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Biomedical subjects

R A Bowen

Publications and source records attributed to R A Bowen.

At least 19 recordsLinked to original sources
PubMed2005

Experimental infection of pigs with West Nile virus.

Young adult and weanling pigs were challenged with the New York 99 strain of West Nile virus through the bite of infected mosquitoes. Each of six adult pigs seroconverted, but virus was isolated from serum of only one pig following challenge. Three of five weanling pigs developed viremia, with peak titers of 10(1.9) and 10(3.1) PFU/mL. Clinical signs attributable to West Nile virus infection were not observed in any of these animals. An additional four pigs were challenged by feeding West Nile virus-infected mice, and none of the four developed a detectable viremia or seroconverted. These results suggest that pigs are unlikely to play a significant role as amplifying hosts of West Nile virus.

Aedes↗
PubMed2001

Response to and efficacy of vaccination against eastern equine encephalomyelitis virus in emus.

OBJECTIVE: To evaluate humoral immune responses of emus vaccinated with commercially available equine polyvalent or experimental monovalent eastern equine encephalomyelitis (EEE) virus and western equine encephalomyelitis (WEE) virus vaccines and to determine whether vaccinated emus were protected against challenge with EEE virus. DESIGN: Cohort study. ANIMALS: 25 emus. PROCEDURE: Birds were randomly assigned to groups (n = 5/group) and vaccinated with 1 of 2 commercially available polyvalent equine vaccines, a monovalent EEE virus vaccine, or a monovalent WEE virus vaccine or were not vaccinated. Neutralizing antibody responses against EEE and WEE viruses were examined at regular intervals for up to 9 months. All emus vaccinated with the equine vaccines and 2 unvaccinated control birds were challenged with EEE virus. An additional unvaccinated bird was housed with the control birds to assess the possibility of contact transmission. RESULTS: All 4 vaccines induced detectable neutralizing antibody titers, and all birds vaccinated with the equine vaccines were fully protected against an otherwise lethal dose of EEE virus. Unvaccinated challenged birds developed viremia (> 10(9) plaque-forming units/ml of blood) and shed virus in feces, oral secretions, and regurgitated material. The unvaccinated pen-mate became infected in the absence of mosquito vectors, presumably as a result of direct virus transmission between birds. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that emus infected with EEE virus develop a high-titer viremia and suggest that they may serve as important virus reservoirs. Infected emus shed EEE virus in secretions and excretions, making them a direct hazard to pen-mates and attending humans. Commercially available polyvalent equine vaccines protect emus against EEE virus infection.

Animals↗
PubMed2001

Expression of human MxA protein in mosquito cells interferes with LaCrosse virus replication.

Human MxA protein inhibits LaCrosse virus (LAC virus; family Bunyaviridae) replication in vertebrate cells and MxA-transgenic mice. LAC virus is transmitted to humans by Aedes triseriatus mosquitoes. In this report, we have shown that transfected mosquito cells expressing the human MxA cDNA are resistant to LAC virus but permissive for Sindbis virus (family Togaviridae) infection.

Aedes↗
PubMed2001

Virulence and viremia characteristics of 1992 epizootic subtype IC Venezuelan equine encephalitis viruses and closely related enzootic subtype ID strains.

Following a 19-year hiatus, Venezuelan equine encephalitis (VEE) reemerged in western Venezuela in December 1992. This outbreak is important in understanding VEE emergence because phylogenetic studies imply that sympatric, enzootic, subtype ID VEE viruses mutated to generate the epizootic/epidemic. Although the 1992-1993 strains belong to subtype IC, a serotype implicated in extensive outbreaks during the 1960s and in 1995, relatively small numbers of human and equine cases occurred in 1992-1993. We, therefore, evaluated the pathogenicity of these Venezuelan enzootic ID and epizootic IC viruses to determine 1) if they exhibit phenotypes like those described previously for more distantly related enzootic and epizootic strains, and 2) if the 1992-1993 outbreak was limited by the inability of these IC viruses to exploit equines as amplification hosts. All strains were virulent in mice and guinea pigs, but were benign for cotton rats, natural hosts of enzootic viruses. However, only the IC strains produced equine disease, with mean peak viremias of 10(5) suckling mouse 50% lethal doses per mL serum, and some titers exceeding 10(7). These viremias approximate those observed previously with VEE strains isolated during more extensive epizootics, suggesting that efficient equine amplification did not limit the scope and duration of the 1992-1993 outbreak. Enzootic ID virus infection protected all horses from challenge with epizootic strain P676, supporting the hypothesis that epizootics bypass regions of enzootic transmission due to natural immunization of equines by enzootic VEE viruses.

Animals↗
PubMed2000

Immune responses in mice, cattle and horses to a DNA vaccine for vesicular stomatitis.

Vesicular stomatitis (VS) virus causes an important clinical disease of cattle and horses in North America. In order for a vaccine to be useful in the control of VS, it must not only protect against disease, but allow ready differentiation of infected and vaccinated animals. In these studies, we evaluated neutralizing antibody responses in outbred mice, calves, and horses that received a DNA vaccine that expressed the glycoprotein (G) gene of VS New Jersey virus. The vaccine elicited antibody titers in individuals from each species, especially when two doses were administered, but the level of neutralizing antibody needed to confer protection is not known. In mice, co-administration of a plasmid that expressed interleukin-2 resulted in a significant, though modest, increase in antibody titers relative to use of the G gene vaccine alone. The effect of co-injecting putative immunostimulatory oligonucleotides was also evaluated. This treatment had no apparent effect in horses and was found to suppress immune responses to the G gene vaccine in mice. If the immune responses obtained in these studies prove to protect cattle and horses from infection with VS virus, DNA vaccination may become a useful tool for control of this disease.

Animals↗
PubMed2000

High dietary 18:3n-3 increases the 18:3n-3 but not the 22:6n-3 content in the whole body, brain, skin, epididymal fat pads, and muscles of suckling rat pups.

The objective of this study was to test the hypothesis that increasing maternal dietary 18:3n-3 by decreasing the 18:2n-6/18:3n-3 ratio will increase the 18:3n-3 and 22:6n-3 content of the whole body, liver, skin (epidermis, dermis, and subcutaneous tissue), epididymal fat pads, and muscles (arms and legs) of 2-wk-old rat pups. Sprague-Dawley dams at parturition were fed semipurified diets containing either a low (18:2n-6 to 18:3n-3 ratio of 24.7:1) or a high (1 8:2n-6 to 18:3n-3 ratio of 1.0:1) 18:3n-3 fatty acid content. During the first 2 wk of life, rat pups received only their dams' milk. Fatty acid composition of the pups' stomach contents (dams' milk), whole body, brain, liver, skin, epididymal fat pads, and muscles was determined. The stomach fatty acid composition of 18:3n-3 reflected the dams' diet. The content of 18:3n-3 in whole body, brain, liver, skin, epididymal fat pads, and muscles was significantly (P< 0.05) greater in rat pups fed the high compared with the low 18:3n-3 fatty acid diet. The 22:6n-3 content of the whole body, brain, skin, epididymal fat pads, and muscles was not quantitatively different in rat pups fed either the low or high 18:3n-3 fatty acid diet. The 20:5n-3 and 22:5n-3 content of the whole body, skin, and epididymal fat pads was significantly increased in rat pups fed the high compared with the low 18:3n-3 fatty acid diet. High content of 18:3n-3 was found in the skin of rat pups fed either a low or high 18:3n-3 fatty acid diet. These findings demonstrate that high maternal dietary 18:3n-3 significantly increases the 18:3n-3 but not the 22:6n-3 content of the whole body, brain, skin, epididymal fat pads, and muscles with approximately 39 and 41% of the whole body 18:3n-3 content being deposited in the skin of suckling rat pups fed either the low or high 18:3n-3 diet, respectively.

Adipose Tissue↗
PubMed1999

Does increasing dietary linolenic acid content increase the docosahexaenoic acid content of phospholipids in neuronal cells of neonatal rats?

The objective of this study was to investigate if increasing maternal dietary linolenic acid (18:3n-3) content, by decreasing the 18:2n-6 to 18:3n-3 ratio, could increase the docosahexaenoic acid (22:6n-3) content in phospholipids of neuronal cells of rat pups at 2 weeks of age. Sprague-Dawley dams at parturition were fed semipurified diets containing decreasing ratios of 18:2n-6 to 18:3n-3 from 21.6:1 to 1:1. During the first 2 weeks of life, the rat pups received only their dam's milk. The fatty acid composition of the pups stomach contents (dam's milk) and the phospholipids from neuronal cells were identified and quantitated by gas-liquid chromatography. The stomach 22:6n-3 content analyzed from the rat pups at 2 weeks of age was altered by the maternal diet. Fatty acid analysis of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS) in neuronal cells of the rat pups showed no significant increase in 22:6n-3 content with increasing 18:3n-3 in the maternal diet (p > 0.05). In contrast, the content of 22:6n-3 in phosphatidylinositol (PI) was significantly increased by change in dietary 18:3n-3 intake from a dietary 18:2n-6 to 18:3n-3 ratio of 7.8:1 to 4.4:1. It is concluded that increasing maternal dietary 18:3n-3 by decreasing the 18:2n-6 to 18:3n-3 ratio does not significantly increase the 22:6n-3 content in PC, PE, and PS in neuronal cells of rat pups at 2 weeks of age.

Animal Nutritional Physiological Phenomena↗
PubMed1999

In vivo transfection and expression of exogenous genes within proximal tubules of rats.

An in vivo technique for expressing exogenous DNA within the renal cortical proximal tubules of rats was was developed and validated. Cationic liposomes were complexed with either water or 25 microg of plasmid DNA containing the lac Z gene, and injected into the left renal artery of anesthetized rats. Under transcriptional control of the chicken beta-actin, SV40, and CMV promoters, beta-galactosidase expression was consistently observed in rats that received plasmid DNA, while no blue staining was observed in kidneys of control rats. Using an injection volume of 400 microl, lac Z expression was confined to the proximal tubules, with no lac Z expression noted within serial sections of the liver, adrenal, lung, spleen, or heart. Because lac Z expression was observed for up to 20 days without apparent systemic or renal insult, this technique may be a valuable tool for evaluating physiological and pathophysiological changes associated with gene expression within this isolated site.

Actins↗
PubMed1998

Cloning and characterization of cDNAs for a bovine (Bos taurus) Mx protein.

Mx proteins are GTPases that are stringently induced in cells from many vertebrates on exposure to type I interferons (IFNs), and expression of some Mx proteins potently inhibits replication of specific viruses. Two cDNAs encoding bovine Mx proteins were isolated from an endometrial phage library. The open reading frames (ORFs) of these two clones predict proteins of 654 (Mxl) and 648 (Mxl-a) residues. Both possess the tripartite GTPase domains, dynamin signature, and leucine zipper motifs conserved in all other Mx proteins identified. The bovine protein sequences show highest identity to ovine Mx (93%) and are substantially similar to human MxA (73%) and mouse Mx1 (63%). Based on differences between the two bovine clones in the coding and 3'-untranslated regions, it was concluded that they represent two alleles of one gene, and heterozygous and homozygous cattle were identified. Expression of Mx mRNA was rapidly induced in cultured bovine cells by treatment with IFN.

Amino Acid Sequence↗
PubMed1997

Expression of a murine gonadotropin-releasing hormone receptor-luciferase fusion gene in transgenic mice is diminished by immunoneutralization of gonadotropin-releasing hormone.

A line of transgenic mice harboring a fusion gene consisting of 1900 bp of proximal 5'-flanking region from the murine GnRH receptor gene linked to the complementary DNA encoding luciferase was established to determine whether this promoter can direct tissue-specific expression in vivo and serve as a model for identifying the molecular mechanisms underlying hormonal regulation of this gene. Of 10 tissues screened, luciferase was detected predominantly in pituitary gland, but also in brain and testis. To assess hormonal regulation, luciferase activity was measured in intact males and ovariectomized females treated with an anti-GnRH serum alone, and in combination with testosterone or 17beta-estradiol. No effect of steroid treatment on transgene expression was detected. However, immunoneutralization of GnRH resulted in decreased serum LH concentrations and suppressed pituitary expression of luciferase. Furthermore, the effects of GnRH antiserum could be prevented by the administration of a noncross-reactive GnRH agonist. Thus, 1900 bp of 5'-flanking DNA from the murine GnRH receptor gene are sufficient to target luciferase expression in transgenic mice to established sites of GnRH receptor gene expression. Furthermore, we suggest that GnRH regulation of GnRH receptor gene expression is mediated by regulatory elements residing within 1900 bp of the 5'-flanking region.

Animals↗
PubMed1995

Pathologic and serologic responses of isogeneic twin lambs to phenotypically distinct lentiviruses.

Viral strain differences in the degree of lymphoid interstitial pneumonia (LIP) and in antibody responses to ovine lentivirus (OvLV) infection have been described in experimentally inoculated neonatal lambs. To rule out the possibility that these differences were due to differences in host genetic factors, one lamb from each of three sets of artificially produced identical twins was inoculated with a lytic strain of OvLV (85/34), and the corresponding twin was inoculated with a persistent strain (84/28). One lamb of a fourth set of twins was inoculated with the lytic strain of OvLV, and the corresponding twin was inoculated with a cell culture supernatant. The degree of LIP, as determined by histologic analysis of the lung sections collected at necropsy, was independent of the virus strain used for inoculation. The amount of OvLV proviral DNA in alveolar macrophages correlated with the degree of LIP. However, differences in the antibody response of genetically identical lambs to OvLV structural proteins indicated that the two strains have different in vivo immunogenic properties. The lack of difference in the degree of LIP between lambs with identical genetic backgrounds suggests that host genetic factors may be important in determining the degree of inflammatory response by the lung.

Animals↗
PubMed1995

Efficient production of transgenic cattle by retroviral infection of early embryos.

Production of transgenic cattle by microinjection of DNA has been difficult and costly. To explore an alternative method, one- to four-cell bovine embryos were exposed to a replication-defective retrovirus by microinjection of retrovirus producer cells into the perivitelline space. Embryos were cultured in vitro for 3-4 days, then transferred to recipient cows for further development. Thirteen of 22 embryos recovered at 15 days gestation and each of four fetuses recovered at 90 days gestation were transgenic. Fetuses harbored between 2 and 12 proviruses, and within each fetus, identical patterns of integration were observed in seven tissues tested. Estimates of the number of proviruses per cell suggested that in three of the four fetuses, most, and possibly all, cells were transgenic. This technique should facilitate application of transgenic technology to cattle and other agriculturally important species.

Animals↗
PubMed1994

Transgenic cattle resulting from biopsied embryos: expression of c-ski in a transgenic calf.

Producing transgenic cattle by microinjection of DNA into pronuclei has been inefficient and costly, in large part because of the cost of maintaining numerous nontransgenic pregnancies to term. We designed a system for early identification of transgenic embryos in which biopsies of embryos were assayed by polymerase chain reaction for presence of the transgene before embryo transfer. A total of 2555 embryos were microinjected with one of two DNA constructs. Of the 533 embryos biopsied, 112 were judged to be potentially transgenic and were transferred nonsurgically to recipients, resulting in production of 29 putative transgenic fetuses. One fetus and one calf (7% of offspring) were subsequently shown to be definitively transgenic. The calf was transgenic for a chicken c-ski cDNA, and several months after birth developed dramatic muscular hypertrophy followed by muscle degeneration. This phenotype was associated with expression of high levels of mRNA from the transgene.

Animals↗
PubMed1993

Development and testing of a bovine trichomoniasis vaccine.

Eighteen culled dairy cows were randomly allocated into 1 of 5 treatment groups. Six cows were vaccinated twice (2V), 21 days apart, 3 with whole cell (2WC) and 3 with fragmented cell membrane (2FC) containing 1 x 10(9)Trichomonas fetus organisms or protein equivalent in a commercial mineral oil adjuvant vaccine. Six more cows were vaccinated once (1V), 3 with whole cell (1WC) and 3 with fragmented cell vaccine (1FC), using the same vaccine, while 6 cows were used as the unvaccinated controls. All cows were challenged with 1 x 10(5) organisms 4 weeks after the second or the only vaccination. After challenge, cervico-vaginal mucus (CVM) samples were cultured for T . fetus weekly for 9 weeks. Whole cell vaccines were superior to fragmented cell vaccines, and both performed better than no vaccination for apparent elimination of trichomonad infections in dairy cows. In addition, 2V was superior to 1V, which, in turn, was superior to no vaccination. Furthermore, clearance time was reduced most by 2V and whole cell vaccination compared with 1V and fragmented cell vaccination. Clearance time was decreased significantly in all vaccinated cows compared with that in unvaccinated cows.

Journal Article↗
PubMed1993

Testing of trichomoniasis vaccine in heifers mated to infected bulls.

This study was conducted to evaluate the effectiveness of a Trichomonas fetus vaccine to protect heifers from infection when bred to infected bulls. The vaccine consisted of a whole cell vaccine of T. fetus organisms stabilized in formaldehyde and adjuvanted in a mineral oil base. In the trial, fewer vaccinated heifers became infected than unvaccinated controls (69.4 vs 93.0%, respectively; P<0.08). The vaccinated heifers tended to clear the infections sooner than the controls (48.9 vs 68.5 days, respectively; P<0.10). The average number of days open was shorter in the vaccinated heifers than in the controls (33.2 vs 56.9 days, respectively; P<0.07). The first service conception rate was higher in the vaccinated heifers than in the controls (66.7 vs 33.3%, respectively; P<0.05). The number of services per conception in conceiving heifers was lower in vaccinated than in control heifers (1.44 vs 1.73, respectively; P<0.16). Cervicovaginal mucus (CVM) samples were collected every 14 days following first challenge (first service). On average, more CVM samples were positive for T. fetus for a longer period of time in the control than in the vaccinated heifers (3.9 vs 1.85 sampling periods, respectively; P<0.08). We concluded that, under the conditions of this trial, some protection to T. fetus was afforded by double vaccination with a whole cell vaccine. However, vaccination does not completely prevent heifers from developing infection.

Journal Article↗
PubMed1990

The effects of methyltestosteone on reproductive function in male greyhounds.

Oral administration of methyltestosterone (MT) at 50 mg/dog/day to intact adult male greyhounds for 90 d resulted in decreased (P < 0.05) mean daily sperm output and mean testicular length. Additionally, the mean diameter of seminiferous tubules in MT-treated dogs tended to decrease (P = 0.08). Mean concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) and concentrations of testosterone in serum were also decreased or tended to decrease (P = 0.0003 to 0.059) at various sampling periods during MT treatment, suggesting alterations in spermatogenesis resulted from decreased serum concentrations of gonadotropins and steroids. Mean daily sperm output, mean testicular length, mean seminiferous tubule diameter and mean concentrations of FSH in serum were not decreased (P > 0.05) at the end of a 90-d recovery period. However, mean concentrations of serum LH and concentrations of testosterone were still lower (P < 0.05) during five of six and one of six sampling times, respectively, during the recovery period than the pretreatment levels, suggesting a prolonged effect of MT treatment on the pituitary/gonadal axis.

Journal Article↗