Comments on “Optimization of the decision threshold for single radioactive counting”

It is argued that in the recent papers by A. Vivier and J. Aupiais (Radiochim. Acta

Optimization of the decision threshold for single radioactive counting

SummaryIn the above mentioned paper several misprints and errors in the formulae have been noticed. In particular, several equations were not properly writtten in terms of variables of integration. We now present the correct data.

Preparation of Radioactively Tagged Ethylene-Propylene Copolymers. Calculation of the Block-Length Distribution from the Kinetic Data

A series of statistical copolymers is available for our studies of the mechanisms of thermal decomposition of ethylene-propylene copolymers and their sequence distribution. However, the analytical evidence can be improved appreciably by the use of radioactively tagged copolymers and radio-gas chromatography. A loss of information occurs when untagged polymers undergo α-scission. Even if the chain breaks directly at the tertiary carbon atom, the scission product stabilizes itself by forming a terminal double bond. Accordingly, the position of double bonds gives no information about the location of methyl side groups in copolymers. However, if the α-methyl groups are radioactively tagged, as shown in the formula above, radioactive counting of linear fragments can demonstrate their original methyl side groups. Thus, α-scissions of copolymers can be directly determined.

Thromboembolic Surveillance Using 125 I Labelled Fibrinogen of 1000 Patients who Underwent Traumatologic and Orthopedic Surgery

From 1975 to 1977, 1006 tests using 125 I fibrinogen have been performed on orthopedic and traumatologic patients who were undergoing a thromboembolic treatment either by means of the association of dipyramidole and aspirin administered orally (24%) or by subcutaneous heparin (76%). The 125 I fibrinogen was injected preoperatively or immediately postoperatively. A daily radioactive counting was performed on the inferior members for approximately 6 to 8 days. 102 venous phlebography controls demonstrated an accuracy of 80% for the 125 I fibrinogen test. Of 1006 patients, 15.2% of the fibrinogen tests were positive, 59.7% of which were positive between the first and fifth postoperative day (p<0.02). The isotopic signs of venous thrombosis occurred in 21% of the hip surgery patients, 14.5% of the lumbar spine surgeries, 13% of the knee surgeries, and 11.5% of the patients who underwent surgery for other traumatic lesions. In these 1006 patients, 9 pulmonary emboli occurred of which 2 were fatal. The 125 I fibrinogen test can only be applied to evolutive thrombosis and does not permit one to differentiate between hematomas and thrombosis, nor to detect pelvic thrombosis. However, this test still remains a simple, faithful, and nontraumatic diagnostic tool in the early detection of thrombosis of the inferior members in patients undergoing traumatologic and orthopedic surgery. Moreover, the labelled fibrinogen test is useful in the determination of the efficacy of antithrombotic preventive medication. Our study has manifested the superiority of subcutaneous heparin (18% positive test) over the association of dipyramidole-aspirin (38.6% positive test) in the prevention of thromboembolic accidents in hip patients (p<0.001).

Platelet Prostaglandin Endoperoxides Formation in Hyperlipidemias

To evaluate the role of prostaglandin endoperoxide formation in the mechanism(s) of platelet hypersensitivity in hyperlipoproteinemias, a study was undertaken in 8 type II patients, 3 type IV, and 8 normal volunteers. Platelet aggregation and release were studied in all subjects. Simultaneously, EDTA-platelets were washed by centrifugation and suspended in modified Ringer’s solution. One ml suspensions (0.8-1x106/μl) were added to 4.5μg of 14C-Arachidonic Acid (AA; sp. act. 50 mCi/mmol) and incubated for 30 sec and 5 min at 37°C. The methylated reaction products were separated by thin layer chromatography. AA, PGE2, PGF2α, and thromboxane B2 (PHD) (Upjohn) were used to identify and locate the respective bands. The products were analyzed by mass spectrometry. TLC-plates were both scanned and scraped for radioactive counting. The chromatograms displayed a pattern similar to that reported by Samuelsson et al. Compared with normal, hypersensitive platelets of type II patients generated 25% more thromboxane A2 (TXA2) after 30 sec incubation with AA, while at 5 min PHD was increased by 30% and TXA2 was still elevated by a factor of 2. The behavior of type IV platelets was similar to normal.Aspirin-treated platelets produced one product (HETE). Among the AA derivatives studied, only eluted TXA2 induced platelet release.Our data suggest that platelet hyperreactivity in type II patients may be mediated by the increased production and long survival of thromboxane A2.