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PubMed1994

Adenosine-induced heterogeneous perfusion accompanies myocardial ischemia in the presence of advanced coronary artery disease.

The aim of the present study was to elucidate the characteristics of patients in whom transient myocardial ischemia was evoked during adenosine infusion. Thallium-201 (Tl-201) myocardial imaging and two-dimensional echocardiography during adenosine infusion were performed simultaneously in 61 consecutive patients enrolled for the diagnosis of coronary artery disease. Transient reduction of systolic wall motion after adenosine infusion was considered evidence of myocardial ischemia. Tl-201 redistribution was noted in 38 patients, and 23 of them showed a wall motion abnormality during adenosine infusion. Stepwise discriminant analysis was applied to eight variables that showed significant differences by the univariate analysis between patients with the presence and the absence of adenosine-induced wall motion abnormality: myocardial infarction, anginal pain, ST depression, collateral vessels, Tl-201 redistribution, number of diseased vessels of > or = 75% or 90% stenosis and number of segments with Tl-201 redistribution. The number of diseased vessels with > or = 75% stenosis (F = 43.5, p < 0.0001), ST depression (F = 16.0, p < 0.0002), collateral vessels (F = 11.7, p < 0.001) and Tl-201 redistribution (F = 5.6, p < 0.02) were the statistically significant discriminators relating to adenosine-induced wall motion abnormality. Adenosine-induced myocardial ischemia was related to the number of coronary stenoses, reflecting the presence of severe coronary artery disease, and well-developed collaterals that might be integral factors in a coronary steal phenomenon.

Adenosine↗
PubMed1992

Dental morphology of 45,XO human females: molar cusp area, volume, shape and linear measurements.

A three-dimensional analysis of the maxillary first molars of five 45,XO females and comparison with normal females and males demonstrated a reduction of cusp areas and volumes in the 45,XO females. Mesiodistal and faciolingual dimensions were also reduced. The reductions in basal area and volume were greater in the later developing, distal cusps. In normal females the second X chromosome apparently does not exert an effect on the cusp height but increases the basal area. The results further indicate that the Y chromosome in normal males increases both cusp height and basal area. The steepest cusps were found in 45,XO females while the shallowest were in the control males. Both sex chromosomes thus seem to affect the shape of the cusp but the resulting phenotypes differ.

Female↗
PubMed1984

Changes in the Bohr effect due to pyridoxylation of the alpha-chain terminal amino groups of hemoglobin.

Deoxyhemoglobins substituted with pyridoxal 5'-phosphate or pyridoxal 5'-deoxymethylenephosphonate at the N-terminal amino groups of the alpha-chains were investigated by 31P-NMR spectroscopy. Titration curves of the 5'-side-chains show a substantial increase in acid strength in alpha-pyridoxylated deoxyhemoglobins when compared to the corresponding CO-liganded hemoglobins. These derivatives therefore contain a new oxygenation-linked acid group which opposes the normal Bohr effect. The loss in stabilization of the monoanion of the phosphate or phosphonate group derived from the three-dimensional structure can account for the lower pK of this ionization in deoxyhemoglobin as compared to CO-liganded hemoglobin. The reduction in the Bohr effect caused by modification of the alpha-chains with pyridoxal 5'-deoxymethyl-enephosphonate is quantitatively equal to the expected contribution of alpha-chain N-terminal amino groups.

Allosteric Regulation↗
PubMed2005

Minimizing urinary bladder radiation dose during brachytherapy for carcinoma of the cervix using balloon inflation technique.

PURPOSE: Radiotherapy is effective in treating cancer of the cervix. However, its success is associated with significant morbidity of the urinary bladder. This study has been designed to reduce the radiotherapy dose from the brachytherapy component of cervical cancer treatment to the urinary bladder to minimize radiation-induced morbidity. MATERIALS AND METHODS: By inflating the balloon of a Foley catheter at the anterior fornix region, attempts were made to displace the urinary bladder in patients undergoing gynecological intracavitary brachytherapy. The radiation dose to the urinary bladder was then studied in 12 insertions without and 31 insertions with balloon inflation. RESULTS: The increase in the distance from the intrauterine tandem source to a reference point in the base of the bladder and the resultant decrease in the radiation dose have been determined. A highly significant reduction in the radiation dose with an increase in distance between the source applicator and bladder base were achieved (p < 0.01 in both cases). CONCLUSION: A significant reduction in radiation dose to the bladder base can be achieved by the technique described in this study. A three-dimensional plan generated using CT images can demonstrate the drawback of ICRU-38 bladder reference point. The technique is simple consistent and reproducible within an acceptable range.

Brachytherapy↗
PubMed2004

New treatment strategies for hypertrophic obstructive cardiomyopathy: alcohol ablation of the septum: the new gold standard?

Hypertrophic cardiomyopathy is a primary myocardial disorder with an autosomal pattern of inheritance characterized by inappropriate myocardial hypertrophy. Annual mortality has been reported to be 1% to 2% and sudden death represents the most common cause. Treatment strategies are 1) medical therapy in patients with mild to moderate symptoms, 2) reduction of septal hypertrophy by surgical myectomy or alcohol ablation, and 3) implantation of an automatic cardioverter-defibrillator in the presence of non-sustained ventricular tachyarrhythmias. A debate has been started on whether surgical myectomy or alcohol ablation of the septum is the appropriate treatment for hypertrophic obstructive cardiomyopathy. Surgical (transaortic) myectomy has been the gold standard in the past 20 to 30 years for treatment of symptomatic patients with significant hemodynamic outflow tract obstruction. However, modern interventional technologies allow reduction of the myocardial septum by injection of alcohol into the first or second septal branch under guidance of two-dimensional (2D)-contrast echocardiography. This percutaneous technique not only has a lower morbidity than surgical myectomy but can be guided precisely by 2D echocardiography. One potential complication is transient (<30%) or permanent (<10%) atrioventricular block III; however, this complication is relatively rare. A randomized trial comparing the two treatment modalities is lacking, and the chance is small that such a trial will be performed because alcohol ablation can be done with high success and low complication rates, leaving only complex interventions (with valvular reconstructions and so on) for surgical myectomy.

Cardiomyopathy, Hypertrophic↗
PubMed1998

Repair of aortico-left ventricular tunnel originating from the left aortic sinus.

We report on a case of an 11-year-old asymptomatic child with aortico-left ventricular tunnel arising from the left aortic sinus. Preoperative transesophageal echocardiography showed a dilated aortic root with mild aortic valve incompetence and demonstrated the course of the tunnel, which originated from the left coronary sinus entering the outlet portion of the left ventricular outflow tract. Patch closure of the aortic end of the tunnel eliminated left ventricular volume overload with immediate marked reduction of cardiomegaly. At 10-month follow-up the child is asymptomatic and receiving no oral medications. Control two-dimensional Doppler echocardiography shows trivial central aortic valve incompetence.

Aorta↗
PubMed2006

Rigid molecular tripod with an adamantane framework and thiol legs. Synthesis and observation of an ordered monolayer on Au111.

Tripod-shaped trithiols 1-3, containing CH2SH groups at the three bridgehead positions of the adamantane framework and a halogen-containing group [Br (1), p-BrC6H4 (2), or p-IC6H4 (3)] at the fourth bridgehead, were synthesized, and self-assembled monolayers (SAMs) were prepared on atomically flat Au111 surfaces. The three-point chemisorption of these tripods was confirmed by polarization modulation infrared reflection absorption spectroscopy, which showed the absence of a S-H stretching band. Scanning tunneling microscopy of the SAM of 1 exhibited a hexagonal arrangement of the adsorbed molecule with a lattice constant of 8.7 angstroms. A unidirectionally oriented, head-to-tail array of 1, which allows the close approach of neighboring molecules, is proposed as a reasonable model of the two-dimensional crystal, where the adsorbed sulfur atoms form a quasi-(radical3 x radical3)R30 degrees lattice. The charge of the electrochemical reductive desorption of the SAM of 1 was in good agreement with the expected surface coverage, while the SAMs of 2 and 3 showed somewhat less (ca. 70%) charge. The large negative reduction peak potentials, observed for the SAM of 1, are taken to indicate a tight anchoring of this tripod by three sulfur atoms.

Journal Article↗
PubMed1998

Human glutathione S-transferases.

Human glutathione S-transferases (GSTs) are a functionally diverse family of soluble enzymes of detoxification that use reduced glutathione (GSH) in conjugation and reduction reactions. Toxic electrophiles, including a variety of carcinogens, are substrates for the GSTs and after conjugation or reduction they are more easily excreted into bile or urine. Many of the GSTs have been cloned, and the three-dimensional structures of GSTs from several species, including humans, have been determined. These data have provided significant insight into how the GSTs function as enzymes. Many GST substrates are inducers of GST gene expression; nonsubstrate inducers include H2O2 and other reactive oxygen species. The regulatory elements of several human GST genes have been partially characterized, and the regulation of the GSTs in humans appears to be very different from that in rodents. Several polymorphisms of GST expression occur commonly in humans and have been associated with an increased susceptibility to certain cancers, particularly when combined with other genetic and environmental factors such as smoking. The role of GSTs in protecting cells from injury by toxic electrophiles continues to be developed.

Animals↗
PubMed2005

Localized waves in nonlinear oscillator chains.

This paper reviews results about the existence of spatially localized waves in nonlinear chains of coupled oscillators, and provides new results for the Fermi-Pasta-Ulam (FPU) lattice. Localized solutions include solitary waves of permanent form and traveling breathers which appear time periodic in a system of reference moving at constant velocity. For FPU lattices we analyze the case when the breather period and the inverse velocity are commensurate. We employ a center manifold reduction method introduced by Iooss and Kirchgassner in the case of traveling waves, which reduces the problem locally to a finite dimensional reversible differential equation. The principal part of the reduced system is integrable and admits solutions homoclinic to quasi-periodic orbits if a hardening condition on the interaction potential is satisfied. These orbits correspond to approximate travelling breather solutions superposed on a quasi-periodic oscillatory tail. The problem of their persistence for the full system is still open in the general case. We solve this problem for an even potential if the breather period equals twice the inverse velocity, and prove in that case the existence of exact traveling breather solutions superposed on an exponentially small periodic tail.

Journal Article↗
PubMed1993

Cardiovascular effects of i.v. induction in children: comparison between propofol and thiopentone.

We have compared the haemodynamic responses to i.v. propofol 2.5 mg kg-1 with those to thiopentone 5.0 mg kg-1 in 41 healthy Chinese children at induction of anaesthesia. They were allocated to four groups according to their age and induction agent received: group 1 < 2 yr, propofol, n = 9; group II < 2 yr, thiopentone, n = 9; group III 2-12 yr, propofol, n = 12; group IV 2-12 yr, thiopentone, n = 11. Anaesthesia was maintained by spontaneous ventilation with 70% nitrous oxide and 0.5% halothane in oxygen. Arterial pressure and heart rate were monitored by automatic oscillotonometer. Stroke volume was measured by two-dimensional echocardiography and pulse Doppler. Measurements were made before induction and at 1-min intervals for 5 min after induction. The reduction in mean arterial pressure was significantly greater after propofol (28-31%) than after thiopentone (14-21%) (P = 0.001). The reduction in cardiac index (10-15%) after induction was not significantly different between the two agents (P = 0.122). Baroreflex mediated increases in heart rate and systemic vascular resistance were less after propofol than after thiopentone. The baroreceptor reflex was more attenuated in children aged less than 2 yr than in older children.

Anesthesia, Inhalation↗
PubMed1997

A model of the electrocortical effects of general anaesthesia.

In an attempt to describe how reduction in synaptic efficiency by general anaesthetic agents results in loss of consciousness, we examined the behaviour of a two-dimensional (a lattice of 80 x 80 cellular elements) cellular automaton (CA) computer model as the connectivity between cellular elements was altered. The lattice was taken to represent cortical elements with variable connectivity to their neighbours. The summation of the active elements of the CA lattice was taken to represent a simulated "EEG" signal. If cellular automation elements had a high probability of connectivity, the simulated EEG showed high frequency predominance and low amplitudes, similar to the desynchronized pattern in an alert person. As connectivity was decreased, median frequency in the simulated EEG decreased and amplitude increased, similar to that in anaesthetized patients. As in our model, we believe it is possible that the human central nervous system in the conscious resting state exists above a critical threshold of synaptic efficiency; awareness is associated with an increase in synaptic efficiency and anaesthesia with a decrease that sharply reduces cortical information transfer.

Anesthetics, General↗
PubMed2001

A nonsense mutation in the NDUFS4 gene encoding the 18 kDa (AQDQ) subunit of complex I abolishes assembly and activity of the complex in a patient with Leigh-like syndrome.

Sequence analysis of mitochondrial and nuclear candidate genes of complex I in children with deficiency of this complex and exhibiting Leigh-like syndrome has revealed, in one of them, a novel mutation in the NDUFS4 gene encoding the 18 kDa subunit. Phosphorylation of this subunit by cAMP-dependent protein kinase has previously been found to activate the complex. The present mutation consists of a homozygous G-->A transition at nucleotide position +44 of the coding sequence of the gene, resulting in the change of a tryptophan codon to a stop codon. Such mutation causes premature termination of the protein after only 14 amino acids of the putative mitochondrial targeting peptide. Fibroblast cultures from the patient exhibited severe reduction of the rotenone-sensitive NADH-->UQ oxidoreductase activity of complex I, which was insensitive to cAMP stimulation. Two-dimensional electrophoresis showed the absence of detectable normally assembled complex I in the inner mitochondrial membrane. These findings show that the expression of the NDUFS4 gene is essential for the assembly of a functional complex I.

Amino Acid Sequence↗
PubMed2004

Changes in cerebral blood flow during cerebrospinal fluid pressure manipulation in patients with normal pressure hydrocephalus: a methodological study.

The combination of cerebral blood flow measurement using (15)O-water positron emission tomography with magnetic resonance coregistration and CSF infusion studies was used to study the global and regional changes in CBF with changes in CSF pressure in 15 patients with normal pressure hydrocephalus. With increases in CSF pressure, there was a variable increase in arterial blood pressure between individuals and global CBF was reduced, including in the cerebellum. Regionally, mean CBF decreased in the thalamus and basal ganglia, as well as in white matter regions. These reductions in CBF were significantly correlated with changes in the CSF pressure and with proximity to the ventricles. A three-dimensional finite-element analysis was used to analyze the effects on ventricular size and the distribution of stress during infusion. To study regional cerebral autoregulation in patients with possible normal pressure hydrocephalus, a sensitive CBF technique is required that provides absolute, not relative normalized, values for regional CBF and an adequate change in cerebral perfusion pressure must be provoked.

Aged↗
PubMedDate not supplied

Factors influencing flow-induced signal loss in MR angiography: an in vitro study.

OBJECTIVE: Signal loss due to poststenotic turbulence is one remaining limitation in the clinical use of MRA. The objective of this study was to determine the factors influencing poststenotic signal loss (PSL) in a stenotic tube system. MATERIALS AND METHODS: With use of a two-dimensional gradient echo sequence (FLASH), the influence of (a) the degree of stenosis (50, 75, and 91% cross-sectional area reduction), (b) flow velocity (12, 47, 71, and 94 cm/s), (c) TE (3, 6, 13, and 20 ms), and (d) flip angle (5, 10, 20, ... , 90 degrees) on the length of PSL was measured in a nonpulsatile stenotic tube system. To quantify the effect of first-order gradient motion refocusing (GMR), the signal intensity ratio from flow-compensated and -uncompensated images was calculated. For statistical analysis, multiple regression analysis and unpaired Student t test were used. RESULTS: In the flow model used, the length of PSL increased significantly with the degree of stenosis (beta ST' = 0.483 mm/%, beta ST" = 0.447 mm/%, p < 0.0001), flow velocity (beta v' = 0.297 s, beta v" = 0.213 s, p < 0.0001), and TE (beta TE = 1.88 mm/ms, p < 0.0001), respectively, whereas no correlation emerged for varying flip angles (beta alpha = 0.0214, p = 0.29). First-order GMR reduced significantly PSL in through-plane measurements (p < 0.0001). Maximal signal-enhancing effects of first-order GMR were observed 1-3 cm distal to the stenosis. CONCLUSION: Flow model parameters (i.e., degree of stenosis, flow velocity) markedly influenced the length of PSL that could be compensate for by use orf shortened TEs and first-order GMR. Varying flip angles had no significant influence on PSL.

Acrylic Resins↗
PubMedDate not supplied

Multi-detector CT of the chest: influence of dose onto quantitative evaluation of severe emphysema: a simulation study.

PURPOSE: Quantitative evaluation of the lung parenchyma might be impaired or unreliable by use of reduced-dose CT protocols. Aim of the study was to define the threshold where reduced dose has significant impact on quantitative emphysema parameters. MATERIALS AND METHODS: Thirty patients with severe centrilobular emphysema underwent multidetector computed tomography (120 kV, 150 mAs). Original CT raw data were simulated using 10 mAs settings (10-100 SIMmAs). Quantitative analysis provided lung volume, emphysema volume, emphysema index, mean lung density, and 4 emphysema volume classes. Simulated low-dose results were compared with original acquisition. RESULTS: Emphysema index showed no clinical relevant variation down to 30 SIMmAs. The large emphysema volume class was significantly different below 50 SIMmAs. The intermediate and small classes showed an overproportional variation below 50 SIMmAs. CONCLUSIONS: Dose reduction down to 30 SIMmAs is possible for clinical routine. Settings below 50 SIMmAs significantly alter the in-detailed 3-dimensional emphysema quantification.

Adult↗
PubMed2006

Volume definition in radiotherapy planning for lung cancer: how the radiologist can help.

Effective treatment for carcinoma of the lung remains one of the biggest challenges in oncology. Radical radiotherapy may be a curative option for patients who are unsuitable for radical surgery either because of disease stage or because of co-morbidity. Long-term disease control with radical radiotherapy is disappointing with only about 6% of patients treated being alive at 5 years. Technological advances involved in the planning and delivery of radiotherapy may improve this. The advent of conformal radiotherapy, utilizing computed tomography and three-dimensional planning systems, allows much more accurate shaping of the radiation fields. This greater accuracy of target volume definition facilitates a reduction in the radiation dose to normal tissues, allowing for dose escalation to the tumour. Delineation of the target volume can be problematic. Conventional CT has limitations in term of distinguishing between benign and malignant tissues, e.g. the size criteria for involved lymph nodes. The oncologist uses a combination of radiological and clinical information when defining the target volume but their radiological interpretation of imaging is inferior to that of a radiologist. The Royal College of Radiologists (RCR) issued guidance in 2004 on the optimal imaging strategies for common cancers. These guidelines address issues regarding the localisation and staging of cancers and treatment planning, and also reporting and training. They recommend the development of closer links between radiologists and oncologists to optimise the interpretation of imaging and target volume definition. This article aims to briefly explain the planning process involved in irradiating lung cancers, highlight problematic areas and suggest ways in which co-operation with radiologists may improve the delivery of radiotherapy and therefore the treatment outcomes for this group of patients.

Humans↗
PubMed2002

Layer-by-layer epitaxy in limited mobility nonequilibrium models of surface growth.

We study, using noise-reduction techniques, layer-by-layer epitaxial growth in limited mobility solid-on-solid nonequilibrium surface growth models, which have been introduced in the context of kinetic surface roughening in ideal molecular beam epitaxy. Multiple hit noise reduction and long surface diffusion length lead to qualitatively similar layer-by-layer epitaxy in (1+1)- and (2+1)-dimensional limited mobility growth simulations. We discuss the dynamic scaling characteristics connecting the transient layer-by-layer growth regime with the asymptotic kinetically rough growth regime.

Journal Article↗
PubMed2003

Two-dimensional diffusion in the presence of topological disorder.

How topological defects affect the dynamics of particles hopping between lattice sites of a distorted, two-dimensional crystal is addressed. Perturbation theory and numerical simulations show that weak, short-ranged topological disorder leads to a finite reduction of the diffusion coefficient. Renormalization group theory and numerical simulations suggest that longer-ranged disorder, such as that from randomly placed dislocations or random disclinations with no net disclinicity, leads to subdiffusion at long times.

Journal Article↗