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Biomedical subjects

M Cheal

Publications and source records attributed to M Cheal.

33 records · Page 2Linked to original sources
PubMed1983

Lifespan ontogeny of breeding and reproductive success in Mongolian gerbils.

An analysis was made of demographic data collected from a colony of Mongolian gerbils (Meriones unguiculatus). The data on births of over 3800 gerbils provide evidence on several aspects of development and fecundity. Approximately 4% more females than males survived to weaning. Mean number of pups per dam per year was estimated to be 48.3, greater reproductive success than reported previously. The shortest period of gestation resulting in viable pups was 25 days. Implantation was delayed by the presence of suckling pups. When gestation was prolonged, there was a direct relationship between the number of pups being suckled concurrently and the length of the delay. Length of gestation did not affect the size of the subsequent litter. Female gerbils gave birth as early as 72 days of age. Gerbils continued to reproduce until after 2 years of age in some cases. There were fewer pups per litter born to older females, fewer pups per litter with increasing parity, and longer intervals between litters with increasing age.

Aging↗
PubMed1982

Implications for multiple transmitter mediation of amphetamine-induced stereotypies.

Gerbils were pretreated with the dopamine (DA) receptor blocker, pimozide, prior to stereotypy-inducing injections of d-amphetamine. Some of the stereotypies induced with amphetamine were blocked, but some were not, supporting the hypothesis that multiple neurotransmitters are involved in the mediation of amphetamine-induced stereotypy. In addition, when apomorphine hydrochloride was injected, different stereotypic motor behaviors were induced than were induced with amphetamine. The behavioral changes following amphetamine treatment could be classified into four groups: (1) those that are probably DA related, based on the fact that they were induced with either amphetamine or apomorphine, and amphetamine induction was blocked with pimozide; (2) those that are probably not DA related because they were not induced by apomorphine, and amphetamine induction was not blocked by pimozide; (3) those behaviors that may be incompatible with stereotypic behaviors, were reduced with either amphetamine or apomorphine, but were not maintained with pimozide; and (4) circling, which was induced with amphetamine, blocked with pimozide, but not induced with apomorphine.

Animals↗
PubMed1982

Attention and habituation: catecholamine interactions and sex differences.

Norepinephrine (NE)-dopamine (DA) interactions in mediation of long-term habituation were tested using the stimulus-elicited investigation paradigm. Systemic injections of clonidine hydrochloride (CLON), an alpha-adrenergic receptor agonist, given before apomorphine (APO) (1 mg/kg SC), a DA receptor agonist, prevented APO-induced disruption of the duration measure of habituation 25-hr later. A lower dose was effective in female gerbils than that required for male gerbils, suggesting that females are more sensitive to the effects of clonidine. In addition, apomorphine, with or without CLON (0.01 mg/kg), increased locomotor activity in male gerbils but reduced activity in female gerbils. The same dose of CLON that prevented APO-induced disruption of 24-hr habituation did not reverse APO-induced reduction of investigation of an object or an odor, or APO-induced changes in activity. Neither CLON nor desmethylimipramine, a blocker of NE reuptake, had any selective effects on investigation of novel stimuli or short-term habituation showing that relative NE-DA activity can be disrupted without interfering with the behavior, However, CLON interfered with the frequency measure of long-term habituation in male gerbils but not in female gerbils at any dose used (0.0100.3 mg/kg). THe data suggest important sex dependent NE-DA interactions in mediation of long-term habituation.

Animals↗
PubMed1977

Regeneration of fungiform taste buds: temporal and spatial characteristics.

The gross morphology of the tongue of the Mongolian gerbil Meriones unguiculatus), the location of papillae and taste buds, and the normal innervation pattern of the tongue and taste buds were determined. The chorda tympani nerve was interrupted to produce degeneration of fungiform taste buds. Regenerating chorda tympani axons followed the original nerve pathways in the tongue en route to the fungiform papillae in the epithelium where they initiated the regeneration of taste buds. The spatial distribution of reinnervated fungiform papillae and reformed taste buds was examined 7 to 19 days following surgery. Beginning at eight days following chorda tympani interruption there was a progressive increase, first, in the proportion of fungiform papillae that were reinnervated, and later in the number of reformed taste buds. On the basis of these measures it was concluded that a taste bud is reformed one to two days after reinnervation of its papilla. From the time course of reinnervation of the fungiform papillae it was calculated that some fibers regenerated at rates in excess of 2 mm/day. Regeneration was precise and systematic. The regenerating chorda tympani fibers accurately returned to the fungiform papillae; they did not follow the pathways of lingual nerve axons. In the initial stages of recovery both reinnervated papillae and reformed taste buds were preferentially located toward the front of the tongue; the reinnervation of posterior fungiform papillae was delayed.

Animals↗
PubMed1977

Taste fiber responses during reinnervation of fungiform papillae.

Crushing or transecting the chorda tympani nerve of the gerbil (Meriones unguiculatus) caused ipsilateral degeneration of taste buds in the fungiform papillae. In less than two weeks some taste fibers regenerated into the tongue and formed new taste buds and receptor cells. The recovery process was evaluated electrophysiologically in 53 gerbils by acute recording proximal to the nerve injury site. Initially the chorda tympani was electrically silent. In gerbils tested at later times spontaneous activity appeared. This was followed by responses to pressure on the tongue. Taste responses returned as early as day 11. The receptive field of regenerated taste fibers was limited to a small number of fungiform papillae. Taste responses were always associated with the presence of one or more taste buds in the receptive field. Taste buds identified as responsive to chemicals contained some fusiform cells. We found that the taste responses of single fiber, few-fiber and multi-unit preparations reflected the diversity of responses found in normal taste axons as determined by recording from 26 normal single fibers and 27 normal whole nerves. The early emergence of a variety of fiber types and responses to many chemicals in regeneration is inconsistent with the proposition that the relative chemical responsiveness of a receptor cell is strictly a function of its age; the response of a given young taste receptor is not necessarily limited to a few of the standard taste stimulants.

Animals↗
PubMed1977

Taste responses of the chorda tympani nerve in the mouse.

Electrophysiological taste responses were obtained from the chorda tympani nerve of the mouse by using a technique whereby a 50 microns nichrome wire electrode was placed against the nerve where it passes through the middle ear.

Animals↗
PubMedDate not supplied

Facilitatory or inhibitory nontarget effects in the location-cuing paradigm.

The effect of nontargets on the identification of targets in the location-cuing paradigm was investigated in order to determine whether observers consistently allocate their attention to a validly cued location and whether the effect of nontargets is to facilitate or to inhibit performance. In four experiments, the effects of a single matching nontarget or a single nonmatching nontarget were compared. In each experiment, it was shown that observers consistently allocate their attention to a cued location when a precue appears and that performance is inhibited more by nonmatching nontargets in the display than it is facilitated by matching nontargets.

Adult↗
PubMedDate not supplied

Understanding diverse effects of visual attention with the VAP-filters metaphor.

The Variable and Permeable Filters (VAP-Filters) metaphor is presented with an explanation of its advantages over other popular metaphors in accounting for attention effects in many different research paradigms. Research from laboratories of the author and others are discussed briefly and shown to result in diverse facilitatory and inhibitory attention effects on visual perception. All of these effects are consistent with the VAP-Filters metaphor.

Attention↗