Electrophysiological effect of the maze procedure on canine sinoatrial node function.

The maze procedure is an operation that has had great initial success in curing atrial fibrillation. This procedure includes several right atrial incisions that may interrupt the integrity of the sinoatrial node or its arterial supply. To assess the effect of the maze procedure on sinus node function (SNF), the following studies were performed: sinus node recovery times (SNRT), corrected SNRT (CSNRT), CSNRT under autonomic blockade maximal heart rate and intrinsic heart rates. Thirty-four dogs underwent a right thoracotomy with cardiopulmonary bypass (CPB). The dogs were divided into three groups. Group 1 (n = 9), the sham group, underwent CPB without any incisions. Group 2 (n = 8) underwent CPB and one of the right atrial incisions. Group 3 (n = 18) underwent CPB and all three of the right atrial incisions. SNF was determined before and after the procedure. Groups 1 and 2 had no significant difference in measured SNF acutely after the procedure. In Group 3 the mean SNRT increased from 552 msec to 1,984 msec (P = 0.005). Sinus node dysfunction was corroborated by all studies. In the chronic studies, a trend toward recovery of SNF was observed. The maze procedure results in significant acute sinus node dysfunction. This dysfunction may resolve spontaneously over the ensuing months. Modifications of the maze procedure that avoid the sinus node or its blood supply area may reduce procedure related sinus node dysfunction.

Abnormal membrane physical properties of red cells in McLeod syndrome.

McLeod red cells (RBCs) lack Kx antigens and have weak expression of the Kell antigens. Individuals who carry the McLeod phenotype have acanthocytic RBCs and a compensated hemolytic state. To elucidate the role of the protein on which the Kx antigens reside in maintaining membrane deformability, the rheologic properties of McLeod RBCs were determined by ektacytometry. RBCs were obtained from normal individuals and from four patients with McLeod syndrome. Osmotic gradient deformability profiles of McLeod RBCs showed decreased whole cell deformability. Resealed ghosts from McLeod RBCs also showed decreased deformability, partly because of the decreased cell surface area and partly because of an intrinsic membrane stiffness in this syndrome. For the measurement of membrane mechanical stability, resealed ghosts were subjected to constant high shear stress in the ektacytomer, and deformability was recorded continuously as the deformable ghosts fragmented into rigid spherical vesicles. Membranes from McLeod RBCs showed a noticeable increase in mechanical stability. Acquired causes of acanthocytosis, such as liver disease, did not cause the rheologic abnormalities observed in McLeod cells. Other abnormalities noted in McLeod RBCs were decreased RBC potassium content and an increased number of dense RBCs, as determined by centrifugation on a discontinuous density gradient. The data indicate that McLeod RBCs are rigid and have decreased surface area and that their membranes are intrinsically rigid with increased mechanical stability. These abnormalities may account for the reduced RBC survival observed in McLeod syndrome. The protein that carries the Kx surface antigen seems to be required for the maintenance of the normal physical function of RBC skeletal proteins.

Periosteal Ewing's sarcoma.

Ewing's sarcoma is a small cell malignant tumor that usually arises in the medullary cavity of bone. Less frequently, it originates in soft tissue and may secondarily invade underlying bone. The origin of Ewing's sarcoma in a periosteal location without extension into either the bone or adjacent soft tissue has not been clearly documented. Other malignant tumors of bone (e.g., osteosarcoma) appear to have a somewhat better prognosis when confined between periosteum and bone. The case of a patient with a periosteal Ewing's sarcoma who received a radical excision and postoperative chemotherapy and who is without evidence of disease with over 2 years follow-up is reported.

Regenerating rib cartilage tentatively used as a source of chondrocytes for transplantation.

In search for cartilage which could serve as a source of chondrocytes for autogeneic transplantation in mature individuals we studied the morphological appearance and digestibility of normal rib cartilage and regenerated cartilage formed after subperichondrial removal of the former in adult dogs. Cells liberated after collagenase digestion were transplanted intramuscularly to see whether they will reconstruct cartilage similarly as it happens after transplantation of fetal chondrocytes. Chondrocytes in normal rib cartilage were arranged in three zones and lay in large isogenous groups. Collagenase dissolved only the peripheral zone. Isolated cells did not reconstruct cartilage after transplantation. No distinct zones could be seen in regenerated cartilage. Chondrocytes lay singly or in pairs but were not numerous. Regenerated cartilage could be completely dissolved by collagenase, but the yield of cells was low owing to their low content in digested material. After transplantation chondrocytes from regenerated cartilage reconstructed cartilage in one out of ten transplants. The possibility of increasing the cellularity of regenerated cartilage by stimulation of the perichondrium with factors known to promote chondrocyte growth in vitro is discussed.

Medial shifting of the canine vocal cord by injection of isolated chondrocytes.

In the search for new materials to fill the unilaterally paralysed vocal cord, auto- and allogeneic chondrocytes were isolated from costal cartilage, and were injected into the canine vocal cord. The produced cartilage caused a thickening and shift of the treated cord towards the median line of the glottis. Such changes occurred in all autogeneic transplants, and persisted for the period of observation (up to 6 weeks). In allogeneic transplants, the effect was present after 6 and 12 weeks, but disappeared after 18 weeks. Cartilage produced by the autogeneic chondrocytes persisted at the site of injection without any signs of resorption. In contrast, allogeneic cartilage became surrounded by infiltrating cells and was slowly resorbed to disappear completely between the 12th and 18th weeks of observation. Immunosuppressive treatment of some of the allogeneic chondrocyte recipients reduced the lymphocytic infiltrations occurring, and inhibited the resorption of the reconstructed cord cartilage. Discontinuation of the immunosuppression, however, resulted in subsequent graft loss.