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Results for “Structural changes”

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PubMed1996

[Radionuclide diagnosis of the degree of structural changes in the testes after herniotomy].

Funiculus spermaticus is exposed to invasive surgical intervention during Inguinal hernia reconstruction. Division or mechanical trauma to the spermatic artery account for serious trophic changes in the testis which, in bilateral herniotomy in particular, give rise to azoospermia. Here utilization of gamma camera scintigraphy of testes is indicated insofar as it may establish the degree of structural changes in testes as a result of mechanical injury to the spermatic chord during herniotomy which, in turn, has important prognostic implications on the fertility potential of patients. Twenty-five patients aged 3 to 48 years are covered by the study. In four of them herniotomy is associated with ipsilateral cryptorchidism and because of that orchiopexy is resorted to. In seven cases complete atrophy of testes following herniotomy is established scintigraphically. The imaging of testes fails, and functional parenchyma is lacking. In case of testicular hypoplasia, gamma-camera scintigraphy yields important information on the blood flow and blood supply to testes, as well as on intercurrent changes taking place. The radionuclide indices undergo alterations consistent with the structural changes in the parenchyma of testes. The severer the structural changes, the lower the values of radionuclide indices.

Adolescent↗

PubMed1991

Cardiovascular structural changes in hypertension: possible regression during long-term antihypertensive treatment.

Arterial hypertension is often complicated by left ventricular hypertrophy (LVH) and by vascular structural changes resulting in decreased proximal and distal compliance. LVH is an adverse prognostic factor because it increases the incidence of sudden death and other morbid events related to ischaemic heart disease, whereas vascular alterations may induce target organ damage and contribute to the maintenance of elevated blood pressure values. Thus, antihypertensive treatment must both reduce blood pressure and halt regression of cardiovascular structural changes. A review of the literature suggests long-term use of calcium antagonists, ACE inhibitors, and beta-blockers may revert LVH. We have found that such long-term drug use not only reduces blood pressure and LVH, but also ventricular arrhythmias that are often related to cardiac hypertrophy; however, diuretics do not have this beneficial effect. As regards vascular disturbances ACE inhibitors partially revert these alterations, whereas beta-blockers do not. Further studies are needed to determine whether there are regional differences in the regression of cardiovascular structural changes or whether different antihypertensive drugs have different effects on these changes.

Animals↗

PubMed1988

Functional versus structural changes of forearm vascular resistance in hypertension.

Structural changes in resistance vessels have been considered an important factor in triggering and maintaining chronic hypertension in humans and in experimental animals. To determine whether the increased forearm vascular resistance observed following vasodilator maneuvers in hypertensive patients is predominantly due to structural or to functional changes, we examined the influence of different vasodilator stimuli on forearm blood flow and blood pressure in 22 male patients with established essential hypertension and in 22 age-matched normotensive men (age range, 28-52 years). Blood pressure was measured directly, and blood flow was measured by venous occlusion plethysmography. The maneuvers applied were 1) arterial occlusion combined with handgrip exercise and local heating, 2) intra-arterial infusion of the calcium entry blocker nifedipine, 3) intra-arterial infusion of the nonspecific vasodilator sodium nitroprusside, 4) arterial occlusion initiated after intra-arterial infusion of nifedipine. Vascular resistance during vasodilation induced by arterial occlusion or infusion of nifedipine or sodium nitroprusside remained significantly higher in the hypertensive than in the normotensive subjects. However, the maximal vasodilation achieved by the combination of arterial occlusion and nifedipine resulted in a similar resistance in both groups (1.6 +/- 0.2 in the hypertensive vs 1.4 +/- 0.2 mm Hg/ml/min/100 ml tissue in the normotensive subjects. These data suggest that there is an important functional component of the elevated resistance in patients with essential hypertension.

Adult↗

PubMed1992

Evaluation of elastic structural change in coronary atherosclerosis using scanning acoustic microscopy.

Coronary atherosclerotic lesions were observed by scanning acoustic microscopy (SAM), a technique which can visualize regions of differing elasticity. Three regions, i.e., dark (dR), intermediate (iR) and bright (bR) demonstrating differences in acoustic reflection intensity and the velocity of surface acoustic waves, were seen in the lesions. Furthermore, lipid-positive areas were found to be dR and iR and fatty crystalline areas were observed only in iR regions by polarizing microscope. These phase transitions of fat affected the acoustic properties in each region. According to SAM images, intimal structural changes were classified into three types, minimum structural change (type I), the overcrowded net-like dR structure (type II) and markedly disturbed structure with a decrease of dR (type III). The medial structure change was also classified into three types paralleling the decrease of dR (types M1, M2 and M3). Intimal type II with a large degree of thickening and intimal type III with medial type M3 were highly prominent in the acute myocardial infarction (AMI) group (P less than 0.01). Therefore these results suggest that the anisotropic elasticity induced by micro-elastic changes in the arterial wall may be associated with functional disturbance of the vascular wall.

Acoustics↗

PubMed1992

Inhibitors of protein and RNA synthesis block structural changes that accompany long-term heterosynaptic plasticity in Aplysia.

Synaptic connections between the sensory and motor neurons of Aplysia in culture undergo long-term facilitation in response to serotonin (5-HT) and long-term depression in response to FMRFamide. These long-term functional changes are dependent on the synthesis of macromolecules during the period in which the transmitter is applied and are accompanied by structural changes. There is an increase and a decrease, respectively, in the number of sensory neuron varicosities in response to 5-HT and FMRFamide. To determine whether macromolecular synthesis is also required for the structural changes, we examined in parallel the effects of inhibitors of protein (anisomycin) or RNA (actinomycin D) synthesis on the structural and functional changes. We have found that anisomycin and actinomycin D block both the enduring alterations in varicosity number and the long-lasting changes in synaptic potential. These results indicate that macromolecular synthesis is required for expression of the long-lasting structural changes in the sensory cells and that this synthesis is correlated with the long-term functional modulation of sensorimotor synapses.

Animals↗

PubMed1998

Coculture of human sperm with bovine oviduct epithelial cells decreases sperm chromatin structural changes seen during culture in media alone.

OBJECTIVE: To compare sperm chromatin structural changes seen in media only culture or in coculture with bovine oviduct epithelial cells. DESIGN: Three freshly ejaculated and three cryopreserved sperm samples in media culture or in oviduct epithelial cell coculture. Sperm in each treatment were evaluated by the sperm chromatin structure assay during a 72-hour time course. SETTING: An academic research laboratory. PATIENT(S): Normospermic donors with children. INTERVENTION(S): Semen collection through masturbation after 48 hours of abstinence. MAIN OUTCOME MEASURE(S): The sperm chromatin structure assay using flow cytometry to detect the susceptibility of sperm in either treatment to denaturation of DNA in situ. RESULT(S): The sperm chromatin structure assay data differed for sperm type (fresh or cryopreserved), over time, and between treatments within 6 hours of culture. In oviduct epithelial cell coculture, fresh sperm chromatin structure assay values for fresh sperm were stable, whereas in control medium higher chromatin degeneration levels were seen by 10 hours. For cryopreserved sperm, chromatin degeneration had increased by 1 hour postthaw in both treatments, although levels were higher in the control treatment thereafter. CONCLUSION(S): Sperm chromatin structural changes occur over time in culture. Such changes were observed within 2 hours for cryopreserved sperm. Coculture of sperm with oviduct epithelial cells results in a stabilizing effect for sperm against chromatin changes.

Animals↗

PubMed1996

Secondary and tertiary structure changes of reconstituted P-glycoprotein. A Fourier transform attenuated total reflection infrared spectroscopy analysis.

The structure of purified P-glycoprotein functionally reconstituted into liposomes was investigated by attenuated total reflection Fourier transform infrared spectroscopy. A quantitative evaluation of the secondary structure and a kinetic of 2H/H exchange of the P-glycoprotein were performed both in the presence and in the absence of MgATP, MgATP-verapamil, and MgADP. This approach was previously shown to be a useful tool to detect tertiary structure changes resulting from the interaction between a protein and its specific ligands, as established for the Neurospora crassa H+-ATPase. 2H/H exchange measurements provided evidence that a large fraction of the P-glycoprotein is poorly accessible to the aqueous medium. Addition of MgATP induced an increased accessibility to the solvent of a population of amino acids, while addition of MgATP-verapamil resulted in a subtraction of a part of the protein from access to the aqueous solvent. No significant changes were observed upon addition of MgADP or verapamil alone. The secondary structure of P-glycoprotein was not affected by addition of ligands. The variations observed in the 2H/H exchange rate when P-glycoprotein interacted with the above ligands therefore represented tertiary structure changes. Fluorescence quenching experiments confirmed that MgATP-induced changes are to be found in the tertiary structure of the enzyme.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1998

Some physico-chemical properties and structural changes of bovine beta-casein upon glycation.

The studies on casein structure modification contribute to better understanding of the role of nonamino acid components in forming casein complexes and improving ways of protein functionality. The objective of the experiments was to explain the influence of bovine milk casein glycation on some physico-chemical properties and structural changes. From the the analysis of glycation rate curve the reaction of the first order range can be assumed during the first 24 h, turning to a mixed type afterwards. The isoelectric point and molecular weight of beta-casein increased after glycation and the electrophoretic mobility was slightly modified. The structural changes were also confirmed by different absorption spectra in UV and a better heat stability of the modified beta-casein. The findings showed higher solubility with modified beta-casein. The glycation caused changes in beta-casein, modifying its susceptibility to the trypsin hydrolysis.

Amino Acids↗

PubMed1984

An electron spin resonance study of temperature-induced structural changes of the spin-labeled myosin head: an evidence for two conformational states of myosin head.

Heavy meromyosin labeled at the SH1 thiol group with an iodoacetamide spin label was studied by electron spin resonance spectroscopy at various temperatures in the presence and absence of nucleotides and PPi. The electron spin resonance spectra of the spin label bound to myosin head showed temperature-dependent changes indicating changes of the structure around the SH1 thiol group of the myosin head. As the temperature was elevated, the bound spin label was more mobilized in all the systems examined. The mobilization of the bound spin label by the elevation of temperature was enhanced in the presence of nucleotides or PPi. The temperature-dependent spectral changes had isosbestic points indicating that the structural changes around the SH1 thiol group took place between two states of the bound spin label, a weakly immobilized and a strongly immobilized state.

Animals↗

PubMed1998

Long-lasting structural changes in CA3 hippocampal and layer V motor cortical pyramidal neurons associated with self-stimulation rewarding experience: a quantitative Golgi study.

Self-stimulation (SS) rewarding experience induced structural changes in CA3 hippocampal and layer V motor cortical pyramidal neurons in adult male Wistar rats has been demonstrated. In the present study, whether these structural changes are transient or of a permanent nature was evaluated. Self-stimulation experience was provided for 1 h daily over a period of 10 days through bilaterally implanted bipolar electrodes in the lateral hypothalamus and the substantia nigra-ventral tegmental area. Following 10 days of SS experience, the rats were sacrificed after an interval of 30 and 60 days for the quantitative analysis of the dendritic morphology in Golgi stained CA3 hippocampal and layer V motor cortical pyramidal neurons. The results revealed a significant increase in the dendritic branching points and intersections in apical and basal dendrites in both types of neurons in 30 days post-SS group compared to sham control. The total number of apical and basal dendrites were significantly increased in both 30 and 60 days post-SS groups of rats. This study suggests that SS experience induced structural changes are sustainable, even in the absence of rewarding experience.

Analysis of Variance↗

PubMed1994

Resolution of structural changes associated with calcium activation of calmodulin using frequency domain fluorescence spectroscopy.

Structural changes associated with the calcium-dependent activation of wheat germ calmodulin (CaM) were assessed through measurements of steady-state and time-resolved changes in the fluorescence associated with (1) the unique tyrosine (Tyr139) located in calcium binding loop IV or (2) N-(1-pyrenyl)-maleimide (PM) or 4-(iodoacetamido)salicylic acid (IASA) covalently attached to Cys27 present in calcium binding loop I. These fluorophores permit the measurement of calcium-dependent changes in (i) the solvent accessibility and rotational dynamics associated with calcium binding loops I and IV and (ii) the hydrodynamic properties of the entire protein. Specific nitration of the unique tyrosine (Tyr139) in calcium binding loop IV permits the use of fluorescence resonance energy transfer to measure both the average spatial separation and distance heterogeneity between Cys27 and Tyr139, providing a direct measurement of the conformational flexibility of the central helix. Upon calcium binding, (i) the solvent accessibility and rotational dynamics of both PM and IASA (covalently bound to Cys27) and Tyr139 increase, (ii) overall protein rotational motion decreases, (iii) the average separation between the chromophores at Cys27 and nitrotyrosine 139 decreases, and (iv) the conformational flexibility associated with the central helix decreases. Therefore, upon calcium binding, the central helix becomes more extended and rigid, while the globular domains adopt a more open tertiary conformation that brings Cys27 and Tyr139 into closer proximity. This calcium-dependent structural change functions to expose the hydrophobic binding sites located within the globular domains, and to enhance the probability of binding target sequences through a reduction in conformational heterogeneity.

Calcium↗

PubMedDate not supplied

Pregnancy-induced structural changes and trophoblastic invasion in the segmental mesometrial arteries of the guinea pig (Cavia porcellus L.).

Light microscopic, electron microscopic and histochemical studies were carried out on the segmental mesometrial arteries of non-pregnant guinea pigs and on pregnant ones at each of the nine weeks of gestation. Pregnant animals show drastic changes in arterial structure and dimensions. Hypertrophy and structural dilatation of the arterial wall are obvious. In midpregnancy, the elastic membranes begin to disappear; only small fragments remain. From the fifth week on, mononuclear cells appear in the media; they form aggregates and occasionally giant cells with signs of phagocytosis in the seventh week of gestation. In the eighth week further degenerative changes can be observed, resulting in widespread destruction of the arterial wall. Deposition of necrotic cell debris is obvious in the ninth week. By this time there appear in the endothelial layer conspicuous single cells, cell aggregates and giant cells with heavily folded nuclei, prominent nucleoli, abundant vesicles, free ribosomes, intracellular lacunae and the histochemical properties of placental trophoblast. These cells in the endothelium are distinctly different from the medial giant cells of mononuclear origin. According to these observations, the segmental mesometrial arteries of pregnant guinea pigs show cytological and structural changes similar to those described for the mesometrial arteries in the hamster and the spiral arteries in man. The results show that, beside structural dilatation, degenerative changes and apparent trophoblastic giant cell invasion occur in the arteries studied. Trophoblastic invasion occurs later than structural dilatation and obviously does not trigger or control the structural dilatation of the segmental mesometrial arteries.

Animals↗

PubMed1982

Severe functional and structural changes caused by lithium in the developing rat kidney.

Lithium (Li) was administered to rats during maternal pregnancy and/or 8 weeks post-natally, to study the effects on renal function and structure in the developing kidney. Plasma Li was 0.5-1.0 mmol/l 3 and 8 weeks post-natally. Functionally, post-natal Li leads to growth retardation, polyuria with lowering of renal concentration ability, and uremia associated with as much as 80% lowering of the normal glomerular filtration rate (GFR). Pre-natal Li alone did not affect the concentrating ability but caused a 20% increase in GFR when evaluated 8 weeks post-natally. Post-natal Li caused very severe structural changes, consisting of up to 3 mm cortical cysts (= dilated distal convoluted tubules), extensive interstitial fibrosis with cell infiltration, and atrophy of the cortical collecting ducts. Morphometric measurements showed a significant reduction in the volume of the proximal tubular cells. Pre-natal Li caused only slight structural changes, and animals treated both pre- and post-natally were less affected than animals treated post-natally only. The structural changes caused by post-natal Li were unrelated to changes in the concentrating ability but showed a significant correlation with the lowering of the GFR. It is concluded that the post-natally developing rat kidney is particularly sensitive to the nephrotoxic effects of Li, which in low concentrations causes impairment of renal function, leading to uremia. Pre-natal Li exposure by maternal lithium treatment had little effect on renal function and structure when evaluated post-natally.

Animals↗

PubMedDate not supplied

[Structural changes in cell nuclei in the physiologic pH range].

Fluorescence of the suspension of cell nuclei from rat liver was investigated under neutral pH range. The pH decrease from 7 to 5 causes the quenching of protein fluorescence of nuclei and leads to an increase of the polarization degree of the fluorescence. Buffering properties of the nuclei in this range were detected. The use of 1-anilino-8-naphthalenesulfonate as the fluorescent probe permits to find the changes of nuclei surface properties with increasing the proton concentration in the solution. Circular dichroism spectra of nuclei were shown to depend on the pH solution too. It was suggested that structure state of the nuclei depends on the pH solution. The structural changes are reversible in the physiological pH range and were concluded to be in the envelope and chromatin of the nuclei. The role of histidine residues of nuclear proteins in the initiation of the structure changes was discussed. It was supposed that structure changes of the nuclei in the physiological pH range have an essential functional role.

Animals↗

PubMed1985

Patterns of structural change in DNA during tissue necrosis indicated by benzoylated DEAE-cellulose chromatography.

Structural change in liver DNA, isolated following administration of a necrogenic dose of carbon tetrachloride to rats, was examined by benzoylated DEAE-cellulose (BD-cellulose) chromatography. Greatest increase in the amount of DNA exhibiting single stranded character was detected 48 h after treatment, at which time massive necrosis was evident histologically. By 72 h after dosing, normal hepatic architecture had been restored and gross structural change in DNA could no longer be detected. The extent of single stranded regions in DNA isolated at various times after carbon tetrachloride intoxication was assessed by caffeine gradient elution of respective samples from BD-cellulose. By this criterion, structural damage to DNA was again most marked 48 h after treatment at which time single stranded regions extending over several kilobases were apparent. At earlier times such lesions were considerably shorter. Single stranded regions of discrete length detected 72 h after administration of the hepatotoxin appeared to be associated with cell division. Structural damage to DNA coincident with toxic injury was further characterized using BD-cellulose, by caffeine gradient elution of preparations subjected to denaturation before chromatography. The data indicate that production of single stranded regions is a major feature of DNA degradation during tissue necrosis. Whilst such degradation might otherwise confound interpretation of structural analyses based only upon strand breakage, the size of these regions suggests a basis for distinguishing between them and lesions specifically associated with repair, replication and transcription of DNA.

Animals↗

PubMed1988

Structural changes in glycogen phosphorylase induced by phosphorylation.

A comparison of the refined crystal structures of dimeric glycogen phosphorylase b and a reveals structural changes that represent the first step in the activation of the enzyme. On phosphorylation of serine-14, the N-terminus of each subunit assumes an ordered helical conformation and binds to the surface of the dimer. The consequent structural changes at the N- and C-terminal regions lead to strengthened interactions between subunits and alter the binding sites for allosteric effectors and substrates.

Adenosine Monophosphate↗

PubMed1999

Structural Change in Dextran: Mechanism of Insolubilization by Adsorption on the Air-Liquid Interface.

To clarify the insolubilization mechanism of water-soluble dextran, the association of dextran in water was studied by dynamic light scattering measurements and a surface chemical approach. Dynamic light scattering measurements indicated that insolubilization of dextran is accompanied by a structural change in dextran. Surface tension data for dextran molecules revealed a structural change in dextran molecules at the air-liquid interface. These results suggest that insolubilization of dextran molecules occurred through an adsorption process at the air-liquid interface. Insolubilization of dextran molecules can be reduced by inhibition of this structural change in dextran molecules. The presence of boron as an impurity was found to trigger precipitation based on inductively coupled plasma mass spectrometry measurements and precipitation tests. Copyright 1999 Academic Press.

Journal Article↗

PubMed1988

Relation between cardiac hypertrophy and forearm vascular structural changes before and during long-term antihypertensive treatment.

In patients with hypertension, structural changes develop in the heart and in the systemic arteries that have a significant role in the maintenance and gradual worsening of the hypertensive disease. Blood pressure, basal and post-ischemic "maximal" forearm blood flow (strain-gauge venous occlusive plethysmography), and echocardiographic left ventricular mass index were measured in 28 hypertensive patients (WHO class I or II, 23 men and five women, aged 26 to 59 years). Minimal vascular resistance (mean arterial pressure/peak blood flow) was taken as an index of vascular structural changes. The same measurements were made in a group of 14 patients before and after long-term antihypertensive treatment: in eight patients after six and 12 months of treatment with captopril (50 mg twice a day, plus 25 mg of hydrochlorothiazide per day if necessary) and in six patients after six months of treatment with nitrendipine (20 mg per day, plus 50 mg of atenolol per day if necessary). A significant but weak direct correlation was found between the degree of left ventricular hypertrophy and mean arterial pressure (r = 0.41) or minimal vascular resistance (r = 0.31). Thus, patients were categorized according to whether they had left ventricular hypertrophy or impaired blood flow; the results suggested that left ventricular hypertrophy may be detected earlier than increased minimal vascular resistance. After six months of treatment, both captopril and nitrendipine significantly reduced left ventricular mass index and minimal vascular resistance. Left ventricular mass index was normalized in 50 percent of the patients, whereas minimal vascular resistance was normalized in one patient only. After 12 months of treatment, left ventricular mass index was normalized in all patients; minimal vascular resistance was on the average further reduced but normalized in only one additional patient. Thus, regression of cardiovascular structure also seems to occur earlier in the heart.

Adult↗