Bruce L. Tedford

Flash and pattern reversal visual evoked potentials in C57BL/6J and B6CBAF1/J mice

Visual system responses (visual evoked potentials) to flash (FVEP) and pattern reversal (PRVEP) stimuli were recorded in mice. Two strains were used: black C57BL/6J mice and agouti B6CBAF1/J mice (first generation offspring of C57BL/6J females and CBA/J males.) Subjects were sedated with ketamine and xylazine. Flash rate (FVEP) and stimulus spatial frequency and pattern reversal rate (PRVEP) were varied to determine optimum stimulus parameters. Normative FVEP and PRVEP data were collected from mice of both strains after determination of optimum parameters. Five positive and four negative alternating peaks were routinely observed in the FVEP, while three positive and three negative alternating peaks were seen with the PRVEP. Varying the flash rate, the pattern reversal rate, and spatial frequency significantly affected nearly all amplitude and latency measures in the responses. Significant differences between strains were seen on some, but not all, latency and amplitude measures when the stimulus parameters were varied.

Daily rhythm of plasma insulin in japanese quail (Coturnix c. japonica) fed Ad libitum

1. Plasma levels of immuno-reactive insulin (IRI) of 6 groups of 5-week-old quail, held on a 16L:8D photoregime, were measured every 4 hr, for 24 hr. 2. Concentrations of plasma IRI varied during the 24 hr period (Anova, P < 0.003). Insulin levels were high (mean = 857 pg/ml) from 6 a.m. (light onset) until 6 p.m. (4 hr before light offset) and low (mean = 185 pg/ml) at 10 p.m. and 2 a.m. 3. IRI concentrations at 6 a.m., 10 a.m., 2 p.m. and 6 p.m. were significantly different from values at 2 a.m. and 10 p.m. by Waller grouping. 4. Low IRI levels at light offset (10 p.m.--when the birds had full crops and were in an absorptive state) and high levels at light onset (6 a.m.--before feeding resumed) indicate that feeding does not fully account for the IRI rhythm.

Postnatal cochlear function development in normal dogs and deaf Dalmatians

Pigmentation‐associated congenital deafness occurs in humans and other species, including dogs (especially Dalmatians). The deafness generally results from degeneration of the stria vascularis after an otherwise normal period of development; time of occurrence is unknown in humans but is early postnatal in several animal species. Noninvasive perinatal studies of audition in dogs are not possible until 2–3 weeks of age, when the ear canals open. Methods developed to follow the postnatal development of peripheral auditory function in dogs and preliminary findings in normal pups and deaf Dalmatians are reported here. Surgery was performed 24–48 h after birth to implant recording electrodes and tubing for auditory stimulation in the sealed ear canal near the tympanum. Pups stayed with mothers except for recordings. Daily recordings (150–3000 Hz, 10 ms) were collected between the implanted electrode and vertex in response to click stimuli (100 μs, 11.4/s, 135 dB SPL [machine setting]) applied through the impla...