Douglas W. Hill

Morphological transformation of Candida albicans in tissues of mice.

Summary A morphological alteration of yeast-like cells of C. albicans and C. stella-toidea has been shown to occur within 1 hour after injection into the subcutaneous tissues of mice. Yeast-like cells of other members of the genus Candida failed to exhibit these alterations under the same conditions. The yeast-like cells of C. albicans had formed elongated pseudomycelia within 1 hour after injection. At later times considerable growth of these filaments with the appearance of septa was observed. Other species of the genus Candida retained their typical yeast-like morphology. It has been postulated that filamentation of C. albicans in vivo serves as a hindrance to ingestion by mouse phagocytes. The results suggest a significant role for these morphologically altered organisms in the pathogenesis of experimental moniliasis in the mouse.

Effect of Millimeter-Wave Irradiation on Growth of Saccharomyces cerevisiae

Cultures of Saccharomyces cerevisiae were exposed for 4 h to millimeter waves in three frequency ranges between 41.650 and 41.798 GHz. The irradiation frequency was stabilized to within ±50 Hz. The temperature difference between irradiated and sham-irradiated samples was maintained to within ±0.01°C. Growth was measured optically during the irradiation, and viability counts were done at the end of the irradiation. At least three experiments were performed at each of 15 frequencies.

Biological activities of monoclonal antibodies reactive with antigenic sites mapped on the g1 glycoprotein of la crosse virus.

Monoclonal antibodies have been prepared which are specific for the G1 glycoprotein of La Crosse virus. By competitive radioimmunoassay, 20 IgG-producing clones were found to map in eight antigenic sites; three distinct and five which showed individual patterns of partial competition indicating they may be in close proximity. Unique in situ trypsin cleavage sites on G1 have helped in orienting these defined epitopes relative to the viral membrane. Antibody molecules belonging to one epitope (H) mapped on the trypsin-resistant part of G1 and had negative or extremely low neutralizing and hemagglutination inhibition activities. Seven epitopes were located on the trypsin-sensitive part of G1, a 25,000-Da region which is probably the amino terminus of the protein. Antibodies binding to six of these seven epitopes (A, B, D, E, F, and G) were positive for neutralization and inhibition of hemagglutination, but exhibited a wide range of activities. Epitopes A, F, and G seem to be in an immunodominant region containing the primary site(s) for attachment to cell receptors. Antibody specific for the remaining epitope (C) was unique in that it bound to a site closely adjacent to neutralizing antibody sites, enhanced antibody binding to epitopes A and G, but lacked the capacity to neutralize viral infectivity or inhibit hemagglutination. Enhancement of antibody binding also occurred between two other closely adjacent sites (B and D) and one other distinct epitope (G). In addition, antibody from an IgM-producing clone competed with antibodies to these same four epitopes (B, C, D, and G), indicating they are in close proximity. These data have been used to construct an antigenic map that may now be used as a working model for the study of virus neutralization.

Overwintering of Western Equine Encephalitis Virus.

Summary 1) Adult garter snakes (Thamnophis spp.) inoculated intraperitoneally, overwintered WEE virus for at least 139 days. There was a steady decline in virus, with only 1 of 14 showing a viremia after 92 days hibernation. With warm spring weather, (139 days after virus inoculation) 9 of 14 animals exhibited a viremia with blood titers varying from 10-1 to 10-3.5. 2) Two of 4 garter snakes inoculated with WEE virus and kept at 4°C, for 17 days harbored the virus in the blood, but not the brain. One snake harbored the virus in the brain but not in the blood. No virus was detected in either blood or brain after 17 days at 4°C in one of the snakes.

The Effect of Proteolytic Cleavage of La Crosse Virus G1 Glycoprotein on Antibody Neutralization

The envelope of the bunyavirus La Crosse contains two glycoproteins, G1 (120 000 mol. wt.) and G2 (38 000 mol. wt.). When incubated with trypsin or plasmin, the G1 glycoprotein of virus grown in cell culture was cleaved, leaving two different sized polypeptides in the envelope (67 000 and 95 000 mol. wt.). Chymotrypsin cleaved G1 leaving polypeptides of 70 000 and 100 000 mol. wt. G2, however, was not altered by these enzymes. When used in antibody neutralization studies, these proteolytically modified viruses were neutralized approximately 1 to 2 log10 units in 60 min while control virus was neutralized by over 4 log10 units in 20 min. Because antibody to G1, but not G2, was involved in La Crosse virus neutralization, cleavage of G1 appeared to be directly responsible for these altered kinetics of neutralization. Antibody did bind to the polypeptides remaining associated with the envelope resulting in infectious virus-antibody complexes. This indicated that a critical site in terms of antibody neutralization was removed from G1 by proteolytic enzymes.

Raman spectroscopy of liposomes exposed to millimeter waves

Several biological effects resulting from exposure to millimeter waves have been reported. In an attempt to determine if millimeter waves might affect the conformational state of membranes, sonicated liposomes have been irradiated with millimeter waves at 41.650 GHz, stabilized in frequency to ±50 Hz. Raman spectra from the lipid vesicles were then collected in the conformational and in the C‐H stretching region. No changes in either the Raman peak locations or relative intensities were detected upon millimeter‐wave irradiation, either below or above the transition temperature of the phospholipid (41 °C).