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Biomedical subjects

E Holmgren

Publications and source records attributed to E Holmgren.

At least 55 records · Page 3Linked to original sources
PubMed1985

Efficient secretion and purification of human insulin-like growth factor I with a gene fusion vector in Staphylococci.

A novel approach for production of small polypeptides, using a staphylococcal protein A vector, is described. This system is used to express, secrete and purify human insulin-like growth factor I (IGF-I). A fusion protein consisting of protein A and IGF-I is recovered in high yield by passing the culture medium through an IgG affinity column. Using site-specific mutagenesis an acid labile asp-pro cleavage site was introduced at the fusion point between the two proteins. The protein A "tail" can thereby be removed from the affinity purified fusion protein by chemical cleavage releasing biologically active IGF-I molecules.

Escherichia coli↗
PubMed1983

Isolation of cDNA sequences coding for a part of human tissue plasminogen activator.

We have isolated a cDNA sequence coding for a part of human tissue plasminogen activator. mRNA coding for tissue plasminogen activator was partially purified, copied into double-stranded cDNA, and cloned into Escherichia coli. Two sets of partially overlapping oligodeoxynucleotide mixtures corresponding to all possible coding sequences for a known portion of the tissue plasminogen activator gene were prepared. One set was used as a probe to screen cDNA containing bacterial clones and both were used as probes in hybridization against purified plasmid DNA. Of 4,200 bacterial clones examined, 1 carried a plasmid that hybridized to both sets of oligonucleotides. This plasmid contained a 370-base-pair cDNA insert, which was shown by nucleotide sequence analysis to code for the cleavage site region in the one-chain form of the human tissue plasminogen activator.

Amino Acid Sequence↗
PubMed1982

Regulation of tryptophan genes in Rhizobium leguminosarum.

Twelve tryptophan auxotrophs of Rhizobium leguminosarum were characterized biochemically. They were grown in complex and minimal media with several carbon sources, in both limiting and excess tryptophan. Missing enzyme activities allowed assignment of all mutant to the trpE, trpD, trpB, or trpA gene, confirming earlier results with the same mutants (Johnston et al., Mol. Gen. Genet. 165:323-330, 1978). In regulatory experiments, only the first enzyme of the pathway, anthranilate synthase, responded (about 15-fold) to tryptophan excess or limitation.

Anthranilate Synthase↗
PubMed1981

A large convexity meningioma followed by liquorrhoea from a nasal encephalocele. A case report.

A 46-year-old woman was readmitted, two years after removal of a large convexity meningioma, because of cerebrospinal fluid rhinorrhoea from a nasal encephalocele eventually visualized by CT-scan. The encephalocele was extirpated via an intracranial approach, and its histological appearance is described. The aetiology of this extracranial brain tissue protrusion is discussed. It is suggested that the mechanisms behind the formation of this encephalocele are a combination of a congenital malformation and the long term increase of the intracranial pressure due to the meningioma.

Brain Neoplasms↗
PubMed1979

Characterization of a succinate dehydrogenase complex solubilized from the cytoplasmic membrane of Bacillus subtilis with the nonionic detergent Triton X-100.

A succinic dehydrogenase (SDH) complex has been purified from Triton X-100-solubilized membranes from Bacillus subtilis by precipitation with specific antibody. Radioactively labeled precipitated complex was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by autoradiography of the gels. The complex contained equimolar amounts of three polypeptides with approximate molecular weights of 65,000, 28,000, and 19,000. Five succinic dehydrogenase-negative mutants, belonging to the citF group, contained the 65,000-dalton polypeptide in a soluble form in the cytoplasm. Each 65,000-dalton polypeptide had about one molecule of flavin bound. Another citF mutant, citF11, which lacks the 65,000-dalton polypeptide, contained a membrane-bound 28,000-dalton polypeptide. The wild-type succinic dehydrogenase complex contained cytochrome, probably a cytochrome b. The 19,000-dalton polypeptide is suggested to represent the apoprotein of this cytochrome. The 65,000-dalton and the 28,000-dalton polypeptides are thought to constitute succinic dehydrogenase and to correspond to the flavoprotein and the ironprotein, respectively, as described for succinic dehydrogenase isolated from beef heart mitochondria or Rhodospirillum rubrum chromatophores. The results presented suggest that in B. subtilis succinic dehydrogenase is attached to a cytochrome b in the membrane via the 28,000-dalton (ironprotein) polypeptide.

Bacillus subtilis↗
PubMed1979

Role of heme in synthesis and membrane binding of succinic dehydrogenase in Bacillus subtilis.

A 5-aminolevulinic acid-requiring mutant of Bacillus subtilis was isolated. When the mutant is shifted from medium containing 5-aminolevulinic acid to medium lacking this growth factor, the bacteria continued to grow at undiminished rate for about three generations. The membranes from these bacteria contained severely reduced amounts of cytochrome. The mutant was used to study the role of heme synthesis on synthesis and membrane binding of succinic dehydrogenase (SDH). The amount of SDH in whole-cell lysates in the soluble cytoplasmic fraction and in membranes was determined by one-dimensional (rocket) immunoelectrophoresis with an SDH-specific antiserum. After heme synthesis was blocked, the relative amount of SDH in the membrane decreased, whereas increasing amounts of SDH antigen were found in the cytoplasm. When heme synthesis was resumed on readdition of 5-aminolevulinic acid, the amount of membrane-bound SDH antigen increased at a much faster rate than net synthesis. During a 3-h growth period without 5-aminolevulinic acid, there was little change in the pattern of membrane proteins as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of radioactively labeled membranes, as compared to membranes from control cultures. However, both the 65,000-dalton and the 28,000-dalton polypeptides of the SDH complex (L. Hederstedt, E. Holmgren, and L. Rutberg, J. Bacteriol. 138:370-376, 1979) were present in decreasing amounts in membranes from 5-aminolevulinic acid-starved bacteria. From these results we suggest that SDH in B. subtilis is synthesized as a soluble protein and becomes membrane bound only when it attaches to a site in the membrane, (part of) which is a cytochrome of b type.

Aminolevulinic Acid↗
PubMed1978

Changes in synaptic function induced by blockage of axonal transport in the rabbit optic pathway.

This study was undertaken to elucidate the physiological significance of material involved in the rapid axonal transport. The effects of colchicine-induced inhibition of axonal transport in the retinal ganglion cells on the electrophysiological properties of the retrobulbar visual pathways were investigated in Albino rabbits. An impaired signal transmission to the contralateral visual cortex, superior colliculus and lateral geniculate body following flash light stimulation as well as direct optic nerve stimulation appeared 4--6 days after an intravitreous injection of 10--25 microgram colchicine. It was concluded that inhibition of the fast axonal transport within the retinal ganglion cells interferes with transsynaptic signal transmission from optic nerve terminals in the subcortical nuclei. This indicates a functional relationship between material supplied via the rapid phase of axonal transport and an unimpaired transsynaptic signal transmission, previously not revealed in the central nervous system of mammals.

Animals↗
PubMed1978

Characterization of succinic dehydrogenase mutants of Bacillus subtilis by crossed immunoelectrophoresis.

Eleven succinic dehydrogenase (SDH) mutants in Bacillus subtilis were analyzed by crossed immunoelectrophoresis with antiserum prepared against wild-type B. subtilis cytoplasmic membrane. A precipitate which stained for SDH was found in Triton X-100-solubilized wild-type membranes and in membranes from two of the SDH mutants. The remaining nine mutants did not show an SDH-staining precipitate. The respective mutations in these nine mutants all map in one locus, citF (Ohné et al., J. Bacteriol. 115:738-745, 1973). An SDH-specific antiserum was prepared by immunizing rabbits with the SDH precipitate obtained in crossed immunoelectrophoresis with solubilized wild-type membrane. Using this antiserum, it was shown that all of the nine citF mutants lack an SDH-specific antigen in the membrane but five of the citF mutants have a soluble SDH-specific antigen. No major differences were found in sodium dodecyl sulfatepolyacrylamide gels of membrane proteins from wild-type B. subtilis and from SDH mutants. A model for the organization of SDH in B. subtilis is proposed.

Bacillus subtilis↗
PubMed1977

Bacillus subtilis mutant with temperature-sensitive net synthesis of phosphatidylethanolamine.

Bacillus subtilis mutants with temperature-sensitive growth on complex media were screened for defects in phospholipid metabolism. One mutant was isolated that showed temperature-sensitive net synthesis of phosphatidylethanolamine. The mutant did not accumulate phosphatidylserine at the nonpermissive temperature. In the presence of hydroxylamine, wild-type B. subtilis accumulated phosphatidylserine at both 32 and 45 degrees C, whereas the mutant did only at 32 degrees C. In vitro phosphatidylethanolamine synthesis with bacterial membranes is no more temperature sensitive with mutant membranes than with wild-type membranes. The mutation probably affects the synthesis indirectly, possibly by altering a membrane protein. The mutant bacteria grew at the nonpermissive temperature, 45 degrees C, in a phosphate buffer-based minimal medium, although net synthesis of phosphatidylethanolamine was also temperature sensitive in this medium. One mutation caused both temperature-sensitive growth on complex media and temperature-sensitive net synthesis of phosphatidylethanolamine. The mutation is linked to aroD by transformation.

Acetates↗
PubMed1976

Evaluation of the pain suppressive effect of different frequencies of peripheral electrical stimulation in chronic pain conditions.

The pain suppressive effect of low (2/s) and high (50-100/s) frequency electrical stimulation was studied in 12 patients with severe chronic pain in the back and/or the legs. All patients were subjected to a thorough physical examination before and 2-3 weeks after a series of stimulation sessions. The stimulation was applied via surface electrodes to areas both segmentally related and segmentally unrelated to the regions of chronic pain. Low frequency stimulation induced a partial pain relief in only one patient whereas stimulation with high frequency gave a suppression of pain in seven patients. The effect was short-lasting in most cases and the pain started to increase usually within 30 min. It is concluded that the observed pain suppression is not due to psychological factors but to more basic neurophysiological mechanisms. Augmentation of the effect after repeated stimulation sessions was not observed, neither was there any alteration in the neuro-orthopedic status nor any lasting pain relief in any patient.

Adult↗
PubMed1975

Increase of pain threshold as a function of conditionsing electrical stimulation. An experimental study with application to electro-acupuncture for pain suppression.

Previous studies have shown that 2 Hz electrical conditioning stimulation of hands and cheeks increased the tooth pain threshold. In the present study the relation between strength of conditioning stimulation and amplitude of pain threshold increase is elucidated. Intense conditioning stimulation, giving subjective beating sensations and extensive muscles twitches, is required to obtain a substantial pain threshold increase. The results are discussed in relation to intensities used in electro-acupuncture and to interindividual variation of the effect. It is suggested that pain relief is obtained due to an inhibitory feed-back mechanism activated, not via low threshold afferents but via high threshold afferents.

Acupuncture Therapy↗
PubMed1975

On acupuncture analgesia and the mechanism of pain.

The effect on the experimental tooth pain threshold of conditioning electrical stimulation via needles or surface electrodes applied to the hands and cheeks was studied in 34 dental students. Conditioning stimulation with 2/sec. gave a slowly increasing pain threshold followed by a slow return to the control level in the post-conditioning period. In each individual the amplitude of the threshold increase was reproduceable. It was concluded that these effects are not due to motivational but to more basic neurophysiological mechanisms. The pain threshold was increased mainly by segmental conditioning stimulation; segmentally unrelated stimulation gave usually only small effects. Conditioning stimulation with 100/sec. produced only a strict segmental short-lasting effect. Effects with characteristics of both 2/sec. and 100/sec. were obtained by conditioning at 10/sec. It is suggested that the transmission of impulses from the pain afferents to ascending pathways is controlled at the segmental level by (a) presynaptic inhibition within the group of afferents giving rise to the flexion reflex of which the pain afferents are assumed to be a part; (b) postsynaptic inhibition between alternate pathway excited by flexion reflex afferents; and (c) descending control from supraspinal systems which may utilize similar segmental mechanisms as the primary afferents.

Acupuncture Therapy↗