Resistance to experimental autoimmune encephalomyelitis development in Lewis rats from a conventional animal facility

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory disease of the brain and spinal cord that is mediated by CD4+ T lymphocytes specific to myelin components. In this study we compared development of EAE in Lewis rats from two colonies, one kept in pathogen-free conditions (CEMIB colony) and the other (Botucatu colony) kept in a conventional animal facility. Female Lewis rats were immunized with 100 microl of an emulsion containing 50 microg of myelin, associated with incomplete Freund's adjuvant plus Mycobacterium butyricum. Animals were daily evaluated for clinical score and weight. CEMIB colony presented high EAE incidence with clinical scores that varied from three to four along with significant weight losses. A variable disease incidence was observed in the Botucatu colony with clinical scores not higher than one and no weight loss. Immunological and histopathological characteristics were also compared after 20 days of immunization. Significant amounts of IFN-gamma, TNF-alpha and IL-10 were induced by myelin in cultures from CEMIB animals but not from the Botucatu colony. Significantly higher levels of anti-myelin IgG1 were detected in the CEMIB colony. Clear histopathological differences were also found. Cervical spinal cord sections from CEMIB animals showed typical perivascular inflammatory foci whereas samples from the Botucatu colony showed a scanty inflammatory infiltration. Helminths were found in animals from Botucatu colony but not, as expected, in the CEMIB pathogen-free animals. As the animals maintained in a conventional animal facility developed a very discrete clinical, and histopathological EAE in comparison to the rats kept in pathogen-free conditions, we believe that environmental factors such as intestinal parasites could underlie this resistance to EAE development, supporting the applicability of the hygiene hypothesis to EAE.     

The eradication of Encephalitozoon cuniculi from a specific pathogen-free rabbit colony.

Encephalitozoan cuniculi was discovered in a large specific pathogen-free rabbit colony during routine quality assurance testing. By using a modified India-ink immunoreaction test we were able to test the entire colony for antibodies to Encephalitozoon cuniculi. The prevalence of the disease was approximately 5%. All seropositive animals were culled, and another test of the entire colony, carried out 4 weeks later, revealed one seropositive rabbit which was also culled. Two subsequent screenings of the whole colony have shown no further seropositive animals.     

The social structure and dominance hierarchy of the Mashona mole-rat, Cryptomys darlingi (Rodentia: Bathyergidae) from Zimbabwe

Cryptomys darlingi is a social subterranean rodent mole which inhabits the mesic regions of south-eastern and central Africa. Mashona mole-rats live in small colonies (5-9 animals) in which reproduction is normally restricted to the largest male and female in the colony. The non-reproductive members in a mature colony cannot be placed into clearly defined work-related groups based on body mass.
The dominance hierarchy of a young colony was found to be linear, with a value of 1.00 calculated from Landau's linearity index, while that of a mature colony of nine mole-rats was almost linear (0.77). Dominance was found to be related to gender in the mature colony, with males more dominant than females, and to age in the young colony. The reproductive mole-rats are the dominant animals within their respective genders. Dominance appears to correlate positively with body mass (rs = 0.77 in the mature colony and rs = 0.93 in the young colony).
Popularity studies show that smaller animals and females tend to be more popular than the larger massed individuals or males. In the mature colony which contained predominantly adult animals, the reproductive pair was among the least popular. While in the young colony, composed predominantly of sub-adult and juvenile animals, the reproductive pair was the most popular.
Social organization within Mashona mole-rat colonies is compared with other southern African Cryptomys species.     

The changes in the dominance hierarchy over time of a complete field-captured colony of Cryptomys hottentotus hottentotus

The common mole-rat, Cryptomys h. hottentotus , is a social subterranean rodent occurring in colonies in which one female and one to three males are involved in reproduction and the remaining colony members are non-reproductive. Within each sex the reproductive animals are usually the largest and most dominant animals.
The dominance hierarchy amongst a field-captured colony was linear ( h = 0.95, calculated from Landau's linearity index) soon after capture. The non-reproductive females were ranked low in the dominance hierarchy; many were subordinate to non-reproductive males. The order of capture of mole-rats was not related to the position in the dominance hierarchy. The hierarchy became non-linear ( h = 0.56) after six months in captivity during which two juvenile animals became adult. The breakdown in the hierarchy may result from the lack of opportunity in captivity for animals to disperse and establish satellite colonies, or from colony members becoming co-dominant in the hierarchy as a result of a rise in rank by young animals.
Dominant mole-rats are involved in a greater proportion of interactive behaviours than subordinates. Popularity studies show that females tend to be more popular animals than males. The largest reproductive male was the least popular animal in the first study, whereas a beta male was the least popular animal in the second study period. The reproductive female was the most popular in both periods.     

Clostridium difficile typhlitis associated with cecal mucosal hyperplasia in Syrian hamsters.

A sudden increase in mortality occurred in a closed breeding colony of Syrian hamsters (Mesocricetus auratus). The colony consisted of approximately 40 hamsters, 8 of which were affected. Four adult males died suddenly. One pregnant female and one weanling died after having been observed as depressed for 1 day and 2 weeks respectively. One weanling and one adult male were euthanized. All affected hamsters had signs of diarrhea. At necropsy, hemorrhagic fluid-filled ceca were noted in five of eight animals. Clostridium difficile cytotoxin B was present in high titers [10(-3) to 10(-8)] in cecal contents of six of six animals tested, whereas C. difficile culture yielded positive results in only one of six animals. Histopathologically, findings consistent with Clostridium-induced typhlitis including necrosis, epithelial denudation, vascular congestion, and hemorrhage were present in six of six ceca evaluated. In addition, signs of a more chronic disease process included cecal mucosal hyperplasia in five of six hamsters. A silver stain of cecal hyperplastic mucosa for intracellular organisms including Campylobacter-like organisms was negative in all affected hamsters. Antibiotics had not been administrated to any hamster in this colony, nor had the affected animals been experimentally manipulated. Testing for antibiotic residues in the feed was negative, and C. difficile was not isolated from feed, water, or feces of unaffected hamsters. Thus C. difficile-induced typhlitis should be included in the differential diagnosis of deaths in hamsters which have no clinical histories of prior antibiotic administration or experimental manipulation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reproductive characteristics of a captive colony of big-eared climbing rats (Ototylomys phyllotis)

The authors analyzed the breeding characteristics of a colony of Ototylomys phyllotis (big-eared climbing rat) from Campeche, México, that was bred in captivity for 6 y. The big-eared climbing rat is a reservoir of Leishmania (Leishmania) mexicana, a causal agent of localized cutaneous leishmaniasis on the Yucatán Peninsula. The colony had been established to facilitate studies analyzing the effectiveness of O. phyllotis as an experimental model for L. (L.) mexicana. The authors describe the housing and husbandry of the colony, the procedures used for mating the animals and the behavior of the animals during mating. They report that the animals showed social behavior and could be bred successfully. Most breeding pairs successfully produced litters; some pairs produced more than one litter. The authors also report data for other parameters, such as the interval between pairing and birth or between births of consecutive litters, litter size, survival to weaning, the timing of sexual maturity and the effects of breeder age on breeding success.     

Identification of rhesus macaques with spontaneous endometriosis

Abstract: Rhesus macaques (Macaca mulatta) with endometriosis were identified using reproductive histories, serum levels CA-125, pelvic ultrasonography, laparoscopy, and histopathology. All animals were evaluated from a large breeding colony and had a history of infertility and/or spontaneous abortions. Laparoscopy and ultrasonography were performed on 40 macaques: 27 macaques from the breeding colony with elevated CA-125 levels, ten macaques from the breeding colony with normal or low serum CA-125 levels, and three macaques from another facility with previously diagnosed spontaneous endometriosis. Clinical endometriosis was diagnosed by laparoscopy in 16/37 (43%) macaques from the breeding colony and was confirmed by histologic examination in all animals biopsied. The disease was classified as minimal (40%), mild (25%), moderate (10%), or severe (25%). The most common sites of endometriosis were the serosal surface of the uterus (75%) and the posterior cul-de-sac (75%). In this study, CA-125 levels were useful in identifying animals from the breeding colony with endometriosis. The rhesus macaque provides a valuable animal model to study endometriosis and potentially to assess efficacy of therapeutic agents for this disease condition.     

Responses to damage in an arborescent bryozoan: Effects of injury location

A common consequence of the predation or physical disturbance of sessile modular animals is the removal of part of the colony. This damage is often sub-lethal, and leaves the remainder of the colony to repair and regenerate lost tissue. Damage may, however, have lasting effects on the life history characteristics of a colony. We examined the effects of damage on growth and reproduction in the arborescent bryozoan Bugula neritina (Linnaeus), with a particular focus on the effects of the location of that damage. We predicted that a damaged colony would initially allocate more energy to damage repair and subsequent growth, increasing in size to decrease the risk of mortality, at the expense of its short-term reproductive potential. A short-term experiment assessed the immediate regenerative capacities of colonies, while a longer-term experiment measured overall colony responses to damage at different colony locations. In this experiment, zooids were removed in three colony regions; all on one colony branch, spread evenly across all growing tips, and a third, intermediate pattern. A third experiment tested the effects of predator-induced damage versus damage alone, by measuring the recovery of colonies subjected to either a predation event by the nudibranch Polycera hedgpethi, or to an imitation predation event, where an equivalent section of the colony was removed manually. Regeneration was rapid, with budding resuming a few days after damage occurred. Removing around 20% of the colony did not consistently alter colony growth rates in any experiment, but the onset of reproduction was delayed by 7 to 20 days, and subsequent colony fecundity reduced by as much as 70% in one damage treatment. The removal of the same amount of tissue by nudibranch predators, or manually removed in a treatment that mimicked this predation, had no detrimental effect on the onset of reproduction or the eventual reproductive output. Nudibranchs removed tissue by consuming whole colony branches, and the experimental treatment that removed one branch also had the least effect of three damage treatments. These results suggest the severity of long-term effects depends on the location of the injury, and that B. neritina does not modify its growth or reproductive patterns to minimise these effects.     

The social structure and reproductive biology of the common mole-rat, Cryptomys h. hottentotus and remarks on the trends in reproduction and sociality in the family Bathyergidae

Cryptomys h. hottentotus occurs in mesic and semi-arid regions of South Africa. It lives in colonies ofup to 14 individuals, in which reproduction is limited to one ofthe largest males and the largest female in the colony.
Reproduction and details of colony size and the number of breeding animals in a colony are described for one complete and two incomplete field-captured colonies. One incomplete colony was kept in captivity for more than 3 years, whereas the complete colony was autopsied.
The social hierarchy of the common mole-rat is almost linear and has a value of 0.7 1 calculated from Landau's linearity index. Subordinate mole-rats weighed less than dominant mole-rats. The reproductive mole-rats are the dominant animals within the colony. The non-reproductive females rank lowest in the hierarchy.
Mating was not confined to a particular season, but occurred more frequently during the summer months. The alpha male initiated pre-copulatory behaviour. The gestation length is 55 to 66 days (n = 2). Two litters each of three pups were born to the colony during captivity. The pups were relatively altricial. They wandered out of the nest 5 days after birth, began to eat solids when 10 days old, and were fully weaned at 4 weeks. When 2 weeks old the pups began to spar with each other and with some of the adult colony members, but levels of aggression were never high. The pups did not disperse but were incorporated into the colony, this suggesting that C. h. hottentotus colonies are largely composed of related individuals.     

The colony structure and dominance hierarchy of the Damaraland mole-rat, Cryptomys damarensis (Rodentia: Bathyergidae), from Namibia

Cryptomys damarensis is one of the few subterranean rodents which is social. This species is found in the semi-arid regions of southwestern and central Africa. The Damaraland mole-rat occurs in coloniesof up to 25 individuals, in which reproduction is limited to one or two of the largest males and the largest female in the colony.
The mean colony size is 18 mole-rats ( n =6 colonies). The mean colony biomass is 2.32 kg and the sex ratio is female biased (0.71–0.78). The number of mole-rats in each colony, the mean body mass and the sex ratio are described for six field-captured colonies, three of which were captured in their entirety.
The dominance hierarchy of two colonies of C. damarensis was found to be linear with a value of between 0.94 and 1.00 calculated from Landau's linearity index. Dominance was found to be related to gender, with the males more dominant than females. The reproductive individuals are the dominant animals within each respective gender. The non-reproductive females rank lowest in the hierarchy.     

Newly identified Mycobacterium species in a Xenopus laevis colony

The University of Massachusetts Medical School maintains 3 separate research colonies of Xenopus laevis, with each colony located in a separate building on campus. After a 5-wk in-house quarantine period, 34 wild-caught X. laevis were transferred into one of the existing colonies. As a result, this colony grew from 51 to 85 frogs. All animals were housed in a recirculating frog housing system. During the first 2 mo, 6 frogs died suddenly, and health reports were generated for another 10 frogs in this colony. The majority of health reports were written in response to acute coelomic distention. These patterns continued until, after 1 y, only 25 of the original 85 animals remained. Necropsies performed showed large accumulations of serosanguinous fluid in the subcutaneous space or body cavity. Granulomatous inflammatory lesions with acid-fast bacilli were generally present in the liver, lung, or spleen. Culture of affected tissues grew Mycobacterium sp. within 40 d. Polymerase chain reaction analysis confirmed the isolated organism to be the same species of Mycobacterium (provisionally named M. liflandii) recently reported by 2 other groups. However, previous clinical publications suggested that this bacterium originated only from X. tropicalis. The cases we present highlight the rapidly lethal effects of M. liflandii in a colony of wild-caught X. laevis and illustrate the need to dedicate further attention to this emerging Xenopus disease.     

Attempted eradication of salmonellosis from a colony of short-tail grey opossums (Monodelphis domestica)

Prior to re-housing a colony of laboratory short-tail grey opossums, the animals were found to harbour salmonella. This paper describes an unsuccessful attempt to eradicate the infection from the colony by means of antibiotic treatment and hygienic measures. A pilot treatment of five animals which received enrofloxacin 10 mg/kg for 5 days appeared to be successful in that no salmonellae were recovered from faeces or organs sampled after treatment. The process was repeated on the whole colony prior to a change of accommodation but 2 animals were found to be still infected, 5 weeks after cessation of treatment.     

A technique for sustained synchronization of hamster estrous cycles by hormonal means

Rapid synchronization of hamster estrous cycles was achieved by administration of two subcutaneous injections of 7.5 μg of estradiol, given 24 hr apart, followed by one injection of 1 mg of progesterone/135 g body weight, given 20 hr after the last estradiol injection. Behavioral estrus occurred 4 hr after the injection of progesterone. Synchronized animals were mated during the second natural estrus following hormone treatment. Abnormal vaginal discharges were noted in most animals during the first few days after treatment, and, occasionally, a dissociation between behavioral and vaginal estrus was observed. However, by the second natural estrus after treatment, 69% of the colony demonstrated synchronized estrous cycles, both vaginally and behaviorally, and all abnormal discharges disappeared. The fertility rate was comparable to that in the colony from which the treated animals were taken, and the gestation period was normal, with an 8-hr range in onset of parturition. Offspring were normal in litter size, body weight, time of eye and vagina opening, sex ratio, and regularity of estrus. It was concluded that the technique is suitable for use by investigators interested in litter size and neonate development, in addition to those requiring time-mated or behaviorally synchronized animals. With the information gained from the experiment, a treatment schedule was devised which would produce 94% synchronization in a colony.     

Anticonvulsant drugs and the genetically epilepsy-prone rat

Anticonvulsant drugs were evaluated in members of two colonies of genetically epilepsy-prone rats (GEPR). Virtually all of the animals in the first colony experience a wild running fit that terminates in a generalized clonic convulsion when they are stimulated by sound. According to our convulsion intensity scoring system, these animals have an audiogenic response score (ARS) of 3 and the colony is designated the GEPR-3 colony. In the second colony, more than 95% of the animals experience a wild running phase terminating in a tonic extensor convulsion when they are stimulated by sound. That is, they have an ARS of 9 and the colony is designated the GEPR-9 colony. All of the established antiepileptic drugs that were tested produced anticonvulsant effects in the GEPR. Three tricyclic antidepressant agents acted as anticonvulsants in doses substantially lower than the toxic doses that produced spontaneous convulsions. Two of the established anticonvulsants, phenobarbital and ethosuximide, produced anticonvulsant effects in very similar doses in members of GEPR-3 and GEPR-9 colonies. Valproic acid produced an anticonvulsant effect in GEPR-3 in significantly lower doses than in GEPR-9. Carbamazepine, phenytoin, imipramine, amitriptyline, and desipramine produced anticonvulsant effects in essentially equimolar doses and in each case the protective dose was significantly lower in GEPR-9 than in GEPR-3 colonies. GEPR did not experience the convulsive effects of imipramine, amitriptyline, and desipramine at lower doses than did control animals. Thus, these epilepsy-prone animals are no more likely to experience convulsions in response to overdose of one of these three drugs than are nonepileptic subjects.     

Development of a Chinese-Indian hybrid (Chindian) rhesus macaque colony at the California National Primate Research Center by introgression

Background  Fullbred Chinese and Indian rhesus macaques represent genetically distinct populations. The California National Primate Research Center introduced Chinese founders into its Indian-derived rhesus colony in response to the 1978 Indian embargo on exportation of animals for research and the concern that loss of genetic variation in the closed colony would hamper research efforts. The resulting hybrid rhesus now number well over a thousand animals and represent a growing proportion of the animals in the colony.
Methods  We characterized the population genetic structure of the hybrid colony and compared it with that of their pure Indian and Chinese progenitors.
Results  The hybrid population contains higher genetic diversity and linkage disequilibrium than their full Indian progenitors and represents a resource with unique research applications.
Conclusions  The genetic diversity of the hybrids indicates that the strategy to introduce novel genes into the colony by hybridizing Chinese founders and their hybrid offspring with Indian-derived animals was successful.     

SNP‐based genetic characterization of the Tulane National Primate Research Center's conventional and specific pathogen‐free rhesus macaque (Macaca mulatta) populations

Background

The rhesus macaque is an important biomedical model organism, and the Tulane National Primate Research Center (TNPRC) has one of the largest rhesus macaque breeding colonies in the United States.

Methods

SNP profiles from 3266 rhesus macaques were used to examine the TNPRC colony genetic composition over time and across conventional or SPF animals of Chinese and Indian ancestry.

Results

Chinese origin animals were the least genetically diverse and the most inbred; however, since their derivation from their conventional forebearers, neither the Chinese nor the Indian SPF animals exhibit any significant loss of genetic diversity or differentiation.

Conclusions

The TNPRC colony managers have successfully minimized loss in genetic variation across generations. Although founder effects and bottlenecks among the Indian animals have been successfully curtailed, the Chinese subpopulation still show some influences from these events.     

The relative age structure and body masses of complete wild-captured colonies of two social mole-rats, the common mole-rat, Cryptomys hottentotus hottentotus and the Damaraland mole-rat, Cryptomys damarensis

The relative ages of individuals in a complete wild-captured colony of 13 Cryptomys hottentotus hottentotus and a complete wild-captured colony of 25 Cryptomys damarensis were determined by means of tooth wear and eruption patterns and through the degree of ossification of their skeletons.
From sequential tooth wear and eruption patterns four relative age classes were discerned in C. h. hottentotus and five in C. damarensis . These relative age class allocations were supported by the studies on the ossification of the skeletons.
In C. damarensis , older animals are not necessarily the larger-sized individuals. In C. h. hottentotus , however, older animals are usually the larger-sized individuals. The reproductive pair in each of the Cryptomys species are the oldest or amongst the oldest individuals in the colony.
Individuals in a second colony of C. damarensis kept under laboratory conditions for three years maintained greatly disparate body masses which were correlated with the role of the individual within the colony and not, where it was known, with the age of the animal.
An analysis of 13 body and skull measurements performed on a complete colony of 13 C. h. hottentotus and a complete colony of 25 C damarensis revealed that only C. damarensis showed sexual dimorphism. This dimorphism was apparent from an early age but became more pronounced in older animals.     

Susceptibility of tamarin (Saguinus labiatus) red blood cell membrane lipids to oxidative stress: implications for wasting marmoset syndrome

Captive Callitrichids frequently suffer a fatal wasting disease, wasting marmoset syndrome (WMS), of unexplained cause. This paper describes studies on the erythrocytes from animals in a breeding colony of tamarins (Saguinus labiatus), in which deaths from anaemia and wasting were occurring, to seek evidence for biochemical changes which could lead to oxidative damage and premature cell lysis. In only one animal of 33 studied did the red blood cell lipids show an increased susceptibility to oxidative damage. This animal, with some degree of certainty, could be diagnosed as having WMS. It was concluded that evidence for a primary deficiency of antioxidants as a cause of unexplained deaths, or WMS, in the colony could not at present be substantiated.     

Effect of the extracellular matrix molecules fibronectin and laminin on the adhesion and growth of primary renal cortical epithelial cells

Primary tubular epithelial cells were isolated from renal cortex following enzymatic dissociation with collagenase. These cells were then grown in chemically defined media containing insulin, transferrin, selenium, tri-iodothyronine and either fibronectin or laminin. The tubular epithelial cells were studied ultrastructurally and compared to another epithelial cell type present in the renal cortex, the glomerular epithelial cell. In contrast to the constant morphology of glomerular epithelial cells grown in chemically defined media, tubular epithelial cell morphology depended on whether the cells were placed in fibronectin or laminin and on the age of the donor animal used for culture. Primary tubular cells grown in laminin formed colonies; cells grown from young animals were rounded, whereas cells grown from adult animals were flattened. Primary tubular cells grown in fibronectin were flattened regardless of age, but cells from young animals formed colonies while those from adult animals formed a monolayer. Despite these differences in gross morphology, scanning and transmission electron microscopy revealed similar ultrastructural features in primary tubular cells from young and adult animals grown in fibronectin or laminin. Quantitative adhesion studies demonstrated that secondary subcultured tubular cells adhered equally well to dimeric and multimeric forms of fibronectin, but not to laminin. Quantitative colony growth studies of subcultured secondary tubular cells showed that laminin supports colony formation of trypsinized tubular cells, while previous work has demonstrated that fibronectin supports colony formation of glomerular cells. These results are consistent with the hypothesis that different extracellular matrix molecules are involved in colony formation of different cell types, with fibronectin stimulating growth of glomerular cells and laminin supporting growth of tubular cells.     

Phenotypic differences in reentrainment behavior and sensitivity to nighttime light pulses in siberian hamsters

Spontaneous reentrainment to phase shifts of the photocycle is a fundamental property of all circadian systems. Siberian hamsters are, however, unique in this regard because most fail to reentrain when the LD cycle (16-h light/day) is phase delayed by 5 h. In the present study, the authors compared reentrainment responses in hamsters from 2 colonies. One colony descended from animals trapped in the wild more than 30 years ago (designated "nonentrainers"), and the other colony was outbred as recently as 13 years ago (designated "entrainers"). As reported previously, only 10% of hamsters from the nonentrainer colony reentrained to a 5-h phase delay of the LD cycle. By contrast, 75% of animals from the entrainer colony reentrained to the phase shift. Another goal of this study was to test the hypothesis that failure to reentrain was a consequence of light exposure during the middle of the night on the day of the 5-h phase delay. This hypothesis was tested by exposing animals to 2 h of light during the early, middle, or late part of the night and then subjecting them on the next day to a 3-h phase delay of the photocycle, which is a phase shift to which all hamsters normally reentrain. All animals from both colonies reentrained when light pulses occurred early in the night, but more animals from the entrainer colony, compared to the nonentrainer colony, reentrained when the light pulse occurred in the middle or late part of the night. The phenotypic variation in reentrainment responses is similar to the variation in photoperiodic responsiveness previously reported for these 2 colonies. Phenotypic variation in both traits is due to underlying differences in circadian organization and suggests a common genetic basis for reentrainment responses and photoperiodic responsiveness.