THE INCORPORATION OF LABELLED ACETATE INTO CEREBROSIDE AND OTHER LIPIDS OF THE DEVELOPING MOUSE BRAIN

—Cerebroside in the brain is highly localized in myelin and has a relatively slow turnover rate. The aim of this study was to evaluate the true cerebroside biosynthetic activity under conditions in which the degradation and reutilization of brain lipids were as small as possible. The 3-week-old mice were decapitated at 0·5, 1, 2·5, 5 and 15 min after the intraperitoneal injection of labelled acetate and the incorporation of radioactivity into each lipid class was examined. Even at 0·5 min, a considerable amount of radioactivity was found in simple lipids, especially in the free fatty acid fraction, and in the course of time the radioactivity of complex lipids increased. On the other hand, the incorporation of radioactivity into cerebrosides was extremely small throughout the experimental period. Results indicated that the low radioactivity of cerebroside might be due to its high content of long-chain fatty acids which were weakly labelled. The radioactivity of the sphingosine moiety was also low. In short, one of the rate-limiting steps of cerebroside synthesis in brain might exist in long-chain fatty acid and sphingosine synthesis. In addition, the incorporation curves of each component of cerebroside were compared with each other and the difference of the incorporation pattern of non-hydroxy fatty acids of cerebroside was noted.     

EFFECTS OF SURGICAL DECENTRALIZATION AND NERVE GROWTH FACTOR ON THE MATURATION OF ADRENERGIC NEURONS IN A MOUSE SYMPATHETIC GANGLION

Abstract— The increase in tyrosine hydroxylase activity in mouse superior cervical ganglion during postnatal development was prevented by administration of the protein synthesis inhibitor cycloheximide. Surgical section of the preganglionic nerves in 4-day-old mice prevented the normal increases in tyrosine hydroxylase and monoamine oxidase activity in the ganglion during development. Surgical decentralization also prevented the developmental increases in ganglion size and cell numbers. The preganglionic fibres thus appear to exert a general regulatory effect on the growth and biochemical maturation of postganglionic adrenergic neurons in sympathetic ganglia. Administration of nerve growth factor to young mice failed to eliminate the differences in ganglion size, cell numbers and tyrosine hydroxylase activity between normally innervated and decentralized ganglia. Nerve growth factor, however, caused an increase in all these parameters in both control and decentralized ganglia–the magnitude of these increases being greatest in the control ganglia. Administration of carbachol and physostigmine to neonatal mice did not influence the normal development of tyrosine hydroxylase activity in the superior cervical ganglion.     

EFFECTS OF DENERVATION ON THE INCORPORATION OF 32P INTO PHOSPHATIDYL INOSITOL AND OTHER PHOSPHOLIPIDS OF RAT DIAPHRAGM

Abstract— At 24 h after denervation of the rat hemidiaphragm, incorporation of ³²P into phosphatidyl inositol was depressed relative to incorporation of ³²P into phosphatidyl choline (measured 75 min after injection of the isotope intraperitoneally). The ratio of the specific radioactivity of phosphatidyl choline to the specific radioactivity of P_i was unaffected by denervation which implies that denervation had depressed incorporation of isotope into phospatidyl inositol. Denervation did not cause a measurable change in the pool size of phosphatidyl inositol relative to that of phosphatidyl choline. The effect of denervation on incorporation of ³²P into phosphatidyl inositol was not entirely a direct consequence of the cessation of ACh release at the motor end-plate since the effect was clearly manifest in strips of muscle not containing motor end-plates, but the magnitude of the denervation effect was slightly greater in the strips of denervated hemidiaphragm which contained motor end-plates.     

ACETYLCHOLINESTERASE OF RAT SYMPATHETIC GANGLION: MOLECULAR FORMS, LOCALIZATION AND EFFECTS OF DENERVATION

Abstract— In sucrose gradient centrifugation, acetylcholinesterase (AChE, EC 3.1.1.7.) from the rat superior cervical ganglion (SCG) has been found to contain four molecular forms, characterized by their sedimentation coefficients (4 S, 6.5 S, 10 S and 16 S). Homogenization of the ganglia in various media showed that the 4 S enzyme was readily solubilized in water whereas solubilization of the 6.5 S and 10 S forms was quantitative only in media containing Triton X-100. In order to solubilize the 16 S form, high concentrations of salt (NaCl 1 M) and detergent had to be present. AChE analysed by non-denaturing polyacrylamide gel electrophoresis separated into five bands. Although both distribution patterns were stable, i.e. each form or band preserved its characteristic sedimentation or electrophoretic migration when reanalysed, there was no 1:1 correlation between the forms isolated by sedimentation and the bands obtained by electrophoresis: one band might contain more than one form of enzyme, and conversely one form gave rise to several bands. It was therefore impossible to derive molecular weights from electrophoretic migration in non-denaturing gels. However, it could be shown that the results obtained by both methods of analysis were consistent. Acetylcholinesterase from other nervous structures was analysed: in pre- and postganglionic nerves, the main forms were 10 S and 6.5 S, with a small proportion of 4 S; the 16 S form was not detected. In other sympathetic ganglia, the distribution of forms was identical to that of the superior cervical ganglion. In rachidian ganglia, no 16 S form could be found. Following the section of the preganglionic nerve, the acetylcholinesterase activity of the superior cervical ganglion decreased by 50% in 3 days, and then rose again to about 80% of its original value after 2 weeks. These effects mainly reflected variations in the major 4 S and 10 S forms. The 16 S form, in contrast to its disappearance from denervated muscles, increased transiently during the first 2 weeks after denervation, reaching about twice its original activity. A concomitant cytochemical study of normal and denervated ganglia showed that after preganglionic denervation, AChE localized in the sympathetic neurones decreased markedly and remained low even during the recovery phase. During this period a cholinesterasic activity appeared in the perineuronal glia. Controls established that the enzyme synthetized in the glia is AChE.     

DEVELOPMENT OF LIPOGENESIS IN RAT BRAIN CORTEX: THE DIFFERENTIAL INCORPORATION OF GLUCOSE AND ACETATE INTO BRAIN LIPIDS IN VITRO

—The oxidation to CO₂ and the incorporation of [U-¹⁴C]glucose and [U-¹⁴C]acetate into lipids by cortex slices from rat brain during the postnatal period were investigated. The oxidation of [U-¹⁴C]glucose was low in 2-day-old rat brain, and increased by about two-fold during the 2nd and 3rd postnatal weeks. The oxidation of [U-¹⁴C]acetate was increased markedly in the second postnatal week, but decreased to rates observed in 2-day-old rat brain at the time of weaning. Both labeled substrates were readily incorporated into non-saponifiable lipids and fatty acids by brain slices from 2-day-old rat. Their rates of incorporation and the days on which maximum rates occurred were different, however, maximum incorporation of [U-¹⁴C]glucose and [U-¹⁴]acetate into lipid fractions being observed on about the 7th and 12th postanatal days, respectively. The metabolic compartmentation in the utilization of these substrates for lipogenesis is suggested. The activities of glucose-6-phosphate dehydrogenase, cytosolic NADP-malate dehydrogenase, cytosolic NADP-isocitrate dehydrogenase, ATP-citrate lyase and acetyl CoA carboxylase were measured in rat brain during the postnatal period. All enzymes followed somewhat different courses of development; the activity of acetyl CoA carboxylase was, however, the lowest among other key enzymes in the biosynthetic pathway, and its developmental pattern paralleled closely the fatty acid synthesis from [U-¹⁴C]glucose. It is suggested that acetyl CoA carboxylase is a rate-limiting step in the synthesis de novo of fatty acids in developing rat brain.     

THE EFFECT OF METHIONINE SULPHOXIMINE ON THE INCORPORATION OF LABELLED GLUCOSE, ACETATE, PHENYLALANINE AND PROLINE INTO GLUTAMATE AND RELATED AMINO ACIDS IN THE BRAINS OF MICE

—The incorporation of radioactivity from labelled glucose, acetate, phenylalanine and proline into glutamate, aspartate and glutamine was measured in mice treated with methionine sulphoximine and in the control animals. The labelled precursors were injected and their incorporation determined before the onset of convulsions. The incorporation of radioactivity from labelled glucose into the dicarboxylic amino acids was reduced, in particular the incorporation into glutamine. The incorporation of radioactivity from labelled acetate and phenylalanine into glutamate and aspartate was increased by methionine sulphoximine, while the incorporation into glutamine was not changed very much. The labelling of glutamine, relative to glutamate, was reduced with all precursors, indicating that glutamine synthetase was inhibited in vivo by methionine sulphoximine. It is very likely that methionine sulphoximine affects many aspects of energy metabolism in brain; in particular the metabolism of glucose seems to be inhibited, while the rate of conversion of substrates other than glucose seems to be increased.     

NO前体和供体对大鼠海马脑片神经元活动的影响

应用细胞记录单位放电技术,在大鼠海马脑片上观察了左旋精氨酸,Ｎ－硝在左旋精氨酸,ＳＩＮ－１,及亚甲基蓝对ＣＡ１区神经元自发放电的影响,旨在了解左旋精氨酸;ＮＯ通路在海马放电中的作用及其可能的机制。实验结果如下：１．用Ｌ－ａｒｇ（１ｍｍｏｌ／Ｌ）灌流海马脑片２ｍｉｎ,在５４个放电单位中有４２个单位放电频率降低,１２个单位无明显反应。     

心房钠尿多肽对麻醉大鼠血压和肾神经传出放电的影响

本实验观察了心房肽Ⅱ(Atriopeptin Ⅱ,APⅡ)对麻醉大鼠血压(AP)、心率(HR)和肾交感神经传出放电(RSNA)的影响,并与硝普钠对 AP 和 RSNA 的影响作比较。结果如下:(1)缓冲神经完整和迷走神经完整条件下(n=12)静脉注射 APⅡ(50μg/kg)后,动脉收缩压(SAP)降低23.0±1.66 mmHg(Μ±SE,p<0.001),HR 减慢9±3.5b/min(p<0.05),RSNA 降低4.89±2.95%(P>0.05)。迷走神经切断后,静脉注射 APⅡ引起的~⊿SAP 虽有所减小,但与切断迷走神经前的反应比较,无统计学意义,HR 减慢不再出现,而 RSNA 则有所增加;(2)缓冲神经切断和迷走神经完整条件下(n=7),静脉注射 APⅡ时 SAP 降低27.4±3.25mmHg(P<0.001),HR 减慢13±3.1b/min(P<0.01),RSNA 降低11.67±1.95%(P<0.001)。切断迷走神经后,静脉注射 APⅡ引起的 SAP 降低程度有明显減小(P<0.01),HR减慢不再出现,RSNA 则反而增加(3)无论在迷走神经完整还是切断条件下,静脉注射硝普钠(n=6) SAP 均明显降低,同时伴有 RSNA 的反射性增加。以上结果表明:APⅡ的降压效应,部分是通过迷走神经传入纤维;在切断缓冲神经条件下,APⅡ可经由迷走神经传入纤维的激活而反射地抑制 RSNA。     

THE METABOLISM OF LABELLED ETHANOLAMINE IN NEURONAL AND GLIAL CELLS OF THE RABBIT IN VIVO1

Abstract— Adult rabbits were injected intraventricularly with [¹⁴C]ethanolamine and the incorporation of the base into the phosphatidylethanolamine and ethanolamine plasmalogen (and their water-soluble precursors) of isolated neuronal and glial cells was investigated. All the radioactivity was incorporated into the base moiety of the ethanolamine lipids for the time intervals examined in both types of cells. In neurons, maximum labelling of the two ethanolamine lipids occurred at 7 h after administration, whereas the highest specific radioactivity for glial phosphatidylethanolamine and ethanolamine plasmalogen was reached at 20 and 36 h, respectively. The two lipids had a faster turnover in neurons than in glia, and in both populations incorporated the base at a faster rate than did whole brain tissue. The maximum incorporation rates for phosphorylethanolamine and CDP-ethanolamine were reached in both types of cell at about 6 h after administration but the content of radioactivity per unit protein for phosphorylethanolamine was much higher in glial than in neuronal cells. It is concluded that the site of most active synthesis of ethanolamine phospholipids in vivo is the neuronal cell, with a possible transfer of intact lipid molecule to the glial compartment.     

颈动脉内注入腺苷对呼吸,血压和肾交感神经活动的影响

在33只麻醉家兔,观察了颈动脉内注入腺苷所诱发的平均动脉压、心率,呼吸和肾交感神经活动的变化。结果如下:(1)颈动脉内注入腺苷后,平均动脉压呈剂量依赖性下降;呼吸加快,深度变化不明显,剪断窦神经后注入腺苷,仍引起平均动脉压下降,而呼吸变化消失。(2)隔离的颈动脉窦灌流液内加入腺苷后,平均动脉压下降,心率减慢;颈动脉体(CB)失活后反应消失。(3)将腺苷灌注到颈动脉窦区后,平均动脉压下降,肾交感神经传出放电活动增加,CB 失活或剪断窦神经后,反应消失。由此提示:腺苷可作为兴奋 CB 的一种物质,引起平均动脉压降低,心率减慢,呼吸加强和肾交感神经放电活动增加。     

刺激猫下丘脑LHA和VMN对小脑皮层神经元电活动的影响

在戊巴比妥钠麻醉的猫,电刺激下丘脑外侧区(LHA)和腹内侧核(VMN)可引起小脑皮层第Ⅵ和Ⅶ小叶浦肯野细胞和非浦肯野细胞抑制性、兴奋性和抑制-兴奋性的电活动,但以抑制性活动为主;这些反应的潜伏期多数为10-20ms,但也可长达90ms;一般刺激LHA比刺激VMN更有效。刺激下丘脑所激发的小脑神经元抑制性电活动可为静脉注射组胺H_1受体阻断剂扑尔敏所阻断。本文对上述观察的可能作用作了讨论。     

CATECHOLAMINES IN SYMPATHETIC GANGLIA OF RAT: EFFECTS OF DEXAMETHASONE AND RESERPINE1

The superior cervical sympathetic ganglion of rats contains a finite amount of epinephrine all of which is of ganglionic origin. Treatment of new-born rats with dexamethasone for 8 days results in a 112-fold increase in the epinephrine concentration, whereas the norepinephrine and dopamine are increased by only 1·4- and 1·9-fold respectively. This epinephrine increase in newborn rats is reversible if treatment is discontinued, and it fails to occur in adult animals. The epinephrine store of normal and dexamethasone treated animals is resistant to the depletion by reserpine. There is no increase in the epinephrine content in organs innervated by axons emanating from the ganglion. The data presented support the localization of epinephrine in small intensely fluorescent cells in the ganglion and we propose that epinephrine may be released from these cells and function as a modulator of ganglionic transmission.     

延髓腹外侧区微量注射L－NNA和SNP对大鼠血压、心率和肾交感神经活动的影响

在麻醉大鼠观察了向延髓腹外侧区微量注射ＮＯ合成酶抑制剂Ｎ－硝基左旋精氨酸（ＬＮＮＡ）和硝普钢（ＳＮＰ）对血压、心率和肾交感神经活动的影响,旨在探讨中枢左旋精氨酸－ＮＯ通路在动脉血压调节中的作用及其机制。实验结果如下：（１）向延髓腹外侧头端区（ＲＶＬＭ）注射Ｌ－ＮＮＡ后,平均动脉压（ＭＡＰ）升高,肾交感神经活动（ＲＳＮＡ）增强;心率（ＨＲ）减慢,但无统计学意义。ＭＡＰ和ＲＳＮＡ的变化持续３０ｍｉｎ以上;此效应可被预先静注左旋精氨酸所逆转。（２）向ＲＶＬＭ微量注射ＳＮＰ,ＭＡＰ降低,ＲＳＮＡ减弱;但ＨＲ的变化无统计学意义。（３）向延髓腹外侧尾端区（ＣＶＬＭ）注射Ｌ－ＮＮＡ,ＭＡＰ降低,ＨＲ减慢,ＲＳＮＡ减弱。（４）向ＣＶＬＭ微量注射ＳＮＰ,ＭＡＰ升高,ＲＳＮＡ增强,而心率无明显变化。以上结果表明,中枢左旋精氨酸－ＮＯ通路对延髓腹外侧部的神经元活动有调变作用。     

电刺激猫小脑顶核对动脉血压和肾交感神经放电的影响

在38只麻醉及人工呼吸的猫,观察到电刺激小脑顶核嘴侧部能引起动脉血压显著升高;肾交感神经放电于刺激期间显著增加。去缓冲神经对刺激顶核所引起的血压反应的幅度和肾交感神经放电均无明显影响,但可明显延长血压反应升高相以及血压恢复期的时间。静脉注射氯庄定引起血压降低、心率减慢及肾交感神经放电的抑制,并能减弱刺激顶核引起的血压反应,但增强了刺激顶核引起的肾神经放电的变化。电解损毁延髓腹外侧面引起血压降低及肾交感神经放电的抑制,然而无论单侧还是双侧损毁延髓腹外侧面都不能阻断刺激顶核所引起的血压和肾交感神经放电的反应。以上结果表明,电刺激顶核能引起明显的心血管反应,其反应的下行性通路可能不通过延髓腹外侧面。     

MORPHOGENETIC STUDIES ON HAWORTHIA: EFFECTS OF INOSITOL ON GROWTH AND DIFFERENTIATION

Effects of inositol on growth and differentiation of Haworthia tissue were studied. Inositol was found to be essential for the survival of the tissue. Growth was increasingly better with the increase in inositol content of the medium. A minimum level of inositol was required for organ differentiation. Organ differentiation was also promoted by the increase in inositol concentration in the medium. The chlorophyll content of the tissue increased with the increasing concentration of inositol. Presence of 2-deoxyglucose in the inositol-containing medium led to inositol deficiency symptoms.     

EFFECTS OF PRE- OR POSTNATAL DEXAMETHASONE, ADRENOCORTICOTROPHIC HORMONE AND ENVIRONMENTAL STRESS ON PHENYLETHANOLAMINE N-METHYLTRANSFERASE ACTIVITY AND CATECHOLAMINES IN SYMPATHETIC GANGLIA OF NEONATAL RATS

Abstract— Injections of dexamethasone (0.1 mg/kg/day, s.c.) on the first 2–3 days of life increased the phenylethanolamine- N -methyltransferase (PNMT) activity and epinephrine content of the superior cervical ganglion (SCG) and stellate ganglion of neonatal rats; the dopamine content was unaltered while norepinephrine was slightly reduced in these ganglia. Dexamethasone did not alter the PNMT activity or epinephrine content of the salivary glands or heart. The PNMT activity and epinephrine content of the SCG remained elevated for 10–14 days. Pretreatment with 6-hydroxydopamine did not alter the dexamethasone effects.
Injections of adrenocorticotrophic hormone (ACTH) (25 munits/rat twice a day) or exposure to a cold stress (4°C, 3 times a day) on the first 2–3 days of life, elevated the plasma concentration of corticosterone, and also increased the PNMT activity and epinephrine content in SCG of neonatal rats. Injecting pregnant rats with dexamethasone or ACTH, or exposing them to cold or restraint stress on the last 3 days of gestation increased the PNMT activity and epinephrine content in the SCG of their pups. These results indicate that the actions of dexamethasone on neonatal sympathetic ganglia may be mimicked by increasing the plasma concentration of endogenous adrenocortical steroids.