scholarly journals TURNOVER OF HELA RIBOSOMAL RNA

1971 ◽  
Vol 50 (3) ◽  
pp. 787-794 ◽  
Author(s):  
C. N. Nair ◽  
E. Knight
Keyword(s):  
Direct Product ◽  
Ribosomal Rna ◽  
Base Composition ◽  
Sucrose Gradient ◽  
Cytoplasmic Component ◽  
Cell Rupture ◽  
Kinetics Of Formation ◽  
Kinetics Of ◽  
Sedimentation Value

A class of RNA in HeLa cytoplasm with a sedimentation value of 22S is described. This RNA is a true cytoplasmic component and is not an artifact of cell rupture or of the method of RNA preparation. The 22S RNA sediments in a sucrose gradient with those ribosomal structures containing 28S ribosomal RNA (60S and 74S particles and polyribosomes). It has a base composition and methyl content similar to those of 28S RNA. The kinetics of formation of 22S suggest that it is not a direct product of transcription but is derived in vivo from "old" molecules of 28S RNA.

scholarly journals A study of nucleated erythrocytes by density-gradient centrifugation in a zonal rotor

1969 ◽  
Vol 111 (4) ◽  
pp. 583-591 ◽  
Author(s):  
A P Mathias ◽  
D. Ridge ◽  
N. St G. Trezona
Keyword(s):  
Molecular Weight ◽  
Ribosomal Rna ◽  
Base Composition ◽  
Density Gradient Centrifugation ◽  
Gradient Centrifugation ◽  
Density Gradients ◽  
Avian Erythrocytes ◽  
Nuclear Rna ◽  
Zonal Rotor

1. Several substances of high molecular weight were examined for their suitability as suspension media in the formation of density gradients for the zonal centrifugation of avian erythrocytes. None proved satisfactory. 2. The behaviour of pigeon erythrocytes in rate-sedimentation experiments in a type A zonal rotor with density gradients of sucrose was examined. The mature cells sediment more rapidly than the younger cells and have a lower RNA/DNA ratio. Maturation is accompanied by a greater loss of RNA from the nucleus than from the cytoplasm. 3. The base composition of the nuclear RNA and of the two species of cytoplasmic ribosomal RNA is reported. 4. The RNA of erythrocytes may be labelled in vivo by injection of inorganic [32P]phosphate. The cells most active in the synthesis of RNA sediment less rapidly than the bulk of the cells. 5. Reticulocyte nuclei sediment more slowly than those from erythrocytes. Reticulocyte nuclei have a mean volume of 35μ3 and are isopycnic with sucrose of density 1·2871 (measured at 20°). Maturation of the nuclei causes them to shrink to a volume of 25μ3 and the density to increase to 1·2944.

Metabolism of high molecular weight, polydisperse, rapidly labeled nuclear RNA in rat liver

1968 ◽  
Vol 46 (12) ◽  
pp. 1497-1505 ◽  
Author(s):  
Maurice Brossard ◽  
Louis Nicole
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Rat Liver ◽  
Ribosomal Rna ◽  
Base Composition ◽  
Orotic Acid ◽  
Chromosomal Origin ◽  
Base Analysis ◽  
Nuclear Rna ◽  
Kinetics Of

Studies of the metabolism of rat liver RNA showed the existence of two species of rapidly labeled nuclear RNA: a 45 S preribosomal type of nucleolar origin, and a 6–50 S polydisperse RNA of chromosomal origin. The kinetics of labeling with orotic acid-14C and the nature of the latter RNA have been investigated. The following findings are reported, (1) This RNA is composed of at least four main classes of RNA having sedimentation coefficients of approximately 45, 35, 24, and 18 S. (2) Except for the 18 S class which seems to be an end product, the three other classes have a rapid turnover and do not appear to leave the nucleus. (3) Base analysis after 32P incorporation indicates that these four classes of RNA have a similar base composition with a G+C/A + U ratio in the range of 0.98–1.07, which resembles DNA more closely than ribosomal RNA. (4) The 6–50 S polydisperse RNA has a different metabolism than that of the 45 S preribosomal type and there is no precursor-to-product relationship between these two species of RNA.

Effect of pH and inhibitors on beta-amyloid fibril assembly

1996 ◽  
Vol 54 ◽  
pp. 752-753
Author(s):  
Beverly E. Maleeff ◽  
Timothy K. Hart ◽  
Stephen J. Wood ◽  
Ronald Wetzel
Keyword(s):  
Amyloid Fibril ◽  
Peptide Fragment ◽  
Hydrophobic Peptides ◽  
Amyloid Fibril Formation ◽  
Effects Of Ph ◽  
Severity Of The Disease ◽  
Kinetics Of ◽  
The Brain

Alzheimer's disease is characterized post-mortem in part by abnormal extracellular neuritic plaques found in brain tissue. There appears to be a correlation between the severity of Alzheimer's dementia in vivo and the number of plaques found in particular areas of the brain. These plaques are known to be the deposition sites of fibrils of the protein β-amyloid. It is thought that if the assembly of these plaques could be inhibited, the severity of the disease would be decreased. The peptide fragment Aβ, a precursor of the p-amyloid protein, has a 40 amino acid sequence, and has been shown to be toxic to neuronal cells in culture after an aging process of several days. This toxicity corresponds to the kinetics of in vitro amyloid fibril formation. In this study, we report the biochemical and ultrastructural effects of pH and the inhibitory agent hexadecyl-N-methylpiperidinium (HMP) bromide, one of a class of ionic micellar detergents known to be capable of solubilizing hydrophobic peptides, on the in vitro assembly of the peptide fragment Aβ.

Kinetics of Various 99mTc-Sn-Pyrophosphate Compounds in the Rat

1977 ◽  
Vol 16 (04) ◽  
pp. 157-162 ◽  
Author(s):  
C. Schümichen ◽  
B. Mackenbrock ◽  
G. Hoffmann
Keyword(s):  
Normal Saline ◽  
Half Life ◽  
Compound A ◽  
Short Half Life ◽  
Low Concentrations ◽  
The Stability ◽  
Kinetics Of ◽  
In Vitro Stability

SummaryThe bone-seeking 99mTc-Sn-pyrophosphate compound (compound A) was diluted both in vitro and in vivo and proved to be unstable both in vitro and in vivo. However, stability was much better in vivo than in vitro and thus the in vitro stability of compound A after dilution in various mediums could be followed up by a consecutive evaluation of the in vivo distribution in the rat. After dilution in neutral normal saline compound A is metastable and after a short half-life it is transformed into the other 99mTc-Sn-pyrophosphate compound A is metastable and after a short half-life in bone but in the kidneys. After dilution in normal saline of low pH and in buffering solutions the stability of compound A is increased. In human plasma compound A is relatively stable but not in plasma water. When compound B is formed in a buffering solution, uptake in the kidneys and excretion in urine is lowered and blood concentration increased.It is assumed that the association of protons to compound A will increase its stability at low concentrations while that to compound B will lead to a strong protein bond in plasma. It is concluded that compound A will not be stable in vivo because of a lack of stability in the extravascular space, and that the protein bond in plasma will be a measure of its in vivo stability.

Hepatobiliary Kinetics of 113mIn-Phenolphthalexon

1981 ◽  
Vol 20 (02) ◽  
pp. 90-93
Author(s):  
P.B. Parab ◽  
U.R. Raikar ◽  
R.D. Ganatra ◽  
M. C. Patel
Keyword(s):  
Biliary Excretion ◽  
Iminodiacetic Acid ◽  
Organ Distribution ◽  
Liver Uptake ◽  
On Line ◽  
Rapid Clearance ◽  
Chemical Purity ◽  
Kinetics Of ◽  
High Liver

Phenolphthalexon, a compound with iminodiacetic acid as a functional group, has been labelled with 113mIn to high chemical purity and its usefulness in studies of biliary excretion patency has been studied. Organ distribution of 113mIn-phenolphthalexon in mice was characterized by high liver uptake (50.8% of the administered dose after 5 min) and rapid clearance through the gall bladder. An animal model for studying obstruction of biliary excretion has been developed. Data on the kinetics of the radiopharmaceutical were obtained by collecting in-vivo data through an on-line computer.

Continuous Quantitative Monitoring of Mural, Platelet-Dependent, Thrombus Kinetics in the Crushed Rat Femoral Vein

1991 ◽  
Vol 65 (04) ◽  
pp. 425-431 ◽  
Author(s):  
F Stockmans ◽  
H Deckmyn ◽  
J Gruwez ◽  
J Vermylen ◽  
R Acland
Keyword(s):  
Thrombus Formation ◽  
Femoral Vein ◽  
Maximum Size ◽  
Digital Analysis ◽  
Video Recordings ◽  
Quantitative Monitoring ◽  
Set Up ◽  
Kinetics Of ◽  
Quantitative Nature

SummaryA new in vivo method to study the size and dynamics of a growing mural thrombus was set up in the rat femoral vein. The method uses a standardized crush injury to induce a thrombus, and a newly developed transilluminator combined with digital analysis of video recordings. Thrombi in this model formed rapidly, reaching a maximum size 391 ± 35 sec following injury, after which they degraded with a half-life of 197 ± 31 sec. Histological examination indicated that the thrombi consisted mainly of platelets. The quantitative nature of the transillumination technique was demonstrated by simultaneous measurement of the incorporation of 111In labeled platelets into the thrombus. Thrombus formation, studied at 30 min interval in both femoral veins, showed satisfactory reproducibility overall and within a given animalWith this method we were able to induce a thrombus using a clinically relevant injury and to monitor continuously and reproducibly the kinetics of thrombus formation in a vessel of clinically and surgically relevant size

Acquired Haemophilia: Functional Study of Antibodies to Factor VIII

1981 ◽  
Vol 45 (03) ◽  
pp. 285-289 ◽  
Author(s):  
J P Allain ◽  
A Gaillandre ◽  
D Frommel
Keyword(s):  
Factor Viii ◽  
Functional Study ◽  
Factor Viii Inhibitor ◽  
Acquired Haemophilia ◽  
Viii Inhibitor ◽  
Kinetics Of ◽  
Antibody Function ◽  
Native Plasma

SummaryFactor VIII complex and its interaction with antibodies to factor VIII have been studied in 17 non-haemophilic patients with factor VIII inhibitor. Low VIII:C and high VIIIR.Ag levels were found in all patients. VIII:WF levels were 50% of those of VTIIRrAg, possibly related to an increase of poorly aggregated and electrophoretically fast moving VIIIR:Ag oligomers.Antibody function has been characterized by kinetics of VIII :C inactivation, saturability by normal plasma and the slope of the affinity curve. Two major patterns were observed:1) Antibodies from 6 patients behaved similarly to those from haemophiliacs by showing second order inhibition kinetics, easy saturability and steep affinity slope (> 1).2) Antibodies from other patients, usually with lower titres, inactivated VIII :C according to complex order kinetics, were not saturable, and had a less steep affinity slope (< 0.7). In native plasma, or after mixing with factor VIII concentrate, antibodies of the second group did not form immune complexes with the whole factor VIII molecular complex. However, dissociation procedures did release some antibodies from apparently low molecular weight complexes formed in vivo or in vitro. For appropriate management of non-haemophilic patients with factor VIII inhibitor, it is important to determine the functional properties of their antibodies to factor VIII.

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