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Biomedical subjects

M Aebi

Publications and source records attributed to M Aebi.

At least 163 records · Page 9Linked to original sources
PubMed1988

The internal skeletal fixation system. A new treatment of thoracolumbar fractures and other spinal disorders.

A new internal skeletal fixation system (ISFS) for stabilizing thoracolumbar fractures and other spinal disorders was developed by Dick in Switzerland. The ISFS is a modification of the Magerl external skeletal fixation system of the spine. The Dick modification consists of a threaded rod connected by clamps to Schanz screws and is located in the vertebral pedicles on both sides of the spine. Due to a stable angle between the rod and Schanz screw, a one-point fixation above and below the diseased vertebra is sufficient. The ISFS provides a short fixation and promotes fusion. Control of lordosis, kyphosis, and rotation of the spine is possible with threaded rod distraction and compression and through manipulation of the Schanz screws held by movable clamps. The advantage of the ISFS is the ability to achieve reduction and fixation with the same instrumentation. ISFS has been used in more than 90 patients and proven most adequate for thoracolumbar fractures and other localized spinal disorders. The Harrington system and its modifications are no longer in use for these problems.

Adult↗
PubMed1988

Correction of degenerative scoliosis of the lumbar spine. A preliminary report.

The use of the spinal internal skeletal fixation system (ISFS), originally developed for fracture treatment by Dick for the segmental correction of scoliosis, is demonstrated in eight adult degenerative lumbar spinal curves. The two main benefits of an intrapedicular screw fixation system, i.e., excellent skeletal stabilization and the ability to freely modify individual segmental vertebral position, are clearly demonstrated in this instrumentation, which is still at the prototype stage. The good preliminary results seen in this series encourages the further development of segmental intrapedicular spinal fixation systems for the treatment of scoliosis.

Adult↗
PubMed1987

5' cleavage site in eukaryotic pre-mRNA splicing is determined by the overall 5' splice region, not by the conserved 5' GU.

We have generated all possible single point mutations of the invariant 5' GT of the large beta-globin intron and determined their effect on splicing in vitro. None of the mutants prevented cleavage in the 5' splice region, but many reduced or abolished exon joining. The mutations GT----TT and GT----CT resulted in a shift of the 5' cleavage site on nucleotide upstream; in the case of the mutation GT----TT, this shift was reverted by a second site mutation within the 5' splice region. Our results suggest that the 5' cleavage site is determined not by the conserved GU sequence but by the 5' splice region as a whole, most probably via base-pairing to the 5' end of the U1 snRNA.

Animals↗
PubMed1987

[Infectious spondylitis].

Nowadays, early diagnosis of spondylitis is possible. Technetium and gallium scintigrams are positive soon after the onset of the disease, while radiographs remain negative for weeks or even months. Blood and urine cultures and serologic tests may provide indications about the underlying infectious agent; however, needle biopsy establishes a precise bacteriologic diagnosis in up to 65% of the cases. Therefore, needle-biopsy is considered to be the most valuable diagnostic measure in spondylitis. Conservative treatment is indicated in cases of minimal destruction of the vertebral body. Surgery may be considered in cases of massive bone loss and kyphosis, and is strictly indicated in cases with spinal instability, abscess formation, and neurologic or septic complications, and when conservative treatment is ineffective.

Bacteria↗
PubMed1987

[Measuring blood flow in microsurgically revascularized, immunosuppressed segmental allogeneic bone transplants using laser Doppler flowmetry].

This paper presents Laser Doppler Flowmetry (LDF) as a method for measuring cortical bone blood flow. The goal of this study was to evaluate the efficacy of LDF as a means to determine cortical bone perfusion as an indicator of persistent patency of microvascular anastomoses. Cortical bone blood flow was measured in an experiment using free vascularized immunosuppressed bone allografts. Disulfine blue demonstrated patency in all grafts at 20 weeks sacrifice date, with 15 percent localized areas of nonperfusion, corresponding to areas of microscopic evidence of devitalization. LDF suggested four out of six anastomoses to be nonpatent at four weeks, and irregular evidence of patency at 20 weeks, depending the site of measurement. The small volume of tissue sampled by the probe limits LDF's ability to assess patency of a vessel supplying a whole graft. Comparing LDF with disulfine blue technique, we conclude that the LDF-results in our experiment did not allow general statements regarding the patency of microvascular anastomoses to large segments of cortical bone.

Animals↗
PubMed1987

[Classification of injuries of the cervical spine].

Recent advances and the technical options that have lately become available in the surgical treatment of spinal injuries mean that clear definition of the indications is essential. Precise observation and classification of each injury to the cervical spine are of paramount importance for this purpose, to allow the comparison of proposed methods of treatment and of the results obtained with them. There are a number of classification systems for injuries to the cervical spine, none of which, however, is generally accepted. These classification systems are based on different criteria, such as nature of the accident at which the injury was sustained, neurologic deficits, morphological criteria, the concept of instability, and implications for treatment and prognosis. These criteria, however, hardly allow the classification of most of the injuries affecting the upper and those affecting the lower cervical spine in a single system. Therefore, the authors propose a system of their own, which draws on the principles of classification suggested by the ASIF for fractures of the extremities. According to this proposed new system, injuries are divided into those of the upper and those of the lower cervical spine, and each of these two main groups is further divided into three subgroups. In the case of the lower cervical spine, injuries are classed according as whether they affect the anterior or the posterior section of the spine more, or both to the same degree. Beyond this, injuries are subdivided with reference to whether they affect primarily bone, bone and ligament equally, or primarily ligament. Further subdivision by severity and implications for treatment allows more detailed differentiation. This classification system is based on the analysis of over 200 cases of injury to the cervical spine treated by the authors and of cases from the literature.

Axis, Cervical Vertebra↗
PubMed1986

Sequence requirements for splicing of higher eukaryotic nuclear pre-mRNA.

We determined the effect on splicing of 24 point mutations in the 5' and 3' splice region of the large rabbit beta-globin intron. In vitro, 3' AG mutations drastically reduce 5' cleavage and abolish splicing. In vivo, the same mutations elicit efficient splicing at a cryptic, rather than the correct, 3' splice site. In vitro, mutations at all but 2 positions of the consensus 5' splice region impair correct splicing and promote joining of exon 1 to exon 3. In vivo, the same mutations show no effect, except for those converting 5' GT to AT or GA, which cause accumulation of lariat intermediate in vitro and in vivo. We conclude that the 5' GT need not be conserved for 5' cleavage and that it plays an important role in cleavage and exon joining at the 3' splice site.

Animals↗
PubMed1986

The TRP4 gene of Saccharomyces cerevisiae: isolation and structural analysis.

The TRP4 gene of Saccharomyces cerevisiae, encoding the anthranilate phosphoribosyl transferase, was isolated and subcloned by functional complementation in yeast. A 2 kb fragment containing information for a polypeptide of 380 amino acids and the 5'- and 3'-flanking regions was sequenced. The TRP4 transcript was identified and mapped with S1 nuclease. Homologies to two prokaryotic genes encoding the same function, and sequences potentially involved in transcription start and termination and in regulation of TRP4 gene expression are discussed.

Amino Acid Sequence↗
PubMed1986

Identification and characterization of four new GCD genes in Saccharomyces cerevisiae.

Mutant strains, resistant against the amino acid analogues 5-methyltryptophan, 5-fluorotryptophan and canavanine were isolated, starting with a trp2 leaky auxotrophic strain. Of 10 such strains, only four turned out to be of the "general control derepressed" (gcd) mutant type. Three other isolates were shown to be defective in the general amino acid permease system, while the remaining three strains displayed low spore viability and were not further investigated. Complementation tests amongst the four new gcd-mutant strains, including strain RH558 gcd2-1 isolated earlier, yielded five complementation groups: GCD2, GCD3, GCD4, GCD5, and GCD6. All mutant strains showed a dual phenotype, which was not separable by wild type backcrosses: "constitutive derepression" and "slow growth". Epistasis of all gcd mutations over gcn1-1, gcn2-1 and gcn3-1 was found with respect to both phenotypes, except for gcd5-1, which was lethal in these combinations. On the other hand gcn4-101 was found to be epistatic over all gcd mutations, but only with respect to the "constitutive derepression" phenotype, and not to "slow growth"; again the combination with gcd5-1 was lethal. Mutation gcd2-1 was mapped on chromosome VII, 50 cM from leu1 and 22 cM from ade6. A new model is discussed, in which GCD-genes are involved in the amino acid uptake into the vacuoles.

Amino Acids↗
PubMed1986

Analysis of 75 operated thoracolumbar fractures and fracture dislocations with and without neurological deficit.

Seventy-five surgically treated patients with thoracolumbar fractures and fracture dislocations, operated on between 1978 and 1982 at the Orthopedic Department of the University of Basel, were analyzed. The follow-up ranged from 18 months to 6 years. There were 45 men and 21 women, and 60% of the patients were not more than 30 years old. Additional injuries were common: 30% of the patients had craniocerebral injuries and 20% were polytraumatized. Ninety-six percent of all patients reached a hospital within 6 h, but only 23% initially presented at a center for spinal surgery. Sixteen patients had anterior surgery (fusion alone or with plating), and two of these had laminectomy as a second operation. Fifty-seven patients had posterior surgery, in 34 cases combined with a laminectomy. The Harrington instrumentation was used 45 times (29 distraction, 14 compression, and two combinations of distraction and compression rods). Luque rods with segmental sublaminar wiring was used seven times, the locking-hook distraction-rod system of Jacobs twice, and miscellaneous procedures five times. A total of 24 patients (greater than 30%) presenting neurological deficits improved postoperatively. None of the 18 patients with normal neurological findings deteriorated during the operation. Neurological improvement was seen more frequently after early than after delayed surgery, but the difference was not statistically significant. Laminectomy had no statistically significant effect on postoperative neurological status. Twenty-two patients required reoperation because of insufficient or failed instrumentation. Luque instrumentation had the highest rate of reoperations. Anterior surgery did not prove superior to posterior procedures. Hospitalization and immobilization time was significantly reduced with surgery for the neurologically normal or minimally damaged patients, but not for completely or incompletely paraplegic patients. Postoperative back pain occurred in 22 patients, of whom 14 had nonanatomic postoperative reductions. Complications directly due to the surgery were rare. It is our conclusion that the instrumentation used in this series was not good enough to be proposed for standardized use. These technically unsatisfactory results induced the development of the internal fixator system in the senior author's (E.M.) department.

Adolescent↗
PubMed1986

Indication, surgical technique, and results of 100 surgically-treated fractures and fracture-dislocations of the cervical spine.

The results of 100 cervical spinal injuries in 67 men and 33 women (20 upper and 80 lower cervical spinal injuries), which were treated operatively, were analyzed. Fifty-three of the patients were less than 30 years old. The period of observation was a minimum of one year. Ninety-three percent of patients were transported to a hospital where first treatment was given within six hours after the accident. Only 25% of these patients had a closed manual or open reduction within these first six hours. One third of all patients improved neurologically. The majority (75%) of the patients with neurologic improvement were reduced within six hours after the accident. Fifty patients were treated by an anterolateral, 40 by a posterior, and ten by a combined anterior/posterior surgical exposure. Complications attributable to technical difficulties were only occasional and were never of significance for the further outcome. The duration of immobilization was a maximum of six weeks or less in more than 85% of all cases. The duration of hospitalization could not be reduced in the group of tetraplegic patients. Immediate reduction of the injury is more important for the further neurologic outcome than improved surgical techniques.

Adolescent↗
PubMed1985

Purification and characterization of the indole-3-glycerolphosphate synthase/anthranilate synthase complex of Saccharomyces cerevisiae.

The indole-3-glycerolphosphate synthase/anthranilate synthase complex from Saccharomyces cerevisiae was purified to apparent homogeneity. The native complex with Mr approximately equal to 130 000 consists of two different subunits, the TRP2 gene product with Mr = 64 000 and the TRP3 gene product with Mr = 58 000. The larger polypeptide was identified as anthranilate synthase and is active in vitro with ammonia as cosubstrate without need of complex formation. The smaller polypeptide carries both glutamine amidotransferase activity and indole-3-glycerolphosphate synthase activity. Various steady-state kinetic parameters as well as the amino acid composition of the two polypeptides were determined.

Amino Acids↗