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PubMedDate not supplied

Structural changes associated with type-A influenza in Mallard duck tracheal organ culture.

Mallard duck tracheal organ cultures were used to study structural changes associated with infection with type-A influenza (A/Turkey/WIS/68) (H9N2) at the light-microscope and electron-microscope levels. Light-microscope changes in infected organ culture were cytoplasmic vacuolization, nuclear swelling, reduction in ciliated epithelium, and sloughing of epithelial cells. Ultrastructural changes included the loss of cilia and microvilli, distortion and swelling of cellular organelles, breakdown of intercellular junction, and apparent phagocytosis of the ciliated epithelium. Numerous budding virions were noted at the plasmalemma. Virus was detected by egg inoculation from all experimental cultures throughout the 192-hour experiment.

Influenza A virus↗

PubMed1989

Structural change of the troponin C molecule upon Ca2+ binding measured in solution by the X-ray scattering technique.

The small-angle X-ray scattering technique was used to characterize the overall structural change as well as the state of aggregation of troponin C upon binding various amount of Ca2+ ions: in the Ca2+-free state and at pCa 6.5 and 4.0. Under these conditions, the forward scattering intensities of troponin C are not much different from each other: i.e., they coincide within 4%. From these intensities, the Ca2+-facilitated dimerization of troponin C was not verified, and no appreciable aggregation of troponin C molecules was detected below pCa 4.0. Thus, the small-angle X-ray scattering profiles from troponin C solutions were analyzed assuming a monomeric molecule. The radii of gyration of troponin C were 27.8 +/- 0.3 A, 23.8 +/- 0.2 A, and 22.6 +/- 0.1 A for the Ca2+-free state and at pCa 6.5 and 4.0, respectively. The maximum dimension of the molecule decreases from 111 to 98 A with increasing Ca2+ concentration. These results indicate that the troponin C molecule shrinks remarkably as Ca2+ ions bind to the high affinity sites of the molecule. Ca2+ binding to the low affinity sites, on the other hand, leads to a less pronounced change. Following the interpretation of scattering from the dumbbell-shaped structure (Fujisawa, T., Ueki, T., Inoko, Y., & Kataoka, M. [1987] J. Appl. Cryst. 20, 349-355), the two domains of the molecule move closer to each other. The distance between the centers of the two domains decreases from 46 to 35 A.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Fine structural changes in the postacrosomal region of the hamster and mouse sperm head at the initial stage of gamete interaction in vivo.

This report documents ultrastructural changes in the postacrosomal region of the hamster and mouse sperm head at the initial stage of gamete interaction in vivo. Prominent structures were sequentially visualized: first, the periodic substructure crossbridging the postacrosomal sheath to the overlying plasma membrane, and then the small, electron-dense, granular structures lining the outer surface of the postacrosomal sheath. The periodic substructure became visible at the restricted region where the sperm plasma membrane was just prior to or in the act of detaching from the periodic substructure. The granular substances lined up along the external face of the postacrosomal sheath immediately after the detachment of the sperm plasma membrane, but before the complete degradation of the periodic substructure. These structural changes were completed before sperm nuclear decondensation started. The region where the granular structures were visualized was close to that of the antigen recognized by the monoclonal antibody MN13, which is supposed to be involved in the association of the periodic substructure with the overlaying plasma membrane (Toshimor et al., 1991). Based upon these results, we present the progress of events at the initial stage of gamete interaction.

Acrosome↗

PubMed1999

The epidural structure changes during deep breathing.

PURPOSE: Previous experience has suggested that the insertion of an epidural catheter becomes easier when the patient takes a deep breath. The purpose of this study is to investigate the effects of respiration on the epidural space. METHODS: We examined the epidural space using a flexible epiduroscope in 20 patients undergoing thoracic epidural anesthesia. A 17-gauge Tuohy needle was inserted using the paramedian technique and the loss-of-resistance method with 5 ml air. The epiduroscope was introduced into the epidural space via the Tuohy needle. Each patient was requested to take a deep breath when the epiduroscope was positioned at the needle tip and at approximately 10 cm cephalad from the needle tip within the epidural space. The changes in the epidural structure during deep breathing at each site were then measured. RESULTS: In 80% of the patients, fatty tissue occupied the needle tip. Through the patients' maximal inspiration, the fatty tissue moved and a visible cavity expanded at the needle tip. Cross section area of the visible cavity at the needle tip was greater at the maximal inspiratory level than at the resting expiratory level: 12.1 +/- 6.7% vs 2.8 +/- 2.1% (mean +/- SD, P < 0.0001). In all patients, the visible cavity within the epidural space, which had already been expanded by injected air, became more expanded after maximal inspiration. Cross section area of the visible cavity at the 10 cm cephalad position was greater at the maximal inspiratory level than at the resting expiratory level: 20.6 +/- 10.0% vs 7.0 +/- 5.3% (P < 0.0001). CONCLUSION: Epiduroscopy showed that deep breathing expanded the potential cavity of the epidural space. We suggest that the changes in the epidural structure during deep breathing may assist in the insertion of an epidural catheter.

Adipose Tissue↗

PubMed2004

Observation of time-resolved structural changes by linear interpolation of highly redundant X-ray diffraction data.

A new experimental strategy is described for obtaining time-resolved protein structural changes using monochromatic X-ray crystallographic data. The method is based on time-dependent linear interpolation of observed intensity variations during conventional X-ray diffraction data collection. The method benefits from high data redundancy. Although the method was developed to examine time-dependent X-ray-induced crystal decay, it is potentially applicable to a variety of time-dependent crystallographic studies, including structural determination of chemical intermediates in enzyme reactions and X-ray-induced unfolding of proteins with multiple disulfide bonds.

Algorithms↗

PubMed1991

Prolonged exercise induces structural changes in SR Ca(2+)-ATPase of rat muscle.

Sarcoplasmic reticulum (SR) isolated from the deep red portion of the gastrocnemius muscle of Sprague-Dawley rats after a single bout of prolonged exercise was shown to have depressed Ca(2+)-stimulated Mg(2+)-dependent ATPase activity over a temperature range of 15 to 42.5 degrees C when compared to SR obtained from control muscle. Inclusion of the calcium ionophore, A23187, failed to restore the depressed ATPase activity from SR of exercised muscle to control values, but it did normalize the stimulatory effect of temperature on ATPase activity. This depression was also manifested as an increased activation energy when the data were converted to an Arrhenius plot. SR vesicles from both groups showed no differences or discontinuities in plots of steady-state fluorescence anisotropy. When the binding characteristics of the fluorescent probe, fluorescein isothiocyanate (FITC), were analyzed, SR vesicles prepared from exercised muscle displayed a 40% reduction in binding capacity with no apparent change in Kd. These findings support the conclusion that a single bout of exercise induces a structural change in the Ca(2+)-ATPase protein of rat red gastrocnemius muscle that is not a direct result of gross lipid alterations or increased muscle temperature.

Animals↗

PubMed2003

Raman microspectroscopic study of effects of Na(I) and Mg(II) ions on low pH induced DNA structural changes.

In this work a confocal Raman microspectrometer is used to investigate the influence of Na(+) and Mg(2+) ions on the DNA structural changes induced by low pH. Measurements are carried out on calf thymus DNA at neutral pH (7) and pH 3 in the presence of low and high concentrations of Na(+) and Mg(2+) ions, respectively. It is found that low concentrations of Na(+) ions do not protect DNA against binding of H(+). High concentrations of monovalent ions can prevent protonation of the DNA double helix. Our Raman spectra show that low concentrations of Mg(2+) ions partly protect DNA against protonation of cytosine (line at 1262 cm(-1)) but do not protect adenine and guanine N(7) against binding of H(+) (characteristic lines at 1304 and 1488 cm(-1), respectively). High concentrations of Mg(2+) can prevent protonation of cytosine and protonation of adenine (disruption of AT pairs). By analyzing the line at 1488 cm(-1), which obtains most of its intensity from a guanine vibration, high magnesium salt protect the N(7) of guanine against protonation. A high salt concentration can prevent protonation of guanine, cytosine, and adenine in DNA. Higher salt concentrations cause less DNA protonation than lower salt concentrations. Magnesium ions are found to be more effective in protecting DNA against binding of H(+) as compared with calcium ions presented in a previous study. Divalent metal cations (Mg(2+), Ca(2+)) are more effective in protecting DNA against protonation than monovalent ions (Na(+)).

Animals↗

PubMed1978

A study of rapid mitochondrial structural changes in vitro by spray-freeze-etching.

The spray-freeze-etching technique has been used to study energy-linked mitochondrial structural changes in rat liver mitochondria incubated in vitro. The technique involves spraying the suspension of mitochondria into liquid propane at -190 degrees C, and does not require the use of cryoprotectants or chemical fixatives. The results confirmed that freshly isolated mitochondria have a condensed matrix and that this expands at the expense of the outer compartment to give the orthodox configuration when the mitochondria are incubated in a K+ medium in the presence of substrate and phosphate. Addition of adenosine diphosphate (ADP) caused a rapid shrinkage of the matrix compartment, and the time-course and extent of this shrinkage has been measured quantitatively by coupling a rapid sampling device to the spray-freezing apparatus. These data show that for orthodox mitochondria the onset of phosphorylation is accompanied by a reduction of 30% in the matrix volume in 20's, and there is no evidence that the decrease in matrical volume affects the phosphorylation efficiency. These results suggest that natural ionophores in the mitochondrial inner membrane make it permeable enough to permit a rapid readjustment of matrix volume after the addition of ADP, and that the associated ion movement does not cause uncoupling of oxidative phosphorylation.

Adenosine Diphosphate↗

PubMed2004

Structural changes in the renal vasculature in streptozotocin-induced diabetic rats without hypertension.

BACKGROUND/AIM: We evaluated in diabetic-streptozotocin rats (STZR) the structural changes of glomeruli, preglomerular vessels, glomerular tuft and renal parenchyma in order to determine the degree of renal injury and the presence of remodeling in afferent arterioles developed by diabetes without overimposed hypertension. METHODS: Renal mass index and histological score (glomerular number, density, tubular lesions and degree of arteriosclerosis) were estimated. In afferent arterioles the ratio of wall thickness/lumen was obtained by stereological methods. RESULTS: STZR developed diabetes without hypertension; renal mass index increased and matched changes in glomeruli (decrease of capillary number and enlargement of mesangium and basement capillary membrane). Both glomerular number and density as well as afferent arteriole number were diminished. Degenerative changes in both proximal (glycogenic and hyaline degeneration) and distal tubules (hyaline casts) were also observed. At variance with preglomerular vessels, the efferent arterioles only presented initial arteriosclerosis. Finally, the stereological study of afferent arterioles showed a significantly lower arteriolar lumen area and arteriolar wall thickness in STZR, resulting in a remodeling without modification of wall/lumen ratio. CONCLUSION: Diabetes, uncomplicated by hypertension, is associated with (1) a reduction in glomerular number; (2) degeneration in parenchyma and renal tubules, and (3) a specific pattern of remodeling in preglomerular vessels different from that induced by hypertension. Although this work demonstrated that these changes are not triggered by hypertension, further investigations are required in order to determine which mediators are involved in diabetic-vascular renal dysfunction.

Animals↗

PubMed1990

Structural changes, ill health, and mortality in Sweden, 1963-1983: a macroaggregated study.

An exploratory time series analysis was performed on selected indicators of structural change, health behavior, and ill health in Sweden in the years 1963-1983. Both synchronic (nonlagged) and asynchronic (lagged) analyses were made. The synchronic analysis of variations in the suicide rate reveals two main contributory factors: level of employment and overtime work. For cardiovascular mortality in men, the synchronic and the two-year time lagged analyses reveal that the sale of alcohol and, to a certain extent, the length of the period of unemployment play a major role. In an analysis with a three-year time lag, only one significant factor for both men and women is revealed, namely the level of employment. In the synchronic analysis of cirrhosis mortality in men, the sale of alcohol plays a dominant role. The results of the synchronic analysis of the variations in sick leave show a similar pattern for both men and women. In both cases, the sale of alcohol is positively associated and the proportion of unemployed industrial workers negatively associated with sick leave. The results give rise to a number of questions. For example, how should these findings be interpreted and how should they be related to existing knowledge about the links between business cycles and changes in the health of the population? The answers to such questions are of importance both from a scientific viewpoint and with regard to health policy. We argue that the answers require further studies of the characteristics of the periods in the business cycle and of how these periods affect people's lives, living conditions, and behavioral patterns in general.

Alcohol Drinking↗

PubMed1986

Structural changes during contraction in vertebrate skeletal muscle as studied by time-resolved X-ray diffraction technique.

To obtain information about the structural changes in vertebrate skeletal muscle during contraction, time-resolved X-ray diffraction studies were performed on the intensity changes of the 59 A and 51 A actin layer lines from bullfrog sartorius muscle during the isometric force development, and the intensity changes of the 143 A and 215 A myosin meridional reflections and of the 1.0 and 1.1 equatorial reflections when isometrically contracting muscle was subjected to sinusoidal length changes (1%, 5-10 Hz) with the following results. The integrated intensities of the 59 A and 51 A actin layer lines increased during the force development by 30-50% for the 59 A reflection, and by about 70% for the 51 A reflection compared to their respective resting values. These intensity changes were greater than those taking place during the transition from rest to rigor state, and observed to precede the intensity changes of the 429 A myosin off-meridional reflection and of equatorial reflections. When sinusoidal length changes were applied to the muscle generating steady isometric force, the resulting periodic intensity changes in the 1.0 and 1.1 equatorial reflections were in phase and in antiphase with the length changes respectively. On the other hand, the 143 A myosin reflection exhibited a characteristic periodic changes; its intensity reached a maximum at each boundary between the stretch and release phases of the length changes. These results are discussed in connection with the behaviour of the cross-bridges during contraction.

Actin Cytoskeleton↗

PubMed1996

G-induced myocardium functional alterations are not related to structural changes in rat heart.

BACKGROUND: Left ventricular myocardial hypertrophy with a redistribution of the isomyosins is classically observed under chronic pressure overload. HYPOTHESIS: Structural changes will also occur in myocardial cells after repeated exposures to high sustained +Gz acceleration. METHOD: Rats were exposed to three plateaus of 30 s at 10 +Gz, 4 times a week, for 4 weeks. The myocardial mass was evaluated by measuring the ratio between left ventricular weight and body weight, and the myocardial fiber cross-sectional area. Changes in capillary density were evaluated using the myosin ATPase method. The distribution of myosin isoforms was determined by electrophoresis. RESULTS: Contrary to expectations, no myocardial hypertrophy developed, and no transition was observed in myosin isoforms of centrifuged rats. CONCLUSION: The functional mechanical and energetic transformations observed in a previous investigation using an identical experimental protocol probably took place at an early stage of myocardial adaptation to +Gz acceleration. We conclude that our protocol of repeated +Gz exposures is a model of chronic overloading very different from classical models.

Acceleration↗

PubMed2004

[Diagnosis of structural changes] of the brain in patients with coronary and asymptomatic carotid atherosclerosis].

AIM: To compare echomorphostructure of atherosclerotic plaques and vascular stenosis degree with structural changes of the brain according to MR image in patients with combined atherosclerotic affection of coronary and carotid arteries in an asymptomatic course of carotid atherosclerosis. MATERIAL AND METHODS: MR imaging was made in 53 men aged 44 to 78 years with stenosing atherosclerotic affection of the internal carotid arteries. Vascular obstruction reached 30-80%. Neurological examination detected no signs of focal brain lesions. Hypertension, myocardial infarction, permanent atrial fibrillation were diagnosed in 19 (36%), 20 (38%) and 12 (23%) patients, respectively. RESULTS: Ultrasound investigation has established that carotid arteries contain more frequently spongy and heterogenic plaques than dense and calcinated. MRI registered structural alterations of cerebral tissue of various degree in 96% cases. CONCLUSION: Significant correlations were established between ischemic affection of the brain with myocardial infarction, arterial hypertension, cardiac fibrillation, type of atherosclerotic plaque.

Adult↗

PubMed2006

Regenerated silk fibroin nanofibers: water vapor-induced structural changes and their effects on the behavior of normal human cells.

Nanofibrous non-woven matrices were prepared by electrospinning a regenerated silk fibroin (SF) solution, and the structural changes of SF nanofibers treated with water vapor were investigated using time-resolved IR and (13)C CP/MAS NMR spectroscopy. Conformational transitions of SF from random coil to beta-sheet structures were induced by water vapor treatment and were strongly dependent on the treatment time and temperature. Water vapor treatment provided a useful means of stabilizing the SF nanofiber matrices, resulting in the formation of matrices with a decreased solubility in water and increased mechanical strength. The adhesion and spreading of both normal human keratinocytes and fibroblasts onto the SF nanofiber matrices were also investigated, and the water vapor-treated SF nanofiber matrices showed good cellular compatibility, in comparison with traditional methanol-treated ones. This approach to controlling the conformational changes of SF nanofibers by water vapor treatment may be useful in the design and tailoring of novel materials for biomedical applications, including wound dressings and scaffolds for tissue engineering.

Cell Adhesion↗

PubMed1996

Analyses of the role of structural changes in the regulation of uncoating and assembly of alphavirus cores.

In the late stages of alphavirus multiplication virus cores accumulate in the cytoplasm as stable structures, whereas they are unstable during the early stages of infection. Three types of explanation can be put forward to understand this phenomenon: (1) A cellular uncoating process is active early which is inactivated later, (2) the core structure differs between stable cores which accumulate and labile cores which are dissociated, (3) both mechanisms cooperate. A model based exclusively on the first principle involving core disassembly by cellular ribosomes has been proposed, but structural changes of the core may cooperate with the cellular uncoating process. We have therefore isolated cores of the Sindbis alphavirus from the cellular cytoplasm, from virus particles (vi-cores), and from low-pH-treated virus particles. Comparative analyses of the structure of these cores, using crosslinking and proteolytic digestion, and of the stability of the cores in the presence of ribosomes in vitro were performed. The structural comparisons indicate that the interactions between the molecular components of these cores are very similar and probably identical. In the presence of ribosomes vi-cores were slightly more stable than the two other types of cores. Evidence for a cellular uncoating mechanism is furnished by experiments which analyze the stability of cores in the presence of postmitochondrial cytoplasm or of 60 S ribosomal subunits derived from either uninfected or Sindbis virus-infected cells. The results obtained indicate that structural alterations of the core do not play a role in the regulation of disassembly and assembly of alphavirus cores.

Animals↗

PubMed1994

Quantification of the calcium-induced secondary structural changes in the regulatory domain of troponin-C.

The backbone resonance assignments have been completed for the apo (1H and 15N) and calcium-loaded (1H, 15N, and 13C) regulatory N-domain of chicken skeletal troponin-C (1-90), using multidimensional homonuclear and heteronuclear NMR spectroscopy. The chemical-shift information, along with detailed NOE analysis and 3JHNH alpha coupling constants, permitted the determination and quantification of the Ca(2+)-induced secondary structural change in the N-domain of TnC. For both structures, 5 helices and 2 short beta-strands were found, as was observed in the apo N-domain of the crystal structure of whole TnC (Herzberg O, James MNG, 1988, J Mol Biol 203:761-779). The NMR solution structure of the apo form is indistinguishable from the crystal structure, whereas some structural differences are evident when comparing the 2Ca2+ state solution structure with the apo one. The major conformational change observed is the straightening of helix-B upon Ca2+ binding. The possible importance and role of this conformational change is explored. Previous CD studies on the regulatory domain of TnC showed a significant Ca(2+)-induced increase in negative ellipticity, suggesting a significant increase in helical content upon Ca2+ binding. The present study shows that there is virtually no change in alpha-helical content associated with the transition from apo to the 2Ca2+ state of the N-domain of TnC. Therefore, the Ca(2+)-induced increase in ellipticity observed by CD does not relate to a change in helical content, but more likely to changes in spatial orientation of helices.

Amino Acid Sequence↗

PubMed1982

Unusual structural changes in mitochondria during spermiogenesis in the oribatid mite, Hafenrefferia gilvipes (Acari).

During spermiogenesis in the oribatid mite, Hafenrefferia gilvipes, striking alterations in the structure and location of mitochondria in spermatids were observed. The structural changes include formation of a single, distended annular crista, which subsequently becomes tubular. Initially, the mitochondria are located in central regions of the cytoplasm, they then move first to the plasmalemma and subsequently to the nuclear envelope, and finally are engulfed in the nuclear material.

Animals↗

PubMed2002

Compositional and structural changes of human dentin following caries removal by Er,Cr:YSGG laser irradiation in primary teeth.

In this in vitro study, the compositional and structural changes of human dentin, and knoop harness of cavity floor following the removal of dental caries by Er,Cr:YSGG laser irradiation in primary teeth was compared with that of the conventional bur cavity. The results confirmed that laser irradiation revealed minimal thermal damage to the surrounding tissues, minimal thermal induced changes of dental hard tissue compositions, and favorable surface characteristic.

Aluminum Silicates↗