scholarly journals Activation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase in homogenates of developing rat brain

1979 ◽  
Vol 182 (2) ◽  
pp. 367-370 ◽  
Author(s):  
W A Maltese ◽  
J J Volpe
Keyword(s):  
Rat Brain ◽  
Cholesterol Synthesis ◽  
Specific Activity ◽  
Postnatal Period ◽  
Developing Brain ◽  
Brain Maturation ◽  
Assay Mixture ◽  
Coa Reductase ◽  
Developing Rat ◽  
Homogenization Medium

The specific activity of 3-hydroxy-3-methylglutaryl-CoA reductase increases when homogenates of developing rat brain are incubated at 37 degrees C or kept on ice. This increase is completely blocked by the addition of F- to the homogenization medium and the assay mixture. The capacity for activation of the reductase is greatest during the early postnatal period and declines as brain maturation proceeds. The data suggest that catalytic modification of the reductase may play a role in the regulation of cholesterol synthesis in the developing brain.

Regulation of tubulin by triiodothyronine in hypothyroid rat brain

1985 ◽  
Vol 5 (8) ◽  
pp. 643-648 ◽  
Author(s):  
Anjana Mazumder ◽  
Kamal Das ◽  
Pranab K. Sarkar
Keyword(s):  
Protein Synthesis ◽  
Rat Brain ◽  
Brain Maturation ◽  
Normal Brain ◽  
Neonatal Brain ◽  
Organ Cultures ◽  
Postnatal Brain ◽  
Enhanced Sensitivity ◽  
Brain Exposure ◽  
Developing Rat

The effect of T3 (triiodothyronine) on the induction of tubulin in hypothyroid developing rat brain has been examined using organ cultures of brains from late fetal, neonatal and postnatalrats. The neonatal brain displayed maximum sensitivity to T3. Hypothyroidism resulted in a 26% decline in the level of tubulin in the neonatal brain as opposed to a 5–15% decline in the fetal or postnatal brain. Exposure of the hypothyroi d neonatal brain to T3 for 2 h in culture led to a 61% rise in the level of tubulin in contrast to a 41% increase seen in the case of normal brain. Total protein synthesis was not significantly affected. The preferential decline of tubulin in the neonatal hypothyroid brain, its enhanced sensitivity to T3 compared to normal brain, and the coincidence of the period of sensitivity to that of brain maturation indicate that the regulation of the level of tubulin by T3 in the developing brain is a natural ontogenic phenomenon.

Effect of neonatal hypothyroidism on maturation of nuclear triiodothyronine (T3) receptors in developing rat brain

1980 ◽  
Vol 95 (4) ◽  
pp. 495-499 ◽  
Author(s):  
Kazumasa Ishiguro ◽  
Yukichi Suzuki ◽  
Tamotu Sato
Keyword(s):  
Rat Brain ◽  
Binding Capacity ◽  
Physiological Role ◽  
Brain Maturation ◽  
Control Group ◽  
High Concentration ◽  
Neonatal Hypothyroidism ◽  
Developing Rat ◽  
T3 Receptors

Abstract. Changes of nuclear T3 receptors during brain maturation were studied in normal and hypothyroid rats. In normal rats, the higher receptor concentration present in the neonatal period (0.35 ± 0.04 ng T3/mg DNA) decreased at the age of 14 days (0.25 ± 0.02 ng T3/mg DNA), and remained at this level thereafter to 35 days of age (0.25 ± 0.03 T3/mg DNA). In contrast, hypothyroid rats showed a significantly higher concentration than that found in an age-matched control group at the age of 14 days (0.38 ± 0.07 ng T3/mg DNA), and maintained this level up to 35 days of age (0.37 ± 0.03 T3/mg DNA). The binding affinity was similar in both groups and throughout maturation (mean ± sd in normal groups: 1.9 ± 0.3 × 1010m−1, in hypothyroid groups: 1.7 ± 0.2 × 1010m−1). Plasma T3 concentrations showed changes reciprocal to those in the binding capacity of T3 receptors. These results indicate that nuclear T3 receptors in rat brain mature by the age of 14 days, in association with a decrease in binding capacity, and this process seems to be T3-dependent. The physiological role of the high concentration of T3 receptors observed in neonatal and hypothyroid rat brain during development is at present not clear.

T3 receptor occupancy and T3 levels in plasma and cytosol during rat brain development

1990 ◽  
Vol 123 (1) ◽  
pp. 95-99 ◽  
Author(s):  
Beatriz Ferreiro ◽  
Rosa Pastor ◽  
Juan Bernal
Keyword(s):  
Thyroid Hormone ◽  
Rat Brain ◽  
Binding Sites ◽  
Thyroid Hormone Receptor ◽  
Receptor Occupancy ◽  
Postnatal Period ◽  
Brain Maturation ◽  
Oligodendrocyte Differentiation ◽  
Nuclear Extracts ◽  
Myelin Gene

Abstract. The concentration and occupancy of the thyroid hormone receptor have been measured in rat brain nuclear extracts at the end of the fetal period and during the postnatal period. Receptor occupancy attained maximal values at postnatal day 15 (52% of total receptor binding sites occupied by T3) and correlated with plasma and cytosol total and free T3. The values for these parameters showed greater differences throughout development than did receptor occupancy. From gestational day 21 to postnatal day 15, total T3 increased in plasma from 0.18 to 1 nmol/l and in cytosol from 1 to 7.5 pmol/l. Free T3 increased in plasma from 1.2 to 6 pmol/l and in cytosol from 8 to 59 pmol/l. Nuclear free T3, calculated on the basis of receptor occupancy, and Kd increased in parallel, from 39.8 to 107 pmol/l at the same ages. Values for nuclear free T3 were between 2 and 5 times those in cytosol and between 10 and 40 times those in plasma, suggesting the presence of a small free T3 gradient from plasma to the nucleus. All of the above changes take place during the critical period of oligodendrocyte differentiation and the start of myelin gene expression, suggesting that thyroid hormone influences these important events of brain maturation.

scholarly journals Acetoacetate and brain lipogenesis: developmental pattern of acetoacetyl-coenzyme A synthetase in the soluble fraction of rat brain (Short Communication)

1973 ◽  
Vol 132 (3) ◽  
pp. 653-656 ◽  
Author(s):  
Brendan M. Buckley ◽  
Dermot H. Williamson
Keyword(s):  
Rat Brain ◽  
Cholesterol Synthesis ◽  
Short Communication ◽  
Coenzyme A ◽  
Soluble Fraction ◽  
Developing Brain ◽  
Developmental Pattern ◽  
Acetyl Coa ◽  
Brain Cytosol

The existence of acetoacetyl-CoA synthetase in rat brain cytosol is reported. The coupling of this enzyme with cytosolic acetoacetyl-CoA thiolase can provide acetyl-CoA for lipogenesis and cholesterol synthesis without the need for mitochondrial participation. This new route for acetoacetate utilization may be important in developing brain.

scholarly journals Exchange of sterols between myelin and other membranes of developing rat brain

1971 ◽  
Vol 122 (5) ◽  
pp. 751-758 ◽  
Author(s):  
N. L. Banik ◽  
A. N. Davison
Keyword(s):  
Rat Brain ◽  
Myelin Sheath ◽  
Cholesterol Synthesis ◽  
Reductase Activity ◽  
Exchange Process ◽  
Total Sterol ◽  
Cholesterol Content ◽  
Equivalent Amount ◽  
Developing Rat ◽  
Ay 9944

1. The effect of inhibition of cholesterol synthesis by a hypocholesterolaemic drug (AY-9944) was studied in rat brain during development. 2. At 2 weeks after administration of AY-9944 to young rats 7-dehydrocholesterol accounted for half the total sterol of myelin and other subcellular components. 3. At 4 weeks after injection of the drug 7-dehydrocholesterol had disappeared whereas the cholesterol content of myelin had increased by an equivalent amount. Our studies show that purified myelin has low 7-dehydrocholesterol reductase activity and suggest that 7-dehydrocholesterol is largely converted into cholesterol outside the myelin sheath. 4. Resultant cholesterol may be re-incorporated into myelin by an exchange process. 5. The metabolism of sterols in developing brain is discussed.

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