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Biomedical subjects

E Sim

Publications and source records attributed to E Sim.

At least 127 records · Page 7Linked to original sources
PubMed1990

An optimal control model for maximum-height human jumping.

To understand how intermuscular control, inertial interactions among body segments, and musculotendon dynamics coordinate human movement, we have chosen to study maximum-height jumping. Because this activity presents a relatively unambiguous performance criterion, it fits well into the framework of optimal control theory. The human body is modeled as a four-segment, planar, articulated linkage, with adjacent links joined together by frictionless revolutes. Driving the skeletal system are eight musculotendon actuators, each muscle modeled as a three-element, lumped-parameter entity, in series with tendon. Tendon is assumed to be elastic, and its properties are defined by a stress-strain curve. The mechanical behavior of muscle is described by a Hill-type contractile element, including both series and parallel elasticity. Driving the musculotendon model is a first-order representation of excitation-contraction (activation) dynamics. The optimal control problem is to maximize the height reached by the center of mass of the body subject to body-segmental, musculotendon, and activation dynamics, a zero vertical ground reaction force at lift-off, and constraints which limit the magnitude of the incoming neural control signals to lie between zero (no excitation) and one (full excitation). A computational solution to this problem was found on the basis of a Mayne-Polak dynamic optimization algorithm. Qualitative comparisons between the predictions of the model and previously reported experimental findings indicate that the model reproduces the major features of a maximum-height squat jump (i.e. limb-segmental angular displacements, vertical and horizontal ground reaction forces, sequence of muscular activity, overall jump height, and final lift-off time).

Biomechanical Phenomena↗
PubMed1990

[Dislocation of the thumb saddle joint as a rare sports injury].

This report deals with 4 dislocations of the carpometacarpal joint of the thumb during the period 1957-1983 as an injury caused by sports. 3 dislocations could be found in boxing, one was caused by a fall from a horizontal bar. All of them were closed: two times the dislocation was to the dorsal, one to the dorso-ulnar and one to the dorso-radial side. Closed dislocations do not require operative treatment. Reduction and immobilisation for four weeks in a plaster splint with inclusion of the thumb were sufficient, recurrence of the dislocation did not occur. Correct bandage and the use of effective boxing gloves are of great importance.

Adolescent↗
PubMed1990

[Augmentation surgery of the anterior cruciate ligament using a carbon fiber band. Results of follow-up studies of 21 cases. I. (clinical aspects)].

Clinic and radiological follow-ups after implanting unidirectional carbon fibres in 21 cases (17 recent traumas, 1 older trauma and 3 chronic instabilities) approximately 34 months after operation. With the recent traumas we only found intraligamental ruptures or longitudinal fraying with ruptures of the femoral or tibial insertion. Postoperative plaster cast fixation for 6 weeks. Stability was examined by the "Arthrostress" (19 kp). In 11 cases no instability of clinical importance could be found, in 6 cases there was a +, in 3 cases a ++ and in 1 case a 3-plus instability.

Adolescent↗
PubMed1990

[Results of magnetic resonance and computerized tomography studies of augmentation plastic surgery of the anterior cruciate ligament using carbon fibers. II].

19 patients out of those described in part I were examined by MRI and CT. We quote MRI as an excellent new mean of imaging without exposure to ionising radiation which renders sufficient information about the internal knee-structures without surgical invasion. The signal density for the neoligament as well intraarticular as in the "over the top"-position gives evidence for the ingrowth of mesenchymal structures. The MRI diagnosis was proved by histological examination in 2 cases. Very good correspondence between clinic examination and the CT-images could be found. On top of that the tibial drilling holes could be shown in an excellent way. The CT-scan is a fine instrument to judge the postoperative state of the anterior cruciate ligament. The density measurement inside and outside the bone gives evidence for mesenchymal growth inside the carbon fibre structure and the existence of a new natural ligament.

Anterior Cruciate Ligament↗
PubMed1990

[Femoral fractures in osteodystrophy deformans (Paget's disease). Treatment results].

Between 1958 and 1986 21 fractures of the femur in Osteodystrophia deformans (Paget's disease) were treated at the accident hospital Meidling; of these 13 patients were female and 8 of male. The average age was 73.4 years. In two cases the basic illness was known, in 19 cases the fracture was the first manifestation of the illness. In 7 cases a polyostotic manifestation was evident. The fractures were localized as follows: 7 in the proximal, 7 in the middle, 1 in the distal third of the shaft, 5 subtrochanteric, 1 supracondylar. Apart from one subtrochanteric torsion fracture, all were flexure fractures without splinters. 19 fractures were stabilized by an operation: 17 by intramedullary nailing (with cerclage), 1 steep plate, 1 Ender nail. One case was treated by an extension, whereas in one case no operation was performed. The following complications were observed: one fracture of the steep plate, one delayed healing of the fracture after intramedullary nailing. No infections could be observed. In general, healing of the fracture in Osteodystrophia deformans does not seem to be delayed. The different possibilities of intramedullary nailing of the femur - possibly together with osteotomies to eliminate curvature - can be recommended for fractures in Osteodystrophia deformans.

Adult↗
PubMed1990

[Indications for and technic in the surgical treatment of tibial shaft fractures with open epiphyseal grooves. A report of 63 cases].

The documentation relating to 63 surgically treated fractures sustained to the shaft of the tibia while epiphyseal growth plates were still in evidence (9 in isolation, 54 as fractures of the lower leg) between 1958 and 1983 was examined with respect to indications for the operation and the method selected. The average age of the patients was 12.9 years. There were 41 closed fractures and 22 open fractures varying in the degree of severity. Bending fractures predominated, with 42 cases, while the other 21 were spiral fractures. The causes were as follow: 32 traffic accidents, 28 sports accidents and 3 of other kinds. Stabilization was achieved either exclusively by wiring of the medulla or cerclage, or by a combination of both methods. Postoperative immobilization was ensured by means of a thigh cast for an average of 12 weeks. In 2 cases, intramedullary nailing was performed. The osteosynthetic material was removed early. Serious complications recorded were infection observed in 2 cases in connection with open fractures. Osseous union occurred in all fractures; no pseudarthroses developed. Absolute surgical indications, in our opinion, are third-degree open fractures, malreduction or instability of second- and first-degree open fractures, secondary dislocations after conservative initial treatment, soft-tissue damage and interposition. Relative indications are first and second-degree open fractures of the tibia and multiple trauma. Pathologic fractures were not considered in the follow up study, in which only 18 patients were examined: their average age was 13.7 (11-16) years.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Inhibition of the covalent binding reaction of complement component C4 by penicillamine, an anti-rheumatic agent.

D(-)-Penicillamine [D(-)-beta beta-dimethylcysteine] is an anti-arthritic drug, but its use is limited by adverse side effects, which include problems in immune-complex clearance. Complement is important as a source of inflammatory mediators in rheumatoid arthritis and is also involved in immune-complex clearance. Thus inhibition of the complement cascade would be likely to contribute to both the therapeutic and the toxic effects of penicillamine. It is shown that penicillamine and cysteine are potent inhibitors of the covalent binding of activated complement component C4 to immune complexes. [35S]Cysteine itself becomes covalently bound to C4b through the thioester site. Penicillamine and cysteine are more reactive with the C4A isotype than with the C4B isotype of the HLA class III protein C4. The limited amino acid sequence differences between C4A and C4B include a cysteine/serine interchange, and it is suggested that the cysteine residue in C4A contributes to the increased rate of reaction of C4A with the alpha-amino-beta-thiol compounds.

Anaphylatoxins↗
PubMed1989

The epidemiology of the acute flank pain syndrome from suprofen.

Suprofen, a new nonsteroidal anti-inflammatory drug, was marketed in early 1986 as an analgesic agent. Until physicians began reporting an unusual acute flank pain syndrome to the spontaneous reporting system, 700,000 persons used the drug in the United States. Through August 1986, a total of 163 cases of this syndrome were reported. To elucidate the epidemiology of the syndrome, a case-control study was performed, comparing 62 of the case patients who had been reported to the spontaneous reporting system to 185 suprofen-exposed control subjects who did not have the syndrome. Case patients were more likely to be men (odds ratio, 3.8; 95% confidence interval, 1.2-12.1), suffer from hay fever and asthma (odds ratio, 3.4; 95% confidence interval, 1.0-11.9); to participate in regular exercise (odds ratio, 5.9; 95% confidence interval, 1.1-30.7), especially in the use of Nautilus equipment (p = 0.02); and to use alcohol (odds ratio, 4.4; 95% confidence interval, 1.1-17.5). Possible risk factors included young age, concurrent use of other analgesic agents (especially ibuprofen), preexisting renal disease, a history of kidney stones, a history of gout, a recent increase in activity, a recent increase in sun exposure, and residence in the Sunbelt. These were findings that were suggestive but did not reach conventional statistical significance. These findings are consistent with the postulated mechanism for this unusual syndrome: acute diffuse crystallization of uric acid in renal tubules.

Acute Kidney Injury↗
PubMed1989

Size polymorphism of the erythrocyte complement receptor type 1 (CR1) in systemic lupus erythematosus induced by hydralazine.

The human erythrocyte complement receptor type 1 (CR1) is polymorphic with respect to molecular weight. Size variants with molecular weights of 190,000 (type A), 220,000 (type B) and 160,000 (type C) daltons have been detected in normal individuals (22 individuals), patients with hydralazine (Hz) lupus (n = 27), a group of Hz controls (n = 30) and the relatives of both Hz groups (27 and 11 individuals, respectively). The method of detection was SDS-polyacrylamide gel electrophoresis of erythrocyte membranes on low-percentage cross-linked gels followed by Western blotting using polyclonal rabbit anti-CR1 antibodies. In normal individuals, 77% had the A allotype and 26% carried the B allotype; amongst Hz lupus patients 67% carried the A allotype, 31% carried the B allotype, and 3% (1 individual) had the C allotype. Amongst the patients who had been on Hz but did not develop SLE, 83% carried the A allotype and 17% carried the B allotype. The AA phenotype was only found in 44% of Hz SLE patients but in 64% of normals and 70% of the Hz control group. Although not statistically significant, the results indicate a relative underrepresentation of the AA phenotype in patients with Hz-induced SLE. In addition, an equal or greater relative amount of the C allotype was detected in an Hz SLE patient with the AC phenotype. This is in contrast to lower relative amounts of the C allotype found in normal individuals with this phenotype.

Erythrocyte Membrane↗
PubMed1989

Drug-induced immune-complex disease.

A range of drugs including hydralazine, isoniazid, procainamide and penicillamine cause toxic side effects which resemble systemic lupus erythematosus (SLE). Deficiencies of C1, C4 and C2 are associated with idiopathic SLE, and these defects may compromise the ability of the patient to deal with immune complexes. Immune complexes with protein as antigen, such as has been reported to be diagnostic of procainamide-induced SLE, interact more with the C4A isotype of C4 than the C4B isotype. It is shown that hydralazine, isoniazid and penicillamine inhibit the covalent binding of C4 to a complement-activating surface and that the drugs themselves become covalently bound to C4. For each of these drugs, C4A is inhibited more than C4B, and it is suggested that this is an important contributory factor in the development of the toxic side effects to these drugs involving immune-complex deposition. For procainamide, it is shown that the hydroxylamine metabolite rather than the drug itself inhibits the covalent binding reaction of C4. Hydralazine, isoniazid and procainamide are metabolised by the polymorphic N-acetyltransferase, and slow acetylators are at increased risk of drug-induced lupus. For procainamide, oxidation to the hydroxylamine form is an alternative metabolic route of increased importance in slow acetylators, and it is suggested that investigation of C4 type in susceptible patients could provide a means of identifying those at greatest risk of immunotoxicity.

Humans↗
PubMed1989

CR1 polymorphism in hydralazine-induced systemic lupus erythematosus: DNA restriction fragment length polymorphism.

The contribution of genetic factors in the reduction in erythrocyte CR1 levels observed in hydralazine (Hz) induced systemic lupus erythematosus (SLE) was investigated by determining the frequency of a HindIII restriction fragment length polymorphism (RFLP) in the CR1 gene. This RFLP is associated with quantitative erythrocyte CR1 expression. Individuals who have developed SLE as a reaction to Hz therapy, consanguinous relatives of the Hz-SLE patients, controls who had been treated with Hz without any adverse reaction, and the consanguinous relatives of these controls were included in this study. No difference was found in the frequency of occurrence of the alleles associated with CR1 expression between the Hz-SLE patients and the control groups (P greater than 0.2). Individuals from the Hz-SLE group who were homozygous for the 7.4 kb 'high expressor' allele had lower mean levels of erythrocytes CR1 (564 +/- 65) than the corresponding homozygous subgroups within the Hz-SLE relative group (774 +/- 46), the Hz control group (756 +/- 80) and the Hz control relatives group (825 +/- 66). In addition, 50% of the Hz-SLE patients in the 'high expressor' subgroup who had less than 500 CR1 per erythrocyte had elevated levels of circulating immune complexes. This study suggests that individuals who are genetically low expressors of erythrocyte CR1 are not predisposed to developing SLE in response to Hz therapy, and that in a subgroup of genetically 'high expressors', low CR1 levels are associated with elevated levels of circulatory immune complexes.

Alleles↗
PubMed1989

[Osteopoikilosis--fracture healing].

Between 1956 and 1988 five cases of osteopoikilosis have been observed. All cases were found by chance. In two cases there were fractures: one of the femur shaft, which has been stabilized by intramedullary nailing, one of the fifth metacarpal bone which has been treated conservatively. In both cases no delay of bony union could be observed. Osteopoikilosis- as a mesenchymal lesion--seems to have no negative influence on fracture healing.

Bone and Bones↗
PubMed1989

[Dislocations of the carpometacarpal joint of the thumb--results of follow-up].

This report deals with twenty-nine dislocations of the carpometacarpal joint of the thumb--twenty-five closed and four compound dislocations, three of which were part of complex injuries of the hand--treated during the period 1957 to 1983. The closed dislocations comprised eighteen dorsal, three dorsal-ulnar, two dorsal-radial, one palmar, and one palmar-ulnar. The compound dislocations comprised one radial (isolated), one palmar-radial, one dorsal-radial, and one palmar-ulnar; the last three occurring together with complex injuries. Eleven patients were followed up after an average period of about eleven years. Closed dislocations including those with minor tears of ligaments and/or the joint capsule do not require operative treatment. Reduction and immobilization for four weeks in a plaster splint with inclusion of the thumb were sufficient; recurrence of the dislocations did not occur. The compound dislocations required temporary transarticular Kirschner wire fixation as the ligament and the capsule were completely torn.

Adolescent↗
PubMed1989

[Comparison of the value of magnetic resonance tomography and computerized tomography in the follow-up of augmentation-plasties with carbon fiber ligaments of the anterior cruciate ligament].

17 patients--treated with unidirectional carbon-fibre-ligaments augmentation for the anterior cruciate ligament--have been followed-up by MRI and CT. The question has been, whether both methods show comparable results. The interval between operation and follow-up has been 34 months in average (43 to 30). Significance was put on the probants bedding. MR-Imaging in two planes seems to be essential to show the artificial ligament's integrity in its extraarticular "over the top"-position. Satisfying corresponding results could be found in MRI and CT.

Adolescent↗
PubMed1988

Metabolites of procainamide and practolol inhibit complement components C3 and C4.

Drug-induced systemic lupus erythematosus arises from toxic side-effects of administration of hydralazine, isoniazid, procainamide and practolol. Hydralazine and isoniazid are nucleophilic drugs and inhibit the covalent binding reaction of complement components, C3 and C4, an effect likely to lead to deposition of immune complexes (a feature of systemic lupus erythematosus). Procainamide and practolol do not themselves inhibit C3 and C4. A range of metabolites and putative metabolites of procainamide and practolol were synthesized, and tested for their ability to inhibit the covalent binding reactions of C3 and C4. The highly nucleophilic hydroxylamine metabolite of procainamide was strongly inhibitory in both tests, as was a putative hydroxylamine metabolite of practolol. These studies indicate a potential role for the hydroxylamine metabolites in mediating the toxic side-effects of procainamide and practolol, and emphasize the need for adequate measurements of hydroxylamine metabolites in human tissue.

Acecainide↗