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Vocalization is rare among non-avian reptiles, with the exception of the crocodilians, the sister taxon of birds. Crocodilians have a complex vocal repertoire. Their vocal and respiratory system is not well understood but appears to consist of a combination of features that are also found in the extremely vocal avian and mammalian taxa. Anatomical studies suggest that the alligator larynx is able to abduct and adduct the vocal folds, but not to elongate or shorten them, and is therefore lacking a key regulator of frequency, yet alligators can modulate fundamental frequency remarkably well. We investigated the morphological and physiological features of sound production in alligators. Vocal fold length scales isometrically across a wide range of alligator body sizes. The relationship between fundamental frequency and subglottal pressure is significant in some individuals at some isolated points, such as call onset and position of maximum fundamental frequency. The relationship is not consistent over large segments of the call. Fundamental frequency can change faster than expected by pressure changes alone, suggesting an active motor pattern controls frequency and is intrinsic to the larynx. We utilized a two-mass vocal fold model to test whether abduction and adduction could generate this motor pattern. The fine-tuned interplay between subglottal pressure and glottal adduction can achieve frequency modulations much larger than those resulting from subglottal pressure variations alone and of similar magnitude, as observed in alligator calls. We conclude that the alligator larynx represents a sound source with only two control parameters (subglottal pressure and vocal fold adduction) in contrast to the mammalian larynx in which three parameters can be altered to modulate frequency (subglottal pressure, vocal fold adduction and length/tension). [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to asses the functional results of eccentric homologous penetrating keratoplasty in respect of diagnosis as well as position and size of the corneal graft., Patients and Methods: In this retrospective study, visual acuity and astigmatism of 117 cases of a round eccentric homologous penetrating keratoplasty in 91 eyes of 91 patients were analysed. The PK became necessary because of a corneal ulcer (104), 6 eyes with corneal scars and 7 eyes with ectatic corneal diseases. Using 84 postoperative slides the following parameters were quantified: graft diameter and transparency, distance of the geometric centre of the cornea from the central trephination margin (distance) as well as from the geometric centre of the graft (decentration). Seventeen grafts were classified as eccentric peripheral keratoplasty (mean diameter 5.0 +/- 1.7 mm) with the optical axis through the host cornea and 67 as eccentric central keratoplasty (7.0 +/- 1.3 mm) with the optical axis through the graft., Results: The average follow-up period was 25 months. The astigmatism after 3/12/24 months was 6.7/6.3/5.5 D, but was irregular and not measurable in 74 %/52 %/49 %. The astigmatism increased with increasing decentration (24 months, p = 0.04). After 3/12/24 months, the VA in ulcers was 0.1/0.16/0.16, in scars 0.2/0.6/0.5 and in ectatic diseases 0.3/0.5/0.6. The position of graft and the visual acuity did not correlate significantly. After 24 months, larger the graft size was associated with better visual acuity. With increasing decentration the visual acuity decreased (p = 0.02) and was significantly lower (0.15) in the case of - 2.0 < distance < 2.0 mm than in the case of distance > 2.0 mm (0.4; p = 0.01)., Conclusion: The diagnosis resulting in eccentric penetrating keratoplasty seems to have a major impact on the long-term functional prognosis of visual acuity. In addition, visual acuity is limited by high and often irregular astigmatism. Our results indicate that an increasing decentration of the graft is not invariably associated with decreasing visual acuity, provided the graft-host junction is not located in direct proximity of the optical axis.