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PubMed1998

Do DNA gel electrophoretic mobilities extrapolate to the free-solution mobility of DNA at zero gel concentration?

The electrophoresis of small DNA fragments has been measured in dilute agarose and polyacrylamide gels cast and run in Tris-acetate-EDTA (TAE) and Tris-borate-EDTA (TBE) buffers. Ferguson plots were constructed to extrapolate the mobilities to zero gel concentration and estimate the free solution mobility of DNA. In polyacrylamide gels, in both TAE and TBE buffers, the extrapolated mobilities at zero gel concentration increased gradually with decreasing DNA molecular weight, went through a maximum at approximately 60 bp, and then decreased again. The increase in the extrapolated mobilities with decreasing molecular weight observed for DNA fragments > or = 60 bp can be attributed to transient interactions between the migrating DNA molecules and the polyacrylamide gel fibers. If such interactions are eliminated by extrapolating the mobilities to both zero gel concentration and zero DNA molecular weight, the apparent free solution mobility of DNA is found to be 3.1 x 10(-4) cm2 V(-1) s(-1) in TAE buffer and 4.2 x 10(-4) cm2 V(-1) s(-1) in TBE buffer at 20 degrees C, reasonably close to the actual free solution mobilities measured in the same two buffers by capillary electrophoresis (N. C. Stellwagen et al., Biopolymers 1997, 42, 687-703). The significantly larger electrophoretic mobility observed in TBE buffer is most likely due to the formation of nonspecific, highly charged deoxyribose-borate complexes in this buffer medium. For DNA molecules < or = 60 bp in size, the decrease in the extrapolated mobilities with decreasing molecular weight parallels the decrease in their free solution mobilities observed by capillary electrophoresis. In agarose gels, the extrapolated mobilities of small DNA molecules at zero gel concentration appear to be independent of molecular weight. The apparent free solution mobilities are found to be (3.0 +/- 0.1) x 10(-4) cm2 V(-1) s(-1) in TAE buffer and (3.2 +/- 0.1) x 10(-4) cm2 V(-1) s(-1) in TBE buffer. The very similar mobilities observed in the two buffer media suggest that the borate ions in TBE buffer primarily form complexes with the galactose residues in the agarose gel fibers, rather than with the migrating DNA molecules, because of mass action effects. The formation of borate-agarose complexes, increasing the net negative charge of the agarose gel fibers, appears to be responsible for the markedly increased electroendosmotic flow observed in agarose gels cast and run in TBE buffer (N. C. Stellwagen, Electrophoresis 1992, 13, 601-603).

Acetates↗

PubMed1991

Procedures and computer program for deriving the Ferguson plot from electrophoresis in a single pore gradient gel: application to agarose gel and a polystyrene particle.

This study presents a computerized evaluation of pore gradient gel electrophoretograms to arrive at estimates for both the particle-free mobility and retardation coefficient, which is related to particle size. Agarose pore gradient gels ranging from 0.2 to 1.1% agarose were formed. Gel gradients were stabilized during their formation by a density gradient of 0-20% 5-(N-2,3-dihydroxypropylacetamido)- 2,4,6-triiodo-N,N'bis-(2,3-dihydroxypropyl)-isophthalamide (Nycodenz). Densitometry of gelled-in Bromophenol Blue showed that these pore gradients exhibited a linear central segment and were reproducible. Migration distances of polystyrene sulfate microspheres (36.5 nm radius) in agarose pore gradient gel electrophoresis were determined by time-lapse photography at several durations of electrophoresis. These migration distances were evaluated as a function of migration time as previously reported (D. Tietz, Adv. Electrophoresis 1988, 2, 109-169). Although this is not necessarily required, the mathematical approach used in this study assumed linearity of both the pore gradient and the Ferguson plot for reasons of simplicity. The data evaluation on the basis of the extended Ogston model is incorporated in a user-friendly program, GRADFIT, which is designed for personal computers (Macintosh). The results obtained are compared with (1) conventional electrophoresis using several gels of single concentration with and without Nycodenz, and (ii) a different mathematical approach for the analysis of gradient gels (Rodbard et al., Anal. Biochem. 1971, 40, 135-157). Moreover, a simple procedure for evaluating linear pore gradient gels using linear regression analysis is presented. It is concluded that the values of particle-free mobility and retardation coefficient derived from pore gradient gel electrophoresis using the different mathematical methods are statistically indistinguishable from each other. However, these values are different, albeit close, to those obtained from conventional Ferguson plots. One of the possible reasons for this relatively minor discrepancy is that the particle-free mobility changed slightly during electrophoresis, which has a different effect on electrophoresis in homogeneous gels (single time measurement) and pore gradient gels (multiple time measurements). The characterization of particles according to size and charge by pore gradient electrophoresis provides a significant operational simplification and sample economy compared to that requiring the use of several gel concentrations, although at the price of increased requirements of instrumentation.

Confidence Intervals↗

PubMed2002

Advances in sol-gel based columns for capillary electrochromatography: sol-gel open-tubular columns.

The development of sol-gel open-tubular column technology in capillary electrochromatography (CEC) is reviewed. Sol-gel column technology offers a versatile means of creating organic-inorganic hybrid stationary phases. Sol-gel column technology provides a general approach to column fabrication for microseparation techniques including CEC, and is amenable to both open-tubular and monolithic columns. Direct chemical bonding of the stationary phase to the capillary inner walls provides enhanced thermal and solvent stability to sol-gel columns. Sol-gel stationary phases inherently possess higher surface area, and thus provide an effective one-step alternative to conventional open-tubular column technology. Sol-gel column technology is applicable to both silica-based and transition metal oxide-based hybrid stationary phases, and thus, provides a great opportunity to utilize advanced material properties of a wide range of nontraditional stationary phases to achieve enhanced selectivity in analytical microseparations. A wide variety of stationary phase ligands can be chemically immobilized on the capillary inner surface using a single-step sol-gel procedure. Sol-gel chemistry can be applied to design stationary phases with desired chromatographic characteristics, including the possibility of creating columns with either a positive or a negative charge on the stationary phase surface. This provides a new tool to control electroosmotic flow (EOF) in the column. Column efficiencies on the order of half a million theoretical plates per meter have been reported for sol-gel open-tubular CEC columns. The selectivity of sol-gel stationary phases can be easily fine-tuned by adjusting the composition of the coating sol solution. Open-tubular columns have significant advantages over their packed counterparts because of the simplicity in column making and hassle-free fritless operation. Open-tubular CEC columns possess low sample capacity and low detection sensitivity. Full utilization of the analytical potential of sol-gel open-tubular columns will require a concomitant development in the area of high-sensitivity detection technology.

Chromatography↗

PubMed2006

Antibiotic-containing hyaluronic acid gel as an antibacterial carrier: Usefulness of sponge and film-formed HA gel in deep infection.

We have developed a novel bioabsorbable antibacterial carrier using hyaluronic acid (HA) gel for prevention and treatment of orthopedic infections. In this study, we investigated the in vivo antibacterial effects of two forms of this new material, an HA gel sponge and an HA gel film. A titanium cylinder was inserted into the intramedullary cavity of each rabbit femur, along with an HA gel sponge or HA gel film containing antibiotics. The HA gel sponge contained gentamycin, vancomycin, tobramycin, or minomycin. The HA gel film contained gentamycin or vancomycin. After 0, 7, and 14 days, the rabbit bone marrow was collected, and the antibacterial activity of the HA gel was determined by agar diffusion test. As a control, we used Septocoll, a commercially available antibacterial carrier. Both the HA gel sponge and HA gel film exhibited antibacterial activity. The present results indicate that HA gel containing antibiotics is a clinically useful bioabsorbable antibacterial carrier.

Animals↗

PubMed1993

Affinity gel electrophoresis of nucleic acids. Specific base- and shape-selective separation of DNA and RNA on polyacrylamide-nucleobase conjugated gel.

Two types of affinity gels consisting of cross-linked polyacrylamide and affinity ligands possessing nucleic acid bases were prepared. One type of gel was polyacrylamide-poly(vinylnucleobase) conjugated gel, where the poly(vinylnucleobase) such as poly(9-vinyladenine) (PVAd) bearing a nucleobase in the side-chain was entrapped in the gel matrix. The other type of gel, in which a nucleobase such as adenine is chemically bonded to polyacrylamide gel, was prepared by copolymerization of acrylamide, cross-linker and 9-vinyladenine. These affinity gels, especially the former, demonstrated characteristic nucleobase- and shape-selective separation of nucleic acids. The gels showed high affinity for single-stranded DNA and both single- and double-stranded polynucleotides and could separate a double-stranded DNA in mixtures of double-stranded DNA and polynucleotides. The electrophoretic mobilities of poly(uridylic acid) and poly(inosinic acid) were selectively retarded even in the presence of 7 M urea. The electrophoretic behaviours of nucleic acids on the polyacrylamide-PVAd conjugated gels were compared with those on the agarose-PVAd conjugated gel. The effects of urea, temperature and concentration of PVAd were also examined. The polyacrylamide-PVAd conjugated gel served to elucidate interactions between PVAd and nucleic acids that could not be detected by usual spectroscopic methods.

Acrylic Resins↗

PubMed2005

Models of protein modification in Tris-glycine and neutral pH Bis-Tris gels during electrophoresis: effect of gel pH.

The pH of conventional Tris-glycine SDS-PAGE gels during a run is determined to be 9.5, in contrast to Bis-Tris-Mes gels where the pH is 7.2. Concentrations of free acrylamide are determined to be less than 10mM in commercial gels of both types, and it is found that of the major components in these gels, only glycine and protein amine or sulfhydryl functions are likely to react with residual acrylamide during the time frame of typical separations. The addition of acrylamide to sulfhydryl groups on proteins is modeled using glutathione and cysteine at acrylamide concentrations found in the commercial gels. Rate constants are determined for these reactions as well as for reaction with glycine at the pH that proteins will encounter in these gel types. The half-life for glutathione sulfhydryl at 10mM acrylamide and pH 7.2 is more than 4h at room temperature. Rates are significantly lower in Bis-Tris-Mes gels than in Tris-glycine gels, reducing the risk of adventitious protein modification. Commercial Bis-Tris-Mes gels provide a sample reduction buffer at pH 8.5 versus the conventional pH 6.8 of Tris-glycine gels. It is shown that significantly less protein degradation occurs during sample preparation at the higher pH used with Bis-Tris gels.

Acrylamide↗

PubMed2000

Solid dosage form preparations from oily medicines and their drug release. Effect Of degree of surface-modification of silica gel on the drug release from phytonadione-loaded silica gels.

A surface-modified silica gel was produced to improve the surface affinity to an oily medicine, phytonadione (VK1). The effect of the degree of surface modification of the silica gel on the drug release behavior from the silica porous matrix was investigated. The silica gels were surface-modified using the silan coupling agent, 3-methacryloxypropyltrimethoxysilane (C7), octadecyltriethoxysilane (C18), or 3,3,3-trifluoropropyltrimethoxysilane (F3). A mixture of VK1 solution and surface-modified silica gel was evaporated under reduced pressure at room temperature, then the resulting powder was dried in vacuo. The degree of surface modification was evaluated based upon elementary analysis. The dissolution profiles of the samples were investigated in Japanese Pharmacopoeia XII, 1st fluid buffer (pH 1.2, 37+/-0.5 degrees C) containing 1.5% sodium lauryl sulfate. The FT-IR spectra of VK1-loaded surface-modified silica gels suggested that the amount of hydrogen-bonded VK1 with the silanol group on the gel surface decreased with increasing hydrophobicity of the silica gel. Since the modified group was rotating on the silica gel surface, and inhibited the adsorption of VK1 to the surface, the attractive molecular interaction between VK1 and the silica gel surface might decrease with increasing length of the modified functional group. However, the characteristics of the affinity of VK1 to the functional groups significantly differed among the groups. The VK1 release from the modified silica gels was initially rapid, slowed markedly after 1 h, and continued for more than 24 h. The amount of VK1 released from the modified surface silica gels by C7, C18 or F3 increased with increasing density of the surface modification group. The mean drug release moment (MDT) decreased with an increase in surface-modified group density.

Adsorption↗

PubMed1997

Fast T1 imaging of dual gel samples for diffusion measurements in NMR dosimetry gels.

Diffusion of iron is one of the major problems limiting the usefulness of NMR gel dosimetry. This was studied in dual gel samples using a 4.7T micro-imaging MR scanner and a fast T1 imaging sequence which allowed the acquisition of a 64 x 128 x 8 data sets (phase encoding x frequency encoding x number of inversion times) in less than 15 min. The procedure enabled us to obtain relative relaxation times for any region of interest within the sample. After the two differently doped gels were brought into contact in the dual gel samples (diameter 12 mm), the diffusion could be observed on subsequent images as a function of time. An inverse square root function was used to fit the change of 1/T1 across the junction between the two gel phases. A diffusion constant of 0.014 +/- 0.003 cm2/h was determined for Fe3+ in a typical dosimetry gel (1.5% agarose, 50 mM H2SO4). This could be lowered by adding a chelating agent such as xylenol orange to the gel. It was also found that diffusion was slower in gelatine gels, however these gels tended not to set properly when H2SO4 was added as required for NMR dosimetry. From the present results we propose that a gel consisting of 1.5% agarose (for stability), 3% gelatine and 0.1 mM xylenol orange (to combat diffusion and allow a visual evaluation) is a suitable base for NMR dosimetry gels. The use of a fast T1 imaging sequence reduces acquisition times and therefore the potential impact of diffusion.

Chelating Agents↗

PubMed1987

Heparin modulates the organization of hydrated collagen gels and inhibits gel contraction by fibroblasts.

We studied the effects of extracellular matrix components on fibroblast contraction of hydrated collagen gels. After 4-h incubations, heparin-containing collagen gels contracted only 10% compared with 50% contraction of control gels. Contraction was not affected by hyaluronic acid, dermatan sulfate, or fibronectin, implying that the activity of heparin was specific. The possibility that heparin inhibited attachment of the cells to the gels was ruled out. Also, addition of heparin to the incubation medium had no effect on contraction. Microscopic examination showed that control collagen gels were composed of a uniform network of interlocking fibrils of similar sizes. Heparin-containing gels, on the other hand, were highly variable with some collagen bundles containing 5-6 collagen fibrils and other regions containing amorphous material. Unlike the control gels, the fibrils of heparin-containing gels were not continuously interconnected. Based on the results, we propose that fibroblasts attach normally to the collagen fibrils of heparin-containing gels and attempt to contract the gels, but the mechanical forces exerted by fibroblasts on individual collagen fibrils cannot be propagated throughout the gels.

Cells, Cultured↗

PubMed2005

Randomized double-blind comparison of lidocaine gel and plain lubricating gel in relieving pain during flexible cystoscopy.

PURPOSE: To compare the pain induced by outpatient flexible cystoscopy in men having local lidocaine jelly application or plain lubricant. PATIENTS AND METHODS: We performed a randomized, double-blind study to compare the anesthetic effect of intraurethral 2% lidocaine gel (N = 45) and plain lubricant (N = 46) in men undergoing outpatient flexible cystoscopy. The age, prostate size, and examination time were similar in the two groups. Before cystoscopy, we filled the urethra with 20 mL of gel, which was held for 15 minutes. A 15.5F flexible cystoscope was then used for examination. A 10-point visual analog pain scale (1 = least to 10 = most painful) and a four-point pain grade (grade 1 = least to grade 4 = most painful) were used to measure the pain perception. The amount of postoperative analgesic used and willingness to adopt the same anesthesia for future cystoscopy were also recorded. RESULTS: The mean pain scores for the lidocaine and plain gel groups were 2.8 +/- 1.1 and 2.5 +/- 1.1, respectively (P = 0.06), while the pain grades for the lidocaine gel and plain gel groups were 1.6 +/- 0.6 and 1.8 +/- 0.7, respectively (P = 0.19). In both groups, many patients (42.2% in the lidocaine gel group and 37% in the plain lubricant group) felt the external sphincter and prostatic urethra were the most uncomfortable areas during cystoscopy. Postcystoscopic analgesics were requested by 12 of 45 patients in the lidocaine group, but only 6 of 46 of the plain-gel group (P = 0.103). When patients were asked if they would desire general anesthesia for better pain control in future examinations, five of the lidocaine group responded positively, while three of the plain-gel group said they would (P = 0.62). The cost of lidocaine gel is about thrice that of the plain gel. CONCLUSION: Using plain lubricant is cheaper and faster than applying lidocaine gel. The pain score, pain grade, postcystoscopic analgesic requirement, and anesthetics requested for the next cystoscopy were similar in the two groups. However, a larger investigation will be needed to achieve more significant statistical power.

Aged↗

PubMedDate not supplied

Comparison of analgesic and anti-inflammatory activity of meloxicam gel with diclofenac and piroxicam gels in animal models: pharmacokinetic parameters after topical application.

Meloxicam, a non-steroidal anti-inflammatory drug, is a preferential inhibitor of cyclooxygenase-2 and has demonstrated potent analgesic and anti-inflammatory activity after oral administration. The present work was carried out to elucidate the anti-inflammatory and analgesic activity of a newer topical gel formulation of meloxicam (1% w/w gel) and compare it with 0.5% w/w piroxicam and 1% w/w diclofenac gels in experimental animal models. The study was also extended to determine the pharmacokinetic profile of a newer formulation of meloxicam gel after topical application on depilated skin of rats. The anti-inflammatory activities of meloxicam, piroxicam and diclofenac gels were compared using carrageenan-induced acute paw oedema and complete Freund's adjuvant-induced chronic paw oedema in rats. Meloxicam gel showed increased protection against inflammation as compared to piroxicam and diclofenac gels. Acetic acid-induced writhing and formalin-induced phase I and phase II pain models were used to compare their analgesic activity. Meloxicam gel showed significant protection in formalin-induced phase II pain whereas its analgesic activity was less as compared to diclofenac and piroxicam gels in writhing test and formalin-induced phase I pain. The pharmacokinetic studies showed peak plasma drug concentration (C(max)) of 48.48 +/- 6.57 microg/ml at 2 h (T(max)) after topical application of 500 mg of meloxicam gel formulation. The area under the curve as calculated from 0 to 6 h was found to be 114.18 +/- 4.23 and 194.13 +/- 3.78 microg x h/ml for 0 to infinity. The results indicate that topical preparation of meloxicam could be an effective alternative to diclofenac and piroxicam gels in inflammatory conditions and its associated pain with the possibility of less systemic side-effects.

Administration, Topical↗

PubMed2002

A comparison of intramuscular temperatures during ultrasound treatments with coupling gel or gel pads.

STUDY DESIGN: A repeated-measures design was used. The independent variable was ultrasound coupling medium with 2 levels: gel pad and traditional gel. The dependent variable was peak intramuscular (IM) tissue temperature. OBJECTIVE: To compare changes in IM temperature during similar ultrasound treatments with 2 different coupling media. BACKGROUND: Gel pads are gaining popularity as an ultrasound coupling medium. Intramuscular temperatures during ultrasound with gel pads and standard gel have not been compared. METHODS AND MEASURES: Subjects were 13 student volunteers (21.3 +/- 1.4 years of age) without lower-extremity pathology. Ultrasound treatments were administered in a laboratory on two separate occasions 48 hours apart, each with a different coupling medium (standard ultrasound gel or gel pad). One-MHz continuous ultrasound was administered for 7 minutes at 1.5 W/cm2 with the transducer head moving 3 to 4 cm/s over an area approximately twice the size of the transducer head. Tissue temperature was measured every 10 seconds using implantable thermocouples inserted at a 3-cm depth to the surface of the right medial calf. Data were analyzed using an ANCOVA with pretreatment temperature as the covariate. RESULTS: Tissue temperatures increased during both treatments, with the mean and standard deviation peak temperature during the gel pad treatment reaching 39.40 +/- 1.5 degrees C compared to 39.20 +/- 2.4 degrees C during the normal gel treatment. Statistical analysis revealed no difference in temperature between ultrasound treatments using gel and those performed using gel pads. CONCLUSIONS: Because temperature changes were similar with both treatments, we conclude that these coupling methods are equivalent under the ultrasound application parameters tested.

Adult↗

PubMed2005

The efficacy and safety of adapalene gel 0.3% in the treatment of acne vulgaris: A randomized, multicenter, investigator-blinded, controlled comparison study versus adapalene gel 0.1% and vehicle.

A randomized, multicenter, investigator-blinded, active- and vehicle-controlled study was conducted to evaluate the efficacy and safety of adapalene gel 0.3% versus adapalene gel 0.1% and the corresponding gel vehicle. Subjects were assigned randomly to receive either adapalene gel 0.3%, adapalene gel 0.1%, or vehicle once daily for 12 weeks. A total of 214 subjects with moderate to moderately severe acne vulgaris were enrolled, and 85% of subjects completed the study. Adapalene gel 0.3% was significantly superior to adapalene gel 0.1% in total and noninflammatory lesion counts and in global severity score (P < .05 for all). A concentration-dependent increase in clinical benefit for all efficacy assessments was observed. As expected, there were also statistically significant differences in all efficacy parameters in the adapalene gel 0.3% group relative to the vehicle group (P < .001 for all). Treatment-related adverse events were mostly mild-to-moderate and similar between active groups. The results of this study show that adapalene gel 0.3% was superior to adapalene gel 0.1% and vehicle in the treatment of moderate to moderately severe acne while retaining a similar safety and tolerability profile to adapalene 0.1% gel.

Acne Vulgaris↗

PubMed1983

Comparison of the growth of normal and neoplastic mouse mammary cells on plastic, on collagen gels and in collagen gels.

The growth of normal and neoplastic mouse mammary cells was compared in primary cultures on plastic, on rat tail collagen gels and in rat tail collagen gels. Cells on plastic grew for the first few days, then stopped with only a 1- to 3-fold increase in cell number after 2 weeks in culture. Cells grown on or in collagen gels grew continuously over the 2-week culture period with up to 10-fold increase in cell number for cultures on collagen gels and a 20-fold increase for cells embedded in collagen gels. The difference in growth rates between cells grown in collagen gel and those grown on collagen gels was due, in part, to the three-dimensional growth of the colonies in collagen gel their two-dimensional growth on collagen gel. Cells grown on and in collagen gel can produce an electron-dense basal lamina-like structure which is associated with collagen IV and laminin as judged by immunofluorescence. Cells grown on plastic do not form this structure. Cis-OH-proline blocks the production of collagen and inhibits the growth of the cultured cells indicating collagen production to be involved in growth. Rat tail collagen gels are a superior substratum for the growth of mouse mammary cells and this may be related to the cells' ability to form a collagen IV-containing basal lamina-like structure.

Animals↗

PubMed2006

A novel gel formation method, microstructure and mechanical properties of calcium polysaccharide gel films.

Hydrophilic gels, formed by the interaction of calcium ions with either sodium alginate or potassium pectinate, can be deposited as a wet coating on to the surface of drug loaded pellets. If the coated pellets are dried, they could be dispensed to a patient in a capsule for oral delivery of the active drug. In contact with the aqueous fluids of the gastrointestinal tract, the gel coat will rehydrate, swell and will sustain the release of active drug from the core. In order to facilitate the development and refinement of this novel coated system, it is beneficial to have a method that can produce free gel films in a manner that closely mimics the way the gel coat is formed and deposited on the pellet surface. Traditional film producing methods would involve the spraying or depositing (by evaporation) the gel forming polysaccharide on to an inert surface, drying it and then exposing the dry film to a solution containing calcium ions. Because the film is dry before it is gelled, it is fundamentally different to the wet gel coats that are deposited on to the pellets. We have developed a method to produce wet gel films and have evaluated different manufacturing conditions in order to optimize the quality of the completed gel film. Additionally, we have used these films to assess the effect that the type of polysaccharide and the environmental conditions experienced during rehydration (pH and ionic strength) has on the mechanical properties and the microscopic morphology of the gel. Irrespective of the rehydration medium, the calcium pectinate gel films were softer, weaker and more porous, than the calcium alginate films. Although calcium alginate gels that were rehydrated in 0.1M NaCl were porous, the same films rehydrated in either water, simulated gastric fluid USP (without pepsin) or 0.1M HCl were stronger and much more dense microscopically. Furthermore, of the four different alginates that were evaluated, those with a high content of guluronic acid saccharides were the strongest but most brittle when rehydrated in water.

Alginates↗

PubMed1988

Mucus glycoprotein gels. Role of glycoprotein polymeric structure and carbohydrate side-chains in gel-formation.

The structure of mucus glycoprotein gels from the pig gastrointestinal tract was investigated by mechanical spectroscopy. Gastric, duodenal, and colonic mucus had the same mechanical profile, characteristic of a viscoelastic gel. The gel structure collapsed on destruction of the polymeric structure of the component glycoprotein by reduction with 0.2M mercaptoethanol or after proteolysis with papain. The progressive weakening of mechanical properties and the decrease in polymeric glycoprotein content were measured as functions of time of reduction. A linear correlation was obtained between the gel quality [defined by tan delta, the ratio of the loss modulus (G'') to the storage modulus (G')] and the proportion of polymeric to subunit glycoprotein in the mucus. Purified mucus glycoprotein, at the same concentration as that in native mucus, resulted in a gel with mechanical properties no different from those of the respective native secretion, demonstrating that the glycoprotein alone could reproduce the gel-forming properties of mucus. After proteolytic digestion, all native secretions and reconstituted mucus showed an absence of Newtonian behaviour in the frequency dependence of dynamic viscosity at low frequencies. This provided evidence that the noncovalent interactions, characteristic of the native gel matrix, were still present after proteolytic digestion when the nonglycosylated protein core accessible to proteinases had been removed. These results were interpreted to show (a) a common mechanism for gel-formation in gastric, duodenal, and colonic mucus; (b) that the polymeric structure of mucus glycoproteins confers the three-dimensional structure necessary for formation of the gel network; and (c) that noncovalent interactions which arise between the glycoprotein molecules by relatively stable interdigitation of the carbohydrate side-chains are involved in formation of the gel network.

Animals↗

PubMed1970

Unified theory for gel electrophoresis and gel filtration.

Unified theory for gel electrophoresis and gel filtration: The behavior of macromolecules in gel filtration and gel electrophoresis may be predicted from Ogston's model for a random meshwork of fibers. This model has been generalized to apply to nonspherical molecules and to several gel types. The model provides equations for inter-relationships between mobility, partition coefficient, gel concentration, and molecular radius; it gives a non-Gaussian distribution of pore sizes as a function of gel concentration. The theory defines conditions for optimal separation and optimal resolution in gel filtration and gel electrophoresis. The difference in resolving power between the two fractionation methods is accounted for by the fact that gel filtration is a form of partition chromatography.

Chromatography, Gel↗

PubMed2002

Radiosurgery for residual or recurrent nonfunctioning pituitary adenoma.

OBJECT: Nonfunctioning pituitary adenomas comprise approximately 30% of all pituitary tumors. The purpose of this retrospective study is to evaluate the efficacy and role of gamma knife radiosurgery (GKS) in the management of residual or recurrent nonfunctioning pituitary adenomas. METHODS: A review was conducted of the data obtained in 42 patients who underwent adjuvant GKS at the University of Pittsburgh between 1987 and 2001. Prior treatments included transsphenoidal resection, craniotomy and resection, or conventional radiotherapy. Endocrinological, ophthalmological, and radiological responses were evaluated. The duration of follow-up review varied from 6 to 102 months (mean 31.2 months). Fifteen patients were observed for more than 40 months. The mean radiation dose to the tumor margin was 16 Gy. Conformal radiosurgery planning was used to restrict the dose to the optic nerve and chiasm. Tumor control after GKS was achieved in 100% of patients with microadenomas and 97% of patients with macroadenomas. Gamma knife radiosurgery was equally effective in controlling adenomas with cavernous sinus invasion and suprasellar extension. No patient developed a new endocrinological deficiency following GKS. One patient's tumor enlarged with an associated decline in visual function. Another patient experienced a deterioration of visual fields despite a decrease in tumor size. CONCLUSIONS: Gamma knife radiosurgery can achieve tumor control in virtually all residual or recurrent nonfunctioning pituitary adenomas. Dose sparing facilitates tumor management even when the adenoma is close to the optic apparatus or invades the cavernous sinus.

Adenoma↗