bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of species identification in ducklings: X. Perceptual specificity in the wood duck embryo requires sib stimulation for maintenance
Authors: Gottlieb Gilbert
Published: January 2005

A critical acoustic feature of the wood duck maternal assembly call is the descending frequency modulation (FM) of its notes. To determine the role of exposure of wood ducklings to conspecific vocalizations in the development of selective responsiveness to the descending FM of the species maternal call, the behavioral response of embryos to synthetic descending and ascending maternal calls was examined. Previous work indicated that selective responsivenness of newly hatched wood ducklings to the descending FM of the maternal call is dependent upon prior exposure to descending FM calls of siblinngs. In advance of auditory experience the youngest embryos were responsive to both ascending and descending call notes, but older aurally isolated embryos became selectively responsive to the descending FM. However, even though the wood duck hatchling vocalizes considerably in aural isolation, self‐stimulation is ineffective in maintaining the perceptual selectivity in the neonate. Unlike the mallard, in which self‐stimulation is adequate, the wood duckling must be exposed to sib vocalizations in order to remain selectively responsive to the critical acoustic feature of the maternal call of its species.
The influence of age and experience on salt preference of the rat
Authors: Midkiff Eleanor E. , Bernstein Ilene L.
Published: January 2005

The degree to which adult taste preferences can be influenced by early taste exposure is a matter of some debate. The present studies characterize the developmental course of saline preference during maturation in the rat and examine whether adult saline preference is influenced by postweaning exposure to saline solutions. Saline intake from weaning to adulthood was examined in Wister rats allowed continuous access to demineralized water and either.0,.9, 1.8, or 2.7% sodium chloride (NaCl) w/v solutions. When rats were immature they expressed greater preference for saline solutions than they did as adults. It is hypothesized that the over consumption of saline by young animals is related to lower sensitivity of the taste system to NaCl in the early postweaning period. Animals that had had continuous access to saline from weaning were compared to those that had not received saline exposure early in life, in life, in order to determine whether extensive experience with salt solutions leads to alterations in adult salt preference. These studies failed to reveal any evidence that rearing condition affects adult salt preference; thus adult salt preference may be maturationally determined and relatively independent of postweaning environmental influences.
The development of self‐recognition: A review
Authors: Anderson James R.
Published: January 2005

The development of self‐recognition has been studied mainly by examining infants' responses to their reflections in mirrors. The definitive test is whether or not the infant is capable of using the reflection to notice and respond to a mark on the face or head by touching the mark. The mark should be inconspicuous to the infant not looking in a mirror. In general, studies agree that this response appears in some infants around 15 months of age and is shown by a majority of infants by 24 months of age. There is less agreement over the existence of a “withdrawal” component in the second year, or the presence of a “social” phase analogous to the reaction of many animals confronted with a mirror. Infants as young as 3 months are differentially responsive to a self‐reflection and a live peer. Various “self‐conscious” reactions and self‐labelling may also indicate self‐recognition in the second year, but their validity is not well established. Studies using videotapes of the self and others show that contingency of mevement is a salient cue which is learned early, and that attempts to engage in contingent play and to imitate representations of oneself are useful measures of early self‐recognition. The validity of the response of turning to look at an object first seen in a mirror as a sign of self‐recognition is questioned. The age at which self‐recognition in still pictures first appears is less clear. Verbal comprehension of self‐relevant labels appears earlier than active self‐labelling. A few studies have addressed the question of cognitive correlates of self‐recognition, but a variety of behaviors that imply self‐awareness and the corrresponding ability to impute mental states to others remains to be studied in relation to self‐recognition. Continued research into self‐recognition and associated abilities in nonhuman primates enhances the overall understanding of the development of self‐awareness.
Sucking behaviors of normal 3‐day‐old female neonates during a 24‐hr period
Authors: Rybski Debra A. , Almli C. Robert , Gisel Erika G. , Powers Joann , Maurer Michael
Published: January 2005

Feeding behaviors were measured during six feeding sessions distributed throughout a 24‐hr period in 10 normal 3‐day‐old female infants. Infants were individually videotaped during feeding sessions at 13:00, 17:00, 21:00, 01:00, 05:00, and 09:00 hours. Total mealtime, nutritive sucking time, pause time, number of nutritive sucks, and amounnt of nutrient consumed were measured. None of these feeding variables were affected by the time of day an infant was fed. Maternal interactions with their infants such as auditory stimulation, caretaking touches or tender touches were unaffected by the time of a feed. These maternal behaviors did not correlate with any of the feeding variables. These findings suggest that 3‐day‐old infants experiencing routine nursery care do not express specific day‐night feeding differences and that certain maternal behaviors do not influence the infants' feeding pattern.
PKU, Learning, and models of mental retardation
Authors: Strupp Barbara J. , Levitsky David A. , Blumstein Lisa
Published: January 2005

Experimental phenylketonuria was induced in male rats by daily injections of α‐methylphenylalanine and phenylalanine on postnatal Days 3–31. Beginning at 8 weeks of age, the animals were subjected to a test of observational learning followed by a test of latent learning (two tests of “advantageous” learning). The animals subjected to the PKU treatment early in life showed significant learning deficits in both tests. The importance of these studies lies in the fact that unlike conventional tests of learning, tests of advantageous learning are sensitive to the kinds of biological insults which cause mental retardation in humans. This differential sensitivity evident in studies of animal models of cognitive pathology is analogized to the areas of dysfunction which characterize human mental retardation. Suggestions for the development of appropriate models of intellectual development of appropriate models of intellectual development are made.
Effects of age of chick on social transmission of pecking preferences from hen to chicks
Authors: Bartashunas Carl , Suboski Milton D.
Published: January 2005

A “pecking” arrow releases and directs pecking by neonatal chicks. Distinctive stimuli placed on or near the tip of the moving arrow lead to pecking that is selectively directed to matching stimuli. A total of 3 min of exposure to such modeling conditions results in remarkable persistence of imitative behavior. Matching stimuli are preferentially pecked 3 days later after three intervening tests without modeling. In contrast to the sensitive period for filial imprinting within the first 3 days posthatch, age of chick at training has no permanent effect on the development of pecking preferences. If anything, filial imprinting inteferes with released‐directed pecking, suggesting that separate processes are in volved.
Spatial memory in preschool infants
Authors: Foreman Nigel P. , Arber Margaret , Savage Joe
Published: January 2005

In order to test the spatial competence of preschool infants, two groups, aged 2 years and 4 years, were tested on a version of the “radial maze” task. They were required to obtain a chocolate sweet from each of eight identically labelled positions in an unfamiliar room. Four‐year‐olds accomplished this with considerable accuracy, rarely revisiting previously sampled positions. Two‐year‐olds performed marginally above chance. Variants of the task were employed, including rotation of the room configuration so that labelled positions were rendered ambiguous with respect to all other environmental stimuli. The latter caused a marked fall in performance in those infants that had been scoring above chance. By these criteria, infants clearly possess a form of intuitive “spatial memory” that is likely to mature during the second and third years. Parameters of performance were remarkably similar to those seen in comparable studies with nonhumans. It is likely that hippocampal development in early infancy underies this evolving skill, assuming cross‐species similarity in the organization of spatial behavior, and that locomotor competence is required for its development.
The effects of retroactive and proactive interference on learning and memory in old and young rats
Authors: Winocur Gordon
Published: January 2005

The effects of interference on learning and memory in old and young rats were compared using a visual discrimination task. In Experiment I, discrimination training was followed by one of three interference treatments and finally by retesting on the discrimination task. There were no age differences in original learning but old rats were significantly impaired in remembering the visual discrimination when a high‐interference treatment involving similar stimuli was introduced between original learning and retesting. In Experiment II, old rats were impaired on discrimination learning when the high interference treatment was administed before discrimination training. Analysis of response patterns showed that the exaggerated susceptibility of old rats to interfence effects resulted in a general behavioral inflexibility similar to that observed in young adult rats with damage to the hippocampal region.
Ontogenesis of learning: IV. Dissociation of memory and perceptual‐alerting processes mediating taste neophobia in the rat
Authors: Vogt Mark B. , Rudy Jerry W.
Published: January 2005

The rat's neophobic response to tastes can be conceptualized as depending on two processes: memory processes That store a representation of an experienced taste so that it can be recongnized as familiar on subequent encounters, and perceptual‐alerting processes that respond differentially to novel versus familiar tastes. We investigated the ontogeny of these processes by studying the preweanling rat's behavioral reaction to a 10% sucrose solution. Experiments I and II suggest that the memory processes mature earlier (by 7–8 days of age) that the perceptual‐alerting processes (about 11 days of age). Experiment III suggests that pups do not acquire and aversion to sucrose paired with illness until they are 12‐days‐old, implying a close correspondence between the maturation of processes mediating neophobia and taste aversion learning. These findings are consistent with our previous work (Vopgt & Rudy, 1984), and our view that ontogenetic dissociations in taste‐guided beghavior reflect caudal‐to‐rostral maturation in the ascending gustatory system.
The effects of early handling on latent inhibition in male and female rats
Authors: Weiner I. , Schnabel I. , Lubow R. E. , Feldon J.
Published: January 2005

Latent inhibition (LI) is a behavioral paradigm in which repeated exposure to stimuli not followed by meaningful consequences renders these stimuli ineffective for subsequent learning. The development of LI is considered to reflect learning not to attend to, ignore, or tune out irrelevant stimuli. The present study investigated the differences in the development of LI between handled and nonhandled males and females. Infantile handled (Days 1–22) and nonhandled, male and female Wistar rats were tested in maturity in the LI paradigm. The LI procedure consisted of two stages: pre‐exposure, where animals received 60 presentations of the to‐be‐conditioned stimulus (tone) and test, where the animals acquired a two‐way active avoidance response with the tone serving as the warning signal. Handled animals reached higher percentage of avoidance responses as compared with nonhandled animals. Latent inhibition was obtained in both the handled and the nonhandled females, but only the handled males showed the LI effect. Nonhandled males failed to develop LI. The results indicate that (a) the effects of handling are evident in learning tasks that do not involve motivational‐emotional variables, i.e., learning to ignore irrelevant stimuli; (b) handling differentially affects males and females, with a much greater impact on males and (c) the nonhandling procedure has significant deleterious consequences on adult behavior.
The effect of age on two kinds of aggressive behavior in inbred strains of mice
Authors: Puglisi‐Allegra Stefano , Cabib Simona
Published: January 2005

Shock‐induced aggressive behavior is absent or very weak in C57BL/6 mice at the age of 12 weeks, increases at the age of 16 weeks and reaches the highest levels at the age of 20 weeks. This age‐dependent increase of aggressive responses is absent in BALB/c and DBA/2 mice at the three ages examined in our experiments. Social isolation induces a clear age‐dependent increase of aggressive behavior in BALB/c and DBA/2 mice (the highest level being evident at 20 weeks of age) but not in C57BL/6 mice which are characterized by the lowest or absence of aggressive responses. These results are discussed in terms of the role of developmental and genetic factors in the expression of shock‐ and isolation‐induced aggressive behavior in the laboratory mouse.
The ontogeny of independent ingestion in mice: Or, why won't infant mice feed?
Authors: Hall W. G. , Browde Joseph A.
Published: January 2005

Unlike infant rats, which show deprivation‐related ingestion in several different test situations, infant mice appeared to be relatively unwilling to feed independently of suckling until 12 days of age. We tested mouse pups that were deprived (of food, water, suckling, and maternal care) for 1, 7, or 24 hr in ingestive tests in which a milk diet was spread on the floor of their test container (Experiment 1). Pups at 3, 6, and 9 days of age consumed small amounts of the diet and showed little increase in intake when deprivation was increased. In contrast (and like rat pups of all ages), mouse pups 12 and 15 days of age actively ingested the diet and increased their intake with increased deprivation. Six‐day‐old mouse pups were similarly unwilling to ingest a 5% sucrose solution, though 12‐day‐old pups showed deprivation‐related intake (Experiment 2). Cellular dehydration (produced by hypertonic saline injection), a potent stimulus for ingestion in infant rats, did not stimulate ingestion in mice younger than 12 days of age (Experiment 3). Finally, when ingestion was tested with diet infusions made through oral cannulas, mouse pups at 6 and 9 days of age showed only a slight increase in intake with increased deprivation. However, by 12 days of age, pups' ingestion increased markedly with deprivation (Experiment 4). Thus, mouse pups seem to be very different from rat pups with respect to the early existence of ingestive systems. The neural substrates for the ingestive responses that subserve independent ingestion are only minimally present in infant mice or are somehow inhibited.
The development of cyclic motility in fetuses of diabetic mothers
Authors: Robertson Steven S. , Dierker Leroy J.
Published: January 2005

The cyclic organization of spontaneous movement was stuied longitudinally in 22 fetuses of diabetic mothers (FDMs) during the third trimester of gestation and quantified with spectral analysis. Cyclic motility at frequencies between. 08 and 1.22 cycles/min was found in all fetuses, although it was temporarily absent in 12 of the 22 fetuses at some time between 25 and 38 weeks. While some parameters of cyclic motility changed little, the frequency of the dominant motility cycle doubled from .24 to .48 cycle/min between 28 and 36 weeks, and the relative strength of motility cycles in the band between .18 and 1.02 cycles/min decreased temporarily at 36 weeks. These developmental changes and the common absence of cyclic motility contrast sharply with previous findings in normal fetuses, and (except for its absence) are accounted for by a subgroup of FDMs whose mother's blood glucose levels were least well controlled during the third trimester of gestation. The presence of cyclic motility in all FDMs provides futher evidence that cyclic activation is a basic property of the developing central nervous system in the human, as it appears to be in other vertebrates. However, the differences between FDMs and normal fetuses suggest that the development of cyclic motility is sensitive to disturbances in the fetal metabolic environment.
Prenatal stress affects mother–infant interaction in norway rats
Authors: Moore Celia L. , Power Karen L.
Published: January 2005

Pregnant Long‐Evans rats were stressed by crowding, and subsequent mother–infant interactions were described after cross‐fostering. Prenatally stressed pups elicited less maternal licking from unstressed forster dams than controls, and previously stressed dams licked unstressed forster pups less than controls. No other differences in mother–infant interactions were detected. Adult offspring reared by foster dams that were stressed during pregnancy were more active in an open field than controls, but prenatally stressed and unstressed animals reared by control dams did not differ. Thus, stress during pregnancy can alter the maternal behavior of stressed dams, and the differential maternal stimulation can affect adult open‐field behavior. Because prenatally stressed pups elicit different maternal care, cross‐fostering does not eliminate the possibility that maternal stimulation may mediate some prenatal stress effects.
Visually imprinted maternal preference in ducklings is redirected by social interaction with siblings
Authors: Lickliter Robert , Gottlieb Gilbert
Published: January 2005

This study examined the influence of social interaction with broodmates on a visually imprinted maternal preference in domestic mallard ducklings (Anas platyrhynchos) during the first three days of postnatal life. Twenty‐four‐hour‐old ducklings were allowed to follow a stuffed mallard hen for 30 min. This experience resulted in a visually imprinted preference for the familier stuffed hen over 4 stuffed ducklings in simultaneous choice tests at 48 and 72 hr after hatching, but only if the imprinted birds were kept in social isolation. Imprinted ducklings reared in a social group containing either (a) same‐age siblings or (b) the stuffed mallard hen and same‐age siblings displayed a visual preference for the stuffed ducklings over the familiar mallard hen at 48 and 72 hr tests. As a first step in the analysis of the features of the social exposure to siblings that are necessary for the redirection of the visually imprinted maternal preference, it was found that direct social interaction is essential to establish the preference for ducklings, but even mere visual exposure to siblings does away with the imprinted maternal preference. These results provide striking evidence of the ready redirection of a species‐specific maternal preference in otherwise imprinted ducklings.
Behavior of infant Japanese monkeys (Macaca fuscata) with congenital limb malformations during their first three months
Authors: Nakamichi Masayuki
Published: January 2005

Locomotion and mother‐infant interactions of a severely malformed, a slightly malformed, and a normal infant were observed in a free‐ranging group of Japanese monkeys (Macaca fuscata). The severely malformed infant had no feet and had hands consisting of 2 digits. The slightly malformed infant had normal feet and hands consisting of 2 digits. The severely malformed infant was more retarded in development of posture and locomotion than the other infant; however, it developed locomotor patterns appropriate to its defects. All infants spent approximately the same amount of time in contact with their mothers. High mother–infant contact of malformed infants was maintained because their mothers were very attentive and carried and held them. Mothers reared their handicapped infants even though the infants lacked the movement necessary for clinging.
A comparison of children's performance on two recognition memory tasks: Delayed nonmatch‐to‐sample versus visual paired‐comparison
Authors: Overman William H. , Bachevalier Jocelyne , Sewell Frank , Drew Jana
Published: January 2005

Although 4‐ to 6‐month‐old children have a significant tendency to look at new stimuli in a visual paired‐comparison task (VPC), they have difficulty in consistently choosing novel objects in a delayed nonmatch‐to‐sample task (DNMS). To evaluate which factors could account for this difficulty, we tested human infants (10–107 months) and adults (17–25 years) in a DNMS task while monitoring eye fixations. The results indicated that children at all ages reliably looked at (VPC scores) or chose (DNMS scores) the new stimuli about 60% of the time, indicating that both tasks measure visual recognition memory. A videotape analysis of visual attention revealed that children younger than 22 months, but not older children, spent significanlty more time visually exploring the objects rather than looking at the food reward under it. Although this visual attraction to objects in children younger than 22 months of age may have impaired the formation of stimulus‐reinforcer association needed to solve the DNMS task, this was not the case for older children, since beyond 22 months of age children consistently looked at the reward while displacing the objects. These results suggest that other cognitive abilities required by the DNMS task may not be fully functional even in children 22 months and older. © 1993 John Wiley & Sons, Inc.
Social rearing effects on HPA axis activity over early development and in response to stress in rhesus monkeys
Authors: Clarke A. S.
Published: January 2005

Previous studies have found evidence of behavioral and psychophysiological differences between nonhuman primates reared in different social environments, however, few of these have employed longitudinal study of the animals over early development. In this study, HPA axis activity was assessed via measurement of ACTH and cortisol values over the first 6 months of life and in response to two stressful housing transitions in 48 infant rhesus monkeys that were either mother‐ or peer‐reared. ACTH and cortisol values declined over the first 6 months in both rearing groups. Peer‐reared monkeys showed lower levels of ACTH over the first 6 months of life than mother‐reared, but the rearing groups did not differ in basal cortisol values over this period. Mother‐reared animals showed a greater ACTH response to the mild stress of being moved to a new cage, and male monkeys showed higher values than females. Mother‐reared animals showed the largest cortisol increase in response to the caging transition. Both groups showed increases in ACTH and cortisol in response to the more severe stress of separation from their rearing partners and housing with unfamiliar agemates. Mother‐reared animals again showed the largest increase in ACTH in response to these events, but increases in cortisol were similar among both sexes and rearing groups. These results suggest an interaction of sex and rearing history in response to stressful events. © 1993 John Wiley & Sons Inc.
Ontogeny of amicable social behavior in the mouse: Gender differences and ongoing isolation outcomes
Authors: Terranova M. Livia , Laviola Giovanni , Alleva Enrico
Published: January 2005

The behavioral repertoire of male and female outbred CD‐1 mice was characterized during development (postnatal Days 23–47). To assess the effects of the rearing condition, half of the subjects were individually housed (IC) at weaning (Day 21), while the remaining mice were housed in pairs (PC) of same‐sex siblings. The occurrence of 22 behavioral items was scored during nine social encounters, 3 days apart, between pairs of unfamiliar same‐sex and same‐condition animals. Individually housed mice were much more involved than paired subjects in solitary play and social interactions (affilitive, investigative, and soliciting behaviors), while less interested in nonsocial behaviors (exploration, and escape‐oriented or maintenance activities). An over‐days increment for elements of social behavior was evident, with a peak of affiliative behavior at 23–32 days of age. For gender differences, in contrast with rat data, a marked female primacy in both social and playful behaviors was found. Overall, these findings clearly indicate that the behavioral repertoire of developing mice during paired encounters is strongly affected by both the sex of the subjects and the housing condition they are experiencing. © 1993 John Wiley & Sons Inc.
Repeated exposure of rat pups to isolation attenuates isolation‐induced ultrasonic vocalization rates: Reversal with naltrexone
Authors: Goodwin Gregory A. , Molina Victor A. , Spear Linda P.
Published: January 2005

Young rat pups are dependent on the dam for their survival, thus isolation of the neonatal rat pup from the dam presents the young organism with a variety of stressors. The question examined in this study concerns the ability of the young rat pup to modify its response to isolation following repeated exposure to that isolation as well as the role played by endogenous opiates in this process. Following repeated isolations, pups were seen to decrease vocalization rates. Altering the context in an attempt to dishabituate animals failed to reverse the decreased vocalization rate. However, opiate receptor blockade attenuated this decrease when administered subsequent to the first isolation period but not prior to the last isolation period. These results suggest that the development of this attenuated response to isolation stress is opiate‐mediated but that once established, its expression is not dependent on endogenous opiate release.© 1994 John Wiley & Sons, Inc.
Infant salt taste: Developmental, methodological, and contextual factors
Authors: Beauchamp Gary K. , Cowart Beverly J. , Mennella Julie A. , Marsh Roger R.
Published: January 2005

Two studies investigated the human infant's response to salt during development. In the first study, measures of intake and sucking were obtained from two groups of infants, newborns and 4‐ to 8‐month‐olds, in response to brief presentations of two concentrations of salt (0.2 or 0.4 M) and water. For several measures of sucking and for intake, there were significant age and concentration effects. Generally, newborn infants tended to reject saline relative to water more than did 4‐ to 8‐month‐old infants. This result, consistent with previously published research, suggests a developmental change in salt acceptability and, probably, sensitivity in the human infant. In the second longitudinal study, the response to salted (0.15 M) versus unsalted formulas was evaluated monthly in infants 2 to 7 months of age. Again, a developmental change was observed: Based on some sucking measures, younger infants appeared to be indifferent to the salted formula relative to the unsalted formula whereas older infants tended to reject the salted formula, presumably because either it was less sweet than the unsalted formulas or because it was novel. These data are consistent with the hypothesis developed from animal model studies that during early human postnatal development, transductive elements sensitive to saltiness mature.©1994 John Wiley & Sons, Inc.
Ontogeny of the ionic specificity of sodium appetite in the rat pup
Authors: Leshem Micah , Neufeld Michal , Canho Sonia Del
Published: January 2005

Sodium‐deficient adult rats prefer NaCl to other monochloride salts (e.g., Denton, 1991; Schulkin, 1991). However, it is not known when or how this specificity develops. Our experiments charted the development of the ionic specificity of sodium appetite aroused by sodium depletion or intracerebroventricular injection of renin. We compared intake of 3% NaCl to three other monochlorides, potassium (K), ammonium (NH4), and lithium (Li), and calcium chloride (CaCl2) at various ages between 72 hr postnatal and weaning. This revealed a biphasic developmental scheme: The adult pattern of discrimination between the salts emerges between 3 and 18 days of age. Subsequently, the preference for Na over the other salts increases into adulthood.©1994 John Wiley & Sons, Inc.
Cocaine alters cyclic motor activity in the fetal rat
Authors: Simonik Diane K. , Robinson Scott R. , Smotherman William P.
Published: January 2005

Individual rat fetuses were exposed to cocaine by injection into the cisterna magna on E20 or E21 of gestation. On E20, cocaine elevated motor activity throughout the 20‐min session, with activity increasing to double SAL‐injected levels by the end of the session. On E21, overall activity also was elevated after cocaine, increasing four‐ to fivefold in the first 5 min of the session, and decreasing to twice the levels of SAL controls thereafter. Movement time series were subjected to spectral analysis to characterize cyclic motor organization. Cyclicity was evident in 67% of control and 97% of cocaine‐injected fetuses. Cocaine increased the number of peaks in the movement spectrum and resulted in greater spectral density at the primary frequency of cyclic movement. Prenatal exposure to cocaine may alter patterns of cyclicity in the fetus, with consequences for the normal development of attention and behavioral state in the neonate.©1994 John Wiley & Sons, Inc.
Potentiation of isolation‐induced vocalization by brief exposure of rat pups to maternal cues
Authors: Hofer Myron A. , Brunelli Susan A. , Shair Harry N.
Published: January 2005

Since their discovery in 1956, the highest rates of ultrasonic vocalization (USV) have been recorded from infant rats when first isolated in an unfamiliar place. We now report that peak USV rates can be doubled by allowing test pups a brief initial period of contact with their anesthetized dam (1–10 min) in the test chamber before isolating the pup by her removal. Potentiation of the isolation response was specific to the dam, for it failed to occur following initial contact with a group of 4 warm, anesthetized littermates. Control experiments showed that potentiation could not be attributed to thermal contrast, experimenter handling, general behavioral activation, novelty of maternal cues, or nursing deprivation. Furthermore, it did not occur when pups were taken for isolation testing directly from prolonged contact with their anesthetized dam in the home cage. Potentiation may be understood in terms of the communicative role of the pups' call and/or prior learning contingencies within the mother–infant interaction.©1994 John Wiley & Sons, Inc.
Sound localization in newborn human infants
Authors: Morrongiello Barbara A. , Fenwick Kimberley D. , Hillier Loretta , Chance Graham
Published: January 2005

Newborns' localization of sounds was examined in two experiments that utilized different psychophysical procedures and imposed different task demands. The results of both experiments were consistent in indicating that neonates not only differentiate the hemifield of a sound source but have some capacity to localize a sound within the hemifields. Adjustment of their initial head turn angle following a within‐hemifield shift in location of an ongoing sound indicated that head orientation in neonates is elicited not only by sound onset but also by changes in location of an ongoing sound. Thus, multiple stimulus parameters impact on this neonatal response. Results are related to research on sound localization in older infants, and discussed in light of early development of the central auditory system.©1994 John Wiley & Sons, Inc.
Developmental changes in the contextual control of recognition
Authors: Earley Linda A. , Bhatt Ramesh S. , Rovee‐Collier Carolyn
Published: January 2005

In three experiments, we explored potential developmental differences in the contextual control of target recognition using elementary perceptual features that differed only in their spatial relations. Three‐and 6‐month‐old infants were trained in the presence of black horizontal and vertical line segments arranged as Ls, Ts, or + s on a pink background and were tested in the presence of the same line segments in a different spatial arrangement. At both ages, target recognition required a match between the primitive perceptual features in the test context and those present during training. Delayed recognition by younger but not older infants also required a match between specific spatial arrangements of the horizontal and vertical segments (+ s versus Ls or Ts), despite the fact that infants of both ages had initially encoded these relations. These data suggest that by 6 months, spatial information in the periphery is detected preattentively via a parallel‐processing mechanism, as it is in children and adults. © 1995 John Wiley & Sons, Inc.
Dissociation of behavioral and neural correlates of early associative learning
Authors: Sullivan Regina M. , Wilson Donald A.
Published: January 2005

Wistar rat pups were trained in an olfactory associative conditioning task on postnatal Day 6, 12, or 20. The training consisted of 20 pairings of a novel odor (peppermint) with footshock (1.5 mA, 1 s) with an intertrial interval of 3 min. Additional pups were trained in either unpaired or naive control conditions. On the day following training, pups were either tested for their behavioral response to the conditioned odor in a two‐odor choice test, or injected with 14C‐2‐deoxyglucose and exposed to the odor for examination of olfactory bulb neural responses to the odor. The results demonstrate that, although pups at all ages learned to avoid the odor, only pups trained during the first postnatal week had a modified olfactory‐bulb glomerular‐layer response to the odor. These results suggest that although olfactory memory is correlated with modification of olfactory bulb glomerular layer function in newborns, these changes are not required for normal memory in older pups. © 1995 John Wiley & Sons, Inc.
Thermal expansion of Portland cement paste, mortar and concrete at high temperatures
Authors: Cruz C. R. , Gillen M.
Published: December 2004

Results of measurements of thermal expansion of Portland cement paste, mortar, concrete and a dolomitic rock aggregate are presented. Test temperatures ranged from 27 to 871°C. Cement paste contracted when subjected to temperatures from 204 to 871°C. Thermal expansion of mortar and concrete was dominated by thermal expansion characteristics of the mineral aggregate. However, expansion was moderated by contraction of the cement paste matrix at elevated temperatures. Average coefficients of expansion, over specific temperature ranges, are given for the materials tested. Equipment developed to control automatically the rate of heating and record strain vs. temperature relationships is described.
The pyrolysis of organic nitriles
Authors: Metcalfe E. , Booth D. , McAndrew H. , Wooley W. D.
Published: December 2004

Detailed quantitative studies are reported on the kinetics of acetonitrile pyrolysis using an isothermal quartz tubular flow reactor at 720–1033 K and 1 atm. Pressure using flow rates, in nitrogen, of 2–200 ml min−1. The pyrolysis of several other nitriles (acrylonitrile, propionitrile, methacrylonitrile and benzonitrile) has also been investigated qualitatively by pyrolysis‐gas chromatography.
Heat release and classification of fire retardant wood products
Authors: östman Birgit A.‐L. , Tsantaridis Lazarous D.
Published: December 2004

A comparison is presented of cone calorimeter heat release data between fire retardant treated and untreated wood products. The test results show significant differences between these two groups. The parameters included in the comparison are time to ignition, rate of heat release (peak and average values) and total heat release. The wood‐based products were also tested in different small‐scale national standard fire tests and in the full‐scale room fire test. Fire retardant wood products achieve an improved classification both in present national systems and in possible new systems based on the cone calorimeter and the room fire test.
A comparison of binding properties and structure of NGF receptor on PC12 pheochromocytoma and A875 melanoma cells
Authors: Buxser Stephen E. , Watson Leslie , Johnson Gary L.
Published: December 2004

Rat PC12 pheochromocytoma and human A875 melanoma cells express nerve growth factor (NGF) receptors on their surfaces. Covalent crosslinking of bound 125I‐NGF to PC12 or A875 intact cells or plasma membrane‐enriched fractions resulted in labelling of a peptide doublet at Mr = 110,000 and a single labelled peptide at Mr = 200,000 for each of the cell and membrane preparations. However, a difference between equilibrium binding properties of NGF‐receptor on PC12 and A875 cells was observed. PC12 cells exhibited biphasic binding properties with two apparent binding sites: KD = 5.2 nM sites and KD = 0.3 nM sites. The high‐affinity PC12 binding sites were trypsin resistant, and 125I‐NGF dissociated slowly from them. A875 cells exhibited sites with homogeneous properties (KD = 1.0 nM), all binding sites were trypsin sensitive, and 125I‐NGF dissociated rapidly in the presence of unlabelled NGF. Membrane‐enriched fractions from either cell type contained binding sites with a uniform low affinity (KD = 3 nM) that were trypsin sensitive, and 125I‐NGF rapidly dissociated from them. Sixty to 80 percent of binding sites in membranes could be converted to the high‐affinity, trypsin‐resistant state by addition of wheat germ agglutinin (WGA). The loss of high‐affinity, trypsin‐resistant sites from PC12 cells during preparation of plasma membrane fractions does not appear to be the result of selective isolation of low‐affinity sites or proteolytic degradation since there is a loss of 125I‐NGF binding immediately after cell lysis which is not blocked by protease inhibitors. Also, high‐affinity, trypsin‐resistant binding sites are not found associated with other cell fractions. The differences between receptor properties on PC12 cells and on A875 cells apparently are the result of differences in the respective intracellular environments. Thus, significant structural homology exists between receptors on A875 and PC12 cells. Cell components other than the binding unit of the NGF receptor may be responsible for the different properties of receptor.
Characterization of isolates and clones of leishmania by analysis of kinetoplast DNA
Authors: Spithill Terry W. , Grumont Raelene J. , Mitchell Graham F.
Published: December 2004

The genetic characterization of pathogenic isolates of Leishmania was attempted by analysis of the molecular properties of kinetoplast DNA (kDNA) minicircles. Unit minicircle size is not conserved during speciation of Leishmania since the minicircles of strains and clones of L t major are smaller (700 bp) than those found in certain strains of L mexicana ssp (820 bp), L donovani (850 bp) or L t tropica (900 bp). Schizodeme analysis of minicircles reveals a high degree of sequence divergence in kDNA of Leishmania with the degree of microheterogeneity varying between species. This sequence divergence allows the discrimination of species, strains, and clones of Leishmania into schizodemes. Southern blot hybridization experiments reveal that at high stringency overall minicircle sequence homology is conserved among clones and strains of one species (L t major) but not between different species. This property of minicircle DNA permits the use of kDNA probes as a species‐specific diagnostic test for the identification of unknown Leishmania isolates. The properties of kDNA from an L t tropica strain LRC‐L32 (a “recidiva” organism) are so diverged from those of L t major strains as to support the classification [22,23] of L t tropica and L t major as separate species of Leishmania rather than subspecies of L tropica.
Characterization of a sheep pituitary‐derived growth factor for rat and human mammary tumor cells
Authors: Ikeda Tatsuhiko , Danielpour David , Sirbasku David A.
Published: December 2004

A growth factor for rat and human mammary tumor cells (MTGF‐Pit) was isolated from lyophilized powders of whole sheep pituitaries by a rapid four‐step procedure utilizing acetic acid extraction, heating at 93°C, and sequential chromatography in 0.10 M acetic acid on sulphopropyl Sephadex and Sephadex G‐50. From 10 g of pituitary powder, 8‐10‐mg amounts of MTGF‐Pit were isolated. By 8 M urea, 0.1% SDS‐12.5% polyacrylamide gel electrophoresis analysis followed by Coomassie blue staining, this preparation was shown to be one major stained band. When assayed for growth effects on cells maintained in serum‐free medium, 5.1‐19.2 nM MTGF‐Pit half replaced the growth of MTW9/PL rat and MCF‐7 and T‐47D human mammary tumor cells in response to 2% to 10% serum. MTGF‐Pit shows mitogenic activity toward normal human diploid fibroblasts only at concentrations in excess of 2.5 × 10−4 M, while rat fibroblasts are unresponsive even at this high concentration. From data available, we conclude that a mitogenic activity for epithelial‐type mammary cells has been isolated, and this growth factor appears to be a previously undetected acid‐ and heat‐stable activity that is highly abundant (estimated at 0.16% or more of the total dry weight of the pituitary powder). The isolated ovine MTGF‐Pit (3,900 ± 200 daltons) does not share the molecular weight of native prolactin (24,000 daltons), “cleaved” prolactin (16,000 daltons), or growth hormone (22,000 daltons), and by all tests applied cannot be replaced with other known hormones and purified growth factors. We conclude a potent new mammary tumor cell mitogenic activity has been identified from sheep pituitaries.
Hepatocyte uptake of α1‐proteinase inhibitor‐trypsin complexes in vitro: Evidence for a shared uptake mechanism for proteinase complexes of α1‐proteinase inhibitor and antithrombin III
Authors: Fuchs Herbert E. , Michalopoulos George K. , Pizzo Salvatore V.
Published: December 2004

In vivo clearance studies have indicated that the clearance of proteinase complexes of the homologous serine proteinase inhibitors α1‐proteinase inhibitor and anti‐thrombin III occurs via a specific and saturable pathway located on hepatocytes. In vitro hepatocyte‐uptake studies with antithrombin III‐proteinase complexes confirmed the hepatocyte uptake and degradation of these complexes, and demonstrated the formation of a disulfide interchange product between the ligand and a cellular protein. We now report the results of in vitro hepatocyte uptake studies with α1‐proteinase inhibitor‐trypsin complexes. Trypsin complexes of α1‐proteinase inhibitor were prepared and purified to homogeneity. Uptake of these complexes by hepatocytes was time and concentration‐dependent. Competition experiments with α1‐proteinase inhibitor, α1‐proteinase inhibitor‐trypsin, and antithrombin III‐thrombin indicated that the proteinase complexes of these two inhibitors arc recognized by the same uptake mechanism, whereas the native inhibitor is not. Uptake studies were performed at 37°C with 125I‐α1‐proteinase inhibitor‐trypsin and analyzed by sodium dodecyl sulfate‐gel electrophoresis in conjunction with autoradiography. These studies demonstrated time‐dependent uptake and degradation of the ligand to low molecular weight peptides. In addition, there was a time‐dependent accumulation of a high molecular weight complex of ligand and a cellular protein. This complex disappeared when gels were performed under reducing conditions. The sole cysteine residue in α1‐proteinase inhibitor was reduced and alkylated with iodoacetamide. Trypsin complexes of the modified inhibitor were prepared and purified to homogeneity. Uptake and degradation studies demonstrated no differences in the results obtained with this modified complex as compared to unmodified α1‐proteinase inhibitor‐trypsin complex. In addition, the high molecular weight disulfide interchange product was still present on sodium dodecyl sulfate‐polyacrylamide gel electrophoresis of solubilized cells. Clearance and clearance competition studies with approteinase inhibitor‐trypsin, alkylated α1‐proteinase inhibitor‐trypsin, antithrombin III‐thrombin, and antithrombin III‐factor IXa further demonstrated the shared hepatocyte uptake mechanism for all these complexes.
Expression and assembly of the erythroid membrane‐skeletal proteins ankyrin (goblin) and spectrin in the morphogenesis of chicken neurons
Authors: Lazarides Elias , Nelson W. James
Published: December 2004

The membrane‐skeleton of adult chicken neurons in the cerebellum and optic system is composed of polypeptides structurally and functionally related to the erythroid proteins spectrin and ankyrin, respectively. Neuronal spectrin comprises two distinct complexes that share a common α subunit (Mr 240,000) but which have structurally distinct polymorphic subunits (β′β spectrin; Mr 220/225,000; γ spectrin, Mr 235,000): the brain‐specific form (αγ spectrin or fodrin) and an erythrocyte‐specific form (αβ′β spectrin). Two structurally related isoforms of ankyrin have also been identified and are termed α (Mr 260,000) and β (Mr 237,000) ankyrin. Immunofluorescence demonstrates that the variants of spectrin and ankyrin, respectively, have different distributions within neurons. On the one hand, αγ spectrin and β ankyrin are present throughout the neuron, in the perikaryon, dendrites and axon, whereas αβ′ spectrin and α ankyrin are localized exclusively in the perikaryon and dendrites where they are actively segregated from αγ spectrin and other components of axonal transport. This asymmetric distribution of spectrin and ankyrin isoforms is established in distinct stages during neuronal morphogenesis. Early in cerebellar and retinal development, αγ spectrin is expressed in mitotic cells. Subsequently β ankyrin and αγ spectrin are co‐expressed in postmitotic cells and gradually accumulate on the plasma membrane in a uniform pattern throughout the neuron during the phase of cell growth. At the onset of synaptogenesis and the cessation of cell growth, their levels of synthesis decline sharply while the assembled proteins remained as stable membrane components. Concomitantly, there is a dramatic induction in the accumulation of α ankyrin and αβ′ spectrin, whose assembly is limited to the plasma membrane of the perikarya and dendrites. These results demonstrate that two successive, developmentally regulated programs of ankyrin and spectrin expression and patterning on the plasma membrane are involved in the assembly of the spectrin‐based asymmetry in the neuronal membrane‐skeleton, and that their asymmetric distribution is actively maintained throughout the life of the neuron.