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At least 253 records · Page 14Linked to original sources
PubMed2004

Safety evaluation of a novel whitening gel, containing 6% hydrogen peroxide and a commercially available whitening gel containing 18% carbamide peroxide in an exaggerated use clinical study.

OBJECTIVES: The aim of this study was to compare the effect on oral soft tissue of a self-applied tooth whitening gel containing 6% hydrogen peroxide (Xtra White) with a marketed paint-on whitening gel containing 18% carbamide peroxide (Colgate Simply White) after 2-weeks of using products four times daily. METHODS: A 2-week, examiner-blind, stratified, parallel design clinical trial was conducted. Twenty subjects were divided into two groups, balanced according to age and gender. Subjects followed a 2-week, twice-daily regimen of brushing with standard fluoride toothpaste and applied gel product to facial aspects of six upper and six lower incisors/canines, twice in succession with 30 min between applications. Soft tissue examinations were performed on Day 1, before the first application of the test products, and on Day 2, 5, 8 and 15. RESULTS: During the 2-week treatment period, twelve adverse reactions were recorded as potentially attributable to the study products, evenly split between the two test groups. All reports were mild in symptoms and resolved without the need of medical intervention. None of the subjects experiencing an adverse event requested to be withdrawn from the study. CONCLUSIONS: Under the exaggerated use conditions of this test, there was no evidence to suggest that either of the whitening gels produced irritation that was building or developing during the course of the study. It is concluded that both products are safe for their intended use.

Adolescent↗
PubMed2000

Low concentration of DMSO stabilizes the bilayer gel phase rather than the interdigitated gel phase in dihexadecylphosphatidylcholine membrane.

We have investigated effects of dimethylsulfoxide (DMSO) on the phase stability of multilamellar vesicles of the ether-linked 1,2-dihexadecyl-sn-glycero-3-phosphatidylcholine (DHPC-MLV), which is known to be in the interdigitated gel (LbetaI) phase in excess water at 20 degrees C. The results of X-ray diffraction experiments indicate that the DHPC membrane was in the Lbeta, phase at X> or =0.12 (X=mole fraction of DMSO in DMSO/water mixture). The result of differential scanning calorimetry indicate that the gel to liquid-crystalline phase transition temperature increased, but the LbetaI to Pbeta, phase transition temperature decreased with an increase in DMSO concentration. These results show that DMSO stabilizes the bilayer gel phase rather than the LbetaI phase at its low concentration. The solubility of phosphorylcholine, which is the same structure as the headgroup of DHPC, decreased with an increase in DMSO concentration, indicating that the interaction free energy of the hydrophilic segments of the membrane with solvents increases with an increase in DMSO concentration. On the basis of the thermodynamic analysis, the mechanism of the stabilization of the bilayer gel phase of DHPC-MLV by DMSO is discussed. The decrease in the repulsive interaction between the headgroups of the phospholipid induced by the low concentrations of DMSO in water plays an important role in this stabilization.

Calorimetry, Differential Scanning↗
PubMed1999

Low pH induces an interdigitated gel to bilayer gel phase transition in dihexadecylphosphatidylcholine membrane.

We have investigated the influence of pH on the structures and phase behaviors of multilamellar vesicles of the ether-linked dihexadecylphosphatidylcholine (DHPC-MLV). This phospholipid is known to be in the interdigitated gel (L(beta)I) phase in excess water at 20 degrees C at neutral pH. The results of X-ray diffraction experiments indicate that a phase transition from L(beta)I phase to the bilayer gel phase occurred in DHPC-MLV in 0.5 M KCl around pH 3.9 with a decrease in pH, and that at low pH values, less than pH 2.2, DHPC-MLVs were in L(beta') phase. The results of fluorescence and light scattering method indicate that the gel to liquid-crystalline phase transition temperature (T(m)) of DHPC-MLV increased with a decrease in pH. On the basis of a thermodynamic analysis, we conclude that the main mechanism of the low-pH induced L(beta)I to bilayer gel phase transition in DHPC-MLV and the increase in its T(m) is connected with the decrease in the repulsive interaction between the headgroups of these phospholipids. As pH decreases, the phosphate groups of the headgroups begin to be protonated, and as a result, the apparent positive surface charges appear. However, surface dipoles decrease and the interaction free energy of the hydrophilic segments with water increases. The latter effect dominates the pure electrostatic repulsion between the charged headgroups, and thereby, the total repulsive interaction in the interface decreases.

Calorimetry, Differential Scanning↗
PubMed1999

Ultra-thin-layer agarose gel electrophoresis. I. Effect of the gel concentration and temperature on the separation of DNA fragments.

A novel, rapid and efficient separation method is described for the analysis of double stranded (ds) DNA fragments in the form of horizontal ultra-thin-layer agarose gel electrophoresis. This separation technique combines the multilane, high-throughput separation format of agarose slab gel electrophoresis with the excellent performance of capillary electrophoresis. The electrophoretic separation of the fluorophore (Cy5)-labeled dsDNA molecules were imaged in real time by a scanning laser-induced fluorescence/avalanche photodiode detection system. Effects of the gel concentration (Ferguson plot) and separation temperature (Arrhenius plot) on the migration characteristics of the DNA fragments are discussed. An important genotyping application is also shown by characterizing the polymorphic region (2 X or 4 X 48 base pair repeats) of the dopamine D4 receptor gene (D4DR, exon III region) for ten individuals, using PCR technology with Cy5-labeled primers and ultra-thin-layer agarose gel electrophoresis.

DNA↗
PubMed2002

Effect of synthesis parameters of the sol-gel-processed spray-dried silica gel microparticles on the release rate of dexmedetomidine.

The objective of this study was to evaluate the possibilities to control the release rate of dexmedetomidine (DMED) from different spray-dried silica gel microparticle formulations. Microparticles were prepared by spray drying a silica sol polymer solution containing the drug. Drug release was investigated both in vitro and in vivo. The influence of sol-gel synthesis parameters, like pH and the water/alkoxide ratio (r) of the sol, on the release behaviour of the drug was studied. Silica gel microparticles had a smooth surface. Microparticles prepared from diluted sol, however, were more aggregated and clustered. The drug release conformed to zero order release from microparticles prepared near the isoelectric point of silica (pH 2.3 and pH 3) and to the square root of time kinetics from microparticles prepared at pH 1 and pH 5. The release also showed a dual-phasic profile with an initial burst and after that a slower release period. The dexmedetomidine release conformed to zero order kinetics from microparticles prepared at water/ alkoxide ratios between r = 6 and r = 35 (at pH 2.3). The release rate was the slowest from microparticles prepared with water/ alkoxide ratio 35. The bioavailability of dexmedetomidine in dogs showed that the release was sustained from silica gel microparticles as compared with a subcutaneously administered reference dose of 0.1 mg.

Analgesics, Non-Narcotic↗
PubMed2000

Transfer of SDS-proteins from gel electrophoretic zones into mass spectrometry, using electroelution of the band into buffer without sectioning of the gel.

Five SDS-proteins, ranging in molecular weight from 14 to 66 kDa, were detected without covalent fluorescent labeling by the automated gel electrophoresis apparatus with intermittent fluorescence scanning (HPGE apparatus, LabIntelligence) during electrophoresis in barbiturate buffer in the presence of Cascade Blue. The SDS-proteins were electroeluted from the gel into 220 microl of buffer by a modification of the procedure of Gombocz and Cortez. The electroeluate was freed of SDS, ultrafiltered and subjected to MALDI-TOF mass spectrometry. The masses of the five native proteins were found to be maintained after electrophoresis and electroelution in the presence of the potential contaminants SDS, barbituric acid and Cascade Blue. The procedure of protein transfer from SDS-PAGE into mass spectrometry, without excision of bands, gel maceration and protein recovery by diffusion, therefore is shown to be suitable for the identification by mass of intact proteins derived from gel electrophoretic bands.

Biochemistry↗
PubMed1990

Morphological study of normal and tumor cells in the head and neck region using irradiated collagen gel embedding technique: morphological study using collagen gel.

Fourteen specimens of normal, benign, or malignant tumor cells from the head and neck region were subjected for culture using 0.2% of irradiated collagen gel embedding technique. Re-differentiation of glands within the gel in serum-free medium was observed. There were marked differences in the growth patterns within the gel between normal or benign and malignant cells. Four normal glands and 5 out of 6 benign tumors showed branch-like growth patterns. On the other hand, malignant tumors showed no branch-like pattern, or could not grow at all. The results showed that the collagen gel technique could be useful for the differential diagnosis of malignancy in head and neck tumors.

Cell Differentiation↗
PubMed1992

Specific base recognition of oligodeoxynucleotides by capillary affinity gel electrophoresis using polyacrylamide-poly(9-vinyladenine) conjugated gel.

Poly(9-vinyladenine) was synthesized and utilized as an affinity macroligand entrapped within the gel matrix. Base-specific separation of oligodeoxynucleotides was achieved with high resolution and high speed by electrophoresis, using capillaries filled with conjugated polyacrylamide-poly(9-vinyladenine) gel. Oligothymidylic acids were selectively separated from the mixture of oligothymidylic and oligodeoxyadenylic acids by utilizing a specific hydrogen bonding between poly(9-vinyladenine) and oligothymidylic acids. Migration time and resolution of oligodeoxynucleotides were influenced by several parameters, such as the size of poly(9-vinyladenine), capillary temperature, and concentrations of poly(9-vinyladenine) and urea. Some guidelines are presented, based on the theoretical formulation of the effect of these parameters, in order to find optimum electrophoretic conditions. Analytical capillary affinity gel electrophoresis was developed for the selective and sensitive base recognition of oligodeoxynucleotides with efficiencies as high as several 10(6) plates/m by using a urea-gel capillary with poly(9-vinyladenine) and temperature-programming.

Adenine↗
PubMed2005

An ion-imprinted functionalized silica gel sorbent prepared by a surface imprinting technique combined with a sol-gel process for selective solid-phase extraction of cadmium(II).

A new ion-imprinted thiol-functionalized silica gel sorbent was synthesized by a surface imprinting technique in combination with a sol-gel process for selective on-line, solid-phase extraction of Cd(II). The Cd(II)-imprinted thiol-functionalized silica sorbent was characterized by FT-IR, the static adsorption-desorption experiment, and the dynamic adsorption-desorption method. The maximum static adsorption capacity of the ion-imprinted functionalized sorbent was 284 micromol g(-1). The largest selectivity coefficient for Cd(II) in the presence of Pb(II) was over 220. The static uptake capacity and selectivity coefficient of the ion-imprinted functionalized sorbent are higher than those of the nonimprinted sorbent. The breakthrough capacity and dynamic capacity of the imprinted functionalized silica gel sorbent for 4 mg L(-1) of Cd(II) at 5.2 mL min(-1) of sample flow rate were 11.7 and 64.3 micromol g(-1), respectively. No remarkable effect of sample flow rate on the dynamic capacity was observed as the sample flow rate increased from 1.7 to 6.8 mL min(-1). The imprinted functionalized silica gel sorbent offered a fast kinetics for the adsorption and desorption of Cd(II). The prepared ion-imprinted functionalized sorbent was shown to be promising for on-line, solid-phase extraction coupled with flame atomic absorption spectrometry for the determination of trace cadmium in environmental and biological samples. All competitive ions studied did not interfere with the determination of Cd(II). With a sample loading flow rate of 8.8 mL min(-1) for 45-s preconcentration, an enhancement factor of 56, and a detection limit (3sigma) of 0.07 microg L(-1) were achieved at a sampling frequency of 55 h(-1). The precision (RSD) for 11 replicate on-line sorbent extractions of 8 mug L(-1) Cd(II) was 0.9%. The sorbent also offered good linearity (r = 0.9997) for on-line, solid-phase extraction of trace Cd(II).

Adsorption↗
PubMed2006

Combined rheological and ultrasonic study of alginate and pectin gels near the sol-gel transition.

The sol-gel transition of biopolymer mixtures has been investigated by rheological and ultrasonic measurements. A scaling analysis of the data was performed for both types of measurements. A gel time was determined from rheology for the pure pectin samples, and the data could be fitted to a universal scaling form near the transition point. Its critical exponents are in good agreement with the predictions of scalar percolation theory. In addition, the ultrasonic signal of the pectin samples close to the transition was analyzed in terms of a high-frequency scaling approach for the attenuation and the velocity. For the alginate samples and the mixtures, for which the gel point cannot be determined reliably from rheology, the ultrasonic measurements were analyzed using the same scaling form as for the pectin sample, thus providing a method for estimating the gel point, even in the absence of rheological data.

Alginates↗
PubMed2006

Effect of gel structure on the dissolution of heat-induced beta-lactoglobulin gels in alkali.

The dissolution of heat-induced beta-lactoglobulin (betaLg) gels in alkaline solution plays an important role in the cleaning-in-place of fouled dairy and other food plants. The dissolution behavior is strongly influenced by the conditions under which the gel is formed. At low alkaline pH values (<13), the dissolution rate constant kg' decreases with longer gelation time and higher temperature. An inverse relationship is observed between the kg' value and the amount of covalently cross-linked proteins in the gel, which is mainly due to disulfide bonds. beta-Elimination kinetics of intramolecular cystines in betaLg have been used to estimate the amount of intermolecular disulfide bonds that are cleaved during dissolution. The results call into question current dissolution models for these systems based on external mass transfer through the fluid next to the swollen gel. At low temperatures, the amount of disulfide cleavage is estimated to be small, indicating that dissolution is likely to involve the (slow) disengagement of large protein clusters, analogous to the dissolution of synthetic polymers.

Chemical Phenomena↗
PubMed2006

Methods to electrophoretically stretch DNA: microcontractions, gels, and hybrid gel-microcontraction devices.

The ability to controllably and continuously stretch large DNA molecules in a microfluidic format is important for gene mapping technologies such as Direct Linear Analysis (DLA). We have recently shown that electric field gradients can be readily generated in a microfluidic device and the resulting field is purely elongational. We present a single molecule fluorescence microscopy analysis of T4 DNA (169 kbp) stretching in the electric field gradients in a hyperbolic contraction microchannel. In addition, we are able to selectively pattern a crosslinked gel anywhere inside the microchannel. With an applied electric field, DNA molecules are forced to reptate through the gel and they moderately stretch as they exit the gel. By placing a gel immediately in front of the hyperbolic contraction, we bypass "molecular individualism" and achieve highly uniform and complete stretching of T4 DNA.

Bacteriophage T4↗
PubMed2006

Universal behaviour of gel formation from acrylamide-carrageenan mixture around the gel point: a fluorescence study.

The steady state fluorescence (SSF) technique was used to study the sol-gel transition, for the solution free radical crosslinking copolymerization of acrylamide (AAm) with various carrageenan content. N, N'- methylenebis (acrylamide) (BIS) and ammonium persulfate (APS) are used as crosslinker and an initiator, respectively. Pyranine (8-hydroxypyrene-1, 3,6-trisulfonic acid, trisodium salt, HPTS) was added as a floroprobe for monitoring the polymerization. Pyranine molecules start to bind to acrylamide polymer chains upon the initiation of the polymerization; thus, the spectra of the bonded pyranines shift to the shorter wavelengths. Fluorescence spectra from the bonded pyranines allows one to monitor the sol-gel transition, without disturbing the system mechanically, and to test the universality of the sol-gel transition as a function of some kinetic parameters like polymer concentration. Observations around the critical point show that the gel fraction exponent beta obeyed the percolation result for low carrageenan concentrations (< 2.0%) however classical results were produced at higher carrageenan concentration (> 2.0%).

Acrylamide↗
PubMed1996

Radiation dose distributions in three dimensions from tomographic optical density scanning of polymer gels: II. Optical properties of the BANG polymer gel.

A newly developed method of radiation dosimetry makes use of the optical properties of polymer gels. The dose-response mechanism relies on the production of light-scattering polymer micro-particles in the gel at each site of radiation absorption. The scattering produces an attenuation of transmitted light intensity that is directly related to the dose and independent of dose rate. For the BANG polymer gel (bis, acrylamide, nitrogen, and gelatin) the shape of the dose-response curve depends on the fraction of the cross-linking monomer in the initial mixture and on the wavelength of light. At 500 nm the attenuation coefficient (mu) increases by approximately 0.7 mm-1 when the dose increases from 0 to 5 Gy. The refractive index of an irradiated gel shows no significant dispersion in the visible region and depends only slightly on the dose. Turbidity difference spectra are compared with theoretical spectra of efficiency factors for total scattering, derived using Mie-Debye theory, and the average sizes of the cross-linked particles produced by radiation, as a function of dose, are established. The particle sizes increase with dose and reach approximately the wavelength of red light. The dependence of the particle sizes on cross-linker fraction parallels a similar dependence of the water proton NMR transverse relaxation rate dose response.

Acrylamide↗
PubMed2004

Skin tolerability and efficacy of combination therapy with hydrogen peroxide stabilized cream and adapalene gel in comparison with benzoyl peroxide cream and adapalene gel in common acne. A randomized, investigator-masked, controlled trial.

BACKGROUND: Combination therapy with antiseptics such as benzoyl peroxide (BP) and topical retinoids is widely used as first-line treatment for acne vulgaris (AV). However, these combinations could have a suboptimal skin tolerability. Recently, a new formulation of hydrogen peroxide (HP) 1% in stabilized cream (Crystacide; Mipharm, Milan, Italy) became available. A previous clinical study has shown that HP cream monotherapy presents a better skin tolerability in comparison with BP in patients with mild AV. OBJECTIVES: To evaluate the tolerability and the efficacy of combination therapy with HP cream and adapalene 0.1% gel in comparison with the combination of BP 4% cream and adapalene 0.1% gel in the treatment of mild to moderate AV. METHODS: In a randomized, investigator-blinded trial, 52 patients (mean +/- SD age 25 +/- 6 years; 19 men and 33 women) with AV were randomly assigned to HP cream and adapalene gel (group HP + A) or to BP cream and adapalene gel (group BP + A), for eight consecutive weeks. Efficacy was assessed by total (TL), inflammatory (IL) and noninflammatory (NL) lesion counts performed at baseline and weeks 4 and 8. Tolerability was assessed by evaluating skin erythema, burning and dryness at weeks 4 and 8. RESULTS: All patients completed the study. At baseline, the mean +/- SD numbers of TL, IL and NL were 44 +/- 9, 25 +/- 7 and 19 +/- 6 in group HP + A and 40 +/- 9, 21 +/- 7 and 19 +/- 9 in group BP + A, respectively. At the end of the treatment period, TL, IL and NL were reduced by 93%, 92% and 95%, respectively, in group HP + A and by 88%, 86% and 90%, respectively, in group BP + A. A significantly (P = 0.0025) greater reduction in NL was observed in group HP + A in comparison with group BP + A. Tolerability was significantly better in group HP + A in comparison with group BP + A (P = 0.02). Skin dryness and burning sensation were more frequent in group BP + A. CONCLUSIONS: The combination of adapalene and HP cream is an effective topical treatment regimen in mild to moderate AV. This combination has shown a better tolerability profile in comparison with the combination of BP and adapalene.

Acne Vulgaris↗
PubMed1980

Pharmaceutical studies of polyacrylic acid aqueous gel bases: absorption of insulin from polyacrylic acid aqueous gel bases following rectal administration in alloxan diabetic rats and rabbits.

The effect of gel preparation on the rate of absorption of a rectally administered insulin which was suspended in a polyacrylic acid aqueous gel base (0.1%, pH 6.5) was investigated in the alloxan diabetic rats and rabbits. The preparation was administered into the in situ rectal loop in rats or infused directly into the rectum in rabbits, and the change in the blood glucose level and plasma insulin value was taken as a measure to evaluate the rate of rectal absorption of insulin. The blood glucose lowering effect in both rats and rabbits was dose-dependent, namely, a slight effect was observed at 1 IU/kg followed by a significant effect with 3 and 5 IU/kg, and a sharp hypoglycemic effect was recorded with 10 IU/kg which lasted for 5 hr. The plasma insulin level exhibited a rapid increase at 30 minutes after the dosing of the insulin by the polyacrylic acid aqueous gel base. However, the plasma level quickly diminished in 1 hr. Contrary to our expectation, an addition of a non-ionic surfactant such as Tween 80 under pH 4--8 did not show further enhancement of the absorption. In an attempt to simulate a clinical condition in which insulin was given after a meal, the insulin gel was administered into the rectal loop in diabetic rats following the i.v. injection of glucose. A satisfactory result was obtained in which 5 IU/kg dose was able to suppress a rise in the blood glucose after the glucose loading.

Acrylic Resins↗
PubMed1994

Effects of tetracycline-containing gel and a mixture of tetracycline and citric acid-containing gel on non-surgical periodontal therapy.

The purpose of this study was to assess the clinical and microbiological effects of a newly developed root conditioning gel system containing tetracycline or a mixture of tetracycline and citric acid on non-surgical periodontal therapy. Sixty-four (64) single-rooted teeth with a probing depth of 4 to 6 mm were randomly subjected to one of the following four treatments; 1) root planing alone (RP group); 2) tetracycline-containing gel alone (TCG group); 3) root planing plus tetracycline-containing gel (RP + TCG group); or 4) root planing plus a mixture of tetracycline and citric acid-containing gel (RP + TC-CAG group). Probing depth, attachment level, and tooth mobility were measured and the presence of dental plaque and gingival inflammation was recorded at baseline and after 2, 4, 8, and 12 weeks. Subgingival plaque samples from each site were collected at the same visits and examined with phase contrast microscopy for proportions of motile rods and spirochetes. Plaque index, gingival sulcus bleeding index (SBI), probing depth, and attachment level decreased significantly in all groups compared to the baseline values (P < 0.05). A significant decrease in probing pocket depth was noted after 12 weeks in RP + TC-CAG group compared to the other groups (P < 0.05). Significantly more gain in attachment was detected in the RP + TC-CAG group compared to the TCG group (P < 0.05). Tooth mobility scores also decreased later in the study. A significant decrease in the proportion of motile rods was found primarily in the RP + TC-CAG group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2001

Monitoring of acidified milk gel formation by ultrasonic shear wave measurements. High-frequency viscoelastic moduli of milk and acidified milk gel.

In the present paper we describe the application of the thickness shear mode resonator technique for the measurement of viscoelastic parameters of milk and acidified milk gels in the megahertz frequency range. The technique provides information on the viscoelasticity of milk and milk gels in the time scale of 10(-8) to 10(-7) s. The length scale of the measurements, determined by the depth of penetration and the wavelength of the shear wave, falls between the submicron and micron range. In milk acidified by glucono-delta-lactone we observed an increase in the high- and low-frequency loss modulus, G", below pH 5.1, indicating aggregation of casein particles into clusters. There was a sharp rise in high- and low-frequency storage (G') and loss (G") moduli between pH 4.85 and 4.7, as a result of gel network formation in acidified milk. Both G" and G' of milk gel in the megahertz frequency range are several orders higher than those we obtained at low frequencies (0.02 to 10 Hz) using dynamic rheology. The high-frequency (5 to 25 MHz) viscosity of milk was found to be the same as at low frequencies. Overall, our results demonstrate the high sensitivity of the ultrasonic shear wave measurements to the changes in the rheological parameters in acidified milk during gelation.

Animals↗