Young rats received single or repeated injections of 2% mepivacaine (Carbocaine) into the tibialis anterior or extensor digitorum longus muscles. Repeated injections consisted of six injections of the anesthetic (100 microliter per injection into the tibialis anterior) on three different schedules, at intervals of 2 1/2 hours, 24 hours, or 4 days. The muscles that had been given injections were examined histologically for evidence of myotoxicity at 0 to 7 and 20 days after the last injection. Single injection studies showed that mepivacaine is a myotoxic drug, producing a lesion which ultimately results in the degeneration and subsequent regeneration of large amounts of muscle. A similar picture was seen with repeated injections except that greater tissue destruction was noted. Long-term studies following a single injection of mepivacaine showed restoration of the original muscle structure whereas after repeated injections some muscles showed persisting foci of increased intersitial connective tissue. This study shows that in rats 2% mepivacaine is a myotoxic drug, but that the damage it produces is to a large extent restored by the regeneration of new muscle fibers.

Animals↗

PubMed1979

Choosing among candidates for scarce medical resources.

Explore the source record for details and available documents.

Decision Making↗

PubMedDate not supplied

Effects of glutamine isomers on human (Caco-2) intestinal epithelial proliferation, strain-responsiveness, and differentiation.

Enteral feeding with small amounts to stimulate bowel motility, and glutamine supplementation, which provides nutrients selectively used by intestinal epithelial cells, might preserve the gut mucosa during fasting. We evaluated the effects of the interaction between mechanical strain and glutamine supplementation in human Caco-2 intestinal epithelial cells, and pursued the finding of equivalent effects of L- and D-glutamine in Caco-2, HT-29, and primary malignant human colonocytes. Caco-2 cells were subjected to repetitive strain in media containing 2 mmol/L of L-glutamine and media supplemented with L- or D-glutamine. Proliferation was determined by automated cell counting. Differentiation and cellular production of L-glutamine were determined spectroscopically. Rhythmic deformation stimulated Caco-2 proliferation in a frequency-dependent manner. Maximal stimulation occurred at 10 cpm, consistent with in vivo frequencies of peristalsis and villous motility. Deformation at 10 cpm and L-glutamine supplementation from 2 to 5 mmol/L concentrations independently stimulated Caco-2 proliferation; the combination further increased proliferation. D-Glutamine supplementation yielded similar results, although with lesser potency. Furthermore, both L- and D-glutamine equivalently reduced Caco-2 dipeptidyl dipeptidase activity. The effects of each isoform were blocked by 1 to 3 mmol/L acivicin, a selective antagonist of glutamine metabolism. Indeed Caco-2 and HT-29 cells and primary malignant colonocytes each metabolized D-glutamine to L-glutamine. Glutamine supplementation in fasting patients might prove synergistic with stimulation of bowel motility by non-nutritive feeding, whereas tissue-specific variations in D-glutamine metabolism might facilitate selective nutripharmaceutical targeting of the gut mucosa.

Caco-2 Cells↗

PubMedDate not supplied

Identification and comparative analysis of human colonocyte short-chain fatty acid response genes.

Short-chain fatty acids (SCFAs) butyrate, propionate, and acetate produced during fiber fermentation promote colonic differentiation and can reverse or suppress neoplastic progression. We sought to identify candidate genes responsible for SCFA activity on colonocytes and to compare the relative activities of independent SCFAs. cDNA was generated from polyA+ mRNA isolated from control Caco-2 cells and cells treated with equimolar butyrate, propionate, and acetate. GeneCalling, a restriction-based differential RNA expression platform linked to a DNA sequence database lookup, was applied. A total of 30,000 individual genetic sequences were analyzed for differential expression among the three SCFAs. Differentially expressed peaks corresponding to cancer-related genes were isolated, sequenced, and cross-referenced to the GenBank human database. Gene identities were independently confirmed by oligonucleotide poisoning. More than 1000 gene fragments were identified as being substantially modulated in expression by butyrate. Butyrate tended to have the most pronounced effects and acetate the least. Five fragments selected for further study were fully sequenced and proved 100% homologous with human sequences for clusterin, amyloid precursor-like protein 2, and caudal homeobox 2 protein, not previously known to be modulated by SCFAs. In each case, a similar order of potency for the three SCFAs studied was observed. The common SCFAs appear to exert different effects. This study suggests the diversity of the SCFA response at the molecular level and facilitates identifying genes important in the biologic activity of dietary fiber.

Alzheimer Disease↗

PubMedDate not supplied

Peptide YY selectively stimulates expression of the colonocytic phenotype.

Peptide YY (PYY) is produced by colonic mucosal endocrine cells and modulates gastrointestinal endocrine activity through specific Y-receptors. The direct effects of PYY on intestinal mucosal growth and differentiation remain uncharacterized. The abundance of PYY in colonic mucosa suggests that PYY acts locally to maintain colonocytic differentiation. We tested this hypothesis in human Caco-2 intestinal epithelial cells, which express alkaline phosphatase (AP) and dipeptidyl dipeptidase (DP), brush-border enzymes differentially concentrated in large and small intestinal mucosa, respectively. The effects of PYY on enzyme specific activity were compared with those of pancreatic polypeptide, neuropeptide-Y, vasoactive intestinal peptide, pentagastrin, bombesin, and selective Y1- and Y2-receptor agonists. Brush-border enzyme activity was assessed by AP and DP specific activity in cell lysates quantitated spectrophotometrically following synthetic substrate digestion. PYY, neuropeptide-Y, pancreatic polypeptide, and vasoactive intestinal peptide (10(-7) mol/L) stimulated AP activity. PYY brought about the greatest increase (38.0%+/-11.0%, n=48). Only PYY decreased DP specific activity (7.9%+/-2.2%, n=48). The Y2-agonist but not the Y1-agonist mimicked these PYY effects (increasing AP 28.3%+/-3.5% and decreasing DP 10.4%+/-3.6%). These data suggest that PYY promotes differentiation toward a colonocytic phenotype in Caco-2 intestinal epithelial cells and that this effect may be mediated through the Y2-receptor subtype.

Alkaline Phosphatase↗

PubMedDate not supplied

Loss of matrix-dependent cytoskeletal tyrosine kinase signals may regulate intestinal epithelial differentiation during mucosal healing.

Intestinal epithelial restitution and the migratory phenotype appear regulated by the extracellular matrix. Since integrin-associated adhesion to matrix triggers tyrosine kinase activity, we hypothesized that matrix-specific tyrosine kinase signals might modulate the intestinal epithelial migratory phenotype, particularly via focal adhesion kinase. Caco-2 cells were seeded at two densities on collagen I, laminin, fibronectin, and tissue culture plastic. Four days later the first cells were confluent, whereas the second cells were not contact inhibited and expressed migratory lamellipodia. Cells were fractionated into membrane/cytoskeletal and cytosolic fractions. Cytoskeletal tyrosine kinase activity in static cells was matrix dependent and, unlike cytoscolic tyrosine kinase, correlated with adhesion, highest on collagen and lowest on plastic. Migrating cells exhibited matrix-dependent increases in cystosolic tyrosine kinase activity. Cytosolic changes in tyrosine kinase activity in motile cells exceeded membrane/cytoskeletal changes. However, matrix-dependent variations in increase in cytosolic tyrosine kinase activity correlated inversely with changes in cytoskeletal tyrosine kinase activity, suggesting cytoskeletal tyrosine kinase translocation to the cytosol during motility. Indeed cytoskeletal focal adhesion kinase activity decreased during migration on collagen. Tyrosine kinase inhibition by genistein both inhibited migration and stimulated expression of brush-border enzymes downregulated during motility. Although enterocyte-matrix interactions alter both cytosolic and cytoskeletal tyrosine kinase activity, matrix-dependent cytoskeletal events are likely to regulate adhesion and differentiation in static cells. Loss of matrix-dependent cytoskeletal tyrosine kinase signals such as focal adhesion kinase during restitution may trigger a phenotypic switch to the "dedifferentiated" migrating intestinal epithelial phenotype.

Caco-2 Cells↗

PubMedDate not supplied

Role of integrins in enterocyte migration.

1. Enterocyte motility depends critically on cell-matrix interactions. Although still incompletely understood, these appear critically dependent upon integrin-mediated cell adhesion. 2. In addition to providing a mechanism for cell adhesion and traction, the integrins are likely to serve as true receptors for the matrix across which cell motility occurs, initiating signals by both mechanical and chemical means that alter cell phenotype and proliferation as well as cell motility. 3. Sound rationale now exists to postulate that soluble growth factors within the extracellular milieu regulate intestinal mucosal healing not only directly but also indirectly by modulating integrin expression and organization.

Cell Adhesion↗

PubMedDate not supplied

Restitution at the cellular level: regulation of the migrating phenotype.

Intestinal epithelial cells migrating across a mucosal defect are generally described as dedifferentiated, a term that suggests a loss of regulatory biology. Since cell biology may be more readily studied in established cell lines than in vivo, a model is developed using the human Caco-2 intestinal epithelial cell migrating across matrix proteins. This resembles in vivo models of mucosal healing in its sheet migration and loss of the brush border enzymes, which are conventional markers for intestinal epithelial differentiation. Immunohistochemical studies of migrating Caco-2 cells suggest, however, that the rearrangements of cytoskeletal, cell-cell and cell-matrix proteins during migration are not random but seem adapted to the migratory state. Indeed, Caco-2 migration may be substantially regulated by a variety of physiologic and pharmacologic stimuli and differentiation, measured by the specific activity of the intestinal epithelial brush border enzymes alkaline phosphatase and dipeptidyl dipeptidase, may be independently pharmacologically programmed during the stimulation or inhibition of cell motility.

Actins↗