Developmental effects of selective breeding for an infantile trait: the rat pup ultrasonic isolation call.

This article describes how continued selection for divergent levels of the 10-day-old infant rat's ultrasonic vocal (USV) response to isolation affects the time course of development of that and other possible co-selected traits from 3 to 21 days postnatally. Since selective breeding for an infantile trait has not been reported before, we collected from colleagues a number of predicted outcomes that reflect the wide range of current opinion on the relationship between microevolutionary and developmental processes. After 15 generations of selective breeding, we found widely divergent USV responses between 10-day-old High USV line (300 USV/2 min) and low USV line (15 USV/2 min) pups. The developmental trajectory of USV responses at 3 and 7 days of age also was markedly altered in both these lines in comparison to the randomly bred controls, but was much less affected in 14-, 18-, or 21-day-old pups, contrary to all predictions. The development of other behavioral responses to isolation generally remained unaffected by the continued selection as did physical traits, measures of temperature regulation and classic developmental milestones. Only two traits showed evidence of co-selection: High line pups showed more urination/defecation in response to isolation from 10 days on, and more rapid ear canal opening at 10 days. These and other findings are presented and discussed in relation to the developmental and evolutionary concepts on which the different predictions were based.     

Selective breeding for infant vocal response: A role for postnatal maternal effects?

N:NIH rats were selectively bred on the basis of high or low rates of ultrasonic vocalization (USV) response to isolation at 10 days of age (Brunelli et al., 1997: Dev Psychobiol 31:255-265). To examine the possibility of postnatal maternal effects in the generational transmission of divergent traits, pups were cross-fostered shortly after birth between dams of the two lines (Low- and High-USV). Controls were fostered to dams of the same line (in-fostered). Additional (population) control data were obtained from the entire 13th generation of the selectively bred lines. USV rates of cross-fostered pups in each line were not significantly different from rates of in-fostered pups of the same line. High USV line pups cross-fostered to Low USV line dams weighed significantly less than in-fostered pups, on the day of testing. The results provide no evidence for a postnatal maternal contribution to the USV phenotype. Prenatal and/or perinatal maternal effects have not been ruled out.     

Potentiation and inhibition of ultrasonic vocalization of rat pups: Regulation by social cues

Eight- and 11- to 12-day-old rat pups were tested in isolation and in the presence of an anesthetized adult under cold conditions. Pups of both ages reduced rates of ultrasonic vocalization (USV) when an adult was placed into the test cage, independent of whether the adult was their dam or an unrelated male. However, afer removal of the dam, pups greatly increased their rates of USV over their first isolation period and in comparison with control pups. USV rates remained low after removal of the male. The temperature challenges faced by the pups in the two experimental conditions were the same. These phenomena are better explained by a hypothesis that postulates USV rate as being multiply determined, including by social cues, rather than a theory that considers thermal challenge only. © 1997 John Wiley & Sons, Inc. Dev Psychobiol 30: 195–200, 1997     

Ethanol dependence in mice: Direct and correlated responses to ten generations of selective breeding

With the goal of producing an animal model of alcohol dependence, genetic selection in mice for severity of the alcohol withdrawal syndrome is underway. Ten generations of selection have been completed, and the lines selected for severe or mild expression of the withdrawal syndrome following a 9-day ethanol treatment period are significantly different from each other. The index of selection is the unrotated first-principal-component score derived from the intercorrelations among seven different measures of severity of ethanol withdrawal. Across the generations, mice from all six closed mating populations have increased their mean consumption of alcohol considerably. This seems to be the result of natural selection operating concurrently with artificial selection. When animals from generation 9 were used to test for possible correlated responses to selection, there was an indication that animals selected for mild expression of withdrawal symptoms are also less sensitive to an acute dose of ethanol.This work was supported by NIAAA Grant AA-03527.     

Selective Breeding for an Infant Phenotype: Rat Pup Ultrasonic Vocalization (USV)

To examine processes underlying generational and developmental influences on anxiety, this laboratory produced two lines of (N:NIH strain) rats, selectively bred on the basis extreme rates of ultrasonic vocalization in 2 minutes of isolation at Postnatal Day 10. The research reviewed in this article focuses on: (1) establishment of the selectively bred lines; (2) defining infant behavioral and physiological phenotypes and (3) determining whether infantile USV phenotypes endure over development. The High and Low lines have diverged widely in their USV rates from each other and from the Random control line, which has maintained N:NIH strain rates overall from generation to generation. Beginning in the 11th generation, High USV pups have shown significantly higher frequencies of defecation and urination during isolation screening than the Low USV and random control line. Both lines show altered autonomic regulation of heart rates (HR) in response to stressors as juveniles and adults. These differences in HR responses in High and Low lines appear to be mediated by changes in the balance of sympathetic versus parasympathetic mechanisms. Other behavioral characteristics of the High line are consistent with an anxious/ depressive phenotype, such as vocalizations to touch in a novel environment, and performance in the Porsolt Swim, whereas Low line shows few differences in anxiety behavior. Future work will resolve the similarities and differences in the High and Low phenotypes and provide a developmental perspective to the growing body of information about affective regulation in humans and animals provided by selectively bred animal models.     

New insights into the relationship of neurogenesis and affect: tickling induces hippocampal cell proliferation in rats emitting appetitive 50-kHz ultrasonic vocalizations

Adult hippocampal cell proliferation (HCP) has been associated with psychopathology, especially depression. However, it is controversial whether a constitutively low rate of HCP is a trait predisposing an individual to psychopathology or whether HCP varies with the subject's affective state. We made use of a so far neglected measure of affect, namely ultrasonic vocalizations, to gain new insights into the relationship of HCP and affect. Rats emit distinct types of ultrasonic vocalizations, which serve as situation-dependent affective signals. In appetitive situations, rats produce 50-kHz-calls, whereas 22-kHz-calls occur in aversive situations. We applied a standardized protocol of repeated tickling and assessed tickling-induced ultrasonic vocalizations as an index of the animals affect. Stereological quantifications of 5-bromo-2′-deoxyuridine (BrdU) and proliferating-cells-nuclear-antigen (PCNA) immunolabeled cells were used to estimate the rate of cell proliferation in the subventricular zone and the subgranular zone of the dentate gyrus in the hippocampus. The rate of cell proliferation was compared between the groups of tickled vs. non-tickled rats and between subgroups of tickled rats defined by the effect of tickling on ultrasonic vocalizations. Tickling induced ultrasonic vocalizations in a subject-dependent manner. HCP correlated positively with appetitive 50-kHz-calls, but negatively with aversive 22-kHz-calls in individual animals, while cell proliferation in the subventricular zone was not associated with the emission of ultrasonic vocalizations. Repeated tickling did not change HCP in all rats, but increased HCP in the subgroup of rats, which experienced this procedure as appetitive, i.e. in rats emitting high numbers of 50-kHz-calls or low numbers of 22-kHz-calls. Together, these data indicate that the effect of tickling on HCP depends on an interaction between a predisposing trait and stimulation-dependent variations of the subject's affective state.     

Development of ultrasonic vocalization responses in genetically heterogeneous National Institute of Health (N:NIH) rats. II. Associations among variables and behaviors

In this study, the first three generations of laboratory-reared, 10-day-old pups of the N:NIH strain were examined for ultrasonic vocalizations (USV) rates in response to 2 min of isolation. The purpose of the study was to determine baseline USV rates in these progenitor (PR1, PR2, PR3) generations prior to selective breeding for high and low rates of USV. In addition, this study aimed to detect sources of variation in USV between and within generations and sexes, and factors associated with USV during isolation across the generations. Data were collected from 532 10 day-old pups in 81 litters. Evaluation by principal component analyses revealed four factors corresponding roughly to constructs indicative of: thermoregulation; maturity and exploratory behavior; distress/anxiety, in which USV consistently appeared; and activity. Different component structures for each sex suggested that USV may represent different dimensions of anxiety for the sexes, with some degree of overlap. Nonetheless, all variables measured during isolation testing accounted for only a small portion of the variance in individual pup USV (less than 9%) at 10 days of age, when the effects of intercorrelations among all variables were taken into account. This suggests that variables currently measured do not represent a comprehensive model for the control of USV. © 1996 John Wiley & Sons, Inc.     

Growth curve analyses are best suited to examine the relation between developmental pathways and selective breeding: comment on Hofer, Shair, Masmela, & Brunelli, Developmental effects of selective breeding for an infantile trait: the rat pup ultrasonic isolation call.

Hofer, Brunelli, Shair, & Masmela (2001) provide valuable information about the effects of selective breeding on rat-pup behaviors and physiology. Although the design and statistical analytic techniques employed are typical of those used to evaluate behavioral development in animals, I offer several suggestions about how to evaluate the influence of selective breeding on developmental pathways using modern statistical techniques. As Hofer et al. demonstrate, the development of rat behavior and physiology can be an excellent model for examining the relation between selection and development.     

The effects of selective breeding for infant ultrasonic vocalizations on play behavior in juvenile rats

For over 25 generations, two lines of rats (High and Low USV lines) have been selectively bred for extreme rates of infantile (45 kHz) ultrasonic vocalizations (USV) in response to maternal separation at postnatal day (P)10. High and low line juveniles (P30-P40) were socially isolated and allowed to play in same-sex sibling pairs for 10 min per day over three days. Measures of play were nape contacts and pinning. Other social and nonsocial behaviors were also scored during the three sessions; two of these, 55 kHz USV and walk-overs, were statistically associated with play. Compared to the Random control line, both High and Low line juveniles showed deficits in play behavior. In the High line, play initiatory behavior (nape contacts) was reduced, but pinning, USV and walk-overs were relatively unchanged. In contrast, nape contacts, pinning, USV and walk-overs were all reduced in Low line juveniles compared to Random line controls. The results suggest that selection for extremes of infant USV rates has produced temperamental differences that are expressed in juvenile play in the High and Low USV lines.     

Development of ultrasonic vocalization responses in genetically heterogeneous National Institute of Health (N:NIH) rats. I. Influence of age,testing experience,and associated factors

The N:NIH strain of rats was developed by the National Institutes of Health to provide a maximally heterogeneous population as a base for selective breeding (Hansen & Spuhler, 1984). Using the N:NIH strain, this laboratory will selectively breed adult animals that exhibited extremes of high or low ultrasonic vocalization (USV) rates as infants. Because nothing was known about USV in N:NIH rats, we characterized the development of isolation-induced USV in the first generation of this strain born in our laboratory. In a longitudinal/cross-sectional study of pups tested at 3, 10, 15, and 18 days postnatally, N:NIH pups emitted their highest rates of USV at 3–4 days postnatally and calling remained high for 10 days before declining. USV rates were found to be a relatively environmentally stable behavioral trait in that repeated testing did not significantly affect the calling rates of either individuals or litters, and only at 3 days postnatal age did naturally occurring ambient temperature variations (6°C range) significantly affect USV responses. Individual differences in USV responses emerged by 10 days of age that were not simply correlations of body weight or rectal temperature, and pups at that age showed isolation calling rates that were highly predictive of their response levels 5 days later. © 1996 John Wiley & Sons, Inc.     

Letter to the editor: Chronicle for an orphan trait: comment on Hofer, Shair, Masmela, & Brunelli, Developmental effects of selective breeding for an infantile trait: the rat pup ultrasonic isolation call.

Hofer, Brunelli, Shair, and Masmela (2001) examined several behavioral and physiological measures in low, high, and unselected lines obtained from a divergent selection for ultrasound production (USP) in young rats. Although the response to selection was clear-cut, few correlated responses appeared. This surprising result could be explained by two reasons. USP has polygenic correlates in this population, and most of the chromosomal regions that are linked with these measures only contribute to a small part of the genetic variance. Therefore, correlated responses to selection might exist, but the common genetic variance between the trait under selection and the indirectly selected trait is too small to be detected by a selective breeding strategy.     

Developmental differences in temporal patterns and potentiation of isolation-induced ultrasonic vocalizations: influence of temperature variables

The present study examined the relationship between the thermal environment and core body temperature in producing age-related patterns of ultrasonic vocalizations (USVs). Implanted telemetry devices allowed on-line measurement of core body temperature during an extended period of isolation and after maternal contact, both as a function of age and thermal environment. At 12 or 17 days of age, rat pups were isolated for 30 min in either a cool or a warm environment, returned home for 5 min, and then re-isolated for 10 min. Number of USVs, body temperature, and behavioral activity were measured. During initial isolation in a cool environment, 12-day-olds displayed relatively stable patterns of ultrasounding and body temperature across time whereas older animals showed a time-dependent increase in USV calling and in core temperature. During re-isolation, 12-day-olds potentiated their USV calling at both ambient temperatures while 17-day-olds did not. The overall results suggest a strong dependence between USV calling, core body temperature, and ambient temperature during initial isolation at both ages-a finding in agreement with interpretations of USVs as an acoustic by-product of thermal challenge. In contrast, during re-isolation, USV calls, core body temperature, and ambient temperature functioned independently-a finding in agreement with interpretations of USVs as a representation of an emotional state.     

Understanding responses to government health recommendations: public perceptions of government advice for managing the H1N1 (swine flu) influenza pandemic

Objective

To explore people's beliefs, perceptions, reasoning, and emotional and contextual factors that may influence responses to government recommendations for managing flu pandemics.

Methods

Eleven focus groups were conducted with a purposive sample of 48 participants. Participants were invited to discuss their perceptions of the H1N1 pandemic and government advice on recommended actions for managing the H1N1 pandemic.

Results

Thematic analysis showed that participants were skeptical about the feasibility and appropriateness of government recommendations for managing the H1N1 pandemic. They expressed doubts about self-diagnosis and concerns regarding the perceived effectiveness and costs of recommendations to stay home if unwell and get vaccinated.

Conclusions

Government advice is a specialized form of health communication with members of the public. People engage in an active process of evaluating government advice in terms of its credibility, feasibility and costs. To improve future pandemic preparedness, attempts should be made to elicit and address common doubts and concerns people have about following recommended advice.

Practical implications

This study provides preliminary information on potential concerns and issues that could be addressed in future pandemic communications. Further research is needed to elicit and address the public perspective so that the impact of future pandemics may be reduced.     

Suitability of 5/6 nephrectomy (5/6NX) for the induction of interstitial renal fibrosis in rats – Influence of sex, strain, and surgical procedure

Chronic renal failure (CRF) is a serious clinical problem and currently there are no adequate therapeutic strategies for treatment. Many possible treatment strategies have been tested in rats with CRF induced by subtotal nephrectomy. However, reports in the literature concerning the consequences of this procedure on rat kidney function are contradictory. For instance, such an intervention in male Sprague-Dawley rats apparently initiates the development of interstitial renal fibrosis, while in our similar studies on female Wistar rats (HW) there was minimal renal fibrosis. Therefore, we carried out experiments in adult rats to investigate the long-term consequences of 5/6 nephrectomy (5/6NX) in relation to (1) sex, (2) strain, and (3) two methods of surgical ablation. Ten weeks after 5/6NX, body weight gain, systolic blood pressure, creatinine clearance, and urinary protein were measured, along with renal hydroxyproline concentration determinations to assess the deposition of extracellular matrix. Also, light microscopic investigations were done to characterize renal damage. The functional parameters clearly indicated the development of CRF, while morphologic investigations showed only moderate fibrotic areas containing atrophic tubules and lymphocytic infiltrates. However, 45-60% of glomeruli were sclerotic. In summary, 5/6NX, using either method of partial nephrectomy, induces signs of moderate glomerulonephritis preferentially in female HW rats. Thus 5/6NX in female HW rats can be recommended as a suitable model in the induction of renal fibrosis.     

Risk factors for severe complications of the novel influenza A (H1N1): analysis of patients hospitalized in Italy

Eighty-one patients affected by the novel influenza A (H1N1), hospitalized in North-western Italy, were studied. The median age was 32 years (range 1–81 years). Fifty-six (69%) had an underlying medical condition, including lung disorders (asthma or chronic obstructive pulmonary disease) in 34% and obesity in 25%. Fifty percent of them had pneumonia, 12% were admitted to the intensive care unit and 3% died. Antiviral treatment was initiated in 75% of patients started within 48 h. Older age and lung and neurocognitive disorders were associated with severe disease and death.