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PubMed2004

Osmium isotope heterogeneity in the constituent phases of mid-ocean ridge basalts.

Radiogenic isotope variations in mid-ocean ridge basalts (MORB) are commonly attributed to compositional variations in Earth's upper mantle. For the rheniumosmium isotope system, constituent MORB phases are shown to possess exceptionally high Re/Os (parent/daughter) ratios, consequently radiogenic 187Os is produced from the decay of 187Re over short periods of time. Thus, in the absence of precise age constraints, Os isotope variations cannot be unambiguously attributed to their source, although Re-Os isotope data for constituent minerals can yield crystallization ages, details of equilibration, and initial Os isotope values that relate directly to the mantle source.

Journal Article↗
PubMed1995

Success, failures and costs of implementing standards in the USA--lessons for infection control.

In the US, extensive standards for performance and 'guidelines for practice' have been instituted by a number of governmental and non-governmental agencies. New governmental plans for health care depend heavily on practice guidelines, and the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) has been especially enthusiastic about continuous quality improvement. Monitoring the appropriateness of care and altering physician practice appeals to insurance carriers and health care management organizations. Some initial data exist to show that the quality of health care has been enhanced by these regulations. The total cost for health care administration in 1990 in the USA was 24.8% of each hospital's spending for health care. Much of this was associated with spending for new initiatives in practice guidelines, physician profiling, quality assurance, and the like. Few data exist to show that the quality of health care or hospital infection control has been enhanced by these expenditures. Regulations and guidelines also have proliferated in infection control. Guides from the JCAHO have been expanded, and recent mandates from the Occupational Health and Safety Administration (OSHA) for protecting employees from blood-borne and respiratory pathogens promise to be especially costly for health care organizations to implement. Little data exist to show that the quality of infection control has been enhanced by these regulations. Standards are difficult to develop, because the science to back them up often is lacking, interpretation of validating data is imprecise, and inherent biological variation makes exceptions common. Seven lessons are important for those developing standards today. These include focusing on objective measures of the impact of the standard, clearly indicating the degree of scientific validity, making the development process inclusive, allowing for local variation, making sure that funding is provided for mandated standards, considering non-scientific implications of standards, and remaining involved in the process after the guideline is developed. Infection control workers should make sure that standards developed take the lessons above into account before they are promulgated.

Financial Support↗
PubMed2004

Prevalence and incidence studies of mood disorders: a systematic review of the literature.

OBJECTIVE: To present the results of a systematic review of literature published between January 1, 1980, and December 31, 2000, that reports findings on the prevalence and incidence of mood disorders in both general population and primary care settings. METHOD: We conducted a literature search of epidemiologic studies of mood disorders, using Medline and HealthSTAR databases and canvassing English-language publications. Eligible publications were restricted to studies that examined subjects aged at least 15 years and over. We used a set of predetermined inclusion and exclusion criteria to identify relevant studies. We extracted and analyzed prevalence and incidence data for heterogeneity. RESULTS: Of general population studies, a total of 18 prevalence and 5 incidence studies met eligibility criteria. We found heterogeneity across 1-year and lifetime prevalence of major depressive disorder (MDD), dysthymic disorder and bipolar I disorder. The corresponding pooled rates for 1-year prevalence were 4.1 per 100, 2.0 per 100, and 0.72 per 100, respectively. For lifetime prevalence, the corresponding pooled rates were 6.7 per 100, 3.6 per 100, and 0. per 100, respectively. Significant variation was observed among 1-year incidence rates of MDD, with a correspond ing pooled rate of 2.9 per 100. CONCLUSIONS: The prevalence of mood disorders reported in high-quality studies is generally lower than rates commonly reported in the general psychiatric literature. When controlled for common methodological confounds, variation in prevalence rates persists across studies and deserves continued study. Methodological variation among studies that have examined the prevalence of depression in primary health care services is so large that comparative analyses cannot be achieved.

Analysis of Variance↗
PubMed1996

The common nodABC genes of Rhizobium meliloti are host-range determinants.

Symbiotic bacteria of the genus Rhizobium synthesize lipo-chitooligosaccharides, called Nod factors (NFs), which act as morphogenic signal molecules on legume hosts. The common nodABC genes, present in all Rhizobium species, are required for the synthesis of the core structure of NFs. NodC is an N-acetylglucosaminyltransferase, and NodB is a chitooligosaccharide deacetylase; NodA is involved in N-acylation of the aminosugar backbone. Specific nod genes are involved in diverse NF substitutions that confer plant specificity. We transferred to R. tropici, a broad host-range tropical symbiont, the ability to nodulate alfalfa, by introducing nod genes of R. meliloti. In addition to the specific nodL and nodFE genes, the common nodABC genes of R. meliloti were required for infection and nodulation of alfalfa. Purified NFs of the R. tropici hybrid strain, which contained chitin tetramers and were partly N-acylated with unsaturated C16 fatty acids, were able to elicit nodule formation on alfalfa. Inactivation of the R. meliloti nodABC genes suppressed the ability of the NFs to nodulate alfalfa. Studies of NFs from nodA, nodB, nodC, and nodI mutants indicate that (i) NodA of R. meliloti, in contrast to NodA of R. tropici, is able to transfer unsaturated C16 fatty acids onto the chitin backbone and (ii) NodC of R. meliloti specifies the synthesis of chitin tetramers. These results show that allelic variation of the common nodABC genes is a genetic mechanism that plays an important role in signaling variation and in the control of host range.

Acylation↗
PubMed2004

Mating within the meiotic tetrad and the maintenance of genomic heterozygosity.

Mating among the products of a single meiosis (automixis or meiotic parthenogenesis) is found in diverse groups of plant, animal, and fungal taxa. Restoration of the diploid stage is often strictly controlled and brings together products separated at the first meiotic division. Despite apparent similarities to diploid selfing, the theoretical prediction is that heterozygosity should be maintained on all chromosomes when it is linked to the centromeres and thus also segregates at the first meiotic division. Using the fungus Microbotryum, we directly test this prediction by linear tetrad analysis. The patterns of meiotic segregation for chromosome size variation (electrophoretic karyotypes) and PCR products (AFLP procedures) were determined for Microbotryum lineages native to North America and Europe. Our data reveal a surprisingly dynamic genome that is rich in heterozygosity and where size-dimorphic autosomes are common. The genetic variation agrees with the prediction of centromere-linked heterozygosity. This was observed to the greatest extent in the lineage of Microbotryum native to North America where there was consistent first-division segregation and independent assortment of multiple linkage groups. The data also show properties that distinguish the fungal sex chromosomes from the autosomes in both lineages of Microbotryum. We describe a scenario where the mating system of automixis with first-division restitution is the result of feedback mechanisms to control exposure of genetic load.

Basidiomycota↗
PubMed1996

Dorsalis pedis artery: variations and clinical significance.

A variation not particularly common in the dorsalis pedis artery was noted in routine classroom dissection. The artery was found to be replaced by a large perforating branch of the peroneal artery instead of the terminal part of anterior tibial artery. This variation has got high clinical significance.

Arteries↗
PubMed2000

Variations of the great arteries in the carotid triangle.

The variations of the common carotid artery, as well as of the external and internal carotid arteries, are described. During anatomic dissection on adult cadavers, we investigated the variability of appearance of 40 carotid arterial systems. Special consideration was given to the topographic relations such as the level of the bifurcation of the common carotid artery, the relationship between the external and internal carotid arteries, and the origin of the great collateral branches. Special attention was paid to the origin of the superior thyroid artery. In this article the practical importance of these variations is stressed.

Adult↗
PubMed2005

Using wavelet de-noised spectra in NMR screening.

Principal component analysis (PCA) is a commonly used algorithm in multivariate analysis of NMR screening data. PCA substantially reduces the complexity of data in which a large number of variables are interrelated. For series of NMR spectra obtained for ligand binding, it is commonly used to visually group spectra with a similar response to ligand binding. A series of filters are applied to the experimental data to obtain suitable descriptors for PCA which optimize computational efficiency and minimize the weight of small chemical shift variations. The most common filter is bucketing where adjacent points are summed to a bucket. To overcome some inherent disadvantages of the bucketing procedure we have explored the effect of wavelet de-noising on multivariate analysis, using a series of HSQC spectra of proteins with different ligands present. The combination of wavelet de-noising and PCA is most efficient when PCA is applied to wavelet coefficients. This new algorithm yields good clustering and can be applied to series of one- or two-dimensional spectra.

Hydrogen↗
PubMed1993

Radial and humeral fractures as predictors of subsequent hip, radial or humeral fractures in women, and their seasonal variation.

Hip fractures are common in elderly women, and early risk assessment of future hip fractures is relevant in relation to prevention. We studied the predictive value of radial and humeral fractures in women. The influence of weather conditions on the risk was also studied. Women aged 20-99 years with a fracture of the distal radius (n = 1162) or proximal humerus (n = 406) were followed for 0 to 9 years. The relative risk (RR) and 95% confidence limits (CL) of subsequent fracture among women suffering radial or humeral fractures compared with the background population were calculated. Women 60-79 years of age who had suffered a fracture of the distal radius or proximal humerus had relative risks of sustaining a hip fracture of 1.9 (1.3-2.6, 95% CL) and 2.5 (1.3-3.6, 95% CL) respectively. The relative risk of hip fracture was highest within the first years following a fracture of the radius or the humerus. Women suffering an upper extremity fracture (radius or humerus) in snowy or icy weather had a marginally increased risk (RR = 1.3, 0.4-2.3, 95% CL and RR = 1.8, 0.3-3.4, 95% CL) for a later hip fracture. A woman 50 years old with a radial or a humeral fracture had an estimated residual lifetime risk of sustaining a subsequent hip fracture of 17% and 16% respectively compared with 11% for the background population.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

An apparently common mechanism of generating antibody diversity: length variation of the VL-JL junction.

The joining of various V, (D) and J gene segments during DNA rearrangement of the antigen receptor genes is one of the principle mechanisms responsible for the generation of antibody diversity. In the absence of N-segment variation, the structures of the coding joints formed during light chain rearrangement are thought to be less complex than their heavy chain counterparts. Consequently, the joining of the VL and JL gene segments during recombination account for all of the junctional diversity seen within the third complementarity determining region (CDR3). We generated kappa light chain transcripts from human fetal liver and peripheral blood lymphocytes and found that approximately one third exhibit a variation in the length of CDR3-independent of the JK gene segment utilized. Nucleotide sequence analysis reveals that many of the nucleotides at the VK-JK joint resulting in length variation of CDR3 are directly encoded by the germline VK and JK gene segments used in these transcripts. However, nearly 20% of the transcripts contain N-segment additions consistent with TdT-like activity. These observations suggest that TdT or an analogous enzyme must be active in a significant percentage of human B-lymphocytes during light chain rearrangement. Length variation in light chain CDR3 expands the potential repertoire and thus contributes an additional means of generating diversity in the antibody molecule.

Amino Acid Sequence↗
PubMed2001

Comparison of Vif sequences from diverse geographical isolates of HIV type 1 and SIV(cpz) identifies substitutions common to subtype C isolates and extensive variation in a proposed nuclear transport inhibition signal.

We compared the Vif sequences from more than 100 group M and O strains of HIV-1 isolated from diverse geographical regions and various subtypes, in order to identify regions of high variability and those amino acid residues that were highly conserved or invariant. Our analysis found that there were 10 highly conserved domains with additional invariant residues located throughout the protein. Our analysis revealed that in the highly conserved amino-terminal domain, all subtype C isolates examined had a methionine-to-leucine substitution at position 8 and most subtype C isolates had an arginine-to-lysine substitution at position 17 of the protein. Our analysis revealed that the MAP kinase phosphorylation sites, and the cysteine residues at positions 114 and 133, were conserved in Vif sequences from group M, group O, and SIV cpz isolates. Our analysis also shows that the RKKR motif at positions 90--93, proposed as a nuclear transport inhibition signal (NTIS), was conserved neither in different geographical group M and O HIV-1 isolates nor in SIVcpz.

Amino Acid Sequence↗
PubMed1997

Structural characterization of the K antigens from Rhizobium fredii USDA257: evidence for a common structural motif, with strain-specific variation, in the capsular polysaccharides of Rhizobium spp.

Rhizobium fredii participates in a nitrogen-fixing symbiosis with soybeans, in a strain-cultivar-specific interaction, and past studies have shown that the cell surface and extracellular polysaccharides of rhizobia function in the infection process that leads to symbiosis. The structural analysis of the capsular polysaccharides (K antigens) from strain USDA257 was performed in this study. The K antigens were extracted from cultured cells with hot phenol-water and purified by size exclusion chromatography. We isolated two structurally distinct K antigens, both containing a high proportion of 3-deoxy-D-manno-2-octulosonic acid (Kdo). The polysaccharides were characterized by matrix-assisted laser desorption ionization-time-of-flight-mass spectrometry, nuclear magnetic resonance spectrometry, and gas chromatography-mass spectrometry analyses. The primary polysaccharide, which constituted about 60% of the K-antigen preparation, consisted of repeating units of mannose (Man) and Kdo, [-->)3-beta-D-Manp-(1-->5)-beta-D-Kdop-(2-->], and a second polysaccharide consisted of 2-O-MeMan and Kdo, [-->)3-beta-D-2-O-MeManp-(1-->5)-beta-D-Kdop-(2-->]. These structures are similar to yet distinct from those of other strains of R. fredii and R. meliloti, and this finding provides further evidence that the K antigens of rhizobia are strain-specific antigens which are produced within a conserved motif.

Antigens, Bacterial↗
PubMed1999

Gene targeting approaches to analyzing hypertension.

Essential hypertension probably results from combinations of small genetic variations that are partly normal variations and may not be appreciably harmful individually. Strategies to identify genes contributing to hypertension are discussed in this review. Gene targeting approaches, especially gene titration, have been used in these studies of hypertension. Gene titration experiments vary the expression of a chosen gene product by generating animals having different numbers of copies of the gene coding for the product. Gene titration is powerful for analyzing quantitative variations seen in common polygenic disorders, such as kidney diseases, diabetes mellitus, and atherosclerosis, as well as hypertension, because it allows tests of causation by determining the effects on a phenotype by changes in expression of the altered gene and because it matches normal quantitative variations more closely than is possible with classic transgenic mice. The use of zero-copy (gene "knockout") animals generated by gene disruption for studies of qualitative gene effects is also discussed. These various gene targeting experiments help identify genes regulating BP, promote a better understanding of the pathophysiology of the condition, and help identify potential targets for therapies.

Animals↗
PubMed1980

Electrophoretic studies on enzymes in the Japanese common liver fluke, Fasciola sp. I. Enzyme variations in the natural population.

A preliminary study on four enzymes, adenylate kinase, phosphoglucomutase, phosphogluconate dehydrogenase and esterase, of Fasciola sp. found in Japan was carried out by horizontal starch gel electrophoresis. Among them, two enzymes, adenylate kinase and phosphoglucomutase, showed variations in the natural population, but the frequencies of the variants were considerably low; the remainders, phosphogluconate dehydrogenase and esterase, showed no variation.

Adenylate Kinase↗