Arterial aneurysms in HIV patients: molecular mimicry versus direct infection?

There is growing literature on the subject of aneurysmal degeneration of arteries in patients who are infected with HIV. A patient recently seen at our medical center with an aneurysm of the carotid artery stimulated our interest in reviewing the mechanisms by which HIV may initiate or predispose to these pathologies. There are at least three major possibilities: (1) immunodeficiency allows bacteria that are known to cause mycotic aneurysms to proliferate without immune restraint; (2) one or more of the HIV envelope proteins sufficiently resemble one or more artery-specific-antigenic proteins (ASAPs) that may trigger an autoimmune response (molecular mimicry); and (3) the HIV virus itself infects arterial-resident cells that maintain the integrity of the load-bearing matrix. The computational searches reported here suggest that the ASAP, matrix cell adhesion molecule-1 (Mat-CAM-1), has a high degree of similarity to known ligands for HIV envelope proteins gp41 and gp120. No similarities of Mat-CAM-1 to the HIV envelope glycoproteins were detected. Accordingly, among the possibilities for explaining the HIV/aneurysm connection, direct infection of aortic fibroblasts by the HIV virus is more likely to be the pathogenetic mechanism than the process of molecular mimicry.

The use of RAPD for identifying and classifying Musa germplasm.

Using the technique of random amplified polymorphic DNA (RAPD), we have identified 116 amplification products in Musa germplasm using nine primers. This has enabled us to identify RAPD markers that are specific to each of nine genotypes of Musa representing AA, AAA, AAB, ABB, and BB genomes. The pattern of variation observed following the application of multivariate analyses to the RAPDs banding data is very similar to the pattern of variation defined using morphological characters and used to assign Musa material into the different genome classes.

Cryopreservation of plant cells.

Cryopreservation, that is, the viable storage of cells at the temperature of liquid nitrogen (-196°C), has wide relevance in many areas of pure and applied biology. Examples of its very successful use can be found in the storage of microbes and of semen (1). More recently, attention has been given to the development of cryopreservation methods for embryos, including those of humans, tissues, and organs for transplantation and blood components. In the context of plant research, realization of the potential applications of cryopreservation has been somewhat latent. However, several clear areas for application can be identified that involve the need to store exact genotypes in a stable state.

Ammonia transport by the turtle urinary bladder.

Ammonia transport across the turtle bladder was examined by adding NH4Cl to the serosal (S) or mucosal (M) solution. With appropriately fixed levels of pH and/or NH4Cl concentration the transepithelial flow of ammonia parallels the extracellular concentration of NH+4 while that of NH3 is kept constant and parallels the extracellular concentration of NH3 while that of NH+4 is kept constant. This suggests that NH+4 as well as NH3 traverses the bladder wall. The apparent S----M permeability to NH3 was 15-18 times greater than that to NH+4. At pH 6.4 in both S and M solutions, the net flow of ammonia was from S----M, but at pH 8.4 in the S and 6.4 in the M or vice versa ammonia transport was of the same magnitude in both directions. The relative permeability of the M membrane to NH+4 was less than that to Na and nearly the same as that to K. The relative permeability of the S membrane to NH+4 was greater than that to K. At S pH of 8.4 and M pH of 6.4, ammonia transport was a linear function of NH4Cl concentration. At S pH of 6.4 and M pH of 6.4, ammonia transport was a saturation function of NH4Cl concentration in that it was linear up to 5 mM and constant and maximal in excess of 7.5 mM. The net transport of methylamine directed from S to M was competitively inhibited by NH4Cl, suggesting that the two substances are transported through a common carrier system. At pH 6.4 in both S and M, the S addition of NH4Cl induced an increase in reverse short-circuit current, the magnitude of which approximated the chemically determined rate of ammonia transport. This means that ammonia transport at pH 6.4 is, at least in part, electrogenic due to the flow of ionic NH+4 through a transbladder conductive path. However, when the S pH was raised to 8.4 the increase in ammonia transport was not associated with an increase in current. The present study demonstrates that the turtle bladder is capable of transporting ammonia with different characteristics of NH+4 and NH3 transport.

Proline: A Novel Cryoprotectant for the Freeze Preservation of Cultured Cells of Zea mays L.

Proline is an effective cryoprotectant for the storage of cultured cells of Zea mays L. in liquid N(2). Increased freeze tolerance can be achieved by pregrowth for 3 to 4 days in medium containing proline. Cells cryoprotected with proline have an increased recovery potential when compared with cells cryoprotected with dimethylsulfoxide and glycerol. They also show a reduced postthaw viability loss and greater tolerance of a range of postthaw culture conditions. It is suggested that the mechanism of action of proline may be similar to that in its putative role of conferring protection against natural stresses. It may be protecting the cell against solution effects caused by dehydration during freezing. These findings are discussed in relation to other freeze tolerance enhancing treatments.

Freeze Preservation of Somatic Embryos and Clonal Plantlets of Carrot (Daucus carota L).

Cell suspensions of carrot (Daucus carota L.) can be cryopreserved by slow freezing (about 2 C per minute) in medium containing dimethylsulfoxide as a cryoprotectant. After storage in liquid nitrogen and thawing they demonstrate a high viability and are able to resume growth. Such a method entirely fails to preserve clonal plantlets; somatic embryos cease organized development at the time of freezing and recover growth only by secondary embryogenesis. Modification of the procedure, involving the removal of superficial moisture from cryoprotectant-treated embryos and plantlets and enclosing them in a foil envelope before freezing, greatly improves their survival potential. The use of dimethylsulfoxide at levels between 2.5 and 20% (v/v) and freezing at rates between 1 and 5 C per minute yielded viable preparations under appropriate thawing conditions. In general, treatments which increased tissue dehydration before or during freezing were most successful when followed by relatively slow thawing. Conversely where dehydration to a lesser degree was achieved, more rapid thawing was advantageous. Postthawing washing or inoculation into liquid media was inhibitory to recovery. On semisolid regrowth medium, somatic embryos resumed normal development, whereas in plantlets the root and shoot meristem regions gave rise to new growth. In both cases, inclusion of activated charcoal in the medium promoted organized growth.