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PubMed1992

Development of the olfactory nerve in the clawed frog, Xenopus laevis: II. Effects of hypothyroidism.

Quantitative and morphological data were obtained on developing olfactory axons in normal and hypothyroid larvae of the African clawed frog Xenopus laevis. Hypothyroid larvae were produced by rearing the animals, beginning at stage 48, in a 0.01% solution of propylthiouracil (PTU), a treatment that blocks synthesis of thyroid hormone. These PTU-treated larvae were compared to their age-matched siblings when these siblings reached stage 52 (premetamorphic larvae; prior to synthesis of thyroid hormone), stage 57 (late premetamorphic larvae; after the onset of thyroid hormone synthesis), or stage 58 (larvae at the onset of metamorphic climax; thyroid hormone levels continue to rise). The number of olfactory axons did not differ between stage 52 control animals and the age-matched, PTU-treated animals, but there were only about half the number of axons in the PTU-treated animals that were age-matched to the stage 57 or 58 controls. Thus, PTU had no effect on olfactory axon number prior to the normal rise in thyroid hormone levels. But PTU significantly reduced the normal increase in olfactory axon number compared to stage 58 control larvae, whose thyroid hormone levels are high. While PTU also produced some changes in several other body measurements, the effect on the olfactory axons was the most consistent and prominent. The results presented here support our previous findings that thyroid hormone plays a significant role in the development of the olfactory system in Xenopus.

Animals↗

PubMed1980

Development of home orientation in hypothyroid and hyperthyroid rat pups.

In order to assess the effects of perinatal hypothyroidism or hyperthyroidism on the development of an integrated behavioral response, we tested hypothyroid, hyperthyroid, and control pups, as well as pups receiving thyroxine replacement therapy, for the development of the home orientation response. Hypothyroidism was induced in the pups by feeding the pregnant or lactating female a diet of .2% propylthiouracil from Day 15 of gestation to Day 22 postpartum. Pups receiving replacement therapy and pups made hyperthyroid were injected daily with thyroxine, starting at birth. The ability of the pups to initiate and maintain locomotion toward the nest was assessed between Days 4 and 22. Hyperthyroid, control, and replacement therapy pups behaved very similarly on the task, showing a peak in the percentage of pups homing between Days 12 and 16. Hypothyroid pups showed a delay in the peak percentage until Day 20, although the percentage of pups was similar to that found in other treatments. An integrated behavioral response can be delayed by hypothyroidism and still emerge apparently intact at a later age.

Animals↗

PubMed1986

Exploratory behavior, learning ability, and thyroid hormonal responses to stress in female rats rehabilitating from postnatal hypothyroidism.

Newborn female Long-Evans rats were divided into groups of normal, hypothyroid [0.1% propylthiouracil (PTU) a reversible antithyroid goitrogen in the litter's drinking water], and hypothyroid rehabilitated (PTU water from birth to day 25, normal water thereafter). The rats were tested for several adaptive behavioral tasks between 40 and 90 days of age. At day 50, serum concentration of TSH and thyroid hormones revealed no detectable amounts of T4 and a 10-fold increase in TSH in the hypothyroid rats. At the same age in the rehabilitated animals, TSH levels were still below normal, a deficit fully normalized by day 90. Normal 50-day-old rats responded to pain stress (electric footshocks) by a significant depression of serum T4 and elevation of T3 levels within 10 min of treatment, whereas the rehabilitated animals exhibited an opposite pattern of response, i.e., an increase in the circulating T4 and a decrease in T3. At 50 days of age, both hypothyroid and rehabilitated rats showed decreased exploratory activity and no habituation in the hole-board test, whereas the locomotor activity of the rehabilitated females was significantly higher than that of the normals. No differences were found in the scores of passive avoidance learning (one trial step-through) among the three groups. Similarly, the rate of acquisition of the active one-way conditioned avoidance response (CAR) of the hypothyroid and rehabilitated rats did not differ significantly from that of the controls. However, the hypothyroid rats required significantly more unconditioned stimuli (footshocks) to acquire CAR and showed longer response latency and less intertrial responses. Although the hypothyroid rats showed no extinction of CAR, the rehabilitated rats were capable of extinction to an extent indistinguishable from normal rats. But compared with the normal animals, the rehabilitated rats showed significantly higher intertrial activity during both the acquisition and extinction phases of CAR.

Animals↗

PubMed1996

Application of capillary zone electrophoresis for analysis of thyreostatics.

Capillary zone electrophoresis was optimized for the separation of thiouracil, methylthiouracil and propylthiouracil. Methylthiouracil could be determined in various types of urine (human, bovine, horse), either without any pretreatment or in ethyl acetate extracts, within 15 min. For identification, the simultaneous detection at three UV wavelengths (216, 245 and 278 nm) was advantageously used while for quantification the wavelength of the absorbance maximum at 278 nm was preferred. Under optimized conditions a linear response of the detector in the concentration range 0.1-100 ppm was obtained. On analysis of untreated urine, a detection limit of 0.5 ppm was found; for urine extracts the detection limit was 0.1 ppm. Univocal peak identification, based on absorption at three wavelength, was only possible above 2 ppm. Relative standard deviation for standard solutions of methylthiouracil, diluted in the background electrolyte, was 1%; for methylthiouracil in extracts dissolved in the background electrolyte it was 4.5%, and for methylthiouracil in untreated urine, 12.7%.

Animals↗

PubMed2004

Plasmapheresis in the treatment of hyperthyroidism associated with agranulocytosis: A case report.

Plasmapheresis, also known as therapeutic plasma exchange, is used in the treatment of several disorders. Temporary improvement after plasmapheresis in cases with thyrotoxicosis has been reported. A 55-year-old woman presented with agranulocytosis induced by propylthiouracil and clinical signs of heart failure. Three sessions of plasmapheresis were performed. We observed an improvement of thyroid hormone levels and clinical findings as well. Plasmapheresis can be an option when drug treatment of thyrotoxicosis fails.

Agranulocytosis↗

PubMed1994

Thyroid-induced changes in the growth of the liver, kidney, and diaphragm of neonatal rats.

Eu-, hypo- and hyper-thyroid rats were studied 12 days postpartum. Hypothyroidism was induced by administering propylthiouracil (PTU) via the mother's drinking water between late gestation and throughout lactation. This procedure effectively blocked the normal early postnatal surge of T3 and T4. In contrast, hyperthyroidism was induced in the young pups by daily injections of T4 from day 3 postpartum. The effects of these experimental manipulations of thyroid status on the rates of protein turnover and growth of the liver, kidney, and diaphragm were studied and compared with measurements made on appropriate euthyroid control tissues. Tissue rates of protein synthesis were decreased in response to hypothyroidism with consequent growth retardation of all three tissues and the whole animal. In contrast, the three body tissues responded very differently to the induction of hyperthyroidism. Hepatic rates of protein synthesis and growth were completely unaffected by thyroid excess. The response of the diaphragm was essentially the reverse of that seen with hypothyroidism, i.e., the enhanced rates of protein synthesis and protein degradation leading to muscle hypertrophy. The rates of protein turnover in the kidney were also increased, but unlike the diaphragm the net result was renal atrophy. Clearly, thyroid hormones influence the normal rapid growth of the neonate and its individual tissues. However, beyond a certain concentration the threshold of responsiveness to these hormones seems to vary between individual tissues.

Animals↗

PubMed1986

Changes in body water and plasma constituents during bullfrog development: effects of temperature and hormones.

The osmoregulatory responses to warmer temperatures and hormone treatment in cold-adapted (5 degrees C) Rana catesbeiana tadpoles and newly metamorphosed frogs were examined. Tadpoles transferred to 11 degrees C and 18 degrees C and left for 5 days lost 7% and 10% of their body weight. Plasma [Na+] was elevated 28% and 21%, respectively. Control (5 degrees C) animals maintained their body weight and plasma [Na+] constant. Daily treatment with either ovine prolactin (oPRL) or ovine growth hormone (oGH) prevented the weight loss and the increase in extracellular [Na+] that occurred when tadpoles were transferred to 18 degrees C. Neither propylthiouracil (PTU) nor arginine vasotocin (AVT) were effective in countering temperature-induced weight loss in tadpoles. Newly metamorphosed frogs transferred to 18 degrees C also lost weight; this was not prevented by daily treatment with saline, oPRL, oGH or PTU. However, in frogs treated daily with AVT, initial BW was regained by day 6. When warm-adapted (18 degrees C) tadpoles were treated daily for 18 days with saline, bPRL, bGH, thyroxine (T4), ergocornine, cortisol, or cortisol + T4, bPRL was most effective in retarding weight loss and maintaining body water content, whereas T4 + cortisol caused the greatest loss of weight and body water. By day 20, the correlations between weight loss and both body water content and hematocrit were highly significant. These data suggest that reported increases in plasma solute concentrations in larval amphibians may actually reflect decreases in extracellular fluid volume, rather than increased amounts of solutes, per se.

Animals↗

PubMed1976

Effects of neonatal hypothyroidism on cerebral and cerebellar synaptosome development.

The effect of hypothyroidism on cerebral and cerebellar synaptosome development has been studied. Neonatal hypothyroidism was induced following addition of 0.3% propylthiouracil to the diet of nursing mothers. Maturation profiles of total synaptosome fraction and specific activities of lactate dehydrogenase, Na+K ATPase, cytochrome c oxidase, and protein were obtained from days 6 to 32 on synaptosomes isolated from Ficoll-sucrose gradients. The greatest changes were found in the total activities of enzymes isolated from the cerebellum. Hypothyroidism induced a retardation of LDH and cytochrome c oxidase in cerebellar synaptosomes, but no change in corresponding specific activities. Maximum rates of 14C-leucine incorporation into cerebellar synaptosome protein was found at 16-20 days, after which a rapid decline occurred to adult levels at 32 days. In neonatal hypothyroidism, synthesis was significantly reduced at 8 and 14 days, but reached control levels or above at 21--32 days. In the cerebrum, maximum rates of 14C-leucine incorporation into synaptosome protein were identified at 8--12 days in normal with a rapid drop to adult levels at approximately 20 days. In neonatal hypothyroidism, peak activities were identified at 14 days and increased activities over control were noted at 14, 20 and 30 days. These observations demonstrate the sensitivity of the developing cerebellar synaptic apparatus to neonatal hypothyroidism, with a protraction in the peak levels of synaptosome protein synthesis in cerebrum and cerebellum.

Adenosine Triphosphatases↗

PubMed1985

Prenatal and postnatal hypothyroidism abolishes lesion-induced noradrenergic sprouting in the adult rat.

The effects of altered thyroid states on regeneration in the central nervous system are equivocal. This work was undertaken to examine the influence of propylthiouracil-induced (PTU-induced) pre- and postnatal hypothyroidism on collateral sprouting of noradrenergic (NA) axons in the habenula (Hb), following lesions in the stria medullaris (SM) of the adult rat. Ten pregnant dams were divided into control and PTU-treated groups. Control rats had free access to food and water and the hypothyroid group received, in addition, 0.05% (w/v) of PTU in their drinking water, beginning on day 12 of gestation and continuing post partum through lactation until the offspring were weaned at age 22 days. The pregnant dams received, in addition, daily injections of thyroxine (25 micrograms/kg, ip) and only male pups were used in the study. At weaning the pups were removed from the dams and placed in cages with free access to food and water. The hypothyroid offspring received 0.05% (w/v) PTU in the drinking water until sacrificed at 10 weeks of age. At 6 weeks, some rats in each group received bilateral lesions in the SM and the remainder were sham-operated. All rats were sacrificed 4 weeks after operation. Thus, four groups were formed: 1) control/sham, 2) control/lesion, 3) PTU/sham, 4) PTU/lesion. Sprouting of NA fibers in discrete regions of the Hb was identified by norepinephrine (NE) levels and by fluorescence histochemistry. Blood levels of thyroid stimulating hormone (TSH) were determined. The results show that pre- and postnatal induced chronic hypothyroidism abolished NA sprouting in the partially deafferented Hb. Furthermore, lesions of the SM resulted in a marked decrease in serum TSH levels.

Adrenergic Fibers↗

PubMed2007

Utilization review of concomitant use of potentially interacting drugs in Thai patients using warfarin therapy.

PURPOSE: In Thailand, there has been no study determining the concomitant use of medications, known to potentially interact with warfarin, in patients receiving warfarin therapy. This paper examined the frequency of which specific interacting drugs were concomitantly used in warfarin users. METHODS: We retrospectively examined the database of warfarin outpatient medical records from a regional 756-bed hospital located in the north of Thailand. All patients receiving warfarin from 10 June 1999 to 4 August 2004 were reviewed to identify all drugs possessing interaction potential with warfarin. The potential of significant interactions were divided into high, moderate and low, according to the extent of evidence documented in textbooks and literature. RESULTS: Among 1093 patients receiving warfarin therapy, 914 (84%) patients received at least one potentially interacting drug and half of them (457 patients) received at least one drug with high potential for interaction. The most frequently concomitant drug that increased INR was acetaminophen (63%, 316/457). Propylthiouracil was the most frequently concomitant drug that decreased INR response (4%, 19/457), while diclofenac was the most frequently concomitant drug that increased bleeding risk (16%, 73/457). CONCLUSIONS: About a half of patients receiving warfarin therapy was prescribed concomitant drug(s) that has a high potential of interactions with warfarin. These patients should be closely monitored and counselled to watch for signs and symptoms of bleeding and thrombosis to avoid adverse events associated with drug interactions.

Acetaminophen↗

PubMed1992

Thyroid hormone differentially regulates cellular development in neonatal rat heart and kidney.

The role of thyroid hormone in the control of cardiac and renal cell development was examined in neonatal rats made hyperthyroid by administration of triiodothyronine (T3, 0.1 mg/kg s.c. on postnatal days 1-5) or hypothyroid by administration of propylthiouracil (PTU, 20 mg/kg s.c. given to dams on gestational day 17 through postnatal day 5 and to pups on postnatal days 1-5). Indices of total cell number (total DNA per tissue), cell packing density (DNA per g tissue), and relative cell size (protein/DNA ratio) were evaluated from birth through young adulthood. PTU administration led to primary shortfalls in cell number that were of similar magnitude in both tissues, but persisted somewhat longer in the kidney than in the heart. Deficits in cell packing density and cell size in the hypothyroid animals were secondary to the effect on cell number, displaying smaller magnitudes of effect and a lag in appearance and disappearance of the deficits compared to that for total DNA; indeed, the phase in which tissues were restoring their cell numbers was accompanied by increased cell packing density, reflecting a more rapid restitution of cell numbers than tissue weight or cell size. In contrast to the relatively similar effects of PTU on developing cardiac and renal cells, the effects of T3 were selective for the heart. Although T3 caused general growth impairment, it evoked marked cardiac overgrowth that was accompanied by a striking increase in cell number and a small increase in cell size. The cardiac hyperplasia is unique to the developing animal, as post-replicative heart cells in adult animals show only hypertrophy in response to thyroid hormone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2002

Relationships between threshold-based PROP sensitivity and food preferences of Tunisians.

The extent to which taste responses--and notably the genetically determined sensitivity to 6-n-propylthiouracil (PROP)--influences food preferences and food use is still a matter of debate. We addressed the issue on the basis of a behavioural and anthropological study performed in Tunis in 1999. The working sample consists of 123 adults of both sexes (38 men, 85 women), aged 19-59, in various social categories. Taste recognition thresholds for sucrose, fructose, sodium chloride, quinine hydrochloride, citric acid, tannic acid, oak tannin and PROP were determined by presenting, in a semi-randomised order (blind-test), series of graded aqueous solutions of each product. Subjects also tasted and rated the pleasantness/unpleasantness of 4 supra-threshold solutions of NaCl and sucrose. All subjects completed a checklist of 43 food items representative of Tunisian diet, rated in terms of flavour, cost, effect on health and prestige on a labelled affective magnitude scale. According to the underlying distribution of PROP thresholds, the subjects were separated into three categories: "non-tasters", "medium-threshold tasters", and "low-threshold tasters". Results bring out the specificity of low-threshold tasters, as exhibiting a greater taste sensitivity for most tested substances. Low-threshold taster status is also linked to higher mean food preferences ratings irrespective of sex, age and socio-cultural influences. Tasters as a group (medium-threshold tasters + low-threshold tasters) do not exhibit a higher percentage of food dislikes; however PROP sensitivity is negatively correlated with hedonic responses to NaCl solutions. These results together with the evidence of a limited set of food actually used by low-threshold tasters suggest that these subjects might have difficulties at overcoming an inherent neophobia.

Adult↗

PubMed1996

Thyroid hormone controls the onset of androgen sensitivity in the developing larynx of Xenopus laevis.

Gonadal differentiation, the onset of androgen-stimulated laryngeal growth and the genesis of a sex difference in laryngeal innervation, all temporally coincide with thyroid hormone (TH)-induced metamorphosis in Xenopus laevis. To explore the role TH plays in the ontogeny of the Xenopus androgen-sensitive vocal neuromuscular system, we examined gonadal and laryngeal development in tadpoles in which metamorphosis had been blocked by treatment with the thyroxine synthesis inhibitor propylthiouracil (PTU). PTU treatment did not arrest gonadal differentiation. Testes from PTU-treated male tadpoles had seminiferous tubules and advanced stage male germ cells, while in females stage 1 oocytes were present. In contrast to the gonads, PTU did block morphological development of the larynx. Tadpoles treated with PTU for 50 or 100 days had larynges which structurally resembled those of stage 54 control tadpoles. PTU-treated animals did not exhibit the extensive development of the laryngeal cartilage seen in untreated animals. Laryngeal cartilages of hypothyroid tadpoles exhibited low density and minimal patterning of chondrocytes; the complex lumen and marked expansion of the dilator muscles characteristic of 50- and 100-day untreated animals were absent. Laryngeal growth evoked by exposure to exogenous androgen (dihydrotestosterone) was entirely prevented by PTU treatment. Hypothyroid tadpoles did not exhibit the decline in laryngeal nerve axon number characteristic of age-matched controls, nor were laryngeal nerve axon numbers sexually dimorphic. PTU treatment also interfered with the myelination of laryngeal axons. We conclude that while gonadal differentiation is independent of TH, androgen sensitive laryngeal development and sexually dimorphic laryngeal innervation require exposure to secreted TH.

Animals↗

PubMed2000

Characterization of audiogenic-like seizures in naive rats evoked by activation of AMPA and NMDA receptors in the inferior colliculus.

The role of glutamate receptors in the inferior colliculus (IC) in audiogenic and audiogenic-like seizures was investigated in adult rats with transient neonatal hypothyroidism by 0.02% propylthiouracil (PTU) treatment through mother's milk (PTU rats) and in naive rats treated intracisternally with N-methyl-d-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazole-proprionic acid (AMPA), or cyclothiazide, an inhibitor of rapid AMPA receptor desensitization. All rats showed audiogenic or audiogenic-like seizures characterized by running fit (RF) and generalized tonic-clonic seizures (GTCS). While systemically administered MK-801 inhibited GTCS, intracisternally administered NBQX inhibited RF and GTCS in both audiogenic and audiogenic-like seizures. Auditory stimulation shortened the latency to GTCS induced by AMPA, but not NMDA, at a subclinical dose and further elongated the shortened duration of RF, but not GTCS, induced by MK-801 pretreatment. Furthermore, Northern blot analysis was used to evaluate the expression of the immediate-early gene c-fos in the IC following induction of audiogenic or audiogenic-like seizures. The significant induction of c-fos mRNA by audiogenic seizures in PTU rats or by AMPA- or cyclothiazide-induced seizures in naive rats was prominent in the IC. MK-801 suppressed c-fos mRNA expression in the IC induced by audiogenic seizures in PTU rats or by AMPA-induced seizures in naive rats. NBQX suppressed the expression of c-fos mRNA in the IC induced by AMPA-induced seizures but did not suppress c-fos mRNA in PTU rats or rats with cyclothiazide-induced seizures. Auditory stimuli failed to affect c-fos mRNA induction by AMPA. The present study suggests that audiogenic-like seizures can be reproduced by glutamate receptor agonists in which AMPA receptors are primarily linked to the initiation of audiogenic seizures (RF) while NMDA receptors presumably located within the IC are involved in the propagation of GTCS in audiogenic seizures.

Acoustic Stimulation↗

PubMed1995

Effect of thyroid state on cardiac electrical activity of the frog Rana esculenta.

The effects of altered thyroid states on the heart rate and ventricular electrophysiological properties of the frog were examined. Hypothyroidism was induced by a 10-day treatment with propylthiouracil and produced decreased serum-free and total triiodothyronine levels below detectable concentrations. Hyperthyroidism, elicited by a 5-day treatment with triiodothyronine, was associated with increased serum thyroid hormone levels. The hypothyroid state was associated with a significantly decreased heart rate measured in vivo and an increased duration of the action potential recorded in vitro from ventricular fibers. Hyperthyroidism was associated with an increased heart rate and a decreased ventricular action potential duration (APD). The dependence of APD on temperature was affected by thyroid status. An increase from 25 to 30 degrees barely shortened the repolarization phase in hyperthyroids, minimally (13.3%) shortened that in euthyroids, and greatly (43.7%) shortened that in hypothyroids; the APD was similar in euthyroid and hypothyroid frogs. The shortening of the repolarization phase, by increased stimulation frequency, was also greater for hypothyroid frogs. In this case, however, the differences in APD among groups remained significant at all the frequencies tested.

Action Potentials↗

PubMedDate not supplied

No modifications of GABAA and benzodiazepine receptors following experimental dysthyroidism in rats.

The effect of a treatment with L-triiodothyronine (T3) or propylthiouracil (PTU) on the characteristics of benzodiazepine and chloride ion channel binding sites in rat hippocampus and cerebral cortex was studied using a radiolabelled technique. In our experimental conditions, neither hyper- nor hypothyroidism modified number and affinity of [3H]flunitrazepam or [3H]butylbicycloorthobenzoate (TBOB) binding sites. These data indicate that neither benzodiazepine nor chloride ionophore sites of the GABA complex are modified in an experimental condition of dysthyroidism.

Animals↗

PubMed1995

Effects of developmental hypothyroidism on auditory and motor function in the rat.

Deafness is a common result of severe hypothyroidism during development in humans and laboratory animals; however, little is known regarding the sensitivity of the auditory system to more moderate changes in thyroid hormone homeostasis. The current investigation compared the relative sensitivity of auditory function, motor function, and growth to the effects of moderate to severe perinatal hypothyroidism in the rat. Rats received propylthiouracil (PTU) in drinking water at concentrations of 0, 1, 5, and 25 ppm from Gestation Day 18 until postnatal day (PND) 21, and the effects on their offspring were evaluated. At 1 ppm, PTU did not affect any of the measured endpoints. Serum thyroxin concentrations were sharply reduced in the 5 and 25 ppm PTU groups at all ages sampled (PND 1, 7, 14, and 21). Marked reductions in serum triiodothyronine (T3) concentrations were also detected for all ages > or = 7 at 25 ppm PTU, whereas no effects of 5 ppm PTU on serum T3 were apparent until PND 21. Compared to the controls, pups exposed to the highest dose of PTU demonstrated a delay in eye opening, reduced body weights, decreased and/or delayed preweaning motor activity, and persistent, postweaning hyperactivity. Only slight and transient effects on eye opening and ontogeny of motor activity were seen at the intermediate dose of PTU (5 ppm). Reflex modification audiometry revealed that, compared to controls, adult offspring from the 5 and 25 ppm treatment groups showed dose-dependent auditory threshold deficits (35 to > 50 dB) at all frequencies tested (1, 4, 16, 32, and 40 kHz). Such dose-dependent effects indicate that the developing auditory system may be sensitive to mild hypothyroidism, suggesting the possible need for routine audiometric screening for infants and children at risk for iodine deficiency, myxedema, and/or exposure to thyrotoxic environmental agents.

Acoustic Stimulation↗

PubMed1984

Incorporation rate of GM1 ganglioside into mouse brain myelin: effect of aging and modification by hormones and other compounds.

The turnover rate of GM1 ganglioside in myelin was examined reveal age-related alterations in the metabolic activity. Three different age groups of mice were given deuterium oxide, and myelin was prepared from cerebella at intervals of two weeks. GM1 was isolated from the total myelin gangliosides by high performance liquid chromatography. Deuterated sugar moieties of GM1 were determined by chemical ionization-mass spectrometry which provided prominent quasimolecular ions. This method made it possible to determine separately the incorporation of deuterium into internal and external galactoses as well as other components. The incorporation rate of GM1 into myelin was clearly shown to be decreased with advancing age. Lower incorporation of newly synthesized sialic acid into GM1 than that of other sugars may indicate reutilization of sialic acid at about 50%. The possibility of modification of the myelin metabolism by exogenous factors was examined by monitoring the incorporation rate of GM1 in animals treated with chemical agents. It was revealed that thyroxine enhanced the incorporation of GM1 into adult brain myelin, whereas propylthiouracil reduced the incorporation. Other chemicals, estradiol, S-adenosylmethionine and LM1 ganglioside, showed only minor effects on the myelin turnover.

Aging↗