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Biomedical subjects

H Boermans

Publications and source records attributed to H Boermans.

7 recordsLinked to original sources
PubMed2001

Molecular cloning and expression of human bile acid beta-glucosidase.

A novel microsomal beta-glucosidase was recently purified and characterized from human liver that catalyzes the hydrolysis of bile acid 3-O-glucosides as endogenous compounds. The primary structure of this bile acid beta-glucosidase was deduced by cDNA cloning on the basis of the amino acid sequences of peptides obtained from the purified enzyme by proteinase digestion. The isolated cDNA comprises 3639 base pairs containing 524 nucleotides of 5'-untranslated and 334 nucleotides of 3'-untranslated sequences including the poly(A) tail. The open reading frame predicts a 927-amino acid protein with a calculated M(r) of 104,648 containing one putative transmembrane domain. Data base searches revealed no homology with any known glycosyl hydrolase or other functionally identified protein. The cDNA sequence was found with significant identity in the human chromosome 9 clone RP11-112J3 of the human genome project. The recombinant enzyme was expressed in a tagged form in COS-7 cells where it displayed bile acid beta-glucosidase activity. Northern blot analysis of various human tissues revealed high levels of expression of the bile acid beta-glucosidase mRNA (3.6-kilobase message) in brain, heart, skeletal muscle, kidney, and placenta and lower levels of expression in the liver and other organs.

Amino Acid Sequence↗
PubMed2000

Flow cytometry as a tool to monitor the disturbance of phagocytosis in the clam Mya arenaria hemocytes following in vitro exposure to heavy metals.

The effectiveness of toxicology biomonitoring programs could be improved by the addition of sensitive biomarkers. In this study the cell viability and sensitivity of phagocytic function of phagocytes from bivalves (Mya arenaria) to selected heavy metals were measured by flow cytometry, a novel approach. Hemocytes (phagocytes) collected from bivalves by puncture of the posterior adductor muscle were incubated in vitro for 18 h in hemolymph containing 10(-9)-10(-3)M of cadmium chloride, zinc chloride, mercuric chloride, methylmercury chloride or silver nitrate, before determining their capacity to phagocytose fluorescent latex beads by flow cytometry. Heterogeneity of the hemocyte cell population was determined by forward scatter (FSC) and side scatter (SSC) cytometric profile which showed two distinct cell populations. At low doses (10(-9), 10(-8) M), all the metal compounds studied stimulated phagocytic activity except silver nitrate. At higher levels of exposure (10(-6), 10(7) M), all metals caused a significant concentration-related decrease in hemocyte phagocytosis activity. From the concentration of each metal inducing 50% suppression (IC50) of the phagocytic activity, the immunotoxic potential of metals with respect to phagocytic function can be ranked in the following increasing order: ZnCl2 < CdCl2 < AgNO3 < HgCl2 < CH3HgCl. Parallel analysis of hemocyte viability showed that suppression of phagocytosis by heavy metals was not solely related to a decreased cell viability. These results reveal the high but different degree of sensitivity of the phagocytosis activity of bivalves with respect to heavy metals, as measured by flow cytometry, and demonstrate that flow cytometry is a potentially useful tool in ecotoxicological monitoring.

Animals↗
PubMed1999

Effect of chlorpyrifos on immune function in rats.

A commercial formulation of chlorpyrifos was evaluated for effects on selected immune system functions in male Fisher 344 rats. Chlorpyrifos in an olive oil vehicle was administered by oral gavage twice weekly for 28 d at a dose of 5.0 mg/kg for each treatment. Body weight and organ/body weight ratios were unaffected by the chlorpyrifos. In contrast, chlorpyrifos impaired T-lymphocyte blastogenesis induced by concanavalin A (P = 0.03) and phytohemagglutinin (P = 0.023), but did not alter B-lymphocyte blastogenesis induced by lipopolysaccharide/dextran (P = 0.082. Humoral immunity (anti-sheep red blood cell), a T-lymphocyte macrophage-dependent response, was also reduced (P = 0.019) when the antibody response was expressed/10(6) spleen cells, although the response expressed/spleen was unaffected (P = 0.32), reflecting increased lymphocyte production. The total splenic lymphocyte counts in the chlorpyrifos-treated rats increased by 91% (P < 0.0001), therefore reducing the antibody response when expressed/10(6) spleen cells. Chlorpyrifos had no effect on macrophage phagocytosis (P = 0.27), but increased the relative percentage expression of CD5+ (P = 0.028) and CD8+ (P = 0.003). The presence of normal antibody and phagocytic responses in association with reduced T-lymphocyte blastogenesis and enhanced expression of specific cell surface antigens indicated that chlorpyrifos induced immune alterations associated with lymphocyte subpopulations.

Animals↗
PubMed1998

Effect of pentachlorophenol on immune function.

The organochlorine compound, pentachlorophenol, was evaluated for effects on immune system function in male Fisher 344 rats. Pentachlorophenol was prepared in an olive oil vehicle and was administered by oral gavage twice weekly for 28 days at a dose of 2.0 mg/kg per treatment. Exposure to pentachlorophenol increased body weight gains (P=0.024) during the treatment period. Liver (P=0.034) and kidney (P=0.012) body weight ratios were also increased. Pentachlorophenol exposure enhanced T-lymphocyte blastogenesis induced by concanavalin A (Con A)(P=0.0001) and phytohemagglutinin (PHA)(P=0.048) evaluated using stimulation indices. Corresponding B-lymphocyte blastogenesis induced by lipopolysaccharide/dextran (LPS/dex)(P=0.0034) was also enhanced by pentachlorophenol exposure. Pentachlorophenol suppressed the antibody response against sheep red blood cells (SRBCs) by 39% when the response was expressed per viable spleen cell (P=0.006). This suppression was not evident when the response was expressed per spleen (P=0.22), suggesting that a compensatory mechanism or extramedullary splenic hemopoiesis was occurring minimizing the overall impact on humoral immunity. The enhanced B- and T-lymphocyte blastogenesis may also reflect compensatory or hemopoietic activity. Pentachlorophenol exposure had no effect on peritoneal macrophage phagocytosis (P=0.31) or lymphocyte cell surface antigen expression. The observed alterations in lymphocyte blastogenesis and humoral immunity subsequent to pentachlorophenol exposure do not appear to be associated with phagocytosis or lymphocyte cell surface antigen expression.

Animals↗
PubMed1998

Effect of 2,4-dicholorophenoxyacetic acid, trifluralin and triallate herbicides on immune function.

The commercial formulations of 3 commonly used herbicides (the amine salt of 2,4-dichlorophenoxyacetic acid, trifluralin and triallate) were evaluated for effects on immune function in male Fisher 344 rats. The herbicides were prepared in an olive oil vehicle and administered by oral gavage twice weekly for 28 d at the following doses: 10.0 mg 2,4-D/kg; 17.5 mg trifluralin/kg; 5.0 mg triallate/kg/treatment. Normal body weight and organ/body weight ratios indicated the rats tolerated the herbicide treatments without difficulty. Exposure to 2,4-D did not alter lymphocyte blastogenesis, 1 gm antibody production (anti-sheep red blood cell), lymphocyte cell surface marker expression or phagocytic function of peritoneal macrophages. Trifluralin acted as a weak mitogen, but impaired T-lymphocyte blastogenesis induced by phytohemagglutinin and concanavalin A. Other immunological measurements were unaffected by trifluralin exposure. Triallate exposure reduced peritoneal macrophage phagocytosis by 33%, showed weak mitogenic properties and impaired T-lymphocyte blastogenesis in the presence of phytohemagglutin. Triallate also increased the anti-sheep red blood cell response expressed/spleen by 43%, a phenomenon suggestive of a compensatory response to minimize the impact on overall immune function. The changes in lymphocyte or macrophage function due to the herbicide treatments were not associated with changes in lymphocyte cell surface antigen expression.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1990

An investigation of bulk tank milk selenium levels in the San Joaquin Valley of California.

We evaluated selenium determination of bulk milk tank samples as an alternative to testing blood selenium for evaluating herd selenium status in DHIA dairy herds in the San Joaquin Valley of California. A method of determining milk selenium levels using inductively coupled plasma spectrometry is described. Mean bulk tank milk selenium levels were 0.0224 mg/L (Range 0.0126-0.0418 mg/L). No statistically significant relationships were found between bulk tank milk selenium levels of a herd and calving interval, days open or log somatic cell counts. Mean herd blood and milk levels were directly proportional to bulk tank milk selenium levels. Within a herd milk selenium levels of a cow were directly proportional to the cow's blood selenium level. Herd selenium levels were not significantly related to soil selenium levels. Determination of bulk tank milk selenium levels has the potential to be a low cost, non-invasive means of evaluating herd selenium levels in order to determine selenium deficiency. Further studies with this technique in areas which are deficient in selenium may provide estimates of the sensitivity, specificity and predictive value of bulk milk tank selenium for determining selenium deficiency in dairy herds.

Analysis of Variance↗