The Half-Life of Mindless Psychology

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.

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The Effect of Carbimazole Following Radioiodine Therapy on Radiation Dose to the Thyroid

Nuklearmedizin ◽

10.1055/s-0037-1620719 ◽

1981 ◽

Vol 20 (02) ◽

pp. 72-75 ◽

Cited By ~ 1

Author(s):

R. Kocak ◽

R.G. Herbert ◽

C.R. Squire ◽

T.M.D. Gimlette

Keyword(s):

Thyroid Gland ◽

Radiation Dose ◽

Half Life ◽

Radioiodine Therapy

Radioiodine in the thyroid gland after a therapy dose of 131I was measured serially in 7 patients without Carbimazole, and in 11 patients starting Carbimazole 60 mg daily fourteen days after the therapy dose. Effective half-life for radioiodine in the gland initially 5.53±1.08 days fell to 4.26±1.12 days (p < 0.01) during Carbimazole, and returned to 5.83±1.21 days (NS) after stopping the drug. The radiation dose to the thyroid from a given therapy dose of 131I followed by Carbimazole was calculated to be 97% of that without Carbimazole when the drug was started after 14 days, and 90% and 75% when the drug was started after 7 days and 1 day respectively.

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Radiation Mould with Radio Isotope Solutions Fluid „Iso-mould”

Nuklearmedizin ◽

10.1055/s-0037-1621152 ◽

1961 ◽

Vol 1 (03) ◽

pp. 246-257

Author(s):

M. O. Roxo-Nobre ◽

D. M. Vizeu

Keyword(s):

Clinical Practice ◽

Remote Control ◽

Lymph Nodes ◽

Half Life ◽

Radioactive Substances

SummaryA technique of mouldage, employing fluid radioactive substances is adopted, to replace the radium-moulding in the treatment of large surfaces. The technique is explained in detail, proving its greater safety by remote control and an adjustment of adequate means of protection. Distribution is obtained by means of a serpentine attached to the mould in question, which follows the Paterson-Parker system. The authors believe the distribution of radiation on curved anatomical areas to be much more uniform by mould system than any other process of application of the same radiation of rectilineal propagation, transmitted at greater focus-skin distances. The isotopes used up to now were the La140 and others of reduced half-life, in order to prevent the danger of eventual contaminations. Although the application of the process still has very little clinical practice, the technique is presented with a view to experimentation in extensive superficial tumours, or those of little depth, such as tumours of the skin, breast, penis, thyrreoid and lymph nodes.

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Binding of 131I-Labeled Tissue-Type Plasminogen Activator on De-Endothelialized Lesions in Rabbits

Nuklearmedizin ◽

10.1055/s-0038-1628893 ◽

1987 ◽

Vol 26 (05) ◽

pp. 224-228 ◽

Cited By ~ 2

Author(s):

Y. Isaka ◽

H. Etani ◽

K. Kimura ◽

S. Yoneda ◽

T. Kamada ◽

...

Keyword(s):

Plasminogen Activator ◽

Abdominal Aorta ◽

Half Life ◽

Balloon Catheter ◽

Biochemical Properties ◽

Tissue Type ◽

Fibrin Deposition ◽

Tissue Type Plasminogen Activator ◽

High Affinity ◽

Type Plasminogen Activator

Tissue-type plasminogen activator (t-PA) which has a high affinity for fibrin in the clot, was labeled with 131I by the iodogen method, and its binding to de-endothelialized lesions in the rabbit was measured to assess the detectability of thrombi. The de-endothelialized lesion was induced in the abdominal aorta with a Fogarty 4F balloon catheter. Two hours after the de-endothelialization, 131I-labeled t-PA (125 ± 46 μCi) was injected intravenously. The initial half-life of the agent in blood (n = 12) was 2.9 ± 0.4 min. The degree of binding of 131I-labeled t-PA to the de-endothelialized lesion was evaluated at 15 min (n = 6) or at 30 min (n = 6) after injection of the agent. In spite of the retention of the biochemical properties of 131I-labeled t-PA and the presence of fibrin deposition at the de-endothelialized lesion, the binding of t-PA to the lesion was not sufficiently strong. Lesion-to-control ratios (cpm/g/cpm/g) were 1.65 ± 0.40 (at 15 min) and 1.39 ± 1.31 (at 30 min), and lesion-to-blood ratios were 1.39 ± 0.32 (at 15 min) and 1.36 ± 0.23 (at 30 min). These results suggest that radiolabeled t-PA may be inappropriate as a radiopharmaceutical for the scintigraphic detection of a pre-existing thrombotic lesion.

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Recombinant Variants of Tissue-Type Plasminogen Activator Containing Amino Acid Substitutions in the Finger Domain

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646342 ◽

1992 ◽

Vol 68 (06) ◽

pp. 672-677 ◽

Cited By ~ 4

Author(s):

Hitoshi Yahara ◽

Keiji Matsumoto ◽

Hiroyuki Maruyama ◽

Tetsuya Nagaoka ◽

Yasuhiro Ikenaka ◽

...

Keyword(s):

Amino Acid ◽

Plasminogen Activator ◽

Half Life ◽

Tissue Type ◽

Clot Lysis ◽

Amino Acid Substitutions ◽

Wild Type ◽

Plasma Clot ◽

Tissue Type Plasminogen Activator ◽

Type Plasminogen Activator

SummaryTissue-type plasminogen activator (t-PA) is a fibrin-specific agent which has been used to treat acute myocardial infarction. In an attempt to clarify the determinants for its rapid clearance in vivo and high affinity for fibrin clots, we produced five variants containing amino acid substitutions in the finger domain, at amino acid residues 7–9, 10–14, 15–19, 28–33, and 37–42. All the variants had a prolonged half-life and a decreased affinity for fibrin of various degrees. The 37–42 variant demonstrated about a 6-fold longer half-life with a lower affinity for fibrin. Human plasma clot lysis assay estimated the fibrinolytic activity of the 37–42 variant to be 1.4-fold less effective than that of the wild-type rt-PA. In a rabbit jugular vein clot lysis model, doses of 1.0 and 0.15 mg/kg were required for about 70% lysis in the wild-type and 37–42 variant, respectively. Fibrinogen was degraded only when the wild-type rt-PA was administered at a dose of 1.0 mg/kg. These findings suggest that the 37–42 variant can be employed at a lower dosage and that it is a more fibrin-specific thrombolytic agent than the wild-type rt-PA.

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Plasma Thrombospondin as an Indicator of Intravascular Platelet Activation in Patients with Vasculitis

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646003 ◽

1987 ◽

Vol 58 (03) ◽

pp. 850-852 ◽

Cited By ~ 15

Author(s):

M B McCrohan ◽

S W Huang ◽

J W Sleasman ◽

P A Klein ◽

K J Kao

Keyword(s):

Platelet Activation ◽

Plasma Levels ◽

Half Life ◽

Degradation Products ◽

Plasma Concentrations ◽

Primary Source ◽

Positive Correlation ◽

Activation Marker ◽

Fibrin Degradation Products ◽

The Mean

SummaryThe use of plasma thrombospondin (TSP) concentration was investigated as an indicator of intravascular platelet activation. Patients (n = 20) with diseases that have known vasculitis were included in the study. The range and the mean of plasma TSP concentrations of patients with vasculitis were 117 ng/ml to 6500 ng/ml and 791±1412 ng/ml (mean ± SD); the range and the mean of plasma TSP concentrations of control individuals (n = 33) were 13 ng/ml to 137 ng/ml and 59±29 ng/ml. When plasma TSP concentrations were correlated with plasma concentrations of another platelet activation marker, β-thromboglobulin (P-TG), it was found that the TSP concentration inei eased exponentially as the plasma β-TG level rose. A positive correlation between plasma levels of plasma TSP and serum fibrin degradation products was also observed. The results suggest that platelets are the primary source of plasma TSP in patients with various vasculitis and that plasma TSP can be a better indicator than β-TG to assess intravascular platelet activation due to its longer circulation half life.

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Investigation by HPLC of the Catabolism of Recombinant Tissue Plasminogen Activator in the Rat

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647645 ◽

1988 ◽

Vol 60 (01) ◽

pp. 107-112 ◽

Cited By ~ 4

Author(s):

Roy Harris ◽

Louis Garcia Frade ◽

Lesley J Creighton ◽

Paul S Gascoine ◽

Maher M Alexandroni ◽

...

Keyword(s):

Molecular Weight ◽

Plasminogen Activator ◽

Tissue Plasminogen Activator ◽

Half Life ◽

Recombinant Tissue Plasminogen Activator ◽

Rat Plasma ◽

High Molecular Weight Complex ◽

Molecular Weights ◽

Major Activity ◽

Tissue Plasminogen

SummaryThe catabolism of recombinant tissue plasminogen activator (rt-PA) was investigated after injection of radiolabelled material into rats. Both Iodogen and Chloramine T iodination procedures yielded similar biological activity loss in the resultant labelled rt-PA and had half lives in the rat circulation of 1 and 3 min respectively. Complex formation of rt-PA was investigated by HPLC gel exclusion (TSK G3000 SW) fractionation of rat plasma samples taken 1-2 min after 125I-rt-PA injection. A series of radiolabelled complexes of varying molecular weights were found. However, 60% of the counts were associated with a single large molecular weight complex (350–500 kDa) which was undetectable by immunologically based assays (ELISA and BIA) and showed only low activity with a functional promoter-type t-PA assay. Two major activity peaks in the HPLC fractions were associated with Tree t-PA and a complex having a molecular weight of ̴ 180 kDa. HPLC fractionation to produce these three peaks at various timed intervals after injection of 125I-rt-PA showed each to have a similar initial rate half life in the rat circulation of 4-5 min. The function of these complexes as yet is unclear but since a high proportion of rt-PA is associated with a high molecular weight complex with a short half life in the rat, we suggest that the formation of this complex may be a mechanism by which t-PA activity is initially regulated and finally cleared from the rat circulation.

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In Vitro Stability of a Tissue-Type Plasminogen Activator Mutant, BM 06.022, in Human Plasma

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648982 ◽

1994 ◽

Vol 72 (06) ◽

pp. 906-911 ◽

Cited By ~ 8

Author(s):

D C Rijken ◽

E Groeneveld ◽

M M Barrett-Bergshoeff

Keyword(s):

Plasminogen Activator ◽

Half Life ◽

Polyacrylamide Gel Electrophoresis ◽

Tissue Type ◽

Single Chain ◽

Tissue Type Plasminogen Activator ◽

Type Plasminogen Activator ◽

Sds Page ◽

Chain Form

SummaryBM 06.022 is a non-glycosylated mutant of human tissue-type plasminogen activator (t-PA) comprising only the kringle-2 and proteinase domains. The in vivo half-life of BM 06.022 antigen is 4- to 5-fold longer than that of t-PA antigen. The in vitro half-life of the activity of BM 06.022 at therapeutic concentrations in plasma is shorter than that of t-PA. In this study the inactivation of BM 06.022 in plasma was further investigated.Varying concentrations of BM 06.022 were incubated in plasma for 0-150 min. Activity assays on serial samples showed a dose-dependent decline of BM 06.022 activity with a half-life from 72 min at 0.3 μg/ml to 38 min at 10 μg/ml. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) followed by fibrin autography showed the generation of several BM 06.022-complexes. These complexes could be completely precipitated with antibodies against Cl-inactivator, α2-antiplasmin and α1-antitrypsin.During the incubation of BM 06.022 in plasma, plasmin was generated dose-dependently as revealed by varying degrees of a2-anti-plasmin consumption and fibrinogen degradation. SDS-PAGE and immunoblotting showed that single-chain BM 06.022 was rapidly (i. e. within 45 min) converted into its two-chain form at concentrations of 5 μg/ml BM 06.022 and higher.In conclusion, BM 06.022 at therapeutic concentrations in plasma was inactivated by Cl-inactivator, a2-antiplasmin and a j-antitrypsin. The half-life of the activity decreased at increasing BM 06.022 concentrations, probably as a result of the generation of two-chain BM 06.022 which may be inactivated faster than the single-chain form.

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