Vibrio cholerae intestinal population dynamics in the suckling mouse model of infection.
(17/1173)
The suckling mouse has been used as a model to identify Vibrio cholerae intestinal colonization factors for over two decades, yet little is known about the location of recoverable organisms along the gastrointestinal (GI) tract following intragastric inoculation. In the present study, we determined the population dynamics of wild-type and avirulent mutant derivatives of both classical and El Tor biotype strains throughout the entire suckling mouse GI tract at various times after intragastric inoculation. Wild-type strains preferentially colonized the middle small bowel with a sharp demarcation between more proximal segments which had manyfold-fewer recoverable cells. Surprisingly, large and stable populations of viable cells were also recovered from the cecum and large bowel. Strains lacking toxin-coregulated pili (TCP(-)) were cleared from the small bowel; however, an El Tor TCP(-) strain colonized the cecum and large bowel almost as well as the wild-type strain. Strains lacking lipopolysaccharide O antigen (OA(-)) were efficiently cleared from the small bowel at early times but then showed net growth for the remainder of the infections. Moreover, large populations of the OA(-) strains were maintained in the large bowel. These results show that for the El Tor biotype neither TCP nor OA is required for colonization of the suckling mouse large bowel. Finally, similar percent recoveries of wild-type, TCP(-), and OA(-) strains from the small bowel at an early time after infection suggest that TCP and OA are not required for strains of either biotype to resist bactericidal mechanisms in the suckling mouse GI tract. (+info)
Stearoyl-coenzyme A desaturase gene expression during growth in adipose tissue from obese and crossbred pigs.
(18/1173)
This investigation addressed the hypothesis that, as a marker of adipocyte differentiation, stearoyl-coenzyme A desaturase (SCD) gene expression would be greater during growth in obese pigs than in crossbred, contemporary pigs. Suckled pigs from a single litter were removed from the sow for sampling at 0, 3, 10, and 17 d. The number of litters at 0, 3, 10, and 17 d of age was zero, two, three, and three (obese sows) and four, two, three, and three (crossbred sows), respectively. Postweaning pigs were removed from the sow at 14 d of age. One set of postweaning pigs was fed a high-fat, milk-based diet from d 28 to 49; pigs were killed on d 28 and 49 for sampling. The grain-fed pigs were switched to a pelleted, grain-based grower diet at d 28, and samples were obtained at 31, 35, or 49 d of age. Adipose tissue from all pigs in a litter for preweaning and postweaning pigs was pooled for the measurement of cellularity and SCD mRNA. There were significant genetic and age effects for adipocyte diameter and volume; overall, adipocytes from obese pigs were larger than those from crossbred pigs. Stearoyl-coenzyme A desaturase mRNA was barely detectable at 0 d of age and increased (P < .01) by 20-fold by 49 d of age. There was a significant genetic x age interaction (P = .026); there was more SCD mRNA in adipose tissue from obese pigs than in that from crossbred pigs during the suckling period, whereas crossbred pigs exhibited greater SCD gene expression than obese pigs during the postweaning period. The lesser SCD gene expression in postweaning obese pigs was caused by a strong depression in SCD gene expression in the grain-fed obese pigs. The data indicate that SCD gene expression provides a marker for terminal differentiation, especially in preweaning pigs. Furthermore, these results provide additional evidence that SCD gene expression is up-regulated by diets high in saturated fatty acids. (+info)
Follicular, hormonal, and pregnancy responses of early postpartum suckled beef cows to GnRH, norgestomet, and prostaglandin F2alpha.
(19/1173)
Cycling (n = 16) and noncycling (n = 24), early postpartum, suckled beef cows of three breeds were assigned randomly to three treatments: 1) 100-microg injection of GnRH plus a 6-mg implant of norgestomet administered on d -7 before 25 mg of PGF2alpha and implant removal on d 0 (GnRH+NORG); 2) 100 microg of GnRH given on d -7 followed by 25 mg of PGF2alpha on d 0 (GnRH); or 3) 2 mL of saline plus a 6-mg implant of norgestomet administered on d -7 followed by 25 mg of PGF2, and implant removal on d 0 (NORG). All cows were given 100 microg of GnRH on d +2 (48 h after PGF2alpha). Blood sera collected daily from d -7 to d +4 were analyzed for progesterone and estradiol-17beta, and ovaries were monitored daily by transrectal ultrasonography to assess changes in ovarian structures. Luteal structures were induced in 75% of noncycling cows in both treatments after GnRH, resulting in elevated (P < .01) progesterone on d 0 for GnRH+NORG-treated cows. Concentrations of estradiol-17beta (P < .01) and LH (P < .05) were greater on d +2 after GnRH for cows previously receiving norgestomet implants. Pregnancy rates after one fixed-time AI at 16 h after GnRH (d +2) were greater (P < .05) in GnRH+NORG (71%) than in GnRH (31%) and NORG (15%) cows. Difference in pregnancy rate was due partly to normal luteal activity after AI in over 87% of GnRH+NORG cows and no incidence of short luteal phases. The GnRH+NORG treatment initially induced ovulation or turnover of the largest follicle, induction of a new follicular wave, followed later by increased concentrations of estradiol-17beta and progesterone. After PGF2alpha, greater GnRH-induced release of LH occurred in GnRH+NORG cows before ovulation, and pregnancy rates were greater after a fixed-time AI. (+info)
Ethological analysis of mother-pup interactions and other behavioral reactions in rats: effects of malnutrition and tactile stimulation of the pups.
(20/1173)
Mother-pup interaction, as well as other behavioral reactions were studied during the lactation period in 24 litters of Wistar rats and their dams fed either a 16% (control - C; 12 litters) or a 6% (malnourished - M; 12 litters) protein diet. The diets were isocaloric. Throughout lactation there was a 36.4% weight loss of M dams and a 63% body weight deficit in the M pups when compared to control pups. During this period, half of the litters were exposed daily to additional tactile stimulation (CS or MS), while the other half were submitted to normal rearing conditions (CN or MN). The tactile stimulation of pups (handling) consisted of holding the animal in one hand and gently touching the dorsal part of the animal's body with the fingers for 3 min. A special camera and a time-lapse video were used to record litter behavior in their home cages. Starting at 6 p.m. and ending at 6 a.m., on days 3, 6, 12, 15, 18 and 21 of lactation, photos were taken at 4-s intervals. An increase in the frequency (154.88 +/- 16.19) and duration (455.86 +/- 18.05 min) of suckling was observed throughout the lactation period in all groups compared to birth day (frequency 24.88 +/- 2.37 and duration 376.76 +/- 21.01 min), but the frequency was higher in the C (84.96 +/- 8.52) than in the M group (43.13 +/- 4.37); however, the M group (470.2 +/- 11.87 min) spent more time suckling as compared with the C group (393.67 +/- 13.09 min). The M dams showed a decreased frequency of resting position throughout the lactation period (6.5 +/- 2.48) compared to birth day (25.42 +/- 7.74). Pups from the C group were more frequently observed separated (73.02 +/- 4.38) and interacting (258.99 +/- 20.61) more with their mothers than the M pups (separated 66.94 +/- 5.5 and interacting 165.72 +/- 12.05). Tactile stimulation did not interact with diet condition, showing that the kind of stimulation used in the present study did not lead to recovery from the changes induced by protein malnutrition. The changes in mother-pup interaction produced by protein malnutrition of both may represent retardation in neuromotor development and a higher dependence of the pups on their mothers. These changes may represent an important means of energy saving and heat maintenance in malnourished pups. (+info)
Pigs with highly prevalent antibodies to human coronavirus and swine haemagglutinating encephalomyelitis virus in the Tohoku District of Japan.
(21/1173)
From 1985 to 1988, a total of 2496 swine sera from 60 farms in the Tohoku District of the Honshu Island of Japan were examined for antibodies to swine haemagglutinating encephalomyelitis virus (HEV), human coronavirus (HCV) and bovine coronavirus (BCV) by haemagglutination-inhibition (HI) test. Antibodies to HEV 67N strain and HCV OC43 strain were highly prevalent with positivity rates of 82.1 and 91.4%, respectively, while seropositivity rate to BCV Kakegawa strain was 44.2%. No clinical signs of HEV infection were noticed in any farms including farms with relatively high seropositivity. The results suggested that HCV or antigenitically related virus(es) as well as HEV might be perpetuated in swine in the Tohoku District. (+info)
An intranasal challenge model for testing Japanese encephalitis vaccines in rhesus monkeys.
(22/1173)
Placebo-controlled field efficacy trials of new Japanese encephalitis (JE) vaccines may be impractical. Therefore, an animal model to evaluate efficacy of candidate JE vaccines is sought. Previous work has shown that exposure of monkeys to JE virus (JEV) via the intranasal route results in encephalitis. Here we report the further development of this model and the availability of titered virus stocks to assess the protective efficacy of JE vaccines. To determine the effective dose of our JE challenge virus, dilutions of a stock JEV (KE-93 isolate) were inoculated into four groups of three rhesus monkeys. A dose-dependent response was observed and the 50% effective dose (ED50) was determined to be 6.0 x 10(7) plaque forming units (pfu). Among animals that developed encephalitis, clinical signs occurred 9-14 days postinoculation. Infection with JEV was confirmed by detection of JEV in nervous tissues and IgM to JEV in the cerebrospinal fluid. Viremia with JEV was also detected intermittently throughout infection. Validation of the model was performed using a known effective JE vaccine and saline control. One ED90 of virus (2.0 x 10(9) pfu) was used as a challenge dose. Four of four animals that received saline control developed encephalitis while one of four monkeys administered the JE vaccine did so. This study demonstrates that the virus strain, route of inoculation, dose, and the outcome measure (encephalitis) are suitable for assessment of protective efficacy of candidate JE vaccines. (+info)
Production of lethal infection that resembles fatal human disease by intranasal inoculation of macaques with Japanese encephalitis virus.
(23/1173)
Twelve rhesus macaques (Macaca mulatta) challenged intranasally with a wild-type Japanese encephalitis virus (JEV) developed clinical signs 11-14 days later. Tissues from the cerebral cortex, cerebellum, brainstem, thalamus, meninges, and all levels of the spinal cord were stained for JEV antigen with hyperimmune mouse ascitic fluid and streptavidin-alkaline phosphatase; immunofluorescent staining was also done on frozen sections. Viral antigen was found in all cell layers of the cerebellum, the gray matter of the thalamus and brainstem, and the ventral horn of all levels of the spinal cord. Staining was limited to neurons and their processes. Histopathologic changes were limited to the nervous system and characterized by nonsuppurative meningoencephalitis. These results were comparable with those of previous studies done with human autopsy tissues. Intranasal inoculation of rhesus monkeys with JEV was effective in producing clinical disease comparable with natural disease in humans and may serve as a model to evaluate protective efficacy of candidate JEV vaccines. (+info)
Potential for evolution of California serogroup bunyaviruses by genome reassortment in Aedes albopictus.
(24/1173)
Aedes albopictus was introduced into the United States in used tires in 1985. Its successful colonization of the upper Midwest has potential to alter the current epidemiology of bunyaviruses that circulate in the region. It is permissive for the replication of several arboviruses, including La Crosse (LACV) and Jamestown Canyon (JCV) bunyaviruses. In this study, we demonstrate the ability of LACV and JCV to coinfect Ae. albopictus mosquitoes and to form all six possible reassortant genotypes. All reassortant viruses infect Ae. albopictus orally and can be transmitted to suckling mice. All reassortants are neurovirulent in mice. However, reassortant viruses carrying the LACV M segment in the foreign genetic background of JCV are more neuroinvasive than JCV, or any other reassortant genotype. In addition, these reassortants can replicate in gerbils and infect Ae. triseriatus, characteristics of LACV, but not JCV. Because Ae. albopictus is spreading into new geographic areas and feeds on a variety of mammals, including humans, it has the potential to transmit new, emerging bunyaviruses in nature. (+info)