Metabolic effects of 3,5-dimethyl-3'-isopropyl-L-thyronine and 3,5,3'-triiodo-L-thyronine in the brain and liver of hypothyroid rats. Similarities and differences

The metabolic effects of 3,5-dimethyl-3'-isopropyl-L-thyronine (DIMIT) on subcellular activities in brain and liver, have been compared to those of T3. Thyroidectomized hypothyroid rats were treated for 10 days with DIMIT (8 micrograms/100 g/day) or T3 (0.25 microgram/100 g/day). In liver mitochondrial oxidative phosphorylation, succinate cytochrome c reductase activities and nuclear RNA polymerases I and II activities were restored to normal level by DIMIT as well as by T3 treatment. In brain T3 treatment normalized both nuclear and mitochondrial activities. On the other hand daily injection of DIMIT restored like T3 nuclear activities whereas that of brain mitochondria were unaffected. We have also examined the early effects of a single injection of T3 (2.5 micrograms/100 g) or DIMIT (80 micrograms/100 g), 20 minutes prior sacrifice. DIMIT is as active as T3 in stimulation of oxidative phosphorylation and succinate cytochrome c reductase activity in liver mitochondria. However DIMIT treatment does not affect the properties of brain mitochondria. On the basis of these observations, it is suggested that there is a tissue specificity of mitochondrial receptors to DIMIT administration as it was shown at the nuclear level.     

Influence of thyroid hormone deficiency on the citrate synthase activity in rat brain regions during early postnatal development

The developmental pattern of citrate synthase activity has been studied in the liver and several brain areas of hypothyroid rats during the 4 first weeks of life. While citrate synthase activity in the liver showed a rise during the 2 first weeks of life, different patterns of enzyme activity were found in the brain regions of euthyroid animals. Citrate synthase activity increased in the cerebellum, decreased in the cerebral cortex and did not change significantly in the brain stem during the period studied. In the liver and brain areas, too, a decrease in citrate synthase activity was observed during hypothyroidism. From the 2nd week of birth, the citrate synthase activity in the brain but not in the liver was found to have recovered. The newly elevated citrate synthase activity coincided with a slight increase in thyroid hormone serum levels.     

Partial purification and characterization of citrate synthase from Dictyostelium discoideum.

The effect of thyroidectomy on oxidative metabolism of rat liver, kidney, and brain mitochondria has been examined. The respiration in liver, kidney, and brain mitochondria was affected differentially after thyroidectomy, the common effect in all the tissues being the impairment in state 3 as well as state 4 rates of succinate oxidation. Thyroidectomy did not have any effect on $\text{ADP}\text{O}$ ratios; however, compared to normal, respiratory control indexes were, in general, somewhat higher. Thyroidectomy also did not alter total ATPase activity of liver, kidney, and brain mitochondria, although the basal ATPase activity had decreased significantly under these conditions. The cytochrome content of the mitochondria also showed tissue-specific changes after thyroidectomy; however, no significant changes in the absorption characteristics of the cytochromes were seen. The succinate and glutamate dehydrogenase activities of mitochondria from liver, kidney, and brain were not affected by thyroidectomy, thereby ruling out the possibility that the decrease in substrate oxidation may be due to alterations in the primary dehydrogenase levels. It is concluded that thyroid hormone(s) may have a tissue-specific role in regulating the metabolic functions of mitochondria.     

Changes in n-6 and n-3 polyunsaturated fatty acids during lipid-peroxidation of mitochondria obtained from rat liver and several brain regions: effect of alpha-tocopherol

The effect of intraperitoneal administration of alpha-tocopherol (100 mg/kg weight/24 h) on ascorbate (0-0.4 mM) induced lipid peroxidation of mitochondria isolated from rat liver, cerebral hemispheres, brain stem and cerebellum was examined. The ascorbate induced light emission in hepatic mitochondria was nearly completely inhibited by alpha-tocopherol (control-group: 114.32+/-14.4; vitamin E-group: 17.45+/-2.84, c.p.m.x10(-4)). In brain mitochondria, 0.2 mM ascorbate produced the maximal chemiluminescence and significant differences among both groups were not observed. No significant differences in the chemiluminescence values between control and vitamin E treated groups were observed when the three brain regions were compared. The light emission produced by mitochondrial preparations was much higher in cerebral hemispheres than in brain stem and cerebellum. In liver and brain mitochondria from control group, the level of arachidonic acid (C20:4n6) and docosahexaenoic acid (C22:6n3) was profoundly affected. Docosahexaenoic in liver mitochondria from vitamin E group decreased by 30% upon treatment with ascorbic acid when compared with mitochondria lacking ascorbic acid. As a consequence of vitamin E treatment, a significant increase of C22:6n3 was detected in rat liver mitochondria (control-group: 6.42 +/-0.12; vitamin E-group: 10.52 +/-0.46). Ratios of the alpha-tocopherol concentrations in mitochondria from rats receiving vitamin E to those of control rats were as follows: liver, 7.79; cerebral hemispheres, 0.81; brain stem, 0.95; cerebellum, 1.05. In liver mitochondria, vitamin E shows a protector effect on oxidative damage. In addition, vitamin E concentration can be increased in hepatic but not in brain mitochondria. Lipid peroxidation mainly affected, arachidonic (C20:4n6) and docosahexaenoic (C22:6n3) acids.     

Changes in n-6 and n-3 polyunsaturated fatty acids during lipid-peroxidation of mitochondria obtained from rat liver and several brain regions: effect of α-tocopherol

The effect of intraperitoneal administration of α-tocopherol (100 mg/kg weight/24 h) on ascorbate (0–0.4 mM) induced lipid peroxidation of mitochondria isolated from rat liver, cerebral hemispheres, brain stem and cerebellum was examined. The ascorbate induced light emission in hepatic mitochondria was nearly completely inhibited by α-tocopherol (control-group: 114.32±14.4; vitamin E-group: 17.45±2.84, c.p.m.×10⁻⁴). In brain mitochondria, 0.2 mM ascorbate produced the maximal chemiluminescence and significant differences among both groups were not observed. No significant differences in the chemiluminescence values between control and vitamin E treated groups were observed when the three brain regions were compared. The light emission produced by mitochondrial preparations was much higher in cerebral hemispheres than in brain stem and cerebellum. In liver and brain mitochondria from control group, the level of arachidonic acid (C20:4n6) and docosahexaenoic acid (C22:6n3) was profoundly affected. Docosahexaenoic in liver mitochondria from vitamin E group decreased by 30% upon treatment with ascorbic acid when compared with mitochondria lacking ascorbic acid. As a consequence of vitamin E treatment, a significant increase of C22:6n3 was detected in rat liver mitochondria (control-group: 6.42 ±0.12; vitamin E-group: 10.52 ±0.46). Ratios of the α-tocopherol concentrations in mitochondria from rats receiving vitamin E to those of control rats were as follows: liver, 7.79; cerebral hemispheres, 0.81; brain stem, 0.95; cerebellum, 1.05. In liver mitochondria, vitamin E shows a protector effect on oxidative damage. In addition, vitamin E concentration can be increased in hepatic but not in brain mitochondria. Lipid peroxidation mainly affected, arachidonic (C20:4n6) and docosahexaenoic (C22:6n3) acids.     

Adenine nucleotide pool size,adenine nucleotide translocase activity,and respiratory activity in newborn rabbit liver mitochondria

The adenine nucleotide content (ATP+ADP+AMP) of newborn rabbit liver mitochondria was 6.0±0.5 nmol/mg mitochondrial protein at birth, increased rapidly to 14.5±1.7 nmol/mg protein by 2 h postnatal, peaked at 6 h, then decreased gradually to 7.8±0.6 nmol/mg protein by 4 days postnatal. There was a strong positive correlation (r=0.82) between the total adenine nucleotide pool size and adenine nucleotide translocase activity in these mitochondria. In contrast, glutamate + malate-supported State 3 respiratory rates remained constant from birth through the first week of life. State 4 rates also remained constant, as did the respiratory control index and uncoupled respiratory rates. The following conclusions are suggested: (1) The maximum rate of translocase activity is limited by the intramitochondrial adenine nucleotide pool size. (2) In newborn rabbit liver mitochondria, the State 3 respiratory rate is not limited by either the adenine pool size or the maximum capacity for translocase-mediated adenine exchange. (3) In contrast to rat, rabbit liver mitochondria are fully functional at birth with regard to respiratory rates and oxidative phosphorylation. (4) The rapid postnatal accumulation of adenine nucleotides by liver mitochondria, now documented in two species, may be a general characteristic of normal metabolic adjustment in neonatal mammals.     

Calcium induced release of mitochondrial cytochrome c by different mechanisms selective for brain versus liver.

Increased mitochondrial Ca2+ accumulation is a trigger for the release of cytochrome c from the mitochondrial intermembrane space into the cytosol where it can activate caspases and lead to apoptosis. This study tested the hypothesis that Ca2+-induced release of cytochrome c in vitro can occur by membrane permeability transition (MPT)-dependent and independent mechanisms, depending on the tissue from which mitochondria are isolated. Mitochondria were isolated from rat liver and brain and suspended at 37 degrees C in a K+-based medium containing oxidizable substrates, ATP, and Mg2+. Measurements of changes in mitochondrial volume (via light scattering and electron microscopy), membrane potential and the medium free [Ca2+] indicated that the addition of 0.3 - 3.2 micromol Ca2+ mg-1 protein induced the MPT in liver but not brain mitochondria. Under these conditions, a Ca2+ dose-dependent release of cytochrome c was observed with both types of mitochondria; however, the MPT inhibitor cyclosporin A was only capable of inhibiting this release from liver mitochondria. Therefore, the MPT is responsible for cytochrome c release from liver mitochondria, whereas an MPT-independent mechanism is responsible for release from brain mitochondria.     

Cellular energy metabolism during fetal development. IV. Fatty acid activation, acyl transfer and fatty acid oxidation during development of the chick and rat

We have investigated developmental profiles of ATP-dependent palmityl-CoA synthetase, acetyl-CoA synthetase, palmitylcarnitine transferase, and fatty acid oxidation in heart and liver of developing chicks and rats. Palmityl-CoA synthetase activity of rat liver and heart homogenates increased 6- to 10-fold during the first postnatal week. Chick embryo heart activity peaked between 13 and 16 days of development. The activity of embryonic chick livers was bimodal with highest activity seen at 7 and 16 days of development. Posthatching values were approximately 50–75% of the peak embryonic levels. Acetyl-CoA synthetase activity of rat liver and heart homogenates was low but also showed developmental increases following birth. Acetyl-CoA synthetase activity of chick embryonic hearts was greatest at 16 days of development. Palmitylcarnitine transferase activity of rat liver and heart homogenates showed a striking increase during the first week of life. Chick heart activity was similar to that observed for palmityl-CoA synthetase with a peak between 13 and 16 days of embryonic development. Coincident with the postnatal rise in fatty acid activation and palmitylcarnitine transferase activity in developing rats, the oxidation of palmityl-CoA plus carnitine and of palmitylcarnitine increased from barely measurable levels at birth to adult levels by 30 days of age. The increases that we observe probably relate to changes in the specific activity of the enzymes as well as to an increase in the absolute number of mitochondria during development.     

Progression of type 2 diabetes in GK rats affects muscle and liver mitochondria differently: pronounced reduction of complex II flux is observed in liver only

Impaired mitochondrial function is implicated in the development of type 2 diabetes mellitus (T2DM). This was investigated in mitochondria from skeletal muscle and liver of the Goto-Kakizaki (GK) rat, which spontaneously develops T2DM with age. The early and the manifest stage of T2DM was studied in 6- and 16-wk-old GK rats, respectively. In GK16 compared with GK6 animals, a decrease in state 3 respiration with palmitoyl carnitine (PC) as substrate was observed in muscle. Yet an increase was seen in liver. To test the complex II contribution to the state 3 respiration, succinate was added together with PC. In liver mitochondria, this resulted in an ～50% smaller respiratory increase in the GK6 group compared with control and no respiratory increase at all in the GK16 animals. Yet no difference between groups was seen in muscle mitochondria. RCR and P/O ratio was increased (P < 0.05) in liver but unchanged in muscle in both GK groups. We observed increased lipid peroxidation and decreased Akt phosphorylation in liver with the progression of T2DM but no change in muscle. We conclude that, during the progression of T2DM in GK rats, liver mitochondria are affected earlier and/or more severely than muscle mitochondria. Succinate dehydrogenase flux in the presence of fatty acids was reduced severely in liver but not in muscle mitochondria during manifest T2DM. The observations support the notion that T2DM pathogenesis is initiated in the liver and that only later are muscle mitochondria affected.     

Regulation of mitochondrial protein turnover by thyroid hormone(s)

1. The effect of thyroidectomy on turnover rates of liver, kidney and brain mitochondrial proteins was examined. 2. In the euthyroid state, liver and kidney mitochondria show a synchronous turnover with all protein components showing more or less identical half-lives compared with the whole mitochondria. The brain mitochondrial proteins show asynchronous turnover, the soluble proteins having shorter half-lives. 3. Mitochondrial DNA (m-DNA) of liver and kidney has half-lives comparable with that of whole mitochondria from these tissues. 4. Thyroidectomy results in increased half-lives of liver and kidney mitochondria, with no apparent change in the half-life of brain mitochondria. 5. A detailed investigation of the turnover rates of several protein components revealed a significant decrease in the turnover rates of mitochondrial insoluble proteins from the three tissues under study. 6. The turnover rates of m-DNA of liver and kidney show a parallel decrease. 7. Thus it is apparent that thyroid hormone(s) may have a regulatory role in maintaining the synchrony of turnover of liver and kidney mitochondria in the euthyroid state. Turnover of brain mitochondria may perhaps be regulated by some other factor(s) in addition to thyroid hormone(s). 8. It seems likely that during mitochondrial turnover m-DNA and insoluble proteins may constitute a major unit. 9. The mitochondrial protein contents of the three tissues are not affected by thyroidectomy. 10. No correlation was seen between the turnover rate of mitochondria and cathepsin activity in any of the tissues under study in normal or thyroidectomized animals. 11. On the other hand, mitochondrial proteinase activity shows good correlation with the turnover rates of mitochondria in normal animals, and a parallel decrease in activity comparable with the decreased rates of turnover is observed after thyroidectomy. 12. It is concluded that mitochondrial proteinase activity may play a significant role in their protein turnover.     

Effects of thyroxine on mitochondrial morphology and uptake of 35S in embryonic chicken livers

Ultrastructural analyses of reactions of mitochondria in hepatocytes of chicken embryos to low levels of exogenous thyroxine (T4) reveal that such reactions (overall swelling accompanied by disruption of crest geometry) first take place at about 10 days of incubation, T4 having been administered on the 6th day. Physically altered mitochondria may be seen after 11-12 days of incubation but are no longer evident by 13 days. Correlated with the initial evidence of T4 effects on mitochondria at 10 days of incubation is a spurt in hepatocyte proliferation. The time correlation observed between T4 induced mitochondrial changes in morphology and abrupt increases in rates of cell proliferation, suggests that liver nuclear receptors for thyroxine are unavailable prior to 9-10 days of incubation. Golgi complexes within the hepatocytes appear to be especially active in the production of electron-opaque vesicles from at least the 8th day of incubation to 11-12 days. Uptake of 35S (probably into chondroitin sulphates) was found to be fifteen times greater on the 8th day of incubation than at 15 days. This correlates with the period of heightened activity of the Golgi complex. In livers exposed to T4 on the 6th day, uptake of 35S was higher on the 9th and 10th days of incubation as compared to controls.     

EFFECT OF PYRIDOXINE DEFICIENCY ON AROMATIC l-AMINO ACID DECARBOXYLASE IN THE DEVELOPING RAT LIVER AND BRAIN

—Maternal pyridoxine deficiency begun 2 weeks before mating and continued throughout pregnancy and the nursing period resulted in diminished wt. gains in the brain, the liver and the body in the first 16 days of life, as well as lowered levels of the aromatic l -amino acid decarboxylase in both brain and liver tissue. The fetus was protected from the effect of vitamin B₆ deficiency during pregnancy, since at birth the body wt., organ weights, and decarboxylase levels in these tissues were comparable to those of control litters. The brain was affected less than the liver, both in rate of wt. increase and decarboxylase activity. The cerebellum normally developed measurable decarboxylase activity only during the second week of life. The cortex normally slowly increased its low decarboxylase activity during the first week postnatally, with a more rapid increase during the second week. This rapid increase was primarily in the holoenzyme moiety. The rest of the brain, which had well developed levels of decarboxylase activity at birth, normally showed a sharp increase during the second week of life which was also largely in the holoenzyme portion. When the increasing weights of these tissues were considered, it became obvious that the total amount of apoenzyme as well as the amount of holoenzyme were increasing in the normally developing rat, although the greatest amount of the change was in the holoenzyme form. The liver normally showed a much more rapid increase in decarboxylase activity than did the brain, and showed the increase much earlier. The holoenzyme normally increased rapidly after the first 4 days, whereas the apoenzyme concentration levelled off at this time. The effect of the pyridoxine deficiency on decarboxylase activity was almost entirely on the holoenzyme form of the decarboxylase, since the apoenzyme form generally remained the same in the control and the deficient pups during development. There appeared to be no decarboxylase inhibitor present in pyridoxine deficient tissues, nor any evidence in control tissues for an enzyme required for the activation of the decarboxylase by cofactor.     

Thyroid status in the obese syndrome of rats

The thyroid function was explored by comparing serum total and free iodothyronine levels in young male genetically obese Zucker rats and in their lean littermates, aged from 6 to 8 weeks old. Total and free thyroxine (T4) and 3,5,3'triiodothyronine (T3) levels were significantly decreased in obese rat serum while total 3,3',5'-triiodothyronine (rT3) remained constant. Radioactive T4 half life is slower in the plasma of obese rats. Peripheral synthesis of T3 from deiodination of T4 is also decreased in obese rat liver homogenate. These modifications produce changes in liver mitochondria oxidative phosphorylation and in marker enzyme activity, which are usually associated with hypothyroidism and hypothalamic disturbances. Genetic obesity probably involves activation of peripheral deiodination of T4 to rT3 which induces biochemical and metabolic changes.     

Alterations to the permeability of plant and animal mitochondria submitted to Ca2+ releasing agents.

1. Mitochondria from different rat tissues and from plants were compared as regards their sensitivity towards Ca2+ in the presence of different Ca2+ releasing agents, and the phospholipase A2 activity was evaluated in the different mitochondrial preparations. 2. The mitochondria were exposed to Ca2+ and an oxidant such as t-butylhydroperoxide or diamide or to Ca2+ and inorganic phosphate, and plant mitochondria were seen to be much more resistant than liver, brain or kidney mitochondria of rats to the deleterious effects of these agents. 3. The phospholipase A2 activity is not directly involved in the alterations of the mitochondrial inner membrane permeability within the first 10 min of incubation under our experimental conditions. 4. The protection conferred by ATP and Mg2+ against Ca2+ efflux from mitochondria or the decrease in the mitochondrial transmembrane electrical potential was also observed under our experimental conditions, but cannot be attributed to an enhancement of the reacylation of lysophospholipids resulting from the phospholipase A2 activity.     

Changes of malic enzyme activity in the developing rat brain are due to both the increase of mitochondrial protein content and the increase of specific activity.

1. The pattern of NADP-linked malic enzyme activity estimated in the whole brain homogenate did not parallel that found in liver of developing rat. 2. Studies on intracellular distribution of malic enzyme in brain showed that the mitochondrial enzyme increased about three-fold between 10th and 40th day of life. Thereafter, a slow gradual increase to the adult level was observed. 3. The extramitochondrial malic enzyme from brain, like the liver enzyme, increased at the time of weaning, although to a lesser extent. At day 5 the brain malic enzyme was equally distributed between mitochondria and cytosol. 4. During the postnatal development, the contribution of the mitochondrial malic enzyme in the total activity was increasing, reaching the value approx. 80% at day 150 after birth. 5. The increase with age of the malic enzyme specific activity was observed in both synaptosomal and non-synaptosomal mitochondria, the changes in the last fraction being more pronounced. 6. The activity of citrate synthase developed markedly between 10-40 postnatal days, increasing about five-fold, while the specific activity of the enzyme did change neither in the synaptosomal nor in non-synaptosomal mitochondria at this period. 7. We conclude that the changes in malic enzyme activity in the developing rat brain are mainly due both to the increase of mitochondrial protein content and to the increase of specific activity of the mitochondrial malic enzyme.     

Alteration of apoptotic protease-activating factor-1 (APAF-1)-dependent apoptotic pathway during development of rat brain and liver.

Brain and liver extracts of rats at different stages after birth were examined for cytochrome c/dATP-dependent caspase (DEVDase)-activation (mitochondria pathway) in vitro. The caspase-activating activity in the brain extracts rapidly decreased after birth, reaching approximately 50 and 5%, at 1 and 2 weeks, respectively, of that in a 3-days- newborn sample, and essentially no caspase-activation was detected in the adult rat brain extracts. Such a dramatic change was not detected in the liver samples, suggesting that the observed abrogation of the cytochrome c-dependent mitochondria pathway after birth is a brain-specific event. In order to determine the factor(s) lacking in adult brain, we separately measured Apaf-1, procaspase 9, and pro-DEVDase activities using a supplementation assay. In adult brain, Apaf-1 activity was scarcely detected, while the tissue retained low but significant amounts of procaspase 9 (16% of that in the fetal tissue) and a pro-DEVDase (3.4%). In contrast, adult liver extracts retained relatively high levels of all of these factors. Immunoblot analyses clearly indicated that the expression of Apaf-1 and procaspase 3 is markedly suppressed within 4 weeks after birth in brain tissue while they are even expressed in adult liver. Considering these results together, we propose that, in the brain, the cytochrome c-dependent mitochondria pathway, which is essential for the programmed cell death during normal morphogenesis, is abrogated within 2-4 weeks after birth, whereas the pathway is still active in other adult tissues such as liver.     

A low degree of fatty acid unsaturation leads to high resistance to lipid peroxidation in mitochondria and microsomes of different organs of quail (Coturnix coturnix japonica)

Birds – particularly long-lived species – have special adaptations for preventing tissue damage caused by reactive oxygen species. The objective of the present study was to analyse the fatty acid composition and non-enzymatic lipid peroxidation of mitochondria and microsomes obtained from liver, heart and brain of quail (Coturnix coturnix japonica), a short-lived bird. Fatty acids located in total lipids of rat liver, heart and brain mitochondria and microsomes were determined using gas chromatography and lipid peroxidation was evaluated using a chemiluminescence assay. The unsaturated fatty acid content found in mitochondria and microsomes of all tissue examined was approximately 50 and 40%, respectively with a prevalence of C18:1 n9. The C18:2 n6 content in brain mitochondria was significantly lower as compared to liver and heart mitochondria. Whereas the C20:4 n6 content in mitochondria from all tissues examined and brain microsomes was approximately 6%, liver and heart microsomes exhibited lower values. C22:6 n3 was absent in liver mitochondria, very low content in liver microsomes and heart organelles (between 0.5 and 1%) and high content in brain organelles, with mitochondria having the highest value (11%). Whereas liver and heart organelles were not affected when subjected to lipid peroxidation, brain mitochondria were highly affected, as indicated by the increase in chemiluminescence and a considerable decrease of C20:4 n6 and C22:6 n3. These results indicate that a low degree of fatty acid unsaturation in liver and heart organelles of quail, a short-lived bird, may confer advantage by decreasing their sensitivity to lipid peroxidation process.     

Association of Cu,Zn-type superoxide dismutase with mitochondria and peroxisomes

The subcellular localization of Cu,Zn-type superoxide dismutase (Cu,Zn-SOD) was investigated in rat tissues and cultured human fibroblasts. Subcellular fractionation, Nycodenz gradient centrifugation, and immunoblot analysis using specific antibodies showed that Cu,Zn-SOD was localized in cytosol, mitochondria, and peroxisomes of rat liver and brain. Treatment of highly purified mitochondria from rat liver with either Chaps or Triton X-100 released the bound Cu,Zn-SOD into supernatant fraction. Depolarization of mitochondria by inorganic phosphate and Ca(2+) released both Cu,Zn-SOD and cytochrome c from mitochondria. Digitonin also released Cu,Zn-SOD but not cytochrome c from mitochondria. Confocal immunofluorescence microscopy revealed that anti-Cu,Zn-SOD antibody in cultured human fibroblasts was found to colocalize with antibodies to Mn-SOD and PMP-70, markers of mitochondria and peroxisomes, respectively. Incubation of human Cu,Zn-SOD with purified mitochondria resulted in their association. These results indicate that Cu,Zn-SOD associates with mitochondria and peroxisomes in various cell types such as those in brain, liver, and skin.     

Immunocytochemical study of the maturation of the hypothalamo-neuro-hypophysial axes in the human fetus (author's transl)]

1. The development of the hypothalamo-neurohypophysial system was studied using immunocytochemistry with various antisera : anti-neurophysin, anti-oxytocin, anti-vasopressin, anti-vasotocin and anti-somatostatin. 2. Immunocytochemical investigation shows that anti-vasopressin and anti-vasotocin sera react with both vasopressin and vasotocin, whereas the anti-oxytocin serum specifically reveals the oxytocin-containing structures (Fig. 1g, h, i). 3. Perikarya stained with anti-neurophysin, anti-vasopressin and anti-vasotocin sera can be seen from the 11th week of fetal life (Fig. 1a) first in the supra-optic nucleus (SON), then in the para-ventricular nucleus (PVN). Their axons reach the neural lobe as early as the 11th week (Fig. 1b, c). 4. Oxytocin-containing perikarya appear simultaneously in the PVN (Fig. 1e) and SON during the 13th week. 5. From the 16th week, neurons stained with the anti-somatostatin serum can be seen among the neurophysin-positive cell-bodies of the SON and PVN. 6. The various populations of magnocellular neurons show a significant increase in number, especially up to the 19th week, and an increase in their hormonal content up to birth.     

Effect of a short-term fasting and altitude hypoxia on the cytochrome oxidase activity of rat brain mitochondria

The effect of short-term fasting and thirst, prolonged fasting and hypoxic hypoxia upon the activity of cytochrome oxidase was studied in mitochondrial fractions obtained from the brain and the liver. The investigation was carried out in two groups of rats, 5 and 60 days old. a) The activity of cytochrome oxidase in mitochondria isolated from the brain cortex, subcortical regions and the medulla oblongata rises, while the changes in liver mitochondrial fractions are reverse. b) A significant increase of mitochondrial cytochrome oxidase was found in 5-day-old rats after both types of fasting and hypoxia in all regions of the brain, as well as in the liver. c) The cytochrome oxidase activity in brain and liver mitochondria of 60-day-old rats was not affected appreciably after 24 h nutritional deprivation, with the exception of a significant rise of activity in the medulla oblongata. Prolonged fasting and hypoxia again markedly increased the activity of this enzyme in all regions of the brain and in the liver.