Biomedical subjects

L G Adams

Publications and source records attributed to L G Adams.

At least 19 recordsLinked to original sources

PubMed2007

Rescuing valuable genomes by animal cloning: a case for natural disease resistance in cattle.

Tissue banking and animal cloning represent a powerful tool for conserving and regenerating valuable animal genomes. Here we report an example involving cattle and the rescue of a genome affording natural disease resistance. During the course of a 2-decade study involving the phenotypic and genotypic analysis for the functional and genetic basis of natural disease resistance against bovine brucellosis, a foundation sire was identified and confirmed to be genetically resistant to Brucella abortus. This unique animal was utilized extensively in numerous animal breeding studies to further characterize the genetic basis for natural disease resistance. The bull died in 1996 of natural causes, and no semen was available for AI, resulting in the loss of this valuable genome. Fibroblast cell lines had been established in 1985, cryopreserved, and stored in liquid nitrogen for future genetic analysis. Therefore, we decided to utilize these cells for somatic cell nuclear transfer to attempt the production of a cloned bull and salvage this valuable genotype. Embryos were produced by somatic cell nuclear transfer and transferred to 20 recipient cows, 10 of which became pregnant as determined by ultrasound at d 40 of gestation. One calf survived to term. At present, the cloned bull is 4.5 yr old and appears completely normal as determined by physical examination and blood chemistry. Furthermore, in vitro assays performed to date indicate this bull is naturally resistant to B. abortus, Mycobacterium bovis, and Salmonella typhimurium, as was the original genetic donor.

Animals↗

PubMed2006

Apoptosis-inducing factor participation in bovine macrophage Mycobacterium bovis-induced caspase-independent cell death.

Mycobacterium tuberculosis complex species survive and replicate in phagosomes of the host cell. Cell death (CD) has been highlighted as one of the probable outcomes in this host-pathogen interaction. Previously, our group demonstrated macrophage apoptosis as a consequence of Mycobacterium bovis infection. In this study, we aimed to identify the contribution of apoptotic effector elements in M. bovis-induced CD. Bovine macrophages were either infected with M. bovis (multiplicity of infection, 10:1) or treated with an M. bovis cell extract (CFE). Structural changes compatible with CD were evaluated. Chromatin condensation was increased three times by the CFE. On the other hand, a terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) assay demonstrated that levels of DNA fragmentation induced by M. bovis and CFE were 53.7% +/- 24% and 38.9% +/- 14%, respectively, whereas control cells had a basal proportion of 8.9% +/- 4.1%. Rates of DNA fragmentation were unaffected by the presence of the pan-caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp (z-VAD). Cells treated with 100 mug of CFE for 12 h had a fivefold decrease in the level of mitochondrial outer membrane permeabilization compared to that of untreated cells. Neither M. bovis infection nor CFE treatment induced activation of caspase 3, 8, or 9. Translocation of apoptosis-inducing factor (AIF) to the nucleus was identified in 32% +/- 3.5% and 26.3% +/- 4.9% of M. bovis-infected and CFE-treated cells, respectively. Incubation of macrophages with z-VAD prior to infection did not alter the percentage of cells showing AIF translocation. Our data suggest that M. bovis-induced CD in bovine macrophages is caspase independent with AIF participation.

Animals↗

PubMed2004

Amplified fragment length polymorphism reveals genomic variability among Mycobacterium avium subsp. paratuberculosis isolates.

Ninety-six primer sets were used for amplified fragment length polymorphism (AFLP) to characterize the genomes of 20 Mycobacterium avium subsp. paratuberculosis field isolates, 1 American Type Culture Collection (ATCC) M. avium subsp. paratuberculosis isolate (ATCC 19698), and 2 M. avium subsp. avium isolates (ATCC 35716 and Mac 104). AFLP analysis revealed a high degree of genomic polymorphism among M. avium subsp. paratuberculosis isolates that may be used to establish diagnostic patterns useful for the epidemiological tracking of M. avium subsp. paratuberculosis isolates. Four M. avium subsp. paratuberculosis-polymorphic regions revealed by AFLP were cloned and sequenced. Primers were generated internal to these regions for use in PCR analysis and applied to the M. avium subsp. paratuberculosis field isolates. An appropriate PCR product was obtained in 79 of 80 reactions, while the M. avium subsp. avium isolates failed to act as templates for PCR amplification in seven of eight reactions. This work revealed the presence of extensive polymorphisms in the genomes of M. avium subsp. paratuberculosis and M. avium subsp. avium, many of which are based on deletions. Of the M. avium subsp. paratuberculosis-specific sequences studied, one revealed a 5,145-bp region with no homologue in the M. avium subsp. avium genome. Within this region are genes responsible for integrase-recombinase function. Three additional M. avium subsp. paratuberculosis-polymorphic regions were cloned, revealing a number of housekeeping genes; all were evaluated for their diagnostic and epidemiological value.

Base Sequence↗

PubMed2003

Pathogenesis of Salmonella-induced enteritis.

Infections with Salmonella serotypes are a major cause of food-borne diseases worldwide. Animal models other than the mouse have been employed for the study of nontyphoidal Salmonella infections because the murine model is not suitable for the study of Salmonella-induced diarrhea. The microbe has developed mechanisms to exploit the host cell machinery to its own purpose. Bacterial proteins delivered directly into the host cell cytosol cause cytoskeletal changes and interfere with host cell signaling pathways, which ultimately enhance disease manifestation. Recently, marked advances have been made in our understanding of the molecular interactions between Salmonella serotypes and their hosts. Here, we discuss the molecular basis of the pathogenesis of Salmonella-induced enteritis.

Animals↗

PubMed2002

The myth of Brucella L-forms and possible involvement of Brucella penicillin binding proteins (PBPs) in pathogenicity.

Brucella spp. L-forms have been proposed to be stationary phase organisms in the evolution of new variants and enduring entities in the host in complicated cases of brucellosis and during latent brucellosis. In vitro formation of Brucella L-forms has been achieved by treating the cells with sub-lethal doses of penicillin. Interestingly, Brucella spp. have classified during the evolution into two groups, penicillin susceptible or penicillin resistant, yet both types grow on 20 microg/ml of methicillin. Strains proven susceptible to penicillin grew in the presence of methicillin as L-forms as demonstrated by light and electron microscopy. In addition, the B. melitensis vaccine strain Rev.1, a penicillin susceptible organism, responded to sheep serum by development of L-form-like structures unlike wild type, strain 16M. The two strains grew normally in sheep macrophages. We propose, for the first time, a model that associates Brucella pathogenicity with the structure and activity of two of their penicillin binding proteins (PBPs). According to the model, PBP1 has evolved as the major cell wall synthesizing enzyme of the genus, capable of responding to host serum growth factor(s) necessary for Brucella survival in the host. This property is associated with high avidity to beta-lactam antibiotics. PBP2 complements the activity of PBP1. New beta-lactam antibiotics and improved vaccines might be developed based on this property.

Animals↗

PubMed2002

Morphologic and molecular characterization of Salmonella typhimurium infection in neonatal calves.

The host response to Salmonella plays a major role in the outcome of infection. The present study was undertaken to further characterize Salmonella typhimurium infection in neonatal calves at both the morphologic and the molecular level using the ligated ileal loop model. Eight 4-5-week-old male Holstein calves underwent laparotomy, and loops were prepared in the ileum. The loops were either inoculated with an S. typhimurium strain pathogenic for cattle or injected with sterile LB broth as control. Samples for histology, transmission and scanning electron microscopy, and RNA extraction were collected at various time points between 5 minutes and 12 hours postinfection. Invasion of both M cells and enterocytes began at 15 minutes postinfection. No specific cell type was the main target for invasion. Intracellular bacteria were observed in the lamina propria after 1 hour postinfection. A severe acute neutrophilic response was associated with invasion of the Peyer's patches. Upregulated expression of CXC chemokines (interleukin [IL]-8, growth-related oncogenes, [GRO] alpha and gamma, and granulocyte chemotactic protein [GCP]2) was detected by reverse transcription polymerase chain reaction beginning at 1 hour postinfection. Expression of proinflammatory (IL-1beta, IL-18, and tumor necrosis factor [TNF]alpha) and anti-inflammatory (IL-10, IL-IRa, and IL-4) cytokines was also assessed. A marked increase in expression of IL-1beta was observed, whereas the profile of expression of IL-18 and TNFalpha did not change after infection. Upregulation of IL-1Ra and IL-4 but not of IL-10 was observed. These findings indicate that infection of bovine ligated ileal loops with S. typhimurium results in an acute neutrophilic inflammatory response that is associated with the upregulation of CXC chemokines (IL-8, GROalpha and gamma, and GCP2), IL-1beta, IL-IRa, and IL-4.

Animals↗

PubMed2001

Ranch-management factors associated with antibody seropositivity for Neospora caninum in consignments of beef calves in Texas, USA.

A study was conducted with a 1998 retained-ownership population of Texas (USA) beef calves to determine the ranch-management practices associated with calf seroprevalence to Neospora caninum. Management practices of 76 Texas ranches that consigned 760 calves to a retained-ownership feedlot program were reviewed from a mailed questionnaire. Ninety-nine of 760 (13%; 95% CI, 9.4%, 17.7%) calves were positive to N. caninum and 59% of the ranches consigned at least one positive calf. In the logistic multiple-regression model which controlled for overdispersion, increased odds of calf-level seropositivity was associated with seasonal calving patterns, with stocking>1cow/calfunit/2.2ha, using a round-bale feeder, allowing wildlife access to the weaning supplement, and self-reared replacement heifers. However, decreased odds of seropositivity was associated with using a cattle-working dog and with using a self-contained cattle feeder. There was substantial overdispersion due to ranch.

Animal Husbandry↗

PubMed2001

Salmonella enterica serovar typhimurium induces cell death in bovine monocyte-derived macrophages by early sipB-dependent and delayed sipB-independent mechanisms.

It was previously demonstrated that Salmonella enterica serovar Typhimurium induces cell death with features of apoptosis in murine macrophages. Mice infected with Salmonella serovar Typhimurium develop systemic disease without diarrhea, whereas the infection in cattle and in humans is localized and characterized by diarrhea. Considering these clinical disease expression differences between mice and cattle, we investigated whether serovar Typhimurium is cytotoxic for bovine macrophages. Macrophages infected with serovar Typhimurium grown in the logarithmic phase quickly underwent cell death. Macrophages infected with stationary-phase cultures or with a mutant lacking sipB underwent no immediate cell death but did develop delayed cytotoxicity, undergoing cell death between 12 and 18 h postinfection. Both pathways were temporarily blocked by the general caspase inhibitor Z-VAD-Fmk and by the caspase 1 inhibitor Z-YVAD-Fmk. Comparisons of macrophages from cattle naturally resistant or susceptible to intracellular pathogens indicated no differences between these two genetic backgrounds in terms of susceptibility to serovar Typhimurium-induced cell death. We conclude that Salmonella serovar Typhimurium induces cell death in bovine macrophages by two distinct mechanisms, early sipB-mediated and delayed sipB-independent mechanisms.

Amino Acid Chloromethyl Ketones↗

PubMed2001

Stable transfection of the bovine NRAMP1 gene into murine RAW264.7 cells: effect on Brucella abortus survival.

Genetically based natural resistance to brucellosis in cattle provides for novel strategies to control zoonotic diseases. Bovine NRAMP1, the homologue of a murine gene (Bcg), has been identified as a major candidate for controlling the in vivo resistant phenotype. We developed an in vitro model for expression of resistance- and susceptibility-associated alleles of bovine NRAMP1 as stable transgenes under the regulatory control of the bovine NRAMP1 promoter in the murine RAW264.7 macrophage cell line (Bcg(s)) to analyze the regulation of the NRAMP1 gene and its role in macrophage function. We demonstrated that the 5'-flanking region of bovine NRAMP1, despite the lack of TATA and CAAT boxes, has a functional promoter capable of driving the expression of a transgene in murine macrophages. A polymorphism within a microsatellite in the 3' untranslated region critically affects the expression of bovine NRAMP1 and the control of in vitro replication of Brucella abortus but not Salmonella enterica serovar Dublin. We did not observe any differences in the production of NO by resting or gamma interferon (IFN-gamma)- and IFN-gamma-lipopolysaccharide (LPS)-treated transfected cell lines, yet the resistant transfected cell lines produced significantly less NO than other cell lines, following stimulation with LPS at 24 and 48 h.

3' Untranslated Regions↗

PubMed2001

Salmonella-induced cell death is not required for enteritis in calves.

Salmonella enterica serovar Typhimurium causes cell death in bovine monocyte-derived and murine macrophages in vitro by a sipB-dependent mechanism. During this process, SipB binds and activates caspase-1, which in turn activates the proinflammatory cytokine interleukin-1beta through cleavage. We used bovine ileal ligated loops to address the role of serovar Typhimurium-induced cell death in induction of fluid accumulation and inflammation in this diarrhea model. Twelve perinatal calves had 6- to 9-cm loops prepared in the terminal ileum. They were divided into three groups: one group received an intralumen injection of Luria-Bertani broth as a control in 12 loops. The other two groups (four calves each) were inoculated with 0.75 x 10(9) CFU of either wild-type serovar Typhimurium (strain IR715) or a sopB mutant per loop in 12 loops. Hematoxylin and eosin-stained sections were scored for inflammation, and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells were detected in situ. Fluid accumulation began at 3 h postinfection (PI). Inflammation was detected in all infected loops at 1 h PI. The area of TUNEL-labeled cells in the wild-type infected loops was significantly higher than that of the controls at 12 h PI, when a severe inflammatory response and tissue damage had already developed. The sopB mutant induced the same amount of TUNEL-positive cells as the wild type, but it was attenuated for induction of fluid secretion and inflammation. Our results indicate that serovar Typhimurium-induced cell death is not required to trigger an early inflammatory response and fluid accumulation in the ileum.

Animals↗

PubMed2001

In vivo and in vitro diagnosis of Mycobacterium bovis infection.

The intradermal delayed type hypersensitivity (DTH) skin test, using purified protein derivative from culture of M. bovis or M. avium, is the most frequently used test for diagnosis of tuberculosis or detection of M. bovis infection in cattle. Many improvements have been made to the original tuberculin test, and molecular approaches to identify and clone antigens may lead to improved specificity and sensitivity of DTH skin tests. Recent advances in technology have allowed the development of new in vitro techniques, such as antibody-based, cell-mediated immunity-based and nucleic acid-based diagnostics, which allow more rapid diagnosis than bacteriological culture. The choice of diagnostic technique should consider both the population being investigated (e.g. apparently healthy animals or a herd with a high prevalence of clinical infection) and the aim of the testing (e.g. the screening of healthy animals or confirmation of infection in animals strongly suspected to be infected). Moreover, any evaluation of a diagnostic test must use a carefully selected control population which is representative of the population to be tested in terms of relative proportions of infected and non-infected animals.

Animals↗

PubMed2001

Serologic survey for canine coronavirus in wolves from Alaska.

Wolves (Canis lupus) were captured in three areas of Interior Alaska (USA). Four hundred twenty-five sera were tested for evidence of exposure to canine coronavirus by means of an indirect fluorescent antibody procedure. Serum antibody prevalence averaged 70% (167/240) during the spring collection period and 25% (46/185) during the autumn collection period. Prevalence was 0% (0/42) in the autumn pup cohort (age 4-5 mo), and 60% (58/97) in the spring pup cohort (age 9-10 mo). Prevalence was lowest in the Eastern Interior study area. A statistical model indicates that prevalence increased slightly each year in all three study areas. These results indicate that transmission occurs primarily during the winter months, antibody decay is quite rapid, and reexposure during the summer is rare.

Alaska↗

PubMed2000

Association of serologic status for Neospora caninum with postweaning weight gain and carcass measurements in beef calves.

OBJECTIVE: To determine the seroprevalence for Neospora caninum in a population of beef calves in a feedlot and the association of serologic status with postweaning weight gain and carcass measurements. DESIGN: Longitudinal observational study. ANIMALS: 1,009 weaned beef steers from 92 herds. PROCEDURE: Samples were obtained from all steers at time of arrival at a feedlot. Serologic status for Neospora spp was determined, using an agglutination test. Results of serologic testing were compared with calf growth and carcass data, using multivariate regression with generalized estimating equations. RESULTS: Of 1,009 calves, 131 (12.98%) were seropositive, and 54 of 92 (58.7%) consignments had > or = 1 seropositive calf. Median within-consignment prevalence for consignments in which there was > or = 1 seropositive calf was 20%. Seropositive status was associated with significant reductions in average daily gain, live body weight at slaughter, and hot carcass weight and an increase in ribeye area-to-hot carcass weight ratio. Seropositive status also was associated with significant increases in cost of treatment and significant reductions in income. Sick seropositive calves had the highest cost of treatment. An economic loss of $15.62/calf was projected for seropositive calves. CONCLUSIONS AND CLINICAL RELEVANCE: Significant reductions in postweaning weight gain, carcass weight, and economic return were associated with detection of antibodies to N caninum in beef calves in a feedlot.

Agglutination Tests↗

PubMed2000

Spatial associations among density of cattle, abundance of wild canids, and seroprevalence to Neospora caninum in a population of beef calves.

OBJECTIVE: To determine the epidemiologic plausibility of a sylvatic transmission cycle for Neospora caninum between wild canids and beef cattle. DESIGN: Spatial analysis study. ANIMALS: 1,009 weaned beef steers from 94 beef herds in Texas. PROCEDURE: Calves were grouped on the basis of seroprevalence for N caninum and ecologic region in Texas. The Morans I test was used to evaluate spatial interdependence for adjusted seroprevalence by ecologic region. Cattle density (Number of cattle/259 km2 [Number of cattle/100 mile2] of each ecologic region) and abundance indices for gray foxes and coyotes (Number of animals/161 spotlight-transect [census] km [Number of animals/100 census miles] of each ecologic region) were used as covariates in spatial regression models, with adjusted seroprevalence as the outcome variable. A geographic information system (GIS) that used similar covariate information for each county was used to validate spatial regression models. Results-Spatial interdependence was not detected for ecologic regions. Three spatial regression models were tested. Each model contained a variable for cattle density for the ecologic regions. Results for the 3 models revealed that seroprevalence was associated with cattle density and abundances of gray foxes, coyotes, or both. Abundances of gray foxes and coyotes were collinear. Results of a GIS-generated model validated these spatial models. CONCLUSIONS AND CLINICAL RELEVANCE: In Texas, beef cattle are at increased risk of exposure to N caninum as a result of the abundance of wild canids and the density of beef cattle. It is plausible that a sylvatic transmission cycle for neosporosis exists.

Animals↗

PubMed2000

Absence of shedding of two B. abortus strains in goats after vaccination with live vaccines.

The objective of this study was to determine if B. abortus rough mutant strains RB51 and rfbK are eliminated in goat milk. Thirty milk goats were divided into two groups. Group I was inoculated with 4x10(10) cfu/ml of B.abortus RB51 strain and Group II with 1x10(9) cfu/ml of B. abortus rfbK strain by subcutaneous route in the right axilary region. Milk samples were taken aseptically on a daily basis for the first 30 days and weekly for the second and third months. The samples were inoculated on Farrell's media and incubated under 5-10% CO(2) at 37 degrees C for 10 days. The suspicious colonies were recultured in Farrell's media. There were no isolations of bacteria with characteristics of Brucella from any of the milk samples collected during 90 days of the study. It was concluded that neither of the strains used at these doses were eliminated by milk in goats inoculated during lactation.

Animals↗

PubMed2000

Failure to identify non-bovine reservoirs of Mycobacterium bovis in a region with a history of infected dairy-cattle herds.

The State of Texas had the most (cumulative) tuberculous cattle herds of any state in the United States during the decade ending in 1997. Of the cumulative 18 infected herds in Texas, 12 herds were concentrated in El Paso County (designated the 'El Paso milkshed'). To identify whether non-bovine reservoirs were a source of Mycobacterium bovis infection of cattle in this region, an investigation was conducted on the premises of 14 dairy herds (12 tuberculous and 2 non-affected herds) between May 1995 and June 1997. None of the 670 mammalian, avian and environmental (soil, water and air) samples collected and cultured from the premises of these herds was positive for the presence of M. bovis. None of the 119 human urine samples obtained from employees of these dairies was culture positive for M. bovis. Of 124 dairy-farm workers with tuberculin skin-test results, 48 showed positive test results. There was, however, no difference in percentages of positive skin-test results between farms without, and farms having, bovine tuberculosis within the last two years or longer. The percentage of positive reactions did not increase with length of time employed at a dairy with a history of confirmed tuberculosis. These findings suggest that non-bovine reservoirs appear not to be a factor responsible for tuberculosis of cattle in the El Paso milkshed.

Adult↗

PubMed2000

Cisplatin versus cisplatin combined with piroxicam in a canine model of human invasive urinary bladder cancer.

PURPOSE: More than 12,000 people are expected to die from invasive transitional cell carcinoma (TCC) of the urinary bladder each year in the United States, indicating that more effective therapy is needed. Drugs inhibiting cyclooxygenase (cox) have recently been found to have chemopreventive and antitumor activity and may potentiate the effects of chemotherapy. The purpose of this study was to determine whether cisplatin combined with the cox-inhibitor piroxicam would induce remission more frequently than cisplatin alone in a relevant animal model of human invasive TCC. METHODS: Pet dogs with naturally occurring, histopathologically confirmed, measurable TCC of the urinary bladder were randomized to receive cisplatin (60 mg/m2 i.v. every 21 days) or cisplatin (same dosage) combined with piroxicam (0.3 mg/kg orally every 24 h). Complete staging was performed prior to and at 6-week intervals during therapy. RESULTS: After eight dogs had been evaluated in each treatment group, a significant difference in remission rate was noted (Fisher's Exact test, P < 0.004). Tumor responses in the cisplatin/piroxicam group included two complete remissions (CR), four partial remissions (PR), two stable disease (SD), and no progressive disease (PD). Tumor responses to cisplatin alone in eight dogs were no CR, no PR, four SD, and four PD. Six additional dogs were treated with cisplatin/piroxicam, and in total 10 of 14 dogs had remission (two CR, eight PR). Renal toxicity of cisplatin/ piroxicam was frequent and dose limiting. CONCLUSIONS: Cisplatin/piroxicam induced remission more frequently than cisplatin alone in a canine model of human invasive TCC. Strategies to reduce renal toxicity need to be developed prior to evaluation of cisplatin/piroxicam in humans or general use of this treatment in pet dogs.

Animals↗

PubMed2000

Identification of four genes of the Brucella melitensis ATP synthase operon F0 sector: relationship with the Rhodospirillaceae family.

We have determined the nucleotide sequence of a cloned DNA fragment from the human and animal pathogen Brucella melitensis. Four genes were identified from a 4069 bp fragment, corresponding to the B. melitensis a, c, b', and b subunits of the ATP synthase F0 sector operon. A duplicated and divergent copy of the b-subunit gene was observed. This feature has been found only in photosynthetic bacteria and chloroplasts. In addition, the gene cluster was separated from the F1 sector, a characteristic described only for the Rhodospirillaceae family.

ATP Synthetase Complexes↗