To predict when food reward was available, 12 New Zealand White rabbits were trained to discriminate between two humans. All subjects had significantly higher response rates and greater behavioral arousal in the presence of the positive stimulus person. The ability to discriminate between individual humans sets the stage for unanticipated Pavlovian conditioning, which may have considerable implications for animal research in behavioral and biomedical settings.

A nonhuman primate model comprising adult male rhesus monkeys (Macaca mulatta) with chronically indwelling subcutaneous central venous access devices provides a unique opportunity to determine plasma pharmacokinetics of new drugs such as anticancer and anti-retroviral agents. The central venous access we use is a low-profile, single-septum, titanium port that is attached to a radiopaque, indwelling catheter; the catheter is implanted in an internal jugular vein. A common complication following placement of the venous access device was migration of the catheter tip. We therefore modified the standard procedure by cutting the silicone catheter and introducing the rigid connector to secure the catheter to the vessel at the insertion site (approximately 9 to 13 cm from the distal end of the catheter). Prior to the use of the connector, three of five catheters migrated within 4 weeks after placement. In contrast, all 13 internal jugular catheters with connectors have remained patent without migration of the catheter tip. Therefore, incorporation of the catheter connector appears to have eliminated the problem of catheter migration.

Insulin resistance was evaluated in South American camelids, llamas and alpacas, by use of the minimal model test and the insulin tolerance test. Animals were catheterized for long-term studies and tamed to minimize stress during evaluation. Results indicated a low insulin sensitivity index (S_I) = 0 to 0.97, median = 0.39 x ^10-4 min/uIU x ml, about a fifth the value in other mammals and humans. The K_ITTwas between 1.43 and 3.19 %/min, also significantly lower than that reported for humans. Glycosylated hemoglobin concentration was 6%, and Hb_A1cconcentration was 5.5%; red blood cell lifetime, as measured by use of the ⁵¹Cr method, was 120 days, similar to the value in humans. We concluded that llamas and alpacas have naturally higher blood glucose concentration than do humans and other mammals during the glucose tolerance test. Using the same mathematical tools to evaluate glucose metabolism as those used in people, South American camelids appear to be resistant to insulin. Thus, the South American camelid may be a useful new animal model for the study of sugar metabolism and various facets of diabetes mellitus, especially protection from the deleterious effects of glycosylation.

A phenomenon of leukocytosis induced by hypervolemic stress was discovered. Although a single injection of 350 μl of saline (equivalent to approx. 70 ml in humans, 1 ml/kg of body weight) did not have an effect on the leukocyte counts in long-term intravenously cannulated, freely behaving rats, a single injection of 750 μl of saline (equivalent to approx. 150 ml in humans, 2.1 ml/kg) induced rapid leukocytosis of 160% within 1 minute followed by a gradual increase up to 180% after 1 hour. Measurement of serum norepinephrine concentration revealed a significant increase in rats of the hypervolemic group, compared with those of the low volume group. Pretreatment with either the β-adrenoceptor antagonist nadolol or the selective _α2-adrenoceptor antagonist yohimbine prevented both leukocyte peaks in the high volume group, suggesting a combined receptor activation. This critical dependence of leukocyte counts on changes in blood volume should be taken into consideration in experiments with laboratory animals (the quantity of volume applications can falsify results of experiments).

Background and Purpose: Detection of mouse parvovirus 1 (MPV) depends on use of serologic and polymerase chain reaction (PCR) assays. These assays were evaluated for their ability to detect virus-specific antibodies or viral DNA in multiple strains and ages of mice inoculated with MPV. Methods: Twelve-week-old ICR, BALB/c, C3H, C57BL/6, and DBA/2 mice and four- and eight-week-old ICR mice were inoculated with MPV. Serum was harvested four weeks after inoculation and analyzed by use of recombinant non structural protein 1 (rNS1) enzyme-linked immunosorbent assay (ELISA), minute virus of mice (MVM) ELISA, and MPV indirect fluorescent antibody (IFA), MVM IFA, and MPV hemagglutination inhibition (HAI) assays. Select tissues were harvested and analyzed by use of an MPV-specific PCR assay. Results: The number of mice in each group with detectable MPV-specific antibodies or MPV DNA varied with mouse strain, mouse age when inoculated, and viral dose. Seroconversion in mice inoculated at 12 weeks of age was detected almost exclusively by use of the MPV IFA and MPV HAI assays, whereas seroconversion in almost all mice inoculated at 4 and 8 weeks of age was detected by use of all immunoassays except the MVM ELISA. Viral DNA was detected by use of PCR analysis in all strains and ages of mice except DBA/2 mice. Conclusions: Mouse strain and age have important roles in seroconversion to nonstructural and structural MPV antigens and persistence of viral DNA in mouse tissues. Therefore, diagnostic serologic testing and PCR analysis should be considered within the context of mouse strain and age at the time of MPV exposure, especially when sentinel mice are used for surveillance.

Background and purpose: Spontaneous animal mutants affected by abnormal formation of myelin in the central nervous system (CNS) are useful in studies on myelinogenesis and remyelination leading to better understanding of cellular and molecular interactions involved in myelin repair. A novel rat mutant, Bouncer Long Evans (LE-bo) is severely dysmyelinated, but with exceptional longevity, and its clinical and pathologic phenotype are described. Methods: Clinical observations, genetic studies, and determination of longevity were performed in a colony of rats, including carriers of LE-bo phenotype producing the mutant animals. Comprehensive histologic studies were performed on all perfusion-fixed tissues, and ultrastructural examination of the optic nerve and thoracic part of the spinal cord also was done in rats 1 to 14 weeks old. Results: The LE-bo phenotype is characterized by whole body tremor, progressively severe ataxia, and severe seizure activity. The LE-bo phenotype is transferred as an autosomal recessive trait and is stable. The LE-bo rat can survive in good health beyond 45 weeks. Neuropathologic changes include severe global dysmyelination, with thin uncompacted myelin sheaths in young rats forming no major dense line, whereas the myelin sheaths of the peripheral nervous system appear normal. Oligodendrocytes degenerate with apparently progressing accumulation of membranous material in the perikaryon. Large numbers of immature glial cells were detected in the CNS of LE-bo rats at 4 to 14 weeks. Conclusion: The LE-bo rat is severely dysmyelinated due to inability of its oligodendrocytes to form myelin sheaths. Similarities of the LE-bo rat and Long Evans Shaker (les) rat neuropathologic features, such as severe dysmyelination, lack of major dense line in uncompacted myelin sheaths, apparent proliferation of oligodendroglial cells, and considerable longevity, are striking and suggest that a LE-bo mutation may functionally affect the myelin basic protein gene.

Mice lacking the NHE2 Na + /H + gene develop gastritis of the glandular mucosa as early as the tenth day of life, achieving maximal intensity of inflammation from 17 to 19 days after birth and maximal atrophy at one year. We assessed the effects of this process in such mice to 16 months of age. The stomach of NHE2 null mutants was examined at 10, 17 to 20, 24 to 35 and 49 to 70 days, and at 12 to 16 months. The NHE2 wild-type (+/+) and NHE2 heterozygous (+/-) mice were compared with the NHE2 homozygous mutant mice (-/-). The stomach of the mutant mice at all ages was characterized by a substantially reduced number of parietal cells. The 10-day-old mouse stomach had a transmural infiltrate of primarily neutrophils. With increasing age, neutrophils were replaced by lymphocytes and plasma cells in the glandular mucosa of the mutant mice. Young adult 49- to 70-day-old mice had surface cell hyperplasia and expansion of the replicating cell population. Hyperplasia of enterochromaffin-like cells and antral gastrin cells accompanied profound fundic gland and surface cell hyperplasia, and became progressively more severe with increasing age of the NHE2-/- mice. Neoplasms were not found in the mutant or control mice. This gastritis differs from that of autoimmune gastritis in that it is transmural, begins in infancy, and is associated with a predominantly neutrophilic infiltrate in its early stages. Some of the histologic changes in the adult mice can be explained on the basis of prolonged achlorhydria. This mouse may be a suitable model for prolonged effects of achlorhydria.

Background and Purpose: The effects of pristane inoculation, ascites accumulation, peritoneocentesis, and analgesics on the well-being of mice used in monoclonal antibody (MAb) production protocols were investigated. Methods: Four experiments, each containing 17 to 21, 6- to 8-week-old male Balb/c mice, were conducted. Each experiment involved a period in which baseline data were collected, followed by intraperitoneal injections of pristane or phosphate-buffered saline (PBS) inoculations into each mouse. One week later mice received intraperitoneal inoculations of either hybridoma cells or PBS. Parameters used to assess well-being throughout each of these periods included: wheel-running activity, food and water consumption, open-field box activity, clinical observation, and plasma corticosterone concentration. Results: Compared to controls, pristane inoculation had slight to no affect on mice. There was no evidence of distress in cell-inoculated mice prior to their gaining 25% of their baseline body weight. The number of times (up to three) that peritoneocentesis was performed did not have a significant impact on mice's well-being, but ascites yields were greater when multiple harvests were performed. Cell-inoculated mice that gained weight slowly or developed high-particulate ascites were at higher risk of being distressed. Conclusion: Ascites yields can be maximized by performing multiple harvests; however, the well-being of mice used in such protocols should be closely monitored, as suggested here.

Most animal models used to study the process of postnatal craniofacial growth require direct manipulation of the craniofacial area, a growth period, then evaluation of the area. However, the scar tissue associated with direct manipulation of the craniofacial structures can produce growth abnormalities that are unrelated to the manipulation itself. To avoid this confounding variable in the study of craniofacial growth, we developed an animal model that involves laryngotracheal separation in a young animal. Our procedure completely separates the trachea from the upper aerodigestive tract and removes the site of scar tissue formation from the region of investigation. The tracheal stomas of the goats we describe were maintained for as long as 9 months. Unlike human patients, goats with laryngotracheal separation require laryngectomy tubes to prevent life-threatening stenosis of the tracheal stoma. Here we describe the operative procedure and post-operative care required for this new animal model.

To determine the prevalence of colonization by Corynebacterium ulcerans, we cultured samples from the cephalic implant-skin margin and pharynx of 26 rhesus macaques and one pig-tailed macaque. All but one of the samples from the cephalic implants yielded a mixed population of bacteria. C. ulcerans grew from the cephalic implants in 56% and from the pharynx in 3% of the implanted animals. We screened nine of these isolates for diphtheria toxin (DT) and phospholipase D (PLD). Polymerase chain reactions (PCR) failed to identify DT in any of the tested isolates, which also lacked DT activity in Elek tests. However, all nine isolates tested had PLD toxin activity as determined by conjoint hemolysis on sheep blood agar plates in the presence of equi factor (Rhodococcus equi). In addition, PCR assays and Southern blot hybridization confirmed the presence of pld in the isolates. The role of the PLD toxin in promoting colonization of cephalic implants by C. ulcerans is unknown. We found C. ulcerans to be a frequent contaminant of the cephalic implant-skin margin. Further studies are necessary to investigate the relative clinical importance of this organism and the efficacy of various implant maintenance protocols in preventing infection.

Ringtail is a pathologic condition of the tail of rats and other rodents that is traditionally attributed to low environmental humidity, although dietary deficiencies, genetic susceptibility, environmental temperature, and degree of hydration of the animal also have been suggested as possible causes. To the authors' knowledge, a detailed histopathologic study that may serve to shed light on the etiopathogenesis of this disease has not yet been published. We describe the histologic findings of ringtail observed in 12 suckling Munich Wistar Fromter (MWF) rats from two litters. Epidermal hyperplasia characterized by orthokeratotic and parakeratotic hyperkeratosis and acanthosis was observed in all affected rats. Numerous often dilated vessels were present in the dermis of tails that appeared of red/brown color at gross examination. In severe cases, the dilated vascular structures were thrombotic and accompanied by dermal hemorrhages and focal coagulative necrosis of the overlying epidermis. These findings suggest that epidermal acanthosis and hyperkeratosis are the main and primary events in the development of ringtail. To clarify the cause of this disease, future studies should be focused on the numerous factors that can induce such epidermal changes.

Background and Purpose: Intestinal adenocarcinoma appears to be the most common malignant neoplasm in macaques, and is a substantial cause of morbidity and mortality in the elderly. Methods: A retrospective review of 32 cases was done. Results: Thirty-two cases were reviewed. Clinical examination had revealed severe weight loss, anorexia, and palpable abdominal mass. Microcytic hypochromic anemia, intermittent fecal occult blood positive test results, hypoproteinemia, and hypoalbuminemia were the predominant clinical laboratory findings. Carcinoembryogenic antigen serologic testing and single-strand conformational polymorphism analysis were performed in selected cases. The most common sites of the intestinal adenocarcinoma were ileocecal junction, colon, ileum, jejunum, and cecum. Metastases were evident in 34% of the cases and involved peripheral nodes, liver, lungs, pancreas, and adrenal gland. Overall survival of 12 macaques that underwent surgical excision was 83% at 6 months, 58% at 1 year, 50% at 1.5 years, 33% at 2 years, and 8% at 4 years. The overall mean survival rate (MSR) was > 483 postoperative days. Conclusion: Intestinal adenocarcinomas should be amenable to surgical resection. Early detection of localized, non-invasive neoplasms will increase surgical cure rate. Survivability could be potentially improved by use of adjuvant therapies.

Potassium chloride (KCl: 330 mg/ml) was assessed as an euthanasia agent in American lobsters (Homarus americanus). Two groups of 10 lobsters (408.2 to 849.9 g) were maintained at 11.9 to 12.1 °C ('warm') and 1.5 to 2.5 °C ('cold') to evaluate the possible effect of ambient temperature on response to KCl. Death was defined as time of cardiac arrest, as viewed and measured by use of ultrasound. The KCl solution was injected (100 mg of KCl/100 g of body weight) at the base of the second walking leg to flood the hemolymph sinus containing the ventral nerve cord with potassium. Disruption of this 'central nervous system' was immediate, followed by cardiac arrest within 60 to 90 seconds. Group median (± SD) baseline heart rate was 42 ± 14 _'warm' and 36 ± 5 _'cold' beats per minute. Time until cardiac arrest ranged from 35 to 90 (57 ± 18) seconds in the 'warm' group and from 40 to 132 (53 ± 34) seconds in the 'cold' group. There was no significant difference between group medians for either parameter. Histologic lesions were limited to mild to moderate acute degeneration, characterized by cell swelling, loss of contraction bands, and occasional mild cytoplasmic vacuolation of skeletal muscle at the injection site. Injectable KCl solution was an effective, reliable method for euthanasia of H. americanus.

Purpose: To obtain large, serial biopsy samples from the liver and spleen by using laparoscopy. Large samples were needed for measurement of inflammatory mediators during various stages of schistosomiasis. Methods: Each of the seven female baboons (Papio sp.) underwent as many as three laparoscopies, for a total of 19 laparoscopic procedures. This process permitted sampling of the liver, spleen, and mesenteric lymph nodes before and at 6 and 9 weeks after infection with Schistosoma mansoni. All surgery was performed through three trocar sites. Postoperative care included preemptive analgesia. After surgery, we monitored the animals' appetite and measured the core body temperature and activity by using implanted radiofrequency transmitters. Results: We obtained samples of the liver and splenic biopsies during all 19 laparoscopic procedures. The mean weight of the liver biopsies was 3.7 g and that of the spleen samples was 5.3 g. We encountered small adhesions during 5 of the 12 reoperations. Eating and activity rapidly returned after surgery. Conclusions: Laparoscopy permitted collection of large, serial biopsies with apparently limited stress to the animals. Laparoscopy can be used for biopsies in studies to characterize disease response, confirm normal organ histology prior to drug toxicity studies, determine target-organ drug concentrations in pharmacokinetic studies, and measure drug residues. This refinement likely will reduce required animal numbers by decreasing the effect of surgery compared to that of the experimental conditions, enhance animal well-being, and permit repeated measurements in an animal that serves as its own control.

A three-year old male cynomolgus macaque (Macaca fascicularis) presented with clinical signs of anorexia and depression that decreased over a 48-hour period. Results of abdominal radiography abdominocente- sis, blood biochemical analysis and CBC suggested septic peritonitis. Exploratory laparotomy revealed multiple perforations along the mesenteric border of the small intestine. Necropsy revealed masses of fibrous material in the stomach and cecum. Multiple mucosal ulcerations, as well as linear fibrous material, were found in the small intestine. The ulceration, perforations, and septic peritonitis were attributed to the ingestion of rope that had been attached to the animal's cage as an environmental-enrichment device.