PubMed Health⌕ Search

Biomedical subjects

A E Ronca

Publications and source records attributed to A E Ronca.

28 records · Page 2Linked to original sources
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↗
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↗
PubMed1991

Heart rate response of the rat fetus and neonate to a chemosensory stimulus.

Resting heart rate (HR) and HR responses of fetal and neonatal rats are described before and after intraoral infusion of isotonic saline or lemon solution. Stable measurements of resting HR were obtained for fetuses over the last three days of gestation (E19, E20, E21) and pups on the day of birth (P0) and four subsequent postnatal ages (P1, P3, P5, P7). Resting HR decreased significantly on P0 relative to the three prenatal ages and exhibited a linear increase thereafter. Variability in resting HR was pronounced on E21, decreased sharply after birth, and gradually increased through P7. Developmental changes in the HR response of fetuses and pups were evident following infusion of lemon. Fetal HR responses to lemon were characterized by bradycardia, which increased in magnitude through P1, diminished after P1, and eventually changed to tachycardia by P7. Both resting HR and HR responses to chemosensory stimulation point to the immediate perinatal period as a time of quantitative and qualitative change during sensory development.

Aging↗
PubMed1990

Heart rate development and sensory-evoked cardiac responses in perinatal rats.

Sensory-evoked changes in heart rate (HR) are often used to assess sensory function in infants, but HR measures have not been applied in studies of perinatal sensory function. Normative HR data are needed to judge whether baseline characteristics and response properties of the late fetal and newborn heart are appropriate as a dependent measure in sensory studies. We compared parameters of HR development and phasic cardiac responses to stimulation across the perinatal period in Norway rats. EKG was measured in cesarean-delivered prenatal rats (embryonic day 20-day of birth; conception = E0) and compared to both cesarean and vaginally delivered neonates (day of birth-postnatal day 2; birth = P0). Resting heart rate increased monotonically across the perinatal period, except between E21 and DOB (Experiment 1). During an hour-long test, HR was strong and stable. Variations in HR across successive measurement intervals (10 sec) were uniformly low (less than 2%) in all age groups. In Experiment 2, fetuses and neonates responded with dramatic HR decelerations (20-80 bpm) to an intraoral infusion of lemon extract. HR responses did not appear to be reflexively mediated by changes in respiration. These findings suggest that parameters of resting HR and cardiac responses to stimulation are well suited to studies of perinatal sensory function.

Animals↗
PubMed1985

Cardiac orienting and habituation to auditory and vibrotactile stimuli in the infant decerebrate rat.

Phasic changes in heart rate were used to evaluate sensory reactivity and habituation in 5- and 12-day-old normal and decerebrate rats. Twenty-four and forty-eight hours after thalamic transection, temporally paired auditory or vibrotactile stimuli were repeatedly presented in a sensory disparity paradigm. While tone stimuli failed to evoke consistent cardiac change, vibrotactile stimuli produced cardiac decelerations, characteristic of the orienting response, in all subject groups. The magnitude of this response was comparable in both normal and decerebrate subjects at 5 days of age, but demonstrated a more notable increase with age in the normal subjects. Habituation of the cardiac response was apparent in all groups, and was not significantly different in the normal and decerebrate subjects. No consistent responses were apparent in any group to the unexpected omission of the second stimulus of the pair. Results indicate that orienting and habituation processes can persist in the absence of the cerebral hemispheres and support the view that lower levels of the neuraxis are capable of mediating a range of adaptive functions.

Acoustic Stimulation↗
PubMed1985

Cardiac reactivity and adaptive behavior.

The relationship between adaptive behavioral function and cardiac reactivity to auditory, somatosensory, and visual stimuli was evaluated using a heterogeneous population of developmentally disabled infants and young children. Stimuli of all sensory modalities resulted predominantly in a cardiac deceleration, and the magnitude of these responses varied systematically between subjects. A multiple regression analysis revealed that 60% of the variance in adaptive behavior, as measured by the Adaptive Behavior Scale for Infants and Early Childhood, could be accounted for by age and the cardiac responses. The factor with the greatest predictive weighting was cardiac reactivity to a vibrotactile stimulus, which showed a correlation of .65 with adaptive behavior scores.

Acoustic Stimulation↗
PubMed1983

The decerebrate human: associative learning.

Phasic changes in cardiac reactivity to innocuous stimuli, presented in a sensory disparity paradigm, were used to evaluate habituation and learning processes in five decerebrate subjects. Three subjects showed systematic changes over trials in the pattern of cardiac response to simple auditory or visual stimuli, indicative of habituation. In addition, tests for associative learning were given after repeated presentations of two paired stimuli. The appearance of a marked cardiac orienting response, to the unpredictable omission of the second stimulus, documented the development of a conditioned association in these same three subjects. One additional subject failed to show a consistent pattern of response to the stimuli, and another demonstrated a consistent response which was not subject to habituation. Overall, these findings support the view that learning processes are not solely the product of the cerebral hemispheres, but reflect general integrative features of the human neuraxis.

Association Learning↗
PubMed1982

Antagonism of tertiary butanol by ACTH4-10, naloxone and dexamethasone.

Male C57 mice were pretreated with naloxone (4 mg/kg), ACTH4-10 (30 micrograms/kg), or saline 15 minutes prior to an injection of tertiary butanol (1.5 g/kg). Both naloxone and ACTH4-10 lengthened induction time (time to lose righting reflex) and shortened the duration of sleep time. Dexamethasone (.6 mg/kg) pretreatment of mice injected with ethanol (3.75 g/kg) or tertiary butanol (1.5 g/kg) lengthened induction time, but did not alter sleep time. The data do not support a primary role for acetaldehyde or TIQ involvement in the acute depressant effects of alcohol, but do suggest that some of the observed effects may in part be mediated through an endogenous opioid system.

Adrenocorticotropic Hormone↗