Peculiarities of proteasome pool formation in rat spleen and liver during postnatal development

Changes in the specific activity and amounts of 26S and 20S proteasome pools in rat spleen and liver during postnatal development and appearance in them of immune subunits were studied. Two decreases in chymotrypsin-like activity of the proteasome pools were recorded during the first three weeks after birth. The activity minimum fell on the 11th and 19th days, and the first decrease was more prolonged and pronounced than the second. The decrease in the specific activity of the 26S proteasome pools was associated with a reduction of their quantity. The 20S proteasome pools displayed no such decreases. Noticeable quantities of immune subunits LMP7 and LMP2 were revealed by Western blotting in the spleen on the 7th day and on the 19th day in the liver, concurrently with the beginning of the decrease in the proteasome activity. It was concluded that during the first three weeks of postnatal development the proteasome pools in rat spleen and liver were replaced twice, and in the spleen (a lymphoid organ) a qualitatively new pool containing immune subunits appeared nearly two weeks earlier than in the liver (a non-lymphoid organ). The appearance of immune proteasomes in different organs and tissues during some weeks after birth seems to explain the immune system inefficiency during embryogenesis and early postnatal development.     

Morphologic and hormonal correlates of true hermaphroditism in the rabbit

A macro-microscopical and histological investigation of the urogenital system organs of a rabbit-hermophrodite has been performed with an aim to compare the content of sex steroids in the peripheral and in the gonadal blood estimated by means of radioimmunological methods. Certain anomalies have been found out in the development of external and internal sex organs, kidneys and urinary bladder. Testosterone and estradiol concentration in blood flowing from the ovotestis is decreased, as it is in the periphral blood. The rabbit urogenital system organs have been studied from the 12th day of the intrauterine development up to the 10th day of the postnatal life. The results of the investigation performed make it possible to consider that the developmental anomalies in the rabbit-hermophrodite have, evidently, appeared between the 20th--25th days of its intrauterine development as a result of certain disbalance of sex steroids.     

Phospholipid biosynthesis in sarcoplasmic reticulum membrane during development.

Biosynthesis of phosphatidic acid, phosphatidylcholine and phosphatidylethanolamine in the sarcoplasmic reticulum membrane has been investigated. The results show that sarcoplasmic reticulum, in addition to its main function, i.e. transport and accumulation of Ca2+, is able to synthetize phospholipids by the same pathways as endoplasmic reticulum of other tissues. The changes of activity of enzymes involved in phospholipid biosynthesis during muscle development have been analysed. The extent of sn-glycero-3-phosphate and lysophosphatidylcholine acylation by acyl-CoA or free fatty acids in the presence of ATP and CoA is the same at every stage of development. The specific activity of glycerolphosphate acyltransferase(s) increases progressively during development up to about the 10th day of postnatal life and then decreases to the adult level. Linoleate esterifies sn-glycero-3-phosphate to a higher extent than palmitate, especially during postnatal period. The main product of sn-glycero-3-phosphate acylation is phosphatidic acid. The specific activity of lysolecithin acyltransferase increases from the embryonic period to a maximum between the 4th and the 9th day of postnatal life followed by a decrease to the adult value. the low embryonic value to a maximum at about the 3rd day of postnatal life, followed by a decrease to the adult value. The activity of cholinephosphotransferase decreases from a high value observed during the earliest embryonic period studied until the 3rd day before birth, and then begins to increase again from about the 5th day of postnatal life. The activity of ethanolaminephosphotransferase decreases continuously with age. The main product of phosphatidylethanolamine methylation is phosphatidylmonomethylethanolamine. The specific activity of phosphatidylethanolamine methyltransferase increases from     

Cytofluorimetric study of the content of glycogen and its fractions in rat liver cells in the course of the 1st week of postnatal ontogeny]

A cytofluorometric study of the total glycogen and its fractions in rat liver cells using the fluorescent PAS reaction was made during 1--7 days of the postnatal development. It was established that glycogen content was small on the first two days of development. The glycogen content increases only on the third day after birth. The glycogen of the rat liver cells during a first week of the postnatal development is different from that detected in adult liver cells in two aspects: in 3 day old hepatocytes soluble and stable glycogen fractions are equal, while in adult rat liver cells the former makes 80--90%; during the first week of the postnatal development, the stable fraction of rat liver cell is more labile, while in the adult rat liver the soluble fraction of glycogen is more labiles.     

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.     

Cyto- and synaptogenesis in the arcuate nucleus of the rat hypothalamus during fetal and early postnatal life

Summary Morphogenesis of the arcuate nucleus of the rat from the 15th fetal day to the 6th postnatal day was investigated light and electron microscopically. The arcuate neurons exhibit a gradual development after the 15th fetal day. All cytoplasmic constituents are present in these nerve cells already during the last days of gestation. Nevertheless, they are not fully differentiated at birth. The first synapse-like structures (presynapses) were observed in 17 day-old, the first synapses in 18 day-old fetuses. During the early postnatal period the number of presynapses decreases, but at the same time there is a gradual increase in the number of the relatively mature synapses. This process starts already during the last days of prenatal life. Although all structural elements of the arcuate nucleus of the adult rat appear to be present at birth, the extent of the neuropil area and the number of the presynapses indicate that the arcuate nucleus is still in a fairly undeveloped stage during the first postnatal days.     

Effect of isoproterenol on 85Sr accumulation in the myocardium of the rat during postnatal ontogeny.

The aim of this study was to establish whether administration of toxic doses of isoproterenol (IPRO) increases the accumulation of strontium--a homologue element of calcium--in the rat heart during postnatal development. It has been shown that in 14-day-old animals 85Sr uptake was not increased; starting from the 30th day of postnatal life this parameter increases significantly up to adulthood.     

Transaminases in rat retina during development

Aspartate, alanine and tyrosine aminotransferase activities have been determined in rat retina during postnatal development. Aspartate transaminase activity is rather low at birth; however, it increases as a function of age, reaching its maximum value at the 23rd day. Alanine transaminase activity increases more rapidly than aspartate transaminase, reaching its maximal value 15 days after birth, but, unlike the latter, this activity considerably decreases during further development. Neonatal tyrosine aminotransferase activity increases by 3 fold between the 5th and 15th day of life.The behaviour of the three enzymes investigated has been related to functional and morphological differentiation of retinal cellular layers.     

Glutamate decarboxylase and GABA transaminase activity in the mitochondrial fraction of the dog brain limbic system during postnatal development

Overall glutamate decarboxylase (GDCase) activity in the initial mitochondrial fraction of the limbic structure is found to be regionally different it increases from the moment of birth up to 1 year, the midbrain reticular formation (RF), where the enzyme activity in the mitochondrial decreases in pups aged 3 month and reincreases in 1 year old dogs being the exception. Overall GABA-transaminase (GABA-T-ase) activity reaches the "adult" level and is the highest: in the hypothalamic and hippocampal mitochondria on the 1st postnatal day; in the limbic cortex (l1 and l2 fields), amygdala and midbrain RF--on the 12-16th postnatal days. During the period from 12-16 postnatal days up to the age of 1 year GABA-T-ase activity in the dog limbic system decreases reliably.     

Proliferation of cardiomyocytes and interstitial cells in the cardiac muscle of the mouse during pre- and postnatal development

Proliferation of cardiomyocytes and interstitial cells in the cardiac ventricle of the mouse during pre- and postnatal development was studied. Furthermore, the number of cardiomyocyte and interstitial cell nuclei per unit area was determined on histological sections. The labelling index of cardiomyocytes decreases from 23% on day 14 of gestation to about zero at 3 weeks after birth. The number of cardiomyocyte nuclei per unit area increases up to day 16 of gestation and then continuously declines. This coincides with the concept that the increase in size of the heart during early fetal life is mainly due to hyperplasia, while during late fetal life and after birth it is mainly, and during adult life exclusively, due to hypertrophy of cardiomyocytes. Proliferation of interstitial cells continues up to 5 days after birth and then decreases. The ratio of cardiomyocytes to interstitial cells decreases by a factor of about 10 between day 14 of gestation and 3 weeks after birth.     

Cysteine oxidase activity in rat retina during development.

Cysteine oxidase activity has been determined in developing rat retina. Enzymic activity is present in 55, 000 × $\text{g}$ supernate and in the crude mitochondria.Activity is rather low at birth; but increases with age; in mitochondria it reaches its maximum value at the 25th day while in supernate it increases more rapidly, reaching its maximum value 20 days after birth; unlike in the mitochondria, the activity of supernate considerably decreases during further development.The reason and significance of the postnatal changes in the mitochondrial cysteine oxidase activity are briefly discussed in relation with taurine formation.     

Development of monoamine oxidase activity during postnatal development of the ground squirrel (Citellus citellus).

1. Monoamine oxidase (MAO) activity in the brain and peripheral tissues of newborn ground squirrel, as well as its evolution during postnatal development were studied. 2. Monoamine oxidase activity in the brain stem and liver, at the day of birth is significantly higher (P less than 0.01; P less than 0.005) than in adults. 3. After that, enzyme activity decreases, but at the 25th day, e.g. at the day of the opening of the eyes, still remains significantly above the adult's value (P less than 0.01). 4. The results indicate some species specificity concerning the level and the evolution of cerebral and hepatic MAO activity as compared to the rats.     

S-Adenosylmethionine Decarboxylase Levels in Rat Retina During Postnatal Development

Abstract: S -Adenosylmethionine decarboxylase from rat retina is similar to that isolated from other rat tissues with regard to kinetic parameters. pH optimum, putrescine requirement, and sensitivity to spermine. The enzymic activity increases during the first 7 days of postnatal life but decreases until the 20th day. After this period AdoMet decarboxylase activity increases, to reach the highest values at the 90th day. This behavior suggests that such enzymic activity is responsible for spermidine and spermine levels in rat retina and that a high content of retinal spermine might have a role in the photoreceptor outer segment renewal.     

Effect of weaning on the activities of glycogen synthase and phosphorylase in rat liver

The effects of weaning on the level of glycogen and the activities of glycogen synthase and phosphorylase were determined in rat liver. Glycogen levels in rat liver increased at the start of the weaning period and reached a plateau on postnatal day 20. The active form of glycogen synthase increased until postnatal day 19 and then declined. Total glycogen synthase (active + inactive) remained high during the suckling period and declined to a new low level during the weaning period. The activity ratio (active/total) increased from day 16 to days 18-22 and then decreased to the same level as found during the suckling period. At the onset of weaning the active form of phosphorylase decreased, whereas total phosphorylase initially increased and then decreased after postnatal day 20. Both forms of phosphorylase increased again at the end of the weaning period. The activity ratio decreased at the start of weaning and remained low throughout the rest of the weaning period. The effects of premature weaning were similar to those observed in normally weaned animals, but the changes occurred sooner and were more pronounced.     

Growth of different types of muscle fibers of the soleus muscle during postnatal ontogeny in the rat

In order to study the development of the m. soleus muscle fibers during postnatal ontogenesis in the rat, methods for revealing ATPase activity of myosin at preincubation in acidic and alcaline medium and lactate dehydrogenase and succinate dehydrogenase activity have been used. The m. soleus undergoes three stages of development. The first stage--from birth of the animal up to the 7th day. During this time the muscle is homogenous. The second stage is characterized by appearance of certain histochemical differences in the muscle fibers. The muscle becomes mixed. During the whole period (in males from the 7th up to the 175th, and in females from the 7th up to the 60th-70th day) transferring of glycolytic fibers into oxidative-glycolytic ones with their successive transformation into oxidative fibers is observed. During the third stage (in males older than 175, and in females older than 60-70 days) the m. soleus converts from the mixed into the homogenous one consisting of oxidative fibers.     

Developmental Expression of the P0 Glycoprotein and Basic Protein mRNAs in Normal and Trembler Mutant Mice

Mice affected by the autosomal dominant Trembler mutation exhibit a severe hypomyelinization of the PNS. Previous biochemical studies have shown that the accumulation of the major PNS myelin proteins, P0 and myelin basic protein (MBP), is strongly diminished in Trembler sciatic nerves during postnatal development. We performed Northern blots which showed that the size of mRNA species for P0 and MBP in normal and mutant mice are indistinguishable. Densitometric analysis of Northern blots showed that, in normal mice, the proportion of P0 mRNA increases up to the 12th day, then decreases slowly. At day 40, the proportion is 60% of the maximal value. In the mutant, the proportion of P0 mRNA increases up to the 12th day and then decreases much faster than in the control. At days 12 and 40, the P0 mRNA proportion measured in Trembler sciatic nerves represents only 40% and 7%, respectively, of the proportion measured in control littermates. The MBP mRNA proportion in the normal mice increases up to the 16th day, and then decreases to attain 45% of the maximum level at day 40. In the Trembler mouse, there is a maximum level at day 12, representing 25% of the normal level, but the MBP mRNA is barely detectable at days 8 or 40. Thus, these data seem to indicate that in the Trembler sciatic nerves, the proportions of P0 and MBP mRNAs are too small to allow the synthesis of normal levels of the corresponding proteins.     

PHOSPHOCHOLINE DIGLYCERIDE TRANSFERASE ACTIVITY DURING DEVELOPMENT OF THE CHICKEN BRAIN

Abstract— The activity of chicken brain phosphocholine diglyceride transferase was followed during pre- and postnatal development. The specific activity of this enzyme increases from the 10th day of embryonic life, reaches a maximum at hatching and decreases thereafter. Total brain activity increases in parallel with the increase of brain lecithins. The apparent K _m of the enzyme for CDP choline is 1.5 × 10^-4 m before the 10th day of embryonic life, 2.5 × 10^-5 m between the 13th day of the embryo and the 10th day after hatching, and finally 1.3 × 10^-4 m after the 38th day of postnatal life. These data suggest the existence of isoenzymes, one of which appears at the beginning of myelination.     

Distribution of histamine in the rat kidney during pregnancy and development

Summary An antiserum against conjugated histamine and two oligonucleotide probes that detect the mRNA encoding L-histidine decarboxylase (HDC) involved in histamine synthesis were used to study the appearance of histamine and its location in the kidneys of fetal, newborn and young postnatal rats and in the kidneys of pregnant rats. On embryonic days 16 and 18 (E16 and E18), some HA-immunoreactive (HA-ir) cells were found within the largest S-shaped bodies. Histamine was found to appear rapidly between the 18th and 20th embryonic days in the convoluted tubules of the kidneys. On postnatal day 0 (P0), the distal convoluted tubules and collecting ducts exhibited bright fluorescence, the intensity of which decreased quickly so that it was faint on day P4 and absent at later stages. In kidneys of pregnant rats HA-ir was found in the epithelium of both the Bowman's capsule, collecting ducts and in a few cells within the tubules. Nonuniform HA-ir was also detected within glomeruli. No evidence for the presence of L-histidine decarboxylase mRNA in kidneys of fetuses or pregnant rats was seen. It is concluded that distinct structures in the developing rat kidney contain histamine during a period around birth from day E20 to day P4. In the pregnant rat, the epithelium that is in direct contact with the urine flow is immunoreactive for histamine from day 16 to 20 of pregnancy. The results suggest that histamine is not synthesized locally in the kidneys but rather originates from other tissues.     

Respiratory enzymes in the heart and liver of the prenatal and postnatal rat

1. Heart and liver tissue samples were obtained from rats in various developmental stages from the 12-day-old embryo to the 120-day-old postnatal animal. 2. The body, heart and liver weights and percentage protein in the liver and heart of the prenatal and postnatal rat were determined. 3. The activities of NADH–, NADPH– and succinate–cytochrome c reductases and cytochrome oxidase were determined also. 4. The specific activities of all the enzymes increased in both heart and liver during late foetal development (16 days to term). The NADH– and succinate–cytochrome c-reductase activities in the heart increased threefold during the neonatal period (0 to 25 days post partum) and then remained constant to 120 days. All reductase activities increased in the liver three- to six-fold during the neonatal period. Cytochrome-oxidase activity in both tissues increased sixfold during this time but plateaued in the liver at 12 days rather than 25 days. 5. A sex difference was observed in NADH–cytochrome c-reductase activity in the liver. Up to 25 days post partum the activity was the same in both sexes, but from that time on the activity continued to increase in the female but remained unchanged in the male. 6. NADPH–cytochrome c-reductase activity increased only in the liver. 7. These results indicate that different electron-transport pathways predominate according to the tissue, developmental stage and sex of the animal.     

Prenatal and postnatal expression of mRNA coding for rat prothrombin.

The levels of prothrombin mRNA in prenatal and postnatal rat tissues were analyzed in order to determine tissue distribution of prothrombin expression and to determine if increases in liver prothrombin mRNA during development correlated with previously documented developmental increases in plasma prothrombin levels. Maternal tissues were also analyzed in order to determine if prothrombin mRNA levels varied due to gestational or postpartum influences. Northern analysis demonstrated that rat liver prothrombin mRNA levels increased several-fold late in gestation and reached maximal levels by 13 days after birth. Prothrombin mRNA was also expressed in diaphragm, stomach, intestine, kidney, spleen and adrenal tissues during development. In maternal tissues during pregnancy, prothrombin mRNA was expressed in liver, diaphragm, stomach, uterus and placenta. Prothrombin mRNA levels in each of these tissues that were positive by Northern analysis were quantitated by solution hybridization analysis. Between gestational day 18 and postnatal day 13, liver prothrombin mRNA levels increased from approx. 600 to 2100 molecules per cell (a 3.5-fold increase). In maternal liver during pregnancy, between day 18 and day 22, prothrombin mRNA levels increased from approx. 1800 to 2100 molecules per cell. Immediately after delivery, maternal liver prothrombin mRNA levels decreased to approx. 50% of preparturition levels. Prothrombin mRNA levels in placental tissue ranged from approx. 100 to 250 molecules per cell. In other fetal, postnatal and maternal tissues, prothrombin mRNA expression was less than 100 molecules per cell. These results demonstrate that the level and tissue-type expression of prothrombin mRNA varies in response to prenatal and postnatal influences.