Zusammenfassung: Eine radioimmunologische Methode zur gleichzeitigen Bestimmung von Thyroxin (T 4 ) und Trijodthyronin (T 3 ) im Urin wurde entwickelt. Die Extraktion der Proben, die Inkubationen mit T 3 -und anschließend T 4 -Antikörper und die Elutionen der jeweiligen gebundenen Fraktionen wurden alle nacheinander auf der gleichen Sephadex Säule durchgeführt. Mit diesem Prinzip wurden gleichzeitig bis zu 120 Bestimmungen durchgeführt. Die InterassayVariationskoeffizienten betrugen 20 J % für T 3 und 10,6% für T 4 . Die Wiederfindung von Urinproben zugesetzten Kalibrierstandards war 107 ± 8% ( ± s) für T 3 und 102 ± 8% für T 4 .Im 24-Stunden-Urin gesunder Kontrollpersonen wurden l ,70 ± 0,40 /zg T 3 und l ,44 ± 0,51 g T 4 gefunden ( ± s; N = 20). Drei-Stunden-Fraktionen des Tagesurins zeigten signifikant höhere Werte der T 4 -Ausscheidung im Vergleich zur Nacht-Fraktion, während die T 3 -Exkretion nur in der Abend-Periode von 18-21 Uhr höher als während der übrigen Beobachtungszeit war. Die T 4 -Ausscheidung ist bei der primären Hypothyreose erniedrigt (0,48 ± 0,47 g/ 24 Stunden, p < 0,0005), wobei die T 3 -Ausscheidung als Zeichen der bekannten T 3 -Restsekretion nur geringfügig vermindert war (1,30 ± 0,80 jug). Eine verminderte T 4 -Ausscheidung (0,85 ± 0,34 g, p < 0,0005) im Gegensatz zu der normalen T 3 -Exkretion weist bei Patienten mit endemischer Struma auf die bekannte präferentielle T 3 -Sekretion bei Jodmangel hin. Bei T 3 -Hyperthyreose fand sich eine erhöhte T 3 -Exkretion bei normaler T 4 -Ausscheidung im Urin. Bei persistierender Suppression der TSH-Werte im Serum nach erfolgreicher Behandlung einer Hyperthyreose fanden sich normale Werte der T 3 -und T 4 -Ausscheidung im Urin. Simultaneous radioimmunoassay for urinary thyroxine (T^) and triiodothyronine (T 3 )Summary: A radioimmunoassay for the determination of thyroxine (T 4 ) and triiodothyronine (T 3 ) in urine was developed. The extraction of a sample, the incubations with T 3 -urid subsequently T 4 -antibody and the elutions of the respective bound fractions are performed all on the same Sephadex column. This principle can be applied to as many as 120 simultaneous determinations. The interassay coefficients of variation were 20.1 % for T 3 and 10.6% for T 4 , respectively. The recovery of standards added to urine was 107 ± 8%(mean ± SD) for T 3 and 102 ± 8%for T 4 .The 24 h collections of urine from healthy controls contained 1.70 ± 0.40 jug T 3 and 1.44 ± 0.51 g T 4 (mean ± SD, N = 20). Three hourly fractions of the urinary excretion collected from 6 a. m. through 9 p. m. showed a significant (p < 0.005) elevation of the T 4 excretion as compared to the night fraction, whereas an increased T 3 excretion was only observed from 6-9 p. m. The T 4 excretion was reduced in primary hypothyroidism (0.48 ± 0.47 g per 24 h, p < 0.0005), whereas the T 3 excretion was not that markedly reduced (1.30 ± 0.80 g/d), pointing to the known residual T 3 secretion. A reduced T 4 excretion (0.85 ± 0.34 g/d p < 0.0005) contrasted with the normal T 3 excretion i...
The effects of various [Ca2+]0 on membrane potential (MP), action potential (AP) frequency, and isometric tension of isolated guinea-pig taenia coli were studied using intracellular recording techniques and simultaneous tension measurement. At 5.9 mM [K+]0 the order of potency of [Ca2+]0 this order is gradually reversed since high [Ca2+]0 becomes more potent in accelerating impulse discharges. At 2.5 mM [Ca2+]0 the line relating MP to log [K+]0 is not straight; its slope for a tenfold change of [K+]0 is 21.1 mV in the range between 5.9 and 17.7 mM [K+]0, and 51.5 mV between 32.45 and 59 mM [K+]0. In general, reducing [Ca2+]0 depolarizes the membrane whereas increasing [Ca2+]0 hyperpolarizes it. The Ca2+-induced changes of MP are reduced at high [K+]0. At 2.5 and 7.5 mM [Ca2+]0 the lines relating AP frequency and tension to the MP are nearly superimposed. In contrast, at 0.83 mM [Ca2+]0 the line is shifted to lower frequency and tension for all MP values studied. In conclusion, in the range of low [Ca2+]0 the system underlying pacemaker activity seems to be dependent on Ca2+ in two ways: 1. by an indirect negative action mediated by an increase of PK+ and by hyperpolarization of the membrane; 2. by a direct positive action which is not mediated by alterations of MP. In the range of normal and high [Ca2+]0 only potential-mediated Ca2+-effects determine AP frequency. The hypothesis is put forward that Ca2+ may carry the background inward current responsible for pacemaker activity.
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