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Biomedical subjects

E Sim

Publications and source records attributed to E Sim.

At least 109 records · Page 6Linked to original sources
PubMed1992

[Spinal internal fixator--analysis of problems in 28 cases].

Problems encountered in the management of thoracolumbar and lumbar spinal fractures with the "fixateur interne" are reviewed. 28 patients were treated between 1986 and 1988. Retrospective analysis identified the following problems: a. Loosening of nuts at the longitudinal rod and/or clamp ends--b. Major corrosion defects of Schanz screws and clamps--c. Large implant volume--d. Non-availability of intermediate rod lengths. Earlier problems, i.e. the absence of an effective press-fit (transverse stabilizer) between the 2 longitudinal rods and the non-availability of a cutter for trimming the Schanz screws, have meanwhile been resolved. Loosening of the nuts at the clamp end may cause substantial loss of reduction and jeopardize the outcome of treatment. The problem of how to identify loosening, which is usually recognizable within 27 days, is discussed at length. Since loosening occurs irrespective of fracture type and site, instrumentation length, ancillary surgical procedures, type of postoperative care, preoperative neurological status and operating surgeon, it appears to be inherent in the system. Alterations in neighbouring vertebral segments attributable to rebundant rod lengths cannot altogether be excluded. The potential occurrence of corrosion defects should prompt implant removal after radiologically confirmed fracture healing.

Adult↗
PubMed1991

N-acetyltransferase polymorphism. Comparison of phenotype and genotype in humans.

N-Acetyltransferase (NAT) isoenzymes are encoded at two loci. One locus encodes an NAT which is expressed widely in tissues, does not vary amongst human individuals and is termed monomorphic NAT (mNAT). The second locus encodes an NAT which is termed polymorphic NAT (pNAT), has a distinct tissue distribution and is responsible for the difference in ability between individuals in acetylating certain arylamine (e.g. sulphamethazine) and hydrazine (e.g. isoniazid) drugs which are polymorphic substrates. We describe a simple DNA based method for genotyping individuals for pNAT. The 'fast' NAT allele (F1) and the three 'slow' alleles (S1, S2 and S3) can be distinguished by using PCR with oligonucleotide primers specific for pNAT followed by restriction enzyme digestion of the amplified product. Heterozygotes are easily identified. The genotype of individual Caucasians compares well with the extent of acetylation of sulphamethazine. The allele distribution of the Caucasian population described here differs from that reported after Southern blot analysis of a Japanese population (Deguchi et al., J Biol Chem 265: 12757-12760, 1990). The most frequent allele at the polymorphic nat locus in Caucasians, S1, is absent in the Japanese population. This difference between the two populations is likely to be the basis of the known interethnic variation in acetylator phenotype frequencies.

Acetylation↗
PubMed1991

Drug metabolising N-acetyltransferase activity in human cell lines.

Many arylamine and hydrazine drugs and xenobiotics are acetylated by N-acetyltransferase (NAT), a cytosolic enzymic activity which has a wide tissue distribution. Humans can be classified as either fast or slow acetylators on the basis of their ability to metabolise isoniazid or sulphamethazine. These are termed polymorphic substrates. The acetylation of other compounds does not vary amongst individuals, e.g., p-aminobenzoic acid, and are termed monomorphic substrates. NAT from human hepatic and non-hepatic tissues, viz., (i) liver, (ii) the hepatoma cell line HepG2, (iii) tonsil lymphocytes and (iv) the monocytic cell line U937 have been compared with respect to substrate specificity towards polymorphic and monomorphic substrates. The chromatographic and centrifugation behaviour of NAT from these sources has also been investigated. NAT from liver shows 2-fold greater activity towards sulphamethazine than towards p-aminobenzoic acid as substrate. All other cell types tested show at least 70-fold greater activity with p-aminobenzoic as substrate compared to sulphamethazine. NAT from HepG2 cells, U937 cells and tonsil lymphocytes migrates as a single peak during ion-exchange chromatography, whereas the liver NAT activity is separated into two peaks. NAT in HepG2 cells resembles extra-hepatic tissue NAT rather than NAT in liver. HepG2 cells do not therefore represent a good in vitro model for investigation of human metabolism of arylamines or hydrazines. The molecular weight of NAT from U937 cells has been determined by a combination of sucrose density gradient centrifugation and gel filtration to be 31,600 +/- 1200 daltons.

Arylamine N-Acetyltransferase↗
PubMed1991

Intramedullary wiring for tibial shaft fractures in children before epiphyseal closure. Indications and technique--experience of 36 patients.

Between 1958 and 1987 36 children underwent intramedullary wiring for tibial shaft fractures. Of these, 29 presented with combined tibial and fibular fractures, and 7 showed isolated tibial shaft fractures. Fractures were simple in 22 and compound in 14 patients. Mean patient age was 13 years (4-16 years). Only bending fractures with and without splinters were wired. The wiring technique and the protocol for postoperative care are reviewed. Mean immobilization time in long-leg casts was 12 weeks; intramedullary wires were removed after a mean interval of 17.7 weeks. Patients were selected for intramedullary wiring because of compound fractures of variable severity (14 patients), brain injuries with associated fractures (1), relative separation of the fracture ends with the fibula intact (2), severe dislocation or expected instability following closed reduction (9), and secondary dislocation or unsatisfactory alignment on skeletal traction (9). Complications included infections of 2nd degree compound fractures (2 patients), transitory peroneal palsy (2) and delayed union (2). Non-union and damage related to immobilization were not seen. A total of 19 patients were available for follow-up. Mean follow-up time was 9 years. Posttreatment lateral displacement was found to be irreversible except in infants but had no functional relevance. Malalignment showed a tendency towards spontaneous correction, which decreased with increasing age. Correction surgery proved to be unnecessary. Differential longitudinal growth was not consistently evaluable because of the heterogeneity of the material; reported data on this parameter from the literature were equally inconclusive.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

[Dorsal technique of vertebral body reconstruction using cortico-cancellous bone chips].

Grafting of cortico-cancellous bone is firmly established in trauma surgery especially as concerns surgical stabilization of the spine. Early references to that procedure can be traced back to Magerl's reports, but it was Daniaux who decisively improved spongiosa reconstruction and published the results. Further modifications were introduced by Thielemann and Holz as well as by Arnold. All techniques applied so far are essentially based on the implantation of cancellous bone. The method presented employs cortico-cancellous grafts.

Bone Transplantation↗
PubMed1991

[Clinical aspects of bedside bars].

The use of a bar at the side of a sick-bed by old confused patients may be the origin of implant failures and dislocations after stabilisation of fractures of the upper third of the femur by various implants or endoprosthesis. An inexpensive possibility of solution is shown.

Aged↗
PubMed1991

The low risk of upper gastrointestinal bleeding in patients dispensed corticosteroids.

PURPOSE: To determine the incidence of upper gastrointestinal bleeding in patients treated with corticosteroids. PATIENTS AND METHODS: The incidence of upper gastrointestinal tract bleeding was assessed in a cohort of 19,880 patients from the Michigan Medicaid billing database with dermatitis and/or asthma treated with corticosteroids during 1980 to 1984. The frequency of upper gastrointestinal bleeding was assessed within 60 days after each corticosteroid prescription. RESULTS: The incidence of upper gastrointestinal bleeding in patients without a past history of upper gastrointestinal bleeding who were exposed to corticosteroids was only 2.8 cases per 10,000 person-months. The rate of upper gastrointestinal bleeding was notably higher in patients receiving anticoagulants and those with a prior history of upper gastrointestinal bleeding (23.0 and 15.9 cases per 10,000 person-months, respectively). CONCLUSION: Because the incidence of upper gastrointestinal bleeding in ambulatory patients treated with corticosteroids is so low, prophylactic therapy should be restricted to high-risk patients, if it is to be used at all.

Adolescent↗
PubMed1991

Expression of N-acetyl transferase in a human monocytic cell-line, U937.

1. N-acetyl transferase (NAT) catalyses the acetylation of arylamine and hydrazine drugs and other xenobiotics. The activity of one isozyme (polymorphic NAT) varies amongst individuals but the other (monomorphic NAT) does not. 2. The human monocytic cell-line U937 transcribes the gene for monomorphic N-acetyl transferase. 3. Although the gene for polymorphic N-acetyl transferase is present in these cells, its expression is not detected. 4. It is concluded that U937 cells are a useful model for studying the metabolism of arylamines and hydrazines by human monomorphic N-acetyl transferase.

Acetyltransferases↗
PubMed1991

[Reposition of dislocated dorsal vertebral wall fragments in fractures of the thoracolumbar transition and the lumbar spine. Experience with 35 cases].

Pre- and postoperative CT scans of 35 patients with fractures of the thoracolumbar and lumbar spine (20 men and 15 women, with a mean age of 35 years), were evaluated with reference to the extent and shape of spinal stenosis. There were 24 patients with wedge-shaped fragments compressing the canal, the wedge being intact in 14 and broken in 10; 3 had fragmented wedges; and in 5, pedicular or arch fragmentation was combined with the dorsal vertebral fractures mentioned. Spinal stenosis was due to flexion-distraction injuries with angulation 3 patients, 1 of whom showed signs of dislocation and compaction. Fixation was done with the fixateur interne (F.I.) in 28 patients (combined with remodeling in 2), while 7 patients underwent plating with Teinturier plates and screws from the USI program. Burst fractures were most commonly encountered (25 patients) followed by flexion-distraction injuries of different types (10 patients). Instrumented reduction of the vertebral fragments was done in 24 patients. The effects of ligamentotaxis alone were relied upon in only 2 patients. Mean spinal canal narrowing amounted to slightly more than 50% (0.56) preoperatively. Residual narrowing postoperatively was just over 25% (0.26). In the patients followed up there was no evidence of secondary dislocation since the postoperative findings had been recorded. (ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Endoscopic management of bleeding peptic ulcers in Singapore: a multimodality approach.

Endoscopic haemostasis is becoming increasingly important in the management of bleeding peptic ulcers. In this study, rather than being confined to one modality of treatment, the endoscopist was allowed to customize the treatment according to the configuration of the ulcer, accessibility, and rate of bleeding in any particular patient. Fifty patients with actively bleeding peptic ulcers or stigmata of recent haemorrhage were treated endoscopically. Initial haemostasis was achieved in 48 (96%) patients. Eleven patients rebled of whom eight underwent repeat endoscopic treatment. Of these eight patients, three rebled of whom two required surgery. Permanent haemostasis was achieved in 43 of 50 patients (86%). The rate of surgery in the endoscopically treated group was 10%. There was one death due to causes not related to bleeding. The multimodality approach is a useful method of treatment in bleeding peptic ulcers, giving flexibility to the endoscopist in deciding on the best way to deal with the problem.

Adolescent↗
PubMed1991

A multimodality approach to endoscopic treatment of bleeding peptic ulcers.

The role of endoscopic haemostasis in the treatment of bleeding peptic ulcers is widely studied. Many trials to date have compared one or more modalities against a medical control with variable results. To date, no single modality has been shown conclusively to be superior to others. As such, in this study we have not confined the endoscopist to one modality of treatment but allowed him to customize the method of endoscopic haemostasis according to the configuration, accessibility and rate of bleeding in any particular patient. Seventy-three patients with non-variceal upper gastrointestinal (GI) bleeding were admitted to the National University Hospital in Singapore between May 1, 1988 and April 30, 1989. All were gastroscoped and 48 were found to have chronic peptic ulcer. Twenty-nine (60%) with actively bleeding peptic ulcer or stigmata of recent haemorrhage (SRH) were treated endoscopically. Initial haemostasis was achieved in 27 (93%) patients. Seven patients rebled (26%) of which four underwent repeat endoscopic treatment. Of these four patients only one rebled again and required surgery. Permanent haemostasis was achieved in 23 of 29 patients (79%). The multimodality approach for the treatment of bleeding peptic ulcers gives the endoscopist flexibility in deciding on the best way to deal with a bleeding gastric or duodenal ulcer. Each instrument has its strengths and weaknesses and the right choice of instrument is often a critical factor especially in treating a bleeding ulcer in a situation where access poses a problem.

Adult↗
PubMed1991

[Computerized tomography after surgical management of scaphoid fractures and pseudarthroses with implants in place. Method and results in 15 cases].

Fifteen patients having undergone open reduction and internal fixation for scaphoid fractures were later examined by computer tomography. Herbert-screws were used in nine cases and Ender-plates in four. In two cases, Ender-plates replaced a small fragment AO-screw as well as one Herbert-screw. Computer tomography of the wrist is not indicated on a routine basis, but whenever standard X-rays are unable to determine whether surgically treated fractures have healed or nonunion has been established. Patient cooperation is of utmost importance, if artifacts due to patient movement are to be avoided. To minimize implant artifacts, axial and radio-ulnar sections are employed; palmar-dorsal sections are advantageous whenever Ender-plates are involved.

Adolescent↗
PubMed1990

Arylamine N-acetyltransferase from fast (C57BL6) and slow (A/J) N-acetylating strains of mice.

Many drugs and xenobiotics which are arylamines or hydrazines are metabolized by N-acetyltransferase. The enzyme is polymorphically expressed in humans and inbred strains of laboratory animals can be classified as fast or slow acetylating strains. N-Acetyltransferase has been partially purified from livers from a fast acetylator, C57BL6, and a slow acetylator, A/J, strain of mouse. The enzyme has been purified 1900- and 955-fold, respectively from the two strains, but still represents less than 20% of the total protein. These studies show that at least 5000-fold purification is required to isolate mouse liver N-acetyltransferase from either strain. During purification, N-acetyltransferase from both strains of mice elute identically as a single peak on ion exchange chromatography. Sucrose density gradient centrifugation of N-acetyltransferase shows partial separation of the activity from A/J mice into two peaks whilst the enzyme from C57BL6 mice migrates as one peak which is distinct from both the major and minor types of N-acetyltransferase in A/J mouse liver. The hydrodynamic parameters of N-acetyltransferase from C57BL6 mice and the major peak of N-acetyltransferase from A/J mice show that these enzymes are likely to be monomers of apparent molecular weights 33,000 +/- 1000 and 30,000 +/- 2000, respectively. These results indicate that the N-acetyltransferase isozymes in liver of these two strains of mice are not identical.

Acetyltransferases↗
PubMed1990

[Hip tumor prosthesis--indication in a trauma center and results].

This is a report about six cases of replacement of the proximal femur by a cementless special prosthesis in modular system done in the Unfallkrankenhaus Wien-Meidling. One of the patients suffered by a lymphoma, three others had fractures caused by bone metastasis. One was a pertrochanteric fracture complicated by osteoporosis, and finally one fracture of the femur preceded by an insufficient implantation of a semitotal hip replacement. The hipsocket was supplied four times by a cementfree Polyäthylensocket, in one case a CLW-ring was implanted. Investigation showed that after a little more than two months the stump of femur became porous and by an average of eleven months the prosthesis was covered by bone. The complications were in one case an incomplete fracture of the diaphysis and in another case a luxation for three times. There are several indications for a tumor prosthesis: 1. Primary and secondary malignant tumors. 2. Bone metastasis with or without fractures. 3. Comminuted fractures complicated by various factors, e.g. osteoporosis. 4. Loosening of prosthesis with poor bone conditions or failed implantation of a standard prosthesis. Although the successes seem to be quite promisingly, this method should be applied in a quite differentiated way, as any retreat is nearly impossible, once started.

Aged↗
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↗