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- Author: A. J. MATTY x
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SUMMARY
1. Thyroidectomy of the teleost parrot fish, Pseudoscarus guacamaia, is described.
2. Pseudoscarus is able to survive for at least 3 months in the absence of the thyroid gland. It is concluded, therefore, that the gland is not essential for the maintenance of life in this species.
3. Thyroidectomy does not result in any change in the oxygen consumption of parrot fish. Likewise, injection of l-thyroxine or an extract of parrot fish thyroid into intact parrot fish does not affect the rate of oxygen uptake.
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Search for other papers by A. J. MATTY in
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SUMMARY
Radiometric estimations of adenyl cyclase and cyclic AMP (cAMP) phosphodiesterase showed significantly higher enzyme activities in the islet tissue of obese-hyperglycaemic mice than in that of their normal litter mates, but the ratios of the two enzymes in both types of islets were found to be the same, i.e. 1:1.
Adenyl cyclase and phosphodiesterase activity increased linearly with incubation time and protein concentration. Sodium fluoride (10 mmol/1) increased cyclase activity in the islets of obese mice by 33·4%; theophylline (10 mmol/1) in the presence of cAMP (1 mmol/1) reduced phosphodiesterase activity by almost 100%.
Glucose (2 g/1) reduced, while adrenaline (10−5 mol/1) increased cyclase activity in islets from both normal and obese animals. An evaluation of the effects of α- and β-adrenergic receptor stimulating and blocking agents on islets of both normal and obese mice showed the stimulation of adenyl cyclase to be a β-adrenergic receptor function and the inhibition an α-adrenergic receptor function. The possible role of the adenyl cyclase system in diabetes mellitus and insulin secretion is discussed.
Search for other papers by C. C. THORNBURN in
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Search for other papers by A. J. MATTY in
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Isolated tissues of the toad Bufo bufo (urinary bladder, skin and kidney) were treated in vitro with thyroxine (T4) or tri-iodothyronine (T3) both with and without prior administration of the hormones in vivo. They were incubated at low temperature, and their oxygen consumption studied for 48 hr. Both hormones had little effect in vitro. Pretreatment with T4 in vivo usually lowered oxygen uptake; the effect of pretreatment with T3 varied. The presence of alanine in the incubating medium caused a marked increase in oxygen consumption. A seasonal effect was also found.
The respiration of isolated toad bladder was stimulated by a wide range of concentrations of thyroxine in vitro, and there were two peaks of stimulation.
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Search for other papers by A. J. MATTY in
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SUMMARY
Young female rats were given a daily injection of 1 mg. thyroxine/kg. body weight for 7 days. They were killed on the eighth day and the small intestine used for a study of the movement of radioactive calcium and inorganic phosphate. The everted sac technique was used.
The results indicate that the passive movement of phosphate was depressed. Both the passive and active transport of calcium were also depressed. It is suggested that the transport of calcium and the transport of phosphate, whether active or passive, are related and that thyroxine affects a single site located perhaps at the basement membrane of the mucosa.
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Thyroxine at 10−6 m concentration enhances water movement from the mucosal to the serosal surface of the isolated toad bladder in the absence of an osmotic gradient. It is suggested that this is caused by the effect of thyroxine on sodium transport which creates a driving force for the increased water movement. Thyroxine caused this effect when applied on either side of the membrane, but was more effective when applied to the serosal surface.
Incubation of different bladders successively in the same triiodothyronine solution indicated that triiodothyronine may be rapidly utilized.
A mixture of thyroxine and triiodothyronine caused a diphasic effect on water loss down an osmotic gradient.
The analogues tetraiodothyroproprionic acid and tetraiodothyroformic acid had no effect on water movement down an osmotic gradient across the isolated toad bladder nor did they affect oxygen uptake or sodium transport.
The results support the concept that thyroxine and triiodothyronine act on permeability processes in and across cell membranes.
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SUMMARY
Isolated tissues of the toad Bufo bufo were treated in vitro with thyroxine and triiodothyronine, and their oxygen uptake determined by conventional Warburg manometry. The respiration of the urinary bladder was stimulated by the hormones, and that of the kidney was reduced. Skin, heart, and muscle were affected to a lesser extent, the effect varying with dose and hormone.
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Search for other papers by C. C. THORNBURN in
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SUMMARY
A quantitative analysis of the iodoamino acids in whole dried parrot-fish thyroid gland was carried out by determination of stable 127I. Mono- and di-iodotyrosine together made up about half of the total iodoamino acids and thyroxine about a third to a half. The tri-iodothyronine content was low, about 5%. The total content of the acids increased with body weight, and there was an indication of a sex difference.
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SUMMARY
l-Thyroxine and 3,5,3′-triiodo-l-thyronine in concentrations of 10−8 m to 10−5 m were shown to increase the oxygen uptake and water transfer down an osmotic gradient in the isolated urinary bladder of Bufo bufo. The increase in water transport after treatment with thyroxine and triiodothyronine was related linearly to the log dose. The increase in O2 uptake and water movement in equimolar concentrations of thyroxine and triiodothyronine were similar but the responses to the latter were more rapid.
Substitution of sodium ions by choline in the incubation medium resulted in a fall of oxygen uptake by the bladder, and a slight lowering of water loss. When thyroxine was added, oxygen uptake increased to the same extent in both media but only in sodium saline did water loss increase greatly.
Specific enzyme inhibitors prevented the thyroxine-induced increase in water loss across the isolated toad bladder, indicating that metabolic energy is necessary for this alteration in permeability.
Triiodothyronine and thyroxine caused an increased water loss across the isolated toad bladder when placed on either the mucosal or serosal surface.
Two analogues of the thyroid hormones, 3,5,3′-triiodothyroacetic acid and 3,5,3′,5-tetraiodothyroacetic acid, caused an extremely rapid, but transient, movement of water across the bladder; their action and that of triiodothyronine and thyroxine is compared.
An hypothesis is proposed tentatively to account for the mode of action of thyroxine on the permeability of the isolated toad bladder, taking into account the close relationship between increases in water permeability and metabolism, particularly that involving sodium transport.
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Search for other papers by A. J. MATTY in
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SUMMARY
Using a new technique for determining transmucosal electrical potential difference (p.d.) and short-circuit current (Isc.) in the rat small intestine in vivo it would appear that aldosterone had no direct effect on these parameters of intestinal activity. However, adrenalectomy decreased the Isc. while after adrenalectomy aldosterone and cortisol (hydrocortisone) restored the lowered independent and probably also the lowered dependent (hexose) Isc.
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Search for other papers by J. E. BARDACH in
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SUMMARY
Exophthalmos was produced by the androgens methyl testosterone and testosterone phenylacetate, but not by oestradiol dipropionate, in two species of teleost fish, Sparisoma squalidum and Scarus croicensis. Marked exophthalmos was produced by l-thyroxine and 3,5,3′-triiodothyronine in the above two species and also in Bathystoma aurolineatum. The thyroidal origin of exophthalmia in fish is discussed.
