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  • 1
    Electronic Resource
    Electronic Resource
    Relationship of progressively increasing albuminuria to apoprotein(a) and blood pressure in Type 2 (non-insulin-dependent) and Type 1 (insulin-dependent) diabetic patients (1993)
    Springer
    Diabetologia 36 (1993), S. 1037-1044 
    Details
    ISSN: 1432-0428
    Keywords: Diabetic nephropathy ; albuminuria ; apoprotein(a) ; blood pressure ; Type 2 (non-insulin-dependent) diabetes mellitus ; Type 1 (insulin-dependent) diabetes mellitus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study has explored the temporal relationship between apoprotein(a), blood pressure and albuminuria over a mean interval of 11 years in a cohort of 107 diabetic patients of whom 26 (14 Type 2 (non-insulin-dependent), 12 Type 1 (insulin-dependent) had progressively increasing albuminuria (‘progressors’). In Type 2 diabetic patients, no significant differences were noted for HbA1, blood pressure, creatinine clearance or serum lipids between progressors and non-progressors. In Type 1 diabetic patients, final systolic and diastolic blood pressures were higher in progressors compared with non-progressors and progressors showed impairment of renal function in association with a rise in blood pressure at the macroalbuminuric stage. Initial apoprotein(a) levels were similar in progressors and non-progressors of either diabetes type. Apoprotein(a) levels increased exponentially with time in 12 of 14 Type 2 progressors but only in 5 of 12 Type 1 progressors (p〈0.01). In Type 2 diabetic patients, the annual increase in apoprotein(a) levels was 9.1±2.4%, which was significantly greater than in non-progressors, 2.0±1.2% (p〈0.01) and also exceeded the rates of increase of apoprotein(a) in progressors with Type 1 diabetes, 4.0±1.4%, (p〈0.05). Apoprotein(a) levels correlated significantly with albuminuria in 8 of 14 Type 2 progressors but only in 3 of 12 Type 1 progressors (p〈0.05). The rate of increase of apoprotein(a) levels was not related to mean HbA1, creatinine or creatinine clearance levels, or to albuminuria. The rate of rise of apoprotein(a) was not influenced by initial apoprotein(a) levels, suggesting that specific apoprotein(a) isoforms do not influence albuminuria-related increases in apoprotein(a). The data are consistent with the hypothesis that apoprotein(a) levels increase in response to albuminuria and may be part of a self-perpetuating process. This study also suggests that increases in apoprotein(a) levels commence during the microalbuminuria stage in diabetic patients, which is earlier than has been documented in non-diabetic proteinuria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02374496
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of aldose reductase inhibitors on glomerular prostaglandin production and urinary albumin excretion in experimental diabetes mellitus (1991)
    Springer
    Diabetologia 34 (1991), S. 225-231 
    Details
    ISSN: 1432-0428
    Keywords: Diabetic nephropathy ; albuminuria ; aldose reductase inhibitors ; prostaglandins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of two structurally unrelated aldose reductase inhibitors, sorbinil and ponalrestat, on glomerular prostaglandin production and urinary albumin excretion was investigated in rats with diabetes induced by streptozotocin. It was found that both aldose reductase inhibitors, when administered from the time of induction of the diabetes, significantly decreased the raised urinary albumin excretion in the diabetic rats, although it remained elevated compared with non-diabetic rats. Glomerular prostaglandin E and 6-ketoprostaglandin F1α production was significantly increased in glomeruli obtained from the diabetic rats. Inhibition of aldose reductase caused a reduction in the raised glomerular prostaglandin production, although this remained above that observed in the non-diabetic rats. Subsequent experiments were performed to determine whether the effects of the aldose reductase inhibitors could be explained by effects on glomerular filtration rate. It was found that ponalrestat, at a dose which markedly reduced urinary albumin excretion, did not significantly affect glomerular filtration rate in non-diabetic rats, rats with untreated streptozotocin-induced diabetes and rats with diabetes partially treated with low dose insulin. Glomerular sorbitol concentrations were significantly elevated in untreated diabetic rats as early as two weeks after the induction of diabetes. It is concluded that the administration of aldose reductase inhibitors from the time of induction of diabetes significantly reduces glomerular prostaglandin production and urinary albumin excretion. The latter effect is not due to an effect on glomerular filtration rate. Increased polyol pathway activity may account in part for the increased glomerular prostaglandin production and urinary albumin excretion in early experimental diabetes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00405080
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  • 3
    Electronic Resource
    Electronic Resource
    Ordination of simulated complex forest succession: A new test of ordination methods (1983)
    Springer
    Plant ecology 51 (1983), S. 141-155 
    Details
    ISSN: 1573-5052
    Keywords: Correlation matrix ; Dispersion matrix ; Forest model ; Hierarchical structure ; Ordination ; Principal components analysis ; Simulation ; Succession
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A model of a 1/12th ha forest stand, FORET, generated 10 000 years of simulated species succession. Approximately the first third of these results were analyzed by principal component analysis as if they were collected field data to give the trajectory of the community particle in a collapsed species space. The ordination axis orientation was performed on a dispersion matrix and correlation matrix between species. In both cases, however, the eigen vectors were applied to the data matrix which had not been transformed to unit species variance. This facilitated comparison of species dispersion and correlation structure; it emerged they were very different. Correlation structure gave large weights to understory species while dispersion emphasized the dominant overstory species. This implies a decomposition of simulated stand behavior into overstory and understory, even though such decomposition was not formally built into the model. This decomposition would seem to pertain to real vegetation. Principal component analysis was able to express insightful differences between data structure with and without the unit variance transformation implicit in the correlation matrix. This flexibility of the ordination method proved valuable in uncovering unsuspected ordering principles in the model. Complex simulated data allow the ordination technique to demonstrate its capacity to generate new hypotheses, which hypotheses can then be simply validated by a return to the structure of the model but with the hindsight of the analysis. The generation of new hypotheses is not possible if the simulation is of a simple coenocline; on the other hand, ordination of test field data does not allow the simple validation of new hypotheses, for in the field there is not a defined algorithm to which the researcher can return.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00129433
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Data transformation as a scaling operation in ordination of plankton (1984)
    Springer
    Plant ecology 56 (1984), S. 147-160 
    Details
    ISSN: 1573-5052
    Keywords: Data transformation ; Ordination ; Phytoplankton ; Principal components analysis ; Scale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Data transformation is seen here as an aspect of scaling such that we are less interested in the quirks and properties of each transformation but are more concerned with the general scaling properties and trends of suites of transformations. Over two years of daily phytoplankton abundance data for 30 species from a temperate lake (Llyn Maelog, North Wales) were subjected to a series of scale-ordered transformations. Two major classes of transformation were systematically varied: binary and smoothing. Binary transformation scaled the cutoff threshold between ‘presence’ and ‘absence’ of a species to various levels of abundance. With successively smaller universes and smoothing windows and successive species exclusion, ordinations of sample dates revealed smaller scaled structures in the order: annual cycles of species turnover, seasonal areas of attraction and uniqueness of individual sample dates. Gradual increases in the length of the smoothing window resulted in gradual shifts in the positions of points in sample data ordination, but not necessarily in the species ordinations. Thus sample data structures are more stable with change in scale than are species data structures. These differences in stability are discussed in the context of filtering characteristics of data collection and data analysis. Transformations producing similar species statistics (means, variances and skews) did not generally give similar ordination results, while some transformations giving similar ordinations differed in species statistical parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00045222
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    Paper (German National Licenses)
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