Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Inversion”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,351 records · Page 75Linked to original sources
PubMed1988

Puerperal inversion of the uterus.

Puerperal inversion of the uterus is a complication of the third stage of labor. The two main reasons are excessive cord traction and Crede fundal pressure. Its frequency in Israel is unknown. A case of acute, complete inversion of the uterus is presented, treated promptly by immediate reposition and manual separation of the placenta. The various modes of treatment are discussed. Puerperal inversion is a rare and dangerous complication. Prompt diagnosis and the proper choice of treatment will decrease the morbidity and mortality associated with this complication.

Adult↗
PubMed1989

Antagonism of ethanol-reinforced behavior by the benzodiazepine inverse agonists Ro15-4513 and FG 7142: relation to sucrose reinforcement.

The partial inverse benzodiazepine agonist Ro15-4513 has been shown to antagonize many of ethanol's actions, including the reduction of behavior reinforced with ethanol presentation. The studies reported here compared the effects of the Ro compound on sucrose reinforcement alone and concurrently available with ethanol reinforcement. Also, a second inverse agonist, FG 7142, was tested. The result indicated that ethanol reinforcement was more sensitive to the inverse agonists compared to sucrose reinforcement. This was seen as a graded effect upon ethanol responding at doses which failed to have any effect upon sucrose-reinforced behavior. The Ro compound was approximately three times more potent than the FG compound in suppressing ethanol-reinforced responding. Possible explanations for the greater sensitivity of ethanol reinforcement compared to sucrose reinforcement was discussed in terms of ethanol's potential actions at the benzodiazepine-GABA receptor complex.

Animals↗
PubMed1991

Inverse agonist properties of the THBC discriminative stimulus: asymmetrical generalization with FG 7142.

Male rats were trained to discriminate the stimulus properties of the beta-carbolines 1,2,3,4-tetrahydro-beta-carboline (THBC) (15.0 mg/kg) or FG 7142 (5.0 mg/kg) from vehicle in a two-lever, food-motivated operant task. Consistent with the serotonergic properties of THBC, administration of the 5HT1B agonists TFMPP and mCPP to THBC-trained rats resulted in THBC-appropriate responding. Norharmane, a beta-carboline metabolite of THBC, also mimicked the THBC discriminative stimulus. In contrast, the benzodiazepine receptor partial inverse agonist FG 7142, the anxiogenic/convulsant pentylenetetrazole (PTZ), two physiological stressors and the alpha 2 adrenergic antagonists yohimbine and idazoxan failed to produce THBC-appropriate responding. In the FG 7142-trained rats, THBC and norharmane dose-dependently mimicked the FG 7142 discriminative stimulus. This generalization was not based upon the serotonergic properties of THBC and norharmane since administration of the serotonin agonist mCPP to FG 7142-trained rats failed to produce FG 7142-appropriate responding. The ability of THBC to substitute for the FG 7142 discriminative stimulus was antagonized by the benzodiazepine receptor mixed agonist/antagonist CGS 9896 and the benzodiazepine receptor antagonist RO 15-1788, indicating that THBC produces an inverse agonist stimulus in FG 7142-trained rats. These results suggest that THBC produces a discriminative stimulus which consists of both serotonergic and inverse agonist components.

Animals↗
PubMed1991

Reduced binocular depth inversion as an indicator of cannabis-induced censorship impairment.

Measurements of binocular depth inversion using a stereoscopic slide projection with polarized light were performed in healthy volunteers before and after cannabis intake. Since binocular depth inversion represents an illusion occurring in the perception of semantically meaningful objects projected in a 3-D inverted fashion, the hypothesis can be tested that cannabis-induced "psychedelic states" represent a condition in which the human CNS is unable to correct implausible perceptual hypotheses. The data demonstrate a strong cannabis-induced impairment of binocular depth inversion.

Adult↗
PubMed1991

Inverse agonist properties of the FG 7142 discriminative stimulus.

A two-lever, food-motivated discrimination was established between the benzodiazepine receptor partial inverse agonist FG 7142 (5.0 mg/kg) and its vehicle. The FG 7142 discriminative stimulus was pharmacologically characterized by testing trained rats with a variety of benzodiazepine receptor ligands. Administration of the inverse agonist DMCM (0.15-0.30 mg/kg) dose-dependently mimicked the FG 7142 stimulus. In contrast, the benzodiazepine receptor agonist chlordiazepoxide, partial agonist ZK 91 296, mixed agonist/antagonist CGS 9896 and antagonist RO 15-1788 blocked the FG 7142 cue. These results indicate that the FG 7142 discriminative stimulus is based on its inverse agonist activity. The generalization of FG 7142 to the anxiogenic/convulsant compound pentylenetetrazole (PTZ), but not to the anorectic agent norfenfluramine, indicates that the anxiogenic properties of FG 7142, rather than its anorectic actions, may underlie the FG 7142 discriminative stimulus.

Animals↗
PubMed1993

Quantitative photoplethysmography: Lambert-Beer law or inverse function incorporating light scatter.

Finger blood volume is commonly determined from measurement of infra-red (IR) light transmittance using the Lambert-Beer law of light absorption derived for use in non-scattering media, even when such transmission involves light scatter around the phalangeal bone. Simultaneous IR transmittance and finger volume were measured over the full dynamic range of vascular volumes in seven subjects and outcomes compared with data fitted according to the Lambert-Beer exponential function and an inverse function derived for light attenuation by scattering materials. Curves were fitted by the least-squares method and goodness of fit was compared using standard errors of estimate (SEE). The inverse function gave a better data fit in six of the subjects: mean SEE 1.9 (SD 0.7, range 0.7-2.8) and 4.6 (2.2, 2.0-8.0) respectively (p < 0.02, paired t-test). Thus, when relating IR transmittance to blood volume, as occurs in the finger during measurements of arterial compliance, an inverse function derived from a model of light attenuation by scattering media gives more accurate results than the traditional exponential fit.

Blood Volume↗
PubMed1993

Transverse dipoles added to DNA chains by drug binding can induce inversion of the long-range chirality of DNA condensates.

The addition of poly(ethylene glycol) (PEG) to a DNA solution induces phase separation of droplets of condensed DNA. These droplets possess liquid crystalline properties and their ordering is cholesteric. It was recently proved that daunomycin, by binding to DNA chains, inverts the long-range chirality of their tertiary packing into aggregates. The present paper suggests one possible mechanism by which this inversion can take place. Daunomycin bears a cationic group in its sugar residue. Its intercalation adds a helicoidal distribution of transverse dipoles to DNA chains. By this mechanism, in favourable cases, ionic or strongly polar groups in drugs which bind DNA can induce handedness inversion of the cholesteric ordering of its condensates. This inversion mechanism was tested experimentally using several, charged and uncharged, homologues of daunomycin. All those bearing the cationic ammonium group inverted the long-range chirality of the PEG-induced DNA mesomorphic state. The effects of the uncharged desamino homologues could not be evaluated because of their lower solubility and binding affinity for DNA.

DNA↗
PubMed1986

Who cares what care?: an inverse interest law?

The paper attempts to systematise some of the ideas on medical dominance as the inverse interest law, which is broadly seen as the more commonplace the problem and the more people affected, the less will be the medical interest. The law or rather laws are exemplified by reference to the symptom iceberg, health education and welfare, hospital expenditure, priority groups and community care and class, locality and ethnicity. The inverse interest laws, which ensure the operation of the inverse care law, are seen as products of medicine definition and practice in relation to their containing society.

Community Health Services↗
PubMed1990

Behavioral neurobiology of inverse agonist FG 7142 induced anxiety syndrome in rats.

1. Neurobehavioral survey of inverse agonist FG 7142 was performed employing a novel anxiety paradigm namely FR-2 Two-Way crossover in a shuttle box. 2. FG syndrome was found to be similar to learned helplessness following shock treatment. Significant increase in mean latency to escape was observed from 0 to 25th trial. Effect of FG 7142 on the behavioral and neurological profile did not deviate significantly from controls. However, a general increase in arousal, darting and sideway movement (weaving) of the head were noted. 3. Drugs with specificity at benzodiazepine (BDZ) receptor site were employed as pretreatments in order to study their influence on FG 7142 induced anxiety syndrome. Diazepam and ZK 91296, significantly blocked the inverse agonist response. Head weaving as well as darting movements were completely abolished although rats demonstrated arousal and vigilance. 4. A dose dependent inhibition of FG response was observed with RO 15-1788, a specific BDZ receptor blocker. ZK 93423 at low doses (1 mg/kg) failed to reverse the escape deficit induced by FG. Higher doses of ZK 93423 could not be tested as significant sedation and ataxia were noted. 5. It is suggested that a careful combination of a BDZ agonist and inverse agonist may be beneficial in the treatment of generalised anxiety disorders.

Animals↗
PubMed1990

The verification of an inverse problem in radiation therapy.

The inverse problem in radiation therapy presents a solution for a fluence distribution based on the specification of a region of dose in a patient. We show results for one such solution based on the inversion of an integral over a function of the fluence profile of a rotating beam. We use Monte Carlo methods and numerical integrations to evaluate dose distributions obtained with the inverse method and show the limitations of this theoretical approach. Our results show that dose to a single circular region at an arbitrary position in a 2-dimensional volume can be calculated. Uniform dose to arbitrarily shaped regions cannot be calculated with this formalism, although practical solutions can still be obtained.

Humans↗
PubMed1986

Beta-carbolines characterized as benzodiazepine receptor agonists and inverse agonists produce bi-directional changes in palatable food consumption.

Drugs which bind to specific benzodiazepine recognition sites fall into three categories: agonists, antagonists, and inverse agonists. A set of biochemical parameters is available which distinguishes between the three. In addition, actions of the drugs result in physiological and behavioural effects which are distinguishable. beta-Carboline derivatives provide a group of compounds which show high affinity for the benzodiazepine sites, and which contains examples belonging to each of the three categories. Evidence is reviewed which shows that beta-carboline benzodiazepine receptor agonists (ZK 93423, ZK 91296) produce increases in the consumption of a palatable diet by non-deprived rats, that beta-carboline inverse agonists (FG 7142, DMCM) produce an anorectic effect, and that the beta-carboline ZK 93426 acts as a benzodiazepine receptor antagonist. The results support the proposal of bi-directional control of feeding responses through the action of drugs at a common benzodiazepine receptor. Furthermore, benzodiazepine receptor inverse agonists provide a novel class of anorectic agents. Evidence is also reviewed which is suggestive of the modulation of food-related reward by drug actions at benzodiazepine receptors.

Animals↗
PubMed1992

Partial angle inversion recovery (PAIR) MR imaging: spin-echo and snapshot implementation.

The effects of varying the inversion or excitation RF pulse flip angles on image contrast and imaging time have been investigated in IR imaging theoretically, with phantoms and with normal volunteers. Signal intensity in an IR pulse sequence as a function of excitation, inversion and refocusing pulse flip angles was calculated from the solution to the Bloch equations and was utilized to determine the contrast behavior of a lesion/liver model. Theoretical and experimental results were consistent with each other. With the TI chosen to suppress the fat signal, optimization of the excitation pulse flip angle results in an increase in lesion/liver contrast or allows reduction in imaging time which, in turn, can be traded for an increased number of averages. This, in normal volunteers, improved spleen/liver contrast-to-noise ratio (9.0 vs. 5.7, n = 8, p less than 0.01) and suppressed respiratory ghosts by 33% (p less than 0.01). Reducing or increasing the inversion pulse from 180 degrees results in shorter TI needed to null the signal from the tissue of interest. Although this decreases the contrast-to-noise ratio, it can substantially increase the number of sections which can be imaged per given TR in conventional IR imaging or during breathold in the snapshot IR (turboFLASH) technique. Thus, the optimization of RF pulses is useful in obtaining faster IR images, increasing the contrast and/or increasing the number of imaging planes.

Abdomen↗
PubMed1993

A chemical shift selective inversion recovery sequence for fat-suppressed MRI: theory and experimental validation.

Fat-suppression techniques are used extensively in routine proton nuclear magnetic resonance imaging to produce images free from chemical shift artifacts and dynamic range problems. A hybrid fat-suppression sequence is studied which combines the principle of short time inversion recovery with chemical shift selective imaging. The aim of this study is to provide a theoretical understanding of the role of the sequence parameters, as well as to compare this hybrid sequence with its most closely related conventional fat-suppression techniques, namely selective pre-saturation and short time inversion recovery (STIR) imaging. The hybrid technique is shown to be robust in normal use, and more tolerant than the conventional methods to mis-settings of parameters such as inversion time, as well as tip angle and frequency bandwidth of the fat selective pulse.

Abdomen↗
PubMed1995

MRI in neurofibromatosis type I: using fluid-attenuated inversion recovery pulse sequences.

Cranial magnetic resonance imaging results of 14 patients with neurofibromatosis type I were examined with T2-weighted fluid-attenuated inversion recovery pulse sequences, as well as conventional T2-weighted spin-echo sequences. Definition was better in 62 of 79 lesions or groups of lesions on fluid-attenuated inversion recovery images than on T2-weighted spin-echo images. The lesions were demonstrated not only in the brainstem, cerebellum, globus pallidus, and cerebral white matter, but also in the hippocampus, pulvinar thalami, and splenium of the corpus callosum. The latter 3 lesions have not been demonstrated or emphasized in previous studies. It is concluded that fluid-attenuated inversion recovery imaging is more effective in detecting multiple lesions in patients with neurofibromatosis type I than conventional T2-weighted spin-echo imaging.

Adolescent↗
PubMed2006

Enhancement of brain tumors in 0.23-T low-field MRI: comparison of edema attenuated inversion recovery (EDAIR) sequences with T1-weighted sequence.

RATIONALE AND OBJECTIVES: The aim of this study is to explore whether edema attenuated inversion recovery (EDAIR) sequences could be used to improve tumor contrast in contrast-enhanced low-field 0.23-Tesla magnetic resonance imaging (MRI) using 0.1 mmol/kg of gadolinium-based contrast agent. MATERIALS AND METHODS: Ten patients with brain tumors were examined by using the following contrast-enhanced sequences: T1-weighted spin echo, EDAIR with inversion time (TI) of 600 milliseconds, and EDAIR with TI of 800 milliseconds. Images were assessed both quantitatively and qualitatively. RESULTS: Results suggest that tumor contrast enhancement in low-field MRI can be improved without increasing contrast agent dose. EDAIR 600 appears to be optimal in most cases. CONCLUSIONS: This inversion recovery sequence could be applicable as an additional sequence in the imaging of metastases in low-field MRI, as well as imaging of any other enhancing brain tumors or lesions in low-field MRI.

Adolescent↗
PubMed2006

Aortic augmentation index is inversely associated with cardiorespiratory fitness in men without known coronary heart disease.

BACKGROUND: We investigated whether the aortic augmentation index (AIx), a measure of arterial wave reflection and stiffness, is associated with cardiorespiratory fitness in men without known coronary heart disease (CHD). METHODS: Asymptomatic men (n = 201, mean age 51 +/- 9.2 years) referred for a screening exercise electrocardiogram (ECG) underwent applanation tonometry to obtain radial artery pulse waveforms, and an ascending aortic pressure waveform was derived by a transfer function. The AIx is the difference between the first and second systolic peak of the ascending aortic pressure waveform, expressed as a percentage of the pulse pressure. Cardiorespiratory fitness was assessed by maximal oxygen consumption (VO2max mL/min/kg) during a symptom-limited graded exercise test. Multivariable regression analyses were used to identify significant independent determinants of AIx and of VO2 max. RESULTS: Diabetes was present in 2.5% of subjects, 34.8% had history of smoking, and 29% were hypertensive. Mean (+/- SD) AIx was 19.9% +/- 9.0% and mean VO(2 max) was 33.9 +/- 6.4 mL/min/kg. In a multivariable linear regression model, AIx was positively associated with age, hypertension, and history of smoking and inversely with heart rate, height, and body mass index (BMI). The VO2 max was significantly inversely related to AIx after adjustment for age, heart rate, height, and BMI (r = -0.22, P = .002), after further adjustment for CHD risk factors (total cholesterol, HDL-cholesterol, history of smoking, diabetes, hypertension) (P = .006), and after additional adjustment for behavioral factors (physical activity score, alcohol intake, and percent body fat) (P = .022). CONCLUSIONS: These findings indicate that AIx, a measure of arterial wave reflection and stiffness, is inversely associated with cardiorespiratory fitness in men without CHD.

Adult↗
PubMed2005

Sex hormone-binding globulin and serum testosterone are inversely associated with C-reactive protein levels in postmenopausal women at high risk for cardiovascular disease.

PURPOSE: C-reactive protein (CRP), androgens, and menopausal loss of endogenous estrogens are associated with cardiovascular disease (CVD). We hypothesized that high androgens, low estradiol, and low sex hormone-binding globulin (SHBG) would be associated with high CRP in postmenopausal women. METHODS: CRP, SHBG, estradiol, and total testosterone were measured using baseline bloods of 221 hormone therapy (HT)-nonusers and 162 HT-users from a cross-sectional analysis in a nested case-control sample of the Women's Health Study. Hormones and CRP were ln-transformed and relationships were assessed with Spearman correlations and linear regression. RESULTS: ln-SHBG (beta=-0.40; p<0.01) and ln-testosterone (beta=-0.24; p=0.04) were the only independent hormonal predictors of ln-CRP among HT-nonusers after adjusting for age, hypertension, smoking, body mass index, diabetes, exercise, HDL cholesterol, alcohol intake, and CVD occurrence during follow-up. Upon stratification, the association between ln-SHBG and ln-CRP persisted among HT nonusers who subsequently developed CVD (beta=-0.55; p=0.01), but not among women who remained CVD-free (p=0.28). The inverse relationship between ln-SHBG and ln-CRP was strongest among the leanest women. None of the sex-hormones predicted ln-CRP among HT-users. CONCLUSIONS: SHBG and total testosterone were inversely associated with CRP among HT nonusers in this study. The relationship between SHBG and CRP was more strongly inverse among leaner women.

Aged↗
PubMed2006

Interaction of valerian extracts of different polarity with adenosine receptors: identification of isovaltrate as an inverse agonist at A1 receptors.

A series of extracts of valerian roots (Valeriana officinalis L.) was prepared with solvents of different polarity. Polar as well as nonpolar extracts were found to interact with adenosine A(1) receptors. While polar extracts activated A(1) receptors (partial agonistic activity), nonpolar extracts showed antagonistic or inverse agonistic activity at A(1) receptors, as demonstrated by GTPgammaS binding assays at human recombinant A(1) receptors stably expressed in Chinese hamster ovary (CHO) cells. Guided by radioligand binding assays, fractionation of a lipophilic petroleum ether:diethyl ether (1:1) extract led to the isolation of isovaltrate, which was characterized as a potent, highly efficacious inverse agonist at adenosine A(1) receptors (K(i) rat A(1): 2.05 microM). In experiments at rat brain slices measuring post-synaptic potentials (PSPs) in cortical neurons, isovaltrate at least partly reversed the reduction in the PSPs induced by the adenosine A(1) receptor agonist N(6)-cyclopentyladenosine (CPA). Isovaltrate may serve as a new lead structure for the development of inverse agonists at adenosine A(1) receptors. The common use of hydrophilic, but not lipophilic valerian extracts as mild sleep-inducing agents is consistent with the opposite actions of hydrophilic and lipophilic extracts on adenosine receptors.

Animals↗