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  • 2000-2004  (3)
  • 1965-1969  (1)
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  • 1
    ISSN: 1432-1076
    Keywords: Key words Hypomagnesaemia ; Tetany ; Calcitriol ; Nasogastric infusion ; Calcium metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Primary infantile hypomagnesaemia is an infrequent cause of neonatal hypocalcaemic seizures but one that responds well to magnesium supplementation. We describe a 22-year-old male, first reported at 4 months of age, who is currently free of neurological deficit but has suffered from intermittent hypomagnesaemic tetany and chronic diarrhoea due to large oral magnesium supplements. Hypothesizing that modest hypercalcaemia might prevent the tetany, we conducted a trial of 5 μg/day 1,25(OH)2D3 over 5 days. Despite the resultant increase in calcium, he developed tetany with the reduction of magnesium intake and decline of serum magnesium from 0.63 to 0.39 mmol/l (normal 〉0.65 mmol/l). After 1,25(OH)2D3 was stopped and the parenteral magnesium injections suspended, 33% of his usual oral supplement was given instead by continuous nasogastric infusion and serum magnesium rose to 0.60 mmol/l. This regimen was better tolerated because of decreased gastrointestinal side-effects and freedom from parenteral injections. We observed that 1,25(OH)2D3 supplements do not promote magnesium retention nor does the resultant hypercalcaemia prevent hypomagnesaemic tetany. Conclusion Continuous nocturnal nasogastric infusion may be considered in lieu of parenteral therapy in primary infantile hypomagnesaemia.
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  • 2
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. The collagen type Iα1 Sp1 (ColIA1) polymorphism has been associated with reduced bone mineral density (BMD) and increased prevalence of osteoporosis. This study examines associations of the ColIA1 genotype with BMD and 5-year rates of change in BMD in elderly men and women. The 243 subjects, aged 65 years and older, were participants in two consecutive studies lasting a total of 5-years. BMD of the total body, femoral neck, and lumbar spine were made by dual-energy X-ray absorptiometry (DXA). The distribution of the genotypes (155 in the SS genotype, 79 in Ss, and 9 in ss) was proportionately similar to those reported by others. Baseline BMD did not differ significantly at any skeletal site. Unadjusted 5-year percent changes in BMD differed significantly by genotype only at the total body (P= 0.009), where the change was −0.29 ± 0.21 (SEM) in the SS genotype, −0.60 ± 0.25 in the Ss genotype, and −3.01 ± 0.72 in the ss genotype. This 9.4% increase in bone loss of the ss genotype relative to the SS genotype was reduced to an 8.9% increase after adjustment for sex, age, weight, and supplementation group. Results at the femoral neck were directionally similar, but not statistically significant. No effect of genotype on change in spine BMD was observed. In conclusion, bone loss from the total body was significantly greater in elderly men and women who were homozygous for the s allele compared with heterozygotes and SS homozygotes. This finding suggests a possible explanation for the association of the ColIA1 polymorphism with increased rates of osteoporotic fracture, but should be interpreted with caution because of the small number of subjects in the unfavorable ss genotype.
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  • 3
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The appearance of biotypes of the annual grass weed black-grass (Alopecurus myosuroides L. Huds), which are resistant to certain graminicides, is the most significant example of acquired resistance to herbicides seen so far in European agriculture. An investigation was perfomed into the basis of the specific cross-resistance to cyclohexanedione (CHD) and aryloxyphenoxypropionoic acid (AOPP) herbicides in the ‘Notts A1’ population of A. myosuroides, which survived treatment of fields with recommended rates of AOPP herbicides. In comparison with the wild-type ‘Rothamsted’ population, the resistant biotype showed over 100-fold resistance to these herbicides in a hydroponic growth system. Biosynthesis of fatty acids and activity of crude extracts of acetyl-CoA carboxylase (ACCase) were commensurately less sensitive to these herbicides in Notts A1 compared with the Rothamsted biotype. These data are consistent with the hypothesis that the highly resistant population has arisen through selection of a mutant ACCase which is much less sensitive to the AOPP and CHD graminicides. Rapidly growing cell suspension cultures established from the Notts A1 population also showed high resistance indices for CHD or AOPP herbicides compared with cultures from the Rothamsted biotype. Fatty acid biosynthesis and ACCase activity in the cell suspensions were similarly sensitive towards the graminicides to those in the foliar tissue counterparts of the resistant and sensitive populations. Moreover, purification of the main (chloroplast) isoform of acetyl-CoA carboxylase showed that this enzyme from the Notts A1 population was over 200-fold less sensitive towards the AOPP herbicide, quizalofop, than the equivalent isoform from the Rothamsted population. These data again fully supported the proposal that resistance in the Notts biotype is due to an insensitive acetyl-CoA carboxylase isoform. Overall, cell suspensions were also demonstrated to be excellent tools for further investigation of the molecular basis of the high level herbicide resistance which is prone to occur in A. myosuroides.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Documenta ophthalmologica 21 (1966), S. 116-238 
    ISSN: 1573-2622
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Les effets d'un certain nombre de substances qui inhibent chez le lapin le métabolisme lors de la formation de l'humeur aqueuse sont décrits. On discute ces effets à la lumière de constatations expérimentales et d'hypothèses expliquant le mécanisme de la formation de l'humeur aqueuse. On examine le transport actif du sodium, et l'on montre que cette hypothèse peut être appuyée par des expériences dans lesquelles on emploie du tissu épithélial ciliaire isolé in vitro. La formation de l'humeur aqueuse est empêchée par l'acétate de fluor, le dinitrophénol et l'ouabaine, tandis que la composition de l'humeur aqueuse ne subit que peu de changement. Cependant, la composition peut être changée facilement par une modification de la molarité du plasma, et l'on suggère que le taux de sécrétion dépend: a) du taux de transport actif du sodium; b) de la molarité du plasma. Le transport actif du sodium dépend de l'oxygène et il est soumis à l'action des corps inhibiteurs du cycle citrique tels que le malonate et l'acétate de fluor, et l'ouabaine qui empêche l'action de l'ATP-ase activé par Na+ - K+ - Mg. Des études histochimiques et biochimiques sur l'épithélium ciliaire suggèrent que la succino-déhydrogenase, l'ATP-ase Na-K-Mg-activé et la cytochrome oxydase se trouvent d'une manière prédominante dans la couche des cellules non-pigmentées de l'épithelium. On admet que le système: cycle citrique, phosphorylation oxydative, synthèse de l'ATP fournit le substrat pour l'ATP-ase Na-K-Mg-activé et que celui-ci est chargé de la sortie du sodium hors de la cellule épithéliale vers la chambre postérieure. Il semble que ce système est localisé dans l'épithélium non-pigmenté. L'importance de la glycolyse dans l'épithélium ciliaire est grande mais elle n'est pas efficace comme source d'énergie pour le transport du Na. L'histochimie fait penser que la glycolyse peut être associée particulièrement à l'épithélium ciliaire du pigmenté. On décrit et discute les effets sur la sécrétion aqueuse d'un certain nombre d'autres substances (antagonistes de l'aldostérone, agents sélectivement toxiques pour l'épithélium pigmenté ciliaire), et on en déduit quel doit être le métabolisme de l'épithélium ciliaire. Dans la partie finale on émet une hypothèse qui tâche de tenir compte du rôle de l'épithélium ciliaire pigmenté dans la production de l'humeur aqueuse. On pense que cette couche peut fonctionner comme membrane chargée électriquement, la charge étant maintenue par le métabolisme de la cellule. Elle agirait comme un ‘filtre permsélectif’, et influerait sur le résultat final de la ‘pompe-Na’ dans la couche non-pigmentée. Dans un appendice on décrit une méthode destinée à mesurer la superficie de l'épithélium ciliaire chez le lapin.
    Abstract: Zusammenfassung Es wird eine Anzahl von Stoffwechselhemmern der Kammerwasserproduktion beim Kaninchen beschrieben: Diese werden im Licht der experimentellen Befunde und der erläuternden Hypothesen über den Prozess der Kammerwasserproduktion, die kurz durchgesehen werden, erörtert. Der Beweis für einen aktiven Natriumtransport wird geprüft, und es wird gezeigt, dass diese Hypothese möglicherweise durch Experimente mit isoliertem Epithelgewebe vom Ciliarkörper in vitro gestützt werden könnte. Kammerwasserproduktion wird von Fluoracetat, Dinitrophenol und Ouabain gehemmt, während die Zusammensetzung des Kammerwassers sich wenig verändert. Die Zusammensetzung kann jedoch durch Änderungen der Plasmaosmolarität leicht verändert werden, und es wird angenommen, dass die Sekretionsgrösse a) von dem Ausmass des aktiven Natriumtransportes und b) von der Plasmaosmolarität abhängt. Aktiver Natriumtransport ist sauerstoffbedingt und unterliegt einer Hemmung durch Inhibitionen des Zitronensäurezyklus wie Malonat und Fluoracetat und Ouabain, welches die Na+-K+-Mg-aktivierte ATP-ase hemmt. Histochemische und biochemische Untersuchungen am Ciliarepithel lassen vermuten, dass die Enzyme Succinatdehydrogenase, Na-K-Mg-aktivierte ATP-ase und Cytochromoxydase vorwiegend in der pigmentfreien Zellage des Epithels vorkommen. Es wird postuliert, dass die Systeme Zitratzyklus, oxydative Phosphorylation, ATP-Synthese das Substrat für die Na-K-Mg-aktivierte ATP-ase bilden, welches für die Verdrängung vom Natrium aus den Epithelzellen in die hintere Augenkammer verantwortlich ist. Dieses System scheint mit dem pigmentfreien Epithel zusammenzufallen. Die Glykolyserate im Ciliarepithel ist zwar gross, ist aber als Energiequelle für den Natriumtransport nicht genug wirksam. Es lässt sich auf Grund der Histochemie vermuten, dass Glykolyse besonders mit dem Pigmentepithel des Ciliarkörpers verbunden ist. Es werden die Wirkungen einer Anzahl anderer Substanzen (Aldosteron Antagonisten, Agenzien mit selektiver auf das Pigmentepithel gerichteter Toxizität) auf die Kammerwassersekretion beschrieben und erörtert, und ein Bericht über den mutmasslichen Stoffwechsel des Ciliarepithels erteilt. Im letzten Abschnitt wird eine Hypothese vorgeschlagen, welche die Rolle des Ciliarepithels bei der Kammerwasserproduktion in Rechnung zu stellen versucht. Es wird angenommen, dass diese Zellschicht als eine elektrisch geladene Membran funktioniere, deren Ladung vom Zellstoffwechsel aufrechterhalten werde, und die als ein ‘permselektives Filter’ wirken und so das Endresultat der aktiven ‘Natriumpumpe’ im pigmentfreien Zellager beeinflussen könnte. In einem Anhang wird ein Verfahren beschrieben, die Oberfläche des Ciliarepithels beim Kaninchen zu bestimmen.
    Notes: Summary The effects of a number of metabolic inhibitors on aqueous formation in rabbits are described: These are discussed in the light of experimental findings and explanatory hypotheses about the process of aqueous humour formation which are briefly reviewed. The evidence for active sodium transport is examined and it is shown that support for this hypothesis may arise from experiments using isolated ciliary epithelial tissue in vitro. Aqueous formation is inhibited by fluoroacetate, dinitrophenol and ouabain whilst the composition of the aqueous undergoes little change. The composition may, however, readily by changed by alterations of plasma osmolarity, and it is suggested that the rate of secretion depends upon: a) the rate of active Na transport b) the plasma osmolarity. Active Na transport is oxygen dependent and subject to inhibition by citrate cycle inhibitors such as malonate and fluoroacetate and by ouabain which inhibits Na+ - K+ - Mg-activated ATP-ase. Histochemical and biochemical studies on ciliary epithelium suggest that the enzymes succinate dehydrogenase, Na-K-Mg-activated ATP-ase and cytochrome oxidase occur predominantly in the non-pigmented cell layer of the epithelium. It is postulated that the systems: citrate cycle, oxidative phosphorylation, ATP synthesis furnish the substrate for Na-K-Mg-activated ATP-ase which is responsible for extruding sodium from the epithelial cell into the posterior chamber. This system appears co-terminous with the non-pigmented epithelium. Glycolysis rates in ciliary epithelium are high, but are not efficient as sources of energy for Na transport. The histochemistry suggests that glycolysis may be associated particularly with the ciliary pigment epithelium. The effects on aqueous secretion of a number of other substances (aldosterone antagonists, agents with selective toxicity to retinal pigment epithelium) are described and discussed, and a conjectural account is given of the metabolism of the ciliary epithelium. In the final section an hypothesis is advanced which attempts to take account of the role of the ciliary pigment epithelium in aqueous production. It is thought that this layer may function as an electrically charged membrane, the charge being maintained from cell metabolism and acting as a ‘permselective filter’ influencing the final result of the active ‘Na-pump’ in the non-pigmented cell layer. In an appendix a description is given of a procedure used to determine the surface area of the ciliary epithelium in rabbits.
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