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J Ringel

Publications and source records attributed to J Ringel.

At least 19 recordsLinked to original sources
PubMed2002

Ribosomal highly basic 23-kDa protein as a reliable standard for gene expression analysis.

BACKGROUND/AIMS: Analysis of gene expression is dependent on normalization using housekeeping genes. However, many of these housekeeping genes (e.g. GAPDH, beta-actin) are upregulated in chronic pancreatitis and pancreatic cancer, and cannot be used for normalization. For this reason we tried to identify a housekeeping gene useful for expression analysis in pancreatic diseases. METHODS: RNA isolated from various tissues and states of disease was subjected to reverse transcription and subsequently amplified by PCR using primers for GAPDH and for the ribosomal highly basic 23-kDa (rb 23-kDa, RPL13A) protein. RESULTS: As anticipated, expression of GAPDH varied markedly in the different tissues, whereas the expression of rb 23-kDa was constant in all samples investigated. CONCLUSION: We recommend the use of the ribosomal highly basic 23-kDa protein as a standard for normalization at least for the pancreas and the prostate.

Gene Expression↗
PubMed2001

Transforming growth factor-beta1 induces desmoplasia in an experimental model of human pancreatic carcinoma.

Proliferation of fibrotic tissue (desmoplasia) is one of the hallmarks of several epithelial tumors including pancreatic adenocarcinoma. This tissue reaction may be deleterious or advantageous to the host or tumor. In a systematic analysis, we identified two growth factors expressed by human pancreatic carcinoma cells that are positively correlated with the ability to induce fibroblast proliferation both in vitro and in vivo, i.e., transforming growth factor (TGF)-beta1 and fibroblast growth factor-2. Here we demonstrate that the overexpression of TGF-beta1 induced up-regulation of matrix proteins and growth factors in the TGFbeta1-transfected pancreatic tumor cells. Furthermore, transfection of PANC-1 cells induces the same change in fibroblasts in either cocultivation experiments or when they are grown in conditioned medium from TGF-beta1-transfected PANC-1 cells. TGF-beta1-transfected pancreatic tumor cells induced a rich stroma after orthotopical transplantation in the nude mouse pancreas. The transfer of a single growth factor, TGF-beta1, conveys the ability to induce a fibroblast response similar to that seen in desmoplasia in human pancreatic adenocarcinoma. This effect cannot only be attributed to direct effects of TGF-beta1 but also results from the up-regulation of several other factors including collagen type I, connective tissue growth factor, and platelet-derived growth factor.

Animals↗
PubMed2001

Alternate splicing at the 3'-end of the human pancreatic tumor-associated mucin MUC4 cDNA.

MUC4 is a membrane-bound mucin and is considered as the human homologue of the rat sialomucin complex (SMC). The deduced structural organization of the wild type-MUC4 cDNA (WT-MUC4) sequence revealed two subunits: a large amino mucin type subunit (MUC4alpha) and a transmembrane subunit (MUC4beta). MUC4beta is a membrane-bound growth factor like subunit and contains three EGF-like domains. The MUC4 gene is expressed in several normal tissues like trachea, lung, and testis. It is not expressed in a normal human pancreas; however, its dysregulation results in high levels of expression in pancreatic tumors and tumor cell lines. Recently, we have demonstrated the presence of alternative splice events in the 3'-end of the MUC4 cDNA that generated new putative variants (sv1-sv10) in normal human testis and in a pancreatic tumor cell line (HPAF). In search of MUC4 variant(s) that are specific to pancreatic adenocarcinoma, we investigated the splicing phenomena in the MUC4 cDNA sequence by using a large panel of pancreatic tumor cell lines. We have identified ten alternative splice events located downstream to the central large tandem repeat domain. These splice events generated 12 variant species (sv4, sv9, sv10-18, and sv21) of MUC4 cDNAs. The deduced amino acid sequence of these variant MUC4 cDNAs revealed two distinct types: a family of secreted and a membrane-associated variant form. Among the members of MUC4 secreted variant family, three (sv4, sv12, and sv13) of ten showed a short 144 residue COOH-terminus compared to 1154 residues in WT-MUC4. The variants with this short COOH-terminus (144 residues) was found in 37% (4/11) of the tumor lines. The putative membrane-bound variant sv10 was detected in 37% (4/11) pancreatic tumor cell lines but not in any normal human tissues. In conclusion, we have identified novel splice variant(s) of MUC4 in pancreatic adenocarcinoma.

3' Untranslated Regions↗
PubMed2001

Metabolic and hemodynamic response of adipose tissue to angiotensin II.

OBJECTIVE: Recent studies have revealed the presence of a local renin-angiotensin system in adipose tissue. To examine the possible role of this system in adipose tissue, we performed microdialysis studies on the effect of angiotensin II (Ang II) on blood flow and metabolism in abdominal subcutaneous adipose tissue (aSAT) and femoral subcutaneous adipose tissue (fSAT) in young healthy men. RESEARCH METHODS AND PROCEDURES: Using the microdialysis technique, two different protocols were run perfusion with Ringer's solution + 50 mM ethanol with the subsequent addition of 125, 250, and 500 microg/liter Ang II (n = 8) and Ringers's solution + 50 mM ethanol with the subsequent addition of isoproterenol (1 microM) alone and in combination with 500 microg/liter Ang II (n = 6). Dialysate concentrations of ethanol, glycerol, glucose, and lactate were measured for estimating blood flow (ethanol dilution technique), lipolysis, and glycolysis, respectively. RESULTS: Perfusion with Ang II resulted in a dose-dependent decrease in blood flow (fSAT > aSAT), lipolysis (fSAT > aSAT), and glucose uptake (fSAT = aSAT). Isoproterenol increased blood flow and lipolysis at both sites and those effects could be returned to baseline values by the addition of Ang II in aSAT but not fSAT. DISCUSSION: In conclusion, our data indicate that in addition to its well-known vasoconstricting effect, Ang II inhibits lipolysis in adipose tissue, whereby femoral fat depots seem to be more sensitive to this effect than abdominal depots.

Adipose Tissue↗
PubMed2001

Tumor necrosis factor-alpha--308 G/A polymorphism in obese Caucasians.

OBJECTIVE: Tumor necrosis factor-alpha (TNF-alpha) is expressed primarily in adipocytes, and elevated levels of this cytokine have been linked to obesity and insulin resistance. Recently, the A allele of a polymorphism in the 5'-flanking region of the TNF-alpha gene (G-308A) has been reported to be more frequent in obese than in lean subjects and has also been associated with increased expression of this cytokine in fat tissue and influences fat mass and insulin resistance. We, therefore, examined the relationship between this variant and obesity in a German Caucasian population. SUBJECTS AND METHODS: We genotyped 176 index subjects recruited within the framework of the BErG (Berlin Ernährung Geschwister)- Study for the TNF-alpha-G-308A polymorphism. Subjects were characterized for weight, height, waist and hip circumference, body mass index (BMI), body composition, glucose tolerance, leptin and angiotensinogen levels. RESULTS: The frequency of the -308A allele (0.18) was similar to that reported previously and genotype distribution was in Hardy-Weinberg equilibrium (GG, n=118; GA, n=53; AA, n=5). There was a significant difference in allele frequencies of the polymorphism by BMI quartiles (I,<27.3 kg/m2; II, 27.3-31.9 kg/m2; III, 31.9-36.5 kg/m2; IV,>36.5 kg/m2, in each quartile n=44) with -308A allele carriers having a higher BMI than G allele carriers (P=0.013). Despite previous smaller studies that have related insulin resistance to the G-308A polymorphism, we found no relationship between glucose and insulin response during an oral glucose tolerance test (OGTT) and the polymorphism. Furthermore, none of the plasma parameters were related to the polymorphism. CONCLUSION: Our findings support the hypothesis that the G-308A polymophism of the TNF-alpha gene is associated with BMI. The G-308A polymorphism may, therefore, represent a genetic marker for increased susceptibility for obesity in Caucasians.

Alleles↗
PubMed2001

Pancreatic adenocarcinoma cell lines show variable susceptibility to TRAIL-mediated cell death.

BACKGROUND AND AIMS: Programmed cell death via the Fas receptor/Fas Ligand and DR4, DR5/TRAIL plays a major role in tumor escape and elimination mechanisms. It also promises to be an effective therapy alternative for aggressive tumors, as has been recently shown for colon, breast, and lung cancer cells. We attempted to clarify the role of these molecules in aggressivity of pancreatic carcinomas and to identify possible pathways as targets for therapy. METHODS: Five pancreatic cell lines were investigated for the expression of FasL/Fas, DcR3, DR4, DR5/TRAIL, DcR1, DcR2, and other death pathways related molecules such as Bax, bcl-xL, bcl-2, FADD, and caspase-3 by flow cytometry, immunoblotting, and RT/PCR, both semiquantitative and real time (TaqMan). The susceptibility of these cell lines to apoptosis mediated by recombinant TRAIL was investigated. The effect of therapeutic agents (gemcitabine) on their susceptibility to TRAIL induced apoptosis was studied as well. RESULTS: Pancreatic adenocarcinomas expressed high levels of apoptosis-inducing receptors and ligands. They showed differential susceptibility to cell death induced by TRAIL, despite expressing intact receptors and signaling machineries. Treatment with commonly used therapeutic agents did not augment their susceptibility to apoptosis. This could be explained by the fact that they expressed differentially high levels of decoy receptors, as well as molecules known as inhibitors of apoptosis. CONCLUSIONS: The data suggest that pancreatic carcinoma cells have developed different mechanisms to evade the immune system. One is the expression of nonfunctional receptors, decoy receptors, and molecules that block cell death, such as bcl2 and bcl-xL. The second is the expression of apoptosis-inducing ligands, such as TRAIL, that could induce cell death of immune cells. The success in treating malignant tumors by recombinant TRAIL might apply to some but not all pancreatic tumors because of their differential resistance to TRAIL-induced cell death.

Adenocarcinoma↗
PubMed2001

CD44 in normal human pancreas and pancreatic carcinoma cell lines.

CD44 is an integral cell-surface glycoprotein. Overexpression of the CD44 standard (CD44st) and its variants (CD44v) has been implicated in transformation and progression of many cancer types. Here, we investigated expression of CD44st, CD44v3-7, CD44v7/8, and v10 in five human pancreatic tumor cell lines and normal human pancreatic duct cells transfected with the SV40 large T antigen. CD44st and its variant proteins were quantified using immunocytochemistry and flow cytometry. CD44v7 was expressed at low levels, whereas CD44st, CD44v3, CD44 v4, CD44v, and CD44v6 were expressed at moderate levels in all pancreatic tumor cell lines. In contrast, CD44v7/8 and CD44v10 were expressed at very low levels in two out of the five pancreatic tumor cell lines. Overall, staining of CD44st and CD44 variants was significantly weaker compared to another surface molecule, ICAM-1, reported to be overexpressed in pancreatic cancer cells. Furthermore, the SV40 large T transfected duct cells showed only a weak staining for CD44st, CD44v5, and CD44v6. To determine a possible mechanism for the regulation of surface expression of CD44st, v5 and v6, we incubated Panc-1 cells with bFGF, TGF-beta1, EGF, TNFalpha, and IFNgamma. Only IFNgamma affected the CD44 expression by down-regulation of CD44v6. The constitutive expression of CD44 variants seems to be associated with the malignant state of invasive carcinoma.

Adenocarcinoma↗
PubMed2001

Mucin (MUC) gene expression in human pancreatic adenocarcinoma and chronic pancreatitis: a potential role of MUC4 as a tumor marker of diagnostic significance.

PURPOSE: Mucins are important biomolecules that frequently display an altered expression under pathological conditions. In a search for a unique and reliable marker(s) specific for pancreatic adenocarcinoma, we investigated the expression of different MUC genes in pancreatic tumors and tumor cell lines, in chronic pancreatitis, and in the normal pancreas. EXPERIMENTAL DESIGN: Total RNA from 16 pancreatic tumors, 10 chronic pancreatitis tissues, 7 normal pancreas tissues, and 15 pancreatic tumor cell lines were analyzed by reverse transcription-PCR with primers specific for MUC1, MUC2, MUC3, MUC4, MUC5AC, MUC5B, MUC6, and MUC7 genes and by RNA slot blot analyses. RESULTS: Our results revealed that of all of the mucins examined, only MUC4 displayed a differential expression that was specific for pancreatic adenocarcinoma. Indeed, a substantial number of tumor tissue samples (12 of 16) and tumor cell lines (11 of 15) expressed MUC4 mRNA, whereas samples from chronic pancreatitis (0 of 10) and the normal pancreas (0 of 7) tissues failed to exhibit any detectable level of this mucin. In contrast, no significant alteration was observed in the expression of the other mucins relative to that in the normal pancreas samples. CONCLUSIONS: Overall, this work demonstrates that pancreatic mucin MUC4 is a tumor-associated mucin. Furthermore, the present study introduces a novel avenue to discriminate between pancreatic adenocarcinoma and pancreatitis. Future investigations of the role played by MUC4 in pancreatic adenocarcinoma may prove to be useful in the formulation of strategies for the diagnosis and therapeutic treatment of this malignancy.

Adenocarcinoma↗
PubMed2000

[Role of the angiotensinogen gene for essential hypertension].

Essential hypertension is a complex disease influenced by different genetic and environmental factors. The renin-angiotensin system (RAS) is implicated in blood pressure regulation. Angiotensinogen (AGT) is the precursor of the biologically active angiotensin II (Ang II). Initial studies on hypertensive siblings and case-control studies indicated the important role of the angiotensinogen gene (AGT) for the predisposition to essential hypertension, preeclampsia and obesity-related hypertension. Recently, different AGT polymorphisms had been identified and analyzed in case-control studies. The aim of present studies is the analysis of potentially functional AGT variants (C-532T, G-6A), which might be responsible for the regulation of gene expression and therefore AGT generation. The A-6 allele is in complete linkage disequilibrium with the T235 allele and is associated with higher AGT expression in vitro. Segregation linkage analysis demonstrated that the C-532T polymorphism influences plasma AGT variability more significantly than the G-6A variant. Since the C-532T polymorphism is located within a AP-2 consensus element, functional promoter analyses are required. The understanding of the molecular basis of RAS in essential hypertension may provide us with new and more specific pharmacological agents and perhaps the ability to individualize antihypertensive treatment.

Alleles↗
PubMed2000

The Trp64Arg polymorphism of the beta3-adrenergic receptor gene is associated with hypertension in men with type 2 diabetes mellitus.

A missense mutation of the beta3-adrenergic receptor gene (ADRB3) resulting in a tryptophan/arginine exchange at position 64 (Trp64Arg polymorphism) has recently been associated with greater capacity to gain weight, a low resting metabolic rate, higher blood pressure, and an early onset of type 2 diabetes. These findings prompted us to examine the relationship between this mutation, blood pressure, and vascular complications in German patients with type 2 diabetes. White patients with type 2 diabetes mellitus (n = 417) were enrolled in the study. The Trp64Arg polymorphism of the ADRB3 gene was detected by polymerase chain amplification and subsequent restriction digest with BstN I. Stepwise logistic regression analysis of the entire study population revealed a significant interaction between gender and genotype (P = .019). We therefore performed separate analyses for men and women. There was a significant relationship between hypertension and the ADRB3 Trp64Arg variant in men (P = .015), but not in women. Furthermore, blood pressure levels in male patients with the minor allele had higher blood pressure levels (P < .05), despite a significantly greater number of antihypertensive medications (P = .01). There was no association between ADRB3 genotype and vascular complications in these patients. In conclusion, our data are compatible with a contribution of this genetic variant of ADRB3 to hypertension in male patients with type 2 diabetes. Further studies will be needed to determine the role of this polymorphism as a predictor of hypertension or vascular complications in patients with type 2 diabetes.

Aged↗
PubMed2000

G-protein beta(3)-subunit C825T genotype and nephropathy in diabetes mellitus.

BACKGROUND: Recent studies have identified a novel polymorphism (C825T) of the gene encoding the beta(3) subunit of heterotrimeric G proteins (G:beta(3)) which is associated with enhanced activation of G-proteins and appears to be more common in hypertensive patients and possibly contributes to decreased kidney allograft survival. METHODS: In the present study we examined the relationship between this genetic variant, type 1 and type 2 diabetes and renal complications of diabetes in 1008 Caucasian patients recruited from an outpatient diabetes clinic and four dialysis centres. We also studied 1940 healthy controls. RESULTS: After multivariate adjustment and in univariate statistics, the G:beta(3) 825TT genotype was not associated with a significantly enhanced risk of diabetes or renal complications. CONCLUSIONS: These findings indicate that the G:beta(3) 825T allele apparently does not contribute to the development of diabetes or associated renal complications in patients with type 1 or type 2 diabetes mellitus.

Adult↗
PubMed1999

Pro12Ala missense mutation of the peroxisome proliferator activated receptor gamma and diabetes mellitus.

Peroxisome proliferator activated receptor-gamma (PPARgamma) is a nuclear receptor that regulates adipocyte differentiation and possibly lipid metabolism and insulin sensitivity. Therefore, PPARgamma is a promising candidate gene for several disorders including diabetes, obesity, and dyslipoproteinemia. Screening for mutations in the entire coding region of the PPARgamma gene yielded a missense C --> G mutation at codon 12, resulting in the substitution of proline with alanine (Pro12Ala). The objective of our study was to examine the relationship between this genetic variant and diabetes and associated diseases in a large group of patients with type 1 (n = 522) and type 2 (n = 503) diabetes. Allelic frequencies of the PPARgamma2 12Ala allele were similar between patients with either type of diabetes and comparable to that in healthy controls (n = 310). There was also no significant relationship between dyslipoproteinemia or obesity and the PPARgamma2 Pro12Ala genotype. Thus, our data, in this large and ethnically homogenous group of patients, do not support the hypothesis that this genetic variant is strongly associated with diabetes, obesity, or dyslipidemia in patients with type 1 or type 2 diabetes mellitus. This genetic marker is therefore unlikely to serve as a clinically useful predictor of these disorders in Caucasian patients with diabetes mellitus.

Adult↗
PubMed1999

Aldosterone synthase gene (CYP11B2) C-344T polymorphism in Caucasians from the Berlin Salt-Sensitivity Trial (BeSST).

OBJECTIVE: Aldosterone synthase (CYP11B2) is a key enzyme in the biosynthesis of aldosterone. Recently, the T allele of a polymorphism in the 5'-flanking region of the CYP11B2 gene (C-344T) has been reported to be more frequent in hypertensives than in normotensives, and has also been associated with increased plasma aldosterone levels. We therefore hypothesized that this variant may be related to increased blood-pressure response to dietary salt intake. SUBJECTS AND METHODS: We genotyped 1 63 young normotensive men recruited within the framework of the Berlin Salt-Sensitivity Trial (BeSST) for the CYP11B2 C-344T polymorphism. Subjects were characterized for family history of hypertension, plasma parameters of the renin-angiotensin-aldosterone system and blood-pressure response to a high (220 mmol/day) and low (20 mmol/day) salt diet RESULTS: The frequency of the -344T allele (0.45) was similar to that reported previously and genotype distribution was in Hardy-Weinberg equilibrium (CC, n = 55; CT, n = 71; TT, n = 37). There was a trend towards a higher frequency of the T allele in subjects with a positive family history of hypertension (0.48 versus 0.42), but the C-344T genotype was not related to blood pressure under either diet Furthermore, when subjects were classified into salt-sensitive and salt-resistant groups, allelic distribution did not differ between the two groups (qT = 0.43 versus qT = 0.45). While renin activity and plasma aldosterone levels were not related to genotype, plasma angiotensinogen was significantly higher in T-allele carriers under both the high (P = 0.02) and low (P = 0.008) salt diet. CONCLUSION: Our findings do not support the hypothesis that the C-344T polymorphism of the CYP11B2 gene is associated with salt sensitivity or increased activity of the renin-angiotensin system in young normotensive subjects. It is, therefore, unlikely that the C-344T polymorphism is a genetic marker for salt sensitivity in young normotensive Caucasian men.

Adult↗
PubMed1999

Donor G protein beta3 subunit 825TT genotype is associated with reduced kidney allograft survival.

Recent studies have identified a novel polymorphism (C825T) of the gene encoding the beta3 subunit of heterotrimeric G proteins (Gbeta3), associated with enhanced activation of G proteins, which appears to be more common in hypertensive patients. In the present study, the relationship between this genetic variant and kidney allograft survival was examined over the first 3 yr after transplantation, in 320 consecutive Caucasian patients recruited from the Berlin-Steglitz transplantation center between 1988 and 1993. Clinical parameters, transplantation data, and details of graft survival were retrieved from clinical records. After multivariate adjustment for covariates (Cox hazard regression), the Gbeta3 825TT donor-genotype was associated with a significantly decreased graft survival representing a relative risk of graft loss of 2.2 (95% confidence interval, 1.1 to 4.8) compared to TC and CC grafts within the observation period. This association between donor TT genotype and graft survival remained stable even after stepwise exclusion of covariates from the multivariate model. In contrast, there was no significant relationship between recipient genotype and allograft function. These findings indicate that individuals receiving renal allografts from donors homozygous for the Gbeta3-825T allele may have an increased risk of developing allograft failure. Additional studies on the role of this genetic marker as well as the role of pertussis toxin-sensitive G proteins in the development of chronic rejection appear warranted.

Adult↗