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Biomedical subjects

W H Peters

Publications and source records attributed to W H Peters.

At least 73 records · Page 4Linked to original sources
PubMed1998

Effects of dietary anticarcinogens on rat gastrointestinal glutathione S-transferase theta 1-1 levels.

Several naturally occurring food components or non-steroidal anti-inflammatory drugs (NSAIDs) may reduce gastrointestinal cancer rates. Recently we have shown that dietary administration of such compounds enhanced the glutathione S-transferase (GST) enzyme activity and class alpha, mu and pi isoenzyme levels in the rat gastrointestinal tract. Elevation of the levels of GSTs, a family of biotransformation enzymes with many functions such as detoxification of carcinogens, might be one of the mechanisms that lead to cancer prevention. We therefore investigated whether the anticarcinogens alpha-angelicalactone, alpha-tocopherol, beta-carotene, coumarin, ellagic acid, flavone, indole-3-carbinol, d-limonene, oltipraz, phenethylisothiocyanate (PEITC) and the sulphoraphane analogue compound-30 affect gastrointestinal rGSTT1-1 protein levels in male Wistar rats. rGSTT1-1 protein levels were determined in cytosolic fractions of liver and oesophageal-, gastric-, small intestinal- and colonic mucosa by densitometrical analyses of western blots after immunodetection with an anti human GSTT1-1 monoclonal antibody, that cross-reacts with rGSTT1-1. In control Wistar rats, gastrointestinal rGSTT1-1 protein levels were highest in the liver and decreased in the order liver > stomach > colon > oesophagus > small intestine. Gastric rGSTT1-1 protein levels were enhanced by alpha-angelicalactone, alpha-tocopherol, coumarin, ellagic acid, oltipraz, PEITC and the sulphoraphane analogue compound-30. Oesophageal rGSTT1-1 protein levels were elevated by a-angelicalactone and coumarin, whereas colonic rGSTT1-1 protein levels were elevated by coumarin. Ellagic acid, on the other hand, reduced hepatic rGSTT1-1 protein levels to 53% of the control. In conclusion, dietary anticarcinogens are capable of inducing rGSTT1-1 protein levels in the rat gastrointestinal tract, and are most pronounced in the stomach. Enhanced rGSTT1-1 protein levels might lead to an increase of enzyme activity and to a more efficient detoxification of carcinogens and thus could contribute to prevention of carcinogenesis.

Animals↗
PubMed1998

Localization of glutathione S-transferases alpha and pi in human embryonic tissues at 8 weeks gestational age.

Glutathione S-transferases (GST) are a family of enzymes involved in the detoxification of xenobiotics. In humans, GST are divided into four different classes, alpha, mu, pi and theta, with partly overlapping substrate specificity and a tissue-specific expression pattern. We studied the cellular distribution of GST alpha and pi in a variety of human embryonic organs obtained from an extra-uterine monozygotic twin pregnancy at 8 weeks' gestational age. Tissues were fixed in 4% paraformaldehyde and embedded in paraffin. Three 4 microm thick sections were used, one for routine haematein and eosin staining, the others for immunohistochemical determination using monoclonal and polyclonal antibodies against GST alpha and pi, respectively. Both GST alpha and pi were present in hepatocytes, gastrointestinal epithelium, adrenal gland medulla, and tela chorioidea in the telencephalon. GST pi, but not alpha, was found in the epithelium of pancreatic and pulmonary glands, trachea, nephrons and urinary collecting ducts, as well as in the pia mater of the telencephalon and in developing nerve tissue in the gastrointestinal muscularis mucosae. In summary, we have demonstrated that immunoreactive protein for both GST alpha and pi is expressed in the human embryo at 8 weeks' gestational age. The early expression of GST alpha and pi in the epithelia of the urinary and digestive tracts and the respiratory system supports the importance of GST in the detoxification of potentially toxic or carcinogenic compounds. Our results suggest that the embryo itself is capable of detoxifying noxious compounds that are generated intracellularly or that cross the trophoblastic tissue.

Adrenal Glands↗
PubMed1998

Liver function following pregnancy complicated by the HELLP syndrome.

Serum levels of aminotransferases, lactate dehydrogenase, gammaglutamyl transferase, alkaline phosphatase, albumin and conjugated bilirubin, measured in 54 women at a median of 31 months (range 3-101) after pregnancies complicated by the HELLP syndrome, were not elevated. Total bilirubin levels, however, were elevated in 20% of these women; this represents a significant difference from the prevalence in 151 women with a previous normal pregnancy (chi2 = 12.23, P < 0.001), or in the normal female population (chi2 = 22.34, P < 0.00001). This raises the possibility that a dysfunction of the bilirubin-conjugating mechanism represents a risk factor for the development of the HELLP syndrome.

Adult↗
PubMed1998

Biomarkers in Barrett's esophagus (review).

Patients with Barrett's esophagus where squamous esophageal epithelium has been replaced by columnar epithelium containing goblet cells have an increased risk of esophageal adenocarcinoma. Unfortunately, most of those adenocarcinomas are detected at an advanced stage in which they are incurable. Many biomarkers have been studied, trying to identify the subset of patients who are at very high risk for adenocarcinoma. Dysplasia is at present the for the risk of adenocarcinoma. However, overexpression of p53, allelic losses, proliferation indices, flow cytometric abnormalities, accumulation of acidic fibroblast growth factor, expression of blood group antigens and sucrase-isomaltase during the Barrett's to adenocarcinoma sequence appear promising. However, additional information is needed to justify routine application in clinical practice and to define their role in surveillance programs.

Adenocarcinoma↗
PubMed1997

Measurement of glutathione S-transferase P1-1 in plasma: pitfalls and significance of screening and follow-up of patients with gastrointestinal carcinoma.

BACKGROUND: Gastrointestinal tumors often contain high amounts of the detoxification enzyme glutathione S-transferase P1-1 (GSTP1-1). Elevated levels of GSTP1-1 were found in serum and plasma from most patients with gastrointestinal tumors. The authors evaluated the role of GSTP1-1 as a plasma tumor marker in patients with gastrointestinal tumors. METHODS: A sensitive and specific sandwich enzyme-linked immunoadsorbent assay for quantification of GSTP1-1 in human plasma was developed. RESULTS: GSTP1-1 levels in serum samples from 10 healthy controls were significantly (P < 0.0001) higher than in corresponding ethylenediaminetetraacetic acid (EDTA) plasma and varied with the type of blood collection tube used. Refrigeration or delayed centrifugation of blood collected in plain EDTA tubes resulted in spuriously high plasma GSTP1-1 levels. Therefore, all plasma samples were collected in silicone-coated EDTA tubes. The distribution of plasma GSTP1-1 levels in 230 blood donors was nearly normalized by logarithmic transformation and an upper normal reference level of 21.8 microg/L was calculated. Males had significantly higher (P < 0.0001) plasma GSTP1-1 levels than females and a significant increase (P < 0.004) in plasma GSTP1-1 with age was noted. In only 20 of 55 patients (36%) with gastrointestinal tumors was the plasma GSTP1-1 level above the upper normal reference limit. No significant decrease in plasma GSTP1-1 was noted in matched pairs of plasma samples collected from 17 patients before and at least 2 weeks after resection of the tumor. CONCLUSIONS: The GSTP1-1 level in serum and plasma depends on the materials and methods used to collect the samples. Only 36% of the patients with gastrointestinal tumors had elevated plasma GSTP1-1 levels that did not decrease after resection of the tumor. These findings argue against the use of GSTP1-1 as a serum or plasma marker for gastrointestinal tumors.

Adolescent↗
PubMed1997

Effect of Brussels sprouts on oxidative DNA-damage in man.

The effect of consumption of Brussels sprouts on the excretion of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) into human urine was investigated. Ten non-smoking volunteers (five males and five females) were randomly assigned to two groups. Five volunteers started on a diet of 300 g of glucosinolate-free vegetables whereas the other five consumed 300 g of Brussels sprouts per day. After 1 week dietary regimes were reversed. Levels of 8-oxodG in 24-h urine samples were measured by high-performance liquid chromatography. In four of five males a reduction in 8-oxodG was found, whereas in the fifth male the 8-oxodG excretion was high in the control period and was even much higher in the sprouts period. In females no effect of consumption of Brussels sprouts on excretion of 8-oxodG was found. Our previous and present findings support the results of epidemiologic studies that consumption of brassica vegetables may diminish cancer risk.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1997

Plasma glutathione S-transferase alpha 1-1 levels in patients with chronic liver disorders.

Recent data suggest that plasma levels of the phase II detoxification enzyme glutathione S-transferase alpha may be a sensitive indicator of hepatocellular integrity in acute liver disorders but little information is available in chronic hepatic disorders. Using a newly developed enzyme linked immunosorbent assay, glutathione S-transferase A1-1 (GSTA1-1) levels were measured in 279 plasma samples from patients with chronic liver disorders. Results were categorized as normal or elevated plasma GSTA1-1 and normal or elevated plasma aspartate aminotransferase (AST) levels. In 24 patients with alcoholic liver cirrhosis, plasma GSTA1-1 levels were not significantly different from a group of 350 healthy controls and only one patient (4%) had an elevated GSTA1-1 level while 10 (42%) patients had elevated AST activities. In samples from patients with primary biliary cirrhosis (n = 150), primary sclerosing cholangitis (n = 26) or chronic hepatitis (n = 79) significantly (P < 0.0001) elevated plasma GSTA1-1 concentrations were detected in 25 (17%), 7 (27%) and 17 (22%) of the samples, respectively. AST activities were increased in a higher percentage of samples in all three disorders: 89%, 88%, and 57%, respectively. Plasma GSTA1-1 and AST levels were significantly correlated (P < 0.005) in the above mentioned disorders but not in alcoholic liver cirrhosis. It is concluded that plasma GSTA1-1 is not a sensitive parameter for the detection of hepatocellular damage in chronic liver disorders.

Alanine Transaminase↗
PubMed1997

Glutathione S-transferases in human ovarian follicular fluid.

OBJECTIVE: To study the levels of glutathione S-transferase Alpha 1-1 and glutathione S-transferase Pi 1-1 in human preovulatory ovarian follicular fluid (FF) and pooled granulosa and cumulus cells. DESIGN: The relation of glutathione S-transferase Alpha 1-1 and glutathione S-transferase Pi 1-1 with P and 17 beta-E2 concentrations were studied. SETTING: The Department of Obstetrics and Gynecology, the Department of Gastroenterology, and the Laboratory of Endocrinology and Reproduction of the University Hospital Nijmegen in Nijmegen, the Netherlands. PATIENT(S): Infertile women participating in an IVF program. RESULT(S): Detectable amounts of glutathione S-transferase Alpha 1-1 and glutathione S-transferase Pi 1-1 were found in ovarian FF and pooled cumulus and granulosa cells. Concentrations of glutathione S-transferase Alpha 1-1 were always much higher than those of glutathione S-transferase Pi 1-1. Both ovarian FF concentrations of glutathione S-transferase Alpha 1-1 and glutathione S-transferase Pi 1-1 did not correlate with ovarian FF concentrations of 17 beta-E2 and P. CONCLUSION(S): The high FF concentrations of glutathione S-transferase Pi 1-1 and especially of glutathione S-transferase Alpha 1-1 suggest that these enzymes may play an important role in the detoxification processes in the follicles. The lack of correlation between follicular P and 17 beta-E2 and glutathione S-transferase Alpha 1-1 and glutathione S-transferase Pi 1-1 indicates that both enzymes presumably are not present as a result of the high steroid levels.

Estradiol↗
PubMed1997

Glutathione S-transferase activity and subunit composition in transitional cell cancer and mucosa of the human bladder.

OBJECTIVES: Clinical data indicate that drug resistance to chemotherapy may occur in all stages of transitional cell cancer (TCC). Glutathione S-transferases (GSTs) are a family of detoxification enzymes composed of four different classes, denoted alpha (GSTA), mu (GSTM), pi (GSTP), and theta (GSTT), each containing one or more homo- or heterodimeric isoforms (GSTA1-1, GSTA1-2, and so forth), GSTs play a prominent role in drug detoxification and have been associated with resistance of tumor cells to anticancer agents. GST activity and isoenzyme levels were studied in TCC and normal bladder mucosa. METHODS: Enzyme activity was studied in samples of TCC (n = 37), adjacent normal bladder mucosa (n = 37), and in bladder mucosa of control patients without TCC (n = 46). GST isoenzyme composition was studied in mucosa and TCC of 14 patients and 11 controls. RESULTS: The mucosa of patients with TCC showed GST activity (191 +/- 21 nmol/min/mg cytosolic protein), similar to the mucosa of controls (176 +/- 15 nmol/min/mg). GST activity was significantly increased in TCC (666 +/- 157 nmol/min/mg) in comparison with adjacent mucosa (P < 0.003). In mucosa samples, the levels of GSTA (A1-1, A1-2, and A2-2) were below the detection limit in 92% of the samples. GSTM (GSTM1-1) was found in 9 controls and in 7 patients with TCC but not in the other 7 patients, whereas GSTP (GSTP1-1) could be detected in all samples. The levels of GSTM1-1 and GSTP1-1 were similar in mucosa of patients and controls. The mean relative increase of GSTP1-1 levels in TCC was 4.6-fold (P < 0.002). In the 7 patients with GSTM1-1-detectable expression in adjacent normal mucosa, mean GSTM1-1 levels in TCC were increased 2.8-fold compared with mean levels in normal adjacent mucosa (P < 0.02). GSTA was measured in five samples of TCC at relatively low levels. CONCLUSIONS: Overexpression of GSTP1-1 and GSTM1-1 may suggest that in the process of TCC carcinogenesis, a selection pressure occurs, resulting in a tumor with enhanced detoxification properties, including that of therapeutic drugs.

Aged↗
PubMed1997

Effect of long time storage on cytosolic glutathione S-transferases.

Glutathione S-transferases are a family of enzymes catalyzing the conjugation of glutathione to a wide variety of compounds. Stability of human liver cytosolic glutathione S-transferase enzyme activity and levels of glutathione S-transferase class Alpha and Mu were assessed. Cytosolic fractions of sixteen different patients were stored up to two years at three different temperatures: -20 degrees, -80 degrees and -196 degrees Celsius. Samples were assayed for glutathione S-transferase enzyme activity and glutathione S-transferase class Alpha and Mu levels, after 3, 6, 12 and 24 months of storage. No significant differences in glutathione S-transferase enzyme activity as well as in isoenzyme levels were found during this 24 months of storage at the three different temperatures. It is concluded that stability of glutathione S-transferases allows long term storage even at -20 degrees C, without significant loss of enzyme activity or enzyme protein.

Cold Temperature↗
PubMed1997

Effects of nonsteroidal anti-inflammatory drugs on glutathione S-transferases of the rat digestive tract.

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been demonstrated to reduce cancer rates in oesophagus, stomach and colon of humans and animals. Earlier, we showed that high human gastrointestinal tissue levels of glutathione S-transferase (GST), a family of detoxification enzymes consisting of class alpha, mu, pi and theta isoforms, were inversely correlated with cancer risk. We investigated whether the NSAIDs indomethacin, ibuprofen, piroxicam, acetyl salicylic acid (ASA), and sulindac, supplemented in the diet for 2 weeks at 25, 400, 400, 400, and 320 ppm, respectively, influenced gastrointestinal GSTs in male Wistar rats. In cytosolic fractions of oesophagus, stomach, intestine and liver, GST activity towards 1-chloro-2,4-dinitrobenzene was measured, GST isozyme levels were determined by densitometrical analysis of Western blots after immunodetection with monoclonal antibodies, and glutathione levels were determined by HPLC. GST activity and GST mu levels were increased (1.2-1.8 x) in oesophagus and small intestine by indomethacin, ibuprofen, piroxicam and sulindac. GST alpha levels were induced (1.2-2.8 x) in stomach by piroxicam, in small intestine by indomethacin, ibuprofen, piroxicam and sulindac, and in liver by piroxicam. GST pi levels were raised (1.9-3.6 x) in stomach by ibuprofen, ASA, and sulindac, and in small intestine by indomethacin, piroxicam, ASA, and sulindac. Glutathione levels were raised (1.2-2.3 x) by indomethacin and ASA in small intestine and by piroxicam in oesophagus. Enhancement of GSTs in the upper part of the digestive tract, resulting in a more efficient detoxification, may explain in part the anticarcinogenic properties of NSAIDs.

Animals↗
PubMed1996

Influence of postnatal overnutrition and pregnancy on non-insulin dependent diabetes induced in Wistar rats by neonatal streptozotocin.

Wistar rats with non-insulin dependent diabetes induced by neonatal streptozotocin (STZ) administration were raised either in large or in small litters. The STZ-treated rats from small litters showed a higher body weight as well as increased blood glucose levels compared with vehicle- and STZ-treated rats reared in large nests at an age of 8 weeks. The higher body weight of these rats was maintained until an age of 15 weeks, whereas the basal blood glucose was normalized. However, both STZ-treated groups exhibited an impaired glucose tolerance. During pregnancy only the glucose tolerance of the STZ-treated animals from large nests was improved although not normalized. The STZ-treated rats from small nests failed to adapt to pregnancy because the blood glucose levels after glucose load were similar to values found in the virgin state. The body weight of pregnant STZ treated rats raised in small litters was significantly lower than in vehicle- or STZ-terated rats from large nests. The number of fetuses per litter was similar in all groups tested. Compared with the vehicle-treated rats from large litters the fetal body weight of STZ-treated rats from small nests was decreased and that of STZ rats raised in large litters was increased. These results suggest that the rats with the more impaired glucose tolerance produce growth-retarded pups and, conversely, rats with rather mild impairment have bigger fetuses than the vehicle-treated ones. In the present study we have examined for the first time the combined effects of postnatal overnutrition and pregnancy on glucose homeostasis of rats treated neonatally with STZ. Our data demonstrate that postnatal overnutrition is an aggravating factor in the development of a diabetic state in these rats, especially at times when the insulin requirement is higher such as puberty and pregnancy.

Animal Nutritional Physiological Phenomena↗
PubMed1996

Effect of oltipraz, alpha-tocopherol, beta-carotene and phenethylisothiocyanate on rat oesophageal, gastric, colonic and hepatic glutathione, glutathione S-transferase and peroxidase.

Four anticarcinogens (oltipraz, alpha-tocopherol, beta-carotene and phenethylisothiocyanate [PEITC]) were studied with respect to their effects on oesophageal, gastric, colonic and hepatic (i) glutathione (GSH) content, (ii) glutathione S-transferase (GST) enzyme activity, (iii) GST isoenzyme levels, and (iv) glutathione peroxidase (GPx) enzyme activity in male Wistar rats. GST enzyme activity was significantly increased in oesophagus (1.9X) and colon (1.2X) by PEITC and in liver (1.4X) by oltipraz. GST Alpha was doubled in the liver by oltipraz, alpha-tocopherol and PEITC. GST Mu levels were increased by beta-carotene and PEITC in stomach and liver, by oltipraz in liver and by alpha-tocopherol in stomach. PEITC induced colonic GST Pi levels (1.3X). GSH content was induced in liver by oltipraz (1.4X) and alpha-tocopherol (1.2X) and in colon by PEITC (1.6X). Each of the anticarcinogens tested increased GPx activity at one or more sites: Se-dependent and total GPx activities were induced in 31.3% and 37.5% of all possibilities, respectively. Major induction in total GPx was found in stomach by alpha-tocopherol (1.8X). In conclusion our data demonstrate that dietary administration of oltipraz, PEITC, alpha-tocopherol and beta-carotene, may exert chemopreventive effects in the digestive tract of the rat by enhancing GST, GPx, and, to a lesser extent, GSH levels.

Animals↗
PubMed1996

Sandwich ELISA for glutathione S-transferase Alpha 1-1: plasma concentrations in controls and in patients with gastrointestinal disorders.

Class Alpha glutathione S-transferases (GST-Alpha) are found in high concentrations in human liver. Increased plasma concentrations of GSTA1-1, the most abundant isoform of GST-Alpha, are a very sensitive marker for hepatocellular leakage. A sandwich-type ELISA was developed, based on a monoclonal antibody specific for human GSTA1-1 and a polyclonal rabbit anti-human GST-Alpha antiserum. The assay is specific for human GSTA1-1, and has a detection limit of 0.04 micrograms/L. The distribution of plasma GSTA1-1 concentrations in 350 blood donors was nearly normalized by logarithmic transformation and an upper normal reference concentration of 5.9 micrograms/L was calculated. Men had significantly higher plasma GSTA1-1 concentrations than women (P <0.0001). In women, but not in men, a significant increase was noted with age (P <0.05). In patients with inflammatory bowel disease (n= 210), gastrointestinal tumors (n= 70), irritable bowel disease (n= 36), or chronic pancreatitis (n= 12), plasma GSTA1-1 concentrations were similar to those of controls. In contrast, plasma GSTA1-1 concentrations were increased to a similar extent as alanine aminotransferase activities in patients with liver disorders (n= 37).

Adult↗
PubMed1995

Glutathione S-transferase pi in colorectal tumors is predictive for overall survival.

Glutathione S-transferases (GSTs) are enzymes involved in the detoxification of xenobiotics and are divided into four subclasses, alpha, mu, pi, and theta, with different although overlapping substrate specificities. Most human gastrointestinal tumors contain increased amounts of GST-pi and GST enzyme activity. The relationship between GST parameters and tumor and patient characteristics, including overall survival, were studied retrospectively in 100 primary colorectal adenocarcinomas. Levels of GST-alpha, GST-mu, GST-pi, and GST enzyme activity were not related to the Dukes stage, differentiation grade, localization, histological type and diameter of the tumor, or gender and age of the patient. Fifty-seven patients died (median survival, 21 months; range, 1-65 months) during follow-up, and 43 patients were still alive at the closing date of the study (median follow-up, 68 months; range, 60-87 months). Optimal dichotomization and uni- and multivariate analyses were done with the Cox proportional hazard model. Multivariate analysis with all clinicopathological parameters revealed higher Dukes stage (hazard ratio, 2.7; P < 0.001) and older age (hazard ratio, 2.8; P = 0.001) to be the only independent prognostic variables for overall survival. In contrast to GST-alpha and GST-mu, high levels of GST-pi (hazard ratio, 3.1; P = 0.002) and GST enzyme activity (hazard ratio, 2.0; P = 0.020) in the tumors were found to have a significant prognostic value independent from the clinicopathological parameters when added separately to this Cox model. Thus, this study indicates that GST subclass levels in colorectal adenocarcinomas are not related to clinicopathological parameters and that the GST-pi level and GST enzyme activity have a prognostic value for the overall survival of the patients.

Adenocarcinoma↗