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Biomedical subjects

E Sim

Publications and source records attributed to E Sim.

At least 91 records · Page 5Linked to original sources
PubMed1993

Effect of thiol compounds on human complement component C4.

Thiol compounds have been investigated as inhibitors of the covalent binding reaction of human complement protein C4 using Sepharose-C1s as a combined activating and binding surface. o- and p-substituted aminothiophenols are equally effective inhibitors, whereas the m-substituted compound is a less potent inhibitor. The anti-hypertensive drug captopril is also shown to inhibit the covalent binding reaction. A comparison of the effects of these compounds on the covalent binding reaction of isolated C4A and C4B has been made. Results suggest that a Pro-to-Leu substitution in C4B is likely to account for the differences in inhibitory potency of C4B compared with C4A observed with the aromatic inhibitors.

Aminophenols↗
PubMed1993

The interaction of soluble human complement receptor type 1 (sCR1, BRL55730) with human complement component C4.

Human CR1 is a membrane-bound protein which plays an important role in the control of the human complement system. In addition to its involvement in the processing and clearance of immune complexes with C3b or C4b on their surface, CR1 acts as a cofactor for the proteolysis of C3b and C4b by Factor I. sCR1 is a recombinant, soluble form of CR1 which retains the cofactor activities of CR1, and is of potential therapeutic value for the suppression of complement-mediated tissue damage in vivo. An assay has been established using microtitre plates to explore the binding of sCR1 to the two isotypes of C4, C4A and C4B, and to C4 fragments. Specific binding of 125I-sCR1 to C4b and ammonia-treated C4 has been demonstrated. The binding of 125I-sCR1 to ammonia-treated C4 is dependent on pH and ionic strength, decreasing with an increase in pH and with an increase in ionic strength. At physiological ionic strength, up to twice as much 125I-sCR1 bound to ammonia-treated C4A as bound to ammonia-treated C4B. This preference of sCR1 for binding to the C4A isotype has implications for the clinical association of immune complex disease with C4A null alleles.

Ammonia↗
PubMed1993

Location of transpedicular screws for fixation of the lower thoracic and lumbar spine. Computed tomography of 45 fracture cases.

Postoperative CT examinations of an unselected group of 45 patients with fractures of the thoracolumbar and lumbar spine including 1 patient with traumatically activated spondylolisthesis were analyzed for the location of the 200 screws, the angles of insertion, and the screw vs pedicle diameters. In all cases transpedicular systems had been used for fixation, i.e., the AO-Fixateur Interne in 28 patients, a combination of Teinturier plates and USI screws in 11 patients, and the VSP system in 7 patients. Using a standardized surgical technique and image intensification in 2 planes throughout, 92 percent of all pedicles were instrumented with acceptable deviations from the anatomic axes. Mismatches between the pedicle and the screw diameters were found in 3 instances, and 2 screws were placed in the transverse processes only. Canal encroachment in 13 patients did not impede neural structures. Slight perforation of the anterior cortex of the vertebral body was recorded in 3 percent of cases, but did not cause any complications.

Bone Screws↗
PubMed1993

Color-coded Duplex sonography of vertebral arteries. 11 cases of blunt cervical spine injury.

In 11 patients with locked cervical spine facets after blunt injury, the patency of the vertebral arteries was evaluated by color-coded Duplex sonography (CCDS) up to 11 years after the accident. In 7 patients the dislocations had been reduced, 2 had been treated conservatively, and 9 had been fused. In 9 patients (3 of them with persistent locking) the mean systolic peak flow velocity was 55 cm/sec and the vessel diameter was 0.35 cm. Only 2 patients had an abnormal CCDS. In 1 with persistent locking the ipsilateral vertebral artery was occluded, and in the other flow signals were abnormal and the vessel diameter was smaller than on the contralateral side. The high coincidence of vertebral artery occlusions and locked dislocations, as well as fracture dislocations reported by others, was not confirmed in our series.

Adolescent↗
PubMed1993

[Choice of femoral reinsertion sites after rupture of the anterior cruciate ligament--a roentgenologic evaluation model].

The position of transcondylar small caliber drill tunnels after reattaching of femoral avulsions of the anterior cruciate ligament usually escapes objective verification by conventional roentgenography. A model of investigation and the results of cadaver studies are presented: Stored CT data are used for 3D-reconstruction of the distal end of the femur. In such manner the sites of perforation of the K wires can be determined unequivocally and distinctly.

Anterior Cruciate Ligament↗
PubMed1993

[Unilateral locking of cervical facet joints. Frequency and value of roentgenologic signs].

Unilateral locking of cervical facet joints is often misdiagnosed and inadequately treated, because it is not readily detected on plain radiographs. Primary radiographs of 17 patients were analysed to evaluate radiographical signs with reference to frequency and significance. Direct signs of locking were present in no more than 53% of cases. Of these, an abrupt change in laminar space width, seen in 88.2%, proved to be the most reliable sign. Displacement of the spinous processes above and below the lesion was found in the same percentage of cases, but it carries less diagnostic weight. While present in all cases, anterolisthesis is only diagnostic if additional oblique views show evidence of lateralized cervical anterolisthesis. Clearly less reliable indirect signs included: the bow tie sign (29.4%), dehiscence of the spinous processes (23.5%), differences in the sagittal diameters of the vertebral bodies above and below the lesion (35.2%), double facet contour (47%) and tilting of the cranial segment of the cervical spine away from the locked facets (58.8%). Abnormalities of disc shape were not seen on a.-p. projections. Those detectable in axial views are irrelevant to locking, as are empty facets. If more than one indirect sign is present and if unilateral locking is suspected but cannot be established unequivocally even on additional oblique views, computed tomography is indicated, because reduction continues to be the first step in the management of fresh injuries.

Adolescent↗
PubMed1993

Changing patterns in the treatment of early breast cancer: a historical perspective and a review of changing local trends.

Over the past 50 years, a variety of surgical procedures have been advocated for the treatment of operable breast cancer, ranging from local excision to supraradical mastectomy. Today, the surgical treatment of breast cancer remains highly contentious. We review the historical development of breast cancer surgery and analyse the available evidence supporting conservative procedures. We also express our opinions on the treatment of early breast cancer and illustrate the changing patterns of surgery with our experience at National University Hospital.

Breast Neoplasms↗
PubMed1992

Arylamine N-acetyltransferase in human red blood cells.

N-Acetyltransferase activities associated with erythrocytes from 20 individuals have been determined with p-aminobenzoic acid as substrate. A three-fold variation in Vmax is found. The N-acetyltransferase genotype of the individuals has been determined and there is no correlation between the extent of acetylation measured in the individuals' erythrocytes and the inheritance of alleles at the polymorphic NAT locus. Folate is confirmed to be an inhibitor of arylamine N-acetyltransferase activity measured in erythrocytes. The content of folate in erythrocytes of individuals also varies. The individual with the maximum folate content has the minimum N-acetyltransferase activity. The monomorphic N-acetyltransferase gene from individuals spanning the range of N-acetyltransferase activity have been amplified, using the polymerase chain reaction. The pattern of restriction enzyme digestion of the monomorphic N-acetyltransferase gene with a series of eight restriction enzymes is the same for individuals spanning the activity range of arylamine N-acetyltransferase in their erythrocytes.

4-Aminobenzoic Acid↗
PubMed1992

The fixateur interne for stabilising fractures of the thoracolumbar and lumbar spine.

Between 1986 and 1988, 27 patients with fractures of the thoracolumbar and lumbar spine were treated by fixateur interne (FI) instrumentation, and 24 were followed up for a mean of 25 months. Complications occurred in 13 cases, mostly due to loosening and corrosion. The results were compared with plate fixation. The radiological parameters and differences between the preoperative and postoperative indices were well within the normal range. The inferiority of FI instrumentation compared to plate fixation during follow up was mainly attributable to the complications. Reduction of the posterior wall fragments by the intact posterior longitudinal ligament was not consistent, so instrumented reduction is usually the method of choice.

Adolescent↗
PubMed1992

Surgical management of right colon diverticulitis.

The infrequent occurrence of right colon diverticulitis in the developed West has led to a controversy in the management of this disease. In Singapore, we continued to avoid colectomy whenever possible because this disease is usually nonprogressive. We reviewed 68 patients treated by conservative surgery to evaluate the effectiveness of this treatment policy. Almost 70 percent of our patients were below 40 years of age, and the clinical presentation was indistinguishable from acute appendicitis. Diverticulectomy was done only for inflamed and perforated diverticula (25 cases), while the nonperforated diverticulum was left alone (40 cases). The inflammation invariably responded to antibiotic therapy. Only three patients had colonic resection since a malignant neoplasm could not be excluded. There were no adverse sequelae over a mean follow-up period of three and one-half years, except for one patient who had recurrent attacks of right colon diverticulitis necessitating colectomy. With this policy of management we encountered no mortality, and morbidity was acceptable.

Adult↗
PubMed1992

Genotyping human polymorphic arylamine N-acetyltransferase: identification of new slow allotypic variants.

Arylamine N-acetyltransferase catalyses the N-acetylation of primary arylamine and hydrazine drugs and chemicals. N-acetylation is subject to a polymorphism and humans can be categorized as either fast or slow acetylators according to their ability to N-acetylate polymorphic substrates in vivo. Previously, slow acetylation has been linked to four distinct polymorphic N-acetyltransferase (pnat) alleles each of which contains one or more point mutations within the coding region of the pnat gene. One new rare slow variant of pnat has been identified by cloning and sequencing the pnat DNA from an individual whose NAT phenotype was determined by in vivo acetylation of the polymorphic substrate sulphamethazine. This allele, designated S1c, differs from the wild type fast allele at nucleotide positions 341 and 803. A second new rare slow allotypic variant, designated S3, has been identified by resistance of the pnat specific DNA to digestion with the restriction enzymes Fok I and Bam HI. A method of genotyping individuals for the arylamine N-acetyltransferase (NAT) polymorphism is presented which correctly predicts the phenotype of greater than 95% (21 of 22) of individuals as measured by the extent of acetylation of sulphamethazine in urine. This refined genotyping method was applied to a clinical population of 48 Caucasians with classical or definite rheumatoid arthritis each receiving daily between 150 and 500 mg of the anti-rheumatic drug, D-penicillamine. There is no difference in the N-acetyltransferase phenotype of the individuals who developed proteinuria and the control group with no adverse effects.

Adult↗
PubMed1992

[Interlocking nailing of the femur--analysis of problems and errors based on 80 fractures].

A series of 79 patients with 80 femoral fractures stabilized by the Grosse-Kempf interlocking femoral nail system (Howmedica) were critically evaluated for the frequency of problems and technical mistakes during surgery. Problems with patient positioning were negligible. In patients with fractures at a suitable site, the Wittmoser table proved useful. Closed reduction should not be attempted at all costs: in borderline cases, open reduction should be given preference to prevent complications. Radiologically relevant problems included: twisted nails, 27.5% of all cases; broken nails, 2.5%; bent nails, 1.2%. Proximal screws were too long in 18.7%, too short in 1.5%, placed too far cranially in 29.6%, shifted (with damage to the thread) in 3.1%. Distal screws were too short in 11.7%, too long in 16.1%, protruding laterally in 2.9%, malpositioned in 1.4%; affected by ectopic calcifications in 4.4%, by cortical fragmentation in 8.8%, and loosing in 10.2%; both screws broke in one case. Technical mistakes during surgery were faulty assessment of the fracture pattern in 7.5%, a wrong impaction site in 23.7%, and bursting of the proximal fragment in 11.2%. Leg shortening was observed in 8% (16 mm, on average) and lengthening in 11.2% (6.2 mm, on average). Rotational malalignment was seen in 23 of 35 patients followed up clinically: inappropriate external rotation (12.5 degrees, on average) in 12 patients and inappropriate internal rotation (10 degrees, on average) in 11. Implant damage was seen in 8.7%. A breakdown of the complications by the operating surgeons involved clearly shows where the problems lies: 80 fractures were treated by 25 surgeons.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

[The long-term behavior of homologous bone transplants in reconstruction of single chamber calcaneus cysts. Conventional and computerized tomography results].

Treatment of four unicameral calcaneal bone cysts by operative packing with homologous trabecular bone grafts was evaluated by conventional radiography and CT after a mean follow-up time of 51 months (range 48-57 months). Data on graft incorporation and remodelling are presented. In all cases trabecular bone showing an orderly arrangement was found to have developed in the cyst space. Homogeneous areas were present in 2 instances. These coincided with the neutral triangle, i.e. a zone in which stresses are physiologically low. Graft incorporation and remodelling followed Wolff's laws of bone transformation and can be regarded as complete before month 27. The final bone pattern is definitely established before month 50. Conventional radiography is sufficient for routinely evaluating the healing pattern. CT should be reserved for research purposes. Impaction of trabecular bone chips may be dispensable. Tight packing without impaction would at least help to save bone graft material. The use of homologous trabecular bone subjected to special pretreatment was found to be unproblematic. It minimizes surgery-related stresses and reduces the operating time.

Adolescent↗
PubMed1992

[Intravenous peripheral digital subtraction angiography after stabilization of medial femoral neck fractures. Results and value].

In patients with medial femoral neck fractures the condition of the blood vessels is the decisive factor as to whether or not femoral capital necrosis will develop. Therefore, conventional angiography has been used both preoperatively for the diagnostic work-up and for selecting the best mode of management and postoperatively for prognostic purposes. Its routine use has, however, been limited by the long examination time, the complexity of the technique and the potential complications. Peripheral intravenous digital subtraction angiography (DSA) for imaging peripheral vessels is a far less demanding procedure. Its usefulness was studied postoperatively in 7 patients. The vascular information obtained was inferior to that of conventional angiography because of the inherently poorer vessel imaging qualities. Moreover, since its applicability is limited to patients with a completely intact cardiovascular system and normal cardiac output, it is not suitable for most geriatric patients. It is, therefore, concluded that peripheral intravenous DSA cannot (yet) be recommended as a routine procedure. It remains to be seen whether technical improvements in system features will improve the diagnostic performance.

Adult↗
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↗