Ultrasound-Assist Extrusion Methods for the Fabrication of Polymer Nanocomposites Based on Polypropylene/Multi-Wall Carbon Nanotubes

Isotactic polypropylenes (iPP) with different melt flow indexes (MFI) were used to fabricate nanocomposites (NCs) with 10 wt % loadings of multi-wall carbon nanotubes (MWCNTs) using ultrasound-assisted extrusion methods to determine their effect on the morphology, melt flow, and electrical properties of the NCs. Three different types of iPPs were used with MFIs of 2.5, 34 and 1200 g/10 min. Four different NC fabrication methods based on melt extrusion were used. In the first method melt extrusion fabrication without ultrasound assistance was used. In the second and third methods, an ultrasound probe attached to a hot chamber located at the exit of the die was used to subject the sample to fixed frequency and variable frequency, respectively. The fourth method is similar to the first method, with the difference being that the carbon nanotubes were treated in a fluidized air-bed with an ultrasound probe before being used in the fabrication of the NCs with no ultrasound assistance during extrusion. The samples were characterized by MFI, Optical microscopy (OM), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), electrical surface resistivity, and electric charge. MFI decreases in all cases with addition of MWCNTs with the largest decrease observed for samples with the highest MFI. The surface resistivity, which ranged from 10¹³ to 10⁵ Ω/sq, and electric charge, were observed to depend on the ultrasound-assisted fabrication method as well as on the melt flow index of the iPP. A relationship between agglomerate size and area ratio with electric charge was found. Several trends in the overall data were identified and are discussed in terms of MFI and the different fabrication methods.     

Reversal of pulmonary hypertension and subsequent repair of atrial septal defect after treatment with continuous intravenous epoprostenol.

We report the first case in the world literature of a patient with an atrial septal defect, severe pulmonary hypertension, and equalization of pulmonary and systemic pressures, who underwent successful closure of an ASD following prolonged therapy with the intravenous vasodilator epoprostenol. Judicious use of continuous prostacyclin in apparently inoperable patients with congenital heart disease may be associated with significant reversal of pulmonary hypertension, and conversion to an operable state.     

Development of a "leak-proof," knitted Dacron vascular prosthesis

We have developed a technique to render knitted Dacron prostheses totally impervious to blood leak by impregnating the cloth with collagen. These grafts were prepared by the manufacturer, sterilized, and have an indefinite shelf life. The objective of this study was to determine whether collagen impregnation has a deleterious effect on surface thrombogenicity and graft healing. The infrarenal aortas of 30 mongrel dogs were replaced with 6 cm X 6 mm Dacron grafts (15 collagen-impregnated and 15 control). The collagen-impregnated prostheses were visibly indistinguishable from the control. After blood flow was restored, no interstitial bleeding occurred in the collagen grafts, in contrast to the control grafts that initially leaked profusely. When they recovered, the dogs were divided into three groups: group I (five collagen, five control), group II (five collagen, four control), and group III (five collagen, three control). The grafts were harvested at 3, 6, and 9 months, respectively. Retroperitoneal healing response, capsular thickness and adherence, completeness of neointimal healing, surface fibrinolytic activator activity, and sections taken for light and scanning electron microscopy were studied and compared in a blinded fashion. In a separate set of experiments, experimental and control grafts were compared for in vivo surface thrombogenicity. The healing data were identical in the experimental and control prostheses in all parameters. Of particular interest was that initial capsule adherence was better and surface thrombogenicity less in the collagen-impregnated prosthesis. We conclude that collagen impregnation of a knitted Dacron prosthesis has no deleterious effect for the term of observation of this experiment.     

IS THE SEVERITY OF OSTEOSCLEROSIS OF FLUOROSIS PROPORTIONAL TO THE DOSE OF FLUORIDE INTAKE?

Histomorphometric study was made on a series of sections of undecalcified epiphyseal femoral specimens from rats with experimental fluorosis. The results revealed osteosclerosis in Group A (5 ppm) being more severe than that in Group B (25 ppm) With the increase of fluoride dose, the parameters fell down instead of increased in parallel. There is seemingly a threshold over which osteosclerosis in fluorosis becomes less severe. In contrast to Bely's conclusion the authors proposed that, fluoride toxi- city, besides decreasing the number of osteoblasts, may also activate the osteoblasts. The number of osteoblasts may be increased with relative lower dose of fluoride also. The net outcome is the in crement in bone volume. When toxic dose of fluoride is higher enough (higher than the proposed threshold), however, the number of osteoblasts and its activity are inhibited. So are the osteocytes. This interpretation may be the cytological basis for osteosclerosis in the experimental fluorosis.     

Adenylate cyclase activity as a predictor of thyroid tumor aggressiveness

Prior studies in our laboratory have shown that human thyroid neoplasms have a greater adenylate cyclase activity in response to thyroid stimulating hormone (TSH) than does the adjacent histologically normal thyroid tissue. However, there is little information relating activity of the TSH receptor-adenylate cyclase system to the type of thyroid neoplasm. Thyroid tissue from 67 patients was divided by clinical and histological criteria into 6 categories: normal (59), benign tumors (20), stage 1 carcinoma—intrathyroidal involvement only (25), stage 2 carcinomaregional lymph node involvement (6), stage 3 and 4 carcinoma—tissue invasion or distant metastasis (11), and medullary carcinoma (3). Adenylate cyclase activity in an 8,000 x g thyroid membrane preparation was determined in the basal state and when maximally stimulated with 300 mU/ml TSH. The cyclase responsiveness was the ratio of TSH stimulated adenylate cyclase activity compared to basal adenylate cyclase activity. The cyclase responsiveness by category is: normal, 2.8±0.2 (mean ± SEM); benign, 17.9±2.4; stage 1 carcinoma, 9.2±1.9; stage 2 carcinoma, 4.0±1.0; stage 3 and 4 carcinoma, 1.6±0.4; and medullary carcinoma, 1.05±0.04 (for the neoplasms,p <0.02 by ANOVA). Tumor stage was the only correlate with this trend as other prognostic risk factors (age, sex, a history of neck irradiation, or papillary versus follicular histology) showed no difference in cyclase responsiveness. These studies demonstrate a consistent inverse correlation between adenylate cyclase responsiveness and tumor stage or aggressiveness. Cyclase responsiveness appears to have clinical application for predicting which thyroid tumors will behave aggressively.

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Resumen Estudios previos en nuestro laboratorio han demostrado que los neoplasmas tiroideos humanos poseen una mayor actividad de adenilato ciclasa en respuesta a la administración de hormona estimulante de la tiroides (TSH) que el tejido tiroideo histológicamente normal adyacente. Sin embargo, existe muy poca información sobre la relation de la actividad del sistema receptor de TSH-adenilato ciclasa y el tipo del neoplasma tiroideo. Tejido tiroideo proveniente de 67 pacientes fue dividido mediante criterios chlínicos e histológicos en 6 categorias: normal (59), tumores benignos (20), extensión intratiroidea solamente en estado 1 (25), carcinoma-extensión ganglionar regional en estado 2 (6), carcinoma-invasión tisular o metástasis distantes en estados 3 y 4 (11), y carcinoma medular (3). La actividad de la adenilato ciclasa en una preparación de membrana tiroidea de 8,000 × g fue determinada en el estado basai y en estado de maxima estimulación con 300 mU/ml TSH. El grado de respuesta de la ciclasa fue la tasa de actividad de la adenilato ciclasa estimulada por TSH comparada con la actividad basai de la adenilato ciclasa. El grado de respuesta por categorías fue: normal, 2.8±0.2; tumor benigno, 17.9±2.4; carcinoma estado 1, 9.2±1.9; carcinoma estado 2, 4.0±1.0; carcinoma estados 3 y 4, 1.6±0.4; y carcinoma medular, 1.05±0.04 (para los neoplasmas,p < 0.02 por ANOVA). El estado del tumor apareció como el único factor de correlatión con esta gradación, ya que otros factures de pronóstico (edad, sexo, historia de irradiación cervical, histología papilar versus folicular) no demostraron diferencia en cuanto al grado de respuesta de la ciclasa. Estos estudios demuestran una consistente relación inversa entre el grado de respuesta de la adenilato ciclasa y el estado o agresividad tumoral. El grado de respuesta de la ciclasa parece tener aplicación clínica para predecir qué tumores tiroideos se habrán de comportar en forma agresiva.

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Résumé Les études antérieures provenant de nos laboratoires ont démontré une augmentation de l'activité enzymatique de l'adénylate-cyclase en réponse à la thyroïd stimulating hormone (TSH) dans le tissu thyroïdien humain tumoral, par rapport au tissu thyroïdien adjacent normal. Cependant il existe peu de données concernant l'activité du système récepteur TSH/adénylatecyclase par rapport au type de tumeur de la thyroïde. Les tissus thyroïdiens provenant de 67 patients différents ont été repartis en 6 groupes selon des critères cliniques et histologiques: normal (59), tumeur bénigne (20), cancer stade 1 (intrathyroïdien uniquement) (25), cancer stade 2 (envahissement ganglionnaire régional) (6), cancer stade 3 et 4 (envahissement tissulaire avoisinant ou métastases à distance (11), et cancer médullaire (3). A partir d'une préparation de membrane thyroïdienne centrifugée à 8,000 × g, l'activité de l'adénylate-cyclase a été déterminée en l'état basai et après stimulation maximale par 300 mU/ml de TSH. La réponse enzymatique a été mesurée comme étant le rapport de l'activité stimulée par la TSH/activité basale. Les résultats selon les 6 groupes étaient (moyen±ET): tissu normal, 2.8±0.2; tumeur bénigne, 17.9±2.4; cancer stade 1, 9.2±1.9; cancer stade 2, 4.0±1.0; cancers stade 3 et 4, 1.6±0.4; et cancer médullaire, 1.05±0.04 (p < 0.02 par l'analyse de variance pour les néoplasies). Le stade tumoral était la seule variable corrélée avec l'activité enzymatique. L'activité enzymatique n'était pas corrélée avec l'âge, le sexe, les antécédents d'irradiation cervicale antérieure ou l'histologie (papillaire vs. folliculaire). Ces études montrent un rapport inversement proportionnel entre l'activité d'adénylate-cyclase et le degré d'agressivité tumorale ou le stade. La réponse d l'adénylate-cyclase paraît avoir une application clinique: prévoir quelles tumeurs thyroïdiennes auront une évolution agressive.

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Presented at the International Association of Endocrine Surgeons in Sydney, Australia, September, 1987.

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Supported in part by the Medical Research Service of the Veterans Administration.     

Neonatal aortic thrombosis.

Thrombosis of the aorta in the neonate is a potentially catastrophic event. The incidence of this problem has increased concomitantly with the widespread use of umbilical artery catheters in the management of infants who are critically ill. The natural history and appropriate management of this complication has not been well established. This is due in part to the wide spectrum of presentations and lack of consensus regarding its classification. Aortic thrombosis may vary from deposition of a fibrin sheath surrounding the length of an umbilical artery catheter to aggregates of nonocclusive thrombus within the aorta or to complete occlusion of the aorta and concomitant occlusion of its main branches. The reported treatments recommended for this problem have ranged from supportive care only to mandatory surgical intervention in all cases. This spectrum of advocated therapies has resulted in considerable confusion regarding the proper management of this problem. This paper presents two cases of neonatal aortic thrombosis: one case was treated medically and the other case was treated with surgical intervention. We review these cases and the current literature, with specific attention directed towards highlighting the critical elements involved in formulating a reasonable approach to the management of neonatal aortic thrombosis. In addition, we offer an algorithm for management of these patients according to the degree of aortic thrombosis, severity of systemic manifestations, and the general condition of each individual patient.