Analysis of pancreatic disease in zebrafish.

One of the appeals of the zebrafish model is the relative ease of studying disease progression from embryonic or larval stages through to adulthood. Because of this, the zebrafish has become an important model for postembryonic pancreatic disease, particularly diabetes and pancreatic cancer. Here we present methods for using the adult zebrafish to analyze pancreas function and structure, with an emphasis on the endocrine pancreas and the beta cells. The methods include fasting, weighing adults, and anesthetizing adults, and intraperitoneal injection of glucose based on body weight. We also present dissection methods for removing the pancreas intact for histological studies and for sterile dissection of the principal islet followed by dissociation for cell culture-based studies of beta-cell function.

Rotation of middle ear ossicles during cetacean development.

Cetacean middle ears are unique among mammals in that they have an elongated tympanic membrane, a greatly reduced manubrium mallei, and an incudal crus longum that is shorter than the crus breve. Elongation of the tympanic membrane and reduction of the manubrium is thought to be related to an evolutionary rotation of the incus and malleus out of the plane of the tympanic membrane. We examined if rotation also occurs during ontogeny by comparing the middle ears of two species of dolphins (Delphinus delphis, Stenella attenuata) at different stages of development. We observed that: the incus has the body and crural proportions as in terrestrial mammals early in development; the incudomallear complex rotates approximately 90 degrees following ossification; the tympanic membrane is not elongated until relatively late in development. Therefore, some of the unique characteristics of the cetacean middle ear develop as modifications of an initially terrestrial-like morphology.

Independent test of the fourth rib aging technique.

The sternal surface of the 4th rib has been suggested as a useful predictor of adult age-at-death (Iscan et al.: Journal of Forensic Sciences 29:1094-1104, 1984; American Journal of Physical Anthropology 65:147-156, 1984). We tested its ability to do so in two tests. In the first, we developed a method of seriation and target age assignment for the 4th rib so that inaccuracy and bias of the method could be assessed by decade. We found that the 4th rib shows characteristic changes in morphology with age and can be included in multifactorial age estimates. In the second test, we applied the phase method developed by Iscan et al. (Journal of Forensic Sciences 29:1094-1104, 1984). The results of our three judges were generally similar to those reported by Iscan and Loth (Journal of Forensic Sciences 31:122-132, 1986). Measures of race differences in 4th rib morphology were included in both tests. Americans of African descent (black) showed a non-significant trend for the rib changes to be delayed compared to Americans of European descent (white). This is in contrast to the work of Iscan et al., which predicted that blacks would show a tendency toward accelerated rib changes compared to whites, especially after the early 30s (phases 5-7) (Iscan et al.: Journal of Forensic Sciences 32(2):452-466, 1987).