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  • Life and Medical Sciences  (3)
  • Intratubular Pressure  (2)
  • Risk factors  (2)
  • 1
    ISSN: 1433-2965
    Schlagwort(e): Bone density ; Prospective studies ; Risk factors ; Vertebral fracture incidence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We evaluated the ability of bone density and vertebral fractures at baseline to predict vertebral fracture incidence in a cohort of postmenopausal women with osteoporosis. The study population was 380 postmenopausal women (mean age 65 years) treated for osteoporosis in a randomized, placebo-controlled, clinical trial of the bisphosphonate etidronate at seven geographic centers in the United States. Baseline measurements of bone mineral density were obtained in 1986 by quantitative computed tomography at the spine and dual-photon absorptiometry at the lumbar spine and hip. Vertebral fractures were documented on serial spine radiographs. Proportional hazards models were used to evaluate the ability to predict the risk of subsequent fractures during an average of 2.9 years of follow-up. Presence of one or two fractures increased the rate of new vertebral fractures 7.4-fold (95% confidence interval = 1.0 to 55.9). Additional fractures at baseline further increased the fracture rate. A decrease of 2 standard deviations in spinal bone density by absorptiometry was associated with a 5.8-fold increase in fracture rate (95% confidence interval = 2.9 to 11.6). The lowest and highest quintiles of bone density had absolute fracture rates of 120 and 6 cases per 1000 patient-years, respectively. In general, the simultaneous use of two predictors (bone density and prevalent fractures or two bone density measurements) improved fracture prediction, compared with the use of a single predictor. We conclude that both bone density and prevalent vertebral fractures are strong, complementary predictors of vertebral fracture risk. The results suggest that physicians can use bone density and prevalent vertebral fractures, individually or in combination, as risk factors to identify patients at greatest risk of new fractures.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1432-2013
    Schlagwort(e): Nephron Filtration Rate ; Saline Diuresis ; Intratubular Pressure ; Retrograde Contamination ; Sampling Pipettes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The theory of a functional coupling between distal tubular fluid composition and glomerular filtration rate implies that the blockade of flow at a proximal site should lead to a marked increase of GFR. This potential alteration of steady state GFR was studied by comparing the influence of sampling from distal or proximal sites on the filtration rate of identical nephrons. During antidiuresis an average GFR of 25.2 nl/min±7.5 S.D. was found in distal collections, while proximally collected samples gave an average GFR of 34.5 nl/min±8.4 S.D. This difference of 9.3 nl/min is highly significant (p〈0.001). During saline diuresis a mean nephron GFR of 41.6 nl/min±5.0 was found by distal sampling and of 45.3 nl/min±5.4 by proximal sampling (p〉0.05). The proximal-distal difference in nephron GFR is interpreted to indicate the operation of a tubulo-glomerular feedback control system. Thus, a true steady-state GFR probably cannot be obtained by proximal fluid collection. Even in the presence of high intratubular pressures and unusually short oil blocks no evidence of sample contamination by retrograde fluid flow past an injected oil block was obtained. The application of a counter-pressure to the sampling pipette which has been recommended by Gertzet al. [5] as a means to standardize fluid collections, was found to lead to abnormally high intratubular pressures. The reason for this finding appears to be an unexpectedly high and inconstant tip resistance to flow during fluid flow into the pipette.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 333 (1972), S. 271-280 
    ISSN: 1432-2013
    Schlagwort(e): Nephron Filtration Rate ; Tubulo-Glomerular Feedback ; Intratubular Pressure ; Polyfructosan
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Two possible artifacts may explain the phenomenon that nephron GFR (N-GFR) measured by distal tubular puncture is smaller than that measured by proximal tubular puncture: a loss of the inulin-like substance used in this laboratory (polyfructosan) from the tubular lumen or unreliable distal punctures. To test these possibilities (a) known amounts of polyfructosan were injected into the proximal tubule and the percentage recovery from the distal tubule measured, (b) N-GFR was measured by distal puncture, subsequently by recollection from the same site and finally by a proximal puncture. On the average, 98.5±7.5% of the proximally injected polyfructosan was recovered from the distal tubule. This is not significantly different from 100% (p〉0.1) and demonstrates that proximal tubule and loop of Henle are impermeable to polyfructosan. The ratio between the N-GFR measured by a distal puncture and that measured by subsequent recollection was 1.016±0.096 and not significantly different from 1.000 (p〈0.20), demonstrating the reliability of distal tubular puncture. The mean distal N-GFR of 27.9±5.3 nl/min was significantly smaller (p〈0.001) than the proximal N-GFR of 35.1±8.0 nl/min. The existence of the proximal-distal N-GFR difference thus is confirmed and two possible artifacts eliminated. The best explanation remains the operation of a tubulo-glomerular feedback mechanism. A current point of dispute is the effect of alterations in intratubular pressure (ITP) on N-GFR. Collection of tubular fluid at ITPs below the previously measured free flow pressure (FFP) resulted in a change of N-GFR of 0.45 nl/min· cm H2O. In contrast, fluid collection at ITPs greater than the FFP resulted in a change of N-GFR of 1.48 nl/min· cm H2O. We conclude that although N-GFR is sensitive to ITP changes in both directions, pressure decreases are of little practical importance for the determination of N-GFR whereas intratubular pressure increases are to be avoided.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Morphology 124 (1968), S. 79-82 
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: A total of 1125 normal chick embryos, representing 25 each of the 45 stages of Hamburger and Hamilton, were removed, fixed in Bouin's solution, stored in 70% ethanol and weighed with a semi-micro analytical balance. Entire blastoderms of stages 1-8 were weighed, whereas only embryos-proper were weighed in stages 9-45. As a consequence, results constituted two groups, each of which showed a geometric rate of growth marked only by minor deviations which were related to specific events of normal growth and development.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Osteoporosis international 4 (1994), S. 1-5 
    ISSN: 1433-2965
    Schlagwort(e): Bone mass ; Bone density ; Fracture incidence ; Fracture prevalence ; Longitudinal studies ; Risk factors
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract A prospective cohort study of 1098 postmenopausal Japanese-American women evaluated the relationship between baseline non-spine fractures and new (incident) spine fractures. At the baseline examination in 1981, prevalent non-spine fractures were ascertained by interview, and prevalent spine fractures by radiograph. Bone mass measurements of the distal radius, proximal radius, calcaneus (1981), the lumbar spine (1984) were obtained and repeated at 1- to 2-year intervals. Women with existing non-spine fractures have a threefold greater risk of subsequent spine fractures, independent of bone mass, and independent of the known association between prevalent spine fractures and subsequent spine fractures. Women with both a prevalent non-spine fracture and low bone mass (50th percentile or lower) have an eightfold greater risk of new spine fractures compared with women above the 50th percentile of bone mass and no prevalent fractures. In addition to low bone mass, both prevalent spine fractures and prevalent non-spine fractures are strong risk factors for subsequent spine fracture. These data suggest that not all osteoporotic risk factors are expressed via bone mass, and that other, unmeasured risk factors, such as bone quality defects, may explain these results. In clinical terms, women with both prevalent fractures and low bone mass should be recognized as being at extremely high risk, and treatment potency should be commensurate with this level of risk.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 161 (1968), S. 247-252 
    ISSN: 0003-276X
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Microcurie amounts of p32, Na22, Fe59, and Cl36 in normally occurring compounds were injected directly into the vitelline vessels of developing chick embryos at stage 24 (Hamburger and Hamilton, '51). The surviving embryos were sacrificed at stage 41. Hearts were removed and examined intact or sectioned for later examination. Coronary vessels were identified, classified according to size (large, diameter = 〉 80 μ; medium, diameter = 40-80 μ; small, diameter 〈 40 μ) and counted. There was a significant increase in the numbers of small and medium vessels which had developed in the presence of gamma radiation emitted by Na22- and Fe59-compounds. The p32- and Cl36-containing compounds did not affect the numbers of vessels of any size. The resulting increased vascularity is shown to be a matter of a distinct increase in numbers of blood vessels as opposed to a simple alteration of the normally occurring vessels.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    ISSN: 0003-276X
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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