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101.
Rotational diffusion of TEMPONE in the cytoplasm of Chinese hamster lung cells. 总被引:10,自引:2,他引:8
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The correlation time for rotational diffusion (tau R) of 2,2,6,6-tetramethyl-4-piperidone-N-oxide (TEMPONE) in Chinese hamster lung (V79) cells has been measured. For these cells in an isosmotic solution at 20 degrees C, tau R = 4.18 X 10(-11) s, approximately 3.6 times greater than tau R = 1.17 X 10(-11) s in water. The relationship between tau R and viscosity was investigated in a number of glycerol-water (0-50%) and sucrose-water (20-40%) solutions and a constant Stokes-Einstein volume of 44 A3 was found for TEMPONE in solutions of less than 20% glycerol and sucrose. This gives an average shear viscosity (for rotation of a small molecule) of 0.038 poise for the cytoplasm. When nonsecular terms were used in the calculation of tau R, the activation energies for rotation of TEMPONE in the above solutions correlated well with the activation energies for shear viscosity. The viscosity increases as the cell is shrunk in hypertonic solutions. It also increases with decreasing temperature with an activation energy of 3.7 kcal/mol, about the same as the activation energy for the viscosity of pure water. The rotational correlation times were carefully calculated considering inhomogeneous line broadening, non-Lorentzian line shapes, the need for accurate tensor values and nonsecular terms. 相似文献
102.
Testosterone metabolism by cytochrome P-450 isozymes RLM3 and RLM5 and by microsomes. Metabolite identification 总被引:3,自引:0,他引:3
Testosterone metabolism by cytochrome P-450 isozymes RLM3 and RLM5 in a reconstituted system and by rat liver microsomes was examined. Eleven metabolites were detected. Two of these, found in spots 2 and 4 of a thin layer plate, were only formed by the rat liver microsomes and may represent reductive metabolites of testosterone. A number of monohydroxy metabolites were conclusively identified by gas chromatography-mass spectrometry. These include the 2-, 6 beta-, 7 alpha-, and 16 alpha-hydroxy isomers. Liver microsomes formed the 2 alpha- and 2 beta-epimers in a 1:2 ratio and both co-chromatographed with a third reduced metabolite in thin layer plate spot 4. In contrast with RLM5 about 90% of the 2-hydroxy isomer was the 2 alpha-epimer. RLM3 did not perform the 2-hydroxylation in detectable amounts. The 6 beta-isomer was a major metabolite of RLM3 and microsomes, but a minor product of metabolism by RLM5. In contrast, the 7 alpha-isomer was a minor metabolite of RLM3, was not formed by RLM5, and was a major microsomal metabolite. Hydroxylation at position 16 alpha was a major activity of RLM5 and the heterogeneous microsomal cytochromes, but with RLM3 it was a minor reaction. One new metabolite was found which appeared to be hydroxylated in the D-ring, had a mass spectrum different from both 16 alpha- and 16 beta-hydroxytestosterone, and was tentatively identified as a 15-hydroxy isomer. In agreement with the literature, androstene-3,17-dione was found to be an oxidative metabolite of testosterone by both microsomes and purified cytochrome P-450. It was a major metabolite of RLM5 but was not produced by RLM3. Studies with 18O2 and H218O conclusively show that oxidation of testosterone at C-17 does not involve transient incorporation of an oxygen atom in this position. A mechanism is suggested whereby cytochrome P-450 acts as a peroxidase in the formation of androstenedione. 相似文献
103.
Metabolism of 9-(1,3-dihydroxy-2-propoxymethyl)guanine, a new anti-herpes virus compound, in herpes simplex virus-infected cells 总被引:18,自引:0,他引:18
Y C Cheng S P Grill G E Dutschman K Nakayama K F Bastow 《The Journal of biological chemistry》1983,258(20):12460-12464
The metabolism of 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG), one of the most promising new anti-herpes virus compounds, in HeLa cells infected with herpes simplex virus type 1 was compared with that in the uninfected HeLa cells. In the virus-infected cells, the uptake of DHPG was enhanced and the major metabolites were found to be the mono-, di-, and triphosphate derivatives. The formation of these metabolites was dependent on the extracellular concentration of DHPG (0.5 to 5.0 microM). Virus-induced thymidine kinase was capable of phosphorylating DHPG to its monophosphate which could be further phosphorylated to the di- and triphosphate derivatives by the host cellular enzymes. Incorporation of the DHPG into DNA was observed in virus-infected cells. In contrast with 9-(2-hydroxyethoxymethyl)guanine, DHPG seemed not to serve as a chain terminator, but to be incorporated internally into DNA strands. 相似文献
104.
J Kruuv D Glofcheski K H Cheng S D Campbell H M Al-Qysi W T Nolan J R Lepock 《Journal of cellular physiology》1983,115(2):179-185
The Arrhenius plot of the rate of V79 Chinese hamster cell inactivation due to hypothermia has a "break" around 7-10 degrees C with optimum storage temperature for unprotected cells being about 10 degrees C. Addition of the membrane lipid perturber, butylated hydroxytoluene, improves survival of cells when compared to controls at temperatures below this break but not above. Arrhenius plots of growth rates of the cells show breaks at 30 and 40 degrees C. Measurements of membrane fluidity by electron spin resonance or membrane polarization anisotropy by fluorescence spectrophotometry techniques as a function of temperature in these cells also reveal "breaks" centered around 8 and 30 degrees C. Hence, the changes in the rate of cell inactivation and growth as a function of temperature may be related to membrane lipid phase changes. 相似文献
105.
The development of the unisexual male and female flowers of Zea mays from bisexual initials in both tassels and ears has been reinvestigated with SEM and TEM. The early stages of spikelet branch primordia, spikelet initiation, and early flower development are similar in both flowers, though differences in rates of growth of glumes, lemmas, and palea were detected. In both tassel and ear flowers, a pair of stamens arises opposite the lemmas and a third stamen initiates later at right angles to the first pair but from a point on the meristem below its insertion. Gynoecia develop on both tassel and ear flowers first as a ridge which overgrows the apical meristem giving rise to the stylar canal and the elongate silk. Male flowers arise in the tassel through selective vacuolation and abortion of the cells of the early gynoecium. The single female flower in each ear spikelet arises through the vacuolation and abortion of stamens in the upper flower and the repression of growth of and the eventual regression of the lower flower in each spikelet. The significance of these selective organ abortions for practical applications is discussed. 相似文献
106.
Kidney slices either were exposed to the cryoprotectants for 1 hr at room temperature and subsequently washed and incubated in fresh KR buffer containing only the radioactive metabolic tracers, or were immediately incubated for 2 hr at 37 °C in KR buffer containing the cryoprotectant and the tracers. Exposure to glycerol by incubation of kidney slices in Krebs-Ringer bicarbonate buffer containing varying concentrations of glycerol from 0 to 70% () resulted in a pronounced inhibitory effect on the protein synthesizing activity, while thymidine incorporation into DNA and the α-aminoisobutyric acid uptake through the cell membranes were less affected. Exposure of the tissue to buffer containing dimethylsulfoxide (Me2SO) in concentrations of 10 to 20% () resulted in a stimulatory effect on metabolism. At higher concentrations, Me2SO was toxic resulting in damaging effects on protein and DNA synthesis as well as on membrane integrity. The stimulatory effects of exposure to low concentrations of Me2SO on protein and DNA synthesis in kidney slices were concluded to be the result of an increased transport of precursors through the cell membranes. 相似文献
107.
Immunohistochemistry of tonin in rat submandibular gland during development, lactation and secretion 总被引:1,自引:0,他引:1
Tonin is a serine protease found in high concentrations in the submandibular gland (SMG) of the adult rat where it has been localized by immunohistochemistry in the granular ducts. The present study examined the development of tonin in the SMG, the effect of lactation and of stimulation of tonin release, using the peroxidase-antiperoxidase technique and antitonin. Tonin-like immunoreactivity first appeared in the primitive striated duct of the SMG on day 19 foetal and increased in intensity as the ducts developed into granular ducts. Reaction product in granules was seen on day 17 postpartum. Its localization within granules was established by immunochemistry of Sepharose beads to which had been coupled the contents of granules isolated from adult rats. The granular ducts of female rats, which are less developed than in the male, showed a marked increase in tonin-immunoreactivity during lactation. Stimulation of tonin secretion by isoprenaline caused massive discharge of tonin-like immunoreactivity into the lumen of the granular ducts during in vitro incubation. However, within one hour complete regranulation was apparent. The secretion was prevented by propranolol. The results indicate that tonin or a tonin-like substance appears in the rat submandibular gland late in gestation in ducts that presumably develop into granular ducts where it is found in abundance in granules in the adult, that the amount in females is increased during lactation, and that most of the granules are discharged during stimulation, only to be rapidly replaced. 相似文献
108.
The recovery of indicator bacteria on selective media 总被引:15,自引:0,他引:15
109.
Himasthla quissetensis: uptake and utilization of glucose by rediae as determined by autoradiography and respirometry 总被引:1,自引:0,他引:1
Daughter rediae of Himasthla quissetensis removed from the digestive gland of Nassarius obsoletus were placed in sterilized seawater fortified with antibiotics. When [3H]-glucose was added to this medium and autoradiographs were made after 3, 9, and 24 hr of exposure, labeling was observed associated with the redial walls and developing germ balls and cercariae within the brood chambers. Respirometric determinations on starved rediae suspended in the seawater medium with and without glucose revealed the rate of oxygen utilization by rediae exposed to exogenous glucose is significantly elevated. These results are interpreted to mean that the daughter rediae of H. quissetensis can take up and utilize glucose. 相似文献
110.