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At least 19 recordsLinked to original sources
PubMed1977

Giant cell tumor of bone: fine structural localization of acid phosphatase.

The fine structural localization of acid phosphatase in the different cells in a benign giant cell tumor of bone has been studied. Stromal cells type 1 and 2 (fibroblast-like and macrophage-like, respectively) showed the presence of lead phosphate precipitate following incubation in a Gomori-type lead salt medium only in conventional lysosomes. In the multinucleated giant cells, the final product was deposited over lysosome-like organelles, and also over Golgi cisternae, vesicles, and vacuoles. Furthermore, evidence for presence of acid phosphatase was obtained in smooth-surfaced tubular, sausage-, horse-shoe-, and ring-shaped structures and over digestive vacuoles of autophagic or heterophagic origin. Finally, in these cells, many of the tubular and vacuolar elements located subjacent to areas of the plasma membrane with microvillous specializations (abortive brush borders?) were shown to carry acid phosphatase.

Acid Phosphatase↗
PubMed1978

Giant cell tumor of bone. Fine structural localization of alkaline phosphatase.

The fine structural localization of nonspecific alkaline phosphatase was elucidated in two giant cell tumors of bone using lead as capturing ion and beta-glycerophosphate as substrate in the incubation solution. Lead phosphate precipitate--indicating presence of alkaline phosphatase--was demonstrated on the plasma membranes, and the membranes bordering vesicles and vacuoles of presumed endocytotic nature, in giant cells and type 1 stromal cells (fibroblast-like cells). The findings support the view that stromal cells type I and giant cells are histogenetically related.

Adult↗
PubMed1987

Local structure analyzers as determinants of preattentive pattern discrimination.

Contemporary literature suggests that preattentive texture or pattern discrimination is induced by differences between local structure features or "textons." This paper presents a model for the description of such local structure features based on the computation of local autocorrelations within the image. By means of this structure model a measure of structure dissimilarity is introduced. Experiments have been carried out to test a hypothesized relation between the detectability of a target pattern in a field of background patterns and the value of the structure dissimilarity measure. The experimental results show that it seems justified to relate, in a quantitative way, the detectability of the target pattern to the value of the structure dissimilarity measure.

Form Perception↗
PubMed1985

Local base dynamics and local structural features in RNA and DNA duplexes.

Local base motion and local structural base information are derived with a simple motional model from site specifically spin-labeled polyribo- and polydeoxyribonucleotides. The model was developed earlier for some nucleic acids and has now been applied to analyze 22 different nucleic acid systems. We conclude that the base motion of the spin-labeled nucleotide in single-stranded RNA, DNA, or non-base-paired bases in duplexes is of the order of 1 ns and that its base mobility decreases by about a factor of 4 upon base pairing. Also, the tether motion of the probe is slower in an RNA than in a DNA duplex.

DNA↗
PubMed1992

Detection of local structures in reduced unfolded bovine pancreatic trypsin inhibitor.

The structure of BPTI and reduced BPTI in concentrated guanidinium HCl (GUHCl) in the presence of glycerol has been probed by measurements of dynamic nonradiative excitation energy transfer between probes attached to its amino groups. Interprobe distance distributions were obtained from analysis of donor fluorescence decay curves and used to characterize local structures in unordered states of the protein. Site specifically fluorescently labeled BPTI derivatives (1-n)BPTI (n = 15, 20, 41, 46) were used, each carrying a 2-methoxy-naphthyl-1-methylenyl group (MNA) at the N-terminal amino group of arg1 and 7-(dimethylamino)-coumarin-4-yl-acetyl residue (DA-coum) at one of its epsilon-NH2 groups of the lysine side chains. Analysis of donor fluorescence decay kinetics gave the interprobe distance distributions in the native and denatured states. The N-terminal-segment, residues 1-15, is in an extended conformation (with an average interprobe distance of 34 +/- 2 A) in the native state. Upon unfolding by reduction with DTT or beta-mercapto ethanol in 6 M GUHCl/glycerol mixture, the conformation of this segment relaxed to a state characterized by a reduced average interprobe distance and a larger width of the distances distribution. The average distance between residues 1 and 26, i.e., between the N-terminus and the turn of the twisted beta sheet element (residues 18-35), increased upon unfolding. At -30 degrees C in the above solvent, the distribution between these two sites was probably composed of two conformational subpopulations. About 45 +/- 20% of the molecules were characterized by a short interprobe distance (like the native state) representing a compact conformation, and 55 +/- 20% of the molecules showed large interprobe distances representing an expanded (unfolded) conformation. Thus local structures seem to exist in reduced denatured BPTI even under denaturing conditions in 6 M GUHCl/glycerol mixtures. Some of those structures are unstable in guanidinium isothiocyanate (GUSCN). The method introduced here is suitable for probing local structures and very long range interactions in unfolded proteins and for search for folding initiation sites (FISs) and early folding intermediates.

Aprotinin↗
PubMed1991

Structural and kinetic aspects of chemical reactions in DNA duplexes. Information on DNA local structure obtained from chemical ligation data.

Chemical ligation of oligonucleotides in double-stranded helices has been considered in its structural-kinetic aspect. A study was made of (i) two series of DNA duplexes with various arrangements of reacting groups in the ligation junction induced by mispairing or by alteration of furanose structure (the replacement of dT unit with rU, aU, IU, xU, dxT ones) and of (ii) eight synthetic water-soluble carbodiimides with different substituents at N1 and N3 atoms. We assumed that some information on the local structure of modified sites in the duplex can be obtained from kinetic parameters of oligonucleotide coupling reaction. The ratio of kinetic constants k3/(k2 + k3) for productive and nonproductive decomposition of the activated phosphomonoester derivative apparently reflects the reaction site structure: for a given duplex this parameter is virtually independent of the condensing agent composition. Based on the analysis of the chemical ligation kinetics a suggestion has been made about the conformation of some modified units in the double helix.

Autoradiography↗
PubMed1990

[Determination of the local structure of the protein insectotoxin I5A from the scorpion Buthus eupeus from 1H-NMR spectroscopy data].

The local structure (torsion angles phi, psi and chi 1 of amino acid residues) of insectotoxin I5A (35 residues) of scorpion Buthus eupeus has been determined from cross-peak integral intensities in two-dimensional nuclear Overhauser enhancement (NOESY) spectra and spin coupling constants of vicinal H--NC alpha--H and H--C alpha C beta--H protons. The local structure determination was carried out by fitting complete relaxation matrix of peptide unit protons (protons of a given residue and NH proton of the next residue in the amino acid sequence) with experimental NOESY cross-peak intensities. The obtained intervals of backbone torsional angles phi and psi consistent with NMR data were determined for all but Gly residues. The predominant C alpha--C beta rotamer of the side chain has been unambiguously determined for 42% of the insectotoxin amino acid residues whereas for another 46% residues experimental data are fitted equally well with two rotamers. Stereospecific assignments were obtained for 38% of beta-methylene groups. The determined torsional angles phi, psi and chi 1 correspond to the sterically allowed conformations of the amino acid residues and agree with the insectotoxin secondary structure established earlier by 1H NMR spectroscopy.

Amino Acids↗
PubMed1979

Fine structural localization of endogeneous peroxidase in the endostyle of ascidians, Ciona intestinalis. A part of phylogenetic studies of the thyroid gland.

The fine structural localization of peroxidase activity in the endostyle of Ciona intestinalis was studied by cytochemistry at electron microscopic level. Only zone 7 cells in this organ are positive for this enzyme activity. The reaction product is recognized in the external surface of the apical plasma membrane, and in the cisternae of the rough endoplasmic reticulum, of the nuclear envelope, and of the Golgi lamellae, and small vesicles of the Golgi region and of the apical cytoplasm. By electron microscopic autoradiography of 125I, the main site of iodination of thyroglobulin-like protein is considered to be the apical plasma membrane region of the zone 7 cells. The possibility of iodination of protein taking place within the endostylar lumen near the zone 7 cell cannot be ruled out. The relationship between the fine-structural localization of peroxidase activity and the site of iodination of protein is discussed.

Animals↗
PubMedDate not supplied

[The task of determining the local structure of proteins by Overhauser effect nuclear spectroscopy addressed once more].

The testing of the earlier developed theoretical method for determining the backbone protein conformations (the local structure) on the basis of the two-dimensional nuclear Overhauser effect (NOE) spectroscopy has been fulfilled. The method approval has been carried out by the calculation (based upon spectral NOE parameters) of the local plastocyanin and bovine pancreatic trypsin inhibitor structures followed by the comparison of the received conformational parameters with the X-ray data. The comparison of the molecular conformations in solution and crystal has been implemented for different fragments of the polypeptide chain (beta-structures, alpha-helices, irregular segments) using the mathematical statistics methods. The verification of the "zero" hypothesis about the similarity of phi and psi variation rows which was carried out at the reliability level of 0.99 showed that in both cases there were no systematic deviations of dihedral angles of the compared conformations and that their dispersion differences were statistically indiscernible. It has been concluded that the approved method permits to determine the local structure of the conformationally rigid proteins (or their fragments) at the level close to that which provides the high resolution X-ray analysis.

Amino Acid Sequence↗
PubMed1975

Fine structural localization of arylsulfatase B activity in the rabbit blood platelets.

Fine structural localization of arylsulfatase in the rabbit blood platelets has been investigated in this study. Among many cell organellae, reaction products were exclusively observed in the alpha granules of the platelets. Within the alpha granules, arylsulfatase activity appeared to localize in variable patterns, i.e. reaction products confined mainly at the peripheral region in many granules, while they deposited heavily throughout the granule matrices in some others. In a blood platelets, each alpha granule showed the different staining pattern which indicated more variable functional heterogeneity in the granules.

Animals↗
PubMed1975

Fine structural localization of alkaline phosphatase in the granular pneumonocytes of hamster lung.

The fine structural localization of nonspecific alkaline phosphatase was studied in the granular pneumonocytes (type II alveolar epithelial cells) of hamster lung by incubating sections of glutaraldehyde-fixed tissues in a medium containing lead ions and sodium beta-glycerophosphate or alpha-naphthyl acid phosphate. The specificity of the reaction was tested by exposing the sections to inhibitors of alkaline phosphatase. The results showed that alkaline phosphatase activity was present in the inclusion bodies of granular pneumonocytes. The enzyme reaction was strong in the membrane lining the inclusion bodies and a weaker reaction was generally detectable in the inclusion contents. Although only a proportion of the inclusion bodies showed enzyme activity, there was no obvious correlation between the reactivity of the inclusions and their intracellular position or size. The other organelles were unreactive. The finding of alkaline phosphatase activity within the inclusion bodies of granular pneumonocytes is an enigma as these organelles are generally considered to be lyosomes.

Alkaline Phosphatase↗
PubMed1991

Alternating zinc fingers in the human male-associated protein ZFY: HX3H and HX4H motifs encode a local structural switch.

The two-finger repeat in the human male-associated protein ZFY provides a model for comparative 2D-NMR studies of classical and variant Zn fingers. This repeat is defined in part by an alternation in spacing between consensus (HX3H) and variant (HX4H) histidine spacings. To investigate the effects of a "switch" between alternative histidine spacings, we have designed an HX3H analogue of a representative HX4H domain of known structure [ZFY-6; Kochoyan, M., Havel, T., Nguyen, D. T., Dahl, C. E., Keutmann, H. T., & Weiss, M. A. (1991) Biochemistry 30, 3371-3386]. The HX3H analogue (designated ZFY-switch) forms a tetrahedral Co2+ complex whose thermodynamic stability is similar to that of the parent peptide. 2D-NMR studies demonstrate that ZFY-switch and ZFY-6, although similar in overall structure, exhibit significant local changes near the site of deletion. Whereas the HX4H site in the native finger forms a nonstandard loop, the HX3H site in ZFY-switch folds as a 3(10) extension of the C-terminal alpha-helix, as observed in the NMR solution structure of a consensus HX3H domain [Lee, M. S., Gippert, G. P., Soman, K. V., Case, D. A., & Wright, P. E. (1989) Science 245, 635-637] and in the crystal structure of a representative Zn finger-DNA complex [Pavletich, N. P., & Pabo, C. O. (1991) Science 252, 809-817]. We propose that variant histidine spacings (HX3H and HX4H) encode a local switch between alternative surface architectures with implications for models of protein-DNA recognition.

Amino Acid Sequence↗
PubMed1990

Automatic definition of recurrent local structure motifs in proteins.

An automatic procedure for defining recurrent folding motifs in proteins of known structure is described. These motifs are formed by short polypeptide fragments of equal size containing between four and seven residues. The method applies a classical clustering algorithm that operates on distances between selected backbone atoms. In one application, we use it to cluster all protein fragments into only four structural classes. This classification is rough considering the observed diversity of local structures, but comparable in homogeneity to the four classes of secondary structure (alpha-helix, beta-strand, turn and coil). Yet, it discriminates between extended and curved coil and distinguishes beta-bulges from beta-strands. In a second application, the clustering procedure is combined with assignment of backbone dihedral angles to allowed regions in the Ramachandran map. This produces an exhaustive repertoire of highly homogeneous families of structural motifs that contains all the beta-hairpins, beta alpha- and alpha beta-loops previously defined by manual procedures, and new structural families of which two examples, a beta alpha-loop and an alpha-helix beginning, are analyzed in detail. The described automatic procedures should be useful in categorizing structure information in proteins, thereby increasing our ability to analyze relations between structure and sequence.

Amino Acid Sequence↗
PubMed1979

Fine structural localization of thiamine pyrophosphatase and acid phosphatase activities in the mouse pancreatic acinar cell.

The fine structural localization of thiamine pyrophosphatase (TPPase) and acid phosphatase (AcPase) was examined in pancreatic acinar cells of fasting and fed mice. The results were not affected by these conditions. TPPase activity was positive in two and sometimes three cisternae of the inner Golgi lamellae as well as in the condensing vacuoles of the trans area, but negative in the rigid lamellae and small vesicles of the trans area. AcPase activity was demonstrated in two and sometimes three cisternae of inner Golgi lamellae, condensing vacuoles, rigid lamellae, lysosomes and smooth or coated vesicles in the trans area. The inner Golgi lamellae and the condensing vacuoles were positive for both enzyme activities. From these facts, the lysosome is considered to be formed not only in the GERL system but also through the rough endoplasmic reticulum-Golgi apparatus route. It is reasonable to consider that Novikoff's GERL is not independent from the Golgi apparatus but represents a part of this organelle.

Acid Phosphatase↗
PubMed1978

Studies on the fine structural localization of zinc iodide-osmium reaction in the brain. III. Some characteristics of localization in the synaptosomes.

Synaptosomes from rat cerebral cortex were impregnated in the zinc iodide--osmium (ZIO) solution. The fine structural localization of the ZIO impregnation product was studied and, in addition, the function-dependent features of the reaction were examined after electrical stimulation or potassium chloride treatment. It was revealed that: (i) Aldehyde prefixation resulted in an increase in the number of reactive synaptic vesicles in all types of synaptosomes; (ii) Electrical stimulation decreased the number of reactive vesicles in a voltage dependent manner; (iii) Potassium chloride treatment also reduced the reactivity of vesicles; the reduction was dependent on the concentration of potassium and duration of treatment; (iv) Experimental interventions leading to the release of neurotransmitters from the synaptic vesicles and to fatigue of the nerve terminals also resulted in a decrease of the ZIO-reaction product of synaptic vesicles in a manner proportional to the strength of stimuli.

Animals↗
PubMed1985

Histone phosphorylation in native chromatin induces local structural changes as probed by electric birefringence.

In order to understand how the phosphorylation of histones affects the chromatin structure, we used electron microscopy, sedimentation velocity, circular dichroism and electric birefringence to monitor the salt-induced filament reversible solenoid transition of phosphorylated and native chromatin. Phosphorylation in vitro of chicken erythrocyte chromatin by cyclic-AMP-dependent protein kinase from porcine heart led to the modification of the histones H3 and H5 only, which were modified at a level of one phosphate and about three phosphate groups per molecule, respectively. In contrast to circular dichroism and sedimentation studies, which tend to suggest that phosphorylation of H3 and H5 does not affect chromatin structure, electron microscopy reveals that phosphorylation causes a relaxation of structure at low ionic strength. Electric birefringence and relaxation time measurements clearly prove that local structural changes are induced in chromatin: we observe a decrease of the steady-state birefringence with the appearance of a negative contribution in the signal and a marked increase of the flexibility of fibres. The component with the negative birefringence presents very short relaxation times, like those exhibited by small DNA fragments or individual nucleosomes. Two possibilities are then suggested. First, the conformational change is consistent with what would be expected from the presence of DNA segments loosely associated with the core histone H3. That the length of such segments could correspond to about one to two base-pairs per nucleosome strongly suggests that phosphorylation induces changes affecting some specific H3-DNA interactions only. This result could corroborate previous observations indicating that the N-terminal region of H3, where the site of phosphorylation is located, plays a decisive role in maintaining the superstructure of chromatin. Second, phosphorylation could introduce hinge points between each nucleosome. In this case, the negative birefringence results from partial orientation of the swinging nucleosomes. A possible mode of action of phosphorylation might be to weaken structural restraints imposed by histone H3, thus facilitating further condensation of chromatin.

Animals↗
PubMed1974

Studies on the fine structural localization of zinc-iodide-osmium reaction in the brain. II. Some characteristics of localization in certain identified synapses.

Samples of the olfactory bulb and cerebellar cortex from rats were impregnated in zinc-iodide-osmium (ZIO) solution. The fine structural localization of ZIO impregnation product was studied and, in addition, the percentage distribution of ZIO-positive synaptic vesicles was ascertained in certain synapses of known function. Spherical vesicles, particularly in aldehyde-prefixed material, were found to be more resistant to ZIO impregnation than ovoid vesicles, both in dendro-dendritic and in axo-dendritic synapses. The different ZIO reactivity of synaptic vesicles in excitatory and inhibitory synapses, apart from reflecting an important difference in the chemical composition of synaptic vesicles, may offer a new method for characterizing synapses in relation to certain functions.

Animals↗
PubMed1992

Information tradeoffs in complex stimulus structure: local and global levels in naturalistic scenes.

An information tradeoff is an increased processing or utilization of information from one stimulus source at the expense of processing or utilization of information from a different source. An experiment was conducted to determine whether information tradeoffs occurred when subjects attended selectively to one of two different structural levels of naturalistic scenes. The subjects' attentional focus was directed to either the global or local structure of a scene (i.e., the scene or an object in the scene, respectively) either before or after presentation of a scene. They then had to use the information obtained from a 100-msec exposure of the scene to choose between two forced-choice alternatives that described one of the levels. The nature of the alternatives was such that both alternatives adequately characterized one of the structural levels on the basis of physical and semantic relations within the scene. Results showed that the subjects were significantly slower and less accurate when their attentional focus and the forced-choice alternatives were at different levels of stimulus structure than when they were at the same level, providing evidence of an information tradeoff when different types of information from a scene were used. When processing information from a particular structural level, information from the other level either was less available or was not used efficiently. Furthermore, the information tradeoffs were more severe in the precue than in the postcue condition, indicating differences in the efficiency of the selectivity process. The results are interpreted with respect to the role of selective attention in processing complex stimuli such as naturalistic scenes.

Adult↗