Biomedical subjects

C Broussard

Publications and source records attributed to C Broussard.

9 recordsLinked to original sources

PubMed2006

Increased level of Eimeria sensitivity to diclazuril after using a live coccidial vaccine.

Anticoccidial vaccine and an anticoccidial drug rotation program were compared to determine which program was more effective in producing coccidia populations sensitive of 1 ppm diclazuril. The study used an anticoccidial drug-sensitivity battery test (AST) to determine the baseline level of diclazuril sensitivity to field isolates of Eimeria spp. from seven broiler complexes that had used diclazuril. Based on percentage reduction in weight gain and lesion scores, 25% or fewer of the isolates were effectively controlled by diclazuril. Following the baseline sampling, four of the complexes switched to a nondiclazuril in-feed anticoccidial drug program and three of the complexes switched to a vaccination program for two broiler grow-out cycles as the sole coccidiosis-control program. This study demonstrated that the vaccine used (Coccivac-B) contained anticoccidial drug-sensitive strains. Eimeria isolates were subsequently collected from the identical houses and diclazuril AST results were compared with the baseline AST results. Following the two grow-out cycles, sensitivity of the isolates to diclazuril from the four complexes that continued to use in-feed anticoccidial drugs remained essentially unchanged. The isolates from the three complexes that switched to the vaccination program demonstrated a marked increase in diclazuril sensitivity, with 60%-100% of the isolates from each complex effectively controlled by diclazuril. Vaccination with the anticoccidial drug-sensitive strains produced a measurable increase in the level of sensitivity to diclazuril.

Animals↗

PubMed2001

Tec kinases: modulators of lymphocyte signaling and development.

The Tec kinases are implicated as important components of the antigen receptor signaling required for proper lymphocyte activation and development. Recent data suggest that these kinases contribute to multiprotein complexes containing LAT and SLP-76 in T cells, and BLNK/SLP-65 in B cells, which are required for activation of PLC-gamma and downstream pathways.

Animals↗

PubMed2000

Tec family kinases modulate thresholds for thymocyte development and selection.

Tec family kinases are implicated in T cell receptor (TCR) signaling, and combined mutation of inducible T cell kinase (Itk) and resting lymphocyte kinase (Rlk)/Txk in mice dramatically impairs mature T cell function. Nonetheless, mutation of these kinases still permits T cell development. While itk(-)(/)- mice exhibit mild reductions in T cells with decreased CD4/CD8 cell ratios, rlk(-)(/)-itk(-)(/)- mice have improved total T cell numbers yet maintain decreased CD4/CD8 ratios. Using TCR transgenics and an in vitro thymocyte deletion model, we demonstrate that mutation of Tec kinases causes graded defects in thymocyte selection, leading to a switch from negative to positive selection in rlk(-)(/)-itk(-)(/)- animals. The reduction in both positive and negative selection and decreased CD4/CD8 ratios correlates with decreased biochemical parameters of TCR signaling, specifically defects in capacitive Ca(2+) influx and activation of the mitogen-activated kinases extracellular signal-regulated kinase 1 and 2. Thus, Tec kinases influence cell fate determination by modulating TCR signaling, leading to altered thresholds for thymocyte selection. These results provide support for a quantitative model for thymic development and provide evidence that defects in negative selection can substantially alter thymic cellularity.

Animals↗

PubMed2000

Conditional deletion of the Bcl-x gene from erythroid cells results in hemolytic anemia and profound splenomegaly.

Bcl-x is a member of the Bcl2 family and has been suggested to be important for the survival and maturation of various cell types including the erythroid lineage. To define the consequences of Bcl-x loss in erythroid cells and other adult tissues, we have generated mice conditionally deficient in the Bcl-x gene using the Cre-loxP recombination system. The temporal and spatial excision of the floxed Bcl-x locus was achieved by expressing the Cre recombinase gene under control of the MMTV-LTR. By the age of five weeks, Bcl-x conditional mutant mice exhibited hyperproliferation of megakaryocytes and a decline in the number of circulating platelets. Three-month-old animals suffered from severe hemolytic anemia, hyperplasia of immature erythroid cells and profound enlargement of the spleen. We demonstrate that Bcl-x is only required for the survival of erythroid cells at the end of maturation, which includes enucleated reticulocytes in circulation. The extensive proliferation of immature erythroid cells in the spleen and bone marrow might be the result of a fast turnover of late red blood cell precursors and accelerated erythropoiesis in response to tissue hypoxia. The increase in cell death of late erythroid cells is independent from the proapoptotic factor Bax, as demonstrated in conditional double mutant mice for Bcl-x and Bax. Mice conditionally deficient in Bcl-x permitted us for the first time to study the effects of Bcl-x deficiency on cell proliferation, maturation and survival under physiological conditions in an adult animal.

Anemia, Hemolytic↗

PubMed1998

Portal decompression by transjugular intrahepatic portosystemic shunt and changes in serum-ascites albumin gradient.

The serum ascites albumin gradient (SAAG) is widely used to help determine the cause of ascites formation. A serum ascites albumin gradient of > or = 1.1 g/dL reliably distinguishes portal hypertension-related ascites from other causes. To date, there are no published data on the impact of portal decompression on this gradient. The recent development of transjugular intrahepatic portosystemic shunt (TIPS) allows for nonsurgical decompression of portal hypertension by radiologically creating a portosystemic shunt. This study examines the short-term impact of portal decompression on the serum ascites albumin gradient (SAAG) in patients with portal hypertension-related ascites undergoing transjugular intrahepatic portosystemic shunt. Portal pressure measurements were obtained before and after TIPS placement. Serum ascites albumin gradient was determined before and at 6 and 24 hours post-TIPS placement. Fifteen patients were enrolled in the study. The mean portosystemic gradient (PSG) before TIPS was 21.0 +/- 9.2 mmHg, whereas the post-TIPS mean PSG was reduced to 11.0 +/- 6.3 mmHg, consistent with portal decompression (p = 0.005). The mean pre-TIPS serum ascites albumin gradient was 1.9 +/- 0.5 g/dL and was reduced to 1.7 +/- 0.5 g/dL at 6 hours (p = 0.003) and 1.4 +/- 0.4 g/dL at 24 hours (p = 0.002) after TIPS placement. These findings further solidify the association between the SAAG and portal hypertension.

Adult↗

PubMed1997

A preliminary analysis of interactive effects between common classroom contingencies and methylphenidate.

To assess the drug-behavior interaction effects with an 8-year-old boy wih attention deficit hyperactivity disorder, common classroom antecedent (e.g., seating arrangement) and consequent (e.g., peer prompts) stimuli were alternated within a school day while drug conditions (methylphenidate vs. placebo) were alternated across days. The results suggested that peer attention maintained disruptive behavior when methylphenidate was absent but not when it was present.

Attention Deficit Disorder with Hyperactivity↗

PubMed1996

A comparison of reinforcer assessment methods: the utility of verbal and pictorial choice procedures.

We compared three methods of stimulus preference assessment for verbal children and specifically evaluated the utility of a verbal choice procedure for assessing relative reinforcer value. Using a token system, relative preference for five categories of reinforcers, representing 15 different stimuli, was assessed by three methods: a reinforcer survey, a verbal stimulus-choice questionnaire, and a pictorial stimulus-choice procedure. Results showed that the verbal and pictorial stimulus-choice assessments accurately identified high- and low-preference categories for 3 of 4 participants. Survey results alone often rated multiple categories as high preference, were less likely to identify low-preference categories, and were less likely to correspond with the results of a reinforcer assessment.

Attention Deficit Disorder with Hyperactivity↗

PubMed1995

The differential effects of teacher and peer attention on the disruptive classroom behavior of three children with a diagnosis of attention deficit hyperactivity disorder.

We conducted functional analyses of classroom disruption during contingent teacher and peer attention conditions for 3 children with attention deficit hyperactivity disorder. Attention provided by peer confederates appeared to function as a distinct form of positive reinforcement for all 3 children.

Attention↗

PubMed1995

A preliminary comparison of reinforcer assessment methods for children with attention deficit hyperactivity disorder.

We evaluated the relative treatment utility of a verbal forced-choice questionnaire, child nomination, and direct observation for identifying the most potent reinforcers for children with attention deficit hyperactivity disorder. Results demonstrated that all three methods were more likely to disagree than to agree, that a forced-choice format may enhance verbal reinforcer assessment, and that further development and evaluation of verbal reinforcer-assessment methods are needed.

Attention Deficit Disorder with Hyperactivity↗