Biography:

In the past Pradeep K. Dudeja has collaborated on articles with Thomas A. Brasitus and Rajvir Dahiya. One of their most recent publications is CommunicationAlterations in the physical state and composition of brush border membrane lipids of rat enterocytes during differentiation. Which was published in journal Archives of Biochemistry and Biophysics.

More information about Pradeep K. Dudeja research including statistics on their citations can be found on their Copernicus Academic profile page.

Pradeep K. Dudeja's Articles: (12)

CommunicationAlterations in the physical state and composition of brush border membrane lipids of rat enterocytes during differentiation

AbstractThe physical state of the membrane lipid of brush border membranes, prepared from rat small intestinal villus and crypt cells, was examined by steady-state fluorescence polarization using three lipid-soluble fluorophors. Membranes prepared from crypt cells were found to possess a higher lipid fluidity than those of villus cells with each probe. Analysis of the composition of these membranes revealed that those from crypt cells had lower ratios of cholesterol/phospholipid (mol/mol), protein/lipid (ww), and saturated fatty acyl chains/unsaturated chains (ww). Alterations in the levels of stearic (18:0) and oleic (18:1) acids were responsible for differences in the latter ratio. The results, therefore, demonstrate that alterations in the lipid composition and fluidity of brush border membranes of enterocytes occur during the process of differentiation.

Identification and partial characterization of phospholipid methylation in rat small-intestinal brush-border membranes

AbstractAn earlier study (Biochim. Biophys. Acta 46 (1961) 205–216) failed to detect the enzymatic synthesis of phosphatidylcholine (PC) from phosphatidylethanolamine (PE) via a transmethylation pathway in rat small-intestinal microsomal membranes. This pathway was therefore assumed to be absent from this organ. Recently, however, in our laboratory it has been demonstrated that this pathway for the synthesis of phosphatidylcholine is present in rat colonic brush-border and basolateral membranes. It was therefore of interest to examine whether phospholipid methylation activity was present in rat small-intestinal brush-border membranes. The results of the present experiments demonstrate for the first time that this pathway for the synthesis of phosphatidylcholine exists in these plasma membranes. Evidence to support the enzymatic nature of this reaction include: (1) loss of activity by heat denaturation and at 0°C, (2) significant inhibition by S-adenosyl-l-homocysteine and (3) saturation kinetics. The predominant product of this brush-border membrane phospholipid methyltransferase is phosphatidyl-N-monomethylethanolamine. This enzymatic activity has an apparent Km for S-adenosyl-l-methionine of 40 μM, a Vmax of 8.4 pmol/mg protein per 5 min, and a pH optimum of 8.0.

BBA reportEstrogen-induced alterations of the acidic and neutral glycosphingolipids of rat kidney

AbstractIn order to determine whether female sex hormones could influence the glycosphingolipid composition of the rat kidney, male albino rats of the Sherman strain were subcutaneously administered the synthetic estrogen, ethinylestradiol (5 mg/kg body wt. per day) or vehicle for 5 days, and the ganglioside, ceramide and neutral glycosphingolipid compositions of the kidneys of these animals were analyzed and compared. The results of these experiments demonstrate that estrogen treatment: (1) increased the ceramide, acidic and neutral glycosphingolipid contents of this tissue; (2) decreased the relative percentages of glucosyl- and globotetraosylceramide and hematoside (GM3), but increased the relative percentage of globotriaosylceramide and ‘other’ gangliosides; (3) increased the relative percentage of N-acetyl- to N-glycolylneuraminic acid in GM3; and (4) altered the long-chain bases of GM3, glucosyl- and globotetraosylceramide in this organ. These data, therefore, demonstrate that estrogen administration induces quantitative and qualitative alterations in the gangliosides, neutral glycosphingolipids and ceramide of the rat kidney. This data as well as a discussion of the possible physiological consequences of these estrogen-induced alterations in kidney glycosphingolipids serve as the basis for this report.

CommunicationAlterations in the physical state and composition of brush border membrane lipids of rat enterocytes during differentiation

AbstractThe physical state of the membrane lipid of brush border membranes, prepared from rat small intestinal villus and crypt cells, was examined by steady-state fluorescence polarization using three lipid-soluble fluorophors. Membranes prepared from crypt cells were found to possess a higher lipid fluidity than those of villus cells with each probe. Analysis of the composition of these membranes revealed that those from crypt cells had lower ratios of cholesterol/phospholipid (mol/mol), protein/lipid (ww), and saturated fatty acyl chains/unsaturated chains (ww). Alterations in the levels of stearic (18:0) and oleic (18:1) acids were responsible for differences in the latter ratio. The results, therefore, demonstrate that alterations in the lipid composition and fluidity of brush border membranes of enterocytes occur during the process of differentiation.

Identification and partial characterization of phospholipid methylation in rat small-intestinal brush-border membranes

AbstractAn earlier study (Biochim. Biophys. Acta 46 (1961) 205–216) failed to detect the enzymatic synthesis of phosphatidylcholine (PC) from phosphatidylethanolamine (PE) via a transmethylation pathway in rat small-intestinal microsomal membranes. This pathway was therefore assumed to be absent from this organ. Recently, however, in our laboratory it has been demonstrated that this pathway for the synthesis of phosphatidylcholine is present in rat colonic brush-border and basolateral membranes. It was therefore of interest to examine whether phospholipid methylation activity was present in rat small-intestinal brush-border membranes. The results of the present experiments demonstrate for the first time that this pathway for the synthesis of phosphatidylcholine exists in these plasma membranes. Evidence to support the enzymatic nature of this reaction include: (1) loss of activity by heat denaturation and at 0°C, (2) significant inhibition by S-adenosyl-l-homocysteine and (3) saturation kinetics. The predominant product of this brush-border membrane phospholipid methyltransferase is phosphatidyl-N-monomethylethanolamine. This enzymatic activity has an apparent Km for S-adenosyl-l-methionine of 40 μM, a Vmax of 8.4 pmol/mg protein per 5 min, and a pH optimum of 8.0.

BBA reportEstrogen-induced alterations of the acidic and neutral glycosphingolipids of rat kidney

AbstractIn order to determine whether female sex hormones could influence the glycosphingolipid composition of the rat kidney, male albino rats of the Sherman strain were subcutaneously administered the synthetic estrogen, ethinylestradiol (5 mg/kg body wt. per day) or vehicle for 5 days, and the ganglioside, ceramide and neutral glycosphingolipid compositions of the kidneys of these animals were analyzed and compared. The results of these experiments demonstrate that estrogen treatment: (1) increased the ceramide, acidic and neutral glycosphingolipid contents of this tissue; (2) decreased the relative percentages of glucosyl- and globotetraosylceramide and hematoside (GM3), but increased the relative percentage of globotriaosylceramide and ‘other’ gangliosides; (3) increased the relative percentage of N-acetyl- to N-glycolylneuraminic acid in GM3; and (4) altered the long-chain bases of GM3, glucosyl- and globotetraosylceramide in this organ. These data, therefore, demonstrate that estrogen administration induces quantitative and qualitative alterations in the gangliosides, neutral glycosphingolipids and ceramide of the rat kidney. This data as well as a discussion of the possible physiological consequences of these estrogen-induced alterations in kidney glycosphingolipids serve as the basis for this report.

CommunicationAlterations in the physical state and composition of brush border membrane lipids of rat enterocytes during differentiation

AbstractThe physical state of the membrane lipid of brush border membranes, prepared from rat small intestinal villus and crypt cells, was examined by steady-state fluorescence polarization using three lipid-soluble fluorophors. Membranes prepared from crypt cells were found to possess a higher lipid fluidity than those of villus cells with each probe. Analysis of the composition of these membranes revealed that those from crypt cells had lower ratios of cholesterol/phospholipid (mol/mol), protein/lipid (ww), and saturated fatty acyl chains/unsaturated chains (ww). Alterations in the levels of stearic (18:0) and oleic (18:1) acids were responsible for differences in the latter ratio. The results, therefore, demonstrate that alterations in the lipid composition and fluidity of brush border membranes of enterocytes occur during the process of differentiation.

Identification and partial characterization of phospholipid methylation in rat small-intestinal brush-border membranes

AbstractAn earlier study (Biochim. Biophys. Acta 46 (1961) 205–216) failed to detect the enzymatic synthesis of phosphatidylcholine (PC) from phosphatidylethanolamine (PE) via a transmethylation pathway in rat small-intestinal microsomal membranes. This pathway was therefore assumed to be absent from this organ. Recently, however, in our laboratory it has been demonstrated that this pathway for the synthesis of phosphatidylcholine is present in rat colonic brush-border and basolateral membranes. It was therefore of interest to examine whether phospholipid methylation activity was present in rat small-intestinal brush-border membranes. The results of the present experiments demonstrate for the first time that this pathway for the synthesis of phosphatidylcholine exists in these plasma membranes. Evidence to support the enzymatic nature of this reaction include: (1) loss of activity by heat denaturation and at 0°C, (2) significant inhibition by S-adenosyl-l-homocysteine and (3) saturation kinetics. The predominant product of this brush-border membrane phospholipid methyltransferase is phosphatidyl-N-monomethylethanolamine. This enzymatic activity has an apparent Km for S-adenosyl-l-methionine of 40 μM, a Vmax of 8.4 pmol/mg protein per 5 min, and a pH optimum of 8.0.

BBA reportEstrogen-induced alterations of the acidic and neutral glycosphingolipids of rat kidney

AbstractIn order to determine whether female sex hormones could influence the glycosphingolipid composition of the rat kidney, male albino rats of the Sherman strain were subcutaneously administered the synthetic estrogen, ethinylestradiol (5 mg/kg body wt. per day) or vehicle for 5 days, and the ganglioside, ceramide and neutral glycosphingolipid compositions of the kidneys of these animals were analyzed and compared. The results of these experiments demonstrate that estrogen treatment: (1) increased the ceramide, acidic and neutral glycosphingolipid contents of this tissue; (2) decreased the relative percentages of glucosyl- and globotetraosylceramide and hematoside (GM3), but increased the relative percentage of globotriaosylceramide and ‘other’ gangliosides; (3) increased the relative percentage of N-acetyl- to N-glycolylneuraminic acid in GM3; and (4) altered the long-chain bases of GM3, glucosyl- and globotetraosylceramide in this organ. These data, therefore, demonstrate that estrogen administration induces quantitative and qualitative alterations in the gangliosides, neutral glycosphingolipids and ceramide of the rat kidney. This data as well as a discussion of the possible physiological consequences of these estrogen-induced alterations in kidney glycosphingolipids serve as the basis for this report.

Chapter 22 - Diabetes Mellitus and Intestinal Niemann-Pick C1–Like 1 Gene Expression

AbstractThe Niemann-Pick type C1–like 1 (NPC1L1) protein is pivotal for intestinal absorption of cholesterol. Targeting NPC1L1 by ezetimibe causes a significant reduction in cholesterol absorption and lowers plasma cholesterol. However, treatment with ezetimibe alone may not be sufficient to decrease plasma cholesterol to a stringent low level set as a therapeutic target for individuals with high risk for developing cardiovascular diseases, such as diabetic patients. Indeed, studies showed that NPC1L1 expression is increased in diabetes mellitus, which may contribute to the pathophysiology of cardiovascular diseases associated with diabetes mellitus. Since NPC1L1-mediated cholesterol uptake is crucial for cholesterol homeostasis, there is an emerging interest to understand the molecular basis for its function and to delineate the regulation of its expression. This chapter summarizes the knowledge about the NCP1L1 structure–function relationship, molecular regulation, and the mechanisms by which NPC1L1 mediates cholesterol absorption. The chapter provides on overall evaluation of current understanding of NPC1L1 regulation and attempts to define potential aspects for future research endeavors.

Research articleCarrageenan-induced innate immune response is modified by enzymes that hydrolyze distinct galactosidic bonds

AbstractThe common food additive carrageenan (CGN) predictably induces intestinal inflammation in animal models. Mechanisms of CGN-induced nuclear factor κB and interleukin-8 (IL-8) stimulation include an immune-mediated pathway involving toll-like receptor 4 (TLR4) and B-cell lymphoma/leukemia 10 (BCL10) and a reactive oxygen species (ROS)-mediated pathway. To determine how the structure of CGN contributes to its initiation of inflammation through these two distinct mechanisms, we treated CGNs with galactosidases and carrageenases (CGNases) and determined the impact on IL-8 secretion and BCL10 production. Hydrolysis of CGN by the enzyme α-1→(3,6)-galactosidase significantly reduced increases in IL-8 and BCL10, but other galactosidases tested, including α-1→6-galactosidase, β-1→4-galactosidase and β-1→3,6-galactosidase, had no effect. In contrast, specific κ-CGNases or ι-CGNases, which hydrolyze β-1,4-galactosidic bonds, produced increases in IL-8 and BCL10 attributable to increased exposure of the immunogenic α-1→3-galactosidic epitope of CGN to TLR4. These results were consistent with induction of innate immune response by an interaction of TLR4 with the unusual α-d-Gal-(1→3)-d-Gal epitope present in CGN. Activation of the ROS-mediated pathway was unaffected by treatment of κ-CGN with either κ-CGNase (3 mg/L), α-1→(3,6)-galactosidase (20 mU/ml) or these enzymes in combination, indicating that changes in IL-8 production were attributable to the effects of induction of inflammation on the TLR4–BCL10-mediated innate immune pathway. These findings provide new information about the specificity of carbohydrate–protein interaction between CGN and TLR4 and may help to devise treatments that modify the immune reactivity induced by carbohydrate antigens.

Review ArticleBile acid receptors and gastrointestinal functions☆

AbstractBile acids modulate several gastrointestinal (GI) functions including electrolyte secretion and absorption, gastric emptying, and small intestinal and colonic motility. High concentrations of bile acids lead to diarrhea and are implicated in the development of esophageal, gastric and colonic cancer. Alterations in bile acid homeostasis are also implicated in the pathophysiology of irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). Our understanding of the mechanisms underlying these effects of bile acids on gut functions has been greatly enhanced by the discovery of bile acid receptors, including the nuclear receptors: farnesoid X receptor (FXR), vitamin D receptor (VDR), pregnane X receptor (PXR), and constitutive androstane receptor (CAR); and G protein-coupled receptors (GPCRs): Takeda G protein-coupled receptor 5 (TGR5), sphingosine-1-phosphate receptor 2 (S1PR2), and muscarinic acetylcholine receptor M3 (M3R). For example, various studies provided evidence demonstrating the anti-inflammatory effects of FXR and TGR5 activation in models of intestinal inflammation. In addition, the activation of TGR5 in enteric neurons was recently shown to increase colonic motility, which may lead to bile acid-induced diarrhea (BAD). Interestingly, TGR5 induces the secretion of glucagon-like peptide-1 (GLP-1) from L-cells to enhance insulin secretion and modulate glucose metabolism. Because of the importance of these receptors, agonists of TGR5 and intestine-specific FXR agonists are currently being tested as an option for the treatment of diabetes mellitus and primary bile acid diarrhea, respectively. This review summarizes current knowledge of the functional roles of bile acid receptors in the GI tract.

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