In vitro model of syndactyly replicates the morphologic features observed in vivo.

Syndactyly is a common congenital hand anomaly that may occur after exposure to teratogens. We have developed an in vitro model of syndactyly to investigate the molecular mechanisms underlying this malformation of digit development. Retinoic acid, which regulates pattern formation in vertebrate limb development and is associated with teratogenic malformations, was used in the development of this syndactyly model system. Pregnant Swiss-Webster mice were given retinoic acid by oral gavage on days 10 and 11 of embryonic development (E10 and E11, respectively). The mice were sacrificed on gestational days 13 and 17 (E13, E17) and immediately postnatally (PN). The fetuses were removed and the forelimbs dissected under the operating microscope. The E13 limbs were cultured for 4 days (E13+4) in an organ culture system using a serumless, chemically defined medium. The E17, PN, and E13+4 forelimbs were critically examined for malformations of digit separation and digit development. Retinoic acid-induced fetal mouse forelimb syndactyly was observed in all the groups; 81 percent of E17 limbs, 75 percent of PN limbs, and 77 percent of E13+4 limbs had syndactyly. The morphology of the digital malformations was similar in the E17, PN, and E13+4 limbs. This in vitro model permits further studies to characterize the molecular changes that occur during the development of a congenital hand anomaly.

Mesenchymal commitment to digital joint formation.

Temporal and spatial commitment of in vivo and in vitro mammalian digital joint development were characterized in a murine model. Alcian blue and alizarin red staining were used to label proteoglycans of cartilage matrix and mineralized matrix in both whole mounts and histological sections. Mesenchymal differentiation toward a joint fate was identified by a lack of matrix deposition in islands of joint precursor cells between phalangeal precursors, and localized lysosomal enzyme activity was later demonstrated in these regions during formation of the joint cavity. Organ-cultured forelimbs and in vivo specimens demonstrated analogous digital joint morphological trends. With a defined developmental window, reverse transcription, polymerase chain reaction, demonstrated differential gene expression of transforming growth factor-beta isotypes, aggrecan core protein, and type II collagen, suggesting a role for transforming growth factor-beta in directing digital joint development.

Medial edge epithelium fate traced by cell lineage analysis during epithelial-mesenchymal transformation in vivo.

Vital cell labeling techniques were used to trace the fate of the medial edge epithelial (MEE) cells during palatal fusion in vivo. Mouse palatal tissues were labeled in utero with DiI. The fetuses continued to develop in utero and tissues of the secondary palate were examined at several later stages of palatal ontogeny. The presence and distribution of DiI was correlated with the presence of cell phenotype-specific markers. During the initial stages of palatal fusion the DiI-labeled MEE were present in the midline position. These cells were attached to an intact laminin-containing basement membrane and contained keratin intermediate filaments. At later stages of palatogenesis the DiI-labeled MEE were not separated from the mesenchyme by an intact basement membrane and did not contain keratin. In late fetal development, DiI-labeled cells without an epithelial morphology were present in the mesenchyme. The transition of the DiI-labeled cells from an epithelial phenotype to a mesenchymal phenotype is consistent with a fate of epithelial-mesenchymal transformation rather than programmed cell death.

Bilateral solitary glomus tumors of the hands.

Solitary glomus tumors of the digits are uncommon, comprising only about 2% of all hand tumors. In this report, we present a case report of a patient with bilateral glomus tumors that became symptomatic 4 years apart. No inheritance pattern was apparent for this patient. An extensive literature review did not uncover a similar patient. Because this condition does not appear to be widely recognized, we suggest that it be considered when patients present with bilateral digital pain.

Opiate modulation of pancreatic polypeptide release by a meal in the dog.

It has been reported that morphine abolished the plasma pancreatic polypeptide (PP) response to a meal in man, but the mechanism of this action is unclear. This study was designed to investigate the effect of low doses of the endogenous opiate peptide. Met-enkephalin and naloxone on basal- and meal-stimulated PP release in order to examine the role of opioid modulation in the release of this hormone. Four gastric fistula dogs underwent a series of six studies, a test meal alone. Met-enkephalin infusion (40 microgram/kg/hr), naloxone infusion, meal plus naloxone infusion and meal plus Met-enkephalin plus naloxone. Gastrin and PP were measured by radioimmunoassay. Basal PP levels averaged 35.1 +/- 3.0 fmol/ml. Although Met-enkephalin had no effect on basal PP levels, it significantly (P less than 0.05) inhibited the mean peak increment of PP stimulated by a meal (control, 331 +/- 39 fmol/ml; Met-enkephalin, 145 +/- 49 fmol/ml; P less than 0.05). This inhibition was completely abolished by naloxone. Naloxone alone did not alter basal- or meal-stimulated plasma PP levels. Neither Met-enkephalin nor naloxone altered basal or stimulated plasma gastrin levels. This study demonstrated that opiate peptides play a role in the regulation of the release of PP by a meal; it thus suggests the possibility of an opioid modulatory mechanism for the release of this hormone.