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PubMed1993

Regional DNA hypermethylation at D17S5 precedes 17p structural changes in the progression of renal tumors.

In a preceding paper for brain tumors, we demonstrate a tight association between regional hypermethylation at locus D17S5 of chromosome 17p and allelic loss of this chromosome. Because 17p allelic losses occur at the earliest stages of brain tumors, the exact temporal relationship between this event and the hypermethylation could not be elucidated. In renal cancers, two linked structural changes on chromosome 17p, allelic loss and p53 gene mutations, generally occur late in progression. We now show that D17S5 hypermethylation is tightly coupled to both of these genetic changes in late stage renal tumors. However, the methylation change is the only one of the 17p abnormalities which occurs at a high incidence in early-stage renal cancers (hypermethylation, 50%; 17p allelic loss, 13%; p53 mutations, 0%). Our results firmly suggest that D17S5 regional hypermethylation precedes the appearance of the consistent 17p genetic changes in renal cancers, suggesting that this event either marks, or may even cause, chromatin changes which predispose to genetic instability.

Alleles↗

PubMed2002

Simulated annealing structure solution of a new phase of dicalcium silicate Ca(2)SiO(4) and the mechanism of structural changes from alpha-dicalcium silicate hydrate to alpha(L)'-dicalcium silicate via the new phase.

A new phase of dicalcium silicate (Ca(2)SiO(4)) was formed by heating alpha-dicalcium silicate hydrate [alpha-Ca(2)(SiO(4)H)OH = alpha-C(2)SH] at temperatures of approximately 663-763 K, and it was transformed into alpha(L)'-Ca(2)SiO(4) (= alpha(L)'-C(2)S) above approximately 1193 K. The crystal structure of the new phase (hereafter called x-C(2)S) has been determined by simulated annealing and refined by the Rietveld method using synchrotron radiation powder diffraction data. The structure consists of isolated SiO(4) tetrahedra and a three-dimensional CaO(n) polyhedral network, forming a new structural type of dicalcium silicate. A structural change from alpha-C(2)SH to x-C(2)S is compelled by large displacements of SiO(4) tetrahedra, accompanied by dehydration, in the direction perpendicular to the two-dimensional Ca(O,OH)(n) polyhedral network in alpha-C(2)SH. With increasing temperature, sizes of CaO(n) polyhedra in x-C(2)S become too large to confine Ca atoms at the sixfold to eightfold coordination sites. Then the structure of x-C(2)S is transformed into alpha(L)'-C(2)S, having eightfold to tenfold coordination sites for the Ca atoms.

Journal Article↗

PubMed1999

Neurotransmitter regulation of circadian structural changes in the fly's visual system.

The visual system of the fly's compound eye undergoes a number of cyclical day/night changes that have a circadian basis. Such responses are seen in the synaptic terminals of the photoreceptors and in their large monopolar-cell interneurons in the first optic neuropile, or lamina. These changes include, in the photoreceptor terminals, rhythms in the numbers of synapses and the vertical migration of screening pigment; and, in the monopolar cells L1 and L2, a rhythm in the transients of the electroretinogram and in the cyclical swelling of L1 and L2 lamina axons, as well as of the epithelial glia that surround these. Some of these changes are seen in both the housefly and the fruit fly, but the time-course of such changes differs between the two species. Many of the changes are influenced by the injection of various transmitter candidates, in a direction that can be reconciled with the possibility of normal endogenous release of two substances, 5HT from the neurites of 5HT-immunoreactive neurons, and pigment dispersing factor peptide from the neurites of PDH cells. Consistent with this interpretation, the immunoreactive varicosities of PDH cells exhibit size changes attributable to their cyclical release of peptide, or to its cyclical synthesis and/or transport from the PDH cell somata. Thus, neurotransmitter substances not only have rapid electrophysiological actions in the optic lobe, but also longer-lasting, presumably indirect, neuromodulatory actions, which are manifest as structural changes among the lamina's neurons and synapses. These actions involve an interplay between aminergic and peptidergic systems, but the exact role and especially the site of action of each has still to be elucidated.

Animals↗

PubMed2002

The treatment of Haemophilus influenzae acute otitis media with amoxicillin protects against reinfection but not against structural changes.

Acute otitis media (AOM) is the most common reason for outpatient antimicrobial therapy today. With increasing problems with antibiotic resistance, a more restrictive use of antibiotics has been advocated for both single and recurrent episodes. The arguments advanced have been immunological as well as ecological. To study the effects of a 5 day course of amoxicillin on recurrent AOM caused by non-typeable Haemophilus influenzae, Sprague-Dawley rats were used. Amoxicillin was introduced at the clinical peak of the first infection. One month later the animals were rechallenged. Local and systemic changes were monitored by otomicroscopy, bacterial cultures, and analyses of systemic IgG responses and histological changes. Antibiotic treatment accelerated the resolution of the primary infection. After resolution, only minor morphological changes were observed. The protective rate at rechallenge was 100% in the treatment group, compared with 80% in the untreated control group. Although the production of serum IgG antibodies was initially slightly impeded by the treatment, it was significantly higher in treated animals after rechallenge. Major structural changes could not be avoided at the second infection, however, and a significantly higher frequency of myringosclerosis was observed in treated animals. These experimental findings constitute support for further studies of antimicrobial drugs and recurrent AOM.

Acute Disease↗

PubMedDate not supplied

[Structural changes in membranes of proliferating leukocytes L-41 as affected by low doses of ionizing radiation].

The dose-dependent effects of gamma-radiation on the leucocyte cultures L-41 has been investigated. Irradiation by the dose of 0.25 Gy stimulates the cell proliferation while that by the doses of 1.0 and 2.0 Gy inhibits this process. In this dose range the radiohormesis effects characterizing structural organization of the probed membranes have been also registered for fluorescence parameters. The zone of qualitative transition of response of the cell membranes to radiation is individual for various effects. The action of radiation in the doses of 0.25 and 0.50 Gy induces a decrease of ANS fluorescence intensity and a decrease of membrane protein immersion in the lipid bilayer of leukocyte membranes. The values of these parameters rise at the doses of 1.0 and 2.0 Gy that reflects different directions of structural changes in various membrane regions. The irradiation in the range of 0.25-1.0 Gy induces the increase of microviscosity in deep regions of membrane lipid matrix while at the dose 2.0 Gy it causes its decrease. Radioactive radiation does not change the membrane protein conformation of leukocytes and polarity of lipid bilayer hydrophobic zones as recorded by fluorescent methods used.

Cell Division↗

PubMed2004

The application of non-contact laser profilometry to the determination of permanent structural changes induced by compaction of pellets. I. Pellets of different composition.

Pellets of different mechanical properties were produced by extrusion and spheronisation process based on various composition (microcrystalline cellulose (MCC), lactose, glyceryl monostearate (GMS), water, ethanol and glycerol). Six hundred milligrams of these pellets were compacted at two different pressures (86.7 and 130MPa) to form flat-faced tablets and stored for 48h in ambient temperature and humidity after which their permanent structural change (plastic deformation) was investigated in terms of surface roughness parameters of both faces of the tablets, using a non-contact laser profilometer. The results were compared with the deformability values obtained from the force/displacement curve as well as the phase angle values obtained from the dynamic scan of a dynamic mechanical analyser. The increase in deformability of the pellets with the increase in porosity, increase in the contents of GMS, lactose or ethanol in the formulations and increase in compaction pressure was illustrated by the reduction of the surface roughness parameters. Analysis of variance identified the significant difference in the mean rugosity values of the tablets from the various formulations, tablet faces and compaction pressures. The deformability values obtained were reasonably comparable to those plasticity values obtained in terms of phase angle from the dynamic scan of the DMA and the force/displacement curves. The laser profilometry technique in conjunction with scanning electro-microscopy (SEM) demonstrated the low and broad based wavelike structure of the pellets after compaction rather than spiky sharp protrusions. This confirms the capability of determining the plastic deformability of the pellets from the surface roughness parameters obtained from non-contact laser profilometry.

Cellulose↗

PubMed1997

Interferon-induced growth arrest is mediated by membrane structural changes.

Interferon-gamma (IFN-gamma) is an immunomodulator shown to augment the expression of major histocompatibility (MHC) class I/class II antigens on the cell surface. In previous studies, we have demonstrated that the enhanced expression of these antigens on the cell surface is in part due to IFN-gamma-mediated abrogation of antigen shedding. In this study, we demonstrate that IFN-gamma induces structural changes in the cell membrane by altering the cholesterol/phospholipid ratio. Furthermore, such changes not only mediate enhanced expression of antigen on the cell surface but may drive the cells to growth arrest and apoptosis. These results were obtained by employing x-ray diffraction, electron microscopy, and DNA analysis.

Adjuvants, Immunologic↗

PubMedDate not supplied

[Structural changes in the brain according to computed tomographic data in patients undergoing combination therapy for hemispheric gliomas].

Basing on CT data, the authors analyze the qualitative changes in the brain of patients with a history of multiple-modality treatment for immature neuroectodermal tumors. Plani- and volumetric parameters of the total brain, the involved and the contralateral hemispheres are compared with the same parameters in the reference group. The pattern and degree of structural changes were found related to the site of the tumor and surgery. The brain matter in both hemispheres was lost mostly in the interstitial and end portions predominantly on the side of the tumor and surgery. Changes of the brain were individual in the patients.

Adolescent↗

PubMed1992

Detection of structural changes upon S1-to-S2 transition in the oxygen-evolving manganese cluster in photosystem II by light-induced Fourier transform infrared difference spectroscopy.

The light-induced Fourier transform infrared (FT-IR) difference spectrum between the S1 and S2 states of the O2-evolving photosystem II (PSII) was obtained for the first time. Detection of an S2/S1 difference spectrum virtually free from contributions by the acceptor-side signals was achieved by employing an exogenous electron acceptor, potassium ferricyanide, to trypsin-treated PSII membranes and using one-flash excitation at 250 K. A synthetic difference spectrum obtained by adding this S2/S1 spectrum to the QA-/QA spectrum measured with Mn-depleted PSII was almost identical with the difference spectrum of the S2QA-/S1QA charge separation measured with untreated PSII. This successful simulation verifies the correctness of the S2/S1 spectrum thus obtained. The observed S2/S1 spectrum reflects the structural changes within the water-oxidizing Mn cluster upon the S1-to-S2 transition, most probably changes in vibrational modes of ligands coordinating to the Mn ion(s) that is (are) oxidized upon the S2 formation and/or changes in protein conformation. The present results demonstrate that FT-IR difference spectroscopy is a promising method to investigate the structure of the intermediates of the Mn cluster involved in photosynthetic water oxidation.

Cell Membrane↗

PubMed2006

Structural changes in the nucleus ambiguus of the medulla oblongata and intracardiac ganglia in growing rats in immobilization stress.

The aim of the present work was to study qualitative and quantitative measures of histological changes in the nucleus ambiguus (NA) of the medulla oblongata and the cardiac autonomic ganglia (CAG) in growing animals in conditions of immobilization stress of different durations. Experiments were performed on 56 mongrel white rats aged 30 days. Immobilization stress was produced by placing rats in a special apparatus with a controllable internal volume for 3, 7, 15, and 30 days. The NA and CAG were studied on paraffin sections using neurohistological methods and quantitative analysis. Morphological and morphometric changes, consisting of a delay in the growth of neurocyte cell and nucleus volumes, as compared with controls, were seen both in the NA of the medulla oblongata and the CAG and were evaluated as impairments in the histogenesis of nerve tissue during postnatal ontogenesis. The extent of structural changes in these components of the autonomous nervous system was directly dependent on the duration of the experimental treatment.

Animals↗

PubMed2005

Thallium-201 single-photon emission computed tomography: quantitative assessment of left ventricular perfusion and structural change in patients with chronic aortic regurgitation.

BACKGROUND: Previously, perfusion defect in the left ventricle was detected by thallium-201 (201T1) single-photon emission computed tomography (SPECT) in aortic regurgitation (AR). The significance of 201T1 SPECT, however, has not been clarified. Limited information is available regarding the relationship between functional characteristics and scintigraphic findings. HYPOTHESIS: The purpose of this study was to elucidate the role of exercise 201T1 SPECT in assessing myocardial perfusion or structural change in chronic AR. We examined the correlation between 201T1 scintigraphic findings and left ventricular (LV) function parameters in 11 patients. METHODS: Defect volume ratio (DVR) in exercise 201T1 SPECT was used as a parameter of the range of abnormal thallium distribution. Left ventricular parameters were obtained by right and retrograde left cardiac catheterizations. The relationship between DVR and the parameters was analyzed. RESULTS: The DVR ranged from 1.0 to 28.3% (average 12.1 + 8.5 %). There was a significant correlation (r = 0.77, p < 0.05) between DVR and end-diastolic volume index (EDVI), a definite correlation (r = 0.66, p < 0.01) between DVR and end-systolic volume index (ESVI), and a good correlation (r = -0.77, p <0.05) between DVR and end-systolic wall stress (ESS)/ ESVI; however, no such correlation was found between DVR and ejection fraction. CONCLUSION: All patients showed abnormal defects in 201T1 accumulation scattered across the entire ventricle. A strong correlation between DVR and ESS/ESVI, an index of myocardial contractility, was a major finding of this study, suggesting a significant association between abnormal myocardial perfusion or structural alteration and reduction in myocardial contractility in chronic AR.

Adult↗

PubMed1990

On the nature of the structural change of the colicin E1 channel peptide necessary for its translocation-competent state.

Acidic pH conditions required in vitro for membrane binding and activity of the channel-forming colicin E1 resulted in an increased susceptibility to proteases of the 178-residue thermolytic channel peptide, an increased accessibility to acrylamide of a fluorescence probe linked to cysteine-505 of the peptide, and an increased partition into nonionic detergent. The structural change in the peptide sensed by the fluorescence probe caused by a transition from pH 6.0 to 3.5 occurred in less than 1 s. The presence of low concentrations of detergents (0.001% SDS or 0.44% octyl beta-D-glucoside) or urea (0.2 M) at pH 6 or 4 also increased the susceptibility of the channel peptide to proteases. The increase in protease susceptibility and acrylamide accessibility at low pH, as well as partition of the peptide into nonionic detergent, suggested that acidic pH or the detergents might cause peptide unfolding. However, the hydrodynamic radius of the channel peptide at pH 6, 21-23 A, was not changed at pH 3.5 or by detergents or urea under conditions that increased the susceptibility of the peptide to protease. The activity of the channel peptide at pH 6 measured with liposomes and planar bilayers, which was a factor of 10(3)-10(4) smaller than that at pH 4, was increased by 2-4 orders of magnitude by 0.001% SDS or 0.44% octyl beta-D-glucoside, with an additional small increment of activity on planar bilayers caused by 0.01% SDS. A small increase in Stokes radius of the peptide in the presence of SDS could be detected that was approximately correlated with increased activity.

Acrylamides↗

PubMed1996

A possible tertiary structure change induced by acrylamide in the DNA-binding domain of the Tn10-encoded Tet repressor. A fluorescence study.

A thorough investigation of the acrylamide fluorescence quenching of F75TetR, a mutant of the Tn10-encoded TetR repressor containing a single Trp residue at position 43, was carried out. The Trp-43 residue is located in a helix alpha-turn-helix alpha (H-t-H) motif involved in the specific binding of F75TetR to the operator site in specific DNA. Distinct Ranges of acrylamide concentration have been assumed. At acrylamide concentrations below 0.15-0.2 M (a usual range of values in fluorescence quenching studies) the observed limited tertiary structure change induced by acrylamide is consistent with a noncooperative local unfolding of the DNA-binding domain. It is suggested that penetration of the neutral quencher could cause the deletion of a hydrophobic tertiary structure contact, partly involving TrP-43, responsible for the anchoring of the H-t-H motif inside the three-helix protein bundle, characterizing the N-terminal part. Correspondingly, the affinity of the mutant repressor for the operator was shown to decrease substantially (about five orders of magnitude), seemingly losing its specificity. A subsequent phase, up to 0.8 M acrylamide, was observed in which the involved intermediate protein structure is not further perturbed, nor is DNA binding.

Acrylamide↗

PubMed2003

Structural changes of poly(butadiene)-poly(ethyleneoxide) diblock-copolymer micelles induced by a cationic surfactant: scattering and cryogenic transmission electron microscopy studies.

Micelles of the diblock copolymer poly(butadiene)-poly(ethyleneoxide) (B40-b-EO62) and mixed micelles of this polymer with the cationic surfactant dodecyltrimethylammonium bromide (C12TAB) were investigated using static and dynamic light scattering and small-angle neutron scattering. It is shown that the surfactant induces a major structural change from large mainly rodlike aggregates to smaller spherical mixed micelles. The rodlike assemblies found in the absence of surfactant have a contour length L of ca. 500 nm and a diameter d approximately 30 nm. The spherical mixed micelles obtained upon addition of C12TAB possess a hydrodynamic radius of 15 nm and still contain several polymer molecules. The results of the scattering experiments are consistent with observations of the aggregates by cryogenic transmission electron microscopy.

Biophysical Phenomena↗

PubMed1985

Serotonin-induced contractile and structural changes in fast and slow skeletal muscles in mice.

The effects of serotonin on the contractile properties of the soleus and extensor digitorum longus muscles in mice were studied after chronic intraperitoneal administration with and without a recovery period, and compared to contractile studies of the same muscles performed after acute administration of serotonin. A curarized in vitro preparation of both muscles was used throughout for the contractile studies. In addition, structural changes were studied in the chronic preparations. Chronic serotonin administration produced histologic changes in type 1 and 2A fibers and a reduction in twitch and tetanic tension and the rate of twitch and tetanic tension development limited to the slow (aerobic) soleus muscle. Acute in vitro administration of serotonin altered the contractile properties of both soleus and extensor digitorum longus muscles with the latter being more involved. The effects of chronic serotonin administration appear to be primarily related to ischemia while the effects of acute administration appear to be mediated by direct, nonvascular action on skeletal muscle.

Animals↗

PubMed1988

[Correlation of functional and structural changes of the cardiovascular system in hypertensive disease].

Dynamics of left ventricular mass, minimal resistance of forearm arterial vessels and compliance of forearm venous vessels were studied in hypertensive patients during a 3-year effective antihypertensive treatment. Our findings suggest that pressure reduction and regression of myocardial hypertrophy develop in a parallel fashion while minimal resistance of vessels remains elevated due to the increasing contractile activity of smooth muscles. The presence of structural changes can only be assessed if the transmural pressure is the same along the whole arterial tree.

Adult↗

PubMed1998

Evidence for a major structural change in Escherichia coli chorismate synthase induced by flavin and substrate binding.

Chorismate synthase (EC 4.6.1.4) catalyses the conversion of 5-enolpyruvylshikimate 3-phosphate (EPSP) into chorismate, and requires reduced FMN as a cofactor. The enzyme can bind first oxidized FMN and then EPSP to form a stable ternary complex which does not undergo turnover. This complex can be considered to be a model of the ternary complex between enzyme, EPSP and reduced FMN immediately before catalysis commences. It is shown that the binding of oxidized FMN and EPSP to chorismate synthase affects the properties and structure of the protein. Changes in small-angle X-ray scattering data, decreased susceptibility to tryptic digestion and altered Fourier-transform (FT)-IR spectra provide the first strong evidence for major structural changes in the protein. The tetrameric enzyme undergoes correlated screw movements leading to a more overall compact shape, with no change in oligomerization state. The changes in the FT-IR spectrum appear to reflect changes in the environment of the secondary-structural elements rather than alterations in their distribution, because the far-UV CD spectrum changes very little. Changes in the mobility of the protein during non-denaturing PAGE indicate that the ternary complex may exhibit less conformational flexibility than the apoprotein. Increased enzyme solubility and decreased tryptophan fluorescence are discussed in the light of the observed structural changes. The secondary structure of the enzyme was investigated using far-UV CD spectroscopy, and the tertiary structure was predicted to be an alpha-beta-barrel using discrete state-space modelling.

Circular Dichroism↗

PubMed2005

Adenosine diphosphate moiety does not participate in structural changes for the signaling state in the sensor of blue-light using FAD domain of AppA.

A sensor of blue light using FAD (BLUF) protein is a flavin adenine dinucleotide (FAD) based new class blue-light sensory flavoprotein. The BLUF domain of AppA was reconstituted in vitro from apoprotein and flavin adenine dinucleotide, flavin adenine mononucleotide or riboflavin. The light-induced FTIR spectra of the domain reconstituted from various flavins and the 13C-labeled apoprotein showed that identical light-induced structural changes occur in both the flavin chromophore and protein for the signaling state in all of the reconstituted holoproteins. The results showed that an adenosine 5'-dinucleotide moiety is not required for signaling-state formation in a BLUF domain.

Adenosine Diphosphate↗