Myocardial localization and isoforms of neural cell adhesion molecule (N-CAM) in the developing and transplanted human heart.

Neural cell adhesion molecule (N-CAM) has been implicated in cellular interactions involved in cardiac morphogenesis and innervation. Immunohistochemical techniques and Western blot analysis were used to determine the localization and isoforms of N-CAM in the developing and extrinsically denervated human heart. Myocardial and conducting cells in the fetal heart (7-24 wk gestation) exhibited sarcolemmal immunoreactivity, the major desialo N-CAM isoforms being 150, 145, 120, 115, and 110 kD. N-CAM expression appeared to be downregulated in the myocardium during adult life, with relatively little sarcolemmal immunoreactivity being detected in normal donor tissues. In contrast to the temporal changes observed in the myocardium, both the developing and mature cardiac innervation displayed N-CAM immunofluorescence staining, localized to neuronal cell bodies, nerve fascicles and fibres. Extrinsically denervated cardiac allografts, obtained 2 d to 91 mo after transplantation, showed extensive sarcolemmal and intercalated disc immunostaining and expression of 125-, 120-, and 115-kD isoforms. Tissues from explanted recipient hearts and atrial appendage samples obtained during coronary bypass graft operations were also examined and displayed varying amounts of N-CAM immunoreactivity. We conclude that the expression of N-CAM immunoreactivity and isoforms in the human heart is developmentally regulated and may be modulated by factors such as cardiac innervation and myocardial hypertrophy.

Perfusion fixation for placental morphologic investigation.

Fifty placentas were collected after vaginal delivery or cesarean section from normal and abnormal pregnancies and were fixed under different conditions of perfusion using a peristaltic roller pump. In each case a physiologic-heparin perfusate was used for less than 10 minutes, followed by a buffered solution of glutaraldehyde-formaldehyde. The best results were obtained with placentas from cesarean sections perfused immediately after delivery with a pressure maintained under 60 mm Hg. Placentas of this group were fixed within 30 minutes and electron microscopy demonstrated good preservation of cellular ultrastructure. Perfusion fixation could be performed up to 6 hours after delivery with satisfactory histologic results. In these cases, electron microscopy revealed ischemic changes 10 minutes after delivery and severe necrosis 1 hour after delivery. When the perfusion pressure was maintained over 60 mm Hg, diffuse damage of the villous morphology was observed. Histomorphometric analysis showed significant differences between terminal villi from nonperfused (immersed-fixed) placentas and perfused-fixed placentas. The mean barrier and trophoblastic thicknesses and the mean volume fraction of trophoblast were significantly (P less than .001) increased in the nonperfused group compared with the perfused group.