Objective: We evaluated the efficacy of intranasal administration of Pasteurella multocida toxin (PMT) and a potassium thiocyanate extract of P. multocida (CN) encapsulated in alginate microspheres, compared with unencapsulated PMT and CN antigens, in protection
of rabbits against pasteurellosis. Methods: New Zealand male rabbits (n=24) were allotted randomly into four intranasally administered vaccine groups: 1, PMT/CN; 2, microencapsulated PMT/CN with or; 3, without subcutaneous priming; and 4, empty microspheres (control). Blood samples
and nasal wash specimens were collected before vaccination and one week after each vaccination (days 7, 21, 35, and 49). Rabbits were primed subcutaneously with either unencapsulated PMT/CN or aluminum hydroxide (control) (day 0), vaccinated intranasally (days 14, 28, and 42), challenged intranasally
with live P. multocida (day 56), and necropsied (day 60). Results: Compared with controls, PMT/CN-immunized rabbits had significantly higher concentrations of serum IgG and IgM, nasal IgG, and bronchoalveolar lavage fluid IgA and IgG against CN. Immunized rabbits had 100%
survival rate and low numbers of bacteria in liver and lungs; the control group had 50% survival rate and higher numbers of bacteria (> 4x) per gram of tissue in liver and lungs. Conclusion: The PMT/CN microspheres stimulated systemic and mucosal immune responses similar in effectiveness
(protection) to those in response to unencapsulated PMT/CN administration.
Background and Purpose: Cryptosporidium parvum establishes a parasitic relationship with epithelial cells of the intestine. Infection with this protozoan is resolved in the immunocompetent host, but persistent life-threatening infection develops in the immunocompromised
host. We propose that γδ T Cells in the intestinal mucosa play a role in immunity to C. parvum. Methods: Intestinal intra-epithelial lymphocyte and lamina propria T-cell subsets were examined in mice infected with C.parvum. The mice are homozygous for a
deletion of the TCR chain gene, TCR (-/-) and, therefore, lack conventional γδ T Cells, but retain a population of γδ T Cells with T-cell receptors. To examine the contribution of γδ T Cells to immunity, these mice were treated with monoclonal antibody GL3-3A,
specific for this T-cell receptor, then were inoculated with C.parvum oocysts. Lymphocyte subsets and hematoxylin and eosin (H&E)-stained intestinal sections from untreated mice were compared with those from mice treated with either a low dose of GL3-3A for 6 weeks, or a high dose
of GL3-3A for 16 weeks. Results: The proportion of γδ T Cells in the lamina propria increased in infected mice. In mice treated with a low dose of GL3-3A, a population of γδ T Cells that had characteristics of activated cells, was still evident 6 weeks after
inoculation. No C.parvum developmental forms were identified in the intestinal sections of mice under these conditions. However, TCR (-/-) mice treated with a high dose of GL3-3A were depleted of γδ T Cells, and 50% of the mice were infected with C.parvum. Conclusions:
The γδ T Cells contribute to protection against C.parvum infection. In the absence of conventional γδ T Cells, activation of intestinal γδ T Cells may prevent infection with this organism.
Background and Purpose: The objectives of the study reported here were to determine whether a change in the plasma arginine vasopressin (AVP) concentration occurred in lactating, compared with non-lactating rats and to examine the involvement of suckling with plasma AVP concentration.
Methods: Experiments were performed on 86 female Wister Imamichi rats, 12 weeks old at parturition, with fast lactation. On day 13 of lactation, AVP concentration and plasma osmotic pressure were measured in lactating and non-lactating rats. Results: Plasma AVP concentration
was always higher in rats of the lactating groups than in non-lactating controls (1.06 0.28 pg/ml), and a conspicuous increase in AVP concentration was seen during the postsuckling period (1.70 0.61 pg/ml before vs. 2.56 1.31 pg/ml after suckling, P < 0.05). Plasma osmotic pressure in lactating
rats with 12 pups (296.6 5.2 mOsmol/kg. H2O) was lower than that in rats of the removed control groups (306.7 5.7 mOsmol/kg. H2O). Conclusion: On the basis of these results, it appears that “low plasma osmotic pressure-high AVP status” develops
in the lactating period, similar to pregnancy, through resetting of the regulatory mechanism of the AVP system. It was concluded that suckling stimulation could release AVP, which could dilute the blood with water resulting in the increase in circulating blood volume.
Background and Purpose: To define the effects of three commonly used anesthetic agents — sodium pentobarbital given intraperitoneally, and inhaled halothane and methoxyflurane — on the pathogenesis of pneumococcal pneumonia and bacteremia in an experimental murine
model. Methods: Swiss outbred mice were anesthetized with either sodium pentobarbital, halothane, or methoxyflurane before intranasal infection with Streptococcus pneumonia. At defined times after infection, bacterial numbers in lungs and blood, markers of acute lung injury,
and lung cytokine levels were compared. Results: Mice anesthetized with inhaled halothane or methoxyflurane prior to intranasal inoculation with type-2 Streptococcus pneumoniae developed pneumonia and bacteremia distinctly different from that in mice anesthetized by intraperitoneal
(IP) administration of sodium pentobarbital. Mice having brief exposure to inhaled halothane or methoxyflurane had significantly greater numbers of bacteria in lungs and blood 48 hours after inoculation, compared with mice anesthetized by IP administration of pentobarbital. Also, mice inhaling
halothane had significantly decreased activities of pro-inflammatory cytokines interleukin 6 and tumor necrosis factor- in lung homogenates at 24 hours after inoculation, compared with those given pentobarbital IP. Conclusion: Effects of anesthesia on murine models of pneumonia
should be considered in the design and interpretation of studies of pneumococcal pathogenesis.
Background and Purpose: Our objective was to map the genes responsible for poor glucose tolerance in a C57BL/6 (B6) mouse model, which provides a human model of non-insulin-dependent diabetes mellitus. Insulin secretion was found to be significantly lower in B6 than in C3H/He
(C3H) mice (analysis of variance, P < 0.05) at 10, 20, and 30 minutes during the intraperitoneal glucose tolerance test (IPGTT: 1.5 g glucose/kg of body weight). Methods: Mean 30-minute blood glucose values during IPGTT at 8, 9, and 10 weeks of age were used as a surrogate
for glucose tolerance. The primers of 87 genetic microsatellite markers (14.9 6.2 cM apart) genome-wide quantitative trait linkage (QTL) analysis in F2 and F3 mice with the highest and lowest (n = 15 for each extreme) 30-minute blood glucose values were used. Results: Genome-wide
QTL analysis confirmed the locus (D2Mit48) on chromosome 2, with a LOD score of 8.3, and the locus (D13Mit48) on chromosome 13, with a LOD score of 4.2 in F3. Direct sequencing of candidate genes, proprotein convertase-2 (PC2) on chromosome 2 and proprotein convertase-1/3 (PC1/PC3)
on chromosome 13, failed to reveal a mutation or polymorphism specific to B6 mice. Conclusions: Use of QTL mapping revealed two loci associated with poor glucose tolerance of B6.
Background and Purpose: Cardiac and arterial responses to prescribed doses of propofol and etomidate in rhesus monkeys were compared. Methods: Intravenously administered induction doses of propofol (2 mg/kg of body weight) or etomidate (1 mg/kg) followed by continuous
intravenous infusions of propofol (200 μg/kg/min) or etomidate (100 μg/kg/min) were administered. Left ventricular and right atrial access catheters were implanted for long-term use, along with a transittime flow probe on the ascending aorta, and pericardial electrocardiogram leads.
A dual sensor 3-F micromanometer was used to measure left ventricular pressure and aortic pressure, and an active redirectional transit-time probe measured aortic flow. Noordergraaf 's four-element model was used to estimate total peripheral resistance and systemic arterial compliance.
Results: Significant (P < 0.01) decreases in mean arterial pressure, heart rate, and myocardial contractility were accompanied by an increase in systemic arterial compliance associated with propofol and etomidate. Only minimal changes in left ventricular diastolic pressure,
cardiac output, stroke volume, and total peripheral resistance were found for both drugs. The changes associated with propofol are comparable to results in human beings, whereas the changes associated with etomidate did not agree with results of published human studies. Conclusion:
The significant cardiovascular alterations associated with both agents were attributed to reductions in heart rate, although the possibility exists that negative inotropic effects may have had a role.
Background and Purpose: Because of their similarity to humans, rabbits are a good animal model for the study of atherosclerosis associated with high serum low-density lipoprotein (LDL) values. Two assays were developed to measure apolipoprotein B (apoB), the major structural
and functional apolipoprotein of LDL in rabbits and to distinguish endogenous LDL in transgenic rabbits from that of human apoB. Methods: Two procedures, an electroimmunoassay (EIA) and an immunonephelometric assay (INA), along with a goat-origin rabbit antiserum were developed
to measure serum apoB concentration in rabbits. Results: Use of either assay resulted in ability to measure rabbit species-specific apoB concentration. Conclusion: These assays should have broad applications: to screen compounds or diets that might lower serum apoB concentrations;
to specifically measure human apoB concentration in transgenic rabbits; to measure serum apoB concentration in rabbits overexpressing other human proteins.
Background and Purpose: In an attempt to find a rapid and reproducible method for routine polymerase chain reaction genotyping of transgenic mice, two novel approaches were developed. Methods: One approach allowed reproducible amplification from crude lysates of tail
snips, using a thermally activated polymerase. In a second approach, for situations in which non-invasive techniques are necessary, oral swab specimens were amplified after DNA extraction by use of an isolation kit. Samples from 10 transgenic factor VIII knockout mice were genotyped after
processing by use of these and other methods. Results: False-negative results were not obtained by use of the two novel approaches. Despite their relative simplicity, both approaches yielded results comparable to those obtained by use of procedures known to be reliable, such as
organic extraction and a DNA extraction kit. Conclusion: Both approaches are useful for PCR-amplification of DNA from mammalian sources.
Background and Purpose: The National Institutes of Health's (NIH) National Center for Research Resources' (NCRR) Division of Comparative Medicine has funded the establishment of specific pathogen-free (SPF) captive macaque colonies. Herpes B-virus (Herpesvirus simiae,
Cercopithecine herpesvirus type 1) has been targeted for elimination. Late seroconversion presents the greatest threat to the integrity of SPF colonies. The purpose of the study reported here was to evaluate that threat through detailed investigation of the patterns of seroreactivity and
housing histories in one colony. Methods: From 1990 through 1997, the B-virus Resource Laboratory screened macaques for B-virus, using ELISA or western immunoblot analysis. In 1993, we combined test results and housing histories to verify the seronegative status of one colony.
Results: Two groups of latently infected macaques were identified as to time and place of transmission. The infection was eradicated within 3 years (1990–1992), as judged by the absence of true positive seroreactivity in any screened macaques. New infections were not identified
in four years of follow-up evaluation. Conclusion: With rigorous surveillance, the SPF status of the colony was achieved and maintained.
Background and Purpose: Two of nine female opossums (Didelphis virginiana) in a closed breeding colony were submitted for necropsy due to a history of poor reproductive performance in the absence of overt clinical disease. On histologic examination, marked granulomatous
to pyogranulomatous pneumonia was identified in these animals. Methods: Lung sections were stained with periodic acid-Schiff and Gomori's methenamine silver nitrate. Results: Pulmonary lesions were characterized by large numbers of foamy macrophages within the alveoli
and interstitium, prominent subpleural and peribronchiolar aggregates of histiocytes, and a few scattered lymphoid nodules. Numerous fungal organisms were evident within the cytoplasm of macrophages on impregnation of histologic sections with the aforementioned stains. Other inciting agents
were not identified. A third opossum lacked pulmonary lesions, but had similar organisms within one auricular sebaceous gland/hair follicle without apparent reaction to the organisms. Conclusion: A fungal agent was associated with granulomatous pneumonia in the opossum, and comparison
was made with endogenous lipid pneumonia previously described in opossums. These findings stress the importance of use of special stains and additional diagnostic techniques when prominent alveolar macrophage accumulation is present on histologic examination of the opossum lung.