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Biomedical subjects

M Ries

Publications and source records attributed to M Ries.

At least 37 records · Page 2Linked to original sources
PubMed2000

Differences between neonates and adults in the urokinase-plasminogen activator (u-PA) pathway of the fibrinolytic system.

This study deals with plasminogen activation kinetics of fetal and adult Glu-plasminogen types 1 and 2 as well as fetal and adult Lys-plasminogen by urokinase in the presence and absence of the lysine analogues epsilon-amino-n-caproic acid (EACA) and tranexamic acid. In addition, activation kinetics of single-chain urokinase-plasminogen activator (scu-PA) by adult and fetal plasmin types were investigated in the absence and presence of soluble fibrin. All Lys-plasminogen isoforms were more readily activated by urokinase than their corresponding Glu-plasminogen types. No substantial differences of the catalytic constants of urokinase-catalyzed plasminogen activation could be obtained when all fetal plasminogen types were compared to the respective adult types. In the case of all Glu-plasminogen isoforms, EACA as well as tranexamic acid first stimulated the activation process and, at higher concentrations, showed inhibitory properties. Again, the relative ability of all fetal plasminogen types to interact with lysine analogues revealed no differences compared to the respective adult glycoforms. In the absence of soluble fibrin, the catalytic efficiency of scu-PA activation by plasmin was significantly lower for both fetal plasmin isoforms. However, there were no differences in catalytic efficiency between fetal and adult plasmin types in the presence of 4 microM soluble fibrin. In conclusion, no substantial differences exist in urokinase-catalyzed plasminogen activation between neonates and adults, which is in contrast to reported data on plasminogen activation by tissue-type plasminogen activator. In the absence of soluble fibrin, scu-PA activation by fetal plasmin is markedly slower than by adult plasmin. However, this is compensated when fibrin is added at a concentration that is close to the physiological fibrinogen concentration in plasma. It can be summarized that the differences in carbohydrate structures of fetal and adult plasminogen are not associated with major differences in the global function of this part of fibrinolysis, despite functional alterations of scu-PA activation.

Adult↗
PubMed2000

Fluid sorption of orthopedic grade ultrahigh molecular weight polyethylene in a serum environment is affected by the surface area and sterilization method.

It is shown in this work that lubricant sorption in ultrahigh molecular weight polyethylene (UHMWPE) increases with available surface area of the component. This has clinical relevance, because sliding and articulation experienced in simulator studies can result in changes in surface roughness and the creation of new surfaces. This study compares the fluid sorption of orthopedic grade UHMWPE with different surface areas (but equivalent volume) for different sterilization methods. For both the gamma radiation and nonsterile control samples, the gain in total fluid absorbed scaled proportionately with surface area. For the EtO sterilization treatment, the fluid gain was nonlinear and substantially less than the radiated and control groups. The findings from this study clearly indicate that the sterilization and surface area affect the fluid uptake and weight gain of UHMWPE.

Adsorption↗
PubMed2000

Diffusion tensor MRI of the spinal cord.

Apparent diffusion tensor (ADT) measurements on the spinal cord using a pulsed-field-gradient (PFG) multi-shot echo-planar imaging (EPI) sequence are presented. In a study of 10 healthy volunteers, the obtained rotationally invariant anisotropy information is compared to the results obtained by the rotationally dependent methods. The water diffusivity in the direction parallel to the fibers was found to be almost 2.5 times higher than the average diffusivity in directions perpendicular to the fibers and showed cylindrically symmetric anisotropy characteristics. The influence of partial volume effects and the point spread function on the measured results was evaluated, and it was the concluded that a resolution of 1 mm in the read and phase directions is required to obtain unbiased values. Possible clinical implications were demonstrated by investigating the diffusion characteristics of 10 patients suffering from narrowing of the cervical canal. The changes in the diffusion characteristics were found to be large enough to allow a robust detection of diffusion changes in the spine, even in cases in which conventional T(2) and T(1) weighted images were unable to detect any lesion.

Anisotropy↗
PubMed2000

Fracture and fatigue properties of acrylic bone cement: the effects of mixing method, sterilization treatment, and molecular weight.

The purpose of this study was to characterize the relative and combined effects of sterilization, molecular weight, and mixing method on the fracture and fatigue performance of acrylic bone cement. Palacos R brand bone cement powder was sterilized using ethylene oxide gas (EtO) or gamma irradiation. Nonsterile material was used as a control. Molecular weights of the bone-cement powders and cured cements were measured using gel permeation chromatography. Hand and vacuum mixing were employed to mold single edge-notched bend specimens for fracture toughness testing. Molded dog-bone specimens were used for fatigue tests. Electron microscopy was used to study fracture mechanisms. Analysis of variance and Student t-tests were used to compare fracture and fatigue performance between sterilization and mixing groups. Our results indicate that vacuum mixing improved significantly the fracture and fatigue resistance (P<.05, P<.07) over hand mixing in radiation-sterilized and EtO-sterilized groups. In vacuum-mixed cement, the degradation in molecular weight resulting from gamma irradiation decreased fracture resistance significantly when compared with EtO sterilization and control (P<.05). A corresponding decrease in fatigue resistance was observed in the cement that was degraded severely by a radiation dose of 10 MRad (P<.05). In contrast, EtO sterilization did not result in a significantly different fracture resistance when compared with unsterilized controls for vacuum-mixed cement (P>.1). For hand-mixed cement, fracture and fatigue resistance appeared to be independent of sterilization method. This independence is believed to be the result of higher porosity that compromised the mechanical properties and obscures any effect of sterilization. Our results indicate that a combination of nonionizing sterilization and vacuum mixing resulted in the best mechanical performance and is most likely to contribute to enhanced longevity in vivo.

Animals↗
PubMed2000

First Croatian auditory brainstem implantation.

A deaf female patient was diagnosed with bilateral acoustic neurinomas. Diagnosis incorporated the standard audiological battery for sensorineural hearing loss, computed tomography and magnetic resonance imaging. The left side had been operated on four years previously in another clinic using the suboccipital approach. The auditory brainstem implant surgery was performed on the 'second side' using the same approach. It was an uneventful operation with good anatomy and no serious post-operative complications. Post-operatively, the patient performed exceptionally well, with up to 50 per cent of words recognized in the opened set and 85 per cent in the closed set, both without lip-reading.

Adult↗
PubMed2000

Hemostatic changes following the modified Fontan operation (total cavopulmonary connection).

Thromboembolism is a serious complication after Fontan operation, which may be caused by alterations of the coagulation system. We therefore investigated pro- and anticoagulant factors in 20 patients aged 4 to 21 years, 4 to 63 months following total cavopulmonary connection. Furthermore we compared markers of thrombin activation and fibrinolysis and in vitro clotting and clot-lysis to age-matched healthy subjects. Compared to results of age-matched controls, the Fontan operated individuals had significant decreases in levels of protein C (0.88 U/ml in controls, 0.67 U/ml in patients; p <0.001) and protein S (1.05 in controls, 0.93 U/ml in patients; p <0.05). Moreover, half of the patients had high values of FVIII (>1.5 IU/ml), which are associated with an increased thrombotic risk. These changes may result in enhanced generation of thrombin and plasmin, indicated by our finding of increased thrombin-antithrombin III (TAT) and plasmin-antiplasmin (PAP) levels and a similar trend in prothrombin fragments F1+2. Clot lysis tests, global coagulation tests, red blood cell count, liver enzymes AST, ALT, but not GGT, were generally within the normal ranges.

Adolescent↗
PubMed2000

Paravertebral and intraspinal malposition of transfemoral central venous catheters in newborns.

We report permanent tetraplegia in a newborn resulting from intraspinal malposition of a transfemoral catheter. In 2 other neonates paravertebral malposition of indwelling Silastic lines was detected. We suggest that left-sided transfemoral catheterization and conditions enhancing collateral flow through the vertebrolumbar pathway may predispose to inadvertent paravertebral catheter placement.

Catheterization, Central Venous↗
PubMed1999

Emergency correction of coagulation for mitral valve replacement in an orally anticoagulated 17-year-old patient with pronounced hepatic dysfunction.

A 17-year-old patient with Shone's disease had to be readmitted to the hospital 3 months after implantation of an artificial aortic valve because of extreme mitral insufficiency with consecutive pulmonary edema and hepatic dysfunction. He had been orally anticoagulated and presented with a high international normalized ratio of 6.7. Emergency replacement of the mitral valve was possible only after administration of prothrombin-complex concentrate, as vitamin K(1) and fresh frozen plasma did not correct the hemostatic defect sufficiently.

Adolescent↗
PubMed1999

Rapid development of hydrops fetalis in the donor twin following death of the recipient twin in twin-twin transfusion syndrome.

Intrauterine death of one fetus in monochorionic twinning is associated with high rates of perinatal morbidity and mortality in the surviving fetus. Subsequent development of hydrops fetalis in the donor twin after fetal demise of the recipient twin has been described in only two case reports and pathophysiology remains unclear. We report on a monochorionic-diamniotic twin pregnancy complicated by severe twin-twin transfusion syndrome. Ultrasound examination at 20 weeks of gestation showed discrepant twins with oligohydramnios in the smaller twins' sac and polyhydramnios in that of the larger twin. Repeated amniocenteses permitted prolongation of the pregnancy. However, the recipient twin developed deteriorating hydrops fetalis and died at 28 weeks of gestation. After this event, subsequent development of hydrops fetalis in the surviving donor twin could be observed, as well as an increase of amniotic fluid. An elective cesarean section was performed at 29 weeks of gestation. Initial hypoxemia could be effectively treated by high frequency oscillatory ventilation, surfactant therapy and inotropic support. The infant was discharged in good condition at the age of 2 months. Although rare, antenatal demise of the recipient twin in a monochorionic pregnancy can be associated with the subsequent development of hydrops fetalis in the surviving donor twin. We speculate that this phenomenon is due to ischemia-reperfusion injury of the previously poorly perfused twin.

Adult↗
PubMed1999

Thrombolysis in newborns and infants.

This review analyses literature reports from 1970 to 1998 assessing the use of streptokinase (SK), urokinase (UK) or recombinant tissue-type plasminogen activator (rt-PA) for thrombolytic therapy in neonates and infants. From 1970 to 1998 182 infants were reported to have received SK (n = 54; 29.5%), UK (n = 41; 22.5%) or rt-PA (n = 87; 48%). During thrombolytic therapy no concomitant heparin administration or low dose heparin therapy (5 U/kg/h) were recorded. To perform reocclusion prophylactics heparin was reinitiated at the end of thrombolytic therapy usually in the recommended dosage of 20 U/ kg/h. The overall thrombolytic patency rate in neonates varied from 39% to 86%. Besides bleeding from local puncture sites or recent catheterisation sites (10.4%), pulmonary embolism was reported in 1.1% of the 182 infants. Major bleeding complications, i.e. pulmonary bleeding (0.6%), gastrointestinal bleeding (0.6%) or intraventricular haemorrhage (IVH 2.7%) are rarely reported side effects and only 2 thrombolysis related deaths due to haemorrhage were mentioned. Bleedings reported in the central nervous system (n = 4) mainly occurred in preterm infants (n = 3). In conclusion, data of this preliminary analysis suggest that there is no big difference (p = 0.09; chi2-test) in the efficacy rate between the 3 thrombolytic agents used in the first year of life. In each case an assessment must be made with respect to the relative benefit conferred by thrombolytic therapy in preventing organ or limb damage versus the potential side effects, costs and inconvenience for the childhood patient. Controlled prospective multicentre studies on thrombolytic therapy in neonates and infants are recommended to evaluate patency rates and adverse effects for the different thrombolytic agents used.

Child, Preschool↗
PubMed1998

Whole blood clot lysis in newborns and adults after adding different concentrations of recombinant tissue plasminogen activator (Rt-PA).

Optimal treatment of newborns with thromboembolic complications likely differs from that for adults because of ontogenetic features of both coagulation and fibrinolysis that affect the thrombotic processes and the response to thrombolytic agents. Although there are data on plasma clot lysis in newborns, the potential for dissolution of whole blood clots has not been explored. We investigated whether there is a difference between newborns and adults in sensitivity of whole blood clots to lysis with recombinant tissue plasminogen activator (rt-PA). Blood was obtained from 15 newborns and from 13 adults and anticoagulated with sodium citrate. Whole blood clots were generated by addition of thrombin and calcium. After 3 hours of retraction the clots were put into tubes containing 1.45 mL plasma of the same patient. After 1 hour of incubation, rt-PA was added to result in final concentrations of 3, 1, 0.3, 0.1, and 0 microg/mL. Clots were weighed after 0.5, 1, 2, and 3 hours. At any time point measured, whole blood clot lysis was more efficient in newborns than it was in adults. This was true for spontaneous clot lysis (p <0.05 at 1, 2, and 3 hours) as well as for all concentrations of rt-PA tested (p <0.05 at 1 hour). Whole blood clot lysis in new-borns was most efficient at 1 microg/mL rt-PA, whereas adults showed best lysis at the highest concentration tested (3 microg/mL rt-PA). The rate of plasminogen consumption was similar in newborns and adults. Recommendations for antithrombotic therapy in new-borns have been loosely extrapolated from recommendations for adults. Our data can be helpful in establishing guidelines for thrombolytic therapy in the neonatal period. Retracted whole blood clots mimic better the in vivo situation than previously reported in studies of lysis of nonretracted plasma clots. Based on our data, we think that despite low levels and slower activation kinetics of fetal plasminogen, the dosage of rt-PA should be lower in newborns than in adults.

Adult↗
PubMed1998

One-stage revision of periprosthetic fractures around loose cemented total hip arthroplasty.

Fourteen cases of femoral fracture occurring about a loose cemented proximal femoral prosthesis are presented. All fractures occurred with relatively minor trauma, and significant preinjury osteolysis was present in all cases. Treatment consisted of immediate surgical revision of the loose femoral component using a long-stem noncemented component in conjunction with cerclage wiring. In most instances, morselized bone graft was used. Strut grafts were used in seven cases to improve stability. Two patients with extensive bone loss were unable to support a prosthesis and were treated with whole femoral allografts. Follow-up ranged from 24 to 84 months (mean, 49 months), except for one patient lost to follow-up at 12 months; evaluations consisted of Harris hip scores and radiographic analysis for fracture healing and implant stability. All fractures healed, and patient function increased dramatically. Postoperative Harris hip scores increased to an average of 74 points. Complications consisted of one postoperative fracture and four patients with femoral component loosening. No cases of component loosening were seen in the five cases in which components were designed for distal stability (four fully porous-coated, one fluted). Of the seven cases relying on proximal stability, two cases of early loosening and two cases of late loosening occurred. We recommend revision with long-stem, cementless implants in conjunction with cerclage wiring and strut grafts for the treatment of femoral fractures about loose cemented hip prostheses. Implant stability distal to the fracture is emphasized.

Aged↗
PubMed1997

Age-related reference values for activation markers of the coagulation and fibrinolytic systems in children.

The physiology of the hemostatic system in infancy and childhood is different from that in adulthood. Despite differences in several components of the coagulation and fibrinolytic systems, there is no evidence that children are at greater risk for hemorrhagic or thrombotic problems compared with adults (1,2). Advances in understanding of the biochemistry of the hemostatic mechanism have led to the development of sensitive immunochemical methods for measuring peptides or enzyme-inhibitor complexes that are liberated with the activation of the coagulation and fibrinolytic systems in vivo (3). Activation markers of coagulation and fibrinolysis have been measured in newborns, infants and children with a variety of underlying disorders (4-16). However, reference ranges for children of different age groups have hitherto not been established. The aim of the present study was to document thrombin-antithrombin III-complex (TAT), prothrombin fragment 1 + 2 (F1 + 2), plasmin-alpha 2-antiplasmin-complex (PAP) and D-dimer in healthy children and to determine whether age-related differences can be demonstrated.

Adolescent↗