Search PubMed⌕ Search

Biomedical subjects

B Risberg

Publications and source records attributed to B Risberg.

At least 181 records · Page 10Linked to original sources
PubMed1989

A new incision for retroperitoneal approach to the aorta.

A new incision for retroperitoneal approach to the abdominal aorta is described. The incision extends from alongside the rectus abdominis muscle across the costal arch over the 7-8th intercostal space. In the upper part only the skin and muscles are divided, allowing wide opening of the incision. The approach is muscle-sparing, since fibers of the transverse abdominal muscle are incised only in the upper part. It permits a good approach even for high aortic reconstruction.

Aorta, Abdominal↗
PubMed1989

Reduced platelet deposition on seeded versus unseeded segments of expanded polytetrafluoroethylene grafts: clinical observations after a 6-month follow-up.

The concept of autologous endothelial cell seeding has proved successful in animal models with respect to decrease of graft thrombogenicity and increase in patency. In the present study, application of this method in humans was explored. In 23 patients, random halves of expanded polytetrafluoroethylene grafts, used for lower limb arterial reconstructions, were seeded with endothelial cells at a seeding density of 3500 cells/cm2. These cells were derived from the saphenous vein by enzymatic harvesting. The other half was sham seeded with culture medium. Graft thrombogenicity was estimated by measuring platelet deposition on graft surface 1 and 6 months after surgery, with indium 111-labeled platelets and external gamma-camera imaging. Seeded graft segments accumulated significantly (p less than 0.03) fewer platelets at all imaging times. It is concluded that seeding of expanded polytetrafluoroethylene vascular grafts in humans reduces graft surface thrombogenicity. The clinical implications of this remain to be demonstrated.

Aged↗
PubMed1988

Heparin and fibrinolysis--comparison of subcutaneous administration of unfractionated and low molecular weight heparin.

The effects on the fibrinolytic system after a single s.c. bolus injection (at 9 a.m.) of either 5000 IU conventional heparin or 5000 anti-Xa U of a fractionated low molecular weight heparin (Fragmin, KabiVitrum, Sweden) were investigated in 9 healthy volunteers. The effects were compared to those of an injection of normal saline in 6 volunteers. Samples for biochemical analyses were taken regularily during 6 hours after drug or placebo administration. In the coagulation system the following parameters were measured: Activated partial thromboplastin time (APTT), anti-Xa activity, thrombin time and fibrinogen. The fibrinolytic system was monitored by analysing: plasminogen, alpha 2-antiplasmin, fibrin(ogen) degradation products (FDP), euglobulin clot lysis time (ECLT), tissue plasminogen activator (t-PA) activity, t-PA antigen and plasminogen activator inhibitor (PAI) activity. Injection of the 2 drugs was followed by elevations in APTT and anti-Xa activity, and were more pronounced for Fragmin than heparin. The fibrinolytic system exhibited a diurnal variation with decreasing PAI activity and increasing t-PA activity during the day. Volunteers receiving normal saline (placebo) showed a similar pattern. The results were unrelated to heparin. It is concluded from this study that neither heparin nor Fragmin had any significant effect on the fibrinolytic parameters when measured after a single s.c. bolus injection since the observed variations were within the diurnal range.

Adult↗
PubMed1988

Determination of plasminogen activator inhibitor in plasma using t-PA and a chromogenic single-point poly-D-lysine stimulated assay.

A two stage method for determination of plasminogen activator inhibitor (PAI) activity in blood plasma is described. In the first stage, an excess of single-chain tissue plasminogen activator (t-PA) is added to plasma. In the second stage, the residual t-PA activity is determined with a plasminogen/chromogenic plasmin substrate assay utilizing poly-D-lysine as a t-PA stimulator. The method proved accurate since it correctly determined the PAI activity (range 0 to 110U/mL) in citrated plasma samples with levels established by time course analysis of t-PA inhibition and by titration with t-PA. Furthermore, correlation was excellent (r = 0.97) with the method of Chmielewska et al Thromb. Res. 31, 427-436, 1983. Plasma samples with increased platelet factor 4, indicative of platelet release, did not show increased levels of PAI activity.

Blood Platelets↗
PubMed1988

Thrombosis prophylaxis with low molecular weight heparin in total hip replacement.

In a randomized prospective trial, the efficacy of low molecular weight heparin (LMWH) (Fragmin) and dextran 70 (Macrodex) in preventing deep vein thrombosis (DVT) in the legs was evaluated in 98 consecutive patients undergoing elective total hip replacement. The patients were randomly allocated to receive either 2500 anti-factor Xa units LMWH twice daily for 7 days, with the first dose given 2 h before surgery; or 500 ml dextran 70 twice during the day of operation, followed by a single infusion of 500 ml on the first and again on the third postoperative day. DVT was assessed by 125I-fibrinogen test for 2 weeks postoperatively, a positive test being followed by phlebography. DVT developed in 22 (45 per cent) of 49 patients receiving dextran 70 and in 10 (20 per cent) of 49 patients in the LMWH group (P less than 0.01). LMWH was thus statistically significantly better than dextran 70 in preventing DVT in the legs. It was not firmly established whether this benefit was also valid in the high ileofemoral region. Two patients with non-fatal pulmonary embolism were found in each group. Per- and postoperative blood loss and blood transfusion requirements were significantly lower in the LMWH group.

Aged↗
PubMed1988

Splenic platelet kinetics and platelet production after major reconstructive vascular surgery.

By using 111In-labelled platelets and dynamic gamma camera scintigraphy, platelet production rate and intrasplenic platelet kinetics were determined in 13 patients at 1 and 4 months after aortic reconstructive vascular surgery with implantation of dacron prostheses. A significant decrease in platelet production rate and venous platelet count was recorded over time after surgery. Irrespective of whether the exchangeable splenic platelet pool was estimated from initial recovery of platelet-bound radioactivity or from compartmental analysis, the size of this pool was significantly lower at the first study; a change in intrasplenic platelet transit time accounted for the observed difference. Platelet mean life-span increased over time after surgery but the difference between the duplicate studies was not statistically significant. It can be concluded that there is a reduction of platelet production rate and venous platelet count over time after major reconstructive vascular surgery. The early postoperative elevation in the platelet count is mainly the result of an increased platelet production and to a lesser degree due to redistribution of platelets between the splenic platelet pool and general circulation.

Aged↗
PubMed1988

Effect of increased hydrostatic pressure on lymphatic elimination of hyaluronan from sheep lung.

The effects of increased hydrostatic pressure on the concentrations of hyaluronan (hyaluronic acid) in lung lymph and serum were investigated in awake sheep with a cannula in the efferent vessel from the caudal mediastinal lymph node. Lung lymph was sampled at base line [left atrial pressure (LAP) 6.5 +/- 1.7 mmHg] and after two increases of LAP to 25.7 +/- 2.2 mmHg (level 1) and 37.0 +/- 5.1 mmHg (level 2). The lung lymph flow increased from 1.9 +/- 0.5 at base line to 9.3 +/- 2.2 and 15.9 +/- 0.7 ml/30 min, and the lymph-to-plasma concentration ratio of total protein decreased from 0.63 +/- 0.02 to 0.32 +/- 0.04 and 0.32 +/- 0.05 at the two elevated levels of LAP, respectively. The hyaluronan concentration in lung lymph was unchanged, and there was a flow-dependent elimination of hyaluronan from the lung that increased from 23 +/- 8 to 87 +/- 19 and 137 +/- 37 micrograms/30 min, respectively. The lung concentration of hyaluronan was 167 +/- 28 micrograms/g fresh lung, and at base line it was calculated that slightly less than 2% of the lung hyaluronan was eliminated by the lymphatic route in 24 h. If extrapolated to 24 h, the elimination rate of hyaluronan seen during elevated LAP would result in lymphatic elimination of 18% of the lung hyaluronan over this time period. Since hyaluronan is responsible for part of the protein exclusion in the extracellular matrix, it is plausible that washout of interstitial hyaluronan contributes to the decrease in albumin exclusion from the interstitium that occurs after an elevation of LAP.

Animals↗
PubMed1988

Local pulmonary activation of proteolytic enzymes after Escherichia-coli-induced lung injury in sheep.

Activation of several cascade systems, e.g. coagulation, fibrinolysis, kallikreinkinin, complement and eicosanoid systems, has been implicated in the etiology of septic-lung microvascular injury. A chronic lung lymph fistula preparation in sheep (n = 9) was used to study coagulation, kallikrein-kinin and eicosanoids during Escherichia coli septicemia. Lung lymph flow and lymph composition indicated an increased lung microvascular permeability approximately 2 h after infusion of bacteria. Stable prothrombin and antithrombin III levels in lymph contradicted local activation of the coagulation cascade in the lung and systemic activation was not evident until 4 h after bacteria infusion. Lymph thromboxane B2 and 6-keto PGF1 alpha peaked early (1 h). Reduced lymph prekallikrein and kallikrein inhibitors indicated local activation of this system in the lung. Systemic activation of kallikrein could not be demonstrated. Thus, (1) changes in systemic blood may not adequately reflect local events and (2) studies of proteolytic enzymes and other inflammatory mediators in lung may contribute to clarifying the etiology of microvascular injury.

Animals↗
PubMed1988

Combined monitoring of thoracic duct and lung lymph during E. coli sepsis in awake sheep.

A thoracic duct lymph fistula in combination with a lung lymph fistula in the awake sheep was used to evaluate effects of thoracic lymph diversion during a septic insult and to monitor systemic and local changes in the lung and gastrointestinal tract. Live Escherichia coli 10(9) kg-1 b.w. were infused in 9 sheep. After sepsis, arterial pressure, cardiac output, partial pressure of oxygen, leukocytes and platelets decreased significantly compared to baseline values. Pulmonary arterial pressure increased significantly throughout the experiment with peak values at 44 +/- 4 mmHg after 15 minutes. Lung lymph flow (QL) (n = 6) increased from 23 +/- 0.5 to 11.2 +/- 2.4 ml/30 minutes after 60 minutes. QL then decreased but remained elevated. Lymph to plasma protein concentration ratio (L/P) in lung lymph decreased from 0.62 +/- 0.02 during baseline to 0.47 +/- 0.04 after 60 minutes. L/P then increased and was, after 150 minutes, no longer different from baseline. These lung lymph data favor increased pulmonary microvascular permeability during sepsis. Lymph flow in the thoracic duct (QT) (n = 9) increased from 34.2 +/- 6 to 58.3 +/- 9 ml/30 minutes during the first 30 minutes after bacterial infusion. QT was, after 90 minutes, back to baseline but then progressively increased. L/P in thoracic lymph steadily increased from 0.56 +/- 0.03 to 0.78 +/- 0.04. Thromboxane B2 and 6-keto PGF1 alpha in thoracic duct and lung lymph increased significantly after bacterial infusion and remained elevated thereafter. Combined monitoring of thoracic duct and lung lymph enabled comparison of systemic and pulmonary reactions in septic sheep.

Animals↗
PubMed1988

Tissue plasminogen activator and its inhibitor following major surgery in relation to ventilatory pattern.

Based on animal data it has been hypothesised that lungs may regulate systemic fibrinolysis. To test this hypothesis 12 patients undergoing infrarenal aortic reconstruction due to arteriosclerotic disease were evaluated for influence of the respiratory pattern on release of tissue plasminogen activator (t-PA) and its inhibitor (PAI) in systemic and pulmonary arterial blood. Blood samples were drawn simultaneously from the pulmonary artery and a radial artery at defined times before and during surgery. Samples were also collected during application of positive end expiratory pressure (PEEP) of 5, 10 and 15 cmH2O. The blood samples were analysed for euglobulin clot lysis time (ECLT), t-PA activity, t-PA antigen and PAI. ECLT was not altered during surgery and t-PA activity was below the detectable limit. Before surgery t-PA antigen was 14.5 +/- 1.3 ng/ml and PAI 15.1 +/- 2.8 U/ml (mean +/- SEM). PAI was significantly elevated at end of surgery. There were no differences between samples from systemic and pulmonary arteries. Following application of 5, 10 and 15 cmH2O PEEP the fibrinolytic parameters were unchanged. Thus, in the present study on arteriosclerotic patients undergoing abdominal aortic reconstructions no influence from the respiratory pattern on systemic fibrinolysis could be demonstrated.

Aged↗
PubMed1988

Seeding of ePTFE carotid interposition grafts in sheep and dogs: species-dependent results.

Autologous endothelial seeding of thin-walled ePTFE vascular prostheses (I.D.4 mm), interposed in the carotid artery, was performed in 10 dogs and 14 sheeps. Aspirin (250 mg/day) and dipyridamole (75 mg/twice daily) were given throughout the study as antiplatelet therapy. Animals were killed 2 and 5 weeks after surgery. Patency rates for seeded grafts in dogs were 75% (6:8) and 83% (10:12) at 2 and 5 weeks, respectively. In control grafts the patency rates were identical. Patency rates for seeded grafts in sheep were 0% (0:5) and 11% (1:9) at 2 and 5 weeks, respectively. Control grafts in sheep had a patency rate of 40% (2:5) and 0% (0:9) at corresponding times. Scanning electron microscopy showed an almost complete endothelialization of seeded grafts in dogs after 5 weeks. Platelet deposition was studied in the dogs by means of chromium-51-labeled autologous platelets. Significantly fewer platelets accumulated on seeded grafts, and the ratio of 6-keto-PCF1 alpha to thromboxane B2 was significantly higher, compared with unseeded grafts, which indicated the presence of a functionally active endothelial lining in seeded grafts. Differences in the hemostatic system could account for the high clotting incidence in sheep, compared with that in dogs. Such species differences make extrapolations to the clinical situation from autologous endothelial seeding in experimental animals hazardous.

Animals↗
PubMed1988

Amputations due to lower-limb ischemia. Analysis of a 3-year series.

Lower-limb amputation was performed on 261 patients from a catchment population of 232,500 in 1984-1986, and 253 of the amputees were retrospectively followed up. In 241 cases amputation was performed because of threatening or manifest gangrene, 95 of them without preceding consultation with vascular surgeons. In 19 cases amputation followed thromboembolectomy. Of the 127 patients seen by vascular surgeons, 66 were judged to be unsuitable for reconstructive surgery, 22 because of poor general health and 44 because of contraindicating vascular status. In the 61 patients with vascular reconstruction prior to amputation, the level of amputation did not differ from that in patients without such antecedent surgery. The proportion of cases rejected for vascular surgery rose from 18% in 1984 to 33% in 1986. The need for amputation could probably be reduced by earlier detection and vascular surgical evaluation of arterial insufficiency.

Adult↗
PubMed1987

Measurement of tissue plasminogen activator in plasma. A comparison of 3 methods and description of a new improved technique.

Three methods for measurement of tissue plasminogen activator (t-PA) activity in plasma were compared with regard to linearity, precision and clinical applicability. Based on this comparison a new improved technique is described. The 3 methods differed in the way the influence of inhibitors in plasma was eliminated. In method A t-PA was measured in acidified plasma, in method B in euglobulin precipitate and in method C after adsorption of plasma on lysine-Sepharose. After addition of 15 IU/ml of t-PA to normal plasma the recovery with method A was 17.4 +/- 2.4 IU/ml, with method B 11.4 +/- 0.5 IU/ml and with method C 9.8 +/- 0.9 IU/ml. When tested on venous stasis plasma from 10 patients the 3 methods correlated well with a correlation coefficient of r = 0.97 - 0.99. Significantly higher values were found in acidified plasma (method A) as compared to the other methods. From this evaluation a method for determination of t-PA activity using acidification and internal standard to abolish the influence of inhibitors and poly-D-lysine as a stimulator was selected. The recovery with this method was 103.4 +/- 8.5% independent of PA inhibitor content in the plasma.

Acids↗
PubMed1987

Comparison of oxidative metabolism in vitro in endothelial cells from different species and vessels.

Oxygen consumption was compared in confluent cultures of endothelial cells from human umbilical cord veins, rat pulmonary arteries, and bovine aortas. A microrespirometric method utilizing oxygenated hemoglobin as oxygen supply and indicator of respiration was used. Respiratory rate was equal in human and murine cells (2.0 X 10(-6) and 2.2 X 10(-6) microliters O2/cell/hour respectively), compared on a cell-to-cell basis, while respiratory rate of the bovine endothelium was significantly lower (0.4 X 10(-6) microliters O2/cell/hour) (P less than .001).

Animals↗
PubMed1987

Lung damage following lymph fistula preparation in sheep.

The effect of preparative trauma on lung microvascular permeability during lung lymph fistula preparation in sheep was investigated. Two groups of anesthetized sheep were used. In group I (controls: n = 3) the lymph fistula was prepared 3 to 4 days before the experiment. In group II (experimental group: n = 13): left atrial and lymph catheters were introduced on the day of the experiment. All animals had catheters in the aorta and pulmonary artery. The stable prostanoid metabolites thromboxane B2 (TxB2) and 6-keto-PGF1 alpha (6-keto) were measured in lymph. In group I systemic (Psa) and pulmonary pressures (Ppa) remained constant. Leukocytes and platelets were unchanged as was pulmonary lymph flow (QL) and the lymph to plasma total protein concentration ratio (L/P). In group II Psa and Ppa remained constant. All sheep developed a temporary leukopenia and thrombocytopenia. TxB2 and 6-keto were low and stable during anesthesia in group I but were elevated immediately following surgery in group II but values normalized during a 4-hr observation period. QL during the first half hour was 1.9 +/- 0.3 ml/30 min and increased over 5 hr to 3.1 +/- 0.7 ml/30 min corresponding to 60 +/- 15% over baseline (P less than 0.01). L/P did not change. These changes could be due either to changing permeability or surface area. These effects of preparative trauma indicated that the model was not in a steady state. This observation should be kept in mind when evaluating studies using the lung lymph fistula in acute experiments.

Animals↗
PubMed1987

Nuclear DNA recordings in gastric carcinoids. A cytofluorometric study on single tumour cells.

Cytofluorometric nuclear DNA analyses were performed on single tumour cells from eight argyrophilic gastric carcinoids. Three tumours displayed grossly diploid DNA values, with a fraction of S-phase cells of 1-8%. Four other tumours were also mainly diploid, but showed an increased number of tetraploid cells, and one tumour was aneuploid with a stem-cell line of triploid cells. These and previous results indicate that gastric carcinoids are relatively heterogenous with respect to their morphology, nuclear DNA profiles and biological behaviour, in contrast to most intestinal "classical" carcinoids. Furthermore, the results are in accordance with the suggestion that gastric carcinoids may represent a highly differentiated variety within a spectrum of neuroendocrine neoplasia analogous to the corresponding variety observed in the bronchus (carcinoid-small cell, undifferentiated carcinoma).

Adult↗
PubMed1987

Reduction in deposition of indium 111-labeled platelets after autologous endothelial cell seeding of Dacron aortic bifurcation grafts in humans: a preliminary report.

Autologous endothelial seeding (AES) of vascular prostheses in dogs increases thrombus-free surface and improves prosthetic prostacyclin production, patency, and the ability to withstand hematogenous challenge with bacteria. No such information is available in human subjects. In the present study one limb of an aortic Dacron bifurcation prosthesis was seeded with autologous endothelial cells (ECs) harvested from the distal portion of the saphenous vein by enzymatic treatment. The deposition of indium 111-labeled platelets on the vascular prostheses was studied 1 and 4 months after operation. In seven of nine patients seeding resulted in decreased accumulation of radiolabeled platelets compared with sham-seeded control limbs (p less than 0.04), when studied 1 month after surgery. A decrease in platelet accumulation occurred over the whole prosthesis between 1 and 4 months, and no significant difference was noted at 4 months between seeded and nonseeded graft limbs. Although the seeding density was very low (440 ECs/cm2), the observed difference in platelet accumulation for AES-treated graft limbs in the early postoperative course merits further investigation of this technique in human beings.

Aged↗