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Biomedical subjects

T Bergman

Publications and source records attributed to T Bergman.

At least 127 records · Page 7Linked to original sources
PubMed1989

Purification and characterization of an 80-kilodalton Trypanosoma cruzi urinary antigen.

A Trypanosoma cruzi antigen eliminated in the urine of experimentally infected dogs was detected by enzyme-linked immunosorbent assay between 9 and 28 days after infection. The parasite urinary antigen (UAg) was purified by affinity chromatography with polyclonal antibodies to T. cruzi. The eluate of the antibody column was subjected to high-performance liquid chromatography and showed a single peak of A280. This antigen was the only parasite component found in the urine of infected dogs during the course of acute T. cruzi infection. Antigen characterization was performed by two-dimensional gel electrophoresis, lectin affinity chromatography, proteolytic digestion, and Western blotting (immunoblotting). The isolated UAg exhibited a relative molecular size of 80 kilodaltons (kDa), an isoelectric point of 6.2 to 6.8, binding to concanavalin A, and sensitivity to trypsin. The parasite antigen was electroeluted from polyacrylamide gels and subjected to acid hydrolysis and amino acid analysis by reverse-phase high-performance liquid chromatography. The 80-kDa glycoprotein was recognized by serum antibodies from a wide variety of T. cruzi-infected hosts. The UAg proved to be a highly antigenic component present in different strains of T. cruzi. This 80-kDa polypeptide resembles one of the parasite antigens previously found in the urine of patients with acute Chagas' disease.

Amino Acids↗
PubMed1989

Microvascular blood flow, volume, and velocity measured by laser Doppler techniques in IDDM.

A laser Doppler device with the capability to simultaneously measure skin blood flow, microvascular volume, and erythrocyte velocity was used to assess blood flow changes in 35 insulin-dependent diabetes mellitus (IDDM) subjects, mean age 33 +/- 1 yr, with average duration of diabetes 14 +/- 1 yr, and in a nondiabetic control group. Blood flow was determined at 35 and 44 degree C at several sites on the upper and lower extremities with a temperature-regulated probe. Blood flow was highest at both temperatures on the pulps of the index finger and the first toe, regions of high density of arteriovenous anastomoses. There was significantly greater blood flow at most locations for the nondiabetic than the diabetic group at 35 degree C, and the differences between the two groups were substantially larger at 44 degree C. At 44 degree C, blood flow in the control group was approximately 40% greater in the upper extremity and 50% greater in the lower extremity than it was in the diabetic subjects. The differences were attributed to decreases of both microvascular volume and velocity in the diabetic group. In the upper extremity, volumes in the diabetic patients were 10-15% lower and velocities 10-40% lower than in the nondiabetic subjects. In the lower extremity, volumes were 20-25% lower and velocities 40-50% lower. We conclude that laser Doppler techniques can be used to assess microvascular changes in the skin of diabetic patients. This approach may be useful to evaluate and model diabetic microangiopathy.

Adult↗
PubMed1988

Guinea-pig liver leukotriene A4 hydrolase. Purification, characterization and structural properties.

Leukotriene A4 hydrolase from perfused guinea-pig liver was purified 1200-fold to near homogeneity with a yield of about 20%. Apparent values of Km and Vmax at 37 degrees C (27 microM and 68 mumol x mg-1 x min-1), turnover number, and activation energy for the conversion of leukotriene A4 into leukotriene B4 were estimated from kinetic data obtained at -10 degrees C, 0 degree C and +10 degrees C (Arrhenius plots). Physical properties including Mr (67,000-71,000), pH optimum, isoelectric point and Stokes' radius were determined. The amino acid composition and N-terminal amino acid sequence were established after carboxymethylation of the enzyme. Unlike liver cytosolic epoxide hydrolase, the purified enzyme did not catalyze the conversion of leukotriene A4 into (5S,6R)-5,6-dihydroxy-7,9-trans-11,14-cis-icosatetraenoic acid.

Amino Acid Sequence↗
PubMed1988

Purification in large scale and characterization of the human leukocyte adhesion glycoprotein GP90 (CD18).

The leukocyte adhesion 90-kDa glycoprotein GP90 (antigen CD18) is non-covalently associated separately with cell-surface glycoproteins GP160 (antigens CD11a, TA-1, LFA-1), GP155 (antigens CD11b, OKM1, MO1) or GP130 (antigens CD 11c, Leu-M5). Large amounts of these protein complexes were purified to homogeneity from blood mononuclear leukocytes by immunoaffinity chromatography using a monoclonal antibody. GP90 was further isolated by preparative gel electrophoresis in the presence of sodium dodecyl sulfate. Rabbit antiserum towards the complex inhibited phorbol-ester-induced adhesion of leukocytes. The antiserum towards purified GP90 reacted more strongly with the denatured GP90 protein, but showed reactivity also with GP160 protein, indicating structural homologies between GP90 and GP160. The amino acid composition of GP90 was determined. Its N-terminus was found to be blocked. Treatment of GP90 with endo-beta-N-acetylglucosaminidase F, but not with endo-beta-N-acetylglucosaminidase H, reduced the apparent molecular mass to 75 kDa, indicating the presence of five or six N-linked complex-type oligosaccharides/molecule.

Amino Acids↗
PubMed1988

95- and 25-kDa fragments of the human immunodeficiency virus envelope glycoprotein gp120 bind to the CD4 receptor.

125I-labeled gp120 (120-kDa envelope glycoprotein) from the BH10 isolate of human immunodeficiency virus is cleaved to a limited extent with the glutamate-specific protease from Staphylococcus aureus. After disulfide bond reduction, fragments with approximate molecular masses of 95, 60, 50, and 25 kDa are produced. Tests for binding to CD4-positive cells show that only two fragments, the 95- and 25-kDa peptides, are observed in cleavage products that retain the selective binding capacity of gp120. Radiosequence analysis of the fragments after sodium dodecyl sulfate/polyacrylamide gel electrophoresis and electroblotting demonstrates that the 95-kDa fragment lacks the N-terminal region of gp120 and starts at position 143 of the mature envelope protein. The 50-kDa fragment starts at the same position. The 25-kDa binding fragment was similarly deduced to be generated as a small fragment from a cleavage site in the C-terminal part of gp120. The identifications of these fragments demonstrate that radiosequence analysis utilizing 125I-labeled tyrosine residues can function as a useful and reliable method for small-scale determination of cleavage sites in proteins. Combined, the data suggest domain-like subdivisions of gp120, define at least two intervening segments especially sensitive to proteolytic cleavage, and demonstrate the presence of a functional region for receptor binding in the C-terminal part of the molecule.

Cell Line↗
PubMed1987

Electroblotting of individual polypeptides from SDS/polyacrylamide gels for direct sequence analysis.

A scheme for electroblotting of individual unstained protein bands from SDS/polyacrylamide gels and subsequent amino acid sequence analysis is described. Principal features are: detection of the polypeptide bands by visualization with KCl; electroblotting of excised gel pieces that correspond to the protein bands only; blotting onto polybrene-pretreated glass-fiber filter discs (12 mm diameter) placed in an electrophoretic concentrator. A high yield over all steps from gel application through electrophoresis, blotting, gas-phase sequencer degradation, and phenylthiohydantoin analysis is obtained with several different types of polypeptide (combined average yield over all steps 20%, spread 10-50%). Background is low and samples can be stored under vacuum for long periods after blotting.

Amino Acid Sequence↗
PubMed1987

Two hydrophobic low-molecular-mass protein fractions of pulmonary surfactant. Characterization and biophysical activity.

Hydrophobic low-molecular-mass proteins were isolated from minced pig lungs and separated into two fractions. Electrophoresis of protein fraction 1 showed two major bands. Calculations of molecular masses from the electrophoretic mobilities are unreliable because of the extreme hydrophobicity of the peptides. However, the two bands were at positions corresponding to apparent molecular masses of about 3 kDa and 14 kDa, while sequence degradation disclosed only one major structure. Electrophoretic separation of protein fraction 2 revealed one band, at an apparent molecular mass of about 6 kDa. Microheterogeneities at the N terminus of both fractions were observed. However, the two fractions had different N-terminal structures and amino acid compositions. Consequently they are concluded to represent different polypeptides without common segments. Bronchoalveolar lavage from humans also contains surfactant polypeptides and at least the fraction 2 peptide is highly similar in human and porcine surfactants. Artificial surfactant preparations, obtained by recombination of protein fraction 1 or 2 with a mixture of synthetic phospholipids, were evaluated with the pulsating bubble method and in experiments on artificially ventilated premature newborn rabbits. The addition of protein fraction 1 to the phospholipid mixture improved surface adsorption from more than 300 s to about 2 s and reduced minimum surface tension from more than 20 mN/m to nearly 0 as measured with a pulsating bubble. When this surfactant preparation was instilled into the airways of newborn rabbits, the tidal volumes at insufflation pressure 25 cm H2O was increased about twentyfold compared to the volumes obtained in non-treated controls. Preparations based on protein fraction 1 had better in vitro and in vivo properties than those based on protein fraction 2. Both these protein-based preparations were decidedly more effective than phospholipids alone.

Amino Acid Sequence↗
PubMed1987

Processing of Bacillus subtilis succinate dehydrogenase and cytochrome b-558 polypeptides. Lack of covalently bound flavin in the Bacillus enzyme expressed in Escherichia coli.

The DNA sequence of the Bacillus subtilis sdh operon coding for the two succinate dehydrogenase subunits and cytochrome b-558 (the membrane anchor protein) has recently been established. We have now determined the extent of N-terminal processing of each polypeptide by radiosequence analysis. At the same time, direct evidence for the correctness of the predicted reading frames has been obtained. The cytochrome showed a ragged N-terminus, with forms lacking one residue, and is inserted across the membrane without an N-terminal leader-peptide. Covalently bound flavin was not detectable in B. subtilis succinate dehydrogenase expressed in Escherichia coli despite normal N-terminal processing of the apoprotein. This provides an explanation to why the succinate dehydrogenase synthesized in E. coli is not functional and demonstrates that host-specific factors regulate the coenzyme attachment.

Amino Acid Sequence↗
PubMed1987

Characterization of domain borders and of a naturally occurring major fragment of staphylococcal alpha-toxin.

A naturally occurring staphylococcal alpha-toxin fragment with an apparent membrane-binding capacity but without toxic activities is shown to be derived from the C-terminal half of the intact polypeptide chain by cleavage between position 134 and 135 in the parent molecule. The resulting N-terminus is slightly ragged with a fragment start not only at position 135 but also at the adjacent position 136. Another naturally occurring fragment starts at position 9, derived from an original cleavage between position 8 and 9 in the parent molecule. Analysis of non-purified fragment mixtures confirmed these positions and established that only one further region, at positions 71-72, is partly sensitive to proteolysis under natural conditions. Trypsin treatment has limited effects on the native toxin molecule, giving essentially only two initial cleavages with resultant large fragments. One of these cleavages is at the peptide bond between position 131 and 132, thus only three residues away from the position of the major naturally occurring cleavage. The other bond sensitive to trypsin is between position 8 and 9, thus identically positioned to the cleavage occurring naturally. Together, all the cleavages define a region in a central segment of the polypeptide chain that has all the properties of an inter-domain segment. The C-terminal half appears to constitute a membrane-binding domain, and the N-terminal half a structure needed for full biological activity, functionally subdividing the parent polypeptide chain.

Amino Acid Sequence↗
PubMed1987

Domain structure of the glucocorticoid receptor protein.

The purified rat liver glucocorticoid receptor protein was analyzed by limited proteolysis and amino acid sequence determination. The NH2 terminus appears to be blocked. The steroid-binding domain, defined by a unique tryptic cleavage site, corresponds to the COOH-terminal part of the protein with the domain border in the region of residue 518. The DNA-binding domain, defined by a region with chymotryptic cleavage sites, is immediately adjacent to the steroid-binding domain and reflects another domain border in the region of residues 410-414. The results described at the protein level in this report confirm functional data previously obtained by mutations at the genetic level.

Amino Acid Sequence↗
PubMed1987

Testing of isokinetic muscle strength in the ankle.

The purpose of this study was to evaluate isokinetic strength measurement in ankle joint. The study was divided into three parts. A comparison of dorsal and plantar flexion with and without consideration to the biomechanical circumstances was done. The series comprised 15 men and 10 women. A comparison of strength measurements of dorsal flexion with and without fixation of the upper trunk. The series consisted of 10 men. A reference series for dorsal and plantar flexion comprising 15 men (mean age = 34 +/- 9 yr) was used for comparison. Strength was tested at 0 degree, 15 degrees, 30 degrees, 60 degrees, 120 degrees, 180, and 240 degrees/s. The readings made without biomechanical adjustment were significantly higher than connected readings. Mean difference at 30 degrees/s was 8.4 +/- 7.1 Nm for dorsal flexion and 18 +/- 3.1 Nm for plantar flexion. The torque values were significantly higher when the upper trunk was not immobilized, and higher standard deviations were obtained. The left (viz. dominant) leg produced significantly higher muscle torque at all velocities for plantar flexors and at all but 180 degrees and 240 degrees/s for dorsal flexors. The regression coefficient was used as a measure of peak torque velocity relation, the coefficient was -0.50 +/- 0.16 for plantar flexion and -0.22 +/- 0.06 for dorsal flexion.

Adult↗
PubMed1986

Isolation and characterization of variant IGF-1 as well as IGF-2 from adult human brain.

The forms of somatomedin present in the adult human brain have been characterized in this study. Two peptides were purified by acidification, size exclusion chromatography, affinity chromatography, FPLC and HPLC. Structural analysis identified these peptides as the variant form of IGF-1 with a truncated N-terminal region earlier isolated from human fetal brain and IGF-2. The presence of the truncated IGF-1 variant and IGF-2 in the human CNS suggests their role as neuropeptides.

Adult↗
PubMed1985

Skeletal muscle function in man: force, relaxation rate, endurance and contraction time-dependence on sex and age.

Two different methods for estimating muscle function were compared; hand grip strength (HGS) and adductor pollicis muscle function after electrical stimulation of the ulnar nerve. Fifty-two 'normal' subjects, who were divided into four groups, according to sex and age, were investigated. Technical modifications of the latter method are presented for the measurement of human skeletal muscle function, independent of the motivation of the subject. Maximal voluntary force, as measured with a hand dynamometer, was higher in males than in females. Young males were stronger than males over 50 years old, and young females were stronger than old women. The statistical analysis of the muscle function variables after electrical stimulation showed that young females developed relatively more force at low stimulating frequencies than females over 50 years old. Females had a significantly longer contraction time to tetany compared to males. The relaxation rate after tetanic stimulation was independent of sex and age. Endurance was reduced in old males compared to females in the same age-group and to young males.

Adult↗
PubMed1981

Interfacing a modern signal averager to a minicomputer.

The design and operation of a bidirectional interface for transfer of data between a signal averager (Nicolet 1170) and a minicomputer (PDP-11/34) are described. The interface has been shown to function reliably using data lines of 20 m.

Computers↗