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At least 1,081 records · Page 60Linked to original sources
PubMed2006

The effect of sodium chloride on the dissolution of calcium silicate hydrate gels.

The use of cement based materials will be widespread in the long-term management of radioactive materials in the United Kingdom. One of the applications could be the Nirex reference vault backfill (NRVB) as an engineered barrier within a deep geological repository. NRVB confers alkaline conditions, which would provide a robust chemical barrier through the control of the solubility of some key radionuclides, enhanced sorption and minimised corrosion of steel containers. An understanding of the dissolution of C-S-H gels in cement under the appropriate conditions (e.g., saline groundwaters) is necessary to demonstrate the expected evolution of the chemistry over time and to provide sufficient cement to buffer the porewater conditions for the required time. A programme of experimental work has been undertaken to investigate C-S-H gel dissolution behaviour in sodium chloride solutions and the effect of calcium/silicon ratio (C/S), temperature and cation type on this behaviour. Reductions in calcium concentration and pH values were observed with samples equilibrated at 45 degrees C compared to those prepared at 25 degrees C. The effect of salt cation type on salt-concentration dependence of the dissolution of C-S-H gels was investigated by the addition of lithium or potassium chloride in place of sodium chloride for gels with a C/S of 1.0 and 1.8. With a C/S of 1.0, similar increases in dissolved calcium concentration with increasing ionic strength were recorded for the different salts. However, at a C/S of 1.8, anomalously high calcium concentrations were observed in the presence of lithium.

Calcium Compounds↗
PubMed2006

High durability cementitious material with mineral admixtures and carbonation curing.

Nuclear waste repositories need highly durable cementitious materials to function for over thousands of years while resisting leaching and degradation. The durability of cementitious material can be effectively improved by reducing permeability and by changing cement hydrates to a less soluble matrix. This paper describes the properties of carbonated new cementitious materials containing belite-rich cement and gamma-2CaO.SiO2 as main components. In addition, the long-term leaching properties are investigated and compared with ordinary Portland cement by using a predictive leaching model.

Carbon↗
PubMed2006

The use of (micro)-X-ray absorption spectroscopy in cement research.

Long-term predictions on the mobility and the fate of radionuclides and contaminants in cementitious waste repositories require a molecular-level understanding of the geochemical immobilization processes involved. In this study, the use of X-ray absorption spectroscopy (XAS) for chemical speciation of trace elements in cementitious materials will be outlined presenting two examples relevant for nuclear waste management. The first example addresses the use of XAS on powdered cementitious materials to determine the local coordination environment of Sn(IV) bound to calcium silicate hydrates (C-S-H). Sn K-edge XAS data of Sn(IV) doped C-S-H can be rationalized by corner sharing binding of Sn octahedra to Si tetrahedra of the C-S-H structure. XAS was further applied to determine the binding mechanism of Sn(IV) in the complex cement matrix. The second example illustrates the potential of emerging synchrotron-based X-ray micro-probe techniques for elucidating the spatial distribution and the speciation of contaminants in highly heterogeneous cementitious materials at the micro-scale. Micro X-ray fluorescence (XRF) and micro-XAS investigations were carried out on Co(II) doped hardened cement paste. These preliminary investigations reveal a highly heterogeneous spatial Co distribution. The presence of a Co(II)-hydroxide-like phase Co(OH)2 and/or Co-Al layered double hydroxide (Co-Al LDH) or Co-phyllosilicate was observed. Surprisingly, some of the initial Co(II) was partially oxidized and incorporated into a Co(III)O(OH)-like phase or a Co-phyllomanganate.

Construction Materials↗
PubMed2006

Caesium sorption by hydrated cement as a function of degradation state: experiments and modelling.

To provide reliable K(d) data for Cs required for the performance assessment of cement-based radioactive waste repositories, two complementary approaches were followed. First, Cs sorption was determined on a range of hydrated cement paste (HCP) and mortar samples of CEM I and CEM V for different degradation states and solution compositions, as well as on some single mineral phases. Second, a surface complexation-diffuse layer model previously developed by Pointeau et al. [Pointeau, I., Marmier, N., Fromage, F., Fedoroff, M., Giffaut, E., 2001. Cs and Pb uptake by CSH phases of hydrated cement. Material Research Society Symposium Proceedings, 663, 105-113] for Cs sorption on synthetic CSH phases was simplified to facilitate its application to whole HCP and mortars or concrete, following re-assessment of the model parameters. All measurements were compared with model predictions. The sorption data obtained on the different solid phases as a function of conditions corroborate that CSH minerals are the main sorbing phase for Cs in HCP. The data also clearly show the important influence of pH and the dissolved concentration of Na, K and Ca on K(d). It is further suggested that a decrease of pH is concomitant with a decrease of the Ca/Si ratio and a corresponding increase in surface sites with high affinity for Cs and, thus, K(d). Elevated concentrations of cations able to compete with Cs for these sites lead to a decrease of K(d), on the other hand. The simplified model was applied to the sorption measurements performed within this study as well as to a variety of literature data, mainly K(d) values for a variety of fresh HCP and mortar or concrete samples based on different samples of Ordinary Portland Cement as well as blended cements. The results show that the model can be applied reasonably well to a very large variety of conditions in terms of solid and solution compositions that cover a range of K(d) values from 10(-4) to ca. 3.2m(3)/kg. The large scatter typically observed for Cs sorption, especially on fresh HCP samples prepared from different formulations, can be explained quantitatively by the variable concentrations of Na and K in the respective solutions, which compete with Cs for fixation sites. On the other hand, the comparatively uniform conditions in degraded HCP typically render the prediction of K(d) values less uncertain than in case of fresh HCP.

Cesium↗
PubMed2026

Reporting and representation of population descriptors in public RNA-seq databases.

Diverse and globally representative datasets are essential to genomic science and medicine. Here, we analyzed population descriptor metadata from RNA sequencing (RNA-seq) studies in two major public repositories: the Sequence Read Archive (SRA) and the Database of Genotypes and Phenotypes. We examined geographic and economic characteristics of institutions depositing the data and compared SRA-deposited descriptors to empirical estimates of genetic ancestry and to those reported in publications, analyzing trends over time. We found that 55% of RNA-seq samples were deposited by United States (US) institutions and 90% by institutions in high-income countries. Only 3% of SRA samples were associated with population descriptors, and among those with US Census terms, 69% were labeled as White. Among samples with continental descriptors, 56% were labeled as European. Our analyses emphasize widespread bias in the composition of public RNA-seq datasets and, more generally, a lack of consistent and careful reporting of population descriptors needing urgent improvement.

Humans↗
PubMed2006

Genetic regulatory networks programming hematopoietic stem cells and erythroid lineage specification.

Erythroid cell production results from passage through cellular hierarchies dependent on differential gene expression under the control of transcription factors responsive to changing niches. We have constructed Genetic Regulatory Networks (GRNs) describing this process, based predominantly on mouse data. Regulatory network motifs identified in E. coli and yeast GRNs are found in combination in these GRNs. Feed-forward motifs with autoregulation generate forward momentum and also control its rate, which is at its lowest in hematopoietic stem cells (HSCs). The simultaneous requirement for multiple regulators in multi-input motifs (MIMs) provides tight control over expression of target genes. Combinations of MIMs, exemplified by the SCL/LMO2 complexes, which have variable content and binding sites, explain how individual regulators can have different targets in HSCs and erythroid cells and possibly also how HSCs maintain stem cell functions while expressing lineage-affiliated genes at low level, so-called multi-lineage priming. MIMs combined with cross-antagonism describe the relationship between PU.1 and GATA-1 and between two of their target genes, Fli-1 and EKLF, with victory for GATA-1 and EKLF leading to erythroid lineage specification. These GRNs are useful repositories for current regulatory information, are accessible in interactive form via the internet, enable the consequences of perturbation to be predicted, and can act as seed networks to organize the rapidly accumulating microarray data.

Animals↗
PubMed2007

hORFeome v3.1: a resource of human open reading frames representing over 10,000 human genes.

Complete sets of cloned protein-encoding open reading frames (ORFs), or ORFeomes, are essential tools for large-scale proteomics and systems biology studies. Here we describe human ORFeome version 3.1 (hORFeome v3.1), currently the largest publicly available resource of full-length human ORFs (available at ). Generated by Gateway recombinational cloning, this collection contains 12,212 ORFs, representing 10,214 human genes, and corresponds to a 51% expansion of the original hORFeome v1.1. An online human ORFeome database, hORFDB, was built and serves as the central repository for all cloned human ORFs (http://horfdb.dfci.harvard.edu). This expansion of the original ORFeome resource greatly increases the potential experimental search space for large-scale proteomics studies, which will lead to the generation of more comprehensive datasets.

Animals↗
PubMed1998

Productive aging: a quality of life agenda.

Although the fact that, in general, the US population is living longer is said to be the public health success story of the 20th century, the boom in the population aged 65 years and older is having and will continue to have major implications for all age groups as well as for the nation's health, social, and economic institutions. The concept of productive aging can provide guidance in addressing these implications. The assumptions of productive aging reflect today's reality that older people are repositories of wisdom and experience and important assets for society; relatively healthy, with the potential for maintaining that condition until late in life; capable of making economic and social contributions that benefit themselves, their families, and their communities; and in need of purposeful and meaningful roles and activities in life. A productive aging activity model emphasizes involvement in paid work, volunteerism, education, fitness and exercise, leisure and travel, advocacy and political action, and consumerism. This article discusses the concept of productive aging, a related activity model, and qualitative focus group research undertaken in conjunction with the 1995 White House Conference on Aging.

Aged↗
PubMed1994

Caring for the female Jehovah's Witness: balancing medicine, ethics, and the First Amendment.

Blood transfusion has been doctrinally forbidden for Jehovah's Witnesses since 1945. Despite serious theologic consequences for its violation, this proscription may not be observed universally by members of the denomination. When a patient declines a lifesaving transfusion, a conflict is generated between the physician's autonomy-based and beneficence-based obligations to the patient. This conflict is intensified when the patient is a woman who had minor dependent children, either in utero or already born. A spectrum of opinion exists regarding the resolution of this conflict. As one of society's repositories of moral and legal values, the court is the most appropriate forum in which religious, medical, and ethical viewpoints may receive a fair and impartial hearing.

Beneficence↗
PubMed1999

Peripartum cardiomyopathy: summary of an international survey on peripartum cardiomyopathy.

OBJECTIVE: The aim of this survey was to assess the evaluation, management, and future recommendations of patients with the diagnosis of peripartum cardiomyopathy and to evaluate the interest in the creation of a prospective database regarding this rare disorder. STUDY DESIGN: A total of 116 surveys were sent to major teaching institutions in the United States (including Puerto Rico), Canada, Crete, and South Korea after a national conference held at the National Institutes of Health regarding peripartum cardiomyopathy. This was an open-ended survey containing 17 specific questions regarding this disorder and its management. RESULTS: A total of 78 (67%) maternal-fetal specialists responded to the survey. Diuretics and digoxin were used as first-line treatment for this disorder. Only 6% used angiotensin-converting enzyme inhibitors during pregnancy. Fifty-eight percent of the perinatologists (58%) recommended either intrauterine contraceptive devices or foam and condoms, whereas oral contraceptives (progesterone-only pill or estrogen-progesterone mix) were recommended in 23% and 41%, respectively. Sixty-six percent (66%) of the respondents would recommend future pregnancy if ventricular function returned to normal. CONCLUSIONS: Fundamental clinical and basic research is lacking regarding this rare but potentially devastating disorder. Major teaching institutions do not have significant numbers of patients with this disorder to provide concrete recommendations, and starting a database will be useful in the gathering of important epidemiologic information. A secondary aim of such a registry would be to establish a repository for tissue and blood samples to answer basic mechanistic questions about this disorder.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

The effect of deep posterior subtenon injection of corticosteroids on intraocular pressure.

PURPOSE: To investigate the effect of posterior subtenon injections of corticosteroids on intraocular pressure in a variety of ocular diseases. METHODS: We retrospectively analyzed 202 consecutive posterior subtenon corticosteroid injections (148 of methylprednisolone acetate, 80 mg, and 54 of triamcinolone acetonide, 40 mg) in 63 eyes of 55 patients (26 male, 29 female; mean age +/- SD, 60.17 +/- 26.55 years). All patients had received topical or systemic corticosteroids before the injection, and no rise in intraocular pressure had been noted. Preinjection and postinjection intraocular pressure measurements were compared by two-tailed paired t test. Statistical analysis was performed separately by patient (first injection of first injected eye), by eye (first injection of each eye), and by all injections. To detect increase in intraocular pressure during follow-up, statistical analysis was performed separately 14 to 90 days, 91 to 150 days, and 151 to 270 days after injection. RESULTS: No statistically significant difference was found between preinjection and postinjection intraocular pressure measurements. A power calculation in the most stringent subanalysis (by patient) proved that there is only a 3.87% chance to statistically miss a clinically significant rise in intraocular pressure from 15 to 21 mm Hg. CONCLUSIONS: Posterior subtenon injection of corticosteroids does not cause an increase in intraocular pressure. All patients in our study had been treated previously with topical or systemic corticosteroids and did not react with an excessive increase in intraocular pressure. This safety of repository corticosteroids may therefore not apply to patients whose status in responding to corticosteroids is not known.

Adolescent↗
PubMed2001

Measuring outcomes in surgical patients.

The current emphasis on quality of healthcare, cost effectiveness, and consumer satisfaction demands a better understanding of the relationship between the process of care and the outcomes of care. As patients become more active in defining healthcare quality, outcome measures are becoming increasingly patient focused. To meet these new demands for understanding the process-outcomes relationship, there exists a tremendous need for physician involvement in developing outcomes assessment programs. Such programs are best designed through the cooperative efforts of clinicians and outcomes statisticians. Advances in outcomes assessment will require a combination of increased precision in measurement, greater analysis of outliers, and the development of computerized repositories of clinical and health status data.

Costs and Cost Analysis↗
PubMed2001

Peer review.

Peer review is essential for ensuring quality medical care. In the 1980s a physician-plaintiff prevailed in lawsuit filed against peer reviewers who excluded the physician from a hospital's medical staff. The peer reviewers had acted to preserve their own economic interests. A multimillion-dollar verdict against the peer reviewers destroyed the community's only multispecialty practice and received national attention. Congress reacted by passing the Health Care Quality Improvement Act that granted sweeping, legal immunity for peer reviewers but also created the National Practitioner's Data Bank. The combination of the establishment of a public repository for physicians malpractice and medical staff privileging activity in combination with the near complete legal protection of peer reviewers has converted peer review from an evaluative to a punitive process. The peer review process and the laws that govern it should be reformed to regain its ability to improve and assure quality without being a threat to physicians.

Humans↗
PubMed1991

Protease nexin-2/amyloid beta-protein precursor in blood is a platelet-specific protein.

The protease inhibitor, protease nexin-2 (PN-2), is the secreted form of the amyloid beta-protein precursor (APP) which contains the Kunitz protease inhibitor domain. PN-2/APP is an abundant platelet alpha-granule protein which is secreted upon platelet activation. PN-2/APP mRNA is present in cultured endothelial cells and the protein has been detected in plasma. In the present studies we quantitated PN-2/APP in platelets, plasma and several different cell types of the vasculature to identify the repository of the protein in the circulatory system. We report that PN-2/APP is predominantly a platelet protein in the vascular compartment. Lysates of unstimulated umbilical vein endothelial cells, granulocytes or monocytes contained little PN-2/APP based on sensitive functional protease binding and immunoblotting assays. Quantitative immunoblotting studies demonstrated that normal citrated-plasma contains less than or equal to 60 pM PN-2/APP. In contrast, platelets can contribute up to 30 nM PN-2/APP, indicating that they are the major source of the protein in blood.

Amyloid beta-Peptides↗
PubMed2002

Human histamine N-methyltransferase pharmacogenetics: gene resequencing, promoter characterization, and functional studies of a common 5'-flanking region single nucleotide polymorphism (SNP).

Histamine N-methyltransferase (HNMT) catalyzes one of two major metabolic pathways for histamine. The levels of HNMT activity and immunoreactive protein in human tissues are regulated primarily by inheritance. Previous studies of HNMT identified two common single nucleotide polymorphisms (SNPs), including a functionally significant nonsynonymous coding SNP (cSNP), (C314T, Thr105Ile), but that polymorphism did not explain all of the phenotypic variation. In the present study, a genotype-to-phenotype strategy was used to search for additional genetic factors that might contribute to the regulation of human HNMT activity. Specifically, we began by resequencing the human HNMT gene using 90 ethnically anonymous DNA samples from the Coriell Cell Repository and identified a total of eight SNPs, including the two that had been reported previously. No new nonsynonymous cSNPs were observed, but three of the six novel SNPs were located in the 5'-flanking region (5'-FR) of the gene-including a third common polymorphism with a frequency of 0.367 (36.7%). That observation directed our attention to possible genetic effects on HNMT transcription. As a first step in testing that possibility, we created and studied a series of reporter gene constructs for the initial 1kb of the HNMT 5'-FR. The core promoter and possible regulatory regions were identified and verified by electrophoresis mobility shift assays. We then studied the possible functional implications of the new common HNMT 5'-FR SNP. However, on the basis of reporter gene studies, that SNP appeared to have little effect on transcription. Phenotype-genotype correlation analysis performed with 112 human kidney biopsy samples that had been phenotyped for their level of HNMT activity confirmed that the common 5'-FR SNP was not associated with the level of HNMT activity in vivo. In summary, this series of experiments resulted in the identification of several novel HNMT polymorphisms, identification of the HNMT core promoter, and a comprehensive functional genomic study of a common HNMT 5'-FR SNP. These results represent an additional step in the definition of molecular genetic mechanisms involved in the regulation of this important autacoid-metabolizing enzyme in humans.

5' Flanking Region↗
PubMed1998

Ahr null alleles: distinctive or different?

Two independent laboratories have generated Ahr "null" or "knockout" mice that share some common characteristics but also have distinct phenotypes. In this Commentary, we will discuss our view of the candidate variables that might account for these differences. More importantly, we hope that this discussion can identify important parameters to be assessed by investigators in the process of characterizing their own modified loci. The variables that we have considered include the possibility that different targeting strategies can result in altered products with unsuspected function or that the targeting event itself can alter the function of neighboring genes. Further, genetic background can have an important influence on phenotype, and differences in genome can be introduced during derivation by the type of embryonic stem cells used and by the random segregation of parental genes in the F2 generation of line propagation. In addition, phenotype may be acutely sensitive to environmental variables, such as pathogen and chemical exposure and stress introduced by crowding and disease. Finally, we discuss approaches to resolving differences between null mice and propose a partial solution, the institution of a repository for detailed information on targeted alleles that may not typically be allowed in today's "fast paced" scientific publications.

Alleles↗
PubMed2003

A genomic approach to mutation analysis of holocarboxylase synthetase gene in three Chinese patients with late-onset holocarboxylase synthetase deficiency.

OBJECTIVE: Multiple carboxylase deficiency (MCD, MIM:253270) is a common organic aciduria and caused by deficiency of either biotinidase or holocarboxylase synthetase (HLCS; EC 6.3.4.10). Patients commonly present during early infancy with acute metabolic derangements and severe metabolic acidosis. Recently, a late onset form of HLCS deficiency was also described. The different phenotypes (early and late presenting) may be related to a spectrum of mutations in HLCS gene. Applications of mutation analysis in HLCS had been limited previously by the requirement of cDNA from living tissue for study. We described here a genomic approach for molecular diagnosis of HLCS deficiency which we have used to detect mutations in Chinese patients who had the late-onset form of HLCS deficiency. In addition, a fibroblast cell line with MCD from Coriell Cell repositories was also studied. DESIGN AND METHODS: Three Chinese patients with late onset HLCS deficiency were studied. The genomic sequence of HLCS was retrieved and newly designed primers were used to cover all coding sequences of the gene. PCR products were analyzed by direct sequencing. Population allelic frequencies of mutations detected were determined by genotyping of control samples by restriction fragment length polymorphism. RESULTS: We found a recurrent mutation, R508W, in the three unrelated Chinese patients. Two were homozygous for this mutation. The other patient was a compound heterozygote of R508W and a novel mutation, D634N. The results suggest that R508W may be an important and relatively prevalent disease-causing mutation in Chinese MCD patients. A fibroblast cell-line from an African patient revealed an additional novel mutation, R565X and a known mutation, V550M. CONCLUSION: R508W is a recurrent mutation in Chinese MCD patients which is associated with the late onset phenotype. This new genomic approach for mutation analysis of HLCS gene provides new opportunities in studies of MCD.

Asian People↗
PubMed1989

X-ray fluorescence: issues surrounding the application of a new tool for measuring burden of lead.

Studies of lead toxicity would greatly benefit from a convenient, noninvasive measure of body lead burden. X-ray fluorescence (XRF) promises to provide such a measure by rapidly estimating lead content in bone, the repository of greater than 95% of an adult's lead stores (73% in children). Two separate XRF techniques exist, L-XRF and K-XRF. They differ in terms of calibration method and type of bone sampled. They also involve different radiation energies; however, radiation doses and concomitant risks are similarly low. Since interpretation of an XRF measurement depends to an extent on the distribution of lead in the skeleton, this topic is reviewed. Available data suggest that trabecular and cortical bone comprise two distinct compartments with regard to lead kinetics. Within each compartment, however, there also appears to be a significant degree of variability. Furthermore, there is evidence to suggest that the subperiosteal surface layer of cortical bone has a pattern of lead absorption and release that is different from the rest of cortical bone. This may have implications for (1) the choice of XRF technique, since the L-XRF technique measures lead in surface bone, whereas the K-XRF technique derives an estimate of lead from the full thickness of bone, and (2) the selection of bone sites for taking XRF measurements. More research is necessary to fully optimize the applicability of the XRF instrument.

Adolescent↗