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Biomedical subjects

A Hellberg

Publications and source records attributed to A Hellberg.

36 records · Page 2Linked to original sources
PubMed2001

Influence of low proximal aortic pressure on spinal cord oxygenation in experimental thoracic aortic occlusion.

BACKGROUND: To evaluate the effect of low proximal aortic pressure on cerebrospinal fluid (CSF) oxygenation in an experimental thoracic occlusion model. METHODS: In nine pigs, continuous intrathecal pO(2), pCO(2) and pH monitoring was used during double descending thoracic aortic clamping following insertion of an aorto-aortic shunt. In five pigs, the shunt was connected to a citrated bag adjusted at approximately 40-45 cm above the heart for partial exsanguination in order to decrease mean proximal aortic pressure (MPAP) to below 50 mmHg. In four animals, sodium nitroprusside infusion was used for this purpose. RESULTS: Intrathecal pO(2) demonstrated a significant decrease from 4.9+/-2.1 to 2.9+/-2.4 kPa after 10 minutes of aortic cross-clamping. Lowering proximal aortic pressure caused a further significant decrease to 1.2+/-1.7 kPa (p<0.05). In seven pigs (5 in the exsanguination and 2 in the vasodilator group), restoration of mean proximal aortic pressure to 94.0+/-27.7 caused a recovery of CSF pO(2) from 1.2+/-1.9 to 2.8+/-3.0 (p<0.05). CONCLUSIONS: The results of this study demonstrate that MPAP which provides spinal cord perfusion through subclavian-vertebral arteries are crucial for maintenance of spinal cord oxygenation during thoracic aortic occlusion in this pig model.

Animals↗
PubMed2000

Influence of segmental spinal cord perfusion on intrathecal oxygen tension during experimental thoracic aortic crossclamping.

PURPOSE: The purpose of this study was to evaluate the possibility of identifying alterations in blood supply to the spinal cord during thoracic aortic crossclamping. METHODS: In 17 pigs, a multiparameter PO(2), PCO(2,) and pH sensor was introduced into the intrathecal space for continuous monitoring of cerebrospinal fluid (CSF) oxygenation during aortic crossclamping. An epidural laser Doppler probe was used to measure spinal cord flux. After insertion of an aortic shunt from the left subclavian to the left iliac artery and interruption of the right subclavian and lumbar arteries (L2-L5), the thoracic aorta just distal to the left subclavian artery was clamped for 60 minutes. By placement of the distal aortic crossclamping below the level of L1 in group A (n = 9 animals), perfusion of only the abdominal visceral arteries was maintained. In group B (n = 8 animals), the distal aortic crossclamping was above the level of T12, and thus some spinal cord perfusion was maintained through the aortic shunt. RESULTS: The significant decrease in CSF PO(2) was observed within 3 minutes after the placement of the proximal aortic crossclamping and was normalized in all animals after establishment of the shunt flow. In group A, distal aortic crossclamping caused a decrease in CSF PO(2) with at least 50% of the preclamping values within 3 minutes. The mean CSF PO(2) of 2.99 +/- 0.70 kPa at 60 minutes of distal aortic crossclamping in group B was significantly higher than in group A (0.11 +/- 0.11 kPa; P <. 001). In group A, PCO(2) measurements showed no significant changes in 3 minutes after distal aortic crossclamping but revealed significantly higher values at 30 and 60 minutes compared with group B. Spinal cord flux values showed similar changes as CSF PO(2) during the whole experiment in both groups. CONCLUSION: In this experimental model of aortic crossclamping, continuous CSF oxygen tension monitoring allows rapid detection of alterations in spinal cord circulation.

Animals↗
PubMed2000

A multivariate analysis of factors affecting patency of femoropopliteal and femorodistal bypass grafting.

BACKGROUND: The most important factors that determine the outcome after femoropopliteal and femorodistal arterial reconstruction are still controversial. This report analysis the factors that determine the early and late patency of distal arterial reconstruction. PATIENTS AND METHODS: A retrospective analysis of patency after femorodistal arterial reconstruction with a new method for evaluation of angiographic runoff was performed for 336 arterial reconstructions. The different pre-, per- and postoperative risk factors were analysed in a Cox proportional hazards model. RESULT: The patency was significantly better for vein grafts in comparison to composite grafts and prosthetic grafts. It was 74% for vein, 46% for composite and 43% for prosthetic reconstructions, respectively, at 12 months after arterial reconstruction. The cumulative life table patency rate in extremities with good, intermediate and poor runoff was 62, 30 and 10%, respectively at 36 months. The patency rates for extremities operated on for claudication was significantly better than for extremities operated on for critical ischaemia. The multivariate analysis of different factors in a Cox analysis revealed that only the status of distal runoff, the graft material and the site of the distal anastomosis independently and significantly influenced the patency rates. CONCLUSIONS: A new model for evaluation of distal runoff proved to predict the patency rate of femoropopliteal and femorodistal arterial reconstructions reasonably well in this retrospective analysis.

Aged↗
PubMed2000

A prolonged spinal cord ischaemia model in pigs. Passive shunting offers stable central haemodynamics during aortic occlusion.

OBJECTIVES: to evaluate the effect of a modified aortic shunt on central haemodynamic variables during experimental thoracic aortic occlusion in a prolonged spinal cord ischaemia model. MATERIAL AND METHODS: central haemodynamic variables were evaluated during aortic cross-clamping. In the shunt group (n=11), after the placement of proximal and distal aortic clamps, distal aortic perfusion was restored through an aortoiliac shunt via the left subclavian artery. In the no-shunt group (n=11), spinal cord ischaemia was achieved with only proximal aortic cross-clamping. The clamping time was 60 minutes in the shunt group and 30 minutes in the no-shunt group. RESULTS: in the no-shunt group, all animals needed inotropic support, vasodilators and buffers during the experiment. None of these drugs were needed in the shunt group. In the no-shunt group, cross-clamping caused a significant increase in mean arterial pressure and heart rate compared to baseline values. These variables were stable in the shunt group during aortic occlusion. In the reperfusion period cardiac output, heart rate and arterial pCO(2)were significantly higher in the no-shunt than in the shunt group. CONCLUSION: the present experimental spinal cord ischaemia model, using double aortic cross-clamping with shunt, offers improved central haemodynamics. This enables the study of prolonged selective spinal cord ischaemia without interaction from vasoactive drugs or systemic reperfusion.

Animals↗
PubMed2000

Relationship between intrathecal oxygen tension and ultrastructural changes in the spinal cord during experimental aortic clamping.

OBJECTIVES: To investigate spinal cord ultrastructure related to cerebrospinal fluid (CSF) oxygenation. DESIGN: experimental aortic occlusion model with intrathecal oxygen tension monitoring. MATERIALS AND METHODS: Two groups of pigs underwent proximal (P) or double (D) aortic occlusion for 30 min followed by 1 h of reperfusion. In a third group (I) segmental arteries distal to T3 were clamped for 90 min. A thin pO(2), pCO(2) and pH sensor was placed intrathecally for continuous monitoring of CSF. Spinal cord segments were studied by electron microscopy (EM). RESULTS: In group P, CSF-pO(2)rapidly decreased during clamping and major changes in pH and pCO(2)were seen. EM demonstrated neuronal degeneration with loss of cellular integrity and severe affection of organelles. In the group D, CSF oxygenation decreased to about half, but with only moderate changes in the metabolic parameters. Group I showed no significant changes in CSF measurements. The latter groups were similar at EM, showing only mild mitochondrial changes. CONCLUSIONS: The level of CSF oxygenation during aortic cross-clamping or segmental artery interruption seems to correlate with ultrastructural changes in the spinal cord. This online intrathecal monitoring technique may provide valuable information on spinal cord circulation during thoracoabdominal aortic surgery.

Animals↗
PubMed2000

A new method of intrathecal PO2, PCO2, and pH measurements for continuous monitoring of spinal cord ischemia during thoracic aortic clamping in pigs.

BACKGROUND: Impaired spinal cord circulation during thoracic aortic clamping may result in paraplegia. Reliable and fast responding methods for intraoperative monitoring are needed to facilitate the evaluation of protective measures and efficiency of revascularization. METHODS: In 11 pigs, a multiparameter PO2, PCO2, and pH sensor (Paratrend 7, Biomedical Sensors Ltd, United Kingdom) was introduced into the intrathecal space for continuous monitoring of cerebrospinal fluid (CSF) oxygenation during thoracic aortic cross-clamping (AXC) distal to the left subclavian artery. A laser-Doppler probe was inserted into the epidural space for simultaneous measurements of spinal cord flux. Registrations were made before and 30 minutes after clamping and 30 and 60 minutes after declamping. The same measuring points were used for systemic hemodynamic and metabolic data acquisition. RESULTS: The mean CSF PO2 readings of 41 mm Hg (5.5 kPa) at baseline decreased within 3 minutes to 5 mm Hg (0.7 kPa) during AXC (P < .01). Spinal cord flux measurement responded immediately in the same way to AXC. Both methods indicated normalization of circulation during declamping. Significant (P < .01) changes were also observed in the CSF metabolic parameters PCO2 and pH. CONCLUSIONS: In this experimental model of spinal ischemia by AXC, online monitoring of intrathecal PO2, PCO2, and pH showed significant changes and correlated well with epidural laser-Doppler flowmetry (P < .01).

Animals↗
PubMed2000

Anastomotic rupture at the site of polytetrafluoroethylene (PTFE) and distal vein cuff of femoropopliteal bypass. Two case reports.

Two female patients, 63 and 78 years of age, underwent femoropopliteal bypass with polytetrafluoroethylene (PTFE) graft and distal vein cuff. They developed graft occlusion due to false aneurysm at the site of vein cuff during one and eight weeks after surgery, respectively. Improper suture technique or weak vein wall might lead to suture disruption leading to false aneurysm as presented in this article.

Aged↗
PubMed1999

Metronidazole resistance in the protozoan parasite Entamoeba histolytica is associated with increased expression of iron-containing superoxide dismutase and peroxiredoxin and decreased expression of ferredoxin 1 and flavin reductase.

To obtain insight into the mechanism of metronidazole resistance in the protozoan parasite Entamoeba histolytica, amoeba trophozoites were selected in vitro by stepwise exposures to increasing amounts of metronidazole, starting with sublethal doses of 4 microM. Subsequently, amoebae made resistant were able to continuously multiply in the presence of a 40 microM concentration of the drug. In contrast to mechanisms of metronidazole resistance in other protozoan parasites, resistant amoebae did not substantially down-regulate pyruvate:ferredoxin oxidoreductase or up-regulate P-glycoproteins, but exhibited increased expression of iron-containing superoxide dismutase (Fe-SOD) and peroxiredoxin and decreased expression of flavin reductase and ferredoxin 1. Episomal transfection and overexpression of the various antioxidant enzymes revealed significant reduction in susceptibility to metronidazole only in those cells overexpressing Fe-SOD. Reduction was highest in transfected cells simultaneously overexpressing Fe-SOD and peroxiredoxin. Although induced overexpression of Fe-SOD did not confer metronidazole resistance to the extent found in drug-selected cells, transfected cells quickly adapted to constant exposures of otherwise lethal metronidazole concentrations. Moreover, metronidazole selection of transfected amoebae favored retention of the Fe-SOD-containing plasmid. These results strongly suggest that peroxiredoxin and, in particular, Fe-SOD together with ferredoxin 1 are important components involved in the mechanism of metronidazole resistance in E. histolytica.

Animals↗
PubMed1999

Cell wall of Thermoanaerobacterium thermosulfurigenes EM1: isolation of its components and attachment of the xylanase XynA.

Thermoanaerobacterium thermosulfurigenes EM1 has a gram-positive type cell wall completely covered by a surface layer (S-layer) with hexagonal lattice symmetry. The components of the cell envelope were isolated, and the S-layer protein was purified and characterized. S-layer monomers assembled in vitro into sheets with the same hexagonal symmetry as in vivo. Monosaccharide analysis revealed that the S-layer is associated with fucose, rhamnose, mannosamine, glucosamine, galactose, and glucose. The N-terminal 31 amino acid residues of the S-layer protein showed significant similarity to SLH (S-layer homology) domains found in S-layer proteins of different bacteria and in the exocellular enzymes pullulanase, polygalacturonate hydrolase, and xylanase of T. thermosulfurigenes EM1. The xylanase from T. thermosulfurigenes EM1 was copurified with the S-layer protein during isolation of cell wall components. Since SLH domains of some structural proteins have been shown to anchor these proteins noncovalently to the cell envelope, we propose a common anchoring mechanism for the S-layer protein and exocellular enzymes via their SLH domains in the peptidoglycan-containing layer of T. thermosulfurigenes EM1.

Amino Acid Sequence↗
PubMed1999

Primary sequence of a putative non-ATPase subunit of the 26S proteasome from Entamoeba histolytica is similar to the human and yeast S2 subunit.

The cDNA coding for a non-ATPase S2 subunit of the 26S proteasome from Entamoeba histolytica was cloned from a cDNA library (EhS2). The open reading frame has 2529 bp and the deduced amino acid sequence encodes a protein with a calculated molecular mass of 92,000 Da. EhS2 has 29-35% identity with the three other known S2 subunit sequences of yeasts and humans.

Amino Acid Sequence↗
PubMed1999

Prospective randomized multicentre study of laparoscopic versus open appendicectomy.

BACKGROUND: A prospective randomized multicentre study was performed to compare the outcome of laparoscopic and open appendicectomy in patients with suspected acute appendicitis. METHODS: A total of 523 patients was randomized, but because of 23 withdrawals the outcome in 500 patients is reported, 244 in the laparoscopic group and 256 in the open group. RESULTS: Patients having laparoscopic appendicectomy recovered more quickly than those having open surgery (13 versus 21 days, P < 0.001). There was no significant difference in duration of sick leave after operation (laparoscopic group 11 days versus open group 14 days). Postoperative pain (at 24 h, 7 days and 14 days) was less after laparoscopic operations and a functional index 1 week after operation was more favourable in these patients (P < 0.001). Operating time was significantly longer in the laparoscopic group (60 versus 35 min, P < 0.01). Hospital stay and complications did not differ between the groups. Thirty laparoscopic procedures (12 per cent) were converted to open appendicectomy. CONCLUSION: Laparoscopic appendicectomy is as safe as open appendicectomy and has the advantage of allowing a quicker recovery.

Acute Disease↗
PubMed1991

Red cell trapping and postischemic renal blood flow. Differences between the cortex, outer and inner medulla.

The distribution of blood flow in the rat kidney after 60 minutes of renal ischemia was studied by single-fiber laser-Doppler flowmetry. Blood flow in superficial cortex and inner medulla was measured with a probe directed towards the kidney surface and exposed papilla, respectively. Outer medullary blood flow was measured with a probe introduced through the renal core. After ischemia the blood flow decreased to 60% of the preischemic value (P less than 0.01) in superficial cortex and to 16% (P less than 0.01) in outer medulla, while inner medullary blood flow increased paradoxically to 125% (P less than 0.01). There was extensive trapping of red blood cells (RBC) in the outer medulla, but not in the inner medulla or cortex. The fractional RBC volume as measured by radiolabeled RBCs was 21% in the inner stripe of the outer medulla, but 2% in this area in a normal kidney. To investigate the influence of RBC trapping on intrarenal distribution of blood flow after ischemia, the hematocrit was reduced from 46% to 31% by isovolemic hemodilution. When performed before ischemia, this maneuver almost completely abolished RBC trapping. In this group blood flow in both outer and inner medulla was almost unchanged after ischemia, while superficial cortical blood flow decreased to 66% (P less than 0.01) of the pre-ischemic value. It is concluded that RBC trapping in the outer medulla causes a large decrease in blood flow in this area and, at the same time, shunting of blood to the inner medulla. In the absence of RBC trapping, blood flow of both outer and inner medulla is well preserved after ischemia.

Animals↗
PubMedDate not supplied

The role of duplex scanning in the selection of patients with critical lower-limb ischemia for infrainguinal percutaneous transluminal angioplasty.

PURPOSE: To investigate the role of duplex scanning in the selection of patients with critical lower-limb ischemia (CLI) for infrainguinal percutaneous transluminal angioplasty (PTA). METHODS: One hundred and sixty-two limbs with CLI (150 patients) that underwent duplex scanning within 3 months prior to conventional diagnostic angiography (n = 88) or infrainguinal PTA (n = 74) were retrospectively studied. The findings obtained from duplex scanning and angiography were analyzed in a masked fashion by two different investigators. RESULTS: The accuracy, sensitivity, specificity, and negative and positive predictive values of duplex scanning in the selection of patients for infrainguinal PTA were 86%, 84%, 89%, 86%, and 87% respectively. Forty-two procedures (57%) were performed at multiple arterial segments. The accuracy of duplex scanning in the selection of femoropopliteal and crural lesions for PTA was over 85%. However, the sensitivity of duplex scanning in the selection of popliteal and crural lesions for PTA was 49% and 38% respectively, compared with 80% for superior femoral artery lesions. In 39% of patients who were correctly selected for PTA, duplex scanning misdiagnosed one of the multiple lesions treated by PTA. CONCLUSION: Duplex scanning can safely be used for the selection of patients for infrainguinal PTA. The sensitivity of duplex scanning in the selection of lesions for PTA was less satisfactory in the popliteal and crural arteries compared with the femoropopliteal arteries.

Acute Disease↗
PubMedDate not supplied

The influence of distal runoff on patency of infrainguinal vein bypass grafts.

This retrospective study was conducted to analyze a new concept of evaluation of the effect of distal runoff on patency in infrainguinal bypass surgery for arterial insufficiency. Distal runoff was evaluated on postreconstruction angiograms in 191 limbs undergoing femoropopliteal and femorodistal reconstruction. Runoff was characterized as good, fair, or poor. Determination of graft patency was made by clinical examination, ankle-brachial index measurement, or duplex scanning at 1 month and thereafter at 6-month intervals. Cumulative patency rates were calculated according to the actuarial life table method. Patency rates in limbs with good runoff were better than in limbs with fair and poor runoff; at 6 months, patency rates were 88.2%, 70.9%, and 21.8%, respectively (p < 0.01). Similar patency rates were found for good runoff in femoropopliteal and femorodistal reconstructions (84.7% in femoropopliteal and 75% in femorodistal reconstructions) at 6 months. The authors conclude that this method of angiographic evaluation accurately predicts patency in infrainguinal bypass reconstructions.

Adult↗
PubMedDate not supplied

Selection of patients with lower limb arterial occlusive disease for endovascular treatment of the iliac arteries with duplex scanning.

The aim of this study was to evaluate the role of duplex scanning in selection of patients with lower limb arterial occlusive disease for endovascular treatment of the iliac arteries. From January 1995 through May 2000, 183 patients having chronic lower limb arterial insufficiency who underwent duplex scanning of the lower extremity arteries with available aortoiliac scans within 3 months before conventional aortoiliac diagnostic angiography and/or endovascular intervention of the iliac arteries were studied retrospectively. The findings obtained from duplex scanning and angiography were analyzed in a blinded manner by 2 investigators. Limbs having category 1, 2, and 3 lesions according to duplex scan findings were interpreted as being suitable for endovascular intervention. The comparison between duplex scan findings and angiography was analyzed by the third investigator. During 93 percutaneous transluminal angioplasty (PTA) procedures, 133 arterial segments, common or external iliac, were dilated with stent placement in 70. Bilateral interventions were performed in 25 cases, and of 68 unilateral interventions, 57 were at only 1 arterial segment. The accuracy, sensitivity, specificity, and negative and positive predictive values of duplex scanning to appropriately categorize the iliac artery lesions into suitable or unsuitable for endovascular intervention were 90%, 95%, 83%, 90%, and 92%, respectively when the inconclusive duplex scans were excluded (11%). In 6 patients with lesions suitable for PTA according to duplex scanning and angiography, PTA was not performed owing to clinical reasons. The accuracy of duplex scanning in predicting the performance of endovascular intervention was 88%. It is concluded that iliac artery endovascular procedures in limbs with chronic occlusive disease can be reliably planned according to duplex scan findings.

Adult↗