The role of vertical larynx movement in vocal frequency (F0) change has attracted the attention of many researchers. Recently, Hirai, Honda, Fujimoto, and Shimada (1994) proposed a mechanism of F0 control by vertical larynx movement based on the measurement of magnetic resonance images (MRI). In F0 changes, the larynx moves vertically along the cervical spine, which displays anterior convexity (lordosis) at the level of the larynx. Therefore, the vertical larynx movement results in the rotation of the cricoid cartilage and vocal fold tension changes. The present study reexamines the above mechanism based on a qualitative analysis of midsagittal MRI data using three male subjects with evident cervical lordosis. Tracings of the jaw, hyoid bone, laryngeal cartilage, and cervical spine were compared in high and low F0 ranges. In the high F0 range, the hyoid bone moved horizontally while the larynx height remained relatively constant. In the low F0 range, the entire larynx moved vertically, and the cricoid cartilage rotated along the cervical lordosis. These results indicate that the vertical movement of the larynx comprises an effective F0 lowering mechanism, and suggest that the human morphologies of low larynx position and spinal curvature contribute to voluntary use of the vocal function.

Cervical Vertebrae↗

PubMedDate not supplied

Isolation and characterization of a Haemophilus paragallinarum mutant that lacks a hemagglutinating antigen.

In an in vivo cross-protection test with Haemophilus paragallinarum strains of serovars B and C, we isolated and characterized a mutant strain, S1M, which lacked a hemagglutinating (HA) antigen when compared biologically and immunologically with isogenic strain S1. Unlike the isogenic strain S1, the mutant strain S1M lacked HA activity against formaldehyde-fixed chicken erythrocytes, even after hyaluronidase treatment, and it did not stimulate hemagglutination-inhibition antibody in chickens immunized with bacterial cells. Dot-blot testing and immunoelectron microscopy with monoclonal antibodies against serovar C-specific HA antigens showed that strain S1M did not react with these monoclonal antibodies. Furthermore, strain S1M was found to be both non-pathogenic and non-immunogenic. In contrast, the isogenic strain S1 reacted with these monoclonal antibodies and was pathogenic and immunogenic. These results suggest that the HA antigen of H. paragallinarum serovar C. strain plays an important role in pathogenicity and immunogenicity.

Animals↗