THE EFFECTS OF ERYTHROMYCIN AND CHLORAMPHENICOL ON THE ULTRASTRUCTURE OF MITOCHONDRIA IN SENSITIVE AND RESISTANT STRAINS OF PARAMECIUM

The effects on cell structure of 12 hr to 6 days of exposure to erythromycin or chloramphenicol, two antibiotics known to inhibit specifically the mitochondrial protein synthesizing system, have been studied in the ciliate Paramecium aurelia. A wild type strain (sensitive to both antibiotics) and three mutant strains carrying cytoplasmically inherited mutations conferring resistance to one or the other antibiotic have been used In sensitive cells both antibiotics lead to a progressive and profound alteration of mitochondrial structure evidenced by an elongation of the organelle, a considerable decrease in the number of cristae, and the appearance of some abnormal lamellar cristae and of rigid plates of periodic structure. The modifications of cell structure, then, are mainly restricted to mitochondrial cristae. The three resistant mutants studied, on the contrary, retain normal or nearly normal mitochondrial structure in the presence of the antibiotic to which they are resistant. This fact is in good agreement with the postulated location in the mitochondrial DNA of the resistance mutations studied. The results are discussed in the light of present knowledge concerning the function of the mitochondrial protein-synthesizing system.     

STUDIES ON THE CONTENT AND ORGANIZATION OF THE RESPIRATORY ENZYMES OF MITOCHONDRIA

(1) The mathematical calculations relating spectrophotometric data with the data of Allard et al. (4, 5) on mitochondrial counts, is presented. Such a calculation indicates that an "average mitochondrion" from rat liver would contain about 17,000 molecules of each cytochrome pigment. (2) Hematocrit determinations relating respiratory pigment content for mitochondria isolated from a variety of tissues have been presented, showing a fivefold variability depending upon the source of the mitochondria. (3) Speculations on the organization of the respiratory enzymes associated with the membrane structure of the mitochondria are discussed.     

THE EFFECTS OF ACTINOMYCIN D ON THE ULTRASTRUCTURE OF THE NUCLEUS OF THE AMPHIBIAN EMBRYONIC CELL

Observations have been made of ultrastructural modifications induced in the nuclei of differentiating amphibian embryonic cells cultured in the presence of Actinomycin D. Of particular interest are regions within the nucleus (regions otherwise rather empty) containing loose groupings of uniform threads having a diameter of around 200 A. These threads have been observed in continuous lengths up to 0.5 µ, and appear to be composed of subfilaments. It is suggested, after taking account of some recent work on lampbrush chromosomes, that these threads are lengths of uncoiled chromosome in a condition of heterosynthetic inhibition. It is further suggested that active and inactive portions of the genome may be distinguishable by the facility with which they can be induced to undergo this ultrastructural modification.     

THE EFFECT OF ETHIDIUM BROMIDE ON MITOCHONDRIAL DNA SYNTHESIS AND MITOCHONDRIAL DNA STRUCTURE IN HELA CELLS

The synthesis of mitochondrial DNA (mDNA) in HeLa cells is selectively inhibited by relatively low concentrations of ethidium bromide. After exposure of cells to strongly inhibitory concentrations of the drug, the apparent superhelix density of mDNA is rapidly increased, as judged by its buoyant density in CsCl in the presence of ethidium bromide. Mitochondrial DNA synthesized in the presence of partially inhibitory concentrations of ethidium bromide is also altered in its buoyant density in the presence of the dye, but is more heterogeneous in this respect. However, the change in buoyant density of newly synthesized mDNA may be explained by changes in structure other than a change in superhelix density, as indicated by its increased resistance to digestion by pancreatic DNase.     

SOD猕猴桃果汁对体液免疫、血清与红细胞丙二醛水平的影响

目的 研究超氧化物歧化酶（ＳＯＤ）猕猴桃果汁姑降低血清、红细胞丙二醛（ＭＤＡ）含量及提高机体免疫球白水平的作用。方法 测定ＳＯＤ弥猴桃果汁服用前后正常妇女红细胞ＭＤＡ及血清ＭＤＡ、免疫球蛋白ＩｇＧ、ＩｇＡ、ＩｇＭ的含量。结果 ＳＯＤ弥桃果汁服用后,红细胞与血清ＭＤＡ含量显著降低血清,免疫球蛋白ＩｇＧ、ＩｇＡ、ＩｇＭ的含量。结果 ＳＯＤ猕猴桃果取用后,红细胞与血清ＭＤＡ量显著降低,免疫球蛋白ＩｇＧ、     

阳离子及ATP对绿豆线粒体膨胀与收缩的影响

本文报道了一价阳离子 K~+、Na~+及两价阳离子 Mg~(++)、Ca~(++)以及 ATP 对绿豆线粒体膨胀和收缩的影响。K~+、Na~+在低渗条件下引起线粒体瞬时的迅速膨胀。在同样离子强度下K~+引起的膨胀大于 Na~+。ATP 和 Mg~(++)能诱发低渗条件下膨胀线粒体的收缩,但对等渗和高渗 KCl 或 Nacl 溶液中膨胀的线粒体无明显作用。生理浓度的 Mg~(++)、Ca~(++)在低渗条件下引起线粒体缓慢的但幅度较大的膨胀,5mmol/l ATP 引起这种膨胀线粒体的部分收缩。1mmol/lca~(++)在含0.125mmol/l KCl 或在含0.25mol/l甘露醇的等渗介质中几乎不引起膨胀,而ATP 促进大幅度膨胀,10mmol/l MgCl_2引起这种膨胀线粒体的部分收缩。2mmol/l MgCl_2在含有0.25mol/l 甘露醇的等渗介质中引起明显膨胀,ATP 促进这种膨胀。0.125mol/lKCl+2mmol/l MgCl_2为肌动蛋白从单体聚合成多聚体所必须的条件。在此条件下,线粒体几乎不膨胀,而加入 ATP 后则促进大幅度膨胀。在电子显微镜下观察了等渗及低渗条件下线粒体形态变化。     

肌肽棉酚对绵羊精子运动及超微结构的影响

肌肽促进绵羊精子运动增强,直线运动精子数目增多;棉酚则强烈抑制精子运动并使精子的运动方式发生改变;肌肽与棉酚混合处理精子,肌肽可不同程度抵消棉酚对精子产生的有害作用。但当棉酚完全抑制精子运动后,再加入肌肽则不能使精子恢复运动。电镜观察,肌肽对绵羊精子超微结构无任何不良影响;棉酚同造成精子严重损伤,导致生物膜系统损害、轴丝崩解、线粒体螺旋鞘紊乱等。本文通过肌肽,棉酚加入的时序不同,探讨两者对绵羊精子     

STUDIES ON THE BIOCHEMISTRY OF MITOCHONDRIA AND CELL MORPHOLOGY IN THE NEONATAL SWINE HEPATOCYTE

Mitochondrial preparations isolated from neonatal swine hepatocytes show a marked increase in oxidative and concomitant phosphorylative capacity between birth and 2 days postpartum. There are no changes in the coupling parameters (respiratory control ratio and adenosine diphosphate/O ratio) with age. Changes in sedimentation properties in a sucrose gradient suggest qualitative changes in the mitochondria. Some of the lipid measurements (increased phospholipid) might be interpreted as supportive of this suggestion, although most could also be regarded as indicative of quantitative changes (increased number of mitochondria). Electron microscopy of isolated mitochondria and of the hepatocyte demonstrated an increased number of mitochondria but no change in shape, size, or structure as the pig developed. An increase in a number of cytoplasmic components (Golgi apparatus and endoplasmic reticulum) and a decrease in glycogen were also observed. The functional changes in mitochondria seem to occur within a short period of time (6–12 hr postpartum).     

BIOCHEMICAL EFFECTS OF VICTORIN ON OAT TISSUES AND MITOCHONDRIA

Victorin, the pathotoxin produced by the plant pathogenic fungus Helminthosporium victoriae, causes changes in respiration and permeability which are typical of diseased plant tissues. To provide information on the site and mode of action of this toxin, the effects of victorin on mitochondria were studied and the nature and quantities of materials released from victorin-treated tissues were determined. Victorin added to isolated mitochondria had no effect on release of electrolytes or on oxidative-phosphorylative capacity. Hence the high respiratory rate found in victorin-treated tissues does not appear to be the result of a direct effect of the toxin on the respiratory centers. With mitochondria extracted from tissue pretreated with victorin, electrolyte release was unaffected but oxygen uptake was slightly higher and phosphate esterification considerably lower than controls. Thus the toxin produces indirect effects on mitochondrial activity, but the relation of these effects to tissue respiration remains undetermined. Victorin-treated tissue lost much larger quantities of certain organic and inorganic materials than control tissue with the most striking difference in the amount of potassium released.     

EFFECTS OF ALTERED OSMOLALITY ON RESPIRATION AND MORPHOLOGY OF MITOCHONDRIA FROM THE DEVELOPING BRAIN

Abstract— The effects of altered osmolality on respiration and fine structure were studied in isolated cerebral mitochondria from mature rats (60-100 days of age) and from rat pups in the first month of postnatal life (5, 10, 20 and 30 days). In the mature cerebral mitochondria, ADP-dependent respiration was inhibited in media of decreased osmolality. There was a transient inhibition of ADP-dependent respiration and a sustained increase in ADP-independent respiration in media of increased osmolality. In contrast, cerebral mitochondria from 5-day-old rats showed both inhibition of ADP-dependent respiration and increased ADP-independent respiration in hypo-osmolal media. In these mitochondria, inhibition of ADP-dependent respiration was stable and ADP-independent respiration was unchanged in media of increased osmolality. The transition to the mature respiratory response occurring with altered osmolality took place between 10 and 30 days of age. During this same age period, cerebral mitochondria showed an increasing resistance to matrix condensation in media of normal and increased osmolality.     

EFFECTS OF ACETATE ON THE GROWTH AND CHLOROPHYLL CONTENT OF GOLENKINIA1

Growth and chlorophyll synthesis by the green alga Golenkinia cease after approximately 60-hr incubation in 0.01 M sodium acetate. These effects are immediately preceded by a rapid rise of the pH of the medium to 8.6–8.8 due to acetate uptake. The pH kinetics are due to a gradual loss of the phosphate buffer, not to the induction or activation of acetate assimilatory enzymes. However, neither high pH nor sodium acetate alone is sufficient to inhibit cell division and bleach the algae; both must be present. Additional experiments support the hypothesis that acetate alters the cells so that they become sensitive to high concentrations of OH^? ions.