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PubMed1999

The effect of face inversion on activity in human neural systems for face and object perception.

The differential effect of stimulus inversion on face and object recognition suggests that inverted faces are processed by mechanisms for the perception of other objects rather than by face perception mechanisms. We investigated the face inversion using functional magnetic resonance imaging (fMRI). The principal effect of face inversion on was an increased response in ventral extrastriate regions that respond preferentially to another class of objects (houses). In contrast, house inversion did not produce a similar change in face-selective regions. Moreover, stimulus inversion had equivalent, minimal effects for faces in in face-selective regions and for houses in house-selective regions. The results suggest that the failure of face perception systems with inverted faces leads to the recruitment of processing resources in object perception systems, but this failure is not reflected by altered activity in face perception systems.

Brain↗
PubMed2001

Inverse planning for photon and proton beams.

The concept of inverse planning for intensity-modulated radiation therapy and its application for photon and charged particle beams is presented. Starting from theoretical solutions of the "inverse problem" in radiation therapy, a clinically applied optimization approach is discussed. A central topic is the mathematical formulation of clinical objectives in terms of physical parameters such as dose levels and irradiated volumes. Examples for practical inverse treatment planning and its clinical application for photon beams are provided. Inverse treatment planning of dose delivery techniques with charged particle beams is discussed by extending the conventional planning concept. A new multimodality inverse planning tool is described and applied to an example of comparative planning between photon and proton IMRT.

Mathematics↗
PubMed2003

Normal and inverse primary kinetic deuterium isotope effects for C-H bond reductive elimination and oxidative addition reactions of molybdenocene and tungstenocene complexes: evidence for benzene sigma-complex intermediates.

The overall reductive elimination of RH from the ansa-molybdenocene and -tungstenocene complexes [Me(2)Si(C(5)Me(4))(2)]Mo(Ph)H and [Me(2)Si(C(5)Me(4))(2)]W(R)H (R = Me, Ph) is characterized by an inverse primary kinetic isotope effect (KIE) for the tungsten system but a normal KIE for the molybdenum system. Oxidative addition of PhH to [[Me(2)Si(C(5)Me(4))(2)]M] also differs for the two systems, with the molybdenum system exhibiting a substantial intermolecular KIE, while no effect is observed for the tungsten system. These differences in KIEs indicate a significant difference in the reactivity of the hydrocarbon adducts [Me(2)Si(C(5)Me(4))(2)]M(RH) for the molybdenum and tungsten systems. Specifically, oxidative cleavage of [Me(2)Si(C(5)Me(4))(2)]M(RH) is favored over RH dissociation for the tungsten system, whereas RH dissociation is favored for the molybdenum system. A kinetics analysis of the interconversion of [Me(2)Si(C(5)Me(4))(2)]W(CH(3))D and [Me(2)Si(C(5)Me(4))(2)]W(CH(2)D)H, accompanied by elimination of methane, provides evidence that the reductive coupling step in this system is characterized by a normal KIE. This observation demonstrates that the inverse KIE for overall reductive elimination is a result of an inverse equilibrium isotope effect (EIE) and is not a result of an inverse KIE for a single step. A previous report of an inverse kinetic isotope effect of 0.76 for C-H reductive coupling in the [Tp]Pt(CH(3))H(2) system is shown to be erroneous. Finally, a computational study provides evidence that the reductive coupling of [Me(2)Si(C(5)Me(4))(2)]W(Ph)H proceeds via the initial formation of a benzene sigma-complex, rather than an eta(2)-pi-benzene complex.

Journal Article↗
PubMed2003

Experimental evidence for a temperature dependent transition between normal and inverse equilibrium isotope effects for oxidative addition of H2 to Ir(PMe2Ph)2(CO)Cl.

The equilibrium isotope effect (EIE) for oxidative addition of H(2) and D(2) to Ir(PMe(2)Ph)(2)(CO)Cl has been measured over a large temperature range, thereby demonstrating that the inverse (<1) EIE previously observed at ambient temperature becomes normal (>1) at high temperature (>90 degrees C). The temperature dependence of the EIE for oxidative addition of H(2) and D(2) to Ir(PH(3))(2)(CO)Cl has been calculated using the geometry and vibrational frequencies obtained from DFT (B3LYP) calculations on Ir(PH(3))(2)(CO)ClH(2) and Ir(PH(3))(2)(CO)ClD(2), and is in accord with the experimentally observed transition from an inverse to normal EIE for oxidative addition of H(2) and D(2) to Ir(PMe(2)Ph)(2)(CO)Cl: the EIE is calculated to be inverse between 0 and 510 K, reach a maximum value of 1.15 at 867 K and then slowly decrease to unity as the temperature approaches infinity. This deviation from simple van't Hoff behavior, and the occurrence of a maximum in the EIE, is the result of the entropy term being temperature dependent. At low temperature, the enthalpy term dominates and the EIE is inverse, whereas at high temperatures the entropy term dominates and the EIE is normal. The observation of both normal and inverse EIEs for the same system indicate that inferences pertaining to the magnitude of an isotope effect at a single temperature may require more detailed consideration than previously realized.

Journal Article↗
PubMed2004

Novel 5-HT7 receptor inverse agonists. Synthesis and molecular modeling of arylpiperazine- and 1,2,3,4-tetrahydroisoquinoline-based arylsulfonamides.

A series of arylpiperazine- and 1,2,3,4-tetrahydroisoquinoline-based arylsulfonamides was synthesized and evaluated for their interactions with the constitutively active 5-HT7 receptor. Effects on basal adenylate cyclase activity were measured using HEK-293 cells expressing the rat 5-HT7. All ligands produced a decrease of adenylate cyclase activity, indicative of their inverse agonism. Additionally, computational studies with a set of 22 inverse agonists, including these novel inverse agonists and inverse agonists known from literature, resulted in a pharmacophore model and a CoMFA model (R2 = 0.97, SE = 0.18). Docking of inverse agonists at the binding site of a model of the helical parts of the 5-HT7 receptor, based on the alpha carbon template for 7-TM GPCRs, revealed interesting molecular interactions and a possible explanation for observed structure-activity relationships.

Adenylyl Cyclase Inhibitors↗
PubMed2005

Inverse sodium hydride: density functional theory study of the large nonlinear optical properties.

"Inverse sodium hydride" (AdzH(+)Na-) is an alkalide compound synthesized in recent experiments containing the unusual charge distribution H+ and Na- (inverse charge state). The new class of compounds interests scientists to investigate their especial structures and properties. In this paper, the structures of three alkalides compounds, (Me)3NH(+)Na-, AdzH(+)Na-, and AdzLi(+)Na-, have been obtained in theory. Especially, the structure of AdzLi(+)Na- is still researched by experimental scientists. We investigated the NLO properties of the alkalides complexes for the first time and found that inverse sodium hydride AdzH(+)Na- has a considerably large NLO response beta0 = 5.7675 x 10(4) au by density functional theory (DFT). To understand the essential features of the large NLO properties, four related systems have been also calculated. Their first hyperpolarizabilities are beta0 = 7.357 x 10(3) au for (Me)3NH(+)Na-, beta0 = 3.9 au for (Me)3NH+, beta0 = 1.10 x 10(2) au for (Me)3NH(+)Cl-, and beta0 = 6.20681 x 10(5) au for AdzLi(+)Na-, respectively. By comparing, we found that, first, the Na- anion plays a crucial role in the considerably large first hyperpolarizability of inverse sodium hydride and, second, the first hyperpolarizability of inverse sodium hydride increases with the charge value of the sodium anion. The above results are useful for designing potential NLO materials.

Journal Article↗
PubMed1996

Moment analysis of stereoselective enterohepatic circulation and unidirectional chiral inversion of ketoprofen enantiomers in rat.

The stereoselective enterohepatic circulation (EHC) and the synchronous chiral inversion of ketoprofen enantiomer in rat were evaluated by moment analysis based on the recirculatory concept. (R)-(-)- and (S)-(+)-ketoprofen were independently administered into rats, and the plasma and bile concentrations of both enantiomers were determined by a column-switching HPLC. (S)-Ketoprofen was generated by the chiral inversion from (R)-ketoprofen, whereas (R)-ketoprofen was not generated from (S)-ketoprofen. Within 30 min after intravenous administrations, the plasma time courses of R- and S-enantiomers were almost the same between rats with laparotomy and those with bile-duct cannula. After 30 min, the plasma concentrations in rats with laparotomy were significantly higher than those in rats with bile-duct cannula. The Laplace-transformed equations for stereoselective EHC and the synchronous chiral inversion were derived by means of the transfer function method on the basis of the recirculatory theory. The global moments (AUC and MRT) which were derived directly from the transformed equations were related to the local moments for the single EHC. The recirculation ratios of (R)- and (S)-ketoprofen for the single EHC were estimated to be 15.4% and 63.6%, respectively. The absorption ratios of (R)- and (S)-ketoprofen for the absorption process from the gastrointestinal tract into the systemic circulation were 87.0% and 83.8%, respectively. The biliary excretion rations of (R)- and (S)-ketoprofen for the disposition process through the systemic circulation into the bile were 17.7% and 75.8%, respectively. The chiral inversion ratio from (R)-ketoprofen into (S)-ketoprofen was 59.5%. The complicated disposition of ketoprofen, i.e., the simultaneous EHC and chiral inversion, was able to be analyzed by a moment method in a simple way.

Animals↗
PubMed1996

Inversion and processing of component and spatial-relational information in faces.

This study compared effects of inversion on perceptual processing of faces with distorted components (eyes and mouths) and faces distorted by altering spatial relations between components. In a rating task, participants inversion reduced the rated grotesqueness of spatially distorted faces but not that of faces with altered components. In a comparison task, pairs of faces were shown side by side; participants judged whether they were identical or different. Inversion greatly reduced the rate at which participants responded within 3 s to pairs that differed spatially, but not pairs that differed componentially. Also, latencies for detecting spatial differences were lengthened by inversion more than latencies for detecting componential differences. Results support the hypothesis that inversion impairs encoding of spatial-relational information more than, or instead of, componential information, depending on the task.

Adult↗
PubMed1995

Physiological effects of inverse agonists in transgenic mice with myocardial overexpression of the beta 2-adrenoceptor.

G-protein-coupled receptors are thought to have an inactive conformation (R), requiring an agonist-induced conformational change for receptor/G-protein coupling. But new evidence suggests a two-state model in which receptors are in equilibrium between the inactive conformation (R), and a spontaneously active conformation (R*) that can couple to G protein in the absence of ligand (Fig. 1). Classic agonists have a high affinity for R* and increase the concentration of R*, whereas inverse agonists have a high affinity for R and decrease the concentration of R*. Neutral competitive antagonists have equal affinity for R and R* and do not displace the equilibrium, but can competitively antagonize the effects both of agonists and of inverse agonists. The lack of suitable in vivo model systems has restricted the evidence for the existence of inverse agonists to computer simulations and in vitro systems. We have used a transgenic mouse model in which there is such marked myocardial overexpression of beta 2-adrenoceptors that a significant population of spontaneously activated receptor (R*) is present, inducing a maximal response without agonist. We show that the beta 2-adrenoceptor ligand ICI-118,551 functions as an inverse agonist, providing evidence supporting the existence of inverse agonists and validating the two-state model of G-protein-coupled receptor activation.

Adrenergic beta-Agonists↗
PubMed2005

Molecular basis of inverse agonism in a G protein-coupled receptor.

G protein-coupled receptors (GPCRs) recognize a wide variety of extracellular ligands to control diverse physiological processes. Compounds that bind to such receptors can either stimulate, fully or partially (full or partial agonists), or reduce (inverse agonists) the receptors' basal activity and receptor-mediated signaling. Various studies have shown that the activation of receptors through binding of agonists proceeds by conformational changes as the receptor switches from a resting to an active state leading to G protein signaling. Yet the molecular basis for differences between agonists and inverse agonists is unclear. These different classes of compounds are assumed to switch the receptors' conformation in distinct ways. It is not known, however, whether such switching occurs along a linear 'on-off' scale or whether agonists and inverse agonists induce different switch mechanisms. Using a fluorescence-based approach to study the alpha2A-adrenergic receptor (alpha(2A)AR), we show that inverse agonists are differentiated from agonists in that they trigger a very distinct mode of a receptor's switch. This switch couples inverse agonist binding to the suppression of activity in the receptor.

Adrenergic alpha-2 Receptor Agonists↗
PubMed2000

Inverse agonism and neutral antagonism at a constitutively active alpha-1a adrenoceptor.

We have studied the antagonist action of prazosin and KMD-3213 in a constitutively active mutant of the human alpha-1a adrenoceptor in which Ala(271) was substituted to Thr and was expressed in CHO cells. Inverse agonism was characterized by up-regulation of receptor density, a decrease in basal GTPgammaS binding, and a reduction in basal inositol-1,4,5-trisphosphate (IP(3)) level. According to the above criteria, prazosin acted as an inverse agonist, whilst KMD-3213 behaved as a neutral antagonist. Compared with the wild-type receptor, mutant receptor exhibited single affinity sites for [(3)H]-prazosin, [(3)H]-KMD and the non-radioactive ligands tested, and displayed significantly higher affinities for several agonists but not for the two antagonists. Administration of KMD-3213 to prazosin-treated CHO cells expressing the mutant receptor reversed the inverse agonism of prazosin resulting in rapid increases in cellular IP(3), in intracellular [Ca(2+)] and in the rate of extracellular acidification. These results indicated that a neutral antagonist can reverse the action of an inverse agonist at the receptor site. The distinct properties of inverse agonist and neutral antagonist in affecting receptor function may be important for the clinical use of such antagonists.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed2001

Pressure-controlled inverse ratio ventilation after cardiac surgery.

BACKGROUND AND OBJECTIVE: Pressure-controlled inverse ratio ventilation was compared with controlled mechanical ventilation in patients after cardiac surgery. METHODS: Ten patients were ventilated after sternal closure using a Siemens Servo 900C ventilator to a target end-tidal PCO2 of 4.0 kPa. They were randomized to receive controlled mechanical ventilation or pressure-controlled inverse ratio ventilation. CO2-based data were recorded on a laptop personal computer, which together with arterial PCO2 permitted measurement of the respiratory dead space. Once measurements were complete the ventilator was switched to the other mode and new measurements taken. RESULTS: PaCO2 and VCO2 were virtually the same in both modes. Peak airway pressure (17.2 +/- 2.7 vs. 20.8 +/- 2.5 cmH2O, P < 0.01) and minute ventilation (4.9 +/- 1.1 vs. 5.3 +/- 1.1 cmH2O, P < 0.01) were less during pressure-controlled inverse ratio ventilation. Physiological dead space fraction (0.39 +/- 0.06 vs. 0.51 +/- 0.05, P < 0.001), airway dead space (56 +/- 15 vs. 81 +/- 15 mL, P < 0.001) and alveolar dead space fraction (0.25 +/- 0.07 vs. 0.31 +/- 0.09, P < 0.01) were all less during pressure-controlled inverse ratio ventilation. There were no differences in heart rate or mean arterial pressure. CONCLUSIONS: The prolonged inspiratory period and pressure-controlled flow pattern of pressure-controlled inverse ratio ventilation reduce the alveolar and airway dead spaces, and give lower peak airway pressures, compared with conventional ventilation, in cardiac surgical patients.

Adult↗
PubMed1996

Vertical inversion of the visual field and REM sleep mentation.

The effects of the vertical inversion of the visual field on REM sleep mental activity were examined to explore the potential involvement of this activity in information processing. In a first experiment, four male subjects slept in the laboratory for two sessions of 6 consecutive nights: 2 adaptation nights, 2 nights of polysomnography and 2 nights of dream collection. During the days preceding Nights 3, 4, 5, 6 of each session, the subjects wore glasses which, during the second session, completely inverted (rotation of 180 degrees) their visual field. In a second experiment with four other male subjects, the order of conditions was reversed and the experimental condition (visual inversion) was introduced twice. The data of the two experiments were combined. Overall, following visual inversion, there were significant increases in the proportion of dreams containing motor and visual difficulties (P < 0.005), misfortunes (P < 0.05) and dreamer confusion (P < 0.05) and a decrease in dreamer participation (P < 0.05). Only 4 of the 8 subjects experienced incorporations of the inverted visual field into their dreams and they tended to perform better on two of three tests of adaptation to the visual inversion. The observed changes in dreams are consistent with the notion of continuity between waking and dreaming since they appear to reflect the waking preoccupation and psychological state associated with visual inversion.

Adolescent↗
PubMed1992

Changes in cardiovascular function during inversion.

Although inversion therapy is used increasingly as a therapy for musculoskeletal back disorders, its effects on cardiovascular function have not been systematically determined. Heart rate, blood pressure and echocardiographic measurements were performed in 20 normal male volunteers before, during and after bent-knee inversion. Compared to control measurements in the supine position, inversion significantly increased heart rate, systolic and diastolic blood pressure, rate-pressure product, systemic vascular resistance and left ventricular (LV) wall stress. Inversion also resulted in a significant decrease in LV diastolic volume, cardiac output and ejection fraction. Thus inversion produces an increase in LV afterload and myocardial oxygen demand concomitantly with a decrease in LV preload and global systolic function, and may be contraindicated in patients with cardiovascular disease.

Adult↗
PubMed2004

Anomalous splittings of torsional sublevels induced by the aldehyde inversion motion in the S1 state of acetaldehyde.

The G6 group-theoretical high-barrier formalism developed previously for internally rotating and inverting CH3NHD is used to interpret the abnormal torsional splittings in the S1 state of acetaldehyde for levels 14(0-)15(0), 14(0-)15(1), and 14(0-)15(2), where 14(0-) denotes the upper inversion tunneling component of the aldehyde hydrogen and 15 denotes the methyl torsional vibration. This formalism, derived using an extended permutation-inversion group G6m, treats simultaneously methyl torsional tunneling, aldehyde-hydrogen inversion tunneling and overall rotation. Fits to the rotational states of the four pairs of inversion-torsion vibrational levels (14(0+)15(0A,E), 14(0-)15(0A,E)), (14(0+)15(1A,E), 14(0-)15(1A,E)), (14(0+)15(2A,E), 14(0-)15(2A,E)), and (14(0+)15(3A,E), 14(0-)15(3A,E)) are performed, giving root-mean-square deviations of 0.003, 0.004, 0.004, and 0.004 cm(-1), respectively, which are nearly equal to the experimental uncertainty of 0.003 cm(-1). For torsional levels lying near the top of the torsional barrier, this theoretical model, after including higher-order terms, provides satisfactory fits to the experimental data. The partially anomalous K-doublet structure of the S1 state, which deviates from that in a simple torsion-rotation molecule, is fitted using this formalism and is shown to arise from coupling of torsion and rotation motion with the aldehyde-hydrogen inversion.

Journal Article↗
PubMed2000

Coronary arterial size late after the atrial inversion procedure for transposition of the great arteries: implications for the arterial switch operation.

BACKGROUND: Coronary flow reserve in the hypertrophied ventricle is reduced. One contributing factor may be the size of the proximal coronary arteries. In patients who undergo atrial inversion procedures for transposition of the great arteries, the left coronary artery supplies the pulmonary ventricle and may be smaller than the right coronary artery. We hypothesized that the dimensions of the coronary arteries may correlate with symptomatic status after atrial inversion and may be an important factor when these patients are considered for the arterial switch operation. METHODS: The proximal left and right coronary arteries were measured in 9 patients with transposition and failure of the systemic right ventricle after atrial inversion, 10 asymptomatic patients after atrial inversion, and 10 patients with normal hearts. The diameters of the coronary arteries were indexed to body surface area and compared. RESULTS: The absolute and indexed diameters of the right coronary artery were greater in symptomatic patients than in asymptomatic patients (indexed: 3.1 +/- 0.6 vs 2.4 +/- 0.4 mm/m(2), P <.001) or control patients (2.0 +/- 0.3, P <.001), and the absolute diameter of the left coronary artery was smaller (2.9 +/- 0. 7 vs 3.6 +/- 0.5 mm, P =.003 [asymptomatic], 3.6 +/- 0.5 mm, P =.01 [control]). In symptomatic patients, the absolute and indexed diameters of the left coronary artery were smaller than those of the right (indexed: 2.1 +/- 0.6 vs 3.1 +/- 0.6 mm/m(2), P <.001). By contrast, there was no difference in asymptomatic patients (2.2 +/- 0.5 vs 2.4 +/- 0.4 mm/m(2), P =.44), and the left coronary artery was larger in normal control patients (2.2 +/- 0.4 vs 2.0 +/- 0.3 mm/m(2), P <.001). CONCLUSIONS: Differences in the sizes of the proximal coronary arteries may be related to symptomatic status in patients with transposition of the great arteries who have undergone an atrial inversion procedure, as well as to the efficacy of ventricular retraining. When pulmonary artery banding and subsequent arterial switch are considered for patients with a Mustard or Senning procedure and a failing systemic right ventricle, the size of the proximal coronary arteries may be an important factor and should be evaluated with preoperative imaging studies.

Adult↗
PubMed1996

Identification and functional separation of retinoic acid receptor neutral antagonists and inverse agonists.

Inverse agonists are ligands that are capable of repressing basal receptor activity in the absence of an agonist. We have designed a series of C-1-substituted acetylenic retinoids that exhibit potent antagonism of retinoic acid receptor (RAR)-mediated transactivation. Comparison of these related retinoid antagonists for their ability to repress basal RAR transcriptional activity demonstrates that the identity of the C-1 substituent differentiates these ligands into two groups: RAR inverse agonists and neutral antagonists. We show that treatment of cultured human keratinocytes with a RAR inverse agonist, but not a RAR neutral antagonist, leads to the repression of the serum-induced differentiation marker MRP-8. While RAR-selective agonists also repress expression of MRP-8, cotreatment with a RAR inverse agonist and a RAR agonist results in a mutual repression of their individual inhibitory activities, indicating the distinct modes of action of these two disparate retinoids in modulating MRP-8 expression. Our data indicate that RARs, like beta2-adrenoreceptors, are sensitive to inverse agonists and that this new class of retinoids will provide insight into the molecular mechanisms of RAR function in skin and other responsive tissues.

Antigens, Differentiation↗
PubMed2001

Identification of determinants of inverse agonism in a constitutively active parathyroid hormone/parathyroid hormone-related peptide receptor by photoaffinity cross-linking and mutational analysis.

We have investigated receptor structural components responsible for ligand-dependent inverse agonism in a constitutively active mutant of the human parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) receptor type 1 (hP1R). This mutant receptor, hP1R-H223R (hP1R(CAM-HR)), was originally identified in Jansen's chondrodysplasia and is altered in transmembrane domain (TM) 2. We utilized the PTHrP analog, [Bpa(2),Ile(5),Trp(23),Tyr(36)]PTHrP-(1-36)-amide (Bpa(2)-PTHrP-(1-36)), which has valine 2 replaced by p-benzoyl-l-phenylalanine (Bpa); this substitution renders the peptide a photoreactive inverse agonist at hP1R(CAM-HR). This analog cross-linked to hP1R(CAM-HR) at two contiguous receptor regions as follows: the principal cross-link site (site A) was between receptor residues Pro(415)-Met(441), spanning the TM6/extracellular loop three boundary; the second cross-link site (site B) was within the TM4/TM5 region. Within the site A interval, substitution of Met(425) to Leu converted Bpa(2)-PTHrP-(1-36) from an inverse agonist to a weak partial agonist; this conversion was accompanied by a relative shift of cross-linking from site A to site B. The functional effect of the M425L mutation was specific for Bpa(2)-containing analogs, as inverse agonism of Bpa(2)-PTH-(1-34) was similarly eliminated, whereas inverse agonism of [Leu(11),d-Trp(12)]PTHrP-(5-36) was not affected. Overall, our data indicate that interactions between residue 2 of the ligand and the extracellular end of TM6 of the hP1R play an important role in modulating the conversion between active and inactive receptor states.

Animals↗