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PubMed1983

ATP-dependent structural changes of the outer dynein arm in Tetrahymena cilia: a freeze-etch replica study.

With the rapid-freeze, deep-etch replica technique, the structural conformations of outer dynein arms in demembranated cilia from Tetrahymena were analyzed under two different conditions, i.e., in the absence of ATP and in the presence of ATP and vanadate. In the absence of ATP, the lateral view of axonemes was characterized by the egg-shaped outer dynein arms, which showed a slightly baseward tilt with a mean inclination of 11.1 degrees +/- 3.4 degrees SD from the perpendicular to the doublet microtubules. On the other hand, in the presence of 1 mM ATP and 100 microM vanadate, the outer arms were extended and slender and showed an increased baseward tilt with a mean inclination of 31.6 degrees +/- 4.9 degrees SD. In ATP-activated axonemes, these two types of arms coexisted, each type occurring in groups along one row of outer arms. These findings strongly suggest that the interdoublet sliding is caused by dynamic structural changes of dynein arms that follow the hydrolysis of ATP.

Adenosine Triphosphatases↗

PubMed1989

Neutrophil accumulation and structural changes in nonpulmonary organs after acute lung injury induced by phorbol myristate acetate.

Multiple nonpulmonary organ failure contributes significantly to the high mortality rate associated with the adult respiratory distress syndrome (ARDS). However, little is known about specific structural and/or functional alterations that occur in nonpulmonary organs in this syndrome. Therefore, the present study was designed to test the hypothesis that inflammatory cell infiltration and structural changes occur both in the lungs and in nonpulmonary organs in ARDS. To test this hypothesis, neutrophil accumulation and structural alterations were evaluated in nonpulmonary organs from dogs with acute lung injury produced by intravenous phorbol myristate acetate (PMA) (30 micrograms/kg; n = 5). As expected, morphologic changes were present in the lungs of the PMA-treated animals and included a diffuse neutrophilic pneumonitis with interstitial, vascular, and alveolar components. PMA-treated dogs had significant increases in neutrophils (expressed as PMN/mm2 tissue section area) compared with those in control animals in the following organs: heart, 14 +/- 3 versus 4 +/- 1; brain, 2.5 +/- 0.3 versus 0.7 +/- 0.3; duodenum, 34 +/- 7 versus 10 +/- 2; liver, 397 +/- 16 versus 103 +/- 12 (p less than 0.025, all comparisons). In addition, severe necrosis and inflammation of vessels, sinusoidal thrombosis, and hepatic necrosis were noted in the liver. Like the changes noted in the lung, hepatic lesions appeared to be vascular in origin and were consistent with lesions produced by the intravascular activation of neutrophils. No microscopic lesions were detected in the brain, kidney, duodenum, and heart. Taken together, the finding of concurrent lung injury, liver injury, and nonpulmonary organ neutrophil accumulation suggests the possibility of a common pathway of injury in this model of ARDS.

Animals↗

PubMed1989

Resistance oscillation of a Millipore DOPH model membrane accompanying structural changes.

A Millipore DOPH model membrane is composed of a Millipore filter whose pores are filled with dioleylphosphate (DOPH), and its electric resistance increases by a factor of 10(4) when Ca2+ ions are combined with it. The concentration of CaCl2 which increases the membrane resistance depends on the density of DOPH adsorbed in the filter and the initial KCl concentration. The surface structure of the membrane changes at the same time as the membrane resistance increases. The structural changes can be directly observed by a stereoscopic microscope: a considerable decrease of the hydrophilic regions of the membrane is caused by the Ca2+ ions. The membrane resistance which become higher with Ca2+ ions oscillates while a constant current and a static pressure stimuli are applied to the membrane. The frequency is dependent of these stimuli. These stimuli change the local membrane surface structure to make the hydrophilic areas. It is conceivable that the structural changes are caused by replacing Ca2+ ions with K+ ions in the hydrophilic bases of DOPH molecules.

Calcium↗

PubMed2000

Phospholipid/fatty acid-induced secondary structural change in beta-lactoglobulin during heat-induced gelation.

Effects of phosphatidylcholine (PC) and the predominant fatty acids (FAs) in milk, butyrate, oleate, and palmitate, on secondary structural changes in beta-lactoglobulin (beta-LG) during heat-induced gelation were analyzed on the basis of circular dichroism (CD) spectra. Small-strain oscillatory measurements were carried out to characterize viscoelastic properties of the heat-induced gels. In the absence of added salt, PC and FAs induced helix formation of beta-LG on heating to 80 degrees C and increased the storage moduli (G') of heat-induced gels. In the presence of 500 mM NaCl, PC did not change the CD spectrum of beta-LG but decreased G'. In contrast, butyrate substantially unfolded beta-LG in 500 mM NaCl on heating, forming very elastic gels with increased G' values. Palmitate and oleate induced beta-LG gel formation at 25 degrees C without heating; heating to 80 degrees C almost completely unfolded beta-LG in 500 mM NaCl.

Fatty Acids↗

PubMed1995

Structural changes of anterior horn neurons and their synaptic input caudal to a low thoracic spinal cord hemisection in the adult rat: a light and electron microscopic study.

Structural changes in lumbosacral ventral horn neurons and their synaptic input were studied at 3, 10, 21, 42, and 90 days following low thoracic cord hemisection in adult rats by light microscopic examination of synaptophysin immunoreactivity (SYN-IR) and by electron microscopy. There was an ipsilateral transient decrease in SYN-IR at the somal and proximal dendritic surfaces of anterior horn neurons which extended caudally from the site of injury over a postoperative (p.o.) period of 42 days. Concomitantly, at 21 days p.o., perineuronal SYN-IR started to recover in upper lumbar segments. By 90 days p.o., a normal staining pattern of SYN was noted in upper and mid lumbar segments, but the perineuronal SYN-IR was still slightly below normal levels in low lumbar and sacral segments. Electron microscopy revealed ultrastructural changes coincident with the alterations in SYN-IR. At 3 days p.o., phagocytosis of degenerating axon terminals by activated microglial cells was observed at the somal and proximal dendritic surfaces of ventral horn neurons. These changes were most prominent up to two segments caudal to the lesion. At 10 days p.o., advanced stages of bouton phagocytosis were still detectable in all lumbosacral motor nuclei. Additionally, abnormal axon terminals, with a few dispersed synaptic vesicles and accumulations of large mitochondria, appeared at the scalloped somal surfaces of anterior horn neurons. At 21 days p.o., several large lumbosacral motoneurons had developed chromatolysis-like ultrastructural alterations and motoneuronal cell bodies had become partially covered by astrocytic lamellae. At 42 days p.o., there was a transient appearance of polyribosomes in some M-type boutons. In addition, at 42 and 90 days p.o., a few degenerating motoneurons were detected in all lumbosacral segments, but most displayed normal neuronal cell bodies contacted by numerous intact synapses as well as by astrocytic processes. In contrast to these striking alterations of synaptic input at somal and proximal dendritic surfaces of motoneurons, relatively few degenerating boutons were detected in the neuropil of motor nuclei at all the p.o. times studied. We suggest that the preferential disturbance of the predominantly inhibitory axosomatic synapses on ventral horn neurons may be involved in the mechanisms which influence the well-established increase in motoneuronal excitability after spinal cord injury.

Animals↗

PubMed2006

Structural analysis of RecA protein-DNA complexes by fluorescence-detected linear dichroism: absence of structural change of filament for pairing of complementary DNA strands.

We have developed a simple measuring system for fluorescence-detected linear dichroism and applied it to the structural analysis of the RecA-DNA complex filaments, which are intermediates of the homologous recombination reaction. Taking advantage of the selectivity of fluorescence signals, we distinguished the linear dichroism signals of ethidium bromide and tryptophan residues in the RecA-DNA-ethidium bromide complex, whereas the conventional (absorption-detected) linear dichroism measurement provides only the sum of the signals because signals overlap each other and that of DNA. We further observed that the tryptophan residue at position 290 of RecA in the RecA-DNA-adenosine-5'-O-(3-thiotriphosphate) complex was oriented parallel to the long axis of the filament, in good agreement with the previous site-specific linear dichroism analysis, and that this orientation was not significantly modified by the pairing of the complementary DNA strand. These results suggest that the pairing reaction occurs without a large structural change of the RecA filament.

DNA, Complementary↗

PubMed2000

The evaluation of structural changes in wool fibre keratin treated with azo dyes by Fourier Transform Infrared Spectroscopy.

Fourier Transform Infrared Spectroscopy spectroscopy is a useful technique for the analysis of structural changes in wool fibres at the molecular and supermolecular levels. Ecological requirements the textile industry has to meet oblige manufacturers to use ecological dyes in the process of fibre dyeing. These dyes should not split into the forbidden, carcinogenic aromatic amines (e.g. benzidine) while used. Wool was dyed with an azo dye, then underwent a chemical reaction. Changes were observed in the region of Amide A, Amide B, Amide I and II, dipolar ions amino acids, and the fingerprint region.

Animals↗

PubMed1975

Correlation of structural changes at different levels of the jejunal villus with positive net water transport in vivo and in vitro.

Experiments were done for indentification and localization of certain structural changes at different levels of jejunal villus of the hamster during positive and negative water transport across the intestine in vivo and in vitro. Positive transport occurred when the mucosal surface of the intestine was bathed (in vitro experiments) or perfused (in vivo experiments) with isotonic Krebs-Ringer bicarbonate solution containing 10 mM glucose, and negative water transport was achieved by rendering this solution hypertonic with 150 mM mannitol. Results indicate that during positive net water transport the intestine in vivo transported more fluid and exhibited a more conspicuous dilatation of the lateral intercellular spaces (L.I.S.) than did the in vitro preparation. Dilatation of the L.I.S. in both preparations was present only in the apical part of the villus, suggesting that this is the principal site of water absorption. When the mucosal solution was made hypertonic with mannitol, the L.I.S. in the in vivo intestine totally collapsed, whereas in the in vitro intestine these spaces remained open very slightly. These morphological changes correspond well with our finding that in the presence of the hypertonic mucosal solution there was a greater net negative water transport in vivo than in vitro. Incubation of the intestine in the isotonic mucosal solution produced subnuclear swelling of the mid-villus epithelial cells, and this morphological change was associated with an increase in the water content of the tissue. Perfusion of the in vivo intestine with the isotonic solution produced neither the swellings nor the increase in water content of the tissue. In the presence of hypertonic mucosal solution there was a water loss from the tissue both in vivo and in vitro, and these swellings were not observed. These results are discussed in relation to intestinal sugar transport and to the maturity of the epithelial cells, and it is concluded that transport studies on in vitro preparations may provide valid information on a qualitative basis, if not on a strictly quantitative basis.

Animals↗

PubMed1996

Structural change in hospitals: the implications for research.

This paper begins by considering briefly the interdependent nature of the health care sector and suggests that most research on structural change in the hospital system has ignored that obvious fact. It then goes on to argue that this failure will become even more significant in the face of the large scale changes that are expected in the way health services are delivered. Its central proposal is that the research horizons should be widened, particularly if change on the scale that appears likely is to be properly evaluated. How that may be done is considered in the final section.

Health Care Sector↗

PubMed1987

[Structural changes in contractile proteins of muscle fibers studied by polarization ultraviolet fluorescence microscopy. X. The effect of ATP, Ca2+, pH change and ionic strength of the washing solution on the structural state of thick filaments].

By the method of polarized ultraviolet fluorescence microscopy, effects of ATP, Ca2+, changes in pH and ionic strength of washing solution of the structural state of thick filaments in both actin-free muscle fibers of rabbit and anisotropic discs (A-discs) of glycerinated fibers of crab were studied. The dependence of tryptophan fluorescence anisotropy of thin filaments upon physico-chemical parameters (compounds) of washing solution has been found. The structural state of thick filaments was suggested to be influenced by ATP, Ca2+, changes in pH and ionic strength of washing solution.

Adenosine Triphosphate↗

PubMed1993

Structural changes underlying compensatory increase of diffusing capacity after left pneumonectomy in adult dogs.

To determine if the functional compensation in diffusing capacity of the remaining lung following pneumonectomy is due to structural growth, we performed morphometric analysis of the right lung in three adult foxhounds approximately 2 yr after left pneumonectomy (removal of 42% of lung) and compared the results to those in normal adult dogs previously studied by the same techniques. Diffusing capacity was calculated by an established morphometric model and compared to physiologic estimates at peak exercise in the same dogs after pneumonectomy. The major structural changes after left pneumonectomy are hyperinflation of the right lung, alveolar enlargement, and thinning of the alveolar-capillary tissue barrier. These changes confer significant functional compensation for gas exchange by reducing the overall resistance to O2 diffusion. The magnitude of compensation in diffusing capacity estimated either morphometrically or physiologically is similar. In spite of morphometric and physiologic evidence of functional compensation, there is no evidence of significant growth of structural components. After pneumonectomy, morphometric estimates of diffusing capacity are on average 23% higher than physiologic estimates in the same dogs at peak exercise. We conclude that the previously reported large differences between morphometric and physiologic estimates of diffusing capacity reflects the presence of large physiologic reserves available for recruitment.

Animals↗

PubMed2005

Structural changes upon photoexcitation into the metal-to-ligand charge-transfer state of [Cu(pqx)(PPh3)2]+ probed by resonance Raman spectroscopy and density functional theory.

The structural changes that occur when [Cu(pqx)(PPh(3))(2)](+) (pqx is 2-(2'-pyridyl)quinoxaline) undergoes excitation through a metal-to-ligand charge-transfer (MLCT) transition are investigated using resonance Raman excitation profiles coupled with density functional theory (DFT). The DFT calculations predict bond lengths to within 3 pm and absolute deviations of 7 cm(-1) for the vibrational frequencies of [Cu(pqx)(PPh(3))(2)](+). TD-DFT calculations of oscillator strengths (f = 0.089) and band positions (419 nm) showed close agreement with experiment (f = 0.07, 431 nm). Resonance Raman spectra show the 527 cm(-1) (nu(29)) and 1476 cm(-1) (nu(75)) modes undergo the largest dimensionless displacement (Delta = 1.5 and 1.1, respectively) following photoexcitation into the MLCT Franck-Condon region. The solvent couples strongly to the MLCT transition and resonance Raman intensity analysis (RRIA) gives a solvent reorganization energy of 3400 cm(-1) for dichloromethane and 2800 cm(-1) for chloroform solutions. A large inner-sphere reorganization of 3430 cm(-1) in dichloromethane solution (3520 cm(-1) in chloroform solution) was found for [Cu(pqx)(PPh(3))(2)](+), indicating that the molecule as a whole undergoes significant distortion following MLCT excitation.

Journal Article↗

PubMed1997

Structural changes in the cardiac microvasculature of the rat in response to acute high glucose levels: a comparison with diabetes.

OBJECTIVE: Isolated rat hearts were used to determine whether structural changes in the coronary microcirculation caused by diabetes mellitus occur soon after the onset of hyperglycemia and whether early changes might be reversed by return to normoglycemic conditions. METHODS: Three experimental groups of hearts were used. The perfusate was Krebs-Henseleit medium with the addition of (a) 25 mmol/L glucose for 60 minutes, (b) as (a) followed by 5 mmol/L glucose for 30 minutes, and (c) hearts from diabetic rats perfused for 15 minutes. All the hearts were fixed and processed for electron microscopy. Measurements were made of various capillary dimensions and basal lamina thickness. RESULTS: The high glucose concentration caused an overall reduction in capillary dimensions which was partly reversed by reperfusion with 5 mmol/L glucose. Diabetic hearts showed enlarged whole capillary and luminal area and thinning of the endothelial cells without any change in cross-sectional area. Endothelial gaps, consistent with increased permeability, were observed in the high glucose group but not in diabetic hearts. The basal lamina was thickened in all three experimental groups compared with controls. CONCLUSIONS: The results show that morphological changes in the microcirculation occur much earlier than was previously thought and, with the possible exception of the basal lamina thickening may be reversible.

Animals↗

PubMedDate not supplied

1,2,3-Triazoles: structural changes on two effective inhibitors of the prostaglandin synthesis in vitro.

This paper describes the synthesis and the biological evaluation of some 1,2,3-triazoles which represent structural modifications of two compounds which are effective inhibitors of the prostaglandin synthesis in vitro. These modifications, concerning the elimination of the methylene bridge and/or the ether oxygen from the active molecules, show that every introduced structural changes caused a strong decrease of activity.

Chemical Phenomena↗

PubMed1976

Vascular injury in transplanted tissues. Fine structural changes in tumor, adult, and embryonic blood vessels.

Adult, embryonic and tumor tissues from the rat were grafted to the chorioallantoic membrane (CAM) of the chick embryo. Fine structural changes in the microvasculature of the transplants were compared, with emphasis on the condition of endothelial cells. Endothelial cells in tumor grafts appeared irreversibly injured 2 h after grafting and most had degenerated by 8 h. In normal adult tissues, endothelial cells disintegrated more slowly, but lipid accumulation and blebbing leading to occlusion of vascular lumina, were prominent by 1 day. Cells were swollen and vacuolated 2 days after grafting and most were disrupted by 3 days. Embryonic endothelial cells were only mildly damaged and vessel lumina were patent for up to 3 days. Vessels were then reperfused with chick blood. It is concluded that the microvasculature in tumor tissue is extremely susceptible to ischemic damage and that this phenomenon may be involved in the central necrosis which develops in many animal tumors after they grow beyond a small size. Furthermore, only blood vessels and endothelium in embryonic tissues were sufficiently resistant to ischemic changes so that the graft microvasculature could be reperfused.

Animals↗

PubMed1993

Regression of vascular structural changes and calcium metabolism in patients with essential hypertension after long-term monotherapy with enalapril.

We investigated the effect of one year of enalapril monotherapy on vascular structural changes and calcium metabolism in ten patients with essential hypertension. BP decreased from 169-10/103 +/- 10 mmHg during the placebo period to 138-12/82 +/- 10 mmHg after enalapril therapy. Minimal vascular resistance assessed by the venous occlusion technique with strain-gauge plethysmography was higher in the hypertensive patients than in the normotensive subjects (2.7 +/- 1.2 vs. 1.2 +/- 0.3 mmHg/ml/min per 100 ml tissue, P < 0.01). Although the elevated minimal vascular resistance seen in essential hypertensives decreased to 1.7 +/- 0.5 mmHg/ml/min per 100 ml tissue after enalapril (P < 0.01), it remained higher than that of normotensives (P < 0.05). Cytosolic free calcium ([Ca2+]i) in platelets measured by a Qiun-2 fluorescent indicator was higher in essential hypertensives than in normotensives (189 +/- 38 nM and 138 +/- 14 nM, respectively; P < 0.01). [Ca2+]i of essential hypertensives was reduced to 138 +/- 19 nM after treatment. Plasma renin activity was significantly increased after enalapril. Although plasma ionized calcium concentration did not change, parathyroid hormone was significantly increased after enalapril (from 0.36 +/- 0.22 to 0.58-0.32 ng/ml, P < 0.05). During the placebo period, minimal vascular resistance was correlated with [Ca2+]i (r = 0.62, P < 0.01). There was a close relationship between the changes in minimal vascular resistance and [Ca2+]i (r = 0.78, P < 0.01); however the change in minimal vascular resistance was not associated with changes in BP, catecholamine or parathyroid hormone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2006

Structural changes in troponin in response to Ca2+ and myosin binding to thin filaments during activation of skeletal muscle.

Contraction of skeletal and cardiac muscle is regulated by Ca2+ -dependent structural changes in troponin that control the interaction between myosin and actin. We measured the orientations of troponin domains in skeletal muscle fibers using polarized fluorescence from bifunctional rhodamine probes on the C and E helices of troponin C. The C helix, in the regulatory head domain, tilts by approximately 30 degrees when muscle is activated in physiological conditions, with a Ca2+ -sensitivity similar to that of active force. Complete inhibition of active force did not affect C-helix orientation, and binding of rigor myosin heads did not affect its orientation at saturating [Ca2+]. The E helix, in the IT arm of troponin, tilted by approximately 10 degrees on activation, and this was reduced to only 3 degrees when active force was inhibited. Binding of rigor myosin heads produced a larger tilt of the E helix. Thus, in situ, the regulatory head acts as a pure Ca2+ -sensor, whereas the IT arm is primarily sensitive to myosin head binding. The polarized fluorescence data from active muscle are consistent with an in vitro structure of the troponin core complex in which the D and E helices of troponin C are collinear. The present data were used to orient this structure in the fiber and suggest that the IT arm is at approximately 30 degrees to the filament axis in active muscle. In relaxed muscle, the IT arm tilts to approximately 40 degrees but the D/E helix linker melts, allowing the regulatory head to tilt through a larger angle.

Animals↗

PubMed2004

Studies of structural changes in the M2 proton channel of influenza A virus by tryptophan fluorescence.

Studies of tryptophan fluorescence of purified influenza A virus M2 protein have identified two pH-dependent structural changes. (1) An increase in fluorescence on reduction of pH from 8 to 6 that involves tryptophan 15 within the N-terminal domain of the protein and may be associated with proton activation of the channel. (2) Quenching of the fluorescence of tryptophan 41 within the transmembrane domain of the channel by histidine 37 below pH 6 which is specifically reversed by drugs that block the M2 channel. The pH dependence of the latter effect, which monitors changes in the protonation of histidine 37, corresponds to that of proton current through the channel and provides evidence for the involvement of histidine 37 in proton permeation.

Amino Acid Sequence↗