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Biomedical subjects

L G Adams

Publications and source records attributed to L G Adams.

At least 55 records · Page 3Linked to original sources
PubMed1997

Novel signal transduction and peptide specificity of glucagon-like peptide receptor in 3T3-L1 adipocytes.

Glucagon-like peptide-1 (7-36) amide (GLP-1), in addition to its well known effect of enhancing glucose-mediated insulin release, has been shown to have insulinomimetic effects and to enhance insulin-mediated glucose uptake and lipid synthesis in 3T3-L1 adipocytes. To elucidate the mechanisms of GLP-1 action in these cells, we studied the signal transduction and peptide specificity of the GLP-1 response. In 3T3-L1 adipocytes, GLP-1 caused a decrease in intracellular cAMP levels which is the opposite to the response observed in pancreatic beta cells in response to the same peptide. In 3T3-L1 adipocytes, free intracellular calcium was not modified by GLP-1. Peptide specificity was examined to help determine if a different GLP receptor isoform was expressed in 3T3-L1 adipocytes vs. beta cells. Peptides with partial homology to GLP-1 such as GLP-2, GLP-1 (1-36), and glucagon all lowered cAMP levels in 3T3-L1 adipocytes. In addition, an antagonist of pancreatic GLP-1 receptor, exendin-4 (9-39), acted as an agonist to decrease cAMP levels in 3T3-L1 adipocytes as did exendin-4 (1-39), a known agonist for the pancreatic GLP-1 receptor. Binding studies using 125I-GLP-1 also suggest that pancreatic GLP-1 receptor isoform is not responsible for the effect of GLP-1 and related peptides in 3T3-L1 adipocytes. Based on these results, we propose that the major form of the GLP receptor in 3T3-L1 adipocytes is functionally different from the pancreatic GLP-1 receptor.

3T3 Cells↗
PubMed1997

The spv genes on the Salmonella dublin virulence plasmid are required for severe enteritis and systemic infection in the natural host.

The pathogenic role of the spv (Salmonella plasmid virulence) genes of Salmonella dublin was determined in the natural, bovine host. Since the lack of overt signs of enteritis or enterocolitis due to Salmonella infections in mice has limited the development of a convenient experimental system to study enteric disease, we used calves to study the contribution of the spv genes to S. dublin-induced salmonellosis. Since the SpvR transcriptional regulator is required for expression of the spvABCD operon, we constructed an spvR knockout mutation in a calf-virulent strain of S. dublin. Calves were infected with the wild-type strain, an spvR mutant, and an spvR mutant containing a complementing plasmid. Calves that were infected with the wild type or the complemented spvR mutant rapidly developed severe diarrhea and became moribund. Calves that were infected with the spvR mutant showed little or no clinical signs of systemic salmonellosis and developed only mild diarrhea. The survival and growth of the wild-type strain and the spvR mutant were determined by using blood-derived bovine monocytes. Wild-type S. dublin survived and grew inside cells, while the spvR mutant did not proliferate. These results suggest that the spv genes of S. dublin promote enhanced intracellular proliferation in intestinal tissues and at extraintestinal sites in the natural host.

Animals↗
PubMed1996

Use of extracorporeal shock wave lithotripsy for treatment of nephrolithiasis and ureterolithiasis in five dogs.

The safety and efficacy of extracorporeal shock wave lithotripsy in 5 dogs with nephrolithiasis and ureterolithiasis was assessed. Three dogs had bilateral nephrolithiasis, 1 had bilateral nephrolithiasis and unilateral ureterolithiasis, and 1 had unilateral nephrolithiasis and unilateral ureterolithiasis. A first-generation lithotriptor was used for all treatments. None of the dogs developed clinically important complications during or after treatment, except for 1 dog treated for bilateral nephrolithiasis that developed transient ureterolithiasis. Renal function was unchanged in all dogs following treatment. Clinical signs resolved in all dogs. Extracorporeal shock wave lithotripsy appears to be a safe and effective means of treating nephrolithiasis and ureterolithiasis in dogs and appears to cause less renal parenchymal damage and renal function loss than does nephrotomy.

Animals↗
PubMed1996

Intracellular survival of Brucella abortus, Mycobacterium bovis BCG, Salmonella dublin, and Salmonella typhimurium in macrophages from cattle genetically resistant to Brucella abortus.

Peripheral blood monocyte-derived macrophages were obtained from a herd of cows selected, bred, and confirmed as resistant or susceptible by in vivo challenge of Brucella abortus Strain 2308. The ability to control in vitro intracellular bacterial replication of B. abortus Strain 2308, Mycobacterium bovis Bacillus Calmette-Guerin (BCG) Montreal Strain 9003, Salmonella dublin Strain 5631, and Salmonella typhimurium Strain 14028 was evaluated in a bactericidal assay. The macrophages from resistant cattle were significantly superior (P < 0.05) in controlling intracellular growth of B. abortus, M. bovis BCG, S. dublin but not of S, typhimurium than macrophages from susceptible animals. Controls of all four pathogens correlated strongly with each other in resistant or susceptible macrophages. Data from resistant cattle had a tighter grouping than that of susceptible cattle, while data from susceptible cattle overlapped considerably with data from resistant animals. Therefore, this assay was considered a phenotypic marker of the resistant trait. For each bacterial species a percent bacterial survival value was used as a cut-off point to designate animals as resistant or susceptible. These data were compared with the in vivo challenged resistant or susceptible classification by using the Chi-square analyses. A cut-off point of 70 percent bacterial survival for B. abortus designated 14 cattle as susceptible and seven as resistant and this correlated 100 percent with the number of animals designated as to the relevant category by in vivo challenge. A value of 65 percent bacterial survival for M. bovis BCG, and 100 percent bacterial survival for S. dublin correlated highly with actual numbers of animals designated as susceptible or resistant.

Animals↗
PubMed1996

Bovine natural resistance associated macrophage protein 1 (Nramp1) gene.

The Bcg/Ity/Lsh locus is a major gene controlling early phases of infection with intracellular parasites in mice. Natural resistance associated macrophage protein 1 (Nramp1) has been shown to be the Bcg gene in mice. Analysis of a bovine cDNA homolog of murine Nramp1, designated as bovine NRAMP1, predicted a 548-amino-acid protein with hydrophobic domains, an amino-terminal SH3-binding domain, and a conserved consensus transport motif. Northern blotting indicated that bovine NRAMP1 was expressed primarily in macrophages and tissues of the recticuloendothelial system. Bovine NRAMP1 was mapped to BTA 2 within syntenic loci conserved on HSA 2q and MMU 1.

Amino Acid Sequence↗
PubMed1996

Immunological response to the Brucella abortus GroEL homolog.

Western blot (immunoblot) analysis of sera from cattle vaccinated with Brucella abortus S19 exhibit an elevated serologic response to Hsp62, the GroEL homolog (BaGroEL). Serologic screening of individual cows vaccinated with B. abortus S19 revealed no correlation between the immune response to BaGroEL and protection against a challenge with virulent organisms. The humoral immune response to BaGroEL was restricted to a region of the mature protein which mapped to amino acids 317 to 355 and may represent a useful diagnostic tool for monitoring exposure to B. abortus. Immunity to a challenge with virulent B. abortus S2308 was not observed in the BaGroEL vaccinated mouse model.

Animals↗
PubMed1996

Identification of a polymorphic nucleotide in oxyR specific for Mycobacterium bovis.

Automated sequence analysis of a 410-bp region of the axyR gene in 105 Mycobacterium tuberculosis complex isolates identified a polymorphic nucleotide that differentiated Mycobacterium bovis isolates from other complex members. All 29 M. bovis isolates sequenced had an adenine residue at nucleotide 285, whereas all 76 other complex isolates had a guanine residue. PCR-restriction fragment length polymorphism analysis of oxyR with restriction endonuclease AluI in an additional 255 complex isolates from widespread intercontinental sources confirmed and extended the unique association of adenine at position 285 with M. bovis isolates.

Adenosine↗
PubMed1996

Molecular epidemiology of Mycobacterium bovis in Texas and Mexico.

Seventy-nine Mycobacterium bovis isolates recovered from Mexican and Texas cattle were categorized into 16 and 25 distinct types on the basis of IS6110 and direct-repeat fingerprint patterns, respectively. By using a combination of both fingerprint patterns, 30 distinct restriction fragment length polymorphism types were defined. Fifty-eight of 79 isolates (73%) were distributed among nine clusters. Clustered isolates were identified within herds, as well as in geographically disperse herds in Texas and Mexico. This observation is consistent with active transmission within herds and among herds, presumably as a result of active or historical cattle movements. The majority of bovine isolates (64 of 79) exhibited a single copy of IS6110. Interestingly, in contrast to previous studies, a high percentage of bovine isolates (15 of 79) exhibited multiple IS6110 copies (two to five) distributed among 11 different restriction fragment length polymorphism types. It is speculated that transmission from noncattle sources may be responsible. Continued fingerprinting of isolates originating from nonbovine sources and herd surveys is expected to provide useful information regarding the epidemiology of tuberculosis in this region.

Animals↗
PubMed1996

The pathogenicity of Brucella suis biovar 4 for bison.

The pathogenicity of Brucella suis biovar 4 for bison (Bison bison) was evaluated by inoculation of 2.1 x 10(7) colony forming units (CFU) in 0.1 ml saline into the conjunctival sac of six pregnant cows. Six pregnant bison were inoculated with 1.27 x 10(7) CFU of Brucella abortus strain 2308 as a positive control. Bison were inoculated on 23 January 1992, and observed until calving or abortion after which they were euthanized, and necropsied. Bacteriological and histological examinations were conducted on lymph nodes, reproductive tract, mammary gland, and internal organs. Terminal serum samples from calves and cows were evaluated by card, rivanol precipitation, standard tube agglutination, cold complement fixation tube, indirect bison conjugated enzyme linked immunosorbent assay (ELISA), competitive ELISA, and particle-concentration fluorescence immunoassay. No clinical signs of brucellosis were seen in bison inoculated with B. suis biovar 4, and infection was found only in lymph nodes of two animals. There was no evidence of metastasis of this organism to the mammary gland or the reproductive tract. There were no detectable levels of antibodies to Brucella spp. in terminal blood samples taken from B. suis biovar 4-challenged bison. Brucella abortus was isolated from several tissues in all control bison. All B. abortus-challenged animals developed uterine infection and five developed mammary gland infection. Reproductive disease resulted in abortions in five B. abortus-challenged bison and neonatal death in the remaining calf. Brucella suis biovar 4 does not appear to be pathogenic for bison.

Abortion, Veterinary↗
PubMed1996

Nephrotoxicity of amphotericin B administered to dogs in a fat emulsion versus five percent dextrose solution.

OBJECTIVE: To determine whether administration of amphotericin B in a fat emulsion solution would reduce the nephrotoxicity of amphotericin B, compared with that associated with administration of amphotericin B in 5% dextrose solution. DESIGN: Prospective controlled study. ANIMALS: 2 groups of 5 adult male Beagles. PROCEDURE: Dogs received amphotericin B (1 mg/kg of body weight/d) prepared in 5% dextrose solution or in 20% fat emulsion daily for 6 doses. Serum biochemical analysis, CBC, urinalysis, and endogenous creatinine clearance was performed on days 0 and 8, 2 days after the last dose of amphotericin B. On day 8, dogs were euthanatized and gross necropsies were performed. Unbiased semiquantitative scoring of the kidneys for the degree of injury was performed by use of light microscopy. RESULTS: There were no significant differences in serum creatinine, urea nitrogen, or potassium concentrations, urine specific gravity, endogenous creatinine clearance, or degree of tubulo-interstitial injury between the 2 groups. CONCLUSION: In this model, the degree of nephrotoxicity of amphotericin B was not significantly different for dogs receiving the drug in a fat emulsion versus its administration in 5% dextrose.

Amphotericin B↗
PubMed1995

Genetic heterogeneity in isogenic homozygous clonal zebrafish.

The C32 isogenic homozygous diploid (IHD) strain of the zebrafish (Danio rerio) was found to be polyallelic at a malate dehydrogenase locus (sMdh-A). A variant allele is thought to have arisen via mutation within the past 10 bisexual generations that have maintained the strain since its last gynogenetic cloning event; this unique allele now predominates at the sMdh-A locus. The estimated mutation rate in this species is sufficiently high that long-term genetic homogeneity of its IHD clones cannot be assumed. Researchers using such bisexually maintained clones should be aware that they are not necessarily using genetically uniform subjects. Genetic uniformity of cloned IHD zebrafish will be maximized if experimental subjects are obtained soon after a cloning event.

Alleles↗
PubMed1995

The lesions of hepatic fatty cirrhosis in sheep.

During a natural outbreak of hepatic fatty cirrhosis (HFC) in western Texas, 500 2-6-year-old Rambouillet ewe sheep were sequentially studied to determine the pattern of lesion development. All sheep developed lesions of HFC. Grossly, changes first began in the subcapsular hepatic parenchyma along the porta hepatis and spread peripherally until, in the final stages of the disease, approximately 80% of the liver was affected. Ascites, hydropericardium, and acquired hepatic vascular shunts were present in sheep with severe HFC. Light microscopic lesions initially appeared as accumulations of fine lipid droplets in the cytoplasm of periacinar hepatocytes but, with time, involved all hepatocytes of the lobule. The fat vacuoles in the periacinar hepatocytes coalesced to form larger vacuoles; and after rupture of adjacent fat-laden hepatocytes, fatty cysts appeared. Fibrosis began in the periacinar zone associated with the ruptured fatty cysts and continued until there was widespread bridging periacinar fibrosis. Islands of regenerating hepatocytes were frequently sequestered within the bands of fibrous tissue. Characteristically, the hepatic and posterior mediastinal lymph nodes, lung, and spleen contain ceroid. No lesions of hepatic encephalopathy were found in any animal. HFC is a progressive, chronic disease of sheep, and the morphology of the hepatic lesions is similar to lipotrope-deficient forms of nutritional cirrhosis. These findings are discussed in relation to similar nutritional deficiencies and toxicoses in sheep.

Animals↗
PubMed1994

Mechanisms of binding of Brucella abortus to mononuclear phagocytes from cows naturally resistant or susceptible to brucellosis.

During the course of bovine brucellosis, Brucella abortus adheres to and infects cells of the mononuclear phagocyte system. Potential mechanisms of binding, as measured by numbers of phagocytosed bacteria, were studied in two populations of cattle genetically resistant (R) or susceptible (S) to infection with B. abortus. Live B. abortus gained entry into cultured bovine macrophages without organism-specific opsonization. Bacterial entry into macrophages from R was inhibited by the peptide RGDS, outer membrane-peptidoglycan complex from B. abortus strain RB51, anti-LFA-1 monoclonal antibody, anti-C3 antiserum, fibronectin, purified O-antigen from B. abortus lipopolysaccharide, mannan and heat-aggregated IgG. Bacterial entry into macrophages from S was inhibited by outer membrane-peptidoglycan complex, anti-LFA-1 monoclonal antibody, O-antigen and heat-aggregated IgG. The peptide RGES did not inhibit entry into macrophages from R or S. These data support the existence of organism-related receptors on monocyte-derived macrophages for B. abortus which mediate binding in the absence of serum. Secondly, there are demonstrable differences in mechanisms of binding of B. abortus to cells from cattle genetically resistant or susceptible to infection by this organism. These findings further substantiate the importance of phagocytosis and clearance functions of the mononuclear phagocyte system in resistance to bovine brucellosis. Perpetuation of infection in susceptible cattle may occur by establishing an intracellular reservoir of viable organisms. Further studies are necessary to investigate receptor affinities, and the potential for an alternate receptor for this organism in S cattle.

Animals↗
PubMed1994

Influence of dietary protein/calorie intake on renal morphology and function in cats with 5/6 nephrectomy.

BACKGROUND: Although still controversial, several studies in humans have suggested That dietary protein restriction may slow the rate of progression of chronic renal failure. Thus, the influence of dietary protein on renal function and progression of renal failure has been the subject of numerous studies in several animal models of chronic renal failure, including rodents, dogs, and baboons. Because of the high incidence of chronic renal failure in aged cats, and the high dietary protein requirements of cats, we studied the effects of dietary protein intake on renal function, proteinuria, and renal morphology in cats with reduced renal mass. EXPERIMENTAL DESIGN: Partial (5/6) nephrectomy was performed in 14 young adult female cats. Sham surgical procedures were performed in eight control cats. Control cats and cats with 5/6 nephrectomy were randomly assigned to diets containing either 27.6% (low) or 51.7% (high) protein and studied for 1 year. RESULTS: Renal mass reduction by 5/6 decreased glomerular filtration rate by 2/3 and significantly increased proteinuria. Cats with remnant kidneys had significantly higher systolic and mean blood pressures than control cats. Increased dietary protein/calorie intake significantly increased glomerular filtration rate and proteinuria in all cats. Glomerular filtration rates remained stable in all cats over the year of study. However, high protein/calorie intake resulted in significant renal morphologic injury in remnant kidney cats that was prevented by dietary protein/calorie restriction. Light and electron microscopic glomerular changes in remnant kidney cats fed the high protein diet were similar to changes previously reported in rats and dogs with remnant kidneys. CONCLUSIONS: Dietary protein/calorie restriction limits proteinuria and glomerular injury in cats with remnant kidneys in a fashion similar to that reported in rats. However, the remnant kidney model in the cat appeared to be associated with a slower rate of progression compared with kidney model in the cat appeared to be associated with a slower rate of progression compared with rats.

Animals↗
PubMed1993

Modulation of the intracellular survival of Brucella abortus by tuftsin and muramyl dipeptide.

Tuftsin, a physiologic bioactive peptide of animal origin, and muramyl dipeptide, a synthetic bioactive glycopeptide of microbial origin, are known to enhance several recognized macrophage functions and increase non-specific resistance of the host against a number of pathogens. The influence of these two bioactive peptides was studied in permissive bovine mammary macrophages that were unable to control the intracellular replication of Brucella abortus and restrictive bovine mammary macrophages that were able to effectively reduce the intracellular survival of B. abortus. Addition of tuftsin (Thr-Lys-Pro-Arg) or muramyl dipeptide significantly (P < 0.03) enhanced the ability of the permissive macrophages to control the intracellular replication of B. abortus strain 2308 and resulted in the functional conversion of the permissive macrophages into restrictive macrophages. Addition of tripeptide tuftsin fragment (Lys-Pro-Arg), a natural inhibitor of tuftsin, to the medium completely abrogated the effect of tuftsin (P < 0.03). No additive effect on the ability of the macrophages to control the survival of B. abortus resulted from the combination of tuftsin and muramyl dipeptide.

Acetylmuramyl-Alanyl-Isoglutamine↗