Immersion In Plasma Research Articles

Covalently‐Attached, Surface‐Eroding Polymer Coatings on Magnesium Alloys for Corrosion Control and Temporally Varying Support of Cell Adhesion

AbstractFor degradable magnesium (Mg) alloy‐based stents it would be desirable to delay early corrosion to maintain mechanical strength. Similarly, early after stent placement reduced thrombogenicity is an important feature, while chronically, endothelial cell adhesion and vessel integration are desirable. In this study, surface eroding polymers of amino‐grafted poly(1,3‐trimethylene carbonate) (PTMC‐NH2) and PTMC‐NH2 combined with sulfobetaine bearing polymer PSB (PTMC‐NHCO‐PSB) are developed, and these polymers are covalently attached onto 6‐phosphonohexanoic acid (PHA)‐coated AZ31 Mg alloy surfaces in sequence. In vitro degradation testing in ovine plasma shows PTMC, PTMC‐NH2, and PTMC‐NHCO‐PSB cast films experience a gradual thickness and mass loss with maintenance of smooth surfaces, confirming surface erosion behavior. The PTMC‐NH2 polymer is firmly bound to the PHA‐modified AZ31 surface and demonstrates a resistance to peeling. PTMC, PTMC‐NH2, and PTMC‐NHCO‐PSB coated AZ31 have a lower corrosion rate versus polylactide‐co‐glycolide coated and untreated AZ31. PTMC‐NHCO‐PSB coated AZ31 inhibits platelet deposition and smooth muscle cell adhesion and growth, but after 2‐week immersion in plasma, this surface supports endothelial cell adhesion and growth. These results suggest PTMC‐NHCO‐PSB surface eroding coating offers a means of controlling corrosion while providing a temporally varying bio‐functionality for biodegradable vascular stent applications.

Evaluation of Fluid Absorbency of Retraction Cords after Immersing in Two Retraction Medicaments - An In-vitro Study.

Dry retraction cords help to displace the gingiva and also to absorb the gingival crevicular fluid and saliva to maintain a dry field. When used along with medicaments whether these medicaments help to improve the absorption of fluid or affect the fluid absorption by decreasing the efficiency of the retraction cord is unknown. The aim of the study was to know the effect of various medicaments on the fluid absorbency of the retraction cords and also, to know whether the thickness of the retraction cords influences it's fluid absorbency. A total of 90 samples of 5cm length retraction cords were taken. Cords were divided into 30 samples for each cord thickness of 0, 1 and 2. Of these 30 samples, 10 samples were used to measure dry weight (Group I), 10 samples were immersed in 15.5% ferric sulfate (Group II) and remaining 10 samples were immersed in 10% aluminium chloride (Group III) for a period of 20 minutes. The excess medicament was removed by blotting paper. Initial weight was recorded. Following this, five cords from each group were immersed in plasma solution and remaining in artificial saliva for 10 minutes. Then these were taken out and measured. The amount of the fluid absorbed was determined by subtracting the weight before fluid immersion (weight after immersion in test medicament) from the weight after fluid immersion (weight after immersion in plasma or artificial saliva). The study was analyzed through one-way ANOVA and Bonferroni post-hoc comparisons for pair wise differences. When immersed in medicaments, there is a significant difference in absorption of fluids (artificial saliva and plasma) between the untreated dry cord and cord treated with 15.5% ferric sulfate (p<0.05). But, there was no significant difference in fluid absorption between the dry untreated cord and cord treated with 10% aluminum chloride and between cords treated with 15.5% ferric sulfate and 10% aluminum chloride. Ferric sulfate (15.5%) is a better medicament for absorption of fluid.

Non-self-sustained glow discharge with electrostatic confinement of electrons sustained by a fast neutral molecule beam

Experimental study of plasma produced at the nitrogen pressure 0.2–1 Pa in the chamber volume V ≈ 0.12 m3 as a result of injection into the chamber of a broad nitrogen molecule beam with 1–4 keV energy and 0.1–1 A equivalent current is carried out, and the study results are presented. Dependences of the plasma density distribution on the beam equivalent current Ib, energy Eb, and gas pressure p indicate a crucial role of fast molecules in gas ionization, and the probe characteristics reveal two groups of plasma electrons with the temperatures Te ∼ 0.4 eV and Te ∼ 16 eV. Immersion in plasma of an electrode isolated from the chamber and application to the electrode of a positive voltage U result in non-self-sustained discharge. When U changes from ∼0.5 to ∼1.5 V, the discharge current I rapidly rises to a certain value I*, and after that the rate of rise dI/dU drops by an order of magnitude. At U ∼ 10 V, the current I rises to I0 ≈ 1.5I*, and dI/dU once again drops by an order of magnitude. Current I0 specifies the number of electrons produced inside the chamber per second, and it grows up with Eb, Ib, and p. At U > 20 V, due to gas ionization by fast electrons emitted by the chamber and accelerated up to the energy ∼eU in the sheath between the plasma and the chamber walls, the current I rises again. When U grows up to ∼50 V, production of fast electrons with energies exceeding the ionization threshold begins inside the sheath, and the ionization intensity rises dramatically. At U > 150 V, contribution of fast electrons to gas ionization already exceeds the contribution of fast molecules, and the plasma density and its distribution homogeneity inside the chamber both grow up substantially. However, even in this case, the discharge is non-self-sustained, and only at U > 300 V it does not expire when the beam source is switched off.

Monocyte Chemoattractant Protein‐1 (MCP‐1) released from alveolar macrophages mediates the systemic inflammation of alveolar hypoxia

Alveolar hypoxia (AH) produces widespread systemic inflammation in rats. The inflammation is initiated by a circulating mediator released from alveolar macrophages (AMØ) activated by the low alveolar PO2. The mediator(s) induces mast cell degranulation (MCD) with release of inflammatory agents. Recent data suggest MCP‐1 as a mediator. If this is true: 1) Circulating levels of MCP‐1 should increase with AH in intact rats; 2) AMØ depletion should prevent this increase; 3) Plasma from intact AH rats, but not AMØ‐depleted AH rats, should produce MCD; 4) MCP‐1 added to normoxic plasma or AMØ supernatant should produce MCD.AH (FIO2 = 0.1 for 60 min) produced a rapid (5 min) and sustained 6‐fold increase in plasma MCP‐1 of intact rats. 2) This increase was abolished by AMØ depletion by tracheal instillation of clodronate‐containing liposomes. 3) Mast cell immersion in plasma from AH intact rats, but not in plasma from AMO‐depleted rats, produced MCD. 4) Dose‐dependent MCD occurred when MCP‐1 was added to normoxic AMØ supernatant or rat plasma, but not when added to normoxic culture medium.ConclusionsIn the intact, conscious rat, AH induces release of MCP‐1 from AMØ, which, in turn, produces MCD and initiates systemic inflammation of AH. To induce MCD, MCP‐1 requires another substance(s) which is present in both normoxic plasma and normoxic AMØ supernatant.Supported by NIH HL39443‐18, AHA 0815652G and APS Frontiers in Biology

Autographa nigrisigna looper (Lepidoptera: Noctuidae) excludes parasitoid egg using cuticular encystment induced by parasitoid ovarian fluid

Autographa nigrisigna (Lepidoptera: Noctuidae) loopers form cuticular cysts on the dorsal site of the penultimate segment by parasitization of endoparasitoid Campoletis chlorideae (Hymenoptera: Ichneumonidae) and interrupt successful parasitization by excluding the parasitoid egg and larva in the hemocoel into the cyst. This study elucidated for the first time the difference in the exclusion rates with host age at the time of parasitization. All parasitized host loopers of D1L1 (Day 1, 1st instars) and D0L2 formed cuticular cysts and nearly 70% could exclude parasitoid eggs successfully; however, the number of loopers that could form cuticular cysts decreased with host aging at the time of parasitization. To elucidate the difference between the encapsulation system and cuticular encystment, it was examined whether the substances encapsulated are excluded by cuticular encystment. A small piece of antenna the same size as an egg used as a biotic foreign substance was absolutely encapsulated and was not excluded by encystment. Further, it was clarified whether parasitoid eggs with a different surface were encapsulated or excluded by cuticular encystment with or without ovarian fluid. UV eggs (with an intact surface and development ceased by UV treatment) were hard to encapsulate, but were excluded with encystment. Plasma eggs with a degenerate surface (treated with heating for 5 min at 60°C after 10-min immersion in plasma of Pseudaletia separata) were encapsulated and not excluded by cuticular encystment, although ovarian fluid increased the cyst formation rate. These results show that cuticular encystment functions to exclude parasitoid eggs incapable of encapsulation.

Terpolymers Composed of Ethyl Acrylate, Methoxypolyethyleneglycol Methacrylate and Methoxypolypropyleneglycol Methacrylate as Pressure Sensitive Adhesives and their Blood Compatibility

Terpolymers composed of ethyl acrylate (EA), methoxypolyethyleneglycol methacrylate (MPEGMA) and methoxypolypropyleneglycol methacrylate (MPPGMA) were synthesized by the photopolymerization technique. The high molecular mobilities for these terpolymers were shown by dynamic contact angle and adhesion tension measurement. The 180-degree peel strength and probe tack for pressure sensitive adhesives (PSA) made of these terpolymers were good but the holding power was not enough to apply them as PSAs. It was found that these terpolymers should be modified to obtain high holding power. The blood compatibility of these terpolymers was also investigated. It was found that they had a significant blood compatibility. Thrombi were not observed on the terpolymer surface after immersion in blood while, on a polystyrene (PSt) surface, many blood clusters were observed. After immersion in platelet-rich plasma (PRP), a few adhered platelets were observed on terpolymer surface but they did not deform and maintained their spherical form, while many platelets were observed on polystyrene.

Nanometer Scale Structures Resulting from Graphite Oxidation

ABSTRACTScanning tunneling microscopy (STM) and spectroscopy (STS) were used to characterize highly oriented pyrolytic graphite (HOPG) which was oxidized by two different methods, furnace heating in atmosphere and immersion in oxygen plasma. The character of the surfaces was found to be dissimilar on a micron scale but comparable on a nanometer scale, at which both appear to be comprised of sharp step edges. Variations in local electronic structure near a step edge were compared.

Factors influencing the ablation of atherosclerotic plaque with the argon laser

This paper describes the ablative effect of argon laser light, delivered fibre optically in vitro, on 234 segments of atherosclerotic human aorta. Variables such as energy density, type of atheroma and immersion media were taken into account. All irradiated specimens were subsequently submitted to histological examination and crater volumes in mm3 were derived from micrometer measurements made at light microscopy. Results showed: (1) a linear relationship between energy dose and crater volume in fibrous atheroma; (2) significantly greater surrounding tissue damage in the higher energy dose groups; (3) a lower dose response in calcified tissue than in fatty streaks or fibrous atheroma; (4) immersion of tissue in blood during ablation resulted in a significantly greater dose response than immersion in plasma or saline, and the corresponding surrounding tissue damage was greatest under blood. Thus, argon laser light is both effective and predictable in response when ablating atheromatous tissue, and the efficiency of the process depends on the immersion medium. The degree of surrounding tissue damage depends on the energy dose.

In Vitro Comparison of the Properties of Polydioxanone, Polyglycolic Acid and Catgut Sutures in Sterile and Infected Urine

The effect of immersion in sterile urine, infected urine and plasma on the breaking strength and stiffness of polydioxanone (PDS), polyglycolic acid (PGA) and chromic catgut was studied. Tests were done under closely controlled conditions with immersion periods varying from zero to ten days.The breaking strength and stiffness of the three suture materials was not significantly changed by immersion in plasma for periods up to ten days.In sterile urine, PDS lost all of its strength after three days of immersion while PGA lost 64% of its initial breaking strength after ten days. Catgut maintained its strength over the ten day study period.In E. coli-infected urine, PDS lost all of its strength in six days while PGA lost 71% and catgut 8% after ten days.In proteus-infected urine, PDS and PGA lost all their breaking strength after one day of immersion while catgut lost 5.8% of its initial strength after 10 days.Corresponding decreases in stiffness were also observed.

Resistance to Bacteria in Hemorrhagic Shock. VII. Demonstration of Leucotoxin in Plasma of Shocked Rabbit.

Summary and Conclusions1) Normal macrophages from the peritoneal cavity of the normal and shocked rabbit, and granulocytes from the irritated peritoneal cavity of the normal rabbit show no significant morphologic injury after immersion in normal rabbit plasma for one hour at 37°C. But after immersion in plasma from rabbits in hemorrhagic shock, a considerable percent of the cells show morphologic injury. A large number of granulocytes show changes similar to those characteristic of the L.E. cells. These changes are reversible if the shock plasma is replaced by normal plasma. 2) Shock plasma produces a severe depression of the phagocytic index; the percent of bacteria ingested is some 40% less than in normal plasma, and the percent of cells containing bacteria is some 30% less than in normal plasma. Shock plasma also reduces the bacteriostatic power of the phagocytes. The granulocyte in this respect appears to be damaged more severely than the macrophage. The extent of the injury produced by the plasma fro...