Characteristics of Pelargonium radula as a mercury bioindicator for safety assessment of drinking water.

Identification of Pelargonium radula as bioindicator for mercury (Hg) detection confers a new hope for monitoring the safety of drinking water consumption. Hg, like other non-essential metals, inflicts the deterioration of biological functions in human and other creatures. In the present study, effects of Hg on the physiology and biochemical content of P. radula were undertaken to understand the occurrence of the morphological changes observed. Young leaves of P. radula were treated with different concentrations of Hg-containing solution (0.5, 1.0 and 2.0 ppb) along with controls for 4 h, prior to further analysis. Elevated Hg concentration in treatment solution significantly prompted an increased accumulation of Hg in the leaf tissues. Meanwhile, total protein, chlorophyll and low molecular mass thiol contents (cysteine, glutathione and oxidized glutathione) decreased as Hg accumulation increased. However, phytochelatin 2 productions were induced in the treated leaves, in comparison to the control. Based on these findings, it is postulated that as low as 0.5 ppb of Hg interferes with the metabolic processes of plant cells, which was reflected from the morphological changes exhibited on P. radula leaves-the colour of the Hg-treated leaves changed from green to yellowish-brown, became chlorosis and wilted. Changes in the tested characteristics of plant are closely related to the Hg-induced morphological changes on P. radula leaves, a potential bioindicator for detecting Hg in drinking water.

Detection of thyroid-stimulating antibodies in thyroid diseases, employing rat thyroid fragment perifusion.

The technique of perifusing rat thyroid fragments was used to investigate the presence of thyroid-stimulating antibodies (TSAb) in the sera of 48 patients. Response to IgG was measured by determining the mean rate of release of T4 (R) during a 30-min perifusion and the secretion peak (Imax) by means of samples taken every 5 min. Values found to be above the mean + 2 SD of the control values of R or Imax were considered to be positive. TSAb were found in all the 17 patients with untreated Graves' disease (GD) and in the 2 treated with antithyroid drugs, but not in the 3 who had undergone surgery or 131I treatment or in the 2 on corticosteroid treatment. TSAb were also found in 2 out of 3 patients with untreated nodular toxic goiter (UNTG) and in 6 out of 8 with diffuse nontoxic goiter (DNG) but at lower levels. In the untreated GD group, R and Imax correlated significantly with the corresponding IgG concentrations (from 90 to 800 micrograms/ml), suggesting TSAb activity which can be compared from one patient to another. TSAb activity did not correlate with thyroid function tests in any group. In all the groups it induced an early secretion peak followed by a decreasing response throughout the stimulation period, as was previously found with 65 mIU/ml TSH. The specificity of this technique was verified by five different control methods: the perifusion technique was checked by using KRBG buffer alone; sera were studied from a group of healthy controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence of direct thyroid-stimulating action of thyrotropin-releasing hormone by perifusion of rat thyroid fragments.

The possibility that TRH has a direct thyroid-stimulating action has never been reported. A number of studies have shown a rise in serum concentrations of thyroid hormone after stimulation with TRH, without a rise in TSH secretion. This has led us to test TRH with rat thyroid fragment perifusion. Significant T4 release was observed for TRH concentrations as low as 1.7 X 10(-11) M. A dose-response curve was determined. The response was immediate, reaching a peak after the sixth minute and continuing for 15 min after the stimulation had ceased. This kinetic pattern is different from the one observed with TSH and with theophylline and suggests that a different mechanism may be involved. TRH seems to be capable of directly stimulating both the secretion of the pituitary hormone (TSH) and the corresponding peripheral gland, like LHRH, which also acts directly on the Leydig cells of the testis.

Use of the perifusion technique on rat thyroid fragments in the study of thyroid hormone secretion: short-term effects of thyrotrophin, theophylline and glucagon.

Perifusion of rat thyroid fragments was performed to study short-term effects of TSH, theophylline and glucagon on thyroid hormone secretion. This technique proved to be relatively convenient and sensitive, and gave reproducible results for at least 3 h, permitting precise kinetic studies of response to hormonal and pharmacological agents without any interference. There was a significant (P less than 0.001) linear correlation between the log TSH concentrations over the range 20-150 mu./ml and thyroid response. A second stimulation, using the same concentration of TSH, did not differ from the first stimulation if they were separated by an active 'washing' period of only 15 min. Theophylline also had a stimulating effect and like TSH induced an early release of the hormone fraction with a peak between 2 and 4 min, but it did not potentiate the TSH effect. Perifusion of rat thyroid fragments was found to be a useful tool for analysing dynamic effects of various substances. These effects were significant for periods of time as short as 20 min. Each thyroid preparation could be used a second time for another pharmacological or hormonal test. Our preliminary results also suggested that there was a direct glucagon effect on thyroid hormone secretion with a dose-response correlation.

[Thyrotrophin releasing hormone (TRH) stimulates the secretion of T4 by perfused thyroid fragments from rats]. / La thyrotrophin releasing hormone (TRH) stimule la sécrétion de T4 par des fragments de thyroïdes de rats en perifusion.

Evidence of a direct stimulating effect of TRH on T4 secretion was found by using the perifusion technique on Rat thyroid fragments. A dose-response curve was plotted and the kinetic pattern of the response was studied.

[Value of the perifusion of fragments of rat thyroid for the dynamic study of thyroid secretion under TSH and theophylline]. / Intérêt de la périfusion de fragments de thyroïdes de rat pour l'étude dynamique de la sécrétion thyroïdienne sous TSH et théophylline.

With the technique of rat thyroid fragment perifusion the kinetics of T4 response to various stimuli can be studied with precision. The response is rapid and brief with theophylline and TSH, which activate membrane adenylcyclase; with the optimal concentrations, however, it is prolonged because only these concentrations can induce the secretion of a more slowly releasable pool of T4.