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Biomedical subjects

K K Mortensen

Publications and source records attributed to K K Mortensen.

34 records · Page 2Linked to original sources
PubMed1992

The effect of indomethacin 1% ophthalmic suspension on the pupil during extracapsular cataract surgery.

Fifty-six patients who underwent extracapsular cataract surgery were randomized in two groups with 28 patients in each group. Group 1 was treated with standard preoperative dilation regime and group 2 received in addition indomethacin 1% ophthalmic solution. Horizontal and vertical pupil diameter measurements were taken before capsulotomy, before exprimation of the lens nucleus and before lens implantation. The size of the pupil at the time of capsulotomy and at the time just before lens exprimation was greatest in the non-indomethacin treated group, but at the time of lens implantation the pupil of the indomethacin treated group was greatest. It is concluded that even though indomethacin seems to be able to inhibit surgically induced miosis, probably through its inhibitory effect on prostaglandin synthesis, the effect is only marginal and from a clinical point of view it cannot be recommended.

Aged↗
PubMed1992

OmpT proteolysis of E. coli initiation factor IF2. Elimination of a cleavage site by site-directed mutagenesis.

A serious problem during purification of the E. coli initiation factor IF2 is a significant loss of native IF2 due to partial degradation. We have previously shown that the major fragment, IF2 gamma (65 kDa), is the result of cleavage of IF2 alpha at the peptide bond between lysine 289 and arginine 290. In this paper we demonstrate that the cleavage is a result of proteolysis by outer membrane protease OmpT occurring immediately after cell lysis and in the S30 supernatant. By protein engineering we have constructed an IF2 mutant Lys289-greater than Met and shown that the IF2 gamma cleavage site in this mutant protein is insensitive to cleavage by OmpT. However the mutant protein is cleaved by OmpT between arginine 279 and alanine 280, which is a novel sequence specificity for this protease.

Amino Acid Sequence↗
PubMed1991

Tandem translation of E. coli initiation factor IF2 beta: purification and characterization in vitro of two active forms.

Two forms of E. coli initiation factor IF2, IF2 alpha and IF2 beta, have been known for several years. Both forms are products of the gene infB with translational initiation at codon 1 (AUG) and codon 158 (GUG) in the same reading frame. In this work we demonstrate that IF2 beta exists in two forms, IF2 beta and IF2 beta' with initiation codons 158 (GUG) and 165 (AUG) and molecular masses of 79.7 kDa and 78.8 kDa respectively. We have recently described a fast purification method for IF2 alpha, using an FPLC procedure consisting of ion-exchange liquid chromatography on Q Sepharose HP, Mono Q and Mono S. After the Mono Q step, an apparently homogeneous IF2 beta was observed when analyzed by SDS-PAGE. However the chromatography on Mono S results in the elution of two peaks containing IF2 beta. The N-terminal amino acid sequence of the two proteins identified the first peak to be IF2 beta and the second as a protein which we term IF2 beta' starting seven residues downstream at the AUG codon 165. The activity in vitro of the two purified forms of IF2 beta was tested by measuring the stimulation of binding of the initiator fMet-tRNA(fMet) to 70S ribosomes in the presence of GTP and poly(A,U,G) as messenger-RNA. In this assay no difference in activity is detected.

Amino Acid Sequence↗
PubMed1991

Visual acuity and refraction in type I diabetic patients aged 25-34 years.

Of the total population of 270 25- to 34-year-old insulin dependent diabetic patients with onset less than or equal to 30 years in the county of Fyn, Denmark, a sample of 138 was drawn for examination. Of the 138 examined patients, 4 (2.9%) were legally blind and 119 (86.2%) had good vision in both eyes. The cause of reduced vision was proliferative retinopathy in the majority of eyes. Refraction, measured objectively with a refractometer in cycloplegia and transformed to spherical equivalents, was -0.25 D or more myopic in approx. 50% of eyes. Correlation analyses did not demonstrate significant association between refraction, and duration of diabetes or Hb-A1c.

Adult↗
PubMed1989

Structure-function relationships of elongation factor Tu. Isolation and activity of the guanine-nucleotide-binding domain.

The guanine-nucleotide-binding domain (G domain) of elongation factor Tu(EF-Tu) consisting of 203 amino acid residues, corresponding to the N-terminal half of the molecule, has been recently engineered by deleting part of the tufA gene and partially characterized [Parmeggiani, A., Swart, G. W. M., Mortensen, K. K., Jensen, M., Clark, B. F. C., Dente, L. and Cortese, R. (1987) Proc. Natl Acad. Sci. USA 84, 3141-3145]. In an extension of this project we describe here the purification steps leading to the isolation of highly purified G domain in preparative amounts and a number of functional properties. The G domain is a relatively stable protein, though less stable than EF-Tu towards thermal denaturation (t50% = 41.3 degrees C vs. 46 degrees C, respectively). Unlike EF-Tu, its affinity for GDP and GTP, as well as the association and dissociation rates of the relative complexes are similar, as determined under a number of different experimental conditions. Like EF-Tu, the GTPase of the G domain is strongly enhanced by increasing concentrations of Li+, K+, Na+ or NH+4, up to the molar range. The effects of the specific cations shows similarities and diversities when compared to the effects on EF-Tu. K+ and Na+ are the most active followed by NH+4 and Li+ whilst Cs+ is inactive. In the presence of divalent cations, optimum stimulation occurs in the range 3-5 mM, Mg2+ being more effective than Mn2+ and Ca2+. Monovalent and divalent cations are both necessary components for expressing the intrinsic GTPase activity of the G domain. The pH curve of the G domain GTPase displays an optimum at pH 7-8, similar to that of EF-Tu. The 70-S ribosome is the only EF-Tu ligand affecting the G domain in the same manner as that observed with the intact molecule, although the extent of the stimulatory effect is lower. The rate of dissociation of the G domain complexes with GTP and GDP as well as the GTPase activity are also influenced by EF-Ts and kirromycin, but the effects evoked are small and in most cases different from those exerted on EF-Tu. The inability of the G domain to sustain poly(Phe) synthesis is in agreement with the apparent lack of formation of a ternary complex between the G domain.GTP complex and aa-tRNA.(ABSTRACT TRUNCATED AT 400 WORDS)

Binding Sites↗
PubMed1987

Properties of a genetically engineered G domain of elongation factor Tu.

The G domain of elongation factor Tu (EF-Tu), representing the N-terminal half of the factor according to its three-dimensional model traced at high resolution, has been isolated by genetic manipulation of tufA and purified to homogeneity. The G domain, whose primary structure shares homology with the eukaryotic protein p21, is capable of supporting the basic activities of the intact molecule (guanine nucleotide binding in 1:1 molar ratio and GTPase activity). However, it is no longer exposed to the allosteric mechanisms regulating EF-Tu. The G-domain complexes with GTP and GDP display similar K'd values in the microM range, in contrast to EF-Tu that binds GDP much more tightly than GTP. Its GTPase shows the characteristics of a slow turnover reaction (0.1 mmol X sec-1 X mol-1 of G domain), whose rate closely corresponds to the initial hydrolysis rate of EF-Tu X GTP in the absence of effectors and lies in the typical range of GTPase of the p21 protein. Of the EF-Tu ligands only the ribosome displays a clear effect enhancing the G-domain GTPase. Our results suggest that the middle and C-terminal domain play an essential role in regulating the activity of the N-terminal domain of the intact molecule as well as in the interactions of EF-Tu with aminoacylated tRNA, elongation factor Ts, and kirromycin. With the isolation of the G domain of EF-Tu, a model protein has been constructed for studying and comparing common characteristics of the guanine nucleotide-binding proteins.

Binding Sites↗
PubMed1987

The effect of indomethacin 1% ophthalmic suspension in preventing surgically induced miosis at extracapsular cataract surgery.

27 patients who underwent extracapsular cataract surgery (ECCE) were randomized in two groups with 12 patients in Group 1 treated with standard preoperative dilation regime and 15 patients in Group 2 receiving in addition Indomethacin 1% ophthalmic solution, one drop the evening before surgery and one drop 45 minutes before surgery. Horizontal pupillary diameter measurements were taken at the beginning of the operation before retrobulbar anesthesia, before capsulotomy, and before lens implantation. A significant decrease in pupillary diameter and area was seen in both groups (P greater than 0.001; t-test) from before capsulotomy until before lens implantation. No significant change was seen from start until before capsulotomy. A significant lesser pupillary constriction expressed as mean calculated pupillary area differences from start until before lens implantation was seen in Group 2 treated with indomethacin (17.70 +/- 6.68(mm)2), than in Group 1 without indomethacin (29.06 +/- 8.82(mm)2); (P greater than 0.05; t-test). It is concluded that local use preoperatively of the antiprostaglandin drug indomethacin in 1% ophthalmic solution (Indocid, MSD) is able to reduce surgically induced miosis during ECCE, thereby facilitating the operative procedure and probably minimizing complications.

Adult↗
PubMed1980

Traumatic hyphaema treated ambulatory and without antifibrinolytic drugs.

Forty-four patients referred consecutively over a period of one year for treatment of traumatic hyphaema have been treated ambulatory and with no drugs. Four patients developed secondary haemorrhage; three regained normal visual acuity. The frequency of secondary haemorrhage is not statistically different from that in two previously published patient groups treated with bed rest and with tranexamic acid, respectively.

Adolescent↗
PubMed1979

Keratitis dendritica. An epidemiological investigation.

One hundred and seven outbreaks of dendritic keratitis have been registered by the ophthalmologists over a 2-year-period in a region with a population of approximately 446 000 persons. The incidence was found to be 12/100 000/year. The average age of our sample was 46.5 years with the same age distribution for males and females, and with a non-significant predominance of males. No seasonal variation of dendritic keratitis was observed. 50% of the patients had previously suffered from dendritic keratitis. In 25% of the patients the onset of the disease had been preceded by an infectious disease, while 6% were on local steroid therapy for non-dendritic eye diseases prior to the dendritic outbreak.

Adolescent↗
PubMed1978

Changes in anterior chamber depth and angle-recession, late complications to ocular contusion.

Of 46 patients consecutively admitted to hospital for ocular contusion with hyphaema in 1964 and 1965, 30 patients were followed-up somewhat more than 10 years later in order to assess late complications. Angle-recession was observed in 17 (57%), while none had developed glaucoma. An average increase in depth of the anterior chamber of 0.06 mm in the affected eye was observed; this differences is highly significant with P less than 0.005. However, as these changes are small in individual patients, measurement of the increase in anterior chamber depth can only be a supplement to gonioscopy.

Adolescent↗
PubMed1978

Secondary haemorrhage following traumatic hyphaema. A comparative study of conservative and tranexamic acid treatment.

Three out of 56 consecutively admitted patients with traumatic hyhaema, treated conservatively, developed secondary haemorrhage. Of the following 64 patients treated with tranexamic acid, none developed secondary haemorrhage. Statistical analysis, using chi2 test with Yate's correction showed no statistical difference with regard to the occurrence of secondary haemorrhage between the two groups.

Adolescent↗
PubMed1977

Unilateral traumatic cataract in children.

A survey is presented of the course of unilateral traumatic cataract in 15 children of 8 years of age and below, admitted consecutively to the Ophthalmological Department of the Odense University Hospital over a period of 9 years. The follow-up examination revealed that four patients had visual acuity of more than 6/18, and of these two retained binocular single vision and used contact lenses. The size of the material does not permit any conclusive statements to be made. Thus it is impossible to select the patients who will have either a good or a poor final result from the treatment, with regard to vision and binocular single vision.

Cataract↗
PubMedDate not supplied

Superexpression and fast purification of E coli initiation factor IF2.

For the production of large quantities of E coli initiation factor IF2 we have constructed an improved overexpression system. The gene infB was cloned into the thermo-inducible runaway plasmid pCP40 [1] and subsequently transformed into the E coli strain C600[pcI857]. In this system the expression of infB is under the control of the strong promoter lambda PL and the cells carry the plasmid pcI857, which contains a thermosensible lambda cI repressor. Overexpression of IF2, which is approximately 30 times higher than the expression in wild-type-cells, is induced at 42 degrees C and continues for 2 h at 37 degrees C. From these cells pure and active IF2 was obtained using a novel 3-step FPLC-procedure consisting of ion-exchange liquid chromatography on Q-sepharose HP, MonoQ and MonoS. In approximately 8 h, 5 mg of pure and active IF2 can be obtained from 10 g overproducing cells. This corresponds to 5 mg of IF2 per litre of medium. The purification was monitored by Western immunoblotting and the activity of the purified factor was tested by measuring the stimulation of binding of the initiator fMet-tRNA(Met)f to 70S ribosomes in the presence of GTP and poly(A,U,G) as messenger RNA. Compared with previous methods our purification procedure avoids the use of materials such as DEAE-cellulose and phosphocellulose which have relatively poor flow rates. In addition to the higher flow capacity of Q-sepharose HP, this new matrix can be loaded with an S30 supernatant.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Proteins↗