A descriptive analysis of nursing behavior in the guinea pig (Cavia porcellus).

Analyzed the nursing behavior in the precocial guinea pig. The behaviors of 6 dams with litters of 3 pups were videotaped under undisturbed conditions during both phases of the light–dark cycle and after reunion during the light phase on Days 1, 2, 3, 6, and 13 postpartum. More time was spent nursing in the light than in the dark and in the 1st wk than on Day 13. Pup licking was not required for nipple attachment to occur even on Day 1. Dams displayed a crouched nursing posture accompanied by 120 sec or more of body plus head immobility, similar to the crouched stance in the rat; body plus head immobility was rarely seen in females not in a crouched stance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Factors influencing cortisol and behavioral responses to maternal separation in guinea pigs.

Infant guinea pigs recently were found to respond to brief maternal separation with an increase in plasma cortisol (COR) levels. The present experiments were conducted to further characterize this response and compare it with the COR separation response previously observed in primates. In Exp 1, separation of guinea pig pups from their mothers did not elevate the plasma COR levels of the pups at either 30 or 180 min when they remained alone in their home cages during the separation. Exp 2 showed that COR levels of pups placed alone in a novel cage were greater at 30, 90, and 180 min than were those of pups placed in the cages together with their mothers. In contrast, the separated pups vocalized more than did pups tested with their mothers during the initial 30 min only. In Exp 3, pups raised on inanimate surrogates responded less intensely to rearing-figure separation in terms of COR and vocalizations than did mother-reared controls. Results indicate differences (response to home cage separation) and similarities (dissociation of COR and vocalization responses, effect of surrogate separation) in the separation responses of guinea pig and primate infants. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ontogeny of behavioral arousal: A comparative study.

Conducted 2 experiments with a total of 110 male Hartley albino neonatal guinea pigs, and 72 male golden neonatal hamsters to study changes in general activity as a function of age. The precocial guinea pig, which has a relatively mature brain at birth, showed little variation in behavioral arousal from 5-100 days of age. However, the altricial hamster displayed a sizable increase in activity between 10-15 days of age followed by a corresponding decline between 15-25 days of age. This pattern of behavioral activity in the hamster parallels the caudal-rostal sequence of brain development, in which the phylogenetically primitive brainstem excitory system reaches maturity before telencephalic inhibitory centers. Direct observation revealed no qualitative changes in response that could account for the differences in behavioral arousal between the 2 species. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Huddling by rat pups: Group behavioral mechanisms of temperature regulation and energy conservation.

Two of 5 experiments examined the effect of huddling on body temperature and oxygen consumption; the other 3 investigated the behavioral dynamics of the group and of individual members while huddling. Body heat loss was attenuated and oxygen consumption was reduced by huddling in litters of developing Ss. Rat pups derive physiological benefits from huddling similar to those enjoyed by adult mammals; these findings contrast with previous characterizations of the altricial rat as poikilothermic. Huddling insulates by lessening the exposed body surface area of the participants, thus retarding heat loss and enhancing the efficiency of thermogenesis. These physical mechanisms of the clump are actively regulated by the pups. A novel quantitative measure of huddle size revealed a form of group regulatory behavior in rat pups whereby the surface expanded and contracted with increases and decreases in ambient temperature. The individual basis of this group regulatory activity was investigated by marking individual Ss and observing them in huddles by means of time-lapse videography. It was found that individual Ss circulate through the huddle, frequently exchanging locations. Ordinarily, the direction of movement was actively downward, into the pile; immobile Ss "floated" on the surface. When the nest temperature was raised to thermoneutral, the direction of S flow reversed, and an immobile S sank to the depths of the huddle. Through individual competitive adjustments the huddle behaves as a self-regulating unit which provides warmth and insulation to all its active members. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Proinflammatory activity and the sensitization of depressive-like behavior during maternal separation.

When guinea pig pups are isolated for a few hours in a novel environment, they exhibit a distinctive passive behavioral response that appears to be mediated by proinflammatory activity. Recently, we observed that pups separated on two consecutive days show an enhanced (sensitized) passive response on the second day. In Experiment 1, pups receiving intracerebroventricular infusion of 50 ng of the anti-inflammatory cytokine interleukin-10 prior to a first separation failed to show a sensitized behavioral response to separation the next day. In Experiment 2, pups separated on Days 1 and 2, or just 2, showed an increase in passive responding during separation on Day 5. Pups injected with the bacterial antigen lipopolysacchride (LPS; 75 μg/kg body weight, intraperitoneal) prior to separation on Day 1 showed an increase in passive behavior several days later not shown by pups injected with saline prior to Day 1 separation. However, injection of LPS without separation on the first day did not enhance responding during an initial separation on the second day. These results suggest that immune activation is necessary, but not sufficient, to account for the sensitization of passive behavior of isolated guinea pig pups the following day, that boosting proinflammatory activity during an initial separation may promote sensitization several days later, and that the sensitized response persists for at least several days. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

An investigation of the effects of maternal separation and novelty on central mechanisms mediating pituitary-adrenal activity in infant guinea pigs (Cavia porcellus).

In mammalian species in which the young exhibit a strong filial attachment (e.g., monkeys, guinea pigs), numerous studies have shown that even brief separation from the attachment figure potently elevates circulating concentrations of glucocorticoids and adrenocorticotropic hormone (ACTH). However, effects of separation on central regulation of this stress response are not known. Therefore, we investigated central mechanisms mediating pituitary-adrenal activation during maternal separation and novelty exposure in guinea pig (Cavia porcellus) pups. Corticotropin-releasing factor (CRF) mRNA expression in the hypothalamic paraventricular nucleus (PVN), and plasma cortisol and ACTH levels, were elevated only during separation in a novel environment. C-Fos activity was elevated in the medial amygdala (MeA) and reduced in the bed nucleus of the stria terminalis (BNST) during novelty exposure, regardless of separation. On the other hand, c-Fos activity was elevated in the PVN during separation, regardless of novelty exposure. These results demonstrate independent and combined effects of separation and novelty in regions of the guinea pig CNS that regulate pituitary-adrenal activity. Moreover, they suggest that a pathway from MeA to BNST to PVN mediates responses to novelty in the guinea pig pup, as in the adult rat, though inputs from other cell populations appear required to fully account for the HPA activity observed here. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sheepskin bedding and the sudden infant death syndrome. New Zealand Cot Death Study Group

A stress protocol--6 h of daily immobilization--was applied throughout male rat sexual development. Immobilization caused a small reduction in food intake and body weight gain whereas pair-fed animals had a marginal decrease only in body weight gain. Stress, confirmed by increased plasma adrenocorticotrophic hormone (ACTH) and corticosterone, caused a decrease in plasma luteinizing hormone (LH) after 15 and 60 days of immobilization and in plasma testosterone after 60 days, but produced an opposite androgenic response in pubertal animals (15 days of immobilization). A persumed sympathetic over-stimulation is suggested to account for increased testosterone levels in pubertal stressed rats.     

Isolation and partial characterization of a major basic protein from rat eosinophil granules

The rat eosinophil granule possesses a major basic protein (MBP) similar to that previously isolated from human and guinea pig eosinophils. This conclusion is based on demonstration that the major protein of the rat eosinophil granule is a low molecular weight, highly basic material with an amino acid composition similar to that of the human and guinea pig MBP.     

Effects of warmth on newborn rats' motor activity and oral responsiveness to an artificial nipple.

Temperature is a powerful regulator of the behavior and physiology of newborn altricial animals. The effects of warmth on newborn rats' oral responsiveness to suckling stimuli and spontaneous motor activity in a thermoneutral environment were investigated. Newborn rat pups' oral grasp responses to an artificial nipple and overall motor activity were recorded for 18 min. Near-term pups were delivered by cesarean section so that their 1st experiences with suckling stimuli could be observed. Experimental pups were warmed for 15 s every 2 min; control pups were not warmed. Warmed pups grasped the nipple fewer times than the not-warmed pups. However, oral grasp durations became longer for the warmed pups but not for the not-warmed pups. Warmth increased pups' motor activity but only while the heat was applied. Warmth in a thermoneutral environment may promote longer nipple attachment during newborns' early feeding experiences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The response of chickens to D-mannoheptulose: feeding behavior and blood glucose

Administration of mannoheptulose (MH) at a concentration of 200-300 mg./kg. body weight, administered intraperitoneally or intracardiacly resulted in a significant increase of plasma glucose concentration (24.3%) four hours after administration. Food consumption was effected by administration of 300 mg./kg. body weight. There was a significant reduction in the mannoheptulose treated animals compared to the saline controls during the second and third hours of testing. The results were similar to those reported for mammals although the increase in plasma glucose concentration was not as drmatic in birds as it is in mammals. Food consumption studies in rat indicate a suppression, however, it is not significant as it was in this study.     

Guinea pig apolipoprotein C-II: expression in E. coli, functional studies of recombinant wild-type and mutated variants, and distribution on plasma lipoproteins

Guinea pig apolipoprotein C-II (apoC-II) lacks four amino acid residues in the amino-terminal, lipid-binding part compared to apoC-II from other mammalian species (Andersson et al. 1991. J. Biol. Chem. 266: 4074-4080). To explore whether this structural difference explains the low ability of guinea pig plasma to activate lipoprotein lipase in vitro, we have expressed guinea pig apoC-II in Escherichia coli and have constructed an insertion mutant with the four missing amino acid residues compared to human apoC-II. With a synthetic emulsion of long-chain triacylglycerols, both the wild-type guinea pig apoC-II and the insertion mutant stimulated lipoprotein lipase similar to human apoC-II, but with chylomicrons from an apoC-II-deficient patient, 5- to 10-fold more of both wild-type guinea pig apoC-II and the insertion mutant were needed. Studies of tryptophane fluorescence indicated a slight difference in how guinea pig apoC-II interacted with liposomes, and presumably with lipoproteins, as compared to human apoC-II. The level of apoC-II (11.5 +/- 5.4 microg/ml) was lower in guinea pig compared to human plasma, and most of guinea pig apoC-II was on HDL-like particles. These had decreased ability to donate apoC-II to lipid emulsions compared to human HDL. Some guinea pig apoC-II was associated with LDL which, as demonstrated by surface plasmon resonance, had higher affinity for lipoprotein lipase than human LDL, and inhibited rather than stimulated the lipase reaction in vitro. We conclude that while guinea pig apoC-II is fully competent to stimulate lipoprotein lipase, the sum of several different factors explains the low ability of guinea pig plasma to accomplish stimulation.     

Cloning and characterization of the guinea pig eosinophil eotaxin receptor, C-C chemokine receptor-3: blockade using a monoclonal antibody in vivo

Certain C-C chemokines, signaling via the eotaxin receptor C-C chemokine receptor-3 (CCR3), are thought to be central mediators of eosinophil accumulation in allergic inflammation. To investigate the role of CCR3 in vivo, we cloned the guinea pig eotaxin receptor (guinea pig CCR3) from a genomic DNA library. We isolated a single-exon open reading frame coding for a 358-amino acid chemokine receptor protein with 67 and 69% homology to human and murine CCR3, respectively. When expressed in stable transfectants, this receptor bound 125I-labeled guinea pig eotaxin, 125I-labeled human monocyte chemotactic protein-3, and 125I-labeled human RANTES. In chemotaxis assays, guinea pig CCR3 transfectants responded only to guinea pig eotaxin, with a maximal effect at 100 nM. mAbs were raised that bound selectively to both guinea pig CCR3 transfectants and guinea pig eosinophils. One of these mAbs, 2A8, blocked both ligand binding to transfectants and their chemotaxis in response to eotaxin. The Ab also inhibited chemotaxis and the elevation of cytosolic calcium in guinea pig eosinophils in response to eotaxin. F(ab')2 fragments of 2A8 were prepared that retained the ability to inhibit eosinophil calcium responses to eotaxin. Pretreatment of (111)In-labeled eosinophils in vitro with F(ab')2 2A8 selectively inhibited their accumulation in response to eotaxin in vivo. These data demonstrate that functional blockade of eosinophil chemokine receptors can be achieved in vivo and provide further support for the development of novel anti-inflammatory drugs targeting eosinophil recruitment through chemokine receptor antagonism.     

Alteration of vascular endothelium and endothelium smooth muscle interaction after carbogen gas perfusion of isolated rat and guinea pig heart

The aim of the study was to alter the vascular endothelium of the mammalian myocardium with respect to coronary flow regulation and vascular permeability. For this purpose, carbogen gas perfusion (GP) of Langendorff-type isolated rat and guinea pig heart was chosen. Perfusion of the hearts with carbogen gas was possible, as well as replacement of the GP by fluid perfusion. The energetic and mechanical state, the creatine kinase release, and the electron microscopic examination of the rat heart indicated only a moderate to minimal alteration of the cardiomyocytes after GP. As a result of GP a massive alteration of the vascular endothelium could be demonstrated in the rat heart, based on the release of the cytosolic endothelial marker enzyme, purine nucleoside phosphorylase, the partly altered vascular permeability and the morphologically detected endothelial damage to arterioles, capillaries and venules. Moreover, the reduced coronary flow response to short periods of anoxia (rat, guinea pig) and the inverted flow response to serotonin administration with maintained response to sodium nitroprusside (rat) in the post-gas perfusion period reflected an alteration of endothelial smooth muscular interaction in the rat and guinea pig heart. Furthermore, the distensibility of the coronary vasculature was increased in the rat and guinea pig heart in the post-gas perfusion period, where a relative autoregulatory behavior was maintained (rat) or partly maintained (guinea pig) in passively predilated vessels. In conclusion, carbogen gas perfusion of isolated hearts allows to induce preferred alteration of endothelium and endothelium-smooth muscle interaction.     

Inhibition of anaphylactic reaction in guinea pigs by antibodies to fragments of Fc from autologous IgG

The effect of antibodies to Fc subfragments of guinea pig IgG on the anaphylactic reaction in guinea pigs has been studied. Control animals were immunized with guinea pig IgG and Fab, human IgG and albumin. All animals with antibodies to fragments of autologous Fc survived challenge with horse serum, whereas the control animals died in anaphylactic shock.     

Cryptopsychobiology: The appearance, disappearance, and reappearance of a species-typical action pattern during early development.

Late in gestation, intraoral infusion of lemon elicits a facial wiping response from rat fetuses. This facial wiping response is isomorphic with that of older pups and adult rats exposed to aversive oral stimulation. Most studies of the postnatal development of aversive responses have demonstrated that facial wiping does not appear in the repertoire of rat pups until the second postnatal week. In certain test situations, however, wiping can be elicited from neonatal rats. This fact suggests that the expression of facial wiping by neonates is constrained or facilitated by the environmental conditions present at the time of testing. In this report, a series of seven experiments is described that document the wiping response of rat fetuses and pups in age-typical environments, and an environmental constraint hypothesis is examined. Examination of the ontogeny of facial wiping in this manner highlights issues that should be addressed in studies of behavioral continuity between the prenatal and the postnatal periods. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increased fat intake during lactation modifies hypothalamic-pituitary-adrenal responsiveness in developing rat pups: a possible role for leptin

High fat feeding reportedly enhances hypothalamus-pituitary-adrenal (HPA) responses to stress in adult rats. The present study tested whether elevated fat intake during suckling could have short and/or long lasting consequences on HPA regulation in the offspring. Mothers were fed either a control (C; 5% fat) or high fat (HF; 20% fat) diet during the last week of gestation and throughout lactation. After weaning (day 21), pups from C and HF mothers were fed a chow diet. Offspring from both C- and HF-fed mothers were tested for ACTH and corticosterone responses to stress on postnatal days 10 and 35. We found that HF feeding produced higher lipid levels in the milk of HF compared with C lactating rat dams and that offspring of these mothers had significantly increased retroperitoneal fat pad weight and relative adipose mass on day 21 as well as elevated plasma leptin levels on days 10 and 21 of age. After weaning, pups from the HF mothers had lower plasma leptin levels than those from C mothers. Maternal dietary fat affected HPA responsiveness in the offspring in an age-related manner. Neonatal pups (day 10) from the HF mothers exhibited a reduction in the ACTH and corticosterone responses to ether stress. However, in 35-day-old offspring from HF-fed dams, stress-induced ACTH secretion was increased compared with that in pups from the C-fed mothers. These results demonstrate that maternal diet and increased fat intake through the milk are important regulators of HPA responsiveness in neonates and prepubertal rats. During neonatal life, the blunted stress responsiveness seen with elevated fat intake and the resulting high leptin levels might protect the pups from excessive HPA activation. After removal of the maternal dietary influence and reduced leptin levels, enhanced ACTH stress responses are observed as in adult rats fed a HF diet. Because of the inverse relationship between plasma levels of leptin and HPA responses in pups, the possibility exists that the effects of the HF diet on stress responsiveness are mediated by changes in leptin exposure during development.     

Comparison of the development of the fatty acid content and composition of the brain of a precocial species (guinea pig) and a non-precocial species (rat)

The fatty acid compositions of the brains of a precocial (guinea pig) and a non-precocial (rat) species have been studied as a function of development. In the rat brain the total fatty acid content expressed as mg g wet wt.-1 increased more than fourfold during the period from 5 days after birth to adulthood. However, the percentage composition of this total fatty acid content when expressed per individual fatty acid remained fairly constant, with the exception of nervonic acid (C24:1) which also increased fourfold on a percentage basis. In the guinea pig brain, however, at birth the total fatty acid content, expressed as mg g wet wt-1, is the same as that of the adult, the concentration doubling during the period from 25 days before birth until birth. Again, if the fatty acid content is analysed and expressed on a percentage basis, the relative concentrations of the individual fatty acids remain fairly constant over the period from 25 days before birth until adulthood, with the exception of nervonic (C24:1) acid which increases about fivefold from 25 days before birth to birth and only marginally (20%) from birth to adulthood. These results are discussed in relationship to the onset of neurological competence in the two species. It is concluded that the increase in fatty acid content (both total and individually) of the brains of these species as a function of the foetal and neonatal development follows a pattern which is similar to the pattern of development of certain key enzymes of energy metabolism and of neurological competence.     

Angiotensin II tachyphylaxis in the guinea pig ileum and its prevention: a pharmacological and biochemical study

Angiotensin II (AII) tachyphylaxis occurs in the guinea pig ileum, but is not induced by analogs lacking the N-terminal amino group or the Arg2 guanidino group. Both AII and Lys2AII increased cell inositol trisphoshate content in cultured intestinal smooth muscle cells. Protein kinase C inhibition by staurosporine or downregulation by prolonged incubation with phorbol reverted tachyphylaxis of the inositol trisphoshate response, but not that of the Na+ uptake response, indicating that the uncoupling of the phosphoinositide signal system by protein kinase C did not involve all processes distal to receptor activation. Tachyphylaxis of the Na+ uptake response was prevented when receptor internalization was blocked by reduction of the temperature (4 degrees C) or by pretreatment of the cells with phenylarsine oxide. Acid washings, which prevented tachyphylaxis of the 24Na+ influx response, also prevented tachyphylaxis of the contractile response of the guinea pig ileum to AII. Although these findings suggest that sequestration or internalization of the AII receptor might be involved in AII tachyphylaxis, binding of [125I]AII and of [125I]Lys2AII to the cells was equally unaffected by repeated administrations of the peptides. The results suggest that conformational change of the AII-receptor complex within the plasma membrane, but not internalization, is the most important factor responsible for tachyphylaxis.     

Cloning, sequencing and functional expression of a guinea pig lung bradykinin B2 receptor

Kinin receptors are classified as B1 and B2 based upon agonist and antagonist potencies and cloning and expression studies. Using sequences from human and rat bradykinin B2 receptors, polymerase chain reaction (PCR) was utilized to isolate cDNA from guinea pig lung. The receptor obtained is predicted to have 372 amino acids and shares > 80% sequence homology with human, rat, rabbit and mouse B2 receptors. In competition binding experiments in Chinese hamster ovary (CHO-K1) cells in which the guinea pig cDNA was expressed, [3H]bradykinin was displaced by kinin receptor ligands with an order of potency consistent with a B2 subtype. In CHO cells expressing the guinea pig receptor, bradykinin caused a concentration 45Ca2+ efflux. A B1 receptor agonist, desArg9-bradykinin, also caused 45Ca2+ efflux but with a potency several orders of magnitude lower than bradykinin. Curiously, several B1 and B2 receptor antagonists induced 45Ca2+ efflux, indicating that this receptor may be coupled differently in CHO cells than in native tissues.     

Ursodeoxycholic acid modifies gut-derived endotoxemia in neonatal rats

We developed a model for the translocation of intraluminal endotoxin in the neonatal animal and used it to examine the capacity of a nonhepatotoxic bile acid, ursodeoxycholic acid (UDCA), to modify endotoxin translocation and cytokine response. Three-d-old Sprague-Dawley rats were randomized to receive enterally either no drug, lipopolysaccharide (LPS, 1 mg/animal), or UDCA (400 micrograms/animal) alone, or UDCA followed by LPS 1 h later. One h after LPS administration, the rats were killed and plasma endotoxin and tumor necrosis factor (TNF) were measured. Control animals had low circulating endotoxin (21.2 +/- 7.6 endotoxin units) and TNF (0.06 +/- 0.02 ng/mL). Enteral administration of LPS 1 h before the rats were killed resulted in significant elevation of endotoxin (249.5 +/- 71.3, p = 0.008) and TNF (3.6 +/- 1.3, p = 0.019). UDCA alone did not alter endotoxin levels (8.7 +/- 2.1). UDCA 1 h before LPS prevented the rise in endotoxin (38.9 +/- 11.2 endotoxin units) and TNF (0.2 +/- 0.05) significantly. Chenodeoxycholic acid was studied in a similar group of experiments and prevented neither the translocation of LPS nor the development of increased TNF levels in animals receiving LPS. In conclusion, LPS can cross the intestinal barrier in the normal neonatal rat. UDCA, administered before LPS, can decrease the translocation of LPS and prevent the cytokine response as measured by TNF levels. We speculate that UDCA, administered prophylactically, might reduce morbidity in clinical conditions leading to gut-derived endotoxemia.