Reproductive performance and weaning success in fur-chewing chinchillas (Chinchilla lanigera)

In captive chinchillas, one of the most challenging behavioral problems is the development of a stress-related abnormal repetitive behavior (ARB) known as “fur-chewing”. We investigated whether there is a relationship between the severity of fur-chewing behavior and reproductive function in male and female chinchillas. Regardless of the severity of abnormal behavior, fur-chewing males did not show significant differences in seminal quality (sperm concentration, motility and viability; integrity of sperm membrane and acrosome) and the response to the process of semen collection (the number of stimuli needed to achieve ejaculation) when compared to those with normal behavior. Also, females showing normal or fur-chewing behavior presented similar reproductive performance in terms of number of litters per female per year and litter size. However, pup survival rate was lower (p = 0.05) in fur-chewing females than in normal females. These results seem to be consistent with data suggesting non-significant effects of ARBs on reproductive performance.     

Morphometric studies of Leydig cells in chinchillas (Chinchilla lanigera) during high and low fertility seasons

The aim of this study was to examine morphometric data of Leydig cells of 10 male chinchillas. Testes, cut into 5-microm thick sections, were stained using the p.a.S. and Masson's methods. Some 3800 Leydig cells have been evaluated. Their dimensions, as well as the diameters of their nuclei and the distances of the nuclei from the boundaries of the cells, have been measured. The areas of the surface and volumes of the nuclei of Leydig cells have been calculated, as well as the areas of the surface of the Leydig cells themselves. The following data have been obtained. The Nuclei of Leydig Cells. The largest diameters: longer cells - 12 microm; shorter cells - 10 microm. Mean diameters: longer cells - 5.67 +/- 3.44 microm, shorter cells - 4.45 +/- 3.44 microm. The largest surface area - 120 microm2, the mean surface area - 28.27 +/- 11.21 microm2. The largest volume - 1200 microm3, the mean volume of nucleus - 171.8 +/- 65.82 microm3. Mean distances of Leydig cell nuclei from the opposite boundaries of the cells amounted to 1.29 +/- 1.41 microm, 4.24 +/- 2.39 microm, 4.09 +/- 2.23 microm, 6.12 +/- 2.33 microm. Leydig cells. The largest diameters: longer cells - 24 microm, shorter cells - 22 microm. Mean dimensions: longer cells - 13.86 +/- 2.76 microm, shorter cells - 10.89 +/- 2.44 microm. The largest area of surface - 528 microm2, the mean area of surface - 155.44 +/- 59.78 microm2. Morphometric analysis confirmed cytologic observations that the shape of the nuclei of Leydig cells is somewhat ellipsoidal. The nuclei are located off-centre and are not situated in the greatest agglomeration of cytoplasm. The shape of Leydig cells is irregular. The obtained results may provide insight on the infertility of chinchilla males, as well as in research on the annual cyclic fertility of these animals. They may be put to use in practice for the purpose of improving breeding of this species.     

A non-invasive method for assessing adrenal activity in the chinchilla (Chinchilla lanigera)

The Chinchilla is a rodent that was once abundant in the central Andes of South America. Excessive hunting for fur greatly reduced its distribution at the beginning of the twentieth century, and today Chinchilla species are nearly extinct in the wild. Although protected, wild populations of chinchilla are still declining. In general, this species has received little research attention and its biology is poorly understood. Improvements in captive breeding, husbandry, and genetic management are needed to ensure the conservation of the species. In this study, a noninvasive corticosteroid hormone monitoring technique was validated for use in Chinchilla lanigera. Two male domestic chinchillas were administered 3H-corticosterone (i.m.) to determine the time course and relative proportion of urinary and fecal steroid metabolites. Most radioactivity was detected in urine and feces 5-10 and approximately 30 h post-isotope administration, respectively. Corticosteroid immunoreactivity was assessed by corticosterone radioimmunoassay (RIA) and cortisol enzyme immunoassay (EIA). High-pressure liquid chromatography (HPLC) separation of corticosteroid metabolites in unprocessed urine revealed the presence of highly polar corticosteroid metabolites, but after enzymatic hydrolysis and diethyl ether extraction, most immunoreactivity co-eluted with unconjugated cortisol. A 'cause-and-effect' relationship between the administration of exogenous adrenocorticotrophic hormone (ACTH), and the appearance of increased urinary corticosteroid metabolites demonstrated the physiological relevance of these measures for evaluating adrenal status in male chinchillas. From a conservation perspective, these methods can aid in situ and ex situ initiatives designed to evaluate how environmental conditions and management strategies affect overall animal health, well-being and reproduction.     

Chinchilla (Chinchilla lanigera) behavioral responses to a visual signal preceding handling

Zoos use ambassador animals in educational programs featuring close contact with humans. Chinchillas (Chinchilla lanigera) at the Saint Louis Zoo are retrieved for programs by a keeper wearing brown handling gloves, but green cleaning gloves are worn during normal husbandry when physical contact with the animal is only incidental. The chinchillas’ primary keeper anecdotally reported more reactivity and movement from chinchillas when approached with handling gloves. Animals’ behavioral reactions to the presence of humans often include locomotion and vigilance, but these responses may be attenuated by predictability. To investigate these behaviors, handling trials involving brief contact attempts with both cleaning and handling gloves were filmed. Results indicated that chinchillas responded to disturbances by moving, jumping, and adopting more alert body postures. Surprisingly, movement was recorded in longer durations when the keeper attempted to touch the animals with cleaning gloves. This higher arousal may indicate that the animal was not expecting to be handled, yet an attempt to do so was being made. This reaction provides evidence that potentially aversive events should be reliably and consistently signaled.     

Reproduction in chinchilla (Chinchilla lanigera): current status of environmental control of gonadal activity and advances in reproductive techniques

In female swine, PGF2α is an important regulator of corpora luteal (CL) function, uterine contractility, ovulation, and embryo attachment. High affinity PGF2α receptors are present in the CL at all stages of the estrous cycle and they are functional. Therefore, a lack of luteolytic capacity of PGF2α is related to other factors that have not been well identified. In female pigs, a single exogenous PGF2α injection produces a short lasting decrease in plasma progesterone levels but does not induce luteolysis before day 12 of the estrous cycle. However, multiple injections of PGF2α can induce luteolysis before day 12 of the estrous cycle and may be utilized in the development of protocols for ovulation synchronization and timed AI. Most commonly, PGF2α is used for the induction of farrowing and so facilitation of cross fostering. Further, since PGF2α is a smooth muscle stimulant, treatment to stimulate myometrial contractions and uterine evacuation of residual products from parturition or infectious debris, may have beneficial effects on post-weaning fertility. Administration of PGF2α at the moment of insemination has been shown to improve reproductive performances when fertility is otherwise low, such as in sow under summer heat stress.     

Year-round testicular volume and semen quality evaluations in captive Chinchilla lanigera

In mammals, reproductive performance is usually associated with seasons. Chinchilla lanigera, an endemic South American rodent, reproduces throughout the year in captivity but its seasonal breeding pattern is not fully understood. The present study was designed to evaluate (bi-weekly) over 1 year: (1) testicular volume variations and (2) seminal volume, sperm concentration and functional activity changes. Five animals were studied; they were individually housed indoors (22.2 +/- 1.0 degrees C) under natural photoperiod in Argentina (Córdoba, 31 degrees S-64 degrees W). Semen was obtained by electroejaculation; a total of 116 ejaculates was evaluated. Monthly values for paired testicular volume were less in the middle of the summer than in other seasons (p < 0.006), while those for seminal volume and total spermatozoa/ejaculate were not significantly different; these variables ranged between 7.2-30.9 cm(3), 10-130 microL and 0.9-432.6 x 10(6), respectively. Spermatozoa concentration was (x 10(6)/mL) 2145.9 +/- 365.3 and the pH of semen was 7.3 +/- 0.0. Spermatozoa functional activity showed no significant differences between monthly evaluations; confidence intervals were calculated for the means of: motility, 92.2-95.8%; viability, 92.2-96.1%; swollen cells (hypo-osmotic swelling test), 81.2-87.7% and viable intact acrosome, 83.5-89.0%. The present study represents the first longitudinal reproductive assessment in the chinchilla male. In conclusion, males produce spermatozoa continuously that exhibit high quality functional activity.     

Assessment of urine and fecal testosterone metabolite excretion in Chinchilla lanigera males

Endemic chinchilla (Chinchilla spp.) populations are nearly extinct in the wild (South America). In captive animals (Chinchilla lanigera and C. brevicaudata), reproduction is characterized by poor fertility and limited by seasonal breeding patterns. Techniques applied for studying male reproductive physiology in these species are often invasive and stressful (i.e. repeated blood sampling for sexual steroids analysis). To evaluate endocrine testicular function, the present experiments were designed to (a) determine the main route of testosterone excretion (14C-testosterone infusion in four males); (b) validate urine and fecal testosterone metabolite measurements (HPLC was used to separate metabolites and immunoreactivity was assessed in all metabolites using a commercial testosterone radioimmunoassay, and parallelism, accuracy and precision tests were conducted to validate the immunoassay); and (c) investigate the biological relevance of the techniques applied (quantification of testosterone metabolite excretion into urine and feces from five males injected with hCG and comparison between 10 males and 10 females). Radiolabelled metabolites of 14C-testosterone were excreted, 84.7+/-4.2 % in urine and 15.2+/-3.9 % in feces. A total of 82.7+/-4.2% of urinary and 45.7+/-13.6% of fecal radioactivity was excreted over the first 24 h period post-infusion (metabolite concentration peaked at 8.2+/-2.5 h and 22.0+/-7.0 h, respectively). Several urinary and fecal androgen metabolites were separated by HPLC but only fecal metabolites were associated with native testosterone; however, there was immunoreactivity in more than one metabolite derived from 14C-testosterone. After hCG administration, an increase in androgen metabolite excretion was observed (p<0.05). Males excreted greater amounts daily of urinary androgen metabolites as compared with females (p<0.05); this difference was not evident in feces. Results of the present study indicate that the procedure used is a reliable and non-invasive method to repeatedly monitor variations in testicular endocrine activity in this species. It can be a useful tool that would help ensure the survival of the wild populations as well as to provide the basis for a more efficient use by the fur industry.     

Diagnosis of sexual cycle by means of vaginal smear method in the chinchilla (Chinchilla lanigera)

An investigation was made as to whether the sexual cycle and pregnancy can be determined by means of vaginal smear in chinchillas. This study represents the first attempt to record changes which occur in the pattern of exfoliated cells in chinchilla's vaginal smear during anoestrus, proestrus, oestrus, metoestrus and pregnancy. Fifteen female chinchillas aged from 8 months to 3 years and bred through harem breeding method were used. The major change during proestrus was an increase in the proportion of superficial cells, with a corresponding decrease in other cells. Goblet cells were observed in the smears prepared by strong aspiration during this cycle. Neutrophils, small and large intermediates and parabasal cells were not found in the smear during oestrus and the smear consisted of superficial cells only. In the proportion of neutrophils, small and large intermediates and parabasal cells increased during metoestrus. In addition, metoestrum and foam cells were found in this cycle. In anoestrus; superficial and parabasal cells were present in small numbers. Also small and large intermediate cells as well as neutrophils were present. Traces of foam and metoestrum cells were found. During pregnancy, neutrophils generally of medium density were present, parabasal; small and large intermediate cells were present at low or medium density, and superficial cells were only present in trace amounts.     

Mapping the Anatomy of Respiratory Syncytial Virus Infection of the Upper Airways in Chinchillas (Chinchilla lanigera)

Although most viral infections of the upper respiratory tract can predispose to bacterial otitis media, human respiratory syncytial virus (HRSV) is the predominant viral copathogen of this highly prevalent pediatric polymicrobial disease. Rigorous study of the specific mechanisms by which HRSV predisposes to otitis media has been hindered by lack of a relevant animal model. We recently reported that the chinchilla, the preferred rodent host for studying otitis media, is semipermissive for upper-airway HRSV infection. In the current study, we defined the anatomy and kinetics of HRSV infection and spread in the upper airway of chinchilla hosts. Chinchillas were challenged intranasally with a fluorescent-protein–expressing HRSV. Upper-airway tissues were recovered at multiple time points after viral challenge and examined by confocal microscopy and immunohistochemistry. HRSV replication was observed from the rostral- to caudalmost regions of the nasal cavity as well as throughout the Eustachian tube in a time-dependent manner. Although fluorescence was not observed and virus was not detected in nasopharyngeal lavage fluids 14 d after infection, the latest time point examined in this study, occasional clusters of immunopositive cells were present, suggesting that the nasal cavity may serve as a reservoir for HRSV. These data provide important new information concerning the time course of HRSV infection of the uppermost airway and suggest that chinchillas may be useful for modeling the HRSV-induced changes that predispose to secondary bacterial infection.Abbreviations: HRSV, human respiratory syncytial virus; rrHRSV, recombinant red fluorescent human respiratory syncytial virus; URT, upper respiratory tractHuman respiratory syncytial virus (HRSV), an enveloped, negative-strand, nonsegmented RNA virus of the family Paramyxoviridae, is the single greatest causative agent of acute respiratory tract infections in infants and children worldwide.²³ Although HRSV infection generally is limited to the upper respiratory tract (URT), in the United States, primary HRSV infection is associated with a 0.5% hospitalization rate for those children who develop severe bronchiolitis or pneumonia.⁹ One of the most interesting aspects of HRSV is its ubiquity: there are annual winter–spring outbreaks in temperate climates,⁵ and approximately 90% of all children have experienced infection by their second birthday.⁹ Although immunity to HRSV is sufficient to prevent reinfection of the lower airway in most human patients, this response is incomplete, resulting in reinfection of the upper airway throughout life.⁹ Although URT infection by HRSV alone does not constitute a serious problem for healthy adults, its association with the development of bacterial otitis media in children^{11-13,17-19,21,25,28,29,34} and exacerbation of asthma in all age groups¹⁶ make it an important health concern.Despite the ubiquity of the virus, the epidemiology of HRSV is not well understood. There is no known animal reservoir, and although new strains emerge over time, many remain in circulation over several seasons or reappear many years after they were first detected.^27,33 Therefore, although antigenic variation driven by development of HRSV immunity in a given population is possible, this hypothesis has not yet been proven. In fact, in one study,¹⁰ human subjects could be infected repeatedly with the same HRSV strain, and the presence of virus-specific antibody provided only short-lived and incomplete protection. Therefore, HRSV may circulate among seropositive persons, and it has been suggested that persistently infected persons may harbor the virus between seasonal outbreaks.^30,32 Therefore, in addition to the important clinical issues surrounding the prevention of HRSV disease, basic scientific questions regarding HRSV circulation and mechanisms of viral immunoevasion remain unanswered.A key hurdle in the study of HRSV pathogenesis has been the lack of a suitable animal model. Most published studies have used BALB/c mice, which have the advantage of many reagents available for the study of immune responses but the disadvantage of relative resistance to HRSV infection.²² Although pulmonary infection is easily detected in HRSV-infected mice, primary infection of the upper airway in this species is minimal^6,7 and secondary infection of the URT does not occur. More susceptible rodent species include the cotton rat (Sigmidon hispidus)²⁶ and chinchilla (Chinchilla lanigera),⁶ which are both relatively permissive for HRSV infection of the upper airway. Given the paucity of URT specimens encountered in general pathology practice, the development of a robust small animal model for the study of HRSV infection and spread in the uppermost airway is particularly important. Moreover, effective vaccine development depends on a better understanding of why this compartment remains susceptible to reinfection in immune hosts.Here we describe the anatomy of HRSV infection in the chinchilla URT over a 2-wk period, using confocal microscopy to monitor the retrograde spread of a recombinant red fluorescent protein-expressing HRSV construct (rrHRSV)⁸ from the site of inoculation. Although rrHRSV has previously been used to study the susceptibility of various cell types to virus infection in vitro,^8,36 our current report is the first wherein this biologic agent has been used to trace the route and extent of infection after intranasal instillation of virus in vivo. To establish the usefulness of our approach, immunohistochemistry and plaque assay were used to verify the sensitivity and specificity of fluorescence detected at 2, 3, 5, and 14 d after infection. By these combined methods, we were able to follow the retrograde spread of virus infection from the respiratory epithelium of the nasoturbinates and nasopharynx (at the earliest time point) to the Eustachian tubes and ethmoid turbinates at later time points. The ability to visualize the anatomy and kinetics of HRSV replication in the uppermost airway can now form the basis for future studies of upper-airway susceptibility to virus reinfection and bacterial coinfection.     

Serotonin 5-HT(2C) receptors regulate anxiety-like behavior

Central serotonin (5-hydroxytryptamine, 5-HT) systems have been implicated in the pathophysiology and treatment of anxiety disorders, which are among the world's most prevalent psychiatric conditions. Here, we report that the 5-HT(2C) receptor (5-HT(2C)R) subtype is critically involved in regulating behaviors characteristic of anxiety using male 5-HT(2C)R knockout (KO) mice. Specific neural substrates underlying the 5-HT(2C)R KO anxiolytic phenotype were investigated, and we report that 5-HT(2C)R KO mice display a selective blunting of extended amygdala corticotropin-releasing hormone neuronal activation in response to anxiety stimuli. These findings illustrate a mechanism through which 5-HT(2C)Rs affect anxiety-related behavior and provide insight into the neural circuitry mediating the complex psychological process of anxiety.     

Peripheral plasma progesterone concentration and haematological indices during normal pregnancy of chinchillas (Chinchilla laniger, M.)

Peripheral plasma progesterone concentration and some haematological indices in pregnant chinchillas were studied. As pregnancy advanced progesterone concentration showed a marked change from high values in early pregnancy (days 9-29), to undetectable values by days 40-60, and from high values in the latter states of pregnancy (days 70-80), to very low values during the 30 days before parturition. Haematocrit value and mean erythrocyte volume change inversely to progesterone concentration fluctuations. White blood cell parameters increased during the first half of pregnancy, then decreased to the lowest level before parturition.     

Seminal quality and neutral alpha-glucosidase activity after sequential electroejaculation of chinchilla (Ch. lanigera)

The objectives of this study of seminal quality of chinchilla (Chinchilla lanigera) males were to evaluate (1) the use of neutral alpha-glucosidase (NAG) as a functional epididymal marker in this species, and (2) the effects of repetitive electroejaculation on sperm function and seminal NAG concentration. Semen was obtained by electroejaculation from sexually mature domestic Ch. lanigera males (n=6) once a week for six consecutive weeks, and evaluated to assess seminal volume and NAG activity, and sperm concentration and functional activity (motility, viability, membrane and acrosome integrity). Body weight was determined in all animals before each electroejaculation procedure. NAG activity was detected in all semen samples obtained, reaching a concentration of 55.4±6.8μU/mL. No significant variations were observed throughout the experimental period in any of the semen quality parameters evaluated. A reduction (P=0.001) in body weight was detected from the third week of experimentation and by the end of the experiments the animals lost a 7.2±0.9% of body weight. Overall, results in the present study confirm that NAG activity is detectable in chinchilla seminal plasma and that repetitive electroejaculation is not deleterious, on a short-term basis, to the semen characteristics.     

Estradiol and neuropeptide Y (intra-lateral septal) reduce anxiety-like behavior in two animal models of anxiety

Anxiolytic-like effects of intra-lateral septal nuclei (LSN) infusions of the neuropeptide Y (NPY) alone or combined with estradiol benzoate were assessed in ovariectomized Wistar rats in two animal models of anxiety-like behavior. In a conflict test, immediately punished responses were assessed: 17-beta-estradiol (50.0microg/rat, P<0.05) plus vehicle (intra-LSN) or intra-LSN infusions of NPY (2.5microg/microl, P<0.05; 3.0microg/mul, P<0.05) plus vehicle (systemic route) or the combination of subthreshold doses of 17-beta-estradiol (25.0microg/kg) plus intra-LSN infusions of NPY (2.0microg/mul, P<0.05) increased the amount of immediately punished reinforcers. In the elevated plus-maze test several spatial-temporal variables were evaluated: 17-beta-estradiol (50.0microg/kg, P<0.05) plus vehicle (intra-LSN) or intra-LSN infusions of NPY (2.5microg/mul, P<0.05; 3.0microg/mul, P<0.05) plus vehicle (systemic route) or the combination of subthreshold doses of 17-beta-estradiol (25.0microg/kg) plus intra-LSN infusions of NPY (2.0microg/mul, P<0.05) produced anxiolytic-like actions without affecting locomotion. It is concluded that estradiol or NPY may produce anxiolytic-like actions and that subthreshold doses of estradiol and subthreshold doses of NPY when combined produced anxiolytic-like actions.     

Ghrelin increases anxiety-like behavior and memory retention in rats

Ghrelin is a peptide found in the hypothalamus and stomach that stimulates food intake and whose circulating concentrations are affected by nutritional state. Very little is known about other central behavioral effects of ghrelin, and thus, we investigated the effects of ghrelin on anxiety and memory retention. The peptide was injected intracerebroventricularly in rats and we performed open-field, plus-maze, and step-down tests (inhibitory avoidance). The administration of ghrelin increased freezing in the open field and decreased the number of entries into the open spaces and the time spent on the open arms in the plus-maze, indicating an anxiogenic effect. Moreover, the peptide increased in a dose-dependent manner the latency time in the step-down test. A rapid and prolonged increase in food intake was also observed. Our results indicate that ghrelin induces anxiogenesis in rats. Moreover, we show for the first time that ghrelin increases memory retention, suggesting that the peptide may influence processes in the hippocampus.     

Auditory cortex basal activity modulates cochlear responses in chinchillas

Background

The auditory efferent system has unique neuroanatomical pathways that connect the cerebral cortex with sensory receptor cells. Pyramidal neurons located in layers V and VI of the primary auditory cortex constitute descending projections to the thalamus, inferior colliculus, and even directly to the superior olivary complex and to the cochlear nucleus. Efferent pathways are connected to the cochlear receptor by the olivocochlear system, which innervates outer hair cells and auditory nerve fibers. The functional role of the cortico-olivocochlear efferent system remains debated. We hypothesized that auditory cortex basal activity modulates cochlear and auditory-nerve afferent responses through the efferent system.

Methodology/Principal Findings

Cochlear microphonics (CM), auditory-nerve compound action potentials (CAP) and auditory cortex evoked potentials (ACEP) were recorded in twenty anesthetized chinchillas, before, during and after auditory cortex deactivation by two methods: lidocaine microinjections or cortical cooling with cryoloops. Auditory cortex deactivation induced a transient reduction in ACEP amplitudes in fifteen animals (deactivation experiments) and a permanent reduction in five chinchillas (lesion experiments). We found significant changes in the amplitude of CM in both types of experiments, being the most common effect a CM decrease found in fifteen animals. Concomitantly to CM amplitude changes, we found CAP increases in seven chinchillas and CAP reductions in thirteen animals. Although ACEP amplitudes were completely recovered after ninety minutes in deactivation experiments, only partial recovery was observed in the magnitudes of cochlear responses.

Conclusions/Significance

These results show that blocking ongoing auditory cortex activity modulates CM and CAP responses, demonstrating that cortico-olivocochlear circuits regulate auditory nerve and cochlear responses through a basal efferent tone. The diversity of the obtained effects suggests that there are at least two functional pathways from the auditory cortex to the cochlea.