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Biomedical subjects

M Persson

Publications and source records attributed to M Persson.

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

Purification and site-specific immobilization of genetically engineered glucose dehydrogenase on thiopropyl-Sepharose.

The gene encoding glucose dehydrogenase (EC 1.1.1.47) from Bacillus subtilis was inserted in a plasmid 1.0 kb downstream from a lac promoter, resulting in a 70-fold higher production of the enzyme when expressed in Escherichia coli. A glucose dehydrogenase mutant containing a cysteine residue at position 44 could also be expressed at the same high level. This single cysteine residue was used as an 'affinity tag' to simplify the purification procedure as well as for site-specific immobilization of glucose dehydrogenase on Thiopropyl-Sepharose. This enzyme was purified to homogeneity with a final recovery of 65% and a specific activity of 240 U/mg. The oriented immobilization resulted in increased thermal stability.

Affinity Labels↗
PubMed1990

Tensile and shear strength of orthodontic bracket bonding with glass ionomer cement and acrylic resin. An in vitro comparison.

The tensile and shear strength for a polyalkeonate luting cement (AquaCEM) and a no-mix acrylic resin (Unite) in orthodontic bracket bonding were compared in an in vitro test. Brackets bonded/cemented to extracted premolar teeth were subjected to loads in a universal testing apparatus and the dislodging forces were recorded. The possible influences of setting time and of bracket base design were also studied. No significant differences between the cement and the resin were found after allowing 24 hours of setting time. This in contrast to the significantly stronger tensile strength but inferior shear strength for the polyalkeonate cement when stress was applied after 15 minutes. A significantly higher tensile strength value was recorded for a foil-meshed bracket base type compared to an integral base type with cut grooves after 15 minutes, but not after 24 hours. While the polyalkeonate cement adhesion mostly fractured within the cement layer, the acrylic bond more often failed in the enamel-adhesive interface. The results support the use of the fluoride-containing cement as an alternative to acrylic adhesives in orthodontic bracket bonding, especially in high-risk caries patients.

Acrylic Resins↗
PubMed1989

[Whipple's resection in cancer of Vater's ampulla and the pancreatic head].

A review is presented of 62 Whipple's resections between 1962 and 1984 for adenocarcinoma of the choledocho-duodenal junction (CDJ) and pancreatic head (PH). The operation was radical in 17 patients with CDJ (94%) and in 34 patients with PH cancer (77%). The cumulative 5-year survival rates were 22% and 9%, respectively. The overall perioperative mortality was 23%, but was lowered to 11% during the last five years. Histology, size of tumour and age also influenced survival. Sixteen of the 32 radically operated patients who survived more than three months had a period without pain. Whipple's resection is still the only hope for cure in otherwise fit patients with CDJ or PH cancer, estimated to be radically resectable by pre- and peroperative investigations. The operation should be centralized in a few departments.

Adenocarcinoma↗
PubMed1989

Long-term spontaneous changes following removal of all first premolars in Class I cases with crowding.

The purpose of the study was to evaluate the result in adults of Class I malocclusion cases who had all their first premolars extracted as the sole treatment of space deficiency in the mixed or early permanent dentition. The mean age at premolar removal was 10 1/2 years. Forty-two out of 44 cases were re-examined at a mean age of 30 years and 4 months. Observations of dental occlusion and oral health were compared to observations of control samples. The average malocclusion in the adults, as judged by a score method, was similar to that reported for an appliance-treated sample. Marked spontaneous arch alignment and residual space closure with age was seen in most cases. Despite earlier tooth removal, on average crowding developed to about the same degree as that of an non-extraction normal occlusion sample. No detrimental effects were seen with regard to overjet or overbite. Neither did the figures for lower incisor position at the follow-up examination differ from that of the normal occlusion sample. Although tipping of adjacent teeth towards the extraction site was frequent, especially in the mandible, no effect on marginal bone height was evident as judged by comparison with a non-extraction control sample. The results reveal a significant capacity for spontaneous improvements with age in dental arch morphology and relationship in extraction cases, provided that specific features have been looked for in case selection.

Adolescent↗
PubMed1988

Enzyme purification by genetically attached polycysteine and polyphenylalanine affinity tails.

Two novel affinity tails, polycysteine and polyphenylalanine, have been genetically attached to galactokinase (EC 2.7.1.6) and beta-galactosidase (EC 3.2.1.23) in order to facilitate their purification. A chemically synthesized DNA linker encoding four cysteine residues was thus fused in frame with the galactokinase gene. The gene product, cysteine galactokinase, was significantly retarded on a column of thiopropyl-Sepharose. Using pulse elution, cysteine galactokinase was eluted at 10 mM DTT. Under the condition used, native galactokinase did not bind to thiopropyl-Sepharose. Homopolymer tailing was employed to prepare a phenylalanine-modified beta-galactosidase. One of the obtained genetic transformants coding for a beta-galactosidase carrying 11 phenylalanine residues at the N-terminus of the enzyme was isolated. With the aid of hydrophobic interaction chromatography the modified enzyme could be purified to homogeneity on fast protein liquid chromatography using a phenyl-Superose column.

Chromatography, Affinity↗
PubMed1988

The relationship between mandibular morphology and apical root curvature in man.

Two samples of individuals, a low-angle group and a high-angle group, were selected on the basis of the inclination of the lower border of their mandible, defined by the mandibular plane angle (ML/SNL) in profile radiographs. Apical root curvature of mandibular first and second premolars and molars on panoramic radiographs was compared between the two groups and related to mandibular morphology. In the low-angle group most teeth had more distally curved roots than in the high-angle group. Significant differences were found for the first premolars on both sides (p less than 0.001, p less than 0.05), the right second premolars (p less than 0.05) and the distal root of left first molars (p less than 0.05). Correlations were calculated between root curvature and two variables reflecting mandibular morphology, the mandibular plane angle and the gonial angle. The strongest associations were found between the first premolar roots and the gonial angle (rs = -0.75, p less than 0.001 and rs = -0.56, p less than 0.01, for right and left sides respectively). The association between mandibular morphology and root curvature is probably indirect, caused by tooth migration during root formation.

Bicuspid↗
PubMed1988

Mortality from stroke among women in a Swedish community, Strömstad. Evaluation of data obtained from official death certificate registers broken down to the community level.

The present paper is an example of an active way of delivering primary health care. Data obtained from the Bureau of Central Statistics on mortality, based on death certificates during the years 1969-1978, were broken down to community level within the County of Göteborg and Bohus. A significantly increased total mortality was observed among women in the community of Strömstad in the northern part of the county, as well as an increased mortality from cardiovascular diseases, especially cerebrovascular diseases. Similar observations were made for the neighbouring communities. In order to evaluate the diagnoses stated in the death certificates, records from patients who died of cerebrovascular disease during the years 1970-1979 were studied. Out of 146 women in whom cerebrovascular disease was stated as main cause of death, it was possible to draw conclusions about diagnosis of death in 140. The vast majority of the subjects had correctly been given the diagnosis of cerebrovascular disease. Based on this "community diagnosis", a special preventive program has been started in the community of Strömstad.

Cardiovascular Diseases↗
PubMed1987

The design of a simple competitive ELISA using human proinsulin-alkaline phosphatase conjugates prepared by gene fusion.

The gene encoding human proinsulin has been fused in-frame with the E. coli alkaline phosphatase gene (pho A) (EC 3.1.3.1). Two constructions are described. One construction consists of the entire proinsulin gene fused to the 5'-terminal end of pho A. In the other construction a 42 base pair DNA fragment has been deleted from the 3'-terminal end of the proinsulin gene. The two purified fusion proteins are enzymatically active showing a specific activity of 10-15 U/mg and 18-25 U/mg, respectively. The first construction exhibited insulin antigenicity and was used to design a simple competitive ELISA for insulin. The lower detection limit was found to be at least 2.5 ng/ml. Both fusion proteins were also shown to have potential for use in a competitive ELISA for proinsulin.

Alkaline Phosphatase↗