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Biomedical subjects

M B Heaton

Publications and source records attributed to M B Heaton.

12 recordsLinked to original sources
PubMed1978

Species-specific auditory discrimination in bobtail quail neonates.

Incubator-hatched bobwhite quail neonates were tested individually in a variety of single call and simultaneous auditory choice tests involving 6 adult quail vocalizations and a chicken exodus call. The quail showed a high degree of responsiveness (100%) to 3 adult quail vocalizations and significantly less responsiveness (40-50%) to 3 other quail calls and to the chicken exodus call in single call tests. In simultaneous choice tests, the quail were selectively responsive to a call of their own species over the chicken call, and they also showed certain intraspecific preferences. Because of their high degree of responsiveness, coupled with selectivity of their approach responses, bobwhite quail neonates are ideal for the laboratory investigation of the development of auditory perception.

Animals↗
PubMed1977

Tectal projection of displaced ganglion cells in avian retina.

Labeled displaced ganglion cells (DGC's) were observed in chick embryos (day 12 to 18) and hatchings following discrete tectal injections of horseradish peroxidase (HRP). Average DGC diameter was 10 to 15 mu, approximately twice the size of orthotopic ganglion cells. Six to 12 DGC's were found per 15 mu section. These findings conclusively demonstrate a tectal projection for the DGC.

Animals↗
PubMed1977

A technique for introducing localized long-lasting implants in the chick embryo.

A technique is described for making chronic, localized implants of drug-impregnated Silastic in early chick embryos. This silicone material has been shown to gradually and uniformly release its impregnated contents under such conditions. Following implantation of pieces of Silastic treated with the metaphase-blocking drugs colchicine and vinblastine into the wing-buds of 41/2-5 day chick embryos, 53-75% survived 4-5 days, at which time they were sacrificed. Non-impregnated (control) Silastic was also implanted in a group of embryos. In this group, 90% survived 4-5 days. The antimitotic effects of the drugs were very well localized to implanted wings, which were reduced in size by approximately 55% at the time of sacrifice (day 8-9 of incubation). In control embryos, the implanted wings were normal in size and general morphology. It is suggested that the technique could have numerous applications for the study of neuroembryology or other aspects of embryogenesis.

Animals↗
PubMed1976

Developing visual function in the red jungle fowl embryo.

The onset of visual system function in the wild red jungle fowl embryo was measured by the pupillary reflex technique and compared with its domesticated descendant, the domestic chick. The first neurally mediated pupillary reflex in the jungle fowl embryos was found at Day 15 of incubation after 77% of incubation was completed. This point did not differ significantly from the onset of this reflex in the domestic chick embryo (after approximately 83% of incubation). Thus, it was concluded that the relatively late onset of overt visual system function in the chick, as compared with several other precocial avian species, was not a result of its history of intense domestication but rather was most likely a normal characteristic of this and other closely related species.

Age Factors↗
PubMed1975

The retrograde transport of horseradish peroxidase from the developing limb of the chick embryo.

Chick embryos ranging in age from 4.0 to 18 days of incubation and 1-2-day-old hatchlings received injections of HRP solutions directly into the leg musculature. After survival periods of from 5 to 25 h motoneurons and cells in the spinal sensory ganglia were found to be stained with the HRP reaction product. It was found that the first appearance of a positive HRP reaction coincided with the time when nerve processes are first detected in the limb-bud by silver techniques (i.e. at 4.5 days of incubation). Only neurons with processes in the region of injection showed a positive reaction. The demonstration of a retrograde transport mechanism in neurons and axons which are still undergoing growth and differentiation provides a possible mechanism for the peripheral regulation of certain features of CNS neurogenesis. The application of this technique during development may also allow one to map neuroanatomical pathways during their formation.

Animals↗
PubMed1975

Behavioral adaptation in neonatal chicks following embryonic vestibular system rearrangement.

Micro-surgery was performed on chick embryos during the second day of incubation (45-50 hours). Either one otocyst was removed or was rotated 180 degrees and reimplanted. The chicks' behavior was studied for 1-13 weeks after hatching. The unilateral loss or rearrangement of vestibular (and auditory) input led initially to abnormal behavior patterns, usually consisting of poor righting reflexes, deficits in locomotion, balance and pecking accuracy, and a pronounced head nystagmus. However, in every case, these abnormalities were corrected within a few days after hatching, so that the operated animals became almost indistinguishable from normal controls. Histological evidence confirmed the extent of the loss of the vestibular and auditory structures and nuclear amalgams. The observed capacity of the neonatal chick to adapt to this sensory loss or disorientation is a rather rare example of infraprimate behavioral adjustment or modifiability, contrasting with the frequent demonstrations of behavioral rigidity in lower forms.

Adaptation, Physiological↗
PubMedDate not supplied

Micro-injections in the avian embryo: technical notes.

Procedures and instrumentation are described for making micro-injections into early avian embryos. Tools for implementing injection include support probes and micro-cannula adapters, both of which greatly reduce embryonic insult. Using these instruments, viability following certain early embryonic injections has been shown to increase from 29 to 95%.

Animals↗