ISSN:0012-1630    

DOI:10.1002/dev.420120602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractOffspring were either adequately nourished or undernourished during the suckling period. They had free access to food from weaning, and were given 2 behavioral tests between 13 and 19 weeks of age. Motivation for water was tested on a variable interval (VI) schedule at 3 levels of deprivation and a test of light‐dark discrimination made at 23.5 hr of water deprivation. The results indicated (1) no clear difference in VI response rate, but (2) significant differences in discrimination performance between the 2 groups. A learning ability or certain relevant abilities rather than motivation for water appeared responsible for the difference in discrimination learnin

ISSN:0012-1630    

DOI:10.1002/dev.420120603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe effects of urine from pregnant and lactating female mice on puberty in young females were examined. In Experiment I urine from pregnant or lactating females painted daily on the external nares of young females led to earlier sexual maturation than treatment with water or urine from singly‐caged, nonlactating, multiparous adult females. In Experiment II urine from either pregnant or lactating females, injected daily into perforated plastic capsules containing cotton, effected earlier maturation in female mice caged with these capsules than did the urine of singly‐caged females or water. In Experiment III the effectiveness of these treatments on reproductionper sewas confirmed: young females reaching maturity earlier as the result of urine treatments were in fact ovulating and were capable of conceiving and bearing young. One explanation for the presence of the urinary pheromone(s) involves changes in hormone levels during pregnancy and/or lactation and urinary excretion levels of hormones, hormone metabolites, or chemical compounds which are hormone dependent. The pheromone excretion, triggered by external factors, may be a general signal to other females that environmental and/or social conditions are favorable for reproductive activit

ISSN:0012-1630    

DOI:10.1002/dev.420120604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe suckling behavior of hamster pups was observed to undergo several transitions during the preweaning period. Pups 10 days of age and younger attached to the nipples of their anesthetized mothers and suckled. After 10 days of age, however, only animals which had been deprived of suckling (and food and water) reliably attached to their mothers' nipples. By 25 days of age, deprived pups no longer suckled. The pattern of response after nipple attachment also changed during development: pups younger than 5 days of age remained on 1 nipple after initial attachment, whereas older pups shifted from 1 nipple to another. The development of suckling in hamster pups resembles that in rat pups, although certain changes or transitions occur at different ages in the 2 species. These changes may provide important markers for neural and behavioral development in each species and for comparisons between the two.

ISSN:0012-1630    

DOI:10.1002/dev.420120605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractKittens at 10, 20, and 40 days of age were made intermittently hypoxic in 10 or 7% oxygen chambers for either 3 or 8 days. Respiration, EKG, EEG, and neck and eye movements were recorded during hypoxia. Compared to 21% oxygen controls, hypoxic kittens had fewer and shorter epochs of active sleep, and longer epochs of quiet sleep. Some hypoxic kittens exhibited slow and labored respiration during quiet sleep and transitional epochs, which reversed during active sleep. Kittens that showed most pronounced respiratory changes or died had less active sleep than kittens that compensated adequately and survived. These results suggest that active sleep may be important for stimulation of respiration during infancy. Suppression of active sleep, augmentation of quiet sleep, or other disturbances to normal sleep‐waking patterns during hypoxia, may increase the risk for hypoxic respiratory depression and deat

ISSN:0012-1630    

DOI:10.1002/dev.420120606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractFrequency and characteristics of apneas were studied in 10‐, 20‐, and 40‐day old kittens during several days of exposure to 21%, 10%, or 7% oxygen atmospheres. Ninety‐seven percent of all apneas occurred during sleep or at transitions between sleep and waking states. Hypoxic kittens, compared to controls, had greatly decreased apnea frequency, but other characteristics of apneas did not differ significantly. Apneas in both control and hypoxic kittens were normal, stereotyped events and were not considered to represent pathological processes.Evaluation of events preceding apneas indicated that a majority of apneas followed augmented breaths and/or brief arousals. We suggest that apnea, heart rate changes during apnea, and frequently concurrent transitions in sleep‐waking state may be causally related to these pre‐apnea events. The results of this study and a parallel study of human infants suggest that below‐normal apnea frequency may indicate hypoxemia and may be associated with higher risk for Sudden Infant D

ISSN:0012-1630    

DOI:10.1002/dev.420120607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractTonic immobility was studied in rabbit pups varying in age from 1 to 30 days. During the 1st 2 postnatal weeks the rabbits were active in an open field, had difficulty walking and executing a righting response, lost body temperature rapidly, and had no, or only short durations of, tonic immobility. After this age they were less active, hopped and righted well, maintained core temperature, and showed increased durations of tonic immobility. Within the 1st 2 postnatal weeks cooling and warming potentiated; thereafter, cooling disrupted and only warming potentiated tonic immobility. The results suggest that rate of heat loss can act as a stimulus to block tonic immobility and increase activity in neonatal rabbits. With development, cooling produces shivering which can disrupt tonic immobility, whereas warming may raise movement initiation thresholds which can potentiate tonic immobility.

ISSN:0012-1630    

DOI:10.1002/dev.420120608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractHead‐turning responses to somesthetic stimulation of the perioral region were studied at weekly intervals in 25 prematurely born infants. No regular changes associated with age were evident. The premature infants were more likely to turn towards than away from a stimulus; however, they were less so than are full‐term infants. The infants were as likely to turn towards the stimulus when it was on the left as when it was on the right; however, they were more likely to turn away from a stimulus on the left than on the right. Comparisons with full‐term infants indicated reduced lateral differences in responding. Such a reduction is in sharp contrast with the previous finding of marked postural asymmetry in a comparable sample of prematurely born infants. These data indicate a possible sequence in the development of head‐turning responses to somesthetic stimulation and the assumption and maintenance of an asymmetrical head posture which consists of (1) a right‐turning postural bias, (2) contralateral responding to somesthetic stimulation, (3) lateral differentiation of contralateral responding, (4) ispilateral responding, and (5) lateral differentiation of ipsilateral r

ISSN:0012-1630    

DOI:10.1002/dev.420120609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractTwo studies are reported that describe the development of spontaneous alternation in the kitten. The first indicates that 3‐ and 4‐week‐old kittens do not alternate whereas animals 5 weeks and older do alternate. The second suggests that inability to discriminate maze arms is an unlikely explanation for the lack of alternation among the youngest animals. The approximate simultaneity between the onset of alternation (described here) and the maturation of the kitten hippocampus (described by others) is taken as support for the notion that hippocampal maturation may be related to the development of spontaneous altern

ISSN:0012-1630    

DOI:10.1002/dev.420120610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractSeventy‐eight kittens from 3 to 7 weeks of age were studied in an open‐field arena. Three major age‐dependent changes were noted: (1) the number of floor squares entered was markedly higher for 5‐ and 6‐week‐olds than for younger animals, and slightly lower for 7‐week‐olds than for 5‐ and 6‐week‐olds; (2) the tendency to backtrack from 1 square to a just‐vacated square decreased with age, the largest change occurring between 4 and 5 weeks of age; (3) the within‐session decrement in locomotion was largest for 3‐week‐old kittens but was smallest for 4‐week‐olds and increased monotonically with age thereafter. The results suggest a possib

ISSN:0012-1630    

DOI:10.1002/dev.420120611

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY