergebnisse werden unter Aspekten der menschlichen Wahrnehmung diskutiert. Darauf basierend wird eine transparente Auslegung der Regelungsstrategie vorgeschlagen, wobei die Eigenschaften von realen Telepräsenzsystemen berücksichtigt werden. Abschließend erfolgt die Validierung der Resulate in einem Telepräsenz-Experiment mit einem Freiheitsgrad.
Quellenlokalisierung auf der Basis räumlich verteilter Konzentrationsmessungen (Source Localization based on Spatially Distributed Concentration Measurements)
Authors: Matthes Jörg
Published: February 2006

In diesem Beitrag wird ein neues, zweistufiges Verfahren zur Lokalisierung von Emissionsquellen vorgestellt. Es wird davon ausgegangen, dass der Stofftransport durch turbulente Diffusion und Advektion hervorgerufen wird. Im ersten Schritt des zweistufigen Verfahrens wird zunächst für jeden Sensor i die Menge von Punkten P
i ermittelt, auf denen sich aus Sicht von Sensor i die Quelle befinden kann. Im zweiten Schritt wird dann ein Schätzwert für den Quellort durch Bilden der Schnittmenge aller P
i bestimmt. Das neue Verfahren umgeht das Problem schlechter Konvergenz iterativer Verfahren, die versuchen den Quellort durch Minimieren des quadratischen Ausgangsfehlers zu ermitteln. Abschließend werden experimentelle Ergebnisse vorgestellt.
Pólya-Eggenberger F-S models of order (k1, k2)
Authors: Sen Kanwar , Agarwal Manju , Bhattacharya Sonali
Published: February 2006

Pólya-Eggenberger F-S Models of order (k1, k2) are proposed and their probability functions obtained. The results are extended to obtain probability functions of Inverse Pólya-Eggenberger F-S models of order (k1, k2). The Binomial Distribution of order (k1, k2) (see[4]) and some new discrete distributions of order (k1, k2) are obtained as particular cases of these models.
On centralizers of semiprime rings with involution
Authors: Vukman Joso , Kosi-Ulbl Irena
Published: February 2006

LetRbe a 2-torsion free semiprime *-ring and letT:R?Rbe an additive mapping such thatT(xx*)=T(x)x* is fulfilled for allx?R. In this caseT(xy)=T(x)yholds for all pairsx,y?R.
Law of the iterated logarithm for self-normalized sums and their increments
Authors: Liang Han-Ying , Baek Jong-Il , Steinebach Josef
Published: February 2006

LetX1,X2,… be independent, but not necessarily identically distributed random variables in the domain of attraction of a stable law with index 0<a<2. This paper usesMn=max1?i?n|Xi| to establish a self-normalized law of the iterated logarithm (LIL) for partial sums. Similarly self-normalized increments of partial sums are studied as well. In particular, the results of self-normalized sums of Horváth and Shao[9]under independent and identically distributed random variables are extended and complemented. As applications, some corresponding results for self-normalized weighted sums of iid random variables are also concluded.
Short-Term Effectiveness of Constructed Barriers at Protecting Apache Trout
Authors: Avenetti Lorraine D. , Robinson Anthony T. , Cantrell Christopher J.
Published: February 2006

Placement of fish migration barriers (primarily of gabion construction) on select streams is one of the major recovery actions used to isolate and protect upstream populations of Apache trout Oncorhynchus gilae apache from downstream populations of nonnative salmonids. However, the effectiveness of the recovery action has not been evaluated. We evaluated the success of constructed barriers at preventing upstream movement of nonnative salmonids into areas occupied by native Apache trout. We collected and marked salmonids downstream of six barriers on six streams in the White Mountains of east-central Arizona and subsequently electrofished upstream of the barriers to determine whether marked fish had moved past them. Only 1 of 1,436 marked salmonids was collected upstream of one of the six barriers evaluated over a 3-year period. Our results showed that the barriers evaluated in our study are effective for a short term; however, long-term evaluation is needed, as these failure rates represent minimum failure rates and they could increase as the number of years since barrier construction increases.
Utility and Validation of Day and Night Snorkel Counts for Estimating Bull Trout Abundance in First- to Third-Order Streams
Authors: Thurow Russell F. , Peterson James T. , Guzevich John W.
Published: February 2006

Despite the widespread use of underwater observation to census stream-dwelling fishes, the accuracy of snorkeling methods has rarely been validated. We evaluated the efficiency of day and night snorkel counts for estimating the abundance of bull trout Salvelinus confluentus in 215 sites within first- to third-order streams. We used a dual-gear approach that applied multiple-pass electrofishing catch data adjusted for capture efficiency to estimate true or baseline fish abundance. Our multiple-pass electrofishing capture efficiency models were based on a prior study and used recapture data for known numbers of individually marked fish. Snorkeling efficiency was estimated by comparing day and night snorkel counts with the baseline. We also evaluated the influence of fish size and stream habitat features on snorkeling efficiency. Bull trout snorkeling efficiency was higher at night (mean = 33.2%) than during the day (mean = 12.5%). Beta-binomial regression indicated that bull trout day and night snorkeling efficiencies were positively related to fish size and negatively related to stream width and habitat characteristics. Day snorkeling efficiency also was positively influenced by water temperature and nonlinearly related to underwater visibility, whereas night snorkeling efficiency was nonlinearly related to water temperature and pool abundance. Although bull trout were our target species, day and night snorkeling efficiencies combined for rainbow trout Oncorhynchus mykiss and subspecies of cutthroat trout O. clarkii averaged 32.3% and 18.0%, respectively. Our ability to detect and accurately count fish underwater was influenced by fish size, species, time of day, and stream habitat characteristics. Although snorkeling is versatile and has many advantages over other sampling methods, the use of raw snorkel counts unadjusted for the effects of these biases will result in biased conclusions. We recommend that biologists adjust underwater count data to minimize the effect of such biases. We illustrate how to apply sampling efficiency models to validate snorkel counts.
Abundance Trends and Status of the Little Colorado River Population of Humpback Chub
Authors: Coggins Lewis G. , Pine William E. , Walters Carl J. , Van Haverbeke David R. , Ward David , Johnstone Helene C.
Published: February 2006

The abundance of the Little Colorado River population of federally listed humpback chub Gila cypha in Grand Canyon has been monitored since the late 1980s by means of catch rate indices and capture–recapture-based abundance estimators. Analyses of data from all sources using various methods are consistent and indicate that the adult population has declined since monitoring began. Intensive tagging led to a high proportion (>80%) of the adult population being marked by the mid-1990s. Analysis of these data using both closed and open abundance estimation models yields results that agree with catch rate indices about the extent of the decline. Survival rates for age-2 and older fish are age dependent but apparently not time dependent. Back-calculation of recruitment using the apparent 1990s population age structure implies periods of higher recruitment in the late 1970s to early 1980s than is now the case. Our analyses indicate that the U.S. Fish and Wildlife Service recovery criterion of stable abundance is not being met for this population. Also, there is a critical need to develop new abundance indexing and tagging methods so that early, reliable, and rapid estimates of humpback chub recruitment can be obtained to evaluate population responses to management actions designed to facilitate the restoration of Colorado River native fish communities.
Estimates of Tackle Loss for Five Minnesota Walleye Fisheries
Authors: Radomski Paul , Heinrich Tom , Jones Thomas S. , Rivers Pat , Talmage Phil
Published: February 2006

Lead poisoning in waterbirds from ingestion of lead fishing items may be a growing problem. There are few studies that quantify tackle loss for recreational fisheries. Tackle loss from large recreational lake fisheries in Minnesota is unknown. The objectives of this study were to determine tackle loss for five large lake fisheries targeting walleye Sander vitreus in Minnesota by means of creel surveys and to estimate recent cumulative losses. Mean rates of tackle loss were low: 0.0127/h for lures, 0.0081/h for large sinkers, 0.0057/h for small sinkers, 0.0247/h for jigs, and 0.0257/h for hooks. Many anglers lost no fishing tackle on a fishing trip. The estimated total loss of tackle for the five water bodies in the summer of 2004 was 214,811 items. Over 100,000 lead-based items were estimated to have been lost, representing about 1 metric ton of lead. Assuming 2004 lead tackle loss rates, estimates of cumulative lead item loss for Lake of the Woods and Mille Lacs and Rainy lakes from 1983 to 2004 were 285,000 (SE = 8,800), 1,033,000 (SE = 39,700), and 211,000 (SE = 8,400) items, respectively. In critical wildlife areas with high angling effort or high tackle loss rates, determining the impacts of lead tackle on wildlife would be prudent, and prohibiting the use of lead tackle may be necessary.
Age-Structured Mark–Recapture Analysis: A Virtual-Population-Analysis-Based Model for Analyzing Age-Structured Capture–Recapture Data
Authors: Coggins Lewis G. , Pine William E. , Walters Carl J. , Martell Steven J. D.
Published: February 2006

We present a new model to estimate capture probabilities, survival, abundance, and recruitment using traditional Jolly–Seber capture–recapture methods within a standard fisheries virtual population analysis framework. This approach compares the numbers of marked and unmarked fish at age captured in each year of sampling with predictions based on estimated vulnerabilities and abundance in a likelihood function. Recruitment to the earliest age at which fish can be tagged is estimated by using a virtual population analysis method to back-calculate the expected numbers of unmarked fish at risk of capture. By using information from both marked and unmarked animals in a standard fisheries age structure framework, this approach is well suited to the sparse data situations common in long-term capture–recapture programs with variable sampling effort.
Evaluation of Oral Health Knowledge and Oral Health Status in Mothers and Their Children with Cleft Lip and Palate
Authors: deCastilho Aline Rogéria Freire , das Neves Lucimara Teixeira , de Carvalho Carrara Cleide Felício
Published: February 2006

Objective:

To assess the oral health knowledge of mothers of children with cleft lip and/or palate, analyzing the practical application of this information on the basis of the oral hygiene of the children and caries prevalence of mothers and children.

Design:

Cross-sectional.

Setting:

Pediatric Dentistry sector of the Hospital for Rehabilitation of Craniofacial Anomalies.

Patients:

Mothers (n = 300) and their children with cleft lip and/or palate, ages 3 years to 5 years 6 months.

Materials and Methods:

An interview with questions related to dietary habits and oral health knowledge and habits was conducted. Children and their mothers also were evaluated by intraoral clinical examination.

Results:

Of the mothers, 47.3% displayed poor oral health status (Group A) and 52.7% had a satisfactory oral health status (Group B). Children in Group A presented a mean dmft of 6.0, whereas children in Group B had a mean dmft of 5.6. No significant differences were observed between groups. Mothers demonstrated a reasonable knowledge on prevention of dental caries and oral hygiene.

Conclusion:

Even though the mothers interviewed had some knowledge on the causes and prevention of dental caries, other factors should be regarded as relevant in the caries process.
Struggling Reader to Struggling Reader: High School Students' Responses to a Cross‐Age Tutoring Program
Authors: Paterson Patricia O. , Elliott Lori N.
Published: February 2006

This qualitative study examines the perceptions and responses of struggling ninth‐grade readers who are teaching reading to struggling second‐ and third‐grade students in a cross‐age tutoring program. The program was designed to overcome the entrenched, negative affective barriers that older students often bring to the required reading class by placing them in a leadership role. It also intended simultaneously to improve their vocabulary, fluency, and comprehension.

Results indicate that the older students developed strong mirroring relationships with their younger counterparts based on shared community strengths and norms, shifted their perspective to see themselves as increasingly competent role models, and applied their developing reading abilities as they selected and modified strategies based on the needs of their younger students. Important implications for literacy teachers include a clearer understanding of the powerful, positive attitudinal effects of a well‐planned, low‐cost tutoring program that provides authentic opportunities for literacy learning for all students involved.
“Real‐World Cognition Doesn't End When the Bell Rings”: Literacy Instruction Strategies Derived From Situated Cognition Research
Authors: Darvin Jacqueline
Published: February 2006

This article discusses situated cognition research and its impact on literacy studies concepts and instruction. It provides a brief historical comparison of cognitive psychology and situated cognition and emphasizes the importance of understanding the complex relationships that exist between learners, the settings in which they engage in cognitive activities, and the reconceptualization of time and its usage. Two classroom strategies derived from the work of Jean Lave and Sylvia Scribner are discussed in depth, as are the lives of students who benefited from these approaches.

The author emphasizes the need for cognitive activities that begin in the classroom to continue after the class has ended and encourages educators and researchers to further examine the nature of adaptive thinking and working intelligence. Instead of teacher training courses placing emphasis on teachers' mastery of “closure” of the 40‐minute lesson, courses should encourage teachers to allow their students to engage in problem‐solving opportunities that will persist after instruction has ended. Finally, the article asserts that processes of deriving meaning from reading and writing require components of positive affect in order to be successful and that further studies are needed to explore the nature of adaptive thinking and working intelligence.
Teaching With Media and Popular Culture
Authors: Trier James
Published: February 2006

Preservice English teachers experienced the concept of teaching with media. They incorporated film, music, television, and visual texts that they viewed as having potential in teaching English classes. They also shared their lessons and media artifacts with one another, exchanging ideas and collaborating on subsequent projects that involved teaching with media.
Mesenchymal Stem Cells and Adipogenesis in Hemangioma Involution
Authors: Yu Ying , Fuhr Jasmin , Boye Eileen , Gyorffy Steve , Soker Shay , Atala Anthony , Mulliken John B. , Bischoff Joyce
Published: February 2006

Hemangioma is a benign tumor of infancy whose hallmark is rapid growth during the first year of life followed by slow regression during early childhood. The proliferating phase is characterized by abundant immature endothelial cells, the involuting phase by prominent endothelial-lined vascular channels and endothelial apoptosis, and the involuted phase by few remaining capillary-like vessels surrounded by loose fibrofatty tissue. Nothing is known about the mechanisms that contribute to the adipogenesis during this spontaneous regression. We postulated that mesenchymal stem cells (MSCs) reside in the tumor and preferentially differentiate into adipocytes. To test this hypothesis, we isolated MSCs from 14 proliferating and five involuting hemangiomas by taking advantage of the well known selective adhesion of MSCs to bacteriologic dishes. These hemangioma-derived MSCs (Hem-MSCs) are similar to MSCs obtained from human bone marrow, expressing the cell surface markers SH2 (CD105), SH3, SH4, CD90, CD29, smooth muscle α-actin, and CD133 but not the hematopoietic markers CD45 and CD14 or the hematopoietic/endothelial markers CD34, CD31, and kinase insert domain receptor (KDR). Hem-MSCs exhibited multilineage differentiation with robust adipogenic potential that correlated with the proliferating phase. The numbers of adipogenic Hem-MSCs were higher in proliferating-phase than in involuting-phase tumors and higher than in normal infantile skin. Furthermore, Hem-MSCs exhibited a random pattern of X-chromosomal inactivation, indicating that these cells are not clonally derived. In summary, we have identified MSCs as a novel cellular constituent in infantile hemangioma. These MSCs may contribute to the adipogenesis during hemangioma involution.
Reverse Serial Analysis of Gene Expression (SAGE) Characterization of Orphan SAGE Tags from Human Embryonic Stem Cells Identifies the Presence of Novel Transcripts and Antisense Transcription of Key Pluripotency Genes
Authors: Richards Mark , Tan Siew-Peng , Chan Woon-Khiong , Bongso Ariff
Published: February 2006

Serial analysis of gene expression (SAGE) is a powerful technique for the analysis of gene expression. A significant portion of SAGE tags, designated as orphan tags, however, cannot be reliably assigned to known transcripts. We used an improved reverse SAGE (rSAGE) strategy to convert human embryonic stem cell (hESC)-specific orphan SAGE tags into longer 3′ cDNAs. We show that the systematic analysis of these 3′ cDNAs permitted the discovery of hESC-specific novel transcripts and cis-natural antisense transcripts (cis-NATs) and improved the assignment of SAGE tags that resulted from splice variants, insertion/deletion, and single-nucleotide polymorphisms. More importantly, this is the first description of cis-NATs for several key pluripotency markers in hESCs and mouse embryonic stem cells, suggesting that the formation of short interfering RNA could be an important regulatory mechanism. A systematic large-scale analysis of the remaining orphan SAGE tags in the hESC SAGE libraries by rSAGE or other 3′ cDNA extension strategies should unravel additional novel transcripts and cis-NATs that are specifically expressed in hESCs. Besides contributing to the complete catalog of human transcripts, many of them should prove to be a valuable resource for the elucidation of the molecular pathways involved in the self-renewal and lineage commitment of hESCs.
Embryonic Stem Cell-Derived Neuronally Committed Precursor Cells with Reduced Teratoma Formation After Transplantation into the Lesioned Adult Mouse Brain
Authors: Dihné Marcel , Bernreuther Christian , Hagel Christian , Wesche Kai O. , Schachner Melitta
Published: February 2006

The therapeutic potential of embryonic stem (ES) cells in neurodegenerative disorders has been widely recognized, and methods are being developed to optimize culture conditions for enriching the cells of interest and to improve graft stability and safety after transplantation. Whereas teratoma formation rarely occurs in xenogeneic transplantation paradigms of ES cell-derived neural progeny, more than 70% of mice that received murine ES cell-derived neural precursor cells develop teratomas, thus posing a major safety problem for allogeneic and syngeneic transplantation paradigms. Here we introduce a new differentiation protocol based on the generation of substrate-adherent ES cell-derived neural aggregates (SENAs) that consist predominantly of neuronally committed precursor cells. Purified SENAs that were differentiated into immature but postmitotic neurons did not form tumors up to four months after syngeneic transplantation into the acutely degenerated striatum and showed robust survival.
Differentiation of Mouse Embryonic Stem Cells after RNA Interference-Mediated Silencing of OCT4 and Nanog
Authors: Hough Shelley R. , Clements Ian , Welch Peter J. , Wiederholt Kristin A.
Published: February 2006

RNA interference (RNAi) holds great promise as a tool to study the basic biology of stem cells or to direct differentiation in a specific manner. Barriers to achieving efficient and specific gene silencing in RNAi experiments include limitations in transfection efficiency and in the efficacy and specificity of RNAi silencing effectors. Here, we combine methods of efficient lipid-mediated delivery with chemically modified RNAi compounds to silence genes related to pluripotency, in order to direct differentiation of mouse embryonic stem cells. After transfection of embryonic stem cells with OCT4- or Nanog-targeted RNAi compounds, levels of OCT4 or Nanog transcript and protein were reduced accordingly. Reduction in OCT4 expression correlated with induction of trophectoderm genes Cdx2, Hand1, and PL-1, with formation of cells with trophoblast giant cell phenotype after 6 days. Reduction in Nanog expression correlated with induction of extraembryonic endoderm genes GATA4, GATA6, and laminin B1, with subsequent generation of groups of cells with parietal endoderm phenotype. Our results indicate that transient inhibition of OCT4 or Nanog by RNAi compounds is sufficient to induce differentiation toward extraembryonic lineages, which supports the model that these transcription factors function in a dose-dependent manner to influence cell fate.
Effects of Aging and Niche Microenvironment on Spermatogonial Stem Cell Self-Renewal
Authors: Ryu Buom-Yong , Orwig Kyle E. , Oatley Jon M. , Avarbock Mary R. , Brinster Ralph L.
Published: February 2006

Aging is evident in most tissues and organ systems, but the mechanisms of aging are difficult to identify and poorly understood. Here, we test the hypothesis that aging results in uncorrected defects in stem cell and/or niche function, which lead to system failure. We used the spermatogonial stem cell (SSC) transplantation assay to determine the effect of aging on testis stem cell/niche function in mice. Between 12 and 24 months of age, male mice experienced a declining level of fertility associated with decreased testis weight, level of spermatogenesis, and total stem cell content. However, when stem cells were consecutively passaged at 3-month intervals to testes of young males, these stem cells continued to produce spermatogenesis for more than 3 years. Thus, SSC self-renewal continues long past the normal life span of the animal when the stem cell is continually maintained in a young niche/microenvironment. Moreover, these data suggest that infertility in old males results from deterioration of the SSC niche and failure to support an appropriate balance between stem cell self-renewal and differentiation.
Luteinizing hormone inhibits Fas-induced apoptosis in ovarian surface epithelial cell lines
Authors: Slot K A , de Boer-Brouwer M , Houweling M , Vaandrager A B , Dorrington J H , Teerds K J
Published: February 2006

Gonadotrophins including LH have been suggested to play an important role in the etiology of epithelial ovarian cancers. The goal of the present study was to obtain more insight in the mechanism of gonadotrophin action on ovarian surface epithelium (OSE) cells. As the Fas system is known to be a major player in the regulation of the process of apoptosis in the ovary, we investigated whether LH interfered with Fas-induced apoptosis in the human OSE cancer cell lines HEY and Caov-3. Activation of Fas receptor by an agonistic anti-Fas receptor antibody induced apoptosis, as was evaluated by caspase-3 activation, poly(ADP-ribose) polymerase fragmentation, phosphatidylserine externalization and morphological changes characteristic of apoptosis. Co-treatment with LH reduced the number of apoptotic cells following activation of Fas in a transient manner, while LH by itself did not affect apoptosis or cell proliferation. The anti-apoptotic effect of LH could be mimicked by the membrane-permeable cAMP analog 8-(4-chlorophenylthio) cAMP (8-CPT-cAMP), and blocked by H89, a specific inhibitor of protein kinase A (PKA). In conclusion, these findings suggest that LH protects HEY cells against Fas-induced apoptosis through a signaling cascade involving PKA. Although it is plausible that in vivo LH might also enhance OSE tumor growth through inhibition of apoptosis, further research is necessary to confirm this hypothesis.
Plasma ghrelin levels in healthy elderly volunteers: the levels of acylated ghrelin in elderly females correlate positively with serum IGF-I levels and bowel movement frequency and negatively with systolic blood pressure
Authors: Akamizu T , Murayama T , Teramukai S , Miura K , Bando I , Irako T , Iwakura H , Ariyasu H , Hosoda H , Tada H , Matsuyama A , Kojima S , Wada T , Wakatsuki Y , Matsubayashi K , Kawakita T , Shimizu A , Fukushima M , Yokode M , Kangawa K
Published: February 2006

Aging is associated with a decrease in growth hormone (GH) secretion, appetite and energy intake. As ghrelin stimulates both GH secretion and appetite, reductions in ghrelin levels may be involved in the reductions in GH secretion and appetite observed in the elderly. However, only preliminary studies have been performed on the role of ghrelin in elderly subjects. In this study, we sought to clarify the physiologic implications of the age-related alterations in ghrelin secretion by determining plasma ghrelin levels and other clinical parameters in healthy elderly subjects. Subjects were ≥ 65 years old, corresponding to the SENIEUR protocol, had not had a resection of the upper gastrointestinal tract and had not been treated with hormones. One hundred and five volunteers (49 men and 56 women) were admitted to this study (73.4 ± 6.3 years old). Plasma levels of acylated ghrelin in elderly female subjects positively correlated with serum IGF-I levels and bowel movement frequency and negatively with systolic blood pressure. In elderly men, desacyl ghrelin levels correlated only weakly with bowel movement frequency. These findings suggest that the plasma levels of the acylated form of ghrelin may influence the age-related alterations in GH/IGF-I regulation, blood pressure and bowel motility. These observational associations warrant further experimental studies to clarify the physiologic significance of these effects.
Glucocorticoids enhance cytotoxicity of cisplatin via suppression of NF-κB activation in the glucocorticoid receptor-rich human cervical carcinoma cell line SiHa
Authors: Lu Yen-Shen , Yeh Pei-Yen , Chuang Shuang-En , Gao Ming , Kuo Min-Liang , Cheng Ann-Lii
Published: February 2006

Glucocorticoids (GCs) are commonly co-administered with cisplatin in the treatment of patients with carcinomas to prevent drug-induced allergic reaction, nausea and vomiting. Although GC receptor (GR) is ubiquitous in carcinoma cells and has been linked to signal transduction pathways pertinent to cell growth and apoptosis, little is known regarding the possible effect of GC on the chemosensitivity of carcinomas. Our previous study demonstrated that dexamethasone (DEX) enhances the cytotoxicity to cisplatin in a GR-rich human cervical carcinoma cell line, SiHa. In this study, we found that this cisplatin cytotoxicity-enhancing effect of DEX correlated well with its effect on abrogating the cisplatin-induced activation of nuclear factor kappa B (NF-κB). RU486, a structural homologue of DEX, partially reversed this cytotoxicity-enhancing effect of DEX, a finding consistent with the well-known partial reversing effect of RU486 on DEX-induced NF-κB suppression. Furthermore, expression of a dominant-negative truncated IκBα gene in SiHa cells completely abolished the cisplatin cytotoxicity-enhancing effect of DEX. Our data suggest that the specific action of DEX on GR may enhance the cytotoxicity of cisplatin in selected GR-rich cancer cells by suppressing NF-κB activation.
Long isoform of prolactin receptor predominates in rat intrahepatic bile ducts and further increases under obstructive cholestasis
Authors: Bogorad R L , Ostroukhova T Y , Orlova A N , Rubtsov P M , Smirnova O V
Published: February 2006

Prolactin participates in the regulation of liver function. However, prolactin receptor (PrlR) expression and its regulation have been described only for hepatocytes. In this study, we investigated the expression and regulation of PrlR isoforms in the other important intrahepatic cellular compartment: the biliary epithelial cells, or cholangiocytes. Our aim was to determine whether prolactin should be considered as a potential regulator of cholangiocyte function under normal and pathological conditions. Cholangiocytes and hepatocytes were differentially isolated from rat liver. PrlR expression was analysed at the mRNA level by isoform-specific semiquantitative PCR, and at the protein level by immunostaining of liver sections. Hormonal regulation of PrlR expression was evaluated by comparing intact rats with gonadectomized, pituitary-grafted or bromocriptine-treated animals. Common bile-duct ligation was used as the experimental model of cholestasis. Our results demonstrate that the expression pattern and regulation of PrlR isoforms is totally different in cholangiocytes compared with hepatocytes: (1) mature rat cholangiocytes express low levels of PrlR, while it is very high in hepatocytes, (2) only the long isoform is detected in cholangiocytes, while the short isoform predominates in hepatocytes and (3) PrlR levels in cholangiocytes are induced by obstructive cholestasis, but not by sex hormones or prolactin, while it is the opposite in hepatocytes. From these data, the actions of prolactin on liver are anticipated to exhibit strong cell-type specificity in both normal and pathological conditions.
Bovine follicle development is associated with divergent changes in activin-A, inhibin-A and follistatin and the relative abundance of different follistatin isoforms in follicular fluid
Authors: Glister Claire , Groome Nigel P , Knight Philip G
Published: February 2006

The aim was to determine whether follicle growth in cattle is accompanied by changes in levels of inhibin-A (inh-A), activin-A (act-A) and different Mr isoforms of follistatin (FS) in bovine follicular fluid (bFF), reflecting differential roles of these proteins during folliculogenesis. Follicles (n=146) from 2–20 mm diameter were dissected from ovaries of ~40 cattle. Immunoassays were used to measure total FS, act-A, inh-A, oestradiol (E) and progesterone (P) levels; immunoblotting was used to quantify the relative abundance of different FS isoforms. Follicle growth from 2–6 mm was associated with a 6-fold increase in inh-A and 30-fold increase in act-A; FS remained uniformly high from 2–10 mm. From 6–2 mm, inh-A remained high while act-A and FS fell 3-fold and 2-fold, respectively. Act-A/FS ratio increased 20-fold from 2–6 mm before falling slightly through to 20 mm. Act-A/inh-A ratio increased 6-fold from 2–6 mm before falling 2-fold from 6 to 17–20 mm. These findings imply a marked increase in relative activin ‘tone’ around the stage at which dominant follicle selection occurs. When larger follicles (13–20 mm) were subdivided according to E/P ratio, those with high ( > 5) E/P ratio had lower (2-fold; P < 0.001) levels of inh-A and act-A in comparison to follicles with low ( < 5) E/P ratio, but there were no significant differences in FS, act-A/inh-A ratio or act-A/FS ratio. Thus follicle size, but not oestrogenic status, has a major influence on the intrafollicular balance between act-A and its opposing factors, inh-A and FS. Six FS isoforms were detected in bFF (apparent Mr: 65, 41, 37, 35, 33 and 31 kDa) averaging 6, 13, 24, 26, 13 and 17% respectively of total FS. During growth from 2–20 mm the proportion of total FS represented by 65, 41 and 37 kDa isoforms increased ~2-fold while the proportion represented by the 33 and 31 kDa isoforms decreased by 3-fold and 1.6-fold, respectively. Treatment of bovine granulosa cells in vitro with FSH and IGF alone or in combination increased total FS secretion up to 12-fold but did not affect the relative abundance of the five different FS isoforms detected. While the functional significance of the intriguing shift in FS isoform abundance in bFF during follicle development remains to be established, we have shown that a marked increase in intrafollicular activin ‘tone’ accompanies bovine follicle growth from 3–6 mm, corresponding to the stage at which the FSH-dependent follicle selection mechanism operates in this species.
Involvement of PDX-1 in activation of human insulin gene transcription
Authors: Le Lay John , Stein Roland
Published: February 2006

Islet β cell-specific transcription of the insulin gene is mediated through the binding of the islet-enriched PDX-1, BETA2, and MafA transcription factors to conserved 5′-flanking region regulatory elements. However, additional non-conserved sequences within this region are also significant in regulating expression. Thus, PDX-1 binds to and activates the GG2 element located between nucleotides −145 and −140 of the human gene, while the corresponding, but non-identical, site in the rodent insulin genes are negatively regulated by the Nkx2.2 transcription factor. Here, we show that despite binding PDX-1 approximately 20-fold less effectively than the conserved insulin A3 and A1 sites in gel mobility shift assays, human GG2 appears to be more important for the activation of transfected human insulin enhancer-driven reporter constructs in β cell lines. Furthermore, functional interaction analysis in non-islet cell lines demonstrated that PDX-1 binding to GG2, A1, and A3 contributes to synergistic activation of insulin gene expression with MafA. Our analysis also illustrated the requirement of poorly conserved human sequences between −293 and −251 in mediating activity through the more upstream A3 binding site. Collectively these experiments have revealed distinct features in control of the human and rodent insulin genes by PDX-1, processes that may be involved in regulating insulin expression under both normal and diabetic conditions in humans.
Soil Acidity and Manganese in Declining and Nondeclining Sugar Maple Stands in Pennsylvania
Authors: Kogelmann Wilhelm J. , Sharpe William E.
Published: February 2006

For decades, the hardwood forests of northern Pennsylvania have been subjected to chronic atmospheric loading of acidifying agents. On marginal, high‐elevation, unglaciated sites, sugar maples (Acer saccharum Marsh.) have experienced severe decline symptoms and mortality. Accelerated soil acidification, base cation leaching, and increased availability of toxic metals have been suggested as predisposing factors contributing to this decline. Manganese, an essential micronutrient, is also a potentially phytotoxic metal that may be a factor associated with poor sugar maple health on soils vulnerable to acidification from anthropogenic sources. We measured Mn levels in four compartments of the soil–tree system (soil, foliage, xylem wood, and sap) on three sugar maple stands in northern Pennsylvania. Two stands were classified as declining and one was in good health. Negative correlations were found between soil pH and Mn levels in the soil, foliage, sap, and xylem wood. Levels of Mn in these pools were consistently higher on declining sites, which correspondingly exhibited lower levels of Ca and Mg. Species differences between red maple (Acer rubrum L.) and sugar maple at the two declining sites suggested different tolerances to excessive Mn. Molar ratios of Mg/Mn and Ca/Mn were different among sites and showed potential as indicators of soil acidification. Significant correlations among soil, sap, foliage, and xylem wood Mn were also noted. These results show clear Mn differences among sites and, when viewed with recent Mn toxicity experiments and other observational studies, suggest that excessive Mn may play a role in the observed decline and mortality of sugar maple.
A Method for Measuring Low‐Weight Carboxylic Acids from Biosolid Compost
Authors: Himanen Marina , Latva‐Kala Kyösti , Itävaara Merja , Hänninen Kari
Published: February 2006

Concentration of low‐weight carboxylic acids (LWCA) is one of the important parameters that should be taken into consideration when compost is applied as soil improver for plant cultivation, because high amounts of LWCA can be toxic to plants. The present work describes a method for analysis of LWCA in compost as a useful tool for monitoring compost quality and safety. The method was tested on compost samples of two different ages: 3 (immature) and 6 (mature) months old. Acids from compost samples were extracted at high pH, filtered, and freeze‐dried. The dried sodium salts were derivatized with a sulfuric acid–methanol mixture and concentrations of 11 low‐weight fatty acids (C1–C10) were analyzed using headspace gas chromatography. The material was analyzed with two analytical techniques: the external calibration method (tested on 11 LWCA) and the standard addition method (tested only on formic, acetic, propionic, butyric, and iso‐butyric acids). The two techniques were compared for efficiency of acids quantification. The method allowed good separation and quantification of a wide range of individual acids with high sensitivity at low concentrations. Detection limit for propionic, butyric, caproic, caprylic, and capric acids was 1 mg kg−1 compost; for formic, acetic, valeric, enanthoic and pelargonic acids it was 5 mg kg−1 compost; and for iso‐butyric acid it was 10 mg kg−1 compost. Recovery rates of LWCA were higher in 3‐mo‐old compost (57–99%) than in 6‐mo‐old compost (29–45%). In comparison with the external calibration technique the standard addition technique proved to be three to four times more precise for older compost and two times for younger compost. Disadvantages of the standard addition technique are that it is more time demanding and laborious.
Isotopic Evidence of Nitrate Sources and Denitrification in the Mississippi River, Illinois
Authors: Panno Samuel V. , Hackley Keith C. , Kelly Walton R. , Hwang Hue‐Hwa
Published: February 2006

Anthropogenic nitrate (NO3−) within the Mississippi–Atchafalaya River basin and discharge to the Gulf of Mexico has been linked to serious environmental problems. The sources of this NO3−have been estimated by others using mass balance methods; however, there is considerable uncertainty in these estimates. Part of the uncertainty is the degree of denitrification that the NO3−has undergone. The isotopic composition of NO3−in the Mississippi River adjacent to Illinois and tile drain (subsurface drain) discharge in agricultural areas of east‐central Illinois was examined using N and O isotopes to help identify the major sources of NO3−and assess the degree of denitrification in the samples. The isotopic evidence suggests that most of the NO3−in the river is primarily derived from synthetic fertilizers and soil organic N, which is consistent with published estimates of N inputs to the Mississippi River. The 1:2 relationship between δ18O and δ15N also indicate that, depending on sample location and season, NO3−in the river and tile drains has undergone significant denitrification, ranging from about 0 to 55%. The majority of the denitrification appears to have occurred before discharge into the Mississippi River.
Reducing Crude Protein in Beef Cattle Diet Reduces Ammonia Emissions from Artificial Feedyard Surfaces
Authors: Todd Richard W. , Cole N. Andy , Clark R. Nolan
Published: February 2006

Concentrated animal feeding operations are major sources of ammonia to the atmosphere. Control methods to reduce emissions include acidifying amendments, urease inhibitors, and absorbents. For beef cattle, decreasing crude protein (CP) in diets may be the most practical and cost‐effective method to reduce ammonia emissions. Our objective was to quantify the effect of reducing CP in beef cattle diet on ammonia emissions. Two groups of steers were fed diets with either 11.5 or 13.0% CP and all urine and feces were collected. Manures from the two diet treatments were applied in a replicated laboratory chamber experiment, and ammonia emission was quantified using acid gas washing. In four seasonal field trials, manures from the two diet treatments were applied to two 10‐m‐diameter, circular, artificial feedyard surfaces, and ammonia emission was quantified using the integrated horizontal flux method. Manure from steers fed 11.5% CP diet had less urine, less urinary N, and a lesser fraction of total N in urine, compared with the 13.0% CP diet. Decreasing crude protein in beef cattle diets from 13 to 11.5% significantly decreased ammonia emission by 44% (p < 0.01) in the closed chamber laboratory experiment, and decreased mean daily ammonia flux by 30% (p = 0.10), 52% (p = 0.08), and 29% (p < 0.01) in summer, autumn, and spring field trials, respectively. No difference was observed in winter. On an annual basis, decreasing crude protein reduced daily ammonia flux by 28%. Reducing crude protein in beef cattle diets may provide the most practical and cost‐effective way to reduce ammonia emissions from feedyards.