scholarly journals Robust 3D Bloch-Siegert based B1+ mapping using Multi-Echo General Linear Modelling

2019 ◽  
Author(s):  
Nadège Corbin ◽  
Julio Acosta-Cabronero ◽  
Shaihan J. Malik ◽  
Martina F. Callaghan
Keyword(s):  
Pulse Sequence ◽  
Quantitative Mri ◽  
General Linear ◽  
Rf Pulses ◽  
Tissue Properties ◽  
In Vivo Experiments ◽  
B1 Mapping ◽  
The Difference ◽  
Sequence Parameters

AbstractPurposeQuantitative MRI applications, such as mapping the T1 time of tissue, puts high demands on the accuracy and precision of transmit field (B1+) estimation. A candidate approach to satisfy these requirements exploits the difference in phase induced by the Bloch-Siegert Shift (BSS) of two acquisitions with opposite off-resonance frequency RF pulses. Interleaving these RF pulses ensures robustness to motion and scanner drifts, however, here we demonstrate that doing so also introduces a bias in the B1+ estimates.MethodsWe show via simulation and experiments that the amplitude of the error depends on MR pulse sequence parameters, such as TR and RF spoiling increment, but more problematically, on the intrinsic properties, T1 and T2, of the investigated tissue. To solve these problems, we present a new approach to BSS-based B1+ estimation that uses a multi-echo acquisition and a general linear model (GLM) to estimate the correct BSS-induced phase.ResultsIn line with simulations, phantom and in-vivo experiments confirmed that the GLM-based method removed the dependency on tissue properties and pulse sequence settings. It also showed greater robustness to hardware imperfections.ConclusionThe GLM-based method is recommended as a more accurate approach to BSS-based B1+ mapping.

scholarly journals In vivo and in vitro toxicity evaluation of liposome-encapsulated sirolimus

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Murilo Batista Abud ◽  
Ricardo Noguera Louzada ◽  
David Leonardo Cruvinel Isaac ◽  
Leonardo Gomes Souza ◽  
Ricardo Gomes dos Reis ◽  
...  
Keyword(s):  
Cell Viability ◽  
Mtt Assay ◽  
Tunel Assay ◽  
In Vitro Toxicity ◽  
In Vivo Experiments ◽  
Significant Difference ◽  
The Difference ◽  
New Formulation

Abstract Background To evaluate the in vivo and in vitro toxicity of a new formulation of liposome-encapsulated sirolimus (LES). Methods In vitro experiments were done using ARPE-19 and HRP cells. An MTT assay was used to determine cell metabolic activity and a TUNEL assay for detecting DNA fragmentation. In vivo experiments were conducted on New Zealand albino rabbits that received intravitreal injections of empty liposomes (EL) or different concentrations of LES. Histopathological and immunohistochemical analyses were performed on the rabbit’s eyes following injection. Results Eighteen eyes of nine rabbits were used. MTT assay cell viability was 95.04% in group 1 (12.5 µL/mL LES). 92.95% in group 2 (25 µL/mL LES), 91.59% in group 3 (50 µL/mL LES), 98.09% in group 4 (12.5 µL/mL EL), 95.20% on group 5 (50 µL/mL EL), 98.53% in group 6 (50 µL/mL EL), and 2.84% on group 8 (50 µL/mL DMSO). There was no statistically significant difference among groups 1 to 7 in cell viability (p = 1.0), but the comparison of all groups with group 8 was significant (p < 0.0001). The TUNEL assay comparing two groups was not statistically significant from groups 1 to 7 (p = 1.0). The difference between groups 1 to 7 and group 8 (p < 0.0001) was significant. Histopathological changes were not found in any group. No activation of Müller cells was detected. Conclusion A novel formulation of LES delivered intravitreally did not cause in vitro toxicity, as evaluated by MTT and TUNEL assays, nor in vivo toxicity as evaluated by histopathology and immunohistochemistry in rabbit eyes.

STUDYING THE POSSIBILITY OF ADSORPTION OF HEAVY METAL IONS ON NANOPARTICLES

2018 ◽  
pp. 46-49
Author(s):  
А.А. Shumakova
Keyword(s):  
Adsorption Isotherm ◽  
Single Layer ◽  
Research Centre ◽  
Isotherm Equation ◽  
In Vivo Experiments ◽  
Federal Research ◽  
The Difference ◽  
Al2o3 Nps

We found both an increase and a decrease in the toxicity of some contaminants (Pb and Cd) when combined with the NP as a result of in vivo experiments conducted in Federal Research Centre of Nutrition and Biotechnology. One possible explanation for the differences in Pb and Cd accumulation levels when combined with NPs can be the difference in the adsorption capacity of NPs with respect to Pb2+ and Cd2+ ions. To verify this hypothesis, an in vitro experiment was carried out, which characterizes the possibility of adsorption of Pb2+ and Cd2+ ions on the NPs in a model system. We calculated Amax (maximum limiting adsorption corresponding to the saturation of the adsorption layer, μmol/mg), b (binding constant for instability (concentration of 50 % binding), μmol/mg) based on the results obtained during the work and constructed the equations of the adsorption isotherms in double inverse coordinates. As a result of studies, we determined that in the case of Pb2+ adsorption on TiO2 NPs, SiO2 NPs and Al2O3 NPs, the equation of a single-layer equilibrium adsorption isotherm according to Langmuir is performed. The maximum adsorption of Pb2+ on the three types of NPs differs slightly. The Langmuir adsorption isotherm equation is not satisfied in the case of the adsorption of Cd2+ on the three NP types. Therefore, with respect to Cd, the constants b and Amax cannot be correctly defined. The reason for this, apparently, is that the process of binding of Cd2+ ions on the studied types of NPs does not obey the model of single-layer, completely reversible adsorption.

scholarly journals Multi T1-weighted contrast imaging and T1 mapping with Compressed sensing FLAWS at 3T

2021 ◽  
Author(s):  
Jeremy Beaumont ◽  
Jurgen Fripp ◽  
Parnesh Raniga ◽  
Oscar Acosta ◽  
Jean-Christophe Ferre ◽  
...  
Keyword(s):  
Compressed Sensing ◽  
T1 Mapping ◽  
Spin Echo ◽  
Acquisition Time ◽  
Contrast Imaging ◽  
Parallel Acquisition ◽  
In Vivo Experiments ◽  
Sequence Parameters

The Fluid And White matter Suppression (FLAWS) MRI sequence allows for the acquisition of multiple T1-weighted contrasts in a single sequence acquisition. However, its acquisition time is prohibitive for use in clinical practice when the k-space is linearly downsampled and reconstructed using the Generalized Autocalibrating Partially Parallel Acquisition (GRAPPA) technique. This study proposes a FLAWS sequence optimization tailored to allow for the acquisition of FLAWS images with a Cartesian phyllotaxis k-space undersampling and compressed sensing (CS) reconstruction at 3T. The CS FLAWS sequence parameters were determined using a method previously employed to optimize FLAWS imaging at 1.5T and 7T. In-vivo experiments show that the proposed CS FLAWS optimization allows to reduce the FLAWS sequence acquisition time from 8 mins to 6 mins without decreasing the FLAWS image quality. In addition, this study demonstrates for the first time that T1-weighted imaging with low B1 sensitivity and T1 mapping can be performed with the FLAWS sequence at 3T for both GRAPPA and CS reconstructions. The FLAWS T1 mapping was validated using in-silico, in-vitro and in-vivo experiments with comparison against the inversion recovery turbo spin echo and MP2RAGE T1 mappings. These new results suggest that the recent advances in FLAWS imaging allow to combine the MP2RAGE imaging benefits (T1-weigthed imaging with low B1 sensitivity and T1 mapping) and with the previous version of FLAWS imaging benefits (multi T1-weighted contrast imaging) in a single 6 mins sequence acquisition.

scholarly journals Simulated basis sets for semi-LASER: the impact of including shaped RF pulses and magnetic field gradients

2020 ◽  
Author(s):  
Oscar Jalnefjord ◽  
Patrick Pettersson ◽  
Lukas Lundholm ◽  
Maria Ljungberg
Keyword(s):  
Magnetic Field ◽  
Pulse Sequence ◽  
Basis Sets ◽  
Rf Pulses ◽  
Strongly Coupled ◽  
In Vivo Measurements ◽  
Field Gradients ◽  
Magnetic Field Gradients ◽  
Metabolite Quantification

Abstract Objective To study the need for inclusion of shaped RF pulses and magnetic field gradients in simulations of basis sets for the analysis of proton MR spectra of single voxels of the brain acquired with a semi-LASER pulse sequence. Materials and methods MRS basis sets where simulated at different echo times with hard RF pulses as well as with shaped RF pulses without or with magnetic field gradients included. The influence on metabolite concentration quantification was assessed using both phantom and in vivo measurements. For comparison, simulations and measurements were performed with the PRESS pulse sequence. Results The effect of including gradients in the simulations was smaller for semi-LASER than for PRESS, however, still noticeable. The difference was larger for strongly coupled metabolites and at longer echo times. Metabolite quantification using semi-LASER was thereby less dependent on the inclusion of gradients than PRESS, which was seen in both phantom and in vivo measurements. Discussion The inclusion of the shaped RF pulses and magnetic field gradients in the simulation of basis sets for semi-LASER is only important for strongly coupled metabolites. If computational time is a limiting factor, simple simulations with hard RF pulses can provide almost as accurate metabolite quantification as those that include the chemical-shift related displacement.

scholarly journals Host resistance directed selectively against H-2-deficient lymphoma variants. Analysis of the mechanism.

1985 ◽  
Vol 162 (6) ◽  
pp. 1745-1759 ◽  
Author(s):  
H G Ljunggren ◽  
K Kärre
Keyword(s):  
Nk Cell ◽  
Cell Activity ◽  
Cell System ◽  
Control Line ◽  
In Vivo Experiments ◽  
Rapid Elimination ◽  
Progressive Growth ◽  
The Difference ◽  
Asialo Gm1

Three independent variants with a profound reduction of cell surface H-2 have been selected from the C57BL/6 mouse-derived RBL-5 and EL-4 T lymphomas. After subcutaneous inoculation of low cell doses in syngeneic mice, the H-2- variants failed to grow out, whereas the H-2+ control lines showed progressive growth. No difference in growth rate or cloning efficiency was detectable in tissue culture. The in vivo difference in tumor outgrowth was analyzed in detail for one of the H-2-low lines. The outgrowth difference remained after the H-2-low variant and the control line had been injected subcutaneously in opposite flanks of the same mouse, and it was not dependent upon activity of mature T cells, since the same result was seen in athymic nude mice. The difference was partially sensitive to irradiation of the hosts. When mice were pretreated with anti-asialo GM1 antiserum, known to depress natural killer (NK) cell activity, the difference in outgrowth was abolished, and both the control line and the H-2- variant showed progressive growth in vivo. Experiments comparing the distribution and survival of isotope-prelabeled variant and wild type cells indicated that a rapid elimination of the former took place within 24 h after intravenous injection. These differences in tumor elimination were not seen in mice treated with anti-asialo GM1 antiserum. We conclude that the reduced tumorigenicity of sublines with impaired H-2 expression is largely, if not exclusively due to rapid elimination by NK cells. These findings may reflect an inverse, indirect relation between factors controlling H-2 expression and NK sensitivity. Another possible explanation is that major histocompatibility complex (MHC)-encoded gene products are directly involved in a regulatory signal in the NK cell system. According to this interpretation, immunological selectivity in the NK cell system would be achieved by the failure to recognize self-MHC, irrespective of the presence of foreign antigens, i.e. by detection of no-self rather than of nonself. This may also explain previous observations on H-2-linked hybrid resistance against lymphoid grafts and changes in H-2 phenotypes associated with tumor progression.

scholarly journals Gentamicin Sponge for Anti-infection, a Controversial Old Topic and Preliminary Exploration of the Solution, in Vitro and in Vivo Experiments

2021 ◽  
Author(s):  
Yongduo Li ◽  
Dong Wang ◽  
Junlin Zhou
Keyword(s):  
Drug Release ◽  
Wound Infection ◽  
Drug Loading ◽  
Physiological Saline ◽  
High Accuracy ◽  
In Vivo Experiments ◽  
The Difference ◽  
Gentamicin Sponge

Abstract Purpose: Our study was to construct drug-loading and drug-release quantitative equation of gentamicin sponge, in addition, obtain the wound infection prevented and treated scheme of gentamicin sponge. Methods: Sterile sponge was cut into 1×1×0.5cm size and immersed into 40mg/ml, 16mg/ml, 8mg/ml, 4mg/ml, 1.6mg/ml, 0.8mg/ml or 0mg/ml gentamicin solution for 12h, 24h, 48h, 96h or 120h to evaluate gentamicin-loading of sponge. Sponge was immersed in gentamicin solution of different concentrations for 48h and then air-dried. Air-dried sponge was immersed into 10ml 0.9% physiological saline to evaluated gentamicin-release. Staphylococcus aureus (MSSA) and Pseudomonas aeruginosa (P. aeruginosa) were used to explore infection prevented scheme of gentamicin sponge. Besides, femur fractured with wound infection rat model was used to discuss the infection treated scheme.Results: The equation of gentamicin-loading of sponge was: z=(0.03718±0.01672)x+(-4.578e-4±0.06253)y+(-2.50935e-4±1.47521e-4)x2+(0.00303±0.00149)y2+(0.00408±3.52827e-4)xy (R2 was 0.97) and drug-release equation was z=(4.37205±1.18048)x+(-7.05921±3.09628)y+(-0.04596±0.01287)x2+(0.3309±0.07912)y2+(0.31559±0.02754)xy (R2 was 0.95). The antibacterial zone sizes of sponges immersed in 40mg/ml, 16mg/ml, 8mg/ml, 4mg/ml, 1.6mg/ml, 0.8mg/ml gentamicin solution were larger than 0mg/ml air-dried sponge, and the difference had statistically significant (p<0.01). Rats of groups of 40mg/ml air-dried sponge, 16mg/ml air-dried sponge, 8mg/ml air-dried sponge had no wound suppuration in both MSSA and P. aeruginosa infection rat model.Conclusions: The quantified equation of gentamicin-loading and release of sponge was with high accuracy. 1.6 mg/ml air-dried sponge and 0.8mg/ml air-dried sponge were enough to prevent wound infection. Besides, if wound were confirmed to be sensitive bacteria infected, we recommended to use 40mg/ml air-dried sponge, 16mg/ml air-dried sponge or 8mg/ml air-dried sponge to treat.

scholarly journals In vivo lung morphometry with hyperpolarized 3He diffusion MRI in canines with induced emphysema: disease progression and comparison with computed tomography

2007 ◽  
Vol 102 (1) ◽  
pp. 477-484 ◽  
Author(s):  
Tariq S. K. Tanoli ◽  
Jason C. Woods ◽  
Mark S. Conradi ◽  
Kyongtae Ty Bae ◽  
David S. Gierada ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Disease Progression ◽  
Pulse Sequence ◽  
Quantitative Computed Tomography ◽  
Diagnostic Tools ◽  
Healthy Humans ◽  
Diffusivity Measurements ◽  
Lung Morphometry ◽  
Sequence Parameters

Despite a long history of development, diagnostic tools for in vivo regional assessment of lungs in patients with pulmonary emphysema are not yet readily available. Recently, a new imaging technique, in vivo lung morphometry, was introduced by our group. This technique is based on MRI measurements of diffusion of hyperpolarized 3He gas in lung air spaces and provides quantitative in vivo tomographic information on lung microstructure at the level of the acinar airways. Compared with standard diffusivity measurements that strongly depend on pulse sequence parameters (mainly diffusion time), our approach evaluates a “hard number,” the average acinar airway radius. For healthy dogs, we find here a mean acinar airway radius of ∼0.3 mm compared with 0.36 mm in healthy humans. The purpose of the present study is the application of this technique for quantification of emphysema progression in dogs with experimentally induced disease. The diffusivity measurements and resulting acinar airway geometrical characteristics were correlated with the local lung density and local lung-specific air volume calculated from quantitative computed tomography data obtained on the same dogs. The results establish an important association between the two modalities. The observed sensitivity of our method to emphysema progression suggests that this technique has potential for the diagnosis of emphysema and tracking of disease progression or improvement via a pharmaceutical intervention.

DIFFERENCES BETWEEN IN-VITRO AND IN-VIVO POTENCIES OF CORTICOTROPHINS: AN INTERPRETATION IN TERMS OF METABOLIC STABILITY

1977 ◽  
Vol 73 (1) ◽  
pp. 79-89 ◽  
Author(s):  
COLIN McMARTIN ◽  
GILLIAN E. E. PURDON ◽  
LOTTE SCHENKEL ◽  
PIERRE-A. DESAULLES ◽  
RENÉ MAIER ◽  
...  
Keyword(s):  
Amino Acid Position ◽  
Metabolic Stability ◽  
Receptor Level ◽  
Adrenal Cells ◽  
Cell Assay ◽  
In Vivo Experiments ◽  
The Difference ◽  
Isolated Cell

SUMMARY Relative activities of a series of corticotrophin analogues have been measured by means of five different bioassays using the rat. Similarities in the relative potencies of various ACTH analogues determined using lipolysis or steroidogenesis in vivo and for the lipolytic and steroidogenic responses of fat pads and adrenal slices in vitro emerged and support the concept of a close structural relationship between the ACTH receptors in adipose and adrenal tissues in the rat. Potencies based on the steroidogenic response of isolated adrenal cells, adrenal slices or in-vivo experiments differed markedly from each other. Inactivation of peptides did not occur in the isolated cell assay, so it is likely that this assay estimates potency at the receptor level. A number of arguments suggest that the difference between the isolated cell assay and the other steroidogenic assays lies solely in the effects of peptide inactivation in the latter, and this allows the relative metabolic stabilities for the peptide analogues in these assays to be calculated. In this way it can be shown that: (1) Replacement of l-Ser by d-Ser in amino acid position 1 markedly increases the metabolic stability of the peptide and has only a slight effect on receptor properties. (2) Shortening at the NH2-terminus reduces the activity of peptides at the receptor level by several orders of magnitude, but increases their relative metabolic stability. (3) Introduction of amide groups at the CO2H-terminus markedly increases receptor potency of (1–16), (1–17) and (1–18) ACTH without affecting their metabolic stability in vivo. However, amidation of the CO2H-terminus does have a large effect on metabolic stability in the adrenal slice assay. (4) Replacement of Arg by Lys in positions 17 and 18 of (1–18) ACTH increases potency at the receptor level (adrenal cells) but has little effect on metabolic stability. The comparison of potencies obtained in the various assays, therefore, throws light on the significance of each assay. In addition, the effects of structural modification of analogues can be separately evaluated with respect to the metabolic stability of a peptide and its potency at the receptor level.

Enhancement of ADP-induced Platelet Aggregation by Adrenaline in Vivo and Its Prevention

1973 ◽  
Vol 29 (02) ◽  
pp. 490-498 ◽  
Author(s):  
Hiroh Yamazaki ◽  
Itsuro Kobayashi ◽  
Tadahiro Sano ◽  
Takio Shimamoto
Keyword(s):  
Platelet Count ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
The Other ◽  
Endothelial Surface ◽  
Important Interaction ◽  
Blood Coagulability ◽  
The Difference

SummaryThe authors previously reported a transient decrease in adhesive platelet count and an enhancement of blood coagulability after administration of a small amount of adrenaline (0.1-1 µg per Kg, i. v.) in man and rabbit. In such circumstances, the sensitivity of platelets to aggregation induced by ADP was studied by an optical density method. Five minutes after i. v. injection of 1 µg per Kg of adrenaline in 10 rabbits, intensity of platelet aggregation increased to 115.1 ± 4.9% (mean ± S. E.) by 10∼5 molar, 121.8 ± 7.8% by 3 × 10-6 molar and 129.4 ± 12.8% of the value before the injection by 10”6 molar ADP. The difference was statistically significant (P<0.01-0.05). The above change was not observed in each group of rabbits injected with saline, 1 µg per Kg of 1-noradrenaline or 0.1 and 10 µg per Kg of adrenaline. Also, it was prevented by oral administration of 10 mg per Kg of phenoxybenzamine or propranolol or aspirin or pyridinolcarbamate 3 hours before the challenge. On the other hand, the enhancement of ADP-induced platelet aggregation was not observed in vitro, when 10-5 or 3 × 10-6 molar and 129.4 ± 12.8% of the value before 10∼6 molar ADP was added to citrated platelet rich plasma (CPRP) of rabbit after incubation at 37°C for 30 second with 0.01, 0.1, 1, 10 or 100 µg per ml of adrenaline or noradrenaline. These results suggest an important interaction between endothelial surface and platelets in connection with the enhancement of ADP-induced platelet aggregation by adrenaline in vivo.

Reliability of a Single β-Thromboglobulin Measurement in a Diabetic Population : Importance of PGE1 in Anticoagulant Mixture

1987 ◽  
Vol 57 (02) ◽  
pp. 201-204 ◽  
Author(s):  
P Y Scarabin ◽  
L Strain ◽  
C A Ludlam ◽  
J Jones ◽  
E M Kohner
Keyword(s):  
In Vitro Release ◽  
Mean Value ◽  
Reliable Estimate ◽  
Diabetic Patients ◽  
Single Measurement ◽  
Diabetic Population ◽  
The Difference ◽  
Vitro Release

SummaryDuring the collection of samples for plasma β-thromboglobulin (β-TG) determination, it is well established that artificially high values can be observed due to in-vitro release. To estimate the reliability of a single β-TG measurement, blood samples were collected simultaneously from both arms on two separate occasions in 56 diabetic patients selected for a clinical trial. From each arm, blood was taken into two tubes containing an anticoagulant mixture with (tube A) and without (tube B) PGE!. The overall mean value of B-TG in tube B was 1.14 times higher than in tube A (p <0.01). The markedly large between-arms variation accounted for the most part of within-subject variation in both tubes and was significantly greater in tube B than in tube A. Based on the difference between B-TG values from both arms, the number of subjects with artifically high B-TG values was significantly higher in tube B than in tube A on each occasion (overall rate: 28% and 14% respectively). Estimate of between-occasions variation showed that B-TG levels were relatively stable for each subject between two occasions in each tube. It is concluded that the use of PGEi decreases falsely high B-TG levels, but a single measurement of B-TG does not provide a reliable estimate of the true B-TG value in vivo.

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