[Dyslexia, a serious disability].
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Adolescent↗
Biomedical subjects
A Olofsson
Publications and source records attributed to A Olofsson.
Crystalline layers and three-dimensional structure of Staphylococcus aureus alpha-toxin.
Interaction of the pore-forming protein alpha-toxin from Staphylococcus aureus with lipid components from platelet membranes induces crystal formation of the toxin oligomers. Structure analysis of crystalline areas in either sodium phosphotungstic acid or a sodium phosphotungstic acid/glucose mixture has been performed with electron microscopy and image processing. Ordered domains extending up to a few micrometers were observed, particularly after application of alpha-toxin to pre-formed lipid layers. The crystals, showing tetragonal symmetry, formed either separate two-dimensional sheets or three-dimensional piles of layers. The corresponding unit cell parameter of the single layer was a = b = 109.4 A (standard deviation 2.1 A, n = 21). Incubation of the toxin with intact membranes or extracted lipids as well as application of the lipid layer technique resulted in congruous crystalline properties. The projected averaged alpha-toxin oligomer shows cyclic symmetry with a stain-filled space in the centre. The bulk of the three-dimensional model consists of four asymmetric protein units forming a ring. In addition, a small domain covers the central cavity at the face of the protein opposite to the underlying lipid. The conditions under which the tetragonal arrays are formed on the lipid layers suggest that the alpha-toxin molecule is in a conformation binding to a hydrophobic surface rather than fully inserted into a lipid bilayer.
Bacterial Toxins↗
TGF-beta 1 binding protein: a component of the large latent complex of TGF-beta 1 with multiple repeat sequences.
TGF-beta occurs in a latent complex of high Mr. We report the cDNA cloning and an initial structural and functional characterization of a component of the large latent TGF-beta 1 complex, denoted TGF-beta 1 binding protein (TGF-beta 1-BP). Most of the sequence of fibroblast TGF-beta 1-BP is made up of cysteine-rich repeats of two different kinds; there are 16 EGF-like repeats and three repeats with a distant resemblance to EGF, but of a distinct type hitherto not found in any other protein. beta-hydroxylated asparagine residues were identified in two of the EGF-like repeats. TGF-beta 1-BP purified from human platelets is considerably smaller than the fibroblast form (125-160 kd vs. 170-190 kd), suggesting that there is alternative splicing of the TGF-beta 1-BP gene or that TGF-beta 1-BP undergoes cell-specific proteolysis. TGF-beta 1-BP was found not to bind and inactive TGF-beta 1; its role in the latent complex is discussed.
Amino Acid Sequence↗
[They help each other to grieve for a beloved person].
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Aged↗
Latent forms of TGF-beta: structure and biology.
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Blood Platelets↗
Digitization of electron micrographs: a comparison of three different types of scanners.
Some aspects of digitization of electron micrographs have been investigated. The performances of a flat-bed, a rotating drum, and a diode array scanner have been evaluated. Estimates have been achieved for resolution, mechanical and optical stability, and optical density response. It is concluded that for routine transmission electron microscopy of, for example, negatively stained biologic specimens, a diode array scanner produces data good enough to obtain resolutions at a level normally expected. High speed is the major advantage with this type of equipment. However, for high-resolution work it is necessary to use a conventional scanner with a relatively slow scan speed.
Analog-Digital Conversion↗
The projection structure of alpha-toxin from Staphylococcus aureus in human platelet membranes as analyzed by electron microscopy and image processing.
Most strains of Staphylococcus aureus produce alpha-toxin, a 33-kDa membrane active protein which is considered to be an important virulence factor of this bacterium. When alpha-toxin interacts with membranes an oligomeric from of the toxin can be seen by electron microscopy as characteristic ring structures in the membrane. A two-dimensional study of these annular structures, incorporated in membranes of human platelets, was performed, introducing a partly new method for rotational alignment of individual particles. It is shown that the averaged oligomer consists of six subunits. At neutral pH the outer diameter of the ring is about 75 A. The stain-filled pore or cavity in the center has a diameter of about 25 A. The size of the hexamer is increased if the pH is lowered.
Blood Platelets↗
Relations between speech intelligibility and psychoacoustical modulation transfer function (PMTF).
The modulation transfer function, MTF, has proved to be a powerful measure for predicting speech intelligibility in speech transmission channels. We extended it to include the ear, by measuring the psycho-acoustical MTF, i.e. the PMTF. Tone thresholds of 11 normal-hearing and 20 hearing-impaired subjects were measured in presence of unmodulated and intensity modulated noise. Octave frequencies from 500 to 4,000 Hz were used. The noise was octave filtered around the frequency of the probe tone. Six modulation frequencies from 1 to 50 Hz were used. From these results the PMTFs were calculated, as well as the corresponding psycho-acoustical speech transmission indices, i.e. the PSTIs. The subjects' speech discrimination scores in quiet and speech reception thresholds in noise were also measured. A correlation coefficient of 0.85 between the speech discrimination score in quiet and the PSTI was obtained. For the speech reception threshold in noise and the PSTI, the correlation was 0.71. The first of these two figures is promising, but our method needs some improvement, as it gave some problems due to fatigue effects.
Hearing Loss, Sensorineural↗
Intraepithelial migration of mucosal mast cells in hay fever: ultrastructural observations.
Evidence has been presented suggesting that a migration of nasal mast cells from the mucosal connective tissue stroma into the epithelium is part of the mucosal response in birch pollen allergy. In a previous study, the identification of these intraepithelial cells as tissue mast cells rather than blood basophils was based on light microscopical morphology and histochemistry. We have now studied the ultrastructure of these cells in mucosal biopsies taken before and during the birch pollen season. Intraepithelial cells with basophil or metachromatic granules were only observed in biopsies taken during the season. Some of these cells had the ultrastructural appearance of tissue mast cells, including cytoplasmic lipid droplets and a granular substructure composed of multilamellar arrays and scrolls, serving to distinguish human mast cells from blood basophils. The ultrastructural traits of the remaining cells were heterogeneous, some reminiscent of human blood basophils, others of globule leucocytes of other species, but entirely typical blood basophils could not be identified. The results thus support our previous suggestion that a migration of mucosal mast cells from the connective tissue stroma into the epithelium is part of the human allergic mucosal response. It cannot be determined whether the ultrastructural heterogeneity of these cells is the result of an adaptation to the intraepithelial environment of one single mast cell type or to the existence of an ultrastructurally distinct mucosal mast cell.
Basophils↗
Can phonemic awareness be trained in kindergarten?
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Auditory Perception↗
MRI acoustic noise: sound pressure and frequency analysis.
The large gradient coils used in MRI generate, simultaneously with the pulsed radiofrequency (RF) wave, acoustic noise of high intensity that has raised concern regarding hearing safety. The sound pressure levels (SPLs) and power spectra of MRI acoustic noise were measured at the position of the human head in the isocenter of five MRI systems and with 10 different pulse sequences used in clinical MR scanning. Each protocol, including magnetization-prepared rapid gradient echo (MP-RAGE; 113 dB SPL linear), fast gradient echo turbo (114 dB SPL linear), and spin echo T1/2 mm (117 dB SPL linear), was found to have the high SPLs, rapid pulse rates, amplitude-modulated pulse envelopes, and multipeaked spectra. Since thickness and SPL were inversely related, the T1-weighted images generated more intense acoustic noise than the proton-dense T2-weighted measures. The unfiltered linear peak values provided more accurate measurements of the SPL and spectral content of the MRI acoustic noise than the commonly used dB A-weighted scale, which filters out the predominant low frequency components. Fourier analysis revealed predominantly low frequency energy peaks ranging from .05 to approximately 1 kHz, with a steep high frequency cutoff for each pulse sequence. Ear protectors of known attenuation ratings are recommended for all patients during MRI testing.
Calibration↗
Two-dimensional structure of membrane-bound annexin V at 8 A resolution.
Two-dimensional (2-D) crystals of annexin V, grown by specific binding to phosphatidylserine-containing planar lipid films, were studied by electron image analysis. Images of negatively stained two-dimensional crystals showed diffraction peaks extending to 11 A. After correcting lattice distorsions and averaging over several crystalline areas, the resolution of the analysis was extended up to 8 A. Observed along a direction perpendicular to the membrane plane, the four homologous domains characteristic of annexin V exhibit a noticeable difference in their distribution of protein density. An unambiguous assignment of the domains was possible due to the similar packing of annexin V molecules in the 2-D crystals and in a 3-D crystal form with pseudo-R3 symmetry. The domains I and IV (numbering according to Huber et al., Embo J., 1990, 9, 3867-3874) appear well resolved. On the other hand, the two other domains, II and III, present an almost continuous density, with a protrusion extending outwards the annexin V molecule. In addition, no hydrophilic opening is resolved at the center of the molecule, yet a stain-filled 13-A structure is present, surrounded by domains I, II, and IV and distant by 5 A from the center of the molecule. We interpret these structural features as reflecting a conformational change in the annexin V structure resulting from its membrane binding.
Analog-Digital Conversion↗
The three-dimensional structure of trypsin-treated Staphylococcus aureus alpha-toxin.
Trypsin treatment of staphylococcal alpha-toxin cleaves the molecule into two roughly equally sized parts, which results in inactivation of the toxin. Tetragonal arrays of oligomers, closely resembling the native ones, can however be formed on lipid layers. From tilted views of negatively stained crystals a 3D structure to 23 A resolution has been determined by electron microscopy and image processing. On comparison with the 3D structure of the native alpha-toxin (Olofsson et al., J. Mol. Biol. 214, 299-306, 1990) the subdomains are more separated, confirming the differences found when comparing the projection maps (Olofsson et al., J. Struct. Biol. 106, 199-204, 1991). The tryptic cleavage takes place in a postulated hinge region. The results are consistent with the hypothesis that the conformational change required for inducing the membrane permeabilizing property takes place in this region. Furthermore, we present a refined projection map at approximately 10 A resolution based on the analysis of a large number of crystals using unbending methods.
Bacterial Toxins↗
Strong suppression by mononuclear leukocytes from cord blood of human newborns on maternal leukocytes associated with differences in sensitivity to prostaglandin E2.
We have tested peripheral mononuclear leukocytes (PML) from the cord blood of newborns, from sera of their mothers, and from sera of nonrelated nonpregnant adult women for sensitivity to suppressive exogenous prostaglandin E2 (PGE2). Endogenous PG production was simultaneously inhibited by indomethacin 2.8 microM. The phytohemagglutinin-stimulated (PHA-simulated) uptake of tritiated thymidine (3H-TdR) by PML from the mothers and the nonpregnant women was suppressed by the exogenous PGE2 at a concentration of 1.4 x 10(-8) M, 100 times less than the one required to suppress the PML from newborns (1.4 x 10(-6) M). In addition, 1.4 x 10(-7) M or less of PGE2 reversed the suppression of neonatal PML to stimulation. The maternal PML were reversed into stimulation at 1.4 x 10(-9) of exogenous PGE2. The amount of endogenous PGE2 synthesized by 1 x 10(6) fresh, nonstimulated neonatal PML according to gas chromatography-mass spectrometry assay was 5 ng (1.4 x 10(-8) M). The synthesis increased to 27 ng/10(6) cells after 18 hours' incubation. These concentrations are similar to the ones of exogenous PGE2 at which neonatal PML were slightly stimulated but the maternal cells were still suppressed. Preincubation for 18 h at 37 degrees C decreased the PGE2 induced suppression of the adult PML but did not change the response of the neonatal PML.
Adult↗
Early language development and kindergarten phonological awareness as predictors of reading problems: from 3 to 11 years of age.
At the end of Grade 4, 481 children on the Danish island of Bornholm were screened using group tests for sentence reading. For 205 of these children, language and speech data from the speech therapist's screening at age 3 were available, as well as language comprehension and linguistic awareness data from the kindergarten year (age 6) and word decoding measures in Grades 2 and 3. A path analysis revealed significant paths from early language abilities at age 3 through expressive and receptive language in kindergarten via language awareness in kindergarten and word decoding in Grade 2 to sentence reading in Grades 3 and 4. The subgroup of children with parents who had reported a history of reading problems at school entry scored significantly below average on sentence reading in Grade 4. The subgroup of children that were reported to show a very low interest in books and story reading before age 5 also scored low on sentence reading in Grade 4. Statistically significant but weak relationships were also found between parents' educational background, parents' library visits, and number of books at home and the child's reading ability in Grade 4.
Awareness↗