Desmosterol in developing rat brain

The brain of the young rat contains appreciable amounts of desmosterol (24-dehydrocholesterol). The peak desmosterol concentration is seen during the first week of life and only traces of this sterol are found at 21 days. The spinal cord also contains some desmosterol. Rat brain desmosterol is distributed in the white matter, gray matter and cerebellum and occurs in the same proportion to cholesterol in each of these brain fractions. Rat brain contains a small amount of sterol ester but no appreciable amounts of desmosterol are present in this fraction. Studies carried out in intact animals injected either intraperitoneally or intracerebrally with mevalonic acid-2-¹⁴C or glucose-U-¹⁴C indicate the biosynthetic origin or brain desmosterol. Rat brain slices (1–20 day old) incubated in suitably fortified medium convert sodium acetate-2-¹⁴C and glucose-U-¹⁴C to desmosterol, whereas brain slices from adult rats yielded no radioactive desmosterol under similar conditions. When labeled desmosterol was incubated with young rat brain slices, it was converted to cholesterol. When pregnant rats were treated with triparanol (20 mg/kg/day) during the course of their pregnancy, they either resorbed the fetuses or gave birth to small, stillborn litters. The brains of the progeny of triparanol treated mothers contained large amounts of desmosterol as well as another sterol which may be Δ^7,24-cholestadiene-3β-ol.     

Fatty acid and sterol specificity of cholesterol esterifying enzyme in developing rat brain

The properties and fatty acid and sterol specificity of cholesterol-esterifying enzyme (EC 3.1.1.13) in rat brain were studied. The enzyme utilized free fatty acid for esterification, and activity was maximal at pH 5.6. Exogenous ATP and CoA did not stimulate the incorporation of free fatty acids into sterol esters. Substrates dispersed in Tween 20 or Triton X-100 were just as effective as the substrates dissolved in acetone solution, while dispersion in propylene glycol or sodium taurocholate was not as effective. Snake venom phospholipase A₂ (EC 3.1.1.4) increased the esterification of cholesterol in the absence of added fatty acid. The fatty acid specificity data indicated that oleic and palmitic acids were the preferred fatty acids. Little or no esterification occurred in the presence of long chain fatty acids (C₂₀–C₂₄). Esterification of cholesterol with palmitate or stearate was not affected by the presence of oleic acid in the mixture. Thus, the nonrequirement of the brain-esterifying enzyme for a bile acid or for an amphiphile such as an unsaturated fatty acid suggests that micellar solubilization of the substrate is not essential for activity. Although the brain enzyme catalyzed the esterification of desmosterol, cholesterol was the preferred substrate. Neither lanosterol (C₂₉ sterols) nor Δ7-dehydrocholesterol was esterified to any significant extent. The presence of low concentrations of desmosterol increased cholesterol esterification slightly, while there was a concentration-dependent inhibition of demosterol esterification by cholesterol. These data on fatty acid and sterol specificity of the esterifying enzyme correlate well with the composition of sterol esters present in developing rat brain.     

The distribution of labeled palmitic acid into the diglycerides and triglycerides of rat adipose tissue

After in vitro incubation of rat epididymal fat pads with radioactive palmitic acid, the distribution of the label in the different lipid classes and in different triglycerides was determined by silica gel and silver nitrate-silica gel thin-layer chromatography (TLC). The radioactivity of the diglycerides was approximately half of the triglycerides. This ratio did not change with alteration in the time of incubation. It remained unaltered even after a subsequent 10-min incubation in a nonradioactive medium. When the fat pads were incubated, first with¹⁴C-, then with³H-labeled palmitic acid, the³H/¹⁴C ratio was slightly lower in diglycerides than in triglycerides. The fully saturated molecules contained 38% of the radioactivity of triglycerides. Addition of oleic acid or norepinephrine to the labeled palmitic acid-containing medium decreased this value. Subsequent incubation with these compounds did not alter the distribution of radioactivity.     

Uptake of fatty acids by the developing rat brain

Polyunsaturated fatty acids are avidly taken up by the developing rat brain. To explore the specificity of this process, [1-¹⁴C]labeled 16∶0, 18∶2n−6, 18∶3n−3, and 22∶6n−3 each were co-injected with [³H]18∶1n−9 into the jugular vein of two-wk-old functionally hepatectomized and shamoperated control rats. The radioactivities present in the brain, liver and serum were assessed 30 min after injection. Uptake of labeled fatty acids into brain lipids steadily increased with increasing degree of unsaturation, with more than twice as much uptake of 22∶6n−3 compared to 16∶0. Phosphatidylcholine was the principal radioactive species in the brain except for animals injected with [1-¹⁴C]22∶6n−3, in which more of the label was incorporated into phosphatidylethanolamine. Determination of watersoluble oxidation products in the brain and serum revealed that the greater uptake of the more unsatrated fatty acids did not result from differences in rates of degradation.     

一种软脂酸镁清净剂的研制

以软脂酸、二氧化碳、活性-60氧化镁为原料合成润滑油类清净剂,实验结果表明,软脂酸质量为5 g,活性-60氧化镁为8 g,甲醇8 mL,70℃反应2 h,可得到碱值为282 mg(KOH)/g的软脂酸镁盐清净剂;红外谱图(IR)显示软脂酸镁清净剂含有无定型的MgCO3。     

Essential fatty acid uptake and metabolism in the developing rodent brain

Studies were carried out to determine whether the brain takes up and metabolizes essential fatty acids during early postnatal development in rodents. Rats and mice were dosed with deuterium-labeled linoleic and linolenic acids either by intraperitoneal injection or by gavage. Animals were killed at different times thereafter, and organs were removed. Brains, livers, and blood were analyzed by gas chromatography— negative-ion-mass spectrometry for labeled fatty acids. To determine whether fatty acids were present in the brain apart from cerebral blood, a subset of animals was exsanguinated by perfusion with buffered saline, and the brain was then fractionated into subcellular components. Results demonstrated that the brain took up both labeled essential fatty acids within 8 h from the time of dosing. There was on average a greater uptake of linolenic acid into the cerebellum than into the cerebral cortex during the first 8 d of life in rats. The amount of linoleic acid taken into either region was similar, however. Docosahexaenoic acid intermediates, 20∶5n−3 and 22∶5n−3, were also found labeled in the brain. Time-course labeling experiments indicated that these intermediates may be converted to 22∶6n−3 within the brain. A rise of labeled 22∶6n−3 in the brain at 24 h appeared to be due to uptake of this fatty acid from the blood. The Amount of labeled 22∶6n−3 in the brain continued to increase beyond 24 h, and this did not appear to be correlated with its blood concentration. These results suggest that, during development in the rodent, different regions within the brain may vary in their capacity to synthesize 22∶6n−3, and this may be correlated with regional growth rates.     

Esterification of palmitic acid in swine aortic homogenates

The incorporation of [1-¹⁴C] palmitic acid into tissue lipids of the medial and intimal layers of swine aortic homogenates was investigated. The homogenates obtained were metabolically active as indicated by their ready incorporation of labeled palmitic acid into phospholipids, diglycerides and triglycerides in the presence of α-glycerophosphate in the incubation medium. Predominantly, labeling of phospholipids and especially of phosphatidylcholine was found when α-glycerophosphate or lysolecithin served as the fatty acid acceptor. Glycerol and monoolein did not serve as fatty acid acceptors. More than 98% of the radioactivity was recovered as the phosphatidylcholine fraction at the level of 0.64 μmoles/ml of lysolecithin in the incubation medium.     

Ketone bodies serve as important precursors of brain lipids in the developing rat

Ketone bodies are readily oxidized for energy by extrahepatic tissues. Since oxidation of ketone bodies produces acetyl coenzyme A (AcCoA), and hence could be an important source of immediate precursors for fatty acid synthesis, we investigated, in whole-brain homogenates of developing rats, the preferential utilization of [3-¹⁴C]acetoacetate (AcAc), [3-¹⁴C]β-hydroxybutyrate (β-OHB), and [U-¹⁴C]glucose for production of CO₂ and lipids, including phospholipids, glycerides, cholesterol, and free fatty acids. Throughout the postnatal period, the rate of AcAc oxidation was 2–3 and 2–6 times the rate for β-OHB and glucose, respectively. The eynthesis of lipids from AcAc was 7- to 11-fold higher than from glucose. The brain’s capacity for lipid synthesis from β-OHB was similar to that from AcAc during the first 8 days of life; however, during the next 10 days, the synthesis of lipids from β-OHB decreased to 60% of AcAc-dependent synthesis. The high rate of lipid synthesis from ketone bodies was accompanied by increased activities of cytoplasmic acetoacetyl CoA synthetase and acetoacetyl CoA thiolase in the developing brain. During the entire postnatal development, the proportion of radioactivity claimed by lipids vs. CO₂ from [3-¹⁴C]AcAc was 44–62% vs. 38–56%; from [3-¹⁴C]β-OHB, 50–81% vs. 19–50%; and from [U-¹⁴C]glucose, 14–43% vs. 57–86%. Phospholipids accounted for more than two-thirds of total lipids synthesized from either ketone bodies or glucose, while diglycerides plus cholesterol and free fatty acids accounted for most of the remainder. Addition of glucose to the incubation medium did not alter lipid production from AcAc throughout the suckling period, but moderately depressed energy production in the brain of 16- to 20-day-old rats. It is clear that in cell-free preparations from the brain of developing rats, ketone bodies are preferred over glucose as precursors for both energy and lipids, mainly phospholipids. These results suggest that ketone bodies are important for the growth and development of the brain.     

Alterations in fatty acid composition of tissue phospholipids in the developing retinal dystrophic rat

Alterations in lipid composition occur in the retinal pigment epithelium and photoreceptor cells of the Royal College of Surgeons (RCS) dystrophic rat, a model for inherited retinal degeneration. With respect to lipid composition of nonretinal tissues, the developmental timing of lipid alterations and the incidence of dystrophy are unknown. We determined the fatty acid composition in choline phosphoglycerides (ChoGpl) and ethanolamine phosphoglycerides (EtnGpl) in the brain, liver, and retina from dystrophic RCS rats and from their nondystrophic congenics (controls) at the ages of 3 and 6 wk. At 3 wk, the fatty acid compositions were specific to individual phospholipid classes without any difference between dystrophic and nondystrophic tissues. In plasma phospholipids, there was an age-related increase in the relative contents of monounsaturated and n-3 polyunsaturated fatty acids, with only minor differences between dystrophic and nondystrophic rats. At 6 wk, the fatty acid compositions in ChoGpl and EtnGpl from dystrophic brain and retina were significantly different from those of nondystrophics. The effect of strain on developmental changes in brain fatty acid composition was significant for 18∶0 and 22∶6n−3 in EtnGpl and for 16∶0, 18∶0, 18∶1n−9, and 20∶4n−6 in ChoGpl. The brain ChoGpl fatty acid composition in nondystrophic rats was similar at 6 wk to that of normal rats, and there were almost no postweaning changes in the dystrophics. In retinal phospholipids, the effect of dystrophy was to increase the 20∶4n−6 content in EtnGpl and to decrease 22∶6n−3 in ChoGpl. The 18∶2n−6 and 22∶6n−3 contents in dystrophic liver ChoGpl were also significantly affected, while no difference was observed in the EtnGpl fraction. The dystrophy affected the phospholipid fatty acid developmental changes in a tissue- and class-specific manner. Fatty acid metabolism could be selectively altered in neural and nonneural tissues of developing dystrophic RCS rats.     

Fatty acid composition of phospholipids in different regions of developing human fetal brain

The fatty acid composition of total phospholipids in different regions, viz., cerebrum, cerebellum and medulla oblongata, of developing human fetal brain was studied. All the brains analyzed in the present investigations were obtained from fetuses whose mothers belonged to the poor socioeconomic section of the population. Palmitic, oleic and stearic acids were found to be the dominant fatty acids, and the pattern was similar in all regions of the brain studied between the ages of 22 and 35 weeks. However at birth there appeared to be an increase in polyenoic acids at the expense of lower chain fatty acids, and these changes were of relatively higher magnitude in the cerebellum than in other regions studied. These changes, in terms of increase in polyunsaturated fatty acids near full term, coincided well with the already observed timing of an overall growth spurt of the brain a few weeks preceding birth.     

1-Docosanol and other long chain primary alcohols in developing rat brain

Long chain alcohols were detected in developing rat brain at ages ranging from 5 to 40 days. They were at their highest level of 0.0109% of the total lipids at the age of 10 days and decreased to 0.0036% at the age of 40 days. They consisted mainly of hexadecanol, octadecanol, octadecenol, eicosanol, docosanol, and tetracosanol. The fact that substantial amounts of fatty alcohols having more than 20 carbon atoms were present in myelinating rat brain indicated a chain length specificity in their utilization for0-alkyl and0-alk-1-enyl glycerolipid biosynthesis.     

Natural and accelerated docosahexaenoic acid accumulation in the prenatal rat brain

The quantity and distribution of docosahexaenoic acid (DHA) in major brain phospholipids (PL) was examined in the fetal rat brain before birth, using thin-layer and capillary column gas chromatography. A rapid increment of DHA content of about 187 μg/g brain/day was observed between 17 to 20 days gestation, as opposed to 39.3±2.9 μg/g brain/day prior to that. Single intraamniotic injections of 5 μL ethyl-docosahexaenoate (Et-DHA) 12 μM, 4.25 mg) administered to 17-day-old fetuses were used to examine the uptake of DHA into brain PL. Three days following injection, the amount of n-3 polyunsaturated fatty acids increased by 28% compared to ethyl-oleate (Et-Ole) injected fetuses. Compared to the n-6 fatty acid family, the relative amount of DHA increased in the phosphoatidylserine (PS), phosphatidylethanolamine and phosphatidylcholine (PC) lipids by 15 (P=0.02), 13 and 14%, respectively. A major increase in the pool size of phosphatidylinositol and PS (110 and 50.3%, respectively), and a decrease in PC (8.2%) were observed 3 d after Et-DHA as compared to Et-Ole administration. The data suggest that a single intraamniotic administration of Et-DHA can modulate membrane PL content and alter PUFA composition.     

棕榈酸改性方解石型重质碳酸钙的研究

以从漆蜡中提取的棕榈酸为改性剂,对方解石型碳酸钙粉体进行改性处理.以浊度、沉降体积作为评价指标,考察了改性温度、料浆质量分数、棕榈酸用量、改性时间及搅拌转速等对样品分散性能的影响.用傅立叶变换红外吸收光谱,热重分析、粒度分析等对改性前后碳酸钙粉体进行了表征.结果表明,在棕榈酸用量为2.0%,碳酸钙料浆质量分数为25.0...     

Lipogenesis in the developing brain: Utilization of radioactive leucine,isoleucine, octanoic acid and β-hydroxybutyric acid

Incorporation of radioactivity from intracranially injected radioactive leucine, isoleucine (ketogenic amino acids), octanoic acid and β-hydroxybutyric acid into the brain lipids of 15 to 16 day-old rats was examined. The results showed that radioactivity from all the above precursors was incorporated into brain lipids. Radioactivity from injected isoleucine was incorporated into odd numbered fatty acids indicating an alternate pathway to α-oxidation for the biosynthesis of these fatty acids in the brain. For some as yet unclear reasons, a substantial portion of the radioactivity from injected octanoic acid was incorporated into free fatty acids. Utilization of these compounds for providing carbon for lipogenesis during development under unstressed normal conditions is discussed.     

Increasing the thermal conductivity of palmitic acid by the addition of carbon nanotubes

Four different methods, acid oxidation, mechanochemical reaction, ball milling, and grafting following acid oxidation, were used to treat multi-walled carbon nanotubes (MWCNTs). During treatment, hydroxyl groups, carboxylic groups, and amidocyanogen were introduced onto the surfaces of the MWCNTs. The MWCNTs were dispersed into palmitic acid (PA) to prepare phase change composites with high thermal conductivity. Both chemical treatment and ball milling help to break the MWCNT aggregates and to enhance their dispersibility. Measurements show that the thermal conductivity increase of the composites is highly dependent on the MWCNT pretreatment process. We propose that the difference in the interfacial thermal resistance between the MWCNTs and the matrix is due to the difference of the MWCNT surface state caused by different treatment processes. In all the MWCNT/PA composites, the one containing MWCNTs with hydroxyl groups, treated by a mechanochemical reaction, has the highest thermal conductivity increase, which, at room temperature, is up to 51.6% for a MWCNT addition of 1.0%.     

Restriction of maternal food intake inhibits fatty acid activation in developing rat hearts

We studied the effect of restricting the diet of pregnant and lactating rats on the β-oxidation of fatty acids by the developing heart in suckling pups. Control pregnant rats were fed a stock diet ad libitum. For the experimental group, food was restricted to half of the control intake on the seventh day of pregnancy and continued through lactation. The pups on the restricted diet were significantly smaller than the controls. At postnatal days 5, 14 and 21, the β-oxidation of [1-¹⁴C] palmitate by heart homogenates was determined in the presence of ATP, carnitine and CoA. At day 21, the production of¹⁴CO₂ was 60% lower in the group on the restricted diet. Consequently, the possibility of inhibiting activation or intramitochondrial transport of fatty acids by heart mitochondria was studied in vitro using [1-¹⁴C] palmitate, [1-¹⁴C] palmitoyl CoA and [1-¹⁴C] palmitoyl carnitine. With [1-¹⁴C]-palmitate, the rate of¹⁴CO₂ produced was 2464±317 cpm/mg protein/min for the control and 1682±91 for the restricted diet group. With [1-¹⁴C] palmitoyl CoA and [1-¹⁴C] palmitoyl carnitine, the oxidation rate of the experimental group was similar to control values, showing clearly that the inhibition of oxidation was from a problem with activation. A significant decrease in palmitoyl CoA synthetase activity in the heart homogenates and mitochondria of the diet-restricted pups took place. Presented at the 74th Annual Meeting of the American Oil Chemists' Society, Chicago, Illinois, May 1983. Deceased.     

Incorporation of radioactive polyunsaturated fatty acids into liver and brain of developing rat

The incorporation of radioactivity from orally administered linoleic acid-1-¹⁴C, linolenic acid-1-¹⁴C, arachidonic acid-³Hg, and docosahexaenoic acid-¹⁴C into the liver and brain lipids of suckling rats was studied. In both tissues, 22 hr after dosing, 2 distinct levels of incorporation were observed: a low uptake (from 18∶2-1-¹⁴C and 18∶3-1-¹⁴C) and a high uptake (from 20∶4-³H₈ and 22∶6-¹⁴C). In adult rats, the incorporation of radioactivity into brain lipids from 18∶2-1-¹⁴C and 20∶4-³H was considerably lower than the incorporation into the brains of the young rats. In the livers of the suckling rats, the activity from the 18 carbon acids was associated mostly with the triglyceride fraction, whereas the activity from the 20∶4-³H₈ and 22∶6-¹⁴C was concentrated in the phospholipid fraction. In the brain lipids, the activity from the different fatty acids was associated predominantly with the phospholipids. In the liver and brain phospholipid fatty acids, some of the activity in the 18∶2-1-¹⁴C and 18∶3-1-¹⁴C experiments was associated with 20 and 22 carbon polyunsaturated fatty acids; however, radioactivity from orally administered 20∶4-³H₈ and 22∶6-¹⁴C was incorporated intact into the tissue phospholipid to a much greater extent compared with the incorporation of radioactivity into 20∶4 and 22∶6 in the experiments where 18∶2-1-¹⁴C and 18∶3-1-¹⁴C, respectively, were administered. Possible reasons for these differences are discussed. Rat milk contains a wide spectrum of polyunsaturated fatty acids, including linoleate, linolenate, arachidonate, and docosahexaenoate. During the suckling period in the rat, there is a rapid deposition of 20∶4 and 22∶6 in the brain. The results of the present experiments suggested that dietary 20∶4 and 22∶6 were important sources of brain 20∶4 and 22∶6 in the developing rat.     

Metabolism of linolenic acid in developing brain: I. Incorporation of radioactivity from 1-14C linolenic acid into brain fatty acids

Twelve-thirteen day old rats were given 1-¹⁴C linolenic acid by intraperitoneal injection. Fatty acids were isolated from the brains of animals sacrificed at the end of 8 and 48 hr and 15 and 45 days. Eight hr after the tracer, radioactivity was found neither in 18∶3 nor its endproduct, 22∶6, and palmitate was the most highly radioactive component. At longer intervals, 22∶6 seemed to retain much of the radioactivity, whereas palmitate showed a precipitous decline in radioactivity. Initial oxidation of linolenate and sparing of the linolenate complexed with polar lipids are discussed.     

Selective use of palmitic acid over stearic acid for synthesis of phosphatidylcholine and phosphatidylglycerol in lung

The incorporation of [³H]palmitic acid and [¹⁴C]stearic acid into phospholipids in rabbit lung tissue was studied. Under equal molar concentrations of palmitate and stearate, palmitate was incorporated to the 1- and 2-positions of phosphatidylcholine (PC) and phosphatidylglycerol (PG) 2–3 times more than stearate. By contrast, palmitate was 30% less than stearate in phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine. These results suggest that preferential utilization of palmitate over stearate, rather than substrate availability, determines the high content of palmitoyl at the 1- and 2-positions of PC and PG in lung.