The encephalomyelitic activity of myelin isolated by ultracentrifugation

A relatively simple preparation of guinea pig brain myelin, free of gross contamination by other cellular elements has been described. Electron microscopic evidence of the predominance of membranous (lamellar) forms was used as the criterion of purity of this fraction. The slight mitochondrial contamination of the myelin fraction was confirmed by its low succinic dehydrogenase activity. Quantitative bio-assay of the encephalitogenic activity of myelin showed it to have a higher specific activity than whole guinea pig brain. The low encephalomyelitic activity of the other subcellular constituents (nuclei and mitochondria) which were removed from myelin by ultracentrifugation in 30 per cent sucrose could be explained by a small amount of myelin contamination. A basic protein of high specific encephalitogenic activity has been isolated from myelin by methods previously applied to whole brain. Although the protein is similar to nuclear histones, the following facts point to certain significant differences. Nuclei prepared by a different procedure from the one developed for the isolation of myelin were found to be non-encephalitogenic. Although basic protein could be extracted readily from these nuclei by dilute HCl, the same extraction procedure yielded little extractable protein from whole myelin. Myelin which had been defatted by cold chloroform-methanol yielded a basic protein which was highly encephalitogenic. The evidence presented thus supports the view that there exists in myelin a new basic protein responsible for the induction of experimental allergic encephalomyelitis, which is distinctly different from nuclear histones. The possible relationship of this protein to myelin structure and function has been discussed.

The consistency of ameba cytoplasm and its bearing on the mechanism of ameboid movement. II. The effects of centrifugal acceleration observed in the centrifuge microscope

Three species of common, free-living amebae, Amoeba proteus, Amoeba dubia, and Chaos chaos were directly observed and photographed while exposed to a range of centrifugal accelerations in two types of centrifuge microscopes. Cytoplasmic inclusions in all three species are displaced discontinuously (at a variable velocity) in apparently all parts of the cell, suggesting non-Newtonian behavior and/or heterogeneous consistency. The ectoplasm of all species shows the highest yield point of any region in the cell; the posterior ectoplasm is less rigid than that in the anterior part of the cell. The axial part of the endoplasm shows evidence of structure (a sharp viscosity transition if not a true yield point) by its: (a) resistance to the displacement of particles carried in that region of the cell, (b) hindrance to the passage through the cell of inclusions displaced from other regions, and its (c) support without visible back-slip of inclusion being resuspended in the axial endoplasm in a centripetal direction at accelerations as high as 170 g. At this acceleration, each crystal "weighs" the equivalent reduced weight of seven times its volume in gold at 1 g. The only regions of the normal, moving cell which show clear evidence of low apparent viscosity are the "shear zone" (see Fig. 8) and the "recruitment zone." Possible reasons for low apparent viscosity in these regions are discussed. A new scheme of ameba "structure" is presented on the basis of the combined results of velocity profile analysis and the present centrifugation study.

Removal of decapacitation factor from seminal plasma by high-speed centrifugation

The fertilizing ability of capacitated rabbit sperm is inhibited by mixing with seminal plasma; this is termed "decapacitation." The decapacitation factor was not destroyed or removed by freezing, heating to 65 C, or by prolonged dialysis, and was retained in the precipitate produced by the treatment of seminal plasma with 100% ethanol at –30 C. However, following centrifugation of seminal plasma for 3 hr or more at 105,000 g, the decapacitation activity disappeared. The disappearance of activity was not due to denaturation. Using spectrophotometry and moving boundary electrophoresis, no change could be detected in the protein components of the supernatants to account for the change in biological activity. It is concluded that the decapacitation effect of seminal plasma is related to a discrete molecule of large size. This may be protein, or conjugated with protein of a relatively heat-stable nature, which interacts with the active surface of the capacitated sperm head.

Electron microscopy of lysosome-rich fractions from rat thymus isolated by density-gradient centrifugation before and after whole-body x-irradiation

Fractions from rat thymuses were isolated by sucrose density-gradient centrifugation, before and after 1000 r whole-body x-irradiation, and examined by electron microscopy. Cytochrome oxidase and acid phosphatase activities of these fractions were tested as well. Electron-opaque bodies with diameters ranging from 0.10 to 0.35 µ, with a mean of 0.25 µ, were found in fractions having high acid phosphatase activity, while the fractions rich in cytochrome oxidase consisted mostly of mitochondria. After irradiation, there was an increased ratio of dense bodies to mitochondria. These particles are considered to be lysosomes similar to those identified in other rat tissues. Their relationship to the mitochondria is discussed.

PROTEIN SYNTHESIS IN MITOCHONDRIA. 4. PREPARATION AND PROPERTIES OF MITOCHONDRIA FROM KREBS II MOUSE ASCITES-TUMOUR CELLS

1. Methods of disrupting Krebs II mouse ascites-tumour cells have been studied. After washing the cells free of ions with sucrose solutions, rapid disruption was obtained in sucrose by use of an Ultra-Turrax disintegrator or a Dounce homogenizer. 2. Disruption of cells after osmotic shock led to the loss of proteins, especially cytochrome c, from the mitochondria. Such losses did not occur when cells were disrupted by shear in 0.3 m-sucrose. 3. The distribution of protein, RNA, DNA, malate dehydrogenase, cytochrome c, cytochrome oxidase and succin-oxidase was measured in the various cell fractions after separation by differential centrifuging. 4. The mitochondrial fraction sedimented at 9500g was further fractionated by equilibrium sedimentation in a sucrose gradient. The distribution of protein and enzyme activity in the gradient indicated that the 9500g pellet contains other material besides mitochondria. 5. Krebs-cell mitochondria contain up to five times as much RNA as do liver mitochondria. 6. After purification by equilibrium centrifugation Krebs-cell mitochondria still contain traces of DNA.

DENSITY-GRADIENT PATTERNS OF STAPHYLOCOCCUS AUREUS CELLS AND CELL WALLS DURING GROWTH AND MECHANICAL DISRUPTION

Huff, Eskin (National Institute of Allergy and Infectious Diseases, Bethesda, Md.), Harriet Oxley, and Carol S. Silverman. Density-gradient patterns of Staphylococcus aureus cells and cell walls during growth and mechanical disruption. J. Bacteriol. 88:1155-1162. 1964.-Procedures capable of rapid disruption of Staphylococcus aureus cells with optimal release of intact cell walls were investigated. This search was implemented by observation of the flotation patterns of cells and subcellular particulate matter after centrifugation in a cesium chloride density gradient. A quantitative evaluation of the light-scatter throughtout the gradient was achieved by transfer of the entire density gradient into an optical cell with wedge-shaped cross section. When this cell was photographed under indirect illumination, each band of light-scattering material appeared on the negative as a shaded curve, with an area proportional to amount of that material present. A series of photographs of known amounts of cells and cell walls was used to estimate the amounts of these materials in mixtures of the two occurring during mechanical disruption. With the methods employed, time studies established the optimal time for release of cell walls as 5 min in a Braun shaker. The use of sucrose gradients in the further purification of cell walls, and chemical analysis of the isolated walls, are described.

THE ISOLATION AND CHARACTERIZATION OF SUBCELLULAR COMPONENTS OF THE EPITHELIAL CELLS OF RABBIT SMALL INTESTINE

1. Homogenization of the epithelial cells of rabbit small intestine in 0.3m-sucrose-5mm-EDTA, pH7.4, maintains intact the microvillus sheets that form the lumenal surface of the cells, the nuclei, the mitochondria and the vesicles (microsomes) formed from the endoplasmic reticulum. 2. These particulate components of the cell, and the cell-sap fraction, have been isolated by differential centrifuging of cell homogenates. 3. The nuclei and microvillus sheets sediment together and it has been impossible to separate these subcellular components by centrifugal methods. 4. The isolated subcellular fractions have been identified by a combination of light-microscopic examination, electron-microscopic examination, chemical analysis and assay for selected enzyme activities.

ISOLATION AND PROPERTIES OF INTACT MITOCHONDRIA FROM SPHEROPLASTS OF YEAST

Duell, E. A. (Western Reserve University, Cleveland, Ohio), Sakae Inoue, and Merton F. Utter. Isolation and properties of intact mitochondria from spheroplasts of yeast. J. Bacteriol. 88:1762-1773. 1964.-Functionally intact mitochondria can be obtained in good yields by osmotic disruption of spheroplasts formed from yeast by treatment with an enzyme mixture from the snail digestive tract. The useful range of this method is extended greatly by pretreatment of the yeast cells with 2-mercaptoethylamine and ethylene-diaminetetraacetate. The concentration of the yeast suspension can be increased greatly, the incubation period can be shortened considerably, and the requirement for log-phase cells is obviated. Mitochondria prepared by this method have been compared with those obtained by mechanical disruption in terms of respiratory control, specific activity on a wide range of oxidizable substrates, heterogeneity during centrifugation, and structures observed by electron microscopy. In all cases, the mitochondria obtained from spheroplasts appear to be much less damaged by the preparative procedures.

ISOLATION OF RELAXING PARTICLES FROM RAT SKELETAL MUSCLES IN ZONAL CENTRIFUGES

Supernatants of rat skeletal muscle homogenates were fractionated by differential centrifugation and by zonal centrifugation in sucrose density gradients. Cytochrome oxidase was employed as an enzymatic marker for locating mitochondria. The subcellular fractions were also assayed for their ability to prevent the ATP-induced contraction of myofibrils. Both the mitochondrial and microsomal fractions obtained by differential fractionation were found to be rich in such relaxing activity, and the microsomal fraction was appreciably contaminated by mitochondria. In contrast to this, when fractionation was carried out by means of zonal centrifugation (4200 RPM x 205 min. to 40,000 RPM x 60 min.), relaxing activity was found to be associated only with particles having the sedimentation characteristics of microsomes (s_20,w estimated to be between 370 and 1880S). Relaxing activity was not detected in the regions of the gradient containing either the starting sample zone (soluble phase) or the mitochondrial peak. The microsomal relaxing particles showed negligible cytochrome oxidase activity.

DRUG RESISTANCE OF ENTERIC BACTERIA. IV. ACTIVE TRANSDUCING BACTERIOPHAGE P1 CM PRODUCED BY THE COMBINATION OF R FACTOR WITH BACTERIOPHAGE P1

Kondo, Eiko (Gunma University, Maebashi, Japan), and Susumu Mitsuhashi. Drug resistance of enteric bacteria. IV. Active transducing phage P1 CM produced by the combination of R factor with phage P1. J. Bacteriol. 88:1266-1276. 1964.-During an investigation of the transduction of R factors with phage P1, a phage lysate capable of transducing the character of chloramphenicol resistance (CM(r)) in extremely high frequency was obtained. The transduction of the CM(r) character with the lysate was consistently accompanied by lysogenization with the phage used for transduction. This lysate exhibits no beneficial effect with normal P1, and no effect is produced by decreasing the multiplicity of infection. A single infection with the phage allows the formation of plaques as well as CM(r) lysogenic cells at the center of the plaque. Both the transducing and plaque-forming activities of the lysate were lost by neutralization with anti-P1 phage serum, and its absorption to the host bacteria was enhanced by the addition of Ca(++). Thus, it was concluded that a derivative of P1 phage (P1 CM) was isolated which had not only the ability to transduce the CM(r) character but also the capacity to form plaques; i.e., the CM(r) gene of R factor is specifically associated with the genome of phage P1. No detectable differences were noted between P1 CM and normal P1 phage in density-gradient analyses in CsCl, in stability of lysogenization, in ability to transduce chromosomal markers, and in the mode of induction from lysogenic cells by ultraviolet irradiation. The instance of transduction of the CM(r) character described here may also be considered as an example of lysogenic conversion, in the sense that the alteration in CM(r) character is inseparable from lysogenicity.

STUDIES ON THE ISOLATION OF METAPHASE CHROMOSOMES

A method for the isolation of metaphase chromosomes from mouse L1210 leukemia cells has been developed. Cells, arrested at metaphase with colchicine, were exposed to hypotonic solution and the pH was then adjusted to 5.6 to stabilize the chromosomes. The metaphase figures were subsequently disrupted and the chromosomes isolated by a series of differential centrifugations in sucrose. The isolated chromosomes were well preserved, as judged by morphological criteria. The effect of various enzymes and chemical agents on the isolated chromosomes was studied. Chymotrypsin, trypsin, and deoxyribonuclease caused a marked disintegration of the chromosomes, whereas treatment with pepsin and ribonuclease induced no significant morphological alterations.

OUTSTANDING CHARACTERISTICS OF THROMBOKINASE ISOLATED FROM BOVINE PLASMA

Thrombokinase has been isolated from bovine plasma by a procedure which begins with the highly purified product of a previously described method, chromatographs it on DEAE-cellulose, and then fractionates it by continuous flow electrophoresis, yielding 0.2 mg per liter of oxalated plasma. The electrophoretic fraction has shown a single boundary in the ultracentrifuge; and its esterase activity on toluenesulfonylarginine methyl ester has been about the same as that of thrombokinase previously isolated by repeated electrophoretic fractionations. Thrombokinase is a euglobulin with minimum solubility near pH 5.0. It is most stable within the pH range 7.5 to 9.5; but there is also a peak in the stability curve near pH 1.8. A few micrograms of thrombokinase per milliliter can activate prothrombin in the presence of EDTA. A few thousandths of a microgram causes rapid production of thrombin in the system: prothrombin, thrombokinase, calcium chloride, phosphatide, "accelerator." But, thrombokinase has less than 1/175 the proteolytic activity of crystallized trypsin.

THE PREPARATION AND PROPERTIES OF BACTERIAL CHROMATOPHORE FRACTIONS

Chromatophore material from the bacterium Rhodopseudomonas spheroides was freed of ribosomes by centrifugation in 27 per cent RbCl and then separated into "heavy" and "light" fractions by centrifugation through a sucrose gradient. The fractions differed from one another in the following ways. (a) The isopycnic density of the heavy fraction was between 1.15 and 1.18 gm/ml and that of the light fraction was 1.14 gm/ml. (b) The heavy fraction was able to bind ribosomes; the light fraction was not. (c) The light fraction was homogeneous in the ultracentrifuge and had a sedimentation constant, extrapolated to infinite dilution, of 153 s_20,w. The heavy fraction was grossly heterogeneous. (d) Both the amount of bacteriochlorophyll relative to protein and the ratio of bacteriochlorophyll to carotenoids were greater in the light fraction. (e) The spectra of the two fractions in the near infra-red were different. Comparisons of the chromatophore fractions from cells with different amounts of bacteriochlorophyll showed that the specific bacteriochlorophyll contents of the two fractions did not change to the same extent as did that of the whole cells. The amount of heavy fraction from pigmented cells was roughly independent of the cellular pigment content and was about equal to that from pigment-free cells. The amount of light fraction depended on the pigment content of the cells; no light fraction was obtained from cells devoid of bacteriochlorophyll. The cytochrome complements of both fractions underwent quantitative as well as qualitative changes with varying growth conditions. The size of the photosynthetic unit in R. spheroides appeared to increase as the total cellular bacteriochlorophyll content increased; however, the number of units per light fraction particle remained constant.