Biomedical subjects

S K Wrobleski

Publications and source records attributed to S K Wrobleski.

24 records · Page 2Linked to original sources

PubMed1991

Deep venous thrombosis in the baboon: an experimental model.

Experimental models of deep venous thrombosis, heretofore, have not been available for laboratory studies. This investigation establishes a novel model of venous thrombosis by inhibiting the protein C system combined with venous stasis and subtle venous injury. Ten adolescent baboons were studied in pairs, with one animal receiving saline solution (B2, B4, B6, B8, B10) and one being exposed to thrombogenic reagents (B1, B3, B5, B7, B9). These reagents represented a combination of a monoclonal antibody (HPC4) to protein C, 1 to 4 mg/kg administered over 5 minutes, and tumor necrosis factor administered over 3 minutes at a dose of 150 micrograms/kg through a catheter placed into the left superficial femoral vein with distal ligation. To encourage stasis, a pediatric size blood pressure cuff was inflated to 40 mm Hg on the right thigh for 50 minutes of every hour during the first experimental day (day 1) in B5 to B10. The animals were observed for a 6-hour period on day 1 and then for an 11- to 15-day period until sacrifice. Hemodynamic and hematologic parameters were recorded along with duplex imaging of the iliac veins and inferior vena cava on a daily basis. Venography was performed on day 1, day 4, and the day of sacrifice. At sacrifice the entire iliac and vena caval system was carefully dissected, opened, and photographed. Experimental animals given the HPC4 and tumor necrosis factor developed left iliac vein thrombosis extending into the inferior vena cava. Duplex imaging, venography, and autopsy revealed that control animals receiving saline solution never developed comparable thrombus. Experimental subjects exhibited thrombus on duplex imaging by day 4 (B1), day 3 (B3), day 2 (B5), 120 minutes (B7), and 360 minutes (B9) after receiving HPC4 and tumor necrosis factor. Venograms performed on day 1 exhibited thrombus in B5, B7, and B9. The extent of thrombus, the timing of its occurrence, and its effect on the animals' left leg followed a dose-dependent relationship for the animals in which the occlusive blood pressure cuff was used. Significantly greater declines in blood pressure, white blood cell count, and platelet count were found in affected animals given HPC4 and tumor necrosis factor reagents as compared to control subjects. All affected animals demonstrated the appearance of fibrin split products and a markedly prolonged prothrombin time. This investigation, for the first time, establishes a reproducible model of deep venous thrombosis involving inhibition of protein C that will facilitate further laboratory studies on venous thrombosis.

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PubMed1990

Reversal of depressed oxygen consumption accompanying in vivo protamine sulphate-heparin interactions by the prostacyclin analogue, iloprost.

Oxygen consumption (VO2) is known to be depressed 50 to 60% during protamine sulphate reversal of heparin anticoagulation. Accompanying this event are systemic hypotension, pulmonary artery hypertension and thrombocytopaenia. The effect of a pro-stacyclin analogue, iloprost, on protamine-induced changes in VO2 was assessed in this investigation. Three groups of anaesthetised adult mongrel dogs were studied: Group I--control subjects received i.v. normal saline infusions (n = 10); Group II--subjects received low-dose i.v. iloprost infusions (25-50 ng/kg/min) over 30 min (n = 7); and Group III--subjects received high-dose i.v. iloprost infusions (175 ng/kg/min) over 30 min (n = 7). All dogs initially received sodium heparin, 150 IU/kg i.v. Protamine sulphate, 1.5 mg/kg i.v., was subsequently administered over 10 s following the first 20 min of saline or iloprost infusion. Continuous measurements included: mixed venous (SvO2) and arterial (SaO2) oxygen saturation, arterial blood pressure, pulmonary artery pressure, heart rate and carotid artery flow (CaQ). Thermodilution cardiac output (CO) allowed calculation of VO2. Platelet counts were performed before and 3 min after protamine infusion. The VO2 declines in Group II and III subjects compared to Group I controls were markedly less. Maximum VO2 declines in Group I control dogs of -38.2 +/- 26.7% and Group II dogs of -34.1 +/- 36.8% at 75 to 90 s post-reversal contrasted to -2.9 +/- 31.9% in Group III animals at the same time interval. VO2 increases occurred 3 to 10 min after protamine exposure in Group III animals, as did attenuation of systemic hypotensive and pulmonary hypertensive responses in this group.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1990

Impaired myocardial function and oxygen utilization due to protamine sulfate in an isolated rabbit heart preparation.

The myocardial effects of protamine, with and without heparin, were documented in this investigation. Isolated rabbit hearts (n = 30) were retrograde perfused with Krebs-Ringers bicarbonate solution aerated with 95% O2/5% CO2 through the aortic root (37 C, 80 mmHg). Developed left ventricular blood pressure, heart rate, coronary artery flow, contractility as reflected by peak +dp/dt, oxygen extraction (a-vO2), and oxygen consumption (VO2) were measured at baseline and continuously throughout the experiment. Protamine (25 micrograms, 50 micrograms, and 250 micrograms per mL of perfusate) was circulated in the Krebs-Ringers buffer to hearts perfused without heparin (groups I, II, and III) or hearts perfused with heparin added to the buffer solution, 0.1 IU/1.0 microgram protamine (groups IV, V, and VI). Blood pressure 4 minutes after protamine was less in groups III (-23 mmHg) and VI (-28 mmHg) than in groups I (-6 mmHg), II (-18 mmHg), IV (-1 mmHg), and V (-7 mmHg). Heart rate changes (beats/minute) at 4 minutes revealed similar dose-dependent reductions (III and VI: -51, -55; II and V: -36, -36; and I and IV: -20, -16, respectively). Coronary artery flow at 4 minutes was slightly increased in groups III (9 mL/minute) and VI (15 mL/minute), but was relatively unchanged in the other groups. Decreases in contractility were apparent in all groups 4 minutes after protamine was started: group I, -14%; II, -16%; III, -30%; IV, -7%; V, -15%; and VI, -34%. Similarly declines in oxygen extraction and consumption were noted in all groups at the same time period and were greater in groups III (-53%, -44%) and VI (-55%, -49%) than in groups I (-25%, -26%), II (-15%, -12%), IV (-48%, -49%) and V (-15%, -18%), with p less than or equal to 0.05 or p less than or equal to 0.01 compared to baseline. Three of ten hearts exposed to high-dose protamine stopped beating after 5 minutes. This investigation establishes, for the first time, that protamine has dose- and time-specific adverse effects on cardiac contractility. In addition protamine decreases myocardial a-vO2 and VO2. These changes may contribute to certain adverse events accompanying the clinical administration of protamine.

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PubMedDate not supplied

Detection of perivenous inflammation in a rat model of venous thrombosis using MRV.

Venous thrombosis is associated with a significant inflammatory response in the vein wall, which can be imaged noninvasively with gadolinium (Gd)-enhanced magnetic resonance venography (MRV). Interleukin-10 (IL-10), a naturally occurring anti-inflammatory cytokine, has been found to decrease the inflammatory response at the proper dosage and timing of administration. The present study determines if MRV with Gd is useful in a rat model of stasis-induced venous thrombosis to document the anti-inflammatory effects of rIL-10. Rats underwent laparotomy and ligation of the inferior vena cava (IVC). Animals were infused with rIL-10 at 2.5 microg (n = 6), rIL-10 at 10 microg (n = 6), or rIL-10 at 40 microg (n = 6). Six animals without IVC ligation or drug infusion served as controls. Two days after thrombosis induction, the rats underwent MRV with both time-of-flight imaging and pre/post-Gd T1-weighted imaging. Inflammation was analyzed by measuring the area of Gd enhancement at the point of IVC thrombosis. Enhancement area was also measured in the distal IVC where flow persisted. All animals with IVC ligation developed thrombosis, and all control rats were free of thrombus. In areas where flow remained, the area of enhancement was 1.8 +/- 0.4 mm2, while controls demonstrated 3.8 +/- 1.0 mm2 enhancement. Enhancement was significantly greater in all groups at the level of thrombus compared to the area of distal IVC flow and control IVCs (p < .001). Animals receiving rIL-10 at 40 microg revealed the most enhancement, 32.7 +/- 6.2 mm2, while the least enhancement was noted with 2.5 microg, 14.7 +/- 1.5 mm2 (p < .05). In conclusion, Gd-enhanced MRV was found useful in this rat model of stasis-induced venous thrombosis to document inflammation noninvasively and to evaluate the effects of anti-inflammatory interventions during stasis-induced IVC venous thrombosis.

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PubMedDate not supplied

Neutrophils are the initial cell type identified in deep venous thrombosis induced vein wall inflammation.

Venous thrombosis and inflammation are interrelated. The authors hypothesized that inferior vena cava thrombosis results in a predictable vein wall inflammatory response, characterized by early neutrophil infiltration. Thrombosis was induced in rats by placement of an inferior vena cava ligature with branch ligation. Animals were killed at baseline, 6 hrs, day 2, and day 6. Analysis included vein wall morphometrics, myeloperoxidase activity, and fluorescence activated cell sorting. At 6 hrs, there was an increase in neutrophils and lymphocytes as compared to sham animals (p < 0.0001 for neutrophils, p < 0.05 for lymphocytes). By day 2, only neutrophils were elevated in the experimental groups (experimental = 75.5 cells/5 high power fields vs. 9.6 cells/ 5 high power fields in shams, p < 0.0001). Myeloperoxidase activity in the experimental group was greater than shams on day 2(34.7 delta optical density/min vs. 5.9 delta optical density/ min, p < 0.0001). Fluorescence activated cell sorting of the neutrophil marker at 6 hrs confirmed the increase in neutrophils (experimental = 63.1%, shams = 39.1%, p < 0.0001), and peaked on day 2 (71.9%). This study suggests that 1) neutrophils are elevated early during the inflammatory response due to thrombus initiation, and 2) neutrophils, because of their early predominance, likely contributed to vein wall injury during venous thrombosis.

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PubMedDate not supplied

Tissue distribution, circulating half-life, and excretion of intravenously administered protamine sulfate.

Intravenous protamine reversal of heparin anticoagulation may cause adverse hemodynamic side effects, but little is known about protamine's tissue distribution, circulating half-life (t/2), and excretion. The latter were assessed by examining 125I Bolton-Hunter (125I BH) radiolabeled protamine kinetics in a rat model. Three groups were studied: Group I controls (n = 5) received intravenous 125I BH label alone; Group II (n = 10) received intravenous 125I BH radiolabeled protamine (0.15 mg/100 g); and Group III (n = 10) received intravenous heparin (15 IU/100 g) followed by intravenous 125I BH radiolabeled protamine (0.15 mg/100 g). Five animals in each group were killed at 3 min, and tissue radioactivity was quantitated. An additional five animals each in Groups II and III were followed up for 60 min to determine protamine's circulating t/2 and its renal excretion. The lungs, heart, and kidneys, compared with other organs, retained the most 125I BH radiolabeled protamine per gram tissue at 3 min. Retention of 125I BH radiolabeled protamine (Groups II & III) was greater (p < 0.05, Kruskal-Wallis) than control 125I BH label alone (Group I). Higher tissue 125I activity was observed in Group II than in Group III rats, suggesting that tissue retention of protamine was greater in the absence of prior heparin administration. Circulating t/2 was shorter (18 vs. 24 min) and urinary protamine 125I excretion was higher (34 vs. 24%) in Group III than in Group II, respectively, suggesting more rapid renal clearance of protamine in the presence of heparin.(ABSTRACT TRUNCATED AT 250 WORDS)

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