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At least 865 records · Page 48Linked to original sources
PubMed2002

Improvement of the functions of osteoblasts seeded on modified poly(D,L-lactic acid) with poly(aspartic acid).

One of the challenges in the field of tissue engineering is the development of biomaterial/cell interactions. For the purposes of the present study, two molecular weights of poly(aspartic acid) (PASP) were used to modify poly(D,L-lactic acid) (PDLLA) films in order to enhance their cell affinity. The properties of the PDLLA-modified surfaces and the controls were investigated by water contact angle measurement and electron spectroscopy for chemical analysis (ESCA). These data reflect the change in the biocompatibility of modified PDLLA surfaces. Then rat osteoblasts were seeded onto these modified surfaces and on controls to examine their effects on cell adhesion and proliferation. Cell morphologies on these surfaces were studied by scanning electron microscopy (SEM), and cell viability was evaluated with a MTT assay. In addition, differentiated cell function was assessed by measuring alkaline phosphatase (ALP) activity. The results suggest that PASP-modified surfaces may enhance the interactions between osteoblasts and PDLLA films.

Alkaline Phosphatase↗
PubMed2002

Osteoblast culture on polished titanium disks modified with phosphonic acids.

Titanium is widely used in dental implants due to its suitable physical properties and its good biocompatibility. However, it is integrated into bone only passively, and the resulting fixation in the bone, which is necessary for the function, is mainly mechanical in nature. With the objective of increasing the chemical interaction between the implant and the bone tissue, several phosphonic acids were synthesized and grafted onto titanium disks. Here we report on the proliferation, differentiation, and protein production of rat osteoblastic cells (CRP10/30) on phosphonic-acid-modified titanium surfaces studied in vitro. No statistical differences were found in osteoblast proliferation among the phosphonic-acid-modified titanium, unmodified titanium, and tissue culture plastic (used as a positive control), indicating that the phosphonic acids used were not cytotoxic to the osteoblasts used. For all surfaces (modified or not), the alkaline phosphatase activity was at least as good as it was on tissue culture plastic. However, the total amount of protein, and especially the collagen type I synthesis, was sensitive to surface modification. On titanium modified with ethane-1,1,2-triphosphonic acid, the total amount of synthesized protein was significantly higher than it was on unmodified titanium surfaces. A significant increase (up to 16%) of collagen type I production was observed on titanium surfaces modified with this acid or with methylenediphosphonic acid compared to unmodified titanium surfaces.

Alkaline Phosphatase↗
PubMed2002

Surface modification of extrasynovial tendon by chemically modified hyaluronic acid coating.

We investigated a method for chemically binding hyaluronic acid (HA) to extrasynovial tendon and the effect of chemically modified HA on the gliding resistance of tendon. Canine peroneus longus (PL) tendons were immersed into one of three different solutions (saline, 1% HA, or 1% chemically modified HA) for 2 h. The gliding resistance of treated PL tendons was measured at 1, 5, 10, 20, 50, and 100 cycles in a saline bath. After treatment with unmodified HA and chemically modified HA, the gliding resistance of the PL tendons decreased significantly compared with the saline-treated tendons (p < 0.05), and this effect of the two HA treatments persisted through 10 cycles. For cycles 20-100, the gliding resistance of PL tendons treated with chemically modified HA remained significantly lower than that of tendons treated either with saline or unmodified HA (p < 0.01). The effect of paratenon removal on gliding resistance was neither statistically significant for repetitions beyond 10 cycles, nor was it an independent predictor of gliding resistance, as the effect (higher resistance after paratenon removal) was mainly seen in the saline-treated tendons. Chemically modified HA-treated extrasynovial tendons may improve gliding of tendon graft and reduce adhesion postoperatively, compared with traditional grafts.

Animals↗
PubMed1995

Surface-modified poly(methyl methacrylate) enhances adsorption and retains anticandidal activities of salivary histatin 5.

Denture-induced stomatitis is a common intraoral disease which is associated with high levels of Candida albicans adhesion to a denture surface. The aim of this study was to produce a surface-modified denture resin, which is usually manufactured from poly(methyl methacrylate) (PMMA), carrying an immobilized anticandidal protein. PMMA was modified by surface polymerization of methyl methacrylic acid to enhance adsorption of a potent candidacidal salivary protein, histatin 5. The modified PMMA showed higher surface adsorption and desorption of histatin 5 than the unmodified material. Because histatin 5 destabilizes C. albicans cell membranes and allows efflux of intracellular molecules, candidacidal activity was monitored by dye release from fungal cells. Adsorbed histatin 5 did not release dye from the yeast cells; however, dye was detected as histatin was desorbed from the surface. In an adhesion assay, modified PMMA decreased human submandibular-sublingual saliva (HSMSL) mediated adherence of yeast cells to the polymer. Precoating histatin 5 onto unmodified PMMA also abolished HSMSL-mediated adhesion. These experiments show that dental acrylic may be surface modified and loaded with histatin 5 as a means of controlled release of histatin 5 to an affected area. This surface modification may additionally reduce adhesion of C. albicans cells to the saliva-coated material.

Adsorption↗
PubMed2003

Interactions of corneal cells with transforming growth factor beta 2-modified poly dimethyl siloxane surfaces.

The downgrowth of corneal epithelial cells at the interface of an artificial cornea and the host eye tissue poses a significant problem to be overcome in developing a successful implant. As a means of inhibiting the proliferation of corneal epithelial cells on the stromal surface of the implant, we examined the immobilization of transforming growth factor beta-2 (TGF-beta2) via a bifunctional poly ethylene glycol (PEG) spacer to poly dimethyl siloxane (PDMS) surfaces. Growth factor immobilization was confirmed by modification with (125)I-labeled TGF-beta 2. The modified surfaces were also characterized by advancing water contact angles, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Although the amount of growth factor covalently bound to the surface was difficult to quantify apparently due to strong interactions between the growth factor and the PEG layer and high levels of adsorption, differences in the modified surfaces, suggestive of the presence of a significant amount of TGF-beta 2, were found. In vitro interactions of the modified surfaces with human corneal epithelial and stromal cells were examined. Growth factor surface concentrations as well as culture in the absence and presence of serum and other adhesive proteins were examined. Corneal stromal and epithelial cells cultured on the TGF-beta 2-modified surfaces consistently gave results opposite to those expected. Likely, the most notable and surprising result was the almost complete lack of adhesion of the stromal cells, with coverage averaging between 3 and 5%. In comparison, corneal epithelial cell growth appeared to be promoted by the presence of the immobilized growth factor, with cell coverage averaging 50-60% at 7 days of culture. A TGF-beta 2 concentration effect was noted with both cell types in the absence of serum, with increases in the coverage at higher TGF-beta 2 concentrations. The observed cell growth appeared to be the result of interactions between the cells and active growth factor, because the addition of anti-TGF-beta 2 to the culture medium reduced cell coverage to levels similar to those noted on control surfaces. Therefore, although TGF-beta 2-modified surfaces may not be suitable as corneal epithelial cell inhibiting surfaces, interactions of surface immobilized growth factor and corneal cells are complex and should be further examined.

Biocompatible Materials↗
PubMed2005

Gene expression in tissue associated with extracellular matrix modified ePTFE.

Previous studies have established that surface modification of ePTFE with extracellular matrix molecules promotes vascularization within and around the implanted material. To understand the molecular basis of this tissue response to modified ePTFE, we analyzed large-scale gene expression in nonmodified and extracellular matrix-modified ePTFE-associated healing. Using a microarray containing 15,000 unique mouse cDNAs and an ANOVA-based analysis, we identified 789 genes related to cell signaling, inflammation, matrix remodeling, and proliferation that were differentially expressed across time, between modifications, or both. Genes were clustered based upon similarity in gene expression, producing 7 unique temporal super-patterns of expression. The clustered data revealed 3 general expression patterns unique to tissue surrounding the nonmodified ePTFE, while 6 unique expression patterns were associated with extracellular matrix-modified ePTFE. The more diverse expression patterns associated with extracellular matrix-modified ePTFE suggests that the tissue surrounding the extracellular matrix-modified ePTFE is more dynamic in terms of transcriptional activity. Taken together, these clusters serve as a "genetic fingerprint" for tissue healing in response to a specific material or material modification. Use of these genetic profiles will aid in the pursuit of improved device biocompatibility and enhanced material function.

Animals↗
PubMed2005

Evaluation of modifying collagen matrix with RGD peptide through periodate oxidation.

The aim of the study is to evaluate the effect of modifying collagen matrices with Arg-Gly-Asp (RGD) peptide through periodate oxidation. The collagen matrices were modified with RGD peptide, by periodate activation. The modified collagen matrices and unmodified matrices were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and electron spectroscopy for chemical analysis (ESCA). Mesenchymal stem cells (MSCs) were used to evaluate the cell compatibility of collagen matrices. In terms of cell growth, the MSCs attached much better on the modified matrix than on the unmodified one. But there was no significant difference between two groups regarding the MSC proliferation. Compared to the unmodified matrices, the mechanical strength of the modified matrix decreased sharply, and its 3D structure was destroyed. Introducing specific RGD receptor-mediated adhesion sites on matrices obviously enhanced the MSC adhesion on collagen matrices, but the coupled method of periodate oxidation would likely result in the declination of the mechanical strength of the matrix, as well as the destruction of the matrix structure. This would affect the cell growth on the matrix, and decrease the histocompatibility of the matrices.

Absorption↗
PubMed2006

Modified aminosilane substrates to evaluate osteoblast attachment, growth, and gene expression in vitro.

Bone cell-substrate interactions are important to understand in the design, selection, and surface modification of bone implants. To gain insight into such interactions, substrates designed with surface species approximating the physiological environment of bone matrix were studied. Osteoblasts (Ob) grown on three such surfaces were used to evaluate cell-substrate effects on attachment, growth, and gene expression as compared with controls. Initial surface preparation consisted of coating glass slides with aminopropyltriethoxy silane (APTES), after which the coated slides were modified with collagen-rich extracellular matrix components obtained from normally mineralizing avian tendon: the tripeptide arginine-glycine-aspartic acid (arg-gly-asp), or a precipitate formed from a metastable solution containing inorganic ions normally found in blood (simulated body fluid). Each of the modified substrates, as well as the nonmodified (APTES) control, provided distinctly different physical (evidenced by differences in rms roughness) and chemical surfaces for seeding primary osteoblasts obtained from 14-day-old normal embryonic chickens. Cell responses to each of the substrates were evaluated over a 21-day period in terms of Ob growth and growth rate, alkaline phosphatase (ALP) activity, and gene expression of type I collagen (COL I), osteopontin (OPN), osteocalcin (OC), and bone sialoprotein (BSP). From these preliminary experiments, indications are that cell attachment and growth in this study possibly are independent processes, an assumption that compels the need for further studies. Collagen-rich matrix-modified substrates had a distinct advantage over others when cell growth rate, ALP activity, and gene expression were considered; cells on these substrates exhibited increased ALP activity and enhanced expression of BSP, OPN, and OC when compared with those of cells on APTES controls or other modified substrates. These results indicate that matrix-modified substrates such as those used in this study provide favorable templates for tissue generation, suggesting their potential in the design of surfaces for bone implants.

Alkaline Phosphatase↗
PubMed2003

Generation of fiber-modified adenovirus vectors containing heterologous peptides in both the HI loop and C terminus of the fiber knob.

BACKGROUND: Fiber-modified adenovirus (Ad) vectors can be effective in overcoming the limitations of conventional Ad vectors, specifically their inefficient gene transfer into cells lacking the primary receptor, the coxsackievirus and adenovirus receptor (CAR). Several types of fiber-modified Ad vectors have been developed. In this study, we evaluated the functionality of several fiber-modified Ad vectors. METHODS: We developed a simple method based on in vitro ligation to construct Ad vectors containing heterologous foreign peptides in both the HI loop and C terminus of the fiber knob. A functional comparison of Ad vectors containing RGD and/or K7 (KKKKKKK) peptide in the HI loop or C terminus of the fiber knob was performed in several types of human, mouse, and rat cells, including CAR-positive and -negative cells, and tumor cells in mice in vivo. RESULTS: In the case of the in vitro experiment, Ad vectors containing RGD peptide in the HI loop of the fiber knob showed a higher level of gene transfer than vectors containing RGD peptide at the C terminus of the fiber knob. Ad vectors containing K7 peptide at the C terminus of the fiber knob showed levels of gene transfer similar to those of Ad vectors containing RGD peptide in the HI loop of the fiber knob, depending on the cell type. Ad vectors containing both peptides in the HI loop or C terminus of the fiber knob showed the highest levels of gene transfer and a broader tropism. For gene transfer into tumor cells in vivo, the Ad vectors containing RGD peptide were the most efficient. CONCLUSIONS: In the experiment using cultured cells, Ad vectors containing both RGD and K7 peptides were the most efficient with a broader tropism. In contrast, in the experiment in vivo, Ad vectors containing RGD peptide in the HI loop of the fiber knob were more efficient than the vectors containing K7 peptide (including double-modified vectors containing both the RGD and K7 peptides). These comparative analyses could provide a systemic reference for the use of fiber-modified Ad vectors. Our simple method, in which the peptide of interest can be expressed in Ad vectors in either the HI loop or the C terminus of the fiber knob, or both, could be a powerful tool for gene transfer into mammalian cells in studies of gene function as well as in gene therapy.

Adenoviridae↗
PubMed2005

A modified projection reconstruction trajectory for reduction of undersampling artifacts.

PURPOSE: To reduce undersampling artifacts for a given number of repetitions of the projection reconstruction (PR) sequence by modifying its k-space trajectory to sample more mid-frequencies while reducing the sampling coverage of the peripheral spatial frequencies. MATERIALS AND METHODS: The single k-space spoke measured per repetition in the standard PR was modified so that one complete and two partial spokes were measured per repetition but with decreased k-space extent. The point spread functions (PSFs) and undersampling artifacts of the modified PR were compared with those of the standard PR for various numbers of projections. Phantom and in vivo images were used to assess the relative performance. RESULTS: PSF analysis indicated that the modified PR method provided reduced undersampling artifacts with somewhat reduced spatial resolution. The phantom and in vivo images corroborated this. CONCLUSION: The modified PR trajectory provides reduced undersampling artifact vs. the standard PR, particularly when the number of projections is limited and the artifact level is high.

Artifacts↗
PubMed2005

Effect of surfactant counterion and organic modifier on the properties of surfactant vesicles in electrokinetic chromatography.

Counterion and organic modifier are two parameters in EKC that can be varied in order to obtain improved solubility, selectivity, and efficiency. The effect of changing surfactant counterion and/or organic modifier on the chromatographic and electrophoretic properties of cetyltrimethylammonium bromide (CTAB)/sodium octyl sulfate (SOS) vesicles is examined in EKC. The vesicles are prepared in a 1:3.66 cationic/ anionic mole ratio for a total surfactant concentration of 69 mM. The cationic CTAB is replaced by cetyltrimethylammonium chloride (CTAC) and the first use of CTAC/SOS vesicles is reported. The mean diameter of the CTAC/SOS vesicles is 96 nm while that of the CTAB/SOS vesicles is 85 nm. A class I modifier (2-amino-1-butanol) and a class II modifier (acetonitrile) have similar effects on the EOF, elution range, methylene selectivity, and the efficiency of the CTAB/SOS vesicles and the CTAC/SOS vesicles. Upon addition of 10% ACN, there is roughly a 10-fold increase in the efficiency of heptanophenone, a model hydrophobic compound, compared to the efficiency using unmodified vesicles. Linear free energy relationship (LFER) analysis using the Abraham solvation model is employed to characterize solute-vesicle interactions. The results suggest that organic modifier-vesicle interactions depend somewhat on the counterion.

Journal Article↗
PubMed2003

A modified large-sample approach to approximate interval estimation for a particular intraclass correlation coefficient.

We consider the problem of constructing a confidence interval for the intraclass correlation coefficient in an interrater reliability study when both raters and subjects are random effects in a two-way random effects model. A simulation study is conducted to investigate and compare the interval coverage per cents of three methods of approximation: (i) Satterthwaite's two moments, the standard approach; (ii) modified three moments, a newer approach; and (iii) modified large sample, the newest approach for this particular problem. One-sided lower and two-sided bounds are examined. For the two-moment approach, coverage of confidence intervals can be understated for not only one-sided bounds but also two-sided bounds. Coverage of confidence intervals for the modified large-sample approach is either correct or conservative and provides narrower two-sided widths than the modified three-moment approach, which can understate coverage on one-sided and two-sided bounds for two or three raters. The competing methods are illustrated with data from a reliability study of four raters evaluating the number of decayed, missing, and filled surfaces in the permanent teeth of ten subjects. Overall, the modified large-sample approach provides the most satisfactory performance of the three methods.

Clinical Trials as Topic↗
PubMed1995

A renal carcinogen ferric nitrilotriacetate mediates a temporary accumulation of aldehyde-modified proteins within cytosolic compartment of rat kidney.

Iron overload with ferric nitrilotriacetate (Fe-NTA) induces acute renal proximal tubular necrosis, a consequence of oxidative tissue damage, that eventually leads to a high incidence of renal adenocarcinoma in rodents. A recent immunohistochemical study has revealed that the materials immunoreactive to the antibody against the aldehyde (4-hydroxy-2-nonenal)-modified proteins are generated in the renal proximal tubules of rats treated with Fe-NTA (S. Toyokuni et al. (1994) Proc. Natl. Acad. Sci. USA 91, 2616-2620). Here we present further evidences that cytosolic proteins modified with lipid peroxidation-derived aldehydes (4-hydroxy-2-nonenal and malondialdehyde) are indeed accumulated in the kidney of rats treated with Fe-NTA. A single intraperitoneal Fe-NTA treatment (15 or 30 mg Fe/kg body wt) induced a rapid accumulation of thiobarbituric acid-reactive substances, a direct consequence of membrane lipid peroxidation, mostly within the cytosolic compartment of rat kidney. The accumulation of lipid peroxidation-derived aldehydes was associated with an apparent accumulation (from 67.9 nmol in untreated controls to 83.3 nmol/mg protein in Fe-NTA-treated rats at 3 h after treatment) and subsequent elimination of aberrant proteins as assessed by a 2,4-dinitrophenylhydrazine postlabeling assay. Immunoblot analysis with two different polyclonal antibodies against 4-hydroxy-2-nonenal-modified and malondialdehyde-modified proteins detected a temporary accumulation of aldehyde-modified proteins in the cytosol. An immunohistochemical technique with serial sectioning revealed that immunoreactivities of these antibodies were observed in the identical portion of the renal proximal tubules. The implications of these data in relation to the nephrotoxicity of Fe-NTA are discussed.

Adenocarcinoma↗
PubMed1999

Age-dependent renal accumulation of 4-hydroxy-2-nonenal (HNE)-modified proteins following parenteral administration of ferric nitrilotriacetate commensurate with its differential toxicity: implications for the involvement of HNE-protein adducts in oxidative stress and carcinogenesis.

In this study, we show that the toxicity of ferric nitrilotriacetate (Fe-NTA) can be correlated with the tissue accumulation of 4-hydroxy-2-nonenal (HNE)-modified protein adducts. It is observed that the toxic manifestations of Fe-NTA gradually increase with the increasing age of animals. A dose of Fe-NTA which produces almost 100% mortality in aged rats causes 70% mortality in adults, 30% in pups, 20% in litters, and less than 10% in neonates. The age-dependent increase in its toxicity is also evident from the data of renal microsomal lipid peroxidation and hydrogen peroxide generation. No significant difference in the generation of H2O2 and induction of renal microsomal lipid peroxidation between saline- and Fe-NTA-treated neonates, litters, and pups could be observed. However, in adult rats, a significant increase in both of the parameters was observed which was even greater in aged rats. On the contrary, renal glutathione levels in these animals show an inverse relationship with the oxidant generation. In neonates, litters, and pups the maximum decrease of glutathione was up to 22%, whereas in adult and aged rats, the depletion was more than 60% of their respective saline-treated controls. Parallel to this data, blood urea nitrogen and creatinine, the indicators of renal damage, show a significant increase in Fe-NTA-treated adult and aged rats only, whereas no significant alterations were observed in other groups. Similarly, the magnitude of ODC induction and [3H]thymidine incorporation was much higher in aged and adult rats in comparison to other groups of animals after Fe-NTA treatment. Additionally, the immunohistochemical localization studies show a significant increase in HNE-modified protein adducts in kidney of adult and aged rats, whereas no significant staining was observed in other groups. A similar increase in the level of protein carbonyls has also been observed with the increasing age of rats. These data suggest that the toxicity of Fe-NTA increases with the increasing age of rats and correlates with the accumulation of HNE-modified protein adducts. It may also be speculated that Fe-NTA-mediated renal toxicity leading to carcinogenesis may be related to the tissue accumulation of HNE-modified protein adducts. However, further studies are needed to establish a definite role of HNE-modified proteins in Fe-NTA-mediated carcinogenesis.

Aging↗
PubMed2001

The enantioselective immunoaffinity extraction of an optically active ibuprofen-modified peptide fragment.

Acyl glucuronides are known to produce the covalently bound protein adducts which may be the cause of hypersensitivity and toxic responses to acidic drugs. The structural analysis of the drug-protein adducts is therefore needed. From this point of view, we developed an enantioselective immunoaffinity extraction method, which employs an immobilized antibody to specifically isolate peptide fragments that have been modified with optically active ibuprofen. Rabbits were immunized with (S)-ibuprofen coupled to bovine serum albumin through a beta-alanine group. The elicited antibody strongly recognizes the asymmetric center and the isobutylphenyl moiety of (S)-ibuprofen and its conjugates but has a low affinity for their anti podes. A 0.5-mL aliquot of the immunosorbent (11.5 mg of IgG/mL gel) prepared by immobilization of the antibody was capable of retaining up to 1 microg of (S)-ibuprofen. When a mixture of substance P with (R)- and (S)-ibuprofen-modified substance P was loaded on the immunosorbent, the (S)-ibuprofen-modified substance P was selectively retained. The modified peptide was quantitatively recovered by elution with 10 mM ammonium acetate buffer (pH 5.0)/methanol (5:95, v/v). The proposed method would be useful for the structural characterization of optically active ibuprofen-modified human serum albumin.

Antibodies↗
PubMed1999

Effect of Charge and Hydrophobicity on Adsorption of Modified Starches on Polyester.

Polyester fabric (poly(ethylene terephthalate)) is a hydrophobic polymer. Its hydrophobic nature can be a disadvantage for certain applications like dyeing, finishing, detergency, etc. Physical or chemical modification of the polyester to make it more hydrophilic is therefore desirable for certain performance characteristics. Surface modification of polyester to make it hydrophilic can be achieved by adsorbing polymers on the polyester surface. Starch is a commonly available, hydrophilic polymer used in many textile applications that can be used to modify polyester. However, it needs to be chemically modified so that it can adsorb on the polyester fabric and physically modify the fabric characteristics. The polymers used in this study are two different modified starches-cationic and anionic starches and mixtures of the two. The adsorption kinetics on a polyester substrate was studied. The effect of charge and hydrophobicity on adsorption was investigated. Cationic starches were shown to readily adsorb on polyester and this was attributed to electrostatic interactions. Hydrophobic substituents on the cationic moiety resulted in increased adsorption. This was attributed to the weak hydrophobic interaction between the polymer chains which could result in a more coiled polymer conformation. It is hypothesized that more starch molecules are required for surface coverage of the polyester, resulting in an increase in adsorption. Anionic starch was adsorbed on the substrate but at a slower rate than the cationic starches. It is likely that there is a H bonding between acid groups on the starch and the ester groups of the polyester. However, the anionic starch is desorbed when the polyester is placed in an aqueous medium. When a blend of cationic starch and anionic starch was used, a low concentration of anionic starch was seen to increase adsorption, indicating that the polyelectrolyte complex itself may be adsorbing on the substrate. Further increases cause a decrease in adsorption as no sites may be available on the complex for adsorption. When hydrophobic substituents are present, addition of the anionic starch causes a decrease in adsorption at all concentrations. This was attributed to the "crosslinking" between the hydrophobically modified starch and the anionic polymer. Copyright 1999 Academic Press.

Journal Article↗
PubMed2002

Effect of pore structure on surface characteristics of zirconium phosphate-modified silica.

Three samples of silica of different pore structure-predominantly microporous, S1; mesoporous, S2; and nonporous, S3-were modified with zirconium phosphate and examined. Pore structure analysis showed that modification had taken place in wider pores of S1 leaving a totally microporous sample, and in large pores of S2 giving a mesoporous sample of narrower pore size distribution. The modification of the nonporous sample decreased the surface area and pore volume to a lower extent than in the other two samples, but resulted in a surface of lower energy toward N2. The different distribution of surface silanol groups on the surfaces of different porosity may result in variable pictures on the modified surfaces as reflected in the differences observed in Brønsted acidity of modified surfaces. The use of these modified silica samples for amino acid adsorption (L-glutamic acid and L-alanine) indicated that both the isoelectric point of the amino acid and the distribution of surface groups on modified solids are controlling the adsorption process.

Adsorption↗
PubMed1997

Neonatal rat cardiomyocytes possess a large population of stable microtubules that is enriched in post-translationally modified subunits.

Microtubules (MTs) may be involved in several differentiation-specific cardiomyocyte functions, including myofibril organization, hypertrophic cell growth, and the negative regulation of heart cell contraction. The functional characteristics of neonatal rat heart cell MTs, which possess subsets that are enriched with either detyrosinated or acetylated tubulin subunits, were analysed. When compared with their non-myocyte neighbors, cardiomyocyte MTs were found to be more resistant to high concentrations (33 microM) of nocodazole (over 10-30 min), cold treatments (10 min to 8 h), or calcium (50-100 microM for 1-10 min, using detergent-extracted cells). These stable MTs were correlated with the modified MT population. Myocytes treated with 10 microM taxol for 4 h showed elevated levels of modified tubulin but only moderate MT bundling or rearrangement, while after an overnight treatment significant changes in intensity and distribution were noted. In contrast, non-myocytes on the same coverslip showed much greater MT rearrangements, but with only a moderate increase in the immunostaining intensity for modified MTs. Finally, hapten-labeled tubulin that was microinjected into the myocytes showed incorporation rates that were similar to those of the non-myocytes in this study as well as to fibroblast rates determined in other studies, suggesting that the modified MTs in cardiomyocytes may be only moderately stable. Thus, a significant subset of MTs in neonatal cardiomyocytes are post-translationally modified, are resistant to depolymerization by a variety of agents, but are still turning over. These MTs may help define myocyte function during heart development.

Animals↗