Lloyd Wolfinbarger

Decellularization reduces calcification while improving both durability and 1-year functional results of pulmonary homograft valves in juvenile sheep

OBJECTIVE The juvenile sheep functional valve chronic implant calcification model was used to compare long-term calcification rates, functional performance, and durability for 3 types of right ventricular outflow tract implants: classically cryopreserved homografts and 2 decellularized pulmonary valved conduits. METHODS Fifteen juvenile sheep were randomly assigned to one of 3 study arms and underwent pulmonary valve replacement. The arms included the following: (1) cryopreserved ovine pulmonary valves; (2) cryopreserved, decellularized, saline (1 degrees C-10 degrees C)-stored ovine pulmonary valves; and (3) cryopreserved, decellularized, glycerolized (-80 degrees C) stored ovine pulmonary valves. Animal growth, serial echocardiographic results (with valve performance assessment), dimensions, and tissue-specific calcification measurements were compared with pre-explant angiographic analysis and right ventricular outflow tract pressure measurements, cardiac magnetic resonance imaging, specimen radiographic analysis, gross explant pathology, and histopathology. Parametric and nonparametric statistical analysis were performed. RESULTS All but 2 study animals receiving implants thrived postoperatively, with similar growth rates, explant valve dimensions, ventricular functions, cardiac output, and indices during the study. As determined by means of echocardiographic analysis, 3 animals in arm 1 (and one in arm 2) had leaflet dysfunction. Valve regurgitation was recognized in 1 survivor each from both arms 1 and 2. Although 1 arm 1 animal died with calcified subacute bacterial endocarditis, and the other 4 had leaflet and conduit wall calcification by the time of death, no arm 2 or arm 3 animals demonstrated leaflet calcium, and no arm 3 and only 1 arm 2 animals had calcium in the conduit wall over the entire year, as determined with any measurement method. All cryopreserved conduit walls had calcium by 20 weeks, whereas only 1 of 10 decellularized conduits (arms 2 plus 3) had wall calcium. CONCLUSION Cryopreserved-decellularized-glycerolized valves retained normal valve function, with absent leaflet and minimal wall calcifications 1 year postoperatively, as opposed to classically cryopreserved allografts. These results might be predictive of the prolonged durability and functionality of a cryopreserved-decellularized-glycerolized allograft valve.

A comprehensive study of physical parameters, biomechanical properties, and statistical correlations of iliac crest bone wedges used in spinal fusion surgery. II. Mechanical properties and correlation with physical parameters.

Iliac crest wedges have been the most frequently used bone graft in spinal fusion procedures since the 1970s. Physical parameters and correlations among physical parameters of allogeneic iliac crest wedges have been described in part I of this series. This article discusses the mechanical properties, as well as their correlations with physical parameters, of iliac crest wedges. A total of 250 frozen-thawed, freeze-dried, and rehydrated iliac crest wedges were used in this study. The axial load-bearing capacities for wedges in the three subgroups showed no statistically significant differences, however, rehydrated wedges appeared to have the greatest load bearing capacity and compressive strength. In addition, rehydrated wedges were more deformable than either the frozen-thawed or freeze-dried wedges. Based on biomechanical properties, it is suggested that rehydrated (1 hour in vacuo), or frozen-thawed iliac crest wedge should be used in spinal fusion procedures, and the direct clinical application of nonrehydrated freeze-dried wedges should be avoided.

The effect of liquid nitrogen submersion on cryopreserved human heart valves.

Cryopreservation and storage of human heart valves have become an accepted means of maintaining a usable supply of heart valves for outflow track reconstructive surgery. Valves are typically stored at the vapor phase temperature of liquid nitrogen, -130 degrees C and below, to reduce the chance of recrystallization within the tissues. Concern over the effects of submersion of the valves in liquid nitrogen, i.e., plunging to -196 degrees C, prompted this study. Cryopreserved valves were plunged into liquid nitrogen, held for 5 min, and then processed (thawed) by standardized protocols. The thawed valves were then assessed using scanning electron microscopy and the more traditional histology at the light microscope level. Cuspal tissues plunged into liquid nitrogen appear to have numerous microfractures over both surfaces of the tissue, penetrating into the collagen/proteoglycan matrix. Control cryopreserved valves do not exhibit these microfractures. Histologically, the submerged valves appear normal. The clinical use of valves which have been submerged in liquid nitrogen is discussed.

A convenient procedure for radiolabeling detritus with [14C]dimethylsulfate

Abstract A new procedure for radiolabeling detrital particles is presented. The methylating reagent dimethylsulfate is used, in radioactive form, to methylate hydroxyl groups present in detrital material collected in the field. The formed covalent bond is stable to autoclaving and extremes of pH. A preliminary analysis of the compounds methylated indicates that cellulose, chitin, and detritus are reactive with the reagent and readily radiolabeled.

A rapid and convenient method for radiolabeling detritus with [14C]acetic anhydride

Abstract A new procedure for radiolabeling detrital particles is presented. The acetylating reagent acetic anhydride is used, in radioactive form, to acetylate primary amines present in detrital material collected in the field. The formed covalent bond is stable to autoclaving and environmental extremes of pH, temperature, and salt concentrations. The acetylation reaction does not significantly alter the chemical identity of the detritus and requires less than 2 h to perform.

Biology of Heart Valve Cryopreservation

Great advances have been made in the cryopreservation of living cells since the early works of Smith and Parkes during the 1950s. These advances have included development of sophisticated computer-controlled freezing equipment, characterization of a variety of cryprotective agents, and establishment of major research and development programs in cryobiology within academia and industry. Most of this research and technologic development has focused on the preservation of dispersed cell suspensions, and it has successfully enlarged our understanding of the basic principles of cryopreservation of biologic systems.

Phase I study of beta-alanyl-melphalan as a potent anticancer drug

SummaryThe dipeptide beta-alanyl-melphalan was synthesized and tested for its potential anticancer activity. It is shown to possess considerable toxicity toward Ehrlich ascites tumor cells and 3T3 mouse embryo cells in in vitro toxicity assays and is a potent anticancer agent when used in vivo in traditional phase I chemotherapy assays. The potential role for small peptide transport mechanisms in transportation of anticancer agents is discussed.