bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of litter age, litter size, and ambient temperature on the milk ejection reflex in lactating rats
Authors: Jans James E. , Woodside Barbara 
Published: January 2005

AbstractUnder a number of circumstances the duration of mother‐young contact in the rat can be drastically reduced while pup growth is maintained. We investigated the possibility that under some of these conditions the timing of milk delivery is changed. We assessed the time of onset and pattern of milk delivery over a nest bout in litters of two different ages (Day 4 or Day 10) and three different sizes (4, 8, or 12 pups). Ambient temperature fluctuated over the course of the study and was found to correlate significantly with the latency to the first milk ejection (ME). Specifically, the warmer the ambient temperature, the quicker the first ME occurred. Durations between successive MEs correlated with ambient temperature in a similar fashion. Analysis of covariance revealed that the onset of the first ME occurred earlier in Day 10 litters than in Day 4 litters, but litter size had no effect. Durations between successive MEs were not affected by either litter age or litter size. These data indicate one possible mechanism by which adequate milk delivery can be maintained despite some reduction in motheryoung contact.
Ontogenesis of trace conditioning in young rats: Dissociation of associative and memory processes
Authors: Moye Thomas B. , Rudy Jerry W. 
Published: January 2005

AbstractHooded rats from 15 to 30 days of age were trained with a Pavlovian trace fear conditioning procedure in order to study the development of their capacity to learn associations between events separated in time. For both the auditory and visual systems, the associative processes necessary to learn about temporally contiguous events emerged earlier during ontogenesis than the processes necessary to integrate events separated in time. Furthermore, the ability of the rats to integrate events separated by increasingly long intervals continued to improve as they got older. We suggest that the emergence of the capacity to integrate temporally separate events reflects the maturation of memory processes that retain representations of stimulus events over time, and that these processes continue to mature for a considerable period after the basic associative processes have become functional.
Salt preference in the preweaning rat
Authors: Bernstein Ilene L. , Courtney Lynn 
Published: January 2005

AbstractSalt (NaCl) preference of 5–20‐day‐old rats was examined using a method which elicits independent ingestive responses. Rats were placed in a warm, moist incubator on toweling which was saturated with water or test solutions. Active mouthing responses were seen which were directed toward the towel soaked with solution and weight gain in a 25‐min test was taken as an index of ingestion. At most ages pups preferred hypertonic saline solutions to water and at 10 days of age rats appeared particularly insensitive to the aversiveness of concentrated (4–8%) NaCl solutions. In contrast to the 10‐, 15‐, and 20‐day‐old rats, the 5‐day‐old rats never preferred NaCl solutions to water and avoided them at concentrations which older rats preferred. This pattern of NaCl preference cannot easily be explained in terms of the known increases in sensitivity of the rat's taste system to NaCl stimulation with age. Ingestion of NH4Cl solutions was also examined and at 10 days of age significant preference for concentrated NH4Cl solutions was evident which contrasts markedly with the behavior of older pups and adult rats when presented with NH4Cl solutions. The relationship between the present findings and available electrophysiological data from the chorda tympani and nucleus of the solitary tract are discussed.
Response of sparrows to songs of deaf and isolation‐reared males: Further evidence for innate auditory templates
Authors: Searcy William A. , Marler Peter 
Published: January 2005

AbstractAdult song sparrows (Melospiza melodia) were tested for response to songs of conspecific males that had been reared in acoustic isolation or deafened early in life. Territorial males responded more aggressively to playback of songs of isolated males than to songs of deafened males but did not discriminate between songs of deafened males and heterospecific songs. Captive females showed an identical pattern when their response was measured in terms of the number and intensity of courtship displays evoked by song. The results support the auditory template theory of song development in demonstrating that species‐identifying features are present in songs of isolates and in showing that males unable to hear their own song production do not incorporate these species‐identifying features into their songs.
Experience during suckling alters later spatial learning
Authors: Cramer Catherine P. , Pfister John P. , Haig Kristine A. 
Published: January 2005

AbstractThese experiments explore the role of preweaning experience in learning during the juvenile period. Pups that had been reared with many nipples available reached criterion on an 8‐arm radial maze in a few trials; conversely, pups reared with only a few nipples required 3 times the number of trials to reach criterion (Experiment 1). Pups that had been reared with relatively few nipples available rarely nipple‐shifted, while those that had been reared with a particularly high density of nipples shifted more frequently (Expt 2). A rearing procedure was devised that allowed precise experimental control of all phases of the suckling experience (Expt 3). Allowing or preventing a single behavior, nipple‐shifting, while holding all other variables constant, was sufficient to affect acquisition of the maze task. In Experiment 4, the specificity of the early experience for later tasks was explored using a variety of nonspatial, lever‐pressing operants. Rearing condition did not affect acquisition of a lever‐pressing operant or of a visual discrimination task. However, pups reared with a high density of nipples responded at higher rates to a variable interval schedule and were more resistant to extinction. The possibility that strategy, rather than learning ability, was affected by rearing condition was assessed using a 2‐arm maze task that was structured to present an optimal strategy of either win‐shift or win‐stay (Expt 5). The ease with which rats acquired the win‐stay task was unaffected by rearing condition; all groups performed at about chance levels. However, pups reared with many nipples more readily acquired the win‐shift task.
Effects of age, sex, and psychological disturbance on immunoglobulin levels in the squirrel monkey
Authors: Coe Christopher L. , Cassayre Perla , Levine Seymour , Rosenberg Leon T. 
Published: January 2005

AbstractThe following research assessed the influence of developmental, hormonal, and psychological factors on immunoglobulin and complement protein levels in the squirrel monkey. A cross‐sectional life span study established that the developmental pattern of immunoglobulins and complement proteins was similar to that observed in humans. IgG and IgM levels rose progressively with age, while the complement system was mature at birth. In contrast to humans, this species showed a significant sex difference in IgG levels with higher levels in males during both infancy and adulthood. Males also showed a greater antibody response to viral challenge than did females, and evaluation of gonadectomized subjects suggested that the sex difference in antibody production was testosterone‐dependent. The effect of acute and sustained psychological disturbance on IgG levels was also evaluated in infant monkeys. Repeated, brief separations from the mother did not alter IgG levels, but IgG levels were suppressed after a 7‐day removal from the mother. Therefore, despite the general view that immunoglobulin levels are relatively stable, these studies have established that immunoglobulin levels can be strongly influenced by hormonal and experiential factors in the squirrel monkey.
Behavioral effects of developmental lead exposure in rhesus monkeys
Authors: Levin Edward D. , Schneider Mary L. , Ferguson Sherry A. , Schantz Susan L. , Bowman Robert E. 
Published: January 2005

AbstractPostnatal lead exposure has been found to cause long‐term learning and memory deficits in monkeys. Pulse‐chronic exposure, consisting of acute high‐level exposure followed by chronic lower‐level exposure, has been particularly effective in causing these impairments. We investigated possible antecedents of lead‐induced cognitive dysfunction by evaluating the behavioral effects of pulse‐chronic lead exposure in rhesus monkeys during the first 6 months of postnatal life. Blood lead pulse‐chronic lead exposure in rhesus monkeys during the first 6 months of postnatal life. Blood lead concentrations in the monkeys reached a peak of 55.8±7.8 ug/dl during week 5 after birth and then averaged between 33.1 and 42.9 ug/dl during the rest of the first 6 months after birth. Zinc protoporphyrin levels were increased by lead exposure, but hematocrits were unaffected. Significant lead‐related effects were detected on a visual exploration test and a neonatal behavioral assessment battery. Lead‐treated monkeys exhibited decreased looking behavior on the visual exploration test and decereased muscle tonus and increased arousal or agitation on the behaiovral assesment battery. No effectw were seen on a Piagetian object permanence task and ton toxic effects on health on growth were detected. In addition to providing indices of behavioral dysfunction during postnatal lead exposure, performance on these early behavioral tests may predict later lead‐induced cognitive dysfunctionn.
Development of salt aversion in the Fischer‐344 rat
Authors: Bernstein Ilene L. 
Published: January 2005

AbstractAdult Fischer‐344 (F‐344) rats fail to prefer NaCl solutions of any concentration to water and, in fact, avoid NaCl at solution concentrations which other strains of rats reliably prefer. In contrast, immature rats of a number of strains have been reported to express an elevated salt preference relative to adults. The present studies examine the development of the F‐344 rat's salt aversion by testing salt preference in the preweaning (Day 10) and weanling (Days 20–24) F‐344 rat. At Day 10, F‐344 rats ingested significantly more 1% and 2% NaCl solutions than water during “towel testing” and their preference was comparable to that displayed by other strains at this age. By the time of normal weaning (Days 20–24) significant avoidance of NaCl solutions in the isotonic range was displayed by F‐344 rats, and their preference was strikingly different from other rat strains. This was evident in a 24‐hr 2‐bottle preference test as well as a 25 min “towel test.” Since NaCl preference of F‐344 rats is comparable to other rat strains at Day 10 but dramatically different by Day 20, a change must occur during this time which reverses the hedonic value of NaCl stimulation. Identification of factors responsible for this reversal may provide insight into the causes both of the F‐344 rat's dislike of salt and the immature rats elevated salt preference.
Alarm call responsivity of mallard ducklings: VIII. Interaction between developmental history and behavioral context
Authors: Blaich Charles F. , Miller David B. , Hicinbothom Gloria 
Published: January 2005

AbstractMallard ducklings (Anas platyrhynchos) inhibit their vocal behavior upon hearing the maternal alarm call of their species. The present study assesses the interaction of the ducklings' experiential history with the environment in which they are tested. If ducklings are reared and tested to the alarm call in small social groups, they respond by dramatically inhibiting their vocalizations. If, however, socially reared ducklings are tested to the alarm call individually in an open field, responsiveness drops precipitously. In addition, individually reared ducklings respond at a far greater level to the alarm call when tested individually, not in groups. Thus, there is an interaction between the rearing history and the testing environment such that the same rearing history leads to different behavioral outcomes depending on the context in which the ducklings are observed. This demonstrates the importance of behavioral context, in addition to developmental history, as one of the determinants of behavior.
Lack of stability in neonatal adrenocortical reactivity because of rapid habituation of the adrenocortical response
Authors: Gunnar Megan R. , Connors Joan , Isensee Jill 
Published: January 2005

AbstractThe purpose of the study was to examine the stability of the adrenocortical response to stimulatin in the human neonate. Forty‐nine healthy newborns were examined twice responding to discharge examinations performed on two consecutive days. The dependent measures were salivary and plasma cortisol and behavioral state. Little evidence of stability was obtained. Instead, the results showeds significant elevations in cortisol only in response to the first discharge examination. No significant elevation in cortisol was noted to the second discharge examination although the newborns continued to exhibit behavioral distress. Time since delivery was not a significant factor in producing these results. The findings are discussed with regard to neonatal coping processes and the importance of novelty in regulating increases in adrenocortical activity.
The performance of human infants on a measure of frontal cortex function, the delayed response task
Authors: Diamond Adele , Doar Bertha 
Published: January 2005

AbstractThe Delayed Response task is the best‐established marker of frontal lobe function in nonhuman primates. This article reports the developmental progression of human infants on that task. It is proposed that maturation of prefrontal cortex may make possible these age‐related improvements in Delayed Response performance. This would suggest the importance of prefrontal cortex functioning very early in life.Twelve infants (6 male, 6 female) were tested longitudinally every two weeks from 6–12 months of age. Another 36 infants (18 male, 18 female) were tested only once: 12 each at 8, 10, and 12 months. We predicted that infants would improve on Delayed Response over these ages because infants' performance on AB improves during this time, and Delayed Response is very similar to AB. The AB task, devised by Piaget, is used to study congnitive development in infants. The ages over which AB performance improves are well established. In both AB and Delayed Response, the subject watches as the experimenter hides a desired object in one of two identical wells. After a brief delay, the subject is allowed to reach. In AB, the object is hidden in the same well on subsequent trials until the subject reaches to the correct well; then side of hiding is reversed and the procedure repeated. In Delayed Response, side of hiding is varied randomly over trials. In the present study of Delayed Response each testing session consisted of 16 trials (eight to the right, eight to the left). We found: (1) the developmental progression for Delayed Response is almost identical to that for AB. (2) Infants of 7 1/2–9 months fail Delayed Response under the same conditions and in the same ways as do monkeys with lesions of dorsolateral prefrontal cortex. It is therefore suggested that AB and Delayed Response require the same congnitive abilities, and that improved performance on these tasks provides an index of maturation of frontal cortex function.
Relative importance of experience, social facilitation, and availability of milk in weaning of rats
Authors: Lichtman Aron H. , Cramer Catherine P. 
Published: January 2005

AbstractThese studies investigated the role that social facilitation, availability of the dam, and milk play in the maintenance of suckling behavior. Beginning at Day 20, rat pups suckling experiences were restricted to testing with an anesthetized dam. In the first experiment, nipple attachment was abandoned by about Day 25 in rats that were testd alone with an anesthetized dam for 1 hr per day. When tested in groups of four, nipple attachment was maintained until about Day 27. Increasing exposure to an anesthetized dam to 2 hr per day prolonged nipple attachment about another 4 days. In the second experiment, pups were given either one or two daily 1‐hr attachment tests and tested with either an anesthetized dam or an anesthetized dam in which the milk letdown reflex was reinstated. Both increasing the daily exposure to an anesthetized dam and reinstating milk letdown significantly prolonged suckling. Pups given two daily exposures to an anesthetized, milk‐laden dam attached until about Day 47, long past the normal age of weaning.
Fetal male masculinization in control and prenatally stressed rats
Authors: Lephart E. D. , Fleming D. E. , Rhees R. W. 
Published: January 2005

AbstractThe present experiments were designed to test the hypothesis that males in utero masculinize the development of other males. This effect was examined during fetal development in males from control and prenatally stressed rats. A code identified the number of cervical‐flanking males between the target male and the cervical end of the uterus. The male parameters morphology (anogenital distance) and body, adrenal, and testis weights were recorded on the eighteenth and twentieth gestational days and categorized by the cervical‐flanking male classificantion. At Day 18, control fetuses with two cervical‐flanking males in utero displayed significantly greater anogenital distance values than did males with no cervical‐flanking male. At Day 20, control fetuses with two cervical‐flanking males had testicular weights significantly greater than those of fetuses with one or zero cervical positioned male. Prenatal stress markedly impaired male fetal development, at gestational Days 18 and 20 while suppressing the cervical‐flanking male effect. These results confirm and extend previous data that indicate: (a) prenatal stress disrupts normal fetal development, resulting in long‐term changes; and (b) androgens via a cervical‐flanking blood‐flow mechanism influence littermate morphology and sexual development during the prenatal period. Our findings also demonstrate that a general masculinizing effect could not be made across the measured male parameters since the effect of males positioned at the cervical‐flanking region in utero appears to be dependent upon maternal sources of variance. Finally, androgens prenatally have an apparent positive interaction with somatic growth.
Physical and physiological correlates of behavioral inhibition
Authors: Rosenberg Allison A. , Kagan Jerome 
Published: January 2005

AbstractPrevious investigations have suggested that the temperamental quality of inhibition is related to the threshold of reactivity to unfamiliar events within certain limbic structures. In earlier work, children in three independent samples who had been selected to be inhibited were more likely to have blue than brown eyes, whereas uninhibited childern were more likely to have brown eyes.The present study, which selected two‐year‐old children on the basis of eye color (blue or brown) rather than behavior, found a significant association between blue eyes and behavioral inhibition, and between brown eyes and an uninhibited style. Although the inhibited childern were more likely to have a high and stable heart rate than were the uninhibited children, there was no relation between eye color and these cardiac measures. Several interpretations of the association between these temperamental categories and iris pigmentation are proposed.
Quantitative analysis of eye movements during REM‐sleep in developing rats
Authors: Van Someren E. J. W. , Mirmiran M. , Bos N. P. A. , Lamur A. , Kumar A. , Molenaar P. C. M. 
Published: January 2005

AbstractDevelopment of eye movements in REM‐sleep was studied in rats during the second and third week of postnatal life. An increased frequency of eye movements was found after eye opening, which was due only to changes in burst activity. Since pups reared in constant darkness showed an increase in eye movement activity similar to that of those exposed to diurnal light‐dark alterations, the change seems to be part of an endogenous developmental timetable rather than due to an increase of visual stimulation by eye opening.
Effects of morphine and naloxone on play‐rewarded spatial discrimination in juvenile rats
Authors: Normansell Larry , Panksepp Jaak 
Published: January 2005

AbstractJuvenile rats were trained on a spatial discrimination task (T‐maze) rewarded by the opportunity to play with a conspecific. Neither morphine (MS; 1 mg/kg) nor naloxone (NX; 1 mg/kg) administration affected choice or running time during the acquisition of the task, even though in the goal box. MS‐treated animals played more than and NX‐treated animals less than vehicle‐treated controls. Thus, brain opioid systems seem to influence the expression of play without affecting the apparent appetitive strength of play motivation. When play reward was no longer available in the goal box. Animals that continued to be treated with MS were more resistant to extinction than either vehicle‐or NX‐treated animals. They continued to complete the task more often and in less time than the controls. NX‐treated rats, on the other hand, extinguished faster than controls. The evidence supports the conclusion that opioid systems are important in the maintenance of social habits.
Effects of prenatal alcohol exposure on rat pups' ability to elicit retrieval behavior from dams
Authors: Ness James W. , Franchina Joseph J. 
Published: January 2005

AbstractResearch on fetal alcohol syndrome (FAS) has historically held that postnatal deficits result directly from prenatal alcohol exposure. Such exposure may alter infant behavior, and this in turn may affect maternal responsiveness and consequently increase the infant's risk for postnatal deficits. This study examined the effect of prental alcohol exposure on postnatal blood ethanol concentrations, pup development, and the ability of pups to elicit retrieval behaviors from the dam. Dams given access to a 15% ethanol solution throughout gestation and lactation showed blood ethanol concentrations of 0.1% whereas their pups had concentrations below the sensitivity of the test. Prenatal alcohol exposure was shown to have pharmacological effects on the pup's righting reflex and nutritional effects on its rate of weight gain. Control pups were better able to elicit retrieval behavior from control and alcoholic dams than were fetally alcoholic pups. These results indicate that that the condition of the pup can influence maternal responsiveness which, in turn, can influence pup development.