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Biomedical subjects

J R Alberts

Publications and source records attributed to J R Alberts.

At least 37 records · Page 2Linked to original sources
PubMed1997

Instrumental learning for a thermal reinforcer in 1-day-old rats.

One-day-old rats in a cool environment (25 degrees C) quickly acquired an instrumental response when rewarded with a 20-s warming of the platform (from 25 degrees C to 36 degrees C) on which they lay. The instrumental response, turning the head to one side, was learned within 30 min after the thermal contingency began and extinguished when the contingency was reversed. This experiment demonstrates rapid operant learning by neonates in a task that does not contain a Pavlovian stimulus-reinforcer contingency. The novel experimental method has wide applicability in psychology and neuroscience.

Animals↗
PubMed1997

Postsuckling behavioral arousal in weanling rats (Rattus norvegicus).

Twenty-day-old litters and their dams were observed in seminatural habitats consisting of a nest compartment and adjacent open field that contained powdered rat chow. It was found that pups displayed marked bursts of activity after suckling. Independent feeding reliably followed nursing bout termination (Experiment 1). Nipple withdrawal, with or without milk transfer, induced behavioral arousal whereas withdrawal of thermotactile and conspecific odor cues did not (Experiments 2-3). Increased thermogenesis was observed following milk transfer (Experiment 4). Finally, preweanling pups (10- to 12-day-olds) also displayed postsuckling arousal within the confines of the nest; full locomotor expression of this arousal was not evident until weaning age (Experiment 5). It was concluded that postsuckling arousal in weanlings functions to stimulate activities performed away from the nest and suckling, propelling pups into the field where feeding begins.

Animals↗
PubMed1996

Environmental temperature modulates onset of independent feeding: warmer is sooner.

Individual dams and their litters were observed from Days 14-22 in a seminatural environment consisting of a nestbox attached to a larger, open field in which powdered chow was available. Ambient temperature in the field was either warm (30 degrees C), moderate (21 degrees C), or cold (10 degrees C); nest temperature was always moderate. Behavior was monitored 12 hr/day by time-lapse video recording. The pups' egressions into the field and onset of independent feeding were temperature-related: Weaning was earliest in the warmth and increasingly late with decreasing ambient temperature. Among subjects in the cold condition, there was a positive correlation between duration in the field and duration feeding. Pup growth was unaffected by the temperature regimes. Environmental temperature has emerged as a determinant for early nest egressions and weaning onset.

Animals↗
PubMed1996

Perinatal stimulation and adaptation of the neonate.

The present report describes psychobiological studies of behavior around the time of birth. An adaptive, ecological perspective is presented in which stimulation of the fetus and newborn is purported to instigate adaptive postpartum behavior. Studies describing the perinatal sensory environment are reviewed, with a consideration of emergent sensory function of the fetus. It is asserted that afferent input associated with parturition perturbs the fetus and neonate, producing a general arousal state that facilitates breathing, suckling, and early learning. The view developed herein is that perinatal sensory input induces and canalizes the newborn's behavior, thereby regulating adaptive postpartum function. Deviations in afferent input may alter ontogenetic trajectories and compromise developmental outcome by reducing availability of conditions necessary for adequate postpartum adaptation.

Adaptation, Psychological↗
PubMed1996

Sampling of prenatal and postnatal offspring from individual rat dams enhances animal use without compromising development.

To assess prenatal and postnatal developmental status in the offspring of a group of animals, it is typical to examine fetuses from some of the dams as well as infants born to the remaining dams. Statistical limitations often arise, particularly when the animals are rare or especially precious, because all offspring of the dam represent only a single statistical observation; littermates are not independent observations (biologically or statistically). We describe a study in which pregnant laboratory rats were laparotomized on day 7 of gestation (GD7) to ascertain the number and distribution of uterine implantation sites and were subjected to a simulated experience on a 10-day space shuttle flight. After the simulated landing on GD18, rats were unilaterally hysterectomized, thus providing a sample of fetuses from 10 independent uteruses, followed by successful vaginal delivery on GD22, yielding postnatal samples from 10 uteruses. A broad profile of maternal and offspring morphologic and physiologic measures indicated that these novel sampling procedures did not compromise maternal well-being and maintained normal offspring development and function. Measures included maternal organ weights and hormone concentrations, offspring body size, growth, organ weights, sexual differentiation, and catecholamine concentrations.

Adrenal Glands↗
PubMed1995

Simulated uterine contractions facilitate fetal and newborn respiratory behavior in rats.

We tested the hypothesis that sensory and nonsensory factors associated with birth stimulate respiratory behavior in the fetal and newborn rat. Late gestation (Day 21) rat fetuses were externalized from the uterus with intact umbilical connections to the dam and exposed to stimuli normally associated with labor and delivery. Onset and maintenance of respiratory movements were monitored. In the first experiment, rat fetuses were exposed to either: (i) simulated uterine contractions; (ii) cooling (26 degrees C); (iii) umbilical cord occlusion; or (iv) air heated to intrauterine temperature (37.5 degrees C). Subjects were videotaped for 1 h, and respiratory movements counted during tape review. Fetuses in each group showed some respiratory behavior although compression significantly elevated respiratory rate compared to other experimental conditions. All subjects in each group were respiring after 1 h, except for pups that received umbilical cord occlusion. The 100% attrition rate of the cord occlusion-alone group was reversed by combining cord occlusion with compression, or with compression and cooling, but not by combining cord occlusion with cooling. Simulated birth pups (i.e., those exposed to compression, cooling and umbilical cord occlusion) and normal, vaginally delivered pups breathed at identical rates and showed a similar pattern of postpartum breathing. These results suggest that mechanical stimulation of the fetus associated with uterine contractions plays a critical role in the maintenance of continuous respiration at birth. Possible mechanisms for the facilitative effects of compression on perinatal breathing are discussed.

Animals↗
PubMed1995

Differential influence of adult and juvenile conspecifics on feeding by weanling rats (Rattus norvegicus): a size-related explanation.

Weanling Sprague Dawley rat pups (Rattus norvegicus) selected between 2 safe palatable diets in concordance with the preferences of either an adult or a juvenile conspecific model (Experiment 1). Nevertheless, weanlings chose to feed more in the vicinity of an adult than in the vicinity of a juvenile, thus fulfilling the prediction of an adaptive feeding strategy (Experiment 2). The weanlings' bias for feeding in the vicinity of an adult was eliminated by increasing the magnitude of pup stimulus to 3 pups (Experiment 3). Thus, weanlings do not possess a specialization rendering them more sensitive to adults than to pups as models for diet selection. By responding to stimulus magnitude, weanlings are more likely to feed with adult conspecifics, choose foods used by them, and derive the benefits correlated with the adults' successful feeding habits.

Animals↗
PubMed1994

Proximal control of fetal rat behavior.

We examined the influence of the amniotic sac on spontaneous movement in late gestation fetal rats. Using techniques for in vivo observation of fetal behavior, Day 21 rat fetuses were exteriorized from the uterus, with umbilical connections to the dam intact, and videotaped for 15 min either: (a) through the intact amniotic membranes, or (b) following removal of the membranes. Analysis of fetal behavior categories replicated the findings of previous investigators: Movements of the head, forelimbs, and rearlimbs were significantly increased by sac removal, as was the total frequency of behavior categories and the simultaneous occurrence of different behavior categories. Frame-by-frame analysis of videotaped behavior revealed that amniotic sac removal increased the frequency of movement bouts without altering the overall amount of time that fetuses spent moving. Movement bout durations ranged from 50 msec to 70 s. The average duration of movement bouts was significantly reduced for fetuses lacking the amniotic sac as compared to fetuses within the sac, as was the overall distribution of movement bout durations. Frequency distributions of movement bout durations and interbout interval (IBIs) revealed that sac removal significantly increased the occurrence of short (1-2 s) movement bouts and reduced the frequency of protracted movement bouts and interbout intervals (> 10-s duration). Taken together, these findings indicate that the quantitative dimensions of fetal rat movements are influenced by proximal features of the uterine environment. During prenatal life, the amniotic sac appears to sustain movement, possibly by providing proprioceptive feedback or physical support to the fetus, or by regulating the chemical milieu.

Animals↗
PubMed1994

Learning as adaptation of the infant.

The present report advocates an adaptive, ecological approach to the study of learning in infants. Concepts of developmental niche and ontogenetic adaptation are applied to early mammalian development. Within this conceptual framework, it is asserted that learning cannot be fully understood separately from a behaving body; that learning is a dimension of behavior and physiology. The role of learning in the development of ingestive behavior, especially suckling and the transition to solid food, is used to illustrate the potential of studying learning in development. These considerations are offered as examples of an alternative approach to the empirical study of learning by infants. The approach advocated herein can be applied to clinical issues: developmental adaptations evolved in contexts that differ from our modern environments. Exposure to contexts or contingencies that are evolutionarily unexpected may inadvertently create pathology.

Adaptation, Physiological↗
PubMed1994

Anatomy and forebrain projections of the olfactory and vomeronasal organs in axolotls (Ambystoma mexicanum).

We examined the anatomy of the nasal cavity and forebrain in the axolotl (Ambystoma mexicanum) to determine whether the olfactory and vomeronasal systems are present in this neotenic aquatic salamander. The current study was motivated by two considerations: (a) little is known of the anatomy of the vomeronasal system in aquatic vertebrates, and (b) the presence of both olfactory and vomeronasal systems in larval amphibians has broad implications for the evaluation of these systems in vertebrates. From cresyl-violet-stained sections of snouts we determined that the nasal cavity of axolotls is much like that of terrestrial salamanders. The main chamber of the nasal cavity contains an olfactory epithelium, which is confined to grooves between longitudinal ridges of connective tissue covered in a nonsensory epithelium which lacks goblet cells. Using transmission electron microscopy, we found morphologically distinct olfactory receptor cells: many receptor cells terminate in microvillar dendrites, and fewer terminate in motile cilia with the 9 + 2 microtubule array typical of vertebrate olfactory receptor cells. The ciliated and microvillar cells occur in clusters with little intermingling. Horseradish peroxidase labeling revealed that axons of the olfactory receptor cells terminate in large glomeruli in the main olfactory bulb at the rostral end of the telencephalon. Lateral to the main chamber of the nasal cavity is a diverticulum that is entirely lined with a vomeronasal epithelium containing basal cells, microvillar receptor cells, sustentacular cells that lack specialized processes on the apical surface, and large ciliated cells that may function to move fluid across the vomeronasal epithelium. Unlike the olfactory epithelium, the vomeronasal epithelium lacks Bowman's glands. Using horseradish peroxidase, we determined that the axons of the vomeronasal receptor cells project to the accessory olfactory bulb, a distinct structure dorsal and caudal to the main olfactory bulb. The presence of both olfactory and vomeronasal systems in axolotls and other neotenic salamanders implies that both systems are pleiomorphic in larval amphibians; we therefore suggest that the vomeronasal system may not have originated as an adaptation to terrestrial life.

Ambystoma mexicanum↗
PubMed1993

Fetal experience revealed by rats: psychobiological insights.

Psychobiological studies of fetal ontogenesis in non-human species, particularly in laboratory rat, now have much to offer students of human development. Psychobiological approaches are 'ecologically' oriented which, for fetal research, implies consideration of the adaptive significance of behavior within the uterine habitat. Consistent with this orientation is a concern for the sensory capabilities of the fetus, especially in relation to the specific forms and levels of stimulation that occur within the uterine milieu. We describe recent advances in these areas, and the impressive range of fetal responses to naturally-occurring (often mother-induced) forms of sensory stimulation. To the psychobiologist, sensory-evoked responses of all kinds constitute the fetus' experience and much has been learned about the roles of such experience in regulating the rate, direction, and form of development. Indeed, experience can be considered a significant, if not neglected, mechanism of development. Finally, we briefly survey some contemporary analyses of the interrelations between developmental and evolutionary processes. We use onset of sensory function (which occurs in a stereotyped sequence in every vertebrate species for which there are data) as a developmental phenotype. Phylogenetic considerations of sensory development are discussed. By identifying and clarifying some of the intellectual questions that guide perinatal research with non-human species, we hope to improve the appreciation of novel insights and interpretive strategies that derive from different approaches. This is bound to enhance the study of human development and to improve the design and use of animal models.

Animals↗
PubMed1993

Maternal contributions to sensory experience in the fetal and newborn rat (Rattus norvegicus).

Using videographic analyses, we identified and quantified maternal contributions to the sensory environment of the perinatal rat (Rattus norvegicus) by analyzing, from the offspring's perspective, the dam's activities during gestation, labor, and delivery. Our observations indicate that pregnant females remain highly active during the final week of gestation, as compared with nonpregnant control animals. Exploratory movements, feeding, drinking, self-grooming, and other activities of the rat dam pitch, turn, accelerate, and expose fetuses to mechanical pressures. During parturition uterine contractions and maternal licking and handling provide vigorous tactile and vestibular stimuli to pups. Newly born pups are exposed to intense thermal stimulation, cooling rapidly to the temperature of the postnatal environment. Our results suggest that fetal and newborn rats are exposed during development to a broad range of maternally produced stimuli.

Animals↗
PubMed1992

Ultrasonic vocalizations by rat pups: the primary importance of ambient temperature and the thermal significance of contact comfort.

We investigated the effects of isolation, huddling, and air temperature on ultrasound production by rat pups. Experiment 1 showed that ultrasound production by 8- to 9-day-olds was minimal at thermoneutrality and increased in response to small deviations of air temperature on either side of the thermoneutral zone. Experiments 2 and 3 showed that suppression of ultrasound production by contact with littermates is consistent with the thermal consequences of huddling. Experiment 4 showed that, contrary to previous conclusions, ultrasound production is not independent of ambient temperature in pups older than 10 days of age. Taken as a whole, these experiments emphasize (1) the importance of ambient temperature for the elicitation of ultrasound by rat pups of all ages studied, (2) the importance of thermal factors in the suppression of ultrasound by littermate contact, and (3) the manner in which different methods can change interpretations of the behavior and physiology of infant rats.

Animals↗
PubMed1992

Thermogenesis during ultrasonic vocalization by rat pups isolated in a warm environment: a thermographic analysis.

Ultrasonic vocalizations, emitted by rat pups when separated from their mother, littermates, and home cage, have been used as a measure of isolation distress. Recently, we demonstrated that cold exposure is the primary component of isolation that induces the vocalization. We were unable, however, to suppress all ultrasound production when transferring pups to a thermoneutral (35 degrees C) environment. Using an infrared thermography system that allows us to estimate noninvasively heat production by brown adipose tissue, we found that pups transferred from the home nest to a 35 degree C test chamber exhibited sizable levels of heat production while they were vocalizing. Moreover, both heat production and ultrasound emission decreased over the 15-min test. Next, we used extreme care to minimize thermal, and therefore respiratory, stimulation of pups before, during, and after the transfer procedure. We found that such precautions prevented both heat production and ultrasound emission following transfer. These results indicate that infant rats' thermal sensitivities are far greater than previously suspected.

Adipose Tissue, Brown↗