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J A Weaver

Publications and source records attributed to J A Weaver.

At least 19 recordsLinked to original sources
PubMed2001

Increased 15-HPETE production decreases prostacyclin synthase activity during oxidant stress in aortic endothelial cells.

Selenium (Se) is an integral component of glutathione peroxidase and is able to detoxify peroxides that can affect arachidonic acid (AA) metabolism, thereby influencing eicosanoid biosynthesis. This study investigated the effects of oxidant stress, a consequence of Se deficiency, on eicosanoid formation and important key enzyme expression in bovine aortic endothelial cells (BAEC). Bovine aortic endothelial cells cultured in Se-deficient media and stimulated with tumor necrosis factor alpha or H2O2 produced significantly less prostacyclin (PGI(2)) and more 15-hydroxyeicosatetraenoic acid, 15-hydroperoxyeicosatetraenoic acid (15-HPETE), and thromboxane than Se-supplemented BAEC. Additionally, reverse transcription polymerase chain reaction and immunoblotting determined that the mRNA and protein levels of the eicosanoid forming enzymes cyclooxygenase-1 (COX1), cyclooxygenase-2 (COX2), and PGI synthase were not significantly changed. The addition of 15-HPETE to Se-supplemented BAEC inhibited the production of PGI(2) suggesting that the accumulation of lipid hydroperoxides during Se-deficiency may be the underlying factor in the altered eicosanoid production during Se deficiency. Furthermore, inhibition of COX and addition of PGH(2) to Se-deficient or Se-supplemented BAEC still resulted in lower PGI(2) formation by Se-deficient cells. Together, these results suggest that Se deficiency modifies eicosanoid production by affecting the activity of key enzymes, particularly PGI synthase, rather than their transcription or translation.

Animals↗
PubMed2001

Selenium modulates 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (PAF) biosynthesis in bovine aortic endothelial cells.

Selenium (Se) deficiency has been reported to increase platelet-activating factor (PAF) production in human endothelial cells; however, the mechanism is unclear. This study demonstrated that tumor necrosis factor-alpha (TNF-alpha) stimulated Se-deficient bovine aortic endothelial cells (BAEC) produced significantly more PAF than Se-supplemented cells. Moreover, the increase in the level of PAF was associated with enhanced activity of two anabolic enzymes in the remodeling pathway: phospholipase A2 and Lyso-PAF:acetyl-coenzyme A acetyltransferase (Lyso-PAF-AcT). In contrast, the activity of the PAF catabolic enzyme, PAF-acetylhydrolase, was not affected by Se status. Interestingly, prostacyclin, a potent vasodilator and inhibitor of platelet aggregation, inhibited the activity of Lyso-PAF-AcT and reduced the PAF production in TNF-alpha-stimulated BAEC. Therefore, we conclude that Se deficiency alters PAF production in TNF-alpha-stimulated BAEC by altering the activity of anabolic enzymes involved in the remodeling pathway partially through the inhibition of prostacyclin production.

Animals↗
PubMed2001

Human aging is associated with altered TNF-alpha production during hyperglycemia and hyperinsulinemia.

Changes in tumor necrosis factor-alpha (TNF-alpha) may provide a mechanism to explain impaired glucose metabolism with advancing age. Hyperglycemic clamps (180 min, 10 mM) were performed on seven older [67 +/- 2 yr; body mass index (BMI) 24.7 +/- 1.0 kg/m(2)] and seven younger (22 +/- 1 yr; BMI 21.8 +/- 1.3 kg/m(2)) healthy sedentary males with normal glucose tolerance. TNF-alpha production at basal and at the end of 180 min of hyperglycemia and hyperinsulinemia was measured ex vivo from lipopolysaccharide-stimulated (1 ng/ml) peripheral blood mononuclear cells. Plasma glucose, insulin, and C-peptide levels were similar in both groups at basal and during the last 30 min of the hyperglycemic clamp. Glucose infusion rates were lower (P < 0.004) in the older group compared with the young, indicating decreased insulin action among the older subjects. Basal TNF-alpha secretion was similar in older and younger subjects. TNF-alpha was suppressed (P < 0.02) in the younger group (230 +/- 46 vs. 126 +/- 49 pg/ml; basal vs. clamp) but not in the older group (153 +/- 37 vs. 182 +/- 42 pg/ml), with significant group differences in response (P < 0.05). A significant correlation was observed between the level of suppression in TNF-alpha production and insulin action (Kendall's rank, tau = 0.40, P < 0.05). Furthermore, the TNF-alpha response during the clamp was related to fat mass (r = 0.88, P < 0.001) and abdominal fat (r = 0.81, P < 0.003). In conclusion, these findings suggest a possible mechanism by which TNF-alpha may modulate glucose metabolism in younger people. Aging and modest increases in adiposity prevent the "normal" suppression of TNF-alpha production after a sustained postprandial-like hyperglycemic-hyperinsulinemic stimulus, which may contribute in part to the decline in insulin sensitivity in older men.

Adult↗
PubMed1998

Immune system activation and fatigue during treadmill running: role of interferon.

UNLABELLED: Extreme fatigue often accompanies infection and other diseases, but the causal mechanisms are unknown. Recent research has focused on various cytokines as potential immune system mediators of fatigue during illness. Interferon-alpha/beta (IFN-alpha/beta) has attracted the most interest in this regard. PURPOSE: The purpose of this research was to study the effect of IFN-alpha/beta on fatigue during treadmill running in mice. METHODS: Mice (male CD-1) were acclimated to treadmill running for 4 d before experimental sessions. In experiment 1 (EXP 1), mice were injected with either polyI:C (pI:C) (5 mg.kg-1 body weight) or saline (CON) 12 or 24 h before the exercise session. These sessions consisted of treadmill running to fatigue (approximately 3 h, 19-24 m.min-1, 5% grade, no shock). In experiment 2 (EXP 2), mice were injected 24 h before exercise with normal rabbit serum (CON), pI:C, or pI:C + anti-IFN-alpha/beta antibody (pI:C + Ab). RESULTS: The results of EXP 1 showed that the plasma IFN-alpha/beta titer was much higher at 24 h than at 12 h after pI:C injection (P < 0.001) and that run time to fatigue was significantly reduced only when the exercise occurred 24 h after injection (P < 0.05). In EXP 2, administration of the anti-IFN-alpha/beta antibody attenuated both the pI:C-induced increase in plasma IFN-alpha/beta (P < 0.001) and the decrease in run time to fatigue (r = -0.81, P < 0.001). CONCLUSIONS: These results suggest that immune system activation by pI:C was associated with early fatigue during prolonged treadmill exercise and that this effect may, at least partially, result from increased IFN-alpha/beta.

Animals↗
PubMed1997

Macrovascular disease and hyperglycaemia: 10-year survival analysis in Type 2 diabetes mellitus: the Belfast Diet Study.

The relationship between macrovascular disease and blood glucose control in long-term follow-up of Type 2 (non-insulin-dependent) diabetes mellitus is difficult to study because of the gradual rise in fasting plasma glucose due to ongoing beta-cell failure. We used time-dependent covariates in Cox's proportional hazards model to allow variables measured annually during a 10-year prospective follow-up to be related to risk of myocardial infarction or cerebrovascular accident. Data for 432 newly diagnosed diabetic patients were available, 112 of whom suffered myocardial infarction (fatal or non-fatal). Analysis of baseline measurements only gave relative hazards (95% CL) of 1.04 (0.99, 1.09) per mmol l(-1) increase in fasting plasma glucose, 1.43 (1.12, 1.83) per decade increase in age and 1.07 (0.98, 1.17) per 10 % increase in percentage of ideal weight. Analysis incorporating ongoing measurements gave corresponding figures of 1.07 (1.02, 1.12) for fasting plasma glucose, 1.64 (1.23, 2.20) for age and 1.06 (0.95, 1.18) for percentage of ideal weight. The risk of myocardial infarction while on insulin treatment 1.09 (0.58, 2.06) or oral agents 1.41 (0.86, 2.31) was not significantly elevated relative to dietary treatment. Baseline smoking status, systolic blood pressure, and previous myocardial infarction were also significant predictors of myocardial infarction. Similar relationships were found for cerebrovascular accident and total mortality. Increasing fasting plasma glucose is a significant independent predictor of macrovascular disease in diabetes.

Adult↗
PubMed1997

Energy requirement for long-term body weight maintenance in older women.

The total dietary energy requirement of healthy, free-living older women was examined by determining the total energy intake (TEI) required for long-term body weight maintenance in nine women aged (mean +/- SD) 67 +/- 9 years (range, 56 to 78). For 14 weeks, each woman consumed defined amounts of foods and beverages prepared at a General Clinical Research Center (GCRC) to provide 0.8 g protein.kg-1.d-1 and a nonprotein energy ratio of 40% fat to 60% carbohydrate. Adjustments to TEI were made to keep body weight within +/-0.5 kg of each woman's starting body weight. All women were asked to maintain their habitual level of daily activity, and the energy cost of physical activity was estimated using the Yale Physical Activity Survey (YPAS). Resting energy expenditure (REE) was measured with each woman in the postabsorptive state just after awakening, using an indirect calorimeter at baseline and week 14. The energy requirement expressed as the ratio of TEI to REE was 1.82 +/- 0.15, a value 21% higher (P < .001) than the energy allowance of 1.5 x REE suggested for women beyond age 50 years in the 1989 Recommended Dietary Allowances (RDAs). Using the RDAs equation to predict REE from body weight (pREE), the ratio of TEI to pREE was 1.73 +/- 0.18 (P < .005, comparison with 1.50 x REE). Estimates of the energy expenditure for physical activity (EEPA) based on the energy intake-balance data and the YPAS data were similar (3.18 +/- 0.92 and 3.14 +/- 1.42 MJ/d, respectively) for the group of women, but were more variable on an individual basis. Results of this long-term energy balance study suggest that the RDAs underestimate the dietary energy requirement of older women.

Aged↗
PubMed1996

ATP depletion affects the phosphorylation state, ligand binding, and nuclear transport of the 4 S polycyclic aromatic hydrocarbon-binding protein in rat hepatoma cells.

In the rat, cytochrome P4501A1 gene expression is thought to be regulated by several trans-acting factors including the 4 S polycyclic aromatic hydrocarbon (PAH)-binding protein. Phosphorylation and dephosphorylation have been suggested to influence the function of many cytosolic receptors and transcription factors. The ATP level within H4IIE rat hepatoma cells could be depleted by treatment with sodium azide or 2,4-dinitrophenol; restoration of the original ATP levels occurred with addition of glucose to the cell culture. ATP depletion reduced the phosphate content of the 4 S protein by approximately 25-30%, which lowered the binding of benzo[a]pyrene (B[a]P) to the 4 S protein by >60%. This effect could not be reversed by the addition of ATP to the binding reaction mixtures. Alkaline phosphatase treatment of the purified 4 S protein in a cell-free system also reduced the B[a]P binding to the protein. Cells treated with a protein phosphatase inhibitor, okadaic acid, and a protein kinase inhibitor, staurosporin, affected the B[a]P binding of the 4 S protein positively and negatively, respectively. These data suggested that phosphorylation is involved in the interaction of the 4 S protein with the PAH. The nuclear translocation of the predominantly cytosolic binding protein has been investigated after ligand binding. Western blots with the immunopurified 4 S PAH-binding protein from cytosolic and nuclear lysates showed significant differences in the distribution of the 4 S receptor between cytosolic and nuclear compartments in control and ATP-depleted cells. Ligand binding stimulated the movement of the receptor into the nucleus, which was completely blocked by reducing the intracellular ATP concentration. These findings provide new information on the role of ATP and phosphorylation on the interaction of B[a]P with 4 S PAH-binding protein and its nuclear translocation.

2,4-Dinitrophenol↗
PubMed1996

Nuclear transcription factor Oct-1 binds to the 5'-upstream region of CYP1A1 and negatively regulates its expression.

The cytochrome P450-dependent monooxygenases, which represent an extended superfamily, catalyze the biotransformation of many endogenous and exogenous substances. One of these hemoproteins, cytochrome P4501A1, is most closely associated with the bioactivation of polycyclic aromatic hydrocarbons such as benzo[a]pyrene, which may play a role in environmental carcinogenesis. A negative regulatory element (NRE) has been localized in the 5'-upstream region of the cytochrome P4501A1 gene (CYP1A1) at -843 to -746 base pairs from the site of transcription. The purpose of this research was to define any interactions of trans-acting proteins with this cis element. Rat liver nuclei were used as the source of trans-acting proteins and a biotinylated NRE-bearing fragment (-782 to -843 bp) from a plasmid which contained the CYP1A1 was prepared by the polymerase chain reaction technique. Gel mobility shift assays were used to demonstrate interactions between this NRE fragment and nuclear proteins. The specific binding to an octamer-containing motif in the 5'-upstream region of CYP1A1 was demonstrated; this was used as a step in the partial purification from rat liver of the transcription factor, Oct-1. Conventional chromatographic procedures and DNA recognition site affinity chromatography were also used. HepG2 human hepatoma cells were transfected with both pMCoLUC+ which contains the luciferase gene as a reporter gene driven by the CYP1A1 promoter (including the NRE), and an Oct-1 expression vector. Luciferase activity/mg protein in the doubly-transfected cells was significantly lower than in cells containing only pMCoLUC+. A nuclear transcription factor Oct-1 interacts with a portion of the NRE of the rat CYP1A1, suppressing the expression of this gene. These findings may help to explain the low level of basal expression of CYP1A1 in mammalian systems.

Animals↗
PubMed1992

Delineation of cis-acting sequences required for expression of Drosophila mojavensis Adh-1.

The control of expression of the Adh-1 gene of Drosophila mojavensis has been analyzed by transforming ADH null Drosophila melanogaster hosts with P element constructs which contain D. mojavensis Adh-1 having deletions of different extent in the 5' and 3' ends. Adh-1 expression in the D. melanogaster hosts is qualitatively similar to expression in D. mojavensis, although expression is quantitatively lower in transformants. Deletions of the 5' end indicate that information required for normal temporal and tissue expression in larvae is contained within 70 bp of the transcription start site. However, deletion constructs to -70 are deficient in ovarian nurse cell expression, whereas the additional upstream sequences present in constructs containing deletions to -257 do support expression in the ovary. Comparison of the nucleotide sequence in the -257 to -70 region of Adh-1 of four species: D. mojavensis and Drosophila arizona, which express Adh-1 in the ovary, and Drosophila mulleri and Drosophila navojoa, which do not, has led to the identification of regions of sequence similarity that correlate with ovary expression. One of these bears a striking similarity to a conserved sequence located upstream of the three heat shock genes that have constitutive ovarian expression and may be an ovarian control element. We have identified an aberrant aspect of Adh-1 expression. In transformants which carry an Adh-1 gene without a functional upstream Adh-2 gene Adh-1 expression continues into the adult stage instead of ceasing at the onset of metamorphosis. In transformants with a functional Adh-2 gene, Adh-1 expression ceases in the third larval instar stage and aberrant expression in the adult stage does not occur.

Alcohol Dehydrogenase↗
PubMed1988

Renal artery stenosis in hypertensive diabetic patients.

The prevalence of secondary forms of hypertension in diabetes is unknown. One hundred and five of 465 patients randomly selected from a diabetic clinic population were found to be hypertensive. Hypertensive patients aged less than 70 years were screened for renal artery stenosis using intravenous digital subtraction angiography. Two angiograms were technically unsatisfactory. All 18 insulin-dependent patients successfully screened had normal renal arteriograms. Five of 24 non-insulin-dependent patients had unilateral renal artery stenosis but functional tests did not clearly suggest that renal artery stenosis was causing the hypertension in these cases. No patient was referred for surgery or angioplasty. We conclude that renal artery stenosis is common in hypertensive non-insulin-dependent diabetics but may not, in many cases, be the cause of the hypertension. The criteria for investigating diabetic hypertensives for renal artery stenosis should be no different from those used in the general hypertensive population.

Adult↗
PubMed1987

The 'wild geese'.

Explore the source record for details and available documents.

History, 19th Century↗
PubMed1986

Natural history of diabetes presenting age 40-69 years: a prospective study of the influence of intensive dietary therapy.

Two hundred and twenty-three newly-diagnosed symptomatic diabetic patients with onset age 40-69 years enrolled in a prospective study of intensive dietary management of diabetes were observed for a period of six years and the data obtained is analysed. The variables studied were weight and fasting levels of plasma glucose and insulin, and of serum total cholesterol and triglyceride. These tests were monitored throughout the study and in addition the oral glucose tolerance test was analysed at entry to the study, after six months intensive dietary management and again after 72 months. Blood pressure, electrocardiogram and the presence of posterior tibial artery pulsation were recorded at entry to the study and at 36 months and 72 months. Approximately 80 per cent of the patients were managed solely by dietary restriction for the entire six years, but 25 patients received oral hypoglycaemic drugs and 26 required insulin treatment. Weight, and fasting glucose and triglyceride values fell in the first few months of intensive dietary management. Analysis of possible risk factors in survivors and patients dead at six years showed no significant differences, apart from a higher mean age at diagnosis in those who died. During the six years of intensive dietary management the mortality from all causes in these diabetic patients was no greater than that for the general population of Northern Ireland.

Adult↗
PubMed1985

Five cases of cyclical Cushing's syndrome.

Reported cases of cyclical Cushing's syndrome are rare. Of 14 successive patients with Cushing's syndrome nine collected sequential urine samples for the estimation of cortisol:creatinine ratio. Five had cyclical Cushing's syndrome while two had considerable variation in urinary cortisol excretion without a cyclical pattern being established. Two of the five patients with a cyclical syndrome had paradoxical responses to dexamethasone. In only one patient with a cyclical pattern did the cortisol:creatinine ratio fall after treatment with bromocriptine or cyproheptadine, or both. The high incidence of the cyclical form of Cushing's syndrome has important clinical implications. A high index of suspicion of the syndrome is required in patients with symptoms or signs of Cushing's syndrome but with normal cortisol values, in patients with fluctuating cortisol values, and in patients with anomalous responses to dexamethasone. Because of possible variations in steroidogenesis the results of drug studies in Cushing's syndrome must be interpreted cautiously.

Adrenocorticotropic Hormone↗
PubMed1985

32P-postlabeling analysis of DNA adducts persisting for up to 42 weeks in the skin, epidermis and dermis of mice treated topically with 7,12-dimethylbenz[a]anthracene.

The initial and persistent levels of 7,12-dimethylbenz[a]-anthracene (DMBA)-DNA adducts in mouse skin, epidermis and dermis after topical carcinogen application were studied by 32P-postlabeling assay. In the major experiment, a single dose of 1.2 mumol of the carcinogen was applied to the shaved backs of adult female BALB/cANN mice, and DNA was isolated from epidermis and dermis, respectively, 24 h and 1, 2, 3, 4, 8, 16, 24, 36 and 42 weeks later. Total binding at 24 h was approximately 34 and approximately 28 adducts in 10(7) normal nucleotides for epidermal and dermal DNA, respectively. (One adduct in 10(7) nucleotides equals 0.3 fmol adduct/microgram DNA.) While initial binding was higher in epidermal DNA, the adducts were approximately 10 times more persistent in dermal DNA: at 42 weeks, total binding levels were approximately 0.17 and approximately 1.7 adducts in 10(7) nucleotides for epidermis and dermis, respectively. To quantitate low levels of DMBA-DNA adducts, 32P-postlabeling assays were run in the presence of a limiting amount of carrier-free [gamma-32P]ATP; this was found to favor labeling of the adducts, thereby leading to a 20- to 100-fold enhancement of the method's sensitivity for individual adducts. One of the three major DMBA-DNA adducts was more persistent than were the others; the level of this adduct remained constant at approximately 60% of the total in epidermal and dermal DNA during the last 18 weeks of the 42-week observation period. Since a [3H]thymidine-labeling experiment showed a normal epidermal DNA turnover 40 weeks after DMBA treatment, it was concluded that the bulk of the persistent adducts was present in subpopulations of dormant cells. We have hypothesized that such cells, in the absence of a promoting stimulus, are incapable of division because of the adduction and/or mutation of genes critical for growth (proto-oncogenes), and may thus correspond to the 'latent tumor cells', as defined by Berenblum and Shubik in their classical analysis of the attributes of tumor initiation and promotion.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1985

Cyclical Cushing's disease: two distinct rhythms in a patient with a basophil adenoma.

A 71-yr-old woman with clinical signs of Cushing's syndrome was studied continuously for an extended period after demonstration of a paradoxical response to dexamethasone. She proved to have a corticotroph cell adenoma of the pituitary which caused secretion of ACTH and cortisol in two distinct rhythms. One rhythm consisted of a period of 40 days of excess cortisol production, followed by a period of 60-70 days of normal production. During the period of excess cortisol production there was a second rhythm, consisting of peaks of cortisol production every 3-6 days with intervening troughs of normal cortisol production. Prolonged clinical remission followed transphenoidal surgery, but the pituitary still has the ability to provoke abnormal amounts of cortisol secretion, as occurred during a postoperative dexamethasone suppression test. The long duration of normal cortisol production phases in this patient demonstrates the difficulty in excluding Cushing's syndrome in patients with suggestive clinical symptoms but normal serum and urinary cortisol levels if these tests are measured for a single short phase of several days.

Adenoma, Basophil↗
PubMed1984

Identification and characterization of the catecholamine transporter in bovine chromaffin granules using [3H]reserpine.

Characterization of the catecholamine transporter in chromaffin granule membranes has been hampered by the lack of a radioligand with high specific activity which binds selectively to the carrier with high affinity. We report here the identification of a high affinity binding site for [3H]reserpine on chromaffin granule membranes isolated from bovine adrenal gland which has the characteristics expected of the catecholamine transporter. [3H]Reserpine bound predominately to a high affinity site with a Kd for [3H]reserpine of 9 nM and a binding site density of 7.8 pmol/mg of protein. Comparison of the characteristics of the high affinity reserpine binding site to the characteristics of catecholamine transport indicated that (a) the Ki and rank order of potency for inhibition of [3H]reserpine binding by various biogenic amines was similar to their Ki for inhibition of catecholamine transport (b) both the inhibition of (-)-[3H]norepinephrine transport and inhibition of [3H]reserpine binding showed similar stereo-specificity, and (c) Kd for binding of reserpine to chromaffin granule membranes was similar to the Ki for reserpine inhibition of catecholamine transport. These results demonstrate that the high affinity binding site for [3H]reserpine on chromaffin granule membranes is associated with the catecholamine transporter.

Adrenal Medulla↗
PubMed1984

Predicting the need for insulin therapy in late onset (40-69 years) diabetes mellitus.

A six-year prospective study of 144 newly diagnosed, symptomatic diabetic patients aged 40-69 years showed that 21 (15%) required insulin therapy, commencing 1-61 months after diagnosis. The plasma insulin response to oral glucose was assessed at the time of diagnosis. All 12 patients with very low peak insulin response (less than or equal to 6 mU/l) required insulin therapy. Thirty-six patients had an intermediate insulin response (greater than 6 less than or equal to 18 mU/l); of these, 7 with a mean weight 88% (range 73-96%) of average body weight required insulin, while 29 with a mean weight 117% (range 98-158%) of average body weight, did not. Ninety-six patients had a peak insulin response (greater than 18 mU/l); 2 patients whose weights were 96% and 100% of average body weight, required insulin, while the remainder did not. Consideration of initial body weight and peak insulin response provides a useful prediction of the eventual need for insulin.

Adult↗