INCORPORATION OF AXONALLY TRANSPORTED SUBSTANCES INTO MYELIN LIPIDS

Abstract— The possibility that axonally transported lipids and/or proteins might undergo transaxonal migration and become incorporated into surrounding myelin lamellae was studied by isolating myelin from optic tracts of myelinating rabbits at various times following intraocular injection of [3-¹⁴C]-serine and [2-³H]glycerol. Myelin isolated by a procedure employing ethylene glycol-bis(β-aminoethyl ether)-.N,N'-tetraacetic acid had relatively constant specific radioactivity with respect to both isotopes over a 21 day period. Myelin lipids showed a gradual increase in ¹⁴C specific radioactivity, attributed to reutilization of [¹⁴C]serine from the axon by a compartment of the oligodendrocyte. Free serine is postulated to arise in the axon from catabolism of axonally transported proteins (and possibly lipids) and to migrate transaxonally into the neighboring oligodendroglia. This reutilization mechanism resulted in synthesis of myelin cerebrosides, sphingomyelin, ethanolamine phosphoglycerides and possibly sulfatides, but not gangliosides or serine phosphoglycerides. The data for choline- and inositol-phosphoglycerides are inconclusive. [³H]Glycerol-labeled myelin lipids decreased slowly in ³H specific radioactivity with time, indicating either that [2-³H]glycerol does not participate in the reutilization pathway or that the label is lost in the process. Evidence is presented that ³H- and ¹⁴C-labeled lipids are true myelin constituents. Lipids from the myelin, axolemma- and axon-enriched fractions tended to converge in specific radioactivity over the 21 days, especially the former two fractions. These results together with isotope ratio changes point to an equilibration process whereby lipids are able to transfer. (or exchange) between the 3 compartments. Protein radioactivity in isolated myelin was suggested to arise from residual axon/axolemma contamination, and no evidence was found for transaxonal migration of protein into myelin. The 2 mechanisms elucidated here are believed to account for a quantitatively small portion of myelin lipid and are considered to represent a form of axon-glia interaction.     

THE INSECTICIDAL ACTIVITY OF SUBSTANCES RELATED TO THE PYRETHRINS

The toxicity as contact insecticides of the esters of (±)-3-methyl-2-allyl-cycfopent-3-en-4-ol-i-one with the natural (+ )-trans and with synthetic (±) -cis-trans-chrysaii- themum monocarboxylic acids has been compared with that of the natural pyrethrins. The comparison was carried out on five species of test-insects.
It was found that the figure for both the absolute and the relative toxicities of these compounds varied with the species used as test-subject.
The factors involved in this variation are discussed. The extremes of variation of relative toxicity for the compounds with the natural acid were from about one-eighth as toxic as the pyrethrum standard when the aphid Macrosiphum solanifolii was used as test subject to nearly four times as toxic as the standard with the larvae of the moth Plutella maculipennis. The fully synthetic material varied from about one-sixteenth as toxic as the standard to Macrosiphum solanifolii to nearly twice as toxic to the larvae of Plutella maculipennis. The compound with the natural acid was approximately twice as toxic as the fully synthetic material to three of the insect species, but the fully synthetic material was considerably more than half as toxic as the partially synthetic to the fourth test-species. It is pointed out that while it is widely recognized that large differences in relative toxicity may occur when the effect of chemicals of widely different structure and mechanism of action are compared on a number of different test-species, the fact that these differences may also occur with related chemicals with, presumably, a similar mechanism of action, has not been clearly stated.
Even when the differences in relative toxicity are taken into account, the two synthetic pyrethrin-like esters still show high insecticidal activity.
It seems reasonable to suppose from the results that economic commercial synthesis of pyrethrin-like insecticides is not impossible.     

PHYTOREMEDIATION OF BTEX HYDROCARBONS: POTENTIAL IMPACTS OF DIURNAL GROUNDWATER FLUCTUATION ON MICROBIAL DEGRADATION

Volatile hydrocarbons have multiple potential fates in phytoremediation. This research investigated the relationship between biodegradation and plant uptake of BTEX compounds in laboratory and field settings. At a phytoremediation site, preliminary studies revealed minimal uptake into trees and enhanced degradation potential in the rhizosphere and in the bulk soil. Increased oxygen transport to the vadose zone caused by diurnal rise and fall of the water table was hypothesized to enhance degradation in the bulk soil. A detailed greenhouse study was then conducted to investigate potential bioremediation impacts using field-site soil and DN34 hybrid poplar trees.

In rhizosphere soils, the contaminated-planted reactor had significantly higher BTEX degrader populations versus the uncontaminated-planted reactor, as was anticipated. The bulk soil in the planted-contaminated reactor had increased degrader populations than the unplanted-contaminated soil or planted-uncontaminated soil, and planting increased degradation throughout the soil profile, not just in the limited volume of rhizosphere soils. Oxygen diffusive and advective transport into reactors was modeled and calculated. Oxygen input in planted reactors was at least 3 to 5 times higher than in unplanted reactors, and increasing oxygen input lead to increased degrader populations in a linear manner. These results combined with the knowledge that high-transpiration trees draw the contaminated groundwater to the capillary fringe and the rhizosphere indicate that phytoremediation can aid microbial degradation via multiple mechanisms: increasing degrader populations, increasing oxygen input via groundwater diurnal fluctuations, and transporting contaminants to the biologically-enriched soil profile.     

体育运动和脂质代谢

一般健康人总胆固醇(T-Ch)、甘油三酯(TG)、高密度和低密度脂蛋白胆固醇(HDL-ch,LDL-cH)的含量随年令而增加。中年组(45-59)HDL-Ch平均值较低,男比女低,这与中国人男性45岁以后患冠心病(CHD)多于女性相吻合。冠心病及脑中风患者的HDL-ch含量比健康人低(P<0.05)。运动员的HDL-Ch含量明显高于一般健康人(P<0.01),其均值且高于不易患动脉粥样硬化(AS)的八种哺乳动物的均值(60.40mg/d1)。运动员的T-ch、TG和HDL-Ch含量低于健康人。     

INCORPORATION OF 32P IN VITRO INTO TRIPHOSPHOINOSITIDE AND RELATED LIPIDS OF RAT SUPERIOR CERVICAL GANGLIA AND VAGUS NERVES

Abstract— Rat sympathetic ganglia, vagus nerve and sciatic nerve were each incubated with inorganic ³²P for various lengths of time and the resultant labelling of their inositol lipids was measured.
At all times up to 3 hr phosphatidylinositol was the most highly labelled lipid of ganglia, while triphosphoinositide was the most active lipid of vagus and sciatic nerves. Removal of calcium ions from the incubation media had no significant effect on the incorporation of phosphate into any of the inositol lipids of sympathetic ganglia.     

LIPIDS AND LIGHT-DEPENDENT SWELLING OF ISOLATED SPINACH CHLOROPLASTS

The light-dependent high-amplitude swelling of spinach chloroplastssuspended in 175 mM NaCl buffered with 50 mM Tris-HCl (pH 7.9)was investigated by a packed weight technique and by electronmicroscopy. Endogenous neutral and charged lipids were releasedby the thylakoid membrane to about the same extent during chloroplastincubation in both the light and the dark. The addition of laurate,oleate, stearate, lecithin and lysolecithin increased chloroplastswelling in the dark, but inhibited swelling in the light. Acetoneincreased chloroplast swelling at low concentrations and inhibitedat high concentrations in both the light and the dark. For 20%acetone, the grana stacks disappeared and a newly formed membranesystem appeared which was similar to a myelin structure. Therole of lipid components in the conformation of the membranestructure is discussed and a mechanism for lightinduced chloroplastswelling based on a hydrogen-sodium exchange is proposed. ¹ Present address: Department of Botanical Sciences, Universityof California, Los Angeles, California 90024.     

有氧锻炼对体质的改善和对脂蛋白及胆固醇水平的影响

对经过3个月中等强度有氧锻炼的学生进行了锻炼前后体质和脂蛋白及胆固醇水平的检测。结果表明,学生体质有明显改善,其中Vo_(2max)、哈佛台阶试验指数等7个指标有非常显著差异(p<0.01),3min台阶试验即刻脉搏有显著差异(p<0.05);TC、LDL-C、Tc/HDL-C、LDL-C/HDL-C均降低,差异非常显著(p<0.01),HDL-C、HDL_2-C、HDL_2-C/HDL_3-C均增高,差异非常显著(p<0.01);测试HDL_2-C比测试HDL-C在评定锻炼效果上更优越。     

RPDS基牙牙周指数及牙菌斑细菌相对分布的检测分析

目的　观察基牙牙周指数及牙菌斑细菌相对分布的动态变化,以深入了解ＲＰＤｓ 对口腔微生态系影响的机理及特点。方法　在预先规定的７ 个观察期,按照文献检测基牙菌斑指数（ＰＬＩ） 、龈炎指数（ＧＩ） 及牙龈出血指数（ＧＢＩ） ;采用刚果红负性染色涂片检查法,检测基牙龈下菌斑细菌相对分布变化。结果　①患者戴用ＲＰＤｓ 后短期内基牙ＰＬＩ、ＧＩ、ＧＢＩ均明显升高（Ｐ＜ ０．０１） ,且在前６ 个月内逐渐升高,６ 个月之后则有所降低并趋于平稳;②戴用ＲＰＤｓ后牙菌斑细菌中球菌比例减小,而梭杆菌和螺旋体的比例升高。结论：戴用ＲＰＤｓ 会引起基牙ＰＬＩ、ＧＩ、ＧＢＩ升高及牙菌斑细菌中致病细菌如螺旋体、梭状杆菌比例增加。这对认识ＲＰＤｓ 对口腔微生态系影响的机制及临床防治ＲＰＤｓ 所致口腔病变具有有效的理论指导价值。     

CUTICULAR LIPIDS OF TERRESTRIAL PLANTS AND ARTHROPODS: A COMPARISON OF THEIR STRUCTURE, COMPOSITION, AND WATERPROOFING FUNCTION

1. Lipids deposited on the surface or embedded within the cuticle of terrestrial plants and arthropods are primarily responsible for the observed low rates of water loss through the cuticle. 2. These lipids are a mixture of long-chain compounds which include hydrocarbons (saturated, unsaturated, branched), wax esters, free fatty acids, alcohols, ketones, aldehydes, and cyclic compounds. 3. The cuticle of both plants and arthropods is a continuous, non-cellular multilayered membrane which overlies the epidermal cells. 4. In arthropods, horizontal division of the cuticle into layers is clearly visible. In plants, the layers comprising the cuticle are not sharply demarcated. 5. The substance responsible for the structural integrity of the plant cuticle (cutin) is composed of cross-esterified fatty acids; structural integrity in arthropod cuticle is provided by a chitin-protein complex. 6. Cuticular lipids are probably formed near the surface in both plants and arthropods; however, specific sites of synthesis are known for only a few species and little is known about their transport from these sites to the surface. The elaborate pore canal and wax canal system of arthropod cuticle is absent from plants. 7. The physical structure and arrangement of the lipid deposits on the cuticular surface that are so important in controlling water movement depend on both quantity and chemical composition, and are, in turn, specific to each species in relation to its environment. 8. Different lipid components are not equally efficient in reducing transpiration. Maximum waterproofing effectiveness is provided by long-chain, saturated, non-polar molecules containing few methyl branches. 9. Plants and arthropods can, within genetic constraints, alter the composition of their cuticular waxes to improve impermeability when conditions require increased water conservation. 10. None of the models proposed to explain the change in arthropod cuticular permeability which occurs at a species-specific temperature (‘transition temperature’) in many species is supported by the experimental data now available.     

牧效黄杆菌对蒽菲芘的降解性能研究

采用定时、定量、逐步提高驯化所用碳源物浓度的方法,以萘为唯一碳源驯化长期被焦化废水污染的泥土浸出液,7周后,平板划线分离出两株黄杆菌FCN1及FCN2。并对这两株菌降解多环芳烃的特性及无机离子对反应的刺激作用进行了研究。结果表明,FCN1及FCN2能降解转化蒽、菲、芘。加入FCN1,反应10h后,蒽、菲、芘去除率分别为84％、69％、80％,而加入FCN2,各物质的去除率分别为76％、40％、71％。反应进行106h,FCN1对蒽、菲、芘所产生的总有机碳（TOC）的去除率分别为70％、54％、69％,而FCN2对相应物的TOC去除率分别为63％、50％、46％。Fe^3 、Mg^2 的加入对FCN1降解多环芳烃有促进作用。     

PHYTOPLANKTON LIPIDS: INTERSPECIFIC DIFFERENCES AND EFFECTS OF NITRATE,SILICATE AND LIGHT-DARK CYCLES1

The lipid content of various phytoplankton species was measured in response to nitrogen and silicon limitation and over the cell cycle in synchronized cultures. In a survey of 30 species it was found that during log-phase growth, green algae contained an average of 17.1% total lipids (% of total dry weight), whereas diatoms contained an average of 24.5%. Nitrogen deprivation for 4 to 9 days resulted in 2- to 3-fold increases in the lipid content of green algae, whereas both increases and decreases were noted in diatoms, depending on the species. The greatest lipid content measured in the study was 72% in Monallantus salina (strain GSB Sticho) which had been deprived of nitrogen for 9 days. Nitrate replenishment in a nitrogen starved culture of Oocystis polymorpha Groover & Bold showed that the excess cellular lipids do not rapidly disappear during recovery, until cell division occurs. A silicate deprivation experiment with Cyclotella cryptica Reimann, Lewin & Guillard (strain 7c) showed an increase in the total cellular lipid fraction from. 30 to 42% of dry weight within 6 h of the onset of silicon limitation, while the mass of lipid material per cell doubled within 12 h. The total lipid fraction in O. polymorpha was found to remain constant over the cell cycle in synchronized cultures regardless of the light regime. The data presented provided the first internally consistent study of phytoplankton lipids for a wide range of species and several growth conditions.