首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
A dispersed particle gel (DPG) was successfully prepared from a polymer gel at room temperature. The polymer gel system, morphology, viscosity changes, size distribution, and zeta potential of DPG particles were investigated. The results showed that zirconium gel systems with different strengths can be cross-linked within 2.5 h at low temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) results showed that the particles were polygonal particles with nano-size distribution. According to the viscosity changes, the whole preparation process can be divided into two major stages: the bulk gel cross-linking reaction period and the DPG particle preparation period. A polymer gel with a 3-dimensional network was formed in the bulk gel cross-linking reaction period whereas shearing force and frictional force were the main driving forces for the preparation of DPG particles, and thus affected the morphology of DPG particles. High shearing force and frictional force reduced the particle size distribution, and then decreased the zeta potential (absolute value). The whole preparation process could be completed within 3 h at room temperature. It could be an efficient and energy-saving technology for preparation of DPG particles.  相似文献   

2.
Summary To develop a strategy for extended primary culture of human hepatocytes, we placed human hepatocytes between two layers of collagen gel, called a “collagen gel sandwich.” Maintenance of hepatocellular functions in this system was compared with that of identical hepatocyte preparations cultured on dry-collagen coated dishes or co-cultured with rat liver epithelial cells. Human hepatocytes in a collagen gel sandwich (five separate cultures) survived for more than 4 wk, with the longest period of culture being 78 d. They maintained polygonal morphology with bile canaliculuslike structures and high levels of albumin secretion throughout the period of culture. In contrast, hepatocytes on dry-collagen became feature-less, and albumin secretion could not be detected after 14 d of culture. This loss of albumin secretion was partially recovered by overlaying one layer of collagen gel. Ethoxyresorufin O-deethylase activity, associated with cytochrome P450 1A2, was detected basally up to 29 d in collagen gel sandwich culture. These activities were induced four- to eightfold after induction with dibenz(a,h)anthracene. Cocultures also maintained basal activity up to 29 d. However, their inducibility was lower than that of hepatocytes in collagen gel sandwich. No ethoxyresorufin O-deethylase activity was detected in hepatocytes cultured on dry-collagen at 7 d. Thus, the collagen gel sandwich system preserves differentiated morphology and functions of human hepatocytes in primary culture for a prolonged period of time. This system is a promising model for studying human hepatocellular function, including protein synthesis and drug metabolism in vitro.  相似文献   

3.
Yeast protoplasts may regenerate the cell wall and revert to cells if immobilized in a 2%–5% Ca-alginate gel and cultured in an osmotically stabilized medium. The method of protoplast immobilization and subsequent isolation from the gel is described in detail. The reversion yield is dependent of the actual gel concentration, gel shape (beads vs. sheets) and of a medium molarity, and it may be up to 90%. The morphology of the cell wall regeneration and morphology of reversion to the cell forms correspond to protoplast development in gelatin or agar gels.  相似文献   

4.
Chitin is known to be natural polymer and it is non-toxic, biodegradable and biocompatible. The chitin-g-poly(epsilon-caprolactone) (chitin-g-PCL) copolymer was prepared by the ring-opening polymerization of epsilon-caprolactone onto chitin gel in the presence of tin(II) 2-ethylhexanoate catalyst by bulk polymerization method under homogeneous system. The prepared copolymer were characterized by FT-IR, (13)C NMR, thermogravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM), solubility and X-ray diffraction (XRD). The degree of substitution of chitin-g-PCL copolymer was found to be 0.48. The TGA analysis showed that chitin-g-PCL was slightly less thermal stability than original chitin. It was due to the grafting of PCL reduced the crystalline structure of chitin. DTA analysis of chitin-g-PCL showed the two exothermic peaks between 300 and 400 degrees C. The first peak at 342 degrees C was due to chitin peak and the second peak was due to PCL. These results suggested that chitin and PCL chains were mixed well at a molecular level. The XRD pattern analysis of chitin-g-PCL showed a weak and broader peak, which demonstrated that the conjugation of PCL with chitin suppressed the crystallization of both chitin and PCL to some extent. The SEM studies showed that the chitin gel seems have a smooth surface morphology, but the chitin-g-PCL showed slightly rough morphology due to the grafting of PCL into chitin. The surface morphology studies also confirmed the grafting reaction.  相似文献   

5.
Egg-jelly is composed of a network of fibrous components and contains substances regulating the sperm-egg interaction. Many studies on the latter have been conducted, whereas the role of the egg-jelly structure in fertilization has not yet been fully assessed. In this study, we examined the fertilization efficiency in the presence and absence of the structure around the egg of the newt, Cynops pyrrhogaster, using a gelatin gel system. Although de-jellied eggs of C. pyrrhogaster can be fertilized with an adequate number of sperm, the fertilization rate was dramatically increased through the use of the gelatin gel. Sperm showed forward motility with straight morphology in the gel, whereas they swam in circles in solution. This result indicates that the gel structure is significant for sperm guidance to the egg surface, and its presence raises the fertilization efficiency in C. pyrrhogaster. When sperm were entangled in the gel structure, they were immediately folded and never showed any forward motility. Sperm with zigzag morphology were observed in the gelatin gel as well as in the egg-jelly, indicating the elimination of sperm by the gel structure. The effect of sperm elimination on successful fertilization was estimated using gelatin gels of different thickness. Though the variation did not affect the fertilization rate, the rate of normal development gradually increased in the thicker gels. This result indicates that sperm elimination in egg-jelly can function in the fertilization system. The roles of sperm guidance and sperm elimination under the physiological condition of internal fertilization of the newt are discussed.  相似文献   

6.
Caprolactonic poloxamer analog: PEG-PCL-PEG   总被引:3,自引:0,他引:3  
The aqueous solution of poly(ethylene glycol)-poly(caprolactone)-poly(ethylene glycol) (PEG-PCL-PEG) triblock copolymers (> 15. wt. %) undergoing "clear sol-gel-turbid sol" transition as the temperature increases from 20 to 60 degrees C has been developed. Light scattering and 13C NMR study suggested that the transition mechanisms are the micellar aggregation for the clear sol to gel transition (lower transition), whereas the increase in PCL molecular motion for gel to turbid sol transition (upper transition). In contrast to the previous thermogelling biodegradable polymers with a sticky paste morphology, the powder form of the PEG-PCL-PEG triblock copolymers makes it easy to handle and allows fast dissolution in water. Therefore, the lyophilization into a powder form followed by facile reconstitution was possible. This system is believed to be promising for drug delivery, cell therapy, and tissue engineering.  相似文献   

7.
The effect of dihydric alcohol (nonsolvent) addition on the rheological and microstructural behavior of cellulose acetate (CA) in a ternary CA, N,N-dimethylacetamide (DMA), nonsolvent system was investigated. Increasing the dihydric alcohol concentration led to enhanced steady shear viscosity and dynamic viscoelastic properties that were dependent on CA concentration. Changing the dihydric alcohol from 1,2-ethanediol to 1,4-butanediol and 1,6-hexanediol increased the moduli and decreased the concentration of nonsolvent at which the sol-gel transition occurred. At 10 wt % CA concentration the modulus and gel morphology of the 1,2-ethanediol and 1,4-butanediol systems were quite similar and distinctly different from that of 1,6-hexanediol. In the former, the gel morphologies were more heterogeneous, evident of more extensive coarsening, and likely obtained via nucleation and growth and spinoidal decomposition of off-critical mixtures. The latter exhibited more uniform dense network morphology, indicative of a spinoidal decomposition of near-critical mixtures. The gels were fractal in nature and exhibited different fractal dimensions in-line with the observed differences in microstructure; D ~ 1.87 ± 0.02 (1,2-ethanediol and 1,4-butanediol) and D ~ 1.97 ± 0.02 (1,6-hexanediol). However, at 15 wt % CA content, the gels exhibited more similar viscoelastic behavior and gel microstructures; D ~ 1.97 ± 0.02 for all three dihydric alcohol systems.  相似文献   

8.
The morphological and cellular changes that occur with differentiation and development of a lentoid structure from cultured mouse lens epithelial cells have been found to be dependent on the presence of lens capsule in association with the cells. The development of the 'lentoid body' is a multiphase process involving cell replication, synthesis of mucosubstances and a basement collagen membrane, cell aggregation and differentiation. Stage-specific synthesis of lens proteins confirms that the genes regulating normal differentiation in vivo are operating in the in vitro system. The hydrated collagen gel studies described in this report demonstrate that the cuboidal morphology and apical-basal polarity of the lens epithelial cells are dependent on their relationship with the lens capsule. Following a replicative phase the cells assume a mesenchyme-like morphology and migrate into the gel. Trypsinized cells freed from the lens capsule replicate but form colonies on the surface of the gel. The implications of these results are discussed with respect to previous observations made on normal lens development and the abnormalities associated with the congenital cataractous embryonic lens.  相似文献   

9.
We studied the effect of lysophosphatidic acid (LPA) on collagen gel contraction by cultured rat hepatic stellate cells (HSCs) in association with the function of Rho-kinase, one of the target molecules of small GTPase Rho. Binding studies showed a single class-binding site of LPA on HSCs. LPA enhanced the contraction of a collagen lattice seeded with HSCs. LPA increased the number of HSCs with polygonal morphology that contained actin stress fibers, and enhanced the phosphorylation of myosin light chain and the assembly of focal adhesion kinase and RhoA around fibronectin-coated beads seeded on HSCs. The electric cell-substrate impedance sensor system showed that LPA enhanced adhesion of HSC to extracellular substrate. All the effects of LPA were suppressed by Y-27632, Rho-kinase inhibitor. These data support the notion that LPA is involved in modulating HSC morphology, its attachment to surrounding extracellular matrix and its contraction by a mechanism involving Rho-kinase.  相似文献   

10.
Erythrocyte membranes from several species were prepared by three different methods of hypotonic hemolysis and examined for variations in protein and glycoprotein content by acrylamide gel electrophoresis in sodium dodecyl sulfate. Significant variations were noted in morphology of the membranes prepared by the different methods without attendant variations in protein patterns of the major membrane proteins for most cases observed, which show a similar pattern of nine common bands for all of the species observed. The significant difference in protein pattern which was noted was attributed to proteolytic digestion of membranes which were fragmented during preparation. Failure to remove white blood cells from membrane preparations was shown to be a significant source of the problem with proteolytic digestion. Glycoproteins were analyzed by acrylamide gel electrophoresis or by column chromatography. Each species appears to have a different major glycoprotein (or group of closely related glycoproteins). Molecular weights of glycoproteins calculated from acrylamide gel electrophoresis were found to vary with the percentage of acrylamide in the gel, indicating that these proteins do not behave in a normal fashion in this electrophoresis system. The molecular weight calculated from gel filtration data for the human membrane glycoproteins (26,000) was quite disparate from those calculated from gel electrophoresis (88,000 to 62,000 in 5 to 10% gels).  相似文献   

11.
α-Actinin-4 (ACTN4), a key regulator of the actin cytoskeleton, is up-regulated in melanoma, though its role in melanoma remains speculative. We have discovered that in WM1158, a highly aggressive melanoma cell line, down-regulation of ACTN4 by shRNA induces a collagen I-dependent amoeboidal-to-mesenchymal transition. Re-expression of low levels of WT ACTN4 but not similar expression levels of ACTN1 successfully restores the amoeboidal morphology and limits collagen I gel compaction. A truncated ACTN4 mutant 1–890, which lacks the C-terminal tail, fails to rescue the amoeboidal morphology and to compact collagen I gel. Interestingly, in three-dimensional collagen I gels, ACTN4 KD cells are more polarized compared with cells in which scrambled shRNA is expressed. Surprisingly, ACTN4 KD cells migrate faster than the ones expressing the scrambled shRNA on a collagen I gel (two-dimensional) although these two cell lines migrate similarly on tissue culture. Most importantly, down-regulation of ACTN4 significantly reduced invasion of WM1158 cells into the three-dimensional collagen I gel, a representative of the dermis. Taken together, these findings suggest that ACTN4 plays an important role in maintaining the amoeboidal morphology of invasive melanoma and thus promoting dissemination through collagen-rich matrices.  相似文献   

12.
Human proximal tubular (PT) epithelial cells were isolated from urine and monoclonally cultured as monolayers for 1 wk, after which they were subcultured between two layers of collagen gel, designated a "collagen gel sandwich." Under these culture conditions, PT cells formed three-dimensional tubular structures exhibiting distinct polarized cell morphology. Scanning and transmission electron microscopic studies showed that they bore numerous microvilli at the apical surface and that they closely contacted the collagen gel at the basal surface. These studies indicate that PT cells exfoliated in urine still exhibit the potential to proliferate and form organized structures mimicking in vivo tubules. Because of the current lack of useful culture systems for human tubular epithelial cells originating from kidney tissue, we suggest that this unique culture system using voided PT cells in urine could open up new avenues to study not only the mechanisms of morphogenesis but also the physiology of human PT cells.  相似文献   

13.
Ceramide is an important bioactive sphingolipid involved in a variety of biological processes. The mechanisms by which ceramide regulates biological events are not fully understood, but may involve alterations in the biophysical properties of membranes. We now examine the properties of ceramide with different acyl chains including long chain (C16- and C18-), very long chain (C24-) and unsaturated (C18:1- and C24:1-) ceramides, in phosphatidylcholine model membranes. Our results show that i) saturated ceramides have a stronger impact on the fluid membrane, increasing its order and promoting gel/fluid phase separation, while their unsaturated counterparts have a lower (C24:1-) or no (C18:1-) ability to form gel domains at 37°C; ii) differences between saturated species are smaller and are mainly related to the morphology and size of the gel domains, and iii) very long chain ceramides form tubular structures likely due to their ability to form interdigitated phases. These results suggest that generation of different ceramide species in cell membranes has a distinct biophysical impact with acyl chain saturation dictating membrane lateral organization, and chain asymmetry governing interdigitation and membrane morphology.  相似文献   

14.
Despite claims made in the literature that polysaccharides maintain a substantially aggregated morphology in the form of "gel particulates" or "gel islands" at a high sugar environment, results of differential scanning calorimetry (DSC) discussed now demonstrate that extensive macromolecular order is not thermodynamically stable. Gelatin, on the other hand, appears to demix from the sugar-rich domains, which promote chain association rather than inhibiting it. DSC evidence is supported by previously published transmission electron microscopy (TEM) work and mechanical analysis.  相似文献   

15.
The objective of the present investigation was to formulate solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) for improving the dermal delivery of a local anesthetic agent lidocaine (LID). SLN and NLC were characterized for particle size distribution, polydispersity index, entrapment efficiency, X-ray powder diffraction pattern (XRD), thermal behavior by differential scanning colorimeter (DSC) and surface morphology by transmission electron microscopy (TEM). LID-loaded SLN and NLC were formulated into hydrogels for topical application. The in vitro permeation profiles of LID SLN gel, LID NLC gel, and a marketed LID formulation (Xylocaine® gel) were evaluated by using guinea pig skin. The in vivo efficacy of LID SLN gel, LID NLC gel, and a marketed LID formulation (Xylocaine® gel) gel was evaluated on guinea pig using pinprick test. LID SLN showed a particle size of 78.1 nm with a polydispersity index of 0.556, whereas LID NLC showed a particle size of 72.8 nm with a polydispersity index of 0.463. The entrapment efficiency of LID in both SLN and NLC was 97% and 95.9%, respectively. The TEM studies revealed the almost spherical nature of LID SLN and NLC formulations. The XRD and DSC studies of LID SLN suggested amorphization of drug in the carrier system. The SLN formulation was stable with respect to particle size, polydispersity, and entrapment efficiency for 6 months at 40°C/75% relative humidity (RH). Negligible leakage was observed for the NLC formulation when stored for 1 month at 40°C/75% RH. In vitro permeation studies indicated that LID SLN gel and LID NLC gel significantly sustained the LID release compared to that of Xylocaine® gel. The in vivo efficacy results supported the results of the in vitro permeation studies wherein the LID SLN gel and LID NLC gel resulted in fivefold and sixfold increase in duration of anesthesia, respectively, compared to that of Xylocaine® gel.  相似文献   

16.
Aranha CC  Gupta SM  Reddy KV 《Cytokine》2008,43(1):63-70
Topical microbicides is an emerging female controlled strategy for preventing the acquisition and transmission of STIs/HIV infections. Since they are intended for repeated vaginal and/or rectal use it is essential to validate their safety. Nisin, a naturally occurring contraceptive antimicrobial peptide (AMP) is currently the focus of clinical trials. The present in vitro vaginal tissue explants culture studies revealed that Nisin did not effect vaginal cell viability analyzed at 15, 30, 45 and 60min following treatment with different concentrations of Nisin gel prepared in 1% polycarbophil gel (30.3, 60.6, 121.2, 242.4 and 484.8 microM/g tissue) and SDS (0.35, 0.70, 1.4, 2.8 and 5.6 microM/g tissue) gels compared to placebo gel treated groups. The levels of various pro-inflammatory (IL-6, IL-8 and TNF-alpha,) and immuno-regulatory cytokines (IL-10 and GM-CSF) in the explant culture supernatants of the Nisin treated cells were unaffected. Repeated intravaginal application of high dose of Nisin gel (15,150 microM/day/14 days) on cervicovaginal epithelium was evaluated in rabbits and the results were compared with SDS treated (56 microM) and 1% polycarbophil gel (placebo) groups. We examined vaginal cell morphology, structural integrity of vaginal epithelium and local production of cytokines (PICs) in the cervicovaginal lavage (CVL) of Nisin treated animals and compared with placebo and SDS treated groups. The results demonstrated no treatment related abnormalities either in the vaginal cell morphology or structural abnormalities in the mucosal epithelium. There was no change in the cytokine levels in cervicovaginal lavage (CVL) compared to SDS gel treated animals indicating Nisin gel did not induce irritation and/or inflammation in the vaginal epithelium. CVL cytokine levels were in accordance with immunohistochemical (IHC) localization of cytokines and flow cytometric evaluation of CD45 immune cell population in cervicovaginal epithelium. The levels of cytokines in the CVLs appear to be sensitive indicators in identifying and/or screening out suitable candidate microbicides before they enter phase-1 trials. In conclusion, the lack of vaginal toxicity of Nisin gel means that it has clinical potential as a safe, prophylactic contraceptive in addition to its antimicrobial activities to curb sexual transmission of HIV in human.  相似文献   

17.
The effect of the frequently used antibiotic sulfadiazine (SD) was studied on a bacteria membrane mimetic model system by using differential scanning calorimetric (DSC), small- and wide-angle X-ray scattering (SWAXS) and freeze-fracture methods. The membrane model system consisted of dipalmitoylphosphatidylethanolamine (DPPE, 0.8 molar ratio) and dipalmitoylphosphatidylglycerol (DPPG, 0.2 molar ratio). The SD molar ratio (relative to the lipids) was varied between 10(-3) and 1. In the presence of SD, two transitions between the gel and liquid crystalline phases appear at 60.5 degrees C and about at 65 degrees C. In the temperature domain of the gel phase, the subcell of the chain packing is strongly temperature dependent indicating the increased dominance of the hydration forces during the first transition and the location of SD molecules in the neighbourhood of the polar lipid head groups. The second transition is accompanied by the changes in the nanometer-scale layer arrangements observed by SAXS and in the mum-scale morphology observed by freeze-fracture. Above the temperature of the second transition, the SD-induced metastable structures undergo further formations to produce a more homogeneous state favoured by the geometrical packing of the cylindrical-shaped lipid molecules.  相似文献   

18.
A comparative study of the polymorphism exhibited by the polymerizable, tubule-forming phospholipid 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3- phosphocholine (DC23PC) and its saturated analog 1,2-ditricosanoyl-sn-glycero-3-phosphocholine (DTPC) in aqueous suspension is reported. Differential scanning calorimetry (DSC), as well as freeze-fracture electron microscopy and Raman spectroscopy, have been used to study the influence on phase behavior of rigid diacetylene groups in the fatty acyl chains of a phosphatidylcholine. DTPC large multilamellar vesicle (MLV) and small unilamellar vesicle (SUV) suspensions were found to retain liposome morphology after chain crystallization had occurred. In marked contrast, diacetylenic DC23PC suspensions do not maintain liposomal morphology in converting to the low temperature phase. Large MLVs of DC23PC with outer diameters in excess of 1 micron convert to a gel phase with cylindrical or tubular morphology at 38 degrees C, just a few degrees below the lipid's chain melting temperature (TM(H), i.e. temperature of an endothermic event observed during a heating scan) of 43.1 degrees C. Unlike the large MLVs, small MLVs or SUVs of DC23PC, with diameters of 0.4 +/- 0.3 micron and 0.04 +/- 0.02 micron, respectively, exhibit metastability in the liquid-crystalline state for several tens of degrees below the chain melting temperature prior to converting to a gel phase which, by electron microscopy, manifests itself as extended multilamellar sheets. Raman data collected at TM(H) -40 degrees C demonstrate that the gel state formed by DC23PC is very highly ordered relative to that of DTPC, suggesting that special chain packing requirements are responsible for the novel phase behavior of DC23PC.  相似文献   

19.
The cytoskeleton is important in the maintenance of cellular morphology and differentiated function in a number of cell types, including hepatocytes. In this study, adult rat hepatocytes sandwiched between two layers of collagen gel were compared to cells cultured on a single collagen gel for differences in the organization and expression of the cytoskeletal proteins actin and tubulin. Hepatocytes cultured between two layers of hydrated rat tail tendon collagen (sandwich gel) morphologically resembled cells in intact liver for several weeks. Actin filaments (F-actin) in these hepatocytes were concentrated under the plasma membrane in regions of cell-cell contact. In contrast, hepatocytes cultured on a single collagen gel were flattened and motile and had F-actin containing stress fibers. This was accompanied by a severalfold increase in actin mRNA. Microtubules formed an interwoven network in hepatocytes cultured in a sandwich gel, but in single gel cultures they formed long parallel arrays extending out to the cell periphery. Tubulin mRNA was severalfold greater in hepatocytes cultured on a single gel. Fibronectin and laminin staining were greater in single gel cultures, and these proteins were concentrated in fibrils radiating from the cell periphery. Overlaying a second collagen gel onto hepatocytes that had been cultured on a single gel (double gel rescue) reversed cell spreading and reduced stress fibers. Double gel rescue also resulted in a decrease in actin and tubulin mRNA to levels present in sandwich gel cultures and freshly isolated hepatocytes. These results show that the configuration of the external matrix has a dynamic effect on cytoskeletal proteins in cultured rat hepatocytes.  相似文献   

20.
The aim of this study was to investigate the potential of surfactant-based nanovesicular system (spanlastics) for topical delivery of fenoprofen calcium (FPCa) to eliminate its oral gastrointestinal adverse effects. FPCa-loaded spanlastics were prepared by thin film hydration (TFH) technique according to a full factorial design to investigate the influence of formulation variables on the drug entrapment efficiency (%EE), particle size (PS), deformability index (DI), and the % drug released after 24 h through the cellulose membrane (Q24h) using Design-Expert® software. The optimized formula (composed of Span 60 and Tween 60 as an edge activator at weight ratio of 8: 2 in presence of Transcutol P as a cosolvent in the hydration media) exhibited the highest %EE (49.91 ± 2.60%), PS of 536.1 ± 17.14 nm, DI of 5.07 ± 0.06 g, and Q24h of 61.11 ± 2.70%; it was also characterized for morphology and physical stability. In vitro release study of FPCa-loaded spanlastic gel and conventional FPCa gel through a synthetic membrane and hairless rat skin were evaluated. The skin permeation study revealed that spanlastic gel exhibited both consistent and prolonged action. Finally, the % inhibition of carrageenan-induced rat paw edema of spanlastic gel was three times higher than the conventional FPCa gel after 24 h. In conclusion, spanlastic-based gel could be a great approach for improving topical delivery of fenoprofen calcium, providing both prolonged and enhanced anti-inflammatory activity in the treatment of arthritis.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号