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Biomedical subjects

N Vinberg

Publications and source records attributed to N Vinberg.

10 recordsLinked to original sources
PubMed2005

Lack of hepatic metabolism of C-telopeptides of type I collagen.

BACKGROUND: Bone biochemical markers have been used in dynamic studies of bone metabolism, and, for accurate interpretation of measured marker levels, it is essential to have information of extra-skeletal metabolism. Therefore, the objective of the present study was to investigate if the circulating C-telopeptides of type I collagen (CTX) was subject to hepatic extraction. METHODS: Splanchnic plasma flow, total plasma volume and the plasma concentration of CTX was determined in an artery and the liver vein of eight healthy female volunteers. For comparison, the concentration of N-terminal propeptide of type I collagen, PINP, was measured. RESULTS: No change in plasma level of CTX could be detected over the liver. In contrast, PINP decreased from an average of 52.9 ng/ml in the artery to 42.4 ng/ml in the vein, corresponding to a 19.8% reduction. CONCLUSIONS: The C-telopeptides of type I collagen (CTX) are not subject to hepatic metabolism.

Adult↗
PubMed2002

Splanchnic extraction and clearance of tissue plasminogen activator (t-PA) after injection of recombinant t-PA (Actilyse) in resting healthy subjects is proportional to the arterial concentration.

The purpose of the study was to evaluate the splanchnic extraction of tissue plasminogen activator (t-PA) in normal healthy fasting subjects after the injection of recombinant t-PA (rt-PA; Actilyse). In nine healthy volunteers (five male, four female), 21-29 years of age, the concentration of t-PA was determined in plasma samples taken simultaneously from a femoral artery and a large liver vein after a bolus injection (5, 10 or 20 mg) of rt-PA. The splanchnic plasma flow rate, the plasma volume, and the splanchnic extraction fraction of t-PA were determined. After the rt-PA injection, the measured arterial concentration of t-PA decreased from 36 750 to 45 pmol/l for t-PA antigen and from 50 700 to 17 pmol/l for active t-PA. The splanchnic extraction fraction decreased from 0.95 to 0.02 for t-PA antigen and from 0.78 to 0.08 (n = 3) for active t-PA. The extraction fraction was proportional to the arterial concentration of t-PA when the arterial concentration of t-PA was above about 300 pmol/l (both t-PA antigen and active t-PA). The median splanchnic plasma flow rate was 911 ml/min (range, 651-1149 ml/min). In the individual subject, the splanchnic plasma flow rate remained constant during the experimental period. The main conclusion of the study is that the splanchnic clearance and extraction fraction of t-PA, following an injection of rt-PA in the resting fasting steady state, depends on the arterial concentration of t-PA. The higher the arterial concentration of t-PA, the higher the extraction fraction of t-PA.

Adult↗
PubMed2001

Mean transit times and the sites of synthesis and catabolism of tissue plasminogen activator and plasminogen activator inhibitor type 1 in young subjects.

Using an invasive technique, we studied the mean transit time, the net quantitative turnover rate, and the sites of synthesis and catabolism of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor type 1 (PAI-1) in healthy young volunteers in the fasting, steady state. Blood was sampled simultaneously from a large hepatic vein, an artery and the inferior caval vein, while measuring the splanchnic plasma flow rate and the plasma volume. We found that the catabolism of active t-PA and t-PA antigen took place in the splanchnic circulation with net rates of 7.2 and 6.3 pmol/min, respectively. The extraction fraction and the mean transit time in the splanchnic circulation were, respectively, 0.63 and 5.6 min for active t-PA and 0.17 and 21 min for t-PA antigen. Active PAI-1 was synthesized in the splanchnic circulation at a rate of 890 IU/min and had a mean transit time of about 9.8 min. No net extraction of PAI-1 antigen took place in the splanchnic circulation. In conclusion, we demonstrated that active t-PA and t-PA antigen are catabolized and active PAI-1 produced in the splanchnic circulation in young healthy subjects during steady state. Furthermore, our data show that active t-PA was also eliminated outside the splanchnic region with a catabolism rate of about 8.4 pmol/min. No net complex formation could be demonstrated in the peripheral circulation. We therefore suggest that active t-PA is eliminated by a re-uptake in the endothelium in the peripheral vessels or in the lung circulation.

Adult↗
PubMed1992

Prolonged binding of radiolabeled recombinant tissue-type plasminogen activator after angioplasty and enclosed thrombolysis of the femoropopliteal arteries.

The authors measured the binding of indium-111-labeled recombinant tissue-type plasminogen activator (rt-PA) within the recanalized femoropopliteal segment after percutaneous transluminal angioplasty (PTA) and enclosed thrombolysis. In patients with long occlusions (n = 3), 91 micrograms of rt-PA was bound 1 hour after the procedure, and the half-time of the final washout curve averaged 114 hours. After PTA in patients with multiple stenoses (n = 6), 45 micrograms of rt-PA was bound, and the half-time averaged 32 hours. These values were significantly smaller than those in patients with occlusions (P < .01). In patients with a single stenosis (n = 4), 19 micrograms of rt-PA was bound, and the half-time averaged 5 hours. These values were significantly smaller than those in patients with multiple stenoses (P < .01). The progressive accumulation of rt-PA at the sites of PTA therapy is most likely related to increasing presence of fibrin with increasing lesion severity. Fibrin accumulation may be partly responsible for early failures after PTA in extensive lesions. Removal of this fibrin with enclosed thrombolysis might improve patency.

Aged↗
PubMed1980

Fission MO-99/Tc-99m Generators -- a study of their performance and quality.

Five 99mTc-generators, based on fission Mo-99, from five different manufacturers were studied in April and May of 1977 -- with regard to their performance and to the quality of the eluates. The study covers types of generators not already dealt with in a previous publication [5]. One generator was overloaded with Mo-99; one generator had Tc-99m yields below 70%. One generator yielded eluates containing appreciable gamma-emitting impurities other than Mo-99. Two generators yielded eluates containing trace amounts of Al+++. The content of alpha- and pure beta-emitting nuclidic impurities (other than Tc-99) were in all cases below the limits set in the DLS 79 [2] monograph on Tc-99m pertechnetate obtained from fission Mo-99.

Drug Contamination↗
PubMed1976

Comparative evaluation of 99mTc-generators.

A total of 34 99mTc-generators from eight different manufactures were studied in 1974 and 1975 with regard to their performance and to the quality of the eluates. With some exceptions the generators performed well and proved their ability to act as a reliable source of 99mTc-pertechnetate. Two cases of mechanical malfunction and two cases with a low elution yield of 99mTc were observed. Four generators were overloaded with 99Mo. The 99mTc-pertechnetate did in most cases fulfil the requirements of the Nordic Pharmacopeia.

Chemical Industry↗