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Biomedical subjects

A Persson

Publications and source records attributed to A Persson.

At least 73 records · Page 4Linked to original sources
PubMed1995

The purification of membranes by affinity partitioning.

We describe affinity partitioning as a preparative method for membranes and membraneous structures such as organelles, cells, and viruses. Biospecific affinity partitioning is carried out in aqueous polymer two-phase systems, commonly with polyethylene glycol and dextran as phase polymers, in an environment compatible with membrane structures. Ideally, two-phase conditions are chosen to partition the bulk of membrane material into one phase, while the affinity ligand, conjugated to the second phase polymer, will selectively pull the membranes to be isolated into this phase. Suitable ligands include lectins, antibodies, and receptor-specific agents. Because the method has so far been used successfully in rather few instances, all using high ligand receptor densities in target membranes, the discussion focuses on factors to be considered when developing affinity partitioning conditions using new ligands.

Affinity Labels↗
PubMed1995

Interactions of pulmonary surfactant protein D (SP-D) with human blood leukocytes.

Surfactant protein D (SP-D) is believed to contribute to nonimmune host defense within the alveoli and distal airways of the lung. SP-D molecules can bind to specific carbohydrates on the surface of bacterial, fungal, and viral organisms and can also interact with membrane glycoconjugates expressed by alveolar macrophages. Because neutrophils (PMN) and monocytes are recruited into the airspaces in association with many types of infection or lung injury, we examined the interactions of these cells with purified natural and recombinant SP-Ds, using a modified Boyden chamber assay and checkerboard analysis. Natural or recombinant rat SP-D (approximately 10(-9) to 10(-13) M) showed dose-dependent effects on human PMN and monocyte migration with a maximal response at a SP-D concentration of 5 ng/ml (approximately 10(-11) M). The migratory response was comparable to that obtained with the optimum concentration of FMLP (10(-8) M). HL-60 cells, after induction of differentiation with DMSO, responded to SP-D with the same dose-response as neutrophils. The effects of SP-D were abrogated by the simultaneous addition of SP-D to the upper chamber or by the addition of antibodies to the carboxy-terminal lectin domain. Migration toward SP-D was markedly inhibited (< 10% of controls) by 10 mM maltose but was not significantly inhibited by to 50 mM lactose. These studies establish that SP-D can bind to specific sites on neutrophils and monocytes and strongly suggest that these interactions involve the saccharide binding domains of SP-D.

Animals↗
PubMed1995

Performance of sulfhydryl boron hydride in patients with grade III and IV astrocytoma: a basis for boron neutron capture therapy.

This study investigated the rationale of boron neutron capture therapy (BNCT) for the treatment of Grade III and IV astrocytoma. The European Community joint research program on BNCT plans to use sulfhydryl boron hydride (BSH) in clinical trials. The work presented here, examines the performance of BSH in eight patients with Grade III and IV astrocytoma using a measurement technique which precisely correlates the boron uptake with the histology of the tumor and the peritumoral brain. Astrocytomas are exceptionally heterogeneous and spread migrating tumor cells into the surrounding brain. The patients were infused with 50 mg BSH per kilogram of body weight at 12, 18, 24 or 48 hours before surgery. At the time of operation, specimens were obtained of the tumor, skin, muscle, dura, blood, urine, and, when surgically possible, the brain adjacent to tumor. In three patients the intracellular boron distribution was investigated by subcellular fractionation. The blood clearance was biphasic with half-lives of 0.6 and 8.2 hours. After 3 days, approximately 70% of the dose injected was excreted in the urine. The maximum boron concentration in the tumor was 20 ppm, 12 hours after the infusion. The tumor-to-blood ratios ranged between 0.2 and 1.4, with the highest values after 18 to 24 hours. In the brain specimens the boron concentration never exceeded 1 ppm. This work confirms a selective uptake of boron in the tumor compared to the surrounding brain and that boron, to some extent, is incorporated in the tumor cells.

Astrocytoma↗
PubMed1994

Molecular structure of pulmonary surfactant protein D (SP-D).

Previous studies have shown that pulmonary surfactant protein D (SP-D) is composed of a 43-kDa polypeptide with a short NH2-terminal domain, a collagen sequence, and a COOH-terminal C-type lectin domain. In the present studies, ultrastructural and biochemical techniques were used to examine the quaternary structure of native rat SP-D (rSP-D). Electron microscopy of freeze-dried preparations demonstrated a highly homogeneous population of molecules with four identical rod-like arms (46 nm in length), each with an 8-9-nm diameter globular terminal expansion. The arms, which are similar in diameter to the type I collagen helix (approximately 4 nm), emanate from the central "hub" in two pairs that closely parallel each other for their first 10 nm. This structure is consistent with hydrodynamic studies that predict an highly asymmetric and extended molecule (f/f0 = 3.26) with a large Stokes radius (Rs = 18 nm). Pepsin digestion gave glycosylated, trimeric collagenous fragments (43 +/- 4 nm, 17 kDa/chain). Trimeric subunits containing intact triple helical domains were also liberated from SP-D dodecamers by sulfhydryl reduction under non-denaturing conditions. Digestion of rSP-D with bacterial collagenase generated a COOH-terminal carbohydrate binding fragment and a smaller peptide (approximately 12 kDa, unreduced) that contains interchain disulfide bonds. Electron microscopy also demonstrated higher orders of multimerization, with as many as 8 molecules associated at the hub. These studies demonstrate that SP-D is assembled as homopolymers of four identical trimeric subunits, that interactions between the amino-terminal domains of the trimers are stabilized by interchain disulfide bonds, and that SP-D molecules can associate to form complex multimolecular assemblies.

Amino Acid Sequence↗
PubMed1994

Recombinant pulmonary surfactant protein D. Post-translational modification and molecular assembly.

Pulmonary surfactant protein D (SP-D) is a member of a family of collagenous C-type lectins that includes the serum mannose binding proteins and surfactant protein A. Recent studies have shown that rat SP-D (rSP-D) molecules are assembled as tetramers of trimeric subunits (12 mers) and that dodecamers can participate in higher orders of molecular assembly involving interactions of the amino-terminal peptide domains. In order to further study the assembly of SP-D in vitro, Chinese hamster ovary K1 cells were transfected with a full-length rat SP-D cDNA, and stable transfectants with high levels of SP-D production (approximately 6 x 10(6) dodecamers/cell/24 h) were obtained using a glutamine synthetase selection system. The secreted molecules (RrSP-D), which were purified by affinity chromatography on maltosyl-agarose, comigrated with rSP-D on SDS-polyacrylamide gel electrophoresis in the presence and absence of reduction, and coeluted with rSP-D dodecamers from 4% agarose. The major bacterial collagenase-resistant peptide showed a decreased mobility on reduction consistent with the formation of intrachain disulfide bonds. A 17-kDa pepsin-resistant fragment was isolated following overnight digestion with pepsin at 27 degrees C, confirming the formation of a triple helical domain comparable in size and thermal stability to that of natural SP-D. The expressed protein contained sialylated endoglycosidase F-sensitive carbohydrate; amino acid analysis of acid and alkaline hydrolysates demonstrated essentially normal levels of hydroxyproline, hydroxylysine, and hydroxylysine-glycosides. Electron microscopic studies showed a molecular structure indistinguishable from lung SP-D, with a similar small subpopulation of molecules showing higher orders of multimerization. Solid-phase neoglycoprotein binding assays gave the same saccharide inhibition profile as natural rat SP-D, and both proteins showed efficient saccharide-dependent agglutination of Escherichia coli. These studies demonstrate that a single genetically distinct chain type can account for the various and complex molecular assemblies of SP-D, and further verify the potential physiologic significance of the disulfide-bonded multimers and higher aggregates isolated from rat, bovine, and human lung lavage.

Agglutination↗
PubMed1994

Lectin-mediated interactions of surfactant protein D with alveolar macrophages.

Surfactant protein D (SP-D) is a calcium-dependent carbohydrate-binding protein that is secreted into the pulmonary airspaces by type II epithelial and Clara cells. Previous studies have shown that SP-D can bind to specific surfactant phospholipids and to glycoconjugates associated with the surface of various microorganisms, consistent with possible roles in surfactant metabolism and pulmonary host defense. We now describe specific saccharide-mediated interactions of SP-D with alveolar macrophages in lung tissue and in vitro. Biotinylated rat SP-D showed specific binding to alveolar macrophages in sections of rat lung; this labeling was inhibited by competing saccharides or EDTA. In addition, the binding of 125I-SP-D to isolated alveolar macrophages in the presence of calcium was time-dependent, saturable, and reversible and was preferentially inhibited by known monosaccharide and disaccharide ligands for SP-D. Scatchard analysis gave an apparent single class of binding sites with a Kd = 1.4 x 10(-6) M. We speculate that the multivalent structure of SP-D mediates bridging interactions between microbial glycoconjugates or surfactant phospholipids and specific glycosylated ligands expressed on the surface of phagocytic cells.

Acetylglucosamine↗
PubMed1994

Quantitative analysis of EMG interference pattern in patients with laryngeal paresis.

Conventional (visual) analysis of EMG was compared to a computerized quantitative method (turns/amplitude). Ten patients with a clinical history of peripheral nerve lesion were examined in order to investigate whether quantitative analysis of EMG increased the diagnostic sensitivity of peripheral nerve lesions to the laryngeal muscles. Quantitative analysis either agreed with conventional analysis or resulted in false negative diagnosis compared to conventional analysis. Thus, conventional analysis turned out to be more sensitive to neurogenic damage than the quantitative method. EMG results were compared to clinical findings.

Adult↗
PubMed1994

Intestinal parasites in refugees and asylum seekers entering the Stockholm area, 1987-88: evaluation of routine stool screening.

In order to evaluate the results of routine screening for intestinal parasites, the medical records of 4592 refugees and asylum seekers arriving in the Stockholm area from January 1987 to December 1988 were reviewed. 3938/4592 (86%) delivered stool specimens for examination and intestinal parasites were demonstrated in 651/3938 (17%). Protozoa, mainly Giardia intestinalis, were found in 403/3938 (10%) and helminths, mainly nematodes, in 277/3938 (7%). Intestinal parasites were most frequently recovered in subjects coming from the Indian subcontinent/Southeast Asia and Africa (infection rates 39% and 25%, respectively). Extensive variations in the prevalence of intestinal parasite infection in various ethnic groups (range 4%-39%) were largely attributable to variations in prevalence of helminthic infections (range 2%-34%). Origin from the tropics or subtropics as well as low age, male sex, rural region of domicile before/during exile and short length of stay in Sweden were related to intestinal parasitic infection. Lack of data on morbidity in untreated asymptomatic carriers, limited risks for transmission of the recovered parasites in Sweden as well as the expenses for screening indicate a need for reconsideration of the present praxis of mass screening in favour of a selective screening of high-risk groups based on country of origin and age.

Adolescent↗
PubMed1993

Electroneurography index: a standardized neurophysiological method to assess peripheral nerve function in patients with polyneuropathy.

An index based on 12 electrophysiological parameters (conduction velocities, F-latencies, and amplitudes) was constructed to obtain an overall estimation of peripheral nerve conduction. The index was expressed as the mean deviation (in SD) compared to controls standardized for age or height. The stability of the index was tested by repeated examinations during intervals of several months in healthy subjects. The use of a compound index enabled detection of slight impairments of nerve conduction. The relatively low interrecording variability of the index makes it suitable to follow the progression of a polyneuropathy.

Adolescent↗
PubMed1993

EEG regional changes during long-term treatment with tetrahydroaminoacridine (THA) in Alzheimer's disease.

Three patients with Alzheimer's disease of mild type received long-term treatment with THA at doses between 40 mg to 160 mg daily. This study describes the effects of THA on EEG, seen during long-term and high dose treatments. After short-term treatment, the changes of the mean frequency in the temporal and parieto-occipital regions varied between patients, but in the frontal region a significant increase of the mean frequency was seen in all patients. The EEG improvement seen in the frontal region was more significant than that for the other regions at low dose of THA (80 mg). During long-term treatment, we observed different types of EEG changes. The early improvement seen in two patients was temporary and reverted to the pre-treatment value. In a third patient who did not show marked improvement after short-term treatment, an improvement was seen in all regions after longer treatment. Treatment with high doses of THA (120 mg or 160 mg) induced a marked increase in the mean frequency not only in the frontal region but also in the temporal and parieto-occipital regions. Higher doses of THA seem to affect larger areas of the brain than lower doses of THA.

Alzheimer Disease↗
PubMed1993

Generation of x rays for medical imaging by high-power lasers: preliminary results.

PURPOSE: To evaluate the use of x-ray imaging performed with a high-power laser system in biologic and medical studies. MATERIALS AND METHODS: A compact terawatt laser system based on chirped pulse amplification in titanium-doped sapphire was used. X rays were generated by irradiating a high-atomic-number target (tantalum). RESULTS: When photons with an energy below 10 keV were removed with use of 3 mm of aluminum, the half-value layer in aluminum for the remaining x rays was approximately 10 mm. The x-ray source allowed performance of biologic magnification radiography. Star-pattern tests indicated an equivalent focal spot size of less than 60 microns. Exposures of a single pulse could be obtained. The duration of a single x-ray pulse was estimated to be of the order of picoseconds. CONCLUSION: With use of subpicosecond laser pulses, x-ray generation can occur with a smaller equivalent focal spot size than with conventional x-ray sources.

Aluminum↗
PubMed1993

Accumulation of surfactant protein D in human pulmonary alveolar proteinosis.

Surfactant protein D (SP-D) is a collagenous calcium-dependent carbohydrate-binding protein that is structurally related to the serum mannose-binding proteins and pulmonary surfactant protein A. SP-D was initially characterized as a biosynthetic product of freshly isolated rat type II cells and first purified in chemical amounts from bronchoalveolar lavage of rats with silica-induced alveolar lipoproteinosis. The present studies describe the characterization of human SP-D isolated from therapeutic bronchoalveolar lavage of patients with pulmonary alveolar proteinosis. Human proteinosis SP-D was extracted from the 10,000 x g pellet of bronchoalveolar lavage with 100 mmol/L glucose or ethylenediamine tetraacetic acid, and specifically bound to and eluted from maltosyl-agarose. The protein cross-reacted with monospecific antibodies to rat SP-D by enzyme-linked immunosorbent assay and immunoblot and eluted near the position of rat SP-D on reverse-phase high performance liquid chromatography. When chromatographed on 4% agarose (A-15M) in the presence of ethylenediamine tetraacetic acid, the solubilized human proteinosis SP-D eluted near the void volume and earlier than rat SP-D dodecamers or human SP-D multimers in the lavage supernatant. Two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting of proteins in the lavage pellet with antibodies to the carbohydrate-binding domain of proteinosis human SP-D demonstrated covalently cross-linked multimers of SP-D monomers (43 kd, reduced) and multimers of trimeric components stabilized by disulfide and non-disulfide bonds. These studies describe the isolation and biochemical characterization of human SP-D and demonstrate the abnormal accumulation of this protein in the air spaces of patients with alveolar proteinosis.

Amino Acid Sequence↗
PubMed1992

Purification of plasma membranes by aqueous two-phase affinity partitioning.

A rapid method for purifying rat liver plasma membranes of high purity and yield is described. Squashed liver was homogenized in an aqueous polyethylene glycol-dextran two-phase system. After phase separation and reextraction of the bottom phase with fresh top phase, the combined polyethylene glycol-rich top phases were affinity partitioned in the presence of borate buffer with new bottom phase containing dextran-linked wheat-germ agglutinin. Under these conditions the lectin selectively pulled plasma membranes into the dextran-rich bottom phase, while other membranes preferentially distributed in the top phase. The lectin-containing bottom phase was reextracted with fresh top phase before collecting the purified plasma membranes by centrifugation. This protocol resulted in a preparation that was 30- to 40-fold enriched compared to the homogenate in plasma membrane markers for both the apical and basolateral domains and had yields of 55-70%. The contamination by other membranes was low. The entire procedure was completed within 90 min. The method should be useful for purifying plasma membranes also from other sources.

Animals↗
PubMed1992

Surfactant protein D: subcellular localization in nonciliated bronchiolar epithelial cells.

Surfactant protein D (SP-D, CP4) is a collagenous surfactant-associated carbohydrate binding protein that was initially characterized as a biosynthetic product of type II pneumocytes. Immunoperoxidase studies of formaldehyde solution-fixed and paraffin-embedded rat lung demonstrated staining for SP-D in the cytoplasm of a subpopulation of bronchiolar epithelial cells as well as type II cells. Accordingly, immunogold-labeling techniques were used to further examine the cellular distribution and subcellular localization of SP-D in the small airways. Lung tissues were fixed with 0.5% glutaraldehyde-3% paraformaldehyde and embedded in LR White resin. Sections were reacted with affinity purified polyclonal antibodies to SP-D, and sites of antibody binding were demonstrated using a biotinylated secondary antibody-streptavidin-gold detection system. Anti-SP-D selectively decorated secretory compartments of nonciliated bronchiolar cells (Clara cells) with strong and specific labeling of apical electron-dense secretory granules. Almost all of the granules in nonciliated columnar cells were labeled; however, labeling was typically nonuniform, with preferential decoration of the periphery of the granule. The largest numbers of immunoreactive epithelial cells were observed in the distal membranous bronchioles, with progressively smaller numbers of cells in more proximal bronchioles. There was no detectable labeling of cells lining the large cartilagenous airways or trachea. These studies provide evidence that SP-D is a secretory product of nonciliated bronchiolar cells. We suggest that Clara cell-derived SP-D is a component of bronchiolar lining material, consistent with our hypothesis that SP-D contributes to surfactant metabolism and/or host defense within small airways.

Animals↗