Donald W. Ott

Incorporation of Nitric Oxide-Releasing Crosslinked Polyethyleneimine Microspheres into Vascular Grafts

Over the years, many attempts have been made to increase the patency of small- to medium-sized prosthetic vascular grafts. However, none of them has greatly affected long-term rates. Recently, nitric oxide (NO) has been shown to inhibit thrombus formation in such grafts, suggesting that local delivery of NO may help to increase graft patency. This study describes the site-specific delivery of NO by entrapping NO-releasing microspheres in the pores of a vascular graft. NO-releasing polyethyleneimine microspheres (PEIX) were developed using a novel water-in-oil emulsion technique involving chemical crosslinking with a bis-epoxide. The PEIX microspheres were then derivatized with NO forming the [N(O)NO]- moiety of the diazeniumdiolates formerly known as NONOates. These polymeric NO-releasing particles were found to spontaneously release 194 nmol NO/mg with a half-life of over 66 h under physiologic conditions. Fluorescein isothiocyanate-labeled microspheres were then embedded into the pores of a 60-micron nonreinforced Gore-tex vascular graft using a simple evacuation technique and evaluated for microsphere placement and NO release. Scanning electron microscopic analysis showed the microspheres entrapped in the pores of the vascular graft releasing 10 nmol NO/mg with a half-life of 51 h. The microspheres remained entrapped in the graft even after immersion and NO release, as confirmed by fluorescence of the medium. These results suggest that NO-releasing particles can be incorporated into the pores of a vascular graft to deliver therapeutic amounts of NO for the prevention of thrombosis in small-diameter prosthetic grafts.

Developmental cytology of the genus Vaucheria II. Sporogenesis in V. fontinalis (L.) Christensen

Vegetative filament apices of Vaucheria which differentiate into zoospores under altered culture conditions have been examined in sections prepared for light and electron microscopy. Soon after the migration and accumulation of cytoplasmic organelles into the filament tip, the centriole pair associated with each nucleus begins to form internal flagella. The flagella and their nuclei converge into many internal flagellar pools which then migrate to the surface of the zoospore and become part of the plasma membrane. These events in the filament apex take place during the septation of the vegetative filament. At the time of zoospore release, all nuclei are positioned just beneath the zoospore surface and are intimately associated with pairs of external flagella.

The Influence of Lamellar Liquid Crystalline Media in the Hydrolysis of 4-Substituted Benzylidene t-Butylamine N-Oxides

Abstract Cationic lamellar liquid crystalline morphologies decrease the rate of hydrolysis of a series of 4-substituted benzylidene t-butylamine N-oxides compared to aqueous solutions. Rate constants for the aqueous acid hydrolysis decrease as the electron releasing effect increases and they are linear when plotted against σ+-substituent constants. Rho-values indicate a less sensitive reactivity series than the benzoic acids and a more sensitive reactivity in lamellar solvents. Reaction rates for the series in the latter solvent parallel the hydrophobic substituent constants. Three different lamellar morphologies were identified in the aqueous surfactant systems.

Xanthophyte, Eustigmatophyte, and Raphidophyte Algae

The Xanthophyceae, Eustigmatophyceae, and Raphidophyceae are three independent classes of stramenopile algae (Heterokontophyta or Ochrophyta); they are not closer related with each other. Most Xanthophytes are unicellular or colonial coccoid algae, others from multicellular filaments and or exhibit thalli composed of multinucleate siphons. The Eustigmatophyceae comprises only coccoid members which are very difficult to distinguish from the coccoid Xanthophytes. Freshwater Raphidophytes are rather distinct, because they form flagellated vegetative stages. The color of Xanthophytes and Eustigmatophytes is yellowish green due to the absence of the brown fucoxanthin, present in Raphidophytes and other stramenopile algae. Only the Eustigmatophytes lack chlorophyll c. Many Xanthophytes and Eustigmatophytes share that they predominately occur in terrestrial habitats, e.g. soil, representing a small group of terrestrial algae with their plastids obtained from an ancestral red alga by secondary symbiosis. For Raphidophytes only three genera are recognized in freshwater yet and they are observed within the plankton.

Evidence of Selfing Hermaphroditism in the Clam Shrimp Cyzicus Gynecia (Branchiopoda Spinicaudata)

The branchiopods display a broad range of reproductive modes, including dioecy, hermaphroditism and parthenogenesis. An order within Branchiopoda, Spinicaudata or the “clam shrimp” are also reported to have all three of these breeding systems; yet parthenogenesis has only been inferred on the basis of a lack of males in several clam shrimp species. Herein we report a detailed analysis of the breeding system of one of these supposed parthenogenetic clam shrimp: Cyzicus gynecia (Mattox, 1950). A RAPD genetic analysis across a three state geographic range (New Jersey, Massachusetts, and New York) showed high levels of genetic differentiation among populations indicative of reproduction without males. Additionally, functional male gametes were found to be produced in a small region of the gonad located just posterior to the head. Thus, we posit that the purported parthenogenetic females of C. gynecia are instead functioning hermaphrodites that produce a small amount of sperm anteriorly in an ovotestis that they then use to fertilize their own eggs. These findings suggest that there are, in fact, no parthenogenetic species within Spinicaudata, but rather all “female” species are most likely self-compatible hermaphrodites.

Effects of polyethyleneimine on cyanobacterium Anabaena flos-aquae during cell flocculation and flotation

For production of cyanobacterial gas vesicles, polyethyleneimine (PEI) was used as flocculent to enhance the collection of buoyant Anabaena flos-aquae cells by flotation. During the flocculation-flotation process, PEI was found to cause the cells to release blue pigment(s) (presumably phycocyanin) and probably other cytoplasmic materials. The kinetic profile of the pigment release was followed and compared with that of the culture flotation. The effects of PEI on the cyanobacterial cells were also examined using transmission electron microscopy. Unlike the previous reports for the effects of PEI on Gram-negative bacteria, our observations did not reveal significant morphological changes of the PEI-exposed cells of A. flos-aquae. There were no apparent negative effects on the desired product, gas vesicles, during the PEI-induced flocculation-flotation process for cell collection.

Cyst development in the conchostracan shrimp, Eulimnadia texana (Crustacea: Spinicaudata)

The fertilized egg (or cyst) of branchiopods is a highly resistant stage in the life cycle of these aquatic crustaceans. Previous examinations of these cysts have determined that early embryonic development arrests at a late blastula stage, resulting in a small, crescent-shaped body within the egg shell of these shrimp. Herein, we examine the early development of these embryos by sectioning eggs in the ovotestis, brood chamber, and several time periods after exit from the brood chamber in the clam shrimp Eulimnadia texana Packard. The early sections find no evidence of internal fertilization in the ovotestis. Eggs in the ovotestis showed no signs of cell division, whereas eggs sectioned from the brood chamber were found to be undergoing early embryonic development. A number of empty egg shells and the lack of unfertilized eggs in the brood chamber suggested that egg yolks quickly degrade after egg extrusion from the ovotestis. Cysts that were allowed to develop for 24, 48, 72, and 96 h, 1 week and 1.5 years were sectioned, and embryonic development did not change after the 48 h time period. Thus, embryos appear to arrest development somewhere between 24 and 48 h after exiting the brood chamber.

Developmental Cytology of the Genus Vaucheria IV. Spermatogenesis

Spermatogenesis among several species of Vaucheria has been examined in sections prepared for light and electron microscopy. Early developmental stages of zoosporogenesis and spermatogenesis are identical; however, cytoplasmic cleavage progresses to completion in the antheridium, while incipient cleavage is rudimentary in the zoosporangium. During morphogenesis of the antheridium, nuclear cyclosis is inhibited and flagella develop from nucleusassociated basal bodies. The flagella project into internal membrane reservoirs (termed flagellar pools) which, unlike their counterparts in zoosporogenesis, fail to migrate to the surface of the antheridium, while chloroplasts are excluded from uninucleate protoplasmic segments by completion of cleavage furrow development.

New Records of Vaucheria Species (Xanthophyceae) with Associated Proales Werneckii (Rotifera) from North America

Abstract The presence of galls on species of Vaucheria was investigated both seasonally and in a number of locations in North America. These galls are induced by the rotifer, Proales werneckii . In an Ohio stream, Vaucheria bursata and V. geminata were found to have galls throughout their growing season; September to January. Galls were most abundant in October and ranged in size from 90–260 μm in width and 140–790 μm in length. New records of Vaucheria with galls from locations in Alabama, California, Georgia, Louisiana, North Carolina, Ohio and Tennessee are reported. Three of the five taxa collected were not previously known to contain galls. In addition, worldwide literature on the distribution of these associated taxa was reviewed.

Developmental cytology of the genus Vaucheria III. Emergence, settlement and germination of the mature zoospore of V. Fontinalis (L.) Christensen

After septum formation and dissolution of the zoosporangial apex wall in Vaucheria fontinalis (L.) Christensen, a multi-flagellated zoospore is released and remains motile for a few hours. Settlement of the zoospore occurs with flagellar retraction, after which a cell wall is formed by peripheral vesicles. Subsequent germination initiates polarity and the development of vegetative filament growth.